Exhaust gas treatment system for alcohol engine, and vehicle

Abstract

The purpose of the present invention is to provide an exhaust gas treatment system that is suitable for an alcohol engine configured so as to use a high-concentration alcohol-containing fuel that contains alcohol at an alcohol concentration of greater than 20% by volume. In the present invention, a catalyst is provided with a carrier that has a passage wall, and a plurality of contours or holes are formed in the passage wall so as to come in contact with exhaust gas molecules in a combustion exhaust gas of the high-concentration alcohol-containing fuel that is produced through combustion of the high-concentration alcohol-containing fuel by an alcohol engine. Accordingly, during a cold start, the decrease in chemical reaction of exhaust gas molecules resulting from the decrease in the average kinetic energy of the exhaust gas molecules in the combustion exhaust gas of the high-concentration alcohol-containing fuel relative to exhaust gas produced by combustion of gasoline fuels or low-concentration alcohol-containing fuels is compensated for, and at high loads, the exhaust gas molecules in the combustion exhaust gas of the high-concentration alcohol-containing fuel are dispersed so that the density of chemical reactions thereof does not become locally concentrated.

Description

Alcohol engine exhaust gas treatment system and vehicle

[0001] The present invention relates to an exhaust gas treatment system for an alcohol engine and a vehicle equipped with the exhaust gas treatment system.

[0002] Patent Document 1 discloses a control technology for optimizing fuel injection control and catalytic exhaust gas purification in an internal combustion engine of a saddle-type vehicle, thereby reducing the emission of harmful substances and easing the environmental load. The saddle-type vehicle described in Patent Document 1 is expected to be able to use a variety of fuels, such as gasoline fuel and fuel containing alcohol.

[0003] International Publication No. 2020 / 162002

[0004] In the exhaust gas treatment system for alcohol engines disclosed in Patent Document 1, the use of high-concentration alcohol-containing fuels with an alcohol concentration of over 20% by volume is desirable. However, compared to gasoline fuels and low-concentration alcohol-containing fuels, high-concentration alcohol-containing fuels pose the following challenges: High-concentration alcohol-containing fuels have a high heat of vaporization and absorb a large amount of heat during combustion. Especially during cold starts, the exhaust gas temperature drops, reducing the average kinetic energy of the exhaust gas molecules. This makes it difficult for the exhaust gas molecules to cross the activation energy barrier, making it difficult for the reaction to proceed. High-concentration alcohol-containing fuels have a low calorific value. This increases the fuel supply rate and the number of reacting molecules per unit volume. Furthermore, the inclusion of oxygen within the molecules promotes localized oxidation reactions. Especially under high loads, the density of chemical reactions in the exhaust gas tends to concentrate locally. Therefore, an exhaust gas treatment system that solves these challenges specific to high-concentration alcohol-containing fuels and is compatible with high-concentration alcohol-containing fuels is needed.

[0005] SUMMARY OF THE INVENTION It is an object of the present invention to provide an exhaust gas treatment system compatible with an alcohol engine configured to use a high alcohol content fuel having an alcohol concentration greater than 20% by volume.

[0006] (1) An exhaust gas treatment system for an alcohol engine according to one embodiment of the present invention is an exhaust gas treatment system for an alcohol engine comprising: an alcohol engine configured to use an alcohol-containing fuel; and a catalyst for treating exhaust gas from the alcohol engine, wherein the alcohol engine is configured to burn a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume; and the catalyst comprises a carrier provided with a passage wall, and the passage wall has a plurality of irregularities or holes formed therein configured to come into contact with exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas generated by the alcohol engine burning the high-concentration alcohol-containing fuel, thereby compensating for a decrease in chemical reaction of exhaust gas molecules caused by a decrease in the average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas compared to exhaust gas generated by burning gasoline fuel or low-concentration alcohol-containing fuel during cold start; and during high load, dispersing the chemical reaction density of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas so that it does not concentrate locally.

[0007] According to the exhaust gas treatment system of (1), it is possible to provide an exhaust gas treatment system that is compatible with an alcohol engine configured to use a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume. More specifically, it is as follows.

[0008] [Compensating for the Decrease in Chemical Reaction Efficiency Due to the Decrease in Exhaust Gas Temperature During Cold Start] High-concentration alcohol-containing fuels have a high heat of vaporization and absorb a lot of heat during combustion. Especially during cold start, the exhaust gas temperature drops, reducing the average kinetic energy of the exhaust gas molecules. This makes it difficult for the exhaust gas molecules to overcome the activation energy barrier, making it difficult for the reaction to proceed. Here, according to the exhaust gas treatment system (1), the multiple irregularities or holes formed on the catalyst passage walls increase the contact area with the exhaust gas molecules, improving the diffusion and contact time of the exhaust gas. This increases the opportunity for the molecules to react, making it easier for them to overcome the activation energy barrier, and furthermore, the uniform temperature distribution promotes the reaction, achieving a combined effect. The average kinetic energy of the exhaust gas molecules is low, making it easier for the exhaust gas molecules to overcome the activation energy barrier, making it easier for the reaction to proceed even at low temperatures. [Preventing Localized Concentration of Chemical Reaction Density Under High Load] In the exhaust gas treatment system (1), when using a high-concentration alcohol-containing fuel with a low calorific value, increasing the fuel supply rate increases the number of reactive molecules in the exhaust gas. The multiple irregularities or holes formed on the catalyst passage walls efficiently disperse reactive molecules, increasing the chances of reaction. In addition, the unburned high-concentration alcohol-containing fuel contained in the exhaust gas from combustion of high-concentration alcohol-containing fuel contains oxygen, which tends to promote local oxidation reactions, and under high loads, chemical reactions may concentrate in specific areas. The catalyst equipped in the exhaust gas treatment system (1) is more likely to distribute reactions evenly due to the multiple irregularities or holes that disperse exhaust gas molecules, thereby suppressing local overheating and catalyst deterioration.

