Engine system

Abstract

To provide an engine system capable of inhibiting blow-by gas of ammonia remaining in a crankcase to flow out into the atmosphere.SOLUTION: An engine system 1 comprises: a second oxygen supply flow passage 30 which connects the upstream side of a main throttle valve 6 in a first oxygen supply flow passage 3 and a crankcase 21 and supplies air into the crankcase 21; a blow-by gas flow passage 31 which connects the crankcase 21 and the downstream side of the main throttle valve 6 in the first oxygen supply flow passage 3 and refluxes blow-by gas of ammonia remaining in the crankcase 21 to the first oxygen supply flow passage 3; a starter 59 for rotating a crankshaft 20; and a controller 60 for controlling the opening of the main throttle valve 6 so that the blow-by gas reflows to the first oxygen supply flow passage 3, when the crankshaft 20 is rotated by the starter 59.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an engine system.

Background Art

[0002] As a conventional engine system, for example, the technology described in Patent Document 1 is known. The engine system described in Patent Document 1 includes an engine block, an intake passage connected to an intake port of the engine block, a throttle valve provided in the intake passage, a fresh air introduction passage that connects the intake passage upstream of the throttle valve and a crank chamber in the engine block to introduce intake air (fresh air) in the intake passage into the crank chamber, a reduction passage that connects the intake passage downstream of the throttle valve and the crank chamber to return blow-by gas remaining in the crank chamber to the intake passage, and a PCV valve provided in the reduction passage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, there is an ammonia engine that uses ammonia as fuel. However, since blow-by gas of ammonia remains in the crankcase, it is desired to suppress the outflow of blow-by gas of ammonia into the atmosphere, for example, during maintenance.

[0005] An object of the present invention is to provide an engine system capable of suppressing the outflow of blow-by gas of ammonia remaining in the crankcase into the atmosphere.

Means for Solving the Problems

[0006] (1) One aspect of the present invention is an engine system comprising an engine having a piston capable of reciprocating in a combustion chamber for burning ammonia, a crankshaft connected to the piston, and a crankcase housing the crankshaft, the system comprising: a first oxygen supply passage connected to the engine and through which oxygen-containing gas supplied to the combustion chamber flows; a flow control valve disposed in the first oxygen supply passage and controlling the flow rate of oxygen-containing gas supplied to the combustion chamber; an exhaust passage connected to the engine and through which exhaust gas generated from the combustion chamber flows; an exhaust catalyst disposed in the exhaust passage and adsorbing and oxidizing ammonia; and a portion of the first oxygen supply passage upstream of the flow control valve and the crankcase The system includes a second oxygen supply passage that connects to the crankcase and supplies oxygen-containing gas into the crankcase, a blow-by gas passage that connects the crankcase to a point downstream of the flow control valve in the first oxygen supply passage and recirculates ammonia blow-by gas remaining in the crankcase into the first oxygen supply passage, a blow-by gas recirculation valve disposed in the blow-by gas passage and adjusting the flow rate of ammonia blow-by gas recirculating into the first oxygen supply passage, a starter that rotates the crankshaft, and a control unit that controls the opening degree of the flow control valve so that blow-by gas is recirculated into the first oxygen supply passage when the crankshaft is rotating by the starter.

[0007] In this engine system, the opening of the flow control valve is controlled so that ammonia blow-by gas is recirculated into the first oxygen supply passage during any period between the time the crankshaft stops rotating due to the completion of ammonia combustion in the engine's combustion chamber and the time when ammonia combustion resumes in the combustion chamber. At the same time, the crankshaft is rotated by the starter. As a result, the combustion chamber side of the first oxygen supply passage becomes negative pressure, causing oxygen-containing gas to flow through the second oxygen supply passage and be introduced into the crankcase. Simultaneously, the blow-by gas recirculation valve opens, allowing the ammonia blow-by gas remaining in the crankcase to flow through the blow-by gas passage together with the oxygen-containing gas and be recirculated into the first oxygen supply passage. The ammonia blow-by gas then flows through the first oxygen supply passage, the engine's combustion chamber, and the exhaust passage together with the oxygen-containing gas to be supplied to the exhaust catalyst, where it is adsorbed and oxidized. As a result, the ammonia blow-by gas remaining in the crankcase is removed. This prevents, for example, the leakage of ammonia remaining in the crankcase into the atmosphere when the crankcase is opened for maintenance. Furthermore, regularly removing the ammonia blow-by gas that remains in the crankcase will prevent large amounts of ammonia from leaking into the atmosphere when the crankcase is opened for maintenance, for example.

