Fuel supply device for engine

Abstract

To provide a fuel supply device for an engine that can suppress freezing of an engine component due to excessive cooling when liquid ammonia is used as fuel.SOLUTION: A fuel supply device 50 includes: a main injector 6 for ejecting liquid ammonia into an intake flow passage 3; an injection timing determination unit 43 for determining an injection timing of liquid ammonia; an injection control unit 45 for controlling the main injector 6 such that liquid ammonia is ejected from the main injector 6 in accordance with the injection timing of the liquid ammonia; and an intake air temperature sensor 40 and an excessive cooling determination unit 42 which detect whether excessive cooling is occurring in the air flowing in the intake flow passage 3. When occurrence of excessive cooling of air is detected, the injection timing determination unit 43 changes the injection timing of the liquid ammonia such that liquid ammonia is ejected so as to avoid a state where air flows in a combustion chamber 16 due to intake air pulsation of an ammonia engine 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel supply system for an engine. [Background technology]

[0002] For example, Patent Document 1 describes an engine equipped with an ammonia injector that injects ammonia as fuel. The ammonia injector injects gaseous or liquid ammonia into the intake port or combustion chamber of the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2023-67498 Summary of the Invention [Problem to be solved by the invention]

[0004] When liquid ammonia is used as fuel, the air taken into the engine may be excessively cooled when the liquid ammonia is vaporized due to its high latent heat of vaporization. In this case, the amount of water vapor in the intake air that changes state to water or ice increases, which may cause freezing of engine parts such as intake valves.

[0005] An object of the present invention is to provide a fuel supply device for an engine that can prevent freezing of engine parts due to excessive cooling when liquid ammonia is used as fuel. [Means for solving the problem]

[0006] (1) One aspect of the present invention is a fuel supply device for an ammonia engine that supplies ammonia as fuel to an air flow path connected to a combustion chamber of the ammonia engine, the device comprising: a liquid ammonia injector that injects liquid ammonia into the air flow path; an injection timing determination unit that determines the injection timing of the liquid ammonia; an injection control unit that controls the liquid ammonia injector to inject liquid ammonia from the liquid ammonia injector in accordance with the injection timing of the liquid ammonia determined by the injection timing determination unit; and a detection unit that detects whether excessive cooling of air flowing through the air flow path or an abnormal combustion in the engine caused by excessive cooling of the air has occurred, and when the detection unit detects that excessive cooling of the air or an abnormal combustion in the ammonia engine has occurred, the injection timing determination unit changes the injection timing of the liquid ammonia so that liquid ammonia is injected from the liquid ammonia injector while avoiding a state in which air flows into the combustion chamber due to intake pulsation of the ammonia engine.

[0007] In such a fuel supply device for an ammonia engine, the liquid ammonia injector is controlled to inject liquid ammonia from the liquid ammonia injector in accordance with the injection timing of the liquid ammonia. Here, it is detected whether excessive cooling of the air flowing through the air flow path or abnormal combustion in the ammonia engine caused by excessive cooling of the air is occurring. When excessive cooling of the air or abnormal combustion in the ammonia engine is detected, the injection timing of the liquid ammonia is changed so that liquid ammonia is injected from the liquid ammonia injector while avoiding a state in which air flows into the combustion chamber due to intake pulsation of the ammonia engine. Therefore, liquid ammonia is injected from the liquid ammonia injector when no air flows into the combustion chamber of the ammonia engine or when the flow rate of air flowing into the combustion chamber is low. Therefore, when the liquid ammonia is vaporized, heat exchange between the liquid ammonia and the air is inhibited, thereby preventing excessive cooling of the air. This reduces the amount of water vapor in the air that changes state to water or ice, thereby preventing freezing of engine parts due to excessive cooling.

[0008] (2) In the above (1), the fuel supply device further includes a gaseous ammonia injector that injects gaseous ammonia into the air flow path, and an injection ratio determination unit that determines an injection ratio of liquid ammonia and gaseous ammonia, wherein the injection timing determination unit determines the injection timing of the liquid ammonia and gaseous ammonia, and the injection control unit controls the liquid ammonia injector and the gaseous ammonia injector to inject liquid ammonia from the liquid ammonia injector and inject gaseous ammonia from the gaseous ammonia injector, according to the injection timing of the liquid ammonia and the gaseous ammonia determined by the injection timing determination unit and the injection ratio of the liquid ammonia and the gaseous ammonia determined by the injection ratio determination unit, and the injection ratio determination unit may decrease the injection ratio of liquid ammonia and increase the injection ratio of gaseous ammonia when the detection unit detects that excessive cooling of the air or abnormal combustion of the ammonia engine has occurred even after the injection timing of the liquid ammonia has been changed.

[0009] In this configuration, even after the injection timing of liquid ammonia is changed, when excessive cooling of the air or abnormal combustion in the ammonia engine is detected, the injection rate of liquid ammonia is reduced and the injection rate of gaseous ammonia is increased. As a result, the injection amount of liquid ammonia from the liquid ammonia injector is reduced and the injection amount of gaseous ammonia from the gaseous ammonia injector is increased. Therefore, while ensuring the total flow rate of ammonia required, the amount of heat exchange between liquid ammonia and air is reduced when liquid ammonia is vaporized, further suppressing excessive cooling of the air.

