Miniature Regeneration Unit

Abstract

A system for controlling the temperature of an exhaust stream from an engine at a location upstream from an exhaust aftertreatment apparatus includes a main exhaust passageway adapted to receive the exhaust stream from the engine. A side branch is in communication with the main exhaust passageway. A regeneration unit is positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway. An ion sensor is operable to output a signal indicative of the presence of fuel combustion. A controller selectively operates the regeneration unit to increase the exhaust temperature. The controller is operable to control a supply of fuel to the regeneration unit based on the ion sensor signal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 12/430,194, filed on Apr. 27, 2009. This application claims the benefit of U.S. Provisional Application No. 61/433,297 filed on Jan. 17, 2011. The entire disclosures of the above applications are incorporated herein by reference.

FIELD

The present disclosure generally relates to a system for treating exhaust gases. More particularly, a miniature regeneration unit for increasing an exhaust gas temperature is discussed.

BACKGROUND

In an attempt to reduce the quantity of NO_x and particulate matter emitted to the atmosphere during internal combustion engine operation, a number of exhaust aftertreatment devices have been developed. A need for exhaust aftertreatment systems particularly arises when diesel combustion processes are implemented. Typical aftertreatment systems for diesel engine exhaust may include one or more of a diesel particulate filter (DPF), a selective catalytic reduction (SCR) system, a hydrocarbon (HC) injector, and a diesel oxidation catalyst (DOC).

During engine operation, the DPF traps soot emitted by the engine and reduces the emission of particulate matter (PM). Over time, the DPF becomes loaded and begins to clog. Periodic regeneration or oxidation of the trapped soot in the DPF is required for proper operation. To regenerate the DPF, relatively high exhaust temperatures in combination with an ample amount of oxygen in the exhaust stream are needed to oxidize the soot trapped in the filter.

The DOC is typically used to generate heat to regenerate the soot loaded DPF. When hydrocarbons (HC) are sprayed over the DOC at or above a specific light-off temperature, the HC will oxidize. This reaction is highly exothermic and the exhaust gases are heated during light-off. The heated exhaust gases are used to regenerate the DPF.

Under many engine operating conditions, however, the exhaust gas is not hot enough to achieve a DOC light-off temperature of approximately 300° C. As such, DPF regeneration does not passively occur. Furthermore, NO_x adsorbers and selective catalytic reduction systems typically require a minimum exhaust temperature to properly operate.

A burner may be provided to heat the exhaust stream upstream of the various aftertreatment devices. Known burners have successfully increased the exhaust temperature of internal combustion engines for automotive use. Some Original Equipment Manufacturers have resisted implementation of prior burners due to their size and cost. Furthermore, other applications including diesel locomotives, stationary power plants, marine vessels and others may be equipped with relatively large diesel compression engines. The exhaust mass flow rate from the larger engines may be more than ten times the maximum flow rate typically provided to the burner. While it may be possible to increase the size of the burner to account for the increased exhaust mass flow rate, the cost, weight and packaging concerns associated with this solution may be unacceptable. Therefore, a need may exist in the art for a miniature regeneration unit to increase the temperature of the exhaust output from an engine while minimally affecting the cost, weight, size and performance of the exhaust system. It may also be desirable to minimally affect the pressure drop and/or back pressure associated with the use of a burner.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A system for controlling the temperature of an exhaust stream from an engine at a location upstream from an exhaust aftertreatment apparatus includes a main exhaust passageway adapted to receive the exhaust stream from the engine. A side branch is in communication with the main exhaust passageway. A regeneration unit is positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway. An ion sensor is operable to output a signal indicative of the presence of fuel combustion. A controller selectively operates the regeneration unit to increase the exhaust temperature. The controller is operable to control a supply of fuel to the regeneration unit based on the ion sensor signal.

