A dual-fuel injection system, injection method, and engine

Abstract

This disclosure provides a dual-fuel injection system, injection method, and engine. The dual-fuel injection system includes: a first subsystem comprising a first pressure-building unit and a first injector; the first injector includes a main injection valve and a pilot control valve, the pilot control valve controlling the opening or closing of the main injection valve; a first fuel capable of flowing to and being injected from the main injection valve; a control oil subsystem comprising a control oil pressure-building unit; control oil capable of flowing to and controlling the main injection valve; and a second subsystem comprising a second pressure-building unit and a second injector; a second fuel capable of flowing to and being injected from the second injector; wherein a switching valve is further provided between the first subsystem and the second subsystem; the second fuel can also flow to and be injected from the first injector of the first subsystem via the switching valve.

Description

Technical Field

[0001] This disclosure relates to a dual-fuel injection system, an injection method, and an engine. Background Technology

[0002] Low-viscosity clean fuels such as methanol and ammonia are widely favored due to their significant carbon reduction potential. Compared to diesel, methanol and ammonia fuels have higher auto-ignition temperatures, making it difficult to achieve compression ignition and combustion of a single fuel. Therefore, some existing technical solutions employ a combination of low-viscosity clean fuel (e.g., methanol, ammonia) low-pressure manifold injection and high-cetane fuel (e.g., diesel) high-pressure direct injection. However, this approach results in poor atomization of the low-viscosity clean fuel and a low fuel substitution rate.

[0003] On the other hand, some solutions adopt the technical route of direct injection of low-viscosity clean fuels into the cylinder. However, for new clean fuels with hazardous chemical properties such as high octane number, low calorific value, low viscosity, low density, and corrosiveness, high-pressure direct injection technology faces many challenges, including difficulty in pressure build-up, poor slippage, poor sealing, and design of the ignition system. Existing high-pressure dual-fuel injection systems are mostly integrated improvements on the basis of traditional fuel high-pressure injection systems, and generally suffer from a bulky and complex system structure; difficulty in pressure build-up of low-viscosity clean fuels, resulting in low pressure; low flexibility and precision in low-viscosity clean fuel injection control; insufficient targeted design for safety aspects such as sealing and leakage of low-viscosity clean fuels; and inability to meet the ignition requirements of all operating conditions and the flexible switching and precise control of single fuel operation under full load when used with traditional fuel injection.

[0004] One comparative scheme achieves wide-range injection of traditional diesel fuel and high-pressure direct injection of low-viscosity new fuels. However, the inventors found that when the comparative scheme operates in pure diesel mode, it needs to achieve both high-pressure direct injection of traditional diesel fuel across the entire operating range and high-pressure, low-volume ignition injection of traditional diesel fuel in the low-viscosity new fuel mode. This puts significant pressure on emissions and fuel consumption in pure diesel mode, and there is still room for further improvement. At the same time, in pure diesel mode, the single diesel injection and combustion leave the low-viscosity new fuel injection subsystem, especially the injector, idle. The low-viscosity clean fuel nozzle may also experience "dry burning," which places higher demands on materials, cooling design, and nozzle spatial layout, and may even introduce certain reliability risks.

[0005] Therefore, there is a need in the art for new fuel injection systems, injection methods, and engines to at least partially solve the aforementioned technical problems. Summary of the Invention

[0006] The purpose of this disclosure is to provide a dual-fuel injection system.

[0007] Another objective of this disclosure is to provide a dual-fuel injection method.

[0008] Another objective of this disclosure is to provide an engine.

[0009] According to a dual-fuel injection system of the first aspect of this disclosure, it includes: a first subsystem comprising a first pressure-building unit and a first injector; the first injector comprising a main injection valve and a pilot control valve; the main injection valve being used for fuel injection, and the pilot control valve being used to open or close the main injection valve; the flow path of the first subsystem being configured such that, after pressure building by the first pressure-building unit, first fuel can flow to the main injection valve and be injected under the control of the pilot control valve; a second subsystem comprising a second pressure-building unit and a second injector; the flow path of the second subsystem being configured such that, after pressure building by the second pressure-building unit, second fuel can flow to the second injector and be injected; and a control oil subsystem comprising a control oil pressure-building unit; the flow path of the control oil subsystem being configured such that, after pressure building by the control oil pressure-building unit, control oil can flow to the pilot control valve for controlling the main control valve; wherein a switching valve is further provided between the first subsystem and the second subsystem, and the second fuel can also flow to the first injector of the first subsystem and be injected through the switching valve.

