JP2007120369A - Fuel reforming device and fuel ignition system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reforming device capable of greatly improving fuel economy by expanding a lean combustion area of an internal combustion engine and fuel ignition system using the same. <P>SOLUTION: The fuel reforming device is provided with a photocatalyst 6, a light source 5 capable of illuminating the photocatalyst with light, and a means retaining and collecting water formed in combustion stroke in a combustion chamber, in the combustion chamber of an internal combustion engine, the photocatalyst 6 absorbs light illuminated from the light source and forms hydrogen from water existing in the combustion chamber. A water trap material as a water retaining and collecting means is provided. An internal EGR and en external EGR are provided as a water retaining and collecting means. A means supplying sacrifice regent 7 is provided. The sacrifice regent is used as fuel. Moreover, a fuel ignition system suitable for fuel reforming device is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel reformer and a fuel ignition system using the same, and more specifically, a fuel reformer capable of improving energy utilization efficiency by utilizing a water splitting reaction by a photocatalyst and a fuel using the same It relates to an ignition system.

One way to reduce carbon dioxide, one of the global warming gases, is to improve the fuel consumption rate through lean combustion. In particular, in an in-cylinder injection gasoline engine, the air-fuel ratio is expanded to about 50 to 60 by strengthening tumble and swirl and strengthening the ignition system.
However, if the air-fuel ratio is higher than this, it becomes difficult for the flame to sufficiently propagate into the cylinder, and the combustion becomes unstable.

  In addition, even in an extremely lean mixture, flames can be sufficiently propagated into the cylinder by making the flame kernel larger, arranging a plurality of spark plugs to increase the flame propagation distance, and further the flame propagation speed. It is known to improve the air-fuel mixture.

For example, it has been proposed to increase the flame kernel by increasing the distance between the electrodes of the plug and supplying a high voltage, but in order to supply a higher voltage, the life of the electrode may be shortened (non- Patent Document 1).
“Spark plug” by Kenmitsu Nishio and Sankaido (1999)

Although it has been proposed to reduce the flame propagation distance by arranging a plurality of ignition plugs, it is difficult to install three or more ignition plugs because of the intake and exhaust valves of the cylinder head (see Patent Document 1). ).
Japanese Patent Publication No.59-18533

  Furthermore, although a method for improving the flame propagation speed by supplying hydrogen has been proposed, it is very expensive because a hydrogen storage tank or a hydrogen storage alloy is used (see Patent Document 2).

JP, 2005-155570, A Furthermore, although the method of generating hydrogen from fuel using plasma is proposed, it is difficult to supply sufficient amount of hydrogen because efficiency is low (refer to patent documents 3). . JP 2005-98226 A

In addition, it has been proposed that an air-fuel mixture with an improved flame propagation speed can be obtained by an alcohol reforming reaction using a catalyst. However, this method requires a high reaction temperature and power consumption required for electrolysis of water. There are also many (refer patent document 4).
JP 58-74504 A

  Thus, all the conventional methods have problems in cost and efficiency, and it is necessary to separately supply a hydrogen generation source such as water and alcohol.

On the other hand, a method using laser light for ignition of an air-fuel mixture is known (see Non-Patent Document 2).
In this method, the focal point is focused at an arbitrary position, and the air-fuel mixture can be ignited at this focal point. Therefore, the degree of freedom of ignition is high and stable combustion can be realized.
Automobile Engineering Society Academic Lecture Preprint 20055007

On the other hand, it is known that hydrogen and oxygen are produced when photocatalyst and water coexist and light is irradiated.
This is because the photocatalyst absorbs light and excites electrons in the valence band to the conduction band to generate electrons and holes, which reduce water to generate hydrogen, and the holes oxidize water. By generating oxygen.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to expand a lean combustion region of an internal combustion engine and greatly improve fuel efficiency and a fuel reformer It is to provide a fuel ignition system using the above.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor solved about 10% of the water generated when the air-fuel mixture is burned together with the photocatalyst and irradiates light. The present inventors have found that this can be done and have completed the present invention.

