超燃冲压发动机自点火条件下波系演化规律试验研究

In order to investigate the evolution law of wave system and flame development in a scramjet combustor under the self-ignition condition，with the inflow condition of Mach number 2.5 and the equivalence ratio of hydrogen being about 0.31，by means of non-intrusion optical measurement methods such as schlieren and Planar laser-induced Fluorescence（PLIF），the evolution process of wave system and flame distribution were studied simultaneously. The results show that the flow field structure in the non-reacting flow stage shows periodic oscillation，which are the inherent characteristics of the cavity-combustor under the studied condition in this paper，and the oscillation frequency measured in the experiment is 143Hz. After the hydrogen is injected into the scramjet combustor，an oblique shock wave generates in the flow field，which is reflected by the bottom wall and then enters into the cavity flow field. This reflected shock wave has little influence on the non-reacting flow structure and the oscillation frequency. But the periodic λ-type shock wave generated by the interaction between the shear layer and the low-velocity recirculation region is strengthened，which has a great effect on the hydrogen self-ignition. When hydrogen is injected into the scramjet combustor for a period of time，and the local equivalence ratio of hydrogen in the back of the cavity reaches the critical value，the periodic λ-type shock wave generates. Then，the self-ignition of hydrogen immediately occurs in the high temperature and pressure region behind the shock wave. Preliminary analysis shows that λ-type shock wave can be used to predict the time of self-ignition accurately in the flow field.