JP7154326B2 - fuel reformer - Google Patents

Description

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

2. Description of the Related Art Conventionally, there is known an apparatus for reforming fuel by oxidizing it with an oxidizing agent (see, for example, Patent Document 1). The apparatus described in Patent Document 1 is configured as a double-tube reactor having a reaction field between an outer tube member and an inner tube member provided coaxially, and a mixture of fuel and air is supplied as a reactant. and discharges a mixture of reformed fuel and air as a product.

JP 2018-178974 A

In the device described in Patent Document 1, the reformed fuel and air are discharged as a mixture, so in order to obtain the reformed fuel, it is necessary to provide a gas-liquid separator after the double-tube reactor. , the configuration of the fuel reformer as a whole becomes complicated.

One aspect of the present invention is a fuel reformer that reforms fuel by an oxidation reaction, which includes an outer tube and an inner tube extending in a vertical direction, and a cylindrical space between the outer tube and the inner tube. with a double tube forming a The outer tube has an introduction hole penetrating the lower portion of the outer tube to introduce fuel and air into the cylindrical space, an air discharge hole penetrating the upper portion of the outer tube to discharge air from the cylindrical space, and a cylindrical space. A fuel discharge hole is provided extending between the inlet hole of the outer tube and the air discharge hole for discharging fuel from the outer tube. The upper and lower ends of the cylindrical space are closed. The double pipe is configured such that the fuel supplied through the introduction hole is oxidized in the presence of a catalyst in the cylindrical space from the lower end to the fuel discharge hole.

According to the present invention, it is possible to provide a fuel reformer with a simple configuration.

1 is a diagram schematically showing an example of the internal configuration of an engine to which a fuel reformer according to an embodiment of the invention is applied; FIG. FIG. 4 is a diagram for explaining the relationship between the octane number of fuel and ignitability; FIG. 4 is a diagram for explaining the degree of progress of the oxidation reaction of fuel; 1 is a diagram schematically showing an example of the configuration of a fuel reformer according to an embodiment of the present invention; FIG. FIG. 5 is a diagram schematically showing an example of a configuration around a switching valve of the fuel reformer of FIG. 4; The figure which shows typically an example of a structure of the reformer of FIG. FIG. 5 is a cross-sectional view of the reformer of FIG. 4; The figure which shows the modification of FIG. 7A. FIG. 5 is a block diagram schematically showing an example of a main configuration around a controller of the fuel reformer of FIG. 4; 4 is a flowchart showing an example of reforming switching processing executed by the fuel reformer according to the embodiment of the present invention; The figure which shows the modification of FIG. 9A. 4 is a flowchart showing an example of reforming rate adjustment processing executed by the fuel reformer according to the embodiment of the present invention; The figure which shows the modification of FIG. 10A. The figure which shows the modification of FIG. FIG. 12 is a block diagram schematically showing an example of a main configuration around a controller of the fuel reformer of FIG. 11;

An embodiment of the present invention will be described below with reference to FIGS. 1 to 12. FIG. A fuel reformer according to an embodiment of the present invention is applied to a compression ignition engine mounted on a vehicle or the like, and reforms fuel supplied to the engine from a fuel tank as necessary.

Greenhouse gases in the atmosphere keep the average temperature of the earth warm enough for life. Specifically, greenhouse gases absorb part of the heat radiated from the ground surface warmed by sunlight into outer space and radiate it back to the ground surface, keeping the atmosphere warm. It's dripping When the concentration of such greenhouse gases in the atmosphere increases, the average temperature of the earth rises (global warming).

The concentration of carbon dioxide in the atmosphere, which contributes greatly to global warming among greenhouse gases, is the balance between the carbon fixed on and in the ground as plants and fossil fuels and the carbon existing in the atmosphere as carbon dioxide. determined by For example, when carbon dioxide in the atmosphere is absorbed by photosynthesis during the growth process of plants, the concentration of carbon dioxide in the atmosphere decreases, and when carbon dioxide is released into the atmosphere by burning fossil fuels, carbon dioxide in the atmosphere concentration increases. In order to curb global warming, it is necessary to replace fossil fuels with renewable energy sources such as solar and wind power, and renewable fuels derived from biomass, thereby reducing carbon emissions.

