JP2008115722A - Reciprocating internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reciprocating internal combustion engine which largely reduces the generated amount of nitrogen oxide and secures a stable engine operation state while restraining corrosion or deterioration of fuel economy with a simple structure. <P>SOLUTION: A diesel engine 11 is provided with: a combustion chamber 15; a fuel injection nozzle 23 for injecting fuel into the combustion chamber 15; an intake passage 17 for supplying air to the combustion chamber 15; a vapor injection nozzle 24 for supplying vapor into the combustion chamber 15; and a vapor supply control device 33 for controlling an injection state of the vapor injection nozzle 24. The vapor supply control device 33 supplies the vapor into the combustion chamber 15 in correspondence with an operation state of the diesel engine 11. The vapor is changed to a supercritical state in the combustion chamber 15, and then, the fuel is burned with a supercritical mixed fluid of the air and the water, and the combustion gas is used as a working fluid of the diesel engine 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reciprocating internal combustion engine that obtains predetermined power by burning a fluid mixture of a fuel fluid and air in a combustion chamber.

  Conventionally, as this type of reciprocating internal combustion engine, for example, a diesel engine that obtains power by using light oil or heavy oil as fuel and mixing it with air in a cylinder and burning it is known. While this diesel engine has the advantage of good combustion efficiency, it has a high combustion temperature, and the removal of denitrogen oxides such as a three-way catalyst using combustion exhaust gas with high oxygen concentration does not work well. There is a problem of increased emissions. Therefore, in recent years, energy saving and exhaust gas regulations have been strengthened, and the demand for diesel engines with good fuel consumption and reduced production of nitrogen oxides is increasing.

  Here, it is widely known that the amount of nitrogen oxides generated can be reduced by supplying water into the engine and lowering the combustion temperature from the specific heat of water or the amount of latent heat of vaporization. Many techniques have been proposed, such as water injection into the interior, use of emulsion fuel mixed with fuel and water, and intake air humidification.

In addition, a technique has been proposed in which supercritical water or subcritical water is introduced into the cylinder to suppress the generation of nitrogen oxides and to improve the fuel consumption. For example, Patent Document 1 discloses a technique in which fuel and supercritical water or subcritical water are mixed outside a cylinder and the mixed fluid is injected into the cylinder. Further, for example, Patent Document 2 discloses a method for operating a reciprocating internal combustion engine that injects supercritical water into a cylinder within a range of 90 ° before top dead center and 30 ° after top dead center.
Special table 2002-508435 gazette JP 2003-148254 A

  However, if a large amount of water is injected into the cylinder, the latent heat of vaporization is lost when the water vaporizes, so that energy is consumed and fuel consumption is greatly reduced. Also, corrosion of the fuel injection nozzle, piston, etc. is likely to proceed. Especially when using a low quality oil fuel containing a large amount of sulfur, sulfate ions which are metal attack species are generated in the water mixed with the low quality oil fuel, Corrosion proceeds significantly. Further, from the viewpoint of preventing misfire, it is difficult to increase the amount of moisture introduced into the cylinder, and it is difficult to significantly reduce nitrogen oxides.

  On the other hand, when the emulsion fuel is used, it is possible to suppress the decrease in fuel consumption while simultaneously reducing the generation of nitrogen oxides and the generation of graphite. However, from the viewpoint of preventing misfire, it is difficult to increase the amount of water in the emulsion fuel and increase the amount of water introduced into the cylinder, and it is difficult to greatly reduce the amount of nitrogen oxide produced.

  By the way, in the technique using supercritical water or subcritical water, there is a problem that supercritical water and subcritical water have very high corrosiveness to various metal materials. Here, in the reciprocating internal combustion engine having the conventional configuration, supercritical water or subcritical water is generated in advance outside the cylinder, and the supercritical water or subcritical water is mixed with fuel or alone in the cylinder. It comes to inject. This necessitates a supercritical water or subcritical water generator, a fuel mixing device, a pipe that leads the supercritical water, subcritical water, or liquid mixture into the cylinder, and the overall configuration of the internal combustion engine is complicated. At the same time, they are always in contact with supercritical water and subcritical water, which are highly corrosive, so that there is a problem that the product life is shortened and maintenance is very troublesome and costly.

  Furthermore, in the prior art in which supercritical water is generated outside the cylinder in advance and then supplied into the cylinder and burned with fuel, a stable engine operating condition can be obtained, for example, at the time of engine start. There was also a fear of not.

