FR2887922A1 - AGGLOMERATION AND COLLECTION ASSEMBLY OF PARTICLES CONTAINED IN EXHAUST GASES OF A MOTOR VEHICLE INTERNAL COMBUSTION ENGINE HAVING A HIGH VOLTAGE POWER SUPPLY DEVICE - Google Patents

Abstract

The agglomeration and collection assembly of the particles contained in the exhaust gas of an internal combustion engine of a motor vehicle is provided with at least one electrostatic agglomeration module comprising an internal electrode and an external electrode. 5 between which is created an electric field, the outer electrode being made of a porous material capable of passing the exhaust gases as well as agglomerated particle clusters during the passage of the exhaust gas through the porous material, and a collection module 12 of particle clusters disposed downstream of the agglomeration module, considering the flow direction of the exhaust gas. The agglomeration assembly further comprises an electric generating device 22 provided with a single step-up transformer capable of enabling a continuous high voltage supply of the agglomeration module and the collection module.

Description

Set of agglomeration and collection of particles

  contained in the exhaust gas of an internal combustion engine of a motor vehicle provided with a high-voltage power supply device.

  The invention relates to the treatment of pollutant components contained in a gaseous medium and, in particular, to the field of exhaust gas filtering assemblies of a motor vehicle internal combustion engine.

  More particularly, the invention relates to a set of agglomeration and collection of particles contained in the exhaust gas of a motor vehicle internal combustion engine which comprises an electrostatic agglomeration module and a collection module of agglomerated particles.

  Electrostatic agglomeration modules generally use an electric field to cause an attraction of the particles contained in the exhaust gas to a treatment substrate.

  In this regard, reference may be made to French patent application No. 03 12635 which describes an assembly provided with such an electrostatic agglomeration module. In this assembly, the agglomeration is carried out by means of an entanglement of metal fibers permeable to gases which internally delimit a passage for the circulation of gases and which are capable of allowing the formation of clusters of agglomerated particles.

  This entanglement constitutes an electrode which, together with a wire electrode disposed along the axis of the passage, creates a first transverse electric field for deflecting the particles carried by the exhaust gases to the external electrode at which the clusters are trained. The clusters of particles are detached from the entanglement of metal fibers as soon as they reach a size sufficient for the friction forces exerted by the exhaust gases tear them.

  The electrostatic agglomeration module is associated with a particle cluster collection module disposed downstream of said agglomeration module, considering the flow direction of the exhaust gas. The agglomeration module may comprise internal and external electrodes for diverting, via a second electrostatic field created, the clusters of particles obtained in the direction of the external electrode to elements adapted to collect them.

  In such an assembly, it is important to feed the high voltage agglomeration and collection modules. In fact, in order to obtain an electrostatic agglomeration of the particles contained in the exhaust gases as well as a recovery of the effective agglomerated particles, it is necessary to supply the internal electrode of each of the modules with a high potential in order to obtain good ionization. of the medium through which the exhaust gas flows in order to deflect the charged particles towards the external electrode.

  Feeding the agglomeration and collection modules directly using the low voltage network of the motor vehicle does not allow to obtain an agglomeration of the particles contained in the exhaust gas and a recovery of optimal particle clusters.

  Also known from WO 96/31939, a power supply device comprising a plurality of high voltage generators connected in parallel with each other, each of the generators being provided with a step-up transformer, so as to be able to deliver inverter. output a high voltage, from a low voltage.

  This device has the disadvantage of being relatively expensive, and offers nothing for a set of agglomeration and collection 5 of particles contained in exhaust gas.

  The present invention therefore aims to overcome these disadvantages by proposing an assembly of agglomeration and collection of particles contained in the exhaust gas of a motor vehicle internal combustion engine that can be properly powered using the electrical network. present on board the vehicle.

  For this purpose, the assembly of agglomeration and collection of particles contained in the exhaust gas of an internal combustion engine of a motor vehicle is provided with at least one electrostatic agglomeration module comprising an internal electrode and a external electrode between which is created a first electric field, the outer electrode being made of porous material capable of passing the exhaust gas as well as clusters of particles agglomerated during the passage of the exhaust gas through the porous material, and a particle cluster collection module disposed downstream of the agglomeration module, considering the flow direction of the exhaust gas.

  The assembly further comprises a power supply or electrical generation device provided with a single step-up transformer adapted to allow a continuous high voltage supply of the agglomeration module and the collection module.

  With such an assembly, it thus becomes possible to be able to supply the two agglomeration and collection modules at high voltage, for example from the low voltage electrical network of the motor vehicle, and this, particularly economically using a single transformer voltage booster.