[0008] (2) In the above (1), the engine system further comprises a reformer that generates a hydrogen-containing reformed gas by reforming ammonia, a reforming oxygen supply passage that supplies oxygen-containing gas to the reformer, a reforming flow control valve disposed in the reforming oxygen supply passage and controlling the flow rate of oxygen-containing gas supplied to the reformer, and a reformed gas passage that supplies the reformed gas generated by the reformer to the combustion chamber, and the control unit may control the opening degree of the reforming flow control valve so that blow-by gas is recirculated into the first oxygen supply passage when the crankshaft is rotating by the starter. In such a configuration, since hydrogen-containing reformed gas is supplied to the combustion chamber of the engine, ammonia is more easily burned in the combustion chamber.

[0009] (3) In (1) or (2) above, the engine system may further include a heating unit for heating the exhaust catalyst. In such a configuration, the exhaust catalyst is heated to a temperature at which it can oxidize ammonia, so that ammonia is rapidly oxidized by the exhaust catalyst. Therefore, even when the engine is cold, ammonia can be effectively purified by the exhaust catalyst.

[0010] (4) In any of (1) to (3) above, the engine system may further include a temperature detection unit for detecting the temperature of the engine oil or engine coolant, and the control unit may control the opening degree of the flow control valve based on the temperature of the engine oil or engine coolant detected by the temperature detection unit. In such a configuration, even if the negative pressure generated in the first oxygen supply passage fluctuates with the engine temperature, the flow control valve can be adjusted to an appropriate opening degree according to the engine temperature. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress the outflow of ammonia blow-by gas remaining in the crankcase into the atmosphere. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing an engine system according to the first embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the ammonia engine and intake system. [Figure 3] Figure 1 is a flowchart showing the procedure for the blow-by gas removal control process performed by the controller. [Figure 4] Figure 2 is a graph showing an example of the flow characteristics of a PCV valve. [Figure 5] This is a schematic diagram showing an engine system according to a second embodiment of the present invention. [Figure 6] Figure 5 is a flowchart showing the procedure for the blow-by gas removal control process performed by the controller. [Figure 7] This is a schematic diagram showing an engine system according to a third embodiment of the present invention. [Figure 8] Figure 7 is a flowchart showing the procedure for the blow-by gas removal control process performed by the controller shown. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will be omitted. [First Embodiment]

[0014] Figure 1 is a schematic diagram showing an engine system according to a first embodiment of the present invention. In Figure 1, the engine system 1 of this embodiment is mounted on a vehicle (not shown). The engine system 1 comprises an ammonia engine 2, a first oxygen supply passage 3, an exhaust passage 4, a main injector 5, and a main throttle valve 6.

[0015] Ammonia engine 2 is an engine that uses ammonia gas (NH3 gas) as fuel. In ammonia engine 2, hydrogen (H2) is mixed with the ammonia gas as a combustion aid to make the non-flammable ammonia gas easier to burn. Ammonia engine 2 is, for example, a four-cylinder engine.

[0016] As shown in Figure 2, the ammonia engine 2 includes a cylinder block 11, a cylinder head 12 assembled to the cylinder block 11, a number of pistons 13 (four in this case) arranged to reciprocate inside the cylinder block 11, a crankshaft 20 connected to the pistons 13, and a crankcase 21 housing the crankshaft 20.

[0017] The ammonia engine 2 has a plurality (here, four) of combustion chambers 14 in which ammonia burns together with hydrogen to generate exhaust gas. The combustion chamber 14 is defined by a space surrounded by a cylinder block 11, a cylinder head 12, and a piston 13.

[0018] The cylinder head 12 is provided with a plurality (here, four each) of intake ports 15 and exhaust ports 16 that communicate with each combustion chamber 14. The intake port 15 is opened and closed by an intake valve 17. The exhaust port 16 is opened and closed by an exhaust valve 18.

[0019] Each piston 13 is connected to a crankshaft 20 via a connecting rod 19. The crankcase 21 is assembled to an end of the cylinder block 11 opposite to the end where the cylinder head 12 is provided. An oil pan 22 for storing engine oil eo is detachably assembled to an end of the crankcase 21 opposite to the end where the cylinder block 11 is provided. The interiors of the crankcase 21 and the oil pan 22 form a crank chamber 23.

[0020] The first oxygen supply passage 3 has an intake manifold 24 connected to each intake port 15 of the ammonia engine 2 and an intake pipe 25 connected to the intake manifold 24. The first oxygen supply passage 3 is a passage through which air supplied to each combustion chamber 14 of the ammonia engine 2 flows. The air is a gas containing oxygen (oxygen-containing gas). An air cleaner 7 for removing foreign substances such as dust and dirt contained in the air is disposed in the intake pipe 25.

[0021] The exhaust passage 4 has an exhaust manifold 26 connected to each exhaust port 16 of the ammonia engine 2 and an exhaust pipe 27 connected to the exhaust manifold 26. The exhaust passage 4 is a passage through which exhaust gas generated from each combustion chamber 14 of the ammonia engine 2 flows.

