U.S. patent application number 13/327166 was filed with the patent office on 2013-06-20 for fluid injection lance with balanced flow distribution.
This patent application is currently assigned to Caterpillar Inc.. The applicant listed for this patent is Yung T. Bui, Arvind Jujare, Jay Venkataraghavan. Invention is credited to Yung T. Bui, Arvind Jujare, Jay Venkataraghavan.
Application Number | 20130152555 13/327166 |
Document ID | / |
Family ID | 48608726 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130152555 |
Kind Code |
A1 |
Bui; Yung T. ; et
al. |
June 20, 2013 |
FLUID INJECTION LANCE WITH BALANCED FLOW DISTRIBUTION
Abstract
An injector configured to introduce a reductant into an exhaust
stream, the injector includes: a body including a conduit with a
first diameter, a nozzle fluidly coupled to the conduit and
disposed at a distal end of the body, and an extension extending
from the distal end of the body, the extension extending from the
distal end of the body by at least a distance equal to the first
diameter.
Inventors: |
Bui; Yung T.; (Peoria,
IL) ; Jujare; Arvind; (Bloomington, IL) ;
Venkataraghavan; Jay; (Dunlap, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bui; Yung T.
Jujare; Arvind
Venkataraghavan; Jay |
Peoria
Bloomington
Dunlap |
IL
IL
IL |
US
US
US |
|
|
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
48608726 |
Appl. No.: |
13/327166 |
Filed: |
December 15, 2011 |
Current U.S.
Class: |
60/295 |
Current CPC
Class: |
F01N 2240/20 20130101;
Y02T 10/24 20130101; F01N 3/2892 20130101; F01N 3/2066 20130101;
Y02T 10/12 20130101; F01N 2610/1453 20130101 |
Class at
Publication: |
60/295 |
International
Class: |
F01N 3/24 20060101
F01N003/24 |
Claims
1. An injector configured to introduce a reductant into an exhaust
stream, the injector comprising: a body including a conduit with a
first diameter; a nozzle fluidly coupled to the conduit and
disposed at a distal end of the body; and an extension extending
from the distal end of the body, the extension extending from the
distal end of the body by at least a distance equal to the first
diameter.
2. The injector assembly of claim 1, wherein the body extends in a
first direction and the extension extends in a second direction
substantially parallel to the first direction.
3. The injector assembly of claim 2, further comprising a
cross-member coupled to the body and extending in a third direction
substantially perpendicular to the first direction.
4. The injector assembly of claim 2, further comprising a ring
mixer coupled to the body.
5. The injector assembly of claim 4, wherein the ring mixer is
disposed with a center of the ring mixer axially aligned with a
center of the nozzle.
6. The injector assembly of claim 1, wherein at least one of the
body and the extension includes a teardrop-shaped
cross-section.
7. The injector assembly of claim 1, wherein the extension is
fluidly isolated from the body.
8. The injector assembly of claim 1, wherein the nozzle extends in
a fourth direction substantially perpendicular to the first
direction.
9. The injector assembly of claim 1, wherein the nozzle includes
only a single nozzle.
10. An aftertreatment module for treating constituents of exhaust
gases of an internal combustion engine, the aftertreatment module
comprising: a housing; an injector disposed within the housing, the
injector including: a body coupled to the housing and including a
conduit with a first diameter; a nozzle fluidly coupled to the
conduit of the body and disposed at a distal end of the body; and
an extension extending from the distal end of the body, the
extension extending from the distal end of the body by at least a
distance equal to the first diameter; and a mixing duct disposed
downstream of the injector and within the housing.
11. The aftertreatment module of claim 10, wherein the body extends
in a first direction and the extension extends in a second
direction substantially parallel to the first direction.
12. The aftertreatment module of claim 11, wherein the body and
extension together extend a distance equal to substantially an
entire diameter of the mixing duct.
13. The aftertreatment module of claim 11, further comprising a
cross-member coupled to the body and extending in a third direction
substantially perpendicular to the first direction.
14. The aftertreatment module of claim 11, further comprising a
ring mixer coupled to the body.
15. The aftertreatment module of claim 10, further including a
diffuser disposed upstream of the mixing duct.
16. The aftertreatment module of claim 10, wherein the body and
extension together extend less than a distance equal to
substantially an entire diameter of the mixing duct.
