Scale Cooling—A Novel Fractal Cooling Structure for Turbine Vanes

Abstract

Additive manufacturing technology provides the possibility of more efficient turbine cooling structures. In this work, a novel structure for turbine air-cooled vane based on fractal structure, named scale cooling structure, was proposed. Fractal channel arrays are arranged on the leading edge, pressure side, and suction side of the novel vane. The design of the fractal channel units takes into account the internal cooling effect, film cooling effect, manufacturing accessibility of the channels, and adaptability to non-uniform thermal loads. The initiated cooling structure allows for the use of larger wall thickness to improve strength. A parameterized design and automated mesh generation technique based on in-house code was developed for the vanes installed with a scale cooling structure. And typical turbine vanes with impingement-film cooling structure and scale cooling structure were evaluated by both infrared (IR) measurement and conjugate heat transfer (CHT) computational fluid dynamics (CFD) analysis. Experimental studies have shown that the local overall cooling effectiveness at the leading edge of the scale cooling structure vane is obviously improved compared to the prototype design with impingement-film structure. The consistency between the IR measurements and the CHT CFD results is favorable. It is found that the improvement in cooling performance of scale cooling structure is mainly due to the improvement of film cooling. Its internal cooling relies on enhanced heat transfer at the branching positions of fractal channels. The scale cooling structure is more sensitive to insufficient coolant supply pressure. It is suggested that the entire pressure difference between the cooling air and the mainstream shall be utilized by the scale cooling structure, which can provide sufficient backflow margin while enhancing internal cooling.