液体中心式同轴离心喷嘴液膜破碎特性仿真研究

Numerical Study on Breakup Characteristics of Liquid Film of Liquid-Centered Swirl Coaxial Injectors

关键词:  液体中心式同轴离心喷嘴  改进延迟分离涡模拟  CLSVOF方法  破碎模式  动量通量比

Key words:  Liquid-centered swirl coaxial injector  IDDES  CLSVOF method  Break-up mode  Momentum flux ratio

摘要:

为了实现对不同工况下液体中心式同轴离心喷嘴液膜破碎特性的数值模拟研究，采用网格自适应加密技术、耦合的Level-set和Volume of Fluid（CLSVOF）方法对气液界面进行捕捉，利用改进延迟分离涡模拟（IDDES）方法模拟湍流。分析了液膜的破碎模式、喷雾锥角、破碎长度以及流场特性。通过观察分析得到：随着气液相互作用的增强，液膜破碎模式依次经历主导表面波发展导致的液膜破碎、Rayleigh-Taylor（R-T）和Kelvin-Helmholtz（K-H）不稳定性引起的液膜破碎，以及气动破碎模式。随着气液动量通量比（Momentum Flux Ratio，MFR）的增大，喷雾锥角和破碎长度逐渐减小且呈渐进趋势，发现无量纲喷雾锥角和破碎长度均与MFR^-A成正比例关系。相同液膜破碎模式而不同工况时，主要流场特征一致。

Abstract:

In order to numerically study breakup characteristics of the liquid film of liquid-centered swirl coaxial （LCSC） injectors under different operating conditions， the adaptive mesh refinement technology and coupled level-set and volume of fluid （CLSVOF） method were adopted to capture the gas-liquid interface， and the improved delayed detached eddy simulation （IDDES） was used to simulate turbulence. The break-up mode of the liquid film， spray angle， break-up length， and flow characteristics were analyzed. With the enhancement of the gas-liquid interaction， the break-up of the liquid film is mainly caused by the dominant surface waves， Rayleigh-Taylor （R-T） and Kelvin-Helmholtz （K-H） instability， and air-blasting breakup. With the increase of the gas-liquid momentum flux ratio （MFR）， the spray angle and break-up length gradually decrease and show a gradual trend. It is found that the dimensionless spray angle and break-up length are proportional to MFR^-A. Although the operating conditions are different， the main flow characteristics are similar when the break-up mode of the liquid film is the same.