US20160194995A1

US20160194995A1 - Flow mixing device for an exhaust after-treatment system

Info

Publication number: US20160194995A1
Application number: US15/067,204
Authority: US
Inventors: Kevin Weiss; Mohamed I. Daoud; Yung T. Bui; Arvind Jujare; Chiranjeevi Mangamuri; Timothy Alcenius
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2016-03-11
Filing date: 2016-03-11
Publication date: 2016-07-07

Abstract

A flow mixing device includes a body having a first end, a second end, and an interior volume defined between them. An inlet plate, coupled to the first end of the body, defines at least two inlet orifices in fluid communication with the interior volume. Similarly, an outlet plate, coupled to the second end defines an outlet passage of the flow mixing device. A diffuser conduit, coupled to the inlet plate, defines an inlet passage disposed in fluid communication with the respective inlet orifices. A separator plate assembly disposed in the interior volume extends partially between the first and second ends of the body. Flow guiding vanes, coupled proximal to the second end, extend partially within the diffuser conduit.

Description

TECHNICAL FIELD

The present disclosure relates to an exhaust gas after-treatment system of an internal combustion engine. More particularly, the present disclosure relates to a flow mixing device of the exhaust gas after-treatment system.

BACKGROUND

Internal combustion engines have been typically known to employ exhaust after-treatment systems to lower or reduce undesired emissions in an exhaust stream. One of the undesired emissions in the exhaust stream may include nitrous oxides (NO_x). A Selective catalytic reduction (SCR) system may be additionally utilized to reduce the quantity of NO_xemissions in the exhaust stream. The SCR system is configured to inject a reductant such as urea in the exhaust stream to convert harmful NOx emissions into harmless nitrogen and water.
A flow mixer may be used to combine multiple exhaust streams generated from the internal combustion engine into a single exhaust stream prior to injection of a reductant. A uniform mixing of the exhaust gases is required to maximize flow uniformity and minimize backpressure prior to entry of the exhaust gases at the reductant injection location.
U.S. Pat. No. 8,814,969 discloses an exhaust gas emission control system for an internal combustion engine. The exhaust gas emission control system includes a cylindrical body through which the exhaust flows. The cylindrical body has an inflow pipe and an outflow pipe. The inflow pipe includes a louvre member defining a plurality of slits having varying height. A height of the slits decreases on moving away from a center of the inflow pipe. Although the louvre member may provide a uniform flow and minimize backpressure to an extent, it does not uniformly mix two separate exhaust streams into a single exhaust stream for effectively reducing NOx.
Hence, there is a need for an improved system that provides uniform mixing of multiple exhaust streams into a single exhaust stream while also minimizing backpressure and maximizing flow uniformity.

SUMMARY OF THE DISCLOSURE

In an aspect of the present disclosure, a flow mixing device for an exhaust after-treatment system of an internal combustion engine includes a body having a first end and a second end disposed distally away from one another. The body defines an interior volume. The flow mixing device further includes an inlet plate coupled to the first end of the body. The inlet plate having at least two inlet orifices formed therein in fluid communication with the interior volume, Further, an outlet plate is coupled to the second end of the body. The outlet plate defines an outlet passage in fluid communication with the interior volume. The flow mixing device further includes a diffuser conduit releasably coupled to the inlet plate and disposed around each of the inlet orifices. The diffuser conduit configured to define an inlet passage disposed in fluid communication with the inlet orifices of the inlet plate and the interior volume of the body. The flow mixing device further includes a separator plate assembly includes a first separator plate and a second separator plate, the first and second separator plates coupled at an angle relative to each other at the first end of the body and converging towards a longitudinal plane defined between the pair of diffuser conduits. The flow mixing device further includes multiple flow guiding vanes coupled to the body proximal to the second end and configured to extend at least partially within the diffuser conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an engine system having a flow mixing device that is used to combine multiple exhaust streams exiting from an internal combustion engine prior to entering a Selective Catalytic Reduction system, in accordance with an embodiment of the present disclosure;

