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 at least in a stroke in which combustion gas in the cylinder is supplied to the decomposition device due to lifting of a piston. The hydrocarbon fuel supply device injects hydrocarbon fuel toward the on-off valve between the on-off valve of the third port and the decomposition device in a stroke in which the on-off valve is opened and in which the piston is lifted.SELECTED DRAWING: Figure 2

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, the time for vaporizing the hydrocarbon fuel and / or the time for decomposing the hydrocarbon fuel may not be sufficiently long. As a result, the carbon and hydrogen gas yields of the fuel reforming system decrease. Hereinafter, the "reaction time" of hydrocarbon fuel refers to the time allowed for 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 longer the reaction time, the more hydrocarbon fuel is decomposed, and therefore the higher the carbon and hydrogen gas yields of the fuel reforming system. The reaction time is primarily determined by the operating state of the reciprocating engine. For example, if the reciprocating engine's rotation speed is high, the reaction time becomes shorter.

[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 at least during a stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises, The hydrocarbon fuel supply device injects hydrocarbon fuel toward the on-off valve of the third port between the on-off valve and the cracker while the on-off valve is open and the piston is in the upward stroke.

[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 when the piston rises after the expansion stroke. Combustion gas in the cylinder pushed by the piston is supplied to the cracker through the third port.

[0017] The hydrocarbon fuel supply device injects hydrocarbon fuel into the third port between the on-off valve and the cracker. The hydrocarbon fuel supply device also injects hydrocarbon fuel toward the on-off valve. The hydrocarbon fuel is injected in a direction opposite to the flow of combustion gas from the cylinder toward the cracker. Injecting the hydrocarbon fuel against the flow of combustion gas generates a strong gas flow in the third port. The strong gas flow quickly vaporizes the hydrocarbon fuel.

[0018] The hydrocarbon fuel is carried to the cracker by the combustion gas flowing from the cylinder to the cracker. The cracker cracks the hydrocarbon fuel using the heat of the combustion gas supplied from the cylinder and the pressure of the combustion gas caused by the rising of the piston. Because the vaporization of the hydrocarbon fuel is promoted, the hydrocarbon fuel is quickly decomposed into carbon and hydrogen gas even with a short reaction time. The yields of carbon and hydrogen gas of the fuel reforming system are increased. The cracker may store carbon. The hydrogen gas may be used as fuel for the reciprocating engine.

[0019] The on-off valve may also be opened during the piston's downward stroke after the hydrocarbon fuel has been supplied to the cracker. As the piston descends, the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder through the third port. Opening the on-off valve during this stroke is advantageous for reducing pumping losses in the reciprocating engine.

[0020] The hydrocarbon fuel supply device may be configured to increase the injection pressure of the hydrocarbon fuel when the reciprocating engine is in a first operating state at a high load compared to when the reciprocating engine is in a second operating state at a load lower than the first operating state.

[0021] When the load of the reciprocating engine is high, the amount of gas in the cylinder is greater than when the load is low, resulting in a higher flow rate of the combustion gas at the third port. When the load of the reciprocating engine is high, the hydrocarbon fuel supply device increases the injection pressure of the hydrocarbon fuel compared to when the load is low. The higher injection pressure increases the amount of hydrocarbon fuel injected into the third port. Even if the amount of hydrocarbon fuel increases, the higher flow rate promotes vaporization of the hydrocarbon fuel. As the amount of hydrocarbon fuel increases, the amount of hydrogen gas obtained by the cracker increases. When the load of the reciprocating engine is high, the amount of fuel required to operate the reciprocating engine increases. When the reciprocating engine operates using hydrogen gas as fuel, the fuel reforming system can accommodate the increased demand for hydrogen gas by increasing the injection pressure of the hydrocarbon fuel as the load of the reciprocating engine increases.

[0022] The hydrocarbon fuel supply device may be configured to increase the injection pressure of the hydrocarbon fuel when the reciprocating engine is in a third operating state at a high rotation speed compared to when the reciprocating engine is in a fourth operating state at a lower rotation speed than the third operating state.