As such renewable fuel, low octane gasoline obtained by FT (Fischer-Tropsch) synthesis is becoming popular. Low octane gasoline is highly ignitable and can be applied to compression ignition engines, but it is still in the process of being popularized and is not sold in some areas. On the other hand, ordinary octane gasoline for spark-ignited engines, which is currently in widespread use, has low ignitability. Therefore, in this embodiment, the fuel supplied from the fuel tank to the engine is reformed as necessary, and the fuel is changed as follows so that both low octane gasoline and normal octane gasoline can be ignited by compression in a single engine. Construct a reformer.

FIG. 1 is a diagram schematically showing an example of the internal configuration of an engine 1 to which a fuel reformer according to an embodiment of the 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 cylinder block 3 in which cylinders 2 are formed, and a cylinder head 4 covering the upper part of the cylinder block 3 . The cylinder head 4 is provided with an intake port 5 through which intake air to the engine 1 passes and an exhaust port 6 through which exhaust gas from the engine 1 passes. The intake port 5 is provided with an intake valve 7 for opening and closing the intake port 5 , and the exhaust port 6 is provided with an exhaust valve 8 for opening and closing the exhaust port 6 . The intake valve 7 and the exhaust valve 8 are driven to open and close by a valve mechanism (not shown).

A piston 9 is arranged in each cylinder 2 so as to be slidable inside the cylinder 2 , and a combustion chamber 10 is formed facing the piston 9 . The engine 1 is provided with an injector 11 facing a 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 opening time)) is controlled by an engine ECU (Electronic Control Unit) 200 (FIG. 6). The engine 1 is also provided with an in-cylinder pressure sensor 12 configured by a quartz piezoelectric 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 into the combustion chamber 10 through the intake port 5 (intake stroke). When the intake port 5 and the exhaust port 6 are closed and the piston 9 rises, the air inside the combustion chamber 10 is compressed and the pressure inside the combustion chamber 10 gradually increases (compression stroke). When fuel is injected from the injector 11 into the combustion chamber 10 near the compression top dead center TDC (Top Dead Center), the mixture of fuel and air in the combustion chamber 10 is compressed, and the pressure in the combustion chamber 10 gradually increases. It rises and the fuel burns by self-ignition. When self-ignition of fuel starts in the combustion chamber 10, the pressure in the combustion chamber 10 rises sharply and the piston 9 descends (expansion stroke). When the intake port 5 is closed, the exhaust port 6 is opened, and the piston 9 rises, the air (exhaust) in the combustion chamber 10 is discharged from the exhaust port 6 (exhaust stroke).

The reciprocating motion of the piston 9 along the inner wall of the cylinder 2 rotates the crankshaft 14 via the connecting rod 13 . A crankshaft 14 of the engine 1 is also provided with a crank angle sensor 15 that detects the rotation angle (crank angle) of the crankshaft 14 . For example, a magnetostrictive torque sensor 16 for detecting the output torque of the engine 1 is also provided. Although not shown, the engine 1 is also provided with a water temperature sensor for detecting the temperature of cooling water of the engine 1 (engine water temperature).

FIG. 2 is a diagram for explaining the relationship between the octane number of fuel and ignitability, and an example of ignition timing ti of a plurality of fuels with different octane numbers is shown as a crank angle [°] with compression top dead center TDC as a reference. show. More specifically, the self-ignition of fuel in the combustion chamber 10 specified 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. An example of a crank angle at which the pressure in the combustion chamber 10 rises rapidly is shown.

As shown in FIG. 2, with low ignitability fuel having an octane number exceeding 70, the ignition timing ti is significantly delayed from compression top dead center TDC, and in this case, the maximum thermal efficiency of the engine 1 is significantly reduced, resulting in poor combustion. become stable. 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°).

Hydrocarbon-based fuels can be oxidatively reformed using a catalyst such as N-hydroxyphthalimide (NHPI) to generate peroxides, thereby improving their ignitability. Specifically, in NHPI, a hydrogen atom is easily abstracted by an oxygen molecule to generate a phthalimido-N-oxyl (PINO) radical. A PINO radical extracts a hydrogen atom from a hydrocarbon (RH) contained in fuel to generate an alkyl radical (R.). Alkyl radicals combine with oxygen molecules to produce alkylperoxy radicals (ROO.). The alkylperoxy radical abstracts a hydrogen atom from the hydrocarbon contained in the fuel to form the peroxide alkyl hydroperoxide (ROOH).

