Symmetry Breaking Phenomenon And Analysis In Supersonic Combustor

It is generally believed the flow in a supersonic combustor should besymmetric under the condition of perfect symmetry in geometry and boundaryconditions. Half of the symmetry structure is usually used in the numericalsimulation to analyze the numerical and experimental results. However, unexpectedbehaviors have been reported previously in the numerical and experimentalinvestigations of supersonic combustors. It is symmetry breaking phenomenon.A three-dimensional scramjet combustor is numerically investigated withsignificant upstream interaction in the isolator, and a series of numericalinvestigations is undertaken in a symmetric supersonic combustor to provide anunderstanding of the key features of symmetry breaking and hysteresis phenomena.Firstly, the catastrophic behavior is studied by raising the back-pressure of theisolator. Secondly, the hysteresis behavior is studied by reducing the back-pressureof the isolator at the catastrophe point. Lastly, the conversions between differentflow patterns, Multi-loop hysteresis coupling behaviors, are investigated in asupersonic combustor. Simulation results indicate that the increase in back pressureincreases the number of vortexes in the isolator which leads to discontinuousmovement of first shock wave. It can therefore be concluded that the symmetrybreaking and hysteresis phenomena have occurred in the supersonic combustor, andthe neglect of multistability and hysteresis phenomena causes the poorunderstanding and delays the establishment of the control law.In this study, asymmetry flow in a symmetry supersonic combustor is the mainresearch. When the level of fuel is sufficiently high in the supersonic combustor,there is a sudden switch of the symmetric flow in the isolator. The flow becomesasymmetric. Randomly one side has much higher turbulence than the other. If the level of fuel is now reduced to the same value as the condition of symmetry flow, nochange in the flow can be observed. This phenomenon is known as symmetrybreaking hysteresis.We do a series of numerical simulation under asymmetry boundary with fuelinjection and in differences supersonic combustor with strut in the isolator to findout new multistability and hysteresis phenomena and analysis the influence ofdisturbance on the flow stability. Finally we give out a new method to postponesymmetry breaking and reduce hysteresis by designing of the structure under theflow mechanism.