JP2023180743A - engine system - Google Patents

Abstract

To provide an engine system capable of suppressing ammonia remaining in an ammonia supply passage to flow out into the atmosphere when the ammonia supply passage is detached after stop of an operation of an engine using ammonia as fuel.SOLUTION: An engine system 1 includes: an ammonia engine 2; an ammonia supply passage 19; an exhaust catalyst provided in an exhaust passage 4; a valve V1 that blocks supply of ammonia from an ammonia tank 10 when closed; an oxygen supply section 30 including an oxygen supply passage 32 that supplies gas containing oxygen to a portion downstream of the valve V1 in the ammonia supply passage 19 and a valve V2 provided in the oxygen supply passage 32 and opened after the valve V1 is closed; an expelling passage 40 connected to a portion downstream of the portion to which the oxygen supply passage 32 is connected in the ammonia supply passage 19 and enabling supply of ammonia present therein to the exhaust catalyst; and valves V3, V4 provided in the expelling passage 40 and opened after the valve V1 is closed.SELECTED DRAWING: Figure 1

Description

The present invention relates to an engine system that uses ammonia as fuel.

BACKGROUND ART Conventionally, an engine (hereinafter, sometimes referred to as an ammonia engine) that uses ammonia as fuel supplied from an ammonia tank through a vaporizer and an ammonia gas flow path is known (for example, Patent Document 1).

JP2020-197211A

In the technical field of ammonia engines such as the above-mentioned conventional technology, for example, after the operation of the ammonia engine is stopped, ammonia remains in the ammonia gas flow path (ammonia supply path), which is the fuel piping. It is desirable to suppress the outflow of ammonia into the atmosphere when removing.

An object of the present invention is to suppress the outflow of ammonia remaining in the ammonia supply route into the atmosphere when the ammonia supply route is removed after the operation of an engine that uses ammonia as fuel is stopped.

An engine system according to one aspect of the present invention includes an engine to which ammonia is supplied from an ammonia amount adjustment section, an ammonia tank that stores ammonia, and an ammonia supply path that connects the ammonia tank and the ammonia amount adjustment section. An exhaust path connected to the engine and into which exhaust gas from the engine flows; an exhaust catalyst installed in the exhaust path to adsorb and oxidize ammonia; a first valve that blocks the supply of the ammonia to the ammonia amount adjustment section; and an oxygen supply path that is connected to a location downstream of the first valve in the ammonia supply path and supplies a gas containing oxygen to the ammonia supply path. and a second valve that is provided in the oxygen supply path and is closed when the first valve is open and is opened after the first valve is closed. , a discharging route connected to a location downstream of the location where the oxygen supply route is connected in the ammonia supply route and capable of supplying internal ammonia to the exhaust catalyst; and a first valve provided in the discharging route. and a third valve that is opened after the valve is closed.

In the engine system according to one aspect of the present invention, the first valve is opened during operation of the engine, and ammonia in the ammonia tank is supplied to the ammonia amount adjustment section via the ammonia supply path. When the engine is stopped, ammonia remains in the ammonia supply path. Therefore, by closing the first valve after the engine is stopped, supply of ammonia in the ammonia tank to the ammonia amount adjustment section is blocked. By closing the first valve and then opening the second and third valves, gas containing oxygen is supplied to the ammonia supply path. Thereby, ammonia remaining inside the ammonia supply path is supplied to the exhaust catalyst through the expulsion path. As a result, the ammonia supplied to the exhaust catalyst can be adsorbed and oxidized by the exhaust catalyst. In this way, when the ammonia supply route is removed after stopping the operation of an engine that uses ammonia as fuel, it is possible to suppress the ammonia remaining in the ammonia supply route from flowing into the atmosphere.

In one embodiment, the exhaust catalyst is a three-way catalyst, and the engine system includes a temperature adjustment path connected at one end to a point downstream of the three-way catalyst in the exhaust path and connected to the ammonia supply path at the other end. , a fourth valve provided in the temperature adjustment path, a part of the ammonia supply path, a part of the expulsion path, a part of the exhaust path, a three-way catalyst, and a temperature adjustment path. The pump may also include a pump that can be used. In this case, since the exhaust catalyst is a three-way catalyst, ammonia supplied to the three-way catalyst is oxidized by the three-way catalyst, and the temperature of the catalyst-passing gas flowing out from the three-way catalyst increases. By operating the pump, a portion of the catalyst passing gas flowing out from the three-way catalyst is supplied to a portion of the ammonia supply path and the expulsion path through the temperature adjustment path. As a result, a portion of the ammonia supply path and the expulsion path are heated, so that, for example, dew condensation caused by latent heat of vaporization of ammonia remaining in the ammonia supply path can be suppressed.

