Rapid Pulse Discharges: A New Approach to Particulate Filter Regeneration

The project will research a radically new approach to cleaning surfaces that uses pulsed electric discharges to efficiently regenerate engine exhaust particulate filters. It has class-leading features that make it potentially both commercially and technically very attractive.IC engines are the major source of motive power in the world, a fact that is expected to continue well into this century. Whilst diesel engines emit low CO2 emissions, and have good fuel economy and good durability, they emit significant amounts of particulate matter (PM) emissions that are potentially harmful. Engine and vehicle legislation introduced in the EU, US and Asia can only be achieved with the use of diesel particulate filters (DPFs) with further reductions proposed for 2013. Without regular cleaning (regeneration) DPFs become clogged after about 150 miles of vehicle operation leading to a high exhaust back-pressure on the engine, resulting in poor performance and fuel economy. Whilst current DPFs yield >95% reductions in PM by forcing the gas stream through a porous ceramic wall, to-date the regeneration systems suffer from high power consumption, unreliability, unacceptably high cost and limited choice of materials, or are simply too bulky and complex. The step-change in regeneration technology proposed here will achieve a more ideal system and could enable wider application of DPFs to a greater number of engines and applications.The research proposed here will achieve the advantages of a non-thermal non-oxidative regeneration system without either the sensitivity to filter geometry and pore structure or a prohibitively high power consumption, bulky, heavy and noisy regeneration system. The new concept uses pulsed electric discharges to rapidly and very efficiently remove the PM from the filter surface without oxidation. Preliminary results suggest that shock waves produced by pulsed electric discharges within the filter overcome surface forces to break the bond of the PM with the filter surface using as little as 10 W electrical power for a whole filter. The combined effect of the pressure waves within the filter and the electric field accompanying the discharge break up the agglomerated particulates and allow efficient removal of the PM from the filter using a small reverse flow. The PM is then captured in a container, from where it can be subsequently destroyed, e.g. by a robust and easily controlled electric heater, or compacted and stored, reducing carbon emissions. The result is the rapid, low power, durable, effective and low cost regeneration of diesel particulate filters without ash accumulation. A very significant additional advantage of electrical discharges are that they are attracted to the most electrically conducting sites within the filter, i.e. once the discharge has cleaned one region it will self select a region with higher PM loadings.The research is strongly supported by key partners Caterpillar and 3DX-Ray Ltd., who will be providing substantial support in terms of cash, equipment, staff time and exploitation paths. This will enhance the impact of the research, which is expected to be high in terms of new scientific and technical knowledge, commercial value and societal benefits to the environment.

This research is expected to have a very significant commercial, technological and scientific impact. The project will also output trained multi-disciplinary researchers capable in state-of-the-art instrumentation and diagnostic methods with the transferable skills necessary to become a future research manager. Loughborough University will benefit from increased research output including patents, journal publications and conference presentations and it is likely to lead to follow-on funding with further industrial collaboration. The UK is the largest European manufacturer of non-road machines, with both smaller machine makers and larger international organisations, such as Caterpillar, employing ~58,000 people with a very high export ratio (85%). This diesel engine market is growing by 5.5% each year. If this technology proves successful, Caterpillar will benefit from additional product differentiation which will promote market growth and profitability. The proposed technology is expected to offer improved performance over existing technologies allowing smaller aftertreatment packages (no ash limit), improved fuel economy (low specific energy regeneration) and independence of precious metal catalysts, reducing the business risk associated with the volatile precious metal market. It is anticipated that this technology will enable DPF application to be extended to smaller engines which are currently cost prohibitive further improving air quality. Considerable warranty issues associated with thermal damage from conventional regeneration systems will be avoided with this non-thermal regeneration technique, reducing the business risk of introducing this new emission aftertreatment technology. The commercial advantage this technology may give to the UK engine would generate new jobs, income and stability. Initial patent applications have been filed and further patents are likely with licensing opportunities which will be managed by Caterpillar. End users of this technology will benefit significantly beyond the initial cost of the aftertreatment systems. Fuel costs will be reduced due to the low specific energy requirement, service costs will be reduced due to the removal of the ash loading limits and durability will be improved, specifically associated with thermal degradation of the filter and lack of dependence on catalysts (susceptible to catalyst poisoning). 3DX-Ray Ltd will directly benefit from the proposed research from further development, application and feedback to their X-ray measurement equipment as they work as an integral part of the research at Loughborough. Technical experience will be gained by applying their technology in new ways e.g. transient PM loading and regenerating studies which will for the first time show PM distribution during loading and regeneration events. Directly measuring PM loading and distribution in a filter is a very new area and publications from this research will potentially generate new business for 3DX-Ray and enhance their market position. The diesel engine industry will also gain experience with this technology which may offer development pathways for future DPF systems within industry. This project will contribute notably in the areas of rapid pulsed discharge formation and interaction with the surroundings enabling plasma technologists to develop new and improved technologies for e.g. material processing. Fundamental data and knowledge will be disseminated through key industrial conferences and scientific journals. Beyond the direct scope of this work, the fundamental studies of aerosol formation and surface cleaning with electrical plasmas will be of benefit to e.g. pharmaceutical industries where repeatable aerosol formation is essential for dosage metering. Meetings will be held with key pharmaceutical companies during the project to discuss the possibility of new spin-off technologies based on pulsed discharge cleaning and aerosol formation.