Effect of Exhaust Gas Recirculation and Injection Pressure on Exhaust Emissions from a Diesel Engine

Abstract

To clarify optimal combination of high-pressure injection and exhaust gas recirculaton (EGR) for simultaneous reduction of nitric oxides (NOχ) and particulate (PM) emissions in the diesel engine exhaust, an experimental and theoretical study was performed on a single cylinder test engine. The measured tendencies of NOχ and PM were evaluated in terms of spray characteristics under various injection conditions and of exhaust recirculation rate. The results suggest that the enhancement of air entrainment and turbulent mixing effectively reduce the PM without deterioration of NOχ emission performance at a high exhaust recirculation rate. From an analysis based on a stochastic diesel combustion model, this phenomenon is due to the change in maximum temperature at which the mixture can arrive.