A Numerical Study on Blade Design and Optimization of a Helium Expander for a Hydrogen Liquefaction Plant

A design process for cryogenic expanders that supplies 0.5 TPD of liquefied hydrogen in hydrogen liquefaction plants is introduced. To improve the efficiency of the expander, the optimum design was conducted by adjusting two rotor shape parameters. The designed expander for hydrogen liquefaction has a target rotation speed of 75,000 rpm, and helium is applied as the working fluid. Since the operating temperature of the expander is as low as 49 K, a design that reflects the real gas properties must be considered. For a high-efficiency hydrogen liquefaction plant, increasing the expander efficiency is one of the most critical issues. In this study, the efficiency of the cryogenic expander was optimized using the response surface method (RSM). The hub and shroud meridional contours and blade beta angle distributions were chosen as the design parameters. As a result, through the optimized design, it was possible to improve the expander efficiency by up to 1.98% compared to the original expander. Flow analysis was conducted to investigate the reason for the efficiency improvement. Through this study, the effect of the blade meridional contour and blade beta angle on the cryogenic expander efficiency was verified.