JP6329340B2 - Internal combustion engine and internal combustion engine system - Google Patents

Description

  The present invention relates to an internal combustion engine driven using a combustible fuel, and more particularly to an internal combustion engine and an internal combustion engine system with reduced cooling loss.

  Generally, in an internal combustion engine, 30% to 40% of the calorific value of fuel supplied to a combustion chamber and combusted is converted into power, and the remaining 50% to 60% is discharged to the outside as waste heat. In the case of a spark ignition type internal combustion engine, it is known that the theoretical cycle is an Otto cycle, and the theoretical thermal efficiency exceeds 60%. However, there are various losses in the actual combustion cycle, and the thermal efficiency is only 30% to 40%.

  One of the major causes of this loss is the loss accompanying cooling of the combustion chamber. This loss is generally referred to as cooling loss and occupies 20% to 30% of the calorific value of the fuel supplied to the internal combustion engine, which accounts for a large portion of the waste heat of the internal combustion engine.

  Therefore, if the combustion chamber of the internal combustion engine can be ideally insulated, that is, if this cooling loss can be eliminated, the actual combustion cycle can be brought close to the theoretical efficiency of the Otto cycle. In addition, waste heat that is discarded as exhaust gas also occupies a relatively large part. For this reason, the heat insulation of the combustion chamber can increase the ratio of waste heat of the exhaust gas, so that the effect of improving the efficiency by exhaust heat recovery of the exhaust gas is increased. In other words, by combining heat insulation and exhaust heat recovery, a significant improvement in the efficiency of the internal combustion engine can be realized. For this reason, the development which improves the heat insulation of a combustion chamber is earnestly performed.

  In order to insulate the combustion chamber, it is important to suppress heat transfer between the combustion gas and the wall surface of the combustion chamber. For example, in the republished patent WO2009-020206 (Patent Document 1), It has been proposed to bring the surface temperature of the combustion chamber closer to the temperature of the combustion chamber gas, reduce the temperature difference between the temperature of the combustion chamber gas and the surface temperature of the combustion chamber, and reduce convective heat transfer. Patent Document 1 describes that a material having extremely low thermal conductivity and specific heat is applied to the material on the outermost surface of the combustion chamber. Examples of the material include applying a composite material including an air layer. In addition to Patent Document 1, in order to insulate the combustion chamber, a method of spraying and coating a ceramic material on the wall surface of the combustion chamber and a method of attaching a heat storage material have been proposed.

Republished patent WO2009-020206

  By the way, in an internal combustion engine that has achieved heat insulation so far, as disclosed in Patent Document 1, it is necessary to apply a composite material having a large number of cavities in terms of thermal and mechanical aspects such as heat resistance and pressure resistance. Is causing problems. That is, in Patent Document 1, in order to reduce convective heat transfer, the wall surface on the combustion chamber side is made of a material having a very low heat transfer coefficient and specific heat. For this reason, a material containing air or inert gas has been proposed as a heat insulating material. The higher the ratio of air or inert gas, the lower the thermal conductivity and specific heat, and the heat insulation performance is improved, but conversely, because it is a material containing air or inert gas, heat resistance, pressure resistance, etc. There is a problem that the thermal and mechanical properties are inferior.

  The object of the present invention is to rapidly increase the temperature of the combustion chamber surface to bring the combustion chamber surface temperature close to the temperature of the combustion gas to improve the heat insulation performance, and to increase the proportion of air or inert gas that enhances heat insulation. An internal combustion engine with improved thermal and mechanical strength and an internal combustion engine system using the internal combustion engine is provided.

  A feature of the present invention is that a radiation absorption layer formed of a material having a high radiation absorption rate is provided on the surface of the combustion chamber, and the surface temperature of the radiation absorption layer is rapidly increased by combustion light to flow from the combustion gas to the outside of the combustion chamber. The heat flux is low.

  According to the present invention, by providing a radiation absorbing layer formed of a material having a high radiation absorption rate on the surface of the combustion chamber, the surface temperature of the combustion chamber can be rapidly increased by radiant heat transfer by the combustion light. The temperature difference between the temperature of the combustion gas and the radiation absorption layer generated by the above is reduced, and the heat insulation performance can be improved by suppressing the heat of the combustion gas from flowing outside the combustion chamber. In addition, since an auxiliary heat insulating mechanism such as air or inert gas can be avoided as much as possible, it is possible to ensure thermal and mechanical strength.