[0010] (3) In the above (1) or (2), the fuel supply device may further include an intake air temperature detection unit that detects the intake air temperature, which is the temperature of the air supplied to the combustion chamber, and the detection unit may detect that excessive cooling of the air is occurring when the intake air temperature detected by the intake air temperature detection unit is equal to or lower than a predetermined specified temperature.

[0011] In such a configuration, the temperature of the air (intake air temperature) supplied to the combustion chamber of the ammonia engine is detected, and it is determined whether the intake air temperature is equal to or lower than a specified temperature, thereby making it possible to easily detect with high accuracy whether excessive cooling of the air is occurring.

[0012] (4) In the above (1) or (2), the fuel supply device may further include a temperature detection unit that detects the temperature of a component that forms the air flow path, and the detection unit may detect that excessive cooling of the air is occurring when the temperature of the component detected by the temperature detection unit is equal to or lower than a predetermined specified temperature.

[0013] In this configuration, by detecting the temperature of the components that form the air flow path and determining whether the temperature of the components is below a specified temperature, it is possible to easily and accurately detect whether excessive cooling of the air is occurring.

[0014] (5) In any of the above (2) to (4), the air flow path may have an intake flow path through which air supplied to the combustion chamber flows, and an upstream reforming flow path through which air supplied to a reformer that reforms ammonia to produce reformed gas containing hydrogen flows, the reformer and the combustion chamber may be connected via a downstream reforming flow path through which the reformed gas produced by the reformer flows, and the liquid ammonia injector may inject liquid ammonia into the intake flow path, and the gaseous ammonia injector may inject gaseous ammonia into the upstream reforming flow path.

[0015] In this configuration, in an engine system in which reformed gas produced by a reformer is supplied to the combustion chamber of an ammonia engine, excessive cooling of the air and reformed gas is suppressed, thereby reducing the amount of water vapor contained in the air and reformed gas that changes state to water or ice, thereby suppressing freezing of engine parts due to excessive cooling in an engine system equipped with a reformer. [Effects of the Invention]

[0016] According to the present invention, when liquid ammonia is used as fuel, freezing of engine parts due to excessive cooling can be suppressed. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram showing an engine system equipped with a fuel supply device according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view of an ammonia engine. [Figure 3] 3 is a flowchart showing a procedure of a fuel supply control process executed by a controller shown in FIG. [Figure 4] FIG. 4 is a schematic configuration diagram showing an engine system equipped with a fuel supply device according to a second embodiment of the present invention. [Figure 5] 5 is a flowchart showing a procedure of a fuel supply control process executed by a controller shown in FIG. 4. [Figure 6] FIG. 10 is a schematic configuration diagram showing an engine system equipped with a fuel supply device according to a third embodiment of the present invention. [Figure 7] 7 is a flowchart showing a procedure of a fuel supply control process executed by a controller shown in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0019] Fig. 1 is a schematic diagram showing an engine system equipped with a fuel supply device according to a first embodiment of the present invention. In Fig. 1, the engine system 1 is mounted on a vehicle (not shown). The engine system 1 includes an ammonia engine 2, an intake passage 3, an exhaust passage 4, a main throttle valve 5, and a main injector 6.

[0020] The ammonia engine 2 is an engine that uses ammonia (NH3) as fuel. In the ammonia engine 2, hydrogen (H2) is mixed with the ammonia as a combustion improver to make the flame-retardant ammonia more combustible. The ammonia engine 2 is, for example, a four-stroke, four-cylinder engine.

[0021] As shown in Fig. 2, the ammonia engine 2 has four cylinders 10, four pistons 11 arranged so as to be able to reciprocate in each cylinder 10, and four connecting rods 13 connecting each piston 11 to a crankshaft 12. Note that Fig. 2 shows only one cylinder 10, one piston 11, and one connecting rod 13.

[0022] Each cylinder 10 is provided in a cylinder block 14. A cylinder head 15 is attached to the top of the cylinder block 14. The space defined by the cylinder 10, the cylinder head 15, and the piston 11 forms a combustion chamber 16 in which ammonia is burned together with hydrogen to generate exhaust gas. The ammonia engine 2 has four combustion chambers 16.

[0023] The cylinder head 15 is provided with an intake port 17 and an exhaust port 18 that communicate with the combustion chamber 16. The intake port 17 is opened and closed by an intake valve 19. The exhaust port 18 is opened and closed by an exhaust valve 20. In addition, an ignition plug 21 is attached to the cylinder head 15. The ignition plug 21 ignites the mixture of ammonia and air to ignite the ammonia.

[0024] The intake passage 3 is connected to each combustion chamber 16 of the ammonia engine 2. The intake passage 3 is an air passage through which air supplied to the combustion chambers 16 flows. The intake passage 3 is made up of an intake pipe 23, which is a pipe connected to the cylinder head 15, and an intake port 17 provided in the cylinder head 15. An air cleaner 7 is disposed in the intake pipe 23 to remove foreign matter such as dust and dirt contained in the air.

[0025] The exhaust flow path 4 is connected to each combustion chamber 16 of the ammonia engine 2. The exhaust flow path 4 is a flow path through which exhaust gas generated in each combustion chamber 16 flows. The exhaust flow path 4 is made up of an exhaust pipe 24, which is a pipe connected to the cylinder head 15, and an exhaust port 18 provided in the cylinder head 15. Although not shown in the figure, the exhaust pipe 24 is provided with a three-way catalyst that purifies unburned fuel such as NH3 and H2 and NOx contained in the exhaust gas, and an SCR catalyst that removes NOx contained in the exhaust gas.

