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

The film cooling performance on a convex curved surface subjected to accele rated free-stream flow was investigated. The thermochromic liquid crystals technique was applied to determine adiabatic film cooling effectiveness val ues and heat transfer coefficients on the test surface. Five different inje ction geometries, three with cylindrical holes and two with shaped holes we re investigated. The experimental results were compared to the results of a previous investigation obtained with constant free-stream velocity to dete rmine the influence of free-stream acceleration. The free-stream accelerati on caused decreasing adiabatic film cooling effectiveness values compared t o constant free-stream velocity, especially further downstream of the point of injection. For the in-line cylindrical injection configurations, an inc rease in adiabatic film cooling effectiveness in the near hole region can b e 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. T he influence of the free-stream acceleration on the Stanton number ratio is generally small. (C) 2001 Elsevier Science Ltd. All rights reserved.