Effect Of Slotted Gas Film Pore Structure On Film Cooling Performance

In modern gas turbine engines,film cooling remains one of the most effective ways to protect heated components such as blades.The special-shaped hole changes the outlet area by changing the outlet shape of the hole,improves the coverage of the air film in the downstream wall surface flow and span,and the blade can be protected by a uniform air film;Slotted air film cooling reduces the jet outlet velocity by changing the jet outlet area,and enhances the wall adhesion of the air film.Changing the slot structure and combining with the circular hole can improve the film cooling effect.Therefore,this paper conducts regular research on special-shaped holes（sector holes,conical holes,crescent holes）and different groove types（transverse groove,arc transverse groove,stepped groove,arc stepped groove,inclined plane stepped groove）.The specific research contents are as follows:Firstly,the film cooling models of basic circular holes,special-shaped holes and different groove types are established.After analyzing and comparing several common turbulence models,it is concluded that the Realizable k-ε model is more suitable for the simulation calculation in this paper,and compared with related experiments to verify the accuracy of the calculation.Secondly,the film cooling effect of different hole types is studied by changing the blowing ratio.Compared with the circular hole,the cooling efficiency of the air film and the cohesiveness of the fan-shaped hole,the conical hole and the crescent hole have been improved to a certain extent.For fan-shaped holes,the air film covers a larger area in the flow and span directions at a low blowing ratio.However,with the increase of the blowing ratio,the air film located in the downstream centerline area of the air film hole is separated from the wall surface,resulting in poor cooling effect of the air film.For tapered holes,the air film holes are similar in structure to circular holes.Therefore,under the conditions of several blowing ratios in this paper,the cooling effect of the tapered hole air film is close to that of the circular hole,but the advantage is smaller.For the crescent hole,whether it is a high blowing ratio or a low blowing ratio,the air film has a high air film cooling efficiency and wall attachment in the downstream,and the cooling effect is significantly improved.Finally,by changing the structural parameters such as the blowing ratio working condition and the slot height,the film cooling efficiency and the Coanda property of different slot types are studied.For various groove types,appropriately increasing the height of the groove and reducing the width of the groove can effectively improve the cooling effect of the air film.For sloped stepped grooves,appropriately increasing the inclination of the sloped surface is beneficial to the improvement of cooling efficiency.For arc stepped grooves and arc transverse grooves,the Coanda effect will occur at the arc structure,forming a high cooling efficiency area,and the high cooling efficiency area has a larger area at a low blowing ratio.