Patent Application
20140311122
The subject invention relates to particulate filter regeneration, and in particular, flow controlled and electrically assisted zone particulate filter regeneration.
The exhaust gas emitted from an internal combustion engine is a heterogeneous mixture that may contain gaseous emissions such as a carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter. Catalyst compositions typically disposed on catalyst supports or substrates are provided in an engine exhaust system to convert certain, or all of the exhaust constituents into non-regulated exhaust gas components.
In an exhaust treatment technology, there are several known filter structures used that have displayed effectiveness in removing the particulate matter from the exhaust gas such as ceramic honeycomb wall flow filters, wound or packed fiber filters, open cell foams, sintered metal fibers, etc. Ceramic wall flow filters have experienced significant acceptance in automotive applications.
Typically, a particulate filter is disposed along an exhaust stream in an exhaust conduit to filter the particulate matter from the exhaust gas. Over time, the particulate filter may become full and regeneration is required to remove any trapped particulates. Regeneration of a particulate filter in vehicle applications is typically automatic and is controlled by an engine or other controller based on signals generated by engine and exhaust system sensors. The regeneration event involves increasing the temperature of the particulate filter to levels that are often above 600° C. causing the accumulated particulate matter on the particulate filter to ignite in order to burn the accumulated particulate matter to enable the continuation of the filtering process. In some configurations, fuel is injected into the exhaust stream to assist in ignition of the particulate matter for regeneration of the particulate filter.
There are drawbacks associated with the regeneration process. For example, excess fuel may be consumed when fuel is added to the exhaust stream to assist in ignition of the particulate matter, thereby reducing fuel efficiency of the engine. Emissions created by the regeneration process (e.g., upward adjustment factors (UAF) for NOx and HC) are another drawback.
In addition, the temperatures involved in regeneration place the particulate filter under stress and may adversely affect the service life of the particulate filter.
Further, during regeneration, the ignited particulate matter on the particulate filter may be susceptible to being extinguished during high flow exhaust scenarios which may occur during vehicle acceleration. In such occurrences, the regeneration of the particulate filter may be prematurely halted and particulate matter may remain on the particulate filter, thereby adversely affecting performance of the particulate filter, and in turn, an operating efficiency of the engine.
Accordingly, it is desirable to provide an apparatus and method for regenerating a particulate filter that will result in reduced fuel consumption, near zero exhaust emission during particulate filter regeneration and which may be regenerated during high flow exhaust scenarios.
In one exemplary embodiment of the invention there is provided a particulate filter assembly configured to receive an exhaust gas stream from an internal combustion engine. The particulate filter assembly includes an inlet end configured to receive the exhaust gas stream, a filter configured to remove particulates from the exhaust gas stream, a heating device positioned upstream from the filter having a plurality of zones, each zone of the plurality of zones independently operable to heat a corresponding region of the filter and an exhaust flow valve positioned downstream from the filter configured to selectively restrict flow of the exhaust gas stream through the filter.
In another exemplary embodiment of the invention, an exhaust gas treatment system for an internal combustion engine is provided. The system includes an exhaust conduit extending from the engine configured to receive an exhaust gas stream from the engine and a particulate filter assembly positioned in fluid communication with the exhaust gas stream. The particulate filter assembly includes an inlet end configured to receive the exhaust gas stream, a filter configured to remove particulates from the exhaust gas stream, a heating device positioned upstream from the filter having a plurality of zones, each zone of the plurality of zones independently operable to heat a corresponding region of the filter, and an exhaust flow valve positioned downstream from the filter configured to selectively restrict flow of the exhaust gas stream through the filter.
In yet another exemplary embodiment of the invention, there is provided a control method for flow controlled zoned regeneration of a filter of a particulate filter assembly of an internal combustion engine. The method includes determining whether regeneration of a particular region of the filter is necessary, activating a zone of a plurality of zones of a heating device to heat the particular region of a plurality of regions of the filter and adjusting a position of a valve plate of a plurality of valve plates of an exhaust flow valve to restrict flow of an exhaust gas stream through the particular region of the filter.
The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
In accordance with an exemplary embodiment of the subject invention, and with reference to
The exhaust gas treatment system 20 includes at least one exhaust gas conduit 30 extending from the engine 22. An exhaust gas stream 25 exits the engine 22 and flows into the exhaust gas conduit 30. The exhaust gas treatment system 20 includes an oxidation catalyst (OC) 32 positioned within the exhaust gas conduit 30 in a flow path of the exhaust gas stream. The oxidation catalyst 32 may include a flow-through metal or ceramic monolith substrate that is packaged in a rigid shell or canister having an inlet and an outlet in fluid communication with the exhaust gas conduit. The substrate may include an oxidation catalyst compound (not shown) disposed thereon which may be applied as a wash coat and may contain platinum group metals such as platinum (Pt), palladium (Pd) rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof. The oxidation catalyst 32 is useful in treating unburned gaseous and non-volatile HC and CO in the exhaust gas stream 25, which are oxidized to form carbon dioxide and water.
