Influence of Streamer-to-Glow Transition on NO Removal by Inductive Energy Storage Pulse Generator

Abstract

Huge amounts of air pollutants like carbon monoxide, unburned hydrocarbons, nitrogen oxides (NOx), and particulate matter have been released into the atmosphere by various sources such as coal, oil, and natural gas-burning electric power generating plants, motor vehicles, diesel engine exhaust, paper mills, metal and chemical production plants, etc., over the last several decades. These pollutants are the main cause of acid rain, urban smog, and respiratory organ disease (Chang, 2001). For pollutants emitted from motor vehicle, the exhaust of gasoline engines is cleaned effectively with the three-way catalyst. However, for diesel and lean burn engines, the three-way-catalyst does not work because the high oxygen content in the exhaust gases prevents the reduction of nitrogen oxide (NO) (Clements et al., 1989). Dry NOx removal technology is one of the conventional processes which may provide a potential solution for such problems (Eliasson and Kogelschatz, 1991). A non-thermal plasma process using a pulse streamer corona discharge is particularly attractive for this purpose (Namihira et al., 2000). During the past decade, numerous studies on this process have been conducted using a diesel engine exhaust gas and/or a simulated gas (Hackam & Akiyama, 2000). Although encouraging results have been obtained from the experiments, it is urgent to design a whole removal system compact enough for vehicle application. Two methods for storing energy are employed in high-power pulse generators: capacitive and inductive storages. When the energy is stored in capacitors, the energy is transferred to a load through closing devices, e.g., high-current nanosecond switches. If the energy is stored in an inductive circuit with current, opening switch is used to transfer energy to a load (Rukin, 1999). For short-pulsed high voltage generation with high impedance load, inductive energy storage (IES) system is more adequate than capacitive energy storage system, if appropriate opening switches are available (Jiang et al., 2007). High-voltage nanosecond pulse generators, in which high-voltage semiconductor diodes are employed for interrupting currents stored as inductive energy, have been developed (Rukin, 1999). The generators using the high-voltage diodes as semiconductor opening switch (SOS) have an all-solid-state switching system and therefore, combine high pulse repetition rate, stability of the output parameters and long lifetime (Grekhov & Mesyats, 2002). SOS pulse generators operating at various institutions demonstrated their high reliability during