Design And Implementation Of PM2.5 Calibration Device Based On Gravimetric Method

In recent years,the word"PM2.5"has been mentioned constantly by people.PM2.5 are the kind of fine particulates with the aerodynamic diameter less than or equal to 2.5μm,it can adsorb heavy metals,bacteria,viruses and other harmful substances,then enter the body through the respiratory movement and cause a variety of diseases.In addition,it is one of the main culprits which lead to“smog”.Monitoring PM2.5 instrument is called PM2.5 monitor and its core components is PM2.5 cutter,the function is to carry out the separation of different size particles.PM2.5 cutter cutting quality directly affects the effect of particle separation,determining the mass concentration of PM2.5 are accurate or not.In our country,because PM2.5 monitoring and research are relatively late and lack of corresponding uniform standards,the correction procedures of PM2.5 cutters in different manufactures are not the same,all of these affect The measurement of PM2.5 mass concentration seriously.Therefore,research and development on the PM2.5 cutter calibration device will be key issue of the accurate measurement of PM2.5.However,there were no devices for direct calibration of cutting efficiency of PM2.5 cutter;and existing technical routes of PM2.5 sampler measurement standard device were also more complex,higher cost,and the accuracy was worth discussing.According to these problems,the paper made a careful study of the working principle of PM2.5 cutter and cutter calibration system design,then designed a PM2.5 cutter calibration device with low complexity,low cost,small volume,high precision,and convenient implementation.The main work of this paper is as follows:（1）The core of the calibration device-static tank system was designed by UG（NX Unigraphics）software,including its mechanical dimensions,shapes,materials and interface,etc.Then the simulation software-Fluent was used to simulate the motion trajectory and the residence time of the PM2.5 particles in the static tank,according to these simulation parameters,the architecture design of the static tank would be optimized,which made the calibration result more accurate.（2）In this paper,the temperature and humidity acquisition module,pressure acquisition module,LCD display module,SD memory module,wireless communication module and other hardware and software modules were designed to real-time monitor the temperature,humidity,air pressure and other environmental parameters in the static tank,and provide the data support for error analysis of experimental results.（3）The designed calibration device was tested and verified.According to the calibration experiments,this paper analyzed and obtained the corresponding relationship between the particle size and cutter trapping efficiency,fitted the experiment curve of PM2.5 cutter,and compared with the standard curve of PM2.5cutter.The experimental results showed that:D_{5 0}=2.367μm,σ_g=1.225,meeting the provisions of the U.S.EPA and HJ 618-2011 of PM2.5 cutter performance:D₅₀=（2.5±0.2）μm,σ_g=1.2±0.1.It is proved that the feasibility of the design of our calibrating device.