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

Engine System

[0001] This application claims priority to Japanese Patent Application No. 2023-140609, filed with the Japan Patent Office on August 31, 2023, the contents of which are incorporated herein by reference.

[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.

[0003] Japanese Patent Application Laid-Open No. 2017-031957

[0004] Fuel gas in the combustion chamber of a cylinder may leak between the cylinder and the piston into the crankcase (this fuel gas is known as blow-by gas). If the concentration of unburned fuel gas in the crankcase is high, there is a risk of the fuel gas igniting. Measures to reduce this risk are preferably implemented while minimizing a 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.

[0006] An engine system according to at least one embodiment of the present disclosure is an engine system comprising: an engine including a cylinder and a piston housed in the cylinder; a fuel gas line for directing fuel gas to a combustion chamber in the cylinder; and a supercharger including a compressor wheel for sending compressed air to the combustion chamber, wherein the engine further comprises: a crankshaft located below the piston and configured to be driven by the piston; and a crankcase that houses the crankshaft, and the engine system further comprises: an air intake line for directing the compressed air delivered by the compressor wheel to the combustion chamber; and an air bleed line for directing the compressed air bled from the air intake line to a crank chamber in the crankcase.

[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.

[0008] Fig. 1 is a schematic diagram of an engine system according to one embodiment; Fig. 2 is a schematic diagram of an engine according to one embodiment; Fig. 3 is a schematic diagram of a crankcase according to a first embodiment; Fig. 4 is a schematic diagram of a crankcase according to a second embodiment; Fig. 5 is another schematic diagram of a crankcase according to the second embodiment; Fig. 6 is a schematic diagram of a crankcase according to a third embodiment; Fig. 7 is a schematic diagram of a crankcase according to a fourth embodiment;

[0009] Several embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure and are merely illustrative examples. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is achieved. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is achieved. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is achieved. On the other hand, the expressions "comprise," "include," or "have" one component are not exclusive expressions that exclude the existence of other components. Note that similar components may be assigned the same reference numerals and descriptions thereof may be omitted.

[0010] 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 into, for example, a power generation facility, includes an engine 5 having a combustion chamber 9 and a crankcase 18 formed therein, a fuel gas line 11 for guiding 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 second fuel gas fg2, or a combination of both fuel gases can be 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 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 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. As described above, various fuel gases can be used for the first fuel gas fg1 and the second fuel gas fg2. However, the following describes an embodiment in which the first fuel gas fg1 is natural gas and the second fuel gas fg2 is hydrogen gas.

[0013] When only natural gas or hydrogen gas is supplied, the combustion of that 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 one 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 that houses the crankshaft 16. A crankpin 81 configured to rotate in conjunction 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, the axial direction of the crankshaft 16 may be abbreviated as the "axial direction."

[0016] The illustrated engine 5 is, as an example, a V-type multi-cylinder engine. More specifically, two axially adjacent pistons 7 are arranged in a generally V-shape at a predetermined bank angle when viewed in the axial direction. The number of cylinder units 8, each including a cylinder 6 and a piston 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 in another example may be an in-line multi-cylinder engine. There are no particular restrictions 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 Figure 2 is an OHV (Over Head Valve) 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 response to 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. When the rocker arm 86 swings about an axis parallel to the axial direction, the intake valve 82 and the exhaust valve 83 included in the valve mechanism open and close the ports of the cylinder 6.

[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 ), which will be described later, flows into the combustion chamber 9 via the air intake pipe 103.

[0019] The type of engine 5 of the present disclosure is not particularly limited, and for example, a pre-chamber gas engine may be employed. More specifically, the combustion chamber 9 includes a pre-chamber to which fuel gas Fg is supplied and a main chamber in which fuel gas Fg supplied from a separate line is combusted using a combustion flame ignited in the pre-chamber. Pre-combustion (pre-combustion) of the fuel gas Fg primarily occurs in the pre-chamber, while combustion of the fuel gas Fg is completed in the main chamber. Exhaust gas Eg generated by the combustion is discharged into an 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 portion of the fuel gas Fg supplied to the combustion chamber 9 leaks into the crank chamber 18 as blow-by gas through the gap between the piston 7 and the cylinder 6. The occurrence of an unburned gas explosion in the crank chamber 18 can be suppressed by keeping the concentration of unburned gas, which is the unburned fuel gas Fg in the crank chamber 18, below the lower explosive limit. If the concentration exceeds the lower explosive limit, the risk of an explosion of the unburned gas in the crank chamber 18 increases. The lower explosive limit varies depending on the type of fuel gas Fg or the hydrogen gas content in the fuel gas Fg. The hydrogen gas content is a parameter correlated with the hydrogen gas concentration 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 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 in 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 crankcase 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 branches 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 crankcase 18.

