Research On The Characteristics Of Jet Breakup And Atomization Of Super Combustion Ramjet Engine

The scramjet is the primary key technology to achieve supersonic flight.The process of liquid kerosene breakup and atomizing in the combustion system has significant impact on the efficient ignition and stable combustion of the engine.The limitation of camera configuration causes smearing of data images,which make more difficult to study the mechanism of kerosene jet breakup and atomization under supersonic crossflow.In the paper,the problem of drag shadow phenomenon was solved based on the laser shadowing method.Combing experimental research and numerical analysis,the article studies the characteristic of breakup,flow field distribution,gas distribution and particle distribution,which enriches the theory of jet breakup and atomization in supersonic crossflow.Firstly,a visualization platform for jet atomization under the supersonic crossflow was built,and the laser was homogenized and planarized by using the solid sol.The laser plane and CCD camera are combined to capture the high-resolution photo of supersonic jet structure without drag shadow.While the existence of surface wave during the breakup process of jet column was proved,the wiredrawing phenomenon,atomization structure and other phenomenon are successfully captured.The breakup and atomization characteristics of jet region are analyzed.The results show that the jet region in supersonic cross flow can be divided into three parts: the crushing region dominated by surface wave,the rapid atomization region and the uniform atomization region.With the increase of orifice diameter or liquid-gas pressure ratio,the empty area and angle of jet will increase,and the penetration depth of jet will also increase at the same position;however,compared with the increase of dynamic pressure ratio,the increase of orifice diameter has more influence on the improvement of jet penetration ability.In addition,the high-speed schlieren method was used to capture the flow field structure under the supersonic crossflow,including bow wave,separated shock wave and separated region.The formation of bow shock is analyzed and the shock region is divided in detail.Moreover,the effects of the diameter of the orifice and the liquid-gas pressure ratio on the shock wave angle were analyzed.The results show that with the liquid-gas pressure ratio or the orifice diameter increasing,the jet blockage degree is increased in the whole flow field,which causes the shock increasing.However,there are differences between the influence of the orifice diameter and liquid-gas pressure ratio on the jet angle.It is found that the orifice diameter has more effect on the shock angle.Based on the DES turbulence model and the DPM particle model,the model under the supersonic crossflow was established,including the turbulence model,gas-liquid control model and fragmentation model.The model parameters are compared for optimization selection by numerical results,and the experimental data obtained by laser shadowing and high-speed schlieren method are used for model verification.After ensuring the accuracy of the numerical model,the paper focus on investigating the influence of orifice diameter and liquid-gas pressure ratio on the atomization characteristics jet atomization and gas phase distribution under the supersonic crossflow.The results show that increasing the orifice diameter or the liquid-gas pressure ratio can improve the kerosene penetration and blocking ability,which enhance the gas phase density upstream of the jet column,while it has little effect on the gas pressure and vorticity distribution under the same inflow conditions;For the kerosene atomization area,the increasing of orifice diameter can improve liquid jet penetration length.During the stable injecting process,the velocity of the jet of small orifice diameter is larger than that of the other orifice.And the particle diameter will also decrease with the decreasing of the orifice.It is easier for the crossflow to affect the jet column and the gas-liquid interface interaction becomes more complicated with the liquid-gas pressure ratio decreasing under the same injecting velocity and orifice diameter.In addition,the gas pressure becomes more intense on the windward side of the jet column and the intensity of the upstream bow shock wave is increased,which are caused by the decreasing orifice diameter.It is easier for jet column of small orifice to deform and the particles of small orifice become more fast and smaller,while the atomization area of small orifice is narrowed.Combining the analysis of the experimental and numerical result,it is found that the orifice diameter has more effect on the jet atomization area under the same crossflow.By adjusting the orifice diameter,the jet atomization area can be adjusted and the atomization quality can be guaranteed.