JP2005232988A - Subsidiary chamber type engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a subsidiary chamber type engine wherein new air compressed in a main chamber flows into the subsidiary chamber via a communication passage opening to the main chamber, a mixture of the new air flowing into the subsidiary chamber and main fuel supplied to the subsidiary chamber is burnt, and flame jet is injected from the subsidiary chamber via the communication passage into the main chamber, having simple construction for giving stable ignition to the mixture in the subsidiary chamber while suppressing the production of NOx in the subsidiary chamber. <P>SOLUTION: In the subsidiary chamber, an igniting fuel injection means is provided for injecting igniting fuel having higher ignitability than the main fuel into the compressed mixture to cause the self-ignition of the mixture to be burnt. The igniting fuel injection means injects the igniting fuel in a plurality of batches. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  According to the present invention, fresh air compressed in the main chamber is caused to flow into the sub chamber via the communication passage that opens to the main chamber, and the fresh air that has flowed into the sub chamber and the main fuel supplied to the sub chamber are The present invention relates to a sub-chamber engine that burns an air-fuel mixture and injects a flame jet from the sub-chamber into the main chamber through the communication passage.

Conventional engines can be broadly divided into single-chamber type and sub-chamber type. The sub-chamber engine includes a main chamber that is in contact with the top of the piston and a sub-chamber that communicates with the main chamber via a communication passage as a combustion chamber, and the piston sucks fresh air that is inhaled into the main chamber or a lean mixture. Compressed fresh air flows into the sub chamber through the communication path, and the fuel (main fuel) directly supplied to the sub chamber is burned using the fresh air that has flowed into the sub chamber Thus, a flame jet is configured to be injected into the main chamber through a communication path that opens to the main chamber (see, for example, Patent Documents 1-3).
Further, such a sub-chamber engine can achieve high efficiency because lean combustion in which fuel is burned in a state where the fuel is lean relative to air in the entire combustion chamber can be realized as compared with a single-chamber engine. In particular, it has been introduced into cogeneration systems and the like that require improved efficiency.

  In such a sub-chamber engine, as a method of igniting the air-fuel mixture compressed in the sub-chamber, a spark ignition method in which the air-fuel mixture is spark-ignited by an ignition plug provided in the sub-chamber is common.

JP 2002-276474 A JP 2001-303958 A JP 2001-263069 A

  However, if the main fuel that is the air-fuel mixture formed in the sub chamber is relatively low in ignitability, such as LP gas, the air-fuel mixture can be obtained simply by generating a spark in the sub chamber using the spark plug. May not be able to ignite, causing a misfire. In order to ignite the air-fuel mixture with certainty, it is conceivable to install a plurality of spark plugs. However, an increase in the number of spark plugs increases the cost, and a plurality of spark plugs are arranged in a relatively small subchamber. There are cases where it is not possible.

  On the other hand, even when the air-fuel mixture can be ignited in the sub chamber, if the combustion speed of the air-fuel mixture is too fast, an increase in the amount of NOx generated due to a rapid temperature rise and an increase in mechanical loss due to a rapid pressure increase are caused. There is a case.

  The present invention has been made in view of the above-described problems. The fresh air compressed in the main chamber is caused to flow into the sub chamber through the communication passage that opens to the main chamber, and the fresh air that has flowed into the sub chamber. And a sub-chamber engine that burns a mixture of the main fuel supplied to the sub chamber and injects a flame jet from the sub chamber into the main chamber through the communication path. Therefore, it is possible to stably ignite the air-fuel mixture in the sub chamber and to provide a sub chamber engine that can suppress NOx generation in the sub chamber.

  In order to achieve the above object, a sub-chamber engine according to the present invention allows fresh air compressed in the main chamber to flow into the sub-chamber via a communication passage that opens to the main chamber, and flows into the sub-chamber. A sub-chamber engine that burns an air-fuel mixture of air and main fuel supplied to the sub-chamber and injects a flame jet from the sub-chamber into the main chamber via the communication path, the first feature thereof In the sub chamber, ignition fuel injection means for igniting and burning the air-fuel mixture by injecting an ignition fuel having higher ignitability than the main fuel into the compressed air-fuel mixture and self-igniting the fuel In addition, the ignition fuel injection means is configured to inject the ignition fuel in a plurality of times.

  According to the first characteristic configuration, by providing the ignition fuel injection means, the temperature of the air-fuel mixture formed by the main fuel is compressed in the sub chamber, and the temperature is increased by the ignition fuel injection means. By injecting an ignition fuel with higher ignitability than the main fuel into the heated mixture, the ignition fuel is self-ignited to generate larger heat energy than the sparks from the spark plug, thereby mixing the main fuel. Qi can be ignited and burned reliably.

