Title:
Burner And Method For The Regeneration Of Filtration Cartridges And Devices Equipped With Such Burner
Kind Code:
A1


Abstract:
A burner for heating a filter cartridge for the exhaust gases of an engine until the oxidation and/or combustion of the solid particulates trapped in the cartridge, including a burner body having a closed end and, on the side opposite this closed end, an opening for removing the said gases. The burner further including at least one intake duct for a mixture of fuel and oxidiser terminating in the burner body tangentially to the burner body, so as to cause the mixture to swirl in the burner; an electrical ignition means for igniting the said mixture positioned inside the burner body; and a closure element obstructing the burner body, to limit the turbulence of the exhaust gases in the volume of the burner body bounded by the said closure element.



Inventors:
Fayard, Jean-claude (Lyon, FR)
Application Number:
12/303050
Publication Date:
11/26/2009
Filing Date:
03/22/2007
Primary Class:
Other Classes:
60/303
International Classes:
F01N3/023; F01N3/10
View Patent Images:



Primary Examiner:
MATTHIAS, JONATHAN R
Attorney, Agent or Firm:
TD Evans, P.C. (Canastota, NY, US)
Claims:
1. A burner for heating at least one filter cartridge for the exhaust gases of an internal combustion engine at a temperature above the oxidation temperature and/or the combustion temperature of the solid particulates trapped in the filter cartridge, said burner comprising: a burner body having side walls, a closed end side and having on a side opposite the closed end side a discharge opening suitable for connection to a duct for removing the exhaust gases; at least one intake duct for a mixture of fuel and oxidiser terminating in the burner body in a direction essentially tangential to the burner body, so as to apply a swirl motion to the mixture inside the burner body; an electrical ignition means for igniting the mixture, positioned inside the burner body; and a closure element obstructing a substantial portion of the burner body, so as to limit turbulence that may be generated by the exhaust gases on fluid flows within a volume of the burner body bounded by the closure element.

2. The burner according to claim 1, wherein an inner surface of the side walls of the burner body is uniform and has an overall symmetry of revolution about an axis of revolution.

3. The burner according to claim 2, wherein the closure element comprises a disc having a diameter slightly smaller than an inside diameter of the burner body, and positioned perpendicular to the axis of revolution, on the closed end side of the burner body.

4. The burner according to claim 3, wherein the disc is perforated with a plurality of holes, whereof at least one of a number and diameters are proportional to the diameter of the disc, the holes being intended for propagating a combustion flame of the mixture throughout the volume of the burner body.

5. The burner according to claim 3, wherein the closure element further comprises a straight cylinder whereof one end is covered by the disc and whereof an opposing end is covered by the closed end of the burner body, the straight cylinder being perforated with a plurality of holes, whereof at least one of a number and diameters are proportional to the diameter of the disc, the holes being configured for propagating a combustion flame of the mixture throughout the volume of the burner body.

6. The burner according to claim 2, wherein the closure element consists of a shutter placed outside the volume of the burner body near the discharge opening, an area of the shutter corresponding substantially to an internal area of the burner body, the shutter being mounted movably under an action of a member.

7. The burner according to claim 1, further comprising two concentric lines, one for the fuel and the other for the oxidiser, the lines being placed upstream of the duct.

8. The burner according to claim 2, wherein the mixture intake duct consists of a pipe extending along the side walls inside the burner body and parallel to the axis of revolution, the pipe having one end bent at a right angle.

9. The burner according to claim 1, further comprising a second electrical ignition means positioned inside the burner body, the first and the second electrical ignition means consisting of a conventional heater plug and a conventional electric arc plug or of at least two heater plugs.

10. The burner according to claim 1, further comprising a second intake duct for a mixture of fuel and oxidizer terminating in the burner body in a direction essentially tangential to the burner body, so as to apply a symmetrical swirl motion to the mixture inside the burner body.

11. The burner according to claim 1, further comprising a control device for controlling an injection flow rate of the oxidiser and fuel according to signals delivered by a temperature sensor located in the burner body and by a pressure sensor indicating a pressure drop due to a clogging of the filter cartridge by the solid particulates.

12. The burner according to claim 1, wherein the oxidiser is air from a turbocharger mounted on the engine.

13. The burner according to claim 1, wherein a ceramic textile, in a form of at least one of a mat, fabric and felt, is placed on the closed end side of the burner body and in contact with at least one electrical ignition means, the ceramic textile being suitable for collecting and for concentrating the mixture in order to promote its ignition.

14. The burner according to claim 1, wherein it comprises, at the side wall partly defining said burner, one or more through orifices, terminating in the burner body above the closure element intended for introducing part of the exhaust gases into the body.

15. The burner according to claim 14, wherein at least one of the through orifices is prolonged inside the burner by a line, whereof an end is curved and pointed towards the closure element.

16. An exhaust line of an internal combustion engine, comprising: at least one inlet orifice for the gases issuing from the internal combustion; at least one filter cartridge for trapping the solid particulates contained in the exhaust gases of the engine; at least one orifice for discharging the gases to the atmosphere, located downstream of the filter cartridge; and at least one burner according to claim 1.

17. The exhaust line according to claim 16, wherein the burner is placed upstream of the filter cartridge, at a location inside the exhaust line, outside the exhaust line, or near the filter cartridge.

18. The exhaust line according to claim 16, further comprising: at least two filter cartridges, the burner being accommodated between the two filter cartridges; and two shutters for stopping the exhaust gas flows respectively reaching each filter cartridge, so as to burn and/or oxidise the particulates alternately in each filter cartridge.

19. The exhaust line according to claim 16, further comprising a flap foldable on an outside wall of the burner, in order to cause the introduction of part of the exhaust gases thereinto.

20. A method for heating at least one filter cartridge for the exhaust gases of an internal combustion engine at a temperature above the oxidation temperature and/or the combustion temperature of the solid particulates trapped in the filter cartridge, by means of a burner comprising a burner body having a symmetry of revolution, the burner body having a closed end and having on the side opposite the closed end a discharge opening suitable for connection to a duct for removing the exhaust gases; said method consisting of: injecting, in a direction essentially tangential to the burner body, a mixture of fuel and oxidiser, so as to apply a swirl motion to the mixture inside the burner body; supplying electricity to an electrical ignition means positioned inside the burner body, in order to ignite the mixture, the burner body comprising a closure element obstructing a substantial portion of the burner body, so as to limit the turbulence that may be generated by the exhaust gases on fluid flows within the volume of the burner body bounded by the closure element; interrupting the mixture injection after the oxidation temperature and/or the combustion temperature has(have) been reached during a period depending on parameters such as a load withstood by the engine and a pressure drop due to a clogging of the filter medium by these solid particulates.

