Research On Monitoring Method Of Rotor Torsional Vibration And Rub Impact Based On Blade Tip-timing Method

As an indispensable key equipment in industrial production,rotating power machinery plays an important role.The torsional vibration and friction of shaft system are common faults of power machinery,and catastrophic accidents will occur in serious cases,which affect the smooth and safe operation of the unit.The torsional vibration and friction monitoring of power machinery can prevent the fault from developing to a more serious direction,and early warning is implemented in advance to avoid causing more serious accidents.The main contents of this paper are as follows:(1)The fatigue life analysis module of Complex Rotor dynamics calculation software was developed based on MATLAB language.The module can evaluate the torsional transient calculation results and estimate the start-up times of rotor system.Combined with the existing test-rig,the torsional dynamic model of three disk rotor shafting considering coupling and motor shaft was established.Through transient calculation and analysis,the torsional dynamic response law of shafting under variable frequency drive excitation was summarized.(2)A nonlinear fixed-point rub impact rotor dynamic model was established by using Newmark-β numerical integration and Newton Raphson iterative method were used to calculate the dynamic response of rub impact.The torsional dynamic response of rub impact under two working conditions(continuous rub impact and short-time rub impact)was studied and summarized by time-domain and frequency-domain analysis methods.The results show that in the low speed range,the first harmonic amplitude of torsional vibration increases due to fixed-point rub impact,and the natural frequency of shafting will be excited under certain conditions;in high speed range,fixed-point rub impact will induce non integer harmonic frequency components of torsional vibration.(3)A modification method of shafting torsional dynamics simulation model considering the influence of electromagnetic stiffness was proposed,which can reduce the error between simulation and experimental results.It is also found that the rigid body mode of torsional vibration is not zero and the first torsional natural frequency deviates due to the effect of electromagnetic stiffness.This conclusion provides a reference for the accurate analysis and prediction of the torsional dynamic performance of the electric drive unit shafting in the future.(4)An improved blade end timing correction algorithm was proposed,which takes into account the blade machining assembly error and the blade vibration caused by the non-uniform spacing error.It can solve the problem that the original BTT method is not accurate in the measurement of torsional vibration.The feasibility of the high-precision torsional vibration measurement software algorithm was verified by simulation,and the torsional vibration sampling rate can be increased by 32 times in theory.The experimental results show that the results of the modified algorithm are almost consistent with the results of the encoder,the processing accuracy is high,and the speed fluctuation caused by rub impact can be accurately monitored.Finally,the application of rub impact fault identification was carried out on the torsional blade test-rig,and the results show that rub impact fault can be monitored as well as blade vibration.