U.S. patent application number 14/031066 was filed with the patent office on 2015-03-19 for system and method for mixing of fluids.
This patent application is currently assigned to Caterpillar Inc.. The applicant listed for this patent is Caterpillar Inc.. Invention is credited to Yung T. Bui.
Application Number | 20150078976 14/031066 |
Document ID | / |
Family ID | 52580039 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150078976 |
Kind Code |
A1 |
Bui; Yung T. |
March 19, 2015 |
SYSTEM AND METHOD FOR MIXING OF FLUIDS
Abstract
A mixing element positioned at an exhaust outlet of a Selective
Catalytic Reduction (SCR) module is provided. The mixing element
includes a base plate having an upper surface and a lower surface.
The base plate is configured to deflect a portion of a flow of a
fluid around the upper surface thereof. The mixing element also
includes a plurality of vanes attached to the lower surface of the
base plate in a spaced apart arrangement. The plurality of vanes is
configured to induce a swirling effect in a flow of the fluid
received therebetween.
Inventors: |
Bui; Yung T.; (Peoria,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc. |
Peoria |
IL |
US |
|
|
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
52580039 |
Appl. No.: |
14/031066 |
Filed: |
September 19, 2013 |
Current U.S.
Class: |
423/212 ;
422/176 |
Current CPC
Class: |
F01N 2240/20 20130101;
F01N 13/009 20140601; B01F 5/0057 20130101; B01D 53/9495 20130101;
F01N 2560/026 20130101; F01N 3/2882 20130101; B01F 2215/0431
20130101; Y02T 10/24 20130101; Y02T 10/12 20130101; B01D 53/94
20130101; F01N 13/008 20130101; B01F 2215/0422 20130101; F01N
3/2066 20130101; B01D 53/9418 20130101; F01N 3/2892 20130101; B01F
3/02 20130101 |
Class at
Publication: |
423/212 ;
422/176 |
International
Class: |
F01N 3/28 20060101
F01N003/28; B01D 53/94 20060101 B01D053/94 |
Claims
1-6. (canceled)
7. An aftertreatment system housing comprising: an exhaust inlet
configured to receive an exhaust flow; a Selective Catalytic
Reduction (SCR) module disposed within the housing, wherein the SCR
module is configured to introduce a reductant into the exhaust
flow; a nitrogen oxide sensor disposed downstream of the SCR
module, the nitrogen oxide sensor configured to measure a nitrogen
oxide content of the exhaust flow exiting the housing; an exhaust
outlet configured to emit the exhaust flow out of the housing; and
a mixing element disposed between the SCR module and the nitrogen
oxide sensor, the mixing element being disposed in fluid
communication with the exhaust outlet, wherein the mixing element
is configured to substantially homogenize the exhaust flow upstream
of the nitrogen oxide sensor, the mixing element comprising: a base
plate having an upper surface and a lower surface, the base plate
configured to deflect a portion of a flow of a fluid around the
upper surface thereof; and a plurality of vanes attached to the
lower surface of the base plate, the plurality of vanes being
provided in a spaced apart arrangement, wherein the plurality of
vanes is configured to induce a swirling effect in a flow of the
fluid received therebetween.
8. The system of claim 7, wherein the mixing element is at least
partially disposed within the housing.
9. The system of claim 7, wherein each of the plurality of vanes
has an airfoil shaped cross section.
10. The system of claim 7, wherein the plurality of vanes are
disposed such that a leading edge of each of the plurality of vanes
face an outside of the base plate, the plurality of vanes being
positioned substantially equidistant from one another about a
periphery of the base plate and defining windows therebetween for
receiving the portion of the flow of the fluid therein.
11. The system of claim 7 further comprising a plurality of
perforations formed on the base plate, the plurality of
perforations configured to allow a portion of the flow of the fluid
to be received into the mixing element.
12. The system of claim 11, wherein the plurality of perforations
is provided in alignment with the plurality of vanes.
13. The system of claim 11, wherein a hole is provided centrally on
the base plate.
