CA2848849C - Multi-fuel injection system and method - Google Patents
Multi-fuel injection system and method Download PDFInfo
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- CA2848849C CA2848849C CA2848849A CA2848849A CA2848849C CA 2848849 C CA2848849 C CA 2848849C CA 2848849 A CA2848849 A CA 2848849A CA 2848849 A CA2848849 A CA 2848849A CA 2848849 C CA2848849 C CA 2848849C
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- fuel injector
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- injection
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Classifications
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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
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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
- 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
- F02D19/0694—Injectors operating with a plurality of fuels
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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
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
-
- 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
-
- 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
-
- 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
- F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
- F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
- F02M45/04—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts with a small initial part, e.g. initial part for partial load and initial and main part for full load
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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
- F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
- F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
- F02M45/04—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts with a small initial part, e.g. initial part for partial load and initial and main part for full load
- F02M45/08—Injectors peculiar thereto
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0027—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures the fuel being gaseous
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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
Abstract
A multi-fuel injection system and method for an internal combustion engine comprises a first fuel injector having a flow area sized for accurate and consistent injection of a pilot amount of a first fuel directly into a combustion chamber, and a second fuel injector in selective communication with a supply of the first fuel and a supply of a second fuel, the second fuel injector having a flow area sized to accommodate injection the first fuel directly into the combustion chamber in amounts required to deliver enough energy to enable operation across a range of engine operating conditions, including high load conditions, with only the first fuel supplied as fuel to the combustion chamber. When the second fuel injector is supplied with the second fuel, it is operable for late- cycle injection of a portion of the second fuel that is required to operate said engine at high load.
Description
, MULTI- FUEL INJECTION SYSTEM AND METHOD
Technical Field [0001] The present disclosure relates to a multi-fuel injection system and method for an internal combustion engine.
Background of the Invention
Technical Field [0001] The present disclosure relates to a multi-fuel injection system and method for an internal combustion engine.
Background of the Invention
[0002] Many technologies are being developed to allow conventional internal combustion engines that are normally fuelled with liquid fuels, to be fuelled at least in part with gaseous fuels. By way of example, gaseous fuels include natural gas, hydrogen, pure methane, propane (sometimes called liquefied petroleum gas or LPG), and blends of such fuels. Natural gas has received the most attention in recent years because it is cleaner burning than most conventional liquid fuels, it is abundant and broadly available around the world, and depending upon the local market conditions, it is generally less expensive than liquid fuel alternatives and with less price volatility. All of these factors make it attractive to substitute at least some fuel consumption, and preferably as much as possible, with natural gas instead of conventional liquid fuels, such as gasoline and diesel.
[0003] One of the early approaches was to pre-mix the natural gas with the intake air and then ignite the air-fuel mixture in the combustion chamber using a spark plug.
An advantage of this approach is that the fuel can be introduced through one fuel injector upstream from the branches of the intake air manifold that lead into each combustion chamber, or through a plurality of fuel injectors, each one being associated with a respective intake air port (for so-called "port injection"). Problems associated with this approach include reduced power output and lower combustion efficiency because this approach typically involves reducing the compression ratio and/or the amount of fuel that is introduced (compared to an equivalently sized diesel engine) to avoid engine knock, which is premature detonation of the pre-mixed air-fuel mixture. Introducing the fuel into the intake air system displaces some of the air that would normally flow into the combustion chambers through the engine intake valves, which can also affect power , output. Lower power output results in users needing to choose a larger engine size, compared to a diesel engine to achieve an equivalent power output. Another problem is managing the air-fuel mixture ratio because natural gas is combustible in only a relatively narrow range of air-fuel mixture ratios, compared to other fuels.
An advantage of this approach is that the fuel can be introduced through one fuel injector upstream from the branches of the intake air manifold that lead into each combustion chamber, or through a plurality of fuel injectors, each one being associated with a respective intake air port (for so-called "port injection"). Problems associated with this approach include reduced power output and lower combustion efficiency because this approach typically involves reducing the compression ratio and/or the amount of fuel that is introduced (compared to an equivalently sized diesel engine) to avoid engine knock, which is premature detonation of the pre-mixed air-fuel mixture. Introducing the fuel into the intake air system displaces some of the air that would normally flow into the combustion chambers through the engine intake valves, which can also affect power , output. Lower power output results in users needing to choose a larger engine size, compared to a diesel engine to achieve an equivalent power output. Another problem is managing the air-fuel mixture ratio because natural gas is combustible in only a relatively narrow range of air-fuel mixture ratios, compared to other fuels.
[0004] Another approach is known in the industry as "dual fuel" and with the typical version of this approach, the fuel is still introduced with the intake air, but instead of a spark, a small pilot quantity of auto-igniting fuel such as diesel for example, is injected directly into the combustion chamber to ignite the natural gas. Dual fuel engines typically have limitations on the amount of natural gas that can be substituted instead of diesel. Reasons for limitations include, limits on the amount of natural gas that can be pre-mixed under high load conditions (to avoid engine knock), and low substitution at low loads because diesel fuel injectors designed for full-diesel operation lack the turn down ratio for accurately and consistently injecting small amounts of pilot fuel.
Consequently, at idle and low loads, dual fuel engines are often fuelled mostly with conventional diesel fuel.
Consequently, at idle and low loads, dual fuel engines are often fuelled mostly with conventional diesel fuel.
[0005] Yet another approach is known in the industry as "high pressure direct injection"
or "HPDI" which injects the gaseous fuel directly into the combustion chamber, late-cycle so that there is reduced risk of engine knock. Examples of this approach are disclosed in co-owned patents US 6,675,748; US 6,761,325; US 6,912,992; US
7,162,995; and US 7,463,967. Depending upon the engine compression ratio and other engine design features which determine the temperature, pressure and other conditions inside the combustion chamber during engine operation, an ignition trigger can still be employed, such as the injection of a pilot amount of diesel fuel, an ignition plug, for example a glow plug or a spark plug. Unlike engines which introduce the gaseous fuel with the intake air, to form a charge of premixed air and fuel, there is much less concern for engine knock when the gaseous fuel is injected directly in the combustion late-cycle, because the timing for injecting the gaseous fuel can be chosen to that combustible mixture does not form before the desired timing for ignition.
or "HPDI" which injects the gaseous fuel directly into the combustion chamber, late-cycle so that there is reduced risk of engine knock. Examples of this approach are disclosed in co-owned patents US 6,675,748; US 6,761,325; US 6,912,992; US
7,162,995; and US 7,463,967. Depending upon the engine compression ratio and other engine design features which determine the temperature, pressure and other conditions inside the combustion chamber during engine operation, an ignition trigger can still be employed, such as the injection of a pilot amount of diesel fuel, an ignition plug, for example a glow plug or a spark plug. Unlike engines which introduce the gaseous fuel with the intake air, to form a charge of premixed air and fuel, there is much less concern for engine knock when the gaseous fuel is injected directly in the combustion late-cycle, because the timing for injecting the gaseous fuel can be chosen to that combustible mixture does not form before the desired timing for ignition.
