Numerical investigation of the effects of cooling jets on flow and cooling film characteristics downstream of air-cooled integrated flameholder

Abstract

Integrated flameholders are widely used in advanced augmented/ramjet combustors to reduce the flow loss and weight of aero-engine. Air cooling is a credible method for restraining the increasingly raised wall temperature of flameholders with the increasing inlet temperature and operation cycle of combustors. In this work, an air-cooled integrated flameholder coupled with wall and radial parts was proposed based on our previous studies. Numerical investigations were performed to understand the influence of cooling jets on the flow and cooling film characteristics of air-cooled integrated flameholder in a simplified afterburner. Results suggest that the cooling jet angles α and β on the oblique and rear plates of the wall part mainly affect the flow and cooling film features in the wall backward-facing step, whereas the hole angle θ on the back wall of the radial part has a significant impact on both of the wall step region and downstream of the radial strut. Furthermore, flow analysis of the interaction of radial and wall cooling jets shows that when α and β remain unchanged, θ not only obviously determines the flow features downstream of the radial part but also has a great impact on the flow field in the step region. On the other hand, when θ is constant, α and β almost only change the flow field in the step region, whereas the flow field downstream of the radial part is mainly affected by the flow rate of radial cooling jets. Notably, since the cooling jets on the wall part can remove the flow resistance loss caused by the sudden contraction upon the oblique and rear plates, all air-cooled integrated flameholder schemes proposed in this work can diminish the total pressure loss of afterburner. The total pressure loss is almost unaffected by the varied α and β while θ=90∘ with the flow rate of radial cooling jets increasing. In addition, the total pressure loss is gradually increased with the mainstream velocity increasing and the mainstream temperature decreasing.