fuel injection device

Abstract

In a fuel injection system, residual fuel in the fuel supply path is properly discharged and treated. [Solution] The system comprises a first fuel supply path that supplies a first fuel having a predetermined ignition property, a first fuel injection valve to which the first fuel supply path is connected, a second fuel supply path that supplies a second fuel having lower ignition properties than the first fuel, a second fuel injection valve to which the second fuel supply path is connected, a purge gas supply device that supplies purge gas to the second fuel supply path, and a fuel discharge path that discharges the second fuel remaining in the second fuel supply path together with the purge gas and supplies it to the combustion unit.

Description

Technical Field

[0001] The present disclosure relates to a fuel injection device.

Background Art

[0002] As a fuel applied to fuel injection devices, the use of carbon-free fuel that generates less harmful substances (such as carbon dioxide) has been considered. However, some carbon-free fuels have poor ignitability, and it has been proposed to use them in combination with fuels having good ignitability. An example of a fuel injection device that injects a plurality of types of fuels is described in Patent Document 1.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] The fuel injection device can switch and inject between a first fuel with good ignitability and a second fuel with poor ignitability. Therefore, the fuel injection device includes a first fuel supply passage and a first fuel injection valve for the first fuel, and a second fuel supply passage and a second fuel injection valve for the second fuel. For example, when switching from an injection state of the second fuel to an injection state of the first fuel, it is preferable for the fuel injection device to recover as much residual second fuel remaining in the second fuel supply passage as possible. However, it is difficult to recover all the second fuel remaining in the second fuel supply passage. Therefore, by supplying purge gas to the second fuel supply passage, part of the remaining second fuel is discharged out of the system, stored in a storage tank, or subjected to detoxification treatment. This results in a problem that a storage tank and a detoxification treatment device are required, which leads to an increase in size of the entire device.

[0005] This disclosure aims to solve the aforementioned problems and to provide a fuel injection system that suppresses the increase in size of the device by appropriately discharging and treating the fuel remaining in the fuel supply path. [Means for solving the problem]

[0006] A fuel injection system of the present disclosure for achieving the above objectives comprises: a first fuel supply path for supplying a first fuel having predetermined ignitability; a first fuel injection valve to which the first fuel supply path is connected; a second fuel supply path for supplying a second fuel having lower ignitability than the first fuel; a second fuel injection valve to which the second fuel supply path is connected; a purge gas supply device for supplying purge gas to the second fuel supply path; and a fuel discharge path for discharging the second fuel remaining in the second fuel supply path together with the purge gas and supplying it to a combustion unit. [Effects of the Invention]

[0007] According to the fuel injection system of this disclosure, the size of the system can be suppressed by appropriately discharging and processing the fuel remaining in the fuel supply path. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram representing a marine diesel engine. [Figure 2] Figure 2 is a schematic diagram showing the fuel injection system of the first embodiment. [Figure 3] Figure 3 is a schematic diagram showing the operating state of the fuel injection system. [Figure 4] Figure 4 is a schematic diagram showing the purge state of the fuel injection system. [Figure 5] Figure 5 is a schematic diagram showing the fuel injection system of the second embodiment. [Figure 6] Figure 6 is a schematic diagram showing a first modified example of the fuel injection system of the second embodiment. [Figure 7] Figure 7 is a schematic diagram showing a second modified example of the fuel injection system of the second embodiment. [Figure 8]Figure 8 is a schematic diagram showing the fuel injection system of the third embodiment. [Figure 9] Figure 9 is a schematic diagram showing a first modified example of the fuel injection system of the third embodiment. [Figure 10] Figure 10 is a schematic diagram showing a second modified example of the fuel injection system of the third embodiment. [Figure 11] Figure 11 is a schematic diagram showing a third modified example of the fuel injection system of the third embodiment. [Modes for carrying out the invention]

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0010] <Marine Diesel Engines> Figure 1 is a schematic diagram representing a marine diesel engine of the first embodiment. In the first embodiment, a marine diesel engine is used as the reciprocating internal combustion engine for explanation. However, the reciprocating internal combustion engine is not limited to a marine diesel engine. That is, the reciprocating internal combustion engine may be a two-stroke internal combustion engine (intake and compression, explosion and exhaust) or a four-stroke internal combustion engine (intake, compression, explosion, exhaust).

[0011] As shown in Figure 1, the marine diesel engine 10 is used, for example, as the main engine for ship propulsion, and is a two-stroke, one-cycle uniflow scavenging type crosshead internal combustion engine.

[0012] The marine diesel engine 10 has a diesel engine body 11. The diesel engine body 11 comprises a cylinder 12, a piston 13, a scavenging trunk 14, an exhaust static pressure pipe 15, an exhaust valve 16, and a fuel injection device 17.

[0013] The cylinder 12 has a cylindrical shape, a cylinder liner (not shown) is disposed inside the cylinder 12, and a cylinder cover 21 is fixed to an upper portion of the cylinder 12. The piston 13 has a cylindrical shape, is disposed inside the cylinder 12, and is supported movably along the axial direction. The upper end of a piston rod 22 is connected to the lower end of the piston 13. Although not shown in the figures, a crankshaft is rotatably supported at a lower part of a diesel engine main body 11, and a lower end of a connecting rod is rotatably connected to the crankshaft via a crank. In the diesel engine main body 11, a crosshead is supported movably in the vertical direction, and the lower end of the piston rod 22 and the upper end of the connecting rod are rotatably connected to the crosshead.

