Fuel reforming system for vehicle mounted with engine

Abstract

To provide a fuel reforming system suitable for mounting to a vehicle.SOLUTION: A fuel reforming system 1 includes: a reciprocal engine 3; a decomposition device 6 that decomposes hydrocarbon fuel into carbon and hydrogen gas; and a hydrocarbon fuel supply device (third port injector 46) that supplies hydrocarbon fuel to the decomposition device. The reciprocal engine includes a third port 37 communicating a cylinder 31 and the decomposition device and opened / closed by an on-off valve 38. The on-off valve is opened in a stroke in which combustion gas in the cylinder is supplied to the decomposition device due to lifting of a piston and in a stroke in which the combustion gas from which carbon and hydrogen gas have been removed is introduced from the third port to the cylinder through lowering of the piston. The hydrocarbon fuel supply device injects hydrocarbon fuel into the third port between the on-off valve and the decomposition device in a stroke in which the on-off valve is closed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed herein relates to a fuel reforming system for an engine-equipped vehicle. [Background technology]

[0002] Patent Document 1 describes an apparatus for directly decomposing hydrocarbons into carbon and hydrogen. This conventional decomposition apparatus includes a reactor containing a catalyst. When a raw gas containing hydrocarbons is supplied to the reactor, carbon produced by a catalytic reaction adheres to the catalyst. A reaction gas containing hydrogen passes through the reactor. A hydrogen purification device downstream of the reactor purifies the hydrogen in the reaction gas to increase the hydrogen concentration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-104521 Summary of the Invention [Problem to be solved by the invention]

[0004] In the field of vehicle technology (for example, four-wheeled automobiles), efforts to achieve carbon neutrality are being sought. To achieve carbon neutrality in vehicles equipped with engines that use hydrocarbon fuels (including gasoline and / or diesel), new technologies for recovering carbon (C) or CO2 from hydrocarbon fuels are required, in addition to improving the thermal efficiency of the engine and / or improving exhaust emission performance.

[0005] To capture carbon or CO2 in a vehicle equipped with an engine that uses hydrocarbon fuel, two possible methods are (1) capturing CO2 after the hydrocarbon fuel is combusted, or (2) decomposing the hydrocarbon fuel into carbon and hydrogen gas before combustion and capturing the carbon. Considering that the captured CO2 or carbon will be stored in the vehicle, option (2) is more advantageous in terms of the vehicle's fuel economy because CO2 is heavier than carbon. Option (2) also makes it possible to use hydrogen gas as engine fuel. Combusting hydrogen gas also has the advantage of not generating carbon oxides due to combustion.

[0006] Therefore, it is conceivable to mount the conventional cracking device described above on a vehicle. The conventional cracking device is equipped with a heating device for raising the temperature of the catalyst. When the conventional cracking device is mounted on a vehicle, it is possible to use the heat of the engine to raise the temperature of the catalyst.

[0007] However, if hydrogen gas is to be used as engine fuel, high-concentration hydrogen gas is required. Conventional cracking devices require a hydrogen purification device that uses the PSA (Pressure Swing Adsorption) method to purify hydrogen from hydrogen-containing reaction gas in order to obtain high-concentration hydrogen gas. However, installing a hydrogen purification device on a vehicle has the disadvantage of increasing the vehicle weight. Conventional cracking devices are not suitable for installation on vehicles.

[0008] The technology disclosed herein provides a fuel reforming system suitable for installation in a vehicle. [Means for solving the problem]

[0009] A membrane reactor, which simultaneously decomposes hydrocarbon fuel and separates hydrogen gas, could be used in a vehicle's fuel reforming system. A membrane reactor uses a catalyst to decompose hydrocarbon fuel into carbon and hydrogen gas, while a separation membrane allows only hydrogen gas to pass through. Despite its compact size, it can produce highly concentrated hydrogen gas. However, to efficiently produce highly concentrated hydrogen gas in a membrane reactor, the pressure of the feed gas containing hydrocarbon fuel supplied to the reactor must be increased.

[0010] The inventors of the present invention have focused on the fact that in a reciprocating engine, the gas inside the cylinder is compressed as the piston rises. That is, the fuel reforming system disclosed herein decomposes hydrocarbon fuel by utilizing the heat of the combustion gas generated in the reciprocating engine and the pressure generated when the combustion gas is compressed as the piston rises. The hydrocarbon fuel decomposition process of the fuel reforming system installed in a vehicle is integrated into the operation of the reciprocating engine.

[0011] However, when using the piston stroke of a reciprocating engine to decompose hydrocarbon fuel, there is a risk that the time for vaporizing the hydrocarbon fuel and / or the time for decomposing the hydrocarbon fuel may not be sufficiently long. If the reaction time required for the vaporization and / or decomposition reaction is not long enough, the yield of carbon and hydrogen gas in the fuel reforming system will decrease. This is because a short reaction time reduces the amount of carbon and hydrogen gas obtained relative to the amount of injected hydrocarbon fuel. Note that the "reaction time" of hydrocarbon fuel here refers to the time required for the reaction from when the hydrocarbon fuel supply device injects the hydrocarbon fuel until the hydrocarbon fuel vaporizes and is decomposed into carbon and hydrogen gas by the decomposer. The reaction time is primarily determined by the operating conditions of the reciprocating engine. For example, if the reciprocating engine's rotation speed is high, the reaction time will be short.

[0012] The techniques disclosed herein increase the carbon and hydrogen gas yield of on-board fuel reforming systems.

[0013] Specifically, the technology disclosed herein relates to a fuel reforming system for an engine-equipped vehicle. a reciprocating engine mounted on a vehicle and having pistons reciprocating within cylinders; a cracker for cracking the hydrocarbon fuel into carbon and hydrogen gas; a hydrocarbon fuel supply device that supplies the hydrocarbon fuel to the cracker, the reciprocating engine has an intake port, an exhaust port, and a third port that connects the cylinder and the cracker and is opened and closed by an on-off valve; the on-off valve opens during a stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises, and during a stroke in which the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder through the third port as the piston descends, The hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker during a stroke in which the on-off valve is closed.

[0014] The fuel reforming system includes a cracker and a hydrocarbon fuel supply.

[0015] The hydrocarbon fuel supply device supplies hydrocarbon fuel to the cracker. The hydrocarbon fuel may be stored in a fuel tank mounted on the vehicle. The hydrocarbon fuel supply device supplies the hydrocarbon fuel from the fuel tank to the cracker.

[0016] The cracker is connected to the cylinder via a third port. The on-off valve opens during the stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises. The combustion gas in the cylinder pushed by the piston is supplied to the cracker through the third port. The cracker cracks the hydrocarbon fuel supplied from the hydrocarbon fuel supply device by utilizing the heat of the combustion gas supplied from the cylinder and the pressure of the combustion gas caused by the piston rising. The cracker may store carbon. Hydrogen gas may be used as fuel for a reciprocating engine.

[0017] The on-off valve also opens during the stroke in which the combustion gas, from which carbon and hydrogen gas have been removed, is introduced into the cylinder through the third port as the piston descends.

[0018] The hydrocarbon fuel supply device injects hydrocarbon fuel into a third port between the on-off valve and the cracker during the stroke in which the on-off valve is closed. The hydrocarbon fuel injected into the third port vaporizes in the third port. When the on-off valve opens and the piston rises, the vaporized hydrocarbon fuel is carried to the cracker by the combustion gas flowing from the cylinder to the cracker. After the piston descends and the on-off valve closes, the hydrocarbon fuel remains in the cracker until the on-off valve opens again. Because the hydrocarbon fuel remains in the cracker for a relatively long time, a sufficiently long reaction time for the hydrocarbon fuel is ensured. This increases the yield of carbon and hydrogen gas in the fuel reforming system.

