Patent Application
20170074140
Exemplary embodiments of the invention are related to exhaust gas treatment systems and, more particularly, to an exhaust gas treatment system for internal combustion engines and vehicles incorporating the same.
Manufacturers of internal combustion engines must meet customer requirements while addressing various regulations for reduced emissions and improved fuel economy. Several types of exhaust treatment systems are used in vehicle applications of internal combustion engines. These systems employ various exhaust treatment devices. One such exhaust treatment system employs a urea Selective Catalyst Reduction (“SCR”) catalyst and a NOx reductant (e.g. urea) that is injected upstream of the SCR catalyst using a fluid injector. The NOx reductant is converted to ammonia in the exhaust gas stream that is then used to reduce the NOx to N2. The use of urea as a reductant necessitates a urea delivery system and an on-board monitoring system for this secondary fluid.
An exhaust treatment technology used to control high levels of particulate matter in the exhaust gas is a Diesel Particulate Filter (“DPF”) device. There are several known filter structures used in DPF devices that have displayed effectiveness in removing particulate matter from 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. The filter is a physical structure for removing particulates from exhaust gas and, as a result, the accumulation of filtered particulate matter will have the effect of increasing the exhaust system backpressure that is experienced by the engine. To address backpressure increases caused by the accumulation of exhaust gas particulates, the DPF device is periodically cleaned or regenerated. Regeneration of a DPF device 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 filter to levels that will combust the accumulated particulate matter.
One method of generating the temperatures required in the exhaust system for regeneration of the DPF device is to deliver unburned hydrocarbon (“HC”) to an oxidation catalyst device that is disposed upstream of the DPF device. The HC may be delivered by injecting fuel directly into the exhaust gas system typically using an exhaust fluid injector. The HC is oxidized in the oxidation catalyst device resulting in an exothermic reaction that raises the temperature of the exhaust gas. The heated exhaust gas travels downstream to the DPF device and burns the particulate accumulation in the filter. While systems that employ SCR catalysts, DPF devices and oxidation catalysts have been used for reduced emissions in exhaust gas flow streams, the packaging of the various devices has been problematic, particularly in relatively small vehicles having short wheelbases, due to the reduced space available to package the combinations of devices and the associated injection systems required for the introduction of the various exhaust treatment fluids described. Various mixers have been proposed but may suffer from detractions.
In an exemplary embodiment a mixing device for an exhaust gas conduit comprises a first, inner sleeve having an upstream end, a downstream end and an inner passage extending therethrough having a diameter “D”; a deflector fin formed in the first, inner sleeve and extending into the inner passage; and a second, outer air-gap shell having an upstream end, a downstream end and a central portion having a diameter “D1” that is larger than the diameter D of the first, inner sleeve. The inner sleeve is disposed in the second, outer air-gap shell and the upstream and downstream ends are sealingly fixed to the first, inner sleeve to thereby define an air-gap about the portion of the first, inner sleeve in which the deflector fin is formed.
In another exemplary embodiment an exhaust gas system for an internal combustion engine comprises an exhaust gas conduit configured to transport exhaust gas from the internal combustion, an exhaust treatment device disposed in the exhaust gas conduit and a mixing device disposed in the exhaust gas conduit, upstream of said exhaust treatment device. The mixing device comprises a first, inner sleeve having an upstream end, a downstream end and an inner passage extending therethrough having a diameter “D”, a deflector fin formed in the first, inner sleeve and extending into the inner passage, and a second, outer air-gap shell having an upstream end, a downstream end and a central portion having a diameter “D1” that is larger than the diameter D of the first, inner sleeve. The inner sleeve is disposed in the second, outer air-gap shell and the upstream and downstream ends are sealingly fixed to the first, inner sleeve to thereby define an air-gap about the portion of the first, inner sleeve in which the deflector fin is formed.
The above features and advantages, and other features and advantages of the invention are readily apparent from the following detailed description for carrying out the invention when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following description of embodiments, the 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. As used herein the term vehicle is not limited to just an automobile, truck van or sport utility vehicle, but includes any self-propelled or towed conveyance suitable for transporting a burden.
Referring now to
A Selective Catalyst Reduction (“SCR”) device 22 may be disposed downstream of the OC device 18. In a manner similar to the OC device, the SCR device 22 has a selective catalyst reduction catalyst compound containing a zeolite and one or more base metal components such as iron (“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium (“V”), or combinations thereof applied thereto. The catalyst compounds operate efficiently to convert NOx constituents in the exhaust gas 16, in the presence of an injected fluid such as an ammonia (“NH3”) reductant. The NH3 reductant 23, supplied from a reductant supply tank 19 through conduit 17, may be injected into the exhaust gas conduit 14 at a location upstream of the SCR device 22 using an injector 26.
