电除尘器内电流体动力学二次流与荷电粒子耦合作用的数值模拟

Numerical Simulation of Interaction of Electrohydrodynamic Secondary Flow and Charge Particles in Wire-plate Electrostatic Precipitators

为分析电流体动力学(electrohydrodynamic,EHD)流动与荷电气溶胶粒子间的相互作用,给出了线板式电除尘器内关于EHD和带电粒子运动学的耦合数值模型。该模型采用有限体积法离散求解电场、空间电荷和带电粒子对流扩散方程,并与FLUENT湍流模型连接耦合。利用这一模型,对2种电场风速下线板式电除尘器内电风作用前后的气流流动形态与带电粒子运动行为进行了细致模拟,并用电流体Reynolds数NEHD分析了二次流动对气流、粒子浓度分布及粒子除尘效率的影响。结果表明,电风二次流动主要通过改变气流速度和湍流度分布来影响粒子向下游区域的对流输运过程。电风效应对粒子的除尘效率存在负面影响,其中对粒径小的粒子更为显著。但随着电场风速或粒子粒径的增加,电风二次流动对带电粒子的作用会逐渐变弱。考虑实际运行电除尘器的电场风速有效范围,这一负面影响最大可使粒径小于1.0μm粒子的捕集效率降低4%。

A numerical model of electrohydrodynamic(EHD)and charged particle kinematics was developed to clarify the interaction between the EHD flow and the charged particles in a wire-plate electrostatic precipitator(ESP).The equations of electric field,space charge and the convection diffusion equations of charged particle were simultaneously solved by using the finite volume method,and seamlessly linked with the turbulent flow model of commercial FLUENT code.The airflow patterns and the dynamic behaviors of charged particles in the ESP were intensively simulated with and without consideration of the EHD flow at two representative flow velocities.The influences of the ionic wind on the bulk flow,the particle concentration distribution and the collection efficiency of charged particles were analyzed by employing the EHD Reynolds number NEHD.The results show that the secondary flow of electric wind affects the convective transport process of particles to the downstream by changing the velocity distribution and has a negative effect on the collection efficiency of charged particle,especially the collection of fine particles.However,as the magnitude of the inlet velocity increases,the effect of secondary flow on the airflow characteristics and the dynamic behavior of charged particles becomes weaker.Considering the effective range of gas velocity within an ESP,the greatest negative effect of the EHD driven secondary flow can result in a reduction of 4%in the collection efficiency of particles(dp≤1.0μm).