17. The aftertreatment module of claim 10, further comprising a
header fluidly coupled to the internal reductant conduit of the
body of the injector.
18. The aftertreatment module of claim 10, further comprising at
least one selective catalytic reduction catalyst disposed
downstream of the mixing duct.
19. The aftertreatment module of claim 10, wherein the injector is
disposed within the mixing duct.
20. An injector configured to introduce a reductant into an exhaust
stream, the injector comprising: a body; a nozzle fluidly coupled
to, and disposed at a distal end of, the body; and an extension
extending from the distal end of the body, the extension configured
to equalize a velocity of exhaust flow over the nozzles in at least
two directions.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an exhaust system, and
more particularly, to an aftertreatment module and fluid injector
lance.
BACKGROUND
[0002] Internal combustion engines, including diesel engines,
gasoline engines, gaseous-fuel powered engines, and other engines
known in the art generate a complex mixture of exhaust gases and
particulates. Components of the exhaust gases may include, among
other things, oxides of nitrogen (NOx). Exhaust emission standards
have become more stringent, and the amount of NOx emitted to the
atmosphere by an engine may be regulated depending on the type,
size and/or class of engine.
[0003] To reduce NOx, some engine manufacturers have implemented a
strategy called selective catalytic reduction (SCR). SCR is an
exhaust aftertreatment process where a reductant, most commonly
urea ((NH.sub.2).sub.2CO) or a water, urea solution, is selectively
injected into the exhaust gas stream of an engine and adsorbed onto
a downstream substrate. The injected urea solution decomposes into
ammonia (NH.sub.3), which reacts with NOx in the exhaust gas to
form water (H.sub.2O) and diatomic nitrogen (N.sub.2).
[0004] In order to maximize an efficiency of conversion of the NOx,
the reductant should be dispersed evenly in the flow of exhaust
gases. This may be problematic due to constraints on the size of an
aftertreatment module. That is, because of packaging concerns for
the power system including the aftertreatment module, the length of
exhaust conduit between the injector and the downstream substrate
may be relatively short. Thus, it is beneficial to obtain an even
distribution of reductant in a short distance in order to ensure an
even distribution of reductant on the downstream substrate.
[0005] U.S. Pat. No. 7,784,276 discloses an exhaust gas purifier
and a method of control therefor.
SUMMARY
[0006] An injector configured to introduce a reductant into an
exhaust stream, the injector includes: a body including a conduit
with a first diameter, a nozzle fluidly coupled to the conduit and
disposed at a distal end of the body, and an extension extending
from the distal end of the body, the extension extending from the
distal end of the body by at least a distance equal to the first
diameter.
[0007] Other features and aspects of this disclosure will be
apparent from the following description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a side elevation view of an embodiment of a
disclosed power system;
[0009] FIG. 2 is an isometric cut-away view of an embodiment of an
aftertreatment module of the disclosed power system;
[0010] FIG. 3 is a top plan illustration of a first embodiment of a
diffuser, reductant injector lance assembly and mixing duct of the
embodiment of an aftertreatment module of the disclosed power
system;
[0011] FIG. 4 is a side elevation illustration of the first
embodiment of the diffuser, reductant injector lance assembly and
mixing duct of the disclosed aftertreatment module;
[0012] FIG. 5 is a partial cross-sectional view of the first
embodiment of the mixing duct and reductant injector lance assembly
of the disclosed system;
[0013] FIG. 6 is a partial cross-sectional view of a second
embodiment of a mixing duct and reductant injector lance assembly
of the disclosed system;
[0014] FIG. 7 is a partial cross-sectional view of a third
embodiment of a mixing duct and reductant injector lance assembly
of the disclosed system;
[0015] FIG. 8 is a side elevation illustration of a fourth
embodiment of a mixing duct and reductant injector lance assembly
of the disclosed system; and
[0016] FIG. 9 a cross-sectional illustration taken along line 9-9'
of FIG. 8 of the fourth embodiment of a mixing duct and reductant
injector lance assembly of the disclosed system.
DETAILED DESCRIPTION
[0017] FIG. 1 illustrates an exemplary power system 10. For the
purposes of this disclosure, power system 10 is depicted and
described as a gen-set including a generator 12 powered by a
multi-cylinder internal combustion engine 14. Generator 12 and
engine 14 may be generally coupled by a frame 16. It is
contemplated, however, that power system 10 may embody another type
of power system, if desired, such as one including a diesel,
gasoline, or gaseous fuel-powered engine associated with a mobile
machine, such as a locomotive, or a stationary machine, such as a
pump.
