Ammonia engine system

Abstract

An ammonia engine system is provided. An ammonia engine system (10) is provided with: a combustor (40) configured so as to generate combustion gas by combusting ammonia gas mixed with air; a reforming catalyst (23b) configured to be warmed up by combustion gas; an ammonia engine (11) configured so as to be supplied with hydrogen gas discharged from the reforming catalyst (23b); and a control unit (37). The control unit (37) is configured so as to execute a combustion process in which the combustor (40) generates combustion gas and a supply process in which ammonia gas is supplied to the reforming catalyst (23b) together with air when the ammonia engine (11) is started. The control unit (37) is configured so as to start the supply process after the start of the combustion process.

Description

Technical Field

[0001] The present disclosure relates to ammonia engine systems. Background Art

[0002] Patent Document 1 discloses an ammonia engine system having a reforming catalyst and an ammonia engine. When air and ammonia are supplied to the reforming catalyst and the reforming catalyst reaches a temperature at which reforming is possible, a reforming reaction occurs by the reforming catalyst. Hydrogen exhausted from the reforming catalyst by the reforming reaction is supplied to the ammonia engine.

[0003] The above-mentioned ammonia engine system may be equipped with a burner. In this case, the burner generates combustion gas by burning ammonia mixed with air. The reforming catalyst can be warmed up by the combustion gas generated by the burner.

[0004] Patent Document 1: International Publication No. 2012 / 090739

[0005] For example, when the supply of air and ammonia to the reforming catalyst is started at the start of the ammonia engine, no reforming reaction based on the reforming catalyst occurs until the reforming catalyst reaches a temperature at which reforming can be performed. Therefore, the ammonia supplied to the reforming catalyst is not consumed by the reforming catalyst but is discharged from the reforming catalyst. It is desirable to reduce the amount of ammonia discharged from the reforming catalyst for this reason. Summary of the invention

[0006] An ammonia engine system according to one embodiment of the present disclosure includes: a burner configured to generate combustion gas by burning ammonia mixed with air; a reforming catalyst configured to be warmed up by the combustion gas; an ammonia engine configured to be supplied with hydrogen exhausted from the reforming catalyst; and a control unit. The control unit is configured to perform a combustion process for causing the burner to generate the combustion gas and a supply process for supplying ammonia together with air to the reforming catalyst when the ammonia engine is started. The control unit is configured to start the supply process after the combustion process starts. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic diagram of an ammonia engine system according to an embodiment.

[0008] Figure 2 Yes means Figure 1 Schematic diagram of the ammonia engine system with a burner, spark plug and ignition unit.

[0009] Figure 3 Yes means Figure 1 Flowchart of the processing procedure of the start control of the ammonia engine system.

[0010] Figure 4 It is a graph showing the relationship between TDC count, throttle opening and time.

[0011] Figure 5 It is a graph showing the relationship between TDC count, injector injection amount and time.

[0012] Figure 6 It is a graph showing the measurement results of the startup time.

[0013] Figure 7 It is a graph showing the amount of ammonia gas exhausted from the reforming catalyst. DETAILED DESCRIPTION

[0014] Hereinafter, one embodiment of the ammonia engine system will be described with reference to the drawings.

[0015] <Schematic structure of ammonia engine system>

[0016] like Figure 1 As shown, the ammonia engine system 10 includes an ammonia engine 11. Alternatively, the ammonia engine system 10 may be mounted on an engine-type vehicle 50. The ammonia engine 11 uses ammonia gas (NH3) as fuel. The ammonia engine 11 includes a combustion chamber 11a therein. The ammonia engine 11 is a multi-cylinder engine. The ammonia engine 11 is, for example, a four-cylinder engine.

[0017] The ammonia engine system 10 includes an intake air flow path 12, an air filter 19, a main injector 14, and a main throttle valve 15. Air is introduced into the combustion chamber 11a through the intake air flow path 12. The air filter 19 removes foreign matter such as dust and dirt contained in the air. The air filter 19 is arranged at the end of the intake air flow path 12. The air from which foreign matter has been removed by the air filter 19 flows into the intake air flow path 12.

[0018] The main injector 14 is, for example, an electromagnetic injection valve. Ammonia is supplied to the main injector 14 from an ammonia supply unit (not shown). The main injectors 14 are provided in a plurality of cylinders. For example, the four-cylinder ammonia engine system 10 has four main injectors 14. Ammonia is injected into the combustion chamber 11a through the main injector 14, and ammonia is supplied to the combustion chamber 11a. The ammonia supplied to the combustion chamber 11a from the main injector 14 is mixed in the combustion chamber 11a with the air introduced into the combustion chamber 11a through the intake air path 12.

[0019] The main throttle valve 15 is disposed in the intake flow path 12. The main throttle valve 15 is, for example, an electromagnetic flow control valve capable of adjusting the opening degree of the intake flow path 12.

