An Enhanced Greitzer Compressor Model Including Pipeline Dynamics and Surge

The single-stage centrifugal compressor in the experimental setup operates with an unshrouded impeller and a vaneless diffuser. The rotor is radially supported by two radial AMBs, and a single thrust AMB provides the axial support.

Compressor characteristic curve for the experimental setup measured at various operating speeds

Schematic drawing of a compression system described by the Greitzer model

Characteristic curve of the compressor fitted to experimental data

Measured characteristic curves at δcl of 0 mils, +6 mils (0.1524 mm) and −6 mils (−0.1524 mm). The predicted curves from Eq. 7 are also plotted at the nominal clearance (solid line), and δcl of +6 mils (0.1524 mm) (dash-dotted line) and −6 mils (−0.1524 mm) (dashed line), respectively.

Experimental Bodes plot from disturbances in the impeller tip clearance (m) to the plenum pressure rise Ψp at 35%, 32%, and 30% throttle valve openings

Comparison between simulated frequency response of the Greitzer model versus experimental Bode plots from tip clearance (m) to plenum pressure rise Ψp. Throttle valve at 32% open.

Block diagram of the pipeline model, modified from Refs. 16,20. The inputs are the pressure and volume flow rate at the pipe boundaries and the outputs are the upstream and downstream characteristics Cu(s) and Cd(s).

Block diagram of the compression system model with pipeline dynamics at the compressor exhaust

Block diagram of the compression system model with the pipeline dynamics at the plenum output

Comparison between simulated the Bode plots from tip clearance (m) to plenum pressure rise Ψp for the compression system with piping acoustics at plenum output versus experimental measurement. Throttle valve at 32% open.

Comparison between simulated the Bode plots from tip clearance (m) to plenum pressure rise Ψp for the compression system with piping acoustics at plenum output versus experimental measurement. Throttle valve at 34% open.

Bode plots from simulation of the compression system with pipeline dynamics at the plenum output, from the impeller tip clearance disturbance (m) to the plenum pressure rise Ψp at 32%, 34%, and 36% throttle valve openings

Comparison between the measured and the simulated plenum pressure rise Ψp during compressor surge

Comparison between the frequency components of the measured and the simulated plenum pressure rise Ψp during compressor surge

Photograph of the experimental setup, including the direction of the inlet and the outlet air flow

Layout of the experimental setup, including the compressor, instrumentations, and the movable throttle valve. Possible throttle valve locations are at 2.2 m, 7.1 m, and 15.2 m along the exhaust piping measured from the compressor.

Block diagram of the Greitzer compression system model. The compression system consists of the compressor, the plenum volume, and the throttle valve.

Comparison between simulated the Bode plots from tip clearance (m) to plenum pressure rise Ψp for the model with piping acoustics at compressor exhaust versus the experimental measurement. Throttle valve at 32% open.

Comparison between simulated the Bode plots from the tip clearance (m) to plenum pressure rise Ψp for the compression system with the modal approximation of the piping acoustics at plenum output versus experimental measurement. Throttle valve at 32% open.