Patent Application
20080264046
The present disclosure is directed to a regeneration device and, more particularly, to a regeneration device having an air-assisted fuel nozzle.
Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants include solid material known as particulate matter or soot. Due to increased attention on the environment, exhaust emission standards have become more stringent, and the amount of particulate matter emitted from an engine is regulated depending on the type of engine, size of engine, and/or class of engine.
One method implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to remove the particulate matter from the exhaust flow of an engine with a device called a particulate trap. A particulate trap is a filter designed to trap particulate matter and typically consists of a wire mesh or ceramic honeycomb medium. However, the use of the particulate trap for extended periods of time may cause the particulate matter to build up in the medium, thereby reducing the functionality of the filter and subsequent engine performance.
The collected particulate matter may be removed from the filter through a process called regeneration. To initiate regeneration of the filter, the temperature of the particulate matter entrained within the filter must be elevated to a combustion threshold, at which the particulate matter is burned away. One way to elevate the temperature of the particulate matter is to inject a catalyst such as diesel fuel into the exhaust flow of the engine and ignite the injected fuel.
Typically, the fuel is atomized during injection for efficient distribution and/or combustion purposes. The fuel is atomized by directing highly pressurized fuel through very small orifices in the injector. Although this method of atomizing the fuel maybe effective, it is also problematic. Specifically, the very small size of the orifices lends itself to frequent fouling and clogging. A fouled injector must be purged to remove the fouling, and replaced if the purging is unable to clear the restriction. In addition, the fuel pressures required for adequate atomization may be expensive to generate and difficult to accommodate.
One attempt at minimizing fouling in an exhaust treatment injector while improving atomization is described in U.S. Patent Publication No. 2006/0101810 (“the '810 publication”) by Angelo et al. published on May 18, 2006. Specifically, the '810 publication discloses an emission control device having a fuel injector. Pressurized fuel and air are supplied to the fuel injector, which mixes the fuel with the air and injects the mixture into an exhaust flow through a nozzle. This injection causes a rapid pressure drop in the mixture that results in the pressurized air expanding rapidly, breaking the fuel spray into fine particles.
In one embodiment disclosed in the '810 publication, the emission control device is positioned upstream from a catalytic converter that is positioned upstream from a diesel particulate filter. When the fuel/air mixture combusts within the catalytic converter, the temperature of the exhaust gas exiting the catalytic converter and traveling to the diesel particulate filter is within a combustion temperature range of the particulate matter trapped on the filter.
In another embodiment disclosed in the '810 publication, the fuel injector can inject the fuel/air mixture directly into the diesel particulate filter without having a preheating process provided by combustion within an upstream catalytic converter. In such an embodiment, the fuel ignites with a catalyst on the diesel particulate filter, thereby causing oxidation of the particulate matter on the filter.
Although the emission control device of the '810 publication may improve atomization and reduce the likelihood of fouling, its use may be limited. Specifically, the emission control device is only a dosing system (i.e., it does not actively ignite the injected fuel/air mixture), which may be operable only at certain engine conditions when the temperature of the exhaust is already above a predetermined threshold. In situations where the exhaust temperatures are below the predetermined threshold, the emission control device may be unable to regenerate the particulate trap.
In addition, because the emission control device of the '810 publication relies on a catalyst for ignition and combustion of the injected fuel/air mixture, the component and maintenance costs of the device may be significant. In particular, the additional catalyst component may increase the initial cost of the device, while service and/or replacement of the catalyst component may increase the maintenance cost. Further, it may be possible that combustion of the injected fuel/air mixture becomes unreliable as the catalyst ages and/or is consumed.
The regeneration device of the present disclosure solves one or more of the problems set forth above.
One aspect of the present disclosure is directed to a regeneration device. The regeneration device may include a housing having a fuel passageway and a first air passageway. The regeneration device may also include an injector disposed in the housing in fluid communication with the fuel passageway and the first air passageway. The regeneration device may further include a combustion canister connected to receive a fuel/air mixture from the injector and combustion air line.
