Diagnosis And Simulation Of Two-phase Flow Characteristics Of Four Combustion-gas Jets And Restricted Liquid

In this paper,the multi-point ignition of bulk-loaded propellant guns is taken as the engineering background.The expansion characteristics of four combustion-gas jets in liquid are researched with both experiment and numerical simulation.The main research contents and results are as follows:(1)Experimental study on the expansion characteristics of four gas jets in fluidThe experimental simulation platform for the expansion of four gas jets in liquid is constructed.Different structural observation chambers are designed to analyze the expansion processes of four combustion-gas jets by the high-speed digital recording system.At the same time,the effect of different nozzle center interval,jet pressures and nozzle diameters on the expansion process are investigated.The results show that the jet expansion is more stable in the larger expanding ratios chamber.The appropriate increase of the nozzle spacing can enhance the radial expansion of the jet.Increasing the diameter of the nozzle and the spacing of the nozzles will increase the jet intensity and axial displacement.(2)Numerical calculation model and method of four gas jets expanding in liquidBased on the experimental results,the hypothesis of the gas jet expansion process is put forward to simplify the mathematical physics model,and then the appropriate turbulence model is selected according to its extended characteristics to establish a three-dimensional unsteady gas-liquid interaction between the four gas jets and the liquid.The turbulent mathematical model simulates the expansion process of four gas jets and performs grid-independence verification on typical working conditions models to improve computational efficiency.The experiment and simulation results are compared and analyzed to verify the accuracy of the model.(3)Numerical simulation of the influence of boundary shape on the expansion characteristics of four gas jetsOn the basis of the experiment,a five-stage cylindrical stepped-wall type,conical and cylindrical observation chambers are designed.The influence of the observation chamber structure on the expansion characteristics of the four gas jets is investigated by numerical simulation.The results show that the radial expansion of the jet in the five-stage cylindrical stepped-wall type observation chamber is more stable,and the core of the jet in the conical observation chamber will be greatly offset,and the radial expansion of the gas in the cylindrical observation chamber is slower.(4)Numerical simulation of the influence of characteristic parameter variation on the expansion characteristics of four gas jetsIn order to analyze the influence of characteristic parameter variation on the expansion characteristics of four gas jets,the numerical simulation of the expansion process of four gas jets in a five-stage cylindrical stepped-wall type observation chamber is carried out under different nozzle center interval,jet pressures and nozzle diameters conditions.The results show that when the spacing of the nozzles is moderate,the core area of the jet will not be offset to the center of the observation chamber;the diameter of the nozzle is too small,the input energy per unit time is limited,and the jet is unstable at the near field.Increasing the jet pressure and nozzle diameter will enhance the gas-liquid turbulent mixing and increase the energy dissipation;therefore,by properly matching these parameters,the jet expansion process can be more stable.