  The present invention has been made in view of such circumstances, and an object thereof is to greatly reduce the amount of nitrogen oxide generated while suppressing the occurrence of corrosion and the reduction in fuel consumption with a simple configuration, and is stable. An object of the present invention is to provide a reciprocating internal combustion engine that can ensure the engine operating condition.

  In order to achieve the above object, the invention according to claim 1 is directed to a cylinder in which a piston with a reciprocating motion is accommodated therein to define a combustion chamber having a variable volume, and a fuel in the combustion chamber of the cylinder. A fuel injection device for injecting a fluid; an air supply passage for supplying air into the combustion chamber; a water vapor supply device for supplying water vapor into the combustion chamber; and a water vapor supply control for controlling a supply status of water vapor by the water vapor supply device The water vapor supply control device controls the water vapor supply device so that water vapor is supplied into the combustion chamber in at least one of an intake stroke and a compression stroke in accordance with operating conditions of the internal combustion engine, and the combustion In the room, after the water vapor is transferred to the supercritical state, the fuel fluid is combusted together with the supercritical fluid mixture of air and water, and the combustion gas becomes the working fluid. And gist to obtain power by.

  In this reciprocating internal combustion engine, water vapor is introduced into the combustion chamber of the cylinder and supercritical water is generated in the combustion chamber, eliminating the need for large-scale peripheral devices for storing and transporting supercritical water. In addition, the piping for the cylinder does not come into contact with the supercritical water. In addition, since the water in the combustion chamber is heated and pressurized from a gaseous state of water vapor, it does not pass through the high corrosion area in the process of generating supercritical water. For this reason, while being able to simplify the structure of an internal combustion engine, the corrosion of a structural member and a peripheral member can be suppressed. Also, when fuel is burned in the combustion chamber, a supercritical fluid mixture of air and water is interposed to increase the combustion efficiency of the fuel and greatly reduce the amount of nitrogen oxide produced while maintaining high fuel efficiency. be able to.

  Moreover, since steam is supplied into the combustion chamber in at least one of the intake stroke and the compression stroke according to the operating conditions of the internal combustion engine, the mixing of water vapor and air is promoted by appropriately adjusting the supply status of the steam. As a result, stable engine operating conditions can be secured.

  According to a second aspect of the present invention, in the reciprocating internal combustion engine according to the first aspect, the water vapor supply control device performs the supply of water vapor into the combustion chamber after completion of the intake of air into the combustion chamber. Thus, the gist is to control the water vapor supply device.

  This reciprocating internal combustion engine can supply a large amount of water vapor with a density higher than the air suction pressure into the combustion chamber without reducing the amount of intake air in the intake stroke. Can be reduced.

  According to a third aspect of the present invention, in the reciprocating internal combustion engine of the first aspect, the water vapor supply control device is configured so that the water vapor is supplied into the combustion chamber as a fluid mixture with the air. The gist is to control the supply device.

  In this reciprocating internal combustion engine, air and water vapor are simultaneously supplied into the combustion chamber, and the mixing of air and water vapor is promoted, so the combustion efficiency of the fuel liquid is improved and the generation of nitrogen oxides The amount can be further reduced.

  The invention according to claim 4 is the reciprocating internal combustion engine according to claim 3, further comprising a supercharger that supercharges air into the combustion chamber, wherein the steam supply controller The gist is to control the water vapor supply device so as to supply water to the compressed air downstream of the supercharger.

  In this reciprocating internal combustion engine, the water supplied from the water vapor supply device is vaporized in contact with the high-temperature supercharged air, whereby a mixed fluid of water vapor and air is generated. At that time, the hot supercharged air is cooled by water. For this reason, it is not necessary to provide an intercooler for cooling the high-temperature supercharged air, and no special device is required for vaporizing water. As a result, the configuration of the internal combustion engine can be simplified and the amount of energy used can be reduced.

  According to a fifth aspect of the present invention, in the reciprocating internal combustion engine according to any one of the first to fourth aspects, the fuel fluid is a supercritical fluid mixture of the air and the water in the combustion chamber. The gist of this is compression and ignition.

  Here, a diesel engine that compresses and ignites a mixed fluid of fuel and air generates a large amount of nitrogen oxides, and the exhaust gas tends to become black smoke. In contrast, in this reciprocating internal combustion engine, fuel in which air is uniformly mixed is burned efficiently at low temperatures, so that the fuel is less likely to be steamed inside the fluid, and nitrogen oxide emissions are greatly reduced. And the generation of black smoke can be suppressed.

