Study Of High Pressure Underexpanded Hydrogen Jets Using Two-Layer Model

Hydrogen energy is a clean and renewable secondary energy source and is one of the best alternatives to fossil energy in the future.At present,the hydrogen storage method used in the commercial process of hydrogen energy is still high-pressure gas storage hydrogen,and the hydrogen storage equipment has the risk of causing a safety accident due to hydrogen leakage.Studying and analyzing the high-pressure under-expanded jet flow field formed after hydrogen leakage is of great significance for the development of relevant norms and guidelines in the field of hydrogen safety.In this paper,based on the two-layer virtual nozzle model,the numerical simulation of the high-pressure under-expansion jet with slab obstacles in the flow field is carried out,and relevant experimental research is carried out.The traditional CFD numerical simulation method for high pressure underexpanded jet has the shortcomings of long simulation time,high computational resources and unstable calculation,and can not meet the practical engineering application of evaluating and analyzing the risk of hydrogen leakage.In this paper,the shock wave structure of high-pressure under-expanded jet is studied.The characteristics of gas flow in the core zone and the mixed boundary zone are analyzed.The reasonable assumptions are made on the boundary conditions of the jet and the conservation relationship in the flow process,combined with the existing shock wave structure.The quantitative empirical formula of the parameters,considering the deviation of the real gas from the ideal gas,introduces the Abel-Noble gas equation of state,and finally establishes a new simplified model of the two-layer virtual nozzle.The accuracy of the simulated high-pressure under-expanded jet is numerically simulated and experimentally verified.The results show that the two-layer model can accurately calculate the high-pressure under-expanded jet flow field.To some extent,the problem that the jet shock structure can not be reflected in the traditional virtual nozzle model and the error in the actual flow field simulation is solved.The surrounding objects will hinder the flow of gas after the hydrogen leaks,and there are relatively few studies on this.In this paper,the two-layer virtual nozzle model is used to simulate the situation of plate obstacles with different angular arrangement and different distances in the jet flow field.The simulation results are compared by qualitative and quantitative analysis to obtain the gas affected by obstacles.The law of flow.When the inclination of the plate is large,the concentration distribution of the gas on the surface of the plate is more uniform.When the inclination is small,the wall effect of the airflow on the edge of the plate is more obvious.As the distance between the plate and the nozzle increases,the gas concentration distribution on the surface of the plate increases.The curve is more gradual.The presence of slab obstacles effectively blocks the flow of gas,allowing most of the flammable domain to be concentrated in the vicinity of the jet centerline.