Modelling Study of the Scavenging Process in a Turbocharged Diesel Engine with Modified Valve Operation

Abstract

The instantaneous gas exchange process in a turbocharged direct injection diesel engine with an intake valve pre-lift and an exhaust valve post-lift has been studied in detail by means of a wave action model. Such a modified valve timing operation allows the internal exhaust gas recirculation and the residual burnt gas ratio in the combustion chamber to be increased and modulated. A simple scavenging model has been included in the global calculation code, in order to obtain information on the instantaneous composition of the gas flow across valves. The analysis sheds light on the intricate flow phenomena produced by the additional valve lift periods, and evaluates the potential of this technique in the control of the residual burnt gas in the cylinder.