Research on jet structure and the virtual nozzle model for high-pressure hydrogen leakage from rectangular nozzles

Abstract

The shockwave structure generated after high-pressure hydrogen leakage presents a challenge for simulations. To simplify the shockwave structure, virtual nozzle models have been proposed. However, these models are based on circular leak openings, lacking research on rectangular nozzles. This study utilizes OpenFOAM to investigate the characteristics of high-pressure rectangular nozzle hydrogen leakage with pressures up to 90 MPa. A real gas model and a new thermophysical model are adopted to better demonstrate the shock wave structure of the jet under high pressure. The study examines the characteristics of jet structures after leakage from rectangular nozzles with different pressures, aspect ratios, and diameters. The critical conditions for forming Mach disks in rectangular jets are proposed, and an empirical relationship for the position of the central compression wave is summarized. By combining the isentropic expansion equation, mass conservation, momentum conservation, energy conservation, and shock wave relationship before and after, a virtual nozzle model for rectangular nozzles is proposed. Using this model as the boundary condition for calculating large-scale diffusion and comparing the results with previous experimental and simulation data demonstrates its accuracy.