[0020] The ammonia engine system 10 has an exhaust flow path 13 and an exhaust catalyst unit 16. The exhaust gas generated at the combustion chamber 11a is introduced into the exhaust flow path 13 from the combustion chamber 11a. The exhaust catalyst unit 16 is arranged in the exhaust flow path 13. The exhaust catalyst unit 16 has a three-way catalyst 17 and an SCR (Selective Catalytic Reduction) catalyst 18. The three-way catalyst 17 oxidizes the ammonia remaining in the exhaust gas flowing in the exhaust flow path 13, thereby removing the ammonia from the exhaust gas. The three-way catalyst 17 is activated by the heat of the exhaust gas. The SCR catalyst 18 is arranged on the downstream side of the exhaust flow path 13 than the three-way catalyst 17. The SCR catalyst 18 is a selective reduction catalyst. The SCR catalyst 18 reduces the nitrogen oxides (NOx) contained in the exhaust gas flowing in the exhaust flow path 13 into nitrogen (N2) by ammonia. In addition, the SCR catalyst 18 collects and removes the ammonia that has passed through the three-way catalyst 17.

[0021] The ammonia engine system 10 has a reformer 23. The reformer 23 has a box-shaped housing portion 23a. The housing portion 23a has a space inside. A reforming catalyst 23b is arranged inside the housing portion 23a. In other words, the ammonia engine system 10 has a reforming catalyst 23b. It is also possible that a carrier of a honeycomb structure, not shown, is arranged inside the housing portion 23a. It is also possible that the reforming catalyst 23b is arranged inside the housing portion 23a by coating the reforming catalyst 23b on the carrier. The reforming catalyst 23b has the function of decomposing ammonia into hydrogen and the function of burning ammonia. The reforming catalyst 23b is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst. The reformer 23 generates a reformed gas containing hydrogen by reforming ammonia using the reforming catalyst 23b.

[0022] The ammonia engine system 10 includes a reformed gas flow path 31, a cooler 32, and a shutoff valve 33. A first end of the reformed gas flow path 31 is connected to the reformer 23. A second end of the reformed gas flow path 31 is connected to the intake flow path 12 downstream of the main throttle valve 15. The reformed gas generated by the reformer 23 is introduced into the reformed gas flow path 31. The reformed gas is introduced into the intake flow path 12 through the reformed gas flow path 31.

[0023] The cooler 32 cools the reformed gas flowing in the reformed gas flow path 31. The cooler 32 cools the reformed gas by exchanging heat between, for example, cooling water flowing in the cooler 32 and the reformed gas. The reformed gas cooled by the cooler 32 is introduced into the intake flow path 12 through the reformed gas flow path 31. Thus, damage to intake system components such as the main throttle valve 15 caused by the heat of the reformed gas can be suppressed. As the reformed gas is cooled, the volume expansion of the reformed gas is suppressed, so that the gas easily flows from the intake flow path 12 into the combustion chamber 11a.

[0024] The shutoff valve 33 is disposed on the downstream side of the cooler 32 in the reformed gas flow path 31. The shutoff valve 33 is, for example, an on-off valve that opens and closes the reformed gas flow path 31.

[0025] The ammonia engine system 10 includes a first air flow path 24a, a first injector 25, and a first throttle valve 26. A first end of the first air flow path 24a is connected to the upstream side of the main throttle valve 15 of the intake flow path 12. A second end of the first air flow path 24a is connected to the reformer 23. A portion of the air introduced into the intake flow path 12 via the air filter 19 is introduced into the first air flow path 24a. The air is introduced into the reformer 23 via the first air flow path 24a.

[0026] The first injector 25 is, for example, an electromagnetic injection valve. Ammonia gas is supplied to the first injector 25 from an ammonia gas supply unit (not shown). The first injector 25 supplies ammonia gas to the first air flow path 24a by injecting ammonia gas into the first air flow path 24a. The ammonia gas supplied from the first injector 25 to the first air flow path 24a is introduced into the reformer 23 together with the air flowing in the first air flow path 24a. Thus, the ammonia gas is supplied to the reforming catalyst 23b together with the air.

[0027] The first throttle valve 26 is disposed in the first air flow path 24a at a position upstream of a portion where ammonia gas is supplied from the first injector 25. The first throttle valve 26 is, for example, an electromagnetic flow control valve capable of adjusting the opening of the first air flow path 24a.

[0028] The ammonia engine system 10 includes a second air flow path 24b, a chamber 27, a second injector 28, a second throttle valve 29, and a burner 40. The first end of the second air flow path 24b is connected to the first air flow path 24a at an upstream side of the first throttle valve 26. The second end of the second air flow path 24b is connected to the chamber 27. A portion of the air flowing in the first air flow path 24a is introduced into the second air flow path 24b. The chamber 27 is box-shaped and has a space formed therein. The air is introduced into the space inside the chamber 27 through the second air flow path 24b.

