boost usersguide

Version 4.0.4

User’s Guide

June 2004

User’s Guide BOOST Version 4.0.4

Address comments concerning this document to:

AVL LIST GmbHA-8020 Graz Hans-List-Platz 1

Phone: +43 316 787-1615Telefax: +43 316 787-1922E-Mail: [email protected] Site: http://www.avl.com

Revision Date Description Document No.A 01-Sep-1995 User’s Guide v2.0 01.0104.0425B 01-Apr-1997 User’s Guide v3.1 01.0104.0426C 01-Aug-1998 User’s Guide v3.2 01.0104.0427D 01-Apr-2000 User’s Guide v3.3 01.0104.0428E 12-Apr-2002 User’s Guide v4.0 01.0104.0429F 03-Mar-2003 User’s Guide v4.0.1 01.0104.0434G 18-Jul-2003 User’s Guide v4.0.3 01.0104.0439H 23-Jun-2004 User’s Guide v4.0.4 01.0104.0449

Copyright © 2004, AVL

All rights reserved. No part of this publication may be reproduced, transmitted, transcribed,stored in a retrieval system, or translated into any language, or computer language in any form orby any means, electronic, mechanical, magnetic, optical, chemical, manual or otherwise, withoutprior written consent of AVL.

This document describes how to run the BOOST software. It does not attempt to discuss all theconcepts of 1D gas dynamics required to obtain successful solutions. It is the user’s responsibilityto determine if he/she has sufficient knowledge and understanding of gas dynamics to apply thissoftware appropriately.

This software and document are distributed solely on an "as is" basis. The entire risk as to theirquality and performance is with the user. Should either the software or this document provedefective, the user assumes the entire cost of all necessary servicing, repair or correction. AVL andits distributors will not be liable for direct, indirect, incidental or consequential damages resultingfrom any defect in the software or this document, even if they have been advised of the possibilityof such damage.

All mentioned trademarks and registered trademarks are owned by the corresponding owners.


AST.01.0104.0449 - 23-Jun-2004 i

Table of Contents1. Introduction _____________________________________________________1-1

1.1. Scope _______________________________________________________________________1-1

1.2. User Qualifications ___________________________________________________________1-1

1.3. Symbols _____________________________________________________________________1-2

1.4. Documentation_______________________________________________________________1-2

1.5. Platforms____________________________________________________________________1-3

1.6. BOOST_HOME Environment Variable _________________________________________1-3

2. Theoretical Basis ________________________________________________2-12.1. The Cylinder_________________________________________________________________2-1

2.1.1. High Pressure Cycle, Basic Equation________________________________________2-1

2.1.1.1. Combustion Models ___________________________________________________2-32.1.1.2. Heat Release Approach ________________________________________________2-4

2.1.1.3. Extended Heat Release Approach ______________________________________2-102.1.1.4. Quasi-dimensional Combustion Models _________________________________2-12

2.1.1.5. Theoretical Combustion Models________________________________________2-222.1.1.6. User Models _________________________________________________________2-23

2.1.2. Gas Exchange Process, Basic Equation _____________________________________2-23

2.1.2.1. Port Massflow Rates__________________________________________________2-24

2.1.2.2. Scavenging __________________________________________________________2-26

2.1.3. Piston Motion ___________________________________________________________2-28

2.1.4. Heat Transfer ___________________________________________________________2-29

2.1.4.1. In Cylinder Heat Transfer ____________________________________________2-292.1.4.2. Port Heat Transfer___________________________________________________2-33

2.1.5. Dynamic In-Cylinder Swirl________________________________________________2-34

2.1.6. Blow-By Losses in the Cylinder____________________________________________2-34

2.1.7. Wall Temperature _______________________________________________________2-35

2.1.8. Direct Gasoline Injection _________________________________________________2-35

2.1.9. Divided Combustion Chamber_____________________________________________2-36

2.1.10. BURN Utility __________________________________________________________2-39

2.2. Plenum (Variable Plenum) ___________________________________________________2-39

2.3. Flow Restriction (Rotary Valve) _______________________________________________2-41

2.4. Check Valve ________________________________________________________________2-42

2.5. Junction____________________________________________________________________2-43

2.6. Turbocharger _______________________________________________________________2-44

2.7. Mechanically Driven Superchargers ___________________________________________2-46

2.8. Fuel Injector or Carburetor___________________________________________________2-47

2.9. Waste Gate _________________________________________________________________2-48

2.10. Pipe Flow _________________________________________________________________2-48

BOOST Version 4.0.4 User’s Guide

ii AST.01.0104.0449 - 23-Jun-2004

2.10.1. Bends _________________________________________________________________2-52

2.10.2. Variable Wall Temperature ______________________________________________2-53

2.10.2.1. Forced Convection __________________________________________________2-532.10.2.2. Free Convection ____________________________________________________2-54

2.10.3. Forward / Backward Running Waves______________________________________2-54

2.10.4. Perforated Pipe ________________________________________________________2-55

2.10.4.1. Perforated Pipe contained in Pipe_____________________________________2-55

2.10.4.2. Perforated Pipe contained in Plenum__________________________________2-56

2.11. Pipe Attachment (System or Internal Boundary)_______________________________2-56

2.12. Assembled Elements________________________________________________________2-58

2.12.1. Catalyst _______________________________________________________________2-58

2.12.2. Particulate Filter _______________________________________________________2-58

2.13. Engine Control Unit and Wire _______________________________________________2-58

2.14. Gas Properties _____________________________________________________________2-60

2.15. Definition of Global Engine Data (SI-Units) ___________________________________2-61

2.15.1. Cylinder Data __________________________________________________________2-62

2.15.2. Gas Exchange Related Data______________________________________________2-65

2.16. Abbreviations ______________________________________________________________2-70

3. Graphical User Interface ________________________________________3-13.1. BOOST Specific Operations ___________________________________________________3-1

3.1.1. Menu Bar________________________________________________________________3-2

3.1.2. BOOST Buttons __________________________________________________________3-4

3.1.3. Elements Tree____________________________________________________________3-4

3.1.4. Model Tree_______________________________________________________________3-8

3.1.5. Data Input Window _______________________________________________________3-9

3.1.5.1. Sub-group Icons______________________________________________________3-10

3.1.6. Table Window ___________________________________________________________3-10

3.2. General Input Data__________________________________________________________3-12

3.2.1. Simulation Tasks ________________________________________________________3-12

3.2.1.1. Date, Project ID and Run ID __________________________________________3-133.2.1.2. Simulation Tasks ____________________________________________________3-13

3.2.2. General Control _________________________________________________________3-13

3.2.2.1. Engine Speed ________________________________________________________3-14

3.2.2.2. Steady State / Transient Simulation____________________________________3-143.2.2.2.1. Engine Only Transient Calculation ___________________________________3-143.2.2.2.2. Driver Transient Calculation ________________________________________3-153.2.2.3. Calculation Modes____________________________________________________3-213.2.2.4. Identical Cylinders ___________________________________________________3-21

3.2.2.5. User-Defined Concentrations __________________________________________3-213.2.2.6. Mixture Preparation__________________________________________________3-21

3.2.2.7. Fuel Data ___________________________________________________________3-213.2.2.8. Reference Conditions _________________________________________________3-22

3.2.2.9. Gas Properties _______________________________________________________3-22


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3.2.3. Time Step Control _______________________________________________________3-23

3.2.4. FIRE Link Control_______________________________________________________3-25

3.2.5. BMEP Control __________________________________________________________3-25

3.2.6. Convergence Control _____________________________________________________3-26

3.2.7. Engine Friction__________________________________________________________3-27

3.2.8. Volumetric Efficiency ____________________________________________________3-27

3.3. Design a BOOST Calculation Model ___________________________________________3-28

3.3.1. Pipe Design _____________________________________________________________3-28

3.4. Specification of Input Data for Elements _______________________________________3-28

3.4.1. Pipe ____________________________________________________________________3-28

3.4.1.1. Bending Radius ______________________________________________________3-29

3.4.1.2. Friction Coefficient___________________________________________________3-303.4.1.3. Heat Transfer Factor _________________________________________________3-30

3.4.1.4. Variable Wall Temperature____________________________________________3-30

3.4.2. Cylinder ________________________________________________________________3-31

3.4.2.1. Combustion Model ___________________________________________________3-333.4.2.2. Divided Combustion Chamber _________________________________________3-47

3.4.2.3. Heat Transfer _______________________________________________________3-483.4.2.4. Scavenging __________________________________________________________3-50

3.4.2.5. Valve / Port Data_____________________________________________________3-51

3.4.3. Measuring Point_________________________________________________________3-58

3.4.4. Boundaries______________________________________________________________3-58

3.4.4.1. System Boundary ____________________________________________________3-58

3.4.4.2. Aftertreatment Boundary _____________________________________________3-603.4.4.3. Internal Boundary ___________________________________________________3-61

3.4.5. Transfer Elements _______________________________________________________3-62

3.4.5.1. Flow Restriction _____________________________________________________3-62

3.4.5.2. Rotary Valve_________________________________________________________3-633.4.5.3. Check Valve _________________________________________________________3-64

3.4.5.4. Fuel Injector / Carburetor _____________________________________________3-643.4.5.5. Pipe Junction________________________________________________________3-65

3.4.6. Volume Elements ________________________________________________________3-67

3.4.6.1. Plenum _____________________________________________________________3-67

3.4.6.2. Variable Plenum _____________________________________________________3-703.4.6.3. Perforated Pipe in Pipe _______________________________________________3-71

3.4.7. Assembled Elements _____________________________________________________3-72

3.4.7.1. Air Cleaner __________________________________________________________3-72

3.4.7.2. Catalyst_____________________________________________________________3-733.4.7.3. Air Cooler ___________________________________________________________3-74

3.4.7.4. Diesel Particulate Filter (DPF) ________________________________________3-75

3.4.8. Charging Elements ______________________________________________________3-76

3.4.8.1. Turbocharger________________________________________________________3-763.4.8.2. Positive Displacement Compressors ____________________________________3-84

3.4.8.3. Turbo Compressor ___________________________________________________3-85


iv AST.01.0104.0449 - 23-Jun-2004

3.4.8.4. Waste Gate __________________________________________________________3-85

3.4.9. External Links Elements _________________________________________________3-86

3.4.9.1. FIRE Link___________________________________________________________3-863.4.9.2. User Defined Element ________________________________________________3-86

3.4.10. Control Elements _______________________________________________________3-87

3.4.10.1. Wire _______________________________________________________________3-87

3.4.10.2. Engine Control Unit_________________________________________________3-883.4.10.3. MATLAB DLL Element______________________________________________3-92

3.4.10.4. MATLAB API Element ______________________________________________3-94

3.4.11. Acoustic Elements ______________________________________________________3-95

3.4.11.1. Microphone ________________________________________________________3-95

3.5. Case Series Calculation ______________________________________________________3-96

3.5.1. Parameters _____________________________________________________________3-96

3.5.1.1. Assign Parameters ___________________________________________________3-963.5.1.1.1. Assign a Model Parameter ___________________________________________3-963.5.1.1.2. Assign an Element Parameter _______________________________________3-973.5.1.1.3. Case Explorer ______________________________________________________3-98

3.6. Running a Simulation________________________________________________________3-99

3.7. Utilities ___________________________________________________________________3-102

3.7.1. BURN _________________________________________________________________3-102

3.7.1.1. Input Data Specification _____________________________________________3-102

3.7.1.2. Run the Calculation _________________________________________________3-1053.7.1.3. Results_____________________________________________________________3-105

3.7.2. Search_________________________________________________________________3-105

3.7.3. License Manager _______________________________________________________3-106

3.7.4. Pack Model ____________________________________________________________3-107

4. External Links___________________________________________________4-14.1. MATLAB____________________________________________________________________4-1

4.1.1. Application Programming Interface (API) ___________________________________4-1

4.1.1.1. Running a MATLAB API Simulation ____________________________________4-2

4.1.2. Real Time Workshop ______________________________________________________4-4

4.1.3. Pure Code Generation_____________________________________________________4-8

4.1.4. System Function (s-function) ______________________________________________4-9

4.1.4.1. Running an s-function Simulation _____________________________________4-12

4.2. AVL FIRE __________________________________________________________________4-13

4.3. AVL CRUISE _______________________________________________________________4-13

5. BOOST Post-processing__________________________________________5-15.1. Analysis of Summary Results __________________________________________________5-1

5.2. Analysis of Cycle Dependent Results____________________________________________5-2

5.3. Analysis of Crank Angle Dependent Results _____________________________________5-9

5.4. Analysis of Composite Elements_______________________________________________5-14

5.5. Analysis of Frequency Dependent Results and Orifice Noise______________________5-15


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5.6. Analysis of Case Series Results________________________________________________5-16

5.7. Analysis of Animated Results _________________________________________________5-17

5.8. Message Analysis____________________________________________________________5-18

5.8.1. Message Description _____________________________________________________5-19

5.8.2. Message Examples _______________________________________________________5-20

5.8.3. Fatal Errors_____________________________________________________________5-21

5.8.3.1. MATLAB API _______________________________________________________5-21

5.9. Analysis of Aftertreatment Analysis Results ____________________________________5-22

6. The BOOST Files ________________________________________________6-16.1. The .bwf Files________________________________________________________________6-1

6.2. The .bst Files ________________________________________________________________6-1

6.3. The .atm Files _______________________________________________________________6-1

6.4. The .rs0 and .rs1 Files ________________________________________________________6-2

6.5. The .uit File _________________________________________________________________6-2

6.6. The .gpf File _________________________________________________________________6-2

6.7. The rvalf.cat File _____________________________________________________________6-2

7. Recommendations _______________________________________________7-17.1. Modeling ____________________________________________________________________7-1

7.2. Analysis of Results ___________________________________________________________7-5

7.3. Important Trends ____________________________________________________________7-6

7.4. Turbocharger Matching ______________________________________________________7-12

8. Literature _______________________________________________________8-1

9. Appendix ________________________________________________________9-19.1. Running The Executable ______________________________________________________9-1

9.1.1. Command Line ___________________________________________________________9-1

9.1.1.1. Options ______________________________________________________________9-1

9.1.1.2. File Search Paths _____________________________________________________9-4

9.1.2. Batch Mode ______________________________________________________________9-5

9.1.2.1. Create Model with GUI ________________________________________________9-59.1.2.2. Preparing the Batch File: ______________________________________________9-5

9.1.2.3. Start the Run_________________________________________________________9-5

9.2. Required Input Data__________________________________________________________9-6

9.2.1. Engine Data _____________________________________________________________9-6

9.2.2. Turbocharging System Data _______________________________________________9-6

9.2.3. Fuel Data ________________________________________________________________9-6

9.2.4. Boundary Conditions______________________________________________________9-6

9.2.5. Drawings ________________________________________________________________9-6

9.2.6. Measurements ___________________________________________________________9-7

9.2.7. For Transient Simulation__________________________________________________9-7

9.3. Available Channel Data _______________________________________________________9-8


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9.4. Compiling and Linking BOOST _______________________________________________9-10

9.4.1. NT Visual Studio ________________________________________________________9-10

9.4.2. UNIX __________________________________________________________________9-10

9.5. Using the BOOST Dynamic Link Library ______________________________________9-10

9.5.1.1. Loading Problems ____________________________________________________9-10

9.6. Flow Coefficients Directions __________________________________________________9-11

9.7. Variation Parameters from V3.3 to V4.0 _______________________________________9-12


AST.01.0104.0449 - 23-Jun-2004 vii

List of FiguresFigure 2-1: Energy Balance of Cylinder (High Pressure Cycle) ........................................................................... 2-2

Figure 2-2: Influence of Excess Air Ratio on IMEP............................................................................................... 2-4

Figure 2-3: Approximation of a Measured Heat Release....................................................................................... 2-6

Figure 2-4: Influence of Shape Parameter 'm' ........................................................................................................ 2-6

Figure 2-5: Superposition of Two Vibe Functions ............................................................................................... 2-10

Figure 2-6: Schematic of the Spray/Package Structure........................................................................................ 2-16

Figure 2-7: Schematic of the Physical Processes taking place in the Package................................................... 2-16

Figure 2-8: Energy Balance of Cylinder (Gas Exchange Process) ...................................................................... 2-24

Figure 2-9: Inner Valve Seat Diameter ................................................................................................................. 2-25

Figure 2-10: User-Defined Scavenging Model ...................................................................................................... 2-28

Figure 2-11: Standard Crank Train ...................................................................................................................... 2-29

Figure 2-12: The Pressure Function ψ.................................................................................................................. 2-41

Figure 2-13: Full Check Valve Model .................................................................................................................... 2-42

Figure 2-14: Flow Patterns in a Y-Junction ......................................................................................................... 2-43

Figure 2-15: Waste Gate ......................................................................................................................................... 2-48

Figure 2-16: Finite Volume Concept ..................................................................................................................... 2-50

Figure 2-17: Linear Reconstruction of the Flow Field ........................................................................................ 2-51

Figure 2-18: Pressure Waves from Discontinuities at Cell Borders................................................................... 2-51

Figure 2-19: Pipe Bend Parameters ...................................................................................................................... 2-52

Figure 2-20: Pipe Bend Loss Coefficient............................................................................................................... 2-52

Figure 2-21: Forward / Backward Running Waves .............................................................................................. 2-54

Figure 2-22: Perforated Pipes contained in Pipe ................................................................................................. 2-55

Figure 2-23: Two perforated Pipes contained in Plenum ................................................................................... 2-56

Figure 2-24: Flow Chart of the ECU ..................................................................................................................... 2-59

Figure 2-25: Considered Mass Fractions .............................................................................................................. 2-61

Figure 2-26: Relation of Gas Exchange Data........................................................................................................ 2-69

Figure 3-1: BOOST - Main Window ........................................................................................................................ 3-1

Figure 3-2: Model Submenu..................................................................................................................................... 3-8

Figure 3-3: Data Input Window............................................................................................................................... 3-9

Figure 3-4: Element Sub-group Submenu ............................................................................................................ 3-10

Figure 3-5: Table Window ...................................................................................................................................... 3-11

Figure 3-6: Graph Context Menu .......................................................................................................................... 3-12

Figure 3-7: Simulation Control – Simulation Tasks Window............................................................................. 3-12

Figure 3-8: Simulation Control – Globals Window .............................................................................................. 3-13

Figure 3-9: Load Characteristic for Engine Only................................................................................................. 3-15

Figure 3-10: Driver Input Window........................................................................................................................ 3-17

Figure 3-11: Shifting Process................................................................................................................................. 3-18

Figure 3-12: Vehicle Input Window....................................................................................................................... 3-20

Figure 3-13: Simulation Control – Constant Gas Properties Window............................................................... 3-22

Figure 3-14: Simulation Control – Time Step Control Window ......................................................................... 3-23

Figure 3-15: Simulation Control – BMEP Control Window................................................................................ 3-25

Figure 3-16: Simulation Control – Convergence Control Window..................................................................... 3-26

Figure 3-17: Example Table Input for Bending Radius ...................................................................................... 3-29

Figure 3-18: Standard Cranktrain......................................................................................................................... 3-31

Figure 3-19: Crank Angle related to Combustion Duration ............................................................................... 3-34

Figure 3-20: Flat Cylinder Head............................................................................................................................ 3-39


viii AST.01.0104.0449 - 23-Jun-2004

Figure 3-21: Disc Chamber Cylinder Head........................................................................................................... 3-39

Figure 3-22: Spherical Cylinder Head................................................................................................................... 3-39

Figure 3-23: Backset Special Cylinder Head ........................................................................................................ 3-40

Figure 3-24: Pent Roof Cylinder Head.................................................................................................................. 3-40

Figure 3-25: Flat Piston Top.................................................................................................................................. 3-41

Figure 3-26: Heron Piston Top .............................................................................................................................. 3-41

Figure 3-27: Spherical Bowl Piston Top ............................................................................................................... 3-41

Figure 3-28: Spherical Piston Top......................................................................................................................... 3-42

Figure 3-29: Pent Roof Piston Top........................................................................................................................ 3-42

Figure 3-30: Definition of Angle between Spark Plug and Bowl/Top Center ................................................... 3-43

Figure 3-31: Definition of Spark Plug Position.................................................................................................... 3-43

Figure 3-32: AVL MCC Combustion Model Window ........................................................................................... 3-47

Figure 3-33: Scavenging Models ............................................................................................................................ 3-50

Figure 3-34: Valve Port Specifications Window................................................................................................... 3-51

Figure 3-35: Calculation of Effective Valve Lift................................................................................................... 3-52

Figure 3-36: Modification of Valve Lift Timing ................................................................................................... 3-52

Figure 3-37: Positive intake valve opening and closing shift (same value) ........................................................ 3-53

Figure 3-38: Positive intake valve closing shift only ............................................................................................ 3-53

Figure 3-39: Positive intake valve opening shift only........................................................................................... 3-53

Figure 3-40: Positive exhaust closing shift and positive intake opening shift ................................................... 3-53

Figure 3-41: Positive exhaust opening and closing shift (same value) ............................................................... 3-54

Figure 3-42: Positive exhaust opening shift only.................................................................................................. 3-54

Figure 3-43: Positive exhaust valve closing shift only.......................................................................................... 3-54

Figure 3-44: Positive exhaust valve closing shift and negative intake opening shift ........................................ 3-54

Figure 3-45: Negative exhaust shifts (same value) and positive intake shifts (same value) ............................ 3-55

Figure 3-46: Interpolation of Flow Coefficients ................................................................................................... 3-55

Figure 3-47: Definition of Window Geometry ...................................................................................................... 3-57

Figure 3-48: Calculation of Minimum Duct Cross Section.................................................................................. 3-57

Figure 3-49: Mounting of a Pipe End.................................................................................................................... 3-59

Figure 3-50: Engine Cylinder Sub-model.............................................................................................................. 3-61

Figure 3-51: Sudden Diameter Change................................................................................................................. 3-62

Figure 3-52: Flow Coefficients of a Junction........................................................................................................ 3-66

Figure 3-53: Perforated Pipe in Plenum Window................................................................................................ 3-69

Figure 3-54: Perforated Pipes Contained in Plenum........................................................................................... 3-69

Figure 3-55: Perforated Pipe in Pipe Window...................................................................................................... 3-71

Figure 3-56: Steady State Air Cleaner Performance ........................................................................................... 3-73

Figure 3-57: Deterioration Factor of a Twin Entry- or Multiple Entry Turbine.............................................. 3-78

Figure 3-58: Compressor Map................................................................................................................................ 3-79

Figure 3-59: Turbine Map ...................................................................................................................................... 3-81

Figure 3-60: PD-Compressor Map ......................................................................................................................... 3-84

Figure 3-61: UDE Input ......................................................................................................................................... 3-86

Figure 3-63: Interaction between BOOST and External-Link Element............................................................ 3-87

Figure 3-64: Selection of ECU Actuator Channels .............................................................................................. 3-89

Figure 3-65: ECU Map Specification..................................................................................................................... 3-90

Figure 3-66: Time Constants for Transient ECU Functions .............................................................................. 3-91

Figure 3-67: MATLAB DLL Element Input ......................................................................................................... 3-92

Figure 3-68: Sensor Channel Selection ................................................................................................................. 3-93

Figure 3-69: Actuator Channel Selection.............................................................................................................. 3-93

Figure 3-70: MATLAB API Element Input .......................................................................................................... 3-94


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Figure 3-71: Microphone Position ......................................................................................................................... 3-95

Figure 3-72: Assign Parameter Menu ................................................................................................................... 3-96

Figure 3-73: Model Parameter Window................................................................................................................ 3-97

Figure 3-74: Case Explorer Window...................................................................................................................... 3-98

Figure 3-75: Run Simulation Window................................................................................................................... 3-99

Figure 3-76: Simulation Status Window.............................................................................................................3-100

Figure 3-77: View Cycle Simulation Logfile Window ........................................................................................3-101

Figure 3-78: View Aftertreatment Analysis Logfile Window............................................................................3-101

Figure 3-79: View Animation Logfile Window ...................................................................................................3-102

Figure 3-80: Burn Utility - Fitting Data Window ..............................................................................................3-103

Figure 3-81: Search Utility Displaying Initialization Data for Pipes...............................................................3-106

Figure 3-82: License Manager Window...............................................................................................................3-106

Figure 4-1: Simulink Settings for the Integration Algorithm .............................................................................. 4-5

Figure 4-2: Simulink Settings for the MAT-Files .................................................................................................. 4-6

Figure 4-3: Simulink Settings for the Boost-DLL Creation.................................................................................. 4-7

Figure 4-4: The BOOST MATLAB/SIMULINK Library..................................................................................... 4-10

Figure 4-5: Mask Parameters Window.................................................................................................................. 4-11

Figure 5-1: Summary Analysis Window.................................................................................................................. 5-2

Figure 5-2: IMPRESS Chart Main Window............................................................................................................ 5-3

Figure 5-3: Show Elements Window ..................................................................................................................... 5-15

Figure 5-4: Microphone position............................................................................................................................ 5-16

Figure 5-5: Create Series Results Window ........................................................................................................... 5-17

Figure 5-6: PP3 Main Window............................................................................................................................... 5-18

Figure 5-7: Message Analysis Window.................................................................................................................. 5-18

Figure 5-8: MATLAB API Error - version mismatch .......................................................................................... 5-21

Figure 7-1: Modeling of Steep Cones....................................................................................................................... 7-1

Figure 7-2: Modeling of an Intake Receiver ........................................................................................................... 7-2

Figure 7-3: Modeling of an Intake Receiver with Pipes and Junctions ............................................................... 7-2

Figure 7-4: Intake Receiver Models......................................................................................................................... 7-3

Figure 7-5: Influence of Intake Receiver Modeling on Volumetric Efficiency and Air Distribution ................ 7-3

Figure 7-6: Exhaust Port Modeling......................................................................................................................... 7-4

Figure 7-7: Modeling Multi-Valve Engines............................................................................................................. 7-5

Figure 7-8: Influence of In-Cylinder Heat Transfer on Engine Performance..................................................... 7-7

Figure 7-9: Influence of Port Flow Coefficients on Engine Performance............................................................ 7-7

Figure 7-10: Influence of IVC on Engine Performance ......................................................................................... 7-8

Figure 7-11: Influence of EVO on the Engine Performance ................................................................................. 7-8

Figure 7-12: Air Feed to Intake Receiver................................................................................................................ 7-9

Figure 7-13: Influence of Air Feed Pipe Length on Engine Performance ......................................................... 7-10

Figure 7-14: Influence of Number of Cylinders on Engine Performance.......................................................... 7-10

Figure 7-15: Intake Running Length .................................................................................................................... 7-11

Figure 7-16: Influence of Intake Runner Length on Engine Performance ....................................................... 7-11

Figure 7-17: Engine Operating Line in the Compressor Map ............................................................................ 7-13

Figure 7-18: Engine Operating Line in the Compressor Map (compressor too small)..................................... 7-14

Figure 7-19: Engine Operating Line in the Compressor Map (compressor too large) ..................................... 7-14

Figure 7-20: Engine Operating Line in the Compressor Map (correct compressor) ........................................ 7-15

Figure 7-21: Engine Operating Point in the Turbine Map ................................................................................. 7-15


23-Jun-2004 1-1

1. INTRODUCTIONBOOST simulates a wide variety of engines, 4-stroke or 2-stroke, spark or auto-ignited.Applications range from small capacity engines for motorcycles or industrial purposes upto large engines for marine propulsion. BOOST can also be used to simulate thecharacteristics of pneumatic systems.

The BOOST program package consists of an interactive pre-processor which assists withthe preparation of the input data for the main calculation program. Results analysis issupported by an interactive post-processor.

The new pre-processing tool of the AVL Workspace Graphical User Interface features amodel editor and a guided input of the required data. The calculation model of the engineis designed by selecting the required elements from a displayed element tree by mouse-click and connecting them by pipe elements. In this manner even very complex engineconfigurations can be modelled easily, as a large variety of elements is available.

The main program provides optimised simulation algorithms for all available elements.The flow in the pipes is treated as one-dimensional. This means that the pressures,temperatures and flow velocities obtained from the solution of the gas dynamic equationsrepresent mean values over the cross-section of the pipes. Flow losses due to three-dimensional effects, at particular locations in the engine, are considered by appropriateflow coefficients. In cases where three-dimensional effects need to be considered in moredetail, a link to AVL's three-dimensional flow simulation code FIRE is available. Thismeans that a multi-dimensional simulation of the flow in critical engine parts can becombined with a fast one-dimensional simulation elsewhere. This feature could be ofparticular interest for the simulation of the charge motion in the cylinder, the scavengingprocess of a two-stroke engine or for the simulation of the flow in complicated mufflerelements.

The IMPRESS Chart and PP3 post-processing tools analyze the multitude of data resultingfrom a simulation. All results may be compared to results of measurements or previouscalculations. Furthermore, an animated presentation of selected calculation results isavailable. This also contributes to developing the optimum solution to the user's problem.A report template facility assists with the preparation of reports.

1.1. ScopeThis document describes the basic concepts and methods for using the BOOST Version4.0.1 program to perform engine cycle simulation.

1.2. User QualificationsUsers of this manual:

Must be qualified in basic UNIX and/or Microsoft Windows.

Must be qualified in basic engine cycle simulation.


1-2 23-Jun-2004

1.3. SymbolsThe following symbols are used throughout this manual. Safety warnings must be strictlyobserved during operation and service of the system or its components.

!Caution: Cautions describe conditions, practices or procedures whichcould result in damage to, or destruction of data if not strictly observed orremedied.

� Note: Notes provide important supplementary information.

Convention Meaning

Italics For emphasis, to introduce a new term or for manual titles.

monospace To indicate a command, a program or a file name,messages, input / output on a screen, file contents orobject names.

SCREEN-KEYS A SCREEN font is used for the names of windows andkeyboard keys, e.g. to indicate that you should type acommand and press the ENTER key.

MenuOpt A MenuOpt font is used for the names of menu options,submenus and screen buttons.

1.4. DocumentationBOOST documentation is available in PDF format and consists of the following:

Release Notes

User's Guide

Primer

Examples

Aftertreatment

Aftertreatment Primer

Linear Acoustics

1D – 3D Coupling

Thermal Network Generator (TNG) User’s Guide

Thermal Network Generator (TNG) Primer

Validation

AVL Workspace Installation Guide (Windows NT and UNIX)

AVL Workspace GUI Introduction

FLEXlm User's Guide


23-Jun-2004 1-3

1.5. PlatformsBOOST has been compiled on the following platforms:

Platform OperatingSystem

Version Bin directory Notes

Windows 2000, XP ia32-unknown-winnt

Silicon Graphics IRIX64 6.5 mips4-sgi-irix6.5 mips4 64bit

Hewlett Packard HP-UX 11.00 pa-risc-hp-hpux11.00 PA-RISC 2.0

IBM AIX 5.1 rs6000-ibm-aix4.3

Linux Linux 2.4 ia32-unknown-linux

1.6. BOOST_HOME Environment VariableIn order for BOOST to locate required files (e.g. gas property files) the environmentvariable BOOST_HOME must be set correctly. This should be done automatically duringinstallation and should point to the bin directory for the appropriate platform. Forexample, an NT installation might have the following settings:

Variable: BOOST_HOME

Value: C:\AVL\BOOST\v4.0.4\bin\bin.ia32-unknown-winnt

The value of this environment variable should be checked before running BOOST.


23-Jun-2004 2-1

2. THEORETICAL BASISTheoretical background including the basic equations for all available elements issummarized in this chapter to give a better understanding of the AVL BOOST program.This chapter does not intend to be a thermodynamics textbook, nor does it claim to coverall aspects of engine cycle simulation.

2.1. The Cylinder

2.1.1. High Pressure Cycle, Basic EquationThe calculation of the high pressure cycle of an internal combustion engine is based on thefirst law of thermodynamics:

( )ααααα d

dmhddQ

ddQ

ddVp

dumd BB

BBwF

cc ⋅−−+⋅−=⋅ ∑ (2.1.1)

( )αd

umd c ⋅ change of the internal energy in the cylinder

αddVpc ⋅− piston work

αddQF fuel heat input

∑ αddQw wall heat losses

αddmh BB

BB ⋅ enthalpy flow due to blow-by

cm mass in the cylinder

u specific internal energy

cp cylinder pressure

V cylinder volume

FQ fuel energy

wQ wall heat loss

α crank angle

BBh enthalpy of blow-by

αddmBB blow-by mass flow


2-2 23-Jun-2004

Figure 2-1: Energy Balance of Cylinder (High Pressure Cycle)

The first law of thermodynamics for high pressure cycle states that the change of theinternal energy in the cylinder is equal to the sum of piston work, fuel heat input, wallheat losses and the enthalpy flow due to blow-by.

Equation 2.1.1 is valid for engines with internal and external mixture preparation.However, the terms, which take into account the change of the gas composition due tocombustion, are treated differently for internal and external mixture preparation.

For internal mixture preparation it is assumed that

• the fuel added to the cylinder charge is immediately combusted

• the combustion products mix instantaneously with the rest of the cylindercharge and form a uniform mixture

• as a consequence, the A/F ratio of the charge diminishes continuously from ahigh value at the start of combustion to the final value at the end ofcombustion.

For external mixture preparation it is assumed that

• the mixture is homogenous at the start of combustion

• as a consequence, the A/F ratio is constant during the combustion

• burned and unburned charge have the same pressure and temperaturealthough the composition is different.

In order to solve this equation, models for the combustion process and the wall heattransfer, as well as the gas properties as a function of pressure, temperature, and gascomposition are required.


23-Jun-2004 2-3

Together with the gas equation

cocc TRmV

p ⋅⋅⋅= 1(2.1.2)

establishing the relation between pressure, temperature and density, equation 2.1.2 or2.1.3 for the in-cylinder temperature can be solved using a Runge-Kutta method. Once thecylinder temperature is known, the cylinder pressure can be obtained from the gasequation.

2.1.1.1. Combustion ModelsThe combustion of fuel in an engine is a chemical process influenced by many parameters.One of these is the ratio between air and fuel. If more air is available than required toburn the fuel completely the combustion is called lean. The opposite is called richcombustion. The ratio between air and fuel at which neither unburned fuel nor airremains after combustion is the stoichiometric air fuel ratio. The following equation forthe stoichiometric air requirement specifies how much air is required for a completecombustion of 1 kg fuel:

−++⋅=

FuelkgAirkgoshcLst

00.3206.32032.401.12

85.137 (2.1.3)

For lean combustion, the total heat supplied during the cycle can be calculated from theamount of fuel in the cylinder and the lower heating value of the fuel. The lower heatingvalue is a fuel property and can be calculated from the following formula:

−⋅+⋅+⋅+⋅= snhcHu 1046562809387034835

[ ]kgkJwo / 244010800 ⋅−⋅− (2.1.4)

uH lower heating value

c mass fraction of carbon in the fuel

h mass fraction of hydrogen in the fuel

o mass fraction of oxygen in the fuel

s mass fraction of sulfur in the fuel

n mass fraction of nitrogen in the fuel

w mass fraction of water in the fuel

In rich combustion, the total heat supplied during the cycle is limited by the amount of airin the cylinder. The fuel is totally converted to combustion products even if the amount ofair available is less than the amount of stoichiometric air.

However, the composition of the combustion products is different if fuel is burned underrich or lean conditions. The composition itself depends on the type of fuel used, the air fuelratio, pressure and temperature. It is always the same if sufficient time is available toreach chemical equilibrium.


2-4 23-Jun-2004

It is well known that under real engine conditions, complete combustion as assumed abovecan never be achieved. This is very important for excess air ratios close to 1.0 (the excessair ratio is defined as the ratio between the amount of air in the cylinder and the amountrequired for stoichiometric combustion).

For this reason, a model for the fuel conversion factor, which considers the incompletecombustion for excess air ratios between 0.9 and 1.2, was included in the BOOST program.

Figure 2-2: Influence of Excess Air Ratio on IMEP

Figure 2-2 shows the Indicated Mean Effective Pressure (IMEP) of a gasoline engine with afixed amount of air in the cylinder as a function of excess air ratio.

2.1.1.2. Heat Release ApproachThe simplest approach to model the combustion process is the direct specification of therate of heat release.

The rate of heat release of an engine at a specific operating point is determined from themeasured cylinder pressure history. By means of a reversed high pressure cycle

calculation, i.e. by solving equations 2.1.2 or 2.1.3 for αd

dQF instead for αd

dTc , the heat

release versus crank angle is obtained.

To simplify this approach, only the dimensionless heat input characteristic must bespecified over crank angle. From the total heat supplied to the cycle, which is determinedby the amount of fuel in the cylinder and by the A/F ratio, BOOST calculates the actualheat input per degree crank angle.

For the direct input of the rate of heat release curve the following options are available:

1. Table

The heat release curve is approximated by specifying reference points versus crankangle. The y-values are scaled to obtain an area of one beneath the curve. Valuesbetween the points specified are obtained by linear interpolation.


23-Jun-2004 2-5

2. Vibe Function

The Vibe function [C13] is often used to approximate the actual heat releasecharacteristics of an engine:

( ) ( )11 +⋅−⋅⋅+⋅∆

= myam

c

eymaddx

αα(2.1.5)

QdQdx = (2.1.6)

c

oyααα

∆−= (2.1.7)

Q total fuel heat input

α crank angle

oα start of combustion

cα∆ combustion duration

m shape parameter

a Vibe parameter a = 6.9 for complete combustion

The integral of the vibe function gives the fraction of the fuel mass which was burnedsince the start of combustion:

( )∫

+⋅−−=⋅= 11 myaedddxx αα

(2.1.8)

x mass fraction burned

Figure 2-3 shows the approximation of an actual heat release diagram of a DI Dieselengine by a vibe function. The start of combustion, combustion duration and shapeparameter were obtained by a least square fit of the measured heat release curve.


2-6 23-Jun-2004

Figure 2-3: Approximation of a Measured Heat Release

In Figure 2-4 the influence of the vibe shape parameter 'm' on the shape of the vibefunction is shown.

Figure 2-4: Influence of Shape Parameter 'm'

3. Vibe Two Zone

For engines with external mixture preparation, the selection of a two zone model ispossible. The rate of heat release, and thus the mass fraction burned, is specified by avibe function. However the assumption that burned and unburned charges have thesame temperature is dropped. Instead the first law of thermodynamics is applied tothe burned charge and unburned charge respectively [C10].

αααααα ddm

hddmh

ddQ

ddQ

ddVp

dudm bBB

bBBb

uWbFb

cbb ,

,−+−+−= ∑ (2.1.9)


23-Jun-2004 2-7

∑ −−−−=ααααα d

dmh

ddmh

ddQ

ddVp

dudm uBB

uBBB

uWuu

cuu ,

, (2.1.10)

index b burned zone

index u unburned zone

The term αd

dmh Bu covers the enthalpy flow from the unburned to the burned zone due

to the conversion of a fresh charge to combustion products. Heat flux between the twozones is neglected.

In addition the sum of the volume changes must be equal to the cylinder volumechange and the sum of the zone volumes must be equal to the cylinder volume.

ααα ddV

ddV

ddV ub =+ (2.1.11)

VVV ub =+ (2.1.12)

Substituting into equation 2.1.11, together with some elementary algebra leads to anequation for the derivative of the burned zone temperature versus crankangle.

( )

∂∂

−−−−

∂∂=

ααααα

α dTud

Tmuuddm

ddQ

ddQ

Tumd

dTb

bbuBbWbF

bb

b

b 1

( ) ( )

−+−−−−

αααβα

αβ

ddRTm

VV

ddRTmTRTR

ddm

ddVp u

uuu

bbbbuubb

bbbb

∂∂

+−αα

δd

Tud

Tmd

dQu

uuWu

b (2.1.13)

with:

ubbu

ubub VV

VVγγ

γα++=

ubbu

bub VV

Vßγγ

γ+

=


2-8 23-Jun-2004

ubbu

bbub VV

VVγ

γδ+∂−=

Tu

RT

u

bu

bubu

bu

∂∂

+∂∂

=,

,,

,γ

A similar equation can be found for the temperature derivative of unburned zone:

( )

∂∂

−−−−

∂∂=

ααααα

αTud

Tmuuddm

ddQ

ddQ

Tumd

dTb

bbubbWbF

uu

u

u 1

( ) ( ) −

−+−−−−

αααα

α ddRTm

VV

ddRTmTRTR

ddmß

ddVpß u

uuu

bbbbuubb

buuu

∂∂∂

+αα

δ Tud

Tmd

dQu

uuwu

u (2.1.14)

The amount of mixture burned at each time step is obtained from the Vibe functionspecified by the user. For all other terms, like wall heat losses etc., models similar tothe single zone models with an appropriate distribution on the two zones are used.

A knock model calculates the minimum octane number required for engine operationfree of knock. The threshold for the onset of knock is exceeded if the integral

( )dtt

t

o iD∫ τ

1(2.1.15)

iDτ ignition delay at the unburned zone’s condition is larger than one before the

end of combustion is reached.

The ignition delay for the knock model depends on the octane number of the fuel andthe gas condition according to

TB

naiD epONA −⋅⋅=τ (2.1.16)


23-Jun-2004 2-9

iDτ ignition delay [ms]

ON octane number of the fuel

p pressure [atm]

T temperature [K]

BnaA ,,, model constants

A = 17.68 ms

a =3.402

n =1.7

B =3800 K

4. Double Vibe Function

The superposition of two vibe functions (Double Vibe) is used to approximate themeasured heat release characteristics of a compression ignition (CI) engine moreaccurately. In this case two vibe functions are specified, the first one is used to modelthe premixed burning peak and the second one to model the diffusion controlledcombustion. If the fuel allotment to each of the vibe functions is known, the heatreleases obtained from the two vibe functions can be added, thus giving a double vibeheat release, Figure 2-5.


2-10 23-Jun-2004

Figure 2-5: Superposition of Two Vibe Functions

2.1.1.3. Extended Heat Release ApproachFor the simulation of engine transients, the above mentioned approaches are not sufficientbecause the heat release characteristics change with engine speed and load. As the speedand load profile for a transient is not known prior to a simulation run, a model predictingthe rate of heat release dependent on the operating point is required.


23-Jun-2004 2-11

WOSCHNI / ANISITS Model

For diesel engines the approach used is based on the model by Woschni and Anisits [C1].The vibe function and the characteristic parameters of one operating point must bedefined. The model predicts the change of the vibe parameters according to the actualoperating conditions:

5.06.0

,

⋅

⋅∆=∆

ref

refrefcc n

nAF

AFαα (2.1.17)

3.0

,

,

6.0

⋅

⋅

⋅

⋅=

refIVC

refIVC

refIVC

IVCrefref n

nT

Tpp

idid

mm (2.1.18)

cα∆ combustion duration

AF air fuel ratio

n engine speed

m Vibe shape parameter

id ignition delay

IVCp pressure at intake valve closes

IVCT in-cylinder temperature at intake valve closes

Index ref at reference operating point

The ignition delay is calculated with the relations found by Andree and Pachernegg [C3]which assume that the ignition of the injected fuel droplets takes place if the integral of gastemperature versus time exceeds a threshold.

HIRES ET AL Model

For gasoline engines the change of the combustion duration and the ignition delay iscalculated from the in-cylinder conditions at ignition timing [C2].

3/23/1

,

⋅

⋅⋅∆=∆

ss

ff

nn refref

refrefcc αα (2.1.19)

3/23/1

⋅⋅

⋅=

ss

ff

nnidid ref

refrefref (2.1.20)

s laminar flame speed

f piston to head distance at ignition timing

The laminar flame speed itself is a function of the in-cylinder conditions, the A/F ratio andthe mole fraction of the residual gases [C4].


