Fuel injection valve, engine fuel injection system including same, and fuel injection method

Abstract

The present invention provides a fuel injection valve that can reduce the mixing rate of auxiliary fuel and suppress emissions of nitrous oxide (N2O) and unburned ammonia compared to conventional techniques, as well as an engine fuel injection system and a fuel injection method that include the fuel injection valve. The fuel injection valve 9 includes a nozzle hole 10 for injecting fuel, and fuel passages 22, 30 for supplying fuel to the nozzle hole 10. During periods when fuel injection is not being performed, the fuel injection valve 9 supplies auxiliary fuel for promoting ignition and combustion and main injection fuel with low ignition and combustibility into the fuel passages 22, 30, and injects the auxiliary fuel and main injection fuel from the fuel injection valve 9 in separate patterns with a time interval between them.

Description

[Technical field]

[0001] The present invention relates to a fuel injection valve, an engine fuel injection system including the same, and a fuel injection method, and more particularly, to an improvement in an injection device for injecting various different types of fuel into a diesel engine. [Background technology]

[0002] A diesel engine type injection device that burns ammonia as the main fuel using a high-pressure injection diffusion combustion method is used as a marine engine (see, for example, Patent Document 1). Also, in order to improve the ignition and combustibility of ammonia, which has poor ignition and combustibility, an engine has been developed that injects ammonia fuel in combination with an auxiliary fuel for ignition and combustion promotion (hereinafter referred to as auxiliary fuel). An example of the configuration of such a conventional diesel engine will be described with reference to the drawings (see Figs. 9 to 11).

[0003] Figure 9 shows an example of the configuration of a conventional technology (stratified injection device of auxiliary fuel-ammonia-auxiliary fuel). In Figure 9, reference numeral 1' denotes an auxiliary fuel tank, 2' denotes an auxiliary fuel supply pump, 3' denotes a fuel injection pump, 4' denotes a plunger, 5' denotes a plunger barrel, 6' denotes a discharge valve, 7' denotes a check pressure regulating valve provided in the bypass of the discharge valve 6', 8' denotes a fuel injection pipe, 9' denotes a fuel injection valve body (hereinafter also simply referred to as a fuel injection valve), 10' denotes a nozzle hole, 11' denotes a needle valve, 12' denotes an oil reservoir, 13' denotes a biasing spring for setting the valve opening pressure of the needle valve 11', 15' denotes an ammonia supply pipe, 16' denotes a control valve, 17' denotes an ammonia supply pipe, 18' denotes an ammonia supply pump, 19' denotes an ammonia tank, and 21' denotes a fuel passage. Reference numeral 14' denotes a check pressure regulating valve for ammonia supply, which prevents ammonia from flowing back to the control valve side. Reference numeral 20' denotes a control device for controlling the amount and timing of ammonia supply, which receives an engine fuel cam angle signal and other engine operating conditions and outputs an opening / closing signal to the control valve 16' via a line 23'.

[0004] As shown in Fig. 10, an auxiliary fuel passage 22' is drilled in the fuel injection valve body 9', and this auxiliary fuel passage 22' connects the fuel injection pipe 8' and the fuel injection valve oil reservoir 12'. Also, the check pressure regulating valve 14' for supplying ammonia is connected to a junction 31' midway through the upper auxiliary fuel passage 22' via an ammonia passage 30' also drilled in the fuel injection valve body 9'.

[0005] Next, the operation of this conventional technique will be described (see Figs. 11 and 12, etc.).

[0006] First, consider the state after one fuel injection cycle ends and before the next fuel injection cycle starts. Here, as an example, consider a low-speed two-stroke cycle diesel engine as a prime mover for propelling a ship. The crank angle of one cycle of the engine is 360 degrees, of which the fuel injection period is only about 20 to 30 degrees, and there is a period of about 330 to 340 degrees from the end of one fuel injection cycle to the start of the next fuel injection cycle, so there is plenty of time. Therefore, by opening and closing the control valve of the ammonia supply system during this period, a predetermined amount of ammonia can be pushed into the auxiliary fuel passage before the start of the fuel injection cycle.

[0007] The specific process will be described below. During the period when the plunger 4' of the fuel injection pump 3' is not discharging fuel, this pre-injection state is detected as the rotation angle of a fuel cam (not shown) by an angle detector (not shown), and a valve open signal is output to the control valve 16' via the control device 20'. When the control valve 16' opens as a result, ammonia pressurized by the ammonia supply pump 18' to a pressure Ps equal to or higher than the valve opening pressure Pw of the ammonia supply check valve 14' is injected into the ammonia passage 30' through the control valve 16' and the ammonia supply check valve 14'.

[0008] Here, the valve opening pressures of the various valves are set as follows. That is, when the valve opening pressures of the check pressure regulating valve 7', the needle valve 11' of the fuel injection valve, and the ammonia supply check valve 14' are Pp, Po, and Pw, respectively, these valve opening pressures are set to be Pp < Pw < Po. Also, by setting the pressure Ps of the ammonia pressurized by the ammonia supply pump 18' to be Pw < Ps < Po, the needle valve 11' of the fuel injection valve is not opened and the check pressure regulating valve 7' of the fuel injection pump is opened, so that ammonia flows into the fuel passage 22' from the ammonia passage 30' and through the junction 31', and the auxiliary fuel is pushed back by the ammonia through the fuel injection pipe 8' in the direction of the fuel injection pump 3, and returns to the plunger chamber in the fuel injection pump through the check pressure regulating valve 7'.