[0029] The second injector 28 is, for example, an electromagnetic injection valve. Ammonia gas is supplied to the second injector 28 from an ammonia gas supply unit (not shown). The second injector 28 supplies ammonia gas to the space inside the chamber 27 by injecting ammonia gas to the space inside the chamber 27. The air introduced into the chamber 27 from the second air flow path 24b and the ammonia gas supplied to the chamber 27 from the second injector 28 are mixed inside the chamber 27. Thus, ammonia gas mixed with air is generated inside the chamber 27. The ammonia gas mixed with air is introduced from the chamber 27 to the burner 40.

[0030] The second throttle valve 29 is disposed in the second air flow path 24b. The second throttle valve 29 is, for example, an electromagnetic flow control valve capable of adjusting the opening degree of the second air flow path 24b.

[0031] The burner 40 generates combustion gas by burning ammonia gas mixed with air. The combustion gas generated by the burner 40 is introduced into the reformer 23.

[0032] like Figure 2 As shown, the burner 40 has a cylindrical shell 41. The first end 41a of the shell 41 is open. A blocking wall 42 is arranged at the second end 41b of the shell 41. The blocking wall 42 is, for example, in the shape of a circular plate. The blocking wall 42 blocks the second end 41b of the shell 41. The shell 41 and the blocking wall 42 are made of a conductive metal material. The conductive metal material is, for example, stainless steel.

[0033] like Figure 1 and Figure 2 As shown, the burner 40 has a plurality of introduction parts 43. The introduction part 43 has, for example, a tubular flow path 43a inside. The introduction part 43 has a first end connected to the chamber 27 and a second end connected to the shell 41. In a cross section of the shell 41 that is orthogonal to the axis L, each of the plurality of introduction parts 43 is connected to the shell 41, for example, in such a manner that the flow path 43a of the introduction part 43 extends in a tangential direction of the inner peripheral surface 41d of the shell 41. Alternatively, the introduction part 43 may be formed integrally with the shell 41. Alternatively, the introduction part 43 may be formed independently of the shell 41 and fixed to the shell 41.

[0034] Ammonia gas mixed with air is introduced from the inside of the chamber 27 to the flow path 43a of the introduction part 43. The ammonia gas mixed with air is introduced into the inside of the housing 41 through the flow path 43a. The ammonia gas and air introduced into the inside of the housing 41 from the introduction part 43 flow in the circumferential direction of the housing 41 along the inner peripheral surface 41d of the housing 41. As a result, a tubular flow flowing along the inner surface of the housing 41 is generated inside the housing 41.

[0035] like Figure 2As shown, the burner 40 has a spark plug 44 and an ignition unit 51. The spark plug 44 is arranged at the second end 41b in the housing 41. The ignition unit 51 has an igniter 52 and a power source 53. The power source 53 performs an on-off operation of the igniter 52. The igniter 52 is connected to the spark plug 44 via an electric wire 54. The igniter 52 supplies a pulse voltage to the spark plug 44 via the electric wire 54.

[0036] When a high voltage is applied to the spark plug 44 by the igniter 52, the spark generated by the spark plug 44 ignites the ammonia gas inside the housing 41. In this way, the ammonia gas burns and generates a flame. When the ammonia gas burns, combustion gas is generated inside the housing 41. The flame grows inside the housing 41. The growth of the flame promotes the generation of combustion gas generated by the combustion of ammonia gas inside the housing 41. The combustion gas is introduced into the reformer 23 from the first end 41a of the housing 41.

[0037] like Figure 1 As shown, the ammonia engine system 10 has a control unit 37 and various switches and sensors for detecting various states of the vehicle 50. The above-mentioned various switches and sensors are connected to the control unit 37. The control unit 37 can be constructed in the form of a circuit (circuitry), including 1) one or more processors that act according to a computer program (software); 2) one or more dedicated hardware circuits such as dedicated hardware (integrated circuit for specific purposes: ASIC) that performs at least part of the various processes; or 3) a combination of the above 1) and 2). The processor may also include a CPU and a memory such as RAM and ROM, and the memory may also store program codes or instructions configured to enable the CPU to execute processing. The memory, that is, the computer-readable medium, includes all available media that can be accessed by a general-purpose or special-purpose computer.

[0038] As a switch, for example, an ignition switch 55 can be cited. If the ignition switch 55 is operated by the driver of the vehicle 50, the ignition switch 55 outputs an operation signal. As a sensor, for example, a temperature sensor 56, a crank position sensor 57, and a cam position sensor 58 can be cited. The temperature sensor 56 detects the temperature of the reformer 23. The crank position sensor 57 is arranged near a crankshaft not shown in the figure. As the crankshaft rotates, the crank position sensor 57 outputs a pulse signal at each predetermined rotation angle. The cam position sensor 58 is arranged near an intake camshaft not shown in the figure. Whenever the rotation phase of the intake camshaft reaches a predetermined phase, the cam position sensor 58 outputs a pulse signal.

