JP2013104364A - Combustion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of the degradation of self ignitability and reduce heat loss due to combustion heat being released from a cylinder wall surface, when reforming fuel so as to increase combustion energy.SOLUTION: A combustion system has a reformer reforming the nature of the fuel on a catalyst such that the combustion energy output from the fuel of a unit quantity is increased even while causing the lowering of a combustion temperature and the degradation of the self ignitability, reformed fuel is distributed in an annular shape (refer to meshed hatch in Fig.4(c)) along the cylinder inner peripheral surface 10a of the internal combustion engine and non-reformed fuel is distributed in a center part of the annular shape (refer to an oblique line hatch in Fig.4(c)) when the reformed fuel reformed in the reformer and the non-reformed fuel not reformed are simultaneously combusted in the combustion chamber of the internal combustion engine. Further, the non-reformed fuel is compressed and self-ignited and the reformed fuel is ignited and combusted using the self-ignition combustion as a flash point.

Description

  The present invention relates to a combustion system that burns reformed fuel in a combustion chamber of an internal combustion engine.

  Conventionally, a technique is known in which the properties of fuel are reformed on a catalyst of a reformer, the reformed fuel is injected into an intake pipe and burned in a combustion chamber (Patent Document 1). According to this, combustion energy can be increased and fuel consumption can be improved (decrease in fuel consumption rate).

  The conventional invention described in Patent Document 1 is based on the premise that an ignition engine is used, and at the time of starting when combustion becomes unstable, fuel is port-injected and ignited and burned. At times other than the starting time, the fuel is reformed so as to improve the self-ignitability, and the reformed fuel is directly injected into the combustion chamber to cause compression auto-ignition. Port injection is used to simultaneously burn reformed fuel and non-reformed fuel.

JP 2004-190586 A

  In the above-described conventional invention, it is assumed that the properties of the fuel are reformed so as to improve the self-ignitability. On the other hand, the present inventor examined reforming the properties of the fuel so as to increase the combustion energy output from the fuel per unit amount, thereby improving the fuel consumption (decreasing the fuel consumption rate).

For example, by reacting alcohol fuel (CH ₃ —OH) such as methanol or ethanol with water (H ₂ O) on a catalyst, it is converted into hydrogen (H ₂ ) and carbon monoxide (CO), and these hydrogen Combusting carbon monoxide as a reformed fuel is a specific example of the reforming.

  However, when this type of reforming (reforming that increases combustion energy) is performed, the self-ignitability is reduced compared to the fuel before reforming, and it becomes difficult to perform compression auto-ignition combustion of the reformed fuel. The present inventor has obtained the following knowledge.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to eliminate the problem of reduced self-ignitability when reforming a fuel so as to increase combustion energy. An object of the present invention is to provide a combustion system that can reduce heat loss due to escape from the cylinder wall surface.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  According to the first aspect of the present invention, the reforming is performed such that the properties of the fuel are reformed on the catalyst so that the combustion energy output from the fuel per unit amount increases while lowering the combustion temperature and the autoignition property. A combustion system that simultaneously burns the reformed fuel reformed by the reformer and the non-reformed non-reformed fuel in the combustion chamber of the internal combustion engine, wherein the reformed fuel is A ring is distributed along the inner circumferential surface of the cylinder, and the non-reformed fuel is distributed in the center of the ring, and the non-reformed fuel is subjected to compression self-ignition combustion, and the reformed fuel is It is characterized in that the non-reformed fuel is ignited and combusted using the combustion type.

  According to the above invention, non-reformed fuel is subjected to compression self-ignition combustion, and the reformed fuel is ignited and combusted using the combustion as a fire type, so that the reformed fuel with reduced self-ignitability can be reliably burned. The problem of reduced self-ignitability due to reforming can be solved.

  Further, in the above invention, the loss of heat loss due to the escape of combustion heat from the cylinder wall surface is achieved by utilizing the fact that the combustion temperature of the reformed fuel is lower than that of the non-reformed fuel. That is, the reformed fuel is distributed in an annular shape along the inner circumferential surface of the cylinder, so that low-temperature combustion by the reformed fuel occurs in the vicinity of the inner circumferential surface of the cylinder (see the halftone dot hatching in FIG. 4C). The high-temperature combustion by the non-reformed fuel occurs at a position away from the inner peripheral surface of the cylinder (see the hatched hatching in FIG. 4C). Therefore, the heat loss can be reduced as compared with the case where high temperature combustion is performed in the vicinity of the cylinder inner peripheral surface.

  According to a second aspect of the present invention, the reformed fuel is supplied from an exhaust port that is opened and closed by an exhaust valve of the internal combustion engine or an intake port that is opened and closed by an intake valve of the internal combustion engine during the intake stroke of the internal combustion engine. It is characterized by being configured to flow into the combustion chamber.

