U.S. patent application number 11/957980 was filed with the patent office on 2008-07-03 for exhaust emission control device with additive injector.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Masatoshi MARUYAMA, Keiji Ohshima.
Application Number | 20080155973 11/957980 |
Document ID | / |
Family ID | 39431990 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080155973 |
Kind Code |
A1 |
MARUYAMA; Masatoshi ; et
al. |
July 3, 2008 |
EXHAUST EMISSION CONTROL DEVICE WITH ADDITIVE INJECTOR
Abstract
An exhaust emission control apparatus is provided which is
equipped with an additive injector to inject additive such as a
urea aqueous solution into an exhaust pipe through which exhaust
emissions flow. The exhaust pipe includes a straight section and a
bent section. A catalyst such as a SCR (Selective Catalytic
Reduction) catalyst is disposed downstream of the straight section.
A hollow protrusion is formed on an outer peripheral wall of the
bent section substantially in parallel to a longitudinal center
line of the straight section. The protrusion has an opening formed
in one of opposed ends thereof which communicates with inside the
bent section. The additive injector is designed to produce a
cone-shaped spray of additive and installed on the other end of the
protrusion to inject the cone-shaped spray of additive into the
exhaust pipe without interfering with at least a downstream edge of
the opening.
Inventors: |
MARUYAMA; Masatoshi;
(Kariya-shi, JP) ; Ohshima; Keiji; (Gamagoori-shi,
JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
39431990 |
Appl. No.: |
11/957980 |
Filed: |
December 17, 2007 |
Current U.S.
Class: |
60/299 ;
60/303 |
Current CPC
Class: |
F01N 3/2066 20130101;
Y02A 50/2325 20180101; Y02T 10/12 20130101; F01N 2610/02 20130101;
Y02A 50/20 20180101; Y02T 10/24 20130101 |
Class at
Publication: |
60/299 ;
60/303 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2006 |
JP |
2006-342319 |
Claims
1. An exhaust emission control apparatus comprising: an exhaust
pipe through which exhaust emission flow, said exhaust pipe
including a straight section and a bent section extending from the
straight section in an upstream direction of a flow of the exhaust
emissions; a catalyst disposed downstream of the straight section
of said exhaust pipe in connection therewith; a hollow protrusion
having a length extending outside the said exhaust pipe from a
peripheral wall of the bent section substantially in parallel to a
longitudinal center line of the straight section, said protrusion
having a first end and a second end opposed to the first end, said
protrusion having an opening formed in the first end which
communicates with inside the bent section of said exhaust pipe; and
an additive injector designed to produce a cone-shaped spray of
additive, said additive injector being installed in the second end
of said protrusion and oriented to inject the cone-shaped spray of
additive into said exhaust pipe through the opening of said
protrusion without interfering with at least a downstream edge of
the opening, the additive being carried by the flow of the exhaust
emissions downstream to said catalyst and used in a given exhaust
emission purification reaction, as induced by said catalyst, to
purify the exhaust emissions.
2. An exhaust emission control apparatus as set forth in claim 1,
wherein said additive injector is so oriented by said protrusion as
to avoid interference of the cone-shaped spray of additive with an
entire edge of the opening of said protrusion.
3. An exhaust emission control apparatus as set forth in claim 1,
wherein said protrusion has a cylindrical inner wall.
4. An exhaust emission control apparatus as set forth in claim 1,
wherein said additive injector has a head in which a spray hole is
formed, and wherein a distance between the downstream edge of the
opening of said protrusion and the head of said additive injector
is so selected as a function of an angle of spread of the additive,
as sprayed from said additive injector, as to avoid interference of
the cone-shaped spray of the additive with the downstream edge of
the opening of said protrusion.
5. An exhaust emission control apparatus as set forth in claim 1,
wherein said additive injector is oriented in alignment of an axis
thereof with that of the straight section of said exhaust pipe.
6. An exhaust emission control apparatus as set forth in claim 1,
wherein said additive injector is oriented in alignment of an axis
with that of said catalyst.
7. An exhaust emission control apparatus as set forth in claim 4,
wherein said additive injector is designed to change the angle of
spread of the additive, and wherein said additive injector is
oriented to avoid interference of the cone-shaped spray of additive
with at least the downstream edge of the opening when the angle of
spread of the additive is maximized.
8. An exhaust emission control apparatus as set forth in claim 1,
wherein said exhaust pipe also includes a second bent section
through which the exhaust gas flows, said second bent section
communicating with the bent section and the straight section at a
branch joint, and wherein the opening of said protrusion leading
inside said exhaust pipe through a wall of the branch joint, said
protrusion extending outside said exhaust pipe substantially in
parallel to the longitudinal center line of the straight
section.