2-12 23-Jun-2004

2.1.1.4. Quasi-dimensional Combustion ModelsSI ENGINES

The quasi-dimensional combustion model for SI engines implemented in BOOST predictsthe rate of heat release in a homogeneous charge engine. Thereby the influence of thefollowing parameters is considered [C10, C11, C12]

• The combustion chamber shape

• The spark plug location and spark timing

• The composition of the cylinder charge (residuals, recirculated exhaust gas, airand fuel vapor)

• The macroscopic charge motion and turbulence level

The thermodynamics of the two zone combustion model is outlined in section 2.1.1.2 - VibeTwo Zone. The two zone vibe is used to calculate the gas conditions of the combustionproducts (i.e. the burned zone) and the remaining fresh charge (i.e. the unburned zone).However the rate of heat release is determined from Equation 2.1.21 rather than a usersupplied vibe function

b

beb mmdt

dmτ−= (2.1.21)

bm total mass burned

em mass entrained into flame

bτ characteristic combustion time

The mass entrained is calculated from the flame surface area, the density of the unburnedzone, the laminar flame speed and the turbulence intensity:

( )( )ittlfu

e eSuAdt

dm τρ /1 −−+′= (2.1.22)

uρ density of unburned zone

fA Flame surface area

u′ turbulence intensity

lS laminar flame speed

itτ characteristic combustion time at ignition timing

t time since ignition

A spherical propagation of the flame from the spark plug through the combustion chamberis assumed. With this assumption the instantaneous flame radius, the flame area and thewetted piston, head and liner surface of the burned and unburned zone can be determinedfrom purely geometrical considerations.


23-Jun-2004 2-13

However, experimental evidence shows that both entrainment and depletion of fuel do notstrictly follow geometrical correlations. This is corrected by an approach by Bargende[C21], which improves the heat release versus crankangle. This approach is referred to asEmpirically Based Combustion Model (EBCM). Therefore, the following correction isintroduced into Equation 2.1.22.

( )( )( ))1(1 /BBmS

tlfu

e YYbbeSuAdt

dmit −+−+′= •

− τρ (2.1.23)

with BY denoting the volume of the burned gas. The parameters Sb and mb are determined

as follows:

Sb = 2.13 - 0.26 X

mb = 2.9 - 5.5(λ - 0.9)² + 0.17ρZZP

where X is the residual gas content.

Since the above mentioned method relies on empirical correlations, a physically basedapproach takes into account the interaction between turbulence and combustion. Thisapproach is referred to as Physically Based Combustion Model (PBCM). This leads toincreased turbulence, which contributes to the entrainment of fresh charge as follows:

( )( ) )( ( )( )XeSXuuAdt

dmitt

lBCfue −−+−′+′= − 111 /τρ (2.1.24)

where XB stands for the mass fraction burned.

The turbulent velocities are weighted by the mass fraction of unburned gas to effect thefresh charge only. Furthermore, Equation 2.1.24 accounts for a decreasing combustionrate, when the mass of residual gas increases. The additional turbulent intensity due tocombustion is estimated as follows:

31

′=′ZZP

BZZPC uu

ρρ

(2.1.25)

For the calculation of the turbulence intensity u′ , a simple ε−k model with the followingassumptions is used:

• The global turbulence is neither influenced by diffusion nor boundary layerflows

• The turbulence is isotropic

• No swirl is generated during the intake stroke

• The turbulence is generated entirely during the intake stroke

• The moment of momentum is conserved according to the rapid distortiontheory

• The overall flow pattern has just one component in the direction of the cylinderaxis


2-14 23-Jun-2004

The turbulent kinetic energy k is defined as:

( ) 2222

235.0 uuuuk zyx ′=′+′+′= (2.1.26)

and ε is its rate of dissipation.

The rate of change of the turbulent kinetic energy is described by

ε−+= DPdtdk

(2.1.27)

dtdkP ρ

ρ32=

2/3klC=ε

P production

D diffusion, this term is neglected i.e. it is set to zero

C model constant

l turbulent length scale

For the prediction of the knocking characteristics, the two zone vibe model is used asdescribed in section 2.1.1.2.

CI ENGINES

BOOST uses two models for the prediction of the combustion characteristics in directinjection compression ignition engines: the method proposed by Hiroyasu and the MCCmodel developed by AVL.

HIROYASU et al. Model

The formulation of Hiroyasu et al. [C14, C15, C16, C17] requires a minimum degree ofuser input based on the overall properties of the engine (geometrical parameters, injectionrate diagram etc..) and then calculates the spreading of an evaporating spray, its ignitionand subsequent high temperature combustion.

Despite the complexity of spray combustion processes in high pressure environments, theformalism is particularly suited to cost-effective, parametric studies on engines with theaim of lowering levels of NOx and soot. This is partly because the governing equationsdraw on a considerable amount of experimental work relating to turbulent flows involvingdroplet combustion. In the following the main theoretical features of the model will bebriefly described. More detailed information is available in the references cited above.


23-Jun-2004 2-15

An important feature of the model is the manner in which the spray enters the combustionchamber. Liquid fuel is introduced into the domain by means of annular packages, shownin Figure 2-6, which behave as self-contained fluid elements. Each individual packageentrains air from and exchanges heat with its surroundings without regard for itsneighboring packages. The liquid fuel is represented as droplets whose size distribution isdetermined by empirical equations. It is assumed that there is no heat, mass andmomentum transfer between the various packages and that each annular section is subjectto circumferential symmetry. The packages move forward so that they always remain incontact and cannot overtake one another, somewhat like a plug flow. The number ofpackages created is determined by the user through his choice of the radial resolution andthe time step used for the calculation. At every time step of the calculation during the fuelinjection period a new cross-sectional array of packages is brought into the computationaldomain.

The evolution of the spray is defined by empirical equations stemming from detailedexperimental investigations. These equations determine the axial location of the packages.The volume or deformation of the packages is controlled by the inter-coupled physicalprocesses such as entrainment of the surrounding cylinder gas into the package, dropletevaporation within the package, heat loss to the walls and heat release resulting from thediffusion flame type combustion. The various physical processes are illustrated in Figure 2-7.


2-16 23-Jun-2004

Figure 2-6: Schematic of the Spray/Package Structure

Figure 2-7: Schematic of the Physical Processes taking place in the Package

The droplet size distribution within a package, expressed in terms of the Sauter meandiameter (the Sauter mean diameter, 32D , is the diameter of a droplet whose ratio of

volume to surface area is equal to that of the entire spray) is given by the followingempirical expressions:

=

DD

DDMAX

DD HSLS

323232 , (2.1.28)

18.054.075.012.032 Re12.4

= −

a

l

a

lLS

WeD

Dρρ

µµ

(2.1.29)


23-Jun-2004 2-17

47.037.032.025.032 Re38.0

−−

=

a

l

a

lHS

WeD

Dρρ

µµ

(2.1.30)

MAX larger of the two values appearing in the square brackets

µ dynamic (absolute) viscosity

ρ density

subscript l liquid

subscript a air

Each individual package has its own Sauter mean diameter, which together with the massof liquid fuel in the package provides a value for the number of droplets in it. Using anenergy and mass balance for a single droplet in each package, ordinary differentialequations can be set up for the rate of change of the droplet temperature and diameterwhich are subsequently solved using a fourth order Runge-Kutta-Gill method. The detailscan be found in [C14].

The solution of these equations yields values for the amount of gaseous fuel available inthe package and the change in temperature which is experienced as a result of the heatingup of the droplet by the surroundings and its subsequent evaporation.

The spray tip is defined by the first set of packages which are injected into the combustionchamber. Experimental studies demonstrate that the spray tip penetration, S is directlyproportional to the time elapsed after the start of injection up to a break-up time, bt , and

that thereafter tSα . The complete set of equations for the penetration length along the

axis of symmetry of the nozzle is as follows:

btt <<0 ,2

l

Pcvρ∆= vtS = (2.1.31)

,btt ≥ ,221

25.0

tDPcv n

a

∆=ρ

α vtS 2= (2.1.32)

where:

2

21

=∆

cv

P injeρ

=

46 n

eDinj

geinj

DNtQN

V πρ

2/12

−

∆=a

NlbPD

Ct

ρρα


2-18 23-Jun-2004

α Constant = 15.8

C Constant = 0.39

p∆ pressure drop across the nozzle

injV injection velocity

eN engine speed

injt injection duration

DN number of nozzle holes

nD nozzle hole diameter

gQ total fuel mass injected

The above empirical equations are strictly speaking only valid for initially quiescent airflows. When the in-cylinder flow has a swirling motion, the following modification isproposed for the penetration length, designated as ScSS SSS =: where

1

301

−

+= S

vNRcinj

eSS

π and SR is the swirl number. It is assumed that the injection

pressure and swirl ratio remain constant during this period.

For off-axis penetration lengths Hiroyasu et al. propose the following modification to

account for the penetration of a package along the thL radial section when counting theaxial one as L = 1:

( )[ ]23 110557.8exp −×−= − LSSL .

The amount of air entrained into a package is treated using the principle of conservation ofmomentum. A simple 1-D analysis yields:

( ) ( )

−−=

ttvtvvmCm

ppinjfuov

ovair δ

δ 11(2.1.33)

ovC coefficient of overall air entrainment

fum fuel mass in the package

( )tvp current package velocity

The velocity can be obtained using the relations described in the previous section. It is tobe expected that such a level of phenomenological analysis of what is a complicated processwould incorporate constants of proportionality. Consequently Hiroyasu’s formulationmodifies the air entrainment prescribed by Equation 2.1.34 when the following physicaleffects also become relevant:

before ignition and wall impingement ovairbig

bigair mCm δδ = ;

after ignition but before wall impingement ovairaig

aigair mCm δδ = ;


23-Jun-2004 2-19

after wall impingement ovairaw

awair mCm δδ = .

The constants require calibration and should be adjusted to reproduce measurements ofthe pressure trace, for example, in an engine. Once they have been suitably calibrated theycan be used as part of a parametric study.

Ignition is modeled in terms of an ignition delay; in other words no explicit chemistry isemployed to account for this. A global ignition criterion is not employed, which means thateach package is considered individually. The ignition delay period comes to an end whenthe following condition has been satisfied in the package:

( )∫ =1

0

1,,

τ

φτ ppTPtd

(2.1.34)

P cylinder pressure

pT package temperature

pφ package equivalence ratio

iτ ignition delay (time)

The integration begins at the start of injection. At every time step the additionalcontribution to the integral is added to the existing sum and when the cumulative valueequals or just exceeds unity then iτ is taken as the ignition delay. The function

( )ppTP φτ ,, is based on the following empirical relation:

( )

= −−−

pppp T

EpxTP*

04.15.23 exp100.4,, φφτ (2.1.35)

*E ratio of activation energy to the universal gas constant (typically 5000)

Generally the consumption of fuel is controlled by the local stoichiometry in the package.

For this purpose upper and lower flammability limits are employed, rfuY and l

fuYrespectively. In addition the combustion can be either evaporation or entrainment rate

controlled, depending on the value of the local fuel mass fraction )( fuY in relation to its

theoretical stoichiometric value )( stfuY . The results are summarized in terms of ratio of fuel

burned in the package, ( )fuYR :

• if lfufu YY < or r

fufu YY > then ( )fuYR = 0. If the mixture strength lies outside

the flammability limits, there will be no combustion.

• if rfufu

stfu YYY ≤≤ , then ( )fuYR = -0.2683 + 0.008106

−YYfu1

. Here

combustion proceeds as fast as entrainment of air into the package allows. The

quantity of fuel consumed (referred to as entrfum∆ ) is limited by the local O2

concentration in that package. Consequently ( )fuentr

stfuentrfu YRmm ×∆=∆ , .


2-20 23-Jun-2004

• if stfufu

lfu YYY << , then ( )fuYR = 1. In this combustion regime the evaporation

of the droplet is rate limiting. Under these circumstances all gaseous fuelpresent are consumed by the local mixture rich in oxygen.

For n-dodecane Yoshizaki et al. [C11] quote the following values: stfuY = 0.06007, r

fuY =

0.232 and lfuY = 0.04. The heat release due to chemical reaction is then taken to be the

sum of all the heat releases in the various packages. The latter is evaluated by multiplyingthe mass of fuel consumed to the fuel’s calorific heating value.

Although all packages are assumed to have the same pressure, their temperatures aredifferent. This is an essential requirement if the NOx predictions are to be realistic. Thetemperature in each package is evaluated using an iterative procedure whereby theenthalpy of the mixture is expressed in terms of the composition and a polynomialexpression involving the temperature. Eleven chemical species are taken intoconsideration, namely: CO, CO2, O2, H2, H2O, OH, H, O, N2, N and NO. Except for NO andN all other species are assumed to be in partial equilibrium. Consequently the calculationof their concentrations does not require a chemical mechanism. The minimization of theGibb’s free energy is sufficient. For rich mixtures, where the equivalence ratio can be lessthan unity, the actual equivalence ratio used for the equilibrium calculation is arbitrarilyset to unity, in order to avoid unrealistically high levels of intermediates from beingpredicted. However, NO formation is a non-equilibrium process. The well-known extendedZeldovich mechanism is employed, which therefore only predicts the thermal contributionto NOX. The details can be found in the aforementioned papers.

The concentration of soot in the exhaust is governed by its formation and oxidationprocesses during the engine cycle. Based on the existing knowledge of soot chemistry, forexample its sensitivity to pressure, temperature and equivalence ratio, the followingsuggestions for the soot formation and consumption rates are postulated:

−=

RTE

PmAdt

dm sfff

sfg

exp5.0 (2.1.36)

−=

RTE

PP

PomAdt

dm Scsc

sc exp8.12 (2.1.37)

Sm soot mass

fgm gaseous fuel mass

sfm soot mass formed

scm soot mass oxidated

sfE Activation energy formation

×=

kmolkcal41025.1

scE Activation energy oxidation

×=

kmolkcal4104.1


23-Jun-2004 2-21

The actual soot formation rate is obtained by taking the difference between Equations(2.1.36) and (2.1.37). The constants fA and cA need to be calibrated for a specific test

case where measurements are available so that they can be used as part of a sensitivityanalysis for that particular engine.

AVL MCC Model

The Mixture Controlled Combustion (MCC) model [C18, C19] requires less input than theHiroyasu model. By shortening the ignition delay due to developments in recent years, thecausal and thus time related connection between injection and combustion have becomevery close. So the heat release is considered to be controlled by the fuel quantity availableand the turbulent kinetic energy density:

( ) ( )VkfQMfCddQ

FMod ,, 21 ⋅⋅=ϕ

(2.1.38)

with

( )LCV

QMQMf FF −=,1 (2.1.39)

( )

⋅=

32 exp,VkCVkf Rate (2.1.40)

ModC Model Constant [kJ/kg/deg CrA]

CRate Constant of mixing rate [s]

k local density of turbulent kinetic energy [m2/s2]

FM injected fuel mass [kg]

LCV lower heating value [kJ/kg]

Q cumulative heat release [kJ]

V instantaneous cylinder volume [m3]

ϕ Crank Angle [deg CrA]

Since the distribution of squish and swirl to the kinetic energy are relatively small, onlythe kinetic energy input from the fuel spray is taken into account. The amount of kineticenergy imparted to the cylinder charge is determined by the injection rate using

32

, 18 FFFkin V

An

ddE

⋅

⋅=µ

ρϕ

(2.1.41)

Aµ effective nozzle hole area [m2]

Fρ fuel density [kg/m3]

FV injection rate [m3/s]


2-22 23-Jun-2004

n engine speed [rpm]

For the calculation of the instantaneous level of kinetic energy the dissipation should betaken into account also. The dissipation is considered as proportional to the kinetic energygiving:

dissFkinDissFkindissFkin En

Cd

dEd

dE,,

,,,

6−=

ϕϕ(2.1.42)

With oxidation the kinetic energy of the jet is transferred to the combustion gas. So formixture preparation, only the kinetic energy of the unburned fuel can be utilized formixture preparation. The local turbulent kinetic energy density k is then given by

( )stoichDiffF

DissFkinTurb mM

ECk

λ+=

1,, (2.1.43)

The constant TurbC considers the efficiency of the transformation from kinetic energy to

turbulent energy.

TurbC constant for turbulence generation [-]

FkinE , kinetic jet energy [J]

DissFkinE ,, kinetic jet energy considering dissipation [J]

stoichm stoichiometric mass of fresh charge [kg/kg]

Diffλ Air Excess Ratio for diffusion burning [-]

2.1.1.5. Theoretical Combustion ModelsFor theoretical investigations, BOOST allows the specification of the following theoreticalcombustion models:

1. Constant Volume

The complete charge is burned instantaneously at the specified crankangle.

2. Constant Pressure

Part of the charge is burned instantaneously at top dead center to achieve the desiredpeak firing pressure. The remaining charge is burned in such a way as to maintain thespecified PFP.

This combination of constant volume and constant pressure combustion is also calledSeiliger process.

If the pressure at the end of the compression stroke already exceeds the specified PFP,combustion starts when the pressure drops below this pressure during the expansionstroke.


23-Jun-2004 2-23

2.1.1.6. User ModelsUSER MODEL

By linking a user supplied subroutine (usrcmb.for) to BOOST, the user may define heatrelease characteristics using BOOST’s high pressure cycle simulation.

USER DEFINED HIGH PRESSURE CYCLE

The user-defined high pressure cycle (user supplied subroutine usrhpr.for) replaces theentire high pressure cycle simulation of BOOST.

2.1.2. Gas Exchange Process, Basic EquationThe Equation for the simulation of the gas exchange process is also the first law ofthermodynamics:

( )e

ei

iwc

c hddmh

ddm

ddQ

ddVp

dumd ⋅−⋅+−⋅−=⋅ ∑∑ ∑ ααααα

(2.1.44)

cm mass in the cylinder



V cylinder volume

wQ wall heat loss

α actual crank angle

idm mass element flowing into the cylinder

edm mass element flowing out of the cylinder

ih enthalpy of the in-flowing mass

eh enthalpy of the mass leaving the cylinder


2-24 23-Jun-2004

Figure 2-8: Energy Balance of Cylinder (Gas Exchange Process)

The variation of the mass in the cylinder can be calculated from the sum of the in-flowingand out-flowing masses:

∑ ∑−=ααα d

dmddm

ddm eic (2.1.45)

2.1.2.1. Port Massflow RatesThe mass flow rates at the intake and exhaust ports are calculated from the Equations forisentropic orifice flow under consideration of the flow efficiencies of the ports determinedon the steady state flow test rig.

From the energy Equation for steady state orifice flow, the Equation for the mass flowrates can be obtained:

ψ⋅⋅

⋅⋅=1

12

oooeff TR

pAdtdm

(2.1.46)

dtdm

mass flow rate

effA effective flow area

1op upstream stagnation pressure

1oT upstream stagnation temperature

oR gas constant


23-Jun-2004 2-25

For subsonic flow,

−

⋅

−=

+κκ

κ

κκψ

1

1

2

2

1

2

1 oo pp

pp

, (2.1.47)

2p downstream static pressure

κ ratio of specific heats

and for sonic flow,

112 1

1

max +⋅

+==

−

κκ

κψψ

κ. (2.1.48)

The actual effective flow area can be determined from measured flow coefficients µσ:

4

2 πµσ ⋅⋅= vieff

dA (2.1.49)

µσ flow coefficient of the port

vid inner valve seat diameter (reference diameter)

The flow coefficient µσ varies with valve lift and is determined on a steady-state flow testrig. The flow coefficient, µσ, represents the ratio between the actual measured mass flowrate at a certain pressure difference and the theoretical isentropic mass flow rate for thesame boundary conditions. The flow coefficient is related to the cross section area. of theattached pipe.

The inner valve seat diameter used for the definition of the normalized valve lift can beseen in the following figure:

Figure 2-9: Inner Valve Seat Diameter

The composition of the gases leaving the cylinder via the exhaust port is determined by thescavenging model.


2-26 23-Jun-2004

2.1.2.2. ScavengingA perfect mixing model is usually used for four-stroke engines. This means that thecomposition of the exhaust gases is the mean composition of the gases in the cylinder, andalso that the energy content of the exhaust gases is equivalent to the mean energy contentof the gases in the cylinder. In this case the change of the air purity over crank angle canbe calculated from the following Formula:

( )αα d

dmRmd

dR i

c

⋅−⋅= 11(2.1.50)

R air purity

In the case of a two-stroke engine, the perfect mixing model is not sufficient for accuratesimulations. For this reason BOOST also offers a perfect displacement scavenging modeland a user-defined scavenging model.

In the perfect displacement model no mixing between intake and residual gases takes placeand pure residual gases leave the cylinder (so long as they are available).

The User-defined scavenging model used in the BOOST code divides the cylinder into thedisplacement zone and the mixing zone.

The mass balance is based on the following scavenging types:

SCAVENGING TYPE A

According to the (positive) Scavenging Quality SCQ the incoming gas delivers both the

displacement and the mixing zone while pure mixing zone gas is leaving the cylinder

0>=IZ

IDSC m

mQ

IDm massflow into the displacement zone

IZm massflow into the cylinder

SCAVENGING TYPE B

According to the (negative) Scavenging Quality SCQ the incoming gas is flowing into the

mixing zone and partially short-circuited to the exhaust port, while shortcut and mixingzone gas is leaving the cylinder.

0<−=IZ

ISSC m

mQ

ISm shortcut massflow

IZm massflow into the cylinder

Taking these two scavenging types into account, the Scavenging Quality Function)(SEQSC is calculated from the user defined Scavenging Efficiency Function SE(SR).


23-Jun-2004 2-27

( ) ( ) ( )Z

ASconstV

const

SREF

AS

VtV

mtmtSR

CY ==

==ρ

ASm aspirated mass

SREFm reference mass of cylinder charge

ASV volume of aspirated charge

ZV cylinder reference volume

( ) ( ) ( )Z

TASconstV

const

ZEVC

TAS

VtV

mtmtSE

CY ==

==ρ

TASm aspirated mass trapped

ZEVCm total mass of cylinder charge at EVC (Exhaust Valve Closing)

TASV volume of aspirated charge trapped

ZV cylinder reference volume

To consider the different zone temperatures (and densities) during the scavenging process,the scavenging efficiency SE(t) (used for calculating the scavenging quality SCQ (t)=

))(( tSEQSC ) is determined as follows:

( )

( )( )

( )( )

( )( )ttm

dmm

tSE

Z

Z

t

t EF

EF

IZ

IZ

ρ

ττρτ

τρτ

∫

−

= 0

IZm mass flow into the cylinder

EFm fresh charge mass flow out of the cylinder

Zm total mass of cylinder charge

IZρ density of mass flow into the cylinder

EFρ density of fresh charge mass flow out of the cylinder

Zρ density of cylinder charge

0t intake valve opening time


2-28 23-Jun-2004

In order to specify the quality of the scavenging system of a two-stroke engine, scavengingefficiency is required as a function of scavenge ratio SE(SR). This can be obtained fromscavenging tests or the literature.

Figure 2-10: User-Defined Scavenging Model

2.1.3. Piston MotionPiston Motion applies to both the High Pressure Cycle (Section 2.1.1) and the GasExchange Process (Section 2.1.2).

For a standard crank train the piston motion as a function of the crank angle α can bederived from Figure 2-11:


23-Jun-2004 2-29

Figure 2-11: Standard Crank Train

( ) ( ) ( )2

sin1coscos

−+⋅−⋅−+⋅−⋅+=

le

lrlrlrs αψαψψ (2.1.51)

+

=lr

earcsinψ (2.1.52)

s piston distance from TDC

r crank radius

l con-rod length

ψ crank angle between vertical crank position and piston TDC position

e piston pin offset

a crank angle relative to TDC

2.1.4. Heat Transfer

2.1.4.1. In Cylinder Heat TransferThe heat transfer to the walls of the combustion chamber, i.e. the cylinder head, thepiston, and the cylinder liner, is calculated from:

( )wicwiwi TTAQ −⋅⋅= α (2.1.53)

wiQ wall heat flow (cylinder head, piston, liner)

iA surface area (cylinder head, piston, liner)

wα heat transfer coefficient

cT gas temperature in the cylinder

wiT wall temperature (cylinder head, piston, liner)


2-30 23-Jun-2004

In the case of the liner wall temperature, the axial temperature variation between thepiston TDC and BDC position is taken into account:

cxeTT

xc

TDCLL ⋅−⋅=

⋅−1, (2.1.54)

=

BDCL

TDCL

TT

c,

,ln (2.1.55)

LT liner temperature

TDCLT , liner temperature at TDC position

BDCLT , liner temperature at BDC position

x relative stroke (actual piston position related to full stroke)

For the calculation of the heat transfer coefficient, BOOST provides the following heattransfer models:

• Woschni 1978

• Woschni 1990

• Hohenberg

• Lorenz (for engines with divided combustion chamber only)

• AVL 2000 Model

WOSCHNI Model

The Woschni model published in 1978 [C5] for the high pressure cycle is summarized asfollows:

( )8.0

,1,1,

1,21

53.08.02.0130

−⋅

⋅⋅

⋅+⋅⋅⋅⋅⋅= −−occ

cc

cDmccw pp

VpTV

CcCTpDα (2.1.56)

1C = 2.28 + 0.308 ⋅ uc / mc

2C = 0.00324 for DI engines

2C = 0.00622 for IDI engines

D cylinder bore

mc mean piston speed

uc circumferential velocity

DV displacement per cylinder

ocp , cylinder pressure of the motored engine [bar]

1,cT temperature in the cylinder at intake valve closing (IVC)

1,cp pressure in the cylinder at IVC [bar]


23-Jun-2004 2-31

The modified Woschni heat transfer model published in 1990 [C6] aimed at a moreaccurate prediction of the heat transfer at part load operation:

8.0

2.02

153.08.02.0 21130

⋅

+⋅⋅⋅⋅⋅⋅= −−− IMEP

VVccTpD TDC

mccwα (2.1.57)

TDCV TDC volume in the cylinder

V actual cylinder volume

IMEP indicated mean effective pressure

In the case that

( ) 2.02

1,1,

1,2 2 −⋅

⋅⋅⋅≥−⋅

⋅⋅

⋅ IMEPV

VcCppVp

TVC TDC

moccc

cD ,

the heat transfer coefficient is calculated according to the formula published in 1978.

For the gas exchange process, both Woschni models use the same Equation for the heattransfer coefficient:

( ) 8.03

53.08.02.0130 mccw cCTpD ⋅⋅⋅⋅⋅= −−α (2.1.58)

mu ccC /417.018.63 ⋅+=

wα heat transfer coefficient

D cylinder bore

mc mean piston speed

uc circumferential velocity

HOHENBERG Model

In the Hohenberg heat transfer model [C7] the following equation is used for thecalculation of the heat transfer coefficient:

( ) 8.04.08.006.0 4.1130 +⋅⋅⋅⋅= −−mccw cTpVα (2.1.59)


2-32 23-Jun-2004

LORENZ Model

The Lorenz Heat Transfer Equation is valid for a cylinder with an attached combustionchamber. In Equation 2.1.56 and 2.1.57 the characteristic speed is:

mC cCw ⋅= 1

Cw characteristic speed in the cylinder

For the Lorenz equation the term Cw is modified:

m

CP

C CCxD

dtdV

w 1..

4+

⋅=

π(2.1.60)

dtdVCP volume flow from the connecting pipe to the cylinder

x clearance between the cylinder head and the piston

AVL 2000 Heat Transfer Model

The heat transfer during gas exchange strongly influences the volumetric efficiencies ofthe engine, especially for low engine speeds. Based on AVL experience the Woschni heattransfer has been modified to take this effect into account. During the gas exchange theheat transfer coefficient is calculated from the following equation:

= −−

8.02

453.08.02.0013.0, in

inWoschni v

ddcTpdMax αα (2.1.61)

α heat transfer coefficients [J/K/M2]

4C = 14.0

d bore [m]

p pressure [Pa]

T temperature [K]

ind pipe diameter connected to intake port [m]

inv intake port velocity [m/s]

The diameter of the intake port directly at the valve is of special significance for thismodel, therefore these diameters of the intake ports should be accurately specified over thewhole port length.


23-Jun-2004 2-33

2.1.4.2. Port Heat TransferDuring the gas exchange process it is essential also to consider the heat transfer in theintake and exhaust ports. This may be much higher than for a simple pipe flow because ofthe high heat transfer coefficients and temperatures in the region of the valves and valveseats. In the BOOST code, a modified Zapf heat transfer model is used:

( ) wcm

A

wud TeTTT p

pw

+⋅−=

⋅⋅−α

(2.1.62)

The heat transfer coefficient, α p , depends on the direction of the flow (in or out of the

cylinder): The formula

[ ]

⋅−⋅⋅⋅⋅⋅−⋅+= −

vi

vviuuup d

hdmTTCTCC 797.015.15.044.02654α (2.1.63)

is used for outflow and the formula

[ ]

⋅−⋅⋅⋅⋅⋅−⋅+= −

vi

vviuup d

hdmTTCTCC 765.0168.168.033.02987α (2.1.64)

is used for inflow.

pα heat transfer coefficient in the port

dT downstream temperature

uT upstream temperature

Tw port wall temperature

Aw port surface area

m mass flow rate

cp specific heat at constant pressure

hv valve lift

dvi inner valve seat diameter

The following table contains the constants used in the formulas above.

Exhaust Valve Intake Valve

4C 1.2809 7C 1.5132

5C -4100451.7 ⋅ 8C -4107.1625 ⋅

6C -7104.8035 ⋅ 9C -7103719.5 ⋅


2-34 23-Jun-2004

2.1.5. Dynamic In-Cylinder SwirlBOOST allows the user to specify the swirl characteristics of an intake port versus valvelift. During the intake process, the moment of momentum of the mass entering thecylinder is calculated from the instantaneous mass flow rate and the swirl produced at theinstantaneous valve lift. The in-cylinder swirl at the end of the time step is calculatedfrom

( ) ( ) ( ) ( )

⋅⋅+⋅⋅

∆+=∆+ swi

piston

pistoniswc

csw n

vv

dmtntmttm

ttn 1(2.1.65)

swn in-cylinder swirl

cm in-cylinder mass

idm in-flowing mass

swin swirl of in-flowing mass

pistonv actual piston velocity

pistonvmean piston velocity

2.1.6. Blow-By Losses in the CylinderBOOST considers blow-by losses in the cylinder using the specified effective blow-by gapand the mean crankcase pressure. The blow-by mass flow rates are calculated at any timestep from the orifice flow Equations (2.1.46 - 2.1.48).

The effective flow area is obtained from the cylinder bore and from the effective blow-bygap:

δπ ⋅⋅= DAeff (2.1.66)


D cylinder bore

δ blow-by gap

If the cylinder pressure exceeds the mean crankcase pressure, the cylinder pressure andtemperature are used as upstream stagnation pressure and temperature. The meancrankcase pressure represents the downstream static pressure. The gas properties aretaken from the cylinder.

The blow-by gas has the same energy content as the gases in the cylinder.

If the cylinder pressure is lower than the mean crankcase pressure, the pressure in thecrankcase is used as upstream stagnation pressure, and the cylinder pressure as thedownstream static pressure. The upstream stagnation temperature is set equal to thepiston wall temperature, and the gas composition is set equal to the composition of the gaswhich left the cylinder just before the reverse flow into the cylinder started.


23-Jun-2004 2-35

2.1.7. Wall TemperatureThe cycle averaged wall temperatures influence the wall heat losses during the highpressure cycle and thus the efficiency of the engine. During the gas exchange, the heattransfer from the cylinder walls heats the fresh charge and lowers the volumetric efficiencyof the engine. The heat balance between the heat flux from the working gas in the cylinderto the cooling medium determines the wall temperatures.

For transient simulations, this energy balance can be calculated for the cylinder head/firedeck, the liner, and the piston. In addition, the heat balance of the port walls may beconsidered. The 1D heat conduction equation is solved using the average heat flux overone cycle as boundary condition at the combustion chamber side and the heat transfer tothe cooling medium on the outside. With these assumptions the heat conduction Equation

2

2

dxTd

cdtdT ⋅=

ρλ

(2.1.67)

T wall temperature

λ conductivity of wall material

ρ density of wall material

c specific heat capacity of wall material

can be solved. The mathematical formulation of the boundary conditions is:

dxdTqin λ−= (2.1.68)

inq average heat flux to the combustion chamber wall

( )CMWOCMout TTq −⋅=α (2.1.69)

outq heat flux to cooling medium

CMα outer heat transfer coefficient

WOT outer combustion chamber wall temperature

CMT temperature of cooling medium

For the piston, another term for the heat flux to the liner is taken into account.

2.1.8. Direct Gasoline InjectionDepending on the operating point, direct gasoline injection engines are operated eitherwith homogenous or stratified charges. The former operating strategy is applied near wideopen throttle (WOT) operation. The fuel is injected into the cylinder early during theintake stroke. The charge is cooled by the evaporating fuel and thus the volumetricefficiency is increased.


2-36 23-Jun-2004

In the stratified operation mode fuel is injected late during the compression stroke. Abalance must be found between sufficient time for the mixture preparation avoiding a fuelcloud spread too wide. Insufficient mixture preparation or a too wide spread of the fuelcloud result in poor fuel consumption and high emissions.

For part load operation the stratified operation strategy is preferred as it allows to controlthe engine load by the quantity of fuel injected at full or only slightly reduced air flowthrough the engine. The engine is less throttled and the reduction of pumping lossesincreases the fuel economy of the engine.

The model for direct gasoline injection in BOOST relies on the specification of the rate ofevaporation. It is assumed that the density of the liquid fuel is much higher compared tothe fuel vapor density. Hence the presence of liquid fuel can be neglected.

In the equation describing the conservation of mass in the cylinder, a term is added toaccount for the fuel evaporation. Similarly the energy conservation equation is extendedby the term

dtdmfq ev

ev ⋅⋅−

evq evaporation heat of the fuel

f fraction of evaporation heat from the cylinder charge

evm evaporating fuel

2.1.9. Divided Combustion ChamberIndirect Injection (IDI)-Diesel engines or lean burn gas engines with ignition in astoichiometric or even rich mixture in a pre-chamber may be modeled in BOOST withdivided combustion chamber.

The combustion chamber is connected to the cylinder. For modeling the fuel or air fuelmixture feed of gas engines to the combustion chamber, pipes may be attached also to thechamber.

The energy Equation of the cylinder (2.1.1) must be modified by a term considering theenergy flow associated with mass flow from the chamber to the cylinder or vice versa.

Thus 2.1.1 becomes:

( )αααααα d

dmh

ddmh

ddQ

ddQ

ddVp

dumd cp

cpBB

BBwF

Cc ⋅+⋅−−+⋅−=⋅ ∑ (2.1.70)

αddm

h cpcp ⋅ enthalpy flow from/to the connecting pipe


23-Jun-2004 2-37

The concentration changes due to the flows from the chamber are:

C

CPCPcc m

dmcidcidci ⋅−= ++ ,1,,1 ααα

1+αCi Concentration at time step 1+α in the Cylinder

CPCi /1+α Conc. at time step 1+α in the connecting pipe

Similar extensions must be made in the energy Equation for the gas exchange.

CONNECTING PIPE MASS FLOW

With a modification of the isentropic flow equation the wall heat flow and the inertia of thegas column in a pipe are taken into account. The downstream states are the same as thepipe states, because no storage effects are taken into account.

( )∫ −=++− 21

2221 2

1 wwdltwqhh w ∂∂

(2.1.71)

223601 WA

nddm ⋅⋅⋅⋅= ρµα

(2.1.72)

21,hh specific enthalpies upstream/downstream

21,WW speed upstream/in the pipe

∫L

dltw∂∂

inertia of the gas column

wq specific wall heat

n engine speed [1/s]

2ρ density in the pipe

µ flow coefficient

The mass flow is obtained from:

ltwqw

TTTcpA

ddm

n

⋅++

−⋅⋅⋅⋅=

∂∂ρµ

α2212

3601

1

212 (2.1.73)

The wall heat is calculated from Equation 2.10.5.


2-38 23-Jun-2004

COMBUSTION CHAMBER

The combustion chamber is treated as a plenum. Heat release, wall heat losses, volumework and mass flows out of or into the plenum are accounted for (refer to Section 2.2).

With the addition of a term for the heat released due to combustion, Equation 2.2.1becomes:

( ) ∑ ∑ ∑ ⋅−⋅++−⋅−=⋅αααααα d

hdmed

hidmiddQ

ddQw

ddVp

dumd eB

PLPl (2.1.74)

QB ..... heat released due to combustion

The Kamel-Watson equation for the wall heat flow is based on the Nußelt-ReynoldsAnalogon and takes into account the swirl in the chamber.

( ) 2.053.08.0013.0 −−− ⋅⋅⋅= PLPLPLPLWK rTwpL (2.1.75)

PLw characteristic speed in the plenum

PLT gas temperature

PLr radius of the plenum

2iPL

PL rmTw⋅

= (2.1.76)

T torque

ir inertia radius

( )∫ −= dtMMT FRADD (2.1.77)

ADDM added Momentum

FRM friction Momentum

cpcpcp

ADD rwdt

dmM ⋅⋅= (2.1.78)

dtdmcp mass flow from the connecting pipe to the chamber

cpw speed in the connecting pipe

cpr eccentricity of the connecting pipe to the center of the torque

53

2 PlPlPl

fFR rCM ⋅⋅⋅= ϖρ(2.1.79)

2,01.0

Re01,0 PlPl

Plf r

sC ⋅

= (2.1.80)


23-Jun-2004 2-39

νϖ 2

Re PlPlPl

r⋅= (2.1.81)

fC coefficient of the friction momentum

Pls swirl radius in the chamber

PlRe Reynolds Number in the chamber

Plϖ angular speed in the chamber

2.1.10. BURN UtilityThe BURN utility can be used for combustion analysis. That is the rate of heat release(ROHR) can be obtained from measured cylinder pressure traces. With the BOOST one-zone model, pressure and temperature of the cylinder is calculated from the specified rateof heat release. The inverse procedure, the determination of the rate of heat release frommeasured pressure traces is called combustion analysis. The BOOST interface offers a toolbased on the algorithms used in the BOOST cylinder to fulfil this task.

The algorithm is based on the first law of thermodynamics shown in equation 2.1.1. Thein-cylinder heat transfer is calculated using the models described in chapter 2.1.4. Pistonmotion and blow by losses are calculated using the approach of chapters 2.1.3 and 2.1.6.

2.2. Plenum (Variable Plenum)The calculation of the gas conditions in a plenum is very similar to the simulation of thegas exchange process of a cylinder, as described in Section 2.1.2:

( )e

ei

iwPl

Pl hddmh

ddm

ddQ

ddVp

dumd ⋅−⋅+−⋅−=⋅ ∑∑ ∑ ααααα

(2.2.1)

Plm mass in the plenum


Plp pressure in the plenum

V plenum volume

wQ wall heat loss

α crank angle

idm mass element flowing into the plenum

edm mass element flowing out of the plenum

ih enthalpy of the in-flowing mass

eh enthalpy of the mass leaving the plenum

For plenums with constant volume, the term of equation 2.2.1 which covers the variationof the volume is equal to zero.


2-40 23-Jun-2004

In the case of a variable plenum, the change of the plenum volume over crank angle iscalculated from the input specified by the user (user-defined), or from the motion of thepiston (crankcase or scavenging pump).

No detailed models for the heat transfer coefficient in a plenum are available. This meansthat the heat transfer coefficient must be specified by the user, depending on the actualshape of the plenum.

As an alternative, BOOST offers a very simple heat transfer model for the plenum whichmay be used if only limited information is available:

( )42.08.0 103.1127.02.01

018.0 −− ⋅⋅+⋅⋅⋅⋅⋅⋅−

⋅= TLuR chcho ρκκα (2.2.2)

3 VLch =

21

ch

pipe

npipech L

Au

nu ∑=

Lch characteristic length

V plenum volume

uch characteristic velocity

n number of pipe attachments

pipeu velocity at the pipe attachment

Apipe cross-section at the pipe attachment

T temperature in the plenum

ρ density in the plenum

oR gas constant


If a variable wall temperature of the plenum must be considered for transient simulations,a similar model is used as for the cylinder (refer to Section 2.1.7).


23-Jun-2004 2-41

2.3. Flow Restriction (Rotary Valve)The simulation of the flow through a restriction is based on the energy equation, thecontinuity equation, and the formulae for the isentropic change of state:

ψα ⋅⋅

⋅⋅⋅=1

12

ooogeo TR

pAm (2.3.1)

m mass flow rate

α flow coefficient

geoA geometrical flow area

1op upstream stagnation pressure

1oT upstream stagnation temperature

oR gas constant

The pressure function ψ depends on the gas properties and on the pressure ratio:

−

⋅

−=

+k

o

k

o pp

pp

1

1

2

2

1

2

1

κ

κκψ (2.3.2)

2p downstream static pressure


Figure 2-12 shows the shape of the pressure function ψ over pressure ratio.

Figure 2-12: The Pressure Function ψψψψ

In the case of subcritical flow, the pressure ratio, which is defined as the downstream staticpressure divided by the upstream stagnation pressure, is higher than the critical pressureratio and less than or equal to 1.0. The pressure function ψ follows the trend shown in thefigure for this range of pressure ratios.


2-42 23-Jun-2004

If the pressure ratio drops to the critical pressure ratio

1

1 12 −

+=

κκ

κo

crit

pp

, (2.3.3)

the flow in the orifice reaches a Mach number of 1.0. The pressure function ψ reaches itsmaximum at the critical pressure ratio. The actual value of ψmax is dependent on thepressure ratio:

112 1

1

max +⋅

+==

−

κκ

κψψ

κ, (2.3.4)

The values of the pressure function ψ shown in Figure 2-12 for pressure ratios less thanthe critical pressure ratio are valid only for supersonic flow in the orifice. However, itshould be pointed out that supersonic flow can never be achieved just by lowering thebackpressure, but always requires a special shape of the pipe upstream of the orifice(Laval-Nozzle).

2.4. Check ValveThe calculation of the flow in a check valve is very similar to the procedure discussed inSection 2.3 for the flow restriction. Two types of models are available. The simple modelconsiders flow coefficients which depend on the difference of the static pressures at the twopipe attachments. This model does not consider the inertia of the valve body. If thisinertia is to be taken into account, in addition to the mass flow rates, also the valve liftmust be calculated over time. For this purpose a spring-damper-mass model as shown inFigure 2-13 is used.

Figure 2-13: Full Check Valve Model

The motion of the valve can be calculated from the following Formula:

( ) vdxcFppAam o ⋅−⋅−−−⋅=⋅ 21 (2.4.1)

m mass of the valve

a acceleration of the valve

A cross-section of the valve

21, pp static pressure


23-Jun-2004 2-43

oF spring pre-load

c spring stiffness

x valve lift

d damping constant

v valve velocity

Equation 2.4.1 describes the motion of a pressure actuated valve under consideration of itsinertia, the spring pre-load, the spring stiffness, and the viscous damping.

The flow coefficient of the check valve is determined as a function of valve lift and is thenused to calculate the mass flow rate as a function of upstream and downstream pressure.

2.5. JunctionThe BOOST program features three models for junctions. The constant pressure modeland the constant static pressure model can be used for all junctions. In the former case thejunction is treated like a plenum without any volume. As for a plenum, the flowcoefficients for flow into the junction and flow out of the junction must be defined for eachpipe attachment. From the gas conditions in the pipe, the static pressure and thetemperature at the center of each junction is calculated.

The constant static pressure model enforces the same static pressure in all pipe crosssections attached to the junction. The flow coefficients are set to 1.

For three pipe junctions a more refined junction model is available. In this case theBOOST code distinguishes between six possible flow patterns in the junction, as shown inthe following figure.

Figure 2-14: Flow Patterns in a Y-Junction

For each of the flow paths indicated in Figure 2-14, the equation for the orifice flow (2.3.2)is solved. The flow coefficients depend on the geometry of the junction, i.e. the area ratiobetween the pipes and the angles between the centerlines of the pipes, and for a specificjunction on the flow pattern and on the mass flow ratio between one branch and thecommon branch.


2-44 23-Jun-2004

As the equations for orifice flow are applied to both separating or joining flows, two sets offlow coefficients are required, (i.e. two times six flow coefficients must be supplied to theprogram). In order to facilitate the application of this model, a database is provided withthe BOOST program. The flow coefficients contained in this database were obtained fromsteady-state flow tests of junctions with different pipe diameters and different branchingangles. The mass flow ratios in the junction as well as the Mach numbers were also variedduring these tests.

