Effect of upstream leakage flow on film cooling characteristic of a turbine convex endwall

The passage crossflow is one of the important secondary flow features that influence the endwall film cooling characteristic. While the upstream leakage flow can not only control the ingestion of mainstream gas but also provide endwall film cooling effectiveness distribution well. Consequently, this paper employed the pressure sensitive paint technique to investigate the film cooling performance of the endwall for the leakage flow. The effect of the passage crossflow on endwall film cooling is analyzed by numerical methods. Moreover, several crucial parameters that mass flow ratio (MFR), leakage slot inclination angle (a), density ratio (DR), and mainstream Reynolds number (Re) are considered for the study. Results indicate that a crescent-shaped uncooled area can be discovered near the suction side due to the existence of an inverse directional crescent-shaped crossflow region, and the uncooled area disappears gradually with the increase of MFR. Reducing the a, the axial velocity of the leakage flow is increased, which improves the film cooling effectiveness of the endwall for all the MFR cases. The effectiveness of the endwall is grown with the reduction of the DR at the low MFR case, however, the effectiveness is hardly influenced by the DR at the condition of MFR = 1.5%. Moreover, the enhancement of the Re that makes the strength of the secondary flow near the endwall reduce, which results in an increase in the endwall cooling effectiveness for all MFR cases.