JP2021042707A - Engine system - Google Patents

Abstract

To provide an engine system capable of removing ammonia remaining in piping when an engine is in a stopped state.SOLUTION: An engine system 1 includes an ammonia engine 2, a reformer 13 for reforming ammonia gas to generate reformed gas containing hydrogen, and a control unit 32. The control unit 32 includes: a first control section 35 for controlling to close a main injector 5 and a reforming injector 16 when stop of the ammonia engine 2 is instructed; a second control section 36 for controlling to open a main throttle valve 6 and a reforming throttle valve 15 and cranking the ammonia engine 2 after control processing is performed by the first control section 35; and a third control section 37 for controlling to close the main throttle valve 6 and the reforming throttle valve 15 after control processing is performed by the second control section 36.SELECTED DRAWING: Figure 1

Description

The present invention relates to an engine system.

As a conventional engine system, for example, the technique described in Patent Document 1 is known. The engine system described in Patent Document 1 includes an engine main body, an engine intake passage and an engine exhaust passage connected to the combustion chamber of the engine main body, a throttle valve arranged inside the engine intake passage, and an engine intake passage. Connected to an ammonia injection valve that injects gaseous ammonia toward the gas, a decomposer that decomposes gaseous ammonia with a catalyst to generate hydrogen, an ammonia supply pipe that supplies gaseous ammonia to this decomposer, and an engine intake passage. Exhaust that purifies the exhaust by being placed in the engine exhaust passage and the air supply pipe that supplies air to the decomposer, the outflow pipe that is connected to the engine intake passage and the gas containing hydrogen generated by the decomposer flows out, and the engine exhaust passage. It is equipped with a purification device.

Japanese Unexamined Patent Publication No. 2014-21115

However, in the above-mentioned prior art, if ammonia remains in the piping after the engine body (engine) is stopped, the ammonia may leak and be released to the atmosphere. In addition, the piping may be corroded by the ammonia remaining in the piping.

An object of the present invention is to provide an engine system capable of removing ammonia remaining in a pipe when the engine is stopped.

The engine system according to one aspect of the present invention includes an engine, an intake passage through which air supplied to the engine flows, an exhaust passage through which exhaust gas generated from the engine flows, and an exhaust catalyst unit arranged in the exhaust passage. It has an ammonia injection valve that injects ammonia toward the engine, a first throttle valve that is arranged in the intake passage and controls the flow rate of air supplied to the engine, and a catalyst that decomposes ammonia into hydrogen. A reforming section that reforms to generate a reforming gas containing hydrogen, an air flow path through which air supplied to the reforming section flows, an ammonia supply valve that supplies ammonia to the reforming section, and an air flow path. A second throttle valve that controls the flow rate of air supplied to the reforming section, a reforming gas flow path through which the reforming gas generated by the reforming section flows toward the engine, and starting the engine. The exhaust catalyst unit oxidizes ammonia, including a motor for causing the engine to stop, a stop instruction unit for instructing the engine to stop, and a control unit for controlling the ammonia injection valve, the first throttle valve, the ammonia supply valve, and the second throttle valve. The control unit has a first control unit that closes and controls the ammonia injection valve and the ammonia supply valve when the stop instruction unit instructs the engine to stop, and the control unit is controlled by the first control unit. After the processing is executed, at least the first throttle valve of the first throttle valve and the second throttle valve is opened and controlled, and the control processing by the second control unit for cranking the engine and the second control unit is executed. After that, it has a third control unit that closes and controls at least the first throttle valve of the first throttle valve and the second throttle valve.

In such an engine system, when an instruction to stop the engine is instructed, the supply of ammonia to the engine and the reforming unit is stopped by controlling the closing of the ammonia injection valve and the ammonia supply valve. In that state, at least the first throttle valve of the first throttle valve and the second throttle valve is opened and controlled, and the engine is cranked, so that the engine is cranked with air flowing at least in the intake passage. Therefore, at least the ammonia remaining in the intake passage is forcibly flowed through the engine to the exhaust passage. Then, the ammonia flowing through the exhaust passage is oxidized and removed by the first catalyst. As a result, at least the ammonia remaining in the piping forming the intake passage is removed when the engine is stopped.

The exhaust catalyst unit may further have a second catalyst which is arranged on the downstream side of the first catalyst in the exhaust passage and collects and removes ammonia that has passed through the first catalyst.

In such a configuration, even if a part of the ammonia flowing through the exhaust passage passes through the first catalyst, the ammonia is collected and removed by the second catalyst. As a result, at least the ammonia remaining in the piping forming the intake passage is further removed when the engine is stopped.

After the control process by the first control unit is executed, the second control unit opens and controls the first throttle valve and the second throttle valve, cranks the engine, and the third control unit uses the second control unit. The first throttle valve and the second throttle valve may be closed and controlled after the control process according to the above is executed.

In such a configuration, after the supply of ammonia to the engine and the reforming section is stopped, the engine is cranked in a state where air flows through the intake passage, the air flow path, and the reforming gas flow path. Therefore, not only the ammonia remaining in the intake passage is forcibly flowed through the engine to the exhaust passage, but also the ammonia remaining in the air flow path and the reformed gas flow path is forcibly flowed through the engine to the exhaust passage. Will be. As a result, when the engine is stopped, ammonia remaining in the pipes forming the intake passage, the air flow path and the reformed gas flow path is removed.

