Effect of Channel Orientation and Rib Pitch-to-Height Ratio on Pressure Drop in a Rotating Square Channel with Ribs on Two Opposite Surfaces

[摘要] The effect of channel orientation and rib pitch-to-height ratio on the pressure drop distribution in a rib-roughened channel is an important issue in turbine blade cooling. The present investigation is a study of the overall pressure drop distribution in a square cross-sectioned channel, with rib turbulators, rotating about an axis normal to the free stream. The ribs are configured in a symmetric arrangement on two opposite surfaces with a rib angle of90∘to themainstream flow. The study has been conducted for three Reynolds numbers, namely, 13 000, 17 000, and 22 000 with the rotation number varying from 0–0.38. Experiments have been carried out forvarious rib pitch-to-height ratios(P/e)with a constant ribheight-to-hydraulic diameter ratio(e/D)of0.1. The testsection in which the ribs are placed on the leading and trailingsurfaces is considered as the base case (orientation angle=0∘, Coriolis force vector normal to the ribbedsurfaces). The channel is turned about its axis in steps of15∘to vary the orientation angle from0∘to90∘. The overall pressure drop does not changeconsiderably under conditions of rotation for the base case.However, for the other cases tested, it is observed that theoverall pressure drop increases with an increase in the rotationnumber for a given orientation angle and also increases with anincrease in the orientation angle for a given rotation number.This change is attributed to the variation in the separation zonedownstream of the ribs due to the presence of the Coriolisforce—local pressure drop data is presented which supports thisidea. At an orientation angle of90∘(ribs on the top andbottom surfaces, Coriolis force vector normal to the smoothsurfaces), the overall pressure drop is observed to be maximumduring rotation. The overall pressure drop for a case with a ribpitch-to-height ratio of5on both surfaces is found to bethe highest among all the rib pitch-to-height ratios covered in thisstudy with the maximum increase in the overall pressure drop beingas high as five times the corresponding no-rotation case at thehighest rotation number of0.38and90∘orientationangle.

[学科分类] 力学，机械学