Film cooling performance evaluation of the furcate hole with cross-flow coolant injection: A comparative study

Turbine blades are consistently exposed to high-temperature gas in an effort to increase the maximum efficiency of gas turbine engines. Therefore, a growing need exists to protect the outer surfaces from high-temperature gas. Film cooling has long been used as an active thermal protection scheme, and the shaped film-hole is one possible solution to the aforementioned problem. Based on the actual coolant supply channel of the turbine blades, the film cooling performance of a novel furcate hole fed by cross-flow coolant injection with 135-deg ribs was experimentally investigated in this study. The Reynolds numbers of the main-flow and cross-flow are 10,000 and 100,000, respectively, and the blowing ratio M ranges from 0.5 to 2.0. The adiabatic film effectiveness eta and heat transfer coefficient of the furcate hole are obtained by the transient liquid-crystal measurement technique, and a detailed comparison between the furcate hole and cylindrical hole geometries, simple and compound hole, is presented. The results show that the span-wise width of the film coverage is significantly more comprehensive than that of the compound hole due to the configuration of the span-wise expansion for the furcate hole. At a lower M, the film coverage gradually narrows, and the eta gradually decreases along the flow direction for the furcate hole. The heat transfer enhancement of the furcate hole is the highest among the studied cases, and the heat transfer uniformity is much impoverished. With an increasing M, the advantages of the high eta of the furcate hole are gradually revealed. The degree of deflection of the film coverage gradually increases toward the +Y side. Both the effectiveness and magnitude of the span-wise eta are improved at M=1.0. At a larger M of 2.0, the heat transfer enhancement is the weakest, and the heat transfer uniformity is improved. The net heat-flux reduction is introduced to comprehensively evaluate the cooling performance. The values of the traditional holes invariably decrease as M increases, whereas that of the furcate hole first increases and then decreases. As M increases to 1.0 and 2.0, the comprehensive benefits of the furcate hole become more apparent. (C) 2020 Elsevier Ltd. All rights reserved.