Dynamic Characteristics Of The Fault Rotor System With Dynamic Vibration Absorber

Rotating machinery is widely used in power,energy,aviation and other fields,and plays an important role in national life,industrial production,and national defense construction.With the development of science and technology,rotating machinery is also developing toward high speed and small clearance between the rotors and stators,which improves the efficiency of rotating machinery,and also increases the probability of various faults caused by vibration problems:high speed causes an increase in severe vibration due to unbalanced forces;the smaller the stator gap is more likely to produce various faults such as rubbing.Therefore,in order to ensure safe operation of the rotor system at high speeds and small gaps,excessive vibration must be controlled.The suppression methods of rotor system vibration are mainly divided into passive suppression and active suppression.Specific measures include changing the stiffness,damping and external excitation of the rotor system.Vibration absorption technology,including passive vibration absorption,semi-active and active vibration absorption are important measures in the field of vibration suppression,so many research applications have been obtained in the rotor system.At present,the research mainly focuses on the vibration suppression of the rotor system imbalance in this aspect,but the dynamic behavior of the rotor system with dynamic vibration absorber under various typical fault conditions is rarely studied.Mastering the dynamic behavior characteristics of the faulty rotor system with dynamic vibration absorbers is beneficial to the rational design of dynamic vibration absorbers and correct fault prediction.Therefore,in addition to the research on the unbalance vibration of the rotor system by the dynamic vibration absorber,the dynamic behavior of various typical fault rotor systems with dynamic vibration absorbers is studied.The vibration behavior and stability of the dynamic vibration absorber to the faulty rotor system are discussed.Specific content includes:(1)Aiming at the problem that the first-order resonance amplitude of the rotor system with unbalanced fault is too large,a new type of dynamic vibration absorber(skyhook type dynamic vibration absorber)is designed and prepared to suppress the vibration of the faulty rotor system.The experimental results show that:the skyhook type dynamic vibration absorber can effectively suppress the first-order resonance of the unbalanced fault rotor system and greatly reduce the resonance amplitude of the system;at the same time,the MS(mass-spring)type dynamic vibration absorber for the undamped unit suppresses the unbalanced fault rotor at the specific working frequency.The vibration of the system has been experimentally studied.The results show that the MS type dynamic vibration absorber can effectively suppress the vibration of the rotor system and greatly reduce the response amplitude;the additional position of the MS type dynamic vibration absorber is closer to the maximum amplitude position on the rotor system without the vibration absorber,and the vibration suppression performance is superior.(2)An experimental study was conducted on a rotor system with a misalignment fault with a dynamic vibration absorber.Firstly,the dynamic equations of the rotor system with misaligned faults with dynamic vibration absorbers are established,and the dynamic characteristics of the rotor system with different fault degrees are studied;then,the experimental platform of the rotor system with misalignment faults with dynamic vibration absorbers is built to test the critical speeds of the rotor system under different fault degrees;finally,the vibration response of the system when the working frequency is measured near the critical speed of 1/2 times,and the obtained result is compared with the response of the rotor system without the dynamic vibration absorber.The results show that the dynamic vibration absorber can suppress the double-frequency superharmonic resonance of the misaligned rotor system,which can effectively improve the system operation state.After the additional dynamic vibration absorber,the axial trajectory of the fault system changes from the outer"8"shape or crescent shape to the elliptical shape and the response amplitude are reduced.By continuously changing the stiffness of the dynamic vibration absorber,the misaligned rotor system can be prevented from generating double-frequency superharmonic resonance.(3)The dynamic characteristics and stability of the air-excited rotor system with dynamic vibration absorber are studied.Firstly,the Muszynska fluid force model is used to simulate the airflow excitation force,and the dynamic model of the airflow excited rotor system with dynamic vibration absorber is established.The Newmark-? iterative method is used to solve the dynamics of the system.The stability of the system is solved by Lyapunov approximation theory.The influence of the parameters of the dynamic vibration absorber on the stability of the air-excited rotor system is studied.The results show that the natural frequency and damping ratio of the dynamic vibration absorber have a great influence on the stability of the rotor system.When the natural frequency of the dynamic vibration absorber is close to the first-order natural frequency of the rotor,the stability of the rotor system is higher;When the the damping ratio of the dynamic vibration absorber is about 0.06,the stability of the rotor system is better;when the dynamic vibration absorber with small damping is added,there is a second-order instability phenomenon in the rotor system.(4)The dynamic characteristics of the rub-impact rotor system with dynamic vibration absorber are studied.The finite element theory is used to model the rub-impact rotor system with skyhook type dynamic vibration absorber,and the dynamic equation is solved by Newmark-? combined with Newton-Raphson iterative method.By analyzing the vibration response,the obtained results are compared with the dynamic characteristics of the rub-impact rotor system without the dynamic vibration absorber.The results show that under the same working conditions,the former enters the working frequency node of the double-cycle motion from the periodic motion.It is slightly earlier than the latter,and the working frequency node that exits the double-period motion and the chaotic motion is slightly later than the latter;in the resonance region,the number of working frequencies of the former chaotic operating state is much less than that of the latter.The simulation and experimental research on the rubbing fault rotor system with MS type dynamic vibration absorber are carried out,and the results are compared with the rubbing fault rotor without dynamic vibration absorber under the same working condition.The results show that when the natural frequency of the dynamic vibration absorber is equal or close to the working frequency,the response amplitude of the former is smaller than the response amplitude of the latter,and the operating state is better than the latter;when the natural frequency of the vibration absorber is equal to 1/2 times the working frequency or 2 times the working frequency.At the time,the former's response amplitude is slightly larger than the latter's response amplitude,and the operating state is slightly worse than the latter.(5)In order to obtain the dynamic vibration absorber with optimal vibration suppression performance,a parameter optimization method is proposed,which is suitable for parameter optimization of dynamic vibration absorber for suppressing vibration of unbalanced fault rotor system.The optimization method combines the finite element theory and the adaptive particle swarm optimization algorithm,and has the advantages of high precision and fast convergence.The parameters of three kinds of dynamic vibration absorbers,such as MS type,Vogit type and skyhook type,were optimized by this method,and the optimization results were compared.The results show that the skyhook type dynamic vibration absorber has better vibration suppression performance in suppressing the first-order resonance of the rotor system.The MS type dynamic vibration absorber has better vibration suppression performance in suppressing the vibration of the rotor at a specific frequency.The closer the additional position of the two types of dynamic vibration absorbers is to the maximum amplitude position,the better the vibration suppression performance.In order to grasp the influence of parameter variation on the optimal vibration suppression performance,the sensitivity of the optimal vibration suppression performance of the skyhook type dynamic vibration absorber and the MS type dynamic vibration absorber to each parameter is analyzed.The results show that the sensitivity of the optimal vibration suppression performance to the parameters of the dynamic vibration absorber is much higher than that of the rotor support stiffness and damping.