global sensitivity analysis of gdi nozzle design
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Global sensitivity analysis of GDI nozzle design parameters Global sensitivity analysis of GDI nozzle design parameters
using ANSYS workbench & OptisLang
Dr.-Ing. Junmei Shi, Ivan Krotow, Continental Automotive
Dr.-Ing. Johannes Einzinger, ANSYS
Global sensitivity analysis of GDI nozzle design parameters Global sensitivity analysis of GDI nozzle design parameters
using ANSYS workbench & OptisLang
Ing. Junmei Shi, Ivan Krotow, Continental Automotive
Ing. Johannes Einzinger, ANSYS
Agenda
� Motivation: GDI injection system for low emission
� Mathematical model & Simulation approach
� Workflow
� Results
2 / Dr. J. Shi / 21.10.2010 © Continental Automotive GmbH
� Summary
Motivation: GDI injection system for low emission
Mathematical model & Simulation approach
CO2 Emission Targets for New Registrations
60
80
100
120
140
160
180
g CO2/km
35 %
65%
25 %
75 %
20 %
80 %
3 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
0
20
40
60
2012 2013 2014
According to the European policy for CO2 regarding new car registrations, the CO
reached step by step on average from 2012 until 2015 as shown in the graph.
The policy accepts an exceeding range in average of 35 % in 2012, 25 % in 2013 and 20 % in 2014.
In 2015 first time the target of 120 g CO2 has to be reached for new car registrations.
In 2020 the standard will be reduced to 95 g CO2.
Emission Targets for New Registrations – Automotive Industry
acceptedexceeding
100 % 100 %
vehicle target
2015 2020 year
exceedingrange
targetreached
regarding new car registrations, the CO2 targets have to be
reached step by step on average from 2012 until 2015 as shown in the graph.
The policy accepts an exceeding range in average of 35 % in 2012, 25 % in 2013 and 20 % in 2014.
has to be reached for new car registrations.
Particle Emission LegislationEU 5/ EU 6 EU Time Scheduling
06/2009 01/201109/2009
4 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Legislation
EU 5
new models
EU 5
new registration
09/201509/201401/2011
Particle Number (PN) limit
for gasoline vehicles
Particle Mass (PM) limit
for gasoline vehicles
EU 5
new registration
EU 6
new models
EU 6
new registration
Injection pressure effect on soot emission
60%
80%
100%
120%
140%
160%
PN
Co
nc
en
tra
tio
n
5 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
0%
20%
40%
60%
50 90
Rail Pressure [bar]
PN
Co
nc
en
tra
tio
nInjection pressure effect on soot emission
120 160 200
Rail Pressure [bar]
Injection pressure effect on CO2 emission
Fuel pressure incidence on CO2Low-CO2 democar
149
150
151
em
issio
n [
g/k
m]
CO2-emission [g/km]
6 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
146
147
148
149
50 100 150
Fuel pressure [bar]
CO
2-e
mis
sio
n [
g/k
m]
Injection pressure effect on CO2 emission
Fuel pressure incidence on CO2-emissionCO2 democar - NEDC
200 250 300
Fuel pressure [bar]
Mixture preparation is the key for emission reduction
Chamber geometry
Mixture formation dependence
Charge motion
Injection system
7 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Precise injection quantity metering
Fast needle dynamic
Suitable penetration
Good atomization
Mixture preparation is the key for emission reduction
Operating conditions
Mixture formation dependence
Injection system
Spray targeting
Precise injection quantity metering
Fast needle dynamic
Suitable penetration
Good atomization
The key component is injector & nozzle
Starting points
- What are the most significant design parameters?
- How do they affect atomization & spray penetration?
- How much improvement potential does the current design have?
- What design concept can be useful for good atomization?
- How to deliver tailed nozzle for each individual engine?
& Approach
8 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
- How to deliver tailed nozzle for each individual engine?
- Systematic approach: global sensitivity analysis
- Physical understanding: local sensitivity analysis
- Virtual engineering: > 200 virtual nozzle prototypes analyzed
- Cross check: spray characterization, engine experiment vs. CFD
What are the most significant design parameters?