[0025] According to the above configuration, the compressed air Ca introduced to the crank chamber 18 through the bleed line 30 mixes with unburned gas leaked from the combustion chamber 9 to the crank chamber 18, thereby reducing the concentration of unburned gas in the crank chamber 18. Furthermore, the rotation speed of the compressor wheel 12 varies depending on the engine load. That is, the flow rate of the compressed air Ca introduced through the bleed line 30 varies depending on the engine load. The amount of unburned gas leaked into the crank chamber 18 also varies depending on the engine load. Therefore, the exact amount of compressed air Ca necessary to reduce the concentration of unburned gas leaking into the crank chamber 18 is introduced to the crank chamber 18, thereby preventing a decrease in engine efficiency. For example, a significant decrease in engine efficiency due to a significant decrease in the amount of compressed air Ca supplied to the combustion chamber 9 caused by an excessive inflow of compressed air Ca into the crank chamber 18 to dilute the unburned gas concentration in the crank chamber 18 can be prevented. 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 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 be provided with the compressed air return line 40. Also, the engine system 1 may not be provided with the air cooler 28. In any embodiment, the above-mentioned technical advantages can be obtained.

[0027] Furthermore, according to the configuration in which the bleed 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, thereby suppressing an increase in the temperature of unburned gas in the crank chamber 18. This further reduces the risk of ignition of unburned gas in the crank chamber 18.

[0028] Furthermore, with the configuration in which the bleed line 30 branches off from the compressed air return line 40 and connects to the crankcase 20, the location where the compressed air Ca is bled from the intake line 25 can be made to coincide with the location 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] 1, the engine system 1 will be further described. The engine system 1 further includes a discharge line 60 for guiding the discharge object Eo to the outside. The discharge object Eo is a gas containing fuel gas Fg (i.e., unburned gas) leaking into the crank chamber 18 and compressed air Ca supplied to the crank chamber 18 from the bleed line 30.

[0030] In this example, the discharge target Eo further includes oil mist. Oil mist can be generated when lubricating oil adhering to moving parts such as the shafts, cams, gears, or pistons 7 that make up the engine 5 is scattered. Alternatively, an oil tank (not shown) that stores lubricating oil is located below the crankcase 18, and oil mist can be generated when a portion of the stored lubricating oil in the form of a liquid pool evaporates. Oil mist also floats within the crankcase 18.

[0031] 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 depending on 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 open and the second on-off valve is closed to supply the fuel gas Fg consisting only of the second fuel gas fg2 as hydrogen gas to the engine 5, the hydrogen gas content in the fuel gas Fg is 0%. In this case, the controller 90 executes control to close the solenoid valve 95. On the other hand, when the first on-off valve is closed and the second on-off valve is open, the hydrogen gas content in the fuel gas Fg is 100%. In this case, 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 in accordance with the combustion ratio of hydrogen gas and natural gas in the combustion chamber 9. The combustion ratio is a concept included in the hydrogen gas content ratio of the fuel gas Fg. The higher the combustion ratio, the higher the concentration of hydrogen gas in the crankcase 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 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 rates of the hydrogen gas and the natural gas. When the 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 accordance with the detection results 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 results of the sensor is a concept included in the hydrogen gas content ratio in the fuel gas Fg. The higher the determined concentration of hydrogen gas, 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 results of the sensor is 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 crankcase 18 is small, and therefore the risk of ignition of the unburned gas in the crankcase 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 through the bleed line 30 can be limited, a decrease in engine efficiency can be suppressed.

[0036] <Crankcase 20 (First Embodiment)> Figure 3 is a schematic diagram showing the crankcase 20A (20) of the engine 5A (5) according to the first embodiment. In the example of Figure 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 be provided with the air cooler 28 (the same applies to the second, third, and fourth embodiments described below).

