Effects of the cooling jets on the flame characteristics and wall temperature of air-cooled wall-strut flameholders

Air-cooled flameholder is a credible solution for restraining the increasingly raised inlet temperature and operation cycle of advanced afterburner/ramjet combustors. In previous study, the effects of cooling jets on the flow and cooling film characteristics of an air-cooled integrated flameholder (coupled with wall and strut parts) have been revealed by numerical analysis. Furthermore, this work aims to reveal the influence of jet cooling schemes and cooling jet conditions on the fuel spray, flame structure, and wall temperature of air-cooled wall-strut flameholder. Experiments were performed to obtain the flame structures and wall temperature distributions. Numerical simulation with a Discrete Phase Model was employed to analyze the distribution characteristics of vapor-phase fuel. The results suggest that the changes of cooling jet angle significantly affect both the vapor-phase fuel distribution in the backward-facing step region and the radial wake region. Moreover, as the mainstream velocity increases, the pilot flame temperature and area decrease, and its radial propagation capability worsens. An increase in the flow rate of radial cooling jet would lead to local extinction and deteriorate flame uniformity. Therefore, the cooling effectiveness of the air-cooled wall-strut flameholder is significantly influenced by the wall and radial cooling jet angles, as well as the aerodynamic conditions. Overall, when cooling hole angles on the wall-type step of α = 30°, β = 30°, and that on the radial strut of θ = 90°, the air-cooled wall-strut flameholder exhibits the best comprehensive performance.