Another aspect of the present disclosure is directed to a method of regenerating a particulate trap that receives a flow of exhaust. The method may include mixing fuel with air prior to an injection event, and injecting the mixture of fuel and air to atomize the fuel during the injection event. The method may further include igniting the atomized fuel outside of the flow of exhaust, and introducing the ignited fuel/air mixture into the flow of exhaust upstream of the particulate trap.
For the purposes of this disclosure, power unit 10 is depicted and described as a four-stroke diesel engine. One skilled in the art will recognize, however, that power unit 10 may be any other type of internal combustion engine such as, for example, a gasoline or a gaseous fuel-powered engine. Power unit 10 may include an engine block 16 that at least partially defines a plurality of combustion chambers (not shown). In the illustrated embodiment, power unit 10 includes four combustion chambers. However, it is contemplated that power unit 10 may include a greater or lesser number of combustion chambers and that the combustion chambers may be disposed in an “in-line” configuration, a “V” configuration, or any other suitable configuration.
As also shown in
Fuel system 12 may include components that cooperate to deliver injections of pressurized fuel into each of the combustion chambers. Specifically, fuel system 12 may be a common rail fuel system and may include a tank 20 configured to hold a supply of fuel such as diesel fuel, and a fuel pumping arrangement 22 configured to pressurize the fuel and direct the pressurized fuel to a plurality of fuel injectors (not shown) by way of a rail 24.
Fuel pumping arrangement 22 may include one or more pumping devices that function to increase the pressure of the fuel and direct one or more pressurized streams of fuel to rail 24. In one example, fuel pumping arrangement 22 may include a low pressure source 26 and a high pressure source 28 disposed in series and fluidly connected by way of a fuel line 30. Low pressure source 26 may embody a transfer pump that provides low pressure feed to high pressure source 28. High pressure source 28 may receive the low pressure feed and increase the pressure of the fuel up to as much as 300 MPa in some cases. High pressure source 28 may be connected to rail 24 by way of a fuel line 32. One or more filtering elements 34, such as a primary filter and a secondary filter, may be disposed within fuel line 32 in series relation to remove debris and/or water from the fuel pressurized by fuel pumping arrangement 22.
One or both of low and high pressure sources 26, 28 may be operatively connected to power unit 10 and driven by crankshaft 17. Low and/or high pressure sources 26, 28 may be connected to crankshaft 17 in any manner readily apparent to one skilled in the art where a rotation of crankshaft 17 will result in a corresponding driving rotation of a pump shaft. For example, a pump driveshaft 19 of high pressure source 28 is shown in
Fuel system 12 may also include components for redirecting a portion of the pressurized fuel to exhaust aftertreatment system 14. For example, as illustrated in
Air assist system 13 may pressurize a fluid, such as air, and provide this pressurized fluid to exhaust aftertreatment system 14 for combustion purposes. For example, compressed air may be directed to mix with injections of fuel from high pressure source 28 and, thereby, aid combustion within exhaust aftertreatment system 14. For these purposes, air assist system 13 may include a fluid supply 44 such as, for example, a compressor, an air pump, or any other suitable source, and a storage reservoir, such as a tank or an accumulator having sufficient volume to complete a combustion process with or without operation of fluid supply 44. A fluid line 40 may fluidly connect fluid supply 44 to the components of exhaust aftertreatment system 14 at any upstream location. A check valve 42 may be disposed within fluid line 40 to ensure that fuel and other contaminates are blocked from flowing through fluid line 40 to fluid supply 44. The flow of fluid through fluid line 40 may be controlled by way of a suitable valve arrangement (not shown).
Exhaust aftertreatment system 14 may include an exhaust manifold 80 configured to expel exhaust generated by power unit 10 towards a housing 82 located downstream from exhaust manifold 80. Housing 82 of exhaust aftertreatment system 14 may be a cylindrical or tubular conduit for directing exhaust gasses and particulates away from power unit 10 for processing by various emission controlling devices. That is, housing 82 may constitute structural support for an aftertreatment device 48.
