Effect of film hole diameter to discharge coefficients and film cooling effectiveness of the lamilloy were experimentally investigated at the blowing ratios ranging from 0.6 to 2.5. Generally, the cooling effectiveness on the test surface is increased with the film hole diameters and blowing ratios increasing, and the variation tendency along the streamwise through the centerline of film holes also keeps consistent. In the upstream, all configurations have a relatively lower cooling effectiveness, however, with the flows to the downstream, cooling effectiveness grows gradually, and the peak values of effectiveness appeared periodically, the position matches the film hole positions. Besides, between the film holes, fluctuation exists simultaneously. By comparison, the cooling effectiveness and discharge coefficients are both increased with the blowing ratio with same film hole diameters, Moreover, under the same blowing ratios, the cooling effectiveness and discharge coefficients are getting higher when hole diameters increase.

According to the design requirements of high-temperature combustion chamber, an advanced shaped hole structure was designed for film cooling. Numerical method was applied in this study to investigate the flow and heat transfer characteristics of shaped holes and compared with those of cylindrical holes. The influence of the forward expansion angle of shaped holes on the flow and heat transfer was studied. The results show that compared to cylindrical holes, the diffused structure of shaped holes decreases the momentum of jet flow, improves the adhesion characteristics of the cooling air film, increases the diffusion of the coolant air outflow and improves the cooling efficiency between adjacent columns of holes in the lateral direction. When the forward expansion angle increases, the expansion section induced the flow vortex, which reduces the radial velocity of coolant flow and enhances the diffusion of cooling air film both in streamwise and spanwise directions. However, as the forward expansion angle increases further, the scale of vortex inside the shaped hole grows. Too large vortex inside the shaped hole increases the coolant eject angle, which weakens the film covering effect. Additionally, the shaped hole results in an increase in lateral spreading and enhances the cooling effect between adjacent columns of the film hole. The enhancement of the film cooling characteristics is due to the change in the shape of the film hole, resulting in the enhancement of the flow vortex, which induces complicated secondary flow.