Effects of the Ceramic Matrix Composites with Anisotropic Thermal Conductivities on the Endwall Film Cooling with Laid-Back Shaped Hole

Abstract

For pursuing higher performance, extremely high inlet temperature is given for prior gas turbine design. This results in a relatively high level of thermal load to the hot component beyond the thermal limit of the nickel-base super-alloy. The ceramic matrix composite (CMC) with low density and high thermal resistance, is always regarded as the potential thermal structure material for the state of art gas turbine and aero-engine. Nowadays, many studies concerning the endwall adiabatic film cooling have been performed within past several decades. However, the conjugate heat transfer analysis of anisotropic thermal conduction in the air-cooling CMC endwall is still not established. The finite element model (FEM) coupled with Three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations with Realizable K-epsilon turbulence model have been solved to conduct the simulation the endwall overall film cooling performance with the anisotropic thermal conductivities. In the present research, a single film hole coolant jet was investigated. The cases with the angle γ, between the principle direction of thermal conductivity and the coolant stream-wise changing within 0°, 30°, 45°, 60°, 90°, were simulated with ratio of principle direction of thermal conductivity to other thermal conductivities R. The numerical results shows that CMC with anisotropic thermal conductivities has a greater influence on the endwall overall cooling performance relative to the conventional super-alloy. The lateral overall cooling is substantially enhanced by increasing the the angle between the principle direction of thermal conductivity and the coolant stream-wise. This can be accounted for the lateral thermal conduction inside the CMC endwall is promoted with the augmentation of the laterally inclined angle γ from 0° to 90°. As a result, the endwall achieves the most uniform overall cooling effectiveness with the γ=90°. Moreover, the thermal conductivities ratio R has great influence on the heat flux distribution inside the CMC endwall,changing the overall cooling effectiveness distribution. Smaller thermal conductivities ratio R helps to obtain larger lateral overall cooling effectiveness and more uniform distribution profile. In addition, upstream area of the film injection hole is more sensitive to the variation of the laterally inclined angle γ and thermal conductivities ratio R. This is because the thermal conduction inside the solid domain dominating the upstream endwall heat transfer. However, the flow structure has marginal effects 2 on the upstream endwall. These results provide further understanding of the CMC endwall cooling performance and aid towards improved design of the efficient CMC endwall cooling system.