JP2007198274A - Internal combustion engine using hydrogen - Google Patents

Abstract

The present invention relates to a hydrogen-utilized internal combustion engine having a function of separating hydrogenated gasoline into hydrogen-rich gas and dehydrogenated gasoline so that high efficiency and low emission can be realized in a wide operation range from a low load range to a high load range. .
When the internal combustion engine is operated in a predetermined operation region, the operation is performed by HCCI combustion using hydrogenated gasoline as fuel, and when the internal combustion engine is operated in a higher load region than the predetermined operation region, Operation by lean combustion is performed using rich gas and dehydrogenated gasoline as fuel.
[Selection] Figure 1

Description

  The present invention relates to a hydrogen-utilizing internal combustion engine, and more particularly to a hydrogen-utilizing internal combustion engine having a function of separating hydrogenated gasoline into hydrogen-rich gas and dehydrogenated gasoline.

  Conventionally, as disclosed in Patent Document 1, for example, a hydrogen-utilizing internal combustion engine that uses hydrogen as a fuel is known. By adding hydrogen to gasoline and using it, the lean burn range of the internal combustion engine can be expanded, and remarkable effects such as improvement of fuel consumption and reduction of NOx generation amount can be obtained.

The hydrogen-utilized internal combustion engine disclosed in the above document generates hydrogen to be used for the operation of the internal combustion engine in the system by dehydrogenating hydrogenated gasoline using a catalyst. Since this dehydrogenation reaction is an endothermic reaction, it is necessary to heat the catalyst to a certain temperature in order to promote the reaction and efficiently obtain hydrogen. In the hydrogen-utilized internal combustion engine disclosed in the above document, a catalyst is disposed in the exhaust passage, and the catalyst is heated using exhaust heat. By generating hydrogen itself in the system, it becomes possible to use hydrogen as fuel without the need for a high-pressure hydrogen cylinder or the like. In addition, gasoline after dehydrogenation (dehydrogenated gasoline) can be used together with hydrogen as fuel for a hydrogen-utilizing internal combustion engine.
Japanese Patent Laying-Open No. 2005-147124 JP 2004-116398 A

  However, in a system that uses exhaust heat to generate hydrogen, the efficiency of hydrogen generation depends on the operating state of the hydrogen-using internal combustion engine. In particular, when a hydrogen-utilizing internal combustion engine is operated in a low load region, the exhaust temperature is low, so the catalyst cannot be heated sufficiently, and the hydrogen generation efficiency may be greatly reduced. In order to continue lean burn operation by hydrogen addition (hydrogen addition lean burn operation) in a system that does not have a high-pressure hydrogen cylinder or large-capacity buffer tank, the necessary amount of hydrogen must be continuously generated. It becomes. For this reason, in a situation where the production efficiency of hydrogen is low, such as in a low load region, the hydrogen addition lean burn operation cannot be continued due to a shortage of hydrogen, and it is necessary to switch to another operation method. However, since the hydrogenated lean burn operation is highly efficient and generates a small amount of NOx, the alternative operation method is as efficient or low emission as the hydrogenated lean burn operation. It is desirable that the driving method be feasible.

  The present invention has been made to solve the above-described problems, and relates to a hydrogen-utilized internal combustion engine having a function of separating hydrogenated gasoline into hydrogen-rich gas and dehydrogenated gasoline, from a low load range to a high load range. The objective is to achieve high efficiency and low emissions in a wide operating range.

In order to achieve the above object, a first invention is a hydrogen-utilizing internal combustion engine,
A tank for storing hydrogenated gasoline;
Fuel separation means for separating hydrogenated gasoline into hydrogen-rich gas and dehydrogenated gasoline;
Fuel supply means for supplying any of hydrogenated gasoline, hydrogen-rich gas and dehydrogenated gasoline selectively or in combination to the internal combustion engine;
When the internal combustion engine is operated in a predetermined operation region, an operation is performed by HCCI combustion using hydrogenated gasoline as a fuel. When the internal combustion engine is operated in a higher load region than the predetermined operation region, hydrogen rich gas and Control means for performing operation by lean combustion using dehydrogenated gasoline as fuel,
It is characterized by having.

According to a second invention, in the first invention,
When the internal combustion engine is operated in a high load side operation region of the operation region by HCCI combustion, the control means adds an ignition device disposed in the combustion chamber while adding hydrogen rich gas to hydrogenated gasoline as fuel. It is characterized by operating.

According to a third invention, in the second invention,
The control means is characterized in that when the internal combustion engine is operated in a higher load range than an operation range in which operation by lean combustion is possible, operation by stoichiometric combustion is performed using dehydrogenated gasoline as fuel.

