Study On Vibration Measurement Method And Experiment For Rotating Machinery Based On Fiber Bragg Grating

Rotary machinery plays an important role in modern industrial production,such as steam turbines,gas turbines,compressors,fans,pumps,turbines,generators and aero engines,which are widely used in power,petrochemical,metallurgy and aerospace sectors.Therefore,the safety of rotating machinery is crucial to the economic development of the country.Rotating machinery vibration is an important cause of mechanical equipment failure.Monitoring of mechanical vibration signals can be used to know the operating conditions of mechanical equipment,thereby effectively preventing mechanical failures and accidents.The existing detection methods for parallel vibration and torsional vibration of rotating machinery are mostly electric magnetic type sensing technology,which is susceptible to electromagnetic interference,not stable enough,and not convenient for multi-point arrangement detection.In recent years,fiber Bragg grating has been applied in many fields because of its advantages of free from electromagnetic interference and distributed measurement.If FBG is applied to vibration detection of rotating machinery,the shortcomings of traditional detection methods can be made up,so it has important research value.This dissertation uses the detection of parallel vibration and torsional vibration of rotating machinery as an application background.Based on the sensing principle of fiber Bragg grating,a FBG two-dimensional vibration sensor with adjustable sensitivity is proposed for the detection of mechanical parallel vibration,and a FBG torsional vibration sensor is proposed for torsional vibration detection in rotating shafting systems.In this dissertation,the sensor characteristics of two kinds of sensors are deeply studied,an integrated system of multi-point vibration detection for rotating machinery experiment table is established.The main work and research achievements in this paper are as follows:1.In view of the current research status of mechanical parallel vibration and torsional vibration detection technology at home and abroad,this paper summarizes the advantages and disadvantages of various testing methods through comparative analysis and exploration,and puts forward the current problems and research work.2.For the detection of parallel vibration of rotating machinery,a FBG based two-dimensional vibration sensor with adjustable sensitivity has been presented.The structural model and the theoretical model of the sensor are established.The modal simulation analysis of the sensor was performed using finite element software.Finally,the sensor was studied through experiments,and the experimental results are in good agreement with the results of theoretical calculation and simulation analysis.The experimental results show that the adjustable range of the sensitivity of the sensor's X and Y are 8.049pm/g⁷6.145pm/g,8.199pm/g⁷5.335pm/g,respectively,and the stable operating frequency range is 0-180Hz.3.In order to detect the torsional vibration of rotating shaft,a FBG based torsional vibration sensor is proposed.Firstly,the torsional vibration model of the rotating shaft is established,the structure and principle of the FBG based torsional vibration sensor are described,and the strain model and vibration model of the sensor are established.Then,the characteristics of the sensor are analyzed by numerical analysis and finite element simulation.Finally,the experimental system is built to test the sensor's sensing characteristics,and the theoretical model and simulation analysis are verified.Experiments show that the linearity of the sensor is1.376%,the fitting equation is??₁+??₃-??₂-??₄=0.3603?+0.0614.The sensitivity of the sensor is 0.3603 pm/?rad/s²?,which is 4.9%larger than the theoretical value.The natural frequencies of the first-order torsional vibrations of the#1 and#2 fiber mass-ball systems of the sensor are 29.39 Hz and 27.35 Hz,respectively,which are in agreement with the exciter excitation test results.4.An integrated system of multi-point vibration detection for rotating machinery experiment table is established,which is used to perform multi-point detection under two conditions of constant speed no-load and sinusoidal excitation load.In this system,the FBG based two-dimensional vibration sensors with adjustable sensitivity are used to detect the parallel vibration of the servo motor and gearbox of the rotating laboratory bench.The designed FBG based torsional vibration sensor is used for the detection of the rotating shaft.According to the detection result the vibration characteristics of rotating machinery are analyzed.