Integrated Design of Self-Circulating Casing Treatment and Axisymmetric Casing Contouring for Axial Flow Compressors

The stability of compressors is paramount for the safe operation of entire aero-engine systems. Enhancing the stability of compressor represents a focal point in aero-engine design. Self-circulating casing treatments have been found effective in expanding the stable operational range of compressors. However, while it enhances the stability margin of the compressor, if there is no significant loss due to severe blockages at the rotor blade tips under design conditions, this structure still tends to cause efficiency reduction, a phenomenon that is particularly common. This study focuses on the high-load axial flow compressor NASA Rotor37. Initially, a self-circulating casing treatment structure was designed to enhance the stability margins improvement by 9.62% with a 1.87% efficiency loss. Using this structure as a baseline, twelve distinct axisymmetric casing contouring schemes were developed to holistically enhance compressor performance, aiming for a dual improvement in stability margins and efficiency. Results demonstrate that all contouring schemes reduce the peak efficiency loss of compressors. While most of the casing contouring schemes with concave-convex characteristics slightly reduce the stability enhancement capability of the self-circulating casing treatment, compared to a single convex or concave-convex contouring, they exhibit a stronger ability to improve the peak efficiency of the compressor. The optimal scheme, relative to the singular self-circulating casing treatment, only reduces the comprehensive stability margin enhancement by 0.49% while increasing efficiency by 0.52%. Moreover, to elucidate the influence of different design schemes on the internal flow within the compressor, research conducted using blockage quantification analysis and loss quantification analysis methods indicates that the single self-circulating casing treatment scheme and the design optimal scheme exhibit the best improvements in reducing blockages in the compressor rotor passages. Compared to all design schemes, the optimal design scheme results in the lowest flow losses, while the single self-circulating casing treatment scheme leads to the highest flow losses in the compressor. The combination of self-circulating casing treatment with axisymmetric casing contouring, compared to the standalone self-circulating casing treatment, can significantly boost compressor efficiency while essentially maintaining stability margin improvements.