JP2009002331A - Sub-chamber gas engine - Google Patents

Abstract

A sub-chamber gas engine is provided that can improve efficiency by advancing the ignition timing and prevent occurrence of knocking.
A sub-chamber type in which a flame (F2) is injected from a sub-chamber tip (61) protruding into a main combustion chamber (10) to burn a mixture of fuel gas and air in the main combustion chamber (10). In the gas engine (100), the fuel gas injection mechanism (8) is disposed in the intake ports (4A, 4B), and the mixture of fuel gas and air produces a swirl in the main combustion chamber (10) during the intake stroke. Therefore, the fuel gas concentration in the region (center region) near the tip (61) of the sub chamber in the main combustion chamber (10) is reduced (center lean).
[Selection] Figure 1

Description

  The present invention relates to a sub-chamber internal combustion engine having a main combustion chamber and a sub-combustion chamber (sub-chamber), and in particular, gaseous fuel (for example, fuel gas such as city gas) is supplied to the main combustion chamber. It relates to a sub-chamber gas engine.

Such a sub-chamber gas engine is used, for example, in a cogeneration system for power generation.
Such a sub-chamber type gas engine tends to increase in size, and there is a demand for higher efficiency for the large gas engine. In order to improve the efficiency, it is necessary to advance the ignition timing and operate in a high efficiency region.

However, if the ignition timing is advanced, the possibility of causing knocking (abnormal combustion) increases. When knocking occurs, it is difficult to improve the efficiency of the gas engine.
Therefore, a technique for avoiding knocking even when the ignition timing is advanced is desired.

As a conventional knocking avoidance technique, for example, a technique related to a sub-chamber gas engine that has a water injection nozzle and avoids knocking by reducing the combustion temperature by water injection from the nozzle has been proposed ( Patent Document 1).
However, in the related art (Patent Document 1), there is a risk that the efficiency of the gas engine may be reduced by lowering the combustion temperature with the water injection nozzle. Therefore, it cannot meet the above-mentioned request for achieving high efficiency.
JP-A-7-127454

  The present invention has been proposed in view of the above-described problems of the prior art, and can improve the efficiency by advancing the ignition timing and can prevent the occurrence of knocking. The purpose is to provide a gas engine.

  The sub-chamber type gas engine of the present invention includes a main combustion chamber (10), a sub-chamber (sub-combustion chamber 20), and an intake port (4A, 4A, which supplies fuel gas and air in communication with the main combustion chamber (10). 4B), and burns secondary fuel (liquid fuel such as fuel gas or various oils) in the sub chamber (20), and the torch from the sub chamber tip (61) protruding into the main combustion chamber (10) Gas injection into the intake ports (4A, 4B) in a sub-chamber gas engine (100) that injects a gas-like flame (F2) to burn a mixture of fuel gas and air in the main combustion chamber (10) The mechanism (8) is arranged, and the mixture of the fuel gas and the air is swirled in the main combustion chamber (10) in the intake stroke, so that the tip of the sub chamber (61) in the main combustion chamber (10). The fuel gas concentration in the area near the center (center area) becomes thinner (becomes center lean). It is characterized by being (claim 1).

  In the present invention, the swirl ratio is preferably 1.0 or more (more preferably 2.0 or more) (Claim 2).

  In the present invention, the swirl (Fs) generated in the main combustion chamber (10) rotates clockwise as viewed from the cylinder head (2) side, and the cylinder at the seat position (4Ao, 4Bo) of the intake valve (4A, 4B). It is preferable that the fuel gas is configured to flow in a region from 6 o'clock to 9 o'clock as viewed from the head (2) side (α: a region indicated by hatching that is lower left in FIG. 5).

  In the present invention, the swirl (Fs) generated in the main combustion chamber (10) rotates counterclockwise as viewed from the cylinder head (2) side, and the seat position (4Ao, 4Bo) of the intake valve (4A, 4B). It is preferable that the fuel gas flows in a region from 3 o'clock to 6 o'clock as viewed from the cylinder head (2) side (β: a region indicated by hatching in the lateral direction in FIG. 5). ).