The engine system further includes a stop valve that opens and closes the reforming gas flow path, and the second control unit opens and controls the first throttle valve after the control process by the first control unit is executed, and the second throttle valve. And the stop valve may be closed and controlled, the engine may be cranked, and the third control unit may close and control the first throttle valve after the control process by the second control unit is executed.

In such a configuration, after the supply of ammonia to the engine and the reforming section is stopped, the engine is cranked in a state where the air does not flow through the air flow path and the reforming gas flow path but flows only through the intake passage. Therefore, only the ammonia remaining in the intake passage is forcibly flowed through the engine to the exhaust passage, and the ammonia remains in the air flow path and the reformed gas flow path. Therefore, when the engine is stopped, the surrounding environment of the reforming portion is maintained in the state where ammonia is present, so that oxidative deterioration of the catalyst of the reforming portion is prevented.

The third control unit determines whether or not the specified time has elapsed since the control process by the second control unit was executed, and when the specified time has elapsed, at least the first of the first throttle valve and the second throttle valve 1 The throttle valve may be closed and controlled.

In such a configuration, it is determined by the elapsed time whether or not the ammonia remaining in the pipe is removed, so that the engine system can be simplified and the cost can be reduced.

The engine system is arranged in the exhaust passage and further includes an ammonia detection unit that detects ammonia, and the third control unit determines whether or not ammonia remains in the exhaust passage based on the detection value of the ammonia detection unit. When it is determined that ammonia does not remain in the exhaust passage, at least the first throttle valve of the first throttle valve and the second throttle valve may be closed and controlled.

In such a configuration, since it is directly detected whether or not ammonia remains in the exhaust passage, it is possible to determine with high accuracy whether or not the residual ammonia in the pipe is removed.

According to the present invention, ammonia remaining in the piping can be removed when the engine is stopped.

It is a schematic block diagram which shows the engine system which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the control system of the engine system shown in FIG. It is a flowchart which shows the detail of the start control processing procedure executed by the start control processing part shown in FIG. It is a flowchart which shows the detail of the stop control processing procedure executed by the stop control processing unit shown in FIG. It is a block diagram which shows the structure of the control system of the engine system which concerns on 2nd Embodiment of this invention. FIG. 5 is a flowchart showing details of a stop control processing procedure executed by the stop control processing unit shown in FIG. It is a schematic block diagram which shows the engine system which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the structure of the control system of the engine system shown in FIG. 7. FIG. 5 is a flowchart showing details of a stop control processing procedure executed by the stop control processing unit shown in FIG.

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 duplicate description will be omitted.

FIG. 1 is a schematic configuration diagram showing an engine system according to the first embodiment of the present invention. In FIG. 1, the engine system 1 of the present embodiment is mounted on an engine-type vehicle. The engine system 1 includes an ammonia engine 2, an intake passage 3, an exhaust passage 4, a plurality of (four in this case) main injectors 5, and a main throttle valve 6.

The ammonia engine 2 is an engine that uses _{ammonia (NH 3) as fuel.} The ammonia engine 2 is, for example, a 4-cylinder engine and has four combustion chambers 2a. _{Hydrogen (H 2} ) is supplied to the combustion chamber 2a together with ammonia. As a result, hydrogen is mixed with ammonia in the combustion chamber 2a, so that ammonia is easily burned.

The intake passage 3 is connected to the combustion chamber 2a. The intake passage 3 is a passage through which the air supplied to the combustion chamber 2a flows. An air cleaner 7 for removing dust and foreign matter such as dust contained in the air is provided in the intake passage 3. The intake passage 3 is formed by an intake pipe (piping).

The exhaust passage 4 is connected to the combustion chamber 2a. The exhaust passage 4 is a passage through which the exhaust gas generated from the combustion chamber 2a flows. The exhaust passage 4 is formed by an exhaust pipe (piping). An exhaust catalyst unit 8 for removing harmful substances contained in exhaust gas is provided in the exhaust passage 4.

The exhaust catalyst unit 8 has a three-way catalyst 40 and an SCR catalyst 41. The three-way catalyst 40 is a first catalyst that oxidizes and removes ammonia remaining in the exhaust passage 4. The SCR catalyst 41 is arranged on the downstream side of the three-way catalyst 40 in the exhaust passage 4. The SCR catalyst 41 is a selective reduction catalyst (Selective Catalytic Ruduction catalyst) that reduces nitrogen oxides (NOx) contained in exhaust gas to nitrogen (N _{2) by ammonia.} The SCR catalyst 41 is also a second catalyst that collects and removes ammonia that has passed through the three-way catalyst 40.

The main injector 5 is an electromagnetic type ammonia injection valve for injecting ammonia gas (NH ₃ gas) toward the combustion chamber 2a. The main injector 5 is connected to a vaporizer 12 described later via an ammonia gas flow path 9. The ammonia gas flow path 9 is a flow path through which ammonia gas flows. The main injector 5 is attached to the ammonia engine 2.

