Direct simulation of turbulent particle transport in electrostatic precipitators

Abstract

The dispersion of particles in turbulent duct flow under the influence of electrostatic fields is studied using direct numerical simulation. In this new approach, particles are moved in the temporally and spatially varying turbulent flow field under the influence of electrostatic and gravitational body forces, as well as fluid dynamic drag. The simulations agree well with previously performed experiments (done in geometries typical of wire-plate and plate-plate electrostatic precipitators) not only in the overall collection efficiency of particles, but in particle concentration profiles at various axial locations in the flo w direction. This gives confidence in the technique that may be used to study different precipitator geometries and flow field configurations, supplementing costly and difficult experiments. Furthermore, in formation is obtained at a much more detailed level than is possible via experiments, allowing insights into the mechanisms dominating particle collection.

Lagrangian simulation of turbulent particle dispersion in electrostatic precipitators

“…Once the flow field is known in detail, particles may be released and followed under the action of the flow field and electrostatic forces. The solution of the fluiddynamic problem was described in a previous article (Soldati et al, 1993) that simulated the turbulent flow of air in a duct at a Reynolds number of 5980 based on the hydraulic diame-ter and the mean velocity. Some aspects of the technique adopted to calculate the flow field are briefly reviewed here.…”

“…The solution of Eq. 3 is obtained by using a pseudospectral method (Kim et al, 1987;Lam and Banerjee, 1992;Soldati et al, 1993) and is based on the decomposition of the flow variables in Fourier series in the x and y directions and in Chebyshev polynomials in the z-direction. Thus, the velocity field has the form:…”

“…In recent years, direct numerical simulation (DNS) has been used as -a powerful tool to fully simulate three-dimensional (3-D) timefluctuating turbulent flow fields (Kim et al, 1987;Lam and Banerjee, 1992;Papavassiliou and Hanratty, 1995, among others). In previous articles (Soldati et al, 1993 and1995b), this method was also applied to simulate particle dispersion in ESPs. The advantage of DNS is that the solution of the Navier-Stokes equations is free from empirical models, or closure laws, that affect methods based on averaging or filtering (e.g., k -E methods).…”

“…To improve understanding of turbulent particle dispersion under the influence of electrostatic forces, a database on particle trajectories was first generated, based on the flow field from a direct numerical simulation of a plate-plate precipitator (Soldati et al, 1993). The efect of various parameters, such as particle size, charge and particle migration velocity, on dispersion and collection efficiency was investigated.…”

Charged Particle Trajectory Statistics and Deposition in a Turbulent Channel Flow

“…Using a direct numerical simulation procedure via a pseudospe ctral code, McLaughlin (1989), Ounis et al (1991bOunis et al ( , 1993, Brook et al (1992), Pedinotti et al (1992), and Squire s and Eaton (1991) analyzed the aerosol particle deposition in a turbulent channel¯ow. Soldati et al (1993) used a direct numerical simulation to study the particle transport in electrostatic precipitators. Recently, Soltani et al (1998) studie d the deposition of charged particles in a channel¯ow using the direct numerical simulation technique .…”