  According to the present invention, in a reciprocating internal combustion engine, the generation amount of nitrogen oxides is greatly reduced and a stable engine operation state is secured while suppressing the complexity of the configuration, the occurrence of corrosion, and the reduction in fuel consumption. can do.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment in which the present invention is embodied in a diesel engine which is a kind of a reciprocating internal combustion engine and an operation method thereof will be described with reference to the drawings.
(First embodiment)
As shown in FIG. 1, a diesel engine 11 as a reciprocating internal combustion engine to which the operation method of the first embodiment is applied has a cylinder 12 and a cylinder head 13 formed of a metal material such as cast iron. ing. In the cylinder 12, a piston 14 is accommodated so as to be able to reciprocate, thereby defining a combustion chamber 15 having a variable volume. The reciprocating motion of the piston 14 is transmitted to an external machine through the crank mechanism 16 as a rotational motion.

  The crank mechanism 16 is provided with a crank angle sensor 16a that detects a rotation angle of a crankshaft (not shown). The position information of the piston 14 is detected from the detection value of the crank angle sensor 16a.

  The cylinder head 13 is formed with an intake passage 17 as an air supply passage for supplying air into the combustion chamber 15 and an exhaust passage 18 for discharging the combustion gas in the combustion chamber 15. An intake valve 20 that opens and closes the intake port 19 is provided in the intake passage 17. An exhaust valve 22 that opens and closes the exhaust port 21 is provided in the exhaust passage 18.

  The cylinder head 13 includes a fuel injection nozzle 23 as a fuel injection device that injects a fuel fluid such as light oil or heavy oil into the combustion chamber 15 between the intake port 19 and the exhaust port 21, and water vapor in the combustion chamber 15. And a steam spray nozzle 24 for spraying and supplying the fuel gas so as to face the inside of the combustion chamber 15. The fuel stored in a fuel tank (not shown) is supplied to the fuel injection nozzle 23.

  The intake passage 17 and the exhaust passage 18 are connected to a supercharger 25. Thereby, when the exhaust side turbine 26 of the supercharger 25 is rotated by the exhaust gas flowing through the exhaust passage 18, the intake side turbine 27 of the supercharger 25 is rotated in conjunction with it, and the intake air is compressed and the combustion chamber 15 is compressed. Be supercharged in. An intercooler 28 for cooling the intake air heated when passing through the supercharger 25 is connected to the intake passage 17 between the supercharger 25 and the intake port 19.

  A steam supply path 29 for supplying steam is connected to the steam injection nozzle 24. In this steam supply path 29, a water tank 30 for storing water, a water pump 31, an exhaust boiler 32 for generating steam using heat of exhaust gas, and supply of steam into the combustion chamber 15 are controlled. A water vapor supply control device 33 is provided. The exhaust boiler 32 is provided between the steam supply passage 29 and the downstream side of the supercharger 25 in the exhaust passage 18, and boiles the water sent by the water feed pump 31 using the heat of the exhaust gas. It is a heat exchanger that vaporizes into water vapor. The water vapor supply control device 33 is configured to supply water vapor into the combustion chamber 15 by the water vapor injection nozzle 24 in accordance with the opening / closing information of the intake valve 20 and the exhaust valve 22 and the position information of the piston 14 based on the detection value of the crank angle sensor 16a. The injection amount and injection timing are controlled.

Next, the operation of the diesel engine 11 will be described.
When the diesel engine 11 is started, the intake valve 20 opens the intake port 19 as the piston 14 descends. Then, the air compressed through the supercharger 25 and cooled by the intercooler 28 is sucked into the combustion chamber 15 (suction process). When the piston 14 is folded back at the bottom dead center position and the intake valve 20 eventually closes the intake port 19, the inside of the combustion chamber 15 becomes a sealed space, and the intake air is compressed (compression stroke).

  Here, the steam supply control device 33 is configured so that the exhaust boiler 32 is between the time when the diesel engine (engine) 11 shifts to the compression stroke and the piston 14 reaches an intermediate point between the top dead center position and the bottom dead center position. The water vapor injection nozzle 24 is controlled so that a predetermined amount of water vapor evaporated in step 4 is injected into the combustion chamber 15 from the water vapor injection nozzle 24. The water vapor injected into the combustion chamber 15 is low-pressure steam having a pressure of 10 MPa or less, preferably 2 MPa or less, and more preferably 1.3 to 1.7 MPa. If it is this pressure, it can pressurize with the water supply pressure of the water supply pump 31, without providing a special high-pressure pump.