In one embodiment, a pump may be provided in the expulsion path. In this case, since the expulsion route is connected to a location downstream of the location where the oxygen supply route is connected in the ammonia supply route, for example, there is no need to force-feed oxygen-containing gas from the oxygen supply route to the ammonia supply route. By operating the pump, ammonia remaining in the ammonia supply path can be supplied to the exhaust catalyst through the expulsion path.

In one embodiment, the engine system includes a temperature detection section that is provided in the temperature adjustment path and detects the gas temperature of the catalyst passing gas flowing through the temperature adjustment path, and when the gas temperature is equal to or higher than a predetermined temperature threshold, The amount of gas supplied from the oxygen supply route to the ammonia supply route may be increased compared to the case where the gas temperature is below the temperature threshold. In this case, it is possible to prevent a portion of the ammonia supply path and the expulsion path from being excessively heated.

According to the present invention, when the ammonia supply route is removed after stopping the operation of an engine that uses ammonia as fuel, it is possible to suppress the ammonia remaining in the ammonia supply route from flowing out into the atmosphere.

FIG. 1 is a schematic configuration diagram of an engine system according to a first embodiment. 2 is a flowchart illustrating an example of control processing of the controller in FIG. 1. FIG. It is a schematic block diagram of the engine system of 2nd Embodiment. 4 is a flowchart illustrating an example of control processing by the controller in FIG. 3. FIG. 4 is a schematic configuration diagram of a modification of the engine system of FIG. 3. FIG.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and overlapping description will be omitted.

[First embodiment]
FIG. 1 is a schematic configuration diagram of an engine system according to a first embodiment. In FIG. 1, an engine system 1 is mounted on a vehicle (not shown). The engine system 1 includes an ammonia engine 2, an intake path 3, an exhaust path 4, a main injector (ammonia amount adjustment section) 5, and a main throttle valve 6.

The ammonia engine 2 is an engine that uses ammonia gas (NH ₃ gas) as fuel. In the ammonia engine 2, hydrogen (H ₂ ) as a combustion aid is mixed with ammonia gas in order to facilitate combustion of flame-retardant ammonia gas. The ammonia engine 2 has a combustion chamber (not shown) in which ammonia gas is burned together with hydrogen to generate exhaust gas. The ammonia engine 2 is, for example, a four-cylinder engine.

The intake path 3 is connected to the combustion chamber of the ammonia engine 2. The intake path 3 is a path through which air supplied to the ammonia engine 2 flows. Note that an air cleaner 7 is disposed in the intake path 3 to remove foreign matter such as dust and dust contained in the air.

The exhaust path 4 is connected to the combustion chamber of the ammonia engine 2. The exhaust path 4 is a path into which exhaust gas from the ammonia engine 2 flows. The exhaust path 4 includes a three-way catalyst 8 that purifies unburned ammonia and nitrogen oxides (NOx), which are harmful components contained in exhaust gas, and an SCR catalyst 9 that adsorbs ammonia contained in exhaust gas. is installed. The three-way catalyst 8 oxidizes the adsorbed ammonia using a gas containing oxygen (for example, air) that flows into the three-way catalyst 8 . Furthermore, the three-way catalyst 8 adsorbs ammonia, although the amount is small compared to the SCR catalyst 9. The SCR catalyst 9 adsorbs ammonia and oxidizes the adsorbed ammonia using nitrogen oxides flowing into the SCR catalyst 9 (nitrogen oxides are reduced).

The ammonia engine 2 is supplied with ammonia gas from the main injector 5. The main injector 5 is an electromagnetic fuel injection valve that injects ammonia gas into the combustion chamber of the ammonia engine 2. The number of main injectors 5 is equal to the number of cylinders of the ammonia engine 2, for example. The main injector 5 operates according to a control command from a controller 50, which will be described later.

The main throttle valve 6 is arranged in the intake path 3. The main throttle valve 6 is an electromagnetic flow control valve that controls the flow rate of air supplied to the ammonia engine 2. The main throttle valve 6 operates according to a control command from a controller 50, which will be described later.

The engine system 1 also includes an ammonia tank 10, a vaporizer 11, a reformer 12, an air passage 13, a reforming throttle valve 14, a reforming injector 15, a reforming gas passage 16, It includes a cooler 17 and a flow rate adjustment valve 18.

The ammonia tank 10 is a container that stores ammonia in a liquid state. Ammonia tank 10 and main injector 5 are connected by an ammonia supply path 19.

