多场耦合作用下荷电液滴吸附细颗粒物机理和特性的研究

Fine particulate matter is an important source of pollutants, such as PM2.5 does serious harm to human health and how to remove fine particles efficiently from the flue gas is an important topic in the field of clean energy utilization and environmental protection. Based on the applicant's invention patent which is intend to remove the fine partiles in the fume by means of high-voltage electrostatic spray, the project proposal is focused on the dynamical process of the particle adsorption by charged droplets under the coupled action of multil field by using high speed camera,laser rainbow measurement method, laser-induced fluorescence method and other advanced optical diagnostics and flow measurement technology, combined with numerical calculation. The particle adsorption characteristics by charged droplets under different factors such as droplet size, charge to mass ration, relativ velocity and etc. could be obtained. The observation of phase interface changes and two-phase micro-flow situation would be carried on during the process of fine particles entering the droplet internal. Under the evaporation conditions, coupling effect of the electric field and temperature field as well as scale effect on the droplet adsorption characteristics of fine particles would be explored. To reveal the adsorption mechanism, the key parameters affecting the adsorption characteristics would be obtained by the investigation. Based on the establishment of the inter-phase model and the model of particle adsorption by charged droplets group, the complex process of particle adsorption by droplets would be simulated by numerical calculation. The impact of key parameters on the adsorption characteristics of fine particulate matter would be obtained through the simulation work which would lay an research foundation for the development of high-efficiency flue gas purification technology.

细颗粒物是重要的污染物来源，如PM2.5严重危害人类健康，如何高效脱除烟气中的细颗粒物是工程热物理和能源利用学科领域的重要基础研究课题。项目在申请人提出的高压静电喷雾去除烟气中细颗粒物发明专利技术的基础上，采用高速数码摄像和激光诱导荧光等一系列先进的现代光学测量和流动显示技术，对荷电液滴吸附细颗粒物的机理和特性进行深入研究。通过捕捉荷电液滴吸附细颗粒物的过程，测量细颗粒物进入液滴内形成的两相微流动，分析在电场和温度场作用下细颗粒的运动规律和相界面变化以及对液滴吸附细颗粒特性的影响，探索荷电液滴的多尺度吸附机制，获得影响吸附特性的关键参数，揭示吸附机理。在理论和实验研究的基础上建立荷电液滴与细颗粒物的相间作用模型及液滴群吸附模型，通过数值计算模拟荷电液滴吸附细颗粒物的复杂多相动力学过程，研究关键参数对液滴吸附细颗粒物特性的影响，为发展高效烟气净化技术提供理论基础。

颗粒物污染严重影响公共健康。颗粒物产生的来源主要是燃煤排放的含尘烟气与汽车尾气。如何提高颗粒物的脱除效率是工业界关注的热点问题，也是环境保护和能源清洁利用领域的重要研究课题。本项目以执行人前期静电喷雾研究为基础，对荷电单液滴吸附颗粒物机理和特性进行了深入探讨。捕捉了荷电液滴吸附细颗粒物过程，对吸附过程中颗粒物的运动特性进行了研究。通过颗粒的瞬时运动速度结合受力分析对其所受静电力、空气阻力以及荷电量等进行了定量计算分析，获得了颗粒物在气相介质中的运动规律。对颗粒物撞击荷电液滴表面行为特性进行了研究。通过分析颗粒物撞击速度、撞击角等与颗粒物吸附、反弹（二次飞散）等动力学行为的相互关系，揭示了吸附机理。利用设计的实验装置观察了颗粒物在荷电液滴表面的沉积情况。通过分析颗粒物吸附至不同速度、荷电量液滴表面的分布特性，获得了颗粒物在荷电液滴表面的沉积规律。利用实验和数值计算手段研究了温度场作用下荷电液滴的蒸发特性。通过分析液滴蒸发速率、表面波动、内部流场等与电场、温度场之间的联动关系，获得了荷电液滴在温度场作用下的蒸发规律。液滴间的相互作用直接影响荷电液滴对颗粒物的捕集效率，实验研究了荷电液滴间的相互作用。研究首次发现高电导率液滴互相接触后会发生“皇冠破碎”，且破碎始终发生在荷负电液滴一侧。研究认为，“皇冠破碎”由瑞利不稳定性引起。以柴油机为尾气源，研究了静电喷雾脱除烟气颗粒物特性，研究发现装置荷电后颗粒物脱除效率最高可提升27.5%，是非荷电喷雾系统的3~4倍，验证了静电喷雾脱除细颗粒物的高效性。综合考虑颗粒物在液滴表面的粘附、反弹和浸入等动力学行为，建立了荷电液滴捕集颗粒物模型，并对捕集过程进行了数值模拟，研究了关键参数对液滴吸附颗粒物特性的影响，为静电喷雾高效烟气净化技术提供了理论基础。