[0009] [Detailed explanation of the effects of a catalyst with multiple asperities or holes formed on the passage wall when used with a high-concentration alcohol-containing fuel] Improvement in low-temperature activity during cold start ∝ (increased contact time due to multiple asperities or holes / activation energy) × temperature uniformity effect. This formula conceptually shows the improvement in low-temperature activity during cold start when used with a catalyst with multiple asperities or holes formed on the passage wall when used with a high-concentration alcohol-containing fuel. 1. Molecules: - Multiple asperities or holes extend the contact time of exhaust gas molecules with low kinetic energy with the catalyst surface. - Longer contact time increases the probability of reaction progression. - Exhaust gas retention, which is particularly important at low temperatures, is achieved. 2. Energy: - Activation energy is the energy barrier required to initiate a reaction. - At low temperatures, the kinetic energy of exhaust gas molecules is low, making it difficult for them to overcome this barrier. - Longer contact time with the catalyst increases the probability of overcoming the energy barrier. 3. Temperature: - Multiple asperities or holes uniformize the temperature distribution on the catalyst surface. - Localized low-temperature areas are reduced, improving reaction efficiency across the entire catalyst. - Uniform temperature distribution is particularly effective in improving activity at low temperatures. The interaction of these three factors improves catalytic activity at low temperatures. In other words, the following combined effects are achieved: - Increasing contact time with the catalyst increases the opportunity for exhaust gas molecules to react, - It makes it easier for them to overcome the activation energy barrier, and - Furthermore, uniform temperature distribution on the catalyst promotes reaction.

[0010] [Detailed explanation of the effects of a catalyst with multiple asperities or holes formed on the passage walls when using gasoline fuel as a comparative example] As a comparative example, the case of gasoline fuel was examined. Improvement in low-temperature activity during cold start ∝ Mass transfer promotion effect × Temperature distribution coefficient This formula conceptually shows the improvement in low-temperature activity during cold start when using a catalyst with multiple asperities or holes formed on the passage walls when using gasoline fuel. 1. Mass transfer: - Multiple asperities or holes thin the exhaust gas boundary layer, promoting mass transfer to the catalyst surface. - The turbulence effect improves the efficiency of the supply of reactants to the catalyst surface. - Mass transfer resistance, which is particularly important at low temperatures, is reduced. 2. Reaction field: - Promotion of mass transfer maintains an appropriate concentration of reactants on the catalyst surface. - Because the reaction rate is slow at low temperatures, uniformity of material supply is important. - Promotion of mass transfer by multiple asperities or holes enables efficient use of the reaction field. 3. Temperature: - Multiple asperities or holes uniformly distribute the temperature on the catalyst surface. - Promoting localized heat transfer stabilizes the temperature of the entire catalyst. - Uniform temperature distribution contributes to effective use of the reaction field. The interaction of these three elements improves catalytic activity at low temperatures. In other words, the following combined effects are achieved: - Promotion of mass transfer optimizes the supply of reactants, - Effective use of the reaction field stabilizes catalyst performance, and - Uniform temperature distribution further improves reaction efficiency.

[0011] [Differences in the Functional Effects of Catalysts with Multiple Asperities or Holes Formed on the Channel Walls for High-Concentration Alcohol-Containing Fuel and Comparative Gasoline Fuel] The functional effects of multiple asperities or holes in both fuels are fundamentally different in their mechanisms and purposes. With high-concentration alcohol-containing fuel, the primary functions are extending the contact time of exhaust gas molecules and overcoming the activation energy barrier, with temperature uniformity supporting this and contributing to improved low-temperature catalyst activity. In other words, this functional mechanism emphasizes reaction promotion at the molecular level. In contrast, with gasoline fuel, the primary function is optimizing the supply of reactants by promoting mass transfer, complemented by stabilizing the reaction field through temperature uniformity, thereby improving the low-temperature catalyst activity. This functional mechanism emphasizes macroscopic mass transfer and uniforming the reaction field. Thus, the functional mechanisms of the two fuels are fundamentally different, and the recognition of the challenge of "overcoming the activation energy barrier" in high-concentration alcohol-containing fuel is a new perspective that differs from the "control of mass transfer and reaction field" in gasoline fuel. Furthermore, the idea of ​​using a catalyst having a plurality of asperities or holes formed on the passage walls to extend the contact time of exhaust gas molecules with the catalyst as a means of solving this problem is a unique concept that could not be conceived from existing knowledge about gasoline fuel. From knowledge about catalysts having a plurality of asperities or holes formed on the passage walls for gasoline fuel, it is difficult to predict the above-mentioned unique action and effect for fuels containing high concentrations of alcohol, and the effect of a catalyst having a plurality of asperities or holes formed on the passage walls for fuels containing high concentrations of alcohol is an unexpected and unique effect that cannot be derived from conventional design concepts.

[0012] [Design of a catalyst having a plurality of irregularities or holes formed in the passage wall] When designing a catalyst having a plurality of irregularities or holes formed in the passage wall, consideration is given to, for example, the type of alcohol contained, the concentration of the alcohol, the shape, size, and density of the irregularities and holes formed in the passage wall of the catalyst, the type and component ratio of the precious metals supported, the thickness of the coating treatment, the component blend, etc. Once the essential difference between the mechanism of action in high-concentration alcohol-containing fuel and that in gasoline fuel is understood, these factors can be adjusted through design and experiments using high-concentration alcohol-containing fuel to adapt to the exhaust gas characteristics of high-concentration alcohol-containing fuel.

