Research On Flow And Mixing Mechanism Of Wall Gaseous Jet In Supersonic Crossflow

The present work studied the the process of flow,mixing and flow control of the wall gas jet under the supersonic flow condition in the scramjet engine by using the large eddy numerical simulation(LES)and the non-contact optical measurement method.Firstly,the structure of transverse jet and the large-scale turbulent structures in the near flowfield are studied.It is found that there exist two pairs of typical vortex structures in the jet near flowfield.One of them is leading edge vortices and the other one is hanging vortices.The leading edge vortices form periodically in the windward shear layer and deliver part of injection into main flow.The hanging vortices gradually transform into the contour-rotating vortex pairs(CVPs)in the downstream.When the jet angle and molecular weight of injection are changed,the two kinds of vortex structures still exist in the near flowfield,but obvious differences are observed in the shear layer of jet plume.The smaller jet angle and the smaller molecular weight jet lead to the reduction of large-scale structure scale in jet plume,also the penetration of the jet plume is reduced,this is due to the increase of the convection Mach number in shear layer.Subsequently,the dual jet is studied.It is found that the orifice spacing have an effect on the penetration height and the distribution of jet plume,which is due to the difference in the momentum and counter-rotating vortex pairs in jet plume upstream.The smaller orifice spacing leads to the lower penetration and mixing efficiency,vice versa.Reducing the jet angle of the jet upstream has little influence on the penetration hight of the jet plume dowmstream,but it can obviously reduce the total pressure loss in the flowfield.Then,a micro-ramp vortex generator is used to control the jet plume.Similar to the dual jet flowfield,the low momentum and counter-rotating vortex pair generated by the vortex generator enhance the penetration and mixing effect of plume.The effect of the low momentum in micro-ramp wake on jet penetration is just limited in the vicinity of jet orifice,while the effect of counter-rotating vortex can be maintained in a long distance downstream the jet orifice.Finally,by changing the distance between the vortex generator and jet orifice,it is found that there is an optimum position downstream the vortex generator to achieve the maximum penetration height and optimum mixing effect.In the combination scheme of two vortex generators,it is found that the two vortex generators placed in the flow direction have a slight lifting effect on the penetration of plume,but two vortex generators placed in spanwise obviously inhibit the penetration of plume.