A New Approach for Compressor Endwall Contouring

Against the background of the high development status of modern axial compressors, a further performance enhancement is linked with the extension of the design space in the development process and the concentration on the essential loss mechanisms in the compressor. The performance of a compressor cascade is considerably influenced by secondary flow effects in the near endwall region, since up to 50 percent (for low aspect ratio) of the losses in the bladed channel of a turbomachinery are linked to the endwalls. In this context the application of non-axisymmetric profiled endwalls provides a potential for compressor improvement. The paper presents the detailed experimental and numerical investigation of controlling the endwall cross flow in a compressor cascade. The general approach is based on a boundary layer fence arrangement, whose application on the compressor endwall works as a non-axisymmetric endwall contour. This non-axisymmetric endwall modification constrains the interaction of the endwall cross flow with the suction side boundary layer, thus the onset of the corner separation is delayed and a significant loss reduction of 8 percent is achieved. The experiments were carried out in a linear compressor cascade at the high-speed cascade wind tunnel of the DLR in Berlin at peak efficiency (design point) and off-design of the cascade at Mach number M = 0.67. Furthermore, high fidelity 3D-RANS flow simulations were performed in order to analyze the complex blade and endwall boundary layer interaction. The combined consideration of experimental and numerical flow pattern allows a detailed interpretation and description of the resulting flow phenomena.