JP2024057726A - Engine System - Google Patents

Abstract

[Problem] To provide an engine system capable of suppressing the outflow of ammonia blow-by gas remaining in a crankcase into the atmosphere. [Solution] The engine system 1 includes a second oxygen supply passage 30 that connects the upstream side of a main throttle valve 6 in a first oxygen supply passage 3 with a crankcase 21 and supplies air into the crankcase 21, a blow-by gas passage 31 that connects the crankcase 21 with the downstream side of the main throttle valve 6 in the first oxygen supply passage 3 and returns the ammonia blow-by gas remaining in the crankcase 21 to the first oxygen supply passage 3, a starter 59 that rotates a crankshaft 20, and a controller 60 that controls the opening of the main throttle valve 6 so that the blow-by gas returns to the first oxygen supply passage 3 when the crankshaft 20 is being rotated by the starter 59. [Selected Figure] Figure 1

Description

The present invention relates to an engine system.

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 to a crank chamber in the engine block and introduces intake air (fresh air) in the intake passage into the crank chamber, a return passage that connects the intake passage downstream of the throttle valve to the crank chamber and returns blow-by gas remaining in the crank chamber to the intake passage, and a PCV valve provided in the return passage.

JP 2012-145057 A

In recent years, ammonia engines have been developed that use ammonia as fuel, but because ammonia blow-by gas remains in the crankcase, it is desirable to prevent ammonia blow-by gas from escaping into the atmosphere, for example during maintenance.

The object of the present invention is to provide an engine system that can prevent ammonia blow-by gas remaining in the crankcase from leaking into the atmosphere.

(1) One aspect of the present invention is an engine system including an engine having a piston capable of reciprocating in a combustion chamber that burns ammonia, a crankshaft connected to the piston, and a crankcase that houses the crankshaft, the engine system including a first oxygen supply flow path connected to the engine and through which oxygen-containing gas to be supplied to the combustion chamber flows, a flow control valve disposed in the first oxygen supply flow path and controlling the flow rate of the oxygen-containing gas to be supplied to the combustion chamber, an exhaust flow path connected to the engine and through which exhaust gas generated from the combustion chamber flows, an exhaust catalyst disposed in the exhaust flow path that adsorbs and oxidizes ammonia, and a portion of the first oxygen supply flow path upstream of the flow control valve and the crankcase. The crankcase is connected to the second oxygen supply passage, which supplies oxygen-containing gas into the crankcase; a blow-by gas passage that connects the crankcase to a location downstream of the flow control valve in the first oxygen supply passage and returns ammonia blow-by gas remaining in the crankcase to the first oxygen supply passage; a blow-by gas return valve that is disposed in the blow-by gas passage and adjusts the flow rate of the ammonia blow-by gas returned to the first oxygen supply passage; a starter that rotates the crankshaft; and a control unit that controls the opening of the flow control valve so that the blow-by gas is returned to the first oxygen supply passage when the crankshaft is rotated by the starter.

In such an engine system, the opening of the flow control valve is controlled so that the ammonia blow-by gas is returned to the first oxygen supply passage during any period between when the rotation of the crankshaft stops due to the end of the combustion of ammonia in the combustion chamber of the engine and when the combustion of ammonia occurs again in the combustion chamber, and the crankshaft is rotated by the starter. Then, the combustion chamber side portion of the first oxygen supply passage becomes negative pressure, so that the oxygen-containing gas flows through the second oxygen supply passage and is introduced into the crankcase, and the blow-by gas return valve opens, so that the ammonia blow-by gas remaining in the crankcase flows through the blow-by gas passage together with the oxygen-containing gas and is returned to the first oxygen supply passage. Then, the ammonia blow-by gas flows through the first oxygen supply passage, the combustion chamber and the exhaust passage of the engine together with the oxygen-containing gas, and is supplied to the exhaust catalyst, where it is adsorbed and oxidized by the exhaust catalyst. As a result, the ammonia blow-by gas remaining in the crankcase is removed. This prevents the ammonia remaining in the crankcase from leaking into the atmosphere when the crankcase is opened for maintenance, for example. Furthermore, if the ammonia blow-by gas remaining in the crankcase is periodically removed, it is possible to prevent a large amount of ammonia from escaping into the atmosphere, for example, when the crankcase is opened for maintenance.