[0006] When a pilot fuel is used to trigger ignition for an HPDI engine, the amount of pilot fuel on average is less than 10%, and more preferably less than 5% of the total fuel consumed on an energy basis. For consistent control of the amount of pilot fuel that is injected, to ensure stable operation, the pilot fuel injector is designed with a flow through capacity suitable for small amounts of fuel. When the pilot fuel injector is designed for this purpose, it is not possible to operate the engine at full load with just pilot fuel, because the flow capacity is too small. Gaseous fuels are not as dense as liquid fuels, so a much higher volumetric flow capacity is required in order to inject between 90% and 95% of the total fuel demanded on an energy basis. Accordingly, with a conventional HPDI engine, if the supply of gaseous fuel is depleted, the engine is de-rated to run in a "limp home mode" when only pilot fuel is available. For on-highway vehicles, this allows the vehicle operator to safely park the vehicle or "limp" a short distance to a refuelling station. This inconvenience can be avoided simply by good management of the fuel on board the vehicle and when gaseous-fueled vehicles receive financial incentives for switching to a cleaner burning fuel, those that give such incentives consider de-rated operation when fuelled only with pilot fuel to be extra incentive to use gaseous fuel instead of pilot diesel fuel.
[0007] However, there are some engine applications like rail or marine where a limp home mode is not acceptable, because the potential distance to be travelled to be re-fueled is too far. Accordingly, there is a need for an HPDI-type engine to operate at full load with just pilot fuel.
Summary
Summary
[0008] An improved multi-fuel injection system for an internal combustion engine comprises a first fuel injector in fluid communication with a supply for a first fuel. The first fuel injector has a flow area sized for accurate and consistent injection of a pilot amount of the first fuel directly into a combustion chamber. There is a second fuel injector in selective fluid communication with one of the supply for the first fuel and a supply for a second fuel. The second fuel injector has a flow area sized to accommodate late-cycle injection directly into the combustion chamber of an accurate and consistent amount of the first fuel up to an amount required to deliver enough energy to enable the internal combustion engine to operate across a range of engine operating conditions including high load conditions, with only the first fuel supplied as fuel to the combustion chamber. When the second fuel injector is in fluid communication with the supply for the second fuel, the second fuel injector is operable for late-cycle injection directly into the combustion chamber of an amount of the second fuel that delivers enough energy to enable the internal combustion engine to operate across a partial range of engine operating conditions, not including high load operating conditions. A flow switching device selectively fluidly connects the second fuel injector to one of the first fuel supply and the second fuel supply. In a preferred embodiment, the first fuel is a liquid fuel and the second fuel is a gaseous fuel. When the second fuel is injected at high pressure it has a pressure of at least 100 bar. The second fuel injector can be a common rail injector.
[0009] In a preferred embodiment, the second fuel injector is actuatable to a first open position having a first flow area and a second open position having a second flow area.
When the second fuel injector is in fluid communication with the supply for the second fuel, the first flow area is sized to enable the internal combustion engine to operate across the partial range of engine operating conditions, not including high load operating conditions, and the second flow area is sized to enable the internal combustion engine to operate at high load operating conditions.
When the second fuel injector is in fluid communication with the supply for the second fuel, the first flow area is sized to enable the internal combustion engine to operate across the partial range of engine operating conditions, not including high load operating conditions, and the second flow area is sized to enable the internal combustion engine to operate at high load operating conditions.
[0010] In another preferred embodiment, the second fuel injector has an actuator that can open the second fuel injector for at least two injection pulses in each engine cycle. When the second fuel injector is in fluid communication with the supply for the second fuel, one injection pulse is timed for early-cycle injection of the second fuel and a second injection pulse is timed for late-cycle injection of the second fuel, such that the total amount of energy associated with the injection pulses enables the engine to operate across the range of engine operating conditions including high load conditions in a mode where only a pilot amount of the first fuel is injected through the first fuel injector and the remainder of the fuel required for the demanded load is provided by the second fuel, which is injected through the second fuel injector.
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[0011] In yet another preferred embodiment, there is a third fuel injector in fluid communication with the supply of the second fuel. The total amount of energy associated with injection of the second fuel by the second fuel injector and the third fuel injector enables the engine to operate across the full range of engine operating conditions in a mode where only a pilot amount of the first fuel is injected through the first fuel injector.
The third fuel injector can be positioned to directly inject fuel into the combustion chamber. Alternatively, the third fuel injector can be positioned upstream from an engine intake valve, such as in an intake port, whereby the second fuel is injectable through the third fuel injector into an intake air system and later introduced into the combustion chamber together with air. In this circumstance, the supply of the second fuel can comprise a low pressure branch in fluid communication with the third fuel injector, and a high pressure branch in fluid communication with the second fuel injector.
The third fuel injector can be positioned to directly inject fuel into the combustion chamber. Alternatively, the third fuel injector can be positioned upstream from an engine intake valve, such as in an intake port, whereby the second fuel is injectable through the third fuel injector into an intake air system and later introduced into the combustion chamber together with air. In this circumstance, the supply of the second fuel can comprise a low pressure branch in fluid communication with the third fuel injector, and a high pressure branch in fluid communication with the second fuel injector.
[0012] When the second fuel is introduced early-cycle, an engine control unit is programmed to receive engine operating data and to limit the amount of second fuel that is introduced early-cycle to prevent the formation of combustible air-fuel mixtures susceptible to premature detonation.
[0013] An improved method of controlling a multi-fuel injection system for an internal combustion engine comprises operating in at least three modes. In a first mode, injecting into a combustion chamber, late-cycle, a pilot amount of a first fuel with a first fuel injector, and injecting into the combustion chamber, late-cycle, an amount of a second fuel with a second fuel injector, with the energy from the first and second fuels being matched to the energy required for operating in the first mode. In a second mode, in which the total energy required is higher than the total energy that can be injected by the first mode of operation, one of injecting a first portion of the second fuel with a second fuel injector and a second portion of the second fuel with a third fuel injector; and actuating the second fuel injector to one of at least two open positions and in the second mode the second fuel injector is opened to a second position having greater flow area compared to when it is opened to a first position in the first mode. In a third mode, selectively injecting the first fuel through both the first fuel injector and the second fuel injector, and controlling the amount of the first fuel that is injected to match the energy required for any commanded operating condition within a normal range of operation associated with the internal combustion engine.
[0014] In a preferred embodiment, in the second mode, pre-mixing the second portion of the second fuel with an intake charge and later injecting late-cycle, the pilot amount of the first fuel through the first fuel injector, and the first portion of the second fuel. The second fuel can be supplied to the second injector at a higher pressure than that of the second fuel that is supplied to the third injector. Preferably, when operating in the second mode, the method further comprises limiting the second portion of the second fuel that is premixed so that the air-fuel ratio remains below the knock limit.
[0015] In another preferred embodiment, the method includes injecting late-cycle, the pilot amount of the first fuel through the first fuel injector and the first portion of the second fuel and the second portion of the second fuel. The first portion and the second portion of the second fuel can be injected in overlapping injection events.
Alternatively or additionally, the first portion of the second fuel can be introduced in two injection events, and the second portion of the second fuel can be introduced in another two injection events.
Brief Description of the Drawings
Alternatively or additionally, the first portion of the second fuel can be introduced in two injection events, and the second portion of the second fuel can be introduced in another two injection events.
Brief Description of the Drawings
[0016] The drawings illustrate specific preferred embodiments of the apparatus and method, but should not be considered as restricting the spirit or scope of the invention in anyway.