[0026] The main throttle valve 5 is disposed in the intake pipe 23 of the intake flow path 3. The main throttle valve 5 is an electromagnetic flow control valve that controls the flow rate of air supplied to each combustion chamber 16 of the ammonia engine 2.

[0027] The main injector 6 is an electromagnetic liquid ammonia injection valve that intermittently injects liquid ammonia into the intake passage 3. The main injector 6 injects liquid ammonia between the main throttle valve 5 and the combustion chamber 16 in the intake passage 3. The main injector 6 can adjust the injection amount of liquid ammonia by changing the time for which the needle valve is opened.

[0028] The engine system 1 also includes an engine ECU 8. The engine ECU 8 is configured with a CPU, RAM, ROM, an input / output interface, etc. The engine ECU 8 is an ECU (electronic control unit) that controls the ammonia engine 2.

[0029] The engine ECU 8 controls the intake valve 19, the exhaust valve 20, and the spark plug 21 of the ammonia engine 2 so that one cycle is made up of four strokes: an intake stroke, a compression stroke, an expansion stroke (combustion stroke), and an exhaust stroke. The four strokes are performed in turn for each of the four cylinders 10.

[0030] In the intake stroke, the piston 11 moves down and draws the mixture of ammonia and air into the cylinder 10. In the compression stroke, the piston 11 moves up to top dead center and compresses the mixture. In the expansion stroke, the ignited mixture burns, the combustion gas expands, and the piston 11 is pushed down to bottom dead center. In the exhaust stroke, the piston 11 moves up due to inertia and pushes the combustion gas out of the cylinder 10. In other words, in one cycle, the piston 11 moves back and forth twice in the cylinder 10, and the crankshaft 12 rotates twice.

[0031] The engine ECU 8 controls the intake valve 19 to open during the intake stroke, the spark plug 21 to ignite during the expansion stroke, and the exhaust valve 20 to open during the exhaust stroke.

[0032] The engine system 1 also includes a reformer 25, an upstream reforming flow path 26, a reforming throttle valve 27, an ammonia tank 28, an evaporator 29, a reforming injector 30, an ammonia flow path 31, an ammonia flow path 32, a downstream reforming flow path 33, a cooler 34, and an on-off valve 35.

[0033] The reformer 25 generates reformed gas containing hydrogen by reforming ammonia using heat generated by burning the ammonia. The reformer 25 has a reforming catalyst that burns the ammonia and decomposes the ammonia into hydrogen. The reforming catalyst is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst. The reformer 25 may also have an electric heater that heats (warms up) the reforming catalyst.

[0034] The upstream reforming passage 26 connects the intake passage 3 and the reformer 25. One end of the upstream reforming passage 26 is connected to the intake passage 3 between the air cleaner 7 and the main throttle valve 5. The other end of the upstream reforming passage 26 is connected to the inlet of the reformer 25. The upstream reforming passage 26 is an air passage through which air supplied to the reformer 25 flows. The upstream reforming passage 26 is connected to each combustion chamber 16 of the ammonia engine 2 via the intake passage 3, the downstream reforming passage 33, and the reformer 25.

[0035] The reforming throttle valve 27 is disposed in the upstream reforming flow path 26. The reforming throttle valve 27 is an electromagnetic flow control valve that controls the flow rate of air supplied to the reformer 25.

[0036] The ammonia tank 28 is a container that stores ammonia in a liquid state. That is, the ammonia tank 28 stores liquid ammonia.

[0037] The ammonia flow path 31 connects the ammonia tank 28 and the main injector 6. The ammonia flow path 31 is a flow path through which liquid ammonia in the ammonia tank 28 flows toward the main injector 6.

[0038] The evaporator 29 is connected to the ammonia tank 28 via an ammonia flow path 38. The ammonia flow path 38 is a flow path through which liquid ammonia in the ammonia tank 28 flows toward the evaporator 29. The evaporator 29 evaporates (vaporizes) the liquid ammonia to generate gaseous ammonia (ammonia gas).

[0039] The reforming injector 30 is an electromagnetic gaseous ammonia injector that intermittently injects gaseous ammonia into the upstream reforming passage 26. The reforming injector 30 injects gaseous ammonia between the reforming throttle valve 27 and the reformer 25 in the upstream reforming passage 26. The reforming injector 30 can adjust the injection amount of gaseous ammonia by changing the time for which the needle valve is opened.

[0040] The ammonia flow path 32 connects the evaporator 29 and the reforming injector 30. The ammonia flow path 32 is a flow path through which the gaseous ammonia generated by the evaporator 29 flows toward the reforming injector 30.

[0041] The downstream reforming passage 33 connects the reformer 25 and the intake passage 3. One end of the downstream reforming passage 33 is connected to the outlet of the reformer 25. The other end of the downstream reforming passage 33 is connected to the intake passage 3 between the main injector 6 and the ammonia engine 2. The downstream reforming passage 33 is a passage through which the reformed gas generated by the reformer 25 flows toward each combustion chamber 16 of the ammonia engine 2.

[0042] The cooler 34 is disposed in the downstream reforming passage 33. The cooler 34 cools the reformed gas flowing through the downstream reforming passage 33. The on-off valve 35 is disposed downstream of the cooler 34 in the downstream reforming passage 33. The on-off valve 35 is, for example, an electromagnetic ON / OFF valve.

