JP3504841B2 - Lean burn gas engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lean burn gas engine in which fuel gas and air are mixed and introduced into a combustion chamber for ignition and combustion by an ignition plug.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing an example of an open combustion chamber type lean burn gas engine according to the prior art. In the engine of FIG. 5, 13A city gas is used as fuel gas, 1 is an engine, 16 is a gas supply main, 14 is a fuel gas supply pipe branched from the gas supply main 16 for each cylinder of the engine, Reference numeral 15 is a gas regulator provided in the supply pipe 14, and 14a is a fuel gas passage opening / closing valve.

Reference numeral 10 is a fuel adjusting valve for adjusting the flow rate of the fuel gas, and the fuel gas supply pipe 14 is provided at the inlet of the adjusting valve 10.
Are connected. 13 is an intake filter for air filtration,
Reference numeral 9 is a gas mixer, and 12 is an air pipe connecting the gas mixer 9 and the intake filter 13. The gas mixer 9 is provided with a venturi 9a for mixing air and fuel gas, and an air-fuel mixture flow rate adjusting valve 7 for adjusting the flow rate of the air-fuel mixture of fuel gas and air.

Reference numeral 11 is a fuel flow rate control device for controlling the opening degree of the fuel adjusting valve 10, and 8 is a load control device for controlling the opening degree of the mixture gas flow adjusting valve 7. Reference numeral 2 is a piston of the engine 1, 3 is a cylinder head, 2a is a combustion chamber formed between an upper surface of the piston 2 and a lower surface of the cylinder head 3, 2b is a piston cavity which is a part of the combustion chamber 2a, and 4b. Is an intake valve. Reference numeral 6 is an intake pipe connecting the gas mixer 9 and the intake valve 4, and reference numeral 5 is an ignition plug.

During operation of the gas engine, the air sucked from the intake filter 13 and the gas supply main 1
After being introduced from 6, the fuel gas whose pressure is regulated by the regulator 15 and further regulated by the fuel regulating valve 10 is mixed in the gas mixer 9 to become gas. The mixed gas is metered by the mixed gas flow rate adjusting valve 7 and introduced into the combustion chamber 2a during the intake stroke in which the intake valve 4 opens from the intake pipe 6. Next, the air-fuel mixture is ignited and burned by the spark plug 5 directly attached to the combustion chamber wall of the cylinder head 3 in the vicinity of TDC (top dead center) of the compression stroke where the piston 2 rises.

The flow rate of the gas fuel is adjusted by changing the opening degree of the fuel adjusting valve 10 by a control signal from the fuel flow rate control device 11. Further, the flow rate of the air-fuel mixture from the gas mixer 9 is adjusted by changing the opening degree of the air-fuel mixture flow rate adjusting valve 7 by a control signal from the load control device 8.

[0007]

In such an open combustion chamber type lean burn gas engine, the excess air ratio is limited to about 1.6 (1.6 times the theoretical air amount). It almost coincides with the ignition limit of 13A gas (city gas) containing methane as a main component. Under such combustion conditions with a high excess air ratio, ignition is unstable, and many problems such as fluctuations in rotation due to misfire, reduction in efficiency due to deterioration of combustion, and increase in unburned exhaust gas are observed. On the other hand, in order to improve the thermal efficiency and reduce NOx in the exhaust gas, the higher the excess air ratio and the leaner the air-fuel mixture, the better the improvement. Therefore, the excess air ratio 2. Stable combustion is required in a range of 0 or more. Further, since the combustion temperature decreases as the excess air ratio increases ,
The durability of the members around the combustion chamber is also improved.

However, in the lean burn gas engine of the open combustion chamber type according to the prior art as shown in FIG. 5, the spark plug 5 is added to the air-fuel mixture in the open combustion chamber 2a mainly including the piston cavity 2b. Since it is a combustion system in which all of them are simultaneously ignited and burned, it is difficult to perform combustion at a high excess air ratio according to the above requirement, and an engine that satisfies the above requirement cannot be obtained.

In view of the problems of the prior art, the present invention enables complete combustion at a high excess air ratio, improves thermal efficiency, reduces NOx in exhaust gas, and improves durability of combustion chamber constituent members. It is intended to provide a lean burn gas engine.