Aftertreatment device 48 may be disposed across the cylindrical width (i.e., cross section) of housing 82 and either removably or fixedly secured at its perimeter to housing 82. Aftertreatment device 48 may be any variety of diesel particulate filter (“DPF”) such as, for example, a corderite or silicon carbide wall-flow filter, a metal fiber flow-through filter or a partial flow filter. As exhaust from power unit 10 flows through aftertreatment device 48, exhaust constituents such as particulate matter may be removed from the exhaust flow by aftertreatment device 48. According to one embodiment of the present disclosure, aftertreatment device 48 may have about 99% efficiency of particulate filtration. Moreover, it is contemplated that exhaust aftertreatment system 14 may include other components such as, for example, a turbine, an exhaust gas recirculation system, a catalytic treatment device, or any other exhaust system component known in the art.
Over time, the particulate matter may build up in aftertreatment device 48 and, if left unchecked, the particulate matter buildup could be significant enough to restrict or even block the flow of exhaust through aftertreatment device 48, allowing backpressure within the power unit 10 to increase. An increase in the backpressure of power unit 10 could reduce the power unit's ability to draw in fresh air, resulting in decreased performance, increased exhaust temperatures, and poor fuel consumption. Therefore, exhaust aftertreatment system 14 may include a regeneration device 50, in fluid communication with housing 82, fuel system 12, and air assist system 13.
Regeneration device 50 may include components configured to periodically reduce the buildup of particulate matter within aftertreatment device 48. For example, regeneration device 50 may include a housing 52, an injector 54, a combustion canister 56, an ignition device 58, and any other components configured to convey fluids thereto or therebetween. Generally, housing 52 may receive and fluidly connect pressurized fuel from fuel line 38 and pressurized air from fluid line 40 with injector 54. Accordingly, regeneration device 50 may supply a mixture of fuel and air, and combust the mixture at a location proximate aftertreatment device 48 for oxidizing and releasing the particulates entrained therein.
It is contemplated that exhaust aftertreatment system 14 may include additional or different components such as, for example, one or more control valves, a controller, a pressure sensor, a flow sensor, a flow blocking device, and other components known in the art. It is further contemplated that exhaust aftertreatment system 14 may also include a Selective Catalytic Reduction (SCR) device and an associated injector (not shown) nearly identical to injector 54 for introducing a reductant such as, for example, urea into the exhaust flow upstream of the SCR device.
Central stepped bore 55 may receive injector 54 such that it is axially oriented toward combustion canister 56. Injector 54 may divide central stepped bore 55 into at least two coaxial and concentric fluid passageways. For example, injector 54 may include a central passageway 70, in fluid communication with fuel inlet 71 via central stepped bore 55. Injector 54 may also include an outer annular passageway 74 running coaxially and concentrically with central passageway 70. Annular passageway 74 may be in fluid communication with first air inlet 69 via air passageway 68 and central stepped bore 55. Injector 54 may also include an injector tip 77 having slotted passageways 76, which extend radially outward from central passageway 70 to annular passageway 74, as well as a nozzle opening 78. According to this embodiment, first air inlet 61, air passageway 68, and annular passageway 74 may provide a relatively fluid impermeable air circuit 72 for conveying air from fluid line 40 to injector tip 77. Fuel inlet 71, central passageway 70, and slotted passageways 76 may provide a relatively fluid impermeable fuel circuit 73 for conveying fuel from fuel line 38 to injector tip 77. One or more check valves (not shown) may be situated in any one or all of these passageways, if desired, to ensure unidirectional flow of the respective fluids and/or to minimize the volumes thereof that could require periodic purging.
