Engine system

Abstract

This engine system is provided with: an engine including a cylinder and a piston housed in the cylinder; an air tank; an air supply system including a starting air line for guiding compressed air stored in the air tank into the cylinder as starting air of the engine; and a fuel gas supply system for supplying fuel gas into the cylinder. The engine further includes a crankshaft located below the piston for driving the piston, and a crankcase housing the crankshaft. The air supply system further includes a bleeding line for bleeding compressed air flowing through the starting air line and guiding the compressed air to the crank chamber in the crankcase.

Description

Technical Field

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

[0002] The present application claims priority based on Japanese Patent Application No. 2023-140611 filed in the Japan Patent Office on August 31, 2023, the contents of which are incorporated herein by reference.Background Art

[0003] An engine system disclosed in PTL 1 includes a cylinder, a piston housed in the cylinder, a crankshaft that is located below the piston and drives the piston, and a crankcase that houses the crankshaft.Citation ListPatent Literature

[0004] [PTL 1] Japanese Unexamined Patent Application Publication No. 2017-031957Summary of InventionTechnical Problem

[0005] A fuel gas in a combustion chamber in the cylinder may leak to the crank chamber in the crankcase through a space between the cylinder and the piston (the fuel gas may be referred to as a blow-by gas). When the concentration of the fuel gas in an unburned state in the crank chamber is high, there is a risk that the fuel gas may ignite. It is preferable to implement measures to reduce the risk, without complicating the configuration of the engine system.

[0006] An object of the present disclosure is to provide an engine system that reduces a risk of ignition of an unburned gas in a crank chamber with a simple configuration. Solution to Problem

[0007] According to at least one embodiment of the present disclosure, there is provided an engine system including: an engine that includes a cylinder and a piston housed in the cylinder; an air supply system that includes an air tank and a starting air line for guiding compressed air stored in the air tank as starting air for the engine into the cylinder; and a fuel gas supply system for supplying a fuel gas into the cylinder, in which the engine further includes a crankshaft that is located below the piston and is configured to be driven by the piston and a crankcase that houses the crankshaft, and the air supply system further includes an air extraction line for extracting the compressed air flowing through the starting air line and guiding the compressed air to a crank chamber in the crankcase.Advantageous Effects of Invention

[0008] According to the present disclosure, it is possible to provide an engine system that reduces a risk of ignition of an unburned gas in a crank chamber with a simple configuration.Brief Description of Drawings

[0009] FIG. 1 is a schematic view showing an engine system according to an embodiment. FIG. 2 is a schematic view showing an engine according to the embodiment. FIG. 3 is a schematic view showing an air supply system according to the embodiment. FIG. 4 is a schematic view showing an engine system according to the embodiment. FIG. 5 is a flowchart showing crank chamber purge control according to the embodiment. FIG. 6 is a flowchart showing engine control according to the embodiment. FIG. 7 is a schematic view showing an engine system according to another embodiment. FIG. 8 is a schematic view showing a crankcase according to a first embodiment. FIG. 9 is a schematic view showing a crankcase according to a second embodiment. FIG. 10 is another schematic view showing the crankcase according to the second embodiment. FIG. 11 is a schematic view showing a crankcase according to a third embodiment. FIG. 12 is a schematic view showing a crankcase according to a fourth embodiment. FIG. 13 is a schematic view showing a crankcase according to a fifth embodiment. FIG. 14 is a schematic view showing an engine system according to still another embodiment. Description of Embodiments

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, dimensions, materials, shapes, relative dispositions, and the like of components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure and are only explanatory examples.

[0011] For example, it is assumed that, strictly speaking, an expression representing relative or absolute disposition, such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial", not only represents the disposition, but also represents a state of relative displacement with a tolerance or a sufficient angle or distance to obtain the same function.

[0012] For example, it is assumed that, strictly speaking, expressions, such as "identical", "equal", and "homogeneous", representing that things are in an equal state not only represent the equal state, but also represent a state in which there is a tolerance or a sufficient difference to obtain the same function.

[0013] For example, it is assumed that an expression representing a shape, such as a quadrangular shape or a cylindrical shape, not only represents a shape, such as a quadrangular shape or a cylindrical shape, in a geometrically strict sense, but also represents a shape including an uneven portion, a chamfered portion, or the like within a range in which the same effect is obtained.

[0014] Meanwhile, expressions such as "being provided with", "including", or "having" one component are not exclusive expressions excluding existence of other components.

[0015] The same configurations are denoted by the same reference numerals, and the description thereof may be omitted.<Overview of Engine System 1>

[0016] FIG. 1 is a schematic view showing an engine system 1 according to an embodiment of the present disclosure. For example, the engine system 1 that may be incorporated into a power generation facility includes an engine 5 in which a combustion chamber 9 and a crank chamber 18 are formed, a fuel gas supply system 70 including a fuel gas line 11 for guiding a fuel gas Fg to the combustion chamber 9, and a turbocharger 15 including a compressor wheel 12 for delivering compressed air Ca to the combustion chamber 9. The engine 5 according to the present example is a stationary engine.

[0017] The fuel gas Fg according to the present example includes a first fuel gas fg1 and a second fuel gas fg2. More specifically, the fuel gas line 11 of the fuel gas supply system 70 includes a first fuel gas line 11a for supplying the first fuel gas fg1 to the combustion chamber 9 and a second fuel gas line 11b for supplying the second fuel gas fg2 to the combustion chamber 9. Further, the fuel gas supply system 70 includes a fuel gas flow regulation valve 73 and a fuel on / off valve 77 that are disposed on the fuel gas line 11 (see FIG. 4). Then, the fuel gas flow regulation valve 73 includes a first fuel flow regulation valve 73a disposed on the first fuel gas line 11a and a second fuel flow regulation valve 73b disposed on the second fuel gas line 11b. In addition, the fuel on / off valve 77 includes a first fuel on / off valve 77a disposed on the first fuel gas line 11a and a second fuel on / off valve 77b disposed on the second fuel gas line 11b. The adoption of the configuration enables exclusive combustion of the first fuel gas fg1, exclusive combustion of the second fuel gas fg2, or mixed combustion of both fuel gases to selectively occur in the combustion chamber 9 shown in FIG. 1.

[0018] The first fuel gas fg1 and the second fuel gas fg2 may be any gas, and the lower explosive limit concentration of the second fuel gas fg2 is lower than the lower explosive limit concentration of the first fuel gas fg1. The first fuel gas fg1 is, for example, a fossil fuel gas and is natural gas as a more specific example. The second fuel gas fg2 is a non-fossil fuel gas and includes at least one of hydrogen gas, biofuel gas, or ammonia gas as a more specific example. However, the second fuel gas fg2 may be, for example, a fossil fuel gas such as propane gas. As described above, various fuel gases can be adopted as each of the first fuel gas fg1 and the second fuel gas fg2. However, hereinafter, an embodiment in which the first fuel gas fg1 is natural gas and the second fuel gas fg2 is hydrogen gas will be described as an example.

[0019] When either the natural gas or the hydrogen gas is exclusively supplied, the exclusive combustion of the gas occurs in the combustion chamber 9. For example, when the hydrogen gas is exclusively supplied, the first fuel on / off valve 77a is in a closed state, and the second fuel on / off valve 77b is in an open state. On the other hand, when the mixed gas is supplied to the combustion chamber 9, the mixed combustion of the hydrogen gas and the natural gas occurs in the combustion chamber 9. At this time, both the first fuel on / off valve 77a and the second fuel on / off valve 77b are in the open state. In the present example, a controller 90 is configured to control the ratio of the supply amount of natural gas to the supply amount of hydrogen gas. More specifically, the controller 90 controls the opening degree of each of the first fuel flow regulation valve 73a (see FIG. 4) and the second fuel flow regulation valve 73b (see FIG. 4) such that a mixed combustion ratio in the combustion chamber 9 can be adjusted.

[0020] The turbocharger 15 shown in FIG. 1 further includes a turbine wheel 14 and a rotor shaft 13 that is connected to the turbine wheel 14 and the compressor wheel 12. In addition, the engine system 1 includes an exhaust gas line 89 for guiding an exhaust gas Eg discharged from the combustion chamber 9 to the turbine wheel 14. The exhaust gas Eg drives the rotor shaft 13 via the turbine wheel 14 such that the compressor wheel 12 is driven. In this way, the compressor wheel 12 generates the compressed air Ca.

[0021] The engine system 1 further includes an intake line 25 for guiding the compressed air Ca delivered by the compressor wheel 12 to the combustion chamber 9 and an air cooler 28 disposed on the intake line 25. The air cooler 28 is a device for cooling the compressed air Ca. The air cooler 28 may be an air-cooled air cooler or a water-cooled air cooler.

[0022] The intake line 25 includes a first intake line 251 for guiding the compressed air Ca to the air cooler 28 and a second intake line 252 for guiding the cooled compressed air Ca discharged from the air cooler 28 to the combustion chamber 9. The cooled compressed air Ca flowing through the second intake line 252 is guided to the combustion chamber 9 via an intake pipe 102 (see FIG. 2) and an intake pipe 103 (see FIG. 2). The intake pipe 102 and the intake pipe 103 will be described below.

