Diesel particulate filter

Others are designed to burn off the accumulated particulate either passively through the use of a catalyst or by active means such as a fuel burner which heats the filter to soot combustion temperatures.

This is accomplished by engine programming to run (when the filter is full) in a manner that elevates exhaust temperature, in conjunction with an extra fuel injector in the exhaust stream that injects fuel to react with a catalyst element to burn off accumulated soot in the DPF filter,[3] or through other methods.

Failure of fuel injectors or turbochargers resulting in contamination of the filter with raw diesel or engine oil can also necessitate cleaning.

Soot and other particles from diesel engines worsen the particulate matter pollution in the air and are harmful to health.

[14] Since then, progressively tighter standards have been introduced for light- and heavy-duty roadgoing diesel-powered vehicles and for off-road diesel engines.

[14] In the European Union, filters are expected to be necessary to meet the Euro.VI heavy truck engine emissions regulations currently under discussion and planned for the 2012-2013 time frame.

In 2000, in anticipation of the future Euro 5 regulations PSA Peugeot Citroën became the first company to make filters standard on passenger cars.

[17] In 2009 the American Recovery and Reinvestment Act provided funding to assist owners in offsetting the cost of diesel retrofits for their vehicles.

[4] In 2018, the UK made changes to its MOT test requirements,[26] including tougher scrutiny of diesel cars.

Each is designed around similar requirements: The most common filter is made of cordierite (a ceramic material that is also used as catalytic converter supports (cores)).

Cordierite filters provide excellent filtration efficiency, are relatively inexpensive, and have thermal properties that make packaging them for installation in the vehicle simple.

Fibrous filters have an advantage over wall flow design of producing lower back pressure.

Soot particulate burn-off forms water and CO2 in small quantities amounting to less than 0.05% of the CO2 emitted by the engine.

Coal mines are common users – the exhaust gas is usually first passed through a water trap to cool it, and then through the filter.

[36] Paper filters are also used when a diesel machine must be used indoors for short periods of time, such as on a forklift being used to install equipment inside a store.

This fuel and exhaust gas mixture passes through the Diesel Oxidation Catalyst (DOC) creating temperatures high enough to burn off the accumulated soot.

Once the pressure drop across the DPF lowers to a calculated value, the process ends, until the soot accumulation builds up again.

When the soot accumulation reaches a level that is potentially damaging to the engine or the exhaust system, the solution involves a garage using a computer program to run a regeneration of the DPF manually.

DPF may be unclogged by high temperature pressure washing (not officially recommended) and/or burn-off oven.

On-board active filter management can use a variety of strategies:[9] All on-board active systems use extra fuel, whether through burning to heat the DPF, or providing extra power to the DPF's electrical system, although the use of a fuel borne catalyst reduces the energy required very significantly.

Running the cycle too often while keeping the back pressure in the exhaust system low will result in high fuel consumption.

In the mid-2010s, scientists at 3M developed a magnesium doped version of traditional iron based catalysts which lowered the temperature required for particulate matter oxidation to just over 200 °C.

The lower reaction temperature is made possible by the dopant allowing the Fe lattice to hold more oxygen.

[52][51] In some cases, in the absence of a fuel-borne catalyst, the combustion of the particulate matter can raise temperatures so high, that they are above the structural integrity threshold of the filter material, which can cause catastrophic failure of the substrate.

[53] Intentionally removing or tampering with a DPF device, known as variously as "deleting", "defeating" or "tuning", is prohibited by the EPA.