That is, the fuel reformer of the present invention comprises a photocatalyst in a combustion chamber of an internal combustion engine, a light source capable of irradiating the photocatalyst with light, and means for holding and collecting water generated in the combustion stroke in the combustion chamber. A fuel reformer comprising:
The photocatalyst absorbs at least a part of the light emitted from the light source, and hydrogen is generated from water existing in the combustion chamber.

  The fuel ignition system of the present invention is characterized by applying the fuel reformer.

  According to the present invention, about 10% of the water generated when the air-fuel mixture is combusted is made to coexist with the photocatalyst and is irradiated with light, so that the lean combustion region of the internal combustion engine is expanded and fuel efficiency is greatly improved. sell.

  Hereinafter, the fuel reformer of the present invention will be described in detail. In the claims and the specification, “%” represents a mass percentage unless otherwise specified.

  The fuel reformer of the present invention includes a photocatalyst in a combustion chamber of an internal combustion engine, a light source capable of irradiating the photocatalyst with light, and means for holding and collecting water generated in the combustion stroke in the combustion chamber. Become.

Thus, the photocatalyst absorbs at least part of the light emitted from the light source, and hydrogen is generated from the water present in the combustion chamber.
In other words, it is not necessary to supply water or alcohol as a hydrogen generation source from the outside as in the prior art, and hydrogen can be generated from water generated by the combustion of fuel in an existing system using a photocatalytic water splitting reaction.

In addition, by supplying the generated hydrogen to the air-fuel mixture, the combustion speed is increased and the lean combustion region is greatly expanded.
Furthermore, as shown in FIG. 1, when the photocatalyst absorbs light having a band gap or more, electrons in the valence band are excited to the conduction band to generate electrons and holes. The electrons reduce water to produce hydrogen, and the holes oxidize water to produce oxygen. As described above, since oxygen is generated at the same time when hydrogen is generated, the oxygen concentration in the air-fuel mixture can be increased, so that the output can be improved.

Here, the above-mentioned photocatalyst needs to have an energy ranking at the lower end of the conduction band on the negative side of the hydrogen generation potential from water.
As the photocatalyst, for example, titanium oxide, niobium oxide, potassium tantalate, or the like can be used.
These photocatalysts can be disposed at any part in the combustion chamber, specifically, at the upper part of the piston head or around the cylinder head. Further, the photocatalyst may be arranged in a form supported on a porous inorganic carrier.
The combustion chamber is not particularly limited, and for example, a hemispherical type, a multispherical type, a wedge type, a bathtub type, a pent roof type, etc. can be used with a desired displacement.

  Moreover, although the said light source changes with the air-fuel | gaseous mixture to be burned, the kind of photocatalyst, etc., a solid laser, a gas laser, a semiconductor laser, an excimer laser, a free electron laser, etc. can be used suitably. Further, a xenon lamp, a halogen lamp, a high pressure mercury lamp, or the like may be used.

  These light sources need only generate light having a wavelength longer than the band gap of the photocatalyst, and may be continuous or pulsed.

In the fuel reformer of the present invention, it is preferable to use a water trap material as the water retention / recovery means.
At this time, the water utilization efficiency can be improved by adsorbing more water in the combustion chamber. Thereby, more hydrogen can be produced | generated and the hydrogen concentration in air-fuel | gaseous mixture can be increased.

As said water trap material, a zeolite, magnesium oxide, etc. can be used, for example.
These water trap materials are preferably in contact with the photocatalyst or disposed in the vicinity of the photocatalyst. Typically, the water trap material is disposed on the photocatalyst or the photocatalyst is disposed on the water trap material. Can be used.

