Three-dimensional flow and turbulence structure in electrostatic precipitator

Stereo PIV is employed to study the three-dimensional velocity and turbulence fields in a laboratory model of a negative corona, barbed-wire, smooth-plate, electrostatic precipitator (figure 1). The study is focused on determining the parametric effects of axial development, mean current density Jm and bulk velocity U0 on secondary flows and turbulence levels and structures due to the action of the three-dimensional electrostatic field on the charged gas. At constant bulk velocity (U0 = 1 m/s) and current density (Jm = 0.4 mA/m2), secondary flows in the form of rolls of axial vorticity with swirl numbers up to S = 0.3-0.4 are found to level off after 4-5 electrodes, being most regular in the central unit cells defined by the periodic geometry of pin-electrodes. The corresponding image-mean turbulence intensity increases to about 20% from the 1st to the 7th electrode with a consistent anisotropy of normal Reynolds stresses. The effects of U0 and Jm on S and Tu (at fixed position between 6th and 7th electrode) are reasonably correlated by the electrohydrodynamic modulus NEHD = (Jm/bi)ly/(½rU02), where bi denotes the ion mobility and ly the electrode-plate distance.