Performance Investigation of Film and Transpiration Cooling

Abstract

This paper presents an experimental investigation of the performance of film and transpiration cooling. Two circular tubes were used as test models, one consisted of sintered porous material with a mean porosity of 21% to create a transpiration cooling effect, and the other was made of solid material with four rows of discrete injection holes to simulate film cooling effect in a gas turbine blade. Two series of tests were carried out in the hot-gas wind tunnel at the Institute of Thermal Turbomachinery at the University of Stuttgart. In the first series, the Reynolds numbers based on the tube diameter were between 1.13×105 and 1.31×105, the apparent temperature on the test models was measured using infrared thermal imaging technique and the corresponding cooling effects were calculated. The test results indicated that in comparison with film cooling, transpiration cooling on the porous tube had a greater stability when the upstream state was changed. In the second series, the static pressure distribution along the test section of the wind tunnel was measured under different coolant blowing ratios, and the corresponding influence on mainstream due to coolant injection through film holes and transpiration pores was analyzed. The tests proved that coolant blowing from the film holes at the leading edge and on the side of the solid tube resulted in a change in static pressure downstream of the injection holes, whereas coolant injection from the pores in the trailing region of the porous tube led to a change in static pressure upstream of the tube.