  Here, when the exhaust valve is opened during the intake stroke, an air flow having a high flow velocity is generated in the vicinity of the exhaust port due to the negative pressure in the combustion chamber. Also, during the intake stroke, an air flow having a high flow velocity is generated in the vicinity of the intake port. In the above-mentioned invention in view of this point, the reformed fuel is caused to flow into the combustion chamber by being put on an air flow having a high flow velocity. Therefore, it is ensured that the reformed fuel is annularly distributed along the inner peripheral surface of the cylinder. Can be improved.

  According to a third aspect of the present invention, the reformed fuel is injected into an exhaust path of the internal combustion engine so as to flow into the combustion chamber from the exhaust port.

  Contrary to the above-described invention, when the reformed fuel is injected into the intake passage and flows from the intake port, the reformed fuel is cooled in a pipe that leads the reformed fuel to the intake pipe, and the reformed fuel is The temperature further decreases by mixing with fresh air in the intake pipe. For this reason, when the temperature of the fuel supplied to the reformer is low and the ignition ignitability is deteriorated, such as when the outside air temperature is low, there arises a problem that the ignitability deterioration is promoted by the temperature decrease. .

  In order to solve this problem, according to the above invention, the reformed fuel is injected into the exhaust path and flows into the combustion chamber from the exhaust port. Therefore, the flow path to the reformed fuel exhaust port is an exhaust pipe having a high ambient temperature. It will be located in the vicinity. Therefore, it is possible to suppress the reformed fuel from being cooled in the flow path. In addition, since the reformed fuel does not mix with fresh air before flowing into the combustion chamber, it is possible to avoid the reformed fuel from being cooled by the fresh air. As described above, in a situation where the fuel supplied to the reformer is at a low temperature and there is a concern about deterioration of ignition ignitability, it is possible to suppress further cooling of the reformed fuel, and to reduce the concern about deterioration of ignition ignitability. it can.

  Further, in the above invention, since the reformed fuel is introduced from the exhaust port, the reformed fuel burns in a state mixed with the exhaust. That is, since the exhaust gas has a lower oxygen concentration than fresh air, the reformed fuel burns in a leaner state than when mixed with fresh air. Therefore, it is possible to promote a reduction in the combustion temperature of the reformed fuel as compared with the case of burning with fresh air. Therefore, the effect of reducing the heat loss that escapes from the cylinder wall surface can be improved. Moreover, when alcohol is employed as the fuel, the reformed fuel (carbon monoxide and hydrogen) can be burned in a leaner state than the non-reformed fuel (alcohol). Therefore, it is possible to burn the reformed fuel in a leaner state, and the improvement of the heat loss reduction effect described above can be promoted.

  According to a fourth aspect of the present invention, when the reformed fuel is introduced into the combustion chamber, the internal combustion engine is provided with a plurality of the exhaust ports for one combustion chamber. One of these is configured to be opened.

  In the above invention, since one exhaust port is opened during the intake stroke, the velocity of the airflow in the vicinity of the exhaust port can be increased compared to the case where a plurality of exhaust ports are opened. Therefore, it is possible to improve the certainty that the reformed fuel is distributed in an annular shape along the inner circumferential surface of the cylinder.

  According to a fifth aspect of the present invention, among the exhaust port and the intake port, a port through which the reformed fuel flows is called a reforming introduction port, and among the cylinder heads forming the exhaust port and the intake port, the modified When a port that forms a path for guiding the reformed fuel to the quality introduction port is referred to as an introduction port, a portion of the introduction port adjacent to the reforming introduction port is defined as the reforming introduction of the inner circumferential surface of the cylinder. It is characterized by being formed in a shape extending in the tangential direction of the portion adjacent to the mouth.

  According to the above invention, the inflow direction (see arrow Y1 in FIG. 4B) when the reformed fuel flows into the combustion chamber from the reforming inlet is tangent to the cylinder inner peripheral surface in the vicinity of the reforming inlet. It can be made the same as the direction (see the dashed line L1 in FIG. 4B). Therefore, it can be promoted that the reformed fuel immediately after flowing into the combustion chamber from the reforming inlet collides with the inner peripheral surface of the cylinder and then flows in an annular shape along the inner peripheral surface of the cylinder. Therefore, it is possible to improve the certainty that the reformed fuel is distributed annularly along the cylinder inner peripheral surface.

  According to a sixth aspect of the present invention, when a port through which the reformed fuel flows in among the exhaust port and the intake port is referred to as a reforming introduction port, a plurality of the reforming introduction ports are provided in one intake stroke. It is characterized by being opened and closed once.

  Contrary to the above-described invention, when the reforming inlet is opened once in one intake stroke, the reformed fuel that has flowed into the combustion chamber can flow along the inner circumferential surface of the cylinder. When the inflow amount of fuel is insufficient, the combustion of the reformed fuel cannot be distributed in an annular shape, as exemplified by the halftone hatching in FIG.