[0010] The technical solutions described above enable independent operation of the first and second subsystems, allowing for single-fuel or dual-fuel high-pressure injection. Furthermore, the control oil subsystem design enables stable and highly precise injection pilot control of the first subsystem, avoiding fuel medium backflow issues during the operation of the first injector and improving safety. Simultaneously, the switching valve design allows the second fuel to be injected from the first injector, facilitating various injection modes and strategies. In particular, it enables switching of the fuel medium within the first subsystem. In the mode where only the second fuel is injected, both the first and second injectors can achieve high-pressure injection of the second fuel, providing significant freedom in combustion organization and creating conditions for configuring various combustion modes and strategies. On the other hand, it avoids the "dry burning" problem at the nozzle that might occur when the first fuel subsystem is idle in existing dual-fuel injection systems. Moreover, by switching the fuel medium within the first subsystem, a compact and functionally integrated design is achieved.

[0011] In one or more embodiments, the control oil subsystem and the second subsystem are connected, allowing the second fuel to flow to the control oil subsystem for use as control oil; and the switching valve is disposed between the control oil subsystem and the first subsystem, allowing the second fuel to flow through the control oil subsystem and the switching valve to the first injector.

[0012] In one or more embodiments, the switching valve is at least one of a mechanical one-way control valve, a pneumatic switching valve, and an electric switching valve.

[0013] In one or more embodiments, the first subsystem further includes a first accumulator module; the first accumulator module includes a first common rail, a first pressure sensor, and a first flow restrictor valve; the first pressure sensor is disposed on the first common rail; the flow path of the first subsystem is configured such that: after pressure is built up by the first pressure building unit, the first fuel can flow to the first common rail for pressure storage, and then flow to the first injector through the first flow restrictor valve.

[0014] In one or more embodiments, the second subsystem further includes a second accumulator module; the second accumulator module includes a second common rail, a second pressure sensor, and a second flow restrictor valve; the second pressure sensor is disposed in the second common rail; the flow path of the second subsystem is configured such that: after being pressurized by the second pressure building unit, the second fuel can flow to the second common rail for accumulating pressure, and then flow to the second injector through the second flow restrictor valve.

[0015] In one or more embodiments, the oil production subsystem further includes a control oil pressure storage module; the control oil pressure storage module includes a control oil common rail, a control oil pressure sensor, and a control oil flow limiting valve; the control oil pressure sensor is disposed in the control oil common rail; the flow path of the control oil subsystem is configured such that: after pressure is built up by the control oil pressure building unit, the control oil can flow to the control oil common rail for pressure storage, and then flow to the first injector through the control oil flow limiting valve.

[0016] In one or more embodiments, the first accumulator module further includes a first pressure limiting valve and / or a first active pressure relief valve disposed on the first common rail.

[0017] In one or more embodiments, the control oil accumulator module further includes a control oil pressure limiting valve disposed on the control oil common rail.

[0018] In one or more embodiments, the first injector and the second injector are integrated into a single injector, the single injector including a first nozzle and a second nozzle.

[0019] In one or more embodiments, the dual-fuel injection system includes a first mode, a second mode, and a third mode; in the first mode, the first injector does not inject, and the second fuel flows to the second injector and is injected; in the second mode, the second fuel flows through the switching valve to the first injector and is injected, and the second fuel flows to the second injector and is injected; in the third mode, the first fuel flows to the first injector and is injected, and the second fuel flows to the second injector and is injected.

[0020] In one or more embodiments, in the first mode, the first pressure-building unit and the control oil pressure-building unit build up pressure in preparation for switching to the second mode or the third mode.

[0021] In one or more embodiments, at least one of the injection quantity, injection timing, and injection pressure of the first subsystem and the second subsystem is controlled to configure multiple injection strategies.

