Case history of magnetic bearing supported hot gas turboexpander

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:390746

Destombes, Y ^[1]; Allaire, P E ^[2]

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1. Societe de Mecanique Magnetique, Saint Marcel (France)
2. Univ. of Virginia, Charlottesville, VA (United States)

A very significant advantage for the use of magnetic bearings in hot gas and cryogenic expanders is that the bearing operating temperature can be much higher or lower than for conventional oil lubricated fluid film or rolling element bearings. This has lead to the increasing development of industrial expanders which are magnetic bearing supported and rather complex bearing oil supply sealing arrangements can be eliminated. As advances in magnetic bearing technology and understanding occur, the design and performance of the magnetic bearings continues to improve. The purpose of this paper is to describe some characteristics of industrial magnetic bearing supported turboexpanders, both hot gas and cryogenic, and present a particular hot gas expander application. This paper discusses the basic principles of operation of the magnetic bearings including the bearing radial and thrust bearings, sensors, control system, and dynamic characteristics. The governing equations are given for upper quadrant radial bearing designs. Design equations relevant to bearing design will be presented to assist potential users of magnetic bearings in understanding their operation. The paper also presents a practical application of magnetic bearings to a hot gas turbogenerator. The bearings support a turbine wheel which converts the exhaust gas energy of a blast furnace into electrical power through a synchronous 6 MW generator. The magnetic bearing allowed the rotor to be constructed as a single shaft machine. The turbine wheel is directly connected to the generator rotor. The unit has been successfully operated for a 8 year period and now has in excess of 70,000 hours in a steel plant in Europe. It has some unique features: (1) it is the heaviest magnetic bearing supported rotor in industrial operation at 8 tons, (2) it has very high unbalance acceptance, (3) it has a special rotor mounted auxiliary bearing design, and (4) only the upper quadrant of the bearing is employed in the unit.

• OSTI ID: 390746
• Report Number(s): CONF-950852--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
CONTROL SYSTEMS
DYNAMIC LOADS
MAGNETIC BEARINGS
PERFORMANCE
TURBOGENERATORS
USES