A valve (first valve) V1 is provided in the ammonia supply path 19. The valve V1 is provided, for example, between the ammonia tank 10 and the vaporizer 11 in the ammonia supply path 19. Valve V1 controls whether or not ammonia is supplied from ammonia tank 10 to main injector 5 and reforming injector 15. When opened, the valve V1 allows ammonia in the ammonia tank 10 to be supplied to the main injector 5 and reforming injector 15. Valve V1 blocks supply of ammonia in ammonia tank 10 to main injector 5 and reforming injector 15 by closing. The valve V1 operates, for example, in response to a control command from a controller 50, which will be described later.

The vaporizer 11 vaporizes liquid ammonia stored in the ammonia tank 10 to generate ammonia gas. Ammonia gas generated in the vaporizer 11 flows through an ammonia supply path 19 and is supplied to the main injector 5, and also flows through an ammonia flow path 20 and is supplied to the reforming injector 15.

The reformer 12 generates a reformed gas containing hydrogen by reforming ammonia gas. The reformer 12 includes a cylindrical housing 21 and a reforming catalyst 22 housed within the housing 21. The housing 21 is made of a metal material such as stainless steel that is resistant to corrosion by ammonia gas. The reforming catalyst 22 is coated on a carrier having, for example, a honeycomb structure. The reforming catalyst 22 is a catalyst that burns ammonia gas and decomposes the ammonia gas into hydrogen. The reforming catalyst 22 is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst.

The air flow path 13 connects the intake path 3 and the reformer 12. The air flow path 13 is a flow path through which air supplied to the reformer 12 flows. One end of the air flow path 13 is connected between the air cleaner 7 and the main throttle valve 6 in the intake path 3 . The other end of the air flow path 13 is connected to the inlet of the casing 21 of the reformer 12.

The reforming throttle valve 14 is arranged in the air flow path 13. The reforming throttle valve 14 is an electromagnetic flow control valve that controls the flow rate of air supplied to the reformer 12. The reforming throttle valve 14 operates according to a control command from a controller 50, which will be described later.

The reforming injector 15 is an electromagnetic fuel injection valve that injects ammonia gas into the air flow path 13. The reforming injector 15 injects ammonia gas between the reforming throttle valve 14 and the reformer 12 in the air flow path 13 . The number of reforming injectors 15 may be a plurality (here, two) or one.

The reformed gas flow path 16 connects the reformer 12 and the intake path 3. One end of the reformed gas flow path 16 is connected to the outlet of the casing 21 of the reformer 12. The other end of the reformed gas flow path 16 is connected between the main throttle valve 6 and the ammonia engine 2 in the intake path 3 . The reformed gas flow path 16 is a flow path through which the reformed gas generated by the reformer 12 flows toward the ammonia engine 2.

The cooler 17 is arranged in the reformed gas flow path 16. The cooler 17 cools the reformed gas flowing through the reformed gas passage 16 using engine cooling water that cools the ammonia engine 2, for example.

The flow rate adjustment valve 18 is disposed downstream of the cooler 17 in the reformed gas passage 16 . The flow rate adjustment valve 18 is a solenoid valve that adjusts the flow rate of the reformed gas supplied to the ammonia engine 2. The flow rate adjustment valve 18 operates according to a control command from a controller 50, which will be described later. The flow rate adjustment valve 18 may be an on-off valve (ON/OFF valve).

The engine system 1 includes an oxygen supply section 30 having an air source 31, an oxygen supply path 32, a valve (second valve) V2, and a check valve 33.

The air source 31 is a source of gas containing oxygen for purging the ammonia supply path 19. The air source 31 supplies atmospheric air, for example, as a gas containing oxygen. Air source 31 includes a pump that delivers atmospheric air. The air source 31 may include an air tank that stores compressed air delivered by a pump.

The oxygen supply path 32 connects the air source 31 and a location downstream of the valve V1 in the ammonia supply path 19. The oxygen supply path 32 is connected, for example, between the valve V1 in the ammonia supply path 19 and the vaporizer 11. The oxygen supply path 32 supplies air to the ammonia supply path 19. Note that the gas containing oxygen may be oxygen instead of air.

The oxygen supply path 32 is provided with a valve V2. The valve V2 is provided, for example, between the air source 31 and the check valve 33 in the oxygen supply path 32. Valve V2 is a flow control valve that controls the flow rate of air supplied from air source 31 to ammonia supply path 19. Valve V2 allows air from air source 31 to be supplied to ammonia supply path 19 by opening. Valve V2 blocks air from air source 31 from being supplied to ammonia supply path 19 by closing. The valve V2 is, for example, an electromagnetic flow control valve, and operates according to a control command from a controller 50, which will be described later.