9. An exhaust emission control apparatus as set forth in claim 1,
wherein the bent section is curved.
10. An exhaust emission control apparatus as set forth in claim 1,
wherein the bent section is flexed to a right angle.
Description
CROSS REFERENCE TO RELATED DOCUMENT
[0001] The present application claims the benefit of Japanese
Patent Application No. 2006-342319 filed on Dec. 20, 2006, the
disclosure of which is totally incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field of the Invention
[0003] The present invention relates generally to an exhaust
emission control device equipped with an additive injector which
may be used with an SCR (Selective Catalytic Reduction) system
working to induce an exhaust gas purification reaction using
additive such as a urea aqueous solution.
[0004] 2. Background Art
[0005] Urea SCR systems designed as exhaust emission control
devices for use in electric power plants, factories, or automobiles
especially equipped with diesel engines are now being developed and
partially put in practical use.
[0006] FIG. 5 illustrates a typical one of the urea SCR
systems.
[0007] The urea SCR system includes generally an SCR catalyst 51,
an exhaust pipe 52 extending between an exhaust emission source
(i.e., an automotive diesel engine) and the catalyst 51, and a urea
solution injection valve 53. The catalyst 51 works to induce NOx
reduction to purify exhaust gas flowing thereinto through the
exhaust pipe 52. The urea solution injection valve 53 is installed
in the exhaust pipe 52 to inject or spray an aqueous urea (i.e., a
urea aqueous solution) to a flow of the exhaust gas within the
exhaust pipe 52 as a reducing agent. Specifically, the urea
solution injection valve 53 is, as clearly illustrated in FIG. 5,
inclined to the length of the exhaust pipe 52 at a given angle to
have a spray hole 53a facing the catalyst 51 so as to orient the
spray of the aqueous urea toward the catalyst 51.
[0008] In operation, the urea solution injection valve 53 sprays
the aqueous solution into the exhaust pipe 52. The aqueous solution
is then carried by the flow of exhaust gas to the catalyst 51
located downstream of the urea solution injection valve 53, so that
the exhaust gas is purified through NOx reduction taken place on
the catalyst 51. In the reduction of NOx emissions, the urea
aqueous solution is hydrolyzed by the thermal energy of the exhaust
gas to produce ammonia (NH.sub.3) which is, in turn, added to the
NOx emissions, as selectively adsorbed by the catalyst 51, so that
the NOx emissions react with the ammonia on the surface of the
catalyst 51 and are converted into harmless products.
[0009] The exhaust pipe 52 is sometimes shaped to have a bend
depending upon the layout of component parts of the vehicle. There
are known urea solution injection valves disposed in such a bend of
the exhaust pipe. For instance, Japanese Patent First Publication
Nos. 2001-3737 and 2003-293739 and Translated PCT Publication No.
2001-516635 teach such a type of urea solution injection valve.
[0010] It is preferable that urea SCR systems having the urea
solution injection valve installed in the bend of the exhaust pipe
are designed to orient a stream of urea aqueous solution in the
same direction as the flow of exhaust gas in order to mix the urea
aqueous solution with the exhaust gas passing through the bend
homogeneously and supply it to the catalyst. However, the urea
solution injection valves, as disclosed in the above second and
third publications, are so disposed as to be exposed inside the
bend, so that they are subjected to intense heat of the exhaust
gas.
[0011] The urea solution injection valve, as disclosed in the above
first publication, is mounted in a protrusion extending outside the
bend of the exhaust pipe in a direction opposite to the catalyst in
order to minimize the exposure of the urea solution injection valve
to the intense heat of exhaust gas. This structure is, however,
needed to select the length of the protrusion from the outer
surface of the bend or regulate the angle of a cone-shaped spread
of urea aqueous solution accurately in order to avoid the adhesion
of a spray of the urea aqueous solution to an inner wall of the
protrusion, which may result in instability in mixing the urea
aqueous solution with the exhaust gas homogeneously.
SUMMARY OF THE INVENTION
[0012] It is therefore a principal object of the invention to avoid
the disadvantages of the prior art.
[0013] It is another object of the invention to provide an exhaust
emission control device equipped with an additive injector which is
designed to protect the additive injector from intense heat of
exhaust gas and ensure the stability in an exhaust gas purification
reaction using additive injected into exhaust gas.
