Poor air-fuel mixing and penetration of the fuel are major design challenges for the liquid-fuelled scramjet combustor. In this study, a strut cavity and a Tandem-Hole injector are proposed for improving the mixing and penetration, respectively. The strut cavity is formed in the space between two struts in tandem. Though few studies exist on the strut cavity, they do not bring out the suitability of the strut cavity for mixing enhancement and the mechanism behind its pressure oscillations. Furthermore, no flow visualization study exists. The Tandem-Hole injector consists of two or more circular orifices arranged in tandem and aligned to the flow. The liquid jet emanating from the first orifice provides the shielding against the supersonic flow for the downstream liquid jets. Because of the shielding, the downstream liquid jets could penetrate further above the upstream one. Few studies are available in the literature related to the Tandem-Hole injector. However, most of the studies were conducted in the subsonic crossflow. They do not compare the benefit of the Tandem-Hole injector with a Single-Hole injector having the same injection area. The existing studies do not report the effect of the distance between the orifices on the penetration. Furthermore, the Tandem-Hole injector was not studied in a scramjet combustor. Hence, the present work focuses on experimenting with the strut cavity and the Tandem-Hole injector under cold and reacting flow conditions to address the research gap. In addition, it is aimed to develop an injection system incorporating the strut cavity for improved mixing and the Tandem-Hole injector for higher penetration.