Effect of grooved nozzle plate on aerothermal performance of rotating impingement-jet and pin-fin channel in axial-flow mode

Abstract

The rotating wedge-shaped impingement and pin-fin channel with lateral discharges configures the axial-flow cooling (AFC) mode in a gas turbine rotor blade. The mainstream of coolant flow parallel to the rotating vector of the test channel assists to moderate the unfavorable Coriolis force effect that deteriorates the cooling performance from its non-rotating condition. The Nusselt number (Nu) contours, Fanning friction factors (f), and aerothermal performance indices (API) of two rotating AFC channels with smooth and grooved nozzle walls are compared. The average Nu on the rotating leading (trailing) endwalls of the impingement and pin-fin regions with and without the grooves are modified to 1.2-2.1(1.31-2.18) and 1.15-1.64(1.2-2.15) times the static-channel references; whereas the minimum endwall Nu over the impingement (pin-fin) regions are reduced to 20-65% (25-55%) and 20-65% (25-60%) of the area-average Nu, respectively. The grooves on the nozzle wall weaken jet-to-jet confinements and guide the cold lateral streams toward pin-fin pass to raise the average Nu on the rotating leading and trailing walls of the impingement (pin-fin) region to 1.11-1.39 (1.17-1.39) and 1.12-1.56 (1.19-1.44) times the values with smooth nozzle-wall. The rotating-to-static f ratios fall between 1.06-1.21 and (1.03-1.16) with API∞ reaching 15-19.8 (10.1-15) for the channels with grooved (smooth) nozzle walls. The correlations of average Nu and f are devised for relevant applications.