[0013] An alcohol-containing fuel is a fuel composition containing alcohol as a primary component. The term "primary component" here means that the alcohol is not an impurity or an unavoidable mixture, and includes, for example, at least 1% by volume. An alcohol-containing fuel may also contain a hydrocarbon fuel. A hydrocarbon fuel may also be included as a primary component. Examples of alcohols include, but are not limited to, methanol, ethanol, propanol, and butanol. The alcohol concentration (volume concentration) may be greater than 0% by volume or substantially 100% by volume. Examples of hydrocarbon fuels include, but are not limited to, gasoline. E3, E10, E15, E20, E22, E25, E27, E85, and E100. E indicates the volume percentage of ethanol in a gasoline-ethanol mixture. A mixture with a different composition but equivalent concentration may also be used. The composition and alcohol concentration of the alcohol-containing fuel are not particularly limited, as long as it is applicable to an alcohol engine. A high-concentration alcohol-containing fuel is an alcohol-containing fuel with an alcohol concentration greater than 20% by volume. The alcohol engine is not particularly limited as long as the upper limit of the alcohol concentration of the applicable alcohol-containing fuel exceeds 20% by volume. Examples of such upper limits include 22, 25, 27, 85, and 100% by volume. A 22% by volume upper limit means that the alcohol engine can use alcohol-containing fuel with an alcohol concentration of up to 22% by volume. The higher the upper limit, the higher the alcohol concentration of the applicable alcohol-containing fuel. The alcohol engine may be configured so that the lower limit of the alcohol concentration of the applicable alcohol-containing fuel exceeds 0% by volume. The alcohol concentration of the applicable alcohol-containing fuel is not particularly limited as long as it is within the above-mentioned upper and lower limits. Furthermore, with regard to the number of cylinders, the alcohol engine includes, for example, a single-cylinder engine and an engine with two or more cylinders. That is, the alcohol engine includes, for example, an engine with one or two or more combustion chambers. The alcohol engine may be, for example, a single-cylinder engine, a two-cylinder engine, a non-equidistant firing three-cylinder engine, or a non-equidistant firing four-cylinder engine.When an alcohol engine has multiple combustion chambers and each of the combustion chambers is connected to an intake passage, the alcohol-containing fuel injection device does not necessarily inject fuel into all of the intake passages. "The alcohol engine is configured to burn a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume" includes, for example, an alcohol engine configured to burn a mixture of high-concentration alcohol-containing fuel and air (high-concentration alcohol-containing fuel mixture) in the combustion chamber. The alcohol engine includes, for example, an alcohol-containing fuel ignition device. The alcohol-containing fuel ignition device is a device that ignites the high-concentration alcohol-containing fuel mixture (high-concentration alcohol-containing fuel and air mixture) introduced into the combustion chamber. The device is, for example, an ignition system. The device does not need to be dedicated to alcohol-containing fuel; it can be a general-purpose device that is also used for gasoline fuel. The exhaust gas treatment system for the alcohol engine further includes, for example, an alcohol-containing fuel injection device. The alcohol-containing fuel injection device may be configured to inject high-concentration alcohol-containing fuel into the intake passage at a rich air-fuel ratio during cold start. Here, "the alcohol-containing fuel injection device injects a high-concentration alcohol-containing fuel into the intake passage at a rich air-fuel ratio" includes, for example, the alcohol-containing fuel injection device injecting a high-concentration alcohol-containing fuel into the intake passage so that the air-fuel ratio of the mixture before combustion, i.e., the high-concentration alcohol-containing fuel mixture, becomes rich. The alcohol-containing fuel injection device is configured, for example, to inject the entire amount of alcohol-containing fuel supplied to the combustion chamber into the intake passage. The alcohol-containing fuel injection device is, for example, an injector. The alcohol-containing fuel injection device may be a dedicated product for alcohol-containing fuel or a general-purpose product that is also used for gasoline fuel. The alcohol-containing fuel injection device can be selected depending on the alcohol concentration of the alcohol-containing fuel. There are no particular limitations on the manner in which the alcohol-containing fuel injection device injects the alcohol-containing fuel into the intake passage.The alcohol-containing fuel injection device may, for example, inject the alcohol-containing fuel into an intake port forming an intake passage, or into an intake pipe forming the intake passage. Here, the intake port is formed in a cylinder head constituting the alcohol engine. The intake pipe is connected to the cylinder head so as to communicate with the intake port. Note that in-cylinder injection is not performed in alcohol engines. The catalyst is provided in the exhaust passage. One catalyst may be provided in the exhaust passage, or multiple catalysts may be provided in the exhaust passage. When multiple catalysts are provided in the exhaust passage, the catalyst according to the present invention is, for example, the catalyst provided most upstream among the multiple catalysts. For example, some of the multiple catalysts may be provided in a silencer. When the alcohol engine has multiple combustion chambers and each of the multiple combustion chambers is connected to an exhaust passage, the catalyst according to the present invention is provided downstream of the position where the multiple exhaust passages converge. The catalyst may, for example, be a three-way catalyst. The three-way catalyst is, for example, a catalytic converter for simultaneously converting carbon monoxide, hydrocarbons, and nitrogen oxides emitted from the alcohol engine. The catalyst may have, for example, a metal honeycomb structure. The surface of the honeycomb structure is coated with a catalytic noble metal (e.g., Pt, Pd, Rh, etc.). In other words, the metal honeycomb structure serves as a carrier. The metal honeycomb structure includes passage walls that form the passages through which exhaust gas flows. The multiple irregularities or holes formed in the passage walls are not particularly limited as long as they contribute to extending the contact time of exhaust gas with the catalyst. The multiple irregularities or holes include, for example, multiple punched holes (through holes), multiple embossments, multiple dimples, multiple protrusions, and multiple recesses. The protrusions may be, for example, small pieces formed by raising a portion of the passage wall from the passage wall so as to face the inside of the passage. The small pieces are formed, for example, so as to protrude from the passage wall. The multiple irregularities or holes may be composed of the same type of irregularities or holes, or may be composed of multiple different types of irregularities or holes. The catalyst may be a dedicated product for alcohol-containing fuels or a general-purpose product that is also used for gasoline fuels. The cold start period