A system is provided to control the temperature of an exhaust stream from an engine at a location upstream from an exhaust aftertreatment apparatus. The system includes a main exhaust passageway adapted to receive the exhaust stream from the engine. A blind side branch is in communication with the main exhaust passageway. A regeneration unit is positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway. The regeneration unit includes a housing positioned within and spaced apart from a sidewall of the side branch, a nozzle for injecting the fuel into a chamber defined by the housing, and an igniter to initiate combustion of the fuel within the housing. A controller selectively operates the regeneration unit to increase the exhaust temperature.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a schematic depicting a system for controlling the temperature of an exhaust from an engine;

FIG. 2 is a sectional side view of a portion of the exhaust aftertreatment system depicted in FIG. 1 including a miniature regeneration unit;

FIG. 3 is a cross-sectional view of an alternate regeneration unit;

FIG. 4 is a cross-sectional view of an alternate regeneration unit;

FIG. 5 is a cross-sectional view of an engine aftertreatment system including a flow diverter;

FIG. 6 is a perspective view of the aftertreatment system including the flow diverter;

FIG. 7 is a partial perspective view of a portion of another alternate regeneration unit;

FIG. 8 is a cross-sectional view of another alternate regeneration unit;

FIGS. 9-13 are perspective views depicting alternate inlet tube portions of the regeneration unit; and

FIG. 14 is a sectional view depicting another alternate exhaust aftertreatment system.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

FIG. 1 depicts an exhaust gas aftertreatment system 10 for treating the exhaust output by an exemplary engine 12 to a main exhaust passageway 14. An intake passage 16 is coupled to engine 12 to provide combustion air thereto. A turbocharger 18 includes a driven member (not shown) positioned in an exhaust stream. During engine operation, the exhaust stream causes the driven member to rotate and provide compressed air to intake passage 16 prior to entry into engine 12.

Exhaust aftertreatment system 10 also includes a miniature regeneration unit 26 positioned downstream from turbocharger 18 and upstream from a number of exhaust aftertreatment devices. In the exemplary aftertreatment system depicted in FIG. 1, the aftertreatment devices include a hydrocarbon injector 28, a diesel oxidation catalyst 30 and a diesel particulate filter 32.

Regeneration unit 26 is positioned within a side branch portion 34 of system 10 in communication with main exhaust passageway 14. Regeneration unit 26 may be used to heat the exhaust passing through passageway 14 to an elevated temperature that will enhance the efficiency of DOC 30 and allow regeneration of DPF 32.

Regeneration unit 26 may include one or more injectors 36 for injecting a suitable fuel and an oxygenator. The fuel may include hydrogen or a hydrocarbon. Injector 36 may be structured as a combined injector that injects both the fuel and oxygenator, as shown in FIG. 1, or may include separate injectors for the fuel and the oxygenator (FIG. 11). A control module 38 is provided to monitor and control the flows through the injector 36 and the ignition of fuel by a first igniter 42 using any suitable processor(s), sensors, flow control valves, electric coils, etc.

Regeneration unit 26 includes a housing 50 constructed as a multi-piece assembly of fabricated metal components. Housing 50 includes an inlet tube 52, a cylindrically-shaped body 54, and an outlet tube 56. An inlet header 58 is fixed to inlet tube 52. Inlet header 58 is fixed to side branch portion 34 and encloses one of its ends. Other single or multi-piece inlet assemblies are also contemplated as being within the scope of the present disclosure. An annular volume 62 exists in a space between an inner surface 64 of side branch portion 34 and an outer surface of housing 50.

An injector mount 65 is fixed to inlet tube 52 and/or inlet header 58 to provide an attachment mechanism for injector 36. A nozzle portion 66 of injector 36 extends into inlet tube 52 such that atomized fuel may be injected within a primary combustion chamber 68 at least partially defined by an inner cylindrical surface 70 of body 54. Injector 36 includes a fuel inlet 72 and an air inlet 74. Fuel inlet 72 is in communication with a fuel delivery system 76 including a fuel tank 78, a fuel filter 80, a fuel pump 82 and a fuel block 84 interconnected by a fuel line 86. Operation of the components of fuel delivery system 76 selectively provides hydrocarbon to injector 36.

