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

Abstract

In the double-wall cooling of turbine blades, coolant migration can lead to uneven flow distribution, which, in severe cases, can cause hot gas intrusion into the film holes, affecting the lifespan of the blade. To mitigate the negative influence of coolant migration, this study proposes a novel double-wall system called the narrow-channel double-wall cooling (NCDW) 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 are 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 demonstrate that narrow-channel double-wall cooling, with or without pin fins, significantly improves the uneven mass flow distribution in the film holes while maintaining an overall cooling effectiveness that is comparable to that of the double-wall effusion cooling (DWEC) 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 discusses 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.