[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 axially through the crank chamber 18, and then flows through the other-side outlet 68 and into the discharge line 60. Because the unburned gas and the compressed air Ca tend to mix axially 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 allows the concentration of unburned gas to be uniformly reduced 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 example shown, both the one-side inlet 37A and the other-side outlet 68 are disposed at positions higher than the crankshaft 16, but the present disclosure is not limited to this. 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 positions lower than the crankshaft 16.

[0040] With the configuration in which the one-side inlet 37A is positioned 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, making it easier for both the compressed air Ca and unburned gas to be discharged into the discharge line 60. This allows the concentration of unburned gas to be uniformly reduced within the crank chamber 18.

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

[0042] The bleed air line 30B of the engine 5B has a first bleed air line 31 and a second bleed air line 32. The first bleed air line 31 is connected to the compressed air return line 40 and one side wall portion 21B (21) of the crankcase 20B. That is, the first bleed air line 31 is configured to guide the compressed air Ca bled from the compressed air return line 40 to the one side wall portion 21B. The second bleed air line 32 branches off from the first bleed air line 31 and connects to the other side wall portion 22B (22) of the crankcase 20B. That is, the second bleed air line 32 is configured to guide the compressed air Ca bled from the first bleed air line 31 to the other 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 first inlet 37B and the second inlet 38 are disposed at a position higher than the crankshaft 16, but the present disclosure is not limited to this. The first inlet 37B may be disposed at a position lower than the crankshaft 16, or at least a portion of the first inlet 37B may be disposed at the same height as the crankshaft 16. Alternatively, both the first inlet 37B and the second inlet 38 may be disposed at a position lower than the crankshaft 16.

[0045] According to the above 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 first discharge line 61 connected to the first side wall portion 21B and a second discharge line 62 connected to the second side wall portion 22B. A first discharge port 67 to which the first discharge line 61 is connected is formed in the first side wall portion 21B, and a second discharge port 68 to which the second discharge line 62 is connected is formed in the second 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 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 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 not shown). When viewed in the axial direction, the first inlet 37B and the second outlet 68 are positioned offset from each other in the horizontal direction (hereinafter sometimes referred to as the width direction). When viewed in the axial direction, the second inlet 38 and the first outlet 67 are positioned offset from each other in the width direction. In the illustrated example, the first inlet 37B and the second inlet 38 are positioned on a first widthwise side relative to the center of the crankcase 20. The first outlet 67 and the second outlet 68 are positioned on a second widthwise side opposite the first widthwise side relative to the center of the crankcase 20. The width direction is the 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 that passes 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 that passes through the one-side discharge port 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 is likely to spread horizontally within the crank chamber 18 as it flows toward the other-side outlet 68. Similarly, the compressed air Ca flowing into the crank chamber 18 from the other-side inlet 38 is likely to spread horizontally within the crank chamber 18 as it flows toward the one-side outlet 67. This makes it easier for unburned gas within the crank chamber 18 to be discharged from the one-side outlet 67 and the other-side outlet 68, thereby making it possible to uniformly reduce the concentration of unburned gas within the crank chamber 18.

[0051] <Crankcase 20 (Third Embodiment)> Figure 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 a first side wall portion 21C (21) at one end in the axial direction, a second side wall portion 22C (22) at the end opposite the first side wall portion 21C, and a side wall portion 23 connected to the first side wall portion 21C and the second side wall portion 22C. The side wall portion 23 is an end of the crankcase 20C on a first side in the width direction.

[0052] The bleed air line 30C (30) according to the third embodiment has a side bleed air 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 air line 33 connects is formed in the central portion 24 of the side wall portion 23 in the axial direction. The side bleed air line 33 is configured to guide 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 one side wall portion 21C (21) and a second-side discharge line 62 connected to the other side wall portion 22C (22). A one-side discharge port 67 and a second-side discharge port 68 are formed in one side wall portion 21C and the other side wall portion 22C, respectively.