According to the present invention having the above-described configuration, the fuel gas concentration in the vicinity region (center region) of the sub-chamber tip (61) in the main combustion chamber (10) is reduced (becomes center lean). Therefore, when the air-fuel mixture in the main combustion chamber (10) is pushed into the sub chamber (20) during the intake stroke, the fuel gas concentration in the vicinity of the tip of the sub chamber (61) is low, so the sub chamber (20) The fuel concentration inside is also reduced.
And since the fuel density | concentration in a subchamber (20) is thin, the flame injected into a main combustion chamber (10) from a subchamber tip (61) becomes weak, and the flame injected into a main combustion chamber (10) Combustion is suppressed. Therefore, the combustion speed in the main combustion chamber (10) becomes gentle, and knocking is difficult to occur even if the ignition timing is advanced.

  Thus, according to the present invention in which knocking is suppressed even when the ignition timing is advanced, the efficiency of the sub-chamber gas engine (100) can be improved by advancing the ignition timing, and the efficiency is improved by knocking. Can be reliably prevented.

In the present invention, if the swirl ratio is configured to be 1.0 or more (Claim 2), the fuel gas concentration distribution in the main combustion chamber (10) is a region near the tip of the sub chamber (61) (central region). ) In the fuel gas concentration can be reduced (center lean).
As the swirl ratio increases (preferably 2.0 or more), the tendency for the fuel gas concentration in the region (central region) near the subchamber tip (61) to become thinner (become central lean) becomes more prominent. .

  In the present invention, when the swirl (Fs) generated in the main combustion chamber (10) rotates in the clockwise direction when viewed from the cylinder head (2) side, the seat position (4Ao, 4Bo) of the intake valve (4A, 4B). ) When viewed from the cylinder head (2) side, the fuel gas flows in the region from 6 o'clock to 9 o'clock (α: the region indicated by the left-downward hatching in FIG. 5) (Claim 3), or When the swirl (Fs) rotates in the counterclockwise direction, a region from 3 o'clock to 6 o'clock as viewed from the cylinder head (2) side of the seat position (4Ao, 4Bo) of the intake valve (4A, 4B) (β : In FIG. 5, if the fuel gas is configured to flow in the hatched region in the horizontal direction (Claim 4), the fuel gas concentration distribution in the main combustion chamber (10) is Fuel gas concentration in the vicinity area (central area) The degree can be made thin (center lean).

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 and 2 show a sub-chamber gas engine 100 according to an embodiment of the present invention.

  1 and 2, the sub-chamber gas engine 100 includes a cylinder 1, a cylinder head 2, and a piston 3. FIG. 1 shows a state where the piston 3 has reached top dead center.

In the center of the top portion 31 of the piston 3, a circular dish-shaped recess portion 32 is formed in the drawing.
The circular dish-like depression 32 constitutes the main combustion chamber 10 together with a space (gap) S formed by the cylinder wall 11, the lower end surface 21 of the cylinder head, and the piston top 31.

A lower end surface 21 of the cylinder head 2 has a circular shape (indicated by reference numeral 22 in FIG. 2), and a sub chamber housing 6 (see FIG. 1) having a sub chamber 20 is provided at the center thereof.
The sub chamber front end 61 of the sub chamber housing 6 protrudes toward the main combustion chamber 10 from the lower end surface 21 of the cylinder head 2.

A sub-combustion chamber (sub-chamber) 20 is formed in the sub-chamber housing 6.
A light oil injection mechanism 7 for injecting light oil is provided in a region above the sub chamber 20 in the sub chamber housing 6.
In FIG. 1, reference numeral F <b> 1 indicates a spray (jet) of light oil injected from the light oil injection mechanism 7 into the sub chamber 20.
The spray (jet) F1 of light oil injected from the light oil injection mechanism 7 is ignited and combusted in the sub chamber housing 6 in a known manner.

