JP2005282566A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine 100 provided with a fuel gas supply means 21 supplying fuel gas G in a fuel gas flow passage 20 to gas A containing oxygen sucked in the combustion chamber 1 to form air fuel mixture including rich/thin distribution of fuel gas G in a combustion chamber 1, and enabling to stably burn air fuel mixture M including rich/thin distribution in the combustion chamber 1 even if EGR is performed to suppress creation of a local high temperature part causing drop of thermal efficiency and increase of NOx creation quantity. <P>SOLUTION: The engine is provided with an EGR means 23 supplying exhaust gas E discharged from the combustion chamber 1 to the fuel gas flow passage 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a fuel gas supply means for supplying the fuel gas in the fuel gas flow path to the oxygen-containing gas sucked into the combustion chamber so as to form an air-fuel mixture having a fuel gas concentration distribution in the combustion chamber. Related to the engine.

  In this type of engine, by operating the fuel gas supply means, in the combustion chamber, an air-fuel mixture having a concentration distribution consisting of a concentrated portion having a relatively high equivalence ratio and a light portion having a relatively low equivalent ratio is formed. Since the mixture can be stratified, it is called a stratified combustion engine. Such a stratified combustion engine is said to be capable of suppressing NOx generation and maintaining a stable combustion state.

  That is, the stratified charge combustion engine has a slow combustion rate due to a decrease in the combustion speed in the light part, and can suppress a local temperature rise, as compared with an engine that burns an air-fuel mixture that is homogeneously mixed in the combustion chamber. Therefore, NOx generation can be suppressed, and furthermore, since the dark portion and the light portion are adjacent to each other, an unstable flame in the light portion can be stabilized by the stable flame generated in the dark portion. A stable combustion state can be maintained.

  Further, in such a stratified combustion engine, an air-fuel mixture having a concentration distribution in the intake region is formed in the intake region of the intake passage where the air-fuel mixture sucked into the combustion chamber exists in the next intake stroke. There has been proposed an engine configured to supply fuel gas to a part or a plurality of parts along the flow direction of (oxygen-containing gas) (see, for example, Patent Documents 1 and 2).

JP 2001-342860 A JP 2001-90540 A

  However, in the stratified combustion engine as described above, the air-fuel mixture having a high equivalence ratio burns in the rich portion, so that the rich portion may locally become a high temperature. And generation | occurrence | production of the local high temperature part in such a combustion chamber becomes a cause of the thermal efficiency fall by the increase in the heat loss to a combustion chamber wall surface, and the increase in NOx production amount.

  Therefore, as a method for suppressing the occurrence of the local high temperature portion as described above, the mixture gas is recirculated to the mixture formed in the combustion chamber by exhaust gas having a relatively large specific heat discharged from the combustion chamber. There is a method of performing so-called exhaust gas recirculation (hereinafter referred to as EGR) that suppresses an increase in combustion temperature by increasing the heat capacity of the gas.

  However, in a stratified combustion engine, when exhaust gas is supplied to an air-fuel mixture having a concentration distribution in order to carry out the above EGR, the exhaust gas is supplied to the air-fuel mixture having a low equivalence ratio in the light portion, and the combustion state suddenly increases. Therefore, misfire, increased combustion fluctuations, and engine stall are likely to occur, and a stable combustion state may not be obtained.

  The present invention has been made in view of the above-mentioned problems, and relates to a so-called stratified combustion engine, the purpose of which is so-called in order to suppress the occurrence of a local high-temperature part that causes a decrease in thermal efficiency and an increase in NOx generation. An object of the present invention is to provide an engine that can stably burn an air-fuel mixture having a density distribution in a combustion chamber even when EGR is performed.

  In order to achieve the above object, an engine according to the present invention provides an oxygen-containing gas that is fed into the combustion chamber with fuel gas in the fuel gas flow path so as to form an air-fuel mixture having a fuel gas density distribution in the combustion chamber The fuel gas supply means for supplying to the engine is characterized in that the first characteristic configuration is provided with EGR means for supplying the exhaust gas discharged from the combustion chamber to the fuel gas flow path.

