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 first subsystem which comprises a first pressure buildup unit and a first injector, and a second subsystem which comprises a second pressure buildup unit and a second injector, the first injector comprises a main injection valve and a pilot control valve, and the pilot control valve is used for controlling opening or closing of the main injection valve; first fuel can flow to the main injection valve and be injected; the control oil subsystem comprises a control oil pressure building unit; a pilot control valve to which control oil can flow for controlling the main injection valve; the second subsystem comprises a second pressure buildup unit and a second ejector; a second fuel can flow to the second injector and be injected; wherein a switching valve is also arranged between the first subsystem and the second subsystem; the second fuel can also flow through the switching valve to the first injector of the first subsystem and 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] Low-viscosity clean fuels such as methanol and ammonia fuels are widely favored due to their huge carbon reduction potential. Compared with diesel, methanol and ammonia fuels have higher auto-ignition temperatures, and it is difficult to achieve compression ignition and combustion of a single fuel. Therefore, among the existing technical solutions, some existing solutions adopt the injection method of low-viscosity clean fuel (such as methanol and ammonia) low-pressure manifold injection combined with high-cetane number fuel (such as diesel) in-cylinder high-pressure direct injection. However, this method of low-viscosity clean fuel has poor atomization effect and low fuel substitution rate.

[0003] On the other hand, there are also some solutions that adopt the technical route of direct injection of low-viscosity clean fuel in the cylinder. However, for new clean fuels, high octane number, low calorific value, low viscosity, low density, and corrosive chemical properties, its high-pressure direct injection technology faces many difficulties such as difficulty in building pressure, poor sliding, poor sealing and ignition system design. The existing high-pressure dual-fuel injection system is mostly integrated and improved on the basis of the traditional fuel high-pressure injection system, and generally has bloated and complex system structure; low viscosity clean fuel pressure is difficult to build, and the pressure is low; low viscosity clean fuel injection control flexibility and accuracy are low; low viscosity clean fuel sealing, leakage and other safety targeted designs are insufficient; traditional fuel injection cannot take into account the ignition requirements of all working conditions and the flexible switching and precise control of full-load single fuel operation.

[0004] In a comparative scheme, wide-range injection for traditional diesel and high-pressure direct injection of low-viscosity new fuel can be achieved. However, the inventors found that when the comparative scheme is running in pure diesel mode, it is necessary to realize high-pressure direct injection of traditional diesel in the cylinder in the full range of operating conditions, and also to realize high-pressure and small-volume pilot injection of traditional diesel in the low-viscosity new fuel mode. This puts great pressure on indicators such as emissions and fuel consumption in the pure diesel mode, and there is still room for further development; at the same time, in the pure diesel mode, the comparative scheme has the problem that the single diesel injection and diesel combustion make the low-viscosity new fuel injection subsystem, especially the injector part, idle; the low-viscosity clean fuel nozzle "dry burning" situation, which puts higher requirements on materials, cooling design and nozzle space layout, and even brings certain reliability risks.

[0005] Therefore, the art requires a new fuel injection system, injection method, and engine to at least partially solve the above technical problems. Summary of the invention

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

[0007] Another object of the present disclosure is to provide a dual fuel injection method.

[0008] Another object of the present disclosure is to provide an engine.

[0009] According to the first aspect of the present disclosure, the dual fuel injection system comprises: a first subsystem, comprising a first pressure building unit and a first injector; the first injector comprises 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 first subsystem flow path is configured as follows: after the 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; a second subsystem, comprising a second pressure building unit and a second injector; the second subsystem flow path is configured as follows: after the 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, the control oil subsystem comprises a control oil pressure building unit; the control oil subsystem flow path is configured as follows: after the 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; 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 through the switching valve and be injected.

