US20150345441A1 - Dual fuel engine having selective compression reduction - Google Patents
Dual fuel engine having selective compression reduction Download PDFInfo
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- US20150345441A1 US20150345441A1 US14/288,728 US201414288728A US2015345441A1 US 20150345441 A1 US20150345441 A1 US 20150345441A1 US 201414288728 A US201414288728 A US 201414288728A US 2015345441 A1 US2015345441 A1 US 2015345441A1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M43/00—Fuel-injection apparatus operating simultaneously on two or more fuels, or on a liquid fuel and another liquid, e.g. the other liquid being an anti-knock additive
- F02M43/04—Injectors peculiar thereto
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/08—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed simultaneously using pluralities of fuels
- F02D19/10—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed simultaneously using pluralities of fuels peculiar to compression-ignition engines in which the main fuel is gaseous
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/12—Transmitting gear between valve drive and valve
- F01L1/18—Rocking arms or levers
- F01L1/181—Centre pivot rocking arms
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
- F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B25/00—Engines characterised by using fresh charge for scavenging cylinders
- F02B25/02—Engines characterised by using fresh charge for scavenging cylinders using unidirectional scavenging
- F02B25/04—Engines having ports both in cylinder head and in cylinder wall near bottom of piston stroke
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/028—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation for two-stroke engines
- F02D13/0284—Variable control of exhaust valves only
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D15/00—Varying compression ratio
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D15/00—Varying compression ratio
- F02D15/04—Varying compression ratio by alteration of volume of compression space without changing piston stroke
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/0639—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels
- F02D19/0642—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/0663—Details on the fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
- F02D19/0686—Injectors
- F02D19/0689—Injectors for in-cylinder direct injection
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/0663—Details on the fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
- F02D19/0686—Injectors
- F02D19/0692—Arrangement of multiple injectors per combustion chamber
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/12—Transmitting gear between valve drive and valve
- F01L1/14—Tappets; Push rods
- F01L1/146—Push-rods
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/26—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder
- F01L1/267—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder with means for varying the timing or the lift of the valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L2820/00—Details on specific features characterising valve gear arrangements
- F01L2820/03—Auxiliary actuators
- F01L2820/033—Hydraulic engines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/02—Engines characterised by their cycles, e.g. six-stroke
- F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
- F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/30—Use of alternative fuels, e.g. biofuels
Definitions
- the present disclosure relates generally to a dual fuel engine and, more particularly, to a dual fuel engine having selective compression reduction.
- Dual-fuel engines are well known in the art and combust a mixture of two different types of fuel.
- One exemplary dual-fuel engine combusts a mixture of liquid fuel (e.g., a diesel fuel) and gaseous fuel (e.g., natural gas).
- liquid fuel e.g., a diesel fuel
- gaseous fuel e.g., natural gas
- advantages of both fuels e.g., efficiency, power, emissions, cost, etc.
- diesel fuel may be more power-dense and, thus, generate a greater amount of power per volume of fuel consumed.
- Natural gas may be more abundant and therefore less expensive than diesel fuel. In addition, natural gas may burn cleaner in some applications,.
- diesel fuel may be compression-ignited at compression ratios of about 18:1, while natural gas may ignite at compression ratios that are much lower (e.g., at about 12:1). Accordingly, when natural gas is introduced into a diesel engine having high compression ratios, pre-ignition (a.k.a., knocking) of the natural gas can occur. This pre ignition can reduce an engine's efficiency, increase noise, and/or cause damage to the engine.
- pre-ignition a.k.a., knocking
- the engine includes an intake valve driving means that drives an intake valve to open and close a port of a combustion chamber.
- a closing of the intake valve is selectively accelerated by the intake valve driving means during operation of a premixed combustion mode, when compared to a diffusion combustion mode. This accelerated closing adjusts the compression ratio of the engine to improve heat efficiency or fuel ignitability, thereby preventing the occurrence of knocking during premixed combustion.
- the intake valve driving means of the '545 patent may be capable of adjusting the compression ratio of a dual fuel engine, it may lack broad applicability. Specifically, because the compression ratio adjustment is achieved via accelerated closing of an intake valve, the intake valve driving means may not be useful in an engine that does not have intake valves. That is, the intake valve driving means may lack applicability in a two stroke engine, Further, by adjusting intake valve operation, it may be possible to cause an undesired increase in pressure, temperature, and/or fuel concentration within an associated intake air box or manifold that could make engine operation unstable. In addition, accelerating only the closing of a valve may not provide enough flexibility to control the compression ratio in all situations.