In one exemplary embodiment of an exhaust treatment system 10, an exhaust gas filter assembly, in this case a diesel particulate filter (“DPF”) device 28 is located within the exhaust gas treatment system, downstream of the SCR device 22 and operates to filter the exhaust gas 16 of carbon and other particulate matter. The DPF device 28 may be constructed using a ceramic wall-flow monolith filter 30 having an inlet and an outlet in fluid communication with exhaust gas conduit 14. Exhaust gas 16 entering the filter 30 is forced to migrate through adjacent longitudinally extending walls (not shown) and it is through this wall-flow mechanism that the exhaust gas 16 is filtered of carbon and other particulate matter. The filtered particulates are deposited in the filter 30 and, over time, will have the effect of increasing the exhaust gas backpressure experienced by the IC engine 12.
In an exemplary embodiment, the increase in exhaust backpressure caused by the accumulation of particulate matter requires that the DPF device 28 be periodically cleaned, or regenerated. Regeneration involves the oxidation or burning of the accumulated carbon and other particulate matter in what is typically a high temperature (>600° C.) environment. For regeneration purposes a second OC device 20 may be located upstream of the filter 30, proximate to its upstream end. In the embodiment illustrated, the second OC device 20 is disposed in the canister 31 of the DPF device 28. It is, however, contemplated that, depending on packaging and other system constraints, the second OC device 20 may also be disposed within a separate canister (not shown) that is located upstream of the DPF device 28 (ex. OC device 18). Disposed upstream of the OC device 20, in fluid communication with the exhaust gas 16 in the exhaust gas conduit 14, is an HC or fuel injector 32. The fuel injector 32 is in fluid communication with liquid hydrocarbon 34 in fuel supply tank 36 through fuel conduit 38. The fuel injector 32 introduces fluid such as unburned HC 34 into the exhaust gas stream 16 for delivery to the OC device 20.
A controller 40, such as a vehicle or engine controller, is operably connected to, and monitors, the exhaust gas treatment system 10 through signal communication with a number of sensors. As used herein the term controller may include 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.
NOx sensors 46 located near the SCR device 22 generate signals indicative of the NOx levels in the exhaust gas 16. Upon a determination that the NOx levels have reached a predetermined level the controller 40 may activate the injector 26 to deliver reductant 23 into the exhaust gas conduit 14 for mixing with the exhaust gas 16. The ammonia/exhaust gas mixture enters the SCR device 22 where the ammonia reduces the NOx to N2.
Oxygen (O2) sensor 42 and backpressure sensor 44, located near the second OC device 20 and the DPF device 28, generate signals indicative of the function of the OC device and the carbon and particulate loading in the ceramic wall flow monolith filter 30. Upon a determination that the backpressure in the DPF device has reached a predetermined level indicative of the need to regenerate the DPF device 28, the controller 40 activates the HC injector 32 to deliver HC 34 into the exhaust gas conduit 14 for mixing with the exhaust gas 16. The fuel/exhaust gas mixture enters the OC device 20 inducing oxidation of the HC in the exhaust gas 16 and raising the exhaust gas temperature to a level (e.g. >600° C.) suitable for regeneration of the carbon and particulate matter in the filter 30. The controller 40 may monitor the temperature of the exothermic oxidation reaction in the second OC device 20 and the ceramic wall-flow monolith filter 30 through temperature sensor 48 and adjust the HC delivery rate of injector 32 to maintain a predetermined temperature.
Referring now to
The exhaust inner sleeve mixer 50 further comprises a second, outer air-gap shell 62 having a first, upstream end 64, a second, downstream end 66 and a central portion 68 having a diameter “D1” that, in an embodiment is larger than the diameter D of the first, inner sleeve 52. In an embodiment, the first, inner sleeve 52 is disposed in the second, outer air-gap shell 62 and the first and second ends 64, 66 of the outer air-gap shell are sealingly welded to the first, inner sleeve 52 to thereby define a leak-free air-gap 70 about that portion of the first, inner sleeve in which the deflector or deflector fins 58 are formed. The application of the second, outer air-gap shell 62 provides several benefits. First, the outer air-gap shell allows for the integration of the deflector fin or fins 58 into the first, inner sleeve resulting in an exhaust gas mixer in that has no additional components assembled into the exhaust gas conduit 14 that may become dislodged with wear-and-tear caused by age or other influences. Additionally, the leak-free, air-gap 70 defines a thermally insulating layer between the hot exhaust gas 16 and the exterior of the exhaust treatment system that is useful to retain heat in the exhaust gas, for the purposes of regenerating the DPF device 28, as well as reducing the thermal load of the exhaust treatment system 10 on vehicle components that may be located in close proximity thereto. For additional thermal isolation, it is contemplated that a layer of heat resistant thermal insulation may be disposed in the air-gap 70.
Referring now to
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 as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the present application.
