Abstract
In the active magnetic bearings (AMBs) supported rotating machinery, touchdown bearings are considered as safety devices to support the rotor in the deficiency of electromagnetic field. Generally, the industrial AMB machines do not have force sensors for touchdown bearings and the system is only equipped with the position sensors to monitor the rotor displacement that disables the opportunity to measure the forces during dropdown events that might be destructive for the safe operation of the rotor system. This study explores the relative severity of dropdowns that are evaluated from a computational rotor model using the rotor displacement data recorded from the position sensors installed in the machine as an input. The model for double-row angular contact ball bearing type touchdown bearings is integrated with the rotor model. The simulation model is verified by comparing the simulated rotor orbits against measured orbits at four different dropdowns. The Fast Fourier transform (FFT) is used to observe the studied dropdown events in frequency domain revealing from the rotor response the following details: harmonics of the operation speed, rub-impact frequencies, pendulum motion of the rotor and the first two bending frequencies of the rotor settled on the touchdown bearings. The critical speed map also verifies the bending frequencies and identified support properties. The model-based approach can be used to evaluate and compare a single dropdown event with respect to previous events providing an insight for decision making whether touchdown bearing should be replaced.
Highlights
At present, there is a high demand for applying active magnetic bearings (AMBs) in high speed machines
The dynamic characteristics and performance of the machine become complicated. These systems demand the installation of touchdown bearings as a safety tool to prevent the rotor failure due to the insufficiency of the electromagnetic field or faults in the control system
AMB supported machines are equipped with a limited number of vibration sensors, while the numerical model used in the transient analysis of rotor dropdown requires considering the initial displacement and velocity along all degrees of freedom
Summary
There is a high demand for applying active magnetic bearings (AMBs) in high speed machines. These systems demand the installation of touchdown bearings as a safety tool to prevent the rotor failure due to the insufficiency of the electromagnetic field or faults in the control system For both the AMB supported rotor and conventional rotor-bearing, research teams and industry become interested in the development of a dynamic model enabling the simulation of the behavior of the system during the operation. Fonseca et al [4] have investigated the nonlinear behavior in dropdown due to rotor unbalance both numerically and experimentally and presented the rotor orbit for three level of unbalances They found that for the low value of unbalance, the rotor oscillates at the lower half of the touchdown bearing while the high value of unbalance causes the rotor to bounce from contact and impacts the bearing, severely. The critical speed map is used to confirm the bending frequencies of the rotor settled in the touchdown bearing and the estimated support properties
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
