本文選題：甲烷氣體 + 溫度影響　； 參考：《山東大學(xué)》2017年碩士論文

【摘要】：氣體檢測技術(shù)應(yīng)用于多個領(lǐng)域。目前的氣體檢測技術(shù)有多種手段,激光光譜方法由于其精度與實時性等優(yōu)點成為發(fā)展的方向。然而,當(dāng)被測氣體的溫度發(fā)生大范圍改變時,被測氣體的物理性質(zhì)也隨之發(fā)生改變,導(dǎo)致激光光譜檢測方法的測量結(jié)果不準(zhǔn)確。針對這個問題,本文提出了一種依賴二次諧波信號并且不需測量被測氣體實際溫度的溫度補償算法。本文分別通過理論分析、算法建模以及驗證測試的方法進行課題研究。首先建模分析溫度對甲烷檢測的影響。建立三種吸收線型的模型,并比較選擇適合課題研究內(nèi)容的吸收線型為Lorenz Profile。然后,分別從氣體分子數(shù)密度、線寬、線強三個方面分析溫度對吸收系數(shù)產(chǎn)生的影響,以及諧波檢測中溫度對二次諧波信號產(chǎn)生的影響。當(dāng)溫度由-30攝氏度變化到120攝氏度,氣體分子數(shù)密度數(shù)值減小了 38.6%,線強減小了 45%,線寬減小了 29.7%,吸收系數(shù)減小了 51.7%,二次諧波信號中心頻率點的數(shù)值減小了 51.6%。目前溫度影響的解決辦法一般采取經(jīng)驗公式或者理論公式方法進行補償校正,但前提是獲取到被測氣體的溫度�；蛘�,同時對兩條吸收譜線進行測試,同時獲得被測氣體溫度與濃度。本文提出一種補償溫度影響的新方法。二次諧波信號包含了被測氣體的濃度信息,選取二次諧波中兩個頻率點對應(yīng)數(shù)據(jù)的差值進行濃度的反演計算,采取這種方法,計算結(jié)果對溫度的依賴性比較小。在算法模型中,以調(diào)制幅度為1為例,當(dāng)溫度由-30攝氏度變化到120攝氏度時,用二次諧波信號中心頻率點的數(shù)值進行濃度反演計算時,相對誤差可達到51.6%;采取本文提出的新方法時,最大值最小值偏差為12.7%,很大程度上減小了測量結(jié)果對于溫度的依賴性。將算法進行驗證測試,采集不同溫度下相同濃度甲烷氣體的濃度數(shù)據(jù),測量結(jié)果與理論模型的分析結(jié)果基本一致。在這些數(shù)據(jù)的基礎(chǔ)上做補償算法的驗證,使溫度對測量結(jié)果的影響減小了 50%,有一定的改善效果。但理論結(jié)果與實驗結(jié)果仍然存在一定的差距,分析是激光器性能以及環(huán)境噪聲的原因。
[Abstract]:Gas detection technology is applied in many fields. At present, there are many methods for gas detection, and laser spectrum method has become the direction of development because of its accuracy and real-time. However, when the temperature of the gas is changed in a wide range, the physical properties of the gas are also changed, which leads to the inaccurate measurement results of the laser spectrum detection method. To solve this problem, this paper presents a temperature compensation algorithm which depends on the second harmonic signal and does not need to measure the actual temperature of the gas being measured. In this paper, the methods of theoretical analysis, algorithm modeling and verification test are studied. Firstly, the influence of temperature on methane detection is analyzed. Three kinds of absorption line models are established, and Lorenz profile is chosen as the suitable absorption line. Then, the influence of temperature on absorption coefficient is analyzed from three aspects of gas molecular number density, line width and line strength, as well as the influence of temperature on second harmonic signal in harmonic detection. When the temperature changes from -30 degrees Celsius to 120 degrees Celsius, the gas molecular number density value decreases by 38.6, the line strength decreases by 45, the linewidth decreases by 29.7m, the absorption coefficient decreases by 51.7 percent, and the value of the center frequency of the second harmonic signal decreases by 51.6. At present, the solutions to the influence of temperature are usually compensated by empirical formula or theoretical formula, but only if the temperature of the measured gas is obtained. Alternatively, two absorption lines are measured at the same time, and the gas temperature and concentration are obtained simultaneously. A new method for compensating the influence of temperature is presented in this paper. The second harmonic signal contains the concentration information of the gas to be measured. The difference between the two frequency points in the second harmonic wave is selected to carry out the inversion calculation of the concentration. By adopting this method, the temperature dependence of the calculation results is relatively small. In the algorithm model, taking the modulation amplitude of 1 as an example, when the temperature changes from -30 degrees Celsius to 120 degrees Celsius, the concentration inversion calculation is carried out with the numerical value of the center frequency point of the second harmonic signal. The relative error can reach 51.6, and the maximum and minimum deviation is 12.7, which greatly reduces the dependence of measurement results on temperature. The algorithm is validated and tested, and the data of methane concentration of the same concentration at different temperatures are collected. The measured results are in good agreement with the analytical results of the theoretical model. On the basis of these data, the effect of temperature on the measurement results is reduced by 50%, and the effect is improved to a certain extent. However, there is still a gap between the theoretical results and the experimental results. The analysis is the reason of the laser performance and ambient noise.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O433;TN24

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