  Advantageously, the transformer is connected at the input to a DC / AC converter powered by a low voltage electrical source, and connected at the output to at least one AC / DC converter connected to the agglomeration and collection modules.

  Preferably, the electrical generating device further comprises means for measuring the voltage and / or the current at the output of the DC / AC converter, and a control unit able to drive the DC / AC converter according to the values measured.

  Advantageously, the transformer comprises at least one primary coil and at least two secondary coils, each secondary coil being connected to an AC / DC converter connected to one of said modules.

  The generation device may comprise means for measuring the voltage and / or current at the output of each AC / DC converter, and a control unit able to control the DC / AC converter as a function of at least one of the measured values. .

  In an alternative embodiment, at least one of the AC / DC converters consists of a diode.

  In one embodiment, the transformer comprises two primary coils connected in series.

  In another embodiment, the transformer comprises two primary coils connected in parallel.

  Preferably, the collection module comprises a first electrode and a second electrode extending in a second electric field, one of said electrodes comprising an agglomerated particle receiving surface.

  The present invention and its advantages will be better understood on studying the detailed description of embodiments taken by way of non-limiting examples and illustrated by the appended drawings, in which: FIG. 1 is a sectional view of a Aggregation and collection assembly according to the invention; FIGS. 2 to 6 show alternative embodiments of a feed device for the agglomeration and collection assembly of FIG.

  As illustrated schematically in FIG. 1, the agglomeration and particle collection assembly essentially comprises a particle filter 10 and a collection module 12 of collected particle clusters. The particulate filter 10 is constituted by an electrostatic agglomeration module ensuring entrapment and agglomeration of the particles carried by the exhaust gas.

  The collection module 12 is disposed downstream of the agglomeration module 10, considering the flow direction of the exhaust gas, and allows a capture of the agglomerated particles extracted from the agglomeration module 10.

  The agglomeration module 10 comprises an intake duct 2, a collector 4, and an agglomeration unit 3 located between the intake duct 2 and the collector 4.

  The agglomeration unit 3 comprises an external electrode 5 of generally cylindrical shape. This electrode 5 delimits internally an axial passage 6 for the exhaust gas which communicates at one of its ends with the pipe 2.

  The outer electrode 5 comprises radial front surfaces 7 and 8. The front surface 7 is in axial contact with a ring 9 for fixing the external electrode 5 to the inlet pipe 2. The ring 9 is connected to the ground . The external electrode 5 is open on the side of its front surface 7, so that the central passage 6 communicates with the intake pipe 2.

  The intake pipe 2 comprises an inlet orifice 13 on the opposite side to the outer electrode 5. A disk 14 abuts axially by a radial surface 15 against the end surface 8 of the external electrode 5 opposite to the intake pipe 2. The disk 14 axially closes the central passage 6 on the opposite side to the intake pipe 2.

  The agglomeration unit 3 also comprises a central electrode 16 in the form of a rod 17 coaxial with the external electrode 5 and one end 18 of which is plugged into an insulating portion of the disk 14. The internal electrode 16 is extends axially from its end 18 beyond the fixing ring 9 being bent to form a radial portion 19 coming out of the inlet pipe 2 through an opening 20. An insulator 21 is disposed in the opening 20 to electrically isolate the wall of the intake pipe 2 of the internal electrode 16. The radial portion 19 is electrically connected to a power supply device 22.

  The collector 4 comprises a cylindrical envelope 23 which surrounds the external electrode 5. The cylindrical envelope 23 extends axially beyond the disk 14. It comprises an inside diameter greater than the outside diameter of the electrode 5, so that it there is an empty annular space 24 between the cylindrical envelope 23 and the external electrode 5. Said envelope finally communicates, on the opposite side to the intake pipe 2, with a pipe 28 opening inside the collection module 12 of the agglomerated particles.

  In operation, the particulate-laden exhaust gases enter the intake pipe 2 through the inlet port 13. They then flow into the central passage 6 of the outer electrode 5, which communicates with the pipe. intake 2, in which they are ionized and the particles they contain electrically charged. As conceived, the disk 14 prevents the axial passage of the exhaust gases. The exhaust gases are then deflected radially and pass through the external electrode 5 which is permeable to gases.

  The external electrode 5 is maintained at a zero potential, the internal electrode 16 being brought to a positive or negative potential. The potential difference created between the external and internal electrode 5 induces the presence of a first electric field in the axial passage 6. If this electric field has a sufficient intensity, in particular in the very close vicinity of the internal electrode 16 , there is a partial or complete ionization of the gases, or medium, between the internal and external electrodes 16 and 5.