According to the first feature, the exhaust gas discharged from the combustion chamber by the EGR means is not directly supplied to the intake passage or the combustion chamber where the air-fuel mixture having the concentration distribution exists, but is supplied with the fuel gas. By supplying the fuel gas flow path through which the fuel gas before being supplied to the oxygen-containing gas by the means flows, the air-fuel mixture formed by the fuel gas supply means is concentrated in the exhaust gas together with the fuel gas. And an air-fuel mixture having a light and dark distribution consisting of a low-concentration light portion together with the fuel gas.
Then, by burning the air / fuel mixture having a concentration distribution of fuel gas and exhaust gas in the combustion chamber, the specific heat of the air / fuel mixture increases due to the high concentration of the exhaust gas in the concentrated portion, similar to the fuel gas. Since the rise in combustion temperature is suppressed, NOx generation is suppressed. On the other hand, in the light part, the exhaust gas concentration is inhibited by the exhaust gas due to the low exhaust gas concentration as in the fuel gas. Thus, stable combustion is achieved without any misfires, an increase in fuel fluctuations, and an engine stall.
Therefore, according to the present invention, even when so-called EGR is performed to suppress the occurrence of a local high-temperature part that causes a decrease in thermal efficiency and an increase in the amount of NOx produced, the air-fuel mixture having a concentration distribution is stably stabilized in the combustion chamber. An engine that can be burned can be realized.

  A second characteristic configuration of the engine according to the present invention is that the EGR means has a mixing promotion structure for promoting mixing of fuel gas and exhaust gas in the fuel gas flow path.

  According to the second characteristic configuration, since the EGR means has the mixing promotion structure, the fuel gas supply means supplies a fuel gas in which exhaust gas is homogeneously mixed with an oxygen-containing gas, and In the fuel gas and the exhaust gas can be formed a gas mixture having a concentration distribution in a state where the exhaust gas exists uniformly, and by burning the gas mixture, the temperature rise is suppressed uniformly uniformly in the dense part, NOx generation can be suppressed satisfactorily.

  According to a third characteristic configuration of the engine according to the present invention, the fuel gas supply means has a concentration distribution in the intake region in the intake region of the intake passage where an air-fuel mixture is introduced into the combustion chamber in the next intake stroke. The fuel gas is supplied to a part or a plurality of parts along the flow direction of the oxygen-containing gas so as to form an air-fuel mixture having

  According to the third characteristic configuration, the fuel gas supply means stably forms a mixture having a concentration distribution in the intake region of the intake passage, and the mixture formed in the intake region is converted into the concentration distribution. Since the combustion chamber can be immediately sucked into the combustion chamber in the next intake stroke while being maintained, the mixture can be stably stratified in the combustion chamber to suppress NOx generation and to stabilize the combustion state. it can.

  According to a fourth characteristic configuration of the engine according to the present invention, the flow of the oxygen-containing gas in the intake passage is stopped from a plurality of supply holes in which the fuel gas supply means is distributed along the flow direction in the intake passage. The fuel gas is supplied to the intake passage in a direction that intersects the flow direction in the intake passage at the time when the air is flowing.

  According to the fourth characteristic configuration, when the flow of air in the intake passage is stopped by the fuel gas supply means from the plurality of supply holes distributed along the flow direction in the intake passage, By supplying the fuel gas in a direction crossing the flow direction in the road, the air-fuel mixture formed in the intake path has a concentrated portion having a high fuel gas concentration and a high equivalence ratio in the air flow direction, It is possible to satisfactorily generate a fuel concentration distribution including a light portion having a small concentration of fuel gas between adjacent rich portions and a low equivalence ratio. Then, the air-fuel mixture in which the light and shade distribution is generated is sucked into the combustion chamber of the engine and stratified combustion is performed, so that the generation of NOx and the stabilization of the combustion state can be realized.

  A fifth characteristic configuration of the engine according to the present invention is that the EGR means is configured to be able to adjust an EGR amount that is a supply amount of the exhaust gas to the fuel gas passage.

