EP1300553A1 - System for treating exhaust gases of an internal combustion engine - Google Patents

Abstract

At least one anode is associated with each inlet channel, sometimes inside it and sometime on the external face of a horizontal wall opposite to that near the cathode so the electrical discharges only occur in the inlet channels. <??>A system for treating combustion engine exhaust gases where the exhaust pipe (14) contains a treatment element (16) with at least one block (28) through which the exhaust gases (G) pass longitudinally and which contains parallel longitudinal inlet and outlet channels (30, 32). Each channel has at least two longitudinal and horizontal upper and lower walls and two longitudinal and vertical side walls (36). Each inlet channel is open at its upstream end (38a) and closed at its downstream end (38b) and each outlet channel is closed at its upstream end (38a) and open at its downstream end (38b). The inlet and outlet channels are stuck to each other alternately by their side walls so the exhaust gases entering the block via the upstream ends of the inlet channels pass through the porous side walls before leaving the block via the downstream ends of the outlet channels. The treatment system includes means of producing high voltage, low intensity electrical discharges between anodes (24) extending longitudinally inside the treatment element and a cathode (26) which is a horizontal plane outside the block and near the horizontal walls of the inlet channels. This is to provoke formation of chemicals favorable to regenerating the treatment element. Each cathode is a horizontal plate or network of conductive wires extending longitudinally and covering the assembly of horizontal walls of the inlet and outlet channels. The treatment element has two blocks on top of each other so the lower wall of each inlet channel in the top block is against the top walls of the inlet channels of the lower block, with cathodes on top of the top block and under the bottom block and anodes between the two blocks. Each anode operates in an inlet channel and the horizontal walls of the inlet channels each have a cathode. Each anode is equidistant from the horizontal walls of the associated inlet channel. A series of treatment elements are stacked vertically and two adjacent elements share a common cathode.

Description

The invention relates to a gas treatment system. combustion engine exhaust.

The invention relates more particularly to a system of exhaust gas treatment of a combustion engine, type which has a processing element arranged in a exhaust line, the processing element comprising at least a block which is crossed by the exhaust gases in a longitudinal direction and which includes an alignment of channels parallel longitudinal inlet and outlet, each channel inlet and outlet with at least two walls longitudinal and horizontal, respectively upper and lower, and having two longitudinal side walls and vertical, of the type in which each input channel is open to its upstream longitudinal end and closed at its end longitudinal downstream, each outlet channel being inversely closed at its upstream longitudinal end and open at its downstream longitudinal end, of the type in which the channels input and output are alternately attached to each other others by their side walls so that the gases exhaust enter the block through the ends longitudinal upstream of the inlet channels to exit the block by the downstream longitudinal ends of the outlet channels, in passing through the side walls which are porous, of the type in which the processing system includes a system of production of high voltage and low electrical discharges intensity between anodes which extend substantially longitudinally inside the processing element and at at least one cathode which is arranged in at least one plane substantially horizontal outside the block and near the horizontal walls of the inlet channels, in order to cause the formation of chemical species favorable to the regeneration of the processing element.

Diesel and petrol engines emit substances pollutants such as unburnt hydrocarbons, oxides nitrogen, carbon oxides and particles in the case of diesel engines. We know that one of the major concerns OEMs and vehicle manufacturers automobiles is the reduction of pollution resulting from the operation of these engines.

Different technical solutions have therefore been considered to try to reduce the pollution levels of these engines.

The treatment of particulate emissions by engines current diesel is possible thanks to the introduction into the line exhaust from these engines a particulate filter as it has already proposed in the state of the art. These are often adapted to trap particles or "soot" contained in exhaust from these engines and to burn them during a filter regeneration phase. Different strategies regeneration are available in the literature, making reference for example at the post injection of fuel to reach the soot combustion temperature (600 ° C minimum), or again for example to additional heating means placed upstream of the particle filter.

The present invention proposes the use of the non-thermal plasma technology in a material catalytic and / or filtering to aid in the treatment of pollutants gas contained in a gasoline engine exhaust or diesel, and among others to the oxide reduction catalysis nitrogen, and / or to induce the combustion of soot trapped in a filter placed in an exhaust line of a petrol engine or diesel.

This technology consists of forming species metastables, radicals and highly reactive ions by collision between the gas molecules and the energetic electrons produced by electric shocks, and this without raising the temperature of the reaction medium.

