US20140318111A1

US20140318111A1 - Decomposition tube for an engine

Info

Publication number: US20140318111A1
Application number: US13/871,382
Authority: US
Inventors: Ronald Zachary Richey; Julian JUSTIN
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2013-04-26
Filing date: 2013-04-26
Publication date: 2014-10-30

Abstract

An exhaust conduit for a diesel engine is disclosed. The exhaust conduit may include a tubular body having a cylindrical side wall, and a plurality of plates arranged substantially parallel with one another and disposed within the tubular body. The exhaust conduit may further include a boss protruding from the side wall of the tubular body. The boss may include an opening configured to receive an injector device, wherein the plates and the boss are aligned such that a line extending along a central axis of the opening is substantially perpendicular to the plates.

Description

TECHNICAL FIELD

The present disclosure relates generally to an engine exhaust component, and, more particularly, to a decomposition tube for an engine exhaust system.

BACKGROUND

In internal combustion engines, including diesel engines, a fuel and air mixture is combusted in combustion cylinders. Reciprocating pistons in the combustion cylinders are moved between top dead center and bottom dead center positions by a crankshaft positioned below the cylinders in a crankcase. As each piston moves toward its top dead center position, it compresses the fuel and air mixture in the combustion chamber above the piston. The compressed mixture combusts and expands, driving the piston downward toward its bottom dead center position.
The exhaust gases of the engine are typically released from the combustion cylinders of the engine into the atmosphere through an exhaust system. These exhaust gases, however, may contain emissions, which may be composed of gaseous compounds, including NO, NO₂, CO, CO₂, unburned hydrocarbons CxHy, water vapor, O₂, and solid carbon particulate matter also known as soot. Due to increased attention on the environment, exhaust emission standards have become more stringent, and the amount of gaseous compounds emitted to the atmosphere from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
A method implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment includes removing the particulate matter from the exhaust flow of an engine with a particulate filter device. The particulate filter is a device designed to collect particulate matter from the exhaust flow of the engine. Another method that has been implemented by engine manufacturers to comply with the regulation of engine emissions has been to employ various catalysts to purify the exhaust gas from the engine before emitting the gas to the atmosphere. Most catalysts either employ conventional lean NOx mechanisms or on-board ammonia production by urea hydrolysis, known as urea selective catalytic reduction. These mechanisms seek to convert harmful NOx into innocuous constituents such as N₂, CO₂, and water, and to neutralize or eliminate NH₃attributed to the urea selective catalytic reduction aftertreatment system.
While a particulate filter can be an effective component for removing particulate matter from the exhaust flow, use of the particulate filter for extended periods of time may result in the accumulation of particulate matter within the filter, which may damage the filter and/or reduce engine performance. One method of restoring the performance of a particulate filter includes regeneration. Regeneration of a particulate filter is accomplished by increasing the temperature of the filter and the trapped particulate matter above the combustion temperature of the particulate matter, thereby burning away the collected particulate matter. This increase in temperature may be accomplished by heating the exhaust gases upstream from the particulate filter with the use of a burner that creates a flame within the exhaust conduit leading to the particulate filter. The burner may include a fuel injector for creating the flame, and the burner may be supplied with air from the intake system of the engine.
In some instances, diesel fuel has been injected into the flow of exhaust via a hole formed directly in the exhaust pipe. A boss having a threaded interior is welded over the hole, such that an injector connected to a fuel line may be attached to the boss. Such direct injection of diesel fuel into the flow of exhaust, however, may not be able to achieve sufficiently high temperatures to burn off particulate matter collected in the particulate filter for effective active regeneration of the filter.
The disclosed decomposition tube is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, an exhaust conduit for a diesel engine is disclosed. The exhaust conduit may include a tubular body having a cylindrical side wall, and a plurality of plates arranged substantially parallel with one another and disposed within the tubular body. The exhaust conduit may further include a boss protruding from the side wall of the tubular body. The boss may include an opening configured to receive an injector device, wherein the plates and the boss are aligned such that a line extending along a central axis of the opening is substantially perpendicular to the plates.
In another aspect, an exhaust conduit for a diesel engine is disclosed. The exhaust conduit may include a tubular body having an inlet with a first diameter, an outlet with a second diameter greater than the first diameter, and a cylindrical side wall. The exhaust conduit may also include a plurality of plates arranged substantially parallel with one another and disposed within the tubular body, and a boss protruding from the side wall of the tubular body. The boss may include an opening configured to receive an injector device, wherein the plates and the boss are fixed to the tubular body and aligned such that a line extending along a central axis of the opening is substantially perpendicular to the plates.
In yet another aspect, an exhaust system for a diesel engine is disclosed. The exhaust system may include a fuel injector and a decomposition tube connected to the fuel injector, wherein the decomposition tube is disposed upstream of a diesel oxidation catalyst and a diesel particulate filter. The decomposition tube may include a tubular body having a cylindrical side wall, and a plurality of plates arranged substantially parallel with one another and disposed within the tubular body. The decomposition tube may further include a boss protruding from the side wall of the tubular body. The boss may include an opening configured to receive the fuel injector, wherein the plates and the boss are aligned such that a line extending along a central axis of the opening is substantially perpendicular to the plates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an engine exhaust system according to an exemplary disclosed embodiment;

