EXHAUST MIXER ELEMENT AND METHOD FOR MIXING
According to one aspect of the invention, a mixer element to be placed between an internal combustion engine exhaust manifold and catalytic converter is provided. The mixer element includes a tubular conduit that receives an exhaust gas flow from the internal combustion engine, a first mixer configured to induce a first vortex of the exhaust gas flow in a first rotational direction and an injector disposed in the tubular conduit downstream of the first mixer, the injector being configured to inject a diesel emission fluid flow into the exhaust gas flow. The mixer element also includes a second mixer positioned downstream of the injector and a third mixer positioned downstream of the second mixer, the third mixer being configured to induce a second vortex of the exhaust gas flow and the diesel emission fluid mixture in a second rotational direction, opposite of the first rotational direction.
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Exemplary embodiments of the invention are related to internal combustion engines, and more particularly, to exhaust after treatment systems of internal combustion engines.
BACKGROUNDManufacturers of internal combustion engines, more particularly diesel engines, are presented with the challenging task of complying with current and future emission standards for the release of nitrogen oxides, particularly nitrogen monoxide, as well as unburned and partially oxidized hydrocarbons, carbon monoxide, particulate matter, and other pollutants. In order to reduce the pollutant emissions of a diesel engine, an exhaust gas after treatment system is used to reduce pollutants within the exhaust gas flowing from the engine.
Exhaust gas after treatment systems typically include one or more after treatment devices, such as oxidation catalysts, catalytic converters, mixer elements and emissions fluid injectors. Emissions fluid injectors for diesel engines (also called diesel emissions fluid injectors or DEF injectors) may inject a urea or other suitable ammonia based fluid into the exhaust flow to improve the performance of catalytic converters. Further, mixer elements are sometimes used to facilitate urea and exhaust gas mixing to improve catalytic converter operation. As emissions standards increase, improving the mixture of urea and exhaust gas prior to entering the catalytic converter is desired. Exhaust after treatment apparatus designed to improve urea and exhaust gas mixing may have an increased overall length of system, thereby causing packaging issues for today's increasingly complex vehicles.
SUMMARY OF THE INVENTIONIn one exemplary embodiment, a mixer element to be placed between an internal combustion engine exhaust manifold and catalytic converter is provided. The mixer element includes a tubular conduit that receives an exhaust gas flow from the internal combustion engine, a first mixer configured to induce a first vortex of the exhaust gas flow in a first rotational direction and an injector disposed in the tubular conduit downstream of the first mixer, the injector being configured to inject a diesel emission fluid flow into the exhaust gas flow. The mixer element also includes a second mixer positioned downstream of the injector and a third mixer positioned downstream of the second mixer, the third mixer being configured to induce a second vortex of the exhaust gas flow and the diesel emission fluid mixture in a second rotational direction, opposite of the first rotational direction.
In another exemplary embodiment, a method for distributing a urea flow within a mixer element is provided, where the method includes receiving an exhaust gas flow from an internal combustion engine into the mixer element, inducing a first vortex of the exhaust gas flow in a first rotational direction in a first region of the mixer element and injecting a urea fluid into the exhaust gas flow downstream of the first region. The method further includes causing a radial component to the urea fluid and exhaust flow in a second region of the mixer element, wherein the second region is downstream of the first region, and inducing a second vortex of a mixture of the fluid and exhaust gas flow in a second rotational direction opposite of the first rotational direction, wherein the second vortex is formed downstream of the second region.
The above features and advantages, and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
The exhaust after treatment apparatus 110 and fluid supply 125 are operationally coupled to and controlled by engine controller 106. The engine controller 106 collects information regarding the operation of the internal combustion engine 102 from sensors 128a-128n, such as temperature (intake system, exhaust system, engine coolant, ambient, etc.), pressure, exhaust flow rates, NOx concentrations and, as a result, may adjust the amount of fluid injected into mixer element 122. As used herein the term controller refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. As depicted, fluid supply 125 is used in catalytic reduction reactions to reduce pollutants in exhaust gases. Fluid supply 125 may include any suitable fluid that can be mixed with exhaust gas from internal combustion engines for the purpose of emission reduction, such as a urea solution for NOx emission reduction and/or hydrocarbons for diesel particulate filter regeneration. In an exemplary exhaust after treatment apparatus 110, the fluid supply 125 includes a water-based urea solution injected into the exhaust gas 118. The ammonia produced by hydrolysis of the urea reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter 124, thereby reducing exhaust gas emissions of the internal combustion engine 102.
The configuration of fluid injector 214 along with mixers 304, 306 and 308 provide a mixed flow 332 of distributed injected fluid and exhaust gas flowing to catalytic converter 124. The exemplary tubular structure 302 of mixer element 122 has a diameter 336, axis 338 and length 339. The illustrated arrangement of mixer element 122 provides a desired distribution and mixture of injected fluid 318 with exhaust gas flow 118 to enhance operation of catalytic converter 124 while limiting length 339 to address packaging needs. Vortexes 312 and 324 improve mixing by having a twisting effect caused by opposing flow directions 314 and 326, respectively. The twisting effect is obtained by utilizing one mixer that has an opposite orientation relative to a downstream mixer, where the opposing orientations cause opposite swirling vortex flows. The mixers 304, 306 and 308 are placed within the mixer element 122 at selected axial positions along length 339 and may be any suitable mixer geometry or orientation to achieve the desired mixing of injected fluid 318 and exhaust gas flow 118. In an exemplary embodiment, a distance 341 between mixer 304 and fluid injector 214 is about the same as diameter 336. Distance 342 between fluid injector 214 and mixer 306 is determined to optimize break up of injected fluid 318. In addition, distance 344 between mixer 306 and 308 may be up to three times diameter 336. Exemplary distances 344 may include half, one, two and three times diameter 336. Non limiting examples of mixers 304, 306 and 308 include helical mixers, swirl mixers and impingement mixers.
