wave check list modeling engine

7/26/2019 WAVE Check List modeling engine

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WAVE Knowledge Center

Building a WAVE Model: Gathering Data: Data Checklist

General Instructions

WAVE is a detailed multi-cylinder reciprocating engine simulation code. Its various sub-models require a

number of input parameters related to combustion chamber geometry, valve flow, manifold configuration,

etc. The data list below contains items that are either necessary or very helpful to successfully construct and

validate a WAVE engine model.

Suggested units are provided where appropriate. Other units may be used, but these should be indicatedclearly when supplied.

Finally, in order to validate the model with a high degree of precision, it is important to have as much

engine test data as possible. Test data can be provided as ASCII text files (preferred) or as printouts from

data acquisition systems.

A) Power Cylinder

Bore _________ [mm]

Stroke _________ [mm]

Connecting rod length, center to center _________ [mm]

Piston pin offset (positive toward major thrust side) _________ [mm]

TDC combustion chamber volume _________ [m3]

Compression ratio _________

Number of cylinders _________

Firing order _________

Firing interval _________ [CA]

Two or four stroke _________

Two-strokes: scavenging curve _________

Heat transfer area of combustion chamber: piston and head surfaces (expressed as

multiple of bore area)

_________

Clearance height between top of piston and top of cylinder _________ [mm]

B) Intake and Exhaust Geometry
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Intake piping and manifold geometry _________

Exhaust piping and manifold geometry _________

EGR circuit geometry _________

C) Valve/Port Data

Duplicate this information for each intake and exhaust valve:

Poppet Valves

Profile of lift vs. crank (or cam) angle - ASCII text file preferred _________

Valve/cam timing events _________

Dynamic valve data (e.g. valve event phase shift vs. engine rpm) _________

Tappet type (hydraulic/fixed) _________

Valve lash (hot) _________ [mm]Rocker arm ratio (if cam lift is prescribed) _________

Inner seat diameter (D) _________ [mm]

Maximum valve lift _________ [mm]

Valve flow data: flow coefficient (forward and reverse) vs. L/D _________

Piston Ported

Number of ports of the same type _________Port geometry and precise location (drawing) _________

Profile of geometrical area (as an alternative to lift profile) _________

Port flow data: flow coefficient _________

Reed Valves

Effective mass _________ [g]

Effective spring constants _________ [N/m]

Effective damping constants _________ [N*sec

Maximum lift to stop _________ [mm]

Spring pre-load distance _________ [mm]

Pressure force area below reed _________ [mm2]

Profile of geometrical open area vs. lift _________

Profile of flow coefficient vs. lift _________


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EGR Valves

Maximum lift to stop _________ [mm]

Cross-sectional area at maximum lift _________ [cm2]

Profile of pressure loss vs. flow _________

Profile of flow coefficient vs. lift _________

D) Turbocharger

Compressor map showing operating points (map) _________

Compressor reference temperature _________ [K]

Compressor reference pressure _________ [bar]

Compressor gas Cp _________ [J/kg/K]Specify total/total or total/static or static/static pressure ratio _________

Compressor speed:

connected to turbine number

geared to crankshaft: supply gear ratio

fixed speed

_________

_________

_________ [rpm]

Compressor inlet diameter _________ [cm]

Compressor exit diameter _________ [cm]

Turbine map showing operating points _________ (map)

Turbine reference temperature _________ [K]

Turbine reference pressure _________ [bar]

Turbine gas Cp _________ [J/kg/K]

Turbine speed:

connected to compressor number

geared to crankshaft: supply gear ratio

fixed speed

_________

_________

_________ [rpm]

Turbine inlet diameter _________ [cm]

Turbine exit diameter _________ [cm]

Mechanical efficiency _________ [%]

Moment of inertia of all rotating parts _________ [kg*m2]

Wastegate (if equipped) _________

Variable geometry turbine (if equipped): provide maps at different settings _________


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1.

Building a WAVE Model: Gathering Data: Geometric Data

Gathering the geometric data can be the most time consuming part of model building. For an engine, the dimensions

of all the intake and exhaust systems, including the ports are required. It is necessary to model each part of these

systems with a high degree of accuracy but they are also the easiest part of the model to get right. Quite often notenough time and thought is given to collecting the information needed to construct an accurate model. All areas of

the geometry are important, but specifically:

Inlet and exhaust manifold pipe lengths are extremely important especially for noise prediction work. They

also determine tuning points for engine performance curves.

