Engine system

Abstract

To provide an engine system that reduces a risk of ignition of unburned gas in a crank chamber while suppressing deterioration of engine efficiency.SOLUTION: An engine system includes: an engine having 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. In the engine system, the engine further includes: a crank shaft located on the lower side of the piston to drive the piston; and a crank case that accommodates the crank shaft. The engine system further includes: an air supply line for guiding the compressed air sent out by the compressor wheel to the combustion chamber; and an extraction line for guiding the compressed air extracted from the air supply line to a crank chamber in the crank case.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The engine system disclosed in Patent Document 1 includes a cylinder, a piston housed in the cylinder, a crankshaft located below the piston and for driving the piston, and a crankcase housing the crankshaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-031957 A Summary of the Invention [Problem to be solved by the invention]

[0004] Fuel gas in the combustion chamber inside the cylinder may leak into the crank chamber inside the crankcase through the gap between the cylinder and the piston (the fuel gas in question is known as blow-by gas). If the concentration of unburned fuel gas in the crank chamber is high, there is a risk that the fuel gas will ignite. It is preferable to take measures to reduce this risk while suppressing any decrease in engine efficiency.

[0005] An object of the present disclosure is to provide an engine system that reduces the risk of ignition of unburned gas in the crankcase while suppressing a decrease in engine efficiency. [Means for solving the problem]

[0006] An engine system according to at least one embodiment of the present disclosure includes: an engine including a cylinder and a piston housed in the cylinder; a fuel gas line for introducing fuel gas into a combustion chamber in the cylinder; a supercharger including a compressor wheel for delivering compressed air to the combustion chamber; An engine system comprising: The engine is a crankshaft located below the piston and configured to be driven by the piston; a crankcase that accommodates the crankshaft; Further comprising: The engine system includes: an air supply line for directing the compressed air delivered by the compressor wheel to the combustion chamber; an air bleed line for guiding the compressed air bled from the air supply line to a crank chamber in the crankcase; It further comprises: Effect of the Invention

[0007] According to the present disclosure, it is possible to provide an engine system that reduces the risk of ignition of unburned gas in the crankcase while suppressing a decrease in engine efficiency. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an engine system according to an embodiment. [Diagram 2] FIG. 1 is a schematic diagram of an engine according to an embodiment. [Diagram 3] FIG. 2 is a schematic view of a crankcase according to the first embodiment. [Figure 4] FIG. 11 is a schematic view of a crankcase according to a second embodiment. [Diagram 5] FIG. 11 is another schematic view of the crankcase according to the second embodiment. [Figure 6] FIG. 11 is a schematic view of a crankcase according to a third embodiment. [Figure 7] FIG. 11 is a schematic view of a crankcase according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0010] <Outline of Engine System 1> 1 is a schematic diagram of an engine system 1 according to an embodiment of the present disclosure. The engine system 1, which may be incorporated in, for example, a power generation facility, includes an engine 5 having a combustion chamber 9 and a crank chamber 18 formed therein, a fuel gas line 11 for introducing fuel gas Fg to the combustion chamber 9, and a supercharger 15 including a compressor wheel 12 for sending compressed air Ca to the combustion chamber 9. The engine 5 in this example is a stationary engine.

[0011] The fuel gas Fg in this 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. By adopting this configuration, the combustion of the first fuel gas fg1, the combustion of the second fuel gas fg2, or the mixed combustion of both fuel gases is selectively performed in the combustion chamber 9.

[0012] The first fuel gas fg1 and the second fuel gas fg2 may be any gas, but the lower explosion limit concentration of the second fuel gas fg2 is lower than the lower explosion limit concentration of the first fuel gas fg1. The first fuel gas fg1 is, for example, a fossil fuel gas, and a more specific example is natural gas. The second fuel gas fg2 is a non-fossil fuel gas, and a more specific example includes at least one of hydrogen gas, biofuel gas, and ammonia gas. However, the second fuel gas fg2 may be, for example, a fossil fuel gas such as propane gas. In this way, various fuel gases can be adopted for the first fuel gas fg1 and the second fuel gas fg2, but below, as an example, an embodiment in which the first fuel gas fg1 is natural gas and the second fuel gas fg2 is hydrogen gas is illustrated.

[0013] When only natural gas or hydrogen gas is supplied, the combustion of the gas occurs in the combustion chamber 9. On the other hand, when a mixed gas is supplied to the combustion chamber 9, a mixed combustion, which is the combustion of a mixed gas containing hydrogen gas and natural gas, occurs in the combustion chamber 9. The type of gas supplied is controlled by a controller 90 of the engine system 1. The controller 90 may also be configured to control the ratio between the amount of natural gas supplied and the amount of hydrogen gas supplied. In this case, the mixed combustion ratio in the combustion chamber 9 can be adjusted.

[0014] The turbocharger 15 of this example further includes a turbine wheel 14, and a rotor shaft 13 connected to the turbine wheel 14 and the compressor wheel 12. The engine system 1 also includes an exhaust gas line 89 for guiding 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, causing the compressor wheel 12 to generate compressed air Ca.

[0015] 2 is a schematic diagram of an engine 5 according to an embodiment of the present disclosure, showing a cross section perpendicular to the axis of a crankshaft 16 of the engine 5. The engine 5 includes a cylinder 6, a piston 7 housed in the cylinder 6, a crankshaft 16 located below the piston 7, and a crankcase 20 housing the crankshaft 16. A crank pin 81 configured to rotate in conjunction with the crankshaft 16 is connected to the piston 7 via a connecting rod 19. As a result, the crankshaft 16 is driven by the piston 7. In the following description, the axial direction of the crankshaft 16 may be abbreviated to "axial direction".

