CN114810436B - Fuel reforming device - Google Patents

Abstract

A fuel reforming device (100) for reforming fuel by oxidation reaction is provided with a double-layer tube (19) having an outer tube (191) and an inner tube (192) extending in the vertical direction, and a cylindrical space (193) is formed between the outer tube (191) and the inner tube (192). The outer tube (191) is provided with an introduction hole (194) penetrating the lower part of the outer tube (191) to introduce fuel and air into the cylindrical space (193), an air discharge hole (195) penetrating the upper part of the outer tube (191) to discharge air from the cylindrical space (193), and fuel discharge holes (196 a,196 b) penetrating between the introduction hole (194) and the air discharge hole (195) of the outer tube (191) to discharge fuel from the cylindrical space (193). The upper end (193 a) and the lower end (193 b) of the cylindrical space are closed. The double-layer pipe (19) is configured such that the fuel supplied through the introduction hole (194) undergoes an oxidation reaction in the presence of a catalyst in a cylindrical space from the lower end (193 b) to the fuel discharge holes (196 a,196 b).

Description

Fuel reforming device

Technical Field

The present invention relates to a fuel reforming device that reforms fuel supplied to a compression ignition engine.

Background

Conventionally, an apparatus for reforming fuel by oxidizing fuel with an oxidizing agent has been known (for example, see patent document 1). The apparatus described in patent document 1 is configured as a double-tube reactor in which a reaction field is formed between an outer tube member and an inner tube member which are coaxially provided, a mixture of fuel and air is supplied as a reactant, and a mixture of reformed fuel and air is discharged as a product.

In the apparatus described in patent document 1, since the reformed fuel and air are discharged as a mixed gas, a gas-liquid separator needs to be provided at the rear stage of the double-pipe reactor in order to obtain the reformed fuel, and the overall configuration of the fuel reforming apparatus is complicated.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2018-178974 (JP 2018-178974A).

Disclosure of Invention

In one embodiment of the present invention, a fuel reforming apparatus for reforming fuel by oxidation reaction includes a double-layer pipe having an outer pipe and an inner pipe extending in a vertical direction, and a cylindrical space is formed between the outer pipe and the inner pipe. The outer tube is provided with an introduction hole penetrating a lower portion of the outer tube to introduce fuel and air into the cylindrical space, an air discharge hole penetrating an upper portion of the outer tube to discharge air from the cylindrical space, and a fuel discharge hole penetrating between the introduction hole of the outer tube and the air discharge hole to discharge fuel from the cylindrical space. The upper and lower ends of the cylindrical space are closed. The double-layer pipe is configured such that the fuel supplied through the introduction hole undergoes an oxidation reaction in the presence of a catalyst in a cylindrical space from the lower end to the fuel discharge hole.

Drawings

The objects, features and advantages of the present invention are further elucidated by the following description of embodiments in connection with the accompanying drawings.

Fig. 1 is a diagram schematically showing an example of the internal structure of an engine to which a fuel reforming device according to an embodiment of the present invention is applied.

Fig. 2 is a graph for explaining the relationship between the octane number and ignitability of the fuel.

Fig. 3 is a diagram for explaining a chemical reaction when reforming fuel.

Fig. 4 is a diagram for explaining the extent of progress of the oxidation reaction of the fuel.

Fig. 5 is a diagram schematically showing an example of the structure of a fuel reforming device according to an embodiment of the present invention.

Fig. 6 is a diagram schematically showing an example of the configuration of the periphery of the switching valve of the fuel reforming device of fig. 5.

Fig. 7 is a diagram schematically showing an example of the structure of the reformer of fig. 5.

Fig. 8A is a cross-sectional view of the reformer of fig. 5.

Fig. 8B is a diagram showing a modification of fig. 8A.

Fig. 9 is a block diagram schematically showing an example of the configuration of the main part around the controller of the fuel reforming device of fig. 5.

Fig. 10A is a flowchart showing an example of reforming conversion processing performed by the fuel reforming device according to the embodiment of the present invention.

Fig. 10B is a diagram showing a modification of fig. 10A.

Fig. 11A is a flowchart showing an example of the reforming rate adjustment process executed by the fuel reforming device according to the embodiment of the present invention.

Fig. 11B is a diagram showing a modification of fig. 11A.

Fig. 12 is a diagram showing a modification of fig. 5.

Fig. 13 is a block diagram schematically showing an example of the configuration of the main part around the controller of the fuel reforming device of fig. 12.

Detailed Description

Embodiments of the present invention will be described below with reference to fig. 1 to 13. The fuel reforming device according to the embodiment of the present invention is applied to a compression ignition engine mounted on a vehicle or the like, and reforms fuel supplied from a fuel tank to the engine as needed.

The average temperature of the earth is kept warm by greenhouse gases in the atmosphere, which is suitable for living things. Specifically, the greenhouse gas absorbs a part of heat radiated from the solar-heated surface to the space and radiates it again to the surface, thereby keeping the atmosphere in a warm state. When the greenhouse gas concentration in the atmosphere increases as described above, the average temperature of the earth increases (global warming).