[0014] A plurality of said cylinders 12 are arranged at intervals in the horizontal direction. A scavenge trunk 14 is connected to lower portions of the plurality of cylinders 12. Each of the plurality of cylinders 12 communicates with the interior of the scavenge trunk 14 via a respective scavenge port 23. Air is supplied into the scavenge trunk 14 through an intake passage 24.

[0015] In the cylinder 12, the cylinder cover 21 is fixed to the upper portion to form an upper space, and the upper space is partitioned by the upper surface of the piston 13, thereby forming a combustion chamber 25. An exhaust static pressure pipe 15 is connected to the cylinder cover 21 via an exhaust pipe 26. That is, the combustion chamber 25 communicates with the exhaust static pressure pipe 15 via the exhaust pipe 26. An exhaust valve 16 is disposed in the combustion chamber 25 and is supported axially movably by the cylinder cover 21. A valve gear 27 is drivingly connected to a shaft portion of the exhaust valve 16. The valve gear 27 can open and close communication between the combustion chamber 25 and the exhaust pipe 26 by driving the exhaust valve 16. The exhaust static pressure pipe 15 discharges exhaust gas to the outside through an exhaust passage 28.

[0016] A fuel injection device 17 includes a first fuel injection device 31 and a second fuel injection device 41. The first fuel injection device 31 is capable of injecting a first fuel having predetermined ignitability. The first fuel is a fossil fuel, for example, a liquid fuel such as light oil or heavy oil used as diesel fuel. The second fuel injection device 41 is capable of injecting a second fuel that has higher volatility and lower (poor) ignitability than the first fuel. The second fuel is a carbon-free fuel that generates a smaller amount of harmful substances, for example, a liquid fuel such as ammonia, methanol, or liquefied petroleum gas (LPG). However, the first fuel and the second fuel are not limited to the above-mentioned fuels. Note that ignitability refers to the ease with which the first fuel or the second fuel ignites.

[0017] The first fuel injection device 31 includes a fuel supply device 32, a fuel supply path 33, and a fuel injection valve 34. The fuel injection valve 34 is attached to a cylinder cover 21. The fuel supply device 32 supplies the first fuel stored in a fuel tank (not shown) to the fuel injection valve 34 via the fuel supply path 33. The fuel injection valve 34 injects the first fuel into a combustion chamber 25 at a predetermined timing. Note that the fuel injection valve 34 may be configured to inject the first fuel into an intake path 24.

[0018] The second fuel injection device 41 includes a fuel supply device 42, a fuel supply path 43, and a fuel injection valve 44. The fuel injection valve 44 is attached to the cylinder cover 21. The fuel supply device 42 supplies the second fuel stored in a fuel tank (not shown) to the fuel injection valve 44 via the fuel supply path 43. The fuel injection valve 44 injects the second fuel into the combustion chamber 25 at a predetermined timing. Note that the fuel injection valve 44 may be configured to inject the second fuel into the intake path 24.

[0019] In the marine diesel engine 10, first, when the piston 13 moves to bottom dead center (solid line position in Figure 1), the scavenging port 23 and the combustion chamber 25 communicate. Then, air from the scavenging trunk 14 is introduced into the combustion chamber 25 from the scavenging port 23. Next, when the piston 13 rises, the communication between the scavenging port 23 and the combustion chamber 25 is blocked by the piston 13. At this time, the exhaust valve 16 rises due to the valve train 27, blocking the communication between the combustion chamber 25 and the exhaust pipe 26. As a result, the air in the combustion chamber 25 is compressed as the piston 13 rises.

[0020] As the piston 13 rises further and moves to top dead center (the position indicated by the dashed line in Figure 1), the pressure in the combustion chamber 25 reaches a predetermined compression pressure, and the fuel injectors 34 and 44 act to inject the first or second fuel into the combustion chamber 25. The air and fuel then mix and burn in the combustion chamber 25, and the combustion energy causes the piston 13 to descend. At this time, the exhaust valve 16 is lowered by the valve train 27, connecting the combustion chamber 25 and the exhaust pipe 26. The exhaust gas generated by combustion is then pushed out of the combustion chamber 25 through the exhaust pipe 26 into the exhaust static pressure pipe 15 and discharged.

[0021] When a ship is underway, it basically uses a second fuel that produces fewer harmful substances such as NOx, SOx, and PM in its exhaust gases, and the second fuel injector 41 injects the second fuel. If, for example, the second fuel becomes insufficient, the second fuel injector 41 stops operating, and the first fuel injector 31 activates and injects the first fuel. In other words, the fuel injector 17 switches between injecting the first and second fuels depending on the ship's navigation conditions.

[0022] When the fuel injector 17 switches from the injection state of the second fuel to the injection state of the first fuel, for example, the operation of the second fuel injector 41 stops and the operation of the first fuel injector 31 begins. At this time, the second fuel remains in the fuel supply path 43. From the standpoint of safety and other considerations, it is preferable for the second fuel injector 41 to discharge the second fuel remaining in the fuel supply path 43. The second fuel injector 41 can discharge the second fuel remaining in the fuel supply path 43 when it is stopped.

[0023] The second fuel injection system 41 will be described in detail below. The first fuel injection system 31 is basically configured the same as the second fuel injection system 41, so the description of the first fuel injection system 31 will be omitted. However, since the second fuel injection system 41 injects a second fuel such as ammonia, it is configured to appropriately discharge any second fuel remaining in the fuel supply path 43 when the vehicle is stopped, taking safety into consideration.

