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Methane Detection Studies Based On Gas In Scattering Media Absorption Spectroscopy

Posted on:2017-09-24Degree:MasterType:Thesis
Country:ChinaCandidate:Y J DingFull Text:PDF
GTID:2348330491462845Subject:Optical Engineering
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Tunable diode laser absorption spectroscopy (TDLAS) is a widely used technology for gas sensing, and it has a great development in methane detection recently. Our research project combines TDLAS with the gas in scattering media absorption spectroscopy (GASMAS), by which the absorption of methane in porous scattering media is investigated.We set up a compact system for methane detection by using an alumina porous ceramic based small gas cell, and a DAQ card based in-out control equipment. Then we use the system to investigate the absorption of methane in porous scattering media.We use a distributed feedback diode laser (DFB) to detect methane, the center wavelength of which is at one of a methane gas absorption peak, i.e.,1653.7 nm at operating temperature of 15? and injection current of 60 mA. We optimize the 2f signal by using sinusoidal modulation wave with amplitude of 75 mV. We also process and analyze the received signal with Fourier transform and Levenberg-Marquardt algorithm (LMA). As a result, a linear correlation of 0.998 between measured and calculated concentration, and a sensitivity of 9.13 ppm with integration time of 120 s is achieved in our measurement system. The time of gas exchange process of our system is about 13 s, which indicates that our measurement system has a good gas exchange dynamics characteristics.
Keywords/Search Tags:tunable diode laser absorption spectroscopy (TDLAS), gas in scattering media absorption spectroscopy (GASMAS), porous scattering media, absorption spectroscopy measurement of methane
PDF Full Text Request
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