Overall Cooling Characteristics of Double-Wall Effusion System Considering Material Selections and Hole Arrangements

Abstract

Enhancing thermal protection of hot components in gas turbines can be accomplished using advanced materials with various thermal conductivities and optimized cooling structures that exhibit high internal-external cooling efficiency. The double-wall effusion system (DWES) stands out as a promising solution for effectively cooling gas turbine hot components. However, its thermal response to new materials remains inadequately explored, and the combined effect of hole arrangement and thermal conductivity within the DWES system has not been thoroughly investigated. In this study, we thoroughly investigate the impacts of material selection and hole arrangement on the overall cooling characteristics of the impingement-pinfin-effusion based DWES. Three different materials with varying thermal conductivities were selected to control Biot number, and various hole arrangements, including effusion-only or impingement-effusion, as well as forward or backward film injection, were compared to quantify the contributions of internal and film cooling on the overall cooling performance. The results showed that the stainless-steel scheme achieves the highest overall cooling effectiveness due to its superior thermal conductivity, while the polycarbonate scheme obtains the lowest overall cooling effectiveness. Compared to their corresponding effusion-only schemes, the area-averaged overall cooling effectiveness of the stainless-steel impingement-effusion scheme demonstrates a remarkable increase of up to 29%. Notably, employing backward film injection yields remarkable improvements in overall cooling effectiveness, with the stainless-steel impingement-effusion scheme exhibiting an increment of up to 16% compared to the forward film injection configuration. Furthermore, we developed correlations that establish the relationship between the overall cooling effectiveness, Biot number, and blowing ratio for various configurations. These correlations can serve as valuable design tools for the development of next-generation gas turbines that incorporate the DWES technology.

Keywords: Gas turbine cooling, double-wall effusion system, conjugate heat transfer, material thermal conductivity, backward film injection