It is sectional drawing which shows the partial cross section of the surface vicinity of the combustion chamber which becomes the 1st Embodiment of this invention. It is sectional drawing which shows the partial cross section of the surface vicinity of the combustion chamber used as the modification of 1st Embodiment shown in FIG. It is sectional drawing which shows the partial cross section of the surface vicinity of the combustion chamber which becomes the 2nd Embodiment of this invention. It is sectional drawing which shows the partial cross section of the surface vicinity of the combustion chamber used as the modification of 2nd Embodiment shown in FIG. It is a figure which shows the example compared about the light absorptivity with respect to the non-oxide of various metal materials, and an oxide. It is a characteristic view which shows the characteristic of the light absorptivity of the solid aluminum and the anodized aluminum. It is a characteristic view which shows the relationship between the monochromatic radiation ability of a cocoon, and the light absorption rate of aluminum. It is a characteristic view which shows the change for every crank angle of the average temperature of combustion chamber gas, and a combustion chamber outermost surface temperature. It is a characteristic view which shows the change for every crank angle of the heat flux in the heat insulation structure which becomes this invention, and the conventional heat insulation structure. It is a characteristic view which shows the relationship between the thermophysical value of a combustion chamber outermost surface, and the integrated heat flux per cycle. It is a block diagram which shows the structure of the internal combustion engine system which combined the fuel reforming system which becomes the 3rd Embodiment of this invention. It is a characteristic view which shows the relationship between the kind of fuel, heat insulation performance, and thermal efficiency. It is a block diagram which shows the modification of the internal combustion engine system which combined the fuel reforming system shown in FIG. It is a block diagram which shows the general | schematic whole structure of a reformer. It is a block diagram which shows the structure of the reaction cell of a reformer. It is a block diagram which shows the structure of the reaction sheet | seat of a reformer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and application examples are included in the technical concept of the present invention. Is also included in the range.

  FIG. 1 shows a partial cross section of a combustion chamber according to the first embodiment of the present invention. The structure of the internal combustion engine is well known and will not be described in detail here. However, the cylinder head lower wall, the cylinder inner wall, the piston top surface, and the intake / exhaust valves are in contact with the combustion gas in the combustion chamber. In some cases, the injector is in contact with the combustion gas in the case of in-cylinder injection, and the spark plug is in contact with the combustion gas in a spark ignition engine. Accordingly, one or more of the above-described components are applicable to this embodiment. In this embodiment, a configuration in which a radiation absorbing layer is formed on a typical cylinder inner wall surface as a combustion chamber will be described.

  In FIG. 1, reference numeral 101 denotes a radiation absorption layer formed from a high radiation absorption material, and a heat insulating layer 102 formed from a low thermal conductivity material is provided on the inside thereof, and further a combustion chamber is formed on the inside thereof. A base body, that is, a cylinder main body 103 constituting a cylinder is provided. Cooling water, which is a cooling medium, flows through the cylinder body 103 as a base material and releases the heat of the cylinder body 103 to the outside. The cylinder body 103 is made of aluminum, aluminum alloy, cast iron, magnesium alloy, or the like. The heat is efficiently released to the cooling water. Further, the radiation absorption layer 101 which is a feature of this embodiment has a function of rapidly increasing the temperature by radiant heat transfer by the combustion light of the combustion gas, and the temperature of the radiation absorption layer 101 which has been increased is used as the cylinder body 103. A heat insulating layer 102 is provided so as not to escape.

  The radiation absorbing layer 101 that is in contact with the combustion gas in the combustion chamber is formed of a material having a high radiation absorption rate. Typically, the following materials can be used. For example, an oxide made of titanium oxide, zinc oxide, zirconium oxide, tungsten oxide, tin oxide, nickel oxide, tungsten carbide, cadmium sulfide, copper, indium, tin, or the like, or carbon is used. These can be used alone or in combination. In short, it is sufficient that the radiation absorption rate is high and a function capable of withstanding high temperatures is provided, and it may be selected appropriately according to the specifications of the internal combustion engine. Furthermore, the thickness of the radiation absorbing layer 101 formed of the material having a high radiation absorption rate is desirably a thickness of 100 μm or less, but this is also appropriate depending on the specifications of the internal combustion engine. It only has to be selected. The reason why the thickness of the radiation absorbing layer 101 is reduced in this way is to increase the rate of temperature rise. In general, a metal oxide is a material having a higher light absorption rate than a non-oxide, and the absorption rate is 70% or more. Therefore, it is important to select a material having a radiation absorption rate of a metal oxide having a predetermined absorption rate or higher, preferably 70% or higher.

