基于Gerris的离心式喷嘴锥形液膜破碎过程数值模拟

Numerical Simulation on Conical Liquid Sheet BreakupProcess of Pressure Swirl Injector Based on Gerris

关键词:  离心式喷嘴  锥形液膜  破碎过程  雾化特性

Key words:  Pressure swirl injector  Conical liquid sheet  Breakup process  Spray characteristics

摘要:

为了实现离心式喷嘴锥形液膜破碎过程的精细可视化和雾化特性的准确计算，基于自适应网格加密技术和VOF方法，建立了一种数值方法，可以捕捉到包含一次雾化和二次雾化的喷雾场结构特征，获得了全场液滴的空间分布和粒径分布，液滴捕捉效果逼真。针对给定结构尺寸的敞口型离心式喷嘴，计算了在不同流量和不同切向孔直径下的液膜锥角、液滴平均粒径SMD的变化，并与高速摄影拍摄的锥形液膜破碎过程图像和PDPA(Phase Doppler Particle Analyzer)测量的液滴SMD对比。结果表明，数值模拟与实验所获得的喷雾场吻合，获得的液膜锥角和液滴平均粒径最大相对误差分别为4.18%和11.82%，结果吻合较好，验证了数值方法的准确性，为离心式喷嘴的精细研究和设计应用提供一种新手段。研究表明，切向孔直径对液膜锥角和液滴平均粒径的影响较显著，在设计加工时，是一个比较重要的结构参数。

Abstract:

In order to realize the refined visualization of liquid sheet spray process and the accurate numerical calculation of spray characteristics， the numerical method based on adaptive mesh refinement technique and VOF method was established for pressure swirl injector. The method was able to capture the structure characteristics of the spray field， including the first spray and the second spray. And the spatial distribution and diameter distribution of droplets in the field could be obtained. The visual effect of droplets captured was almost lifelike. For the open-end swirl injector of given structure size， the spray characteristics， such as cone angle of liquid film and droplets average diameter SMD， have been calculated under the different flows and the different diameters of tangential orifices， and were compared with the breakup process images of conical liquid sheet photographed with high-speed photography and the droplets SMD measured by PDPA (phase doppler particle analyzer) system. The results are in good agreement between simulation and experiment， and the maximum relative errors of cone angle of liquid film and droplets SMD are respectively 4.18% and 11.82%， which shows that the numerical method is relatively accurate and provides a new method for the refined research and design of pressure swirl injector. In addition， the research also shows that the diameter of tangential orifice has a relatively significant impact on the cone angle of liquid film and droplets SMD. So the diameter of tangential orifice plays a more important role in the structure design and manufacturing.