JP2002357138A - Auxiliary chamber type gas engine with control valve and operation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auxiliary chamber type gas engine with a control valve capable of keeping the operation of the engine in an operation region of high thermal efficiency at all times, reducing NOx exhaust amount markedly with high thermal efficiency, and reducing combustion noises of the engine while avoiding the occurrence of knocking, and provide an operation method therefore. SOLUTION: This auxiliary chamber type gas engine 1 with the control valve is provided with EGR system 47, 48, 49, a control means 50 for adjusting control valve opening time, an EGR gas flow rate, and an air-fuel ratio, and a knocking sensor 51 for detecting the occurrence of knocking. It is constituted such that the control for avoiding knocking is performed when the control means 50 detects the occurrence of knocking by the knocking sensor 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas engine having a main chamber and a sub-chamber, and a sub-chamber type gas engine with a control valve provided with an on-off valve between the main chamber and the sub-chamber. is there.

[0002]

2. Description of the Related Art Natural gas, CO (carbon monoxide), H
₂ Gas engines that use gas fuel that is difficult to mix with air such as (hydrogen) and have a high ignition temperature and are difficult to ignite include spark ignition, direct injection, and premixed compression ignition.

In this spark ignition type gas engine, similarly to a gasoline engine, a mixer, a single-point fuel injection device or a multi-point combustion injection device is attached to an intake passage to convert gaseous fuel into a pre-mixed gas, and then a piston intake. It is introduced into the cylinder during the stroke, and immediately before the top dead center in the latter half of the compression stroke, the premixed gas is ignited by a spark plug and burned.

A gas engine of this type has been put to practical use, and has a tendency to be harder to knock than a gasoline engine. Therefore, the compression ratio can be relatively increased, and the thermal efficiency is about 37%, which is higher than that of a gasoline engine.

[0005] However, although knocking resistance is higher and the compression ratio can be slightly higher than that of gasoline engines, the compression ratio is limited due to the occurrence of knocking, and the thermal efficiency is lower than that of diesel engines. However, there is a problem that complicated maintenance is required.

In a direct injection type gas engine, similarly to a diesel engine, high pressure gaseous fuel is injected into a cylinder immediately before compression top dead center and burned. With this gas engine, the compression ratio can be made comparable to a diesel engine,
Thermal efficiency is comparable to diesel engines.

However, a device for compressing gaseous fuel to a pressure equal to or higher than the compression top dead center pressure and a fuel injection device are required.
There is a problem that the device becomes complicated, and there is a problem that an ignition device is required, and as with the spark ignition system, this ignition device is expensive and complicated maintenance is required. Therefore, only a few have been put to practical use.

In the gas engine of the premixed compression ignition system, a new combustion system is employed in which fuel is directly injected into an intake passage or a combustion chamber at an early stage of a compression stroke, and the premixed gas self-ignites near a top dead center. I have. Currently in the research stage, it will be a gas engine with high thermal efficiency and ultra-low NOx.

In this gas engine, it is difficult to control the ignition of the premixed gas near the compression top dead center, knocking is likely to occur, and the operating range is narrow.

[0010]

In order to solve the problem of the gas engine of the homogeneous charge compression ignition system, the combustion chamber is divided into a main chamber and a subchamber, and a subchamber and a piston top provided on the cylinder head side. An open / close valve (control valve) is provided at the communication port between the two main chambers, which communicates with each other. Engines are being developed.

In this sub-chamber gas engine with a control valve, the control valve is provided in the sub-chamber to enable compression ignition of the premixed gas supplied to the main chamber while keeping the fuel supply pressure low. By controlling the opening timing of the control valve, the combustion in the main chamber can be controlled, thereby realizing a compression ignition engine that does not require an ignition device or a complicated direct injection device, and achieves high thermal efficiency. As an engine, there is great potential.

However, in this sub-chamber engine with a control valve, natural gas, CO (carbon monoxide), H ₂
Gas fuels such as (hydrogen) are difficult to mix with air,
Since the ignition temperature is as high as 800 ° C. or higher, it is difficult to ignite, but once ignition combustion occurs, there is a characteristic that combustion progresses at a stretch, so when premixed air flows from the main chamber to the sub-chamber and ignites, There is a problem that knocking easily occurs due to intense combustion in the sub-chamber, and the occurrence of knocking hinders smooth operation of the engine and improvement in thermal efficiency.