  According to the first aspect of the invention, when the internal combustion engine is operated in a relatively low load region, the operation by HCCI combustion using hydrogenated gasoline as fuel is performed. HCCI combustion burns an ultra-lean mixture that exceeds the lean flammability limit, so the amount of NOx produced can be kept even lower than normal lean combustion (lean combustion by flame propagation), and higher thermal efficiency can be achieved. Can be realized. However, the HCCI combustion has a feature that its ignition performance changes depending on the in-cylinder temperature and is difficult to self-ignite in a low load region. In this regard, the first invention solves this problem by using hydrogenated gasoline as the fuel. This is because hydrogenated gasoline has a lower octane number than ordinary gasoline (dehydrogenated gasoline) and is easy to ignite at a lower temperature.

  In HCCI combustion, the generation of combustion noise becomes more pronounced as the load increases. Therefore, in the first invention, when the internal combustion engine is operated in a relatively high load region, the operation is switched from the operation by HCCI combustion to the operation by lean combustion. Dehydrogenated gasoline used as fuel has a high octane number, and furthermore, by adding a hydrogen-rich gas containing hydrogen that is excellent in combustibility, generation of combustion noise can be prevented even in a relatively high load range.

  As described above, according to the first invention, by HCCI combustion using hydrogenated gasoline as a fuel in a relatively low load region, and by lean combustion using dehydrogenated gasoline and hydrogen-rich gas as a fuel in a relatively high load region. By operating the internal combustion engine, high efficiency and low emission can be realized in a wide operation range from a low load range to a high load range.

  When HCCI combustion and lean combustion are compared, HCCI combustion has higher thermal efficiency and can reduce the amount of NOx generated. Therefore, the operating range that can be operated by HCCI combustion is desired to be expanded to the high load range as much as possible. According to the second aspect of the invention, hydrogenated gasoline can be self-ignited using the combustion of the hydrogen rich gas added to the hydrogenated gasoline as a trigger. Therefore, the combustion start timing of HCCI combustion is indirectly determined by the operation timing of the ignition device. Can be controlled. Thereby, generation | occurrence | production of the combustion sound accompanying the fluctuation | variation of a combustion start time can be suppressed, and the driving | operation by HCCI combustion is attained in a wider driving | running area | region compared with the case where only hydrogenated gasoline is used as a fuel.

  Further, according to the third aspect of the invention, in a higher load range than the operation range by lean combustion, the exhaust emission is deteriorated while knocking is prevented by performing the operation by stoichiometric combustion using dehydrogenated gasoline having a high octane number as fuel. Can also be prevented.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.

  In the first embodiment, the present invention is applied to a power system of a vehicle such as an automobile. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine (hereinafter referred to as an engine) according to a first embodiment of the present invention. The engine according to the present embodiment is a spark ignition type four-stroke engine, and includes a spark plug 16 in a combustion chamber 4 formed in the engine body 2. This engine has a configuration capable of realizing HCCI (Homogeneous Change Compression Ignition) combustion not based on flame propagation in addition to flame propagation combustion realized by igniting a fuel mixture with an ignition plug 16. Specifically, the intake valve or both intake / exhaust valves have a variable valve mechanism (not shown), and the valve compression and intake valve closing timing are controlled to achieve a substantial compression ratio. It is configured to be changeable. When flame propagation combustion is selected as the combustion type, the setting of the variable valve mechanism is changed to the low compression ratio side. When HCCI combustion is selected as the combustion type, the setting of the variable valve mechanism is set to the high compression ratio side. It has been changed.

  The engine according to the present embodiment is a hydrogen-based internal combustion engine that can use gasoline and hydrogen as fuel. In the present embodiment, gasoline as one fuel is supplied from the outside (for example, a fueling facility such as a gasoline station), while hydrogen as the other fuel is generated in the system. . Specifically, hydrogen is generated from gasoline by the configuration described below.

  As shown in FIG. 1, an intake pipe 6 and an exhaust pipe 8 are connected to the combustion chamber 4. From the combustion chamber 4 to the exhaust pipe 8, high-temperature combustion gas obtained by combustion of fuel in the combustion chamber 4 is discharged. An exhaust gas purification device 20 disposed in the vicinity of the engine body 2 and an exhaust gas purification device 22 disposed downstream of the exhaust pipe 8 and below the vehicle floor are mounted on the exhaust pipe 8. The exhaust gas purification device 22 is integrated with the dehydrogenation reactor. Specifically, a NOx storage purification catalyst is disposed inside the exhaust pipe 8, and a dehydrogenation catalyst is disposed so as to surround the outside of the exhaust pipe 8. As the dehydrogenation catalyst, for example, a platinum catalyst can be used. Hereinafter, the dehydrogenation reactor in which the exhaust gas purifying device is integrated is simply referred to as a dehydrogenation reactor 22.