In the illustrated example, eight nozzle holes 62 are formed in the sub chamber tip 61.
The direction of the torch-like flame injected from the eight nozzle holes 62 is directed obliquely downward. The eight nozzle holes 62 are arranged at an equal pitch in the circumferential direction. And the torch-like flame injected from the nozzle hole 62 is configured to be injected radially from the center of the cylinder toward the cylinder wall 11 (or outward in the radial direction).
More specifically, in FIG. 1, the sub chamber front end 61 and the eight injection holes 62 are arranged so that the torch-like flame injection F <b> 2 collides with the vicinity of the circular corner portion 33 in the circular dish-shaped depression 32. It is configured.

The sub-chamber gas engine 100 according to the illustrated embodiment includes a first intake port 4A and a second intake port 4B.
On the lower end surface 21 of the cylinder head 2, openings (valve seat portions) 4 </ b> Ao and 4 </ b> Bo of two intake ports 4 </ b> A and 4 </ b> B are formed at a portion facing the main combustion chamber 10. The opening portions 4Ao and 4Bo of the intake port are arranged so as to be approximately 90 ° with respect to the cylinder center point O in the illustrated example, and are arranged at intervals.
1 and 2, the exhaust port and the exhaust port opening are not shown.
Reference numerals 4A1 and 4B1 (left side walls of the intake ports 4A and 4B) in FIG. 2 will be described later in relation to the flow of the fuel gas.

Openings (valve seat portions) 4Ao and 4Bo of the intake ports 4A and 4B are opened and closed by intake valves 5A and 5B (FIG. 1).
In FIG. 2, one intake port is branched into two intake ports 4A and 4B at a branch portion 4Y on the upstream side of the intake ports 4A and 4B.
A fuel gas injection mechanism 8 is provided in the vicinity of the branch portion 4Y. A plurality of fuel gas injection holes 81 are formed in the fuel gas injection mechanism 8.
From this fuel gas injection hole 81, fuel gas is injected toward the downstream side of the intake ports 4A, 4B (the main combustion chamber 10 side). And it is comprised so that the fuel gas injected from the fuel gas injection hole 81 may be mixed with the fresh air (air) which flows through two intake port 4A, 4B.
Here, the intake ports 4A and 4B (shown in cross section in FIG. 7) and the shape of the fuel gas injection mechanism 8 provided at the branch portion are shown in detail in FIG.
In addition, the code | symbol Ff in FIG. 2 has shown the injection jet of fuel gas.

The fuel gas injected from the fuel injection mechanism 8 and the new (air) are mixed when flowing through the intake ports 4A and 4B. The mixture of the fuel gas and the new (air) is supplied into the main combustion chamber 10 through the openings (valve seat portions) 4Ao and 4Bo.
In particular, as clearly indicated by the arrow Fs in FIG. 2, in the illustrated embodiment, the mixture of fuel gas and new (air) in the main combustion chamber 10 flows over the vortex, forming a so-called “swirl”. is doing.

  FIG. 1 shows a configuration in which light oil is injected (F1) into the sub chamber 20 from the light oil injection mechanism 7. However, secondary fuel other than light oil, for example, high concentration fuel gas or various types of fuel oil may be supplied to the sub chamber 20.

In the illustrated embodiment, the main combustion chamber 10 is configured so that the fuel gas concentration is reduced (becomes “central lean”) in the vicinity of the sub chamber tip 61 (the central region of the main combustion chamber) during the intake stroke. Has been. As described above, the sub chamber tip 61 is a member that injects (F2) the flame (torch) generated in the sub chamber 20 into the main combustion chamber 20.
An example of the simulation result of the fuel gas concentration distribution in the case of such “central lean” is shown in FIG.

The identification band B shown in the upper part of FIG. 3 identifies and displays the concentration of the combustion gas in the mixture in the main combustion chamber 10 and the sub chamber 20 shown in the lower part of FIG. Yes.
The identification band B has the lowest concentration of fuel gas at the right end d1 and the highest concentration of fuel gas at the left end d10.
In FIG. 3, for convenience, the display is divided into 10 levels, but in actuality, the shading changes steplessly.