[0022] According to a dual-fuel injection method of the second aspect of this application, the first fuel and the second fuel are injected using a dual-fuel injection system as described in the first aspect, or only the second fuel is injected.

[0023] A dual-fuel engine according to a third aspect of this application includes a dual-fuel injection system as described in the first aspect. Attached Figure Description

[0024] The above and other features, properties, and advantages of this disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features. It should be noted that these drawings are merely illustrative and are not drawn to scale, and should not be construed as limiting the scope of protection actually claimed by this disclosure, wherein:

[0025] Figure 1 This is a schematic diagram of a dual-fuel injection system according to one embodiment.

[0026] Figure 2 This is a schematic diagram of the injection mode flow of a dual-fuel injection system according to an embodiment.

[0027] Figure 3A , Figure 3B This is a schematic diagram of the structure of the first fuel injector in a dual-fuel injection system according to an embodiment. Detailed Implementation

[0028] Reference will now be made in detail to various embodiments of this disclosure, examples of which are shown in the accompanying drawings and described below. Although this disclosure will be described in conjunction with exemplary embodiments, it should be understood that this disclosure is not intended to be limited to those exemplary embodiments. Rather, this disclosure is intended to cover not only these exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of this disclosure as defined by the appended claims.

[0029] This disclosure uses specific terms to describe embodiments of the present disclosure. For example, "an embodiment" and / or "one embodiment" refers to a particular feature, structure, or characteristic associated with at least one embodiment of the present disclosure. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" mentioned twice or more in different locations in this disclosure does not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the present disclosure can be appropriately combined.

[0030] In the following description, the terms "upper," "lower," "inner," "outer," "front," "rear," or other directional terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These are used solely for the convenience of describing this disclosure and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed in a specific orientation, or be implemented in a specific orientation. Therefore, they should not be construed as limitations on this disclosure. In this disclosure, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying positional relationships or order of importance.

[0031] As mentioned above, on the one hand, existing low-viscosity clean fuel injection technologies mainly rely on low-pressure manifold injection of low-viscosity clean fuels combined with high-pressure direct injection of high-cetane fuels. This approach suffers from poor atomization of low-viscosity clean fuels and a low fuel substitution rate. On the other hand, high-pressure direct injection of low-viscosity clean fuels is considered a more efficient injection technology, and dual-fuel high-pressure direct injection technology combining low-viscosity clean fuels and high-cetane fuels is rapidly developing. However, for novel clean fuels with properties such as high octane rating, low calorific value, low viscosity, low density, and corrosiveness, high-pressure direct injection technology faces numerous challenges, including difficulty in pressure build-up, poor slippage, poor sealing, and complex ignition system design. Existing high-pressure dual-fuel injection systems are mostly integrated improvements on the basis of traditional high-pressure fuel injection systems, and generally suffer from a bulky and complex system structure; difficulty in building up pressure with low-viscosity clean fuels, resulting in low pressure; low flexibility and precision in low-viscosity clean fuel injection control; insufficient targeted design for safety aspects such as sealing and leakage of low-viscosity clean fuels; and inability to simultaneously meet the ignition requirements of all operating conditions and the flexible switching and precise control of single-fuel operation under full load when used with traditional diesel injection. In particular, this disclosure further develops the injection mode and injection strategy for single-fuel medium injection, while also solving the "dry burning" problem existing in dual-fuel injection systems.

[0032] Based on the above considerations, the inventors, after in-depth research, proposed a dual-fuel injection system, injection method, and engine, which is applicable to marine diesel engines, but not limited thereto, and is also applicable to other applications that require dual-fuel injection.

[0033] In this disclosure, the "first fuel" is generally a low-viscosity clean fuel (e.g., methanol fuel), also known as a "new type of fuel," but is not limited thereto; the "second fuel" is generally a high cetane number fuel (e.g., diesel fuel), also known as a "conventional fuel," but is not limited thereto.

