Investigation of Acoustic Phenomena at the Inlet and the Outlet of a Centrifugal Compressor for Pressure Ratio 4.5

Abstract

The effects of the interaction between impeller and diffuser and the influence of distortions in the inlet flow on noise generation in a high speed centrifugal compressor were investigated. Therefore, an existing test rig was modified to allow acoustic measurements in the upstream and downstream ducts of the compressor. Anechoic ends designed according to the standards for low speed fans were inserted at both sides of the compressor in order to prevent disturbing reflections. Three slit tube microphone probes were installed in each duct to determine the noise level at the compressor inlet and the compressor outlet. In addition, a measurement plane for microphone traverses was set to allow the evaluation of the sound field. The tests provided fundamental insight into the main noise sources and the structure of the sound field at the inlet and the outlet of a high speed compressor stage.