[0009] After a certain time, when the control valve 16 is closed by a valve closing signal from the control device 20', the injection of ammonia is stopped. At this point, the auxiliary fuel-ammonia-auxiliary fuel is layered in the passage inside the fuel injector as viewed from the needle valve 11' side of the fuel injector 9' in the following order: auxiliary fuel remaining from the previous cycle injection, ammonia injected from the ammonia supply check valve 14', and auxiliary fuel pushed back beyond that.

[0010] Next, when the fuel cam (not shown) rotates and the plunger 4' of the fuel injection pump 3' starts discharging fuel, the auxiliary fuel and ammonia in the fuel injection pipe 8' are injected from the fuel injection valve 9' in the order in which they are arranged in layers, that is, auxiliary fuel-ammonia-auxiliary fuel (see Figs. 11 and 12). In the cylinder of the diesel engine (not shown), the auxiliary fuel injected first is ignited and burned, the ammonia injected next is ignited and burned by the flame of the auxiliary fuel, and finally the auxiliary fuel is injected again into the combustion region and burned.

[0011] In this way, conventional technology aims to burn ammonia, which has poor ignition and combustibility, smoothly by taking advantage of the effects of stratified injection. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2020-180567 A Summary of the Invention [Problem to be solved by the invention]

[0013] However, the above-mentioned conventional techniques have the following problems.

[0014] First, one of the problems with using the above-mentioned stratified injection technology is that it is difficult to reduce the mixing ratio of auxiliary fuel to ammonia fuel. In other words, in order to promote the ignition and combustion of ammonia, it is necessary to increase the mixing amount of auxiliary fuel to a certain extent, so the mixing ratio of auxiliary fuel must be increased. However, even though the CO2 emissions from the combustion of ammonia fuel are zero, the CO2 emitted from the combustion of auxiliary fuel is emitted depending on the mixing ratio, which is a problem in terms of the global environment.

[0015] Here, as auxiliary fuels (to improve the ignition and combustion of ammonia, which has poor ignition and combustion properties), petroleum fuels such as diesel and heavy oil A, which have good ignition and combustion properties, are commonly used because of their ease of availability and handling.

[0016] Furthermore, in the low ammonia combustion temperature range of 1400K or less, nitrous oxide (N2O), which is said to have a global warming potential 265 times that of CO2, is emitted, as well as unburned ammonia (NH3), and these emissions pose a problem for the global environment.

[0017] In order to consider the above-mentioned problems with the stratified injection technology phenomenologically, the following points can be considered when focusing on the influence of the difference in the physical properties of the two fuels.

[0018] First, the energy density (or calorific value) per unit volume of ammonia fuel is about one-third that of petroleum fuel, so to achieve the same output, the amount of ammonia injected must be about three times that of petroleum.

[0019] In addition, the latent heat of vaporization of ammonia fuel is about seven times greater than that of petroleum fuel, causing a drop in the temperature of the surrounding fuel.

[0020] If we consider the situation in the first half of the ignition and combustion process while keeping in mind the differences in fuel properties, the following phenomenon is of concern. That is, in the first half of the stratified injection process, that is, in the contact area between the auxiliary fuel and ammonia fuel spray, the temperature of the auxiliary fuel spray around the ammonia spray will drop due to the influence of ammonia fuel, which has a spray volume about three times larger and a latent heat of vaporization about seven times larger, and it is assumed that the support effect of the auxiliary fuel in improving ignition and combustion will be impaired, and as a result, there is a concern that the improvement of ammonia ignition and combustion will not proceed smoothly as intended. Furthermore, there is a concern that this will result in a drop in the temperature of ammonia combustion, causing the emission of nitrous oxide (N2O) and unburned ammonia.

[0021] In order to alleviate these concerns, one of the improvement methods for promoting the ignition and combustion of ammonia is to increase the mixing ratio of the auxiliary fuel in the first half.

[0022] Furthermore, in the latter half of the stratified injection process, i.e., in the ammonia-auxiliary fuel combustion event, one of the improvement methods to reduce the above-mentioned emissions of nitrous oxide (N2O) and unburned ammonia is to activate the latter combustion and reburn the nitrous oxide (N2O) and unburned ammonia. In order to realize such reburning, it is assumed that the mixing ratio of the auxiliary fuel in the latter half will be increased to increase the temperature of the ammonia combustion.

[0023] However, although these improvement techniques aim to improve ammonia combustion, they ultimately result in nothing but an increase in the mixing ratio of auxiliary fuel.

[0024] On the other hand, the temperature of the ammonia combustion region is in a trade-off relationship with the mixing ratio of this auxiliary fuel. If one tries to suppress the mixing ratio to a relatively low level when the activation of ammonia combustion is stagnant, the ammonia combustion temperature will not rise to a certain level, resulting in the emission of nitrous oxide (N2O) and unburned ammonia.

[0025] To summarize the above, with conventional technology, the major challenges are reducing the mixing ratio of auxiliary fuel and suppressing emissions of nitrous oxide (N2O) and unburned ammonia.

