JP2009299593A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the exhaust of unburned hydrocarbon, and to improve an engine efficiency. <P>SOLUTION: A main chamber 9 facing a piston 6 and a sub chamber 11 communicated with the main chamber 9 through an injection hole 10 are provided as a combustion chamber N; a first check valve 18 opened by reduction of pressure of the sub chamber 11 and permitting supply of fuel gas to the sub chamber is disposed in a sub fuel supply passage 17 for supplying the fuel gas to the sub chamber 11; the sub fuel supply passage 17 is equipped with an upstream flow passage part 17b having a downstream end in which the first check valve 18 is arranged and a downstream flow passage part 17a having an upstream end in which the first check valve 18 is arranged and a downstream end communicated with the sub chamber 11; and a second check valve 20 opened by increase of the pressure of the sub chamber 11 and permitting flow of the gas from the downstream side flow passage part 17a to a branch passage 19 is provided in the branch passage 19 branching from the downstream flow passage part 17a in the sub fuel supply passage 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes, as a combustion chamber, a main chamber facing the piston, and a sub chamber communicating with the main chamber via an injection hole, and a sub fuel supply path for supplying fuel gas to the sub chamber includes The present invention relates to an engine provided with a first check valve that opens due to a pressure drop in a sub chamber and allows fuel gas to be supplied to the sub chamber.

In recent years, the introduction of a cogeneration system using a gas engine using natural gas as fuel has been promoted from the viewpoint of environment and economy. And since the system using a gas engine has high power generation efficiency, it has become the mainstream of a natural gas cogeneration system. In the cogeneration system, gas engines have been put into practical use from a small size of 1 kW class to a large size of several MW class, and different engine types and combustion methods are adopted depending on the size of the engine.
For example, in a medium-sized cogeneration system of 1-2 MW class, a high efficiency can be realized, so that a sub-chamber type spark ignition lean mirror cycle engine has become mainstream. The sub-chamber type engine includes a combustion chamber called a sub chamber communicating with the main chamber via an injection hole in addition to a normal combustion chamber called a main chamber. Then, the intake valve is opened in the intake stroke, the lean mixture is introduced into the main chamber, the combustion gas is introduced into the sub chamber, and the intake stroke and the lean mixture that has flowed from the main chamber into the sub chamber through the nozzle holes in the compression stroke. An air-fuel mixture is formed by mixing the fuel gas supplied to the sub chamber. Then, the air-fuel mixture formed in the sub chamber is spark-ignited by an ignition plug and burned, and a flame jet is injected from the sub chamber to the main chamber through the nozzle hole, and the lean air-fuel mixture formed in the main chamber is combusted. It is configured to let you. Therefore, as compared with a single-chamber engine having only a normal combustion chamber, it is possible to realize lean combustion in which the fuel gas is burned in a lean state with respect to air as a whole combustion chamber, and high efficiency is achieved. be able to.

As such a sub-chamber engine, there has been provided a mechanical on-off valve in a sub-fuel supply path for supplying fuel gas to the sub-chamber and a control device for controlling the opening / closing operation of the mechanical on-off valve. (For example, refer to Patent Document 1). Conventional sub-chamber engines have been mainly provided with mechanical on-off valves, but in recent years, those with check valves instead of mechanical on-off valves are being put into practical use (for example, , See Patent Document 2). This is because the configuration with a check valve is simpler than the mechanical on-off valve that opens and closes with an external driving force, making it easier to manufacture, reducing size and reducing costs. It is because it can plan.
This check valve has a structure in which the fuel gas does not flow in the reverse direction from the sub chamber to the sub fuel supply passage, and the fuel gas can be allowed to flow in the forward direction from the sub fuel supply passage to the sub chamber. ing. The check valve is in a closed state by bringing a valve body such as a ball into contact with the valve seat by the biasing force of the spring. When the pressure in the sub chamber decreases as the piston moves down during the intake stroke and the pressure difference between the upstream side and the downstream side of the check valve becomes a certain value or more, the pressure is increased in a direction against the biasing force of the spring. By acting, the valve body is separated from the valve seat to be opened, and the fuel gas is supplied to the sub chamber.

