Research On Flame Stabilization In A Symmetric Expansion Supersonic Combustor

Under the simulated flight Ma6 of the incoming flow,the combustion characteristics of ethylene and liquid kerosene in the supersonic flow were studied in this paper.Experiments on the flame stabilization of a bilateral expansion supersonic combustor with a parallel cavity were carried out.The injection positions are all located in the upstream of the parallel cavity,and the expansion walls on the top and bottom sides injected fuel into the supersonic combustor at the same time.When ethylene is chosen as the fuel,the symmetrical combustor with parallel cavity exhibits a variety of steady flame burning modes at different equivalence ratios.For high equivalent ratio,the flame zone is symmetrical as the main flow is subsonic,and the experimental results of the injection away from the cavity show that flame in the combustor moves back and forth between the fuel injector position and the cavity to form an oscillation.Shock wave system was not observed at high equivalent ratio burning process,and the jet penetration depth of the two walls is almost close.High equivalence ratio injection near the cavity,the flame oscillation range becomes weakness.In the moderate equivalence ratio of fuel and airflow,the phenomenon of asymmetric combustion can be observed under different injection position,the main performance of the expansion of the wall side of the jet wake steady flame mode,the other side of the expansion wall is the cavity shear layer stable flame mode.And the conversion of the burning mode can be detected in the combustion process.Under lower equivalence ratio,this phenomenon of asymmetric combustion is more significant.At an asymmetric combustion,the large amount of heat released forms a high backpressure zone,and the upstream separation zone is continuously evolving.The results of numerical calculation show that the development of separation zone in flow process is random and asymmetric.Asymmetric development of the separation zone makes the large separation area of the side wall fuel injection jet penetration depth to enhance the mixing and combustion process,the side of the combustion mode will be in the jet wake-steady flame mode.The development of the separation zone on one side will suppress the wall on the other side,making the jet depth and the degree of fuel mixing weaker,and the combustion process more easily in the stationary cavity flame mode.When the fuel is liquid kerosene,continuous combustion of high equivalence ratio liquid jet horizontal injection is realized.Compared with ethylene,the same equivalent ratio and the corresponding experimental conditions,the penetration depth of liquid kerosene is lower,the peak pressure of wall surface of parallel concavity chamber is reduced,and the flame image brightness and combustion area are also smaller.Asymmetric combustion process also occurs in the combustion process of liquid kerosene with high equivalence ratio.Both the jet wake combustion mode and the cavity shearlayer combustuion mode exist simultaneously.Compared with cold flow injection,jet configuration and jet direction of liquid kerosene combustion are complex and diverse.Different jet flow direction of the same flow direction receives downstream development unbalanced pressure effects are exhibited in jitter images with jet instabilities.The experimental results show that the different injection positions have little effect on the flame morphology of the high equivalence ratio liquid kerosene combustion process.