[0019] Another fuel reforming system disclosed herein includes: a reciprocating engine mounted on a vehicle and having pistons reciprocating within cylinders; a cracker for cracking the hydrocarbon fuel into carbon and hydrogen gas; a hydrocarbon fuel supply device that supplies the hydrocarbon fuel to the cracker, the reciprocating engine has an intake port, an exhaust port, and a third port that connects the cylinder and the cracker and is opened and closed by an on-off valve; the on-off valve opens during a stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises, and during a stroke in which the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder through the third port as the piston descends, the cracker includes a catalyst section that cracks the hydrocarbon fuel using a catalyst, and a space that is on the opposite side of the catalyst section from the third port and is connected to the catalyst section, The hydrocarbon fuel supply device injects the hydrocarbon fuel into the space while the on-off valve is open and the piston is in the upward stroke.

[0020] In this fuel reforming system, the hydrocarbon fuel supply device injects hydrocarbon fuel during the stroke in which the on-off valve is open and the piston is ascending. The hydrocarbon fuel supply device injects hydrocarbon fuel into a space on the opposite side of the catalyst unit from the third port side. The injected hydrocarbon fuel is carried from the space to the catalyst unit by the flow of combustion gas returning from the cracker to the cylinder as the piston descends. After the on-off valve closes, the hydrocarbon fuel remains in the catalyst unit until the on-off valve is next opened. Because the hydrocarbon fuel remains in the catalyst unit for a relatively long time, a sufficiently long reaction time for the hydrocarbon fuel is ensured. The yield of carbon and hydrogen gas in the fuel reforming system is increased.

[0021] The hydrocarbon fuel supply device may inject the hydrocarbon fuel into the third port immediately after the on-off valve that has been open is closed.

[0022] If the hydrocarbon fuel is injected into the third port immediately after the on-off valve closes, the time from when the hydrocarbon fuel is injected until when the on-off valve opens and the hydrocarbon fuel is transported to the cracker can be used for vaporization, which is advantageous for improving the carbon and hydrogen gas yields of the fuel reforming system.

[0023] The hydrocarbon fuel supply device may inject the hydrocarbon fuel into the space during the latter half of the piston's upward stroke.

[0024] During the latter half of the piston's upward stroke, the pressure and temperature in the third port, which contains the cracker, increase. Because the hydrocarbon fuel is injected into the space under high pressure and temperature, the hydrocarbon fuel is favorably vaporized. The vaporized hydrocarbon fuel can be decomposed into carbon and hydrogen gas in a short time, improving the carbon and hydrogen gas yields of the fuel reforming system.

[0025] The reciprocating engine is an intake stroke in which at least intake air is introduced into the cylinder through the intake port as the piston descends; a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rise of the piston; an expansion stroke in which the piston descends due to combustion of the air-fuel mixture; a recompression stroke in which the combustion gas is compressed by the rise of the piston; a re-expansion stroke in which the piston descends; and a six-stroke cycle having an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises; The on-off valve may be opened during the recompression stroke and the re-expansion stroke, and closed during the intake stroke, compression stroke, expansion stroke, and exhaust stroke.

[0026] A reciprocating engine operates in a six-stroke cycle, which, in contrast to the usual four-stroke cycle with intake, compression, expansion, and exhaust strokes, adds a recompression stroke, in which the piston rises to compress the burned gases, and a re-expansion stroke, in which the piston descends, between the expansion and exhaust strokes.

[0027] The on-off valve opens during the recompression stroke and the re-expansion stroke. The fuel reforming system can decompose hydrocarbon fuel by utilizing the heat and pressure of the combustion gas during the recompression stroke. The on-off valve closes from the exhaust stroke following the re-expansion stroke until the expansion stroke.

[0028] When the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker, the hydrocarbon fuel is injected between the exhaust stroke and the expansion stroke. The hydrocarbon fuel supply device may inject the hydrocarbon fuel into the third port during the exhaust stroke so as to maximize the reaction time of the hydrocarbon fuel.

[0029] When the hydrocarbon fuel supply device injects the hydrocarbon fuel into the space on the opposite side of the catalyst unit from the third port, the hydrocarbon fuel supply device injects the hydrocarbon fuel during the recompression stroke. The hydrocarbon fuel supply device may inject the hydrocarbon fuel into the space in the latter half of the recompression stroke so that the hydrocarbon fuel is injected in an environment where the pressure and temperature in the cracker and the third port are high.

[0030] The reciprocating engine is a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rise of the piston; an expansion stroke in which the piston descends due to combustion of the air-fuel mixture; a recompression stroke in which the combustion gas is compressed by the rising of the piston; and a modified four-stroke cycle having a scavenging stroke in which exhaust gas in the cylinder is discharged through the exhaust port while at least intake air is introduced into the cylinder through the intake port as the piston descends; The on-off valve may be opened during the recompression stroke and the scavenging stroke, and closed during the compression stroke and the expansion stroke.

[0031] Reciprocating engines operate on a modified four-stroke cycle. In this modified four-stroke cycle, instead of the intake stroke and exhaust stroke of a normal four-stroke cycle, which has an intake stroke, compression stroke, expansion stroke, and exhaust stroke, a recompression stroke occurs after the expansion stroke, in which the combustion gases are compressed as the piston rises, and a scavenging stroke occurs as the piston descends after the recompression stroke, in which both exhaust and intake are performed simultaneously.

[0032] The on-off valve opens during the recompression stroke following the expansion stroke and during the scavenging stroke, and closes during the compression stroke and expansion stroke. The fuel reforming system can decompose hydrocarbon fuel by utilizing the heat and pressure of the combustion gas during the recompression stroke.

[0033] When the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker, the hydrocarbon fuel is injected between the compression stroke and the expansion stroke. The hydrocarbon fuel supply device may inject the hydrocarbon fuel into the third port during the compression stroke so as to maximize the reaction time of the hydrocarbon fuel.

[0034] When the hydrocarbon fuel supply device injects the hydrocarbon fuel into the space on the opposite side of the catalyst unit from the third port, the hydrocarbon fuel supply device injects the hydrocarbon fuel during the recompression stroke. The hydrocarbon fuel supply device may inject the hydrocarbon fuel into the third port in the latter half of the recompression stroke so that the hydrocarbon fuel is injected in an environment where the pressure and temperature in the cracker and the third port are high. [Effects of the Invention]

[0035] The fuel reforming system for an engine-mounted vehicle is suitable for installation in a vehicle and can increase the yield of carbon and hydrogen gas. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 shows a fuel reforming system installed in a vehicle. [Figure 2] FIG. 2 shows a cracker for cracking hydrocarbon fuels. [Figure 3] FIG. 3 shows the vehicle control system. [Figure 4] Figure 4 shows each step of the six-stroke cycle. [Figure 5] FIG. 5 shows a control map for a reciprocating engine. [Figure 6] FIG. 6 shows the lift curves of the intake valve, the exhaust valve, and the on-off valve. [Figure 7] FIG. 7 is a flowchart of engine control. [Figure 8] FIG. 8 shows the injection timing of hydrocarbon fuel. [Figure 9] FIG. 9 shows a decomposer according to a modified example. [Figure 10] FIG. 10 shows the injection timing of hydrocarbon fuel according to a modified example. [Figure 11] Figure 11 shows the steps of a modified four-stroke cycle. [Figure 12] FIG. 12 shows each stroke of a modified irregular four-stroke cycle. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, an embodiment of a fuel reforming system for an engine-equipped vehicle will be described with reference to the drawings. The system described here is an example.

