喷雾碰壁形成的附壁油膜沸腾实验研究

Boiling Phenomenon of Wall Fuel Film Formed from Spray/Wall Impingement

内燃机内喷雾碰壁后,一部分燃油发生飞溅,而另一部分则附着在气缸壁或活塞表面形成附壁油膜.附壁油膜因为气化相对更慢成为燃烧后产生污染物的主要原因之一.因为气缸内温度较高,附壁油膜很可能发生沸腾现象,而油膜沸腾与表面蒸发的相变特性明显不同,从而会影响混合气的形成.针对现有研究对附壁油膜的沸腾现象研究较少的现状,实验研究中以正丁醇为实验对象,应用高压共轨喷油系统和高速摄像技术开展附壁油膜沸腾实验.结果表明,沸腾现象的发生一定程度上可以促进附壁油膜的气化;增大喷油持续期以及降低喷油压力都可以使沸腾现象更剧烈.

In combustion engines,part of the fuel splashes after the spray impinges on the wall,while the other part forms the fuel film on the surface of the piston and cylinder wall.Wall fuel film is one of the main causes for the generation of pollutants after combustion because of its poor vaporization rate.Due to the relatively high tem-perature in the cylinder,the boiling phenomenon of fuel film on the wall is likely to occur,and the phase transi-tion characteristics of boiling and surface evaporation are significantly different,which will affect the formation of the mixture.In view of the fact that there have been few researches on the boiling phenomenon of the fuel film at-tached on the wall,in the experimental study,n-butanol was used as the test fuel,and the high-pressure com-mon-rail fuel injection system and high-speed camera technology were used to carry out the boiling experiment on the fuel film attached on a heated wall.The results show that the occurrence of boiling phenomenon can promote the vaporization of the fuel film to a certain extent;increasing the fuel injection duration and reducing the fuel injection pressure can intensify the boiling phenomenon.