FIG. 3 is a diagram for explaining the degree of progress of the fuel oxidation reaction, and shows an example of changes in the peroxide concentration c1 and the oxide concentration c2 as the oxidation reaction progresses. As shown in FIG. 3, as the oxidation reaction progresses, the peroxide concentration c1 increases. As c1 decreases, oxide concentration c2 increases.

In order to increase the peroxide concentration c1 in the fuel and improve the ignitability of the fuel to a state suitable for compression ignition, it is necessary to adjust the degree of progress of the oxidation reaction within an appropriate range. Specifically, the peroxide concentration c1 in the reformed fuel is set to a predetermined concentration c0 (for example, 0.15 [ mol/l]) or more. The peroxide concentration c1 in the reformed fuel can be detected by an appropriate concentration sensor.

When the peroxide concentration c1 is less than the predetermined concentration c0, the peroxide concentration c1 is equal to or higher than the oxide concentration c2 when the oxidation reaction progresses insufficiently, and the peroxide concentration c1 when the oxidation reaction progresses excessively. becomes less than the oxide concentration c2. When the hydrocarbons contained in the fuel are decomposed into oxides, the calorific value of the reformed fuel is reduced and the engine output is reduced. That is, the output torque of the engine 1 is proportional to the product of the calorific value of the reformed fuel and the fuel injection amount. The oxide concentration c2 can be estimated based on the fuel injection amount of the engine 1 and the output torque.

4 to 8 are diagrams schematically showing an example of the configuration of a fuel reforming device (hereinafter referred to as device) 100 according to an embodiment of the present invention. As shown in FIG. 4, the apparatus 100 includes a reforming unit 20 which 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 the fuel; a controller 50 for controlling the operation of the quality unit 20;

The fuel tank 17 is provided with a remaining amount meter 17 a for detecting the remaining amount of fuel stored in the fuel tank 17 . The remaining amount gauge 17 a is composed of, for example, a float-type level sensor, and outputs a signal corresponding to the level of the fuel in the fuel tank 17 .

As shown in FIGS. 4 and 5, the fuel supply path 18 includes a first path 18a from the fuel tank 17 through the reformer 19 to the injector 11 of the engine 1, and a first path 18a from the fuel tank 17 to the reformer 19. and a second path 18 b leading to the injector 11 of the engine 1 by detouring.

The reforming unit 20 includes a fuel pump 21a for pumping the fuel stored in the fuel tank 17, a flow meter 22 for detecting the flow rate of the fuel, and a first path 18a from the fuel tank 17 to the reformer 19. It has an on-off valve 23 for opening and closing one path 18 a and a mixer 24 . Also, on the first path 18a from the reformer 19 to the injector 11 of the engine 1, there are a concentration sensor 26 for detecting the peroxide concentration c1 in the reformed fuel and a high pressure pump 27 for pumping the fuel. The concentration sensor 26 is composed of, for example, a capacitance type concentration sensor that measures the dielectric constant of the reformed fuel, and outputs a signal corresponding to the peroxide concentration c1 in the reformed fuel.

As shown in FIGS. 4 and 5, the reforming unit 20 has a fuel pump 21b that pumps up the fuel stored in the fuel tank 17 also on the second path 18b, and the fuel pumped by the fuel pump 21b is It is supplied to the high pressure pump 27 via the second path 18b. The operation (fuel pressure) of the high-pressure pump 27 is controlled by the engine ECU 200 (FIG. 8).

As shown in FIG. 5, the reforming unit 20 has a switching valve 28 that switches the fuel supply path 18 between the first path 18a and the second path 18b. When the fuel supply path 18 is switched to the first path 18a, the fuel stored in the fuel tank 17 is supplied to the reformer 19 and reformed according to the operation of the high pressure pump 27, and the reformed fuel is supplied to the high pressure pump 27. to the injector 11 and injected into the combustion chamber 10 (FIG. 1). When the fuel supply path 18 is switched to the second path 18b, the fuel stored in the fuel tank 17 is directly fed through the high pressure pump 27 without being reformed by the reformer 19 in response to the operation of the high pressure pump 27. is supplied to the injector 11 and injected into the combustion chamber 10 (FIG. 1).