[0026] Therefore, an object of the present invention is to provide a fuel injection valve that can reduce the mixing rate of auxiliary fuel and suppress emissions of nitrous oxide (N2O) and unburned ammonia compared to conventional techniques, and an engine fuel injection system and a fuel injection method that include the same. [Means for solving the problem]

[0027] In order to solve the above problems, the present inventors have conducted various studies and have come to know something that leads to solving the problems. The present invention based on the above-mentioned knowledge is a fuel injection valve, comprising: A single fuel injector; a nozzle hole provided in the fuel injection valve for injecting fuel; a fuel passage for supplying fuel to the nozzle hole; Equipped with This fuel injection valve is characterized by supplying auxiliary fuel for promoting ignition and combustion and main injection fuel with low ignition and combustibility into the fuel passage during periods when fuel is not being injected, and injecting the auxiliary fuel and main injection fuel from the fuel injection valve in separate patterns with a time interval between them.

[0028] The above fuel injector employs two technical measures based on the above findings. First, in the conventional stratified injector, the auxiliary fuel and ammonia come into contact with each other in the first half of the injection process, and are injected in a continuous stratified form. In the fuel injector according to the present invention, a time interval is provided between the auxiliary fuel and the ammonia, and the two fuels are injected in a separate form without coming into contact with each other. In other words, the auxiliary fuel is injected first, and then the ammonia is injected after a time interval.

[0029] Next, in the latter half of the injection process, the conventional technology has a pattern of injecting auxiliary fuel continuously after ammonia injection, whereas the fuel injector of the present invention stops the injection of auxiliary fuel after ammonia injection and changes to only injecting ammonia in the latter half of the injection process.

[0030] In the fuel injection valve according to the present invention as described above, the auxiliary fuel and the ammonia are injected in a separated form with a space between them without contacting each other, so that the auxiliary fuel is not affected by the ammonia fuel spray, which has a large volume and latent heat of vaporization compared to the auxiliary fuel, and the auxiliary fuel spray temperature is not lowered, and the auxiliary fuel can exhibit its inherently good ignition and combustion performance. At this time, a flame of the auxiliary fuel is formed in the combustion chamber, and the ammonia fuel spray rushes into this flame, causing the ammonia to ignite and burn.

[0031] As described above, the fuel injection valve according to the present invention makes it possible to reduce the mixing ratio of auxiliary fuel by using two means that lead to solving the problem, while suppressing the generation of nitrous oxide (N2O) and unburned ammonia, and further enabling the reduction of CO2 emissions and GHG (Green House Gas) emissions.

[0032] Another aspect of the present invention is an engine fuel injection system comprising: The fuel injection valve as described above; a main injection fuel tank for storing main injection fuel; a supply pipe for supplying main injection fuel from the main injection fuel tank to a fuel injection valve; an auxiliary fuel tank for storing auxiliary fuel; an auxiliary fuel passage for supplying auxiliary fuel from the auxiliary fuel tank to a fuel injection valve; a pressurizing device that applies energy to the main fuel in the supply pipe or the auxiliary fuel in the auxiliary fuel passage so as to inject the main fuel or the auxiliary fuel from the fuel injection valve; An engine fuel injection system comprising:

[0033] The engine fuel injection system as described above may include only one fuel injector.

[0034] The engine fuel injection system as described above may further include a fuel passage branched off from the fuel passage that supplies fuel to the nozzle hole of the fuel injection valve, and an auxiliary fuel passage connecting the fuel passage with an auxiliary fuel tank.

[0035] The engine fuel injection system as described above may further include a fuel passage branched off from the fuel passage that supplies fuel to the nozzle hole of the fuel injection valve, and a main injection fuel passage connecting the fuel passage with a main injection fuel tank.

[0036] In the engine fuel injection system as described above, the main injection fuel may be ammonia.

[0037] Another aspect of the present invention is a marine diesel engine equipped with an engine fuel injection system as described above.

[0038] A method according to one aspect of the present invention is a fuel injection method, comprising the steps of: A single fuel injection valve including a nozzle hole for injecting fuel and a fuel passage for supplying fuel to the nozzle hole, During periods when fuel is not being injected, auxiliary fuel for ignition and combustion promotion and main injection fuel with low ignition and combustibility are supplied into the fuel passage, This is a fuel injection method characterized in that auxiliary fuel and main injection fuel are injected from a fuel injection valve in separate patterns with a time interval therebetween.