[0018] Multiple separate sub-systems may be included within power
system 10 to promote power production. For example, power system 10
may include among other things, an air induction system 18 and an
exhaust system 20. Air induction system 18 may be configured to
direct air or an air/fuel mixture into combustion chamber(s) of
power system 10 for subsequent combustion. Exhaust system 20 may
treat byproducts of the combustion process and discharge them to
the atmosphere. Air induction and exhaust systems 18, 20 may be
mechanically coupled to each other by way of one or more
turbochargers 21.
[0019] Exhaust system 20 may include components that condition and
direct exhaust from the cylinders of engine 14 to the atmosphere.
For example, exhaust system 20 may include one or more exhaust
passages 22 fluidly connected to the cylinders of engine 14, one or
more turbines of the turbochargers 21 driven by exhaust flowing
through exhaust passages 22, and an aftertreatment module 24
connected to receive and treat exhaust from exhaust passages 22
after flowing through the one or more turbines of the turbochargers
21. As the hot exhaust gases exiting the cylinders of engine 14
move through the one or more turbines and expand against vanes (not
shown) thereof, the one or more turbines may rotate and drive one
or more compressors of the turbochargers 21 of the air induction
system 18 to pressurize inlet air. Aftertreatment module 24 may
treat, condition, and/or otherwise reduce constituents of the
exhaust generated by engine 14 before the exhaust is discharged to
the atmosphere.
[0020] As shown in FIG. 2, aftertreatment module 24 may include a
base support 30, a generally box-like housing 32 (elements of which
are illustrated as being transparent in order to clearly show
internal elements of the aftertreatment module 24), one or more
inlets 34, and one or more outlets 36 (also illustrated in FIG. 1).
Base support 30 may be fabricated from, for example, a mild steel,
and rigidly connected to frame 16 of power system 10 (referring to
FIG. 1). Housing 32 may be fabricated from, for example, welded
stainless steel, and connected to base support 30 in such a way
that housing 32 can thermally expand to some degree relative to
base supported 30 when housing 32 is exposed to elevated
temperatures. Inlets 34 and outlets 36 may be located at one end of
housing 32 such that flows of exhaust may exit housing 32 in a
direction substantially perpendicular to the flow of exhaust
entering housing 32. Inlets 34 may be operatively coupled to
exhaust passages 22 (referring to FIG. 1) while outlets 36 may be
operatively coupled to passages leading to the atmosphere (e.g.,
additional exhaust tubing leading to an exterior space (not shown).
One or more access panels, for example a pair of oxidation catalyst
access panels 40 and a pair of SCR catalyst access panels 42, may
be located at strategic locations on housing 32 to provide service
access to internal components of aftertreatment module 24.
[0021] Aftertreatment module 24 may house a plurality of exhaust
treatment devices. For example, FIG. 2 illustrates aftertreatment
module 24 as housing a first aftertreatment device consisting of
one or more banks of diesel oxidation catalysts ("DOCs") 44, a
second aftertreatment device consisting of a reductant dosing
arrangement 46, and a third aftertreatment device consisting of one
or more banks of SCR catalysts 48. It is contemplated that
aftertreatment module 24 may include a greater or lesser number of
aftertreatment devices of any type known in the art, as desired.
DOCs 44 may be located downstream of inlets 34 and upstream of a
diffuser 50.
[0022] Exhaust enters the aftertreatment module 24 via the inlets
34. The exhaust passes into the DOCs 44. After passing through the
DOCs 44 and diffuser 50, the exhaust is exposed to the reductant
dosing arrangement 46 through a mixing duct 51. After passing
through the reductant dosing arrangement 46, the exhaust flows
through the SCR catalysts 48. Next, the exhaust may flow through
clean up catalysts (not shown) before exiting the aftertreatment
module 24 through outlets 36.
[0023] The DOCs 44 may each include a porous ceramic honeycomb
structure, a metal mesh, a metal or ceramic foam, or another
suitable substrate coated with or otherwise containing a catalyzing
material, for example a precious metal, that catalyzes a chemical
reaction to alter a composition of exhaust passing through DOCs 44.
