WO2020195426A1

WO2020195426A1 - Ammonia engine

Info

Publication number: WO2020195426A1
Application number: PCT/JP2020/007055
Authority: WO
Inventors: 竹内秀隆
Original assignee: 株式会社豊田自動織機
Priority date: 2019-03-25
Filing date: 2020-02-21
Publication date: 2020-10-01
Also published as: JP2020159211A; JP7074103B2

Abstract

An ECU (10) in this ammonia engine (100) executes: first control in which, when a start-up signal is input, the degree of opening of a reforming throttle (32) is complete closure, and the degree of opening of a stop valve (38) is a predefined initial degree of opening; second control in which, with the degree of opening of the reforming throttle (32) being complete closure, a reforming injector (35) is made to inject fuel in a predefined fuel injection pattern; and third control in which, with the degree of opening of the reforming throttle (32) being complete closure, and on the basis of the amount of fuel injected in the second control and a predefined estimated displacement volume, a displacement time by which the remaining gas in a reformer is to be displaced by the fuel injected in the second control is calculated, and the degree of opening of the stop valve (38) is decreased such that the degree of opening of the stop valve (38) reaches complete closure no later than the displacement time.

Description

Ammonia engine

The present invention relates to an ammonia engine including a reformer that reforms fuel into reforming gas.

Conventionally, a reformer for reforming fuel into reforming gas, a reforming flow path provided with the reformer, and a reformer downstream valve provided on the downstream side of the reformer in the reforming flow path. An engine including the above is known (for example, Patent Document 1). In the engine described in Patent Document 1, after the output of the engine start command, when it is determined that the catalyst is activated and the reformer can generate reforming gas, the reformer downstream valve is opened and modified. Quality gas is supplied to the intake flow path and the starter is activated.

Japanese Unexamined Patent Publication No. 2007-11342

When starting the ammonia engine, the reformer is warmed up. It is desirable that the reformer be warmed up in a reducing atmosphere in order to suppress deterioration due to oxidation, for example. To create a reducing atmosphere, for example, ammonia as a fuel may be used to replace the residual gas in the reformer. However, in this case, the ammonia gas flowing out to the intake flow path through the reforming flow path may leak to the external environment through the intake flow path or the exhaust flow path of the ammonia engine.

An object of the present invention is to provide an ammonia engine capable of warming up the reformer in a reducing atmosphere while suppressing leakage of ammonia at the time of starting.

The ammonia engine according to one aspect of the present invention is an ammonia engine including a reformer that reforms ammonia as a fuel into a reforming gas, and has an intake flow path for passing the intake air of the ammonia engine and the reformer. It is provided in a reforming flow path for flowing reforming air through the reformer and for flowing reforming gas from the reformer to the intake flow path, and on the upstream side of the reformer in the reforming flow path. A reforming fuel injection valve provided between the reformer upstream valve and the reformer upstream valve and the reformer in the reforming flow path and injecting fuel into the reforming flow path, and a reforming flow path. The reformer downstream valve provided on the downstream side of the reformer, the start signal output unit that outputs the start signal for operating the starter of the ammonia engine, and the amount of fuel injected by the reformer fuel injection valve. A control unit for controlling the reformer upstream valve, the reforming fuel injection valve, and the reformer downstream valve is provided based on the start signal, and the control unit is modified when the start signal is input. A state in which the opening of the reformer upstream valve is fully closed and the opening of the reformer upstream valve is fully closed by executing the first control in which the opening of the reformer downstream valve is set to a predetermined initial opening. Then, the second control for injecting fuel into the reforming fuel injection valve in a predetermined fuel injection pattern is executed, and the fuel injected in the second control with the opening of the reformer upstream valve fully closed. The replacement timing at which the residual gas of the reformer is replaced by the fuel injected in the second control is calculated based on the injection amount of the reformer and the predetermined replacement estimated volume amount, and the reformer downstream valve is replaced at the latest at the replacement timing. The third control for reducing the opening degree of the reformer downstream valve is executed so that the opening degree is fully closed.

In the ammonia engine according to one aspect of the present invention, when the start signal is input, the opening degree of the reformer upstream valve is fully closed, and the opening degree of the reformer upstream valve is fully closed. The second control for injecting fuel into the reforming fuel injection valve is executed. As a result, it is possible to prevent the fuel ammonia from leaking to the external environment through the reformer upstream valve. Further, when the opening degree of the reformer upstream valve is fully closed, the opening degree of the reformer downstream valve is reduced so that the opening degree of the reformer downstream valve is fully closed at the latest at the replacement timing. 3 Control is executed. As a result, the residual gas of the reformer can be replaced by using the fuel injected by the reforming fuel injection valve while suppressing the leakage of fuel ammonia to the external environment through the reformer downstream valve. Be done. As a result, with the opening of the reformer upstream valve fully closed and the opening of the reformer downstream valve fully closed, the fuel injected by the reforming fuel injection valve created a reducing atmosphere. The reformer is warmed up. Therefore, according to the ammonia engine according to one aspect of the present invention, it is possible to warm up the reformer in a reducing atmosphere while suppressing the leakage of ammonia at the time of starting.

In the ammonia engine according to one aspect of the present invention, in the second control, the control unit injects fuel into the reforming fuel injection valve in the first fuel injection pattern in which fuel is continuously injected as the fuel injection pattern. In 3 control, the opening degree of the reformer downstream valve is maintained at the initial opening until the replacement timing, and the opening degree of the reformer downstream valve is fully closed at the replacement timing. May be reduced. In this case, the opening degree of the reformer downstream valve is fully closed with most of the residual gas pushed out from the reformer by the fuel injected by the reforming fuel injection valve. Therefore, the reformer can be made into a reducing atmosphere more reliably.

In the engine according to one aspect of the present invention, in the second control, the control unit injects fuel into the reforming fuel injection valve in the second fuel injection pattern in which the fuel is intermittently injected as the fuel injection pattern, and the third In the control, the opening degree of the reformer downstream valve may be gradually reduced according to the increase in the injection amount of the fuel injected in the second control. In this case, since the fuel is injected in the second fuel injection pattern in which the fuel is injected intermittently, the fuel is suppressed from being mixed with the residual gas of the reformer, and the reformer is more reliably made into a reducing atmosphere. be able to. In addition, since the opening degree of the reformer downstream valve is gradually reduced as the fuel injection amount increases, it is suppressed that the pressure inside the reformer suddenly increases, and the pressure balance allows the reformer fuel injection valve to be used. It is possible to extend the time until the fuel cannot be injected. Therefore, it is possible to prevent the fuel from being difficult to be injected from the reforming fuel injection valve due to the increase in pressure.