  In FIG. 3, the fuel gas concentration is low (thin: symbol d <b> 1) in the inside of the sub chamber 20 and in the region near the sub chamber tip 61 in the main combustion chamber 10 (the central region of the main combustion chamber), and the main combustion chamber 10. The fuel gas concentration is high (intensified: reference signs d7 to d10) at the peripheral edge of.

The inventor includes a gas engine (central lean gas engine) according to the illustrated embodiment, a gas engine configured to have a uniform fuel gas concentration in the main combustion chamber (a gas engine having a uniform concentration), Combustion experiments were performed using a gas engine (central rich gas engine) showing a fuel gas concentration distribution opposite to that of the embodiment.
Here, “a gas engine showing a fuel gas concentration distribution opposite to that of the illustrated embodiment (central rich gas engine)” is described in the vicinity of the sub-chamber tip 61 in the case of the gas engine having the illustrated configuration (main engine). The fuel gas concentration is high in the central region of the combustion chamber, and the fuel gas concentration is low in the peripheral portion of the main combustion chamber 10.

As a result of the inventor's combustion experiment, among the above-described three types of gas engines (central lean gas engine, uniform concentration gas engine, central rich gas engine), the central lean gas engine does not cause knocking. It was confirmed that the ignition timing can be advanced (advanced) the fastest.
That is, it has been found that knocking can be most suppressed even if the ignition timing is advanced if it is configured so as to have a central lean as in the gas engine according to the illustrated embodiment.

Further, in the combustion experiment by the inventor, the amount of heat release per unit time when a flame (torch) was injected into the main combustion chamber 10 from the sub chamber 20 (rate of heat release) was measured.
As a result, when the flame is injected from the sub chamber 20 into the main combustion chamber 10 (F2), the calorific value per unit time is the lowest in the central lean gas engine, the uniform concentration gas engine, and the central rich gas. It was higher in order of engine.
As is well known, knocking is suppressed as the amount of heat generated per unit time when a flame is injected from the sub chamber 20 into the main combustion chamber 10 is lower. Therefore, also from the result of the combustion experiment, the central lean gas engine having the lowest calorific value (the calorific value per unit time when the flame is injected into the main combustion chamber 10 from the sub chamber 20) is knocked. It became clear that it could be suppressed most.

It is estimated that knocking is suppressed in the central lean gas engine for the following reasons.
In the sub-chamber gas engine 100, the air-fuel mixture in the main combustion chamber 10 is pushed into the sub-chamber 20 during the intake stroke.
Here, in the central lean gas engine, in the main combustion chamber 10, the fuel concentration in the region near the sub chamber tip 61 (center region) is low. Therefore, in the gas engine of the central lean, the fuel concentration of the air-fuel mixture in the main combustion chamber 10 that is pushed into the sub chamber 20 in the intake stroke is reduced, and the fuel concentration in the sub chamber 20 is also reduced.
If the fuel concentration in the sub chamber 20 is low, the flame injected from the sub chamber 20 into the main combustion chamber 10 becomes weak, or the combustion of the flame injected into the main combustion chamber 10 is suppressed. As a result, the combustion speed in the main combustion chamber 10 becomes moderate, and even if the ignition timing is advanced, knocking hardly occurs.

In the embodiment shown in the drawing, a vortex (swirl) of the air-fuel mixture is generated in the main combustion chamber 10 so that the center lean is achieved. This is because it has been confirmed by the inventor's simulation that a mixture of fuel gas and fresh air (air) becomes a central lean when a swirl occurs in the main combustion chamber 10.
Further, by controlling the injection direction of the fuel gas, the flow direction of the fuel gas in the main combustion chamber 10 and the timing of the fuel gas injection, the inside of the main combustion chamber 10 is made the central lean in the illustrated embodiment.

In particular, as clearly shown in FIG. 2, in the illustrated embodiment, two intake ports 4A, 4B are provided. Here, the two intake ports 4 </ b> A and 4 </ b> B are configured to generate a strong swirl in the main combustion chamber 10.
In other words, the gas engine according to the illustrated embodiment is configured to have a high swirl.
Here, “high swirl” means “strong swirl”, and means that the swirl ratio is large (the swirl ratio is 1.0 or more). The swirl ratio is indicated by the number of swirls with respect to the engine speed.
In the illustrated embodiment, at least the swirl ratio is 1.0 or more, and preferably the swirl ratio is 2.0 or more.