21. The method according to claim 20, wherein the fuel and the oxidiser are mixed in stoichiometric proportions.

22. A machine for regenerating the filter cartridges of particulate filters, wherein it comprises a burner according to claim 1 and a site for accommodating at least one filter cartridge to be regenerated.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage filing under 35 U.S.C. §371 of PCT Application No. PCT/FR2007/050982, filed Mar. 22, 2007. This application also claims the benefit of French Application No. 0652501, filed Jun. 7, 2006. The entirety of both applications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates in general to the field of the reduction, or even the complete removal, of the solid particulates such as soot contained in the exhaust gases of an internal combustion engine, and issuing in particular from diesel engines.

More particularly, the invention relates to a method for regenerating the filter cartridge(s) by burning the soot trapped therein. The term “regeneration” means the restoration of the filter cartridge to an operating state similar to its initial state.

BACKGROUND OF THE INVENTION

The authorities have established increasingly stringent standards to require automobile manufacturers to develop engines producing the least possible pollutant emissions. The automakers therefore strive to develop internal combustion engines, in particular diesel engines and lean burn engines, releasing the least possible unburnt particulates.

For this purpose, besides the development of new engines with steadily reduced fuel consumption, a special effort has been made to develop novel exhaust systems, designed to reduce the emission of unburnt pollutant gases and solid particulates.

Thus, the automakers have developed catalytic converters generally consisting of a stainless steel sheath, a thermal insulation and a honeycomb support impregnated with precious metals such as platinum (Pt) or rhodium (Rh). Such catalysts serve to reduce the emissions of polycylic hydrocarbons and carbon monoxide (CO), in a proportion of about 90%.

However, they have no effect on the emissions of solid particulates. Thus, such catalysts provide no significant improvement in the emissions of diesel engines producing numerous solid particulates.

In fact, modifying the combustion of the engines is no longer sufficient to comply with the directives on releases. This is why it is now indispensable to implement exhaust gas filtration methods and devices with regeneration of the filters by combustion. Such a filtration serves to reduce the total mass of particulates emitted by diesel engines by over 90%.

In a manner known per se, the solid particulates are generally trapped by a filter cartridge constituting the particulate filter. To operate properly, a particulate filter requires regeneration in order to burn the particulates trapped in its filtering portions, mainly in the filter cartridge.

To withstand the high temperatures reached in particular during the burning, a filter cartridge may consist of a porous body of cordierite, quartz or silicon carbide. Moreover, it generally has a honeycomb structure to maximise its filtration surface area and to have a sufficient retention capacity to prevent its clogging, and thereby to avoid a deterioration in engine performance.

In addition to decreasing the engine performance due to the pressure drops caused by the clogging of the particulate filter, engines equipped with a particulate filter of the prior art are liable to undergo another detrimental process.

This is because, since the clogging misadjusts the engine, the exhaust temperature is liable to rise, thereby causing the sudden and unintended combustion of a large mass of solid particulates, so that the temperature rises to levels much higher than 1000° C., possibly exceeding the thermal resistance of the abovementioned materials constituting the filter cartridge. The thermal shock resulting from such a combustion may therefore have a detrimental impact on the structure of the particulate filter.

However, the major difficulty for ensuring the operation of such particulate filters resides in the possibility of implementing the phases of oxidation and combustion of the solid particulates retained by the filter cartridge. This is because, in city driving, the exhaust gases only with difficulty reach a sufficient temperature to ensure the uniform and/or complete combustion of the solid particulates and thereby regenerate the filter while significantly limiting its clogging.

In fact, in the absence of chemical additives, the carbonaceous particles produced by the combustion of diesel fuel in a diesel engine only begin to oxidise above a temperature of 450° C. and to be consumed from 550° C. However, such temperatures are practically never reached in practice in city driving conditions. This is why it is necessary to implement a chemical method to facilitate the removal of these solid particulates. Various techniques have thus been used to obtain their combustion.

A first method of the prior art consists in placing, upstream of the filter cartridge, a catalyst for the oxidation of the nitric oxide (NO) contained in the exhaust gases to nitrogen dioxide (NO2). Nitrogen dioxide (NO2) has the property of catalysing the combustion of the carbonaceous particles from a temperature of 250° C. This technique, called Continuous Regenerating Trap (CRT), combines the action of the particulate filter and the nitric oxide (NO) oxidation catalyst.

However, this method requires the use of a diesel with a sulphur content lower than 50 ppm (parts per million), to preserve a sufficient efficiency of the conversion of the nitric oxide (NO) to nitrogen dioxide (NO2). Such fuels are only available in a few countries that impose such a limit on their sulphur content, a limit that is nonexistent in many emerging countries.

Moreover, to ensure satisfactory operation of the filters, this technique requires a regular regeneration in order to limit the pressure drop of the filter while eliminating the risk of uncontrolled regeneration, which is therefore too exothermic and destructive for the filter cartridge.

In the opposite case, due to the excessive concentration of carbonaceous particulates clogging the filter, the abovementioned violent reactions occur, consisting of an excessively rapid combustion of a large mass of solid particulates, which generally leads to destruction of the filter by thermal shock, since the temperatures obtained may be very high locally.

Alternatively, one prior art solution proposes to use organometallic additives with the diesel, such as cerium (Ce), iron (Fe), strontium (Sr), calcium (Ca) or others. This solution serves to obtain an effect similar to that obtained with nitrogen dioxide (NO2), by catalysing the combustion of the carbonaceous materials at temperatures close to 370° C.

A first drawback of such a solution resides in the very high cost of the additives to be used. Moreover, it is necessary to provide a device for introducing the supplementary additive, which further increases the cost of such a solution.

Furthermore, the additives present in the carbonaceous materials contribute to the even faster fouling of the filter cartridge. In consequence, a solution of this type increases the risk of clogging of the particulate filter and hence of uncontrolled reactions, when the temperatures reached in operation are not sufficiently high.

Moreover, another combustion method has been implemented in recent “common rail” direct injection diesel engines. It comprises a step of post-injection of the diesel used to raise the exhaust gas temperature and thereby to oxidise and burn the carbonaceous particles retained on the particulate filter. The “common rail” direct injection method, which uses electromagnetic injectors, serves to make a new diesel injection into the combustion chamber at the time when the exhaust valve opens, thereby producing a homogenous mixture with the exhaust gases and thus initiating an oxidation of the freshly injected diesel. This oxidation reaction proceeds to near completion on the oxidation catalyst located between the engine exhaust port and the particulate filter.

The prior art also teaches methods for post-injecting liquid of the diesel type intended for regenerating filtration means placed downstream of combustion catalysts in diesel engine exhaust systems. These methods are described in particular in the following documents: U.S. Pat. No. 5,207,990, EP-A-1 158 143, U.S. Pat. No. 6,023,930, JP-A-07 119444 and U.S. Pat. No. 5,522,218.

However, such methods have the common drawback, on the one hand, of not allowing optimal, safe and economical regeneration of the filtration means, and, on the other, of undergoing thermal degradation and coking of the regeneration liquid, particularly when the fuel is diesel, especially in the post-injection injector nozzles. The post-injection means are thereby rapidly damaged by the heat generated by the exhaust manifold, thereby reducing their reliability and efficiency.