As shown in FIG. 4, the reforming unit 20 includes an air filter 31, an air pump 32 for pumping air, and a flow meter for detecting the flow rate of air on an air supply path 30 for supplying air to the mixer 24. 33 and an on-off valve 34 for opening and closing the air supply path 30 . Fuel supplied to the mixer 24 via the fuel supply path 18 (first path 18a) according to the operation of the high-pressure pump 27 and fuel supplied to the mixer 24 via the air supply path 30 according to the operation of the air pump 32 The supplied air is mixed in the mixer 24 and supplied to the reformer 19 .

FIG. 6 is a diagram schematically showing an example of the configuration of the reformer 19. As shown in FIG. As shown in FIG. 6, the reformer 19 has an outer tube 191 and an inner tube 192 extending in the vertical direction, and a double-walled tube forming a cylindrical space 193 between the outer tube 191 and the inner tube 192 . Configured as a tube reactor.

In the outer tube 191 of the reformer 19, the lower portion of the outer tube 191 is extended so as to introduce the fuel and air mixed in the mixer 24 (FIG. 4) into the cylindrical space 193 through the first path 18a. An introduction hole 194 is provided therethrough. Also, an air discharge hole 195 is provided through the upper portion of the outer tube 191 so as to discharge air from the cylindrical space 193 via the third path 18c. Further, fuel discharge holes 196a and 196b are provided to penetrate between the introduction hole 194 of the outer tube 191 and the air discharge hole 195 so as to discharge the fuel from the cylindrical space 193 through the first path 18a. The air discharged from the cylindrical space 193 is supplied to the intake port 5 of the engine 1 through the third path 18c (Fig. 1) and sucked into the combustion chamber 10 together with fresh air.

A space radially inside the inner pipe 192 of the reformer 19 is configured as a recirculation path 197 through which engine cooling water as a heat medium is recirculated. That is, the cooling water of the warmed-up engine 1 is supplied from below the recirculation path 197 to raise the temperature of the reformer 19 and is recirculated to the engine 1 from above the recirculation path 197 . Since the engine water temperature after warming up is maintained in the temperature range of 70 to 110° C., the oxidation reaction of the fuel is favorably promoted.

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

A cylindrical space 193 from the lower end 193b to the fuel discharge holes 196a and 196b corresponding to the liquid surface of the fuel functions as a reaction chamber 198 in which the fuel and oxygen in the air react (oxidation reaction) to produce reformed fuel. . On the other hand, a cylindrical space 193 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 gas-liquid separation.

7A and 7B are VII-VII cross-sectional views of the reformer 19 shown in FIG. As shown in FIG. 7A , a catalyst 190 such as an NHPI catalyst is supported on the inner wall 191 a of the outer tube 191 and the outer wall 192 a of the inner tube 192 that constitute the inner wall of the reaction chamber 198 (wall surface support). reaction is accelerated.

The reformer 19 is configured such that the gap g between the inner wall 191a of the outer tube 191 and the outer wall 192a of the inner tube 192 is two times or less the flame extinction distance, for example, twice the flame extinction distance. As a result, the inner wall 191a of the outer tube 191 or the outer wall 192a of the inner tube 192 always exists within the quenching distance from the reactant, so the safety of the reformer 19 can be enhanced. To further increase safety, the reformer 19 may be configured such that the gap g is less than or equal to the maximum safety gap, for example the maximum safety gap. By configuring the reaction chamber 198 in which the fuel oxidation reaction progresses with the maximum safety gap, for example, even if a flame enters from an adjacent device, it will be extinguished immediately, so the safety of the reformer 19 can be further enhanced.

As shown in FIG. 6B, the reaction chamber 198 of the reformer 19 is filled with a solid catalyst 190 in which the catalyst is supported on a carrier such as a silica tablet, instead of being supported on the wall surface. The gap g of the catalyst 190 may be configured to be twice the quenching distance or the maximum safe gap.

