Multi Cylinder TPA and DI Pulse Model Development using GT-SUITE. Lakshmidhar Reddy Isuzu Technical Center America

Transcription

1 Multi Cylinder TPA and DI Pulse Model Development using GT-SUITE Lakshmidhar Reddy Isuzu Technical Center America

2 V2017 and Earlier TPA Model Overview V2018 TPA Model Steps to Develop Combustion Model 1. Data collection and validation 2. TPA model setup and validation 3. Combustion model calibration (DI Pulse)

3 Data used for Multi Cylinder TPA Instrumentation: Crank angle averaged Cylinder pressure for all cylinders for 200 cycles Crank angle averaged Intake manifold high pressure signal for 200 cycles Crank angle averaged Exhaust manifold high pressure signal for 200 cycles Intake and Exhaust manifold temperature using shielded thermocouples Intake manifold species concentration to calculate EGR % from CO 2 concentrations Engine out emissions concentrations Injector current signal Temperature and Pressure sensors before and after subsystems Data collected: Engine operating range Without EGR Engine operating range with EGR Rail Pressure variation EGR variation Each point is stabilized for 5 minutes before data collection for engine operation stability

4 Test Points

5 Three Pressure Analysis ( TPA) Three Pressure analysis: Intake, Cylinder and Exhaust pressure profiles are used to calculate the burn rate and incylinder trapped conditions Calculated burn rate profile imposed and cylinder pressure calculations are performed based on model setup conditions The above process continues till the pressures, temperatures and mass flow converge

6 TPA Model Setup Intake pressure profile Developed from 3D CAD data Injector Rate Map is used to replicate actual injection pulses Exhaust pressure profile Key model parameters (calibratables): Air flow Exhaust temperature (Manifold heat transfer multiplier) Log P-Log V curve or Gas exchange process (Valve timings, valve lash, blowby flow) IMEP (In-cylinder heat transfer multiplier)

7 Log P-Log V Analysis Log P-Log V curves for two operating conditions were shown above Pumping loop trend from initial TPA results were not matching

8 Pumping Loop Analysis Exhaust gas recompression was observed in measured data With the baseline valve timings this is not observed Adjusted valve timings keeping lift constant to match exhaust recompression

9 Pumping Loop Analysis Same kind of behavior was seen at different engine operating condition

10 Intake and Exhaust Valve Timings Intake and Exhaust valve timings were adjusted to decrease valve overlap. Decrease in valve overlap increases recompression of exhaust gases in-cylinder

11 Log P-Log V After Valve timings Adjusted Same operating conditions after valve timing adjustment were matching with measured data

12 Blowby Model Leak path diameter was calibrated to match blowby flow assuming constant crank case pressure and temperature

13 Model Validation Air Flow Air flow error was less than 4% at all points

14 Model Validation Exhaust Temperature Exhaust temperature error was very high at low speeds This was due to engine operated at high load for longer time before actual test conducted. This leads to heating of gas by pipe wall temperatures Stabilization time needs to be function of temperature delta to overcome this effect.

15 Model Validation - IMEP At less than 10% of load values of IMEP are vey low Small deviation in absolute values leads to higher relative errors

16 Log P-Log V curve Six Example Points

17 DI Pulse Calibration DI Pulse Model: DI Pulse is Direct Injection Diesel Multi Pulse model to predict heat release as calculated in the Cylinder pressure analysis DI Pulse model calibrated using: 1. Entrainment rate multiplier 2. Ignition Delay Multiplier 3. Premixed Combustion rate Multiplier 4. Diffusion Combustion rate Multiplier

18 DI Pulse Model Calibration V2017 and Earlier DI Pulse Model V2018 DI Pulse Model Model setup same as TPA model 60 Points selected with varying speed and load Multi Objective Genetic Algorithm available in GT-POWER was used for optimization Burn rate RMS error and Absolute peak cylinder pressure error were defined as objectives for optimization

19 DI Pulse Results 16 Example Points Heat Release Rate Crank Angle

20 DI Pulse Results 16 Example Points Pressure Normalized Crank Angle

21 Conclusions and Future Work Significant Improvement in Air flow accuracy from Single cylinder to Multi cylinder TPA because of capturing manifold dynamics Both models were unable to capture variation in Peak Cylinder pressure. This is due to unequal distribution of Air and EGR for different cylinders Combustion model was sensitive to changes in model setup once completed Sub-system models were developed very carefully to predict same flow, pressure and temperature boundary conditions for combustion model Future Work Development of NO x, HC and CO emission models Integrate sub-system models with combustion model and validate detailed Engine model Using model to support Engine calibration and hardware selection for future Engine family

22 Acknowledgements Krishna Natti and Nick keeler for helping in Engine Dyno setup and data collection. Kevin Roggendorf, Navin Fogla and Syed Wahiduzzaman from Gamma Technologies Inc for providing constant support and Beta version of V2018 GT-SUITE. Bruce Vernham, Yasuo Fukai, Yifan Wei and ISUZU Global CAE team for their constant support.

23 Contact details: Lakshmidhar Reddy Model Based Development Engineer Isuzu Technical Center NA Discussions and Questions

24 Back Up Slides

25 Cylinder Pressure Variation Since Optimization is setup to match Peak Cylinder pressure of average of 4 Cylinders it is very tough to see C to C variation. EGR distribution also plays key role in this variations between cylinders which is very tough to correlate in 1D flow dynamic model.

26 Intake and Exhaust Valve Timings Sweep

27 Intake and Exhaust Valve Lash Sweep