14. A method comprising: introducing an exhaust flow into an
exhaust inlet of a housing; receiving the exhaust flow into a
Selective Catalytic Reduction (SCR) catalyst disposed within the
housing; introducing a reductant into the exhaust flow upstream of
the SCR catalyst; receiving the exhaust flow from the SCR catalyst
into an exit chamber of the housing; and directing the exhaust flow
towards an exhaust outlet of the housing, wherein the directing the
exhaust flow comprises: deflecting a portion of the directed
exhaust flow away from the exhaust outlet; receiving the deflected
exhaust flow into a mixing element disposed within the housing; and
inducing a swirling effect in the received exhaust flow.
15. The method of claim 14, wherein the directing the exhaust flow
further comprises exiting the exhaust flow from the exhaust
outlet.
16. The method of claim 14 further comprising receiving the exhaust
flow from the exhaust outlet into a nitrogen oxide sensor.
17. The method of claim 14 further comprising allowing a portion of
the exhaust flow to be directly received into the mixing element.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a system and method for
mixing one or more fluids, and more specifically the disclosure
relates to a mixing element for homogenizing a flow of the one or
more fluids.
BACKGROUND
[0002] Usually, an aftertreatment system is employed in an engine
for treating an exhaust flow of the engine. The aftertreatment
system reduces and/or converts constituents such as carbon
monoxide, sulfur dioxide, nitrogen oxides and so on present in the
exhaust flow into other compounds, such as H.sub.2O and N.sub.2 as
per emission requirements. The aftertreatment system utilizes one
or more sensors located at varying locations along the
aftertreatment system. For example, a nitrogen oxide, also referred
to as NOx, sensor may be located upstream and/or downstream of a
Selective Catalytic Reduction (SCR) module for measuring a
concentration of nitrogen oxides present in the exhaust flow
entering and/or exiting the SCR module, respectively.
[0003] The SCR module may contain one or more SCR catalysts. Once
exiting the one or more SCR catalysts, the exhaust stream may
contain localized areas of relatively higher and lower NOx
concentration. The NOx sensor positioned downstream of the SCR
module may sample a region of this non-uniform exhaust flow that is
non-representative of the total NOx concentration of the exhaust
flow exiting the SCR module. This may provide inaccurate nitrogen
oxide content readings.
[0004] In known systems, a mixing element is located upstream of
the SCR module to allow for mixing of a reductant or diesel exhaust
fluid (DEF) with the exhaust flow. However, this arrangement does
not provide mixing of the exhaust flow downstream of the SCR module
to homogenize the uneven distribution of the nitrogen oxides
present in the exhaust flow received by the NOx sensor positioned
post the SCR module.
[0005] U.S. Pat. No. 8,141,353 discloses such an exhaust mixer for
use in an engine exhaust system downstream from an additive
injector. The mixer includes a first disc-shaped wall structure
with a plurality of flow openings formed therein. The mixer also
includes a second wall structure carrying a set of mixer vanes. The
second wall structure includes a cone shape extending radially
outwardly from and intersecting the first wall structure such that
the first wall structure is frusto-conical in shape.
SUMMARY OF THE DISCLOSURE
[0006] In one aspect of the present disclosure, a mixing element
positioned at an exhaust outlet of a Selective Catalytic Reduction
(SCR) module is provided. The mixing element includes a base plate
having an upper surface and a lower surface. The base plate is
configured to deflect a portion of a flow of a fluid around the
upper surface thereof The mixing element also includes a plurality
of vanes attached to the lower surface of the base plate in a
spaced apart arrangement. The plurality of vanes is configured to
intuce a swirling effect in a flow of the fluid received
therebetween.
[0007] In another aspect of the present disclosure, an
aftertreatment system housing is provided. The system includes an
exhaust inlet configured to receive an exhaust flow. The system
includes a Selective Catalytic Reduction (SCR) module disposed
within the housing such that the SCR module may introduce a
reductant into the exhaust flow. The system includes a nitrogen
oxide sensor disposed downstream of the SCR module. The nitrogen
oxide sensor is configured to measure a nitrogen oxide content of
the exhaust flow exiting the housing. The system also includes an
exhaust outlet configured to emit the exhaust flow out of the
housing. The system further includes a mixing element disposed
between the SCR module and the nitrogen oxide sensor. The mixing
element is disposed in fluid communication with the exhaust outlet.
