Vibration Monitoring Of Compressor Based On Fiber Bragg Grating

Gas turbines are widely used in energy,power and military fields as the energy conversion machinery and play an important role in this fields.However,due to the complicated structure of the gas turbine,various faults are likely to occur during the operation.Once the faults occur,it will cause huge safety accidents and economic losses.Therefore,it is a very important research task to ensure the normal and efficient operation of the gas turbine.Compressor is one of the three major components of gas turbine.To ensure the safety of compressor is a major prerequisite to ensure the continuous high-efficiency output of the gas turbine.In this dissertation,the structure of the compressor is studied based on the fiber Bragg grating(FBG)sensor.The natural frequency and vibration mode of the turbine blade of the compressor and the vibration of the compressor are studied respectively.The overall study of compressor vibration is realized,which lays a foundation for the fault diagnosis of compressor under complex working conditions.The structural parameters of each sensor are optimized by finite element method,and the optimal strain transfer coefficient and temperature response time are obtained.In this dissertation,the multiple multiplexing techniques of FBG are compared,and the space division-time division hybrid multiplexing technique is selected to perform the multiplexing demodulation of the fiber grating array.Secondly,basic research on the turbine blades of the compressor was carried out.The FBG is used to detect the natural frequency and vibration mode of the turbine blade structure of the compressor.By arranging the FBG on the surface of the blade,the natural frequencies of the blade and the corresponding basic vibration modes are obtained by inversion.The simulation results and the actual blade tapping test results are consistent,which shows the feasibility of using FBG to test the basic vibration mode of the blade inside the casing.At the same time,the rotation characteristics of the blade are analyzed,and the critical speed of the blade under various levels is determined by the Campbell curve,which provides reference and guidance for the actual design of the compressor working speed.Finally,the casing vibration of the compressor during its operation is studied.The FBG sensors are used to monitor the strain and temperature during the vibration process of the compressor casing under different working conditions.Distributed multi-parameter monitoring and analysis of the time-domain signals of the sensors are realized by designing the position and direction of the FBG sensor on the casing surface.The temperature and strain distribution of the measured points on the casing surface are obtained,and the rise and fall speed,surge process of the compressor during the whole working time are judged.From the real-time frequency domain,the rise and fall speed and the steady state of the compressor can be judged by monitoring the frequency change.The natural frequencies of the compressor are 50 Hz and 150 Hz.The surge can be accurately judged by monitoring the amplitude changes of the natural frequencies and the frequencies related to the rotational speed.This indicates the feasibility of monitoring the natural frequencies to monitor the surge of the compressor,and provides a new idea for the safe and efficient operation of the compressor and the prevention of fault diagnosis.