Investigation On Flow Field Characteristics In A Supersonic Inlet And Its Control Mechanism With Vortex Generator

As one of the core parts of fighter aircraft,missile engine,especially of ramjet,the performance of the supersonic inlet has a direct effect on the whole performance of the engine.In order to obtain a higher compression efficiency of the supersonic inlet,it is often to use curves or several surfaces to complete the initial compression of airflow,and due to the viscosity of the airflow,it will gradually accumulates thicker boundary layer on curves or surfaces.In the throat area,the shock wave and boundary layer interaction,causing the separation of boundary layer.The separation of the thickened boundary layer and the boundary layer changes the structure of wave system,reduces the effective flow area of the inlet and causes the decline of engine thrust;it even causes inlet blocked,resulting in the inlet unstart.This paper studies a typical binary mixed compression supersonic inlet,in which some complex flow problems are mentioned such as the flow field structure and the shock wave and boundary layer interaction,uses vortex generator to research the flow control,and explores the effect of the vortex generator in the inlet flow field control.The research results of the flow field characteristics of supersonic inlet shows that in the upstream of the inlet,the airflow realizes the energy conversion through the compression of oblique shock wave,causes the change of aerodynamic parameters.Airflow runs through the wall and generates boundary layer,the separation bubble formats with the interaction of shock wave,due to its poor ability of anti-pressure gradient,the separation zone moves forward,destroys the designed wave structure of the inlet;leading to the serious distortion in the downstream of the inlet flow.Therefore,decreasing the thickness of boundary layer,improving the energy of the low-energy flow group of boundary layer,reducing the intensity of shock wave,can achieve inhibition of boundary layer separation,improve the structure of the flow field,and ultimately enhance the purpose of promoting the inlet performance.The detailed 2d and 3d numerical simulation and comparison analysis research using RANS SA,DES,LES three commonly used methods shows that all the three methods can simulate the basic structure of the inlet flow field,can describe the basic changing discipline of the aerodynamic parameters.SA requires low quality of the grid,easily converges and can obtain basic structure of flow field,and it has the best performance ratio for engineering applications.LES requires very high of mesh grid,especially the mesh grid near the wall,it has much difficulty in convergence,and the cost of computing increases with the times of index,but it has obvious advantages of capturing details of inner vortex structure of the inlet and turbulence flow,it is suitable for the inlet with the installation of vortex generator.DES is the mixture simulation method of SA and LES,its operating difficulty and detail simulation ability is between the two methods,it has advantage of prediction of the inlet performance parameters and the critical state(starting or not),but,due to its closing wall adapting SA to simulate,it is not appropriate to simulate inlet contained a vortex generator.After the installation of micro vortex generator,its generating flow vortex brings in high energy flow to the low-energy flow area of the boundary layer,improves the capacity of anti-pressure gradient of the boundary layer,improves the field structure of the downstream flow,and finally raises the performance of the inlet.