  A raw fuel injector 24 is assembled in the dehydrogenation reactor 22. The raw fuel injector 24 is connected to the raw fuel tank 30 by pipe lines 50 and 52. The pipe 50 on the raw fuel tank 30 side and the pipe 52 on the raw fuel injector 24 side are connected by a switching valve 34. The raw fuel stored in the raw fuel tank 30 is supplied to the raw fuel injector 24 by the pump 40 disposed in the pipe 50. The raw fuel injector 24 is opened by receiving a drive signal supplied from the outside, so that an amount of raw fuel corresponding to the valve opening time can be injected into the dehydrogenation reactor 22.

  Hydrogenated gasoline (also called hydrogen-rich gasoline) is used as the raw fuel. Hydrogenated gasoline means organic hydride, that is, gasoline having a higher content of saturated hydrocarbons that can generate hydrogen by dehydrogenation reaction than ordinary gasoline. Hydrogenated gasoline can be produced by reforming or blending a fraction rich in organic hydrides in an oil refining process. Hydrogenated gasoline can also be produced by adding hydrogen to unsaturated hydrocarbons contained in ordinary gasoline. Examples of the hydrogen addition method include a method of reacting gasoline with a hydrogen rich gas on a heated catalyst.

In the present embodiment, hydrogenated gasoline containing a naphthenic hydrocarbon such as methylcyclohexane C ₇ H ₁₄ as a main component is used. The raw fuel tank 30 is provided with a fuel filler port 30a communicating with the outside of the vehicle. The raw fuel tank 30 is supplied with hydrogenated gasoline from the outside through the fuel filler port 30a.

The dehydrogenation catalyst in the dehydrogenation reactor 22 is heated by the exhaust heat of the engine radiated from the exhaust pipe 8 during operation of the engine. When hydrogenated gasoline is supplied onto the heated dehydrogenation catalyst, a chemical reaction as shown in Formula (1) occurs.
C ₇ H ₁₄ → 3H ₂ + C ₇ H ₈ (1)
The chemical reaction of the above formula (1) is a dehydrogenation reaction of methylcyclohexane C ₇ H ₁₄ . By this dehydrogenation reaction, methylcyclohexane C ₇ H ₁₄ is separated into hydrogen H ₂ and toluene C ₇ H ₈ which is dehydrogenated gasoline.

  Hydrogen-rich gas (gas containing hydrogen as a main component) and dehydrogenated gasoline generated by the dehydrogenation reaction in the dehydrogenation reactor 22 are discharged from the bottom of the dehydrogenation reactor 22 together with unreacted hydrogenated gasoline. . The bottom of the dehydrogenation reactor 22 is connected to the separator 32 by a pipe line 64. A heater 28 is attached to the pipe line 64. A cooling pipe 68 through which cooling water flows passes through the separator 32. By being cooled by the cooling pipe 68, the hydrogen rich gas and the dehydrogenated gasoline supplied from the dehydrogenation reactor 22 are separated into a liquid phase and a gas phase in the separator 32. Specifically, dehydrogenated gasoline (including unreacted hydrogenated gasoline) liquefied by cooling is accumulated at the bottom of the separator 32, and the hydrogen-rich gas remaining as a gas is accumulated at the top of the separator 32. It has become.

  A hydrogen injector 10 is disposed in the intake pipe 6 that leads to the combustion chamber 4. The hydrogen injector 10 is connected to the upper portion of the separator 32 through pipes 56 and 60. A switching valve 36 is provided between the two pipes 56 and 60. The switching valve 36 is also connected to the upstream side of the dehydrogenation reactor 22 in the exhaust pipe 8 by a pipe line 58. By operating the switching valve 36, the supply destination of the hydrogen rich gas from the separator 32 can be selectively switched between the two pipe lines 58 and 60. When the switching valve 36 opens the pipe 60 side, the hydrogen rich gas accumulated in the separator 32 is supplied to the hydrogen injector 10 through the pipes 56 and 60, and when the pipe 58 side is opened, The hydrogen rich gas is supplied into the exhaust pipe 8. A check valve 46 is disposed in a pipe line 56 connecting the separator 32 and the switching valve 36, and a pressure pump 42 and a small buffer tank 38 are connected to a pipe line 60 connecting the switching valve 36 and the hydrogen injector 10. Is provided. The hydrogen injector 10 is opened by receiving a drive signal supplied from the outside, so that an amount of hydrogen rich gas corresponding to the opening time can be injected into the intake pipe 6.