  In the compression stroke, water vapor is adiabatically compressed with air and mixed with air until the critical point of 22.1 MPa and 374 ° C. is exceeded immediately before the end of the compression stroke, and a supercritical mixed fluid of air and supercritical water. It becomes.

  In this state, fuel is injected into the combustion chamber 15 from the fuel injection nozzle 23 under the command of the control unit of the diesel engine 11 (not shown). The injected fuel is uniformly mixed with a supercritical fluid mixture of air and water until compression ignition is performed, and a uniform supercritical fluid mixture of fuel, air and water is generated. When the piston 14 reaches the top dead center, the supercritical mixed fluid containing the fuel is compression-ignited, and the piston 14 is pushed down toward the bottom dead center side by the rapid volume expansion of the combustion gas accompanying the combustion of the fuel. (Expansion process). In this expansion stroke, the temperature and pressure of the combustion gas are rapidly reduced by adiabatic expansion. Thereby, the supercritical water in the combustion chamber 15 does not satisfy the supercritical condition and is returned to water vapor. In this way, the supercritical water is only generated just before the compression ignition and during the very initial stage of the expansion stroke.

  When the piston 14 reaches bottom dead center and the piston 14 starts to rise, the exhaust valve 22 opens the exhaust port 21, the exhaust gas is pushed away by the piston 14, and is discharged from the exhaust port 21 to the exhaust passage 18 ( Exhaust stroke). The diesel engine 11 repeats a series of these intake, compression, expansion, and exhaust strokes, converts the reciprocating motion of the piston 14 therebetween into a rotational motion of a crankshaft (not shown) via the crank mechanism 16, and the crankshaft. Power for rotating an external machine, such as a wheel, a screw, or a propeller, connected to the motor is obtained.

  The exhaust gas discharged from the combustion chamber 15 is guided to the exhaust side turbine 26 of the supercharger 25 to rotate the exhaust side turbine 26. The exhaust gas exiting the supercharger 25 is supplied to the exhaust boiler 32, and the water in the water vapor supply path 29 is vaporized by the heat of the exhaust gas. The exhaust gas cooled by the exhaust boiler 32 is exhausted by atmospheric release or the like.

Next, various effects such as reduction in the amount of nitrogen oxide generated by the operation method of the diesel engine 11 will be described.
FIG. 2A shows fuel consumption (fuel consumption) and nitrogen oxidation when water vapor is injected into the combustion chamber 15 and the fuel is burned under the condition that the pressure of the combustion chamber 15 at the time of ignition does not reach the supercritical state. It is the figure which showed the relationship with the generation amount of a thing. Here, the steam is injected into the combustion chamber 15 at the initial stage of the compression stroke of 200 ° C., 1 MPa, and 160 ° before top dead center at the engine rotation angle. In addition, each curve in the figure indicates that the fuel injection timing is 22.5 °, 20 °, 17.5 °, 15 ° before the top dead center at the engine rotation angle, and no water vapor injection and water vapor fuel injection amount 1 respectively. It is data under the condition of double to 4 times. As shown in FIG. 2A, it can be seen that as the water vapor injection amount increases, the curve shifts downward in the graph, and the generation amount of nitrogen oxides is greatly reduced. On the other hand, as the steam injection amount increases, the curve shifts to the right side of the graph, and it can be seen that the fuel consumption increases, that is, the fuel consumption deteriorates. Further, as for the fuel injection timing, it is understood that the amount of nitrogen oxide generated is smaller as the fuel is injected closer to the top dead center, but the fuel consumption deteriorates.

  On the other hand, FIG. 2B shows a condition in which water vapor is injected into the combustion chamber 15 under the same conditions as FIG. 2A, and the pressure of the combustion chamber 15 at the time of ignition is increased so as to reach a supercritical state. It is the figure which showed the relationship between the amount of fuel consumption (fuel consumption) when a fuel is burned in, and the generation amount of nitrogen oxides. As shown in FIG. 2 (b), as the water vapor injection amount increases, the curve shifts downward in the graph as in the case of FIG. 2 (a), and the generation amount of nitrogen oxides is greatly reduced. I understand that. Moreover, even when the water vapor injection amount is increased, the curve hardly shifts to the right side of the graph, and the fuel consumption amount hardly changes, that is, high fuel consumption is maintained. Thus, by interposing supercritical water during the combustion of the fuel, it is possible to prevent the deterioration of fuel consumption while largely suppressing the generation of nitrogen oxides. The relationship between the fuel injection timing, the amount of nitrogen oxides generated, and the fuel consumption was the same as in the case of FIG.