How do they affect atomization & spray penetration?
How much improvement potential does the current design have?
What design concept can be useful for good atomization?
How to deliver tailed nozzle for each individual engine?How to deliver tailed nozzle for each individual engine?
Systematic approach: global sensitivity analysis
Physical understanding: local sensitivity analysis
Virtual engineering: > 200 virtual nozzle prototypes analyzed
Cross check: spray characterization, engine experiment vs. CFD
Design parameters investigation
Sensitivity analysis
R
Lochposition X
α
L /
D
R
Lochposition X
α
L /
D
9 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Design parameter Unit Range
SPL X-position [mm]
SPL Angle α [°]
Rounding radius R [µm]
Hole diameter D [mm]
L over D [-]
DD
Design benchmark:
- L/D
- Sac height effect
- Injection hole position
- Injection hole diameter
- Inlet rounding
- Seat-sac variation
- Injection hole shape
- Needle shape
Evaluation criteria is still a research area
Examples of evaluation quantities:
-Turbulence energy
- Injection velocity
- Vapour volume fraction
- Mass flow rate
10 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
- Mass flow rate
- Discharge Coefficient
- Energy efficiency
- Needle force
- … … … …
Spray measurement and engine validation important !
Evaluation criteria is still a research area
Spray measurement and engine validation important !
Global sensitivity analysis model
Global sensitivity analysis allows to change all the input parameters simultaneously.
Stochastic sampling method: Latin Hypercube sampling for each design parameter over the total design space
Sensitivity analysis model: optiSLang Metal Model of Optimal Prognosis (MOP) for correlation analysis.
11 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Coefficient of Prognosis:
Global sensitivity analysis allows to change all the input parameters simultaneously.
Stochastic sampling method: Latin Hypercube sampling for each design parameter over
Sensitivity analysis model: optiSLang Metal Model of Optimal Prognosis (MOP) for
CFD model
Inlet total pressure 101 bar
Outlet static pressure 1 bar
n-heptane:
ρ= 680 [kg/m3], µ = 3.885e-4 [Pa.s]
12 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Rayleigh-Plesset cavitation model
k-omega SST turbulence model
2nd order spatial discretization
2nd time discretization
Inlet
Periodic
Needle
Inlet
Periodic
Needle
Outlet
Interface
Housing
Outlet
Interface
Housing
Workflow: CAE tool integration & process automation
1)
R
Lochposition X
α
L /
D
R
Lochposition X
α
L /
D
13 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
3)DD
Workflow: CAE tool integration & process automation
2)
Inlet
Periodic
Interface
Needle
Inlet
Periodic
Interface
Needle
5)
4)Outlet
Interface
Housing
Outlet
Interface
Housing
Coupling optiSLang – ANSYS Workbench
14 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
ANSYS Workbench
Coupling optiSLang – ANSYS Workbench
15 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
ANSYS Workbench
Turbulence kinetic energy @outlet [J/kg]
16 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Turbulence kinetic energy @outlet [J/kg]
Injection velocity
17 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Discharge Coefficient
18 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
Summary
� ANSYS workbench + optiSLang have been applied to design sensitivity analysis.
� Workflow has been successfully proved.
� The global sensitivity analysis has reached the following results:
- Identified the most important influencing parameters
- Worked out the improvement potential and direction
19 / Dr. J. Shi / 04.11.2010 © Continental Automotive GmbH
- Worked out the improvement potential and direction
- Significant product imporvement confirmed by OEMs & a number of inventions
� The predicted trends have been confirmed by spray and engine experiment results.
� A predictive methodology (trend) for GDI nozzle design analysis developed
� Understanding of atomization mechanism improved.
ANSYS workbench + optiSLang have been applied to design sensitivity analysis.
Workflow has been successfully proved.
The global sensitivity analysis has reached the following results:
Identified the most important influencing parameters
Worked out the improvement potential and directionWorked out the improvement potential and direction
Significant product imporvement confirmed by OEMs & a number of inventions
The predicted trends have been confirmed by spray and engine experiment results.
for GDI nozzle design analysis developed
Understanding of atomization mechanism improved.
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