Among greenhouse gases, the concentration of carbon dioxide in the atmosphere, which has a large influence on global warming, is determined by the balance between carbon fixed on the ground and underground in the form of plant and fossil fuel and carbon existing in the atmosphere in the form of carbon dioxide. For example, when carbon dioxide in the atmosphere is absorbed by photosynthesis during plant growth, the carbon dioxide concentration in the atmosphere decreases, and when carbon dioxide is discharged into the atmosphere by combustion of fossil fuel, the carbon dioxide concentration in the atmosphere increases. In order to suppress global warming, renewable energy sources such as sunlight and wind power, renewable fuels derived from biomass, and the like are required to replace fossil fuels to reduce carbon emissions.

As such renewable fuels, low-octane gasoline obtained by FT (Fischer-Tropsch) synthesis is becoming popular. Low octane gasoline has high ignitability and can be used in compression ignition engines, but in the process of popularization, there are areas where sales are not made. On the other hand, the conventional octane number gasoline for spark ignition engines, which is currently popular, has low ignitability, and when used directly for compression ignition engines, it is difficult to ensure exhaust gas performance, and there is a possibility that there is even no ignition. Therefore, in the present embodiment, in order to reform the fuel supplied from the fuel tank to the engine as needed, both the low-octane gasoline and the normal-octane gasoline are compression-ignited in a single engine, and the fuel reformer is configured as follows.

Fig. 1 is a diagram schematically showing an example of the internal structure of an engine 1 to which a fuel reforming device according to an embodiment of the present invention is applied. The engine 1 is a compression ignition gasoline engine, and is mounted on a vehicle, for example.

As shown in fig. 1, an engine 1 has a block 3 forming a cylinder 2 and a cylinder head 4 covering an upper portion of the block 3. An intake port 5 through which intake air that enters the engine 1 passes and an exhaust port 6 through which exhaust gas that is discharged from the engine 1 passes are provided in the cylinder head 4. An intake valve 7 for opening and closing the intake port 5 is provided in the intake port 5, and an exhaust valve 8 for opening and closing the exhaust port 6 is provided in the exhaust port 6. The intake valve 7 and the exhaust valve 8 are opened and closed by a valve train not shown.

A piston 9 slidable in the cylinder 2 is disposed in each cylinder 2, and a combustion chamber 10 is formed facing the piston 9. An injector 11 is provided in the engine 1 so as to face the combustion chamber 10, and fuel is injected from the injector 11 into the combustion chamber 10. The operation of the injector 11 (fuel injection timing (valve opening timing), fuel injection amount (valve closing timing)) is controlled by an engine ECU (Electronic Control Unit: electronic control unit) 200 (fig. 7). The engine 1 is further provided with an in-cylinder pressure sensor 12, which is constituted by a piezoelectric crystal type pressure sensor or the like, for detecting the pressure in the combustion chamber 10.

When the intake port 5 is opened, the exhaust port 6 is closed, and the piston 9 descends, air (fresh air) is sucked from the intake port 5 into the combustion chamber 10 (intake stroke). When the intake port 5 and the exhaust port 6 are closed and the piston 9 is raised, air in the combustion chamber 10 is compressed, and the pressure in the combustion chamber 10 is gradually raised (compression stroke). When fuel is injected from the injector 11 into the combustion chamber 10 in the vicinity of the compression top dead center TDC (Top Dead Center), the mixture of fuel and air in the combustion chamber 10 is compressed, the pressure in the combustion chamber 10 gradually increases, and the fuel is combusted by self-ignition. When the fuel starts to self-ignite in the combustion chamber 10, the pressure in the combustion chamber 10 increases sharply, and the piston 9 decreases (expansion stroke). When the intake port 5 is closed, the exhaust port 6 is opened, and the piston 9 is raised, air (exhaust gas) in the combustion chamber 10 is discharged from the exhaust port 6 (exhaust stroke).

The crankshaft 14 is rotated by means of the connecting rod 13 by reciprocating the piston 9 along the inner wall of the cylinder 2. A crank angle sensor 15 that detects a rotation angle (crank angle) of the crankshaft 14 is also provided to the crankshaft 14 of the engine 1. Further, a magnetostrictive torque sensor 16, for example, is provided that detects the output torque of the engine 1. The engine 1 is further provided with a water temperature sensor or the like for detecting the temperature of cooling water (engine water temperature) of the engine 1, which is not shown.

Fig. 2 is a diagram for explaining a relationship between the octane number and ignitability of fuel, and shows an example of ignition timing ti of a plurality of kinds of fuel having different octane numbers as a crank angle "° with respect to compression top dead center TDC. More specifically, an example of a crank angle at which self-ignition of fuel in the combustion chamber 10 is started, which is determined based on the pressure in the combustion chamber 10 detected by the in-cylinder pressure sensor 12 and the crank angle detected by the crank angle sensor 15, and the pressure in the combustion chamber 10 rapidly increases, is shown.

As shown in fig. 2, in the fuel having low ignitability, the octane number of which exceeds 70, the ignition timing ti is significantly later than the compression top dead center TDC, and in this case, the maximum thermal efficiency of the engine 1 is significantly lowered, and the combustion becomes unstable. In order to ensure sufficient combustion performance of the engine 1, it is necessary to reform the fuel when the ignition timing ti is equal to or greater than a predetermined crank angle ti0 (for example, 10 °).

