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Title: Rapid pulsed electric discharge particulate filter regeneration system
Author: Mason, Alex
ISNI:       0000 0004 7971 0549
Awarding Body: Loughborough University
Current Institution: Loughborough University
Date of Award: 2015
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Diesel Particulate Filters (DPFs) have been used for engine out Particulate Matter (PM) control for over a decade in diesel engine applications and are likely to see usage in future gasoline engine applications. However, reliability and cost effectiveness of regeneration systems still require improvement. To that end this research introduces a new, novel approach to particulate filter regeneration enabled by rapidly pulsed electric discharges. Presented is an experimental investigation into the regeneration technique, leading to a thorough understanding of its underlying processes. The regeneration system is shown to have three distinct regeneration phases, each with individual qualities. In the first phase of regeneration it has been shown that there is a distributed current flow and absence of any single spark discharge within the filter. Measurements show that the primary mode of regeneration is oxidation of trapped PM via ohmic heating, creating conditions for the second phase to begin. The second phase provides the majority of PM removal from the filter. Schlieren imaging has shown the regeneration mechanic to be a mechanical cleaning effect caused by spark discharge produced shock waves. Optical inspection, combined with digital image processing techniques and electrical circuit simulation have been able to put forward arobust explanation of the 'auto-selective' quality exhibited by the discharge. Discharge location is influenced by the balance between the electric field produced by electrodes and PM concentration and location within the filter. The basis for this is posited to lie with the conductivity of diesel PM (resistivity measured at ~ 1-20Ωm for typical diesel PM bulk densities). The final phase holds a spatially fixed discharge. Analysis suggests that the discharge loses the auto-selective attribute owing to the electric field of the electrodes becoming dominant. A reduction in applied voltage re-enables the auto-selective quality. This allows time for discharges to form elsewhere with preference returning to areas of PM concentration. The system is operable independent of filter temperature, does not expose the filter to high thermal stresses or temperatures and does not require any catalyst. Regeneration performance appeared non-uniform and significant PM of 5 g/l remained inside the filter post regeneration. Suitable usage would therefore include off-vehicle application where it would be capable of regenerating highly loaded DPFs which may be unrecoverable to other systems.
Supervisor: Not available Sponsor: EPSRC ; Caterpillar
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Mechanical Engineering not elsewhere classified ; Diesel ; Particulate ; Filter ; Plasma ; Spark ; Discharge ; Auto-selective ; Phases ; DPF