[0010] The technical solution introduced above realizes the independent operation of the first subsystem and the second subsystem, and the high-pressure injection of a single fuel or a dual fuel; and the design of the control oil subsystem can realize the stable and high-precision injection pilot control of the first subsystem, and can also avoid the fuel medium oil return problem during the operation of the first injector, thereby improving safety; at the same time, the switching valve design enables the second fuel to be injected from the first injector, which is suitable for a variety of injection modes and injection strategy configurations, and especially realizes the switching of the fuel medium in the first subsystem. In the mode of injecting only the second fuel, the first injector and the second injector can both realize the high-pressure injection of the second fuel, which brings great freedom to the combustion organization and creates conditions for the configuration of a variety of combustion modes and combustion strategies; on the other hand, it avoids the nozzle "dry burning" problem that may be caused by the first fuel subsystem being in an idle state in the existing dual-fuel injection system; in addition, by switching the fuel medium in the first subsystem, a compact structure and functional integrated design are achieved.

[0011] In one or more embodiments, the control oil subsystem and the second subsystem are connected, so that the second fuel can flow to the control oil subsystem to be used as the control oil; and the switching valve is arranged between the control oil subsystem and the first subsystem, so that the second fuel can flow to the first injector through the control oil subsystem and the switching valve.

[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 also includes a first pressure accumulation module; the first pressure accumulation module includes a first common rail pipe, a first pressure sensor, and a first flow limiting valve; the first pressure sensor is arranged on the first common rail pipe; the flow path of the first subsystem is configured as follows: after the pressure is built up by the first pressure building unit, the first fuel can flow to the first common rail pipe for pressure accumulation, and then flow to the first injector through the first flow limiting valve.

[0014] In one or more embodiments, the second subsystem also includes a second pressure accumulation module; the second pressure accumulation module includes a second common rail pipe, a second pressure sensor, and a second flow limiting valve; the second pressure sensor is arranged on the second common rail pipe; the flow path of the second subsystem is configured as follows: after the second pressure building unit builds pressure, the second fuel can flow to the second common rail pipe to accumulate pressure, and then flow to the second injector through the second flow limiting valve.

[0015] In one or more embodiments, the oil control subsystem also includes a control oil pressure accumulation module; the control oil pressure accumulation 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 arranged on the control oil common rail; the control oil subsystem flow path is constructed as follows: after the control oil pressure building unit builds pressure, the control oil can flow to the control oil common rail to accumulate pressure, and then flow to the first injector through the control oil flow limiting valve.

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

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

[0018] In one or more embodiments, the first injector and the second injector are integrated into an integral injector, and the integral injector includes 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 to the first injector through the switching valve 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 to prepare for switching to the second mode or the third mode.

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

[0022] According to a dual fuel injection method of the second aspect of the present application, the dual fuel injection system as described in the first aspect is used to inject the first fuel and the second fuel, or only inject the second fuel.

[0023] A dual-fuel engine according to a third aspect of the present application comprises the dual-fuel injection system as described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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:

[0025] Figure 1 Schematic diagram of the structure of a dual fuel injection system according to an embodiment.

[0026] Figure 2 FIG. 1 is a schematic diagram of an injection mode flow chart of a dual fuel injection system according to an embodiment of the present invention.

[0027] Figure 3A , Figure 3B FIG. 1 is a schematic structural diagram of a first fuel injector of a dual fuel injection system according to an embodiment. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] As mentioned above, on the one hand, the existing low-viscosity clean fuel injection technology is mainly based on low-pressure manifold injection of low-viscosity clean fuel and high-cetane number fuel high-pressure direct injection technology. This technical solution has poor atomization effect of low-viscosity clean fuel and low fuel substitution rate; on the other hand, low-viscosity clean fuel high-pressure direct injection technology is considered to be a more efficient low-viscosity clean fuel injection technology route, and dual-fuel high-pressure direct injection technology of low-viscosity clean fuel and high-cetane number fuel is developing rapidly. However, for new clean fuels, such as high octane number, low calorific value, low viscosity, low density, and corrosive chemical properties, the high-pressure direct injection technology faces many problems such as difficulty in building pressure, poor sliding, poor sealing, and ignition system design. Most of the existing high-pressure dual-fuel injection systems are integrated and improved on the basis of traditional fuel high-pressure injection systems. There are many problems, such as bloated and complex system structures; difficulty in building pressure for low-viscosity clean fuels, and low pressure; low flexibility and precision in low-viscosity clean fuel injection control; insufficient targeted design of safety such as sealing and leakage of low-viscosity clean fuels; and the inability to take into account the ignition requirements of all working conditions and the flexible switching and precise control of full-load single fuel operation for traditional diesel injection. In particular, the present disclosure further develops the injection mode and injection strategy of single fuel medium injection, and also solves the "dry burning" problem existing in dual-fuel injection systems.

