Experimental investigation on effect of small auxiliary holes on film cooling effectiveness

Experimental study was conducted to investigate the effect of small auxiliary holes on the film cooling performance. The steady-state thermochromic liquid crystal (TLC) method was used to obtain the adiabatic effectiveness distributions on the flat surface. Measurements of adiabatic effectiveness were presented for cylindrical hole, fan-shaped hole, furcated hole and parallel hole with main flow Reynolds number at 2900, blowing ratio ranging from 0.3 to 3.0 and density ratio at 1.06. Results show that the film coverage and adiabatic effectiveness downstream of furcated hole and parallel hole are evidently superior to those of cylindrical hole at blowing ratios range from 0.3 to 3.0. While fan-shaped hole increases the adiabatic effectiveness compared with cylindrical hole only in cases of blowing ratios greater than 1.0. A higher blowing ratio means more obvious improvement of the adiabatic effectiveness.