Exhaust Gas Aftertreatment System For Engines Equipped With Exhaust Gas Recirculation

Abstract

A system for treating exhaust of an internal combustion engine having an exhaust recirculation system and a turbocharger includes an exhaust passageway adapted to receive exhaust from the engine. A heat exchanger is adapted to be positioned within the exhaust gas recirculation system. A pressurized air supply system includes a conduit containing pressurized air and extending within the heat exchanger. A regeneration unit for combusting a fuel and heating the exhaust flowing through the exhaust passageway is supplied air from the air supply system that has been heated by the heat exchanger. An exhaust treatment device is positioned downstream from the regeneration unit in receipt of the heated exhaust.

Description

FIELD

The present disclosure generally relates to a system for treating exhaust gas emitted from an internal combustion engine. More particularly, a regeneration unit for increasing an exhaust gas temperature is combined with an exhaust gas recirculation system to efficiently transfer heat energy within one portion of the exhaust system to an exhaust treatment device.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

A number of exhaust aftertreatment devices have been developed to reduce the quantity of NO_x and particulate matter emitted to the atmosphere during internal combustion engine operation. A need for exhaust aftertreatment systems particularly arises when diesel combustion processes are used. 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).

Other emissions control systems include exhaust gas recirculation arrangements operable to reduce combustion temperatures within the engine and reduce NO_x emissions. Many exhaust gas recirculation systems are operable to vary the rate of exhaust gas supplied to the intake of the internal combustion engine. As the rate of recirculation increases, combustion temperatures are reduced to decrease the energy content due to the reduced quantity of oxygen, thereby reducing the NO_x emissions. Unfortunately, lower exhaust temperatures tend to include an increased quantity of particulate matter, as well as the reduced oxygen content.

Typical DPFs are integrated in most, if not all, on-road diesel engine vehicles. As the rate of exhaust gas recirculation increases, difficulty arises in managing the soot load on the DPFs. As the exhaust gas recirculation rate increases, the percentage of time at which passive regeneration of the DPF occurs is reduced due to the reduced exhaust temperature and increased particulate matter. Similarly, many active regeneration devices include catalysts which require minimum temperatures to reduce the NO_x content of the exhaust. Accordingly, it may be beneficial to provide an exhaust aftertreatment system including an exhaust gas recirculation with a regeneration unit in a diesel particulate filter to maximize the use of energy in the exhaust while reducing the cost and complexity to remove NO_x and particulate matter.

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 treating the exhaust of an internal combustion engine having an exhaust recirculation system and a turbocharger includes an exhaust passageway adapted to receive exhaust from the engine. A heat exchanger is adapted to be positioned within the exhaust gas recirculation system. A pressurized air supply system includes a conduit containing pressurized air and extending within the heat exchanger. A regeneration unit for combusting a fuel and heating the exhaust flowing through the exhaust passageway is supplied air from the air supply system that has been heated by the heat exchanger. An exhaust treatment device is positioned downstream from the regeneration unit in receipt of the heated exhaust.

A system for treating the exhaust of an internal combustion engine includes an exhaust passageway adapted to receive the exhaust from the engine. A heat exchanger is adapted to be positioned within the exhaust passageway. A regeneration unit is positioned within a side branch in communication with the exhaust passageway. The regeneration unit combusts a fuel and heats the exhaust flowing through the exhaust passageway. The regeneration unit is supplied a source of oxygen that has been heated by the heat exchanger. An exhaust treatment device is positioned downstream from the regeneration unit in receipt of the heated exhaust.

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 an exhaust treatment system equipped with an exhaust gas recirculation system, a heat exchanger and a regeneration unit positioned upstream of an exhaust treatment device;

FIG. 2 is a schematic depicting an exhaust treatment system including a regeneration unit, a diesel particulate filter and a heat exchanger positioned downstream from the diesel particulate filter;

FIG. 3 is schematic depicting another exhaust treatment system including a regeneration unit positioned within a side branch of an exhaust passageway and a heat exchanger positioned downstream from an exhaust treatment device; and

FIG. 4 depicts another alternate exhaust treatment 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 is a schematic depicting an exhaust gas treatment system 10 for use with an exemplary internal combustion engine 12 having an exhaust manifold 13 and an exhaust gas recirculation system 14. An intake passage 16 is coupled to provide combustion air thereto. An air intake filter 18 is positioned upstream from intake passage 16. A turbocharger 20 includes a driven member 22 positioned within an exhaust passage 24. Turbocharger 20 also includes a compressor member 26 positioned within intake passage 16 to provide pressurized air to an intake manifold 28 coupled to engine 12. A charge air cooler 30 reduces the temperature of compressed air downstream from compressor member 26.

