Multifunctional fuel injector valve in a dual fuel system and method of

Abstract

A fuel injector in a fuel system having a first fuel supply of a first fuel and a second fuel supply of a second fuel, the fuel injector including a multi-function control valve movable in the fuel injector to control the first fuel to enter a combined fuel outlet passage, and control a timing of a fuel charge containing the first fuel and an injection pressure. In one embodiment, the first fuel includes a compression ignition fuel, such as diesel, and the second fuel includes an alcohol fuel, such as methanol. Related apparatus and methods are disclosed.

Description

Technical Field

[0001] The present invention generally relates to a dual-fuel system, and more specifically to a multi-functional control valve operable to allow a first fuel to enter a fuel injector to form a fuel charge and to control its injection timing and injection pressure. Background Technology

[0002] Dual-fuel engine systems have been known for decades. While conventional engine systems typically use a single fuel type, such as diesel, gasoline, or natural gas, dual-fuel engine systems usually burn two different fuels together in the engine cylinders, each with different desired characteristics.

[0003] In one known strategy, a relatively small ignition charge of a compressed ignition fuel (e.g., diesel) is used to ignite a relatively large main charge of a gaseous fuel (e.g., natural gas). Diesel fuel is relatively easily ignited by the increased temperature and pressure in the cylinder, and the ignition of diesel fuel triggers the ignition of the more difficult-to-ignite gaseous fuel.

[0004] Recently, engineers have proposed a dual-liquid fuel strategy using both lead and tail fuels in liquid form, injected as a single fuel charge. U.S. Patent No. 11,384,721B1 discloses a strategy that operates by injecting a first fuel and a second fuel from the same channel into the engine cylinder for combustion. While the '721 patent undoubtedly has practical applications, there is always room for improvement and the development of alternative strategies. Summary of the Invention

[0005] In one aspect, a fuel injector includes an injector housing forming a low-pressure fuel space, a first fuel nozzle supply passage, a second fuel nozzle supply passage, a combined fuel outlet passage fluidly connected to both the first and second fuel nozzle supply passages and extending to a plurality of nozzle outlets, and a nozzle check valve control chamber. The fuel injector also includes a nozzle check valve movable between a closed position and an open position that blocks the plurality of nozzle outlets from the combined fuel outlet passage. The fuel injector further includes a control valve movable between a first position that blocks the low-pressure fuel space from both the first fuel nozzle supply passage and the nozzle check valve control chamber, and a second position that fluidly connects the low-pressure fuel space to both the first fuel nozzle supply passage and the nozzle check valve control chamber.

[0006] In another aspect, a fuel system includes a first fuel supply of a first fuel, a second fuel supply of a second fuel, and a fuel injector forming a low-pressure fuel space fluidly connected to the first fuel supply, a first fuel nozzle supply passage, a second fuel nozzle supply passage, a combined fuel outlet passage extending to a plurality of nozzle outlets, and a nozzle check valve chamber. The fuel injector also includes a control valve movable between a first position and a second position, wherein the first position blocks the low-pressure fuel space from both the first fuel nozzle supply passage and the nozzle check valve chamber, and the second position provides fluid connectivity between the low-pressure fuel space and both the first fuel nozzle supply passage and the nozzle check valve chamber.

[0007] In another aspect, a method of operating a fuel system includes: supplying a first fuel to a first fuel inlet of a fuel injector; supplying a second fuel to a second fuel inlet of the fuel injector; and operating a control valve in the fuel injector to allow the first fuel to enter an outlet passage in the fuel injector. The method further includes pressurizing the fuel charge of the first fuel contained in the outlet passage and injecting the fuel charge by operating the control valve to release the closing hydraulic pressure on the nozzle check valve of the fuel injector. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of an internal combustion engine system according to one embodiment;

[0009] Figure 2 This is a cross-sectional side view of a fuel injector according to one embodiment;

[0010] Figure 3 Is it like this? Figure 2 Another cross-sectional side view of the fuel injector shown;

[0011] Figure 4 Is it like this? Figure 2 and Figure 3 A side view of a cross-section of a portion of the fuel injector shown;

[0012] Figure 5 Is it like this? Figure 2 and Figure 3 Another cross-sectional side view of a portion of the fuel injector shown;

