Experiment Research On The Spray Combustion Characteristics Of Diesel Engine

With the improvement of people’s awareness of environmental protection and the consummation of national laws and regulations for emission of vehicle, the high particulate emissions of direct-injection diesel engine has become an important factor which limiting the development of the diesel engine which has become focus of some researchers. Recent studies show that the air entrainment rate of direct injection diesel spray combustion has an important influence on the formation of soot. The direct-injection diesel engine flame lift-off length and spray angle can affect the air entrainment rate by affecting fuel and gas mixture.This paper designed and improved the equipment of constant volume bomb and software systems to adapt parameter measurements of the fuel spray combustion. And measured the flame lift-off length of diesel by this improved system. And the changes of temperature, pressure in vessel was measured by temperature sensors, pressure sensors and so on. Based on this date, the effect of the initial temperature and initial density in the constant volume bomb, injection pressure and fuel temperature on the flame lift-off length was studied. Comparing studies of some foreign researchers, calculated air entrainment rate changes with variation of these parameters, and then analyzed the effect of combustion parameters on soot.It was found that increasing initial temperature environment, pressure and density could reduce the flame lift-off length under steady-state conditions, thereby reducing air entrainment rate. And the flame float length under the experimental conditions is more sensitive to ambient temperature than ambient pressure. The flame lift-off length increases with the increasing injection pressure. In this paper, based on qualitative analysis for the change trend of flame lift-off length, quantitative analysis was did. And an empirical formula of the flame lift-off length was obtained by a software named 1stOpt under the steady-state conditions. Thus the effect of the experimental conditions in this paper on air entrainment rate and soot formation was obtained in this paper.Kerosene fuel was used as comparison fuel and the same experiment was did in this paper. The results showed the dimension and changing trend of flame lift-off length. And figures of comparative analysis for these two fuels were drawn. In figures of comparative analysis for both, we called the curve contour lines phenomenon which indicated both fuel has the same lift-off length. The difference of changing trend for both fuels was got by analying the moveing of the curve contour lines. According to the difference of hydrocarbon group components of these two fuel, explained this phenomenon and predicted the effect of other hydrocarbon fuel on flame lift-off length. This study for the lift-off length will contribute to changing air entrainment as well as lift-off length by improving the combustion parameters for research of diesel engine in the future. So as to control the generation of soot and achieve further reduce emissions.