雾滴内部流动及二氧化硫吸收过程的数值模拟

发布时间：2019-02-21 09:11

【摘要】：喷雾烟气脱硫过程中液滴在流场中运动时,在表面剪切力的作用下形成内部循环流动,影响液滴内部传质特性,进而影响雾滴吸收SO_2的过程.以单个悬浮液滴为研究对象,采用VOF(volume of fluid)方法计算了不同雷诺数下雾滴内部流动特性和SO_2气体在水雾雾滴内部的扩散,探讨了不同雷诺数下雾滴表面的速度分布以及雾滴内部循环流动对雾滴内部SO_2浓度分布的影响.数值计算结果表明:气流流场中的液滴与气流存在相对运动时,在表面剪切力的作用下液滴内部会产生2个相互对称的涡流,涡心距离液滴中心的距离为2/3R_d,涡流速度随着雷诺数的增加而增大.雾滴对SO_2的吸收过程受到2种机理的控制:一种是在浓度梯度推动下向雾滴内部的径向扩散;另一种是雾滴内部循环流动诱发的扩散传质.通过SO_2在雾滴中径向扩散时间与涡流形成的特征时间、内部循环流动诱发SO_2传质的特征时间的对比,表明在雾滴内部,循环涡流流动对吸附传质过程具有重要的影响,随着雷诺数的不断增加,雾滴内部循环流动对SO_2传质影响逐渐增大.
[Abstract]:In the process of spray flue gas desulfurization (FGD), the droplet moves in the flow field, and the internal circulation flow is formed under the action of the surface shear force, which affects the internal mass transfer characteristics of the droplet and further affects the process of the droplet absorption of SO_2. VOF (volume of fluid) method was used to calculate the internal flow characteristics of droplets and the diffusion of SO_2 gas in droplets with different Reynolds numbers. The velocity distribution on the droplet surface under different Reynolds numbers and the effect of the circulating flow within the droplet on the concentration distribution of SO_2 in the droplet were investigated. The numerical results show that when the droplet and the airflow are in relative motion in the flow field, two symmetric eddy currents will occur in the droplet under the action of the surface shear force, and the distance from the center of the vortex center to the droplet center is 2 / 3 RSD. The eddy current velocity increases with the increase of Reynolds number. The absorption of SO_2 by droplets is controlled by two mechanisms: one is the radial diffusion to the droplet interior driven by the concentration gradient, the other is the diffusion mass transfer induced by the circular flow inside the droplet. By comparing the characteristic time of radial diffusion of SO_2 in droplets with the characteristic time of eddy current formation and the characteristic time of SO_2 mass transfer induced by internal circulation flow, it is shown that the circulating eddy current flow has an important influence on the adsorption and mass transfer process in the droplet. With the increase of Reynolds number, the influence of droplet circulation on SO_2 mass transfer increases gradually.
【作者单位】：江苏大学能源与动力工程学院;韩国庆尚国立大学机械与航空学院;
【基金】：国家自然科学基金资助项目(51106064,11502097) 江苏省自然科学基金资助项目(20150511) 江苏大学青年基金资助项目(FCJJ2015001)
【分类号】：O35

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