Furthermore, the known post-injection methods only operate satisfactorily if a minimum exhaust gas temperature of about 300° C. is reached during at least 5% of the operating time. In consequence, the devices and methods implementing diesel post-injection in the exhaust gases upstream of an oxidation catalyst become inadequate when the temperature is too low.

Another drawback of these systems resides in the spurious and pollutant hydrocarbon emissions generated during the injection phase, when the temperatures are too low, for example around 300° C.

Other techniques consist in employing devices comprising supplementary heating means of the electrical resistor type or other. These supplementary heating means are only used when the cartridge displays incipient clogging, that is during an increase in the pressure drop. Such a regeneration device operates when the engine is running, that is in the presence of a high exhaust gas flow rate. Such a device therefore requires high heating power to raise the exhaust gases and the mass of the filter cartridge to the right temperature.

To achieve the combustion of the solid particulates retained on the filter, the prior art also proposes the use of a burner at the filter inlet and to ignite it when the vehicle engine is stopped. In fact, this implies numerous drawbacks, among which mention can be made of the difficulty of controlling, or even simply initiating, the combustion in the burner, the difficulty of thermally insulating the filter, the high temperature rise of the burner during the combustion phase (above 1400° C.) and the necessity to have a high filtration capacity to ensure sufficiently long service, that is between two engine stops.

In most cases, the use of a burner to provide the heat necessary for combustion of the solid particulates is only satisfactory when the engine is stopped or idling, that is at the time when the regeneration conditions are the least favourable, because the exhaust gas temperature is then low. Moreover, due to the burning powers required, most of the devices have a size that is incompatible with the volume generally available in the particulate filter.

Furthermore, such burners encounter serious difficulties in operating satisfactorily during the normal running of the engine, due to the difficulty of igniting the burner due to the high turbulence prevailing in the exhaust line and hence in the burner.

Such burners consequently demand bulky and sophisticated systems, which are therefore expensive, to overcome these problems. It is the object of the present invention to propose a method and a device to burn the solid particulates issuing from the internal combustion of an internal combustion engine that resolves the drawbacks of the prior art methods.

The object of the invention thereby serves to obtain the temperature increase necessary for complete combustion of the solid particulates, or soot, deposited on the filter cartridge, while being adaptable to numerous diesel engines and to a wide variety of engine running conditions.

A further object of the invention is to provide a method and a device for burning solid particulates, that avoids any risk of holdup of the particulates in the filter cartridge and hence any risk of accidental regeneration, regardless of the engine running conditions, in particular for urban transport applications.

Moreover, the invention also proposes a solution of quantitative reduction, or even complete removal, of the solid particulates, or soot, contained in the exhaust gases, by means of a regular, efficient and complete regeneration, that is without interruption, using an oxidation reaction produced above 200° C. and a complete combustion below 400° C., the use of an additive for avoiding any risk of holdup of the particulates in the filtration means despite a low temperature regeneration phase.

A further object of the invention is to provide a burner for the quantitative reduction, or even the complete removal, of the soot contained in the exhaust gases of internal combustion engines, this burner discharging at the inlet of the particulate filter and having small dimensions, thereby making it compact and easily integrable with the exhaust line of a vehicle.

A further object of the invention is to permit the regeneration of the filtration means used that does not cause an excessive increase in the temperature of the gases leaving the filtration device nor any significant extra consumption of fuel.

Furthermore, it is an object of the invention to achieve a quantitative reduction, or even the complete removal, of the particulates contained in the exhaust gases of an internal combustion engine, permitting the use of a catalyst with a low precious metal concentration.

A further object of the invention is to provide a solution for the quantitative reduction, or even the complete removal, of the soot contained in the exhaust gases of an internal combustion engine, that is relatively economical, reliable, flexible, and delays the clogging of the filter to the maximum, or even eliminates it, regardless of the engine load, without necessarily being affected by the possible presence of sulphur bearing compounds, such as sulphur dioxide in the exhaust gases. The object of the invention thereby serves to use diesel fuels with a high sulphur content.

A supplementary object of the invention is to provide a method and a device for burning solid particulates that are adaptable to machines for regenerating particulate filters to remove the ash deposited during their operation on a vehicle.

Moreover, the invention proposes a method and a device for burning solid particulates that are adaptable to applications other than the combustion of the soot in particulate filters. For example, given the small dimensions and the perfect control of the high energy combustion, it is possible to consider the use of the object of the invention for drying foods, cereals and other vulnerable products.

SUMMARY OF THE INVENTION

The object of the invention therefore relates to a burner for heating at least one filter cartridge for the exhaust gases of an internal combustion engine at a temperature above the oxidation temperature and/or the combustion temperature of the solid particulates trapped in the said filter cartridge.

This burner comprises a burner body which has a closed end and on the side opposite this closed end, a discharge opening suitable for connection to a duct for removing the exhaust gases.

According to the invention, the burner further comprises: at least one intake duct for a mixture of fuel and oxidiser terminating in the burner body in a direction essentially tangential to the burner body, so as to apply a swirl motion to the said mixture inside the burner body; electrical ignition means for igniting the said mixture, positioned inside the burner body; a closure element obstructing a substantial portion of the burner body, so as to limit the turbulence that may be generated by the said exhaust gases on the fluid flows within the volume of the burner body bounded by the said closure element.

In other words, the burner of the invention comprises means limiting the turbulence to a level compatible with the ignition of the mixture, regardless of the engine speed, and therefore regardless of the pressure variations liable to occur in the exhaust, the said mixture being injected in a manner favourable to ignition. This serves to easily ignite the mixture in a zone protected from turbulence, this ignition zone being bounded by the closure element. The combustion of the mixture can then take place throughout the volume of the burner body, thereby producing gases at a high temperature which can heat a filter cartridge until the solid particulates are completely burned therein.

In practice, the inner surface of the side walls of the burner body may be uniform and has an overall symmetry of revolution.

In the context of the present invention, “uniform” means a smooth surface (according to the common acceptance of the term and not according to its mathematical definition), that is free of irregularities or, in the case of a surface with a symmetry of revolution, a surface whereof the generating line has a high radius of curvature. It may, for example, be a straight cylinder, a shape that is relatively inexpensive to obtain and easy to join to other elements. Such a feature serves to further limit the turbulence in the burner body.

According to a first embodiment of the invention, the closure element may comprise a disc having a diameter slightly lower than the inside diameter of the burner body, and positioned perpendicular to the axis of revolution, on the closed end side of the burner body.

A disc thus dimensioned and positioned serves to “break” the turbulence of the exhaust gas streams flowing in the burner body.

According to a practical form of this first embodiment of the invention, the disc may be perforated with a plurality of holes, whereof the number and/or the diameters are proportional to the diameter of the disc, the said holes being intended for propagating the combustion flame of the mixture throughout the volume of the burner body.

After the mixture is ignited, this serves to “develop” the combustion flame of the mixture throughout the volume of the burner body.

