Experimental investigation of surge characteristics in a centrifugal compressor at different surge conditions

In this paper, the surge characteristics of a centrifugal compressor are investigated under various operating conditions through experimental analysis. The stable operational range of the centrifugal compressor at low flow rates is predominantly constrained by the presence of unstable phenomena such as stall and surge. The aerodynamic features spanning from the stall stage (preceding surge occurrence) to the surge stage (following surge occurrence) are comprehensively documented within the experimental framework. The power spectrum density (PSD) of mass flow rate and pressure is utilized to elucidate the fluid dynamics within the centrifugal compressor at deep surge condition (5° valve opening), moderate surge condition (12°), and mild surge condition (15°), respectively. Subsequently, a thorough comparison is conducted between the time-domain and frequency-domain distributions of pressure fluctuations during the transitional zone between the stall and surge stages. The evolution trend of mass flow rate and pressure are compared at deep, moderate, and mild surge conditions, and the transition zone between the stall stage and the surge stage, which could be detected in advance and contribute to prevent surge, is pointed out. The utilization of probability density function (PDF) distribution is implemented to deeply explore a detailed examination of pressure fluctuation disparities between the stall and surge stages, elucidating the impact of surge-induced fluctuations on flow stability within the centrifugal compressor. The characteristics of shaft vibration are deeply explored. The above comparison can provide a profound insight into understanding the physical mechanism of centrifugal compressor at surge conditions.