Patent Application
20220372942
TECHNICAL FIELD
The present disclosure relates generally to ducted fuel injection, and more particularly to a nested-check ducted fuel injector with a non-rotating outer check.
Modern internal combustion engines include one or more cylinders each with an associated piston to define a combustion chamber. Fuel for combustion is delivered into the combustion chamber by, for example, directly injecting the fuel using a fuel injector. Such fuel injectors have at least one and typically several spray orifices, the opening and closing of which is controlled by way of an electrically or hydraulically actuated outlet check.
Varying fuel and air mixtures, different fuel delivery parameters, equivalence ratios and other factors can produce a range of results during combustion. Certain constituents in exhaust from an internal combustion engine are often filtered, chemically reduced, or otherwise treated to limit discharge of those constituents to the environment. In recent years there has been great interest in controlling and/or managing the manner and mechanisms of combustion in an effort to control the exhaust emissions profile of internal combustion engines. Notable amongst the emissions it is generally desirable to limit are particulate matter and oxides of nitrogen or “NOx.”
Ducted fuel injection assemblies have been implemented in internal combustion engines to enhance mixing and reduce the amount of particulate matter, namely, soot, formed within the combustion chamber. Ducted assemblies typically include one or more tubular structures coupled to the cylinder head in the engine and positioned such that the ducts receive fuel spray jets from the fuel injector. The fuel spray tends to interact with the ducts, to ultimately enhance mixing of the fuel with air, in particular by increasing the so called “liftoff length” of the fuel spray jets to enable air to mix with the plumes of fuel.
One known ducted fuel injection application is set forth in U.S. Pat. No. 10,012,196B1 and entitled Duct Structure for Fuel Injector Assembly. While known ducted fuel injection techniques show promise for widespread application, there is always room for improvement and alternative strategies.
In one aspect, a fuel injector includes an injector housing having a nozzle piece defining an injector axis, and including spray orifices formed therein arranged in a first orifice set and a second orifice set. An outer check is within the nozzle piece and movable between a closed position, where each of the first orifice set and the second orifice set are blocked, and an open position, and includes transfer passages formed therein. An inner check is within the outer check and movable relative to the outer check between a closed position, where the transfer passages are blocked, and an open position. Spray ducts are coupled to the nozzle piece and each arranged for ducting spray jets of fuel from one of the spray orifices. The outer check is supported at a fixed angular orientation about the injector axis, such that the transfer passages are each in circumferential alignment with one of the spray orifices of the first orifice set.
In another aspect, a method of operating a fuel injector includes moving an inner check nested with an outer check in a fuel injector from a closed position to an open position to fluidly connect a first fuel passage formed between the inner check and the outer check to transfer passages formed in the outer check and fluidly connected to lower-flow spray orifices formed in a nozzle piece of the fuel injector. The method further includes spraying fuel from the lower-flow spray orifices based on the moving of the inner check from a closed position to an open position. The method further includes moving the outer check from a closed position to an open position to fluidly connect a second fuel passage formed between the outer check and the nozzle piece to both the lower-flow spray orifices and higher-flow spray orifices formed in the nozzle piece. The method still further includes spraying fuel from both the lower-flow spray orifices and the higher-flow spray orifices based on the moving of the outer check from a closed position to an open position, and ducting all of the fuel sprayed from the lower-flow spray orifices and from the higher-flow spray orifices through spray ducts coupled to the nozzle piece.
In still another aspect, a fuel injector nozzle assembly includes a nozzle piece defining an injector axis and having an outer nozzle surface, an inner nozzle surface forming a nozzle seat, and having spray orifices formed therein extending from the inner nozzle surface to the outer nozzle surface. The spray orifices include lower-flow spray orifices forming a first orifice set, and higher-flow spray orifices forming a second orifice set, each orifice set having a circumferential distribution about the injector axis. The assembly further includes spray ducts coupled to the nozzle piece and arranged for ducting spray jets of fuel from the first orifice set and the second orifice set, and an outer check within the nozzle piece and movable between a closed position in contact with the nozzle seat, where the second orifice set is blocked, and an open position, and the outer check has an outer check surface, an inner check surface forming a check seat, and having transfer passages formed therein extending from the inner check surface to the outer check surface. The assembly further includes an inner check within the outer check and movable relative to the outer check between a closed position in contact with the check seat, where the transfer passages are blocked, and an open position.
Referring to
Engine system 10 further includes a fuel system 22. Fuel system 22 includes a fuel tank 24, a low pressure transfer pump 26, and a high pressure pump 28. High pressure pump 28 could feed pressurized fuel at an injection pressure to a common rail in some embodiments. High pressure pump 28 could alternatively be one of a plurality of so-called unit pumps each associated with one, or more than one but less than all, of a plurality of fuel injectors each associated with one combustion cylinder in engine 11. At least one fuel conduit 43 extends to a fuel injector 30. Fuel injector 30 is positioned for direct injection of fuel into combustion cylinder 14, and includes an injector housing 32, a nozzle assembly 34, and a nested check assembly 36, as further described herein. Fuel injector 30 may include a first electrical actuator 38 operable to control opening and closing of a first check in check assembly 36, and a second electrical actuator 40 operable to control opening and closing of a second check in check assembly 36. Fuel system 22 also includes or is controlled by an electronic control unit 42 structured to selectively energize and deenergize electrical actuators 38 and 40. Those skilled in the art will appreciate that electrical actuators 38 and 40 can be associated with control valves (not shown) that are moved within fuel injector 30 to vary a closing hydraulic pressure on the checks in nested check assembly 36. As will be further apparent from the following description fuel injector 30 is ducted, to provide for certain improvements in performance respecting emissions and/or efficiency.
