Research On A Novel Passive Eddy Current Damper Using Combined Arc-ring Magnets For The Suppression Of Lateral Vibrations

Due to the high progressive development in machines technology in home and abroad,excessive vibrations occur in rotating structures,which are directly related to high operating speeds and eccentricities producing additional weight.The most severe of these vibrations are the lateral vibrations that mostly affected on the bearings,seals,and lubrication systems,therefore suppressing the lateral vibrations are noticeably challenging.However,for safe operating of rotating structures without damage,progress towards the development of powerful damping mechanisms using an eddy current(ECs)has come to rise.Furthermore,the dampers that have been designed for suppressing the vibration have typically been ineffective for suppressing of vibration of rotating structures,incompatible with practical systems,and cumbersome to the structure resulting in significant mass loading and changes to the dynamic response.To improve these issues,this thesis presents original research on new structure with significant configuration of a novel passive eddy current damper(PECD)based on combined arc-ring magnets for the suppression of lateral vibrations.The significant configuration is developed using novel PECD with not totally depend on the source of power,non-contact in nature,and permits for free cost of maintenance and lubrication.This significant configuration has been presented in the development processes and then employed in suppressing of lateral vibrations powerfully.This thesis carries out the following main researches content.Firstly,for studying the lateral vibration deeply,the proposed model of single rotor system(SRS)with an offset disc was mathematically modeled,and then the novel analytical method using an integrated multi-body dynamics and finite element analysis based on MSC ADAMS was established.This proposed model of SRS consists of a DC motor,shaft,bearings,coupling and disc.In order to let this novel analytical method profoundly,three markers were placed on the locations of the left and right bearings and the mass center of the shaft.The effects of bearing force caused by lateral and torsional vibrations were also analyzed.The results showed that the lateral vibration has a great effect on the dynamic of single rotor-system when lowering motor speed.It was found that,as motor speed increased,the motion of the system becomes more stable with steady fluctuates of the displacement response.The calculated natural frequency of SRS is compared with theoretical results to verify the transient solver.This novel method is practical in analyzing the lateral and torsional vibration of the SRS under various speeds and eccentricities.This contribution can help the designers and researchers for understanding the dynamic parameters of lateral vibration.Secondly,because of a complicated structure of PECD,modelling and approximating parameters that can affect on PECD is a challenging task.These parameters involve the damping force,repulsive force,stiffness,the magnetic flux density(MFD)distribution,and eddy current induced.For studying these parameters in details,mathematical derivation of MFD has been provided.The 3D modelling of PECD was created and then numerically simulated using a novel transient analysis method.These novel multi-physics transient analysis methods studied the damping effect which formed as a result of induced eddy current and the drag force which produced as the result of repulsive force between the same axially poled magnets.This novel transient analysis method achieved a good result by configuring the conductor and permanent magnets symmetrically.The development of PECD,thus,permits to add damping to the rotordynamic system without bringing the mass loading and additional stiffness that are normally common with other methods of damping.The non-contact nature makes the PECD compatible with the rotordynamic needed to suppress the lateral vibration and enhance the performance of rotating structures.This novel method is validated and can be used by scholars and engineers for analyzing the dynamic parameters of other PECDs in future.Thirdly,in order to verify the results,the PECD was accurately manufactured with the specific dimensions and then experimentally tested.The experiments were conducted in three cases: with no magnets,with only magnets,with PECD mechanism.The results showed that the PECD successfully adds 4.8 Ns/m of viscous damping to the system.Furthermore,the influence of the dynamic parameters such as natural frequency,system stiffness,damping ratio,damping coefficient were experimentally determined.The comparison of predicated both damping coefficient and damper stiffness were successfully conducted.The first use of this novel PECD structure for suppression the lateral vibrations can be successfully applied damping forces to the rotordynamic structures with contactless and without power supply.Besides,this novel PECD addresses and minimizes the dangerous of excessive lateral vibrations which occur in rotating structure,and therefore save the money by keeping the rotating structures work safely.As compared with previous PECD,this type of damper is more flexible because of its ability of moving the arc magnets radially.In engineering applications,this novel PECD can be used as either a magnetic bearing or damping mechanism.