Research On Numerical Method, Experimental Verification And Application In Simulating Jet Interaction In Supersonic External Flow

The jet interaction in supersonic external flow was studied by means of numerical simulation and experimental investigation. The development, validation and application of the CFD algorithms for various jet interactions were focused on in the dissertation. And the heterogeneous gas jet interaction characteristics, unsteady jet interaction control and combustion characteristics and so on were studied.The uniform CFD algorithms for the simulation of laminar flows, turbulent flows, chemical nonequilibrium reaction flows were developed. The leading characteristics of the algorithms are: (1) NS equations plus a two-equation turbulence model(Menter's Shear-Stress Transport model), species conservation equations are used as the governing equations, and an uncoupled method is adopted to simulate chemical nonequilibrium reaction flow which has the stiffness problem. (2) a finite difference method is used based on structured girds, Runge-Kutta method is used for time integration, which could go beyond the limit of difference schemes in time splitting technique, NND-1 scheme and WAF scheme for convection terms'discretization, and central difference scheme for viscous terms'discretization. Numerical validation showed that the uniform CFD algorithms are of higher-order accuracy, and suitable for the simulation of unsteady flows (especially the unsteady chemical nonequilibrium reaction flows).Based on PLIF (Planar Laser-Induced Fluorescence) technique and schlieren technique, a model experiment was designed and carried out for typical jet interaction research. The model experiment showed: (1) PLIF technique and schlieren technique are suitable for the optic diagnosis of jet interaction, and PLIF technique is capable of capturing the flow field of heterogeneous gas jet interaction; (2) the physical parameters (the ratio of specific heats and the gas constant) of jet have an effect upon jet interaction.The CFD algorithms were used to simulate typical heterogeneous gas jet interactions. Firstly, after simulating a solid rocket engine's jet interaction, it showed that one of the reasons for the shield board's dropout in experiment is the ejection effect of jet. Secondly, after simulating the lateral jet flow fields of a missile with wings for some different ratios of specific heats and gas constants of the lateral jet, the thrust force amplification factor versus the lateral jet's ratio of specific heats for typical case was obtained, and a method for correlating the data of cold jet case and hot jet case was constructed by adjustting jet's total pressure. Thirdly, after simulating the inner flow field of a typical scramjet combustion chamber with fuel jet and cavity structure, the unsteady dynamic phenomenon that fuel jet moves downstream and diffuses into the cavity is captured (The corresponding experiment fails to capture that phenomenon).According to the vitiated air effects in supersonic combustion experiments, an CFD example, which is the oscillating shock-induced combustion of a blunt body with random and vitiated air flow coming from the far field, was designed and simulated for analyzing the effects of the random disturbance on the unsteady chemical nonequilibrium reaction flow field. On condition the mean parameters of the vitiated air were equal to the flight air parameters, the CFD results of vitiated air case and flight air case were compared. The results showed that, when the maximal relative error is smaller than 5%, the random disturbance has less effect upon the basic flow structures, but has an effect upon the variety of typical flow parameters versus time, and the effect is ruleless and nonlinear.According to the problem of enhancing mixing and combustion in supersonic combustion researches, based on the flow mechanism of vortex's enhancement on mixing and combustion, an"innovative fuel injector with alternate and impulse jet for scramjet"was designed by an unsteady flow control technique with multiple impulse jets, and its application characteristics were simulated furthermore. The results showed that the innovative fuel injector injects fuel into the combustor dollop by dollop, which could enhance the mixing and combustion of fuel and air, and reduce the combustion zone length in the main flow direction, so it is favorable to reduce the length of isolator and combustor, and the weight of scramjet by using the innovative fuel injector.