[0038] (Configuration of fuel reforming system) FIG. 1 shows a fuel reforming system 1 mounted on a vehicle. A hydrocarbon fuel is stored in a fuel tank mounted on the vehicle. The hydrocarbon fuel is, for example, gasoline. The hydrocarbon fuel is not limited to gasoline. The fuel reforming system 1 decomposes the hydrocarbon fuel into carbon and hydrogen gas. The carbon is stored in a decomposer 6, which will be described later. The hydrogen gas is used as fuel for a reciprocating engine 3. The fuel reforming system 1 achieves carbon neutrality for vehicles that are equipped with hydrocarbon fuel.

[0039] The fuel reforming system 1 includes a reciprocating engine 3. The reciprocating engine 3 has a cylinder 31 and a piston 32 that reciprocates within the cylinder 31. The reciprocating engine 3 has a plurality of cylinders 31. The plurality of cylinders 31 are aligned, for example, in the direction in which the crankshaft of the reciprocating engine 3 extends. The piston 32 of each cylinder 31 is connected to the crankshaft via a connecting rod. The connecting rod converts the reciprocating motion of the piston 32 into rotation of the crankshaft. The crankshaft is connected to the drive wheels via a transmission. The reciprocating engine 3 outputs driving force for running the vehicle. The reciprocating engine 3 may also be used as a driving source for driving a generator.

[0040] The reciprocating engine 3 has an intake port 33. The intake port 33 is connected to the cylinder 31. Each cylinder 31 has one or more intake ports 33. Each cylinder 31 may have, for example, two intake ports 33. The intake port 33 is connected to an intake pipe. As will be described later, intake air is introduced into the cylinder 31 through the intake port 33. The intake air includes at least fresh air. The intake air may also include EGR (Exhaust Gas Recirculation) gas.

[0041] The reciprocating engine 3 has an intake valve 34. The intake valve 34 is a poppet valve that opens and closes the intake port 33. When the intake valve 34 opens, intake air is introduced into the cylinder 31. An intake valve train 41 shown in FIG. 3 opens and closes the intake valve 34. The intake valve train 41 has, for example, an intake camshaft mechanically connected to the intake valve 34. The intake valve train 41 can continuously change the valve timing of the intake valve 34 (so-called S-VT (Sequential-Valve Timing)). The intake valve train 41 can also continuously change the valve lift of the intake valve 34 (so-called CVVL (Continuously Variable Valve Lift)). A known hydraulic or electric mechanism can be used for the intake valve train 41. The intake valve train 41 changes the valve timing and / or valve lift depending on the operating state of the reciprocating engine 3.

[0042] The reciprocating engine 3 has exhaust ports 35. The exhaust ports 35 are connected to the cylinders 31. Each cylinder 31 has one or more exhaust ports 35. Each cylinder 31 may have, for example, one exhaust port 35. The exhaust ports 35 are connected to an exhaust pipe. As will be described later, exhaust gas is discharged from inside the cylinders 31 through the exhaust ports 35.

[0043] The reciprocating engine 3 has an exhaust valve 36. The exhaust valve 36 is a poppet valve that opens and closes the exhaust port 35. When the exhaust valve 36 opens, exhaust gas is discharged to the outside of the cylinder 31. An exhaust valve train 42 shown in FIG. 3 opens and closes the exhaust valve 36. The exhaust valve train 42 has, for example, an exhaust camshaft mechanically connected to the exhaust valve 36. The exhaust valve train 42 can continuously change the valve timing of the exhaust valve 36 (so-called S-VT). The exhaust valve train 42 can also continuously change the valve lift of the exhaust valve 36 (so-called CVVL). A known hydraulic or electric mechanism can be used for the exhaust valve train 42. The exhaust valve train 42 changes the valve timing and / or valve lift depending on the operating state of the reciprocating engine 3.

[0044] The reciprocating engine 3 has a third port 37. The third port 37 is in communication with the cylinders 31. Each cylinder 31 has at least one third port 37. Each cylinder 31 may have, for example, one third port 37.

[0045] A typical reciprocating engine has two intake ports and two exhaust ports per cylinder. One of the two exhaust ports may be converted into a third port 37. The reciprocating engine 3 in FIG. 1 has two intake ports 33, one exhaust port 35, and one third port 37 per cylinder 31. Note that for ease of understanding, the exhaust port 35 and the third port 37 are depicted in offset positions in FIG. 1.

[0046] One of the two intake ports may be converted into the third port 37. However, two intake ports 33 have the advantage of being able to introduce a large amount of fresh air into the cylinder 31. If an exhaust port or an intake port is converted into the third port 37, a general reciprocating engine can be used as the reciprocating engine 3 of the fuel reforming system 1. The reciprocating engine 3 may have two intake ports 33, two exhaust ports 35, and one third port 37 per cylinder 31.

[0047] The reciprocating engine 3 has an on-off valve 38. The on-off valve 38 is a poppet valve that opens and closes a third port 37. A third valve train 43 shown in FIG. 3 opens and closes the on-off valve 38. The third valve train 43 has, for example, a third camshaft mechanically connected to the on-off valve 38. The third valve train 43 may open the on-off valve 38 twice in one cycle (see FIG. 6). The third valve train 43 can also stop the on-off valve 38 from opening or closing. A known hydraulic or electric mechanism can be used as a valve stop mechanism that stops the on-off valve 38 from opening or closing. The valve stop mechanism may be incorporated, for example, into a rocker arm interposed between the third camshaft and the on-off valve 38. The valve stop mechanism may also be incorporated into a lash adjuster that supports the rocker arm. The on-off valve 38 may be mechanically connected to an intake camshaft or an exhaust camshaft.

[0048] An intake port injector 44 is attached to the reciprocating engine 3. An injection hole of the intake port injector 44 faces the inside of the intake port 33. The intake port injector 44 injects hydrocarbon fuel into the intake port 33. A hydrocarbon fuel supply unit 45 is connected to the intake port injector 44. The hydrocarbon fuel supply unit 45 has a fuel tank that stores hydrocarbon fuel and a fuel pump that pressure-feeds the hydrocarbon fuel. The hydrocarbon fuel supply unit 45 supplies hydrocarbon fuel to the intake port injector 44.

[0049] A third port injector 46 is attached to the reciprocating engine 3. An injection hole of the third port injector 46 faces the third port 37. More specifically, in the example of FIG. 1 , the third port injector 46 is located in the third port 37 between the cracker 6 and the on-off valve 38. The third port injector 46 injects hydrocarbon fuel into the third port 37. The third port injector 46 is an example of a hydrocarbon fuel supply device. A hydrocarbon fuel supply unit 45 is also connected to the third port injector 46. The hydrocarbon fuel supply unit 45 selectively supplies hydrocarbon fuel to the intake port injector 44 and the third port injector 46.

[0050] A hydrogen injector 47 is attached to the reciprocating engine 3. The injection holes of the hydrogen injector 47 face the inside of the cylinder 31. The hydrogen injector 47 injects hydrogen gas into the cylinder 31.

