U.S. patent application number 12/342675 was filed with the patent office on 2009-06-25 for emission control system.
Invention is credited to Michihiro Hata, Hajima Ishii, Kazuhito Kawashima, Hiroyuki Kimura, Kazuo Koga, Mitsutaka KOJIMA, Kazuto Maehara, Kojiro Okada, Kei Shigahara.
Application Number | 20090158722 12/342675 |
Document ID | / |
Family ID | 40474784 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090158722 |
Kind Code |
A1 |
KOJIMA; Mitsutaka ; et
al. |
June 25, 2009 |
EMISSION CONTROL SYSTEM
Abstract
An emission control system, includes: an exhaust pipe portion,
adapted to guide exhaust gas from an engine to outside; a catalyst,
accommodated in the exhaust pipe portion; an additive injection
valve, provided at the exhaust pipe portion located at upstream
side of the catalyst, and configured to inject additives to be
supplied to the catalyst toward a flow of the exhaust gas in the
exhaust pipe portion. The exhaust pipe portion has a flow path
section located at upstream side of the catalyst, which intersects
an injection flow of the additives injected by the additive
injection valve, and the flow path section is made to have
substantially the same shape as an injection region of the
injection flow which confronts the exhaust gas.
Inventors: |
KOJIMA; Mitsutaka;
(Okazaki-shi, JP) ; Kimura; Hiroyuki; (Ohbu-shi,
JP) ; Okada; Kojiro; (Nagoya-shi, JP) ;
Shigahara; Kei; (Anjo-shi, JP) ; Hata; Michihiro;
(Okazaki-shi, JP) ; Kawashima; Kazuhito;
(Okazaki-shi, JP) ; Koga; Kazuo; (Okazaki-shi,
JP) ; Maehara; Kazuto; (Anjo-shi, JP) ; Ishii;
Hajima; (Okazaki-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
40474784 |
Appl. No.: |
12/342675 |
Filed: |
December 23, 2008 |
Current U.S.
Class: |
60/297 ;
60/299 |
Current CPC
Class: |
F01N 3/035 20130101;
B01F 2005/0091 20130101; Y02T 10/26 20130101; B01F 5/0652 20130101;
F01N 3/0807 20130101; F01N 3/2033 20130101; F01N 13/08 20130101;
F01N 2470/10 20130101; B01F 5/0471 20130101; F01N 3/0842 20130101;
F01N 13/009 20140601; F01N 3/2892 20130101; Y02T 10/12 20130101;
B01F 3/04049 20130101; F01N 3/36 20130101 |
Class at
Publication: |
60/297 ;
60/299 |
International
Class: |
F01N 3/18 20060101
F01N003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2007 |
JP |
P.2007-332379 |
Dec 25, 2007 |
JP |
P.2007-332380 |
Claims
1. An emission control system, comprising: an exhaust pipe portion,
adapted to guide exhaust gas from an engine to outside; a catalyst,
accommodated in the exhaust pipe portion; an additive injection
valve, provided at the exhaust pipe portion located at upstream
side of the catalyst, and configured to inject additives to be
supplied to the catalyst toward a flow of the exhaust gas in the
exhaust pipe portion, wherein the exhaust pipe portion has a flow
path section located at upstream side of the catalyst, which
intersects an injection flow of the additives injected by the
additive injection valve, and the flow path section is made to have
substantially the same shape as an injection region of the
injection flow which confronts the exhaust gas.
2. The emission control system as set forth in claim 1, wherein the
flow path section is an exhaust gas induction portion that is
formed at the exhaust pipe portion located at upstream side of the
catalyst, which intersects the injection flow of the additives
injected by the additive injection valve, and that has a shape
being identical with an injection region of the injection flow as
viewed from a direction which intersects the flow of the exhaust
gas.
3. The emission control system as set forth in claim 2, wherein the
exhaust gas induction portion has a shape that expands towards a
leading end of the injection flow and that is shaped in such a
manner that an upstream side of the injection flow is thin and a
downstream side of the injection flow is thick.
4. The emission control system as set forth in claim 3, wherein the
exhaust pipe portion located at upstream side of the catalyst is
formed in such a manner as to intersect the injection flow of the
additives at an acute angle and to confront the catalyst, and the
exhaust gas induction portion is formed from an upstream part of
the exhaust pipe portion which intersects the injection flow of the
additives.
5. The emission control system as set forth in claim 3, wherein the
exhaust pipe portion located at upstream side of the catalyst is
formed in such a manner as to intersect the injection flow of the
additives in a substantially normal direction and to confront the
catalyst, and the exhaust gas induction portion is formed from an
upstream part of the exhaust pipe portion which intersects the
injection flow of the additives.
6. The emission control system as set forth in claim 5, wherein a
release portion where a contact with the injection flow of the
additives which is deflected as a result of collision with the
exhaust gas is avoided, is formed at a downstream part of the
exhaust pipe portion which intersects the injection flow of the
additives.
7. The emission control system as set forth in claim 2, wherein the
exhaust gas induction portion is formed in such a manner as to keep
an area of a flow path from an upstream side of the exhaust pipe
portion constant.
