U.S. patent application number 12/303050 was filed with the patent office on 2009-11-26 for burner and method for the regeneration of filtration cartridges and devices equipped with such burner.
Invention is credited to Jean-Claude Fayard.
Application Number | 20090288399 12/303050 |
Document ID | / |
Family ID | 37670723 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090288399 |
Kind Code |
A1 |
Fayard; Jean-Claude |
November 26, 2009 |
Burner And Method For The Regeneration Of Filtration Cartridges And
Devices Equipped With Such Burner
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) |
Correspondence
Address: |
MARJAMA MULDOON BLASIAK & SULLIVAN LLP
250 SOUTH CLINTON STREET, SUITE 300
SYRACUSE
NY
13202
US
|
Family ID: |
37670723 |
Appl. No.: |
12/303050 |
Filed: |
March 22, 2007 |
PCT Filed: |
March 22, 2007 |
PCT NO: |
PCT/FR07/50982 |
371 Date: |
May 20, 2009 |
Current U.S.
Class: |
60/295 ;
60/303 |
Current CPC
Class: |
F01N 2240/14 20130101;
F01N 3/0256 20130101; Y02T 10/47 20130101; F01N 9/002 20130101;
Y02T 10/40 20130101 |
Class at
Publication: |
60/295 ;
60/303 |
International
Class: |
F01N 3/023 20060101
F01N003/023; F01N 3/10 20060101 F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2006 |
FR |
0652501 |
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
[0001] This application is a National Stage filing under 35 U.S.C.
.sctn.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
[0002] 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.
[0003] 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
[0004] 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.
[0005] 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.
[0006] 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%.
[0007] 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.
[0008] 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%.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.degree. 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.
[0013] 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.
[0014] 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.degree. C. and to be consumed from 550.degree. 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.
[0015] 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 (NO.sub.2). Nitrogen dioxide (NO.sub.2) has the property of
catalysing the combustion of the carbonaceous particles from a
temperature of 250.degree. C. This technique, called Continuous
Regenerating Trap (CRT), combines the action of the particulate
filter and the nitric oxide (NO) oxidation catalyst.
[0016] 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 (NO.sub.2). 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.
[0017] 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.
[0018] 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.
[0019] 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
(NO.sub.2), by catalysing the combustion of the carbonaceous
materials at temperatures close to 370.degree. C.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] Furthermore, the known post-injection methods only operate
satisfactorily if a minimum exhaust gas temperature of about
300.degree. 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.
[0026] 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.degree. C.
[0027] 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.
[0028] 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.degree. C.) and the
necessity to have a high filtration capacity to ensure sufficiently
long service, that is between two engine stops.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.degree. C. and a complete combustion below 400.degree. 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] In practice, the inner surface of the side walls of the
burner body may be uniform and has an overall symmetry of
revolution.
[0046] 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.
[0047] 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.
[0048] A disc thus dimensioned and positioned serves to "break" the
turbulence of the exhaust gas streams flowing in the burner
body.
[0049] 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.
[0050] After the mixture is ignited, this serves to "develop" the
combustion flame of the mixture throughout the volume of the burner
body.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] A shutter thus positioned and dimensioned also serves to
limit the turbulence of the exhaust gases in the burner body.
[0055] 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.
[0056] This relative arrangement of these two lines is suitable for
promoting the mixing of the fuel with the oxidiser.
[0057] 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.
[0058] 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.
[0059] These plugs represent an inexpensive, easy-to-mount means
for igniting the mixture.
[0060] 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.
[0061] This serves to distribute the mixture uniformly in the
ignition zone.
[0062] 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.
[0063] 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.
[0064] In practical terms, the oxidiser may be air issuing from a
turbocharger member mounted on the engine.
[0065] This serves to obtain a suitable air flow rate and a very
uniform mixture with a high air speed for the mixture.
[0066] 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.
[0067] 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.
[0068] 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%.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] In practice, the burner may be placed upstream of the filter
cartridge inside or outside the exhaust line or near the filter
cartridge.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] In practice, the fuel and the oxidiser may be mixed in
stoichiometric proportions.
[0083] 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
[0084] 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:
[0085] FIG. 1A is a schematic representation of a cross section of
an exhaust line equipped with a burner according to the
invention;
[0086] 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;
[0087] FIG. 2A is a schematic representation in two cross sections
of a burner according to a first embodiment of the invention;
[0088] FIG. 2B is a schematic representation in two cross sections
of a burner illustrating an alternative of the first embodiment of
the invention;
[0089] FIG. 3 is a schematic representation in two cross sections
of a burner according to another embodiment of the first embodiment
of the invention;
[0090] 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;
[0091] 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;
[0092] 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;
[0093] 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;
[0094] FIG. 7 is a schematic representation of a cross section of a
burner according to a second embodiment of the invention;
[0095] 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;
[0096] 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;
[0097] FIG. 10 is a schematic representation of a cross section of
a burner according to the invention mounted on a filtration
device;
[0098] 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;
[0099] FIG. 12 is a schematic representation of a cross section of
another embodiment of an exhaust line according to the
invention;
[0100] FIG. 13A is a schematic representation of a longitudinal
cross section of the burner used in the line in FIG. 12;
[0101] 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
[0102] 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.degree. C. at
idling and 400.degree. 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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] 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.
[0108] 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.
[0109] 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.
[0110] 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.
[0111] 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.
[0112] 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.degree. C. and
800.degree. 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.degree. 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.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.degree.
C. and typically reach 1300.degree. C. to 1400.degree. C.
[0117] 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.
[0118] 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.
[0119] 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".
[0120] 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
cm.sup.3/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.
[0121] 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.
[0122] 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.
[0123] 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.
[0124] 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.
[0125] 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.
[0126] 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.
[0127] 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.times.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.
[0128] 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.degree. C.
and 400.degree. C. The heater plug used is a BERU.RTM. make plug
like those mounted on Renault 1.9 DCI 120 HP engines.
[0129] 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.
[0130] 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.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] 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.
[0135] 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.
[0136] 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.
[0137] 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.
[0138] 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.
[0139] 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.
[0140] 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.
[0141] 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
"DeNox", 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.
[0142] 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.
[0143] 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.degree. C. and 800.degree. 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.degree. 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.
[0144] 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.
[0145] 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.
[0146] For example, in the case of a 177 kW engine operating at
half-load, with inlet exhaust gas temperatures of 300.degree. C.
and while waiting, during each combustion, for the temperature of
the filter cartridge to be between 295.degree. C. and 300.degree.
C., tests were conducted by two different methods.
[0147] 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.degree.
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.
[0148] Thus, for a burner power corresponding to a diesel
consumption of 50 cm.sup.3/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.degree. 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.degree. 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.degree. 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.degree. C. on the two filter cartridges 5. For the same
cartridge plugging level, that is 6 g/l temperature peaks exceeding
650.degree. C. were measured.
[0149] 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.
[0150] 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.
[0151] 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).
[0152] 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.
[0153] 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.degree. C. without additive, or 350 to 400.degree. C.
with additive.
[0154] 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.
[0155] Once the combustion phase is terminated, the temperature of
the filter cartridge rises to a temperature of between 650 and
700.degree. 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.
[0156] 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.
[0157] 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.
[0158] 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.
[0159] 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.
[0160] 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.
[0161] 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.
[0162] 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.
[0163] 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.
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