QCM对颗粒物吸附特性研究及硬件测试平台设计

发布时间：2018-04-10 18:30

本文选题：QCM + 质量浓度　；参考：《太原理工大学》2017年硕士论文

【摘要】：随着国家对固定污染源颗粒物浓度监测的要求日益严格,开发针对低浓度排放、可实时在线测量的颗粒物监测系统已势在必行。QCM是一种结构简单、敏感度高、测量精度能达到纳克级的质量传感器,因此,本设计结合QCM压电效应和高压静电除尘原理,研究了一种高精度、能连续监测低浓度环境中颗粒物质量浓度的方法及装置。论文主要工作和结论如下:(1)高压静电室设计。采用QCM阵列的方式提高QCM对颗粒物吸附率和系统的可靠性,设计了一个两级串联的高压静电检测室。清洗、烘干都可在装置的内部进行,且还可以施加不同强度的电压以及调整探针头与晶振片的距离;(2)硬件电路设计。设计使QCM稳定振荡、带负载能力强的振荡电路,采用电容补偿的方法,消除并联电容对谐振频率的影响,同时加入差分电路,使晶体对电路的振动频率控制作用得到加强;使用巴特沃斯带通滤波器,消除通带以外杂波对信号造成的干扰;通过自动增益电路形成反馈网络,实现控制电路稳定输出;系统额外增加一参比晶振,接入两个独立的振荡电路,削弱非质量因素造成的误差;选用FPGA对石英晶体的谐振频率进行测量,并通过串口将数据发送至单片机,完成数据的处理与显示;(3)研究不同工况下QCM对颗粒物吸附率的影响,所得结论如下:在相同极距下,电压越高,QCM对颗粒物的吸附率越大;QCM对颗粒物的吸附率随着距离的增加先升高后降低;QCM对颗粒物的吸附率随流速的减小而增加;在同一电压下,正电晕的颗粒物吸附率要比负电晕高;(4)颗粒物发生装置设计。由于实际工况中烟道内气体的浓度不能随实验的需求调节,故自行研发了一套颗粒物发生装置,实现了配置的气体浓度低至10mg/m~3。研究专门针对小粒径固体粉料输送的需求,设计一种沉降式微量给料器,可实现给粉速率小于20mg/min的需求,给粉量的误差在±4%以内,且给粉速率越快误差越小。
[Abstract]:With the increasingly strict requirements for the concentration monitoring of particulate matter from stationary pollution sources, it is imperative to develop a monitoring system for particulate matter which can be measured in real time and online for low concentration emissions. QCM is a kind of simple structure and high sensitivity.The precision of the mass sensor can reach the level of ng. Therefore, combining with the QCM piezoelectric effect and the principle of high voltage electrostatic precipitation, a high precision method and a device for continuously monitoring the mass concentration of particulate matter in low concentration environment are studied in this paper.The main work and conclusions are as follows: 1) Design of high voltage electrostatic chamber.By using QCM array to improve the adsorption rate of QCM to particles and the reliability of the system, a two-stage series high voltage electrostatic detection chamber was designed.The cleaning and drying can be carried out inside the device, and the voltage of different strength can be applied and the distance between the probe and the wafer can be adjusted.The oscillation circuit with strong load capacity and stable oscillation of QCM is designed. The effect of parallel capacitance on resonant frequency is eliminated by using capacitor compensation method. At the same time, differential circuit is added to strengthen the control effect of crystal on the vibration frequency of the circuit.Using the Butterworth band-pass filter to eliminate the interference caused by the clutter outside the passband, to form a feedback network through the automatic gain circuit, to realize the stable output of the control circuit, and to add an extra reference crystal oscillator to the system,Two independent oscillating circuits are connected to reduce the error caused by non-quality factors. The resonant frequency of quartz crystal is measured by FPGA, and the data is sent to the single chip microcomputer through serial port.The effect of QCM on the adsorption rate of particulate matter under different working conditions is studied. The results are as follows: at the same polar distance,The higher the voltage, the greater the adsorption rate of QCM to particles. The adsorption rate of QCM on particles increases first with the increase of distance and then decreases with the decrease of flow rate. At the same voltage, the adsorption rate of QCM on particles increases with the decrease of flow rate.The particle adsorption rate of positive corona is higher than that of negative corona.Because the concentration of gas in flue can not be adjusted according to the demand of experiment, a set of particle generator is developed, and the gas concentration is as low as 10 mg / m ~ (3).In order to meet the demand of small particle size solid powder transportation, a kind of settling micro feeder is designed, which can realize the requirement that the powder feeding rate is less than 20mg/min, the error of powder feeding is less than 卤4%, and the error of powder feeding rate is smaller than that of 20mg/min.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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