Effect of blade rotation on aerothermal characteristics of blade tip with different cavity scales

The tip structure with cavity is a common design scheme to improve the aerothermal performance of turbines. It is very important to control tip clearance leakage and tip heat transfer in the aeroengine. Current studies focus on the conventional squealer tip with small-scale depth, but there are few studies on cavity with large-scale depth that has the potential to inhibit clearance leakage and tip heat transfer. The squealer scale effect is interwoven with the blade rotation factor, resulting in a complex coupling relationship and variation patterns between tip leakage flow and heat transfer. Therefore, the coupling mechanism between rotating state and squealer tip with large-scale depth remains to be researched. This paper takes high pressure turbine with squealer tips as the research object, and analyzes the influence of blade rotation effect on the aerothermal characteristics of squealer tip by using steady numerical method. The research shows that, blade rotation increases scraping vortex in the tip clearance. The combined action of scraping vortex and rib corner vortex inside cavity improves suppression of leakage flow and reduces entropy increase loss of blade outlet. The relative leakage mass flow decreased by 42.71 %, and average heat transfer coefficients of cavity floor, squealer top, rim wall and whole tip region decreased by 15.73 %, 58.84 %, 55.88 % and 46.46 %, respectively. The blade speed increase can enlarge the scale of scraping vortex on squealer tip with large scale, reduce leakage flow and flow loss. In terms of heat transfer, as the rotational speed increases, average heat transfer coefficients at squealer top and whole tip region of large-scale squealer tip first decreases and then increases. The average heat transfer coefficient at squealer top is relatively sensitive to variation of rotational speed.