FIG. 2 is a front perspective view of the flow mixing device, in accordance with an embodiment of the present disclosure;

FIG. 3 is a rear perspective view of the flow mixing device from FIG. 1;

FIG. 4 is a front view of the flow mixing device of FIGS, 2-3;

FIG. 5 is an isometric view of the flow mixing device of FIGS. 1-4 taken along a section plane AA′ of FIG. 4;

FIG. 6 is a rear perspective view of the flow mixing device, in accordance with another embodiment of the present disclosure; and

FIG. 7 is an isometric view of the flow mixing device from FIG. 6 taken along a section plane CC′ of FIG. 6

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to same or like parts. Moreover, references to various elements described herein are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claims.
As shown in FIG. 1, an engine system 100 includes an engine 102 and an after-treatment system 104 to treat exhaust streams 106 produced by the engine 102. The engine 102 may include other features not shown, such as controllers, fuel systems, air systems, cooling systems, peripheries, drivetrain components, turbochargers, exhaust gas recirculation systems, etc.
The engine 102 may be any type of engine (internal combustion, gas, diesel, gaseous fuel, natural gas, propane, etc.), may be of any size, with any number of cylinders, and in any configuration (“V,” in-line, radial, etc.). The engine 102 may be used to power any machine or other device, including on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, locomotive applications, marine applications, pumps, stationary equipment, or other engine powered applications.
As shown in the embodiment of FIG. 1, the after-treatment system 104 includes two exhaust conduits: a first exhaust conduit 110 and a second exhaust conduit 112. Each of the first and second exhaust conduits 110, 112 includes one or more of the following: a Diesel Oxidation Catalyst (DOC) 114 and a Diesel Particulate Filter (DPF) 116. The DOC 114 oxidizes Carbon Monoxide (CO) and unburnt hydrocarbons (HC) into Carbon Dioxide (CO2). The DPF 116 collects particulate matter or soot. The DOC 114 and the DPF 116 may be packaged in the same canister as shown, or separately from each other.
Exhaust gases 106 from the first and second exhaust conduits 110, 112 are passed through a flow mixing device 118 to combine the two separate exhaust streams 106 into a single combined exhaust stream 120. As shown in the embodiment of FIG. 1, the DOC 114 and the DPF 116 can be located upstream of the flow mixing device 118 and within the first and second exhaust conduits 110 and 112. However, in various embodiments, the first and second exhaust conduits 110, 112 may not include either the DOC 114 or the DPF 116. In an embodiment, at least one of the DOC 114 and DPF 116 may be located downstream of the flow mixing device 118. A Selective Catalytic Reduction (SCR) system 122 is provided to reduce NO emissions in the combined exhaust stream 120 downstream of the flow mixing device 118.
The SCR system 122 includes a reductant supply system 124 and an SCR catalyst 126. The reductant supply system 124 can include one or more of the following: a reductant 128, a reductant source 130, a pump 132, a valve 134 and an injector 136. The reductant 128 is drawn from the reductant source 130 via the pump 132 and delivery to the injector 136 that is controlled via the valve 134. The flow of reductant 128 may also be controlled by operation of the pump 132. While other reductants 128 are possible, urea is the most commonly used reductant 128. Reductant 128 decomposes or hydrolyzes into ammonia (NH₃) and is then adsorbed or otherwise stored in the SCR catalyst 126. The SCR catalyst 126, provided downstream of the injector 136, includes a catalyst material disposed on a substrate. The substrate may consist of cordierite, silicon carbide, other ceramic, or metal. The substrate may include a plurality of through going channels and may form a honeycomb structure.
After passing through the SCR system 122, the exhaust stream 120 may be circulated back to an exhaust gas recirculation system (not shown), a turbocharger (not shown) or discharged in atmosphere.
