Influence of anisotropic thermal conductivity on leading edge cooling performance of a film cooled CMC turbine vane

Application of Ceramic matrix composites (CMCs) in high-pressure turbine vane designs have gained increasing attention due to their superior thermal-mechanical performance. The present study investigates the impact of thermal conductivity anisotropy on the cooling performance of a film cooled CMC turbine vane at the leading edge. Based on a typical streamwise lay-up fabrication structure, four anisotropic thermal conductivity configurations of CMCs are implemented to represent individual variations along the thickness-wise, streamwise and spanwise directions. Influences on the overall cooling effectiveness and on the separate cooling schemes of hole channel cooling, external film cooling and internal plenum cooling are analysed. The relative contribution by each cooling scheme under different thermal conductivity configurations is discussed, and the effect of blowing ratio is also examined. Results show the dominant contributor of the overall cooling effectiveness transitions from the hole cooling at upstream regions to the film cooling at downstream. For the anisotropic behaviour, the hole cooling is sensitive to the thickness-wise and streamwise thermal conductivities, the film cooling is responsive to the thickness-wise and spanwise conductivities, and the plenum cooling is only marginally affected by the thickness-wise conductivity. Both the magnitude and the uniformity of the overall cooling effectiveness exhibit the highest dependence on the thickness-wise thermal conductivity. While the relative significance of each cooling scheme remains unchanged under different blowing ratios, the effect of the CMC anisotropy on the cooling performance is enhanced at a higher blowing ratio.