Influence of endwall contouring domain on the aerodynamic performance in simulated ceramic matrix composite turbine cascades

Due to the inherent manufacturing constraints of ceramic matrix composites, CMC turbine blades usually require larger curvature radii, which lead to thicker trailing edges and limited spanwise shaping capability. These geometric features tend to increase the front loading of the blade, alter the aerodynamic matching between blade rows, and influence the flow development in the endwall region. As a result, additional aerodynamic losses are introduced, and the control of these losses has become an important issue in the engineering application of CMC blades. In the present study, a high pressure turbine cascade is first modified under the geometric constraints of CMC materials, and one of the modified cascades is then selected for non-axisymmetric endwall contouring. The results show that the control effect of endwall contouring is closely related to the streamwise extent of the contoured region. The main novelty of this work lies in treating the contouring extent as an independent aerodynamic design parameter, rather than as a predefined geometric domain in conventional endwall optimization. The present study demonstrates that this extent directly affects the redistribution of the upstream cross passage pressure field and further influences the development of the passage vortex system. Different contouring extents lead to different vortex structures and flow characteristics. A systematic investigation of the contouring extent is carried out, and a more favorable extent is identified. Under this configuration, the secondary flow structure is clearly modified, and the aerodynamic loss is noticeably reduced compared with the non contoured configuration. These results indicate that, for CMC constrained turbine cascades, the streamwise extent of the endwall contouring region can be regarded as a physically meaningful parameter for secondary flow control.