Effect of Upstream Wake on Aerothermal Characteristics at Squealer Tip with Large-scale Depth

The squealer tip is a general shape used to raise the aerothermal performance of turbine. However, in complex working environment of an aircraft engine, the scale effect of cavity depth is coupled with the unsteady disturbances formed by the periodic sweeping of upstream wake, causing complicated coupling characteristics of tip heat transfer. This paper concentrates on the goal of reducing heat load of tip. Regarding the squealer tip, clarify the underlying mechanism about the effect of depth scales on tip heat transfer at the first; afterwards, for the cavity with large-scale depth, consider the effect of upstream wake on tip heat transfer, illustrate mechanism of upstream wake's effect on heat transfer, and analyze transient characteristics of tip heat transfer. The outcome indicate that the transport effect can effectively reduce tip heat transfer. Under influence of upstream wake, the average heat transfer coefficient of tip is significantly reduced, the rate of decline corresponding to top of rim, rim wall, cavity bottom and entire tip are 14%, 21.54%, 24.03% and 19.63% respectively. The periodic sweeping of the upstream wake causes periodic fluctuations in heat transfer of cavity bottom near leading edge of suction side. When the upstream wake transports to the vicinity of blades, the average heat transfer coefficient at cavity bottom decreases, and as the influence of wake on blades is relatively small, the average heat transfer coefficient at cavity bottom increases, exceeding the corresponding time-averaged average heat transfer coefficient by 11.7%. Overall, based on the advantages of squealer tip with large-scale depth, the mechanism and pulsation pattern of heat transfer at blade tip under the influence of upstream wake transport are revealed, and the engineering reference database for the design of squealer tip with large-scale depth is improved.