氢氧同轴离心式喷嘴自激振荡数值研究

Numerical Research on Self-Pulsation Oscillation of Hydrogen-Oxygen Swirl Coaxial Injector

关键词:  液体火箭发动机  超临界工况  气液同轴离心喷嘴  自激振荡  数值研究

Key words:  Liquid rocket engine  Supercritical condition  Gas-liquid swirl coaxial injector  Self-pulsation oscillation  Numerical research

摘要:

在某氢氧液体火箭发动机热试车过程中出现了燃烧不稳定现象，初步分析由气液同轴离心式喷嘴自激振荡引起。为获得超临界工况下气液同轴离心式喷嘴自激振荡特性，采用氢氧作为工质，通过RNG k-ε湍流模型、Volume of Fluid气液两相流模型以及Peng-Robinson状态方程进行数值仿真研究。喷嘴流场周期性变化过程以及不同工况参数下自激振荡幅频特性变化规律表明：超临界工况下自激振荡主频由液膜周期性挤占气体通道产生，频率高达5kHz以上；次要频率由不同振荡源产生，包括涡系脱落和进动涡核（Precessing Vortex Core）脱落。当氢氧气液动量比很低时，喷嘴自激振荡基本消失，随着气液动量比增大，自激振荡频率和强度均有所增加，但气液动量比增大导致液膜形态发生改变时自激振荡频率出现陡降。

Abstract:

Combustion instability occurred during firing tests of a hydrogen-oxygen liquid rocket engine， which was caused by the self-pulsation oscillation of swirl coaxial injectors. In order to obtain self-pulsation oscillation characteristics of gas-liquid swirl coaxial injectors under supercritical condition， numerical simulations were carried out by using hydrogen and oxygen as working medium， and the calculation methods adopted RNG k-ε turbulence model and VOF two-phase flow model and Peng-Robinson equation model. The periodic variation process of injector flow field and the law of amplitude-frequency characteristics of self-pulsation oscillation under different operating conditions show that， the main frequency of self-pulsation oscillation under supercritical condition is produced by liquid film blocking gas channel periodically， which is above 5kHz. The secondary frequencies are produced by the shedding of complex small vortex system and precessing vortex core （PVC）. The self-pulsation oscillation disappears basically when the gas-liquid momentum of hydrogen-oxygen is very low， and the frequency and intensity of self-pulsation oscillation increase with the increase of gas-liquid momentum ratio. However， the self-pulsation oscillation frequency decreases sharply when the form of liquid film changes caused by the increase of gas-liquid momentum ratio.