[0013] Figure 6 Is it like this? Figure 2 and Figure 3 A schematic diagram of a portion of the fuel injector shown;

[0014] Figure 7 Is it like this? Figure 2 and Figure 3 Another schematic diagram of a portion of the fuel injector shown;

[0015] Figure 8 Is it like this? Figure 2 and Figure 3 A perspective cross-sectional schematic diagram of a portion of the fuel injector shown; and

[0016] Figure 9 This is a graph illustrating fuel system and engine events during an engine cycle according to one embodiment. Detailed Implementation

[0017] Reference Figure 1 An internal combustion engine system 10 according to one embodiment is illustrated. The engine system 10 includes an internal combustion engine 12 having an engine housing 14. The engine housing 14 includes a cylinder block 16 and a cylinder head 18 connected to the cylinder block 16. A plurality of cylinders 20 are formed in the cylinder block 16 and may include any number of cylinders in any suitable arrangement, such as inline, V-shaped, or other configurations. Pistons are conventionally positioned in the cylinders 20 and can move between top dead center and bottom dead center positions in a generally conventional manner, typically in a four-stroke engine cycle. The engine 12 can be used for any known purpose, including operating generators, pumps, compressors, or drivetrains in land vehicles or ships, to name just a few. The engine 12 also includes a cam gear 34 in the engine gear train, which is coupled to a camshaft 36 having a plurality of cams 38. Each corresponding cam 38 may define a base circle 40 and a convex angle 42, as discussed further herein.

[0018] Engine system 10 also includes fuel system 22. Fuel system 22 may include a dual-fuel system having a first fuel supply 24 for a first fuel and at least one fuel pump 28 configured to supply the first fuel to a fuel supply conduit 26 extending to engine 12, i.e., extending to cylinder head 18 in the illustrated embodiment. Fuel system 22 may also include a second fuel supply device 30 for a second fuel and at least one fuel pump 33 configured to deliver the second fuel to a second fuel supply conduit 32 extending to engine 12. The first fuel may be supplied at a relatively high pump outlet pressure, while the second fuel may be supplied at a relatively low pump outlet pressure, but the invention is not limited thereto.

[0019] In one embodiment, the first fuel may include a suitable compression-ignition fuel, such as a liquid diesel fraction. Alternatives may include higher-octane fuels blended with cetane enhancers, dimethyl ether, biodiesel, or various other substances including fuel blends. The second fuel may include higher-octane fuels such as ethanol fuels. Methanol and various methanol blends provide practical implementation strategies, although alternatives including various blends such as gasoline and others are also within the scope of this invention.

[0020] Fuel system 22 also includes a plurality of fuel injectors 44. Fuel injectors 44 may extend into each corresponding cylinder 20 and will therefore be understood as direct fuel injectors. Each fuel injector 44, sometimes referred to in the singular hereinafter, may include various internal components, including a nozzle check valve 46, a fuel pressurization plunger 48, and a valve assembly 50. As will become further apparent from the description below, fuel injectors 44 are configured to form and inject a fuel charge consisting of a first fuel as a lead fuel and a second fuel as a tail fuel. According to known principles, the first fuel in the combined fuel charge may have a relatively small quantity and is compressed and ignited in the corresponding cylinder 20 to trigger the ignition of a relatively large quantity of the second fuel. Fuel system 22 and fuel injectors 44 may also be configured to inject a fuel charge consisting entirely or at least primarily of the first fuel, for example, in so-called pure diesel mode.

[0021] The plunger 48 is shown as cam-actuated; however, in other embodiments, different fuel pressurization strategies, such as hydraulic actuation of the plunger, may be used. The fuel system 22 also includes an electronic control unit or ECU 52, which includes a suitable computerized controller and machine-readable memory, configured to electronically control the fuel injectors 44 and potentially, more generally, monitor and / or control other operating parameters of the fuel system 22 and / or engine system 10. As will become further apparent from the description below, each fuel injector 44 may be uniquely configured to control fuel intake and fuel charge formation and timing, potentially controlling, for example, the manner of rate shape and the pressure of the injected fuel charge.

