Rigid Mode Vibration Control and Dynamic Behavior of Hybrid Foil-Magnetic Bearing (HFMB) Turbo Blower

2016 ◽  
Author(s):  
Sena Jeong ◽  
Jungwan Kim ◽  
Doyoung Jeon ◽  
Yong Bok Lee
Keyword(s):  
Vibration Control ◽  
Dynamic Behavior ◽  
Magnetic Bearing ◽  
Experimental Results ◽  
Low Speed ◽  
Vibration Stability ◽  
Turbo Blower ◽  
Foil Bearing ◽  
Aerodynamic Instability ◽  
Bearing System

In this study, experimental and analytical analyses of the vibration stability of a 225 kW class turbo blower with a hybrid foil-magnetic bearing (HFMB) were performed. First, critical speed and unbalance vibration responses were examined as part of the rotordynamic research. Then, an experimental double-suction turbo blower with an HFMB was built. The turbo blower consisted of an impeller at each end and a permanent magnet motor in the center. Its shaft diameter was 71.5 mm, its total length was 693 mm, and the weight of the rotor was 17.8 kg. The air foil bearing (AFB) utilized was 50 mm long and had a 0.7 aspect ratio. The results of analyses indicate that rigid mode (conical mode) occurred close to 8,036 rpm, and the results of natural frequency analysis and dynamic behavior prediction of the rotor-bearing system were similar to those obtained experimentally. However, in the experiments conducted, excessive vibration and rotor motion instability occurred in the range 12,000–15,000 rpm, which resulted from insufficient dynamic pressure caused by the length of the foil bearing being too short. Consequently, as the rotor speed increased, excessive rotor motion attributable to aerodynamic and bearing instability became evident. This study therefore focused on improving rotordynamic performance by rectifying rigid mode unstable vibration at low speed, 20,000 rpm, and asynchronous vibration due to aerodynamic instability by using HFMB with vibration control. Although the normal operating speed is 39,000 rpm, the experiments were conducted at 20,000 rpm. The experimental results obtained were compared for each bearing type (AFB and HFMB) to improve the performance of the vibration in the low speed region. The experimental results show that the HFMB technology results in superior vibration stability for unbalance vibration and aerodynamic instability in the range 12,000–15,000 rpm (200–250 Hz). The remarkable vibration reduction achieved from vibration control of the hybrid foil-magnetic rotor-bearing system show that oil-free turbomachinery can achieve excellent performance.

Rigid Mode Vibration Control and Dynamic Behavior of Hybrid Foil–Magnetic Bearing Turbo Blower

2016 ◽  
Vol 139 (5) ◽  
Author(s):  
Sena Jeong ◽  
Doyoung Jeon ◽  
Yong Bok Lee
Keyword(s):  
Vibration Control ◽  
Dynamic Pressure ◽  
Magnetic Bearing ◽  
Experimental Results ◽  
Low Speed ◽  
Vibration Stability ◽  
Turbo Blower ◽  
Foil Bearing ◽  
Vibration Responses ◽  
Aerodynamic Instability

In this study, experimental and analytical analyses of the vibration stability of a 225 kW class turbo blower with a hybrid foil–magnetic bearing (HFMB) were performed. First, critical speed and unbalance vibration responses were examined as part of the rotordynamic research. Its shaft diameter was 71.5 mm, its total length was 693 mm, and the weight of the rotor was 17.8 kg. The air foil bearing (AFB) utilized was 50 mm long and had a 0.7 aspect ratio. In the experiments conducted, excessive vibration and rotor motion instability occurred in the range 12,000–15,000 rpm, which resulted from insufficient dynamic pressure caused by the length of the foil bearing being too short. Consequently, as the rotor speed increased, excessive rotor motion attributable to aerodynamic and bearing instability became evident. This study therefore focused on improving rotordynamic performance by rectifying rigid mode unstable vibration at low speed, 20,000 rpm, and asynchronous vibration due to aerodynamic instability by using HFMB with vibration control. The experimental results obtained were compared for each bearing type (AFB and HFMB) to improve the performance of the vibration in the low-speed region. The experimental results show that the HFMB technology results in superior vibration stability for unbalance vibration and aerodynamic instability in the range 12,000–15,000 rpm (200–250 Hz). The remarkable vibration reduction achieved from vibration control of the HFMB–rotor system shows that oil-free turbomachinery can achieve excellent performance.