When the fuel mixture in the sub chamber is ignited and combusted by the injection of the fuel for ignition by the fuel injection means for ignition, the fuel injection means for ignition has a predetermined injection amount that can surely ignite the mixture. If the fuel is injected once, an increase in the amount of NOx generated due to a rapid temperature rise in the sub chamber, and further an increase in mechanical loss due to a rapid pressure increase may occur.
Therefore, the ignition fuel injection means is configured to inject a predetermined amount of ignition fuel into the air-fuel mixture that has been compressed in the sub chamber and heated in a plurality of times, thereby increasing the temperature and pressure in the sub chamber. In addition, while suppressing the increase of NOx generation amount and mechanical loss, the igniting fuel injected into the sub chamber is disturbed to promote the mixing of the igniting fuel and the air. The fuel for use can be diffused and burned well, and the air-fuel mixture comprising the main fuel can be ignited by the diffusion combustion.

  Therefore, according to the present invention, a simple structure in which a predetermined amount of fuel for ignition is injected into the sub-chamber in a plurality of times by the fuel injection means for ignition with respect to the air-fuel mixture compressed and heated in the sub-chamber. Thus, it is possible to realize a sub-chamber engine that can stably ignite the air-fuel mixture and suppress NOx generation in the sub-chamber.

  The second characteristic configuration of the sub-chamber engine according to the present invention is that the main fuel is a gaseous fuel and the ignition fuel is a liquid fuel.

According to the second characteristic configuration, since the main fuel is supplied to the sub chamber at a time when the sub chamber is in a relatively low pressure state such as the initial stage of the intake stroke or the compression stroke, it is difficult to highly compress the main fuel. Gas fuel such as natural gas can be used, and the ignition fuel is injected into the sub chamber when the sub chamber is in a relatively high pressure state after the compression stroke. Liquid fuel such as light oil.
That is, the main fuel supplied to the sub chamber mainly to obtain motive power is a gas fuel, and the ignition fuel injected into the sub chamber to ignite the gas fuel is a liquid fuel. High efficiency and low NOx can be achieved in sub-chamber engines that mainly consume gaseous fuel and obtain power

  A third characteristic configuration of the sub-chamber engine according to the present invention is that it includes an injection state control means for controlling an injection state of the ignition fuel by the ignition fuel injection means based on an engine load.

According to the third characteristic configuration, the injection state control means controls the injection state such as the injection amount, the number of injections, or the injection interval of the ignition fuel by the ignition fuel injection means based on the engine load. Thus, even when the engine load changes and the pressure in the sub chamber changes, the combustion speed of the fuel for ignition in the sub chamber is made appropriate, and NOx generation and mechanical loss are suppressed, and the ignition fuel is improved. The fuel for ignition can be injected in an appropriate injection state in which the air-fuel mixture is surely ignited by diffusion combustion by diffusion combustion.
That is, when the engine load is reduced, the injection state control means determines that it is difficult to ignite the air-fuel mixture in the sub chamber, although the maximum in-cylinder pressure of the sub chamber is low. By adjusting the injection state so as to promote the acceleration, it is possible to improve the ignition performance of the premixed compression ignition air. On the other hand, when the engine load increases, it becomes easy to ignite the air-fuel mixture in the sub chamber, but it is determined that NOx and mechanical loss are likely to increase due to a sudden increase in temperature and pressure in the sub chamber. The injection state can be adjusted so as to slow down the diffusion combustion of the ignition fuel, and the temperature and pressure rise in the sub chamber can be suppressed.
In addition, by increasing the injection amount per time of the ignition fuel as the injection state and increasing the energy generated by the combustion of the ignition fuel, the diffusion combustion of the ignition fuel can be promoted. Further, by increasing the number of injections of the ignition fuel as the injection state or shortening the injection interval of the ignition fuel as the injection state, the disturbance generated in the ignition fuel injected into the sub chamber is increased. Thus, diffusion combustion of the ignition fuel can be promoted.
On the contrary, the injection amount per one injection of the ignition fuel is reduced as the injection state, or the number of ignition fuel injections is reduced as the injection state, or the injection interval of the ignition fuel is set as the injection state. By making it longer, diffusion combustion of the ignition fuel can be slowed down.

