低温透平膨胀机内平衡凝结两相流动的数值模拟

Numerical Simulation of Equilibrium Condensation Two-Phase Flow in Cryogenic Turboexpander

采用Peng-Robinson方程及零压多项式拟合了低温空气二元混合物的物性,利用商业软件ANSYS CFX对设计工况下的单相流动及进口升压降温后平衡凝结两相流动进行了数值模拟,得到了全低压空气分离流程中的低温两相透平膨胀机喷嘴和工作轮的温度场、压力场、流线及带液量云图,同时推导了该工况下膨胀机的等熵效率。结果表明,工作轮流道内吸力面壁面处的涡流会延迟凝结相变发生,叶片后缘处的尾迹使得吸力面壁面处的带液量有所减小。最后,通过实验验证了模拟结果,表明利用平衡凝结相变模型能够模拟小带液量透平膨胀机流道内的两相流动。该结果可为低温两相膨胀机研究提供参考。

The binary mixture properties of cryogenic air were fitted by the PR equations and the zero pressure polynomial.The single-phase flow under the design conditions and the equilibrium condensation of two-phase flow at higher pressure and lower temperature were numerically simulated by ANSYS CFX.For a cryogenic turboexpander in air separation process,the temperature field,pressure field,streamlines and liquid mass fraction in the nozzle and impeller were obtained.The isentropic efficiency of the turboexpander was calculated.The results show that the eddy occurring on the suction side of the impeller would delay the phase-change condensation,and the wake at the trailing edge of the blade would lead to the decrease in the local liquid mass fraction.The simulation results agree well with the experimental data,confirming that the model of the equilibrium condensation can be applied to the simulation of the two-phase flow turboexpander having a small liquid mass fraction.