  Here, the characteristics of supercritical water will be described. As shown in FIG. 3, water exists in various states such as gas (water vapor), liquid (water), and solid (ice) depending on the relationship between temperature and pressure. The state is determined by the relationship between the attractive force (cohesive force) acting between water molecules and the thermal kinetic force (diffusion force) of each molecule. Under the condition that the cohesive force is larger than the diffusive force (low temperature and high pressure), it becomes solid (ice) or liquid (water). Conversely, under conditions where the cohesive force is smaller than the diffusive force (high temperature and low pressure), gas (water vapor) is formed.

  On the other hand, in the supercritical state, the diffusive force, which is an infinite force as a function of temperature, distinguishes between liquid and gas that exceed the critical point where the cohesive force, which is a finite force, exceeds the maximum value, both in temperature and pressure. It is a high temperature and high pressure state. In the case of water, the critical point is a temperature of 374 ° C. and the pressure is 22.1 MPa. Supercritical water in a supercritical state has a high kinetic energy close to that of a gas and has a high activity with a high density comparable to a liquid.

  Furthermore, it is known that dielectric constant and ion product, which are important parameters of chemical reaction fields such as combustion, can be controlled by temperature and pressure. Here, the dielectric constant of supercritical water is close to that of a nonpolar organic substance, and supercritical water mixes well with hydrocarbon fuel, which is a nonpolar organic substance, and gas. For this reason, hydrocarbon fuel and air are uniformly mixed using supercritical water as a medium. In addition, water molecules act as collision factors and reactants in the gas phase radical reaction in the supercritical state, and have an effect of promoting the combustion of hydrocarbon fuel. Combustion efficiency is greatly improved by the synergistic effect of homogeneous mixing effect and combustion promotion effect by these supercritical waters, so fuel consumption is reduced while reducing the amount of nitrogen oxide produced as the amount of steam added increases. Can be improved.

  Usually, in diesel combustion (compression ignition), the liquid fuel sprayed in the gas phase is first subjected to phase change (vaporization) for combustion. On the other hand, in combustion using supercritical water as a medium, liquid fuel is used for combustion without phase change. Therefore, it is easy to perform uniform combustion, and a local high-temperature field is not easily generated in the combustion chamber 15. The generation of oxides is suppressed, and the inside of the fuel droplets is hardly steamed and the generation of soot is suppressed. For this reason, by using supercritical water, the exhaust color is improved and the generation of black smoke is suppressed.

  FIG. 4 shows the ratio of the amount of water added to fuel and nitrogen when fuel is burned under the condition that water vapor is injected into the combustion chamber 15 and the pressure of the combustion chamber 15 at the time of ignition is increased to reach a supercritical state. It is the figure which showed the relationship with the generation amount of an oxide. As shown by the broken line in FIG. 4, when water vapor is injected at 145 ° before top dead center, as in the case of FIGS. 2 (a) and 2 (b), the water addition amount ratio increases. It can be seen that the amount of nitrogen oxide produced is reduced.

  On the other hand, the solid line in FIG. 4 shows the generation of nitrogen oxides when the ratio of water addition is substantially constant and the water vapor injection timing is changed to 115 °, 130 °, 145 °, and 160 ° before top dead center. Shows the change in quantity. As shown by the solid line, it can be seen that the closer the water vapor injection timing is to the bottom dead center, the more the amount of nitrogen oxide produced.

  When supercritical water is generated outside the combustion chamber 15 as in the prior art, the liquid water is pressurized with a high-pressure pump to increase the density, and then heated to shift to the supercritical state. A method of following the path B is common. In this path B, there is a problem that the passage through the highly corroded area is unavoidable, and the high-pressure water heating part in the supercritical water generation process and the member in contact with the supercritical water are easily corroded.

  On the other hand, according to the operation method of the diesel engine 11 of this embodiment, as shown by a path A in FIG. 3, water is injected into the combustion chamber 15 as gaseous water vapor. The temperature is increased by adiabatic compression and the pressure is increased to become supercritical water. Further, after combustion, the supercritical water is cooled and depressurized by adiabatic expansion and returned to gaseous water vapor. For this reason, the combustion chamber 15, the cylinder head 13, the fuel injection nozzle 23, the water vapor injection nozzle 24, the intake valve 20, and the exhaust valve 22 do not pass through the high corrosion region in any of the generation and disappearance processes of supercritical water. Corrosion of members that may come into contact with supercritical water, such as, is suppressed.

