The Study Of Dynamic Characteristics Of Asymmetric Slender Shaft Rotor System With The Torsional Excitation

Asymmetric rotor system with the main features of the elongate shaft is its asymmetry shaft stiffness, and the processing and using, easy to form the mass eccentricity and initial bending, this will cause asymmetric stiffness rotor system to generate parametric excitation in the running state, and will show the complex dynamic characteristics. With the rapid development of economy and technology, the rotor system is being developed to larger, more overload, and more slender the development of the long and thin rotor system, the operation of the rotor system is more complicated, the running state of the rotor system will be more complicated. The drive torque and load torque is not equal by the multiple factors which has make the system run in a state of imbalance, it has lead the unit to withstand a difference certain amount of torque, the difference can be equivalent to a torque excitation applied imposed on the rotor system, the shaft will lose balance with the moment function, and then the operation status of the unit is abnormal, the rotor will show a rich running state. To study the transient response of the critical speed and the characteristic of the relatively stable running state has more important practical significance.An asymmetric stiffness transformation model is proposed in this paper, and a rotor dynamics equation is established based on Jeffcott rotor model, taking into account the different length diameter ratio and torque excitation, a torque is added in rotor bending vibration differential equation, and torque factor is introduced, and the drive torque rotor movement differential equation is established by using the D'Alembert's principle. Study on the transient and steady state vibration characteristics with the torque excitationunder of the asymmetric elongate shaft of the rotor system. Using Fourth Order- Runge-Kutta method to solve differential equations of motion of the system,the transient vibration characteristics has been analysed, that rotor system has been influenced by the initial deflection, asymmetric stiffness ratio, eccentricity, eccentric angle and impact torque incentives,when accelerated through the critical speed. The results showed: with the increase of non-symmetry axis stiffness difference, eccentricity increases, initial deflection increase and decrease the eccentric angle will cause increase of dynamic deflection amplitudes, phase angle and precession angle will followed changes in laws. The rotor vibration amplitude increased in the torque shock excitations, he phase angle and precession angle will appear discontinuous change, and the phase angle and precession angle will appear discontinuous change. More frequency components will be excited by harmonic torque excitationwhen to the rotor with asymmetric stiffness.Amplitude frequency characteristic will change with difference of the asymmetric stiffness coefficient, compared with symmetric rigid rotor, amplitude increase, will allow the rotor to generate a second harmonic component; constant drive torque excitation and harmonic torque excitation has a great influence to transverse vibration of asymmetric rigidity shaft rotor system. A combined frequency of frequency and excitation frequency will be excited under external excitation with rotor transverse vibration frequency and disc pendulum vibration frequency. In addition, the long diameter ratio has a great influence on the vibration frequency of the disk.Comprehensive theoretical analysis, combined with rotor test device, the stability and transient response of the asymmetric rotor system are verified and analyzed through applying the corresponding external torque. It can provide the basis for vibration characteristics analysis of asymmetric stiffness rotor and improve the accuracy of fault diagnosis for rotor system.