[0023] FIG. 2 is a schematic view showing the engine 5 according to the embodiment of the present disclosure and shows a cross section orthogonal to an axis line of a crankshaft 16 of the engine 5. The engine 5 includes a cylinder 6, a piston 7 housed in the cylinder 6, the crankshaft 16 located below the piston 7, and a crankcase 20 housing the crankshaft 16. A crank pin 81 configured to rotate in operative association with the crankshaft 16 is connected to the piston 7 via a connecting rod 19. In this way, the crankshaft 16 is driven by the piston 7. In the following description, an axial direction of the crankshaft 16 may be abbreviated as an "axial direction".

[0024] The engine 5 shown in the drawings is, for example, a V-type multi-cylinder engine. More specifically, two pistons 7 adjacent to each other in the axial direction are disposed in a substantially V-shape at a predetermined bank angle when viewed from the axial direction. The number of cylinder units 8 (the number of cylinders) each of which includes the cylinder 6 and the piston 7 and which are arranged in the axial direction is, for example, 12, 14, 16, 18, 20, 24, or the like. The crankcase 20 according to the present example is long in the axial direction (see FIG. 8). In addition, an engine 5 according to another example may be an in-line multi-cylinder engine. The number of cylinders is not particularly limited. For example, the number of cylinders may be 2, 4, 6, 8, or the like.

[0025] The engine 5 shown in FIG. 2 is an overhead valve (OHV) engine in which each cylinder unit 8 includes a cylinder head and a valve mechanism provided in the cylinder head. More specifically, the engine 5 includes a cam shaft 85 that extends in the axial direction, a cam (not shown) that is provided on the cam shaft 85, a push rod 87 that is configured to be displaced up and down by the rotation of the cam, a rocker arm 86 that is configured to swing with the displacement of the push rod 87, and an intake valve 82 and an exhaust valve 83 that are connected to one end portion of the rocker arm 86. The intake valve 82 and the exhaust valve 83 that are included in the valve mechanism open and close the ports of the cylinder 6 as the rocker arm 86 swings around an axis line parallel to the axial direction.

[0026] The combustion chamber 9 of the engine 5 is defined by various components such as an inner peripheral surface of the cylinder 6 and an upper end surface of the piston 7. The engine 5 includes the intake pipe 102 and the intake pipe 103, and the compressed air Ca supplied from the intake line 25 (see FIG. 1) to the intake pipe 102 flows into the combustion chamber 9 via the intake pipe 103.

[0027] The type of the engine 5 according to the present disclosure is not particularly limited. However, for example, a sub-chamber-type gas engine may be adopted. More specifically, the combustion chamber 9 includes a sub-chamber to which the fuel gas Fg is supplied and a main chamber in which the fuel gas Fg supplied from another line is combusted using a combustion flame ignited in the sub-chamber. In the sub-chamber, pre-combustion (preliminary combustion) of the fuel gas Fg mainly occurs due to an ignition operation of a spark plug 45 (see FIG. 4), and the combustion of the fuel gas Fg is completed in the main chamber. The exhaust gas Eg generated by combustion is discharged to the exhaust gas line 89 (see FIG. 1) via an exhaust pipe 105 which is a component of the engine 5.

[0028] The crank chamber 18 is formed in the crankcase 20. A portion of the fuel gas Fg supplied to the combustion chamber 9 leaks as a blow-by gas into the crank chamber 18 through a space between the piston 7 and the cylinder 6. The concentration of the unburned gas, which is the fuel gas Fg in an unburned state, in the crank chamber 18 is lower than the lower explosive limit concentration such that the occurrence of an unburned gas explosion in the crank chamber 18 is suppressed. When the concentration is equal to or higher than the lower explosive limit concentration, the risk of explosion of the unburned gas in the crank chamber 18 increases. In addition, the lower explosive limit concentration varies depending on the type of the fuel gas Fg, the proportion of the hydrogen gas contained in the fuel gas Fg, or the like.

[0029] Returning to FIG. 1, the engine system 1 further includes an air supply system 120 for supplying starting air for the engine 5 to the combustion chamber 9 (more specifically, the sub-chamber and the main chamber) in the cylinder 6. The starting air is air that is delivered into the cylinder 6 when the engine 5 in the stopped state starts to be operated. The starting air is supplied into the cylinder 6 such that the crankshaft 16 that has been stopped starts to rotate.

[0030] The air supply system 120 includes a compressor 129, an air tank 126 that stores compressed air Cb delivered from the compressor 129, and a starting air line 125 for guiding the compressed air Cb in the air tank 126 as the starting air to the combustion chamber 9.

[0031] The air supply system 120 according to the present example further includes an air pressure sensor 128 for measuring the pressure in the air tank 126, a compressed air supply line 127 for guiding the compressed air Cb from the compressor 129 to the air tank 126, and a control valve 124 that is disposed on the compressed air supply line 127. When a measured value of the air pressure sensor 128 is less than a prescribed value, the control valve 124 is switched from a closed state to an open state, and the compressed air Cb is supplied from the compressor 129 to the air tank 126. The supply of the compressed air Cb may be controlled by the controller 90 constituting the engine system 1.

[0032] The air supply system 120 further includes an air extraction line 30 that extracts the compressed air Cb flowing through the starting air line 125 and guides the compressed air Cb to the crank chamber 18 in the crankcase 20. The supply of the compressed air Cb (that is, the starting air) from the starting air line 125 to the combustion chamber 9 is ended upon completion of the start of the engine 5. On the other hand, the supply of the compressed air Cb from the air extraction line 30 to the crank chamber 18 is executed during the steady operation of the engine 5. As a more specific example, when it is determined that the concentration of the unburned gas in the crank chamber 18 exceeds the allowable concentration, the compressed air Cb is supplied from the air extraction line 30 to the crank chamber 18. Here, the concentration of the unburned gas (hereinafter, also referred to as an unburned gas concentration) may be the concentration of the natural gas or the concentration of the hydrogen gas. It is preferable to monitor the concentration of the hydrogen gas whose lower explosive limit concentration is low.

[0033] Even when the unburned gas leaks from the combustion chamber 9 to the crank chamber 18, the compressed air Cb flowing into the crank chamber 18 from the air extraction line 30 is mixed with the unburned gas, and the compressed air Cb is purged. That is, the unburned gas concentration in the crank chamber 18 is reduced by the compressed air Cb guided to the crank chamber 18 by the air extraction line 30. This makes it possible to reduce the risk of ignition of the unburned gas in the crank chamber 18. In addition, since the compressed air Cb flowing through the starting air line 125 provided for starting the engine 5 is used to reduce the unburned gas concentration in the crank chamber 18, it is possible to simplify the configuration of the engine system 1. In this way, the engine system 1 in which the risk of ignition of the unburned gas in the crank chamber 18 is reduced with a simple configuration is achieved.

[0034] The description of the engine system 1 will continue with reference to FIG. 1. The engine system 1 further includes a discharge line 60 for guiding a discharge target gas Eo to the outside. The discharge target gas Eo is a fluid including the fuel gas Fg (that is, the unburned gas) leaking into the crank chamber 18 and the compressed air Cb supplied from the air extraction line 30 to the crank chamber 18.

[0035] Oil mist is further included in the discharge target gas Eo according to the present example. The oil mist can be generated by the scattering of a lubricant adhering to movable components such as shafts, cams, gears, or the pistons 7 constituting the engine 5. Alternatively, an oil tank (not shown) storing the lubricant is disposed below the crank chamber 18, and the oil mist can be generated by evaporation of a portion of the stored lubricant as a pool of liquid. The oil mist also floats in the crank chamber 18.<Outline of Air Supply System 120>

[0036] FIG. 3 is a schematic view showing the air supply system 120 according to the embodiment of the present disclosure. The air supply system 120 includes the starting air line 125 for guiding the compressed air Cb from the air tank 126 to the combustion chamber 9 in the cylinder 6. An air control valve 203 and an on / off valve 110 are disposed in the starting air line 125 in this order from the upstream side. The air extraction line 30 is connected to the starting air line 125 between the air control valve 203 and the on / off valve 110. An air extraction valve 3 is disposed on the air extraction line 30.

[0037] When the engine system 1 is started, the on / off valve 110 is opened, and the starting air is supplied to the combustion chamber 9. When combustion is normally performed in the combustion chamber 9, the on / off valve 110 is closed.<Purge Control of Crank Chamber 18 According to Embodiment>

[0038] FIG. 4 is a schematic view showing an engine system 1A (1) according to an embodiment. The engine system 1A includes a gas analyzer 51 for measuring a gas concentration correlated with the unburned gas concentration in the crank chamber 18. The gas analyzer 51 is configured to measure at least one of the concentration of the natural gas or the concentration of the hydrogen gas. When the concentration of each of both gases is measured, the gas analyzer 51 may be configured by two sensors.

[0039] The gas analyzer 51 according to the present example is configured to measure only the concentration of the hydrogen gas. More specifically, the gas analyzer 51 is disposed in the crankcase 20 and is configured to directly measure the hydrogen gas concentration in the crank chamber 18. That is, in the present example, the measured value of the gas analyzer 51 is treated as the hydrogen gas concentration in the crank chamber 18.