8. The emission control system as set forth in claim 2, wherein the
exhaust pipe portion is provided with; a bent portions connected to
an upstream side of the catalyst, and formed by bending the exhaust
pipe portion; and a projecting portion, one end of which is opened
to a wall surface of the bent portion, and which projects to an
opposite side of the catalyst in a direction of a central axis of
the catalyst, and the additive injection valve is provided at the
other end of the projecting portion.
9. The emission control system as set forth in claim 1, wherein an
additive mixing portion is formed at the exhaust pipe portion
located at upstream side of the catalyst, through which the
injection flow of the additives injected by the additive injection
valve passes, and has a shape being identical with a section of an
injection region of the injection flow.
10. The emission control system as set forth in claim 9, wherein
the additive mixing portion is formed in such a manner as to keep
an area of a flow path from an upstream side of the exhaust pipe
portion constant.
11. The emission control system as set forth in claim 10, wherein
an outlet of the additive mixing portion is expanded into a bell
mouth shape.
12. The emission control system as set forth in claim 10, wherein
the exhaust pipe portion is provided with: a bent portion,
connected to an upstream side of the catalyst, and formed by
bending the exhaust pipe portion; and a projecting portion, one end
of which is opened to a wall surface of the bent portion, and which
projects to an opposite side of the catalyst in a direction of a
central axis of the catalyst, and the additive injection valve is
provided at the other end of the projecting portion.
Description
BACKGROUND OF THE INVENTION
[0001] For purification of exhaust emissions from a car (a vehicle)
having a diesel engine, an emission control system is used in which
a adsorption type NOx catalyst, a selective reduction type NOx
catalyst and a diesel particulate filter are combined together to
prevent the emission of NOx (oxides of nitrogen) and PM
(particulate matter) which are contained in exhaust emissions from
a diesel engine to the atmosphere
[0002] An emission control system like this adopts a construction
in which a catalyst referred to as a pre-stage catalyst such as an
oxidation catalyst, a NOx trap catalyst or a selective reduction
type NOx catalyst is provided in an interior of an exhaust pipe
portion which expels exhaust gases discharged from the engine to
the outside thereof, and a fuel injection valve (such as one for
adding a reducing agent) which injects a fuel required for reaction
of the catalyst to an upstream side of the catalyst, for example,
the oxidation catalyst.
[0003] In the emission control system, for efficient reaction of
the pre-stage catalyst, it becomes important that the injected fuel
is sufficiently mixed with the exhaust gases before the fuel flows
into the pre-stage catalyst.
[0004] For this to happen, a sufficient fuel spray travel needs to
be secured in a segment from the fuel adding valve to the
catalyst.
[0005] However, as it is required that a location where a catalyst
is installed is secured in the vicinity of an exhaust side of an
engine in order to meet the recent tendency of enhancing the
exhaust emission purifying efficiency at the time of cold start, it
becomes difficult to ensure such a sufficient fuel spray travel. An
example of an engine adopting the aforesaid construction is
disclosed in JP-A-2005-127260.
[0006] Namely, in order to make full use of the catalyst
installation design described above, as is disclosed in
JP-A-2005-127260, a fuel injection valve has to be provided at a
part of an exhaust pipe which lies directly upstream of the
catalyst, that is, for example, at a bent portion of the exhaust
pipe. To make this happen, it becomes difficult to ensure a long
enough fuel spray travel for mixture of fuel with exhaust gases
between the fuel injection valve and the catalyst.
[0007] From the reasons regarding the installation of the fuel
injection valve and the catalyst, the situation in which the fuel
spray travel for mixture of fuel with exhaust gases becomes
difficult to be ensured is seen not only the emission control
system in which the bent portion is provided in the exhaust pipe
but also in an emission control system in which no such bent
portion is provided.
[0008] To cope with this, as is disclosed in JP-A-2004-44483, an
emission control system is proposed which has a construction in
which a fuel injection valve is disposed in a position lying far
apart from an exhaust pipe portion so that fuel is injected from
the position which lies far away from the flow of exhaust
gases.
[0009] However, even with this proposed emission control system,
from the limitations on the installation of the fuel injection
valve and the catalyst, which are similar to the aforesaid one,
there still remains the situation in which the fuel spray travel
for mixture of fuel with exhaust gases is difficult to be
ensured.
[0010] Due to this, in an emission control system, it remains
difficult to mix injected fuel with exhaust gases sufficiently.
This has caused a problem that uniformly atomized fuel is difficult
to be supplied to a catalyst and hence the catalyst cannot fulfill
its function.
SUMMARY
[0011] It is therefore an object of the invention to provide an
emission control system which enables a sufficient mixture of a
reducing agent with exhaust gases even though a fuel spray travel
necessary for the aforesaid mixture is not ensured between an
additive injection valve and a catalyst.
[0012] In order to achieve the object, according to the invention,
there is provided an emission control system, comprising;
[0013] an exhaust pipe portion, adapted to guide exhaust gas from
an engine to outside;
[0014] a catalyst accommodated in the exhaust pipe portion;
[0015] an additive injection valve, provided at the exhaust pipe
portion located at upstream side of the catalyst, and configured to
inject additives to be supplied to the catalyst toward a flow of
the exhaust gas in the exhaust pipe portion, wherein
[0016] the exhaust pipe portion has a flow path section located at
upstream side of the catalyst, which intersects an injection flow
of the additives injected by the additive injection valve, and
[0017] the flow path section is made to have substantially the same
shape as an injection region of the injection flow which confronts
the exhaust gas.