[0051] It is also possible to attach an injector that injects hydrocarbon fuel to the reciprocating engine 3 so as to face the inside of the cylinder 31, and attach a hydrogen injector that injects hydrogen gas to the reciprocating engine 3 so as to face the inside of the intake port 33.

[0052] The hydrogen gas supply unit 5 is connected to the hydrogen injector 47. The hydrogen gas supply unit 5 supplies hydrogen gas to the hydrogen injector 47. As described above, the hydrogen gas is hydrogen gas decomposed from a hydrocarbon fuel.

[0053] The cracker 6 is connected to the third port 37. The cracker 6 cracks the hydrocarbon fuel into carbon and hydrogen gas. The cracker 6 is attached to each cylinder 31. The cracker 6 may be common to multiple cylinders 31.

[0054] Figure 2 shows the structure of the cracker 6. The cracker 6 uses a catalyst to decompose the hydrocarbon fuel into carbon and hydrogen gas, and separates the hydrogen gas using a separation membrane 63. The cracker 6 is a so-called membrane reactor. The decomposition of a hydrocarbon fuel, for example, isooctane, is represented by the following chemical reaction formula:

[0055] iC8H 18 (g) = 8C(s) + 9H2 The recovery of solid carbon prevents the weight of the vehicle from increasing. The fuel reforming system 1 is suitable for use as an in-vehicle system.

[0056] The cracker 6 has a catalyst support 61. A catalyst that can be used to crack hydrocarbon fuel is, for example, a Ni-Al-Fe alloy. Various catalysts can be used as long as they can be used to crack hydrocarbon fuel.

[0057] The support 61 can be, for example, an aluminum oxide plate. The catalyst is applied to the surface of the plate. The support 61 is supported on the inner surface of a case 62 of the cracker 6. The case 62 is, for example, cylindrical. The shape of the support 61 is not limited to a specific shape. Carbon produced by the cracking of the hydrocarbon fuel adheres to the surface of the support 61. The cracker 6 also stores the carbon.

[0058] The decomposer 6 has a separation membrane 63. The separation membrane 63 is located more inward of the support 61 in the case 62. The separation membrane 63 has, for example, a cylindrical shape. The separation membrane 63 has a function of allowing only hydrogen gas to permeate. The separation membrane 63 is, for example, a Pd alloy membrane. However, the separation membrane 63 is not limited to a Pd alloy membrane.

[0059] The third port 37 is connected to a first end of the case 62. The second end of the case 62 is closed. Combustion gas from the cylinder 31 and hydrocarbon fuel injected by the third port injector 46 flow into the space between the catalyst support 61 and the separation membrane 63, as shown by the black arrows in FIG. 2. The catalyst decomposes the hydrocarbon fuel into carbon and hydrogen gas. The decomposed hydrogen gas permeates the separation membrane 63, as shown by the white arrows in FIG. 2.

[0060] The cracker 6 has a catalyst section 64 including the above-mentioned catalyst support 61 and separation membrane 63. The catalyst section 64 is located on the third port 37 side of the case 62, and a space 65 is formed in the case 62 on the opposite side of the third port 37 from the catalyst section 64. As will be described later, gas remaining inside the cracker 6 at the start of the recompression stroke is pushed into the space 65 as the combustion gas and hydrocarbon fuel flow into the cracker 6. As a result, the hydrocarbon fuel spreads throughout the catalyst section 64, accelerating the cracking of the hydrocarbon fuel.

[0061] A hydrogen gas passage 50 is connected to one end of the tube made of separation membrane 63. The hydrogen gas passage 50 is connected to a hydrogen gas supply unit 5 (see FIG. 1). The hydrogen gas passage 50 guides hydrogen gas from the cracker 6 to the hydrogen gas supply unit 5. The hydrogen gas is sent to the hydrogen injector 47 via the hydrogen gas supply unit 5. The hydrogen gas supply unit 5 has, for example, a hydrogen gas tank and a hydrogen gas pump.

[0062] (Control system configuration) 3 is a block diagram of the control system 2 of the vehicle equipped with the fuel reforming system 1. The control system 2 has a controller 21. The controller 21 is composed of hardware such as a processor, memory, and interface, and software such as a database and control program.

[0063] The crank angle sensor 22 is electrically connected to the controller 21. The crank angle sensor 22 is attached to the reciprocating engine 3. The crank angle sensor 22 outputs a measurement signal corresponding to the rotation angle of the crankshaft to the controller 21. The controller 21 can grasp the rotation speed of the reciprocating engine 3 based on the measurement signal of the crank angle sensor 22.

[0064] The accelerator position sensor 23 is electrically connected to the controller 21. The accelerator position sensor 23 is attached to the accelerator pedal. The accelerator position sensor 23 outputs a signal corresponding to the depression amount of the accelerator pedal to the controller 21. The controller 21 can grasp the required load of the reciprocating engine 3 based on the measurement signal of the accelerator position sensor 23.

[0065] The intake valve train 41, exhaust valve train 42, and third valve train 43 described above are each electrically connected to the controller 21. The controller 21 outputs control signals to the intake valve train 41, exhaust valve train 42, and third valve train 43, respectively, depending on the operating state of the reciprocating engine 3. The intake valve train 41 changes the valve timing and / or valve lift of the intake valve 34 based on the control signal from the controller 21. The exhaust valve train 42 changes the valve timing and / or valve lift of the exhaust valve 36 based on the control signal from the controller 21. The third valve train 43 switches the on-off valve 38 between open and closed states based on the control signal from the controller 21.

[0066] The intake port injector 44, the third port injector 46, and the hydrogen injector 47 are each electrically connected to the controller 21. The controller 21 outputs a control signal to each of the intake port injector 44, the third port injector 46, and the hydrogen injector 47. The intake port injector 44 injects a predetermined amount of hydrocarbon fuel into the intake port 33 at a predetermined timing based on the control signal from the controller 21. The third port injector 46 injects a predetermined amount of hydrocarbon fuel into the third port 37 at a predetermined timing based on the control signal from the controller 21. The hydrogen injector 47 injects a predetermined amount of hydrogen gas into the cylinder 31 at a predetermined timing based on the control signal from the controller 21.

[0067] The control system 2 has an ignition plug 26. The ignition plug 26 is attached to the reciprocating engine 3 and faces the inside of a cylinder 31. The ignition plug 26 is electrically connected to the controller 21. The controller 21 outputs a control signal to the ignition plug 26. The ignition plug 26 ignites the air-fuel mixture in the cylinder 31 at a predetermined timing based on the control signal from the controller 21.

[0068] The control system 2 also has an electric motor 27. The electric motor 27 is an assist motor that compensates for insufficient output of the reciprocating engine 3. The electric motor 27 is operated by receiving power supplied from a battery via an inverter 28. The electric motor 27 and the reciprocating engine 3 may be connected in series or in parallel. The combination of the reciprocating engine 3 and the electric motor 27 can output the driving force required to run the vehicle. The inverter 28 is electrically connected to the controller 21. The controller 21 outputs a control signal to the inverter 28. The inverter 28 operates the electric motor 27 based on the control signal from the controller 21.

[0069] The hydrocarbon fuel supply unit 45 and the hydrogen gas supply unit 5 described above are each electrically connected to the controller 21. The controller 21 outputs a control signal to the hydrocarbon fuel supply unit 45 or the hydrogen gas supply unit 5.

[0070] (6-stroke cycle) The reciprocating engine 3 performs a six-stroke cycle in order for the cracker 6 to crack the hydrocarbon fuel. Figure 4 shows the steps involved in the six-stroke cycle.