In the ammonia engine according to one aspect of the present invention, the reformer is a mixture of a reforming catalyst for reforming fuel and a residual gas provided so as to cover the inflow surface of the reforming catalyst upstream of the reforming catalyst. It may have a restraining member. In this case, the mixture of the fuel injected by the reforming fuel injection valve and the residual gas of the reformer is physically suppressed by the residual gas mixing suppressing member. As a result, the fuel can suitably exert the action of pushing the residual gas out of the reformer.

According to the present invention, it is possible to warm up the reformer in a reducing atmosphere while suppressing the leakage of ammonia at the time of starting.

It is a schematic block diagram of the ammonia engine which concerns on one Embodiment. It is a block diagram of the structure for the control of the ammonia engine of FIG. It is a top view of an example of the residual gas mixing suppression member. It is a timing chart which shows the operation example of the ammonia engine of FIG. It is a timing chart which shows the other operation example of the ammonia engine of FIG. It is a flowchart which shows the reformer warm-up process of the ECU of 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 of an engine of one embodiment. As shown in FIG. 1, the ammonia engine 100 of the present embodiment includes an ECU [Electronic Control Unit] (control unit) 10, an engine main unit 20, and a reforming unit 30. The ammonia engine 100 is an internal combustion engine that burns an air-fuel mixture containing ammonia (NH ₃ ), and is configured as, for example, a 4-cycle reciprocating engine. The ammonia engine 100 is mounted on an industrial vehicle such as a forklift that performs cargo handling work. The ammonia engine 100 may be mounted on other vehicles such as passenger cars, trucks, and buses.

The engine main part 20 includes an engine main body 21, an intake flow path 22, a main throttle 23, a main injector 24, an exhaust flow path 25, a three-way catalyst 26, and SCR [Selective Catalyst] as an example of an ammonia adsorption catalyst. Reduction] 27 and.

The engine body 21 is the main part of the ammonia engine 100 for burning the air-fuel mixture, and is composed of a cylinder block, a cylinder head, a piston, and the like. In the engine body 21, a combustion chamber is defined by a cylinder block, a cylinder head, and a piston. The cylinder head is provided with, for example, a spark plug. The engine body 21 has a starter for starting the ammonia engine 100.

The intake flow path 22 is a flow path for passing intake air to the engine body 21 of the ammonia engine 100, and includes, for example, piping, a surge tank, an intake manifold, an intake port, and the like. At the inlet of the intake flow path 22, for example, an air cleaner 28 for filtering the intake air is provided.

The main throttle 23 is a valve that adjusts the flow rate of the air sucked through the air cleaner 28. The main throttle 23 is provided on the downstream side of the air cleaner 28 in the intake flow path 22. The main throttle 23 is, for example, an electronically controlled throttle valve. The main throttle 23 is electrically connected to the ECU 10. The operation of the main throttle 23 is controlled by the ECU 10.

The main injector 24 is a valve that injects fuel into the intake flow path 22. The main injector 24 is provided on the downstream side of the main throttle 23 in the intake flow path 22. The number of main injectors 24 may be one or a plurality. When the number of main injectors 24 is one, the main injectors 24 may be provided, for example, in the intake port of the engine body 21. When the number of main injectors 24 is plural, the main injectors 24 may be provided, for example, in the surge tank of the engine body 21. The main injector 24 injects ammonia gas that does not contain reforming gas as fuel. The main injector 24 is electrically connected to the ECU 10. The operation of the main injector 24 is controlled by the ECU 10. The main injector 24 may be provided on the upstream side of the main throttle 23 in the intake flow path 22. Alternatively, instead of the main injector 24, fuel may be supplied from a fuel supply device such as a mixer provided in the intake flow path 22.

The exhaust flow path 25 is a flow path through which the exhaust gas from the engine body 21 of the ammonia engine 100 flows, and includes, for example, an exhaust port, piping, an aftertreatment device, a silencer, and the like. The three-way catalyst 26 and the SCR 27 as an example of the ammonia adsorption catalyst are provided in the exhaust flow path 25 in this order. The three-way catalyst 26 is adapted to purify the oxidation of H ₂ in the exhaust gas, a catalyst for purifying by reducing NOx in the exhaust gas. SCR27 is a selective reduction catalyst that purifies NOx contained in exhaust gas by a reduction reaction. The SCR27 may be a catalyst made of another material (for example, zeolite-based) that adsorbs ammonia.

The reforming section 30 includes a reforming flow path 31, a reforming throttle (reformer upstream valve) 32, an NH ₃ tank 33, a vaporizer 34, and a reforming injector (reformer fuel injection valve). It has 35, a reformer 36, a cooler 37, and a stop valve (reformer downstream valve) 38.

The reforming flow path 31 is a flow path for reforming fuel into reforming gas. The reforming flow path 31 is provided, for example, so as to connect the upstream side of the main throttle 23 and the downstream side of the main throttle 23 in the intake flow path 22. The reforming flow path 31 allows reforming air to flow from the upstream side of the main throttle 23 in the intake flow path 22 to the reformer 36, and from the reformer 36 to the downstream side of the main throttle 23 in the intake flow path 22. Distribute the reformed gas. The reforming air is the air used for reforming the fuel into a reforming gas in the reformer 36. A reformer 36 is provided in the reforming flow rate 31. The reforming flow path 31 is not connected to the upstream side of the main throttle 23 in the intake flow path 22, and the outside air sucked through the dedicated air cleaner can be distributed to the reformer 36 as reforming air. It may be configured in.

The reforming throttle 32 is a valve that adjusts the flow rate of reforming air. The reforming throttle 32 is provided on the upstream side of the reformer 36 in the reforming flow path 31. The reforming throttle 32 is, for example, an electronically controlled throttle valve. The reforming throttle 32 is electrically connected to the ECU 10. The operation of the reforming throttle 32 is controlled by the ECU 10.

The opening degree of the reforming throttle 32 can be changed continuously or stepwise between fully closed and fully opened by controlling the ECU 10. The fully closed state of the reforming throttle 32 means an opening degree at which gas cannot flow through the reforming throttle 32. The fully closed reforming throttle 32 may be the minimum opening degree of the reforming throttle 32, or a minute amount within a range in which gas flow through the reforming throttle 32 is substantially impossible. It may be the opening degree. Fully opening the reforming throttle 32 means that the opening degree of the reforming throttle 32 is the largest.