  In the case of an internal electrode 16 brought to a negative potential, the particles present in the exhaust gases are mainly charged by collision and combination with free electrons. Given the low concentration of particles in the exhaust gas, the probability that an electron moving rapidly from the inner electrode 16 to the outer electrode 5 strikes a particle and combines with the latter is low.

  In order to charge the particles in a suitable manner for their electrostatic agglomeration, it is thus necessary to cause a sufficient electronic avalanche. The internal electrode 16 must therefore be carried, by means of the electrical generating device 22, at a high potential, for example between 50 and 150 kV. The increase in the potential at which the internal electrode 16 is carried also has the effect of ionizing a gaseous medium in a larger volume. However, the ionization of the entire volume between the internal and external electrodes 16 requires a large amount of energy.

  In the case of an internal electrode 16 brought to a positive potential, the particles present in the exhaust gas pass through an ionized medium. There is a greater probability, in this case, that a particle encountering an ionized molecule combines to form a positively charged particle. An internal electrode 16 allows an ionization of the volume between said electrode and the internal electrode 5 with a low energy input, being brought to a lower potential, for example being between 1 kV and 50 kV.

  The nearly homogeneous electric field in the inter-electrode space deflects the charged particles that migrate to the porous outer electrode. The electric field is heterogeneous only in the vicinity of the two electrodes 16 and 5. When the particles are in the vicinity of the external electrode 16, of the order of 1 mm, the electric field lines converge towards the fibers of said electrode 16 The particles are then precipitated against the fibers by the large local increases in the electric field.

  Since the electric field is zero inside the porous electrode and its developed surface is small, the majority of particles reaches the electrode from the first row of fibers and almost no depth capture takes place. The charged particles deposited on the inner face of the electrode 16 agglomerate by electrostatic interactions and by Van der Waals forces. The particle clusters grow to a size sufficient for the friction forces exerted by the exhaust gases to tear them off. The particle clusters grow to their ejection out of the porous electrode 16 in the form of agglomerates which are then collected by the collection module 12. By way of example, the size ratio between the particles of the gases The exhaust emissions emitted by the engine and the clusters of particles thus collected, is from 100 to 1000. The majority of the agglomerated particles then has a size greater than 5 mm.

  The collection module 12 essentially comprises an internal electrode 29, which may be of wired type, and an external electrode 30 of generally cylindrical shape so as to allow the passage of the exhaust gases.

  The electrode 29 extends axially inside the electrode 30 being bent at each of its ends to form two radial portions 31 and 32 coming out of the supply line 28 through two openings 33 and 34. Two insulators 35 and 36 are mounted inside the openings 33 and 34 to electrically isolate the electrode 29. The electrode 29 is preferably supplied by the device 22 used for biasing the internal electrode 16 of the agglomeration module 10 .

  The electrode 30 is connected to ground (not shown).

  The electrode 30 includes a surface 37 for collecting or collecting agglomerated particles and discs 38 extending radially inwardly from said surface 37, being axially spaced relative to one another. A device of the heating cord type 39 is disposed at the level of the surface 37 and connected to an electrical control system 40, itself connected to a current source 41 which makes it possible to generate a heating of the deposition of particle clusters and to provoke their combustion.

  In operation, a second electric field is created between the inner electrode 29 and the outer electrode 30. As it is conceived, under the action of this electric field, the particles are deflected and attracted to the surface 37 and stopped by the Discs 38. The agglomerated particles are then burned using the heating cord 39. The power source 41 can supply the heating cord 39 periodically as a function, for example, of the kilometers traveled, of the operating time, or also by way of a probe measuring the quantity of particle clusters stored on the heating cord 39. The exhaust gas thus treated is then discharged via line 42.

  Of course, it is possible to provide other types of particle collection modules comprising for example a cyclone type mechanical collector, or a propeller manifold. It is also conceivable to provide the supply of the heating cord 39 via the device 22.

  With reference to FIG. 2, the main elements of the electrical device 22 supplying high-voltage DC power to the agglomeration module 10 and the collection module 12 will now be described.

  The device 22 for generating or supplying comprises a transformer 43 provided with primary and secondary coils 43a, 43b provided respectively with a number of turns N43a and N43b may be different. The primary coil 43a is connected to a DC / AC converter 44, for example an inverter, itself connected to a DC low voltage source 45. Advantageously, the source 45 is constituted by the electrical network of the vehicle.

  The secondary coil 43b is connected to a first AC / DC converter 46, for example a rectifier with or without a voltage multiplier, connected to the agglomeration module 10 and to the collection module 12.

