Experimental and Numerical Crossover Jet Impingement in a Rib Roughened Airfoil Trailing Edge Cooling Channel

Abstract

Local and average heat transfer coefficients were measured in a test section simulating a ribroughened trailing edge cooling cavity of a turbine airfoil. The test rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel, simulating the cooling cavity adjacent to the trailingedge cavity, supplied the cooling air to the trailingedge channel through a row of racetrackshaped slots on the partition wall between the two channels. Eleven crossover jets, issued from these slots entered the trailingedge channel, impinged on eleven radial ribs and exited from a second row of racetrack shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles of 0 deg and 5 deg and a range of jet Reynolds number from 10,000 to 35,000 were tested and compared. The numerical models contained the entire trailingedge and supply channels with all slots and ribs to simulate exactly the tested geometries. They were meshed with allhexa structured mesh of high nearwall concentration. A pressurecorrection based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. The realizable kخµ turbulence model was employed in combination with an enhanced wall treatment approach for the near wall regions. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each crossover and each exit hole from the total flow for different geometries. The major conclusions of this study were: (a) except for the first and last crossflow jets, which had different flow structures, other jets produced the same heat transfer results on their target surfaces; (b) tilted crossover jets produced higher heat transfer coefficients on the target surface towards which they were tilted and lower values on the opposite surface, and (c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases thus CFD could be considered a viable tool in airfoil cooling circuit designs.