Experimental investigation of effects of distributed riblets on aerodynamic performance of a low-speed compressor

It is well known that riblet applied on compressor blades is a promising flow control technique. However, detailed investigation of its effects on the flow field of turbomachinery is rare in existing literatures. This paper presents a detailed experimental investigation of effects of distributed riblet on the flow field of an axial compressor isolated-rotor stage. The research was performed in a large-scale facility respectively with two configurations, including grooved hub, and grooved surface on both hub and partial suction surface. The riblet film is rectangle grooved type with a height of 0.1 mm. The flow field at 10% chord downstream from the cascade trailing edge was measured using a mini five-hole pressure probe and a total pressure probe. The testing was conducted at several operational points under two reduced rotational speeds. Stagnation pressure loss in rotational frame was calculated and compared with the control test in which a smooth film was applied to the corresponding position. Results show that with the grooved hub configuration at the design operation point of the lower rotational speed, the riblet film provides an obvious improvement of a 48% reduction of total pressure loss in rotational frame. Also, a distinct weaken hub corner vortex was identified. In the meantime, there exists a deviation of flow angle about 5 degrees at 20%-80% span which previously was not considered to be the affected region.