  The transformer 43 thus enables the voltage delivered by the source 45 to be raised so as to obtain a desired DC high voltage for the modules 10 and 12. The ratio between the number of turns N43a and N43b is thus determined as a function of this tension.

  The electrical generation device 22 is associated with a control unit 47 providing control of the high voltage delivered to the 10 agglomeration and collection modules 10, 12.

  For this purpose, the device 22 comprises a first means 48 for measuring the value of the output voltage of the AC / DC converter 46. The control unit 47 is able to drive the DC / AC converter 44 according to the detected measurements. by said measuring means 48. Advantageously, the measuring means 48 comprises at least two electrical resistors forming a resistive voltage divider.

  Of course, it is also conceivable to also provide a current measurement at the output of the AC / DC converter 46 to control the operation of the DC / AC converter 44.

  In the variant embodiment illustrated in FIG. 3, in which the identical elements bear the same references, a transformer 49 is provided with a primary coil 49a and first and second secondary coils 49b and 49c. Said primary and secondary coils 49a, 49b, 49c are respectively connected to the DC / AC converter 44, to the first AC / DC converter 46 connected to the collection module 12, and to a second AC / DC converter 50 itself connected to the agglomeration module 10.

  The generation device 22 thus makes it possible to feed the modules 10, 12 either with high voltages of different values or with high voltages of equal values, depending on the number of turns of the coils 49b and 49c.

  The device 22 also comprises a second voltage and / or current measurement means 51 at the output of the AC / DC converter 50 which is connected to the control unit 47 to carry out the functional control of the generation device 22. The first measuring means 48 is here connected to the output of the AC / DC converter 46.

  In the variant embodiment illustrated in FIG. 4, the AC / DC converter 46 is replaced by a diode 52a that can be connected to a voltage limiter 52b itself connected to the collection module 12. The replacement of an AC / DC converter continuous by a diode makes it possible to obtain a device 22 of particularly economical generation. Of course, it may also be possible to replace the AC / DC converter 50 with a diode.

  The embodiments illustrated in FIGS. 5 and 6 differ from the embodiment of FIG. 3 in that a transformer 53 comprises first and second primary and secondary coils 53a to 53d. The first and second secondary coils 53c, 53d are respectively connected to the AC / DC converters 50, 46. The first and second primary coils are connected to the DC / AC converter 44 and are either connected in series (Fig. 5), or connected in parallel. (Figure 6).

  The assembly according to the invention thus makes it possible to obtain an agglomeration and a collection of the particles contained in the exhaust gases of the combustion engine of the motor vehicle in a particularly efficient and economical manner by using, for example, the electrical network present on board the vehicle. vehicle.

Claims (1)

  A set of agglomeration and collection of particles contained in the exhaust gas of a motor vehicle internal combustion engine provided with at least one electrostatic agglomeration module (10) comprising an internal electrode (16) and an external electrode (5) between which is created a first electric field, the outer electrode being made of porous material capable of passing the exhaust gases as well as clusters of particles agglomerated during the passage of the exhaust gas through the porous material, and a collection module (12) of particle clusters disposed downstream of the agglomeration module, considering the flow direction of the exhaust gas, characterized in that the assembly further comprises an electric generating device (22) provided with a single voltage booster transformer (43; 49; 53) adapted to allow a continuous high voltage supply of the agglomeration module ( 10) and the collection module (12).   2. An assembly according to claim 1, wherein the transformer is connected as input to a DC / AC converter (44) fed by a low voltage electrical source, and connected at the output to at least one AC / DC converter (46) connected to the Agglomeration and collection modules.   3. The assembly of claim 2, wherein the generating device further comprises means for measuring (48, 51) the value of the voltage and / or amplitude of the output intensity of the continuous converter. / alternative, and a control unit (47) capable of driving the DC / AC converter according to the measured values.   An assembly according to any one of the preceding claims, wherein the transformer comprises at least one primary coil and at least two secondary coils, each secondary coil being connected to an AC / DC converter connected to one of said modules, and wherein the generation device comprises means for measuring the value of the voltage and / or amplitude of the output intensity of each AC / DC converter, and a control unit (47) able to control the DC / AC converter according to at least one of the measured values.   5. The assembly of claim 4, wherein at least one of the AC / DC converters consists of a diode.   6. The assembly of claim 4 or 5, wherein the transformer comprises two primary coils connected in series.   7. The assembly of claim 4 or 5, characterized in that the transformer comprises two primary coils connected in parallel.   An assembly according to any one of the preceding claims, wherein the collection module comprises a first electrode and a second electrode extending into a second electric field, one of said electrodes comprising an agglomerated particle receiving surface.