[0032] Based on the above considerations, the inventors have conducted in-depth research and proposed a dual-fuel injection system, injection method and engine, which are suitable for marine diesel engines, but are not limited thereto and are also suitable for other applications requiring dual-fuel injection.

[0033] In the present disclosure, the "first fuel" is generally a low-viscosity clean fuel (such as methanol fuel), also known as a "new fuel", but not limited to this; the "second fuel" is generally a high-cetane number fuel (such as diesel), also known as a "traditional fuel", but not limited to this.

[0034] refer to Figure 1As shown, the dual fuel injection system includes: a first subsystem, which includes 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 first subsystem flow path is configured as follows: after the first pressure-building unit 11 builds pressure, the first fuel can flow to the main injection valve and be injected under the control of the pilot control valve 18; the second subsystem includes a second pressure-building unit 9 and a second injector; the second subsystem flow path The structure is as follows: after the 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 control oil subsystem flow path is structured as follows: after the 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 solution introduced above realizes the independent operation of the first subsystem and the second subsystem, and the high-pressure injection of a single fuel or a dual fuel; and the design of the control oil subsystem can realize the stable and high-precision injection pilot control of the first subsystem, and can also avoid the fuel medium oil return problem during the operation of the first injector, thereby improving safety; at the same time, the design of the switching valve 107 enables the second fuel to be injected from the first injector, which is suitable for a variety of injection modes and injection strategy configurations, and especially realizes the switching of the fuel medium in the first subsystem. In the mode of injecting only the second fuel, the first injector and the second injector can both realize the high-pressure injection of the second fuel, which brings great freedom to the combustion organization and creates conditions for the configuration of a variety of combustion modes and combustion strategies; on the other hand, it avoids the nozzle "dry burning" problem that may be caused by the first fuel subsystem being in an idle state in the existing dual-fuel injection system; in addition, by switching the fuel medium in the first subsystem, a compact structure and functional integrated design are achieved.

[0036] Specifically, the first subsystem may be an independent high-pressure pump skid, which is composed of a high-pressure pump driven by a motor, a safety valve group, a sensor, a filter element and other components, and has functions such as high-pressure pressure building, 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 a fuel storage room, etc., with a compact and free layout. If the pump skid is placed next to the machine, a fully enclosed explosion-proof design can also be adopted.

[0037] Optionally, the first injector is a leak-free injector with a leak-free injector structure, and the control oil system is also used as sealing oil for the leak-free injector. Such a design does not require the provision of a dedicated sealing oil circuit, and is particularly suitable for situations where medium and high-speed machine conditions are limited and compactness is required.

[0038] Optionally, the second pressure building unit 9 of the second subsystem can be a single pump, such as a mechanical or electronically controlled single pump, etc.; 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 single 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 beside the machine or in a fuel storage room or other location 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 both operate independently of the whole machine, and the two constitute an external auxiliary pressure building module 1 .

[0041] In one or more embodiments, the control oil subsystem and the second subsystem are connected, so that the second fuel can flow to the control oil subsystem to be used as the control oil; and the switching valve 107 is arranged between the control oil subsystem and the first subsystem, so that the second fuel can flow to the first injector through the control oil subsystem and the switching valve 107.

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

[0043] In one or more embodiments, the switching valve 107 is a mechanical one-way control valve, or a pneumatic switch valve, or an electric switch valve. Such a design can realize the control of the flow direction, flow rate and pressure of the fuel medium.

