本文關鍵詞：乙炔近紅外吸收光譜理論及檢測技術研究　出處：《安徽大學》2017年碩士論文　論文類型：學位論文

  更多相關文章： 乙炔 可調(diào)諧半導體激光光譜技術 新譜線 長程吸收池技術Savitzky-Golay 二階微分算法

【摘要】：隨著化工工業(yè)的迅速發(fā)展,乙炔已經(jīng)成為化工生產(chǎn)過程中有機合成最重要的原材料。但因其易燃的特性,與空氣混合形成爆炸性混合物,這嚴重威脅化工生產(chǎn)的安全。因此,準確檢測乙炔氣體濃度對保障工業(yè)生產(chǎn)安全具有重要的意義。伴隨激光光譜技術的發(fā)展,可調(diào)諧半導體激光吸收光譜技術(TDLAS)因其高靈敏度、高分辨率、快速響應和無損探測的優(yōu)點已經(jīng)廣泛應用于氣體檢測領域。直接吸收光譜(DAS)作為一種直接的光譜方法,通過檢測分子與激光相互作用時的光強變化量,并結(jié)合郎伯-比爾定律與非線性最小二乘法擬合算法,即可反演出分子的濃度信息。吸收光譜所依賴的HITRAN數(shù)據(jù)庫中的光譜參數(shù)均為理論計算結(jié)果,在實際應用中需要對其進行測量校正,以提高濃度反演的精確度。本文選用工作在近紅外波段的半導體激光器作為光源,對乙炔在1.5μm處泛頻v1+v3吸收帶譜線參數(shù)進行了深入研究,并對部分線強大于10-20cm/molecule強吸收譜線參數(shù)進行了校正,實驗結(jié)果與HITRAN12數(shù)據(jù)庫對比,線強和加寬系數(shù)的相對誤差小于2%;實驗中,發(fā)現(xiàn)6526cm-1和6532 cm-1波段范圍內(nèi),存在大量未被報道且吸收強度相對較弱的新譜線,本文通過結(jié)合長程吸收池技術和多光譜擬合算法,首次系統(tǒng)地研究了該光譜范圍內(nèi)的弱譜線參數(shù)。最終,我們計算了部分已知譜線與22條新譜線線強,并對新譜線的中心位置進行了歸屬,結(jié)果顯示已知弱吸收譜線線強的相對誤差基本小于10%,本文報道的乙炔新譜線參數(shù)將有利于HITRAN數(shù)據(jù)庫的升級。此外,本文結(jié)合長程吸收池技術,搭建了一套痕量乙炔氣體檢測系統(tǒng)。根據(jù)乙炔1.5 μm處v1+v3吸收帶譜線參數(shù)測量結(jié)果,以位于6578.5761 cm-1處的R9e(線強為1.34×10-20 cm/molecule)吸收譜線為目標測量譜線,通過選擇激光器不同的波長掃描模式,利用直接吸收光譜技術(DAS)展開了乙炔濃度的測量研究。在72.44 m的吸收光程下,利用激光器的波長快速掃描功能,該系統(tǒng)實現(xiàn)了信噪比為1 dB時1.8 ppm的探測靈敏度;當使用激光器的波長慢速掃描時,根據(jù)艾倫偏差分析(Allan Variance),在1 s的積分時間內(nèi)實現(xiàn)了 43.6 ppb的探測極限,當積分時間增加至133 s時,該系統(tǒng)的可探測限約為9.6 ppb。為了抑制信號噪聲,論文中首次將Savitzky-Golay(SG)二階微分算法應用于光譜信號處理中,模擬了該微分算法在不同濾波參數(shù)情況下對不同信噪比的模擬光譜信號的降噪效果,模擬與實驗研究表明該微分算法具有很好的濾波效果。進一步用該二階微分算法處理實驗吸收光譜信號,結(jié)果顯示SG二階微分信號的幅值與氣體濃度之間具有良好的線性關系,未來可以將其應用于工業(yè)氣體檢測、大氣環(huán)境監(jiān)測及醫(yī)學氣體檢測等領域。
[Abstract]:With the rapid development of chemical industry, acetylene has become the most important raw material for organic synthesis in the process of chemical production. But because of its flammable characteristics, it is mixed with air to form an explosive mixture, which seriously threatens the safety of chemical production. Therefore, it is of great significance to detect the concentration of acetylene to ensure the safety of industrial production. With the development of laser spectroscopy, tunable diode laser absorption spectroscopy (TDLAS) has been widely applied in gas detection for its advantages of high sensitivity, high resolution, fast response and nondestructive detection. As a direct spectral method, direct absorption spectroscopy (DAS) can detect molecular concentration information by detecting the amount of light intensity interaction between molecules and laser, and combining the fitting algorithm of Bill's law and nonlinear least square algorithm. The spectral parameters in the HITRAN database which are dependent on the absorption spectrum are all theoretical calculation results. In practice, we need to measure and correct them, so as to improve the accuracy of concentration inversion. The work of semiconductor laser in the near infrared region as the light source of acetylene at 1.5 m v1+v3 overtone absorption band spectrum parameters is studied, and the portion of the line more than 10-20cm/molecule strong absorption spectrum parameters are corrected, and the experimental results of HITRAN12 database comparison, relative error and strong line broadening the coefficient is less than 2%; in the experiment, 6526cm-1 and 6532 cm-1 wavelength range, there are a lot of has not been reported and the absorption intensity is relatively weak in this new line, through a combination of long path absorption cell technology and multi spectral fitting algorithm, the first systematic study of the spectral line parameters of weak spectral range. Finally, we calculate the known spectral lines and 22 new spectral line intensities, and the center position of the new lines were assigned. The results showed that the relative error of known weak absorption spectral line intensities of less than 10%, the new acetylene line parameters will help HITRAN database upgrade. In addition, in this paper, a set of trace acetylene gas detection system has been set up with the technology of long range absorption pool. According to the acetylene 1.5 m v1+v3 absorption band spectra line parameters in 6578.5761 cm-1 R9e (line 1.34 * 10-20 cm/molecule) absorption spectrum as the target spectrum measurement, by selecting different laser wavelength scanning mode, using direct absorption spectroscopy (DAS) launched a study on measurement of acetylene concentration. In the optical path of 72.44 m, the laser wavelength scanning function, the system realizes the SNR detection sensitivity of 1.8 ppm 1 dB; when using the laser wavelength scanning slow, according to Alan (Allan Variance), deviation analysis in the integration time of 1 s is achieved in the detection limit of 43.6 ppb when the integration time is increased to 133 s, but the detection limit of the system is about 9.6 ppb. In order to suppress the noise signal, the first Savitzky-Golay (SG) two order differential algorithm is applied to spectral signal processing, simulation of the noise reduction effect of the simulated spectrum signal of the differential algorithm for different signal-to-noise ratio in different filtering parameters under the condition of the simulation and experimental research show that the differential algorithm has a good filtering effect. Further the two order differential algorithm experimental absorption spectrum showed a good linear relationship between the amplitude and the gas concentration SG two order differential signal, the future can be applied to industrial gas detection, environmental monitoring and medical gas detection etc..
【學位授予單位】：安徽大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ221.242;O657.33

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