Research On Measuring Method Of Axial Vibration Of Steam Turbine Shrouded Blisk

Steam turbines have been widely applied to thermal power,metallurgy,chemistry,marine power.As the key part of steam turbine,shrouded blisk is easy to vibrate under the influence of variable working conditions and harsh working environment,which leads to fatigue failure.Therefore,it is very important to realize on-line vibration monitoring of shrouded blisk.However,the circumferential energy of shrouded blisk is consumed due to collision and friction between the shrouded blisk and the main form of vibration is axial vibration.It is difficult to measure the axial vibration of shrouded blisk of steam turbine which working in steam medium by using radially mounted sensors.At the same time,the vibration measurement results are easily affected by environmental factors such as temperature,gap and so on.In order to solve the above problems,this paper proposes an eddy current sensor monitoring method for axial vibration of turbine shrouded blisk which integrates real-time gap compensation.completes software and hardware design of the measurement system,and carries out static calibration experiment,dynamic experiment and error analysis.The main research contents are as follows:(1)Aiming at the high reliability,high precision,high frequency response and noninvasive measurement requirements of the axial vibration measurement of the turbine shrouded blisk,the vibration form and characteristics of the turbine shrouded blisk are introduced,and the commonly used axial vibration measurement sensors are analyzed and compared.The measurement errors introduced by the parameters such as temperature and clearance are analyzed,and a general scheme for realizing the axial vibration measurement system of the turbine shrouded blisk is proposed.(2)An eddy current sensor monitoring method for axial vibration of turbine shrouded blisk with real-time compensation is proposed.According to the features such as protrusions and cracks in the crown of the blade shroud,this method adopts the variable area eddy current sensor which is radially mounted,obtains the vibration amplitude and frequency by using the analytical algorithm of axial vibration parameters based on short-time Fourier transform.According to the gap measurement results,realtime compensation is carried out to realize high-precision on-line monitoring of axial vibration of turbine shrouded blisk.(3)The structure design of eddy current sensor with low noise and corrosion resistance is completed.The program of real-time acquisition,processing and transmission of vibration data based on FPGA is designed,and the PC software based on Visual Studio platform is developed.Combined with the existing signal conditioning module,the axial vibration measurement system of the turbine shrouded blisk was built,which realized the functions of online monitoring and storage of vibration frequency and amplitude data,system parameter configuration and data offline analysis.(4)An eddy current sensor calibration device is designed,a static calibration experiment of the eddy current sensor is carried out,and the calibration errors introduced by each degree in the calibration process are analyzed.The axial vibration dynamic measurement experiment of the turbine shrouded blisk was carried out.The experimental results show that the designed system can meet the vibration measurement requirements of the turbine shrouded blisk with a linear velocity of 628m/s,the vibration frequency resolution is 1Hz,and the vibration amplitude measurement uncertainty is 49.1μm.