Patent Application
20110072805
Embodiments described herein relate to a system, method and device for heating exhaust gas. More specifically, embodiments described herein relate to a system, method and device for heating exhaust gas to create a regeneration event at a diesel particulate filter.
Exhaust gas aftertreatment systems in diesel vehicles are located downstream of the engine for treating exhaust gases emitted from the engine. The aftertreatment systems typically include a diesel oxidation catalyst, and a diesel particulate filter. Particulate matter from the exhaust gas accumulates on the diesel particulate filter, and if left unchecked, can create a back pressure in the aftertreatment system.
A regeneration event is the periodic oxidation of the collected particulate matter in the aftertreatment system during routine diesel engine operation. When the diesel particulate filter of the exhaust system experiences a build-up of particulate matter, the particulate matter is oxidized to “regenerate” the filter. Regeneration is typically initiated by increasing engine load and activating a post-injection of diesel fuel into the exhaust stream. This post-injection provides sufficient heat to oxidize the trapped particulate matter within the diesel particulate filter.
Exhaust gas is a relatively poor conductor of heat. As such, the loading of the engine must be increased to provide a sufficiently heated exhaust gas to initiate the regeneration downstream at the diesel particulate filter. During low speed and low load operation of the engine, the resulting exhaust gas may not have a sufficiently high temperature to initiate the regeneration.
An exhaust gas aftertreatment system for a vehicle having an engine includes a fluid passageway extending from the engine to an ambient for fluidly communicating exhaust gas. A diesel particulate filter is disposed on the fluid passageway downstream of the engine. Disposed downstream of the engine and upstream of the diesel particulate filter is an electric diesel oxidation catalyst having a substrate. A first electrode and a second electrode are attached to the electric diesel oxidation catalyst. The first electrode selectively delivers current through the catalyst substrate to the second electrode to generate heat at the catalyst substrate.
A method of regenerating an exhaust aftertreatment system of an engine having a diesel particulate filter includes the steps of providing a fluid passageway from the engine to an ambient, providing a substrate upstream of the diesel particulate filter, and heating the substrate electrically. The method of regeneration also includes the steps of heating the exhaust gas flowing through the heated substrate, and delivering the heated exhaust gas to the diesel particulate filter to initiate regeneration.
An electric diesel oxidation catalyst for an exhaust aftertreatment system of an engine includes a housing that substantially encloses a substrate. The housing has an inlet and an outlet configured for permitting a flow of exhaust gas through the housing. A first electrode extends through the housing and is configured for providing an electric current to the substrate. A second electrode extends from the housing and is configured for receiving the electric current from the substrate.
Referring to
A first portion 22 of the exhaust pipe assembly 12 extends from the engine 14 to an electric diesel oxidation catalyst (EDOC) 24. A second portion 26 of the exhaust pipe assembly 12 extends from the EDOC 24 to a diesel oxidation catalyst (DOC) 28, which is upstream of diesel particulate filter (DPF) 30. A third portion 27 of the exhaust pipe 12 assembly extends from the DPF 30 to the outlet 16. Other portions of the exhaust pipe may be disposed between various components on the aftertreatment system 10, such as between the engine 14 and an exhaust brake 29, between the exhaust brake and the EDOC 24, or between the DOC 28 and the DPF 30.
The DPF 30 is a filter constructed from a very high temperature resistant material. The DPF 30 catches and holds particulate matter entrained within the exhaust gases discharged into the exhaust aftertreatment system 10. The DPF 30 is periodically regenerated to limit increases in exhaust aftertreatment system 10 back pressure and to maintain engine 14 efficiency.
The DOC 28 is a flow-through device that includes a substrate, typically a ceramic or a metal covered with a catalyst. As the exhaust gases F flow through the DOC 28, carbon monoxide, gaseous hydrocarbons and liquid hydrocarbon particles (unburned fuel and oil) are oxidized, thereby reducing emissions.
Upstream of the DPF 30 and the DOC 28 is the EDOC 24. The EDOC 24 has a housing 32 that substantially encloses a substrate 34 having a structure that permits the flow of exhaust gas F through the substrate and that is distributed within the cross-section of the EDOC, for example a grid-shape, a swirl-shape, a honeycomb-shape, a circuitous-shape, a mesh-shape, or any other shape. The substrate 34 is made of metal, however other highly conductive materials are possible.
The housing 32 may be generally cylindrical or have any other shape that permits the flow of exhaust gas F from an inlet 36 to an outlet 38 and through the substrate 34. The first portion 22 of the pipe assembly 12 provides the fluid passageway 20 for the flow of exhaust gas F into the EDOC 24 at the inlet 36, and the second portion 26 of the pipe assembly provides the fluid passageway for the flow of exhaust gas F out of the EDOC at the outlet 38. The housing 32 of the EDOC 24 may be metal, however other materials are possible.
A first electrode 40 is electrically connected to a power source on the vehicle, such as the engine 14, with a first transmission wire 42. The first electrode 40 extends through the housing of the EDOC 24, and may extend generally the radius or generally half the width of the EDOC, however other lengths of extension into the EDOC are possible. The first electrode 40 contacts the substrate 34 generally at the cross-sectional center C of the EDOC 24 and the substrate. An isolator sleeve 44 is disposed about the first electrode 40 to prevent the contact of the first electrode with the housing 32 of the EDOC 24. The isolator sleeve 44 co-extends with the first electrode 40 less than the entire length of the first electrode 40 so that a portion of the first electrode is exposed. When current is run to the first electrode 40, the current is isolated from the housing 32 and the current is directed to the general cross-sectional center C of the EDOC 24.
A second electrode 46 extends from the housing 32 of the EDOC 24 and is also electrically connected to the engine 14 with a second transmission wire 48. While the second electrode 46 extends from the housing, it is also possible that the second electrode 46 may contact the substrate 34.
The first electrode 40 does not contact the second electrode 46, but instead the electrodes are spaced from each other and separated by the substrate 34 within the EDOC 24. The electrodes 40, 46 may also be spaced from each other a distance D along the length of the EDOC 24. The first electrode 40 delivers current from the engine 14 through the substrate 34 to the second electrode 48. It is possible that the selective introduction of current into the EDOC 24 can be at the activation of a user or an automatic activation, such as by an engine control module.
When the current flows from the first electrode 40, through the substrate 34, and to the second electrode 48, heat is created at the substrate. When current is delivered to the general cross-sectional center C of the substrate 34, the heat created is generally uniform across the substrate 34. The exhaust gases F that flow through the EDOC 24 are heated by the substrate 34 and the housing 32, and the heated exhaust gases flow to the DOC 28 and to the DPF 30. At the DPF 30, the heated exhaust gases F provide sufficient heat to initiate regeneration of the DPF.
While the aftertreatment system 10 of
By electrically heating the EDOC 24, the DPF 30 on the aftertreatment system 10 can be regenerated without having to increase the loading on the engine 14, which allows regeneration at low engine speed and low engine loading.
| Number | Date | Country | |
|---|---|---|---|
| 61246012 | Sep 2009 | US |