[0023] When the rotation speed of the reciprocating engine is high, the flow velocity of the combustion gas at the third port is higher than when the rotation speed is low. When the rotation speed of the reciprocating engine is high, the injection pressure of the hydrocarbon fuel can be increased compared to when the rotation speed is low, and the hydrocarbon fuel can be injected toward the combustion gas flowing in at a high speed, thereby making the gas flow at the third port more intense. The intense gas flow can further promote the vaporization of the hydrocarbon fuel. When the rotation speed of the reciprocating engine is high, the reaction time is shorter, but increasing the injection pressure of the hydrocarbon fuel is advantageous for improving the carbon and hydrogen gas yield of the fuel reforming system by promoting the vaporization of the hydrocarbon fuel.

[0024] the fuel reforming system for the engine-equipped vehicle further includes a variable mechanism that is located at a position in the third port closer to the on-off valve than the hydrocarbon fuel supply device, and that changes the flow velocity of the combustion gas flowing from the cylinder toward the cracker, The variable mechanism may be configured to increase the flow velocity of the combustion gas when the reciprocating engine is in a first operating state of low load and low rotation speed compared to when the reciprocating engine is in a second operating state of higher load and higher rotation speed than the first operating state.

[0025] When the variable flow mechanism increases the flow velocity of the combustion gas in the third port, vaporization of the hydrocarbon fuel injected into the third port is further promoted. The variable flow mechanism relatively increases the flow velocity of the combustion gas when the reciprocating engine is in a first operating state at a low load.

[0026] When the reciprocating engine is in a first operating state, the amount of gas introduced into the cylinder is relatively small. Therefore, the flow velocity of the combustion gas introduced from the cylinder to the third port is relatively low. When the variable mechanism relatively increases the flow velocity of the combustion gas in the third port, the vaporization of the hydrocarbon fuel is promoted. The variable mechanism promotes the vaporization of the hydrocarbon fuel when the reciprocating engine is in an operating state that is unfavorable for the vaporization of the hydrocarbon fuel. The variable mechanism contributes to improving the carbon and hydrogen gas yield of the fuel reforming system.

[0027] the fuel reforming system for the engine-equipped vehicle further includes a variable mechanism that is located at a position in the third port closer to the on-off valve than the hydrocarbon fuel supply device, and that changes the flow velocity of the combustion gas flowing from the cylinder toward the cracker, The variable mechanism may be configured to increase the flow velocity of the combustion gas when the third port is at a low temperature compared to when the third port is at a high temperature.

[0028] A low temperature at the third port is unfavorable to vaporization of the hydrocarbon fuel injected into the third port. The variable temperature mechanism relatively increases the flow velocity of the combustion gas at the third port when the third port is low. The increased flow velocity of the combustion gas promotes vaporization of the hydrocarbon fuel even when the third port is low. The variable temperature mechanism increases the carbon and hydrogen gas yield of the fuel reforming system when the third port is low.

[0029] the on-off valve is a poppet valve, the variable mechanism is a mechanism for changing the lift amount of the on-off valve, The variable mechanism may decrease the lift amount when the flow velocity of the combustion gas is increased, and increase the lift amount when the flow velocity of the combustion gas is decreased.

[0030] When the lift amount of the on-off valve is small, the area through which the combustion gas passes becomes smaller, resulting in an increased flow rate of the combustion gas. When the lift amount of the on-off valve is large, the area through which the combustion gas passes becomes larger, resulting in a decreased flow rate of the combustion gas. The on-off valve can adjust the flow rate of the combustion gas according to the operating state of the reciprocating engine or the temperature of the third port. The on-off valve can also function as a variable mechanism. Using the on-off valve as a variable mechanism makes it possible to adjust the flow rate of the combustion gas without affecting the structure of the third port.