  In the above invention in view of this point, since the reforming inlet is opened and closed several times in one intake stroke, even when the inflow amount of reformed fuel is insufficient, the reforming inlet in FIG. As illustrated in the halftone hatch, it is possible to promote the annular distribution of the reformed fuel combustion. Therefore, it is possible to improve the certainty that the high temperature combustion by the non-reformed fuel is generated at a position away from the cylinder inner peripheral surface.

  In the seventh aspect of the invention, a port through which the reformed fuel flows into the exhaust port and the intake port is referred to as a reforming introduction port, and among the cylinder heads forming the exhaust port and the intake port, the intake air When a port that forms a path for introducing fresh air to the mouth is called an intake port, a portion of the intake port adjacent to the intake port is formed in a shape extending in a direction away from the reforming introduction port. Features.

  Here, contrary to the above-described invention, if the portion of the intake port adjacent to the intake port is formed in a shape extending toward the reforming introduction port, the flow of fresh air flowing from the intake port into the combustion chamber Colliding with the flow of reformed fuel flowing in from the mouth. Then, the reformed fuel diffuses in the combustion chamber, which hinders the reformed fuel from being distributed annularly along the inner circumferential surface of the cylinder.

  In view of this point, in the above invention, the portion of the intake port adjacent to the intake port is formed in a shape extending in a direction away from the reforming introduction port, so that fresh air collides with the flow of the reformed fuel and diffuses. Can be suppressed. Therefore, it is possible to promote the annular distribution of the reformed fuel along the cylinder inner peripheral surface.

The figure which shows the combustion system concerning 1st Embodiment of this invention. The figure explaining in detail the hardware constitutions of the reformer shown in FIG. The figure explaining the on-off valve timing of the supply valve shown in FIG. 1, and the on-off valve timing of an exhaust valve. FIG. 4 is a diagram illustrating a state in the combustion chamber when the valve is opened and closed as illustrated in FIG. 3, where (a) illustrates a flow of exhaust, (b) illustrates a flow of intake air and reformed fuel, and (c) ) Is a diagram showing the combustion distribution of reformed fuel and non-reformed fuel. The figure explaining the combustion distribution concerning 2nd Embodiment of this invention. The figure which shows the combustion system concerning 3rd Embodiment of this invention.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
The combustion system described below is assumed to be applied to a stationary internal combustion engine. For example, a stationary internal combustion engine installed as a drive source for driving a generator is given as a specific example.

  The internal combustion engine shown in FIG. 1 is a multi-cylinder engine having a plurality of cylinders, and these cylinders are configured by assembling a cylinder head 20 to a cylinder block 10. The cylinder block 10 accommodates the piston 11 and forms a combustion chamber 12. Further, water jackets 10w and 20w are formed in the cylinder block 10 and the cylinder head 20, and the cooling water discharged from the water pump 30 circulates through the water jackets 10w and 20w, so that the cylinder block 10 and the cylinder head 20 are circulated. The head 20 is cooled. The water pump 30 may be a mechanical type that is driven to rotate by the driving force of the internal combustion engine, or an electric type that is driven to rotate by an electric motor.

  An intake port 21 and an exhaust port 22 are formed in the cylinder head 20. An intake port 21 a of the intake port 21 is opened and closed by an intake valve 31, and an exhaust port 22 a of the exhaust port 22 is opened and closed by an exhaust valve 32. An intake manifold 33 that distributes fresh air to each cylinder is connected to the intake port 21.

  An exhaust manifold 34 (exhaust pipe) is connected to the exhaust port 22. However, a heat insulating material 34 a is interposed between the exhaust port 22 of the cylinder head 20 and the exhaust manifold 34. A collective exhaust pipe 35 (exhaust pipe) that collects and exhausts exhaust gas from each cylinder is connected to the downstream side of the exhaust manifold 34. The collective exhaust pipe 35 is connected to NOx and HC in the exhaust gas. A purification device 36 for purifying CO and the like is attached.

  A fuel injection valve 37 is attached to the cylinder head 20. The liquid fuel stored in the fuel tank 38 is pumped to the fuel injection valve 37 by the fuel pump 39, and when the fuel injection valve 37 is opened, the liquid fuel is directly injected into the combustion chamber 12. In addition, alcohol (for example, methanol CH3-OH) is used for the liquid fuel. Further, a part of the fuel pumped from the fuel pump 39 is reformed by a reformer 40, which will be described in detail later, and injected into the exhaust port 22, and then flows into the combustion chamber 12 from the exhaust port 22a. It is configured.

  As described above, an air-fuel mixture of non-reformed fuel (alcohol fuel not reformed by the reformer 40) injected from the fuel injection valve 37 and fresh air flowing from the intake port 21a is generated in the combustion chamber 12. Adiabatic compression and self-ignition combustion. On the other hand, the mixture of the reformed fuel flowing in from the exhaust port 22a and the fresh air flowing in from the intake port 21a is ignited by using the self-ignition combustion of the non-reformed fuel as a fire type and burns. In short, non-reformed fuel tends to self-ignite because its self-ignition temperature is lower than that of reformed fuel. On the other hand, the minimum energy required for ignition by ignition is smaller for reformed fuel than for non-reformed fuel. Therefore, in this embodiment, first, the non-reformed fuel is self-ignited, and the reformed fuel is combusted using the combustion as a fire type.

