Dual-fuel injection system, injection method and engine

Abstract

The invention provides a dual-fuel injection system, an injection method and an engine. The dual-fuel injection system comprises a control unit, a fuel injection control unit, a fuel injection control unit and a fuel injection control unit, the first injection subsystem comprises a first fuel pressure source and a first injector; the first fuel pressure source is communicated with the first injector, so that first fuel can flow to the first injector and be injected; the second injection subsystem comprises a second fuel pressure source, a water pressure source, a first valve and a second injector; the second fuel pressure source and the water pressure source communicate with the first valve, the first valve communicates with the second ejector, and the first valve is used for switching communication between the second fuel pressure source and the second ejector or communication between the water pressure source and the second ejector. A second fuel or water can flow to the first valve and then flow to the second injector to be injected.

Description

Technical Field

[0001] The present disclosure relates to a dual fuel injection system, an injection method and an engine. Background Art

[0002] Internal combustion power can effectively achieve green and low-carbon by burning low-carbon (zero-carbon) fuels such as methanol fuel and ammonia fuel. Alcohol fuels such as methanol fuel and ethanol fuel are liquid at room temperature and easy to store. They burn quickly because they contain oxygen, making them carbon-neutral fuels with broad development prospects. Alcohol fuels are difficult to compression ignite and require high-cetane fuels such as diesel to ignite. Therefore, dual-fuel engines mostly use two combustion modes, namely pure diesel mode and low-carbon fuel mode, to operate. Generally, for dual-fuel direct injection systems, alcohol fuel or high-cetane fuel will be sprayed in pure diesel mode to reduce the heat load of the alcohol nozzle, thereby avoiding problems such as nozzle ablation.

[0003] The existing dual-fuel direct injection scheme has the following technical problems: 1) In pure diesel mode, the scheme of micro-spraying alcohol fuel with an alcohol nozzle may not be able to provide effective cooling due to untimely supply of alcohol fuel, while micro-spraying a small amount of high cetane number fuel may produce local over-rich areas and deteriorate combustion; 2) The diesel nozzle and alcohol nozzle of the dual-fuel high-pressure integrated injector are arranged on different axes. Compared with the diesel nozzle center-mounted scheme, fuel consumption and emissions will increase in pure diesel mode.

[0004] Therefore, it is necessary to continue to develop dual-fuel in-cylinder direct injection solutions to at least partially solve the above technical problems. Summary of the invention

[0005] An object of the present disclosure is to provide a dual fuel injection system.

[0006] Another object of the present disclosure is to provide a dual fuel injection method.

[0007] Another object of the present disclosure is to provide an engine.

[0008] According to one aspect of the present disclosure, a dual fuel injection system includes: a control unit for controlling injection; a first injection subsystem, including a first fuel pressure source and a first injector; the first fuel pressure source is connected to the first injector, so that the first fuel can flow to the first injector and be injected; a second injection subsystem, including a second fuel pressure source, a water pressure source, a first valve, and a second injector; the second fuel pressure source and the water pressure source are both connected to the first valve, the first valve is connected to the second injector, and the first valve is used for switching the connection between the second fuel pressure source and the second injector or the water pressure source and the second injector, so that the second fuel or water can flow to the first valve, and then flow to the second injector and be injected.

[0009] The design of the second injection subsystem can realize the switching of injecting the second fuel or injecting water, avoiding problems such as nozzle ablation caused by the inability to effectively provide cooling due to the untimely supply of the second fuel in pure diesel mode; and, water is easier to obtain in production operations than alcohol fuels. As a working fluid carrying heat energy, the latent heat of evaporation of water is 2.1 times that of methanol and 2.6 times that of ethanol, and the specific heat capacity of water is larger than that of air; therefore, direct injection of water into the cylinder is more conducive to reducing the temperature of the injector alcohol nozzle in pure diesel mode and improving the reliability of the nozzle; on the other hand, it reduces the combustion temperature in the cylinder and reduces heat transfer during compression and combustion, which can also reduce fuel consumption and NOx emissions.

[0010] In one or more embodiments, the second injection subsystem further includes a second valve; the second valve is disposed between the second fuel pressure source and the first valve.

