FR2923532A3 - Particles filtering system for oil engine of motor vehicle, has particle trap destructing part of particles of exhaust gas, and particle filter placed downstream of particle trap for permitting other parts of particles to be traversed - Google Patents

Abstract

The system has an exhaust line (6) for exhausting combustion gas, and with an oxidation catalyst device and a particle filter (9) that accumulates particles of the exhaust gas, where the filter is regulated in a controlled manner. The device is constituted by a particle trap (8) trapping a part of the particles of the exhaust gas and destructing the part by action of an oxidation catalyst. The filter is placed downstream of the particle trap for permitting other parts of the particles to be traversed. The device has a series of corrugated metal layers and non-woven metal fiber supports. An independent claim is also included for a vehicle comprising an oxidation catalyst device.

Description

B07-2793 - EGA / EVH

Société par actions simplifiée known as: RENAULT s.a.s. Filtration system for particles emitted by an internal combustion engine Invention of: FASOLO Bertrand

The invention relates to the field of internal combustion engines of a motor vehicle, and in particular particulate filtration systems emitted by these engines. In this field, there are particle traps that include channels that can be traversed by the exhaust gas. Such particle traps have the advantage of not risk clogging because the flow of exhaust gas is only deflected. Part of the particles is trapped. The proportion of trapped particles does not generally exceed 50%. Such particle traps do not achieve the low level of particle emissions tolerated by the standards applicable to diesel type vehicles. There are also particulate filters including channels clogged at their ends and porous walls in which the particles contained in the exhaust gases are deposited. These filters make it possible to retain almost all the particles. However, the particles gradually clog the particulate filter. This causes a counterpressure opposing the evacuation of the combustion gases and decreases the performance of the engine. To regenerate the particulate filter, it is common to temporarily increase the internal temperature of the particulate filter to 500 ° C or 600 ° C. This burns soot in the form of CO2 and water vapor. Regeneration allows the particulate filter to regain its filtering efficiency. This type of regeneration is said to be active because it is necessary periodically to raise the temperature within the particulate filter.

Patent application EP 1 270 885 describes a device for purifying diesel engine exhaust gases. The device successively comprises an oxidation catalyst, a particulate filter, and a NOx catalyst. The oxidation catalyst described has a cordierite or honeycomb structure comprising active alumina. The oxidation catalyst is used to oxidize nitrogen monoxide NO, carbon monoxide CO and HC hydrocarbons into, respectively, NO2, CO2 and H2O. The combination of the oxidation catalyst and the particulate filter makes it possible to regenerate a portion of the particles that can be oxidized at low temperature by NOx mono- or dioxides nitrogen through the particulate filter. However, the disadvantage of this device is that the particulate filter must be of sufficient size to stop all the soot escaping from the engine. This imposes a volume all the more cumbersome that the desired level of filtering is severe. The evolution of the standards regulating the polluting emissions of vehicles equipped with engines of type Diesel are more and more severe. In addition, the vehicles are designed to allow maximum room for the passenger compartment. The increase in the required levels of depollution increases the problems of implantation of particulate filters in the vehicle. The invention proposes a filtration system and a vehicle equipped with such a system that overcomes the above disadvantages. An object of the invention is to provide a filtration system with easy implantation in the vehicle. According to one embodiment, the particle filtration system emitted by an internal combustion engine of a motor vehicle comprises a combustion gas exhaust line equipped with an oxidation catalyst device and a filtering device. particles for accumulating exhaust gas particles and being regenerated in a controlled manner. The oxidation catalyst device comprises means for trapping part of the particles of the exhaust gas and for destroying the said part by the action of the catalyst, the particle filter device being arranged downstream of the catalyst device. oxidation to be crossed by the other part of the particles.

The fact that is implanted, upstream of the particulate filter, not a simple oxidation catalyst but a device provided with means for trapping particles allows only a proportion of the particles to be filtered by the particulate filter. Thanks to the catalyst of the catalytic particle trap, the particles trapped in said trapping means, as well as in the particulate filter can undergo a passive regeneration at low temperature. The amount of soot to undergo controlled active regeneration is thus reduced. This makes it possible to have a particle filter of smaller dimensions. This facilitates the implementation of the particle treatment system in a vehicle. In addition, it is common to use in particle filters a silicon carbide substrate. The biggest contribution to the cost of a particulate filter is often the volume of the necessary substrate. Thus, by reducing the volume of the particles to be filtered, the overall cost of the particle treatment is greatly reduced. Advantageously, the oxidation catalyst device comprises means for deflecting the flow of exhaust gas to non-woven metal fiber parts impregnated with catalytic material. The trapping means may in particular be constituted by the nonwoven fiber parts. The metal fiber parts allow a catalyst temperature rise faster than traditional cordierite supports. This faster temperature rise allows for more efficient passive regeneration of soot. It also allows a better oxidation treatment of carbon monoxide and nitrogen. Advantageously, the oxidation catalyst device has, alternately, a series of corrugated metal layers with a series of non-woven metal fiber supports.