Fig. 3 is a diagram for explaining a chemical reaction at the time of reforming a fuel. Fuel containing hydrocarbon as a main component can be oxidized and reformed to produce peroxide by using a catalyst such as N-hydroxyphthalimide (NHPI) to improve ignitability. Specifically, NHPI readily abstracts a hydrogen atom by an oxygen molecule to generate phthalimide-N-oxygen (PINO) radicals. The PINO radical abstracts a hydrogen atom from a hydrocarbon (RH) contained in the fuel to generate an alkyl group (R.cndot.). The alkyl groups combine with oxygen molecules to form alkyl peroxy radicals (ROO. Cndot.). The alkyl peroxy radical abstracts a hydrogen atom from a hydrocarbon contained in the fuel to generate alkyl hydroperoxide (ROOH) as a peroxide.

Fig. 4 is a diagram for explaining the extent of progress of the oxidation reaction of the fuel, and shows an example of changes in the peroxide concentration c1 and the oxide concentration c2 when the oxidation reaction proceeds. As shown in fig. 4, when the oxidation reaction proceeds, the peroxide concentration c1 increases, and when the oxidation reaction proceeds further, the peroxide is decomposed into oxides of ethanol, aldehyde, ketone, and the like, the peroxide concentration c1 decreases and the oxide concentration c2 increases.

In order to increase the peroxide concentration c1 in the fuel, the ignitability of the fuel is improved until the state is suitable for compression ignition, and the extent of progress of the oxidation reaction needs to be adjusted within an appropriate range. Specifically, it is necessary to adjust the octane number of the fuel (reformed fuel) after oxidation reforming to 70 or less (fig. 2) and the peroxide concentration c1 in the reformed fuel to a predetermined concentration c0 or more (for example, 0.15 mol/l). The peroxide concentration c1 in the reformed fuel can be detected by an appropriate concentration sensor.

When the peroxide concentration c1 is lower than the predetermined concentration c0, the peroxide concentration c1 is equal to or higher than the oxide concentration c2 when the oxidation reaction is not sufficiently advanced, and the peroxide concentration c1 is lower than the oxide concentration c2 when the oxidation reaction is excessively advanced. When hydrocarbons contained in the fuel are decomposed into oxides, the amount of heat generated by the reformed fuel decreases, and the engine output decreases. That is, the output torque of the engine 1 is proportional to the product of the heat generation amount of the reformed fuel and the fuel injection amount. The oxide concentration c2 can be estimated based on the fuel injection amount and the output torque of the engine 1.

Fig. 5 to 9 are diagrams schematically showing an example of the structure of a fuel reforming device (hereinafter referred to as device) 100 according to an embodiment of the present invention. As shown in fig. 5, the apparatus 100 includes a reforming unit 20 and a controller 50, wherein the reforming unit 20 is interposed in a fuel supply path 18 from a fuel tank 17 to an injector 11 of the engine 1, and has a reformer 19 for oxidizing and reforming fuel, and the controller 50 controls the operation of the reforming unit 20.

The fuel tank 17 is provided with a residual quantity meter 17a for detecting the residual quantity of the fuel stored in the fuel tank 17. The residual quantity meter 17a is constituted by, for example, a float type liquid level sensor, and outputs a signal corresponding to the liquid level of the fuel in the fuel tank 17.

As shown in fig. 5 and 6, the fuel supply path 18 has a 1 st path 18a from the fuel tank 17 through the reformer 19 to the injector 11 of the engine 1 and a 2 nd path 18b from the fuel tank 17 to the injector 11 of the engine 1 bypassing the reformer 19.

The reforming unit 20 includes a fuel pump 21a that draws fuel stored in the fuel tank 17, a flow meter 22 that detects a flow rate of the fuel, an on-off valve 23 that opens and closes the 1 st path 18a, and a mixer 24 in the 1 st path 18a from the fuel tank 17 to the reformer 19. Further, a concentration sensor 26 for detecting the peroxide concentration c1 in the reformed fuel and a high-pressure pump 27 for pressure-feeding the fuel are provided in the 1 st path 18a from the reformer 19 to the injector 11 of the engine 1. The concentration sensor 26 is constituted by, for example, a capacitive concentration sensor for measuring the dielectric constant of the reformed fuel, and outputs a signal corresponding to the peroxide concentration c1 in the reformed fuel.

As shown in fig. 5 and 6, the reforming unit 20 also has a fuel pump 21b for sucking the fuel stored in the fuel tank 17 in the 2 nd path 18b, and the fuel sucked by the fuel pump 21b is supplied to the high-pressure pump 27 via the 2 nd path 18b. The operation (fuel pressure) of the high-pressure pump 27 is controlled by the engine ECU200 (fig. 9).

As shown in fig. 6, the reforming unit 20 has a switching valve 28 that switches the fuel supply path 18 to either one of the 1 st path 18a and the 2 nd path 18b. When the fuel supply path 18 is switched to the 1 st path 18a, the fuel stored in the fuel tank 17 is supplied to the reformer 19 to be reformed according to the operation of the high-pressure pump 27, and the reformed fuel is supplied to the injector 11 by the high-pressure pump 27 and injected into the combustion chamber 10 (fig. 1). When the fuel supply path 18 is switched to the 2 nd path 18b, the fuel stored in the fuel tank 17 is directly supplied to the injector 11 by the high-pressure pump 27 without being reformed in the reformer 19 according to the operation of the high-pressure pump 27, and is injected into the combustion chamber 10 (fig. 1).