  Further, the heat insulating layer 102 formed between the cylinder body 103 and the radiation absorption rate layer 101 is made of a low thermal conductivity material, and the following materials can be typically used. For example, an organic silicon compound containing zirconia, titanium, silicon, carbon, silicon, oxygen, or the like, or a ceramic fiber having high heat resistance and high strength can be used. These can also be used alone or in combination. In short, it is only necessary to suppress the flow of heat of the radiation absorbing layer 101 to the cylinder body 103 side and to have a function to withstand high temperatures, and it may be selected appropriately according to the specifications of the internal combustion engine. In this case, the heat insulating layer 102 is selected to have good bondability between the radiation absorbing layer 101 and the cylinder body 103.

  FIG. 2 shows a modification of the embodiment shown in FIG. 1, in which a heat insulating layer 102 is formed inside the radiation absorbing layer 101. In this case, the low thermal conductivity material may be dispersed inside the above-described high radiation absorptivity material. However, the heat insulating layer 102 is formed of a gas such as air or an inert gas or a decompressed cavity (including a vacuum). It may be formed.

  As described above, in this embodiment, the heat insulating layer 102 is formed on the upper surface of the cylinder body 103, and the radiation absorbing layer 101 is further formed on the upper surface. Therefore, when a combustion flame is formed in the combustion chamber, Radiation heat transfer due to combustion light occurs in the radiation absorbing layer 101 which is the outermost surface material of the combustion chamber, and the temperature of the radiation absorbing layer 101 rapidly increases. Moreover, since the radiation absorption layer 101 is formed in a thin layer of 100 μm or less in this embodiment, the radiation absorption layer 101 instantaneously reaches a high temperature because of its small heat capacity. Thereby, the temperature difference between the radiation absorption layer 101 and the combustion gas is reduced, and the heat of the combustion gas can be prevented from flowing into the radiation absorption layer 101.

  Further, since the heat insulating layer 102 shields between the cylinder body 103 that releases heat and the radiation absorbing layer 101 that needs to maintain a high temperature, the heat of the radiation absorbing layer 101 can flow to the cylinder body 103. It can be reduced as much as possible. For this reason, it can suppress that the temperature of the radiation absorption layer 101 falls, and can maintain the temperature of the radiation absorption layer 101 in a high state. As shown in FIG. 2, when a heat insulating layer 102 containing air or an inert gas is provided inside the radiation absorbing layer 101, the radiation absorbing layer 101 can be used for radiation absorption due to scattering at the time of radiation absorption and reduction of the specific heat of the material. The rate of temperature increase can be increased.

  In this way, the temperature difference between the radiation absorbing layer 101 and the combustion gas is reduced, thereby suppressing the heat of the combustion gas from flowing into the radiation absorbing layer 101, resulting in less cooling loss. It becomes possible to do.

  Furthermore, since the radiation absorbing layer 101 is provided, an auxiliary heat insulating mechanism such as air or inert gas can be avoided as much as possible, so that it is possible to ensure thermal and mechanical strength. is there. This reason will be described in detail based on FIG. 10 described later.

  Next, a second embodiment of the present invention will be described with reference to FIG. 3, which also shows a partial cross section of the combustion chamber. In FIG. 3, a cavity is formed between the cylinder body 103 and the radiation absorbing layer 101 as the heat insulating layer 102, and this cavity forms the heat insulating layer 102 by being directly formed in the cylinder body 103. The cavity is filled with air or inert gas and may be a decompressed cavity. The shape of the cavity is not limited to that shown in FIG. 3, and various structures such as a porous structure can be adopted.

  In FIG. 3, the radiation absorbing layer 101 is formed by subjecting the surface of the cylinder body 103 to an oxidation treatment. That is, the radiation absorbing layer 101 is formed by subjecting the base material itself to an oxidation treatment to form an oxide film. For example, a porous oxide film containing many micropores 104 as shown in FIG. 3 is formed by preferably performing an anodizing process as an oxidizing process. For example, if the cylinder body 103 is made of aluminum, anodization is performed on the cylinder body 103 to form alumite. This alumite has a higher radiation absorption rate than aluminum and can be used as the radiation absorption layer 101. As described above, it is possible to reduce the temperature difference between the coating portion of the alumite and the combustion gas, and the temperature difference between the radiation absorbing layer 101 and the combustion gas is reduced as in the first embodiment. Can be suppressed from flowing to the radiation absorbing layer 101, and as a result, the cooling loss can be reduced. The cylinder body 103 is not limited to aluminum, but other metal materials such as a magnesium alloy can be used without any problem, and the present invention is not limited to this embodiment.

