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In order to explore the mechanism of high-speed diesel engine combustion system parameters on the combustion properties, the matching laws between fuel injection system parameters and combustion chamber structures in high speed direct injection ( HSDI) diesel engine was studied by using three-dimensional CFD numerical simulation method. The spatial distribution of fuel vapour and characteristics of fuel /air mixing were analyzed. In order to quantitatively describe the performance of fuel/air mixing, the parameters about the rate of turbulent mixing and concentration variance of mixture were established. Moreover, weight analysis of the effect of fuel injection system and combustion chamber structural parameters on indicated power was carried out using orthogonal method. The results show that diesel engine power decreases after increasing with the increase of chamber caliber-depth ratio. When the caliber-depth ratio equals to 6. 4, diesel engine is the most powerful, mixing is the most uniform. For different combustion chamber, fuel injection system parameters are of different weights for power. With the combustion chamber caliber-depth ratio increases, the weight of injection pressure decreases, the weight of spray angle of increases, the weight of nozzle number and diameter reduces, the weight of injection timing decreases and then increases. [ABSTRACT FROM AUTHOR]

In order to investigate the reasons for the degradation of dynamic performance of diesel engines under plateau environment, multi-dimensional simulation under different altitudes was conducted to study the combustion process. A set of characteristic parameters accounting for mixing in combustion chamber was established, basing on it, quantitative analysis of the influence of plateau environment on mixing process was conducted. And then the influence of plateau environment on combustion process was investigated mainly by analyzing the heat release rate in the engine. The results show that, under plateau environment, near the wall of combustion chamber easily forms rich mixture, which leads to a reducing of air utilization rate in the center of combustion chamber, a mass of rich mixture still exists at late combustion process. With the rise of altitude, the center area of high temperature moves to the wall of combustion chamber, and causes the deterioration of combustion efficiency. The influence of plateau environment on pre-mixing combustion is not obvious, however, with the rise of altitude, heat release rate of diffusion combustion reduces gradually, and the duration of combustion increases sharply. [ABSTRACT FROM AUTHOR]