[0040] As another example, the gas analyzer 51 may be configured to measure the concentration of the hydrogen gas in any one of the intake pipe 103, the combustion chamber 9, or the discharge line 60. In this case, the concentration of the hydrogen gas in the crank chamber 18 is obtained as an estimated value through the measurement of the gas analyzer 51. As a more specific example, a physical model or a statistical model in which the measured value of the gas analyzer 51 and the concentration of the hydrogen gas in the crank chamber 18 are associated with each other is used. The physical model is a model based on a static equilibrium equation or a state equation derived from physical knowledge. The statistical model is a model using a neural network, multiple regression analysis, or the like. An example of the statistical model is a machine learning model.

[0041] In FIG. 4, an air extraction valve 3A (3) of the engine system 1A is controlled according to the measurement result of the gas analyzer 51. More specifically, an air extraction control unit 911, which is a component of a controller 90A (90) of the engine system 1A, is configured to control the air extraction valve 3A. When the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 calculated from the measured value of the gas analyzer 51 exceeds the allowable concentration, the air extraction control unit 911 controls the air extraction valve 3A such that the air extraction valve 3A is switched from a closed state to an open state.

[0042] According to the above-described configuration, when it is necessary to reduce the unburned gas concentration (hydrogen gas concentration in the present example) in the crank chamber 18, the air extraction valve 3A is switched from the closed state to the open state. This makes it possible to suppress the amount of compressed air Cb extracted from the starting air line 125 and to effectively use the compressed air Cb stored in the air tank 126.

[0043] The engine system 1A shown in FIG. 4 includes a pressure sensor 52 for measuring the pressure in the crank chamber 18. In addition, the air extraction valve 3A according to the present example is a flow control valve capable of regulating the flow rate of the compressed air Cb in the air extraction line 30. The air extraction control unit 911 is configured to control the opening degree of the air extraction valve 3A such that the measured value of the pressure sensor 52 is equal to or less than the allowable pressure. For example, when it is determined that the measured value of the pressure sensor 52 exceeds the allowable pressure, the air extraction control unit 911 executes control to reduce the opening degree of the air extraction valve 3A. The control may be executed after the measured value exceeds the allowable pressure or may be executed before the measured value exceeds the allowable pressure. When it is determined that the measured value of the pressure sensor 52 does not exceed the allowable pressure, the air extraction control unit 911 may execute control to further increase the opening degree of the air extraction valve 3.

[0044] According to the above-described configuration, the opening degree of the air extraction valve 3A is controlled such that the pressure in the crank chamber 18 is equal to or less than the allowable pressure. This makes it possible to suppress the leakage of the unburned gas containing the hydrogen gas in the crank chamber 18 from the crankcase 20 via an unintended path different from the discharge line 60.

[0045] When the air extraction valve 3A is switched to the open state through the control of the air extraction control unit 911 and the compressed air Cb flows into the crank chamber 18, it is basically possible to make the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 equal to or less than the allowable concentration. However, even when the compressed air Cb flows into the crank chamber 18, the unburned gas concentration calculated from the measured value of the gas analyzer 51 may still exceed the allowable concentration. In this case, control to change the combustion environment of the engine 5 is executed. Specifically, control to change the ignition timing of the spark plug 45, control of the flow rate of the compressed air Ca flowing into the combustion chamber 9 from the intake line 25, and control of the supply amount of the fuel gas Fg are executed. Hereinafter, a specific configuration for executing these control operations will be described in order.

[0046] The control to change the ignition timing will be described. The engine system 1A includes a phase sensor 53 (see FIG. 2) for measuring a rotational angle phase of the crankshaft 16. In addition, the controller 90A (see FIG. 4) further includes an ignition control unit 913 for controlling the spark plug 45 based on the rotational angle phase measured by the phase sensor 53. The ignition operation of the spark plug 45 is periodically performed through the control of the ignition control unit 913.

[0047] When the unburned gas concentration (in the present example, the hydrogen gas concentration) is still not equal to or less than the allowable concentration even after the compressed air Cb has flowed into the crank chamber 18, the ignition control unit 913 is configured to advance the ignition timing of the spark plug 45, as compared to when the unburned gas concentration is equal to or less than the allowable concentration.

[0048] In the present example, when the unburned gas concentration (in the present example, the hydrogen gas concentration) is equal to or less than the allowable concentration during the operation of the engine 5, a first ignition control unit controls the spark plug 45. In addition, even after the unburned gas concentration exceeds the allowable concentration, the first ignition control unit controls the spark plug 45 unless it is determined that the unburned gas concentration is still not equal to or less than the allowable concentration even when the compressed air Cb is supplied to the crank chamber 18. On the other hand, when it is determined that the unburned gas concentration is still not equal to or less than the allowable concentration, instead of the first ignition control unit, a second ignition control unit controls the spark plug 45.

[0049] According to the above-described configuration, when the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 is still not equal to or less than the allowable concentration even after the air extraction valve 3A has been switched to the open state through the control of the air extraction control unit 911, the ignition timing of the spark plug 45 is advanced. Therefore, since the fuel gas Fg in the combustion chamber 9 is changed into the exhaust gas Eg at an earlier timing, the concentration of the unburned gas leaking to the crank chamber 18 is reduced. As a result, the unburned gas concentration in the crank chamber 18 can be equal to or less than the allowable concentration.

[0050] Next, the control of the flow rate of the compressed air Ca flowing into the combustion chamber 9 will be described with reference to FIG. 4. The engine system 1A further includes an intake flow regulation valve 253 that is disposed on a second intake line 252 of the intake line 25. In addition, the controller 90A further includes a charge air amount control unit 914 for controlling the intake flow regulation valve 253. The charge air amount control unit 914 is configured to control the intake flow regulation valve 253 such that the flow rate of the compressed air Ca in the intake line 25 increases when the unburned gas concentration (in the present example, the hydrogen gas concentration) is still not equal to or less than the allowable concentration even after the compressed air Cb has flowed into the crank chamber 18. The intake flow regulation valve 253 may be disposed on a first intake line 251 instead of the second intake line 252.

[0051] According to the above-described configuration, when the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 is still not equal to or less than the allowable concentration even after the air extraction valve 3A has been switched to the open state through the control of the air extraction control unit 911, the flow rate of the compressed air Ca supplied to the combustion chamber 9 increases. Therefore, the concentration of the unburned gas leaking from the combustion chamber 9 to the crank chamber 18 is reduced. As a result, the unburned gas concentration in the crank chamber 18 can be equal to or less than the allowable concentration.

[0052] Next, the control of the supply amount of the fuel gas Fg will be described with reference to FIG. 4. The controller 90A further includes a fuel gas amount control unit 915 for controlling the fuel gas flow regulation valve 73. The fuel gas amount control unit 915 is configured to control the fuel gas flow regulation valve 73 such that the flow rate of the fuel gas Fg in the fuel gas line 11 is reduced when the unburned gas concentration (in the present example, the hydrogen gas concentration) is not equal to or less than the allowable concentration even after the compressed air Cb has flowed into the crank chamber 18. Some specific examples of the control of the fuel gas flow regulation valve 73 will be described below.

[0053] For example, when the mixed combustion of the natural gas and the hydrogen gas occurs in the combustion chamber 9, it is preferable to reduce the supply amount of the hydrogen gas whose lower explosive limit concentration is relatively low. The fuel gas amount control unit 915 controls the second fuel flow regulation valve 73b such that the opening degree of the second fuel flow regulation valve 73b decreases (at this time, the second fuel flow regulation valve 73b may not be switched to the closed state and may be maintained in the open state). Alternatively, control to reduce the supply amount of the natural gas may be executed. That is, the fuel gas amount control unit 915 may control the first fuel flow regulation valve 73a such that the opening degree of the first fuel flow regulation valve 73a decreases.

[0054] As another example, when the exclusive combustion of the second fuel gas fg2 occurs in the combustion chamber 9, the fuel gas amount control unit 915 may perform control such that only the opening degree of the second fuel flow regulation valve 73b of the first fuel flow regulation valve 73a and the second fuel flow regulation valve 73b is reduced.

[0055] According to the above-described configuration, when the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 is still not equal to or less than the allowable concentration even after the air extraction valve 3A has been switched to the open state through the control of the air extraction control unit 911, the flow rate of the fuel gas Fg supplied to the combustion chamber 9 is reduced. Therefore, the ratio of the supply amount of the fuel gas Fg to the supply amount of the compressed air Ca to the combustion chamber 9 is reduced. Therefore, the concentration of the unburned gas leaking from the combustion chamber 9 to the crank chamber 18 is reduced. As a result, the unburned gas concentration in the crank chamber 18 can be equal to or less than the allowable concentration.

[0056] When the unburned gas concentration (in the present example, the hydrogen gas concentration) is still not equal to or less than the allowable concentration even after the fuel gas amount control unit 915 has controlled the fuel gas flow regulation valve 73, a fuel valve control unit 916, which is a component of the controller 90A, may stop the supply of the hydrogen gas. For example, when the mixed combustion of the natural gas and the hydrogen gas occurs in the combustion chamber 9, the fuel valve control unit 916 may control the second fuel on / off valve 77b such that the second fuel on / off valve 77b is switched from the open state to the closed state. In this case, the first fuel on / off valve 77a is maintained in the open state, but the second fuel on / off valve 77b is switched from the open state to the closed state. That is, the combustion in the combustion chamber 9 is switched from the mixed combustion of the natural gas and the hydrogen gas to the exclusive combustion of the natural gas.