  A gasoline injector 12 is also arranged in the intake pipe 6 along with the hydrogen injector 10. The gasoline injector 12 is connected to the lower part of the separator 32 through a pipe line 62, and a pump 44 is provided in the middle of the pipe line 62. The gasoline injector 12 is also connected to the switching valve 34 described above via a pipeline 54. The switching valve 34 can selectively switch the supply destination of the hydrogenated gasoline from the raw fuel tank 30 between the two pipelines 52 and 54, and the hydrogenated gasoline can be supplied to both the pipelines 52 and 54. It can also be supplied. When the pump 44 is operated with the pipe 54 side of the switching valve 34 closed, the dehydrogenated gasoline accumulated in the separator 32 is supplied to the gasoline injector 12 through the pipe 62. When the pump 40 is operated by opening the pipe 54 side of the switching valve 34, hydrogenated gasoline in the raw fuel tank 30 is supplied to the gasoline injector 12 through the pipes 50 and 54. The gasoline injector 12 is opened in response to a drive signal supplied from the outside, so that an amount of gasoline corresponding to the opening time can be injected into the intake pipe 6.

  Next, the operation of the engine according to the present embodiment will be described. The operation of the engine is controlled by an ECU (Engine Control Unit) 70. Various devices such as the injectors 10, 12, 24 and the spark plug 16 are connected to the output section of the ECU 70, and various sensors such as the engine speed sensor 72 and the accelerator opening sensor 74 are connected to the input section. ing. The ECU 70 is configured to drive devices such as the injectors 10, 12, 24 and the spark plug 16 according to a predetermined control program based on signals from the sensors.

  The engine according to the present embodiment has, as its operation method, a lean burn operation (hereinafter referred to as a hydrogen addition lean burn operation) performed by adding a hydrogen rich gas to gasoline, and an operation based on gasoline HCCI combustion (hereinafter referred to as HCCI combustion operation). And can be selected. FIG. 2 is a diagram for explaining the operation during the hydrogen addition lean burn operation of the engine according to the present embodiment, and FIG. 3 is a diagram for explaining the operation during the HCCI combustion operation. In each figure, a pipeline indicated by a solid line means that fluid is being supplied, and a pipeline indicated by a broken line means that fluid supply is being stopped.

  At the time of the hydrogen addition lean burn operation, as shown in FIG. 2, the pipe 52 side of the switching valve 34 is opened, and hydrogenated gasoline is supplied from the raw fuel tank 30 to the raw fuel injector 24 by the pump 40. Then, hydrogenated gasoline is supplied into the dehydrogenation reactor 22 by the operation of the raw fuel injector 24. The supplied hydrogenated gasoline undergoes a dehydrogenation reaction on the dehydrogenation catalyst and is separated into a hydrogen rich gas and a dehydrogenated gasoline. The hydrogen-rich gas and dehydrogenated gasoline produced in the dehydrogenation reactor 22 flow out to the separator 32 and are cooled in the separator 32 to be separated into a gas phase (hydrogen-rich gas) and a liquid phase (dehydrogenated gasoline). .

  Further, during the hydrogen addition lean burn operation, the switching valve 36 is switched to the pipe line 60 side, and the operation of the pressurizing pump 42 supplies the hydrogen rich gas in the separator 32 to the hydrogen injector 10. At the same time, the dehydrogenated gasoline in the separator 32 is supplied to the gasoline injector 12 by the operation of the pump 44. The dehydrogenated gasoline is injected into the intake pipe 6 by the operation of the gasoline injector 12, and the hydrogen rich gas is injected into the intake pipe 6 by the operation of the hydrogen injector 10. The hydrogen-rich gas and dehydrogenated gasoline injected into the intake pipe 6 are sucked into the combustion chamber 4 while being mixed with air, and are ignited by the spark plug 16 to burn (flame propagation combustion).

  On the other hand, during the HCCI combustion operation, as shown in FIG. 3, the pipe line 54 side of the switching valve 34 is opened and the pipe line 52 side is closed. By closing the pipe 52 side of the switching valve 34, the supply of hydrogenated gasoline from the raw fuel tank 30 to the raw fuel injector 24 is shut off. Accordingly, the supply of hydrogenated gasoline into the dehydrogenation reactor 22 by the raw fuel injector 24 is also stopped.

