A study of vortex generator effects on fan-shaped hole cooling performance

To improve film cooling performance, many shaped holes have been developed. Among them, laidback fan-shaped hole is widely applied. Expansion at the outlet increases cooling effectiveness (η) greatly but decreases jet inertia. Facing crossflow, it may reduce η instead. Therefore, a chevron structure was added to the expansion part to improve the jet inertia. Its effects were studied by PSP experiments and numerical simulations. Mainstream Reynolds number (Re) was 10000 based on the characteristic length of film hole diameter. Five momentum ratios (I) and three expansion widths (L_w) at the outlet were set as test cases. The results show that the averaged-η increases with I until 1.73. And the chevron hole indicates better cooling performance especially in downstream. As to L_w effect, it widens film width but shortens film length. Case of L_w = 2.3d gets the best cooling performance. Moreover, in cases of I = 0.11, large L_w weakens film spread along spanwise direction due to lower momentum along spanwise, reducing η on both sides of the expansion. The chevron structure helps to solve the problem and ensure high cooling performance in wide range of I. And it can help to resist crossflow effect.