  According to the fifth characteristic configuration, since the EGR means can adjust the supply amount of exhaust gas to the fuel gas, that is, the EGR amount, the intake air amount that is the amount of the air-fuel mixture sucked into the combustion chamber, and the air-fuel mixture The combustion state in the rich portion of the air-fuel mixture having a light and shade distribution can be made stable while suppressing the production of NOx.

Embodiments of the present invention will be described with reference to the drawings.
The engine 100 shown in FIG. 1 includes a combustion chamber 1 defined by the inner surface of the cylinder 3 and the top surface of the piston 2, an intake passage 12 connected to the combustion chamber 1 via an intake valve 7, and a combustion chamber 1. And an exhaust passage 13 connected via an exhaust valve 8, and an engine control unit (hereinafter referred to as an ECU) 50 including a computer for performing various controls.

  The piston 2 is swingably connected to the connecting rod 4, and the reciprocating motion of the piston 2 is obtained as a rotational movement of one crankshaft 5 by the connecting rod 4, and such a configuration is not different from a normal engine. .

  Air A (an example of an oxygen-containing gas) flowing through the intake passage 12 is appropriately supercharged by a supercharger or the like, and then fueled by a natural gas-based city gas by a fuel gas supply valve 21 (an example of a fuel gas supply means). The gas G is supplied to form an air-fuel mixture M, and the air-fuel mixture M is taken into the combustion chamber 1.

  The engine 100 compresses the air-fuel mixture M sucked into the combustion chamber 1 by raising the piston 2 and raises the temperature to the ignition point, so that it is self-ignited and combusted, or The air-fuel mixture M sucked into the combustion chamber 1 is compressed as the piston 2 rises, and is then configured as a so-called spark ignition engine that is ignited by a spark plug (not shown) and burned.

The fuel gas supply valve 21 is supplied with the fuel gas G from the fuel gas supply path 20 at a constant pressure. The fuel gas supply valve 21 has an opening that is orthogonal to the flow direction of the air A in the intake path 12. A portion 21a is formed.
Therefore, the fuel gas supply valve 21 supplies the fuel gas G from the opening 21 a to a part along the flow direction of the air A in the intake passage 12, orthogonal to the flow direction of the air A in the intake passage 12. .

  In addition, the flow state of the air A flowing through the intake passage 12 varies periodically with the cycle period as the intake valve 7 opens and closes. That is, in the intake path 12, in the intake stroke in which the intake valve 7 is opened, the air A is sucked into the combustion chamber 1 and the pressure is reduced, and in other strokes, the pressure is not sucked in the air A. Pulsation that does not decrease occurs.

  Therefore, the pressure in the vicinity of the opening 21a of the fuel gas supply valve 21 changes in synchronization with the pulsation of the air A in the intake passage 12, and specifically, in the middle stage of the intake stroke where the flow velocity of the air A is the highest. The pressure in the vicinity of the opening 21a is the lowest.

  The supply amount of the fuel gas G from the fuel gas supply valve 21 to the intake passage 12 changes periodically with the cycle period due to the pulsation of the air A as described above. At the moment when the flow of the air A in the intake passage 12 stops in the closed state, a large amount of the fuel gas G is supplied to the air A due to the inertia in the flow of the fuel gas G. Therefore, in the intake passage 12, the fuel gas G is thicker than the other portions at intervals corresponding to the amount of the air-fuel mixture M sucked into the combustion chamber 1 during the intake stroke, and the rich portion R In other words, an air-fuel mixture M having a so-called light and shade distribution in which the light portions L in which the fuel gas G is thin is alternately expressed along the flow direction is formed. Then, in the intake region IA where the air-fuel mixture M sucked into the combustion chamber 1 in the next intake stroke of the intake passage 12 exists, one concentrated portion R exists.

