Numerical Study And Nonlinear Analysis Of Supersonic Mixing Layer In Dual-Combustor Ramjet

Numerical study and nonlinear analysis of supersonic mixing layer in Dual-Combustor Ramjet is conducted in this thesis.2-dimension supersonic combustor flow field is studied by RANS simulation method. The combustion in supersonic combustor is weak without the setting for combustion enhancement. The thickness of clapboard basic has an active effect on ignition, flame stabilization and streams mixing. On the condition of a steady Ma of hot air and convection Ma less than 0.5, lower rich-fuel gas results in rapider development of mixing layer. Combustion efficiency increases evidently when the temperature of hot gas rises. The bigger non-matching extent of pressure results in the heavier deflection of mixing layer after being affected by shock wave. When the air/gas pressure ratio rises, the region of mixing layer and heat release is much bigger. At a lower flight Ma, there is higher combustion efficiency as well as larger total pressure loss.The details in supersonic mixing layer related to 2-dimension supersonic combustor are investigated by LES simulation method. With the weak combustion, it is a little effect on configuration of mixing layer, while the latter dominates the former entirely. With thicker basic of clapboard and bigger stream angle, the K-H instability phase of mixing layer is shorter. The bigger the expanded angle of expanded sect is, the more adequate development of mixing layer in expanded sect is. Small flow path induces restraint of large eddy owing to the mutual effect of large eddy and top wall. Streams mix more intensely when hot gas Ma is larger. Pressure ratio of top stream and down stream rising, mixing layer development accelerates greatly. Weak echo shock wave and large eddy produce distortion greatly after the mutual effect of the both, resulting in large eddy restrained. The incidence of strong shock wave in mixing layer induces acceleration of local mixing layer development, while it blocks mixing in the backward sect because of the saturation of eddy absorbing turbulence kinetic energy of the average flow.Pilot study is carried out on mixing enhancement measures for specifical supersonic mixing layer in this paper. Added streamwise surge at low velocity flow inlet, the positive impact on mixing enhancement is evident, and burning intensity increased, however it still belong to weak combustion. The frequency determines the location and scale of vortices assembling region, and the swing determines uniform degree of vortices distributed and assembled. With 3-dimension flow field studied, streamwise vortices induced by interleaving configuration of clapboard bottom accelerate mixing layer development greatly. Armed at different structure of interleaving clapboard bottom, longer distance of wedge acme and bigger wedge angle induce greater streamwise vortices. 3-dimension combustion flow field refer to the enlarged configuration of better clapboard analyzed, the quantity of CO production is the most at the cores of streamwise vortice in space regions. With mixing layer developing and streamwise vortice vorticity transferring into circumambience, the quantity of CO production increases enormously.Instantaneous pressure is picked up in order to analyze nonlinear time serial through LES simulation of supersonic mixing layer. Mixing layer development and stability is studied by nonlinear invariants at the center line in mixing layer, including correlation dimension D and the biggest Lyapunov exponent. Feasibility of this method is testified by an example given. Nonlinear time serial analysis theory is applied to the measure of mixing layer development firstly, and Low-cost experiment method of measuring mixing layer thickness is put forward. It is proved to universality of the distributing accordance between correlation dimension and streamwise turbulent intensity at portrait section and feasibility of this experiment method.