Interstage matching characteristics of two-stage series-connected helium turbine expander in hydrogen liquefaction system

The helium turbine expander, a pivotal component within a hydrogen liquefaction system, is crucial for effective cooling. Through the use of a multistage series-connected turbine expander, the system is able to accommodate more complex operating conditions and provide enhanced refrigeration efficiency by a gradual and controlled reduction in temperature, thereby optimizing overall performance. In this study, the interstage characteristics of a two-stage series-connected helium turbine expander in a hydrogen liquefaction system employing the inverse Brayton cycle are analyzed in depth. After validation of the reliability of the numerical simulation results using a rigorous on-site joint test system incorporating the helium turbine expander, the operational performance of each expander stage and that of the second-stage expander under various operating conditions are obtained. In addition, the energy loss distributions within various through-flow components and the primary loss zones within the impeller are comprehensively analyzed on the basis of entropy production theory. The findings presented in this paper represent a significant contribution in providing a foundational reference for the development of multistage series-connected cryogenic gas turbine expanders.