  The reformer 40 is disposed inside the exhaust manifold 34. Hereinafter, the structure of the reformer 40 will be described with reference to FIG.

  The reformer 40 includes a wall body 41 that forms an exhaust passage 41a, and a pipe 42 that forms a fuel passage 42a. A catalyst is supported on the inner surface of the pipe 42. The wall body 41 is made of a material (for example, ceramic) having a higher heat retention performance than that made of metal. The exhaust gas flowing through the exhaust passage 41a as shown by the dotted arrow heats the catalyst to the activation temperature or higher and heats the fuel flowing through the fuel passage 42a as shown by the solid arrow.

  The reformer 40 further includes a header pipe 43 that distributes the fuel to the plurality of fuel passages 42a, and a footer pipe 44 that collects the fuel that has passed through the plurality of fuel passages 42a. The reformer 40 is provided for each cylinder, and fuel is distributed and supplied from the distribution pipe 60 to the header pipe 43 of the reformer 40 provided for each cylinder.

The header pipe 43 is formed with an inlet 43a through which exhaust gas flows, and a reed valve 43b (check valve) is attached to the inlet 43a. Thereby, exhaust gas is mixed with the fuel in the header pipe 43. Then, on the catalyst on the inner surface of the pipe 42, the liquid fuel (methanol CH ₃ —OH) supplied from the header pipe 43 reacts with water contained in the exhaust gas, and hydrogen (H ₂ ) and carbon monoxide (CO). Is converted (modified). That is, these hydrogen and carbon monoxide are the reformed fuel, and flow into the combustion chamber 12 from the exhaust port 22a and burn.

  A reformed fuel pipe 45 for allowing the reformed fuel to flow to the vicinity of the exhaust port 22a is connected to the footer pipe 44. A part of the reformed fuel pipe 45 is inserted into the cylinder head 20, and the downstream opening 45 a of the reformed fuel pipe 45 is located in the vicinity of the exhaust port 22 a in the exhaust port 22. Therefore, the fuel reformed by the reformer 40 flows through the reformed fuel pipe 45 and is injected into the vicinity of the exhaust port 22a.

  As shown in FIG. 1, the fuel pumped from the fuel pump 39 flows through the branch pipe 61 and is supplied to a supply valve 62 attached to the distribution pipe 60. Therefore, when the supply valve 62 is opened, the fuel pumped from the fuel pump 39 passes through the branch pipe 61 → the supply valve 62 → the distribution pipe 60 → the header pipe 43 → the pipe 42 → the footer pipe 44 → the reformed fuel pipe 45. It flows in order and is injected in the exhaust port 22 from the downstream opening part 45a.

  Further, a heat exchanger 46 (see FIG. 1) is attached to the reformed fuel pipe 45 and the branch pipe 61, and the heat exchanger 46 exchanges heat between the fuel before reforming and the reformed fuel. That is, the reformed fuel whose temperature has been raised by the exhaust gas inside the reformer 40 is cooled by the fuel before reforming. In other words, the fuel before reforming is heated by the reformed fuel.

  Further, a part of the reformed fuel pipe 45 is disposed in the water jacket 20 w of the exhaust port 22. As a result, the reformed fuel and the cooling water exchange heat. That is, the reformed fuel whose temperature has been raised by the exhaust gas inside the reformer 40 is cooled by the cooling water circulating in the water jacket 20w.

  The valve opening operation of the supply valve 62 and the fuel injection valve 37 is controlled by an electronic control unit (ECU 70). Hereinafter, the valve opening timing control of the supply valve 62 by the ECU 70 will be described with reference to FIG.

  The uppermost stage in FIG. 3 shows the timing of the top dead center and the bottom dead center of the piston 11 in an arbitrary cylinder separately from the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke. Further, (a) shows the opening / closing valve timing of the intake valve 31, and (b) shows the opening / closing valve timing of the exhaust valve 32. The intake valve 31 and the exhaust valve 32 are opened and closed by a camshaft that is rotationally driven by a crankshaft of the internal combustion engine, and the opening / closing valve timing is specified by the profile of the cam attached to the camshaft.

  The exhaust valve 32 is once closed at time t1 with the end of the exhaust stroke. Thereafter, during the intake stroke immediately after the exhaust stroke, the valve is opened again at time t2, and then closed again at time t3. That is, the exhaust valve 32 is opened twice, once in the exhaust stroke and in the intake stroke in one combustion cycle. Then, the supply valve 62 that supplies fuel to the reformer 40 is opened during the valve closing period t1 to t2 immediately before the exhaust valve 32 is opened in the intake stroke.