As shown in fig. 5, the reforming unit 20 includes an air cleaner 31, an air pump 32 for pressure-feeding air, a flow meter 33 for detecting the flow rate of air, and an on-off valve 34 for opening and closing the air supply path 30 in the air supply path 30 for supplying air to the mixer 24. The fuel supplied to the mixer 24 through the fuel supply path 18 (1 st path 18 a) according to the operation of the high-pressure pump 27 and the air supplied to the mixer 24 through the air supply path 30 according to the operation of the air pump 32 are mixed in the mixer 24 and supplied to the reformer 19.

Fig. 7 is a diagram schematically showing an example of the structure of the reformer 19. As shown in fig. 7, the reformer 19 includes an outer tube 191 and an inner tube 192 extending in the vertical direction, and is configured as a double-tube reactor in which a cylindrical space 193 is formed between the outer tube 191 and the inner tube 192.

An introduction hole 194 penetrating the lower portion of the outer tube 191 is provided in the outer tube 191 of the reformer 19 so that the fuel and air mixed in the mixer 24 (fig. 5) are introduced into the cylindrical space 193 through the 1 st path 18 a. Further, an air discharge hole 195 penetrating the upper portion of the outer tube 191 is provided so that air is discharged from the cylinder space 193 through the 3 rd path 18 c. Further, fuel discharge holes 196a,196b penetrating between the introduction hole 194 of the outer tube 191 and the air discharge hole 195 are provided so that the fuel is discharged from the cylinder space 193 through the 1 st path 18 a. The air discharged from the cylindrical space 193 is supplied to the intake port 5 of the engine 1 via the 3 rd path 18c (fig. 1), and is sucked into the combustion chamber 10 together with fresh air.

The space radially inside the inner tube 192 of the reformer 19 is configured as a circulation flow path 197, and engine cooling water as a heat transfer medium circulates. That is, the cooling water of the engine 1 after the warm-up is supplied from below the circulation path 197, and the reformer 19 is warmed up, and circulated to the engine 1 from above the circulation path 197. The engine water temperature after warming up is maintained in the temperature range of 70 to 110 ℃, so that the oxidation reaction of the fuel is properly promoted.

The upper end 193a and the lower end 193b of the cylindrical space 193 of the reformer 19 are closed. The fuel (liquid) introduced into the cylinder space 193 through the introduction hole 194 flows through the cylinder space 193 from the lower end 193b to the fuel discharge holes 196a,196b, and is discharged through the fuel discharge holes 196a,196 b. The air (gas) introduced into the cylinder space 193 through the introduction hole 194 passes through the cylinder space 193 from the lower end 193b to the upper end 193a, and is discharged through the air discharge hole 195.

The cylindrical space 193 from the lower end 193b to the fuel discharge holes 196a,196b corresponding to the liquid surface of the fuel functions as a reaction chamber 198 in which the fuel reacts with oxygen in the air (oxidation reaction) to generate reformed fuel. On the other hand, the cylindrical space 193 extending from the fuel discharge holes 196a,196b corresponding to the liquid surface of the fuel to the upper end 193a functions as a gas-liquid separation chamber 199 for performing gas-liquid separation.

Fig. 8A and 8B are sectional views of reformer 19 shown in fig. 7 taken along line VII-VII, showing a section of a portion corresponding to reaction chamber 198. As shown in fig. 8A, a catalyst 190 (wall surface support) such as NHPI catalyst is supported on an inner wall 191a of an outer tube 191 and an outer wall 192a of an inner tube 192, which constitute an inner wall of a reaction chamber 198, to promote an oxidation reaction in the reaction chamber 198.

The reformer 19 may have a gap g between the inner wall 191a of the outer tube 191 and the outer wall 192a of the inner tube 192 of 2 times or less the quenching distance, for example, 2 times the quenching distance. Accordingly, the inner wall 191a of the outer tube 191 or the outer wall 192a of the inner tube 192 is necessarily present within a range within a quenching distance from the reactant, and therefore, the safety of the reformer 19 can be improved. In order to further improve safety, the reformer 19 may be configured such that the gap g is equal to or less than the maximum safety gap, for example, the maximum safety gap. By configuring the reaction chamber 198 in which the oxidation reaction of the fuel proceeds with the maximum safety gap, for example, fire is immediately extinguished even when a flame intrudes from an adjacent device, and therefore, the safety of the reformer 19 can be further improved.

As shown in fig. 8B, instead of the wall surface supporting, the reaction chamber 198 of the reformer 19 may be filled with a solid catalyst 190 having a catalyst such as NHPI catalyst supported (surface-supported) on a carrier such as a silicon wafer, and the gap g of the solid catalyst 190 as the reaction field of the oxidation reaction may be set to 2 times the quenching distance or the maximum safety gap.