[0039] <Combustion reaction in the reformer>

[0040] like Figure 1As shown, air and ammonia are introduced into the reformer 23 from the first air flow path 24a, and combustion gas is introduced into the reformer 23 from the burner 40. The reforming catalyst 23b is warmed up by the combustion gas. As a result, a combustion reaction of ammonia occurs in the reformer 23, in which ammonia reacts chemically with oxygen in the air as shown in the following formula 1.

[0041] NH3+3 / 4O2→3 / 2H2O+1 / 2N2+Q…(Formula 1)

[0042] By utilizing the combustion reaction of the ammonia gas, the reformer 23 generates a mixed gas including water (H2O) and nitrogen (N2). The temperature of the reformer 23 is increased by the combustion heat generated by the combustion reaction of the ammonia gas.

[0043] <Reforming reaction in the reformer>

[0044] When the temperature of the reformer 23 reaches a temperature at which reforming is possible, reforming of ammonia by the reforming catalyst 23b is started. The temperature at which reforming is possible is, for example, about 300° C. to 400° C. In the reforming of ammonia, specifically, a reforming reaction occurs in the reformer 23 in which ammonia is decomposed into hydrogen (H2) and nitrogen by combustion heat as shown in the following formula 2.

[0045] NH3→3 / 2H2+1 / 2N2-Q…(Formula 2)

[0046] By utilizing such a reforming reaction, the reformer 23 generates a reformed gas containing hydrogen and nitrogen. The reformed gas is discharged from the reforming catalyst 23b. That is, the hydrogen contained in the reformed gas is discharged from the reforming catalyst 23b. After being introduced from the reformer 23 into the reformed gas flow path 31, the reformed gas is introduced into the intake gas flow path 12 via the reformed gas flow path 31.

[0047] <Supply of reformed gas to combustion chamber>

[0048] The reformed gas introduced from the reformed gas flow path 31 into the intake flow path 12 is supplied from the intake flow path 12 to the combustion chamber 11a of the ammonia engine 11. That is, the ammonia engine 11 is supplied with hydrogen exhausted from the reforming catalyst 23b. The reformed gas is supplied to the combustion chamber 11a together with the air in the intake flow path 12. The ammonia supplied from the main injector 14 to the combustion chamber 11a and the hydrogen in the reformed gas are mixed at the combustion chamber 11a, so the ammonia is easily burned at the combustion chamber 11a. In the combustion chamber 11a, the ammonia burns together with the hydrogen in the reformed gas.

[0049] <Control Department>

[0050] Alternatively, the control unit 37 includes a CPU, a RAM, a ROM, and an input / output interface. The control unit 37 performs various controls on the ammonia engine system 10 based on signals output from, for example, the ignition switch 55, the temperature sensor 56, the crank position sensor 57, and the cam position sensor 58. The control unit 37 controls the main injector 14, the main throttle valve 15, the first injector 25, the first throttle valve 26, the second injector 28, the second throttle valve 29, the shutoff valve 33, the power supply 53, and the like.

[0051] When the ignition switch 55 is turned on, power is supplied to the control unit 37. As a result, the control unit 37 performs a start control to start the ammonia engine 11. When the ignition switch 55 is turned off during the operation of the ammonia engine 11, the control unit 37 performs a stop control to stop the operation of the ammonia engine 11. When the operation of the ammonia engine 11 is stopped by the execution of the stop control, power supply to the control unit 37 is cut off.

[0052] In the start control, the control unit 37 controls a starter motor (not shown) to crank the ammonia engine 11. In addition, in the start control, the control unit 37 controls the main throttle valve 15, the first throttle valve 26, the second throttle valve 29, and the shutoff valve 33.

[0053] <Cylinder identification processing>

[0054] In the start control, the control unit 37 performs a cylinder discrimination process for discriminating a cylinder. That is, the control unit 37 performs a cylinder discrimination process when the ammonia engine 11 is started. In the cylinder discrimination process, the control unit 37 discriminates which stroke of the intake stroke, compression stroke, combustion stroke, and exhaust stroke each cylinder is in based on the pulse signal output from the crank position sensor 57 and the cam position sensor 58. If the control unit 37 discriminates the cylinder most suitable for starting combustion in the combustion chamber 11a based on the discrimination result, the cylinder discrimination process ends.

[0055] <Combustion treatment>

[0056] In the start-up control, the control unit 37 performs a combustion process for causing the burner 40 to generate combustion gas. That is, the control unit 37 performs the combustion process when the ammonia engine 11 is started. In the combustion process, the control unit 37 generates combustion gas at the burner 40 by injecting ammonia gas from the second injector 28 and controlling the power supply 53 to turn on the igniter 52.

