水温对空化流动影响的数值研究

Numerical Study of Effects of Water Temperature on Cavitating Flow

关键词:  液体火箭发动机  温度  空化模型  热力学效应  翼型表面

Key words:  Liquid rocket engine  Temperature  Cavitation model  Thermodynamic effect  Hydrofoil surface

摘要:

为了研究温度升高对翼型表面空化流动的影响，以水为介质，首先对几种现有空化模型的预测能力进行了对比分析，发现Singhal模型能够较准确预测空化区的形状、压力和温度分布。通过添加空化引起的能量源项、耦合介质物性参数与温度关系等方式考虑了热力学效应的影响，并利用现有实验数据充分验证了仿真方法的可靠性，发现考虑热力学效应对压力分布影响较小，但是会导致空化区最大温降减小10%左右。基于建立的仿真方法，对298K~393K温度范围内空化流动进行数值仿真，发现空化区温降随温度升高而增大，但是空化区面积随温度变化在T=353K存在拐点，T<353K时，空化区面积随温度升高而增大；而T≥353K时，空化区随温度升高而减小。最后研究了雷诺数变化对空化发展的影响，发现雷诺数增大有一定促进作用，而温度升高同时导致热力学效应增强（抑制空化）和雷诺数增大（促进空化），正是这两种相反作用之间的平衡决定着温度对空化流动的影响。

Abstract:

In order to study the effects of increasing temperature on cavitating flow on surface of hydrofoil, a comparison analysis of the predicted ability of different cavitation models was performed firstly using water as working fluid. It was found that Singhal model can accurately predict the cavity appearance, pressure and temperature distribution. The thermodynamic effect was taken into account by adding the energy source term caused by cavitation and coupling with the relationship between physical properties and temperature, the validity of the numerical method is verified by available experimental data. Little influence on the pressure distribution is identified after considering thermodynamic effect, but the maximum temperature depression is decreased by about 10%. Numerical simulations of cavitating flow within temperature range 298K~393K were conducted based on the developed numerical method. It was found that the temperature depression increased with increasing temperature, whereas there is an inflection point at T=353K of the curve of cavitation area versus temperature, the cavitation area increased with increasing temperature when T<353K, while decreased after T≥353K. At last the influence of Reynolds number on cavitation development was identified, elevated Reynolds number is found to have promotion effect, and increasing temperature produces both stronger thermodynamic effect (suppress cavitation) and larger Reynolds number (promote cavitation), the influence of temperature on the cavitating flow depends on the balance between these two inverse effects.