The mixing element is configured to substantially homogenize the
exhaust flow upstream of the nitrogen oxide sensor. The mixing
element includes a base plate having an upper surface and a lower
surface. The base plate is configured to deflect a portion of a
flow of a fluid around the upper surface thereof. The mixing
element includes a plurality of vanes attached to the lower surface
of the base plate in a spaced apart arrangement. The plurality of
vanes is configured to induce a swirling effect in a flow of the
fluid received therebetween.
[0008] In yet another aspect of the present disclosure, a method is
provided. The method introduces an exhaust flow into an exhaust
inlet of a housing. The method includes receiving the exhaust flow
into a Selective Catalytic Reduction (SCR) catalyst disposed within
the housing. The method includes introducing a reductant into the
exhaust flow upstream of the SCR catalyst. The method includes
receiving the exhaust flow from the SCR catalyst into an exit
chamber of the housing. The method includes directing the exhaust
flow towards an exhaust outlet of the housing. The directing the
exhaust flow includes deflecting a portion of the directed exhaust
flow away from the exhaust outlet. The directing the exhaust flow
also includes receiving the deflected exhaust flow into a mixing
element disposed within the housing. The directing the exhaust flow
further includes inducing a swirling effect in the received exhaust
flow.
[0009] Other features and aspects of this disclosure will be
apparent from the following description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an exemplary module of an aftertreatment
system;
[0011] FIG. 2 is a perspective view of an exemplary embodiment of a
mixing element;
[0012] FIG. 3 is a side view of the exemplary embodiment of a
mixing element showing a flow of a fluid therethrough; and
[0013] FIGS. 4 and 5 are flowcharts of exemplary methods utilizing
the exemplary embodiment of the mixing element of FIG. 2.
DETAILED DESCRIPTION
[0014] Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or similar parts.
Referring to FIG. 1, an exemplary module 100 of an aftertreatment
system is illustrated. More specifically, the module 100 is
illustrated as a Selective Catalytic Reduction (SCR) module,
although one of ordinary skill in the art would recognize that the
present disclosure may be applied to a variety of different
modules. The module 100 is configured to introduce a reductant into
a fluid, such as an exhaust flow of an engine (not shown). The
exhaust flow may contain one or more constituents such as carbon
monoxide, sulfur dioxide, nitrogen oxides and so on in gaseous
state. In one embodiment, the module 100 may introduce a suitable
reductant to reduce and/or convert an amount of nitrogen oxides
(NOx) present in the exhaust flow into other compounds using one or
more chemical reactions and/or processes.
[0015] The module 100 includes a housing 102. The housing 102
includes a first end 104 and a second end 106. The housing 102 is
configured to enclose and/or support one or more elements of the
module 100. The first end 104 of the housing 102 includes an
exhaust inlet 108. The exhaust inlet 108 is configured to receive
the exhaust into the housing 102 from the engine or other
aftertreatment components, such as, but not limited to, diesel
oxidation catalysts, diesel particulate filters, etc. It should be
noted that location of the module 100 in the aftertreatment system
may vary as per system design and requirements.
[0016] The module 100 includes a bank of SCR catalysts 110 disposed
within the housing 102. The bank of SCR catalysts 110 may include a
plurality of individual SCR catalysts 112. Each of the plurality of
SCR catalysts 112 may have similar dimensions and properties. In
the illustrated embodiment, the bank of SCR catalysts 110 includes
three cylindrical shaped SCR catalysts 112. A person of ordinary
skill in the art will appreciate that the plurality of SCR
catalysts 112 may vary based on the application. Moreover, each of
the plurality of SCR catalysts 112 has a corresponding SCR inlet
114 and an SCR outlet 116.