The position of the opening 21a of the fuel gas supply valve 21 is the position of the concentrated portion R along the flow direction in the intake region IA when the flow of the air A in the intake passage 12 is stopped. It is set to be close to the rear end side.
As shown in FIG. 2, the concentrated portion R is not yet taken into the combustion chamber 1 in the intermediate period of the intake stroke (for example, 90 ° ATDC) in which the flow of air A becomes strong, as shown in FIG. In addition, since intake is performed at a time slightly before the end time of the intake stroke (for example, 180 ° ATDC) in which the flow of air A becomes weak, diffusion of the concentrated portion R in the combustion chamber 1 is suppressed, In the combustion chamber 1, a mixed gas mixture M stratified so as to have a concentration distribution of the fuel gas G is formed, and the mixed gas M is stratified in the combustion chamber 1 to suppress NOx generation. Furthermore, a stable combustion state can be maintained.

A plurality of the fuel gas supply valves 21 or their openings 21a are provided along the air flow direction in the intake passage 12, and a plurality of concentrated portions R are developed along the flow direction in the intake region IA of the intake passage 21. You may comprise so that the air-fuel | gaseous mixture M which has a light and shade distribution may be formed.
Further, the opening direction of the opening 21a is set to a direction opposite to the flow direction of the air A in the intake passage 12, or the flow of the air A in the intake passage 12 is used instead of the fuel gas supply valve 21 to the intake passage 12. By providing a venturi mixer for attracting the fuel gas G, the amount of fuel gas supplied to the intake passage 12 may be changed according to the pulsation of the air A in the intake passage 12.

  Further, the position of the fuel gas supply valve 21 can be adjusted along the flow direction of the air A in the intake passage 1 to adjust the position of the concentrated portion R in the intake region IA so that the concentrated portion R is burned. The density distribution state in the combustion chamber 1 may be adjusted by adjusting the timing of intake into the chamber 1.

  Further, the engine 100 has an EGR connecting the exhaust passage 13 and the fuel gas passage 20 as EGR means for supplying a part of the exhaust gas E discharged from the combustion chamber 1 to the exhaust passage 13 to the fuel gas passage 20. A flow path 23 is provided.

That is, a part of the exhaust gas E discharged from the combustion chamber 1 to the exhaust passage 13 by the EGR passage 23 is supplied to the fuel gas passage 20 using the back pressure in the exhaust passage 13, and the fuel gas G Mixed with.
Therefore, in the air-fuel mixture M formed by the fuel gas supply valve 21, the concentrated portion R has a high concentration of the exhaust gas E together with the fuel gas G, so that the heat capacity is increased. The exhaust gas E is in a low concentration state together with the gas G.
Then, by causing stratified combustion in the combustion chamber of the air-fuel mixture M having such a concentration distribution, in the concentrated portion R, as in the case of the fuel gas G, an increase in the combustion temperature is suppressed by the high-concentration exhaust gas E. On the other hand, in the light portion L, the low-concentration fuel gas G can be stably burned without being inhibited by the low-concentration exhaust gas E. Increase in fuel fluctuations and engine stall can be prevented.

In addition, in the concentrated portion R of the mixture M that undergoes stratified combustion in the combustion chamber 1, the fuel gas G and the exhaust gas E are uniformly present, and the temperature increase is uniformly suppressed as a whole, and NOx generation is suppressed satisfactorily. In addition, as shown in FIG. 4, the connection portion of the EGR flow path 23 to the fuel gas flow path 20 is a mixing promotion structure 25 that promotes mixing of the fuel gas G and the exhaust gas E in the fuel gas flow path 20. Yes.
Specifically, the mixing promoting structure 25 is disposed on the downstream side of the mixing chamber 27 to which the fuel gas G and the exhaust gas E are supplied and to mix the fuel gas G and the exhaust gas E uniformly. And a rectifying unit 26 made of a metal mesh, a punching plate, or the like.
The mixing promoting structure 25 can adopt any configuration as long as it promotes the mixing of the fuel gas G and the exhaust gas E. For example, instead of the rectifying unit 26, the fuel gas G and the exhaust gas E Mixing is promoted by providing a swirl flow path that promotes mixing by circulating the gas or generating turbulent flow in one of the fuel gas G or exhaust gas E and supplying the other to the turbulent flow part. It can also be configured to.

The EGR flow path 23 is provided with an EGR amount adjustment valve 24 for adjusting the EGR amount that is the supply amount of the exhaust gas E to the fuel gas flow path 20.
Then, the ECU 50 adjusts the opening degree of the EGR amount adjusting valve 24 based on, for example, the intake air amount determined by the opening degree of the throttle valve and the rotation speed of the crankshaft 5 and the operating state such as the engine output. Control the amount.

