双区静电除尘器的数值模拟研究

Numerical simulation study of two-stage electrostatic precipitator

采用数模拟的方法研究了双区静电除尘器内流场分布、颗粒荷电及颗粒运动等难以直接测量的物理过程,构建了双区静电除尘过程完整的数值模型.采用泊松方程、电流连续性方程和匀强电场方程描述电场,采用N-S方程和雷诺应力标准湍流模型描述流场,采用拉格朗日法描述颗粒运动轨迹.通过截面风速与颗粒去除率的模拟值与实验值的对比,验证了数值模型在模拟内部流场和颗粒运动时的准确性.数值模拟结果表明:双区静电除尘器内部流场分布对入口风速的变化非常敏感;颗粒荷电方式占比由颗粒粒径决定;荷电区内颗粒向极板的趋近过程由流体曳力和电场力共同完成,收尘区内的趋近过程则由电场力主导;入口流速通过改变颗粒前进速度和内部流场形态来影响颗粒运动轨迹.

A complete numerical model was developed for the dust removal process in the two-stage electrostatic precipitator(ESP).Numerical simulation method was used to study velocity distribution,particle charging characteristics,particle moving tracks and other physical processes which were difficult to measure directly.The electric field was analyzed using Poisson equation,current continuity equation and homogeneous electric field equation.Fluid flow was elucidated using N-S equation and the standard k-εturbulent model.Particle tracks were described using Lagrangian method.The accuracy of the numerical model was verified by comparing the numerical results with the experimental data of the cross-sectional velocity and the particle removal rate.Numerical simulation results showed that the fluid flow distribution in two-stage ESP was sensitive to the inlet wind speed.The proportion of charge with different charging methods was determined by particle diameter.And the particles of different sizes had different dominant charging methods.Moreover,the approach of particles to plates was caused by the interaction of the electric force and the drag force in pre-charger,while the approach in dust collection part was dominated by electric force.It was also found that the inlet velocity influenced the particle tracks by changing particle advance speed and internal flow field.