Heat Transfer Enhancement in Double-Wall Blade Suction Side Using Large Eddy Simulation

Double-wall cooling scheme represents a crucial and advanced strategy that can significantly enhance the performance of turbine blade cooling systems. Various techniques are used to achieve highly effective convective heat transfer in double-wall cooling, such as pin-fins, dimples and protrusions. This study explores various heat transfer enhancement devices within curved cooling passages of actual turbine blade, including cylinder-shaped and diamond-shaped pin-fins, dimples, and protrusions, utilizing large eddy simulation. The work was carried out under the actual blade-shaped geometries and operating conditions of turbine blades. Flow patterns were analyzed to elucidate the unsteady flow physics and heat transfer augmentation within suction side cooling passages featuring various turbulators. The results show that these devices disturb the coolant flow and introduce various turbulent motions, contributing to heat transfer augmentation. Differences in flow patterns result in varying degrees and extents of the heat transfer enhancement on the target wall. Pin-fin structures can notably achieve heat transfer performance and promote unsteady behavior of heat transfer, resulting from a sequence of turbulent motions. The vortex systems induced by dimples and protrusions are characterized by small spatial scales and rapid decay in the downstream flow, resulting in significant spatial limitations of heat transfer enhancement, especially for dimples. This work contributes the knowledge of the double-wall cooling involving pin-fins, dimples, or protrusions on suction side for internal cooling designs of turbine blades.