考虑热力学效应的空化模型修正及其适用性研究

为了研究热力学效应对不同温度水和低温流体空化影响,针对Zwart、Merkle和Singhal 3种典型空化模型,基于Antoine方程,考虑汽化潜热引起的饱和蒸汽压变化以及湍动能对当地汽化压强的影响,通过CFX前处理编辑分别对3种空化模型进行了修正,提出了全新的考虑热力学效应的空化模型。针对不同温度水为介质的NACA0015翼型,分别采用3种不同空化模型及修正后的空化模型进行了数值模拟。结果表明,修正后的Merkle模型更加接近实验值。基于修正后的Merkle模型,模拟了不同温度液氮为介质的HORD翼型,并与实验结果进行了对比。研究发现,考虑热力学效应时,空化区域产生温度下降、对应饱和压力下降,致使空化强度减弱,空穴长度缩短,当地空化数均大于远场空化数。相比温度为77. 64 K的工况,83. 06 K工况下的热力学敏感性更高,压降更多,空化受抑制更加明显。

Modification and Validation of Cavitation Model with Considering Thermodynamic Effects

During the growth and breakup of cavitation, thermodynamic effects will influence cavitation on water at different temperatures and cryogenic fluid. Combined Antoine equation and considered the change of saturated vapor pressure caused by latent heat of vaporization and impact of turbulent energy turbulence kinetic energy on local vaporization pressure, three kinds of cavitation models (Zwart, Merkle and Singhal) were modified. The hydrofoil NACA0015 at different water temperatures was numerically simulated by using three cavitation models and modified models. The conclusion showed that the simulated result of modified Merkle model was more consistent with experimental data. The HORD hydrofoil at different liquid nitrogen temperatures was numerically simulated based on the modified Merkle model. The results compared with experimental data showed that temperature and corresponding saturated vapor pressure were decreased in the cavity, leading to cavitation intensity decreased, the cavity length shortened and local cavitation number was over far field cavitation number. The liquid nitrogen temperature at 83.06K compared with it at 77.64K was more sensitive to thermodynamics, the pressure drop was larger and the cavitation intensity was weaker. The results can provide a new correction method of cavitation model for studying cavitation of water and cryogenic fluids at different temperatures. In addition, the modified cavitation model was of great significance for studying the thermodynamic effects in the cavitation process and it can be applied to cryogenic cavitation in engineering problems.