Patent Application
20080053072
As also shown in
Common rail fuel system 12 may include components that cooperate to deliver injections of pressurized fuel into each of the combustion chambers. Specifically, common rail fuel system 12 may include a tank 20 configured to hold a supply of 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 common 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 common rail 24. In one example, fuel pumping arrangement 22 includes 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 to the range of about 30-300 MPa. High pressure source 28 may be connected to common 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 operably connected to power unit 10 and driven by crankshaft 18. Low and/or high pressure sources 26, 28 may be connected with crankshaft 18 in any manner readily apparent to one skilled in the art where a rotation of crankshaft 18 will result in a corresponding driving rotation of a pump shaft. For example, a pump driveshaft 36 of high pressure source 28 is shown in
Purge system 13 may pressurize a gas and provide this pressurized gas to auxiliary regeneration system 14 for purging and/or combustion purposes. For example, a gas such as compressed air may be directed to auxiliary regeneration system 14 to purge components thereof of residual fuel and/or contaminates. Alternatively or additionally, this purge gas may be directed to mix with fuel and, thereby, aid combustion within auxiliary regeneration system 14. For these purposes, purge system 13 may include a gas source 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 purging and/or combusting process with or without operation of gas source 44. A purge passageway 40 may fluidly connect the components of auxiliary regeneration system 14 to gas source 44 at any upstream location. A check valve 42 may be disposed within purge passageway 40 to ensure that fuel and other contaminates are blocked from flowing through purge passageway 40 to gas source 44. The flow of purge gas through purge passageway 40 may be controlled by way of a suitable valve arrangement (not shown).
Auxiliary regeneration system 14 may be associated with an exhaust treatment device 46. In particular, as exhaust from power unit 10 flows through exhaust treatment device 46, particulate matter may be removed from the exhaust flow by wire mesh or ceramic honeycomb filtration media 48. Over time, the particulate matter may build up in filtration media 48 and, if left unchecked, the particulate matter buildup could be significant enough to restrict, or even block the flow of exhaust through exhaust treatment device 46, allowing for 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.
As illustrated in
Housing 50 may be an assembly of components that, together, form a combustion chamber 56. In particular, housing 50 may include a mounting element 58, a swirler plate 60, and a can 62. Swirler plate 60 may be received within mounting element 58, while can 62 may be connected to a bottom portion of mounting element 58.
Mounting element 58 may receive and fluidly connect fuel injector 52 and spark plug 54 with fuel, air, and coolant. In particular, mounting element 58 may be formed in or connected to an outer wall portion of exhaust treatment device 46, and include a stepped bore 64 for receiving fuel injector 52, and a stepped bore 66 for receiving spark plug 54. Stepped bore 64 may be in communication with common rail fuel system 12 to communicate fuel injector 52 with the pressurized fuel of pumping arrangement 22, with the compressed air of gas source 44, and/or with the heat transferring medium of a coolant system (not shown). Each of these systems may have passages that open into stepped bore 64 at different axial locations to communicate their respective fluids therewith. Stepped bore 66 may be in communication with purge system 13 via purge passageway 40.
Swirler plate 60 may be situated to conduct an electrical current to mounting element 58. That is, swirler plate 60 may be fabricated from an electrical conducting material such as, for example, a stainless steel, and press-fitted into a recess of mounting element 58. Swirler plate 60, together with mounting element 58, may form an air chamber 68, which may be supplied with compressed air from purge system 13. It is contemplated that swirler plate 60 may additionally or alternatively be connected to mounting element 58 by way of a snap-ring 70, a threaded fastener (not shown), welding, or in any other manner known in the art, if desired.
Swirler plate 60 may include a through hole 72, a grounded electrode 74, and a plurality of annularly disposed air vents 76. Grounded electrode 74 may be located at a periphery of through hole 72 to interact with spark plug 54. Air vents 76 may mix air from purge system 13 with injections of fuel inside can 62. The mixing of air and fuel within can 62 may improve combustion. It is contemplated that air vents 76 may additionally or alternatively be directed to the outer periphery of can 62 for cooling and/or insulating purposes, if desired.
Can 62 may embody a tubular member configured to axially direct an ignited fuel/air mixture from auxiliary regeneration device 14 into the exhaust flow of treatment device 46. In particular, can 62 may include a central opening 78 that fluidly communicates fuel from fuel injector 52 and air from chamber 68 with the exhaust flow. Can 62 may be generally straight and may have a predetermined length set during manufacture according to a desired flame introduction location (the distance that a flame resulting from the ignition of the fuel/air mixture extends from can 62 into the exhaust flow). In one example, this desired introduction location may be about 12 inches from an outlet 80 of can 62.