[0017] The bank of SCR catalysts 110 is configured to receive the
exhaust through the exhaust inlet 108. Each of the plurality of SCR
catalysts 112 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. The SCR catalysts 112 may
introduce the reductant into the exhaust. The reductant, and/or
decomposition byproducts thereof, disposed on the SCR catalysts 112
may react with NOx present in the exhaust to form water (H.sub.2O)
and diatomic nitrogen (N.sub.2). The exhaust may exit the bank of
SCR catalysts 110 via the SCR outlet 116.
[0018] The exhaust may flow out of the SCR outlet 116 and enter
into an exit chamber 117 defined within the housing 102. The exit
chamber 117 may be fluidly connected to an exhaust outlet 118
provided on the second end 106 of the housing 102. The exhaust
outlet 118 is configured to exit the exhaust leaving the bank of
SCR catalysts 110 from the module 100. It should be noted that the
housing 102 may additionally include a number of compartments or
divisions in order to assist in directing the exhaust within the
housing 102. Further, a NOx sensor 120 is provided in the exhaust
outlet 118 and downstream of the bank of SCR catalysts 110. The NOx
sensor 120 is configured to detect a concentration of nitrogen
oxides or NOx content in the exhaust exiting the bank of SCR
catalysts 110 through the SCR outlets 116. The location of the NOx
sensor 120 within the exhaust outlet 118 may vary as per system
configuration and requirements. For example, as shown in the
accompanying figure, the NOx sensor 120 may be located in the
exhaust outlet 118 at a suitable distance from the housing 102.
Alternatively, the NOx sensor 120 may be located in the exhaust
outlet 118 and in a plane corresponding to that of a wall of the
housing 102 having the exhaust outlet 118.
[0019] It should be noted that the exhaust exiting the SCR outlets
116 may contain an uneven distribution of NOx. This may be due to
each of the plurality of SCR catalysts 112 receiving a varying
amount of the exhaust and/or reductant. For example, the SCR
catalyst 112 disposed relatively closer to the exhaust inlet 108
may receive a higher amount of the exhaust as compared to the SCR
catalyst 112 disposed farther away from the exhaust inlet 108 or
vice versa. Accordingly, the exhaust exiting the each of the
plurality of SCR catalysts 112 may contain a varying concentration
of residual NOx after a catalytic reduction in the respective SCR
catalyst 112.
[0020] Alternatively, or in addition, exhaust may become
laminarized along the conduit on which the NOx sensor 120 is
disposed. The exhaust may have different NOx concentrations at
different distances away from the exhaust conduit. Laminarization
of the exhaust may be prevented by the present disclosure.
[0021] Referring to FIG. 1, the module 100 also includes a mixing
element 122 having a longitudinal axis X-X. The mixing element 122
is disposed at least partially within the housing 102. The mixing
element 122 is provided in fluid communication with the exhaust
outlet 118. The mixing element 122 is configured to provide mixing
and homogenization of the exhaust exiting from the each of the
plurality of SCR catalysts 112 prior to the exhaust entering into
the NOx sensor 120. Accordingly, the mixing element 122 is provided
downstream of the SCR outlets 116 and upstream of the NOx sensor
120 relative to the exhaust direction.
[0022] FIG. 2 illustrates a perspective view of the mixing element
122. The mixing element 122 includes a base plate 202 having an
upper surface 204 and a lower surface 206. In the illustrated
embodiment, the base plate 202 has a circular plate like
configuration having a diameter. The diameter of the base plate 202
may be substantially equal to or lesser than a diameter of the
exhaust outlet 118. In another embodiment, the base plate 202 may
have a rectangular or a triangular configuration having suitable
dimensions. It should be noted that the configuration and
dimensions of the base plate 202 may vary as per system
requirements. The base plate 202 is configured to deflect a portion
of the exhaust exiting the SCR outlets 116 away from the mixing
element 122 and into the exit chamber 117 defined within the
housing 102. As shown in FIG. 3, the base plate 202 deflects the
exhaust substantially perpendicular to the longitudinal axis X-X of
the mixing element 122.