(2) In the above (1), the engine system further includes a reformer that generates a reformed gas containing hydrogen by reforming ammonia, a reforming oxygen supply passage that supplies an oxygen-containing gas to the reformer, a reforming flow control valve that is disposed in the reforming oxygen supply passage and controls the flow rate of the 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 of the reforming flow control valve so that blow-by gas is returned to the first oxygen supply passage when the crankshaft is rotated by the starter. In this configuration, the reformed gas containing hydrogen is supplied to the combustion chamber of the engine, making it easier for ammonia to be burned in the combustion chamber.

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

(4) In any of (1) to (3) above, the engine system may further include a temperature detection unit that detects the temperature of the engine oil or the engine coolant, and the control unit may control the opening of the flow control valve based on the temperature of the engine oil or the engine coolant detected by the temperature detection unit. In this configuration, even if the negative pressure generated in the first oxygen supply flow path varies depending on the engine temperature, the flow control valve can be adjusted to an appropriate opening according to the engine temperature.

The present invention makes it possible to prevent ammonia blow-by gas remaining in the crankcase from leaking into the atmosphere.

1 is a schematic configuration diagram showing an engine system according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the ammonia engine and intake system shown in FIG. 2 is a flowchart showing a procedure of a blow-by gas removal control process executed by a controller shown in FIG. 1 . 3 is a graph showing an example of flow characteristics of the PCV valve shown in FIG. 2 . FIG. 5 is a schematic configuration diagram showing an engine system according to a second embodiment of the present invention. 6 is a flowchart showing a procedure of a blow-by gas removal control process executed by a controller shown in FIG. 5 . FIG. 11 is a schematic configuration diagram showing an engine system according to a third embodiment of the present invention. 8 is a flowchart showing a procedure of a blow-by gas removal control process executed by a controller shown in FIG. 7 .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are designated by the same reference numerals, and duplicated description will be omitted.
[First embodiment]

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

The ammonia engine 2 is an engine that uses ammonia gas ( _NH3 gas) as fuel. In the ammonia engine 2, hydrogen ( _H2 ) is mixed with the ammonia gas as a combustion improver to facilitate combustion of the flame-retardant ammonia gas. The ammonia engine 2 is, for example, a four-cylinder engine.

As shown in FIG. 2, the ammonia engine 2 has a cylinder block 11, a cylinder head 12 attached to the cylinder block 11, a number of pistons 13 (four in this example) arranged to be capable of reciprocating motion inside the cylinder block 11, a crankshaft 20 connected to the pistons 13, and a crankcase 21 housing the crankshaft 20.

The ammonia engine 2 has multiple (four in this example) combustion chambers 14 in which ammonia is burned together with hydrogen to generate exhaust gas. The combustion chambers 14 are defined by a space surrounded by a cylinder block 11, a cylinder head 12, and a piston 13.

The cylinder head 12 is provided with multiple intake ports 15 and exhaust ports 16 (four in this example) that are connected to each combustion chamber 14. The intake ports 15 are opened and closed by intake valves 17. The exhaust ports 16 are opened and closed by exhaust valves 18.

Each piston 13 is connected to a crankshaft 20 via a connecting rod 19. The crankcase 21 is attached to the end of the cylinder block 11 opposite the end where the cylinder head 12 is provided. An oil pan 22 that stores engine oil eo is removably attached to the end of the crankcase 21 opposite 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.

The first oxygen supply flow 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 this intake manifold 24. The first oxygen supply flow passage 3 is a flow passage through which air flows to be supplied to each combustion chamber 14 of the ammonia engine 2. The air is a gas containing oxygen (oxygen-containing gas). An air cleaner 7 is provided in the intake pipe 25 to remove foreign matter such as dust and dirt contained in the air.