JP 2003-278548 A JP 2001-3753 A

  In an engine that has a check valve in the auxiliary fuel supply path, there is no space to provide a check valve around the auxiliary chamber due to interference with the spark plug, etc. ing. In such a case, the auxiliary fuel supply path is divided into an upstream flow path portion in which a check valve is disposed at the downstream end portion, and a check valve is disposed in the upstream end portion so that the downstream end portion is And a downstream flow passage portion communicating with the sub chamber, and the downstream flow passage portion is constituted by a narrow communication passage. During the intake stroke, the check valve is opened due to the pressure drop in the sub chamber, fuel gas is supplied to the sub chamber, and the downstream flow path portion is filled with gas. During the compression stroke, the check valve is closed, and the gas in the downstream flow path is compressed as the pressure in the combustion chamber increases due to compression. At this time, since the downstream flow path portion is a narrow communication path, the gas in the downstream flow path portion is hardly mixed with the lean air-fuel mixture flowing from the main chamber into the sub chamber and is compressed without being diluted. become. As a result, the concentration does not enter the flammable range. Further, after that, the air-fuel mixture is ignited in the sub chamber and the air-fuel mixture burns. However, since the downstream flow passage portion is a narrow communication passage, the flame is extinguished and does not reach the downstream flow passage portion. Gas does not burn. In the expansion stroke, the pressure in the combustion chamber decreases as the piston moves down, and the gas having a high concentration of the fuel gas compressed in the downstream flow path portion gradually flows out into the combustion chamber. However, since the temperature in the combustion chamber is also lowered in the latter half of the expansion stroke, the outflowed gas stays without burning and is discharged in the exhaust stroke. As a result, the amount of unburned hydrocarbons increases, leading to a decrease in engine efficiency.

  The present invention has been made paying attention to such a point, and an object thereof is to provide an engine capable of reducing the amount of unburned hydrocarbons and improving the engine efficiency.

In order to achieve this object, a characteristic configuration of an engine according to the present invention includes, as a combustion chamber, a main chamber facing a piston, and a sub chamber communicating with the main chamber via an injection hole, the sub chamber In the engine provided with a first check valve that opens the sub-fuel supply path to supply fuel gas to the sub-chamber and allows the supply of the fuel gas to the sub-chamber,
The auxiliary fuel supply passage has an upstream flow path portion in which the first check valve is disposed at the downstream end portion, and the first check valve is disposed in the upstream end portion and the downstream end portion is A downstream flow passage portion communicating with the sub chamber, and the branch passage branched from the downstream flow passage portion in the sub fuel supply passage is opened by the pressure increase of the sub chamber and the downstream The second check valve is provided to allow the gas flow from the side flow path portion to the branch path.

According to this characteristic configuration, when the pressure in the sub chamber decreases, the second check valve remains closed, but the first check valve opens, so that the fuel gas flows from the upstream flow path portion. The fuel gas can be supplied to the sub chamber by flowing into the downstream channel portion and flowing into the sub chamber from the downstream channel portion. Conversely, when the pressure in the sub chamber rises, the first check valve remains closed, but the second check valve opens, so that the gas in the sub chamber flows into the downstream flow path portion. The gas that has filled the downstream channel portion flows into the branch channel from the downstream channel portion. As a result, for the gas in the downstream flow path portion, in the intake stroke and compression stroke, as in the conventional engine, fuel gas is supplied into the sub chamber, and the gas having a high concentration of fuel gas in the downstream flow path portion. Is compressed, but differs from the conventional engine in the expansion stroke.
In other words, when the air-fuel mixture is ignited in the sub chamber, the pressure in the sub chamber rises and the second check valve is opened. As a result, the burned gas in the sub chamber flows into the downstream flow path portion, and the unburned gas compressed in the downstream flow path portion flows into the branch path. Therefore, the downstream flow path portion is filled with the already burned gas. In the expansion stroke, the pressure in the sub chamber decreases due to the lowering of the piston, the second check valve is closed, and the gas in the downstream flow passage portion gradually flows out into the combustion chamber. The gas in the flow path portion is filled with the already burned gas, and the unburned gas can be prevented from flowing into the combustion chamber.
From the above, it has become possible to realize an engine that improves the engine efficiency by reducing the amount of unburned hydrocarbon emissions.

