Research On The Characteristics Of Fine Particulate Matter Diffusion Sources And Control Technologies Under Building Environment

In recent years,the environmental pollution is highly provoked;the fine particulate matter sources in building environment are characterized by a wide variety of sources and complex composition.The fine particulate matter pollutants in building environment require urgent solution concerning its serious effects on air quality and people’s health.The typical fine particulate matter pollutants in building environment are beyond the well-known large amount of pollutants,and also a growing concern for the invisible contaminants.In fact,there are various types of invisible fine particulate matter diffusion sources in the buildings,and most emissions of the pollution sources produced in building environment are periodic or paroxysmal dynamic fluctuations.Traditional evaluation methods using fresh air dilution theory lack the consideration of the spatial distribution of pollutant concentration and inhomogeneity of pollution source emission.So the calculation result of the control wind amount of the pollution source and control effect evaluation are quite different from the actual situation.However,the age of air and particle residence time can be used to describe the removal capacity and time of the particulate pollutants in building environment,respectively.The air age and particle residence time in building environment are reasonable indexes for evaluating the particulate pollution source control effect.This thesis mainly focuses on the following research and the findings are as follows:（1）The any instantaneous equation of the pollutant concentration and control wind amount was established in building environment,and the analytical relation was obtained between the control ventilation volume and pollutant source strength.The study results show that the variation of pollutant source intensity with the time has an important influence on the pollutant control ventilation volume.On this basis,for dispersive description of fine particulate matter diffusion sources in building environment,the description models of persistent sources,periodic sources and paroxysmal sources were established for extracting rules.（2）The numerical analysis model of the air age and particle residence time in building environment was established based on the Euler method and Lagrange method.The evaluating indexes of the fine particulate matter source in building environment has been studied based on the relationship between the pollutant control ventilation volume and source strength together with the numerical model,moreover,the main factors affecting the fine particulate matter concentration in building environment was obtained,and were applied to actual cases.（3）The model cases were explored based on the description models.The experimental study on the diffusion characteristics of different fine particulate matter sources in building environment was carried out through the typical representative of common cigarette burning as the persistent source,the typical representative of invisible fine particulate matter sources—subway tunnel wind and surgical smoke as the periodic and paroxysmal source,respectively.ⅰ)Taking cigarette combustion as an example,the emission characteristics of persistent fine particulate matter sources in a closed chamber without the ventilating and air-conditioning system were experimentally investigated.The particle size distribution and the emission law of cigarette particles of 12 brands of the high,middle and low domestic and foreign cigarettes in the smoldering-method and smoking-method were tested and analyzed.Moreover,the particulate matter source strength was obtained by the cumulate method.The results show that PM_2.5.5 diffusion accumulation produced in the smoking-method of different level cigarettes displayed fluctuating.ⅱ)Taking subway tunnel wind as an example,the pollution characteristics of periodic fine particulate matter source in subway environment with the ventilation and air-conditioning system were experimentally investigated.The PM_2.5 pollutant source intensity at the connection entrance of the rail line and platform was analyzed by the instantaneous method,moreover,PM_2.5 and PM₁₀concentration variations in different units of the subway stations,PM_2.5/PM₁₀ ratio law of different station platforms,and particle size distribution in subway environment were obtained.The study results show that consistent,time-varying trends were exhibited by PM_2.5 concentrations in platforms,station halls,and rail areas.As the result,the time-varying trends of PM₁₀ and PM_2.5concentrations in platforms and station halls were similar to each other.Activities within the station led to most of the inhalable particles within the station area.Moreover,the mass concentration ratios of PM_2.5 and PM₁₀ in platforms were within the range of 0.65⁰.93,and it was shown that fine particles were the dominant components.ⅲ)Taking surgical smoke as an example,the pollution characteristics of paroxysmal fine particulate matter source in the operating room with the cleaning air-conditioning system were experimentally investigated.The surgical smoke PM_2.5 source intensity at the peaks near the breathing zone of the operating surgeon was analyzed by the instantaneous method,moreover,PM_2.5 and PM₁₀ concentration variations at monitoring points,and particle size distribution were obtained.The results show that the PM_2.5 concentration appears a series of peaks in the respiratory area of the surgeon in the operation due to laminar flows from the ceiling.Interactions of thermal plumes caused by surgical smoke and laminar flows from the ceiling,lead to the accumulation of fine particles in the vicinity of the surgery table.Moreover,the main components of surgical smoke are fine particles whose diameters range from 0.3μm to 0.4μm.（4）Based on the numerical model of the air age and particle residence time in building environment,the study improved the current domestic indoor smoke control room and operating room,and applied the air age and particle residence time to evaluate the actual control effect.The method of CFD was adopted to design the orthogonal experiments with interaction,so the optimal scheme and also significant influence factors of the air curtain working parameters were obtained in the operating room.