As shown in fig. 5 and 7, the outer tube 191 of the reformer 19 is provided with a plurality of (2 in the example of the drawing) fuel discharge holes 196a,196b in the vertical direction, and the reforming unit 20 has a switching valve 29 that switches the fuel discharge holes 196a,196 b. When the fuel discharge holes 196a,196b are shifted, the liquid level of the fuel changes, the heights h1a, h1b of the reaction chamber 198 change, and the heights h2a, h2b of the gas-liquid separation chamber 199 change. By changing the heights h1a and h1b of the reaction chamber 198, the reaction time of the oxidation reaction in the reformer 19 can be adjusted.

The reformer 19 is configured such that the heights h2a, h2b of the gas-liquid separation chamber 199 from the fuel discharge holes 196a,196b to the upper end 193a are equal to or greater than the height h0 at which gas-liquid separation is possible. The inner wall 191a of the outer tube 191 and the outer wall 192a of the inner tube 192, which constitute the inner wall of the gas-liquid separation chamber 199, are subjected to surface treatment such as teflon (registered trademark) processing. By performing such surface treatment, the capillary phenomenon in the gas-liquid separation chamber 199 can be suppressed, and the height h0 at which gas-liquid separation can be performed can be minimized.

Fig. 9 is a block diagram schematically showing an example of the configuration of the main portion around the controller 50. As shown in fig. 9, the controller 50 is constituted by an Electronic Control Unit (ECU) including a computer having a CPU (central processing unit) 51, a memory 52 such as a ROM (read only memory) and a RAM (random access memory), and other peripheral circuits not shown such as an I/O (input/output) interface.

The controller 50 is electrically connected to sensors such as the in-cylinder pressure sensor 12, the crank angle sensor 15, the torque sensor 16, the flow meters 22 and 33, the residual meter 17a, and the concentration sensor 26, and receives signals from the sensors. The controller 50 is electrically connected to actuators of the fuel pumps 21a and 21b, the opening/closing valves 23 and 34, the switching valves 28 and 29, the air pump 32, and the like, and control signals are sent from the controller 50 to the respective actuators. The controller 50 is configured to be capable of communicating with other onboard ECUs such as the engine ECU200 via a communication network such as a CAN (Controller Area Network: controller area network) mounted on the vehicle.

The memory 52 stores various control programs, threshold values used in the programs, and other information. The CPU51 has a reforming unit control unit 53, an oil supply determination unit 54, a reforming/non-reforming determination unit 55, and an oxidation progress estimation unit 56 that control the operation of the reforming unit 20 as functional components. That is, the CPU51 functions as a reforming unit control section 53, an oil supply determination section 54, a reforming/non-reforming determination section 55, and an oxidation progress degree estimation section 56.

The fueling determination unit 54 determines whether or not to supply fuel to the fuel tank 17 based on the change in the remaining amount of fuel stored in the fuel tank 17 detected by the remaining amount meter 17a. For example, each time the vehicle and the controller 50 are started, the previous fuel level is compared with the current fuel level, and whether or not fuel is supplied to the fuel tank 17 is determined. Whether or not oil is supplied can also be determined by detecting the opening and closing of the filler cap.

When the fuel supply determination unit 54 determines that the fuel is supplied, the reforming-or-not determination unit 55 determines whether or not the reforming is necessary based on the ignition timing ti of the fuel. Specifically, the ignition timing ti of the fuel is calculated based on the pressure in the combustion chamber 10 detected by the in-cylinder pressure sensor 12 and the crank angle detected by the crank angle sensor 15, and when the ignition timing ti is equal to or greater than a predetermined crank angle ti0 (fig. 2), it is determined that the reforming is necessary. When the ignition timing ti is lower than the prescribed crank angle ti0, it is determined that no reforming is necessary.

The reforming determination unit 55 may determine whether reforming is necessary based on the peroxide concentration c1 in the reformed fuel. Specifically, when the peroxide concentration c1 in the reformed fuel detected by the concentration sensor 26 is lower than the predetermined concentration c0 (fig. 4), it is determined that reforming is necessary, and when the peroxide concentration is equal to or higher than the predetermined concentration c0, it is determined that reforming is not necessary.

When the reforming determination unit 55 determines that the reforming is necessary, the reforming unit control unit 53 switches the fuel supply path 18 to the 1 st path 18a (reforming on) through the switching valve 28 so that the fuel stored in the fuel tank 17 is supplied to the injector 11 after being reformed by the reformer 19. On the other hand, when the whether or not the reforming determination unit 55 determines that the reforming is not necessary, the fuel supply path 18 is switched to the 2 nd path 18b (reforming off) by the switching valve 28 so that the fuel stored in the fuel tank 17 is supplied to the injector 11 without being reformed in the reformer 19.

The oxidation progress estimating unit 56 determines whether or not the progress of the oxidation reaction (oxidation progress) in the reformer 19 is within an appropriate range based on the ignition timing ti of the fuel at the time of the start of reforming. Specifically, the ignition timing ti of the reformed fuel is calculated based on the pressure in the combustion chamber 10 detected by the in-cylinder pressure sensor 12 and the crank angle detected by the crank angle sensor 15, and when the ignition timing ti is lower than a predetermined crank angle ti0 (fig. 2), it is determined that the oxidation proceeds to a proper extent. When the ignition timing ti is equal to or greater than the predetermined crank angle ti0, it is determined that the oxidation proceeds to a degree outside the proper range.

