多场作用下细颗粒物在液滴表面沉积行为的研究

It is common that different physical fields coexist in the gas cleaning process of the industry and atmosphere. The deposition behaviors of fine particles toward the droplet surface in these coupled fields are the basis of wet scrubbing and wet deposition processes. The process of particle deposition includes particle migration toward the droplet surface in the gas phase, impaction on the surface and deposition evolution on the surface. This program intends to study the process of fine particle migration in the gas phase and impaction on the liquid surface while fine particles flow around the droplet by experiment and numerical simulation. The mechanisms of fine particle migration in the gas phase and impaction behaviors are elucidated. The dynamic evolution characteristics of particle occurrence on the droplet surface are analyzed. The influences of boundary layer separation and droplet deformation on particle migration in the gas phase are discussed and an improved prediction method for particle collision efficiency in multi-coupled fields are developed. The behaviors modes of fine particle impaction on liquid surface and the corresponding criteria to ascertain impaction behavior mode are proposed. The prediction method of attachment efficiency is established. A calculation method for fine particle capture efficiency by droplet is established in consideration of particle collision efficiency and attachment efficiency. It is analyzed how the particle deposition evolution on the droplet surface influences the continuous capture performance of the droplets. The research results obtained in this program are significant for developing new industrial wet scrubbing technology and enhancing the self-clean function of the atmospheric environment.

大气环境和工业烟气净化过程中存在多种物理场。多场作用下细颗粒物在液滴表面的沉积行为是湿沉降和湿法洗涤过程的基础。颗粒在液滴表面的沉积过程包括颗粒向液滴表面的气相迁移、撞击液面与在液面上的沉积演变。本项目实验研究与数值模拟相结合，研究细颗粒物在绕流液滴时的气相迁移与撞击液面过程；探明多场作用下细颗粒物气相迁移行为机制、撞击液面行为机制以及颗粒在液滴表面沉积形貌的动态演变特征；分析边界层分离与液滴变形对细颗粒物气相迁移的影响，界定各主要迁移机制单独或联合作用的参数区间，修正多场作用下细颗粒物碰撞效率的预测方法；提出细颗粒物撞击液面的行为模式与模式识别判据，建立细颗粒物粘附效率的预测方法；结合颗粒碰撞和粘附效率的预测，建立液滴捕集细颗粒物效率的预测方法，并分析颗粒在液面沉积形貌演变对液滴持续捕集颗粒能力的影响。项目研究成果对开发新型工业烟气净化技术、增强大气环境自清除细颗粒物机能有重要意义。

大气环境和工业烟气净化过程中存在多种物理场。多场作用下细颗粒物在液滴表面的沉积行为是湿沉降和湿法洗涤过程的基础。颗粒在液滴表面的沉积过程包括颗粒向液滴表面的气相迁移、撞击液面与在液面上的沉积演变。本项目实验研究与数值模拟相结合，研究了颗粒在绕流液滴时的气相迁移与撞击液面过程。探明在常规工业烟气或大气环境中气溶胶绕流液滴时，微米颗粒以惯性捕集为主、亚微米颗粒以热泳捕集为主；获得了在边界层分离和非稳态流动条件下，颗粒在多场作用下的迁移、沉积行为机制，分析了传统捕集效率公式计算偏差大的原因，建立了高精度的液滴捕集颗粒效率预测方法；研究了液滴变形对颗粒惯性、热泳运动与沉积行为的影响规律和机制，建立了考虑液滴变形修正的液滴惯性与热泳捕集效率预测方法。研究了微米颗粒以不同角度撞击液面的运动行为，探明了微米级颗粒正向和斜向撞击液面过程中颗粒和液面的运动特征、撞击动力学和能量转化机制，建立了预测微米颗粒撞击液面行为模式的临界沉没判据，准确预测了实验结果；研究了椭球形颗粒正向撞击液面行为与机制，揭示了轴比对微米级椭球颗粒撞击液面行为和动力学的影响，构建了可预测非球形颗粒撞击行为的模式相图。基于考虑颗粒撞击液滴时粘附概率修正的颗粒捕集效率预测方法，对湿法脱硫协同除尘过程进行分析，探明了塔内气液两相浓度、温度和速度的分布特征以及不同粒径颗粒物的主要捕集机制与区域，获得了烟气流速和温度、喷淋速度和温度、液滴尺寸、液气比等运行参数对除尘效率的影响规律，提出了增强脱硫塔协同除尘性能的优化方法。项目研究成果对于开发新型工业烟气净化技术、理解大气环境自清除细颗粒物机能有重要意义。