During the combustion of fuels, the engine produces many exhaust soot particles which are harmful to the environment and to people’s health like carbon (CO), unburned hydrocarbons (UHCs), nitrogen oxides (NOx) and, in the case of a diesel engine,particulate matter (PM) which is smaller than about 10 micrometers, referred to as PM10.
Particulate filters are devices which trap PM10 (up to 99%) and, as any other filters, need to be cleaned out regularly to prevent the blocking and resulting damages to the car: an overfilled filter can damage the engine and can itself be damaged or destroyed.
The cleaning of the particulate filter, that is the combustion of the PM10 trapped inside the filter, is called regenerationand it takes place automatically every 400-800 km more or less, depending on the quantity of particulate inside the filter and the driving behaviour.
The regeneration process is connected to the backpressure value, that is the difference between the incoming pressure of the air in the filter and the outcoming pressure: the more the filter is clogged, the higher is the difference, until the car recognizes the limit value and let the regeneration begin.
The most common particulate filters are FAP and DPF which are different in functioning but especially in the regeneration strategy.
