旋线除雾技术的理论建立与应用检验

基于孤立圆柱状纤维对颗粒捕集机理和颗粒运动方程，分别建立了拦截、惯性碰撞以及离心分离除雾效率及其复合机理除雾效率理论表达式。为验证其合理性，实验中采用筒径500 mm双层旋线除雾器，旋线采用直径3 mm聚酯纤维，每层分别布置100根和200根旋线，旋线转速250~800 r·min⁻¹，在水雾中位径20.1 μm、水雾入口浓度约4 100 mg·m⁻³、除雾器断面风速2.5 m·s⁻¹的条件下，当转速500 r·min⁻¹时，每层100根旋线的除雾器总效率约95%，每层200根旋线的除雾器总效率超过98%，表明增加旋线层根数的提效作用显著。根据总捕集效率与分级效率的经验关系式，得出旋线除雾器的分级效率经验预估值，并与所建立的旋线除雾器复合机理分级效率理论值比较，结果表明，旋线除雾器复合机理分级效率理论值与分级效率经验预估值相当吻合，在雾径0~40 μm范围内，双层旋线除雾器分级效率理论值和实验预估值的平均误差小于1.4%。对不同机理的除雾作用进行比较，发现旋线的惯性碰撞效应起主导作用，旋流分离次之，拦截效率极低，当每层200根旋线时，对20 μm雾滴的拦截效率仅2.5%左右，旋流离心分离除雾效率服从指数规律，且是雾径的平方和转速的平方的函数，对较大雾滴的提效作用明显。

Demisting theory development and its validation of rotary thread demister

Based on the particle capture mechanisms of an isolated cylinder normal to the gas flow and the particle motion equations in vortex flow, the theoretical demisting efficiencies of the interception, the inertial impaction, the centrifugal separation, and the combination demisting efficiency of the independent mechanisms of a rotary thread demister were developed. To test the theoretical demisting efficiencies, a rotary thread demister with diameter of 500 mm was used in this experiment. Two rotary thread layers were arranged in the rotary thread demister. The threads were made from polyester with diameter of 3 mm. The rotary speed of the threads ranges from 250 to 800 r·min−1. The medium diameter of the dorplets is 20.1 μm. The inlet concentration of water sprary is about 4100 mg·m−3. The gas velocity in the rotary thread demister is 2.5 m·s−1. Experimental results indicated that the overall separation efficiency could be greatly enhanced by increasing the thread number. For instance, when the rotary speed was 500 r·min−1, the overall efficiencies of the double rotary thread layer demister with 100 threads per layer and with 200 threads per layer were 95% and 98% respectively. According to the empirical equation of the relation between the overall collection efficiency and the fractional efficiency, the approximate prediction of the fractional efficiency of the rotary thread demister can be found from the experimental value of overall collection efficiency. The comparison results show that the theoretical fractional efficiency of the combination mechanism fitted well with the empirical prediction values. In the range of droplet diameters from zero to 40 μm, the mean deviation was less than 1.4%. From the comparison of the independent mechanisms, it was found that the inertial impaction was predominant, the centrifugal separation was lesser, while the interception was negligible since the interception efficiency was only about 2.5% for 20 μm droplet collection at 200 threads per layer. The centrifugal separation efficiency of the vortex flow created by the fast spinning threads followed the exponential mode which was the function of the square of drop diameter and rotary speed. Thus, the centrifugal separation effect is distinct for larger water droplets.