Transient flow characteristics for fluid-structure interaction on hydrogen decompression valve in high-pressure hydrogen storage systems

As a core component in high-pressure hydrogen storage systems for hydrogen fuel cell vehicles, the spring-loaded hydrogen decompression valve (SHDV) directly affects the performance of the hydrogen fuel cells. In this study, the transient flow characteristics of fluid - structure interaction in SHDV are investigated using the dynamic mesh method and real gas model. The complete closure of the valve spool is realized by the porous medium model. Adverse pressure gradients, flow separation, and unsteady vortex evolution in the decompression valve are numerically calculated with large eddy simulation, and the reliability of the calculation is verified by the experiments and theoretical model. Results show that the characteristic curve of the SHDV startup process can be divided into three phases: rapid response phase, closure phase, and equilibrium phase. The change in spool angle slightly affects the rapid response phase but substantially affects the fluctuations of pressure and flow during the closure and equilibrium phases. In the equilibrium phase, typical adverse pressure gradients and flow separation occur downstream of the spool, gradually propagating into the control chamber and causing pressure instability. Backflow under the large-angle spool is primarily caused by adverse pressure gradient and wall shear stresses, whereas backflow under the small-angle spool is mainly formed by the obstruction of the upper wall at the control chamber. By adding a convex cylinder structure to the spool, adverse pressure gradients and flow separation downstream of the large-angle spool can be effectively suppressed.