is, for example, at least a part of the period from the start of the start operation until the inlet temperature of the catalyst reaches a predetermined temperature.The start of the starting operation refers to, for example, the start of operation of a motor that applies driving force to the crankshaft of the alcohol engine when the alcohol engine is started. The predetermined temperature is, for example, the temperature at which the catalyst is activated. Cold start refers to, for example, the period from the start of the starting operation to complete combustion. Complete combustion refers to a state in which the crankshaft of the alcohol engine is driven independently by the combustion of a high-concentration alcohol-containing fuel mixture of high-concentration alcohol-containing fuel and air without the need for an external driving force such as a motor. The number of ignitions required to achieve complete combustion is not particularly limited; complete combustion may be achieved by the first ignition, or by a second or subsequent ignitions. After complete combustion, the alcohol-containing fuel injection device may, for example, inject high-concentration alcohol-containing fuel into the intake passage at an air-fuel ratio that is leaner than that during cold start. An air-fuel ratio that is leaner than that during cold start is, for example, an air-fuel ratio that is at or close to the stoichiometric air-fuel ratio. "Injecting high-concentration alcohol-containing fuel into the intake passage at an air-fuel ratio leaner than that during cold start" includes, for example, injecting high-concentration alcohol-containing fuel into the intake passage so that the air-fuel ratio of the mixture before combustion, i.e., the high-concentration alcohol-containing fuel mixture, is leaner than that during cold start. Cold start refers to, for example, the period from the start of the starting operation to the first injection before complete combustion or the first explosion injection. The first explosion refers to, for example, the first combustion of the high-concentration alcohol-containing fuel mixture in the combustion chamber after the start of the starting operation. The first explosion injection refers to, for example, the injection of high-concentration alcohol-containing fuel that constitutes the high-concentration alcohol-containing fuel mixture related to the first explosion. The exhaust gas treatment system for an alcohol-containing engine further includes, for example, a control device. The control device controls, for example, the alcohol-containing fuel injection device to inject high-concentration alcohol-containing fuel into the intake passage at an air-fuel ratio richer than that during cold start. The control device determines whether or not cold start is occurring based on, for example, the output of at least one sensor. The at least one sensor includes, for example, a sensor for measuring the temperature of cooling water that cools the alcohol engine or a sensor for measuring the temperature of a catalyst. The control device controls the alcohol-containing fuel injection device so that, for example, during high load, the high-concentration alcohol-containing fuel is injected into the intake passage at an air-fuel ratio that is leaner than during cold start.A high-load state refers to, for example, a period when the temperature and / or pressure of exhaust gas emitted from an alcohol engine are high, resulting in a high load on the catalyst. A high-load state refers to, for example, a period when the engine speed of an alcohol engine is in a high engine speed range. A high engine speed range refers to, for example, the highest engine speed range obtained by dividing the range from the idling speed of the alcohol engine (e.g., the idling speed during steady operation) to the engine speed at the rev limit into thirds. During a high-load state, for example, high-concentration alcohol-containing fuel is injected into the intake passage at an air-fuel ratio that is leaner than during a cold start. Therefore, the amount of excess alcohol-containing fuel contained in the exhaust gas is reduced compared to during a cold start. The tendency for the exhaust gas temperature to decrease due to the vaporization of the excess alcohol-containing fuel is suppressed. As a result, the exhaust gas temperature tends to increase during a high-load state. An exhaust gas treatment system for an alcohol engine further includes, for example, a sensor that detects the alcohol concentration of the alcohol-containing fuel. Based on the output of the sensor, the control device, for example, sets a stoichiometric air-fuel ratio and / or a rich air-fuel ratio according to the detected alcohol concentration. The sensor may be provided, for example, in an alcohol-containing fuel tank containing alcohol-containing fuel, in a pipe connecting the alcohol-containing fuel tank to an alcohol-containing fuel injection device, or in the alcohol-containing fuel injection device. A rich air-fuel ratio is, for example, an air-fuel ratio lower than the stoichiometric air-fuel ratio, i.e., an air-fuel ratio in which the fuel ratio is higher than stoichiometric. The stoichiometric air-fuel ratio of an alcohol-containing fuel is determined, for example, by the type of alcohol contained and the concentration of the alcohol. The exhaust gas treatment system for an alcohol engine further includes, for example, a sensor that detects the oxygen concentration in the exhaust gas. The control device controls, for example, the air-fuel ratio based on the output of the sensor. The sensor may be, for example, an oxygen sensor or an air-fuel ratio sensor. The control device controls the air-fuel ratio based, for example, on the output of a sensor that detects the oxygen concentration in the exhaust gas and the output of a sensor that detects the alcohol concentration of the alcohol-containing fuel. The exhaust gas treatment system for an alcohol engine is not, for example, configured to adjust the alcohol concentration of the high-concentration alcohol-containing fuel injected into the intake passage depending on the situation.The system may include, for example, an alcohol-containing fuel tank configured to store high-concentration alcohol-containing fuel having a predetermined alcohol concentration, and an alcohol-containing fuel injection device connected to the fuel tank configured to inject the high-concentration alcohol-containing fuel supplied from the fuel tank into the intake passage. The system may be configured to use the supplied high-concentration alcohol-containing fuel as is. Here, "using the supplied high-concentration alcohol-containing fuel as is" includes, for example, refueling with high-concentration alcohol-containing fuel having an alcohol concentration different from that of the high-concentration alcohol-containing fuel previously refueled and using the high-concentration alcohol-containing fuel. Changes in alcohol concentration due to refueling are not included in adjusting the alcohol concentration according to the situation. "Adjusting the alcohol concentration according to the situation" means, for example, changing the alcohol concentration between a cold start and after the cold start. The system may include, for example, a fuel tank configured to store gasoline and a fuel tank configured to store alcohol or alcohol-containing fuel to be mixed with gasoline, but is not configured to adjust the mixture ratio of gasoline and alcohol or alcohol-containing fuel according to the situation.