[0031] the variable mechanism is an opening adjustment valve that is located in the third port between the hydrocarbon fuel supply device and the on-off valve and changes the effective opening area of ​​the third port, The variable mechanism may reduce the degree of opening of the degree of opening adjustment valve when the flow velocity of the combustion gas is to be increased, and increase the degree of opening of the degree of opening adjustment valve when the flow velocity of the combustion gas is to be decreased.

[0032] The effective opening area of ​​the third port corresponds to the area through which the combustion gas passes. When the opening of the aperture control valve is small, the area through which the combustion gas passes is small, and therefore the flow rate of the combustion gas in the third port increases. When the opening of the aperture control valve is large, the area through which the combustion gas passes is large, and therefore the flow rate of the combustion gas decreases. The aperture control valve can adjust the flow rate of the combustion gas in the third port according to the operating state of the reciprocating engine or the temperature of the third port. An aperture control valve that is separate from the on-off valve omits the variable mechanism from the drive device of the on-off valve.

[0033] 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 rising 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 open during the recompression stroke and the re-expansion stroke, and closed during the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke.

[0034] 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.

[0035] The on-off valve opens during the recompression stroke and the re-expansion stroke. The on-off valve closes from the exhaust stroke following the re-expansion stroke until the expansion stroke. The hydrocarbon fuel supply device injects hydrocarbon fuel during the recompression stroke. The fuel reforming system can decompose the hydrocarbon fuel by utilizing the heat and pressure of the combustion gas during the recompression stroke.

[0036] The reciprocating engine is a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rising 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.

[0037] 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.

[0038] 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 hydrocarbon fuel supply device injects hydrocarbon fuel during the recompression stroke. The fuel reforming system can decompose the hydrocarbon fuel by utilizing the heat and pressure of the combustion gas during the recompression stroke. [Effects of the Invention]

[0039] 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]

[0040] [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 the relationship between the fuel injection pressure and the engine speed and the engine load. [Figure 10] FIG. 10 shows a third port according to a modified example. [Figure 11] FIG. 11 is a flowchart of engine control according to a modified example. [Figure 12] FIG. 12 shows the relationship between the change in opening of the opening adjustment valve and the engine load and rotation speed, and the relationship between the change in opening of the opening adjustment valve and the temperature of the third port. [Figure 13] FIG. 13 shows the change in the inflow velocity of the third port due to the change in the lift amount of the on-off valve. [Figure 14] Figure 14 shows the steps of a modified four-stroke cycle. DETAILED DESCRIPTION OF THE INVENTION

[0041] 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.

[0042] (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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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:

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] (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.

[0067] 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.

[0068] 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.

[0069] The temperature sensor 24 is electrically connected to the controller 21. The temperature sensor 24 outputs a measurement signal corresponding to the temperature of the third port 37 to the controller 21. The controller 21 can grasp the temperature of the third port 37 based on the measurement signal of the temperature sensor 24. The temperature sensor 24 may be a water temperature sensor. The water temperature sensor outputs a measurement signal corresponding to the temperature of the cooling water of the reciprocating engine 3 to the controller 21.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] (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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] S14 is a recompression stroke. In the recompression stroke S14, the reciprocating engine 3 compresses the combustion gas in the cylinder 31 by raising the piston 32. 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. Also, in the recompression stroke S14, the third port injector 46 injects hydrocarbon fuel into the third port 37. The hydrocarbon fuel 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] After the exhaust stroke S16, the reciprocating engine 3 returns to the intake stroke S11.

[0086] Instead of or together with opening the on-off valve 38 in the re-expansion stroke S15, the on-off valve 38 may be opened in the intake stroke S11. If the on-off valve 38 is opened in the intake stroke S11, the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder 31 through the third port 37. This combustion gas becomes EGR gas.

[0087] If the on-off valve 38 does not open in the re-expansion stroke S15, the hydrocarbon fuel introduced into the cracker 6 in the re-compression stroke S14 will remain in the cracker 6 for a long time, which has the advantage of promoting the cracking reaction of the hydrocarbon fuel.

[0088] 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.

[0089] 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.

[0090] If the amount of carbon stored in the decomposer 6 increases, the carbon is recovered from the decomposer 6.

