Research On Flow And Temperature Compound Sensing Based On Fiber Bragg Grating

The monitoring of flow and temperature occupies a pivotal position in modern industrial production,and is an important measurement parameter in scientific research and production processes.Due to the limitation of principle and structure,traditional flowmeters have disadvantages such as large measurement errors,susceptibility to electromagnetic interference,and single measurement parameters.As a new type of sensing element,fiber Bragg grating is widely used in measurement field because of its small size,fast response,anti-electromagnetic interference and other advantages.Based on this,this paper carried out the research on the flow and temperature compound sensor based on fiber Bragg grating.The main research contents of this paper are as follows:1)Based on fiber Bragg grating coupled mode theory,elasticity theory and material mechanics theory,a fiber Bragg grating sensing model is established;the spectral characteristics and sensing mechanism of fiber Bragg grating are studied,and the cross-sensitivity characteristics of fiber Bragg grating are analyzed.Bragg grating strain-temperature composite sensing mechanism;a theoretical model of sensing under polymer encapsulation was established,revealing the wavelength drift of the sensing grating and the mapping law of measured parameters,combined with the principle of flow measurement,a fiber Bragg grating-based flow-temperature composite transmission was proposed.Sensation mechanism.2)The existing dual-fiber Bragg grating flowmeter mostly calculates the change of environmental parameters through the wavelength difference of two FBGs,which causes the position of the FBG to be pasted and the loss during the transmission process will have an impact on the measurement accuracy.Question,this article comprehensively analyzes the influence of fluid characteristics and packaging methods on the wavelength drift of the fiber Bragg grating,establishes a sensor unit model,analyzes the FBG packaging technology,designs a composite sensor structure;studies the FBG sensitivity enhancement mechanism,selects packaging materials,Design the sensor polymer packaging method.3)The simulation experiment of flow and temperature composite sensing based on fiber Bragg grating was carried out.The experiment was carried out with a combination of finite element simulation and numerical analysis.The experimental results showed that the temperature and the wavelength drift of FBG are in a good linear relationship,and the sensitivity of the two FBGs to temperature is basically the same,which is 13.8pm/℃.It shows that in the same temperature field,when the temperature change is the same,the wavelength change of the FBG is also the same;at a constant temperature,the center wavelength of FBG1 remains unchanged,that is,FBG1 is not affected by strain,which provides a good precondition for temperature compensation.After FBG1 is used for temperature compensation of FBG2,the drift of its center wavelength has a quadratic relationship with the fluid flow rate.4)Build a flow temperature composite sensor experimental system platform;carry out temperature and flow composite sensing experiments,the experimental results show that the temperature and wavelength drift are in a linear relationship,the linearity is above 99%,and the sensor’s temperature resolution is 0.04℃,the temperature measurement error is 1.8%,the flow resolution is 0.33m³/h,and the flow measurement error is 2%.A decoupling method of FBG flow and temperature composite sensor based on particle swarm algorithm is proposed,and the designed particle swarm algorithm is used to study the flow and temperature decoupling of experimental data.The research results show that the sensor is at 3m³/h after decoupling.Within the range of 3m³/h～8m³/h,the maximum error of flow is 0.014m³/h,the maximum error of temperature is 0.021℃,the error of flow measurement is 0.28%,the error of temperature measurement is 1.5%,and the mean square error of flow is1.16×10^-4m³/h,The temperature mean square error is 1.53×10^-4℃.After comparing the performance with the BP neural network algorithm,the result shows that the particle swarm algorithm used has a good decoupling effect and effectively improves the measurement accuracy of the sensor.In summary,this paper has carried out the research on the flow and temperature compound sensor based on fiber Bragg grating.First,combining the fiber Bragg grating sensing theory and the flow-temperature composite sensing theory,the flow-temperature composite sensing mechanism based on the fiber Bragg grating is studied.Secondly,a composite fiber Bragg grating flow and temperature sensor with an integrated target structure with a hollow cylindrical cantilever beam is designed.Thirdly,using the method of combining finite element simulation and numerical analysis,the designed composite sensor is studied on the flow temperature simulation experiment.Finally,a flow temperature experimental system platform was built,temperature and flow composite sensing experiments were carried out,and a FBG flow temperature composite sensing decoupling method based on particle swarm algorithm was proposed.The designed particle swarm algorithm was used to analyze the experimental data.After researching the decoupling of flow and temperature,and comparing the performance with the BP neural network algorithm,the results show that the decoupling effect of the adopted particle swarm algorithm is good,which has important practical significance for improving the measurement accuracy of the sensor.