CFD analysis of split-strut spacing and fuel injection angles in a DLR model scramjet combustor

In hypersonic air-breathing propulsion systems, fuel injection and fuel-air mixing strategies play crucial role in ignition and positioning a sustainable flame in available very short residence time. This study numerically investigates the influence of geometric parameters and injection orientation on the performance of a model scramjet combustor, based on split strut fuel injection system, placed parallel to the flow. The performance and stability of scramjet combustors are strongly influenced by two key factors: the spacing between struts and the angle at which the fuel is injected into the supersonic flow. The influence of spacing between the struts, (varied as 1H, 2H, and 3H, where H represents the strut height), and the fuel injection orientation (45° inward or outward) on the fuel-air mixing, and combustion efficiency was investigated. The results, based on experimentally validated numerical model, demonstrate that the strut spacing had a strong influence on the shock interactions. The 3H strut spacing configuration yielded an optimal fuel distribution, which reduced the unburnt hydrogen mass-fraction by 20% and led to almost complete combustion. This model also increases the temperature, mixing efficiency, and combustion efficiency by 90%, 41%, and 60% respectively compared to the base model. The findings of the present study contribute to the development of efficient split-strut fuel injector configurations for scramjet combustors by providing valuable insights into the optimization of strut spacing and fuel injection angles, while achieving an appropriate balance between fuel–air mixing, combustion performance, and total pressure losses.