[0017] FIG. 1 is a schematic view of a first embodiment that combines a first fuel injector and a second fuel injector in a single body with concentric valve needles.
[0018] FIG. 2 is a schematic view of a second embodiment that combines a first fuel injector and a second fuel injector in a single body with side by side valve needles.
[0019] FIG. 3 is a schematic view of a third embodiment that employs a first fuel injector for a first fuel and a second fuel injector for a second fuel in separate bodies. Also shown in this embodiment is an optional third fuel injector for injecting the second fuel into the intake air system.
[0020] FIG. 4 is a flow chart that illustrates a method of switching back and forth between operating with both a first fuel and a second fuel and operating with the first fuel only.
[0021] FIG. 5 is a schematic partial view of a multi-fuel injection system illustrating a flow switching device according to one embodiment.
Detailed Description of the Preferred Embodiments
Detailed Description of the Preferred Embodiments
[0022] Referring to FIG. 1, multi-fuel injection system 10 is illustrated according to a first embodiment. Engine 20 comprises combustion chamber 30, which in this example is defined by cylinder wall 40, cylinder head 50 and piston 60. Only one such combustion chamber is shown in FIG. 1 although as would be known by those skilled in the technology engine 20 normally comprises two or more combustion chambers, and the technique disclosed herein applies to any engine having one or more combustion chambers. An intake charge is supplied to combustion chamber 30 from an intake manifold (not shown) of engine 20 from where it is communicated along intake port 70 and past opened intake valve 80. Direct injector 90 is a concentric needle-type injector that can introduce a first fuel and a second fuel separately and independently into combustion chamber 30. Direct injector 90 comprises first fuel injector 100 for injecting the first fuel through first nozzle holes (not shown) and second fuel injector 110 for injecting the second fuel through second nozzle holes (not shown). In preferred embodiments the first fuel is a liquid fuel such as diesel, and the second fuel is a gaseous fuel such as natural gas. A gaseous fuel is any fuel in the gas state at standard temperature and pressure, which in the context of this disclosure is 20 degrees Celsius ( C) and 1 atmosphere (atm) respectively. Similarly, a liquid fuel is any fuel in the liquid state at standard temperature and pressure.
[0023] First fuel source 150 supplies the first fuel at a predetermined pressure within a first range of tolerance along conduit 160. Conduit 160 branches into conduit 160a towards direct fuel injector 90 and conduit 160b towards a first port of flow switching device 170. Conduit 160a fluidly connects with first fuel injector 100 in direct injector 90 such that the first fuel can be selectively injected through the first nozzle holes. Second fuel source 180 supplies the second fuel at a second predetermined pressure within a second range of tolerance along conduit 190 towards a second port of flow switching device 170. In a preferred embodiment the second predetermined pressure is greater than at least 100 bar. Conduit 200 extends between a third port of flow switching device 170 and direct fuel injector 90. Flow switching device 170 is actuatable to a first position to fluidly connect conduit 160b with conduit 200, and to a second position to fluidly connect conduit 190 with conduit 200. Flow switching device can be for example an arrangement of two-way valves, as illustrated in FIG. 2, or a three-way valve as illustrated in FIG. 2, and both of these figures will be discussed with respect to other embodiments. Flow switching device 170 is illustrated as a logical block within the figures, and components that make up the flow switching device are not necessarily collocated. Conduit 200 is fluidly connected with second fuel injector 110 in direct injector 90 such that the first fuel can be selectively injected through the second nozzle holes when flow switching device 170 is in the first position, and the second fuel can be selectively injected through the second nozzle holes when the flow switching device is in the second position.
[0024] Direct injector 90 is now discussed in more detail. The density of liquid fuels is greater than that of gaseous fuels in terms of energy and mass. As an illustrative comparison, if liquid fuel pressure is substantially equal to gaseous fuel pressure, to introduce an equivalent amount of gaseous fuel, with respect to either energy or mass, during injection events having equivalent pulse widths the second nozzle holes in second fuel injector 110 would need to be larger than the first nozzle holes in first fuel injector 100. The first fuel (liquid fuel) normally acts as a pilot fuel and the second fuel (gaseous fuel) is a main fuel, and engine 20 consumes preferably on average about 5%
pilot fuel and 95% main fuel. As a result, in previous high pressure direct injection engines in order to achieve the flow capacity needed for the larger amount of gaseous fuel, which also has a lower density, the flow area that determines the flow capacity for the main nozzle holes was significantly larger than that of the pilot nozzle holes. Direct injector 90 can be actuated to introduce only the first fuel through the first nozzle holes, and can be actuated to introduce only the second fuel through the second nozzle holes, and can be actuated to introduce both the first and second fuels through the first and second nozzle holes respectively. Multi-fuel injection system 10 is configured such that the first fuel can be selectively introduced through the second nozzle holes in addition to the first nozzle holes. First fuel injector 100 comprises a first fuel injection valve having a first valve member and a first valve seat (both not shown), and when the first fuel injection valve is open it and the downstream first nozzle holes have a flow area sized for accurate and consistent injection of a pilot amount of the first fuel directly into combustion chamber 30. Second fuel injector 110 comprises a second fuel injection valve having a second valve member and a second valve seat (both not shown). When the second fuel injection valve is open it and the downstream second nozzle holes have a second flow area sized for late-cycle injection of an amount of the second fuel that delivers enough energy to enable engine 20 to operate across a partial range of engine operating conditions not including operating conditions at high load. Within this disclosure operating conditions specified as high load are those operating conditions with a fuelling demand above a predetermined value FDT, which includes operating near and at full load.
Fuelling demand refers to an amount of fuel on an energy equivalent basis that must be introduced to combustion chamber 30 during the current engine cycle to meet engine load and engine speed demand. The second flow area is also sized to accommodate late-cycle injection directly into combustion chamber 30 of an accurate and consistent amount of the first fuel up to an amount required to deliver enough energy to enable engine 20 to operate across a range of engine operating conditions including high load conditions, when only the first fuel is supplied to the combustion chamber. As used herein late-cycle injection refers to start of injection timing beginning no earlier than 120 degrees before top dead center ( BTDC) as piston 60 travels towards cylinder head 50 during the compression stroke, and early-cycle refers to start of injection timing beginning anytime during the intake stroke and before 120 BTDC in the compression stroke. To allow engine 20 to accurately and consistently inject pilot amounts of a liquid fuel that atomizes in combustion chamber 30 the first flow area is sized relatively small, but as a result the engine cannot fuel exclusively at high load with the first fuel injected only through first fuel injector 100. To allow engine 20 to accurately fuel at any point in the engine map of engine 20 with only the first fuel the second flow area is sized to allow accurate and consistent injections of the first fuel, which atomizes in combustion chamber 30, such that the combined fuel introduced through first and second fuel injectors 100 and 110 is sufficient to meet the fuelling demand at high load. Alternatively, the first fuel can be exclusively introduced through the second fuel injector 110 to fuel at least high load operating conditions, and preferably at any operating point of engine 20. As a result second fuel injector 110 cannot meet the energy requirement at high load when engine 20 is fuelled with both the first and second fuels, since the second fuel is a gaseous fuel that is significantly less dense than the first fuel, which is a liquid fuel, and requires a significantly larger flow area to deliver an equivalent amount of fuel on an energy equivalent basis. If the second flow area of second fuel injector 110 was sized to handle the high load energy requirement when engine 20 is fuelled with the first and second fuels then this would be like a prior art fuel injection for an HPDI engine and the second flow area would be too large to enable liquid fuel injection. That is, the injection performance when injecting the first fuel through the second fuel injector would be reduced resulting in inaccurate fuel injection and reduced atomizing performance when operating only on the first fuel. With reference still to FIG. 1, second fuel injector 110 comprises an actuator 120 that is capable of actuating the second injection valve to open for at least two injection events (pulses) during each engine cycle. When the second injection valve is injecting the second fuel, this allows second fuel injector 110 to introduce a first portion of the second fuel, early-cycle, which forms a homogenous mixture with the intake charge that burns with a premixed flame, and a second portion of the second fuel, late-cycle, which forms a stratified charge that burns with a diffusion flame. The operation of second fuel injector 110 will be explained in more detail below.