Advantageously, the oxidation catalyst device comprises a multitude of channels having connecting fins capable of diverting the combustion gases from one channel to the other. This allows the exhaust gases to be dispersed and mixed over the entire surface that may trap the particles. This increases the efficiency of particle trapping. Advantageously, the oxidation catalyst device and the particulate filter are assembled in the same box. The fact of introducing in the same box the particle filter device and the oxidation catalyst device makes it possible to lower the costs, to densify the particle treatment system and to facilitate its implantation in the vehicle. According to another aspect, the invention relates to a vehicle equipped with an engine and a filtration system. According to one embodiment, the oxidation catalyst device is implanted in an engine compartment. Such an implementation makes it possible to benefit from the proximity of the powertrain. This makes it possible to treat hot exhaust gases. The passive regeneration of soot in the oxidation catalyst device is more efficient. This reduces the volume and therefore the cost of the necessary particulate filter. This advantage is found as much in an embodiment where the particle filter is also located in the engine compartment, as in an implementation mode where the particulate filter is remote off the rear of the vehicle. According to one embodiment, the engine is equipped with a turbo compressor, the oxidation catalyst device and the particulate filter device being located immediately downstream of the turbo compressor. This first mode of implantation of the filtration or particle treatment system can benefit both from the advantage of the proximity of the powertrain, and from the conditioning of the particle filter device and the oxidation catalyst device in a single device. box. According to one embodiment, the particulate filter is implanted in an underfloor zone. This second mode of implantation of the particle treatment system is possible because the necessary particulate filter volume is reduced. In addition, this mode of implementation reduces the size in the engine compartment or increase the passenger compartment.