[0057] According to the above-described configuration, when the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 is still not equal to or less than the allowable concentration even after the flow rate of the fuel gas Fg has been reduced through the control of the fuel gas amount control unit 915, the second fuel on / off valve 77b is switched from the open state to the closed state. Therefore, since the amount of hydrogen gas contained in the unburned gas leaking from the combustion chamber 9 to the crank chamber 18 is reduced, it is possible to reduce the risk of ignition of the unburned gas in the crank chamber 18.

[0058] Crank chamber purge control executed by the controller 90A will be described with reference to FIGS. 5 and 6. The crank chamber purge control is control to purge the unburned gas in the crank chamber 18 with the compressed air Cb such that the unburned gas concentration in the crank chamber 18 is equal to or less than the allowable concentration. For example, the control is periodically started while the engine 5 is being operated in the steady state. Here, it is assumed that, during the steady operation of the engine 5, the mixed combustion of the natural gas and the hydrogen gas occurs in the combustion chamber 9. In addition, before the crank chamber purge control is started, all of the air control valve 203, a first pilot control valve 201, and a second pilot control valve 202 are in the closed state.

[0059] The crank chamber purge control is executed by a processor constituting the controller 90A (hereinafter, may be simply referred to as a "processor"). In the following description, a "step" may be abbreviated as "S".

[0060] First, the processor determines whether or not the unburned gas concentration (in the present example, the hydrogen gas concentration) in the crank chamber 18 calculated from the measured value of the gas analyzer 51 is equal to or less than the allowable concentration (S11). When it is determined that the unburned gas concentration is equal to or less than the allowable concentration (S11: YES), the processor ends the crank chamber purge control.

[0061] On the other hand, when it is determined that the unburned gas concentration exceeds the allowable concentration (S11: NO), the processor executes control to switch the air extraction valve 3A from the closed state to the open state (S13). In S13, the processor may control the opening degree of the air extraction valve 3A such that the measured value of the pressure sensor 52 is equal to or less than the allowable pressure. The processor that executes S13 is an example of the air extraction control unit 911.

[0062] Then, the processor determines again whether or not the unburned gas concentration in the crank chamber 18 is equal to or less than the allowable concentration (S15). S15 is the same process as S11. When the unburned gas concentration is equal to or less than the allowable concentration (S15: YES), the processor ends the crank chamber purge control. On the other hand, when the unburned gas concentration still exceeds the allowable concentration (S15: NO), the processor executes engine control to change the combustion environment of the engine 5 (S17).

[0063] The engine control will be described with reference to FIG. 6. The processor switches the ignition timing of the spark plug 45 from a first ignition timing to a second ignition timing (S31). Then, the processor controls the intake flow regulation valve 253 such that the flow rate of the compressed air Ca in the intake line 25 increases (S33). Then, the processor controls the fuel gas flow regulation valve 73 such that the flow rate of the fuel gas Fg in the fuel gas line 11 decreases (S35). The processor that executes S31 is an example of the ignition control unit 913, the processor that executes S33 is an example of the charge air amount control unit 914, and the processor that executes S35 is an example of the fuel gas amount control unit 915.

[0064] Then, the processor determines whether or not the unburned gas concentration is equal to or less than the allowable concentration (S37). S37 is the same processing as S11. When the unburned gas concentration is equal to or less than the allowable concentration (S37: YES), the processor returns to the crank chamber purge control and ends the process. On the other hand, when the unburned gas concentration still exceeds the allowable concentration (S37: NO), the processor executes control to switch the second fuel on / off valve 77b from the open state to the closed state (S39). Then, the combustion in the combustion chamber 9 is switched from the mixed combustion of the natural gas and the hydrogen gas to the exclusive combustion of the natural gas. Since the hydrogen gas is not supplied to the combustion chamber 9, the unburned gas concentration is equal to or less than the allowable concentration. The processor returns to the crank chamber purge control and ends the process. The processor that executes S39 is an example of the fuel valve control unit 916.

[0065] Further, in the engine control, at least one of S31, S33, and S35 may be executed. For example, S31 and S33 may be executed, and S35 may not be executed. Alternatively, even when all of S31, S33, and S35 are executed, the same determination process as that in S11 may be executed after each step is executed. For example, it may be determined whether or not the unburned gas concentration is equal to or less than the allowable concentration after S31 is executed and before S33 is executed. When it is determined that the unburned gas concentration is equal to or less than the allowable concentration, the processor may return to the crank chamber purge control and end the process, without executing the process after S33.<Purge Control of Crank Chamber 18 According to Another Embodiment>

[0066] FIG. 7 is a schematic view showing an engine system 1B (1) according to another embodiment. In FIG. 7, the same components as those in the engine system 1A (see FIG. 4) are denoted by the same reference numerals, and a description thereof will be omitted or simplified below.

[0067] An air extraction valve 3B (3) of the engine system 1B is an on / off valve and does not have a function of continuously regulating the flow rate of the compressed air Cb. The flow rate of the compressed air Cb is regulated by a flow control valve 4 that is disposed on the air extraction line 30. A controller 90B (90) of the engine system 1B includes a flow control unit 912 for controlling the opening degree of the flow control valve 4. The flow control unit 912 is configured to control the opening degree of the flow control valve 4 such that the measured value of the pressure sensor 52 is equal to or less than the allowable pressure. The processor controls the flow control valve 4 to implement the flow control unit 912 (a detailed description of the control flow will be omitted).

[0068] In addition, the controller 90B may include at least one of the ignition control unit 913, the charge air amount control unit 914, the fuel gas amount control unit 915, or the fuel valve control unit 916 described with reference to FIG. 4.<Crankcase 20 (First Embodiment)>

[0069] FIG. 8 is a schematic view showing a crankcase 20A (20) of an engine 5A (5) according to a first embodiment. In the example shown in FIG. 8, the air extraction valve 3 disposed on the air extraction line 30 is not shown (the same applies to FIGS. 9, 11, and 12).

[0070] The crankcase 20A includes a one-side wall portion 21A (21), which is an end portion on one side in the axial direction, and the other side wall portion 22A (22) which is an end portion opposite to the one-side wall portion 21. A one-side introduction port 37A (37) to which the air extraction line 30A is connected is formed in the one-side wall portion 21A (21), and the other side discharge port 68 is formed in the other side wall portion 22A (22).

[0071] According to the above-described configuration, the compressed air Cb that has passed through the one-side introduction port 37A flows through the crank chamber 18 in the axial direction and then flows through the discharge line 60 via the other side discharge port 68. Since the unburned gas and the compressed air Cb easily mix with each other in the axial direction in the crank chamber 18, the compressed air Cb is easily discharged to the discharge line 60 together with the unburned gas. Therefore, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber 18.

[0072] In the example shown in FIG. 8, at least a portion of the one-side introduction port 37A (37) is disposed at the same height position as the other side discharge port 68. In the shown example, both the one-side introduction port 37A and the other side discharge port 68 are disposed at a position higher than the crankshaft 16. However, the present disclosure is not limited thereto. For example, the one-side introduction port 37A may be disposed at a position lower than the crankshaft 16, or at least a portion of the one-side introduction port 37A may be disposed at the same height as the crankshaft 16. Alternatively, both the one-side introduction port 37A and the other side discharge port 68 may be disposed at a position lower than the crankshaft 16.

[0073] According to the configuration in which the one-side introduction port 37A is disposed at a position lower than the other side discharge port 68, the compressed air Cb flowing through the crank chamber 18 also moves upward while flowing toward the other side discharge port 68. Therefore, the compressed air Cb can spread in the crank chamber 18, and both the compressed air Cb and the unburned gas are easily discharged to the discharge line 60. As a result, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber 18.<Crankcase 20 (Second Embodiment)>

[0074] FIG. 9 is a schematic view showing a crankcase 20B (20) of an engine 5B (5) according to a second embodiment. In FIG. 9, the same components as those in the engine 5A (see FIG. 8) are denoted by the same reference numerals, and a description thereof will be omitted or simplified below.

[0075] An air extraction line 30B of the engine 5B has a one-side air extraction line 31 and the other side air extraction line 32. The one-side air extraction line 31 is connected to the starting air line 125 and a one-side wall portion 21B (21) of the crankcase 20B. That is, the one-side air extraction line 31 is configured to guide the compressed air Cb extracted from the starting air line 125 to the one-side wall portion 21B. The other side air extraction line 32 branches from the one-side air extraction line 31 and is connected to the other side wall portion 22B (22) of the crankcase 20B. That is, the other side air extraction line 32 is configured to guide the compressed air Cb extracted from the one-side air extraction line 31 to the other side wall portion 22B.

[0076] A one-side introduction port 37B (37) to which the one-side air extraction line 31 is connected is formed in the one-side wall portion 21B, and the other side introduction port 38 to which the other side air extraction line 32 is connected is formed in the other side wall portion 22B. In the shown example, at least a portion of the one-side introduction port 37B (37) is disposed at the same height position as the other side introduction port 38.

[0077] In the example shown in FIG. 9, both the one-side introduction port 37B and the other side introduction port 38 are disposed at a position higher than the crankshaft 16. However, the present disclosure is not limited thereto. The one-side introduction port 37B may be disposed at a position lower than the crankshaft 16, or at least a portion of the one-side introduction port 37B may be disposed at the same height as the crankshaft 16. Alternatively, both the one-side introduction port 37B and the other side introduction port 38 may be disposed at a position lower than the crankshaft 16.

