Experimental investigation of the influence of inlet guide vane prewhirl on the unsteady flowfield in the vaned diffuser

Experimental investigation of unsteady flow in the vaned diffuser of a centrifugal compressor stage was performed under different inlet guide vane (IGV) prewhirl angles and directions in this paper. Detailed instantaneous flow was measured at several different measuring positions using a hot-wire anemometer with the phase-locked ensemble-averaged technique, the influence of the IGV prewhirl angle and direction on the unsteady flowfield in the vaned diffuser was studied. In the existence of IGV prewhirl angle, the results show that the turbulence intensity increases at most of the position in the vaned diffuser; the unsteadiness in the vaned diffuser reduces due to the influence of the IGV wake and large size vortice, and the amplitude of the reduction under the negative IGV prewhirl is smaller than that under positive IGV prewhirl angle; the base frequency of the flow in the vaned diffuser decreases under the IGV prewhirl.