Study On Ion Wind Characteristics And Particle Motion In An Electric Precipitator

In this paper,a numerical study is performed on characteristics of internal ion wind and motion of particulate matters in an electrostatic precipitator.The COMSOL software based on the finite element method is used to numerically simulate the three-dimensional model of the electrostatic precipitator and combined effect of the main air current and the electro-hydrodynamic(EHD)flow on the internal flow field of the electrostatic precipitator is analyzed.Corona discharge is simulated by coupling Poisson’s equation with current continuity equation.The steady-state incompressible Navier-Stokes equation and standard k-ε turbulence model are used to solve airflow performance.The particle flow module of fluid flow is used to solve the particle motion process.Following conclusions are obtained:Firstly,the electric field,flow field distribution and interaction in the electrostatic precipitator are numerically studied.On the one hand,the influence of ion wind on electric and flow fields and the disturbance of main air flow field by ion wind under positive and negative corona discharge are investigated.On the other hand,the effect of temperature on electric and turbulent fields is studied.The results show that the ionic wind manifests itself as a vortex.When there is no inlet wind speed,the flow field in the single-line electrode electrostatic precipitator appears as four vortices,and in the double-line electrode electrostatic precipitator appears as eight vortices.With the increase of the inlet wind speed,the effect of the ion wind will be weakened until the main airflow occupies the entire flow field when the inlet wind speed is 1.0 m/s.Under the condition of positive corona discharge,the existence of the ion wind can improved the main airflow speed,and during negative corona discharge,the ion wind increases the air velocity in the direction of the dust collecting plate.As the temperature increases,the air density decreases,the halo voltage decreases,the ion wind effect weakens,and the average velocity of the air flow in the turbulent field is increased.Secondly,the effects of inlet flow velocity,particle diameter,applied voltage,with or without the EHD flow,and temperature on motion trajectory and collection efficiency of particles from 1.0 μm to 10 μm are studied.With the increase of the inlet flow rate,the collection efficiency decreases.As the particle diameter increases,the particle trajectory is prolonged,and higher collection efficiency can be obtained.With the increase of the applied voltage,the particle is more easily collected by the dust collecting plate,compared with single-line electrodes,double-line electrodes can obtain more obvious effect.With the EHD flow,the landing points of particles on the dust collecting plate are more concentrated,but it has little effect on the collection efficiency of particles in the range of 1.0 μm to 10 μm.As the temperature rises,the viscosity of the airflow increases,and the particles follow better,and it is easier to escape from the dust collector with the airflow,so the collection efficiency at high temperature will decrease.Thirdly,three types of electrostatic precipitator models with wire electrode arrangements are set-up.The effects of inlet velocity and applied voltage on particle collection efficiency in the range of 0.2 μm to 1.0 μm are investigated,and the dust collection performances of three wire electrode arrangements at different inlet velocity and applied voltage conditions are compared.The results show that as the inlet velocity increases from 0.8 m/s to 1.2 m/s,the decent range of the linear collection efficiency is the largest,and the decent range of the X-type collection efficiency is the smallest.Under the three inlet flow rates,Y-type and X-type have the best collection effect of particulate matters in the range of0.8 μm to 1.0 μm and 0.2 μm to 0.6 μm respectively;as the applied voltage is increased from30 k V to 60 k V,the Y-type collection efficiency is improved largest and the improvement in X-type collection efficiency is the smallest.When the applied voltage is 30 k V,the X-type distribution has the best dust collection effect.When the voltage is applied at 60 k V,Y type and X type have best effect for collecting particles in the range of 0.5 μm to 1.0 μm and 0.2μm to 0.5 μm,respectively.