Detailed Flow and Heat Transfer Analyses in a Rib-Roughened Trailing-Edge Cooling Cavity With Impingement

Abstract

A rig, simulating two adjacent cooling cavities on the trailing side of an airfoil, made up of two trapezoidal channels is tested. Eleven crossover holes on the partition wall between the two channels create the jets. Two exit flow arrangements are investigated—(a) jets, after interaction with the target surface, are turned toward the target channel exit axially and (b) jets exit from a row of racetrack-shaped slots along the target channel. Flow measurements are reported for individual holes and heat transfer coefficients on the eleven target walls downstream the jets are measured using liquid crystals under steady-state conditions. Smooth as well as ribbed target surfaces with four rib angles are tested. Correlations are developed for mass flow rate through each crossover hole, varying the number of crossover holes. Heat transfer coefficient variations along the target channel are reported for a range of 5000–50,000 local jet Reynolds numbers. Major conclusions are: (1) Correlations are developed to successfully predict the air flow rate through each crossover hole for partition walls with six to eleven crossover holes, based on the pressure drop across the holes, (2) impingement heat transfer coefficient correlates well with local jet Reynolds number for both exit flow arrangements, and (3) case of target channel flow exiting from the channel end, at higher jet Reynolds numbers, produce higher heat transfer coefficients than those in the case of flow exiting through a row of slots along the target channel opposite to the crossover holes.