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 considers jet impingement using square, or sharp edged orifices, to create the jets. However, for gas turbine cooling applications, the edge of the jet orifices generally has some degree of filleting (or rounding) along the edges. The rounding may be a result of casting the airfoils or material wear due to long-term operation. In addition, within the engine, it is likely the jet orifice is not perfectly round. 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. In this investigation, 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 inclusion of the fillet 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 including the geometrical parameters investigated in this study. The newly developed correlations accurately capture the geometrical effects and their deviations from the current experimental results are 10% and 19% for the Nusselt numbers and discharge coefficients, respectively. Engine designers can predict the level of heat transfer and pressure loss for leading edge jet impingement using these correlations.

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This paper provides a detailed experimental investigation of heat transfer and pressure loss for leading edge jet impingement using square-edged, racetrack jets. Experiments were carried out over various parameters: jet-to-jet spacings (s/d) of 2, 4, 8; jet-to-target surface spacings (z/d) of 2 and 4; jet plate thicknesses (l/d) of 1.33, 2.6, and 4; and Reynolds numbers from 10,000 to 100,000. The results show that pressure loss and heat transfer decrease with increasing s/d and z/d. There is an interesting observation for jet plate thickness at l/d = 2.6—a local minima for both heat transfer and pressure loss is measured with the racetrack shaped jets. Using the exhaustive experimental data, design correlations are developed to estimate the surface Nusselt number and discharge coefficients within the domain of geometric and flow parameters. The novel correlations account for the parametric effects and can accurately predict the Nusselt number and discharge coefficient with deviations of 19.8% and 15.9%, respectively. These provide a capability for the engine designers to predict the heat transfer and pressure loss for leading edge jet impingement.