[0022] Returning to Figure 1, the exhaust passage 4 is equipped with a three-way catalyst 8 that purifies unburned ammonia and nitrogen oxides (NOx), which are harmful substances contained in the exhaust gas, and an SCR catalyst 9 that adsorbs unburned ammonia. The three-way catalyst 8 and the SCR catalyst 9 are installed in the exhaust pipe 27 described above.

[0023] The three-way catalyst 8 primarily uses the air flowing into it to oxidize ammonia. The three-way catalyst 8 also adsorbs ammonia, albeit in small amounts compared to the SCR catalyst 9. The SCR catalyst 9 adsorbs ammonia and also uses NOx flowing into it to oxidize it. The NOx is then reduced. The three-way catalyst 8 and the SCR catalyst 9 constitute the exhaust catalyst installed in the exhaust flow path 4.

[0024] The main injector 5 is an electromagnetic fuel injection valve that injects ammonia gas into the combustion chamber 14 of the ammonia engine 2. There are, for example, as many main injectors 5 as there are cylinders in the ammonia engine 2 (in this case, four). The main injectors 5 operate in response to control commands from the controller 60, which will be described later.

[0025] The main throttle valve 6 is located in the first oxygen supply passage 3. The main throttle valve 6 is an electromagnetic flow control valve that controls the flow rate of air supplied to the ammonia engine 2. The main throttle valve 6 operates in response to control commands from the controller 60, which will be described later.

[0026] Furthermore, the engine system 1 includes a second oxygen supply passage 30, a blow-by gas passage 31, and a PCV valve 32 (Positive Crankcase Ventilation valve).

[0027] The second oxygen supply passage 30 is a passage that connects the section of the first oxygen supply passage 3 upstream of the main throttle valve 6 to the crankcase 21. The second oxygen supply passage 30 supplies air, which is an oxygen-containing gas, into the crankcase 21 (crank chamber 23).

[0028] As shown in Figure 2, the second oxygen supply passage 30 includes a pipe 33 connecting the area between the air cleaner 7 and the main throttle valve 6 in the intake pipe 25 to the cylinder head 12 of the ammonia engine 2, and a passage 34 provided in the cylinder head 12 and cylinder block 11 to connect the pipe 33 to the crankcase 23.

[0029] The blow-by gas passage 31 is a passage that connects the crankcase 21 to a point in the first oxygen supply passage 3 downstream of the main throttle valve 6. The blow-by gas passage 31 is a passage that recirculates the ammonia blow-by gas remaining in the crankcase 21 (crank chamber 23) back into the first oxygen supply passage 3.

[0030] As shown in Figure 2, the blow-by gas passage 31 includes a pipe 35 connecting the cylinder head 12 of the ammonia engine 2 to the area between the main throttle valve 6 and the intake manifold 24 in the intake pipe 25, and a passage 36 provided in the cylinder head 12 and cylinder block 11 to connect the pipe 35 to the crankcase 23.

[0031] The PCV valve 32 is located in the blow-by gas passage 31. The PCV valve 32 is a blow-by gas recirculation valve that adjusts the flow rate of ammonia blow-by gas recirculating to the first oxygen supply passage 3. As shown in Figure 2, the PCV valve 32 is mounted, for example, on the cylinder head 12 of the ammonia engine 2. The PCV valve 32 is located between the piping 35 and the passage 36 in the blow-by gas passage 31.

[0032] The PCV valve 32 comprises housings 37A and 37B assembled to be aligned axially, a valve body 38 movably housed within housing 37A, and a spring 39 that biases the valve body 38 toward housing 37B. The PCV valve 32 directs blow-by gas in only one direction, from the crankcase 23 side to the first oxygen supply passage 3 side.

[0033] When the pressure inside the intake manifold 24 is positive, the biasing force of the spring 39 presses the valve body 38 against the valve seat 37a located at the end of the housing 37B on the housing 37A side, thereby blocking the passage and closing the PCV valve 32. When the pressure inside the intake manifold 24 becomes negative, the valve body 38 moves against the biasing force of the spring 39 towards the first oxygen supply passage 3, forming a passage and opening the PCV valve 32 (see A in Figure 2).

[0034] Returning to Figure 1, the engine system 1 comprises an ammonia tank 40, a vaporizer 41, a reformer 42, a reforming oxygen supply passage 43, a reforming throttle valve 44, a reforming injector 45, a reforming gas passage 46, a cooler 47, and a flow control valve 48.

[0035] The ammonia tank 40 is a container for storing ammonia in a liquid state. In other words, the ammonia tank 40 stores liquid ammonia.

[0036] The vaporizer 41 is connected to the ammonia tank 40 via an ammonia supply channel 49. The vaporizer 41 vaporizes the liquid ammonia stored in the ammonia tank 40 to produce ammonia gas. The ammonia gas generated in the vaporizer 41 flows through the ammonia supply channel 50 and is supplied to the main injector 5, and also flows through the ammonia supply channel 51 and is supplied to the reforming injector 45.

