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

Multi Cylinder TPA and DI Pulse Model Development using GT-SUITE

Lakshmidhar Reddy Isuzu Technical Center America

GT CONFERENCE NA 2017

OverviewSteps to Develop Combustion Model1. Data collection and validation2. TPA model setup and validation3. Combustion model calibration (DI

Pulse)

V2017 and Earlier TPA Model V2018 TPA Model

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 CO2 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


Data used for Multi Cylinder TPA


Test Points

Three Pressure analysis: • Intake, Cylinder and Exhaust pressure profiles are used to calculate the burn rate and in-

cylinder 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


Three Pressure Analysis ( TPA)


TPA Model Setup Developed from 3D CAD data

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)

Exhaust pressure profile

Intake pressure profile

Injector Rate Map is used to replicate actual injection pulses

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



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


Pumping Loop Analysis

Same kind of behavior was seen at different engine operating condition


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


Log P-Log V After Valve timings Adjusted

Same operating conditions after valve timing adjustment were matching with measured data


Blowby Model

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


Model Validation – Air Flow

Air flow error was less than 4% at all points


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.


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


Log P-Log V curve – Six Example Points

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


DI Pulse Calibration

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


DI Pulse Model Calibration V2017 and Earlier DI Pulse Model V2018 DI Pulse Model


DI Pulse Results – 16 Example Points

Crank Angle

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DI Pulse Results – 16 Example Points

Crank Angle

Pr

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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


Conclusions and Future Work

Future Work Development of NOx, 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

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.


Acknowledgements


Discussions and QuestionsContact details:Lakshmidhar Reddy Model Based Development EngineerIsuzu Technical Center [email protected]

Back Up Slides



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.


Intake and Exhaust Valve Timings Sweep


Intake and Exhaust Valve Lash Sweep

Documents

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