Dynamic Analysis For Rotor-Bearing Systems Of Large General Machinery

Large-scale general machines are important equipment that play important roles in energy and petrochemical industries.Problems of vibration and stability,especially the coupling-related problems among multiple physical fields e.g.fluid,solid and thermal,of rotor-bearing systems have been encountered as the rotary machines become high-speed, heavily-loaded,light-weighted and automated.It has been a concern to both the academic and engineering communities to synthetically consider excitations induced by multiple fields and accurately determine vibration and stability characteristics of the rotary system.The present thesis aims to study all elemental parts of rotor-bearing systems and assemble them based on existent research.The dynamic characteristic of large rotor-bearing systems in operation is investigated through fast and reliable numerical analysis developed by the author.The appropriate Reynolds equation is adopted with various lubricant conditions for the system.The difference method is used to compute the dynamic lubricant parameters,i.e. stiffness and damping coefficients,of sliding bearings.The finite element method is used to model the rotor assembly of the machine and analyze the critical speeds,modes and unbalanced response.The source code for this method is developed by using the Matlab software and verified through examples.A practical problem of computing wet critical speeds for a centrifugal pump manufacture by a domestic company by using the code and ANSYS software.The outline of the author's work is:(1) To Comprehensive previous researches theory,Corresponding lubrication equation is adopted with various lubricant conditions and speeds for the system.(2) The difference method is used to compute film pressure distribution of Reynolds Equation,static pressure(bearing capacity),attitude angle,eight stiffnesses and damping coefficients of small disturbance in turn.(3) The finite element model of rotor systems was established.(4) Rotor-bearing systems critical speed,vibration mode and unbalance response are calculated.Calculation results are analyzed.Stability of systems is judged. Conclusions are obtained.(5) Using the code and ANSYS software,a practical problem of computing wet critical speeds for a centrifugal pump manufacture by a domestic company.