[0011] In one or more embodiments, the second injection subsystem includes a level sensor disposed at the second fuel pressure source.

[0012] In one or more embodiments, the first injection subsystem further includes a first common rail pipe; the first common rail pipe is disposed between the first fuel pressure source and the first injector, so that the first fuel flows to the first common rail pipe and then flows to the first injector.

[0013] In one or more embodiments, the second injection subsystem further includes a second common rail; the second common rail is disposed between the first valve and the second injector, so that the second fuel or water flows to the second common rail and then flows to the second injector.

[0014] In one or more embodiments, the first injector and the second injector are integrated into an integral injector.

[0015] In one or more embodiments, the injection system includes a first injection mode and a second injection mode; in the first injection mode, the first injection subsystem can serve as a main injection system to inject the first fuel, and the second injection subsystem can serve as an auxiliary injection system to inject the second fuel or water; in the second injection mode, the first injection subsystem can serve as an auxiliary injection system to inject the first fuel, and the second injection subsystem can serve as a main injection system to inject the second fuel.

[0016] In one or more embodiments, in the first injection mode, the second injection subsystem preferentially injects the second fuel, and in the case that the second fuel is insufficient or the second fuel injection flow path fails, the second injection subsystem injects water.

[0017] In one or more embodiments, in the first spraying mode, the second spraying subsystem sprays only water.

[0018] A dual fuel injection method according to a second aspect of the present disclosure includes: using the dual fuel injection system described in the above embodiment to inject the first fuel and the second fuel, or inject the first fuel and water.

[0019] An engine according to a third aspect of the present disclosure comprises the dual fuel injection system described in the above embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features, properties and advantages of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings and embodiments. In the accompanying drawings, the same reference numerals always represent the same features. It should be noted that these drawings are only examples and are not drawn according to the conditions of equal scale, and should not be used as a limitation on the actual scope of protection claimed by the present disclosure, wherein:

[0021] Figure 1 is a structural schematic diagram of a dual fuel injection system according to an embodiment;

[0022] Figure 2 is a schematic flow chart of a dual fuel injection method according to an embodiment;

[0023] Figure 3 FIG. 4 is a flow chart of a dual fuel injection method according to an embodiment.

[0024] Description of reference numerals:

[0025] 1. Cylinder; 2. Integrated injector; 21. First injector; 22. Second injector; 3. Second common rail; 4. First valve; 5. Water pump; 6. Water tank; 7. Second valve; 8. Second fuel pump; 9. Second fuel tank; 10. First common rail; 11. First fuel pump; 12. First fuel tank. DETAILED DESCRIPTION

[0026] Reference will now be made in detail to various embodiments of the present disclosure, examples of which are shown in the accompanying drawings and described below. Although the present disclosure will be described in conjunction with the exemplary embodiments, it should be appreciated that the present disclosure is not intended to be limited to those exemplary embodiments. On the contrary, the present disclosure is intended to cover not only these exemplary embodiments, but also various alternative forms, modifications, equivalent forms and other embodiments that may be included within the spirit and scope of the present disclosure as defined by the appended claims.

[0027] The present disclosure uses specific words to describe the embodiments of the present disclosure. For example, "one embodiment" and / or "an embodiment" means a certain feature, structure or characteristic related to at least one embodiment of the present disclosure. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" mentioned twice or more in different locations in the present disclosure does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of the present disclosure can be appropriately combined.

[0028] In the following description, the orientation or positional relationship indicated by "upper", "lower", "inner", "outer", "front", "back", or other orientation terms is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and / or implemented in a specific orientation, and therefore cannot be understood as limiting the present disclosure. In the present disclosure, the terms "first", "second", etc. are only used for distinguishing descriptions, and cannot be understood as indicating or implying a positional relationship or an order of importance.

[0029] The present disclosure uses flowcharts to illustrate the operations performed according to the embodiments of the present disclosure. It is understood that, according to actual conditions, the operations are not necessarily performed in the order of the steps shown in the diagram, and other operations may be added to these processes, or one or more operations may be removed from these processes.

[0030] It can be understood that the dual-fuel injection system, injection method, and engine disclosed herein are applicable to marine diesel engines, but are not limited thereto and can also be applied to other applications requiring a dual-fuel injection solution, such as heavy vehicles, railway trains, etc.