In one embodiment, DOCs 44 may include palladium, platinum,
vanadium, or a mixture thereof that facilitates a conversion of NO
to NO.sub.2. In another embodiment, DOCs 44 may alternatively or
additionally perform particulate trapping functions (i.e., DOCs 44
may be a catalyzed particulate trap), hydro-carbon reduction
functions, carbon-monoxide reduction functions, and/or other
functions known in the art.
[0024] In the depicted embodiment, three separate banks of DOCs 44
are disclosed as being arranged to receive exhaust in parallel from
a pair of inlets 34. Each bank of DOCs 44 may include two or more
substrates disposed in series and configured to receive exhaust
from inlets 34. In one example, a space may exist between
substrates of a single bank of DOCs 44, if desired, the space
simultaneously promoting exhaust distribution and sound
attenuation. It is contemplated that any number of banks of DOCs 44
including any number of substrates arranged in series or parallel
may be utilized within aftertreatment module 24, as desired.
[0025] The mixing duct 51 has an upstream open end 52 in fluid
communication with the output of the DOCs 44 and a downstream end
53 in fluid communication with the one or more banks of SCR
catalysts 48. In the depicted embodiment, diffuser 50 is configured
as a cylinder with a flapper-type diffusing member disposed on one
end thereof distal to the mixing duct 51, although any diffuser
geometry known in the art may be utilized. In the arrangement of
FIG. 2, the diffuser 50 may be configured to distribute exhaust in
a substantially uniform manner across the upstream open end 52 of
the mixing duct 51. A reductant injector lance assembly 54 may be
located at, within, or near upstream open end 52 and configured to
inject a reductant into the exhaust flowing through mixing duct 51.
A gaseous or liquid reductant, most commonly a water/urea solution,
ammonia gas, liquefied anhydrous ammonia, ammonium carbonate, an
ammine salt, or a hydrocarbon such as diesel fuel, may be sprayed
or otherwise advanced into the exhaust passing through mixing duct
51.
[0026] Reductant injector lance assembly 54 may be located a
distance upstream of SCR catalysts 48 and at an inlet portion of
mixing duct 51 to allow the injected reductant sufficient time to
mix with exhaust from power system 10 and to sufficiently decompose
before entering SCR catalysts 48. That is, an even distribution of
sufficiently decomposed reductant within the exhaust passing
through SCR catalysts 48 may enhance NO.sub.x reduction therein.
The distance between reductant injector lance assembly 54 and SCR
catalysts 48 may enhance NO.sub.x reduction therein. The distance
between reductant injector lance assembly 54 and SCR catalysts 48
(i.e., approximately the length of mixing duct 51) may be based on
a flow rate of exhaust exiting power system 10 and/or on a
cross-sectional area of mixing duct 51. In the example depicted in
FIGS. 2 and 3, mixing duct 51 may extend a majority of a length of
housing 32, with reductant injector lance assembly 54 being located
at upstream open end 52. The mixing duct 51 may be a conduit having
an inner diameter 55 and an outer diameter 56 as illustrated in
more detail in FIGS. 5-7. The reductant injector lance assembly 54
may be configured to provide beneficial flow characteristics as
will be discussed in more detail with respect to FIGS. 3-9.
[0027] Each SCR catalyst 48 may be substantially identical in
shape, size and composition. In particular, each SCR catalyst 48
may include a generally cylindrical substrate fabricated from or
otherwise coated with a ceramic material such as titanium oxide; a
base metal oxide such as vanadium and tungsten; zeolites; and/or a
precious metal. With this composition, decomposed reductant
entrained within the exhaust flowing through mixing duct 51 may be
adsorbed onto the surface and/or adsorbed within each SCR catalyst
48, where the reductant may react with NO.sub.x (either NO,
NO.sub.2 or both) in the exhaust gas to form water (H.sub.2O) and
diatomic nitrogen (N.sub.2).
[0028] FIGS. 3-5 illustrate a first embodiment of a diffuser 50,
reductant injector lance assembly 54 and mixing duct 51 of the
embodiment of an aftertreatment module 24 of the disclosed power
system 10. FIG. 5 illustrates a partial cross-sectional view of the
first embodiment of the mixing duct 51 and reductant injector lance
assembly 54 as viewed from the mixing duct 51 looking toward the
reductant injector lance assembly 54. The reductant injector lance
assembly 54 and the mixing duct 51, including upstream open end 52
and downstream end 53, together form the reductant dosing
arrangement 46. The reductant injector lance assembly 54 includes a
lance body 60, a nozzle 62 and a lance extension 64.