[0078] According to the above-described configuration, the compressed air Cb flows into the crank chamber 18 from both sides in the axial direction. Therefore, the compressed air Cb can spread in the crank chamber 18. This makes it possible to uniformly reduce the concentration of the unburned gas in the crank chamber 18.

[0079] The description of the configuration of the engine 5B will be continued. The discharge line 60 shown in FIG. 9 includes a one-side discharge line 61 connected to the one-side wall portion 21B and the other side discharge line 62 connected to the other side wall portion 22B. A one-side discharge port 67 to which the one-side discharge line 61 is connected is formed in the one-side wall portion 21B, and the other side discharge port 68 to which the other side discharge line 62 is connected is formed in the other side wall portion 22B.

[0080] In the present example, at least a portion of the one-side discharge port 67 is disposed at a position higher than the other side discharge port 68. More specifically, the entire one-side discharge port 67 is disposed at a position higher than the other side discharge port 68. In addition, at least a portion of the one-side discharge port 67 is disposed at a position higher than the one-side introduction port 37B (37). More specifically, the entire one-side discharge port 67 is disposed at a position higher than the one-side introduction port 37B. Further, in the present example, at least a portion of the other side discharge port 68 is disposed at the same height position as the other side introduction port 38.

[0081] FIG. 10 is a conceptual perspective view showing the crankcase 20B (the crankshaft 16 is not shown). As viewed from the axial direction, the one-side introduction port 37B and the other side discharge port 68 are disposed at positions that deviate from each other in a horizontal direction (hereinafter, may be referred to as a width direction). In addition, as viewed from the axial direction, the other side introduction port 38 and the one-side discharge port 67 are disposed at positions that deviate from each other in the width direction. In the shown example, the one-side introduction port 37B and the other side introduction port 38 are disposed on a first side in the width direction with respect to the center of the crankcase 20 in the width direction. Further, the one-side discharge port 67 and the other side discharge port 68 are disposed on a second side opposite to the first side in the width direction with respect to the center of the crankcase 20 in the width direction. The width direction is the horizontal direction orthogonal to the axial direction.

[0082] In the present example, as the discharge target gas Eo, at least a portion of the compressed air Cb guided to the crank chamber 18 from the one-side introduction port 37B passes through the other side discharge port 68. The discharge target gas Eo passing through the other side discharge port 68 is discharged to the outside via the other side discharge line 62. Similarly, as the discharge target gas Eo, at least a portion of the compressed air Cb guided from the other side introduction port 38 to the crank chamber 18 passes through the one-side discharge port 67. The discharge target gas Eo passing through the one-side discharge port 67 is discharged to the outside via the one-side discharge line 61.

[0083] According to the above-described configuration, the compressed air Cb flowing into the crank chamber 18 from the one-side introduction port 37 easily spreads horizontally in the crank chamber 18 while flowing toward the other side discharge port 68. Similarly, the compressed air Cb flowing into the crank chamber 18 from the other side introduction port 38 easily spreads horizontally in the crank chamber 18 while flowing toward the one-side discharge port 67. Therefore, the unburned gas in the crank chamber 18 is easily discharged from the one-side discharge port 67 and the other side discharge port 68. As a result, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber 18.<Crankcase 20 (Third Embodiment)>

[0084] FIG. 11 is a schematic view showing an engine 5C (5) according to a third embodiment and is a plan view showing the engine 5C. The engine 5C includes a one-side wall portion 21C (21) which is an end portion on one side in the axial direction, the other side wall portion 22C (22) which is an end portion opposite to the one-side wall portion 21C, and a side wall portion 23 connected to the one-side wall portion 21C and the other side wall portion 22C. The side wall portion 23 is an end portion of the crankcase 20C on the first side in the width direction.

[0085] An air extraction line 30C (30) according to the third embodiment includes a side air extraction line 33 that is connected to the starting air line 125 and the side wall portion 23. A side introduction port 39 to which the side air extraction line 33 is connected is formed in a central portion 24 of the side wall portion 23 in the axial direction. The side air extraction line 33 is configured to guide the compressed air Cb extracted from the starting air line 125 to the side introduction port 39.

[0086] In addition, the discharge line 60 shown in FIG. 11 includes a one-side discharge line 61 connected to the one-side wall portion 21C (21) and the other side discharge line 62 connected to the other side wall portion 22C (22). A one-side discharge port 67 and the other side discharge port 68 are formed in the one-side wall portion 21C and the other side wall portion 22C, respectively.

[0087] According to the above-described configuration, the compressed air Cb that has flowed into the crank chamber 18 from the side introduction port 39 formed in the central portion 24 of the side wall portion 23 can flow toward one side and the other side in the axial direction. This makes it possible to spread the compressed air Cb in the crank chamber 18. Therefore, the unburned gas in the crank chamber 18 is easily discharged from the one-side discharge port 67 and the other side discharge port 68. As a result, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber 18.

[0088] Further, the air extraction line 30C may further include at least one of a plurality of connection air extraction lines 35 (see FIG. 12) according to a fourth embodiment which will be described below, in addition to the side air extraction line 33. In this case, it is also possible to obtain the above-described technical advantages.<Crankcase 20 (Fourth Embodiment)>

[0089] FIG. 12 is a schematic view showing an engine 5D (5) according to a fourth embodiment and is a plan view showing the engine 5D. The engine 5D is a V-type multi-cylinder engine in which a plurality of cylinder units 8 are disposed along the axial direction. The cylinder unit 8 of the engine 5D includes a plurality of cylinder units 8A that are disposed on the first side of the axial center of the crankshaft 16 in the width direction and a plurality of cylinder units 8B that are disposed on the second side of the axial center of the crankshaft 16 in the width direction. The number of cylinder units 8A is equal to the number of cylinder units 8B.

[0090] A crankcase 20D (20) of the engine 5D includes a one-side wall portion 21D (21) which is an end portion on one side in the axial direction, the other side wall portion 22D (22) which is an end portion opposite to the one-side wall portion 21D, a first-side wall portion 27 which is an end portion on the first side in the width direction, and a second-side wall portion 26 which is an end portion opposite to the first-side wall portion 27.

[0091] The engine 5D further includes at least one bulkhead 29. The bulkhead 29 extends in the width direction and is connected to the first-side wall portion 27 and the second-side wall portion 26. Further, the bulkhead 29 partitions one or more of the plurality of cylinder units 8 from the other cylinder units 8 in a plan view.

[0092] As a more specific example, the cylinder unit 8 shown in FIG. 12 includes a plurality of pairs of cylinder units 8, each of which is composed of the cylinder units 8A and 8B adjacent to each other in the axial direction, and each of a plurality of bulkheads 29 is disposed to partition each pair of cylinder units 8 from another pair of cylinder units 8. In the crank chamber 18, spaces 17, the number of which corresponds to half the number of cylinders of the engine 5D, are formed by the plurality of bulkheads 29, and a pair of cylinder units 8 is disposed in each of the spaces 17 in a plan view. For example, when the number of cylinders of the engine 5D is 18, the crank chamber 18 is partitioned into nine spaces 17 (the number of bulkheads 29 is 8). However, the bulkhead 29 according to the present disclosure is not limited to the above-described embodiment. The number of bulkheads 29 may be two (not shown). In this case, the crank chamber 18 is partitioned into three spaces 17, and three pairs of cylinder units 8 are disposed in each of the spaces 17. As another example, the number of bulkheads 29 may be one (not shown).

[0093] An air extraction line 30D of the engine 5D includes a plurality of connection air extraction lines 35 that are connected to the first-side wall portion 27 to communicate with the plurality of spaces 17, respectively. In addition, a discharge line 60 of the engine 5D includes a plurality of connection discharge lines 65 that are connected to the second-side wall portion 26 so as to communicate with the plurality of spaces 17, respectively.

[0094] A plurality of side introduction ports 41, to which the plurality of connection air extraction lines 35 are connected, respectively, are formed in the first-side wall portion 27, and a plurality of side discharge ports 42, to which the plurality of connection discharge lines 65 are connected, respectively, are formed in the second-side wall portion 26. In each space 17, the side introduction port 41 may be disposed at a position lower than the side discharge port 42. However, the present disclosure is not limited thereto. The side introduction port 41 may be disposed at a position higher than the side discharge port 42, or the side introduction port 41 and the side discharge port 42 may be disposed at the same height.

[0095] According to the above-described configuration, since one or more cylinder units 8 are disposed in each of the plurality of spaces 17 partitioned by the bulkhead 29 in a plan view, the unburned gas can leak into each of the spaces 17. However, the compressed air Cb flows into each space 17 from each connection air extraction line 35, and the discharge target gas Eo including the compressed air Cb and the unburned gas is discharged from each space 17 via each connection discharge line 65. Since the unburned gas in each space 17 can be more reliably diluted with the compressed air Cb, it is possible to reduce the risk of ignition of the unburned gas in the crank chamber 18.

