Tech Briefs
Toward cleaner diesels

Electrocat DPF model

Development of efficient techniques for dealing with passenger car diesel ex- haust particulates is a challenge that has been occupying automotive engineers and chemists for many years. AEA Technology in the UK is developing the Electrocat Diesel Particulate Filter (DPF), which it says operates at low exhaust temperatures, is self-cleaning, does not require fuel additives, and is apparently unaffected by sulfur levels in fuel. AEA describes it as a self-cleaning system, using plasma filter regeneration "to remove all types of carbonaceous particulates, including ultrafines, as well as gaseous hydrocarbons including suspected carcinogenic polyaromatic hydrocarbons." Electrocat DPF is said to be "in the late stages" of development, with vehicle testing under way.

AEA explains that its system uses proprietary Electrocat technology that employs a gas plasma. A plasma is a gas that has been at least partially ionized by having an electrical current passed through it, becoming chemically reactive because of the electrons and free radicals it contains. This reactivity can be engineered to perform chemical reactions under low-temperature conditions (non-thermal plasmas) in which reactivity would not normally be expected. This property makes plasma particularly suitable for the environmental treatment of gases so that, for example, an organic contaminant can be removed from a gaseous waste stream, such as an engine's exhaust, without the need for thermal or catalytic oxidation.

The Electrocat DPF system consists of: 1. A dual-voltage alternator. 2. A power supply. 3. A combined muffler/diesel particulate filter.

AEA believes that plasma technology will play a vital role in future automotive aftertreatment systems. A problem has been scaling up plasma-based aftertreatment systems for onboard vehicle use. But AEA says its new Electrocat DPF demonstrates that advanced plasma technology can be successfully integrated into a production vehicle by allowing the DPF to double as an exhaust muffler. AEA adds that for initial applications, the Electrocat technology package includes a 90% efficient dual-voltage alternator in readiness for 42-V systems. "This advanced component has the potential in its own right to deliver a fuel efficiency benefit."