[0018] The flow path section may be an exhaust gas induction
portion that is formed at the exhaust pipe portion located at
upstream side of the catalyst, which intersects the injection flow
of the additives injected by the additive injection valve, and that
has a shape being identical with an injection region of the
injection flow as viewed from a direction which intersects the flow
of the exhaust gas.
[0019] The exhaust gas induction portion may have a shape that
expands towards a leading end of the injection flow and that is
shaped in such a manner that an upstream side of the injection flow
is thin and a downstream side of the injection flow is thick.
[0020] The exhaust pipe portion located at upstream side of the
catalyst may be formed in such a manner as to intersect the
injection flow of the additives at an acute angle and to confront
the catalyst. The exhaust gas induction portion may be formed from
an upstream part of the exhaust pipe portion which intersects the
injection flow of the additives.
[0021] The exhaust pipe portion located at upstream side of the
catalyst may be formed in such a manner as to intersect the
injection flow of the additives in a substantially normal direction
and to confront the catalyst. The exhaust gas induction portion may
be formed from an upstream part of the exhaust pipe portion which
intersects the injection flow of the additives.
[0022] A release portion where a contact with the injection flow of
the additives which is deflected as a result of collision with the
exhaust gas is avoided, may be formed at a downstream part of the
exhaust pipe portion which intersects the injection flow of the
additives.
[0023] The exhaust gas induction portion may be formed in such a
manner as to keep an area of a flow path from an upstream side of
the exhaust pipe portion constant.
[0024] The exhaust pipe portion may be provided with: a bent
portion, connected to an upstream side of the catalyst, and formed
by bending the exhaust pipe portion; and a projecting portion, one
end of which is opened to a wall surface of the bent portion, and
which projects to an opposite side of the catalyst in a direction
of a central axis of the catalyst. The additive injection valve may
be provided at the other end of the projecting portion.
[0025] An additive mixing portion may be formed at the exhaust pipe
portion located at upstream side of the catalyst, through which the
injection flow of the additives injected by the additive injection
valve passes, and have a shape being identical with a section of an
injection region of the injection flow.
[0026] The additive mixing portion may be formed in such a manner
as to keep an area of a flow path from an upstream side of the
exhaust pipe portion constant.
[0027] An outlet of the additive mixing portion may be expanded
into a bell mouth shape.
[0028] The exhaust pipe portion may be provided with: a bent
portion, connected to an upstream side of the catalyst, and formed
by bending the exhaust pipe portion; and a projecting portion, one
end of which is opened to a wall surface of the bent portion, and
which projects to an opposite side of the catalyst in a direction
of a central axis of the catalyst. The additive injection valve may
be provided at the other end of the projecting portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a partially sectional side view showing the
construction of an emission control system according to a first
embodiment of the invention.
[0030] FIG. 2 is a sectional view of an exhaust gas induction
portion taken along the line A-A in FIG. 1.
[0031] FIG. 3 is a schematic perspective view showing the exhaust
gas induction portion.
[0032] FIG. 4 is a sectional side view showing the construction of
an emission control system according to a second embodiment of the
invention.
[0033] FIG. 5 is a sectional view taken along the line B-B in FIG.
4.
[0034] FIG. 6 is a sectional side view showing in an enlarged
fashion of the vicinity of an inlet of a catalyst of an emission
control system according to a third embodiment of the
invention.
[0035] FIG. 7 is a sectional view taken along the line C-C in FIG.
6.
[0036] FIG. 8 is a side view showing an emission control system
according to a fourth embodiment of the invention.
[0037] FIG. 9 is a sectional view taken along the line D-D in FIG.
8.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] Hereinafter, the invention will be described based on a
first embodiment shown in FIGS. 1 to 3.
[0039] FIG. 1 shows an exhaust system of an internal combustion
engine, for example, a diesel engine. In FIG. 1, reference numeral
1 denotes an engine main body of the diesel engine, 1a an exhaust
manifold (only part of which is shown) of the engine main body 1 of
the diesel engine, and 2 a supercharger or, in this embodiment, a
turbocharger connected to an outlet of the exhaust manifold 1a.
[0040] An emission control system 3 is provided at an exhaust
outlet of the turbocharger 2. A system in which a NOx removing
system 3a for adsorbing NOx (oxides of nitrogen) contained in
exhaust gases and periodically reduction removing the adsorbed NOx
and a PM (particulate matter) capturing system 3b for capturing PM
are combined together is used for the emission control system
3.
[0041] For example, used for the NOx removing system 3a is a
configuration in which a catalytic converter 6, a catalytic
converter 9 and a fuel addition valve (an additive injection valve)
23 are combined together. The catalytic converter 6 is coupled to
the turbocharger 2 in such a manner as to extend downwards from the
exhaust outlet of the turbocharger 2 and incorporates therein a
pre-stage oxidation catalyst 5 (corresponding to the catalyst of
the subject patent application). The catalytic converter 9 is
coupled horizontally to the rear of the catalytic converter 6 and
incorporates therein a NOx trap catalyst 8. The fuel addition valve
23 supplies a catalyst reaction promoting fuel which constitutes
additives to the oxidation catalyst 5, which will be described
later. In addition, a configuration is adopted for the capturing
system 3b in which a catalytic converter 12 which incorporates
therein a particulate filter 11 is coupled to the catalytic
converter 9. An exhaust pipe portion 15 for inducing exhaust gases
discharged from the diesel engine (the engine main body 1) to the
outside thereof is made up of the catalytic converters 6, 9, 12 and
connecting portions 13 which connect the catalytic converters.