The exhaust flow path 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 flow path 4 is a flow path through which exhaust gas generated from each combustion chamber 14 of the ammonia engine 2 flows.

Returning to FIG. 1, the exhaust flow path 4 is provided 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 provided in the exhaust pipe 27.

The three-way catalyst 8 oxidizes ammonia mainly using the air that flows into the three-way catalyst 8. The three-way catalyst 8 also adsorbs ammonia, although in smaller amounts than the SCR catalyst 9. The SCR catalyst 9 adsorbs ammonia and oxidizes the ammonia using NOx that flows into the SCR catalyst 9. The NOx is reduced. The three-way catalyst 8 and the SCR catalyst 9 constitute an exhaust catalyst disposed in the exhaust flow path 4.

The main injector 5 is an electromagnetic fuel injection valve that injects ammonia gas toward the combustion chamber 14 of the ammonia engine 2. For example, the number of main injectors 5 is equal to the number of cylinders of the ammonia engine 2 (four in this example). The main injectors 5 operate in response to control commands from the controller 60, which will be described later.

The main throttle valve 6 is disposed 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 a control command from a controller 60, which will be described later.

The engine system 1 also includes a second oxygen supply passage 30, a blow-by gas passage 31, and a PCV valve 32 (Positive Crankcase Ventilation valve).

The second oxygen supply passage 30 is a passage that connects a portion 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, to the crankcase 21 (crank chamber 23).

As shown in FIG. 2, the second oxygen supply passage 30 has a pipe 33 that connects the intake pipe 25 between the air cleaner 7 and the main throttle valve 6 to the cylinder head 12 of the ammonia engine 2, and a passage 34 provided in the cylinder head 12 and the cylinder block 11 to connect the pipe 33 to the crank chamber 23.

The blow-by gas flow passage 31 is a flow passage that connects the crankcase 21 to a location downstream of the main throttle valve 6 in the first oxygen supply flow passage 3. The blow-by gas flow passage 31 is a flow passage that returns ammonia blow-by gas remaining in the crankcase 21 (crank chamber 23) to the first oxygen supply flow passage 3.

As shown in FIG. 2, the blow-by gas flow passage 31 has a pipe 35 that connects the cylinder head 12 of the ammonia engine 2 to a location in the intake pipe 25 between the main throttle valve 6 and the intake manifold 24, and a passage 36 provided in the cylinder head 12 and the cylinder block 11 to connect the pipe 35 to the crank chamber 23.

The PCV valve 32 is disposed in the blow-by gas flow passage 31. The PCV valve 32 is a blow-by gas recirculation valve that adjusts the flow rate of ammonia blow-by gas recirculated to the first oxygen supply flow passage 3. As shown in FIG. 2, the PCV valve 32 is attached to, for example, the cylinder head 12 of the ammonia engine 2. The PCV valve 32 is disposed between the pipe 35 and the passage 36 in the blow-by gas flow passage 31.

The PCV valve 32 has housings 37A, 37B assembled so as to be arranged next to each other in the axial direction, a valve body 38 movably accommodated in the housing 37A, and a spring 39 that biases the valve body 38 toward the housing 37B. The PCV valve 32 allows blow-by gas to flow in only one direction, from the crank chamber 23 side to the first oxygen supply passage 3 side.

When the pressure inside the intake manifold 24 is positive, the force of the spring 39 presses the valve body 38 against the valve seat 37a provided at the end of the housing 37B on the housing 37A side, 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 force of the spring 39 toward the first oxygen supply flow path 3, forming a passage and opening the PCV valve 32 (see A in Figure 2).

Returning to FIG. 1, the engine system 1 includes 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 reformed gas passage 46, a cooler 47, and a flow control valve 48.

The ammonia tank 40 is a container that stores ammonia in a liquid state. In other words, the ammonia tank 40 stores liquid ammonia.

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

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

The housing 52 is made of a metal material such as stainless steel that is resistant to corrosion by ammonia gas. The reforming catalyst 53 is applied to a carrier having, for example, a honeycomb structure. The reforming catalyst 53 is a catalyst that burns ammonia gas and decomposes the ammonia gas into hydrogen. The reforming catalyst 53 is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst.

