Optimization in GT-Power
Objective:
To explore an example Diesel_4cyl_DIpulse_injratemap and and optimize the result for minimum NO and bsfc.
Model:
The engine is a 4-cylinder, four-stroke, direct injection, 2L diesel engine. Combustion is modeled by the DiPulse method, a predictive combustion model using the detailed injection profiles. In-cylinder heat transfer is modeled using the Woschni model.
Non-Predictive and Predictive Combustion Models:
Non-Predictive Models:
- Burn rate prescribed/imposed explicitly by the user
- requires experimental combustion data at each operating condition for best accuracy
- Not affected by operating conditions (i.e. Speed, load, a/f)
- Fast computation
- Imposed combustion burn rate removes an unknown from simulation
Predictive Models:
- No measurements/tests required (except for initial model correlation)
- Self-adjusting for transient conditions
- Spatial resolution gives more detailed output (i.e. NOx, knock, heat transfer)
Engine Cylinder Gometry:
Case Setup:
We are running our engine model for high spped (4000 RPM) and at low speed(2000 RPM).
Optimization Setup:
Parameters-SOI, Rail Pressure
Response- NO and bsfc minimum
Case 1: 4500RPM,14 bar, Target BMEP = 14
Result:
NOX vs BSFC plot:
NOx countour Map:
BSFC Contour Map:
Case 2: 2000 RPM,16 bar, Target BMEP = 16
Result:
NOX vs BSFC plot:
NOx countour Map:
BSFC Contour Map:
Conclusion:
1. As the Rail Preasure increases,the better atomisation of fuel takes place,this increases the fuel efficiency and hence decrease BSFC.As Rail preasure increases,Temperature inside the engine increases and hence NOx emmision increases.
2. From NOX vs BSFC plot, it is seen that as the value of BSFC increases there is reduction in NOx value and vice-versa.So,there is trade of between the bsfc and NOx value.
3. If we inject the fuel too early,preasure and temperature inside the engine is low which will increases the ignition delay and hence BSFC Increases.If we inject the fuel after TDC,preasure and temperature inside the engine will be high which will decrease the ignition delay and hence BSFC decreases.Hence,Injection time is need to be Advanced.However, advancing Injection timing increases NOx emmision.But we have aftreatment devices such as EGR and SCR to reduce NOx emmision.