In addition, as the water holding / recovering means, it is also preferable to use one or both of internal EGR (Exhaust Gas Recirculation) and external EGR.
At this time, by supplying water generated in the combustion stroke by the EGR into the combustion chamber, hydrogen is generated by the photocatalytic water splitting reactant, and the hydrogen concentration in the air-fuel mixture can be increased. In addition, when using EGR, it is desirable to arrange | position in the combustion chamber combining the said water trap material, and to adsorb the supplied water.
For example, as shown in FIG. 3, an external EGR composed of an EGR control valve, an EGR valve, a thermo valve, and a diaphragm can be installed to collect water in the exhaust gas discharged from the exhaust valve 4 to the intake side. .

In the fuel reforming apparatus of the present invention, it is preferable to include means for supplying a sacrificial reagent from the viewpoint of promoting the oxidation reaction by the photocatalyst.
In the photocatalytic water splitting reaction, a reduction reaction that generates hydrogen from water proceeds easily, but an oxidation reaction that generates oxygen by oxidizing water hardly proceeds. For this reason, as shown in FIG. 2, if a sacrificial reagent is supplied to promote the oxidation reaction, it is possible to prevent the generation of hydrogen from being inhibited by the reduction reaction of water, which is effective.
Examples of the sacrificial reagent supply means include those that use part of pilot injection or main injection.

As the sacrificial reagent, typically, fuel can be used.
At this time, by using water generated in the combustion process and a fuel that is more easily oxidized than water as a sacrificial reagent, hydrogen can be generated smoothly by these photocatalytic water splitting reactants, and the hydrogen concentration in the mixture can be reduced. Can increase.
In other words, in the oxidation-reduction reaction, which is a semi-reaction in the water splitting reaction, fuel is used instead of water for the oxidation reaction, so that the reduction reaction of water is promoted and the amount of hydrogen generation can be increased.

  In addition, the said fuel typically means the fuel injected as a mixed gas into the combustion chamber of a general internal combustion engine, such as gasoline, light oil, and LPG.

In addition, alcohol can be used as the sacrificial reagent.
At this time, by using water generated in the combustion process and alcohol more easily oxidized than the above fuel as a sacrificial reagent, hydrogen can be generated more smoothly by these photocatalytic water splitting reactants, and the hydrogen concentration in the mixture Can be increased.
In other words, in the oxidation-reduction reaction, which is a semi-reaction in the water splitting reaction, alcohol is used in the oxidation reaction instead of water, so that the reduction reaction of water can be further promoted and the amount of hydrogen generated can be increased.

In addition, as said alcohol, methanol, ethanol, propanol etc. can be used, for example.
In addition to the use of a single substance or a mixture of a plurality of types of alcohol, for example, ethanol can be added to a fuel such as gasoline or light oil, or biofuel can be used. .

Furthermore, unburned hydrocarbons recovered from the exhaust can be used as the sacrificial reagent.
At this time, by using water generated in the combustion process and hydrocarbon as a sacrificial reagent, hydrogen can be generated more smoothly by these photocatalytic water splitting reactants, and the hydrogen concentration in the air-fuel mixture can be increased.
In other words, since hydrocarbons become carbon dioxide and water when oxidized, they are much more effective than water in which the reverse reaction proceeds.

In addition, as said hydrocarbon, ethylene, propylene, benzene, toluene etc. are mentioned, for example.
In order to use unburned hydrocarbons in the exhaust, internal EGR or external EGR may be used as appropriate.

Next, the fuel ignition system of the present invention will be described in detail.
The fuel ignition system of the present invention is formed by applying the fuel reformer described above.
Specifically, for example, as shown in FIG. 3, the combustion chamber formed by the cylinder 2 and the piston 1 is provided with an intake valve 3, an exhaust valve 4, and ignition means (not shown). The fuel reformer includes a light source 5, a photocatalyst 6, and a water trap material 7.

As shown in FIG. 3, first, water generated in the combustion stroke is adsorbed by a water trap material disposed in the vicinity of the photocatalyst 6 in the exhaust stroke, the intake stroke, and the compression stroke.
Further, in the intake stroke to the compression stroke until the air-fuel mixture is exploded, it is decomposed into hydrogen by the action of light irradiated from the light source 5 to the photocatalyst 6.
Next, the air-fuel mixture whose hydrogen concentration has been increased in the compression stroke is ignited by the ignition means.