[0042] In these catalytic converters, a cylindrical housing 17 of
the catalytic converter 6 which accommodates therein the oxidation
catalyst 5 is bent at an upper portion in such a way as is shown in
FIG. 1, so that an inlet portion 17a is disposed horizontally for
connection to the turbocharger 2 which is situated thereabove. In
additions an outlet portion 17b which communicates with the
catalytic converter 9 lying therebelow is disposed in such a manner
as to be oriented downwards. A bent portion 15a of the exhaust pipe
portion 15 is formed in such a manner as to be bent in a position
lying directly after an exhaust side of the diesel engine by the
housing 17. A catalyst installation space is secured in a portion
lying directly below the bent portion 15a. The oxidation catalyst 5
is installed in a position lying in the vicinity of the exhaust
side of the diesel engine.
[0043] The fuel addition valve 23 is made to inject a fuel required
for catalyst reaction to the oxidation catalyst 5 and is provided
in a position lying directly above the oxidation catalyst 5, for
example, on the bent portion 15a or on an outer circumferential
wall portion lying downstream of the bent portion 15a to fulfill
the aforesaid function. The fuel addition valve 23 has a fuel
injecting portion for injecting the fuel at a distal end portion
thereof. The fuel addition valve 23 is installed at an end of a
cylindrical portion 24 which branches off at an outer
circumferential portion of the exhaust pipe portion 15 which lies
downstream of the bent portion 15a in such a manner as to extend
outwards by the use of a mounting flange 24a and a base seat 25.
The cylindrical portion 24 is a projecting portion projecting to an
opposite side of the oxidation catalyst 5 in a direction of a
central axis of the oxidation catalyst 5. One end of the projecting
portion is opened to the wall portion of the bent portion 15a and
the fuel addition valve 23 is provided at the other end of the
projecting portion. By this configuration, the fuel injecting
portion at the distal end portion of the fuel addition valve 23 is
made to face a fuel injection path 24b which is formed by an
interior space of the cylindrical portion 24. The fuel injection
path 24b extends in such a manner as to be inclined to an opposite
side to a direction in which the bent portion 15a is bent, and an
outlet end thereof is oriented towards a circumferential edge of an
inlet end face of the oxidation catalyst 5 rather than towards a
center thereof (that is, towards the inlet portion 17a). By this
configuration, the fuel promoting the reaction of the oxidation
catalyst 5 is made to be injected from the position lying far apart
from a flow of exhaust gases to the oxidation catalyst 5 from a
direction which intersects the flow of exhaust gases which passes
through the bent portion 15a. Specifically, the fuel is made to be
injected downwards, that is, towards a mixing chamber 19 defined in
front of the inlet end face of the oxidation catalyst 5 from a
direction which intersects a flowing direction a of the flow of
exhaust gases at an acute angle .theta.1 as is shown in FIG. 1. By
this configuration, a downstream portion of a flow of injected fuel
.alpha. where a spray penetration becomes weak is made to collide
with exhaust gases in a position directly upstream of the oxidation
catalyst 5. In addition, reference numeral 25a denotes a coolant
channel formed in an interior of the base seat 25.
[0044] On the other hand, on an exhaust pipe part which lies
upstream of the oxidation catalyst 5, an exhaust gas induction
portion 28 is provided in a position where the exhaust pipe part
intersects the flow of injected fuel .alpha. injected from the fuel
addition valve 23, that is, at an exhaust pipe part S which
constitutes an area extending, for example, from the bent portion
15a to the mixing chamber 19. As is shown in a sectional view shown
in FIG. 2 and a perspective view shown in FIG. 3, the exhaust gas
induction portion 28 is formed in such a manner that a sectional
shape of a flow path of the exhaust pipe part S which intersects
the flow of injected fuel .alpha. equates to a side view of an
injection region of the flow of injected fuel .alpha. as viewed
from a transverse direction in which the flow of injected fuel
.alpha. intersects exhaust gases. Specifically, the exhaust gas
induction portion 28 is formed in such a manner that the sectional
shape of the flow path of the exhaust pipe part S is formed into a
fan-like shape which is substantially the same shape as a shape of
a downstream side of the flow of injected fuel .alpha. as projected
from the transverse direction. By being formed in the way described
above to thereby have the same shape as that of the flow of
injected fuel .alpha. which expands towards the leading end
thereof, the exhaust gas induction portion 28 is made to have a
flow path whose sectional shape is such that a portion
corresponding to an upstream side of the flow of injected fuel
.alpha. becomes thin, whereas an opposite portion corresponding to
the downstream portion of the flow of injected fuel .alpha. becomes
thick. In FIG. 2, reference numeral 28a denotes one of the portions
where the flow path section becomes thin, and 28b denotes the other
portion where the flow path section becomes thick. A flow of
exhaust gases is made to be distributed uniformly over the flow of
injected additives in the exhaust gas induction portion by the
exhaust gas induction portion 28 being configured as has been
described above, whereby an opportunity is given where the flow of
injected additives is allowed to contact exhaust gases
sufficiently.