  FIG. 4 is a diagram showing the state in the combustion chamber 12 when the valves 31, 32, 62 are opened and closed as shown in FIG. In FIG. 4, it is assumed that two intake ports 21 a and 21 b and two exhaust ports 22 a and 22 b are provided in the cylinder head 20 for one combustion chamber 12, and the exhaust indicated by reference numeral 22 b. The reformed fuel from the reformed fuel pipe 45 is not injected into the exhaust port 22 forming the mouth. Therefore, the exhaust valve 32 that opens and closes the exhaust port 22a is opened again at time t2 in the intake stroke as shown in FIG. 3B, whereas the exhaust valve 32 that opens and closes the exhaust port 22b is opened. The cam profile is set to prevent the valve from opening again at times.

  Therefore, during the exhaust stroke, exhaust gas is discharged from the two exhaust ports 22a and 22b as shown by the arrows in FIG. 4A, whereas t2 that opens the exhaust port 22a in the intake stroke. In the period t3, the reformed fuel flows into the combustion chamber 12 from the exhaust port 22a as indicated by an arrow Y1 in FIG.

  Here, the reformed fuel that has flowed in from the exhaust port 22a is configured to flow annularly along the cylinder inner peripheral surface 10a as indicated by an arrow Y2 in FIG. Will be described later). On the other hand, the non-reformed fuel injected from the fuel injection valve 37 is configured to be injected toward the center of the reformed fuel flowing in an annular shape. Specifically, the fuel injection valve 37 that injects non-reformed fuel is disposed in the center portion of the combustion chamber 12 as viewed from above, and is configured to inject non-reformed fuel toward the center of the combustion chamber 12. Yes.

  Therefore, during the combustion stroke, combustion by the reformed fuel occurs in the vicinity of the cylinder inner peripheral surface 10a (the halftone dot hatched portion in FIG. 4C), and combustion by the non-reformed fuel is separated from the cylinder inner peripheral surface 10a. This occurs at the center position of the combustion chamber 12 (shaded hatched portion in FIG. 4C).

  Next, a specific configuration for allowing the reformed fuel to flow annularly along the cylinder inner peripheral surface 10a will be described in detail.

  In the following description, a port through which the reformed fuel flows in the two exhaust ports 22a and 22b is referred to as a reforming introduction port 22a. Of the exhaust ports 22 formed in the cylinder head 20, a port that forms a path for guiding the reformed fuel to the reforming introduction port 22a is referred to as an introduction port. An alternate long and short dash line L1 in FIG. 4B indicates a tangent of a portion of the cylinder inner peripheral surface 10a adjacent to the reforming introduction port 22a.

  Then, a portion of the introduction port 22 adjacent to the reforming introduction port 22a (portion indicated by reference numeral 22P in FIG. 4B) is formed in a shape extending in the direction of the tangent L1 described above. According to this, the cylinder in the portion closest to the reforming inlet 22a in the inflow direction (see arrow Y1 in FIG. 4B) when the reformed fuel flows into the combustion chamber 12 from the reforming inlet 22a. This can be the same as the tangential direction of the inner peripheral surface 10a (see the one-dot chain line L1 in FIG. 4). Therefore, it can be promoted that the reformed fuel immediately after flowing into the combustion chamber 12 from the reforming inlet 22a collides with the cylinder inner peripheral surface 10a and then flows in an annular shape as it is along the cylinder inner peripheral surface. Therefore, it is possible to improve the certainty that the reformed fuel is annularly distributed along the cylinder inner peripheral surface 10a.

  Further, when the one exhaust port 22a (reforming introduction port) is opened to allow the reformed fuel to flow into the combustion chamber 12, the other exhaust port 22b is closed. Therefore, compared with the case where both the exhaust ports 22a and 22b are opened, the speed of the airflow in the vicinity of the reforming introduction port 22a can be increased. Therefore, it is possible to improve the certainty that the reformed fuel is distributed in an annular shape along the cylinder inner peripheral surface 10a.

  Further, a portion of the intake port 21 adjacent to the intake port 21a (a portion indicated by reference numeral 21P in FIG. 4B) is formed in a shape extending in a direction away from the exhaust port 22a (reforming introduction port). That is, the reforming introduction port 22a is not positioned on the center line L3 of the portion 21P of the intake port 21. Therefore, the flow of fresh air flowing into the combustion chamber 12 from the intake port 21a (see arrow Y3 in FIG. 4B) is the flow of reformed fuel flowing in from the reforming inlet 22a (in FIG. 4B). (See arrow Y1) can be avoided, so that it is possible to promote the annular distribution of the reformed fuel along the cylinder inner peripheral surface 10a.

  Further, the introduction port 22 is introduced so that the portion adjacent to the reforming introduction port 22a (the portion indicated by reference numeral 22P in FIG. 4B) is adjacent to the cylinder inner peripheral surface 10a when viewed from above. Port 22 is arranged. Therefore, it is possible to suppress a reduction in the flow rate due to the reformed fuel flowing into the combustion chamber 12 from the reforming inlet 22a colliding with the cylinder inner peripheral surface 10a. Therefore, it is possible to improve the certainty that the reformed fuel is distributed in an annular shape along the cylinder inner peripheral surface 10a.