As shown in FIGS. 4 and 6, the outer tube 191 of the reformer 19 is provided with a plurality of (two in the illustrated example) fuel discharge holes 196a and 196b in the vertical direction. , a switching valve 29 for switching between the fuel discharge holes 196a and 196b. When the fuel discharge holes 196a and 196b are switched, the liquid level of the fuel changes, the heights h1a and h1b of the reaction chamber 198 change, and the heights h2a and 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. An inner wall 191a of the outer tube 191 and an 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 a surface treatment, capillary action in the gas-liquid separation chamber 199 can be suppressed, and the height h0 at which gas-liquid separation is possible can be minimized.

FIG. 8 is a block diagram schematically showing an example of the main configuration around the controller 50. As shown in FIG. As shown in FIG. 8, the controller 50 is composed of an electronic control unit (ECU) including a computer having a CPU 51, a memory 52 such as ROM and RAM, and other peripheral circuits such as an I/O interface (not shown). be.

Sensors such as the in-cylinder pressure sensor 12, the crank angle sensor 15, the torque sensor 16, the flow meter 170, and the concentration sensor 26 are electrically connected to the controller 50, and signals from each sensor are input. The controller 50 is electrically connected to actuators such as the fuel pumps 21a and 21b, the on-off valves 23 and 34, the switching valves 28 and 29, and the air pump 32, and a control signal is transmitted from the controller 50 to each actuator. . Further, the controller 50 is configured to be able to communicate with other in-vehicle ECUs such as the engine ECU 200 via a communication network such as a CAN (Controller Area Network) mounted in the vehicle.

The memory 52 stores information such as various control programs and threshold values used in the programs. The CPU 51 has, as functional configurations, a reforming unit control section 53 that controls the operation of the reforming unit 20 , an oil supply determination section 54 , a reforming necessity determination section 55 , and an oxidation progress estimation section 56 . That is, the CPU 51 functions as a reforming unit control section 53 that controls the operation of the reforming unit 20 , an oil supply determination section 54 , a reforming necessity determination section 55 , and an oxidation progress estimation section 56 .

The fuel supply determining unit 54 determines whether or not fuel is being supplied 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 gauge 17a. For example, each time the vehicle and the controller 50 are activated, it is determined whether or not fuel has been supplied to the fuel tank 17 by comparing the previous remaining amount of fuel with the current remaining amount of fuel. The presence or absence of refueling may be determined by detecting the opening and closing of the fuel lid.

When the refueling determination unit 54 determines that refueling has been performed, the reforming necessity determining unit 55 determines whether reforming is necessary based on the ignition timing ti of the fuel. Specifically, the fuel ignition timing ti 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. If the angle ti is greater than or equal to 0, it is determined that modification is necessary. If the ignition timing ti is less than the predetermined crank angle ti0, it is determined that reforming is unnecessary.

The reforming necessity 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 less than a predetermined concentration c0, it is determined that reforming is necessary. Decide that quality is unnecessary.

When the reforming unit control unit 53 determines that reforming is necessary by the reforming necessity determination unit 55 , the fuel stored in the fuel tank 17 is reformed by the reformer 19 and supplied to the injector 11 . Thus, the switching valve 28 switches the fuel supply path 18 to the first path 18a (reforming ON). On the other hand, when the reforming necessity determining unit 55 determines that reforming is not necessary, the switching valve is adjusted so that the fuel stored in the fuel tank 17 is supplied to the injector 11 without being reformed by the reformer 19 . 28 switches the fuel supply path 18 to the second path 18b (reforming off).

When the reforming is on, the oxidation progress estimator 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. . 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 the ignition timing ti is set to a predetermined value. If the crank angle is less than ti0, it is determined that the degree of progress of oxidation is within the proper range. If the ignition timing ti is greater than or equal to the predetermined crank angle ti0, it is determined that the degree of progress of oxidation is out of the proper range.

The oxidation progress estimator 56 may determine whether the oxidation progress 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 a predetermined concentration c0, it is determined that the degree of progress of oxidation is within an appropriate range, and the peroxide concentration c1 is determined to be within the appropriate range. If the concentration is less than the predetermined concentration c0, it is determined that the degree of progress of oxidation is out of the proper range.