  A further characteristic configuration of the engine according to the present invention is that the branch passage is configured to connect a downstream side of the second check valve to an intake passage for sucking fresh air into the main chamber. is there.

  According to this feature configuration, since the branch path is connected to the intake path, the unburned gas that has flowed into the branch path when the second check valve is opened flows into the intake path. Therefore, in the next intake stroke, unburned gas flowing into the intake passage is sucked into the main chamber. As a result, since combustion occurs in the main chamber, efficiency is not reduced and unburned hydrocarbons are not discharged. The amount of unburned hydrocarbons is accurately reduced, and engine efficiency can be improved accurately.

  A further characteristic configuration of the engine according to the present invention is that the second check valve is configured to open at a pressure lower than a maximum in-cylinder pressure during combustion in the combustion chamber. is there.

  According to this feature configuration, after the air-fuel mixture is ignited in the auxiliary chamber and the air-fuel mixture is combusted, the second check valve is opened before the pressure in the combustion chamber reaches the maximum in-cylinder pressure. Therefore, the second check valve can be opened at an accurate timing, and the burned gas in the sub chamber flows into the downstream flow path portion, and the downstream flow path portion is accurately filled with the burned gas. be able to.

An embodiment of an engine according to the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the engine 1 is configured by connecting a cylinder head 2, a cylinder block 3, a crankcase (not shown), and an oil pan (not shown) so as to overlap each other. An intake valve 4 and an exhaust valve 5 that can be freely opened and closed are provided. The piston 6 is slidably accommodated in the cylinder block 3, and the reciprocating operation force of the piston 6 is transmitted from the crank mechanism 7 to the crankshaft 8 and output as rotational power. Although not shown, the power from the crankshaft 8 is transmitted to a camshaft or the like that opens and closes the intake valve 4 and the exhaust valve 5.

  As the combustion chamber N, a main chamber 9 facing the upper surface of the piston 6 on the lower surface side of the cylinder head 2 and a sub chamber 11 communicating with the main chamber 9 through the injection hole 10 are provided. The engine 1 uses a fuel gas such as a gaseous fuel gas or a city gas, and in the main chamber a lean mixture of fuel gas and air (a mixture of air and a small amount of fuel gas) is taken in the intake stroke. 9, fuel gas is supplied to the sub chamber 11, and a lean air-fuel mixture is flowed from the main chamber 9 into the sub chamber 11 through the nozzle hole 10 in the compression stroke to form a gas mixture in the sub chamber 11. The air-fuel mixture combusted in the sub chamber 11 by ignition with the ignition plug 12 of the chamber 11 is configured to be injected as a flame jet F into the main chamber 9 through the nozzle hole 10.

  Although one combustion chamber N is shown in FIG. 1, the engine 1 is composed of a multi-cylinder engine having a plurality of pistons 6 and a plurality of combustion chambers N. Then, the engine 1 transmits the driving force from the crankshaft 8 to a generator (not shown) to generate electric power, and recovers exhaust heat from the engine via a heat medium so that it can be supplied to a heat consuming terminal or the like. Used in cogeneration systems.

  The main chamber 9 is provided with an intake passage 13 for taking in fresh air that is a lean mixture, and a main fuel supply passage 14 for supplying fuel gas to the intake passage 13 is provided. Although not shown in the drawing, the intake passage 13 is provided with a throttle valve, a supercharger that supercharges air, and the like on the upstream side of the connection point with the main fuel supply passage 14.

  The sub chamber 11 is formed inside a base 15 having a nozzle hole 10 formed at the lower end, and the base 15 is supported by the cylinder head 2 with the lower end protruding into the main chamber 9. An ignition unit 16 having an ignition plug 12 is provided above the base 15, and the ignition plug 12 is provided so that its ignition point 12 a is located in the sub chamber 11.

