PIV Applied to a Transonic Centrifugal Compressor

Abstract

In the present application PIV was chosen to analyze the complex flow phenomena inside a vaned diffuser of a new generation transonic centrifugal compressor, as this planar technique is capable of detecting unsteady flow structures and to resolve even high velocity gradients as well as unsteady shock configurations previously undetectable with point-wise techniques such as laser-2-focus velocimetry (L2F). Measurements were carried out at rotational speeds between 35,000 and 50,000 rpm. The compressor stage was designed for a pressure ratio of 6:1. Due to the advanced impeller geometry the diffuser section has a conical shape and a constant passage height of 8.1 mm. With a special light sheet periscope probe is was possible to adjust the light sheet to three vane span locations chosen for flow investigation: center plane (50%), one plane close to the hub (19%) and one close to the tip (74%).