Interaction and combined cooling effects of mid-passage gap leakage with blade coolant in suction side and corner cooling

With the increase in turbine inlet temperatures, effective cooling is essential for all regions of the turbine. However, most previous studies have focused on the thermal protection of individual components, often neglecting marginal areas. From the perspective of multi-zone interactions within the cascades, this study numerically investigates the combined cooling effects between mid-passage gap (MPG) leakage and blade coolant, with a focus on the suction side (SS) and corner cooling. An interesting corner cooling phenomenon is observed, involving interactions among the blade film coolant, leakage flow, and secondary flow. Results show that corner cooling is enhanced when the coolant is either guided by a counter leakage vortex or when the vortex is weakened by leakage. The combined effects of MPG leakage and blade coolant expand the cooling coverage on the suction side and contribute to achieving full surface thermal protection. Additionally, while a compound angle improves blade cooling, its effect is limited and mainly improves the peak value of laterally-averaged cooling effectiveness (ηl). When the blowing ratio of blade coolant (Mb) increases from 0.5 to 1.5 at leakage mass flow rate (MFRg) = 1%, the peak value of ηl on the blade suction side increases by 51%. Under this condition, when film holes are with a compound angle (β) value of 30°, the peak value of ηl further increases by 17.9%. These findings highlight the importance of considering the synergistic effects of passage vortices and leakage flows in future blade cooling designs to achieve more comprehensive and effective suction-side coverage.