[0039] The fuel injection method as described above may further include the step of discharging at least a portion of the main injection fuel remaining in the fuel passage from the fuel passage before injecting the auxiliary fuel. Effect of the Invention

[0040] According to the present invention, it is possible to provide a fuel injection valve that is capable of reducing the mixing rate of auxiliary fuel and suppressing emissions of nitrous oxide (N2O) and unburned ammonia compared to conventional techniques, and an engine fuel injection system and a fuel injection method including the same. [Brief description of the drawings]

[0041] [Figure 1A] FIG. 1 is a diagram showing a configuration example of an ammonia engine fuel injection system according to an embodiment of the present invention. [Figure 1B] FIG. 2 is a diagram showing the operation of the ammonia engine fuel injection system during injection of auxiliary fuel. [Figure 1C] FIG. 2 is a diagram showing the operation of the ammonia engine fuel injection system when injecting ammonia fuel. [Figure 1D] FIG. 13 is a diagram showing the operation of the ammonia engine fuel injection system when the remaining ammonia fuel is discharged with auxiliary fuel after the ammonia fuel is injected. [Figure 1E] FIG. 13 is a diagram showing the operation of the ammonia engine fuel injection system when ammonia fuel is supplied to an oil passage after the ammonia fuel is discharged by auxiliary fuel. [Diagram 2] 1 is a cross-sectional view showing an example of a configuration of a fuel injection valve. [Diagram 3] FIG. 2 is a diagram showing a schematic pattern of a fuel injection process in an ammonia engine fuel injection system. [Figure 4] 1A and 1B are diagrams showing an outline of the fuel injection process and the outline of the shapes of ammonia fuel and auxiliary fuel before combustion formed thereby, respectively, in accordance with the present invention and in accordance with the prior art. [Diagram 5] FIG. 11 is a graph showing a comparison of heat generation rates between the case where fuel is separately injected by the ammonia engine fuel injection system of this embodiment, and the case where fuel is injected by the pilot injection method and the stratified injection method of the conventional technology, in which (A) the mixing ratio of auxiliary fuel is 3% and (B) the mixing ratio of auxiliary fuel is 6%, respectively, in an ammonia combustion simulation simulating a rapid compression and expansion device. [Figure 6] FIG. 1 shows the results of an ammonia combustion simulation simulating a rapid compression and expansion device when the auxiliary fuel mixing ratio is 3%, in the case where fuel is separately injected by the ammonia engine fuel injection system of this embodiment, and the case where fuel is injected by the pilot injection method and the stratified injection method of the conventional technology. (A) is a graph showing a comparison of heat generation rates, and (B) is a table showing a comparison of exhaust gas characteristics. [Figure 7] FIG. 10 is a graph showing a comparison of heat generation rates, showing the results of an ammonia combustion simulation simulating a rapid compression and expansion device when the mixing ratio of auxiliary fuel is 9%, between the case where fuel is separately injected by the ammonia engine fuel injection system of this embodiment and the case where fuel is stratified injected by the conventional technology. [Figure 8] FIG. 11 is a table showing a comparison of exhaust gas characteristics, showing the results of an ammonia combustion simulation simulating a rapid compression and expansion device when the mixing ratio of auxiliary fuel is 9%, between the case where fuel is separately injected by the ammonia engine fuel injection system of this embodiment and the case where fuel is stratified injected by a conventional method. [Figure 9] FIG. 1 is a diagram showing an example of the configuration of a prior art (auxiliary fuel-ammonia fuel-auxiliary fuel stratified injector). [Figure 10] FIG. 1 is a vertical cross-sectional view showing an example of the configuration of a conventional fuel injection valve body. [Figure 11] 1 is a graph showing an example of an injection pattern of auxiliary fuel-ammonia fuel-auxiliary fuel according to the prior art. [Figure 12] 1A to 1D are diagrams showing the injection process in a conventional stratified injector for auxiliary fuel-ammonia-auxiliary fuel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] A preferred embodiment of the present invention will be described in detail with reference to the drawings (see FIGS. 1 to 4).

[0043] 1A to 2 show an example of the configuration of an ammonia engine fuel injection system 100 and its fuel injection valve 9 according to an embodiment of the present invention. In the drawings, reference numeral 1 denotes an auxiliary fuel tank, 2 denotes an auxiliary fuel supply pump, 3 denotes a fuel injection pump (main body), 4 denotes a plunger, 5 denotes a plunger barrel, 6 denotes a discharge valve, 7 denotes a check pressure regulating valve provided in a bypass of the discharge valve 6, 8 denotes a fuel injection pipe, 9 denotes a fuel injection valve, 10 denotes a nozzle hole, 11 denotes a needle valve, 12 denotes an oil reservoir, 13 denotes a biasing spring for setting the valve opening pressure of the needle valve 11, 14 denotes a check pressure regulating valve for ammonia supply (prevents backflow of ammonia to the control valve 16 side), 15 denotes an ammonia supply pipe, 16 denotes a control valve, 17 denotes an ammonia supply pipe, 18 denotes an ammonia supply pump, and 19 denotes an ammonia tank. Reference numeral 20 denotes a control device for controlling the amount and timing of ammonia supply, which inputs a fuel cam angle signal of the engine and other engine operating conditions and outputs an opening / closing signal to the control valve 16 via a line 23.

[0044] In this embodiment, a three-way valve 40 is provided in the middle of the fuel injection pipe 8, and an auxiliary fuel passage 81 heading in the direction of symbol A and an auxiliary fuel passage 82 heading in the direction of symbol B are provided downstream of this, and a three-way valve 41 is further provided in the auxiliary fuel passage 82 to divide it into two passages, an auxiliary fuel passage 83 heading in the direction of symbol C and an auxiliary fuel passage 84 heading in the direction of symbol D, and a hydraulically driven piston 42 is provided in the middle of the auxiliary fuel passage 83, and a hydraulically driven piston 43 is provided in the middle of the auxiliary fuel passage 84. These hydraulically driven pistons 42 and 43 have the function and action of transmitting energy required for injection of auxiliary fuel and ammonia fuel to the downstream side, and if the friction loss of the contact surface of the hydraulically driven piston is zero, the fluid dynamic characteristic values ​​(pressure, speed) acting on both sides are the same.