The NH ₃ tank 33 is a tank for storing ammonia as a fuel. The NH ₃ tank 33 is not particularly limited, but for example, a general steel cylinder can be used. In the NH ₃ tank 33, for example, ammonia is pressurized so as to maintain a liquid state. The NH ₃ tank 33 is connected to the vaporizer 34.

The vaporizer 34 vaporizes the ammonia derived from the NH ₃ tank 33. The vaporizer 34 is connected to the main injector 24 and the reforming injector 35. The vaporized ammonia (ammonia gas) is guided to each of the main injector 24 and the reforming injector 35. A regulator that regulates the pressure of ammonia gas may be provided between the vaporizer 34, the main injector 24, and the reforming injector 35.

The reforming injector 35 is a fuel injection valve that injects reforming ammonia gas (fuel) into the reforming flow path 31. The reforming injector 35 is provided on the upstream side of the reformer 36 in the reforming flow path 31. The reforming injector 35 is provided between the reforming throttle 32 and the reformer 36 in the reforming flow path 31. The number of reforming injectors 35 is, for example, one. The reforming injector 35 is electrically connected to the ECU 10. The operation of the reforming injector 35 is controlled by the ECU 10.

The reformer 36 reforms the reforming ammonia gas to generate the reforming gas. The reformer 36 here reforms the reforming ammonia gas into a reforming gas containing hydrogen gas (H ₂ ). The reformer 36 has a reformer heater 36a, a reforming catalyst 36b for reforming ammonia gas for reforming, and a perforated plate member (residual gas mixing suppressing member) 36c. The reformer 36 has, for example, a case having a substantially cylindrical outer shape in which the inlet and the outlet are reduced in diameter, and the reformer heater 36a, the reforming catalyst 36b, and the perforated plate member 36c are in the axial direction of the case. It is arranged in the case so as to line up along. At the inlet of the case of the reformer 36, the reforming flow path 31 is connected to substantially the center of the cross section of the case when viewed along the axial direction of the case (hereinafter, also referred to as a cross-sectional view of the case). The perforated plate member 36c does not necessarily have to be provided. The order of the reformer heater 36a and the perforated plate member 36c may be reversed.

The reformer heater 36a is provided on the upstream side of the reforming catalyst 36b and is used for warming up the reforming catalyst 36b. The reformer heater 36a is, for example, a substantially spiral electric heater. The inflow surface of the reformer heater 36a extends along the inflow surface of the reformer catalyst 36b. The inflow surface is a surface of the reforming flow path 31 facing upstream in the gas flow direction. The outflow surface of the reformer heater 36a extends along the outflow surface of the reformer catalyst 36b. The outflow surface is a surface of the reforming flow path 31 facing the downstream side in the gas flow direction. The reformer heater 36a is electrically connected to the ECU 10. The operation of the reformer heater 36a is controlled by the ECU 10. The reformer heater 36a may be a small combustor.

The reforming catalyst 36b reforms the reforming ammonia gas injected by the reforming injector 35 with the reforming air. The reforming catalyst 36b here is an ATR [Autothermal Reformer] type ammonia reforming catalyst. The reforming catalyst 36b utilizes the heat of the reformer heater 36a or the reaction heat of the reforming catalyst 36b to thermally dissociate the reforming ammonia gas with the reforming air, thereby causing hydrogen gas and ammonia. Generates reformed gas containing gas. The reforming catalyst 36b here is mainly used in a reducing atmosphere (that is, an atmosphere in an NH _3- rich state) in order to suppress deterioration due to oxidation, for example. A low temperature reaction catalyst may be used for the reforming catalyst 36b.

The perforated plate member 36c is provided upstream of the reforming catalyst 36b along the inflow surface of the reforming catalyst 36b. The perforated plate member 36c is, for example, a plate-shaped member provided on the upstream side of the reformer heater 36a. The perforated plate member 36c is arranged so as to cover substantially the entire inflow surface of the reformer heater 36a.

FIG. 3 is a plan view of the perforated plate member 36c. FIG. 3 shows the inflow surface of the perforated plate member 36c (in the cross-sectional view of the case) when viewed along the axial direction of the case. Note that, for convenience, only the perforated plate member 36c is shown in FIG.

As shown in FIG. 3, the outer shape of the perforated plate member 36c is, for example, substantially a disk shape, and a plurality of through holes H1, H2, H3, and H4 are formed. The through holes H1, H2, H3, and H4 are gas flow holes for communicating the space on the upstream side and the space on the downstream side of the perforated plate member 36c in the reformer 36.

The total opening area of the through holes H1, H2, H3, and H4 is set according to, for example, the injection amount of the reforming ammonia gas injected by the reforming injector 35. In the through holes H1, H2, H3, and H4, for example, the through holes have an opening area that allows the reforming ammonia gas to flow uniformly into the inflow surfaces of the reformer heater 36a and the reforming catalyst 36b. At least one of the size of the hole diameter and the number of through holes is adjusted.

For example, in the perforated plate member 36c, the diameter of the through hole H1 is smaller than the diameter of the through hole H2. The diameter of the through hole H2 is smaller than the diameter of the through hole H3. The diameter of the through hole H3 is smaller than the diameter of the through hole H4. That is, the through hole H1 has the smallest diameter among the through holes H1, H2, H3, and H4. The through hole H4 has the largest diameter among the through holes H1, H2, H3, and H4.

For example, in the perforated plate member 36c, the number of through holes H2 is larger than the number of through holes H1. The number of through holes H3 is larger than the number of through holes H2. The number of through holes H4 is larger than the number of through holes H3.

Further, the through holes H1, H2, H3, and H4 are arranged so as to have an opening area of the through holes so that the reforming ammonia gas can uniformly flow into the inflow surfaces of the reformer heater 36a and the reforming catalyst 36b. Has been done.