[0071] S11 is the intake stroke. During the intake stroke S11, the reciprocating engine 3 introduces intake air into the cylinder 31 as the piston 32 descends. During the intake stroke S11, the intake valve 34 opens. The intake air is introduced into the cylinder 31 through the intake port 33. The intake air includes at least fresh air. The intake air may also include EGR gas. This EGR gas is so-called external EGR gas that has been recirculated to the intake pipe through the EGR passage. During the intake stroke S11, the exhaust valve 36 may open. When the exhaust valve 36 opens, exhaust gas is introduced into the cylinder 31 through the exhaust port 35. The exhaust gas introduced into the cylinder 31 is so-called internal EGR gas. Note that the opening / closing valve 38 of the third port 37 is closed.

[0072] 4, the hydrogen injector 47 injects hydrogen gas into the cylinder 31 during the intake stroke S11. The hydrogen injector 47 may inject hydrogen gas during the compression stroke S12 following the intake stroke S11. The hydrogen injector 47 may inject hydrogen gas during the period from the intake stroke S11 to the compression stroke S12.

[0073] If there is a shortage of hydrogen gas, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the intake stroke S11 to make up for the shortage. Also, if there is no hydrogen gas, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the intake stroke S11, instead of the hydrogen injector 47. If there is a shortage of hydrogen gas to be supplied into the cylinder 31, the intake port injector 44 injects hydrocarbon fuel, thereby ensuring the required amount of fuel for the reciprocating engine 3. The reciprocating engine 3 can be operated using hydrocarbon fuel or both hydrocarbon fuel and hydrogen gas.

[0074] S12 is the compression stroke. In the compression stroke S12, the reciprocating engine 3 compresses the air-fuel mixture in the cylinder 31 by the upward movement of the piston 32. The intake valve 34, the exhaust valve 36, and the on-off valve 38 are all closed.

[0075] The spark plug 26 ignites the air-fuel mixture in the cylinder 31 near the top dead center of the compression stroke. The air-fuel mixture begins to burn. S13 is the expansion stroke. During the expansion stroke S13, the piston 32 descends due to the combustion of the air-fuel mixture. The intake valve 34, exhaust valve 36, and on-off valve 38 are all closed.

[0076] S14 is a recompression stroke. In the reciprocating engine 3, the piston 32 rises during the recompression stroke S14 to compress the combustion gas in the cylinder 31. In the recompression stroke S14, the on-off valve 38 opens. The compressed combustion gas is introduced into the cracker 6 through the third port 37. As will be described later, the hydrocarbon fuel injected into the third port 37 by the third port injector 46 during the exhaust stroke S16 is introduced into the cracker 6 together with the combustion gas. In the cracker 6, the hydrocarbon fuel is decomposed into carbon and hydrogen gas by the heat of the combustion gas and the catalyst. The carbon is stored in the cracker 6. The hydrogen gas permeates the separation membrane 63 of the cracker 6 due to the pressure of the combustion gas and is sent to the hydrogen gas supply unit 5.

[0077] Because the high pressure of the combustion gas in the recompression stroke S14 is applied to the cracker 6, the hydrogen gas produced in the cracker 6 quickly permeates the separation membrane 63. Because the hydrogen gas on the right side of the chemical reaction equation described above is discharged from the cracker 6, the cracking reaction of the hydrocarbon fuel in the cracker 6 is accelerated. The cracker 6, which utilizes the pressure of the recompression stroke S14 of the reciprocating engine 3, can produce the amount of hydrogen gas required to operate the reciprocating engine 3, even if it is small in size.

[0078] S15 is a re-expansion stroke. In the re-expansion stroke S15, the piston 32 descends. The on-off valve 38 opens in the re-expansion stroke S15. When the on-off valve 38 opens, the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder 31 from the third port 37. Opening the on-off valve 38 in the re-expansion stroke S15 is advantageous in reducing pumping loss in the reciprocating engine 3.

[0079] S16 is the exhaust stroke. During the exhaust stroke S16, the piston 32 of the reciprocating engine 3 rises, causing the combustion gas in the cylinder 31 to be discharged through the exhaust port 35. During the exhaust stroke S16, the exhaust valve 36 opens. Note that during the exhaust stroke S16, the intake valve 34 and the on-off valve 38 are closed. As will be described in detail later, during the exhaust stroke S16, the third port injector 46 injects hydrocarbon fuel into the third port 37.

[0080] After the exhaust stroke S16, the reciprocating engine 3 returns to the intake stroke S11.

[0081] In this way, the fuel reforming system 1 including the reciprocating engine 3 that runs a six-stroke cycle stores the carbon produced by the decomposition of hydrocarbon fuel in the cracker 6. Furthermore, because the reciprocating engine 3 burns the hydrogen gas produced by the decomposition of hydrocarbon fuel, no carbon oxides are produced due to combustion. The fuel reforming system 1 can achieve carbon neutrality.

[0082] Furthermore, since this fuel reforming system 1 utilizes the heat and pressure generated by the reciprocating engine 3, there is no need for a separate dedicated device to generate the heat and / or pressure required to decompose the hydrocarbon fuel. The fuel reforming system 1 is useful as an on-board system.

[0083] If the amount of carbon stored in the decomposer 6 increases, the carbon is recovered from the decomposer 6.

[0084] (Switching between 6-stroke and 4-stroke cycles) The reciprocating engine 3 included in the fuel reforming system 1 is also an engine that outputs driving force for running the vehicle. The operating state of the reciprocating engine 3 varies greatly from low load to high load and from low rotation to high rotation. When the rotation speed of the reciprocating engine 3 is low, the time per cycle is relatively long, so the cracker 6 can efficiently decompose the hydrocarbon fuel into carbon and hydrogen gas. However, when the rotation speed of the reciprocating engine 3 is high, the time per cycle is short, so it becomes difficult to ensure the time for the decomposition reaction of the hydrocarbon fuel, in other words, the reaction time.

[0085] Therefore, the vehicle control system 2 switches between a six-stroke cycle that decomposes hydrocarbon fuel and a four-stroke cycle that does not decompose hydrocarbon fuel depending on the operating state related to the rotation speed and required load of the reciprocating engine 3.

[0086] 5 shows a control map 101 of the reciprocating engine 3. The control map 101 corresponds to an operating region of the reciprocating engine 3 defined by the engine speed and required load. The controller 21 operates the reciprocating engine 3 in accordance with the control map 101.

[0087] The control map 101 divides the operating range of the reciprocating engine 3 into a first range 102 and a second range 103. The first range 102 is a range where the rotation speed is lower than the first rotation speed N1. The first range 102 also includes a range where the rotation speed is equal to or higher than the first rotation speed N1 and where the required load is lower than the load Pe1. The second range 103 is a range where the rotation speed is equal to or higher than the first rotation speed N1 and where the required load is equal to or higher than the load Pe1. The first rotation speed N1 may be a rotation speed included in the medium rotation speed range when the operating range of the reciprocating engine 3 is divided into three equal parts in the rotation speed direction into a low rotation speed range, a medium rotation speed range, and a high rotation speed range. The load Pe1 may be a load included in the medium load range when the operating range of the reciprocating engine 3 is divided into three equal parts in the load direction into a low load range, a medium load range, and a high load range.

