Comparison of measurement data at the impeller exit of a centrifugal compressor measured with both pneumatic and fast-response probes

The main goal of these investigations was the refined measurement of unstea dy high-speed flow in a centrifugal compressor using the advanced FRAP(R) f ast-response aerodynamic probe system. The present contribution focuses on the impeller exit region and shows critical comparisons between fast-respon se (time-resolving) and conventional pneumatic probe measurement results. T hree probes of identical external geometry (one fast and two pneumatic) wer e used to perform wall-to-wall traverses close to the impeller exit. The da ta shown refer to a single running condition near the best point of the sta ge. The mass flow obtained from different probe measurements and from the s tandard orifice measurement were compared. Stage work obtained from tempera ture rise measured with a FRAP(R) probe and from impeller outlet velocity v ectors fields by using Euler's turbine equation are presented. The comparis on in terms of velocity magnitude and angle distribution is quite satisfact ory, indicating the superior DC measurement capabilities of the fast-respon se probe system.