[0091] (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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] (Structure that promotes vaporization of hydrocarbon fuel) The fuel reforming system 1 decomposes hydrocarbon fuel using the piston stroke of the reciprocating engine 3. Because the fuel reforming system 1 is coupled to the operation of the reciprocating engine 3, it may be difficult to ensure a sufficiently long reaction time for the hydrocarbon fuel. If the reaction time is not long enough, the yield of carbon and hydrogen gas produced by the fuel reforming system 1 may be reduced.

[0109] The fuel reforming system 1 has the characteristic of being able to promote vaporization of hydrocarbon fuel. As a result of promoting vaporization of hydrocarbon fuel, even if the reaction time of the hydrocarbon fuel cannot be secured sufficiently long, a decrease in the yield of carbon and hydrogen gas in the fuel reforming system 1 is suppressed.

[0110] FIG. 2 shows the arrangement of the third port injector 46. The third port injector 46 injects hydrocarbon fuel toward the on-off valve 38, i.e., toward the right of the page in FIG. 2 . More specifically, the axis X of the third port injector 46 is inclined at a predetermined angle θ with respect to the central axis of the third port 37. The third port injector 46 injects hydrocarbon fuel so as to face the combustion gas flowing through the third port 37 from the cylinder 31 toward the cracker 6 during the recompression stroke. Injecting hydrocarbon fuel against the flow of combustion gas generates a strong gas flow within the third port 37. The strong gas flow quickly vaporizes the hydrocarbon fuel. The hydrocarbon fuel is also carried to the cracker 6 by the combustion gas. Because the vaporization of the hydrocarbon fuel is promoted, the cracker 6 can quickly decompose the vaporized hydrocarbon fuel into carbon and hydrogen gas. As a result, the yields of carbon and hydrogen gas of the fuel reforming system 1 are increased.

[0111] Fig. 8 shows the fuel injection timing of the third port injector 46. The dashed line in chart 801 in Fig. 8 illustrates the inflow velocity of combustion gas into the third port 37 during the recompression stroke. Reference numeral 461 in Fig. 8 indicates the injection rate of fuel injection from the third port injector 46. Furthermore, chart 802 in Fig. 8 shows the valve lift of the on-off valve 38.

[0112] The third port injector 46 injects hydrocarbon fuel into the third port 37 immediately after the on-off valve 38 opens during the recompression stroke. This is because the velocity of the combustion gas flowing into the third port 37 increases due to the pressure difference between the cylinder 31 and the third port 37 immediately after the on-off valve 38 opens. At this timing, the hydrocarbon fuel is injected in a direction opposite to the flow of the combustion gas, generating a vigorous gas flow within the third port 37. This further promotes the vaporization of the hydrocarbon fuel.

[0113] The third port injector 46 injects all of the required amount of hydrocarbon fuel at this timing. The third port injector 46 is an injector with high injection pressure. The third port injector 46 can be an in-cylinder direct injection injector. The in-cylinder direct injection injector atomizes the injected fuel, which is also advantageous for vaporizing the hydrocarbon fuel. Note that the amount of hydrocarbon fuel injected at the above timing does not have to be all, but may be most of it.

[0114] The injection pressure of the hydrocarbon fuel may be increased in proportion to the flow velocity of the combustion gas at the third port 37. Figure 9 shows a relationship 901 of the injection pressure of the third port injector 46 with respect to the rotation speed and the required load of the reciprocating engine 3.

[0115] When the load of the reciprocating engine 3 is high, the amount of gas in the cylinder 31 is greater than when the load is low, and the flow velocity of the combustion gas at the third port 37 is therefore increased. When the load of the reciprocating engine 3 is high, the injection pressure of the third port injector 46 is increased compared to when the load is low, thereby increasing the amount of hydrocarbon fuel injected into the third port 37. As the amount of hydrocarbon fuel increases, the amount of hydrogen gas obtained by the cracker 6 also increases. When the load of the reciprocating engine 3 is high, the amount of hydrogen gas required as fuel to operate the reciprocating engine 3 increases, and increasing the injection pressure of the third port injector 46 can accommodate the increased required amount of hydrogen gas.

