Characteristics of unsteady flow in frequency domain in a centrifugal compressor

Performances prediction using steady RANS solver and validation are performed on a 56 mm turbocharger compressor under three working speed-line in this paper. Unsteady flow simulation in near-surge condition at a high rotation speed is then carried out and frequency-amplitude characteristics in an impeller, vaneless diffuser and volute are studied. Results show that unsteady effect lies mainly in an impeller and is the main reason for inducing aero-acoustics in a centrifugal compressor, while in the volute, unsteady effects decrease significantly and has less contribution to acoustics level.