For example, the through holes H1, H2, H3, and H4 are arranged so as to be substantially radial in the radial direction in the circular portion of the perforated plate member 36c. Each of the through holes H1, H2, H3, and H4 is arranged in the circular portion of the perforated plate member 36c so that through holes having the same diameter are arranged on the circumference having the same radius from the center. The through hole H1 is provided in the central region of the circular portion of the perforated plate member 36c. The through hole H2 is provided in a region surrounding the region where the through hole H1 is provided in the circular portion of the perforated plate member 36c. The through hole H3 is provided in a region surrounding the region where the through hole H2 is provided in the circular portion of the perforated plate member 36c. The through hole H4 is provided in the region of the outer edge portion of the circular portion surrounding the region where the through hole H3 is provided in the circular portion of the perforated plate member 36c.

Here, since the reforming flow path 31 with respect to the inlet of the reformer 36 is connected in the positional relationship as described above, the reforming ammonia gas flowing into the reformer 36 from the reforming flow path 31 Inflows into the reformer 36 on the inlet side of the case of the reformer 36 with an inflow distribution such that the density becomes higher toward the center of the cross section of the case. In the perforated plate member 36c, the inflowing reforming ammonia gas flows through the through holes H1, H2, H3, and H4 as described above in the outer edge portion of the circular portion of the perforated plate member 36c than in the central portion. Easy to do. Therefore, the reforming ammonia gas that has flowed into the reformer 36 with the inflow distribution as described above is equalized in the cross-sectional view of the case by passing through the through holes H1, H2, H3, and H4 of the perforated plate member 36c. To. Therefore, the perforated plate member 36c brings the flow of the reforming ammonia gas to the reformer heater 36a and the reforming catalyst 36b closer to the parallel flow.

Further, since the space on the upstream side and the space on the downstream side of the perforated plate member 36c in the reformer 36 are partitioned by the perforated plate member 36c to a certain extent, the reforming ammonia gas and the reformer It is physically suppressed from being mixed with the residual gas of. For example, when the reforming ammonia gas is injected by the reforming injector 35, it is possible to prevent the reforming ammonia gas and the residual gas of the reformer from being directly mixed by the force of the injection. Further, when the reforming ammonia gas is injected by the reforming injector 35, the pressure in the space on the upstream side of the perforated plate member 36c is higher than that in the space on the downstream side, so that the space on the upstream side is on the downstream side. Ammonia gas for reforming easily flows unilaterally into the space through the through holes H1, H2, H3, and H4. Therefore, in the space on the downstream side, the reforming ammonia gas pushes out the residual gas in a plane toward the downstream side.

The cooler 37 is provided on the downstream side of the reformer 36 in the reforming flow path 31. The cooler 37 cools the reformed gas from the reformer 36. As the cooler 37, for example, a heat exchanger using the cooling water of the ammonia engine 100 or the running wind of the vehicle as a low temperature heat source can be used.

The stop valve 38 is provided on the downstream side of the reformer 36 in the reforming flow path 31. The stop valve 38 here is, for example, an electromagnetic valve provided between the cooler 37 and the intake flow path 22. The stop valve 38 adjusts the flow rate of the gas flowing from the reforming flow path 31 to the intake flow path 22. The stop valve 38 is electrically connected to the ECU 10. The operation of the stop valve 38 is controlled by the ECU 10.

The opening degree of the stop valve 38 can be changed continuously or stepwise between fully closed and fully opened by the control of the ECU 10. The fully closed state of the stop valve 38 means an opening degree at which gas cannot flow through the stop valve 38. The fully closed stop valve 38 may be the minimum opening of the stop valve 38, or may be a minute opening within a range in which gas flow through the stop valve 38 is substantially impossible. Good. Fully opening the stop valve 38 means that the opening degree of the stop valve 38 is the largest.

FIG. 2 is a block diagram of a configuration for controlling the ammonia engine of FIG. As shown in FIG. 2, the ECU 10 is electrically connected to the key switch (starting signal output unit) 1.

The ECU 10 is an electronic control unit that controls the ammonia engine 100. The ECU 10 is a controller having a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a communication circuit, and the like. In the ECU 10, for example, various functions are realized by loading the program stored in the ROM into the RAM and executing the program loaded in the RAM in the CPU. The ECU 10 may be composed of a plurality of electronic units.

The key switch 1 is a switch that outputs a start signal for starting the ammonia engine 100. The key switch 1 is, for example, an ignition switch for operating the starter of the engine body 21 by its operation. The key switch 1 is operated by being rotated as the key is inserted. The key switch 1 has a key cylinder including a physical contact inside. A plurality of switch states of the key cylinder can be switched according to the operation position of the key switch 1. Examples of the switch state include OFF, ON (key switch on) and ST (starter switch on). The key switch 1 outputs a signal related to the switch state to the ECU 10. In addition, instead of the key switch 1, a button for outputting a start signal for starting the ammonia engine 100 may be used.

The key switch 1 outputs an OFF signal to the ECU 10 by switching the driving circuit on the vehicle side to the open state, for example, when the switch state is OFF. The key switch 1 outputs an ON signal to the ECU 10 by switching the driving circuit on the vehicle side to the closed state when the switch state is ON, for example. The key switch 1 outputs an ST signal (starting signal) to the ECU 10 by switching the starting circuit on the vehicle side to the closed state, for example, when the switch state is ST. The key switch 1 may be configured by using an electronic circuit that outputs each of the above signals in response to an operation by the driver of the vehicle.

Next, the functional configuration of the ECU 10 will be described. The ECU 10 includes an engine state acquisition unit 11, a first control execution unit 12, a second control execution unit 13, a third control execution unit 14, and a start permission unit 15.

The engine state acquisition unit 11 acquires the engine state, which is the state of the ammonia engine 100. The engine state acquisition unit 11 acquires the switch state of the key switch 1 described above based on the signal regarding the switch state from the key switch 1. When the start signal is input, the engine state acquisition unit 11 determines, for example, that the ammonia engine 100 is in the start preparation state. The start-preparation state is a state in which preparations are made for starting the ammonia engine 100. In the start preparation state, after the start signal is input, the reforming catalyst 36b is made into a reducing atmosphere and the reforming catalyst 36b is warmed up. When the warm-up of the reforming catalyst 36b is completed, the start preparation state is completed and the starter is operated. The operation of the starter may be started before the start preparation state is completed.

When the engine state acquisition unit 11 determines that the first control execution unit 12 is in the start preparation state, the first control execution unit 12 energizes the reformer heater 36a. As a result, the temperature of the reformer heater 36a rises. The heat of the reformer heater 36a is transferred to the reforming catalyst 36b by the flow of the reforming ammonia gas to the downstream side when the reforming ammonia gas is injected by the reforming injector 35 in the second control described later. Will be done.