The program interpolates a suitable set of flow coefficients from this database.

2.6. TurbochargerFor steady state engine operation the performance of the turbocharger is determined bythe energy balance or the first law of thermodynamics. The mean power consumption ofthe compressor must be equal to the mean power provided by the turbine:

Tc PP = (2.6.1)

The power consumption of the turbo compressor depends on the mass flow rates in thecompressor and the enthalpy difference over the compressor. The latter is influenced bythe pressure ratio, the inlet air temperature, and the isentropic efficiency of thecompressor.

( )12 hhmP cc −⋅= (2.6.2)

cP compressor power consumption

cm mass flow rate in the compressor

2h enthalpy at the outlet of the compressor

1h enthalpy at the inlet to the compressor

−

⋅⋅⋅=−

−

1pp

Tc1

hh

1

1

21p

c,s12

κκ

η(2.6.3)

cs,η isentropic efficiency of the compressor

pc mean value of the specific heat at constant pressure between compressor inlet

and outlet

1T compressor inlet temperature

12 , pp compressor pressure ratio


23-Jun-2004 2-45

The power provided by the turbocharger turbine is determined by the turbine mass flowrate and the enthalpy difference over the turbine. Furthermore, it is conventional toallocate all mechanical losses of the turbocharger to the turbine side:

( )43, hhmP TCmTT −⋅⋅= η (2.6.4)

TP turbine power

Tm turbine mass flow

3h enthalpy at the turbine inlet

4h enthalpy at the turbine outlet

TCm,η mechanical efficiency of the turbocharger

−⋅⋅⋅=−

−κκ

η

1

3

43,43 1

ppTchh pTs (2.6.5)

⋅Ts,η isentropic turbine efficiency

⋅pc mean specific heat at constant pressure between turbine inlet and outlet

3T turbine inlet temperature

34 , pp turbine expansion ratio

The overall turbocharger efficiency is defined as follows:

csTsTCmTC ,,, ηηηη ⋅⋅= (2.6.6)

TCη overall turbocharger efficiency

For steady state engine performance a simplified turbocharger model may be used for thesimulation. Within this model the dynamics of the turbocharger (i.e. the variation of theturbocharger speed) are not considered. Furthermore, the turbocharger efficiency is keptconstant during the engine cycle. As many test calculations have proven, this modelprovides good accuracy for steady state engine calculations. It is very convenient to workwith this model, as only the mean values for the compressor efficiency, the turbineefficiency, and the mechanical efficiency of the turbocharger must be specified. Thisreduces the required input dramatically in comparison to the full turbocharger modelwhere entire compressor and turbine maps must be defined. Since turbine performancemaps cannot be provided by turbocharger manufacturers very often, this simplifiedsolution is usually the only alternative.

In BOOST, three calculation modes for the simplified model are available:

1. In the turbine layout calculation, the desired pressure ratio at the turbo compressor isspecified as input to the calculation. The program adjusts the flow resistance of theturbine automatically, until the energy balance over the turbocharger is satisfied.


2-46 23-Jun-2004

2. For the boost pressure calculation, the actual turbine size is specified in the input.By solving the energy balance over the turbocharger, the actual boost pressure iscalculated.

3. For the waste gate calculation, both the turbine size as well as the desired pressureratio at the turbo compressor are specified in the input. The program bypasses acertain percentage of the exhaust gases in order to achieve the energy balance over theturbocharger. If the desired compressor pressure ratio cannot be achieved with thespecified turbine size, the program switches over to the boost pressure calculationmode.

For unsteady engine operation the rotor dynamics of the turbocharger must be consideredbecause the wheel speed of the charger changes. From the balance of momentum at theturbocharger wheel the change of wheel speed is obtained:

TC

cT

TC

TC PPIdt

dω

ω −⋅= 1(2.6.7)

TCω turbocharger wheel speed

TCI turbocharger wheel inertia

The turbocharger full model requires the input of the compressor and turbine map.The speed of the turbocharger wheel is calculated using Equation 2.6.7.

With the instantaneous wheel speed and the mass flow rate through the compressor, thecompressor's isentropic efficiency and the pressure ratio are interpolated from thecompressor map. The efficiency and the swallowing capacity of the turbine areinterpolated from the turbine map using the wheel speed and the pressure ratio across theturbine. If a variable geometry turbine (VGT) is used, the vane position or someequivalent information is also required.

In this case the turbine data is obtained from interpolation in the two maps valid for vanepositions nearest to the instantaneous one and from linear interpolation afterwards.

2.7. Mechanically Driven SuperchargersFor the simulation of mechanically driven superchargers, the performance characteristicsalong a line of constant supercharger speed proportional to the steady state engine speedor the complete supercharger map for transient simulations are required. The maps areprovided by the supercharger manufacturer. In the course of the calculations the pressureratio over the compressor is adjusted depending on the actual mass flow rate (andsupercharger speed if the full model is used). From the pressure ratio and the isentropicefficiency of the compressor, the compressor outlet temperature can be obtained:

−

⋅+⋅=

−

111

1

1

212

κκ

η ppTT

s

(2.7.1)


23-Jun-2004 2-47

2T compressor outlet temperature

1T air inlet temperature

sη isentropic efficiency of the compressor

2p compressor outlet pressure

1p compressor inlet pressure


The power consumption of the mechanically driven compressor can be calculated from thefollowing formula:

−

⋅⋅⋅⋅=

−

111

1

21

κκ

η ppTcmP

totp (2.7.2)

P compressor power consumption

m mass flow rate

pc specific heat at constant pressure

totη total efficiency of the compressor = sm ηη ⋅

mη mechanical efficiency of the compressor

2.8. Fuel Injector or CarburetorThe fuel injector model in BOOST is based on the calculation algorithm of the flowrestriction (refer to Section 2.3). This means that the air flow rate in the fuel injectordepends on the pressure difference across the injector and is calculated using the specifiedflow coefficients. In addition, the amount of fuel specified is fed into the air flow.

In the case of the carburetor model, the fuel flow is set to a specified percentage of theinstantaneous mass flow.

For the fuel injector model, a measuring point must be specified at the location of the airflow meter. In this case the mean air flow at the air flow meter location during the lastcomplete cycle is used to determine the amount of fuel. As is the case for continuous fuelinjection, the fuelling rate is constant over crank angle.

The fuel is added in gaseous form to the pipe flow. No evaporation is considered.


2-48 23-Jun-2004

2.9. Waste GateThe waste gate models a valve actuated by the pressure difference on a diaphragm (Figure2-15). The flow through the valve is treated in the same way as for the flow restriction(refer to Section 2.3). The flow coefficients required are specified versus the lift of thevalve. The instantaneous valve lift is calculated from the solution of the motion equationof the valve body (refer to Section 2.4). A defined leakage between the high pressure andthe low pressure of the actuation diaphragm may be taken into account.

Figure 2-15: Waste Gate

This type of valve is used mostly to control the boost pressure of a turbocharged engine.The boost pressure is fed to the high pressure side of the actuation diaphragm. The lowpressure side is connected to the ambient. If the pressure difference exceeds a certainvalue, set by the spring pre-load, the valve opens and a part of the exhaust gases isbypassed around the turbine thus diminishing the energy available at the turbine andpreventing a further increase of the boost pressure.

2.10. Pipe FlowThe one dimensional gas dynamics in a pipe are described by the continuity Equation

( )dxdA

Au

xu

t⋅⋅⋅−⋅−= 1ρ

∂ρ∂

∂∂ρ

, (2.10.1)

the equation for the conservation of the momentum

( ) ( )VF

xA

Au

xpu

tu R−⋅⋅⋅−+⋅−=⋅

∂∂ρ

∂ρ∂

∂ρ∂ 12

2

, (2.10.2)

and by the energy Equation

( )[ ] ( )Vq

dxdA

ApEu

xpEu

tE w+⋅⋅+⋅−+⋅−= 1

∂∂

∂∂

. (2.10.3)


23-Jun-2004 2-49

ρ density

u flow velocity

x coordinate along the pipe axis

A pipe cross-section

t time

p static pressure

RF wall friction force

V cell volume ( )dxA ⋅=

E energy content of the gas

⋅⋅+⋅⋅= 2

21 uTcV ρρ

Vc specific heat at constant volume

T temperature

wq wall heat flow

The wall friction force can be determined from the wall friction factor λ f :

uuDV

F fR ⋅⋅⋅⋅

= ρλ

2(2.10.4)

fλ wall friction coefficient

D pipe diameter

Using the Reynold's analogy, the wall heat flow in the pipe can be calculated from thefriction force and the difference between wall temperature and gas temperature:

( )TTcuDV

qwp

fw −⋅⋅⋅⋅⋅

= ρλ

2(2.10.5)

pc specific heat at constant pressure

wT pipe wall temperature

During the course of the numerical integration of the conservation laws defined in theEquations 2.10.1 to 2.10.3, special attention should be focused on the control of the timestep. In order to achieve a stable solution, the CFL criterion (stability criterion defined byCourant, Friedrichs and Lewy) must be met:

auxt+∆≤∆ (2.10.6)

t∆ time step

x∆ cell length

u flow velocity

a speed of sound


2-50 23-Jun-2004

This means that a certain relation between the time step and the lengths of the cells mustbe met. The BOOST program determines the time step to cell size relation at thebeginning of the calculation on the basis of the specified initial conditions in the pipes.However, the CFL criterion is checked every time step during the calculation. If thecriterion is not met because of significantly changed flow conditions in the pipes, the timestep is reduced automatically.

An ENO scheme [P1, P2] is used for the solution of the set of non-linear differentialequations discussed above. The ENO scheme is based on a finite volume approach. Thismeans that the solution at the end of the time step is obtained from the value at thebeginning of the time step and from the fluxes over the cell borders:

Figure 2-16: Finite Volume Concept

For the approach shown in Figure 2-16, the calculation of the mass, momentum andenergy fluxes over the cell borders at the middle of the time step is required. This can bedone using the basic conservation equations, which give a direct relation between agradient in the x-direction and the gradient over time.

The gradient in the x-direction is obtained by a linear reconstruction of the flow field atthe beginning of the time step.


23-Jun-2004 2-51

Figure 2-17: Linear Reconstruction of the Flow Field

From this information, the mass, momentum and energy fluxes at the cell borders of eachcell can be calculated. Normally the flux at the right cell border will not be equal to theflux at the left cell border of the adjacent cell, which is a necessary condition to meetcontinuity requirements. To overcome this problem, a Riemann-Solver is used to calculatethe correct mean value from the two different fluxes at the cell border, as shown in thefollowing figure.

Figure 2-18: Pressure Waves from Discontinuities at Cell Borders

The main advantage of an ENO scheme is that it allows the same accuracy to be achievedas can be obtained with second order accurate finite difference schemes, but has the samestability as first order accurate finite difference schemes.


2-52 23-Jun-2004

2.10.1. BendsBOOST features a simple model which considers the influence of the bend of a pipe on theflow losses. The bend model in the BOOST program increases the wall friction lossesdependent on a loss coefficient, ζ.

2

2vp ρζ=∆ (2.10.7)

This loss coefficient is a function of the bend angle and the ratio between the bend radiusand the pipe diameter. For this reason the variation of bend radius over pipe length mustbe specified. The bend radius is defined as the bend radius of the pipe centerline.

r

D

θ

Figure 2-19: Pipe Bend Parameters

Figure 2-20: Pipe Bend Loss Coefficient

This model is only valid as long as no significant flow separations occur in the pipe. In thecase of a distinct flow separation, it is recommended to place a flow restriction at thatlocation and to specify appropriate flow coefficients.


23-Jun-2004 2-53

2.10.2. Variable Wall TemperatureBOOST can also model variable pipe wall temperatures. This takes account of the effect ofthe heat transfer between the gas in the pipe and the heat transfer from the outer surfaceof the pipe to the surrounding ambient. The latter is modeled using convective heattransfer (heat transfer between a moving fluid and a solid surface). The rate of convectiveheat is given by Newton’s Law of Cooling written as:

)( ∞−=′′ TThq s

q ′′ convective heat flux (W/m2)

h local convective heat transfer coefficient

Ts surface temperature

T∝ fluid temperature

The convection coefficient (average or local) is expressed in a non-dimensional form calledthe Nusselt Number, the expression for which is given below:

fkLhNu =

kf thermal conductivity of the fluid

L characteristic dimension (outer diameter of the pipe).

There are two main classifications of convective heat transfer, forced convection and freeconvection. Forced convection occurs when the fluid flow is being driven over the surfaceby external means, such as a pump or a fan or atmospheric wind (non-zero characteristicvelocity). Free convection occurs in buoyancy driven flows, i.e. temperature gradients inthe fluid lead to density gradients causing a ‘free’ convective current to be established.Models for both types of convective heat transfer are available in BOOST and are describedbelow.

2.10.2.1. Forced ConvectionFor forced convection the non-dimensional convective heat transfer coefficient, the Nusseltnumber is given by the following:

nmLCNu PrRe=

Re is the Reynolds Number givenµρVL=Re

Pr is the Prandtl Number given by αν=Pr .

The other properties are as follows:

ρ density of the fluid.

µ dynamic viscosity of the fluid.

α thermal diffusivity of the fluid.

ν kinematic viscosity of the fluid and ν = µ/ρL characteristic dimension of the model.

For air, Pr = 0.7, under standard conditions.

The values of C, m and n are functions of the geometry and the Reynolds number range.


2-54 23-Jun-2004

2.10.2.2. Free ConvectionIn free convection correlations, another non-dimensional parameter called the Grashoffnumber is used. The Grashoff number, Gr, is defined as:

2

3)(ν

β LTTgGr sL

∞−≡

β volumetric thermal expansion coefficient of the fluid, a thermodynamic property.

The volumetric thermal expansion coefficient brings in the effects of buoyancy in freeconvection flows; for an ideal gas, β = 1/T, where T is the absolute temperature of the gas.The Grashoff number plays the same role in free convection that the Reynolds numberplays in forced convection in that it is the ratio of buoyancy forces to viscous forces on thefluid

nmLCGrNu Pr=

2.10.3. Forward / Backward Running WavesThe flow conditions at each location in a pipe is the result of a superposition of forward andbackward running waves. Shock capturing schemes, as used in BOOST, do not provide thisinformation as they solve the set of partial differential equations directly. Therefore, thisinformation must be constructed from the solution afterwards.

Figure 2-21: Forward / Backward Running Waves

An outline of the procedure is shown in the above figure. The reference state is determinedas the time average of gas velocity and sound speed. At each instant those conditions arecalculated, by which it is possible to come from the reference state to the instantaneouscalculated state by two simple waves only. The two simple waves are the forward runningwave or λ - characteristic, and the backward running wave or β - characteristic.

The conditions between the reference state, the state behind the waves and the calculatedstates are linked by the compatibility equations along the respective characteristics.


23-Jun-2004 2-55

The path from the reference state to the state behind the forwards running wave(λ - characteristic) is along a β - characteristic. Thus, the following equation is valid.

constcu =−

+1

2κ

Similarly the path from the state behind the forward running wave and the calculatedstate is along an λ - characteristic. The compatibility equation along an λ - characteristic is

constcu =−

−1

2κ

The two equations are solved for the gas velocity and sound speed of the state behind theforward running wave.

The pressure is calculated from the isentropic equation from the calculated state.

The state behind the backward running wave is calculated analogously with the role of λ -and β - characteristics exchanged.

2.10.4. Perforated PipeThis element is specially suited for the refined modeling of, for example, silencing elementsin an exhaust system.

2.10.4.1. Perforated Pipe contained in PipeThe model consists of two pipes of identical length who are connected via perforationsalong this length. Because of the pipes are the same length, the spatial discretization of theouter and inner pipes is the same, so that each individual inner pipe cell is connected toone cell of the outer pipe.

Figure 2-22: Perforated Pipes contained in Pipe

The calculation of the mass flow per unit of pipe length between these cells is based on thefollowing formula:

ltw

TRpp

pp

pp

TRpdm

∂∂

⋅

−

−

⋅

−⋅

⋅⋅⋅⋅⋅=

+

0

2

0

1

0

2

000

11

2 κκκ

κ

κκαπ (2.10.8)


2-56 23-Jun-2004

m mass flow through perforation per unit of pipe-length

d pipe diameter

α ratio of effective flow area to total (porosity*flowcoefficient)

p static pressure downstream of the perforation holes

00 ,Tp stagnation pressure and temperature upstream of the perforation holes

κ,R gas constant and ratio of specific heats

l characteristic flow length (function of perforation hole diameter and wallthickness)

tw∂∂

acceleration of gas column through perforation holes

2.10.4.2. Perforated Pipe contained in PlenumDue to the nature of the plenum model (no spatial discretization and velocity state) all cellsof contained perforated pipes are connected to the same single cell of the plenum. The flowthrough the perforations is calculated using the same formula (2.10.8) as for the perforatedpipe in pipe.

Figure 2-23: Two perforated Pipes contained in Plenum

2.11. Pipe Attachment (System or Internal Boundary)The flow at the end of a pipe is calculated from the pressure in the pipe, the ambientpressure and the effective flow area at the pipe end.

The flow direction is determined from the calculated pressure if the pipe end was closed. Ifthis pressure exceeds the ambient pressure, flow out of the pipe will result. If this pressureis lower than the ambient pressure, flow into the pipe will occur.

Depending on the ratio between the static pressure downstream and the stagnationpressure upstream of the orifice, subsonic, sonic, or even supersonic flow may result.

Zero mass flow may also be obtained at the pipe end, either as a result of zero effective flowarea, or as a result of zero pressure difference.


23-Jun-2004 2-57

Based on the quasi steady-state equation for orifice flow the flow conditions at the end ofthe pipe can be calculated:

−

⋅

−⋅

⋅⋅⋅=

+κκ

κ

κκα

1

0

2

000 1

2pp

pp

TRpm (2.11.1)

m specific mass flow rate

α flow coefficient

p static pressure downstream of the orifice

00 ,Tp stagnation pressure and temperature upstream of the orifice

κ,R gas constant and ratio of specific heats

If the actual pressure ratio is lower than the critical pressure ratio

1

0 12 −

+=

κκ

κppk , (2.11.2)

kp critical pressure

but supersonic flow is not feasible, the mass flow is dependent on the actual pressure ratio:

1122 1

1

00 +

⋅

+⋅

⋅⋅⋅=

−

κκ

κα

κ

TRpm . (2.11.3)

From the instantaneous mass flow rates at a system boundary, the orifice noise can bedetermined.

By means of a Fourier analysis the amplitudes of the mass flow rates over frequency can beobtained. They are considered sources of the noise generation and allow the instantaneoussound pressure at a certain microphone position to be calculated using a directivityfunction.

Ground reflections can also be considered by assuming an image source region [A1, A2, A3].


2-58 23-Jun-2004

2.12. Assembled Elements

2.12.1. CatalystIn the BOOST cycle simulation the catalyst is purely considered as flow element, where nochemical reaction behavior is calculated. The gas dynamics of a catalyst is modeled usingthe same model equations as given for the pipe flow (see Section 2.10). The modeladditionally takes into account that a honeycomb-type catalytic converter consists of ahuge number of small and individual channels. These small channels are the reason forvery small Reynolds numbers and therefore for a flow in the laminar regime. In this casethe friction coefficient is evaluated applying the Hagen-Poisseuille law, whereas in theturbulent region (if reached at all) a turbulent friction coefficient used. The possibility ofdifferent channel shapes is taken into account by Fanning friction factors that are appliedin both, the laminar and turbulent region.

If the catalyst is simulated in the aftertreatment analysis mode, a simplified fluidmechanical approach (compared to the full Riemann Problem described in Section 2.10) isused. More detailed information about this approach can be found in the BOOSTAftertreatment Manual.

2.12.2. Particulate FilterThe diesel particulate filter as a flow device is treated, similar to the catalytic converter, asan assembled element. It consists of a regular pipe, to which two plenums at each end areattached. The open cross-sectional areas of the individual channels are replaced by a pipeof an equivalent cross-sectional area. Thus, the flow through a particulate filter isrepresented by a flow through a pipe described in the section for pipe flows. Thespecification of the cellular filter structure is made similar to the catalytic converter modelas described in Section 2.12.1. In a simplifying way the model of filter friction and pressuredrop is also similar to the one of the catalytic converter. If the particulate filter issimulated in the aftertreatment analysis mode, a simplified fluid mechanical approach(compared to the full Riemann Problem described in Section 2.10) is used. More detailedinformation about this approach can be found in the BOOST Aftertreatment Manual.

2.13. Engine Control Unit and WireIn most modern engine concepts some functions of the engine are controlled by anelectronic engine management system. It is necessary to model such a control deviceespecially for the simulation of transients.

Usually engine control units are state machines. This means that the same input to theunit produces different output depending on the state of the unit. The engine controlmodel in BOOST features three states:

• Steady state

• Engine acceleration

• Engine deceleration


23-Jun-2004 2-59

The transition from steady state to the state of engine acceleration is triggered if thegradient of the load signal versus time exceeds a threshold specified by the user. Thetransition to engine deceleration is triggered the same way when the negative gradient ofthe load signal exceeds the user specified threshold.

Maps up to two dimensions are used to link the output (Actuators) of the control unit tothe input (Sensors). Figure 2-24 shows the principle of the calculation of an output value:

Figure 2-24: Flow Chart of the ECU

In the diagram x, y values = Sensor channels

output value = Actuator channel

A baseline steady state value is taken from the baseline map. This value may be subjectedto corrections by adding values from correction maps or by multiplying it by factors fromcorrection maps. In the case of acceleration or deceleration, other corrections may beapplied to the steady state value. Then it is checked whether the output is withinpredefined bounds which themselves may be defined as maps.

Either the load signal or a desired engine speed can be selected as the guiding input signalof the control.

For the full range of input (Sensor-Channels) and output (Actuator-Channels) please referto the table in Chapter 9.3.


2-60 23-Jun-2004

2.14. Gas PropertiesThe gas properties like the gas constant or the heat capacities of a gas depend ontemperature, pressure and gas composition. BOOST calculates the gas properties in eachcell at each time step with the instantaneous composition. Thus BOOST can simulateexhaust gas recirculation without the need for a special treatment. For the calculation ofthe gas properties of exhaust gases the air fuel ratio is used as a measure for the gascomposition. Air fuel ratio in this context means the air fuel ratio at which the combustiontook place from which the exhaust gases under consideration originate. The compositionof the combustion gases is obtained from the chemical equilibrium considering dissociationat the high temperatures in the cylinder.

For engines with internal mixture preparation the average air fuel ratio of the gas is usedfor the calculation of the gas properties. Pure air is considered as a gas with infinite airfuel ratio. If air and exhaust gases mix the average (higher) air fuel ratio is determined.This approach is valid as long as the excess air ratio of the exhaust gases is higher thanapproximately 1.1.

For engines with external mixture preparation, typically operated with rich mixtures atfull load, combustion gases and air must be kept apart. Therefore conservation equationsfor combustion products (together with the air fuel ratio characteristic for them) and fuelvapor are solved.

The mass fraction of air is calculated from

CPFVair µµµ −−= 1 (2.14.1)

airµ mass fraction of air

FVµ mass fraction of fuel vapor

CPµ mass fraction of combustion products

The air fuel ratio characteristic for the combustion products is calculated from

FB

FBCPCPAF

µµµ −= (2.14.2)

CPAF air fuel ratio of combustion products

FBµ mass fraction of burned fuel


23-Jun-2004 2-61

Figure 2-25 shows the relations of the mass fractions to each other.

Figure 2-25: Considered Mass Fractions

2.15. Definition of Global Engine Data (SI-Units)

� Note: Some definitions have been refined since Version 3.3.

Average (mean) values over the cycle duration CD:

( ) αα dyCD

yCD

⋅⋅= ∫1

( )αy variable depending on α

α crank angle

y average value of y

CD cycle duration

Mass flow weighted temperature:

( ) ( )

( ) αα

ααα

dm

dmTT

CD

CDMS ⋅

⋅⋅=

∫

∫

MST mass flow weighted temperature

( )αT temperature depending on α

( )αm mass flow rate depending on α


2-62 23-Jun-2004

2.15.1. Cylinder DataCompression ratio:

C

DC

VVV +=ε

DC VV + maximum cylinder volume

CV minimum cylinder volume (combustion chamber volume)

DV displacement

� Note: The same definition is used for two and four stroke engines.

Indicated mean effective pressure:

dVpV

IMEPCD

cD

⋅⋅= ∫1


V cylinder displacement

Indicated torque:

πcycle

D

kVIMEPIT ⋅=

IT indicated torque

cyclek cycle parameter:

2 for two-stroke engines

4 for four-stroke engines

Number of cycles per second:nncycle = for two-stroke engines

2nncycle = for four-stroke engines

n crankshaft-revolutions per second

Indicated specific torque:

Ds V

ITIT =


23-Jun-2004 2-63

Indicated power:

cycleDi nVIMEPP ⋅⋅=

Indicated specific power:

D

iis V

PP =

Inj. Fuelmass:

FVinjm , total mass of fuel directly injected

Asp. Fuelmass:

FVinjFVcFVastr mmm ,,, −=

FVastrm , mass of fuel aspirated trapped

Fuelmass (tot.):

FVcm , total mass of fuel trapped in the cylinder

Trapping Efficiency Fuel:

FVt

FVcFtr m

m

,

,, =η

FVtm ,total mass of fuel added

Indicated fuel consumption (trapped fuel mass):

i

cycleFVctr P

nmISFC

⋅= ,

Indicated fuel consumption (total fuel mass):

i

cycleFVttt P

nmISFC

⋅= ,


2-64 23-Jun-2004

Friction mean effective pressure:

cycleD

fr

nVP

FMEP⋅

=

frP friction power

� Note: FMEP does not contain the Work caused by Scavenging Pumps,Crankcase Scavenging or mechanically driven Supercharging Devices

Scavenging mean effective pressure (individual cylinder):

cycleD

S

nVPSMEP⋅

=

SP required power of related Scavenging Pump or Crankcase Scavenging

Auxiliary Drives mean effective pressure (overall engine):

cycleDE

MCCSSP

nVPPPAMEP

⋅++=

CSP required power of Scavenging Pumps

CSP required power of Crankcase Scavenging

CSP required power of mechanically driven Supercharging Devices

DEV Engine Displacement

Brake mean effective pressure (individual cylinder):

SMEPFMEPIMEPBMEPC −−=

Brake mean effective pressure (overall engine):

AMEPFMEPIMEPBMEPE −−=

Mechanical efficiency:

IMEPFMEP

FMEPBMEPBMEP

IMEPBMEP

m −=+

== 1η


23-Jun-2004 2-65

Brake specific fuel consumption:

m

ISFCBSFCη

=

Indicated efficiency:

uFVc

CDc

T Hm

dVp

⋅

⋅=∫

,

η

uH lower heating value

2.15.2. Gas Exchange Related DataIMEP exhaust stroke (only four-stroke):

∫=

⋅⋅=360

180

1

α

dVpV

IMEP cD

ex

IMEP intake stroke (only four-stroke):

∫=

⋅⋅=540

360

1

α

dVpV

IMEP cD

in

IMEP gas exchange (= pumping mean effective pressure PMEP; only four-stroke):

∫=

⋅⋅=540

180

1

α

dVpV

PMEP cD

Air fuel ratio of Combustion:

FVc

tAcCmb m

mAF

,

,=

tAcm , total mass of air in the cylinder


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Excess air ratio:

Stc

Cmb

AFAF=λ

λ Excess air coefficient

StcAF Stoichiometric A/F-ratio

Total mass at Start of High Pressure Cycle (SHP, all ports closed):

SHPcm , total in-cylinder mass at SHP

Airmass at SHP:

tAcm , total mass of air in the cylinder at SHP

Airpurity:

SHPc

tAc

mm

AP,

,=

Residual gas content:

SHPc

CPc

mm

RG,

,=

CPcm , mass of combustion products in the cylinder at SHP

� Note: Recirculated exhaust gas is added to the residuals.

Air delivered:

Aasm , mass of air aspirated

Air delivery ratio related to ambient conditions:

aDR

Aas

cycleDa

AasaD m

mnV

m

,

,,, =

⋅⋅=ρ

λ

Aasm , mass flow of air aspirated

aDRm , reference mass (ambient conditions)

aρ ambient air density


23-Jun-2004 2-67

Air delivery ratio related to intake manifold conditions:

mDR

Aas

cycleDm

AasmD m

mnV

m

,

,,, =

⋅⋅=ρ

λ

mDRm , reference mass (manifold conditions)

mρ air density in the intake manifold (specified measuring point or

plenum)

Mass delivered:

asm mass of fresh charge aspirated

Airmass trapped:

Atrm , mass of air trapped

Trapping efficiency air:

Aas

Atrtr m

m

,

,=η

Volumetric efficiency related to ambient conditions:

aDR

Atr

cycleDa

AtraV m

mnV

m

,

,,, =

⋅⋅=ρ

η

Atrm , mass flow of air trapped

Volumetric efficiency related to intake manifold conditions:

mDR

Atr

cycleDm

AtrmV m

mnV

m

,

,,, =

⋅⋅=ρ

η

Scavenge ratio:

( ) SR

as

cycleCDref

as

mm

nVVmSR =

⋅+⋅=ρ

asm aspirated mass flow

SRm reference mass for scavenge ratio


2-68 23-Jun-2004

Scavenge Loss:

as

sl

as

sl

mm

mmSL ==

slm mass flow lost during scavenging

slm mass lost during scavenging

Scavenging efficiency:

C

trSC m

m=η

trm total mass trapped

Cm total mass of cylinder content

Mean wall heat transfer coefficient in the cylinder ( M. Eff. HTC ):

( )∫ ⋅⋅=CD

ww dhCD

h αα1

( )αwh wall heat transfer coefficient depending on crank angle

wh mean wall heat transfer coefficient

Effective mean gas temperature for wall heat transfer in the cylinder (M. Eff.Temp.):

( ) ( ) ααα dhThCD

TCD

Gw

effg ⋅⋅⋅⋅

= ∫1

,

GT gas temperature

Air fuel ratio ( Reference value at EO ):

EVOFBc

EVOFBcEVOCPcEO m

mmAF

,,

,,,, −=

EVOCPcm ,, mass of combustion products in the cylinder at Exhaust Valve Opening

EVOFBcm ,, mass of burned fuel in the cylinder at EVO

� Note: Gas Exchange data is defined in accordance with SAE standardJ604 [G8].

The relation between the different data characterizing the gas exchange can be seen in thefollowing figure:


23-Jun-2004 2-69

mSR reference mass for scavenge ratiomDR reference mass for delivery ratiomas mass of fresh charge aspiratedmas, A mass of air aspiratedmas, CP mass of combustion products aspirated

(= mas, CPst for IMP)mtr mass of fresh charge trappedmsl mass lost during scavengingmtr,CP mass of combustion products trapped

(= mtr, CPst for IMP)mtr, CPA mass of air included in trapped

combustion products (= 0 for IMP)mtr, A mass of air trappedmtr,FV mass of fuel trapped (= 0 IMP)minj,FV total mass of fuel directly injectedminj,ge,FV mass of fuel injected during gas

exchangeminj,tr,FV mass of injected fuel trapped during

gas exchange (= 0 for IMP)minj,sl,FV mass of injected fuel lost during

gas exchange (= 0 for IMP)mrg,CP mass of residual gasmrg, CPA mass of air included in residual gasmc total in-cylinder massmc,A mass of air in the cylinder

(= mc, At for IMP)

mc,At total mass of air in the cylindermc,CP mass of combustion products in the

cylinder at SHP (=mc,CPst for IMP)mc,CPA mass of air included in combustion

products,cylinder (= 0 for IMP)mc,CPst mass of stoichiometric combustion

products, cylindermc,FV total mass of fuel trapped in the cylinder

(= minj,FV for IMP)

mSR

msl

mDR

mtr,CP

mas

mtr,CPA

mtr

mtr,A

mtr,FV

SHP

minj,ge,FV

minj,FV

minj,tr,FV

minj,sl,FV

mc,

FV

mc,

At

mc,

CPA

mc,

CPs

t

mc

mrg

,CP

mrg

,CPA

mc,

Am

c,C

P

Figure 2-26: Relation of Gas Exchange Data


2-70 23-Jun-2004

2.16. AbbreviationsThe following abbreviations are used in this manual:

µσ Flow coefficients of the ports

BDC Bottom dead center

BMEP Brake mean effective pressure

BSFC Brake specific fuel consumption

CRA Crank angle

DPF Diesel Particulate Filter

EVC Exhaust valve closing

EVO Exhaust valve opening

FIE Fuel injection equipment

FMEP Friction mean effective pressure

IMEP Indicated mean effective pressure

ISFC Indicated specific fuel consumption

IVC Intake valve closing

IVO Intake valve opening

PFP Peak firing pressure

PMEP Pumping mean effective pressure

TDC Top dead center

VGT Variable geometry turbine

VNT Variable nozzle turbine


23-Jun-2004 3-1

3. GRAPHICAL USER INTERFACEBased on the AVL Workspace Graphical User Interface (AWS GUI), the pre-processingtool assists the user in creating an engine model for a BOOST simulation.

For the general handling of the AWS GUI please refer to the AVL Workspace GraphicalUser Interface Manual. The BOOST specific operations are described as follows:

3.1. BOOST Specific Operations

BOOST Menu Bar Icon Bar Element/Model Working AreaButton Bar Tree Area

Figure 3-1: BOOST - Main Window


3-2 23-Jun-2004

3.1.1. Menu BarElement Parameters Displays the parameters for the selected element.

Parameters can be added or deleted. Alternativelyclick on an element with the right mouse button andselect Parameters from the submenu. Refer toSection 3.5.1 or the AWS GUI Manual, Section 2.4 forfurther information.

Properties Displays the dialog box for defining the values for theselected element. Alternatively click on an elementwith the right mouse button and select Propertiesfrom the submenu.

Copy Data First select the source element type in the workingarea or model tree, then data can be copied from theselected source element to the selected target(s).

Model Parameters Defines values for the model. Refer to Section 3.5.1 orthe AWS GUI Manual, Section 2.4 for furtherinformation.

Case Explorer Displays the case explorer for the current model.

Simluation Run Displays the run dialog box. This displays both thecases for the current model and the tasks to beperformed. The calculation can be started from thispoint.

Status Displays the simulation status dialog box.

Control Defines parameters used to control the simulation anddefine the global values used in the simulation. Referto Section 3.2 for further information.

VolumetricEfficiency

Displays and sets the reference element to be usedfor volumetric efficiency calculations. This can beeither a measuring point or a plenum. Refer to Section3.2.8 for further information.

Create SeriesResults

Prepares the procedure for the Case Series results.Refer to Section 3.5 for further information.

Create AnimationResults

Prepares the Animation for PP3. Refer to Section 5.6for further information.

Show Summary Cycle SimulationAftertreatment

Opens the ASCII browser and displays the summaryvalues from either the cycle simulation oraftertreatment analysis.

Show Results Opens the IMPRESS Chart post-processor which canbe used to examine and plot the simulation results.


23-Jun-2004 3-3

Show Messages Cycle SimulationAftertreatment

Opens the Message browser and displays themessages generated by the solver during the cyclesimulation or aftertreatment analysis.

Show Elements Cycle Simulation

Opens a browser to display more detailed informationon compound perforated elements.

Show Animation Opens the PP3 post-processor.

Import Results Prepares results of a BOOSTFILENAME.bst file runoutside the graphical user interface.

View Logfile Displays the screen output of the calculation kernelduring the simulation or model creation.

Optimization Refer to the Optimization of Multi-body System

using AVL Workspace and iSIGHT manual.

Options Job Submission Parallel processing (currently not available).

Lock Properties Locks Property dialogs (currently not available).

Frame Set of graphical elements used for page layout, e.g.rectangle (frame), logo and text elements.

None: Removes the frame from the page.

AVL Report: The standard AVL frame.

Frame Definitions Customized settings of the current frame. Specify textand the customer logo for the frame.

Units Used to display and set the units used. Refer to theAWS GUI Manual, Section 2.4.2.

Utilities BURN Tool for Combustion Analysis. Refer to Section 3.7.1for further information.

Search Displays tables of the input data used in the model.These can be saved in HTML format. Refer to Section3.7.2 for further information.

License Manager Controls availability and usage of licenses. Refer toSection 3.7.3 for further information.

Pack Model Creates a compressed tape archive of all relevantmodel information. Refer to Section 3.7.4 for furtherinformation.

Help Contents Opens the HTML help system.

Search Searches the HTML help system for information.

About Displays version information.


3-4 23-Jun-2004

3.1.2. BOOST ButtonsIf selected the mouse can be used to connect a pipe between twoelements. Refer to Section 3.4.1 for further information.If selected the mouse can be used to connect a wire between twoelements. Refer to Section 3.4.10.1 for further information.If selected the mouse can be used to insert a perforated pipe into aplenum. Refer to Section 3.4.6.1 for further information.If selected the mouse can be used to connect aftertreatmentboundaries to aftertreatment elements (catalyst, dpf) for runningsimulations in analysis mode. Refer to the Aftertreatment Manual.Reverses the positive flow direction of the selected pipe. Refer to theAWS GUI Manual, Section 2.2.Changes the attachments of a selected pipe or a wire. Refer to theAWS GUI Manual, Section 2.2.Rotates the selected object counter-clockwise (90 degrees steps)

Rotates the selected object clockwise (90 degrees steps)

Opens the input window for general simulation control (globals) data,equivalent to Simulation|Control.Runs the Simulation, equivalent to Simulation|Run.

Search Tool – Refer to Section 3.7.2 for further information.

3.1.3. Elements TreeCylinder Engine cylinder element. Refer to Section

3.4.2 for further information.

MeasuringPoint

Access to flow data and gas conditions overcrank angle at a certain location in a pipe.Refer to Section 3.4.3 for furtherinformation.

Boundaries System Boundary Provides the connection of the calculationmodel to a user-definable ambient. Refer toSection 3.4.4.1 for further information.

AftertreatmentBoundary

Provides the connection of theaftertreatment analysis model to a user-definable ambient.

Internal Boundary Allows boundary conditions for thecalculation model to be specified directly inthe last cross section of a pipe where amodel ends. Refer to Section 3.4.4.3 forfurther information.


23-Jun-2004 3-5

Transfer Restriction Considers a distinct pressure loss at acertain location in the piping system. Referto Section 3.4.5 for further information.

Rotary Valve Controls the air flow in a pipe as a functionof crank angle or time. Refer to Section3.4.5.2 for further information.

Check Valve A pressure actuated valve used to preventreverse flow. Refer to Section 3.4.5.3 forfurther information.

Injector Used for engines with external mixturepreparation to add the fuel to the air in theintake system. Refer to Section 3.4.5.4 forfurther information.

Junction Used to connect three or more pipes. In thecase of three pipes, a refined junctionmodel may be used. This considersgeometric information such as the area ratioof the connected pipes and the anglesbetween the pipes. In other cases a simpleconstant pressure model is available. Referto Section 3.4.5.5 for further information.

Volumes Plenum An element in which spatial pressure andtemperature differences are not considered.Refer to Section for 3.4.6.1 furtherinformation.

Variable Plenum Considers the change of the volume andsurface area of the plenum over time. Referto Section 3.4.6.2 for further information.

Perforated Pipe inPipe

Single element representing two pipes. Aninner perforated pipe and an outer pipe.Refer to Section 3.4.6.3 for furtherinformation.

Assembled Air Cleaner The instantaneous pressure loss isdetermined from the pressure loss specifiedin a reference point at steady stateconditions. Refer to Section 3.4.7.1 forfurther information.


3-6 23-Jun-2004

Catalyst The pressure loss in the catalyst must bedefined for a reference mass flow. Itscharacteristics are determined from thisinput and additional geometricalinformation. It is important to note thatchemical reactions in the catalyst are notconsidered by the cycle simulation model.Refer to Section 3.4.7.2 for furtherinformation. Using the aftertreatmentanalysis mode, chemical reactions can besimulated. Refer to the AftertreatmentManual.

Cooler The treatment of the Air Cooler is similar tothe Air Cleaner. The pressure loss, coolingperformance and the corresponding steadystate mass flow must be defined asreference values. Refer to Section 3.4.7.3for further information.

Diesel ParticulateFilter

Pressure drop, loading, regeneration ofparticulate filters can be simulated using theaftertreatment analysis mode. Refer to theAftertreatment Manual.

Charging Turbocharger Turbocharger element. Both simple and fullmodels are available. Refer to Section3.4.8.1 for further information.

PositiveDisplacementCompressor

Either a constant mass flow and a constantcompressor efficiency, an iso-speed line ora full map may be specified. The iso-speedline of the positive displacementcompressor is defined by mass flow andefficiency versus the pressure ratio acrossthe compressor. Refer to Section 3.4.8.2for further information.

Turbo Compressor Either a constant pressure ratio and aconstant compressor efficiency, an iso-speed line or a full map may be specified. Ifan iso-speed line or a compressor map isdefined, the pressure ratio and theefficiency are determined according to theinstantaneous mass flow rate and the actualcompressor speed. Refer to Section3.4.8.3 for further information.


23-Jun-2004 3-7

Waste Gate A valve actuated by the pressure differenceon the valve body plus the pressuredifference on a diaphragm mechanicallylinked to the valve body. Refer to Section3.4.8.4 for further information.

External Fire Link Simulation of three dimensional (3D) flowpatterns. Refer to Section 3.4.9.1 forfurther information.

User DefinedElement

Allows the user to implement algorithms.For maximum support, the UDE handles thedata of the pipe attachments. Emptysubroutines are shipped with the BOOSTinstallation as a guide for the User toincorporate into his model. Furthermoreresults obtained from the UDE may beanalysed in the post-processor. Refer toSection 3.4.9.2 for further information.

Control Engine Control Unit Models all the important functions of anelectronic engine control. The output of theECU, such as ignition timing, start ofinjection or the setting of a control valve iscalculated from maps dependent onspecified input parameters. Possible inputparameters are engine speed or ambientconditions and data from measuring pointsand plenums. The parameters specified inthe baseline maps may be modified by anumber of corrections for ambientconditions, acceleration or deceleration ofthe engine. Refer to Section 3.4.10.2 forfurther information.

MATLAB DLL The Dynamic Link Library element can beused to include control algorithms orcomplete engine control models createdwith a commercial control algorithm designsoftware (e.g. MATLAB/SIMULINK).Information channels are passed betweenelements and this junction using wires. Theinformation channels include both sensorand actuator channels. The DLL may bewritten in any programming languageprovided the compiler supports mixedlanguage programming. This junction isalso used to link with the MATLAB s-function. Refer to Chapter 4 for furtherinformation.


3-8 23-Jun-2004

MATLAB API Passes information to and from MATLAB.Information channels are passed betweenelements and this junction using wires. Theinformation channels include both sensorand actuator channels. Refer to Section3.4.10.3 for further information.

Acoustic Microphone A microphone element can be added to anyBOOST model in order to extract acousticdata such as overall dB(A) levels or orderplots. The microphone is not attached toany pipes but linked in the input for themicrophone to one or more systemboundaries. Refer to Section 3.4.11.1 forfurther information.

3.1.4. Model TreeA list of elements and connections used in the model is displayed. Click on the requireditem with the left mouse button, then click the right mouse button and select the requiredoption from the following submenu.

Figure 3-2: Model Submenu

Properties opens the selected element's properties window as shown in Figure 3-3.

Parameters opens the selected element's parameters window as shown in Figure 3-72.

Group Elements links all selected elements together.

Sort Elements by Id organizes elements according to their Id.

Sort Elements by Name organizes elements according to their name.

Expand or expands the model tree.

Collapse or closes the tree.

Data can be copied from a selected element type in the model tree or working area byselecting Element|Copy Data. A window opens where the source element can be selectedand copied to the target element.


