Experimental investigation of unsteady fan flow interaction with downstream struts

Abstract

Pressure signals were taken on a rotor blade surface of a single-stage, low-speed axial flow compressor. The data showed unsteady, stationary pressure perturbations that correlated with the locations of five large downstream support struts. In the present work, these data are thoroughly analysed. Strut-induced pressure amplitudes as measured on the rotor are presented as a function of the downstream strut locations. Unsteady lift and moment are calculated by integrating the pressures measured by the blade-mounted transducers. In addition, a sequence of instantaneous pressure distributions on the blade surfaces presented over time shows how the rotor is influenced by the potential effect of the struts. The strut is shown to produce a significant effect on rotor flow. This effect exceeds the unsteady stator effect at design rotor-stator-strut spacing, but falls off rapidly as the struts are moved downstream.