MULTIPLE JET IMPINGEMENT HEAT TRANSFER CHARACTERISTIC - EXPERIMENTAL INVESTIGATION OF IN LINE AND STAGGERED ARRAYS WITH CROSS FLOW

摘要

Extensive experimental results for heat transfer characteristics have been obtained for configurations designed to model the impingement cooled midchord region of air cooled gas turbine airfoils. The configurations tested were inline and staggered two-dimensional arrays of circular jets with ten spanwise rows of holes. The cooling air was constrained to exit in the chordwise direction along the channel formed by the jet orifice plate and the heat transfer surface. Tests were run for chordwise jet hole spacing of five, ten, and fifteen hole diameters;spanwise spacing of four, six, and eight diameters;and channel heights of one, two, three, and six diameters. Mean jet Reynolds numbers ranged from 5x10 to 5x10. The thermal boundary condition at the heat transfer test surface was isothermal. Tests were run for sets of geometrically similar configurations of different sizes. Mean and chordwise resolved Nusselt numbers were determined utilizing a specially constructed test surface which was segmented in the chordwise direction. Based on these results, both mean and chordwise resolved heat transfer characteristics are presented in graphical form and discussed in detail as a function of mean jet Reynolds number and the geometric parameters, including hole pattern effects. Results for the maximum chordwise resolution of one-third the chordwise hole spacing reflect the periodic variations of the chordwise heat transfer coefficient profiles. Results resolved to one or two chordwise hole spacing’s show more clearly the nature of the profiles smoothed across the periodic variations. A complete tabulation of mean and resolved Nusselt number values for all test conditions covered is included as an appendix.