The Influence of Turbine Clearance Gap Leakage on Passage Velocity and Heat Transfer Near Blade Tips: Part II—Source Flow Effects on Blade Suction Sides

An experimental study has been designed and conducted to investigate turbine blade suction side heat transfer and flow near the tip clearance gap. Modeling of the phenomena was carried out in a water tunnel with injection through an adjustable streamwise corner slot in a square test channel. A thin stainless steel ohmic-heated test surface adjacent to the slot simulated the airfoil surface and permitted fine resolution of local heat transfer rates. Mean and fluctuating flow field measurements were conducted with a laser-Doppler anemometer to aid interpretation of the heat transfer results and to provide a basis for comparison with future numerical predictions. The results indicate that flow leakage from the turbine tip clearance gap into the suction side hot gas path results in more extensive and complex heat transfer effects than those measured for the blade pressure side in the companion Part I study. The character of the heat transfer andflow field deviations from closed gap conditions is strongly dependent on the particular combination of flow and geometry parameters present. The observed characteristics have been partitioned into categories of similar behavior, and the parameter combinations that define the boundaries between categories have been tentatively identified for the benefit of designers. The overall conclusions of this study and of the parallel study reported in Part I are that the effects of tip leakage flow on airfoil surface heat transfer near the blade tip can be very significant on both pressure and suction sides, and should be taken into account in blade cooling specification and design.