- the engine of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.
- the present disclosure is directed to an engine system.
- the engine system may include an engine block that at least partially defines a cylinder bore, and a cylinder liner disposed within the cylinder bore.
- the engine system may also include at least one air intake port radially formed within the cylinder liner, a piston slidingly disposed within the cylinder liner and configured to open and close the at least one air intake port, a cylinder head configured to close off an end of the cylinder liner and form a combustion chamber, and at least one exhaust valve disposed within the cylinder head.
- the engine system may further include a valve actuation system configured to cyclically move the at least one exhaust valve between open and closed positions, and a variable timing device configured to selectively interrupt cyclical movement of the at least one exhaust valve to change a compression ratio of the engine system.
- the present disclosure is directed to a method of operating an engine.
- the method may include directing air radially into a combustion chamber, selectively injecting gaseous fuel into the cylinder liner, and selectively injecting liquid fuel into the combustion chamber.
- the method may also include igniting a mixture of gaseous and liquid fuels within the combustion chamber to move a piston and produce mechanical power.
- the method may further include cyclically moving an exhaust valve to relieve charge from the combustion chamber, and selectively interrupting cyclical movement of the exhaust valve to adjust a compression ratio of the engine based on the mixture of gaseous and liquid fuels.
- FIGS. 1 and 2 are cross-sectional end-view illustrations of an exemplary disclosed engine system
- FIG. 3 is an exemplary disclosed timing chart associated with the engine system of FIGS. 1 and 2 .
- FIG. 1 illustrates a portion of an exemplary internal combustion engine 10 .
- Engine 10 is a two-stroke dual fuel (e.g., a compression ignition fuel such as diesel, and a gaseous fuel such as natural gas) engine haying, among other things, an engine block 12 defining at least one cylinder bore 14 .
- a cylinder liner 16 may be disposed within cylinder bore 14
- a cylinder head 18 may be connected to engine block 12 to close off an end of cylinder bore 14 .
- a piston 20 may be slidably disposed within cylinder liner 16 , and piston 20 together with cylinder liner 16 and cylinder head 18 may define a combustion chamber 22 .
- engine 10 may include any number of combustion chambers 22 and that combustion chambers 22 may be disposed in an “in-line” configuration, in a “V” configuration, in an opposing-piston configuration, or in any other suitable configuration.
- Piston 20 may be configured to reciprocate within cylinder liner 16 between a top-dead-center (TDC) position and a bottom-dead-center (BDC) position.
- piston 20 may be pivotally connected to a crankshaft 24 , which is rotatably disposed within engine block 12 , so that a sliding motion of each piston 20 within cylinder liner 16 results in a rotation of crankshaft 24 .
- a rotation of crankshaft 24 may result in a sliding motion of piston 20 .
- piston 20 may move through two full strokes (i.e., from TDC to BDC to TDC).
- Engine 10 (as a two-stroke engine) may undergo a complete combustion cycle within this time that includes a power/exhaust/intake stroke (TDC to BDC) and an intake/compression stroke (BDC to TDC).
- air may be drawn and/or forced into combustion chamber 22 via one or more intake ports 25 located within an annular surface 26 of cylinder liner 16 .
- intake ports 25 located within an annular surface 26 of cylinder liner 16 .
- a position will eventually be reached at which intake ports 25 are no longer blocked by piston 20 and instead are fluidly communicated with combustion chamber 22 .
- intake ports 25 are in fluid communication with combustion chamber 22 and a pressure of air at intake ports 25 is greater than a pressure within combustion chamber 22 , air will pass through intake ports 25 into combustion chamber 22 .
- Gaseous fuel (e.g., natural gas) may be mixed with the air before, during, and/or after the air enters combustion chamber 22 .
- a single radial fuel injector 27 is shown as being associated with one of intake ports 25 (i.e., to inject gaseous fuel through the corresponding port 25 ). It is contemplated however, that any number of injectors 27 may be utilized, and that injectors 27 may be disposed within air intake ports 25 or located elsewhere within engine 10 , as desired. The gaseous fuel from injector 27 may mix with the air from intake ports 25 to form a fuel/air mixture within combustion chamber 22 .
- a liquid fuel injector 28 may axially inject a quantity of high-pressure liquid fuel (e.g., diesel fuel, DME, heavy fuel, or another compression ignition fuel). This injection may initiate combustion of the air/fuel mixture already inside of combustion chamber 22 , resulting in a sudden release of chemical energy. This release may result in a further and significant increase in the pressure and temperature within combustion chamber 22 .
