Engine system

Abstract

Provided is an engine system comprising: an engine including a cylinder and a piston accommodated in the cylinder; a fuel gas line for guiding fuel gas to a combustion chamber in the cylinder; and a supercharger including a compressor wheel for sending compressed air to the combustion chamber. The engine further includes a crankshaft positioned below the piston and for driving the piston, and a crankcase for accommodating the crankshaft. The engine system further comprises: an air supply line for guiding the compressed air delivered by the compressor wheel to the combustion chamber, and a bleeding line for guiding the compressed air bled from the air supply line to a 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. 2023-140609 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 so-called 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 while suppressing a reduction in engine efficiency.

[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 while suppressing a reduction in engine efficiency.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; a fuel gas line for guiding a fuel gas to a combustion chamber in the cylinder; and a turbocharger that includes a compressor wheel for delivering compressed air to the combustion chamber, 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 engine system further includes an intake line for guiding the compressed air delivered by the compressor wheel to the combustion chamber and an air extraction line for guiding the compressed air extracted from the intake line 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 while suppressing a reduction in engine efficiency.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 a crankcase according to a first embodiment. FIG. 4 is a schematic view showing a crankcase according to a second embodiment. FIG. 5 is another schematic view showing the crankcase according to the second embodiment. FIG. 6 is a schematic view showing a crankcase according to a third embodiment. FIG. 7 is a schematic view showing a crankcase according to a fourth 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 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 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. 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.

[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, and 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. On the other hand, when the mixed gas is supplied to the combustion chamber 9, mixed combustion, which is the combustion of a mixed gas containing the hydrogen gas and the natural gas, occurs in the combustion chamber 9. The type of gas supplied is controlled by a controller 90 of the engine system 1. In addition, the controller 90 may be configured to control the ratio of the supply amount of natural gas to the supply amount of hydrogen gas. In this case, it is possible to adjust the mixed combustion ratio in the combustion chamber 9.

[0020] The turbocharger 15 according to the present example 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 generates the compressed air Ca.

[0021] 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".

[0022] 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. 3). 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.

[0023] 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.

[0024] 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 an intake manifold 102 and an intake pipe 103, and the compressed air Ca supplied to the intake manifold 102 from an intake line 25 (see FIG. 1), which will be described below, flows into the combustion chamber 9 via the intake pipe 103.

[0025] 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. Precombustion (preliminary combustion) of the fuel gas Fg mainly occurs in the sub-chamber, 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.

[0026] 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. The proportion of the hydrogen gas contained is a parameter that is correlated with the concentration of the hydrogen gas in the crank chamber 18.

[0027] Returning to FIG. 1, the engine system 1 further includes the intake line 25 for guiding the compressed air Ca delivered by the compressor wheel 12 to the combustion chamber 9 (see FIG. 2) 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.

[0028] 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 the intake manifold 102 and the intake pipe 103 (see FIG. 2).

[0029] The engine system 1 according to the present example further includes a compressed air return line 40 for extracting the cooled compressed air Ca discharged from the air cooler 28 and returning the cooled compressed air Ca to the compressor wheel 12. The compressed air return line 40 is configured to extract the compressed air Ca from the second intake line 252. The compressed air Ca guided by the compressed air return line 40 hits the compressor wheel 12 to suppress a rise in the temperature of the compressor wheel 12.

[0030] The engine system 1 further includes an air extraction line 30 for guiding the compressed air Ca extracted from the intake line 25 to the crank chamber 18. The air extraction line 30 according to the present example is connected to the compressed air return line 40 and the crankcase 20. That is, the air extraction line 30 according to the present example branches from the compressed air return line 40 and is configured to guide the compressed air Ca extracted from the compressed air return line 40 to the crank chamber 18.