Referring also now to
Injector housing 32 includes a nozzle piece 44 defining an injector axis 48. Nozzle piece 44 includes a plurality of spray orifices formed therein arranged in a first orifice set and a second orifice set. In the section plane of
Nested check assembly 36 includes an outer check 54 within nozzle piece 44 and movable between a closed position, in contact with nozzle seat 98, where first orifice set 50 is not blocked and second orifice set 52 is blocked, and an open position where each of first orifice set 50 and second orifice set 52 is not blocked. Outer check 54 further includes an outside or outer check surface 104 and an inside or inner check surface 106 forming a check seat 108. Transfer passages 56 are formed in outer check 54 and extend from inner check surface 106 to outer check surface 104. It can also be seen from the Figures that outer check 54 includes an outside tip surface 72 and nozzle piece 44 includes an inside sac surface 74. A sac 76 is formed between outside tip surface 72 and inside sac surface 74. Each of outside tip surface 72 and inside sac surface 74 may be continuous, meaning uninterrupted, such that whatever volume is formed by sac 76 is closed and unconnected to combustion cylinder 14 when outer check 54 is closed. Nested check assembly 36 further includes an inner check 58 within outer check 54 and coaxially arranged therewith. Inner check 58 is movable relative to outer check 54 between a closed position, in contact with check seat 108 such that transfer passages 56 are blocked, and an open position.
A first fuel passage 64 is formed between outer check 54 and inner check 58, and a second fuel passage 66 is formed between nozzle piece 44 and outer check 54. At the open position of outer check 54 all of the spray orifices of first orifice set 50 and second orifice set 52 are fluidly connected to second fuel passage 66. When inner check 58 is at an open position and outer check 54 is at a closed position, spray orifices of first orifice set 50 are fluidly connected to first fuel passage 64 by way of transfer passages 56. Thus, when inner check 58 is open and outer check 54 is closed fuel can be injected into combustion cylinder 14 through first orifice set 50 only. When outer check 54 is open fuel can be injected through both first orifice set 50 and second orifice set 52. In an implementation a total number of transfer passages 56, for example from four transfer passages to nine transfer passages, is equal to a total number of spray orifices in first orifice set 50. A circumferential distribution of transfer passages 56 about injector axis 48 may be matched to a circumferential distribution of spray orifices in first orifice set 50.
Outer check 54 may be supported at a fixed angular orientation about injector axis 48, such that transfer passages 56 are each in circumferential alignment with one of the spray orifices of first orifice set 50. In the illustrated embodiment, injector housing 32 includes a stack 82. A stack piece (not numbered) in stack 82 includes a fixed anti-rotation surface 80. Outer check 54 includes a guide surface 78 in axial sliding contact with anti-rotation surface 80. Guide surface 78 could be a flat surface and/or a protruding surface of outer check 54 that mates with surface 80 to prevent outer check 54 from rotating around injector axis 48. It should be appreciated that any of a variety of anti-rotation strategies could be used, including complementary-shaped curved or angular surfaces, flat surfaces, or still another strategy. It will also be appreciated that fuel injector checks are conventionally permitted to rotate during service. According to the present disclosure it is desirable to maintain transfer passages 56 in circumferential alignment with first orifice set 50, hence outer check 54 is prevented from rotating to maintain the desired alignment. Inner check 58 may be permitted to rotate during service, however.
As noted above, fuel injector 30 is ducted. Fuel injector 30 includes spray ducts coupled to nozzle piece 44 and each arranged for ducting spray jets of fuel from one of the spray orifices of the respective first orifice set 50 and second orifice set 52. In an implementation the spray ducts include a first spray duct set 60 arranged for ducting spray jets of fuel from first orifice set 50, and a second spray duct set 62 arranged for ducting spray jets of fuel from second orifice set 52. Referring also now specifically to
Referring to the drawings generally, but still focusing on
Typically just after, but potentially during, spraying fuel from spray orifices of first orifice set 50 based on the moving of inner check 58 from a closed position to an open position, outer check 54 can be moved from a closed position to an open position to fluidly connect second fuel passage 66 formed between outer check 54 and nozzle piece 44 to both spray orifices of first orifice set 50 and spray orifices of second orifice set 52 formed in nozzle piece 44. Thus, spraying of fuel from first orifice set 50 may be ended prior to commencing spraying of fuel from both orifice set 50 and orifice set 52, although the present disclosure is not thereby limited. Fuel can be supplied to second fuel passage 66 by way of an inlet passage 68 extending through stack 82, as depicted in
From the foregoing description it can be appreciated that fuel injector 30 can be operated to produce separate fuel injections through first orifice set 50 and through both orifice set 50 and orifice set 52. The separate injections could include, respectively, a smaller pilot injection followed by a larger main injection. The two injections could alternatively include, respectively, a main injection, through both orifice sets, followed by a post injection. Either of the pilot then main, or main then post, or potentially pilot, then main, then post, could occur in the same engine cycle. In other instances smaller-quantity injections could be used during lower load operation, through orifice set 50, and larger-quantity injections could be used during higher load operation, through both orifice sets 50 and 52, such as operation at a rated load level. In still other instances, the injection profiles could be overlapped such as to vary the so-called rate shape of a fuel injection in a continuous fuel injection. It should also be appreciated that spray orifices of first orifice set 50 may include lower-flow spray orifices, and spray orifices of second orifice set 52 may be higher-flow spray orifices. The terms “lower-flow” and “higher-flow” are relative terms used herein in relation to each other. Analogously, other uses of the terms “higher” or “greater” and “lesser” or “smaller” are also to be understood herein in a relative sense. Spray orifices of first orifice set 50 may be lesser in flow area, such as a cross-sectional flow area, than spray orifices of second orifice set 52.
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
