FR2912462A1 - Exhaust gas treating system for oil engine of motor vehicle, has injector mounted inside profiled wing shaped body that includes hydrocarbon supply pipe connecting injector to nozzle formed on trailing edge of end surface - Google Patents

Abstract

The system has a particle filter (4) arranged in an exhaust gas conveying pipe (1), and an oxidation catalyst (3) mounted upstream of the filter. A hydrocarbon injector (2) is mounted upstream of the catalyst, and introduces hydrocarbon in the pipe. The injector is mounted inside a profiled wing shaped body (5) that is asymmetrically arranged in an exhaust gas flow and has a plane free end surface (8) near an axis of the pipe. The body has a hydrocarbon supply pipe (10) connecting the injector to a deflector nozzle (11) formed on a trailing edge (7) of the surface. An independent claim is also included for a method for dispersing hydrocarbon in the exhaust gas coming from an oil type internal combustion engine of a motor vehicle and circulating in an exhaust gas conveying pipe.

Description

B06 / 3902EN / GBO PJ6856 / VRX Simplified Joint Stock Company: RENAULT

  s.a.s. Exhaust gas treatment system comprising a hydrocarbon injector Invention of: BIGOT Benjamin CAPELLE Sébastien Exhaust gas treatment system comprising a hydrocarbon injector

  The present invention relates to systems for treating exhaust gases from an internal combustion engine of a motor vehicle. In particular, the present invention relates to treatment systems comprising a particulate filter, and the regeneration of the particulate filter. Internal combustion engines, especially of the diesel type, produce soot, or particles, because of their combustion mode by auto-ignition of the fuel-air mixture in the combustion chamber. The treatment of soot, or particles, in the exhaust gas of an engine, for example diesel, is important to meet anti-pollution standards A possible solution to the treatment of particles is the use of particulate filters. In the presence of oxygen and at a temperature for example of the order of 400 C, the particles retained by the particulate filter are burned, in particular by oxidation, therein and thus a regeneration of the particulate filter is obtained.

  Currently, particulate filters are associated with catalytic elements capable of oxidizing hydrocarbons, including unburnt combustion hydrocarbons. The oxidation of the hydrocarbons is highly exothermic and makes it possible to increase the temperature of the exhaust gases arriving on the particulate filter placed downstream of the catalytic element. The temperature of the particulate filter then increases and can cause the combustion of the filtered particles: the regeneration of the particulate filter is obtained. For cold starts of a combustion engine, a rapid increase in the operating temperature of the particulate filter may be desired. This is possible by introducing hydrocarbons into the exhaust gas conduit, in particular by a post-injection of hydrocarbons during the emptying of the combustion chamber. However, it is then preferable to have a certain level of vehicle load, that is to say to have a moving vehicle, to improve the delivery of post-injection hydrocarbons from the combustion chamber to the elements. Catalysts of the gas pipeline.

  One solution for making the regeneration of the particulate filter of the engine load independent is to use one or more injectors arranged in the exhaust gas conduit. These injectors are intended to introduce into the delivery line, hydrocarbons that will allow, by oxidation on catalytic elements, to increase the temperature of the particulate filter. It is then possible to regenerate the particulate filter when the combustion engine is at very low load, or even at a standstill, which corresponds to an urban use of a vehicle.

  Current solutions tend to obtain a homogeneous and uniform air-hydrocarbon mixture at the inlet of the exhaust gas treatment devices. US Pat. Nos. 3,964,875 and 3,749,130 thus relate to devices capable of uniformly distributing the exhaust gases at the inlet of an exhaust gas treatment device. However, these devices introduce a significant additional pressure drop in the exhaust gas pipe.