[0044] like Figure 3A , Figure 3BAs shown, specifically, the mechanical one-way control valve can be used, and when the opening pressure is reached, the mechanical one-way control valve automatically opens to allow the second fuel to flow to the first subsystem; or, the pneumatic switch valve or the electric switch valve can be used to identify the pressure through the electronic control system, and when the predetermined pressure is reached, the pneumatic switch valve or the electric switch valve is opened to control the second fuel to flow to the first subsystem. Taking the mechanical pressure one-way valve as an example, the switching valve 107 can 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 to each chamber of the first subsystem through the throttle hole 113, that is, the first fuel is replaced. The flow capacity of the valve core 115, the valve body 114 and the throttle hole 113 needs to be determined in combination with the engine speed, the oil pump supply capacity, etc. The size and matching relationship of the flow capacity determine the function and performance index after the original first fuel is replaced by the second fuel in the single fuel injection mode.

[0045] Continue to refer Figure 1 In one or more embodiments, the first subsystem further includes a first pressure accumulation module 13; the first pressure accumulation module 13 includes a first common rail pipe 22, a first pressure sensor 17, and a first flow limiting valve 14; the first pressure sensor 17 is arranged on the first common rail pipe 22; the flow path of the first subsystem is configured as follows: after the first pressure building unit 11 builds pressure, the first fuel can flow to the first common rail pipe 22 for pressure accumulation, and then flow to the first injector through the first flow limiting valve 14. Such a design means that the high-pressure common rail technology is adopted in the first subsystem, so that the first subsystem has a more stable medium pressure environment in multiple modes, creates pressure conditions for high-precision fuel injection control, and can also realize free control of injection timing, injection pressure, etc.

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

[0047] In one or more embodiments, the second subsystem also includes a second pressure accumulation module; the second pressure accumulation module includes a second common rail pipe, a second pressure sensor, and a second flow limiting valve; the second pressure sensor is arranged on the second common rail pipe; the flow path of the second subsystem is configured as follows: after the second pressure building unit 9 builds pressure, the second fuel can flow to the second common rail pipe to accumulate pressure, and then flow to the second injector through the second flow limiting valve.

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

[0049] The high-pressure common rail technology is adopted in the second subsystem, which, on the one hand, enables the second subsystem to achieve a more stable medium pressure environment in multiple modes, and on the other hand, is more conducive to the free control of the second fuel dual injection mode; when the first subsystem and the second subsystem both adopt high-pressure common rail injection, the second fuel can be directly injected into the cylinder of the first subsystem and the second subsystem at high pressure, and the injection amount, injection timing and injection pressure of the two independent subsystems can be freely controlled, thereby realizing multiple injection strategies of a single fuel injection, for example, distinguishing the two independent subsystems into main injection, pre-injection or post-injection, etc., which brings great freedom to the combustion organization of a single fuel injection.

[0050] In one or more embodiments, the control oil subsystem further includes a control oil pressure accumulation module 4; the control oil pressure accumulation module 4 includes a control oil common rail pipe 23, a control oil pressure sensor 8, and a control oil flow limiting valve 6; the control oil pressure sensor 8 is arranged on the control oil common rail pipe 23; the control oil subsystem flow path is configured as follows: after the control oil pressure building unit 2 builds pressure, the control oil can flow to the control oil common rail pipe 23 to accumulate pressure, and then flow to the first injector through the control oil flow limiting valve 6. The high-pressure common rail technology is used in the control oil subsystem, so that the control oil subsystem can achieve 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 oil pipe 3 and a control oil rail device oil pipe 5, which respectively connect the control oil pressure accumulation module 4 with 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 accumulation 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 pipe 22 ; such a design improves the safety of the system.

[0054] Specifically, when the first fuel is over-pressured, the first pressure-limiting valve 15 opens, or according to the whole machine safety control strategy, the first active pressure relief valve 16 is used to actively release pressure and enter the corresponding independent first fuel return system.