The main throttle valve 6 is arranged between the air cleaner 7 and the ammonia engine 2 in the intake passage 3. The main throttle valve 6 is a first throttle valve that controls the flow rate of air supplied to the ammonia engine 2. As the main throttle valve 6, an electromagnetic flow control valve is used.

Further, the engine system 1 includes an ammonia tank 11, a vaporizer 12, a reformer 13, an air flow path 14, a reforming throttle valve 15, a reforming injector 16, an electric heater 17, and a reforming gas. It includes a flow path 18, a reformed gas cooler 19, and a stop valve 20.

The ammonia tank 11 stores ammonia in a liquid state. That is, the ammonia tank 11 stores liquid ammonia. The vaporizer 12 vaporizes the liquid ammonia stored in the ammonia tank 11 to generate ammonia gas.

The reformer 13 is a reforming unit that reforms ammonia gas to generate a reformed gas containing hydrogen. The reformer 13 has, for example, a carrier 13a having a honeycomb structure. The carrier 13a is coated with a reforming catalyst 13b that decomposes ammonia into hydrogen. The reforming catalyst 13b has a function of burning ammonia in addition to a function of decomposing ammonia into hydrogen. The reforming catalyst 13b is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst.

The air flow path 14 connects the intake passage 3 and the reformer 13. Specifically, one end of the air flow path 14 is branched and connected to a portion of the intake passage 3 between the air cleaner 7 and the main throttle valve 6. The other end of the air flow path 14 is connected to the reformer 13. The air flow path 14 is a flow path through which the air supplied to the reformer 13 flows. The air flow path 14 is formed by piping.

The reforming throttle valve 15 is arranged in the air flow path 14. The reforming throttle valve 15 is a second throttle valve that controls the flow rate of air supplied to the reformer 13. As the reforming throttle valve 15, an electromagnetic flow control valve is used.

The reforming injector 16 is connected to the vaporizer 12 via an ammonia gas flow path 21. The ammonia gas flow path 21 is a flow path through which the ammonia gas generated by the vaporizer 12 flows. The reforming injector 16 is an electromagnetic fuel injection valve that injects ammonia gas toward the reformer 13. Specifically, the reforming injector 16 injects ammonia gas between the reforming throttle valve 15 and the reformer 13 in the air flow path 14. Therefore, air and ammonia gas flow through the portion of the air flow path 14 between the reforming throttle valve 15 and the reformer 13. The reforming injector 16 constitutes an ammonia supply valve that supplies ammonia gas to the reformer 13.

A pressure reducing valve 23 is provided in the ammonia gas flow path 21. The pressure reducing valve 23 decompresses the ammonia gas supplied to the ammonia engine 2 and the reformer 13. The pressure reducing valve 23 maintains the pressure of the ammonia gas supplied to the ammonia engine 2 and the reformer 13 at a predetermined pressure.

The electric heater 17 raises the temperature of the reformer 13 by heating the ammonia gas supplied to the reformer 13. The electric heater 17 has a heating element 24 arranged in the air flow path 14 and a power supply 25 for energizing the heating element 24. The heating element 24 has, for example, a honeycomb structure. The heat of the ammonia gas heated by the electric heater 17 is transferred to the reformer 13, so that the temperature of the reformer 13 rises. The electric heater 17 may directly heat the reformer 13 to raise the temperature of the reformer 13.

The reforming gas flow path 18 connects the reformer 13 and the intake passage 3. Specifically, one end of the reforming gas flow path 18 is connected to the reformer 13. The other end of the reformed gas flow path 18 is branched and connected to a portion of the intake passage 3 between the main throttle valve 6 and the ammonia engine 2. The reformed gas flow path 18 is a flow path through which the reformed gas generated by the reformer 13 flows toward the ammonia engine 2. The reformed gas flow path 18 is formed by piping.

The reformed gas cooler 19 is arranged in the reformed gas flow path 18. The reformed gas cooler 19 cools the reformed gas supplied to the ammonia engine 2. By providing the reformed gas cooler 19, the intake system parts such as the main throttle valve 6 are prevented from being damaged by heat, and the volume expansion of the reformed gas is suppressed, so that the air is in the combustion chamber of the ammonia engine 2. It becomes easy to be sufficiently inhaled in 2a.

The stop valve 20 is arranged between the reformed gas cooler 19 and the intake passage 3 in the reformed gas flow path 18. The stop valve 20 is an on-off valve that opens and closes the reformed gas flow path 18.

Further, the engine system 1 includes a temperature sensor 28, an ignition switch 30 (IG switch), a starter motor 31, and a control unit 32.

The temperature sensor 28 is a sensor that detects the temperature of the reformer 13. The temperature sensor 28 detects, for example, the temperature at the upstream end of the reforming catalyst 13b of the reformer 13. The ignition switch 30 is a manually operated switch for instructing the driver of the vehicle to start and stop the ammonia engine 2. The ignition switch 30 constitutes a stop instruction unit for instructing the stop of the ammonia engine 2. The starter motor 31 is a motor for starting the ammonia engine 2.

The control unit 32 is composed of a CPU, RAM, ROM, an input / output interface, and the like. The control unit 32 includes a main injector 5, a main throttle valve 6, a reforming throttle valve 15, a reforming injector 16, a stop valve 20, and an electric heater 17 based on the operation signal of the ignition switch 30 and the detected value of the temperature sensor 28. Controls the power supply 25 and the starter motor 31 of the above.