[0045] Here, the liquid discharged from fuel injection pump 3 and flowing through fuel injection pipe 8 and auxiliary fuel passages 82, 83, and 84 is a working medium for transmitting the energy required for fuel injection to fuel injection valve 9, and is not ultimately injected into the combustion chamber from nozzle hole 10 of the fuel injection valve. N In this embodiment, the passages denoted by the reference numerals 81 to 84 are called "auxiliary fuel passages", but this is merely a matter of convenience in consideration of the auxiliary fuel Fs. do not have .

[0046] The operation of three-way valve 40 will be described later, but when the flow direction of three-way valve 40 is directed to the auxiliary fuel passage 81 side, the liquid flowing therethrough returns to auxiliary fuel tank 1 in which auxiliary fuel Fs is stored.

[0047] Furthermore, in this embodiment, a new auxiliary fuel passage 85 is provided from the auxiliary fuel tank 1, an auxiliary fuel supply pump 44 is provided midway through the passage, a solenoid valve 45 is provided behind the solenoid valve 45, and a check pressure regulating valve 46 is provided behind the solenoid valve 45. The auxiliary fuel flowing from this check pressure regulating valve 46 is connected to an auxiliary fuel passage 47 newly drilled in the fuel injection valve 9, and this auxiliary fuel passage 47 is connected to the auxiliary fuel passage 22.

[0048] 2, an auxiliary fuel passage 22 is drilled in the fuel injection valve body 9, and this auxiliary fuel passage 22 is connected to a hydraulically driven piston 42 (see FIG. 1A, etc.). This auxiliary fuel passage 22 also communicates with a fuel injection valve oil reservoir 12. On the other hand, a check pressure regulating valve 14 for supplying ammonia is connected to a junction 31 in the middle of the upper auxiliary fuel passage 22 via an ammonia passage 30 also drilled in the fuel injection valve body 9.

[0049] In this embodiment, a new fuel passage 48 is provided behind the hydraulically driven piston 43. This fuel passage 48 branches into two directions near the fuel injector 9, one of which is connected to the fuel passage 21 drilled in the fuel injector 9, and the other is connected to the ammonia supply pipe 15 and the control valve 16. 。

[0050] The ammonia passage 49 drilled in the fuel injection valve 9 and the ammonia tank 19 are connected by a main injection fuel passage 51. A solenoid valve 50 is provided in the main injection fuel passage 51. The wake of this solenoid valve 50 returns to the ammonia tank 19.

[0051] The operation of the ammonia engine fuel injection system 100 according to this embodiment will be described below.

[0052] Here, as an example, an ammonia engine fuel injection system 100 applied to a low-speed two-stroke cycle diesel engine will be described. First, a state after one fuel injection cycle ends and before the next fuel injection cycle starts will be considered. Here, the operation after that will be considered in a state in which auxiliary fuel Fs is supplied to the passage near the oil reservoir 12 of the fuel injection valve 9 before the fuel injection of the next cycle starts.

[0053] The crank angle of one cycle of the low-speed two-stroke cycle diesel engine is 360 degrees, and the fuel injection period is only about 20 to 30 degrees, and there is a period of about 330 to 340 degrees from the end of one fuel injection cycle to the start of the next fuel injection cycle, so there is plenty of time. Therefore, by opening and closing the control valve (control valve 16) of the ammonia supply system during this period, a predetermined amount of ammonia fuel Fm can be pushed into the passage of the auxiliary fuel Fs before the start of the fuel injection cycle.

[0054] During the period when the plunger 4 of the fuel injection pump 3 is not discharging the auxiliary fuel, if the angle detector (not shown) detects this pre-injection state as the rotation angle of the fuel cam (not shown) in the ammonia engine fuel injection system 100, a valve opening signal is output to the solenoid valve 16 via the control device 20. When the solenoid valve 16 opens in response to this, ammonia pressurized by the ammonia supply pump 18 to a pressure Ps equal to or higher than the valve opening pressure Pw of the ammonia supply check valve 14 is injected into the ammonia passage 30 via the solenoid valve 16 and the ammonia supply check valve 14. At this point, the ammonia fuel Fm is injected into the ammonia supply pipes 15 and 17 as well as the fuel passage 48, the fuel passage 21, etc. (see FIG. 1A). Note that the auxiliary fuel Fs remains in the space from the hydraulically driven piston 42 to the auxiliary fuel passage 22.

[0055] Here, the valve opening pressures of the various valves are set as follows. That is, when the valve opening pressures of the check pressure regulating valve 7, the needle valve 11 of the fuel injection valve 9, and the ammonia supply check valve 14 are respectively Pp, Po, and Pw, these valve opening pressures are set so that Pp < Pw < Po. As described above, if there is no friction loss of the hydraulically driven piston 42 and the hydraulically driven piston 43, the flows before and after them are equivalent in terms of fluid dynamics. That is, in this embodiment, it is considered that the pressure of the auxiliary fuel passage 22 is equivalent to the pressure of the fuel injection pipe 8 and is linked to the check pressure regulating valve 7.