- high-pressure liquid fuel e.g., diesel fuel, DME, heavy fuel, or another compression ignition fuel
- exhaust valves 30 located within cylinder head 18 may open to allow pressurized exhaust within combustion chamber 22 to exit into an associated exhaust manifold 32 via corresponding exhaust ports 34 .
- a position will eventually be reached at which exhaust valves 30 move to fluidly communicate combustion chamber 22 with exhaust ports 34 .
- exhaust will pass from combustion chamber 22 through exhaust ports 34 into exhaust manifold 32 .
- movement of exhaust valve(s) 30 may be cyclically controlled, for example by way of a cam 36 that is mechanically connected to crankshaft 24 .
- crankshaft 24 may be rotatably connected to cam 36 by a gear train, belt, or chain (not show), and cam 36 may, in turn, be connected to exhaust valves 30 by way of an actuation assembly 38 .
- actuation assembly 38 shown in FIGS. 1 and 2 , a push rod 40 is connected at one end to a roller 42 that rides on a lobe 44 of cam 36 , and at an opposing end to a rocker arm 46 .
- Rocker arm 46 may be configured to pivot about a point 48 when lifted by the motion of can 36 via pushrod 40 , and push down on exhaust valves 30 via a bridge 50 . In this way, a rotation of crankshaft 24 can be translated into a cyclical lifting movement of exhaust valves 30 at a particular timing relative to the motion of piston 20 . It is contemplated that actuation assembly 38 may have another configuration, if desired.
- VTD variable timing device
- VTD 52 is a lost-motion mechanism configured to change operation of rocker arm 46 .
- rocker arm 46 may include two opposing arms 54 , 56 that are pinned to each other at pivot point 48 .
- Arm 54 may engage push rod 40
- arm 56 engages bridge 50 .
- Both arms 54 , 56 may be free to pivot somewhat independently about point 48 , and VTD 52 may limit the range of free pivoting.
- VTD 52 when locked in a first position (shown in FIG. 1 ), may rigidly connect arm 54 to arm 56 , such that all movement of pushrod 40 is directly transmitted to bridge 50 . But when VTD 52 is locked in a second position (shown in FIG.
- arm 54 may be allowed to freely pivot through a desired range before engaging VTD 52 and transferring motion to arm 56 .
- VTD 52 may only have two discrete positions or, alternatively, any number of positions between the first and second positions.
- VTD 52 may take any lost motion configuration known in the art. In the disclosed embodiment, however, VTD 52 is a hydraulic piston connected at one end to arm 54 and at another end to arm 56 . When completely filed with pressurized fluid, the piston becomes hydraulically locked in the first position, thereby locking any motion of arm 54 to a corresponding motion of arm 56 . When partially filled (or not filled at all), some motion of arm 54 may be lost and not transferred to arm 56 . That is, arm 54 may be able to pivot through a range of angles limited by the amount of fluid in the piston of VTD 52 before engaging VTD 52 and transferring motion to arm 56 .
- FIG. 3 An exemplary timing chart associated with engine 10 is shown in FIG. 3 . This chart will be discussed in more detail below to further illustrate the disclosed concepts.
- the disclosed engine system may be used in any machine or power system application where it is beneficial to reduce emissions of harmful gases, while also delivering inexpensive power.
- the disclosed engine system finds particular applicability within mobile machines, such as within locomotives, which can be subjected to large variations in load and emissions requirements.
- the disclosed engine system may provide an efficient way to selectively deliver gaseous fuel known to produce lower levels of regulated exhaust emissions, liquid fuel known to produce greater amounts of power, and/or mixtures of gaseous fuel and liquid fuel.
- the timing chart of FIG. 3 illustrates the opening and closing of exhaust valves 30 relative to a rotation angle of crankshaft 24 .
- exhaust valves 30 When operating using primarily liquid fuel, exhaust valves 30 may open at about 100° after TDC and close at about 240° after TDC. VTD 52 may be locked in the second position to achieve this timing and, at this timing, the motion of piston 20 may result in a compression ratio of about 18:1. As described above, this compression ratio may be sufficient to compression ignite the injected liquid fuel. However, if gaseous fuel or a mixture of gaseous fuel and liquid fuel were to be introduced into combustion chamber 22 , the compression ratio could cause the fuel to ignite prematurely.
- the timing chart of FIG. 3 also illustrates the opening and closing of exhaust valves 30 that can selectively be used during gaseous fuel operation.
