A Novel Integrated Optical Fiber Sensor For Temperature,Pressure And Flow Measurement

Pipe is a kind of special equipment to transport fluid under certain temperature and pressure and flow rate.It is widely used in petroleum,chemical,metallurgy,electricity industry and public life,such as city gas and heating system.Temperature,pressure and flow rate are three important parameters of fluid pipeline structure.The accurate measurement of the three parameters is important to guarantee the safety and efficiency of production.However,there are various types of sensors to measure only one of the three parameters,and a little sensors to measure the three parameters simultaneously.At the same time,traditional electrical sensors are easily to produce spark,and it is not suitable to measure the flammable and explosive fluid.Optical fiber sensor was developed as a new type of sensors in the mid-70s.Due to using the light as the carrier of sensitive information and using the optical fiber as the transmission medium of sensitive information,optical fiber sensor has the advantage of intrinsic safety.Fiber Bragg grating(FBG)is one of the mature optical fiber sensor with mature craftsmanship and low price.The thesis was focused on the three parameters of temperature,pressure and flow rate and used FBG as the central sensitive component.The structure design,theoretical analysis and experimental study have been carried out.The thesis was intended to design the integrated sensor for practical temperature,pressure and flow rate measurement.The main contents of the thesis were listed as follows:Firstly,the temperature,pressure and flow rate sensors based on FBG at home and abroad were introduced.The merit and demerit of various kinds of FBG sensors proposed by predecessor were summarized.Secondly,the basic sensing principle of FBG was analyzed,including temperature,strain measuring principle and cross sensitivity problem.Moreover,the existing package options of FBG was summarized with the consideration of FBG's fragility.Thirdly,the structure of the integrated sensor was proposed.The hollow cylinder cantilever and thin-walled cylinder was used to make the temperature,pressure and flow rate of fluid converted to the wavelength signal of FBG.The temperature-strain cross sensitivity problem was solved by differential measurement method.The theoretical model of integrated sensor was established.The parameters of the structure was preliminarily confirmed by finite element emulation analysis with the software of COMSOL Multiphysics.Fourth,the integrated sensor was fabricated and the calibration experiment system was established.The primary calibration experiment was carried out.The structure parameters and package options was optimized with the analysis of the primary experiment results.Then,the integrated sensor was re-fabricated and the parameters of the new sensor was obtained with the calibration results.The upper computer interface was written and the temperature,pressure and flow rate accuracy of the integrated sensor were tested.The proposed integrated optical fiber sensor has simple structure,tiny volume for temperature,pressure and flow rate measurement.It is convenient to be installed and has wide application prospect.The measurement range of temperature is 15??95? and the accuracy is ±1?.The measurement range of pressure is 0MPa?10MPa and the accuracy is 0.17%.The measurement range of flow rate is 3.6m3/h?18.5m3/h and the accuracy is 0.671%.