NUMERICAL ANALYSIS OF MULTI-STAGE IMPINGEMENT COOLING STRUCTURE: FLOW AND HEAT TRANSFER CHARACTERISTICS

Impingement cooling is widely employed for thermal regulation of high-temperature components in gas turbine engines, owing to its high local convective heat transfer coefficients. However, the effectiveness of this method is compromised by the external crossflow caused by spent air from upstream jets, particularly in single-stage narrow channels with significant external crossflow. This study explores the flow and heat transfer characteristics of an innovative multi-stage impingement cooling structure. Our numerical analysis reveals that this multi-stage configuration significantly reduces the adverse effects of external crossflow, while also improving coolant utilization efficiency. Compared to the single-stage configuration, the multi-stage structure achieves higher Nusselt numbers on the target surface with only half the coolant consumption at an equivalent Reynolds number. The analysis indicates that single-stage configuration is inferior in terms of coolant mass flow rate and Nusselt number distribution, especially at minimal jet-to-target distances. In contrast, the multi-stage configuration effectively manages external crossflow, leading to a more uniform distribution of coolant and Nusselt number on the target surface. The superiority of the multi-stage configuration is further evidenced by its overall thermal efficiency, which considers both flow resistance and heat transfer. Moreover, a small transition chamber height in the second-stage can induce strong internal crossflow, potentially affecting optimal impingement cooling performance.