Klaus Semmler

Film cooling on a convex surface with zero pressure gradient flow

Abstract The adiabatic film cooling effectiveness and heat transfer increase due to film injection was investigated on a convex surface at zero pressure gradient flow. Film cooling results were obtained using thermochromic liquid crystals to measure the local wall temperature distribution. Five different injection configurations, three with cylindrical and two with shaped holes were examined. Coolant injection with cylindrical holes indicates decreased film cooling effectiveness and increased heat transfer at moderate and high blowing rates. Significant higher film cooling effectiveness values and lower heat transfer increase due to film injection were achieved by shaped hole injection compared to cylindrical hole injection.

An experimental investigation of film cooling on a convex surface subjected to favourable pressure gradient flow

Abstract The film cooling performance on a convex curved surface subjected to accelerated free-stream flow was investigated. The thermochromic liquid crystals technique was applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Five different injection geometries, three with cylindrical holes and two with shaped holes were investigated. The experimental results were compared to the results of a previous investigation obtained with constant free-stream velocity to determine the influence of free-stream acceleration. The free-stream acceleration caused decreasing adiabatic film cooling effectiveness values compared to constant free-stream velocity, especially further downstream of the point of injection. For the in-line cylindrical injection configurations, an increase in adiabatic film cooling effectiveness in the near hole region can be obtained for higher blowing rates. It is assumed that this effect is due to the reduced tendency of jet separation in the accelerated free-stream. The influence of the free-stream acceleration on the Stanton number ratio is generally small.