This paper presents the analysis of the instabilities inception in a transoniccentrifugal compressor for different rotation speeds. The analysis was conducted fromexperimental results obtained with unsteady pressure sensors implanted in the inducer,vaneless diffuser and vaned diffuser. Beyond the stability limit the compressor entersinto a deep surge without any precursor, whatever the speed. The surge process isinitiated in the vaned diffuser by a massive boundary layer separation. For low speeds,together with the surge which remains triggered in the diffuser, aerodynamic instabilitiesare detected in the inducer. These instabilities can be understood as “tip clearancerotating disturbances” because they are generated at the leading edge of the impeller mainblades and move along the tip clearance trajectory.