pilot fuel and 95% main fuel. As a result, in previous high pressure direct injection engines in order to achieve the flow capacity needed for the larger amount of gaseous fuel, which also has a lower density, the flow area that determines the flow capacity for the main nozzle holes was significantly larger than that of the pilot nozzle holes. Direct injector 90 can be actuated to introduce only the first fuel through the first nozzle holes, and can be actuated to introduce only the second fuel through the second nozzle holes, and can be actuated to introduce both the first and second fuels through the first and second nozzle holes respectively. Multi-fuel injection system 10 is configured such that the first fuel can be selectively introduced through the second nozzle holes in addition to the first nozzle holes. First fuel injector 100 comprises a first fuel injection valve having a first valve member and a first valve seat (both not shown), and when the first fuel injection valve is open it and the downstream first nozzle holes have a flow area sized for accurate and consistent injection of a pilot amount of the first fuel directly into combustion chamber 30. Second fuel injector 110 comprises a second fuel injection valve having a second valve member and a second valve seat (both not shown). When the second fuel injection valve is open it and the downstream second nozzle holes have a second flow area sized for late-cycle injection of an amount of the second fuel that delivers enough energy to enable engine 20 to operate across a partial range of engine operating conditions not including operating conditions at high load. Within this disclosure operating conditions specified as high load are those operating conditions with a fuelling demand above a predetermined value FDT, which includes operating near and at full load.
Fuelling demand refers to an amount of fuel on an energy equivalent basis that must be introduced to combustion chamber 30 during the current engine cycle to meet engine load and engine speed demand. The second flow area is also sized to accommodate late-cycle injection directly into combustion chamber 30 of an accurate and consistent amount of the first fuel up to an amount required to deliver enough energy to enable engine 20 to operate across a range of engine operating conditions including high load conditions, when only the first fuel is supplied to the combustion chamber. As used herein late-cycle injection refers to start of injection timing beginning no earlier than 120 degrees before top dead center ( BTDC) as piston 60 travels towards cylinder head 50 during the compression stroke, and early-cycle refers to start of injection timing beginning anytime during the intake stroke and before 120 BTDC in the compression stroke. To allow engine 20 to accurately and consistently inject pilot amounts of a liquid fuel that atomizes in combustion chamber 30 the first flow area is sized relatively small, but as a result the engine cannot fuel exclusively at high load with the first fuel injected only through first fuel injector 100. To allow engine 20 to accurately fuel at any point in the engine map of engine 20 with only the first fuel the second flow area is sized to allow accurate and consistent injections of the first fuel, which atomizes in combustion chamber 30, such that the combined fuel introduced through first and second fuel injectors 100 and 110 is sufficient to meet the fuelling demand at high load. Alternatively, the first fuel can be exclusively introduced through the second fuel injector 110 to fuel at least high load operating conditions, and preferably at any operating point of engine 20. As a result second fuel injector 110 cannot meet the energy requirement at high load when engine 20 is fuelled with both the first and second fuels, since the second fuel is a gaseous fuel that is significantly less dense than the first fuel, which is a liquid fuel, and requires a significantly larger flow area to deliver an equivalent amount of fuel on an energy equivalent basis. If the second flow area of second fuel injector 110 was sized to handle the high load energy requirement when engine 20 is fuelled with the first and second fuels then this would be like a prior art fuel injection for an HPDI engine and the second flow area would be too large to enable liquid fuel injection. That is, the injection performance when injecting the first fuel through the second fuel injector would be reduced resulting in inaccurate fuel injection and reduced atomizing performance when operating only on the first fuel. With reference still to FIG. 1, second fuel injector 110 comprises an actuator 120 that is capable of actuating the second injection valve to open for at least two injection events (pulses) during each engine cycle. When the second injection valve is injecting the second fuel, this allows second fuel injector 110 to introduce a first portion of the second fuel, early-cycle, which forms a homogenous mixture with the intake charge that burns with a premixed flame, and a second portion of the second fuel, late-cycle, which forms a stratified charge that burns with a diffusion flame. The operation of second fuel injector 110 will be explained in more detail below.
[0025] The first fuel has a cetane number that makes it suitable for compression ignition.
During the compression stroke of piston 60 the first fuel is compression ignited in combustion chamber 30 such that the second fuel, when present, is subsequently ignited due to the pressure and temperature resulting from combustion of the first fuel. After the power stroke, the exhaust products from the combustion of the first and second fuels are evacuated from combustion chamber 30 when exhaust valve 30 opens and on through exhaust port 140 to an exhaust pipe (not shown) as piston 60 travels towards cylinder head 50 during the exhaust stroke. In other embodiments engine 20 can comprise a turbocharger such that the exhaust products from combustion chamber 30 drive a turbine that is used to drive a compressor to compress intake air to boost the air pressure of the intake charge entering combustion chamber 30. In still other embodiments exhaust gas recirculation can be employed to recirculate at least a portion of the exhaust products from combustion chamber 30 into the intake charge.
During the compression stroke of piston 60 the first fuel is compression ignited in combustion chamber 30 such that the second fuel, when present, is subsequently ignited due to the pressure and temperature resulting from combustion of the first fuel. After the power stroke, the exhaust products from the combustion of the first and second fuels are evacuated from combustion chamber 30 when exhaust valve 30 opens and on through exhaust port 140 to an exhaust pipe (not shown) as piston 60 travels towards cylinder head 50 during the exhaust stroke. In other embodiments engine 20 can comprise a turbocharger such that the exhaust products from combustion chamber 30 drive a turbine that is used to drive a compressor to compress intake air to boost the air pressure of the intake charge entering combustion chamber 30. In still other embodiments exhaust gas recirculation can be employed to recirculate at least a portion of the exhaust products from combustion chamber 30 into the intake charge.
[0026] Controller 210 monitors and manages the operation of multi-fuel injection system and engine 20. Various sensors and actuators (not shown) throughout system 10 and 10 engine 20 send respective engine operating data to controller 210, and this transfer of engine operating data is represented collectively by communication line 220, which is illustrated showing bi-directional communication lines since controller 210 can send commands for example to drivers and actuators, and to some sensors, and also receives information from the sensors. In the figures, dotted lines represent electrical communication lines, and the arrows at the ends of these communication lines represent that information, such as status information and commands, can be transmitted in the direction of these arrows. Controller 210 commands first fuel source 150 to supply the first fuel to conduit 160 pressurized to the first predetermined value.