In particular, once knocking occurs, the temperature of each part of the engine rises sharply, so that more intense knocking occurs. When such intense knocking occurs, a large pressure wave reciprocates in the cylinder and reaches a specific frequency. As a result, the engine may be damaged or the engine noise may increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. In a sub-chamber gas engine with a control valve, the operation of the engine is always kept in an operation region having high thermal efficiency while avoiding knocking. It is an object of the present invention to provide a sub-chamber gas engine with a control valve which can be maintained, has high thermal efficiency, significantly reduces NOx emissions, and has low engine combustion noise, and a method of operating the same.

[0015]

A sub-chamber gas engine with a control valve for achieving the above object is constituted as follows.

1) A sub-chamber and a main chamber, and a control valve provided between the sub-chamber and the main chamber and opened during a compression process of a piston, wherein gas fuel is supplied to the sub-chamber and the main chamber. A sub-chamber gas engine that starts the combustion in the main chamber by igniting in the sub-chamber and opening the control valve, returning a part of the exhaust gas to the intake passage, An EGR system for supplying the main chamber together with the premixed air; a control means for adjusting a control valve opening timing, an EGR gas flow rate and an air-fuel ratio; and a knocking sensor for detecting the occurrence of knocking. When the occurrence of knocking is detected by the knocking sensor, knocking avoidance control is performed.

2) In the sub-chamber gas engine with a control valve described above, the control means controls the knocking avoidance control for each cycle, at fixed time intervals, for each cylinder, or a combination thereof. Configured to do.

3) In the sub-chamber gas engine with a control valve described above, the knocking avoidance control is performed by any one or a combination of advancement of the control valve opening timing, reduction of the air-fuel ratio, and increase of the EGR amount. It is comprised so that it may contain.

The operation method of the sub-chamber gas engine with the control valve for achieving the above object is configured as follows.

1) A sub-chamber and a main chamber, and a control valve provided between the sub-chamber and the main chamber and opened during a compression process of a piston, for supplying gaseous fuel to the sub-chamber and the main chamber. By igniting in the sub-chamber and opening the control valve, thereby starting combustion in the main chamber, returning a part of exhaust gas to the intake passage, and supplying it to the main chamber together with premixed air. EGR
A sub-chamber gas engine having a system and a control means for adjusting a control valve opening timing, an EGR gas flow rate, and an air-fuel ratio, and having a knocking sensor for detecting occurrence of knocking; When knocking occurrence is detected from a signal, knocking avoidance control is performed.

2) In the operation method of the sub-chamber type gas engine with the control valve, the knocking avoidance control is performed every cycle and at regular time intervals. It is configured to perform this operation for any one of the cylinders or a combination thereof.

3) In the operating method of the sub-chamber gas engine with the control valve, the knocking avoidance control may be performed by any one of advancement of the control valve opening timing, reduction of the air-fuel ratio, and increase of the EGR amount. Alternatively, it is configured to perform the combination.

According to the sub-chamber gas engine with the control valve having the above-described configuration and the operating method thereof, when knocking is detected by the knocking sensor, the advance of the control valve opening timing and the EGR flow rate are performed according to the operating condition of the engine. By increasing the air-fuel ratio or reducing the air-fuel ratio or a combination thereof, the operating state is such that knocking is unlikely to occur, so that severe knocking can be avoided, and the operating state can always be maintained in a good state.

The knocking includes one in which the rate of pressure rise becomes excessive at the initial stage of combustion, similar to diesel knocking.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sub-chamber gas engine with a control valve according to the present invention and a method of operating the same will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a combustion chamber of a sub-chamber type gas engine with a control valve according to the present invention, and FIG. 2 is a diagram showing a system configuration of a sub-chamber type gas engine with a control valve. . FIG. 3 is a diagram showing a control flow of the engine operation.

As shown in FIG. 1, the combustion chamber of the sub-chamber type gas engine 1 with a control valve has a main chamber 13 formed above a cylinder 11 and a piston 12 for each cylinder. The main chamber 13 has a sub-chamber 14 which communicates with the control valve 15 via an opening / closing section of the control valve 15. The cylinder 11 includes a head liner 11a and a cylinder liner 11b, and the sub chamber 14 is formed in a cylinder head 17.

As shown in FIG. 2, the control valve 15 is controlled by a controller (ECU) 50 as a control means.
The valve is opened during the compression process.

