DETAILED FLOW MEASUREMENTS IN A CENTRIFUGAL-COMPRESSOR VANELESS DIFFUSER

Hot-wire anemometer measurements have been made in the vaneless diffus er of a 1-m-dia low-speed backswept centrifugal compressor using a pha se lock loop technique. Radial tangential, and axial velocity measurem ents have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wa ke flow pattern and the blade wakes. The passage wake is located on th e shroud side of the diffuser and mixes out slowly as the flow moves t hrough the diffuser. The blade wakes, on the other hand, distort and m ix out rapidly in the diffuser. Contours of turbulent kinetic energy a re also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced.