Note: Descriptions are shown in the official language in which they were submitted.
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B~CK~RO~ND OF THE INVENTION
_
~ ith any internal combustion eng~ne it is
desirable to treat the exhaust gases so that they can be
safely dissharged into the atmosphere. In some engines,
particularly of the diesel type~ among the most prevalent
operating problems is the presence of particulates which
are carried in the exhaust gas stream.
Primarily, the particulates are normally bits of
carbon. They result from the incomplete combustion of the
hydrocarbon ~uel under certain engine operating conditions.
However, the operating efficiency of the engine is also a
contributing factor to the amount of carbon produced.
The presence of relatively large amounts of carbon
particles in any exhaust gas stream may be evidenced by a
dark, smoky, undesirable effluent. Such smoke is not only
offensive aesthetically; in large quantities it can be
unhealthy.
Means have been provided and are known to the
prior art, for the elimination or minimization of the
particulate content in exhaust discharge streams. However,
it has been found that whlle the particulates can be
eliminated by a suitable fllter of proper construction,
eventually the latter can become saturated and/or inoperable
due to excessive particulate accumulations.
It is further known that the overall engine
exhaust gas treating process can be expedited. This is
achieved not only b~ passing the hot gas stream through a
filter medium, but by providing the filter With a catalyst
which ~ill promote combustion of the retained particles.
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It should be appreciated that the generation of
carbon particles is pre~alent under all diesel engine
operating conditions. It is further appreciated that the
quantity and quality of an exhaust gas stream created in
any internal combustion engine will vary in accordance with
the operating characteristics of the engine.
For example, the temperature range experienced by
the diesel exhaust gas stream can vary between slightly
above ambient air temperature, and temperatures in excess
of 1200 F. When the exhaust gas is hot enough, the
carbon particles trapped in a filter will be combusted.
However, the engine operating condition where this rejuvena-
tion can occur is seldom reached in diesel passenger cars.
Where it is ~ound that an engine continuously
operates under such circumstances that the particulates are
continuously produced and accumulated in the filter, the
particulate trapping filter bed must be occasionally
re~uvenated.
Under usual circumstances, rejuvenation will
conslst of merely introducing the hot exhaust gas stream,
containing su~ficient oxygen, into the filter bed to contact
and ignite or incinerate the retained carbon particles~
The combustion of any large and contained carbon accumulation
can, however~ produce temperatures greatly in excess of
that of the exhaust gasO The result is that at such
excessive temperatures, the filter bed or element is
susceptible to thermal shock, damage or distortiQn.
Toward achieving a satisfactory or limited rate
of carbon removal from an exhaust gas system without
0 incurring resultlng damage to the filter, the unit presently
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disclosed is provided. The instant system thus comprises
in brief`, the reaction chamber or section which contains a
catalyst bed through which at least a portion of the
exhaust gas stream is passed. This catalyst segment can
be incorporated within the particulate trapping bed, or
it can precede it.
To assure that the main or primary filter bed
or beds always remain functional, the exhaust gas stream
is periodically and regularly heated to a temperature in
excess of the temperature required to initiate combustion
of retained particles.
Physically, the heating step is achieved by
adding a desired amount of a flammable fluid directly into
the exhaust gas stream. This fuel mixes with the diesel
exhaust, which has excess oxygen. When the mixture contacts
the catalyst, an exotherm will occur and raise the
temperature of the exhaust gas stream at least to the
combustion temperature of the carbon particles which are
retained in the main filter bed.
The main filter bed will thus be regularly and
at periodic intervals, reJuvenated. Such treatment, i~
repeated at predetermined intervals will preclude any
carbon accumulation which might otherwise lead to thermal
stress or damage to the bed at such time as the accumulation
is combusted.
It is therefore an ob~ect of the invention to
provide a filter of the type disclosed which is capable
of containing combustible particulates from an exhaust
gas stream, and subsequently being periodically re~uvenated
by burning said particulates.
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A Eurther object is -to provide a particulate filter
of the type disclosed which is capable of removing solid ele-
ments from an exhaust gas stream while permitting periodic
rejuvenation of the filter element. ~he rejuvenation can be
accomplished while the engine is operating at conditions that
would normally not result in exhaust gas temperatures suffi-
cient to accomplish the task.
A still further object is to provide an exhaust gas
treating unit which ls capable of removing particulates from
]0 an exhaust gas stream without jeopardizing -~he integrity of the
filter bed by subjecting the latter to thermal shock or damage.
In summary, the invention provides, according to a
first aspect, the combination with an automotive internal com-
bustion engine which operates on an air/fuel mixture, -the com-
bustion of which forms and discharges from the engine exhaust
manifold a stream of hot exhaust gas containing an amount of
particulate combus-tible matter, of; a filter element having a
reaction chamber with an inlet port communicated to a source
of said exhaust gas, and having a main filter bed positioned
in said reaction chamber to receive a unidirectional flow of
said exhaust gas and to contact and retain particulate matter
therefrom, a pre-filter bed disposed upstream of said filter
bed and having a catalytic Eiltering media therein, an injec-
tion means including an injection metering apparatus having an
inlet communicated with a source of combustible fluid and having
a discharge port openiny into said filter element upstream of
said pre-filter bed, injection control means controllably con-
nected to said injection means and being operable to periodical-
ly actuate the latter to inject an amount oE combustible fluid
into said pre-filter bed~ to form a fuel/exhaust mixture there-
in, whereby contact of said fuel/exhaust gas mixture with said
catalytic filtering media will cause said mixture to be ignited,
thereby to raise the temperature of -the exhaust gas passing
through the pre-filter bed to a temperature in excess of the
ignition temperature of said combus-tible particulate matter
thus to incinerate the latter.
According to a second aspect, the invention provides
a method for removing combustible particulate matter from a
stream of exhaust gas which comprises the steps of; passing a
continuous, unidirectional flow of said exhaust gas stream into
a filter bed -to retain within the bed at least a portion of
said particulate matter/ periodically heating at least a por-
ti.on oE said exhaust gas stream prior to its entering said bed
to a temperature in excess of the ignition temperature of said
retained combustible particulate matter, and passing heated
exhaust gas into contact with said particulate retaining fil-
ter bed to combust said retained particles~
The invention will now be described in greater detail
with reference to the accompanying drawings, in which:
Figure 1 illustrates a diesel engine of the type
contemplated with whi.ch the present filter cooperates; and
Figure 2 is an enlarged view in cross-section, of the
filter element shown of Figure 1.
To facili-tate the present description, the internal
combustion engine 10 or source of exhaust gas, will be consid-
ered to be of the diesel type. In the latter, air is sequen-
tially introduced to the various combustion chambers~ from an
air filter 11, by way of manifold 1~. Fuel is thereafter
injected into each combustion chamber from a fuel pump 13 by
way of an engine control lin~age 14.
The hot exhaust gas stream is carried from exhaust
manifold 16 and conducted through an exhaust pipe 18 to a
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t
smoke ~ilter 17. Although a sound absorbing ~luffler could be
inserted into the exhaust pipe, su~h an element is not essen-
tial to the instant system.
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The exhaust gas stream, subsequent to lea~ing
exhaust manifold 16, will be at a temperature within the
range of about 200 to 1200F. The precise temperature
will depend on the operating conditions of the engine. For
example, at low and idle speeds, the exhaust gas will be
relatively cool or only slightly heated. Consequen~ly, as
the exhaust gas stream enters filter 17, the particulates
carried in the stream will be retained along the many diverse
passages within the filter bed 19.
While the exhaust gas is comprised primarily of
a combination of gases, it normally embodies sufficient
oxygen content to support at least a limited degree of
combustion within the stream itself.
~ilter 17 comprises in essence an elongated
metallic casing 21 having opposed end walls 22 and 23 which
define an internal reaction chamber 24 therebetween.
The latter chamber is occupied to a large e~tent by at
least one bed 19 ~ormed of material particularly adapted to
provide a plurality of irregular passages.
The function of this bed, or similar beds which
supplement it, is to define a series o~ passages along
which the gas will pass. During such passage, the particulate
matter carried on the stream will be retained along the
various passage walls.
In one embodiment, bed 1~ can be ~ormed of a
metallic mesh-like mass such as steel wool or the like
which is shaped to substantially fill the ~ilter reaction
chamber.
Bed 1~ can be optionally supported at its
0 upstream and downstream ends by perforate panels 26 and 27
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or other similar transverse members. The latter are carried
on the casing 21 wall to support the one or more beds
therein.
The ~ilter upstream wall 23 is provided with inlet
port 2~ for introducing gas to the ups-tream side of the bed
19. In a similar manner the downstream panel 26 is
communicated with an outlet port 29 to carry away gases
which leave the bed.
To best achieve the filtering action on the exhaust
1~ gas stream, filter bed 19 can be comprised as noted of a
suitable medium which is oapable of retaining the solid
particles from the stream. However, to facilitate subsequent
combustion of the retained particles, the filter medium can
be provided on its surface with a suitable catalyst of the
type which will promote oxidation of fuel and the combustible
particles.
When filter bed 19 is utilized without the benefit
of a catalyst, in accordance with the present invention,
the forward or upstream end thereof is provided with a
pretreating segment 19a. The latter includes a catalyst
materlal which will be capable of producing the desired
oxidation of fuel and the particles. This pre-filtering
chamber l9a can be physically a part of the filter bed 19,
or it can be a discrete segment thereof.
The pre-filter segment l9a can for example be
positioned in the for~rard portion of the casing 21 whereby
to contact incoming exhaust gas as soon as the ]atter enters
the filter casing.
Toward achieving the present preheating of the
G exhaust gas stream, an in~ection system is provided which
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embodies primarily a source of a com~ustible fuel together
wlth means for insertlng a measured amount of said fuel
into the heated exhaust gas stream. Said fuel source can
be in either liquid or gaseous form to achieve the desired
preheating function.
The supplementary fuel source can, as presently
shown, be diesel fuel utilized for powering internal
combustion engine 10. Alternatively it can be a compressed
gas such as propane or the like which is carried for the
express purpose of in~ection into the pre-~iltering chamber.
In brief, the supplementary fuel can be any of a number of
known volatile substances, hydrocarbon or otherwise, which
are capable of reacting in the catalyst chamber.
The in;ection system thus is provided with a
pump 31, or other suitable metering means, having the inlet
side 32 thereof co~nected to the fuel source 13. The
pump 31 in turn is communicated with an in~ector 33 which
can be provided with one or more nozzles 37 disposed at
the forward end of the catalyst-containing pre-filtering
~ l9
chamber ~
C As pump 31 is periodically actuated by the in~ector
control means 36, a measured amount of the combustible
fluidized fuel will be passed directly into the pre-filtering
~ q~
chamber ~ wherein it will be ignited by contact with the
heated exhaust gas in the presence of the oxidizing catalyst.
~ o achieve the periodic exhaust gas heating step,
pump 31 control system 36 is designed particularly to actuate
the pump at regular preset periods o~ time. These intervals
can be determined on the basis of the mileage the engine
has logged or on the actual time the engine has run.
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Further actuation can be a function of the tempe~ature
within the filter element. In any instance, the purpose of
the injection timing is such that the carbon will be
periodically incinerated from the filter regardless of
engine operating conditions. The spacing of the intervals
is such as to avoid any excess accumulation o~ carbon even
under the worst engine operating conditions.
Other modifications and variations o~ the
invention as hereinbefore set forth can be made without
departing from the spirit and scope thereof, and therefore,
only such limitations should be imposed as are indicated
in the appended claims.
