Research On Film-hole Mechanism And Cascade Characteristics Of Gas Turbine Film Cooling

Film cooling is widely used in modern gas turbines for the protection of the hot components against hot gases from the combustion process. The paper discusses the film cooling mechanism in the plate model, the film cooling characteristics in the cascade environment as well as the film cooling performance in the approximately real operation conditions, based on the experimental measurement, numerical simulation and theoretical analysis.Film cooling, a 3-D complicated turbulent flow and heat transfer process, is controlled by turbulent and scalar transportation, so the flow field of film cooling plays a very important role in the film cooling performance. It is summarized the direction and mechanism of improving the film cooling effectiveness of film-hole unit by analyzing the influence mechanism of the classical film holes on the film cooling performance step by step. A novel film hole, named SYCEE hole is established based on the improvement direction and the influence mechanism, and its film cooling characteristics are validated and discussed in plate model as well as cascade environment with different conditions.In the vane cascade test rig for film cooling mechanism research, the vane film cooling performance is studied experimentally with different kinds of film-hole, round-hole, shaped-hole and SYCEE hole,and the paramenters blowing ratio, suppling program of cooling gas are considered as well. It is resulted that SYCEE hole also keeps the advantage of film cooling effectiveness comparing to the traditional round-hole and shaped-hole in the cascade environment. Blowing ratio augmentation has a positive effect on the sycee-hole and shaped-hole film cooling performance, but has a negative effect on the round-hole film cooling performance in the cascade environment.In the blade cascade test rig,the blade tip film cooling is studied experimentally, and the influence characteristics of the parameters blowing ratio, density ratio and tip clearance on the film cooling performance are analysized for the flat tip and squealer tip.In the highly subsonic cascade test rig, the ful film cooling performance of the vanefrom the first stageof an F-class turbine is tested in the conditions with approximately real operation Mach number, and influence characteristic on the cascade film cooling is discussed as well by comparing with experimental results in low Mach number. It is obtained that the design target can be generally achieved for the vane film cooling performance of the F-class turbine in the design conditions. But during the changing conditions, the film cooling effectiveness on the vane surface is not proportional to the total mass amount of the cooling gas, as the cooling gas anounts in different rows of film holes are allocated balancing with the non-uniform pressure distributionon the vane surface.Moreover, it is concluded that SYCEE hole still has a better film cooling performance than the shaped-hole in conditions with the approximately real operation Mach number, based the 3-D simulations.