EXHAUST SYSTEM HAVING REDUCTANT NOZZLE FLOW DIVERTER
An exhaust system for use with an engine is disclosed. The exhaust system may have an exhaust passage with an indentation having an upstream wall and a downstream wall. The exhaust system may also have a nozzle disposed within the downstream wall, and a flow diverter cantilevered from the upstream wall partway into the exhaust passage.
The present disclosure is directed to an exhaust system and, more particularly, to an exhaust system having a reductant nozzle flow diverter.
BACKGROUNDInternal combustion engines, including diesel engines, gasoline engines, gaseous fuel-powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants are composed of gaseous compounds including, among other things, the oxides of nitrogen (NOX). Due to increased awareness of the environment, 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 of engine, size of engine, and/or class of engine.
In order to comply with the regulation of NOX, some engine manufacturers have implemented a strategy called selective catalytic reduction (SCR). SCR is a process where a reductant, most commonly urea ((NH2)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 (NH3), which reacts with NOX in the exhaust gas to form water (H2O) and diatomic nitrogen (N2).
Although reductant injections can successfully reduce NOX, the reductant can also be problematic when utilized under certain conditions. For example, solid urea and urea-byproducts such as cyanuric acid, biuret, melamine, etc., can be deposited near an injection site when exhaust temperatures and velocities are too low. Formation of near-injector deposits can be an irreversible process, causing blockage of the injector and/or restriction on exhaust flow, which can lead to degradation of the NOX conversion process and engine operation.
An exemplary SCR-equipped system for use with a combustion engine is disclosed in US Patent Publication No. 20100107614 of Levin et al. published on May 6, 2010 (the '614 publication). This system includes an injector boss disposed within an exhaust passage at a pipe bend. The injector boss forms a recess in a wall of the passage for mounting an injector that sprays reductant into exhaust gas upstream of a catalytic converter. A gas deflector is positioned upstream of the injector and configured to create a high-pressure zone upstream of the deflector and a low-pressure zone downstream of the deflector surrounding an outlet of the injector. The system also includes a bypass flow passage configured to divert a portion of an exhaust flow from the high-pressure zone, and a collector having openings for allowing the bypassed portion of exhaust to flow into the exhaust gas stream and form a gas shield for the liquid reductant spray.
SUMMARYOne aspect of the present disclosure is directed to an exhaust system. The exhaust system may include an exhaust passage having an indentation with an upstream wall and a downstream wall. The exhaust system may also include a nozzle disposed within the downstream wall, and a flow diverter cantilevered from the upstream wall partway into the exhaust passage.
A second aspect of the present disclosure is directed to another exhaust system. This exhaust system may include an exhaust passage configured to receive exhaust from an engine and having a bend portion with an indentation. The exhaust system may also include a flow diverter located in the bend portion and configured to generate a vortex in the exhaust at the indentation.
A third aspect of the present disclosure is directed to yet another exhaust system. This exhaust system may include an exhaust passage configured to receive exhaust from an engine, and an aftertreatment device located within the exhaust passage. The exhaust system may also include a reductant nozzle located upstream of the aftertreatment device and having a tip mounted generally flush with an interior wall of the exhaust passage. The exhaust system may additionally include a flow diverter located upstream of the reductant nozzle and configured to increase a speed of exhaust impinging upon the tip of the reductant nozzle.
An exemplary exhaust system 10 is shown in
Each of first and second treatment canisters 12, 14 may include an inlet 18, an outlet 20, and at least one treatment device 22 located between inlet 18 and outlet 20. In the embodiment shown in
In one embodiment, exhaust passage 16 may be generally axially-parallel with first and second treatment canisters 12, 14 and connected at opposing ends to an outer cylindrical surface 24, for example to an end cap, of each canister 12, 14 by way of first and second bend portions 26, 28, respectively. First and second bend portions 26, 28, in this embodiment, may be cobra-head type couplings that are capable of bending through an angle of about 90 degrees. First and second bend portions 26, 28 may have generally elliptical openings at cylindrical surfaces 24 and generally circular openings at a central straight portion 30 that extends between first and second bend portions 26, 28. It is contemplated that first and second bend portions 26, 28 may be integral with straight portion 30 or separate components that are joined to straight portion 30, as desired. It is also contemplated that first and second bend portions 26, 28 may embody couplings other than cobra-head types, if desired.