  Furthermore, the opening area of the reforming introduction port 22a, which is one of the two exhaust ports 22a and 22b, is set smaller than the opening area of the other exhaust port 22b. As a result, the speed of the airflow in the vicinity of the reforming inlet 22a is increased, so that it is possible to improve the certainty that the reformed fuel is distributed in an annular shape along the cylinder inner peripheral surface 10a.

Here, when the alcohol fuel is reformed by the reformer 40 according to the present embodiment, the combustion temperature of the reformed fuel (CO, H ₂ ) by the reforming is that of the non-reformed fuel (CH ₃ —OH). It becomes lower than the combustion temperature. According to the present embodiment, as described above, the reformed fuel is distributed annularly along the cylinder inner peripheral surface 10a, and the non-reformed fuel is distributed in the annular central portion. Of these, the non-reformed fuel undergoes compression self-ignition combustion at the center position, and the reformed fuel is ignited and combusted (ignition combustion) in the vicinity of the cylinder inner peripheral surface 10a using the self-ignition combustion as a fire type. That is, high temperature self-ignition combustion is performed at a central position away from the cylinder inner peripheral surface 10a, and low temperature ignition combustion is performed at a position near the cylinder inner peripheral surface 10a.

  Therefore, according to the present embodiment, it is possible to reduce heat loss due to the combustion heat escaping to the cylinder block 10 as compared with the case where high-temperature self-ignition combustion is performed in the vicinity of the cylinder inner peripheral surface 10a.

  In addition, since the reformed fuel is introduced from the exhaust port 22a, the reformed fuel burns in a state (lean state) mixed with the exhaust having a low oxygen concentration. Therefore, since the combustion temperature reduction of the reformed fuel can be promoted, reduction of heat loss due to the combustion heat escaping to the cylinder block 10 can be promoted. In this embodiment, the reformed fuel is burned in a leaner state than stoichiometric, the non-reformed fuel is burned in a stoichiometric or lean state, and the reformed fuel is leaner than the non-reformed fuel. It is set to become.

  Furthermore, according to the embodiment described above in detail, the following effects can be obtained. That is, the reformed fuel is injected into the exhaust port 22 and flows into the combustion chamber 12 from the exhaust port 22a, so that the reformed fuel flow path (reformed fuel pipe 45) is an exhaust pipe (exhaust manifold) having a high ambient temperature. 34). Therefore, it is possible to suppress the reformed fuel from being cooled in the flow path. In addition, since the reformed fuel is not mixed with fresh air before flowing into the combustion chamber 12, it is possible to avoid the reformed fuel from being cooled by the fresh air. As described above, in a situation where the fuel supplied to the reformer 40 is at a low temperature and there is a concern about deterioration of ignitability, the reformed fuel can be further prevented from being cooled, and the concern about deterioration of ignitability can be reduced. .

  Here, it is assumed that the reformed fuel is ignited using the self-ignition combustion of the direct injection fuel as a fire type. However, if the reformed fuel becomes excessively hot due to the exhaust gas, there is a concern that self-ignition may occur contrary to the assumption. Become so. On the other hand, in the present embodiment, the reformed fuel in the reformed fuel pipe 45 is cooled by the fuel before reforming and the cooling water, so that the reformed fuel assumed to be ignited and burned is self-ignited and combusted. You can avoid that. Furthermore, since the fuel before reforming is heated by the reforming fuel by the heat exchanger 46, the reforming efficiency on the catalyst can be improved.

  Since the reformer 40 is disposed inside the exhaust pipe (exhaust manifold 34), the temperature of the catalyst of the reformer 40 can be increased to the activation temperature or higher by using the exhaust gas temperature. The catalyst temperature can be easily raised without using a heating means such as the above. Furthermore, it is possible to easily improve the reforming efficiency by raising the fuel temperature in the reformer.

  Since the heat insulating material 34a is interposed between the cylinder head 20 and the exhaust pipe (exhaust manifold 34), the temperature rise of the reformer 40 can be promoted and the reforming efficiency can be improved. Since the exhaust gas temperature is lowered by exchanging heat with the reformer 40, the exhaust gas temperature flowing into the purification device 36 is lowered. Therefore, even if the heat insulating material 34a is interposed, it is possible to avoid that the purifier 36 exceeds the upper limit value and becomes hot and damaged.

  Since a heat storage material (for example, ceramic) is employed for the wall body 41 forming the exhaust passage 41a in the reformer 40, it is possible to promote improvement of reforming efficiency by maintaining the reformer 40 in a high temperature state. .

  Since the opening of the supply valve 62 is prohibited at times other than the intake stroke, the reformed fuel injected into the exhaust path (exhaust port 22) does not flow into the exhaust manifold 34 together with the exhaust gas without flowing from the exhaust port 22a. It is possible to avoid being discharged.