Similarly, controller 210 commands second fuel source 180 to supply the second fuel to conduit 190 pressurized to the second predetermined value. Flow switching device 170 is selectively commanded by controller 210 to the first position, where conduit 160b is fluidly connected with conduit 200, and to the second position, where conduit 190 is fluidly connected with conduit 200. Direct injector 90 is commanded by controller 210 to separately and independently inject the first fuel through the first nozzle holes and either the first fuel or the second fuel through the second nozzle holes, as will be explained in more detail below.
Similarly, controller 210 commands second fuel source 180 to supply the second fuel to conduit 190 pressurized to the second predetermined value. Flow switching device 170 is selectively commanded by controller 210 to the first position, where conduit 160b is fluidly connected with conduit 200, and to the second position, where conduit 190 is fluidly connected with conduit 200. Direct injector 90 is commanded by controller 210 to separately and independently inject the first fuel through the first nozzle holes and either the first fuel or the second fuel through the second nozzle holes, as will be explained in more detail below.
[0027] Multi-fuel injection system 10 is operated in at least three modes. In a first mode, direct injector 90 introduces a pilot amount of the first fuel and a main amount of the second fuel during respective late-cycle fuel injection events. The energy from the first and second fuels is matched to the energy required for operating in the first mode, which are those parts of the engine map of engine 20 outside of high load operating conditions.
In the first mode fuel switching device 170 is in the second position such that the second fuel from conduit 190 is supplied to second fuel injector 110 in direct injector 90 through conduit 200. Engine 20 normally operates in the first mode, such as operating in idle, where over-leaning of fuel is reduced by injecting the fuel late-cycle, and typical steady state and transient operation of the engine.
In the first mode fuel switching device 170 is in the second position such that the second fuel from conduit 190 is supplied to second fuel injector 110 in direct injector 90 through conduit 200. Engine 20 normally operates in the first mode, such as operating in idle, where over-leaning of fuel is reduced by injecting the fuel late-cycle, and typical steady state and transient operation of the engine.
[0028] In a second mode the total energy required to operate is higher than the total energy that can be injected in the first mode of operation. To meet the total energy requirement second fuel injector 110 is actuated in two injection events. A
first portion of the second fuel is introduced during a first injection event occurring early-cycle and a second portion of the second fuel is introduced during a second injection event occurring late-cycle. The first portion of the second fuel forms a substantially homogenous mixture with the intake charge in combustion chamber 30 since it has significantly more time to mix than the second portion. The first portion of the second fuel burns with a premixed flame and the second portion burns with a diffusion flame. The combined energy of the pilot amount of the first fuel and the first and second portions of the second fuel can meet the total energy requirement for high load operating conditions of engine 20.
Alternatively or additionally, second fuel injector 110 can be the type of fuel injector capable of partial strokes where the second valve member can be actuated to two or more desired lift positions that are commanded by controller 210. Each lift position adjusts the choke point of fluid flow in the second fuel injector and has a respective flow area such that as the flow area increases the amount of the second fuel that can be delivered to combustion chamber 30 is increased. When the fuelling demand of engine 20 increases beyond the predetermined value FDT into high load operating conditions controller 210 commands second fuel injector 110 to a lift position having a flow area that can meet the fuelling demand. The adjustment of the choke point for each increased lift position is characterized for example by an increase in the number of fuel injection nozzle holes that can deliver the second fuel to combustion chamber 30, and/or by an increase in flow area through the second injection valve.
first portion of the second fuel is introduced during a first injection event occurring early-cycle and a second portion of the second fuel is introduced during a second injection event occurring late-cycle. The first portion of the second fuel forms a substantially homogenous mixture with the intake charge in combustion chamber 30 since it has significantly more time to mix than the second portion. The first portion of the second fuel burns with a premixed flame and the second portion burns with a diffusion flame. The combined energy of the pilot amount of the first fuel and the first and second portions of the second fuel can meet the total energy requirement for high load operating conditions of engine 20.
Alternatively or additionally, second fuel injector 110 can be the type of fuel injector capable of partial strokes where the second valve member can be actuated to two or more desired lift positions that are commanded by controller 210. Each lift position adjusts the choke point of fluid flow in the second fuel injector and has a respective flow area such that as the flow area increases the amount of the second fuel that can be delivered to combustion chamber 30 is increased. When the fuelling demand of engine 20 increases beyond the predetermined value FDT into high load operating conditions controller 210 commands second fuel injector 110 to a lift position having a flow area that can meet the fuelling demand. The adjustment of the choke point for each increased lift position is characterized for example by an increase in the number of fuel injection nozzle holes that can deliver the second fuel to combustion chamber 30, and/or by an increase in flow area through the second injection valve.
[0029] In a third mode, engine 20 is exclusively fuelled with the first fuel.
There can be a variety of reasons why engine 20 consumes only the first fuel. For example, there can be a component failure in second fuel source 180 that prevents it from supplying the second fuel or that prevents it from being able to pressurize the second fuel to a predetermined value. During start-up engine 20 can be fuelled exclusively with the first fuel under certain operating conditions (such as low ambient temperatures) that warrant a start-up fuel with a higher cetane number, or when the second fuel requires too much time to pressurize before it can be injected. In other circumstances, the supply of the second fuel can be empty. There can be a number of reasons for this. In some operating environments, the gaseous fuel refueling infrastructure is still being built, and in other cases driver error can result in the depletion of the gaseous fuel supply onboard a vehicle.
In the third mode, controller 210 actuates flow switching device 170 to fluidly connect conduit 160b with conduit 200 such that the first fuel can be selectively injected through both first fuel injector 100 and second fuel injector 110. For example, the first fuel can be injected through second fuel injector 110 exclusively for all engine operating conditions, or can be injected through both the first and second fuel injectors. The amount of the first fuel that is injected is controlled to match the energy required for any commanded operating condition within a normal range of operation associated with engine 20, including high load operating conditions. Because the second flow area is sized for the required flow capacity for the first fuel, and not the second fuel, the engine can operate across the entire engine operating range fuelled with just the first fuel with accurate fuelling and the desired atomization of fuel for efficient combustion. In the third mode the pressure of the first fuel can be increased compared to the pressure during the first and second modes. This allows more fuel to be introduced within a predefined injection window and further improves atomization.
There can be a variety of reasons why engine 20 consumes only the first fuel. For example, there can be a component failure in second fuel source 180 that prevents it from supplying the second fuel or that prevents it from being able to pressurize the second fuel to a predetermined value. During start-up engine 20 can be fuelled exclusively with the first fuel under certain operating conditions (such as low ambient temperatures) that warrant a start-up fuel with a higher cetane number, or when the second fuel requires too much time to pressurize before it can be injected. In other circumstances, the supply of the second fuel can be empty. There can be a number of reasons for this. In some operating environments, the gaseous fuel refueling infrastructure is still being built, and in other cases driver error can result in the depletion of the gaseous fuel supply onboard a vehicle.