[0045] A flow path area of the portion of the exhaust pipe portion
15 which extends from the inlet portion 17a which constitutes an
upstream end of the exhaust pipe portion 15 to the exhaust gas
induction portion 28 is held constant to a predetermined flow path
area. Of course, the sectional shape of the flow path is
constructed in such a manner as to change gradually so as to follow
the shape of the flow of injected additives .alpha. in the exhaust
gas induction portion 28, whereby the generation of an unnecessary
passage resistance is prevented.
[0046] In addition, a portion of the exhaust pipe portion 15 which
lies downstream of the exhaust gas induction portion 28 is formed
in such a manner as to be expanded in a radial direction. The fuel
and exhaust gases which have collided with each other completely
are supplied to the inlet end face of the oxidation catalyst 5
while being expanded in the radial direction by an expanded portion
29 which results from the radial expansion of the portion of the
exhaust pipe portion 15. It is effective to form the expanded
portion 29 into a flared shape (a bell mouth shape) as well as a
conical shape in supplying the mixture of fuel and exhaust gases to
the oxidation catalyst 5 under uniform distribution.
[0047] In addition, the fuel injected from the fuel addition valve
23 is used to generate a reducing agent as a result of reaction
with the oxidation catalyst 5, so as to reduce to remove NOx and
SOx which are adsorbed on to the NOx trap catalyst 8 by the use of
the reducing agent so generated or to obtain heat as a result of
reaction with the oxidation catalyst 5, so as to burn to remove PM
captured by the particulate filter 11. Because of this, the fuel
addition valve 23 is controlled by a control unit for controlling
the diesel engine, for example, an ECU (not shown) to inject the
fuel when a catalytic reaction is required during operation of the
diesel engine for reduction removal of NOx and SOx and burning
removal of PM.
[0048] Next, the function of the emission control system 3
configured as has been described above will be described.
[0049] Exhaust gases discharged from the diesel engine during
operation thereof are, as is shown in FIG. 1, expelled to the
outside air through the exhaust manifold 1a, the turbocharger 2,
the bent portion 15a, the exhaust gas induction portion 28, the
oxidation catalyst 5, the NOx trap catalyst 8 and the particulate
filter 11.
[0050] NOx and SOx which are contained in exhaust gases are
adsorbed on to the NOx trap catalyst 8, and PM is similarly
captured by the particulate filter 11.
[0051] Assuming that the fuel addition valve 23 is activated as
time has arrived to remove the adsorbed NOx and SOx and captured
PM.
[0052] Then, the fuel for removing NOx, SOx and PM is injected from
the fuel injecting portion of the fuel addition valve 23 from the
acute angle direction through the fuel injection path 24b to the
flow of exhaust gases which is flowing in the exhaust pipe part S.
By this action, the flow of injected fuel .alpha. and the flow of
exhaust gases are made to collide with each other.
[0053] As this occurs, since the exhaust gas induction portion 28,
which has the flow path whose sectional shape is substantially the
same as that of the injection region of the flow of injected fuel
.alpha. as viewed from the transverse direction, is formed in the
exhaust pipe part S which intersects the flow of injected fuel
.alpha. at the portion directly upstream of the downstream portion
of the flow of injected fuel .alpha. where the spray penetration
becomes weak, the exhaust gases which have passed through the
exhaust gas induction portion 28 pass over the flow of injected
fuel .alpha. while being distributed uniformly thereover.
[0054] By this action, there is provided an opportunity where the
exhaust gases in the flow of exhaust gases and the fuel in the flow
of injected fuel .alpha. are allowed to contact each other
sufficiently, whereby the exhaust gases and the fuel contact each
other uniformly for sufficient mixture of the exhaust gases with
the furl.
[0055] As this occurs, since the flow velocities of the fuel and
the exhaust gases are such that fuel in the upstream part of the
flow of injected fuel .alpha. which is near from the fuel addition
valve 23 and in which the spray penetration is strong collides with
exhaust gases of a high flow velocity whose flow velocity has been
increased at the portion 28a where the section of the flow path is
narrow, while fuel in the downstream part of the flow of injected
fuel .alpha. which is far away from the fuel addition valve 23 and
in which the spray penetration is weak collides with exhaust gases
of a low flow velocity whose flow velocity is reduced at the
portion 28b where the section of the flow path is wide, a further
uniform mixture of additives and exhaust gases can be obtained. The
fuel and exhaust gases which are mixed uniformly then flow
downwards towards the oxidation catalyst 5 while expanding in the
radial direction due to the expanded portion 29.
[0056] Here, since the flow of exhaust gases and the flow of
injected fuel .alpha. intersect each other at the acute angle to
thereby suppress the deflection of the flow of injected fuel
.alpha. that would otherwise be produced by the flow of exhaust
gases, the fuel and exhaust gases which have been mixed with each
other in the way described above are supplied to a predetermined
position of the oxidation catalyst 5, for example, to a
substantially central portion of the inlet end face thereof.
[0057] Consequently, even though the necessary distance or fuel
spray travel is ensured between the fuel addition valve 23 and the
oxidation catalyst 5, the fuel which is uniformly mixed with the
exhaust gases can be supplied to the catalyst due to the formation
of the exhaust gas induction portion 28.