The heater 54 is disposed upstream of the reforming catalyst 53 in the housing 52. The heater 54 heats the reforming catalyst 53. The heater 54 heats the ammonia gas flowing inside the housing 52, and uses the heat of the ammonia gas to heat the reforming catalyst 53. For example, an electrically heated catalyst (EHC) or the like is used as the heater 54. The heater 54 may also directly heat the reforming catalyst 53.

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

The reforming throttle valve 44 is disposed 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 a control command from a controller 60, which will be described later. The reforming throttle valve 44 constitutes a reforming flow control valve that controls the flow rate of the oxygen-containing gas supplied to the reformer 42.

The reforming injector 45 is an electromagnetic fuel injection valve that injects ammonia gas toward 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. The number of reforming injectors 45 may be multiple (two in this example) or may be one. The reforming injector 45 operates in response to a control command from the controller 60, which will be described later.

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

The cooler 47 is disposed in the reformed gas flow passage 46. The cooler 47 cools the reformed gas flowing through the reformed gas flow passage 46, for example, by using engine cooling water that cools the ammonia engine 2.

The flow rate control valve 48 is disposed downstream of the cooler 47 in the reformed gas flow passage 46. The flow rate control valve 48 is an electromagnetic valve that adjusts the flow rate of the reformed gas supplied to the combustion chamber 14 of the ammonia engine 2. The flow rate control valve 48 operates in response to a control command from a controller 60, which will be described later. The flow rate control valve 48 may be an on-off valve (ON/OFF valve).

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.

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

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

During steady-state operation of the ammonia engine 2, the controller 60 controls the opening of the main injector 5, the opening of the main throttle valve 6, the opening of the reforming injector 45, and the opening of the reforming throttle valve 44 so as to obtain an air-fuel ratio that corresponds to the accelerator opening.

The controller 60 also performs control to remove ammonia blow-by gas remaining in the crankcase 21 (crank chamber 23) of the ammonia engine 2 during any period between the end of combustion of ammonia gas in the combustion chamber 14 of the ammonia engine 2, causing the crankshaft 20 to stop rotating, and the start of combustion of ammonia gas again in the combustion chamber 14. The blow-by gas is unburned gas that leaks into the crank chamber 23 from the gap between the cylinder block 11 and the piston 13.

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

Figure 3 is a flowchart showing the procedure of the blow-by gas removal control process executed 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 issues an instruction to remove the blow-by gas using a manual switch or the like, for example, before getting off the vehicle or before performing maintenance on the ammonia engine 2.

When the combustion of ammonia gas ends in the combustion chamber 14 of the ammonia engine 2, 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.

In FIG. 3, the controller 60 first controls the opening of the main throttle valve 6 and the reforming throttle valve 44 (step S101). The controller 60 controls the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 so that the blow-by gas flows back to the first oxygen supply passage 3. More specifically, when the starter 59 restarts the rotation of the crankshaft 20, the controller 60 controls the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 so as to maintain a negative pressure inside the intake manifold 24.

At this time, the main throttle valve 6 and the reforming throttle valve 44 only need to be opened to such an extent that the blow-by gas can be returned to the first oxygen supply passage 3 when the rotation of the crankshaft 20 is resumed by the starter 59, and may be fully closed (zero opening).

Then, the controller 60 starts the starter 59 (step S102). Then, the crankshaft 20 of the ammonia engine 2 rotates, and the inside of the intake manifold 24 becomes negative pressure. Note that step S102 may be performed before step S101, or steps S101 and S102 may be performed simultaneously.

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 crank chamber 23, and this air flows through the blow-by gas passage 31 via the PCV valve 32 together with the ammonia blow-by gas remaining in the crank chamber 23 and is returned to the first oxygen supply passage 3. In addition, because 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.