[0022] Still referencing Figure 2 and 3The fuel injector 44 includes an injector housing 54 that forms a low-pressure fuel space 56 fluidly connected to a first fuel inlet 58, which receives a supply of first fuel from a fuel supply conduit 26. The injector housing 54 also forms a first fuel nozzle supply passage 60, a second fuel inlet 62 receiving a supply of second fuel from a fuel supply conduit 32, and a second fuel nozzle supply passage 64. In the illustrated embodiment, a first fitting 63 forms or is fluidly connected to the second fuel inlet 62, and a second fitting 65 receives an outlet supply of second fuel via a second fuel outlet 67 for return to the second fuel supply 30.

[0023] The injector housing 54 also forms a combined fuel outlet passage 66 fluidly connected to the first fuel nozzle supply passage 60 and the second fuel nozzle supply passage 64. The combined fuel outlet passage 66 extends to a plurality of nozzle outlets 68 fluidly connected to a corresponding cylinder 20. The injector housing 54 also forms a nozzle check valve control chamber 70. A nozzle check valve 72 is movable within the injector housing 54 between a closed position where the nozzle outlets 68 are blocked and the combined fuel outlet passage 66 is closed, and an open position where the nozzle outlets 68 are fluidly connected to the combined fuel outlet passage 66. In the illustrated embodiment, the first fuel nozzle supply passage 60 extends through a nozzle check element 72, wherein the nozzle check element 72 forms a plurality of transmission orifices 86 fluidly connected to a passage section 84 of the first fuel nozzle supply passage 60 and fluidly connected to the combined fuel outlet passage 66.

[0024] Providing first fuel to the combined fuel outlet passage 66 via the first fuel injector supply passage 60 and through the transfer orifice 86 can displace some of the second fuel residing in the combined fuel outlet passage 66, forming a segmented combined fuel charge with a first fuel leader and a second fuel follower as discussed herein. In the so-called diesel-only mode, allowing the first fuel to enter the combined fuel outlet passage 66 can displace sufficient second fuel to form a fuel charge consisting entirely of the first fuel if needed.

[0025] As described above, valve assembly 50 is located within injector housing 54. In the illustrated embodiment, valve assembly 50 includes an overflow valve 74 and an electric actuator subassembly 76, such as a solenoid actuator subassembly. Injector housing 54 also forms plunger chamber 80. Overflow valve 74 is movable between a closed position and an open position blocking plunger chamber 80 from second fuel inlet 62. Plunger 48 is directly or indirectly coupled to tappet 78, which contacts a corresponding cam 38. Plunger 48 may include multiple parts joined together without physical attachment, although the invention is not limited thereto, and plunger 48 may be connected to tappet 78 for direct reciprocating motion based on tappet 78 movement. Also in the illustrated embodiment, plunger chamber 80 is fluidly connected to nozzle check control chamber 70 via control valve 82 via second fuel nozzle supply passage 64, combined fuel outlet passage 66, and first fuel nozzle supply passage 60. Those skilled in the art will be familiar with the direct hydraulic control of the nozzle check valve, wherein a closing hydraulic pressure is applied to the nozzle check valve to maintain it in the closed position, and then selectively released to allow pressurized fuel in the fuel injector to cause the nozzle check valve to open and begin fuel injection. When it is desired that fuel injection has ended, the closing hydraulic pressure can be increased to cause the nozzle check valve to close. As described above, the fuel injector 44 is uniquely configured to control the intake of the first fuel and to control the injection timing and injection pressure of fuel injection comprising both the first fuel and the second fuel, or substantially only one of the first fuel or the second fuel.

[0026] Still referencing Figure 4-8 The fuel injector 44 includes a control valve 82 movable between a first position and a second position. In the first position, the low-pressure fuel space 56 is blocked from both the first fuel nozzle supply passage 60 and the nozzle check control chamber 70. In the second position, the low-pressure fuel space 56 is fluidly connected to both the first fuel nozzle supply passage 60 and the nozzle check control chamber 70. This described configuration allows the control valve 82 to sometimes open the low-pressure fuel space 56 to the first fuel nozzle supply passage 60 to allow first fuel to be injected into the combined fuel outlet passage 66, while at other times, fluid communication is established between the low-pressure fuel space 56 and the nozzle check control chamber 70 to selectively release the hydraulic pressure of the first fuel in the nozzle check control chamber 70 to allow the nozzle check 72 to open.

