Design and implementation of a surge controller for an AMB supported compressor in the presence of piping acoustics

Active control of compressor surge using the thrust Active Magnetic Bearing (AMB) for unshrouded centrifugal compressors is revisited here. Based on a recently presented enhanced compression system model with variable impeller tip clearance and pipeline acoustics, a surge controller is designed. This controller calculates the command clearance between the impeller and the static shroud to create the necessary pressure modulation in the system to suppress the surge instability. The commanded impeller clearance is later fed to the thrust AMB to actuate the axial position of the compressor rotor. The proposed surge control method is derived and implemented on an experimental compressor setup, and test results for the surge controller are presented in this paper. Observations from the experimental surge testing demonstrate that the presented method is able to stabilize the compression system when operating in the unstable surge region, extending the stable flow range by over 21%. Also the derived controller shows good robustness to the internal AMB dynamics.