23-Jun-2004 3-9

3.1.5. Data Input WindowDouble click the required element in the Element tree to display it in the working area.Select the displayed element with the right mouse button and select Properties from thesubmenu to open the relevant data input window. The following window relates to thegeneral data of the pipe.

Figure 3-3: Data Input Window

Data input windows are available for sub-groups displayed in the tree shown in the abovefigure by clicking on the required sub-group with the left mouse button.

New or existing parameters can be inserted in the input fields by clicking on the label tothe left of the field with the right mouse button and selecting the required option from thesubmenu. Refer to section 3.5.1 for further information.

While inputting data, the following options are available:

Apply: The specified data is saved when the error check is valid. The sub-groupicon turns green.

Accept: The specified data is saved but no error check is executed and/orinsufficient data is accepted by the user after a warning dialog. The sub-group icon turns yellow.

Reset: Returns to the previous applied settings.

Revert: Returns to the default settings.

Help: Online help is available.

OK: Confirms data input completion and exits the element.

Cancel: Modified data input is not saved. This also exits the element.


3-10 23-Jun-2004

If all required data for the element is applied and/or accepted, the red exclamation pointdisappears, indicating that the input process for that element is completed.

If any input data is missing after selecting apply or accept, a window appears with a list ofthe missing data and a red exclamation point is displayed on the element. However, theuser should be aware that incomplete or incorrect data usually renders a calculation of thedata set impossible.

After confirming the element input data, the calculation model must be stored in a filewith the extension .BWF by selecting FileSave as.

3.1.5.1. Sub-group IconsThe Sub-group icons inform the user as to their status as follows:

Green Sub-group Icon: Valid data has been specified.

White Sub-group Icon: Data has not yet been specified.

Grey Sub-group Icon: Disabled.

Red Sub-group Icon: Insufficient data.

Yellow Sub-group Icon: Insufficient data has been accepted by the user.

Select a Sub-group icon with the right mouse button to open the following submenu.

Figure 3-4: Element Sub-group Submenu

Expand or displays all available items in a folder.

Collapse or closes a folder.

Show All displays the complete list of items in the tree.

Show Enabled Only displays the available green and white sub-group icons.

Show Invalid Only displays the gray sub-group icons.

3.1.6. Table WindowDepending on the selected sub-group, the user can enter a constant value or a list of values

where the Table icon is displayed. The Table window represents a standard windowused throughout the program to specify values dependent on a certain parameter.

As shown in Figure 3-5, select the Table icon and select Table from the submenu.Then select the Table button which appears on the input field to open the followingwindow.


23-Jun-2004 3-11

Figure 3-5: Table Window

Select Insert Row to add a line and enter the relevant values. Select Remove Row todelete a selected line.

New or existing parameters can be inserted in the table by clicking on the active field withthe right mouse button and selecting the required option from the submenu. Refer tosection 3.5.1 for further information.

Large data arrays can be read from an external file by selecting Load. If the data has beenspecified in the pre-processor, it may be saved in an external file by selecting Store. Thesefiles have the default extension .dat. It is ASCII format with one pair of data in eachrecord. The values are separated by one or more blanks. No heading lines are allowed.

If data is defined versus time, the total time interval for which the values are specified maybe less than, equal to or greater than the cycle duration. If the time interval is shorterthan the specified maximum calculation period, BOOST treats the specified function as aperiodic function.

�Note: A data point at 0 degrees and 360 degrees or 720 degrees isneeded to obtain a period of 360 or 720 degrees for the specified function.

0 degree crank angle corresponds to the Firing Top Dead Center (TDC) ofcylinder 1 (or the selected cylinder at the cylinder input).

The data entered in the table is plotted in the graph as shown in Figure 3-5. The axes andlegend of the graph can be manipulated as desired. Click with the left mouse button, thenclick the right mouse button and select the required option from the following contextmenu.


3-12 23-Jun-2004

Figure 3-6: Graph Context Menu

3.2. General Input DataSince the general input data is used to control the input process for each element, BOOSTrequires the specification of the general input data prior to the input of any element.

The Global input data must be defined first. Select SimulationControl to open thefollowing window. This data is used to prepare the input process for each element.

3.2.1. Simulation Tasks

Figure 3-7: Simulation Control – Simulation Tasks Window


23-Jun-2004 3-13

3.2.1.1. Date, Project ID and Run IDThe date is when the BOOST data set was last changed. It is automatically inserted by thepre-processor.

Project-ID and Run-ID are comment lines which may be specified to identify thecalculation. Both may have a length of up to 50 characters.

3.2.1.2. Simulation TasksDepending on the new tasks before starting with the model at least one of the followingshould be selected:

Cycle Simulation: Gas exchange and combustion BOOST calculation

Aftertreatment Analysis: Simulation of chemical and physical processes foraftertreatment devices

Linear Acoustics: Frequency domain solver to predict the acoustic performanceof components

3.2.2. General ControlSelect General Control to open the following window:

Figure 3-8: Simulation Control – Globals Window


3-14 23-Jun-2004

3.2.2.1. Engine SpeedThe engine speed is the revolution speed of the crankshaft. For steady state simulations, itis kept constant. For transient simulations it is the starting value and is kept constant forthe first three cycles to dampen excessive gas dynamics due to the initialization.Afterwards, the instantaneous engine speed is calculated from solving the moment ofmomentum equation applied to the crankshaft at each time step.

3.2.2.2. Steady State / Transient SimulationSteady state simulations are default. BOOST can also simulate engine and vehicleacceleration or deceleration processes by selecting Transient Calculation. Additional inputmust be defined for Engine Only or Driver sub-groups as described below. The relevantinertia data must also be defined.

3.2.2.2.1. Engine Only Transient CalculationIn the Globals window, select Engine Only for the Transient Calculation. The inertiainput field is activated.

Input the average inertia of the cranktrain plus all auxiliary drives and the inertia of theload reduced to engine speed. The inertia and the coefficients may depend on time or

crank angle, therefore input the values in the Table .

For converting the mass of a vehicle to a rotational inertia related to engine speed, thefollowing formula may be used:

2

2

irmI TV ⋅= (3.2.1)

I rotational inertia of the vehicle

Tr (dynamic) tire radius

i total gear ratio between engine and drive wheels, given:

w

e

nni= (3.2.2)

en engine speed

wn wheel speed


23-Jun-2004 3-15

The following input fields are also activated when the Engine Only sub-group is selected inthe tree.

Figure 3-9: Load Characteristic for Engine Only

The load torque is calculated from the formula:

2ss

s

dncnbnaM +++= (3.2.3)

M load torque

dcba ,,, coefficients

Coefficients a, b, c and d should be selected in such a way that for example, the road load isapproximated in the speed range of interest. It should be noted that the torque, like theinertia, is related to engine speed. Thus the load torque can be calculated from:

irDM T⋅= (3.2.4)

D drag and rolling resistance of the vehicle

3.2.2.2.2. Driver Transient CalculationThe Driver transient calculation allows the user to simulate the dynamic behavior of thetwo-body system vehicle and engine which can be decoupled by a gear shift. The ECU(Section 3.4.10), which has to be present when executing the driver model, tries to follow aspecified speed course by calculating the load signal depending on the deviation of theactual vehicle speed from the desired one.

Select Desired Engine Speed for the ECU guiding input (the value or table of the DesiredEngine Speed is not taken into account).


3-16 23-Jun-2004

The following combustion models are available for the Driver Transient Calculation:

• Single Vibe function

• Double Vibe function

• Single Zone Table

• Woschni/Anisits

• Hires et al.

• Constant Volume Combustion

• Constant Pressure Combustion

• Motored

In the Globals window, select Driver for the Transient Calculation. The inertia inputfield is activated. Input the inertia of the engine plus all auxiliary drives (not includingmechanically driven supercharging devices, inertia of drivetrain and inertia of vehicle).

Input can be a constant value or a Table of time or crank angle dependent values.

The crank angle dependent inertia caused by the translatory moved masses of a standardcrank train (no piston pin offset considered) can be calculated from:

−

+=

)(sin2

2)2sin(

)sin(4

22

2

α

α

α

sl

smIt (3.2.5)

tI inertia of translatory moved masses [kgm2]

m translatory moved masses [kg]

s stroke [m]

l con-rod length [m]


23-Jun-2004 3-17

The following input fields are also activated when the Driver sub-group is selected in thetree.

Figure 3-10: Driver Input Window

1. Clutch

The transferred torque of the implemented model of the clutch has the followingstates:

a. The clutch does not slip (transferred torque is smaller than the maximumtransferable torque)

b. The clutch slips (transferred torque is equal to the maximum transferabletorque)

The maximum transferable torque is given by the formula

cccmtm ptt = (3.2.6)

tmt maximum transferable torque [Nm]

cmt maximum clutch torque [Nm]

ccp clutch-control position [ 1]

Specify the maximum clutch torque cmt [Nm].


3-18 23-Jun-2004

2. Driver

During the Shifting process the load signal and clutch-control position are determinedaccording to the following figure. The input parameters for the shifting process are:

Shifting Time: Period of shifting process st [s]

Clutch Pedal On: End of decoupling period s

d

tt

[1]

Acceleration Pedal Off: End of the load-signal decreasing period s

ld

tt

[1]

Acceleration Pedal On: Start of the load-signal increasing period s

lc

tt

[1]

Clutch Pedal Off: Start of coupling period s

c

tt

[1]

Figure 3-11: Shifting Process


23-Jun-2004 3-19

ls Load signal [1]

0ls Load signal at start of shifting process [1]

ccp Clutch-control position [1]

st Period of shifting process [s]

s

d

tt

End of decoupling period [1]

s

c

tt

Start of coupling period [1]

s

ld

tt

End of the load signal decreasing period [1]

s

lc

tt

Start of the load signal increasing period [1]

3. Gear Shifting

Minimum Engine Speed: A gear shift downwards is initiated if the engine speedfalls below the minimum engine speed [rpm].

Maximum Engine Speed: A gear shift upwards appears by exceeding the maximumengine speed [rpm].

4. Vehicle Velocity

Based on the deviation of the actual vehicle speed from the specified value(s), the ECUcalculates the load signal according to the formula

( ) ( ) ( )∫ −+−+−=t

desdesdes nndnninnpls0 dt

ddt

ls load signal [1]

p proportional control gain [1/rpm]

i integral control gain [1/rpms]

d differential control gain [s/rpm]

desn desired vehicle speed reduced to crank shaft speed[rpm]


The desired vehicle speed is interpolated from a specified constant value or a Table of time dependent values.

5. Gearbox

To initialize the gearbox, input the gear step which will calculate the vehicle speed atthe start of the calculation (the corresponding engine speed is specified inSimulation|Control|Globals).


3-20 23-Jun-2004

Input a table of corresponding gear ratios in ascending order [1].

Definition of the total gear ratio:

w

e

nni = (3.2.7)

i gear ratio [1]

en engine speed [rpm]

wn driving wheel speed [rpm]

Vehicle CharacteristicsWhen Driver is selected for the Transient Calculation, the following input fields of theVehicle sub-group are activated.

Figure 3-12: Vehicle Input Window

Specify Inertia of Drivetrain, Vehicle Mass and Rolling Radius.

The vehicle load is calculated from the formula:

2vdvcbvaF +++= (3.2.8)

F vehicle load [N]

v vehicle speed

dcba ,,, vehicle load coefficients

( in general determined by : b ... rolling resistance, uphill gradient;

c ... friction caused by laminar flow; d ... air resistance )

Input a constant value for Coefficient a or a Table of time dependent values.Coefficients b, c, d are treated analogous.


23-Jun-2004 3-21

3.2.2.3. Calculation ModesTwo calculation modes are available:

• Single calculation: Calculation of a single operating point of one engineconfiguration; full output is available for a detailed analysis of the flow in theengine.

• Animation: Special output for the animated display of the results with theBOOST post-processor is provided for last calculated cycle.

3.2.2.4. Identical CylindersBOOST features individual cylinders which means that each cylinder can have its ownspecifications. If this feature is not required, it is recommended to select identicalcylinders in order to simplify the input process. In this case, only the specifications forcylinder 1, the firing order and the firing intervals must be specified.

Provided that the cylinders feature identical data, the ROHR transfer option to othercylinders may be activated. In this case, the Quasi-dimensional combustion model is onlyapplied to Cylinder 1 to calculate the rate of heat release curve. The obtained curve istransferred to the remaining cylinders. For these cylinders, the high pressure cycle will besimulated with a single zone model.

This also applies to the Hiroysau and AVL MCC combustion models.

3.2.2.5. User-Defined ConcentrationsBOOST calculates the distribution of an arbitrary number of tracer gases (gases which donot influence engine performance). The required number of tracer gases is specified by thenumber of user-defined concentrations.

3.2.2.6. Mixture PreparationTwo types of mixture preparation are available:

• Internal: The fuel is added to the cylinder during the high pressure cycle.

• External: The fuel is fed to the intake system by a carburetor or a fuelinjector or is aspirated together with the air from the ambient.DGI engines have to be defined as External.

3.2.2.7. Fuel DataBOOST provides accurate gas properties for the following fuels:

• Gasoline

• Diesel

• Methane

• Methanol

• Ethanol

• Hydrogen

• Butane

• Pentane

• Propane


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For each fuel, default values for the lower heating value and for the stoichiometric air/fuelratio are also available. If more accurate data is available, the default values may beoverwritten.

3.2.2.8. Reference ConditionsThe reference conditions (pressure and temperature) are required in order to calculatespecific engine performance data such as delivery ratio, volumetric efficiency etc. related toambient conditions. It is the user's responsibility to ensure that these conditions matchthe conditions at the system boundary from which the engine aspirates its air. Otherwise,the results might be misleading.

3.2.2.9. Gas PropertiesIn general, BOOST uses variable gas properties, which means that at any location in thesystem the gas properties are determined from the actual gas composition, actual pressureand actual temperature.

If there is no cylinder in the calculation model, constant gas properties may be used inorder to simplify the calculation. For the calculation of constant gas properties usedthrough out the model, reference conditions and a reference gas composition must bedefined.

Select Constant Gas Properties and then select the Gas Properties sub-group in the treeto open the following window.

Figure 3-13: Simulation Control – Constant Gas Properties Window


23-Jun-2004 3-23

3.2.3. Time Step ControlSelect the Time Step Control sub-group in the tree to open the following window.

Figure 3-14: Simulation Control – Time Step Control Window

1. Cycle

Select 2-Stroke or 4-Stroke.

2. Maximum Calculation Period

The maximum calculation period sets the crank angle interval after which thesimulation stops and the results will be written to the .bst file. For steady statesimulations it must be sufficiently long in order to achieve stable calculation results. Itis recommended to use a multiple of the cycle duration. The required calculationperiod until stable conditions are achieved depends upon the engine configuration.

With an increasing number of cylinders, the calculation period may become shorter.4-stroke engines need shorter calculation periods than 2-stroke engines. Forturbocharged (TC) engines, especially if the BOOST pressure is calculated from theturbine size, significantly longer calculation periods are required than for naturallyaspirated (NA) engines. For an initial estimate, the following data may be used:

• Single cylinder NA 4-stroke engine: 7200 degrees CRA

• Multi cylinder NA 4-stroke engine: 4320 degrees CRA

• Multi cylinder TC 4-stroke engine: 14400 degrees CRA

• Single cylinder 2-stroke engine: 7200 degrees CRA

• Multi cylinder 2-stroke engine: 4320 degrees CRA


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It is recommended to check whether stable conditions have been achieved using thetransient analysis feature of the BOOST post-processor.

3. Pipes

BOOST allows the user to specify either the calculation time step in degreecrankangles or a target cell size in mm. From the stability criterion for the pipe flow,(refer to Chapter 2.11) and from the input time step or target cell size, BOOST willcalculate the required cell size or the required time step respectively.

The time step for the calculation determines the accuracy (especially the frequencyresolution) of the calculation result. However, the number of cells in the pipe systemincreases dramatically with decreasing time step, which increases the required CPUtime.

To avoid unnecessary large output files, a separate time step for saving the results(time step for traces and animation output) must be specified.

� Note: CFL Multiplier is for advanced users and is currently underdevelopment.

4. Restart and Time Reset

Restart allows a calculation to be continued from a previously saved point.

Deselect Restart to start the new calculation with the initial values specified in thedata set. A data saving interval may be specified in order to save restart data atregular crank angle intervals. With a data saving interval of 0 degrees crankangle, norestart data will be written to the hard disk.

The restart files have same name as the model with the extension .rs0 and .rs1. Thefirst restart file is written to .rs0 and the second to .rs1. The third restart file iswritten to .rs0, thus only the penultimate and last restart files exist.

In the case of a restart, the program checks for the most recent file and takes thestored conditions for the initialization. The same directory as the input file is checkedfirst and then the parent directory of the input file (one level up) for each restart file.This allows individual cases to be restarted from other cases provided it cannot findboth restart files in its own case directory. Note that the restart file for a case is copiedto the parent directory on completion of that case. If neither .rs0 nor.rs1 exist, theprogram run will be interrupted with an error message.

Select Restart to start the new calculation with initial conditions taken from a restartfile. For a single calculation the maximum calculation period is the sum of thecalculation period of the initial calculation and that of the restart calculation.

To avoid long transient output, select Time Reset. In a restart, this causes only thetransient results from the restart on to be written to the .bst-file. The transientresults will be lost from the calculation where the restart file was obtained. If TimeReset is deselected, the complete history will be stored on the .bst-file and can beanalyzed using the transient analysis feature of the BOOST post-processor.

Refer to Section 3.2.6 for Convergence Control.


23-Jun-2004 3-25

3.2.4. FIRE Link ControlPlease refer to the BOOST-FIRE 1D-3D Coupling Manual for further information.

3.2.5. BMEP ControlThe BMEP Control offers a convenient way to reach a target BMEP value without theneed of using an ECU element.

According to the following formula (3.2.9) either the injected fuel mass (DI, GDI) ofselected cylinders or the flow-coefficient of selected restrictions (throttle, turbine waste-gate) is controlled.

( ) ( )∫ ⋅−−+=t

desCDUR

lowerupperguess dtBMEPBMEPt

ivcvcvcvc0

(3.2.9)

vc controlled value (injected fuel mass [kg] or flow coefficient [1] )

guessvc initial value for controlled value ([kg] or [1] )

uppervc , lowervc upper and lower limit for controlled value ([kg] or [1] )

i integral control gain [1/Pa]

CDURt cycle duration [s]

desBMEP target BMEP [Pa]

BMEP current BMEP[Pa]

Select BMEP Control in the Simulation Control / Globals window (Figure 3-8). Then selectthe BMEP Control sub-group in the tree to open the following window.

Figure 3-15: Simulation Control – BMEP Control Window

Specify the controlled elements and required parameters.


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3.2.6. Convergence ControlA convergence control can be performed, where either a convergence flag is set or thecalculation stops, if a prescribed convergence criterion is fulfilled.

Select Convergence Control in the Time Step Control window (Figure 3-14), then selectthe Convergence Control sub-group in the tree to open the following window.

Figure 3-16: Simulation Control – Convergence Control Window

The controlled elements, parameters and the corresponding threshold values can bespecified. Also Finish or Flag should be specified.

The convergence criterion is that the variation of the cycle averaged values (transients) ofsome parameters in BOOST elements over the last three consecutive cycles is less than aprescribed threshold.

The following elements and variables can be used for convergence control:

1. Cylinder:

• IMEP

2. Measuring point:

• Convergence (combination of pressure, velocity and temperature)

3. Turbocharger:

• Rotational speed

• Turbine discharge coefficient

• Turbine-to-total massflow

• Turbine work

• Compressor work


23-Jun-2004 3-27

• Compressor pressure ratio

• Boost pressure

4. Turbo Compressor:

• Compressor work


• Boost pressure

5. Positive Displacement Compressor:

• Compressor work


• Boost pressure

6. Plenum:

• Pressure

• Temperature

• Mass

For each selected variable the threshold value has to be specified.

3.2.7. Engine FrictionFor the calculation of the brake mean effective pressure (BMEP) and the brake specificfuel consumption (BSFC), the specification of friction mean effective pressure (FMEP) overengine speed and engine load is required.

Select the Engine Friction sub-group with the right mouse button and then select Add. Ifthe Engine Friction list is already available, click on it with the left mouse button to showthe input window. Select it with the right mouse button to access Edit, Remove and Add.

The engine friction may be defined versus engine speed for several loads expressed byBMEP. If only one friction curve is input, this curve will be used irrespective of the actualengine load. Values which are not specified explicitly in the table are obtained byinterpolation.

3.2.8. Volumetric EfficiencyThe BOOST pre-processor allows a plenum or a measuring point to be specified as areference location for the calculation of the air delivery ratio and the volumetric efficiencyrelated to intake manifold conditions.

Select SimulationVolumetric Efficiency and then select the desired element with the leftmouse button to display the relevant information. Select OK to complete the selectionprocess.


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3.3. Design a BOOST Calculation ModelTo create a calculation model, double-click the required element in the Element tree withthe left mouse button. In the working area move the displayed element to the desiredlocation with the left mouse button.

The positioning of the elements in the working area is assisted by a grid. The spacing ofthe grid points and the total size of the working area may be adjusted by selectingFile|Page Setup. If a symbol must be positioned between grid points, snapping to the gridcan be suppressed by pressing the shift key together with the left mouse button.

It is recommended to locate all required elements in the working area and then connectthem with the pipes. Finally the measuring points should be located in the pipes. Theelements are numbered automatically in the order which they were inserted.

3.3.1. Pipe Design

Select to insert a pipe. All possible points for a pipe attachment are indicated bysmall circles. Triangles are displayed for cylinders, air cleaners, catalysts and coolers torepresent intake and exhaust connections. Select the desired circle (or triangle) with theleft mouse button to attach the pipe to the element.

Define the shape of the pipe by placing as many reference points in the working area asrequired with the left mouse button. The last of the series of points must be located at apossible pipe attachment and then click the right mouse button to complete theconnection.

The appearance of a pipe may be modified by selecting it with the mouse and then selecting

. The pipe defined points become visible and can be moved with the left mousebutton. Additional points may be inserted by clicking the line between two referencepoints with the left mouse button. The modification is finished by clicking the right mousebutton.

Attachment points of pipes at a plenum, a variable plenum, an air cleaner, catalyst or aircooler may be relocated by dragging the attachment point with the left mouse button. Thedirection in which the pipe was designed is suggested as the direction of positive flow

(indicated by an arrow). The direction can be reversed by selecting .

3.4. Specification of Input Data for ElementsOnce the engine model is designed, the input data for each element must be specified.

3.4.1. PipeFor thermodynamic engine simulation programs which consider the gas dynamics of theintake and exhaust systems, the pipe element is one of the most important elements in theengine model. One dimensional flow is calculated in the pipes by solving the appropriateequations. This means that the pipe is the only element where the time lag caused by thepropagation of pressure waves or the flow itself is considered.


23-Jun-2004 3-29

BOOST allows the pipe diameter (given the same cross-sectional area), bend radius,friction coefficient, wall heat transfer factor, wall temperature, as well as the initial valuesfor pressure, gas temperature, A/F ratio, concentration of fuel vapor and concentration ofcombustion products to be specified depending on the location in the pipe by selecting

Table . If this feature is used, the pipe length must be specified first.

3.4.1.1. Bending RadiusFor table input of the pipe bend radius, the pipe radius for a whole section is taken as thevalue at the highest (or furthest) point defined. That is, the first value defined for tableinput of bend radius will effectively be ignored.

For example, in the following table the bending radius is,

120mm from 0 - 105mm (along the length of the pipe)

60mm from 105mm to 210mm

10000mm from 210mm to 315mm

Figure 3-17: Example Table Input for Bending Radius

The bend angle for a pipe section is then calculated from the length of the defined sectiondivided by the bending radius.

Using the same example as before, between 105mm and 210mm:

degrees 100radians 75.160

105 - 210 angle bend ===


3-30 23-Jun-2004

3.4.1.2. Friction CoefficientThe pipe wall friction coefficient depends on the surface roughness of the pipe, pipediameter and the Reynolds number of the flow in the pipe. For fully turbulent flow, thestandard values for the friction coefficient may be taken from the following table:

Pipe Diameter [mm]Material

(Roughness [mm]) 30 60 100 150

Plastics (0.0015) 0.011 0.01 0.01 0.01

Steel new (0.05) 0.023 0.019 0.017 0.016

Steel old (0.17) 0.032 0.027 0.023 0.021

Cast Iron (min. 0.25) 0.037 0.029 0.026 0.023

Cast Iron (max. 0.5) 0.044 0.037 0.031 0.028

Values between the specified diameters may be obtained by linear interpolation.

If the shape of the pipe cross-section is not circular, the friction coefficient must beincreased by the ratio of the geometric diameter and the hydraulic diameter. Thehydraulic diameter is defined as

CAdh

4= (3.4.1)

A cross-sectional area

C circumference of the cross-section

3.4.1.3. Heat Transfer FactorThe heat transfer coefficient for the calculation of the heat flux from or to the pipe walls iscalculated from the Reynolds’ analogy. The heat transfer factor allows the user to increaseor to reduce the heat transfer as the calculated heat transfer coefficient is multiplied bythis factor.

3.4.1.4. Variable Wall TemperatureBOOST can model the variation of the pipe wall temperature. This takes into account theheat transfer from the outer pipe wall to a surrounding ambient and heat flux from the gasflow to the pipe wall.

Additional input required for the variable wall temperature model is as follows,

• wall thickness of the pipe.

• specific heat capacity of the pipe material.

• temperature in the ambient of the pipe.

• cooling medium (air or water).

• characteristic velocity.


23-Jun-2004 3-31

The outer heat transfer coefficient is calculated using the cooling medium (air or water)and a characteristic velocity of the coolant. For a characteristic velocity of zero, a formulafor free convection is used for the calculation of the heat transfer coefficient. A forcedconvection formula is used for a non-zero characteristic velocity.

The following table gives some property values of materials used typically for enginemanifolds:

Density Specific Heat Specific HeatMaterial

[kg/m3] [kJ/kgK] Capacity [kJ/m3K]

Cast Iron 7200 0.545 3900

Steel 7840 0.46 3600

Aluminum 2700 0.91 2460

PVC (Plastics) 1390 0.98 1360

Ceramics 3500 0.84 2940

3.4.2. CylinderThe specifications for the cylinders cover the basic dimensions of the cylinder and thecranktrain (bore, stroke, compression ratio, conrod length, piston pin offset, firing order),plus information on the combustion characteristics, heat transfer, scavenging process andthe valve/port specifications for the attached pipes. Furthermore, initial conditions for thecalculation in the cylinder must be specified.

If a standard cranktrain is used, the piston motion is calculated from the stroke, conrodlength and piston pin offset. The direction of positive piston pin offset is defined as thedirection of the rotation of the crankshaft at Top Dead Center (TDC).

Figure 3-18: Standard Cranktrain


3-32 23-Jun-2004

Alternatively, BOOST allows a user-defined piston motion to be specified. This gives theuser freedom to simulate an unconventional powertrain. For a user-defined piston motionthe relative piston position should be specified over crank angle. The relative pistonposition is defined as the distance of the piston from the TDC position relative to the fullstroke. Zero degree crank angle corresponds to the Firing TDC of the selected cylinder.

Considering blow-by from the cylinder, an equivalent effective blow-by gap must bespecified as well as the average crankcase pressure. The actual blow-by mass flow iscalculated from the conditions in the cylinder and the pressure in the crankcase, and froman effective flow area which is calculated from the circumference of the cylinder and theeffective blow-by gap. The blow-by mass flow is lost. No recirculation to the intake may beconsidered.

For the specification of the combustion characteristics, either a heat release approach, atheoretical combustion cycle, a user-written subroutine or a truly predictive model can beselected from the pull down menu.

Thereby the total heat released during the combustion is calculated from the amount offuel which is burned in the cylinder and the lower heating value of the fuel.

For engines with internal mixture preparation the fuel is injected directly into the cylinderand the fueling is therefore part of the cylinder specification. For convenience, the fuelingmay be specified as the fuel mass which is injected into the cylinder or as a target A/Fratio, where the actual fueling is calculated every cycle from the mass of air in the cylinderand the specified target air/fuel ratio.

In the case of external mixture preparation, the fuel is fed to the intake system and thetotal heat supply is calculated from the amount of fuel in the cylinder at intake valveclosing. For modeling of gasoline direct injection engines, fuel may be added to thecylinder charge directly. In this case Cylinder Evaporation must be On and thenormalized rate of evaporation must be specified.

As for engines with internal mixture preparation, the evaporating fuel mass or the targetA/F-ratio can be set by the user. If the target A/F-ratio is selected, the injected fuel masswill be determined as the fuel mass required in addition to the aspirated fuel mass toachieve the desired A/F-ratio. If the A/F-ratio is already lower than the target A/F-ratio, nofuel will be added. The evaporation heat is used to calculate the cooling of the cylindercharge due to the evaporation of the fuel. The following table may be used to determinethe evaporation heat of different fuels:

Fuel Evaporation Heat [kJ/kg]

Methanol 1109

Ethanol 904

Gasoline 377-502

Gasoline (Premium) 419

Diesel 544-795

By specifying Heat from Wall greater than 0, the amount of evaporation heat covered fromthe combustion chamber walls can be input.


23-Jun-2004 3-33

For the definition of the heat release characteristics over crank angle, the following optionsare available:

• Single VIBE function

• Double VIBE function

• Single Zone Table

• Two Zone Table

• Woschni/Anisits (internal mixture preparation only)

• Hires et al. (external mixture preparation only)

• User Defined Model

• User Defined High Pressure Cycle

• Constant Volume Combustion

• Constant Pressure Combustion

• Motored

• Vibe 2 Zone

• Quasi-dimensional (external mixture preparation only in conjunction witheither a Physically Based or Empirically Based Combustion Model)

• Hiroyasu (internal mixture preparation only)

3.4.2.1. Combustion ModelSingle Vibe Function

The Vibe function is a very convenient method for describing the heat releasecharacteristics. It is defined by the start and duration of combustion, a shape parameter'm' and the parameter 'a'. These values can be specified either as constant values ordependant on engine speed (in rpm) and engine load (expressed as BMEP in bar). Select

Map to specify these values.

The heat release characteristic of gasoline engines, with essentially homogeneous mixturedistribution in the cylinder, is mainly determined by the flame propagation speed and theshape of the combustion chamber. A high flame propagation speed can be achieved withhigh compression ratio and high turbulence levels in the cylinder. In diesel engines on theother hand, the combustion characteristic depends strongly on the capabilities of the fuelinjection system, compression ratio and the charge air temperature.

For accurate engine simulations the actual heat release characteristic of the engine, (whichcan be obtained by an analysis of the measured cylinder pressure history), should bematched as accurately as possible. To obtain an estimate on the required combustionduration to achieve a certain crank angle interval between 10% and 90% mass fractionburned, the following chart may be used.


3-34 23-Jun-2004

Figure 3-19: Crank Angle related to Combustion Duration

For example:

A shape parameter of 1.5 is selected and the duration between 10% and 90% MFB is 30degrees CRA. The crankangle interval between 10% and 90% MFB related to thecombustion duration is 0.46. (read from the graph). Hence the combustion duration is30/0.46 = 65 degrees CRA. The point of 50% MFB is at 10 degrees CRA ATDC. Accordingto the graph the location of 50 % MFB after combustion start related to the combustionduration is 0.4. Thus the combustion start is calculated from 10 – 65 * 0.4 = -16 = 16degrees BTDC.

If measured heat release data is not available, the following standard values may be used tocomplete the engine model.


23-Jun-2004 3-35

Operating Point Comb. Duration Par. m

Gasoline Engine Standard Combustion System (2-Valve Engine)

1500 rpm WOT 60 degrees CRA 2.3


Standard Combustion System (4-Valve Engine)



Fast Burn Concepts



Passenger Car Naturally Aspirated (Full Load)

Diesel Engine (IDI) Rated Speed 90 degrees CRA 0.5

30% Rated Speed 65 degrees CRA 0.5

Turbocharged (Full Load)

Rated Speed 90 degrees CRA 1.0


Turbocharged Intercooled (Full Load)



Passenger Car Naturally Aspirated (Full Load)

Diesel Engine (DI) Rated Speed 80 degrees CRA 0.4









3-36 23-Jun-2004

Heavy Duty Naturally Aspirated (Full Load)

Truck Engine (DI) Rated Speed 70 degrees CRA 0.5








Medium SpeedEngines (DI, TCI)

Rated Output 65 degrees CRA 1.0

The start of combustion must be defined considering fuel consumption, peak cylinderpressure limitation, or knocking characteristics for gasoline engines.

The Vibe parameter 'a' characterizes the completeness of the combustion. For completecombustion, a value of 6.9 is required.

Double Vibe Function

For a good approximation of the double peak heat release characteristics of DI dieselengines (first peak due to premixed burning, second peak due to diffusion burning),BOOST allows two Vibe functions to be specified. These are superimposed during thecalculation process. Besides the start of combustion, the fuel allotment must be specified.The fuel allotment is defined as the fraction of fuel burnt with the characteristics of Vibe 1.

For each Vibe function, the combustion duration and the shape parameter 'm' must also bespecified.

Single Zone Table

For an optimum approximation of the actual heat release characteristics of an engine,BOOST allows reference points for the rate of heat release over crank angle to be specified.As the specified heat release characteristics will be normalized by the BOOST code (i.e.converted to percent of the total heat input per degree CRA), the dimension of the heatrelease values is of no importance.

Woschni/Anisits Model

The Woschni/Anisits Model predicts the Vibe parameter for engines with internal mixturepreparation if the parameters for one operating point are known. This model should beused for transient simulations as the heat release characteristics will change with differentoperating conditions. In addition to the Vibe parameters, the following data must bespecified to characterize the baseline operating point:

a) Engine speed

b) Dynamic injection nozzle openingc) Ignition delay

d) A/F ratioe) Cylinder conditions at intake valve closes


23-Jun-2004 3-37

Hires et al. Model

For gasoline engines the Hires et al. Model may be used for transient simulations.Similarly to the Woschni/Anisits model, the heat release characteristic is calculated fromthe Vibe parameters and some characteristic data of a baseline operating point.

User Model

If the heat release characteristics are set to User Defined Model, the subroutine usrcmb iscalled for the calculation of the rate of heat release. The source code of this subroutine isavailable for the user and any model may be implemented provided it is translated intovalid FORTRAN 90, compiled and linked to the rest of the code.

User-Defined High Pressure Cycle

If the User-Defined High Pressure Cycle is selected, the complete high pressure cycle isreplaced by the subroutine usrhpr.

� Note: Only experienced users should add user-defined subroutines.

Constant Volume Combustion

If Constant Volume Combustion is selected, the entire combustion takes place at thecrankangle specified by the user. In theory, constant volume combustion yields maximumefficiency at a certain compression ratio if no peak firing pressure limits have to beconsidered and the combustion timing is set to firing TDC.

Constant Pressure Combustion

If the combustion characteristics are set to Constant Pressure Combustion, BOOSTdetermines the rate of heat release with the following strategy from the specified peakcylinder pressure:

• If the maximum cylinder pressure at the end of compression is lower than thespecified peak cylinder pressure, the cylinder pressure is raised to the specifiedvalue by a constant volume combustion and the remaining fuel is burned insuch a way that this pressure is kept constant. This combination of constantvolume/constant pressure combustion is called the Seiliger process.

• If the maximum cylinder pressure at the end of compression exceeds thespecified value, constant pressure combustion is initiated when the cylinderpressure drops below the specified value during the expansion stroke.

In theory constant pressure combustion yields maximum efficiency for a certain peak firingpressure if the compression ratio is selected to achieve the maximum sustainable peakfiring pressure at the end of the compression stroke.

The Seiliger process yields maximum efficiency for a certain combination of peak firingpressure and compression ratio.

Motored

If the heat release characteristics are set to Motored, no combustion will take placeirrespective of the amount of fuel aspirated or injected.


3-38 23-Jun-2004

Vibe 2 Zone Combustion Model

For the Vibe 2 zone combustion model, the same input as for the single Vibe function isrequired. However, instead of one mass averaged temperature, two temperatures (burntand unburned zone) are calculated. This model also predicts the knocking characteristicsof the engine, provided the actual rate of heat release is described properly by the Vibefunction specified.

Quasi-Dimensional Combustion Model

The quasi-dimensional approach, as the physically or empirically based combustion model(PBCM or EBCM), in BOOST predicts the rate of heat release for homogenous chargespark ignition engines. The combustion simulation is triggered at ignition timing.

A simple turbulence model is used for the determination of the entrainment rate of freshcharge into the flame. The input required by this model are model constants for thecalculation of the turbulent kinetic energy and turbulent length scale at intake valvecloses.

If the design of the combustion chamber features a small piston to head clearance, aimingto produce squish flow at the end of the compression stroke, a modified turbulence modelcan be used. In this case a Flow Constant for the turbulence generation by squish flowmust be specified by the user.

Provided that the cylinders feature identical data, the ROHR transfer option to othercylinders may be activated. In this case, the quasi-dimensional combustion model is onlyapplied to Cylinder 1 to calculate the rate of heat release curve. The obtained curve istransferred to the remaining cylinders. For these cylinders, the high pressure cycle will besimulated with a single zone model.

In addition to the model constants, the quasi-dimensional combustion model requires atable specifying the contact areas between burned zone and head, liner, piston andunburned zone (i.e. the free flame area) and the burned zone volume versus flame radiusand crankangle (piston position).

For simple geometries, the table can be generated by BOOST. Select the ChamberGeometry Calculation subgroup to input the main dimensions of the combustion chamber.

For the cylinder head, the following shapes can be considered (required input as shown inthe sketches):


23-Jun-2004 3-39

Figure 3-20: Flat Cylinder Head

Figure 3-21: Disc Chamber Cylinder Head

Figure 3-22: Spherical Cylinder Head


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Figure 3-23: Backset Special Cylinder Head

Figure 3-24: Pent Roof Cylinder Head

In addition, the user must select the shape of the piston top from the following list(required input as shown in the sketches):


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Figure 3-25: Flat Piston Top

Figure 3-26: Heron Piston Top

Figure 3-27: Spherical Bowl Piston Top


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Figure 3-28: Spherical Piston Top

Figure 3-29: Pent Roof Piston Top

If there is an offset between spark plug location and the cylinder axis as well as an offsetbetween the center of the piston bowl or top, the angle between spark plug and bowl or topcenter must be input according to the definition shown in the following sketch.


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Figure 3-30: Definition of Angle between Spark Plug and Bowl/Top Center

For a pent roof head or a pent roof piston, the spark plug position must be defined by tworectangular coordinates as shown in Figure 3-30.

Alternatively, the table can be generated externally and the name of the file can bespecified by the user. The file must be a sequential formatted ASCII file and may containcomment lines marked with a “#” in the first column.

� Note: The geometry file format has changed from version 3.2.

Figure 3-31: Definition of Spark Plug Position


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The file format can be seen in the following example.

TYPE 2

#

# Bore = 84.0mm, Stroke = 90.0mm, Compression Ratio = 9.0

# Headtype: flat

# Spark Plug Position: x = 0.0mm, y = 0.0mm, z = 0.0mm

# (Position x=0, y=0, z=0 means center of bore at head bottom)

# Pistontype: flat

# Number of flame radii

NUMFLARAD 101

# Number of piston positions

NUMPISPOS 101

# total head area [mm2]

TOTHEADAREA 5541.77

# minimal liner area [mm2]

MINLINAREA 2968.81

# total piston area [mm2]

TOTPISAREA 5541.77

# volume in head [mm3]

HEADVOL 0.00

# volume in piston [mm3]

PISVOL 0.00

# minimum piston position [-]

PISPMIN 0.00

# maximum piston position [-]

PISPMAX 90.00

# increment of piston position [-]

PISPINC 0.03

# minimum flame radius [mm]

FRADMIN 0.00

# maximum flame radius [mm]

FRADMAX 99.32

# increment of flame radius [mm]

FRADINC 0.99

# minimum burned zone volume[mm3]

BVMIN 0.00

# maximum burned zone volume[mm3]

BVMAX 525001.01

# flame front radii:

FLAMERADII

0.000000E+00 0.993177 ...

# contact area burned zone - cylinder head versus flame front radius [mm2]

HEADAREA

0.000000E+00 3.09887 ...

# depending on piston position:

# contact area burned zone - liner versus flame front radius [mm2]

# contact area burned zone - piston versus flame front radius [mm2]

# contact area burned zone - unburned zone versus flame front radius [mm2]

# burned zone volume versus flame front radius [mm3]

# data for piston position:

PISPOS 0.000000

LINERAREA


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0.000000E+00 0.000000E+00 ...

PISTONAREA

0.000000E+00 0.000000E+00 ...

FREEFLAMES

0.000000E+00 6.19773 ...

BURNEDVOL

0.000000E+00 2.05182 ...

# data for piston position:

PISPOS 0.027930

LINERAREA

0.000000E+00 0.000000E+00 ...

PISTONAREA

0.000000E+00 0.000000E+00 ...

FREEFLAMES

0.000000E+00 6.19773 ...

BURNEDVOL

0.000000E+00 2.05182 ...

.

Hiroyasu Combustion Model

The combustion model developed by Professor Hiroyasu predicts the rate of heat release ofDI Diesel engines. The model requires the swirl ratio as input for the in-cylinder chargemotion. In addition, the combustion bowl diameter, limiting the free spray length, shouldbe specified. The density and temperature at which the fuel is injected is required for theproperties of the liquid fuel. The fuel’s activation energy influences the ignition delay. Ifthe diameter of a fuel droplet gets smaller than the minimum droplet size specified,immediate evaporation is assumed. For calculating the spray behavior, the number ofnozzle holes, their diameter and discharge coefficient must be specified. The number ofpackages in radial direction defines the number of subdivisions in radial direction of thespray.

The rate of injection defining the amount of fuel injected per degree crankangle must bespecified. The specified curve is normalized, so that the area beneath the curve is equal toone. The actual amount of fuel injected is obtained from multiplying the normalized rateof injection with the total fuel mass.

For each radial subdivision of the spray, define a Sauter mean diameter and a relativemass content in the Package Data subgroup. The relative mass content influences theradial fuel mass distribution in the spray. The model constants for calibrating the modelfor a particular engine comprise of constants for the calculation of the ignition delay, theair entrainment into the spray (overall, before ignition and wall impingement and afterwall impingement) the thickness of the spray at the wall after impingement, theentrainment of burnt gases into the spray and a constant for the amplification ofturbulence intensity. Constants for the soot model influencing soot formation and itsconsumption (oxidation) complete the input for the Hiroyasu combustion model for thecylinder under consideration.


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Provided that the cylinders feature identical data the ROHR transfer option to othercylinders may be activated. In this case Hiroyasu’s model will only be applied to cylinderone to calculate the rate of heat release curve. The obtained curve is transferred to theremaining cylinders. For these cylinders, the high pressure cycle will be simulated with asingle zone model.

AVL MCC Model

The AVL MCC model requires the number of injector holes, the hole diameter, thedischarge coefficient of the injector holes and the rail pressure to calculate with theeffective hole area, the velocity and thus the kinetic energy of the fuel jet.

The table containing the rate of injection determines injection rate. The input isnormalized and used with the fuel specified in the general cylinder box to determine thefuel injected each time step.

The ignition delay is calculated using the modified ignition delay model developed byAndree and Pachernegg. To fit the delay to measured data it can be influenced by theignition delay calibration factor.

The model parameters are normalised, therefore with a value of 1 good results should beobtained. The following parameters control the rate of heat release and the NOxproduction.

1. The ignition delay calibration factor influences the ignition delay, higher values resultin longer ignition delays.

2. The combustion parameter has the greatest influence on the ROHR shape. A highervalue results in a faster combustion.

3. The turbulence parameter controls the influence of the kinetic energy density whilethe dissipation parameter influences the dissipation of the kinetic energy.

