Research On High Sensitivity Optical Fiber Flow Sensor Based On FBG

Flow measurement plays an important role in today's industrial production.The harsh measurement environment during flow measurement can affect the performance and even damage the traditional flow sensors and measuring instruments.And in the flow measurement,other parameters are often measured at the same time,which will result in dense measurement points and complicated test systems.Today,Optical fiber sensing flow measurement method has become an important direction of current research because of its small size,light weight,anti-electromagnetic interference,corrosion resistance,high sensitivity,fast measurement speed,large information capacity,strong adaptability and easy series multiplexing.However,the current fiber grating flow sensor used for flow measurement often has problems such as low measurement sensitivity and relatively complicated overall structure,which greatly limits the application of optical fiber sensing technology in the field of flow detection.Therefore,it is very important to design a fiber grating flow sensor with simple structure and high measurement sensitivity.In this paper,the fiber-optic sensing theory is combined with the traditional flow measurement method,and two kinds of tube-wrapped fiber grating flow sensors are developed,which can simultaneously measure the fluid flow rate and temperature,and have high measurement sensitivity.The main research work and achievements of this thesis are as follows:Firstly,by comparing the advantages and disadvantages of the existing fiber grating flow sensor,a design scheme of a novel fiber grating target flow sensor is proposed,which has extremely high measurement sensitivity.Secondly,the numerical modeling and analysis of the new fiber grating target flow sensor is carried out,and the reason why the sensor has high sensitivity is theoretically analyzed.The finite element simulation of the sensor was carried out by ANSYS analysis.The results of ANSYS analysis were similar to those of numerical simulation,which confirmed the rationality of the design of the sensor.At the same time,the initial design of the fiber grating target flow sensor was optimized and improved.The improved sensor can greatly reduce the loss of optical transmission and facilitate large-scale series multiplexing of sensors.The improved flow sensor sensitivity was analyzed using numerical modeling and analyzed by ANSYS software.Finally,the fabrication process of each of the curved and linear flow sensors is discussed.In particular,the fabrication of the fiber grating base and the bonding process of the grating on the base are described in detail.A simulated flow detection test device was built,and two flow sensors were tested separately.By fitting the test data,the relationship between the grating center wavelength shift and the water flow rate in the two sensors is obtained.The curved flow sensor experiment can measure the minimum flow rate of 0.1681mL/s,the curve of the center wavelength shift and flow after fitting is: ? = 0.9264-0.9233 + 4.8466.The linear flow sensor experiment can measure the minimum flow rate of 0.7951mL/s,and the fitted curve is: ? =0.3222-0.2845 + 2.2583.This is basically consistent with the simulation results.