The Comparative Characteristics of Five Types of Ionic Wind

The force from ionic wind (IW), caused by a corona discharge, is one of the particle collecting forces in an electrostatic precipitator, which has recently been studied. The ionic wind is classified into five types by different discharge electrode polarity and discharge generation methods. These are : positive, negative, alternating current (AC), secondary and back discharge ionic wind. This paper outlines the characteristics of these types of ionic wind and gives comparisons between them when observed in a needle to plate electrode system. To study back discharge ionic wind, mica of thickness 1mm and are 226×229(mm)^2 with some 1mm diameter holes was placed on the plate electrode. The results may summarised as follows : (1) The peak value of ionic wind velocity at the same applied voltage is highest for positive ionic wind, lower for negative and lower still for AC. (2) The peak value of ionic wind velocity is proportional to the square root of the corona current and the slope of this straight line is highest for positive IW, less for negative and smaller still for AC. (3) With AC ionic wind, the special phenomenon of an arrow-current of air is observed, and this is named Arrow Type IW. (4) Back discharge IW occurs when the applied voltage exceeds about 17kV at a discharge distance of 50mm. Although back discharge IW becomes strong with increasing applied voltage, it tends to be suppressed by negative IW from the discharge electrode.