- exhaust valves 30 When operating using primarily gaseous fuel, exhaust valves 30 may open at an earlier timing of about 80° after TDC and close at an extended timing of about 260° after top dead center. VTD 52 may be locked in the first position to achieve this timing and, at this timing, the motion of piston 20 may result in a compression ratio of about 12:1. Specifically, by opening exhaust valves 30 earlier and closing exhaust valves 30 later, a greater amount of charge within combustion chamber 22 may be released into exhaust manifold 32 and not be compressed by piston 20 . Accordingly, by releasing more charge into exhaust manifold 32 , a pressure within combustion chamber 22 may be lower. As described above, this compression ratio may be sufficient to compress the gaseous fuel without causing pre-ignition.
- the timing of exhaust valves 30 should be controlled to produce a compression ratio somewhere between 18:1 and 12:1, depending on the mixture.
- engine 10 should be caused to have the highest compression ratio possible, without causing pre-ignition of the gaseous fuel.
- a higher compression ratio should be implemented.
- a lower compression ratio should be implemented.
- This compression ratio may be set to a desired level by selectively filling the piston of VTD 52 with varying amounts of pressurized fluid, thereby causing varying amounts of the motion of push rod 40 to be lost and exhaust valves 30 to consequently be opened and closed at different times.
- the transition should be generally smooth and linear, such that operation of the engine is not significantly impacted.
- the transition may be made over multiple engine cycles (e.g., over about five cycles or during about one second of engine operation), with the timing changing no more than about 2°/cycle. In this manner, the power output and stability of engine 10 may be maintained.
- the disclosed system may be applicable to any type of dual fuel engine, including both two and four-stroke engines.
- control over intake air pressure, temperature, and fuel concentration may be maintained.
- the disclosed system may also allow for fine adjustments to valve opening and closing times, which may provide for greater flexibility in engine control.
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Abstract
Description
- The present disclosure relates generally to a dual fuel engine and, more particularly, to a dual fuel engine having selective compression reduction.
- Dual-fuel engines are well known in the art and combust a mixture of two different types of fuel. One exemplary dual-fuel engine combusts a mixture of liquid fuel (e.g., a diesel fuel) and gaseous fuel (e.g., natural gas). By combusting two different types of fuel, advantages of both fuels (e.g., efficiency, power, emissions, cost, etc.) can be realized. For example, diesel fuel may be more power-dense and, thus, generate a greater amount of power per volume of fuel consumed. Natural gas, however, may be more abundant and therefore less expensive than diesel fuel. In addition, natural gas may burn cleaner in some applications,.
- In order to realize full benefits of operating a dual-fuel engine, care should be taken to ensure proper combustion of the different fuels, That is, diesel fuel may be compression-ignited at compression ratios of about 18:1, while natural gas may ignite at compression ratios that are much lower (e.g., at about 12:1). Accordingly, when natural gas is introduced into a diesel engine having high compression ratios, pre-ignition (a.k.a., knocking) of the natural gas can occur. This pre ignition can reduce an engine's efficiency, increase noise, and/or cause damage to the engine.
- An exemplary dual-fuel engine is disclosed in JP Patent 2008/202545 (“the '545 patent”). The engine includes an intake valve driving means that drives an intake valve to open and close a port of a combustion chamber. A closing of the intake valve is selectively accelerated by the intake valve driving means during operation of a premixed combustion mode, when compared to a diffusion combustion mode. This accelerated closing adjusts the compression ratio of the engine to improve heat efficiency or fuel ignitability, thereby preventing the occurrence of knocking during premixed combustion.
- Although the intake valve driving means of the '545 patent may be capable of adjusting the compression ratio of a dual fuel engine, it may lack broad applicability. Specifically, because the compression ratio adjustment is achieved via accelerated closing of an intake valve, the intake valve driving means may not be useful in an engine that does not have intake valves. That is, the intake valve driving means may lack applicability in a two stroke engine, Further, by adjusting intake valve operation, it may be possible to cause an undesired increase in pressure, temperature, and/or fuel concentration within an associated intake air box or manifold that could make engine operation unstable. In addition, accelerating only the closing of a valve may not provide enough flexibility to control the compression ratio in all situations.
- The engine of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.