  Moreover, in this method, the supercritical water is only instantaneously generated near the top dead center position of the piston 14. Further, the combustion chamber 15 and the inner wall surface of the cylinder head 13 are kept at a low temperature by the cooling of the cylinder 12, and supercritical water is hardly in contact with the inner wall surface due to the presence of a temperature boundary between them. Absent. As described above, in the operation method of the diesel engine 11, corrosion due to supercritical water is suppressed, and without using an expensive pressure-resistant and corrosion-resistant material, the generation amount of nitrogen oxides is reduced, the generation of black smoke is suppressed, and the fuel consumption is reduced. Suppression can be realized at the same time.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) In this diesel engine 11, a large amount of low-temperature and low-pressure water vapor is introduced into the combustion chamber 15 to generate supercritical water in the combustion chamber 15, so that members such as piping for the cylinder 12 of the diesel engine 11 are provided. There is no contact with supercritical water. Moreover, since the water in the combustion chamber 15 is heated and pressurized from the water vapor in the gaseous state, it does not pass through the highly corroded region in the process of generating supercritical water. For this reason, the corrosion of the structural member of the diesel engine 11 can be suppressed. When the fuel is burned in the combustion chamber 15, a large amount of water is interposed in a supercritical state, so that an excessive increase in the combustion temperature is suppressed and the fuel and air are uniformly mixed, so that the combustion of the fuel It is possible to greatly reduce the amount of nitrogen oxide produced while increasing efficiency and maintaining high fuel efficiency.

  In addition, the steam supply control device 33 adjusts the supply timing of the steam (that is, the injection timing of the steam injection nozzle 24) according to the operating conditions such as the warm-up state of the diesel engine 11, so that the diesel engine 11 is supplied into the combustion chamber 15. Water vapor can be sufficiently adiabatically compressed to shift to a supercritical state more reliably, and a stable engine operation state can be ensured.

  (2) In this diesel engine 11, fuel is injected into a supercritical fluid mixture of air and water. For this reason, the supercritical water serves as a medium to promote uniform mixing of the fuel and air, and the effect (1) is more efficiently exhibited.

  (3) In the diesel engine 11, water vapor is supplied into the combustion chamber 15 in the initial stage of the compression stroke. For this reason, the temperature and pressure of water vapor can be rapidly increased by adiabatic compression in the compression stroke, and the water vapor can be shifted to a supercritical state by the time of fuel combustion.

  Further, since the pressure and temperature in the combustion chamber 15 are reduced by adiabatic expansion immediately after the combustion of the fuel, the supercritical water is generated only in the vicinity of the combustion for a very short time. Moreover, since the wall surfaces of the combustion chamber 15 and the cylinder head 13 are cooled, a temperature boundary is formed in an extremely narrow region between the combustion chamber 15 and the wall surface of the cylinder head 13 and the combustion gas even during combustion of fuel. The wall surfaces of the combustion chamber 15 and the cylinder head 13 can be in a state where they are hardly in contact with supercritical water. For this reason, the progress of corrosion on the wall surfaces of the combustion chamber 15 and the cylinder head 13 can be further suppressed.

  (4) In the diesel engine 11, water vapor is injected into the combustion chamber 15 from the water vapor injection nozzle 24 after the intake is completed, that is, after the intake valve 20 is closed. In such a case, it is possible to supply a large amount of water vapor having a density equal to or higher than the air suction pressure into the combustion chamber 15 without reducing the amount of intake air in the intake stroke. For this reason, the production amount of nitrogen oxides can be further reduced.

  (5) In the diesel engine 11, the pressure of water vapor injected into the combustion chamber 15 is 10 MPa or less (for example, 1.3 to 1.7 MPa). For this reason, the water vapor supplied into the combustion chamber 15 can be pressurized with a normal water supply pressure in the water supply pump 31 without providing a special high-pressure pump, and the configuration of the diesel engine 11 is suppressed from being complicated. Can do.