[0034] refer to Figure 1As shown, the dual-fuel injection system includes: a first subsystem comprising a first pressure-building unit 11 and a first injector; the first injector includes a main injection valve and a pilot control valve 18; the main injection valve is used for fuel injection, and the pilot control valve 18 is used to open or close the main injection valve; the flow path of the first subsystem is configured such that, after pressure is built up by the first pressure-building unit 11, the first fuel can flow to the main injection valve and be injected under the control of the pilot control valve 18; a second subsystem comprising a second pressure-building unit 9 and a second injector; the flow path of the second subsystem is configured such that, after pressure is built up by the first pressure-building unit 11, the first fuel can flow to the main injection valve and be injected under the control of the pilot control valve 18; and a second subsystem comprising a second pressure-building unit 9 and a second injector; the flow path of the second subsystem is configured such that, after pressure is built up by the first pressure-building unit 11, the first fuel can flow to the main injection valve and be injected under the control of the pilot control valve 18. The flow path is configured such that, after pressure is built up by the second pressure-building unit 9, the second fuel can flow to the second injector and be injected; the control oil subsystem includes a control oil pressure-building unit 2; the flow path of the control oil subsystem is configured such that, after pressure is built up by the control oil pressure-building unit 2, the control oil can flow to the pilot control valve 18 for controlling the main control valve; wherein, a switching valve 107 is also provided between the first subsystem and the second subsystem, and the second fuel can also flow to the first injector of the first subsystem through the switching valve 107 and be injected.

[0035] The technical solutions described above enable independent operation of the first and second subsystems, allowing for single-fuel or dual-fuel high-pressure injection. Furthermore, the control oil subsystem design enables stable and highly precise injection pilot control of the first subsystem, avoiding fuel medium backflow issues during the operation of the first injector and improving safety. Simultaneously, the switching valve 107 design allows the second fuel to be injected from the first injector, facilitating various injection modes and strategies. In particular, it enables switching of the fuel medium within the first subsystem. In the mode of injecting only the second fuel, both the first and second injectors can achieve high-pressure injection of the second fuel, providing significant freedom in combustion organization and creating conditions for configuring various combustion modes and strategies. On the other hand, it avoids the "dry burning" problem at the nozzle that might occur when the first fuel subsystem is idle in existing dual-fuel injection systems. Moreover, by switching the fuel medium within the first subsystem, a compact and functionally integrated design is achieved.

[0036] Specifically, the first subsystem can be an independent high-pressure pump skid, which consists of a motor-driven high-pressure pump, safety valve assembly, sensors, filter elements and other components, and has functions such as high-pressure build-up and safety monitoring and alarm. The high-pressure pump skid can also operate independently of the whole machine and be placed next to the machine or in the fuel storage room, etc., with a compact and flexible layout. If the pump skid is placed next to the machine, it can also adopt a fully enclosed explosion-proof design.

[0037] Optionally, the first injector is a leak-free injector with a leak-free injector structure, and the control oil system also serves as the sealing oil for the leak-free injector. This design eliminates the need for a dedicated sealing oil circuit, making it particularly suitable for medium- and high-speed machines with limited space requirements and where compactness is a greater priority.

[0038] Optionally, the second pressure-building unit 9 of the second subsystem can be a unit pump, such as a mechanical or electronically controlled unit pump; in this case, the injection timing and injection pressure of the second subsystem can be controlled by the cam profile, plunger profile and speed regulating mechanism of the unit pump.

[0039] Optionally, the control oil pressure building unit 2 of the control oil subsystem adopts a machine-mounted high-pressure oil pump or an independent high-pressure pump skid; when a pilot high-pressure pump skid is adopted, the pump skid can operate independently of the whole machine and can be set at the machine side or fuel storage room according to the layout requirements of the whole machine.

[0040] Optionally, the first pressure-building unit 11 of the first subsystem and the control oil pressure-building unit 2 of the control oil subsystem operate independently of the whole machine, and the two together form an external auxiliary pressure-building module 1.

[0041] In one or more embodiments, the control oil subsystem and the second subsystem are connected, allowing the second fuel to flow to the control oil subsystem as the control oil; and the switching valve 107 is disposed between the control oil subsystem and the first subsystem, allowing the second fuel to flow through the control oil subsystem and the switching valve 107 to the first injector.

