Mechanical Design Of PM2.5 Online Monitoring System And Experimental Research

PM2.5 on-line monitoring is the key to environmental protection work in China, the domestic online monitoring instrument accuracy and reliability by sampling separator and the restriction of online monitoring instrument technology level, with foreign instrument gap is larger. Online monitoring of PM2.5, the author of this paper, the simulation analysis of the influence of sampling for particle collection efficiency of separator structure, integrates the beta ray method monitoring instrument, and through the experimental study analyzes the factors affecting the measurement results and the correction methods, provides the reference for PM2.5 online monitoring instrument design.Finally, two kinds of manual and online automatic particulate matter detection methods and the operating principle of corresponding instrument were analyzed in this paper firstly. Based on the theory of fluid flow, using computer simulation software internal flow field of cyclone separator are analysed and studied the movement behavior of particles in the separator and the separator, the factors affecting the separation efficiency. Simulation results showed that there is double vortex flow in the cyclone separator, tangential velocity takes on Rankine vortex and the internal static pressure of cyclone separator is axisymmetric characteristics. Dynamic pressure is the largest in the forced vortex and free vortex boundary surface. With the increase of particle size and inlet flow separation efficiency of separator increases; With the decrease of cylinder diameter of the top of separator.Secondly, particle separator is designed and monitoring instrument based on beta ray method of key parts of the mechanical structure, according to the monitoring instrument working conditions, and the precision requirement, design the PM10 cutting head end cap body and circular cone, the body of the middle, the bottom of the cone and the main body of the PM2.5 separator. Design the monitoring instrument based on beta ray method of filter paper tape drive unit structure, carbon source seal fixed structure, and the fixed structure of the photomultiplier tube, on the basis of mechanical optimization design and processing, to integration of instruments, to verify the reliability and rationality of the design.Finally, the standard weighing method is adopted to monitoring instrument based on beta ray method through the contrast experiments, the measurement accuracy results show that the measurement data correlation is better. By establishing regression equation to the data results after correction, the relative error was reduced by 3.1%.Compares with monitoring station data and the results show that the measurement error of the main factors for the humidity change, in order to ensure the accuracy of measurement, humidity of control instrument should in a certain range, sampling room air temperature and air flow temperature difference of no more than plus or minus five degrees. On the basis of the mass absorption coefficient was calculated by the experimental methods and lay the foundation for the accuracy of the instrument measurement data in the future.