06 DPF Diesel Particulate Filter

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DPF (Diesel Particulate Filter) DPF is a device that forces the burned gases to pass through a porous medium: the particles larger than the porous are removed when the gas go through the filtering wall. The particulate matter accumulates in the filter that periodically (when the back pressure is too high) must be regenerated, by oxidising the carbon deposits. Because they have to stand high temperatures, DPF are commonly made of ceramic or metal elements with a honeycomb structure, where half the cells are closed at the inlet and the other half are closed at the outlet ends. Exhaust gases are forced to pass the porous wall and as the filter blocks the particles, the pressure drop in the exhaust system gradually increases. When the pressure drop is too high and affects the performances of the engine, the filter must be regenerated. Diesel PM ignites at about 600°C, a value above the normal temperature of exhaust gas (around 300°C). Thus, different strategies can be used: 1) Reduction of oxidation temperature at which oxidation reaction takes place by adding some additives (cerium oxides) in the fuel. The ignition temperature of the deposits decrease up to about 450°C and in this case a continuous regeneration is done. 2) Increasing exhaust gas temperature by means of a heater placed between the exhaust manifold and DPF. This can be continuous or discontinuous regeneration (controlled by a pressure controller). 3) Increasing temperature and changing composition of exhaust gases by changing the amount of EGR in the combustion chamber or it is common to use a post injection in order to force regeneration, but this obviously decreases the efficiency and the overall fuel consumption. 4) Utilization of Oxidizer Catalytic, placed upstream the DPF. It is able to oxidize by…