[0031] In the present disclosure, the "first fuel" generally uses a high cetane number fuel, such as diesel, but not limited thereto; the "second fuel" generally uses a low-viscosity clean fuel, such as alcohol fuel, but not limited thereto. The "first injection mode" mainly injects the first fuel, also known as the "pure diesel mode"; the "second injection mode" mainly injects the second fuel, also known as the "clean fuel mode".

[0032] As introduced above, the present disclosure aims to at least partially solve the problems of the dual-fuel injection system, in which, in pure diesel mode, the micro-sprayed clean fuel cannot be supplied in time, resulting in nozzle ablation, the micro-sprayed high-cetane number fuel produces local over-rich areas, resulting in deteriorated combustion, and the dual-fuel injection system's nozzles are arranged in an eccentric manner in the cylinder, resulting in increased fuel consumption and pollutant emissions.

[0033] like Figure 1As shown, the inventors of the present disclosure have proposed a dual-fuel injection system after in-depth research, which includes: a control unit for controlling injection; a first injection subsystem, including a first fuel pressure source and a first injector 21; the first fuel pressure source is connected to the first injector 21, so that the first fuel can flow to the first injector 21 and be injected; a second injection subsystem, including a second fuel pressure source, a water pressure source, a first valve 4, and a second injector 22; the second fuel pressure source and the water pressure source are both connected to the first valve 4, the first valve 4 is connected to the second injector 22, and the first valve 4 is used for switching the connection between the second fuel pressure source and the second injector 22 or the water pressure source and the second injector 22, so that the second fuel or water can flow to the first valve 4, and then flow to the second injector 22 and be injected.

[0034] Specifically, the first fuel pressure source may include a first fuel tank 12 and a first fuel pump 11 connected to each other, and the first fuel pump 11 is used to pressurize and pump the first fuel from the first fuel tank 12 to the first injector 21 for injection; similarly, the second fuel pressure source may include a second fuel tank 9 and a second fuel pump 8 connected to each other, and the water pressure source may include a water tank 6 and a water pump 5 connected to each other; the first valve 4 may be a reversing valve, such as a two-position three-way valve, capable of switching the connection between the second fuel injection flow path and the water injection flow path. The control unit is electrically connected to the first valve 4, the first fuel pump 11, the second fuel pump 8, the water pump 5, etc. to control the operation of each component; optionally, the control unit is arranged in the engine controller.

[0035] The principle of the technical solution achieving the advanced technical effect is that the second injection subsystem can realize the switching of injecting the second fuel or injecting water, that is, it realizes the replacement of the second fuel or the first fuel with water, which is used for injection from the second injector 22 in the pure diesel mode, reducing the heat load of the second injection subsystem, avoiding the nozzle ablation caused by the failure to effectively provide cooling due to the untimely supply of the second fuel, and avoiding the problems of the micro-spraying of the first fuel in a comparative scheme causing the local over-concentrated area to worsen the combustion; moreover, water is easier to obtain in production operations than alcohol fuels. As a working fluid carrying heat energy, the latent heat of evaporation of water is 2.1 times that of methanol and 2.6 times that of ethanol, and the specific heat capacity of water is larger than that of air. Therefore, water is more suitable for reducing the temperature of the injector nozzle in the pure diesel mode, improving the reliability of the nozzle, especially extending the structural life of the injection outlet, thereby increasing the service life of the dual-fuel injection system; moreover, it can also reduce the combustion temperature in the cylinder during compression and combustion, reduce heat transfer, and play a role in reducing fuel consumption and reducing NOx emissions; in addition, both the second fuel and water can circulate in the second injection subsystem, and the structure is compact.

[0036] like Figure 1 As shown, in one or more embodiments, the second injection subsystem further includes a second valve; the second valve is arranged between the second fuel pressure source and the first valve 4. Specifically, the second valve may be a shut-off valve, but is not limited thereto, and the second valve may be used to cooperate with the first valve 4 to implement flow path switching of the second injection subsystem or provide safety protection, etc.; for example, when water injection is required, the second valve is closed, and the water injection flow path of the first valve 4 is partially opened; when the second fuel injection is required, the second valve is opened, and the second fuel injection flow path of the first valve 4 is partially opened.