  Also, during the HCCI combustion operation, hydrogenated gasoline is supplied from the raw fuel tank 30 to the gasoline injector 12 by the operation of the pump 40, while the supply of dehydrogenated gasoline from the separator 32 to the gasoline injector 12 by the pump 44 is stopped. The The supply of the hydrogen rich gas from the separator 32 to the hydrogen injector 10 by the pressurizing pump 42 is also stopped. During the HCCI combustion operation, only the gasoline injector 12 operates, and hydrogenated gasoline is injected into the intake pipe 6. Hydrogenated gasoline containing naphthenic hydrocarbons such as methylcyclohexane as the main component has a lower octane number and easier to ignite at lower temperatures than dehydrogenated gasoline containing aroma-based hydrocarbons such as toluene as the main component. Is suitable. The hydrogenated gasoline injected into the intake pipe 6 is mixed with air, sucked into the combustion chamber 4, and compressed to self-ignite and burn.

  Of the two operation methods that can be executed in the engine according to the present embodiment, according to the hydrogen addition lean burn operation, the lean burn operation using only gasoline as a fuel is performed by adding the hydrogen rich gas with excellent combustibility. In comparison, the air-fuel ratio can be made leaner, and the lean burn region can be expanded to the high load side, so that further improvement in fuel consumption and reduction in NOx generation amount can be achieved. In addition, in the present embodiment, by using dehydrogenated gasoline having a high octane number instead of hydrogenated gasoline which is a raw fuel, more stable combustion in a high load range becomes possible. However, as a matter of course, hydrogen-rich gas is necessary to perform the hydrogen-added lean burn operation, and the hydrogen-added lean burn operation cannot be executed in a situation where the hydrogen-rich gas is insufficient. In the case of a system that generates hydrogen rich gas by dehydrogenating hydrogenated gasoline as in the present embodiment, in a low load region where the exhaust heat of the engine is low and the dehydrogenation catalyst cannot be heated sufficiently, The amount of hydrogen rich gas required for the additive lean burn operation cannot be generated.

  On the other hand, according to the HCCI combustion operation, an ultra-lean air-fuel mixture that exceeds the combustion limit of flame propagation combustion can be burned. As a result, the amount of NOx produced can be further reduced as compared with the hydrogen addition lean burn operation which is one form of flame propagation combustion, and higher thermal efficiency can be realized. In the present embodiment, hydrogenated gasoline having a low octane number and easy to ignite at low temperatures is used as a fuel, so that stable HCCI combustion in a low load range is possible. However, on the other hand, in HCCI combustion, combustion noise becomes more pronounced when the engine load becomes higher, so it is difficult to execute the HCCI combustion operation in the middle and high load range.

  Therefore, in the engine according to the present embodiment, the operation method of the engine is selected according to the engine operation region according to the map of FIG. The map in FIG. 4 is a multi-dimensional map with the engine load and the engine speed as axes. The low load region of the engine operation region is set to the region where HCCI combustion operation is performed, and the medium and high load region is the hydrogen addition lean burn operation. It is set to the area to perform.

  In the map of FIG. 4, the boundary between the operation region where the HCCI combustion operation is selected and the operation region where the hydrogen addition lean burn operation is selected means a limit load at which HCCI combustion becomes difficult. That is, the map of FIG. 4 is created so that the HCCI combustion operation is prioritized over the hydrogen addition lean burn operation, and the HCCI combustion operation is selected in the widest possible operation region. This is because, when comparing HCCI combustion operation with hydrogen addition lean burn operation, HCCI combustion operation has higher thermal efficiency than hydrogen addition lean burn operation, and it is possible to suppress the amount of NOx generated to an extremely low level. It is.

  According to the map of FIG. 4, the low load region where the hydrogen addition lean burn operation becomes difficult due to the lack of the hydrogen rich gas can be supplemented by the HCCI combustion operation, and the HCCI combustion operation becomes difficult due to the generation of combustion noise. The zone can be supplemented by a hydrogenated lean burn operation. Therefore, by switching the engine operation method according to the map of FIG. 4, it is possible to realize high efficiency and low emission in a wide operation region from a low load region to a high load region.

  The operation of the engine according to the present embodiment is controlled by the ECU 70, and the switching of the engine operation method is also determined by the ECU 70. In the engine according to the present embodiment, the operation method of the engine is switched according to the routine shown in the flowchart of FIG.

  In the first step S100 of the routine shown in FIG. 5, the current engine speed and accelerator opening are acquired, and the engine load (load factor) is calculated from the engine speed and accelerator opening. Then, in the next step S102, it is determined whether or not the current operation state belongs to the region where the HCCI combustion operation is selected in the map of FIG.