As shown in FIG. 2, the control unit 32 includes a start control processing unit 33 that executes control processing when the ammonia engine 2 is started, and a stop control processing unit 34 that executes control processing when the ammonia engine 2 is stopped. have.

FIG. 3 is a flowchart showing details of the start control processing procedure executed by the start control processing unit 33. Before the execution of this process, the main injector 5, the main throttle valve 6, the reforming throttle valve 15, the reforming injector 16, and the stop valve 20 are in a fully closed state.

In FIG. 3, the start control processing unit 33 first determines whether or not the ignition switch 30 has been turned on based on the operation signal of the ignition switch 30 (procedure S101). When the start control processing unit 33 determines that the ignition switch 30 has been turned on, the start control processing unit 33 controls the power supply 25 so as to energize the heating element 24 of the electric heater 17 (procedure S102). As a result, the heating element 24 will generate heat.

Subsequently, the start control processing unit 33 controls to open the stop valve 20 (procedure S103). Subsequently, the start control processing unit 33 controls to open the reforming injector 16 (procedure S104). As a result, ammonia gas is injected from the reforming injector 16 and the ammonia gas is supplied to the reformer 13. At this time, since the ammonia gas is heated by the heating element 24, the reformer 13 is heated by the heat of the ammonia gas. Subsequently, the start control processing unit 33 controls to open the reforming throttle valve 15 (procedure S105). As a result, air is supplied to the reformer 13.

Subsequently, the start control processing unit 33 controls the starter motor 31 so as to crank the ammonia engine 2 (procedure S106). As a result, the ammonia engine 2 is started.

Subsequently, the start control processing unit 33 controls to open the main throttle valve 6 and controls to open the main injector 5 (procedure S107). As a result, air is supplied to the ammonia engine 2, ammonia gas is injected from the main injector 5, and ammonia gas is supplied to the ammonia engine 2.

Subsequently, the start control processing unit 33 determines whether or not the temperature of the reformer 13 is equal to or higher than the specified temperature based on the detected value of the temperature sensor 28 (procedure S108). The specified temperature is a temperature at which ammonia gas can be burned, and is, for example, about 200 ° C. When the start control processing unit 33 determines that the temperature of the reformer 13 is equal to or higher than the specified temperature, the start control processing unit 33 controls the power supply 25 so as to stop the energization of the heating element 24 (procedure S109).

The control processing procedure executed by the start control processing unit 33 is not particularly limited to the above flow. For example, step S106 may be performed after step S108.

As shown in FIG. 2, the stop control processing unit 34 has a first control unit 35, a second control unit 36, and a third control unit 37.

When the ignition switch 30 instructs the first control unit 35 to stop the ammonia engine 2, the first control unit 35 closes and controls the main injector 5 and the reforming injector 16.

After the control process by the first control unit 35 is executed, the second control unit 36 opens and controls the main throttle valve 6 and the reforming throttle valve 15 and cranks the ammonia engine 2.

The third control unit 37 closes and controls the main throttle valve 6 and the reforming throttle valve 15 after the control process by the second control unit 36 is executed.

FIG. 4 is a flowchart showing details of the stop control processing procedure executed by the stop control processing unit 34. Before the execution of this process, the main injector 5, the main throttle valve 6, the reforming throttle valve 15, the reforming injector 16 and the stop valve 20 are in an open state.

In FIG. 4, the stop control processing unit 34 first determines whether or not the ignition switch 30 has been turned off based on the operation signal of the ignition switch 30 (procedure S111).

When it is determined that the ignition switch 30 has been turned off, the stop control processing unit 34 controls to close the main injector 5 and the modification injector 16 (procedure S112). At this time, the stop control processing unit 34 fully closes the main injector 5 and the modified injector 16. As a result, the injection of the ammonia gas from the main injector 5 is stopped, so that the ammonia gas is not supplied to the ammonia engine 2. Further, since the injection of the ammonia gas from the reforming injector 16 is stopped, the ammonia gas is not supplied to the reformer 13.

Subsequently, the stop control processing unit 34 controls to change the opening degree of the main throttle valve 6 and the reforming throttle valve 15 (procedure S113). At this time, the opening degree of the main throttle valve 6 and the reformed throttle valve 15 is removed by sufficiently oxidizing the ammonia gas remaining in the intake passage 3, the air flow path 14 and the reformed gas flow path 18 by the three-way catalyst 40. The opening is such that the amount of air that can be achieved is secured. As a result, the ammonia engine 2 is cranked in a state where only air is flowing through the intake passage 3, the air flow path 14, and the reformed gas flow path 18.

Subsequently, the stop control processing unit 34 determines whether or not a predetermined time has elapsed after controlling the opening of the main throttle valve 6 and the reforming throttle valve 15 to be changed (procedure S114). The specified time is a time during which the maximum amount of ammonia gas remaining in the intake passage 3, the air flow path 14, and the reformed gas flow path 18 is removed by the air flow, and is determined in advance by an experiment or the like.

When it is determined that the specified time has elapsed, the stop control processing unit 34 controls to close the main throttle valve 6, the reforming throttle valve 15, and the stop valve 20 (procedure S115). At this time, the stop control processing unit 34 fully closes the main throttle valve 6 and the reforming throttle valve 15. As a result, the ammonia engine 2 is stopped.