[0027] Fluid flow is connected from the plunger chamber 80 to the nozzle check control chamber 70. When the plunger 48 advances to increase fuel pressure in the fuel injector 44, and the overflow valve 74 is closed, the already increased and increasing fuel pressure can be supplied to the nozzle check control chamber 70, keeping the nozzle check 72 closed until the control valve 82 is actuated to connect the nozzle check control chamber 70 to the low-pressure fuel space 56 and to initiate injection. This feature allows the control valve 82 to be selectively opened when the desired injection pressure is reached in the fuel injector 44.

[0028] As also shown in the accompanying drawings, the injector housing 54 forms a fuel ring 88 extending circumferentially around the control valve 82. A fuel passage 90 extends between the fuel ring 88 and a first fuel nozzle supply passage 60. The injector housing 54 also forms a cavity 98. The cavity 98 is fluidly connected to the fuel ring 88, the first fuel nozzle supply passage 60, and a second fuel passage 102, which is connected to a nozzle check control chamber 70 via a valve 82. The injector housing 54 also forms a valve seat 92. When the control valve 82 is in a first position, a gap 94 is defined between the control valve 82 and the injector housing 54, and the gap 94 fluidly connects the fuel ring 88 to the nozzle check control chamber 70. A pressure control passage 96 extends into the nozzle check control chamber 70. A first fuel inlet-outlet passage 97 is fluidly connected between the valve seat 92 and a low-pressure fuel space 56.

[0029] In one embodiment, valve seat 92 includes a lower valve seat, and fuel injector 44 also forms an upper valve seat 100 that contacts control valve 82 in a second position. Fuel ring 88 may be continuously fluidly connected to the first fuel nozzle supply passage 60 and blocks pressure control passage 96 when control valve 82 contacts upper valve seat 100 in the second position, as discussed further below. Second fuel passage 102 extends between valve seat 92 and the first fuel nozzle supply passage 60. Fuel injector 44 may also include a check valve 104 that is movable in three-way chamber 98 to a closed position blocking the first fuel nozzle supply passage 60 from low-pressure fuel space 56. A spring biaser 106 may be provided to bias check valve 104 toward the closed position. In some embodiments, the biaser for check valve 104 is omitted.

[0030] Concentrated Figure 8Above, it is shown that the check valve 104 blocks the fluid communication between the first fuel nozzle supply passage 60 and the second fuel passage 102 approximately when it is likely to be in the closed position. However, in the closed position of the check valve 104, fluid communication is maintained between the first fuel nozzle supply passage 60 and the fuel passage 90 extending to the fuel ring 88. Thus, as long as the control valve 82 remains in the first position, the increased pressure in the plunger chamber 80 during fuel pressurization can communicate through the fuel passage 90 and the fuel ring 88 through the gap 94 to the pressure control passage 96. The check valve 104 can move to the closed position in response to the increased pressure in the first fuel nozzle supply passage 60. However, the fluid communication between the first fuel nozzle supply passage 60 and the second fuel passage 102 is blocked, thereby preventing the increased fuel pressure from ultimately communicating back through the inlet-outlet passage 97.

[0031] In the illustrated embodiment, the injector housing 54 includes a cluster of clamped components, including a tip 110 forming a nozzle outlet 68 located within the injector housing 112. Therefore, a low-pressure fuel space 56 is defined between the stack 108 and the housing 112. It should be understood that the low-pressure fuel space can be further defined as any fuel space discontinuously fluidly connected to the nozzle check valve control chamber 70, into which fuel pressure can be released. Furthermore, the valve assembly 50 is described as integrating an overflow valve 74 and a control valve 82. In other embodiments, these components may be separable to different locations within the fuel injector, or even possibly located outside the fuel injector.