  As a specific configuration for increasing the swirl generated in the main combustion chamber 10 to achieve a high swirl, in FIG. 4, the maximum distance δ between the first intake port 4A and the second intake port 4B is shown in FIG. Increase Then, the radius of curvature R at the place farthest from the first intake port 4A in the second intake port 4B may be reduced.

The inventor simulates the fuel gas concentration in the main combustion chamber 10 when the swirl ratio is 2.0 (in the case of high swirl), and the main combustion in the case where the swirl ratio is 0.5 (in the case of low swirl). The fuel gas concentration in the chamber 10 was simulated. As a result, in the case of the high swirl, a concentration distribution (as shown in FIG. 3) in which the tendency of the central lean is remarkable was obtained.
From the result of the simulation, it was found that the higher the swirl ratio, the stronger the tendency of central lean and the suppression of knocking.

  Here, when the intake valves 4A and 4B and the exhaust valve EV (shown by dotted lines in FIGS. 4 and 5) are arranged as shown in FIG. 5, in the illustrated embodiment, they are viewed from the cylinder head 2 side. Thus, when a swirl rotating in the clockwise direction is generated in the main combustion chamber 10, the seat position 4Ao, 4Bo of the intake valves 4A, 4B arranged in the 6 o'clock direction when the exhaust valve EV is viewed in the 12 o'clock direction The fuel gas is injected from the fuel injection mechanism 8 so that the fuel gas flows in the region α (region indicated by the left-downward hatching in FIG. 5) when viewed from the cylinder head 2 side.

In order for the fuel gas to flow in the region α between 6 o'clock and 9 o'clock when viewed from the cylinder head 2 side at the seat position of the intake valves 4A and 4B, the intake ports 4A and 4B shown in FIG. 2 have a rectangular cross section. In this case, for example, the fuel gas injection hole 81 in the fuel injection mechanism 8 is positioned in the vicinity of the upper wall of the intake ports 4A and 4B, and the fuel gas injection port 81 is located on the left side wall (the radius of curvature of the intake ports 4A and 4B). It suffices to face the larger wall surface 4Al, 4Bl). However, it may differ depending on the position of the fuel injection mechanism 8 and the cross-sectional shapes of the intake ports 4A and 4B.
More specifically, in the illustrated embodiment, at the seat position of the intake valves 4A and 4B, in order to allow the fuel gas to flow in the region α (FIG. 5) from 6 o'clock to 9 o'clock as viewed from the cylinder head 2 side. 8, the fuel gas injected from the fuel gas injection port 81 may be configured to go to the area AU above the left side wall of the intake ports 4A and 4B shown in cross section (area shown by the dotted line in FIG. 8). .

  On the other hand, if the swirl in the main combustion chamber 10 is counterclockwise, the cylinders at the seat positions 4Ao and 4Bo of the intake valves 4A and 4B arranged in the 6 o'clock direction when the exhaust valve EV is viewed in the 12 o'clock direction. The fuel gas is injected from the fuel injection mechanism 8 so that the fuel gas flows in a region β (region indicated by horizontal hatching in FIG. 5) from 3 o'clock to 6 o'clock when viewed from the head 2 side.

According to the inventor's experiment, when a swirl rotating in the clockwise direction when viewed from the cylinder head 2 side is generated, the seat positions 4Ao and 4Bo of the intake valves 4A and 4B are viewed from the 6th to 9th when viewed from the cylinder head 2 side. If the fuel gas is injected so that the fuel gas flows into the time region α, the fuel gas is supplied to the peripheral portion of the main combustion chamber 10 by the swirl, but not so much supplied to the central portion of the main combustion chamber 10. It has been confirmed.
Similarly, when a swirl in the counterclockwise direction is generated, the fuel gas is also injected by the swirl in the case where the fuel gas is injected so that the fuel gas flows in a region β from 3 o'clock to 6 o'clock when viewed from the cylinder head 2 side. It is supplied to the peripheral part of the main combustion chamber 10 and is not supplied so much to the central part of the main combustion chamber 10.
Therefore, if the fuel gas is injected from the fuel injection mechanism 8 so that the fuel gas flows in the injection region α (in the case of the clockwise swirl) or the region β (in the case of the counterclockwise swirl), in the main combustion chamber 10 The fuel gas concentration distribution is in a state of central lean.

