Measurements of Quasi-Steady and Unsteady Flow Effects in a Supersonic Compressor Stage

In the present paper results of measurements are discussed that give a survey of the flow through rotor and stator of a supersonic compressor stage. In order to analyze the flow, piezoelectric and semiconductor transducers are used for measuring the unsteady pressure distributions along the casing on the one hand and schlieren photography procedure and stroboscopic technique for flow visualization on the other. The pressure transducers are mounted at the casing and shifted along the test region by different series of measurements. The effects of the unsteady flow to the stator produced by the rotor, on the behavior of the flow in the stator channels were analyzed. The oscillation of the pressure at the entrance region of the stator is reduced in axial direction by the cascades, so that the amplitudes diminish at the exit region of the stator. Nevertheless the frequency, induced by the rotor, can be well recognized in the unsteady pressure distribution downstream of the stator. These measurements were completed by the visualization of the flow through the stator. The optical system is working by a modified coincidence method. The starting procedure of the stage up to design speed was observed using shadow and schlieren method at continuous and stroboscopic illumination. The development of the shock waves, the shock-boundary-layer-interaction, and the influence of the rotor-wakes to the stator-flow are discussed.