Dynamic Modeling And Analysis Of Rotor System

As a key energy conversion device,rotating machinery has been widely applied in several important economic production sectors,such as energy and power,machinery manufacturing,chemicals and petroleum,mine and metallurgy,and hydraulic engineering.Thus,the dynamic characteristics of rotating machinery receive extensive attention from experts and scholars both at home and abroad.The exact equivalence and perfection of modeling,as the foundation and premise of dynamics analysis,directly affects the reliability of the results.Thus,in this paper,taken the pump shaft system of a domestic 600 MW supercritical steam turbine unit as a numerical example,studies how the parameters of each part impact shafting precession frequency and critical speed based on the finite element and lumped mass model of rotors with the lumped parameter method.Then it gives several equivalent modeling methods with high accuracy.The main content is as follows:(1)Theoretically elaborate on the vibration shape mechanism,vortex frequency and critical speed of the rotor shaft system,and derive differential equation of bending vibration model of elastic support unit disk rotor.Finally,the paper makes discrete simplified model for the feed pump shaft system of the 600 MW supercritical steam turbine unit by a complete and accurate lumped parameter method,and makes equivalence to bearing characteristics of sliding bearing.(2)Based on theoretical analysis and analogue simulation,this paper studies the influence of rotational inertia on the critical speed of rotors.The research includes two parts: One is to study the formation mechanism of the gyroscopic effect of rotor and elaborate on how the gyroscopic effect influences the modal frequency to change with the rotate speed;the other is to study the formation mechanism of the swinging inertia effect of rotors,and elaborate on the influence of this characteristic on the critical speed of rotation.(3)It studies the relations among whole forging,shrink-on impeller and flexural rigidity of rotors,this paper firstly analyzes the influence characteristics of monobloc forging and or shrink-on rotors,explores the variates that influence these characteristics,and then make induction and conclusion.Secondly,it puts forward the equivalent stiffness diameter method and elastic modulus coefficient strengthening method on the basis of influence rule of variates on these characteristics.Thirdly it draws equivalent stiffness diametral curves and elastic modulus strengthening coefficient curves of disks in different specifications with a large number of data,and finally fits the calculation formula of equivalent stiffness diameter and strengthening coefficients,which lays the foundation for the calculation method of the equivalent stiffness of monobloc-forgingimpeller and shrink-on impeller.(4)The supporting characteristics of sliding bearing are critical to the calculation of critical speed.Thus,this paper,based on theoretical analysis and analogue simulation,puts forward a more practical bearing modeling method,namely the sliding bearing dynamic parameter modeling method,and calculates the critical speed of the finite element model of rotors.In addition,the influence the parameters such as the oil wedges,load,width-diameter ratio,and bearing types on the supporting characteristics of oil film is analyzed and compared combined with bearing data sheet and Matlab calculation software.