[0014] According to one aspect of the present invention, the exhaust gas treatment system for an alcohol engine can employ the following configuration: (2) The exhaust gas treatment system for an alcohol engine according to (1), wherein the catalyst is configured such that at least a portion of the passage wall on which the plurality of irregularities or holes are formed is located upstream of the silencer in the exhaust passage, thereby further compensating for the decrease in chemical reaction of exhaust gas molecules caused by a decrease in the average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during cold start compared to exhaust gas generated by burning gasoline fuel or low-concentration alcohol-containing fuel, and dispersing the chemical reaction density of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during high load so that it does not concentrate locally.

[0015] According to the exhaust gas treatment system of (2), the plurality of irregularities or holes can be positioned upstream of the silencer, which provides excellent effects during cold start-up and high load operation. More specifically, this is as follows.

[0016] During cold start-up: Exhaust gas reaches the catalyst with minimal heat loss. This promotes catalyst temperature rise, improving the kinetic energy of exhaust gas molecules. Combined with the extended contact time of exhaust gas due to the multiple asperities or holes, this helps overcome the activation energy barrier. Chemical reactions are more likely to proceed even at low temperatures, improving low-temperature activity. During high load: By utilizing the high flow rate and high pressure of exhaust gas upstream of the muffler, the reaction dispersion effect of the multiple asperities or holes is further enhanced. In particular, the mixing effect of promoting turbulence and the dispersion effect of the multiple asperities or holes work synergistically, preventing the reaction density in the exhaust gas from concentrating locally in specific areas, making it easier for reactions to proceed evenly throughout the catalyst. Overheating and catalyst deterioration are suppressed, enabling stable exhaust gas treatment over the long term. In other words, the exhaust gas treatment system (2) effectively solves problems that are specific to fuels containing high concentrations of alcohol, such as reduced activity at low temperatures and concentrated reaction density at high loads, and the synergistic effect of multiple irregularities or holes and their arrangement significantly improves the efficiency of exhaust gas treatment.

[0017] [Variations] According to this configuration, at least some of the multiple asperities or holes formed in the passage wall are located in the exhaust pipe. Note that at least some of the multiple asperities or holes formed in the passage wall may be located in both the exhaust pipe and the silencer. As long as at least some of the multiple asperities or holes formed in the passage wall are located in the exhaust pipe, the remaining some may be located in the silencer.

[0018] According to one aspect of the present invention, the exhaust gas treatment system for an alcohol engine can employ the following configuration: (3) The exhaust gas treatment system for an alcohol engine according to (1) or (2), wherein the catalyst is configured such that the passage walls are metallic passage walls, and the metallic passage walls are arranged to have metallic thermal conduction with a metallic exhaust pipe and / or a metallic silencer, so that, under high load, heat is released to the outside via the metallic exhaust pipe and / or the metallic silencer while dispersing the chemical reaction density in the high-concentration alcohol-containing fuel combustion exhaust gas so as not to be concentrated locally.

[0019] According to the exhaust gas treatment system of (3), the heat conduction effect between the multiple asperities or holes and the metals acts synergistically, greatly improving temperature control, reaction efficiency, and system reliability. First, from the perspective of temperature control, the efficient dispersion and release of reaction heat stabilizes the temperature of the catalyst and prevents overheating. The temperature is uniform throughout the catalyst, maintaining a stable reaction field. Chemical reactions are more likely to proceed sustainably. Furthermore, the dispersion effect of the reaction due to the multiple asperities or holes prevents localized concentration of reaction density, maintaining a uniform temperature distribution in the catalyst and improving reaction efficiency. Thermal degradation of the catalyst is suppressed, ensuring the long-term stability of the exhaust gas treatment system and improving maintainability. Stable catalyst performance and long-term durability are achieved, especially under high loads.

[0020] The exhaust pipe and / or muffler constitute an exhaust passage through which exhaust gas flows. The exhaust pipe and / or muffler can also be referred to as an exhaust passage. The exhaust pipe is connected to the cylinder head of an alcohol engine. The exhaust pipe is connected to the muffler. The exhaust pipe is provided between the cylinder head and the muffler. Metallic heat conduction means that heat is transferred from a metal passage wall to a metal exhaust passage (exhaust pipe and / or muffler) via metal. Another metal part (e.g., a metal stay) may be interposed between the passage wall and the exhaust passage. The metals may be in contact with each other. The metals may be welded to each other. However, the metals do not have to be welded as long as they are in contact with each other. [Variations] The metallic heat-conducting portion may be located in the exhaust pipe. The metallic heat-conducting portion may be located in both the exhaust pipe and the muffler. The metallic heat-conducting portion may be located in the muffler.

[0021] According to one aspect of the present invention, an exhaust gas treatment system for an alcohol engine can employ the following configuration: (4) An exhaust gas treatment system for an alcohol engine according to any one of (1) to (3), wherein the alcohol-containing fuel is a high-concentration alcohol-containing fuel having an alcohol concentration of more than 85% by volume, and the system is configured to exhibit qualitatively different behavior compared to exhaust gas from gasoline fuel or low-concentration alcohol-containing fuel during cold start, with the average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas being reduced and undergoing a phase change from gas phase to liquid phase, and to be configured such that under high load, the chemical reaction density in the high-concentration alcohol-containing fuel combustion exhaust gas is locally and nonlinearly concentrated, forming a specific reaction path.