[0043] The engine system 1 also includes an intake air temperature sensor 40 and a controller 41.

[0044] The intake air temperature sensor 40 is disposed in the intake air flow path 3 near the ammonia engine 2. The intake air temperature sensor 40 is an intake air temperature detection unit that detects the temperature of the intake air supplied to the combustion chamber 16 of the ammonia engine 2 (intake air temperature).

[0045] The controller 41 is composed of a CPU, RAM, ROM, an input / output interface, etc. The controller 41 controls the main throttle valve 5, the main injector 6, the reforming throttle valve 27, and the reforming injector 30 based on the state quantities of the ammonia engine 2. The state quantities of the ammonia engine 2 include the rotation speed of the ammonia engine 2 and the load of the ammonia engine 2 (accelerator opening).

[0046] The controller 41 includes an excessive cooling determination unit 42 , an injection timing determination unit 43 , an injection ratio determination unit 44 , and an injection control unit 45 .

[0047] The excessive cooling determination unit 42 determines whether excessive cooling of the intake air and reformed gas flowing through the intake air flow path 3 is occurring based on the detection value of the intake air temperature sensor 40. The excessive cooling determination unit 42 constitutes a detection unit that cooperates with the intake air temperature sensor 40 to detect whether excessive cooling of the air flowing through the intake air flow path 3 is occurring.

[0048] The injection timing determination unit 43 determines the injection timing of liquid ammonia from the main injector 6 and the injection timing of gaseous ammonia from the reforming injector 30 based on the state quantities of the ammonia engine 2.

[0049] In normal times when the excessive cooling determination unit 42 has determined that excessive cooling of the intake air and the reformed gas is not occurring, the injection timing determination unit 43 determines the injection timing of liquid ammonia and gaseous ammonia so that the intake air and the reformed gas flow into the combustion chamber 16 due to the intake pulsation of the ammonia engine 2. In other words, the injection timing determination unit 43 determines the injection timing of liquid ammonia and gaseous ammonia so that the intake air and the reformed gas are supplied to the combustion chamber 16 with the intake valve 19 open during the intake stroke of the ammonia engine 2.

[0050] When the excessive cooling determination unit 42 determines that excessive cooling of the intake air and the reformed gas is occurring, the injection timing determination unit 43 changes the injection timing of liquid ammonia so that the liquid ammonia is injected from the main injector 6 while avoiding a state in which the intake air and the reformed gas flow due to the intake pulsation of the ammonia engine 2.

[0051] The injection ratio determination unit 44 determines the injection ratio of liquid ammonia from the main injector 6 and the injection ratio of gaseous ammonia from the reforming injector 30 based on the state quantities of the ammonia engine 2. At this time, the injection ratio determination unit 44 determines the injection ratio of liquid ammonia and the injection ratio of gaseous ammonia so that an appropriate air-fuel ratio (A / F) according to the state quantities of the ammonia engine 2 is ensured.

[0052] When the excessive cooling determination unit 42 determines that excessive cooling of the intake air and the reformed gas is occurring even after the injection timing of the liquid ammonia is changed by the injection timing determination unit 43, the injection ratio determination unit 44 reduces the injection ratio of liquid ammonia from the main injector 6 and increases the injection ratio of gaseous ammonia from the reforming injector 30.

[0053] The injection control unit 45 controls the main injector 6 and the reforming injector 30 so that liquid ammonia is injected from the main injector 6 and gaseous ammonia is injected from the reforming injector 30, according to the injection timings of liquid ammonia and gaseous ammonia determined by the injection timing determination unit 43 and the injection ratios of liquid ammonia and gaseous ammonia determined by the injection ratio determination unit 44.

[0054] As described above, the main injector 6, the ammonia tank 28, the evaporator 29, the reforming injector 30, the ammonia flow paths 31, 32, 38, the intake air temperature sensor 40, the excessive cooling determination unit 42, the injection timing determination unit 43, the injection ratio determination unit 44, and the injection control unit 45 constitute a fuel supply device 50 that supplies ammonia as fuel to the intake flow path 3, which is an air flow path connected to the ammonia engine 2, and to the upstream reforming flow path 26.

[0055] 3 is a flowchart showing the procedure of the fuel supply control process executed by the controller 41. This process is executed when the ammonia engine 2 is in a steady state after startup.

[0056] 3, the controller 41 first determines whether the temperature of the intake air (intake air temperature) detected by the intake air temperature sensor 40 is equal to or lower than a predetermined first specified temperature (step S101). The first specified temperature is a temperature threshold for determining whether the intake air and the reformed gas have been excessively cooled. The first specified temperature is, for example, the temperature (0°C) at which water vapor contained in the intake air and the reformed gas changes state to ice.

[0057] When the controller 41 determines that the intake air temperature is equal to or lower than the first specified temperature, it changes the injection timing of liquid ammonia from the main injector 6 (step S102). Specifically, the controller 41 changes the injection timing of liquid ammonia so that liquid ammonia is injected from the main injector 6 while avoiding a state in which intake air flows into the combustion chamber 16 due to intake pulsation of the ammonia engine 2. In other words, the controller 41 changes the injection timing of liquid ammonia so that heat exchange between the liquid ammonia and the intake air and reformed gas becomes difficult. The injection timing of liquid ammonia after the change occurs, for example, when the flow velocity in the portion of the intake flow path 3 where the main injector 6 is located is zero, at a low velocity peak, or when it is smaller than a predetermined flow velocity.

