Boiler Smoke Temperature Online Monitoring Technology Research Based On Fiber Bragg Grating

Boiler exhaust smoke temperature is a very important parameter in the operationof coal-fired power plants, but due to the complexity of the flue gas composition, theconditions and strong electromagnetic interference by electrostatic precipitator, thetraditional electrical sensors require additional power, test temperature error is bigger.Fiber Bragg grating sensor for the passive components, the use of wavelengthencoding and measurable parameter, high measurement precision and multiplexingcapability is strong, high temperature resistance, resistance to electromagneticinterference, intrinsically safe is the best choice of the exhaust temperaturemonitoring of power plant boiler.The aim of the research task is that on the basis of Probing into thecharacteristics of FBG to research the demodulation method of fiber grating sensors,to select the most appropriate way of demodulation, designing optical fiber gratingtemperature online monitoring system.Firstly, this paper first explains the theory model of fiber Bragg grating, and thecoupled mode theory and transfer matrix method and fourier analysis method areintroduced, and based on transfer matrix method of optical fiber Bragg gratingreflective spectrum are simulated. Stress, temperature sensing model of fiber Bragggrating, cross sensitivities and encapsulation process are discussed, compared withcommon fiber Bragg grating sensor demodulation technology. Secondly, a universalsensing demodulation system is designed based on fiber F-P tunable filter. Theperformance parameters of the desired optical device in the demodulation system isanalyzed, and focus on the impact of optical fiber F-P tunable filter’s parameters tothe demodulation system’s performance. Photoelectric conversion and amplificationcircuit are designed, four-pass amplification and filter circuit, A/D sensor dataacquisition module and FFP-TF sawtooth scanning circuit voltage signal, throughthe simulation verify the feasibility of the system scheme, general polynomial fitting method is introduced for demodulation algorithm and fast phase correlationalgorithm, and the fast phase correlation algorithm is improved, and improved theprecision of the demodulation. The PC monitoring software is developed by VC++software, to realize the graphical display of the monitoring data and online real-timemonitoring. Finally has carried on the experiment and the temperature measurementexperiment temperature sensing properties, combined with the experimental data ofthree peak algorithm comparison, proved a cubic polynomial fitting method, therelative error of the smallest, the improved fast phase correlation algorithm stabilityis best.