  The invention aims to remedy these drawbacks. The object of the invention is to improve the operation of the particulate filter, and in particular its regeneration, while limiting additional pressure drops. The invention thus proposes a system for treating exhaust gases from an internal combustion engine, particularly of the diesel type, of a motor vehicle. The treatment system comprises a particulate filter disposed in an exhaust gas conduit, an oxidation catalyst mounted upstream of the particulate filter, and an injector mounted upstream of the oxidation catalyst and capable of introducing hydrocarbons into the exhaust gas pipeline. The injector is mounted inside a profiled wing-shaped body disposed in the flow of the exhaust gas and having a free end face adjacent the axis of the conveying pipe, the shaped wing-shaped body comprising a hydrocarbon feed channel connecting the injector to a nozzle formed on the trailing edge of the free end face. The profiled wing-shaped body allows the introduction of hydrocarbons into the conveying line and decreases, thanks to its profiled shape, the pressure drop that it creates in the exhaust gas pipe. However, the profiled wing-shaped body also aims to mix the hydrocarbons it introduces into the delivery pipe, with the exhaust gas. In particular, the profiled wing-shaped body makes it possible to create, in the flow of the exhaust gas and despite its streamlined shape, turbulences capable of mixing the hydrocarbons and the exhaust gases before the oxidation catalyst is sprayed. . This thus makes it possible to obtain a uniform increase in the temperature at the level of the oxidation catalyst, and therefore a better regeneration of the particulate filter. Thus, the profiled wing-shaped body on the one hand to introduce hydrocarbons into the conveying line, and secondly to mix with the exhaust gas. A compact device is therefore obtained which makes it possible to limit the additional pressure losses in the conveying pipe thanks to its profiled shape, but which also makes it possible to mix the hydrocarbons and the exhaust gases by the formation of localized turbulence. According to one embodiment, the shaped wing-shaped body has an asymmetrical shape. The asymmetric shape makes it possible to create turbulence in the flow of the exhaust gases, and in particular near the trailing edge of the free end face, where the injection nozzle is located.

  According to another embodiment, the shaped wing-shaped body is asymmetrically disposed in the flow of the exhaust gas. This may be a symmetrical or asymmetrical body. In particular, in the case of a symmetrical body, the asymmetrical positioning in the conveying duct makes it possible to create the desired turbulences. Preferably, the profiled wing-shaped body is able to rotate about an axis parallel to the trailing edge of said profiled wing-shaped body. Thus, depending on the angle of rotation between the flow direction of the exhaust gas and the shaped wing-shaped body, it is possible to increase or decrease the turbulence created by the profiled wing-shaped body. , as well as the pressure drop induced by the profiled wing shaped body. According to another embodiment, the shaped wing-shaped body has a twisting. The twisting of the profiled wing shaped body can make it possible to find a compromise between low pressure drops and turbulence capable of mixing the hydrocarbons and the exhaust gases. Preferably, the profiled wing-shaped body is capable of generating, in the gas flow, a marginal vortex. The turbulence considered here is the marginal vortex that can form at the end of a profiled wing. Thus, the profiled wing-shaped body limits the pressure drop in the conveying line, while creating localized turbulence adapted to the mixture of introduced hydrocarbons and exhaust gases. Preferably, the profiled wing-shaped body also comprises a temperature sensor and / or a pressure sensor. The volume of the profiled wing shaped body is used to add additional sensors, without introducing additional head losses or integration problems.

  The invention also relates to a process for dispersing hydrocarbons in the exhaust gases from an internal combustion engine, particularly of the diesel type, of a motor vehicle and circulating in a delivery pipe comprising a filter with particles. According to the process, hydrocarbons are injected into the exhaust gas transport pipe, and the injected hydrocarbons are oxidized upstream of the particulate filter. In addition, turbulence is generated in the flow of the exhaust gas and the hydrocarbons are injected into the turbulence of the exhaust gas. Preferably, turbulence is a marginal vortex. Other advantages and features will become apparent upon consideration of the detailed description of non-limiting embodiments, and the accompanying drawings in which: - Figure 1 schematically shows a sectional view, from the side, of an embodiment of FIG. an exhaust gas treatment system comprising a deflector nozzle, and - Figures 2 to 4 show different embodiments of the deflector nozzle, seen from above.