[0058] Therefore, the function of the oxidation catalyst 5 can be
made to be exhibited sufficiently by the use of the exhaust gas
induction portion 28. Of course, when the expanded portion 29 is
used in parallel, the fuel can be supplied to the oxidation
catalyst 5 while being distributed more uniformly. On top of this,
since the exhaust gas induction portion 28 is formed in such a
manner that the flow path area is held constant to the
predetermined flow path area from the upstream of the exhaust pipe
portion 15, there is caused no increase in flow path resistance in
the exhaust pipe portion 15, whereby a reduction in engine output
can be suppressed.
[0059] In particular, in the event that the exhaust gas induction
portion 28 is adopted in the fuel injection construction in which
the flow of exhaust gases is made to intersect the flow of injected
fuel .alpha. at the acute angle, the exhaust gases and the fuel can
be mixed together sufficiently while enjoying the benefit of the
method in which the fuel is injected to the predetermined position
while suppressing the deflection of the flow of injected fuel
.alpha..
[0060] FIGS. 4 and 5 show a second embodiment of the invention. In
FIGS. 4 and 5, like reference numerals are imparted to like
portions to those of the first embodiment, and the description
thereof will be omitted.
[0061] In the second embodiment, the invention is applied to an
emission control system in which a flow of exhaust gases does not
intersect a flow of injected fuel .alpha. at an acute angle as done
in the first embodiment but intersects the flow of injected fuel
.alpha. at substantially right angles.
[0062] Specifically, in the emission control system of this
embodiment, as with the first embodiment, an injecting direction of
a fuel addition valve 23 is determined to lie in a position which
is offset from an oxidation catalyst 5. A path is formed in an
exhaust pipe part lying upstream of the oxidation catalyst 5 in
such a manner as to intersect a flow of injected fuel .alpha.
injected from the fuel addition valve 23 in a substantially right
angle direction so as to be directed towards the oxidation catalyst
5. By this configuration, on the contrary to the first embodiment,
a construction is realized in which the flow of injected fuel
.alpha. is pushed by the flow of exhaust gases, so as to deflect
the flow of injected fuel .alpha. from the initial offset position
to a desired position, whereby the fuel is injected to a
predetermined position. In addition, as with the first embodiment,
an exhaust gas induction portion 28 whose flow path section at the
exhaust pipe part, which is something like one shown in a sectional
view of FIG. 5, is made to have substantially the same shape as a
side view of an injection region of the flow of injected fuel
.alpha. is provided directly upstream of an exhaust pipe part S of
the exhaust pipe part lying upstream of the oxidation catalyst 5
which intersects the flow of injected fuel .alpha. injected from
the fuel addition valve 23.
[0063] By this configuration, even with the emission control system
in which the flow of injected fuel .alpha. is deflected by the flow
of exhaust gases, which is opposite to or differs from the
configuration of the first embodiment, so that the fuel is injected
to the predetermined position, by enjoying the benefit of the
method adopted therein, the exhaust gases can be mixed with the
fuel sufficiently by the use of the exhaust gas induction portion
28.
[0064] In particular, in the second embodiment, for example, a
curved recessed portion 30 is formed as a release portion on a wall
surface of a downstream side exhaust pipe part T which intersects
the flow of injected fuel .alpha. in such a manner that nothing in
the exhaust pipe portion 15 is affected by the flow of injected
fuel .alpha. when it is deflected. By this recessed portion 30, the
contact of the flow of injected fuel .alpha. which is deflected
with the wall portion of the exhaust pipe part T can be avoided,
whereby a good mixture of the exhaust gases with the fuel can be
promised. Moreover, since a wall portion of the recessed portion 30
causes exhaust gases which have come into contact with the recessed
portion 30 to bounce back towards the flow of injected fuel .alpha.
as is indicated by arrows b so as to cause the exhaust gases to
collide with the fuel in the flow of injected fuel .alpha., it can
be expected that the mixture of the fuel with the exhaust gases is
promoted further.
[0065] In addition, FIGS. 6 and 7 show a third embodiment of the
invention. In FIGS. 6 and 7, like reference numerals are imparted
to like portions to those of the first embodiment, and the
description thereof will be omitted.
[0066] As is shown in an enlarged fashion in FIG. 6, a fuel mixing
portion (an additive mixing portion) 38 is provided in a position
of an exhaust pipe part lying upstream of an oxidation catalyst 5
where a flow of injected fuel .alpha. injected from a fuel addition
valve 23 passes, specifically, an exhaust pipe part U on an outlet
side of a bent portion 15a which constitutes a portion where
injected fuel and exhaust gases are made to collide with each
other. This fuel mixing portion 38 is configured in such a manner
that only a sectional shape of a flow path at the exhaust pipe part
U is, as is shown in FIG. 7, has substantially the same shape as a
sectional shape of an injection region of the flow of injected fuel
.alpha. which passes through the exhaust pipe part U, that is, that
the sectional shape of the flow path has the same shape of the
sectional shape of the injection region. Fuel injected is made to
be given by the fuel mixing portion 38 an opportunity where the
fuel is uniformly distributed in an interior of the exhaust pipe
part so as to be brought into sufficient contact with exhaust gases
directed to the oxidation catalyst 5. In addition, a flow path area
of a portion, including the fuel mixing portion 38, of an exhaust
pipe portion 15 extending up to an inlet portion 17a which
constitutes an upper end of the exhaust pipe portion 15 is held
constant to a predetermined flow path area from upstream, so that
an unnecessary passage resistance is not generated.