  The supply valve 62 for supplying fuel to the reformer 40 is opened during the valve closing period t1 to t2 immediately before the exhaust valve 32 is opened in the intake stroke. Therefore, it is possible to lengthen the time that the fuel supplied to the reformer 40 stays in the fuel passage 42a of the reformer 40, and to improve the reforming efficiency. Moreover, since the residence time until the liquid fuel supplied from the supply valve 62 flows into the exhaust port 22a can be increased, the liquid fuel can be sufficiently vaporized.

(Second Embodiment)
In the first embodiment, the reforming inlet 22a is opened only once during the intake stroke (see FIG. 3B). Then, when the amount of fuel supplied from the supply valve 62 to the reformer 40 is insufficient and the reformed fuel flowing into the combustion chamber 12 is insufficient, the reformed fuel is removed from the cylinder inner peripheral surface. Even if the fuel can flow along 10a, the combustion of the reformed fuel cannot be distributed in an annular shape as illustrated by the halftone hatch W in FIG.

  In this embodiment, the cam profile of the exhaust valve 32 is set so that the reforming inlet 22a is opened and closed a plurality of times during one intake stroke. For this reason, the reformed fuel intermittently flows into the combustion chamber 12, so even if the reformed fuel inflow amount is insufficient, the halftone hatch W in FIG. Thus, the combustion of the reformed fuel can be distributed annularly. Therefore, it is possible to improve the certainty of causing the high temperature combustion by the non-reformed fuel to occur at a position away from the cylinder inner peripheral surface 10a.

(Third embodiment)
In the first embodiment, the internal combustion engine provided with a plurality of exhaust ports 22a and 22b is targeted. However, in the present embodiment, the exhaust port 220a (reforming introduction port) is targeted for one internal combustion engine. In the present embodiment, a portion of the introduction port 220 adjacent to the reforming introduction port 220a (a portion indicated by reference numeral 220P in FIG. 6) is formed in a shape extending in a direction away from the center of the combustion chamber 12. In other words, the center line L20 of the portion 220P of the introduction port 220 is formed so as to deviate from the center of the combustion chamber 12.

  According to this, the reformed fuel that has flowed into the combustion chamber 12 from the reforming inlet 220a can be prevented from colliding frontally with the cylinder inner peripheral surface 10a. Therefore, after the reformed fuel (see arrow Y1) immediately after flowing into the combustion chamber 12 from the reforming inlet 220a collides with the cylinder inner peripheral surface 10a, it flows in an annular shape along the cylinder inner peripheral surface 10a (arrow Y2). See). Therefore, even if the exhaust port 220a is one internal combustion engine, it can be realized that the reformed fuel is distributed in an annular shape along the cylinder inner peripheral surface 10a.

  Further, the downstream opening 45a is eccentrically arranged on the side closer to the cylinder inner peripheral surface 10a than the center line L20. According to this, it can accelerate | stimulate that the reformed fuel injected in the introductory port 220 from the downstream opening part 45a flows cyclically | annularly along the cylinder internal peripheral surface 10a.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In each of the above embodiments, the water component necessary for reforming is mixed with the fuel by mixing the exhaust gas with the fuel supplied to the reformer 40, but the fuel stored in the fuel tank 38 is Water may be mixed in advance and the above-described exhaust gas mixing may be abolished. In short, instead of storing alcohol in the fuel tank 38, alcohol water may be stored. According to this, the reed valve 43b can be eliminated, but on the other hand, the fuel tank 38 is increased in size.

  In each of the above embodiments, the reformed fuel is injected into the portion of the exhaust port 22 in the exhaust path. However, the present invention is not limited to the injection into the exhaust port 22, and for example, the exhaust manifold 34 Or may be injected into the collective exhaust pipe 35. However, it is desirable to inject to the portion closer to the exhaust port 22a than the reformer 40. Further, the portion closer to the exhaust port 22a is desirable in that the possibility that the reformed fuel injected from the downstream opening 45a remains without flowing from the exhaust port 22a can be reduced.

  In each of the above embodiments, the reformed fuel pipe 45 is connected to the exhaust port 22 and the reformed fuel is introduced from the exhaust ports 22a and 220a. However, the reformed fuel pipe 45 is connected to the intake port 21 and You may make it make reformed fuel flow in from the opening | mouth 21a. In this case, it is desirable to adjust the injection amount of the reformed fuel so that the reformed fuel burns in a lean state.

  In each of the above embodiments, the reformed fuel pipe 45 is connected to the exhaust port 22 and the reformed fuel is allowed to flow from the exhaust ports 22a and 220a, but the reformed fuel pipe 45 is connected to the combustion chamber 12 and modified. The quality fuel may be allowed to flow directly into the combustion chamber 12.

  In each of the above embodiments, the reformer 40 is disposed inside the exhaust manifold 34 (exhaust pipe), but may be disposed inside the collective exhaust pipe 35 (exhaust pipe). In this case, piping for distributing the reformed fuel from one reformer 40 to a plurality of cylinders is necessary. However, the provision of the reformer 40 for each cylinder is abolished, and one reformer 40 is provided. It can be shared. Further, the reformer 40 may be disposed outside the exhaust pipes 34 and 35.