Performance of a Foil-Magnetic Hybrid Bearing

2000 ◽  
Author(s):  
Erik E. Swanson ◽  
Hooshang Heshmat ◽  
James Walton
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Experimental Program ◽  
Turbine Engine ◽  
Foil Bearing ◽  
Speed Performance ◽  
Hybrid Bearing ◽  
High Load Capacity ◽  
Bearing System

To meet the advanced bearing needs of modern turbomachinery, a hybrid foil-magnetic hybrid bearing system was designed, fabricated and tested in a test rig designed to simulate the rotor dynamics of a small gas turbine engine (31 kN to 53 kN thrust class). This oil-free bearing system combines the excellent low and zero-speed capabilities of the magnetic bearing with the high load capacity and high speed performance of the compliant foil bearing. An experimental program is described which documents the capabilities of the bearing system for sharing load during operation at up to 30,000 RPM and the foil bearing component’s ability to function as a back-up in case of magnetic bearing failure. At an operating speed of 22,000 RPM, loads exceeding 5300 N were carried by the system. This load sharing could be manipulated by an especially designed electronic control algorithm. In all tests, rotor excursions were small and stable. During deliberately staged magnetic bearing malfunctions, the foil bearing proved capable of supporting the rotor during continued operation at full load and speed, as well as allowing a safe rotor coast-down. The hybrid system tripled the load capacity of the magnetic bearing alone and can offer a significant reduction in total bearing weight compared to a comparable magnetic bearing.

Composition of a magnetic-bearing system for horizontal shaft and its experimental results

1983 ◽  
Vol 103 (5) ◽  
pp. 121-128 ◽  
Author(s):  
Fumio Matsumura ◽  
Yoshimi Tanaka ◽  
Mamoru Kido ◽  
Yuji Akiyama
Keyword(s):  
Magnetic Bearing ◽  
Experimental Results ◽  
Horizontal Shaft ◽  
Bearing System

Modal Testing and Parameter Identification of Active Magnetic Bearing System

1995 ◽  
Author(s):  
Chong-Won Lee ◽  
Young-Ho Ha ◽  
Cheol-Soon Kim ◽  
Chee-Young Joh
Keyword(s):  
Parameter Identification ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Magnetic Bearing ◽  
Experimental Results ◽  
Active Magnetic Bearing ◽  
Modal Testing ◽  
Modal Parameters ◽  
Bearing System

Abstract Complex modal testing is employed for parameter identification of a four-axis active magnetic bearing system. In the test, magnetic bearings are used as exciters while the system is in operation. The experimental results show that the directional frequency response function, which is properly defined in the complex domain, is a powerful tool for identification of bearing as well as modal parameters.

Vibration control of high-speed rotor supported by hybrid foil-magnetic bearing with sudden imbalance

2015 ◽  
Vol 23 (8) ◽  
pp. 1296-1308 ◽  
Author(s):  
Sena Jeong ◽  
Yong Bok Lee
Keyword(s):  
Mass Loss ◽  
Vibration Control ◽  
High Speed ◽  
Turbine Rotor ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Control Force ◽  
Transient Vibration ◽  
Stability Performance ◽  
Foil Bearing