(6) A diesel engine that compresses and ignites a mixed fluid of fuel and air generates a large amount of nitrogen oxides, and the exhaust gas tends to become black smoke. On the other hand, in the diesel engine 11, the liquid fuel is efficiently burned without causing a phase change and without being excessively heated in a state of being uniformly mixed with air. For this reason, it becomes difficult for the fuel to be steamed inside the droplets, emission of nitrogen oxides is greatly reduced, and generation of black smoke can be suppressed. Thus, this internal combustion engine operating method is particularly suitable as a diesel engine operating method.
(Second Embodiment)
Next, the diesel engine 11 and its operation method according to the second embodiment will be described with reference to FIG. 5 with a focus on differences from the first embodiment. In the diesel engine 11 of the second embodiment, the method for introducing water into the combustion chamber 15 is different from that of the first embodiment.

  As shown in FIG. 5, in the diesel engine 11, a water injection nozzle 41 is provided in the cylinder head 13 so as to face the intake passage 17 downstream of the supercharger 25 instead of the water vapor injection nozzle 24. Further, the intercooler 28 and the exhaust boiler 32 are omitted.

  In the diesel engine 11, the water in the water tank 30 is introduced into the air sucked from the supercharger 25 into the combustion chamber 15 in the intake stroke via the water injection nozzle 41 based on the control of the steam supply control device 33. Sprayed in a liquid state. Here, the water sprayed in the intake passage 17 is vaporized by the heat of the air (supercharged air) compressed in the supercharger 25 to become water vapor, and simultaneously into the combustion chamber 15 together with the intake air. Supplied. Then, after the mixed fluid of air and water vapor is compressed in the combustion chamber 15 to be in a supercritical state, liquid fuel is injected into the combustion chamber 15 from the fuel injection nozzle 23 and compression ignition is performed.

Therefore, according to this embodiment, in addition to the effects (1) to (3), (5) and (6) of the first embodiment, the following effects can be obtained.
(7) In the diesel engine 11, water and water vapor are simultaneously supplied into the combustion chamber 15 by water being sprayed and vaporized by the high-temperature supercharged air passing through the intake passage 17 downstream of the supercharger 25. It has come to be. For this reason, the contact time of air and water vapor | steam becomes long, and mixing of air and water vapor | steam is accelerated | stimulated. As a result, the miscibility of fuel and air using supercritical water as a medium is improved and the combustion efficiency of the fuel is improved, so that the amount of nitrogen oxide produced can be further reduced.

  (8) Further, the water sprayed on the supercharged air is vaporized by the heat of the supercharged air heated by the adiabatic compression in the supercharger 25, and the water is supercharged by removing latent heat of evaporation from the high-temperature supercharged air. In order to cool the air, an intercooler for cooling the supercharged air can be omitted. For this reason, the structure of the diesel engine 11 can be simplified.

  (9) Moreover, it is only necessary to spray water on the supercharged air in a liquid state, and it is not necessary to make water vapor in advance. For this reason, the exhaust boiler 32 can be omitted, and the configuration of the diesel engine 11 can be simplified. In addition, it is not necessary to preheat water for steam generation, and the amount of energy used can be reduced.

(Third embodiment)
Next, the diesel engine 11 and its operation method according to the third embodiment will be described with reference to FIG. 6 with a focus on differences from the first embodiment. As shown in FIG. 6, in the diesel engine 11 of the third embodiment, a bypass passage 51 is formed in parallel with the supercharger 25 in the exhaust passage 18, and a flow path switching valve 52 is located upstream of the supercharger 25. Is provided. In addition, a part or all of the high-temperature exhaust gas before being introduced into the exhaust-side turbine 26 of the supercharger 25 is directly introduced into the exhaust boiler 32 as necessary.

Therefore, according to this embodiment, the following effects can be obtained in addition to the effects (1) to (6).
(10) In the diesel engine 11, for example, when the exhaust gas temperature is low, such as when the diesel engine 11 is started or during low load operation, a part or all of the high temperature exhaust gas is not used for work in the supercharger 25. Then, it can be introduced into the exhaust boiler 32 to ensure the amount of heat necessary for generating steam in the steam supply passage 29.

(Fourth embodiment)
Next, the diesel engine 11 and its operation method according to the fourth embodiment will be described with reference to FIG. 7 with a focus on differences from the first embodiment.

  As shown in FIG. 7, in this diesel engine 11, one steam injection nozzle 24 is provided so as to face the combustion chamber 15, and another one is provided so as to face the intake passage 17 of the cylinder head 13. . In the diesel engine 11, not only water vapor is directly injected into the combustion chamber 15, but also water vapor can be injected into intake air.