When the engine state acquisition unit 11 determines that the first control execution unit 12 is in the start preparation state, the first control execution unit 12 fully closes the opening degree of the reforming throttle 32 and opens the opening degree of the stop valve 38 to a predetermined initial position. The first control is executed. When the engine state acquisition unit 11 determines that the first control execution unit 12 is in the start preparation state, the first control execution unit 12 executes the first control while, for example, the reformer heater 36a is energized.

The initial opening degree of the stop valve 38 is an initial value of the opening degree of the stop valve 38 in the third control described later. The initial opening degree is larger than the fully closed stop valve 38. The initial opening degree can be set to such an opening degree that the gas (residual gas) remaining in the reformer 36 before the start-preparation state can be discharged to the outside of the reformer 36. The initial opening degree may be stored in the ECU 10 in advance.

The second control execution unit 13 executes the second control with the opening degree of the reforming throttle 32 fully closed. The second control is a control in which the reforming injector 35 is injected with the reforming ammonia gas in a predetermined fuel injection pattern. The fuel injection pattern can be a pattern in which the valve opening time of the reforming injector 35 is defined in time series. The fuel injection pattern may be defined as a time series from the time when the start signal is input. For example, the second control execution unit 13 maintains the opening degree of the reforming throttle 32 in a fully closed state after the first control described above, and executes the second control. A specific example of the second control will be described later.

The third control execution unit 14 executes the third control with the opening degree of the reforming throttle 32 fully closed. The third control is a control that reduces the opening degree of the stop valve 38 so that the opening degree of the stop valve 38 reaches the fully closed position at the latest at the replacement timing.

The replacement timing is the timing at which the residual gas of the reformer 36 is replaced by the reforming ammonia gas injected in the second control. "The residual gas of the reformer 36 is replaced by the reforming ammonia gas" means that the reforming catalyst 36b has a reducing atmosphere with the reforming ammonia gas. The replacement timing may be, for example, a time when it is estimated that the residual gas of the reformer 36 is completely replaced by the reforming ammonia gas, or the residual gas of the reformer 36 is replaced by the reforming ammonia gas. It may be at a time when it is estimated that the gas has been replaced at a predetermined rate.

The third control execution unit 14 calculates the replacement timing based on the time-integrated value of the injection amount of the reforming ammonia gas injected in the second control and the estimated replacement volume amount. The replacement estimated volume amount is a volume threshold value for estimating whether or not the residual gas of the reformer 36 has been replaced by the reforming ammonia gas. The estimated replacement volume may be at least the volume value from the reforming throttle 32 to the stop valve 38. The estimated replacement volume can be, for example, the volume value of the reforming flow path 31 from the reforming throttle 32 to the stop valve 38 and the reformer 36.

The injection amount of the reforming ammonia gas here is the injection amount of the reforming ammonia gas for pushing the residual gas out of the reformer 36 by the reforming ammonia gas (the injection amount of the reforming ammonia gas for starting). Means. The injection amount of the reforming ammonia gas is based on, for example, the injection pressure of the reforming injector 35 (for example, the discharge pressure of the NH ₃ tank 33 or the regulation pressure of the regulator) and the injection time of the reforming ammonia gas. It can be calculated.

For example, the third control execution unit 14 maintains the opening degree of the reforming throttle 32 in a fully closed state after the first control described above, and is injected by the second control while executing the second control. The third control is executed based on the injection amount of the reforming ammonia gas.

Specific examples of the second control and the third control will be described with reference to FIGS. 4 and 5.

As an example, FIG. 4 is a timing chart showing an operation example of the ammonia engine of FIG. FIG. 4A shows a change over time in the injection pressure of the reforming ammonia gas injected by the reforming injector 35 so as to correspond to the first fuel injection pattern. The period during which the injection pressure is P1 means the valve opening period of the reforming injector 35. FIG. 4B shows the change over time in the amount of gas replacement. FIG. 4C shows the change over time in the opening degree of the stop valve 38.

As shown in FIGS. 4A to 4C, a start signal is input at time t1 and the engine state acquisition unit 11 determines the start preparation state. At time t1, the first control execution unit 12 starts energizing the reformer heater 36a. At time t1, the first control execution unit 12 executes the first control. Specifically, the first control execution unit 12 sets the opening degree of the reforming throttle 32 to be fully closed (not shown), and the opening degree of the stop valve 38 to be the initial opening degree S1. Here, the opening degree of the stop valve 38 is defined as the initial opening degree S1. The opening degree of the stop valve 38 may be set to the initial opening degree S1 in advance before the time t1 as in the example of FIG. 4C. After that, the second control execution unit 13 and the third control execution unit 14 maintain the state in which the opening degree of the reforming throttle 32 is fully closed, and the second control and the third control are executed.

As shown in FIG. 4A, reforming from the reforming injector 35 by the second control execution unit 13 at time t2 (for example, when the energizing time of the reformer heater 36a reaches a predetermined time). Ammonia gas injection is started. After time t2, the second control execution unit 13 maintains the valve opening of the reforming injector 35 at a predetermined injection pressure P1, and the reforming ammonia gas is continuously injected. That is, in the second control, the second control execution unit 13 injects the reforming ammonia gas into the reforming injector 35 in the first fuel injection pattern in which the reforming ammonia gas is continuously injected.

As shown in FIG. 4B, at time t2, the third control execution unit 14 sets the injection pressure of the reforming injector 35 and the reforming ammonia gas injection time (elapsed time from time t2). Based on this, the calculation of the injection amount of the reforming ammonia gas and the calculation of the gas replacement amount are started. The gas replacement amount is a time-integrated value of the injection amount of the reforming ammonia gas injected by the reforming injector 35. With the passage of time from the time t2, the amount of gas replacement calculated by the third control execution unit 14 increases. At time t3, the gas replacement amount calculated by the third control execution unit 14 reaches the replacement estimated volume amount Th. That is, the time t3 is the replacement timing.

As shown in FIG. 4C, at time t3, the opening degree of the stop valve 38 is fully closed by the third control execution unit 14. That is, in the third control, the third control execution unit 14 maintains the opening degree of the stop valve 38 at the initial opening degree until the replacement timing, and stops so as to fully close the opening degree of the stop valve 38 at the replacement timing. The opening degree of the valve 38 is reduced.