[0016] The illustrated engine 5 is, as an example, a V-type multi-cylinder engine. More specifically, two pistons 7 adjacent to each other in the axial direction are arranged in a substantially V-shape at a predetermined bank angle when viewed in the axial direction. The number of cylinder units 8 including the cylinders 6 and the pistons 7 arranged in the axial direction (the number of cylinders) is, for example, 12, 14, 16, 18, 20, or 24. The crankcase 20 in this example is long in the axial direction (see FIG. 3). Note that the engine 5 according to another example may be an in-line multi-cylinder engine. There is no particular restriction on the number of cylinders, and the number of cylinders may be, for example, 2, 4, 6, or 8.

[0017] The engine 5 illustrated in Fig. 2 is an OHV (Over Head Valve) type 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 camshaft 85 extending in the axial direction, a cam (not shown) provided on the camshaft 85, a push rod 87 configured to be displaced up and down by rotation of the cam, a rocker arm 86 configured to swing in accordance with the displacement of the push rod 87, and an intake valve 82 and an exhaust valve 83 connected to one end of the rocker arm 86. The intake valve 82 and the exhaust valve 83 included in the valve mechanism open and close the ports of the cylinder 6 by the rocker arm 86 swinging about an axis parallel to the axial direction.

[0018] A combustion chamber 9 of the engine 5 is defined by various components such as the inner circumferential surface of the cylinder 6 and the upper end surface of the piston 7. The engine 5 includes an air intake chamber 102 and an air intake pipe 103, and compressed air Ca supplied to the air intake chamber 102 from an air intake line 25 (see FIG. 1) described below flows into the combustion chamber 9 via the air intake pipe 103.

[0019] There is no particular restriction on the type of engine 5 of the present disclosure, but for example, a pre-chamber type gas engine may be adopted. More specifically, the combustion chamber 9 includes a pre-chamber to which the fuel gas Fg is supplied, and a main chamber in which the fuel gas Fg supplied from a separate line is burned using a combustion flame ignited in the pre-chamber. In the pre-chamber, pre-combustion (preliminary combustion) of the fuel gas Fg mainly occurs, and the combustion of the fuel gas Fg is completed in the main chamber. The exhaust gas Eg generated by the 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.

[0020] A crank chamber 18 is formed inside the crankcase 20. A part of the fuel gas Fg supplied to the combustion chamber 9 leaks into the crank chamber 18 as blow-by gas through between the piston 7 and the cylinder 6. The concentration of unburned gas, which is the fuel gas Fg in an unburned state in the crank chamber 18, is lowered below the lower explosion limit concentration to suppress the occurrence of an unburned gas explosion in the crank chamber 18. If the concentration is equal to or higher than the lower explosion limit concentration, the risk of explosion of the unburned gas in the crank chamber 18 increases. The lower explosion limit concentration varies depending on the type of fuel gas Fg or the content ratio of hydrogen gas in the fuel gas Fg. The content ratio of hydrogen gas is a parameter that correlates with the concentration of hydrogen gas in the crank chamber 18.

[0021] Returning to Fig. 1, the engine system 1 further includes an air 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 arranged on the air 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 air intake line 25 has a first air intake line 251 for guiding the compressed air Ca to the air cooler 28, and a second air 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 air intake line 252 is adapted to be guided to the combustion chamber 9 via the air intake chamber 102 (see FIG. 2) and the air intake pipe 103 (see FIG. 2).

[0023] The engine system 1 of this example further includes a compressed air return line 40 for bleeding the cooled compressed air Ca discharged from the air cooler 28 and returning it to the compressor wheel 12. The compressed air return line 40 is configured to bleeding the compressed air Ca from the second air supply line 252. The compressed air Ca guided by the compressed air return line 40 hits the compressor wheel 12, thereby suppressing a temperature rise of the compressor wheel 12.

[0024] The engine system 1 further includes an air bleed line 30 for guiding the compressed air Ca bled from the air intake line 25 to the crank chamber 18. The air bleed line 30 in this example is connected to a compressed air return line 40 and the crankcase 20. That is, the air bleed line 30 in this example is branched off from the compressed air return line 40, and is configured to guide the compressed air Ca bled from the compressed air return line 40 to the crank chamber 18.

[0025] According to the above configuration, the compressed air Ca led to the crank chamber 18 by the bleed line 30 mixes with the unburned gas leaked from the combustion chamber 9 to the crank chamber 18, so that the concentration of the unburned gas in the crank chamber 18 can be reduced. Furthermore, the rotation speed of the compressor wheel 12 varies according to the engine load. That is, the flow rate of the compressed air Ca led by the bleed line 30 varies according to the engine load. The amount of the unburned gas leaked to the crank chamber 18 also varies according to the engine load. Therefore, the amount of compressed air Ca required to reduce the concentration of the unburned gas leaked to the crank chamber 18 is led to the crank chamber 18 without excess or deficiency, so that it is possible to suppress a decrease in engine efficiency. For example, it is possible to suppress a significant decrease in the compressed air Ca supplied to the combustion chamber 9 due to an excessive flow of the compressed air Ca for diluting the unburned gas concentration inside the crank chamber 18 into the crank chamber 18, which causes a significant decrease in engine efficiency. As a result, an engine system 1 is realized that reduces the risk of explosion of unburned gas in the crank chamber 18 while suppressing a decrease in engine efficiency.