Furthermore, when the oxidation progress estimation unit 56 determines that the oxidation progress is outside the appropriate range, it determines whether the oxidation progress 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 by 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 the fuel pressure (command value to the high-pressure pump 27) and the fuel injection amount (injector 11 command value to) and may be calculated based on.

If the oxide concentration c2 is equal to or higher than the peroxide concentration c1 detected by the concentration sensor 26, the oxidation progress estimation unit 56 determines that the oxidation progress is excessive. , it is determined that the degree of progress of oxidation is insufficient. It may be determined that the degree of oxidation progress is excessive when the oxide concentration c2 is equal to or higher than a predetermined concentration c0, and that the degree of oxidation progress is insufficient when it is less than a predetermined value.

The reforming unit control section 53 controls the operation of the reforming unit 20 and adjusts the reforming rate of the reformer 19 according to the progress of the oxidation reaction estimated by the oxidation progress estimation section 56 . Specifically, the operation of the switching valve 29 is controlled according to the progress of oxidation, the fuel discharge holes 196a and 196b are switched, the heights h1a and h1b of the reaction chamber 198 are changed, and the oxidation reaction in the reformer 19 is controlled. Adjust the reaction time. When switching to the fuel discharge hole 196a, the reaction time is shortened corresponding to the height h1a of the reaction chamber 198, and the reforming rate of the reformer 19 is lowered. When switching 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 by the reformer 19 increases.

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

9A and 9B are flowcharts showing an example of the reforming switching process executed by the CPU 51 of the controller 50. FIG. The processes of FIGS. 9A and 9B are initiated, for example, when the vehicle and controller 50 are activated.

In the process of FIG. 9A, first, in step S1, the refueling determining unit 54 determines whether fuel has been replenished to the fuel tank 17 while the vehicle and the controller 50 are stopped. If the result in step S1 is affirmative, the process proceeds to step S2A, and if the result is negative, the process ends. In step S2A, the ignition timing ti is calculated by the processing in the reforming necessity determination unit 55, and it is determined whether or not the ignition timing ti is equal to or greater than a predetermined crank angle ti0.

If the result in step S2A is affirmative, the ignitability of the fuel is insufficient, and the process proceeds to step S3. Switching to the path 18a, the reforming in the reformer 19 is turned on, and the process ends. On the other hand, if the result in step S2A is NO, it is determined that the ignitability of the fuel is sufficient, and the process proceeds to step S4. Switching to the second path 18b, the reforming in the reformer 19 is turned off, and the process ends.

In the process of FIG. 9B, instead of step S2A of FIG. 9A, in step S2B, the process in the reforming necessity determination unit 55 determines whether the peroxide concentration c1 is less than the predetermined concentration c0, Determine whether or not the ignitability of the fuel is insufficient and reforming is necessary.

In this way, the ignitability of the fuel in the fuel tank 17 after refueling is evaluated based on the ignition timing ti and the peroxide concentration c1 (steps S1, S2A, and S2B). The fuel is reformed by the reformer 19 and then supplied to the engine 1 (step S3). Therefore, it is possible to ensure sufficient combustion performance of a compression ignition engine installed in an FFV (Flexible Fuel Vehicle) that can be refueled with low octane gasoline or normal octane gasoline.

10A and 10B are flowcharts showing an example of the reforming rate adjustment process executed by the CPU 51 of the controller 50. FIG. The processes of FIGS. 10A and 10B are started, for example, when reforming by the reformer 19 is turned on.

In the process of FIG. 10A, first, in step S5, it is determined whether reforming by the reformer 19 is ON. If the result in step S5 is affirmative, the process proceeds to step S6A, and if the result is negative, the process ends. In step S6A, the ignition timing ti of the reformed fuel is calculated by the processing in the oxidation progress estimation unit 56, and it is determined whether or not the ignition timing ti is less than a predetermined crank angle ti0. If the result in step S6A is affirmative, it is determined that the degree of progress of oxidation in the reformer 19 is within the proper range, and the process is terminated.