A secondary air system 90 includes a secondary air filter 92 and a MAF sensor 94. A compressor 96 is in receipt of air that is passed through secondary air filter 92 and MAF sensor 94. Compressor 96 may include a portion of a supercharger, a turbocharger or a stand-alone electric compressor. Output from compressor 96 is provided to air inlet 74. When exhaust heating is desired, fuel is injected via fuel inlet 72 and the oxygenator is provided via air inlet 74 to inject a stream of atomized fuel. First igniter 42 is mounted to side branch portion 34 downstream of inlet header 58 and is operable to combust the fuel provided by injector 36 within primary combustion chamber 68.

Side branch portion 34 intersects exhaust passageway 14 at an angle A of substantially 30 degrees. The flame produced by regeneration unit 26 extends into exhaust passageway 14 at substantially the same angle.

An elongated aperture 110 extends through a pipe 112 defining main exhaust passageway 14. A portion of body 54 and outlet tube 56 are positioned within exhaust passageway 14. Exhaust provided from engine 12 impinges on housing 50 and cools it during operation of regeneration unit 26. Furthermore, because housing 50 minimally intrudes within passageway 14, exhaust back pressure is also minimally increased. It should also be appreciated that side branch portion 34 and injector 36 minimally radially outwardly extend from pipe 112. Such an arrangement allows an Original Equipment Manufacturer to more easily package the miniature regeneration unit on the vehicle.

In the present aftertreatment system, first igniter 42 also includes an ion sensor 44 coupled to a coil 46. Ion sensor 44 may be in the form of an electrode positioned within combustion chamber 68. A voltage may be applied to the ion sensor to create an electric field from the sensor to a ground such as housing 50. When voltage is applied, an electric field radiates from the sensor to the ground. If free ions are present in the field, a small ion current may flow. The magnitude of the ion current provides an indication of the density of the ions. Control module 38 detects and receives signals from ion sensor 44 to determine the presence or absence of a flame. Ion sensor 44 may also determine if igniter 42 is fouled.

Fouling may occur through deposition of soot, oil or other contaminants. When igniter 42 is fouled, proper combustion may not occur. Control module 38 is operable to supply and discontinue the supply of fuel to fuel inlet 72, air to air inlet 74 and electrical energy to igniter 42. Prior to initiating the supply of fuel and air to injector 36, control module 38 determines whether igniter 42 has been fouled via the signal provided by ion sensor 44. If the igniter is determined to be ready for operation, control module 38 may account for a number of engine and vehicle operating conditions such as engine speed, ambient temperature, vehicle speed, engine coolant temperature, oxygen content, mass air flow, pressure differential across diesel particulate filter 32, and any number of other vehicle parameters. If control module 38 determines that an increase in exhaust gas temperature is desired, fuel and secondary air are provided to injector 36. Coil 46 supplies electrical energy to igniter 42 to initiate combustion within primary combustion chamber 68.

Control module 38 may also evaluate a number of other parameters including presence of combustion and temperature of the exhaust gas within passageway 14 at a location downstream from regeneration unit 26 to determine when to cease the supply of fuel and air to injector 36. For example, control module 38 may receive signals from one or more temperature sensors located within regeneration unit 26, side branch portion 34 or within main passageway 14 to perform a closed loop control by operating regeneration unit 26 to maintain a desired temperature at a particular location. If combustion unexpectedly extinguishes, control module 38 ceases the supply of fuel. Other control schemes are also within the scope of the present disclosure.

FIG. 3 depicts an alternate regeneration unit 26a coupled to side branch portion 34. Regeneration unit 26a is substantially similar to regeneration unit 26 except that the reduced or necked-down outlet tube portion of housing 50 has been removed. As such, like elements will be identified with an “a” suffix. Main body portion 54a includes a substantially constant diameter that terminates at an outlet opening 53a.

