Dynamic Characteristics Analysis On Rotor System With Unbanlance-misalignment-Pedestal Looseness Coupling Faults

Among the various types of faults in the rotor system,unbalance,misalignment,and pedestal looseness are three common faults.Unbalance and misalignment usually appear in the process of rotor design,production,revolve etc.Unbalance and misalignment can exacerbate the vibration of the system,which can easily cause the system to loosen.In this work,the three kinds of faults are taken as the research object.The dynamics models of the rotor-roller system under unbalanced-misalignment coupling faults and unbalanced-misalignment-pedestal looseness coupling faults are established,and the dynamic characteristics of the rotor system with coupling faults are analyzed by simulation.Coupling faults may accelerate the vibration of the system,which leads to the geometric nonlinearity of displacement-strain of shaft more prominent.Therefore,in this work,the vibration characteristic of the rotor system with geometric nonlinearity is further explored.In addition,control strategies such as tuned mass damper(TMD)and multiple tuned mass damper(MTMD)are used to control the Jeffcott rotor system for suppressing vibration.The main research contents and results are as follows:(1)The rotor system under unbalanced-misalignment coupling faults is taken as the research object.The influence of the misalignment,the quality of the coupling,the different supporting conditions and the rolling bearing's clearance on the dynamic characteristic of the rotor system are discussed by means of numerical analysis.It's concluded that misalignment can cause the system to have a "protrusion" in the vibration amplitude near the one-half critical speed.In addition,under the rolling bearing,the vibration amplitude would jump after the speed exceeds the one-half critical speed.As the clearance of the bearing increases,the "jump" phenomenon of the vibration amplitude near the one-half critical speed of the system becomes more and more obvious.(2)The rotor system under the unbalance-misalignment-pedestal looseness coupling faults is taken as the research object.The effects of unbalance,misalignment and loose clearance on the dynamic characteristics of the rotor system are discussed by numerical analysis.It is found that compared with the rotor system without looseness,there is a speed range in the system with the increase of the unbalanced fault and the misalignment fault.Among the speed rage,the vibration amplitude of the system jumps slightly when it gets close to the maximum vibration amplitude.And with the increase of unbalance,misalignment and looseness,another provoke strong vibration emerges when exceeding the critical speed.In severe condition,the vibration amplitude will be greater than the vibration amplitude at the critical speed.(3)The single rotor system is taken as the research object.The displacement-strain geometric nonlinear problem of the rotating shaft is taken into consideration.And the effects of unbalance,misalignment,shaft radius and shaft length on the dynamic characteristics of the system are discussed.By numerical calculation,it is found that the critical speed and one-half of the critical speed of the rotor system and its corresponding vibration amplitude increase with the increase of the unbalance and misalignment.With a small enough unbalance and misalignment,the geometric nonlinearity of the system is negligible.The radius and the length of the shaft directly influence how serious the nonlinear problem of the shaft is.(4)The Jeffcott rotor system is taken as the research object.The control effect of TMD and MTMD of Jeffcott rotor system is compared.It is found that the control effect of MTMD is superior to that of TMD.Moreover,under the non-optimal frequency ratio,the damping effect of MTMD is also better than the damping effect of TMD.