CONTROL PARAMETERS OPTIMIZATION IN AUTOMOTIVE DIESEL ENGINES VIA TWO ZONE MODELLING

Abstract

The paper deals with the optimization of control parameters of High Speed Direct Injection (HSDI) Diesel engines by means of a two zone thermodynamic model. The proposed methodology is aimed to support the engine control design for common-rail Diesel engines with multiple injections, where the large number of control parameters requires a large experimental tuning effort. The modelling approach is based on a semi-empirical two-zone combustion model coupled with an intensive identification analysis. Fuel spray motion, air entrainment and combustion are predicted assuming two control volumes (fuel spray and surrounding air) and a semi-empirical formulation that accounts for the occurrence of premixed and diffusive regimes is implemented for the heat release rate. NOx and soot exhaust emissions are predicted according to the well known mechanisms proposed by Zeldovich and Hiroyasu, respectively. Model accuracy has been successfully tested over a wide set of experimental data, composed of 90 operating points measured on a commercial common-rail Diesel engine. Simulation results evidenced that the model can predict the effects of different injection parameters, in case of single and multiple injection, in a short computational time. An optimization analysis has been performed aimed at minimizing NO emissions with constraints on soot emissions and engine performance (IMEP). The results evidenced that an average reduction of 20% can be achieved by optimal tuning of EGR, rail pressure, injection timing and duration.