The Effect Of Intake Condition On High Density-Low Temperature Disesel Combustion And Emissions

The HC and CO emissions of diesel engine are much less than that of gasoline engine .However, both reducing NOx and soot emissions of diesel engine are very difficult because the emissions have"trade-off" relationship. Although the after processing technology of diesel engine has a great development, it is still far from putting the technology into use. Many scholars have tried to explore the new diesel combustion model to both decrease emissions of NOx and soot. High density - low temperature combustion proposes time scale control of the combustion process (TSCC) concept based on chemical processes from the mixing time scale control. The volumetric density can be improved by increasing the supercharge pressure as the initial temperature is reduced. On the high-load condition of Modern Heavy Duty Diesel Engine, the max compression pressure is more than 10MPa; temperature is greater than 1000K; and the traditional sense of the ignition delay is only 100μА. So, how to improve the thermal efficiency and achieve ultra-low NOx and particulate emissions is an important issue for new generation of internal combustion engine combustion theory and technology on this"extreme"condition. High density - low temperature combustion mode may be an effective way to solve this problem. Numerical simulation is a common way to study the diesel engine combustion process beside experimental.In this paper, the 3-dimentional numerical simulation method of the combustion process is discussed, the mechanism of gas turbulence model, spray model, and modeling combustion model are analyzed. Diesel engine model is proposed using simulation software FIRE, and the accuracy of the model is verified. Experiment program is set using orthogonal pilot. The effect of initial conditions (intake air temperature, air pressure and EGR) on diesel engine combustion process was simulated using model and the performance indicators have been got. The results indicate that:1) EGR has greatest impact on the combustion, intake air temperature and air pressure followed;2) The optimal combinations of ISFC are: 50% of the load; EGR is 0, intake air temperature is 400C, inlet pressure is 2.7bar 75% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 100% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 3) The optimal combinations of IMEP are: 50% of the load; EGR is 0, intake air temperature is 400C, inlet pressure is 2.7bar 75% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 100% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 4)The optimal combinations of mass fraction of Soot are: 50% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 75% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 100% of the load; EGR is 0, intake air temperature is 200C, inlet pressure is 2.8bar 5) The optimal combinations of mass fraction of NOx are: 50% of the load; EGR is 0.2, intake air temperature is 200C, inlet pressure is 2.6bar 75% of the load; EGR is 0.2, intake air temperature is 400C, inlet pressure is 2.8bar 100% of the load; EGR is 0.2, intake air temperature is 200C, inlet pressure is 2.6bar Finally, the best combination based on overall balance of the program is: 50% of the load; EGR is 0.1, intake air temperature is 400C, inlet pressure is 2.7bar 75% of the load; EGR is 0.1, intake air temperature is 200C, inlet pressure is 2.8bar 100% of the load; EGR is 0.1, intake air temperature is 200C, inlet pressure is 2.8bar...