Intake valve pre-lift effect on the performance of a turbocharged diesel engine

摘要

A detailed study on the gas exchange process in a six-cylinder heavy-duty turbocharged diesel engine with an intake valve pre-lift is performed by means of a wave action model. The analysis of the instantaneous intake and in-cylinder pressure evolution on the original engine configuration permits the detection of the angular period where the pre-lift should be produced. This drastic modification in the valve timing diagram greatly increases the internal exhaust gas recirculation and consequently the burnt gas ratio at the start of combustion. On the other hand, the turbocharger operation can be deteriorated, and the intake mass flow rate reduced. The down-sizing of the turbine is appraised on the efficiency of recovering the intake air mass, still maintaining the internal EGR levels.