As shown in FIG. 2, the sub-chamber gas engine 1 with the control valve includes an engine main body 10 having a main chamber 13 and a sub-chamber 14, a supercharger 20, and a gas in the main chamber 13. A first fuel supply passage 30 for supplying fuel F, a second fuel supply passage 35 for supplying gaseous fuel F to the sub-chamber 14, and a main chamber 1
An intake passage 40 for supplying air A to the exhaust gas passage 3, an exhaust passage 45 for discharging exhaust gas G, and an EGR passage 47 for recirculating the EGR gas Ge are provided.

The first fuel supply passage 30 is connected to a supply source of the gaseous fuel F, and includes a first fuel flow control device 31 and a first fuel supply device 32 and is formed to communicate with the main chamber 13. , The second fuel supply passage 35 is connected to a gas fuel supply source, and the second fuel flow control device 36 and the second fuel
A fuel supply device 37 is provided to communicate with the sub-chamber 14.

The intake passage 40 is connected to the main chamber 13 via the compressor 21 of the supercharger 20 via the air flow controller 41, while the exhaust passage 45 exiting from the engine body 10 is connected to the supercharger. It communicates with outside air via a turbine 22 and the like.

The EGR passage 47 includes an EGR flow control device 48 composed of an EGR valve and the like and an EGR cooler 49, and is provided between the exhaust passage 45 downstream of the turbine 22 and the air flow control device 41 and the compressor 21. Intake passage 4
It is formed by connecting 0. The EGR cooler 49 serves to cool the EGR gas Ge and suppress the generation of NOx.

That is, the gas fuel F is supplied to the sub chamber 14 and the main chamber 13.
First and second fuel supply passages 30, 35 for supplying both
And an EGR passage 47 that returns a part of the exhaust gas G to the intake passage 40 and supplies it to the main chamber 13 together with the premixed air.

Further, although not shown, a knocking sensor 51 for detecting occurrence of knocking is provided in the engine body 10. As this knocking sensor, there is a method for detecting vibration of an engine block, cylinder pressure, combustion noise, and the like.

In the method of detecting the vibration of the engine block, the vibration level of a specific frequency is increased by the occurrence of knocking when the cylinder block or the like is mounted. Therefore, the vibration level is detected. There are piezoelectric knock sensors and magnetostrictive knock sensors.

The controller (ECU) 50
Engine speed, knocking, misfire, Pmax, fuel flow, air flow, EGR gas flow, intake temperature, intake pressure,
By inputting engine information such as exhaust temperature, exhaust pressure, crank angle, etc., the control valve opening timing variable device 16, the supercharger 20, the first
Fuel flow control device 31, second fuel flow control device 36, air flow control device 41, EGR flow control device 51, and EGR
By controlling the cooler 52 and the like, the valve opening timing of the control valve 16, E
It is configured to adjust and control the GR gas flow rate, the air-fuel ratio, and the like.

The EGR gas flow rate is controlled by adjusting the EGR gas flow rate by adjusting the EGR flow rate control device 51 such as an EGR valve. The air-fuel ratio is controlled by the first fuel flow rate control device 31 and the EGR gas flow rate control device. (2) Adjustment of the fuel flow rate by the adjustment control of the fuel flow rate control device 36, and adjustment of the air flow rate by the control of the supercharger 20 and the adjustment control of the air flow rate control device 41.

Next, a gas engine combustion method using the sub-chamber gas engine 1 with the control valve will be described.

In the sub-chamber gas engine 1 with the control valve, the gas fuel F is introduced into the sub-chamber 14, and the mixture of the gas fuel F and the air A and the EGR gas Ge are introduced into the main chamber 13, respectively. When the valve 15 is opened at an appropriate time during the compression stroke of the piston 12, the mixture in the main chamber 13 and the EGR gas G
e rapidly flows into the sub-chamber 14 to form an air-fuel mixture in the sub-chamber 14.

When the piston 12 approaches the top dead center, the air-fuel mixture formed in the sub-chamber 14 is first ignited by the temperature rise due to compression, and the gas burned by this ignition expands and the piston 12 descends. Then, the combustion gas in the sub-chamber 14 blows out to the main chamber 13, and the high-temperature combustion gas mixes with the mixture in the main chamber 13, and the mixture in the main chamber 13 ignites.

