Dynamics Of Rotor-Bearing-Damper System Of Flywheel Energy Storage System

Flywheel energy storage is an important mechanical energy storage method.The hybrid support with permanent magnetic bearing(PMB)and spiral groove bearing is a classical support for the Flywheel energy storage system(FESS).Recently,to develop 100kg-class FESS in this field has been an important object.However,how to improve the capacity of the hybrid support and how to improve the dynamic stability of flywheel rotor system are two urgent problems to be solved for the 100kg-class FESS.In the paper,a series of researches are carried out to resolve these problems.(1)The innovative design of flywheel rotor-bearing-damper systemFirstly,the innovative design of 100kg-class flywheel rotor-bearing-damper system is carried out,a new upper supporting of the radial magnetic pendulum TMD separated from the axial PMB is developed,and the pendulum TMD with rolling joints is designed.Then,the load capacity of the hybrid support with PMB and spiral groove bearing is analyzed and tested,and the structure of bearings is optimized.The results show that the axial load and frictional resistance of the pendulum TMD are low,and the optimal hybrid support has large load capacity and low frictional loss.(2)Dynamic analysis of flywheel rotor-bearing-damper systemBased on the Lagrange eqution,a series of four degrees of freedom dynamics models of flywheel rotor-bearing-damper system,including a linear free vibration model,a nonlinear steady-state dynamic model,a transient dynamic model under constant acceleration and a linear perturbation equation of synchronous periodic responses,are founded.A series of dynamics properties of flywheel rotor-bearing-damper system,such as the modes,unbalance responses,transmitted force of bearing and the stability of flywheel rotor system,etc.,are analyzed.The effects of characteristics parameters of the upper and lower dampers on the dynamics properties are discussed,and then the major characteristics parameters are optimized.The results are as follows:The frequency of flywheel 1st-order forward mode is much less than that of flywheel2nd-order forward mode,and the flywheel rotor system hasn't the critical speed caused by theflywheel 2nd-order forward mode;the flywheel 1st-order forward mode damping ratio and the unbalance responses of system at the 1st-order critical speed mainly depend on the parameters of upper damper;the flywheel 2nd-order forward mode damping ratio,the vibration amplitude and transmitted force of low bearing mainly depend on the parameters of lower damper;the natural frequency of the upper and lower damper should be equal to the frequencies of flywheel 1st and2 nd forward modes in theory,separately;the oil-film force of lower damper is the main factor of the instability of flywheel rotor system,and the stability of system can be improved by changing the characteristic parameters of dampers,for example,increasing radial clearance of lower damper,decreasing the stiffness of pivot and so on.(3)Experimental study on kinetic characteristics of flywheel rotor-bearing-damper systemA series of experimental systems,including parameter identification device of the pendulum TMD,modal identification system of flywheel rotor system,and unbalance response test system,are built to test the kinetic characteristics of flywheel rotor-bearing-damper system.The parameters identification method of vibration system based on the particle swarm optimization is applied to estimate the parameters of system from the test data.By these tests,the physics parameters(the stiffness,damping,vibration mass,etc.),the modal parameters(mode frequency,mode shape,mode damping ratio,etc.)and unbalance responses are obtained,and the damping performances of pendulum TMD are assessed.The results are as follows:Compared with traditional axial magnetic pendulum TMD,the radial magnetic pendulum TMD has lower stiffness and natural frequency,larger flywheel 1st-order mode damping ratio,and can suppress the flywheel 1st-order forward whirling more efficiently;the flywheel rotor can run smoothly after it passes the 1st-order critical speed,and the calculated values of unbalance responses agree with the test values at high speed.In conclusion,the 100kg-class flywheel rotor-bearing-damper system with PMB and spiral groove bearing is developed in the paper.The innovative design of the key parts,such as the rotor,bearing,and damper,etc.,the dynamic modeling,analysis,and experimental research of flywheel rotor system are conducted successfully.The research can provide some theoretical foundation for the dynamics design and analysis of FESS with PMB and spiral groove bearing.