Advanced Determination and Control of Steady and Dynamic Excitations for Turbopumps Using Magnetic Bearings

The design, fabrication, and testing of a pump rig supported by a magnetic bearing system is described. This rig will boost pump technology by: (1) permitting accurate determination of impeller force and moment coefficients by electromagnetic impulse excitation, orbit control, and bearing force and displacement measurement during operation, and (2) use of control theory to suppress cavitation-surge and rotating stall, the primary constraints on pump flow range. A pump with such technology would be self-diagnosing and self-correcting during operation. Proof of concept and careful calibration of the magnetic bearing system and instrumentation will be conducted on an annular seal rig. Subsequent tests will use a complete turbopump stage mou nted in the same rig, in a test loop permitting cavitating and non-cavitating pump operation over broad flow range. By improving pump range and reliability, potential application of the proposed technology is sebstantial throughout the aerospace and commercial pump industry. The 5% of U.S. energy and 25 cents of each maintenance dollar used by pumps leaves significant room for improvement. Rotating stall and rotating cavitation are serious problems for pump efficiency and reliability. The dynamics of these phenomena can be measured and controlled by this unique application of magnetic bearings.