| The faults of rotor system are important factors that restrict the performance of rotating machinery.Under the conditions of high speed,high power and complicated operation environment,it is easy for the machine to get unbalanced or misaligned.If those faults cannot be diagnosed immediately,they will cause secondary faults like rubbing or foundation looseness,which accelerate the failure of the equipment.Once the rotating machinery is in trouble,the faults often occur in the form of multiple failures.In the rotor system,unbalance,misalignment and rubbing are the three most common faults.Based on these three faults,this paper establishes a dynamic model of rotor system under multi-faults conditions.Based on the simulations and experiments,it studies the vibration response characteristics of the rotor system under multi-faults,which provides a reference for fault diagnosis.The rotating machinery is a complex mechanical system,the whole body vibration is an important indicator of its working performance.The whole body vibration monitor test of the blade rotor rigs has been performed.Combined with the related theories and the modal test of the case,an effective analysis has been made.The full text is as follows:(1)Using lumped mass method and the Lagrange principle,a single span rotor dynamics model based on the blade rotor test rig with unbalance,misalignment and rubbing fault is established.Meanwhile the Runge-Kutta algorithm is used to obtain the vibration response of the system,the influence of unbalance and misalignment on the vibration characteristics of the rotor system under multiple faults is analyzed using the time domain,frequency domain and order waterfall graphs.In the rotor system with unbalance-misalignment faults,there is a 2nd harmonic component resonance phenomenon existing at half of the critical speed of the system.With the degree of misalignment increased,the amplitude of frequency-doubling increase and the orbit is also changed from ellpise to double loop ellipse.For the system with rubbing fault,there are higher harmonic and sub-harmonic phenomena in the frequency domain.With the degree of unbalance increased,the rubbing speeds range will expand and the degree of rubbing will intensify.For the rotor system with those three faults,the impact degree of rubbing will sharpen with the increasing of unbalance or misalignment;the 3rd harmonic component would decline at the speed range of sub harmonic.(2)Based on the CUT-2 rotor experimental rig,the multi-faults experiments of unbalancemisalignment,unbalance-rubbing and unbalance-misalignment-rubbing are carried out.It is observed that in rotor system with unbalance and misalignment;the larger the degree of misalignment is,the greater the 2nd harmonic component in the corresponding direction will be;and the power frequency component will change.The axis orbit will turn into double loop ellipse.When the critical speed is half,there is 2nd harmonic resonance phenomenon.When the system is rubbing,it is found that there is higher harmonic component.With the degree of unbalance or misalignment increased,the rubbing speeds range will enlarge and the degree of rubbing will aggravate.The experimental results verify the correctness of some simulation results qualitatively and demonstrate the effectiveness of the simulation dynamic model.(3)The vibration monitoring experiments of the running blade rotor rig are carried out,and the vibration data of the rotating shaft,the bearing seat,the foundation and the casing are collected.Using time domain,frequency spectrum and waterfall diagram to analyze the test data,it is found that there are high harmonic components in the data collected at the end away from the motor side so that the rubbing fault is found preliminarily.Modal shape and frequency are obtained by the modal test of the casing.The natural frequency of the casing is obtained from the running data by the order tracking,which are consistent with the multi-order frequency of the modal test. |
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