According to another form of this first embodiment of the invention, the closure element may further comprise a straight cylinder whereof one end is covered by the said disc and whereof the other end is covered by the closed end of the burner body, the straight cylinder being perforated with a plurality of through orifices, whereof the number and/or the diameters are proportional to the diameter of the disc, the said orifices being intended for propagating the combustion flame of the mixture throughout the volume of the burner body.

Such a structure of the closure element serves to sharply limit the turbulence in the mixture ignition zone, the mixture combustion flame can then propagate via the orifices throughout the volume of the burner body.

According to a second embodiment of the invention, the closure element may consist of a shutter placed outside the volume of the burner body near the discharge opening, the area of the shutter corresponding substantially to the internal area of the burner body, the shutter being mounted movably under the action of a member such as a cylinder.

A shutter thus positioned and dimensioned also serves to limit the turbulence of the exhaust gases in the burner body.

In practice, the burner may further comprise two concentric lines, one for the fuel intake and the other for the oxidiser intake, the lines being placed upstream of the duct.

This relative arrangement of these two lines is suitable for promoting the mixing of the fuel with the oxidiser.

According to a particular embodiment of the invention, the mixture intake duct may consist of a pipe extending along the said side walls inside the burner body and parallel to the axis of revolution, the pipe having one end bent at a right angle.

In practice, the burner may further comprise a second electrical ignition means also positioned inside the burner body, these electrical ignition means consisting of a conventional heater plug and a conventional electric arc plug or of at least two heater plugs.

These plugs represent an inexpensive, easy-to-mount means for igniting the mixture.

According to a particular embodiment of the invention, the burner may comprise a second intake duct for a mixture of fuel and oxidiser terminating in the burner body in a direction essentially tangential to the burner body, so as to apply a symmetrical swirl motion to the said mixture inside the burner body.

This serves to distribute the mixture uniformly in the ignition zone.

According to a practical embodiment of the invention, the burner may further comprise a control device for controlling the oxidiser and fuel injection flow rates according to the signals delivered by a temperature sensor located in the burner body and by a pressure sensor indicating the pressure drop due to the clogging of the said filter cartridge by the said solid particulates.

When the burner is, for example, installed on a vehicle exhaust line, this serves to control its ignition and its extinction via the onboard computer.

In practical terms, the oxidiser may be air issuing from a turbocharger member mounted on the engine.

This serves to obtain a suitable air flow rate and a very uniform mixture with a high air speed for the mixture.

According to an advantageous embodiment of the invention, a ceramic textile, in the form of a mat, fabric or felt, may be placed on the closed end side of the burner body and in contact with at least one electrical ignition means, the said ceramic textile being suitable for collecting and for concentrating the said mixture in order to promote its ignition.

According to another particular embodiment of the invention, the side wall partly defining the burner body may comprise one or more through orifices, terminating in the said body above the closure element. These through orifices are intended to permit the introduction into the burner body of part of the exhaust gases, when they still comprise a high proportion of oxygen not burnt in the engine itself.

This case generally occurs with supercharged diesel engines, for which it is not uncommon to observe a proportion of oxygen in the exhaust gases that is higher than 10%.

In such a case, the energy liberated by the combustion of this residual oxygen is used, thereby serving to limit the quality of fuel required for the operation of the burner.

In an alternative of this embodiment, at least one of the orifices in question may be prolonged into the burner by a line, whereof the end is directed towards the closure element, in order to promote the concentration of the combustion in the bottom zone of the burner, thereby favouring the flame, and further serving to reduce the flame tube, and hence the dimensions of the said burner.

The invention relates to an exhaust line of an internal combustion engine, comprising at least one inlet orifice for the gases issuing from the internal combustion, at least one filter cartridge trapping the solid particulates contained in these exhaust gases, and at least one orifice for discharging the gases to the atmosphere, located downstream of this filter cartridge. According to the invention, this line comprises at least one burner of the type discussed above.

An exhaust line thus equipped serves to regenerate its filter cartridge by oxidising and/or by burning the solid particulates retained therein, and regardless of the engine load.

In practice, the burner may be placed upstream of the filter cartridge inside or outside the exhaust line or near the filter cartridge.

This layout in the vicinity of the filter cartridge limits the heat losses between the burner and the said cartridge. This thereby serves to completely burn the solid particulates with a minimum consumption of diesel.

According to a particular embodiment of the invention, the exhaust line may comprise: at least two filter cartridges, the said burner being accommodated between the two filter cartridges; two shutters for stopping the exhaust gas flows respectively reaching each filter cartridge, so as to burn and/or oxidise the said particulates alternately in each filter cartridge.

Such a structure serves on the one hand to minimise the distance, and hence the heat losses and diesel consumption, between the burner and the filter cartridges, and, on the other, to regenerate the particulate filter in turn, half by half.

According to another embodiment of the invention, the exhaust line comprises a folding flap, suitable for allowing the introduction of part of the exhaust gases into the burner via through orifices with which the latter may be provided, and thereby to permit the combustion, in the said burner, of the residual oxygen that may still be present in the said exhaust gases.

Furthermore, the invention also relates to a method for heating at least one filter cartridge for the exhaust gases of an internal combustion engine at a temperature above the oxidation temperature and/or the combustion temperature of the solid particulates trapped in this filter cartridge, by means of a burner comprising a burner body having a symmetry of revolution, this burner body having a closed end and having on the side opposite this closed end a discharge opening suitable for connection to a duct for removing the exhaust gases.

According to the invention, this method comprises the steps consisting: in injecting, in a direction essentially tangential to the burner body, a mixture of fuel and oxidiser, so as to apply a swirl motion to the said mixture inside the burner body; in supplying electricity to an electrical ignition means positioned inside the burner body, in order to ignite the mixture, the burner body comprising a closure element obstructing a substantial portion of the burner body, so as to limit the turbulence that may be generated by the exhaust gases on the fluid flows within the volume of the burner body bounded by the said closure element; in interrupting the injection of the mixture after the temperature in the burner body has exceeded a predefined threshold in order to exceed this oxidation temperature and/or this combustion temperature in the filtration medium during a period that depends on parameters such as the load withstood by the engine and the pressure drop due to the clogging of the filter medium by these solid particulates.

In other words, the method according to the present invention serves to ignite the mixture in the burner regardless of the exhaust gas flows, because means limit their turbulence therein to a level compatible with the ignition of the mixture, injected in a manner suitable for ignition. This serves to easily ignite the mixture in a zone protected from turbulence, bounded by the closure element.

The combustion of the mixture can then proceed throughout the volume of the burner body, thereby producing gases at a high temperature capable of heating a filter cartridge until the solid particulates are completely burnt therein.

In practice, the fuel and the oxidiser may be mixed in stoichiometric proportions.