At the seat positions 4Ao and 4Bo of the intake valves 4A and 4B, the fuel gas is injected so that the fuel gas flows into the region α (FIG. 5) from 6 o'clock to 9 o'clock when viewed from the cylinder head 2 side. FIG. 9 shows the result of simulating the fuel gas concentration distribution in the main combustion chamber 10 when a swirl that rotates clockwise as viewed from the side is generated.
In FIG. 9, a region where the fuel gas concentration in the main combustion chamber 10 is high is shown as a region where there are many fine dots, and a region where the fuel gas concentration is low is shown as a region where there are few fine dots.
As is clear from FIG. 9, the fuel gas concentration distribution in the main combustion chamber 10 is in a central lean state, and the fuel gas concentration in the region near the tip 61 of the sub chamber 6 is low. Therefore, the concentration of the fuel gas flowing into the sub chamber 6 is also reduced, and the concentration of fuel in the sub chamber 6 is also reduced. And the flame injected into the main combustion chamber 10 from the sub chamber tip 61 also becomes weak, and the combustion of the flame injected into the main combustion chamber 10 is suppressed. As a result, the combustion speed in the main combustion chamber 10 becomes gentle, and knocking hardly occurs even if the ignition timing is advanced.

In the illustrated embodiment, the main combustion chamber 10 can be set to the central lean by controlling the fuel gas injection timing.
In FIG. 6 showing the fuel gas injection timing, the fuel gas injection timing displayed as “reference condition” (block arrow A) and the fuel gas injection timing displayed as “early supply” (block arrow B). Is shown.

Here, as shown in FIG. 2, in the illustrated embodiment, fuel gas is injected from the fuel injection mechanism 8 disposed in the intake ports 4A and 4B, and mixed with fresh air (air) to be mixed with the main combustion chamber 10. Flows in. Therefore, even when the fuel gas is injected from the fuel injection mechanism 8 at the same timing, the timing to reach the main combustion chamber 10 differs depending on the position where the fuel injection mechanism 8 is provided, the fuel gas injection amount, and the fuel gas injection pressure. The injection timing shown in FIG. 6 is a timing at which the fuel gas is injected from the fuel injection mechanism 8 and is not a timing at which the fuel gas flows into the main combustion chamber 10.
FIG. 6 shows the valve lift amounts Li and Lx of the intake valve and the exhaust valve with respect to the crank angle θ. In FIG. 6, TDC indicates the top dead center, and BDC indicates the bottom dead center.

In FIG. 6, the fuel gas injection timing indicated as “reference condition” (block arrow A) is the fuel gas supplied from the fuel injection mechanism 8 so that the same fuel gas supply as in the conventional sub-chamber gas engine is performed. The case where the gas injection timing is set is shown.
On the other hand, the fuel gas injection timing displayed as “early supply” in FIG. 6 indicates the fuel gas injection timing from the fuel injection mechanism 8 in the illustrated embodiment.
As is clear from FIG. 6, the fuel gas injection timing “early supply” (block arrow B) according to the illustrated embodiment is compared with the injection timing displayed as “reference condition” (block arrow A), The start period Ts and the end period Te of fuel injection are earlier.

Here, the term “early supply” does not have a strict definition. It does not matter if the end of fuel injection (fuel gas supply) is earlier than the timing at which intake valves 5A and 5B are closed.
FIG. 3 shows a simulation result of the fuel gas concentration distribution in the main combustion chamber 10 when fuel gas is injected at the injection timing (timing in the illustrated embodiment) indicated as “early supply” in FIG. The inventor compared the result of simulating the fuel gas concentration distribution in the main combustion chamber when the fuel gas was injected at the injection timing indicated as “reference condition”. As a result, the tendency of “central lean” was more noticeable in the simulation result of the injection timing (timing in the illustrated embodiment) displayed as “early supply”.