On the other hand, if the result of step S6A is NO, it is determined that the degree of progress of oxidation in the reformer 19 is out of the proper range, and the process proceeds to step S7 to calculate the oxide concentration c2 in the reformed fuel and calculate the oxide concentration c2. is greater than or equal to the peroxide concentration c1. If the result in step S7 is affirmative, the process proceeds to step S8, and if the result is negative, the process proceeds to step S9. In step S8, it is judged that the degree of progress of oxidation is excessive, and the reforming unit control section 53 controls the operation of the switching valve 29 to switch to the fuel discharge hole 196a, shortens the reaction time, and reduces the reformer 19 is reduced, and the process returns to step S6A.

In step S9, it is determined whether or not the oxide concentration c2 is less than the peroxide concentration c1 by processing in the oxidation progress estimation unit 56. If the result in step S9 is affirmative, the process proceeds to step S10, and if the result is negative, the process proceeds to step S11. In step S10, it is determined that the degree of progress of oxidation is insufficient, and the reforming unit control section 53 controls the operation of the switching valve 29 to switch to the fuel discharge hole 196b, lengthens the reaction time, and 19 is increased, and the process returns to step S6A. In step S11, it is determined that the device 100 is out of order, for example, a fault code is transmitted to the engine ECU 200, and the process ends.

In the process of FIG. 10B, instead of step S6A of FIG. 10A, in step S6B, the oxidation progress estimation unit 56 determines whether the peroxide concentration c1 in the reformed fuel is equal to or higher than the predetermined concentration c0. judge.

Thus, by estimating the degree of progress of oxidation in the reformer 19 (steps S6A, S6B, S7, S9) and adjusting the reforming rate of the reformer 19 according to the degree of progress of oxidation (steps S8, S10 ), the fuel can be reformed to a state suitable for compression ignition. In addition, even when gasolines with various octane numbers are refueled or when a plurality of gasolines with different octane numbers are mixed in the fuel tank 17, the compression ignition engine mounted on the FFV has sufficient combustion performance. can be secured.

FIG. 11 is a diagram schematically showing an example of the configuration of a device 100A that is a modification of the device 100. As shown in FIG. The apparatus 100A has, in addition to the configuration of the apparatus 100, a catalyst tank 40 in which a catalyst solution obtained by mixing a catalyst (powder) such as an NHPI catalyst in an appropriate solvent is stored. In addition, the device 100A includes a filter 42, a catalyst pump 43 for pressure-feeding the catalyst, a flow meter 44 for detecting the flow rate of the catalyst, and the catalyst supply path 41 on the catalyst supply path 41 for supplying the catalyst to the reformer 19. and an on-off valve 45 that opens and closes the .

The reformer 19 of apparatus 100A functions as a fluidized bed reactor in which the catalyst solution flows with the reactants within the reactor. In this case, the particle size of the catalyst (powder) can be reduced, and the reaction efficiency can be improved. In addition, the NHPI catalyst does not need to be separated from the reformed fuel, and can be supplied to the injector 11 as it is, so that the overall structure of the device can be simplified.

The reforming unit control unit 53 of the apparatus 100A controls the operation of the catalyst pump 43 to adjust the amount of catalyst in addition to adjusting the reaction time, the amount of air, and the amount of heat medium. can be adjusted. Specifically, the operation of the catalyst pump 43 is controlled to reduce the amount of catalyst supplied to the reformer 19, thereby reducing the reforming rate of the reformer 19 and reducing the amount of catalyst supplied to the reformer 19. By increasing the amount, the reforming rate of the reformer 19 can be increased.

According to this embodiment, the following effects can be obtained.
(1) The device 100 for reforming fuel by oxidation reaction has an outer tube 191 and an inner tube 192 extending vertically, and a cylindrical space 193 is formed between the outer tube 191 and the inner tube 192. A reformer 19 is provided (FIG. 6). The outer tube 191 has an introduction hole 194 penetrating the lower portion of the outer tube 191 to introduce fuel and air into the cylindrical space 193, and an air inlet 194 penetrating the upper portion of the outer tube 191 to discharge air from the cylindrical space 193. A discharge hole 195 and fuel discharge holes 196a and 196b penetrating between the introduction hole 194 of the outer tube 191 and the air discharge hole 195 are provided to discharge the fuel from the cylindrical space 193 (FIG. 6). An upper end 193a and a lower end 193b of the cylindrical 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 and 196b. As a result, the oxidation reaction can be performed in the lower reaction chamber 198 of the reformer 19, which is a single double-tube reactor, and the gas-liquid separation can be performed in the upper gas-liquid separation chamber 199, so that the entire apparatus 100 can be simplified. can be configured.