In the third mode, controller 210 actuates flow switching device 170 to fluidly connect conduit 160b with conduit 200 such that the first fuel can be selectively injected through both first fuel injector 100 and second fuel injector 110. For example, the first fuel can be injected through second fuel injector 110 exclusively for all engine operating conditions, or can be injected through both the first and second fuel injectors. The amount of the first fuel that is injected is controlled to match the energy required for any commanded operating condition within a normal range of operation associated with engine 20, including high load operating conditions. Because the second flow area is sized for the required flow capacity for the first fuel, and not the second fuel, the engine can operate across the entire engine operating range fuelled with just the first fuel with accurate fuelling and the desired atomization of fuel for efficient combustion. In the third mode the pressure of the first fuel can be increased compared to the pressure during the first and second modes. This allows more fuel to be introduced within a predefined injection window and further improves atomization.
[0030] Referring now to FIG. 2, multi-fuel injection system 12 is illustrated according to a second embodiment that is similar to the first embodiment and with respect to this and all other embodiments like reference numerals to the first embodiment describe like components, which may not be discussed in detail if at all. Direct injector 92 comprises first fuel injector 102 and second fuel injector 210 that are separate side by side injection valve needles within a common injector housing 230. First fuel injector 102 is in fluid communication with first fuel source 150 and comprises first nozzle holes (not shown) sized to introduce a pilot amount of the first fuel during late-cycle injections in combustion chamber 30, similar to first fuel injector 100 of direct injector 90 in FIG. 1.
Second fuel injector 112 is in selective fluid communication with first and second fuel sources 150 and 180 respectively and comprises second nozzle holes (not shown) sized to introduce the first fuel such that when engine 20 is exclusively fuelled with the first fuel the engine can operate at any operating point in its engine map including high load operating conditions, similar to second fuel injector 110 of direct injector 90 in FIG. 1.
Direct injector 92 is simplified compared to direct injector 90 since concentric needle-type fuel injectors that introduce two fuels are inherently more complicated than a fuel injector that introduces a single fuel. However, for injection valves with the same flow capacity, direct injector 90 with its concentric arrangement has a smaller envelope such that a smaller bore diameter in cylinder head 50 is required compared to direct injector 92, and the first and second fuel spray pattern in direct injector 90 is more symmetrical compared to direct injector 92, in addition to other advantages. Multi-fuel injection system 12 is operated in the first, second and third modes described above with reference to FIG. 1, where first fuel injector 102 is operated like first fuel injector 100, and second fuel injector 112 is operated like second fuel injector 110.
Second fuel injector 112 is in selective fluid communication with first and second fuel sources 150 and 180 respectively and comprises second nozzle holes (not shown) sized to introduce the first fuel such that when engine 20 is exclusively fuelled with the first fuel the engine can operate at any operating point in its engine map including high load operating conditions, similar to second fuel injector 110 of direct injector 90 in FIG. 1.
Direct injector 92 is simplified compared to direct injector 90 since concentric needle-type fuel injectors that introduce two fuels are inherently more complicated than a fuel injector that introduces a single fuel. However, for injection valves with the same flow capacity, direct injector 90 with its concentric arrangement has a smaller envelope such that a smaller bore diameter in cylinder head 50 is required compared to direct injector 92, and the first and second fuel spray pattern in direct injector 90 is more symmetrical compared to direct injector 92, in addition to other advantages. Multi-fuel injection system 12 is operated in the first, second and third modes described above with reference to FIG. 1, where first fuel injector 102 is operated like first fuel injector 100, and second fuel injector 112 is operated like second fuel injector 110.
[0031] Referring now to FIG. 3, multi-fuel injection system 13 is illustrated according to a third embodiment. First fuel injector 103 is a direct injector that is in fluid communication with first fuel source 150, and second fuel injector 113 is a direct injector that is in selective fluid communication with first fuel source 150 and second fuel source 180. Multi-fuel injection system 13 is operated in the first, second and third modes described above with reference to FIG. 1, where first fuel injector 103 is operated like first fuel injector 100, and second fuel injector 113 is operated like second fuel injector 110. Alternatively or additionally to second fuel injector 113, third fuel injector 240 can optionally be employed to introduce a portion of the second fuel upstream from intake valve 80. Third fuel injector 240 in the illustrated embodiment is a port fuel injector disposed in intake port 70. When third fuel injector 240 is installed in intake port 70, or a respective intake runner (not shown), the second fuel injected by the third fuel injector is inducted into a respective combustion chamber only during intake strokes. As used herein an intake port is an integrated fluid passageway in a cylinder head and an intake runner is a passageway fluidly connecting an intake manifold with the intake port.
Alternatively, third fuel injector 240 can be disposed further upstream in an intake manifold (not shown) such that the second fuel can be delivered to more than one combustion chamber along respective intake runners and ports. When engine 20 is running at high load, third fuel injector 240 is used to introduce a first portion of the second fuel, early-cycle, during the intake stroke of piston 60 or early in the compression stroke, and a second portion is introduced from the second fuel injector 113. The pressure of the second fuel supplied to third fuel injector 240 is not required to be as high as the pressure of the second fuel supplied to second fuel injector 112 since the pressure upstream from intake valve 80 is relatively low and the total fuel injection period allowed for third fuel injector 240 can be relatively long. Accordingly, third fuel injector 240 can be supplied from a low pressure supply of the second fuel from second fuel source 180 along conduit 250, which reduces parasitic losses in multi-fuel injection system 13 since less of the second fuel is required to be pressurized to a high pressure and supplied from the second fuel source along conduit 190 to second injector 113. It is possible that the second fuel delivered through conduit 190 and the second fuel delivered through conduit 250 are from the same supply of second fuel, or they can be from different supplies, within second fuel source 180.
When the second fuel is stored as a cryogenic fluid, an example of a low pressure source of the second fuel is boil-off gas from a cryogenic vessel. Second fuel injector 113 is not required to perform both early-cycle and late-cycle injections when third fuel injector 240 is present, and to simplify the second fuel injector it can be designed for late-cycle injection only. For example, the actuator associated with second fuel injector 113 does not need to be capable of performing multiple injection pulses for each injection event.
The cost and complexity of fuel injectors increase when they are required to perform accurate injections for both a wide range of fuelling quantities over a wide range of differential pressures between in-cylinder pressure and fuel rail pressure, such as encountered when they are required to perform both early-cycle and late-cycle injections.
By employing third fuel injector 240 the cost and complexity of second fuel injector 113 can be reduced. The cost and complexity of third fuel injector 240, which is required to perform relatively low pressure injections with relatively wide pulse widths when it is a port fuel injector, is significantly less compared to second fuel injector 113. Port fuel injectors are commercially available and relatively inexpensive compared to direct fuel injectors. In the first mode of operation first and second injectors 103 and 113 introduce the first and second fuels respectively. In the second mode, first fuel injector 103 introduces the first fuel, and second and third fuel injectors 113 and 240 introduce the second fuel. In the third mode of operation first and second fuel injectors 103 and 113 introduce the first fuel exclusively into combustion chamber 30. In other embodiments, third fuel injector 240 can be a direct injector having a nozzle disposed in combustion chamber 30, and second fuel injector 113 and third fuel injector 240 can each be configured in cylinder head 50 or cylinder wall 40. In these embodiments, in the second mode of operation second and third fuel injectors 113 and 240 preferably each inject the second fuel, late-cycle, in one overlapping injection event such that the second fuel is continuously introduced. Alternatively, there can be two overlapping late-cycle injection events where the injection of the second fuel is suspended briefly, that is both second and third fuel injectors 113 and 240 perform a first overlapping injection event followed by a second overlapping injection event. In between the first and second overlapping injection events first fuel injector 103 can be actuated to introduce a pilot amount of the first fuel.
