The properties of the needle-ring shaped DC ion airflow generator

A DC ion airflow generator with needle-ring electrode arrangement has been investigated for use in electrostatic elimination systems. The experimental results show that the amount of drawing-off ion airflow I/sub 2/ and the drawing-off efficiency /spl eta/ can be greatly increased by connecting an inducing resistor in series with the inducing ring, and they reach saturation values as the resistance increases. While the hole diameter of the inducing ring is 3.0 mm, the needle-ring distance zero, the total corona current 25.0 /spl mu/A and the air flow rate 7.0 m/sup 3//h, I/sub 2/ and /spl eta/ can be increased from 1.0 /spl mu/A and 4% to saturation values of 4.75 /spl mu/A and 19% respectively, with the resistance increasing from zero to 150 M/spl Omega/ and over. I/sub 2/ and /spl eta/ can also be increased with the airflow rate, and reduced with needle-ring distance and the hole diameter of the inducing ring. With an inducing resistance of 200 M/spl Omega/, hole diameter of 1.5 mm, needle-ring distance of zero, air flow rate of 5.6 m/sup 3//h and corona voltage of -15.0 kV, I/sub 2/ and /spl eta/ grow to 17.4 /spl mu/A and 30% respectively. When corona voltage and corona current are increased, I/sub 2/ is increased, but /spl eta/ is reduced. These results are valuable to the design and performance improvement of DC ion airflow electrostatic eliminators, electrostatic spraying and coating guns and negatively ionized air generators.