In the above process, the opening degrees of the main throttle valve 6 and the reforming throttle valve 15 are changed in the procedure S113, but if the required amount of air is secured, the main throttle valve 6 and the reforming throttle are changed. It is not necessary to change the opening degree of the valve 15.

Here, the first control unit 35 executes the procedures S111 and S112. The second control unit 36 executes the procedure S113. The third control unit 37 executes the procedures S114 and S115. Therefore, the procedure S114 determines whether or not a predetermined time has elapsed since the control process by the second control unit 36 was executed.

In the engine system 1 as described above, when the ignition switch 30 is turned on, the heating element 24 of the electric heater 17 is energized and the heating element 24 generates heat. Then, when the reforming injector 16 opens, ammonia gas is injected from the reforming injector 16 and the ammonia gas is supplied to the reformer 13. At this time, the ammonia gas is heated by the heat of the heating element 24, and the heat of the warmed ammonia gas is transferred to the reformer 13, so that the temperature of the reformer 13 rises. Then, when the reforming throttle valve 15 is opened, air is supplied to the reformer 13.

Subsequently, the ammonia engine 2 is started by the starter motor 31. Further, when the main throttle valve 6 and the main injector 5 are opened, air is supplied to the combustion chamber 2a of the ammonia engine 2, and ammonia gas is injected from the main injector 5 to the combustion chamber 2a of the ammonia engine 2. Ammonia gas is supplied. As a result, the ammonia gas begins to burn in the combustion chamber 2a.

When the temperature of the reformer 13 reaches the specified temperature, the energization of the heating element 24 is stopped, but the reforming catalyst 13b of the reformer 13 burns ammonia gas, and the combustion heat further raises the reformer 13. Warm up. Specifically, as shown in the following formula, a combustion reaction of ammonia occurs due to a chemical reaction (oxidation reaction) between a part of ammonia and oxygen in the air.
NH ₃ + 3/4O ₂ → 1 / 2N ₂ + 3 / 2H ₂ O + Q

Then, when the temperature of the reformer 13 reaches a temperature at which reforming is possible (for example, about 300 ° C. to 400 ° C.), the reforming catalyst 13b of the reformer 13 starts reforming the ammonia gas and contains hydrogen. A reforming gas is generated. Specifically, as shown in the following formula, a reforming reaction occurs in which ammonia is decomposed into hydrogen and nitrogen by the heat of combustion of ammonia, and a reforming gas containing hydrogen and nitrogen is generated.
NH ₃ → 3 / 2H ₂ + 1 / 2N ₂ −Q

The reformed gas flows through the reformed gas flow path 18 and is supplied to the combustion chamber 2a of the ammonia engine 2. As a result, the ammonia gas burns together with the hydrogen in the reformed gas in the combustion chamber 2a. As described above, the engine system 1 is in steady operation after the warming up of the reformer 13 is completed.

When the ignition switch 30 is turned off during steady operation, the main injector 5 and the reforming injector 16 are closed first, so that the injection of ammonia gas from the main injector 5 and the reforming injector 16 is stopped. Therefore, the ammonia gas is not supplied to the ammonia engine 2 and the reformer 13. Therefore, the cranking of the ammonia engine 2 is continued with only air being supplied to the ammonia engine 2 and the reformer 13.

As a result, the intake passage 3, the air flow path 14, and the reformed gas flow path 18 are purged by air. Therefore, the ammonia gas remaining in the intake passage 3, the air flow path 14, and the reforming gas flow path 18 passes through the combustion chamber 2a of the ammonia engine 2 and flows into the exhaust passage 4.

The ammonia gas flowing through the exhaust passage 4 is oxidized and removed by the three-way catalyst 40. Further, even if a part of the ammonia gas flowing through the exhaust passage 4 passes through the three-way catalyst 40, the ammonia gas is collected by the SCR catalyst 41.

Then, when the specified time elapses, the main throttle valve 6, the reforming throttle valve 15, and the stop valve 20 are closed, so that the supply of air to the ammonia engine 2 and the reformer 13 is stopped. As a result, the ammonia engine 2 coasts several times and then completely stops.

As described above, in the present embodiment, when the stop of the ammonia engine 2 is instructed, the main injector 5 and the reforming injector 16 are closed and controlled, so that the ammonia gas to the ammonia engine 2 and the reformer 13 is controlled. Supply is stopped. In that state, the main throttle valve 6 and the reforming throttle valve 15 are opened and controlled, and the ammonia engine 2 is cranked so that air flows through the intake passage 3, the air flow path 14, and the reforming gas flow path 18. Then, the ammonia engine 2 cranks. Therefore, the ammonia gas remaining in the intake passage 3, the air flow path 14, and the reforming gas flow path 18 is forcibly flowed through the ammonia engine 2 to the exhaust passage 4. Then, the ammonia gas flowing through the exhaust passage 4 is oxidized and removed by the three-way catalyst 40. As a result, when the ammonia engine 2 is stopped, the ammonia gas remaining in the pipes forming the intake passage 3, the air flow path 14, and the reformed gas flow path 18 is removed. As a result, it is possible to prevent the ammonia gas from leaking and being released to the atmosphere. In addition, it is possible to prevent the pipe from being corroded by the ammonia gas remaining in the pipe.