Exhaust gas recirculation system 14 includes a high pressure branch 34 in receipt of exhaust from engine 12 having an upstream end 36 positioned upstream from driven member 22 of turbocharger 20. An exhaust gas cooler 38 receives exhaust passing through high pressure branch 34. A valve 40 may be controlled to vary the rate of exhaust gas supplied to intake manifold 28. More particularly, charged air provided downstream from charge air cooler 30 is mixed with recirculated exhaust gas in a mixing tube portion 42 for supply to intake manifold 28.

Exhaust gas treatment system 10 also includes a regeneration unit 50 positioned downstream from driven member 22 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 52 and a diesel particulate filter 54. It should be appreciated that the aftertreatment device may alternatively include a diesel oxidation catalyst, a lean NO_x catalyst or many other types of catalytic converters.

Injector 52 includes a fuel inlet 60 and an air inlet 62. Fuel inlet 60 is in communication with a fuel delivery system 66 including a fuel tank 68, a fuel filter 70, a fuel pump 72 and a fuel block 74 interconnected by a fuel line 76. Fuel delivery system 66 is operable to provide pressurized hydrocarbon to injector 52. A secondary air supply system 90 includes an air filter 92 and a mass air flow (MAF) sensor 94. A compressor 96 may be formed as a portion of a supercharger, a turbocharger or a stand-alone electric compressor. Output from compressor 96 is provided to air inlet 62 after passing through a heat exchanger 98 positioned in high pressure branch 34.

Heat exchanger 98 includes a housing 100 in receipt of exhaust passing through high pressure branch 34 as well as an internal conduit 102 containing pressurized air supplied from compressor 96. As the air passes through conduit 102 it is heated by the energy from the engine exhaust passing through housing 100. A controller 112 is in communication with compressor 96, an igniter 106, and fuel block 74 to actively control regeneration of DPF 54.

When regeneration of DPF 54 is desired, controller 112 causes fuel to be injected via fuel inlet 60 and heated air to be injected via air inlet 62 to supply atomized fuel within regeneration unit 50. Igniter 106 is mounted to regeneration unit 50 at a position to combust the fuel provided by injector 52 within a primary combustion chamber 108. By constructing exhaust gas treatment system 10 in this manner, the energy contained within high pressure EGR branch 34 may be leveraged to increase the temperature of the air supplied to regeneration unit 50 and minimize fuel penalty disadvantages associated with injecting fuel from tank 68.

FIG. 2 depicts an alternate exhaust gas treatment system identified at reference numeral 200. Exhaust system 200 is substantially similar to exhaust system 10 with the exception that the heat source for the secondary air supply provided to the regeneration unit is downstream of the exhaust treatment device instead of being located within an exhaust gas recirculation system. Accordingly, like elements will retain their previously introduced reference numerals including an “a” suffix. More particularly, exhaust passage 24a is in receipt of exhaust provided from internal combustion engine 12a and flowing through exhaust manifold 13a. The exhaust is routed into regeneration unit 50a upstream of diesel particulate filter 54a.

A heat exchanger 202 is positioned downstream from DPF 54a. Heat exchanger 202 includes a housing 204. A portion of a secondary air conduit 206 is positioned within housing 204 in a heat transfer relationship with the exhaust flowing through heat exchanger 202. As previously discussed, the secondary source of air is provided and pressurized by air supply system 90a. The air provided by system 90a is heated within heat exchanger 202 and supplied to air inlet 62a. The heated and compressed air is mixed with fuel entering fuel inlet 60a such that atomized, heated fuel is injected within regeneration unit 50a. An igniter 106a is energized to combust fuel and air within regeneration unit 50a. The heat generated during the combustion process within regeneration unit 50a is efficiently utilized by positioning heat exchanger 202 downstream from, and in relative close proximity to, regeneration unit 50a.

FIG. 3 relates to another alternate exhaust treatment system identified at reference numeral 300. Exhaust treatment system 300 includes a regeneration unit 302 positioned within a side branch portion 304 of system 300. Certain elements from exhaust treatment system 10 and exhaust treatment system 200 are also included within exhaust treatment system 300. As such, similar elements will be identified with like reference numerals including a “b” suffix. Side branch portion 304 is in fluid communication with exhaust passage 24. Regeneration unit 302 may be used to heat the exhaust passing through exhaust passage 24 to an elevated temperature that will enhance the efficiency of a diesel oxidation catalyst (DOC) 306 and facilitate regeneration of DPF 54b. Exhaust treatment system 300 includes a heat exchanger 202b positioned downstream from DOC 306 and DPF 54b. Exhaust flows through housing 204b and across secondary air conduit 206b to heat secondary air provided by heated air supply system 90b.