FIG. 2 shows a perspective view of the flow mixing device 118, according to an embodiment of the present disclosure. The flow mixing device 118 is formed from a body 138 of any regular or irregular geometric shape, such as a polyhedral body. For example, the body 138 can include multiple polygon faces joined together. The polygon faces at the top and the bottom of the body 138 may be arranged such that an interior volume of the flow mixing device 118 increases in the direction of flow of the exhaust gases. The polygon faces at the sides of the body 138 may be arranged such that the volume of the flow mixing device 118 may decrease in the direction of flow of the exhaust gases. The polygon faces of the body 138 may be sheet metal parts formed by a stamping process. The stamped sheet metal parts may have tabs at ends which may fit into corresponding inserts provided in complementary parts. After assembling the flow mixing device 118 through tabs and inserts, welding or any other joining process may be used to provide final shape to the body 138. The polygon faces may also be formed by bending sheet metal parts into suitable shapes. Shapes of sheet metal parts may be varied to suit the needs of different applications. Though, in the present embodiment, the body 138 is explained as made up of stamped sheet metal parts or bent sheet metal parts, it may be evident to a person of ordinary skill in the art that any other suitable material and processes may be used to prepare the body 138.
As shown in FIG. 2, the body 138 has a first end 140 and a second end 142 located distally away from the first end 140. Further, an inlet plate 144 is affixed at the first end 140 of the body 138. The inlet plate 144 may be a sheet metal part prepared in the same manner as the body 138. In an embodiment, the inlet plate 144 may have tabs and inserts through which the inlet plate 144 may be affixed to the body 138 proximal to the first end 140. The inlet plate 144 defines at least two inlet orifices: a first inlet orifice 146 and a second inlet orifice 148. The first inlet orifice 146 and the second inlet orifice 148 can be coupled to a first diffuser conduit 150 and a second diffuser conduit 152, respectively, through stiffener rings 154 and 156 provided on the inlet plate 144 along the periphery of the first and second inlet orifices 146, 148. In various embodiments, the diffuser conduits 150, 152 are coupled to the inlet plate 144 through any other means known in the art.
The first and the second diffuser conduits 150, 152 define a first inlet passage 158 and a second inlet passage 160, respectively. Each of the first and the second inlet passages 158, 160 is in fluid communication with the respective first and the second orifices 146, 148. Exhaust stream 106 flowing through the first exhaust conduit 110 is received at the first inlet passage 158 and passes on to the first inlet orifice 146, through the first diffuser conduit 150. Similarly, the exhaust stream 106 flowing through the second exhaust conduit 112 is received at the second inlet passage 160 and passes on to the second inlet orifice 148, through the second diffuser conduit 152.
As shown in FIG. 3, the flow mixing device 118 includes an outlet plate 162 affixed at the second end 142 of the body 138. The flow mixing device 118 is substantially hollow and defines an interior volume between the inlet plate 144 and the outlet plate 162. The interior volume is in fluid communication with the first and the second inlet passages 158, 160 and an outlet passage 163 defined by the outlet plate 162.
The flow mixing device 118 has a first inner surface 164 and a second inner surface 166. The first inner surface 164 and the second inner surface 166 are mutually opposed to each other and extend between the inlet plate 144 and the outlet plate 162.
The flow mixing device 118 further includes a separator plate assembly 168. The separator plate assembly 168 is located in the interior volume coupled to the body 138. As shown in the sectional view of FIG. 5, taken along a section AA′ of FIG. 4, the separator plate assembly 168 includes a first separator plate 170 and a second separator plate 172. The first and the second separator plates 170, 172 are coupled to an inside surface of the inlet plate 140 and extending toward the second end 142. The first and the second separator plates 170, 172 are inclined to each other at an angle ‘α’, and form a substantial V shape towards the second end 142 of the body 138. Further, the separator plate assembly 168 extends from the first inner surface 164 to the second inner surface 166. The first and second separator plates 170, 172 may intersect each other at a longitudinal plane BB′. The plane BB′ may extend longitudinally between the first and second ends 140, 142. In one embodiment, the plane BB′ may be located symmetrically between the first and second diffuser conduits 150, 152. In another embodiment, the plane BB′ is located at an offset towards any of the first and the second diffuser conduits 150, 152. Also, the plane BB′ may be orthogonal to the inlet plate 144. The separator plate assembly 168 ensures gradual and uniform mixing of exhaust gases from the first and the second diffuser conduits 150, 152.
