Diesel PM Collection for Marine and Automobile Emissions Using EHD Electrostatic Precipitators

The collection of low resistive particulate matter (PM) generated from marine and automobile diesel engines have been known to be difficult by conventional electrostatic precipitators (ESPs). The collection efficiency for three types ESPs, namely, the conventional dc-energized ESP, the trapezoidal-waveform-energized ESP (TW ESP), and the electrohydrodynamically assisted ESP (EHD ESP) were investigated. Low resistive PMs are detached from the collection plate by the electrostatic repulsion force caused by induction charge resulting in particle reentrainment. The EHD ESP utilizes ionic wind combined with an electrostatic force to transport the charged particles into the zero electric field zone (pocket zone) attached to the collection plate effectively. The conventional dc-energized ESP showed good collection efficiency for particle sizes less than 300 nm where adhesion force was dominated over electrostatic repulsion force but showed a severe reentrainment for particle sizes greater than 1000 nm, while the TW ESP suppressed the particle reentrainment for larger particles but still showed negative collection efficiency. On the other hand, the EHD ESP showed an excellent collection efficiency for particle sizes up to 1000 nm and a significant reentrainment suppression was observed even for particle sizes greater than 2000 nm.