Minimizing Pressure Pulsations in a Centrifugal Compressor

As a centrifugal impeller rotates, it converts shaft mechanical power into fluid power - static and dynamic pressure. As a result of this aerodynamic process, the flow in the compressor has steady and unsteady components. The latter is undesirable as it can manifest itself as pressure pulsations that consequently cause machine vibration, noise and alternating stress in the impeller. Typically a centrifugal compressor has strong pressure pulsation amplitude at the blade passing frequency and /or its harmonics. The installation of diffuser vanes to enhance the compressor peak efficiency further increases the magnitude of these pressure pulsations. Dominant pulsations typically occur at the impeller exit and diffuser entrance region, and are a major excitation source to a centrifugal compressor and its associated piping. This internal aeroacoustic energy source propagates pressure waves through various paths in the compressor system and eventually couples to the structure and impeller and causes structural vibration and sound radiation. This paper focuses on a technique to control pressure pulsations in a centrifugal compressor. Two examples along with test data will be discussed.