An experimental investigation of turbine blade heat transfer and turbine blade trailing edge cooling

摘要

This experimental study contains two points; part1 ? turbine blade heat transferunder low Reynolds number flow conditions, and part 2 ? trailing edge cooling andheat transfer. The effect of unsteady wake and free stream turbulence on heat transferand pressure coefficients of a turbine blade was investigated in low Reynolds numberflows. The experiments were performed on a five blade linear cascade in a low speedwind tunnel. A spoked wheel type wake generator and two different turbulence gridswere employed to generate different levels of the Strouhal number and turbulenceintensity, respectively. The cascade inlet Reynolds number based on blade chordlength was varied from 15,700 to 105,000, and the Strouhal number was varied from 0to 2.96 by changing the rotating wake passing frequency (rod speed) and cascade inletvelocity. A thin foil thermocouple instrumented blade was used to determine thesurface heat transfer coefficient.A liquid crystal technique based on hue value detection was used to measurethe heat transfer coefficient on a trailing edge film cooling model and internal model ofa gas turbine blade. It was also used to determine the film effectiveness on the trailingedge. For the internal model, Reynolds numbers based on the hydraulic diameter ofthe exit slot and exit velocity were 5,000, 10,000, 20,000, and 30,000 andcorresponding coolant ? to ? mainstream velocity ratios were 0.3, 0.6, 1.2, and 1.8 forthe external models, respectively. The experiments were performed at two differentdesigns and each design has several different models such as staggered / inline exit,straight / tapered entrance, and smooth / rib entrance. The compressed air was used incoolant air. A circular turbulence grid was employed to upstream in the wind tunneland square ribs were employed in the inlet chamber to generate turbulence intensityexternally and internally, respectively.