[0088] In the first region 102, the controller 21 causes the reciprocating engine 3 to execute a six-stroke cycle. Specifically, the controller 21 causes the intake valve 34 and the exhaust valve 36 to open at predetermined timings through the intake valve train 41 and the exhaust valve train 42, and also causes the on-off valve 38 to open at predetermined timings through the third valve train 43.

[0089] Figure 6 shows an example of lift curves for the intake valve 34, exhaust valve 36, and on-off valve 38. The horizontal axis of Figure 6 represents crank angle, and the vertical axis represents valve lift. Chart 601 shows an example of lift curves for the intake valve 34, exhaust valve 36, and on-off valve 38 during a six-stroke cycle.

[0090] In chart 601, the on-off valve 38 opens during the re-compression stroke and also opens during the re-expansion stroke. During the re-compression stroke, the combustion gas in the cylinder 31 is introduced into the third port 37, and during the re-expansion stroke, the combustion gas flows from the third port 37 into the cylinder 31.

[0091] Chart 601 shows a lift curve when the required load is relatively low. In the exhaust stroke following the re-expansion stroke, the exhaust valve 36 opens. Exhaust gas in the cylinder 31 is discharged to the exhaust port 35. Then, in the intake stroke following the exhaust stroke, the exhaust valve 36 opens again. Some of the exhaust gas in the exhaust port 35 is reintroduced into the cylinder 31 as EGR gas. When the load of the reciprocating engine 3 is relatively low, the exhaust valve 36 opens in the intake stroke, for example, at maximum lift. Also, in the intake stroke, the intake valve 34 opens. In chart 601, the intake valve 34 has maximum lift. A relatively large amount of fresh air is introduced into the cylinder 31, and a relatively small amount of EGR gas is introduced.

[0092] Here, when the reciprocating engine 3 is executing a six-stroke cycle, there are two more strokes per cycle than when it is executing a four-stroke cycle. The output of the reciprocating engine 3 when executing a six-stroke cycle is two-thirds of the output when it is executing a four-stroke cycle. When the required load of the reciprocating engine 3 is high, it is difficult for the reciprocating engine 3 when executing a six-stroke cycle to meet the required load.

[0093] Therefore, in the vehicle control system 2, when the reciprocating engine 3 is running a six-stroke cycle and the required load of the reciprocating engine 3 is equal to or greater than the load Pe2, the electric motor 27 is operated (see FIG. 5). The electric motor 27 functions as an assist motor that compensates for the insufficient output of the reciprocating engine 3. The reciprocating engine 3 and the electric motor 27 work together to output the driving force required to run the vehicle.

[0094] The load Pe2 may be a load included in the high load range when the operating range of the reciprocating engine 3 is divided into three equal parts in the load direction: low load, medium load, and high load.

[0095] When the required load is low, the amount of combustion gas introduced into the cracker 6 decreases. Even if the rotational speed of the reciprocating engine 3 is high and the reaction time is short, the cracker 6 can crack the hydrocarbon fuel if its cracking power is high. Therefore, in the control map 101 of FIG. 5, the first region 102 in which the six-stroke cycle is executed is expanded to the high rotational speed, low load region. Expanding the first region 102 narrows the region in which hydrocarbon fuel is combusted, which is advantageous for carbon neutralization. Note that the first region 102 may only be the region where the rotational speed is lower than the first rotational speed N1.

[0096] The controller 21 also causes the reciprocating engine 3 to operate in a four-stroke cycle in the second region 103. Specifically, the controller 21 opens the intake valve 34 and the exhaust valve 36 at predetermined timing via the intake valve train 41 and the exhaust valve train 42, while stopping the opening of the on-off valve 38 via the third valve train 43. Chart 602 in FIG. 6 shows lift curves of the intake valve 34 and the exhaust valve 36 when the four-stroke cycle is being performed. When the four-stroke cycle is being performed, the recompression stroke and the re-expansion stroke are omitted, thereby reducing pumping losses in the reciprocating engine 3. Although the reciprocating engine 3 runs on hydrocarbon fuel, its fuel consumption can be reduced. The reciprocating engine 3 has a mechanism for changing the speed ratio between the crankshaft and the camshaft when switching between the six-stroke cycle and the four-stroke cycle.

[0097] The flowchart in Fig. 7 shows a control procedure for switching between a six-stroke cycle and a four-stroke cycle. In step S131 after starting, the controller 21 reads various signals. In the following step S132, the controller 21 determines whether the operating state of the reciprocating engine 3 is in the first region 102 based on the read signals and the control map 101. If the determination in step S132 is Yes, that is, if the operating state of the reciprocating engine 3 is in the first region 102, the controller 21 opens and closes the on-off valve 38 of the third port 37 in step S133. Furthermore, in step S134, the controller 21 causes the third port injector 46 to inject hydrocarbon fuel into the third port 37. The reciprocating engine 3 operates in a six-stroke cycle.

[0098] In step S135, the controller 21 adjusts the opening of the intake valve 34 and / or the exhaust valve 36 in accordance with the required output. In step S136, the controller 21 determines whether the required load Pe is equal to or greater than the load Pe2. If the determination in step S136 is Yes, the controller 21 operates the electric motor 27 in step S137 to cause the electric motor 27 to assist the reciprocating engine 3. If the determination in step S136 is No, the controller 21 does not operate the electric motor 27.

[0099] Returning to step S132, if the determination in step S132 is No, the controller 21 stops the on-off valve 38 in step S138. The reciprocating engine 3 executes a four-stroke cycle.

[0100] In step S139, the controller 21 adjusts the opening of the intake valve 34 and / or the exhaust valve 36 according to the required output.

[0101] (Fuel injection timing) The fuel reforming system 1 decomposes hydrocarbon fuel by utilizing the piston stroke of the reciprocating engine 3. In this case, it is necessary to ensure a sufficiently long reaction time for the hydrocarbon fuel, because if a long reaction time cannot be ensured, the yield of carbon and hydrogen gas in the fuel reforming system 1 will decrease.

[0102] The fuel reforming system 1 is characterized by the timing at which the third port injector 46 injects fuel.

[0103] Fig. 8 shows the fuel injection timing of the third port injector 46. A chart 801 in Fig. 8 shows the valve lifts of the intake valve 34, the exhaust valve 36, and the on-off valve 38, and the fuel injection timing of the third port injector 46. In the chart 801 in Fig. 8, the fuel injection timing of the third port injector 46 is indicated by reference numeral 461. Furthermore, a chart 802 in Fig. 8 shows the pressure changes in the third port 37 and the cracker 6.

[0104] The third port injector 46 injects hydrocarbon fuel into the third port 37 while the on-off valve 38 is closed. More specifically, as shown in S16-S13 of Fig. 8 , the third port injector 46 injects hydrocarbon fuel into the third port 37 between the cracker 6 and the on-off valve 38 during the exhaust stroke. In other words, the third port injector 46 injects fuel upstream of the cracker 6 with reference to the flow of fuel gas flowing from the cylinder 31 to the cracker 6. The injected hydrocarbon fuel vaporizes while the on-off valve 38 is closed, more specifically, while the reciprocating engine 3 passes through the exhaust stroke, intake stroke, compression stroke, and expansion stroke.

[0105] The third port injector 46 is an injector with a high injection pressure so that the required amount of hydrocarbon fuel can be injected while the on-off valve 38 is closed. An in-cylinder direct injection injector can be used as the third port injector 46. An in-cylinder direct injection injector atomizes the injected fuel, which is also advantageous for vaporizing the hydrocarbon fuel.