[0029] The lance body 60 may include an internal reductant conduit
(illustrated in FIG. 9) extending throughout in order to convey
reductant to the nozzle 62; that is, the lance body 60 may be
hollow having an external diameter 61 and internal diameter 63
(illustrated in FIG. 9). The reductant conduit may have a
predetermined diameter determined according to desired reductant
flow rates based on the specific application of the power system 10
and desired performance of aftertreatment module 24. In one
embodiment, the diameter of the reductant conduit may be 2.5 cm.
The lance body 60 extends with a longitudinal axis in a first
direction 66.
[0030] The nozzle 62 extends substantially perpendicular to the
longitudinal axis of the lance body 60 at a distal end of the lance
body 60. That is, the nozzle 62 extends downstream into the exhaust
flow from the lance body 60. The nozzle 62 receives reductant from
the lance body 60 and injects the reductant into the exhaust
flowing within the mixing duct 51. In one embodiment, the nozzle 62
may be configured as an air-assisted injection nozzle such that a
combination of air, or other gas, and reductant is injected into
the exhaust. In some embodiments, air-assisted injection of
reductant provides advantages for increasing reductant flow rate
and dispersal of reductant along mixing duct 51; however,
alternative embodiments include configurations wherein air-assisted
injection is omitted and reductant is supplied exclusively via
alternative means, e.g., a reductant pump. In some embodiments,
disposing the nozzle 62 perpendicularly downstream from the lance
body 60 provides advantages for reductant dispersal as the nozzle
62 is moved further from a turbulent wake in the exhaust caused by
the lance body 60. If the nozzle 62 were to be formed in the lance
body 60 itself, this turbulent wake may cause undesirable deposit
formation thereon which could lead to a reduction in reductant flow
therethrough. In one embodiment, the nozzle 62 may be a single
nozzle 62. In such an embodiment, the nozzle 62 may be centered
within the mixing duct 51. In another embodiment, the nozzle 62 may
include more than one nozzle 62.
[0031] The lance extension 64 extends from the lance body 60. In
one embodiment, the lance extension 64 extends substantially
parallel to the first direction 66. Alternative embodiments include
configurations wherein the lance extension 64 extends in a
different direction, e.g., in a direction angled with respect to
the lance body 60 such as extending at an angle into the exhaust
flow or at an angle toward the mixing duct 51. As illustrated in
FIGS. 3-5, the lance body 60 extends to the nozzle 62 while the
lance extension 64 extends beyond the nozzle 62. The lance
extension 64 may extend from the lance body 60 by a distance at
least equal to the predetermined diameter of the internal reductant
conduit of the lance body 60. When the lance extension 64 extends
to, or beyond, this distance, improved mixing of reductant with
exhaust may be achieved as discussed in more detail below. In one
embodiment (not shown), the lance body 60 and lance extension 64
may together extend a distance equal to substantially the entire
inner diameter 55 of the mixing duct 51.
[0032] In one embodiment, the lance extension 64 may be fluidly
coupled to the internal reductant conduit of the lance body 60;
that is, the lance extension 64 may also include an internal
reductant conduit (not shown) capped at a furthermost extension of
the lance body 60 in the first direction 66. In an alternative
embodiment, the lance extension 64 may be fluidly isolated from the
lance body 60 such that the lance extension 64 does not include an
internal reductant conduit and the lance extension 64 may be hollow
or solid.
[0033] Referring to FIGS. 3-5, the reductant injector lance
assembly 54 may be coupled to the aftertreatment module 24 through
a through-hole 70 in housing 32. The through-hole 70 may be
configured to be substantially a same shape as a cross-section of
the reductant injector lance assembly 54, such that the reductant
injector lance assembly 54 may be inserted into the aftertreatment
module 24 therethrough. In one embodiment, the reductant injector
lance assembly 54 may be coupled to a header 72. The header 72 may
seal the aftertreatment module 24 such that exhaust does not exit
via the through-hole 70. The header 72 may also be fluidly coupled
to the internal reductant conduit of the lance body 60 of the
reductant injector lance assembly 54. A connection port 74 may be
disposed on the header 72 for supplying reductant to the internal
reductant conduit of the lance body 60.