[0096] In addition, even when the engine 5D is an in-line multi-cylinder engine, the above-described technical advantages can be obtained.<Crankcase 20 (Fifth Embodiment)>

[0097] FIG. 13 is a schematic view showing an engine 5E (5) according to a fifth embodiment. In FIG. 13, the same components as those in the engine 5D are denoted by the same reference numerals. A discharge line 60 shown in FIG. 13 includes a one-side discharge line 61 that is connected to a one-side discharge port 67 formed in a one-side wall portion 21D and the other side discharge line 62 that is connected to the other side discharge port 68 of the other side wall portion 22D. The one-side discharge line 61 is configured to guide the discharge target gas Eo discharged from the one-side discharge port 67 to the outside. The other side discharge line 62 is configured to guide the discharge target gas Eo discharged from the other side discharge port 68 to the outside.

[0098] According to the above-described configuration, the compressed air that has flowed into a crank chamber 20E (20) from the side introduction port 41 can flow toward one side and the other side in the axial direction. This makes it possible to spread the compressed air in the crank chamber 20E. Therefore, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber 20E.<Other Embodiments>

[0099] An engine system 1C (1) according to another embodiment will be described with reference to FIG. 14. The engine system 1C includes an exhaust gas line 990 for guiding the exhaust gas Eg discharged from the combustion chamber 9 to the turbine wheel 14, a bypass exhaust gas line 991 for extracting the exhaust gas flowing through the exhaust gas line 990 and discharging the exhaust gas to the outside while bypassing the turbine wheel 14, and a bypass flow regulation valve 993 for controlling the flow rate of the exhaust gas flowing through the bypass exhaust gas line.

[0100] A controller 90C (90) includes a bypass exhaust gas amount control unit 917. When the unburned gas concentration calculated from the measured value of the gas analyzer 51 is not equal to or less than the allowable concentration even after the air extraction valve 3 has been switched to the open state through the control of the air extraction control unit 911, the bypass exhaust gas amount control unit 917 controls the bypass flow regulation valve 993 such that the flow rate of the exhaust gas flowing through the bypass exhaust gas line 991 is reduced.

[0101] According to the above-described configuration, when the unburned gas concentration in the crank chamber 18 is not equal to or less than the allowable concentration even after the air extraction valve 3 has been switched to the open state through the control of the air extraction control unit 911, the flow rate of the exhaust gas Eg supplied to the turbine wheel 14 is increased through the control of the bypass flow regulation valve 993 by the bypass exhaust gas amount control unit 917. With this configuration, the rotation speed of the compressor wheel 12 increases, and the flow rate of the compressed air Ca supplied to the combustion chamber 9 increases. Therefore, the concentration of the unburned gas leaking from the combustion chamber 9 to the crank chamber 18 is reduced. As a result, the unburned gas concentration in the crank chamber 18 can be equal to or less than the allowable concentration.<Others>

[0102] The turbocharger 15 may not include the turbine wheel 14. The turbocharger 15 may be an electric compressor that includes the rotor shaft 13 and the compressor wheel 12 connected to the rotor shaft 13.

[0103] The controller 90 is configured by a computer and includes a processor, a memory (storage medium), and an external communication interface. The processor is a CPU, a GPU, an MPU, a DSP, or a combination thereof. A processor according to another embodiment may be implemented by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to temporarily or non-temporarily store various types of data and is implemented by, for example, at least one of a RAM, a ROM, and a flash memory. The processor executes various control processes according to instructions of a program loaded into the memory.<Summary>

[0104] For example, the content described in some embodiments described above is understood as follows. 1) According to at least one embodiment of the present disclosure, there is provided an engine system (1) including: an engine (5) that includes a cylinder (6) and a piston (7) housed in the cylinder; an air supply system (120) that includes an air tank (126) and a starting air line (125) for guiding compressed air (Cb) stored in the air tank as starting air for the engine into the cylinder; and a fuel gas supply system (70) for supplying a fuel gas (Fg) into the cylinder, in which the engine further includes a crankshaft (16) that is located below the piston and is configured to be driven by the piston, and a crankcase (20) that houses the crankshaft, and the air supply system further includes an air extraction line (30) for extracting the compressed air flowing through the starting air line and guiding the compressed air to a crank chamber in the crankcase.

[0105] According to the configuration of 1), even when an unburned gas, which is a fuel gas in an unburned state, leaks from the combustion chamber to the crank chamber, the concentration of the unburned gas in the crank chamber is reduced by the compressed air guided to the crank chamber by the air extraction line. This makes it possible to reduce the risk of ignition of the unburned gas in the crank chamber. In addition, since the compressed air flowing through the starting air line provided for starting the engine is used to reduce the concentration of the unburned gas in the crank chamber, it is possible to simplify the configuration of the engine system. In this way, the engine system in which the risk of ignition of the unburned gas in the crank chamber is reduced with a simple configuration is achieved.

[0106] 2) In some embodiments, in the engine system according to 1), the air supply system further includes an air extraction valve (3) that is disposed on the air extraction line, and the engine system further includes a gas analyzer (51) for measuring a gas concentration correlated with an unburned gas concentration, which is a concentration of the fuel gas in an unburned state, in the crank chamber, and an air extraction control unit (911) for controlling the air extraction valve such that the air extraction valve is switched from a closed state to an open state when the unburned gas concentration in the crank chamber calculated from a measured value of the gas analyzer exceeds an allowable concentration.

[0107] According to the configuration of 2), when it is necessary to reduce the unburned gas concentration in the crank chamber, the air extraction valve is switched from the closed state to the open state. This makes it possible to suppress the amount of compressed air extracted from the starting air line and to effectively use the compressed air stored in the air tank.

[0108] 3) In some embodiments, the engine system according to 2) further includes a pressure sensor (52) for measuring pressure in the crank chamber, in which the air extraction control unit is configured to control an opening degree of the air extraction valve such that a measured value of the pressure sensor is equal to or less than an allowable pressure.

[0109] According to the configuration of 3), the opening degree of the air extraction valve is controlled such that the pressure in the crank chamber is equal to or less than the allowable pressure. This makes it possible to suppress the leakage of the unburned gas in the crank chamber to the outside via an unintended path.

[0110] 4) In some embodiments, in the engine system according to 2), the air supply system further includes a flow control valve (4) that is disposed on the air extraction line, and the engine system further includes a pressure sensor (52) for measuring pressure in the crank chamber, and a flow control unit (912) for controlling an opening degree of the flow control valve such that a measured value of the pressure sensor is equal to or less than an allowable pressure.

[0111] According to the configuration of 4), the opening degree of the flow control valve is controlled such that the pressure in the crank chamber is equal to or less than the allowable pressure. This makes it possible to suppress the leakage of the unburned gas in the crank chamber to the outside via an unintended path.

[0112] 5) In some embodiments, in the engine system according to any one of 2) to 4), the engine further includes a spark plug (45) that is disposed in a combustion chamber (9), the engine system further includes a phase sensor (53) for measuring a rotational angle phase of the crankshaft, and an ignition control unit (913) for controlling the spark plug based on the rotational angle phase measured by the phase sensor, and the ignition control unit is configured to advance an ignition timing of the spark plug when the unburned gas concentration in the crank chamber calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit, as compared to when the unburned gas concentration is equal to or less than the allowable concentration.

[0113] According to the configuration of 5), when the unburned gas concentration in the crank chamber is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit, the ignition timing of the spark plug is advanced. Therefore, since the concentration of the unburned gas leaking from the combustion chamber to the crank chamber is reduced, the unburned gas concentration in the crank chamber can be equal to or less than the allowable concentration.

[0114] 6) In some embodiments, the engine system according to any one of 2) to 5) further includes: a turbocharger (15) that includes a compressor wheel (12) for delivering compressed air; an intake line (25) for guiding the compressed air from the compressor wheel into the cylinder; an intake flow regulation valve (253) that is disposed on the intake line; and a charge air amount control unit (914) for controlling the intake flow regulation valve such that a flow rate of the compressed air in the intake line is increased when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit.

[0115] According to the configuration of 6), when the unburned gas concentration in the crank chamber is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit, the flow rate of the compressed air supplied to the fuel chamber increases. Therefore, the concentration of the unburned gas leaking from the combustion chamber to the crank chamber is reduced. As a result, the unburned gas concentration in the crank chamber can be equal to or less than the allowable concentration.

[0116] 7) In some embodiments, the engine system according to 2) further includes: a turbocharger (15) that includes a compressor wheel (12) and a turbine wheel (13) for driving the compressor wheel; an exhaust gas line (990) for guiding an exhaust gas (Eg) discharged from the engine to the turbine wheel; a bypass exhaust gas line (991) for extracting the exhaust gas flowing through the exhaust gas line and discharging the exhaust gas to an outside while bypassing the turbine wheel; a bypass flow regulation valve (993) for controlling a flow rate of the exhaust gas flowing through the bypass exhaust gas line; and a bypass exhaust gas amount control unit (917) for controlling the bypass flow regulation valve such that the flow rate of the exhaust gas flowing through the bypass exhaust gas line is reduced when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit.

[0117] According to the configuration of 7), when the unburned gas concentration in the crank chamber is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit, the flow rate of the exhaust gas supplied to the turbine wheel increases through the control of the bypass flow regulation valve by the bypass exhaust gas amount control unit. With this configuration, the rotation speed of the compressor wheel increases, and the flow rate of the compressed air supplied to the combustion chamber increases. Therefore, the concentration of the unburned gas leaking from the combustion chamber to the crank chamber is reduced. As a result, the unburned gas concentration in the crank chamber can be equal to or less than the allowable concentration.

