Structural analysis and multi-objective optimization of sealing structure for cryogenic liquid hydrogen triple-offset butterfly valve

Addressing the issue of sealing failure in liquid hydrogen triple-offset butterfly valves within rocket fuel delivery systems under ultra-low temperature conditions due to insufficient cold shrinkage compensation capability, this paper first proposes a soft-sealing elastic compensation structure. Its sealing performance is evaluated using a thermo-mechanical coupling method. Secondly, sensitivity analysis using the Spearman method identifies key optimization variables: radial offset distance D_e, third offset angle α, sealing surface width B, and sealing surface interference T. The optimization objectives are the maximum contact stress P_1max and average contact stress P_1ave during forward sealing, and the maximum contact stress P_2max and average contact stress P_2ave during reverse sealing. Finally, an optimal Latin hypercube sampling method is used to construct the sample space, and a high-precision RBF surrogate model combined with the NSGA-II algorithm is employed to find excellent Pareto front solutions. After optimization, the Maximum contact stress of the butterfly valve sealing structure during forward sealing decreased by 23.43%, and the average contact stress decreased by 22.41%; during reverse sealing, the Maximum contact stress increased by 51.07%, and the average contact stress increased by 48.83%. The optimized butterfly valve sealing structure achieves reliable bidirectional sealing under liquid hydrogen ultra-low temperature conditions.