Study On Spray Quality Evaluation Of LPG/Diesel Mixed Fuel

Spray technology has been widely applied to the production and livelihood of the vast majority of mankind areas. In combustion equipment, spray will affect the quality of ignition, combustion efficiency, combustion stability, temperature distribution, exhaust pollution and other aspects of performance. There is closely relationship between spray combustion technology and the progress of combustion technology. They promote each other in the progress. Spray quality evaluation is too vitally important because of the importance of the spray. More influencing factors can be research in details by theoretical calculations, which can not be replaced by experimental study.Droplet size distribution function and joint droplet size and velocity distribution function are derived by Cao Jianming based on the maximum entropy principle, the law of conservation of mass and the law of conservation of momentum. On this basis, this paper established the diesel and L30 (LPG liquid quality accounted for 30 percent of the LPG/diesel mixed liquid) spray droplet size distribution model. And the comparative analysis showed that the calculation results fits well with the experimental data. And joint droplet size and velocity distribution model for diesel and L30 is established. The computation program is programmed by FORTRAN language. The prediction on joint droplet size and velocity distribution for diesel and L30 is conducted. The results show that the large number of droplets is concentrated in low velocity zone, while the droplets with the high velocity are little. The middle size droplets accounted for larger percent than small and large size droplets.D-U contour map is applied to analyze the inter-dependence between size and velocity. The inter-dependence between the size and the velocity of the sprayed droplets are quit evident from this joint distribution. For smaller droplets, the distribution becomes increasingly broader in velocity space, while the velocity distribution turns narrow for larger droplets. And for lower velocity droplets, the distribution becomes increasingly broader in size space, while the size distribution turns narrow for higher velocity droplets. The core region of the D-U contour map is "droplet pattern". The "droplet" region, formed by L30 droplets, is slightly smaller than the diesel's and it converge faster the diesel. The results indicate that more small size and low velocity droplets are obtained when jet L30 and the spray quality is better than diesel. The trends of large droplets of L30 evaporated completely go ahead of diesel. Broader velocity distribution is obtained by L30 droplets in smaller droplets region.The paper also primarily probe into the effect on the model from the initial guess of the Lagrange factor. After repeated attempts, it finds that Lagrange factor could be a good convergence when the initial values of Lagrange factor coefficients are 0.08 and 0.06 for the joint distribution of diesel and L30.