- In one aspect, the present disclosure is directed to an engine system. The engine system may include an engine block that at least partially defines a cylinder bore, and a cylinder liner disposed within the cylinder bore. The engine system may also include at least one air intake port radially formed within the cylinder liner, a piston slidingly disposed within the cylinder liner and configured to open and close the at least one air intake port, a cylinder head configured to close off an end of the cylinder liner and form a combustion chamber, and at least one exhaust valve disposed within the cylinder head. The engine system may further include a valve actuation system configured to cyclically move the at least one exhaust valve between open and closed positions, and a variable timing device configured to selectively interrupt cyclical movement of the at least one exhaust valve to change a compression ratio of the engine system.
- In another aspect, the present disclosure is directed to a method of operating an engine. The method may include directing air radially into a combustion chamber, selectively injecting gaseous fuel into the cylinder liner, and selectively injecting liquid fuel into the combustion chamber. The method may also include igniting a mixture of gaseous and liquid fuels within the combustion chamber to move a piston and produce mechanical power. The method may further include cyclically moving an exhaust valve to relieve charge from the combustion chamber, and selectively interrupting cyclical movement of the exhaust valve to adjust a compression ratio of the engine based on the mixture of gaseous and liquid fuels.
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FIGS. 1 and 2 are cross-sectional end-view illustrations of an exemplary disclosed engine system; and -
FIG. 3 is an exemplary disclosed timing chart associated with the engine system ofFIGS. 1 and 2 . -
FIG. 1 illustrates a portion of an exemplaryinternal combustion engine 10.Engine 10 is a two-stroke dual fuel (e.g., a compression ignition fuel such as diesel, and a gaseous fuel such as natural gas) engine haying, among other things, anengine block 12 defining at least one cylinder bore 14. Acylinder liner 16 may be disposed withincylinder bore 14, and acylinder head 18 may be connected toengine block 12 to close off an end ofcylinder bore 14. Apiston 20 may be slidably disposed withincylinder liner 16, andpiston 20 together withcylinder liner 16 andcylinder head 18 may define acombustion chamber 22. It is contemplated thatengine 10 may include any number ofcombustion chambers 22 and thatcombustion chambers 22 may be disposed in an “in-line” configuration, in a “V” configuration, in an opposing-piston configuration, or in any other suitable configuration. - Piston 20 may be configured to reciprocate within
cylinder liner 16 between a top-dead-center (TDC) position and a bottom-dead-center (BDC) position. In particular,piston 20 may be pivotally connected to acrankshaft 24, which is rotatably disposed withinengine block 12, so that a sliding motion of eachpiston 20 withincylinder liner 16 results in a rotation ofcrankshaft 24. Similarly, a rotation ofcrankshaft 24 may result in a sliding motion ofpiston 20. Ascrankshaft 24 rotates through about 180°,piston 20 may move through two full strokes (i.e., from TDC to BDC to TDC). Engine 10 (as a two-stroke engine) may undergo a complete combustion cycle within this time that includes a power/exhaust/intake stroke (TDC to BDC) and an intake/compression stroke (BDC to TDC). - During a final phase of the intake stroke, air may be drawn and/or forced into
combustion chamber 22 via one ormore intake ports 25 located within anannular surface 26 ofcylinder liner 16. In particular, aspiston 20 moves downward withincylinder liner 16, a position will eventually be reached at whichintake ports 25 are no longer blocked bypiston 20 and instead are fluidly communicated withcombustion chamber 22. Whenintake ports 25 are in fluid communication withcombustion chamber 22 and a pressure of air atintake ports 25 is greater than a pressure withincombustion chamber 22, air will pass throughintake ports 25 intocombustion chamber 22. - Gaseous fuel (e.g., natural gas) may be mixed with the air before, during, and/or after the air enters
combustion chamber 22. In the disclosed embodiment, a singleradial fuel injector 27 is shown as being associated with one of intake ports 25 (i.e., to inject gaseous fuel through the corresponding port 25). It is contemplated however, that any number ofinjectors 27 may be utilized, and thatinjectors 27 may be disposed withinair intake ports 25 or located elsewhere withinengine 10, as desired. The gaseous fuel frominjector 27 may mix with the air fromintake ports 25 to form a fuel/air mixture withincombustion chamber 22. - During the beginning of the compression stroke described above, air may still be entering
combustion chamber 22 viaintake ports 25 aspiston 20 starts its upward stroke to mix any residual gas with air and fuel incombustion chamber 22. Eventually,intake ports 25 may be blocked bypiston 20, and further upward motion ofpiston 20 may compress the mixture. As the mixture withincombustion chamber 22 is compressed, the mixture will increase in pressure and temperature. At a point near the end of the upward piston stroke, aliquid fuel injector 28 may axially inject a quantity of high-pressure liquid fuel (e.g., diesel fuel, DME, heavy fuel, or another compression ignition fuel). This injection may initiate combustion of the air/fuel mixture already inside ofcombustion chamber 22, resulting in a sudden release of chemical energy. This release may result in a further and significant increase in the pressure and temperature withincombustion chamber 22. - After
