Influence of structural deformation on the rotordynamic characteristics of shaft labyrinth seals in cryogenic liquid turbine expanders under thermal-fluid-solid coupling

The study is focused on the rotordynamic characteristics of shaft labyrinth seals in cryogenic liquid turbine expanders. The critical operational conditions (-170 °C, 6–8 MPa) for cryogenic liquid turbine expanders have made its shaft labyrinth seal rotordynamic characteristics a thermal-fluid-solid coupled problem. The previous study performed by the team of authors indicates that seal structural deformation in cryogenic environments may not be negligible, whereas it calls for an in-depth study to identify their influence on the shaft labyrinth seal rotordynamic characteristics. This study develops a computational framework that combines the thermal-fluid-solid coupling approach and the whirling rotor method to predict the rotordynamic characteristics of labyrinth seals in cryogenic environments. This framework incorporates the influence of the seal structural deformation on the rotordynamic characteristics. It also circumvents the need for time-consuming transient analysis associated with rotor whirl. Consequently, it can enhance the reliability and efficiency of predicting the rotordynamic characteristics of labyrinth seals. In the present study, this framework is applied to investigate how multi-physics coupling-driven seal structural deformation affects rotordynamic characteristics of labyrinth seals for cryogenic liquid turbine expanders. Results demonstrate that multi-physics coupling-driven seal structural deformation alters the seal clearance profile, leading to significant changes in leakage flow behaviors, seal forces, rotordynamic coefficients, and seal stability. This primarily proves that the cryogenic structural deformation is an influential factor for the rotordynamic characteristics of labyrinth seals. Therefore, accounting for structural deformation is essential in the design and analysis of labyrinth seals for cryogenic liquid turbine expanders.