According to one embodiment, the oxidation catalyst device and the particulate filter are located in a communication tunnel between an engine compartment and an underfloor zone. This third implementation mode of the particle treatment system is a compromise between the two previous modes of implantation. One can both benefit from the proximity of the powertrain, and therefore the heat of the exhaust gas to be treated, without overcrowding the engine compartment. In addition, this implementation mode allows to house the two devices in the same box and further reduce the cost of particle processing. Advantageously, the engine is equipped with a turbo compressor located near the vehicle tunnel, the oxidation catalyst device being located near the turbo compressor. Other features and advantages of the invention will appear on reading the detailed description of some embodiments taken as non-limiting examples and illustrated by the accompanying drawings, in which: - Figure 1 is an illustration of a first embodiment of a particle filtration system in a vehicle - Figure 2 is an illustration of a second embodiment of a particle filtration system in a vehicle - Figure 3 is an illustration a third embodiment of the particle filtration system in a vehicle - Figure 4 is a cross-section of an oxidation catalyst device; - Figure 5 is a longitudinal section along the plane V-V of Figure 4, the oxidation catalyst device; and - Figure 6 is a longitudinal section along the plane VI-VI of Figure 4, the oxidation catalyst device. With reference to FIGS. 1 to 3, three modes of implantation of the particle filtration system emitted by an internal combustion engine 1 in a motor vehicle, comprising in particular an engine compartment 2 and a passenger compartment 3, are described. separated by a front partition 4 and a floor 5. The system is also equipped with a gas exhaust line 6, starting from the engine 1 and successively comprising a turbocharger 7, an oxidation catalyst device 8 and a filter device In the implantation mode illustrated in FIG. 1, the oxidation catalyst device 8 and the particulate filter 9 are located in the same box 10. The oxidation catalyst device 8 is located upstream of the filtration filter. particles 9, that is to say on the side of a connection manifold 11 joining the box 10 to the turbine 7. The particle filter 9 is located in the box 10 downstream, that is to say the side of an outlet manifold 12. The oxidation catalyst device comprises trapping means not visible in FIGS. 1 to 3 and detailed in FIGS. 4 to 6. Advantageously, the common box 10 is situated just below the turbocharger 7 so that the connection manifold 11 is As a result, the temperature of the exhaust gas reaching the oxidation catalyst device 8 is high because of the proximity of the engine 1. In a variant, the vehicle does not include no turbocharger 7, and the connection manifold 11 directly connects the oxidation catalyst device 8 to the internal combustion engine 1. When starting the vehicle, the temperature of the exhaust gas is relatively cold, for example, between 200 ° C and 250 ° C. At this temperature, the proportion of particles capable of being passively regenerated in the oxidation catalyst device 8 is small. Nevertheless, the trapping means begin to immobilize a proportion of the particles. When the engine 1 gradually heats up, the temperature of the exhaust gas passing through the particle trap 8 rapidly reaches 300 ° C. because of the proximity of the oxidation catalyst device 8 with respect to the engine 1. The catalyst device of FIG. oxidation 8 may have two phases of operation. In a normal operating phase, most of the hydrocarbons were consumed in the combustion chamber of the engine 1, and the oxidation catalyst is used to oxidize the remaining hydrocarbons as well as carbon monoxide CO and NO nitrogen. At a temperature of 300 ° C., the nitrogen monoxides and dioxides NO and NO 2 contribute to oxidizing a part of the particles trapped in the particle trap 8. This cold regeneration is called passive regeneration. It takes place permanently. The oxidation catalyst 8 may also have a second mode of operation during which the exhaust gases comprise unburned hydrocarbons, for example hydrocarbons post-injected at the end of the expansion of the combustion cycle of the engine 1. The catalyst of oxidation makes it possible to oxidize these unburned hydrocarbons and causes an artificial increase in the temperature of the exhaust gases passing through the particulate filter 9. The temperature can reach 600 ° C., and contributes to burning all the particles filtered in the filter This second operation corresponds to an active regeneration phase, triggered on command. Having the oxidation catalyst device 8 and the particle filter device 9 both near the engine 1, allows the temperature of 300 ° C to be achieved more rapidly and increases the time period during the course of time. which is the passive regeneration. Similarly, the temperature of 600 ° C can be achieved with reduced post-injected hydrocarbon consumption, thus, the active regeneration of all particles of the particulate filter 9 can consume less post-injected fuel. In the implantation of the filtration system illustrated in FIG. 2, the oxidation catalyst device 8 is located in the engine compartment 2. The particle filter 9 is offset along the outlet manifold 12, in a zone under the floor 5 The particle filter 8 is thus housed in a box 13 of smaller volume than the previous implantation mode box 10. This allows to leave more space in the engine compartment 9 for other parts of the vehicle, or to increase the passenger compartment 3 of the vehicle.

In this implantation, the passive regeneration phase retains its efficiency because of the proximity of the oxidation catalyst device 8 with respect to the engine 1. The active regeneration can be carried out in another manner than that described in the previous mode, by For example, it is possible to artificially elevate the temperature of the particulate filter 9, for example, electrically, or by adding another oxidation catalyst. In the implantation mode of the filtration system illustrated in FIG. 3, the oxidation catalyst device 8 and the particulate filter device 9 are arranged in the same box 15 located in a tunnel 16 of the vehicle, for example below or below next to the gearbox of the powertrain 1. The tunnel 16 ensures the transition between the engine compartment 2 and the underfloor zone 5. This mode of implantation of the filtration system has the advantage of having a high level of passive regeneration due to the proximity of the particle trap 8 to the engine 1. In addition, the fact that a single box 15 includes the oxidation catalyst device 8 and the particle filter device 9, reduces the cost of production and assembly of the filtration system. Finally, the active regeneration phase uses the oxidation catalyst present in the particle trapping means 8. With reference to FIGS. 4 to 6, an embodiment of the particle trap 8, which can be housed indifferently in the boxes 10, 13 or 15 of the implantation modes described above.

