In order to adapt to the high-efficiency and low-resistance performances required by the new generation of gas turbine, a new type of two-pass rectangular channel with cross bridge and oval-shaped dimple structure is proposed for internal cooling of blade mid chord region. Firstly, the flow structure, heat transfer and friction characteristics of the novel channels under stationary and rotating conditions are numerically analyzed and compared in detail. Then the effects of cross bridge type/layout and dimple dimension/arrangement on the cooling performance are discussed. And the coupling mechanism of cross bridge, turning bend, oval-shaped dimple and rotation effect is revealed. The results show that the introduction of the cross bridge enables the coolant flow into the second pass in a distributed manner, which weakens the flow aggregation and extrusion in the tip turning bend region, thus the flow structure is optimized. Although the heat transfer is slightly weakened, the friction factor is reduced by 66.3% and 51.4%, and the overall thermal performance is improved by 16.7% and 11.6% (different cases) at most, for stationary and rotating conditions, respectively. The oval-shaped dimple achieves local heat transfer enhancement by controlling flow separation and reattachment. Furthermore, the optimized cross bridge type/layout and dimple dimension/arrangement are also obtained. This research will provide important reference data for the development of high-efficiency mid chord cooling technology for gas turbine blade.

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