Referring to
Referring to
In an exemplary embodiment of mixer element 400, mixer 404 is a swirl mixer 600 and mixer 406 is an impingement mixer 700. The swirl mixer 404, 600 generates a vortex that enhances fluid 416 droplet break-up in exhaust gas flow 118, entrainment and increases mixing length, thereby improving the mixture with exhaust 118. The impingement mixer 406, 700 generates additional turbulence downstream 340 to enhance distribution of injected fluid 416.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the present application.
Claims
1. A mixer element to be placed between an internal combustion engine exhaust manifold and a catalytic converter, the mixer element comprising:
- a tubular conduit that receives an exhaust gas flow from the internal combustion engine;
- a first mixer configured to induce a first vortex of the exhaust gas flow in a first rotational direction;
- an injector disposed in the tubular conduit downstream of the first mixer, the injector being configured to inject a diesel emission fluid into the exhaust gas flow;
- a second mixer positioned downstream of the injector; and
- a third mixer positioned downstream of the second mixer, the third mixer being configured to induce a second vortex of the exhaust gas flow and the diesel emission fluid mixture in a second rotational direction, opposite of the first rotational direction.
2. The mixer element of claim 1, wherein the second mixer is configured to induce a radial flow of diesel emission fluid.
3. The mixer element of claim 1, wherein the exhaust gas flow and the diesel fluid mixture flow from the third mixer comprises axial and tangential flow components.
4. The mixer element of claim 1, wherein the first mixer comprises a helical mixer and the third mixer comprises a helical mixer.
5. The mixer element of claim 4, wherein the third mixer has a substantially opposite orientation relative to the first mixer.
6. The mixer element of claim 1, wherein the first mixer comprises a helical mixer and the third mixer comprises a swirl mixer.
7. The mixer element of claim 1, wherein the third mixer comprises swirl blades with thru holes to improve a break up of diesel emission fluid droplets.
8. The mixer element of claim 1, wherein the second mixer comprises an impingement mixer.
9. The mixer element of claim 1, wherein the first vortex comprises a first axial flow component that is less than a second axial flow component, wherein the second axial flow component is closer an axis of the tubular than the first axial conduit flow component.
10. The mixer element of claim 1, wherein the diesel emission fluid comprises urea.
11. A method for distributing a urea flow within a mixer element, the method comprising:
- receiving an exhaust gas flow from an internal combustion engine into the mixer element;
- inducing a first vortex of the exhaust gas flow in a first rotational direction in a first region of the mixer element;
- injecting a urea fluid into the exhaust gas flow downstream of the first region;
- causing a radial component to the urea fluid and exhaust gas flow in a second region of the mixer element, wherein the second region is downstream of the first region; and
- inducing a second vortex of the fluid and exhaust gas flow in a second rotational direction opposite of the first rotational direction, wherein the second vortex is formed downstream of the second region.
12. The method of claim 11, wherein inducing the second vortex of the fluid and exhaust gas flow comprises forming axial and tangential flow components.
13. The method of claim 11, wherein inducing the first vortex through a helical mixer.
14. The method of claim 13, wherein forming the second vortex comprises forming the second vortex by one of a helical mixer and a swirl mixer.
15. The method of claim 11, comprising forming a flow tunnel within the first vortex, wherein a magnitude of a first axial component of the first vortex is less than a magnitude of a second axial component of the exhaust gas flow, wherein the second axial component is closer to an axis of the mixer element than the first axial component.
16. The method of claim 11, wherein forming the second vortex comprises breaking up droplets of the mixture by swirl blades.
17. The method of claim 11, wherein causing the radial component to the urea flow comprises flowing the urea flow through an impingement mixer.
18. A mixer element to be placed between an exhaust manifold and catalytic converter, the mixer element comprising:
- a tubular that receives an exhaust gas flow;
- a first mixer configured to form a first vortex of the exhaust gas flow in a first rotational direction;
- an injector disposed on the tubular downstream of the first mixer, the injector being configured to inject a fluid flow into the exhaust gas flow; and
- a second mixer positioned downstream of the injector, the second mixer comprising blades, wherein droplets of the fluid flow impact the blades to form small droplets that are directed by the blades to mix with the exhaust gas flow.
19. The mixer element of claim 18, wherein the first mixer comprises a swirl mixer and the second mixer comprises an impingement mixer.
20. The mixer element of claim 18, wherein the fluid flow comprises diesel emission fluid or hydrocarbons.
Type: Application
Filed: Feb 14, 2011
Publication Date: Aug 16, 2012
Applicant: GM GLOBAL TECHNOLOGY OPERATIONS LLC (Detroit, MI)
Inventors: Jianwen Li (West Bloomfield, MI), Rahul Mital (Rochester Hills, MI), Kimberly O'Kane (Davisburg, MI), Shouxian Ren (Ypsilanti, MI)
Application Number: 13/026,654
International Classification: F01N 3/18 (20060101);