[0037] In one or more embodiments, the second injection subsystem includes a liquid level sensor disposed at the second fuel pressure source. Such a design facilitates detection of the remaining amount of the second fuel, so that the second injection subsystem can be switched to the water injection flow path in a timely manner when the second fuel is insufficient.

[0038] Optionally, the dual fuel injection system further includes a liquid level sensor provided at the first fuel pressure source and the water pressure source.

[0039] like Figure 1 As shown, in one or more embodiments, the first injection subsystem further includes a first common rail pipe 10; the first common rail pipe 10 is arranged between the first fuel pressure source and the first injector 21, so that the first fuel flows to the first common rail pipe 10 and then flows to the first injector 21. The first common rail pipe 10 is similar in meaning to the high-pressure common rail system (Common Rail) in the art. For example, the first common rail pipe 10 can be in the form of an assembly, including a rail pressure sensor for controlling injection, etc., which will not be repeated here; the first common rail pipe 10 is designed to provide a more stable and controllable pressure environment, so that the first fuel can flow to the first common rail pipe 10 to accumulate pressure, which is conducive to the precise control of the first fuel injection pressure, injection flow, injection timing, etc.

[0040] like Figure 1As shown, in one or more embodiments, the second injection subsystem further includes a second common rail pipe 3; the second common rail pipe 3 is arranged between the first valve 4 and the second injector 22, so that the second fuel or water flows to the second common rail pipe 3, and then flows to the second injector 22. The second common rail pipe 3 is similar in meaning to the high-pressure common rail system (Common Rail) in the art. For example, the second common rail pipe 3 can be in the form of an assembly, including a rail pressure sensor for controlling injection, etc., which will not be repeated here; the second common rail pipe 3 is designed to provide a more stable pressure environment, so that the second fuel or water can flow to the second common rail pipe 3 for pressure accumulation, and is conducive to the precise control of the second fuel injection pressure, injection flow, injection timing, etc.

[0041] like Figure 1 As shown, in one or more embodiments, the first injector 21 and the second injector 22 are integrated into an integrated injector 2. Such a design enables functional integration and compact structure, and is particularly suitable for the case where the engine cylinder diameter is small. Specifically, the first injector 21, the second injector 22, or the integrated injector 2 can use the cylinder direct injection technology to inject fuel or water into the cylinder 1.

[0042] Optionally, the first injector 21 and the second injector 22 may also be provided independently of each other.

[0043] In one or more embodiments, the injection system includes a first injection mode and a second injection mode; in the first injection mode, the first injection subsystem can be used as a main injection system to inject the first fuel, and the second injection subsystem can be used as an auxiliary injection system to inject the second fuel or water; in the second injection mode, the first injection subsystem can be used as an auxiliary injection system to inject the first fuel, and the second injection subsystem can be used as a main injection system to inject the second fuel. The first injection mode is also a pure diesel mode, and the second injection mode is also a clean fuel mode; the main injection system is a system for providing the main power source; in the first mode, the second injection subsystem is used as an auxiliary system to provide cooling to avoid nozzle ablation, optimize combustion, reduce emissions, etc.; in the second mode, the first injection subsystem is used as an auxiliary system to ignite the second fuel, etc.

[0044] In one or more embodiments, in the first injection mode, the second injection subsystem preferentially injects the second fuel, and in the case that the second fuel is insufficient or the second fuel injection path fails, the second injection subsystem injects water.

[0045] Specifically, at this time, the second fuel high-pressure source may include a liquid level sensor for detecting the remaining amount of the second fuel. When the remaining amount of the second fuel reaches a preset value, the control unit may control an alarm signal to be issued, or may automatically switch the second injection subsystem to be connected to the water injection flow path to replace the second fuel micro-injection with water.

[0046] With such a design, the micro-injection of the second fuel can be used in the first mode to improve combustion in the cylinder and reduce NOx and smoke emissions. At the same time, the second fuel injection flow path can be kept running at a low load to improve its reliability.

[0047] In one or more embodiments, in the first spraying mode, the second spraying subsystem sprays only water.