[0037] The reformer 42 produces a hydrogen-containing reformed gas by reforming ammonia gas. The reformer 42 has a cylindrical housing 52 and a reforming catalyst 53 and a heater 54 housed inside the housing 52.

[0038] The housing 52 is made of a metal material such as stainless steel that is corrosion-resistant to ammonia gas. The reforming catalyst 53 is coated on a carrier exhibiting a honeycomb structure, for example. The reforming catalyst 53 is a catalyst that burns ammonia gas and decomposes ammonia gas into hydrogen. The reforming catalyst 53 is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst.

[0039] The heater 54 is located upstream of the reforming catalyst 53 within the housing 52. The heater 54 heats the reforming catalyst 53. The heater 54 heats the ammonia gas flowing through the housing 52, utilizing the heat from the ammonia gas to heat the reforming catalyst 53. For example, an electrically heated catalyst (EHC) can be used as the heater 54. Alternatively, the heater 54 may directly heat the reforming catalyst 53.

[0040] The reforming oxygen supply channel 43 connects the first oxygen supply channel 3 to the reformer 42. The reforming oxygen supply channel 43 is a channel through which air supplied to the reformer 42 flows. One end of the reforming oxygen supply channel 43 is connected to the section between the air cleaner 7 and the main throttle valve 6 in the first oxygen supply channel 3. The other end of the reforming oxygen supply channel 43 is connected to the inlet of the housing 52 of the reformer 42. The reforming oxygen supply channel 43 supplies oxygen-containing gas to the reformer 42.

[0041] The reforming throttle valve 44 is located in the reforming oxygen supply passage 43. The reforming throttle valve 44 is an electromagnetic flow control valve that controls the flow rate of air supplied to the reformer 42. The reforming throttle valve 44 operates in response to control commands from the controller 60, which will be described later. The reforming throttle valve 44 constitutes a reforming flow control valve that controls the flow rate of oxygen-containing gas supplied to the reformer 42.

[0042] The reforming injector 45 is an electromagnetic fuel injection valve that injects ammonia gas towards the reformer 42. The reforming injector 45 injects ammonia gas between the reforming throttle valve 44 and the reformer 42 in the reforming oxygen supply passage 43. There may be multiple reforming injectors 45 (two in this case) or just one. The reforming injector 45 operates in response to control commands from the controller 60, which will be described later.

[0043] The reformed gas passage 46 connects the reformer 42 and the first oxygen supply passage 3. One end of the reformed gas passage 46 is connected to the outlet of the housing 52 of the reformer 42. The other end of the reformed gas passage 46 is connected to the point between the main throttle valve 6 and the ammonia engine 2 in the first oxygen supply passage 3. The reformed gas passage 46 is a passage that supplies the reformed gas produced by the reformer 42 to the combustion chamber 14 of the ammonia engine 2.

[0044] The cooler 47 is installed in the reformed gas passage 46. The cooler 47 cools the reformed gas flowing through the reformed gas passage 46 using, for example, engine coolant used to cool the ammonia engine 2.

[0045] The flow control valve 48 is located downstream of the cooler 47 in the reformed gas flow path 46. The flow control valve 48 is a solenoid valve that adjusts the flow rate of reformed gas supplied to the combustion chamber 14 of the ammonia engine 2. The flow control valve 48 operates in response to control commands from the controller 60, which will be described later. The flow control valve 48 may also be an on / off valve.

[0046] The engine system 1 also includes a starter 59 and a controller 60. The starter 59 rotates the crankshaft 20 of the ammonia engine 2.

[0047] The controller 60 is an electronic control unit having, for example, a CPU, ROM, RAM, and an input / output interface. The controller 60 loads a program stored in ROM into RAM and executes that program with the CPU, thereby performing various control functions, including drive control of the ammonia engine 2.

[0048] When the vehicle is started, the controller 60 activates the power supply 55 to the starter 59 and heater 54, and controls the main injector 5, main throttle valve 6, reformer injector 45, and reformer throttle valve 44 to open. As a result, ammonia gas and air are supplied to the combustion chamber 14 and reformer 42 of the ammonia engine 2, and the reformed gas produced by the reformer 42 is supplied to the combustion chamber 14, so that the ammonia gas burns together with hydrogen in the combustion chamber 14.

[0049] During steady-state operation of the ammonia engine 2, the controller 60 controls the opening of the main injector 5, the main throttle valve 6, the modified injector 45, and the modified throttle valve 44 so that an air-fuel ratio corresponding to the accelerator opening is obtained.

[0050] Furthermore, the controller 60 controls the removal of ammonia blow-by gas remaining in the crankcase 21 (crank chamber 23) of the ammonia engine 2 during any period between the time the crankshaft 20 stops rotating due to the completion of ammonia gas combustion in the combustion chamber 14 of the ammonia engine 2, and the time when ammonia gas combustion occurs again in the combustion chamber 14. Blow-by gas is unburned gas that leaks into the crank chamber 23 through the gap between the cylinder block 11 and the piston 13.

