Experimental study of the flow in an electrostatic precipitator (ESP)

Thorvald U. Ullum
Department of Mechanical Engineering, Technical University of Denmark, Denmark

In an electrostatic precipitator the induced charge density of gas ions results in a complex three-dimensional, turbulent gas flow. A spatially periodic body force arises as a consequence of the applied electrostatic field, which may be determined from the Maxwell equations. This body force drives secondary flows and generates turbulence and hereby affects the efficiency by which the precipitation of the suspended solid matter takes place.

An experimental study has been carried out to investigate flow structures in a laboratory ESP. The filter section is a 0.2 x 0.2 x 1.0-m wind tunnel with 2 grounded aluminum plates and 2 glass side-walls supporting up to 7 discharge HVDC electrodes. The incoming air is seeded with atomized 1-5 m m diameter olive oil droplets. These particles become negatively charged and hence precipitate on one of the two aluminum collector plates. For measuring the particle velocities a 2-D LDA and a stereo digital PIV system is used. Based on various combinations of air bulk velocity and mean current density in the filter, velocities have been measured and statistics of turbulence have been calculated.

In parallel to the experimental work, a computational study of the ESP flow is carried out using large eddy simulations (LES).