Numerical analysis of tip recess in a micro turbine with hot streaks

In the turbine rotor passage, hot streaks migrate radially toward the blade tip region, heating the tip surface and potentially causing localized high-temperature ablation. This issue is particularly pronounced in micro turbines due to the absence of cooling mechanisms. To address this challenge, numerical simulations were performed using a modified blade model, where only the blade tip geometry was adjusted. This study examines the tip temperature distributions of blades with various recessed tip designs under hot-streak conditions, elucidates the mechanism by which recess structures mitigate hot-streak migration, and proposes an optimized design. The results reveal that the unenclosed and inclined recess introduces low-temperature fluid at the leading edge, enhances overall airflow velocity, and significantly lowers the air temperature within the recess. Furthermore, the oblique angle formed between the pressure and suction sides intensifies the induced vortex at the trailing edge. This strengthened vortex effectively prevents direct contact between the hot streak and the blade tip surface, thereby reducing the tip surface temperature. With the proposed design, the average blade tip temperature decreases by approximately 18.5 K compared to the baseline blade, while the maximum tip temperature is reduced from 1112.1 K to 1074.2 K.