[0023] Referring to FIG. 2, the base plate 202 includes a plurality
of vanes 208 fixedly attached to the lower surface 206 of the base
plate 202. The plurality of vanes 208 is provided perpendicular to
the base plate 202 and in a circumferentially spaced apart
arrangement with respect to the base plate 202. Each of the
plurality of vanes 208 has a substantially curved configuration.
The curved configuration of the each of the plurality of vanes 208
defines a vane angle "V" with respect to the longitudinal axis X-X
and/or a circumference of the base plate 202. The curved
configuration of the each of the plurality of vanes 208 is provided
to induce a swirling effect in a portion of the exhaust received
therebetween. The swirling effect created in the exhaust may lead
to the homogenization of the exhaust such that the exhaust may now
contain an even distribution of the NOx content. It should be noted
that the mixing element 122 is at least partially positioned within
the housing 102 so as to receive the portion of the exhaust from
the exit chamber 117 of the housing 102.
[0024] As shown in FIG. 2, in one embodiment, the plurality of
vanes 208 are disposed such that a leading edge of each of the
plurality of vanes 208 face an outside of the base plate 202. Also,
the plurality of vanes 208 may be positioned substantially
equidistant from one another about a periphery of the base plate
202. A number of windows 210 are defined between the each of the
plurality of vanes 208. As shown in FIG. 3, each of the windows 210
is configured to receive at least a portion of the exhaust
deflected by the base plate 202. In one embodiment, the plurality
of vanes 208 may have an airfoil shaped cross section. In another
embodiment, the plurality of vanes 208 may have a partial C-shaped
or a bent plate like configuration. It should be noted that the
cross sectional shape of the plurality of vanes 208 may vary as per
system design and requirements.
[0025] Dimensional parameters of the plurality of vanes 208 such as
the vane angle "V" associated with the each of the plurality of
vanes 208, a spacing between adjacent vanes 208, a height "H" of
the each the plurality of the vanes 208, curve lengths "A", "B" and
"C" associated with the each of the plurality of the vanes 208
and/or the shape of the cross section of the each of the plurality
of vanes 208 may vary as per system configuration. These
dimensional parameters may be selected based on a required
intensity of the swirling effect to be created in the exhaust and
also based on the aftertreatment system with which the mixing
element 122 is associated. For example, the plurality of vanes 208
may have the vane angle "V" ranging from approximately 5 to 15
degrees, the height "H" ranging from approximately 3 to 5.5 inches,
the curve length "A" ranging from approximately 50 to 180
millimeters, the curve length "B" ranging from approximately 7 to
10 millimeters, and the curve length "C" ranging from approximately
20 to 30 millimeters. It should be noted that dimensional ranges
mentioned herein are exemplary and may vary as per system design
and configuration.
[0026] Further, the plurality of vanes 208 is fixedly attached to
the exhaust outlet 118 and/or an outlet of the housing 102 leading
to the exhaust outlet 118, in order to attach the mixing element
122 to the exhaust outlet 118 and/or the housing 102 respectively.
The homogenized exhaust may be directed to enter into the exhaust
outlet 118. The plurality of vanes 208 may be attached to the
exhaust outlet 118 and/or the housing 102 by any fastening means
known in the art such as welding, brazing, soldering, bolting,
riveting and so on.
[0027] Referring to FIG. 2, the base plate 202 may be provided with
a plurality of perforations 212. A portion of the exhaust may be
directly received into the mixing element 122 through the plurality
of perforations 212. This may allow for a reduction in backpressure
in the exhaust flowing towards the exhaust outlet 118 or the NOx
sensor 120. In the illustrated embodiment, the plurality of
perforations 212 is provided in a manner such that the perforations
212 are aligned with the positioning of the vanes 208 on the base
plate 202. In the illustrated embodiment, each of the plurality of
perforations 212 has a circular configuration. Alternatively, the
plurality of perforations 212 may be formed as vertical or
horizontal slots, squares, rectangles, crosses and so on. In
another embodiment, a central hole may be provided on the base
plate 202. It should be noted that shape, size, location and
arrangement of the plurality of perforations 212 on the base plate
202 may vary as per system design and configuration.
