Research On Optical Fiber Force Sensing System For Wear Test Of Heat Transfer Tube

The safe operation of nuclear power plant is of great significance for production and life.Once nuclear leakage and other accidents occur,the first thing to bear the brunt is personal safety,which also has a serious impact on the surrounding ecological environment and industrial production.As the hub of primary and secondary circuit in nuclear power plant,it is very important to ensure the steam generator in normal working condition.As an important part of steam generator,the heat transfer tube and the support structure will have fretting wear under the action of flow induced vibration,and the heat transfer tube bundle will collide with each other,both of which will cause the wear failure of the heat transfer tube.To analyze and evaluate these two effects,it is necessary to measure the friction force between the heat transfer tube and the supporting structure and the impact force between the heat transfer tube and the tube bundle,and the wear condition of the heat transfer tube can be obtained by measuring these two forces.The working environment of the heat transfer tube is 350℃ and 20 MPa high temperature water environment.Because the fiber Fabry-Perot sensor has the advantages of high temperature and high pressure resistance,strong electromagnetic interference resistance,small volume,good water resistance and high sensitivity,it can be used for the stress measurement of heat transfer tube wear.Based on the principle of Fabry-Perot multi beam interference,two kinds of optical fiber force sensors are designed to measure the friction force and impact force when the heat transfer tube is worn.The optical characteristics of the two force sensors are analyzed,and the optical failure model is established;The mechanical characteristics of the two kinds of force sensors are analyzed,and the mechanical model and the force transfer model are established,which provides a theoretical basis for the parameter design and the determination of the structure size of the force sensor;Two kinds of fiber Fabry-Perot force sensors are designed according to the measurement conditions of heat transfer tube wear experiment,and the assembly of the two kinds of force sensors is completed;The hardware circuit of the force sensing system is designed,including the design of power supply,signal conditioning and data communication circuit.Gaussian fitting algorithm is implemented in DSP(Digital Signal Processing)to improve the demodulation accuracy.In this thesis,the performance of two kinds of fiber Fabry-Perot force sensors and their demodulation system are tested.The results show that the demodulation rate of the fiber Fabry-Perot force sensor system can reach 1KHz,the range of the fiber Fabry-Perot force sensor is 4.7N ～ 2.775 KN,and the sensitivity is 3.1nm/N at 350℃;The optical fiber Fabry-Perot impact force sensor has a range of 0.208 N ～ 2.274 KN and a sensitivity of 70.35nm/N.The optical fiber Fabry-Perot force sensing system designed in this thesis has good stability,and can be used to measure the friction and impact force in the heat transfer tube wear experiment.