At this time, by allowing the main chamber 13 to contain an appropriate amount of the EGR gas Ge, the combustion can be made a gentle combustion without knocking. Since the combustion in the main chamber 13 is the self-ignition of the premixed gas, the heat release rate pattern has a high peak in spite of gentle combustion, and the combustion is a good combustion with a short combustion period.

The overall heat generation pattern is a two-peak pattern in which a low peak due to combustion in the sub-chamber 14 in the first half of combustion and a high peak due to combustion in the main chamber 13 in the second half. The low peak in the first half suppresses the excessive pressure rise due to the combustion in the second half, and plays a role in achieving quiet combustion. In addition, the amount of NOx emission is an extremely low value of 1/10 to 1/100 of the diesel engine. By constantly performing such combustion, high-efficiency and ultra-low NOx combustion is achieved.

The combustion of the sub-chamber gas engine 1 with the control valve is greatly affected by the valve opening timing of the control valve 15, the EGR rate, and the air-fuel ratio, and the operating conditions are reduced due to the occurrence of excessive knocking and misfire. Because it is limited, it is necessary to always keep it under optimal conditions. In particular, the occurrence of knocking is greatly affected by the control valve opening timing and the EGR rate.

Therefore, the occurrence of knocking and the operating state of the engine, such as the temperature of each part of the engine, intake pressure, exhaust pressure, etc., are constantly monitored during operation by the controller 50 which inputs the value detected by the knocking sensor 51, and knocking occurs. If not, set the optimal conditions according to the operation command, and if knocking occurs, open the control valve,
The EGR rate and the air-fuel ratio are controlled on a cycle-by-cycle or a fixed period basis, and, if necessary, on a cylinder-by-cylinder basis to always achieve optimal combustion.

Next, the operation flow of the engine will be described with reference to FIG.

When the operation of the engine is started and the control flow is started, an operation command relating to the operation of the engine and information of the engine indicating the state of the engine are read in step S11.

The operation command includes the target engine speed, load, etc., and the engine information includes the engine speed, knocking, misfire, P
max, fuel flow, air flow, EGR gas flow, intake temperature, intake pressure, exhaust temperature, exhaust pressure, crank angle, and the like.

Then, in the next step S12, it is determined whether or not the read engine operation command includes an operation stop command. If so, the process proceeds to step S18 to perform engine operation stop processing. Stop control.

In step S12, if there is no operation stop command, the flow proceeds to the next step S13, where the fuel amount, the air-fuel ratio, the valve opening timing of the control valve 15, A process for setting or changing operation parameters such as an EGR gas flow rate is performed.

Then, in the next step S14, it is determined whether or not knocking has occurred. If it is determined that knocking has not occurred, the operation is optimized and the fuel consumption is reduced in step S15. The parameters are updated, the engine is operated for a predetermined time in step S17, and if it is determined that knocking has occurred, knocking avoidance processing in step S16 is performed to update the operating parameters. In step S17, the engine is operated for a predetermined time (engine control interval).

The operation optimizing / fuel-saving process in step S15 includes a process for reducing the air-fuel ratio, a process for delaying or optimizing the opening timing of the sub-chamber valve, and a process for decreasing the EGR gas flow rate (EGR rate). The knocking avoiding process in step S16 includes a process for increasing the air-fuel ratio, a process for advancing the sub chamber valve opening timing, and a process for increasing the EGR gas flow rate (EGR rate).

When the operation of the engine during the predetermined time in step S17 is completed, the process returns to step S11, and the operation of the engine is continued based on this control flow until an engine operation stop command is issued.

According to the sub-chamber gas engine 1 with the control valve having this configuration and its operating method, the knocking sensor 51 and the controller 50 monitor the occurrence of knocking while controlling the control valve opening timing, the EGR rate, and the air-fuel ratio. By controlling by a method such as feedback control for each cycle, for a fixed period, or for each cylinder, the engine can be operated at a high thermal efficiency point while preventing the occurrence of knocking.

[0054]

As described above, according to the sub-chamber gas engine with the control valve and the method of operating the same according to the present invention, the control valve opening timing and the EGR are monitored while the occurrence of knocking is monitored.
By controlling the rate and the air-fuel ratio for each cycle, for a fixed period, or for each cylinder, the engine can always be operated at a high thermal efficiency point while preventing occurrence of knocking.