  Here, in this embodiment, since the radiation absorbing layer 101 is formed by the constituent material itself of the cylinder body 103, in addition to the effect that the forming method can be simplified, the joining property when using different materials, etc. A secondary effect that there is little need to consider this can be expected.

  Further, the embodiment shown in FIG. 4 shows a modification of the embodiment of FIG. 3, and in this modification, the radiation absorbing layer 101 and the heat insulating layer 102 are formed of a material different from that of the cylinder body 103. That is, this is a method of forming the radiation absorbing layer 101 by oxidizing the material of the heat insulating layer 102, for example, anodizing. In FIG. 4, titanium is used as the material of the heat insulating layer 102, and this titanium is joined to the cylinder body 103 made of an aluminum alloy. The titanium is anodized to form titanium oxide, and the titanium oxide is formed as a porous oxide film layer containing a large number of fine holes 104.

  Furthermore, as another material instead of titanium shown in FIG. 4, it is advantageous to use a material having a lower thermal conductivity than that of the cylinder body 103. For example, an aluminum alloy, cast iron, or the like can be used for the cylinder body 103, and a titanium alloy, a magnesium alloy, or the like can be used for the material of the heat insulating layer 102. Then, the surface of the titanium alloy or magnesium alloy is anodized to form an anodized film layer. As a result, the temperature of the anodic oxide coating layer of the titanium alloy or magnesium alloy rises rapidly due to radiant heat transfer (light absorption), and since the titanium alloy and magnesium alloy have low thermal conductivity, heat conduction to the cylinder body 103 can be achieved. It becomes possible to suppress. By adopting such a configuration, the cylinder body 103 can be made of a generally widely used aluminum alloy or the like.

  Thus, also in this modified example, it becomes possible to reduce the temperature difference between the anodized film portion functioning as the radiation absorbing layer 101 and the combustion gas, and the radiation absorbing layer 101 and the combustion gas can be reduced as in the first embodiment. The temperature difference between them becomes small, and this makes it possible to suppress the heat of the combustion gas from flowing into the radiation absorbing layer 101, and as a result, cooling loss can be reduced.

  FIG. 5 shows a comparison of the light absorptivity of non-oxides and oxides of various metal materials. For example, in magnesium, the light absorptance of a non-oxide is 0.27, whereas the light absorptance of an oxide is 0.75. By using an oxide, the light absorptance is improved. I understand that. Similarly, it can be seen that also in nickel, titanium, aluminum, and iron, the light absorption rate of the oxide is higher than that of the non-oxide. In general, a metal oxide is a material having a higher light absorption rate than a non-oxide, and the absorption rate is 70% or more.

  Also, as shown in FIGS. 3 and 4, since the anodic oxide film has a porous structure, the surface area is increased, and the light absorption rate can be further increased. Therefore, if a material having excellent functions of the heat insulating layer 102 and the radiation absorbing layer 101 is selected and the heat insulating layer 102 and the radiation absorbing layer 101 are formed, the temperature difference between the combustion gas and the radiation absorbing layer 101 is further increased. It can be reduced. Further, the configuration can be simplified.

  FIG. 6 is an example in which the light absorptance is compared between a sample in which anodization is applied to aluminum to form an alumite layer that is the radiation absorption layer 101 and a solid aluminum sample that has not been subjected to anodization. . The anodized anodized layer can increase the light absorption rate in a wide wavelength range. Therefore, since the wavelength selectivity is small, light of many wavelengths accompanying combustion can be absorbed, and the temperature of the alumite layer can be rapidly increased by radiant heat transfer.

  Here, when anodizing treatment is performed, the material surface of the cylinder body 103 or the heat insulating layer 102 is chemically treated in an electrolyte solution, so that durability and manufacturing stability can be ensured. In addition, the anodization treatment can change the conditions such as voltage and time, thereby making the fine holes 104 in the surface of the radiation absorbing layer 101, and adjusting the depth and interval thereof. Specifically, the thickness of the oxide film can be controlled in the range of 0 to 100 μm.