In other embodiments, when third fuel injector 240 is a direct injector, it can also inject fuel early-cycle.
Alternatively, third fuel injector 240 can be disposed further upstream in an intake manifold (not shown) such that the second fuel can be delivered to more than one combustion chamber along respective intake runners and ports. When engine 20 is running at high load, third fuel injector 240 is used to introduce a first portion of the second fuel, early-cycle, during the intake stroke of piston 60 or early in the compression stroke, and a second portion is introduced from the second fuel injector 113. The pressure of the second fuel supplied to third fuel injector 240 is not required to be as high as the pressure of the second fuel supplied to second fuel injector 112 since the pressure upstream from intake valve 80 is relatively low and the total fuel injection period allowed for third fuel injector 240 can be relatively long. Accordingly, third fuel injector 240 can be supplied from a low pressure supply of the second fuel from second fuel source 180 along conduit 250, which reduces parasitic losses in multi-fuel injection system 13 since less of the second fuel is required to be pressurized to a high pressure and supplied from the second fuel source along conduit 190 to second injector 113. It is possible that the second fuel delivered through conduit 190 and the second fuel delivered through conduit 250 are from the same supply of second fuel, or they can be from different supplies, within second fuel source 180.
When the second fuel is stored as a cryogenic fluid, an example of a low pressure source of the second fuel is boil-off gas from a cryogenic vessel. Second fuel injector 113 is not required to perform both early-cycle and late-cycle injections when third fuel injector 240 is present, and to simplify the second fuel injector it can be designed for late-cycle injection only. For example, the actuator associated with second fuel injector 113 does not need to be capable of performing multiple injection pulses for each injection event.
The cost and complexity of fuel injectors increase when they are required to perform accurate injections for both a wide range of fuelling quantities over a wide range of differential pressures between in-cylinder pressure and fuel rail pressure, such as encountered when they are required to perform both early-cycle and late-cycle injections.
By employing third fuel injector 240 the cost and complexity of second fuel injector 113 can be reduced. The cost and complexity of third fuel injector 240, which is required to perform relatively low pressure injections with relatively wide pulse widths when it is a port fuel injector, is significantly less compared to second fuel injector 113. Port fuel injectors are commercially available and relatively inexpensive compared to direct fuel injectors. In the first mode of operation first and second injectors 103 and 113 introduce the first and second fuels respectively. In the second mode, first fuel injector 103 introduces the first fuel, and second and third fuel injectors 113 and 240 introduce the second fuel. In the third mode of operation first and second fuel injectors 103 and 113 introduce the first fuel exclusively into combustion chamber 30. In other embodiments, third fuel injector 240 can be a direct injector having a nozzle disposed in combustion chamber 30, and second fuel injector 113 and third fuel injector 240 can each be configured in cylinder head 50 or cylinder wall 40. In these embodiments, in the second mode of operation second and third fuel injectors 113 and 240 preferably each inject the second fuel, late-cycle, in one overlapping injection event such that the second fuel is continuously introduced. Alternatively, there can be two overlapping late-cycle injection events where the injection of the second fuel is suspended briefly, that is both second and third fuel injectors 113 and 240 perform a first overlapping injection event followed by a second overlapping injection event. In between the first and second overlapping injection events first fuel injector 103 can be actuated to introduce a pilot amount of the first fuel.
In other embodiments, when third fuel injector 240 is a direct injector, it can also inject fuel early-cycle.
[0032] Referring now to FIG. 4, algorithm 300 illustrates a method of switching back and forth between operating with both the first and second fuels and operating with the first fuel only. Controller 210 is programmed with algorithm 300 and carries out the steps therein. Step 310 represents an entry point for algorithm 300. The entry point can be the beginning of each engine cycle. Alternatively or additionally, the entry point can be event driven such as when select engine operating conditions change, for example when second fuel source 180 can no longer supply the second fuel, when engine 20 is accelerating, and when engine 20 is starting up. In step 320 controller 210 determines whether engine 20 is to be fuelled with both the first and second fuels or with the first fuel only. When engine 20 is fuelled with both the first and second fuels, algorithm 300 proceeds to step 330 where controller 210 determines whether the fuelling demand of engine 20 is above the predetermined value FDT. Algorithm 300 proceeds to step 340 where engine 20 is operated in the first mode when the fuelling demand is less than or equal to the predetermined value FDT, and to step 350 where engine 20 operates in the second mode when the fuelling demand is above the predetermined value FDT. Returning to step 320, when engine 20 is to be fuelled only with the first fuel, algorithm 300 proceeds to step 360 where the engine operates in the third mode.
[0033] Referring now to FIG. 5, flow switching device 170 is illustrated with an alternative valve arrangement in multi-fuel injection system 14. Two-way valve 171 can be selectively actuated to enable flow of the first fuel from conduit 160b to conduit 200, and two-way valve 172 can be selectively actuated to enable flow of the second fuel from conduit 190 to conduit 200. As previously discussed, the components that make up flow switching device 170 are not required to be collocated, and two-way valve 171 is not required to be collocated with two-way valve 172. Check valve 173 can be employed to prevent the flow of the first fuel into conduit 174 when two-way valve 171 is opened, particularly when two-way valve 172 is located substantially away from two-way valve 171.
[0034] While particular embodiments of the apparatus and method have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the spirit and scope of the present disclosure, particularly in light of the foregoing teachings.
Claims (20)
1. A multi-fuel injection system for an internal combustion engine comprising:
a first fuel injector in fluid communication with a supply for a first fuel, said first fuel injector having a flow area sized for accurate and consistent injection of a pilot amount of said first fuel directly into a combustion chamber; and a second fuel injector in selective fluid communication with one of said supply for said first fuel and a supply for a second fuel, said second fuel injector having a flow area sized to accommodate late-cycle injection directly into said combustion chamber of an accurate and consistent amount of said first fuel up to an amount required to deliver enough energy to enable said internal combustion engine to operate across a range of engine operating conditions including high load conditions, with only said first fuel supplied as fuel to said combustion chamber, or when in fluid communication with said supply for said second fuel, said second fuel injector is operable for late-cycle injection directly into said combustion chamber of an amount of said second fuel that delivers enough energy to enable said internal combustion engine to operate across a partial range of engine operating conditions, not including high load operating conditions.
a first fuel injector in fluid communication with a supply for a first fuel, said first fuel injector having a flow area sized for accurate and consistent injection of a pilot amount of said first fuel directly into a combustion chamber; and a second fuel injector in selective fluid communication with one of said supply for said first fuel and a supply for a second fuel, said second fuel injector having a flow area sized to accommodate late-cycle injection directly into said combustion chamber of an accurate and consistent amount of said first fuel up to an amount required to deliver enough energy to enable said internal combustion engine to operate across a range of engine operating conditions including high load conditions, with only said first fuel supplied as fuel to said combustion chamber, or when in fluid communication with said supply for said second fuel, said second fuel injector is operable for late-cycle injection directly into said combustion chamber of an amount of said second fuel that delivers enough energy to enable said internal combustion engine to operate across a partial range of engine operating conditions, not including high load operating conditions.