[0032] Industrial applicability

[0033] Operating the fuel system 22 and engine system 10 according to the invention may include supplying a first fuel to a first fuel inlet 58 and a second fuel to a second fuel inlet 62. A control valve 82 may be operated to allow the first fuel to enter a combined fuel outlet passage 66, as discussed herein. The fuel charge containing the first fuel may be pressurized by a plunger 48 in the combined fuel outlet passage 66. The fuel charge may be re-injected by operating the control valve 82 to release the closing hydraulic pressure on the nozzle check valve 72. In one embodiment, the first fuel may be supplied to the fuel injector 44 at a pressure higher than the pressure at which the second fuel is supplied to the fuel injector 44. The at least moderately higher pressure of the first fuel may facilitate the first fuel displacing the second fuel in the combined fuel outlet passage 66.

[0034] It has been determined that certain events described in conjunction with the operation of fuel system 22 and fuel injector 44 can occur at optimized timing. It should be understood that, for example, when the internal fuel pressure is high, such as when plunger 48 advances and overflow valve 74 is closed, the first fuel cannot be practically allowed to enter the fuel injector. In one embodiment, control valve 82 is operated to allow the first fuel to enter when cam 38 contacts the tappet 78 of plunger 48 coupled to the base circle 40 of cam 38 and / or when plunger 48 retracts. When cam 38 contacts tappet 78 on the base circle 40, the second fuel within fuel injector 44 is relatively stationary and can be easily and controllably displaced by the first fuel. Operating control valve 82 to release the closing hydraulic pressure on nozzle check valve 70 may include operating control valve 82 when cam 38 contacts tappet 78 via cam lob 42. Thus, when tappet 78 is pushed down by cam lob 42 and fuel pressure in fuel injector 44 increases, control valve 82 is opened at the desired timing corresponding to the desired fuel injection pressure.

[0035] Now refer to Figure 9 A graph 200 is shown, illustrating the crank angle on the X-axis and the valve lift on the Y-axis. The opening and closing of the exhaust valve is shown in trajectory 202, and the opening and closing of the intake valve is shown in trajectory 204. During the engine cycle, the first fuel injection 206 can occur approximately at the top dead center position of the corresponding piston, followed by the expansion stroke until the exhaust valve opening 202 begins. Another fuel injection event 208 is then shown. A fuel inlet event is shown at trajectory 210, corresponding to the engine crank angle timing range, as the exhaust valve opens and subsequently the intake valve opens and the associated cam rotates on the base circle. The fuel inlet window, or metering range, is shown approximately by dashed box 212. Therefore, it can be understood that a metering range 212 exists between fuel injection events, which allows for a variable and controllable amount of the first fuel to form a combined fuel charge or a single fuel charge in the fuel injector 44.

[0036] This specification is for illustrative purposes only and should not be construed as limiting the scope of the invention in any way. Therefore, those skilled in the art will understand that various modifications can be made to the currently disclosed embodiments without departing from the full and reasonable scope and spirit of the invention. Other aspects, features, and advantages will become apparent from a study of the accompanying drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items and are interchangeable with “one or more”. The term “a” or similar language is used where only one item is desired. Furthermore, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Additionally, the phrase “based on” is intended to mean “at least partially based on”, unless otherwise explicitly stated.

Claims

1. A fuel injector comprising: an injector housing forming a low pressure fuel space, a first fuel nozzle supply passage, a second fuel nozzle supply passage, a combined fuel outlet passage fluidly connected to both the first fuel nozzle supply passage and the second fuel nozzle supply passage and extending to a plurality of nozzle outlets, and a nozzle check control cavity; a nozzle check valve movable between a closed position blocking the plurality of nozzle outlets from the combined fuel outlet passage and an open position; and a control valve movable between a first position blocking the low pressure fuel space from both the first fuel nozzle supply passage and the nozzle check control cavity and a second position in which the low pressure fuel space is fluidly connected to both the first fuel nozzle supply passage and the nozzle check control cavity.

2. The fuel injector of claim 1, wherein the first fuel nozzle supply passage extends through the nozzle check valve to a plurality of delivery orifices fluidly connected to the combined fuel outlet passage.

3. The fuel injector of claim 1 or 2, wherein: the injector housing forms a second fuel inlet and a plunger cavity (80), and the fuel injector further comprises a spill valve movable between a closed position blocking the plunger cavity from the second fuel inlet and an open position; and the plunger cavity is fluidly connected to the nozzle check control cavity via the second fuel nozzle supply passage, the combined fuel outlet passage, and the first fuel nozzle supply passage.