FIG. 4 depicts another alternate regeneration unit identified at reference numeral 26b. Regeneration unit 26b is substantially similar to regeneration unit 26 except that a length L has been increased to cause a greater portion of housing 50b to be positioned within exhaust passageway 14. Like elements will include a “b” suffix. The location of igniter 42b has been changed to be further from an end of nozzle 66.

FIGS. 5 and 6 depict another alternate arrangement including a diverter plate 140 positioned within pipe 112 upstream of miniature regeneration unit 26. Diverter plate 140 includes a D-shaped aperture 142 extending therethrough. Diverter plate 140 is positioned at an angle as depicted in FIG. 5 to urge exhaust flowing through passageway 14 to flow toward and around housing 50. The diverted exhaust flow transfers heat from regeneration unit 26 to the exhaust flowing through pipe 112.

FIG. 7 depicts a portion of another alternate regeneration unit identified at reference numeral 26c. Regeneration unit 26c is substantially similar to regeneration unit 26 except that outlet tube 56c is increased in length and includes a plurality of apertures 144 extending therethrough. The extended outlet tube length and apertures 144 assure that the combustion flame is properly maintained and directed during operation of regeneration unit 26c. As exhaust flows through passageway 14, some of the exhaust passes through apertures 144 creating a mixing effect resulting in a more desirable temperature distribution, flame stability and flame quality.

FIG. 8 depicts another alternate regeneration unit identified at reference numeral 26d. Regeneration unit 26d includes the components of regeneration unit 26 as well as an additional housing portion 145 defining a secondary combustion chamber 146. A second igniter 148 extends into secondary combustion chamber 146. A plurality of apertures 149 extends through second housing 145 to allow exhaust gas to enter secondary combustion chamber 146. Enhanced exhaust heating and mixing may be achieved through the use of regeneration unit 26d.

FIGS. 9-13 depict alternate inlet tube configurations that may be used in lieu of inlet tube 52. Each of the modified inlet tubes includes a plurality of circumferentially spaced apart apertures 150 extending through an end wall 152. Apertures 150 allow exhaust gas flowing through passageway 14 to enter primary combustion chamber 68. By providing oxygen into primary combustion chamber 68 via apertures 150, the pressure of secondary air provided by compressor 96 to injector 36 may be reduced. The cost and size of compressor 96 may also be reduced.

Inlet tube 52e shown in FIG. 9 includes a plurality of flaps 156e attached at one end to end wall 152e. Flaps 156e are arranged to induce gas passing through apertures 150e to swirl. FIG. 10 depicts rectangularly shaped apertures 150f with no flaps. FIG. 11 depicts a plurality of flaps 156g attached at a radial inner extent of apertures 150g. Flaps 156g extend at an angle to exhaust flow in a radially outward direction. FIG. 12 refers to another alternate inlet tube assembly 52h having a plurality of apertures 150h and a plurality of flaps 156h. Flaps 156h radially inwardly extend.

FIG. 13 shows a plurality of circular apertures 150i circumferentially spaced apart from one another. No flaps partially block the apertures. Each of the arrangements depicted in FIGS. 9-13 provide a substantially homogenous distribution of flow within primary combustion chamber 68.

It is also contemplated that any one of the described miniature regeneration unit arrangements including apertures 150 may be equipped with an injector 36j having a relocated secondary air inlet 74j, to inject compressed air at a relatively low pressure into annular volume 62, as shown in FIG. 14. Fuel inlet 72j positioned to inject atomized fuel within primary combustion chamber 68j, as previously discussed. Some of the air injected into annular volume 62j passes through apertures 150i and the remaining portion of the secondary air passes over an outside surface of housing 50j to cool miniature regeneration unit 26j.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A system for controlling the temperature of an exhaust stream from an engine at a location upstream from an exhaust aftertreatment apparatus, the system comprising:

a main exhaust passageway adapted to receive the exhaust stream from the engine;

a side branch in communication with the main exhaust passageway;

a regeneration unit positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway;

an ion sensor operable to output a signal indicative of the presence of fuel combustion; and

a controller for selectively operating the regeneration unit to increase the exhaust temperature, the controller being operable to control a supply of fuel to the regeneration unit based on the ion sensor signal.