[0051] Specifically, the controller 60 is configured as a control unit that controls the opening degree of the main throttle valve 6 and the opening degree of the reforming throttle valve 44 so that when the rotation of the crankshaft 20 is restarted by the starter 59, blow-by gas is returned to the first oxygen supply passage 3 via the PCV valve 32 and the blow-by gas passage 31.

[0052] Figure 3 is a flowchart showing the procedure for the blow-by gas removal control process performed by the controller 60. In this embodiment, this process is started by the driver's instruction after the rotation of the crankshaft 20 has stopped. The driver instructs the driver to perform blow-by gas removal using a manual switch or the like, for example, before getting out of the vehicle or before performing maintenance on the ammonia engine 2.

[0053] Furthermore, when the combustion of ammonia gas in the combustion chamber 14 of the ammonia engine 2 is completed, the main injector 5, the main throttle valve 6, the reforming injector 45, and the reforming throttle valve 44 are basically in a closed state.

[0054] In Figure 3, the controller 60 first controls the opening of the main throttle valve 6 and the modified throttle valve 44 (step S101). The controller 60 controls the opening of the main throttle valve 6 and the modified throttle valve 44 so that blow-by gas recirculates into the first oxygen supply passage 3. More specifically, when the rotation of the crankshaft 20 is restarted by the starter 59, the controller 60 controls the opening of the main throttle valve 6 and the modified throttle valve 44 so that negative pressure is maintained inside the intake manifold 24.

[0055] At this time, the main throttle valve 6 and the modified throttle valve 44 only need to be open enough to allow blow-by gas to be recirculated into the first oxygen supply passage 3 when the crankshaft 20 is restarted by the starter 59, and may be fully closed (open to zero).

[0056] Next, the controller 60 activates the starter 59 (step S102). This causes the crankshaft 20 of the ammonia engine 2 to rotate, creating a negative pressure inside the intake manifold 24. Step S102 may be performed before step S101, or steps S101 and S102 may be performed simultaneously.

[0057] At this time, because there is negative pressure inside the intake manifold 24, the air in the first oxygen supply passage 3 flows through the second oxygen supply passage 30 and is supplied to the crankcase 23. This air, along with the ammonia blow-by gas remaining in the crankcase 23, flows through the PCV valve 32 and the blow-by gas passage 31, returning to the first oxygen supply passage 3. In addition, since the main throttle valve 6 and the reforming throttle valve 44 are closed, the amount of air flowing through the second oxygen supply passage 30 increases accordingly.

[0058] Here, as shown in Figure 4, the PCV valve 32 has a flow characteristic in which the blow-by gas flows more easily as the negative pressure in the intake manifold 24 increases until it reaches a specified pressure N, but when the negative pressure in the intake manifold 24 exceeds the specified pressure N, the blow-by gas flows less easily. For this reason, it is preferable for the controller 60 to control the opening of the main throttle valve 6 and the modified throttle valve 44 so that the negative pressure in the intake manifold 24 becomes the specified pressure N. The specified pressure N is the negative pressure that maximizes the airflow rate per unit time through the PCV valve 32.

[0059] By controlling the opening of the main throttle valve 6 and the reforming throttle valve 44 in this way, the flow rate of air returning to the first oxygen supply passage 3 through the PCV valve 32 is directly controlled. Therefore, blow-by gas can be discharged more efficiently compared to using a simple check valve.

[0060] In the engine system 1 described above, when the driver instructs the removal of blow-by gas, the starter 59 is activated, which rotates the crankshaft 20 and adjusts the opening of the main throttle valve 6 and the modified throttle valve 44.

[0061] As a result, negative pressure is created inside the intake manifold 24, causing the air in the first oxygen supply passage 3 to flow through the piping 33 and passage 34 of the second oxygen supply passage 30 and be supplied to the crankcase 23. This air, along with the ammonia blow-by gas remaining in the crankcase 23, flows through the passage 36 of the blow-by gas passage 31, the PCV valve 32, and the piping 35 of the blow-by gas passage 31 and is returned to the first oxygen supply passage 3.

[0062] The ammonia blow-by gas then flows from the first oxygen supply passage 3 through the combustion chamber 14 and exhaust passage 4 of the ammonia engine 2 and is supplied to the three-way catalytic converter 8 and the SCR catalytic converter 9. The ammonia blow-by gas is then purified in the three-way catalytic converter 8 and the SCR catalytic converter 9.

[0063] Specifically, when the temperature of the three-way catalyst 8 is above its activation temperature, ammonia is primarily oxidized and burned by the three-way catalyst 8. When the temperature of the three-way catalyst 8 is below its activation temperature, ammonia is adsorbed by the SCR catalyst 9. This suppresses the discharge of ammonia blow-by gas through the exhaust passage 4.

