Shape Optimization of the Laidback Fan-Shaped Film Cooling Hole on Pressure Surface of Turbine Guide Vane

Abstract

The present study employed computational fluid dynamics (CFD) to explore the effect of the shape parameters of fan-shaped holes on film cooling effectiveness, and the optimum values and variation laws of each shape parameter to maximize the averaged film cooling effectiveness were presented. Meanwhile, experimental verification was used in the optimum holes and reference cylindrical holes. Among the shape parameters of a laidback fan-shaped film hole, the injection angle, the hole diameter and the hole length were fixed as 30 degrees, 0.5 millimeter and 2 millimeters, respectively, and the three shape parameters, the forward expansion angle, the lateral expansion angle, and the shaped-length ratio, were selected as design variables by the Box-Behnken Design (BBD) method. And RSM (Response Surface Methodology) was used to obtain the optimized values of each parameter. Results show that the film cooling effectiveness of the optimized hole (15-20-0.25) was higher than that of the reference cylindrical holes by 336%. The factors influence analysis showed the film cooling effectiveness increased as the forward expansion angle increased, and increased and then decreased with the lateral expansion angle and the shaped-length ratio. The points of the change in trends were when the lateral expansion angle was almost equal to 15 degrees and the shaped-length ratio was nearly 0.475, respectively. Moreover, there was the oscillation of the film cooling effectiveness distribution, possibly due to the asymmetric and irregular distribution of velocity w of the injected coolant along the downstream direction, when the holes outlet area was excessive. In general, the variation laws were not monotonous; therefore, all shape parameters should be considered simultaneously to achieve shape optimization of the laidback fan-shaped film cooling hole on pressure surface of turbine guide vane.