Numerical And Experimental Research On Cavity Flow And Combustion In A Supersonic Combustor With One-side Divergence

A one-side diverging supersonic combustor with cavity- flameholders was studied in present work. Combining experimental study and numerical study, this thesis focused on the influence of the cavity’s location and the diverging angle of the combustor on flow field and combustion.Flow filed of the combustor with cavities in different locations were studied via experiments and 2D LES method. Results showed that: Compared with non- diverging combustor, the cavity shear layer in diverging combustor was inclining to cavity itself, and the greater the diverging angle was, the more obvious the inclining was. When changing the diverging angle, the flow structure was mainly the same except the intensity of impinging shock on the rare side of the cavity and the size of main recirculation zone.Non-reaction jet flow filed with gaseous fuel transversely injected upstream of cavity flameholders was inve stigated. When flowing through cavities, only a small part of gaseous fuel got into cavities and most part of the fuel flowed into downstream region. Shocks in flow field interacted with the jet and tended to promote instabilities of the jet mixing layer and the fuel-air mixing process. It was founded that in 3.5 degree combustor, the cavity shear layer was more likely compressed by the jet and the jet was more close to the bottom wall and the shear layer was more inclining to the cavity, boosting the interaction of the shear layer and the jet as well as the mass and energy exchange between the cavity and the main flow. However, the 3.5 degree combustor totally showed lower mixing efficiency and total pressure loss.Reactive jet flow filed with fuel transversely injected upstream of cavity flameholders and the distribution laws of combustion region were also researched both experimentally and numerically. It was concluded that with the same diverging angle, the combustion in the cavity was less stronger and the main combustion region was a little downstream if the cavity was located in the horizontal plane. In the study situation, enlarging the cavities properly could evidently contribute to the enlargement of the combustion region and the pressure rise in the cavity and downstream region. In reactive flow field, the fuel jet was further from the bottom wall and deeper into the main stream in the 3.5 degree combustor and resulting in less stronger interaction between the fuel jet and the cavity shear layer, which is disadvantageous to the cavity stabilized combustion. However, the 3.5 degree indicted higher combustion efficiency and total pressure loss.