Numerical investigation of cooling performance in the integrated afterburner heat shield with structural modifications under reacting flow conditions

To enhance the cooling performance of an integrated afterburner heat shield under reacting flow conditions, a novel annular jet-assisted cooling configuration was proposed. Using numerical simulation, this study investigated the effects of the cooling hole inclination angle and annular gap height on the cooling characteristics of the heat shield under the combustion state. The results revealed that the airflow at the cooling hole outlet participated in both the combustion process and the film-cooling mechanism. At the inclination angle of 15°, the majority of the cold air flowed adjacently to the wall, resulting in weak interaction with the annular jet and a thin air film. Consequently, elevated near-wall CO₂ concentrations and higher wall temperatures were observed, diminishing the overall cooling efficiency. As the inclination angle increased, the interaction between the cooling air and the annular jet was strengthened. However, excessively steep angles allowed high-temperature gases to flow into the cooling holes, obstructing the cold air and leading to a non-uniform distribution of the cooling film across the heat shield. Furthermore, increasing the inclination angle caused the static pressure ratio to drop below 1.0, triggering hot gas ingress and the formation of a recirculation zone within the cooling holes that intensified the blockage effect. The highest overall cooling performance was achieved at an inclination angle of 30°, with adiabatic cooling efficiency ranging between 0.8 and 1.0. While increasing the annular gap height augmented the coupling between the jet and the cooling air—thereby significantly enhancing protection in the upstream and midstream sections (Zones 1 and 2)—it simultaneously reduced the total cooling air volume, which detrimentally affected the downstream sections (Zones 3 and 4).