Experimental and analytical investigation for diesel smoke elimination
Lin, Chao-Hsin
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Permalink
https://hdl.handle.net/2142/22139
Description
Title
Experimental and analytical investigation for diesel smoke elimination
Author(s)
Lin, Chao-Hsin
Issue Date
1989
Director of Research (if dissertation) or Advisor (if thesis)
Soo, Shaolee
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
Increasingly stringent control of the fugitive diesel particulate will be required by EPA in the 1990's. Diesel smoke elimination via electrostatic precipitation was studied. A diesel smoke eliminator with corona charging and particle collection sections was developed, built, and tested. This device, with its high efficiency and a minimal increase in back pressure of the engine, appears to be the most promising one to counter the challenging requirements in the future. Electrohydrodynamic analysis was conducted by solving the mass, momentum conservation equations, the k-$\varepsilon$ turbulence model, and the electric as well as the particle diffusion governing equations.
Tests have been conducted on an International Harvester 4-stroke, 6-cylinder diesel engine with a through flow of 25 to 85 liter/s and soot concentration of 0.1 to 0.3 mg/liter determined by a photometer calibrated by an isokinetic sampler. The corona charger has a needle at a typical 4 cm from a 4.5 cm diameter attractor opening through which the exhaust gas flowed. At an arc voltage of 12 kV, the corona current was 0.02 mA at clean air flow and a limiting current of 2 mA was set for the high smoke condition when the voltage would automatically adjust to 11 kV. Results show that the conductivity of the exhaust varies from 20 times that of clean air at low smoke condition and more than 200 times at high smoke condition without arcing. The charge-to-mass ratio of 0.1 coul/kg was measured by a high-temperature charge-to-mass ratio probe, which was devised in the present study, and an electrometer. Particle size distribution with respect to particle number concentration was also determined, the dominant size span was 0.5-1.4 $\mu$m due to agglomeration in the exhaust piping. A commercialized high voltage power source with automatic feedback control circuitry was successfully adapted to the current system.
The three-dimensional flow field, the particle mass concentration, and the electrical potential, and the electric field distributions in the corona charging chamber were obtained, which provide a means for design optimization and determination of electrical conductivity of diesel smoke by combining the experimentally measured voltage/current characteristics.
Results of particle collection on plates spaced at 2 mm apart at low velocity of 1 to 3 m/s in a passage of 40 cm long gave efficiencies of 60 to 75% depending on flow rate and smoke condition. The pressure drop was below 1 cm Hg. These results show that the emission standard of 0.25 g/bhp.hr. for 1991 and 0.1 g/bhp.hr. for 1994 stipulated by EPA can be met.
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