[0022] High-concentration alcohol-containing fuels with an alcohol concentration of over 85% by volume have the following physicochemical properties during cold start. [Unique Phenomena During Cold Start] 1. Effects of Heat of Vaporization In the present invention, high-concentration alcohol-containing fuels have a significant cooling effect due to their high heat of vaporization, significantly reducing the temperatures of the combustion chamber and exhaust system. This cooling effect is particularly pronounced during cold start, causing frequent gas-liquid phase changes. 2. Condensation and Liquid Film Formation In the present invention, when high-concentration alcohol-containing fuels are burned, unburned alcohol components in the exhaust gas may condense, forming a liquid phase in the exhaust pipe. This can result in the formation of a localized liquid film, which can affect the exhaust flow and catalytic reaction. 3. Changes in Molecular Motion In the present invention, when fuel contains high-concentration alcohol, the molecular kinetic energy in the gas phase decreases, promoting the transition to the liquid phase under certain conditions. Furthermore, the presence of the liquid phase causes special molecular interactions at the gas-liquid interface. 4. In this study, the condensation of high-concentration alcohol-containing fuels may affect the reaction on the catalyst surface and change the exhaust gas purification performance. This physical factor is a characteristic not seen in gasoline fuels or low-concentration alcohol fuels, and requires a new approach to exhaust gas treatment.

[0023] High-concentration alcohol-containing fuels with an alcohol concentration of over 85% by volume exhibit the following characteristic chemical reaction pattern under high loads. [Unique Reaction Behavior Under High Loads] 1. Nonlinear Reaction Density Concentration: In the present invention, it has been confirmed that the use of high-concentration alcohol-containing fuels results in localized reaction concentrations beyond normal prediction, forming regions where the reaction density increases exponentially. This results in the appearance of sudden heat generation points on the catalyst surface. 2. Formation of Unique Reaction Pathways: In the present invention, it has been confirmed that high-concentration alcohol-containing fuels accelerate autocatalytic reactions due to oxygen in alcohol molecules, resulting in the accumulation of intermediate products and the progression of chain reactions. This results in the generation of new reaction intermediates not seen in conventional fuels. 3. Qualitative Changes in the Reaction Field: In the present invention, the use of high-concentration alcohol-containing fuels results in the formation of unique adsorption states on the catalyst surface under high loads, causing a sudden change in the local concentration gradient of reactants. It has also been confirmed that new reaction fields are generated due to the uneven distribution of reaction heat. The phenomenon of the present invention is clearly different from the reactions observed with conventional low-concentration alcohol fuels and has the following mechanism of action.・Rather than simply increasing the reaction rate, the reaction mechanism itself is altered. ・New reaction pathways become dominant, resulting in reaction behavior at high loads that is significantly different from that of conventional fuels.

[0024] The interaction effect of multiple asperities or holes in high-concentration alcohol fuels with an alcohol concentration of over 85% will be described. Specifically, the following characteristics are observed regarding the interaction with multiple asperities or holes during cold start. 1. Effect on gas-liquid phase change: In the present invention, multiple asperities or holes have been shown to be effective in maintaining and controlling the liquid phase. In particular, stably maintaining a liquid film in the recesses ensures a reaction field, and multiple asperities or holes enable control of the liquid phase distribution using surface tension effects. Furthermore, gradual evaporation from the liquid phase maintains a sustained reaction. 2. Complementary effect on molecular kinetic energy: In the present invention, multiple asperities or holes have the effect of complementing molecular kinetic energy. This effect is proportional to the product of the extension of contact time due to the asperities or holes and the energy transfer efficiency during phase change. Specifically, temporary capture of molecules by the recesses, control of molecular kinetic energy due to the complex surface shape, and promotion of special molecular interactions at the gas-liquid interface are observed. 3. Formation of a local temperature field: In the present invention, multiple asperities or holes have the effect of generating a minute temperature gradient. In particular, the recessed portions have a temperature retention effect, and the protrusions have enhanced heat conduction, and the latent heat generated by the phase change is effectively utilized to form a local temperature field. These characteristics enable advanced reaction control that was not possible with conventional fuel structures.

[0025] The interaction effect of multiple asperities or holes under high loads in high-concentration alcohol fuels with alcohol concentrations above 85% will be described. Under high loads, the multiple asperities or holes have the following properties: 1. Nonlinear Reaction Control Effect: In the present invention, the multiple asperities or holes have the effect of spatially dispersing the reaction density. Specifically, the three-dimensional dispersion of the reaction field by the asperities or holes alleviates local reaction concentration and effectively disperses reaction heat, improving reaction stability. 2. Control of Specific Reaction Paths: In the present invention, the multiple asperities or holes have the effect of controlling specific reaction paths. This control effect is proportional to the spatial distribution of the asperities or holes and the control efficiency of reaction intermediates. Specifically, intermediate products can be temporarily retained in the recesses, achieving stepwise reaction promotion and spatial control of chain reactions. 3. Formation of Self-Organizing Reaction Fields: In the present invention, the multiple asperities or holes have the effect of optimizing the formation of self-organizing reaction fields. In particular, the concentration gradient of the reactants is controlled, which effectively utilizes the catalytic active sites, and the heat of reaction is locally controlled, optimizing the entire reaction field. These characteristics enable stable and efficient reactions even under high loads.

[0026] The mechanism by which the synergistic effect occurs in high-concentration alcohol fuels with an alcohol concentration of over 85% is explained below. The effects under both conditions are synergistically driven by the following factors: 1. Structural Factors: In the present invention, it has been confirmed that the depth and distribution of multiple asperities or pores contribute to both phase change control during cold start and reaction dispersion under high load. This improves reaction efficiency and stability. 2. Physicochemical Factors: In the present invention, it has been shown that controlling molecular behavior on the catalyst surface has the effect of simultaneously promoting reaction in low-temperature environments and suppressing reaction in high-temperature environments. This enables optimal reaction control under different operating conditions. 3. Thermodynamic Factors: In the present invention, thermal control through the microstructure contributes to maintaining activity during cold start and preventing overheating under high load. This ensures reaction continuity and safety. These synergistic effects make it possible to achieve new, unprecedented synergistic effects that address issues specific to high-concentration alcohol fuels with an alcohol concentration of over 85%.