piston 20 reaches TDC, the increased pressure caused by combustion may forcepiston 20 downward, thereby imparting mechanical power tocrankshaft 24. During a return of piston 20 (i.e., during the ensuing upward movement of the exhaust stroke), one ormore exhaust valves 30 located withincylinder head 18 may open to allow pressurized exhaust withincombustion chamber 22 to exit into an associatedexhaust manifold 32 viacorresponding exhaust ports 34. In particular, aspiston 20 moves upward withincylinder liner 16, a position will eventually be reached at whichexhaust valves 30 move to fluidly communicatecombustion chamber 22 withexhaust ports 34. Whencombustion chamber 22 is in fluid communication withexhaust ports 34 and a pressure incombustion chamber 22 is greater than a pressure atexhaust ports 34, exhaust will pass fromcombustion chamber 22 throughexhaust ports 34 intoexhaust manifold 32. - In the disclosed embodiment, movement of exhaust valve(s) 30 may be cyclically controlled, for example by way of a
cam 36 that is mechanically connected tocrankshaft 24. In particular,crankshaft 24 may be rotatably connected tocam 36 by a gear train, belt, or chain (not show), andcam 36 may, in turn, be connected toexhaust valves 30 by way of anactuation assembly 38. In theexemplary actuation assembly 38 shown inFIGS. 1 and 2 , apush rod 40 is connected at one end to aroller 42 that rides on alobe 44 ofcam 36, and at an opposing end to arocker arm 46. Rockerarm 46 may be configured to pivot about apoint 48 when lifted by the motion of can 36 viapushrod 40, and push down onexhaust valves 30 via abridge 50. In this way, a rotation ofcrankshaft 24 can be translated into a cyclical lifting movement ofexhaust valves 30 at a particular timing relative to the motion ofpiston 20. It is contemplated thatactuation assembly 38 may have another configuration, if desired. - As will be described in more detail below, it may be advantageous to selectively alter the timing at which
exhaust valves 30 are opened relative to the movement ofcrankshaft 24 andpiston 20. In particular, the timing at whichexhaust valves 30 open and close may dictate a pressure and/or a temperature subsequently generated withincombustion chamber 22 by the upward movement ofpiston 20. And in some applications, the pressure and/or temperature may be great enough to cause premature ignition of the air/fuel mixture incombustion chamber 22. Premature ignition can result in inefficiency, noise, and/or damage toengine 10. Accordingly, in some applications, a variable timing device (VTD) 52 may be used to selectively reduce a compression ratio ofpiston 20, such that premature ignition is inhibited. - In the disclosed embodiment,
VTD 52 is a lost-motion mechanism configured to change operation ofrocker arm 46. Specifically,rocker arm 46 may include two opposingarms pivot point 48.Arm 54 may engagepush rod 40, whilearm 56 engagesbridge 50. Botharms point 48, andVTD 52 may limit the range of free pivoting. For example,VTD 52, when locked in a first position (shown inFIG. 1 ), may rigidly connectarm 54 toarm 56, such that all movement ofpushrod 40 is directly transmitted to bridge 50. But whenVTD 52 is locked in a second position (shown inFIG. 2 ),arm 54 may be allowed to freely pivot through a desired range before engagingVTD 52 and transferring motion toarm 56. In other words, whenVTD 52 is in the second position, some motion ofpush rod 40 may be lost during the time thatarm 54 freely pivots. It is contemplated thatVTD 52 may only have two discrete positions or, alternatively, any number of positions between the first and second positions. -
VTD 52 may take any lost motion configuration known in the art. In the disclosed embodiment, however,VTD 52 is a hydraulic piston connected at one end toarm 54 and at another end toarm 56. When completely filed with pressurized fluid, the piston becomes hydraulically locked in the first position, thereby locking any motion ofarm 54 to a corresponding motion ofarm 56. When partially filled (or not filled at all), some motion ofarm 54 may be lost and not transferred toarm 56. That is,arm 54 may be able to pivot through a range of angles limited by the amount of fluid in the piston ofVTD 52 before engagingVTD 52 and transferring motion toarm 56. - An exemplary timing chart associated with
engine 10 is shown inFIG. 3 . This chart will be discussed in more detail below to further illustrate the disclosed concepts. - The disclosed engine system may be used in any machine or power system application where it is beneficial to reduce emissions of harmful gases, while also delivering inexpensive power. The disclosed engine system finds particular applicability within mobile machines, such as within locomotives, which can be subjected to large variations in load and emissions requirements. The disclosed engine system may provide an efficient way to selectively deliver gaseous fuel known to produce lower levels of regulated exhaust emissions, liquid fuel known to produce greater amounts of power, and/or mixtures of gaseous fuel and liquid fuel.