[0056] Furthermore, by setting the pressure Ps of the ammonia pressurized by the ammonia supply pump 18 to Pw < Ps < Po, the needle valve 11 of the fuel injection valve is not opened and the check pressure regulating valve 7 of the fuel injection pump 3 is opened, and the hydraulically driven piston 42 moves toward the three-way valve 41 with the flow in this direction, and ammonia flows from the ammonia passage 30 through the junction 31 into the fuel passage 22, and a part of the fuel passage 22 is filled with ammonia.

[0057] After a certain time, when the control valve 16 is closed by a valve closing signal from the control device 20, the injection of ammonia is stopped. At this point, the auxiliary fuel-ammonia (auxiliary fuel Fs and ammonia fuel Fm) are arranged in the passage in the fuel injector 9 in the order of the auxiliary fuel Fs supplied after the injection of the previous cycle and the ammonia fuel Fm injected from the ammonia supply check valve 14, as viewed from the needle valve 11 side of the fuel injector 9 (see FIG. 1B).

[0058] Next, when a fuel cam (not shown) rotates and plunger 4 of fuel injection pump 3 starts to discharge fuel, the fuel pressure in fuel injection pipe 8 rises and the energy required for fuel injection is transmitted to three-way valve 40. Here, the operation of three-way valve 40 and three-way valve 41 will be explained in chronological order with reference to FIG.

[0059] The time before the plunger 4 starts to operate is defined as T0, the time when the injection of the auxiliary fuel Fs starts is defined as T1, and the time when the injection ends is defined as T2. After a time interval, the time when the injection of the ammonia fuel Fm starts is defined as T3, and the time when the injection ends is defined as T4, and the time when the injection of the auxiliary fuel in the next cycle starts is defined as T5.

[0060] The three-way valve 40 opens in the direction of symbol B from T0 to T2 (see FIG. 1B), is controlled to close in the direction of symbol B and open in the direction of symbol A during the period from T2 to T3, and is further controlled to open in the direction of symbol B during the period from T3 to T4. On the other hand, the three-way valve 41 opens in the direction of symbol C from T0 to T2 (see FIG. 1B), and is controlled to close in the direction of symbol C and open in the direction of symbol D during the period when the three-way valve 40 opens in the direction of symbol A from T2 to T3 (see FIG. 1C).

[0061] As a result, the pressure increased within the fuel injection pipe 8 moves the hydraulically driven piston 42 during the period from T1 to T2, and the pressure acting on both sides of the hydraulically driven piston 42 is transmitted to the fuel passage 22 inside the fuel injection valve 9 (see FIG. 1B).

[0062] That is, the energy required for injection of the auxiliary fuel Fs is transmitted to the fuel passage 22 and finally to the oil sump 12. As a result, the pressure in the oil sump 12 of the fuel injection valve 9 rises, and when it reaches or exceeds the valve opening pressure of the needle valve 11, injection of the auxiliary fuel Fs is started and the injection of the auxiliary fuel Fs is performed during the period from T1 to T2 (see FIG. 1B). Furthermore, the direction of the three-way valve 40 is controlled, and when the direction of symbol B is closed, the pressure rise ends and the injection of the auxiliary fuel Fs ends.

[0063] Furthermore, if the three-way valve 41 opens in the direction of symbol D after T3, the pressure that has risen in the fuel injection pipe 8 moves the hydraulically driven piston 43 during the period from T3 to T4, and the pressure acting on both sides of the hydraulically driven piston 43 is transmitted to the fuel passage 21 inside the fuel injection valve 9 (see Fig. 1C and Fig. 2). Therefore, when the pressure in the oil reservoir 12 of the fuel injection valve 9 finally rises and exceeds the valve opening pressure of the needle valve 11, the injection of ammonia fuel Fm is started, and the injection of ammonia fuel Fm is performed during the period from T3 to T4. Furthermore, the direction of the three-way valve 40 is controlled, and the pressure rise ends when the three-way valve 40 closes in the direction of symbol B, and the injection of ammonia fuel Fm ends.

[0064] In this manner, the auxiliary fuel Fs and the ammonia fuel Fm are controlled to be injected from the fuel injector 9 separately with a time interval in the arranged order (see FIG. 4(A)).

[0065] In the cylinder of a diesel engine (not shown), the first injected auxiliary fuel Fs ignites and burns well without being affected by the latent heat of vaporization, forming a combustion flame. The subsequently injected ammonia fuel Fm ignites and burns in a pattern in which it enters the flame of the auxiliary fuel Fs described above (see FIG. 4(A)).

[0066] In this way, according to the fuel injector 9 in this embodiment and the ammonia engine fuel injection system 100 including the same, it is possible to smoothly burn the ammonia fuel Fm, which has poor ignition and combustibility, by utilizing the combustion promotion effect of the auxiliary fuel Fs.

[0067] Incidentally, after the fuel injection process of a certain cycle is completed, and before the fuel injection process of the next cycle is started, the fuel in the fuel passage of the fuel injector 9 is replaced. That is, after the injection is completed, the ammonia fuel Fm remains in the fuel passage 22, the junction 31, the oil reservoir 12, and the fuel passage 30.