[0031] According to the above-described configuration, since the compressed air Ca guided to the crank chamber 18 by the air extraction line 30 is mixed with the unburned gas leaking from the combustion chamber 9 to the crank chamber 18, it is possible to reduce the concentration of the unburned gas in the crank chamber 18. Further, the rotation speed of the compressor wheel 12 varies depending on the engine load. That is, the flow rate of the compressed air Ca guided by the air extraction line 30 varies depending on the engine load. In addition, the amount of unburned gas leaking into the crank chamber 18 also varies depending on the engine load. Therefore, since the amount of compressed air Ca required to reduce the concentration of the unburned gas leaking into the crank chamber 18 is guided to the crank chamber 18 without excess or deficiency, it is also possible to suppress a reduction in engine efficiency. For example, it is possible to suppress a significant reduction in engine efficiency caused by a significant reduction in the amount of compressed air Ca supplied to the combustion chamber 9 due to the excessive flow of the compressed air Ca for diluting the unburned gas concentration in the crank chamber 18 into the crank chamber 18. In this way, the engine system 1 that reduces the risk of explosion of the unburned gas in the crank chamber 18 while suppressing a reduction in engine efficiency is achieved.

[0032] In addition, the air extraction line 30 may be configured to directly extract the compressed air Ca from the first intake line 251 or the second intake line 252 instead of the compressed air return line 40. In this case, the engine system 1 may not include the compressed air return line 40. In addition, the engine system 1 may not include the air cooler 28. In any embodiment, the above-described technical advantages can be obtained.

[0033] In addition, according to the configuration in which the air extraction line 30 guides the compressed air Ca cooled by the air cooler 28 to the crank chamber 18, the compressed air Ca cooled by the air cooler 28 is guided to the crank chamber 18. Therefore, it is possible to suppress a rise in the temperature of the unburned gas in the crank chamber 18. This makes it possible to further reduce the risk of ignition of the unburned gas in the crank chamber 18.

[0034] Further, according to the configuration in which the air extraction line 30 branches from the compressed air return line 40 and is connected to the crankcase 20, a location where the compressed air Ca is extracted from the intake line 25 can coincide with a location where the compressed air return line 40 and the intake line 25 are connected to each other. Therefore, it is possible to suppress the loss of the flow of the compressed air Ca in the intake line 25. This makes it possible to suppress a reduction in engine efficiency.

[0035] 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 gas including the fuel gas Fg (that is, the unburned gas) leaking into the crank chamber 18 and the compressed air Ca supplied from the air extraction line 30 to the crank chamber 18.

[0036] 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.<Solenoid Valve 95>

[0037] As shown in FIG. 1, the engine system 1 according to some embodiments further includes a solenoid valve 95 that is disposed on the air extraction line 30 and the controller 90 for controlling the solenoid valve 95 according to the proportion of the hydrogen gas contained in the fuel gas Fg. When the solenoid valve 95 is in a closed state, the air extraction line 30 stops extracting the compressed air Ca. When the solenoid valve 95 is in an open state, the air extraction line 30 extracts the compressed air Ca.

[0038] As a first example, the controller 90 is configured to control the solenoid valve 95 according to the type of the fuel gas Fg flowing through the fuel gas line 11. Specifically, the fuel gas line 11 further includes a first on / off valve (not shown) and a second on / off valve (not shown) that are provided on the first fuel gas line 11a and the second fuel gas line 11b, respectively. When the first on / off valve is in an open state and the second on / off valve is in a closed state to supply the fuel gas Fg including the second fuel gas fg2 as the hydrogen gas to the engine 5, the proportion of the hydrogen gas contained in the fuel gas Fg is 0%. At this time, the controller 90 executes control to switch the solenoid valve 95 to the closed state. On the other hand, when the first on / off valve is in a closed state and the second on / off valve is in an open state, the proportion of the hydrogen gas contained in the fuel gas Fg is 100%. At this time, the controller 90 executes control to switch the solenoid valve 95 to the open state.

[0039] As a second example, the controller 90 may control the solenoid valve 95 according to the mixed combustion ratio of the hydrogen gas and the natural gas in the combustion chamber 9. The mixed combustion ratio is a concept included in the proportion of the hydrogen gas contained in the fuel gas Fg. The higher the mixed combustion ratio, the higher the concentration of the hydrogen gas in the crank chamber 18 tends to be. In the second example, the fuel gas line 11 further includes a first flow regulation valve (not shown) and a second flow regulation valve (not shown) that are provided on the first fuel gas line 11a and the second fuel gas line 11b, respectively. The mixed combustion ratio in the combustion chamber 9 is calculated based on the opening degree of each of the first flow regulation valve and the second flow regulation valve or the flow rate of each of the hydrogen gas and the natural gas. Then, when the mixed combustion ratio is equal to or greater than a prescribed value, the controller 90 executes control to switch the solenoid valve 95 to the open state.

