The Application of PIV in the Study of Impeller-Diffuser Interaction in Centrifugal Fan: Part II — Impeller-Vaned Diffuser Interaction

Abstract The real flow inside a turbomachinery passage is unsteady and strongly affected by wakes between stator and rotor. The aim of this study was to help our understanding of the complex unsteady flow associated with the interaction between the impeller and its vaned diffuser of a centrifugal plexiglass fan where the number of impeller and diffuser blades are 13 for each. The purpose of this paper is to present the first trial of measuring the instantaneous whole field in a part of the impeller and diffuser together at different relative locations between them. The velocity measurements utilizing a PIV system from Dantec Measurement Technology were performed. The measurements were performed at medium, maximum and minimum flow rate, near the hub, the middle and near the shroud. The Laser sheet is adjusted to go through the outer casing, the diffuser and to reach the impeller blades. The instantaneous whole field velocity measurements were taken at the exit half of the impeller and the inlet half of the diffuser including the vaneless space before the diffuser blades. The absolute radial and circumferential velocities are measured. The unsteady interaction between the impeller and vaned diffuser was measured at different relative positions between the impeller and diffuser. Further analyses concerning the relative velocity, streamlines and vorticity are also presented.