[0034] FIG. 6 illustrates a partial cross-sectional view of the
mixing duct 51 and a second embodiment of a reductant injector
lance assembly 154 as viewed from the mixing duct 51 looking toward
the reductant injector lance assembly 154. The reductant injector
lance assembly 154 includes a lance body 160, a nozzle 162 and a
lance extension 164, similar to the previous embodiment, and also
includes a cross-member 167 coupled to the lance body 160 and
extending in a second direction 68 substantially perpendicular to
the first direction 66. The cross-member 167 may provide improved
mixing of reductant with exhaust as discussed in more detail
below.
[0035] FIG. 7 illustrates a partial cross-sectional view of the
mixing duct 51 and a third embodiment of a reductant injector lance
assembly 254 as viewed from the mixing duct 51 looking toward the
reductant injector lance assembly 254. The reductant injector lance
assembly 254 includes a lance body 260, a nozzle 262 and a lance
extension 264, similar to the previous embodiments, and also
includes a ring mixer 267 coupled to the lance body 260. In one
embodiment, the ring mixer 267 is disposed with a center of the
ring mixer 267 axially aligned with a center of the nozzle 262. The
ring mixer 267 may provide improved mixing of reductant with
exhaust as discussed in more detail below.
[0036] FIG. 8 is a side elevation illustration of a mixing duct and
a fourth embodiment of a reductant injector lance assembly 354 of
the disclosed system as viewed from the mixing duct 51 looking
toward the reductant injector lance assembly 354. FIG. 9 is a
cross-sectional illustration taken along line 9-9' of FIG. 8. The
reductant injector lance assembly 354 includes a lance body 360, a
nozzle 362 and a lance extension 364, similar to the previous
embodiments, and also includes a baffle 367 coupled to the lance
body 360. In one embodiment, the baffle 367 is coupled to at least
one of the lance body 360 and lance extension 364. Embodiments
include configurations wherein the baffle 367 may be formed
separately from the lance body 360 and lance extension 364 and
configurations wherein the baffle 367 may be formed as a single,
unitary and indivisible component of either the lance body 360,
lance extension 364 or both. The baffle 367 is provided to control
flow of the exhaust passing thereby, e.g., in one embodiment the
baffle 367 may reduce tribulation in the exhaust passing thereby.
In one embodiment, the baffle 367 and lance body 360 and/or lance
extension 364 together form a teardrop-shaped cross section. The
baffle 367 provides improved mixing of reductant with exhaust as
discussed in more detail below.
[0037] While the above description has described four embodiments
of a reductant injector lance assembly 54, 154, 254 and 354,
additional embodiments combining aspects of the previous
embodiments are also within the scope of this disclosure. For
example, another embodiment of the present disclosure may include
baffling 367 disposed on the ring mixer 267 or the cross-member
167. Similarly, the cross-member 167 may be combined with the ring
mixer 267, etc. The benefits of these configurations are discussed
in more detail below.
INDUSTRIAL APPLICABILITY
[0038] The aftertreatment module 24 of the present disclosure may
be applicable to any power system 10 configuration where exhaust
gas conditioning is desired. The aftertreatment module 24 includes
at least one of the reductant injector lance assemblies 54, 154,
254 and/or 354. The various embodiments provide improved mixing of
reductant with exhaust as described in more detail below.
[0039] When the power system 10 is in operation, exhaust passes
through the aftertreatment module 24 for treatment as described
above the aftertreatment module 24 includes the reductant dosing
arrangement 46 and SCR catalysts 48. The exhaust passes through the
reductant dosing arrangement 46 and carries injected reductant onto
the SCR catalysts 48. In order to maximize efficiency of the SCR
catalysts 48 and to minimize the total amount of reductant needed
to achieve satisfactory saturation of all SCR catalysts 48, a
substantially uniform distribution of reductant across each SCR
catalyst 48 is desired. However, disposing components, such as a
reductant injector, in the exhaust stream may lead to imbalances in
the stream that are not effectively dispersed within the length of
the mixing duct 51. Such a phenomenon may lead to uneven
distribution of reductant on the SCR catalysts 48.