In the example of FIG. 4C, at time t3, the opening degree of the stop valve 38 reduced by the third control reaches full closure. That is, in the third control of FIG. 4C, the opening degree of the stop valve 38 is reduced so that the opening degree of the stop valve 38 is fully closed at the latest at the replacement timing.

In the examples of FIGS. 4 (a) to 4 (c) described above, since the opening degree of the reforming throttle 32 is fully closed by the first control, the reforming injector 35 injects the gas in the second control. It is possible to prevent the reformed ammonia gas from flowing (backflow) through the reforming throttle 32. Since the opening degree of the stop valve 38 is set to the initial opening degree S1 by the first control and the reforming ammonia gas is continuously injected by the second control, the reformer 36 is made by the reforming ammonia gas. Residual gas is pushed out. Further, since the opening degree of the stop valve 38 is fully closed at the replacement timing by the third control, the opening degree of the reforming throttle 32 is fully closed and the opening degree of the stop valve 38 is fully closed. Then, the reformer 36, which has a reducing atmosphere with the fuel injected by the reforming injector 35, is warmed up.

As another example, FIG. 5 is a timing chart showing another operation example of the ammonia engine of FIG. FIG. 5A shows a change over time in the injection pressure of the reforming ammonia gas injected by the reforming injector 35 so as to correspond to the second fuel injection pattern. The period during which the injection pressure is P1 means the valve opening period of the reforming injector 35. FIG. 5B shows the change over time in the amount of gas replacement. FIG. 5C shows a change over time in the opening degree of the stop valve 38.

As shown in FIGS. 5A to 5C, a start signal is input at time t4, and the engine state acquisition unit 11 determines the start preparation state. At time t4, as in the example of FIG. 4, the first control execution unit 12 starts energization of the reformer heater 36a and executes the first control. After that, the second control execution unit 13 and the third control execution unit 14 maintain the state in which the opening degree of the reforming throttle 32 is fully closed, and the second control and the third control are executed.

As shown in FIG. 5A, reforming from the reforming injector 35 by the second control execution unit 13 at time t5 (for example, when the energizing time of the reformer heater 36a reaches a predetermined time). Ammonia gas injection is started. After time t5, the reforming injector 35 is opened by the second control execution unit 13 at a predetermined injection pressure P1, and the reforming ammonia gas is intermittently injected. More specifically, time t5 to time t6 (hereinafter, first valve opening time), time t7 to time t8 (hereinafter, second valve opening time), time t9 to time t10 (hereinafter, third valve opening time), and The reforming injector 35 is opened from time t11 to time t12 (hereinafter, the fourth valve opening time). That is, the second control execution unit 13 injects the reforming ammonia gas into the reforming injector 35 in the second fuel injection pattern in which the reforming ammonia gas is intermittently injected as the second control.

As shown in FIG. 5B, at time t5, the third control execution unit 14 uses the reforming ammonia gas based on the injection pressure of the reforming injector 35 and the reforming ammonia gas injection time. Calculation of the injection amount and calculation of the gas replacement amount are started. More specifically, from time t5 to time t7, the third control execution unit 14 calculates a gas replacement amount corresponding to the injection amount of the reforming ammonia gas injected during the first valve opening time, and the gas replacement amount G1. To reach. From time t7 to time t9, the third control execution unit 14 calculates a gas replacement amount corresponding to the injection amount of the reforming ammonia gas injected during the first and second valve opening times, and sets the gas replacement amount to G2. Reach. From time t9 to time t11, the third control execution unit 14 calculates a gas replacement amount corresponding to the injection amount of the reforming ammonia gas injected during the first to third valve opening times, and sets the gas replacement amount to G3. Reach. From time t11 to time t13, the third control execution unit 14 calculates a gas replacement amount corresponding to the injection amount of the reforming ammonia gas injected during the first to fourth valve opening times, and the replacement estimated volume amount Th. To reach. That is, the time t13 is the replacement timing.

As shown in FIG. 5C, at time t5, the third control execution unit 14 starts reducing the opening degree of the stop valve 38 according to the injection amount of the reforming ammonia gas. More specifically, from time t5 to time t7, the opening degree of the stop valve 38 is opened from the initial opening degree S1 according to the first reduction gradient set by the third control execution unit 14 according to the first valve opening time. The degree is reduced to S2. From time t7 to time t9, the opening degree of the stop valve 38 is reduced from the opening degree S2 to the opening degree S3 according to the second reduction gradient set according to the second valve opening time by the third control execution unit 14. To. From time t9 to time t11, the third control execution unit 14 reduces the opening degree of the stop valve 38 from the opening degree S3 according to the third reduction gradient set according to the third valve opening time. From time t11 to time t12, the opening degree of the stop valve 38 is increased according to the fourth reduction gradient (here, equal to the third reduction gradient) set by the third control execution unit 14 according to the fourth valve opening time. Subsequently, it is reduced to the fully closed opening. That is, as the third control, the third control execution unit 14 gradually reduces the opening degree of the stop valve 38 according to the increase in the injection amount of the reforming ammonia gas injected in the second control.

In the example of FIG. 5C, at time t12, the opening degree of the stop valve 38 reduced by the third control reaches full closure. That is, in the third control of FIG. 5C, the opening degree of the stop valve 38 is reduced so that the opening degree of the stop valve 38 is fully closed at a timing earlier than the replacement timing.

In the examples of FIGS. 5A to 5C described above, since the opening degree of the reforming throttle 32 is fully closed by the first control, the reforming injector 35 injects the gas in the second control. It is possible to prevent the reformed ammonia gas from flowing (backflow) through the reforming throttle 32. The opening degree of the stop valve 38 is set to the initial opening degree S1 by the first control, and the reforming ammonia gas is intermittently injected by the second control. Therefore, the reformer 36 is made of the reforming ammonia gas. Residual gas is gradually pushed out. In particular, the second valve opening time is longer than the first valve opening time, the third valve opening time is longer than the second valve opening time, and the fourth valve opening time is longer than the third valve opening time. In the initial stage of the start-up preparation state, the gas flow of the reforming ammonia gas is weakened, and the mixing of the reforming ammonia gas and the residual gas is suppressed. Instead of gradually increasing the valve opening time, the valve may be opened at the same time or at an arbitrary time. For example, the valve opening time may be constant, the magnitude relationship opposite to the above example may be used, or the magnitude relationship may be irregular. Further, the number of valve openings may be any number as long as it is two or more times. Further, a fuel injection pattern in which the injection pressure is changed while continuously injecting fuel may be used.