[0010]

In order to solve the above problems, the present invention provides, as a first invention thereof, gas fuel and air are mixed in a gas mixer to form a gas mixture, and the gas mixture is supplied to a piston. An open combustion chamber type lean that is introduced into a combustion chamber formed between the upper surface of a piston having a cavity and a cylinder head and is ignited and burned by an ignition plug.
In the combustion gas engine, the piston on the upper surface of the piston
Recess a part of the cylinder head facing the cavity.
Ignition recess that is opened to the piston cavity side
The spark plug 5 emits sparks at the center of the upper part of the ignition recess.
A gas inlet that injects fuel gas while facing the electric part
A fuel injector, and the fuel gas
It is branched from the outlet gas passage of the ejector and
Around the spark discharge part through multiple jetted gas passages that open
We propose a lean-burn gas engine, which is characterized in that it is configured to be ejected toward .

In addition to the first invention, a second invention is,
The ignition recess is filled with a lean mixed gas with an excess air ratio of about 2.
Fuel from the gas injector under
Spark plug spark discharge in the ignition recess due to gas injection
An injector control device is provided for changing the gas around the section to a gas with a high mixing ratio .

According to this invention, the fuel gas is injected from the gas injector through the plurality of gas injection passages into the air-fuel mixture in the ignition recess in synchronization with the ignition timing of the spark plug. Due to the injection of the fuel gas, a mixed gas having a rich mixing ratio is accommodated around the spark plug, and when spark discharge is generated from the spark plug to the rich mixing ratio gas, the rich mixture is quickly ignited and the ignition is performed. The flame is propagated into the lean mixture in the combustion chamber, and the ignition / combustion of the lean mixture proceeds.

As described above, according to the present invention, by injecting the fuel gas into the periphery of the spark plug in the ignition recess by the gas injector, a rich mixture ratio region can be formed around the spark plug. Then, a spark discharge is generated in the rich mixing ratio region to ignite it, and this ignition flame is transferred into the lean mixture in the combustion chamber, so that the excess air ratio is high (about 2).
It is possible to reliably ignite and burn the lean air-fuel mixture.

Further, the gas in the rich mixing ratio region formed by the injection of the fuel gas from the gas injector easily diffuses, but the rich gas is formed in the ignition recess formed locally in the upper portion of the combustion chamber 2a. By forming the mixed gas and injecting the fuel gas into the ignition recess from the plurality of injection gas passages, it is possible to prevent the rich mixture ratio gas from diffusing to the combustion chamber 2a side.

In addition to the first invention, the third invention is based on the above
It is fixed to almost the center of the cylinder head and
It has a plug support member to which the spark plug is attached.
Then, an ignition recess is provided in the lower part of the support member,
Supports the plurality of injection gas passages formed in the support member
A ring provided on the outer circumference of the member and provided on the outer circumference of the support member.
Through the connecting groove and the outlet gas passage of the gas injector
It is characterized by making it possible to communicate.

Further, the concentration of the air-fuel mixture supplied to the combustion chamber is increased.
Concentration detecting means for detecting the degree and the gas injector
The injection timing is synchronized with the ignition timing of the spark plug, and
Suitable for the mixture concentration input from the concentration detection means
Ignition gas concentration control device for injecting the gas fuel with an injection amount
It is also effective to equip the ignition gas concentration control device.
The fuel gas is injected from the injector into the ignition recess at an injection timing that is synchronized with the ignition timing of the spark plug, and with an injection amount that matches the concentration (excess air ratio) of the lean mixture introduced into the combustion chamber. can in injected, it is possible to perform the injection control of the fuel gas from the gas injector with high accuracy, the effect of reducing the increase and NOx of additional heat efficiency is obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the constituent parts described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Only.

FIG. 1 is an overall configuration diagram of a lean burn gas engine according to a first embodiment of the present invention, FIG. 2 is an enlarged sectional view in the vicinity of a spark plug mounting portion, and FIG. 3 is a sectional view taken along the line AA of FIG. is there. In FIG. 1, 1 is an engine, 16 is a gas supply main, 14 is a fuel gas supply pipe branched from the gas supply main 16 for each cylinder of the engine, and 15 is the supply pipe 14
A gas regulator 14a is provided in the fuel gas passage opening / closing valve.

Reference numeral 10 is a fuel adjusting valve for adjusting the flow rate of the fuel gas, and the fuel gas supply pipe 14 is provided at the inlet of the adjusting valve 10.
Are connected. Reference numeral 13 is an intake filter for air filtration, 9 is a gas mixer, and 12 is an air pipe connecting the gas mixer 9 and the intake filter 13. The gas mixer 9 is provided with a venturi 9a for mixing air and fuel gas, and an air-fuel mixture flow rate adjusting valve 7 for adjusting the flow rate of the air-fuel mixture of fuel gas and air.