[0057] The control unit 37 determines whether the temperature of the reformer 23 is above a predetermined temperature based on the detection value of the temperature sensor 56. The predetermined temperature is a temperature at which ammonia can burn, for example, about 200°C. The control unit 37 ends the combustion process when it is determined that the temperature of the reformer 23 is above the predetermined temperature. At the end of the combustion process, the control unit 37 stops the injection of ammonia from the second injector 28 and closes the second throttle valve 29. As a result, the introduction of air and ammonia supplied from the chamber 27 to the burner 40 is stopped. At the end of the combustion process, the control unit 37 controls the power supply 53, thereby disconnecting the igniter 52 using the power supply 53. The combustion of ammonia at the burner 40 stops, thereby stopping the introduction of combustion gas from the burner 40 to the reformer 23.

[0058] <Supply Processing>

[0059] In the start-up control, the control unit 37 performs the supply process. That is, the control unit 37 performs the supply process when the ammonia engine 11 is started. In the supply process, the control unit 37 causes ammonia gas to be injected from the first injector 25. When the supply process is performed, the first throttle valve 26 is opened to introduce air from the first air flow path 24a to the reformer 23. Therefore, in the supply process, the control unit 37 supplies ammonia gas to the reforming catalyst 23b together with air. If the supply process is performed, a combustion reaction and a reforming reaction occur in the reformer 23, thereby discharging a reformed gas containing hydrogen from the reforming catalyst 23b.

[0060] <Operation of Ammonia Engine>

[0061] In the start control, the control unit 37 starts combustion in all cylinders in sequence, starting from the cylinder most suitable for starting combustion determined by the cylinder determination process, thereby starting the operation of the ammonia engine 11. The control unit 37 starts the operation of the ammonia engine 11 by controlling the injection from the main injector 14 and the ignition by the ignition device (not shown) for each cylinder.

[0062] Alternatively, during the operation of the ammonia engine 11, the control unit 37 may adjust at least one of the opening of the main throttle valve 15 and the injection timing of the main injector 14. In the stop control, the control unit 37 stops the injection of ammonia gas from the main injector 14 and the first injector 25. In the stop control, the control unit 37 closes the main throttle valve 15, the first throttle valve 26, and the shutoff valve 33. Thus, the ammonia engine 11 stops.

[0063] <Startup control process>

[0064] use Figure 3 An example of the processing procedure of the start control performed by the control unit 37 will be described. The control unit 37 starts the start control on the condition that the ignition switch 55 is turned on.

[0065] like Figure 3 As shown in FIG. 1 , when the start control is started, the control unit 37 opens the plurality of valves (step S110). The valves opened by the control unit 37 in step S110 are the main throttle valve 15, the first throttle valve 26, the second throttle valve 29, and the shutoff valve 33. Next, after the control unit 37 starts the cylinder discrimination process (step S120), it starts the combustion process (step S130).

[0066] Next, the control unit 37 determines whether the cylinder discrimination process has been completed (step S140). While the control unit 37 determines that the cylinder discrimination process has not been completed (step S140: No), the control unit 37 repeatedly executes the process of step S140. If the control unit 37 determines that the cylinder discrimination process has been completed (step S140: Yes), the control unit 37 starts the supply process (step S150). Next, the control unit 37 starts the operation of the ammonia engine 11 (step S160) and ends the start control.

[0067] <Relationship between cylinder identification processing and throttle valve>

[0068] Figure 4 An example of the relationship between the TDC count C, the opening A1 of the first throttle valve 26, the opening A2 of the second throttle valve 29, and time is shown. The TDC count C is a numerical value related to the number of revolutions of the ammonia engine 11. For example, when the ammonia engine 11 rotates once, the TDC count C increases by 1. Figure 4 In the illustrated example, the time when the control unit 37 starts the startup control in response to the on-operation of the ignition switch 55 is represented as time 0 (zero).

[0069] like Figure 4 As shown in FIG. 1 , when the control unit 37 starts the startup control, the cylinder identification process is started, and the first throttle valve 26 and the second throttle valve 29 are opened. The control unit 37 executes the cylinder identification process during the execution period T. Figure 4 In the illustrated example, the control unit 37 controls each of the first throttle valve 26 and the second throttle valve 29 so that the opening degree A2 of the second throttle valve 29 is larger than the opening degree A1 of the first throttle valve 26 .

[0070] exist Figure 4 In the example shown, after the cylinder discrimination process by the control unit 37 is completed, the first throttle valve 26 and the second throttle valve 29 are opened. When the cylinder discrimination process by the control unit 37 is completed, the supply process and the operation of the ammonia engine 11 are started by the control unit 37, so that the TDC count C increases with the rotation of the ammonia engine 11.