FIG. 4 depicts another alternate exhaust treatment system identified at reference numeral 400. System 400 combines a side branch mounted regeneration unit positioned upstream of a diesel oxidation catalyst and diesel particulate filter with a heat exchanger positioned within an EGR system. Once again, similar elements will be identified with like reference numerals including a “c” suffix. Secondary air provided by air supply system 90c travels through heat exchanger 98c that is positioned within the high pressure loop of EGR system 14c. Heated and pressurized secondary air is provided to air inlet 62c of regeneration unit 50c. Fuel is provided to injector 52c via fuel delivery system 66c. Combustion occurs partially within regeneration unit 50c and within the portion of exhaust passage 24c immediately upstream of DOC 306c to increase the temperature of the exhaust as it enters DOC 306c. The temperature of the exhaust is further increased within DOC 306c to regenerate DPF 54c.

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 treating the exhaust of an internal combustion engine, the exhaust treatment system comprising:

an exhaust passageway adapted to receive the exhaust from the engine;

a heat exchanger adapted to be positioned within the exhaust passageway;

a side branch in communication with the exhaust passageway;

a regeneration unit positioned within the side branch for combusting a fuel and heating the exhaust flowing through the exhaust passageway, the regeneration unit being supplied a source of oxygen heated by the heat exchanger; and

an exhaust treatment device positioned downstream of the regeneration unit in receipt of heated exhaust.

2. The system of claim 1, wherein the source of oxygen includes a secondary air supply system including an air compressor.

3. The system of claim 2, wherein the secondary air supply system includes a conduit for transferring air that passes through the heat exchanger.

4. The system of claim 3, wherein the vehicle includes a turbocharger and the heat exchanger is adapted to be positioned upstream of the turbocharger.

5. The system of claim 4, wherein the exhaust treatment device includes a particulate filter selectively regenerated by the regeneration unit.

6. The system of claim 1, wherein the regeneration unit includes a hydrocarbon injector having a heated oxygen inlet and a fuel inlet, the injector atomizing the fuel and heated oxygen for combustion within the regeneration unit.

7. The system of claim 1, further including a controller for selectively operating the regeneration unit to increase the exhaust temperature, the controller being operable to control a supply of fuel and heated oxygen to the regeneration unit.

8. The system of claim 1, wherein the heat exchanger is positioned downstream of the exhaust treatment device.

9. The system of claim 8, further including a diesel oxidation catalyst positioned immediately upstream of the diesel particulate filter.

10. The system of claim 1, wherein the vehicle includes an exhaust gas recirculation system having a branch communicating exhaust to an intake of the engine, the heat exchanger being adapted to be positioned within the exhaust gas recirculation system.

11. A system for treating the exhaust of an internal combustion engine having an exhaust gas recirculation system and a turbocharger, the exhaust treatment system comprising:

an exhaust passageway adapted to receive the exhaust from the engine;

a heat exchanger adapted to be positioned within the exhaust gas recirculation system;

a pressurized air supply system including a conduit containing pressurized air, a portion of the conduit extending with the heat exchanger;

a regeneration unit for combusting a fuel and heating the exhaust flowing through the exhaust passageway, the regeneration unit being supplied air from the air supply system that has been heated by the heat exchanger; and

an exhaust treatment device positioned downstream of the regeneration unit in receipt of heated exhaust.

12. The system of claim 11, wherein the oxygen supply system includes a compressor separate from the turbocharger.

13. The system of claim 12, wherein the heat exchanger is adapted to be positioned upstream of the turbocharger.

14. The system of claim 13, wherein the exhaust treatment device includes a particulate filter selectively regenerated by the regeneration unit.

15. The system of claim 14, wherein the regeneration unit includes a hydrocarbon injector having a heated air inlet and a fuel inlet, the injector atomizing the fuel and heated air for combustion within the regeneration unit.

16. The system of claim 11, further including a controller for selectively operating the regeneration unit to increase the exhaust temperature, the controller being operable to control a supply of fuel and heated air to the regeneration unit.

17. The system of claim 11, wherein the heat exchanger is positioned downstream of the exhaust treatment device.

18. The system of claim 17, further including a diesel oxidation catalyst positioned immediately upstream of the diesel particulate filter.