Study On Adsorption Characteristics Of Particulate Matter Of QCM And The Design Of Hardware Testing Platform

The requirements of the state for the detection of the concentration of particulate matter in fixed pollution sources are becoming more and more strict,it is imperative to develop a real-time and on-line measurement system for low concentration emissions.QCM is a kind of mass sensor which can reach the accuracy of nanogram,and has a simple structure and high sensitivity.Therefore,in this paper,combined with QCM piezoelectric effect and high voltage electrostatic dust removal principle,a high precision and continuous monitoring method for monitoring the mass concentration of particulate matter in low concentration environment is studied.The major work and conclusions of present paper as follows:(1)The design of high-voltage electrostatic chamber.Using QCM array to improve the adsorption rate of QCM on particles and the reliability of the system.The design of a two series high-voltage electrostatic detection chamber.Cleaning,drying can be carried out inside the device,and can also be applied to different intensity of the voltage and adjust the probe head and the distance between the crystal;(2)The design of Hardware Circuit.Design of a shock circuit,which has a strong load capacity and can make QCM stable shock,The capacitance compensation method is used to eliminate the influence of the static capacitance on the resonant frequency,at the same time,the amplifying circuit is added to control the vibration frequency of the crystal;Using the Butterworth band pass filter to eliminate the interference caused by the clutter;The feedback circuit is formed by the automatic gain circuit to realize the stable output of the control circuit;The system adds a reference crystal oscillator,access to two separate oscillation circuit,weaken the error caused by non quality factors;FPGA is used to measure the resonant frequency of quartz crystal,and the data is sent to the MCU through the serial port to complete the data processing and display;(3)The effect of QCM on the adsorption rate of particulate matter under different working conditions was studied,The conclusions are as follows:At the same distance,The adsorption rate of QCM on particulate matter increased with the increase of voltage;The adsorption rate of QCM on particulate matter increased and then decreased with the increase of the distance;The smaller the gas flow rate,the larger the adsorption rate of particles;At the same voltage,the particle adsorption rate of positive corona is higher than that of negative corona.(4)The design of particle generation device.Due to the inconvenience of extracting smoke,and the concentration of gas can not be adjusted according to the requirement of experiment in real working condition,Therefore,the particle generation device is developed,achieved configuration gas concentrations as low as 10mg/m~3.In order to meet the requirements of small diameter solid powder conveying,a kind of settling micro feeder is designed.the feeder meet the requirements of powder feeding rate less than 20mg/min,the error of powder feeding is less than 4%,and the faster the rate of powder,the smaller the error.