[0071] <Relationship between cylinder identification processing and injectors>

[0072] Figure 5 FIG. 2 shows an example of the relationship between the TDC count C, the injection amount S1 injected from the first injector 25, the injection amount S2 injected from the second injector 28, and time. Figure 5 In the example shown, Figure 4 Similarly, the time when the control unit 37 starts the startup control in response to the turning-on operation of the ignition switch 55 is indicated as time 0 (zero).

[0073] like Figure 5 As shown, when the control unit 37 starts the start control, the cylinder discrimination process is started, and the injection from the second injector 28 is started by executing the combustion process. The injection from the second injector 28 is started during the execution period T of the cylinder discrimination process. That is, the control unit 37 starts the combustion process during the execution of the cylinder discrimination process. Figure 5 In the example shown, even after the cylinder discrimination process by the control unit 37 is completed, the injection from the second injector 28 is continued.

[0074] The control unit 37 starts the injection from the first injector 25 by executing the supply process after the injection start time of the injection from the second injector 28 accompanying the combustion process. That is, the control unit 37 starts the supply process after the combustion process starts. In the present embodiment, the injection start time of the injection from the first injector 25 is later than the execution period T of the cylinder discrimination process by a predetermined period Tp. That is, the control unit 37 starts the supply process after the cylinder discrimination process ends. The control unit 37 starts the supply process after the predetermined period Tp has passed after the cylinder discrimination process ends. In addition, Figure 5 In the illustrated example, the control unit 37 controls each of the first injector 25 and the second injector 28 so that the injection amount S1 from the first injector 25 is larger than the injection amount S2 from the second injector 28 .

[0075] <Relationship between the start time of supply processing and the start time>

[0076] like Figure 6 As shown, in the ammonia engine system 10, the start time is measured when the start time of the supply process performed by the control unit 37 is changed. In addition, the start time refers to the time required from the time when the ignition switch 55 is turned on to the start of the operation of the ammonia engine 11. The start time is measured under the condition that the cylinder discrimination process is performed during the period from TDC count C from 1 to 2. In addition, the start time is measured under the condition that the main throttle valve 15, the first throttle valve 26, the second throttle valve 29 and the shut-off valve 33 are opened when the TDC count C is 1.

[0077] The first measured value P1 indicates the start time measured when the combustion process is started when the TDC count C is 1. The first measured value P1 is a value obtained by measuring the corresponding start time of the supply process at different start times during the period from TDC count C 2 to 8. In addition, as a comparative example for the first measured value P1, a second measured value P2 is measured. The second measured value P2 is the start time measured when both the combustion process and the supply process are started by the control unit 37 when the TDC count C is 2.

[0078] When the first measured value P1 and the second measured value P2 are compared when the supply process is started when the TDC count C is 2, the first measured value P1 is smaller than the second measured value P2. Therefore, if the start time of the supply process is delayed from the start time of the combustion process, the startup time is shortened.

[0079] When the supply process is started during the period from TDC count C 2 to 5, the first measured value P1 is smaller than the second measured value P2. On the other hand, when the supply process is started at the time when TDC count C is 8, the first measured value P1 and the second measured value P2 are equal. Figure 6 In the embodiment, the predetermined period Tp from the end of the cylinder discrimination process to the start of the supply process is set to be less than the period Tp1. The period Tp1 of the present embodiment corresponds to the period from 2 to 5 of the TDC count C, which is a period during which the start time can be expected to be shortened. If the predetermined period Tp is longer than the period Tp1, the start time becomes the same as that in the case where the combustion process and the supply process are started simultaneously just after the cylinder discrimination process is completed.

[0080] <Relationship between the start timing of the combustion process and the supply process and the amount of ammonia gas discharged>

[0081] like Figure 7 As shown, the start timings of the combustion process and the supply process are made different and the emission amount of ammonia gas discharged from the reformer 23 to the reformed gas flow path 31 is measured. The first emission amount E1 is the emission amount of the above-mentioned ammonia gas in the case where both the combustion process and the supply process are started at the same time after the cylinder discrimination process is completed. The second emission amount E2 is the emission amount of the above-mentioned ammonia gas in the case where the combustion process is started during the execution of the cylinder discrimination process and the supply process is started just after the cylinder discrimination process is completed. The third emission amount E3 is the emission amount of the above-mentioned ammonia gas in the case where the combustion process is started during the execution of the cylinder discrimination process and the supply process is started at the moment when the TDC count C increases by 1 after the cylinder discrimination process is completed. In addition, the start timing of the combustion process during the execution of the cylinder discrimination process is the same when the second emission amount E2 is measured and when the third emission amount E3 is measured.