An injector 34 may be positioned downstream from the oxidation catalyst 32. The injector 34 is in fluid communication with the exhaust gas conduit 30 and is configured to periodically and selectively inject a reductant such as urea or ammonia, or a combination thereof, into the exhaust gas stream 25. Other suitable methods of delivery of the reductant to the exhaust gas stream 25 may be used. The reductant is supplied from a reductant supply tank (not shown) through a supply conduit (not shown). The reductant may be in the form of a gas, a liquid or an aqueous urea solution and may be mixed with air in the injector 34 to aid in the dispersion of the injected spray in the exhaust gas.
The exhaust gas treatment system 20 further includes a selective catalytic reduction (SCR) device 36 disposed within the exhaust gas conduit 30 downstream from the oxidation catalyst 32 and injector 34. The SCR device 36 is positioned in fluid communication with the exhaust gas stream 25. Similar to the oxidation catalyst 32, the SCR device 36 may also include a flow-through ceramic or metal monolith substrate which is packaged in a rigid shell or canister having an inlet and an outlet in fluid communication with the exhaust gas conduit. The substrate has an SCR catalyst composition (not shown) applied thereto. The SCR catalyst composition preferably contains a zeolite and one or more base metal components such as iron (“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium (“V”) which can operate efficiently to convert NOx constituents in the exhaust gas in the presence of the reductant.
The exhaust gas treatment system 20 further includes a particulate filter assembly 40. The particulate filter assembly 40 is in fluid communication with the exhaust gas stream 25 in the exhaust gas conduit 30 and is configured to receive the exhaust gas stream 25. The particulate filter assembly 40 may be positioned downstream from the selective catalyst reduction device 36 and operates to filter the exhaust gas stream 25 of carbon and other particulates.
In an exemplary embodiment, the particulate filter assembly 40 includes an inlet end 42, a heating device 44, a filter 46, an exhaust flow valve 48 and an outlet end 50. The particulate filter assembly 40 may be formed as a section along the exhaust gas conduit 30. The exhaust gas stream 25 is received through the inlet end 42, passes through the heating device 44, filter 46, and exhaust flow valve 48, and exits the particulate filter assembly at the outlet end 50.
The heating device 44 is positioned within particulate filter assembly 40 and is configured to heat the filter 46 for regeneration purposes. The heating device 44 is disposed on or near a front face, i.e. a face disposed nearest the inlet end 42, of the filter 46. In an exemplary embodiment, the heating device 44 is an electrical heating device. The heating device 44 may be operated, for example, by supplying power to a resistive pathway of the heating device 44.
Referring to
Referring again to
The individual zones Z1, Z2, Z3, Z4 are configured to heat corresponding regions of the filter 46. That is, a particular zone Z1, Z2, Z3, Z4 of the heating device 44 is configured to heat a region of the filter 46 that generally corresponds to the size, shape and position (radial and circumferential) of the particular zone. Accordingly, the filter 46 may be heated in stages based on operation of the heating device 44, so that a staged regeneration may be performed.
Referring to
Referring to
In an exemplary embodiment, each valve plate 52 is rotatably mounted and movable between an open position and a closed positioned. Referring to
Referring again to
In addition, at least one temperature sensor 58 may also be positioned in the exhaust gas conduit 30. In an exemplary embodiment, the at least one temperature sensor 58 may be positioned at a downstream end of the particulate filter assembly 40, adjacent to the outlet end 50, downstream from the exhaust flow valve 48. The at least one temperature sensor 58 is configured to measure a temperature of the exhaust gas stream 25 after passing through the particulate filter assembly 40
A controller 60 such as a vehicle or engine controller is operably connected to, and monitors, the engine 22 and exhaust gas treatment system 20 through signal communication with various sensors, including the first and second NOx sensors 54, 56 and at the least one temperature sensor 58. The controller 60 may include, for example, an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. In addition, the controller 60 may be communicatively connected to the injector 34, the heating device 44 and the exhaust flow valve 48. Accordingly, the controller 60 may selectively operate the injector 34, heating device 44 and exhaust flow valve 48 to control a staged regeneration of the filter 46 as described below. Controlling of the staged regeneration of the filter 46 may be in response, at least partially, to signals received from the various sensors, including the first and second NOx sensors 54, 56 and at least one temperature sensor 58.
