Experimental Study Of Diesel Fuel And Its Mixtures Spray Impingement

In order to realize the efficient and clean combustion of diesel engine,early spray technology has been widely used to improve the gas-mixing process in the internal combustion engine.But the too early injection time can make the fuel "wet wall" more intensified,leading to the combustion deterioration in engine cylinder and affecting emissions.At present,there was few research of diesel and mixing fuels impingement on the lubricating film.Most of the researches focus on the diesel and mixing fuels impingement on the dry wall or the same fuel film.In this paper,the experimental study of diesel fuel and its mixtures spray impingement has been made using the visualization experiment system constructed by ourselves.In the paper,the high-speed photography method was used to record the fuel spray impingement and the formation process of mixture gas.The command parameters include fuel temperature,ambient temperature,wall temperature,ambient pressure and wall distance,etc.The results of this research were as follows.Firstly,for the diesel fuel,ambient temperature affects the fuel spray and film evaporation at the edge of the film area.Secondly,the influence of wall temperature on the fuel was similar to the environmental temperature.Thirdly,as the fuel temperature increases,the fuel characters,viscosity and surface tension will have a great change,and it should change the fuel flow characteristics on the wall surface and entrainment effect with the surrounding gas.As to its mixtures,when the fuel temperature increases,the spreading radius and entrainment height of the mixtures spray impingement were different.With the increasing of ambient temperature,the mixtures spray spreading radius and entrainment height reduced,the reducing degree mainly depends on the boiling point of the alternative fuel.With the increasing of environmental pressure and wall distance,the entrainment height and spreading radius decreased.In this paper,the characteristics of the adhering fuel film from a vertical spray impingement were investigated.The adhering fuel film shape data was captured by using an oil sensor.The experimental results of adhering fuel film were as follows.For the fuel spray impinging the dry wall vertically,when the distance from the nozzle to the wall increases,the adhering fuel ratios of these fuels increase.The wall with the lubricating film showed similar case to the dry wall,but the adhering fuel ratio of the wet wall was larger than that of the dry wall.As the wall distance increases,the diameter of the adhering fuel film from these fuels for the impingement on the dry wall increases gradually.The diameter of the adhering fuel film of the impinged wet wall was larger than that of the impinged dry wall.With the vertical fuel spray impinging the dry wall,the adhering fuel film was the thickest in the center of the wall where a convex platform structure was formed.The farther from the center,the smaller the film thickness was.However,the adhering fuel film shape of the wet wall impingement might be different from that of the dry wall impingement.For the wet wall,lubricating film,vertical impingement,the largest adhering fuel film thickness was not at the center of the wet wall,and the adhering fuel film had a pit at the center and just looked like a crater.