Reference numeral 11 indicates the opening of the fuel adjusting valve 10 by the line 1.
Reference numeral 1a is a fuel flow rate control device, and 8 is a load control device that controls the opening degree of the air-fuel mixture flow rate adjusting valve 7 via a line 8a. Reference numeral 2 is a piston of the engine 1, 3 is a cylinder head, 2a is a combustion chamber formed between an upper surface of the piston 2 and a lower surface of the cylinder head 3, and 6 is an intake air connecting the gas mixer 9 and the intake valve 4. Tubes 5 are spark plugs. The above configuration is similar to that of the conventional technique shown in FIG.

1 to 3, 5a is a supporting member,
The cylinder head 3 is fixed to a substantially central portion, and the spark plug 5 is attached to the central portion. An ignition recess 3a is provided in the lower portion of the support member 5a, and a spark discharge portion 5b of the spark plug 5 is provided in the upper center of the ignition recess 3a.
Is facing. The lower part of the ignition recess 3a is open to the combustion chamber 2a.

A gas injector 17 is fixed to the cylinder head 3. 2 to 3, 3b is an injection gas passage communicating with the gas outlet of the gas injector 17, 3d is an outer peripheral surface of the support member 5a, and an annular communication groove 3c is provided to open the injection gas passage 3b. Is a branched injection gas passage formed in the support member 5a.

As shown in FIGS. 2 to 3, a plurality of branch injection gas passages 3c are arranged in the circumferential direction so as to open in the vicinity of the spark discharge portion 5b of the spark plug 5 in the ignition recess 3a. (4 pieces in the example) are provided, and the inlet side is opened to the communication groove 3d. In addition, the branch gas passage 3c
As shown in FIG. 3, any number of the plurality may be shifted in the axial direction.

In FIG. 1, reference numeral 20 denotes a gas cylinder filled with fuel gas, and the outlet of the gas cylinder 20 is connected to the gas injector 17 via a jet gas supply pipe 18. Reference numeral 19 is an injection gas regulator provided in the gas supply pipe 18, and adjusts the fuel gas pressure to the gas injector 17. Reference numeral 21 is a gas injector control device, 23 is a rotation detector for detecting the rotation of the engine 1, and 2 is a rotation detector.
Reference numeral 2 is an ignition control device.

The rotation signal of the engine 1 detected by the rotation detector 23, that is, the crank angle signal of the engine 1 is the gas injector control device 21 and the ignition control device 22.
Entered in. And the gas injector control device 2
1 sends a control signal of the injection timing and injection amount of the gas injector 17 based on the rotation signal to the gas injector 17 through the line 21a to operate it. Also,
The ignition control device 22 sends a control signal of the ignition timing of the spark plug 5 based on the rotation signal to the spark plug 5 via a line 22a.

During operation of the lean burn gas engine having such a structure, the air sucked from the intake filter 13 is introduced into the gas mixer 9 through the air pipe 12. On the other hand, the fuel gas enters the fuel gas supply pipe 14 from the fuel gas supply main pipe 16 and is pressure-regulated by the regulator 15,
The fuel is adjusted from the fuel gas supply pipe 14 by the fuel adjusting valve 10 into the gas mixer 9, and is jetted from the venturi 9a to be mixed with air. The air-fuel mixture ratio, that is, the air-fuel ratio is determined by the differential pressure between the air pressure and the fuel gas pressure in the venturi 9a portion of the gas mixer 9.
The air-fuel ratio can be changed by changing the opening degree of 0. In the embodiment of the present invention, the opening degree of the fuel adjusting valve 10 is adjusted by the fuel flow rate control device 11,
The air amount is adjusted to about twice the theoretical air amount of the fuel gas, that is, a lean mixed gas having an excess air ratio = 2, and mixed with the gas mixer 9. The flow rate of this mixture is adjusted (load adjustment) by adjusting the opening of the mixture flow rate adjusting valve 7.

Then, the measured air-fuel mixture is taken into the intake pipe 6
And the intake valve 4 is opened in the intake stroke of the engine 1 and is sucked into the combustion chamber 2a. In the compression stroke of the piston 2, the lean mixed gas in the combustion chamber 2a is compressed to the upper part of the combustion chamber 2a by the rise of the piston 2, and the ignition recess 3a is also filled with the lean mixed gas.

