Some unsteady flow phenomena downstream of an axial compressor stage.

A detailed investigation of some unsteady flow phenomena occurring downstream of the rotor row in a single-stage, axial flow compressor, having three blade rows is described. Measurements of both unsteady , and mean flow properties in the vicinity of the stator row are presented. Experimental mean velocity distributions are compared with values from potential flow calculations and excellent agreement is obtained in areas outside viscous flow regions. A quasi-steady model based on the interaction of wakes from the inlet guide vane and rotor rows is used to explain a circumferential variation observed in the unsteady flow; this variation originates downstream of the rotor and continues undisturbed through the stator row. Specifically, this variation occurs in the decay of the rotor wake velocity defect and there is an associated circumferential variation in the apparent turbulence level and mean velocity downstream of the rotor. General unsteady flow phenomena occurring in the vicinity of the stator blades are examined with particular reference to the leading and trailing edge regions. Other work in the field of unsteady flow in axial turbomachinery is discussed.