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

Abstract

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.

Effects of eccentricity and vibration response on high-speed rigid rotor supported by hybrid foil-magnetic bearing

“…To experimentally determine the optimal regions of load distribution of both bearings and to compensate for the AFB's disadvantage, the stiffness of the HFMB was changed by varying the controls k P and k D . The proportional gain (k P ) is proportional to the stiffness of the magnetic bearing, whereas the derivative gain (k D ) is inversely proportional to the derivative time constant (T D ), as shown in equation (5). In other words, the damping ratio of the magnetic bearing is inversely proportional to the derivative gain.…”

“…4 Furthermore, the dynamic behavior and performance of hybrid bearings have been studied experimentally, and the changes in the control parameters of the magnetic bearings have been investigated. 5 Pham and Ahn attempted to optimize a HFMB such that it could support a flexible rotor. They were able to optimize the controller for the bearing in order to improve the vibration performance at the bending critical speed and reduce the energy consumption of the driving motor at speeds of up to 10,000 r/min.…”

Theoretical investigation of hybrid foil-magnetic bearings on operation mode and load sharing strategy

“…Tian and Sun [30] presented an adaptive control method to simplify the controller design and improve the performance of the rotor-HFMB system. Jeong and Lee [31] used a control algorithm to reduce the sudden imbalance vibration amplitudes of a rigid rotor which was operated at up to 12,000rpm. Basumatary et al [32] presented a dynamic model that coupled dynamics of gas foil bearings and electromagnetic actuator to discusses the effect of electromagnetics actuators on the stability of a rotor supported on gas foil bearings.…”

“…The stiffness and equivalent viscous damping change with the excitation frequency. Jeong and Lee 38 used a control algorithm to reduce the sudden imbalance vibration amplitudes of a rigid rotor which was operated at up to 12,000rpm. It was experimentally verified that using the HFMB made sudden imbalance vibration control possible during rotor operation with an air foil bearing.…”

Mitigation of nonlinear rub-impact of a rotor system with magnetorheological damper

“…Because the rub-impact of the rotor/stator may be caused by different faults, the optimal design parameters of a rotor system with a passive damper under certain rub-impact situations may not be optimal or even harmful in the case of other rub-impact situations. The second method is active control, for example, using an active-controlled journal bearing or active magnetic bearing (Fang et al, 2013;Jeong and Lee, 2017;Sun et al, 1998). Active control can automatically adjust its parameters to the optimal values to adapt to environmental changes.…”