单区静电除尘器捕集烟尘过程的数值模拟

通过得到烟尘的颗粒尺度谱(PSD)演变过程的详细信息来定量描述静电除尘器(ESP)对烟尘的捕集过程，此时需要同时考虑静电力、流体对颗粒的水平输运力和颗粒横向湍流和布朗扩散作用等烟尘捕集机制。发展事件驱动常体积法来求解考虑烟尘捕集的通用动力学方程以得到颗粒尺度谱的演变过程。对于典型的火电厂单区ESP进行的数值模拟结果表明：ESP对直径大于10mm的烟尘具有良好的捕集效果，也能有效脱除直径小于0.02mm 的烟尘，但是对粒径范围在0.02~10mm的烟尘的除尘效率相对较低；这种"U"型分级除尘效率主要是由于颗粒自身惯性力与静电力之间的相互竞争的结果；布朗扩散机制对任何尺度颗粒的捕集效果影响很小；减小气流输运速度和增加电场强度有利于任何粒径的烟尘颗粒的脱除。

Numerical Simulation of Single-stage Electrostatic Precipitator for Collecting Fly Ashes

The detailed information of evolution of fly ash particle size distribution(PSD) was used to describe quantitatively the collection process of Electrostatic Precipitator (ESP), in which the electrostatic force, the convection force and the transverse particle diffusion were considered simultaneously to simulate the performance of single-stage wire-plate ESP for collecting fly ashes from power boilers. A new event-driven constant volume method was introduced to solve general dynamic equation for the collection of fly ashes to obtain the evolution of its size distribution. As far as a typical single-stage wire-plate ESP of power plant is considered, numerical results of the stochastic approach show that ESP collects effectively fly ashes with diameter 10mm or greater as well as fly ashes with diameter 0.02mm or smaller; however those intermediate size fly ashes (>0.02mm and <10mm) have comparatively slower collection efficiency; the "U" shape of grade number efficiency of collection ascribes to the competition between the inertia force and the electric force; the transverse particle Brownian diffusion has a very weak influence on the collection of fly ashes with any size; the measures including the decrease of the average flow velocity and the increase of the electric field strength will improve the performance of ESP for collecting polydisperse particles.