Abstract
It is significantly important to improve not only diesel emission but also fuel consumption simultaneously. It is difficult to achieve high NOx conversion by catalyst for low and middle engine load operations so that clean diesel combustion must be achieved by both innovative combustion technology and fuel technology. The aim of this study is to enhance clean diesel combustion operation range (engine-out emission: NOx < 0.2 g/kWh, Soot < 0.02 g/kWh). In this study, performance of a single-cylinder test engine which has a hydraulic valve actuation system and ultra-high pressure fuel injection system was investigated. And also it was clarified how fuel properties, such as auto-ignitability, volatility and aromatic hydrocarbon component, would influence on combustion performance. The results show that lots of EGR (exhaust gas recirculation) could dramatically reduce NOx but increase soot. However low cetane number fuel could suppress soot formation because it elongated premixing periods of fuel and air. And high volatile fuel could also decrease soot formation because it promoted fuel evaporation and mixing with air. Cetane number and aromatic hydrocarbon component could affect on combustion performance with the hydraulic valve actuation system which can change compression ratio of the test engine to control auto-ignition and combustion timings, and with the ultra-high pressure fuel injection system which can make significant turbulence in the combustion chamber to achieve well-mixed mixtures. From the results from this study, it was concluded that an optimal fuel for a next-generation diesel engine has lower cetane number (CN: 40-45) and no aromatic hydrocarbon.
