INVESTIGATION OF THE HEAT TRANSFER PERFORMANCE IN A DOUBLE-WALL COOLING CONFIGURATION UNDER THE EFFECT OF WALL CURVATURE AT ROTATING CONDITIONS

This paper presents an experimental investigation of a double-wall model derived from simplified real turbine blades. The study examines the influence of three distinct wall curvatures and rotation on the internal flow patterns and heat transfer characteristics within the double-wall cooling configuration. It elucidates the mechanisms by which wall curvature and rotation effects impact the performance of the double-wall cooling unit. Conducting flow characteristic experiments on three different wall curvature specimens (flat, convex curvature, concave curvature), experiments were carried out under stationary conditions and at different rotational speeds (30rpm, 60rpm, and 120rpm) for each respective condition. The Particle Image Velocimetry (PIV) experimental results reveal that the flow within the cavity of the double-layer wall cooling configuration is characterized by a complex, three-dimensional, multi-vortex flow, primarily dominated by impingement/effusion dynamics. Wall curvature modifies internal flow characteristics by altering the geometry of the impacted surface and the relative shock distance. Notably, this curvature has a substantial impact on mainstream flow rates and key vortex structures. Additionally, rotation induces centrifugal and Coriolis forces, which enhance the heat transfer capabilities of the double-wall cooling mechanism. The flow can reflect heat transfer, and the analysis of the results from the flow characteristic experiments reveals that, compared to the square double-wall structure, the double-wall structure with convex curvature overall exhibits better heat transfer efficiency, while the one with concave curvature shows poorer heat transfer performance. This is primarily due to the influence of wall curvature on the flow in the main flow region inside the cavity, as well as on vortex structures that play a crucial role in heat exchange. At lower rotational speeds, rotation enhances the heat transfer efficiency of the double-wall cooling structure.