Numerical and Experimental Investigation of High-Pressure Hydrogen Jet Dispersion from Leakage at 70 MPa.

High-pressure hydrogen storage has become the mainstream technical route for fuel cell vehicles due to its high energy density and favorable economic efficiency, with operating pressures gradually increasing from 35 to 70 MPa. However, the complex shock wave structures formed during high-pressure leakage pose significant challenges to numerical simulation. Existing CFD models based on incompressible assumptions or low Mach number conditions are prone to numerical oscillations, nonconvergence, or even computational failure when dealing with the strong nonlinearity and solution discontinuities induced by intense shock waves. Conventional numerical schemes often face a dilemma: low-dissipation schemes may introduce nonphysical oscillations, whereas high-dissipation schemes tend to excessively smooth shock structures, leading to distorted flow characteristics and reduced prediction accuracy. In this study, a numerical model for high-pressure hydrogen jet diffusion is established by considering the functional relationship between the influence range of shock waves at discontinuities and the time step. Validated through 70-MPa schlieren experiments, the model predicts the Mach disk position with an error of 8.7%. The research indicates that local low-pressure zones as low as 25,000 Pa appearing in the flow field significantly reduce the critical autoignition temperature of hydrogen, and the flammable range is primarily concentrated at the wrinkled edges of the hydrogen cloud and near-wall "air entrapment zone." These findings provide a quantitative basis for optimizing the placement of leak detection sensors and designing explosion venting solutions.