JP2009515083A - Purification system for exhaust gas discharged from an internal combustion engine - Google Patents

Abstract

    The catalyst muffler (3) connected in series and the anti-particle filter (4) continuously traversed by the exhaust gas flow discharged from the internal combustion engine (2), the anti-particle filter (4) is discharged Exhaust gas exhausted by the internal combustion engine (2) arranged upstream of the catalyst muffler (3) to be traversed by hot exhaust gas from the internal combustion engine (2) before the gas is substantially cooled System for purifying.

Description

  The present invention relates to a system for purifying exhaust gas discharged from an automobile internal combustion engine, particularly a diesel engine.

  Pollutants contained in diesel engine exhaust are known to consist mainly of unburned hydrocarbons (HC), nitrogen oxides (NOx) and solid carbon particles, commonly known as particulates. Yes.

  In order to reduce unburned hydrocarbons and nitrogen oxides, diesel engine purification systems typically have catalyst mufflers, which are exhausted from the engine before they are released into the air. And a catalyst that causes the chemical reactions necessary to reduce nitrogen oxides and oxidize unburned hydrocarbons.

  Specifically, the catalyst muffler comprises a series of active components that are continuously traversed by the exhaust gas, the series of active components including an oxidation pre-catalyst, a catalyst, and a muffler.

  In order to reduce particulate matter, the purification system is equipped with a suitable anti-particle filter placed inside the catalyst muffler between the oxidation pre-catalyst and the catalyst, which retains the particulate matter and passes through the gas phase It is made of a porous material. The most widespread anti-particle filters are currently made of ceramic materials, typically silicon carbide, but metal filters made of sintered metal, for example, are also known.

  In use, the anti-particle filter is usually clogged very quickly, and therefore undergoes a regenerative operation periodically, and the filter is exposed to high temperatures so that the trapped carbon particles can be burned away from the filtration wall.

  The normal operating temperature currently used for anti-particle filters is approximately 300 ° C., and such a temperature is insufficient to guarantee the combustion of particulate matter performed at elevated operating temperatures above 600 ° C. .

  Thus, the regeneration operation is accomplished by introducing an appropriate mixture of oxygen and an easily combustible gas into the anti-particle filter, possibly in contact with the filtration wall, possibly covered with a catalyst, spontaneously. Burn.

  In particular, the regeneration mixture can be introduced directly by means of a suitable injection device or indirectly by appropriately adjusting the air / fuel ratio of the engine supply system.

  A disadvantage of the known anti-particle filters is that many areas of their filtration walls do not reach the temperature necessary to burn the regeneration mixture. Thus, combustion occurs only at some of the hottest points on the filtration walls and cannot be completely removed from the particulates that accumulate from the filtration walls, resulting in a loss of system efficiency.

  Such a phenomenon is substantially caused by two causes. First, during normal operation, anti-particle filters are heated by exhaust gases, typically in a non-uniform manner, and the lower the thermal conductivity of their constituents, the greater the temperature difference. That's what it means.

  Secondly, the carbon particles contained in the exhaust gas are aggregated with each other during the passage of the exhaust gas and are accumulated unevenly on the filtration wall of the anti-particle filter. This fact means that not all accumulated particulates, but conditions for the combustion of the regeneration mixture exist, only the area of the largest clogging region can be efficiently burned. .

  German Patent DE 103 23 385 discloses an exhaust gas filtration device in an internal motor motor vehicle, wherein the anti-particle filter intersects the hot flow of exhaust gas upstream of the catalyst device and the motor. It is attached near.

  The object of the present invention is to solve the above drawbacks in the category of simple, reasonable and low cost solutions.

  This object is achieved by a system for purifying exhaust gas exhausted by an internal combustion engine, comprising a catalyst muffler connected in series and an anti-particle filter that is continuously traversed by the exhaust gas flow exhausted from the internal combustion engine. .

  According to the present invention, the anti-particle filter is placed upstream of the catalyst muffler so that the hot exhaust gas leaving the internal combustion engine traverses before the exhaust gas is substantially cooled.

  According to such a configuration, the anti-particle filter is heated to a higher average operating temperature than in the prior art, so that the entire area of the relative filtration wall reaches the minimum combustion temperature of the regeneration mixture. It is possible to make it. In this way, the regeneration process affects the whole anti-particle filter and thus the useful life is effectively increased.

  Preferably, the anti-particle filter is placed in close proximity to the engine to reach an average operating temperature in excess of 600 ° C., so that the combustion of accumulated particles is usually without the need to introduce a specific regeneration mixture. Can be performed continuously during system operation.

  According to the present invention, the anti-particle filter can be composed of any known porous material if it can withstand temperatures of about 600-800 ° C., however, preferably a ceramic or metallic material filter is used.

  In particular, metallic materials have higher mechanical strength, higher maximum storage capacity and high durability against thermal stress. It also makes it possible to construct a thin wall filter that guarantees a high regeneration rate and a very uniform heating due to the high conductivity of the material.