Further, in the present embodiment, the SCR catalyst 41 is arranged on the downstream side of the three-way catalyst 40 in the exhaust passage 4. Therefore, even if a part of the ammonia gas flowing through the exhaust passage 4 passes through the three-way catalyst 40, the ammonia gas is collected and removed by the SCR catalyst 41. As a result, when the ammonia engine 2 is stopped, the ammonia gas remaining in the pipes forming the intake passage 3, the air flow path 14, and the reformed gas flow path 18 is further removed.

Further, in the present embodiment, not only the ammonia gas remaining in the intake passage 3 forcibly flows through the ammonia engine 2 to the exhaust passage 4, but also the ammonia gas remaining in the air flow path 14 and the reforming gas flow path 18. Is forced to flow through the ammonia engine 2 to the exhaust passage 4. As a result, after the ammonia engine 2 is stopped, the ammonia gas remaining in the piping is sufficiently removed.

Further, in the present embodiment, it is determined from the elapsed time whether or not the ammonia gas remaining in the pipes forming the intake passage 3, the air flow path 14, and the reformed gas flow path 18 has been removed, so that the engine system 1 can be used. It is possible to simplify and reduce the cost.

Further, in the present embodiment, when removing the ammonia gas remaining in the pipe forming the intake passage 3, the air flow path 14, and the reformed gas flow path 18, the three-way catalyst 40 sufficiently oxidizes the ammonia gas. Since the air that can be removed flows through the SCR catalyst 41, the physique of the SCR catalyst 41 can be miniaturized and the cost of the SCR catalyst 41 can be reduced.

FIG. 5 is a block diagram showing a configuration of a control system of an engine system according to a second embodiment of the present invention. In FIG. 5, the control unit 32 of the engine system 1 of the present embodiment has a stop control processing unit 34A instead of the stop control processing unit 34 of the first embodiment described above. The stop control processing unit 34A includes the first control unit 35, the second control unit 36A, and the third control unit 37A.

After the control process by the first control unit 35 is executed, the second control unit 36A opens and controls the main throttle valve 6, closes and controls the reforming throttle valve 15 and the stop valve 20, and shuts down the ammonia engine 2. Let them rank.

The third control unit 37A closes and controls the main throttle valve 6 after the control process by the second control unit 36 is executed.

FIG. 6 is a flowchart showing details of the control processing procedure executed by the stop control processing unit 34A.

In FIG. 6, the stop control processing unit 34A sequentially executes the procedures S111 and S112 in the same manner as the stop control processing unit 34 in the first embodiment. Subsequently, the stop control processing unit 34A controls to close the reforming throttle valve 15 and the stop valve 29 (procedure S117). As a result, the supply of air to the reformer 13 is stopped.

Subsequently, the stop control processing unit 34A controls to change the opening degree of the main throttle valve 6 (procedure S113A). At this time, the opening degree of the main throttle valve 6 is such that the amount of air sufficient to sufficiently oxidize and remove the ammonia gas remaining in the intake passage 3 by the three-way catalyst 40 is secured. .. As a result, the ammonia engine 2 is cranked while the air is flowing through the intake passage 3.

Subsequently, the stop control processing unit 34A determines whether or not a predetermined time has elapsed after controlling the main throttle valve 6 to change the opening degree (procedure S114A). The specified time is a time during which the maximum amount of ammonia gas remaining in the intake passage 3 is removed by the flow of air, and is determined in advance by an experiment or the like.

When it is determined that the specified time has elapsed, the stop control processing unit 34A controls to close the main throttle valve 6 (procedure S115A). As a result, the ammonia engine 2 is stopped.

In the above process, the opening degree of the main throttle valve 6 is changed in the procedure S113A, but if the required amount of air is secured, the opening degree of the main throttle valve 6 does not have to be changed. ..

Here, the first control unit 35 executes the procedures S111 and S112. The second control unit 36A executes the procedures S117 and S113A. The third control unit 37A executes the procedures S114A and S115A.

In the engine system 1 as described above, when the ignition switch 30 is turned off, the main injector 5 and the reforming injector 16 are closed first, so that ammonia gas is not supplied to the ammonia engine 2 and the reformer 13. ..

Further, since the reforming throttle valve 15 and the stop valve 20 are closed, air is not supplied to the reformer 13. Therefore, the cranking of the ammonia engine 2 is continued with only air being supplied to the ammonia engine 2.

As a result, the intake passage 3 is purged by air. Therefore, the ammonia gas remaining in the intake passage 3 passes through the combustion chamber 2a of the ammonia engine 2 and flows into the exhaust passage 4. The ammonia gas flowing through the exhaust passage 4 is removed by the three-way catalyst 40 and the SCR catalyst 41 in the same manner as in the first embodiment described above.

Then, when the specified time elapses, the main throttle valve 6 is closed, so that the supply of air to the ammonia engine 2 is stopped. As a result, the ammonia engine 2 coasts several times and then completely stops.

