Pulsed plasma processing for control of diesel engine emissions
Abstract
Electrical discharges can be used as an after treatment for diesel exhaust. We are presently involved in research to determine the feasibility of this process. These discharges have been shown to remove nitric oxide, sulfur dioxide, particulates, and many organic compounds. A key issue is the efficiency of this removal since it effects both capital and operating costs. These discharges must be of short duration, less than one microsecond, to avoid energy losses due to heating of bulk gas molecules. The voltage must be kept below the voltage breakdown limit where ion heating creates an arc discharge. The basic process is the acceleration of electrons which then collide with gas molecules to form radicals such as O and OH. These radicals then react with and eliminate pollutants. Two basic electrode geometries are used to generate these discharges. The barrier discharge is when one or both of the electrodes is insulated and the pulse length is limited by charging of the insulator. This discharge must be driven by alternating current to permit alternating charging of the insulator. The other geometry is when one electrode has a peak voltage stress five or more times the average stress. We have been investigating the high stress geometry which uses a small wire inside a pipe. The principal experimental apparatus utilized by this effort uses a closed loop gas system. This system permits the production of various gas combinations prior to testing. Analysis can be conducted during or after these tests. The recirculated gas can be heated up to 400 F. This system can measure the energy used and the pollutant removal to determine efficiency. Our primary goal is the simultaneous removal of nitric oxide and particulates typical of diesel exhaust. <This is expected to be accomplished in one or more metal tubes no larger than two inches in diameter and 36 inches long.
- Publication:
-
Presented at the Annual Automotive Development Technology Contractors' Coordination Meeting
- Pub Date:
- February 1993
- Bibcode:
- 1993adtc.meet....2V
- Keywords:
-
- Combustion Products;
- Diesel Engines;
- Electric Potential;
- Energy Dissipation;
- Exhaust Emission;
- Exhaust Gases;
- Gas Heating;
- Molecules;
- Operating Costs;
- Arc Discharges;
- Electrical Faults;
- Electrodes;
- Electrons;
- Nitric Oxide;
- Organic Compounds;
- Particulates;
- Sulfur Dioxides;
- Mechanical Engineering