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

[0056] Specifically, when the control oil pressure exceeds the limit pressure, the control oil pressure limiting 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 flow channel, and vacuum or inert gas purge is performed according to the whole machine operation specifications and the purge control strategy. The inert gas is, for example, nitrogen. The purge interfaces 105 and 106 of the purge flow channel can be set at the machine belt end or the external auxiliary pressure building module 1. The first subsystem can also perform inert gas purge through the first active pressure relief valve 16.

[0058] In one or more embodiments, the first injector and the second injector are integrated into an integrated injector 19, and the integrated injector 19 includes a first nozzle 20 and a second nozzle 21. At this time, the integrated injector 19 is the final actuator, which further makes the structure compact and the functions integrated.

[0059] Furthermore, the integrated injector 19 may include a control valve 18 and a control oil return collection passage 101; the integrated injector 19 may also be 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 the pilot injection; when both the first subsystem and the second subsystem 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 the original pilot injection to the main injection of the second fuel; that is, for the injection of the second fuel, the two nozzles of the integrated injector 19 and their corresponding flow passages, control valve components, etc. are optimized for small oil volume and full-load large oil volume wide-range injection, so that the design creates conditions for stable injection of multiple injection modes and injection strategies. In addition, the first nozzle 20 and the second nozzle 21 can be adjusted to achieve spatial matching of two-way fuel medium injection.

[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 to the first injector through the switching valve 107 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] Such a design enables the dual-fuel injection system to operate in the three combustion modes mentioned above, realizing single fuel injection or dual fuel injection. Especially in the second mode, different combustion strategy configurations can be performed on the first subsystem and the second subsystem. For example, the first subsystem and the second subsystem can be divided into main injection and pre-injection, or main injection and post-injection, etc. By controlling the injection amount of the second fuel and the dual spray in time and space matching, the predetermined combustion organization requirements can be met, which greatly expands the degree of freedom of the combustion organization of the single fuel injection.

[0062] Specifically, the first mode may be that when the whole machine is started or operates normally, the second pressure building unit 99 starts to build pressure, and when the pressure reaches the needle valve start-up pressure in the second injector, or when other predetermined injection conditions are met, the second fuel is prepared for injection. This mode operates with a single fuel medium of the second fuel, and its injection amount and injection pressure are determined according to actual operating conditions, and are controlled by injection timing and injection pressure.

[0063] The second mode may be that when the opening pressure of the valve core 115 of the switching valve 107 is reached, the second fuel flows into each chamber of the first subsystem through the throttle hole 113.

[0064] The third mode may be that the control oil pressure building unit 2 builds pressure first, the control oil enters the control oil pressure accumulator module 4 through the control oil pump rail oil 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 oil 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 pressure 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, and when the pressures of the two media reach the set values, the first fuel is ready for injection; when the whole machine is started or operates normally, the second pressure building unit 9 starts to build pressure, and when the pressure reaches the needle valve start-up pressure in the second injector, the second fuel is ready for injection. In this mode, the second fuel assumes the function of pilot injection under all operating conditions.

[0065] Continue to refer 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 pressure to prepare for switching to the second mode or the third mode. Such a design enables the first mode to be switched to the second mode or the third mode at any time and without feeling.

[0066] In one or more embodiments, at least one of the injection amount, injection timing, and injection pressure of the first subsystem and the second subsystem is controlled to configure multiple injection strategies. In particular, when the first subsystem and the second subsystem both adopt high-pressure common rail injection technology, the injection timing, injection pressure, and injection amount of the two independent subsystems can be freely controlled. For example, the first subsystem and the second subsystem are divided into main injection, pre-injection, post-injection, etc., which is more conducive to the configuration of the injection strategy.

[0067] According to a dual fuel injection method of the second aspect of the present application, the dual fuel injection system as described in the first aspect is used to inject the first fuel and the second fuel, or only inject the second fuel.

