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Automated Multi-Reference Control for Centrifugal Compressor

This paper describes the approach, technical considerations and milestones in reaching the goal of safely delivering up to 6 barg at the exhaust of the compressor by means of automated multi-reference (speed control/valve control) control. The term "multi-reference control" is based on the method involving two internal reference parameters, motor speed and valve opening, to control air pressure. A hybrid speed/valve control system was successfully designed and tested with a 315 kW two-stage centrifugal air compressor, used to feed high pressure air into an experimental aircraft combustion chamber. Compressor performance map is defined based on working lines. The difference between them resides in having different air flows at the same given pressure. The innovation in this paper is that there is no need for a flow instrumentation line or a flow-based control loop besides the existing pressure loop.