[0064] As described above, in this embodiment, the opening of the main throttle valve 6 and the reforming throttle valve 44 are controlled so that ammonia blow-by gas flows back into the first oxygen supply passage 3 during any period between the time the crankshaft 20 stops rotating due to the completion of ammonia gas combustion in the combustion chamber 14 of the ammonia engine 2 and the time when ammonia gas combustion occurs again in the combustion chamber 14, and the crankshaft 20 is rotated by the starter 59. As a result, a negative pressure is created inside the intake manifold 24, which is part of the first oxygen supply passage 3, so that air flows through the second oxygen supply passage 30 and is introduced into the crankcase 21, and the PCV valve 32 opens, causing the ammonia blow-by gas remaining in the crankcase 21 to flow through the blow-by gas passage 31 together with the air and flow back into the first oxygen supply passage 3. The ammonia blow-by gas then flows along with air through the first oxygen supply passage 3, the combustion chamber 14 of the ammonia engine 2, and the exhaust passage 4 to the three-way catalytic converter 8, where it is adsorbed and oxidized. As a result, the ammonia blow-by gas remaining in the crankcase 21 is removed. This prevents, for example, the leakage of ammonia remaining in the crankcase 21 into the atmosphere when the oil pan 22 is removed and the crankcase 21 is opened during maintenance. Furthermore, by regularly removing the ammonia blow-by gas remaining in the crankcase 21, it prevents large amounts of ammonia from leaking into the atmosphere when, for example, the oil pan 22 is removed and the crankcase 21 is opened during maintenance.

[0065] Furthermore, in this embodiment, since hydrogen-containing reformed gas is supplied to the combustion chamber 14 of the ammonia engine 2, ammonia is more easily burned in the combustion chamber 14 of the ammonia engine 2. [Second Embodiment]

[0066] Figure 5 is a schematic diagram showing an engine system according to a second embodiment of the present invention. In Figure 5, the engine system 1A of this embodiment differs from the engine system 1 of the first embodiment in that it further includes an electric heater 61 and a temperature sensor 62, and also includes a controller 60A instead of the controller 60.

[0067] The electric heater 61 constitutes a heating unit that heats the three-way catalyst 8. The electric heater 61 may be positioned around the three-way catalyst 8 or upstream of the three-way catalyst 8. The temperature sensor 62 is a sensor that detects the temperature of the three-way catalyst 8.

[0068] The controller 60A activates the electric heater 61 at any time between the time the crankshaft 20 stops rotating due to the end of ammonia gas combustion in the combustion chamber 14 of the ammonia engine 2, and the time when ammonia gas combustion occurs again in the combustion chamber 14. After activating the electric heater 61, if the temperature of the three-way catalytic converter 8 detected by the temperature sensor 62 exceeds a specified temperature, the controller 60A controls the opening of the main throttle valve 6 and the reforming throttle valve 44, and activates the starter 59 to rotate the crankshaft 20, so that ammonia blow-by gas is returned to the first oxygen supply passage 3.

[0069] Figure 6 is a flowchart showing the procedure for the blow-by gas removal control process performed by controller 60A, and corresponds to Figure 3.

[0070] In Figure 6, the controller 60A first starts the electric heater 61 (step S111). This causes the three-way catalyst 8 to heat up. Next, the controller 60A determines whether the temperature of the three-way catalyst 8 is above a specified temperature based on the value detected by the temperature sensor 62 (step S112). The specified temperature is, for example, the activation temperature (oxidation temperature) of the three-way catalyst 8.

[0071] When the controller 60A determines that the temperature of the three-way catalyst 8 is above a specified temperature, it terminates the operation of the electric heater 61 (step S113). This stops the heating of the three-way catalyst 8.

[0072] The controller 60A then controls the opening degree of the main throttle valve 6 and the modified throttle valve 44 (step S101). Next, the controller 60A activates the starter 59 (step S102). This causes the crankshaft 20 to rotate, creating a negative pressure state inside the intake manifold 24.

[0073] In this embodiment, the three-way catalyst 8 is heated to a temperature (activation temperature) at which it can oxidize ammonia, thereby rapidly oxidizing the ammonia. Therefore, even when the ammonia engine 2 is cold, the three-way catalyst 8 can effectively purify the ammonia. As a result, in some cases, the SCR catalyst 9 may not need to be used.

[0074] In this embodiment, after the electric heater 61 is started and the temperature of the three-way catalytic converter 8 rises to a specified temperature, the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 are controlled, and the crankshaft 20 is rotated by the starter 59. However, this method is not limited to this. After the electric heater 61 is started, the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 may be controlled, and the crankshaft 20 may be rotated by the starter 59 after a predetermined time has elapsed. [Third Embodiment]

[0075] Figure 7 is a schematic diagram showing an engine system according to a third embodiment of the present invention. In Figure 7, the engine system 1B of this embodiment differs from the engine system 1 of the first embodiment in that it further includes a temperature sensor 65 and includes a controller 60B instead of the controller 60. This embodiment may be combined with the second embodiment described above.