Further, the flow mixing device 118 includes multiple flow guiding vanes 174 located in the interior volume and on either side of the separator plate assembly 168. The flow guiding vanes 174 extend from the first end 140 of the body 138 to the second end 142 of the body 138. The flow guiding vanes 174 extend longitudinally between the first inner surface 164 and the second inner surface 166. In an embodiment, the flow guiding vanes 174 may also extend partway between the first and second inner surfaces 164, 166. In another embodiment, the flow guiding vanes 174 may extend fully between the first inner surface 164 and the second inner surface 166.
As shown in the embodiment of FIG. 5, the flow guiding vanes 174 can have a first longitudinal portion 176, an inclined portion 178 and a second longitudinal portion 180. The inclined portion 178 is inclined at an angle between both the first and the second longitudinal parts 176, 180. The first and the second longitudinal parts 176, 180 have upper ends located at planes of different elevation. The first longitudinal part 176 continues to extend longitudinally partway inside the diffuser conduits 150, 152. The inclined portion 178 may be parallel to the incline angle of either of the first and second separator plates 170, 172. In another embodiment shown in FIG. 7, taken along a sectional plane CC′ of FIG. 6, the flow guiding vanes 174 have one longitudinal part 182 and a slant part 184. The longitudinal part 182 and the slant part 184 are inclined at an angle to each other. The longitudinal part 182 extend partially inside the diffuser conduits 150, 152. The slant part 184 may be parallel to either of the first and second separator plates 170, 172.
With continued reference to FIGS. 3-5, the flow guiding vanes 174 are coupled to a first pair of horizontal plates 186 and a second pair of horizontal plates 188. Specifically, each of the second longitudinal portions 180 of the flow guiding vanes 174 can be coupled to the first and second pair of horizontal plates 186, 188. In another embodiment, as shown in FIG. 7, each of the slant parts 184 of the flow guiding vanes 170 can be coupled to the pair of horizontal plates 186, 188. The first and second pair of horizontal plates 186, 188 are fixedly coupled to a third inner surface 190 and a fourth inner surface 192 of the flow mixing device 118 and extend towards the separator plate assembly 168. The pair of first and second horizontal plates 186, 188 may provide structural rigidity to the flow guiding vanes 174 and help in avoiding any break off or vibration due to flow of exhaust streams 106. Also, the pair of first and second horizontal plates 186, 188 safeguard flow guiding vanes 174 against being cantilevered by their own weight.
In an embodiment as shown in FIG. 6 and FIG. 7, the flow mixing device 118 additionally may include a perforated plate 194 coupled to the outlet plate 162. As shown in FIG. 6, the perforated plate 194 can include one or more flanges 195 that may couple with the outlet plate 162. In an embodiment, the outlet plate 162, and the perforated plate 194 including the flanges 195 may be manufactured from the same sheet metal part.
The perforated plate 194 is further supported on the outlet plate 162 through a cross member 196. The cross member 196 is a structural element that may include two sheet metal bars joined together in an intersecting manner so as to form a support structure for the perforated plate 194. The perforated plate 194 is coupled to the cross member 196 along the length of the two bars. Also, the perforated plate 194 is located around the center of the second end 142 leaving an open space 198 between the periphery of the perforated plate 194 and the outlet plate 162. Further, in an embodiment, the perforations provided in the perforated plate 194 may be uniform in size. Alternatively, the perforations may vary in size and in proportion to the distance from a center of perforated plate 194.