  A first check valve 18 that opens due to a pressure drop in the sub chamber 11 and allows the supply of fuel gas to the sub chamber 11 is disposed in the middle portion of the sub fuel supply passage 17. The first check valve 18 is closed by bringing a valve body such as a ball into contact with the valve seat by the biasing force of the spring, and the pressure difference between the upstream side and the downstream side is constant due to the pressure drop in the sub chamber 11. When the value exceeds the value, the pressure acts in the direction against the urging force of the spring, the valve body is separated from the valve seat and is opened, and the supply of the fuel gas to the sub chamber 11 is allowed. Yes.

  The auxiliary fuel supply path 17 includes an upstream flow path portion 17b in which a first check valve 18 is disposed at a downstream end portion, and a downstream end portion in which a first check valve 18 is disposed at an upstream end portion. Is provided with a downstream flow passage portion 17 a communicated with the sub chamber 11. The downstream flow path portion 17 a is configured to extend from the outside of the ignition unit 16 to the inside thereof and communicate with the sub chamber 11. The downstream-side channel portion 17a and the upstream-side channel portion 17b are configured by narrow communication passages having a narrow channel width.

  A branch passage 19 branched from the downstream flow passage portion 17 a and connected to the intake passage 13 is provided. A middle portion of the branch passage 19 is opened by the pressure increase of the sub chamber 11 and from the sub fuel supply passage 17. A second check valve 20 that allows gas flow to the branch path 19 is provided. The second check valve 20 is configured such that the direction allowing the gas flow is opposite to that of the first check valve 18, and basically has the same configuration as the first check valve 18. I am doing. For example, when the pressure in the sub chamber 11 becomes lower than the maximum in-cylinder pressure at the time of combustion in the combustion chamber N, the second check valve 20 has a spring biasing force so as to open. Etc. have been adjusted.

The engine 1 is configured to sequentially perform intake, compression, expansion, and exhaust strokes by opening and closing the intake valve 4 and the exhaust valve 5 as in a normal four-stroke internal combustion engine.
In the intake stroke, the intake valve 4 is opened and the piston 6 descends, so that fresh air that is a lean air-fuel mixture is sucked into the main chamber 9 from the intake passage 13. At this time, as the pressure in the main chamber 9 decreases, the sub chamber 11 also decreases in pressure. Therefore, the second check valve 20 remains closed, and the upstream side and the downstream side of the first check valve 18 are kept closed. When the pressure difference becomes equal to or greater than a certain value, the first check valve 18 is opened, and the fuel gas flows into the sub chamber 11 via the upstream flow path portion 17b and the downstream flow path portion 17a of the sub fuel supply path 17. Supplied and the downstream flow path portion 17a is filled with gas.

In the compression stroke, the lean air-fuel mixture in the main chamber 9 is compressed by raising the piston 6 with the intake valve 4 closed. At this time, the lean air-fuel mixture flows from the main chamber 9 to the sub-chamber 11 through the nozzle hole 10, and the fuel gas and the lean air-fuel mixture supplied in the auxiliary fuel supply path 17 during the intake stroke are generated. As a result of the mixing, an air-fuel mixture having a high concentration of fuel gas is formed in the sub chamber 11. Moreover, the 1st check valve 18 will be in a valve closing state with the pressure rise of the subchamber 11, and the gas with which it filled in the downstream flow-path part 17a will be compressed.
At the ignition timing (set timing near or near top dead center), the spark plug 12 is actuated to ignite the sub chamber 11 with spark ignition. By injecting the combustion gas combusted in the sub chamber 11 into the main chamber 9 as the flame jet F through the nozzle hole 10, the lean air-fuel mixture in the main chamber 9 is combusted. At this time, when the pressure in the sub chamber 11 becomes lower than the maximum in-cylinder pressure during combustion in the combustion chamber N, the second check valve 20 is opened. The first check valve 18 remains closed. As a result, the burned gas in the sub chamber 11 flows into the downstream flow path portion 17a, and the unburned gas compressed in the downstream flow path portion 17a flows into the branch path 19, and the downstream side The flow path portion 17a is filled with the already burned gas. Further, the unburned gas that has flowed into the branch path 19 flows into the intake path 13.

