Flow and heat transfer mechanism of U-shaped channel considering variable cross-section and rotating effects

Abstract

With the increasing inlet temperature of gas turbine, blade internal cooling as the most effective cooling technolpogy has become more important for the safety of gas turbine. In engineering practice, the U-shaped cooling channel inside the blade midchord is characterized as variable cross-section due to the influence of blade structure. In this paper, four different variable cross-section U-shaped channels are constructed. Through numerical analysis, the heat transfer enhancement mechanism considering variable cross-section and rotating effects is revealed, the quantitative heat transfer resistance performance data are given. The results show that under stationary condition (Re = 10,000–50,000), the Nu/Nu0 of the expanded cross-section channel is increased by 22.1% and f/f0 is decreased by 54.2%. The Nu/Nu0 of the reduced cross-section channel is increased by 26.7%, but f/f0 is also increased significantly. Under rotating condition (Ro = 0–0.4), the Nu/Nu0 of the expanded cross-section channel is increased by 22.1% and the f/f0 is decreased by 85.9%. Although the reduced cross-section channel enhances the heat transfer, it produces a large additional resistance loss. In general, the expanded cross-section channel has better heat transfer performance and lower resistance loss. Among them, HR = 1:4 channel has excellent comprehensive thermal performance.