[0024] [First Embodiment] <Configuration of the second fuel injection system> Figure 2 is a schematic diagram showing the fuel injection system of the first embodiment.

[0025] As shown in Figure 2, the second fuel injection system 41 includes a fuel supply device 42, a fuel supply path (second fuel supply path) 43, and a fuel injection valve (second fuel injection valve) 44, as well as a purge gas supply device 51 and a fuel discharge path 52.

[0026] The purge gas supply device 51 supplies purge gas to the fuel supply path 43. The fuel discharge path 52 discharges the second fuel remaining in the fuel supply path 43 together with the purge gas and supplies it to the combustion unit 53. Here, the combustion unit 53 includes at least a scavenging trunk 14, an exhaust static pressure pipe 15, an intake path 24, a combustion chamber 25 (cylinder 12), and an exhaust path 28.

[0027] The fuel supply path 43 is a recirculation path. That is, the fuel supply path 43 sends the second fuel supplied from the fuel supply device 42 to the fuel injector 44, and the fuel injector 44 supplies the required amount of second fuel to the combustion chamber 25. The fuel supply path 43 returns any excess second fuel that the fuel injector 44 did not inject back to the fuel supply device 42.

[0028] The fuel supply path 43 has a supply path 61 and a return path 62. The supply path 61 and the return path 62 are connected at their respective ends to form a circulation path. A fuel supply device 42 is connected to one side of the fuel supply path 43, and a fuel injection valve 44 is connected to the other side. The fuel supply device 42 has, for example, a second fuel tank 63, an outlet path 64, and an outlet valve 65. The second fuel tank 63 stores second fuel inside. The second fuel tank 63 is connected to the fuel supply path 43 via the outlet path 64. The outlet valve 65 is a solenoid valve and is provided in the outlet path 64.

[0029] Multiple fuel injectors 44 are arranged corresponding to the cylinders 12 (combustion chambers 25) of the diesel engine body 11. Each of the multiple fuel injectors 44 is connected to the fuel supply path 43 via a branch path 66. Therefore, the fuel supply path 43 is divided into two parts: the supply path 61 is the path through which the second fuel is supplied from the connection point of the outlet path 64 to the connection point of the fuel injector 44, and the return path 62 is the path through which the second fuel is returned from the connection point of the fuel injector 44 to the connection point of the outlet path 64.

[0030] The supply path 61 is equipped with a supply pump 67 and on-off valves 68 and 69. The supply pump 67 constitutes part of the fuel supply device 42 and supplies the second fuel from the supply path 61 to the fuel injection valve 44. The on-off valves 68 and 69 are solenoid valves that can open and close the supply path 61. The return path 62 is equipped with a flow control valve 71 and on-off valves 72 and 73. The flow control valve 71 adjusts the flow rate of the second fuel flowing through the return path 62. The on-off valves 72 and 73 are solenoid valves that can open and close the return path 62.

[0031] In the fuel supply path 43, a purge gas supply device 51 is connected to one side (upstream) of the flow direction of the second fuel relative to the connection point to which the fuel injection valve 44 is connected, and a fuel discharge path 52 is connected to the other side (downstream) of the flow direction of the second fuel relative to the connection point. However, in the fuel supply path 43, the fuel discharge path 52 may be connected to one side (upstream) of the flow direction of the second fuel relative to the connection point to which the fuel injection valve 44 is connected, and the purge gas supply device 51 may be connected to the other side (downstream) of the flow direction of the second fuel relative to the connection point.

[0032] The purge gas supply device 51 is connected to the supply path 61 in the fuel supply path 43. The purge gas supply device 51 supplies purge gas to the supply path 61. The supply path 61 has an upstream path 61a and a downstream path 61b. The upstream path 61a is the path from the connection point of the outlet path 64 to the on-off valve 68, and the downstream path 61b is the path from the on-off valve 69 to the connection point of the fuel injection valve 44. The purge gas supply device 51 is connected to the downstream path 61b in the supply path 61. In this case, it is preferable that the purge gas supply device 51 is connected near the on-off valve 69 in the downstream path 61b.

[0033] The fuel discharge path 52 is connected to the return path 62 in the fuel supply path 43. The fuel discharge path 52 discharges the second fuel remaining in the supply path 61 and part of the return path 62 together with the purge gas and supplies it to the combustion unit 53. The return path 62 has an upstream path 62a and a downstream path 62b. The upstream path 62a is the path from the connection point of the fuel injection valve 44 to the on-off valve 72, and the downstream path 62b is the path from the on-off valve 73 to the connection point of the outlet path 64. The fuel discharge path 52 is connected to the path between the supply path 61 and the return path 62 in the return path 62, that is, the path between the on-off valve 72 and the on-off valve 73.

[0034] The fuel discharge path 52 connects the return path 62 and the combustion unit 53. The fuel discharge path 52 is equipped with a discharge valve 74 and a primary storage section 75. The discharge valve 74 is a solenoid valve that can open and close the fuel discharge path 52. The primary storage section 75 is a space that temporarily stores and vaporizes the discharged second fuel. The supply path 61 and the primary storage section 75 are connected by an auxiliary discharge path 76. One end of the auxiliary discharge path 76 is connected between the on-off valves 68 and 69 in the supply path 61, and the other end is connected to the primary storage section 75. The auxiliary discharge path 76 is equipped with a discharge valve 77. The discharge valve 77 is a solenoid valve that can open and close the auxiliary discharge path 76.

