Experimental investigation on enhancement method of flame diffusion width in a supersonic multi-strut fan-shaped annular combustor

To enhance the combustion performance of supersonic combustors, the flame propagation characteristics of a multi-strut fan-shaped combustor using kerosene fuel were investigated experimentally. The effects of fuel injection strategy and combustor configuration on the flame diffusion process were studied under the conditions of a total temperature of 1680 K and a Mach number of 2.7 at the combustor inlet. Experimental investigations reveal that a crossing-flame can not be established solely by wall injectors when strut spacing exceeds critical threshold. Following the addition of spoiler devices, the wall flame intensity is significantly enhanced. Fuel injected from wide-spaced struts is successfully ignited by the wall flame in the downstream region of the combustor. Driven by thermal choking effects, the crossing-flame propagates upstream along the lower-wall boundary layer to establish global combustion. Consequently, a novel flame-broadening methodology integrating spoiler devices with fuel injection is developed. This approach reduces strut count requirements by 40% for stable combustion while increasing the cold-flow total pressure recovery coefficient by 9%. Further analysis of the flame kernel strength shows that the equivalence ratio of the ignition strut has a significant nonlinear effect on the flame propagation process. Peak combustion efficiency and flame propagation speed are achieved near 0.32 equivalence ratio. The synergistic mechanisms through which combustor geometry and wall injection promote supersonic counterflow flame propagation are elucidated. The research results provide a new technical approach for the design of low aerodynamic drag and lightweight supersonic combustors in the future.