Patent Application
20130061579
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.
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 NOx 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 NOx 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 NOx 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 NOx 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 NOx and particulate matter.
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.
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.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
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
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.
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.
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.
