Numerical studies on two-phase flow in cryogenic radial-inflow turbo-expander using varying condensation models

An accurate condensation model plays an important role in the development of high-efficiency turbine. Many efforts have been devoted into the research on steam non-equilibrium condensation. However, aiming at the cryogenic gas at high-speed flow the studies on the condensation model are still inadequate and incomprehensive. In present paper, different condensation models, established via the alternations of nucleation model and droplet growth model are compiled into commercial CFD software to simulate the non-equilibrium condensation flow within a cryogenic radial-inflow turbo-expander. Firstly, the rotation effect on droplets diameter and distribution within the impeller passage are analyzed. The results point out the region where large droplets are prone to form and gather. Furthermore, the influence mechanism of heat and mass transfer in varying condensation models on the flow fields, including rapid nucleation, supercooled degree, liquid mass fraction, droplet diameter, are revealed based on the analysis of Nusselt number and Knudsen number. The results imply that the predicted location of condensation onset is little sensitive to the droplet growth model. At last, the effect of modifications for nucleation rate and droplet growth rate on the thermodynamic losses in turbo-expander are quantificationally discussed.