基于阻抗相消的新型C~4D传感器设计及其应用

发布时间：2018-06-15 03:32

本文选题：C~4D + 阻抗相消　；参考：《浙江大学》2016年硕士论文

【摘要】：流体广泛存在于石油、化工、冶金、能源、食品、制药等众多工业生产过程中。电导率是流体的一项重要基本物理参数,它的测量具有重要的工业应用价值。然而,目前工业生产过程中广泛应用的电导率测量技术是接触式测量,存在着电极极化效应以及电化学腐蚀反应等问题,其应用受到一定限制。电容耦合式非接触电导检测(Capacitively Coupled Contactless Conductivity Detection,简写为C4D)技术是一种新型电导率测量技术,可有效克服接触式电导率测量技术所存在的问题。然而,耦合电容的存在极大地限制了现有C4D传感器的测量范围、测量分辨率以及测量灵敏度。为克服耦合电容的影响,研究者们提出了诸如高频法、电压差法、谐振法以及PSD (Phase Sensitive Demodulation)法等方法。但这些方法还存在着实现复杂或激励频率不可调等不足,因此仍需寻求新的克服耦合电容影响的思路和方法。本文基于阻抗相消原理,设计了一种新型C4D传感器,以克服传统C4D传感器中耦合电容的影响,并将其应用于流体电导率测量和气液两相流参数测量当中。本文的主要工作和创新点概括如下：(1)提出了一种基于阻抗相消的新型C4D测量方法。该方法通过构建容性阻抗,将其阻抗信号与耦合电容的阻抗信号进行差分,从而消除耦合电容的不利影响。提高了C4D传感器的测量分辨率和适用范围,并从原理上降低了C4D传感器对激励频率的要求。(2)设计研发了阻抗相消模块,该模块由阻抗提取模块、容性阻抗模块、差分模块三个子模块构成,可有效地消除C4D传感器测量通路中耦合电容的影响。(3)设计了一种基于阻抗相消的新型C4D传感器,研制了由阻抗相消模块、传感元件、信号处理电路以及数据采集模块组成的硬件系统,编写了相应的软件程序。(4)在1.8 mm、3.3 mm、5.4 mm和7.6 mm四种内径的管道中对新型C4D传感器进行了电导率测量、频率特性和输出特性对比实验研究。实验结果表明：所设计的新型C4D传感器是成功的,其电导率测量性能令人满意,电导率测量值与商业型接触式电导率仪的参考值相比,最大相对偏差小于5%；新型C4D传感器的激励频率可在150 kHz - 400 kHz范围内调节,整体输出特性一致,减小了C4D传感器对激励频率的依赖；新型C4D传感器有效克服了耦合电容对测量造成的不利影响,具有较好的测量灵敏度。(5)将基于阻抗相消的新型C4D传感器应用于气液两相流参数检测,搭建了一套气液两相流参数测量系统。在内径为3.3 mm和3.8 mm的管道内进行了初步的实验研究,获取了气液两相流在不同流型下的电导率测量信号,分析了不同流型下的电导率信号特征,并对典型的段塞流/泡状流进行了气液两相流相关流速测量实验。实验结果表明：所设计的新型C4D传感器的输出信号能够反映气液两相流不同流型下的流动特性,可应用于气液两相流的参数测量。总体而言,本研究提出的基于阻抗相消的新型C4D测量方法是可行的。该方法可克服C4D传感器中耦合电容的不利影响,可有效提高C4D传感器的测量分辨率和适用范围,减小C4D传感器对激励频率的依赖。所设计的基于阻抗相消的新型C4D传感器是成功的。该新型C4D传感器具有良好的测量性能,可应用于流体电导率测量和气液两相流参数测量。
[Abstract]:Fluid is widely used in many industrial processes, such as petroleum, chemical, metallurgical, energy, food, and pharmaceuticals. Electrical conductivity is an important basic physical parameter of the fluid. Its measurement has important industrial application value. However, the electrical conductivity measurement technology widely used in the process of industrial production is contact measurement, and there is an electrode pole. The application of chemical effect and electrochemical corrosion reaction is limited. The capacitive coupling non-contact conductivity detection (Capacitively Coupled Contactless Conductivity Detection, abbreviated C4D) technology is a new electrical conductivity measurement technology, which can effectively overcome the problems existing in the contact conductivity measurement technology. In order to overcome the influence of coupling capacitance, researchers have proposed methods such as high frequency method, voltage difference method, resonance method and PSD (Phase Sensitive Demodulation) method to overcome the influence of coupling capacitance. It is still necessary to seek new ideas and methods to overcome the influence of coupling capacitance. Based on the principle of impedance cancellation, a new type of C4D sensor is designed to overcome the influence of the coupling capacitance in the traditional C4D sensor and is applied to the measurement of the conductivity of the fluid and the measurement of the parameters of the gas-liquid two phase flow. The work and innovation points are summarized as follows: (1) a new C4D measurement method based on impedance cancellation is proposed. By constructing the capacitive impedance, the impedance signal is separated from the impedance signal of the coupled capacitance, thus eliminating the adverse effect of the coupling capacitance. The measurement resolution and the scope of application of the C4D sensor are improved and the principle is obtained from the principle. The requirements of the C4D sensor on the excitation frequency are reduced. (2) the impedance cancellation module is designed and developed. The module consists of the impedance extraction module, the capacitive impedance module and the differential module three sub modules, which can effectively eliminate the influence of the coupling capacitance in the measurement path of the C4D sensor. (3) a new type of C4D sensor based on impedance cancellation is designed. The hardware system composed of impedance cancellation module, sensing element, signal processing circuit and data acquisition module is made, and the corresponding software program is written. (4) the conductivity measurement, frequency characteristic and output characteristic comparison experiment of the new C4D sensor are carried out in the 1.8 mm, 3.3 mm, 5.4 mm and 7.6 mm internal diameter pipes. Experimental results are compared. The results show that the new C4D sensor is successful and its conductivity measurement performance is satisfactory. Compared with the reference value of commercial type contact conductivity meter, the maximum relative deviation is less than 5%. The exciting frequency of the new C4D sensor can be adjusted in the 150 kHz to 400 kHz enclosure, the overall output characteristic is consistent, and the C4D is reduced. The sensor is dependent on the excitation frequency; the new C4D sensor effectively overcomes the adverse effect of the coupling capacitance on the measurement, and has a better measurement sensitivity. (5) a new C4D sensor based on the impedance cancellation is applied to the gas liquid two phase flow parameters detection, and a set of gas liquid two phase flow parameters measurement system is set up. The internal diameter is 3.3 mm and 3.8. A preliminary experimental study was carried out in the MM pipeline. The conductivity signal of the gas-liquid two phase flow under different flow patterns was obtained. The characteristics of the conductivity signal under different flow patterns were analyzed. A typical slug / bubbly flow was measured by the measurement of the flow velocity of the gas-liquid two phase flow. The results showed that the new C4D sensor was designed. The output signal can reflect the flow characteristics of the gas-liquid two phase flow, and can be applied to the measurement of the parameters of the gas-liquid two phase flow. In general, the new C4D measurement method based on the impedance cancellation proposed in this study is feasible. This method can overcome the non profit effect of the coupling capacitance in the C4D sensor and can effectively improve the measurement of the C4D sensor. The discrimination rate and the scope of application reduce the dependence of the C4D sensor on the excitation frequency. The new type of C4D sensor based on impedance cancellation is successful. The new C4D sensor has good measurement performance and can be applied to the measurement of fluid conductivity and gas liquid two phase flow parameters.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP212

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