Further, by the third control, the opening degree of the stop valve 38 is gradually reduced according to the increase in the injection amount of the reforming ammonia gas, so that the pressure in the reformer 36 is suppressed from suddenly increasing, and the pressure is suppressed. The equilibrium can extend the time until the reforming ammonia gas cannot be injected from the reforming injector 35. In particular, the magnitude of the second reduction gradient is smaller than the magnitude of the first reduction gradient, the magnitude of the third reduction gradient is smaller than the magnitude of the second reduction gradient, and the magnitude of the fourth reduction gradient is the magnitude of the third reduction gradient. Since it is smaller than the size of, the opening of the stop valve 38 is rapidly reduced in the early stage of the start preparation state, and the opening of the stop valve 38 is gradually reduced in the state of being close to fully closed in the latter stage of the start preparation state. To. As a result, the increase in pressure in the reformer 36 is moderated while suppressing the sudden outflow of the reforming ammonia gas to the intake flow path 22 side in the initial stage of the start preparation state. As a result, it becomes easy to continue pushing out the residual gas with the reforming ammonia gas in a state where the opening degree of the stop valve 38 is close to fully closed and the ammonia gas does not easily leak in the latter stage of the start preparation state.

Further, since the opening of the stop valve 38 is fully closed at a timing earlier than the replacement timing, the suppression of the leakage of ammonia gas becomes more reliable. Then, with the opening degree of the reforming throttle 32 fully closed and the opening degree of the stop valve 38 fully closed, the reformer 36 has a reducing atmosphere with the fuel injected by the reforming injector 35. Is warmed up.

The start permission unit 15 permits the start of the ammonia engine 100 when the opening degree of the stop valve 38 reduced by the third control is fully closed. The start permission unit 15 permits the start of cranking of the starter when the warm-up of the reformer 36 is completed, for example, when the opening degree of the stop valve 38 reduced by the third control is fully closed. .. In the warm-up of the reformer 36, for example, the floor temperature of the reformer 36b becomes about 200 ° C. or higher because the elapsed time from the input of the start signal exceeds a predetermined time set in advance based on an experiment or the like. If it is presumed to have been completed, it can be considered complete. The start permission unit 15 may allow the start of the ammonia engine 100 before the opening degree of the stop valve 38 is fully closed.

Next, an example of processing by the ECU 10 will be described with reference to FIG. FIG. 6 is a flowchart showing the reformer warm-up process of the ECU 10.

As shown in FIG. 6, the ECU 10 determines in S11 whether or not a start signal is input by the engine state acquisition unit 11. The engine state acquisition unit 11 determines whether or not the ammonia engine 100 is in the start preparation state, for example, as a determination of whether or not a start signal is input. When the engine state acquisition unit 11 determines that there is no input of the start signal (S11: NO), the ECU 10 ends the process of FIG.

On the other hand, when it is determined by the engine state acquisition unit 11 that the start signal has been input (S11: YES), the ECU 10 executes the first control by the first control execution unit 12 in S12. The first control execution unit 12 makes, for example, the opening degree of the reforming throttle 32 fully closed and the opening degree of the stop valve 38 a predetermined initial opening degree while energizing the reformer heater 36a. Take control.

In S13, the ECU 10 executes the second control by the second control execution unit 13 with the opening degree of the reforming throttle 32 fully closed. For example, the second control execution unit 13 injects the reforming ammonia gas into the reforming injector 35 in the first fuel injection pattern in which the reforming ammonia gas is continuously injected in the second control. Alternatively, the second control execution unit 13 may inject the reforming ammonia gas into the reforming injector 35 in a second fuel injection pattern in which the reforming ammonia gas is intermittently injected as the second control.

In S14, the ECU 10 executes the third control in the state where the opening degree of the reforming throttle 32 is fully closed by the third control execution unit 14. The third control execution unit 14 calculates the replacement timing based on, for example, the time-integrated value of the injection amount of the reforming ammonia gas injected in the second control and the estimated replacement volume amount. In the third control, the third control execution unit 14 maintains the opening degree of the stop valve 38 at the initial opening degree until the replacement timing, and closes the opening degree of the stop valve 38 at the replacement timing. Reduce the opening of. Alternatively, as the third control, the third control execution unit 14 may gradually reduce the opening degree of the stop valve 38 according to the increase in the injection amount of the reforming ammonia gas injected in the second control.

In S15, the ECU 10 determines whether or not the opening degree of the stop valve 38 has reached full closure by the third control execution unit 14. When the third control execution unit 14 determines that the opening degree of the stop valve 38 has not reached full closure (S15: NO), the ECU 10 repeats the processes of S13 and S14.

On the other hand, when the third control execution unit 14 determines that the opening degree of the stop valve 38 has been fully closed (S15: YES), the ECU 10 permits the start of the ammonia engine 100 by the start permission unit 15 in S16. I do. The start permission unit 15 permits the start of cranking of the starter, for example, when the warm-up of the reformer 36 is completed.

[Action and effect]
As described above, in the ammonia engine 100, when the start signal is input, the opening degree of the reforming throttle 32 is fully closed, and the opening degree of the reforming throttle 32 is fully closed. The second control of injecting the reforming ammonia gas into the reforming injector 35 is executed. As a result, it is possible to prevent the fuel ammonia from leaking to the external environment through the reforming throttle 32. Further, in a state where the opening degree of the reforming throttle 32 is fully closed, the third control for reducing the opening degree of the stop valve 38 is executed so that the opening degree of the stop valve 38 reaches the fully closed position at the latest at the replacement timing. Will be done. As a result, the residual gas of the reformer 36 is replaced by the reforming ammonia gas injected by the reforming injector 35 while suppressing the fuel ammonia from leaking to the external environment through the stop valve 38. Is planned. As a result, with the opening of the reforming throttle 32 fully closed and the opening of the stop valve 38 fully closed, the reforming ammonia gas injected by the reforming injector 35 creates a reducing atmosphere. The reformer 36 is warmed up. Therefore, according to the ammonia engine 100, it is possible to warm up the reformer 36 in a reducing atmosphere while suppressing the leakage of ammonia at the time of starting.