[0040] In one configuration wherein a reductant injector lance
assembly (not shown) omits a lance extension, exhaust flow over the
most distal portion of the lance body may cause unwanted vortex
shedding that deflects injected reductant towards a side of the
mixing duct 51 from which the reductant injector lance assemblies
54, 154, 254 and/or 354 extends. In such a configuration a
variability from catalyst to catalyst of up to 20% may be observed.
However, in embodiments wherein a lance extension 64, 164, 264 or
364 is included, the unwanted vortex shedding may be reduced,
eliminated, or moved significantly away from the nozzle 62, 162,
262 or 362 such that deflection of reductant from nozzle 62, 162,
262 or 362 is reduced or eliminated.
[0041] Referring specifically to FIGS. 3-5 and the first embodiment
of the reductant injector lance assembly 54, the lance extension 64
is disposed at the distal end of the lance body 60 and, in one
embodiment, extends from the lance body 60 by a distance at least
equal to a diameter of the internal reductant conduit of the lance
body 60. If the lance extension 64 extends significantly less than
this amount, a reduction in deflection of reductant from the nozzle
62 may not result in a significantly more uniform distribution of
reductant onto catalyst 48. However, as the length of the lance
extension 64 increases, a corresponding increase in reduction of
deflection of reductant from the nozzle 62 resulting in a more
uniform distribution of reductant onto catalyst 48 may be
observed.
[0042] Similarly, referring to FIGS. 6-9, reductant injector lance
assemblies 154, 254 and 354 also include lance extensions 164, 264
and 364. In addition, each of reductant injector lance assemblies
154, 254 and 354 includes an additional feature for improving
mixing of reductant with exhaust. Referring to FIG. 6, the
cross-member 167 presents a wake in the exhaust flow similar to the
wake of the lance extension 164 in that similar exhaust flow
characteristics are presented at the nozzle 162 from at least four
sides corresponding to the lance body 160, the lance extension 164
and the two portions of the cross-member 167 disposed on opposite
sides of the nozzle 162. Referring to FIG. 7, the ring mixer 267
similarly presents a wake in the exhaust flow which allows a more
uniform exhaust flow over the nozzle 262 from multiple sides, such
as a circumference surrounding the nozzle 262. That is, the ring
mixer 267 may be disposed with a center thereof axially aligned
with a center of the nozzle 262. Referring to FIGS. 8 and 9, the
baffle 367 presents a surface which allows for laminar flow of
exhaust gas therealong in a third direction 69. This baffling may
alleviate non-uniformity of reductant deposition due to
fluctuations in the velocity of exhaust gas in the second
direction. The baffling 367 exerts a smoothing effect on exhaust
gas flowing thereover.
[0043] The present disclosure also presents embodiments of injector
lance assemblies 54, 154, 254 and 354 configured to introduce a
reductant into an exhaust stream, the injector lance assemblies
154, 254 and 354 including; lance bodies 60, 160, 260 and 360;
nozzles 62, 162, 262 and 362 fluidly coupled to, and disposed at a
distal end of, the lance bodies 60, 160, 260 and 360; and lance
extensions 64, 164, 264 and 364 extending from the distal end of
the lance bodies 60, 160, 260 and 360, the lance extensions 64,
164, 264 and 364 configured to equalize a velocity of exhaust flow
over the nozzles 62, 162, 262 and 362 in at least two directions.
That is, the lance extensions 64, 164, 264 and 364 are configured
such that exhaust flow over the nozzles 62, 162, 262 and 362 is
more uniform, e.g., a flow velocity from a direction corresponding
to the lance bodies 60, 160, 260 and 360 is substantially equal to
a flow velocity from a direction corresponding to the lance
extensions 64, 164, 264 and 364. The embodiment including the
cross-member 167 may equalize a velocity of exhaust flow over the
nozzle 162 in at least four directions. The embodiment including
the ring mixer 267 may equalize a velocity of exhaust flow over the
nozzle 262 in substantially all directions.
[0044] It will be apparent to those skilled in the art that various
modifications and variations can be made to the exhaust system 20
and aftertreatment module 24 of the present disclosure without
departing from the scope of the disclosure. Other embodiments will
be apparent to those skilled in the art from consideration of the
specification and practice of the system and module disclosed
herein. It is intended that the specification and examples be
considered as exemplary only, with a true scope of the disclosure
being indicated by the following claims and their equivalent.
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