[0067] As is shown in FIG. 7, a wall surface of an end of a housing
17 which continuously follows an outlet of the fuel mixing portion
38 is formed into a bell mouth shape which expands in a radial
direction. Fuel injected from the fuel mixing portion 38 is made to
be supplied to an inlet end face of the oxidation catalyst 5 while
being allowed to expand in the radial direction by a bell mouth
portion 39 formed at the outlet of the fuel mixing portion 38.
[0068] An exhaust pipe part lying in a position where it collides
with a flow of injected fuel .alpha. and exhaust gases is formed
into the fuel mixing portion 38 which has the flow path section
which is substantially identical in shape to the section of the
injection region of the flow of injected fuel .alpha. joins the
exhaust gases thereat. Because of this, when the flow of injected
fuel .alpha. passes through the fuel mixing portion 38, the flow of
injected fuel .alpha. passes therethrough while being distributed
uniformly thereover.
[0069] By this configuration, since an opportunity is given where
exhaust gases in the flow of exhaust gases and fuel in the flow of
injected fuel .alpha. are allowed to contact with each other
sufficiently, the exhaust gases and the fuel are allowed to contact
uniformly, and a sufficient mixture of the exhaust gases with the
fuel occurs.
[0070] The fuel and exhaust gases which have emerged from the fuel
mixing portion 38 are atomized while being allowed to expand in the
radial direction by the bell mouth portion 39, so as to be supplied
to the inlet end face of the oxidation catalyst 5 while the fuel is
being distributed uniformly.
[0071] Consequently, by the formation of the fuel mixing portion
38, even though a required distance or fuel spray travel for
mixture with exhaust gases is not ensured between the fuel addition
valve 23 and the oxidation catalyst 5, uniformly atomized fuel can
be supplied to the catalyst. Needless to say, of course, in the
event that this configuration is adopted in parallel with the
construction in which fuel is injected from a position which lies
far away from the flow of exhaust gases, a good mixture of exhaust
gases with fuel can be achieved.
[0072] Consequently, the function of the oxidation catalyst 5 can
be exhibited sufficiently. In particular, since exhaust gases from
a turbocharger 2 are introduced into the exhaust pipe portion 15
while being swirled, a better mixture of exhaust gases with fuel
can be expected due to the swirling flow of exhaust gases produced
then.
[0073] Moreover, since the flow path area of the exhaust pipe part
including the fuel mixing portion 38 is configured in such as to be
held constant to the predetermined flow path area from the upstream
portion of the exhaust pipe portion 15, the flow path resistance in
the exhaust pipe portion 15 is increased in no case, whereby a
reduction in engine output can be suppressed.
[0074] On top of this, since the exhaust gases and fuel which have
flowed out from the fuel mixing portion 38 are directed uniformly
to the oxidation catalyst 5 (the catalyst) while being allowed to
expand in the radial direction of the housing 17 due to the
formation of the bell mouth portion 39 at the outlet of the fuel
mixing portion 38, the fuel can be supplied to the oxidation
catalyst 5 while being distributed uniformly.
[0075] FIGS. 8 and 9 show a fourth embodiment of the invention. In
FIGS. 8 and 9, like reference numerals are imparted to like
portions to those of the first embodiment, and the description
thereof will be omitted here.
[0076] In this embodiment, the invention is applied to an emission
control system 3 in which a fuel addition valve 23 and an oxidation
5 are installed in an exhaust pipe portion 15 without forming a
bent portion 15a.
[0077] Specifically, in the emission control system 3 of this
embodiment, a straight-line exhaust pipe portion 15 is used, and an
oxidation catalyst 5 is provided in the exhaust pipe portion 15. In
addition, a fuel addition valve 23 is provided directly upstream of
the oxidation catalyst 5. Additionally, a sectional shape of a flow
path of a straight-line exhaust pipe part U of the exhaust pipe
portion 15 where a flow of injected fuel .alpha. passes is made to
equate to a sectional shape of an injection region of the flow of
injected fuel .alpha. which passes through the exhaust pipe portion
15t whereby a fuel mixing portion 31 is provided. FIG. 9 shows the
sections of the fuel mixing portion 38 and the flow of injected
fuel .alpha..
[0078] Even with the emission control system 3 configured as has
been described above, in the event that the fuel mixing portion 38
is formed, as with the first embodiment, even though a required
distance of fuel spray travel for mixture is not ensured between
the fuel addition valve 23 and the oxidation catalyst 5, uniformly
distributed atomized fuel can be supplied to the oxidation catalyst
5 (the catalyst).
[0079] Note that the invention is not limited to the embodiments
that have been described heretofore, and hence, the invention may
be modified variously without departing from the spirit and scope
thereof. For example, in the embodiments, while the exhaust gases
are described as being made to intersect the flow of injected fuel
or additives at the acute angle or at right angles, the invention
is not limited thereto. In addition, in the embodiments that have
been described heretofore, while the invention is described as
being applied to the emission control system in which the oxidation
catalyst is used as a catalyst lying directly downstream of the
bent portion and the NOx trap catalyst and the particulate filter
are provided downstream of the oxidation catalyst, the invention is
not limited thereto. Thus, the invention may be applied to emission
control systems which adopt other exhaust gas purifying approaches.
