The operating range of a pump or compressor is limited due to the occurrence of instabilities such as rotating stall and surge. A model compressor, operating with water instead of air, is used for the investigation of such instabilities.
The inlet pipe as well as the impeller casing are made out of plexiglas to allow observation and recording of the development of instability vortical structures. The rotational speed of the compressor is held low in order to achieve a better visualization of the flow as well as to ensure the similarity in Reynolds numbers between water and air flow. Transient pressure sensors further help measure the frequency and cell count of the rotating flow separations.
