Experimental investigation of rough blade tip-surface effects under varying attack angles and clearances in compressor linear cascades

Tip leakage flow, as one of the major sources of loss in axial compressors, plays a crucial role in determining compressor efficiency and stability. During long-term operation, blade surface degradation caused by fouling, erosion, and wear alters the internal flow characteristics of the compressor, leading to a more complex secondary flow loss mechanism. In this study, linear cascade experiments are conducted to investigate the performance deterioration caused by tip-surface fouling under varying attack angles and tip clearances. Aerodynamic measurements are obtained using a five-hole probe, while oil-flow visualization is employed to reveal flow structures. The research results indicate that surface roughness at the blade tip increases momentum loss in the near-tip region, reducing axial momentum within the vortex core. This roughness-induced increase in near-tip momentum loss aggravates tip-region blockage, elevates the total pressure loss coefficient, and ultimately deteriorates the compressor's aerodynamic performance. As the tip clearance decreases and the attack angle increases, the performance degradation becomes more pronounced, with the maximum aerodynamic loss increment reaching 6.9% at a 1 mm clearance and an attack angle of +8°. Furthermore, the influence of tip-surface roughness is mainly confined to the near-tip region—within approximately 15% of the blade span—indicating that its primary effect manifests through modification of the leakage flow pattern rather than a global change in the secondary flow structure.