On the other hand, the fuel gas accumulated in the gas cylinder 20 is regulated by the injection gas regulator 19 and is constantly supplied to the gas injector 17. When the piston 2 is near the top dead center of the compression stroke and a little before the spark discharge of the spark plug 5, the gas injector control device 21
Controls the injection timing and injection amount based on the rotation signal detected by the rotation detector 23 to open the gas injector 17. As a result, the fuel gas advanced from the gas injector 17 is injected into the ignition recess 3a through the injection gas passage 3b, the continuous groove 3d and the plurality of branch injection gas passages 3c. The ignition recess 3a is first filled with a lean mixed gas having an excess air ratio of about 2. However, the injection of fuel gas from the gas injector 17 causes ignition recess 3a.
The gas in the inside, especially in the vicinity of the spark plug spark discharge part 5b, has a rich mixing ratio.

Then, at the ignition timing controlled by the ignition control device 22, the spark plug 5 causes a spark discharge into the gas of the rich mixing ratio. As a result, the air-fuel mixture in the ignition recess 3a is quickly ignited, and this ignition flame is propagated to the lean air-fuel mixture (lean air-fuel mixture having an excess air ratio of about 2) in the combustion chamber 2a, so that the air-fuel mixture is ignited and burned. It progresses and complete combustion is done.

As described above, according to this embodiment,
Fuel gas can be ejected in the vicinity of the spark discharge portion 5b of the spark plug 5 in the ignition recess 3a to form a rich mixing ratio region, and a spark discharge is generated in the rich mixing ratio region to ignite the ignition flame. Since the air-fuel mixture is propagated in the lean air-fuel mixture, the lean air-fuel mixture having a high excess air ratio (about 2) can be reliably ignited and burned.

Further, although the gas in the rich mixing ratio region formed by the injection of the fuel gas from the gas injector 17 is easy to diffuse, it is in the ignition recess 3a formed locally in the upper part of the combustion chamber 2a. While forming the rich mixed gas, the ignition recesses 3a are formed from a plurality of branch injection gas passages 3c.
By injecting the fuel gas into the inside, the diffusion of the rich mixing ratio gas can be prevented.

Therefore, according to the embodiment of the present invention, the lean mixed gas combustion equivalent to that of the sub-chamber ignition type gas engine can be realized, and the pressure of the sub-chamber injection hole which is a problem of the sub-chamber ignition type gas engine can be realized. There is no loss, the thermal efficiency of the engine can be improved and the amount of NOx generated can be suppressed, and the durability of the members around the combustion chamber due to the decrease in the combustion temperature can be improved.

FIG. 4 is an overall configuration diagram of a lean burn gas engine according to a second embodiment of the present invention. In FIG.
An ignition gas concentration control device 27 is connected to each of the fuel flow rate control device 24 and the gas injector control device 25.

The fuel flow control device 24 controls the opening degree of the fuel adjusting valve 10 and, as with the fuel flow control device 11 in the first embodiment, the lean mixture supplied to the combustion chamber 2a of the engine 1. The excess air ratio of the air is detected and calculated and sent to the ignition gas concentration control device 27.

In the ignition gas concentration control device 27, together with the detection signal of the excess air ratio, the ignition control device 2
6, the ignition timing of the ignition plug 5 is input, and the timing of spark discharge of the ignition plug 5 and the ignition recess from the gas injector 17 are determined based on the excess air ratio in the combustion chamber 2a, that is, the concentration of the lean air-fuel mixture and the ignition timing. 3a is synchronized with the timing at which the fuel gas is injected into 3a, and the injection amount of the fuel gas suitable for the concentration (excess air ratio) of the lean mixture is calculated and output to the gas injector control device 25. . In the gas injector control device 25, the fuel gas is injected from the gas injector 17 at the injection timing and injection amount controlled by the ignition gas concentration control device 27.

Therefore, according to such an embodiment, the ignition gas concentration control device 27 adjusts the ignition timing of the spark plug 5 at a timing correctly synchronized with the concentration (excess air ratio) of the lean air-fuel mixture in the combustion chamber 2a. Since the fuel gas can be injected from the gas injector 17 with this injection amount, injection control of the fuel gas from the gas injector can be performed with higher accuracy than in the case of the first embodiment, and further thermal efficiency can be improved. The effect of improvement and reduction of NOx can be obtained.