[0014] According to one aspect of the invention, there is provided
an exhaust emission control apparatus which may be used as a urea
SCR (Selective Catalytic Reduction) system for automotive internal
combustion engines which works to convert harmful emissions into
less harmless substances. The exhaust emission control apparatus
comprises: (a) an exhaust pipe through which exhaust emissions
flow, the exhaust pipe including a straight section and a bent
section extending from the straight section in an upstream
direction of a flow of the exhaust emissions; (b) a catalyst
disposed downstream of the straight section of the exhaust pipe in
connection therewith; (c) a hollow protrusion having a length
extending outside the exhaust pipe from a peripheral wall of the
bent section substantially in parallel to a longitudinal center
line of the straight section, the protrusion having a first end and
a second end opposed to the first end, the protrusion having an
opening formed in the first end which communicates with inside the
bent section of the exhaust pipe; and (d) an additive injector
designed to produce a cone-shaped spray of additive, the additive
injector being installed in the second end of the protrusion and
oriented to inject the cone-shaped spray of additive into the
exhaust pipe through the opening of the protrusion without
interfering with at least a downstream edge of the opening. The
additive is carried by the flow of the exhaust emissions downstream
to the catalyst and used in a given exhaust emission purification
reaction, as induced by the catalyst, to purify the exhaust
emissions.
[0015] Specifically, the protrusion extends outside the exhaust
pipe. The additive injector is retained by the protrusion without
being exposed directly to the exhaust emissions flowing through the
exhaust pipe, thereby minimizing the transmission of intense heat
of the exhaust emissions to the additive injector. Additionally,
the additive injector is also so held by the protrusion as to avoid
the interference of the cone-shaped spray of the additive with at
least the downstream edge of the opening that is a portion of the
opening located farthest away from the additive injector. Further,
the protrusion is formed to extend substantially parallel to the
longitudinal center line of the straight section of the exhaust
pipe. The additive injector is secured to the second end of the
protrusion. In other words, the center axis of the cone-shaped
spray, that is, a path along which the additive is sprayed from the
additive injector is aligned with the longitudinal center line of
the straight section of the exhaust pipe, thereby minimizing the
adhesion of the additive to an inner wall of the protrusion and
mixing the additive to the exhaust emissions homogeneously which
are, then, carried to the catalyst.
[0016] In the preferred mode of the invention, the additive
injector is so oriented by the protrusion as to avoid interference
of the cone-shaped spray of additive with an entire edge of the
opening of the protrusion.
[0017] The protrusion has a cylindrical inner wall, thereby
facilitating machining of the protrusion and also minimizing the
adhesion of the spray of additive thereto.
[0018] The additive injector has a head in which a spray hole is
formed. The distance between the downstream edge of the opening of
the protrusion and the head of the additive injector is so selected
as a function of an angle of spread of the additive, as sprayed
from the additive injector, as to avoid interference of the
cone-shaped spray of the additive with the downstream edge of the
opening of the protrusion.
[0019] The additive injector is oriented in alignment of an axis
thereof with that of the straight section of the exhaust pipe,
thereby resulting in a uniform distribution of the spray of
additive over the straight section of the exhaust pipe and carrying
a homogeneous mixture of the additive and the exhaust emissions to
the catalyst.
[0020] The additive injector may also be oriented in alignment of
an axis with that of the catalyst.
[0021] The additive injector may be designed to change the angle of
spread of the additive. The additive injector is oriented to avoid
interference of the cone-shaped spray of additive with at least the
downstream edge of the opening when the angle of spread of the
additive is maximized.
[0022] The exhaust pipe may also include a second bent section
through which the exhaust gas flows. The second bent section
communicates with the bent section and the straight section at a
branch joint. The opening of the protrusion leads inside the
exhaust pipe through a wall of the branch joint. The protrusion
extends outside the exhaust pipe substantially in parallel to the
longitudinal center line of the straight section.
[0023] The bent section is curved smoothly or flexed to a right
angle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present invention will be understood more fully from the
detailed description given hereinbelow and from the accompanying
drawings of the preferred embodiments of the invention, which,
however, should not be taken to limit the invention to the specific
embodiments but are for the purpose of explanation and
understanding only.
[0025] In the drawings:
[0026] FIG. 1 is a schematic view which shows an exhaust emission
control apparatus according to the invention;
[0027] FIG. 2 is a partially enlarged sectional view of FIG. 1;
[0028] FIG. 3 is a side view which shows a first modification of
installation of a urea solution injection valve installed in the
exhaust emission control apparatus of FIG. 1;
[0029] FIG. 4(a) is a side view which shows a second modification
of installation of a urea solution injection valve installed in the
exhaust emission control apparatus of FIG. 1;
[0030] FIG. 4(b) is a side view which shows a third modification of
installation of a urea solution injection valve installed in the
exhaust emission control apparatus of FIG. 1; and
[0031] FIG. 5 is a partially sectional view which shows
installation of a urea solution injection valve used in a
conventional urea SCR systems
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Referring to the drawings, particularly to FIG. 1, there is
shown a urea SCR (Selectively Catalytic Reduction) system according
to the invention which is engineered, like the one in FIG. 5, as an
exhaust emission control device to convert NOx emissions contained
in exhaust gas from an automotive diesel engine (not shown) into
harmless products.