[0042] This further achieves a compact structure and integrated function design. At this point, when the control oil pressure reaches the opening condition of the switching valve 107, the control oil supply increases, allowing the second fuel to be injected into the first subsystem.

[0043] In one or more embodiments, the switching valve 107 is a mechanical one-way control valve, a pneumatic switching valve, or an electrically switching valve. This design enables control over the direction, flow rate, and pressure of the fuel medium.

[0044] like Figure 3A , Figure 3BAs shown, specifically, a mechanical one-way control valve can be used. When the opening pressure is reached, the mechanical one-way control valve automatically opens, allowing the second fuel to flow to the first subsystem. Alternatively, a pneumatic or electric switching valve can be used. The pressure is identified by an electronic control system, and when a predetermined pressure is reached, the pneumatic or electric switching valve opens, controlling the flow of the second fuel to the first subsystem. Taking a mechanical pressure one-way valve as an example, the switching valve 107 may include a first fuel high-pressure inlet 109, a first fuel high-pressure outlet 110, a second fuel high-pressure inlet 111, and a second fuel high-pressure outlet 112. When the valve core 115 opening pressure is reached, the second fuel flows through the throttle orifice 113 to each chamber of the first subsystem, thus replacing the first fuel. The flow capacity of the valve core 115, valve body 114, and throttle orifice 113 needs to be determined in conjunction with engine speed, fuel pump supply capacity, etc. The magnitude and matching relationship of the flow capacity determine the function and performance indicators after the original first fuel is replaced by the second fuel in a single fuel injection mode.

[0045] Continue to refer to Figure 1 In one or more embodiments, the first subsystem further includes a first accumulator module 13; the first accumulator module 13 includes a first common rail 22, a first pressure sensor 17, and a first flow restrictor valve 14; the first pressure sensor 17 is disposed in the first common rail 22; the flow path of the first subsystem is configured such that after pressure is built up by the first pressure-building unit 11, the first fuel can flow to the first common rail 22 for pressure accumulation, and then flow to the first injector through the first flow restrictor valve 14. This design employs high-pressure common rail technology in the first subsystem, enabling the first subsystem to have a more stable medium pressure environment in multiple modes, creating pressure conditions for high-precision fuel injection control, and also enabling free control of injection timing, injection pressure, etc.

[0046] Specifically, the first subsystem may include a first pump rail unit 12 and a first rail device unit 24. The first pump rail unit 12 connects the first pressure building unit 11 and the first pressure accumulator module 13, and the first rail device unit 24 connects the first injector and the first pressure accumulator module 13. Considering that the first fuel may have hazardous chemical properties that could cause safety issues, the first pump rail unit 12 may also include a first abnormal leakage collection oil channel 104.

[0047] In one or more embodiments, the second subsystem further includes a second accumulator module; the second accumulator module includes a second common rail, a second pressure sensor, and a second flow restrictor valve; the second pressure sensor is disposed in the second common rail; the flow path of the second subsystem is configured such that: after being pressurized by the second pressure building unit 9, the second fuel can flow to the second common rail for accumulating pressure, and then flow to the second injector through the second flow restrictor valve.

[0048] Specifically, the second subsystem may include a second pump rail pipe unit 10 and a second rail device pipe unit. The second pump rail pipe unit 10 connects the second pressure building unit 9 and the second pressure accumulator module, and the second rail device pipe unit connects the second injector and the second pressure accumulator module. The second pump rail pipe unit 10 may also include a second abnormal leakage collection oil passage 102 and a second normal return oil collection oil passage 103.

[0049] The use of high-pressure common rail technology in the second subsystem enables a more stable medium pressure environment in multiple modes and provides greater freedom of control over the dual-injection mode of the second fuel. When both the first and second subsystems use high-pressure common rail injection, the second fuel can be directly injected into the cylinder at high pressure in both subsystems. Furthermore, the injection quantity, injection timing, and injection pressure of the two independent subsystems can be freely controlled, thereby enabling multiple injection strategies for a single fuel injection. For example, the two independent subsystems can be classified as main injection, pre-injection, or post-injection, giving the combustion organization of a single fuel injection a great deal of freedom.