[0082] like Figure 7As shown, the second emission amount E2 and the third emission amount E3 are less than the first emission amount E1. Therefore, it can be seen that if the start time of the supply process is made later than the start time of the combustion process, the emission amount of ammonia discharged from the reformer 23 to the reformed gas flow path 31 is reduced. In addition, the third emission amount E3 is less than the second emission amount E2. Therefore, it can be seen that: compared with the case where the supply process is started just after the cylinder discrimination process is completed, the case where the supply process is started after a certain interval of time after the end of the cylinder discrimination process further reduces the emission amount of ammonia discharged from the reformer 23 to the reformed gas flow path 31. Based on the measurement results, in the present embodiment, the predetermined period Tp from the end of the cylinder discrimination process to the start of the supply process is set to the period from the end of the cylinder discrimination process to the increase of the TDC count C by 1.

[0083] [Effects of implementation methods]

[0084] Next, the operation of this embodiment will be described.

[0085] like Figure 1 As shown, the control unit 37 starts the combustion process during the execution of the cylinder discrimination process, and starts the supply process after the combustion process starts. That is, the control unit 37 starts the combustion process before the supply process. If the combustion process is started, the injection of ammonia gas from the second injector 28 is started. As a result, ammonia gas mixed with air is supplied to the burner 40, and combustion gas is generated at the burner 40. The generated combustion gas is introduced from the burner 40 into the reformer 23. The reforming catalyst 23b is warmed up by the combustion gas introduced into the reformer 23. In this way, the warming-up of the reforming catalyst 23b is started before the supply process is performed.

[0086] When the control unit 37 starts the supply process, the ammonia gas starts to be injected from the first injector 25. Thus, the ammonia gas is supplied to the reforming catalyst 23b together with the air. At this time, the warming up of the reforming catalyst 23b is promoted by the combustion gas, so the time required for the reforming reaction by the reforming catalyst 23b is shortened.

[0087] When the reforming catalyst 23b is warmed up to a temperature at which reforming is possible, the reformer 23 generates a reformed gas containing hydrogen and nitrogen through a reforming reaction of the reforming catalyst 23b. The reformed gas is supplied from the reforming catalyst 23b to the combustion chamber 11a of the ammonia engine 11 via the reformed gas flow path 31 and the intake flow path 12. The ammonia supplied to the combustion chamber 11a from the main injector 14 is burned in the combustion chamber 11a together with the hydrogen in the reformed gas.

[0088] [Effects of Embodiment]

[0089] According to the above-described embodiment, the following effects can be obtained.

[0090] (1) The control unit 37 performs a combustion process for causing the burner 40 to generate combustion gas and a supply process for supplying ammonia gas to the reforming catalyst 23b together with air when the ammonia engine 11 is started. The control unit 37 starts the supply process after the combustion process starts. Therefore, after the warm-up of the reforming catalyst 23b starts by the combustion gas, ammonia gas is supplied to the reforming catalyst 23b together with air. As a result, compared with the case where the combustion process and the supply process are started at the same time, the time for the supply process to be performed until the reforming catalyst 23b reaches a temperature at which reforming is possible is shortened. Therefore, the reforming reaction of the reforming catalyst 23b is not conducive and the time for ammonia gas to be discharged from the reforming catalyst 23b is shortened, and therefore, the amount of ammonia gas discharged from the reforming catalyst 23b can be reduced.

[0091] (2) The control unit 37 performs a cylinder discrimination process for performing cylinder discrimination when the ammonia engine 11 is started, starts the combustion process during the execution of the cylinder discrimination process, and starts the supply process after the cylinder discrimination process is completed. Therefore, compared with the case where both the combustion process and the supply process are started during the execution of the cylinder discrimination process, the time from the start of the combustion process to the start of the supply process becomes longer. Until the start of the supply process, the warm-up of the reforming catalyst 23b is further promoted, so the time for executing the supply process until the reforming catalyst 23b reaches a temperature at which reforming is possible is further shortened. Therefore, the amount of ammonia gas discharged from the reforming catalyst 23b can be further reduced.

[0092] (3) The control unit 37 starts the supply process after a predetermined period Tp has elapsed after the cylinder discrimination process is completed. Therefore, compared with the case where the supply process is started immediately after the cylinder discrimination process is completed, the time from the start of the combustion process to the start of the supply process becomes longer. Until the start of the supply process, the warm-up of the reforming catalyst 23b is further promoted, so the time for the supply process to be performed until the reforming catalyst 23b reaches a temperature at which reforming is possible is further shortened. Therefore, the amount of ammonia gas discharged from the reforming catalyst 23b can be further reduced.

[0093] (4) The control unit 37 starts the combustion process during the execution of the cylinder discrimination process, and starts the supply process after the cylinder discrimination process is completed. The predetermined period Tp from the end of the cylinder discrimination process by the control unit 37 to the start of the supply process is set to be less than the period Tp1. Therefore, compared with the case where the combustion process and the supply process are started simultaneously just after the cylinder discrimination process is completed, the time from the execution of the supply process to the reforming catalyst 23b reaching a temperature capable of reforming is shortened. Hydrogen is discharged from the reforming catalyst 23b as soon as possible after the start of the supply process, so that hydrogen can be supplied to the ammonia engine 11 as soon as possible after the reforming catalyst 23b. Therefore, the start time of the ammonia engine 11 can be shortened.

