Investigation On Mixing Enhancement Mechanism Of Transverse Pulsed Jet And Its Combinations In Supersonic Crossflow

The future application prospect of the scramjet(supersonic combustion ramjet)engine is broad.Combustion and heat release occur during the the process of the engine’s work,then burned gas flow accelerate and expand passing through the nozzle to attain thrust.The fuel-air mixing in engine is the basis for efficient combustion,and excellent mixing is the key to obtain excellent engine performance.However fuel-air mixing is very difficult in the supersonic air flow,therefore it is necessary to use various mixing enhancement methods to achieve great mixing performance.This paper introduced the typical flow field characteristics of transverse jet in supersonic flow,and summarized the flow field characteristics of various mixing enhancement methods as well as the current research situation at home and abroad,including transverse pulsed jet,incident shock wave mixing enhancement,cavity and its combinations aided mixing enhancement.Then summarized the research trends of mixing enhancement methods and analyzed the necessity of conducting study on combination of mixing enhancement methods.The numerical methods used in this paper are introduced,including the control equations,Finite Volume Method and turbulence model,and the numerical method accuracy is verified according to the published experimental data.The numerical method used in this paper is accurate for the simulation of the mixed flow field.Finally,according to the results of grid independence analysis,the moderate mesh will be used for calculation.Aiming at the transverse pulsed jet,Comparing the average and instantaneous flowfields of pulsed jet with steady jet to consider the influence of the frequency on the flow field structure and mixing performance.The improvement of the pulsed jet on the mixing effiency is found.The fuel jet and air jet combination is investigated.The influence of the jet hole spacing on the flow field is considered,the introduction of the air jet increases the ability to roll air,and fuel mixes with air on both sides of the plume,improveing the mixing efficiency of the flow field,and mixing is finished fully in the downstream far field,but the dual injection will increase the total pressure loss of the flow field.The difference between applying pulse excitation to fuel jet and air jet was studied,and the performance of air pulse jet convection field improved less.In view of the combination of mixing enhancement methods,The flow field characteristics of the incident oblique shock wave in the jet field are studied.The influence of the mixing performance of the current field at different shock wave incident locations is considered,The shock wave incident in the downstream of the jet hole is found to be better,but the introduction of incident shock wave will inevitably result in the total pressure loss in the flow field and the decrease of jet penetration depth.Then the effect of pulsed jet on the oblique shock wave flow field is considered,the flow field performance improvement is found.Finally the characteristics of the flow field under the combination of incident shock wave and cavity as well as transverse pulsed jet are considered.