Injector 54 may create a mixture of fuel and air within injector tip 77 as pressurized fuel travels through central passageway 70 and outwards through slotted passageways 76 to intersect with pressurized air traveling through annular passageway 74. Injector 54 may direct the mixture of fuel and air out of injector tip 77 through nozzle opening 78. Injector 54 may therefore provide a desirably atomized fuel spray to combustion canister 56. Injector 54 may be operable to inject the atomized fuel/air mixture into combustion canister 56 at predetermined timings, pressures, and flow rates. The timing of injection into canister 56 may be synchronized with sensory input received from a thermocouple (not shown), one or more pressure sensors (not shown), a timer (not shown), or any other similar sensory devices such that the injections of fuel substantially correspond with a buildup of particulate matter within aftertreatment device 48 (referring to
Housing 52 may further include an ignition device 58 received through an external surface (not shown) of housing 52 for ignition of the atomized fuel from injector 54. In particular, ignition device 58 may include external threads that engage internal threads of housing 52. During a regeneration event or when a catalyst within aftertreatment device 48 requires an elevated temperature, the temperature of the exhaust exiting power unit 10 may be too low to cause auto-ignition of the fuel and air sprayed from injector 54. To initiate combustion of the fuel/air mixture and, subsequently, the trapped particulate matter, the mixture may be sprayed or otherwise injected toward ignition device 58 to create a locally rich atmosphere readily ignitable by ignition device 58. In an embodiment in which ignition device 58 is a spark plug, a spark therefrom may ignite the fuel/air mixture creating a flame, which may be jetted or otherwise advanced toward the trapped particulate matter. As the fuel/air mixture ignites, the temperature may rise to a level that causes combustion of the particulate matter trapped within aftertreatment device 48 and/or to a level that supports efficient operation of a catalyst. It is further contemplated that ignition device 58 may alternatively include an electrical heater to reduce any fouling of the injector tip 77, if desired.
Housing 52 may still further include a depending flange 62 having a central recessed opening 64. Central recessed opening 64 may receive a swirler plate 66. Swirler plate 66 may be an annular planar member disposed around injector tip 77 and within central recessed opening 64 of flange 62. Swirler plate 66 may be press-fitted completely within central recessed opening 64 and/or held in place with a snap ring. Swirler plate 66 may also be centrally aligned with injector 54 and housing 52, and angularly oriented with respect to housing 52 by way of one or more dowel pins.
Swirler plate 66, together with annular bore 60 of housing 52, may define air chamber 63, which may be supplied with compressed combustion air via second air inlet 59. Swirler plate 66 may include a plurality of annularly disposed air vents 67 fluidly communicating air from air chamber 63 with combustion canister 56. Air vents 67 may mix combustion air from second air inlet 59 with the mixture of fuel and air from injector 54 inside combustion canister 56 to improve combustion therein. Air vents 67 may be oriented in alternating or opposite directions so as to generate cross flow throughout combustion canister 56. It is contemplated that air vents 67 may additionally or alternatively direct pressurized air to the outer periphery of combustion canister 56 for cooling and/or insulating purposes, if desired. Swirler plate 66 may also include openings (not shown) to accommodate ignition device 58.
Depending flange 62 of housing 52 may receive and seat an annular end of combustion canister 56. Combustion canister 56 (referring to
The regeneration device of the present disclosure may be applicable to a variety of exhaust treatment devices requiring selectively elevated temperatures for regeneration. For example, the disclosed regeneration device may elevate temperatures in an aftertreatment device of a power unit by injecting an atomized mixture of fuel and air, igniting the atomized mixture, and directing the ignited mixture toward the aftertreatment device of the power unit. By using air assist for generating the atomized mixture of fuel and air, the presently disclosed regeneration device may obviate the need for small, easily-clogged injector orifices and high pressure fuel injection. The operation of power unit 10 will now be explained.
Referring to
Aftertreatment device 48 may be regenerated to prevent the undesired buildup of particulate matter therein. Regeneration may be periodic or based on a triggering condition such as, for example, an elapsed time of engine operation, a pressure differential measured across aftertreatment device 48, a temperature of the exhaust flowing from power unit 10, or any other condition known in the art.
