Optimum control of an automotive direct injection diesel engine for low exhaust emissions

The paper presents the latest results of a wide investigation performed at the University of Genoa on the control of automotive direct injection (DI) diesel engines. A dedicated procedure was developed which enables analysis of the behaviour of engine operating parameters as a function of two control variables with a limited amount of experimental information and the definition of proper control strategies. A first application of the procedure is presented in the paper with reference to a typical turbocharged DI diesel engine for automotive applications. The exhaust gas recirculation (EGR) rate and the position of the turbocharger waste-gate regulating valve were assumed as control variables and the behaviour of the most important engine parameters was analysed in a wide range for 15 steady state operating conditions related to the European driving cycle. Particular attention was paid to the most significant pollutant emissions and to the exhaust boundary conditions for the application of a low temperature lean dc-NOx, catalyst. Two different control strategies were also developed by which the catalyst conversion efficiency and the NOx engine tail pipe emission were individually optimized, taking account of some operating limits for specific parameters.