[0050] In one or more embodiments, the control oil subsystem further includes a control oil accumulator module 4; the control oil accumulator module 4 includes a control oil common rail 23, a control oil pressure sensor 8, and a control oil flow restrictor valve 6; the control oil pressure sensor 8 is disposed in the control oil common rail 23; the flow path of the control oil subsystem is configured such that, after pressure build-up by the control oil pressure building unit 2, the control oil can flow to the control oil common rail 23 for pressure accumulation, and then flow to the first injector through the control oil flow restrictor valve 6. The use of the high-pressure common rail technology in the control oil subsystem enables a more stable medium pressure environment in multiple modes, creating pressure conditions for high-precision fuel injection control.

[0051] Specifically, the control oil subsystem may include a control oil pump rail pipe 3 and a control oil rail device pipe 5, which respectively connect the control oil accumulator module 4 to the control oil pressure building unit 2 and the first injector.

[0052] Optionally, the switching valve 107 may be disposed between the control oil pump rail pipe 3 and the first pump rail pipe unit 12.

[0053] In one or more embodiments, the first pressure accumulator module 13 further includes a first pressure limiting valve 15 and / or a first active pressure relief valve 16 disposed on the first common rail 22; such design improves the safety of the system.

[0054] Specifically, when the first fuel is overpressurized, the first pressure relief valve 15 opens, or according to the overall machine safety control strategy, the first active pressure relief valve 16 actively relieves pressure and enters the corresponding independent first fuel return system.

[0055] In one or more embodiments, the control oil accumulator module 4 further includes a control oil pressure limiting valve 7 disposed on the control oil common rail 23; this design improves the safety of the system.

[0056] Specifically, when the control oil pressure exceeds the limit, the control oil pressure relief valve 7 opens, the high-pressure control oil is depressurized, and enters the corresponding independent low-pressure control oil return system.

[0057] Optionally, the first subsystem includes a purge channel, which performs vacuuming or inert gas purging according to the overall machine operation specifications and purging control strategy. The inert gas is, for example, nitrogen. The purge interfaces 105 and 106 of the purge channel can be located at the belt end or the external auxiliary pressure building module 1. The first subsystem can also perform inert gas purging through the first active pressure relief valve 16.

[0058] In one or more embodiments, the first injector and the second injector are integrated into a single injector 19, which includes a first nozzle 20 and a second nozzle 21. In this case, the single injector 19 serves as the final actuating device, further enhancing the compact structure and integrated functionality.

[0059] Furthermore, the integrated injector 19 may include a control valve 18 and a control oil return and collection channel 101. The integrated injector 19 can also be configured such that, when the first subsystem injects the first fuel and the second subsystem injects the second fuel, the first nozzle 20 is used for the main injection of the first fuel, and the second nozzle 21 is used for ignition injection; when both the first and second subsystems inject the second fuel, the first nozzle 20 is used for the main injection, pre-injection, or post-injection of the second fuel, and the second nozzle 21 is changed from being used for ignition injection to being used for the main injection of the second fuel. That is, for the second fuel injection, the two nozzles of the integrated injector 19, along with their corresponding flow channels and control valves, are optimized for both small-volume and full-load large-volume wide-range injection, thus creating conditions for stable injection under various injection modes and strategies. In addition, spatial matching of the two fuel medium injection paths can be achieved by adjusting the first nozzle 20 and the second nozzle 21.

[0060] like Figure 2 As shown, in one or more embodiments, the dual-fuel injection system includes a first mode, a second mode, and a third mode; in the first mode, the first injector does not inject, and the second fuel flows to the second injector and is injected; in the second mode, the second fuel flows through the switching valve 107 to the first injector and is injected, and the second fuel flows to the second injector and is injected; in the third mode, the first fuel flows to the first injector and is injected, and the second fuel flows to the second injector and is injected.

[0061] This design enables the dual-fuel injection system to operate in the three combustion modes mentioned above, achieving single-fuel injection or dual-fuel injection. In particular, in the second mode, different combustion strategies can be configured for the first subsystem and the second subsystem. For example, the first subsystem and the second subsystem can be distinguished as main injection and pre-injection, or main injection and post-injection. By controlling the injection quantity of the second fuel and the dual sprays in time and space, the predetermined combustion organization requirements can be met, greatly expanding the degree of freedom of combustion organization for single-fuel injection.