[0054] According to the above configuration, 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 be distributed throughout the crank chamber 18, making it easier for unburned gas in the crank chamber 18 to be discharged from the one-side discharge port 67 and the other-side discharge port 68. This allows the concentration of unburned gas to be uniformly reduced within the crank chamber 18. Note that the bleed line 30C may further include, in addition to the side bleed line 33, at least one of a plurality of connecting bleed lines 35 (see FIG. 7 ) according to a fourth embodiment described below. Even in this case, the above-described technical advantages can be obtained.

[0055] <Crankcase 20 (Fourth Embodiment)> Figure 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 the 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 29. The partition wall 29 extends in the width direction and connects to the first side wall 27 and the second side wall 26. Furthermore, the partition wall 29 separates one or more of the plurality of 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 multiple pairs of cylinder units 8, each pair being axially adjacent cylinder units 8A, 8B. Each of the multiple partition walls 29 is arranged to separate each pair of cylinder units 8 from the other pairs of cylinder units 8. In the crank chamber 18, the multiple partition walls 29 form spaces 17, the number of which is half the number of cylinders of the engine 5D. A pair of cylinder units 8 is arranged in each space 17 in plan view. For example, if the engine 5D has 18 cylinders, the crank chamber 18 is divided into nine spaces 17 (the number of partition walls 29 is eight). However, the partition walls 29 of the present disclosure are not limited to the above embodiment. The number of partition walls 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 that connect 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 that connect to the second side wall portion 26 so as to communicate with each of the plurality of spaces 17.

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

[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 portions 29 in a plan view, which may result in leakage of unburned gas into each space 17. However, compressed air Ca flows into each space 17 from each connecting bleed line 35, and the discharge target Eo containing the compressed air Ca and unburned gas in each space 17 is discharged via each connecting discharge line 65. Since the unburned gas in each space 17 can be more reliably diluted with compressed air Ca, the risk of ignition of unburned gas in the crank chamber 18 can be reduced. Note that the above technical advantages can be obtained even if the engine 5D is an in-line multi-cylinder engine.

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

[0063] The controller 90 described above is configured by a computer and includes a processor, a memory (storage medium), and an external communication interface. The processor may be a CPU, a GPU, an MPU, a DSP, or a combination thereof. The processor according to other embodiments 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 data and may be implemented by at least one of a RAM, a ROM, or a flash memory, for example. The processor executes various control processes according to instructions from a program loaded into the memory.

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

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

[0066] According to the configuration 1), the compressed air introduced into the crankcase through the bleed line mixes with unburned gas, which is unburned fuel gas leaked from the combustion chamber into the crankcase, thereby reducing the concentration of unburned gas in the crankcase. Furthermore, the rotational speed of the compressor wheel varies depending on the engine speed and engine load. That is, the flow rate of compressed air introduced through the bleed line varies depending on the engine speed and load. The amount of unburned gas leaking into the crankcase also varies depending on the engine speed and load. Therefore, the exact amount of compressed air necessary to reduce the concentration of unburned gas leaking into the crankcase is introduced into the crankcase, thereby suppressing a decrease in engine efficiency. For example, a significant decrease in engine efficiency due to a significant decrease in the amount of compressed air supplied to the combustion chamber caused by an excessive inflow of compressed air for diluting the unburned gas into the crankcase can be suppressed. As a result, an engine system is realized that suppresses a decrease in engine efficiency while reducing the risk of unburned gas ignition in the crankcase.

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

[0068] According to the configuration of 2), the compressed air cooled by the air cooler is introduced into the crankcase, which prevents the temperature of the unburned gas in the crankcase from rising, thereby further reducing the risk of ignition of the unburned gas in the crankcase.

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

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

[0071] 4) In some embodiments, the engine system is as described in 3) above, wherein 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 has a first side wall portion (21) which is an end portion on one side in the axial direction, and a second side wall portion (22) which is an end portion opposite to the first side wall portion, and the bleed line has a first bleed line (30) which connects to the compressed air return line and the first side wall portion, and a second bleed line (30) which branches off from the first bleed line and connects to the second side wall portion.

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

[0073] 5) In some embodiments, in the engine system described in any one of 1) to 4) above, 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) having a lower explosion limit concentration than the first fuel gas to the combustion chamber; and the engine system further includes: an electromagnetic valve (95) arranged in the extraction line; and a controller (90) for controlling the electromagnetic valve in accordance with the content ratio of the second fuel gas in the fuel gas.