The oxidation progress estimating unit 56 may determine whether or not the oxidation progress degree is within an appropriate range based on the peroxide concentration c1 in the reformed fuel. Specifically, when the peroxide concentration c1 in the reformed fuel detected by the concentration sensor 26 is equal to or higher than the predetermined concentration c0 (fig. 4), it is determined that the oxidation proceeds to an appropriate extent, and when the peroxide concentration c1 is lower than the predetermined concentration c0, it is determined that the oxidation proceeds to an extent outside the appropriate extent.

When it is determined that the oxidation progress level is out of the proper range, the oxidation progress level estimating unit 56 determines whether the oxidation progress level is excessive or insufficient based on the oxide concentration c2 in the reformed fuel. The oxide concentration c2 in the reformed fuel can be estimated based on the fuel injection amount of the injector 11 and the output torque of the engine 1 detected by the torque sensor 16. The fuel injection amount may be calculated based on the fuel flow rate detected by the flow meter 22, and may be calculated based on the fuel pressure (command value for the high-pressure pump 27) and the fuel injection amount (command value for the injector 11) obtained by communication with the engine ECU 200.

When the oxide concentration c2 is equal to or higher than the peroxide concentration c1 detected by the concentration sensor 26, the oxidation progress level estimating unit 56 determines that the oxidation progress level is excessive, and when it is lower than the peroxide concentration c1, it determines that the oxidation progress level is insufficient (fig. 4). The oxidation may be determined to be excessively advanced when the oxide concentration c2 is equal to or higher than the predetermined concentration c0, and the oxidation may be determined to be insufficiently advanced when the oxide concentration c2 is lower than the predetermined value.

The reforming unit control unit 53 controls the operation of the reforming unit 20 based on the oxidation reaction progress estimated by the oxidation progress estimating unit 56, and adjusts the reforming rate of the reformer 19. Specifically, the operation of the switching valve 29 is controlled in accordance with the progress of oxidation, and the heights h1a and h1b of the reaction chambers 198 are changed by switching the fuel discharge holes 196a and 196b, so that the reaction time of the oxidation reaction in the reformer 19 is adjusted. When switching to the fuel discharge hole 196a, the reaction time becomes short corresponding to the height h1a of the reaction chamber 198, and the reforming rate of the reformer 19 decreases. When the reaction time is changed to the fuel discharge hole 196b, the reaction time becomes longer corresponding to the height h1b of the reaction chamber 198, and the reforming rate of the reformer 19 increases.

The reforming unit control section 53 may control the operation of the air pump 32 to adjust the amount of air supplied to the reformer 19 and adjust the reforming rate of the reformer 19, in addition to the adjustment of the reaction time due to the switching of the fuel discharge holes 196a and 196 b. The reaction temperature may be adjusted by adjusting the flow rate of cooling water circulating between the engine 1 and the reformer 19, and the reforming rate of the reformer 19 may be adjusted.

Fig. 10A and 10B are flowcharts showing an example of the reforming conversion process executed by the CPU51 of the controller 50. The process of fig. 10A and 10B begins when, for example, the vehicle and controller 50 are started.

In the process of fig. 10A, first, in S1 (S: process step), it is determined whether or not fuel is supplied to the fuel tank 17 while the vehicle and the controller 50 are stopped, by the process of the fuel supply determination unit 54. When S1 is affirmative (S1: yes), S2A is entered, and when negative (S1: yes), the process is ended. In S2A, the ignition timing ti is calculated by the processing of the reforming determination section 55, and it is determined whether or not the ignition timing ti is equal to or greater than a predetermined crank angle ti0.

If S2A is affirmative (S2A: yes), the ignitability of the fuel is insufficient, the flow proceeds to S3, and the operation of the switching valve 28 is controlled by the process in the reforming unit control section 53 to switch the fuel supply path 18 to the 1 st path 18a, and the reforming in the reformer 19 is started to end the process. On the other hand, if S2A is negative (S2A: no), the ignitability of the fuel is sufficient, the process proceeds to S4, and the operation of the switching valve 28 is controlled by the process in the reforming unit control section 53 to switch the fuel supply path 18 to the 2 nd path 18b, thereby closing the reforming in the reformer 19, and ending the process.

In the process of fig. 10B, instead of S2A of fig. 10A, in S2B, the process of the reforming/non-reforming determination unit 55 determines whether or not the peroxide concentration c1 is lower than the predetermined concentration c0, and determines whether or not the reforming is required due to insufficient ignitability of the fuel.

In this way, the ignitability of the fuel in the fuel tank 17 after the refueling is evaluated based on the ignition timing ti and the peroxide concentration c1 (S1, S2A, S B), and when the ignitability is not suitable for compression ignition, the fuel is reformed by the reformer 19 and then supplied to the engine 1 (S3). Therefore, sufficient combustion performance of the compression ignition engine mounted on an FFV (Flexible Fuel Vehicle: flexible fuel vehicle) capable of adding low-octane gasoline or normal-octane gasoline can be ensured.

