Heat Transfer and Pressure Loss Correlations for Leading Edge, Jet Impingement Using Racetrack-Shaped Jets With Filleted Edges

Abstract

This paper presents an experimental investigation of heat transfer and pressure loss for leading edge jet impingement using racetrack shaped jets. The majority of literature for gas turbine cooling applications considers jet impingement using square, or sharp-edged orifices. However, the edge of the jet orifices generally has some degree of filleting (or rounding) along the edges, due to casting the airfoils or material wear due to long-term operation. Engineers need data under realistic engine configurations to improve the utilization of coolant while adequately protecting the airfoil. The current experimental study is a parametric investigation of heat transfer and pressure loss for leading edge jet impingement, where the effects of jet Reynolds number (Re = 10,000 - 100,000), jet - to - jet spacing (s/d = 2 - 8), jet - to - target surface spacing (z/d = 2 - 4), surface curvature (D/d = 2.67 - 5.33), and jet fillet - to - jet plate thickness (r/l = 0.16 - 0.5) are each considered. The edge rounding at both the inlet and outlet of the jet plate yields reduced heat transfer compared to the square edged jets. However, the fillets significantly improve the discharge coefficients associated with the racetrack shaped orifices. With the extensive testing completed in this study, design correlations have been developed to predict the surface Nusselt number and discharge coefficients, with 10% and 19% deviation from experimental results, respectively. Engine designers can predict the level of heat transfer and pressure loss for leading edge jet impingement using these correlations.