[0035] Although not shown in the diagram, the second fuel injection system 41 has a control device. The control device is a computer, for example, a CPU (Central Processing Unit) or MPU (Micro Processing Unit), which executes various programs stored in the memory using RAM as the working area. The control device can control the fuel injection valve 44, purge gas supply device 51, outlet valve 65, supply pump 67, on-off valves 68, 69, flow control valve 71, on-off valves 72, 73, and discharge valves 74, 78 according to the engine operating state.

[0036] <Activation of the second fuel injection system> Figure 3 is a schematic diagram showing the operating state of the fuel injection system.

[0037] Figure 2 is a schematic diagram showing the stopped state of the fuel injection system. As shown in Figure 2, when the second fuel injection system 41 is stopped, the outlet valve 65, on-off valves 68, 69, and on-off valves 72, 73 are closed. Also, the purge gas supply system 51 stops operating. Therefore, the marine diesel engine 10 is either stopped or operating with only the first fuel injection system.

[0038] As shown in Figure 3, when the second fuel injector 41 is activated, the outlet valve 65, on-off valves 68, 69, and on-off valves 72, 73 are opened. Meanwhile, the discharge valves 74, 77 are closed. The supply pump 67 is activated, and the purge gas supply device 51 remains inactive. As a result, when the supply pump 67 is activated, the second fuel from the second fuel tank 63 is supplied to the fuel injector 44 through the supply path 61 of the fuel supply path 43. The fuel injector 44 operates at a predetermined timing, injecting a predetermined amount of the second fuel into the combustion chamber 25. The excess second fuel that was not injected by the fuel injector 44 is returned through the return path 62 of the fuel supply path 43 and circulates. Therefore, the marine diesel engine 10 is in an operating state due to the second fuel injector 41.

[0039] <Fuel injection system purge operation> Figure 4 is a schematic diagram showing the purge state of the fuel injection system.

[0040] As shown in Figure 3, when the operation switches from a state in which the second fuel injector 41 injects the second fuel to a state in which the first fuel injector 31 (see Figure 1) injects the first fuel, the operation of the second fuel injector 41 stops, and the second fuel remains in the fuel supply path 43. At this time, by operating the purge gas supply device 51, the second fuel remaining in the fuel supply path 43 is discharged from the fuel discharge path 52.

[0041] As shown in Figure 4, when the second fuel injector 41 is purged, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74 and 77 are opened. Also, the supply pump 67 is stopped and the purge gas supply device 51 is activated. As a result, the supply of the second fuel from the fuel supply path 43 to the supply path 61 is stopped because the supply pump 67 stops operating. The fuel injector 44 also stops operating.

[0042] Meanwhile, when the purge gas supply device 51 is activated, purge gas is supplied to the downstream path 61b of the supply path 61 in the fuel supply path 43. At this time, the fuel supply path 43 is partitioned into the downstream path 61b of the supply path 61 and the upstream path 62a of the return path 62 from the other paths by the closing of the on-off valves 69 and 73. Therefore, the purge gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The purge gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the combustion unit 53 from the fuel discharge path 52 for processing. In addition, the second fuel remaining in the path between the on-off valve 68 and the on-off valve 69 is supplied to the combustion unit 53 from the auxiliary discharge path 76 for processing. At this time, the marine diesel engine 10 is in an operating state with the first fuel injection device 31 (see Figure 1).

[0043] The second fuel injection system 41 of the first embodiment includes a purge gas supply system 51 that supplies purge gas to the fuel supply path 43, and a fuel discharge path 52 that discharges the second fuel remaining in the fuel supply path 43 along with the purge gas and supplies it to the combustion unit 53. When the operation of the second fuel injection system 41 stops, the purge gas supply system 51 is activated to supply the second fuel remaining in the fuel supply path 43 to the combustion unit 53 from the fuel discharge path 52 for processing. Therefore, by properly discharging and processing the second fuel remaining in the fuel supply path 43, storage tanks and abatement treatment devices become unnecessary, and the size of the device can be suppressed. In addition, by supplying the second fuel remaining in the fuel supply path 43 to the combustion unit 53 for processing, the second fuel can be effectively utilized without being discarded.

[0044] [Second Embodiment] Figure 5 is a schematic diagram showing the fuel injection system of the second embodiment. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0045] The second embodiment specifically describes the purge gas supply device 51 in relation to the first embodiment.

[0046] As shown in Figure 5, the diesel engine body 11 of the marine diesel engine 10 comprises a cylinder 12, a piston 13, a scavenging trunk 14, an exhaust static pressure pipe 15, an exhaust valve 16, and a fuel injector 17. The scavenging trunk 14 is connected to an intake passage 24, through which air is drawn in from the outside. The exhaust static pressure pipe 15 is connected to an exhaust passage 28, through which exhaust gas from the combustion chamber 25 is discharged to the outside.

[0047] A supercharger 81 is provided in the intake passage 24 and the exhaust passage 28. The supercharger 81 is composed of a compressor 82 and a turbine 83 connected by a rotating shaft 84. The compressor 82 has a compressor wheel located in the intake passage 24, and the turbine 83 has a turbine wheel located in the exhaust passage 28. In the supercharger 81, the turbine wheel is rotated by the exhaust gas flowing through the exhaust passage 28, and the rotational force is transmitted to the compressor wheel via the rotating shaft 84. As the compressor wheel rotates, it compresses and supercharges the air flowing through the intake passage 24. In addition, an air cooler 85 is provided between the compressor 82 and the scavenging trunk 14 in the intake passage 24.