  Figure 1 shows a side sectional view of an embodiment of the exhaust gas treatment system according to the invention. In Figure 1 is shown a pipe 1 of the exhaust gas. The conveying line 1 is placed downstream of an internal combustion engine (not shown), for example of the diesel type, of a motor vehicle. The conveying line 1 comprises, in the flow direction of the exhaust gas in the conveying line 1, a hydrocarbon injector 2 integrated in the delivery pipe 1, an oxidation catalyst 3 and a particulate filter 4. The oxidation catalyst 3 and the particulate filter 4 may be in contact so as to minimize the travel time of the exhaust gas between the oxidation catalyst 3 and the particulate filter 4. It is It is also possible to replace the oxidation catalyst and the particulate filter with a particulate filter comprising catalyst elements. It is considered for the rest of the description that the particle filter 4 is capable of oxidizing the particles retained at a temperature of the order of 400 C. The oxidation catalyst 3 makes it possible to trigger an oxidation reaction of the hydrocarbons introduced. by the injector 2. The oxidation reaction being highly exothermic, one obtains on the one hand an increase in the temperature of the oxidation catalyst 3 and on the other hand an increase in the temperature of the exhaust gas passing through the catalyst. These hot gases then pass through the particulate filter 4 and thus increase its temperature to the temperature of, for example, 400 ° C., at which the oxidation reaction of the particles retained by the particulate filter 4 may take place. The combination of the hydrocarbon injector 2 and the oxidation catalyst 3 thus makes it possible to introduce, without intervention of the engine control, thermal energy into the transport pipe 1, in particular upstream of the particulate filter 4. Thus, during cold starts, for example, it is possible to increase the temperature of the particulate filter 4 more quickly and by limiting the energy losses thanks to the proximity of the oxidation catalyst 3 and the filter particles 4. The increase of the temperature of the particulate filter 4 makes it possible to regenerate it. Regeneration is generally triggered when the pressure difference between the upstream and downstream of the particulate filter 4 exceeds a predefined threshold. The pressure measurement can be ensured, for example, by two sensors (not shown) of absolute pressure: a first sensor placed upstream of the particulate filter 4 and a second sensor placed downstream of the particle filter 4. The two sensors of pressure make it possible to determine the fouling of the particulate filter 4 due to the particles retained, via the resistance of the particulate filter 4 to the flow of the exhaust gas.

  The hydrocarbon injector 2 is placed in a streamlined shaped body 5. The profile of the body 5 is for example of elliptical shape with a circular leading edge 6, a trailing edge 7 of leaky shape and a flat free end face 8. The body 5 may also comprise an axis of rotation AR parallel to the leading and trailing edges 7, and perpendicular to the axis of the conveying line 1. The body 5 limits, due to its profiled shape, losses additional charge. In addition, its size may be much larger than the injector 2, it is also possible to place in the body 5 one or more sensors. Thus, in the present case, it is considered that the body 5 comprises a temperature sensor 12 placed in the vicinity of, for example, the leading edge 6. The temperature sensor 12 thus makes it possible to know the temperature of the exhaust gases arriving on the oxidation catalyst 3 and possibly deduce the amount of hydrocarbons to be introduced into the feed pipe 1 so that the oxidation catalyst 3 has the desired temperature. It is also possible to place in the body 5 a pressure sensor, such as one of the pressure sensors used to determine when the particle filter 4 is to be regenerated. More generally, it is possible to use for the body 5 any profile used in the aeronautics and adapted to the realization of aircraft wing. In particular, the shape of the body 5 or its position in the conveying line 1 are chosen so as to create a pressure difference between the two blanks of the body 5 which can then be assimilated to the extrados (blank with a depression) and the intrados (blank presenting an overpressure) of an airplane wing. The pressure difference between the two blanks of the body 5 leads to the formation of a marginal vortex 9 on the trailing edge of the free end face 8, that is to say at the intersection of the trailing edge 7 and the free end face 8. The vortex 9 will have a conical general form of confinement in which the hydrocarbons will be injected. For this, the body 5 comprises a feed channel 10 capable of conveying the hydrocarbons from the injector 2 to a nozzle 11 located on the trailing edge of the free end face 8. The hydrocarbons introduced into the conveying line 1 are thus directly driven into the marginal vortex 9 and mixed with the exhaust gas. More particularly, the hydrocarbon jet will be stirred and dispersed by centrifugation on the inlet section of the oxidation catalyst 3, and thus allow a uniform temperature rise of the oxidation catalyst 3 and a better regeneration of the particulate filter 4 In Figures 2 to 4 are shown, seen from above, different embodiments of the body 5. The elements of Figures 2 to 4 common to Figure 1 have the same references. In Figure 2, the body 5 has an asymmetric profile and is positioned symmetrically in the conveying line 1. The body 5 thus has a blank 13 which constitutes the intrados and a blank 14 which constitutes the extrados. More particularly, the blank 13 has a larger lateral surface than that of the blank 14, thus creating a pressure difference between the two blanks 13, 14, even when the body 5 is positioned symmetrically in the conveying line 1. The body 5 may also comprise, in this embodiment, the rotation axis AR in order to accentuate or on the contrary reduce the marginal vortex 9 formed by the body 5.