  Further features and advantages of the present invention will become apparent from the following description, given by way of non-limiting example, with reference to the accompanying drawings.

  The system 1 has a plurality of exhaust collecting pipes 10, each of which is connected to each of the cylinders of the diesel engine 2 to carry the exhaust gas generated by combustion to a common junction 11. Yes. An exhaust conduit 12 extends from the common junction 11 to direct the exhaust gas stream to an outlet 13 leading to the atmosphere.

  The basic design of the system 1 is purely indicative and varies greatly depending on the form of the engine 2 and / or the form of the vehicle on which the system 1 is mounted without departing from the scope of the present invention. There is a possibility.

  A conventional catalyst muffler 3 is disposed along the exhaust conduit 12 through which the exhaust gas flow from the diesel engine 2 passes and is a suitable catalyst that promotes nitrogen oxide (NOx) reduction and unburned hydrocarbon (HC) oxidation. Is housed.

  According to the present invention, the anti-particle filter 4 is accommodated and arranged in a suitable casing upstream of the catalyst muffler 3 with respect to the flow direction, and is mixed with exhaust gas in order to prevent release into the atmosphere. It is possible to hold the particulate matter carried by

  Preferably, the anti-particle filter 4 is made of a metal material such as a sintered metal. However, the anti-particle filter 4 may also be composed of any porous material suitable for the purpose, for example a ceramic material.

  In operation, the anti-particle filter 4 is traversed by hot exhaust gas generated directly from the engine 2 before being substantially cooled by flowing substantially over the entire length of the exhaust conduit 12.

  In this way, under substantial heating, each of the relative filter wall regions is able to substantially reach the lowest temperature for spontaneous combustion of the regeneration mixture that occurs during the regeneration operation.

  In fact, this degree of heating determines the temperature of the exhaust gas through the anti-particle filter 4 and therefore varies with the distance between the anti-particle filter 4 and the engine 2, i.e. the total length of the conduits connecting them.

  Preferably, the anti-particle filter 4 is placed in close proximity to the engine 2 so as to be heated to an average operating temperature of at least over 600 ° C.

  According to such a configuration, the necessary conditions for the natural combustion of the normal exhaust gas discharged by the engine 2 enable continuous regeneration at each of the operating stages without introducing a specific regeneration mixture. In order to do so, it can be recovered inside the anti-particle filter 4.

  Several possible configurations for achieving the above temperature level are discussed below.

  According to the embodiment shown in FIG. 1, the anti-particle filter 4 is exhausted immediately downstream of the point 11 where the exhaust collecting pipe 10 joins, preferably upstream of any turbo compressor turbine, if present. Located along the conduit 12.

  According to the embodiment shown in FIG. 2, the anti-particle filter 4 is divided into a plurality of smaller filters 40 having the same number as the cylinders of the engine 2, and each filter 40 is upstream of the junction 11. The exhaust collecting pipe 10 is disposed along each of the exhaust collecting pipes 10.

1 is a schematic view of a system according to the present invention for purifying exhaust gases emitted by a diesel engine of an automobile. FIG. 2 is a schematic diagram of another embodiment of the system of FIG.

Claims (7)

Exhaust gas exhausted by the internal combustion engine (2) having a catalyst muffler (3) connected in series and an anti-particle filter (4) continuously traversed by the exhaust gas flow exhausted from the internal combustion engine (2) In the system to purify
In relation to the direction of the gas flow, the anti-particle filter (4) allows the catalyst muffler (3) to cross the hot exhaust gas leaving the internal combustion engine (2) before the exhaust gas is substantially cooled. A system characterized by being arranged upstream of the system.   2. The anti-particulate filter (4) is arranged close to the internal combustion engine so as to be heated by the exhaust gas to an average operating temperature allowing continuous combustion of the particulate matter. System.   2. System according to claim 1, characterized in that the anti-particle filter (4) is arranged close to the internal combustion engine so that it is heated by the exhaust gas to an average operating temperature in excess of 600 ° C.   It has an assembly of exhaust collecting pipes (10) for individually carrying exhaust gases discharged from the respective cylinders of the internal combustion engine (2) to a common junction (11), and the anti-particle filter (4) is the above-mentioned common 2. System according to claim 1, characterized in that it is arranged immediately downstream of the confluence (11).   It has an assembly of exhaust collecting pipes (10) that individually carry exhaust gases discharged from the respective cylinders of the engine (2) to a common junction (11), and the anti-particle filter (4) is an exhaust collecting pipe 2. System according to claim 1, characterized in that it comprises an assembly of separation filters (40) arranged individually along each of (10).   2. System according to claim 1, characterized in that the anti-particle filter (4) consists of a ceramic material.   The system according to claim 1, characterized in that the anti-particle filter (4) is made of a metallic material.

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