Patent Application
20240200513
The present disclosure relates generally to a gaseous fuel engine, and more particularly to a non-axisymmetric fuel admission valve and operation thereof in a gaseous fuel engine.
Internal combustion engines operate by delivering a combustible fuel into a cylinder where the fuel is ignited with air to produce a controlled combustion reaction causing a rapid rise in temperature and pressure that moves a piston. While all manner of different fuels have been the subject of experimentation in engines for well over a century, recent years have seen continued and even increased interest in the use of certain gaseous fuels. Operation of an engine using a gaseous fuel, or a dual fuel combination of a gaseous fuel and a liquid fuel, may be associated with reduced emissions of certain types.
Gaseous fuels commonly used include natural gas, methane, and various blends. In one typical gaseous fuel engine design the gaseous fuel is admitted by way of fumigation into an intake system, whereas in others the gaseous fuel is injected closer to combustion cylinders at port injection locations or directly injected. A variety of mechanisms are used for igniting a gaseous fuel charge, including spark ignition, prechamber spark ignition, and liquid fuel ignition where a small shot of a liquid fuel compression ignites to initiate combustion of a larger, main charge of gaseous fuel.
Known systems and strategies have worked well for many years. There remains room for improvement, however, particularly with regard to how gaseous fuels are admitted into cylinders and dispersed. In some instances, it can be desirable for the gaseous fuel to mix relatively thoroughly with air within the cylinder, whereas in other instances it can be less important or even undesirable to achieve thorough mixing. One known internal combustion engine design capable of utilizing gaseous fuel is set forth in U.S. Pat. No. 9,188,069 B2 to Steffen.
In one aspect, a gaseous fuel engine includes an engine housing having a cylinder block with a combustion cylinder formed therein, and an engine head including a fire deck, and an intake port, an exhaust port, a fuel port, and an igniter bore, each extending to the fire deck. The gaseous fuel engine further includes a fuel admission valve defining an axis of reciprocation and translatable relative to the engine head along the axis of reciprocation between a closed position blocking the fuel port, and an open position. The fuel port includes an inner port surface. A clearance is defined between the inner port surface and the fuel admission valve and is non-axisymmetric circumferentially around the axis of reciprocation.
In another aspect, a method of operating a gaseous fuel engine includes opening an intake valve in an engine to convey pressurized air into a combustion cylinder in the engine, and opening a fuel admission valve defining an axis of reciprocation and positioned at least partially within a fuel port formed in an engine head of the engine. The method further includes conveying a gaseous fuel through the fuel port into the combustion cylinder, and directing a flow of the gaseous fuel from the fuel port into the combustion cylinder in a directionally biased flow pattern that is based on a non-axisymmetric profile of a clearance within the fuel port. The method further includes combusting the gaseous fuel and pressurized air within the combustion cylinder.
In still another aspect, an engine head assembly includes an engine head having formed therein an intake port, an exhaust port, a fuel port, and an igniter bore, each extending to a fire deck. The igniter bore defines an igniter bore axis, and the intake port and the exhaust port extend, respectively, to a plurality of intake openings and a plurality of exhaust openings, each having a distribution circumferentially around the igniter bore axis. The engine head assembly further includes a fuel admission valve defining an axis of reciprocation and translatable relative to the engine head between a closed position blocking the fuel port, and an open position. A clearance is defined between the engine head and the fuel admission valve within the fuel port and is non-axisymmetric, circumferentially around the axis of reciprocation, such that a flow of gaseous fuel from the fuel port is directionally biased.
Referring to
A gaseous fuel engine as contemplated herein includes an engine structured to operate, at least at times, principally on a gaseous fuel such as natural gas, methane, ethane, landfill gas, biogas, hydrogen gas, various blends of these and still others. A gaseous fuel engine as contemplated herein might also include a dual fuel engine where a pilot quantity of a liquid fuel, such as a diesel distillate fuel, is directly injected into cylinder 16 to compression ignite and initiate combustion of a larger, main charge of a gaseous fuel.
Engine system 8 also includes a fuel system 22 having a fuel supply 24, a fuel pump 48, and a fuel conduit 50 extending to engine head 14. Fuel supply 24 could include a supply of cryogenically stored liquified natural gas (LNG), a pressurized gaseous fuel in a storage vessel, or a connection to a line gas supply such as might be available at a well field or a mine, for example. An intake conduit 26 extends to intake port 28 to provide a supply of pressurized intake air, typically from a compressor in a turbocharger, to intake port 28 and thenceforth into cylinder 16 by way of an intake valve 30. Exhaust port 32 extends to an exhaust conduit 36 by way of an exhaust valve 34. Exhaust from exhaust conduit 36 can be conveyed to suitable aftertreatment apparatus in some embodiments.
An igniter 38 is supported in engine head 14 within igniter bore 39. Igniter 38 can include a sparkplug forming a spark gap 44 within cylinder 16. Spark gap 44 could be located within a prechamber in a sparkplug in some embodiments. In still other instances a prechamber ignition device having a spark gap within a prechamber and being equipped with a direct feed of a combustible liquid or gaseous fuel might also be used. As alluded to above, an igniter within the scope of the present disclosure could include a liquid fuel injector. An electronic control module (ECM) 42 in an ignition system 38 operates igniter 40 in the illustrated embodiment. Engine head 14 and some or all of the components formed in or supported in engine head 14 may comprise an engine head assembly 15.
