Research On The Stability Of Spline Connected Rotor System

Spline couplings which have simple structure,high reliability and can compensate torque transmission error are widely used in aero-engines.Spline Couplings can induce self-sustained oscillation which leads to the instability of the rotor system.The issue has not been solved very well.Therefore,it is of great importance to study the instability mechanism and the influence factors of the spline connected rotor system as well as the effect rules of spline coupling on the rotor system stability which provides guidance for the spline connected rotor system design and improves the security and the reliability of aero-engines.Spline force has something to do with the spline stiffness of tooth pairs.In the thesis,the computing model of the spline stiffness of tooth pairs is firstly established.A modified integral method is proposed on the deficiency of trapezoid method,rectangle method and integral method.The tooth pairs stiffness of spline coupling without tooth profile error is calculated which is proved to be accurate and fast compared to the FEA method.As for the spline tooth pairs stiffness with tooth profile error,the spline model with tooth profile errors is established.The spline stiffness has been calculated with FEA method considering torsional deformation of the foundation,the slipping and the friction between the tooth surfaces.The effect on the spline stiffness has been obtained.The physical mechanism of the spline connected rotor system instability has been analyzed and spline force model has been derived which is represented as lateral and angular stiffness,lateral and angular damping,lateral cross stiffness and angular cross stiffness.The effects of tooth profile errors,action radius,friction coefficients and rotating speed on the spline force has been studied.The instability mechanism has been verified using energy method.The dynamic model of the spline connected rotor system has been established.The critical speed and the vibration modes have been obtained.The influence of the spline force on the rotor system has been analyzed using complex eigenvalue method.The effect of the lateral and angular stiffness,the lateral and angular damping as well as the lateral cross stiffness and angular cross stiffness on the system stability has been researched.What is more,the effects rules of friction coefficients,load torque,tooth profile error and external damping on the system stability have been studied.The spline connected rotor test rig has been set up.The instability phenomenon of spline connected rotor system has reoccurred.The critical speed and the threshold speed of the rotor system have been studied under different conditions of spline lubrication,external damping,load torque,fit type and tooth profile error.The instability characteristics of spline connected rotor system have been obtained as well as the effect rules of the influence factors on spline connected rotor system stability.The test results verify the established dynamic model of spline coupling and the calculating results.