2. The system of claim 1, further including supplying a secondary source of oxygen to the regeneration unit.

3. The system of claim 2, wherein the regeneration unit includes a housing defining a primary combustion chamber, the fuel and the secondary source of oxygen being supplied directly to the primary combustion chamber.

4. The system of claim 3, wherein the housing includes a reduced diameter portion at a free distal end.

5. The system of claim 3, wherein the housing includes a first end supported by the side branch and an unsupported second end, the first end including a plurality of apertures extending therethrough for receipt of a portion of the exhaust stream.

6. The system of claim 5, wherein the apertures are defined by displaced flaps of housing material, the flaps being oriented to change the direction of exhaust flow as it enters the housing.

7. The system of claim 6, wherein the flaps are substantially rectangular having three free edges and one edge fixed to the housing.

8. The system of claim 7, wherein the fixed edge is positioned radially outward of an opposite free edge.

9. The system of claim 3, wherein the housing at least partially extends into the main exhaust passageway to cool the housing.

10. The system of claim 3, wherein the regeneration unit includes a housing defining a primary combustion chamber, the fuel being supplied directly to the primary combustion chamber, the secondary source of oxygen being supplied to an external surface of the housing, the housing including apertures to allow a portion of the secondary source of oxygen to enter the primary combustion chamber.

11. The system of claim 1, further including a diverter plate positioned within the main exhaust passageway upstream from the regeneration unit, the diverter plate including an aperture shaped and positioned to direct the exhaust flow toward the regeneration unit.

12. The system of claim 11, wherein the aperture is substantially shaped as the letter D.

13. The system of claim 1, wherein the controller ceases the supply of fuel when the ion sensor signal represents an unexpected extinguishment of combustion.

14. The system of claim 1, wherein the side branch intersects the main exhaust passageway at substantially thirty degrees.

15. The system of claim 1, wherein the side branch has a distal end extending off of the main exhaust passageway that is not in receipt of exhaust.

16. A system for controlling the temperature of an exhaust stream from an engine at a location upstream from an exhaust aftertreatment apparatus, the system comprising:

a main exhaust passageway adapted to receive the exhaust stream from the engine;

a blind side branch in communication with the main exhaust passageway;

a regeneration unit positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway, the regeneration unit including a housing positioned within and spaced apart from a sidewall of the side branch, a nozzle for injecting the fuel into a chamber defined by the housing, and an igniter to initiate combustion of the fuel within the housing; and

a controller for selectively operating the regeneration unit to increase the exhaust temperature.

17. The system of claim 16, further including supplying a secondary source of oxygen to the regeneration unit.

18. The system of claim 17, wherein the housing includes a reduced diameter portion at a free distal end.

19. The system of claim 18, wherein the housing includes a first end supported by the side branch and an unsupported second end, the first end including a plurality of apertures extending therethrough for receipt of a portion of the exhaust stream.

20. The system of claim 19, wherein the apertures are defined by displaced flaps of housing material, the flaps being oriented to change the direction of exhaust flow as it enters the housing.

21. The system of claim 20, wherein the flaps are substantially rectangular having three free edges and one edge fixed to the housing.

22. The system of claim 21, wherein the fixed edge is positioned radially outward of an opposite free edge.

23. The system of claim 16, wherein the housing at least partially extends into the main exhaust passageway to cool the housing.

24. The system of claim 16, further including a secondary air source being supplied to a zone between the housing and the sidewall.

25. The system of claim 16, further including a diverter plate positioned within the main exhaust passageway upstream from the regeneration unit, the diverter plate including an aperture shaped and positioned to direct the exhaust flow toward the regeneration unit.

26. The system of claim 25, wherein the aperture is substantially shaped as the letter D.