In FIG. 6, the injection timing (the timing in the illustrated embodiment) displayed as “early supply” (block arrow B) is that the fuel gas is injected from 50 ° before top dead center to 65 ° after top dead center. Yes.
Further, in FIG. 6, at the injection timing indicated as “reference condition” (block arrow A), the fuel gas is injected from 10 ° before top dead center to 100 ° after top dead center.
These injection timings are experimental examples and are not in a general range. For example, as described above, the numerical value varies depending on the position of the fuel injection mechanism 8 disposed in the intake ports 4A and 4B, the fuel gas injection amount, and the fuel gas injection pressure.

In FIG. 6, the injection timing (the timing in the illustrated embodiment) displayed as “early supply” (block arrow B) is that the fuel gas is injected from 50 ° before top dead center to 65 ° after top dead center. FIG. 10 and FIG. 11 show the simulation results of the fuel gas concentration distribution in the main combustion chamber 10 when the fuel gas is injected at such timing.
In FIG. 10, when the intake valves 5 </ b> A and 5 </ b> B are closed, the fuel gas injection start timing and injection end timing become early, so that the fuel gas is unevenly distributed in the region below the main combustion chamber 10, and the main combustion chamber 10 The upper region 10U (region indicated by a dotted line in FIG. 10) is lean.
In FIGS. 10 and 11, as in FIG. 9, the region of the main combustion chamber 10 with a lot of fine dots has a high fuel gas concentration, and the region with a small number of fine dots has a low fuel gas concentration.

The lean region existing above the main combustion chamber 10 in the stage of FIG. 10 is collected in the central portion of the main combustion chamber 10 by the tumble flow Ft generated in the compression stroke shown in FIG. Becomes the central lean.
Even if the tumble flow Ft is weak, the fuel gas injection timing becomes early, so that the upper part of the combustion chamber 10 remains lean in the compression stroke as well as in the compression stroke as shown in FIG. Accordingly, the fuel gas concentration in the region near the tip 61 of the sub chamber 6 is low, and the concentration of the fuel gas flowing into the sub chamber 6 is also low.
The concentration of fuel in the sub chamber 6 is also reduced, and the flame injected from the sub chamber tip 61 into the main combustion chamber 10 is weakened, so that the combustion of the flame injected into the main combustion chamber 10 is suppressed. . As a result, the combustion speed in the main combustion chamber 10 becomes gentle, and knocking hardly occurs even if the ignition timing is advanced.

As described above, FIG. 9 shows the inside of the main combustion chamber 10 in the case where a swirl is generated by injecting the fuel gas so that the fuel gas flows in the region α from 6 o'clock to 9 o'clock as viewed from the cylinder head 2 side. The result of simulating the fuel gas concentration distribution is shown.
A swirl is generated so that the fuel gas concentration distribution in the main combustion chamber 10 becomes the simulation result shown in FIG. 9, and the injection timing (block arrow B) is displayed as “early supply” in FIG. 6 (block arrow B). FIG. 3 shows the result of simulating the fuel gas concentration distribution in the main combustion chamber 10 when the fuel gas is injected from 50 ° before top dead center to 65 ° after top dead center as the timing in the illustrated embodiment. .
In other words, FIG. 3 shows the simulation result of the fuel gas concentration distribution when the swirl is generated and the “early supply” of fuel gas (arrow B in FIG. 6) is performed.

Although not clearly shown, it may be configured such that when fuel gas is injected, the fuel gas first flows into the main combustion chamber 10 and fresh air flows after the inflow of the fuel gas is completed. .
This is because the tendency to become a central lean becomes conspicuous.

  As described above, according to the illustrated embodiment, the fuel gas concentration distribution in the main combustion chamber 10 is configured to be the central lean, so that knocking is suppressed even if the ignition timing is advanced. Is done. As a result, the sub-chamber gas engine according to the illustrated embodiment can achieve high efficiency.