As described above, in the present embodiment, when the stop of the ammonia engine 2 is instructed, the main injector 5 and the reforming injector 16 are closed and controlled to supply the ammonia gas to the ammonia engine 2 and the reformer 13. Stops. In that state, the main throttle valve 6 is opened and controlled, and the ammonia engine 2 is cranked, so that the ammonia engine 2 is cranked while the air flows through the intake passage 3. Therefore, the ammonia gas remaining in the intake passage 3 is forced to flow through the ammonia engine 2 to the exhaust passage 4. Then, the ammonia gas flowing through the exhaust passage 4 is oxidized and removed by the three-way catalyst 40. As a result, when the ammonia engine 2 is stopped, the ammonia gas remaining in the piping forming the intake passage 3 is removed.

Further, in the present embodiment, after the supply of ammonia gas to the ammonia engine 2 and the reformer 13 is stopped, the air does not flow through the air flow path 14 and the reforming gas flow path 18, but flows only through the intake passage 3. Then, the ammonia engine 2 is cranked. Therefore, only the ammonia gas remaining in the intake passage 3 is forcibly flowed to the exhaust passage 4 through the ammonia engine 2, and the ammonia gas remains in the air flow path 14 and the reforming gas flow path 18. It becomes the state of. Therefore, when the ammonia engine 2 is stopped, the ambient environment of the reformer 13 is maintained in a state in which ammonia gas is present, so that oxidative deterioration of the reforming catalyst 13b of the reformer 13 is prevented.

FIG. 7 is a schematic configuration diagram showing an engine system according to a third embodiment of the present invention. In FIG. 7, the engine system 1 of the present embodiment includes an ammonia sensor 45 arranged in the exhaust passage 4. The ammonia sensor 45 is an ammonia detection unit that detects ammonia. The ammonia sensor 45 is arranged, for example, on the downstream side of the SCR catalyst 41 in the exhaust passage 4.

Further, as shown in FIG. 8, the control unit 32 of the engine system 1 of the present embodiment has a stop control processing unit 34B instead of the stop control processing unit 34 of the first embodiment. The stop control processing unit 34B includes the first control unit 35, the second control unit 36, and the third control unit 37B.

The third control unit 37B determines whether or not ammonia gas remains in the exhaust passage 4 based on the detection value of the ammonia sensor 45, and when the ammonia gas does not remain in the exhaust passage 4, the main throttle The valve 6 and the modified throttle valve 15 are closed and controlled.

FIG. 9 is a flowchart showing details of the stop control processing procedure executed by the stop control processing unit 34B.

In FIG. 9, the stop control processing unit 34B sequentially executes the procedures S111 to S113 in the same manner as the stop control processing unit 34 in the first embodiment. Subsequently, the stop control processing unit 34B determines whether or not ammonia gas remains in the exhaust passage 4 based on the detected value of the ammonia sensor 45 (procedure S114B). At this time, the stop control processing unit 34B determines whether or not the amount of ammonia gas remaining in the exhaust passage 4 is equal to or less than a predetermined value, and the amount of ammonia gas remaining in the exhaust passage 4 is equal to or less than a predetermined value. At this time, it may be determined that no ammonia gas remains in the exhaust passage 4. Therefore, if only a small amount of ammonia gas remains to the extent that the presence of ammonia gas does not affect it, it is considered that no ammonia gas remains.

When the stop control processing unit 34B determines that no ammonia gas remains in the exhaust passage 4, the stop control processing unit 34B closes the main throttle valve 6, the reforming throttle valve 15, and the stop valve 20 as in the first embodiment described above. (Procedure S115). Here, the procedures S114B and S115 are executed by the third control unit 37B.

As described above, in the present embodiment, since it is directly detected whether or not the ammonia gas remains in the exhaust passage 4, it is possible to determine with high accuracy whether or not the ammonia gas remaining in the pipe is removed. ..

The present invention is not limited to the above embodiment. For example, in the first embodiment described above, when the ignition switch 30 is turned off, the main injector 5 and the reforming injector 16 are controlled to be closed, and the main throttle valve 6 and the reforming throttle valve 15 are maintained in an open state. However, the form is not particularly limited. When the ignition switch 30 is turned off, the main injector 5, the reforming injector 16, the main throttle valve 6 and the reforming throttle valve 15 are controlled to be closed, and then the main throttle valve 6 and the reforming throttle valve 15 are opened. The starter motor 31 may be controlled so as to crank the ammonia engine 2.

Further, in the second embodiment described above, when the ignition switch 30 is turned off, the main injector 5, the reforming injector 16 and the reforming throttle valve 15 are controlled to be closed, and the main throttle valve 6 is opened. It is maintained, but not particularly limited to its form. When the ignition switch 30 is turned off, the main injector 5, the reforming injector 16, the main throttle valve 6 and the reforming throttle valve 15 are controlled to be closed, and then the main throttle valve 6 is controlled to be opened, and ammonia is used. The starter motor 31 may be controlled so as to crank the engine 2.

Further, in the first embodiment described above, the stop valve 20 is arranged between the reformed gas cooler 19 and the intake passage 3 in the reformed gas flow path 18, but the form is not particularly limited and the stop valve 20 is not particularly limited. 20 may be omitted.