The check valve 33 is disposed downstream of the valve V2 in the oxygen supply path 32. The check valve 33 prevents ammonia from flowing from the ammonia supply path 19 into the oxygen supply path 32 . The check valve 33 closes the ammonia supply route 19 even if the pressure in the ammonia supply route 19 is higher than the pressure in the oxygen supply route 32 due to remaining ammonia when the ammonia engine 2 that was in operation is stopped. The flow of ammonia from the oxygen supply path 32 into the oxygen supply path 32 is blocked. The check valve 33 allows ammonia to flow from the oxygen supply route 32 into the ammonia supply route 19 when the remaining ammonia is reduced and the pressure in the ammonia supply route 19 becomes lower than the pressure in the oxygen supply route 32. do.

The engine system 1 includes an expulsion path 40 that is provided to be able to supply ammonia remaining inside the ammonia supply path 19 to the exhaust catalyst. The expulsion route 40 connects, for example, a location in the ammonia supply route 19 downstream of the location to which the oxygen supply route 32 is connected, and a location upstream of the three-way catalyst 8 in the exhaust route 4 . The expulsion route 40 includes, for example, a first expulsion route 41, a second expulsion route 42, and a third expulsion route 43.

The first expulsion path 41 is connected to the ammonia flow path 20 near the reforming injector 15 . A valve (third valve) V3 is provided in the first expulsion path 41. Valve V3 is a flow control valve that controls the flow rate of ammonia expelled from ammonia flow path 20 to exhaust path 4. When opened, the valve V3 allows ammonia in the ammonia flow path 20 to be supplied to the exhaust catalyst. When the valve V3 is closed, the ammonia in the ammonia flow path 20 is blocked from being supplied to the exhaust catalyst. The valve V3 is, for example, an electromagnetic flow control valve, and operates according to a control command from a controller 50, which will be described later.

The second expulsion path 42 is connected to the ammonia supply path 19 near the main injector 5 . A valve (third valve) V4 is provided in the second expulsion path 42. The valve V4 is a flow control valve that controls the flow rate of ammonia expelled from the ammonia supply path 19 to the exhaust path 4. When opened, the valve V4 allows ammonia in the ammonia supply path 19 to be supplied to the exhaust catalyst. By closing, the valve V4 blocks supply of ammonia in the ammonia supply path 19 to the exhaust catalyst. The valve V4 is, for example, an electromagnetic flow control valve, and operates in response to a control command from a controller 50, which will be described later.

The first expulsion route 41 and the second expulsion route 42 merge on the downstream side of the valves V3 and V4. The third expulsion route 43 connects the point where the first expulsion route 41 and the second expulsion route 42 join and the upstream side of the three-way catalyst 8 in the exhaust route 4 . Note that each of the first expulsion path 41 and the second expulsion path 42 may be connected to the upstream side of the three-way catalyst 8 in the exhaust path 4 without merging.

The engine system 1 includes a controller 50. The controller 50 is, for example, an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output interface, and the like. The controller 50 realizes various functions including operation of the ammonia engine 2 by loading a program stored in the ROM into the RAM and executing the program loaded into the RAM by the CPU.

An example of the operation of the engine system 1 will be described with reference to FIG. 2. FIG. 2 is a flowchart illustrating an example of control processing by the controller in FIG. The controller 50 causes the ammonia in the ammonia tank 10 to be supplied to the main injector 5 via the ammonia supply path 19 by opening the valve V1 while the ammonia engine 2 is operating. When the valve V1 is open, the controller 50 closes the valves V2, V3, and V4 (step S01). Due to the operation of the ammonia engine 2, the three-way catalyst 8 and the SCR catalyst 9 are at or above the activation temperature (light off).

When the ammonia engine 2 that has been in operation is stopped, the controller 50 closes the valve V1 to cut off the supply of ammonia in the ammonia tank 10 to the main injector 5 via the ammonia supply path 19 ( Step S02). At this time, ammonia remains in the ammonia supply path 19.

The controller 50 opens the valve V2 after the operation of the ammonia engine 2 is stopped. That is, the controller 50 closes the valve V1 that was open, and then opens the valve V2. Further, the controller 50 opens the valves V3 and V4 after the ammonia engine 2 stops operating. That is, the controller 50 closes the valve V1 that was open, and then opens the valves V3 and V4. As an example, after stopping the operation of the ammonia engine 2, the controller 50 closes the valve V1, opens the valves V3 and V4 (step S03), and then opens the valve V2 (step S04). By opening valves V3 and V4 before valve V2 in this way, even if the pressure in the ammonia supply path 19 is higher than the pressure in the oxygen supply path 32 due to remaining ammonia, the ammonia The pressure in the supply path 19 can be quickly reduced. Note that the controller 50 may open the valve V2 before opening the valves V3 and V4.

