低温流体空化特性的数值计算研究

采用数值计算的方法研究了液氮和液氢的空化流动特性。为了考虑温度影响,控制方程采用了连续方程、动量方程及能量方程,并应用二次开发方法在商业软件中引入Merkle 空化模型及物质属性,物性参数随流场温度变化而不断更新。分别对液氮和液氢几个工况进行了计算,并与实验结果进行了对比。结果发现,在液氮和液氢中,当流体温度接近临界点时,热力学效应表现显著。热力学效应显著主要表现在空穴变短、水蒸汽含量减少和汽液界面变的模糊。由于密度比、饱和蒸汽压随温度变化梯度等物质属性的不同,相对液氮,液氢的热力学效应更加明显。

NUMERICAL STUDY OF CAVITATION IN CRYOGENIC FLUIDS

The numerical simulations of cavitation in liquid nitrogen and liquid hydrogen are presented.In order to consider the influence of temperature,the solver control equation including the continuity,momentum and energy equations are adopted,computations are conducted by implementing a Merkle cavitation model and the material property,and the material parameters update with temperature in the flow.A few cases are conducted in liquid nitrogen and hydrogen,and the simulation results are compared with experimental ones.It is found that the thermal effects of cavitation are more obviously in both the liquid nitrogen and hydrogen when the fluid is operating close to its critical temperature.The thermal effect more obviously in liquid nitrogen and hydrogen shows that: the cavity length is shorter;the water vapour volume fraction is decreased and the cavity becomes less distinct.The thermal effect of liquid hydrogen is more distinctly compared with liquid nitrogen due to the difference of the density ratios,vapour pressure and other variable properties of the fluids.