  When the HCCI combustion operation is selected from the operating state of the engine, as shown in the operation diagram of FIG. 3, hydrogenated gasoline in the raw fuel tank 30 is directly supplied to the gasoline injector 12, and hydrogen from the gasoline injector 12 is supplied. HCCI combustion operation is executed by the injection of the liquefied gasoline (step S104).

  When the hydrogen addition lean burn operation is selected from the engine operating state, the hydrogenated gasoline in the raw fuel tank 30 is supplied to the dehydrogenation reactor 22 as shown in the operation diagram of FIG. Thus, the hydrogen rich gas is separated from the gasoline (step S106). Then, the hydrogen-added lean burn operation is executed by injecting the separated hydrogen rich gas from the hydrogen injector 10 and injecting dehydrogenated gasoline from the gasoline injector 12 (step S108).

  In the present embodiment, the ECU 70 executes the routine shown in FIG. 5, thereby realizing the “control unit” of the first invention.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to FIGS.

  The engine according to the present embodiment has the configuration shown in FIG. As the operation method, hydrogen-added lean burn operation and HCCI combustion operation can be selected, and further, HCCI combustion operation (hereinafter referred to as hydrogen-added HCCI combustion operation) performed by adding a hydrogen rich gas to hydrogenated gasoline, A stoichiometric combustion operation using dehydrogenated gasoline as a fuel can be selected. FIG. 6 is a view for explaining the operation of the engine according to the present embodiment during the hydrogenation HCCI combustion operation, and FIG. 7 is a view for explaining the operation during the stoichiometric combustion operation. In each figure, a pipeline indicated by a solid line means that fluid is being supplied, and a pipeline indicated by a broken line means that fluid supply is being stopped. The operation during the hydrogen addition lean burn operation is described with reference to FIG. 2 as in the first embodiment, and the operation during the HCCI combustion operation is described with reference to FIG. 3 as in the first embodiment.

  The hydrogenation HCCI combustion operation is performed in an operation region where the temperature of the dehydrogenation catalyst can be maintained at the activation temperature or higher. During the hydrogenated HCCI combustion operation, as shown in FIG. 6, the pipe 52 side of the switching valve 34 is opened, and hydrogenated gasoline is supplied from the raw fuel tank 30 to the raw fuel injector 24 by the pump 40. Then, hydrogenated gasoline is supplied from the raw fuel injector 24 into the dehydrogenation reactor 22, and the supplied hydrogenated gasoline is separated into hydrogen rich gas and dehydrogenated gasoline by a dehydrogenation reaction on the dehydrogenation catalyst. The hydrogen-rich gas and dehydrogenated gasoline produced in the dehydrogenation reactor 22 flow out to the separator 32 and are cooled in the separator 32 to be separated into a gas phase (hydrogen-rich gas) and a liquid phase (dehydrogenated gasoline). .

  Further, during the hydrogen addition HCCI combustion operation, the pipe line 54 side of the switching valve 34 is also opened, and hydrogenated gasoline is directly supplied from the raw fuel tank 30 to the gasoline injector 12 by the pump 40. At the same time, the operation of the pressurizing pump 42 supplies the hydrogen rich gas in the separator 32 to the hydrogen injector 10. Hydrogenated gasoline is injected into the intake pipe 6 by the operation of the gasoline injector 12, and a very small amount of hydrogen rich gas is injected into the intake pipe 6 by the operation of the hydrogen injector 10 for a very short time.

  Unlike the normal HCCI combustion operation, the spark plug 16 is operated during the hydrogen addition HCCI combustion operation. The ignition of the spark plug 16 burns hydrogen-rich gas with excellent combustibility. The combustion of the hydrogen rich gas occurs in a volumetric manner in the entire combustion chamber 4, and the combustion of the hydrogen rich gas triggers the HCCI combustion of the hydrogenated gasoline.

  When HCCI combustion and lean burn are compared, HCCI combustion has higher thermal efficiency, and the amount of NOx generated can be kept lower. However, HCCI combustion has a problem that the combustion start timing cannot be directly controlled, and the combustion start timing varies depending on operating conditions such as the intake air temperature, and combustion noise is likely to be generated in the middle and high load regions. In particular, hydrogenated gasoline has a low octane number, so there is a high possibility that combustion noise will be generated. In this regard, according to the hydrogenated HCCI combustion operation described above, hydrogenated gasoline can be self-ignited with the combustion of the hydrogen rich gas as a trigger, and therefore the combustion start timing of HCCI combustion is indirectly determined by the ignition timing of the spark plug 16. Can be controlled. As a result, the generation of combustion noise associated with fluctuations in the combustion start timing can be suppressed, and operation by HCCI combustion can be performed up to the operation region on the higher load side as compared with the case where only hydrogenated gasoline is used as fuel. .