As described above, according to the engine system 1 of the first embodiment, the valve V1 is opened during operation of the ammonia engine 2, and ammonia in the ammonia tank 10 is supplied to the main injector via the ammonia supply path 19. 5. When the ammonia engine 2 that was in operation is stopped, ammonia remains in the ammonia supply path 19. Therefore, by closing the valve V1 after the operation of the ammonia engine 2 is stopped, the supply of ammonia in the ammonia tank 10 to the main injector 5 is blocked. Air (gas containing oxygen) is supplied to the ammonia supply path 19 by closing the valve V1 and then opening the valves V2, V3, and V4. As a result, ammonia remaining inside the ammonia supply path 19 is supplied to the three-way catalyst 8 through the expulsion path 40. As a result, the ammonia supplied to the three-way catalyst 8 can be adsorbed and oxidized by the three-way catalyst 8. In this way, when the ammonia supply route 19 is removed after the ammonia engine 2 is stopped, it is possible to suppress the ammonia remaining in the ammonia supply route 19 from flowing into the atmosphere. Furthermore, ammonia can be removed without using any special equipment for treating ammonia.

[Second embodiment]
FIG. 3 is a schematic configuration diagram of an engine system according to a second embodiment. In FIG. 3, the engine system 1A includes an oxygen supply section 30A instead of the oxygen supply section 30, an expulsion route 40A instead of the expulsion route 40, a controller 50A instead of the controller 50, and a temperature adjustment section 60. The engine system 1 differs from the engine system 1 of the first embodiment in that it is further provided.

In addition to the configuration of the oxygen supply section 30 described above, the oxygen supply section 30A further includes an oxygen supply path 34 and a valve V5. The oxygen supply path 34 connects the air source 31A and a location downstream of the third valve in the expulsion path 40. In the example of FIG. 3, the oxygen supply path 34 is connected to a location downstream of the valve V3 in the first expulsion path 41. The oxygen supply path 34 is provided with a valve V5. Valve V5 is a flow control valve that controls the flow rate of air supplied from the air source 31A to the oxygen supply path 34. Valve V5 allows air from air source 31A to be supplied to oxygen supply path 34 by opening. Valve V5 blocks air from air source 31A from being supplied to oxygen supply path 34 by closing. Valve V5 is, for example, an electromagnetic flow control valve, and operates according to a control command from controller 50A.

The temperature adjustment section 60 includes a temperature adjustment path 61, a valve (fourth valve) V6, a check valve 62, and a temperature sensor (temperature detection section) 63.

The temperature adjustment path 61 connects a location downstream of the three-way catalyst 8 in the exhaust path 4 and a location downstream of the valve V1 in the ammonia supply path 19. In the example of FIG. 3, one end of the temperature adjustment path 61 is connected between the three-way catalyst 8 and the SCR catalyst 9 in the exhaust path 4. The other end of the temperature adjustment path 61 is connected between the valve V1 in the ammonia supply path 19 and the vaporizer 11. The temperature adjustment path 61 refluxes the catalyst passing gas that has passed through the three-way catalyst 8 to the ammonia supply path 19 . The catalyst passing gas is exhaust gas from the ammonia engine 2, and has a higher temperature than the outside air during operation of the ammonia engine 2 and immediately after the operation is stopped. During the operation of the ammonia engine 2, the catalyst passing gas receives heat generated by the purification (oxidation reaction) of the exhaust gas at the three-way catalyst 8. The catalyst passing gas receives residual heat from the three-way catalyst 8 immediately after the ammonia engine 2 stops operating.

A valve V6 is provided in the temperature adjustment path 61. The valve V6 is a flow control valve that controls the flow rate of the catalyst passing gas that is returned to the ammonia supply path 19 from downstream of the three-way catalyst 8 in the exhaust path 4. When opened, the valve V6 allows the catalyst passing gas to be returned to the ammonia supply path 19. Valve V6 blocks the catalyst passing gas from being returned to the ammonia supply path 19 by closing. Valve V6 is, for example, an electromagnetic flow control valve, and operates according to a control command from controller 50, which will be described later.

The check valve 62 is disposed downstream of the valve V6 in the temperature adjustment path 61. The check valve 62 prevents ammonia from flowing from the ammonia supply path 19 into the temperature adjustment path 61 . Even if the pressure in the ammonia supply path 19 is higher than the pressure in the temperature adjustment path 61 because the check valve 62 closes the valve V6 when the ammonia engine 2 that was in operation is stopped, The flow of ammonia from the ammonia supply path 19 to the temperature adjustment path 61 is blocked. When the ammonia remaining in the ammonia supply route 19 is reduced and the pressure in the ammonia supply route 19 becomes lower than the pressure in the temperature adjustment route 61, the check valve 62 stops the flow from the temperature adjustment route 61 to the ammonia supply route 19. Allow inflow of catalyst passing gas.