In the disclosed embodiment, first bend portion 26 may be located upstream of second bend portion 28 and configured to receive a nozzle 32. Nozzle 32 may be located at or near an upstream end of straight portion 30 and configured to inject a reductant into the exhaust flowing through exhaust passage 16 and into second treatment canister 14 via second bend portion 28. A gaseous or liquid reductant, most commonly a water/urea solution, ammonia gas, liquefied anhydrous ammonia, ammonium carbonate, an ammine salt solution, or a hydrocarbon such as diesel fuel, may be sprayed or otherwise advanced by nozzle 32 into the exhaust passing through straight portion 30. Straight portion 30 may have a length sufficient to allow the injected reductant time to mix with exhaust and to decompose before entering second treatment canister 14. The length of exhaust passage 16 (i.e., of straight and second bend portions 30, 28) may be based on a flow rate of exhaust passing through exhaust system 10 and/or on a cross-sectional area of straight portion 30. In the example depicted in
As shown in
As shown in
Flow diverter 48 may embody a generally curved protrusion fixedly connected to upstream wall 38 by, for example, welding. Alternatively, flow diverter 48 may be an integral portion of upstream wall 38, if desired. As shown in
As shown in
Double vortex 56 may continue in the length direction of straight portion 30. Specifically, as can be seen in
In addition to the increased velocities at nozzle tip 44 helping to reduce or even eliminate deposit buildup of liquid reductant near nozzle tip 44, the extension of double vortex 56 along the length of straight portion 30 may also enhance mixing of exhaust and reductant within exhaust passage 16. In addition, transient vortex shedding created by double vortex 56 (i.e., the swirling motion along passage 16) may cause reductant injections at nozzle tip 44 to oscillate vertically (up and down) along plane 50 (referring to
The exhaust system of the present disclosure may be applicable to any engine configuration requiring injections of fluid as part of an exhaust treatment process, where depositing and/or mixing of the fluid is an important issue. The disclosed exhaust system may help to reduce or eliminate buildup of the deposits and enhance mixing by generating a double vortex within an exhaust flow at a location of the fluid injection. Operation of exhaust system 10 will now be described.
Referring to
As the exhaust flows into first bend portion 26, the exhaust may approach narrowed flow area 46 and, because of the associated restriction, increase in pressure and velocity. A center portion of this flow may then be obstructed by flow diverter 48 and caused to divert from its original flow path toward the sides of flow diverter 48. This diversion may initiate the swirling motion of double vortex 56 at downstream wall 40. The motion of double vortex 56 may cause high-velocity exhaust to flow past and impinge upon tip 44 of nozzle 32, thereby removing existing and inhibiting future deposits of injected fluid. The swirling exhaust may then continue through first bend portion 26 and into straight portion 30, wherein the swirling motion may generate oscillations in a spray pattern of nozzle 32 and facilitate blending of reductant sprayed by nozzle 32 with exhaust.
The exhaust flow from straight portion 30, now entrained with fluid from nozzle 32, may enter second treatment canister 14 via second bend portion 28 and inlet 18. Within treatment device 22 of second treatment canister 14, the exhaust, in the presence of the injected fluid, may undergo additional treatment processes. In one example the additional treatment processes may include, among other things, a reduction process where NOx in the exhaust flow is reduced to innocuous substances. The exhaust may exit second treatment canister 14 via outlet 20.
It will be apparent to those skilled in the art that various modifications and variations can be made to the exhaust system 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 exhaust system 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.