[0040] As a third example, the controller 90 controls the solenoid valve 95 according to the detection result of the sensor for detecting the concentration of the hydrogen gas in the combustion chamber 9, the crank chamber 18, the discharge line 60, or the exhaust pipe 105. The concentration of the hydrogen gas specified by the detection result of the sensor is a concept included in the proportion of the hydrogen gas contained in the fuel gas Fg. The higher the specified concentration of the hydrogen gas, the higher the actual concentration of the hydrogen gas in the crank chamber 18 tends to be. In the third example, when the concentration of the hydrogen gas specified based on the detection result of the sensor is equal to or higher than the prescribed concentration, the controller 90 executes control to switch the solenoid valve 95 to the open state.

[0041] When the proportion of the hydrogen gas is low, the amount of hydrogen gas contained in the unburned gas in the crank chamber 18 is small. Therefore, the risk of ignition of the unburned gas in the crank chamber 18 is low. In this case, the controller 90 can close the solenoid valve 95. It is possible to limit the period during which the compressed air Ca is extracted by the air extraction line 30 and thus to suppress a reduction in engine efficiency.<Crankcase 20 (First Embodiment)>

[0042] FIG. 3 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. 3, an air extraction line 30A (30) according to the first embodiment branches from the compressed air return line 40 and is connected to the crankcase 20. However, the compressed air return line 40 may branch from the first intake line 251 and may be connected to the crankcase 20, and the engine 5A (5) may not include the air cooler 28 (the same applies to a second embodiment, a third embodiment, and a fourth embodiment which will be described below).

[0043] 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).

[0044] According to the above-described configuration, the compressed air Ca 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 Ca easily mix with each other in the axial direction in the crank chamber 18, the compressed air Ca 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.

[0045] In the example shown in FIG. 3, 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.

[0046] According to the configuration in which the one-side introduction port 37A is disposed at the position lower than the other side discharge port 68, the compressed air Ca flowing through the crank chamber 18 also moves upward while flowing toward the other side discharge port 68. Therefore, the compressed air Ca can spread in the crank chamber 18, and both the compressed air Ca 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)>

[0047] FIG. 4 is a schematic view showing a crankcase 20B (20) of an engine 5B (5) according to the second embodiment. In FIG. 4, the same components as those in the engine 5A (see FIG. 3) are denoted by the same reference numerals, and a description thereof will be omitted or simplified below.

[0048] 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 compressed air return line 40 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 Ca extracted from the compressed air return line 40 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 Ca extracted from the one-side air extraction line 31 to the other side wall portion 22B.

[0049] 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.

[0050] In the example shown in FIG. 4, 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.

[0051] According to the above-described configuration, the compressed air Ca flows into the crank chamber 18 from both sides in the axial direction. Therefore, the compressed air Ca 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.

[0052] The description of the configuration of the engine 5B will be continued. The discharge line 60 shown in FIG. 4 includes the 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.

[0053] 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.

[0054] FIG. 5 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.

[0055] In the present example, as the discharge target gas Eo, at least a portion of the compressed air Ca 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 Ca 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.

[0056] According to the above-described configuration, the compressed air Ca 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 Ca 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)>

[0057] FIG. 6 is a schematic view showing an engine 5C (5) according to the 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.

[0058] An air extraction line 30C (30) according to the third embodiment includes a side air extraction line 33 that is connected to the compressed air return line 40 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 Ca extracted from the compressed air return line 40 to the side introduction port 39.

[0059] In addition, the discharge line 60 shown in FIG. 6 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.

[0060] According to the above-described configuration, the compressed air Ca 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 for the compressed air Ca to spread 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.

[0061] Further, the air extraction line 30C may further include at least one of a plurality of connection air extraction lines 35 (see FIG. 7) according to the 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)>

[0062] FIG. 7 is a schematic view showing an engine 5D (5) according to the 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.