[0026] The bleed line 30 may be configured to directly bleed the compressed air Ca from the first air supply line 251 or the second air supply 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. Also, the engine system 1 may not include the air cooler 28. In any embodiment, the above technical advantages can be obtained.

[0027] Furthermore, according to the configuration in which the compressed air Ca cooled by the air cooler 28 is guided to the crank chamber 18 by the bleed line 30, the compressed air Ca cooled by the air cooler 28 is guided to the crank chamber 18, so that it is possible to suppress an increase in the temperature of the unburned gas in the crank chamber 18. This further reduces the risk of ignition of the unburned gas in the crank chamber 18.

[0028] Furthermore, according to the configuration in which the bleed line 30 branches off from the compressed air return line 40 and connects to the crankcase 20, the place where the compressed air Ca is bled from the intake line 25 can be made to coincide with the place where the compressed air return line 40 and the intake line 25 connect, thereby suppressing loss of the flow of the compressed air Ca in the intake line 25. This makes it possible to suppress a decrease in engine efficiency.

[0029] The engine system 1 will be described further with reference to Fig. 1. The engine system 1 further includes an exhaust line 60 for guiding the exhaust object Eo to the outside. The exhaust object Eo is a gas containing the fuel gas Fg (i.e., unburned gas) leaking into the crank chamber 18 and the compressed air Ca supplied from the bleed line 30 to the crank chamber 18.

[0030] The discharge target object Eo in this example further includes oil mist. The oil mist may be generated when the lubricating oil adhering to the movable parts such as the shaft, cam, gear, or piston 7 constituting the engine 5 is scattered. Alternatively, an oil tank (not shown) that stores the lubricating oil is disposed below the crank chamber 18, and the oil mist may be generated when a part of the stored lubricating oil as a liquid pool evaporates. The oil mist also floats inside the crank chamber 18.

[0031] <Solenoid valve 95> 1, the engine system 1 according to some embodiments further includes a solenoid valve 95 disposed in the bleed line 30, and a controller 90 for controlling the solenoid valve 95 in accordance with the content of hydrogen gas in the fuel gas Fg. When the solenoid valve 95 is in a closed state, the bleed line 30 stops bleeding the compressed air Ca. When the solenoid valve 95 is in an open state, the bleed line 30 performs bleeding of the compressed air Ca.

[0032] As a first example, the controller 90 is configured to control the solenoid valve 95 according to the type of 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) provided in 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 consisting only of the second fuel gas fg2 as hydrogen gas to the engine 5, the content ratio of hydrogen gas in the fuel gas Fg is 0%. At this time, the controller 90 executes control to close the solenoid valve 95. 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 content ratio of hydrogen gas in the fuel gas Fg is 100%. At this time, the controller 90 executes control to open the solenoid valve 95.

[0033] As a second example, the controller 90 may control the solenoid valve 95 according to the mixed combustion ratio of hydrogen gas and natural gas in the combustion chamber 9. The mixed combustion ratio is a concept included in the content ratio of hydrogen gas in the fuel gas Fg. The higher the mixed combustion ratio, the higher the concentration of hydrogen gas in the crank chamber 18 tends to be. In the second example, the fuel gas line 11 further includes a first flow control valve (not shown) and a second flow control valve (not shown) provided in 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 control valve and the second flow control 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 specified value, the controller 90 executes control to open the solenoid valve 95.

[0034] As a third example, the controller 90 controls the solenoid valve 95 in response to the detection result of a sensor for detecting the concentration of hydrogen gas in the combustion chamber 9, the crank chamber 18, the exhaust line 60, or the exhaust pipe 105. The concentration of hydrogen gas determined by the detection result of the sensor is a concept included in the content ratio of hydrogen gas in the fuel gas Fg. The higher the concentration of hydrogen gas determined, the higher the actual concentration of hydrogen gas in the crank chamber 18 tends to be. In the third example, when the concentration of hydrogen gas determined based on the detection result of the sensor becomes equal to or higher than a specified concentration, the controller 90 executes control to open the solenoid valve 95.

[0035] When the hydrogen gas content is low, the amount of hydrogen gas contained in the unburned gas in the crank chamber 18 is small, and 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. Since the period during which the compressed air Ca is bled by the bleed line 30 can be limited, a decrease in engine efficiency can be suppressed.

[0036] <Crankcase 20 (First embodiment)> Fig. 3 is a schematic diagram showing a crankcase 20A(20) of an engine 5A(5) according to the first embodiment. In the example of Fig. 3, the bleed line 30A(30) according to the first embodiment branches off from the compressed air return line 40 and is connected to the crankcase 20, but the compressed air return line 40 may branch off from the first air supply line 251 and be connected to the crankcase 20, and the engine 5A(5) may not include the air cooler 28 (the same applies to the second, third and fourth embodiments described later).

[0037] The crankcase 20A has a first side wall portion 21A (21) which is an end portion on one side in the axial direction, and a second side wall portion 22A (22) which is an end portion opposite to the first side wall portion 21. A first side inlet 37A (37) to which the extraction line 30A is connected is formed in the first side wall portion 21A (21), and a second side outlet 68 is formed in the second side wall portion 22A (22).

