Conjugate heat transfer analysis of internally cooled superalloy turbine blades with grooved channels

Abstract

The present work reports a conjugate heat transfer analysis of a turbine blade exposed to high-temperature compressible gas flow and the convection cooling inside the blade. A nickel-based superalloy material CMSX-4 with better mechanical and anticorrosive properties has been introduced for blade materials, and grooved channels are proposed for heat transfer enhancement in internal convection. Each channel contains nine mini-grooves having groove-depth to channel-diameter ratio in the range of 0.08–1.12. Three prominent turbulence models, namely, k-ε, k-ω shear stress transport (SST), and γ-θ transition SST, are used to capture the flow turbulence in a transonic boundary layer flow. Simulations have been performed for actual operating conditions of turbine blades with a wall-to-gas temperature ratio of 0.84 and an inlet-to-outlet pressure ratio of 1.69. The inlet Reynolds number is 5.3 × 105 for the hot gas region, and for coolant flow, the Reynolds number varies from 16 000 to 70 000. The Mach number reaches to a maximum value of 1.14 in the external hot gas flow. Boundary layer transition and wake flow from nearby blades affect the flow in the suction side of the blade. The incorporation of scalable wall function improves the performance of the k-ε turbulence model. Compared to the smooth channel, a 25 K reduction in the average blade surface temperature and 27.3% enhancement in the Nusselt number in blade cooling are obtained for the grooved cooling channel.