  That is, the ECU 50 determines the amount of fuel gas G supplied to the air A by the fuel gas supply valve 21 when the throttle valve opening and the rotation speed of the crankshaft 5 increase to increase the intake air amount. When the equivalence ratio of the air-fuel mixture M increases to determine that NOx is likely to be generated in the combustion chamber 1, the opening degree of the EGR amount adjusting valve 24 is increased to increase the EGR amount, and vice versa. In addition, when the throttle valve opening and the rotational speed of the crankshaft 5 are decreased to reduce the intake air amount, or the amount of the fuel gas G supplied to the air A by the fuel gas supply valve 21 is decreased. When the equivalence ratio of the air-fuel mixture M is reduced, NOx is hardly generated in the combustion chamber 1, but it is determined that combustion is likely to become unstable, and the opening degree of the EGR amount adjusting valve 24 is decreased to reduce the EGR amount. Decrease

[Another embodiment]
Next, another embodiment of the present invention will be described.
In the above embodiment, the fuel gas G is supplied to the intake passage 12 by the fuel gas supply valve 21 provided in a part of the intake passage 12 along the flow direction of the air A, so that the rear end side of the intake region IA Although the thick portion R is formed in the combustion chamber 1 and the concentration distribution of the fuel gas G is formed in the combustion chamber 1, the concentration distribution of the fuel gas G may be formed in the combustion chamber 1 by another configuration. For example, the fuel gas G can be directly supplied to, for example, the sub chamber of the combustion chamber 1 to form a density distribution of the fuel gas G in the combustion chamber 1. Even in this case, the EGR flow path 23 as the EGR means The exhaust gas E can be supplied to the fuel gas G in advance.

  For example, the engine 100 shown in FIG. 5 includes a plurality of supply holes 32 dispersedly arranged along the flow direction of the air A in the intake passage 12 as fuel gas supply means, and the intake passage 12 extends from the supply holes 32. A fuel supply mechanism 30 is provided to supply the fuel gas G to the air A flowing through the air and form the air-fuel mixture M in the intake passage 12, and the characteristic configuration will be described below.

  The fuel supply mechanism 30 is configured by forming a mixture having a concentration distribution in the intake passage 12 and by arranging a plurality of supply holes 32 for supplying the fuel gas G along the flow direction in the intake passage 12. Has been.

  The plurality of supply holes 32 eject the fuel gas G in a direction intersecting the flow direction in the intake passage 12 at a time when the flow of the air A in the intake passage 12 is stopped, that is, at a time other than the intake stroke. An air-fuel mixture M having a density distribution is formed in the intake passage 12.

  Specifically, the fuel supply mechanism 30 is provided with a cylindrical casing member 34 to which fuel gas G is supplied from the fuel supply passage 20, and the intake passage 12 is formed therein and a supply hole 32 is formed therein. It is provided in a state of surrounding the intake pipe 12a.

  Further, a rectifying member 35 to which fuel gas G is supplied is provided inside the casing member 34, and the fuel gas G supplied to the inside of the rectifying member 35 includes a plurality of fuel gases G provided outside the rectifying member 35. From the opening, the fuel flows out into the fuel supply chamber 37 outside the rectifying member 35 and reaches the supply hole 32. The fuel supply chamber 37 is provided with a cylindrical punching plate 38 between the intake pipe 12 a provided with the supply hole 32 and the rectifying member 35, and is supplied to the supply hole 32 by the punching plate 38. The flow direction and pressure of the fuel gas G can be adjusted.

  The supply holes 32 are distributed at regular intervals along the flow direction of the air A in the intake passage 12, and are further distributed at regular intervals in the circumferential direction around the axial center of the intake passage 12.