[0033] The urea SCR system includes a DOC (Diesel Oxidation
Catalyst) 21, an exhaust pipe 10, and a SCR (Selectively Catalytic
Reduction) catalyst 20, and a urea solution injection valve 50. The
exhaust gas, as emitted from the diesel engine, flows through the
exhaust pipe 10 in a direction A.
[0034] The urea solution injection valve 50 is installed in a
portion the exhaust pipe 10 between the DOC 21 and the SCR catalyst
20. The urea solution injection valve 50 is controlled in operation
by a controller (not shown) to inject or spray a urea aqueous
solution as a reducing agent (also called reducer) to the exhaust
gas flowing from the DOC 21 to the SCR catalyst 20. The urea
aqueous solution is then carried by the stream of exhaust gas to
the SCR catalyst 20 and used in NOx reduction.
[0035] Specifically, the SCR catalyst 20 works to induce the NOx
reduction, that is, induce, for example, reactions below.
4NO+4NH.sub.3+O.sub.24N.sub.26H.sub.2O (1)
6HO.sub.2+8NH.sub.27N.sub.2+12H.sub.2O (2)
NO+NO.sub.2+2NH.sub.32N.sub.2+2H.sub.2O (3)
[0036] The ammonia (NH.sub.3) that is used as a reducing agent for
the NOx reduction in the above reaction formulas is supplied by the
urea solution injection valve 50 disposed upstream of the SCR
catalyst 20.
[0037] The urea solution injection valve 50 is of a known structure
similar to typical fuel injectors and works to produce, as
indicated by an arrow F in FIG. 2, a cone-shaped spray of urea
aqueous solution through a spray hole 75 formed in a head thereof.
The urea solution injection valve 50 is supplied with the urea
aqueous solution from a urea solution tank (not shown) through a
urea solution supply pipe.
[0038] The exhaust pipe 10 is, as can be seen from FIG. 1, made up
of three sections: a hollow cylindrical straight section 11 joined
directly to the SCR catalyst 20, a curved section 12 extending from
the straight section 11, and a curved section 13 joined to the DOC
21. The curved section 13 is bent in a direction opposite to the
curved section 12 and connected thereto to define an S-shaped
portion of the exhaust pipe 10. The curved section 12 has formed
thereon a protrusion 14 in which the urea solution injection valve
50 is installed.
[0039] The protrusion 14 is hollow cylindrical and opens into the
curved section 12 of the exhaust pipe 10, as illustrated in FIG. 1,
in alignment of a longitudinal center line (i.e., an axis) 25
thereof with a longitudinal center line of the straight section 11.
The protrusion 14 extends from an outer peripheral wall of the
curved section 12 away from the straight section 11. The protrusion
14 may be machined to have a cylindrical inner wall. The SCR
catalyst 20 is disposed in alignment of a longitudinal center line
thereof with the longitudinal center line of the straight section
11.
[0040] The protrusion 14 has an end wall 18 to which the urea
solution injection valve 50 is secured. Specifically, the urea
solution injection valve 50 is joined to the end wall 18 of the
protrusion 14 through a heat insulator 22 to have the head (i.e.,
the spray hole 75) thereof exposed inside the protrusion 14. The
spray hole 75 is, as can be seen in FIG. 2, formed in the center of
a top end wall of the head of the urea solution injection valve 50
to align a jet of urea aqueous solution with the SCR catalyst
20.