In the expansion stroke, the piston 6 is lowered, but the pressure in the sub chamber 11 is lowered by the lowering of the piston 6 so that the second check valve 20 is closed, and the gas in the downstream flow path portion 17a is gradually increased. It flows out into the combustion chamber. At this time, since the gas filling the downstream flow path portion 17a is already burned gas, the unburned gas can be prevented from flowing into the combustion chamber N. Therefore, the amount of unburned hydrocarbon emissions can be reduced, and engine efficiency can be improved. Further, the unburned gas that has flowed into the branch path 19 is sucked into the main chamber 9 in the next intake stroke, and is burned in the main chamber 9 so that the efficiency is not reduced and the unburned hydrocarbon is not discharged. .
In the exhaust stroke, the exhaust valve 5 is opened and the piston 6 is raised, so that the combustion exhaust gas is exhausted to the exhaust passage 21.

As described above, the engine according to the present invention can reduce the amount of unburned hydrocarbons and improve the engine efficiency. The engine according to the present invention has a 10% reduction in the amount of unburned hydrocarbons in the exhaust gas compared to a conventional engine in which the first check valve 18 is simply provided in the auxiliary fuel supply path 17, and the efficiency It has been confirmed by experiment that is improved by 0.2 points. In this experiment, the bore diameter was 180 mm, the piston stroke was 230 mm, the number of cylinders was 12, the valve opening pressure of the second check valve was 15 MPa, and the gas flow rate was just downstream of the second check valve in the branch path. This was done using an engine with a 0.2 mm diameter orifice to limit.
Here, in the expansion stroke, when the second check valve 20 is opened, the pressure is reduced and the amount of work to be taken out is reduced, but the downstream side flow passage portion 17a in the auxiliary fuel supply passage 17 is reduced. In addition, by making the upstream flow passage portion 17b a sufficiently narrow communication passage and sufficiently increasing the pressure at which the second check valve 20 is opened, the pressure drop can be suppressed to a small level, and the efficiency due to the pressure drop can be reduced. The decrease can be suppressed slightly. Therefore, engine efficiency can be improved.

[Another embodiment]
(1) In the above embodiment, the branch path 19 is connected to the intake path 13. However, the flow path is not limited to the intake path 13 as long as it is a flow path other than the exhaust path, and may be connected to various flow paths. it can.

(2) In the above embodiment, the pressure at which the second check valve 20 is opened can be changed as appropriate, and is limited to a pressure lower than the maximum in-cylinder pressure during combustion in the combustion chamber N. is not.

  The present invention includes, as a combustion chamber, a main chamber facing the piston, and a sub chamber communicating with the main chamber via an injection hole, and a sub fuel supply path for supplying fuel gas to the sub chamber includes A first check valve that opens due to a pressure drop in the sub chamber and allows fuel gas to be supplied to the sub chamber is provided to reduce unburned hydrocarbon emissions and improve engine efficiency. It can be adapted to various types of engines.

Schematic diagram of the engine

Explanation of symbols

6 piston 9 main chamber 10 nozzle hole 11 sub chamber 13 intake passage 17 sub fuel supply passage 17a downstream flow passage portion 17b upstream flow passage portion 18 first check valve 19 branch passage 20 second check valve N combustion chamber

Claims (3)

As a combustion chamber, it comprises a main chamber facing the piston, and a sub chamber communicating with the main chamber via a nozzle hole,
An engine provided with a first check valve that opens due to a pressure drop in the sub chamber and allows supply of the fuel gas to the sub chamber is provided in the sub fuel supply passage that supplies fuel gas to the sub chamber. Because
The auxiliary fuel supply passage has an upstream flow path portion in which the first check valve is disposed at the downstream end portion, and the first check valve is disposed in the upstream end portion and the downstream end portion is A downstream flow path portion communicating with the sub chamber,
A branch path branched from the downstream flow path portion in the sub fuel supply path is opened by the pressure increase in the sub chamber to allow gas flow from the downstream flow path portion to the branch path. An engine provided with a second check valve.   2. The engine according to claim 1, wherein the branch passage is configured to connect a downstream side of the second check valve to an intake passage that sucks fresh air into the main chamber.   The engine according to claim 1 or 2, wherein the second check valve is configured to open at a pressure lower than a maximum in-cylinder pressure during combustion in the combustion chamber.

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