[0048] The exhaust path 28 is connected to a turbocharger 81, and downstream of it, an SCR catalyst device 86 and a reducing agent supply device 87 are provided. The SCR catalyst device 86 has an SCR reactor. The reducing agent supply device 87 supplies a reducing agent that reduces nitrogen oxides (NOx) to the exhaust gas flowing through the exhaust path 28, and the SCR catalyst device 86 (SCR reactor) removes and reduces NOx in the exhaust gas by promoting the reaction between NOx and the reducing agent supplied to the exhaust gas. Examples of reducing agents include aqueous ammonia, gaseous ammonia, and aqueous urea.

[0049] In the second fuel injection system 41 of the second embodiment, the purge gas supply system 51 includes a purge gas storage tank 91, a purge gas supply path 92, and an on-off valve 93. The purge gas storage tank 91 stores an inert gas such as nitrogen. The purge gas supply path 92 connects the purge gas storage tank 91 to the downstream path 61b of the supply path 61 in the fuel supply path 43. The on-off valve 93 is provided in the purge gas supply path 92. The on-off valve 93 is a solenoid valve and can be opened and closed by a control device (not shown).

[0050] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the on-off valve 93 in the purge gas supply device 51 is opened. As a result, the inert gas from the purge gas storage tank 91 is supplied from the purge gas supply path 92 to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the inert gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The inert gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the combustion unit 53 from the fuel discharge path 52 for processing.

[0051] The second fuel injection system 41 of the second embodiment is equipped with a purge gas storage tank 91 for storing inert gas as a purge gas supply device 51. Therefore, it is possible to store pressurized inert gas at a predetermined pressure and supply inert gas at a constant pressure from the purge gas storage tank 91 to the fuel supply path 43, and regardless of the engine operating state, the second fuel remaining in the fuel supply path 43 can be properly discharged.

[0052] <First variation> Figure 6 is a schematic diagram showing a first modified example of the fuel injection system of the second embodiment.

[0053] As shown in Figure 6, the purge gas supply device 51 has a purge gas supply path 101 and an on-off valve 102. The purge gas supply path 101 connects the intake path 24 and the downstream path 61b of the supply path 61 in the fuel supply path 43. In this case, the end of the purge gas supply path 101 is connected between the compressor 82 (compressor wheel) of the supercharger 81 and the air cooler 85 in the intake path 24. The on-off valve 102 is provided in the purge gas supply path 101. The on-off valve 102 is a solenoid valve and can be opened and closed by a control device (not shown).

[0054] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the on-off valve 102 in the purge gas supply device 51 is opened. As a result, the intake air (compressed air) from the intake path 24 is supplied from the purge gas supply path 101 to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the compressed air supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The compressed air and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the combustion unit 53 from the fuel discharge path 52 for processing.

[0055] In the first modified example, the second fuel injection device 41 and the purge gas supply device 51 supply the intake air (compressed air) from the intake passage 24 to the fuel supply passage 43. This allows the oxygen concentration of the purge gas to be maintained, and the discharged second fuel and purge gas (air) to be properly processed (combusted) in the combustion unit 53. Furthermore, by supplying high-temperature air upstream of the air cooler 85 to the fuel supply passage 43, the second fuel remaining in the fuel supply passage 43 is heated and becomes easier to vaporize, thus shortening the purging time.

[0056] <Second variation> Figure 7 is a schematic diagram showing a second modified example of the fuel injection system of the second embodiment.

[0057] As shown in Figure 7, the purge gas supply device 51 has a purge gas supply path 111 and an on-off valve 112. The purge gas supply path 111 connects the exhaust path 28 and the downstream path 61b of the supply path 61 in the fuel supply path 43. In this case, one end of the purge gas supply path 111 is connected between the exhaust static pressure pipe 15 in the exhaust path 28 and the turbine 83 of the supercharger 81. The on-off valve 112 is provided in the purge gas supply path 111. The on-off valve 112 is a solenoid valve and can be opened and closed by a control device (not shown).

[0058] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the on-off valve 112 in the purge gas supply device 51 is opened. As a result, the exhaust gas from the exhaust path 28 is supplied from the purge gas supply path 111 to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the exhaust gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The exhaust gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the combustion unit 53 from the fuel discharge path 52 and processed.

[0059] In the second modified example, the second fuel injection system 41 and the purge gas supply system 51 supply exhaust gas from the exhaust passage 28 to the fuel supply passage 43. As a result, the oxygen concentration of the purge gas is reduced, improving safety by decreasing its flammability. In addition, by supplying high-temperature exhaust gas to the fuel supply passage 43, the second fuel remaining in the fuel supply passage 43 is heated and becomes easier to vaporize, thus shortening the purging time.

[0060] [Third Embodiment] Figure 8 is a schematic diagram showing the fuel injection system of the third embodiment. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0061] The third embodiment specifically describes the fuel discharge path 52 compared to the first embodiment.

[0062] As shown in Figure 8, in the second fuel injection device 41 of the third embodiment, one end of the fuel discharge path 52 is connected between the on-off valves 72 and 73 of the return path 62 in the fuel supply path 43, and the other end is connected to the intake path 24 that constitutes the combustion unit 53 (see Figure 2). In this case, the other end of the fuel discharge path 52 is connected to the air intake upstream of the compressor 82 (compressor wheel) of the supercharger 81 located in the intake path 24.