Therefore, according to this embodiment, in addition to the effects (1) to (3) and (5) to (7), the following effects can be obtained.
(11) In the diesel engine 11, with respect to the supply of water vapor, the amount of water vapor supplied into the combustion chamber 15 can be increased by using both direct injection into the combustion chamber 15 and injection into the intake air. For this reason, the combustion temperature in the combustion chamber 15 can be further lowered, and the amount of nitrogen oxide produced can be further reduced.

The above embodiment may be changed to another embodiment (another example) as follows.
In the first and third embodiments, for example, when the temperature of the cylinder 12 is not sufficiently increased during a warm-up operation or the like, the time during which the water vapor is adiabatically compressed by injecting water vapor during the intake stroke is set. It may be extended to increase the temperature and pressure of the water vapor. In this way, water vapor can be more reliably transferred to the supercritical state even under low temperature conditions such as during warm-up operation.

  In each of the above embodiments, the reciprocating internal combustion engine of the present invention is embodied in the diesel engine 11 and its operating method, but may be embodied in other reciprocating internal combustion engines such as a gasoline engine and a gas engine. Good.

  In each of the above embodiments, the fuel is exemplified as light oil or heavy oil, but for example, other mineral oils such as kerosene and gasoline, methane, propane, various alcohols, cyclohexane, benzene, dimethyl ether, etc. A cyclic, aromatic hydrocarbon compound, vegetable oil-derived fuel or the like may be used as the fuel.

In the fourth embodiment, liquid state water may be sprayed on the intake passage 17 instead of water vapor.
In each of the above embodiments, water vapor generated without using exhaust heat of exhaust gas may be supplied into the combustion chamber 15.

The schematic block diagram which shows the diesel engine to which the driving | running method of 1st Embodiment is applied. Injecting water vapor into the cylinder, (a) under the condition that does not reach the supercritical state, (b) under the supercritical condition, the relationship between the amount of fuel consumed and the amount of nitrogen oxide generated when burned Graph showing. The figure which shows the state of water as a function of temperature and pressure. The graph which shows the influence of water addition amount ratio and water vapor | steam injection timing. The schematic block diagram which shows the diesel engine to which the driving | running method of 2nd Embodiment is applied. The schematic block diagram which shows the diesel engine to which the driving | running method of 3rd Embodiment is applied. The schematic block diagram which shows the diesel engine to which the driving | running method of 4th Embodiment is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Diesel engine as a reciprocating internal combustion engine, 12 ... Cylinder, 14 ... Piston, 15 ... Combustion chamber, 17 ... Intake passage as an air supply path, 23 ... Fuel injection nozzle as a fuel injection device, 24 ... Steam supply Steam injection nozzle as a device, 25 ... supercharger, 33 ... water vapor supply control device, 41 ... water injection nozzle constituting a part of the water vapor supply device.

Claims (5)

A cylinder having a variable-volume combustion chamber defined by accommodating a piston in a reciprocating manner therein, a fuel injection device for injecting a fuel fluid into the combustion chamber of the cylinder, and supplying air into the combustion chamber An air supply path, a water vapor supply device that supplies water vapor into the combustion chamber, and a water vapor supply control device that controls the supply status of water vapor by the water vapor supply device,
The water vapor supply control device controls the water vapor supply device so that water vapor is supplied into the combustion chamber in at least one of an intake stroke and a compression stroke according to an operating condition of the internal combustion engine;
In the combustion chamber, after the water vapor is transferred to a supercritical state, the fuel fluid is burned together with a supercritical fluid mixture of air and water, and the combustion gas becomes a working fluid to obtain power. A reciprocating internal combustion engine. 2. The reciprocating motion according to claim 1, wherein the water vapor supply control device controls the water vapor supply device so that the water vapor is supplied into the combustion chamber after the intake of air into the combustion chamber is completed. Type internal combustion engine. The reciprocating internal combustion engine according to claim 1, wherein the water vapor supply control device controls the water vapor supply device so that the water vapor is supplied into the combustion chamber as a fluid mixture with the air. A supercharger that supercharges air in the combustion chamber is provided, and the water vapor supply control device controls the water vapor supply device so that the water vapor supply device supplies water to compressed air downstream of the supercharger. The reciprocating internal combustion engine according to claim 3, wherein: The reciprocating internal combustion engine according to any one of claims 1 to 4, wherein in the combustion chamber, the fuel fluid is compressed and ignited together with a supercritical fluid mixture of the air and the water. .

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