  With such a structure, the radiation absorbing layer 101, which is an anodized film formed on the outermost surface of the cylinder body 103 on the combustion chamber side, absorbs the light of the combustion flame, and the temperature near the radiation absorbing layer 101 rapidly increases. To rise. As a result, the temperature difference between the temperature of the combustion gas in the combustion chamber and the radiation absorbing layer 101 is reduced, so that convective heat transfer can be suppressed and cooling loss can be suppressed.

  As described above, according to the internal combustion engine of the present invention represented by the embodiment shown in FIGS. 1 to 4, the combustion light in the combustion chamber reaches the radiation absorbing layer 101 formed of the high radiation absorptivity material. Later, convective heat transfer with hot combustion gases takes place. For this reason, since the radiation absorption layer 101 made of a high radiation absorptivity material is formed on the surface inside the combustion chamber, the temperature of this portion is rapidly increased by the radiation heat transfer of the combustion light. As a result, the temperature difference between the combustion gas temperature in the combustion chamber and the radiation absorbing layer 101 on the combustion chamber surface is reduced, and as a result, the heat flux from the combustion gas in the combustion chamber to the combustion chamber wall surface is reduced.

  The heat flux from the combustion chamber of an internal combustion engine is generally affected by convective heat transfer and radiant heat transfer. For example, in the case of a diesel engine, the heat flux by radiant heat transfer occupies about 20%. In general, aluminum alloys and cast iron are often used in the combustion chamber. Since both materials have low radiation absorption rates, the heat flux due to radiant heat transfer is small.

  FIG. 7 shows the relationship between the radiation intensity B of each soot wavelength contained in the diesel flame and the radiation absorption rate A of aluminum. As can be seen from this figure, in the case of aluminum, the radiation absorption rate A is low in the wavelength region where the radiation intensity B of the soot is high. On the other hand, in the region where the radiation absorption rate A is high, the radiation intensity of the soot is low, and it can be seen that sufficient light energy is not generated. This reduces radiant heat transfer. Therefore, if the radiation absorption rate A is increased in a region where the radiation intensity B is high, the radiation heat transfer can be increased. To this end, as described with reference to FIG. 6, the anodized anodized layer can increase the light absorption rate in a wide wavelength range. Therefore, since the wavelength selectivity is small, light of many wavelengths accompanying combustion can be absorbed, and the temperature of the alumite layer can be rapidly increased by radiant heat transfer. Thus, it is effective to increase the radiation heat transfer by forming the radiation absorbing layer 101. Although FIG. 7 shows the case of alumite, the same can be said for other metal oxides.

  FIG. 8 shows an example of the history of the average temperature of the combustion gas and the temperature history of the radiation absorbing layer 101 on the outermost surface of the combustion chamber when the radiation absorbing layer 101 made of the high radiation absorbing material is formed on the outermost surface of the combustion chamber. . FIG. 8 is a history of temperature at the crank angle from the start of combustion to the end of combustion. It can be seen that the temperature of the radiation absorbing layer 101 on the outermost surface of the combustion chamber is higher than the average temperature of the combustion gas due to the effect of radiant heat transfer in the early stage of combustion. Thereafter, as the combustion proceeds, the average temperature of the combustion gas becomes higher than the temperature of the radiation absorbing layer 101 on the outermost surface of the combustion chamber, but the temperature difference is small. Therefore, the heat flux flowing from the combustion gas to the cylinder body via the radiation absorbing layer 101 is reduced.

  FIG. 9 shows changes in the heat flux of the conventional heat insulation structure described in Patent Document 1 and the heat flux of the heat insulation structure according to the present invention at the crank angle from the start of combustion to the end of combustion. As can be seen from this figure, it can be understood that the heat insulation structure of the present invention has a smaller heat flux over the whole and the cooling loss is suppressed.

  FIG. 10 shows the thermophysical properties of the radiation absorbing layer 101 formed on the outermost surface of the combustion chamber. In this case, the horizontal axis represents the thermal conductivity, the vertical axis represents the specific heat, and the contour lines of the heat flux (total per cycle) are shown. Show. A broken line shows the heat insulation structure of Patent Document 1, and a solid line shows the heat insulation structure of the present invention. As can be seen from this figure, since the radiation absorbing layer 101 is formed using a high radiation absorbing material in the heat insulating structure of the present invention, even a material having a higher thermal conductivity and specific heat than the conventional heat insulating structure can be used as a heat flow. The bundle is to get smaller.

