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Electrostatic removal of diesel particulate matter.

Dallas, TX: Southern Methodist University, 2008 May; :1-151
Diesel engines are the most efficient internal combustion engines. The high concentration and carcinogenicity of diesel particulate matter, however, help impede universal use of these engines in passenger vehicles, and diesel powered machinery in the workplace has been linked to occupational cancers. Methods developed so far to reduce diesel particulate matter emissions have focused on the use of mechanical filters and/or catalysts. Even the most advanced diesel particulate filters create a backpressure which can result in increased fuel consumption. In addition, filters need to be regenerated periodically to reduce back pressure and prevent plugging. A regeneration method applicable to all diesel engine applications has not been developed. The primary objectives of this study were to develop a technique to reduce diesel particulate matter emissions into the environment and into the workplace, and to investigate electrostatic precipitation to capture diesel particulate matter. Electrostatic precipitators have been widely used in industry for more than a century, but they have not been successfully miniaturized for particulate removal from mobile sources or diesel powered machinery. The first part of this study was focused on designing and constructing a small-scale ESP, an investigating its fundamental electrical properties (corona onset voltage, voltage-current relationship, and sparkover voltage). Classic theories for large industrial electrostatic precipitators were compared to the experimental data. One of the primary conclusions was that the value of the mobility of air ions, an important parameter in ESP design, should be modified for small plate-to-plate distance precipitators to accurately predict the electrostatic properties of small-scale units. This portion of the research should benefit not only this diesel exhaust project, but also other efforts to use small scale electrostatics for air purification. The small-scale ESP was then used to remove diesel particles from the exhaust of a 5.5kW diesel powered electric generator. Tests were performed with two different fuels and at two different load conditions to examine their effects on performance. The ESP showed an average mass removal efficiency of 80 percent and an average number removal efficiency of 90 percent with low sulfur diesel and at medium load. However, number efficiency dropped by 30 percent when the load was removed. The study also showed a drop of up to 20 percent in mass removal efficiency when the concentration of sulfur in the diesel was reduced. To reduce the incidence of wire breakage, a new design with wires parallel to the flow was introduced and tested. The new design showed better removal efficiencies, especially at idle load conditions. Power consumption never exceeded 65 watts in any of the tests. The small-scale ESP designed, constructed, and tested for this project demonstrated the feasibility of using electrostatics to significantly reduce emissions of particulate from diesel powered machinery and vehicles.
Particulate-dust; Diesel-exhausts; Diesel-emissions; Dust-particles; Dust-inhalation; Airborne-particles; Electrostatic-precipitators; Electrostatic-filters; Emission-sources
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Electrostatic Removal of Diesel Particulate Matter
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Southern Methodist University