Abstract
In this paper, the overall cooling effectiveness of double wall cooling structures with pins is experimentally investigated on the low-speed wind tunnel. The analysis of the single cooling technology contributions to improve the double wall cooling performance is provided. The effect of Biot number (Bi = 0.03, 0.32, 2.25) and the film hole size (de= 2 mm, 3 mm, 5 mm) on the overall cooling effectiveness are also studied. In order to further improve the overall cooling performance, the present study proposes two new shapes of film hole patterns with compound angles (compound configuration, double configuration). By numerically analyzing the cooling effectiveness of the outer film cooling and the heat transfer performance of the inner target wall, the mechanism by which film hole size and new film hole patterns affect the overall cooling performance of double wall structures is clarified. The results show that the area-averaged overall cooling effectiveness of the double cooling technology is more than 30% higher than that of the two single cooling technologies and the contribution of impingement cooling is higher than that of effusion cooling at high blowing ratios. The cooling performance of the double wall structure is greatly influenced by the Biot number of effusion plates. Low Biot number means higher thermal conductivity, resulting in higher overall cooling effectiveness under the same thermal load conditions. Increasing the film hole size could enhance the film cooling performance outside of the effusion plate, suppressing the unfavorable results of lower heat transfer performance at the inner side. The fitting correlation equation obtained using the binary linear regression method agrees well with the experimental results, with a maximum deviation of less than 4%. Both of the two compound structures can effectively improve the overall cooling performance of the double wall structure. The double configuration has the best cooling performance and the area-averaged cooling effectiveness improves by 15.1% compared to the reference configuration under the condition of M = 1.5. The experimental results provide a vital database for the future double wall cooling design.
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