【作者】 杨荣清；

【导师】 吴新；

【作者基本信息】 东南大学 ， 热能工程， 2006， 硕士

【摘要】 可吸入颗粒物的污染在国内外已经引起广泛重视,燃烧源可吸入颗粒物的形成与控制技术更是备受广大科研工作者的关注。化石燃料的燃烧是大气颗粒物主要排放源,进行燃烧源可吸入颗粒物的动力学特性的研究已十分必要。众多的研究表明,作为主要污染源的电站其飞灰中含大量磁性物质,其它排放源的排放物也都不同程度地含有磁性物质。2002年,国家科技部正式将燃烧源可吸入颗粒物的形成与控制技术基础研究纳入973计划进行立项研究,磁场中可吸入颗粒物的动力学特性研究被列为其子课题。本文建立了试验台对磁性颗粒在高梯度磁场的动力学特性进行了试验研究。到目前为止,还缺少成熟的可吸入颗粒物微观运动特性的可视化试验研究手段,商业PIV(如TSI和DANTEC等)技术无法直接用于相应的两相流的研究中。文章中利用先进的ELPI对同时加磁场与铁磁格栅前后经过磁场试验段的颗粒物浓度进行在线测量,并以此为基础,从气溶胶流量、外加磁场磁通密度、格栅组成铁磁性金属丝的饱和磁化强度和丝径及格栅排数等方面分析其对颗粒物在磁场中运动的影响规律。结果表明:减小气溶胶流量,增加外加均匀磁场的磁通密度,选用饱和磁化强度大的铁磁性金属丝组成格栅,减小金属丝的直径和增加格栅的排数都可以使格栅对颗粒物的捕集能力得以提高。文中应用Femlab多重物理场耦合分析软件对磁场试验段内的颗粒运动特性建立数学模型进行了数值研究。利用软件的网格生成功能进行计算域的网格划分,采用非结构化三角形网格;静磁场采用2次Lagrange算法,流场的计算采用Lagrange-P2P1算法。借助软件的数值模拟,进行了磁场、流场和颗粒场的可视化研究,弥补了试验中无法实现可视化的不足。同时还利用模型对颗粒的运动进行了定性、定量分析,在与试验值比较后发现,数值模拟结果与试验值所反映的趋势是一致的。更多还原

【Abstract】 The pollution of particulate matter with aerodynamic diameters<10μm (PM10) has been attracting much attention both inside or outside China. The formation mechanism and the control techniques of PM10 from combustion are being paid much attention by more and more scientific researchers. The combustion of fossil fuels is the main resource of particulate matter in the air, and it’s very necessary to study the kinetic characteristic of PM10 from combustion. Lots of researches indicates that fly ash from power plant,which is the main pollution resource, contains much magnetic matter. PM10 from other resources contains certain magnetic matter. The formation theory and control techniques of PM10 from combustion was brought into‘973 Program’by Ministry of Science and Technology of P.R. China,and the kinetic characteristic of PM10 in magnetic field was included.A test-facility was founded in this paper to make experimental research in the characteristic of magnetic particles in high gradient magnetic field. So far there’ve been no experimental methods for the visualization of the characteristic of the microcosmic movement of PM10. Commercial PIV techniques (TSI and DANTEC etc.) can not be used directly in this two-phase flow research. Electrical Low Pressure Impactor was used in the experiment of this paper to measure the number concentration of the particles without and with magnetic field and bar at the outlet of the passage, respectively. Further more, the influence of aerosol flux, magnetic flux of applied magnetic field, the saturated magnetization and the diameter of ferromagnetic wires, and the number of the rows of the bar were taken into account when analyzing the movement of the particles in high gradient magnetic field. The results indicated that decreasing aerosol flux, improving applied magnetic flux, using wires which have higher saturated magnetization,reducing the diameters of the wires and increasing the number of the bar will improve the capture capability of the bars which have ferromagnetic wires.The software Femlab called as multiple physics field coupling analysis was used in this paper to analyze the movement characteristic of the ferromagnetic particles in the experimental section through the mathematical model, which was also deduced in the paper. Computing mesh was generated by the software, and unstructured triangular mesh was utilized here. Lagrange-Quadratic method and Lagrange-P2P1 were used when calculating the static magnetic field and fluid field, respectively. Visualization of the magnetic field,fluid field, particle field was carried out according to the numerical simulation. And it made up the shortage of the experiment in some sense. Meanwhile, qualitative and quantitative analysis was also made to find that the results from both mathematical simulation and experiment accorded with each other in tendency.更多还原