| dc.description.abstract | Heat transfer and discharge coefficients are investigated for leading edge jet impingement using racetrack shaped jets of aspect ratio 2:1. Very few studies discuss heat transfer results for the racetrack shaped jets and less information is available for the pressure losses. The experiment was conducted for varying parametric levels of flow rate (Reynolds number from 10,000 to 100,000), jet-to-jet spacing (s/d = 2 - 8), jet to-target surface spacing (z/d = 2, 4), surface curvature (D/d = 2.665, 5.33), jet nozzle length (jet plate thickness) (l/d = 1.33 – 4) and fillet radius on the jet orifice (r/l = 0-0.5). For heat transfer, a steady state technique was used to obtain regional heat transfer coefficients, which were reduced to stagnation Nusselt numbers. For discharge coefficients, the total and static pressures were obtained at the supply inlet and jet exit, respectively. The results followed established trends for Reynolds number, jet-to-jet spacing and jet-to-target surface spacing. For jet nozzle length (jet plate thickness), the heat transfer depended on the length of reattachment (based on Reynolds number) due to the vena contracta effect. After a certain length, jet plate thickness becomes irrelevant to either improving heat transfer or improving discharge coefficients, due to higher pressure losses across greater lengths. The addition of fillets helps to improve discharge coefficients at the cost of heat transfer, with minimal difference in the degree of filleting. Existing design correlations were developed over a narrow range of flow parameters for round holes, so their use is limited. To expand the domain, new heat transfer correlations were developed over 95 test cases which provide 10% deviation with 90% confidence. These correlations have been compared with existing literature to further validate their use. Literature does not contain equations for pressure losses and hence, correlations are developed for discharge coefficients, which produce 10% deviation with 88% confidence. These correlations provide gas turbine blade designers with a convenient tool to quickly and accurately estimate heat transfer and pressure loss for leading edge jet impingement with racetrack shaped jets. | en |