A hybrid foil-magnetic bearing (HFMB) was successfully studied as a vibration isolator by introducing a sudden imbalance or an unexpected disturbance during turbine/rotor operation. This HFMB is used to achieve stability during transient vibration behavior. The HFMB consists of two oil-free bearing technologies: an active magnetic bearing (AMB) and air foil bearing (AFB). Using both technologies takes advantage of the strengths of each bearing while compensating for their inherent weaknesses. In addition, the HFMB has good dynamic characteristics, and the damping can be adjusted using the appropriate gain selection for the AMB controller. Based on these unique features, dynamic stability can be enhanced, even if a sudden imbalance occurs while the rotor is operating. In this study, a rigid rotor was operated at up to 12,000 rpm and tested using a control algorithm to reduce the sudden imbalance vibration amplitudes. The experiment was conducted under the situation that the mass dropped out at 6,000 rpm. In order to validate the stability performance of the HFMB with a sudden mass loss, the vibration response results for the AFB and HFMB were compared. When applying the HFMB, the asynchronous vibration was suppressed, and the 1x vibration results showed reductions of almost 30%. When the sudden mass loss occurred, the magnetic control force was remarkably effective at reducing the asynchronous vibration of the rotor supported by the HFMB. In conclusion, it was experimentally verified that using the HFMB made sudden imbalance vibration control possible during rotor operation with an air foil bearing. In this respect, the HFMB has the characteristics of high stiffness/damping, which prevent rubbing and suppress excessive vibration due to a sudden imbalance event.

Contact Dynamic Response With Misalignment in a Flexible Rotor/Magnetic Bearing System

2004 ◽  
Author(s):  
Patrick S. Keogh ◽  
Matthew O. T. Cole
Keyword(s):  
Dynamic Behavior ◽  
Experimental System ◽  
Magnetic Bearing ◽  
Contact Dynamics ◽  
Radial Clearance ◽  
Flexural Mode ◽  
Non Linear ◽  
Auxiliary Bearing ◽  
Run Up ◽  
Bearing System

This paper investigates the vibration characteristics of rotor displacement signals in a magnetic bearing system under conditions when rotor contact with auxiliary bearings is possible. Since these signals may be used for feedback control, it is necessary to determine how they may affect the ability of the controller to regain rotor levitation. An experimental system is used to demonstrate the sensitivity of the rotor non-linear dynamic behavior to unbalance, which is sufficient to cause contact during rotor run up through rigid body and flexural mode critical speeds. Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus an alternative procedure for assessing the non-linear rotor dynamic behavior is established with the potential for identification of appropriate control forces. The contact dynamics are also considered in the presence of auxiliary bearing misalignment. Misalignment may arise through physical translation of a housing or through steady state offset errors in sensor measurements. A misalignment of 50% of the nominal radial clearance is applied at an auxiliary bearing. Various contact modes are evident as the rotor is run up in speed. During run down different contact dynamics may be encountered and the level of such hysteresis is assessed.

Contact Dynamic Response With Misalignment in a Flexible Rotor/Magnetic Bearing System

2004 ◽  
Vol 128 (2) ◽  
pp. 362-369 ◽  
Author(s):  
P. S. Keogh ◽  
M. O. T. Cole
Keyword(s):  
Dynamic Behavior ◽  
Experimental System ◽  
Magnetic Bearing ◽  
Contact Dynamics ◽  
Radial Clearance ◽  
Flexural Mode ◽  
Auxiliary Bearing ◽  
Run Up ◽  
Control Forces ◽  
Bearing System

This paper investigates the vibration characteristics of rotor displacement signals in a magnetic bearing system under conditions when rotor contact with auxiliary bearings is possible. Since these signals may be used for feedback control, it is necessary to determine how they may affect the ability of the controller to regain rotor levitation. An experimental system is used to demonstrate the sensitivity of the rotor nonlinear dynamic behavior to unbalance, which is sufficient to cause contact during rotor run-up through rigid-body and flexural mode critical speeds. Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus, an alternative procedure for assessing the nonlinear rotor dynamic behavior is established with the potential for identification of appropriate control forces. The contact dynamics are also considered in the presence of auxiliary bearing misalignment. Misalignment may arise through physical translation of a housing or through steady-state offset errors in sensor measurements. A misalignment of 50% of the nominal radial clearance is applied at an auxiliary bearing. Various contact modes are evident as the rotor is run up in speed. During rundown, different contact dynamics may be encountered and the level of such hysteresis is assessed.

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