Further, in the above embodiment, a plurality of main injectors 5 for injecting ammonia gas into each combustion chamber 2a of the ammonia engine 2 are attached to the ammonia engine 2, but the number of main injectors 5 is one. May be good. In this case, the main injector 5 may be arranged so as to inject ammonia gas into the intake passage 3.

Further, in the above embodiment, the air flow path 14 through which the air supplied to the reformer 13 flows is branched and connected to the intake passage 3, but the present invention is not particularly limited to that form, and the intake air connected to the ammonia engine 2 is connected. Air may be supplied to the air passage 14 from a route different from that of the passage 3. In this case, it is possible to prevent the influence of the pulsation of the intake passage 3.

Further, in the above embodiment, the reforming injector 16 for injecting ammonia gas toward the reformer 13 is connected to the ammonia gas flow path 21, but the embodiment is not particularly limited, and for example, the reforming injector. A flow rate adjusting valve may be used instead of 16. In this case, the ammonia gas flow path 21 is connected to the air flow path 14, and a flow rate adjusting valve is provided in the ammonia gas flow path 21. By using the flow rate adjusting valve, ammonia gas can be continuously supplied to the reformer 13. At this time, the flow rate adjusting valve constitutes an ammonia supply valve.

Further, although the engine system 1 of the above embodiment is mounted on an engine type vehicle, the present invention can be applied to, for example, a high lid type vehicle.

1 ... engine system, 2 ... ammonia engine (engine), 3 ... intake passage, 4 ... exhaust passage, 5 ... main injector (ammonia injection valve), 6 ... main throttle valve (first throttle valve), 8 ... exhaust catalyst unit , 13 ... Reformer (reformer), 13b ... Reform catalyst (catalyst), 14 ... Air flow path, 15 ... Reform throttle valve (second throttle valve), 16 ... Reform injector (ammonia supply valve) , 18 ... reforming gas flow path, 20 ... stop valve, 30 ... ignition switch (stop indicator), 31 ... starter motor (motor), 32 ... control unit, 35 ... first control unit, 36, 36A ... second Control unit, 37, 37A, 37B ... Third control unit, 40 ... Three-way catalyst (first catalyst), 41 ... SCR catalyst (second catalyst), 45 ... Ammonia sensor (ammonia detection unit).

Claims (6)

With the engine
The intake passage through which the air supplied to the engine flows and
The exhaust passage through which the exhaust gas generated from the engine flows, and
An exhaust catalyst unit arranged in the exhaust passage and
An ammonia injection valve that injects ammonia toward the engine,
A first throttle valve arranged in the intake passage and controlling the flow rate of air supplied to the engine.
A reforming unit having a catalyst that decomposes the ammonia into hydrogen and reforming the ammonia to generate a reformed gas containing the hydrogen.
An air flow path through which the air supplied to the reforming unit flows, and
An ammonia supply valve that supplies the ammonia to the reforming part,
A second throttle valve arranged in the air flow path and controlling the flow rate of the air supplied to the reforming unit, and
A reformed gas flow path through which the reformed gas generated by the reformed portion flows toward the engine, and
The motor that starts the engine and
A stop instruction unit that instructs the engine to stop,
The ammonia injection valve, the first throttle valve, the ammonia supply valve, and a control unit for controlling the second throttle valve are provided.
The exhaust catalyst unit has a first catalyst that oxidizes and removes the ammonia.
The control unit is
When the stop instruction unit instructs the engine to stop, the first control unit that closes and controls the ammonia injection valve and the ammonia supply valve.
After the control process by the first control unit is executed, at least the first throttle valve of the first throttle valve and the second throttle valve is opened and controlled, and the second control unit that cranks the engine. ,
An engine system including a first throttle valve and a third control unit that closes and controls at least the first throttle valve of the second throttle valve after the control process by the second control unit is executed. The first aspect of claim 1, wherein the exhaust catalyst unit is arranged on the downstream side of the first catalyst in the exhaust passage, and further has a second catalyst that collects and removes the ammonia that has passed through the first catalyst. Engine system. After the control process by the first control unit is executed, the second control unit opens and controls the first throttle valve and the second throttle valve, and cranks the engine.
The engine system according to claim 1 or 2, wherein the third control unit closes and controls the first throttle valve and the second throttle valve after the control process by the second control unit is executed. Further equipped with a stop valve for opening and closing the reformed gas flow path,
After the control process by the first control unit is executed, the second control unit opens and controls the first throttle valve, closes and controls the second throttle valve and the stop valve, and shuts down the engine. Let me rank
The engine system according to claim 1 or 2, wherein the third control unit closes and controls the first throttle valve after the control process by the second control unit is executed. The third control unit determines whether or not a specified time has elapsed since the control process by the second control unit was executed, and when the specified time has elapsed, the first throttle valve and the second throttle The engine system according to any one of claims 1 to 4, wherein at least the first throttle valve is closed-controlled among the valves. Further provided with an ammonia detection unit, which is arranged in the exhaust passage and detects the ammonia,
The third control unit determines whether or not the ammonia remains in the exhaust passage based on the detection value of the ammonia detection unit, and when the ammonia does not remain in the exhaust passage, the third control unit determines. The engine system according to any one of claims 1 to 4, wherein at least the first throttle valve of the first throttle valve and the second throttle valve is closed-controlled.

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