基于声弛豫吸收谱线峰值点的气体传感技术研究

发布时间：2019-04-18 10:38

【摘要】：气体传感技术在工业过程控制、环境污染治理、化工石油等领域有着重要的地位。基于超声特性的气体传感技术具有可实时检测、快速响应、结构简单及工作稳定等突出的优势,因此在近几年成为最有潜力的气体传感技术之一。设计制造可实时定性定量检测未知气体的智能超声波传感器,其先决条件是找到适合实际应用的气体超声参量,并基于该参量建立探测理论模型。本文首先对超声气体传感技术应用背景、研究现状进行了介绍,并分析了超声气体传感技术现阶段所存在的问题,然后从以下三个方面开展研究工作：第一,传统的超声气体传感技术主要依赖于整条声弛豫吸收谱线,通过观察谱线的变化来进行气体实时的监测。针对实际探测中整条声弛豫吸收谱线很难获得的问题,引入了声弛豫吸收谱线峰值点这一新的探测参量。基于声弛豫吸收谱线峰值点坐标可以由两个频率点处声速值和声吸收系数值恢复这一基本物理事实,给出了基于谱线峰值点坐标定位的气体探测方法。该方法将环境温度和气体浓度作为一组二维参量,构建了混合气体的有效弛豫区域,通过两点探测方法,将测得的实验值定位到有效弛豫区域中,即可得到未知气体组分和浓度信息。第二,当混合气体中同时存在两种强弛豫特性的气体时,解耦合模型是无法准确预测混合气体声弛豫吸收谱线峰值点的,这也造成了有效弛豫区域预测的不准确性。本文对解耦合模型做了进一步的拓展,将多个解耦合后的单一弛豫时间再次耦合到一起计算得到混合气体的总弛豫时间。耦合弛豫时间模型的提出,避免了解耦合模型错误地将第一弛豫时间作为总弛豫时间计算峰值点坐标,所预测得到的理论峰值点结果与实验数据更为吻合。第三,本文将耦合弛豫时间理论应用到基于峰值点探测方法中,给出了如何构建混合气体的有效弛豫区域,然后基于二氧化碳-氮气和甲烷-氮气中的仿真实验结果,验证了耦合弛豫时间理论模型可有效取代解耦合模型进行未知气体探测区域的构造。此外,对于同时存在两种强弛豫过程的混合气体,如二氧化碳-甲烷混合气体,本文所提出的耦合弛豫时间理论模型预测得到的峰值点坐标比解耦合模型的预测结果更符合实际中两点探测方法。并结合空气中一氧化碳气体探测和低品质天然气探测这两个实际例子讨论了本文提出的峰值点坐标定位方法在实际气体探测领域中的应用。
[Abstract]:Gas sensing technology plays an important role in industrial process control, environmental pollution control, chemical petroleum and other fields. Gas sensing technology based on ultrasonic characteristics has many outstanding advantages, such as real-time detection, fast response, simple structure and stable operation, so it has become one of the most potential gas sensing technologies in recent years. An intelligent ultrasonic sensor for real-time qualitative and quantitative detection of unknown gases is designed and manufactured. The precondition of the sensor is to find the gas ultrasonic parameters suitable for practical application and to establish the detection theoretical model based on the parameters. In this paper, the application background and research status of ultrasonic gas sensing technology are introduced firstly, and the existing problems of ultrasonic gas sensing technology are analyzed, then the research work is carried out from the following three aspects: first, The traditional ultrasonic gas sensing technology mainly depends on the whole acoustic relaxation absorption spectrum. The real-time monitoring of the gas is carried out by observing the change of the spectral line. In order to solve the problem that the whole acoustic relaxation absorption spectrum line is difficult to obtain in practical detection, a new detection parameter, the peak point of the sound relaxation absorption spectrum line, is introduced. Based on the basic physical fact that acoustic relaxation absorption line peak point coordinates can be recovered from sound velocity and acoustic absorption coefficient values at two frequency points, a gas detection method based on spectral line peak point coordinates is presented. In this method, the ambient temperature and gas concentration are regarded as a group of two-dimensional parameters, and the effective relaxation region of the mixture is constructed. The experimental values are located in the effective relaxation region by two-point detection method. The unknown gas composition and concentration information can be obtained. Second, when there are two kinds of gas with strong relaxation characteristics in the mixture gas, the decoupling model can not accurately predict the peak point of the acoustic relaxation absorption line of the mixture gas, which also results in the inaccuracy of the prediction of the effective relaxation region. In this paper, the decoupling model is further extended and the total relaxation time of the mixed gas is calculated by coupling the single relaxation time of several decoupled gases together again. The coupling relaxation time model is proposed to avoid taking the first relaxation time as the peak point coordinate of the total relaxation time. The predicted theoretical peak point results are more consistent with the experimental data. Thirdly, the coupling relaxation time theory is applied to the peak-point detection method, and how to construct the effective relaxation region of mixed gases is given, and then based on the simulation results of carbon dioxide-nitrogen and methane-nitrogen. It is verified that the coupled relaxation time model can effectively replace the decoupling model for the construction of unknown gas detection regions. In addition, for gas mixtures that have two strong relaxation processes at the same time, such as carbon dioxide-methane mixtures, The predicted peak coordinates of the coupling relaxation time theoretical model proposed in this paper are more consistent with the actual two-point detection method than the predicted results of the coupled relaxation time model. Combined with the practical examples of carbon monoxide gas detection in air and low quality natural gas detection, the application of the proposed method of peak point coordinate location in the field of practical gas detection is discussed in this paper.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP212

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