Numerical simulation of equilibrium condensation two-phase flow in cryogenic turboexpander

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.