Study On Flow Characteristics Of Shock Induced Vectoring Nozzle For Engine

Thrust vectoring technology can effectively improve engine performance.Shock-induced vectoring nozzle is a kind of fluid thrust vectoring nozzle.It refers to the nozzle which can control the main flow direction by injecting secondary flow in the non-mechanical deflection state and then realize the deflection of air flow vector.In this paper,the detached eddy simulation method was used to simulate the single-slit and two-slits models of three-dimensional shock-induced thrust vectoring nozzle.After verifying the independence of the grid,the calculated dimensionless pressures on the upper and lower wall centerlines of the nozzle were compared with the experimental results of Waithe K.A.et al,it can be seen that the calculated results are accurate and reliable.The effects of the nozzle pressure ratio and the secondary flow pressure ratio on the flow field structure and the thrust vectoring angle of the one-slit and two-slits nozzles were analyzed.The Q criterion method was used to deal with the three-dimensional flow field,and the vortex structure of the flow field in the nozzle was analyzed.The position and shape of shock wave were analyzed by analyzing the circumferential section of nozzle.The pressure oscillation intensity of the nozzle was analyzed by the root mean square distribution of the fluctuating pressure.The distributions of streamline,Mach number,pressure coefficient,vorticity coefficient,entropy and density gradient on the symmetrical surface of single-slit and two-slits nozzles during one cycle of unsteady flow were observed,and the flow characteristics of nozzles were obtained.Finally,Fourier mode decomposition technique was used to analyze the pressure field on the symmetrical surface of single-slit and two-slits nozzles.Two main frequencies were extracted for each nozzle,and the corresponding modes of specific frequencies were evolved in time domain to obtain their potential dynamic information.The first-order mode of the one-slit vectoring nozzle is mainly represented by the pressure fluctuation around "?" shock wave and oblique shock wave on the lower wall.The first-order mode of the two-slits vectoring nozzle is mainly represented by the pressure oscillation of the downstream secondary jet inlet and the upper shear layer of wake.The second-order modes of both cases show the vortex shedding at the upper and lower shear layers of wake.