[0116] Furthermore, when the rotation speed of the reciprocating engine 3 is high, the flow velocity of the combustion gas at the third port 37 is higher than when the rotation speed is low. When the rotation speed of the reciprocating engine 3 is high, the injection pressure of the third port injector 46 can be increased compared to the injection pressure when the rotation speed is low, and the fuel can be injected toward the combustion gas flowing in at high speed, thereby making the gas flow at the third port 37 caused by the fuel injection of the third port injector 46 even more intense. The intense gas flow can further promote the vaporization of the hydrocarbon fuel. When the rotation speed of the reciprocating engine 3 is high, the reaction time is shorter, but increasing the injection pressure of the third port injector 46 is advantageous in improving the yield of carbon and hydrogen gas in the fuel reforming system 1 by promoting the vaporization of the hydrocarbon fuel.

[0117] 7, the controller 21 sets the injection pressure of the third port injector 46 based on the rotation speed and required load of the reciprocating engine 3 in accordance with the relationship 901 in FIG. 9. The maximum injection pressure of the third port injector 46 may be, for example, one digit MPa or higher.

[0118] As shown by the dashed line in chart 801, the inflow velocity of the combustion gas during the recompression stroke increases immediately after the on-off valve 38 opens, and then decreases temporarily. Thereafter, as the upward velocity of the piston 32 increases, the inflow velocity of the combustion gas also increases again. Then, when the piston 32 reaches top dead center, the inflow velocity becomes substantially zero.

[0119] The third port injector 46 may inject hydrocarbon fuel into the third port 37 throughout the period during which combustion gas flows into the third port 37 during the recompression stroke. The hydrocarbon fuel injected counter to the flow of combustion gas is diffused by the combustion gas flowing from the cylinder 31 toward the cracker 6. As a result, vaporization of the hydrocarbon fuel is promoted. Note that if the injection period of the third port injector 46 is long, the injection pressure of the third port injector 46 may be lower than the injection pressure of the in-cylinder direct injection injector.

[0120] Thus, the placement of the third port injector 46 allows the fuel reforming system 1 to enhance the vaporization of the hydrocarbon fuel, thereby increasing the carbon and hydrogen gas yield of the fuel reforming system 1 coupled to the operation of the reciprocating engine 3.

[0121] (Variation 1) 10 shows a modified example of the third port 37. The reciprocating engine 3 has a butterfly valve 39 located in the third port 37. The butterfly valve 39 is located in the third port 37 between the third port injector 46 and the on-off valve 38. In other words, with respect to the flow direction of the combustion gas from the cylinder 31 toward the cracker 6, the butterfly valve 39 is located upstream of the third port injector 46.

[0122] The opening of the butterfly valve 39 can be continuously adjusted. When the opening of the butterfly valve 39 is small, the effective opening area of ​​the third port 37 becomes small, and the speed of the combustion gas flowing from the cylinder 31 to the cracker 6 increases. When the opening of the butterfly valve 39 is large, the effective opening area of ​​the third port 37 becomes large, and the speed of the combustion gas flowing from the cylinder 31 to the cracker 6 decreases. The butterfly valve 39 is an example of a variable mechanism that changes the flow speed of the combustion gas flowing from the cylinder 31 to the cracker 6.

[0123] The controller 21 outputs a control signal to the butterfly valve 39 so as to change the opening degree of the butterfly valve 39. The butterfly valve 39 receives the control signal from the controller 21 and changes its opening degree.

[0124] Fig. 11 shows a flow relating to the operation control of the reciprocating engine 3 having the butterfly valve 39. Compared to the flow of Fig. 7, the flow of Fig. 11 adds step S1310 between step S134 and step S135. When the operating state of the reciprocating engine 3 is in the first region 102 and the on-off valve 38 is to be opened, the controller 21 sets the opening degree of the butterfly valve 39 in step S1310 according to the load and rotation of the reciprocating engine 3 and the temperature of the third port 37.

