Recent research progress on transverse injection technique for scramjet applications-a brief review

Abstract With the advancement of the air-breathing propulsion system, the supersonic vehicle technique has drawn a significant interest worldwide. The mixing and combustion process in supersonic combustors has been the subject of interest in aerospace engineering that gives rise to a remarkable distinction to the engineering recognition of the scramjet engine. To achieve a high degree of fuel-air mixing, the transverse injection strategy has been proved to be a typical and simple fuel supply approach for residence-time-limited supersonic combustor; of the order of millisecond and hence widely investigated by scramjet researchers. In this review, the recent research progress on the transverse injection technique for scramjet applications is covered from three perspectives, namely multi-porthole injection strategy, parametric sensitivity to the jet properties, and finally the geometric features of the wall surface. This review reveals that the multi-porthole injection strategy is favourable in accelerating the wall cooling and near-field mixing along with reducing the loss of total pressure whereas a parametric investigation has a promising effect on jet penetration as well as mixing improvement in supersonic cross-flow. Additionally, the formation of the shock upstream of the fuel jet is greatly helpful in the mixing process in the scramjet engines, hence sinusoidal as well as a wavy wall are used in transverse injection flow-field. Finally, a brief discussion regarding the future study on the transverse injection technique is also provided.