FR2800418A1 - Regenerating vehicle exhaust gas particle filter by fitting heat proof electrical resistance across filter entry to ignite collected particles when excessive deposition is detected by temperature - Google Patents

Abstract

An electrically conducting heat proof resistance (22) is located at the entry (15) to a particle filter box (30) and may be disposed as a straight line, circle or spiral. The resistance is energized from a control unit (26) using battery or alternator energy when the motor functioning point is suitable and the filter temperature indicates that there has been excessive particle accumulation in the filter.

Description

The invention relates to a particulate filter regeneration device.

The invention relates more particularly to a device for regenerating a particulate filter for the pollution control of the exhaust gases of a combustion engine, in particular a diesel or lean gasoline engine.

The invention also relates to a pollution control system comprising such a regeneration device. Diesel engines and certain gasoline engines emit polluting substances such as particles. Particles are soot to which insoluble unburnt hydrocarbons are attached. Indeed, during the combustion of the fuel, some areas of the combustion chamber contain a fuel-air mixture too rich fuel. The combustion is then incomplete for local lack of oxygen. This results in the formation of particles. They translate into polluting black smoke. For reasons of respect for the environment, it is necessary to strongly reduce or eliminate these particles.

knows exhaust gas treatment systems that can reduce particulate emissions.

Oxidation catalysts reduce these fumes. However, their effectiveness is not enough.

Another method of treating these particles is to filter them with a filter called a particulate filter. The latter is clogged, which causes a loss of load in the exhaust pipe and therefore a decrease in engine performance. It is therefore necessary to periodically regenerate the particulate filter.

To provoke the combustion of the particles, it is necessary to bring them to a temperature of approximately 450 to 550 C. However, the exhaust gases of the diesel engines do not reach this temperature since for example in city, this one varies between 150 and 350 C. It is then necessary to specifically increase the temperature of the exhaust gas during the regeneration phase so that it reaches the combustion temperature of the particles in the particulate filter.

Different systems are proposed in the state of the art. Systems propose to increase the temperature of the exhaust gas by injecting an additional amount of fuel into at least one of the combustion chambers in the form of a post-injection. That is to say, after having injected the amount of fuel required for the "conventional" operation of the engine, an additional quantity of fuel is injected in a second time. Some of this extra fuel ignites by producing an increase in the temperature of the exhaust gas, the rest of this amount being converted into partial oxidation products such as carbon monoxide CO and HC hydrocarbons.

In order for the temperature to reach the combustion temperature of the particles, it is necessary for the partial oxidation products to react by exothermic reactions before their arrival in the particulate filter.

Exothermic reactions are obtained especially during the crossing of an oxidation catalyst.

The system therefore requires the presence of an oxidation catalyst upstream of the particulate filter and post-injection management.

Electrical resistance heating systems, in particular electric heating grids, also make it possible to bring the temperature of the exhaust gases to a value sufficient to cause the combustion of the particles in the filter. However, these systems require significant electrical power to ensure the heating of the entire engine exhaust flow, in addition, they complicate the exhaust line.

Finally, systems allow the local heating of particles stored on the particulate filter, at a temperature above the combustion temperature of the particles. French patent application No. 97.14737 proposes candles such as glow plugs for diesel engines. These systems are placed sufficiently close to the entry face of the particulate filter to, during the regeneration phase of the filter, raise to a temperature above the combustion temperature of the particles one or more areas of the particles stored in the filter. However such a system is bulky, expensive and complicated to implement, indeed the candle must be powered by an electrical circuit that delivers a high voltage. This document also proposes as variants, to use an electrical resistance of local heat input.

With the aim of optimizing these devices, the invention proposes a device for regenerating a particulate filter for decontamination of the combustion engine exhaust gases, in particular a diesel or lean gasoline engine, of the type in which an electrical resistor, located near the inlet face of the particulate filter, provides heat locally over the inlet face of the particulate filter to cause ignition of the particles in the least one defined area, characterized in that electrical resistance comprises at least one refractory conductive wire which extends in the transverse plane of the inlet face of the particulate filter.

According to other characteristics of the regeneration device - the conducting wire is rectilinear and in particular of radial orientation; the conductive wire extends at the periphery of the transverse input face of the particulate filter; the conducting wire extends forming a double parallel spiral; the heat input is effected when the loading level value of the particle filter reaches a predefined threshold value; the value of the particulate loading level of the particulate filter is evaluated by measuring the temperature of the exhaust gas; - value of the particulate loading level of the particulate filter is evaluated by the measurement of the back pressure in the exhaust line; a chemical additive which makes it possible to lower the combustion temperature of the particles stored in the particulate filter is added to the fuel before combustion.

