Film Cooling in a Separated Flow Field on a Novel Lightweight Turbine Blade

Abstract

The primary contribution of this research is to clarify the feasibility of a novel lightweight turbine blade with internal and external cooling, which is invented, aiming at drastic reduction in weight. With a considerably thinner airfoil, an extensive separation bubble is formed on the pressure side, and film cooling performance in such a flow field has to be investigated. Experimental results with a curved duct setup, which simulates the flow field around the proposed airfoil, show that a film cooling is still an effective measure of cooling even in the vastly separated region, and it behaves quite similarly to the conventional correlation, except for lower blowing ratios, where the thermal field is strongly affected by the intense recirculation flow. Comparisons between the experimental and numerical results verify that an affordable Reynolds-averaged Navier–Stokes simulation is useful to investigate the detailed physics of this flow field. With the numerical modeling, a cooling performance of the proposed blade under a typical engine operating condition is simulated, and the metal temperatures of the blade are also predicted with a fluid-solid conjugate calculation. The resultant thermal distribution in the airfoil suggests that the trailing edge portion is inevitably most critical in the temperature, and also a considerable thermal gradient across the blade is induced. Thermal profile, however, is partly recovered with some of the film coolant being bypassed from the pressure side to the suction side.