Flow Analysis in a Transonic Centrifugal Compressor Rotor Using 3-Component Laser Velocimetry

Abstract

The paper describes the flow conditions found inside an optimized transonic, high pressure ratio centrifugal compressor rotor operated with a rotor tip speed of 586 m/s. The rotor was coupled with a vaned diffuser of rather small exit radius ratio. Measurements and calculations were carried out on this device. A newly developed 3-component hybrid Laser velocimeter was applied for the optical measurements inside the rotating system. For the first time the new measurement technique delivered three velocity components instead of only two for such a compact machine with very narrow flow channels. An available 3D calculation system with an embedded Navier-Stokes solver was used for the theoretical approach. The flow field development is described with the help of optical measurement results taken at measurement planes located at the rotor inlet and exit as well as at 40% and 60% flow path length. The measured 3D effects were highest in the middle of the flow channel, where the flow is turned from axial to radial. Here the curvature effects in the meridional plane and the enhancement of secondary flow are significant. The agreement between the theoretically and experimentally obtained third velocity component is quite good, especially in the area with strong secondary flows.