Evaluation of Cooling loss and Polytropic Index of CI Engine Using Heat Flux Measurement

Abstract

For improvement of thermal efficiency of diesel engines, it is effective to control the fuel injection by using the model-based control (MBC) on the ECU (on-board) with cycle-by-cycle calculation. The authors previously developed an on-board in-cylinder wall temperature prediction model and wall heat transfer prediction model for MBC. For the validation of the developed models, the present study measured the time evolution of local wall temperature and pressure in the combustion chamber and calculated wall surface heat flux and evaluated the errors of heat loss results obtained from model. Also, the polytropic index prediction model was evaluated using the result of in-cylinder pressure. As a result, it was confirmed that heat loss results during compression and expansion strokes show 1.3% errors and polytropic index prediction model shows 0.1% errors comparing with experiment data.