[0063] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the purge gas supply device 51 is activated. As a result, purge gas is supplied to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the purge gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The purge gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the intake path 24 from the fuel discharge path 52. The second fuel supplied to the intake path 24 is mixed with the air taken in from the air intake of the intake path 24 and supplied to the combustion chamber 25 for combustion and processing.

[0064] In the third embodiment, the second fuel injection device 41 supplies the second fuel discharged from the fuel supply path 43 to the intake path 24 via the fuel discharge path 52. Therefore, the second fuel in the fuel discharge path 52 can be smoothly supplied to the intake path 24 by differential pressure. In this case, by supplying the second fuel upstream of the compressor 82 in the intake path 24 via the fuel discharge path 52, the differential pressure becomes even larger, and the second fuel can be supplied to the intake path 24 more efficiently. As a result, it becomes unnecessary to provide a blower or pump in the fuel discharge path 52, and the installation can be simplified.

[0065] <First variation> Figure 9 is a schematic diagram showing a first modified example of the fuel injection system of the third embodiment.

[0066] As shown in Figure 9, one end of the fuel discharge path 52 is connected between the on-off valves 72 and 73 of the return path 62 in the fuel supply path 43, and the other end is connected to the intake path 24. In this case, the other end of the fuel discharge path 52 is connected between the compressor 82 (compressor wheel) of the supercharger 81 located in the intake path 24 that constitutes the combustion unit 53 (see Figure 2) and the combustion chamber 25. However, it is preferable that the other end of the fuel discharge path 52 is connected between the compressor 82 (compressor wheel) of the supercharger 81 located in the intake path 24 and the air cooler 85. Furthermore, it is preferable that an electric blower 121 is provided in the fuel discharge path 52.

[0067] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the purge gas supply device 51 is activated. The electric blower 121 is also activated. As a result, the purge gas is supplied to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the purge gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The purge gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the intake path 24 from the fuel discharge path 52. The second fuel supplied to the intake path 24 is mixed with air cooled by the air cooler 85 and supplied to the combustion chamber 25 for combustion and processing.

[0068] In the first modified example, the second fuel injection system 41 supplies the second fuel discharged from the fuel supply path 43 to the intake path 24 via the electric blower 121 through the fuel discharge path 52. Therefore, the second fuel from the fuel discharge path 52 can be properly supplied to the intake path 24 by the electric blower 121.

[0069] <Second variation> Figure 10 is a schematic diagram showing a second modified example of the fuel injection system of the third embodiment.

[0070] As shown in Figure 10, one end of the fuel discharge path 52 is connected between the on-off valves 72 and 73 of the return path 62 in the fuel supply path 43, and the other end is connected to the combustion chamber 25 that constitutes the combustion unit 53 (see Figure 2). In this case, the diesel engine body 11 is provided with an injection valve 131 in the cylinder 12. The fuel discharge path 52 is provided with an electric pump 132, and the other end is connected to the injection valve 131.

[0071] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the purge gas supply device 51 is activated. The electric pump 132 is also activated. As a result, the purge gas is supplied to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the purge gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The purge gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the injection valve 131 from the fuel discharge path 52. The control device operates the injection valve 131 in conjunction with the operation of the fuel injection valve 34 and the exhaust valve 16, so that the second fuel is supplied to the combustion chamber 25 and burned and processed.

[0072] In the second modified example, the second fuel injector 41 supplies the second fuel discharged from the fuel supply path 43 to the injection valve 131 via the fuel discharge path 52 using an electric pump 132, and injects it into the combustion chamber 25 by the injection valve 131. Therefore, the second fuel from the fuel discharge path 52 can be directly supplied to the combustion chamber 25, and the second fuel can be properly burned and processed. In addition, blow-by during intake and exhaust overlap can be reduced.

[0073] <Third variation> Figure 11 is a schematic diagram showing a third modified example of the fuel injection system of the third embodiment.

[0074] As shown in Figure 11, one end of the fuel discharge path 52 is connected between the on-off valves 72 and 73 of the return path 62 in the fuel supply path 43, and the other end is connected to the exhaust path 28 that constitutes the combustion unit 53 (see Figure 2). In this case, the other end of the fuel discharge path 52 is connected between the turbine 83 (turbine wheel) of the supercharger 81 and the SCR catalyst 86 (reducing agent supply device 87) in the exhaust path 28.

[0075] When purging the fuel supply path 43, the on-off valves 68, 69 and on-off valve 73 are closed. On the other hand, the on-off valve 72 and the discharge valves 74, 77 are opened. Then, the purge gas supply device 51 is activated. As a result, the purge gas is supplied to the downstream path 61b of the supply path 61 in the fuel supply path 43. Therefore, the purge gas supplied to the downstream path 61b of the supply path 61 pushes the second fuel remaining in the downstream path 61b to the upstream path 62a of the return path 62. The purge gas and second fuel that have moved to the upstream path 62a of the return path 62 are then supplied to the exhaust path 28 from the fuel discharge path 52. The second fuel supplied to the exhaust path 28 is supplied to the SCR catalyst device 86 for processing. That is, when the second fuel is ammonia as a carbon-free fuel, the second fuel is used as a reducing agent supplied from the reducing agent supply device 87. In other words, the second fuel discharged from the fuel supply path 43 is properly treated by being supplied to the SCR catalytic converter 86 via the exhaust path 28 from the fuel discharge path 52.

[0076] In the third modified example, the second fuel injector 41 supplies the second fuel discharged from the fuel supply path 43 to the exhaust path 28 via the fuel discharge path 52. Therefore, the second fuel in the fuel discharge path 52 can be properly treated by using it as a reducing agent in the SCR catalyst 86.