Referring also now to
Gaseous fuel engine 10 also includes a fuel admission valve 54. Fuel admission valve 54 defines an axis of reciprocation 66, shown in drawings later described, and is translatable relative to engine head 14 along axis of reciprocation 66 between a closed position blocking fuel port 52, and an open position not blocking fuel port 52. An actuator 56 is coupled with fuel admission valve 54.
Referring also now to
It can further be noted from
Directional bias and like terms used herein refer to a mass flow of gaseous fuel tending to occur more in one direction away from axis of reciprocation 66 than in other directions. Thus, directionally biased toward igniter bore 40 means that a volume of gaseous fuel flow in first direction 68 away from fuel port 52 is greater than volumes of gaseous fuel flow in any other direction away from fuel port 52. The geometry of at least one of fuel admission valve 54 or fuel port 52 enables directionally biasing a flow of gaseous fuel as well as varying the directional biasing as further discussed herein.
To this end, fuel port 54 includes an inner port surface 84, and a clearance 86 is defined between inner port surface 84 and fuel admission valve 54. Clearance 86 is non-axisymmetric circumferentially around axis of reciprocation 66, such that a flow of gaseous fuel from fuel port 54 is directionally biased. Focusing now on
Referring back to
Engine head 14 may further form a valve seat 88, from casted and machined engine head material or from an interference fitted valve seat insert within engine head 14, for example. Valve head 76 may include conical or spherical, for example, valve seating surface 90 that contacts valve seat 88 at the closed position, and does not contact valve seat 88 at the open position.
Engine head 14 may further include structure for cooperating with fuel admission valve 54 in producing the directionally biased flow patterns. To this end, engine head 14 may include a flow feature 92 within fuel port 54. Fuel admission valve 54 may be rotatable between a first angular orientation about axis of reciprocation 66 at which scallop 82 is in alignment with flow feature 92, and a second angular orientation at which scallop 82 is not in alignment with flow feature 92. Between the first angular orientation and the second angular orientations different relative extents of alignment between scallop 82 and flow feature 92 may be obtained.
In the illustrated embodiment flow feature 92 includes a first profile relief feature 94 formed on a first axial side of valve seat 96 and a second profile relief feature 95 formed on a second axial side of valve seat 96. A profile relief feature may include a negative profile relief feature as illustrated, where material of engine head 14 within fuel port 52 is removed to provide additional space for gaseous fuel to flow. Embodiments are contemplated where a profile relief feature is formed on only one of a first axial side and a second axial side of a valve seat, as well as embodiments where no profile relief feature is used at all and instead directionally biasing of gaseous fuel flow is achieved solely by way of features such as a scallop on fuel admission valve 54.
Referring now also to
Turning to
Referring now to
Referring to the drawings generally, operating a gaseous fuel engine according to the present disclosure may include opening an intake valve to convey pressurized air into a combustion cylinder in the engine. Typically while the intake valve is open, although not necessarily, a fuel admission valve may be opened to convey a gaseous fuel through a fuel port as discussed herein into a combustion cylinder. A flow of the gaseous fuel from the fuel port into the combustion cylinder may be directed in a directionally biased flow pattern that is based on a non-axisymmetric profile of a clearance within a fuel port defined between an inner port surface and the fuel admission valve. The gaseous fuel and pressurized air may be combusted within the combustion cylinder such as by way of spark ignition.
It is contemplated that the use of different directionally biased flow patterns may be advantageous when operating under different engine conditions. For example, is some instances it may be desirable to advance gaseous fuel directly towards an ignition source. In other instances it may be desirable to more thoroughly mix gaseous fuel with air prior to ignition. In a practical implementation, fuel admission valve 54 may be rotated from a first angular orientation about axis of reciprocation 66 in a first engine cycle to a second angular orientation about axis of reciprocation 66 in a second engine cycle. In the first engine cycle a flow of gaseous fuel from the fuel port may be directed in a first directionally biased flow pattern. In the second engine cycle a second flow of the gaseous fuel may be directed in a second flow pattern different from the directionally biased flow pattern, such as a second, different directorially biased flow pattern.
At least one of an engine load or an engine speed may be lower in the first engine cycle and the first directionally biased flow pattern may be directionally biased in a first target direction. At least one of an engine load or an engine speed may be higher in the second engine cycle, and the second flow pattern may include a second directionally biased flow pattern directionally biased in a second target direction different from the first target direction. The first target direction might include an igniter direction, and the second target direction might include an intake valve direction, an exhaust valve direction, or a swirl direction, for example.
In this way, when ignition may be relatively more difficult to achieve, such as when an engine is operating on a lean mixture of gaseous fuel and air and/or at a low load, the fuel may be delivered predominantly towards the ignition source such as a spark igniter. At higher loads and/or at potentially richer fuel and air mixtures where ignition is relatively easier to achieve the gaseous fuel may be more thoroughly mixed. Those skilled in the art will envision various other situational factors affecting where and when one might choose to directionally bias a flow of admitted gaseous fuel.
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 openended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