4. Dissipation parameter controls the turbulence dissipation.

5. The NOx production parameter has influence on the NOx result.

6. The EGR influence parameter controls the influence of EGR on combustion.

7. The premixed combustion parameter determines the fraction of fuel injected duringignition delay burned during premixed combustion, a value of 0.7 should be used asdefault.


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Figure 3-32: AVL MCC Combustion Model Window

3.4.2.2. Divided Combustion ChamberIf an engine with divided combustion chamber is to be simulated, the user may specify thepre chamber data after selecting Chamber Attachment in the General folder of theCylinder element. The basic input of the pre chamber is its volume and the initialconditions (pressure, temperature and gas composition) at exhaust value opens. Thegeometry of the connecting pipe is described by its length and diameter. In addition theturbulent wall friction coefficient, the wall temperature and a heat transfer amplificationfactor must be input.

In order to consider particular pressure losses resulting from multi dimensional flowphenomena at the connecting pipe orifice, BOOST requires the specification of flowcoefficients for in-flow and out-flow at the connecting pipe. The flow coefficients aredefined as the ratio between the actual mass flow and the loss-free isentropic mass flow forthe same stagnation pressure and the same pressure ratio.

The flow coefficients may be specified either as constant values or in a Table asfunctions of time in seconds, time in degrees crank angle or pressure difference betweencylinder and chamber.

For in-flow (flow into the chamber) the pressure difference is defined as the static pressurein the connecting pipe minus the pressure in the chamber. For out-flow it is defined as thepressure in the chamber minus the static pressure in the connecting pipe.

The flow coefficients for flow from the chamber into a pipe depend mainly on theprotrusion of the pipe end through the wall in which it is installed and on its bellmouthcharacteristics.


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The following table may be used to determine flow coefficients for well manufactured pipeattachments. Values between the specified points can be obtained by linear interpolation.

Relative Inlet RadiusRelative Edge

Distance 0.0 .02 .06 .12 .20

0.0 .815 .855 .910 .950 .985

0.025 .770 .840 .910 .950 .985

0.075 .750 .830 .910 .950 .985

0.20 .730 .825 .910 .950 .985

>0.50 .710 .820 .910 .950 .985

The relative inlet radius is defined as the inlet radius divided by the (hydraulic) pipediameter.

The relative edge distance is defined as the protrusion of the pipe end through the wall inwhich it is mounted divided by the (hydraulic) pipe diameter. A relative edge distanceequal to zero represents a pipe mounted flush with the wall.

To specify the heat release characteristics in the chamber, the user may use a Vibe-function, a double Vibe function or a single zone table.

If the wall heat transfer in the chamber is turned on, the box for the input of the requireddata is accessed. The data comprise the chamber geometry (spherical or user-defined), thefriction coefficient for the calculation of the friction torque, the connecting pipeeccentricity, the chamber wall temperature and a calibration factor. For a user definedchamber geometry the surface area, the characteristic radius for the calculation of the heattransfer coefficient by the Nußelt equation, and the inertia radius of the chamber are to bedefined by the user.

If a variable wall temperature is to be considered, the wall thickness of the pre chamber,the conductivity of the material and its heat capacity as well as the coolant temperatureand the outer heat transfer coefficient must be input.

3.4.2.3. Heat TransferThe following heat transfer models are available for the cylinder:

• Woschni 1978 and 1990

• Hohenberg

• Lorenz 1978 and 1990 (Cylinders with attached chamber only)

• AVL 2000

Alternatively, None can be selected.

In addition to the heat transfer coefficient provided by the heat transfer model, the surfaceareas and wall temperatures of the piston, cylinder head and liner must be specified.

The wall temperatures are defined as the mean temperature over the surface.

A calibration factor for each surface may be used to increase or to reduce the heat transfer.


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For the surface areas the following guidelines may be used:

Piston:

DI diesel engines with a bowl: Surface area is approximately 1.3 to 1.5 times the bore area.

SI engines: Surface area is approximately equal to the bore area.

Cylinder Head:

DI diesel engines: Surface area is approximately equal to the bore area.

SI engines: Surface area is approximately 1.1 times the bore area.

Liner with Piston at TDC:

The area may be calculated from an estimated piston to head clearance times thecircumference of the cylinder.

Wall temperature must be specified at the piston TDC and BDC positions. Between thosepositions a special temperature profile is assumed (refer to Section 2.1.1).

Refined Liner Layer Discretization:

If detailed information about the liner wall temperature distribution along the liner isavailable, the option “Layer Discretization” allows the User to input the wall temperaturedependent on the distance from cylinder head.

This discretization can also be used in combination with an external link element (LinerLayer Wall Temperature Actuator, Liner Layer Wall Heat Flow Sensor).

For both Woschni formulae, the user must specify whether the engine features a dividedcombustion chamber.

Select IDI for IDI diesel engines (swirl chamber or pre-chamber combustion system).Select DI for DI diesel engines and gasoline engines.

In order to consider the influence of the in-cylinder charge motion on the heat transfercoefficient, the in-cylinder swirl ratio (defined as the speed of the charge rotation relativeto engine speed) must be specified.

Select Variable Wall Temperature to calculate the heat balance of the combustion chamberwalls. For each wall (head, piston and liner) an effective wall thickness together withmaterial data must be specified. Conductivity and heat capacity are required and thefollowing list provides some typical materials:

Heat Capacity ConductivityMaterial

[kJ/m3K] [W/mK]

Cast Iron 3900 53

Steel 3600 48

Aluminum 2460 221

Ceramics 2940 5.5

For the heat transfer to the coolant (head and liner) and engine oil (piston), an averageheat transfer coefficient and the temperature of the medium must be specified.

For the heat transfer in the ports, a modified Zapf-model is used (refer to Section 2.1.2).


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3.4.2.4. ScavengingThree scavenging models are available in the General window:

• Perfect mixing: The gas flowing into the cylinder is mixed immediately withthe cylinder contents. The gas leaving the cylinder has the same compositionas the mixture in the cylinder. The perfect mixing model is the standardscavenging model for the simulation of 4-stroke engines.

• Perfect displacement: A pipeline model is used to determine the exhaustgas composition. This means that all residual gases in the cylinder areexhausted first. Only when no more residual gases are left in the cylinder, isfresh charge lost to the exhaust.

• User-defined scavenging model: For the simulation of 2-stroke engines,the specification of the scavenging efficiency over scavenge ratio is required todefine the quality of the port arrangement with respect to scavenging flow.This data are usually taken from literature or from the results of scavengingtests. The scavenging efficiency is defined as the volume of fresh air in thecylinder related to the total cylinder volume. The scavenge ratio is defined asthe total volume of air which entered the cylinder related to the total cylindervolume.

Figure 3-33 shows a comparison of the scavenging efficiency curves of the perfectdisplacement and the perfect mixing models.

Figure 3-33: Scavenging Models


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3.4.2.5. Valve / Port DataFor each pipe attached to a cylinder, the user must specify whether this port is controlledby a valve or by the piston (piston control is only feasible for 2-stroke engines). If thecylinder features a combustion chamber, the pipe may be also declared to be attached tothe chamber. In this case, the port may be either controlled by a valve or with thestandard definition of flow coefficients.

Click on the input field with the left mouse button to open the submenu shown in thefollowing window.

Figure 3-34: Valve Port Specifications Window

If the heat transfer in the intake and exhaust ports must be considered, the specification ofthe port surface area and the mean port wall temperature is required (valve controlled portonly).

For the calculation of the heat balance of the port wall, similar data as for the combustionchamber walls (i.e. the average thickness, the heat capacity and the conductivity of thematerial) is required.

For the calculation of the summed up intake and exhaust mass flow characteristics, theuser must specify whether the considered port is an intake or exhaust port. A pipeattached to the combustion chamber is considered as an intake.

For valve controlled ports the inner valve seat diameter is required for the calculation ofthe port wall heat transfer coefficient, as well as for the conversion of normalized valve liftto effective valve lift.

The valve lift is defined by the valve lift curve and by the valve clearance.

By specifying the crank angle of the first valve lift value and the cam length, the crankangle range in the table is defined. The number of reference points for the valve lift curvecan be specified directly or by inputting a constant crank angle interval between two valvelift points.

After completing the input of reference points, the input is presented in the graphicswindow for immediate control purposes.

If a valve lift curve is already specified in the table, a new specification of the timing of thefirst valve lift shifts the entire valve lift curve.


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If the cam length is changed, a shorter or longer valve lift curve will be calculated from thebaseline valve lift curve under the assumption of similar valve velocities.

The actual valve lift at a certain crank angle is calculated from the valve lift, specified inthe valve lift curve, minus the valve clearance, as shown in the figure below:

Figure 3-35: Calculation of Effective Valve Lift

For Valve Controlled valves a modification of the baseline valve lift curve can be specifiedin the Modification of Valve Lift Timing. This is possible for each individual valveconnected to a cylinder so that different modifications can be applied to different intake (orexhaust) valves of a multiple valve model.

Figure 3-36: Modification of Valve Lift Timing


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The possible modifications using these options is shown in the following figures(dashed lines are the baseline valve lift curves before modification).

Figure 3-37: Positive intake valve opening and closing shift (same value)

Figure 3-38: Positive intake valve closing shift only

Figure 3-39: Positive intake valve opening shift only

Figure 3-40: Positive exhaust closing shift and positive intake opening shift


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Figure 3-41: Positive exhaust opening and closing shift (same value)

Figure 3-42: Positive exhaust opening shift only

Figure 3-43: Positive exhaust valve closing shift only

Figure 3-44: Positive exhaust valve closing shift and negative intake opening shift


23-Jun-2004 3-55

Figure 3-45: Negative exhaust shifts (same value) and positive intake shifts (samevalue)

To consider particular pressure losses resulting from multi dimensional flow phenomenawhich cannot be directly predicted by the program, BOOST requires the specification offlow coefficients of the ports. The flow coefficients are defined as the ratio between theactual mass flow and the loss-free isentropic mass flow for the same stagnation pressureand the same pressure ratio.

BOOST allows the specification of the flow coefficients of ports as a function of thepressure ratio at the port. For the flow into the cylinder, the pressure ratio is defined asthe pressure in the cylinder divided by the stagnation pressure in the port (pressure ratio<1). For flow out of the cylinder, the pressure ratio is defined as the cylinder pressuredivided by the static pressure in the port (pressure ratio > 1).

BOOST interpolates linearly the flow coefficients of pressure ratios which are less thanand greater than one. It does not interpolate between the largest pressure ratio smallerthan one and the smallest pressure ratio larger than one. Outside the defined range thevalue for the smallest/largest pressure ratio is taken. Figure 3-46 illustrates thisprocedure:

Figure 3-46: Interpolation of Flow Coefficients

The program interprets the specified flow coefficients of the ports are related to the cross-section of the pipe attached to the cylinder. If the measured flow coefficients of the portsare related to a different cross-section, the scaling factor for the effective flow area may beused to overcome this and achieve the correct effective flow areas.

Usually, the flow coefficients are related to the inner valve seat area. In this case, thescaling factor may be calculated easily from the following formula:


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2

2

pi

vivsc d

dnf ⋅= (3.4.2)

scf scaling factor

vn number of valves modeled with the port under consideration

vid inner valve seat (= reference) diameter

pid attached pipe diameter

The flow coefficients of the ports must be specified over valve lift. This can be done eitherby specifying the flow coefficients directly over valve lift or over the normalized valve lift.The latter is defined as valve lift related to the inner valve seat diameter (AVL definition).The advantage of using the normalized valve lift as a parameter is that the flowcoefficients of similar ports can be used without modification.

For intake ports, the swirl characteristics versus valve lift may also be specified by theuser. With this input, a dynamic in-cylinder swirl is calculated. In addition, a static swirlwith AVL's standard lift curve and the engines actual lift curve will be calculated for eachport.

The following options are available to specify the flow characteristics and the openingcharacteristics of the ports of 2-stroke engines:

• Specification of the effective flow area: The user may specify theeffective flow area over piston position or over crank angle. If, in addition tothe effective flow area, the port geometry is specified, the pre-processorcalculates the flow coefficients for the port automatically. They may be used todetermine effective flow areas for slightly modified ports (e.g. modified timing).

• Specification of port geometry and flow coefficients: Instead ofspecifying the effective flow area directly, the user may specify the portgeometry over piston position or crank angle, and the flow coefficients of theport depending on the port opening. The port geometry, i.e. the port widthover piston position or crank angle must be specified for each port opening. Ina BOOST model one port may feature more than one opening so the number ofopenings must be specified.

Similar to the valve controlled ports, BOOST allows the effective flow areas of the ports asa function of pressure ratio at the port to be specified. The definition of pressure ratio isthe same as described for valve controlled ports.

The scaling factor may be used to increase or to decrease the specified flow areas by aconstant factor.

The effective flow areas of the ports may be specified either as a function of the distancebetween the actual position of the piston and its TDC position, or on crank angle. If theeffective flow area is specified over crank angle, the full crank angle range between portopening and port closing must be covered. It is the user’s responsibility to ensure that thetiming relative to BDC is symmetrical.


23-Jun-2004 3-57

The flow coefficients are defined as the actual mass flow related to the specific mass flowrates calculated from the isentropic flow equations for the same stagnation pressure andtemperature and for the same pressure ratio.

The definition of the port geometry consists of the specification of the port openings, theport width (either as chord or as developed length) over the distance from the upper portedge, and the minimum duct cross-section.

The port opening timing may be specified either in degrees crank angle after TDC or as thedistance between the upper port edge and the TDC position of the piston top (location ofupper port edge below TDC), Figure 3-47.

Figure 3-47: Definition of Window Geometry

The minimum duct cross-section is required to determine the upper limit for the geometriccross-section of the port. It may be specified directly or calculated from the port openingdimensions and the port angles (angles between the port centerline and the horizontal andradial planes), Figure 3-48.

Figure 3-48: Calculation of Minimum Duct Cross Section


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The flow coefficients of the ports of two-stroke engines are related to the actual portopening area which varies with piston position. They must be specified as a function ofdistance from the upper port edge.

3.4.3. Measuring PointUsing measuring points, the user can access flow data and gas conditions over crank angleat a certain location in a pipe. The location of the measuring point must be specified as itsdistance from the upstream pipe end.

The user may select the output for a measuring point.

Standard : pressure, flow velocity, temperature, Mach number and mass flow rates.

Extended : Additional output of stagnation pressure, stagnation temperature, enthalpyflow, fuel concentration, combustion products concentration, fuel flow,combustion products flow, forward and backward pressure and velocity waves.Additional acoustic data is also written to the acoustic folder for measuringpoints with extended output selected.

3.4.4. Boundaries

3.4.4.1. System BoundaryThe system boundary element provides the connection of the calculation model to a user-definable ambient.

General

Select Saving of Energy and Mass for Backflow to determine the temperature conditionfor Inflow by the accumulated Outflow.

Boundary Type:

Standard is the default setting for a system boundary. No special featuresare used.

Anechoic Termination suppress backward pressure waves. This can beused for the termination of an acoustic model.

Acoustic Source generates a varying pressure in the ambient. Used forgenerating source conditions for acoustic models.

Boundary Conditions

Both local or global boundary conditions can be set. In the later case one of the predefinedglobal sets can be used to specify the boundary conditions.

The ambient conditions (pressure, temperature, air/fuel ratio, fuel vapor and combustion

products) must be specified either as constant values or in a Table as functions of timeor crank angle.


23-Jun-2004 3-59

If internal mixture preparation is considered, the input of fuel vapor and combustionproducts is disabled. In this case the A/F ratio represents the A/F ratio of the mixture ofair and combustion products in the ambient and no unburned fuel in the ambient isallowed.

If external mixture preparation is considered, the A/F ratio represents the A/F ratio of thecombustion gases in the ambient. In addition, the mass fractions of the combustionproducts and the fuel vapor must be specified.

The input of user-defined concentrations is disabled if the number of user-definedconcentrations was set to zero.

Flow Coefficients

The flow coefficients for flow from the ambient into a pipe depend mainly on theprotrusion of the pipe end through the wall in which it is installed and on its bellmouthcharacteristics.


Relative Inlet RadiusRelative Edge

Distance 0.0 .02 .06 .12 .20

0.0 .815 .855 .910 .950 .985

0.025 .770 .840 .910 .950 .985

0.075 .750 .830 .910 .950 .985

0.20 .730 .825 .910 .950 .985

>0.50 .710 .820 .910 .950 .985

The relative inlet radius is defined as the inlet radius divided by the (hydraulic) pipediameter r/Dh.

The relative edge distance is defined as the protrusion of the pipe end through the wall inwhich it is mounted, divided by the (hydraulic) pipe diameter L/Dh. A relative edgedistance equal to zero represents a pipe mounted flush with the wall, refer to Figure 3-49.

Figure 3-49: Mounting of a Pipe End


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For flow out of a pipe into the ambient, a flow coefficient of 1.0 is normally used if there isno geometrical restriction in the orifice.

Acoustic Source

The numerical generation of an acoustic periodic signal (white noise) is carried out as thesum of N sinusoidal pressure oscillations with a fixed amplitude, ∆p, and frequencymultiple of the fundamental frequency, f.

( )∑=

+∆+=N

nno ftpptp

12sin)( ϕπ

po is a constant value representing the mean ambient pressure. A random phase is used foreach sinusoidal component of the sum.

Minimum frequency: This is also the fundamental frequency for the pressurecalculation.

Maximum frequency: Frequency is incremented from the minimum frequency insteps of the fundamental frequency (also the minimum frequency) until the maximumfrequency is reached.

Mean Pressure, po: Base pressure about which the pressure is varied. This can beused to control the mean flow during the simulation depending on the terminationconditions.

Delta Pressure, ∆p: The acoustic pressure of the source.

3.4.4.2. Aftertreatment BoundaryThe aftertreatment boundary element provides the connection of the aftertreatmentanalysis model to a user-definable ambient. Two aftertreatment boundaries (one inlet andone outlet) can be connected to one catalytic converter model or one diesel particulatefilter. The application of this type of boundary can only be used for aftertreatment analysissimulations. More detailed information can be found in the BOOST AftertreatmentManual.

�Note: Input values for an aftertreatment boundary are considered to beperiodic. This means the defined period is repeated until the end of thesimulation.


23-Jun-2004 3-61

3.4.4.3. Internal BoundaryThe internal boundary element allows boundary conditions for the calculation model to bespecified directly in the last cross section of a pipe where a model ends. It is extremelyhelpful if measured boundary conditions in the intake and exhaust pipe of a cylinder areavailable. In this case a simplified sub-model of the engine between the two measuringpoints is made. An internal boundary is placed at the location of the measuring point, andthe measured pressure and temperature over crank angle are specified.

Figure 3-50: Engine Cylinder Sub-model

General

Select Save Energy and Mass for Backflow to determine the temperature boundarycondition when flow is into the pipe from the accumulated flow out of the pipe into theboundary.

Boundary Conditions

Both local or global boundary conditions can be set. In the later case one of the predefinedglobal sets can be used to specify the boundary conditions.

The gas conditions in the pipe (pressure, temperature, air/fuel ratio, fuel vapor and

combustion products) must be specified either as constant values or in a Table as afunction of time or crank angle.

If internal mixture preparation is selected, the input of fuel vapor and combustionproducts is disabled. In this case the A/F Ratio represents the A/F Ratio of the mixture ofair and combustion products in the pipe, and no unburned fuel in the pipe is allowed.

If external mixture preparation is considered, the A/F ratio represents the A/F ratio of thecombustion products in the pipe. In addition, the mass fractions of the combustionproducts and of the fuel vapor in the pipe must be specified.

The input of user-defined concentrations is disabled if the number of user-definedconcentrations has been set to zero.


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3.4.5. Transfer Elements

3.4.5.1. Flow RestrictionThe flow restriction element is used to consider a distinct pressure loss at a certainlocation in the piping system. This pressure loss may be caused by a geometricalrestriction of the pipe cross-section (e.g. a butterfly valve, an orifice plate, etc.), or by aflow separation at that location caused by a step in the diameter of the piping or by anarrow elbow.

For a flow restriction, flow coefficients must be specified for both possible flow directions.The flow coefficients are defined as the ratio between the actual mass flow and the loss-free isentropic mass flow for the same stagnation pressure and the same pressure ratio.

The flow coefficients of restrictions depend very much on the design details of therestriction (control valve, orifice, flow separation, sudden change of diameter etc.).Standard values for the flow coefficients can only be given for a sudden change of thediameter.

For a sudden expansion of the flow (flow direction from a smaller to a larger diameterpipe), the flow coefficients depend mainly on the cross-sectional area ratio. This influenceis considered automatically by the BOOST program. The values specified in the inputcover only the deterioration over the ideal geometry. Therefore, a value of 1.0 isrecommended for a well manufactured diameter step.

For a sudden contraction of the flow (flow from a larger to a smaller diameter pipe), theflow coefficients depend again mainly on the cross-sectional area ratio and on the relativeradius at the inlet to the smaller pipe. This is defined as the actual radius divided by the(hydraulic) diameter of the smaller pipe (refer to Figure 3-51).

Figure 3-51: Sudden Diameter Change


23-Jun-2004 3-63

Area Ratio (d/D)²Relative

Radius (r/d) 0.0 .4 .7 .9 1.0

0.0 .815 .865 .915 .960 1.0

0.02 .855 .895 .935 .970 1.0

0.06 .910 .935 .960 .980 1.0

0.12 .955 .970 .980 .990 1.0

>0.20 .985 .990 .995 .998 1.0

Values between the specified points can be obtained by linear interpolation.

For all other types of restriction, the flow coefficients must be determined by steady stateflow tests or estimated from the geometrical restriction of the pipe cross-section.

� Note: In BOOST the flow coefficients of restrictions are always related tothe minimum attached pipe cross-section.

BOOST allows the values for the user-defined concentrations to be defined at each flowrestriction by selecting the respective switch. If this option is selected, the specified valuesfor the user-defined concentrations will be permanently attributed to the mass flow at thislocation.

3.4.5.2. Rotary ValveRotary valves are used to control the air flow in a pipe as a function of crank angle or time.A typical application is the control of the intake process of a two-stroke engine. In theBOOST system the rotary valve is treated in a similar way to the flow restriction

For the rotary valve the flow coefficients must be specified for both possible flow directionsdepending on the time in seconds or on crank angle.

The flow coefficients are defined as the ratio between the actual mass flow in the loss-freeisentropic mass flow for the same stagnation pressure and the same pressure ratio.

� Note: For the rotary valve, the flow coefficients are related to theminimum pipe cross-section attached.

BOOST allows the values for the user-defined concentrations to be defined at each rotaryvalve by selecting the respective switch. If this option is selected the specified values forthe user-defined concentrations will be attributed to the mass flow at this location.


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3.4.5.3. Check ValveA check valve is a pressure actuated valve used to prevent reverse flow. Two models areavailable:

1. Simplified Check Valve Model

The flow resistance of the valve only depends on the pressure difference over the checkvalve. No inertia effects of the valve are considered. In this case BOOST requires thespecification of flow coefficients for both possible flow directions as a function of thepressure difference over the check valve.

2. Full Check Valve Model

The dynamic valve lift is calculated using an equivalent spring-damper-mass system.The flow coefficients must be specified as a function of the valve lift.

The moving masses, damping coefficient, valve spring pre-load and valve spring ratemust be defined. Furthermore, the specification of reference areas is required in orderto calculate the forces acting on the valve resulting from the pressure difference overthe valve. BOOST allows different reference areas for the closed valve and openedvalve to be specified.

The maximum valve lift may be limited as is often the case in real check valveconfigurations.

Flow coefficients as a function of valve lift must be specified for both possible flowdirections.

BOOST allows the values for the user-defined concentrations to be defined for each checkvalve by selecting the respective switch. If this option is selected, the specified values forthe user-defined concentrations will be permanently attributed to the mass flow at thislocation.

3.4.5.4. Fuel Injector / CarburetorThe injector element is used for engines with external mixture preparation to add the fuelto the air in the intake system.

� Note: Wall film transport and evaporation model for the fuel are currentlynot available. Only completely vaporized fuel is added.

To consider the particular pressure losses resulting from multi-dimensional flowphenomena which cannot be predicted by the program, BOOST requires the specificationof flow coefficients at the fuel injector. The flow coefficients are defined as the ratiobetween the actual mass flow and a loss-free isentropic mass flow for the same stagnationpressure and the same pressure ratio.

The fuel supply is specified by the A/F ratio.


23-Jun-2004 3-65

If the carburetor model is used, the instantaneous mass flow at the carburetor position isused together with the specified A/F ratio to calculate the amount of fuel supplied. Due tooscillating flow at the carburetor location a considerable enrichment of the mixture mayoccur.

�Note: It is necessary to check the actual A/F ratio in the cylinder and tocorrect the A/F ratio at the carburetor if the values are different to thosedesired.

For the fuel injector model, a measuring point at the position of the air flow meter mustbe specified. In this case the fueling is calculated from the mass flow at the air flow meterposition and the specified A/F ratio. As the air flow meter usually serves more than oneinjector, the percentage of the total air flow served by each injector must be specified.

3.4.5.5. Pipe JunctionFor the junction of pipes three sub-models are available:

1. Constant Pressure Model

Flow coefficients for flow to the junction and flow out of the junction must be specifiedexplicitly by the user for each pipe attachment. The flow coefficients for the pipeattachments may be specified either as constant values or as functions of time inseconds, time in degrees crank angle or on the pressure difference at the pipeattachment. For in-flow (flow into the junction), the pressure difference is defined asthe static pressure in the pipe minus the pressure at the junction, and for out-flow asthe pressure at the junction minus the static pressure in the pipe.

� Note: This model corresponds to a plenum with zero volume. Themomentum of flow into the constant pressure junction is lost.

2. Constant Static Pressure Model

This junction model enforces the same static pressure in all pipe cross sectionsattached to the junction.

3. Refined Model (Three-way Pipe Junctions)

An accurate calculation model based on the equations for orifice flow is available. Thismodel requires flow coefficients for each flow path in each possible flow pattern, whichadds up to two times six flow coefficients. Figure 3-52 shows the qualitative trend ofthese flow coefficients versus the ratio of the mass flow in a single branch to the massflow in the common branch for a joining flow pattern.


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Figure 3-52: Flow Coefficients of a Junction

The actual values depend on the geometry of the junction, i.e. the area ratio and theangle between the pipes. BOOST interpolates suitable flow coefficients for theconsidered junction from a database (RVALF.CAT) delivered with the program.

The database contains the flow coefficients of six junctions, covering a wide range ofarea ratios and angles. The data was obtained from measurements on a steady stateflow test rig. The file RVALF.CAT is a formatted ASCII file. The user may addmeasured flow coefficients for special junctions or for an extension of the catalogue.

The structure of the file is as follows:

MEASURED 0 30 1.3158 1.6900

11 0 0.7600 0.0000 0.2332 0.4385 0.6072 0.7400 0.8380 0.9032 0.9381 0.9462 0.9314 0.9029

12 30 0.5917 0.0000 0.1732 0.3530 0.5208 0.6624 0.7691 0.8375 0.8696 0.8727 0.8595 0.8490

21 30 1.6900 0.0000 0.0785 0.1517 0.2205 0.2859 0.3486 0.4087 0.4661 0.5202 0.5702 0.6192

22 150 1.2844 0.0000 0.0740 0.1430 0.2077 0.2690 0.3268 0.3807 0.4294 0.4712 0.5036 0.5418

31 0 1.3157 0.0000 0.1311 0.2565 0.3696 0.4696 0.5567 0.6315 0.6954 0.7507 0.8001 0.8241

33 150 0.7785 0.0000 0.1212 0.2297 0.3249 0.4061 0.4735 0.5271 0.5680 0.5972 0.6163 0.6351

41 0 1.3157 0.0000 0.1498 0.2997 0.4495 0.5133 0.5964 0.6811 0.7619 0.8453 0.9498 1.0800

42 30 1.6900 0.0000 0.1710 0.3420 0.5130 0.6099 0.7049 0.7894 0.8606 0.9216 0.9812 1.0400

51 30 0.5917 0.0000 0.0410 0.0831 0.1266 0.1720 0.2196 0.2698 0.3231 0.3795 0.4394 0.5023

52 150 0.7785 0.0000 0.0672 0.1290 0.1862 0.2394 0.2894 0.3366 0.3812 0.4234 0.4632 0.4944

61 0 0.7600 0.0000 0.0489 0.1006 0.1552 0.2135 0.2761 0.3439 0.4180 0.4995 0.5896 0.6862

62 150 1.2844 0.0000 0.1275 0.2319 0.3197 0.3952 0.4620 0.5226 0.5785 0.6304 0.6678 0.6959

S1 0 1.3157 0.6192 0.6892 0.7526 0.8059 0.8452 0.8687 0.8767 0.8720 0.8593 0.8456 0.8241

S2 30 1.6900 0.8241 0.8456 0.8593 0.8720 0.8767 0.8687 0.8452 0.8059 0.7526 0.6892 0.6192

CATALOGUE 0 90 1.6900 1.3158

11 0 0.5917 0.0000 0.2751 0.5096 0.6916 0.8227 0.9069 0.9510 0.9644 0.9643 0.9603 0.9496

12 90 0.7600 0.0000 0.1051 0.2158 0.3242 0.4236 0.5095 0.5796 0.6337 0.6739 0.7042 0.7380

21 90 1.3157 0.0000 0.0858 0.1615 0.2304 0.2943 0.3540 0.4098 0.4608 0.5055 0.5417 0.5715

22 90 0.7785 0.0000 0.1377 0.2595 0.3673 0.4626 0.5465 0.6196 0.6818 0.7328 0.7715 0.7985

31 0 1.3157 0.0000 0.0828 0.1701 0.2610 0.3545 0.4486 0.5403 0.6259 0.7006 0.7490 0.7705

32 90 0.7785 0.0000 0.0863 0.1697 0.2491 0.3241 0.3942 0.4589 0.5175 0.5691 0.6128 0.6575

41 0 1.6900 0.0000 0.1103 0.2298 0.3531 0.4760 0.5969 0.7167 0.8389 0.9698 1.1182 1.3000

42 90 1.3157 0.0000 0.1391 0.2488 0.3375 0.4121 0.4778 0.5385 0.5966 0.6532 0.7080 0.7520

51 90 0.7600 0.0000 0.0611 0.1255 0.1904 0.2538 0.3142 0.3708 0.4236 0.4730 0.5200 0.5609

52 90 1.2844 0.0000 0.1019 0.2085 0.3155 0.4192 0.5166 0.6054 0.6842 0.7523 0.8098 0.8446

61 0 0.5917 0.0000 0.0529 0.1057 0.1583 0.2112 0.2646 0.3193 0.3757 0.4349 0.4975 0.5619

62 90 0.7785 0.0000 0.0829 0.1565 0.2240 0.2874 0.3482 0.4075 0.4653 0.5213 0.5745 0.6217

S1 0 1.6900 0.5715 0.6028 0.6318 0.6617 0.6901 0.7149 0.7350 0.7501 0.7602 0.7665 0.7705

S2 90 1.3157 0.7705 0.7665 0.7602 0.7501 0.7350 0.7149 0.6901 0.6617 0.6318 0.6028 0.5715


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The lines are described as follows:

1st line:• Measured: The flow coefficients are used for a junction with the same area

ratio and the same angle between the pipes.

• Catalogue: The flow coefficients are used for the interpolation of flowcoefficients if no suitable measured flow coefficients are found. They are notused even if the specified junction in the data set exactly matches the junctionfrom which the catalogue data was obtained.

• Deflection angle for flow path 1 (a → c), flow pattern 1

• Deflection angle for flow path 2 (a → b), flow pattern 1

• Area ratio between pipe a and c

• Area ratio between pipe b and c

2nd to 13th line:

• The first two characters indicate the flow pattern and the flow path.

• Deflection angle of the specific flow path

• Area ratio between the pipe attachments upstream and downstream of thespecific flow path

• Flow coefficients for the mass flow ratio 0, 0.1, 0.2, 0.9, 1.0 between the flow inthe specific flow path and the total mass flow through the junction.

14th and 15th line:

Additional flow coefficients for the special treatment of injector effects in flow pattern4 (joining flow). These lines must be omitted if there is no flow against a pressuregradient.

3.4.6. Volume Elements

3.4.6.1. PlenumA plenum is defined as an element in which spatial pressure and temperature differencesare not considered. This means that the momentum of the flow in the plenum is neglected.

General

Specify the volume of the plenum.

In case of contained perforated pipes the effective volume is calculated by subtracting thevolume of the contained pipes from the specified one.

Wall Heat Transfer may be selected or deselected.

If selected, input fields in the Wall Heat Transfer sub-group are activated. Thespecification of the plenum surface, the wall temperature, and the heat transfer coefficientare required. The user may specify the heat transfer coefficient directly or use a simplifiedheat transfer model for plenums incorporated in BOOST. In this case, the calculated heattransfer coefficient may be increased or decreased by means of an amplification factor.

In order to determine the transient wall temperature, the wall thickness of the plenums,its material properties and data describing the ambient of the plenum are required.


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Initialization

The initial conditions (pressure, temperature, gas composition and user-definedconcentrations) must be specified for a plenum, as well as flow coefficients for each pipeattachment.

Flow Coefficients

In order to consider particular pressure losses resulting from multi-dimensional flowphenomena which cannot be directly predicted by the program, BOOST requires thespecification of flow coefficients for in-flow and out-flow at each pipe attachment. The flowcoefficients are defined as the ratio between the actual mass flow and the loss-freeisentropic mass flow for the same stagnation pressure and the same pressure ratio.

The flow coefficients for each pipe attachment may be specified either as constant values or

in a Table as functions of time in seconds, time in degrees crank angle or pressuredifference at the pipe attachment.

For in-flow (flow into the plenum) the pressure difference is defined as the static pressurein the pipe minus the pressure in the plenum and for out-flow as the pressure in theplenum minus the static pressure in the pipe.

The flow coefficients for flow from the plenum into a pipe depend mainly on the protrusionof the pipe end through the wall in which it is installed, and on its bellmouthcharacteristics.


Relative Inlet RadiusRelativeEdge

Distance0.0 .02 .06 .12 .20

0.0 .815 .855 .910 .950 .985

0.025 .770 .840 .910 .950 .985

0.075 .750 .830 .910 .950 .985

0.20 .730 .825 .910 .950 .985

>0.50 .710 .820 .910 .950 .985

The relative inlet radius is defined as the inlet radius divided by the (hydraulic) pipediameter.

The relative edge distance is defined as the protrusion of the pipe end through the wall inwhich it is mounted divided by the (hydraulic) pipe diameter. A relative edge distanceequal to zero represents a pipe mounted flush with the wall.

For flow out of a pipe into the plenum, a flow coefficient of 1.0 is normally used if there isno geometrical restriction in the orifice.


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Perforated Pipe

Select to insert a perforated pipe in the plenum.

Specify the following perforation data:

Porosity and Porosity Discharge Coefficient for both flow directions, which determine theeffective perforation flow area.

Perforation Hole Diameter and Perforation Wall Thickness which have influence on theinertia of the flow across the perforation (Porosity, Perforation Hole Diameter andPerforation Wall Thickness can be specified pipe location dependent).

Figure 3-53: Perforated Pipe in Plenum Window

In addition to the specification of standard pipe and perforation data, input for the pipeends is necessary. Four types of connection for a perforated pipe end are available asshown in the following figure:

Figure 3-54: Perforated Pipes Contained in Plenum


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1. If the pipe end is attached to the plenum boundary and there is no outside pipeconnected to the same anchor: this results in the pipe end being connected to a systemboundary. This system boundary will be automatically generated but not shown on thescreen. Additional data for this system boundary has to be specified. The data for thissystem boundary can be input in the data window for the appropriate perforated pipe.

2. If the pipe end is attached to a plenum boundary and an outside pipe connects to thesame anchor: This results in a connection via a restriction element between these twopipes. The restriction will be automatically generated but not shown on the screen.Additional data for this restriction has to be specified. The data for this restriction canbe input in the data window for the appropriate perforated pipe.

3. If a single pipe end is attached to an anchor point inside the plenum: This results in aconnection between the pipe end and the plenum. The flow coefficients for the inflowand outflow from this pipe have to be specified in the data window for the plenum.

4. If two pipe ends are attached to the same anchor point inside the plenum: This resultsin a connection via a restriction element between these two pipes. The restriction willbe automatically generated but not shown. Additional data for this restriction has to bespecified.

3.4.6.2. Variable PlenumThe variable plenum is similar to a standard plenum and in addition considers the changeof the volume and surface area of the plenum over time. The user may specify the volumeover time explicitly by selecting one of the following:

1. User-Defined

BOOST allows the volume and the surface area to be specified depending on time inseconds or on time in degrees crank angle. Zero volume is not allowed as input.

2. Crankcase

The user must specify the number of the cylinder to which the defined crankcase isrelated. By specifying the geometrical crankcase compression ratio, which is defined asthe volume of the crankcase with the piston at TDC divided by the volume of thecrankcase with the piston at BDC, the geometrical definition of the crankcase iscompleted.

For consideration of the wall heat transfer in a crankcase BOOST requires thespecification of the minimum plenum surface area (piston at BDC), the walltemperature, and the heat transfer coefficient. Similar to the plenum data for thecalculation of the heat balance of the variable plenum wall can be specified by the user.The heat transfer coefficient may be specified directly or a simplified heat transfermodel for plenums incorporated in BOOST can be used.

3. Scavenging Pump

A scavenging pump is defined as a pumping cylinder which is directly actuated by thecrankshaft. This means that the speed of the scavenging pump is equal to enginespeed.

For consideration of the power consumption of the scavenging pump the user mustspecify to which cylinder the scavenging pump is attached.


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The geometrical specifications of a scavenging pump cover the TDC delay relative tothe attached cylinder, the bore and the stroke of the pumping cylinder as well as thecon-rod length and the piston pin offset. The definition of the volume of thescavenging pump over crank angle is completed by the specification of the scavengingpump compression ratio, which is defined as the BDC volume divided by the TDCvolume.

3.4.6.3. Perforated Pipe in PipeIn addition to the standard pipe data for inner and outer pipe, the following perforationdata should be specified in the following window:

Figure 3-55: Perforated Pipe in Pipe Window

Porosity and Porosity Discharge Coefficient for both flow directions, which determine theeffective perforation flow area.

Perforation Hole Diameter and Perforation Wall Thickness which have influence on theinertia of the flow across the perforation (Porosity, Perforation Hole Diameter andPerforation Wall Thickness can be specified pipe location dependent).

Heat transfer between the two pipes is not considered and the wall heat transfer dialog forthe inner pipe is disabled.

�Note: The geometric outer pipe diameter should be input (not thediameter) to give the effective flow area in the outer pipe. This is becausethe effective flow area of the outer pipe is calculated from its crosssectional area less the cross sectional area of the inner pipe.


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3.4.7. Assembled Elements

3.4.7.1. Air CleanerFor the air cleaner, the performance characteristics at the design point must be specified inaddition to the geometrical data. BOOST automatically creates a more refined calculationmodel of a plenum-pipe-plenum type for the air cleaner. This is used to model the gasdynamic performance of the air cleaner as well as the pressure drop over the air cleanerdepending on the actual flow conditions.

Geometrical Properties

The input of the total air cleaner volume, the inlet and outlet collector volumes and thelength of the filter element is required. In addition, the user must specify what pipes areconnected to the inlet and outlet of the air cleaner. It is important to note that the lengthof the filter element is also used to model the time a pressure wave needs to travel throughthe cleaner.

Flow Coefficients

Particular flow resistances at the inlet to and at the outlet from the air cleaner can beconsidered. The flow coefficients for the pipe attachments may be specified as a function oftime in seconds, time in degrees crank angle or pressure difference at the pipe attachment.For in-flow (flow into the air cleaner) the pressure difference is defined as the staticpressure in the pipe minus the pressure in the air cleaner collector, and for out-flow as thepressure in the air cleaner collector minus the static pressure in the pipe.

Gas Properties

The air cleaner performance is specified by means of a reference mass flow, the targetpressure drop (defined as the static pressure difference at the inlet and the outlet pipeattachment) at the reference mass flow and the inlet air conditions (temperature andpressure), Figure 3-56.


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Figure 3-56: Steady State Air Cleaner Performance

On the basis of this information, the wall friction loss of the model is adjusted by theprogram.

3.4.7.2. CatalystFor the catalyst, the performance characteristics at the design point must be specified inaddition to the geometrical data. As for the air cleaner (refer to 3.4.7.1) BOOSTautomatically creates a more refined calculation model of the catalyst. This is used tomodel the gas dynamic performance of the catalyst as well as the pressure drop over thecatalyst depending on the actual flow conditions.

�Note: The catalyst model in the BOOST cycle simulation is a purely gasdynamic model and does not include chemical reactions. Chemicalreactions can be simulated using the aftertreatment analysis mode (refer tothe Aftertreatment Manual).


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The input of the total catalyst volume (i.e. the monolith volume consisting of the gas andalso the solid structure), the inlet and outlet collector volumes and the length of themonolith is required. For the specification of the honeycomb cell structure the user canchoose between the input of a square cell or general catalyst. In the first case the cellstructure can be defined via CPSI values and wall thickness, in the latter the user candirectly input the catalysts open frontal area (OFA), the channel hydraulic unit (diameteror area) the geometric surface area (GSA). The friction of the catalyst either can bespecified by reference conditions and a target pressure drop(refer to 3.4.7.1) or by using afriction coefficient and a friction multiplier. This friction coefficient is applied for turbulentflows, whereas for laminar flow the Hagen-Poisseuille law is evaluated. The input of thefriction multiplier can be used for taking different channel shapes into account in both thelaminar and turbulent flow region (refer to the Aftertreatment Manual). In addition, theuser must specify what pipes are connected to the inlet and outlet of the catalyst.

Flow Coefficients

Particular flow resistances at the inlet to and at the outlet from the catalyst can beconsidered. The flow coefficients for the pipe attachments may be specified as a function oftime in seconds, time in degrees crank angle, or on the pressure difference at the pipeattachment. For in-flow (flow into the catalyst) the pressure difference is defined as thestatic pressure in the pipe minus the pressure in the catalyst collector, and for out-flow asthe pressure in the catalyst collector minus the static pressure in the pipe.

Gas Properties

The catalyst performance is specified by means of a reference mass flow, the targetpressure drop at the reference mass flow, and the inlet air conditions (temperature andpressure). On the basis of this information, the wall friction loss of the model is adjustedby the program.

3.4.7.3. Air CoolerFor the air cooler the performance characteristics at the design point must be specified inaddition to the geometrical data. BOOST automatically creates a more refined calculationmodel of the air cooler (plenum-pipe-plenum). This is used to model the gas dynamicperformance of the air cooler as well as the pressure drop over the air cooler depending onthe actual flow conditions. In addition, a model for the cooling performance of the aircooler is created based on the layout data.


The input of the total air cooler volume, the inlet and outlet collector volumes, and thelength of the cooling core is required. In addition, the user must specify what pipes areconnected to the inlet and outlet of the air cooler.


23-Jun-2004 3-75

Flow Coefficients

Particular flow resistances at the inlet to and at the outlet from the air cooler can beconsidered. The flow coefficients for the pipe attachments may be specified as a function oftime in seconds, time in degrees crank angle, or on the pressure difference at the pipeattachment. For in-flow (flow into the air cooler), the pressure difference is defined as thestatic pressure in the pipe minus the pressure in the air cooler collector, and for out-flow asthe pressure in the air cooler collector minus the static pressure in the pipe.

Gas Properties

The gas dynamic performance is specified by means of a reference mass flow, the targetpressure drop at the reference mass flow, and the inlet air conditions (temperature andpressure). The cooling performance is specified by the coolant temperature and the targetoutlet temperature or the target efficiency. The cooler efficiency is the achievedtemperature difference related to the maximum possible temperature difference:

coolin

outinc TT

TT−−=η (3.4.3)

cη cooler efficiency

inT inlet temperature

outT outlet temperature

coolT coolant temperature

On the basis of this information, the wall friction loss and the heat transfer in the pipemodeling the cooling core are adjusted by the program.