Fig. 11A and 11B are flowcharts showing an example of the reforming rate adjustment process executed by the CPU51 of the controller 50. The process of fig. 11A and 11B starts when, for example, the reforming of the reformer 19 is turned on.

In the process of fig. 11A, first, at S5, it is determined whether reforming of the reformer 19 is on. When S5 is affirmative (S5: yes), the process proceeds to S6A, and when negative (S5: no), the process ends. In S6A, the oxidation progress estimating unit 56 calculates the ignition timing ti of the reformed fuel, and determines whether or not the ignition timing ti is lower than a predetermined crank angle ti0. When S6A is affirmative (S6A: yes), it is determined that the degree of progress of oxidation in the reformer 19 is within an appropriate range, and the process is ended.

On the other hand, when S6A is negative (S6A: NO), it is determined that the oxidation progress degree in the reformer 19 is out of the proper range, the flow proceeds to S7, where the oxide concentration c2 in the reformed fuel is calculated, and it is determined whether or not the oxide concentration c2 is equal to or higher than the peroxide concentration c1. S8 is entered when S7 is affirmative (S7: yes), and S9 is entered when negative (S7: no). In S8, the operation of the control switching valve 29 is switched to the fuel discharge hole 196A by the processing in the reforming unit control section 53, and the reaction time is shortened to reduce the reforming rate of the reformer 19, and the flow returns to S6A.

In S9, by the processing in the oxidation progress estimating part 56, it is determined whether or not the oxide concentration c2 is lower than the peroxide concentration c1. S10 is entered when S9 is affirmative (S9: yes), and S11 is entered when negative (S9: no). In S10, the operation of the switching valve 29 is switched to the fuel discharge hole 196b by the processing performed in the reforming unit control section 53, and the reaction time is prolonged to increase the reforming rate of the reformer 19, and the flow returns to S6A. In S11, it is determined that device 100 has failed, and the failure code end process is transmitted to engine ECU200, for example.

In the process of fig. 11B, instead of S6A of fig. 11A, in S6B, it is determined whether or not the peroxide concentration c1 in the reformed fuel is equal to or higher than the predetermined concentration c0 by the process of the oxidation progress estimating unit 56.

By estimating the oxidation progress level in the reformer 19 (S6A, S6B, S, S9) in this way, the reforming rate of the reformer 19 is adjusted according to the oxidation progress level (S8, S10), whereby the fuel can be reformed to a state suitable for compression ignition. Even when various kinds of gasoline having different octane numbers are added, and when a plurality of kinds of gasoline having different octane numbers are mixed in the fuel tank 17, sufficient combustion performance of the compression ignition engine mounted on the FFV can be ensured.

Fig. 12 and 13 schematically show an example of the structure of an apparatus 100A as a modification of the apparatus 100. The apparatus 100A has a catalyst tank 40 in addition to the constitution of the apparatus 100, and the catalyst tank 40 stores a catalyst solution obtained by mixing a catalyst (powder) such as NHPI catalyst into an appropriate solvent. The apparatus 100A includes a filter 42, a catalyst pump 43 for pressure-feeding the catalyst solution, a flow meter 44 for detecting the flow rate of the catalyst solution, and an on-off valve 45 for opening and closing the catalyst supply path 41 in the catalyst supply path 41 for supplying the catalyst to the reformer 19.

Reformer 19 of apparatus 100A functions as a fluidized bed reactor in which the catalyst solution and reactants flow together within the reactor. In this case, the particle diameter of the catalyst (powder) can be reduced, the specific surface area can be enlarged, and the reaction efficiency can be improved. Further, since the NHPI catalyst can be directly supplied to the injector 11 without being separated from the reformed fuel, the entire apparatus can be simply constructed.

The reforming unit control section 53 of the apparatus 100A can adjust the reforming rate of the reformer 19 by controlling the operation of the catalyst pump 43 to adjust the catalyst amount in addition to the reaction time, the air amount, and the heat transfer medium amount. Specifically, the amount of catalyst supplied to the reformer 19 can be reduced by controlling the operation of the catalyst pump 43, thereby reducing the reforming rate of the reformer 19, and the reforming rate of the reformer 19 can be increased by increasing the amount of catalyst supplied to the reformer 19.

The present embodiment can provide the following effects.

(1) The apparatus 100 for reforming fuel by oxidation reaction includes a reformer 19, and the reformer 19 includes an outer pipe 191 and an inner pipe 192 extending in the vertical direction, and a cylindrical space 193 (fig. 7) is formed between the outer pipe 191 and the inner pipe 192. The outer tube 191 is provided with an introduction hole 194, an air discharge hole 195, and fuel discharge holes 196a,196b, wherein the introduction hole 194 penetrates a lower portion of the outer tube 191 to introduce fuel and air into the cylindrical space 193, the air discharge hole 195 penetrates an upper portion of the outer tube 191 to discharge air from the cylindrical space 193, and the fuel discharge holes 196a,196b penetrate between the introduction hole 194 of the outer tube 191 and the air discharge hole 195 to discharge fuel from the cylindrical space 193 (fig. 7). The upper end 193a and the lower end 193b of the cylinder space 193 are closed. The reformer 19 is configured such that the fuel supplied through the introduction hole 194 undergoes an oxidation reaction in the presence of a catalyst in the cylindrical space 193 from the lower end 193b to the fuel discharge holes 196a,196 b. This enables the oxidation reaction to proceed in the reaction chamber 198 in the lower part of the reformer 19, which is a single double-tube reactor, and the gas-liquid separation in the gas-liquid separation chamber 199 in the upper part, thereby simplifying the configuration of the entire apparatus 100.