[0062] Specifically, the first mode can be that when the whole machine starts or runs normally, the second pressure building unit 9 starts to build pressure. When the pressure reaches the injection pressure of the needle valve in the second injector, or when other predetermined injection conditions are met, the second fuel is prepared for injection. This mode uses the second fuel as a single fuel medium. Its injection quantity and injection pressure are determined according to the actual working conditions and controlled by injection timing and injection pressure.

[0063] The second mode can be that when the valve core 115 of the switching valve 107 reaches the opening pressure, the second fuel flows through the throttle orifice 113 to each chamber of the first subsystem.

[0064] The third mode can be as follows: the control oil pressure building unit 2 first builds pressure, the control oil enters the control oil accumulator module 4 through the control oil pump rail pipe unit, and then enters the pilot control valve 18 in the first injector through the control oil flow limiting valve 6 and the control oil rail pipe; when the control oil pressure reaches the set value, the first pressure building unit 11 starts to build pressure, the first fuel enters the first accumulator module 13 through the first pump rail fuel pipe unit, and then enters the main injection valve in the first injector through the first flow limiting valve 14 and the first rail fuel pipe; the first fuel and the control oil pressure communicate with the ECU through the first fuel pressure sensor and the control oil pressure sensor 8 and their corresponding data acquisition units, respectively. When both medium pressures reach the set value, the first fuel prepares for injection; when the whole machine starts or runs normally, the second pressure building unit 9 starts to build pressure, and when the pressure reaches the needle valve injection pressure in the second injector, the second fuel prepares for injection. In this mode, the second fuel undertakes the function of ignition injection under all operating conditions.

[0065] Continue to refer to Figure 2 In one or more embodiments, in the first mode, the first pressure-building unit 11 and the control oil pressure-building unit 2 build up pressure in preparation for switching to the second mode or the third mode. This design enables seamless and instantaneous switching from the first mode to the second or third mode.

[0066] In one or more embodiments, at least one of the injection quantity, injection timing, and injection pressure of the first subsystem and the second subsystem is controlled to configure multiple injection strategies. In particular, when both the first subsystem and the second subsystem employ high-pressure common rail injection technology, the injection timing, injection pressure, and injection quantity of both independent subsystems can be freely controllable. For example, classifying the first subsystem and the second subsystem into main injection, pre-injection, and post-injection, etc., facilitates the configuration of injection strategies.

[0067] According to a dual-fuel injection method of the second aspect of this application, the first fuel and the second fuel are injected using a dual-fuel injection system as described in the first aspect, or only the second fuel is injected.

[0068] A dual-fuel engine according to a third aspect of this application includes a dual-fuel injection system as described in the first aspect.

[0069] In summary, the advanced technical effects of this disclosure include, but are not limited to, at least one of the following:

[0070] The system enables independent operation of the first and second subsystems, allowing for single-fuel or dual-fuel high-pressure injection. The control oil subsystem design provides stable and precise injection pilot control of the first subsystem, avoiding fuel medium backflow issues during first injector operation and improving safety. Simultaneously, the switching valve design allows the second fuel to be injected from the first injector, facilitating various injection modes and strategies. Specifically, it enables switching of the fuel medium within the first subsystem. In the mode where only the second fuel is injected, both the first and second injectors can achieve high-pressure injection of the second fuel, providing significant freedom in combustion organization and creating conditions for configuring various combustion modes and strategies. Furthermore, it avoids the "dry burning" problem at the nozzles that might occur in existing dual-fuel injection systems where the first fuel subsystem is idle. Moreover, switching the fuel medium within the first subsystem achieves a compact structure and integrated functionality.

[0071] While this disclosure has described above with reference to preferred embodiments, it is not intended to limit the scope of this disclosure. Any changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this disclosure. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this disclosure, without departing from the content of the technical solution of this disclosure, shall fall within the protection scope defined by the claims of this disclosure.