[0077] In the third embodiment described above, when the second fuel discharged from the fuel supply path 43 to the fuel discharge path 52 by the purge gas supply device 51 is supplied to the intake path 24 as a combustion unit 53 for processing, it is preferable to apply a corrosion-resistant (alkali corrosion-resistant) material to the air cooler 85. When the second fuel discharged from the fuel supply path 43 to the fuel discharge path 52 by the purge gas supply device 51 is supplied to the intake path 24 and exhaust path 28 as a combustion unit 53 for processing, a compressor for pressurizing the mixed gas may be provided.

[0078] In the embodiment described above, the second fuel discharged from the fuel supply path 43 to the fuel discharge path 52 of the marine diesel engine 10 by the purge gas supply device 51 is supplied to its own combustion unit 53 for processing. However, the configuration is not limited to this. If an internal combustion engine for power generation is located nearby to the marine diesel engine 10, the second fuel discharged from the fuel supply path 43 of the marine diesel engine 10 may be supplied to the combustion unit of the internal combustion engine for power generation for processing. In this case, the combustion unit may be an internal combustion engine, or it may be a combustion unit such as a gas turbine or a boiler.

[0079] [Effects of this embodiment] The fuel injection system according to the first embodiment includes a fuel supply path (first fuel supply path) 33 for supplying a first fuel having predetermined ignition properties, a fuel injection valve (first fuel injection valve) 34 to which the fuel supply path 33 is connected, a fuel supply path (second fuel supply path) 43 for supplying a second fuel having lower ignition properties than the first fuel, a fuel injection valve (second fuel injection valve) 44 to which the fuel supply path 43 is connected, a purge gas supply device 51 for supplying purge gas to the fuel supply path 43, and a fuel discharge path 52 for discharging the second fuel remaining in the fuel supply path 43 together with the purge gas and supplying it to the combustion unit 53.

[0080] According to the fuel injection system of the first embodiment, when the operation of the second fuel injection system 41 stops, the purge gas supply system 51 supplies purge gas to the fuel supply path 43, and the remaining second fuel is supplied to the combustion unit 53 from the fuel discharge path 52 for processing. Therefore, by properly discharging and processing the second fuel remaining in the fuel supply path 43, storage tanks and abatement treatment devices become unnecessary, and the size of the system can be suppressed. In addition, by supplying the second fuel remaining in the fuel supply path 43 to the combustion unit 53 for processing, the second fuel can be effectively utilized without being discarded.

[0081] The fuel injection system according to the second embodiment is a fuel injection system according to the first embodiment, further comprising: a purge gas supply device 51 connected to one side in the flow direction of the second fuel with respect to the connection portion to which the fuel injection valve 44 is connected in the fuel supply path 43; and a fuel discharge path 52 connected to the other side in the flow direction of the second fuel with respect to the connection portion. This makes it possible to appropriately discharge the second fuel remaining in the path to which the fuel injection valve 44 is connected in the fuel supply path 43.

[0082] The fuel injection system according to the third embodiment is a fuel injection system according to the first or second embodiment, further comprising a fuel supply path 43 which is a circulation path, a purge gas supply device 51 which is connected to a supply path 61 in the fuel supply path 43, and a fuel discharge path 52 which is connected to a return path 62 in the fuel supply path 43. This allows for the proper discharge of the second fuel remaining in the fuel supply path 43 by flowing purge gas along the flow direction of the second fuel in the fuel supply path 43.

[0083] The fuel injection system according to the fourth embodiment is a fuel injection system according to any one of the first to third embodiments, further comprising a purge gas supply device 51, a purge gas storage tank 91, a purge gas supply path 92 connecting the purge gas storage tank 91 and the fuel supply path 43, and an on / off valve 93 provided in the purge gas supply path 92. This allows an inert gas at a constant pressure stored in the purge gas storage tank 91 to be supplied to the fuel supply path 43, and enables the proper discharge of the second fuel remaining in the fuel supply path 43 regardless of the engine operating state.

[0084] The fuel injection system according to the fifth embodiment is a fuel injection system according to any one of the first to third embodiments, and further, the purge gas supply device 51 has a purge gas supply path 101 that connects an intake path 24 that takes air into the combustion chamber 25 and a fuel supply path 43, and an on / off valve 102 provided in the purge gas supply path 101. This makes it possible to maintain the oxygen concentration of the purge gas and to properly process (combust) the discharged second fuel and purge gas (air) in the combustion unit 53.

[0085] The fuel injection system according to the sixth embodiment is a fuel injection system according to any one of the first to third embodiments, further comprising a purge gas supply device 51 which includes a purge gas supply path 111 connecting an exhaust path 28 from which exhaust gas is discharged from the combustion chamber 25 to a fuel supply path 43, and an on / off valve 112 provided in the purge gas supply path 111. This reduces the oxygen concentration of the purge gas, thereby lowering its flammability and improving safety.

[0086] The fuel injection system according to the seventh embodiment is a fuel injection system according to any one of the first to sixth embodiments, further comprising: a combustion unit 53 having an intake passage 24 for taking air into the combustion chamber 25; and a fuel discharge passage 52 having one end connected to a fuel supply passage 43 and the other end connected to the intake passage 24. This allows the second fuel from the fuel discharge passage 52 to be smoothly supplied to the intake passage 24 by differential pressure.