Physical characteristics of electric shocks vary depending on the intended application, consumption and conversion levels required for engine applications, especially motor vehicle (frequency, voltage and variable intensity).

Metastable, radical and strongly electron species energy products are promoters of reduction chemical, for example nitrogen oxides and particles of soot, by direct interactions of these lifelong species very short with pollutants.

It is known to associate a particulate filter with a plasma discharge reactor. This type of device includes minus a filter block placed between the two electrodes of the plasma discharge reactor.

This block is generally of rectangular shape and it is crossed by the exhaust gases in a direction longitudinal. The block has filtration channels longitudinal which are joined to each other at the level of their longitudinal walls so as to present a structure of the "honeycomb" type.

The block being placed between the two electrodes of the reactor with plasma discharges, electric discharges occur in all filtration channels, crossing certain walls.

This then results in possible degradation of the walls. crossed by electric shocks. In addition, the landfills pass through all the filtration channels, including those not covered with soot, which is unnecessary and reduces the effectiveness of the device

The present invention provides a processing system in which electric shocks only form in the canals covered with soot.

The invention therefore provides a gas treatment system exhaust of the type described above, characterized in that at least one anode is associated with each input channel, and is arranged either inside an inlet channel or on the face exterior of a horizontal wall of an inlet channel, this wall being opposite the horizontal wall of the nearby inlet channel of which the cathode is arranged, so that the discharges only form in the input channels.

• chaque cathode est un réseau de fils conducteurs qui s'étendent longitudinalement et qui recouvrent l'ensemble des parois horizontales des canaux d'entrée et de sortie ;
• chaque cathode est une plaque conductrice sensiblement horizontale, recouvrant l'ensemble des parois horizontales des canaux d'entrée et de sortie ;
• l'élément de traitement comporte deux blocs qui sont superposés verticalement, de sorte que la paroi inférieure de chaque canal d'entrée du bloc supérieur soit sensiblement en vis-à-vis de la paroi supérieure d'un canal d'entrée du bloc inférieur, et en ce que les faces extérieures des parois supérieures des canaux d'entrée du bloc supérieur et les faces extérieures des parois inférieures des canaux d'entrée du bloc inférieur reçoivent chacune au moins une cathode, et en ce que les anodes sont interposées entre les deux blocs ;
• les parois horizontales des canaux d'entrée reçoivent chacune au moins une cathode ;
• chaque anode est agencée sensiblement à équidistance des parois horizontales du canal d'entrée associé ;
• il est constitué d'une superposition verticale d'éléments de traitement et en ce que deux éléments de traitement adjacents comportent une cathode commune.

According to other characteristics of the invention:

• each cathode is a network of conductive wires which extend longitudinally and which cover all of the horizontal walls of the inlet and outlet channels;
• each cathode is a substantially horizontal conductive plate, covering all of the horizontal walls of the inlet and outlet channels;
• the processing element comprises two blocks which are vertically superimposed, so that the lower wall of each inlet channel of the upper block is substantially opposite the upper wall of an inlet channel of the lower block , and in that the outer faces of the upper walls of the inlet channels of the upper block and the outer faces of the lower walls of the inlet channels of the lower block each receive at least one cathode, and in that the anodes are interposed between the two blocks;
• the horizontal walls of the input channels each receive at least one cathode;
• each anode is arranged substantially equidistant from the horizontal walls of the associated inlet channel;
• it consists of a vertical superposition of treatment elements and in that two adjacent treatment elements comprise a common cathode.

• la figure 1 représente schématiquement une ligne d'échappement d'un moteur à combustion équipée d'un système de traitement des gaz d'échappement conforme à l'invention ;
• la figure 2 représente, de façon schématique et en perspective, un système de traitement des gaz d'échappement conforme à l'invention ;
• la figure 3 est une vue axiale en bout de l'extrémité amont du système de traitement conforme à l'invention ;
• la figure 4 représente, de façon schématique et en perspective, une variante de réalisation du système de traitement conforme à l'invention ; et
• la figure 5 représente, de façon schématique et en perspective, une autre variante d'un système de traitement conforme à l'invention.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings among which:

• Figure 1 schematically shows an exhaust line of a combustion engine equipped with an exhaust gas treatment system according to the invention;
• Figure 2 shows, schematically and in perspective, an exhaust gas treatment system according to the invention;
• Figure 3 is an axial end view of the upstream end of the processing system according to the invention;
• Figure 4 shows, schematically and in perspective, an alternative embodiment of the processing system according to the invention; and
• Figure 5 shows, schematically and in perspective, another variant of a treatment system according to the invention.

