EFFECT OF IMPINGEMENT SUPPLY CONDITION ON LEADING EDGE HEAT TRANSFER WITH ROUNDED IMPINGING JETS

Jet impingement is often used to efficiently cool the leading edge of modern turbine airfoils. This investigation employs cylindrical jets with varying edge conditions and inlet flow conditions to obtain detailed Nusselt number distributions on a leading edge model of a turbine airfoil. Jet Reynolds numbers of 13600 and 27200 are investigated. For each test, a set mass flow rate is supplied to the test section; the radial supply flow is then bypassed to achieve the desired jet Reynolds numbers. The results are compared to baseline tests with equivalent jet Reynolds numbers and no radial bypass. Three inlet and exit conditions are investigated for the cylindrical jets: a square edge, a partially filleted edge, and a fully filleted edge. The ratio of the fillet radius to hole diameter (r/d(jet)) is set at 0.25 and 0.667 for the partially and fully filleted holes, respectively. The relative jet - to - jet spacing (s/d(jet)) is maintained at 8, the jet - to - target surface spacing (z/d(jet)) is maintained at 4, the jet - to - target surface curvature (D/d(jet)) is maintained at 5.33, and the relative jet length (t/d(jet)) is maintained at 1.33. Results indicate the amount of bypass flow can significantly change the shape of the stagnation region as well as the magnitude of the Nusselt numbers obtained on the cylinder. Similarly, the relative size of the fillet further influences the enhancement (or degradation) of the Nusselt numbers on the target surface.