2. The multi-fuel injection system of claim 1 wherein said second fuel injector is actuatable to a first open position having a first flow area and a second open position having a second flow area, wherein when said second fuel injector is in fluid communication with said supply for said second fuel, said first flow area is sized to enable said internal combustion engine to operate across said partial range of engine operating conditions, not including high load operating conditions, and said second flow area is sized to enable said internal combustion engine to operate at high load operating conditions.
3. The multi-fuel injection system of claim 1 wherein said second fuel injector has an actuator that can open said second fuel injector for at least two injection pulses in each engine cycle, whereby when in fluid communication with said supply for said second fuel, one injection pulse is timed for early-cycle injection of said second fuel and a second injection pulse is timed for late-cycle injection of said second fuel, whereby the total amount of energy associated with said injection pulses enables said engine to operate across said range of engine operating conditions including high load conditions in a mode where only a pilot amount of said first fuel is injected through said first fuel injector and the remainder of the fuel required for the demanded load is provided by said second fuel, which is injected through said second fuel injector.
4. The multi-fuel injection system of claim 1 further comprising a third fuel injector in fluid communication with said supply of said second fuel, whereby the total amount of energy associated with injection of said second fuel by said second fuel injector and said third fuel injector enables said engine to operate across said full range of engine operating conditions in a mode where only a pilot amount of said first fuel is injected through said first fuel injector.
5. The multi-fuel injection system of claim 4 wherein said third fuel injector is positioned to directly inject fuel into said combustion chamber.
6. The multi-fuel injection system of claim 4 wherein said third fuel injector is positioned upstream from an engine intake valve whereby said second fuel is injectable through said third fuel injector into an intake air system and later introduced into said combustion chamber together with air.
7. The multi-fuel injection system of claim 6 wherein said supply of said second fuel comprises a low pressure branch in fluid communication with said third fuel injector, and a high pressure branch in fluid communication with said second fuel injector.
8. The multi-fuel injection system of claim 6 wherein said third fuel injector is installed in an intake port.
9. The multi-fuel injection system of any one of claims 3 through 8 further comprising an engine control unit that receives engine operating data and that is programmed to limit the amount of second fuel that is introduced early-cycle to prevent the formation of combustible air-fuel mixtures susceptible to premature detonation.
10. The multi-fuel injection system of claim 1 wherein said second fuel is a gaseous fuel.
11. The multi-fuel injection system of claim 1 wherein said second fuel injector is a common rail injector.
12. The multi-fuel injection system of claim 1 wherein said second fuel is injected with an injection pressure of at least 100 bar.
13. The multi-fuel injection system of claim 1 wherein said second fuel injector is selectively fluidly connected to one of said first fuel supply and said second fuel supply by operation of a flow switching device.
14. A method of controlling a multi-fuel injection system for an internal combustion engine comprising operating in at least three modes:
in a first mode, injecting into a combustion chamber, late-cycle, a pilot amount of a first fuel with a first fuel injector, and injecting into said combustion chamber, late-cycle, an amount of a second fuel with a second fuel injector, with the energy from said first and second fuels being matched to the energy required for operating in said first mode;
in a second mode, in which the total energy required is higher than the total energy that can be injected by said first mode of operation, one of:
injecting a first portion of said second fuel with a second fuel injector and a second portion of said second fuel with a third fuel injector; and actuating said second fuel injector to one of at least two open positions such that in said second mode said second fuel injector is opened to a second position having greater flow area compared to when it is opened to a first position in said first mode; and in a third mode, selectively injecting said first fuel through both said first fuel injector and said second fuel injector, and controlling the amount of said first fuel that is injected to match the energy required for any commanded operating condition within a normal range of operation associated with said internal combustion engine.
in a first mode, injecting into a combustion chamber, late-cycle, a pilot amount of a first fuel with a first fuel injector, and injecting into said combustion chamber, late-cycle, an amount of a second fuel with a second fuel injector, with the energy from said first and second fuels being matched to the energy required for operating in said first mode;
in a second mode, in which the total energy required is higher than the total energy that can be injected by said first mode of operation, one of:
injecting a first portion of said second fuel with a second fuel injector and a second portion of said second fuel with a third fuel injector; and actuating said second fuel injector to one of at least two open positions such that in said second mode said second fuel injector is opened to a second position having greater flow area compared to when it is opened to a first position in said first mode; and in a third mode, selectively injecting said first fuel through both said first fuel injector and said second fuel injector, and controlling the amount of said first fuel that is injected to match the energy required for any commanded operating condition within a normal range of operation associated with said internal combustion engine.
15. The method of claim 14 further comprising supplying said second fuel to said second injector at a higher pressure than that of said second fuel that is supplied to said third injector.
16. The method of claim 14 further comprising in said second mode pre-mixing said second portion of said second fuel with an intake charge and later injecting late-cycle, said pilot amount of said first fuel through said first fuel injector, and said first portion of said second fuel.
17. The method of claim 16 wherein when operating in said second mode, said method further comprises limiting said second portion of said second fuel that is premixed so that the air-fuel ratio remains below the knock limit.
18. The method of claim 14 further comprising injecting, late-cycle, said pilot amount of said first fuel through said first fuel injector and said first portion of said second fuel and said second portion of said second fuel.
19. The method of claim 18 wherein said first portion and said second portion of said second fuel are injected in overlapping injection events.
20. The method of claim 18 wherein said first portion of said second fuel is introduced in two injection events, and said second portion of said second fuel is introduced in another two injection events.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2848849A CA2848849C (en) | 2014-04-11 | 2014-04-11 | Multi-fuel injection system and method |
| PCT/CA2015/050284 WO2015154183A1 (en) | 2014-04-11 | 2015-04-08 | Multi-fuel injection system and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2848849A CA2848849C (en) | 2014-04-11 | 2014-04-11 | Multi-fuel injection system and method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2848849A1 CA2848849A1 (en) | 2014-06-25 |
| CA2848849C true CA2848849C (en) | 2015-12-08 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2848849A Expired - Fee Related CA2848849C (en) | 2014-04-11 | 2014-04-11 | Multi-fuel injection system and method |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2848849C (en) |
| WO (1) | WO2015154183A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2530761A (en) * | 2014-10-01 | 2016-04-06 | Delphi Internat Operations Luxembourg S Ã R L | Fuel injection equipment |
| EP4183998A1 (en) * | 2021-11-22 | 2023-05-24 | Volvo Truck Corporation | A system, a method of controlling a system, and a vehicle comprising a system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6202601B1 (en) * | 2000-02-11 | 2001-03-20 | Westport Research Inc. | Method and apparatus for dual fuel injection into an internal combustion engine |
| US6598582B1 (en) * | 2001-10-15 | 2003-07-29 | Ronald F Murawsky | Rotary heat engine |
| US7270089B2 (en) * | 2003-06-11 | 2007-09-18 | Clean Air Power, Inc. | Method and apparatus for controlling transition between operating modes in a multimode engine |
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2014
- 2014-04-11 CA CA2848849A patent/CA2848849C/en not_active Expired - Fee Related
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| Publication number | Publication date |
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| CA2848849A1 (en) | 2014-06-25 |
| WO2015154183A1 (en) | 2015-10-15 |
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