Injector 52 may be disposed within mounting element 58 and connected to fuel line 32 by way of a fuel passageway 82 and a main control valve 84 (referring to
Main control valve 84 (referring to
Spark plug 54 may facilitate ignition of fuel sprayed from injector 52 into can 62 during a regeneration event. Specifically, during a regeneration event, the temperature of the exhaust exiting power unit 10 may be too low to cause auto-ignition of the particulate matter trapped within exhaust treatment device 46 or of the fuel sprayed from injector 52. To initiate combustion of the fuel and, subsequently, the trapped particulate matter, a small quantity (i.e., a pilot shot) of fuel from injector 52 may be sprayed or otherwise injected toward the space between spark plug 54 and grounded electrode 74 to create a locally rich atmosphere readily ignitable by spark plug 54. A spark developed across electrode of spark plug 54 and grounded electrode 74 may ignite the locally rich atmosphere creating a flame, which may be jetted or otherwise advanced toward the trapped particulate matter. The flame jet propagating from injector 52 may raise the temperature within exhaust treatment device 46 to a level that readily supports efficient ignition of a larger quantity (i.e., a main shot) of fuel from injector 52. As the main injection of fuel ignites, the temperature within exhaust treatment device 46 may continue to rise to a level that causes ignition of the particulate matter trapped within filtration media 48, thereby regenerating exhaust treatment device 46.
Spark plug 54 may include multiple components that cooperate to ignite the fuel sprayed from injector 52. In particular, spark plug 54 may include a body 86, a terminal 88 extending from one end of body 86, and a center electrode 90 extending from an opposing second end of body 86. Body 86 may be threadingly received within stepped bore 66, and separated from center electrode. 90 by an insulating element 92. Center electrode 90 may be electrically connected to terminal 88. It is contemplated that terminal 88 may alternatively be integral with center electrode 90 or omitted, if desired.
An electrical arc may be generated between center electrode 90 and grounded electrode 74. That is, center electrode 90 may have a base end 94 operatively fixed to body 86, a free tip end 96, and a side portion 98 extending from base end 94 to free tip end 96. When spark plug 54 is assembled within housing 50, the free tip end 96 may extend from a first surface 99 of swirler plate 60 through hole 72 past a second surface 100 of swirler plate 60. Grounded electrode 74 may have a base end 102 connected to the second surface 100 of swirler plate 60 (i.e., integrally formed with swirler plate 60), and a free tip end 104. The free tip end 104 of grounded electrode 74 may extend toward the side portion 98 of center electrode 90, and terminate at a radial position between the base end 102 and the side portion 98. The distance between the free tip end 96 and the free tip end 104 may be designed such that, when a charge is directed through terminal 88 to center electrode 90, an arc may form from the free tip end 96 to the free tip end 104 of grounded electrode 74. This arc may facilitate ignition of the fuel/air mixture within can 62.
The spark plug arrangement of the present disclosure may be applicable to a variety of exhaust treatment devices including, for example, particulate regeneration devices and catalytic warming devices that utilize a spark to ignite a fuel flow. In fact, the disclosed spark arrangement may even be implemented into the primary combustion chambers of an engine to ignite the fuel injected during the typical power-generating cycle. The disclosed spark arrangement may ensure optimal combustion of the fuel flow by minimizing the likelihood of fuel spray blockage and unintentional arcing, while protecting the spark arrangement from residual fuel and contamination. The operation of power unit 10 will now be explained.
Referring to
To prevent the undesired buildup of particulate matter within exhaust treatment device 46, filtration media 48 may be regenerated. Regeneration may be periodic or based on a triggering condition such as, for example, a lapsed time of engine operation, a pressure differential measured across filtration media 48, a temperature of the exhaust flowing from power unit 10, or any other condition known in the art.
As illustrated in
Between and/or during regeneration events, spark plug 54 may be selectively purged of fuel and/or contaminates to ensure proper operation of spark plug 54. To purge spark plug 54, purge gas from source 44 may be directed through purge passageway 40, past check valve 42, through stepped bore 66. The purge gas flowing into stepped bore 66 may force any remaining fuel within this bore out into combustion chamber 56. By removing the fuel and/or contaminates from stepped bore 66, the likelihood of arcing at a point other than the free tip end 94 of center electrode 90 may be ensured.
Because grounded electrode 74 may be attached to housing 50, proper orientation of spark plug 54 may be ensured. That is, because the orientation of grounded electrode 74 is independent of the angular engagement of spark plug 54 with stepped bore 66, it may be ensured that grounded electrode 74 is always correctly oriented with respect to fuel injector 52, regardless of the angular orientation of spark plug 54. This correct orientation may minimize the likelihood of grounded electrode 74 undesirably blocking fuel spray from fuel injector 52, and center electrode 90 may always be positioned-correctly between fuel injector 52 and grounded electrode 74.
In addition, because grounded electrode 74 may extend from housing 50 (i.e., from swirler plate 60), the likelihood of unintentional arcing may be minimized. Specifically, because grounded electrode 74 may extend from swirler plate 60, its cantilevered distance may be short. This short cantilevered distance may minimize the amplitude of vibration induced within grounded electrode 74. By minimizing the induced amplitude vibration, the proper distance between center electrode 90 and grounded electrode 74 may be consistently maintained, thereby minimizing the likelihood of arcing at a point other that the free tip end 96 of center electrode 90, the likelihood of arcing with an improper current, and/or arcing at an improper timing. Further, the minimized vibration amplitude may correspond with an increased component life of grounded electrode 74. The increased cross-section of grounded electrode 74 afforded by its connection to swirler plate 60 may further help to reduce the amplitude of vibrations induced therein.
It will be apparent to those skilled in the art that various modifications and variations can be made to the spark plug arrangement 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 spark plug arrangement disclosed herein. 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.