Claims

1. A dual-fuel injection system, characterized in that, include: The first subsystem includes a first pressure-building unit and a first injector; the first injector includes a main injection valve and a pilot control valve; the main injection valve is used for fuel injection, and the pilot control valve is used to open or close the main injection valve; the flow path of the first subsystem is configured such that after pressure is built up by the first pressure-building unit, the first fuel can flow to the main injection valve and be injected under the control of the pilot control valve. The second subsystem includes a second pressure-building unit and a second injector; the flow path of the second subsystem is configured such that after pressure is built up by the second pressure-building unit, the second fuel can flow to the second injector and be injected. A control oil subsystem, comprising a control oil pressure building unit; the flow path of the control oil subsystem is configured such that, after pressure is built up by the control oil pressure building unit, the control oil can flow to the pilot control valve for controlling the main control valve. The control oil subsystem and the second subsystem are connected, allowing the second fuel to flow to the control oil subsystem and be used as control oil; and a switching valve is disposed between the control oil subsystem and the first subsystem, allowing the second fuel to flow to the first injector through the control oil subsystem and the switching valve.

2. The dual-fuel injection system as described in claim 1, characterized in that, The switching valve is at least one of a mechanical one-way control valve, a pneumatic switching valve, or an electric switching valve.

3. The dual-fuel injection system as described in claim 1, characterized in that, The first subsystem further includes a first accumulator module; the first accumulator module includes a first common rail, a first pressure sensor, and a first flow restrictor valve; the first pressure sensor is disposed on the first common rail; the flow path of the first subsystem is configured such that: after pressure is built up by the first pressure building unit, the first fuel can flow to the first common rail for pressure storage, and then flow to the first injector through the first flow restrictor valve.

4. The dual-fuel injection system as described in claim 3, characterized in that, The first pressure accumulator module also includes a first pressure limiting valve and / or a first active pressure relief valve disposed on the first common rail.

5. The dual-fuel injection system as described in claim 1, characterized in that, The second subsystem further includes a second accumulator module; the second accumulator module includes a second common rail, a second pressure sensor, and a second flow restrictor valve; the second pressure sensor is located in the second common rail; the flow path of the second subsystem is configured such that after pressure is built up by the second pressure building unit, the second fuel can flow to the second common rail for pressure storage, and then flow to the second injector through the second flow restrictor valve.

6. The dual-fuel injection system as claimed in claim 1, characterized in that, The control oil subsystem further includes a control oil accumulator module; the control oil accumulator module includes a control oil common rail, a control oil pressure sensor, and a control oil flow restrictor valve; the control oil pressure sensor is located in the control oil common rail; the flow path of the control oil subsystem is configured such that after pressure is built up by the control oil pressure building unit, the control oil can flow to the control oil common rail for pressure storage, and then flow to the first injector through the control oil flow restrictor valve.

7. The dual-fuel injection system as described in claim 6, characterized in that, The control oil accumulator module also includes a control oil pressure limiting valve installed on the control oil common rail.

8. The dual-fuel injection system as claimed in claim 1, characterized in that, The first injector and the second injector are integrated into a single injector, which includes a first nozzle and a second nozzle.

9. The dual-fuel injection system as claimed in claim 1, characterized in that, The dual-fuel injection system includes a first mode, a second mode, and a third mode; In the first mode, the first injector does not inject, and the second fuel flows to the second injector and is injected; In the second mode, the second fuel flows through the switching valve to the first injector and is injected, and the second fuel flows to the second injector and is injected. In the third mode, the first fuel flows to the first injector and is injected, and the second fuel flows to the second injector and is injected.

10. The dual-fuel injection system as claimed in claim 9, characterized in that, In the first mode, the first pressure building unit and the control oil pressure building unit build up pressure in preparation for switching to the second mode or the third mode.

11. The dual-fuel injection system as claimed in claim 1, characterized in that, Control at least one of the injection quantity, injection timing, and injection pressure of the first subsystem and the second subsystem to configure multiple injection strategies.

12. A dual-fuel injection method, characterized in that, The first fuel and the second fuel are injected using a dual-fuel injection system as described in any one of claims 1-11, or only the second fuel is injected.

13. An engine, characterized in that, Includes the dual-fuel injection system as described in any one of claims 1-11.

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