Moreover, the invention also relates to a machine for regenerating filter cartridges of particulate filters comprising a burner as described above and a site for accommodating at least one filter cartridge to be regenerated.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention and its advantages will appear clearly from a reading of the description that follows, with reference to the appended drawings which show, in a non-limiting manner, exemplary embodiments of the invention and in which:

FIG. 1A is a schematic representation of a cross section of an exhaust line equipped with a burner according to the invention;

FIG. 1B is a schematic representation of a cross section of an exhaust line equipped with a burner according to the invention, according to an alternative to FIG. 1A with regard to the layout of the burner;

FIG. 2A is a schematic representation in two cross sections of a burner according to a first embodiment of the invention;

FIG. 2B is a schematic representation in two cross sections of a burner illustrating an alternative of the first embodiment of the invention;

FIG. 3 is a schematic representation in two cross sections of a burner according to another embodiment of the first embodiment of the invention;

FIG. 4 is a schematic representation in two cross sections of a burner according to another alternative embodiment to the invention shown in FIG. 3;

FIG. 5A is a schematic representation in two cross sections of a burner according to another alternative embodiment of the invention shown in FIG. 3, in which the burner comprises two heater plugs and a ceramic textile;

FIG. 5B is a schematic representation in two cross sections of a burner according to another alternative embodiment of the invention illustrated in FIG. 3, in which the burner is equipped with an electric arc plug of the same type as the one used on controlled ignition engines;

FIG. 6 is a schematic representation in two cross sections of a burner according to another alternative of the first embodiment of the invention illustrated in FIGS. 2A and 2B. In this alternative, the burner body is at least partially covered by a thermally insulating material;

FIG. 7 is a schematic representation of a cross section of a burner according to a second embodiment of the invention;

FIG. 8 is a schematic representation of a cross section of a burner according to the invention mounted on an exhaust line of an engine, the burner being supercharged by turbocharger;

FIG. 9 is a schematic representation of a cross section of an alternative to FIG. 8 for the compressed air supply of a burner according to the invention;

FIG. 10 is a schematic representation of a cross section of a burner according to the invention mounted on a filtration device;

FIG. 11 is a schematic representation of a cross section of a machine for regenerating particulate filters independently of the exhaust line of an engine;

FIG. 12 is a schematic representation of a cross section of another embodiment of an exhaust line according to the invention;

FIG. 13A is a schematic representation of a longitudinal cross section of the burner used in the line in FIG. 12;

FIG. 13B is a schematic representation of a cross section of the burner used in the line in FIG. 12.

DETAILED DESCRIPTION OF THE INVENTION

In the exhaust lines shown in FIGS. 1A and 1B, the exhaust gases from the diesel engine reach the filtration device via an inlet 1, at a temperature which may be between 80° C. at idling and 400° C. under load. Such exhaust lines are each equipped with a catalyst 4, followed by a filter cartridge 5, upstream of which a burner according to the invention is mounted.

In the present case, the burner has a burner body 2 with a symmetry of revolution comprising, according to one feature of the invention, a closure element 3 positioned within the burner body 2.

An intake duct 7 for a mixture of fuel and oxidiser discharges tangentially into the burner body 2, in order to convey the diesel or other fuel therein, led into the duct 7 via a capillary 6, itself fed by an injector 61. Means (not shown) are in fact provided for communicating an appropriate momentum to the oxidiser and to the fuel for applying a swirl movement to the mixture in the burner body 2. Typically, the speed of injection of the mixture into the burner body 2 may reach 300 m/s. “Tangentially” means tangentially to a circular cross section of the burner body 2 across the axis of the revolution of the burner.

The burner body 2 also has one end closed by a base and, on the side opposite this closed end, a discharge opening connected to the exhaust line.

In general, the fuel injected into the duct 7 is diesel issuing from the same tank as that of the internal combustion engine of the vehicle equipped with the exhaust line. Similarly, the oxidiser is generally oxygen contained in the air injected into the duct 7, for example from an air source of the engine. According to one feature of the invention, the fuel and the oxidiser are mixed in stoichiometric proportions.

Nevertheless, other fuels and/or oxidisers could be used while remaining within the scope of the invention. In the example in FIG. 2, the lines at 6, 7 conveying the diesel and air are mounted concentrically. Furthermore, the duct 7 has a length defined in order to permit the homogenisation of the said mixture of air and diesel upstream of its connection to the burner body 2. Thus, a more homogenous mixture is easier to ignite.

The duct 7 is therefore supplied with air to form a combustible mixture of air and diesel, which is then discharged tangentially into the burner via a connecting orifice 14. The burner body 2 further houses an electrical ignition means in the form of a heater plug 8 to cause the ignition and combustion of this mixture of air and diesel, and also a temperature sensor 9, whereof the measurement serves to control the combustion process. The heater plug 8 is of the incandescent type here, that is like the cells used in the chambers of the internal combustion diesel engine. The plug could also be of the impedance type, thereby permitting direct contact of the carburetted mixture with the filament heated to incandescence.

In practice, to economise the vehicle battery, it is possible to interrupt the power supply to the plug when the flame is sufficiently hot and “spirited” to burn the mixture subsequently injected. In practice, the moment of interruption is defined by a temperature threshold within the burner body. The injection of the mixture, hence the combustion thereof, is then maintained for a predefined period so that the filter cartridge 5 exceeds the oxidation and/or combustion temperature of the solid particulates.

Furthermore, it is possible to slightly tilt the duct 7 towards the closed end of the burner body 2 (downwards in FIGS. 2 to 6), in order to further guide the mixture towards the plug 8.

The overall device is controlled by a control device or computer 10 which, using the measurements taken by a pressure sensor 11 and by the temperature sensors 9 and 12, controls the starting of the burner to carry out the regeneration phase, and then adjust the capacity of the burner in order to complete the regeneration operation. The exhaust gases are removed via a manifold 13.

In the present case, the ignition of the burner by the computer 10 comprises the phases consisting: in supplying electric power to the heater plug 8; in injecting into the burner body 2 a controlled air flow via the tubular duct 7; after a predetermined period, substantially corresponding to the time required for the heater plug 8 to reach a temperature between 600° C. and 800° C., in proceeding, under the control of the computer 10, with micro-injections of diesel using the injector 61 via a capillary 6 terminating in the mixing duct 7, until the ignition of a flame in the burner body 2, that is until the temperature sensor 9 detects a significant temperature rise in the burner chamber; in simultaneously increasing the diesel flow rate and the air flow rate controlled by the computer 10, in quantities and in proportions such that the exhaust gas temperature, measured by the temperature sensor 12 at the inlet of the filter cartridge, remains below 600° C., a temperature withstandable by the catalyst 4 and by the filter cartridge 5, this temperature being controlled by the computer 10, which also has data on the engine running conditions; in stopping the combustion in the burner by a command from the computer 10, according to the operating time, the measurement of the clogging of the filter cartridge 5 by the pressure sensor 11 and/or the temperature measured downstream of the filtration device 4,5 towards the exhaust manifold 13.

It is an object of the invention to ensure satisfactory operation and above all satisfactory starting of the burner, regardless of the engine running conditions. In particular, the burner of the invention is suitable for igniting the mixture despite an engine at full power, that is when extreme fluid turbulence conditions prevail in the burner, because the exhaust gases then flow in the exhaust line at high speed and high flow rate.