[0048] Such a design means that in the first injection mode, the second injection subsystem as an auxiliary injection system only injects water and does not inject the second fuel, which is beneficial to saving the second fuel usage and can also reduce fuel consumption and NOx emissions.

[0049] As described above, the present disclosure further provides a dual-fuel injection method, which includes: using the dual-fuel injection system described in the above embodiments to inject the first fuel and the second fuel, or inject the first fuel and water.

[0050] Specifically, the dual-fuel injection method is executed through the control of the control unit, and may include: according to the working requirements of the engine, switching the dual-fuel injection system to the first injection mode or the second injection mode; obtaining the speed and load information of the engine; in the first injection mode, determining the injection ratio of the first fuel and the injection ratio of the second fuel according to the speed and load information, or determining the injection ratio of the first fuel and the injection ratio of water, so as to reduce the thermal load of the injector nozzle and improve combustion; in the second injection mode, determining the injection ratio of the first fuel and the injection ratio of the second fuel according to the speed and load information, so as to maximize the replacement rate of the second fuel for the first fuel.

[0051] Such a design effectively avoids the problem of injector nozzle ablation, improves combustion, substantially reduces fuel consumption and reduces pollutant emissions.

[0052] like Figure 2 Specifically, the dual fuel injection method may include the following steps:

[0053] Step S100: determining that the dual-fuel injection system is in the first injection mode or the second injection mode according to the working requirements of the engine;

[0054] Step S110: In the first spray mode, the control unit outputs a first mode signal, and step S120 is executed; in the second spray mode, the control unit outputs a second mode signal, and step S130 is executed;

[0055] Step S120: determine whether the liquid level of the second fuel is higher than a preset value, if yes, execute step S140, if no, jump to step S150;

[0056] Step S130: determine whether the liquid level of the second fuel is higher than a preset value, if yes, execute step S160, if no, jump to step S150;

[0057] Step S140: switching the second injection subsystem to be connected to the second fuel injection flow path; obtaining the speed and load information of the engine; determining the injection ratio of the first fuel and the injection ratio of the second fuel according to the speed and load information; the first injector 21 outputs the first fuel main injection mode, and the second injector 22 outputs the second fuel micro injection mode;

[0058] Step S150: switching the second injection subsystem to be connected to the water injection flow path; obtaining the speed and load information of the engine; determining the injection ratio of the first fuel and the injection ratio of water according to the speed and load information; the first injector 21 outputs the first fuel main injection mode, and the second injector 22 outputs the water micro-spray mode;

[0059] Step S160: Switch the second injection subsystem to connect the second fuel injection flow path; obtain the speed and load information of the engine; determine the injection ratio of the second fuel and the injection ratio of the first fuel according to the speed and load information to maximize the replacement rate of the second fuel for the first fuel; the first injector 21 outputs the first fuel micro-injection mode, and the second injector 22 outputs the second fuel main injection mode.

[0060] Such an injection method design can, when the dual-fuel injection system is switched to the second injection mode and the liquid level of the second fuel is not higher than a preset value, the dual-fuel injection system jumps to the first injection subsystem as the main injection system to inject the first fuel, and the second injection subsystem as the auxiliary injection system to inject water, effectively avoiding the problem of power supply not meeting demand due to insufficient second fuel.

[0061] Specifically, the step 140 may also include: the injection flow rate, injection pressure and injection timing of the second fuel injected by the second injector 22 are respectively executed according to the micro-injection flow map, micro-injection pressure map and micro-injection timing map of the second fuel in the first injection mode; the micro-injection timing of the second fuel may be before or after the main injection timing of the first fuel; the injection interval of the second fuel may be executed for 5-10 engine cycles; the injection flow rate, injection pressure and injection timing of the first fuel injected by the first injector 21 are respectively executed according to the main injection flow map, main injection pressure map and main injection timing map of the first fuel in the first injection mode.