  In the illustrated embodiment, the swirl formed in the main combustion chamber 10 is configured so that the swirl ratio is at least 1.0 or more, preferably 2.0 or more. It is easy to make the concentration distribution of the fuel gas inside the center lean.

  Further, in the illustrated embodiment, as viewed from the cylinder head 2 side, the fuel gas is injected so that the fuel gas flows in the region α from 6 o'clock to 9 o'clock in the seat position 4Ao, 4Bo of the intake valve, or counterclockwise When the swirl is generated, the fuel gas is injected so that the fuel gas flows in the region β from 3 o'clock to 6 o'clock at the seat position 4Ao, 4Bo of the intake valve as viewed from the cylinder head 2 side. The concentration distribution of the fuel gas in the combustion chamber 10 can be set to the central lean.

  In addition to this, according to the illustrated embodiment, the fuel gas is supplied earlier than the conventional sub-chamber type gas engine (ie, the early supply), and as a result, in the main combustion chamber 10 The concentration distribution of the fuel gas can be set to the central lean.

  It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.

The fragmentary sectional view which shows the principal part of embodiment of this invention. The top view which shows embodiment. The figure which shows an example of the simulation of fuel gas concentration distribution in the state of a center lean. The top view explaining the structure for making a swirl ratio high in embodiment. The top view explaining the other conditions which make a swirl ratio high. Explanatory drawing which shows fuel gas supply timing. The perspective view which shows the structure of the fuel gas injection mechanism vicinity. FIG. 3 is a cross-sectional view showing a region in an intake port where fuel gas is injected from a fuel gas injection port in the illustrated embodiment. The figure which shows the result of having simulated the fuel gas concentration distribution in the main combustion chamber at the time of generating a swirl in embodiment of illustration. The figure which shows the simulation result of the fuel gas concentration distribution in the main combustion chamber in the time of an intake valve closing, when performing early injection. The figure which shows the simulation result of the fuel gas concentration distribution in the main combustion chamber in a compression stroke when performing early injection, Comprising: The figure which shows that a tumble flow arises.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... Cylinder head 3 ... Piston 4A, 4B ... Intake port 5A, 5B ... Intake valve 6 ... Sub chamber housing 7 ... Light oil injection mechanism 8 ... Fuel gas injection mechanism 10 ... main combustion chamber 11 ... cylinder wall 20 ... sub combustion chamber / sub chamber 61 ... sub chamber tip 100 ... sub chamber type gas engine

Claims (4)

  A main combustion chamber, a sub chamber, and an intake port that communicates with the main combustion chamber and supplies fuel gas and air, burns secondary fuel in the sub chamber, and from the tip of the sub chamber protruding into the main combustion chamber In a sub-chamber type gas engine that injects a torch-like flame to burn a mixture of fuel gas and air in the main combustion chamber, a fuel gas injection mechanism is arranged at the intake port, and in the main combustion chamber during the intake stroke A sub-chamber gas engine characterized in that a mixture of fuel gas and air produces a swirl, and thus the fuel gas concentration in the region near the tip of the sub-chamber in the main combustion chamber is reduced. .   The sub-chamber type gas engine according to claim 1, wherein the swirl ratio is configured to be 1.0 or more.   The swirl generated in the main combustion chamber rotates in the clockwise direction when viewed from the cylinder head side, and the exhaust valve is viewed in the 12 o'clock direction, and the seat position of the intake valve disposed in the 6 o'clock direction is viewed from the cylinder head side. The sub-chamber type gas engine according to any one of claims 1 and 2, wherein the fuel gas is configured to flow in a region from 9:00 to 9:00.   The swirl generated in the main combustion chamber rotates counterclockwise when viewed from the cylinder head side, and when viewed from the cylinder head side of the seat position of the intake valve disposed at 6 o'clock when the exhaust valve is viewed at 12 o'clock. The sub-chamber type gas engine according to any one of claims 1 and 2, wherein the fuel gas is configured to flow in a region between 3 o'clock and 6 o'clock.

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