[0037]

As described above, according to the present invention, it is possible to form a rich mixture ratio region around the spark plug by injecting the fuel gas around the spark plug in the ignition recess by the gas injector. Then, the spark discharge is ignited by spark discharge in the rich mixture ratio region, and this ignition flame is transferred into the lean air-fuel mixture in the combustion chamber, so that the lean air-fuel mixture having a large excess air ratio can be surely ignited and burned. .

Further, the gas in the rich mixing ratio region formed by the injection of the fuel gas from the gas injector forms the gas having the rich mixing ratio in the ignition recess continuously provided in the upper portion of the combustion chamber, and By injecting the fuel gas into the ignition recess from a plurality of injection gas passages, the fuel gas is not diffused into the combustion chamber, remains in the ignition recess, and can be used for ignition combustion as described above.

According to the third aspect of the present invention, the concentration of the lean air-fuel mixture (excess air ratio) introduced into the combustion chamber at the injection timing synchronized with the ignition timing of the spark plug by the ignition gas concentration control device. The fuel gas can be injected from the gas injector into the ignition recess with an injection amount adapted to. Thereby, the injection control of the fuel gas from the gas injector can be performed with higher accuracy, and the effect of further improving the thermal efficiency and the reduction of NOx can be obtained.

In short, according to the present invention, the lean combustion gas combustion equivalent to that of the sub-chamber ignition type gas engine can be realized, and the pressure loss of the sub-chamber injection hole which is a problem of the sub-chamber ignition type gas engine is eliminated . The thermal efficiency of the engine can be improved and the amount of Nox generated can be suppressed, and the durability of the members around the combustion chamber due to the decrease in the combustion temperature can be improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a lean burn gas engine according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the vicinity of a spark plug attachment portion in the first embodiment.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is an overall configuration diagram of a conventional gas engine.

[Explanation of symbols]

1 engine 2a combustion chamber 3a ignition recess 3b Injection gas passage 3c Branch injection gas passage 5 spark plugs 7 Mixture flow rate control valve 8 load control device 9 gas mixer 10 Fuel control valve 11, 24 Fuel flow control device 14 Fuel gas supply pipe 17 Gas injector 18 Injection gas supply pipe 21, 25 Gas injector control device 22 Ignition control device 23 Rotation detector 26 Ignition control device 27 Ignition gas concentration control device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02D 19/08 F02D 19/08 C 41/02 325 41/02 325K (56) Reference JP-A-6-299854 (JP, A ) JP-A-59-105923 (JP, A) JP-A-9-250369 (JP, A) Actual exploitation Sho-58-37949 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 21/02 F02M 21/02 301 F02B 17/00 F02B 43/02 F02D 19/08 F02D 41/02 325

Claims (3)

(57) [Claims] 1. A a gas fuel and air to form a mixture by mixing by gas mixer, the mixture, the piston cavitation
In a lean combustion gas engine of an open combustion chamber type , which is introduced into a combustion chamber formed between an upper surface of a piston having a cylinder and a cylinder head, and is ignited and burned by a spark plug, a cylinder facing the piston cavity on the upper surface of the piston.
And retract a part of the head to the piston cavity side.
Form an ignition recess to be opened, and center the upper part of the ignition recess.
While facing the spark discharge part of the spark plug,
A gas injector for injecting gas is provided, and the fuel gas is an outlet gas passage of the gas injector.
A plurality of injection gases that are branched from each other and open in the ignition recess
To be ejected toward the spark discharge area through the passage
A lean burn gas engine characterized by being constructed . 2. The inside of the ignition recess has a rare air ratio of about 2.
When the gas mixture is filled with a thin gas mixture,
Ignition in the ignition recess by injection of fuel gas from the engine
The lean-burn gas engine according to claim 1, further comprising an injector control device that changes a gas around the plug spark discharge portion to a gas having a rich mixing ratio . 3. The cylinder head is fixed substantially at the center of the cylinder head.
And the spark plug is attached to its center
A plug support member, and an ignition recess at the bottom of the support member.
The plurality of recesses are formed in the support member while being recessed.
The injection gas passage is opened to the outer peripheral side of the support member,
Gas injection through an annular connecting groove on the outer circumference
It is characterized in that it is connected to the outlet gas passage
The lean burn gas engine according to claim 1 .