JP4452200B2 - Gas engine with EGR system and method of operating the same - Google Patents

Description

  In the present invention, fuel gas and air are mixed by a mixer, and the mixture is supplied to an engine through an air supply passage that is opened and closed by a throttle valve to be ignited and burned, and EGR gas (exhaust gas recirculation) is supplied to an EGR valve. The present invention relates to a gas engine with an EGR system configured to be able to be supplied to an engine through an EGR passage opened and closed by the above, and a method for operating the gas engine.

  Fuel gas and air are mixed by a mixer, and this mixture is supplied to the engine through the supply air passage for ignition and combustion, and EGR gas (exhaust gas recirculation) is supplied to the engine through the EGR passage opened and closed by the EGR valve. As one of the gas engines with an EGR system configured as described above, there is a technique proposed in Japanese Patent Application Laid-Open No. 10-131742.

  In such a technique, fuel gas and air are mixed by a mixer, and EGR gas diverted from the exhaust gas in the exhaust passage is installed in an air supply passage at the mixer outlet through an EGR passage opened and closed by an EGR valve. In a gas engine that is fed to an EGR mixer, mixes the air-fuel mixture from the mixer and EGR gas in the EGR mixer and supplies the mixture to the engine for ignition and combustion. The EGR valve is closed to stop the EGR, and when the load is higher than the limit load factor, the EGR valve is opened to perform the EGR, thereby increasing the knocking limit.

JP-A-10-131742

In a gas engine configured to mix fuel gas and air with a mixer and supply the mixture to the engine through an air supply passage opened and closed by a throttle valve to cause ignition and combustion, the gas engine is operated at low load or at low temperatures. When the engine is operated with a low air density and a large intake air amount (weight), the engine output becomes larger than the target output. Therefore, the engine is normally operated with a small throttle valve opening.
For this reason, during operation with the throttle valve opening reduced as described above, the pump loss due to the throttle valve passage being throttled increases, and the engine thermal efficiency decreases. .

  However, in Patent Document 1 (Japanese Patent Laid-Open No. 10-131742), in a gas engine equipped with an EGR system, EGR is stopped until the limit load factor at the time of engine load is reached, and the limit load is reduced. Only means for increasing the knocking limit by opening the EGR valve and performing EGR at a high load exceeding the rate is disclosed, and the EGR is controlled to operate the engine at a low load or at a low temperature air supply operation. There is no mention of engine pump loss.

  In view of the problems of the prior art, the present invention reduces engine pump loss caused by throttle valve throttle during low load operation of the engine or operation under low temperature air supply, and prevents a decrease in thermal efficiency due to the pump loss. As a result, an object of the present invention is to provide a gas engine with an EGR system that can increase the thermal efficiency during such operation.

The present invention achieves such an object. Fuel gas and air are mixed by a mixer, and this mixture is supplied to an engine through an air supply passage opened and closed by a throttle valve to be ignited and burned. In an operation method of a gas engine with an EGR system configured to be able to supply EGR gas (exhaust gas recirculation gas) branched from exhaust gas to the engine through an EGR passage opened and closed by an EGR valve, the supply air temperature exceeds a certain temperature when operation range, is operated by the reference throttle opening defined by the operating characteristics of the engine, when the supply air temperature is cold operation range below the predetermined temperature, the opening degree of the throttle valve by the operation characteristics of the engine and sets an excessive degree larger by opening increment ΔS than prescribed reference throttle opening,該過large opening The EGR gas in the flow rate of the EGR valve opening corresponding to the air-fuel mixture amount corresponding to the opening increase amount ΔS is supplied to the engine together with the air-fuel mixture during the mixing of fuel gas and air supplied to the engine The ratio of the air amount in the engine is reduced by the EGR gas to maintain the engine output at the target output .

In addition, the invention of the apparatus used for the operation method of the gas engine mixes fuel gas and air with a mixer, supplies the mixture to the engine through an air supply passage opened and closed by a throttle valve, and ignites and burns it. In a gas engine with an EGR system configured to be able to supply EGR gas (exhaust gas recirculation gas) branched from exhaust gas in an exhaust passage to an engine through an EGR passage opened and closed by an EGR valve, an air supply temperature of the engine is set. An air supply temperature sensor for detecting is provided, and when the detected value of the air supply temperature sensor is in an operating range exceeding a certain temperature, a controller that operates according to a reference throttle valve opening degree defined by an engine operating characteristic is provided. when the detected value of the fed-air temperature sensor is cold operation range below the predetermined temperature, the operation of the engine The opening is opened and the throttle valve opening setting means, said EGR valve during the該過large opening to be set excessive opening larger by opening increment ΔS than the reference throttle valve opening defined by gender It includes the increase ΔS corresponding flow rate of the EGR gas in the mixed gas quantity corresponding to the opening can be fed into the air supply and an EGR valve opening setting means for setting an excessive opening by the throttle valve opening setting means The EGR gas is supplied to the engine together with the mixture by the EGR valve opening set by the EGR valve opening setting means during the degree setting period, and the air in the mixture of fuel gas and air supplied to the engine The engine is characterized in that the engine output can be maintained at the target output by reducing the ratio of the amount by EGR gas .