- The timing chart of
FIG. 3 illustrates the opening and closing ofexhaust valves 30 relative to a rotation angle ofcrankshaft 24. When operating using primarily liquid fuel,exhaust valves 30 may open at about 100° after TDC and close at about 240° after TDC.VTD 52 may be locked in the second position to achieve this timing and, at this timing, the motion ofpiston 20 may result in a compression ratio of about 18:1. As described above, this compression ratio may be sufficient to compression ignite the injected liquid fuel. However, if gaseous fuel or a mixture of gaseous fuel and liquid fuel were to be introduced intocombustion chamber 22, the compression ratio could cause the fuel to ignite prematurely. - The timing chart of
FIG. 3 also illustrates the opening and closing ofexhaust valves 30 that can selectively be used during gaseous fuel operation. When operating using primarily gaseous fuel,exhaust valves 30 may open at an earlier timing of about 80° after TDC and close at an extended timing of about 260° after top dead center.VTD 52 may be locked in the first position to achieve this timing and, at this timing, the motion ofpiston 20 may result in a compression ratio of about 12:1. Specifically, by openingexhaust valves 30 earlier and closingexhaust valves 30 later, a greater amount of charge withincombustion chamber 22 may be released intoexhaust manifold 32 and not be compressed bypiston 20. Accordingly, by releasing more charge intoexhaust manifold 32, a pressure withincombustion chamber 22 may be lower. As described above, this compression ratio may be sufficient to compress the gaseous fuel without causing pre-ignition. - When operating
engine 10 using a mixture of gaseous and liquid fuels, the timing ofexhaust valves 30 should be controlled to produce a compression ratio somewhere between 18:1 and 12:1, depending on the mixture. Ideally,engine 10 should be caused to have the highest compression ratio possible, without causing pre-ignition of the gaseous fuel. Thus, for a greater concentration of liquid fuel, a higher compression ratio should be implemented. And for a greater concentration of gaseous fuel, a lower compression ratio should be implemented. This compression ratio may be set to a desired level by selectively filling the piston ofVTD 52 with varying amounts of pressurized fluid, thereby causing varying amounts of the motion ofpush rod 40 to be lost andexhaust valves 30 to consequently be opened and closed at different times. - Care should be taken when transitioning between liquid fuel operation at higher compression ratios and gaseous fuel operation at lower compression ratios. For example, the transition should be generally smooth and linear, such that operation of the engine is not significantly impacted. In one embodiment, the transition may be made over multiple engine cycles (e.g., over about five cycles or during about one second of engine operation), with the timing changing no more than about 2°/cycle. In this manner, the power output and stability of
engine 10 may be maintained. - In some embodiments, it may be possible to vary the opening and closing timings of
exhaust valves 30 independently. Specifically, it may be possible to causeVTD 52 to move between the first and second positions whileexhaust valves 30 are open. This may allow forexhaust valve 30 to open at a conventional timing and close early, or open late and close at a conventional timing. And doing so may provide finer control over the compression ratio ofcombustion chamber 22. It may also be possible to vary the opening and/or closing timings of oneexhaust valve 30 associated with onecombustion chamber 22 separately and independently of another exhaust valve associated with adifferent combustion chamber 22. This may allow for even finer control over engine operation. - The disclosed system may be applicable to any type of dual fuel engine, including both two and four-stroke engines. In addition, by releasing charge from
combustion chamber 22 intoexhaust manifold 32 via exhaust ports 34 (as opposed to through intake ports 25), control over intake air pressure, temperature, and fuel concentration may be maintained. The disclosed system may also allow for fine adjustments to valve opening and closing times, which may provide for greater flexibility in engine control. - It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed engine systems without departing from the scope of the disclosure. Other embodiments of the engine systems will be apparent to those skilled in the art from consideration of the specification and practice of the engine systems disclosed herein. For example, the disclosed embodiment of
VTD 52 is exemplary only. Other “lost motion” actuators may be paired withexhaust valves 30 to achieve the desired opening and closing timings described above. 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.