Muffler and air cleaner volumes are extremely important especially for noise prediction work. They also

determine tuning points for engine performance curves.

Geometric data is usually found from engineering design drawings. In most cases this is sufficient. It is, however,

very useful to have access to the part that needs modeling, especially air cleaners, exhaust mufflers, and throttle

bodies. Exhaust mufflers are particularly useful if they have been cut open, allowing the internal geometry to be

viewed and compared to the drawings. Quite often the production item has some differences from the design

specification, which may or may not be important. A typical example: pipe edges that are shown on a drawing as a

clean cut may, in reality, have a sharp burr which intrudes into the pipe. This can be detrimental to flow and reduce

the effective diameter. Studying the real item also tends to give a better idea of how it performs and can give you a

good idea of how the flow will behave in certain parts of the system.

It is also useful to view intake manifolds so that the junction between the inlet runner and the main volume can be

modeled accurately. Throttle bodies and carburetors need to be carefully simulated for obvious

reasons. Carburetors, typically only used for small engine applications nowadays, usually come with a nominal

diameter specified by the manufacturer. However, quite often this nominal diameter is not the true effective

diameter that will need to be modeled; or, the nominal diameter refers to a certain section of the component rather

than the minimum diameter.

The component surface finish determines the flow losses due to wall friction. The material thermal properties are

used to determine the heat transfer when the structural conduction model is activated, otherwise simple heattransfer coefficients are implemented.

As a general rule it is best to gather as much information and as many actual components as possible in order to

build the most accurate model possible.


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2. Building a WAVE Model: Gathering Data: Engine Data

Engine data refers to all dimensions and characteristics associated with the actual engine itself. This includes the

cylinder head and inlet and exhaust ports. For the basic engine only minimal information is required:

Bore

Stroke

Connecting Rod length

Wrist Pin offset

Compression ratio

Firing order and timing

Mechanical Friction details

The ports require more detailed information which can only be collected from testing the ports on a steady state

flow rig. Typical information needed is:

Port flow coefficients taken from measured data

Valve diameters

Valve event timings

Valve lift or Cam profiles

It is often very useful to make molds of the ports. This allows you to measure the lengths and diameters more

accurately. This is particularly true of a 3/4/5 valve per cylinder engine when the multiple ports branch off from one

entry volume in the cylinder head. The modeling of this junction volume is very important.

If a complex combustion model is to be simulated, it is necessary to use a more detailed representation of an engine

cylinder (in WAVE this is called anIRIS cylinder). This type of cylinder can require more geometric information

relating to:

Shape of the cylinder head, ports, and combustion chamber

Position of valves in the combustion chamber and position of spark plug

Orientation and size of piston top shapese.g. re-entrant bowls

Wall temperature characteristics and transfer coefficients

Piston ring and cylinder liner friction
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3. Building a WAVE Model: Gathering Data: Operating Parameters

Operating Parameters refer to conditions at which the simulation will be run. Typical data required for an engine

are:

Inlet and exhaust wall temperatures

Engine operating speed

Fuel flow rate or fuel/air ratio

Piston, Head, and Liner average surface temperatures

Ambient conditions

Combustion data

These are the minimum conditions required to get the basic model running. It is necessary to have temperatures in

several locations in the exhaust system as this varies greatly and has a significant effect on predicted performance. If

a complete range of temperatures is not known, then it is recommended that WAVE structural conduction model is

activated. This module allows the exhaust ducts to reach an equilibrium temperature during the engine simulation. If

you do not have measured data available, a range of typical operating temperatures for various parts of the engine is

given at the end of this tutorial in the example model. In-cylinder temperatures are rarely measured but typical

values can be found. Combustion data should be measured from and correlated to a test engine.

Further test data is later required to perform the correlation of the model, including:

Dynamic intake and exhaust pressures

Cylinder pressure trace

Engine performance - IMEP, BMEP, volumetric efficiency, etc.

wave check list modeling engine

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