Abstract
Magnetic bearings are oil-free bearings that are widely employed in turbo machineries such as turbo refrigerant compressors in order to eliminate lubrication systems, avoid contamination, and increase efficiency. We have developed a 145 refrigerant ton (RT)-class turbo refrigerant compressor using homopolar-type radial hybrid magnetic bearings (HMBs) and thrust magnetic bearings. The thrust magnetic bearing comprises a thrust HMB and a permanent magnet that generate downward forces to overcome high upward thrust forces of 2000 N at 21 000 rpm. A test rig and controller for the compressor with magnetic bearings were fabricated, and rotordynamics such as the unbalance response and axial displacement were investigated. Rotordynamics analyses using the finite element method predicted that the 1st bending mode is located at a high frequency with sufficient margin from the operating speeds. Further, the zero-to-peak displacement caused by the unbalanced response was sufficiently small. The rotor was stably supported with few vibrations across the entire range of the operational speeds. Our results demonstrate that the advantages of oil-free bearings can be easily exploited in turbo machineries such as turbo refrigerant compressors by adopting HMBs.
Highlights
Turbo refrigerant compressors are key components of many heating, ventilation, and air conditioning (HVAC) systems such as air conditioners used in buildings or vehicles, temperature-humidity controllers, environmental test equipment, and food storage systems
Magnetic bearings comprising homopolar-type radial hybrid magnetic bearings (HMBs) and a thrust magnetic bearing are designed for 145 refrigerant ton (RT)-class turbo refrigerant compressors
Rotordynamics analyses using the finite element method predicted that the 1st bending mode will be located at a high frequency with sufficient margin from the operating speeds
Summary
Turbo refrigerant compressors are key components of many heating, ventilation, and air conditioning (HVAC) systems such as air conditioners used in buildings or vehicles, temperature-humidity controllers, environmental test equipment, and food storage systems. We present a design procedure for magnetic bearings that can support a 145 refrigerant ton (RT)-class turbo refrigerant compressor. The rotor is setup vertically so that the radial magnetic bearings do not have to support the rotor weight, thereby minimizing the required force. Employed in this study in order to minimize the size of the magnetic bearings and maximize efficiency. We used both homopolar-type radial HMBs and thrust HMBs comprising both permanent and electromagnets. Our magnetic bearings are designed to support a 2000 N thrust force generated by a compressor at an operating speed of 21 000 rpm. A test rig and controller were fabricated, and the unbalance responses and axial displacements were investigated
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