[0058] The changed injection timing of liquid ammonia is determined by experiments, simulations, etc., taking into consideration the opening and closing of the intake valves 19 of all combustion chambers 16 of the ammonia engine 2 and the propagation time of intake pulsation due to the distance from the main injector 6 to the ammonia engine 2. If the distance from the main injector 6 to the ammonia engine 2 is short, the changed injection timing of liquid ammonia can also be set to when the intake valve 19 is closed.

[0059] Thereafter, the controller 41 again determines whether the intake air temperature is equal to or lower than the first specified temperature (step S103). When the controller 41 determines that the intake air temperature is equal to or lower than the first specified temperature, the controller 41 reduces the injection rate of liquid ammonia from the main injector 6 and increases the injection rate of gaseous ammonia from the reforming injector 30 (step S104). The amount by which the injection rate of liquid ammonia is reduced and the amount by which the injection rate of gaseous ammonia is increased are determined so that the total flow rate of the liquid ammonia injected from the main injector 6 and the gaseous ammonia injected from the reforming injector 30 is constant.

[0060] Next, the controller 41 determines whether the intake air temperature is equal to or higher than a predetermined second specified temperature (step S105). The second specified temperature is a temperature threshold for determining whether the excessive cooling of the intake air and the reformed gas has been resolved. The second specified temperature is a temperature higher than the first specified temperature. When the controller 41 determines that the intake air temperature is not equal to or higher than the second specified temperature, it executes the above-mentioned step S104 again. In other words, when the excessive cooling of the intake air and the reformed gas has not been resolved, the above-mentioned step S104 is executed again. At this time, the amount of decrease in the injection rate of liquid ammonia and the amount of increase in the injection rate of gaseous ammonia are, for example, constant amounts.

[0061] When the controller 41 determines that the intake air temperature is equal to or higher than the second specified temperature, it returns the injection rate of liquid ammonia from the main injector 6 and the injection rate of gaseous ammonia from the reforming injector 30 to their original states (step S106). The original states are the states immediately before the injection rate of liquid ammonia is reduced and the injection rate of gaseous ammonia is increased in step S104.

[0062] Then, the controller 41 returns the injection timing of liquid ammonia from the main injector 6 to the original state (step S107), and executes the above step S101 again. The original state is the state immediately before the injection timing of liquid ammonia from the main injector 6 is changed in step S102.

[0063] When the controller 41 determines in step S103 that the intake air temperature is not equal to or lower than the first specified temperature, the controller 41 also returns the injection timing of liquid ammonia from the main injector 6 to the original state (step S107) and executes the above step S101 again.

[0064] Here, steps S101, S103, and S105 are executed by the excessive cooling determination unit 42. Steps S102 and S107 are executed by the injection timing determination unit 43. Steps S104 and S106 are executed by the injection ratio determination unit 44.

[0065] Incidentally, the density of liquid ammonia is higher than the density of gaseous ammonia. Therefore, the flow rate of liquid ammonia per unit volume is higher than the flow rate of gaseous ammonia per unit volume. Therefore, by using the main injector 6 which is a liquid ammonia injector that injects liquid ammonia into the intake passage 3, the flow rate of ammonia supplied to the ammonia engine 2 increases compared to when a gaseous ammonia injector that injects gaseous ammonia into the intake passage 3 is used, and therefore the output (power) of the ammonia engine 2 can be increased.

[0066] On the other hand, because the latent heat of vaporization of liquid ammonia is high, when liquid ammonia vaporizes (evaporates), it absorbs a large amount of heat from the intake air and the reformed gas, which makes it easy for the intake air and the reformed gas to cool. In this case, the amount of water vapor contained in the gas components of the intake air and the reformed gas that changes state to water or ice increases, which can cause engine parts such as the intake valve 19 to freeze.

[0067] To address such a problem, in this embodiment, the main injector 6 is controlled to inject liquid ammonia from the main injector 6, and the reforming injector 30 is controlled to inject gaseous ammonia from the reforming injector 30, according to the injection timings of liquid ammonia and gaseous ammonia and the injection ratios of liquid ammonia and gaseous ammonia. Here, it is detected whether excessive cooling of the intake air flowing through the intake passage 3 is occurring. Then, when it is detected that excessive cooling of the intake air is occurring, the injection timing of the liquid ammonia is changed so that liquid ammonia is injected from the main injector 6, avoiding a state in which intake air flows into the combustion chamber 16 due to intake pulsation of the ammonia engine 2. For this reason, liquid ammonia is injected from the main injector 6 in a state in which intake air does not flow into the combustion chamber 16 of the ammonia engine 2 or when the flow velocity of intake air flowing into the combustion chamber 16 is low. Therefore, when the liquid ammonia is vaporized, the amount of intake air that is the target of heat exchange with the liquid ammonia is small. This makes it difficult for heat to be exchanged between the liquid ammonia and the intake air, so that heat exchange between the liquid ammonia and the intake pipe 23, etc., which has a large heat capacity, becomes dominant, and excessive cooling of the intake air is suppressed. This reduces the amount of water vapor in the intake air that changes state to water or ice, and suppresses freezing of engine parts due to excessive cooling.