[0068] This state is detected as the rotation angle of a fuel cam (not shown) by an angle detector (not shown), and an open signal is output to the solenoid valve 45 via the control device 20. As a result, the auxiliary fuel Fs supplied by the auxiliary fuel supply pump 44 flows through the check pressure regulating valve 46 and further through the fuel passage 47 into the fuel passage 22, the junction 31, the oil reservoir 12, and the fuel passage 30, and acts to push out the ammonia fuel Fm (see FIG. 1D).

[0069] At this timing, the control device 20 outputs an open signal to the solenoid valve 50. As a result, the ammonia fuel Fm returns to the ammonia tank 19 via the fuel passage 49 and the solenoid valve 50 (see FIG. 1D).

[0070] In this way, after the fuel injection process is completed, the passage inside the fuel injection valve 9 is filled with the auxiliary fuel Fs, and then, as described above, a valve opening signal is output to the solenoid valve 16 via the control device 20, and the ammonia fuel Fm pressurized by the ammonia supply pump 18 to a pressure Ps equal to or higher than the valve opening pressure Pw of the ammonia supply check valve 14 is injected into the ammonia passage 30 via the solenoid valve 16 and the ammonia supply check valve 14, and the auxiliary fuel-ammonia (auxiliary fuel Fs and ammonia fuel Fm) is arranged in the passage inside the fuel injection valve 9 as viewed from the needle valve 11 side of the fuel injection valve 9 by the time fuel injection of the next cycle starts (see FIG. 1E). With the above-mentioned fuel arrangement preparations, the process moves to the fuel injection process of the next cycle.

[0071] The above-mentioned embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this embodiment and can be modified in various ways without departing from the scope of the present invention. For example, the above-mentioned embodiment describes the case where ammonia fuel Fm is used, but this is only one preferred example of the main injection fuel. In addition to ammonia fuel Fm, the present invention can also be applied to the case where fuels with poor ignition and combustion properties, such as methanol and synthetic fuel (e-fuel), are used as the main injection fuel.

[0072] In addition, in the above-described embodiment, the case has been described on the premise that the device for supplying the energy required for injecting the auxiliary fuel Fs and the ammonia fuel Fm is a jerk type fuel injection device. However, the present invention can also be applied to a case where, for example, an electronically controlled common rail type injection device is used. EXAMPLES

[0073] In the case of separate injection of fuel (injection in separate patterns with a time interval) by the above-mentioned fuel injection valve 9 and the ammonia engine fuel injection system 100 including it, and in the case of injection by the pilot injection method and the stratified injection method of the conventional technology, ammonia combustion simulation calculation was performed with respect to the diffusion state of the fuel spray and the ignition and combustion state in a model simulating a rapid compression and expansion device when the mixing ratio of auxiliary fuel was set to 3%, and the difference between the two was confirmed. The confirmed contents will be explained below as Example 1 (see Fig. 5 and Fig. 6).

[0074] In the case of this embodiment, as intended based on new findings and concepts, good ignition and combustion were confirmed even in the region where the auxiliary fuel Fs mixture ratio is low (see FIG. 5). Specifically, in the case of separate injection as in this embodiment, it was confirmed that stable ignition and combustion were achieved even when the auxiliary fuel mixture ratio was as small as about 3%. On the other hand, in the case of the stratified injection method of the conventional technology, ignition did not occur when the auxiliary fuel mixture ratio was 3% (see FIG. 5(A)), and ignition finally occurred when the mixture ratio was increased to 6%, so that stagnation of ignition and combustion was confirmed in the region where the auxiliary fuel mixture ratio was low, and it was confirmed that it was necessary to increase the mixture ratio of the auxiliary fuel to promote ammonia combustion (see FIG. 5(B)). In addition, in the case of the pilot injection method, it was confirmed that ignition and combustion were achieved, but the amount of N2O emissions was high (see FIG. 6(B)). EXAMPLES

[0075] As in the above, ammonia combustion simulation calculation was performed to confirm the difference between the diffusion state of the fuel spray and the ignition and combustion state in a model simulating a rapid compression and expansion device when the mixing ratio of auxiliary fuel is 9% in the case of separate injection as in this embodiment and the case of injection by the conventional stratified injection method. The confirmed contents will be explained below as Example 2 (see Figures 7 and 8).

[0076] When the injection timing of the auxiliary fuel was examined, it was confirmed that when the amount of auxiliary fuel is increased in separate injection as in this embodiment, the injection period becomes longer and the end of combustion also becomes longer. Therefore, when early injection was examined, it was confirmed that the end of combustion can be advanced and N2O emissions are reduced compared to stratified injection (see Figure 8).