  By the way, in the above hydrogenated HCCI combustion operation, although hydrogen rich gas is used as fuel among hydrogen rich gas and dehydrogenated gasoline obtained by dehydrogenation reaction of hydrogenated gasoline, dehydrogenated gasoline is not used and separated as it is. It will be stored in the vessel 32. In the engine according to the present embodiment, the remaining dehydrogenated gasoline is used in a stoichiometric combustion operation described below.

  The stoichiometric combustion operation is executed in a higher load region than the operation region in which the hydrogen addition lean burn operation is executed. During the stoichiometric combustion operation, as shown in FIG. 7, the operation of the pump 40 is stopped and the supply of hydrogenated gasoline from the raw fuel tank 30 to the raw fuel injector 24 or the gasoline injector 12 is shut off. Further, the pressurizing pump 42 is not operated, and the injection of the hydrogen rich gas from the hydrogen injector 10 is not performed. During the stoichiometric combustion operation, only the pump 44 is operated and the dehydrogenated gasoline in the separator 32 is supplied to the gasoline injector 12. Then, dehydrogenated gasoline is injected into the intake pipe 6 by the operation of the gasoline injector 12. The injection amount of dehydrogenated gasoline is set to be the stoichiometric air-fuel ratio in relation to the intake air amount. The dehydrogenated gasoline injected into the intake pipe 6 is sucked into the combustion chamber 4 while being mixed with air, and burned (flame propagation combustion) by being ignited by the spark plug 16. Dehydrogenated gasoline mainly composed of aromatic hydrocarbons has a high octane number and is effective in preventing knocking in a high load range.

  In the engine according to the present embodiment, a map shown in FIG. 8 is used as a map for selecting an engine operating method. The map of FIG. 8 is a multi-dimensional map with the engine load and the engine speed as axes, and the engine operation region is divided into four regions A, B, C, and D in order from the low load side. Of these, the HCCI combustion operation using hydrogenated gasoline as fuel is selected in the region A on the lowest load side, the hydrogen addition HCCI combustion operation is selected in the next region B, and the hydrogen addition lean burn operation in the next region C. And the stoichiometric combustion operation is selected in the region D on the highest load side.

  In the map of FIG. 8, the boundary between the operation region where the HCCI combustion operation is selected and the operation region where the hydrogenated HCCI combustion operation is selected is that HCCI combustion is difficult due to the generation of combustion noise unless the combustion start timing is controlled. Means a critical load. In addition, the boundary between the operation region in which the hydrogenated HCCI combustion operation is selected and the operation region in which the hydrogenated lean burn operation is selected means a limit load that makes HCCI combustion difficult even when the combustion start timing is controlled. Yes. The boundary between the operation region in which the hydrogen addition lean burn operation is selected and the operation region in which the stoichiometric combustion operation is selected means a limit load at which lean burn is difficult even when hydrogen is added.

  By switching the engine operation method according to the map of FIG. 8, as in the first embodiment, it is possible to realize high efficiency and low emission in a wide operation region from a low load region to a high load region. Furthermore, according to this map, since the operation by HCCI combustion can be selected even in the middle load region, the NOx generation amount can be suppressed to a lower level.

  In the engine according to the present embodiment, the operation method of the engine is switched according to the routine shown in the flowchart of FIG.

  In the first step S200 of the routine shown in FIG. 9, the current engine speed and accelerator opening are acquired, and the engine load (load factor) is calculated from the engine speed and accelerator opening. In the next step S202, it is determined in which operating region in the map of FIG. 8 the current operating state determined from the engine speed and the engine load.

  When the current engine operating state belongs to region A in the map of FIG. 8, as shown in the operation diagram of FIG. 3, hydrogenated gasoline in the raw fuel tank 30 is directly supplied to the gasoline injector 12, and the gasoline injector The HCCI combustion operation is executed by injection of hydrogenated gasoline from 12 (step S204).

  When the current engine operating state belongs to the region B or C in the map of FIG. 8, hydrogenated gasoline in the raw fuel tank 30 is supplied to the dehydrogenation reactor 22, and hydrogen is separated from gasoline by the dehydrogenation reaction. (Step S206). After the execution of step S206, the operation region is determined again (step S208).

  If the current operating state of the engine belongs to region B in the map of FIG. 8, the process of step S210 is selected. In step S210, as shown in the operation diagram of FIG. 6, the hydrogenated gasoline in the raw fuel tank 30 is directly supplied to the gasoline injector 12, and the hydrogen rich gas generated in step S206 is supplied from the separator 32 to the hydrogen injector 10. To be supplied. And hydrogen addition HCCI combustion operation is performed by adding hydrogen rich gas to hydrogenated gasoline which is fuel. In the hydrogenation HCCI combustion operation, ignition timing control is performed.