In operation, an increase in exhaust backpressure caused by the accumulation of particulate matter requires that the filter 46 is periodically cleaned, or regenerated. Regeneration involves the oxidation or burning of the accumulated carbon and other particulates, in what is typically a high temperature (>600° C.) environment. According to an exemplary embodiment of the subject invention, the filter 46 may be regenerated in stages. That is, individual regions of the filter 46 may be regenerated in sequence. In an exemplary embodiment, the regions of the filter 46 correspond to the zones Z1, Z2, Z3 and Z4 of the heating device 44. Thus, the filter 46 may include four regions corresponding to respective zones Z1, Z2, Z3 and Z4 of the heating device 44. Accordingly, the staged regeneration may be selectively performed for each region of the filter 46, such that one region is subsequently heated after another to ignite the particulate matter accumulated in that region and regenerate that region of the filter 46. It is understood that the regions of the filter 46 described above are for exemplary purposes only, and that any other number of suitable regions are envisioned based on the number of zones of the heating element 44. In various embodiments, the number, size, shape and position of the regions of the filter 46 corresponds to the number, size, shape and position of the zones of the heating device 44. However, the number, size, shape and position of the regions may vary from the number, size, shape and position of the zones.
To regenerate a particular region of the filter 46, at least one valve plate 52 of the exhaust flow valve 48 is moved to the closed position so as to restrict flow of the exhaust gas stream 25. Power is supplied to a zone Z1, Z2, Z3, Z4 of the heating device 44 is positioned generally at a location where the exhaust gas stream 25 is limited due to the closed at least one valve plate 52. Thus, a region of the filter 46 is heated by the operable zone Z1, Z2, Z3, Z4 in an area where the exhaust gas stream flow is limited or restricted. The accumulated particulate matter in the region of the filter 46 that is heated by a corresponding zone Z1, Z2, Z3, Z4 of the heating device and where the flow is restricted may then be ignited so that it may burn off. Accordingly, that region of the filter 46 may be regenerated. Because the flow of the exhaust gas stream 25 is restricted in that region, the ignited particulate matter is less susceptible to being extinguished. When regeneration of that region is complete, the at least one closed valve plate 52 is moved to an open position and the power is turned off to the operable zone of the heating device 44 so that the operable zone no longer provides heat to the filter sufficient for regeneration.
In an exemplary embodiment, the process above is carried out in stages, such that after one region of the filter 46 is regenerated, another zone Z1, Z2, Z2, Z4 of the heating device 44 is operated to provide heat to another correspond region of filter 46. In addition, another valve plate 52 is closed to restrict the flow of the exhaust gas stream 25 in an area generally corresponding to the operable zone and region of the filter 46 to be regenerated. This process is carried out sequentially for each zone Z1, Z2, Z3, Z4 of the heating device 44 so that all of the corresponding regions of the filter 46 are regenerated. Accordingly, the filter 46 may be regenerated, as a whole, in stages, i.e., region-by-region, based on the selective operation of the zones Z1, Z2, Z3, Z4 of the heating device and the respective valve plates 52.
If the flow of the exhaust gas stream 25 does not correspond to a target zone or region of the filter 46, the controller 60 adjusts the position of a valve plate or plates 52 at 235, and continues the method at 230.
That is, based on temperature information received from the at least one temperature sensor 58, the controller 60 may determine which zone or region of the filter 46 is to be regenerated. The controller 60 operates the exhaust flow valve 48 to move a valve plate 52 to a closed position in a location that generally corresponds to a zone or region of the filter 46 to be regenerated, so as to restrict or limit the flow of exhaust gas through that zone or region to be regenerated.
At 250, the controller 60 determines if accumulated particulate matter on the filter 46 has been ignited. If the accumulated particulate matter has been ignited, the heating device 44, and in particular, the energized zone of the heating device 44 is turned off at 255 and the method continues at 250. At 260, if no accumulated particulate matter is ignited, the controller 60 determines that regeneration for the region of the filter 46 corresponding to the energized zone of the heating device is complete. At 270, the controller 60 operates the exhaust flow valve 48 to open the closed valve plate 52 and carry out the regeneration in the next zone or region. That is, this process is then repeated to regenerate the filter 46 in other regions, by selectively closing the other valve plates 52 and energizing the other zones Z1, Z2, Z3, Z4 of the heating device 44 as described above. At 280, the method is exited. If the controller 60 determines that the regeneration for the zone is not complete at 260, the controller 60 exits the process at 280, and begins a new loop for the process. Further, if the controller 60 determines that regeneration is not necessary at 210, the controller exits the process at 280 and being a new loop for the process.
In the exemplary embodiments above, it is appreciated that filter 46 is heated in regions via the use of the heating device 44. It is contemplated that the filter 46 may be segmented into a plurality of regions using a plurality of heating device 44 formats. Therefore, the present invention is not limited to the embodiments described above and shown in
In the exemplary embodiments above, fuel may be conserved as fuel is not required to be injected into the exhaust gas stream 25 to ignite the particulate matter. In addition, upward adjustment factors (UAF) emission penalties associated with the regeneration of the filter may be reduced or eliminated. Further still, by regenerating the filter in zones, the filter may be subjected to less thermal stress. Accordingly, the service life of the filter may be improved and warranty costs associated with regeneration may be reduced.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application.
