Experimental Study of Full Coverage Film Cooling Effectiveness for a Turbine Blade With Compound Shaped Holes

Abstract

The film coverage of a turbine blade surface is determined by all the film cooling structures. The direct study of full coverage film cooling is relatively rare, especially for related research on turbine blades. In this paper, the pressure-sensitive paint (PSP) measurement technique is used to carry out experiments under different turbulence intensities and mass flux ratios, and the distribution of the film cooling effectiveness on the entire surface is studied in detail. In this study, a basic turbine blade and an improved turbine blade are investigated. The film cooling hole position distribution on the improved blade is the same as that on the basic blade, but the film cooling hole shape on the suction surface and the pressure surface is changed from cylindrical holes to laid-back fan-shaped holes. Both blades have 5 rows of cylindrical holes at the leading edge and 4 rows of film cooling holes on the suction surface and the pressure surface. The leading edge, suction surface, and pressure surface have their own coolant inlet cavities. This kind of design is not only close to the actual working conditions in a flow distribution but also conveniently eliminates the mutual interference caused by the uneven flow distribution between the pressure surface and the suction surface to facilitate the independent analysis of the pressure surface and the suction surface. In this paper, the film cooling effectiveness of two kinds of turbine blades under different turbulence intensities and mass flux ratios is studied. The results show that the average cooling effectiveness of the improved blade is much better than that of the basic blade. The laid-back fan-shaped hole rows improve the cooling effectiveness of the suction surface by 60% to 100% and 50% to 120% on the pressure surface. The increase in turbulence intensity will reduce the cooling effectiveness of the blade surface; however, the effect of the turbulence intensity becomes weaker with an increase in the mass flux ratio. Compared with the multiple rows of cylindrical holes, the cooling effectiveness of the laid-back fan-shaped holes is more affected by the turbulence intensity under the small mass flux ratio.