As shown in FIG. 4, the PCV valve 32 has a flow characteristic in which the higher the negative pressure in the intake manifold 24 is, the easier it is for blow-by gas to flow until it reaches the specified pressure N, but once the negative pressure in the intake manifold 24 exceeds the specified pressure N, the blow-by gas becomes less able to flow. For this reason, it is preferable for the controller 60 to control the opening of the main throttle valve 6 and the reforming 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 flow rate of air through the PCV valve 32 per unit time.

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. This makes it possible to more efficiently exhaust blow-by gas than when a simple check valve is used.

In the engine system 1 described above, when the driver issues a command to remove blow-by gas, the starter 59 is started to rotate the crankshaft 20 and adjust the opening of the main throttle valve 6 and the reforming throttle valve 44.

As a result, negative pressure is created inside the intake manifold 24, and the air in the first oxygen supply passage 3 flows through the piping 33 and passage 34 of the second oxygen supply passage 30 and is supplied to the crank chamber 23. The air, together with the ammonia blow-by gas remaining in the crank chamber 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.

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 catalyst 8 and the SCR catalyst 9. The ammonia blow-by gas is purified in the three-way catalyst 8 and the SCR catalyst 9.

Specifically, when the temperature of the three-way catalyst 8 is equal to or higher than the activation temperature, ammonia is primarily oxidized and burned by the three-way catalyst 8. When the temperature of the three-way catalyst 8 is lower than the activation temperature, ammonia is adsorbed by the SCR catalyst 9. This prevents ammonia blow-by gas from flowing through the exhaust passage 4 and being discharged.

As described above, in this embodiment, the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 are controlled so that the ammonia blow-by gas is returned to the first oxygen supply passage 3 during any period between when the rotation of the crankshaft 20 stops due to the end of the combustion of ammonia gas in the combustion chamber 14 of the ammonia engine 2 and when the combustion of ammonia gas occurs again in the combustion chamber 14, and the crankshaft 20 is rotated by the starter 59. Then, the inside of the intake manifold 24, which is a part of the first oxygen supply passage 3, becomes negative pressure, so that air flows through the second oxygen supply passage 30 and is introduced into the crankcase 21, and the PCV valve 32 opens, so that the ammonia blow-by gas remaining in the crankcase 21 flows together with the air through the blow-by gas passage 31 and is returned to the first oxygen supply passage 3. Then, the ammonia blow-by gas flows together with the air through the first oxygen supply passage 3, the combustion chamber 14 of the ammonia engine 2, and the exhaust passage 4 to be supplied to the three-way catalyst 8, where it is adsorbed and oxidized by the three-way catalyst 8. As a result, the ammonia blow-by gas remaining in the crankcase 21 is removed. This prevents the ammonia remaining in the crankcase 21 from leaking into the atmosphere when, for example, the oil pan 22 is removed and the crankcase 21 is opened during maintenance. In addition, if the ammonia blow-by gas remaining in the crankcase 21 is periodically removed, a large amount of ammonia is prevented from leaking into the atmosphere when, for example, the oil pan 22 is removed and the crankcase 21 is opened during maintenance.

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

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 includes a controller 60A instead of the controller 60.

The electric heater 61 constitutes a heating section that heats the three-way catalyst 8. The electric heater 61 may be disposed around the three-way catalyst 8, or may be disposed upstream of the three-way catalyst 8. The temperature sensor 62 is a sensor that detects the temperature of the three-way catalyst 8.

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

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

In FIG. 6, the controller 60A first activates the electric heater 61 (step S111). This causes the temperature of the three-way catalyst 8 to rise. Next, the controller 60A determines whether the temperature of the three-way catalyst 8 is equal to or higher than a specified temperature based on the detection value of the temperature sensor 62 (step S112). The specified temperature is, for example, the activation temperature (oxidization temperature) of the three-way catalyst 8.

When the controller 60A determines that the temperature of the three-way catalyst 8 is equal to or higher than the specified temperature, it stops the operation of the electric heater 61 (step S113). This stops the temperature rise of the three-way catalyst 8.

Then, the controller 60A controls the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 (step S101). Next, the controller 60A starts the starter 59 (step S102). This causes the crankshaft 20 to rotate, creating a negative pressure inside the intake manifold 24.

