DPF (A Diesel Particulate Filter) removes the diesel particulate matter from the exhaust gas of a diesel vehicle, so reducing particulate emissions. Diesel Particulate Filters generally remove extra 85% of the soot.
Looking like to an exhaust silencer diesel particulate filters work by push engines gasses to flow through a complex ceramic honeycomb structure as the channels of the filter are blocked at rotate ends, the gasses are forced to flow through the cell walls in order to exit the filter and because the cell walls are porous, the gasses are allowed to pass through, but the particulate matter is deposited on the walls. This ensures that just the clean exhaust gasses can exit, and the particulate matter is trapped in the filter. Even though, they have to be emptied frequently to maintain performance, this is done in the following two ways:
Passive Regeneration means passive regeneration takes place automatically on motorway-type runs when the temperature of the exhaust is higher, but problems can take place when cars don’t reach this sort of temperature on a normal basis which many cars don’t. So that’s why manufacturers have come up with a solution called “Active Regeneration”.
Active Regeneration (AR) takes place when the soot level in the filter builds up to around 45%. The ECU makes small adjustments to the fuel injection timing and increases the exhaust gas temperature. This increases the exhaust temperature which then initiates the regeneration process, burning away the soot trapped in the DPF.
Types of Filter
Cordierite filters: – Cordierite filters offer exceptional filtration efficiency and are comparatively inexpensive. As the name suggests, they are made from a ceramic material called cordierite, which is also used in catalytic converters. The single problem with cordierite wall flow filters is the low melting point, which has been known to melt down during filter regeneration.
Silicon Carbide Wall Flow Filters: – Silicon carbide wall flow filters are the second most common filter. They have a far superior melting point than cordierite filters although they are not as thermally stable.
Ceramic Fibre Filters: – Ceramic fibre filters are manufactured by mixing different types of ceramic fibre, to create a porous media. This can then be formed into any shape to suit different applications. The main advantage of ceramic fibre filters is that they have a lower back pressure.
Metal Fibre Flow through Filters: – Metal fibre Flow through filters is made by weaving metal fibres into a monolith. They have the skill to pass electrical current through, which can heat the monolith for regeneration purposes. This type of filter tends to be extra costly.