Abstract: Diesel engine using exhaust gas recirculation to reduce nitrogen oxides, take measures to reduce particulate emissions is necessary, which use particle Filter Is an effective way. This paper describes the type of the particulate filter, regeneration methods and the associated exhaust gas recirculation filtration system model.

1. Foreword With the engine emissions on the environment, increasing pollution, the engine's emission control, more and more cause for concern. The type and quantity of emissions due to aircraft, fuel systems and different operating conditions. Diesel emissions in hc, co the concentration is much lower than gasoline, nox emissions and gasoline is almost, but particulate emissions than gasoline engines by about 30 ~ 70 times. Therefore, controlling the emission of pollutants from diesel engines focus on reducing nox emissions and particulate emissions from diesel engines. This article on the use of egr reduce nox emissions increase when the particles caused by issues related solutions.

2.egr on Diesel Engine Performance
EGR is part of the emissions into the combustion chamber to participate in the combustion process. As the main component of the exhaust is an inert gas (co2, h2o, n2, etc.), they have a higher specific heat, when the new mixture and exhaust mixture, heat capacity is increased with the reduction of the maximum combustion temperature; while egr dilution of the new mixture, but also a corresponding reduction in oxygen concentration, so nox formation in the combustion process is suppressed.

2.1 egr on emissions We all know, egr (exhaust gas recirculation) has been made in reducing nox great success, it is often the same time reducing nox emissions would increase in other emissions, especially particulate emissions. egr dilution effect so that the maximum combustion temperature decreases, effectively inhibited the formation of nox, but due to reduce the concentration of oxygen in the mixture, combustion is incomplete, so that unburned hydrocarbons, carbon monoxide and particulate emissions increase, increased particulate particularly evident, is more harmful for the environment. Particulates and nitrogen oxides, while control is a pressing problem.

2.2 egr on the impact of oil and engine parts
Recycling of exhaust particulate matter into the cylinder contains will adhere to the surface of the cylinder wall oil film in the work process in the engine, the piston ring material substance of these micro-scraping into the crankcase, so that insoluble in oil increased, resulting in piston rings, valves and other parts of the wear and tear, this needs to be back exhaust filter, which for the installation of the diesel engine turbocharger is particularly important. If equipped with diesel engines use turbochargers reduce nitrogen oxides egr, egr removed at least 99% of gas particles.

3. Particulate filter and regeneration This recycled exhaust filtering system designed to control nitrogen oxides, the system is in the exhaust into the recycling line before (that is, before entering the cylinder) and use it to trap filter, and then exhaust again cyclic working process.

Now use have a lot of particles on the filter, these measures do not completely solve the recycling of internal combustion engine exhaust particles too, especially to install a turbocharger diesel engine damage. Filter recycling exhaust system, while reducing nox particles to achieve the objective of reducing, recycling and regeneration of the exhaust filter element is the key.

3.1 filters brief Particulate filter includes a filter with a pore independent media to capture particles. Were collected mostly dry carbon soot (soot) and carbon adsorption are sof gray. Generally made of ceramic and metal mesh filter, as ceramics can withstand high temperatures and high filtration efficiency, it becomes the main filter media.

Filter is mainly the overall wall-flow ceramic (wall-flowmonolith), the synthesis of cordierite and silicon carbide ceramics made of cordierite has a certain mechanical strength and good thermal shock resistance, low coefficient of thermal expansion Its weakness is a lack of high temperature, generally not more than 1200 , thermal conductivity coefficient is small, the Regeneration, the internal combustion heat easily spread, resulting in pillow melting or burning split filter. Silicon carbide is a good new filter, it is more uniform pore size than cordierite, and have good communication flow, filtration efficiency, high temperature (over 1600 ), through the good characteristics such as cordierite and Synthesis of silicon carbide ceramic filter media is common.

Generally classified into the surface of the filter type and depth filtration type filter. Surface-type filter is the filter soot deposited on the surface, but more and more thick soot, the filter pressure drop to increase too fast, it's filtration efficiency is mainly affected by the impact of the material pore size and pore size affect the filter collection efficiency. The depth filter type is captured particles accumulate in the body of filter material, fiber material and adhesive forces between particles and the cohesion between particles and particles to improve the efficiency of trapping particles play an important role, this filter filter is made of ceramic or metal fibers, a more stable collection efficiency and pressure drop, but the collection efficiency is too low, requiring high pressure drop and thick filters.

3.2 Regeneration of the filter
Remove particulate material deposited on the filter is called filter regeneration. Engine Filtration System The real challenge is the regeneration of the filter. Filtration system regeneration cycle can also occur continuing to collect the particles through the oxidation gas (the ideal state is carbon dioxide) was removed, the regeneration of particulate filters by the total accumulated amount of particles, particle density and distribution of storage, exhaust flow rate, filters out the situation and the particles heat capacity of activation.

(1) high heat regeneration Order to be able to make particles under various conditions of oxidation into carbon dioxide gas, so that the temperature of particles above the minimum oxidation temperature is necessary. Usually reduce the particle ignition temperature or increase the minimum exhaust temperature of the ways to achieve the regeneration of particulate filters.

If regeneration is not sufficient, particulate filters will overload the engine back pressure. In extreme cases, the filter is blocking the engine stopped running. On the other hand if a high load of soot filters suddenly exposed to high temperature exhaust gas and begin regeneration, in the reaction gives off a lot of heat, causing thermal stress and effects of filter stability of the filter. In extreme cases, melt or cartridge filter will rupture.

Under normal working conditions in the internal combustion engine, internal combustion engine exhaust gas temperature is generally 200 ~ 500 , while the light particles is generally 500-600 , the temperature dependent internal combustion engine exhaust filter regeneration is difficult to make. For particulate trap regeneration to reduce the ignition or increase exhaust temperature. By fuel, exhaust filter with additive or surface coating can reduce the particulate catalyst layer burning. This

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