[0063] 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.

[0064] 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.

[0065] As a more specific example, the cylinder unit 8 shown in FIG. 7 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. In still another example, the number of bulkheads 29 may be one (not shown).

[0066] 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.

[0067] 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.

[0068] According to the above-described configuration, since one or more cylinder units 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 Ca flows into each space 17 from each connection air extraction line 35, and the discharge target gas Eo including the compressed air Ca 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 Ca, it is possible to reduce the risk of ignition of the unburned gas in the crank chamber 18.

[0069] In addition, even when the engine 5D is an in-line multi-cylinder engine, the above-described technical advantages can be obtained.<Others>

[0070] 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.

[0071] 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>

[0072] For example, the content described in some embodiments described above is understood as follows.

[0073] 1) An engine system (1) according to an embodiment of the present disclosure includes: an engine (5) that includes a cylinder (6) and a piston (7) housed in the cylinder; a fuel gas line (11) for guiding a fuel gas (Fg) to a combustion chamber (9) in the cylinder; and a turbocharger (15) that includes a compressor wheel (12) for delivering compressed air to the combustion chamber, 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 engine system further includes an intake line (25) for guiding the compressed air delivered by the compressor wheel to the combustion chamber, and an air extraction line (30) for guiding the compressed air extracted from the intake line to a crank chamber (18) in the crankcase.

[0074] According to the configuration of 1), the compressed air guided to the crank chamber by the air extraction line is mixed with the unburned gas, which is the fuel gas in an unburned state, leaking from the combustion chamber to the crank chamber. Therefore, it is possible to reduce the concentration of the unburned gas in the crank chamber. Further, the rotation speed of the compressor wheel varies depending on the engine speed and the engine load. That is, the flow rate of the compressed air guided by the air extraction line varies depending on the engine speed and the engine load. In addition, the amount of unburned gas leaking into the crank chamber also varies depending on the engine speed and the engine load. Therefore, since the amount of compressed air required to reduce the concentration of the unburned gas leaking into the crank chamber is guided to the crank chamber without excess or deficiency, it is also possible to suppress a reduction in engine efficiency. For example, it is possible to suppress a significant reduction in engine efficiency caused by a significant reduction in the amount of compressed air supplied to the combustion chamber due to the excessive flow of the compressed air for diluting the unburned gas into the crank chamber. In this way, the engine system that reduces the risk of ignition of the unburned gas in the crank chamber while suppressing a reduction in engine efficiency is achieved.

[0075] 2) In some embodiments, the engine system according to 1) further includes an air cooler (28) that is disposed on the intake line and cools the compressed air, in which the air extraction line is configured to guide the compressed air cooled by the air cooler to the crank chamber.

[0076] According to the configuration of 2), the compressed air cooled by the air cooler is guided to the crank chamber. Therefore, it is possible to suppress a rise in the temperature of the unburned gas in the crank chamber. This makes it possible to reduce the risk of ignition of the unburned gas in the crank chamber.

[0077] 3) In some embodiments, the engine system according to 2) further includes a compressed air return line (40) for extracting the compressed air discharged from the air cooler and returning the compressed air to the compressor wheel, and in which the air extraction line branches from the compressed air return line and is connected to the crankcase.

[0078] According to the configuration of 3), the location where the compressed air is extracted from the intake line can coincide with the location where the compressed air return line and the intake line are connected to each other. Therefore, it is possible to suppress the loss of the flow of the compressed air in the intake line. This makes it possible to suppress a reduction in engine efficiency.

[0079] 4) In some embodiments, in the engine system according to 3), 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, and the other side wall portion (22) which is an end portion opposite to the one-side wall portion, and the air extraction line includes a one-side air extraction line (31) that is connected to the compressed air return line and 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.

[0080] According to the configuration of 4), the compressed air flows into the crank chamber from both sides in the axial direction. Therefore, the compressed air can spread in the crank chamber. This makes it possible to uniformly reduce the concentration of the unburned gas in the crank chamber.