INDUSTRIAL APPLICABILITY
[0028] The NOx sensor located downstream of the SCR catalysts is
used for measuring the concentration of nitrogen oxides in the
exhaust. The concentration of the nitrogen oxides may in turn be
used to determine an amount of the diesel exhaust fluid (DEF)
dosing to be provided in the exhaust by the DEF module of the
aftertreatment system. In order for the DEF module to perform
efficiently, it is required that an output of the NOx sensor
provided downstream of the SCR module is consistent without
considerable noise and/or sudden surges. This may be achieved by
providing the exhaust to the NOx sensor located downstream of the
SCR module having substantially homogenized concentration of the
nitrogen oxides.
[0029] Known systems include providing the mixing element
downstream of the DEF module and upstream of the SCR module. This
location of the mixing element provides for mixing of the exhaust
prior to the exhaust entering into the SCR catalysts.
[0030] The mixing element 122 disclosed herein may be utilized for
mixing and homogenizing the exhaust downstream of the SCR catalysts
112. The mixing element 122 provides for an effective mixing and
homogenization of the exhaust within a confined space of the module
100. Further, design and configuration of the mixing element 122
prevents considerable backpressure in the exhaust.
[0031] FIGS. 4 and 5 illustrate exemplary methods 400, 500 of
mixing the exhaust downstream of the SCR catalysts 112. As shown in
FIG. 4, at step 402, the exhaust is introduced into the exhaust
inlet 108 of the housing 102. At step 404, the exhaust is received
into the SCR inlet 114 of the SCR catalyst 112 disposed within the
housing 102. At step 406, the reductant is introduced into the
exhaust upstream of the SCR outlet 116. A person of ordinary skill
in the art will appreciate that the reductant may be introduced
using any known method in the art. At step 408, the exhaust is
received from the SCR outlet 116 into the exit chamber 117 of the
housing 102. At step 410, the exhaust is directed towards the
exhaust outlet 118 of the housing 102.
[0032] FIG. 5 illustrates the method 500 of directing the exhaust
towards the exhaust outlet 118 in detail. At step 502, the portion
of the exhaust is deflected away from the exhaust outlet 118. More
specifically, the exhaust may compact against the base plate 202 of
the mixing element 122, causing the compacted exhaust to be
deflected substantially perpendicular to the longitudinal axis X-X
of the mixing element 122. In one embodiment, some portion of the
deflected exhaust may re-enter into the exit chamber 117.
[0033] At step 504, at least the portion of the deflected exhaust
may be received into the mixing element 122. The deflection of the
exhaust on compacting or hitting against the base plate 202 of the
mixing element 122 may cause a change in direction of the deflected
exhaust, resulting in the deflected exhaust being received into the
windows 210 defined between the each of the plurality of vanes 208.
In one embodiment, some portion of the exhaust may directly be
received into the mixing element 122 through the plurality of
perforations 212 provided on the base plate 202.
[0034] At step 506, the swirling effect is induced within the
received exhaust. The swirling effect provides mixing and
homogenization of the exhaust received into the mixing element 122.
The homogenized exhaust may be discharged from the exhaust outlet
118 of the housing 102. In one embodiment, the homogenized exhaust
flow may be received into the NOx sensor 120.
[0035] Though the mixing element 122 disclosed herein is described
in relation to the aftertreatment system of the engine, it should
be noted that the mixing element 122 may be employed for other
alternate applications. The alternate applications may include
industries including, but not limited to, chemicals, oil and gas,
pharmaceuticals, dairy and food, and so on. The alternate
applications may include mixing and homogenization of mixtures
containing two or more combinations of gas-gas constituents,
gas-liquid constituents and/or liquid-liquid constituents.
[0036] While aspects of the present disclosure have been
particularly shown and described with reference to the embodiments
above, it will be understood by those skilled in the art that
various additional embodiments may be contemplated by the
modification of the disclosed machines, systems and methods without
departing from the spirit and scope of what is disclosed. Such
embodiments should be understood to fall within the scope of the
present disclosure as determined based upon the claims and any
equivalents thereof.
* * * * *