INDUSTRIAL APPLICABILITY

The flow mixing device 118, explained in the present disclosure, minimizes a backpressure while mixing two or more exhaust streams and output a single exhaust stream. Further, the flow mixing device 118 helps in maintaining a desired flow profile of the exhaust stream prior to injection of the reductant. The flow mixing device 118 helps in providing the exhaust stream a low velocity profile at center which allows the reductant to be injected substantially symmetrically and uniformly.
In order to explain functioning of the flow mixing device 118, reference will now be made to FIGS. 1-5. The flow mixing device 118 receives the exhaust stream 106 flowing through the first exhaust conduit 110 at the first inlet passage 158 defined by the first diffuser conduit 150. Similarly, the exhaust stream 106 flowing through the second exhaust conduit 112 is received at the second inlet passage 160 defined by the second diffuser conduit 152.
After passing through the first and the second diffuser conduits 150, 152, the exhaust stream 106 from the first and the second exhaust conduits 110, 112 flow across the flow guiding vanes 174. As the flow guiding vanes 174 have one or more bends, the exhaust stream 106 gradually change flow directions along the bends. Thereafter, exhaust streams 106 from the first and second. exhaust conduits 110, 112 mix with each other to form the combined exhaust stream 120. Uniform flow profile of the combined exhaust stream 120 is provided by the separator plate assembly 168 and the flow guiding vanes 174 effecting gradual and uniform mixing of the exhaust streams 106 from the two exhaust conduits 110, 112.
In another embodiment of the current disclosure as shown in FIGS. 6-7, the flow mixing device 118 additionally includes a perforated plate 194 coupled to the outlet plate 162 of the body 138 and further supported through the cross member 196. After the exhaust streams 106 from the first and second exhaust conduits 110, 112 pass through flow guiding vanes 170, the combined exhaust stream 120 pass through the perforated plate 194. The perforated plate 194 has perforated structure which may cause the combined exhaust stream 120 to have a further uniform flow profile. Also, as shown in the FIGS. 6 and 7, the perforated plate 194 is located around the center of the second end 142 leaving open space 198 between the periphery of the perforated plate 194 and the outlet plate 162. Thus, larger volume of the combined exhaust stream 120 flows from the periphery as compared to that flowing through the perforated plate 194. As larger volume of the combined exhaust stream 120 flows through the open space 198, around the peripheral region of the perforated plate 194, the velocity flow profile at the circumferential regions is higher as compared to the velocity flow profile at the center of the combined exhaust stream 120 exiting from the outlet passage 163. Such flow profile is desired to achieve a more uniform mixing of reductant 128 with the combined exhaust stream 120.
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.

Claims

What is claimed is:

1. A flow mixing device for an exhaust after-treatment system of an internal combustion engine, the flow mixing device comprising:

a body having a first end and a second end disposed distally away from one another, the body configured to define an interior volume therein;

an inlet plate coupled to the first end of the body, the inlet plate having at least two inlet orifices formed therein in fluid communication with the interior volume;

an outlet plate coupled to the second end of the body, the outlet plate defining an outlet passage in fluid communication with the interior volume;

a diffuser conduit releasably coupled to the inlet plate and disposed around each of the inlet orifices, the diffuser conduits configured to define an inlet passage disposed in fluid communication with the inlet orifices of the inlet plate and the interior volume of the body;

a separator plate assembly comprising a first separator plate and a second separator plate, the first and second separator plates coupled at an angle relative to each other at the first end of the body and converging towards a longitudinal plane defined between the pair of diffuser conduits; and

a plurality of flow guiding vanes coupled to the body proximal to the second end and configured to extend at least partially within the diffuser conduits.

2. The flow mixing device of claim 1 further including a perforated plate coupled to the outlet plate of the body, the perforated plate configured to allow a substantially uniform flow profile of a fluid exiting the body.