[0118] 8) In some embodiments, in the engine system according to any one of 2) to 7), the fuel gas supply system further includes a fuel gas line (11) for guiding the fuel gas into the cylinder, a fuel gas flow regulation valve (73) that is disposed on the fuel gas line, and a fuel gas amount control unit (915) for controlling the fuel gas flow regulation valve such that a flow rate of the fuel gas in the fuel gas line is reduced when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit.

[0119] According to the configuration of 8), when the unburned gas concentration in the crank chamber is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit, the flow rate of the fuel gas supplied to the combustion chamber is reduced. Therefore, the concentration of the unburned gas leaking from the combustion chamber to the crank chamber is reduced. As a result, the unburned gas concentration in the crank chamber can be equal to or less than the allowable concentration.

[0120] 9) In some embodiments, in the engine system according to 8), the fuel gas supply system includes a first fuel gas line (11a) for guiding a first fuel gas to a combustion chamber (9) of the engine, a first fuel on / off valve (77a) that is disposed on the first fuel gas line, a second fuel gas line (11b) for guiding a second fuel gas, whose lower explosive limit concentration is lower than a lower explosive limit concentration of the first fuel gas, to the combustion chamber, and a second fuel on / off valve (77b) that is disposed on the second fuel gas line, when the air extraction control unit controls the air extraction valve, at least the second fuel on / off valve of the first fuel on / off valve and the second fuel on / off valve is in an open state, and the engine system further includes a fuel valve control unit (916) for controlling the second fuel on / off valve such that the second fuel on / off valve is switched from the open state to a closed state when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the flow rate of the fuel gas has been reduced through the control of the fuel gas amount control unit.

[0121] According to the configuration of 9), when the unburned gas concentration in the crank chamber is not equal to or less than the allowable concentration even after the flow rate of the fuel gas has been reduced through the control of the fuel gas amount control unit, the second fuel on / off valve is switched from the open state to the closed state. Therefore, since the proportion of the second fuel gas contained in the unburned gas leaking from the combustion chamber to the crank chamber is reduced, it is possible to reduce the risk of ignition of the unburned gas in the crank chamber.

[0122] 10) In some embodiments, in the engine system according to any one of 1) to 9), the engine is a multi-cylinder engine in which a plurality of cylinder units (8), each of which includes the cylinder and the piston, are disposed along an axial direction of the crankshaft, the engine system further includes a discharge line (60) for guiding a discharge target gas (Eo), which is a fluid including the compressed air, in the crank chamber to an outside, the crankcase includes a one-side wall portion (21) which is an end portion on one side in the axial direction, and the other side wall portion (22) which is an end portion opposite to the one-side wall portion, a one-side introduction port (37) to which the air extraction line is connected is formed in the one-side wall portion, and the other side discharge port (68) to which the discharge line is connected is formed in the other side wall portion.

[0123] According to the configuration of 10), the compressed air that has passed through the one-side introduction port flows through the crank chamber in the axial direction and then flows through the discharge line via the other side discharge port. Since the unburned gas and the compressed air easily mix with each other in the axial direction in the crank chamber, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber.

[0124] 11) In some embodiments, in the engine system according to 10), the one-side introduction port is disposed at a position lower than the other side discharge port.

[0125] According to the configuration of 11), the compressed air flowing through the crank chamber also moves upward while flowing toward the other side discharge port. This makes it possible to spread the compressed air in the crank chamber. Therefore, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber.

[0126] 12) In some embodiments, the engine system according to 10) or 11) further includes: a one-side discharge line (61) that is connected to the one-side wall portion and guides the discharge target gas to the outside; and the other side discharge line (62) that is connected to the other side wall portion and guides the discharge target gas to the outside, in which the air extraction line includes a one-side air extraction line (31) for guiding the compressed air extracted from the intake line to the one-side wall portion, and the other side air extraction line (32) that branches from the one-side air extraction line and is connected to the other side wall portion, a one-side discharge port (67) to which the one-side discharge line is connected is further formed in the one-side wall portion, the other side introduction port (38) to which the other side air extraction line is connected is further formed in the other side wall portion, and when viewed from the axial direction of the crankshaft, the one-side introduction port and the other side discharge port are disposed at positions that deviate from each other in a horizontal direction, and the other side introduction port and the one-side discharge port are disposed at positions that deviate from each other in the horizontal direction.

[0127] According to the configuration of 12), the compressed air flowing into the crank chamber from the one-side introduction port easily spreads horizontally in the crank chamber while flowing toward the other side discharge port. Similarly, the compressed air flowing into the crank chamber from the other side introduction port easily spreads horizontally in the crank chamber while flowing toward the one-side discharge port. Therefore, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber.

[0128] 13) In some embodiments, in the engine system according to any one of 1) to 9), the engine is a multi-cylinder engine in which a plurality of cylinder units (8), each of which includes the cylinder and the piston, are disposed along an axial direction of the crankshaft, the crankcase includes a one-side wall portion (21) which is an end portion on one side in the axial direction, the other side wall portion (22) which is an end portion opposite to the one-side wall portion, a first-side wall portion (27) which is an end portion on a first side in a horizontal direction (width direction) orthogonal to the axial direction, a second-side wall portion (26) which is an end portion opposite to the first-side wall portion, and at least one bulkhead (29) that is connected to the first-side wall portion and the second-side wall portion to partition one or more of the plurality of cylinder units from the other cylinder units in a plan view, the air extraction line includes a plurality of connection air extraction lines (35) that are connected to the first-side wall portion to communicate with each of a plurality of spaces (17) of the crank chamber partitioned by the at least one bulkhead, and the discharge line includes a plurality of connection discharge lines (65) that are connected to the second-side wall portion to communicate with each of the plurality of spaces of the crank chamber.

[0129] According to the configuration of 13), since one or more cylinder units are disposed in each of the plurality of spaces partitioned by the bulkhead in a plan view, the unburned gas leaks into each space. However, the compressed air flows into each space from each connection air extraction line, and the compressed air and the unburned gas in each space are discharged via each connection discharge line. Since the unburned gas in each space can be more reliably diluted with the compressed air, it is possible to reduce the risk of ignition of the unburned gas in the crank chamber.

[0130] 14) In some embodiments, in the engine system according to any one of 1) to 9), the engine is a multi-cylinder engine in which a plurality of cylinder units (8), each of which includes the cylinder and the piston, are disposed along an axial direction of the crankshaft, the crankcase includes a one-side wall portion (21) which is an end portion on one side in the axial direction, the other side wall portion (22) which is an end portion opposite to the one-side wall portion, and a side wall portion (23) that is connected to the one-side wall portion and the other side wall portion, the air extraction line includes a side air extraction line (33) that is connected to the compressed air return line and the side wall portion, and a side introduction port (39) to which the side air extraction line is connected is formed in a central portion (24) of the side wall portion in the axial direction of the crankshaft.

[0131] According to the configuration of 14), the compressed air that has flowed into the crank chamber from the side introduction port formed in the central portion of the side wall portion can flow toward one side and the other side in the axial direction. This makes it possible to spread the compressed air in the crank chamber. Therefore, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber.

[0132] 15) In some embodiments, the engine system according to any one of 1) to 9) further includes: a discharge line (60) for guiding a discharge target gas, which is a fluid including the compressed air, in the crank chamber to an outside, in which the discharge line includes a one-side discharge line (61) that is connected to a one-side discharge port (67) formed in the one-side wall portion and guides the discharge target gas discharged from the one-side discharge port to the outside, and the other side discharge line (62) that is connected to the other side discharge port (68) formed in the other side wall portion and guides the discharge target gas discharged from the other side discharge port to the outside.

[0133] According to the configuration of 15), the compressed air that has flowed into the crank chamber from the side introduction port can flow toward one side and the other side in the axial direction. This makes it possible to spread the compressed air in the crank chamber. Therefore, it is possible to uniformly reduce the concentration of the unburned gas in the crank chamber.Reference Signs List

[0134] 1: Engine system 3: Air extraction valve 4: Flow control valve 5: Engine 6: Cylinder 7: Piston 8: Cylinder unit 9: Combustion chamber 11: Fuel gas line 11a: First fuel gas line 11b: Second fuel gas line 12: Compressor wheel 13: Rotor shaft 14: Turbine wheel 15: Turbocharger 16: Crankshaft 17: Space 18: Crank chamber 19: Connecting rod 20: Crankcase 21: One-side wall portion 23: Side wall portion 24: Central portion 25: Intake line 26: Second-side wall portion 27: First-side wall portion 28: Air cooler 29: Bulkhead 30: Air extraction line 31: One-side air extraction line 32: The other side air extraction line 33: Side air extraction line 35: Connection air extraction line 37: One-side introduction port 38: The other side introduction port 39: Side introduction port 41: Side introduction port 42: Side discharge port 45: Spark plug 51: Gas analyzer 52: Pressure sensor 53: Phase sensor 60: Discharge line 61: One-side discharge line 62: The other side discharge line 65: Connection discharge line 67: One-side discharge port 68: The other side discharge port 70: Fuel gas supply system 73: Fuel gas flow regulation valve 73a: First fuel flow regulation valve 73b: Second fuel flow regulation valve 77: Fuel on / off valve 77a: First fuel on / off valve 77b: Second fuel on / off valve 81: Crank pin 82: Intake valve 83: Exhaust valve 85: Cam shaft 86: Rocker arm 87: Push rod 89: Exhaust gas line 90: Controller 102, 103: Intake pipe 105: Exhaust pipe 110: Pilot valve 111: First pilot valve 112: Second pilot valve 116: Pilot air line 117: First pilot air line 118: Second pilot air line 119: Upstream-side main air line 120: Air supply system 121: First main air line 122: Second main air line 123: Main air line 124: Control valve 125: Starting air line 126: Air tank 127: Compressed air supply line 128: Air pressure sensor 129: Compressor 201: First pilot control valve 202: Second pilot control valve 203: Air control valve 251: First intake line 252: Second intake line 253: Intake flow regulation valve 911: Air extraction control unit 912: Flow control unit 913: Ignition control unit 914: Charge air amount control unit 915: Fuel gas amount control unit 916: Fuel valve control unit 917: Bypass exhaust gas amount control unit 990: Exhaust gas line 991: Bypass exhaust gas line 993: Bypass flow regulation valve Ca, Cb: Compressed air Eg: Exhaust gas Eo: Discharge target gas Fg: Fuel gas P1: Connection point fg1: First fuel gas fg2: Second fuel gas

