Heat transfer in a smooth rotating multi-passage channel with hub turning vane and trailing-edge slot ejection

Abstract

This paper experimentally investigates the effects of rotation, turning vane, trailing edge ejection, and channel orientation on heat transfer (HT) in a typical turbine blade three-passage internal cooling test model. The cross section of the first and second passage are rectangular with aspect ratio 1:1 (AR=1) and 2:1 (AR=2) respectively, while the third passage is wedged shaped with slot discharge configuration to simulate the trailing edge ejection design. The flow direction in the first passage is radial outward, after the 180° tip turn, the flow turns radial inward at the second passage. The flow finally redirected to radial outward by the 180° hub turn and discharges through the slot configuration at the third passage. Data measurements are conducted in the second and third passages (includes the hub turn regions). The first passage is not instrumented and serves as flow inlet only. The effects of rotation on the heat transfer coefficients (HTC) were investigated at rotation numbers (Ro) up to 0.32 and Reynolds numbers (Re) from 10,000 to 40,000. This study concludes that the rotating utilizes a positive and negative effect on HT on the radial inward flow leading and trailing surfaces respectively. A reverse trend is concluded for radial outward flow. Rotation also suppresses HT in the turn portion. The effect is most severe at the hub turn side wall. The effect of turning vane slightly reduces and increases HT on all interested surfaces in radial inward and outward flow passages respectively. The turning vane effect is diluted in the hub turn area under rotation. Radial outward flow (third passage) HT is substantially impacted by the channel orientation. Combine with the discharge configuration, under rotating scheme, HT levels in β=45° is significant lower then β=90°. Regional HTCs are correlated with rotation numbers for multi-pass rectangular smooth channel with hub turning vane and trailing edge ejection.