Unsteady flow behavior and two-phase region prediction in the SCO2 centrifugal compressor

Abstract

In this study, unsteady numerical calculations of centrifugal compressors with volute were carried out. The unsteady evolution of two-phase regions and flow behavior in impeller passages were determined. The results show that the two-phase regions in impeller passages are governed mainly by the low static pressure strip LP1 on the casing wall. Meanwhile, the unsteady trajectory of a two-phase region is consistent with the trajectory of LP1. The unsteady evolution of a two-phase region undergoes two stages: In the first stage, it appears near the middle streamwise position and simultaneously expands to the leading edge (LE) and trailing edge (TE) of the blade. In the second stage, it shifts from the middle streamwise position to the LE of the blade and finally disappears. Moreover, based on the rotor enthalpy conservation, the prediction model for the formation of two-phase region in the impeller passage under different inlet conditions was determined.