[0027] (5) A vehicle equipped with an exhaust gas treatment system for an alcohol engine according to any one of (1) to (4).

[0028] According to the vehicle (5), in a vehicle equipped with an exhaust gas treatment system for an alcohol engine that uses fuel containing a high concentration of alcohol, a catalyst suitable for both cold start and high load usage can be provided.

[0029] A vehicle is a device for transportation. A vehicle is configured to operate in a manned or unmanned (automated) manner. A vehicle can be a personal transportation vehicle. For example, a vehicle may be a public transportation vehicle such as a bus. Examples of personal transportation vehicles include automobiles and saddle-type vehicles. A vehicle may or may not have wheels. Examples of vehicles without wheels include ships with propellers, drones and helicopters with propellers, snowmobiles, and watercraft. A vehicle may or may not have a cabin. Examples of vehicles with a cabin include automobiles and helicopters. An example of a vehicle is a small vehicle for one or two passengers. An example of a vehicle is a saddle-type vehicle. A saddle-type vehicle is a vehicle equipped with a saddle-type seat. A saddle-type vehicle is a vehicle configured so that a passenger sits astride a saddle. The saddle-type vehicle is not limited to scooter-type, moped-type, off-road-type, and on-road-type motorcycles, but also includes snowmobiles, watercraft, all-terrain vehicles (ATVs), and the like. The saddle-type vehicle may have at least one front wheel and at least one rear wheel. The saddle-type vehicle is not limited to motorcycles, but may be a three-wheeled vehicle having a pair of front or rear wheels, or a four-wheeled vehicle having a pair of front and rear wheels, respectively. The saddle-type vehicle may be configured to be able to turn in a lean position toward the inside of a curve. A saddle-type vehicle capable of turning in a lean position requires the rider to shift their weight when turning or performing other actions. Therefore, maneuverability, agility, and ease of use are required for saddle-type vehicles capable of turning in a lean position. Therefore, there is a strong demand for smaller and lighter saddle-type vehicles capable of turning in a lean position. The exhaust gas treatment system for an alcohol engine of the present invention can adapt the catalyst to both cold start and high load usage scenarios, and is therefore suitable for saddle-ride vehicles that are capable of turning in a lean position and for which there is a strong demand for compactness and light weight. Therefore, the exhaust gas treatment system for an alcohol engine of the present invention can be suitably applied to saddle-ride vehicles that are configured to be able to turn in a lean position.A straddle-type vehicle configured to be able to turn in a lean position is suitable as the vehicle of the present invention. A vehicle configured to be able to turn in a lean position may be, for example, a tilting vehicle whose body tilts when turning. In a tilting vehicle, for example, the wheels may tilt together with the body when turning. A tilting vehicle may be configured, for example, so that a rider does not ride in a position straddling the saddle. Other examples of the vehicle include golf cars, caterpillar-type snowmobiles, and snowplows.

[0030] The above and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention taken in conjunction with the accompanying drawings. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, the use of the terms "including," "comprising," or "having" and variations thereof specifies the presence of stated features, steps, operations, elements, components, and / or equivalents thereof, but may include one or more of the steps, operations, elements, components, and / or groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms, such as those defined in commonly used dictionaries, should be interpreted to have a meaning consistent with the meaning in the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein. It is understood that numerous techniques and processes are disclosed in the description of the present invention. Each of these has distinct advantages, and each can also be used with one or more, or in some cases all, of the other disclosed technologies. Therefore, for the sake of clarity, this description will refrain from unnecessarily repeating all possible combinations of individual steps. Nevertheless, the specification and claims should be read with the understanding that all such combinations are within the scope of the present invention and the claims. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. The present disclosure is to be considered as an example of the present invention and is not intended to limit the invention to the specific embodiments illustrated in the following drawings or description.

[0031] According to the present invention, it is possible to provide an exhaust gas treatment system that is compatible with an alcohol engine that is configured to use a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume.

[0032] 1 is an explanatory diagram showing the configuration and working mechanism of an exhaust gas treatment system for an alcohol engine according to an embodiment of the present invention, together with a comparative example; FIG. 2 is a schematic configuration diagram showing a modified example of an exhaust gas treatment system for an alcohol engine according to an embodiment of the present invention; FIG. 3 is a schematic configuration diagram showing a modified example and variations of an exhaust gas treatment system for an alcohol engine according to an embodiment of the present invention; FIG. 4 is an explanatory diagram showing the characteristics of a high-concentration alcohol fuel having an alcohol concentration of over 85%; and FIG. 5 is an explanatory diagram showing the interaction effect between a high-concentration alcohol fuel having an alcohol concentration of over 85% and a plurality of asperities or holes.

[0033] Hereinafter, details of an exhaust gas treatment system for an alcohol engine according to an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example. The present invention should not be construed as being limited in any way by the embodiment described below.

[0034] An exhaust gas treatment system 20 for an alcohol engine (hereinafter simply referred to as the exhaust gas treatment system) according to an embodiment of the present invention will be described with reference to Figure 1. Figure 1(A) shows a schematic configuration of the exhaust gas treatment system 20, and Figure 1(B) shows the difference between the mechanism of action of a fuel containing a high concentration of alcohol and the mechanism of action of a gasoline fuel.

[0035] The exhaust gas treatment system 20 is employed in a vehicle 10. The vehicle 10 has, for example, a plurality of wheels. Power generated by an alcohol engine 22 is transmitted to one of the plurality of wheels. This allows the vehicle 10 to move.