[0125] 12 illustrates relationships 1201 and 1202 used by the controller 21 in setting the opening of the butterfly valve 39 in step S1310. The relationships 1201 and 1202 are stored in the memory of the controller 21. The relationship 1201 indicates the relationship between the load and rotation of the reciprocating engine 3 and the opening of the butterfly valve 39, and the relationship 1202 indicates the relationship between the temperature of the third port 37 and the opening of the butterfly valve 39.

[0126] The controller 21 reduces the opening of the butterfly valve 39 when the load and rotation speed of the reciprocating engine 3 are low compared to when the load and rotation speed are high. When the load of the reciprocating engine 3 is low, the amount of gas in the cylinder 31 is relatively small, and the amount of fuel supplied to the cylinder 31 is also small. When the load and rotation speed of the reciprocating engine 3 are low, the flow velocity of the combustion gas introduced from the cylinder 31 to the third port 37 is low. When the load and rotation speed of the reciprocating engine 3 are low, the controller 21 reduces the opening of the butterfly valve 39, thereby increasing the flow velocity of the combustion gas flowing through the third port 37. As a result, vaporization of the hydrocarbon fuel injected from the third port injector 46 is promoted.

[0127] The opening degree of the butterfly valve 39 may be increased linearly as the load and rotation speed of the reciprocating engine 3 increase. Note that the opening degree of the butterfly valve 39 may be increased in stages as the load and rotation speed of the reciprocating engine 3 increase.

[0128] Furthermore, the opening of the butterfly valve 39 may be kept constant at a large opening when the load and rotational speed of the reciprocating engine 3 exceed a predetermined load and rotational speed. The opening of the butterfly valve 39 may be kept constant at a maximum opening when the load and rotational speed of the reciprocating engine 3 exceed a predetermined load and rotational speed. As the load on the reciprocating engine 3 increases, the amount of gas in the cylinder 31 increases, and the amount of fuel supplied to the cylinder 31 also increases. As the rotational speed increases, the duration of each stroke shortens. As a result, as the load and rotational speed of the reciprocating engine 3 increase, the flow velocity of the combustion gas introduced from the cylinder 31 to the third port 37 increases. Therefore, the opening of the butterfly valve 39 may be kept constant at a large opening. Increasing the opening of the butterfly valve 39 reduces the flow resistance of the third port 37, which has the advantage of reducing pumping losses in the reciprocating engine 3.

[0129] The controller 21 also reduces the opening of the butterfly valve 39 when the temperature of the third port 37 is low compared to when the temperature is high. This is because the hydrocarbon fuel injected into the third port 37 is less likely to vaporize when the temperature of the third port 37 is low. When the temperature of the third port 37 is low, the controller 21 reduces the opening of the butterfly valve 39, thereby increasing the flow rate of the combustion gas flowing through the third port 37. As a result, even when the temperature of the third port 37 is low, the strong flow of the combustion gas is utilized to promote vaporization of the hydrocarbon fuel injected from the third port injector 46. The temperature of the third port 37 is based on the measurement signal of the temperature sensor 24.

[0130] 12, the opening degree of the butterfly valve 39 may be increased linearly as the temperature of the third port 37 increases. Note that the opening degree of the butterfly valve 39 may be increased stepwise as the temperature of the third port 37 increases.

[0131] Furthermore, the opening of the butterfly valve 39 may be kept constant at a large opening when the temperature of the third port 37 exceeds a predetermined temperature. The opening of the butterfly valve 39 may be kept constant at a maximum opening when the temperature of the third port 37 exceeds a predetermined temperature. This is because, as the temperature of the third port 37 increases, the vaporization of the hydrocarbon fuel is promoted by that temperature. By increasing the opening of the butterfly valve 39, the pumping loss of the reciprocating engine 3 is reduced.

[0132] The controller 21 may store relational expressions corresponding to the relationships 1201 and 1202 in memory instead of the relationships 1201 and 1202.