A temperature sensor 63 is provided in the temperature adjustment path 61 . The temperature sensor 63 is disposed, for example, between the valve V6 and the check valve 62 in the temperature adjustment path 61. The temperature sensor 63 detects the gas temperature of the catalyst passing gas flowing through the temperature adjustment path 61. The temperature sensor 63 transmits information on the detected gas temperature to the controller 50.

The expulsion route 40A further includes a pump 44 in addition to the configuration of the expulsion route 40 described above. The pump 44 is provided in a closed circuit formed by a portion of the ammonia supply path 19, the expulsion path 40, a portion of the exhaust path 4, the three-way catalyst 8, and the temperature adjustment path 61. In the example of FIG. 3, the pump 44 is arranged in the third expulsion path 43. That is, the pump 44 is provided in the expulsion path 40. The pump 44 is, for example, an electric pump, and operates according to control commands from the controller 50A.

An example of the operation of the engine system 1A will be described with reference to FIG. 4. FIG. 4 is a flowchart illustrating an example of control processing by the controller in FIG. 3. The controller 50A causes the ammonia in the ammonia tank 10 to be supplied to the main injector 5 via the ammonia supply path 19 by opening the valve V1 while the ammonia engine 2 is operating. When the valve V1 is open, the controller 50 closes the valves V2, V3, V4, V5, and V6 (step S11).

When stopping the ammonia engine 2 that was being operated, the controller 50A closes the valve V1 to cut off the supply of ammonia in the ammonia tank 10 to the main injector 5 via the ammonia supply path 19. At this time, ammonia remains in the ammonia supply path 19. As an example, after the operation of the ammonia engine 2 is stopped, the controller 50A closes the valve V1 (step S12), opens the valves V3 and V4 (step S13), and then opens the valve V2 (step S13). Step S14). Further, the controller 50A opens the valves V5 and V6 (step S15), and operates the pump 44 of the expulsion path 40 (step S16).

More specifically, the controller 50A operates the pump 44 to circulate the gas in the closed circuit. In the example of FIG. 3, when the pump 44 provided in the third expulsion path 43 is activated, the gas in the first expulsion path 41 and the second expulsion path 42 is sent upstream of the three-way catalyst 8 in the exhaust path 4. be done. When the pump 44 draws in the gas from the first expulsion route 41 and the second expulsion route 42, the gas remaining in a part of the ammonia supply route 19 located further upstream is also pulled toward the pump 44 side. In the example of FIG. 3, a part of the ammonia supply route 19 refers to the part from the connection point with the valve V1 to the connection point with the first expulsion path 41, and the part from the connection point with the valve V1 to the second expulsion path 42. This corresponds to the part up to the connection point.

In addition, when the pump 44 is provided in the expulsion path 40 in this way, the gas remaining in a part of the ammonia supply path 19 is pulled toward the pump 44 side by its operation. In this case, the air source 31A does not necessarily have to force-feed air to the ammonia supply path 19. The air source 31A may have a configuration in which a pump and an air tank for storing compressed air are omitted. Incidentally, after the operation of the ammonia engine 2 was stopped, the controller 50A closed the valve V1, opened the valves V3 and V4, and then opened the valve V2, but the controller 50A did not leave the valve V2 closed. Air may be supplied to the three-way catalyst 8 by opening the valve V5. Even in this case, since the pump 44 is provided in the expulsion path 40, it is sufficient to circulate the gas in a closed circuit using the pump 44, and the ammonia in the ammonia supply path 19 is not necessarily used with the air from the oxygen supply path 32. You don't have to push it out.

The controller 50A supplies air from the air source 31A to the expulsion path 40A (first expulsion path 41 in the example of FIG. 3) by opening the valve V2. The air supplied to the expulsion route 40A via the valve V5 is supplied to the three-way catalyst 8 via the exhaust route 4. Therefore, the amount of oxygen for oxidizing ammonia in the three-way catalyst 8 increases. Here, in the initial stage of ammonia expulsion after the operation of the ammonia engine 2 is stopped, the air supplied from the oxygen supply path 32 by opening the valve V2 expels the ammonia remaining inside the ammonia supply path 19. However, there is a period (predetermined period) in which the three-way catalyst 8 is not reached. During this predetermined period, the oxygen concentration in the three-way catalyst 8 is insufficient relative to the ammonia concentration. Therefore, by supplying air from the air source 31A to the expulsion path 40A via the valve V5, the shortage of oxygen concentration relative to the ammonia concentration in the three-way catalyst 8 is alleviated. Therefore, ammonia can be more appropriately oxidized by the three-way catalyst 8 in the initial stage of expelling ammonia. Note that the controller 50A may open the valve V5 for the predetermined period after the ammonia engine 2 stops operating.