(2) When the gap g between the inner wall 191a of the outer tube 191 and the outer wall 192a of the inner tube 192 is set to 2 times the quenching distance, the heights h2a, h2b from the fuel discharge holes 196a,196b to the upper end 193a are equal to or greater than the height h0 at which gas-liquid separation can be performed in the cylindrical space 193 from the fuel discharge holes 196a,196b to the upper end 193 a. The inner wall 191a of the reformer 19 is present in a range within the quenching distance from the reactant, and thus the safety of the reformer 19 can be improved.

(3) When the gap g between the inner wall 191a of the outer tube 191 and the outer wall 192a of the inner tube 192 is the maximum safety gap, the heights h2a, h2b from the fuel discharge holes 196a,196b to the upper end 193a are equal to or greater than the height h0 at which the gas-liquid separation can be performed in the cylindrical space 193 from the fuel discharge holes 196a,196b to the upper end 193 a. The safety of the reformer 19 can be further improved by configuring the reaction chamber 198 in which the oxidation reaction proceeds with the maximum safety gap.

(4) The fuel discharge holes 196a,196b are provided in plurality in the vertical direction. The reaction time of the oxidation reaction can be adjusted by changing the heights h1a and h1b of the reaction chamber 198 by switching the plurality of fuel discharge holes 196a and 196 b. In this case, since it is not necessary to adjust the flow rates of the heat medium, air, and catalyst, the entire apparatus can be configured more simply.

In the above embodiment, the description has been given taking the oxidation reaction for reforming the normal octane gasoline to a level equivalent to that of the low octane gasoline as an example, but the fuel reforming apparatus is not limited to the example shown as long as the fuel is reformed by the oxidation reaction. For example, it is also possible to reform gasoline fuel into ethanol fuel by oxidation.

In the above embodiment, the specific octane number of the fuel, the peroxide in the reformed fuel, and the concentration of the oxide are described as examples of the threshold value for evaluating whether the ignitability of the fuel is suitable for compression ignition, but the threshold values are not limited to these.

In the above embodiment, the example in which the fuel reforming device is applied to the engine 1 mounted on a vehicle (FFV) has been shown, but the fuel reforming device is not limited to an in-vehicle engine, and may be applied to a generator, a working machine, or other products.

One or more of the above embodiments and modifications may be arbitrarily combined, or the modifications may be combined with each other.

The invention can provide a fuel reforming device with simple structure.

While the invention has been described in connection with preferred embodiments, it will be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the disclosure of the following claims.

Claims (4)

1. A fuel reforming device (100) for reforming fuel by oxidation reaction, comprising a double-layer tube (19), wherein the double-layer tube (19) comprises an outer tube (191) and an inner tube (192) extending in the vertical direction, a cylindrical space (193) is formed between the outer tube (191) and the inner tube (192),

the outer tube (191) is provided with an introduction hole (194), an air discharge hole (195), and fuel discharge holes (196 a,196 b), the introduction hole (194) penetrates through the lower portion of the outer tube (191) to introduce fuel and air into the cylindrical space (193), the air discharge hole (195) penetrates through the upper portion of the outer tube (191) to discharge air from the cylindrical space (193), the fuel discharge holes (196 a,196 b) penetrate between the introduction hole (194) and the air discharge hole (195) of the outer tube (191) to discharge fuel from the cylindrical space (193),

the upper end (193 a) and the lower end (193 b) of the cylinder space (193) are closed,

the double-layer pipe (19) is configured such that the fuel supplied through the introduction hole (194) undergoes an oxidation reaction in the presence of a catalyst in the cylindrical space (193) from the lower end (193 b) to the fuel discharge holes (196 a,196 b).

2. The fuel reforming apparatus (100) according to claim 1, wherein,

when the gap between the inner wall (191 a) of the outer tube (191) and the outer wall (192 a) of the inner tube (192) is 2 times the quenching distance, the height from the fuel discharge holes (196 a,196 b) to the upper end (193 a) is equal to or greater than the height at which gas-liquid separation can be performed in the cylindrical space (193) from the fuel discharge holes (196 a,196 b) to the upper end (193 a).

3. The fuel reforming apparatus (100) according to claim 1, wherein,

when the gap between the inner wall (191 a) of the outer tube (191) and the outer wall (192 a) of the inner tube (192) is set to be the maximum safety gap, the height from the fuel discharge holes (196 a,196 b) to the upper end (193 a) is equal to or greater than the height at which gas-liquid separation can be performed in the cylindrical space (193) from the fuel discharge holes (196 a,196 b) to the upper end (193 a).

4. The fuel reforming apparatus (100) as defined in any one of claims 1 to 3, wherein,

the fuel discharge holes (196 a,196 b) are provided in plurality in the vertical direction.