Claims

1. An engine system comprising: an engine that includes a cylinder and a piston housed in the cylinder; an air supply system that includes an air tank and a starting air line for guiding compressed air stored in the air tank as starting air for the engine into the cylinder; and a fuel gas supply system for supplying a fuel gas into the cylinder, wherein the engine further includes a crankshaft that is located below the piston and is configured to be driven by the piston, and a crankcase that houses the crankshaft, and the air supply system further includes an air extraction line for extracting the compressed air flowing through the starting air line and guiding the compressed air to a crank chamber in the crankcase.

2. The engine system according to Claim 1, wherein the air supply system further includes an air extraction valve that is disposed on the air extraction line, and the engine system further comprises a gas analyzer for measuring a gas concentration correlated with an unburned gas concentration, which is a concentration of the fuel gas in an unburned state, in the crank chamber, and an air extraction control unit for controlling the air extraction valve such that the air extraction valve is switched from a closed state to an open state when the unburned gas concentration in the crank chamber calculated from a measured value of the gas analyzer exceeds an allowable concentration.

3. The engine system according to Claim 2, further comprising: a pressure sensor for measuring pressure in the crank chamber, wherein the air extraction control unit is configured to control an opening degree of the air extraction valve such that a measured value of the pressure sensor is equal to or less than an allowable pressure.

4. The engine system according to Claim 2, wherein the air supply system further includes a flow control valve that is disposed on the air extraction line, and the engine system further comprises a pressure sensor for measuring pressure in the crank chamber, and a flow control unit for controlling an opening degree of the flow control valve such that a measured value of the pressure sensor is equal to or less than an allowable pressure.

5. The engine system according to Claim 2, wherein the engine further includes a spark plug that is disposed in a combustion chamber, the engine system further comprises a phase sensor for measuring a rotational angle phase of the crankshaft, and an ignition control unit for controlling the spark plug based on the rotational angle phase measured by the phase sensor, and the ignition control unit is configured to advance an ignition timing of the spark plug when the unburned gas concentration in the crank chamber calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit, as compared to when the unburned gas concentration is equal to or less than the allowable concentration.

6. The engine system according to Claim 2, further comprising: an intake line for guiding the compressed air from a compressor wheel into the cylinder; an intake flow regulation valve that is disposed on the intake line; and a charge air amount control unit for controlling the intake flow regulation valve such that a flow rate of the compressed air in the intake line is increased when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit.

7. The engine system according to Claim 2, further comprising: a turbocharger that includes a compressor wheel and a turbine wheel for driving the compressor wheel; an exhaust gas line for guiding an exhaust gas discharged from the engine to the turbine wheel; a bypass exhaust gas line for extracting the exhaust gas flowing through the exhaust gas line and discharging the exhaust gas to an outside while bypassing the turbine wheel; a bypass flow regulation valve for controlling a flow rate of the exhaust gas flowing through the bypass exhaust gas line; and a bypass exhaust gas amount control unit for controlling the bypass flow regulation valve such that the flow rate of the exhaust gas flowing through the bypass exhaust gas line is reduced when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit.

8. The engine system according to Claim 2, wherein the fuel gas supply system further includes a fuel gas line for guiding the fuel gas into the cylinder, a fuel gas flow regulation valve that is disposed on the fuel gas line, and a fuel gas amount control unit for controlling the fuel gas flow regulation valve such that a flow rate of the fuel gas in the fuel gas line is reduced when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the air extraction valve has been switched to the open state through the control of the air extraction control unit.

9. The engine system according to Claim 8, wherein the fuel gas supply system includes a first fuel gas line for guiding a first fuel gas to a combustion chamber of the engine, a first fuel on / off valve that is disposed on the first fuel gas line, a second fuel gas line for guiding a second fuel gas, whose lower explosive limit concentration is lower than a lower explosive limit concentration of the first fuel gas, to the combustion chamber, and a second fuel on / off valve that is disposed on the second fuel gas line, when the air extraction control unit controls the air extraction valve, at least the second fuel on / off valve of the first fuel on / off valve and the second fuel on / off valve is in an open state, and the engine system further comprises a fuel valve control unit for controlling the second fuel on / off valve such that the second fuel on / off valve is switched from the open state to a closed state when the unburned gas concentration calculated from the measured value of the gas analyzer is not equal to or less than the allowable concentration even after the flow rate of the fuel gas has been reduced through the control of the fuel gas amount control unit.

10. The engine system according to Claim 1, wherein the engine is a multi-cylinder engine in which a plurality of cylinder units, each of which includes the cylinder and the piston, are disposed along an axial direction of the crankshaft, the engine system further comprises a discharge line for guiding a discharge target gas, which is a fluid including the compressed air, in the crank chamber to an outside, the crankcase includes a one-side wall portion which is an end portion on one side in the axial direction, and the other side wall portion which is an end portion opposite to the one-side wall portion, a one-side introduction port to which the air extraction line is connected is formed in the one-side wall portion, and the other side discharge port to which the discharge line is connected is formed in the other side wall portion.

11. The engine system according to Claim 10, wherein the one-side introduction port is disposed at a position lower than the other side discharge port.

12. The engine system according to Claim 10, wherein the discharge line includes a one-side discharge line that is connected to the one-side wall portion and guides the discharge target gas to the outside, and the other side discharge line that is connected to the other side discharge port of the other side wall portion and guides the discharge target gas to the outside, the air extraction line includes a one-side air extraction line that is connected to the one-side introduction port of the one-side wall portion and guides the compressed air extracted from the starting air line to the one-side introduction port, and the other side air extraction line that branches from the one-side air extraction line and is connected to the other side wall portion, a one-side discharge port to which the one-side discharge line is connected is further formed in the one-side wall portion, the other side introduction port to which the the other side air extraction line is connected is further formed in the other side wall portion, and when viewed from the axial direction of the crankshaft, the one-side introduction port and the other side discharge port are disposed at positions that deviate from each other in a horizontal direction, and the other side introduction port and the one-side discharge port are disposed at positions that deviate from each other in the horizontal direction.

13. The engine system according to Claim 1, wherein the engine is a multi-cylinder engine in which a plurality of cylinder units, each of which includes the cylinder and the piston, are disposed along an axial direction of the crankshaft, the crankcase includes a one-side wall portion which is an end portion on one side in the axial direction, the other side wall portion which is an end portion opposite to the one-side wall portion, a first-side wall portion which is an end portion on a first side in a horizontal direction orthogonal to the axial direction, a second-side wall portion which is an end portion opposite to the first-side wall portion, and at least one bulkhead that is connected to the first-side wall portion and the second-side wall portion to partition one or more of the plurality of cylinder units from the other cylinder units in a plan view, the air extraction line includes a plurality of connection air extraction lines that are connected to the first-side wall portion to communicate with each of a plurality of spaces of the crank chamber partitioned by the at least one bulkhead, the engine system further comprises a discharge line for guiding a discharge target gas, which is a fluid including the compressed air, in the crank chamber to an outside, and the discharge line includes a plurality of connection discharge lines that are connected to the second-side wall portion to communicate with each of the plurality of spaces of the crank chamber.

14. The engine system according to Claim 1, wherein the engine is a multi-cylinder engine in which a plurality of cylinder units, each of which includes the cylinder and the piston, are disposed along an axial direction of the crankshaft, the crankcase includes a one-side wall portion which is an end portion on one side in the axial direction, the other side wall portion which is an end portion opposite to the one-side wall portion, and a side wall portion that is connected to the one-side wall portion and the other side wall portion, the air extraction line includes a side air extraction line that is connected to the starting air line and the side wall portion, and a side introduction port to which the side air extraction line is connected is formed in a central portion of the side wall portion in the axial direction of the crankshaft.

15. The engine system according to Claim 14, further comprising: a discharge line for guiding a discharge target gas, which is a fluid including the compressed air, in the crank chamber to an outside, wherein the discharge line includes a one-side discharge line that is connected to a one-side discharge port formed in the one-side wall portion and guides the discharge target gas discharged from the one-side discharge port to the outside, and the other side discharge line that is connected to the other side discharge port formed in the other side wall portion and guides the discharge target gas discharged from the other side discharge port to the outside.

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