  Thus, since the fuel ignition system of the present invention performs ignition after increasing the hydrogen concentration of the air-fuel mixture, an internal combustion engine with an extended lean limit and excellent fuel utilization efficiency can be realized.

In addition, as said ignition means, it can carry out by changing the wavelength of the light irradiated with the light source 5, for example, The irradiation angle of the light source 5, an irradiation range, etc. can be adjusted and ignition timing can be controlled.
It can also be ignited by spark ignition using a conventional spark plug. Examples of the spark plug include a U-groove type, a protruding type, a two-pole type, a creeping type, a wide U-type, a wide type, a four-pole type, a register built-in type, and a racing type.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
0.1 g of titanium oxide was disposed as a photocatalyst in the combustion chamber. Further, a xenon lamp was provided as a light source capable of irradiating the photocatalyst with light.
Next, a model gas containing water (10% in terms of mass) equivalent to the water generated in the combustion stroke and containing methane and oxygen in a ratio of 1: 2 is supplied into the combustion chamber, and the light source to the photocatalyst is 300 to Irradiated with 400 nm light.
When the hydrogen concentration in the fuel chamber was measured after the light irradiation, it was 0.1%.

(Example 2)
The same operation as in Example 1 was repeated except that 0.1 g of zeolite was disposed as a water trap material in the vicinity of the photocatalyst.
When the hydrogen concentration in the fuel chamber was measured after the light irradiation, it was 0.13%.

(Example 3)
Further, the model gas was modified by repeating the same operation as in Example 2 except that 2% methanol was mixed as a sacrificial reagent with the model gas.
When the hydrogen concentration in the combustion chamber was measured after the light irradiation, it was 0.3%.

According to the fuel reformers of Examples 1 to 3, which are preferred embodiments of the present invention, it has been found that the hydrogen concentration increases. In particular, when a water trap material or a sacrificial reagent is used, the hydrogen generating ability is greater.
In the fuel ignition system according to the fourth embodiment, which is a preferred embodiment of the present invention, the lean limit increases due to an increase in the hydrogen concentration of the air-fuel mixture. It is clear that good energy efficiency can be obtained in an internal combustion engine such as the above.

It is the schematic which shows the water splitting reaction by a photocatalyst. It is the schematic which shows the water splitting reaction by a photocatalyst when a sacrificial reagent is used. It is the schematic of the fuel ignition system using external EGR. It is the schematic which shows each process of a fuel ignition system.

Explanation of symbols

1 Piston 2 Cylinder 3 Intake valve 4 Exhaust valve 5 Light source 6 Photocatalyst 7 Sacrificial reagent

Claims (8)

In a combustion chamber of an internal combustion engine, a fuel reformer comprising a photocatalyst, a light source capable of irradiating the photocatalyst with light, and means for holding and collecting water generated in the combustion stroke in the combustion chamber,
A fuel reformer characterized in that a photocatalyst absorbs at least part of light emitted from a light source, and generates hydrogen from water present in a combustion chamber.   2. The fuel reformer according to claim 1, further comprising a water trap material as water holding / recovering means.   The fuel reformer according to claim 1 or 2, further comprising an internal EGR and / or an external EGR as water retention / recovery means.   The fuel reformer according to any one of claims 1 to 3, further comprising means for supplying a sacrificial reagent, wherein the oxidation reaction by the photocatalyst can be promoted.   The fuel reformer according to claim 4, wherein the sacrificial reagent is a fuel.   The fuel reformer according to claim 4, wherein the sacrificial reagent is alcohol.   The fuel reformer according to claim 4, wherein the sacrificial reagent is unburned hydrocarbons recovered from the exhaust.   A fuel ignition system to which the fuel reformer according to any one of claims 1 to 7 is applied.

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