[0077] From these examples, it was confirmed that the fuel injection valve 9 of the present embodiment and the ammonia engine fuel injection system 100 including the same improve the ignition and combustion of the ammonia fuel Fm, and that the smooth promotion of the combustion of the ammonia fuel Fm, which is the original role of the auxiliary fuel Fs, can be expected. It was also confirmed that the mixing ratio of the auxiliary fuel Fs can be reduced compared to that of the conventional technology. In addition, it was also confirmed that in the first half of the combustion process, the combustion of the auxiliary fuel Fs and the ammonia fuel Fm is promoted and the combustion temperature rises, so that the generation of nitrous oxide N2O and unburned ammonia is suppressed, and there is no need to inject the auxiliary fuel in the second half of the combustion process. [Industrial Applicability]

[0078] The present invention is suitable for application to an ammonia engine fuel injection system, and further to a diesel engine for a ship or the like. [Explanation of symbols]

[0079] 1,1'...Auxiliary fuel tank 2,2'...Auxiliary fuel supply pump 3,3'…Fuel injection pump 4,4'...Plunger 5,5'...Plunger barrel 6,6'...Discharge valve 7,7'...Return check pressure regulating valve 8,8'…Fuel injection pipe 9,9'…Fuel injector 10,10'...Nozzle hole 11,11'...Needle valve 12,12'...Oil pool 13, 13'... Spring for setting the needle valve opening pressure 14'...Check pressure regulating valve 14…Ammonia supply check valve 15,15'...Ammonia supply pipe (supply pipe) 16,16'...Control valve 17, 17'...Ammonia supply pipe (supply pipe) 18,18'...Ammonia supply pump 19,19'...Ammonia tank (main injection fuel tank) 20,20'...Control device 21,21'...Fuel passage 22,22'...Auxiliary fuel passage (fuel passage) 23,23'...Line 30,30'...Ammonia passage (fuel passage) 31,31'...junction 40...Three-way valve 41...Three-way valve 42...Hydraulic actuated piston (pressurizing device) 43...Hydraulic actuated piston (pressurizing device) 44…Auxiliary fuel supply pump 45...Solenoid valve 46... Pressure regulating valve 47…Auxiliary fuel passage 47…Fuel passage 48…Fuel passage 49...Ammonia passage (fuel passage) 50...Solenoid valve 51…Main injection fuel passage 81…Auxiliary fuel passage 82…Auxiliary fuel passage 83…Auxiliary fuel passage 84…Auxiliary fuel passage 85…Auxiliary fuel passage 100...Ammonia engine fuel injection system (engine fuel injection system) Fm...Ammonia fuel (main injection fuel) Fs…Auxiliary fuel N2O…nitrous oxide NH3…ammonia Po: Needle valve opening pressure Pp: Opening pressure of check pressure regulating valve Ps: ammonia pressure (pressurized by ammonia supply pump) Pw: Ammonia supply check valve opening pressure

Claims

1. 1. An engine fuel injection system comprising: a single fuel injection valve having a nozzle hole for injecting fuel and a plurality of fuel passages for supplying fuel to the nozzle hole; a main injection fuel tank for storing main injection fuel; a supply pipe for supplying the main injection fuel from the main injection fuel tank to the fuel injection valve; an auxiliary fuel tank for storing auxiliary fuel; an auxiliary fuel passage for supplying the auxiliary fuel from the auxiliary fuel tank to the fuel injection valve; a pressurizing device that applies energy to the main fuel in the supply pipe or the auxiliary fuel in the auxiliary fuel passage for injecting the main fuel or the auxiliary fuel from the fuel injection valve; Equipped with an auxiliary fuel for promoting ignition and combustion is supplied into one of the plurality of fuel passages, and a main injection fuel having low ignition and combustibility is supplied into the other fuel passages, and the auxiliary fuel and the main injection fuel are injected from the fuel injection valve in a separated pattern with a time interval such that the auxiliary fuel is not affected by the latent heat of vaporization of the main injection fuel; after injection, a portion of the auxiliary fuel is directed into the other fuel passage to replace at least a portion of the main fuel remaining in the other fuel passage during one fuel injection cycle, and the auxiliary fuel and main fuel are positioned so that the auxiliary fuel is injected first during a next fuel injection cycle.

2. a fuel passage branched from a fuel passage for supplying fuel to a nozzle hole of the fuel injection valve; an auxiliary fuel passage connecting the fuel passage and the auxiliary fuel tank; 10. The engine fuel injection system of claim 1 further comprising:

3. a fuel passage branched from a fuel passage for supplying fuel to a nozzle hole of the fuel injection valve; a main injection fuel passage connecting the fuel passage and the main injection fuel tank; 10. The engine fuel injection system of claim 1 further comprising:

4. 2. The engine fuel injection system of claim 1, wherein the main injection fuel is ammonia.

5. A marine diesel engine comprising an engine fuel injection system according to any one of claims 1 to 4.

6. A fuel injection method for an engine fuel injection system having a single fuel injection valve equipped with a nozzle hole for injecting fuel and a plurality of fuel passages for supplying fuel to the nozzle hole, comprising the steps of: An auxiliary fuel for promoting ignition and combustion is supplied into one of the plurality of fuel passages, and a main injection fuel having low ignition and combustibility is supplied into the other fuel passages; Injecting the auxiliary fuel and the main injection fuel from the fuel injection valve in separate patterns with a time interval such that the auxiliary fuel is not affected by the latent heat of vaporization of the main injection fuel; After injection, a portion of the auxiliary fuel is flowed into the other fuel passage to replace at least a portion of the main fuel remaining in the other fuel passage during one fuel injection cycle, and the auxiliary fuel and the main fuel are arranged so that the auxiliary fuel is injected first during the next fuel injection cycle. A fuel injection method comprising:

Images