FIG. 1 shows a processing system 10 of the exhaust gases "G" of a combustion engine 12. The engine 12 can in particular be a diesel engine or a gasoline operating in a lean mixture such as a gasoline with direct injection.

An exhaust line 14 allows the evacuation of gases "G" from the engine to the atmosphere. The treatment system 10 intended to purify the exhaust gases "G" is interposed in the line 14. It mainly consists of a processing element 16 arranged in a room 18.

The processing system 10 also includes a system of production of electric shocks 20.

The system for producing electric shocks 20 comprises a pulse generator 22 connected to anodes 24 and at least one cathode 26 which are arranged in the line exhaust 14 so that electric shocks from high voltage and low intensity occur between anode 24 and cathode 26.

The technology used is that of plasmas not thermal.

Therefore, electric shocks are produced at a frequency that can range from a single shot to several tens of kHz for a high applied voltage (up to several tens of kV) between the anode (s) and the cathode (s), and they consist of high current pulses (up to several kA) and of short duration.

Electric shocks are produced so that they propagate in the exhaust gases "G" to treat soot and produce oxidative activated species favoring the combustion of particles.

For security reasons, in particular to limit the risk of short circuits, the pulse generator 22 supplies the anode 24, located inside the treatment element 16, under a high voltage, and the cathode 26, arranged at the periphery of the processing element 16 is connected to the electrical ground of the system.

FIGS. 2 and 3 show a system of gas treatment 10 "G" arranged in a chamber 18 of the exhaust line 14. The processing system 10 comprises a processing element 16 and a system for producing electric shocks 20.

The processing element comprises at least one block 28 which is crossed by the exhaust gases "G" in a direction longitudinal.

Block 28 has an alignment of longitudinal channels parallel inlet 30 and longitudinal outlet channels 32. These input and output channels 30, 32 are here in the form substantially rectangular with rectangular section.

Each input and output channel 30, 32 thus comprises two longitudinal and horizontal walls 34i, 34s, respectively upper and lower, and it has two side walls longitudinal and vertical 36.

Each input channel 30 is open at its end upstream longitudinal 38a and is closed at its longitudinal end downstream 38b, conversely, each output channel 32 is closed at its upstream longitudinal end 38a and is open at its end downstream longitudinal 38b.

Input and output channels 30, 32 are alternately joined to each other by their walls side 36 adjacent. The side walls 36 are porous of so that the exhaust gases "G" enter the block 28 by the upstream longitudinal ends 38a of the inlet channels 30 to come out of the block 28 via the downstream longitudinal ends 38b of the outlet channels 32, passing through the side walls porous 36.

When the gases "G" pass from the inlet channels 30 to go into the outlet channels 32 through the walls side 36, the soot particles are retained by the walls side 36 inside the inlet channels 30. Almost all soot is thus contained in the inlet channels 30 alone, especially on the inner faces of their walls.

Each cathode 26 consists of a conductive plate substantially horizontal. It is arranged in a plan substantially horizontal outside the block 28 and near the lower or upper walls 34i, 34s of the inlet channels 30. Preferably, the cathode 26 covers all of the walls 34i, 34s of the input and exit 30, 32.

According to a variant not shown of the invention, the cathode 26 is a network of conductive wires that extend longitudinally and which cover all the walls 34i, 34s of the input and exit 30, 32.

The anodes 24 are cylindrical rods which extend longitudinally inside the processing element 16. According to the invention, so that the electric shocks only form in soot-covered canals (i.e. the input channels 30), the anodes 24 are associated exclusively at input channels 30.

Thus, each anode 24 is arranged either inside a inlet channel 30, either on an outer face 40 of a wall lower 34i or higher 34s of an input channel 30. This wall is opposite to the wall covered by the cathode 26. Thus, for example, when the cathode 26 covers the upper wall 34s of an input channel 30, the anode 24 is located on the face outside 40 of the bottom wall 34i of the inlet channel 30.

Furthermore, so that the regeneration of the element of treatment 16 is total, at least one anode 24 is associated with each input channel 30.