  Then, an orthogonal direction as a direction intersecting the flow direction in the intake passage 12 from each supply hole 32 at a time when the flow of the air A in the intake passage 12 is stopped, that is, at a time other than the intake stroke. The fuel gas G is supplied toward The fuel gas G supplied to the intake passage 12 proceeds in a direction crossing the intake passage 12 in a state where the fuel gas G is suppressed from being mixed with each other. Therefore, in the intake passage 12 where the flow of the air A has stopped, the fuel gas formed between the rich portion R to which the fuel gas G is supplied and the adjacent rich portion R in the flow direction of the air A in the intake passage 12. The air-fuel mixture M is formed in a state where a light and shade distribution consisting of the light portion L with a small amount of G is generated.

  Thus, the air-fuel mixture M having a concentration distribution formed in the intake passage 21 is sucked into the combustion chamber 1 in the next intake stroke or the like while the mixture suppression state maintaining the concentration distribution is maintained.

  Further, also in such a fuel supply mechanism 30, the exhaust gas E is supplied to the fuel gas G in advance by the EGR flow path 23 as the EGR means, and the fuel gas G mixed with the exhaust gas E has a concentration distribution. By stratified combustion of the gas M, in the concentrated portion R, the increase in combustion temperature is suppressed by the high-concentration exhaust gas E similarly to the fuel gas G, so that the generation of NOx can be suppressed. In the part L, the low-concentration fuel gas G is combusted stably without being inhibited by the low-concentration exhaust gas E, so that misfire, increase in fuel fluctuations, and engine stall can be prevented. it can.

  In the above-described embodiment, the EGR amount is adjusted by adjusting the opening degree of the EGR amount adjusting valve 24 provided in the EGR passage 23. However, instead of the EGR amount adjusting valve 24, the EGR passage 23 of the exhaust passage 13 A back pressure adjustment valve may be provided downstream of the branch position, and the EGR amount may be adjusted by adjusting the opening of the back pressure adjustment valve.

  In the above embodiment, the natural gas city gas is used as the fuel gas G. However, as the fuel gas G, a gaseous fuel other than the natural gas city gas can be used.

Schematic showing the state of the engine at the beginning of the intake stroke (0 ° ATDC) Schematic showing the state in the middle of the intake stroke of the engine (90 ° ATDC) Schematic showing the state in the late stage of the intake stroke of the engine (180 ° ATDC) Schematic showing the structure of the mixing promotion structure of EGR means Schematic which shows the structure of the engine of another embodiment.

Explanation of symbols

1: Combustion chamber 7: Intake valve 8: Exhaust valve 12: Intake passage 13: Exhaust passage 20: Fuel gas supply passage 21: Fuel gas supply valve (fuel gas supply means)
23: EGR flow path (EGR means)
24: EGR amount adjustment valve 25: Mixing promotion structure 26: Rectification unit 27: Mixing chamber 32: Supply hole 50: Engine control unit (ECU)
100: Engine A: Air G: Fuel gas M: Air-fuel mixture IA: Intake region

Claims (5)

An engine comprising fuel gas supply means for supplying fuel gas in a fuel gas passage to oxygen-containing gas sucked into the combustion chamber so as to form an air-fuel mixture having fuel gas concentration distribution in the combustion chamber. ,
An engine provided with EGR means for supplying exhaust gas discharged from the combustion chamber to the fuel gas passage.   The engine according to claim 1, wherein the EGR means has a mixing promotion structure that promotes mixing of fuel gas and exhaust gas in the fuel gas flow path.   The fuel gas supply means includes an oxygen-containing gas so as to form an air-fuel mixture having a concentration distribution in the air intake region in the air intake region of the air intake passage where the air-fuel mixture is sucked into the combustion chamber in the next intake stroke. The engine according to claim 1, wherein the engine is configured to supply a fuel gas to a part or a plurality of parts along a gas flow direction.   The fuel gas supply means flows from the plurality of supply holes distributed along the flow direction in the intake passage when the flow of oxygen-containing gas in the intake passage is stopped. The engine according to any one of claims 1 to 3, wherein the engine is configured to supply the fuel gas to the intake passage in a direction crossing the direction.   The engine according to any one of claims 1 to 4, wherein the EGR means is configured to be able to adjust an EGR amount that is a supply amount of the exhaust gas to the fuel gas flow path.

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