[0106] When the third port injector 46 injects hydrocarbon fuel, there is substantially no gas flow through the third port 37. This is because the on-off valve 38 is closed. A high injection pressure of the third port injector 46 is advantageous for promoting vaporization of the hydrocarbon fuel when the hydrocarbon fuel is injected into the third port 37, where there is substantially no gas flow.

[0107] The third port injector 46 may inject hydrocarbon fuel while the on-off valve 38 is closed, but the longest time for vaporizing the hydrocarbon fuel can be ensured by injecting fuel at the timing furthest from the timing at which the on-off valve 38 opens. The third port injector 46 may also inject hydrocarbon fuel immediately after the on-off valve 38 closes. The timing immediately after the on-off valve 38 closes corresponds to the exhaust stroke described above.

[0108] As described above, the on-off valve 38 opens during the recompression stroke. As indicated by the black arrow in S14, combustion gas flows from the cylinder 31 toward the cracker 6. The combustion gas carries the hydrocarbon fuel in the third port 37 toward the cracker 6. A catalytic reaction in the cracker 6 decomposes at least a portion of the hydrocarbon fuel into carbon and hydrogen gas. The carbon is stored in the cracker 6, and the hydrogen gas is sent to the hydrogen gas supply unit 5 through the hydrogen gas passage 50. When the piston 32 reaches top dead center during the recompression stroke, the combustion gas containing the hydrocarbon fuel and a portion of the carbon and hydrogen gas pass through the catalyst unit 64 of the cracker 6 and flow into the space 65.

[0109] In the re-expansion stroke following the re-compression stroke, the on-off valve 38 opens and the piston 32 descends. As the piston 32 descends, the gas in the third port 37 flows from the cracker 6 toward the cylinder 31 (see the open arrow in S15). The combustion gas containing hydrocarbon fuel and a portion of the carbon and hydrogen gas in the space 65 flow with the gas flow toward the catalyst section 64 and remain there.

[0110] When the on-off valve 38 closes during the exhaust stroke after the re-expansion stroke, the on-off valve 38 remains closed during the subsequent exhaust stroke, intake stroke, compression stroke, and expansion stroke (see S16-S13). Because the hydrocarbon fuel remains in the catalyst section 64, a sufficiently long time is ensured for the hydrocarbon fuel to decompose during the period until the on-off valve 38 opens during the re-compression stroke S14.

[0111] The third port injector 46 injects the hydrocarbon fuel during the stroke when the on-off valve 38 is closed, which ensures a long time for the hydrocarbon fuel to vaporize and a long time for the hydrocarbon fuel to remain in the catalyst section 64 of the cracker 6, thereby increasing the yield of carbon and hydrogen gas in the fuel reforming system 1.

[0112] During the exhaust stroke from S16 to S13, as described above, the third port injector 46 injects hydrocarbon fuel to promote vaporization. In the subsequent recompression stroke at S14, the vaporized hydrocarbon fuel is transported to the catalyst section 64 by the combustion gas.

[0113] (Modification of fuel injection timing to the third port) 9 shows a modified example of the third port injector 46. In this modified example, the third port injector 46 is located in the space 65 of the cracker 6 and injects hydrocarbon fuel into the space 65. In other words, the third port injector 46 is located downstream of the catalyst section 64 of the cracker 6 with respect to the flow direction of the combustion gas flowing from the cylinder 31 to the cracker 6.

[0114] Fig. 10 shows the fuel injection timing of the third port injector 46 that injects hydrocarbon fuel into the space 65. A chart 801 in Fig. 10 shows the valve lifts of the intake valve 34, the exhaust valve 36, and the on-off valve 38, and the fuel injection timing of the third port injector 46. In the chart 801 in Fig. 10, the fuel injection timing of the third port injector 46 is indicated by reference numeral 462. Furthermore, a chart 802 in Fig. 10 shows the pressure changes in the third port 37 and the cracker 6.

[0115] The third port injector 46 injects hydrocarbon fuel into the space 65 while the on-off valve 38 is open and the piston 32 is moving up. More specifically, as shown in S14 in Fig. 10, the third port injector 46 injects hydrocarbon fuel into the space 65 of the cracker 6 during the recompression stroke.

[0116] Here, the third port injector 46 may inject the hydrocarbon fuel into the space 65 in the latter half of the recompression stroke. The latter half of the recompression stroke may be the latter half of the recompression stroke when the recompression stroke is divided into an equal first half and a second half. This is because the pressure in the third port 37 and the cracker 6 is high and the temperature in the third port 37 and the cracker 6 is also high in the latter half of the recompression stroke, which is advantageous for vaporizing the injected hydrocarbon fuel. Furthermore, as will be described later, in order to retain the hydrocarbon fuel in the catalyst section 64 by utilizing the gas flow in the re-expansion stroke, it is advantageous to inject the hydrocarbon fuel into the space 65 in the latter half of the recompression stroke.

[0117] In the re-expansion stroke following the recompression stroke, the injected hydrocarbon fuel travels from the space 65 to the catalyst section 64 of the cracker 6 along with the gas flow from the cracker 6 toward the cylinder 31, and remains there (see S15). Thereafter, while the on-off valve 38 is closed, specifically during the exhaust stroke, intake stroke, compression stroke, and expansion stroke, the hydrocarbon fuel vaporizes and is decomposed into carbon and hydrogen gas by the catalyst (see S16-S13). The carbon adheres to the surface of the catalyst support 61.

[0118] The on-off valve 38 then opens during the recompression stroke (see S14). As indicated by the black arrows, the combustion gas flows from the cylinder 31 toward the cracker 6. Due to the gas flow within the third port 37, the hydrogen gas passes through the separation membrane 63 to the hydrogen gas passage 50, and is then sent to the hydrogen gas supply unit 5 through the hydrogen gas passage 50.

[0119] Then, during the recompression stroke, the third port injector 46 injects hydrocarbon fuel into the space 65 as previously described.

[0120] The third port injector 46 injects the hydrocarbon fuel during the stroke in which the on-off valve 38 is open and the piston 32 is rising, thereby ensuring a long period of time for the hydrocarbon fuel to vaporize and a long period of time for the hydrocarbon fuel to remain in the catalyst section 64 of the cracker 6, thereby increasing the yield of carbon and hydrogen gas in the fuel reforming system 1.

[0121] (Atypical 4-stroke cycle) The reciprocating engine 3 may execute a modified four-stroke cycle instead of a six-stroke cycle. Figure 11 shows the strokes included in the modified four-stroke cycle. In Figure 11, the third port injector 46 injects hydrocarbon fuel between the cracker 6 and the on-off valve 38.

[0122] S21 is the compression stroke. In the compression stroke S21, the reciprocating engine 3 compresses the air-fuel mixture in the cylinder 31 by the upward movement of the piston 32. The intake valve 34, the exhaust valve 36, and the on-off valve 38 are all closed.

[0123] The hydrogen injector 47 injects hydrogen gas into the cylinder 31 during the compression stroke S21. If there is a shortage of hydrogen gas, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the scavenging stroke S24 described below to make up for the shortage. If there is no hydrogen gas, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the scavenging stroke S24 instead of the hydrogen injector 47. If there is a shortage of hydrogen gas to be supplied into the cylinder 31, the intake port injector 44 injects hydrocarbon fuel, thereby ensuring the required amount of fuel for the reciprocating engine 3. The reciprocating engine 3 can be operated using hydrocarbon fuel or both hydrocarbon fuel and hydrogen gas.