[0133] Due to layout constraints of the reciprocating engine 3, the cracker 6 may be located far from the cylinder 31. If the cracker 6 is located far from the cylinder 31, the temperature of the combustion gas may decrease as it passes from the cylinder 31 to the cracker 6 through the third port 37, or the pressure of the cracker 6 may not be able to be increased significantly. The cracker 6 is unlikely to reach high temperatures and / or high pressures, especially when the load on the reciprocating engine 3 is low or the temperature of the third port 37 is low. When the cracker 6 is unlikely to reach high temperatures and / or high pressures, a variable mechanism for changing the flow rate of the combustion gas is effective because it can promote the vaporization of the hydrocarbon fuel and thereby increase the yield of carbon and hydrogen gas in the fuel reforming system 1. The variable mechanism expands the operating range of the reciprocating engine 3 in which fuel reforming is possible.

[0134] (Variation 2) Fig. 13 shows a modified example of the variable mechanism. Chart 1301 in Fig. 13 shows the inflow velocity of the combustion gas into the third port 37 during the recompression stroke and the injection rate 461 of the fuel injection from the third port injector 46. Chart 1302 in Fig. 13 shows the valve lift of the on-off valve 38.

[0135] The variable valve mechanism changes the flow velocity of the combustion gas flowing through the third port 37 by changing the lift amount of the on-off valve 38. The third valve train 43 that opens and closes the on-off valve 38 is a so-called CVVL. The third valve train 43 can continuously change the valve lift of the on-off valve 38. The third valve train 43 is an example of a variable valve mechanism. Note that if the lift amount of the on-off valve 38 is variable, the butterfly valve 39 is omitted.

[0136] As indicated by the open arrow in chart 1302, when the lift of the on-off valve 38 decreases, the effective cross-sectional area through which the combustion gas flows in the third port 37 decreases, thereby increasing the flow velocity of the combustion gas (see the open arrow in chart 1301). The controller 21 changes the valve lift of the on-off valve 38 through the third valve gear 43 in accordance with the load of the reciprocating engine 3 and the temperature of the third port 37. For example, the vertical axes of the relationships 1201 and 1202 shown in FIG. 12 may represent the lift of the on-off valve 38 instead of the opening degree of the butterfly valve 39. The controller 21 reduces the lift of the on-off valve 38 when the load of the reciprocating engine 3 is low compared to when the load is high. As a result of the increase in the flow velocity of the combustion gas flowing through the third port 37, vaporization of the hydrocarbon fuel injected from the third port injector 46 is promoted.

[0137] The lift amount of the on-off valve 38 may be increased linearly as the load on the reciprocating engine 3 increases. Note that the lift amount of the on-off valve 38 may be increased stepwise as the load on the reciprocating engine 3 increases. Also, the lift amount of the on-off valve 38 may be kept constant at a large lift amount when the load on the reciprocating engine 3 exceeds a predetermined load. The lift amount of the on-off valve 38 may be kept constant at a maximum lift amount when the load on the reciprocating engine 3 exceeds a predetermined load.

[0138] The controller 21 also reduces the lift amount of the on-off valve 38 when the temperature of the third port 37 is low compared to when the temperature is high. Even when the temperature of the third port 37 is low, the velocity of the combustion gas increases, which promotes vaporization of the hydrocarbon fuel injected from the third port injector 46.

[0139] The lift amount of the on-off valve 38 may be increased linearly as the temperature of the third port 37 increases. Alternatively, the lift amount of the on-off valve 38 may be increased stepwise as the temperature of the third port 37 increases. The lift amount of the on-off valve 38 may be constant at a large lift amount when the temperature of the third port 37 exceeds a predetermined temperature. The lift amount of the on-off valve 38 may be constant at a maximum lift amount when the temperature of the third port 37 exceeds a predetermined temperature.