[0041] The urea solution injection valve 50 is so retained by the
end wall 18 as to orient the cone-shaped spray F of urea aqueous
solution to an oval opening 65, as defined by a joint between the
curved section 12 of the exhaust pipe 10 and the protrusion 14,
without physically interfering with a lower edge 15 of the oval
opening 65 (i.e., the most downstream portion of the joint between
the curved section 12 and the protrusion 14 in a direction of flow
of the exhaust gas). In other words, the angle .theta. of spread of
the urea aqueous solution and the distance L between the lower edge
15 of the opening 65 and the top end (i.e., the spray hole 75) of
the urea solution injection valve 50 are so selected as to avoid
the adhesion of the urea aqueous solution to the lower edge 15 of
the opening 65. In this embodiment, the angle .theta. and the
distance L are also selected so as to avoid the interference of the
cone-shaped spray F of urea aqueous solution with an upper edge 16
of the oval opening 65 (i.e., the most upstream portion of the
joint between the curved section 12 and the protrusion 14 in the
direction of flow of the exhaust gas). It is also advisable that
the angle .theta. and the distance L be selected so as to avoid the
interference of the cone-shaped spray F of urea aqueous solution
with an entire edge of the oval opening 65. The urea solution
injection valve 50 may be designed to change the angle .theta. of
spread of the urea aqueous solution in response to a change in
operating condition of the engine. In this case, it is advisable
that the urea solution injection valve 50 be installed in the
protrusion 14 so that the spray of urea aqueous solution does not
interfere with at least the lower edge 15 of the opening 65 when
the angle .theta. is maximized.
[0042] The beneficial advantages of the urea SCR system will be
described below.
[0043] The urea solution injection valve 50 is, as described above,
secured to the end wall 18 of the protrusion 14, so that it is not
exposed directly to the intense heat of the exhaust gas flowing, as
indicated by an arrow A, in the exhaust pipe 10. The use of the
heat insulator 22 further minimizes the transmission of the heat to
the urea solution injection valve 50.
[0044] The urea solution injection valve 50 is oriented in
alignment of the longitudinal center line thereof with that of the
straight section 11 of the exhaust pipe 10 (i.e., the SCR catalyst
20), thereby directing the cone-shaped spray F of the urea aqueous
solution uniformly over the entire inlet surface of the SCR
catalyst 20. Specifically, the urea aqueous solution and the
exhaust gas which are mixed homogeneously reach the entire surface
of the SCR catalyst 20.
[0045] The location where the urea solution injection valve 50 is
mounted on the protrusion 14 and the structure of the protrusion 14
are so determined that the urea aqueous solution is injected into
the curved section 12 of the exhaust pipe 10 without interfering
with at least the lower edge 15 of the opening 65 of the exhaust
pipe 10, thus mixing the urea aqueous solution with the exhaust gas
within the exhaust pipe 10 without the adhesion thereof to the
inner wall of the protrusion 14.
[0046] FIG. 3 illustrates the first modification of the
installation of the urea solution injection valve 50 to the exhaust
pipe 10.
[0047] Specifically, the exhaust pipe 10 includes an L-shaped
section 12a instead of the curved section 12 of FIG. 1. The
L-shaped section 12a is bent at right angles and connected between
the sections 11 and 13. The protrusion 14 extends from the L-shaped
section 12a away from the straight section 11. The urea solution
injection valve 50 is installed in the protrusion 14 in alignment
of the longitudinal center line thereof with that of the straight
section 11.
[0048] FIG. 4(a) illustrates the second modification of the
installation of the urea solution injection valve 50.
[0049] The exhaust pipe 10 includes two curved sections 12b and 12c
each of which is joined to one of DOCs (not shown). The curved
sections 12b communicate with the SCR catalyst 20 through the
straight section 11. The protrusion 14 is formed on a branch joint
19 of the curved sections 12b and 12c. The urea solution injection
valve 50 is disposed in the protrusion 14 in alignment of the
longitudinal center line thereof with that of the straight section
11 (i.e., the SCR catalyst 20).
[0050] FIG. 4(b) illustrates the third modification of the
installation of the urea solution injection valve 50.
[0051] The exhaust pipe 10 includes a T-shaped section 12e joined
at two inlets thereof to DOCs (not shown), respectively. The
T-shaped section 12e is also joined at an outlet thereof to the SCR
catalyst 20 through the straight section 11. The protrusion 14 is
formed on the outer surface of the T-shaped section 12e in
alignment with the outlet of the T-shaped section 12e. The urea
solution injection valve 50 is disposed in the protrusion 14 in
alignment of the longitudinal center line thereof with that of the
straight section 11 (i.e., the SCR catalyst 20).
[0052] The urea SCR system may be used with engines other than
diesel engines such as gasoline engines (e.g., spark ignition
engines) or another type of exhaust emission control device. The
urea SCR system may also be designed to use a reducing agent other
than urea.
[0053] While the present invention has been disclosed in terms of
the preferred embodiments in order to facilitate better
understanding thereof it should be appreciated that the invention
can be embodied in various ways without departing from the
principle of the invention. Therefore, the invention should be
understood to include all possible embodiments and modifications to
the shown embodiments witch can be embodied without departing from
the principle of the invention as set forth in the appended
claims.
* * * * *