Relevance of valve overlap for meeting Euro 5 soot emissions requirements during load transient process in heavy duty diesel engines

This work describes the influence on performance and soot emissions of using different valve overlap camshafts during load transient processes in a heavy duty (HD) diesel engine equipped with a variable geometry turbine (VGT) in its turbocharger and a selective catalyst reactor (SCR) in the exhaust line. Based on the results of experiments and calculations, in this paper a description is given of how the valve timing affects the instantaneous exhaust and intake pressure, the short-circuit of the air mass flow, the prejudicial backflows, the performance of the turbine and hence the general performance and pollutant emissions of a VGT equipped HD diesel engine during a transient process. The paper concludes that very low or no overlap is imperative if a VGT is used to meet forthcoming pollutant emissions restrictions and to improve the transient response of HD turbocharged diesel engines. Copyright © 2006 Inderscience Enterprises Ltd.