[0038] According to the above configuration, the compressed air Ca that has passed through the one-side inlet 37A flows in the axial direction through the crank chamber 18, and then flows through the discharge line 60 via the other-side discharge port 68. Since the unburned gas and the compressed air Ca tend to mix in the axial direction within the crank chamber 18, the compressed air Ca is likely to be discharged together with the unburned gas into the discharge line 60. This makes it possible to uniformly reduce the concentration of unburned gas within the crank chamber 18.

[0039] In the example of FIG. 3, at least a portion of the one-side inlet 37A (37) is disposed at the same height as the other-side outlet 68. In the illustrated example, both the one-side inlet 37A and the other-side outlet 68 are disposed at a higher position than the crankshaft 16, but the present disclosure is not limited thereto. For example, the one-side inlet 37A may be disposed at a lower position than the crankshaft 16, or at least a portion of the one-side inlet 37A may be disposed at the same height as the crankshaft 16. Alternatively, both the one-side inlet 37A and the other-side outlet 68 may be disposed at a lower position than the crankshaft 16.

[0040] According to the configuration in which the one-side inlet 37A is disposed at a position lower than the other-side outlet 68, the compressed air Ca flowing through the crank chamber 18 also moves upward as it flows toward the other-side outlet 68. This allows the compressed air Ca to be distributed throughout the crank chamber 18, and makes it easier for both the compressed air Ca and the unburned gas to be discharged to the exhaust line 60. Therefore, the concentration of unburned gas in the crank chamber 18 can be uniformly reduced.

[0041] <Crankcase 20 (Second embodiment)> Fig. 4 is a schematic diagram showing a crankcase 20B (20) of an engine 5B (5) according to a second embodiment. In Fig. 4, the same components as those of the engine 5A (see Fig. 3) are given the same reference numerals, and their description will be omitted or simplified below.

[0042] The bleed line 30B of the engine 5B has a first bleed line 31 and a second bleed line 32. The first bleed line 31 is connected to the compressed air return line 40 and the first side wall portion 21B (21) of the crankcase 20B. That is, the first bleed line 31 is configured to guide the compressed air Ca bled from the compressed air return line 40 to the first side wall portion 21B. The second bleed line 32 branches off from the first bleed line 31 and connects to the second side wall portion 22B (22) of the crankcase 20B. That is, the second bleed line 32 is configured to guide the compressed air Ca bled from the first bleed line 31 to the second side wall portion 22B.

[0043] A one-side inlet 37B (37) to which the one-side bleed line 31 is connected is formed in the one-side wall portion 21B, and a other-side inlet 38 to which the other-side bleed line 32 is connected is formed in the other-side wall portion 22B. In the illustrated example, at least a portion of the one-side inlet 37B (37) is disposed at the same height as the other-side inlet 38.

[0044] 4, both the one-side inlet 37B and the other-side inlet 38 are disposed at a position higher than the crankshaft 16, but the present disclosure is not limited thereto. The one-side inlet 37B may be disposed at a position lower than the crankshaft 16, or at least a portion of the one-side inlet 37B may be disposed at the same height as the crankshaft 16. Alternatively, both the one-side inlet 37B and the other-side inlet 38 may be disposed at a position lower than the crankshaft 16.

[0045] According to the above-described configuration, the compressed air Ca flows into the crank chamber 18 from both sides in the axial direction, and therefore the compressed air Ca can be distributed throughout the crank chamber 18. This makes it possible to uniformly reduce the concentration of unburned gas within the crank chamber 18.

[0046] Continuing with the description of the configuration of the engine 5B, the discharge line 60 illustrated in Fig. 4 includes a one-side discharge line 61 connected to the one-side wall portion 21B and an 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 a other-side discharge port 68 to which the other-side discharge line 62 is connected is formed in the other-side wall portion 22B.

[0047] In this example, at least a portion of the one-side discharge port 67 is disposed at a higher position than the other-side discharge port 68, more specifically, the entire portion of the one-side discharge port 67 is disposed at a higher position than the other-side discharge port 68. Also, at least a portion of the one-side discharge port 67 is disposed at a higher position than the one-side inlet 37B (37), more specifically, the entire portion of the one-side discharge port 67 is disposed at a higher position than the one-side inlet 37B. Also, in this example, at least a portion of the other-side discharge port 68 is disposed at the same height as the other-side inlet 38.

[0048] FIG. 5 is a conceptual perspective view of the crankcase 20B (the crankshaft 16 is omitted). In the axial view, the one-side inlet 37B and the other-side outlet 68 are arranged at positions shifted from each other in the horizontal direction (hereinafter, sometimes referred to as the width direction). In addition, in the axial view, the other-side inlet 38 and the one-side outlet 67 are arranged at positions shifted from each other in the width direction. In the illustrated example, the one-side inlet 37B and the other-side inlet 38 are arranged on a first side in the width direction with respect to the center of the width direction of the crankcase 20. In addition, the one-side outlet 67 and the other-side outlet 68 are arranged on a second side opposite to the first side in the width direction with respect to the center of the width direction of the crankcase 20. The width direction is a horizontal direction perpendicular to the axial direction.

[0049] In this example, at least a portion of the compressed air Ca introduced from the one-side inlet 37B to the crank chamber 18 passes through the other-side outlet 68 as the discharge object Eo. The discharge object Eo passing through the other-side outlet 68 is discharged to the outside via the other-side discharge line 62. Similarly, at least a portion of the compressed air Ca introduced from the other-side inlet 38 to the crank chamber 18 passes through the one-side outlet 67 as the discharge object Eo. The discharge object Eo passing through the one-side outlet 67 is discharged to the outside via the one-side discharge line 61.