[0087] The fuel injection system according to the eighth embodiment is a fuel injection system according to the seventh embodiment, wherein the other end of the fuel discharge path 52 is connected to the air intake of a supercharger 81 which is located in the intake path 24. This allows the second fuel in the fuel discharge path 52 to be smoothly supplied to the upstream side of the supercharger 81 in the intake path 24 by differential pressure.

[0088] The fuel injection system according to the ninth embodiment is a fuel injection system according to the seventh embodiment, wherein the fuel discharge path 52 is connected to the intake path 24 between the supercharger 81 and the combustion chamber 25, with the other end of the supercharger 81 located in the intake path 24. This allows the second fuel from the fuel discharge path 52 to be properly supplied to the intake path 24.

[0089] The fuel injection system according to the tenth embodiment is a fuel injection system according to any one of the first to sixth embodiments, further comprising a combustion unit 53 having a combustion chamber 25 partitioned by a cylinder 12 and a piston 13, and a fuel discharge path 52 having one end connected to a fuel supply path 43 and the other end connected to the combustion chamber 25. This allows the second fuel from the fuel discharge path 52 to be directly supplied to the combustion chamber 25, and the second fuel to be properly burned and processed.

[0090] The fuel injection system according to the eleventh embodiment is a fuel injection system according to any one of the first to sixth embodiments, further comprising: a combustion unit 53 having an exhaust path 28 through which exhaust gas is discharged from the combustion chamber 25; and a fuel discharge path 52 having one end connected to a fuel supply path 43 and the other end connected to the exhaust path 28. This allows the second fuel in the fuel discharge path 52 to be properly treated by using it as a reducing agent in the SCR catalyst 86. [Explanation of symbols]

[0091] 10 Marine Diesel Engines 11 Diesel engine body 12 cylinders 13 pistons 14. Scavenging Trunk 15 Exhaust static pressure pipe 16 Exhaust valve 17 Fuel injection device 24 Intake path 25 Combustion chamber 26 Exhaust pipe 28 Exhaust path 31 1st fuel injection device 32 Fuel supply device 33. Fuel supply route (First fuel supply route) 34 Fuel Injector (First Fuel Injector) 41 Second fuel injection device 42 Fuel supply system 43. Fuel supply route (Second fuel supply route) 44 Fuel Injector (Second Fuel Injector) 51 Purge gas supply device 52 Fuel Emissions Pathways 53 Combustion Unit 61 Supply routes 62 Return Route 63 Second fuel tank 64 Exit Route 65 Outlet valve 66 Branch Routes 67 Supply pump 68, 69, 72, 73 Shut-off valves 71 Flow control valve 74,77 Discharge valve 75 Primary Storage Unit 76. Auxiliary discharge route 81 Supercharger 82 Compressor 83 Turbine 84 Rotation axis 85 Air Cooler 86 SCR Catalyst Device 87 Reducing agent supply device 91 Purge gas storage tank 92,101,111 Purge gas supply routes 93,102,112 Shut-off valves 121 Electric Blower 131 Injector valve 132 Electric pump

Claims

1. A first fuel supply path that supplies a first fuel having predetermined ignition properties, The first fuel injection valve to which the first fuel supply path is connected, A second fuel supply path that supplies a second fuel with lower ignition properties than the first fuel, The second fuel injection valve to which the second fuel supply path is connected, A purge gas supply device that supplies purge gas to the second fuel supply path, A fuel discharge path that discharges the second fuel remaining in the second fuel supply path together with the purge gas and supplies it to the combustion unit, A fuel injection system equipped with the following features.

2. The second fuel supply path is configured such that the purge gas supply device is connected to one side in the flow direction of the second fuel relative to the connection portion to which the second fuel injection valve is connected, and the fuel discharge path is connected to the other side in the flow direction of the second fuel relative to the connection portion. The fuel injection device according to claim 1.

3. The second fuel supply path is a circulation path, the purge gas supply device is connected to the supply path in the second fuel supply path, and the fuel discharge path is connected to the return path in the second fuel supply path. The fuel injection device according to claim 2.

4. The purge gas supply device comprises a purge gas storage tank, a purge gas supply path connecting the purge gas storage tank and the second fuel supply path, and an on / off valve provided in the purge gas supply path. The fuel injection device according to claim 1.

5. The purge gas supply device includes a purge gas supply path connecting an intake path for taking air into the combustion chamber and the second fuel supply path, and an on / off valve provided in the purge gas supply path. The fuel injection device according to claim 1.

6. The purge gas supply device includes a purge gas supply path connecting an exhaust path from which exhaust gas is discharged from the combustion chamber to the second fuel supply path, and an on / off valve provided in the purge gas supply path. The fuel injection device according to claim 1.

7. The combustion unit has an intake path for taking air into the combustion chamber, and the fuel discharge path has one end connected to the second fuel supply path and the other end connected to the intake path. The fuel injection device according to claim 1.

8. The other end of the fuel discharge path is connected to the air intake section of a turbocharger located in the intake path. The fuel injection device according to claim 7.

9. The fuel discharge path has its other end connected to the intake path between the supercharger and the combustion chamber, which is located in the intake path. The fuel injection device according to claim 7.

10. The combustion unit has a combustion chamber partitioned by a cylinder and a piston, and the fuel discharge path has one end connected to the second fuel supply path and the other end connected to the combustion chamber. The fuel injection device according to claim 1.

11. The combustion unit has an exhaust path through which exhaust gas is discharged from the combustion chamber, and the fuel discharge path has one end connected to the second fuel supply path and the other end connected to the exhaust path. The fuel injection device according to claim 1.

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