For this purpose, the interior of the burner body 2 has a closure element 3 disposed substantially horizontally in FIGS. 1A and 1B. The closure element 3 is located in a plane situated at a lower level than the orifice 14 for connecting the duct 7 to the burner 2. According to one embodiment of the invention, the closure element 3 comprises a disk having a slightly lower diameter than the inside diameter of the burner body 2, and positioned perpendicular to the axis of revolution, on the side of the closed end of the burner body 2. Moreover, this disc is perforated with several holes (two here, and about 1 to 10 depending on the diameter of the burner). In the example in the figures, the diameter of each of the holes is 7 mm. In general, the number and diameters of the holes can be selected in proportion to the dimensions of the burner body 2.

The closure element 3 performs two functions contributing to the above mentioned objective. Firstly, it obstructs a substantial portion of the burner body 2 in order to arrange a cavity 15 under its surface in which a controlled turbulence prevails, by “breaking” the exhaust gas streams.

Secondly, it serves to “adhere” and stabilise the flame during operation, that is the combustion of a mixture of air and diesel. The verb “to adhere” reflects the mechanism whereby the flame is concentrated and stabilised around this closure element 3, before propagating towards the rest of the burner body 2 via the holes of the disc. Once the flame is durably established throughout the burner body 2, the temperature therein may exceed 1000° C. and typically reach 1300° C. to 1400° C.

Furthermore, the closure element 3 defines a cavity 15 in which the heater plug 8 intended for ignition is accommodated, at least its active portion, as shown in FIG. 1A, and also the temperature sensor 9, as shown in FIGS. 2A, 2B, 6 and 7. The plug 8 is thus positioned on the side of the closed end of the burner body 2, at a predefined distance from the opening of the duct 7 in order to ignite the mixture.

In the example in the figures, the temperature sensor 9 is positioned in the burner body close to the closure element 3, in order to detect the ignition of the mixture, and then to adjust the fuel-air ratio thereof to optimise the temperature and combustion time of solid particulates retained in the filter cartridge 5.

In the example described here, highly satisfactory results were thus obtained by placing the temperature sensor 9 projecting from the exterior of the closure element 3 and opposite the point of connection of the duct 7 in the burner 2. This positioning serves in fact to obtain a flame temperature that depends on the fuel-air ratio of the mixture when the burner is in “steady state conditions”.

As a non-limiting example, satisfactory operation of the burner with efficient ignition was obtained with a burner having the following dimensions: a cylindrical burner 2 with an inside diameter of 60 mm fed with air by a straight tangential tube 7 with an inside diameter of 8 mm, accommodating a capillary 6 with an inside diameter of 1 mm for a maximum diesel flow rate of 150 cm3/min, representing a power of about 85 kW. The portion of the burner 2 located above the closure element 3 has a length of 150 mm. The closure element 3 is located 5 mm below the connection of the duct 7 in the burner 2; it has a diameter of 59 mm and is perforated with two 8 mm diameter holes. The surface of the closure element 3 bounds, with the bottom of the burner 2, a cavity 15 having a height of 25 mm. In the present summary, the term “cylinder” is used in its common acceptance, and therefore designates a straight cylinder with a circular base.

When the burner reaches its steady state condition, the air flow is adjusted by the computer 10 in order to maintain the flame inside the cylinder defined by the burner body 2. The high turbulence and the high temperature inside the burner favour a rapid combustion that occurs along about ten centimeters inside this cylinder.

FIG. 1B shows an alternative in which the burner is placed directly inside the exhaust line. This layout of the burner serves to recover all the heat liberated during the combustion of the mixture conveyed via the duct 7.

With a burner having the structure shown in FIGS. 2A and 2B, similar to the one described with regard to FIG. 1, the burner 2 may be arranged horizontally as shown. However, it may also be arranged vertically, in which case it is indispensable to place the heater plug 8 on the bottom of the burner body 2 to obtain proper ignition. In FIGS. 2A and 2B, the orifice 14 represents the connection of the duct 7 in the burner 2, in this case an intersection between two cylinders of different diameters.

FIG. 2B shows an alternative in which a portion of the fuel is directly injected, during the ignition phase, through a heater plug terminating in the cavity 15. This plug may be of the same type as the one used in the additional burners of the automobile heating circuit. Such an injection serves to control the fuel-air ratio of the mixture and to distribute it in the cavity defined by the closure element 3.

For a burner operating vertically, a structure can be considered like the one shown in FIGS. 3, 4 and 5. This structure is similar to those shown in FIGS. 1, 2A and 2B. However, it has the special feature of having a flame “adhesion” closure element 3, composed of a cylindrical and laterally perforated close-end tube, of which the upper end is in fact covered by a solid disc. Moreover, the chamber defined by this tube houses at least one heater plug 8, which may or may not be centred on the base of the burner 2.

The closure element 3 here consists of a stainless steel tube with a thickness of 1.5 mm and an inside diameter of 35 mm, covered by a solid disc. The tube may be plugged at its bottom end by the base of the burner. The cylindrical or lateral surface of the closure element 3 is perforated with four 8 mm diameter holes arranged in opposite pairs and at two different heights. These holes enable the flame to propagate throughout the burner body 2.

Other geometries are feasible for the burner components, while remaining within the scope of this invention. Thus, similar results to those previously reported were obtained by using a square-section parallelepiped measuring 34 mm×34 mm, centred on the axis of revolution of the burner body 2, also plugged at its ends and only having two 8 mm diameter holes perforated facing one another.

The use of these circular- and square-section chambers yields similar results as to the quality of ignition. Thus, with a burner with an inside diameter of 60 mm and a height of 170 mm, placed perpendicular to the inlet cross section of a particulate filter of a “Renault Trucks Euro 2 MIDS 620*45” 270 HP engine, the burner may in fact be ignited from idling speed up to maximum speed, and for exhaust gas temperatures of between 80° C. and 400° C. The heater plug used is a BERU® make plug like those mounted on Renault 1.9 DCI 120 HP engines.

Furthermore, according to another embodiment of the invention, it is possible, to achieve the ignition phase, to mount a plurality of heater plugs in the burner chamber as shown in FIG. 5A. The additional plugs may be placed inside or outside the cavity bounded by the closure element 3.

Moreover, the installation of a ceramic textile 201, woven, felt or mat, near or in contact with the heater plug favours the mixture ignition phase, because it is suitable for collecting and concentrating the diesel mixture. It may be disposed as shown in FIG. 5A, that is accommodated between the wall of the burner body 2 and the heater plug 8 at least on a portion of the lateral circumference of the burner body 2. Similarly, this ceramic textile 201 could be incorporated in the burners described in relation to FIGS. 2A and 2B.

It could even be feasible to use a conventional sparking or electric arc plug as a second plug, like those used in controlled ignition engines, placed substantially like the second plug 81 shown in FIG. 5B.