FIG. 2 is an isometric view of an exemplary decomposition tube;

FIG. 3 is a view along line 3-3 of the decomposition tube shown in FIG. 2;

FIG. 4 is a cross-sectional view along line 4-4 of the decomposition tube shown in FIG. 3; and

FIG. 5 is an alternative view of the decomposition tube shown in FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates a power source 10, which may include an engine, for example, a diesel engine. An exhaust manifold 12 may connect an exhaust flow of power source 10 to a common inlet 14, which leads to an exhaust passage 16, also referred to herein as an exhaust pipe 16. A decomposition tube 20 may be disposed in a section of the exhaust pipe 16 downstream of the common inlet 14. The decomposition tube 20 may also be referred to herein as a tube, a hydrocarbon decomposition tube, an exhaust conduit, or the like. As shown in FIG. 1, an injector device 26, such as a fuel injector, may be connected to the decomposition tube 20.
Downstream of the decomposition tube 20, an oxidation catalyst 18 may also be disposed along the exhaust pipe 16. The oxidation catalyst 18 may be a device with a porous ceramic honeycomb-like or metal mesh structure coated with a material that catalyzes a chemical reaction to reduce pollution. The oxidation catalyst 18 may oxidize any NO constituents into NO₂, which may be more susceptible to catalytic treatment. A particulate filter 25 may be disposed along the exhaust pipe 16 downstream of the oxidation catalyst 18. In one example, the particulate filter 25 may be disposed about 2.54 cm (about 1 inch) downstream of the oxidation catalyst 18. Where the power source 10 is a diesel engine, the particulate filter 25 may be a diesel particulate filter (“DPF”), and the oxidation catalyst may be a diesel oxidation catalyst (“DOC”). The particulate filter 25, which may be configured to remove soot from the flow of exhaust emissions, can be any type of particulate filter, including a catalyzed or un-catalyzed DPF. An exhaust passage outlet 22 may be located downstream of the particulate filter 25, from which a flow of exhaust 24 may exit the exhaust system and enter the atmosphere.
FIG. 2 shows an isometric view of the decomposition tube 20 not installed in an exhaust system. The decomposition tube 20 may include a hollow inner tubular body 29 having a side wall 30, a hollow outer tubular body 33 having a side wall 31, and a boss 28 protruding from the side wall 30. The inner tubular body 29 may be referred to as a first tubular body, the outer tubular body 33 may be referred to as a second tubular body, and the inner and outer tubular bodies 29, 33 may be collectively referred to as a single tubular body. As shown in FIG. 2, the side walls 30, 31 may be cylindrical side walls 30, 31. The boss 28 may also be referred to herein as a projecting member, a mounting member, a port, or the like. The boss 28 may include an opening 36 extending through the side wall 30, and a flange 38 surrounding the opening 36. In some instances, an internal wall of the boss may include threads (not shown) configured to receive a threaded portion of the injector device 26. Other means of connecting the injector device 26 to the boss 28 may also be employed. Additionally, the opening 36 of the boss 28 may be sized to fit a variety of injector devices.
The decomposition tube 20 may include an inlet 32 at one end of the tube 20 and an outlet 34 at another end of the tube 20. The inlet 32 may be referred to as a first end or an upstream end, and the outlet 34 may be referred to as a second end or a downstream end. Disposed within the decomposition tube 20 between the inlet 32 and the outlet 34 may be a plurality of plates, including plate 40, wherein each plate may include one or more fins 42 projecting from a face of the plate. The plurality of plates is described in more detail with reference to FIGS. 3 and 4.
