Effects of mainstream Reynolds number, boundary layer thickness, and turbulence intensity on film cooling with a fan-shaped hole by direct numerical simulation

• Main Authors: Chao,Wei-Siang, 趙偉翔
• Other Authors: Fu, Wu-Shung
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/63287w

博士 === 國立交通大學 === 機械工程系所 === 106 === The aim of this thesis is to investigate film cooling problems with a fan-shaped cooling hole. In order to simulate this subject realistically, the viscosity and compressibility of the gas are taken into consideration simultaneously. Several methods, such as Roe scheme, preconditioning and dual time stepping matching the LUSGS method, are adopted in the current CFD code to solve compressible flow problems. Firstly, the mainstream Reynolds number is varied to study its effect on film cooling. Results indicate that the blow-off phenomenon happens when the mainstream Reynolds number equals to 480. On the contrary, at the higher Reynolds number, the coolant jet is deflected by the mainstream fluid. Thus, a better film cooling performance is achieved with higher mainstream Reynolds number (Re=3200). A detailed comparison of the vortex structure is presented in this study. Secondly, the Boundary layer thickness is varied to study its influence on film cooling. Results reveal that a horseshoe vortex appears with a thicker mainstream boundary layer, and thus the lateral coverage of the coolant fluid is increased significantly. Also, the increase of turbulence intensity eliminates the blow-off phenomenon, which happens in a thin mainstream boundary layer condition.