[0124] Furthermore, in the compression stroke S21, the third port injector 46 injects hydrocarbon fuel into the third port 37. As described above, a long period of time is ensured for the hydrocarbon fuel to vaporize.

[0125] The spark plug 26 ignites the air-fuel mixture in the cylinder 31 near the top dead center of the compression stroke. The air-fuel mixture begins to burn. S22 is the expansion stroke. During the expansion stroke S22, the piston 32 descends due to the combustion of the air-fuel mixture. The intake valve 34, exhaust valve 36, and on-off valve 38 are all closed.

[0126] S23 is a recompression stroke. In the recompression stroke S23, the reciprocating engine 3 compresses the combustion gas in the cylinder 31 by raising the piston 32. In the recompression stroke S23, the on-off valve 38 opens. The compressed combustion gas is introduced into the cracker 6 through the third port 37. The hydrocarbon fuel that was injected into the third port 37 in the compression stroke S21 is introduced into the cracker 6 together with the combustion gas. As described above, in the cracker 6, the hydrocarbon fuel is decomposed into carbon and hydrogen gas by the heat of the combustion gas and the catalyst. The carbon is stored in the cracker 6. The hydrogen gas permeates the separation membrane 63 of the cracker 6 due to the pressure of the combustion gas and is sent to the hydrogen gas supply unit 5.

[0127] S24 is a scavenging stroke. In the scavenging stroke S24, the piston 32 descends. The on-off valve 38 opens in the scavenging stroke S24. When the on-off valve 38 opens, the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder 31 through the third port 37.

[0128] In the scavenging stroke S24, the exhaust valve 36 opens. Combustion gas in the cylinder 31 is discharged to the exhaust port 35. In the scavenging stroke S24, the intake valve 34 also opens. Intake air is introduced into the cylinder 31 through the intake port 33. The intake air includes at least fresh air. The intake air may also include EGR gas. This EGR gas is so-called external EGR gas that has been recirculated to the intake pipe through the EGR passage. The reciprocating engine 3 performs gas exchange in the cylinder 31 in the scavenging stroke S24.

[0129] After the scavenging stroke S24, the reciprocating engine 3 returns to the compression stroke S21.

[0130] In this way, the fuel reforming system 1 including the reciprocating engine 3 that runs a modified four-stroke cycle can store the carbon produced by the decomposition of hydrocarbon fuel in the cracker 6. Furthermore, because the reciprocating engine 3 burns the hydrogen gas produced by the decomposition of hydrocarbon fuel, no carbon oxides are produced due to combustion. The fuel reforming system 1 can achieve carbon neutrality.

[0131] Furthermore, since the third port injector 46 injects hydrocarbon fuel into the third port 37 during the compression stroke S21, when the on-off valve 38 is closed, a long period of time can be secured for the hydrocarbon fuel to vaporize and also for the hydrocarbon fuel to decompose.

[0132] 12 shows a modified third port injector 46 for a reciprocating engine 3 running a modified four-stroke cycle. The third port injector 46 injects hydrocarbon fuel into a space 65 in the cracker 6.

[0133] The third port injector 46 injects hydrocarbon fuel into the space 65 during the recompression stroke S23 when the on-off valve 38 is open and the piston 32 is ascending. As described above, the hydrocarbon fuel injected into the space 65 reaches the catalyst unit 64 during the subsequent scavenging stroke S24 due to the gas flow from the cracker 6 to the cylinder 31. The hydrocarbon fuel is then decomposed into carbon and hydrogen gas during the compression stroke S21 and the expansion stroke S22. Because the third port injector 46 injects hydrocarbon fuel downstream of the catalyst unit 64 during the recompression stroke S23 when the on-off valve 38 is open and the piston 32 is ascending, a long period of time can be secured for the hydrocarbon fuel to vaporize and for the hydrocarbon fuel to be decomposed.

[0134] It should be noted that the technology disclosed herein is not limited to the above configuration. For example, the reciprocating engine 3 may be a compression ignition engine.

[0135] Furthermore, the cracker 6 of the fuel reforming system 1 is not limited to a membrane reactor. The cracker 6 may have any structure as long as it can crack the hydrocarbon fuel using the heat and pressure of the combustion gas. [Explanation of symbols]

[0136] 1 Fuel reforming system 3 Reciprocating engine 31 cylinders 32 piston 33 Intake port 35 exhaust port 37 Third Port 38 On-off valve 6 Decomposer 64 Catalyst section 65 spaces S11 Intake stroke S12 compression stroke S13 Expansion stroke S14 Recompression process S15 Re-expansion stroke S16 Exhaust stroke S21 compression stroke S22 Expansion stroke S23 Recompression process S24 Scavenging stroke

Claims

1. a reciprocating engine mounted on a vehicle and having pistons reciprocating within cylinders; a cracker for cracking the hydrocarbon fuel into carbon and hydrogen gas; a hydrocarbon fuel supply device that supplies the hydrocarbon fuel to the cracker, the reciprocating engine has an intake port, an exhaust port, and a third port that connects the cylinder and the cracker and is opened and closed by an on-off valve, the on-off valve opens during a stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises, and during a stroke in which the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder through the third port as the piston descends, A fuel reforming system for an engine-equipped vehicle, wherein the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker during a stroke in which the on-off valve is closed.

2. a reciprocating engine mounted on a vehicle and having pistons reciprocating within cylinders; a cracker for cracking the hydrocarbon fuel into carbon and hydrogen gas; a hydrocarbon fuel supply device that supplies the hydrocarbon fuel to the cracker, the reciprocating engine has an intake port, an exhaust port, and a third port that connects the cylinder and the cracker and is opened and closed by an on-off valve, the on-off valve opens during a stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises, and during a stroke in which the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder through the third port as the piston descends, the cracker includes a catalyst section that decomposes the hydrocarbon fuel using a catalyst, and a space that is on the opposite side of the catalyst section from the third port and is connected to the catalyst section, A fuel reforming system for an engine-equipped vehicle, wherein the hydrocarbon fuel supply device injects the hydrocarbon fuel into the space while the on-off valve is open and the piston is in an upward stroke.

3. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, The hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port immediately after the open / close valve closes.

4. 3. The fuel reforming system for an engine-equipped vehicle according to claim 2, A fuel reforming system for an engine-equipped vehicle, wherein the hydrocarbon fuel supply device injects the hydrocarbon fuel into the space during the latter half of the piston's upward stroke.

5. 3. The fuel reforming system for an engine-equipped vehicle according to claim 1, The reciprocating engine is an intake stroke in which at least intake air is introduced into the cylinder through the intake port as the piston descends; a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rise of the piston; an expansion stroke in which the piston descends due to combustion of the air-fuel mixture; a recompression stroke in which the combustion gas is compressed by the rise of the piston; a re-expansion stroke in which the piston descends; and a six-stroke cycle having an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises; The on-off valve opens during the recompression stroke and the re-expansion stroke, and closes during the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke.

6. 3. The fuel reforming system for an engine-equipped vehicle according to claim 1, The reciprocating engine is a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rise of the piston; an expansion stroke in which the piston descends due to combustion of the air-fuel mixture; a recompression stroke in which the combustion gas is compressed by the rising of the piston; and a modified four-stroke cycle having a scavenging stroke in which exhaust gas in the cylinder is discharged through the exhaust port while at least intake air is introduced into the cylinder through the intake port as the piston descends; The on-off valve opens during the recompression stroke and the scavenging stroke, and closes during the compression stroke and the expansion stroke.

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