According to a first embodiment of the invention shown in Figures 2 and 3, the processing element includes two blocks 28s and 28i which are vertically superimposed.

In this embodiment, the cathodes 26 cover the upper walls 34s of the inlet and outlet channels 30, 32 of the upper block 28s and the lower walls 34i of the channels input and output 30, 32 of the lower block 28i.

The anodes 24 are then interposed between the two blocks 28s and 28i and each is located on the upper wall 34s of the inlet channel 30 associated with the lower block 28i and on the wall 34i of the associated input channel 30 of the upper block 28s.

The two blocks 28s and 28i are superimposed so that the bottom wall 34i of an inlet channel 30 of the upper block 28s either facing the upper wall 34s of an inlet channel 30 of the lower block 28i.

This avoids that an output channel 32 of a block 28s or 28i is not included between a cathode 26 associated with this same block 28s or 28i and an anode 24 associated with an input channel 30 on the other block 28i or 28s. In this hypothesis, it would then be in possible effect of electric shocks occurring in the outlet channel 32, which is contrary to the object of the invention.

According to a second embodiment of the invention shown in Figures 4 and 5, the processing element 16 has a single block 28.

Thus, the lower and upper walls 34i, 34s of input and output channels 30, 32 each receive at least a cathode 26, and each anode 24 is located inside the associated input channel 30.

The diameter of each anode 24 is less than or equal to the transverse width of the associated inlet channel 30. So the electric shocks occur in the entire volume inside the inlet channel 30.

Maintaining the anodes 24 in the elements of processing is provided by an intermediate element 42. The element intermediate can be of the same nature as the input channels and outlet 30, 32 and its thickness is at least equal to anode diameter 24.

When the processing element 16 has two blocks 28, the intermediate element 42 is disposed between the two blocks 28 and it is connected to the input and output channels 30, 32.

When the processing element 16 comprises a single block 28, the intermediate element 42 is disposed between the walls side 36 of each input channel 30. It is obvious that when the diameter of the anodes 24 is equal to the width transverse of the inlet channels 30, the processing element 16 does not have an intermediate element 42 and the anodes 24 are attached to the processing element 16 for example at their longitudinal ends.

The distance between the electrodes depends on the characteristics of the filter material. However, this distance must be less than or equal to a maximum distance "d" allow a uniform formation of discharges.

For these reasons, when the processing element 16 does not includes a block 28, the anodes 24 are arranged substantially equidistant between the lower walls and upper 34i, 34s of the associated input channel 30. In addition, the distance between the lower and upper walls 34i, 34s of the input channel is double the distance "d".

The distance "d" can be reduced and it can therefore limit the effectiveness of a treatment element 16. To adapt the processing system capacity 10 to engine 12 the system 10 has a vertical stack of elements of processing 16. The stack is such that two elements of treatment 16 adjacent have a common cathode.

When the processing element 16 is saturated, that is to say the quantity of particles stored is greater than a threshold predetermined, its regeneration is initiated.

The loading state of the particulate filter 16 can be determined by a differential pressure measurement sensor, not shown, which provides the value of the pressure drop produced by the particulate filter 16 between the inlet and the outlet of the room 18. When the value of the pressure drop is greater than a predetermined value, this means that the filter 16 is saturated, its regeneration is then initiated.

During the regeneration phase, the generator of pulses 22 produces electrical discharges which are homogeneously distributed in the processing element 16. The homogeneous distribution of discharges in the treatment element 16 is mainly due to the symmetry of the system formed by the processing element 16, the anode 24 and the cathode 26

This allows the formation of activated species oxidants in the immediate vicinity of the walls of the the processing element 16 which are charged with particles. This proximity as well as the homogeneous distribution of oxidized species promote the combustion of stored particles in the processing element.

Thus, the regeneration of the treatment system 10 is optimized.

In order to overcome mechanical constraints that can be related to vibrations or expansion of materials constituting the treatment system 10, a strip of wool thermal 44 can be arranged between the inner wall of the chamber 18 and cathode 26.

The thermal wool band 44 makes it possible to produce a mechanical decoupling between the wall of the chamber 18 and the processing element 16. In addition, it provides insulation treatment element 16 so as to limit the temperature of the external face of the wall of the chamber 18, and at favor the rise in temperature inside the element of treatment 16, which further facilitates system regeneration treatment 10.

