Study On General Trends Of The Performance And Operational Parameters For High Speed Diesel Engines

Internal combustion engine will still be the mainstream automotive power device in the long-term future. Light duty diesel vehicle market in China also have great potential. During the conceptual design phase of engine design and development, the establishment of engine modulus, limitation of computing conditions, selection of boundary conditions, and analysis of calculated result requires some engineering experience as a support. This limitatio n restricts the shortening of engine development time and the reducing of overall cost of engine design. This paper start with the studies of the general trends of the performance with the operational parameters of high-speed diesel engines, trying to establish the intrinsic link between engine performance and operational parameters, to improve the accuracy and efficiency of the engine design and development.In this paper, the performance parameters, emissions parameters and combustion characteristics in full load and universal characteristics of four high-speed diesel engines are measured and recorded by using engine benchmarking techniques. And also, the general trends of the emission performance and combustion characteristics with the main operational parameters such as engine speed, load, excess air coefficient, EGR rate, in-cylinder dilution parameter are summed up based on the test data.Results indicate that:Diesel engine’s NOx and PM emissions decrease while excess air coefficient and in-cylinder dilution parameter increase, and the trend tend to be stable when excess air coefficient or in-cylinder dilution parameter is greater than a certain value. NO x emissions decrease as EGR rate increases, PM emissions increase as EGR rate increases.Diesel engine’s combustion efficiency have linear relationship with excess air coefficient when the excess air coefficient is smaller than a certain value, and combustion efficiency decreases as excess air c oefficient increases when the excess air coefficient is bigger than the value. Combustion duration shortened as excess air coefficient and in-cylinder dilution parameter increase, extended as engine speed and EGR rate increase. The gravity center of heat release rate curve is gradually moving to TDC as load increases, and the peak heat release rate decreases as load increases. R ate of heat release curve shape factor(Vibe index) decreases as load decreases, decreases as engine speed increases.The general trends summed up above can guide the setting of initial and boundary conditions during the conceptual design phase of engine design and development, thus a significant reduction in development time and overall cost of the engine, make the engines have the potential to adapt to market competition.