[0050] According to the above configuration, the compressed air Ca flowing into the crank chamber 18 from the one-side inlet 37 tends to spread horizontally within the crank chamber 18 as it flows toward the other-side exhaust port 68. Similarly, the compressed air Ca flowing into the crank chamber 18 from the other-side inlet 38 tends to spread horizontally within the crank chamber 18 as it flows toward the one-side exhaust port 67. This makes it easier for unburned gas in the crank chamber 18 to be discharged from the one-side exhaust port 67 and the other-side exhaust port 68, thereby making it possible to uniformly reduce the concentration of unburned gas within the crank chamber 18.

[0051] <Crankcase 20 (Third embodiment)> 6 is a schematic diagram of an engine 5C (5) according to a third embodiment, showing a plan view of the engine 5C. The engine 5C has one side wall portion 21C (21) which is an end portion on one side in the axial direction, another side wall portion 22C (22) which is an end portion opposite to the one side wall portion 21C, and a side wall portion 23 which is 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 a first side in the width direction.

[0052] The bleed line 30C (30) according to the third embodiment has a side bleed line 33 that connects to the compressed air return line 40 and the side wall portion 23. A side inlet port 39 to which the side bleed line 33 connects is formed in the central portion 24 of the side wall portion 23 in the axial direction. The side bleed line 33 is configured to guide the compressed air Ca bled from the compressed air return line 40 to the side inlet port 39.

[0053] 6 includes a one-side discharge line 61 connected to the one side wall portion 21C (21) and an other-side discharge line 62 connected to the other side wall portion 22C (22). A one-side discharge port 67 and an other-side discharge port 68 are formed in the one side wall portion 21C and the other side wall portion 22C, respectively.

[0054] According to the above configuration, the compressed air Ca that flows into the crank chamber 18 from the side inlet 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 allows the compressed air Ca to spread throughout the crank chamber 18, so that the unburned gas in the crank chamber 18 is easily discharged from the one-side exhaust port 67 and the other-side exhaust port 68. This allows the concentration of unburned gas in the crank chamber 18 to be uniformly low. The bleed line 30C may further include at least one of a plurality of connecting bleed lines 35 (see FIG. 7) according to a fourth embodiment described below, in addition to the side bleed line 33. Even in this case, the above-mentioned technical advantages can be obtained.

[0055] <Crankcase 20 (fourth embodiment)> FIG. 7 is a schematic diagram of an engine 5D (5) according to a fourth embodiment, showing a plan view of the engine 5D. The engine 5D is a V-type multi-cylinder engine in which a plurality of cylinder units 8 are arranged along the axial direction. The cylinder units 8 of the engine 5D include a plurality of cylinder units 8A arranged on a first side in the width direction from the axis of the crankshaft 16, and a plurality of cylinder units 8B arranged on a second side in the width direction from the axis. The number of cylinder units 8A is the same as the number of cylinder units 8B.

[0056] The crankcase 20D (20) of the engine 5D has 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 the one side wall portion 21D, a first side wall portion 27 which is an end portion on a first side in the width direction, and a second side wall portion 26 which is an end portion opposite the first side wall portion 27.

[0057] The engine 5D further has at least one partition wall portion 29. The partition wall portion 29 extends in the width direction and connects to the first side wall portion 27 and the second side wall portion 26. Furthermore, the partition wall portion 29 separates one or more of the multiple cylinder units 8 from the other cylinder units 8 in a plan view.

[0058] As a more specific example, the cylinder unit 8 shown in FIG. 7 includes a plurality of pairs of cylinder units 8, each pair being cylinder units 8A, 8B adjacent to each other in the axial direction, and each of the plurality of partition wall portions 29 is arranged to separate each pair of cylinder units 8 from the other pair of cylinder units 8. In the crank chamber 18, the plurality of partition wall portions 29 form spaces 17 whose number is half the number of cylinders of the engine 5D, and a pair of cylinder units 8 is arranged in each space 17 in a plan view. For example, when the number of cylinders of the engine 5D is 18, the crank chamber 18 is divided into nine spaces 17 (the number of partition wall portions 29 is eight). However, the partition wall portions 29 of the present disclosure are not limited to the above embodiment. The number of partition wall portions 29 may be two (not shown). In this case, the crank chamber 18 is divided into three spaces 17, and three pairs of cylinder units 8 are arranged in each space 17. As yet another example, the number of partition wall portions 29 may be one (not shown).

[0059] The bleed line 30D of the engine 5D includes a plurality of connecting bleed lines 35 connected to the first side wall portion 27 so as to communicate with each of the plurality of spaces 17. In addition, the exhaust line 60 of the engine 5D includes a plurality of connecting exhaust lines 65 connected to the second side wall portion 26 so as to communicate with each of the plurality of spaces 17.

[0060] A plurality of side inlets 41 to which the plurality of connecting bleed lines 35 are respectively connected are formed in the first side wall portion 27, and a plurality of side outlets 42 to which the plurality of connecting exhaust lines 65 are respectively connected are formed in the second side wall portion 26. In each space 17, the side inlets 41 may be disposed at a lower position than the side outlets 42. However, the present disclosure is not limited thereto, and the side inlets 41 may be disposed at a higher position than the side outlets 42, or the side inlets 41 and the side outlets 42 may be disposed at the same height as each other.