[0140] (Atypical 4-stroke cycle) When the fuel reforming system 1 reforms hydrocarbon fuel, the reciprocating engine 3 may execute a modified four-stroke cycle instead of a six-stroke cycle. Figure 14 shows each stroke included in the modified four-stroke cycle.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] S23 is a recompression stroke. During the recompression stroke S23, the reciprocating engine 3 compresses the combustion gas in the cylinder 31 by raising the piston 32. During 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. During the recompression stroke S23, the third port injector 46 injects hydrocarbon fuel into the third port 37. As shown in FIG. 2, the third port injector 46 injects the hydrocarbon fuel toward the on-off valve 38. Vaporization of the hydrocarbon fuel is promoted. The injection pressure of the hydrocarbon fuel is changed depending on the rotation speed and required load of the reciprocating engine 3. The hydrocarbon fuel 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 a 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.

[0145] 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.

[0146] 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.

[0147] After the scavenging stroke S24, the reciprocating engine 3 returns to the compression stroke S21.

[0148] 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.

[0149] 10, the reciprocating engine 3 that executes a modified four-stroke cycle may have a butterfly valve 39 as a variable mechanism in the third port 37. The controller 21 sets the opening degree of the butterfly valve 39 in accordance with the load of the reciprocating engine 3 and the temperature of the third port 37.

[0150] Furthermore, in the reciprocating engine 3 that executes a modified four-stroke cycle, the lift amount of the on-off valve 38 may be set in accordance with the load of the reciprocating engine 3 and the temperature of the third port 37 .

[0151] 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.

[0152] 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]

[0153] 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 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 at least during a stroke in which the combustion gas in the cylinder is supplied to the cracker as the piston rises, a hydrocarbon fuel supply device that injects hydrocarbon fuel toward the on-off valve of the third port between the on-off valve and the cracker while the on-off valve is open and the piston is in an upward stroke.

2. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, A fuel reforming system for an engine-equipped vehicle, wherein the hydrocarbon fuel supply device increases the injection pressure of the hydrocarbon fuel when the reciprocating engine is in a first operating state under high load compared to when the reciprocating engine is in a second operating state under a lower load than the first operating state.

3. 3. The fuel reforming system for an engine-equipped vehicle according to claim 1, The hydrocarbon fuel supply device is a fuel reforming system for an engine-equipped vehicle, which increases the injection pressure of the hydrocarbon fuel when the reciprocating engine is in a third operating state at high revolutions compared to when the reciprocating engine is in a fourth operating state at lower revolutions than the third operating state.

4. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, a variable mechanism that is located in the third port at a position closer to the on-off valve than the hydrocarbon fuel supply device and that changes the flow velocity of the combustion gas flowing from the cylinder toward the cracker, The variable mechanism increases the flow rate of the combustion gas when the reciprocating engine is in a first operating state of low load and low rotation compared to when the reciprocating engine is in a second operating state of higher load and higher rotation than the first operating state.

5. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, a variable mechanism that is located in the third port at a position closer to the on-off valve than the hydrocarbon fuel supply device and that changes the flow velocity of the combustion gas flowing from the cylinder toward the cracker, A fuel reforming system for an engine-equipped vehicle, wherein the variable mechanism increases the flow velocity of the combustion gas when the third port is at a low temperature compared to when the third port is at a high temperature.

6. 6. The fuel reforming system for an engine-equipped vehicle according to claim 4 or 5, the on-off valve is a poppet valve, the variable mechanism is a mechanism for changing the lift amount of the on-off valve, The variable mechanism reduces the lift amount when the flow velocity of the combustion gas is increased, and increases the lift amount when the flow velocity of the combustion gas is decreased.

7. 6. The fuel reforming system for an engine-equipped vehicle according to claim 4 or 5, the variable mechanism is an opening adjustment valve that is located in the third port between the hydrocarbon fuel supply device and the on-off valve and changes the effective opening area of ​​the third port, A fuel reforming system for an engine-equipped vehicle, wherein the variable mechanism reduces the opening of the opening adjustment valve when the flow rate of the combustion gas is increased, and increases the opening of the opening adjustment valve when the flow rate of the combustion gas is decreased.

8. 2. 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 rising 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.

9. 2. 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 rising 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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