Study On Combustion Characteristics Of Supersonic Combustion Chamber Wall Fuel Jet

The scramjet engine faces the problem of insufficient regenerative cooling capacity under high Mach number operating condition,so we can improve the cooling capacity by introducing film cooling.Furthermore,there is still a large amount of energy available inside the endothermic hydrocarbon fuel after entering the combustion chamber by the wall jet to complete the cooling task.Based on this,this paper studies whether the fuel can be burned in the combustion chamber and expand in the nozzle to improve engine efficiency.In this paper,the supersonic mixing and combustion process in the combustion chamber is studied by numerical simulation.A wall fuel jet mixing and combustion model in 2-D supersonic combustion chamber is established.The turbulence model and the combustion model are respectively SST k-w model and eddy dissipation conception model.The chemical reaction mechanism uses 40 components and 141 steps simplified mechanism.Then the calculated results of the model and numerical method are compared with the experimental data of NASA Louis Research Center in the United States to verify the accuracy and feasibility of the numerical calculating model.In order to clarify the mixing characteristics in the supersonic combustion chamber,the basic cold flow field structure in the combustion chamber was calculated by the RANS model,and the effects of different jet and mainstream inlet conditions on flow and mixing were analyzed.It is found that shock waves and expansion waves are generated at the main stream and the jet inlet respectively,and the smaller the jet velocity and the jet thickness are,the stronger the fluid mixing is in the flow field,but the mainstream temperature change does not affect the mixing.At the same time,it is also found that the wall friction coefficient will change under different conditions,and decreasing the jet velocity,the jet thickness and the total temperature of the main stream would decrease the wall friction coefficient,which can reduce the frictional resistance in the combustion chamber and improve the engine push-esistance ratio.The flow field structure of the combustion field is analyzed.Studies have shown that the fire location is on the boundary layer and that combustion affects the flow mixing within the boundary layer.The influence of different inlet parameters was studied.It was found that decreasing the jet velocity,decreasing the jet thickness and the lower the total temperature of the main stream would delay the fire position and distribute the flame away from the boundary layer.At the same time,the combustion will significantly reduce the wall friction coefficient,the greater the flame strength is,the more the reduction of the friction coefficient is.Finally,the effect of shock waves on the combustion of the combustion chamber is studied.It is found that the shock wave will make the jet and the mainstream mixing area closer to the main flow area,enhancing the mixing and combustion between the jet and main flow.At the same time,the shock wave will cause the flame to occur in advance when it is before the firing position,and the flame intensity will increase when the shock wave is after the firing position.Increasing the intensity of the shock wave would enhance the mixing in the combustion chamber,and the flame strength is enhanced when combustion occurs.