Experimental Investigations of Centrifugal Compressor Surge Noise

Surge is a crucial problem for achieving a good working range of centrifugal compressor and power cycle safety. Effective and early detection of the surge is essential to avoid its onset. In this paper, experiments measuring the pressure and acoustic signals have been conducted to investigate the surge. The compressor prototype used in this study consists of an impeller wheel with backward blades, a vaneless diffuser, and a downstream discharge volute. The compressor prototype was instrumented with steady pressure and temperature sensors to characterize the performance map, a fast dynamic pressure sensor to measure the surge-induced pressure fluctuation, and 13 microphones to record the acoustic pressure on the inlet duct wall and in the far field. The transient experimental data were analyzed in time and frequency domains. The noise related to surge is identified as a chord sound from multiple sources that radiate acoustic impulse synchronously at the compression system surge frequency (below 10 Hz in the current experiment). A previously rarely discussed surge inception is identified from the acoustic spectrogram within the frequency range of 30–85 Hz, but not reflected by the pressure signal, in which an increase of the sound pressure level (SPL) is detected before the mass flow rate achieves the surge point. The mechanism is that the pressure fluctuation corresponding to the inception is too weak, within the detecting range of microphones that measures acoustic signals, and lower than the bottom limit of the commonly used dynamic pressure sensors. It suggests that acoustic measurement may have advantages in surge inception detection and prediction.