[0068] Furthermore, in this embodiment, even after the injection timing of liquid ammonia is changed, when it is detected that excessive cooling of the intake air is occurring, the injection rate of liquid ammonia is decreased and the injection rate of gaseous ammonia is increased. As a result, the injection amount of liquid ammonia from the main injector 6 is decreased and the injection amount of gaseous ammonia from the reforming injector 30 is increased. Therefore, while ensuring the total flow rate of ammonia required, the amount of heat exchanged between the liquid ammonia and the intake air is reduced when the liquid ammonia is vaporized, further suppressing excessive cooling of the intake air.

[0069] Moreover, in this embodiment, the temperature of the intake air (intake air temperature) supplied to the combustion chamber 16 of the ammonia engine 2 is detected, and it is determined whether the intake air temperature is equal to or lower than a first specified temperature, thereby making it possible to easily detect with high accuracy whether excessive cooling of the intake air is occurring.

[0070] Furthermore, in this embodiment, in the engine system 1 in which the reformed gas generated by the reformer 25 is supplied to the combustion chamber 16 of the ammonia engine 2, excessive cooling of the intake air and the reformed gas is suppressed, thereby reducing the amount of water vapor contained in the intake air and the reformed gas that changes state to water or ice. As a result, in the engine system 1 equipped with the reformer 25, freezing of engine parts due to excessive cooling is suppressed.

[0071] Fig. 4 is a schematic diagram showing an engine system equipped with a fuel supply device according to a second embodiment of the present invention. In Fig. 4, a fuel supply device 50A of this embodiment includes a temperature sensor 47 instead of the intake air temperature sensor 40 in the first embodiment.

[0072] The temperature sensor 47 is a temperature detection unit that detects the temperature of components that form the intake flow path 3. The temperature sensor 47 detects the temperature of components that form the intake flow path 3 between the main injector 6 and the combustion chamber 16 of the ammonia engine 2. The temperature sensor 47 directly detects the temperature of the cylinder head 15, which is a component that forms the intake flow path 3. In this case, the temperature sensor 47 is attached to the inner wall or outer wall of the cylinder head 15 near the intake valve 19. Note that the temperature sensor 47 may also directly detect the temperature of the intake pipe 23, which is a component that forms the intake flow path 3.

[0073] The fuel supply device 50A also includes a controller 41A instead of the controller 41 in the first embodiment. The controller 41A includes an excessive cooling determination unit 42A, an injection timing determination unit 43, an injection ratio determination unit 44, and an injection control unit 45.

[0074] The excessive cooling determination unit 42A determines whether excessive cooling of the intake air and reformed gas flowing through the intake air flow path 3 is occurring based on the detection value of the temperature sensor 47. The excessive cooling determination unit 42A constitutes a detection unit that cooperates with the temperature sensor 47 to detect whether excessive cooling of the air flowing through the intake air flow path 3 is occurring.

[0075] FIG. 5 is a flowchart showing the procedure of the fuel supply control process executed by the controller 41A, and corresponds to FIG.

[0076] In FIG. 5, the controller 41A first determines whether the temperature of the components forming the intake air flow path 3, detected by the temperature sensor 47, is equal to or lower than a predetermined first specified temperature (step S101A).

[0077] When the controller 41A determines that the temperature of the components forming the intake passage 3 is equal to or lower than the first specified temperature, the controller 41A changes the injection timing of the liquid ammonia from the main injector 6 (step S102).

[0078] Thereafter, the controller 41A again determines whether the temperature of the components forming the intake passage 3 is equal to or lower than the first specified temperature (step S103A). When the controller 41A determines that the temperature of the components forming the intake passage 3 is equal to or lower than the first specified temperature, the controller 41A decreases the injection rate of liquid ammonia from the main injector 6 and increases the injection rate of gaseous ammonia from the reforming injector 30 (step S104).

[0079] Next, the controller 41A determines whether the temperature of the components forming the intake flow path 3 is equal to or higher than a predetermined second specified temperature (step S105A). If the controller 41A determines that the temperature of the components forming the intake flow path 3 is not equal to or higher than the second specified temperature, it executes the above-mentioned step S104 again.

[0080] When the controller 41A determines that the temperature of the components forming the intake flow path 3 is equal to or higher than the second specified temperature, it returns the injection rate of liquid ammonia from the main injector 6 and the injection rate of gaseous ammonia from the reforming injector 30 to their original states (step S106).

[0081] After executing step S106, or when it is determined in step S103A that the intake air temperature is not equal to or lower than the first specified temperature, the controller returns the injection timing of liquid ammonia from the main injector 6 to the original state (step S107), and executes the above step S101A again.

[0082] Here, steps S101A, S103A, and S105A are executed by the excessive cooling determination unit 42A. Steps S102 and S107 are executed by the injection timing determination unit 43. Steps S104 and S106 are executed by the injection ratio determination unit 44.

[0083] In this embodiment, the temperature of the components that form the intake flow path 3 is detected and it is determined whether the temperature of the components is below a first specified temperature, thereby making it possible to easily and accurately detect whether excessive cooling of the intake air is occurring.

[0084] Fig. 6 is a schematic diagram showing an engine system equipped with a fuel supply device according to a third embodiment of the present invention. In Fig. 6, a fuel supply device 50B of this embodiment includes a pressure sensor 48 instead of the intake air temperature sensor 40 in the first embodiment.

[0085] The pressure sensor 48 is disposed in the intake passage 3 near the ammonia engine 2. The pressure sensor 48 is a sensor that detects the pressure of the intake air supplied to the combustion chamber 16 of the ammonia engine 2 (intake air pressure).