[0076] The temperature sensor 65 is a temperature detection unit that detects the temperature of the engine oil eo (see Figure 2) stored in the oil pan 22 of the ammonia engine 2 or the engine coolant (not shown) that cools the ammonia engine 2.

[0077] The controller 60B controls the opening of the main throttle valve 6 and the reforming throttle valve 44, and also activates the starter 59, based on the temperature of the engine oil eo or engine coolant detected by the temperature sensor 65, during any period between the time the crankshaft 20 stops rotating due to the end of ammonia gas combustion in the combustion chamber 14 of the ammonia engine 2 and the time when ammonia gas combustion occurs again in the combustion chamber 14, so that ammonia blow-by gas is returned to the first oxygen supply passage 3.

[0078] Figure 8 is a flowchart showing the procedure for the blow-by gas removal control process performed by controller 60B, and corresponds to Figure 3.

[0079] In Figure 8, the controller 60B first acquires the value detected by the temperature sensor 65 (step S121). Then, based on the value detected by the temperature sensor 65, the controller 60B controls the opening degree of the main throttle valve 6 and the opening degree of the modified throttle valve 44 (step S101).

[0080] Specifically, when the temperature of the engine oil or engine coolant is higher than ambient temperature, the ammonia engine 2 is more likely to rotate than at ambient temperature, which tends to increase the negative pressure inside the intake manifold 24. In this case, the controller 60B increases the opening of the main throttle valve 6 and the modified throttle valve 44 compared to ambient temperature so that the negative pressure inside the intake manifold 24 reaches the specified pressure N (as described above).

[0081] On the other hand, when the temperature of the engine oil or engine coolant is lower than ambient temperature, the ammonia engine 2 is less likely to rotate than at ambient temperature, so the negative pressure in the intake manifold 24 tends to be lower. In this case, the controller 60B reduces the opening of the main throttle valve 6 and the modified throttle valve 44 to less than at ambient temperature so that the negative pressure in the intake manifold 24 reaches the specified pressure N (as described above).

[0082] Next, the controller 60B activates the starter 59 (step S102). This causes the crankshaft 20 to rotate, creating a negative pressure inside the intake manifold 24.

[0083] In this embodiment, by controlling the opening degree of the main throttle valve 6 and the reforming throttle valve 44 based on the temperature of the engine oil or engine coolant, the main throttle valve 6 and the reforming throttle valve 44 can be adjusted to an appropriate opening degree according to the temperature of the ammonia engine 2, even when the negative pressure generated in the first oxygen supply passage 3 fluctuates due to the temperature of the ammonia engine 2.

[0084] It should be noted that the present invention is not limited to the embodiments described above. For example, in the above embodiments, the three-way catalyst 8 is mainly used as the exhaust catalyst, but the exhaust catalyst is not particularly limited in form, and it is sufficient to adsorb and oxidize ammonia using one or more types of catalysts. For example, the above SCR catalyst 9 may be mainly used as the exhaust catalyst, or an oxidation catalyst may be used instead of the three-way catalyst 8 and the SCR catalyst 9.

[0085] Furthermore, in the above embodiment, the second oxygen supply passage 30 has a pipe 33 connecting the first oxygen supply passage 3 to the cylinder head 12 of the ammonia engine 2, and a passage 34 provided in the cylinder head 12 and cylinder block 11 to connect the pipe 33 to the crankcase 23, but it is not limited to such a configuration. The second oxygen supply passage 30 may also be a pipe that directly connects the first oxygen supply passage 3 to the crankcase 23.

[0086] Furthermore, in the above embodiment, the blow-by gas passage 31 has a pipe 35 connecting the first oxygen supply passage 3 and the cylinder head 12, and a passage 36 provided in the cylinder head 12 and cylinder block 11 so as to connect the pipe 35 and the crankcase 23, but it is not limited to such a configuration. The blow-by gas passage 31 may be a pipe that directly connects the crankcase 23 and the first oxygen supply passage 3. In this case, the PCV valve 32 will be installed in the pipe.

[0087] Furthermore, in the above embodiment, the blow-by gas removal process is performed by the driver's instruction, but the system is not limited to this configuration, and the blow-by gas removal process may be started automatically.

[0088] Furthermore, in the above embodiment, the blow-by gas removal control process is executed at the driver's instruction before the driver exits the vehicle or before maintenance of the ammonia engine 2, but the system is not limited to such configurations. The blow-by gas removal control process can be executed at the driver's instruction or automatically during any period between the time the crankshaft 20 stops rotating due to the completion of ammonia gas combustion in the combustion chamber 14 of the ammonia engine 2 and the time when ammonia gas combustion occurs again in the combustion chamber 14. For example, the blow-by gas removal control process may be executed when the crankshaft 20 is rotated by the starter 59 after idling stop. Even in this case, the ammonia blow-by gas remaining in the crankcase 21 can be removed periodically, thus suppressing the leakage of ammonia blow-by gas into the atmosphere, for example, during maintenance.