[0062] Specifically, the step 150 may also include: the injection flow rate, injection pressure, and injection timing of the water injected by the second injector 22 are respectively executed according to the micro-injection flow map, micro-injection pressure map, and micro-injection timing map of the water in the first injection mode; the water micro-injection timing may be before the main injection timing of the first fuel. The water injection amount may be 10%-30% of the fuel mass, and the water injection flow rate increases with the increase of load, and the maximum does not exceed 30%; the water injection pressure may be 30-60MPa, and the water injection pressure gradually increases with the increase of load; the water injection timing may be set at the early or late stage of the compression stroke, and the water injection timing is gradually delayed with the increase of load to maximize the evaporation and diffusion efficiency of water; further, the optimal values ​​of the water injection flow rate, injection pressure, and injection timing may be determined according to the working conditions of the engine and taking into account the emission and thermal efficiency; the injection flow rate, injection pressure, and injection timing of the first fuel injected by the first injector 21 are respectively executed according to the main injection flow map, main injection pressure map, and main injection timing map of the first fuel in the first injection mode.

[0063] Specifically, the step 160 may also include: when the second injector 22 injects the second fuel, the injection flow rate, injection pressure, and injection timing of the second fuel injected by the second injector 22 are respectively executed according to the main injection flow rate map, main injection pressure map, and main injection timing map of the second fuel in the second injection mode; the main injection timing of the second fuel may be after the micro-injection timing of the first fuel. The injection flow rate, injection pressure, and injection timing of the first fuel injected by the first injector 21 are respectively executed according to the micro-injection flow rate map, micro-injection pressure map, and micro-injection timing map of the first fuel in the second mode.

[0064] Optionally, when the first injector 21 and the second injector 22 are integrated into an integrated injector 2, the work performed by the first injector 21 and the second injector 22 is adaptively transformed to be implemented by the first fuel injection line and the second fuel injection line of the integrated injector 2 respectively.

[0065] Figure 3 The figure shows a flow chart of a dual fuel injection method according to another embodiment of the present disclosure. Specifically, the dual fuel injection method may include the following steps:

[0066] Step S200: determining that the dual-fuel injection system is in the first injection mode or the second injection mode according to the working requirements of the engine;

[0067] Step S210: In the first spray mode, the control unit outputs a first mode signal, and step S230 is executed; in the second spray mode, the control unit outputs a second mode signal, and step S220 is executed;

[0068] Step S220: determine whether the liquid level of the second fuel is higher than a preset value, if yes, execute step S240, if no, jump to step S230;

[0069] Step S230: switching the second injection subsystem to be connected to the water injection flow path; obtaining the speed and load information of the engine; determining the injection ratio of the first fuel and the injection ratio of water according to the speed and load information; the first injector 21 outputs the first fuel main injection mode, and the second injector 22 outputs the water micro-spray mode;

[0070] Step S240: Switch the second injection subsystem to connect the second fuel injection flow path; obtain the speed and load information of the engine; determine the injection ratio of the second fuel and the injection ratio of the first fuel according to the speed and load information to maximize the replacement rate of the second fuel for the first fuel; the first injector 21 outputs the first fuel micro-injection mode, and the second injector 22 outputs the second fuel main injection mode.

[0071] Such a design of the injection method enables step S230 to be directly executed in the first injection mode, that is, in the pure diesel mode, only water is injected to prevent nozzle ablation, etc., thereby saving the usage of the second fuel; and in the second injection mode, when the liquid level of the second fuel is not higher than the preset value, the dual-fuel injection system jumps to the first injection subsystem as the main injection system to inject the first fuel, and the second injection subsystem as the auxiliary injection system to inject water, effectively avoiding the problem of insufficient second fuel causing power supply not meeting demand.

[0072] Specifically, when the second injector 22 injects water, the injection flow rate is executed according to the micro-injection flow map in pure diesel mode, the injection pressure is executed according to the micro-injection pressure map, and the injection timing is executed according to the micro-injection timing map. The water micro-injection timing can be before the main injection timing of the first fuel; preferably, the water injection amount can be 10%-30% of the fuel mass, the water injection pressure can be 30-60MPa, and the water injection timing can be set at the early or late stage of the compression stroke; the map calibration of water injection timing, pressure and flow is performed according to the working conditions of the engine to optimize the combustion and emission performance of the engine. When the dual-fuel injector injects the first fuel, the injection flow rate, pressure and timing are executed according to the main injection flow map, main injection pressure map and main injection timing map of the first fuel in pure diesel mode.

