Rotor-wake influence on axial-compressor-stator boundary layers

Abstract

The boundary-layer development on blades in an axial-flow compressor is an important design consideration. The influence of upstream-blade wake segments on downstream-blade boundary layers is not yet satisfactorily modeled for design purposes. To clarify the effects of wake segments on boundary layers, we used surface hot-film gages to sense the influence of rotor-wake segments on stator-surfac e boundary layers at midspan in a low-speed, axial-flow compressor stage. It was clear that rotor-wake segments moved along the stator-blade pressure and suction surfaces much like a turbulent spot would; the region of influence of each wake segment became larger further downstream. Boundary-layer transition was not expected on the low-speed, stator-blade surface until about midchord. Nevertheless, the laminar boundary-layer flow on the forward portion of the stator blade appeared to be turbulent when a rotor-wake segment was present. This periodic alternating of the stator boundary-layer flow was observed further aft on the blade also.