[0036] The exhaust gas treatment system 20 includes an alcohol engine 22 and a catalyst 26 .

[0037] The alcohol engine 22 is configured to use an alcohol-containing fuel, and is configured to burn a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume.

[0038] The catalyst 26 includes a carrier 27 having a passage wall 271. The passage wall 271 has a plurality of irregularities or holes formed therein, which are configured to come into contact with exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas generated by the alcohol engine 22 burning the high-concentration alcohol-containing fuel. In the example shown in FIG. 1 , protrusions 272 constituting the plurality of irregularities and a plurality of holes 275 are shown. As a result, the catalyst 26 is configured to compensate for a decrease in the chemical reaction of exhaust gas molecules during cold start, which occurs due to a decrease in the average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas compared to exhaust gas generated by burning gasoline fuel or low-concentration alcohol-containing fuel, and to disperse the chemical reaction density of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during high load operation so that the chemical reaction density does not locally concentrate.

[0039] According to the exhaust gas treatment system 20, it is possible to provide an exhaust gas treatment system that is compatible with an alcohol engine configured to use a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume.

[0040] As shown in Fig. 2(A), the catalyst 26 may be provided in an exhaust pipe 29. As shown in Fig. 2(B), at least a portion of the catalyst 26 may be provided in a silencer 30.

[0041] As shown in Fig. 3(A), the catalyst 26 may include a metal carrier 27 configured to provide metallic thermal conduction to a metal exhaust pipe 29. As shown in Fig. 3(B), the metal carrier 27 may be configured so that the entire metal carrier 27 provides metallic thermal conduction to a metal exhaust pipe 29. As shown in Fig. 3(C), the metal carrier 27 may be configured so that at least a portion of the metal carrier 27 provides metallic thermal conduction to a metal silencer 30.

[0042] The alcohol-containing fuel may be a high-concentration alcohol-containing fuel having an alcohol concentration of more than 85%. Such a high-concentration alcohol-containing fuel exhibits the characteristics shown in Figures 4 and 5.

[0043] (Other Embodiments) The embodiments and variations described and / or illustrated in this specification are intended to facilitate understanding of the present disclosure and are not intended to limit the scope of the present disclosure. The above-described embodiments and variations may be modified or improved without departing from the spirit of the present disclosure. This spirit encompasses equivalent elements, modifications, deletions, combinations (e.g., combinations of features across embodiments and variations), improvements, and modifications that would be recognized by a person skilled in the art based on the embodiments disclosed herein. The limitations in the claims should be interpreted broadly based on the terms used in the claims and should not be limited to the embodiments and variations described in the specification or prosecution of this application. Such embodiments and variations should be construed as non-exclusive. For example, in this specification, the terms "preferably" and "good" are non-exclusive and mean "preferably but not limited to" or "good but not limited to."

[0044] REFERENCE SIGNS LIST 10 Vehicle 20 Exhaust gas treatment system for alcohol engine 22 Alcohol engine 26 Catalyst 27 Support 271 Passage wall 272 Convex portion 275 Hole 29 Exhaust pipe 30 Muffler

Claims

1. An exhaust gas treatment system for an alcohol engine comprising: an alcohol engine configured to use an alcohol-containing fuel; and a catalyst for treating exhaust gas from the alcohol engine, wherein the alcohol engine is configured to burn a high-concentration alcohol-containing fuel having an alcohol concentration of more than 20% by volume; and the catalyst comprises a carrier having a passage wall, and the passage wall has a plurality of irregularities or holes formed therein configured to come into contact with exhaust gas molecules in a high-concentration alcohol-containing fuel combustion exhaust gas generated by the alcohol engine burning the high-concentration alcohol-containing fuel, thereby compensating for a decrease in chemical reaction of exhaust gas molecules caused by a decrease in the average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during cold start compared to exhaust gas generated by burning gasoline fuel or a low-concentration alcohol-containing fuel, and dispersing the chemical reaction density of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during high load so as not to concentrate locally.

2. An exhaust gas treatment system for an alcohol engine as described in claim 1, wherein the catalyst is configured such that at least a portion of the passage wall on which the plurality of irregularities or holes are formed is located upstream of the muffler in the exhaust passage, thereby further compensating for the decrease in chemical reaction of exhaust gas molecules caused by the decrease in average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during cold start compared to exhaust gas generated by burning gasoline fuel or low-concentration alcohol-containing fuel, and dispersing the chemical reaction density of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas during high load so that it does not become locally concentrated.

3. An exhaust gas treatment system for an alcohol engine as described in claim 1 or 2, wherein the catalyst is configured such that the passage wall is a metallic passage wall, and the metallic passage wall is arranged to have metallic thermal conduction with a metallic exhaust pipe and / or a metallic silencer, whereby, during high load, heat is released to the outside via the metallic exhaust pipe and / or the metallic silencer while dispersing the chemical reaction density in the high-concentration alcohol-containing fuel combustion exhaust gas so as not to be locally concentrated.

4. An exhaust gas treatment system for an alcohol engine as set forth in any one of claims 1 to 3, wherein the alcohol-containing fuel is a high-concentration alcohol-containing fuel having an alcohol concentration of more than 85 volume %, and is configured to exhibit qualitatively different behavior compared to exhaust gas from gasoline fuel or low-concentration alcohol-containing fuel during cold start, with the average kinetic energy of exhaust gas molecules in the high-concentration alcohol-containing fuel combustion exhaust gas being lowered and accompanied by a phase change from a gas phase to a liquid phase, and to be configured such that, during high load, the chemical reaction density in the high-concentration alcohol-containing fuel combustion exhaust gas is locally and nonlinearly concentrated to form a specific reaction path.

5. A vehicle equipped with an exhaust gas treatment system for an alcohol engine according to any one of claims 1 to 4.

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