初始液滴尺寸分布对超高压喷雾大涡模拟的影响

分别在100、200MPa常规喷油压力和300MPa超高压喷油压力条件下,研究了不同初始液滴尺寸分布对柴油喷雾结构的预测性能.基于OpenFOAM开源平台比较了欧拉-拉格朗日喷雾仿真中常用于计算初始液滴尺寸分布的两种方法——Blob和Rosin-Rammler.结果表明:在300 MPa超高喷油压力下,Blob方法和初始液滴平均尺寸为喷嘴有效直径的Rosin-Rammler函数分布对喷雾贯穿距随时间发展的预测几乎没有影响,而减小液滴平均尺寸使喷雾贯穿距稍微降低.虽然初始液滴尺寸分布对索特平均直径(SMD)影响比较大,但随着喷油压力的提高,影响逐渐减小.超高喷油压力会产生大量直径小于1μm的液滴,初始液滴尺寸分布对该尺寸液滴形成过程的计算有重要影响.

Effect of Initial Droplet Size Distribution on Large Eddy Simulation of Diesel Spray Under Ultra-high Injection Pressure

The different initial droplet size distributions are studied for their performance on the prediction of diesel spray structures under conventional injection pressures of 100,200 MPa and ultra-high injection pressure of 300 MPa.The Blob method and the Rosin-Rammler distribution,which are commonly used to calculate the initial droplet size distribution in Eulerian-Lagrangian spray simulation,are compared based on the open-source platform OpenFOAM.The results show that at ultra-high injection pressure of 300 MPa,the spray penetration evolution is rather insensitive to the Blob method and the Rosin-Rammler distribution with a initial mean droplet diameter which is equivalent to the nozzle effective diameter,while is slightly reduced by reducing the initial mean droplet diameter.Although the initial droplet size distribution has a great influence on the sauter mean diameter(SMD),the effect decreases with the increase of injection pressure.A large number of droplets with diameter less than 1μm will be produced at ultra-high injection pressure,and the initial droplet size distribution has a significant influence on the calculation of the formation process of droplets within this size range.