[0086] Furthermore, the fuel supply device 50B includes a controller 41B instead of the controller 41 in the first embodiment. The controller 41B includes a combustion abnormality determination unit 49, an injection timing determination unit 43, an injection ratio determination unit 44, and an injection control unit 45.

[0087] The combustion abnormality determination unit 49 determines whether or not a combustion abnormality has occurred in the ammonia engine 2 due to excessive cooling of the intake air flowing through the intake passage 3, based on the detection value of the pressure sensor 48. The combustion abnormality determination unit 49 cooperates with the pressure sensor 48 to form a detection unit that detects whether or not a combustion abnormality has occurred in the ammonia engine 2 due to excessive cooling of the air flowing through the intake passage 3.

[0088] FIG. 7 is a flowchart showing the procedure of the fuel supply control process executed by the controller 41B, and corresponds to FIG.

[0089] 7, the controller 41B first determines whether the intake pressure detected by the pressure sensor 48 is equal to or greater than a predetermined first specified pressure (step S111). The first specified pressure is a pressure threshold for determining whether a combustion abnormality has occurred in the ammonia engine 2 due to excessive cooling of the intake air and reformed gas. If the intake air is cooled excessively, the intake pressure is likely to rise, making it more likely that a combustion abnormality will occur in the ammonia engine 2.

[0090] When the controller 41B determines that the intake pressure is equal to or higher than the specified pressure, it changes the injection timing of liquid ammonia from the main injector 6 in the same manner as in the first embodiment (step S102).

[0091] Thereafter, the controller 41B again determines whether the intake pressure is equal to or greater than the first specified pressure (step S112). When the controller 41B determines that the intake pressure is equal to or greater than the first specified pressure, the controller 41B decreases the injection rate of liquid ammonia from the main injector 6 and increases the injection rate of gaseous ammonia from the reforming injector 30, as in the first embodiment described above (step S104).

[0092] Next, the controller 41B determines whether the intake pressure is equal to or lower than a second specified pressure (step S113). The second specified pressure is a pressure threshold for determining whether the combustion abnormality in the ammonia engine 2 caused by excessive cooling of the intake air and the reformed gas has been resolved. The second specified pressure is a pressure lower than the first specified pressure. When the controller 41B determines that the intake pressure is not equal to or lower than the second specified pressure, it executes the above-mentioned step S104 again. In other words, when the combustion abnormality in the ammonia engine 2 caused by excessive cooling of the intake air and the reformed gas has not been resolved, the above-mentioned step S104 is executed again. At this time, the amount of decrease in the injection rate of liquid ammonia and the amount of increase in the injection rate of gaseous ammonia are, for example, constant amounts.

[0093] When the controller 41B determines that the intake pressure is equal to or lower than the second specified pressure, it returns the injection rate of liquid ammonia from the main injector 6 and the injection rate of gaseous ammonia from the reforming injector 30 to their original states (step S106), similarly to the first embodiment described above.

[0094] After executing step S106, or when determining in step S112 that the intake pressure is not equal to or higher than the first specified pressure, the controller 41B returns the injection timing of liquid ammonia from the main injector 6 to the original state (step S107), and executes the above-mentioned step S111 again.

[0095] Here, steps S111, S112, and S113 are executed by the combustion abnormality determination unit 49. Steps S102 and S107 are executed by the injection timing determination unit 43. Steps S104 and S106 are executed by the injection ratio determination unit 44.

[0096] In this embodiment, it is detected whether or not a combustion abnormality in the ammonia engine 2 is occurring due to excessive cooling of the intake air flowing through the intake passage 3. When it is detected that a combustion abnormality in the ammonia engine 2 is occurring due to excessive cooling of the intake air, the injection timing of the liquid ammonia is changed so that the liquid ammonia is injected from the main injector 6, avoiding a state in which air flows into the combustion chamber 16 due to intake pulsation of the ammonia engine 2. Therefore, the liquid ammonia is injected from the main injector 6 in a state in which no intake air flows into the combustion chamber 16 of the ammonia engine 2, or in a state in which the flow velocity of the intake air flowing into the combustion chamber 16 is low. Therefore, when the liquid ammonia is vaporized, heat exchange between the liquid ammonia and the intake air is made less likely, and excessive cooling of the intake air is suppressed. This reduces the amount of water vapor in the intake air that changes state to water or ice, and suppresses freezing of engine parts due to excessive cooling.

[0097] In this embodiment, the pressure (intake pressure) of the intake air supplied to the combustion chamber 16 of the ammonia engine 2 is detected to determine whether or not a combustion abnormality has occurred in the ammonia engine 2 due to excessive cooling of the intake air flowing through the intake flow path 3, but the present invention is not limited to such a configuration.

[0098] For example, a pressure sensor may be disposed in the combustion chamber 16 of the ammonia engine 2 to detect the pressure in the combustion chamber 16 (in-cylinder pressure) and determine whether or not a combustion abnormality in the ammonia engine 2 caused by excessive cooling of the intake air has occurred. Alternatively, a rotation speed sensor may be disposed to detect the rotation speed of the crankshaft 12, and whether or not a combustion abnormality in the ammonia engine 2 caused by excessive cooling of the intake air may be determined from the amount of fluctuation in the rotation speed of the crankshaft 12. Alternatively, an NOx sensor and an NH3 sensor may be disposed in the exhaust pipe 24 that forms the exhaust flow path 4, and whether or not a combustion abnormality in the ammonia engine 2 caused by excessive cooling of the intake air may be determined from the amounts of NOx and NH3 present in the exhaust flow path 4.