The controller 50A opens the valve V6 to recirculate the catalyst passing gas downstream of the three-way catalyst 8 in the exhaust path 4 to the ammonia supply path 19 via the temperature adjustment path 61. When the catalyst passing gas is refluxed to the ammonia supply path 19, the catalyst passing gas heats the ammonia supply path 19. In the ammonia supply path 19, when the ammonia remaining in the ammonia supply path 19 is expelled to the expulsion path 40A, there is a possibility that dew condensation may occur due to the latent heat of vaporization of ammonia. Since the catalyst passing gas heats the ammonia supply path 19, dew condensation caused by the latent heat of vaporization of ammonia can be suppressed. Note that, for example, if the ammonia remaining inside the ammonia supply path 19 has been sufficiently expelled but dew condensation remains in the ammonia supply path 19, the controller 50A may leave the valve V6 open and close the valve. V2 and valve V5 may be closed to stop the supply of air from the air source 31A.

The controller 50A controls the supply of ammonia from the oxygen supply path 32 to the ammonia supply path 19 when the gas temperature is equal to or higher than a predetermined temperature threshold when the valve V6 is opened, compared to when the gas temperature is less than the temperature threshold. The amount of air used may be increased (steps S17, S18). The temperature threshold is a temperature threshold of the catalyst passing gas for determining whether or not the ammonia supply path 19 is excessively heated by the catalyst passing gas. When the gas temperature is equal to or higher than a predetermined temperature threshold, the amount of air supplied from the oxygen supply route 32 to the ammonia supply route 19 is increased, so that the catalyst passing gas is cooled by the air. Thereby, even if the gas temperature is equal to or higher than a predetermined temperature threshold, excessive heating of the ammonia supply path 19 can be suppressed.

As explained above, according to the engine system 1A of the second embodiment, since the exhaust catalyst is the three-way catalyst 8, the ammonia supplied to the three-way catalyst 8 is oxidized by the three-way catalyst 8, and The temperature of the catalyst passing gas flowing out from the original catalyst 8 increases. By operating the pump 44, a portion of the catalyst passing gas flowing out from the three-way catalyst 8 is supplied to a portion of the ammonia supply path 19 and the expulsion path 40A through the temperature adjustment path 61. As a result, a portion of the ammonia supply path 19 and the expulsion path 40A are heated, so that, for example, dew condensation caused by latent heat of vaporization of ammonia remaining in the ammonia supply path 19 can be suppressed.

In the engine system 1A, an expulsion route 40A is connected to a location downstream of a location in the ammonia supply route 19 to which the oxygen supply route 32 is connected, and a pump 44 is provided in the expulsion route 40A. As a result, for example, even without pumping air from the oxygen supply route 32 to the ammonia supply route 19, by operating the pump 44, ammonia remaining in the ammonia supply route 19 is expelled and supplied to the three-way catalyst 8 through the route 40A. be able to.

The engine system 1A includes a temperature sensor 63 that is provided in the temperature adjustment path 61 and detects the gas temperature of the catalyst-passing gas flowing through the temperature adjustment path 61. The engine system 1A increases the amount of air supplied from the oxygen supply path 32 to the ammonia supply path 19 when the gas temperature is equal to or higher than a predetermined temperature threshold, compared to when the gas temperature is less than the temperature threshold. Thereby, it is possible to suppress excessive heating of a portion of the ammonia supply path 19 and the expulsion path 40A.

[Modified example]
Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. The present invention can be implemented in various forms including the embodiments described above, with various changes and improvements based on the knowledge of those skilled in the art.

For example, the engine system 1A of the second embodiment can be transformed into an engine system 1B as shown in FIG. 5. In FIG. 5, the engine system 1B according to the modification differs from the engine system 1A mainly in that a pump 64 is provided in the temperature adjustment path 61 instead of the pump 44 in the third expulsion path 43. There is. In the engine system 1B, the expulsion path 40A is returned to the expulsion path 40, and the temperature adjustment section 60 is a temperature adjustment section 60B. Note that in the temperature adjustment section 60B, a temperature sensor is omitted in the temperature adjustment path 61.

In the engine system 1B, since the pump 64 is provided in the temperature adjustment path 61, compared to the case where the pump 44 is provided in the third ejection path 43 as in the example of FIG. The gas in the second expulsion path 42 is less likely to be pulled toward the pump 64 side. Therefore, the oxygen supply section 30B differs from the oxygen supply section 30A of the second embodiment in that the air is returned to the air source 31 of the first embodiment that can pump air. Further, in the engine system 1A of the second embodiment, the controller 50A circulates gas in the closed circuit using the pump 44 while keeping the valve V2 closed, and circulates the air three times by opening the valve V5. Although the ammonia gas could have been supplied to the original catalyst 8, in the engine system 1B, the pump 64 exclusively performs pressure-feeding for refluxing the catalyst-passing gas to the ammonia supply path 19. For example, the controller 50B may cause the air from the oxygen supply path 32 to push out ammonia in the ammonia supply path 19 by opening the valve V2.