For this reason, while avoiding the occurrence of knocking, N is always high in the operating region with high thermal efficiency and N
The operation can be performed in a state where the amount of Ox emission is extremely small and the combustion noise of the engine is low.

Therefore, a low fuel consumption and low pollution engine can be realized, and the engine can be applied to liquid fuels such as alcohol fuel and gasoline, which are difficult to ignite and burn with a normal diesel engine.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a combustion chamber of a sub-chamber gas engine with a control valve according to an embodiment of the present invention.

FIG. 2 is a diagram showing a system configuration of a sub-chamber gas engine with a control valve according to the embodiment of the present invention.

FIG. 3 is a diagram showing a control flow of operation of the sub-chamber gas engine with a control valve according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sub-chamber type gas engine 12 Piston 13 Main chamber 14 Sub-chamber 15 Control valve 40 Intake passage 47 EGR passage 48 EGR gas flow control device (EGR valve) 49 EGR cooler 50 Controller (control means) 51 Knocking sensor F Gas fuel G Exhaust Gas Ge EGR gas

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02B 19/10 F02B 19/10 P F02D 15/04 F02D 15/04 G 21/08 301 21/08 301A 311 311Z 41/02 351 41/02 351 41/22 355 41/22 355 43/00 301 43/00 301E 301N 301W 301Z 45/00 345 45/00 345B 368 368A F02M 21/02 F02M 21/02 G L P 301 301A 301J 25/07 550 25/07 550G 550R 570 570Z F-term (reference) 3G023 AA05 AA06 AB05 AC03 AC04 AC07 AD23 AD30 AF00 AF03 AG03 3G062 AA00 BA00 BA02 CA00 DA01 DA05 EA10 ED01 BA01 A08 BA01 A08A01 A08A08 FA25 FA39 3G092 AA07 AA11 AA17 AB08 AB09 BA04 DD09 EA01 EA03 EA 05 FA16 FA17 GA00 HB00X HC05Y HD07X HE00X 3G301 HA05 HA06 HA11 HA13 HA22 JA22 MA00 MA01 NE23 PC08Z

Claims (6)

[Claims] 1. A sub-chamber and a main chamber, and a control valve provided between the sub-chamber and the main chamber and opened during a compression process of a piston, wherein gas fuel is supplied to the sub-chamber and the main chamber. By igniting in the sub-chamber and opening the control valve,
A sub-chamber gas engine for starting combustion of the main chamber, wherein an EGR system that returns a part of exhaust gas to an intake passage and supplies the main chamber with premixed air; a control valve opening timing, an EGR gas flow rate; A control device for adjusting an air-fuel ratio is provided, and a knocking sensor for detecting occurrence of knocking is provided, and when the occurrence of knocking is detected by the knocking sensor, the control device performs knocking avoidance control. Item 6. A sub-chamber gas engine with a control valve according to Item 1. 2. A control valve with a control valve according to claim 1, wherein the control means performs the knocking avoidance control at every one cycle, at certain time intervals, at each cylinder, or a combination thereof. Subchamber gas engine. 3. The knocking prevention control according to claim 1, wherein the control includes at least one of an advance of a control valve opening timing, a decrease in an air-fuel ratio, and an increase in an EGR amount. Sub-chamber gas engine with control valve. 4. A sub-chamber and a main chamber, and a control valve provided between the sub-chamber and the main chamber and opened during a compression process of a piston, wherein gas fuel is supplied to the sub-chamber and the main chamber. By igniting in the sub-chamber and opening the control valve,
An EGR system that starts combustion in the main chamber, returns a part of exhaust gas to the intake passage, and supplies the premixed air to the main chamber, and a control unit that adjusts a control valve opening timing, an EGR gas flow rate, and an air-fuel ratio. In the sub-chamber gas engine provided with a knocking sensor for detecting occurrence of knocking, knocking avoidance control is performed when the control means detects occurrence of knocking from a signal from the knocking sensor. Operating method of sub-chamber gas engine with control valve. 5. The sub-chamber gas engine with a control valve according to claim 4, wherein the knocking avoidance control is performed at every one cycle, at certain time intervals, at each cylinder, or a combination thereof. Driving method. 6. The knocking control according to claim 4, wherein the knocking avoidance control is performed by any one or a combination of advance of a control valve opening timing, reduction of an air-fuel ratio, and increase of an EGR amount. Method of operating a sub-chamber gas engine with a control valve.