Diesel Particulate Filter

What are they?

A diesel particulate filter removes particulate matter from diesel exhaust by physical filtration. The most common type is a ceramic (cordierite or silicon carbide) honeycomb monolith. The structure like an emissions catalyst substrate but with the channels blocked at alternate ends. The exhaust gases must therefore flow through the walls between the channels and the particulate matter is deposited on the walls.

Other filter types are available, using sintered metal plates, foamed metal structures, fibre mats and other materials as the filtration medium.

The filtration efficiencies of diesel particulate filters is > 99% for solid matter. Since diesel particulate matter has a non-solid portion, the total efficiency for DPM is lower than this, > 90%.

A variant on these systems is the partial filter. Partial filters are not designed to be 100% efficient. They can be designed to trap, for example, 60% of the particulate matter. The advantages are lower back pressure and a lower risk of blocking.

All particulate filter systems include some means of regeneration.