An Experimental and Numerical Investigation of Impingement Heat Transfer in Airfoils Leading-Edge Cooling Channel

Abstract

To enhance the heat transfer coefficient along the leading edge of an airfoil, the cooling flow enters the leading edge cavity from the adjacent cavity through a series of crossover holes, cast on the partition wall between the two cavities. The crossover jets impinge on the leading-edge wall, then form a crossflow that moves towards the airfoil tip. In this experimental setup, there were nine crossover holes with racetrack-shaped cross sections on the partition wall. To investigate the effects of crossflow created by the upstream jets on the flow through each hole and on the impingement heat transfer coefficients, five crossover flow arrangements were studied. These flow arrangements were for 0, 1, 2, 3, and 4 jets upstream of the crossover hole # 5 for which the impingement heat transfer coefficients were measured. Jet to target wall distance ratio, Z/Dh, of 2.81 and local jet Reynolds numbers ranging from 7000 to 32,000 were tested. All tested geometries were meshed with all-hexa structured mesh of high near-wall concentration. Boundary conditions identical to those of experiments were applied and several turbulence model results were compared. The major conclusions of this study were: a) the crossflow produced by the upstream jets caused a slight reduction in impingemen heat transfer coefficients, b) there could be a significant variation in mass flow rate through the crossover holes, and c) the numerical predictions using the standard high Reynolds number k−ε turbulence model along with the generalized wall function, were in good agreement with the measured values for most cases, thus CFD could be considered a viable tool in airfoil cooling circuit designs.