For example, the invention may be applied to an emission control
system in which a NOx trap catalyst is used as a catalyst to be
installed directly downstream of a bent portion, a particulate
filter is provided downstream of the NOx trap catalyst, and an
addition valve is provided upstream of the NOx trap catalyst, an
emission control system in which a NOx trap catalyst is used as a
catalyst to be installed directly downstream of a bent portion, a
NOx trap catalyst, an oxidation catalyst and a particulate filter
are provided downstream of the NOx trap catalyst, and an addition
valve is provided upstream of the NOx trap catalyst, or an emission
control system in which an addition valve is provided upstream of a
selective reduction type catalyst and a particulate filter.
[0080] Furthermore, in the embodiments, while the fuel is described
as being used as the additives, any substances may be adopted,
provided that they can be supplied to catalysts. For example, as a
reducing agent, substances may be used which include gas oil,
gasoline, ethanol, dimethyl ether, natural gas, propane gas, urea,
ammonia, hydrogen, carbon monoxide and the like. In addition, any
substances other than reducing agents may be used, and these
substances include, for example, air, nitrogen or carbon dioxide
used to cool the catalyst, or air or ceria which promotes the
burning removal of soot captured on to the particulate filter.
[0081] In addition, in the embodiments that have been described
above, while the injecting configuration of the fuel addition valve
23 is described as being formed into a conical shape, a fuel
addition valve having an injecting configuration which expands in a
flat fan-shaped fashion or a fuel addition valve in which additives
is injected from a plurality of injection holes may be adopted. In
the case of a plurality of injection holes being provided, an
outline of a plurality of flows of injected fuel constitutes an
injection region.
[0082] According to an aspect of the invention, since the flow of
exhaust gases is distributed uniformly over the flow of injected
additives by the exhaust gas induction portion, the opportunity can
be given where exhaust gases in the flow of exhaust gases and
additives in the flow of injected additives are allowed to contact
with each other sufficiently.
[0083] Consequently, the exhaust gases can be mixed with the
additives sufficiently, and even though a required distance or fuel
or additive spray travel for mixture is not ensured between the
additive injection valve and the catalyst, the additives which is
mixed with the exhaust gases uniformly can be supplied to the
catalyst. As a result, the function of the catalyst can be
exhibited sufficiently.
[0084] According to an aspect of the invention, the flow velocities
of the additives and the exhaust gases after they have collided
with each other are such that additives in the upstream part of the
flow of injected additives in which the spray penetration is strong
collides with exhaust gases of a high flow velocity whose flow
velocity has been increased at the portion where the section of the
flow path is narrow, while additives in the downstream part of the
flow of injected additives in which the spray penetration is weak
collides with exhaust gases of a low flow velocity whose flow
velocity is reduced at the portion where the section of the flow
path is wide, whereby a uniform mixture of additives and exhaust
gases can be promoted, and the additives and exhaust gases which
are mixed uniformly can be supplied to the oxidation catalyst
5.
[0085] According to an aspect of the invention, furthermore, by
enjoying the benefit of the method in which the additives are
injected to the predetermined position by suppressing the
deflection of the flow of injected additives, the exhaust gases and
the additives can be mixed with each other sufficiently.
[0086] According to an aspect of the invention, furthermore, by
enjoying the benefit of the method in which the additives are
injected to the predetermined position by deflecting the flow of
injected additives by the flow of exhaust gases, which is opposite
to or different from the method described above, the exhaust gases
and the additives can be mixed with each other sufficiently.
[0087] According to an aspect of the invention, even though the
flow of injected additives is deflected by the flow of exhaust
gases, the additives in the flow of injected additives which is so
deflected are prevented from being brought into contact with the
wall surface of the exhaust pipe part by the release portion, a
good mixture of the additives with the exhaust gases can be
promised.
[0088] According to an aspect of the invention, since the flow path
area of the exhaust pipe portion is held constant from the upstream
portion to the exhaust gas induction portion, the flow path
resistance is increased in no case, whereby a reduction in engine
output occurs in no case.
[0089] According to an aspect of the invention, the opportunity can
be given by the additive mixing portion where the exhaust gases in
the flow of exhaust gases and the additives in the flow of injected
additives are allowed to contact with each other sufficiently
upstream of the catalyst, whereby the exhaust gases and the
additives can be mixed together to a sufficient level.
[0090] Consequently, even though a required distance or additive
spray travel for mixture is not ensured between the additive
injection valve and the catalyst, the uniformly distributed
atomized additives can be supplied to the catalyst, whereby the
function of the catalyst can be exhibited sufficiently.
[0091] According to an aspect of the invention, since the flow path
area of the exhaust pipe portion is held constant from the upstream
portion to the additive mixing portion, the flow path resistance is
increased in no case, whereby a reduction in engine output occurs
in no case.
[0092] According to an aspect of the invention, furthermore, in
addition to the advantages that have been raised above, since the
exhaust gases and the additives which have flowed out from the
additive mixing portion are directed uniformly towards the catalyst
while being allowed to expand in the radial direction by the bell
mouth-shaped outlet of the additive mixing portion, the additives
can be supplied to the catalyst while being distributed
uniformly.
* * * * *