3.4.7.4. Diesel Particulate Filter (DPF)For the DPF, the performance characteristics at the design point must be specified inaddition to the geometrical data. As for the air cleaner (refer to 3.4.7.1) BOOSTautomatically creates a more refined calculation model of the DPF. This is used to modelthe gas dynamic performance of the DPF as well as the pressure drop over the DPFdepending on the actual flow conditions.

�Note: The DPF model in the BOOST cycle simulation is a purely gasdynamic model and does not include chemical reactions. Chemicalreactions can be simulated using the aftertreatment analysis mode (refer tothe Aftertreatment Manual).


The input of the total DPF volume consisting of the gas and the solid volume fraction, theinlet and outlet collector volumes in conjunction with the length of the monolith isrequired. For the specification of the honeycomb cell structure the user can choosebetween a square cell or general DPF. For the former, the cell structure may be defined viaCPSI values and wall thickness, in the latter the user can directly input the DPF openfrontal area (OFA), the channel hydraulic unit (diameter or area) the geometric surfacearea (GSA).


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The friction of the DPF either can be specified by reference conditions and a targetpressure drop (refer to 3.4.7.1), or by using a friction coefficient and a friction multiplier.This friction coefficient is applied for turbulent flows, whereas for laminar flow the Hagen-Poisseuille law is evaluated. The input of the friction multiplier can be used for takingdifferent channel shapes into account in both the laminar and turbulent flow region (referto the Aftertreatment Manual).

Flow Coefficients

Particular flow resistances at the inlet to and at the outlet from the DPF can beconsidered. The flow coefficients for the pipe attachments may be specified as a function oftime in seconds, time in degrees crank angle, or on the pressure difference at the pipeattachment. For in-flow (flow into the DPF) the pressure difference is defined as the staticpressure in the pipe minus the pressure in the DPF collector, and for out-flow as thepressure in the DPF collector minus the static pressure in the pipe.

Gas Properties

The DPF performance is specified by means of a reference mass flow, the target pressuredrop at the reference mass flow, and the inlet air conditions (temperature and pressure).On the basis of this information, the wall friction loss of the model is adjusted by theprogram.

3.4.8. Charging Elements

3.4.8.1. TurbochargerTwo types of turbocharger models are available:

1. Simplified Model

This model is only suitable for steady state simulations. BOOST considers the meancompressor and turbine efficiencies over the cycle in order to calculate theturbocharger energy balance. The advantage of this model is that it only requireslimited data to describe the turbocharger performance characteristics. Furthermore,this model provides three modes for the turbocharger simulation:

• Boost pressure calculation: The boost pressure is calculated from the specifiedturbine size and turbocharger efficiency.

• Turbine layout calculation: The required turbine size is calculated from thetarget pressure ratio across the compressor and the turbocharger efficiency.

• Waste-gate calculation: The waste-gate mass flow is calculated from the targetpressure ratio across the compressor, the turbocharger efficiency and the specifiedturbine size. If the target pressure ratio cannot be achieved even with the waste-gate closed, the boost pressure which can be achieved will be calculated from thespecified turbine size.

Input data and calculation result relative to the turbocharger mode are shown in thefollowing table:


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Boost Pressure Turbine Layout Waste Gate

Turbine size input result input

Compressorpressure ratio

result input input

Turbine to totalmass flow rate

1 1 result

The turbine size is specified by the equivalent discharge coefficient of the turbine. Theeffective flow area of the turbine is calculated from the equivalent discharge coefficientand the cross-section of the pipe representing the turbine outlet. The conversion of theswallowing capacity taken from the turbine map at a certain pressure ratio to aneffective flow area is done with Equation 3.4.4:

1

2−

•

⋅

= ψR

poTomAeff (3.4.4)


poTom

• swallowing capacity

R gas constant

ψ pressure function

The pressure function ψ is evaluated at the pressure ratio at which the effective flow

area is to be determined. Typical values for the gas constant R and the ratio of specificheats of combustion gases are 287 J/kgK and 1.36 respectively. When evaluating thepressure function ψ it must be observed whether the pressure ratio is supercritical.

In this case, maxψ must be used instead of ψ .

To determine the swallowing capacity from an effective turbine flow area obtained by aturbine layout calculation, Equation 3.4.4 must be solved for

poTom

. .

The equivalent turbine discharge coefficient may be specified as a function of the

turbine expansion ratio (Table ).

The compressor efficiency can be taken from the compressor performance map usingthe expected pressure ratio and compressor mass flow data.

The turbine efficiency can be taken either from a full turbine operating map (ifavailable), or from any equivalent information provided by the turbocharger supplier.The turbocharger overall efficiency is the product of compressor efficiency, turbineefficiency and mechanical efficiency of the turbocharger.


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For twin entry turbines and multiple entry turbines, the reduction of the turbineefficiency due to the unequal flow distribution at unequal pressure ratios across theflows is taken into account by a reduction of the turbine efficiency. Figure 3-57 showsthe factor by which the turbine efficiency is multiplied depending on the pressure ratiobetween the flows.

Figure 3-57: Deterioration Factor of a Twin Entry- or Multiple Entry Turbine

�Note: The turbine efficiency output in the global results or in thetransients is the mass flow weighted average of the calculated efficiencyover one cycle.

For the BOOST pressure calculation the pressure ratio at the compressor onlyrepresents an initial value for the start of the calculation. Similarly, the equivalentdischarge coefficient of the turbine only represents an initial value for the turbinelayout calculation.

In the case of a twin entry turbine or a multiple entry turbine, an inlet flow coefficientmust be specified in order to describe the interference between the attached pipes. Theinlet interference flow coefficient is related to the cross-section of the pipe representingthe turbine inlet. For radial type turbines, an inlet interference flow coefficient of 0.2is recommended and for axial type turbines a value of 0.05 is recommended.

In the case of a waste-gate calculation, an initial value for the ratio between the massflow through the turbine and the total exhaust mass flow (through turbine and waste-gate) also must be specified.

The attachment type of each pipe (compressor inlet/outlet, turbine inlet/outlet) isknown from the sketch of the model and can be checked in the Pipe Attachments sub-group.


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2. Full Model

This model requires the input of the entire compressor and the entire turbine map.

Compressor

In the compressor map, iso speed lines (pressure ratio versus mass or volume flow) andlines of constant isentropic efficiency are plotted. The map is limited to the left side bythe surge line. Beyond this line the mass flow through the compressor becomesunstable and the compressor will be destroyed if operated too often in this area.

On the right side the map is limited by choked flow either through the compressorwheel or the diffuser. This is indicated by the steep gradient of the iso speed lines, seethe following figure.

Figure 3-58: Compressor Map

Before the map can be input, the unit of the wheel speed and the x-axis of the mapmust be set. They may be related to a reference condition defined in the box. Thesuitable units may be selected from the list. For the specification of the compressormap points defined by the mass or volume flow, the pressure ratio, the wheel speed andthe isentropic efficiency must be input by the user.

In addition the x-axis of the compressor map can be scaled with the mass flow scalingfactor and the efficiencies modified additively by the efficiency offset.

Turbine

The following turbine types are available for defining the turbine performance map:

• Single entry

• Single entry - Variable Turbine Geometry (VTG): For each vane position amap must be defined.

• Twin entry - simplified model: Only one map is specified. The map ismeasured with the same pressure ratio across both flows of the turbine. Theinteraction between the flows can be modeled by the definition of a suitableinlet interference coefficient.


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• Twin entry - full model: For each ratio of the total pressures at the turbineentry, a map containing the swallowing capacity of the two flows must bespecified.

• Twin entry – VTG - simplified model: For a twin entry VTG only thesimplified model is available.

• Multiple entry - simplified model: Only one map is specified. The map ismeasured with the same pressure ratio across all flows of the turbine. Theinteraction between the flows can be modeled by the definition of a suitableinlet interference coefficient.

• Multiple entry – VTG - simplified model

The vane position must be set for VTG’s.

In a turbine map (Figure 3-59) the swallowing capacity is plotted versus the pressureratio across the turbine with the wheel speed as parameter. The isentropic efficiencycan be plotted in the same way or it can be plotted versus the blade speed ratio.BOOST supports the input of both map types. The suitable units for the definition ofthe swallowing capacity and the reference conditions can be selected from predefinedlists. Similar to the compressor map, the data for the definition of each point in themap must be input by the user. For each map a mass flow scaling factor allows theuser to scale the swallowing capacities specified and an efficiency offset to modify theefficiencies additively.

For steady state simulations, an internal boost pressure control may be activated. Forfixed geometry turbines an internal waste-gate is simulated, similar to the simplifiedmodel. For turbines with variable geometry, the vane position is determined. SelectInternal Wastegate Simulation / Determination of vane position to activate the boostpressure control. The user must specify the target compressor pressure ratio and theinitial value for the turbine to total massflow ratio (fixed geometry turbine only) in thiscase.

� Note: It is assumed that vane position 0 is the fully closed position andvane position 1 is the fully open position.

In addition to the maps, the total inertia of the turbocharger wheel together with thesetting of the unit and the mechanical efficiency of the turbocharger must be defined.


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Figure 3-59: Turbine Map

The BOOST pre-processor features an import filter for digital compressor and turbinemaps as ASCII-files according to SAE standard J1826 [T2].

The format of the files is:

Compressor:

Line 1: Description (supplier, model name, compressornomenclature, reference test number) A15, A10,A20, A10

Line 2: Inlet diameter (mm), outlet diameter (mm), inlet type,outlet type, impeller inertia (N-m-s²) F10, F10, A15,A15, F10)

Line 3, 4, 5: Additional comments (can be left blank) A80

Line 6 – N: Corrected speed (r/min), corrected mass flow (kg/s),pressure ratio (T-S), efficiency (decimal) F10, F10,F10, F10

� Note: Corrected mass flow rates and speeds are listed in ascendingorder.


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The following table shows an example

supplier model compressor name ref. #

30.000 40.000 inlet type outlet type 0.0011

comment 1

comment 2

comment 3

20000 0.006 1.075 0.4

20000 0.025 1.05 0.42

40000 0.009 1.12 0.3

40000 0.05 1.02 0.5

80000 0.0368 1.3 0.65

80000 0.0515 1.26 0.7

80000 0.0632 1.233 0.7

80000 0.0794 1.15 0.65

100000 0.0368 1.5 0.65

100000 0.05 1.475 0.7

100000 0.1 1.26 0.65

120000 0.0441 1.74 0.65

120000 0.1 1.577 0.77

120000 0.125 1.38 0.65

140000 0.0574 2.04 0.65

140000 0.0735 2.01 0.7

Turbine:

Line 1: Description (supplier, model name, turbinenomenclature, reference test number) A15, A10,A20, A10

Line 2: Test compressor, housing type, dischargeconnection description A20, A20, A20

Line 3: Inlet gas temperature (°C) or turbine inlet-to-compressor discharge temperature ratio (K/K), oiltype, oil temperature (°C), rotor/shaft inertia(N-m-s²) F10, A10, F10, F10

Line 4: Cooling liquid description (if any), inlet temperature(°C), inlet pressure (kPa) A20, F10, F10

Line 5, 6, 7: Additional comments (can be blank) A80

Line 8 – N: Speed parameter (r/min – K), mass flow parameter(kg – K/s-kPa), expansion ratio (T-S), turbine xmechanical efficiency (decimal) F10, F10, F10, F10

� Note: Expansion ratios and speeds are listed in ascending order.


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The following table shows an example

supplier model turbine name ref. #

test compressor housing type discharge connect.

800.00 oiltype 100.000 0.0011

cooling liquid 120.000 1500.00

comment 1

comment 2

comment 3

44000 4.33 1.5 0.52

44000 4.47 1.54 0.53

44000 4.53 1.58 0.53

55000 4.8 1.71 0.52

55000 5 1.8 0.54

55000 5.07 1.88 0.53

66000 5.2 2.02 0.52

66000 5.4 2.15 0.54

66000 5.53 2.28 0.55

The following table gives an overview about the usage of the different models and theirmodes together with the external waste gate element for steady state and transientsimulations:

simplified modelFull

model boost pressure turbine layout waste gate

With internal

boost

pressure

control

Without

internal boost

pressure

control

calculation mode

Steady state

Without wastegate element

Yes Yes Yes Yes Yes

With waste gateelement

No Yes Yes No No

Transient

Without wastegate element

No Yes No No No

With waste gateelement

No Yes No No No


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3.4.8.2. Positive Displacement CompressorsFor a mechanically driven positive displacement compressor, BOOST requires thespecification of the performance characteristics along a line of constant compressor speed(Simplified Model) or the full performance map (Full Model).

The full set of performance characteristics consists of the mass flow or volume flowcharacteristics, the temperature increase or isentropic efficiency and the powerconsumption or total efficiency as a function of pressure ratio.

Figure 3-60: PD-Compressor Map

The flow characteristics of the compressor may be specified either as the corrected massflow over pressure ratio (defined as the actual mass flow multiplied by the ratio betweeninlet air temperature and reference air temperature, and the ratio between reference inletpressure and air inlet pressure), or by the volume flow over pressure ratio.

If the corrected mass flow is selected, the reference inlet pressure and the reference inlettemperature must be specified also.

For the specification of the internal efficiency of the compressor, either the temperatureincrease over pressure ratio for reference inlet conditions or the isentropic efficiency maybe specified.

The information on the mechanical losses of the blower is obtained from the specificationof the power consumption over pressure ratio at reference conditions or from thespecification of the total efficiency.

Using the Simplified Model all performance characteristics may be specified in a Table as a function of pressure ratio at the compressor (iso-speed line) or in a simplified way as aconstant value.

Applying the Full Model all performance characteristics have to be specified in thecompressor operating map.

In order to facilitate the input of operating maps provided by various hardware suppliers,BOOST allows the selection of the most suitable dimensions.

The attachment type of each pipe (inlet/outlet) is known from the sketch of the model.They can be checked by clicking pipe attachments.


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3.4.8.3. Turbo CompressorFor the simulation of a mechanically driven turbo-compressor, BOOST requires thespecification of the mechanical efficiency, the specification of the performancecharacteristics of the turbocompressor along a line of constant compressor speed(Simplified Model) or the full map similar to the map of the compressor of a turbocharger(Full Model) refer to Figure 3-58.

Using the Simplified Model the pressure ratio and the isentropic efficiency may bespecified over the corrected mass flow or over the corrected volume flow for a line of

constant turbo-compressor speed (Table ). For a simplified approach, constant valuesof pressure ratio and isentropic efficiency may also be specified.

The corrected volume flow is defined as the actual volume flow multiplied by the squareroot of the ratio between reference and actual air inlet temperature.

The corrected mass flow is defined as the actual mass flow multiplied by the square root ofthe ratio between inlet and reference inlet air temperature, and the ratio betweenreference and actual air inlet pressure.

To match the actual calculated flow characteristics to the corrected volume or mass flowdata, BOOST requires the specification of the reference temperature and referencepressure related to the correct flow data. They must be taken from the performance mapsprovided by the supplier.

In order to facilitate the input of operating maps provided by various hardware suppliers,BOOST allows the selection of the most suitable dimensions.

The attachment type of each pipe (inlet/outlet) is known from the sketch of the model andcan be checked in the Pipe Attachments sub-group.

3.4.8.4. Waste GateA waste gate is a valve actuated by the pressure difference on the valve body plus thepressure difference on a diaphragm mechanically linked to the valve body.

The instantaneous valve lift is calculated using an equivalent spring-damper-mass system.The flow coefficients must be specified as a function of valve lift.

General

The area on the high and low pressure side of the diaphragm are required in order tocalculate the forces acting on the valve resulting from the respective pressures. Themaximum lift of the valve may be limited.

Flow coefficients for flow must be specified. A leakage through the control diaphragm canbe modeled by the input of a suitable flow coefficient for flow from the high to the lowpressure side and vice versa. This flow is treated in the same way as the flow through aflow restriction.

Valves

The area of the valve body exposed to the high pressure with the valve closed and openedand the area of the valve body exposed to the low pressure are required. The movingmasses, damping coefficient, valve spring pre-load and valve spring rate must be defined.


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Flow Coefficients

Flow coefficients as a function of valve lift must be specified in both possible flowdirections. If an electronically controlled waste gate is modeled, a flow restrictioninfluenced by the engine control unit should be used.

3.4.9. External Links Elements

3.4.9.1. FIRE LinkPlease refer to the FIRE–BOOST 1D-3D Coupling Manual for further information.

3.4.9.2. User Defined ElementThe User-Defined-Element (UDE) allows the user to include user-defined elements in thecalculation model. The UDE is supported in both the pre and post-processor. Specialsubroutines allow user written code to simulate the element. The user written routinesmust be compiled and linked to create a new BOOST executable to run the model. TheAppendix includes the options for compiling and linking a new BOOST executable.

Data handling for all the pipe attachments is done by the UDE. The output generated bythe user’s algorithm may be analyzed with the BOOST post-processor provided that theBOOST interface routines are used. For this purpose, the Number of Output Values mustbe input in the UDE General window. This defines the size of the vector for the outputvalues. For each value a time average will be output in the TRANSIENT section andcrank angle resolved data in the TRACES section.

In addition to the number of output values, the flow coefficients at each pipe attachmentmust be defined. Similar to the system boundary or the plenum, different flow coefficientsmay be defined for in- and outflow of the UDE. The flow coefficients may also depend ontime in degree crank angles or seconds or on the pressure difference between the UDE andthe attached pipe cross section.

Figure 3-61: UDE Input

Please request the user written source code from [email protected].

mailto:[email protected]


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3.4.10. Control ElementsThere are two main types of engine control element available in BOOST:

Internal Control Element: ECU

External Link Elements: MATLAB API and MATLAB DLL

The link to an External Control Element Library is a complementary element to theEngine Control Unit (ECU) element. It may be used to incorporate complex models ofengine control and management systems developed with MATLAB/SIMULINK (MATLAB-API Element, MATLAB-DLL Element) or any commercial software featuring C-codegeneration (MATLAB-DLL Element). All the important functions of an electronic enginecontrol device can be simulated. Figure 3-62 shows a flowchart giving an overview of theinteraction between BOOST and the External Link.

Figure 3-62: Interaction between BOOST and External-Link Element

3.4.10.1. WireThe wire element is a visual representation of a connection (information channel) betweenan engine control element (Engine Control Unit, MATLAB DLL, MATLAB API) and theelements. No specific input is required for the wire. The wire can represent both anactuator channel and a sensor channel.

Elements providing sensor data to an External Link Element (or ECU) and elementscontrolled by actuators need to be connected to the External Link Element (or ECU) by awire (exception: global engine data).

The sensor channel and actuator channel selections are made in the control elementsconnected to the wires.


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3.4.10.2. Engine Control UnitIn order to facilitate the input of the Engine Control Unit specifications, the input isorganized in several layers.

In the first box the guiding input of the ECU is selected. Possible guiding inputs are:

• Load signal: The load signal is a fictive input to the ECU. It can beunderstood as the drivers' command in a drive-by-wire arrangement.

• Desired Engine Speed: The engine control calculates the load signal usingthe control gains proportional, integral and differential together with thedeviation of the actual engine speed from the desired engine speed:

( ) ( ) ( )∫

−⋅⋅+⋅−+−⋅=t

desdesdes dt

nndddtnninnpls0

(3.4.5)

ls load signal

p proportional control gain

i integral control gain

d differential control gain

n engine speed

desn desired engine speed

Both guiding inputs may be specified in the Table dependent on time.

�Note: The user must ensure that the available load signal is usedcorrectly to control the engine load, i.e. to influence the flow restriction(s)modeling the throttle(s) for mixture aspirating engines or to influence thefueling for engines with internal mixture preparation.

For the activation of dynamic functions thresholds for the maximum and minimum loadgradient allowed must be defined.

Then the Control Interaction Timestep (Cyclic / Every Calculation Timestep / SpecifiedTimestep) must be selected.

The selection of parameters to be controlled by the ECU is done inside the Mapspecification sub-group (elements connected by Wire and their possible actuatorchannels).


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Figure 3-63: Selection of ECU Actuator Channels

If the cylinders have identical specifications, only cylinder one is listed and the data istransferred to all other cylinders.

The user must input maps for each actuator channel. First it must be determined whethera baseline map value or the last actual value should be used as starting value for thecorrection procedure. In the first case, the baseline map must be defined.

The value in a map can depend on up to two sensor channels which are selected in the pulldown menu for the element (global or wire connected) and the respective sensor channel. Ifonly a table is defined either x- or y-value keeps it’s default setting none. If no dependencyis specified this is equivalent to the specification of a constant value.

Please refer to Chapter 9.3 for a list of available Actuator and Sensor Channels.


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Figure 3-64: ECU Map Specification

Before inputting map values, the size should be customized using Insert Row/RemoveRow and Insert Col./Remove Col. Maps can be written to a separate file using Store orthey can be read in from an external file using Load.

Minimum and maximum maps are defined in the same way.

If the baseline value is to be corrected depending on other parameters (e.g. ambienttemperature or pressure) correction maps can be added by pressing the left mouse buttonon the tree item. In addition to the specification of the map the type of correction(multiplication or addition) must be defined.

�Note: Corrections are done in the same sequence as they are specified,i.e. a correction value added to the baseline value followed by amultiplicative correction will produce a different output than the samecorrections done in the reverse order.

If the positive gradient of the load signal exceeds the threshold specified in the first box,the corrections for acceleration become active. Their number, the maps themselves andthe type of correction are specified in the same way as for the steady state corrections.


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A time lag for the activation and deactivation of the correction and the respective timeconstant (the time between 0 % and 99 % correction or 100 % and 1 % correction) completethe input of the acceleration corrections. Figure 3-65 shows the definition of the timeintervals:

Figure 3-65: Time Constants for Transient ECU Functions

The procedure for the definition of the deceleration corrections is the same as for theacceleration corrections.


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3.4.10.3. MATLAB DLL ElementThe MATLAB DLL junction can be used to exchange information between elements in aBOOST model and MATLAB/Simulink from Mathworks. This can be done by connectingwires between the MATLAB DLL junction and the appropriate element. The wire is usedto pass both sensor (BOOST to MATLAB) and actuator (MATLAB to BOOST) data.

Figure 3-66: MATLAB DLL Element Input

There are two ways of using this element:

MATLAB DLL

BOOST can be run from the graphical user interface and dynamically loads a sharedobject created by MATLAB/Simulink. The full name and absolute path of this sharedobject must be given in the DLL Name input box (if the shared object isn’t located inthe *.bst input-file directory the name has to contain the absolute path).

• Feature supported for MATLAB V.5.3, V.6.0 and later versions.

• Simulation should be run using the GUI (Simulation|Run)

• The shared object must be created on the same operating system/platform on whichBOOST is being run.

• The MATLAB s-function link should not be selected.

MATLAB s-function

The BOOST model is run from MATLAB/Simulink via a system function.

• Feature supported for MATLAB V.6.0 and later versions only.

• The BOOST model should be created but not run by the BOOST GUI. The BOOSTinput file (*.bst) created should be specified as the BOOST input file name in the s-function mask.

• Select the MATLAB s-function link. No DLL Name is required and will be grayedout when the check box is selected.


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CHANNEL SPECIFICATIONS

Sensor Channels

Figure 3-67: Sensor Channel Selection

For the definition of the index of a Sensor value in the vector the channel numbers mustbe specified. This vector is passed to the External Link Element as input. If a type value isset to external (the External Link Element only), the user must supply its value either as a

constant or in a Table as a function of time in seconds. Possible applications of anexternal input are gain coefficients of a control or a guiding input.

Actuator Channels

After selecting Actuator Specification, a box appears listing all elements connected to theDLL element which can have at least one parameter controlled by the DLL element. Anexample of this input is shown in the following figure:

Figure 3-68: Actuator Channel Selection


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If the cylinders have identical specifications, only cylinder one is listed and the data istransferred to all other cylinders.

Similar to the sensor channels, the channel number defines the index of the Actuator valuein the Actuator vector.

Please refer to Chapter 9.3 for a list of currently available Actuator and Sensor Channels.

3.4.10.4. MATLAB API ElementThis element should be used when the model is to be run using the link to MATLAB usingthe API.

Figure 3-69: MATLAB API Element Input

In addition to the input of the Simulink-model (or m-Function) name, which performs thecontrol algorithm, the name of the Sensor-channel and Actuator-channel vector must bespecified (if the model isn’t located in the *.bst input-file directory the model name has tocontain the absolute path). These vectors are introduced as members of the MATLABWorkspace and the Simulink-model (or m-Function).

Then the Control Interaction Timestep (Cyclic / Every Calculation Timestep / SpecifiedTimestep) must be specified.

The Channel Specifications are done analogous to the MATLAB-DLL Element.


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3.4.11. Acoustic Elements

3.4.11.1. MicrophoneA microphone element can be added to any BOOST model in order to extract acoustic datasuch as overall dB(A) levels or order plots. The microphone is not attached to any pipes butlinked in the input for the microphone to one or more system boundaries.

Axis, x

Vertical, z

Lateral, y

0

Ground (optional)

Height (optional) MICROPHONE

ORIFICE

Figure 3-70: Microphone Position

The position of each system boundary relative to the microphone is defined as shown in thefigure above.

Results from each microphone in a model can be found in the Acoustics folder and theTransients folder.


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3.5. Case Series CalculationStarting from a single case model, it is possible to create a case series calculation. Thisallows parameters to be assigned for a set of cases so that a series of operating points orengine variants can be calculated at one time.

3.5.1. ParametersParameters can be assigned to input fields and are defined in Model|Parameters orElement properties windows. There are two types of parameters:

1. Global Parameters :

These can be used for any element.

2. Local Parameters

These can only used for individual elements and are used for:

• Creating simplified and protected model views

• Overriding commonly defined values by element-specific, local values.

3.5.1.1. Assign ParametersTo assign a new or existing parameter in the properties dialog of an element, click the labelto the left of the input value with the right mouse button to open the following submenu.

Figure 3-71: Assign Parameter Menu

Select Assign new parameter (global) or Assign new parameter (local), then enter aname for the new parameter, e.g. Speed. Select OK and it will replace the original inputvalue.

Select Assign existing parameter, then locate the predefined parameter in the dialog box.

� Note: Parameter names should not have any spaces.

3.5.1.1.1. Assign a Model ParameterSelect Model|Parameters to show parameters for all elements used in the model (as shownin the following figure).


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Figure 3-72: Model Parameter Window

The parameter tree on the left shows all existing parameters for all elements of the model.Global parameters can be found at the top of the tree (e.g. Speed). On the right, the valuesof the parameters can be edited. Constant values or expressions can be used to define avalue.

Select Model and then select New Parameter to add new global parameter values. Adefault parameter name is automatically entered and this can be typed over as required.

Select the required element and then select New Parameter to add new local parametervalues. A default parameter name is automatically entered and this can be typed over asrequired. Enter the relevant value in the Value input field and select the relevant unitfrom the pull-down menu by clicking on the Unit input field.

Select Delete to remove the selected parameter.

3.5.1.1.2. Assign an Element ParameterSelect Element|Parameters to show the parameters of the selected element. Only theparameters in the element's domain can be edited in the table.

To edit parameters for one element only, select the element in the working area and thenselect Parameters from the Element menu, or click the element with the right mousebutton and select Parameters from the submenu.


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3.5.1.1.3. Case ExplorerThe Case Explorer defines parameter variations for the model. Select Model|CaseExplorer to open the following window.

Figure 3-73: Case Explorer Window

In this window 5000rpm is the active case as it has a red circle. To make a case active,double click on it with the left mouse button in the tree and it turns red. The assignedglobal parameters of the active case are displayed by selecting Model|Parameters.

New case parameters, i.e. parameters that will be subject to variation, can be added byclicking Parameters. Then double click on the toggle switch with the left mouse button toadd the required parameter. Enter the relevant values for each case.

In this window Engine Speed is the main parameter as it follows State. To define it as amain parameter, select it first in the Add/Remove Parameters window.

�Note: Only global parameters can be subject to variation with the CaseExplorer. When a parameter is defined in the case table, the parametervalue is disabled in the MODEL|PARAMETERS dialog.


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3.6. Running a SimulationSelect SimulationRun to open the following window.

Figure 3-74: Run Simulation Window

Cases: Select the required case(s) to be run. Select All allows all the cases to beactivated.

Tasks: Select Model Creation to create a calculation kernel input file (.bst file) in thecase sub-directory.

Select Cycle Simulation to run the standard cycle simulation. This passes theinput file (.bst file) to the calculation kernel.

Select Aftertreatment Analysis to run the aftertreatment analysis mode. Thispasses the input file (.atm file) to the calculation kernel.

Select Animation to create animation results suitable for loading into PP3.This will be done after completion of the simulation run.

Deselect All and Select All allows all the available tasks to be eitherdeactivated or activated, respectively.

� Note: Animation task is only active if the Calculation Mode is set toanimation in Simulation|Control Globals.

� Note: Aftertreatment Analysis task is only active if there is validaftertreatment model.

Then select Run to start the simulation. The following window then opens which providesan overview of the status of the simulation.


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Figure 3-75: Simulation Status Window

Simulation states are listed below:

new No job has been submitted for that model case yet.

queued A simulation job for that particular model case was submitted usinga queuing system but that job is not running yet.

submitted A simulation job was submitted as a background process and thesimulation kernel is about to start.

running Simulation kernel is processing simulation task(s).

completed Simulation job processed successfully.

error Simulation job processed with errors. Check the output from thecalculation kernel for more information. This can be done byselecting View Logfile then Task Cycle Simulation orAftertreatment Analysis.

stoppedprocess

The current simulation kernel process has been stopped along withall parent job submission scripts.

killedprocess

The simulation kernel process was killed by the user with the KillProcess button.

missingprocess

Simulation kernel process terminated unexpectedly.

Select View Logfile to view more detailed information on the different simulation tasks.

• Select Model Creation to show messages generated by the GUI as to whether themodel was created successfully.

• Select Cycle Simulation task to show the information from the calculation kernelduring the cycle simulation.


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Figure 3-76: View Cycle Simulation Logfile Window

• Select Aftertreatment Analysis task to show the information from the calculationkernel during the aftertreatment simulation.

Figure 3-77: View Aftertreatment Analysis Logfile Window


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• Select Animation task to show the information about the creation of animationresults.

Figure 3-78: View Animation Logfile Window

3.7. Utilities

3.7.1. BURNThe BURN utility can be used for combustion analysis. That is, the rate of heat release(ROHR) can be obtained from measured cylinder pressure traces. The resulting ROHR canbe used to specify the combustion characteristics of a single zone model.

3.7.1.1. Input Data SpecificationSelect BURN from the Utilities menu to open the following figure. In this example twooperation points are loaded and Fitting Data is displayed.


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Figure 3-79: Burn Utility - Fitting Data Window

Alternatively while inputting the cylinder data for a BOOST model, select Table under theCombustion sub-group. In this case the resulting ROHR can be accepted immediatelyafter calculation.

It is possible to perform the analysis for more than one operating point with a singleprocedure. Therefore two types of input data are available:

• Data independent of the operating point, e.g. cylinder geometry, mixturepreparation and fuel type.

• Data describing the operating point, e.g. engine speed, wall temperatures, valvetiming and mass flows.

1. Global and Cylinder Data

This data is independent of the operating point. If a BOOST model is loaded or theBURN tool is applied while specifying the combustion data for a BOOST model, thisdata can be copied from a BOOST model by selecting a cylinder from the pull-downmenu and then selecting Copy. Additional operating point data can be loaded for thefirst operating point to be calculated. The necessary global and cylinder datacorresponds to the data required for the preparation of a BOOST model.

2. Operating Point Data

Select the Operation Point sub-group folder to add or remove operating points byusing Insert Row and Operating Point and Remove Row and Operating Point. Thevalues for engine speed and load cannot be specified directly in the table but afterspecifying data each operating point, the table can be used to examine these values.


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Select the required Operating Point, e.g. OP(1) and specify the following:

• Engine Speed.

• Load as BMEP. The load does not influence the results and is used only todescribe the operating point.

• The valve timing is specified to determine the range in which the analysisshould be performed. For a standard four-stroke engine Start of High Pressurecorresponds to intake valve closing (IVC) and

• End of High Pressure to exhaust valve opening (EVO).

• Ignition Time/Start of Injection is used to determine the compression phase ofthe high pressure cycle. This range is used to perform the fitting of thepressure curve.

• Air Massflow and Fuel Massflow should be specified for the whole cylinder.The value for a single cylinder is determined from the number of cylinders inthe engine assuming an even distribution to the cylinders.

• If the assumption is not valid Trapping Efficiency Air and Trapping EfficiencyFuel also can be used to consider such an effect.

• Wall Temperature must be defined for piston head and liner in the same wayas it is done for BOOST.

Select the Pressure Trace sub-group and specify the required data or read it in as atable. The pressure traces are required over a whole cycle.

Select the Fitting sub-group to determine the absolute pressure level, top dead center(TDC) and compression ratio as required. From the pull-down menus, the user canselect Manual to specify a value or Automatic to perform the fitting processautomatically for Fixed Pressure Offset, Fixed TDC Offset and Fixed CompressionRatio. The None option turns off the process.

The fitting procedures are based on the compression phase of the high pressure. Bycomparing the shape of the calculated compression curve and the measured one theoffsets and the compression ratio are determined.

� Note: Choosing all three types of fitting may increase calculation time forone operating point.

Distortions of the pressure traces can be improved by using the Cut Off FrequencyFilter. The user can select Manual from the pull-down menu to specify a value or selectAutomatic. If Automatic is selected the cut off frequency is calculated from the enginespeed using:

][23][ rpmnHzf enginecutoff ⋅=


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3.7.1.2. Run the CalculationAfter specifying the data select Save Data and save it as an input file. This can be used forlater examination by selecting Load Data.

Select Calculate to start the calculation. A window appears in which the customer cancheck the operating points. Then select Run Calculation(s) to perform the calculation ofall operating points.

3.7.1.3. ResultsThe results for each operating point can be examined under the Results sub-group. Theresults of the fitting procedures are shown and the energy balance confirms the validity ofthe analysis.

Energy Balance is defined as the ratio between the energy set free through combustion andlost to the exhaust divided by the energy brought in by the caught fuel. A valid analysisshould show an energy balance value less than but close to 1.

In the ROHR sub-group, the resulting rate of heat release is shown. In addition to the heatrelease, the net heat release (net ROHR) is also shown, which does not consider the wallheat transfer.

In the Calculated Pressure Trace sub-group, the pressure traces after fitting and filteringare shown.

If the analysis is started from modeling an engine with BOOST, the user is asked to acceptthe resulting ROHR for one of the operating points and the resulting ROHR is used asinput data for the table.

3.7.2. SearchThe Search utility can be used to displays tables of the input data used in the model. Thesecan be saved in HTML format. The current search options are:

• Initialization data =ALL=

• Initialization data =PIPES=

• Geometry of and initial conditions in the Pipes

• Volumes

• Flow coefficients =RESTRICTIONS=

• Vibe


3-106 23-Jun-2004

Figure 3-80: Search Utility Displaying Initialization Data for Pipes

3.7.3. License ManagerSelect Utilities|License Manager to open the following window:

Figure 3-81: License Manager Window

The active configuration is shown on the left with the different license options:

License is available and not checked out.

License is available and checked out.

License is not available.

For a new configuration, turn on the toggle switch for the required license and then restartBOOST.


23-Jun-2004 3-107

3.7.4. Pack ModelThis creates a compressed tape archive of all files related to the current active model.These include input data, results, model layout, simulation messages and systeminformation. On success, a message box will be displayed showing the path and name of thecreated file. The base name of the created file will match the current active model and willhave the extension .tar.gz.

This utility can be used for passing models to the BOOST support team to check problemsor errors.


23-Jun-2004 4-1

4. EXTERNAL LINKS4.1. MATLAB

4.1.1. Application Programming Interface (API)By running a BOOST model containing the MATLAB-API Element, theMATLAB/SIMULINK workspace is dynamically linked to the BOOST Executable.

The user has runtime access to all control-related data. This allows parallel post-processingby using the full capability of the MATLAB Workspace. There are three options for viewingthe data in MATLAB/Simulink:

1. Scopes can be used inside the SIMULINK model.

2. Based on the names assigned to the vectors these names can be used to generate plotsfrom the MATLAB command window.

3. Plots can be generated automatically by using m-functions.

Further details on plotting in MATLAB/Simulink can be found in the documentation fromThe Mathworks.

A Restart Calculation with a saved Control-Unit State in the MATLAB-Workspace(according to the BOOST Restart procedure) is possible.

�Note: To use the restart option it is mandatory that the relatedBOOSTMODELNAME doesn’t start with a number (analogous to therestriction for a SIMULINK model or an m-function file name) .

Additional MATLAB-API Element Specification

In addition to the input of the Simulink-model (or m-Function) name, which performs thecontrol algorithm, the name of the Sensor-channel and Actuator-channel vector must bespecified. These vectors are introduced as members of the MATLAB Workspace and theSimulink-model (or m-Function).

At every interaction step the values of the Sensor-channel are evaluated by BOOST,submitted to the MATLAB Workspace, the Simulink-model (or m-Function) performs acontrol algorithm step and returns the values of the Actuator-channel back to BOOST.

The following settings are available for the interaction step size:

• every BOOST cycle

• every BOOST calculation timestep

• specified timestep


4-2 23-Jun-2004

Required MATLAB API Libraries

For each platform two MATLAB libraries are required by BOOST to dynamically load therequired functions. These libraries should be located in the following directory:

<matlab>/extern/lib/$Arch

where <matlab> is the MATLAB root directory and $Arch is your system architecture.This subdirectory and the platform dependent name of these libraries are listed in thefollowing table.

Platform Subdirectory Required Libraries

Windows win32 libeng.dlllibmx.dll

Hewlett Packard hpux libeng.sllibmx.sl

Compaq alpha libeng.solibmx.so

IBM Ibm_rs libeng.alibmx.a

Linux glnx86 libeng.solibmx.so

4.1.1.1. Running a MATLAB API SimulationThere are several key steps to running a MATLAB API simulation with BOOST dependenton the platform being used. These are listed below:

Windows NT/95/98/2000

1. Check the required libraries have been installed.

2. The required library paths should have been set during installation (check with yoursystem administrator if the required libraries cannot be loaded).

3. Check that there is a valid MATLAB license available.

UNIX

1. Check the required libraries have been installed for the current platform.

2. Set the library path environment variable LD_LIBRARY_PATH.

In C shell, the command to set the library path is

setenv LD_LIBRARY_PATH

<matlab>/extern/lib/$Arch:$LD_LIBRARY_PATH


23-Jun-2004 4-3

In Bourne shell, the commands to set the library path are

LD_LIBRARY_PATH=<matlab>/extern/lib/$Arch:$LD_LIBRARY_PATH

export LD_LIBRARY_PATH

where <matlab> is the MATLAB root directory and $Arch is your systemarchitecture.

The environment variable (LD_LIBRARY_PATH in this example) varies on severalplatforms. The following table lists the different environment variable names to beused on these systems.

Platform Library Path Variable

HP700 SHLIB_PATH

IBM RS/6000 LIBPATH

SGI 64 LD_LIBRARY64_PATH

It is convenient to place these commands in a startup script such as ~/.cshrc for Cshell or ~/.profile for Bourne shell.

3. Add the path to the MATLAB script/executable (matlab) so that it can be started byBOOST.

In C shell, the command to set the path is

setenv PATH <matlab>:$PATH

In Bourne shell, the commands to set the library path are

PATH=<matlab>:$PATH

export PATH

where <matlab> is the MATLAB root directory.

4. Check that there is a valid MATLAB License available.

5. If running on a remote host, set the DISPLAY environment variable to the currenthost.

setenv DISPLAY <hostname>:0.0


4-4 23-Jun-2004

Restart

If data of the MATLAB workspace must be saved in addition to the Simulink model, itshould be stored on the Structure variable RestartState using the MATLAB-CallbackRoutine StopFcn.

Modification of the MATLAB Workspace variable FinalState during the simulation willlead to erroneous results (it is reserved to save the State at the end of every simulationtimestep).

The MATLAB dialog that ordinarily appears on the MATLAB Command Window isredirected to the file SIMULINKMODELNAME_buffer.dat.

If a script-file SIMULINKMODELNAME_startup.m is present in the MATLAB workingdirectory (containing the performed Simulink-model or m-Function) it is executed at thestart of the co-simulation, while SIMULINKMODELNAME_close.m is carried out at theend.

4.1.2. Real Time WorkshopThe following procedure may be used for the program development of the DLL. Thisprocedure works with MATLAB v5.3, v6.0, v6.1, v6.5 and higher.

By typing mex –setup on the MATLAB command line a menu appears were the c++compiler for the DLL generation has to be selected.

Depending on the MATLAB version, the following path must be added to theMATLAB/Simulink path:

MATLAB V.5.3: BOOST_HOME..\..\matlab\version5.3

executing the MATLAB command addpath(‘path_to_add’)

MATLAB V.6.0 (V.6.1and higher):

BOOST_HOME..\..\matlab\version6.0

(BOOST_HOME..\..\matlab\version6.1)

via the MATLAB GUI (File ⇒ Set Path… ⇒ Add Folder..and then SAVE)

(BOOST_HOME is defined as an environmental variable of the operating system)


23-Jun-2004 4-5

The following figures show the Real-Time Workshop options for the generation of the DLLin the SIMULINK Tools menu:

1. Solver

Figure 4-1: Simulink Settings for the Integration Algorithm

In the Solver window shown above, the integration algorithms and the incrementationmust be selected. The incrementation must be constant (Fixed-step) and adapted to theselected incrementation of BOOST. It is recommended to use approximately a tenth ofthe BOOST incrementation.

The entries for start time and stop time are not relevant.

Select Fixed-step for the Type of Solver Options and ode1 (Euler) for the integrationalgorithm. Select 0.01 for the Fixed step size. Select Single Tasking for the mode.

�Note: If no integrators, memory blocks, etc were used in the model, thevalue for the Fixed step size incrementation is ignored and isautomatically set to the BOOST time step.


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2. Workspace I/O

Figure 4-2: Simulink Settings for the MAT-Files

In the Workspace I/O window shown above, certain data of the SIMULINK blockdiagram can be output to a MATLAB readable file which is characterized by the fileextension MAT. After running the simulation this MAT file can be loaded into theWorkspace from MATLAB. This file has the same name as the model.

The actual time Time, the state variables States or the output values outputs, etc. canbe selected for storing. The Output vector contains all output values. If a ' Scope'-blockor 'To Workspace'-block was used, then this data will also be written to the MAT file. Ifnone of the possible items were selected and in the block diagram no blocks for storingwere used, no MAT file will be produced. Format determines whether the values will berecorded in a simple matrix or structured (with or without time).


23-Jun-2004 4-7

3. Real-Time Workshop

Figure 4-3: Simulink Settings for the Boost-DLL Creation

In the Real-Time Workshop window shown above, the settings for the DLL generationare input.

System target file defines the type of the code which can be produced. Enter grt.tlc(general real-time).

Template makefile defines the name of the template file from which the new Make fileis generated. For the generation of the desired DLL file using the VC++ V6.0compiler, enter the template file avl_grt_dll_nt.tmf(UNIX: avl_grt_dll_unix.tmf). This file must be in the directory%MATLABROOT%\rtw\c\grt or in the current work directory otherwise the completepath name must be entered.

Enter make_rtw for Make command. Enter PROGRAM=new_name to define the filename of the DLL. Alternatively the model name is used and an underscore is placed infront. If the DLL file name should be equal to the MDL file name, an underscore mustbe placed in front (refer to the following table), otherwise no valid C-MEX DLL will begenerated, as the MDL file in MATLAB could be not opened any longer, because it isalways checked first whether there is DLL file with same name available.

Make command Simulink-Model Created DLL

make_rtw example.mdl _example.dll

make_rtw PROGRAM=example example.mdl _example.dll

make_rtw PROGRAM=test example.mdl test.dll

Select Build to generate a c-code. Then the Makefile will be produced, nmake.exe will becalled with this Makefile and the object files will be linked to the DLL.