[0081] 5) In some embodiments, in the engine system according to any one of 1) to 4), the fuel gas line includes a first fuel gas line (11a) for guiding a first fuel gas (fg1) to the combustion chamber, and a second fuel gas line (11b) for guiding a second fuel gas (fg2), whose lower explosive limit concentration is lower than a lower explosive limit concentration of the first fuel gas, to the combustion chamber, and the engine system further includes a solenoid valve (95) that is disposed on the air extraction line, and a controller (90) for controlling the solenoid valve according to a proportion of the second fuel gas contained in the fuel gas.

[0082] According to the configuration of 5), when the proportion of the second fuel gas is low, that is, when the risk of ignition of the unburned gas in the crank chamber is low, the controller can close the solenoid valve. It is possible to limit the period during which the compressed air is extracted by the air extraction line and thus to suppress a reduction in engine efficiency.

[0083] 6) In some embodiments, in the engine system according to any one of 1) to 5), 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 gas 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.

[0084] According to the configuration of 6), 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.

[0085] 7) In some embodiments, in the engine system according to 6), the one-side introduction port is disposed at a position lower than the other side discharge port.

[0086] According to the configuration of 7), 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.

[0087] 8) In some embodiments, the engine system according to 6) or 7) 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.

[0088] According to the configuration of 8), the compressed air flowing into the crank chamber from the one-side introduction port easily spreads horizontally in the crank chamber in the process of 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.

[0089] 9) In some embodiments, in the engine system according to 3), 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, the engine system further includes a discharge line for guiding a discharge target gas, which is a gas including the compressed air, in the crank chamber to an outside, 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.

[0090] According to the configuration of 9), 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.

[0091] 10) In some embodiments, in the engine system according to 3), 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.

[0092] According to the configuration of 10), 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.Reference Signs List

[0093] 1: Engine system 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 18: Crank chamber 19: Connecting rod 20: Crankcase 21: One-side wall portion 22: The other 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 40: Compressed air return line 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 81: Crank pin 82: Intake valve 83: Exhaust valve 85: Cam shaft 86: Rocker arm 87: Push rod 89: Exhaust gas line 90: Controller 95: Solenoid valve 102: Intake manifold 103: Intake pipe 105: Exhaust pipe 251: First intake line 252: Second intake line Ca: Compressed air Eg: Exhaust gas Eo: Discharge target gas Fg: Fuel gas 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; a fuel gas line for guiding a fuel gas to a combustion chamber in the cylinder; and a turbocharger that includes a compressor wheel for delivering compressed air to the combustion chamber, 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 engine system further comprises an intake line for guiding the compressed air delivered by the compressor wheel to the combustion chamber, and an air extraction line for guiding the compressed air extracted from the intake line to a crank chamber in the crankcase.

2. The engine system according to Claim 1, further comprising: an air cooler that is disposed on the intake line and cools the compressed air, wherein the air extraction line is configured to guide the compressed air cooled by the air cooler to the crank chamber.

3. The engine system according to Claim 2, further comprising: a compressed air return line that extracts the compressed air discharged from the air cooler and returns the compressed air to the compressor wheel, wherein the air extraction line branches from the compressed air return line and is connected to the crankcase.

4. The engine system according to Claim 3, 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, and the other side wall portion which is an end portion opposite to the one-side wall portion, and the air extraction line includes a one-side air extraction line that is connected to the compressed air return line and the one-side wall portion, 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.

5. The engine system according to any one of Claims 1 to 4, wherein the fuel gas line includes a first fuel gas line for guiding a first fuel gas to the combustion chamber, and 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 the engine system further comprises a solenoid valve that is disposed on the air extraction line, and a controller for controlling the solenoid valve according to a proportion of the second fuel gas contained in the fuel gas.

6. The engine system according to any one of Claims 1 to 4, 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 gas 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.

7. The engine system according to Claim 6, wherein the one-side introduction port is disposed at a position lower than the other side discharge port.

8. The engine system according to Claim 6, further comprising: 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 wall portion and guides the discharge target gas to the outside, wherein the air extraction line includes a one-side air extraction line for guiding the compressed air extracted from the intake line to the one-side wall portion, 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 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.

9. The engine system according to Claim 3, 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 gas 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.

10. The engine system according to Claim 3, 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 compressed air return 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.

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