[0061] According to the above configuration, one or more cylinder units are arranged in each of the multiple spaces 17 separated by the partition wall portion 29 in a plan view, so that unburned gas may leak into each space 17. However, compressed air Ca flows into each space 17 from each connecting bleed line 35, and in each space 17, the discharge target Eo containing the compressed air Ca and unburned gas is discharged via each connecting exhaust line 65. Since it is possible to more reliably dilute the unburned gas in each space 17 with the compressed air Ca, the risk of ignition of unburned gas in the crank chamber 18 can be reduced. Incidentally, even if the engine 5D is an in-line multi-cylinder engine, the above technical advantages can be obtained.

[0062] <Other> The turbocharger 15 does not have to include the turbine wheel 14. The turbocharger 15 may be an electric compressor including a rotor shaft 13 and a compressor wheel 12 connected to the rotor shaft 13.

[0063] The above-mentioned 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. The processor according to other embodiments may be realized 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 data, and is realized by at least one of a RAM, a ROM, and a flash memory, for example. The processor executes various control processes according to instructions of a program loaded into the memory.

[0064] <Summary> The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0065] 1) An engine system (1) according to one embodiment of the present disclosure includes: An engine (5) including a cylinder (6) and a piston (7) housed in the cylinder; a fuel gas line (11) for introducing fuel gas (Fg) into a combustion chamber (9) in the cylinder; a supercharger (15) including a compressor wheel (12) for delivering compressed air to the combustion chamber; An engine system comprising: The engine is A crankshaft (16) located below the piston and configured to be driven by the piston; A crankcase (20) that houses the crankshaft; Further comprising: The engine system includes: an air supply line (25) for directing the compressed air delivered by the compressor wheel to the combustion chamber; an air bleed line (30) for guiding the compressed air bled from the air supply line to a crank chamber (18) in the crankcase; It further comprises:

[0066] According to the above configuration 1), the compressed air led to the crank chamber by the bleed line mixes with the unburned gas, which is the unburned fuel gas leaked from the combustion chamber to the crank chamber, so that the concentration of the unburned gas in the crank chamber can be reduced. Furthermore, the rotation speed of the compressor wheel varies according to the engine speed and the engine load. That is, the flow rate of the compressed air led by the bleed line varies according to the engine speed and the load. Furthermore, the amount of the unburned gas leaked to the crank chamber also varies according to the engine speed and the load. Therefore, the amount of compressed air required to reduce the concentration of the unburned gas leaking to the crank chamber is led to the crank chamber without excess or deficiency, so that it is possible to suppress a decrease in engine efficiency. For example, it is possible to suppress a significant decrease in the compressed air supplied to the combustion chamber due to an excessive flow of compressed air for diluting the unburned gas into the crank chamber, which causes a significant decrease in engine efficiency. As described above, an engine system is realized that reduces the risk of ignition of the unburned gas in the crank chamber while suppressing a decrease in engine efficiency.

[0067] 2) In some embodiments, the engine system described in 1) above, an air cooler (28) arranged on the air supply line for cooling the compressed air; The bleed line is configured to guide the compressed air cooled by the air cooler to the crankcase.

[0068] According to the above configuration 2), the compressed air cooled by the air cooler is introduced into the crank chamber, so that the temperature of the unburned gas in the crank chamber can be prevented from increasing, thereby further reducing the risk of ignition of the unburned gas in the crank chamber.

[0069] 3) In some embodiments, the engine system described in 2) above, a compressed air return line (40) for extracting the compressed air discharged from the air cooler and returning it to the compressor wheel; The bleed line branches off from the compressed air return line and connects to the crankcase.

[0070] According to the above configuration 3), the location where the compressed air is extracted from the intake line can be aligned with the location where the compressed air return line and the intake line are connected, so that loss of the compressed air flow in the intake line can be suppressed, thereby suppressing a decrease in engine efficiency.

[0071] 4) In some embodiments, the engine system described in 3) above, the engine is a multi-cylinder engine in which a plurality of cylinder units (8) including the cylinders and the pistons are arranged along the axial direction of the crankshaft, The crankcase includes: One side wall portion (21) which is an end portion on one side in the axial direction; The other side wall portion (22) is the end portion opposite to the one side wall portion. having The bleed line is a first side bleed line (30) connected to the compressed air return line and the first side wall portion; a second bleed line (30) branching off from the first bleed line and connecting to the second wall portion; has.

[0072] According to the above configuration 4), the compressed air flows into the crank chamber from both sides in the axial direction, so that the compressed air can be distributed throughout the crank chamber, thereby uniformly reducing the concentration of unburned gas in the crank chamber.

[0073] 5) In some embodiments, the engine system according to any one of 1) to 4) above, The fuel gas line is a first fuel gas line (11a) for introducing a first fuel gas (fg1) into the combustion chamber; a second fuel gas line (11b) for introducing a second fuel gas (fg2) having a lower explosion limit concentration than the first fuel gas into the combustion chamber; Including, The engine system includes: a solenoid valve (95) disposed in the extraction line; a controller (90) for controlling the solenoid valve in accordance with a content ratio of the second fuel gas in the fuel gas; It further comprises:

[0074] According to the above configuration 5), when the content ratio of the second fuel gas is small, that is, when the risk of ignition of unburned gas in the crankcase is low, the controller can close the solenoid valve. Since the period during which compressed air is bled through the bleed line can be limited, a decrease in engine efficiency can be suppressed.

