Numerical analysis and optimization on flow and heat transfer performance of a steam-cooled ribbed channel

Abstract

It aims to enhance the heat transfer performance and reduce the pressure loss of the steam-cooled ribbed channels in the gas turbine blades. Numerical calculations were performed to analyze the flow and heat transfer characteristics in the steam-cooled ribbed channel for different inlet Reynolds number (10,000 ≦ Re ≦ 90,000), rib angle (30° ≦ α ≦ 90°), rib height ratio (0.05 ≦ e/D ≦ 0.15) and rib pitch ratio (0.5 ≦ P/D ≦ 1.5). The flow and heat transfer analysis, response surface analysis, significance analysis and parameter optimization were performed by using the Response Surface Methodology. The results show that the variations of Re, α, e/D and P/D change the size, shape and swirling strength of the secondary flows in different extent, leading to the change of flow and heat transfer characteristics in the steam-cooled ribbed channel. Increasing Re and e/D, and decreasing P/D at the low-medium level of e/D obviously enhance the Nu/Nu0; Decreasing Re and e/D, and increasing P/D result in a reduction in the f/f0. An increment in α first increases and then decreases both the Nu/Nu0 and f/f0. Among the four influence parameters Re, α, e/D and P/D, Re is the most significant parameter affecting the Nu/Nu0, followed by e/D, α and P/D; e/D has the most significant influence on the f/f0, followed by α, Re and P/D. The multi-objective optimization for lower pressure drop and higher heat transfer is achieved at Re of 90,000, α of 41.5152, e/D of 0.1157 and P/D of 0.9747. Compared with the reference channel, the optimized channel has a 86.19% enhancement in heat transfer coefficient and a 38.32% improvement in comprehensive thermal coefficient, at the same Reynolds number (Re = 90,000).