Claims (20)
Priority Applications (3)
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US14/288,728 US9194344B1 (en) | 2014-05-28 | 2014-05-28 | Dual fuel engine having selective compression reduction |
CN201510275985.3A CN105275597A (en) | 2014-05-28 | 2015-05-27 | Dual fuel engine having selective compression reduction |
DE102015006785.0A DE102015006785A1 (en) | 2014-05-28 | 2015-05-27 | Dual fuel engine with selective reduction of compression |
Applications Claiming Priority (1)
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US14/288,728 US9194344B1 (en) | 2014-05-28 | 2014-05-28 | Dual fuel engine having selective compression reduction |
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US9194344B1 US9194344B1 (en) | 2015-11-24 |
US20150345441A1 true US20150345441A1 (en) | 2015-12-03 |
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US14/288,728 Active US9194344B1 (en) | 2014-05-28 | 2014-05-28 | Dual fuel engine having selective compression reduction |
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US (1) | US9194344B1 (en) |
CN (1) | CN105275597A (en) |
DE (1) | DE102015006785A1 (en) |
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US10072561B2 (en) * | 2016-07-25 | 2018-09-11 | Caterpillar Inc. | Piston |
US9903284B1 (en) | 2016-10-31 | 2018-02-27 | General Electric Company | Dual-fuel engine system and method having the same |
KR102217236B1 (en) * | 2017-03-06 | 2021-02-18 | 가부시키가이샤 아이에이치아이 | Uniflow scavenging two-cycle engine |
IL275972B (en) * | 2019-08-17 | 2022-05-01 | Zhmudyak Alexandra | Method of gas exchange for four-stroke engine |
Family Cites Families (14)
Publication number | Priority date | Publication date | Assignee | Title |
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SE504145C2 (en) | 1995-03-20 | 1996-11-18 | Volvo Ab | Exhaust valve mechanism in an internal combustion engine |
DE102004057438A1 (en) | 2004-11-27 | 2006-06-01 | Man B & W Diesel Ag | Gear train consists of tilt lever that operates with gas exchange valve and is connected to push rod that has adjustment system that comprises an adjustable oscillating lever that works with a tappet shaft and cam |
CN100510352C (en) | 2005-02-11 | 2009-07-08 | 沃尔沃拉斯特瓦格纳公司 | Device for internal-combustion engine |
JP4492523B2 (en) * | 2005-10-31 | 2010-06-30 | トヨタ自動車株式会社 | Internal combustion engine with variable compression ratio and valve characteristics |
JP4946173B2 (en) * | 2006-05-17 | 2012-06-06 | 日産自動車株式会社 | Internal combustion engine |
JP4749988B2 (en) * | 2006-10-23 | 2011-08-17 | 日立オートモティブシステムズ株式会社 | Start control device for internal combustion engine |
JP2008202545A (en) | 2007-02-21 | 2008-09-04 | Mitsubishi Heavy Ind Ltd | Dual fuel engine |
JP4367547B2 (en) * | 2007-11-06 | 2009-11-18 | トヨタ自動車株式会社 | Spark ignition internal combustion engine |
EP2108800B1 (en) * | 2008-04-10 | 2010-05-26 | C.R.F. Società Consortile per Azioni | Turbo-charged gasoline engine with variable control of the intake valves |
WO2011015603A2 (en) | 2009-08-04 | 2011-02-10 | Eaton Srl | Lost motion valve control apparatus |
JP4993010B2 (en) * | 2010-08-21 | 2012-08-08 | マツダ株式会社 | Spark ignition multi-cylinder engine |
JP5143877B2 (en) | 2010-09-21 | 2013-02-13 | 日立オートモティブシステムズ株式会社 | Control device for variable valve timing mechanism |
JP5851918B2 (en) * | 2012-04-11 | 2016-02-03 | 三菱重工業株式会社 | Dual fuel diesel engine and operating method thereof |
JP6050130B2 (en) * | 2013-01-25 | 2016-12-21 | 本田技研工業株式会社 | Premixed compression self-ignition engine |
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2014
- 2014-05-28 US US14/288,728 patent/US9194344B1/en active Active
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2015
- 2015-05-27 CN CN201510275985.3A patent/CN105275597A/en active Pending
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DE102015006785A1 (en) | 2015-12-03 |
CN105275597A (en) | 2016-01-27 |
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