In the ammonia engine 100, in the second control, the ECU 10 injects the reforming ammonia gas into the reforming injector 35 in the first fuel injection pattern in which the reforming ammonia gas is continuously injected as the fuel injection pattern. 3 In the control, the opening degree of the stop valve 38 is maintained at the initial opening degree S1 until the replacement timing, and the opening degree of the stop valve 38 is reduced so that the opening degree of the stop valve 38 is fully closed at the replacement timing. As a result, the opening degree of the stop valve 38 is fully closed while most of the residual gas is pushed out from the reformer 36 by the reforming ammonia gas injected by the reforming injector 35. Therefore, the reformer 36 can be more reliably used as a reducing atmosphere.

In the ammonia engine 100, in the second control, the ECU 10 injects the reforming ammonia gas into the reforming injector 35 in the second fuel injection pattern in which the reforming ammonia gas is intermittently injected as the fuel injection pattern. In the third control, the opening degree of the stop valve 38 is gradually reduced according to the increase in the injection amount of the reforming ammonia gas injected in the second control. As a result, the reforming ammonia gas is injected in the second fuel injection pattern in which the reforming ammonia gas is intermittently injected, so that the reforming ammonia gas is prevented from being mixed with the residual gas of the reformer 36. Therefore, the reformer 36 can be made into a reducing atmosphere more reliably. Further, since the opening degree of the stop valve 38 is gradually reduced according to the increase in the injection amount of the reforming ammonia gas, it is suppressed that the pressure in the reformer 36 suddenly increases, and the reforming injector is suppressed by the pressure balance. It is possible to extend the time from 35 until the reforming ammonia gas cannot be injected. Therefore, it is possible to prevent the reforming ammonia gas from being easily injected from the reforming injector 35 due to the increase in pressure.

In the ammonia engine 100, the reformer 36 is provided so as to cover the reforming catalyst 36b for reforming the reforming ammonia gas and the inflow surface of the reforming catalyst 36b upstream of the reforming catalyst 36b. It has a hole plate member 36c and. As a result, the perforated plate member 36c physically suppresses the mixing of the reforming ammonia gas injected by the reforming injector 35 and the residual gas of the reformer 36. As a result, the reforming ammonia gas can suitably exert the action of pushing out the residual gas from the reformer 36.

[Modification example]
Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments.

In the above embodiment, the reforming throttle 32 is illustrated as the reformer upstream valve, but for example, an electromagnetic valve or the like may be used.

In the above embodiment, the number of the reforming injectors 35 is, for example, one, but may be a plurality.

In the above embodiment, the stop valve 38 is exemplified as the reformer downstream valve, but instead of the solenoid valve, for example, a butterfly valve or a three-way valve provided at the position of the intake flow path 22 may be used.

In the above embodiment, the three-way catalyst 26 is provided, but it may be omitted.

In the examples of FIGS. 5A to 5C of the above embodiment, the opening degree of the stop valve 38 is gradually reduced so that the opening degree of the stop valve 38 is fully closed earlier than the replacement timing. For example, if the opening degree of the stop valve 38 is not fully closed when the replacement timing is reached, the third control execution unit 14 may forcibly close the opening degree of the stop valve 38 at that time. ..

In the above embodiment, the perforated plate member 36c is provided on the upstream side of the reformer heater 36a, but may be provided between the reformer heater 36a and the reformer catalyst 36b. The outer shape of the perforated plate member 36c may have a shape other than a substantially disk shape. The perforated plate member 36c does not necessarily have to cover substantially the entire inflow surface of the reformer heater 36a. The residual gas mixing suppressing member is not limited to the perforated plate member 36c, and may be, for example, a net-like member or a porous member. Further, the perforated plate member 36c may be omitted.

1 key switch (start signal output section)
10 ECU (control unit)
22 Intake flow path 31 Reformation flow path 32 Reformation throttle (reformer upstream valve)
35 Injector for reforming (fuel injection valve for reforming)
36 Reformer 36b Reform catalyst 36c Perforated plate member (residual gas mixing suppression member)
38 Stop valve (reformer downstream valve)
100 ammonia engine

Claims

An ammonia engine equipped with a reformer that reforms the fuel ammonia into reforming gas.
The intake flow path through which the intake air of the ammonia engine flows, and
The reformer is provided, and a reforming flow path for flowing reforming air through the reformer and for flowing the reforming gas from the reformer to the intake flow path,
A reformer upstream valve provided on the upstream side of the reformer in the reforming flow rate,
A reforming fuel injection valve provided between the reformer upstream valve and the reformer in the reforming flow rate and injecting the fuel into the reforming flow rate.
A reformer downstream valve provided on the downstream side of the reformer in the reformer
A start signal output unit that outputs a start signal for operating the starter of the ammonia engine, and
A control unit that controls the reformer upstream valve, the reformer fuel injection valve, and the reformer downstream valve based on the fuel injection amount of the reformer fuel injection valve and the start signal. ,
With
The control unit
When the start signal is input, the first control is executed in which the opening degree of the reformer upstream valve is fully closed and the opening degree of the reformer downstream valve is set to a predetermined initial opening degree.
With the opening degree of the reformer upstream valve fully closed, the second control for injecting the fuel into the reforming fuel injection valve in a predetermined fuel injection pattern is executed.
With the opening degree of the reformer upstream valve fully closed, the fuel was injected by the second control based on the injection amount of the fuel injected by the second control and the predetermined replacement estimated volume amount. The replacement timing at which the residual gas of the reformer is replaced by the fuel is calculated, and the opening degree of the reformer downstream valve is opened so that the opening degree of the reformer downstream valve reaches full closure at the latest at the replacement timing. Ammonia engine that performs a third control to reduce.
The control unit
In the second control, the fuel is injected into the reforming fuel injection valve in the first fuel injection pattern in which the fuel is continuously injected as the fuel injection pattern.
In the third control, the opening degree of the reformer downstream valve is maintained at the initial opening until the replacement timing, and the opening degree of the reformer downstream valve is fully closed at the replacement timing. The ammonia engine according to claim 1, which reduces the opening degree of the reformer downstream valve.
The control unit
In the second control, the fuel is injected into the reforming fuel injection valve in the second fuel injection pattern in which the fuel is intermittently injected as the fuel injection pattern.
The ammonia engine according to claim 1, wherein in the third control, the opening degree of the reformer downstream valve is gradually reduced according to an increase in the injection amount of the fuel injected in the second control.
The reformer has a reforming catalyst for reforming the fuel and a residual gas mixing suppressing member provided along the inflow surface of the reforming catalyst upstream of the reforming catalyst. The ammonia engine according to any one of Items 1 to 3.