The oxidation catalyst device 8 comprises trapping means consisting of alternating corrugated layers 17a, 17b, 17c and metal fiber supports 18a, 18b. The corrugated layers 17a, 17b, 17c each comprise a metal sheet 19. The metal fiber supports 18a, 18b bear on the top of the corrugations. The undulations are parallel to each other and coincide with their vertices. The corrugated layers 17a, 17b, 17c form as many channels successively represented by 20a, 20b, 20c, parallel to each other, alternately on one side or the other of the metal sheet 19 and traversed by a portion of metal fibers 18a, 18b. The metal fiber supports 18a, 18b each comprise a nonwoven support impregnated with precious metals such as platinum, palladium, etc. The exhaust gases flow, perpendicular to Figure 4, along the channels 20a, 20b, 20c. Each of the channels 20a, 20b, 20c comprise means for deflecting the flow of exhaust gas. The deflection means comprise a succession of fins 21a, 21b, 21c distributed longitudinally along said channels.

FIG. 5 illustrates how the fins 21a, 21b, 21c allow a mixture of the flow of exhaust gas passing through the channels 20a, 20b, 20c. The fins 21a, 21b, 21c are offset longitudinally relative to each other. The fin 21b takes a portion of the flow of exhaust gas passing through the channel 20b, and deflects it towards, on the one hand, the channel 20a, and on the other hand, towards the channel 20c, located on the side and other channel 20b. It is the same for the other fins 21a, 21c. The fin 21b makes it possible to deflect part of the gases flowing in the upper part of the channel 20b towards the channel 20c. This deflection creates a local overpressure in the lower part of the channel 20c and causes the particulate laden exhaust to deposit on the metal fiber support 18a to join the upper part of the channel 20c. As illustrated in FIG. 6, the fin 21b deflects a portion of the gases flowing in the channel 20b to mix with those flowing in the channel 20c. Similarly, a fin 24 deflects part of these gases to mix with those of a channel 22 located above by depositing soot on a metal fiber support 23, parallel to the support 18a.

Thus, the distribution of fins 21a, 21b, 21c, 24 allows the exhaust gas passing through the channels 20a, 20b, 20c, 22, to exchange between them a portion of the gas stream and to force it to deposit the particles on the nonwoven metal support 18a, 18b, 23 without risk that the particle trap is clogged because none of the channels is obstructed. The trapping means cause the exhaust gases to discharge a portion of their particles without obstructing the exhaust flow unlike the particulate filter 9. The particles trapped in the oxidation catalyst device 8 are treated by passive regeneration by precious metals impregnating nonwoven metal fibers 18a, 18b, 23.

Claims (10)

A particle filtration system emitted by a motor vehicle internal combustion engine (1), comprising an exhaust line (6) of the combustion gases equipped with an oxidation catalyst device (8) and a particulate filter device (9) for accumulating exhaust gas particles and being regenerated in a controlled manner, characterized in that the oxidation catalyst device (8) comprises means for trapping a portion of the particles of the exhaust gases and destruction of the said part by the action of the catalyst, the particulate filter device (9) being arranged downstream of the oxidation catalyst device (8) to be traversed by the other part of the particles. The system of claim 1, wherein the oxidation catalyst device (8) comprises exhaust gas flow diverting means to non-woven metal fiber portions impregnated with catalytic material. The system of claim 2, wherein the oxidation catalyst device (8) alternately has a series of corrugated metal layers (17a, 17b, 17c) with a series of nonwoven metal fiber supports (18a, 18b). ). 4. System according to any one of the preceding claims, wherein the oxidation catalyst device (8) comprises a plurality of channels (20a, 20b, 20c) having connecting fins (21a, 21b, 21c) able to deviate flue gases from one channel to another. 5. System according to any one of the preceding claims, wherein the oxidation catalyst device (8) and the particulate filter device (9) are assembled in the same box (10, 15). 6. Vehicle equipped with a motor and a filtration system according to any one of the preceding claims, wherein the oxidation catalyst device (8) is located in a motor compartment (2). 7. Vehicle equipped with a filtration system according to any one of claims 1 to 5, wherein the engine is equipped with a turbo compressor (7), the oxidation catalyst device (8) and the filter device with particles (9) being implanted immediately downstream of the turbo compressor (7). 8. Vehicle equipped with a filtration system according to any one of claims 1 to 5, wherein the particulate filter (8) is located in a subfloor area (5). 9. Vehicle equipped with a filtration system according to any one of claims 1 to 5, wherein the oxidation catalyst device (8) and the particulate filter (9) are located in a communication tunnel (16). between an engine compartment (2) and a subfloor area (5). Vehicle according to claim 9, in which the engine is equipped with a turbo compressor (7) implanted near the vehicle tunnel (16), the oxidation catalyst device (8) being located close to the turbo compressor ( 7).