IOSR Journal of Applied Physics (IOSR-JAP) e-ISSN: 2278-4861. Volume 3, Issue 2 (Mar. - Apr. 2013), PP 11-15 www.iosrjournals.org www.iosrjournals.org 11 | Page Experimental Studies on Corona Discharge Ionization V. S. Sawant Department of Physics, Y.C. Institute of Science. Satara-415001, Maharashtra, India, Abstract: This study investigates the possibility of corona discharge ionization technique for reduction of fog. For corona discharge ionization a high voltage power supply is designed and developed indigenously. The high output voltage is developed by using isolation transformer, autotransformer, and high voltage neon transformer and it is converted into DC voltage by using Wheatstone bridge circuit and high voltage capacitor. Formation of negative corona, positive corona and voltage-current characteristics of corona ionization was studied. By selecting -9 kV voltages to discharge electrode, the performance of this circuit was tested for removal of fog, Fog was generated by using ultrasonic water fogger collected in closed glass container. Various runs were carried out. The light intensity was measured for each run as a function of time, in presence and absence of the discharge. After continuous operation of device for 6 minutes, 90% to 95% of the aerosols were removed from container in addition to the natural decay effect. Keywords: Corona discharge, High voltage, Ionization of Air, Positive Corona, Negative Corona I. INTRODUCTION Fog is a weather phenomenon where in tiny water droplets suspended in the vicinity of the earth‟s surface cause a reduction in visibility. The poor visibility leads to severe disruption and delay in rail, road and air traffic, causing great economic loss [1]. Fog along with other pollutants is responsible for reduction in agricultural yield considerably. It is essential to search for solution for fog dispersal. Hence it is needed to have detailed information about the optical nature of fog particulate system (water droplet + fog condensation nuclei), leading to poor visibility. Atmospheric fog is composed of sub-micron size range up to tens of micron [2]-[5]. Daniels (2002) reported that negative air ions (NAIs) reduce aerosol particles, airborne microbes, odors and volatile organic compounds (VOCs) in indoor air [6]. The particle removing mechanisms by NAI is due to particle charging by emitted ions and electromigration which increases migration velocity of particles [7]-[9]. Several studies have been conducted for particle removing efficiency using ionic cleaners to remove particles from the air [10]-[12]. Ozone in troposphere levels is highly poisonous for plants and animals and the high voltage used for corona discharge, produces Ozone above threshold voltage of 16000 volts [13]. Hence precaution is to be taken to avoid Ozone production which is an air pollutant at ground level that can be harmful to breathe and damages crops, trees and vegetation [http://www.epa.gov/oar/particlepollution]. Several studies have been conducted for particle removing efficiency using ionic cleaners to remove particles from the air. Removal of the atmospheric pollutants such as suspended particle, pollutant gases CO, NO x and Volatile organic compounds is urgent need of the future to control air pollution[14]-[18]. The Oxygen ion production using corona discharge is powerful tool for removing effect of above pollutants along with removing suspended biological species. In this paper we present construction of corona discharge instrument with experiment on fog and its removal by using corona discharge ionization. II. METHODOLOGY 2.1 Design & Testing High voltage power supply layout used in corona discharge ionization instrument is shown in “Fig.1”. The ac mains supply is connected to an isolation transformer which isolates the high voltage side from the line. The output is connected to a autotransformer that supplies the input to neon transformer. The neon transformer output (variable output of 0-15 kV) is connected to a bridge rectifier configuration. Total 52 diodes are used and each arm consists of 13 high voltage diodes. High voltage epoxy/resin combination is used surrounding to the diode chain and resisters to avoid shorting of the components in any weather condition. The rectified output is filtered and stored in a large 1 μF capacitor. The diode terminals and connections have covered with a thick layer of silicon sealant to prevent arcing or corona discharge. The capacitor used for the power supply circuit has a rating of 1 μF ±10 % at 50 kV dc. The voltage across the capacitor is measured with a high resistance voltage divider with 100:1 input to output ratio by a high input impedance digital voltmeter. All high voltage components, switches, plugs, meters are mounted on non-conducting polycarbonate sheet.