[0075] 6) In some embodiments, the engine system according to any one of 1) to 5) above, the engine is a multi-cylinder engine in which a plurality of cylinder units (8), each including the cylinder and the piston, are arranged along the axial direction of the crankshaft, The engine system further includes a discharge line (60) for guiding a discharge target (Eo), which is a gas containing the compressed air in the crank chamber, to the outside, The crankcase includes: One side wall portion (21) which is an end portion on one side in the axial direction; The other side wall portion (22) is the end portion opposite to the one side wall portion. having a one-side inlet (37) to which the extraction line is connected is formed in the one-side wall portion, The other side wall portion is formed with a other side discharge port (68) to which the discharge line is connected.

[0076] According to the above configuration 6), the compressed air that has passed through the inlet on one side flows in the axial direction through the crank chamber, and then flows through the exhaust line via the exhaust port on the other side. Since the unburned gas and the compressed air tend to mix in the axial direction in the crank chamber, the concentration of unburned gas can be uniformly reduced in the crank chamber.

[0077] 7) In some embodiments, the engine system described in 6) above, The one-side inlet is disposed at a lower position than the other-side outlet.

[0078] According to the above configuration 7), the compressed air flowing through the crank chamber also moves upward as it flows toward the other exhaust port. This allows the compressed air to be distributed throughout the crank chamber, thereby uniformly reducing the concentration of unburned gas in the crank chamber.

[0079] 8) In some embodiments, the engine system according to 6) or 7) above, a one-side discharge line (61) connected to the one side wall portion and for leading the discharge object to the outside; a second discharge line (62) connected to the second side wall portion and for leading the discharge object to the outside; Further equipped with The bleed line includes: a one-side bleed line (30) for guiding the compressed air bled from the air supply line to the one-side wall portion; a second bleed line (30) branching off from the first bleed line and connecting to the second wall portion; having The one side wall portion is further formed with a one side discharge port (67) to which the one side discharge line is connected, The other-side wall portion is further formed with a other-side inlet (38) to which the other-side extraction line is connected, When viewed in the axial direction of the crankshaft, the one-side inlet and the other-side outlet are disposed at positions horizontally offset from each other, and the other-side inlet and the one-side outlet are disposed at positions horizontally offset from each other.

[0080] According to the above configuration 8), the compressed air flowing into the crank chamber from the inlet on one side is likely to spread horizontally throughout the crank chamber as it flows toward the outlet on the other side. Similarly, the compressed air flowing into the crank chamber from the inlet on the other side is likely to spread horizontally throughout the crank chamber as it flows toward the outlet on one side. This makes it possible to uniformly reduce the concentration of unburned gas in the crank chamber.

[0081] 9) In some embodiments, the engine system described in 3) above, the engine is a multi-cylinder engine in which a plurality of cylinder units (8) including the cylinders and the pistons are arranged along the axial direction of the crankshaft, The crankcase includes: 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 the end 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) perpendicular to the axial direction; a second side wall portion (26) which is an end portion opposite to the first side wall portion; At least one partition wall portion (29) connected to the first side wall portion and the second side wall portion so as to separate one or more of the plurality of cylinder units from the other cylinder units in a plan view; having The bleed line is a plurality of connection bleed lines (35) connected to the first side wall portion so as to communicate with each of a plurality of spaces (17) of the crankcase partitioned by the at least one partition wall portion; The engine system further includes a discharge line for guiding a discharge target, which is a gas containing the compressed air in the crank chamber, to the outside. The discharge line is a plurality of connecting exhaust lines (65) connected to the second side wall portion so as to communicate with each of the plurality of spaces of the crank chamber; 4. The engine system according to claim 3.

[0082] According to the configuration of 9) above, one or more cylinder units are arranged in each of the multiple spaces separated by the partition wall portion in a plan view, so that unburned gas leaks into each space. However, compressed air flows into each space from each connecting bleed line, and the compressed air and unburned gas in each space are discharged via each connecting exhaust line. Since it is possible to more reliably dilute the unburned gas in each space with compressed air, the risk of ignition of unburned gas in the crankcase can be reduced.

[0083] 10) In some embodiments, the engine system described in 3) above, the engine is a multi-cylinder engine in which a plurality of cylinder units (8), each including the cylinder and the piston, are arranged along the axial direction of the crankshaft, The crankcase includes: 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 the end opposite to the one side wall portion; a side wall portion (23) connected to the one side wall portion and the other side wall portion; having The bleed line includes a side bleed line (30) connected to the compressed air return line and to the side wall portion; A side inlet (39) to which the side bleed line is connected is formed in a central portion (24) of the side wall portion in the axial direction of the crankshaft.

[0084] According to the above configuration 10), the compressed air that flows into the crank chamber from the side inlet port formed in the center of the side wall can flow toward one side and the other side in the axial direction, which allows the compressed air to be distributed throughout the crank chamber, thereby uniformly reducing the concentration of unburned gas in the crank chamber. [Explanation of symbols]

[0085] 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: Crankcase 19: Connecting rod 20: Crankcase 21: One side wall 22 :Other side wall part 23: Side wall 24: Central part 25: Air supply line 26: Second side wall portion 27: First side wall 28: Air cooler 29: Partition wall 30: Extraction line 31: One side extraction line 32: Other side extraction line 33: Side bleed line 35: Connection extraction line 37: One side inlet 38: Other side inlet 39: Side inlet 40: Compressed air return line 60: Discharge line 61: One-side discharge line 62: Other side discharge line 65: Connection discharge line 67:One side outlet 68:Other side outlet 81: Crank pin 82: Air supply valve 83: Exhaust valve 85: Camshaft 86: Rocker arm 87: Push rod 89: Exhaust gas line 90: Controller 95: Solenoid valve 102: Air supply room 103: Air supply pipe 105: Exhaust pipe 251: First air supply line 252: Second air supply line Ca: Compressed air Eg: Exhaust gas Eo: Discharge target Fg: Fuel gas fg1: First fuel gas fg2: Second fuel gas