  In FIG. 3, the body 5 has a symmetrical profile and is asymmetrically positioned or not in the conveying duct 1. Thus, depending on the positioning of the body 5 in the conveying duct, a blank which will be the underside 13 will have a smaller lateral surface than that of the opposite blank which will be the extrados 14. In contrast, when the body 5 is positioned symmetrically, then the pressure on the blanks of the body 5 is identical and there is not forming a marginal vortex. The axis of rotation AR of the body 5 here makes it possible to define the periods of hydrocarbon injection and the periods without hydrocarbon injection. In the first case, the body 5 is rotated about its axis AR so as to take the incidence and create a marginal vortex 9. On the contrary, when there is no hydrocarbon injected, the body 5 can to be rotated in symmetrical position so as to create less pressure losses, in particular by the absence of marginal vortex 9. In Figure 4, the body 5 has a twisted profile with a base and a free end face 8 symmetrical. The twisted shape allows to have a lower drag (and therefore a smaller pressure drop) and a marginal vortex 9 equivalent to that produced by a non-twisted body having an identical free end face. The increasing angular offset is called, as we approach the free end face 8 of the body 5, of the profile with respect to the base of the body 5. In particular, in the embodiment shown in Figure 4, the base of the body 5 is positioned symmetrically to reduce the pressure losses, whereas because of the twisting of the body 5, the free end face 8 is positioned asymmetrically, creating Thus a marginal vortex 9. It can thus both limit the pressure drop and obtain a marginal vortex 9. The body 5 thus has a blank 13 along which the pressure will decrease as one s' approach of the free end face 8, while the pressure on the other blank 14 will increase as we approach the free end face 8. The pressure difference between the two sides 13, 14 of the body 5 increases as we approach of the free end face 8. It is also possible, according to another embodiment, to have a plurality of profiled wing shaped bodies as described above, along the circumference of the conveying conduit. This allows for example to rotate the exhaust gas and improve the hydrocarbon-exhaust gas mixture, although this may increase the pressure drop.

Claims (9)

  A system for treating exhaust gases from an internal combustion engine, particularly of the diesel type, of a motor vehicle comprising: a particle filter (4) arranged in a delivery pipe (1); exhaust gas, - an oxidation catalyst (3) mounted upstream of the particulate filter (4), - an injector (2) mounted upstream of the oxidation catalyst (3) and capable of introducing hydrocarbons into the the exhaust gas supply pipe (1), characterized in that the injector (2) is mounted inside a profiled wing shaped body (5) disposed in the gas flow exhaust pipe and having a free end face (8) in the vicinity of the axis of the conveying pipe (1), the shaped wing-shaped body (5) comprising a feed channel (10) in hydrocarbons connecting the injector (2) to a nozzle (11) formed on the trailing edge of the free end face (8).   An exhaust gas treatment system according to claim 1, wherein the shaped wing shaped body (5) has an asymmetric shape.   An exhaust gas treatment system according to claim 1 or 2 wherein the shaped wing shaped body (5) is asymmetrically disposed in the exhaust gas flow.   4. exhaust gas treatment system according to one of claims 1 to 3 wherein the body (5) profiled shaped wing is able to rotate about an axis (AR) parallel to the trailing edge ( 7) of said shaped wing body (5).   5. exhaust gas treatment system according to one of claims 1 to 3 wherein the body (5) profiled shaped wing has a twisting.   6. Exhaust gas treatment system according to one of claims 1 to 5 wherein the body (5) profiled shaped wing is capable of generating, in the flow of gases, a marginal vortex (9) .   7. Exhaust gas treatment system according to one of claims 1 to 6 wherein the shaped body shaped wing (5) also comprises a temperature sensor (12) and / or a pressure sensor.   8. A process for dispersing hydrocarbons in the exhaust gases from an internal combustion engine, particularly of diesel type, of a motor vehicle and circulating in a delivery pipe (1) comprising a particulate filter ( 4), in which: - hydrocarbons are injected into the exhaust gas conveying line (1), and - injected hydrocarbons are oxidized upstream of the particulate filter (4), characterized in that turbulence in the flow of the exhaust gas and the hydrocarbons are injected into the turbulence of the exhaust gas.   9. The method of claim 8 wherein the turbulence is a marginal vortex (9).