FIG. 3 illustrates a view along line 3-3 of the decomposition tube 20 show in FIG. 2. Specifically, FIG. 3 is a view looking into the inlet 32 of the decomposition tube 20. The decomposition tube 20 shown in FIG. 3 includes six plates 40, 44, 46, 48, 50, 52. However, in other embodiments, additional or fewer plates may be installed within the tube 20. The plates 40, 44, 46, 48, 50, 52 may be referred to individually as first, second, third, fourth, fifth, and sixth plates, respectively. The plates 40, 44, 46, 48, 50, 52 may also be referred to collectively as a mixer or a mixing device. As shown in FIG. 3, the plates 40, 44, 46, 48, 50, 52 may be oriented substantially parallel to each other within the decomposition tube 20. In some instances, the plates 40, 44, 46, 48, 50, 52 may also be evenly spaced from each other.
The phrase “substantially parallel,” as it refers to the relationship between the plates 40, 44, 46, 48, 50, 52, includes instances in which the plates 40, 44, 46, 48, 50, 52 are parallel to each other such that an angle between the plates 40, 44, 46, 48, 50, 52 is 0°. The phrase “substantially parallel” also includes instances in which the plates 40, 44, 46, 48, 50, 52 are arranged at angles that vary slightly from 0° with respect to each other. For example, if two or more of the plates 40, 44, 46, 48, 50, 52 are arranged at an angle of about 5° or less with respect to each other, the two or more plates 40, 44, 46, 48, 50, 52 may be referred to as being “substantially parallel” to each other.
The inner tubular body 29 of the decomposition tube 20 may have a first or inner diameter defined by an outermost wall of the side wall 30. The outer tubular body 33 of the decomposition tube may have a second or outer diameter defined by an outermost wall of the side wall 31, wherein the inner diameter is smaller than the outer diameter. As an example, the outer diameter may be about 10.4 cm (about 4.12 inches) or about 13.0 cm (about 5.12 inches), or any value therebetween. The inner diameter 54 may be about 10.2 cm (about 4.0 inches) or about 12.7 cm (about 5.0 inches), or any value therebetween. Additionally, the thickness of the side walls 30, 31 may be about 1.5 mm (about 0.06 inches). The inner diameter and/or the outer diameter may be sized so that the exhaust pipe 16 fits within the tube 20 at one or both of the inlet 32 and the outlet 34. As such, a diameter of the exhaust pipe 16 may vary along a length of the exhaust pipe 16, such that the exhaust pipe diameter is slightly smaller than the diameter at a location where the exhaust pipe 16 connects with the inlet 32, and slightly smaller than the diameter at a location where the exhaust pipe 16 connects with the outlet 34. Alternatively, the inner diameter of the inner tubular body 29 may be sized such that the inlet 32 of the tube 20 fits within the exhaust pipe 16. While the exemplary decomposition tube 20 described herein includes an inner tubular body 29 having one diameter and an outer tubular body 33 having another diameter of different value, in other instances a decomposition tube may have the same diameter at the inlet and outlet of the tube.
As shown in FIG. 3, the boss 28 may be aligned with the plates 40, 44, 46, 48, 50, 52 with reference to a centerline 58 extending along a central axis of the boss 28. In particular, the centerline 58 may be substantially parallel to a wall of the boss, and extend along a central axis of the opening 36 of the boss 28. The boss 28 may be referred to as being “aligned” with the plates 40, 44, 46, 48, 50, 52 based on the centerline 58 being substantially perpendicular to the plates 40, 44, 46, 48, 50, 52, as illustrated by FIGS. 3 and 4. The phrase “substantially perpendicular,” as it refers to the relationship between the centerline 58 and the plates 40, 44, 46, 48, 50, 52, includes instances in which the plates 40, 44, 46, 48, 50, 