Of Lpg / Diesel Blended Fuel Spray Research

The fuel spray is very important to the power performance, fuel consumption , exhaust emission of diesel .In order to research the spray of LPG/diesel mixed fuel, it is the first time that this work studied the atomization characteristics of LPG/diesel, including spray angle, droplet size distribution, mean diameter, typical diameter, diffusion degree and impenetrate distance by using a high spatial resolution digital camera. At the same time, comparison of these characteristics of diesel and two kinds of LPG/diesel mixed fuel was taken. We can conclude that mixing diesel with some LPG is contribution to fine atomization of diesel and more ratio of LPG more high quality of atomization because of the flash boiling effect of diesel fuel containing dissolved gas. The SMD of LPG/diesel fuel reduced by 6%~11% comparing with that of diesel. The method of high-resolution digital camera is convenient, reliable and efficient .It can be popularized to apply to comparing spray characteristics. This paper has set up the mathematic models of droplet size and velocity joint distribution, droplet velocity distribution and droplet size distribution by utilizing maximum entropy principle and conservation laws of mass and kinetic energy to the spray process. The velocity distribution graphs show the number of low and high speed droplets is small, yet the number of moderate speed droplets is big .The droplet velocity distribution curve of small dimension droplet is flat and wide, and high speed particles are more, which indicates the velocity range of small particles wide. More high injection speed is, more small dimension droplets are produced and spray quality is enhanced. The similarity of velocity distribution curves of diesel and L30 indicates the diesel and L30 distributions have little difference. However the peak of L30 velocity distribution graph is little lower than that of diesel and move for high-speed droplets direction, which illuminates high-speed particles of L30 increased relative to diesel injection. The spray size distribution curve peak of L30 is higher and moves for small particles direction comparing with that of diesel ,which shows that L30 injection produced more small particles than diesel .Studying the effects of evaporation and coalescence on droplet size distribution, we find the effects lead to reduce droplet number and the size distribution curves move for big diameter droplets direction and more distance are away from the nozzle more numbers of big diameter droplets appear. Comparing the results of experiments and prediction, we gain the good accordance of diesel distribution curve between measurement and prediction. Yet the curve peak of L30 moves for big dimension particle direction because of ignorance great evaporation of fuel L30 droplets. When fuel rejects into atmosphere, evaporation has little influence on diesel atomization yet the effect of coalescence is dominant. On the contrary, evaporation effect is dominant in spray of fuel L30.