  For example, in the case where the integrated heat flux is 0.4, the heat insulating structure of the present invention indicated by a solid line is more thermally conductive than the conventional heat insulating structure indicated by a broken line even if the integrated heat flux is 0.4. The specific heat is increasing. In other words, this means that there is little need to increase the heat insulation performance of the heat insulation layer 102 so much when obtaining the same heat insulation performance. For this reason, compared with the conventional heat insulation structure, since the heat insulation layer 102 can be formed of a material having a low ratio of cavities enclosing air or inert gas, it is possible to provide sufficient thermal and mechanical strength.

  In this way, by forming the radiation absorbing layer 101 made of a high radiation heat absorbing material on the surface of the combustion chamber, the temperature difference between the radiation absorbing layer and the combustion gas is reduced, whereby the temperature of the combustion gas is reduced to the radiation absorbing layer. As a result, it is possible to reduce the cooling loss.

  Furthermore, since the high radiant heat absorption material has a high emissivity, the surface temperature of the combustion chamber is more likely to be lower than that of the conventional material during the intake stroke, and as a result, an increase in the intake temperature in the combustion chamber can be suppressed. As a result, it is possible to improve the charging efficiency of the air sucked into the combustion chamber and to further improve the knocking resistance. For this reason, high torque and high thermal efficiency of the internal combustion engine can be realized.

  Since the internal combustion engine according to the present invention described above can suppress the heat flux flowing to the wall surface of the combustion chamber during combustion, the thermal efficiency can be increased. However, the heat trapped in the combustion chamber has a function of increasing the ratio of the exhaust heat. I have. Normally, waste heat from internal combustion engines can be categorized as waste heat from cooling and waste heat from exhaust, but as described above, if heat insulation is improved by reducing the heat escaping from the combustion chamber, the proportion of waste heat from cooling decreases. As a result, the ratio of waste heat due to exhaust increases. Therefore, an efficient exhaust heat recovery system can be realized by easily combining exhaust heat recovery systems. Above all, by combining with a heat recovery system using a fuel reformer, the effect can be increased synergistically.

  Hereinafter, embodiments in which the internal combustion engine and the exhaust heat recovery system according to the present invention are combined will be described. FIG. 11 is a block diagram showing a combination of the internal combustion engine with improved heat insulation according to the present invention and an exhaust heat recovery system using a fuel reformer.

This system includes a reformer 110 in an exhaust pipe, and supplies heat from the exhaust to the reformer 110. By supplying the first fuel from the first fuel supply device 111 to the reformer 110 that has recovered the exhaust heat, the fuel passes through the fuel reforming catalyst filled in the reformer 110, so that the hydrogen is removed. The reformed gas is reformed. The supply amount of the first fuel is adjusted by the first fuel supply device 111. Further, the reformed gas obtained by the reformer 110 is supplied via the reformed gas supply device 112 so that the supply amount thereof is adjusted and supplied to the intake air sucked into the internal combustion engine. Further, the first fuel supplied to the internal combustion engine is supplied to the internal combustion engine after the supply amount is adjusted by the second fuel supply device 113. In the reformer 110, for example, the following reforming reaction occurs.
CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ -164 kJ
In the case of this reforming reaction, an endothermic reaction that absorbs heat of 164 kJ occurs before and after the reaction. By using the exhaust gas having a high exhaust temperature in this way for the reforming reaction, the exhaust heat of the internal combustion engine can be recovered as fuel energy. In general, the endothermic reaction has a higher conversion efficiency as the reforming temperature is higher. Therefore, since the exhaust gas temperature is increased by using the internal combustion engine with improved heat insulation performance as described above, the conversion efficiency of the reformer is increased and the amount of exhaust heat recovered during reforming can be increased.

  The reformed gas is supplied to the combustion chamber as a fuel for the internal combustion engine. However, since the reformed gas is a gas containing hydrogen, lean combustion can be realized compared to other hydrocarbon fuels, and highly efficient combustion can be realized. In addition, hydrogen can burn faster than hydrocarbon fuels such as gasoline, so it approaches the Otto cycle and the theoretical thermal efficiency increases. In the case of a conventional internal combustion engine, rapid combustion increases cooling loss and the effect of improving the thermal efficiency is small. However, as shown in FIG. 12, the effect of improving the thermal efficiency during rapid combustion increases as the combustion chamber is insulated.

  From the above, the efficiency is improved synergistically by combining the heat insulation of the combustion chamber with the exhaust heat recovery using fuel reforming. Such a system combining an internal combustion engine and a fuel reformer can be applied to various fuels such as gasoline, light oil, methanol, ethanol, DME, and ammonia in addition to methane as a fuel.