52 are either precisely perpendicular to the centerline 58 or arranged at an angle slightly less than or greater than 90° with respect to the centerline 58. For example, if the plates 40, 44, 46, 48, 50, 52 are arranged at an angle between about 80° and 100° with respect to the centerline 58, the plates 40, 44, 46, 48, 50, 52 may still be referred to as being “substantially perpendicular” to the centerline 58. As shown in FIGS. 3 and 4, the plates 40, 44, 46, 48, 50, 51 may be disposed in order with plate 40 being located furthest from the boss 28 and plate 52 being located closest to the boss 28.
FIG. 4 illustrates a cross-sectional view along line 4-4 of the decomposition tube 20 show in FIG. 3. A variety of techniques may be used to connect the exhaust pipe 16 to the decomposition tube 20, such as butt welding the exhaust pipe 16 to the inner tubular body 29 and the outer tubular body 33, The exhaust pipe 16 may be sealably connected to the tube 20 such that the inlet 32 and outlet 34 are circumferentially sealed to the exhaust pipe 16.
As illustrated in FIG. 4, each of the fins 42 may be a raised portion of a corresponding plate 40, 44, 46, 48, 50, 52, whereby providing the fins 42 creates apertures 55 in the corresponding plate 40, 44, 46, 48, 50, 52. For each fin 42 of a given plate 40, 44, 46, 48, 50, 52, there may be a corresponding aperture 55, and there may be multiple fins 42, and therefore multiple apertures 55, on each plate 40, 44, 46, 48, 50, 52. The fins 42 may be said to extend or project in a direction towards the opening 36 of the boss 28, as shown in FIG. 4. Various plates, such as plates 40, 44, 46, 48, 50, may also include extended portions 57 of the fins 42 adjacent to the outlet 34 of the decomposition tube 20. For a given plate, some of the extended portions 57 may be said to extend or project in a direction towards the opening 36 of the boss 28, while other extended portions 57 may said to extend or project in a direction opposite the opening 36.
Consistent with FIG. 3, the boss 28 may be aligned with the plates 40, 44, 46, 48, 50, 52 as the centerline 58 extending along the central axis of the opening 36 of the boss 28 is substantially perpendicular to the plates 40, 44, 46, 48, 50, 52. Additionally, the centerline 58 may be spaced a distance 65 from a plate edge reference line 59 extending from a first, or upstream, edge of the plates 46, 48, 50, 52. The plate edge reference line 59 may also be spaced a distance 67 from an inner tube edge reference line 61 extending from an edge of the inner tubular body 29. In one instance, the distance 65 may be about 25.40 mm (about 1.00 inch) and the distance 67 may be about 21.10 mm (about 0.83 inches). In other instances, the distance 67 may vary while the distance 65 may remain about 25.40 mm (about 1.00 inch). Although FIG. 4 shows the flange 38 of the boss 28 extending to the inlet 32, the flange 38 may not extend all the way to the inlet 32, or the flange 38 may extend beyond the inlet 32. In other examples, the flange 38 may not be included as part of the boss 28.
FIG. 5 is an alternative view of the decomposition tube 20 shown in FIG. 2. FIG. 5 may be referred to as a view looking along the centerline 58 through the opening 36 of the boss 38. Consistent with FIG. 4, a fin 42 of plate 40 may be visible through the opening 36, and a portion of plate 44 may also be visible. Because, as shown in FIG. 4, plates 46, 48, 50, 52 may not extend as close to the inlet 32 as plates 42, 44, plates 46, 48, 50, 52 may not be visible through the opening 36 of the boss 28.
The decomposition tube 20, including the inner tubular body 29, the outer tubular body 33, the boss 28, and/or the plates 40, 44, 46, 48, 50, 52, may be constructed of various materials, including any type of metal. As an example, the entire tube 20 may be constructed of steel, such as low carbon stainless steel.