4-8 23-Jun-2004

4.1.3. Pure Code GenerationThe engine control model can also be compiled to a DLL from user written code so that thefollowing entry points are defined and exported:

_mdlInterfaceInitialize

_mdlInterfaceStep

_mdlInterfaceTerminate

The definition of each routine is:

void _mdlInterfaceInitialize

( double*stepSize, double**u, int*nu, double**y, int* ny);

This routine initializes the DLL and is called once at the beginning of a simulation.The passed parameter list is as follows,

• stepSize = defined interaction step size in seconds.

• u = sensor vector u with one value per channel

• nu = number of sensor channels

• y = actuator vector with one value per channel

• ny = number of actuator channels

The stepSize can be used to set the frequency (in seconds) of the interactionbetween the DLL and BOOST. If set to zero they will interact every BOOST timestep.

Both channel vectors ( u and y ) must be allocated memory in the DLL code. Thenumber of both the sensors (nu) and the actuators (ny) must also be set in the usercode.

void _mdlInterfaceStep (void)

This routine controls the calculation of a time step in the DLL. BOOST passescopies of the sensor channels to the DLL. The DLL should set new values for theactuator channels y.

Note that this routine is only called after an initial settling period of three BOOSTcycles and then once every stepSize or every BOOST time step is stepSize is set tozero.

void _mdlInterfaceTerminate (void)

This routine terminates the Dynamic Link and is called once at the end of thesimulation.


23-Jun-2004 4-9

4.1.4. System Function (s-function)BOOST can be run from MATLAB/SIMULINK using a masked subsystem block. Thiscontains a C-MEX s-function that dynamically loads the BOOST calculation kernel from ashared object (dynamic link library).

A BOOST model can pass information to the s-function using wires representing bothsensors and actuators connected to the MATLAB-DLL Element.

1. MATLAB-DLL Element Specifications for BOOST Model

To enable the BOOST model to pass information to MATLAB, select MATLAB s-function link in the main window of the MATLAB-DLL Element Specification Box.This will be displayed if the MATLAB DLL element in the BOOST model is doubleclicked.

Required Files

File Description Installation Location

boost.mdl The MATLAB library filefor the s-function

../boost/v4.0.3/matlab/v6.x MATLAB path

BOOST_model.dll* The MATLABs-function dll for BOOST

../boost/v4.0.3/matlab/v6.x MATLAB path.

boost.dll The dynamic link libraryof the BOOST solver.

../boost/v4.0.3/bin/platform BOOST_HOME

� Note: On UNIX, the MATLAB s-function dll has the mexplatformextension.

Time Control

The time stepping of the simulation is controlled by BOOST and the simulationduration is controlled by MATLAB. BOOST constantly stores data during aMATLAB/Simulink run so when the simulation has finished, the last complete cycle ofdata will be available in the BOOST output.

The BOOST model cannot run longer than the Max.Calc.Period [degCRA] specified inthe Globals section. If this value is exceeded by BOOST during a simulation using thes-function then the MATLAB/Simulink model will stop at this point and an errormessage will be issued. To avoid this problem the max. crank angle for the BOOSTmodel should be set to a higher crank angle than will be reached during the simulation.


4-10 23-Jun-2004

2. Specifications for MATLAB/Simulink Model

The s-function has been written for MATLAB Version 6.x only (earlier versions are notsupported) on the following platforms.

Platform Operating System Version

Windows NT 4.0

Compaq OSF1 5.10

IBM AIX 4.3.3.0

Linux Linux 2.2.16

The BOOST block is supplied as a MATLAB/Simulink library called BOOST.

Figure 4-4: The BOOST MATLAB/SIMULINK Library

This can be displayed by typing boost at the MATLAB command prompt and the iconcan be dragged into the model in the same way as any other MATLAB/Simulink block.


23-Jun-2004 4-11

Mask Parameters

Double click the block to open the following window:

Figure 4-5: Mask Parameters Window

Input the following data to run a BOOST model via the s-function:

BOOST input file name is the name of the file for the BOOST input. This willtypically have the bst extension and can be generated by the GUI by selectingModel Creation in the Simulation|Run dialog box.

Number of actuator channels is an integer value defining the number of inputsto the BOOST model (actuators). This must match the number used in theBOOST model.

Number of sensor channels is an integer value defining the number of outputsfrom the BOOST model (sensors). This must match the number used in theBOOST model.

Interaction allows the user to select how often BOOST and MATLAB/Simulinkexchange information. The options available are,

• BOOST time step : information exchange every BOOST time step.

• Cyclic : information exchange every set number of BOOST cycles as given inthe Defined input section (see below).

• SIMULINK : information exchange every SIMULINK time step.

• Defined : information exchange every set number of seconds as given in theDefined input section (see below).

Defined is only used if Interaction is set to Cyclic or Defined, otherwise it isignored.


4-12 23-Jun-2004

• Cyclic : number of cycles between information exchange.

• Defined : seconds between information exchange

Pre-Converge is an optional check box that causes the model to run for anumber of cycles before interacting with MATLAB/Simulink. This allows themodel to pre converge.

Synchronise is an optional check box that synchronises the BOOST time andthe MATLAB/Simulink time.

Verbose/debug is an optional check box that writes additional information tothe screen in case of errors or difficulties.

Path Settings

The path to the BOOST library model (boost.mdl) and the BOOST s-function(BOOST_model.dll on Windows) must be added to the MATLAB/Simulink path so thatthe necessary files can be accessed. This can be done via the MATLAB GUI (File ⇒ SetPath… ⇒ Add Folder.. and then SAVE). If this is not done, the files are missing or thepath is incorrect then a bad link error as shown below will be given byMATLAB/SIMULINK.

The BOOST_HOME environment variable also needs to be set correctly as the BOOSTdynamic link library is loaded from this directory.

� Note: BOOST_HOME should be set in the User Variables and not theSystem Variables.

4.1.4.1. Running an s-function SimulationThe stages in building, running and analyzing a BOOST/MATLAB simulation are asfollows:

1. Open/Create a BOOST model in the graphical user interface (GUI).

2. The BOOST model must include a MATLAB DLL element with MATLAB s-function link selected in the General input for this element. Wires should beconnected between elements in the BOOST model and the MATLAB DLL junction.The sensor and actuator channels should also be selected.

3. Create a BOOST solver input file (.bst file). In the GUI, select Simulation|Run,select Model Creation only for Tasks and then select Run. A message box willinform the user of the name and location of the file that has been created.

4. Open/Create a model in MATLAB (.mdl file).


23-Jun-2004 4-13

5. The model should include the MATLAB BOOST library element (boost.mdl). Ifthe paths have been set correctly this can be displayed by typing boost at theMATLAB prompt.

6. The mask parameters for the BOOST element should be set. This includes the'BOOST input file name' created at stage 3.

7. Run the model in MATLAB by selecting Simulation|Start.

8. After completing the simulation the results from the BOOST model can beexamined in the GUI. With the BOOST model still active in the GUI selectSimulation|Import Results and select the BOOST input file created in 3 and usedat stage 6.

9. The Simulation|Show Summary, Show Results, Show Messages and ShowAnimation should now work as for a standard BOOST simulation run through theGUI.

4.2. AVL FIREPlease refer to the 1D-3D Coupling Manual for further information.

4.3. AVL CRUISEThe BOOST dynamic link library (DLL) can be called by AVL CRUISE.

During a CRUISE-BOOST co-simulation the engine model is controlled by CRUISE via theLoad Signal, thus the presence of an ECU Element is mandatory.

Time Step Control

The BOOST model cannot run longer than the Max.Calc.Period [degCRA] specified in theGlobals. If this value is exceeded during the CRUISE-BOOST co-simulation an error willappear. To avoid this problem the Max.Calc.Period for the BOOST model should be set toa higher crank angle than will be reached during the simulation. Transient Calculation inSimulation Control / Globals of the boost model has to be disabled because the transientbehavior of the engine is calculated by Cruise.


23-Jun-2004 5-1

5. BOOST POST-PROCESSINGThe IMPRESS Chart post-processing tool is used to display Traces, Transients, Acousticand Series results and the PP3 post-processing tool is used for Animation results.

For the general handling of the IMPRESS Chart and PP3 post-processing tools please referto Chapter 3 of the AVL Workspace Graphical User Interface Manual.

To accelerate the analysis process and to support the understanding of the complex flowphenomena in an internal combustion engine, the following analysis of the calculationresults are available:

• SUMMARY – Analysis of global engine performance data

• TRANSIENTS – Analysis of global calculation results over the cycles calculated

• TRACES – Analysis of calculation results over crank angle

• ACOUSTIC – Analysis of orifice noise

• CASE-SERIES – Analysis of the results of a case-series calculation

• ANIMATION – Analysis of animated results

• MESSAGES – Analysis of messages from the main calculation program

Before starting a detailed analysis of the calculation run (Traces, Acoustic, Series,Animation, Summary), it is recommended to check MESSAGES for convergence failureand TRANSIENTS for achieved steady-state conditions.

5.1. Analysis of Summary ResultsSelect Simulation|Show Summary to display the summary results of the calculationtogether with detailed information of the calculation model and the important boundaryconditions for the calculation. An example of summary results displayed in the Ascii FileBrowser window is shown in the following figure:


5-2 23-Jun-2004

Figure 5-1: Summary Analysis Window

To access additional features for manipulating files select File from the menu bar of theAscii File Browser.

5.2. Analysis of Cycle Dependent ResultsTRANSIENTS: The analysis of transients (the development of the solution over the cyclescalculated) provides valuable information for the engineer.

In a steady-state engine simulation, the transients should be checked to ensure thatsteady-state operating conditions have been achieved.

If the reaction of the engine to modified settings of control elements was simulated,transients become the most important part when analyzing the calculation results.

Select Simulation|Show Results to open the IMPRESS Chart main window and then selectthe Results tab to display the results as shown in the following figure:


23-Jun-2004 5-3

Figure 5-2: IMPRESS Chart Main Window

The result tree is shown in the window area. Double-click Results.ppd to load the resultsdata. Click the right mouse button in the window area to display the submenu as shownabove. Select Model View to display the model and select the required element to displaythe relevant results in the working window. Performance data for the entire engine can beanalyzed.

In the Engine 1 subfolder average values of all cylinders or the sum of all cylinders areshown. Further values of each cylinder according to the firing order with an offsetmatching the firing interval are displayed in Engine 1|Cylinders.


5-4 23-Jun-2004

Transients plot the variable versus the cycle number and Traces plot the variable versusthe crankangle for the last complete cycle.

The following data is available for each element in the Transients subfolder:

Element Data Unit CommentPIPE:

WALLHEAT J/cycle integral wall heat losses

ENGINE:

END OF CYCLE TIME sec time of Cylinder 1 FTDC

CYCLE AVERAGED SPEED rpm

CYCLE FREQUENCY Hz

CYCLE PERIOD s

IMEP bar indicated mean eff. pressure

ISFC1 g/kWh ind. fuel cons. excl. scav. losses

ISFC2 g/kWh ind. fuel cons. incl. scav. losses

TORQUE Nm eff. engine torque

POWER kW eff. engine power

IMEP_EX bar exhaust work

IMEP_IN bar intake work

IMEP_GE bar gas exchange work

DELIVERYRATIO_AMB - tot. mass at IC rel. to amb. cond.

AIRDELIVERYRATIO_AMB - air del. ratio rel. to amb. cond.

TOTAL FUEL MASS kg aspirated and injected fuel mass

PISTONWALLHEATFLOW J/cycle

HEADWALLHEATFLOW J/cycle

LINERWALLHEATFLOW J/cycle

PEAKCYLINDERPRESSURE Pa

SWIRL

BLOWBY kg/cycle

AMEP bar Auxiliary Drives mean effective

pressure

BMEP bar brake mean eff. pressure

FMEP bar friction mean eff. pressure

BSFC g/kWh brake specific fuel consumption

AIRDELIVERYRATIO_INT - air del. ratio rel. to intake mean

cond.

VOLUMETRICEFFICIENCY_AMB - vol. eff. rel. to amb. cond.

VOLUMETRICEFFICIENCY_INT - vol. eff. rel. to intake man. cond.

ACCUMULATED NOX g/kWh for two and multi zone models

ACCUMULATED SOOT g/kWh for two and multi zone models

SYSTEMBOUNDARY:

for the ATTACHEDPIPE

MASSFLOW kg/cycle

FLOWCOEFFICIENT -

INTERNALBOUNDARY:


MASSFLOW kg/cycle

FLOWCOEFFICIENT - set equal to one (w/o meaning)


23-Jun-2004 5-5

MEASURINGPOINT:

PRESSURE Pa

VELOCITY m/s

TEMPERATURE K

MASSFLOWAVERAGED TEMP K

MACHNUMBER -

MASSFLOW kg/cycle

ENTHALPYFLOW J/cycle

WALLTEMPERATURE K

A/F_RATIO - − total for internal mixture

preparation

− of the combustion products for

external mixture preparation

FUELCONCENTRATION -

COMBUSTIONPRODUCTCONCENTRA

TION

-

CONVERGENCE - sum of pressure temperature and

velocity deviation between cycles

PLENUM:

PRESSURE Pa

TEMPERATURE K

MASS kg

WALLHEATFLOW J/cycle

WALLTEMPERATURE K

for each ATTACHEDPIPE

MASSFLOW kg/cycle

FLOWCOEFFICIENT -

VARPLENUM:

PRESSURE Pa

TEMPERATURE K

MASS kg

VOLUME m3

VOLUMEWORK J/cycle

WALLHEATFLOW J/cycle

WALLTEMPERATURE K


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

CYLINDER:

additional x-axis

IMEP bar indicated mean eff. pressure

ISFC1 g/kWh ind. fuel cons. excl. scav. losses

ISFC2 g/kWh ind. fuel cons. incl. scav. losses

IMEP_EX bar exhaust work

IMEP_IN bar intake work

IMEP_GE bar gas exchange work

MASS kg total mass at IC

DELIVERYRATIO_AMB - tot. mass at IC rel. to amb. cond.

AIRDELIVERYRATIO_AMB - air del. ratio rel. to amb. cond.


5-6 23-Jun-2004

A/F_RATIO - air fuel ratio for the combustion

FUELMASS kg aspirated or injected fuel mass

PISTONWALLHEATFLOW J/cycle

HEADWALLHEATFLOW J/cycle

LINERWALLHEATFLOW J/cycle

PEAKCYLINDERPRESSURE Pa Peak Cylinder Pressure

PEAKCYLINDERPRESSURE CRA degCRA Peak Cylinder Pressure Crankangle

PEAKCYLINDERTEMPERATURE K Peak Cylinder Temperature

PEAKCYLINDERTEMPERATURE

CRA

degCRA Peak Cylinder Temperature

Crankangle

PEAKPRESSURERISE Pa/degCrA Peak Pressure Rise

PEAKPRESSURERISE CRA degCRA Peak Pressure Rise Crankangle

BLOWBY kg/cycle

SWIRL - dynamic swirl at IVC

BMEP bar brake mean eff. pressure

FMEP bar friction mean eff. pressure

BSFC g/kWh brake specific fuel consumption

AIRDELIVERYRATIO_INT - air del. ratio rel. to intake mean

cond.

VOLUMETRICEFFICIENCY_AMB - vol. eff. rel. to amb. cond.

VOLUMETRICEFFICIENCY_INT - vol. eff. rel. to intake man. cond.

LOAD bar

ENGINESPEED rpm av. engine speed over last cycle

PISTONTEMPERATURE K

HEADTEMPERATURE K

LINERTDCTEMPERATURE K

LINERBDCTEMPERATURE K

IGNITIONTIMING degCRA

INJECTIONSTART degCRA dynamic injection nozzle opening

IGNITIONDELAY degCRA

COMBUSTIONSTART degCRA

COMBUSTIONDURATION degCRA

MASSFRACTION BURNED 02 CRA degCRA 2% Mass Fraction Burned Crankangle






VIBEPARAMETER_M -

COMBUSTION_NOISE db(A)

PEAK TEMP BURNED ZONE K for two and multi zone models

ACCUMULATED NOX g/kWh for two and multi zone models

ACCUMULATED SOOT g/kWh for two and multi zone models

COMCHAM_MASS kg total mass in the chamber at IC


23-Jun-2004 5-7

COMCHAM_WALLHEATFLOW J/cycle chamber wallheatflow

COMCHAM_FUELMASS kg fuel mass in the chamber, aspirated

or injected

COMCHAM_AIRMASSFLOW kg/s

COMCHAM_PEAKPRESSURE Pa

COMCHAM_PEAKTEMP K

COMCHAM_A/F_RATIO -

COMCHAM_FUELVAPOUR -

COMCHAM_COMBPROD -

COMCHAM_FUELFRACTION -

CYL_CHAM_A/F_RATIO -

COMCHAM_PARAMETERM - Vibe parameter m for the chamber

COMCHAM_COMBDUR degCRA chamber comb. duration

COMCHAM_SOC degCRA chamber start of combustion

COMCHAM_WALLTEMP K

CONNPIPE_MASSFLOW kg/cycle mean massflow conn.pipe

CONNPIPEWALLHEATFLOW J/cycle


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

VALVE PORT OPENING CRA Valve Port Opening Crank Angle

VALVE PORT CLOSING CRA Valve Port Closing Crank Angle

PORTWALLHEAT J/cycle

PORTWALLTEMPERATURE K

RESTRICTION:


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

ROTARYVALVE:


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

CHECKVALVE:


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

FUELINJECTOR:

ADDEDFUEL kg/cycle


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

WASTEGATE:


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

AIRCOOLER:

INLETPRESSURE Pa

INLETTEMPERATURE K

INLETMASS kg


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OUTLETPRESSURE Pa

OUTLETTEMPERATURE K

OUTLETMASS kg

REJECTEDHEAT J/cycle


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

AIRCLEANER:

INLETPRESSURE Pa

INLETTEMPERATURE K

INLETMASS kg

OUTLETPRESSURE Pa

OUTLETTEMPERATURE K

OUTLETMASS kg


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

CATALYST:

INLETPRESSURE Pa

INLETTEMPERATURE K

INLETMASS kg

OUTLETPRESSURE Pa

OUTLETTEMPERATURE K

OUTLETMASS kg


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

TURBOCHARGER:

COMPRESSORWORK J/cycle

COMPRESSORRATIO - mass flow averaged

TURBINEWORK J/cycle

TURBINERATIO - mass flow averaged

BOOST PRESSURE Pa

DISCHARGECOEFFICIENT -

TURBINETOTOTAL -

ROTATIONALSPEED rpm

COMPRESSOREFFICIENCY -

TURBINEEFFICIENCY -

VANEPOSITION -


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

PD-COMPRESSOR:



ROTATIONALSPEED rpm




23-Jun-2004 5-9

MASSFLOW kg/cycle

FLOWCOEFFICIENT -

TURBOCOMPRESSOR:



BOOST PRESSURE Pa

ROTATIONALSPEED rpm



MASSFLOW kg/cycle

FLOWCOEFFICIENT -

JUNCTION:


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

FIRE:


MASSFLOW kg/cycle

FLOWCOEFFICIENT -

ECU:

LOAD SIGNAL -

5.3. Analysis of Crank Angle Dependent ResultsTRACES: The detailed analysis of the results from the last cycle calculated isrecommended. The comparison of results (e.g. pressure, temperature, flow velocity)obtained at different locations in the engine model or the analysis of physically relatedresults may help to locate problem areas in an engine, or to create new ideas on how tomake improvement.

Select Simulation|Show Results to open the IMPRESS Chart main window (refer toFigure 5-2). Double-click Results.ppd to load the results data.

The following data is available for each element in the Traces subfolder:

Element Data Unit Comment

ENGINE:

TIME s time

ENGINESPEED rpm instantaneous revolution speed

of the crank shaft

TORQUE Nm instantaneous torque at the

crank shaft

SYSTEMBOUNDARY:


MASSFLOW kg/s

FLOWCOEFFICIENTS -

INTERNALBOUNDARY:


MASSFLOW kg/s

FLOWCOEFFICIENTS - set equal to one (w/o meaning)


5-10 23-Jun-2004

MEASURINGPOINT:

PRESSURE Pa

VELOCITY m/s

FORWARDPRESSURE Pa forward moving wave

BACKWARDPRESSURE Pa backward moving wave

FORWARDVELOCITY m/s forward moving wave

BACKWARDVELOCITY m/s backward moving wave

TEMPERATURE K

MACHNUMBER -

STAGNATIONPRESSURE Pa

STAGNATIONTEMPERATURE K

MASSFLOW kg/s

ENTHALPYFLOW J/s

A/F_RATIO - − total for internal mixture

preparation

− of the combustion products

for external mixture

preparation

FUELCONCENTRATION -


TION

-

FUELFLOW kg/s

COMBUSTIONPRODUCTFLOW kg/s

SPECIESCONCENTRATION - user defined concentration

SPECIESFLOW kg/s

PLENUM:

PRESSURE Pa

TEMPERATURE K

MASS kg

WALLHEATFLOW J/s

A/F_RATIO - see measuring point

FUELCONCENTRATION -


TION

-

SPECIESCONCENTRATION -


MASSFLOW kg/s

FLOWCOEFFICIENTS -

VARPLENUM:

PRESSURE Pa

TEMPERATURE K

MASS kg

VOLUME m3

VOLUMEWORK Nm

WALLHEATFLOW J/s

A/F_RATIO -

FUELCONCENTRATION -


TION

-


23-Jun-2004 5-11



MASSFLOW kg/s

FLOWCOEFFICIENTS -

CYLINDER:

PRESSURE Pa

TEMPERATURE K

MASS Kg

VOLUME m3

VOLUMEWORK J/degCrA

HEATTRANSFERCOEFFICIENT W/m2/K

PISTONWALLHEATFLOW J/degCrA

HEADWALLHEATFLOW J/degCrA

LINERWALLHEATFLOW J/degCrA

RATEOFHEATRELEASE J/degCrA

BLOWBY kg/s

SWIRL - dynamic in-cylinder swirl

INTAKEMASSFLOW kg/s

EXHAUSTMASSFLOW kg/s

PRESSURERISE Pa/degCrA

TEMPERATURERISE K/degCrA

A/F_RATIO -

FUELCONCENTRATION -


TION

-


BURNED ZONE MASS K for two and multi zone models

BURNED ZONE TEMPERATURE K for two and multi zone models

UNBURNED ZONE TEMPERATURE K for two and multi zone models

ACCUMULATED NOX kg for two and multi zone models

NOX FORMATION kg/s for two and multi zone models

SOOT FORMATION kg/s for two and multi zone models


MASSFLOW kg/s

FLOWCOEFFICIENTS -

EFFECTIVE FLOW AREA m2

PORTWALLHEATFLOW J/s

COMCHAM_PRESSURE Pa Data of att. chamber

COMCHAM_TEMPERATURE K

COMCHAM_MASS kg

COMCHAM_WALLHEATFLOW J/s

COMCHAM_HEATTRANSFCOEFF W/m2/K

COMCHAM_A/F_RATIO -

COMCHAM_COMBPROD -

COMCHAM_FUELVAPOUR -

CONNPIPEMASSFLOW kg/s Data of conn. pipe

CP_ENTHALPYFLOW J/s

CONNPIPEVELOCITY m/s

CONNPIPEWALLHEATFLOW J/s


5-12 23-Jun-2004

RESTRICTION:


MASSFLOW kg/s

FLOWCOEFFICIENTS -

ROTARYVALVE:


MASSFLOW kg/s

FLOWCOEFFICIENTS -

CHECKVALVE:

VALVELIFT m


MASSFLOW kg/s

FLOWCOEFFICIENTS -

FUELINJECTOR:

ADDEDFUEL kg/s


MASSFLOW kg/s

FLOWCOEFFICIENTS -

WASTEGATE:

VALVELIFT m


MASSFLOW kg/s

FLOWCOEFFICIENTS -

AIRCOOLER:

INLETPRESSURE Pa

INLETTEMPERATURE K

INLETMASS kg

INLET_A/F_RATIO -

INLETFUELCONCENTRATION -

INLETCOMBUSTIONPRODUCTCONC

ENTRATION

-

INLETSPECIESCONCENTRATION -

OUTLETPRESSURE Pa

OUTLETTEMPERATURE K

OUTLETMASS kg

OUTLET_A/F_RATIO -

OUTLETFUELCONCENTRATION -

OUTLETCOMBUSTIONPRODUCTCON

CENTRATION

-

OUTLETSPECIESCONCENTRATION -


MASSFLOW kg/s

FLOWCOEFFICIENTS -

AIRCLEANER:

INLETPRESSURE Pa

INLETTEMPERATURE K

INLETMASS kg

INLET_A/F_RATIO -


23-Jun-2004 5-13



ENTRATION

-


OUTLETPRESSURE Pa

OUTLETTEMPERATURE K

OUTLETMASS kg

OUTLET_A/F_RATIO -



CENTRATION

-



MASSFLOW kg/s

FLOWCOEFFICIENTS -

CATALYST:

INLETPRESSURE Pa

INLETTEMPERATURE K

INLETMASS kg

INLET_A/F_RATIO -



ENTRATION

-


OUTLETPRESSURE Pa

OUTLETTEMPERATURE K

OUTLETMASS kg

OUTLET_A/F_RATIO -



CENTRATION

-



MASSFLOW kg/s

FLOWCOEFFICIENTS -

TURBOCHARGER:

COMPRESSORPOWER J/s

TURBINEPOWER J/s

ROTATIONALSPEED rpm


TURBINEEFFICIENCY -

COMPRESSORPRESSURERATIO -

TURBINEPRESSURERATIO -


MASSFLOW kg/s

FLOWCOEFFICIENTS -


5-14 23-Jun-2004

PD-COMPRESSOR:

COMPRESSORPOWER J/s

MECHPOWER J/s

ROTATIONALSPEED rpm



MASSFLOW kg/s

FLOWCOEFFICIENTS -

TURBOCOMPRESSOR:

COMPRESSORPOWER J/s

MECHPOWER J/s

ROTATIONALSPEED rpm


COMPRESSORPRESSURERATIO -


MASSFLOW kg/s

FLOWCOEFFICIENTS -

JUNCTION:

PRESSURE Pa

TEMPERATURE K

FLOWPATTERN -


MASSFLOW kg/s

FLOWCOEFFICIENTS -

FIRE:


MASSFLOW kg/s

FLOWCOEFFICIENTS -

5.4. Analysis of Composite ElementsSome elements are displayed on the screen as composite elements but consist of morefundamental components in the actual input file. Examples of such elements are:

• Perforated pipe in pipe

• Perforated pipe in plenum.

Some junctions are also not displayed on the screen and the perforated pipes use the samenumbering scheme as the standard pipes although this is not shown. This effects:

• Perforated pipe numbers

• Pipe end junctions for perforated pipes in plenum (restriction or systemboundary).

• Pipe end junctions for pipes of perforated pipe in pipe elements (restriction orsystem boundary).


23-Jun-2004 5-15

To assist in post-processing data from such hidden elements, the fundamental contents ofcomposite elements can be displayed by selecting Simulation|Show Elements to open theelements window. This information can then be used to post-process the data from therequired location of composite elements.

� Note: This is only possible after completing a successful simulation.

Figure 5-3: Show Elements Window

5.5. Analysis of Frequency Dependent Results andOrifice NoiseACOUSTIC: The acoustic folder contains the simulation results against frequency.


ENGINE:

EngineOrder -

Engine order versus frequency.

Can be used as the x-axis to

generate plots versus engine

order

SYSTEMBOUNDARY:

SpecificMassflow kg/s/m2

For use with the orifice noise

post processing operation

described below

MEASURING POINT:

PhaseAngle Deg

RealPressure Pa

ImagPressure Pa

Linear : SoundPressure dB In duct sound pressure level

MICROPHONE:

PhaseAngle Deg

Pressure Pa

A-weighted : SoundPressure dB(A) A-weighted sound pressure level

Linear : SoundPressure dB Linear sound pressure level


5-16 23-Jun-2004

The microphone element described in Chapter 3 is recommended for determining orificenoise although the post processing operation described here is still supported.

However, note that the post processing operation only supports single source data to amicrophone whereas the microphone element can handle multiple sources.

The orifice noise is determined from the calculated mass flow characteristics at the systemboundaries.

Select Simulation|Show Results to open the IMPRESS Chart main window. Click on theOperations tab and the acoustic operations are available in the Data Analysis folder.

Click on the Results tab and select the Acoustic folder in Results.ppd to plot theAmplitude curve at the required system boundary.

Additional input of the microphone position relative to the location of the orifice inCartesian coordinates is required.

Axis, x

Vertical, z

Lateral, y

0

Ground (optional)

Height (optional) MICROPHONE

ORIFICE

Figure 5-4: Microphone position

From this information the sound pressure levels in dB are calculated and displayed overfrequency in a graphics window. In addition, the orifice noise in dB(A) is calculated anddisplayed in the acoustics window.

5.6. Analysis of Case Series ResultsFor the Analysis of case series applications the full range of Transients result types (listedin 5.2) are available

Select Simulation | Create Series Results.

A one step solution for creating series results for all case sets is available. For each case setthe main variation parameter can be freely chosen.


23-Jun-2004 5-17

Figure 5-5: Create Series Results Window

• First column: defines if the results should be created

• Second column: shows all available case sets

• Third column: allows the definition of the main parameter for the results creation, this will be x-axis in IMPRESS Chart.

• Last column: shows the state of the creation process

Select Run Creation to start the processes of result creation.

Then select Simulation | Show Results to open the IMPRESS Chart main window whichshows one folder for each case set (name.case_set.case_no) and an additional foldercontaining the series related results (name.case_set).

5.7. Analysis of Animated ResultsANIMATION: The display of animated results helps the user to comprehend the interactionof flow phenomena within the pipe system of an engine.

Spatial Plots

Depending on the specified output interval of Traces results, spatial plots for each pipe andtime step can be accessed by selecting Simulation|Show Results(working_directory/bwf_file_name.Case_Set_X.CaseY/simulation.dir/Results.ppd).

Animated Results

An animated view on the whole system can be performed by selecting Simulation|ShowAnimation to open the PP3 main window.


5-18 23-Jun-2004

Figure 5-6: PP3 Main Window

The available animation data is:

• Pressure

• Gas velocity

• Gas Temperature

• A/F ratio of the combustion products

• Fuel vapour

• Combustion products

5.8. Message AnalysisMESSAGES: Displaying messages after the calculation process allows the user to checkfor information, warnings and errors generated by the solver.

Select Simulation|Show Messages to open the Message Browser as shown in the followingwindow:

Figure 5-7: Message Analysis Window


23-Jun-2004 5-19

From the Sorted by pull down menu, select Message Type, Message ID, Element Nameor Position for the desired display. Select the respective values in the Start from and Endat pull down menus to display messages occurring within a certain crank angle interval.

The global information is shown and more detailed information can be shown by clicking<RUNINFO> with the mouse. Click the expand button + to show the detailed informationin the folder.

In a steady-state engine simulation it is strongly recommended to check the messages fromthe main calculation program displayed during the last calculated cycle. If majorirregularities have occurred, it is essential to check whether the calculation results areplausible.

5.8.1. Message DescriptionMessages generated by the BOOST solver consist of a message header followed by textgiving more detailed information. The format and components of the message header aredescribed as follows:

<TYPE> <CODE> <ELEMENT> <NUMBER> <ROUTINE> <CRANK ANGLE> DEGCRA

1. Type

The first part of the message header is the basic type of the message. The possibletypes and a brief description are given in the following table.

Message Type Description

FATALERROR A fatal error that causes the simulation to stop.

READERRORAn error occurred reading a value. This usually causesthe simulation to stop.

INVALIDINPUTThe value has been read correctly but the value or stringis invalid in this context. This also causes the simulationto stop.

CONVERGENCEFAILAn iteration loop has reached the maximum number ofiterations without converging. The loop will be exited andthe simulation will continue. This message is not fatal.

RUNINFOContains useful information about the simulation. Thisincludes the names and paths of loaded files andchanges in default values.

WARNINGA warning about values or conditions in the currentsimulation. The simulation will continue to run.

OUTOFRANGEA value is out of the permitted range. The acceptedrange is typically given in the body of the text. This isusually not fatal.

FILEERRORAn error occurred in reading or writing to files used byBOOST. This is a fatal error.

MEMORYERRORA memory allocation error has occurred. Typically causedby insufficient memory available on the current host. Thisis a fatal error.


5-20 23-Jun-2004

2. Code

A number associated with the message which is useful for tracking the exact locationin the code that generated the message.

3. Element

If the message is generated by a specific BOOST element such as a cylinder or junction,this will be displayed at this location. Otherwise, a character string describing thecurrent process, such as ‘INPUT’ or ‘CONTROL’, will be displayed.

4. Number

The element number that generated the message. If the message is not associated witha particular element number then a zero will be displayed.

5. Routine

The BOOST routine which generated the message.

6. Crank Angle

The simulation crank angle when the message was generated. This will be in degrees.

5.8.2. Message Examples

RUNINFO 0 CONTROL 0 STWINP 0.00 DEGCRA

Opened file : C:/Program Files/avl/BOOST/v4.0/files/BENZIN.GPF

The message states the name and path of a file that has been loaded by BOOST during thesimulation. In this case it is the gas property file (.gpf) for benzin. The message wasissued at 0.00 degrees crank angle by the routine STWINP (i.e. at the beginning of thesimulation).

WARNING 183658 TURBOCHARGER 1 TLVOLL 2880.22 DEGCRA The operating point of the compressor crossed the surge line of the performance map. Massflow: 0.036kg/s, Pressure ratio: 1.60

Warning number 183658 concerning the compressor operating point was issued byturbocharger number 1 at 2880.22 degrees crank angle in the routine TLVOLL.

CONVERGENCEFAIL 143302 JUNCTION 3 PSTP0 6336.58 DEGCRA The iteration of the junction massflow failed to converge at flowpattern 6. calculated values: type 1 type 2 difference in % of total massflow attached pipe 1: 0.000609 0.000609 0.000000 attached pipe 2: 0.007190 0.007366 2.206129 attached pipe 3: 0.007970 0.007800 2.133474


23-Jun-2004 5-21

5.8.3. Fatal Errors

5.8.3.1. MATLAB API

FATALERROR 121901 DLL 1 INIDLL 106.00 DEGCRA MATLAB-ENGINE run error - Check that matlab executable directory is in PATH. - Check that a valid license is available. The calculation has been stopped.

This message is generated when running with the MATLAB API option. There are severalreasons this message is generated. MATLAB is not found in the directories listed in thePATH environment variable, a valid license is not available or there is a clash of MATLABversions. For the last case this can happen when the version of the MATLAB mdl file doesnot match the version of MATLAB that BOOST is attempting to load. This can happenwhen there is more than one MATLAB version is installed on the computer. The followingdialog box will be generated in such a case.

Figure 5-8: MATLAB API Error - version mismatch

The solution is to make sure the version of the MATLAB model (mdl file) matches theMATLAB version listed first in the PATH.


5-22 23-Jun-2004

5.9. Analysis of Aftertreatment Analysis ResultsAll data from the aftertreatment analysis simulations is given as transient values atdifferent spatial positions of the element. The spatial position (can be defined by the user)is part of the folder and curve name respectively. The following data is available inCatalyst Analysis and Particle Filter Analysis subfolder:


CATALYST:

SOLID TEMPERATURE K Temperature of the solid substrate.

This temperature is used for all

conversion reactions.

GAS TEMPERATURE K Temperature of the gas phase.

PRESSURE Pa The pressure data are relative

values related to the pressure at

the catalyst.

VELOCITY m/s The velocity is a interstitial

velocity inside the catalyst

channels. For the evaluation of the

superficial velocity the open

frontal area of the catalyst has to

be applied.

MASS FRACTION <<XX>> kg/kg <<XX>> represents any species

defined in Globals/Aftertreatment

Analysis, e.g. CO, CO2, C3H6,

NO2,...

PARTICULATE FILTER :

SOLID TEMPERATURE K Temperature of the solid substrate.

This temperature is used for all

regeneration reactions.

GAS TEMPERATURE K Temperature of the gas phase.

PRESSURE Pa The pressure is given as relative

value. A pressure difference is

calculated between the pressure at

the end of the filter outlet

channel and the pressure at the

corresponding axial position in the

filter inlet channel.

VELOCITY m/s The velocity is an interstitial

velocity inside an ‘theoretically’

combined channel, where the inlet

and outlet channel are put

together.

MASS FRACTION <<XX>> kg/kg <<XX>> represents any species

defined in Globals/Aftertreatment

Analysis, e.g. CO, CO2, C3H6,

NO2,... This gas composition can be

understood as part of the outlet

channel.


23-Jun-2004 5-23

SOOT MASS kg/m3Filter The soot mass is given as volume

specific value, where the overall

volume of the filter is used as

reference.

SOOT HEIGHT m The soot height is evaluated

assuming that soot is equally

distributed over the entire inlet

channel cross section.

WALL VELOCITY - The wall velocity is given by

normalized values.

INLET CHANNEL VELOCITY m/s Th inlet channel velocity is the

interstitial velocity inside the

filter inlet channel.

OUTLET CHANNEL VELOCITY m/s The outlet channel velocity is the

interstitial velocity inside the

filter outlet channel.

INLET CHANNEL PRESSURE Pa Absolute pressure in the inlet

channel.

OULLET CHANNEL PRESSUER Pa Absolute pressure in the outlet

channel.


23-Jun-2004 6-1

6. THE BOOST FILES6.1. The .bwf Files

The BOOSTFILENAME.bwf files contains all graphics and input data of the BOOST model.

6.2. The .bst FilesThe BOOSTFILENAME.bst file is the input file of the calculation kernel. It is generated byselecting Simulation|Run|Model Creation and is written into the subfolderBOOSTFILENAME.Case_X (X...Index of the Case Set).

As it is an ASCII formatted file, it can be transferred to and executed on every platform orcomputer where a BOOST calculation kernel is available.

The BOOSTFILENAME.bst file consists of the following sections:

• SECTION HEADER: Contains the total number of elements for each type ina calculation model.

• SECTION INPUT: Contains all input data.

• SECTION MESSAGES: Summary of the messages from the maincalculation program.

• SECTION TRANSIENTS: Average results of each element over each cyclecalculated (GIDAS format).

• SECTION TRACES: Covers the crank angle dependent calculation resultsfrom the last calculated cycle (GIDAS format). In an animation calculationthis section is not available.

• SECTION ANIMATION: Summary of the results of an animationcalculation (GIDAS format). In a single calculation this section is not available.

• SECTION SUMMARY: Contains the global calculation results. In a seriescalculation, this section is available for each of the calculated operating pointsor engine variants.

6.3. The .atm FilesThe BOOSTFILENAME.atm is similar to the BOOSTFILENAME.bst but it is used to run theBOOST calculation kernel in aftertreatment analysis mode.

The BOOSTFILENAME.atm file consists of the following sections:

• SECTION HEADER: Contains the total number of elements for eachtype in a calculation model.

• SECTION INPUT: Contains all input data.

• SECTION MESSAGES: Summary of the messages from the maincalculation program.

• SECTION CAT_ANALYSIS: Transient results of catalyst analysissimulations (GIDAS format).


6-2 23-Jun-2004

• SECTION DPF_ANALYSIS: Transient results of diesel particulate filteranalysis simulations (GIDAS format).

• SECTION SUMMARY: Contains the global calculation results andadditional simulation data.

6.4. The .rs0 and .rs1 FilesThe BOOSTFILENAME.rs0 and BOOSTFILENAME.rs1 files are restart files. As they areASCII formatted files, a data set can be transferred together with the restart files to adifferent platform and the calculation continued with a restart.

6.5. The .uit FileThis file is written by the main calculation program. It is used for writing debuginformation during the development of the code and can be deleted after a simulation runwithout any consequence.

6.6. The .gpf FileThese files contain the tables of gas properties in dependence on pressure, temperatureand excess air ratio (located in $BOOST_HOME\..\..\files).

6.7. The rvalf.cat FileThis file contains the catalogue of flow coefficients for three-way junctions. It should belocated in the directory $BOOST_HOME\..\..\files.


23-Jun-2004 7-1

7. RECOMMENDATIONS7.1. Modeling

In principle, the following requirements must be met by the engine model:

1. The lengths in the piping system must be considered correctly.

2. The total volumes of the intake and exhaust systems must be correct.

As experience shows, major problems may occur when specifying the dimensions of pipes.The length of a pipe is determined along the centerline and may be difficult to measure.Also, the engine model should meet the requirement that both the lengths of the singlepipes and the total length (e.g. the distance between inlet orifice and intake valves of thecylinder) are considered properly.

The modeling of steep cones or even steps in the diameter of a pipe by specifying a variablediameter versus pipe length should be avoided. A flow restriction should be used instead.

Figure 7-1: Modeling of Steep Cones

If the modeling of steep cones is necessary, the mass balance (i.e. the difference of the in-flowing at out-flowing mass) of this pipe should be checked carefully by the user. In thiscontext it is important to mention that the plenum elements do not feature a length in thesense of a distance which must be passed by a pressure wave. For this reason it issometimes difficult to decide on a correct modeling of a receiver; on one hand a plenumcould represent a convenient modeling approach while on the other a more detailedmodeling with several pipes and junctions could be required. The decision must be madeon the basis of the crank angle interval which pressure waves need to propagatethroughout the receiver. This means that for high engine speeds a detailed pipe junctionmodel is required, whereas for low engine speeds a plenum model may produce excellentresults.

The following figure illustrates both options for the example of the intake receiver of a fourcylinder engine with frontal air feed.


7-2 23-Jun-2004

Figure 7-2: Modeling of an Intake Receiver

The plenum model may predict equal air distribution whereas in reality this is often acritical issue especially for long receivers with small cross sectional areas. For the latter,the pipe junction model is preferred. The step in the cross sectional area at the inlet to theintake receiver is modeled with a flow restriction. Ensure correct modeling of the length ofthe intake runners (refer to Figure 7-15).

Figure 7-3: Modeling of an Intake Receiver with Pipes and Junctions


23-Jun-2004 7-3

The following figure shows three different models for an intake receiver of a four cylinderengine:

Figure 7-4: Intake Receiver Models

The first model is a simple plenum model. The second is a pipe and junction model withlateral inlet, and the third is a pipe and junction model with central inlet. The totalvolume of the receiver was kept constant. Figure 7-5 shows the predicted volumetricefficiency and air distribution for the three models. The air distribution is expressed as thedifference between the maximum and minimum volumetric efficiency of an individualcylinder related to the average volumetric efficiency.

Figure 7-5: Influence of Intake Receiver Modeling on Volumetric Efficiency and AirDistribution


7-4 23-Jun-2004

The predicted overall volumetric efficiency is similar for all three models, except for shiftsin the resonance speeds. As the plenum model does not account for pressure waves in theintake receiver, equal volumetric efficiencies are calculated for all cylinders. The lateralair feed proves to be most critical with respect to air distribution especially at higherengine speeds.

Modeling of the ports deserves special attention, especially modeling of the exhaust ports.The flow coefficients are measured in an arrangement similar to the following figure:

Figure 7-6: Exhaust Port Modeling

The measured mass flow rate is related to the isentropic mass flow rate calculated with thevalve area and the pressure difference across the port. The model shown on the bottomleft of the above figure would produce mass flow rates which are too high (too low in thecase of a nozzle shaped exhaust port), because the diffuser modeled causes a pressurerecovery increasing the pressure difference at the entry of the pipe modeling the port. Themass flow rate is calculated with the increased pressure difference and the valve area, andis therefore greater than the measured one. This problem can be overcome either by acorrection of the flow coefficients or by switching to a model as shown on the bottom rightof the above figure. Due to modeling the pipe as a straight diameter pipe with flange area,there is no pressure recovery. However, the flow coefficients need to be corrected by theratio of the different areas. This can be done easily by the scaling factor.