4. The fuel injector of any of claims 1-3, wherein: the injector housing forms a fuel ring extending around the control valve, a fuel passage extending between the fuel ring and the first fuel nozzle supply passage, and a valve seat; and a gap is defined between the control valve and the injector housing when the control valve is in the first position, and the gap fluidly connects the fuel ring to the nozzle check control cavity.

5. The fuel injector of any of claims 1-4, wherein the injector housing forms a second fuel passage extending between the valve seat and the first fuel nozzle supply passage, and further comprising a check valve movable to a closed position blocking the second fuel passage from the first fuel nozzle supply passage in response to an increase in pressure in the first fuel nozzle supply passage; and the fuel injector further comprises a biaser biasing the check valve toward the closed position.

6. The fuel injector of any of claims 1-5, wherein the injector housing forms a first fuel inlet-outlet passage fluidly connected between the valve seat and the low pressure fuel space.

7. A fuel system comprising: a first fuel supply of a first fuel; a second fuel supply of a second fuel; a fuel injector forming a low pressure fuel space fluidly connected to the first fuel supply, a first fuel nozzle supply passage, a second fuel nozzle supply passage, a combined fuel outlet passage extending to a plurality of nozzle outlets, and a nozzle check control cavity; and the fuel injector further comprising a control valve movable between a first position blocking the low pressure fuel space from both the first fuel nozzle supply passage and the nozzle check control cavity, and a second position fluidly connecting the low pressure fuel space to both the first fuel nozzle supply passage and the nozzle check control cavity.

8. The fuel system of claim 7, wherein the fuel injector forms a fuel ring extending around the control valve, and a cavity fluidly connected to the fuel ring, the first fuel nozzle supply passage, and the nozzle check control cavity through the control valve.

9. The fuel system of claim 7 or 8, wherein the fuel injector further comprises a check valve movable within the cavity to a closed position to block the first fuel nozzle supply passage from the low pressure fuel space.

10. The fuel system of any one of claims 7-9, wherein the fuel injector further comprises a nozzle check valve, and the first fuel nozzle supply passage extends through the nozzle check valve.

11. The fuel system of any one of claims 7-10, wherein: the fuel injector forms a second fuel inlet fluidly connected to the second fuel supply, and a plunger cavity fluidly connected to the second fuel nozzle supply passage; and the fuel injector further comprises a plunger movable within the plunger cavity from a retracted position to an advanced position to pressurize a combined fuel charge in the combined fuel outlet passage containing the first fuel entering via the control valve and the second fuel entering through the plunger cavity.

12. The fuel system of any one of claims 7-11, wherein the fuel injector further forms a valve seat, and the control valve is in contact with the valve seat at the first position; wherein the valve seat comprises a lower valve seat, and the fuel injector further forms an upper valve seat in contact with the control valve at the second position, and a gap defining around the control valve at the first position and fluidly connecting the nozzle check control cavity to the first fuel nozzle supply passage.

13. A method of operating a fuel system, comprising: supplying a first fuel to a first fuel inlet of a fuel injector; supplying a second fuel to a second fuel inlet of the fuel injector; operating a control valve in the fuel injector to allow the first fuel to enter an outlet passage in the fuel injector; pressurizing a fuel charge in the outlet passage containing the first fuel; and injecting the fuel charge by operating the control valve to release a closing hydraulic pressure on a nozzle check valve of the fuel injector.

14. The method of claim 13, wherein the outlet passage extends through a nozzle check valve of the fuel injector, and the fuel charge contains the first fuel as a leading fuel and the second fuel as a trailing fuel.

15. The method of claim 13 or 14, wherein: the supplying the first fuel includes supplying the first fuel at a higher pressure; the supplying the second fuel includes supplying the second fuel at a lower pressure; the pressurizing the fuel charge includes advancing a plunger in a plunger cavity; the operating the control valve to allow the first fuel to enter further includes operating the control valve when a cam contacts a tappet coupled to the plunger on a base circle of the cam or when the plunger is retracted; and the operating the control valve to release the closed hydraulic pressure further includes operating the control valve when a cam contacts a tappet on a lobe of the cam and the plunger is advanced.

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