INDUSTRIAL APPLICABILITY

The disclosed decomposition tube 20 may have a variety of industrial applications and be used in various areas, such as the areas of emissions regulation and aftertreatment. The decomposition tube 20 may be installed in an exhaust system of a diesel engine, such an automotive, marine, or locomotive diesel engine. The decomposition tube 20 may also be used in a variety of stationary power applications.
Operation of the decomposition tube 20 when the tube 20 is installed in a section of an exhaust system will now be described. Exhaust gas generated during operation of the power system 10, such as a diesel engine, flows through the exhaust gas manifold 12 and into the common outlet 14. From the common outlet 14, the exhaust gas flows through the exhaust pipe 16 and into the decomposition tube 20. As the exhaust gas continually flows through the decomposition tube 20, the injector device 26 connected to the tube 20 may inject fuel into exhaust gas flowing through the tube 20. Due to the alignment of the boss opening 36 and the plates 40, 44, 46, 48, 50, 52, the fuel, which may be raw diesel fuel, may exit from a nozzle of the injector device 26 in a direction substantially perpendicular to the plates 40, 44, 46, 48, 50, 52. Fuel injected into the tube 20 may be atomized and mixed with the exhaust gas within the decomposition tube 20.
Based on the position of the boss 28 with respect to the plates 40, 44, 46, 48, 50, 52, the fuel injected by the injector device 26 may impinge on the plates 40, 44, 46, 48, 50, 52. The plates 40, 44, 46, 48, 50, 52, which together constitute a mixer, mix the injected fuel with the exhaust gas, while the fins 42, apertures 55, and/or extended portions 57 may impart turbulence into the mixture as it flows through the tube 20. Due to the turbulence in the flow of the exhaust gas/fuel mixture, as well as the surface area of the plates 40, 44, 46, 48, 50, 52, an amount of liquid fuel may be evaporated prior to exiting the decomposition tube 20.
After exiting the tube 20, the exhaust flow containing a mixture of exhaust gases and fuel passes through the oxidation catalyst 18, which may release an amount of heat. The release of heat from the catalyst 18 may increase the temperature of the downstream particulate filter 25 as the exhaust mixture flows from the oxidation catalyst 18 to the particulate filter 25. Due to the increased temperature of the exhaust flowing through the particulate filter 25, an amount of soot trapped within the filter 25 may be burned off. Burning off soot from the particulate filter 25 in this manner may be referred to as active regeneration of the particulate filter 25. After exiting the particulate filter 25, the flow of exhaust 24 may exit the exhaust system from the exhaust outlet 22.
Employing the decomposition tube 20 described herein, in which the boss opening 36 is aligned with the plates 40, 44, 46, 48, 50, 52 as described, may facilitate effective fuel injection and uniform mixing with a flow of exhaust gas. This, in turn, may release an appropriate amount of heat from the oxidation catalyst 18, increase the temperature of the particulate filter 25, and burn off soot trapped therein. Due to the location of the boss opening 36 (and thus the location of the injector device 26 as the boss opening 36 provides a mounting location for the injector device 26), with respect to the plates 40, 44, 46, 48, 50, 52, pooling of liquid fuel injected into the decomposition tube 20 may be prevented. As described herein, atomized fuel injected into the tube 20 impinges on the plates 40, 44, 46, 48, 50, 52, and an amount of the fuel may evaporate from the surface area of the plates 40, 44, 46, 48, 50, 52. Evaporating liquid fuel before the exhaust mixture reaches the oxidation catalyst 18 can assist engine performance by preventing possible damage from liquid fuel passing through the catalyst 18.
Additionally, because the boss 28 may be fixed in a position on the side wall 30 of the inner tubular body 29, and because the plates 40, 44, 46, 48, 50, 52 may be fixed in a position within the tubular body 29, 33, the alignment between the boss opening 36 and the plates 40, 44, 46, 48, 50, 52 may be constant and fixed. Accordingly, the decomposition tube 20 may be installed in an exhaust system without having to align any part of the tube 20 with any other part of the exhaust system. Regardless of whether the tube 20 is rotated during installation to connect sections of exhaust pipe 16, the alignment between the boss opening 36 and the plates 40, 44, 46, 48, 50, 52 remains fixed.
In addition to providing a fixed alignment between the boss opening 36 and the plates 40, 44, 46, 48, 50, 52, the decomposition tube 20 described herein is a compact part that may be installed between sections of the exhaust pipe 16 by, for instance, welding the tube 20 in place. Furthermore, the tubular body 29, 33 may surround and protect the plates 40, 44, 46, 48, 50, 52 from possible damage during system operation. Moreover, the entire decomposition tube 20 may be made as a single, integral piece, including the plates 40, 44, 46, 48, 50, 52, the tubular body 29, 33, and the boss 28. Therefore, if necessary, the tube 20 may be removed from an exhaust system and quickly replaced with another similar or identical tube 20. As an alternative, one or more of the components of the decomposition tube 20, such as the boss 28, may be provided separately from the tube 20, and may be connected to the tube 20 via a conventional connection method such as welding.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed decomposition tube. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed decomposition tube. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