  On the other hand, if the current engine operating state belongs to region C in the map of FIG. 8, the process of step S212 is selected. In step S212, as shown in the operation diagram of FIG. 2, the hydrogen rich gas generated in step S206 is supplied from the separator 32 to the hydrogen injector 10, and dehydrogenated gasoline is supplied from the separator 32 to the gasoline injector 12. The The hydrogen-added lean burn operation is executed by injecting hydrogen-rich gas from the hydrogen injector 10 and injecting dehydrogenated gasoline from the gasoline injector 12.

  If the current engine operating state belongs to the region D in the map of FIG. 8 as a result of the operation region determination in step S202, the dehydrogenated gasoline is fed from the separator 32 to the gasoline injector 12 as shown in the operation diagram of FIG. The stoichiometric combustion operation is executed by the injection of dehydrogenated gasoline from the gasoline injector 12 (step S214).

  In the present embodiment, the “control means” according to the second and third aspects of the present invention is implemented by the ECU 70 executing the routine shown in FIG. 9.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the configuration of FIG. 1, the hydrogen injector 10 is arranged in the intake pipe 6, but the arrangement is not limited to this. That is, the hydrogen injector 10 may be incorporated in the engine body 2 so that hydrogen can be directly injected into the cylinder. Similarly, the gasoline injector 12 can also be incorporated into the engine body 2.

  In the configuration of FIG. 1, the dehydrogenation reactor 22 is arranged in the exhaust pipe 8, but the arrangement is not limited to this. That is, it is only necessary to be disposed at a site where the dehydrogenation catalyst can be heated by engine exhaust heat, and the dehydrogenation reactor 22 may be attached to the engine body 2.

  In the second embodiment, the ignition plug 16 is used as an ignition device that ignites the hydrogen rich gas during the hydrogenation HCCI combustion operation. However, a dedicated ignition device may be provided separately from the ignition plug 16.

1 is a diagram illustrating a schematic configuration of an engine according to a first embodiment of the present invention. It is a figure for demonstrating the operation | movement at the time of the hydrogen addition lean burn operation | movement of the engine shown in FIG. It is a figure for demonstrating the operation | movement at the time of the HCCI combustion driving | operation of the engine shown in FIG. It is a figure which shows the map used for selection of the operating method of an engine in Embodiment 1 of this invention. It is a flowchart shown about the routine used for switching of the operating method of an engine in Embodiment 1 of this invention. It is a figure for demonstrating the operation | movement at the time of the hydrogenation HCCI combustion driving | operation of the engine shown in FIG. It is a figure for demonstrating the operation | movement at the time of the stoichiometric combustion driving | operation of the engine shown in FIG. It is a figure which shows the map used for selection of the operating method of an engine in Embodiment 2 of this invention. It is a flowchart shown about the routine used for switching of the operating method of an engine in Embodiment 2 of this invention.

Explanation of symbols

2 Engine body 4 Combustion chamber 6 Intake pipe 8 Exhaust pipe 10 Hydrogen injector 12 Gasoline injector 16 Spark plug 22 Dehydrogenation reactor 24 Raw fuel injector 30 Raw fuel tank 32 Separator 34 Switching valve 70 ECU (Electronic Control Unit)

Claims (3)

A tank for storing hydrogenated gasoline;
Fuel separation means for separating hydrogenated gasoline into hydrogen-rich gas and dehydrogenated gasoline;
Fuel supply means for supplying any of hydrogenated gasoline, hydrogen-rich gas and dehydrogenated gasoline selectively or in combination to the internal combustion engine;
When the internal combustion engine is operated in a predetermined operation region, an operation is performed by HCCI combustion using hydrogenated gasoline as a fuel. When the internal combustion engine is operated in a higher load region than the predetermined operation region, hydrogen rich gas and Control means for performing operation by lean combustion using dehydrogenated gasoline as fuel,
An internal combustion engine using hydrogen.   When the internal combustion engine is operated in a high load side operation region of the operation region by HCCI combustion, the control means adds an ignition device disposed in the combustion chamber while adding hydrogen rich gas to hydrogenated gasoline as fuel. 2. The hydrogen-utilizing internal combustion engine according to claim 1, wherein the internal combustion engine is operated. The control means performs operation by stoichiometric combustion using dehydrogenated gasoline as fuel when the internal combustion engine is operated in a higher load region than an operation region in which operation by lean combustion is possible. The hydrogen-utilizing internal combustion engine described.

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