陶瓷基复合材料端壁气膜冷却特性实验数值研究

In order to solve the problem of temperature distribution caused by anisotropic thermal conductivities of ceramic matrix composites（CMC），the thermal conductivity of CMC endwall is set along X，Y and Z directions using the equivalent macroscopic thermal conductivity method based on the conjugate heat transfer simulation in this paper. The influence of thermal conductivity ratio（R）which refers to the ratio of main thermal conduction and the secondary thermal conduction and the angle（γ）between two thermal conduction directions on the endwall overall cooling efficiency distribution was studied. The cooling stripe twists towards the main heat transfer direction when the thermal conductivity of the endwall presents anisotropy characteristics. And this distortion became more obvious with the increasing of R. The maximum laterally averaged cooling effectiveness when γ= 0° is 15%~16% lower than that of γ=90°，while the maximum downstream centerline overall cooling effectiveness is 11.1%~26.2% higher. The cooling stripe appears to be more sensitive to the main heat transfer direction and the thermal conductivity ratio at the upstream region without film coverage. Experiments were implemented with multi rows staggered cylindrical film hole endwall structure to compare the overall cooling effectiveness of superalloy and CMC. When the blowing ratio M varies within 3 to 5，the overall cooling effectiveness of CMC endwall is 4.32%~5.10% lower than the superalloy endwall. This gap is mainly caused by thermal conductivity difference along thickness direction. The experimental results agree well with the theoretical analogy principles，therefore which verifies the accuracy of the analogy principles.