The invention also proposes a system for the depollution of the exhaust gases of a combustion engine, in particular a lean-burn diesel or gasoline engine, characterized in that it comprises a particulate filter and a regeneration device of the type described above.

Other features and advantages will appear on reading the detailed description which follows for the understanding which will be referred to the appended figures among which - Figure 1 schematically shows an exhaust line of a combustion engine equipped with a catalyst and a particulate filter; - Figure 2 is a longitudinal sectional view, on a larger scale, the particle filter, in the input face of which disposed a conductive wire according to the invention; - Figure 3 is a sectional view along the line 3-3 of a particle filter, in the input face of which extends radially conductive wire, according to a first embodiment of the invention; FIG. 4 is a view similar to that of FIG. 3, in which the conductive wire extends at the periphery of the inlet face of the particle filter, according to a second embodiment of the invention; - Figure 5 is a view similar to that of the figure which the conductive wire extends in double spiral in the input face of the particle filter, according to a third embodiment of the invention.

FIG. 1 shows a system 10 for treating the exhaust gases G of a combustion engine 12. The engine 12 is a diesel engine or a gasoline engine operating in a lean mixture such as a gasoline engine. direct injection comprising at least one combustion chamber and a piston.

Advantageously, a chemical additive which decreases the combustion temperature of the particles is added to the fuel of the engine 12. These are in particular "EOLYS" based on cerium Ce marketed in France by Rhodia. An exhaust line 14 allows the gas flow G of the engine 12 to the atmosphere. A treatment system for purifying the exhaust gas G interposed in the line 14. It consists mainly of a particulate filter 16 located in a chamber 18. Advantageously, an oxidation catalyst 20 is also inserted into the line 14 exhaust upstream of the particulate filter 16.

Advantageously, the particulate filter 16 is covered with a catalytic impregnation.

The particulate filter 16 is of the honeycomb type. It has an upstream inlet face 15 and a downstream outlet face 17 of the gases G. It is composed of alternately clogged and open channels at the inlet and which are inversely open and plugged at the outlet. The particulate filter walls 16 are porous and allow exhaust gas filtration G.

Upstream of the particulate filter 16, the treatment device 10, according to the invention, comprises a conductive and refractory wire 22 which locally heats the determined zone 24 of the inlet face 15 of the particulate filter 16.

defined area 24 is shown in Figures 3 to 5 by a shaded area.

The wire 22 extends near the transverse input face 15 of the particle filter 16, that is to say, at a distance of less than 5 mm, in a transverse plane perpendicular to the general axis of flow of the exhaust gas which is substantially parallel to the input upstream plane in which the channels 19 open. Advantageously, the wire 22 may be in contact with the input face 15 of the particulate filter According to a first variant, according to FIG. 3, the conducting wire 22 extends radially in the transverse input face 15 of the particulate filter 16.

According to a second variant, in accordance with FIG. 4, the conductive wire 22 extends at the periphery of the transverse input face 15 of the particulate filter 16, whose distance, here circular, it marries at a distance.

According to a third variant, according to FIG. 5, the conductive wire 22 extends forming a double spiral in the inlet face 15 of the particulate filter 16.

The choice of the arrangement of the conducting wire 22 according to one of the preceding variants depends on the dimensions of the determined zone 24 which is necessary for the regeneration of the particulate filter 16.

The wire 22 is connected at each of its ends to an electronic control system 26 supercharging which is itself connected to measuring means 28 such as pressure sensors and temperature sensors which are arranged on the exhaust line 14 .

The chamber 18 of the particulate filter 16 is shown in more detail in FIG.

It comprises a body or casing 30 which is for example cylindrical with axis X-X which encloses the particle filter 16. The body is connected to the tube of the line 14 by an inlet cone 32.

The conductive wire 22 passes transversely through the chamber 18 at the connection of the body 30 and the inlet cone 32. Electrical insulation between the conductive wire 22 and the parts 32 of the chamber 18 is formed by intermediate elements 34 made of insulating material. They are for example cylindrical and are introduced into a radial bore made, for example, at the front end of the body 30.

The electrical insulation may also consist in sandwiching the electrical wire 22 between two electrically insulating joints, these seals are placed between the body 30 and the inlet cone 32. For example, MAT type seals marketed by the company 3M which usually serve as catalytic monolith packaging can be used.

Thus, introduction of the lead 22 requires virtually no modification compared to the processing system 10 which is not equipped with such a wire 22.