[0089] Furthermore, in the above embodiment, the reforming oxygen supply channel 43 is connected to the first oxygen supply channel 3, but the reforming oxygen supply channel 43 is not particularly limited in form and may be a channel through which air supplied from a route different from the first oxygen supply channel 3 flows.

[0090] Furthermore, in the above embodiment, the reformer 42 has a reforming catalyst 53 that has both the function of burning ammonia gas and the function of decomposing ammonia gas into hydrogen, but it is not limited to such a configuration. The reformer 42 may have a combustion catalyst for burning ammonia gas and a reforming catalyst for decomposing ammonia gas into hydrogen separately.

[0091] Furthermore, in the above embodiment, air is supplied to the ammonia engine 2 and the reformer 42, but instead of air, only oxygen may be supplied to the ammonia engine 2 and the reformer 42.

[0092] Furthermore, in the above embodiment, a reformed gas containing hydrogen is produced by the reformer 42 and supplied to the ammonia engine 2 together with ammonia. However, the present invention is also applicable to engine systems in which hydrogen is not supplied to the ammonia engine 2. [Explanation of symbols]

[0093] 1, 1A, 1B... Engine system, 2... Ammonia engine (engine), 3... First oxygen supply passage (oxygen supply passage), 4... Exhaust passage, 6... Main throttle valve (flow control valve), 8... Three-way catalytic converter (exhaust catalytic converter), 9... SCR catalytic converter (exhaust catalytic converter), 13... Piston, 14... Combustion chamber, 20... Crankshaft, 21... Crankcase, 30... Second oxygen supply passage, 31... Blow-by gas passage, 32... PCV valve (blow-by gas recirculation valve), 42... Reformer, 43... Oxygen supply passage for reforming, 44... Reformation throttle valve (flow control valve for reforming), 46... Reformed gas passage, 59... Starter, 60, 60A, 60B... Controller (control unit), 61... Electric heater (heating unit), 65... Temperature sensor (temperature detection unit).

Claims

1. An engine system comprising an engine having a piston capable of reciprocating within a combustion chamber for burning ammonia, a crankshaft connected to the piston, and a crankcase housing the crankshaft, A first oxygen supply channel is connected to the engine and through which oxygen-containing gas supplied to the combustion chamber flows, A flow control valve is provided in the first oxygen supply channel and controls the flow rate of the oxygen-containing gas supplied to the combustion chamber, An exhaust passage is connected to the aforementioned engine and through which exhaust gas generated from the combustion chamber flows, An exhaust catalyst is installed in the aforementioned exhaust passage and adsorbs and oxidizes ammonia, A second oxygen supply channel connects the first oxygen supply channel upstream of the flow control valve to the crankcase and supplies the oxygen-containing gas into the crankcase, A blow-by gas passage connects the crankcase to a point downstream of the flow control valve in the first oxygen supply passage, and recirculates the ammonia blow-by gas remaining in the crankcase to the first oxygen supply passage. A blow-by gas recirculation valve is provided in the blow-by gas passage and adjusts the flow rate of the ammonia blow-by gas that recirculates to the first oxygen supply passage. A starter that rotates the aforementioned crankshaft, The system includes a control unit that controls the opening degree of the flow control valve so that the blow-by gas flows back into the first oxygen supply passage when the crankshaft is rotating due to the starter, The first oxygen supply channel is connected to the engine and has an intake manifold located downstream of the flow control valve. The control unit controls the opening degree of the flow control valve so that the negative pressure in the intake manifold is set to a specified pressure that maximizes the airflow rate per unit time through the blow-by gas recirculation valve when the crankshaft is rotating due to the starter.

2. A reformer that produces a hydrogen-containing reformed gas by reforming ammonia, A reforming oxygen supply channel for supplying the oxygen-containing gas to the reformer, A reforming flow control valve is provided in the reforming oxygen supply channel and controls the flow rate of the oxygen-containing gas supplied to the reformer. The system further comprises a reformed gas flow path for supplying the reformed gas generated by the reformer to the combustion chamber, The control unit controls the opening of the flow control valve and the reforming flow control valve so that the blow-by gas is returned to the first oxygen supply passage when the crankshaft is rotating by the starter. The engine system according to claim 1, wherein the control unit controls the opening of the flow control valve and the reforming flow control valve so that the negative pressure in the intake manifold becomes the specified pressure when the crankshaft is rotating by the starter.

3. The engine system according to claim 1, further comprising a heating unit for heating the exhaust catalyst.

4. It further includes a temperature detection unit for detecting the temperature of engine oil or engine coolant, The engine system according to claim 1, wherein the control unit controls the opening degree of the flow control valve based on the temperature of the engine oil or engine coolant detected by the temperature detection unit.

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