[0073] As described above, the present disclosure further provides an engine, which includes the dual fuel injection system described in the above embodiments.

[0074] In summary, the advanced technical effects of the present disclosure include but are not limited to at least one of the following:

[0075] The second injection subsystem can realize the switching of injecting the second fuel or injecting water, that is, it realizes the replacement of the second fuel with water, which is used for injection from the second injector in pure diesel mode, reducing the heat load of the second injection subsystem, avoiding the nozzle ablation caused by the inability to effectively provide cooling due to the untimely supply of the second fuel, and avoiding the problems of local over-concentrated areas and worsening combustion caused by the micro-spraying of the first fuel in a comparative scheme; moreover, water is easier to obtain in production operations than alcohol fuels. As a working fluid carrying heat energy, the latent heat of evaporation of water is 2.1 times that of methanol and 2.6 times that of ethanol, and the specific heat capacity of water is larger than that of air. Therefore, water is more suitable for reducing the temperature of the injector nozzle in pure diesel mode, improving the reliability of the nozzle, especially extending the structural life of the injection outlet, thereby increasing the service life of the dual-fuel injection system; moreover, it can also reduce the combustion temperature in the cylinder during compression and combustion, reduce heat transfer, and play a role in reducing fuel consumption and reducing NOx emissions; in addition, both the second fuel and water can circulate in the second injection subsystem, and the structure is compact.

[0076] Although the present disclosure is disclosed as above with preferred embodiments, it is not intended to limit the present disclosure, and any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, any modification, equivalent change and modification made to the above embodiments based on the technical essence of the present disclosure without departing from the content of the technical solution of the present disclosure shall fall within the protection scope defined by the claims of the present disclosure.

Claims

1. A dual fuel injection system, characterized in that: include: a control unit for controlling the injection; A first injection subsystem includes a first fuel pressure source and a first injector; The first fuel pressure source is connected to the first injector, so that the first fuel can flow to the first injector and be injected; The second injection subsystem includes a second fuel pressure source, a water pressure source, a first valve, and a second injector; the second fuel pressure source and the water pressure source are both connected to the first valve, the first valve is connected to the second injector, and the first valve is used to switch the connection between the second fuel pressure source and the second injector or the water pressure source and the second injector, so that the second fuel or water can flow to the first valve, and then flow to the second injector and be injected.

2. The injection system according to claim 1, characterized in that The second injection subsystem further includes a second valve; the second valve is disposed between the second fuel pressure source and the first valve.

3. The injection system according to claim 1, characterized in that The second injection subsystem includes a level sensor disposed at the second fuel pressure source.

4. The injection system according to claim 1, characterized in that The first injection subsystem further includes a first common rail pipe; the first common rail pipe is disposed between the first fuel pressure source and the first injector, so that the first fuel flows to the first common rail pipe and then flows to the first injector.

5. The injection system according to claim 1, characterized in that The second injection subsystem further includes a second common rail pipe; the second common rail pipe is arranged between the first valve and the second injector, so that the second fuel or water flows to the second common rail pipe and then flows to the second injector.

6. The injection system according to claim 1, characterized in that The first injector and the second injector are integrated into an integral injector.

7. The injection system according to claim 1, characterized in that The injection system is provided with a first injection mode and a second injection mode; In the first injection mode, the first injection subsystem can be used as a main injection system to inject the first fuel, and the second injection subsystem can be used as an auxiliary injection system to inject the second fuel or water; In the second injection mode, the first injection subsystem can serve as an auxiliary injection system to inject the first fuel, and the second injection subsystem can serve as a main injection system to inject the second fuel.

8. The injection system according to claim 7, characterized in that In the first injection mode, the second injection subsystem preferentially injects the second fuel, and in the case where the second fuel is insufficient or the second fuel injection flow path fails, the second injection subsystem injects water.

9. The injection system according to claim 7, characterized in that In the first spraying mode, the second spraying subsystem sprays water only.

10. A dual fuel injection method, characterized in that: include: The dual fuel injection system according to any one of claims 1 to 9 is used to inject the first fuel and the second fuel, or to inject the first fuel and water.

11. An engine, characterized in that: Comprising a dual fuel injection system as claimed in any one of claims 1-9.

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