Optimization design of LNG-NG cryogenic mixed-flow pump based on multi-physics field coupling analysis

With the growing importance of natural gas in the global energy landscape, efficient liquefied natural gas (LNG) transportation is facing challenges. However, most of the high-pressure pumps in LNG receiving stations handle pure liquids and require single-phase flow treatment before entry to ensure stable operation, but the process of unidirectional flow treatment is prone to triggering instability. To solve this problem, this paper proposes a new type of gas-liquid mixing pump, using CFturbo and Fluent software to carry out structural design, mesh division and numerical simulation analysis of its structure. Numerical simulations show that the mixing pumps can increase the pressure from 0.8 MPa to 0.95 MPa and reach 10.2 MPa with a multistage centrifugal pump in series. The effects of inlet gas content and gas-liquid phase temperature on pump performance were investigated. Higher gas content reduced flow but increased head, while higher gas temperature lowered flow and efficiency and delayed the phase transition in the pump. Therefore, Inlet conditions should be optimized based on the characteristic curve to improve efficiency under different conditions. Finally, The deformation and stress of key components with and without pre-stress are analyzed using fluid-solid coupling and modal analysis, supporting structural optimization.