  Further, as shown in FIG. 13, the first fuel can be supplied to the reformer 110, and the second fuel can also be applied to a multiple fuel supply type internal combustion engine that supplies the combustion chamber directly. In this case, a high octane fuel such as gasoline, methanol, ethanol, and ammonia is used as the first fuel, and a high cetane fuel such as light oil, heavy oil, and biodiesel is used as the second fuel.

  The supply amount of the second fuel is adjusted by a second fuel supply device 113 that directly injects the fuel into the combustion chamber. The first fuel is supplied to the reformer 110 via the first fuel supply device 111, and the flow rate of the reformed gas that has exited from the reformer 110 is adjusted via the reformed gas supply device 112. Is supplied to the intake pipe.

  In general, in a multiple fuel supply type internal combustion engine, the first fuel is supplied so as to be premixed in the intake pipe of the internal combustion engine without passing through the reformer 110. Is difficult to burn, lowers the combustion efficiency, and has a problem that a large amount of unburned hydrocarbon is discharged. However, since this system can generate hydrogen by the first fuel passing through the reformer 110, it can stably burn even under conditions with a high excess air ratio, improving combustion efficiency, and suppressing emission of unburned hydrocarbons. Is possible.

  In addition, by improving the heat insulation of the combustion chamber of the internal combustion engine, the temperature of the combustion chamber wall surface is increased during combustion, and the temperature non-uniformity of the air-fuel mixture is reduced. Can burn. In other words, by combining the heat insulation of the combustion chamber and exhaust heat recovery using fuel reforming, it is possible to synergistically improve the combustion efficiency, and also to suppress the emission of unburned hydrocarbons, greatly improving efficiency. It is possible.

  The detailed structure of the reformer 110 shown in FIGS. 11 and 13 is shown in FIGS. 14A, 14B, and 14C.

  As shown in FIG. 14A, the reformer 110 includes a plurality of reaction cells 31 whose outer shape has a cylindrical shape, and a cylindrical first casing 32 that accommodates the plurality of reaction cells 31. Then, the first fuel 1 flows through each reaction cell 31, and high-temperature exhaust gas flows outside the reaction cell 31 and through the first casing 32. The 1st casing 32 and the 2nd casing 34 mentioned below are formed with metal (for example, SUS) so that heat conductivity may become high. In addition, the shape of the 1st casing 32 and the 2nd casing 34 is not limited to a cylindrical shape, For example, a square cylinder shape and a polygonal cylinder shape may be sufficient.

  As shown in FIG. 14B, the reaction cell 31 includes a plurality of stacked reaction sheets 33 and a second casing 34 that accommodates the plurality of reaction sheets 33.

  As shown in FIG. 14C, each reaction sheet 33 includes a base metal foil 35, a porous layer 36 formed on each surface of the metal foil 35, and a catalyst 37 supported on the porous layer 36. Yes. That is, each reaction sheet 33 has a three-layer structure in which a porous layer 36 carrying a catalyst 37, a metal foil 35, and a porous layer 36 carrying a catalyst 37 are laminated in this order. Note that a gap is formed between the reaction sheets 33 adjacent in the thickness direction so that the first fuel and the reformed gas containing the generated hydrogen can flow therethrough.

  Further, since the reaction sheet 33 is in the form of a sheet, its heat capacity is small, heat is quickly conducted through the reaction sheet 33, and the temperature of the catalyst 37 is quickly raised to a temperature at which the catalyst functions well. Thereby, the efficiency of the decomposition reaction which decomposes | disassembles the fuel 1 into the reformed gas containing hydrogen is high.

  Further, each reaction sheet 33 is formed with a plurality of through holes 33a. As a result, the heat of the exhaust gas is conducted well in the thickness direction, and the reformed gas containing the first fuel and the generated hydrogen flows well in the thickness direction. The metal foil 35 is made of, for example, an aluminum foil and has a thickness of about 50 to 200 μm. However, the metal foil 35 may not be provided, or instead of the metal foil 35, a porous layer serving as a base may be provided, and the entire reaction sheet 33 may have a porous structure.

  The porous layer 36 is a layer for supporting the catalyst 37 and has a plurality of pores through which the reformed gas containing the first fuel and the generated hydrogen can flow. Such a porous layer 36 is made of an oxide mainly composed of alumina, for example.

