Experimental Investigation on the Effect of Multiple Injection Strategies on Emissions, Noise and BSFC of an Automotive DI C.R. Diesel Engine

High-pressure common-rail injection systems with after-treatment technologies, exhaust gas recirnowadays allow a very high degree of flexibility in the culation (EGR), injection shaping [3] and electronic timing and quantity control of multiple injections, which engine control [4, 5]. can be used to obtain significant reductions in engine noise Further improvements have recently been and emissions. The aim of this study is to develop a better obtained thanks to the common-rail fuel injection understanding of the relationship between injection stra- system, which allows a higher level of injection tegies and the combustion and emission formation process. pressure and a more flexible control of the injecSome multiple injection strategies (pilot± pilot± main and tion strategy [6± 10]. The injected fuel quantity per pilot± main± after) have therefore been analysed to highlight cycle can be split into several injections, in order to their influence on the soot, NOx , combustion noise and achieve a better control of engine emissions and b.s.f.c. (brake specific fuel consumption) of a passenger car noise (see Fig. 1). direct injection diesel engine prototype. Finally, the main It is well known that pilot injections can be very combustion characteristics were determined, for each effective in reducing combustion noise, as they can operating condition, on the basis of a heat release analysis shorten the ignition delay, thus reducing the preand a correlation was attempted between the combustion mixed combustion phase and the rapid pressure rise parameters and emissions, noise and b.s.f.c.