[0094] [Example of Change]

[0095] The above-described embodiment can be implemented with modifications as follows. The above-described embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0096] The predetermined period Tp from the end of the cylinder identification process by the control unit 37 to the start of the supply process may be longer than the period Tp1.

[0097] The control unit 37 may start the supply process after a predetermined period Tp or longer has elapsed after the cylinder identification process is completed.

[0098] ○ The period from the end of the cylinder identification process by the control unit 37 to the start of the supply process may be less than the predetermined period Tp. For example, the control unit 37 may start the supply process immediately after the cylinder identification process is completed. In this case, the control unit 37 also starts the supply process after the cylinder identification process is completed.

[0099] The control unit 37 may start both the combustion process and the supply process during the execution of the cylinder discrimination process. In short, the control unit 37 may start the combustion process during the execution of the cylinder discrimination process, and may start the supply process after the combustion process starts.

[0100] ○ The control unit 37 may start both the combustion process and the supply process after the cylinder identification process is completed. In short, the control unit 37 may start the supply process after the combustion process is started.

[0101] ○ The control unit 37 may also control the second throttle valve 29 to open in addition to controlling the second injector 28 and the power supply 53 during the combustion process. In this case, the control unit 37 Figure 3 In step S110, the second throttle valve 29 is not opened, and in step S130, the second throttle valve 29 is opened.

[0102] ○ The control unit 37 may control the first throttle valve 26 and the second throttle valve 29 in the start control so that the opening A1 of the first throttle valve 26 is larger than the opening A2 of the second throttle valve 29. The control unit 37 may control the first throttle valve 26 and the second throttle valve 29 in the start control so that the opening A1 of the first throttle valve 26 and the opening A2 of the second throttle valve 29 become the same opening.

[0103] ○ The control unit 37 may control the first injector 25 and the second injector 28 in the startup control so that the injection amount S2 from the second injector 28 is greater than the injection amount S1 from the first injector 25. The control unit 37 may control the first injector 25 and the second injector 28 in the startup control so that the injection amount S1 from the first injector 25 and the injection amount S2 from the second injector 28 become the same amount.

[0104] Alternatively, the control unit 37 may cause the burner 40 to generate combustion gas by introducing air and ammonia gas into the burner 40 during the combustion process. In this case, for example, some of the multiple introduction units 43 may introduce only ammonia gas into the housing 41, and other introduction units 43 may introduce only air into the housing 41.

[0105] ○The number of inlet parts 43 of the burner 40 may be less than 3, or may be more than 5. In short, the burner 40 only needs to have at least one inlet part 43. In addition, the expression "at least one" used in this specification refers to "more than one" of the desired options. As an example, if the number of options is two, the expression "at least one" used in this specification refers to "only one option" or "both options". As another example, if the number of options is more than 3, the expression "at least one" used in this specification refers to "only one option" or "a combination of any two or more options".

[0106] The burner 40 may generate combustion gas by burning ammonia mixed with air. For example, the housing 41 of the burner 40 may be a cylindrical shape other than a cylindrical shape. For example, the introduction portion 43 of the burner 40 may be connected to the housing 41 in a cross section of the housing 41 orthogonal to the axis L so that the flow path 43a extends in a direction different from the tangent direction of the inner peripheral surface 41d of the housing 41.

[0107] The first air flow path 24a may not be connected to the intake flow path 12. In this case, for example, air may flow into the first air flow path 24a from a path different from the intake flow path 12.

[0108] The main injector 14 may inject ammonia gas into an intake port connected to the combustion chamber 11 a of each cylinder.

[0109] The ammonia engine system 10 may also be applied to a hybrid vehicle 50 .

Claims

1. An ammonia engine system, characterized in that: have: a burner configured to generate combustion gas by burning ammonia gas mixed with air; a reforming catalyst configured to be warmed by the combustion gas; an ammonia engine configured to be supplied with hydrogen exhausted from the reforming catalyst; as well as a control unit configured to execute a combustion process for causing the burner to generate the combustion gas and a supply process for supplying ammonia gas to the reforming catalyst together with air when the ammonia engine is started, The control unit is configured to start the supply process after the combustion process is started.

2. The ammonia engine system according to claim 1, characterized in that: The control unit is configured as follows: executing a cylinder identification process for identifying a cylinder when the ammonia engine is started, The combustion process is started during the execution of the cylinder identification process. The supply process is started after the cylinder identification process is completed.

3. The ammonia engine system according to claim 2, characterized in that: The control unit is configured to start the supply process after a predetermined period of time has elapsed after the cylinder identification process is completed.

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