[0074] According to the configuration of 5) above, 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 is the engine system described in any one of 1) to 5) above, wherein 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, and the engine system further includes a discharge line (60) for guiding the discharge object (Eo), which is a gas including the compressed air in the crank chamber, to the outside, and the crankcase has a one side wall portion (21) which is an end portion on one side in the axial direction, and a other side wall portion (22) which is an end portion opposite to the one side wall portion, and a one side inlet (37) to which the bleed line is connected is formed in the one side wall portion, and a other side outlet (68) to which the discharge line is connected is formed in the other side wall portion.

[0076] According to the configuration of 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 outlet on the other side and into the discharge line. Since the unburned gas and compressed air tend to mix in the axial direction within the crank chamber, the concentration of unburned gas can be uniformly reduced within the crank chamber.

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

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

[0079] 8) In some embodiments, the engine system described in 6) or 7) above further comprises: a one-side discharge line (61) connected to the one side wall portion and for guiding the discharge object to the outside; and a other-side discharge line (62) connected to the other side wall portion and for guiding the discharge object to the outside; wherein the bleed line has: a one-side bleed line (30) for guiding the compressed air bled from the air supply line to the one side wall portion; and a other-side bleed line (30) branching from the one-side bleed line and connecting to the other side wall portion; wherein the one side wall portion is further formed with a one-side discharge port (67) to which the one-side discharge line is connected; and the other side wall portion is further formed with a other-side inlet (38) to which the other-side bleed line is connected; and when viewed in the axial direction of the crankshaft, the one-side inlet and the other-side discharge port are arranged at positions horizontally offset from each other, and the other-side inlet and the one-side discharge port are arranged at positions horizontally offset from each other.

[0080] According to the configuration of 8) above, the compressed air flowing into the crankcase from the inlet on one side is likely to spread horizontally throughout the crankcase as it flows toward the outlet on the other side. Similarly, the compressed air flowing into the crankcase from the inlet on the other side is likely to spread horizontally throughout the crankcase as it flows toward the outlet on one side. This allows the concentration of unburned gas to be uniformly reduced within the crankcase.

[0081] 9) In some embodiments, the engine system described in 3) above is provided, wherein 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 has: one side wall portion (21) at one end in the axial direction; another side wall portion (22) at an end opposite to the one side wall portion; a first side wall portion (27) at a first end in a horizontal direction (width direction) perpendicular to the axial direction; and a second side wall portion (26) at an end opposite to the first side wall portion; and 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, and the bleed line includes a plurality of connecting 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 the discharge target, which is gas containing the compressed air in the crankcase, to the outside, and the discharge line includes a plurality of connecting discharge lines (65) connected to the second side wall portion so as to communicate with each of the plurality of spaces in the crankcase. The engine system described in 3) above.

[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 walls in a plan view, which causes unburned gas to leak 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. This makes it possible to more reliably dilute the unburned gas in each space with compressed air, thereby reducing the risk of ignition of unburned gas in the crankcase.

[0083] 10) In some embodiments, the engine system is as described in 3) above, wherein 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 has one side wall portion (21) at one end in the axial direction, another side wall portion (22) at the opposite end from the one side wall portion, and a side wall portion (23) connecting the one side wall portion and the other side wall portion, the bleed line has a side bleed line (30) connecting the compressed air return line and the side wall portion, and 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 configuration of 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 both sides in the axial direction, thereby distributing the compressed air throughout the crank chamber and uniformly reducing the concentration of unburned gas within the crank chamber.

[0085] REFERENCE SIGNS LIST 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: Supercharger 16: Crankshaft 18: Crankcase 19: Connecting rod 20: Crankcase 21: One side wall portion 22: Other side wall portion 23: Side wall portion 24: Central portion 25: Air supply line 26: Second side wall portion 27: First side wall portion 28: Air cooler 29: Partition wall portion 30: Bleed line 31: One side bleed line 32: Other side bleed line 33: Side bleed line 35: Connecting bleed 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: Connecting discharge line 67: One side discharge port 68: Other side discharge port 81: Crank pin 82: Air intake valve 83: Exhaust valve 85: Camshaft 86: Rocker arm 87: Push rod 89: Exhaust gas line 90: Controller 95: Solenoid valve 102: Air intake chamber 103: Air intake pipe 105: Exhaust pipe 251: First air intake line 252: Second air intake line Ca: Compressed air Eg: Exhaust gas Eo: Object to be discharged Fg: Fuel gas fg1 : First fuel gas fg2 : Second fuel gas