[0099] Although several embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, in the above-described embodiments, when excessive cooling of intake air or abnormal combustion in the ammonia engine 2 is not improved and step S104 in Figures 3, 5, and 7 is executed again (steps S105, S105A, S113 are NO), the amount of decrease in the injection rate of liquid ammonia and the amount of increase in the injection rate of gaseous ammonia are the same as those in the previous execution, but the present invention is not particularly limited to such an embodiment. When step S104 is executed again, the amount of decrease in the injection rate of liquid ammonia and the amount of increase in the injection rate of gaseous ammonia may be gradually increased.

[0100] Furthermore, although the fuel supply devices 50, 50A, 50B of the above-described embodiments are applied to the engine system 1 equipped with the reformer 25, the present invention is also applicable to an engine system not equipped with a reformer. In this case, liquid ammonia is injected into the intake passage 3 from the liquid ammonia injector, and gaseous ammonia is injected into the intake passage 3 from the gaseous ammonia injector.

[0101] Furthermore, in the above embodiment, the main injector 6 that injects liquid ammonia and the reforming injector 30 that injects gaseous ammonia are provided, but the present invention is also applicable to a fuel supply device that is provided with only a liquid ammonia injector that injects liquid ammonia as a fuel injection valve. [Explanation of symbols]

[0102] 2...ammonia engine (engine), 3...intake flow path (air flow path), 6...main injector (liquid ammonia injection valve), 15...cylinder head (component), 16...combustion chamber, 25...reformer, 26...upstream reforming flow path (air flow path), 30...reforming injector (gaseous ammonia injection valve), 33...downstream reforming flow path, 40...intake air temperature sensor (intake air temperature detection unit, detection unit), 42, 42A...excessive cooling determination unit (detection unit), 43...injection timing determination unit, 44...injection ratio determination unit, 45...injection control unit, 47...temperature sensor (temperature detection unit, detection unit), 48...pressure sensor (detection unit), 49...combustion abnormality determination unit (detection unit), 50, 50A, 50B...fuel supply device.

Claims

1. A fuel supply device for an ammonia engine that supplies ammonia as fuel to an air flow path connected to a combustion chamber of the ammonia engine, a liquid ammonia injector that injects liquid ammonia into the air flow path; an injection timing determination unit that determines the injection timing of the liquid ammonia; an injection control unit that controls the liquid ammonia injector so as to inject the liquid ammonia from the liquid ammonia injector in accordance with the injection timing of the liquid ammonia determined by the injection timing determination unit; a detection unit that detects whether excessive cooling of the air flowing through the air flow path or abnormal combustion in the engine caused by the excessive cooling of the air is occurring, the injection timing determination unit, when the detection unit detects that excessive cooling of the air or abnormal combustion in the ammonia engine has occurred, changes the injection timing of the liquid ammonia so that the liquid ammonia is injected from the liquid ammonia injector while avoiding a state in which air flows into the combustion chamber due to intake pulsation of the ammonia engine.

2. a gaseous ammonia injector that injects gaseous ammonia into the air flow path; an injection ratio determination unit that determines an injection ratio of the liquid ammonia and the gaseous ammonia, the injection timing determination unit determines injection timings of the liquid ammonia and the gaseous ammonia, the injection control unit controls the liquid ammonia injector and the gaseous ammonia injector to inject the liquid ammonia from the liquid ammonia injector and the gaseous ammonia from the gaseous ammonia injector, according to the injection timings of the liquid ammonia and the gaseous ammonia determined by the injection timing determination unit and the injection ratios of the liquid ammonia and the gaseous ammonia determined by the injection ratio determination unit, 2. The fuel supply device for an ammonia engine according to claim 1, wherein when the detection unit detects that the air is being excessively cooled or that a combustion abnormality in the ammonia engine is occurring, the injection ratio determination unit decreases the injection ratio of the liquid ammonia and increases the injection ratio of the gaseous ammonia, even after the injection timing of the liquid ammonia is changed.

3. an intake air temperature detection unit that detects an intake air temperature, which is the temperature of air supplied to the combustion chamber; 2. The fuel supply device for an ammonia engine according to claim 1, wherein the detection unit detects that excessive cooling of the air is occurring when the intake air temperature detected by the intake air temperature detection unit is equal to or lower than a predetermined specified temperature.

4. a temperature detection unit that detects the temperature of a component that forms the air flow path; 2. The fuel supply device for an ammonia engine according to claim 1, wherein the detection unit detects that excessive cooling of the air is occurring when the temperature of the component detected by the temperature detection unit is equal to or lower than a predetermined specified temperature.

5. the air flow path includes an intake flow path through which air supplied to the combustion chamber flows, and an upstream reforming flow path through which air supplied to a reformer that reforms the ammonia to generate a reformed gas containing hydrogen flows, the reformer and the combustion chamber are connected via a downstream reforming flow path through which the reformed gas generated by the reformer flows, the liquid ammonia injector injects the liquid ammonia into the intake passage, 3. The fuel supply device for an ammonia engine according to claim 2, wherein the gaseous ammonia injector injects the gaseous ammonia into the upstream reforming passage.

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