고압/저압 EGR 공급 비율에 따른 디젤 엔진의 연소 및 배기 특성

Abstract

The effects of high pressure and low pressure exhaust gas recirculation (HP/LP EGR) portion on dieselengine combustion and emissions characteristics were investigated in a 2.2 L passenger-car diesel engine. The po3rtionof HP/LP EGR was varied from 0 to 1 while fixing the mass flow rate of fresh air. The intake manifold temperature waslowered with the increasing of the portion of LP EGR, which led to the retardation of heat release by pilot injection. Thelowered intake manifold temperature also resulted in low nitrogen oxide (NOx) emissions due to decreased in-cylindertemperature and prolonged ignition delay, however, the carbon monoxide (CO) emission showed opposite trend to NOxemissions. The brake specific fuel consumption (BSFC) was decreased as the portion of LP EGR increased due tolowered exhaust manifold pressure by wider open of turbocharger vane. Consequently, the trade-off relationshipbetween NOx and BSFC could be improved by increasing the LP EGR portion.