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An upgraded multizone model is developed in order to study the effects of fuel injection characteristics on DI diesel engine soot and NOx emissions. Effects of fuel spray characteristics, the movement and evaporation of droplet, and spray wall impingement are considered. NOx emission is predicted by the extended Zeldovich mechanism and soot emission is simulated by the current soot formation and oxidation model. The multizone model can be used to calculate cylinder pressure, heat release rate, engine performance, NOx and soot emissions, etc. In this paper, the boot injection and split injection are simulated. The simulation shows that the fuel injection characteristics have significant effects on the process of engine combustion and emissions. The NOx and PM emissions from DI diesel engine can be reduced simultaneously by optimizing the shape of injection rate, especially by boot injection.

This model is developed based on the concept of Hiroyasu's multizone combustion model. It takes nozzle injection (spray) parameters, induction swirl, air and fuel composition into consideration. The models of zone velocity, air entrainment rate, fuel droplet evaporation rate, mixture combustion rate are upgraded according to the latest papers. Various parameters, such as cylinder pressure, heat release rate, NOx and soot emissions, etc. are simulated. The simulated zone velocity and spray tip penetration are compared with those computed by Hiroyasu. The simulation results show good agreement with the experimental data.

Engine misfire (total or partial) causes a negative effect on the engine power and the exhaust emissions such as HC, CO and NOx. Moreover, it causes damage to the three-way-catalyst(TWC) system permanently. So, Engine misfire should be detected and eliminated. This study introduces a new system concept which is detecting combustion misfire using breakdown voltage (BDV) characteristics between electrodes. The focus of this study is that the detection and decision of misfire criterion through the misfire intensity calculation with BDV signal, which is derived by the application of a high bias voltage (30kV) to the spark-plug gap in the engine continuously. This study is driven to check the relation among BDV signal and misfire intensity inside an engine cylinder.