Numerical Investigation On Overall Cooling Effectiveness of Narrow-Channel Double-Wall Cooling

Abstract In the double-wall cooling of turbine blades, the migration of coolant can lead to uneven flow distribution. In severe cases, it can cause hot gas intrusion into the film holes, affecting the lifespan of the blade. In order to mitigate the negative influence of coolant migration, this study proposes a novel double-wall system called narrow-channel double-wall cooling system, where thin walls are arranged inside the internal channel of double-wall cooling to achieve a more balanced coolant distribution for film holes. However, the addition of thin walls alters the flow and heat transfer distributions within the double-wall structure, ultimately affecting the overall cooling effectiveness. Therefore, numerical methods were employed in this study to analyze the flow distribution characteristics, overall cooling effectiveness, and internal heat transfer characteristics of the narrow-channel double-wall cooling. The numerical results demonstrated that narrow-channel double-wall cooling, with or without pin fins, significantly improved the uneven mass flow distribution in the film holes while maintaining an overall cooling effectiveness comparable to that of the double-wall effusion cooling system. It is worth noting that although the overall cooling effectiveness difference is slight, there are significant differences in the internal heat transfer characteristics between the two double-wall cooling systems. Additionally, the study discussed the influence of narrow wall thickness on the overall cooling effectiveness and flow distributions, revealing that a thinner wall can lead to higher overall cooling effectiveness in narrow-channel double-wall cooling.