  In each of the above embodiments, the combustion system according to the present invention is applied to a stationary internal combustion engine. However, it can also be applied to an internal combustion engine mounted on a vehicle. In this case, at the time of cold start of the internal combustion engine, the effect of suppressing the deterioration of ignitability by reducing the degree of cooling the reformed fuel in the reformed pipe 45 with the cooling water and flowing it from the exhaust port 22a. It is desirable not to be disturbed. For example, it is desirable to employ an electric water pump 30 and stop the water pump 30 during the cold start period or reduce the discharge amount from the water pump 30.

  Even when the mechanical water pump 30 is adopted, the engine speed is low at the time of cold start, so the water pump 30 is also low. For this reason, at the cold start, the circulating flow rate of the cooling water is reduced and the degree of cooling of the reformed fuel is also reduced, so that the concern that the effect of suppressing the deterioration of ignitability is hindered is reduced.

  In each of the above embodiments, one supply valve 62 is provided for the plurality of reformers 40 provided in each cylinder, but a supply valve 62 is provided for each of the plurality of reformers 40. It may be. According to this, the above-described effects (improvement of reforming efficiency and promotion of vaporization of liquid fuel) by opening the supply valve 62 during the valve closing period t1 to t2 immediately before the exhaust valve 32 is opened in the intake stroke, It becomes more prominent.

  -Regarding the opening of the exhaust valve, in the above embodiment, the profile of the cam attached to the camshaft is set so that the valve opening lift amount during the exhaust stroke and the valve opening lift amount during the intake stroke are the same. Yes. On the other hand, the valve opening lift amount during the intake stroke may be set to be smaller than the valve opening lift amount during the exhaust stroke. According to this, since the inflow speed when the reformed fuel flows in from the exhaust port 22a can be increased, the reformed fuel injected into the exhaust port 22 does not flow into the exhaust port 22a without flowing into the exhaust port 22a. The possibility of remaining on the substrate can be reduced.

  DESCRIPTION OF SYMBOLS 10a ... Inner peripheral surface of a cylinder, 21a ... Intake port, 22 ... Exhaust port (exhaust path, introduction port), 22a, 220a ... Exhaust port (reformation introduction port), 31 ... Intake valve, 32 ... Exhaust valve, 40 ... Modified A genitalia.

Claims (7)

A reformer that reforms the properties of the fuel on the catalyst so as to increase the combustion energy output from the fuel per unit amount while causing a decrease in the combustion temperature and a reduction in autoignition,
In the combustion system in which the reformed fuel reformed by the reformer and the unreformed non-reformed fuel are simultaneously burned in the combustion chamber of the internal combustion engine,
The reformed fuel is distributed in an annular shape along the inner peripheral surface of the cylinder of the internal combustion engine, and the non-reformed fuel is configured to be distributed in the annular central portion.
In addition, the combustion system is configured such that the non-reformed fuel is subjected to compression auto-ignition combustion, and the reformed fuel is ignited and combusted using combustion of the non-reformed fuel as a fire type.   In the intake stroke of the internal combustion engine, the reformed fuel is caused to flow into the combustion chamber from an exhaust port opened and closed by an exhaust valve of the internal combustion engine or an intake port opened and closed by an intake valve of the internal combustion engine. The combustion system according to claim 1.   The combustion system according to claim 2, wherein the reformed fuel is injected into an exhaust path of the internal combustion engine and flows into the combustion chamber from the exhaust port. Applied to an internal combustion engine provided with a plurality of exhaust ports for one combustion chamber;
The combustion system according to claim 3, wherein when the reformed fuel flows into the combustion chamber, one of the plurality of exhaust ports is opened. Of the exhaust port and the intake port, a port through which the reformed fuel flows is referred to as a reforming introduction port, and among the cylinder heads forming the exhaust port and the intake port, the reformed fuel is supplied to the reforming introduction port. When the port that forms the route that leads to is called the introduction port,
The portion of the introduction port adjacent to the reforming introduction port is formed in a shape extending in a tangential direction of the portion of the cylinder inner peripheral surface adjacent to the reforming introduction port. 5. The combustion system according to any one of 4. In the case where a port through which the reformed fuel flows in the exhaust port and the intake port is called a reforming introduction port,
The combustion system according to any one of claims 2 to 5, wherein the reforming introduction port is opened and closed a plurality of times in one intake stroke. Of the exhaust port and the intake port, a port through which the reformed fuel flows is referred to as a reforming introduction port, and among the cylinder heads forming the exhaust port and the intake port, a path for introducing fresh air to the intake port When the port to be formed is called an intake port,
The combustion system according to any one of claims 2 to 6, wherein a portion of the intake port adjacent to the intake port is formed in a shape extending in a direction away from the reforming introduction port.

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