A flow field investigation in the diffuser of a high-speed centrifugal compressor using digital particle imaging velocimetry

Digital particle imaging velocimetry (DPIV) has become a widely used optical diagnostic technique for the study of both transient and steady state hows. The DPIV technique provides instantaneous planar maps of the flow velocity. The challenges remaining are in implementing the PIV technique in real world test facilities, where the instantaneous, planar velocity measurements provide researchers with information in less time than traditional point-based measurement techniques. The instantaneous planar velocity measurements obtained using PIV make it an attractive technique for use in the study of the complex flow fields encountered in turbomachinery. This paper discusses techniques for optical access, light sheet delivery, CCD camera technology and particulate seeding requirements for the successful application of PIV to turbomachinery. Time-averaged results obtained in the diffuser region of a high-speed centrifugal compressor are presented and discussed. In addition, combined correlation/particle-tracking results yielding super-resolution velocity measurements are presented.