  The catalyst 37 is a catalyst for decomposing the first fuel and generating a reformed gas containing hydrogen. Such a catalyst 37 is composed of at least one selected from, for example, platinum, nickel, palladium, rhodium, iridium, ruthenium, molybdenum, rhenium, tungsten, vanadium, osmium, chromium, cobalt, iron and the like. Of course, it goes without saying that a plurality of materials may be used in combination in some cases.

  To sum up the present invention, the present invention is provided with a radiation absorbing layer formed of a material having a high radiation absorption rate on the surface of the combustion chamber, and the surface temperature of the combustion chamber is rapidly increased by the radiation absorbing layer to thereby convert the combustion chamber into the combustion chamber. The convective heat transfer that flows to the outside is suppressed.

  According to such a configuration, the surface temperature of the combustion chamber can be rapidly increased by radiant heat transfer by providing a radiation absorption layer formed of a material having a high radiation absorption rate on the surface of the combustion chamber. The temperature difference between the generated combustion gas and the radiation absorption layer is reduced, and the heat insulation performance can be improved by suppressing the heat of the combustion gas from flowing outside the combustion chamber. In addition, auxiliary such as air and inert gas Thus, it is possible to ensure the thermal and mechanical strength because it is possible to avoid the use of a typical heat insulation mechanism as much as possible.

  Further, when the internal combustion engine and the exhaust heat recovery system as described above are combined, the temperature of the exhaust gas discharged from the internal combustion engine becomes high, so the fuel flowing through the reformer can be reformed more efficiently. As a result, the amount of exhaust heat recovered during reforming can be increased.

  DESCRIPTION OF SYMBOLS 101 ... Radiation sudden layer layer, 102 ... Heat insulation layer, 103 ... Cylinder main body, 104 ... Micropore

Claims (9)

In an internal combustion engine having a combustion chamber to which a combustible fuel is supplied and extracting the power by burning the combustible fuel,
The combustion chamber is
A metal substrate made of the same metal material with good heat transfer to release heat,
A heat insulating layer that is bonded to the metal substrate and has a lower thermal conductivity than the metal substrate, and is made of a material different from the material of the surface of the metal substrate;
Provided in the heat insulating layer on the opposite side of the metal substrate, formed from a radiation absorbing layer having a high radiation absorption rate of combustion light made of a material different from the metal substrate,
An internal combustion engine characterized in that the temperature of the radiation absorbing layer is rapidly increased by combustion light, and the heat of the radiation absorbing layer is suppressed from flowing to the metal substrate by the heat insulating layer. The internal combustion engine according to claim 1,
The internal combustion engine, wherein the radiation absorbing layer is made of a material different from that of the metal base and the heat insulating layer. The internal combustion engine according to claim 1,
The heat insulating layer is made of a metal having a lower thermal conductivity than the metal base material, and the radiation absorbing layer is formed by oxidizing the metal forming the heat insulating layer. A characteristic internal combustion engine. The internal combustion engine according to claim 3,
The internal combustion engine, wherein the radiation absorbing layer is a coating layer formed by anodizing a metal forming the heat insulating layer. The internal combustion engine according to any one of claims 1 to 4,
The internal combustion engine, wherein the radiation absorption layer is a coating layer having a radiation absorption rate of 70% or more. The internal combustion engine according to any one of claims 1 to 4,
The internal combustion engine, wherein the radiation absorbing layer has fine pores on the surface thereof. The internal combustion engine according to any one of claims 1 to 4,
The internal combustion engine, wherein the radiation absorbing layer has a thickness of 100 μm or less.   A reformer capable of generating a reformed gas containing hydrogen is provided in the exhaust pipe of the internal combustion engine according to any one of claims 1 to 7, and the reformed gas obtained by the reformer is used as the reformed gas. A reformed gas supply device for supplying the combustion chamber of the internal combustion engine is provided, a first fuel supply device for supplying fuel to the reformer, and the fuel without passing through the reformer. An internal combustion engine system comprising a second fuel supply device that supplies the combustion chamber.   A reformer capable of generating a reformed gas containing hydrogen is provided in the exhaust pipe of the internal combustion engine according to any one of claims 1 to 7, and the reformed gas obtained by the reformer is used as the reformed gas. A reformed gas supply device for supplying the combustion chamber of the internal combustion engine is provided, a first fuel supply device for supplying a first fuel to the reformer, and a second fuel for the combustion chamber of the internal combustion engine. An internal combustion engine system provided with a second fuel supply device for supplying to the engine.

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