In the above embodiment, an example was explained in which the three-way catalyst 8 is mainly used as an exhaust catalyst, but the exhaust catalyst only needs to be able to adsorb and oxidize ammonia with one or more types of catalysts, and the SCR catalyst 9 is mainly used as an exhaust catalyst. Alternatively, an oxidation catalyst may be used in place of these.

In the above embodiment, the main injector 5 is illustrated as an example of the ammonia amount adjustment section, but the ammonia amount adjustment section may be a carburetor.

In the above embodiment, the valves V1 to V6 operate in response to control commands from the controllers 50, 50A, and 50B in conjunction with the stoppage of the ammonia engine 2, as shown in the flowcharts of FIGS. 2 and 4. , but not limited to. For example, an operation section such as a button that can be operated by an operator from the outside may be provided, and the ammonia engine 2 may be started by operating the operation section after the ammonia engine 2 has stopped operating (for example, automatic service/purge mode, etc.). operating mode).

In the above embodiment, the valves V1 to V6 are electromagnetic flow control valves, and operate according to control commands from the controllers 50, 50A, and 50B, but the present invention is not limited thereto. For example, valves V1 to V6 may be manual flow control valves. In this case, the above-mentioned effects can be achieved by the operator manually performing steps similar to those shown in the flowcharts of FIGS. 2 and 4 as a residual fuel processing method.

In the embodiment described above, the expulsion route 40 was previously incorporated into the ammonia engine 2, but the expulsion route 40 is not limited thereto. The expulsion path 40 may be attached to the ammonia engine 2 as a retrofitted member when the ammonia supply path 19 of the ammonia engine 2 is removed. In this case, a coupler or the like can be used to connect the ejection path 40.

1, 1A, 1B...Engine system, 2...Ammonia engine (engine), 4...Exhaust route, 5...Main injector (ammonia amount adjustment part), 8...Three-way catalyst (exhaust catalyst), 10...Ammonia tank, 19... Ammonia supply route, 30, 30A, 30B...Oxygen supply unit, 32, 34...Oxygen supply route, 40, 40A...Expulsion route, 44, 64...Pump, 60, 60B...Temperature adjustment unit, 61...Temperature adjustment route, 63 ...Temperature sensor (temperature detection section), V1... valve (first valve), V2... valve (second valve), V3, V4... valve (third valve), V6... valve (fourth valve).

Claims (4)

an engine to which ammonia is supplied from an ammonia amount adjustment section;
an ammonia tank that stores ammonia;
an ammonia supply path connecting between the ammonia tank and the ammonia amount adjustment section;
an exhaust path connected to the engine and into which exhaust gas from the engine flows;
an exhaust catalyst that is provided in the exhaust path and adsorbs and oxidizes ammonia;
a first valve that is provided in the ammonia supply path and shuts off the ammonia in the ammonia tank from being supplied to the ammonia amount adjustment section;
an oxygen supply route that is connected to a location downstream of the first valve in the ammonia supply route and supplies oxygen-containing gas to the ammonia supply route; an oxygen supply unit having a second valve that is closed when the first valve is closed and opened after the first valve is closed;
an expulsion route connected to a location downstream of a location to which the oxygen supply route is connected in the ammonia supply route, and provided to be able to supply internal ammonia to the exhaust catalyst;
An engine system comprising: a third valve provided in the expulsion path and opened after the first valve closes. The exhaust catalyst is a three-way catalyst,
A temperature adjustment path having one end connected to a location downstream of the three-way catalyst in the exhaust path and the other end connected to the ammonia supply path, and a fourth valve provided in the temperature adjustment path. an adjustment section;
The engine system according to claim 1, comprising: a pump provided in a closed circuit formed by a portion of the ammonia supply path, the expulsion path, a portion of the exhaust path, the three-way catalyst, and the temperature adjustment path. The engine system according to claim 2, wherein the pump is provided in the expulsion path. A temperature detection unit provided in the temperature adjustment path and configured to detect the gas temperature of the catalyst passing gas flowing through the temperature adjustment path,
Claim: When the gas temperature is equal to or higher than a predetermined temperature threshold, the amount of the gas supplied from the oxygen supply route to the ammonia supply route is increased compared to when the gas temperature is less than the temperature threshold. The engine system according to 2 or 3.

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