An embodiment of a sub-chamber engine according to the present invention will be described based on the drawings.
A sub-chamber engine 100 shown in FIG. 1 includes a piston 2 and a cylinder 3 that houses the piston 2 and forms a main chamber 1 together with the top surface of the piston 2, and reciprocates the piston 2 in the cylinder 3. The intake valve 4 and the exhaust valve (not shown) are opened and closed to take in fresh air into the main chamber 1, and various strokes of intake, compression, combustion / expansion, and exhaust are performed in the main chamber 1, and the piston 2 reciprocates. The movement is output as a rotational movement of a crankshaft (not shown) by a connecting rod (not shown), and such a configuration is not different from a normal four-stroke internal combustion engine.

In the sub-chamber engine 100 of the present embodiment, the bore diameter of the cylinder 3 is 110 mm, the stroke length of the piston 2 is 106 mm, and the minimum combustion chamber volume when the position of the piston 2 is the top dead center position The compression ratio which is the maximum combustion chamber volume ratio when the position of the piston 2 with respect to the bottom dead center position is 17, and the displacement obtained by subtracting the minimum combustion chamber volume from the maximum combustion chamber volume is 1007 cc (1007 × 10 ³ mm ³ ). The sub-chamber engine 100 is operated at a crankshaft rotation speed of 1200 rpm.

  The sub-chamber engine 100 uses city gas (13A), which is a gaseous fuel, as the main fuel G. In the intake stroke, the intake valve 4 is opened and air and a small amount of main fuel are placed in the main chamber 1. The fresh air I, which is a lean mixture with G, is sucked, and the sucked fresh air I is compressed in the compression stroke to burn the main fuel G.

The cylinder head 9 of the sub chamber type engine 100 is provided with a main chamber 1 as a combustion chamber, and is provided with a sub chamber 11 communicating with the main chamber 1 through a communication passage 20. The structure of the chamber mechanism 10 will be described below.
The volume of the sub chamber 11 is about 1/10 of the total combustion chamber volume that is the sum of the volumes of the main chamber 1 and the sub chamber 11 when the position of the piston 2 is top dead center. (7 × 10 ³ mm ³ ).

  A so-called deep dish-shaped recess 2 a is formed at the center of the top surface of the piston 2. By forming the concave portion 2a as described above, squish flowing from the outer peripheral portion of the top surface of the piston 2 to the central portion of the concave portion 2a is generated when the piston 2 rises in the compression stroke.

A main fuel supply valve 30 capable of supplying the main fuel G to the sub chamber 11 with a supply pressure of 0.2 MPa (Gauge) is provided above the sub chamber 11.
Furthermore, an ignition fuel G ′, which is light oil having a higher ignitability than the main fuel G, is injected into the air-fuel mixture compressed in the sub chamber 11 above the sub chamber 11 for self-ignition. There is provided an ignition fuel injection valve 32 (an example of an ignition fuel injection means) that ignites and burns the air-fuel mixture.
The ignition fuel injection valve 32 can adjust the injection timing by injecting an ignition fuel G ′ from an injection port having a diameter of 0.25 mm at an injection pressure of 80 MPa by a common rail system and operating a piezoelectric actuator. It is configured.

  The sub-chamber engine 100 employs the above-described configuration to compress the fresh air I sucked into the main chamber 1 by ascending the piston 2, and the compressed fresh air I into the main chamber 1. The air-fuel mixture of the fresh air I flowing into the sub chamber 11 and the main fuel G supplied by the main fuel supply valve 30 is ignited by the ignition fuel injection valve 32. The fuel gas G ′ is injected and self-ignited so that the air-fuel mixture is combusted and the flame jet F is injected from the sub chamber 11 into the main chamber 1 through the communication passage 20. An operation state of one cycle in the engine 100 will be described below.

As shown in FIG. 2, in the sub-chamber engine 100, first, the intake valve 4 is opened, and the piston 2 is lowered from the TDC (top dead center), so that the fresh air I that is a lean air-fuel mixture in the main chamber 1 is obtained. An intake stroke is performed in which the air is inhaled.
At this time, the main fuel supply valve 30 installed in the sub chamber 11 is opened at a time slightly delayed from the opening timing of the intake valve 4, and the supply of the main fuel G to the sub chamber 11 is started.

  Later, the intake valve 4 and the main fuel supply valve 30 are closed at the same time, and a so-called compression stroke is performed in which the fresh air I taken into the main chamber 1 is compressed by the rise of the piston 2.

  In addition, when the sub chamber 11 at the initial stage of the compression stroke is still in a low pressure state, the main fuel supply valve 30 may be opened to supply the fuel G to the sub chamber 11.