Claims

1. An engine system comprising: an engine including a cylinder and a piston housed in the cylinder; a fuel gas line for directing fuel gas to a combustion chamber in the cylinder; and a supercharger including a compressor wheel for sending compressed air to the combustion chamber, wherein the engine further comprises: a crankshaft located below the piston and configured to be driven by the piston; and a crankcase housing the crankshaft, and the engine system further comprises: an air intake line for directing the compressed air delivered by the compressor wheel to the combustion chamber; and an air bleed line for directing the compressed air bled from the air intake line to a crank chamber in the crankcase.

2. The engine system according to claim 1, further comprising an air cooler arranged on the air supply line for cooling the compressed air, the bleed line being configured to guide the compressed air cooled by the air cooler to the crankcase.

3. The engine system according to claim 2, further comprising a compressed air return line for bleeding the compressed air discharged from the air cooler and returning it to the compressor wheel, the bleeding line branching off from the compressed air return line and connecting 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 including the cylinder and the piston, are arranged along the axial direction of the crankshaft, the crankcase has one side wall portion which is an end portion on one side in the axial direction, and another side wall portion which is an end portion opposite to the one side wall portion, and the bleed line has a one-side bleed line connected to the compressed air return line and the one side wall portion, and a other-side bleed line branching off from the one-side bleed line and connecting to the other side wall portion.

5. An engine system as claimed in 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 having a lower explosion limit concentration than the first fuel gas to the combustion chamber, and the engine system further includes: an electromagnetic valve disposed in the extraction line; and a controller for controlling the electromagnetic valve in accordance with a content ratio of the second fuel gas 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 including the cylinder and the piston, are arranged along the axial direction of the crankshaft, and the engine system further comprises an exhaust line for guiding an object to be exhausted, which is a gas including the compressed air in the crank chamber, to the outside, and the crankcase has a one side wall portion which is an end portion on one side in the axial direction, and a other side wall portion which is an end portion opposite to the one side wall portion, and a one side inlet port to which the extraction line is connected is formed in the one side wall portion, and a other side outlet port to which the exhaust line is connected is formed in the other side wall portion.

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

8. An engine system as claimed in claim 6, further comprising: a one-side discharge line connected to the one side wall portion and for guiding the object to be discharged to the outside; and a other-side discharge line connected to the other side wall portion and for guiding the object to be discharged to the outside; wherein the bleed line has: a one-side bleed line for guiding the compressed air bled from the air supply line to the one side wall portion; and a other-side bleed line branching off from the one-side bleed line and connecting to the other side wall portion; wherein the one side wall portion is further formed with a one-side discharge port to which the one-side discharge line is connected; and the other side wall portion is further formed with a other-side inlet port to which the other-side bleed line is connected; and when viewed in the axial direction of the crankshaft, the one-side inlet port and the other-side exhaust port are arranged at positions horizontally offset from each other, and the other-side inlet port and the one-side exhaust port are arranged at positions horizontally offset from each other.

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 the axial direction of the crankshaft, the crankcase has: one side wall portion which is an end portion on one side of the axial direction; another 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 perpendicular 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 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, the bleed line includes a plurality of connecting bleed lines connected to the first side wall portion so as to communicate with each of a plurality of spaces of the crank chamber partitioned by the at least one partition wall portion, the engine system further includes an exhaust line for guiding an exhaust object, which is a gas including the compressed air in the crank chamber, to the outside, the exhaust line being The engine system of claim 3 , further comprising 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 crankcase.

10. The engine system according to claim 3, wherein the engine is a multi-cylinder engine in which a plurality of cylinder units, each including the cylinder and the piston, are arranged along the axial direction of the crankshaft, the crankcase has 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 connecting the one side wall portion and the other side wall portion, the bleed line has a side bleed line connecting the compressed air return line and the side wall portion, and a side inlet to which the side bleed 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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