In this embodiment, the three-way catalyst 8 is heated to a temperature (activation temperature) at which the three-way catalyst 8 can oxidize ammonia, so that the ammonia is quickly oxidized by the three-way catalyst 8. Therefore, even when the ammonia engine 2 is in a cold state, the three-way catalyst 8 can effectively purify ammonia. As a result, in some cases, it is not necessary to use the SCR catalyst 9.

In this embodiment, when the temperature of the three-way catalyst 8 rises to a specified temperature after the electric heater 61 is started, 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, but the present invention is not limited to this method. It is also possible to control the opening of the main throttle valve 6 and the opening of the reforming throttle valve 44 and rotate the crankshaft 20 by the starter 59 when a predetermined time has elapsed after the electric heater 61 is started.
[Third embodiment]

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.

The temperature sensor 65 is a temperature detection unit that detects the temperature of the engine oil eo (see FIG. 2) stored in the oil pan 22 of the ammonia engine 2 or the engine cooling water (not shown) that cools the ammonia engine 2.

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

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

In FIG. 8, the controller 60B first obtains the detection value of the temperature sensor 65 (step S121). Then, the controller 60B controls the opening degree of the main throttle valve 6 and the opening degree of the reforming throttle valve 44 based on the detection value of the temperature sensor 65 (step S101).

Specifically, when the temperature of the engine oil or engine coolant is higher than room temperature, the ammonia engine 2 is in a state in which it is easier to rotate than at room temperature, and the negative pressure in the intake manifold 24 is likely to become high. In this case, the controller 60B increases the opening of the main throttle valve 6 and the reforming throttle valve 44 to a value greater than that at room temperature, so that the negative pressure in the intake manifold 24 becomes the specified pressure N (described above).

On the other hand, when the temperature of the engine oil or engine coolant is lower than room temperature, the ammonia engine 2 is less likely to rotate than at room temperature, and the negative pressure in the intake manifold 24 is more likely to be low. In this case, the controller 60B reduces the opening of the main throttle valve 6 and the reforming throttle valve 44 to a smaller value than at room temperature so that the negative pressure in the intake manifold 24 becomes the specified pressure N (described above).

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

In this way, in this embodiment, by controlling the opening 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 according to the temperature of the ammonia engine 2 even if the negative pressure generated in the first oxygen supply passage 3 varies depending on the temperature of the ammonia engine 2.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the three-way catalyst 8 is mainly used as the exhaust catalyst, but the exhaust catalyst is not particularly limited to that form, and it is sufficient that one or more types of catalyst adsorb and oxidize ammonia. 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.

In the above embodiment, the second oxygen supply flow path 30 has a pipe 33 that connects the first oxygen supply flow path 3 and the cylinder head 12 of the ammonia engine 2, and a passage 34 provided in the cylinder head 12 and the cylinder block 11 to communicate the pipe 33 with the crank chamber 23, but is not limited to such a form. The second oxygen supply flow path 30 may be a pipe that directly connects the first oxygen supply flow path 3 and the crank chamber 23.

In the above embodiment, the blow-by gas flow passage 31 has a pipe 35 that connects the first oxygen supply flow passage 3 and the cylinder head 12, and a passage 36 provided in the cylinder head 12 and the cylinder block 11 to communicate the pipe 35 with the crank chamber 23, but is not limited to this form. The blow-by gas flow passage 31 may be a pipe that directly connects the crank chamber 23 with the first oxygen supply flow passage 3. In this case, the PCV valve 32 is disposed in the pipe.

In addition, in the above embodiment, the blow-by gas removal process is performed in response to a driver's instruction, but this is not limited to a specific form, and the blow-by gas removal process may be started automatically.