Horizontal, vertical and transverse orientations have been defined by way of nonlimiting example to facilitate the understanding of the invention. It will be understood that it is possible to adopt a different convention without going beyond the ambit of the invention.

It will also be understood that mechanical inversions simple may constitute alternative embodiments of the invention. For example, the anodes 24 can be arranged at the outside of the treatment element 16 and the cathodes can be arranged inside the processing element 16.

The invention therefore allows filtration of exhaust gases. "G" by the use of a particle filter which includes means for its regeneration, these means of regeneration allowing the combustion of trapped particles, without damage the particulate filter components, which prevents the user of the vehicle that includes this device, any concerns About the maintenance of the particulate filter.

Claims (7)

System for treating (10) the exhaust gases (G) of a combustion engine (12), of the type which comprises a treatment element (16) disposed in an exhaust line (14), the treatment (16) comprising at least one block (28) which is crossed by the exhaust gases (G) in a longitudinal direction and which comprises an alignment of parallel longitudinal inlet and outlet channels (30, 32), each inlet and outlet channel (30, 32) comprising at least two longitudinal and horizontal walls, respectively upper and lower (34s, 34i), and comprising two longitudinal and vertical side walls (36), of the type in which each channel d inlet (30) is open at its upstream longitudinal end (38a) and closed at its downstream longitudinal end (38b), each outlet channel being inversely closed at its upstream longitudinal end (38a) and open at its downstream longitudinal end (38b ), of the type in which inlet and outlet channels (30, 32) are alternately joined to one another by their side walls (36) so that the exhaust gases (G) enter the block via the upstream longitudinal ends (38a) of the inlet channels (30) for emerging from the block (28) through the downstream longitudinal ends (38b) of the outlet channels (32), passing through the side walls (36) which are porous, of the type in which the treatment system (16) comprises a system for producing high voltage and low intensity electric shocks (20) between anodes (24) which extend substantially longitudinally inside the treatment element (16) and at least one cathode (26) which is arranged in at least one substantially horizontal plane outside the block (28) and near the horizontal walls (34s, 34i) of the inlet channels (30), in order to cause the formation of chemical species favorable to the regeneration of the element treatment (16), characterized in that at least one anode (24) is associated with each input channel (30), and is arranged either inside an input channel (30), or on the outer face of a horizontal wall (34s, 34i) of an inlet channel (30), this wall being opposite to the horizontal wall (34i, 34s) of the inlet channel (30) near which is arranged the cathode (26), so that electrical discharges are formed only in the inlet channels (30). Exhaust gas treatment system (10) (G) according to claim 1, characterized in that each cathode (26) is a network of conductive wires which extend longitudinally and which cover all of the horizontal walls (34s , 34i) input and output channels (30, 32). Exhaust gas treatment system (10) (G) according to claim 1, characterized in that each cathode (26) is a substantially horizontal conductive plate, covering all the horizontal walls (34s, 34i) of the channels d 'entry and exit (30, 32). Exhaust gas treatment system (10) according to any one of the preceding claims, in which each anode (24) is arranged on the external face of a horizontal wall (34s, 34i) of a channel inlet (30), characterized in that the treatment element (10) comprises two blocks (28i, 28s) which are superimposed vertically, so that the bottom wall (34i) of each inlet channel (30) of the upper block (28s) is substantially opposite the upper wall (34s) of an inlet channel (30) of the lower block (28i), and in that the outer faces of the upper walls (34s ) inlet channels (30) of the upper block (28s) and the outer faces of the lower walls (34i) of the inlet channels (30) of the lower block (28i) each receive at least one cathode (26), and in that the anodes (24) are interposed between the two blocks (28s; 28i). An exhaust gas treatment system (10) according to any one of the preceding claims in which each anode (24) is arranged in an inlet channel (30), characterized in that the horizontal walls (34s , 34i) input channels each receive at least one cathode (26). Exhaust gas treatment system (10) (G) according to claim 5, characterized in that each anode (24) is arranged substantially equidistant from the horizontal walls (34s, 34i) of the associated inlet channel (30) . Exhaust gas treatment system (10) according to any one of the preceding claims, characterized in that it consists of a vertical superposition of treatment elements (16) and in that two elements adjacent treatment cells (16) have a common cathode (26).

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