For reasons of size, the intake of the carburetted mixture inside the burner 2 can also be provided by a pipe 16 connected to the bottom edge of the burner 2, as shown in FIG. 4. Such a mixture intake type consists of a pipe 16 extending along the side walls inside the burner body 2 and parallel to the axis of revolution, the pipe 16 having an end bent at a right angle discharging tangentially at the burner body 2. Such a pipe 16 comprises a lateral orifice 17, which terminates tangentially at the burner body 2 and serves to send the carburetted mixture in the direction D. In the example in FIG. 4, the burner has the same dimensions as previously. Thus, the pipe 16 made from stainless steel, has an inside diameter of 8 mm with a 4 mm diameter orifice terminating tangentially on the wall of the burner 2. Such a pipe 16 serves to decrease the size of the burner, thereby facilitating the accessibility and fabrication of the burner.

FIG. 6 shows, according to one feature of the invention, an alternative in which a thermally insulating coating 180 lines the burner 2, in order to preserve the heat produced by the flame inside the burner and to minimise the heat exchanges of the wall of the burner 2 with the exterior. This coating may be a refractory metal of the Inconel type or a ceramic such as cordierite, mullite, alumina, etc. Moreover, it is also possible to use a ceramic coating 180 combined with a sheath 181 of thin refractory steel, that is between 0.5 mm and 1.5 mm thick, in order to protect the ceramic from thermal shocks. Such a thermal insulation serves to reach the oxidation and/or combustion temperature of the solid particulates more rapidly in the filter cartridge 5, while economising the fuel injected into the burner.

Thus, in view of the speed of combustion and the maintenance of the walls at a high temperature, it is possible to burn any type of liquid or even solid fuel, without necessarily providing a high excess of air. The use of a longer burner 2 serves in fact to prolong the mixture combustion time to complete the combustion.

To promote the combustion and the ignition, a burner according to the invention may advantageously find an application for drying cereals or plants, in which the air is generally heated by natural gas. In this case, to limit or eliminate undesirable emissions, a catalytic coating may advantageously be placed on the outside wall of the burner 2. Such a catalytic coating serves to oxidise the last traces of hydrocarbons and carbon monoxide (CO). Moreover, a catalyst may be placed at the burner outlet, in the form of a honeycomb to increase its heat exchange surface.

For applications exhibiting very high turbulence, the burner of the invention may be equipped with a closure element in the form of a disc defining a shutter 18, as shown in FIG. 7. According to the invention, the shutter 18 controlled by a cylinder 19 substantially obstructs the burner body 2, in this case the burner discharge orifice, in order to limit the turbulence of the gas flows in the burner. When starting, the cylinder 19 controlling the shutter 18 may be simply controlled by an air bypass feeding the burner. When the flame is detected by the temperature sensor 19, it can be placed in a free position, or “at neutral point”, that is without a pressure difference between its chambers. Advantageously, this shutter 18 may be associated with a closure element 3, as described above in relation to FIGS. 1 to 6.

Furthermore, in the embodiment shown in FIG. 7, the bottom of the burner 2 is a portion of sphere. The temperature sensor 9 is placed, like the one shown in FIG. 2, on the bottom of the burner 2. The ignition plug 8 is placed on the side or at the centre according to whether the burner is intended to operate horizontally or vertically.

Moreover, it is necessary to provide a source of compressed air to feed the burners mounted on the exhaust lines of engines of buses, trucks and other high powered diesel engines. For this purpose, in all the operating conditions, use can be made of the air stored at about 10 bar in the tank designed to supply the vehicle accessories.

When such a compressed air source is unavailable, a booster may be mounted or the air of the engine supercharging circuit can be used, as shown in FIGS. 8 and 9. Thus, the compressed air is taken from a turbocharger 20 at the engine intake by means of a bypass duct 21, suitable for bypassing the air flow required to feed the burner. A controller 22 controls the air flow rate in the bypass duct 21 in order to regulate the quantity of air entering the filtration device, under the control of the computer 10.

As an alternative, as shown in FIG. 9, a compressed air tank 23 can be provided for the air feed, also via a bypass 21 issuing from the turbocharger and a nonreturn valve 24. The burner feed rate is also adjusted by the flow controller 22, which may for example consist of a variable-opening valve. To increase the air flow rate by the use of supercharging air, it is also possible to use a small turboblower machine placed between the compressed air tank 23 and the flow controller 22, to increase the flow rate and pressure available in the bypass duct 21. The turboblower machine may, for example, consist of a vane pump, supplied with electricity and generating a pressure difference of 400 mbar.

Furthermore, many diesel engines are factory-equipped with a catalyst for reducing the emissions of hydrocarbons and carbon monoxide (CO), in order to meet the emission standards. Alternatively, the diesel engines, like those which comply with the EURO 4 standard, may be equipped with an “SCR” nitrogen oxide reduction system incorporating a denitrification catalyst called “DéNox”, suitable for reducing, on the one hand, the nitrogen oxides (NOx) by means of a urea injection, in addition to the use of an oxidation catalyst to reduce any excess urea, and, on the other, the emissions of hydrocarbons and carbon monoxide (CO) remaining from the exhaust gases. A filtration device only comprising a burner according to the present invention therefore serves, in such applications, to propose a unit without oxidation catalyst, that is simple and economical.

Thus, the burner shown in FIG. 10 is placed between two filter cartridges 5 each comprising a conventional filter cartridge, terminating on the inlet face of each of the cartridges, which are also equipped with an obstruction shutter 25 controlled by a cylinder 26 with air- or electrical drive. The obstruction shutter 25 serves to regenerate one cartridge after the other by combustion of the carbon particulates retained on their filter cartridges, thereby avoiding excessive outlet temperatures. Each of the filter cartridges 5 is equipped with a temperature sensor 27, performing a function similar to that of the temperature sensor 9 shown in FIG. 1. Moreover, a temperature sensor 273 placed on the burner outlet duct serves to accurately control the exhaust gas exit temperatures by controlling the obstruction of the shutter 25 of the filter cartridge 5 to be regenerated.

As previously, a pressure sensor measures the back-pressure due to the pressure drops by clogging of the filter cartridges 5, in order to indicate the clogging level of the filter cartridges. Beyond a predefined clogging threshold, the computer controls the start of the burner in order to regenerate the filter. For this purpose, a starting method comprises the steps consisting in: supplying electricity to the heater plug 8; injecting an air flow via the duct 7; closing one of the two shutters 25 controlled by a cylinder 26; after a predefined time corresponding substantially to the time required for the heater plug 8 to reach a sufficient temperature of between 600° C. and 800° C., and proceeding, under the control of the computer 10, with micro-injections of diesel through the capillary 6 and the tube 7 by means of the injector 14, until the temperature sensor 9 detects a significant increase in the temperature prevailing in the chamber 2 of the burner; maintaining the combustion as long as the temperatures measured by the temperature sensors 27 at the outlet of the filter cartridge are lower than 500° C., a threshold above which the combustion of the carbon occurs in the corresponding filter cartridge; after exceeding this threshold, in controlling simultaneously, via the computer, the stopping of the burner and the opening of the shutter 25 of the obstructed filter cartridge 5.