  By supplying the fuel to the sub chamber 11 in this way, a part of the main fuel G supplied to the sub chamber 11 flows out to the main chamber 1 through the communication passage 20. Since the cross-sectional area ratio is set to be very small, the outflow amount is about 5% of the total sub chamber main fuel supply amount supplied to the sub chamber 11.

In the next compression stroke, as the piston 2 moves up, the volume of the main chamber 1 decreases and the fresh air I in the main chamber 1 flows into the sub chamber 11 through the communication passage 20. A new airflow is generated upward from 20, and the new airflow reaches the ignition fuel injection region of the ignition fuel injection valve 32.
Therefore, in the injection region, the fresh air I and the main fuel G are mixed to form an air-fuel mixture having an equivalent ratio within the spark ignition possible range.

In this compression stroke, the communication passage 20 works like a so-called throttle valve, and the pressure in the main chamber 1 becomes a pressure substantially equal to the compression ratio, but the maximum ultimate pressure in the sub chamber 11 is the maximum ultimate pressure in the main chamber 1. The pressure is slightly lower than the pressure.
Therefore, at the end of the compression stroke, the sub-chamber 11 contains an air-fuel mixture whose equivalence ratio is within a spark ignition range with a relatively low pressure field, and the main chamber 1 has an equivalence ratio with a relatively high pressure field. There will be a lean air-fuel mixture with a value of about 0.55. As the equivalent ratio of the air-fuel mixture formed in the sub chamber 11 is increased from the theoretical equivalent ratio, the NOx generation amount in the sub chamber 11 can be reduced and the sub chamber with respect to the main fuel supply amount to the main chamber 1 can be reduced. By increasing the ratio of the main fuel supply amount to 11, the air-fuel mixture combusted in the main chamber 1 can be diluted to further reduce NOx.

  Then, the sub-chamber engine 100 operates the ignition fuel injection valve 32 in the vicinity of 5 ° BTDC where the air-fuel mixture is compressed and heated to inject the ignition fuel G ′ into the sub-chamber 11. Start.

  Then, in the sub chamber 11, the injected ignition fuel G ′ is self-ignited, mixed with the air-fuel mixture in the sub chamber 11, diffusely combusted, and the air-fuel mixture is combusted by the energy generated by the diffusion combustion. Become.

  Since the pressure in the sub chamber 11 is the same as that of a normal SI engine, the combustion of the air-fuel mixture proceeds without a rapid pressure increase, and the flame jet F is generated together with the main fuel G not combusted in the sub chamber 11. It is ejected to the main chamber 1 through the communication passage 20.

On the other hand, in the main chamber 1, the lean air-fuel mixture is burned by the flame jet F ejected from the communication passage 20 in a high pressure field. Combustion to become NOx is performed.
Although the combustion state in the main chamber 1 is a state close to that of a normal SI engine, knocking does not occur even when the compression ratio is set high, so that the thermal efficiency can be improved. Further, even when the equivalent ratio of the fresh air I sucked into the main chamber 11 is increased and the output is increased, knocking can be avoided well, so that the equivalent ratio at the knocking limit can be increased. A wide output adjustment range can be ensured.
Moreover, since the sub chamber 11 is set to the side where the equivalence ratio of the air-fuel mixture is high and the main chamber 1 is set to the equivalent ratio of the air-fuel mixture, the generation of NOx can also be suppressed.

Further, the sub-chamber engine 100 stably ignites the air-fuel mixture in the sub-chamber 11, and further, in order to suppress NOx generation in the sub-chamber 11, the ignition fuel injection valve 32 ignites a predetermined injection amount. The fuel G ′ for use is divided into a plurality of times and injected into the sub chamber 11.
That is, by injecting the ignition fuel G ′ in a plurality of times, the temperature and pressure rise in the sub chamber 11 can be made slow, and the increase in NOx generation amount and mechanical loss can be suppressed. Further, the ignition fuel G ′ injected into the sub chamber 11 is repeatedly injected and stopped to cause a disturbance, thereby promoting the mixing of the ignition fuel G ′ and the air-fuel mixture, and the ignition fuel G ′. The air-fuel mixture composed of the main fuel G can be reliably ignited by the diffusion combustion with good diffusion combustion.

