Abstract
This study features a rotating, blade-shaped, two-pass cooling channel, which follows the contour and shape of realistic airfoils. Effects of two different 45-deg rib orientations on the heat transfer and pressure loss were investigated and discussed. The cross section and orientation with respect to rotation vary in the serpentine cooling channel. The first passage of the channel is oriented at 50 deg from the direction of rotation, and the second passage is angled at 105 deg. The radially outward first passage has an aspect ratio (AR) = 4:1. After a 180-deg blade-shaped tip turn, the coolant flows radially inward into the AR = 2:1 s passage. The copper plate method was applied to calculate average heat transfer coefficients in each region of the cooling channel. The 45 deg angled ribs with a profiled cross section are placed on the leading and trailing surfaces in two ways: unusual and criss-cross. The rib spacing is P/e = 10, and rib height is e/H = 0.16. In this study, the Reynolds number ranges from 10,000 to 45,000 in the first passage, resulting in Re = 16,000 to 73,000 in the second passage. The rotational speed varies from 0 to 400 rpm, corresponding to maximum rotation numbers of 0.38 and 0.15 in the first and second passages, respectively. From the results, the 45-deg usual and unusual ribs generally have higher heat transfer than the criss-cross ribs. However, the criss-cross ribs have the lowest pressure loss penalty among the three cases. Taking both heat transfer and pressure loss into account, the 45-deg unusual ribs have a higher thermal performance under the stationary condition while the criss-cross ribs are better than other rib orientations under rotating conditions. Thus, the 45-deg unusual and criss-cross ribs can be considered for applications in real engines. The heat transfer and pressure loss data in this study provide important information for internal cooling of gas turbine blades.