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

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

[0070] The first subsystem and the second subsystem can operate independently of each other, and can perform single fuel or dual fuel high pressure injection; and the control oil subsystem design can realize stable and high-precision injection pilot control of the first subsystem, and can also avoid the fuel medium oil return problem during the operation of the first injector, thereby improving safety; at the same time, the switching valve design enables the second fuel to be injected from the first injector, which is suitable for a variety of injection modes and injection strategy configurations, and especially realizes the switching of fuel medium in the first subsystem. In the mode of injecting only the second fuel, both the first injector and the second injector can realize high pressure injection of the second fuel, which brings great freedom to the combustion organization and creates conditions for the configuration of a variety of combustion modes and combustion strategies; on the other hand, it avoids the nozzle "dry burning" problem that may be caused by the first fuel subsystem being in an idle state in the existing dual fuel injection system; in addition, by switching the fuel medium in the first subsystem, a compact structure and functional integrated design are achieved.

[0071] 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: 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 for opening or closing the main injection valve; the flow path of the first subsystem is configured such that after the 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 the 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, the control oil subsystem comprising a control oil pressure building unit; the control oil subsystem flow path is configured such that after the control oil pressure building unit builds pressure, the control oil can flow to the pilot control valve to control the main control valve; 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 through the switching valve and be injected.

2. The dual fuel injection system according to claim 1, characterized in that: The control oil subsystem and the second subsystem are connected, so that the second fuel can flow to the control oil subsystem for use as the control oil; and the switching valve is arranged between the control oil subsystem and the first subsystem, so that the second fuel can flow to the first injector through the control oil subsystem and the switching valve.

3. The dual fuel injection system according to claim 1, characterized in that: The switching valve is at least one of a mechanical one-way control valve, a pneumatic switch valve, and an electric switch valve.

4. The dual fuel injection system according to claim 1, characterized in that: The first subsystem also includes a first pressure accumulation module; the first pressure accumulation module includes a first common rail pipe, a first pressure sensor, and a first flow limiting valve; the first pressure sensor is arranged on the first common rail pipe; the flow path of the first subsystem is configured as follows: after the pressure is built up by the first pressure building unit, the first fuel can flow to the first common rail pipe for pressure accumulation, and then flow to the first injector through the first flow limiting valve.

5. The dual fuel injection system according to claim 1, characterized in that: The second subsystem also includes a second pressure accumulation module; the second pressure accumulation module includes a second common rail pipe, a second pressure sensor, and a second flow limiting valve; the second pressure sensor is arranged on the second common rail pipe; the flow path of the second subsystem is configured as follows: after the second pressure building unit builds pressure, the second fuel can flow to the second common rail pipe to accumulate pressure, and then flow to the second injector through the second flow limiting valve.

6. The dual fuel injection system according to claim 1, characterized in that: The control oil subsystem also includes a control oil pressure accumulation module; the control oil pressure accumulation 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 arranged on the control oil common rail; the control oil subsystem flow path is constructed as follows: after the control oil pressure building unit builds pressure, the control oil can flow to the control oil common rail to accumulate pressure, and then flow to the first injector through the control oil flow limiting valve.

7. The dual fuel injection system according to claim 3, characterized in that: The first pressure storage module further includes a first pressure limiting valve and / or a first active pressure relief valve disposed on the first common rail pipe.

8. The dual fuel injection system according to claim 5, characterized in that: The control oil pressure accumulation module further includes a control oil pressure limiting valve arranged on the control oil common rail pipe.

9. The dual fuel injection system according to claim 1, characterized in that: The first injector and the second injector are integrated into an integrated injector, and the integrated injector includes a first nozzle and a second nozzle.

10. The dual fuel injection system according to 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 to the first injector through the switching valve 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.

11. The dual fuel injection system according to claim 10, characterized in that: In the first mode, the first pressure building unit and the control oil pressure building unit build up pressure to prepare for switching to the second mode or the third mode.

12. The dual fuel injection system of claim 1, wherein: At least one of the injection amount, injection timing, and injection pressure of the first subsystem and the second subsystem is controlled to configure a plurality of injection strategies.

13. A dual fuel injection method, characterized in that: The dual fuel injection system according to any one of claims 1 to 12 is used to inject the first fuel and the second fuel, or only the second fuel.

14. An engine, characterized in that: Comprising a dual fuel injection system as claimed in any one of claims 1-12.

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