  For example, the ignition fuel injection valve 32 causes the injection interval of the ignition fuel G ′ equivalent to 1/5 of the calorific value ratio of the main fuel G supplied per cycle to be injected three times. According to an experiment assuming a case where the fuel is injected at 0.5 ms, the shaft end efficiency is improved by 0.5 points compared with the case where the same amount of ignition fuel G ′ is injected at one time, and NOx in the exhaust gas is increased. The concentration has been reduced from 500 ppm to 250 ppm, and the unburned hydrocarbon concentration in the exhaust gas has been reduced from 2000 ppm to 800 ppm, so that the air-fuel mixture can be stably ignited and NOx generation in the sub chamber 11 can be suppressed. Was confirmed.

In the sub-chamber engine 100 as described above, as the engine load decreases, the sudden temperature rise and pressure rise in the sub-chamber 11 are alleviated. Conversely, when the ignition fuel G ′ is injected, When the pressure of the air-fuel mixture becomes low, the air-fuel mixture may become incompletely combusted.
Therefore, the control device 15 comprising a computer provided in the sub-chamber engine 100 functions as an injection state control means for controlling the injection state of the ignition fuel G ′ by the ignition fuel injection valve 32 based on the engine load. Even when the engine load is reduced by the injection state control means in which the control device 15 functions, the ignition fuel injection means 32 injects the ignition fuel G ′ in the injection state suitable for it, The air-fuel mixture is configured to reliably burn.
Further, the engine load can be recognized from the rotational speed of the crankshaft when the torque applied to the crankshaft is constant.

  Specifically, as shown in FIG. 3, the control device 15 performs the injection amount and number of injections of the ignition fuel G ′ as the injection state of the ignition fuel G ′ based on the engine load. , And at least one of the injection intervals.

  That is, when the control device 15 controls the injection amount per time of the ignition fuel G ′, the control device 15 increases the injection amount as the engine load decreases, thereby causing the combustion of the ignition fuel G ′. The generated energy is increased to promote the diffusion combustion of the ignition fuel G ′, thereby preventing the incomplete combustion of the air-fuel mixture when the engine load is reduced.

  Similarly, when the number of injections of the ignition fuel G ′ is controlled, the control device 15 increases the number of injections as the engine load decreases, so that the ignition fuel G injected into the sub chamber 11 is increased. A large turbulence is generated in the 'and the diffusion combustion of the ignition fuel G' is promoted, thereby preventing the incomplete combustion of the air-fuel mixture when the engine load is reduced.

  Similarly, when controlling the injection interval of the ignition fuel G ′, the control device 15 shortens the injection interval as the engine load decreases, thereby igniting fuel generated when the injection is stopped. Immediately injecting the next ignition fuel G ′ against the disturbance of G ′ promotes diffusion combustion of the ignition fuel G ′, thereby preventing incomplete combustion of the air-fuel mixture when the engine load is reduced. be able to.

The sub-chamber engine according to the present invention exhibits an excellent effect when using a gaseous fuel such as city gas as described in the above embodiment, and as such a gaseous fuel, In addition to the city gas, there are gaseous fuels other than hydrocarbons mainly composed of CO and H ₂ such as hydrogen and propane. In addition, the sub-chamber engine according to the present invention can of course use a fuel other than the gaseous fuel, for example, gasoline, alcohol, methanol, ethanol, or any fuel.

Schematic diagram of sub-chamber engine Time chart showing the operating state of the sub-chamber engine The figure explaining the injection state control of the fuel for ignition

Explanation of symbols

1: Main chamber 4: Intake valve 10: Sub chamber mechanism 11: Sub chamber 15: Control device (injection state control means)
20: Communication passage 30: Main fuel supply valve 32: Ignition fuel injection valve (ignition fuel injection means)
100: Sub-chamber engine G: Main fuel G ': Ignition fuel

Claims (3)

Fresh air compressed in the main chamber is caused to flow into the sub chamber through a communication passage that opens into the main chamber, and a mixture of fresh air that has flowed into the sub chamber and the main fuel supplied to the sub chamber is combusted. A sub-chamber engine for injecting a flame jet from the sub-chamber to the main chamber via the communication path,
The sub-chamber includes ignition fuel injection means for igniting and burning the air-fuel mixture by injecting an ignition fuel having higher ignitability than the main fuel into the compressed air-fuel mixture to cause self-ignition.
A sub-chamber engine in which the ignition fuel injection means is configured to inject the ignition fuel in a plurality of times.   The sub-chamber engine according to claim 1, wherein the main fuel is a gaseous fuel, and the ignition fuel is a liquid fuel.   The injection ignition type engine according to claim 1, further comprising an injection state control unit that controls an injection state of the ignition fuel by the ignition fuel injection unit based on an engine load.

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