Investigation of combustion characteristics in a scramjet combustor using a modified flamelet model

Abstract

In this study, the characteristics of supersonic combustion inside an ethylene-fueled scramjet combustor equipped with multi-cavities were investigated with different injection schemes. Experimental results showed that the flames concentrated in the cavity and separated boundary layer downstream of the cavity, and they occupied the flow channel further enhancing the bulk flow compression. The flame structure in distributed injection scheme differed from that in centralized injection scheme. In numerical simulations, a modified flamelet model was introduced to consider that the pressure distribution is far from homogenous inside the scramjet combustor. Compared with original flamelet model, numerical predictions based on the modified model showed better agreement with the experimental results, validating the reliability of the calculations. Based on the modified model, the simulations with different injection schemes were analysed. The predicted flame agreed reasonably with the experimental observations in structure. The CO masses were concentrated in cavity and subsonic region adjacent to the cavity shear layer leading to intense heat release. Compared with centralized scheme, the higher jet mixing efficiency in distributed scheme induced an intense combustion in posterior upper cavity and downstream of the cavity. From streamline and isolation surfaces, the combustion at trail of lower cavity was depressed since the bulk flow downstream of the cavity is pushed down.