Dynamic Stability Research On Bearing-rotor System Of Double Stage Power Turbine

The power turbine rotor supported by rolling bearings is a common power output structure for micro gas turbine,turboshaft and turboprop engine.Since the rotor structure usually works in the high-speed and high-torque environment,its dynamic stability which depends on the dynamic characteristics of rotor and the stability of the connection structure plays a vital role in the entire unit.The supporting mechanism of the power turbine rotor is usually a large cantilever structure which is more complex than that of the common freely supported structure.In addition,the rigidity of the bearing seat and the outer casing are usually larger for the ground gas turbine.If the elastic supporting is not used,the supporting stiffness of the rotor mainly depends on the support stiffness of the bearing.Therefore,the premise of rotor dynamics analysis is to calculate the stiffness of rolling bearings accurately.For the rotor of multistage power turbine,the turbine disk is often prestress connected by rod and the force and torque between the disk and the rotating shaft are transmitted through the rough surface friction.If the prestressed force is not suitable,it is very easy to lose stability.Therefore,it is necessary to carry out the multidisk rotating test to verify the stability of the rotor connection structure.This paper is based on bearing rotor system of large cantilever double stage power turbine of QD40 gas turbine.And it has a research on dynamic stability of the bearing rotor system,which provide theoretical and experimental support for the reliable operation of the gas turbine.The main research achievements are as follows:1.Derivate the relationship between load and deformation of line contact cylindrical roller bearing.point contact ball bearing;analyze the kinematic and interaction force relationship between roller,holder,inner and outer race;lay a theoretical foundation for analyzing stiffness characteristics of rolling bearings.2.Establish the static analytical stiffness model of cylindrical bearing,analyze the effects of structural and operating condition parameters on bearing stiffness,then verify the solution with finite element method.3.Finite element method is applied to carry out a research on the stiffness behavior of three point contact ball bearing in consideration of the axial load,analyze the effects of structural and operating condition parameters on bearing stiffness,which can provide the basis for rotor dynamics analysis.4.Considering the large cantilever rotor structure of double stage power turbine,APDL parametric modeling method is applied to solve the critical speed,modal shape,unbalance and transient response of bearing rotor system.And the solution verified the validity of rotor's rigidity,which can provide the basis for optimization of rotor structure and method of dynamic balance.5.Concerning the prestress connected by rod of double stage power turbine,a overspeed test of double stage disk was conducted.The structural strength of disk as well as the stability of the structural of prestress connected by rod is verified by the test.