What is claimed is:

1. An exhaust conduit for a diesel engine, comprising:

a tubular body having a cylindrical side wall;

a plurality of plates arranged substantially parallel with one another and disposed within the tubular body; and

a boss protruding from the side wall of the tubular body, wherein the boss includes an opening configured to receive an injector device,

wherein the plates and the boss are aligned such that a line extending along a central axis of the opening is substantially perpendicular to the plates.

2. The exhaust conduit of claim 1, wherein the line is substantially parallel to a wall of the boss.

3. The exhaust conduit of claim 1, wherein a distance between the central axis of the opening to a first edge of one of the plurality of plates is about 1.00 inch.

4. The exhaust conduit of claim 3, wherein the one of plurality of plates is located closer to the boss than the other plates.

5. The exhaust conduit of claim 1, wherein the tubular body comprises a first tubular body disposed within a second tubular body.

6. The exhaust conduit of claim 1, wherein the tubular body includes a first end and a second end, the first end having a first diameter and the second end haying a second diameter greater than the first diameter.

7. The exhaust conduit of claim 6, wherein the second diameter is about 4.12 inches or about 5.12 inches.

8. The exhaust conduit of claim 6, wherein the first diameter is about 4 inches or about 5 inches.

9. The exhaust conduit of claim 6, wherein the tubular body comprises a first tubular body disposed within a second tubular body, and wherein the first end is part of the first tubular body and the second end is part of the second tubular body.

10. The exhaust conduit of claim 3, wherein a distance between the first edge and an edge of the tubular body is about 0.83 inches.

11. The exhaust conduit of claim 1, wherein the alignment between the plates and the boss is fixed.

12. The exhaust conduit of claim 1, wherein the tubular body, the plurality of plates, and the boss are integral with each other.

13. An exhaust conduit for a diesel engine, comprising:

a tubular body having an inlet with a first diameter, an outlet with a second diameter greater than the first diameter, and a cylindrical side wall;

wherein the plates and the boss are fixed to the tubular body and aligned such that a line extending along a central axis of the opening is substantially perpendicular to the plates.

14. The exhaust conduit of claim 13, wherein a distance between the central axis of the opening to a first edge of one of the plurality of plates is about 1.00 inch.

15. The exhaust conduit of claim 14, wherein a distance between the first edge and an edge of the tubular body is about 0.83 inches.

16. The exhaust conduit of claim 13, wherein the second diameter is between about 4.12 inches and about 5.12 inches.

17. The exhaust conduit of claim 13, wherein the tubular body, the plurality of plates, and the boss are integral with each other.

18. An exhaust system for a diesel engine, comprising:

a fuel injector; and

a decomposition tube connected to the fuel injector, wherein the decomposition tube is disposed upstream of a diesel oxidation catalyst and a diesel particulate filter, and wherein the decomposition tube comprises:

a tubular body having a cylindrical side wall;

a boss protruding from the side wall of the tubular body, wherein the boss includes an opening configured to receive the feel injector,

19. The exhaust system of claim 18, wherein the decomposition tube is configured to evaporate liquid fuel before the liquid fuel reaches the diesel oxidation catalyst.

20. The exhaust system of claim 18, wherein the fuel injector is configured to inject fuel in a direction substantially perpendicular to the plates such that the fuel impinges on the plates.