Claims
1. An exhaust system, comprising:
- an exhaust passage having an indentation with an upstream wall and a downstream wall;
- a nozzle disposed within the downstream wall; and
- a flow diverter cantilevered from the upstream wall partway into the exhaust passage.
2. The exhaust system of claim 1, wherein the flow diverter is tilted relative to the upstream wall by an angle less than about 30 degrees.
3. The exhaust system of claim 1, wherein the flow diverter tapers in width from a base end to a tip end at an angle less than about 20 degrees.
4. The exhaust system of claim 1, wherein a cantilevered length of the flow diverter is about 0.2 to 1.5 times a width of the flow diverter.
5. The exhaust system of claim 1, wherein a width of the flow diverter is about 0.2 to 0.8 times a width of the indentation.
6. The exhaust system of claim 1, wherein a thickness of the flow diverter is about 1 to 2 mM.
7. The exhaust system of claim 1, wherein the flow diverter is curved and has an axis of curvature parallel with a length direction.
8. The exhaust system of claim 1, wherein the indentation is located within a bend portion of the exhaust passage.
9. The exhaust system of claim 8, wherein the indentation restricts exhaust flow through the bend portion.
10. The exhaust system of claim 1, wherein the flow diverter increases near-nozzle exhaust velocities and swirling in a plane generally parallel with the downstream wall.
11. The exhaust system of claim 10, wherein the flow diverter increases near-nozzle exhaust velocities by about 100%.
12. The exhaust system of claim 10, wherein the increased velocities continue in a length direction of the exhaust passage.
13. The exhaust system of claim 12, wherein the increased velocities continue for about ½ of a length of the exhaust passage.
14. The exhaust system of claim 1, wherein the flow diverter causes injections from the nozzle to oscillate relative to a plane of symmetry through the flow diverter.
15. The exhaust system of claim 14, wherein the flow diverter causes the injections to oscillate through a range of about 20-90°.
16. The exhaust system of claim 14, wherein the flow diverter causes the injections to oscillate across an entire diameter of the exhaust passage.
17. The exhaust system of claim 1, wherein the flow diverter reduces reductant deposits at the nozzle by about 50-95%.
18. An exhaust system, comprising:
- an exhaust passage configured to receive exhaust from an engine and having a bend portion with an indentation; and
- a flow diverter located in the bend portion and configured to generate a vortex in the exhaust at the indentation.
19. The exhaust system of claim 18, wherein the flow diverter tapers in width from a base end to a tip end at an angle less than about 20 degrees.
20. The exhaust system of claim 18, wherein a length of the flow diverter is about 0.2 to 1.5 times a width of the flow diverter.
21. The exhaust system of claim 18, wherein the flow diverter is curved and has an axis of curvature parallel with a length direction.
22. The exhaust system of claim 18, wherein the flow diverter extends from the indentation partway through the exhaust passage.
23. The exhaust system of claim 18, wherein the vortex is located within a plane generally perpendicular to a flow direction through the bend portion.
24. The exhaust system of claim 23, wherein the vortex increases near-nozzle exhaust velocities by about 100%.
25. The exhaust system of claim 23, wherein the vortex continues in a length direction of the exhaust passage.
26. The exhaust system of claim 25, wherein the vortex continues for about ½ of a length of the exhaust passage.
27. An exhaust system, comprising:
- an exhaust passage configured to receive exhaust from an engine;
- a treatment device located within the exhaust passage;
- a reductant nozzle located upstream of the aftertreatment device and having a tip mounted generally flush with an interior wall of the exhaust passage; and
- a flow diverter located upstream of the reductant nozzle and configured to increase a speed of exhaust impinging upon the tip of the reductant nozzle.
Type: Application
Filed: Nov 23, 2010
Publication Date: May 24, 2012
Inventor: Haiping HONG (Peoria, IL)
Application Number: 12/952,831
International Classification: F01N 1/00 (20060101);