热力学效应对液氮空化流动的影响

为了研究低温流体空化流动特性,采用数值计算的方法研究了液氮空化流动特性.计算中应用二次开发方法在商业软件CFX中引入修正的Kunz空化模型及能量方程,其物性参数随流场温度变化而不断更新.对绕翼型和对称回转体在液氮中的空化流动进行了计算,基于计算结果分析了热力学效应对空化特征的影响.结果表明,计算与实验的结果基本一致.当液氮工作温度接近临界点时,热力学效应更加显著.它主要表现在空穴变短、蒸气体积分数减少和汽液界面变得模糊.在空化产生的区域,流场的温度由于吸收蒸发潜热降低,在空穴尾部区域,空穴溃灭释放潜热而导致温度升高.同时发现,由于热力学效应温降在0.5～2.5K之间.

Study of Liquid Nitrogen Cavitation Flow

Thermal effects substantially impact the cavitation dynamics of cryogenic fluids. In order to study the cavitation characteristics in cryogenic fluids, numerical simulations of cavitation in liquid nitrogen are presented in this study. The present article focuses on simulating cryogenic cavitation by implementing the modified Kunz cavitation model coupled with energy equation and iterative update of the real fluid properties at local temperatures using CFX software. Computations were conducted on a 2D quarter caliber hydrofoil and an axisymmetric ogive in liquid nitrogen, based on which the cavitation characteristics with thermal effects were explored. The numerical results were obtained and they were agreement with the experimental data basically. The results show that, when the fluid is operating close to its critical temperature, thermal effects of cavitation are more obvious in liquid nitrogen. The cavity length is shortened, the cavity content becomes less and the cavity shows more porous. In the cavity region, the temperature depresses due to absorb the evaporation latent heat, and there is a temperature rise at the cavity rear end attributed to the release of latent heat during the condensation process. It is also observed that the temperature depression due to evaporative cooling is found to be only within 0.5~2.5 K.