For modeling a multi-valve engine two options are available:

1. A pipe is connected to each valve (refer to Figure 7-7, left side):

The branched part of the intake and exhaust port is modeled by two pipes anda junction. For this junction, the refined model should be used exclusively, asthe constant pressure model causes very high pressure losses. This modeling isrequired only if the two valves feature different valve timings, the geometry ofthe runner attached to each valve is different or a valve deactivation systems isused.


23-Jun-2004 7-5

2. All intake and all exhaust valves are modeled by one pipe attachment (refer toFigure 7-7, right side):

The number of valves is taken into account by specifying the flow coefficientsand scaling factor in such a way that the total effective flow area of allconsidered valves is obtained. This modeling is preferred as it requires fewerelements and is therefore less complicated and more efficient.

Figure 7-7: Modeling Multi-Valve Engines

7.2. Analysis of ResultsThe BOOST post-processor assists the user efficiently in the analysis of calculation results,as it allows several trends to be displayed over crank angle simultaneously. This makesthe comparison of pressure or mass flow histories over crank angle very simple at differentlocations in the engine model.

An important parameter for the analysis of gas dynamic pressure wave motion is the crankangle interval, which is required by a pressure wave to propagate over a certain distance.The speed of the pressure wave propagation is determined by the speed of sound and theflow velocity (a ± u). Mostly the Mach number of the flow in the pipe is relatively low,which allows the influence of the flow velocity to be neglected. In this case, the crankangle interval required for the propagation of a pressure wave over one meter distance canbe calculated from the following formula:

anvW⋅= 6

(7.2.1)

wv pressure wave propagation speed [degrees CRA/m]


a speed of sound [m/s]

The speed of sound can be calculated from the gas temperature in the pipe. A typical valuefor the intake system is 345 m/s. In the exhaust system, the speed of sound varies typicallybetween 550 m/s (diesel engines) and 650 m/s (gasoline engines).

When using the Equation 7.2.1, it should be noted that the influence of the flow velocity isneglected.


7-6 23-Jun-2004

Another important effect in the analysis of gas dynamic calculation results is thecharacteristics of the pressure wave reflection:

• At an open pipe end (α ∼1.0), a pressure wave is reflected as a depression wave,and a depression wave as a pressure wave.

• At a closed pipe end (α ∼0), a pressure wave is reflected as a pressure wave, anda depression wave as a depression wave.

The reflection of pressure waves at a plenum is more complex, as normally the pressure inthe plenum varies over time. For that reason, the characteristics of the pressure wavereflection depend on the volume of the plenum:

• If the plenum is very large, the pressure in the plenum remains almostconstant and the reflection characteristics are similar to those of a pipe open tothe ambient as discussed above.

• If the plenum volume approaches zero, the variation of the pressure in theplenum is similar to the pressure variation inside the pipe.

The behavior of diffusers and cones is also of special interest. A pressure wave propagatinginto a diffuser is weakened due to the expansion resulting from the increasing cross-section. As a consequence, depression waves are reflected by the diffuser:

• If a depression wave propagates into a diffuser, the depression wave is alsoweakened and pressure waves are reflected.

• If a pressure wave propagates into a cone, the pressure wave becomes strongerand pressure waves are reflected.

• If a depression wave propagates into a cone, the depression wave becomesstronger and depression waves are reflected.

7.3. Important TrendsThis section summarizes some typical influences of important parameters on engineperformance. They may be used to get an overview of required parameter modifications inan engine model to obtain calculated performance characteristics closer to the targetengine performance.

The example figures shown in this chapter reflect the general trend. They were obtainedfrom a simplified model of a 4-cylinder SI engine. The actual influence of the parametervaried may be different on other engines due to the presence of other effects.

The influence of heat transfer is two-fold. It influences the heating of the fresh chargeduring the gas exchange and thus the volumetric efficiency. This effect is morepronounced from low to mid-engine speeds as more time is available for the heat transferto take place.

Secondly, the heat transfer influences the efficiency of the high pressure cycle byinfluencing the wall heat losses. Figure 7-8 shows the effect of the variation of the in-cylinder heat transfer on the engine performance.


23-Jun-2004 7-7

Figure 7-8: Influence of In-Cylinder Heat Transfer on Engine Performance

The influences of the flow coefficients and wall friction losses are more pronounced at highengine speeds, where the flow velocities in the system are relatively high. They have littleinfluence on engine performance in the low and mid-speed range.

Figure 7-9: Influence of Port Flow Coefficients on Engine Performance

Intake valve closing mainly influences the volumetric efficiency of the engine. Advancedintake valve closing improves the engine air flow at low engine speeds and retarded intakevalve closing favors high engine speeds.


7-8 23-Jun-2004

Figure 7-10: Influence of IVC on Engine Performance

Figure 7-11: Influence of EVO on the Engine Performance

There may be a significant influence of the valve train dynamics and/or of the differencesbetween the valve clearances between a cold and hot engine on the engine air flowcharacteristics. This depends on valve train design.

Inertia effects in the intake system may be used for a gas dynamic supercharging of theengine. This effect is important at higher engine speeds because the inertia of the gas inthe intake runner becomes significant only at high velocities.

Another possibility of gas dynamic supercharging is the use of resonance effects in theintake system. The resonance frequency of such system can be determined roughly fromthe Helmholtz formula:


23-Jun-2004 7-9

VlAaf⋅

⋅⋅

=π2

(7.3.1)

f resonance frequency [Hz]

a speed of sound [m/s]

A pipe cross-section [m²]

l tuning pipe length [m]

V plenum volume [m³]

By selecting the dimensions, a resonance system may be tuned to low or high speeds. Atuning for low speeds can be achieved with a long tuning pipe, a large plenum volume anda small pipe cross-section. However, the plenum is usually located between the tuning pipeand the cylinders, which provide the excitation of the resonance system. For this reason, alarge plenum volume lowers the resonance frequency but also increases the damping of theexcitation, which is detrimental to gas dynamic tuning.

The effects of these two tuning strategies can be seen in the following figures. If the lengthof the air feed pipe to the intake receiver is varied, as defined in the following sketch, itmainly influences the low frequency resonance peak in the volumetric efficiency curve.

Figure 7-12: Air Feed to Intake Receiver


7-10 23-Jun-2004

Figure 7-13: Influence of Air Feed Pipe Length on Engine Performance

Using the dimensions of the air feed pipe for tuning purposes depends on the number ofcylinders. The excitation of the low frequency system decreases when the number ofcylinders is increased.

Figure 7-14: Influence of Number of Cylinders on Engine Performance

Although the intake runner length as shown in the next sketch, determines the highfrequency resonance, it has also a certain influence on the low frequency peak.


23-Jun-2004 7-11

Figure 7-15: Intake Running Length

Figure 7-16: Influence of Intake Runner Length on Engine Performance

The performance characteristics of two-stroke engines are more unstable than four-strokeengines. This is caused by the strong interference between the intake and exhaust systemsduring the scavenging period. As a consequence, a large number of cycles must becalculated until steady conditions are achieved. Minor inaccuracies in the engine model orminor modifications to an engine configuration may result in large differences in theengine performance.

The tuning of a two-stroke engine with symmetrical port timing can almost be achieved viathe exhaust system alone, as the conditions in the cylinder at the beginning of the highpressure cycle are determined by exhaust port closing. For this reason, the influence ofcombustion on the gas exchange process is also relatively strong (via the exhaust gastemperature and the speed of sound in the exhaust system). This is not the case for four-stroke engines.


7-12 23-Jun-2004

7.4. Turbocharger MatchingAnother application of BOOST is to determine a suitable compressor and turbine size for aturbocharged engine. The simplified turbocharger model with its three calculation modes(turbine layout, boost pressure and waste gate calculation) supports the user in this task.

The following steps outline the procedure for the layout of a conventional waste gateturbocharger:

1. The first step is to estimate the air flow requirement for engine full load at the enginespeed when the waste gate starts to open. A common layout is around maximumtorque speed. The air flow can be calculated from the target Brake Mean EffectivePressure (BMEP), Brake Specific Fuel Consumption (BSFC) and the required Air/FuelRatio. The latter is estimated from emission targets considerations.

91016.2 ⋅⋅⋅⋅⋅⋅=

⋅

c

Dair

nBSFCnVBMEPAFRm (7.4.1)

airm⋅

air flow [kg/s]

AFR air fuel ratio [-]

BMEP brake mean effective pressure [bar]

DV displacement [l]


cn 1 for two stroke engines

2 for four stroke engines

BSFC brake specific fuel consumption [g/kWh]

2. With another estimate of the intake manifold temperature and the volumetricefficiency of the engine, the target BOOST pressure is calculated from

106

⋅⋅⋅⋅⋅⋅⋅=

⋅

nVnTRmP

DV

cmairm η

(7.4.2)

mP intake manifold pressure [bar]

R gas constant of air, 287 J/kg K

mT intake manifold temperature [K]

Vη volumetric efficiency related to intake manifold conditions [-]

3. Substituting Equation 7.4.1 into Equation 7.4.2 yields

9106.3 ⋅⋅⋅⋅⋅⋅=

V

mm

TRBSFCBMEPAFRPη

(7.4.3)


23-Jun-2004 7-13

4. With the pressure loss of the inter cooler and air cleaner, the compressor pressure ratiois known

cleaneramb

coolermco PP

PP∆−∆+=Π

coΠ compressor pressure ratio [-]

coolerP∆ inter cooler pressure loss [bar]

ambP ambient pressure [bar]

cleanerP∆ air cleaner pressure loss [bar]

5. Using a turbine layout calculation, an equivalent turbine discharge coefficient and anoperating point of the engine in the compressor map is obtained. Making twoadditional calculations with the first turbine discharge coefficient at the lowest enginefull load speed in the BOOST pressure calculation mode and at the highest full loadspeed in the waste gate calculation mode, yields another two operating points of theengine in the compressor map. The compressor pressure ratio for the waste gatecalculation can be determined again from Equation 7.4.3. Figure 7-17 shows the threeoperating points in the compressor map.

Figure 7-17: Engine Operating Line in the Compressor Map

6. With this information a suitable compressor can be selected. If the compressor is toosmall, the rated speed operating point is beyond the speed limit of the compressor or inthe choked flow region, Figure 7-18.


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Figure 7-18: Engine Operating Line in the Compressor Map (compressor too small)

If the compressor is too large, low and/or mid speed operating points are located left ofthe surge line in Figure 7-19.

Figure 7-19: Engine Operating Line in the Compressor Map (compressor too large)


23-Jun-2004 7-15

If the correct compressor is selected, the entire engine operating line is located withinthe map, Figure 7-20.

Figure 7-20: Engine Operating Line in the Compressor Map (correct compressor)

7. To determine the necessary turbine, the equivalent turbine discharge coefficient mustbe converted to a swallowing capacity and plotted in the turbine map, Figure 7-21.

Figure 7-21: Engine Operating Point in the Turbine Map

8. After selecting possible turbines and compressors, the calculations must be repeated inthe BOOST pressure and waste gate calculation modes to consider the actualefficiencies and swallowing capacities from the maps.

For turbochargers with variable turbine geometry, the turbine layout calculation modemay be used at all engine speeds. The location of the engine operating point in thecompressor and turbine map must be checked and the actual efficiencies compared tothe assumed efficiencies of the calculation. If a larger difference between theefficiencies is detected, the calculation must be repeated with updated efficiencies.


23-Jun-2004 8-1

8. LITERATUREThis guide contains important information about the theoretical basis used for thedevelopment of the code. For further reading, refer to the following list:

General Literature:

[G1] Heywood, J. B., Internal Combustion Engine Fundamentals, McGraw-Hill, 1988,ISBN 0-07-100499-8

[G2] Pischinger, R. et al., Thermodynamik der Verbrennungskraftmaschine, Springer,1989, ISBN 3-211-82105-8

[G3] Benson, R. S., The Thermodynamics and Gas Dynamics of Internal CombustionEngines, Volume 1, Clarendon Press, Oxford, 1982, ISBN 0-198562101

[G4] Shapiro, A. H., The Dynamics and Thermodynamics of Compressible Fluid Flow,Volume 1/2, Ronald Press Company, 1954

[G5] Fried, E., Flow Resistance (A Design Guide for Engineers), I.E. IdelchickHemisphere Publishing Corporation, 1989, ISBN 0-89116-435-9

[G6] Watson, N. and Janota, M. S., Turbocharging the Internal Combustion Engine, TheMacmillan Press Ltd., London, ISBN 0-33-24290-4

[G7] Laimböck, F. J., The Potential of Small Loop-Scavenged Spark-Ignition Single-Cylinder Two-Stroke Engines, SP 847 Society of Automotive Engineers, Inc.,Warrendale, PA 15096-0001

[G8] Engine Terminology and Nomenclature – General, NN, SAE - Standard J604, sl,June 1995

Pipe Flow:

[P1] Giannattasio, P. et al., Applications of a High Resolution Shock Capturing Schemeto the Unsteady Flow Computation in Engine Ducts, Imech 1991, C430/055

[P2] Harten, A. et al., High Order Accurate Essentially Non-Oscillatory Schemes III,Journal of Computational Physics, Volume 71, Number 2, August 1987

[P3] Winterbone, D. E. and Pearson, R. J., Design Techniques for Engine Manifolds,Wave Action Methods for IC Engines, Professional Engineering Publishing, 1999.

[P4] Winterbone, D. E. and Pearson, R. J., Theory of Engine Manifold Design, WaveAction Methods for IC Engines, Professional Engineering Publishing, 2000.

[P5] Onorati, A., Nonlinear fluid dynamic modeling of reactive silencers involvingextended inlet/outlet and perforated ducts, Noise Control Eng. J. 45 (1), 1997

[P6] Bartsch, P., Bachner, B., Borzi, A. and Schuemie, H. A., On the Simulation of aConcentric Tube Resonator, 5th ISAIF, Gdansk, 2001

[P7] Konstandopoulos, A. G., Kostoglou, M., Skaperdas, E., Papioannou, E., Zarvalis D.,and Kladopoulou, E., Fundamental Studies of Diesel Particulate Filters: TransientLoading, Regeneration and Ageing, SAE 2000-01-1016 , 2000.

[P8] Konstandopoulos, A. G., Skaperdas, E., Warren, J., and Allansson, R., OptimiseFilter Design and Selection Criteria for Continuously Regenerating DieselParticulate Traps, SAE 1999-01-0468, 1999.


8-2 23-Jun-2004

[P9] Peters, B. and Gosman, A. D., Numerical Simulation of Unsteady Flow in EngineIntake Manifolds, SAE 930609 , 1993.

[P10] Shah, R. K. and London, A. L., Laminar Flow Forced Convection in Ducts: ASourcebook for Compact Heat Transfer Exchange Analytical Data, Academic Press,1978.

[P11] Peters, B. and Dziugys, A., Numerical Modeling of Electrified Particle LayerFormation on the Surface of Filtration Fabric, Environmental Engineering ,9:4:191-197, 2001.

[P12] Peters, B. and Dziugys A., Numerical Simulation of the Motion of GranularMaterial using Object-oriented Techniques, Comput. Methods Appl. Mech. Eng. ,191:1983-2001, 2002.

Cylinder:

[C1] Woschni, G. and Anisits, F., Eine Methode zur Vorausberechnung der Änderungdes Brennverlaufs mittelschnellaufender Dieselmotoren bei geändertenBetriebsbedingungen, MTZ 34, 1973

[C2] Hires, S. D., Tabaczynski, R. J. and Novak, J. N., The Prediction of Ignition Delayand Combustion Intervals for a Homogenous Charge Spark Ignition Engine, SAE780232

[C3] Andree, A. and Pachernegg, S. J., Ignition Conditions in Diesel Engines, SAE690253

[C4] Rhodes, D. B. and Keck, J. C., Laminar Burning Speed Measurements of Indoline-Air-Dilunet Mixtures at High Pressures and Temperatures, SAE 850047

[C5] Woschni, G., A Universally Applicable Equation for the Instantaneous HeatTransfer Coefficient in Internal Combustion Engines, SAE 6700931

[C6] Woschni, G., Einfluß von Rußablagerungen auf den Wärmeübergang zwischenArbeitsgas und Wand im Dieselmotor, in proceedings to „Der Arbeitsprozeß desVerbrennungsmotors“, Graz 1991

[C7] Hohenberg, G., Experimentelle Erfassung der Wandwärme von Kolbenmotoren,Habilitationsschrift TU-Graz, 1980

[C8] Zapf, M., Beitrag zur Untersuchung des Wärmeübergangs während desLadungswechsels in einem Viertakt-Dieselmotor, MTZ 30, 1969

[C9] Gorenflo, E., Einfluß der Luftverhältnisstreuung auf die zyklischen Schwankungenbeim Ottomotor, Wiesloch, VDI Fortschrittsberichte , Reihe 12, Nr 322

[C10] Noske, G., Ein quasi-dimensionales Modell zur Beschreibung des ottomotorischenVerbrennungsablaufes, Eggenstein, VDI, Fortschrittsberichte, Reihe 12, Nr 211

[C11] Jungbluth, G. und Noske, G., Ein quasi-dimensionales Modell zur Beschreibungdes ottomotorischen Verbrennungsablaufes – Teil 1, MTZ 52, 1991

[C12] Jungbluth, G. und Noske, G., Ein quasi-dimensionales Modell zur Beschreibungdes ottomotorischen Verbrennungsablaufes – Teil 2, MTZ 52, 1991

[C13] Vibe, I. I., Brennverlauf und Kreisprozeß von Verbrennungsmotoren, VerlagTechnik, Berlin, 1970


23-Jun-2004 8-3

[C14] Hiroyasu, H. and Kadota, T., Models for Combustion and Formation of NitricOxide and Soot in Direct Injection Diesel Engines, in SAE Paper 760129, pages513-526. 1976

[C15] Hiroyasu, H., Kadota T. and Arai, M., Development and Use of a Spray CombustionModel to Predict Diesel Engine Efficiency and Pollutant Emissions (Part 1.Combustion Modelling), Bulletin of the JSME, 26:569-575, 1983

[C16] Imanishi, T., Yoshizaki, K. and Hiroyasu, H., Simulation Study of Effects ofInjection Rate Profile and Air Entrainment Characteristics on D.I. DieselCombustion, in SAE Paper 962059, pages 135-144, 1996

[C17] Yoshizaki, K., Nishida, T. and Hiroyasu, H., Approach to Low NOx and SmokeEmission Engines by Using Phenimenogical Simulation, in SAE Paper 930612,1993

[C18] Chmela, F. and Orthaber, G., Rate of Heat Release Prediction for Direct InjectionDiesel Engines Based on Purely Mixing Controlled Combustion, SAE Paper 199901 0186

[C19] Chmela, F., Orthaber, G. and Schuster, W., Die Vorausberechnung desBennverlaufs von Dieselmotoren mit direkter Einspritzung auf der Basis desEinspritzverlaufs, MTZ 59 (1998) 7/8

[C20] Wolfer, H., Der Zündverzug im Dieselmotor, VDI-Forschungsarbeiten, Heft 392,VDI-Verlag GmbH Berlin (1938)

[C21] Bargende, M., Hemispherical Flame Propagation – A Tool for Simulating InternalCombustion Effects, In 4th Symposium, The Working Process of the InternalCombustion Engine, Technical University - Graz, September 1993.

[C22] Blizzard, N. C. and Keck, J. C., Experimental and Theoretical Evaluation ofTurbulent Burning Model for Internal Combustion Engines, SAE 740191.

[C23] Tallio, K. V. and Colella, P., A Multi-Fluid CFD Turbelent EntrainmentCombustion Model: Formulation and One-Dimensional Results, SAE 972880.

[C24] Tabaczynski, R. J., Ferguson, C. R. and Radhakrishnan, K., A TurbulentEntrainment Model for Spark Ignition Engine Combustion, SAE 770647.

[C25] Tabaczynski, R. J., Trinker, F. H. and Shannon, B. A. S., Further Refinement andValidation of a Turbulent Flame Propagation Model for Spark Ignition Engines,Combustion and Flame, 1980.

[C26] Groff, E. G., An Experimental Evaluation of an Entrainment Flame-PropagationModel, Combustion and Flame, 1987.

[C27] Poulos, S. G. and Heywood, J. B., The Effect of Chamber Geometry on SparkIgnition Engine Combustion, SAE 830334.

[C28] Heywood, J. B., Internal Combustion Engine Fundamentals, McGraw-HillInternational Editions, 1986.

[C29] Morel, T., Rackmil, C. I., Keribar, R. and Jennings, M. J., Model for Heat Transferand Combustion in Spark Ignited Engines and it’s Comparison with Experiments,SAE 880198.


8-4 23-Jun-2004

[C30] Jennings, M. J., Multi-Dimensional Modeling of Turbulent Premixed ChargeCombustion, SAE 920589.

[C31] Bielert, U., Klug, M. and Adimiet, G., Application of Front Tracking Techniques tothe Turbulent Combustion Processes in a Single Stroke Device, Combustion andFlame, 1996.

Acoustics:

[A1] Blair, G. P. and Spechko, J. A., Sound Pressure Levels Generated by InternalCombustion Engine Exhaust Systems, SAE Automotive Congress, Detroit, January1972, SAE 720155

[A2] Blair, G. P. and Coates, S. W. Noise Produced by Unsteady Exhaust Efflux from anInternal Combustion Engine, SAE Automotive Congress, Detroit, January 1973,SAE 730160

[A3] Coates, S. W. and Blair, G. P., Further Studies of Noise Characteristics of InternalCombustion Engines, SAE Farm Construction and Industrial Machinery Meeting,Milwaukee, Wisconsin, September 1974, SAE 740713

Turbocharger:

[T1] Turbocharger Nomenclature and Terminology, SAE – Standard J 922, sl, June1995

[T2] Turbocharger Gas Stand Test Code, SAE – Standard J 1826, sl, March 1995


23-Jun-2004 9-1

9. APPENDIX9.1. Running The Executable

9.1.1. Command LineIt is recommended to run the BOOST executable from the graphical user interface(Simulation|Run). However, it is also possible to run the BOOST executable (calculationkernel) on its own from a shell or command prompt. This executable (boost orboost.exe) can be found in the platform dependent bin directory of the BOOSTinstallation ($BOOST_HOME). It is also possible to use command line arguments and inputfile specification for this executable. Running the executable without any command linearguments will result in a command prompt requesting the input file name. This is similarbehavior to previous BOOST releases.

This section also includes important information on the directories from which gasproperty files and other auxiliary files used by BOOST are loaded.

9.1.1.1. OptionsCommand line arguments are specified using a preceding dash (-). For some options only asingle command line option or input files will be processed. That is, in some cases ifmultiple command line options are used followed by a BOOST input file (e.g. boost –help –v 4t1cal.bst) only the first command line option is processed beforetermination. See details on each option for more information.

1. Version (-v)

This displays the current version number of the BOOST executable to screen.

> ./boost -vv4.0.3


9-2 23-Jun-2004

2. Help (-help)

This is used display some information on the executable, how to use it and a supportcontact.

> ./boost -help

A V L B O O S T

Version: v4.0.3 Platform: ia32-unknown-winnt Build: <build date>

Usage: boost [-v|-help|-dirs|-plat|-what|-lic] or boost [-verbose] [-debug<number>] [-atm|-burn] [-stop]<filename(s)>

Options: -v Print version number -help Print this help information -dirs Print directory information -plat Print platform type -what Print executable information -lic Print license information

-verbose Run in verbose mode -debug<number> Run in debug level <number> mode Debug level from 0 (min) to 5 (max) -stop Stop on error (multiple bst only)

Run modes: (default is cycle simulation)

-atm Aftertreatment analysis -burn High pressure analysis

Examples: boost 4t1calc.bst boost -atm aftertreatment.atm boost -burn burn.brn

Support: [email protected]

This message will also be displayed for any unrecognized options.

3. Directories (-dirs)

This option displays the directories used by BOOST when executed on input files in thesame manner.


23-Jun-2004 9-3

> ./boost -dirs

A V L B O O S T

Version: <Version> Platform: <platform> Build: <build date>

Executable directory: <executable directory> Working directory: <working directory> BOOST_HOME: <BOOST_HOME if set>

If BOOST_HOME has not been set then a message stating this will be displayed rather than ablank following the BOOST_HOME.

4. Platform (-plat)

This displays the build platform for the executable.

> ./boost -platia32-unknown-winnt

5. What (-what)

This displays more detailed information on the executable. The information displayed issimilar to the UNIX ‘what’ command.

> ./boost -what AVL BOOST v4.0.3 ia32-unknown-winnt (Jun 27 2003 09:15:19)

6. License (-lic)

This displays information on the available licenses.

> ./boost -lic AVL BOOST v4.0.3 checking licenses.... $Id: @(#) ASTFlexlm v8.4 (Feb 12 2003 13:30:36) ia32-unknown-winnt $ Searching for feature "boost_main" version: "4.0" .... found This license is available Searching for feature "boost_advanced" version: "4.0" .... not found Searching for feature "boost_basic" version: "4.0" .... not found Searching for feature "boost_acoustic" version: "4.0" .... not found Searching for feature "boost_hpa" version: "4.0" .... not found Searching for feature "boost_egat" version: "4.0" .... found This license is available Searching for feature "boost_charging" version: "4.0" .... not found Searching for feature "boost_control" version: "4.0" .... not found Searching for feature "boost_external" version: "4.0" .... not found AVL BOOST v4.0.3 finished checking licenses


9-4 23-Jun-2004

7. Verbose (-verbose)

This option also runs the input file(s) through the solver. All messages that are written tothe input file are also sent to the screen.

8. Debug (-debug<number>)

This option also runs the input file(s) through the solver. A number must also be givenfrom 0 (minimum) to 5 (maximum). This selects debug options for certain features so thatmore checks are done. This typically causes a longer run time and an earlier exit due toerrors.

9. Stop (-stop)

This option stops a multiple simulation run (e.g. ./boost *.bst) whenever a fatal erroroccurs.

9.1.1.2. File Search PathsBOOST uses a number of auxiliary input files such as the gas property files. These files areopened by BOOST from the following directories, listed in order of priority:

1. Same directory as the BOOST input file.

2. BOOST_HOME files directory ($BOOST_HOME/../files)

3. BOOST_HOME files directory ($BOOST_HOME/../../files)

4. Same directory as the BOOST executable.

5. Current working directory. This is usually the same as 1 or 4 but can bedifferent.

6. Parent directory of the BOOST input file.

As soon as the particular file is successfully opened from any of these directories BOOSTwill stop searching and continue. If it fails to open the file from any of these directories therun will fail unless the file has been specified as optional. Optional files are sometimes usedfor developmental features. No message is generated for failing to open an optional file.The error message includes the list of the directories specified above. The command lineargument for directories (-dirs) can be used if BOOST has problems opening these files.

If a file exists in more than one of the allowed locations, the first successfully opened filewill be used and the other(s) ignored. A RUNINFO message type specifying the name andpath of the file loaded will be written. This is true for optional files also.


23-Jun-2004 9-5

9.1.2. Batch Mode

9.1.2.1. Create Model with GUIThe model set-up and the creation of the kernel input files ( *.bst) has to be done with helpof the GUI. The bst-files are created as follows:

1. Select Simulation | Run from the Menu bar.

2. In the Run window select Model Creation, deselect Simulation and then select Run.

9.1.2.2. Preparing the Batch File:For this example run.bat was used for the name of the batch-file. The working directory is

D:\support\Batch_test\boost

This means in this case all bwf-files for this run are in this directory and the exampleBOOST files are:

test1.bsttest2.bsttest3.bst

The following lines shows the content of run.bat

================= Start of run.bat==================

#!/bin/shcd "D:\support\Batch_test\boost\test1.Case_Set_1.Case_1"boost_batch v=4.0 simulation test1cd "D:\support\Batch_test\boost\test2.Case_Set_1.Case_1"boost_batch v=4.0 simulation test2cd "D:\support\Batch_test\boost\test3.Case_Set_1.Case_1"boost_batch v=4.0 simulation test3exit

================= End of run.bat==================

9.1.2.3. Start the RunOpen a “bash-window” from the desktop

Start | Programs | AVL | AWS3.1 | Bash

Start the batch-file with the command:

sh run.bat


9-6 23-Jun-2004

9.2. Required Input DataThe following list is a summary of data required as input for a BOOST model.

9.2.1. Engine Databore, stroke, number of cylinders, con rod length,

numbering of cylinders, principle arrangement of manifolds (diagram or sketch)

compression ratio, firing order and firing intervals,

number of valves, inner valve seat diameters,

valve lift curves, cold valve clearances,

flow coefficients of the ports (incl. reference area), swirl number (incl. definitions)

9.2.2. Turbocharging System Datacompressor and turbine maps including efficiencies,

mass flow characteristic of waste-gate valve,

intercooler size and hot effectiveness

9.2.3. Fuel Datalower heating value, stoichiometric air-fuel ratio

9.2.4. Boundary Conditionsambient pressure, ambient temperature,

max. permissible charge air temperature,

pressure loss of air cleaner and intercooler,

pressure loss of exhaust system,

dimensions of engine compartment

9.2.5. Drawingsdetailed drawings of the complete intake and exhaust system,

(including all receivers, mufflers, throttles and pipes),

drawings of the cylinder head,

(including the port geometry, flange areas and valve positions)


23-Jun-2004 9-7

9.2.6. Measurementsmeasured full load performance of the engine,

(BMEP, BSFC, air-fuel ratio, fuelling, air flow, volumetric efficiency),

mean pressures and temperatures in the intake and the exhaust system,

(including location of the measuring points),

combustion data, cylinder pressure traces,

friction measurement results (including definition of procedure)

9.2.7. For Transient SimulationInertia of engine and power consumption devices

Inertia of rotor assembly (TC)

Inertia of supercharger reduced to drive shaft (mechanically driven compressors)


9-8 23-Jun-2004

9.3. Available Channel Data

Element Actuator Channel Units Sensor Channel Units

Global Load Torque Nm External (Ext.Cnt.) -

Speed rpm

Mean Speed rpm

Speed Gradient rpm/s

Mean Speed Gradient rpm/s

Ambient Pressure Pa

Ambient Temperature K

Crank Angle (Ext. Cnt.) deg

Absolute Crank Angle (Ext. Cnt.) deg

LOAD 0-1

Load Torque Nm

Engine Torque Nm

Mean Engine Torque Nm

Time (Ext. Cnt.) S

BMEP Pa

System Boundary Pressure Pa Pressure Pa

Temperature K Temperature K

Flow Coefficient 0-1 Flow Coefficient 0-1

Residual Gas Concentration (Ext) kg/kg Residual Gas Concentration (Ext.) kg/kg

A/F Ratio kg/kg A/F Ratio kg/kg

Fuel Concentration (Ext.) kg/kg Fuel Concentration (Ext.) kg/kg

Internal Boundary Pressure Pa Pressure Pa

Temperature K Temperature K

Residual Gas Concentration (Ext.) kg/kg Residual Gas Concentration (Ext.) kg/kg

A/F Ratio kg/kg A/F Ratio kg/kg

Fuel Concentration (Ext.) kg/kg Fuel Concentration (Ext.) kg/kg

Cylinder Fuelling (Int) kg Pressure Pa

Start of Injection (Int) deg Temperature K

Ignition Timing deg A/F-Ratio kg/kg

Piston Wall Temperature K Mean Piston Wall Heat Flow W

Head Wall Temperature K Mean Head Wall Heat Flow W

Liner Segment Wall Temperature K Mean Liner Segment Heat Flow W

Intake Port Wall Temperature K Mean Intake Port Wall Heat Flow W


23-Jun-2004 9-9

Element Actuator Channel Units Sensor Channel Units

Cylinder Exhaust Port Wall Temperature Mean Exhaust Port Wall Heat Flow W

Intake Cam Phasing (VC) deg Mean Liner Wall Heat Flow W

Exhaust Cam Phasing (VC) deg (Octane Number (Quad)) -

Cooler Coolant temperature K Coolant temperature K

Heat flow J/s

Measuring Point Pressure Pa

Mean Pressure Pa

Temperature K

Mean Temperature K

Mass Flow kg/s

Mean Mass Flow kg/s

Residual Gas Concentration kg/kg

Fuel Concentration (Ext) kg/kg

A/F Ratio kg/kg

Plenum Pressure Pa

Mean Pressure Pa

Temperature K

Mean Temperature K

Residual Gas Concentration kg/kg

Fuel Concentration kg/kg

A/F Ratio kg/kg

Turbocharger VTG-Position (VTG) 0-1 Rotational Speed rpm

Mean Rotational Speed rpm

Turbocompressor Clutch-Engagement (full) 0-1

PDC Clutch-Engagement (full) 0-1

Fuel injector Flow Coefficient 0-1

A/F-Ratio kg/kg

Restriction Flow Coefficient 0-1

ConditionsECU for ECU Element onlyExt External Mixture PreparationInt Internal Mixture PreparationVC Valve Controlled PortsVTG VTG-Turbinefull Full Model of TCP and PDCQuad Quasi-dimensional, Vibe 2 Zone, Table 2 Zone


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9.4. Compiling and Linking BOOSTThe BOOST installation includes all the files necessary to create a new executable to usemore advanced features such as the user defined element. This section covers the platformspecific operations necessary to create this new executable.

9.4.1. NT Visual StudioA new BOOST executable can be created on Windows 98/2000/NT/XP using MicrosoftVisual Studio, Microsoft Visual C++ (Version 6.0) and HP (Compaq) Visual Fortran(Version 6.6C). A ready-to-use visual studio project can be requested [email protected].

Further information can also be found at

http://www.compaq.com/fortran/visual/faq.html

http://msdn.microsoft.com/vstudio/techinfo/techfaq.asp

9.4.2. UNIXThe BOOST static library, the main object, and all the precompiled fortran 90 module files(*.mod) are available on each of the supported UNIX platforms. The recommended practiceis to create a Makefile to build the new executable which links the platform specificlibraries and objects to create the new executable. Makefiles also can be requested [email protected].

9.5. Using the BOOST Dynamic Link LibraryThe BOOST installation includes dynamic link libraries (or shared objects) of thecalculation kernel on all the supported platforms (boost.dll). This is used for links toexternal programs (e.g. AVL CRUISE or MATLAB/Simulink). The BOOST dynamic linklibrary is dynamically loaded at run time by the linking program.

9.5.1.1. Loading ProblemsSome possible problems during loading are listed below together with their solution.

• Entry Point Not Found

The problem is that an older version of dformd.dll is being used. This can be updated fromthe installation CD or downloaded from the following web site:

http://www.compaq.com/fortran/visual/redist.html

In this example the problem has occurred using the MATLAB s-function link so thedformd.dll used by MATLAB needs to be updated. The location of dformd.dll that needs tobe updated is installation dependent (e.g. C:\MATLAB6p5\bin\win32\dformd.dll).

http://www.compaq.com/fortran/visual/faq.html

http://msdn.microsoft.com/vstudio/techinfo/techfaq.asp

http://www.compaq.com/fortran/visual/redist.html


23-Jun-2004 9-11

9.6. Flow Coefficients DirectionsFLOWCOEFFICIENTS

INFLOW OUTFLOW

System Boundary Flow into pipe * Flow out of pipe **

Plenum Flow into plenum Flow out of plenum

Variable Plenum Flow into plenum Flow out of plenum

Air Cleaner Flow into cleaner Flow out of cleaner

Catalyst Flow into catalyst Flow out of catalyst

Air Cooler Flow into cooler Flow out of cooler

Junction(Constant Pressure)

Flow into junction Flow out of junction

User defined Element Flow into element Flow out of element

* (typically less than 1 for flow from large volume into pipe)

** (typically 1 for flow out of pipe into a large volume )

The outflow coefficient should generally be less than one (flow into a pipe from a volume)but this is dependent on the actual volume (and other factors) so there is no hard and fastrule. The exception is the system boundary where the outflow (pipe to boundary) shouldtypically be one and the inflow (boundary to pipe) less than one.

Refer to the online help (Flow Coefficients - Standard Values) for more information.


9-12 23-Jun-2004

9.7. Variation Parameters from V3.3 to V4.0For the advanced BOOST v3.3 user the following equivalence table may be helpful.

Variation Parametersin v.3.3

ParameterType

Path to Specify this Parameter in v. 4.0

Engine Speed m Simulation Control | General | Engine Speed

Fuelling m Cylinder | Combustion | Fuelling | Fuel Mass

Throttle Setting m Restriction | Flow Coefficients | Flow Coefficients(for both directions)

Intake ValveClosing/Phase Shift

m Cylinder/Modification/Intake Valve Closing(Phase Shift)

Intake ValveClosing/Adjusted CamLength (IO constant)

m Cylinder/Modification/Intake Valve Closing(Modified cam length)

Exhaust ValveOpening/Phase Shift

m Cylinder/Modification/Exhaust Valve Closing(Phase Shift)

Exhaust ValveOpening/Adjusted Cam

Length (IE constant)

m Cylinder/Modification/Exhaust Valve Opening (Modified Cam length)

Intake ValveOpening/Fixed Exhaust

Valve Closing

m Cylinder/Modification/Intake Valve Opening only

Intake ValveOpening/Modified Exhaust

Valve Closing

m Cylinder/Modification/Intake Valve Opening combined withExhaust Valve Closing (Same direction)

Exhaust Valve Closing/Fixed Intake Valve

Opening

m Cylinder/Modification/Exhaust Valve Closing only

Exhaust Valve Closing/Modified Intake Valve

Opening

m Cylinder/Modification/Exhaust Valve Closing combinedwith Intake Valve Opening (Opposite direction)

Cam Spread m Cylinder/Modification/Cam Spread

Boost Pressure m Turbocharger/Simplified Model/Compressor pressure ratio


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Turbine Size m Turbocharger/Full Model/Turbine/ Mass Flow scalingfactor

Positive DisplacementCompressor (PDC) Mass

Flow

m Turbocharger/Full Model/Compressor /CompressorScaling/Mass Flow scaling factor

Pipe Length m Pipe/General/Pipe length

Pipe Diameter m Pipe/General/Pipe diameter

Element Position m Pipe/General/Pipe length (of related pipes)

Plenum Volume m Plenum/General/Volume

Control Valve Setting m Restriction/Flow coefficients/Flow coefficients

Start of Combustion SOC m,d Cylinder/Combustion/Vibe, Double Vibe, Vibe 2-Zone,Constant volume/Start of Combustion

Combustion Duration CD m,d Cylinder/Combustion/Vibe, Vibe 2-Zone, Double Vibe(Vibe1,Vibe2), Woschni/Anisits, Hires et al/Combustion

duration

CombustionDuration/Timing of Mass

Fractions

m Cylinder/Combustion/Vibe/Combustion duration

(Timing of Mass Fraction will be possible in BOOST v4.1)

Compression Ratio m Cylinder/General/Compression ratio

Parameter type: main/dependent

BOOST V 3.3 list of dependent variation parameters according to main variationparameters.

Operation process, Element: Main variation parameter

• Dependent variationparameter

Path in BOOST V 4.0

Combustion: Engine speed• Fuelling Cylinder/Combustion/Fuelling/Fuel Mass

Combustion: Engine speed, Throttle Setting

• A/F-RatioCylinder/Initialization/Initial Gas Composition/Ratiovalue

Combustion: Engine speed, Fuelling, Throttle Setting• Start of Combustion Cylinder/Combustion/Vibe/Start of Combustion• Combustion Duration Cylinder/Combustion/Vibe/Combustion duration• Vibe Shape Parameter

mCylinder/Combustion/Vibe/Shape parameter m

• Ignition TimingCylinder/Combustion/Hires et al, Quasidimensional,KCM, KCS/Ignition Timing

• Ignition TimingCylinder/Combustion/AVL MCC/Ignition DelayCalibration Factor


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• Ignition TimingCylinder/Combustion/Woschni Anisits, Hires etal/Ignition Delay

• Ignition TimingCylinder/Combustion/Vibe, Double Vibe, Vibe 2 Zone,Const. Volume/Start of Combustion

Heat Transfer: Engine speed, Fuelling, Throttle Setting• Piston Temperature Cylinder/Heat transfer/Piston/Wall Temperature• Cylinder Head

TemperatureCylinder/Heat transfer/Cylinder Head/WallTemperature

• Liner Temperature(Piston at TDC)

Cylinder/Heat transfer/Liner/Wall Temp. (Piston atTDC)

• Liner Temperature(Piston at BDC)

Cylinder/Heat transfer/Liner/Wall Temp. (Piston atBDC)

• Port WallTemperature…

Cylinder/Valve Port Specifications/Port/Wall Temp.

• Pipe WallTemperature…

Pipe/General/Wall Temperature

• Plenum WallTemperature…

Plenum/Heat Transfer/Wall Temperature

Valve Timing: Engine speed, Fuelling, Throttle Setting

• Intake Cam PhasingCylinder/Modification/Intake Valve Closing (PhaseShift)

• Exhaust Cam PhasingCylinder/Modification/Exhaust Valve Closing(Phase Shift)

Chamber Data: Engine speed, Fuelling, Throttle Setting• Fuel Fraction Cylinder/Chamber/Combustion/Fuel Fraction

• Combustion StartCylinder/Chamber/Combustion/Vibe/Start ofCombustion

• Combustion DurationCylinder/Chamber/Combustion/Vibe/CombustionDuration

• Shape parameter mCylinder/Chamber/Combustion/Vibe/ShapeParameter m

• Wall TemperatureCylinder/Chamber/Combustion/Wall HeatTransferWall Temperature

Intake Valve Closing by: Intake Valve Closing

• Phase ShiftCylinder/Modification/Intake Valve Closing (PhaseShift)

• Adjusted Cam Length(IO constant)

Cylinder/Modification/Intake Valve Closing(Modified Cam length)

Exhaust Valve Opening by: Exhaust Valve Opening

• Phase ShiftCylinder/Modification/Exhaust Valve Closing(Phase Shift)

• Adjusted Cam Length(IO constant)

Cylinder/Modification/Exhaust Valve Closing(Modified Cam length)

Intake Valve Opening by: Intake Valve Opening• Fixed Exhaust Valve

ClosingCylinder/Modification/Intake Valve Opening only


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• Modified Exhaust ValveClosing

Cylinder/Modification/Intake Valve Openingcombined with Exhaust Valve Closing (Samedirection)

Exhaust Valve Closing by: Exhaust Valve Closing• Fixed Intake Valve

OpeningCylinder/Modification/Exhaust Valve Closing only

• Modified Intake ValveOpening

Cylinder/Modification/Exhaust Valve Closingcombined with Intake Valve Opening (Oppositedirection)

Exhaust Valve Closing by: Exhaust Valve Closing• Fixed Intake Valve

OpeningCylinder/Modification/Exhaust Valve Closing only

• Modified Intake ValveOpening

Cylinder/Modification/Exhaust Valve Closingcombined with Intake Valve Opening (Oppositedirection)

Turbocharger data (onlysimplified model):

Engine Speed, Fuelling:

• Equivalent dischargecoefficient

Turbocharger/Simplified Model/Equiv. TurbineDischarge Coeff.

• Maximum compressorpressure ratio

Turbocharger/Simplified Model/CompressorPressure Ratio

• Compressor efficiencyTurbocharger/Simplified Model/CompressorEfficiency

• TC-overall efficiencyTurbocharger/Simplified Model/Turbo Chargeroverall Efficiency

Turbocompressor data (only ifa constant operating point isspecified):

Engine Speed:

• Pressure ratio TurboCompressor/Simplified Model/Pressure ratio

• Isentropic efficiencyTurboCompressor/Simplified Model/IsentropicEfficiency

• Mechanical efficiencyTurboCompressor/Simplified Model/MechanicalEfficiency

Positive displacementcompressor data (only if aconstant operating point isspecified):

Engine Speed:

• Corrected massflow/volume flow

TurboCompressor/Full Model/Compressor/CompressorScaling/Massflow Scaling Factor

• Temperatureincrease/isentropicefficiency

TurboCompressor/Full Model/Compressor/CompressorScaling/Efficiency Offset

• Powerconsumption/totalefficiency

TurboCompressor/Full Model/Compressor/Powerconsumption/total efficiency

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