The -section of the conductive wire 22 is indifferent it can be including square, triangular or round.

The area of the section, as well as the length and the material of the conductive wire 22, are determined in particular according to the dimensions of the particulate filter 16 and the determined zone 24 to be heated locally.

The operation of the treatment system 10 is as follows.

The exhaust G produced by the engine 12 are sent in line 14. As they pass through the chamber 18, the particles contained in the gases G are stopped by the particulate filter 16, and in particular near its inlet face. That is, in the input plane of the channels 19.

Periodically the particles thus trapped in the particulate filter 16 are burned during a regeneration phase.

For this purpose, the measuring means 28 transmit information to the electronic control system 26 representative of the loading level of the particle filter 16.

The electronic control system 26 takes into account the loading level of the particulate filter, as well as the operating point of the motor 12 to trigger the regeneration phase.

When triggering a particulate filter regeneration phase 16, the electronic control system energizes the lead 22. The power supply of the conductor 22 is continuous. The necessary intensity and voltage are produced by means existing on all motor vehicles. The electrical energy comes for example directly from the battery or the alternator.

The current flowing through the conductor wire 22 causes the latter to heat up due to the Joule effect.

The refractory material, as well as the area of the conductive wire section 22, are determined so as to allow the 22 to be traversed by a current of sufficient intensity to reach a temperature greater than the ignition temperature of the particles, without suffering damage such as a merger.

Conductive wire 22 then causes a local increase in the temperature of the particles deposited on the determined input zone 24 of the particulate filter 16.

temperature reached on the determined zone 24 greater than the ignition temperature of the particles, which makes it possible to begin their combustion. This combustion start occurs only in the determined zone 24, is located near the electric wire 22.

As a result, combustion is self-sustaining. Indeed, combustion particles initially heated by the wire generates a significant heat flow. The heat produced by combustion of the particles allows the heating of the not yet inflamed particles immediately adjacent to a temperature above the autoignition temperature.

Thus, even if the power supply of the conducting wire 22 is stopped, the combustion propagates from the determined zone 24 over the entire surface of the inlet face 15 of the particulate filter 16 as well as inside the channels 19 in which particles are stored.

According to one variant, a plurality of conducting wires 22 are arranged in the plane of the input transverse face 15 of the particulate filter 16.

The regeneration device according to the invention is economical, in fact, once the combustion of the particles is initiated, the electronic control system 26 can stop the power supply of the conducting wire 22, the regeneration of the particulate filter 16 continuing without external input of energy.

device according to the invention makes it possible to regenerate a particulate filter 16 very simply and economically. Indeed, requires neither modification of the active internal structure of the particulate filter, nor additional material for its implementation. The solution thus proposed is therefore inexpensive.

In addition, the conductive wire 22 requires a small footprint which does not modify the exhaust line 14 of the motor 12.

Claims (9)

<U> CLAIMS </ U> 1. Regeneration device of a particulate filter (16) for the clearance of the exhaust (G) of a combustion engine (12), including a diesel or lean gasoline engine, of the type in wherein an electrical resistance, located near the inlet face (15) of the particulate filter, provides heat locally to the inlet face (15) of the particulate filter (16) to cause particle ignition in at least one predetermined zone (24), characterized in that the electrical resistance comprises at least one conductive and refractory wire (22) extending in the transverse plane of the inlet face (15) of the particulate filter ( 16). 2. Device according to the preceding claim, characterized in that the (22) conductor is rectilinear and in particular of radial orientation. 3. Device according to any one of the preceding claims, characterized in that the wire (22) conductor extends to the periphery of the input transverse face (15) of the particulate filter (16). 4. Device according to any one of the preceding claims, characterized in that the wire (22) conductor extends forming a double parallel spiral. 5. Device according to any one of the preceding claims, characterized in that the heat input is effected when the value of the loading level of the particulate filter (16) reaches a predetermined threshold value. 6. Device according to the preceding claim, characterized in that the value of the particle loading level of the particulate filter (16) is evaluated by measuring the temperature of the exhaust gas (G). 7. Device according to one of claims 5 or 6, characterized in that the value of the particle loading level of the particulate filter (16) is evaluated by measuring the back pressure in the line (14) of exhaust. 8. Device according to any one of the preceding claims, characterized in that a chemical additive which allows to lower the combustion temperature particles stored in the particulate filter (16) is added to the fuel before combustion. 9. Exhaust gas pollution control system of a combustion engine 2), in particular a diesel engine or gasoline lean mixture, characterized in that comprises a particulate filter (16) and a regeneration device according to one any of claims 1 to 8.