Subsequently, the combustion continues in the filter cartridge 5, but however without reaching a prohibitive gas temperature at the outlet of the filter cartridge, because the carbon combustion gases issuing from a filter cartridge 5 are mixed with those issuing from the neighbouring filter cartridge 5 in which no combustion reaction has begun. In fact, the regeneration of the other filter cartridge is only initiated subsequently and after a period of time programmed in the computer 10, sufficiently long for the combustion on the filter cartridge 5 to be complete or until the temperatures measured by the probes 27 are equal.

Thus, by such a method, the power of the burner is only used to heat a single cartridge at a time, thereby substantially reducing its operating time and hence the quantity of fuel consumed for this operation.

For example, in the case of a 177 kW engine operating at half-load, with inlet exhaust gas temperatures of 300° C. and while waiting, during each combustion, for the temperature of the filter cartridge to be between 295° C. and 300° C., tests were conducted by two different methods.

Firstly, the method described above for sequential regeneration of the filter cartridges 5 was implemented. The two filter cartridges 5 were then simultaneously regenerated. For each test, the burner was stopped when the temperature measured downstream of the filtering filter cartridge 5 reached 500° C. The filter cartridge 5 employed for these tests was made from silicon carbide and each cartridge had a diameter of 143.8 mm for a length of 254 mm.

Thus, for a burner power corresponding to a diesel consumption of 50 cm3/min, the following operating times were obtained: for sequential operation, the duration varied from 20 to 25 s, and the outlet temperature did not exceed 470° C., a temperature corresponding substantially to the case in which the burner is stopped with simultaneous opening of the shutter obstructing the other filter cartridge 5. Shortly thereafter, this temperature approached 450° C. during the combustion of the carbon, and then, at the end of the combustion, fell back to the level of the exhaust gas inlet temperature, that is about 300° C.; when the two cartridges communicated, the complete combustion times were between 85 and 100 s. Differences in heating between the two filter cartridges 5 were also observed. The differences thus observed in the duration were due to the fact that the burner was stopped only when the outlet temperature was higher than 500° C. on the two filter cartridges 5. For the same cartridge plugging level, that is 6 g/l temperature peaks exceeding 650° C. were measured.

These tests consequently show that the “sequential” filter regeneration serves to significantly reduce the extra consumption of diesel required for each combustion. Thus, in the above example, the extra consumption is halved.

Moreover, in terms of safety, as shown previously, the shutters 25 also satisfy safety considerations by reducing the outlet temperatures substantially, and hence eliminating the need for considerable thermal insulation of the outlet line. This shutter device can therefore be advantageously incorporated with the devices comprising a burner.

According to a preferred feature of the device of the invention, each of the filter cartridges 5 has a flow obstruction means, placed upstream or downstream, and controlled by at least one computer integrating the engine running conditions, in order to isolate at least one filter cartridge 5 whenever the accelerator position is at zero (non-accelerated).

According to another embodiment of the invention, the burner of the invention can advantageously be used on a machine designed to regenerate the filter cartridges of particulate filters to renovate them, after the vehicle has traveled several tens of thousands of kilometres. In fact, even if the carbon combustion is perfectly complete in the filtration device, after several thousand kilometres, the ash produced by combustion of the engine oil, or even the combustion additives employed, tends to progressively clog the pores of the filter cartridge. This is why a regeneration carried out on a machine, with a device blowing hot air in countercurrent flow to the operating direction, serves to suitably regenerate the filter cartridge outside the vehicle.

Such a machine for regenerating particulate filters is shown in FIG. 11, in which the burner 2 operates in a horizontal position inside a chamber 32, which is itself supplied by an air turboblower machine 31. The turboblower delivery and the power of the burner 2 are controlled by a computer (not shown), so as to adjust the outlet temperature of the chamber 32 to a temperature set point indicated by the temperature sensor 28. The principle consists in progressively raising the air temperature in the burner to a temperature close to that at which the carbon combustion occurs, that is 500° C. without additive, or 350 to 400° C. with additive.

At the outlet of a filter cartridge to be regenerated 29, a second temperature sensor 30 is placed, in order to permanently compare the temperature at the outlet 13 with the inlet temperature measured by the sensor 28. In the case in which the outlet temperature exceeds the inlet temperature, means are employed to slow down the combustion in the filter, like reduction of the air flow rate, reduction of the burner power. This method of slowing the combustion serves to burn all the carbon and the wastes contained in the filter, without reaching excessive temperatures that are liable to jeopardise the integrity and service life of the filter cartridge.

Once the combustion phase is terminated, the temperature of the filter cartridge rises to a temperature of between 650 and 700° C. in order to reduce the waste to ash. A high flow is then generated by the turboblower machine in order to extract this ash from the filter cartridge to be renovated. The hot gases are removed via a thermally insulated line 34, comprising a special high capacity filter 35 suitable for stopping all the ash and waste. An oxidation catalyst 36 is placed downstream of this special filter to oxidise the hydrocarbons and carbon monoxide (CO) that may be formed during the combustion phase. The gases are then discharged via a duct 37.

According to another alternative of the invention, more particularly described with regard to FIGS. 12 and 13, the residual oxygen present in the exhaust gases is exploited for its combustion in the burner. This case is encountered in particular in supercharged diesel engines.

For this purpose, the burner body is perforated with one or more through orifices 38, terminating on the side wall defining the said body, at a higher level than the closure element 3. These orifices 38 are advantageously directed substantially tangentially to the said side wall, also for the purpose of contributing to the swirl movement applied to the flows inside the burner.

In order to cause the introduction of part of the exhaust gases in the burner, the exhaust line is provided with a flap 39, hinged to the inside wall of the said line, and adjustably foldable on the outside wall of the burner, upon command from the computer 10 according to the parameters already discussed, and as a corollary, causing the introduction of a more or less large quantity of the said exhaust gases in the burner.

In doing so, the energy liberated by the combustion of the oxygen in the burner is exploited, and as a corollary, the quantity of fuel required for the operation therefore is reduced.

Furthermore, at least one 40 of the said orifices is prolonged into the burner by a line 41, whereof the end 42 is curved and directed towards the closure element 3.

In doing so, the combustion is concentrated at the closure element, thereby favouring the flame and, as a corollary, serving to reduce the length of the said burner.

The burner of the present invention therefore serves to reduce, or even to completely remove, the solid particulates contained in a filter cartridge, while using a catalyst with a low precious metal concentration. In fact, such a burner allows complete combustion of the diesel without undesirable emission of hydrocarbons or of carbon monoxide, contrary to the devices in which diesel is injected directly on the catalyst.

Other embodiments of the invention are feasible while remaining within the scope of this invention. Thus, as shown in FIG. 3, the burner may comprise a second intake duct for a mixture of fuel and oxidiser, discharging in the burner body also in a direction essentially tangential to the burner body, in order to apply a symmetrical swirl movement to the said mixture in the burner body.