Algorithm for Controlling a Centrifugal Compressor An algorithm has been developed for controlling a centrifugal compressor that serves as the prime mover in a heatpump system. Experimental studies have shown that the operating conditions for maximum compressor efficiency are close to the boundary beyond which surge occurs. Compressor surge is a destructive condition in which there are instantaneous reversals of flow associated with a high outlet-to-inlet pressure differential. For a given cooling load, the algorithm sets the compressor speed at the lowest possible value while adjusting the inlet guide vane angle and diffuser vane angle to maximize efficiency, subject to an overriding requirement to prevent surge. The onset of surge is detected via the onset of oscillations of the electric current supplied to the compressor motor, associated with surge-induced oscillations of the torque exerted by and on the compressor rotor. The algorithm can be implemented in any of several computer languages.

This program was written by Scott M. Benedict of Mainstream Engineering Corp. for Johnson Space Center. For further information,contact:

Mainstream Engineering Corp.
200 Yellow Place
Rockledge, FL 32955
Telephone No.: (321) 631-3550 .

Refer to MSC-23016.

NASA Tech Briefs Magazine

This article first appeared in the April, 2004 issue of NASA Tech Briefs Magazine.

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