(2) The heights h2a and h2b from the fuel discharge holes 196a and 196b to the upper end 193a are obtained 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 twice the quenching distance. , the height h0 or more at which gas-liquid separation is possible in the cylindrical space 193 from the fuel discharge holes 196a, 196b to the upper end 193a. Since the inner wall 191a of the reformer 19 exists within the quenching distance from the reactant, the safety of the reformer 19 can be enhanced.

(3) The heights h2a and h2b from the fuel discharge holes 196a and 196b to the upper end 193a are determined 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 safe clearance. The height h0 or more enables gas-liquid separation in the cylindrical space 193 from the discharge holes 196a, 196b to the upper end 193a. The safety of the reformer 19 can be further enhanced by forming the reaction chamber 198 in which the oxidation reaction proceeds with the maximum safety gap.

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

In the above embodiment, the oxidation reaction for improving the ignitability of normal octane gasoline and reforming it to a low octane gasoline is explained as an example, but the fuel reformer reforms the fuel by the oxidation reaction. It is not limited to the exemplified ones. For example, gasoline fuel may be reformed into alcohol fuel by an oxidation reaction.

In the above embodiment, examples of threshold values for evaluating whether the ignitability of the fuel is suitable for compression ignition include the specific octane number of the fuel and the concentrations of peroxides and oxides in the reformed fuel. However, each threshold is not limited to these.

In the above embodiment, an example in which the fuel reformer is applied to the engine 1 mounted on a vehicle (FFV) was shown, but it is not limited to the vehicle engine, and may be applied to products such as generators and working machines.

The above description is merely an example, and the present invention is not limited by the above-described embodiments and modifications as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and it is also possible to combine modifications with each other.

Reference Signs List 1 engine 10 combustion chamber 11 injector 12 in-cylinder pressure sensor 17 fuel tank 17a fuel gauge 18 fuel supply path 18a first path 18b second path 19 reformer 20 reforming unit 23 , 34, 45 on-off valve, 26 concentration sensor, 28 switching valve, 32 air pump, 40 catalyst tank, 43 catalyst pump, 50 controller, 51 CPU, 52 memory, 53 reforming unit control section, 54 oil supply determination section, 55 reform Quality Necessity Determining Part 56 Oxidation Progress Estimating Part 100, 100A Fuel reformer (apparatus) 191 Outer tube 192 Inner tube 193 Cylindrical space 193a Upper end 193b Lower end 194 Introduction hole 195 Air discharge hole , 196a, 196b fuel discharge hole, 197 reflux path, 198 reaction chamber, 199 gas-liquid separation chamber

Claims (4)

A fuel reformer that reforms fuel by an oxidation reaction,
A double tube having an outer tube and an inner tube extending in a vertical direction and forming a cylindrical space between the outer tube and the inner tube,
The outer tube has an introduction hole penetrating the lower part of the outer tube to introduce fuel and air into the cylindrical space, and an air outlet penetrating the upper part of the outer tube to discharge air from the cylindrical space. a hole 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 said cylindrical space are closed;
The fuel reformer, wherein the double pipe is configured such that the fuel supplied through the introduction hole is oxidized in the presence of a catalyst in the cylindrical space from the lower end to the fuel discharge hole. Device. The fuel reformer of claim 1, wherein
The height from the fuel discharge hole to the upper end is the distance from the fuel discharge hole to the upper end when the gap between the inner wall of the outer tube and the outer wall of the inner tube is twice the flame extinction distance. A fuel reformer having a height equal to or higher than that capable of separating gas and liquid in a cylindrical space. The fuel reformer of claim 1, wherein
The height from the fuel discharge hole to the upper end is the cylindrical space from the fuel discharge hole to the upper end when the gap between the inner wall of the outer pipe and the outer wall of the inner pipe is the maximum safe clearance. A fuel reformer characterized by having a height higher than that at which gas-liquid separation is possible. In the fuel reformer according to any one of claims 1 to 3,
A fuel reformer, wherein a plurality of said fuel discharge holes are provided in a vertical direction.

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