In preparation for regeneration of aftertreatment device 48, fuel system 12 may provide a supply of pressurized fuel to regeneration device 50 via fuel line 38, and air assist system 13 may provide a supply of pressurized air to regeneration device 50 via fluid line 40. Pressurized fuel may enter regeneration device 50 at fuel inlet 71 and flow to injector 54 in central stepped bore 55. Fuel may flow through central passageway 70 of injector 54 in the direction of injector tip 77 and radially outward towards annular passageway 74 through slotted passageways 77. Pressurized air may simultaneously enter regeneration device 50 at first air inlet 69 and flow through air passageway 68 to injector 54 in central stepped bore 55. Air may flow through annular passageway 74 of injector 54 and may be intersected and mixed with fuel flowing through slotted passageways 76, as it approaches injector tip 77. A fuel/air mixture may therefore be generated within injector tip 77 and then expelled out through nozzle opening 78. As the fuel/air mixture exits nozzle opening 78, a rapid pressure drop in the mixture may result in rapid expansion and break down of the fuel into atomized particles.
Simultaneously, combustion air may enter annular bore 60 of regeneration device 50 through second air inlet 59. Combustion air within air chamber 63 may be directed into combustion canister 56 through air vents 67. Due to the angles of air vents 67, combustion air entering combustion canister 56 may cross-flow and mix with atomized fuel spray from injector 54.
To initiate regeneration, the atomized fuel from injector 54 and combustion air from air chamber 63 may be selectively injected into combustion canister 56 at a desired rate, and ignited. As an injection of atomized fuel and air sprays into combustion canister 56, a spark from ignition device 58 may ignite the atomized fuel and air. Alternatively, heat from an electrical coil or another ignition source may ignite the atomized fuel and air. Combustion canister 56 may direct the ignited fuel and air into housing 82 of exhaust manifold 80 and toward aftertreatment device 48. The ignited flow of fuel and air may raise the temperature of particulate matter trapped within aftertreatment device 48 to the combustion threshold of the entrapped particulate matter, thereby, burning away the particulate matter and regenerating aftertreatment device 48.
Because the presently disclosed regeneration device atomizes the fuel by mixing it with pressurized air prior to injection, reliance on high pressure fuel injection may be obviated. For example, conventional methods for generating atomized fuel, such as high-pressure sources and small nozzle orifices may be unnecessary. The use of larger nozzle orifices in the presently disclosed regeneration device may be advantageous due to their lower sensitivity to debris. Therefore, the orifices may be more robust and less likely to clog or foul. Moreover, the ability to use standard fuel pressure reduces the need for expensive and complex fuel systems, which employ dual-fuel supplies and complicated algorithms to achieve high atomization pressures. Accordingly, manufacturing, maintenance, and replacement costs of the present system are reduced.
Still further, because the presently disclosed regeneration device actively ignites the injected fuel/air mixture, it may be operated at any engine condition, including in situations where the exhaust temperatures are below a threshold for passive regeneration. Therefore, the system may be more reliable and may ensure continued and successful regeneration events in an efficient manner with components having a prolonged useful life.
It will be apparent to those skilled in the art that various modifications and variations can be made to the regeneration device of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the regeneration device disclosed herein. For example, although the disclosed regeneration device is illustrated as drawing pressurized fuel from a fuel system, the disclosed regeneration device may alternatively draw pressurized fuel from a separate dedicated source, if desired. Further, although general examples have illustrated the disclosed regeneration device as being associated with fuel for particulate regeneration purposes, it is contemplated that injector 54 may just as easily be adapted to inject ammonia, AdBlue, and/or urea within a Selective Catalytic Reduction (SCR) device, if desired. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
| Number | Date | Country | |
|---|---|---|---|
| 60924089 | Apr 2007 | US |
