Analysis of vortex characteristics and energy losses in a cryogenic hydrogen turbo-expander for a 5 t/d hydrogen liquefier

Abstract

The cryogenic hydrogen turbo-expander (CHTB) is the most core component which determines the dependability and efficiency of hydrogen liquefiers. In present study, CFD method are adopted to simulate the internal flow field inside a CHTB for a 5 t/d hydrogen liquefier. The Ω method and entropy generation method are implemented to identify vortex structures and calculate energy losses. The results show tip leakage vortex is the primary vortex and causes energy losses through strong fluid shear but not rotation effect. The turbulent dissipation is the main energy dissipation. The total entropy generation of CHTB impeller is significantly higher than nozzle because of tip clearances. As tip clearances increase from 0% to 1.6%, total entropy generation increases by 83%, and output shaft power and isentropic efficiency reduce by 9% and 6% respectively. Working conditions mainly affect the inlet angle of attack and significantly impact vortex characteristics and energy losses in the CHTB.