In the above embodiment, the blow-by gas removal control process is executed by the driver's instruction before the driver gets off the vehicle or before maintenance of the ammonia engine 2, but the present invention is not limited to such a form. The blow-by gas removal control process may be executed by the driver's instruction or automatically during any period between the end of the combustion of ammonia gas in the combustion chamber 14 of the ammonia engine 2, which causes the crankshaft 20 to stop rotating, and the starter 59 to start rotating the crankshaft 20 again. For example, the blow-by gas removal control process may be executed when the engine is switched from idling stop to rotating the crankshaft 20. Even in this case, the ammonia blow-by gas remaining in the crankcase 21 can be periodically removed, so that the ammonia blow-by gas can be prevented from leaking into the atmosphere during maintenance, for example.

In addition, in the above embodiment, the reforming oxygen supply flow passage 43 is connected to the first oxygen supply flow passage 3, but the reforming oxygen supply flow passage 43 is not limited to this form and may be a flow passage through which air supplied from a route other than the first oxygen supply flow passage 3 flows.

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 is not limited to such a form. The reformer 42 may have a combustion catalyst that burns ammonia gas and a reforming catalyst that decomposes ammonia gas into hydrogen separately.

In addition, 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.

In addition, in the above embodiment, the reformer 42 generates a reformed gas containing hydrogen, and the reformed gas is supplied to the ammonia engine 2 together with ammonia, but the present invention is also applicable to engine systems in which hydrogen is not supplied to the ammonia engine 2.

1, 1A, 1B... engine system, 2... ammonia engine (engine), 3... first oxygen supply flow path (oxygen supply flow path), 4... exhaust flow path, 6... main throttle valve (flow control valve), 8... three-way catalyst (exhaust catalyst), 9... SCR catalyst (exhaust catalyst), 13... piston, 14... combustion chamber, 20... crankshaft, 21... crankcase, 30... second oxygen supply flow path, 31... blow-by gas flow path, 32... PCV valve (blow-by gas return valve), 42... reformer, 43... reforming oxygen supply flow path, 44... reforming throttle valve (reforming flow control valve), 46... reforming gas flow path, 59... starter, 60, 60A, 60B... controller (control unit), 61... electric heater (heating unit), 65... temperature sensor (temperature detection unit).

Claims (4)

An engine system including an engine having a piston capable of reciprocating in a combustion chamber for burning ammonia, a crankshaft connected to the piston, and a crankcase accommodating the crankshaft,
a first oxygen supply passage connected to the engine and through which an oxygen-containing gas to be supplied to the combustion chamber flows;
a flow control valve disposed in the first oxygen supply passage and configured to control a flow rate of the 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 configured to adsorb and oxidize ammonia;
a second oxygen supply passage connecting a portion of the first oxygen supply passage upstream of the flow control valve to the crankcase and supplying the oxygen-containing gas into the crankcase;
a blow-by gas flow passage that connects the crankcase and a portion of the first oxygen supply flow passage downstream of the flow control valve and returns ammonia blow-by gas remaining in the crankcase to the first oxygen supply flow passage;
a blow-by gas reflux valve disposed in the blow-by gas passage and configured to adjust a flow rate of the ammonia blow-by gas refluxed to the first oxygen supply passage;
A starter that rotates the crankshaft;
a control unit that controls an opening degree of the flow control valve so that the blow-by gas is returned to the first oxygen supply passage when the crankshaft is rotated by the starter. a reformer that generates a reformed gas containing hydrogen by reforming ammonia;
a reforming oxygen supply passage for supplying the oxygen-containing gas to the reformer;
a reforming flow rate control valve disposed in the reforming oxygen supply passage for controlling a flow rate of the oxygen-containing gas supplied to the reformer;
a reformed gas flow path that supplies the reformed gas generated by the reformer to the combustion chamber,
2. The engine system according to claim 1, wherein the control unit controls an opening degree of the reforming flow control valve so that the blow-by gas is returned to the first oxygen supply passage when the crankshaft is rotated by the starter. The engine system according to claim 1, further comprising a heating section for heating the exhaust catalyst. A temperature detector for detecting a temperature of engine oil or engine coolant is further provided.
2. The engine system according to claim 1, wherein the control unit controls an opening degree of the flow control valve based on the temperature of the engine oil or the engine coolant detected by the temperature detection unit.

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