Claims

1. an engine including a cylinder and a piston housed in the cylinder; a fuel gas line for introducing fuel gas into a combustion chamber in the cylinder; a supercharger including a compressor wheel for delivering compressed air to the combustion chamber; An engine system comprising: The engine is a crankshaft located below the piston and configured to be driven by the piston; a crankcase that accommodates the crankshaft; Further comprising: The engine system includes: an air supply line for directing the compressed air delivered by the compressor wheel to the combustion chamber; an air bleed line for guiding the compressed air bled from the air supply line to a crank chamber in the crankcase; The engine system further comprises:

2. An air cooler is further provided on the air supply line for cooling the compressed air, The bleed line is configured to guide the compressed air cooled by the air cooler to the crankcase. The engine system of claim 1 .

3. a compressed air return line for extracting the compressed air discharged from the air cooler and returning the compressed air to the compressor wheel; The bleed line branches off from the compressed air return line and connects to the crankcase. The engine system of claim 2 .

4. the engine is a multi-cylinder engine in which a plurality of cylinder units, each including the cylinder and the piston, are arranged along an axial direction of the crankshaft, The crankcase includes: One side wall portion which is an end portion on one side in the axial direction; the other side wall portion which is the end portion opposite to the one side wall portion; having The bleed line includes: a first side bleed line connected to the compressed air return line and the first side wall portion; a second bleed line branching off from the first bleed line and connected to the second wall portion; have The engine system according to claim 3.

5. The fuel gas line is a first fuel gas line for introducing a first fuel gas into the combustion chamber; a second fuel gas line for introducing a second fuel gas having a lower explosion limit concentration than the first fuel gas into the combustion chamber; Including, The engine system includes: a solenoid valve disposed in the extraction line; a controller for controlling the solenoid valve in accordance with a content ratio of the second fuel gas in the fuel gas; Further equipped 5. An engine system according to any one of claims 1 to 4.

6. the engine is a multi-cylinder engine in which a plurality of cylinder units, each including the cylinder and the piston, are arranged along an axial direction of the crankshaft, The engine system further includes a discharge line for guiding a discharge target, which is a gas containing the compressed air in the crank chamber, to the outside. The crankcase includes: One side wall portion which is an end portion on one side in the axial direction; the other side wall portion which is the end portion opposite to the one side wall portion; having The one side wall portion is formed with a one side inlet port to which the extraction line is connected, The other side wall portion is formed with an other side discharge port to which the discharge line is connected.

5. An engine system according to any one of claims 1 to 4.

7. The one-side inlet is disposed at a lower position than the other-side outlet. The engine system of claim 6.

8. a one-side discharge line connected to the one side wall portion and configured to guide the discharge object to the outside; a second discharge line connected to the second side wall portion and configured to guide the discharge object to the outside; Further equipped with The bleed line includes: a first bleed line for guiding the compressed air bled from the air supply line to the first side wall portion; a second bleed line branching off from the first bleed line and connected to the second wall portion; having The one side wall portion further has a one side discharge port to which the one side discharge line is connected, The other side wall portion is further formed with a other side inlet to which the other side extraction line is connected, When viewed in the axial direction of the crankshaft, the one-side inlet and the other-side outlet are disposed at positions horizontally shifted from each other, and the other-side inlet and the one-side outlet are disposed at positions horizontally shifted from each other. The engine system of claim 6.

9. the engine is a multi-cylinder engine in which a plurality of cylinder units, each including the cylinder and the piston, are arranged along an axial direction of the crankshaft, The crankcase includes: One side wall portion which is an end portion on one side in the axial direction; a second side wall portion which is an end portion opposite to the first side wall portion; A first side wall portion that is an end portion on a first side in a horizontal direction perpendicular to the axial direction; a second side wall portion at an end opposite to the first side wall portion; At least one partition wall portion connected to the first side wall portion and the second side wall portion so as to separate one or more of the plurality of cylinder units from the other cylinder units in a plan view; having The bleed line includes: a plurality of connection bleed lines connected to the first side wall portion so as to communicate with each of a plurality of spaces of the crankcase partitioned by the at least one partition wall portion; The engine system further includes a discharge line for guiding a discharge target, which is a gas containing the compressed air in the crank chamber, to the outside. The discharge line is a plurality of connecting exhaust lines connected to the second side wall portion so as to communicate with each of the plurality of spaces of the crank chamber; The engine system according to claim 3.

10. the engine is a multi-cylinder engine in which a plurality of cylinder units, each including the cylinder and the piston, are arranged along an axial direction of the crankshaft, The crankcase includes: One side wall portion which is an end portion on one side in the axial direction; a second side wall portion which is an end portion opposite to the first side wall portion; a side wall portion connected to the one side wall portion and the other side wall portion; having the bleed line includes a side bleed line connecting the compressed air return line and the side wall portion; A side inlet port to which the side bleed line is connected is formed at a center portion of the side wall portion in the axial direction of the crankshaft. The engine system according to claim 3.

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