Research Papers: Gas Turbines: Structures and Dynamics

Development of a 125 kW AMB Expander/Generator for Waste Heat Recovery

[+] Author and Article Information
Lawrence A. Hawkins

 Calnetix, Inc., 23695 Via Del Rio, Yorba Linda, CA 92887lhawkins@calnetix.com

Lei Zhu

 Calnetix, Inc., 23695 Via Del Rio, Yorba Linda, CA 92887lzhu@calnetix.com

Eric J. Blumber

 Calnetix Power Solutions, Inc., 23695 Via Del Rio, Yorba Linda, CA 92887eblumber@calnetix.com

J. Eng. Gas Turbines Power 133(7), 072503 (Mar 16, 2011) (6 pages) doi:10.1115/1.4002660 History: Received May 09, 2010; Revised May 12, 2010; Published March 16, 2011; Online March 16, 2011

The development and testing of an integrated power module (IPM) for a waste heat recovery system is described. The IPM is part of a waste heat recovery system based on the organic Rankine cycle. The waste heat system can recover energy from a wide variety of heat sources including landfill gas, reciprocating engine exhaust, solar, geothermal, boilers, and other industrial processes. The IPM incorporates a high performance, high speed permanent magnet generator with an integrated expansion turbine and low loss magnetic bearings. The IPM operates between 20,000 rpm and 26,500 rpm depending on the energy available from the heat source. The varying frequency voltage supplied by the generator is connected to the grid using an active/active power electronics package that can deliver power at 400480Vac (50 Hz or 60 Hz). Active magnetic bearings (AMBs) were chosen for the application because they can operate directly in the working fluid, have low losses, and provide high reliability and remote monitoring capabilities. This system has a flow-through design and an inboard impeller layout that produces desirable rotordynamics for a simple magnetic bearing control. An extensive shop testing procedure is described, and measurements and predictions are presented, showing good correlation. Shop testing of the IPM in the waste heat system has been completed for 15 systems. The magnetic bearings and backup bearings have performed as designed. The thrust balancing system has limited the thrust load that must be reacted by the axial magnetic bearings to 25% of the design load capacity in the worst case. The first field unit was installed in April 2009 at a biogas site.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

WHG process flow diagram

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Figure 2

Calnetix WHG125 prepackaged skid

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Figure 3

Cross section of the IPM

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Figure 4

Thrust balancing scheme for the IPM

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Figure 5

Free/free natural frequency map for the IPM rotor

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Figure 6

Plant transfer function measurement, 0 rpm

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Figure 7

Sensitivity transfer function measurement, 0 rpm

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Figure 8

Synchronous response data from the position sensors

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Figure 9

Measured axial load versus current. Comparison of several measurements and theory.



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