DETECTION OF FLOW INDUCED AERODYNAMIC PERFORMANCE CHARACTERISTICS OF CENTRIFUGAL COMPRESSORS USING ACOUSTIC MEASUREMENTS

Inline centrifugal compressors are prevalent in the oil & gas industry. The process conditions for these compressors necessitate operation over a range of inlet flows, suction & discharge pressures and speeds. In many instances, operation is at high pressures in excess of 200 bar. The aerodynamic performance characteristics vary as a function of the inlet flow. The head versus flow map depicts the operating range of the compressor, with typical operation near a flow condition located in the mid portion of the map (i.e., the design operating point or the best-efficiency point). Upstream or downstream demand can necessitate changes to the flow conditions during operation. As flow is throttled, the compressor approaches the surge line. The onset of reversal of flow near surge can trigger flow induced characteristics in the downstream piping, which can result in elevated non-synchronous vibrations on the shaft displacement probes. On the high flow side, choking of the flow triggers flow induced characteristics that often result in super-synchronous vibrations on the shaft probes. In this paper, the use of acoustic microphones as a tool to aid in detecting flow induced characteristics at various locations on a head-flow map in a high pressure environment are presented. The influence of vaned diffusers on the flow induced characteristics is also presented. Case studies are presented in this paper that illustrate the use of acoustic devices in detecting flow induced vibration characteristics for centrifugal compressors, both in low pressure and high pressure conditions.