According to the present invention, when the operating range of the supply air temperature exceeds a predetermined temperature, is operated by the reference throttle opening defined by the operating characteristics of the engine, when the supply air temperature is cold operation range below the certain temperature The throttle valve opening setting means sets the opening of the throttle valve to an excessive opening that is larger by the opening increase amount ΔS than the reference throttle opening defined by the engine operating characteristics, and by the EGR valve opening setting means. While opening the EGR valve and setting the opening so that the EGR gas having a flow rate corresponding to the air-fuel mixture amount corresponding to the opening increase amount ΔS can be supplied during the air supply, the EGR gas is mixed with the engine and the engine. When the engine has an excessive output that is higher than the predetermined output (target output) when the supply air temperature is low, the slot is The valve is set to an excessive opening larger than the reference opening to increase the actual air-fuel mixture amount above the specified air-fuel mixture amount, and the EGR valve is opened to mix the EGR gas with the air-fuel mixture. By supplying the supply air to the engine, even when the throttle valve opening is set to the excessive opening, the ratio of fresh air (air mixture) in the supply air is reduced by EGR gas and combustion is performed. Can be suppressed.

As a result, when the supply air temperature is low, the engine output can be suppressed to a predetermined output (target output) even if the throttle valve opening is set to the excessive opening. Therefore, when the supply air temperature is low, the throttle It is possible to reduce the pump loss due to the throttle of the valve being prevented, and it is possible to prevent a decrease in the thermal efficiency of the engine due to the pump loss, resulting in an increase in the thermal efficiency of the engine during low temperature operation of the supply air temperature. be able to.
Further, when the supply air temperature is low, the mixture supply air, which is a mixture of EGR gas and the mixture gas, is supplied to the engine. The ratio of EGR gas is increased, and the NOx reduction effect is improved.

In this invention, specifically, it is preferable to configure as the following (1) and (2).
(1) The EGR passage is connected to a portion of the air supply passage downstream of the throttle valve, and the EGR gas is mixed with the air-fuel mixture that has passed through the throttle valve.
When EGR gas is mixed downstream of the throttle valve, a sufficient amount of EGR gas can be secured because of a large pressure difference from the intake side. As a result, the throttle valve can be set to an excessive opening, and pump loss can be reduced.
(2) The EGR passage is connected to an air passage on the upstream side of the mixer, and the EGR gas is mixed with the air in the air passage and introduced into the mixer.
If comprised in this way, after mixing air and EGR gas in the upstream of a mixer, since the air and fuel gas which EGR gas mixed in the mixer are mixed, mixing of EGR gas and fuel gas-air Mixing time with the air (fresh air) can be ensured, the dilution of the supply air can be promoted, and the amount of NOx generated can be reduced.

As described above, according to the present invention, when the supply air temperature of the engine is low, a mixed supply of fresh air and EGR is supplied to the engine, so that the throttle valve opening is set to an excessive opening. Even so, the ratio of fresh air in the supply air can be reduced by the EGR gas, and the engine output can be suppressed to a predetermined output (target output), so that the throttle valve can be operated when the supply air temperature is low. It is possible to reduce the pump loss due to the narrowing of the passage of the engine, prevent a decrease in the engine thermal efficiency due to the pump loss, and as a result, increase the engine thermal efficiency during low temperature operation of the supply air temperature. Can do.
Further, when the supply air temperature is low, the mixture supply air, which is a mixture of EGR gas and the mixture gas, is supplied to the engine. The ratio of EGR gas is increased, and the NOx reduction effect is improved.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

FIG. 1 is an overall configuration diagram of a gas engine equipped with an EGR system according to a first embodiment of the present invention.
In FIG. 1, 100 is an engine, 101 is a cylinder of the engine (6 cylinders in this example), 112 is a crankshaft, 103 is an air supply manifold, 114 is an air supply pipe, 104 is an exhaust manifold, and 105 is an exhaust pipe. 111 is an air cleaner, 113 is a fuel gas supply pipe, 110 is a mixer that mixes fuel gas from the fuel gas supply pipe 113 with air that has passed through the air cleaner 111 to generate a lean air-fuel mixture, and 4 is supplied to the engine 100. A throttle valve 41 for adjusting the flow rate of the lean air-fuel mixture, 41 is a throttle valve driving device for driving the throttle valve 4.

Reference numeral 102 denotes an EGR pipe branched from the exhaust pipe 105 and connected to the air supply pipe 114 to recirculate a part of exhaust gas (EGR gas) flowing through the exhaust pipe 105 to the air supply pipe 114. The EGR pipe 102 is connected to a portion of the air supply pipe 114 downstream of the throttle valve 4 (8 is a joining portion of the air supply pipe 114 and the EGR pipe), and the EGR gas is supplied to the air-fuel mixture passing through the throttle valve 4. Is supposed to be mixed.
The EGR pipe 102 is provided with an EGR cooler 107 that cools the EGR gas, and an EGR valve 3 that adjusts the flow rate of the EGR gas. Reference numeral 31 denotes an EGR valve drive device that drives the EGR valve 3.

Reference numeral 5 denotes an engine speed detector that detects the speed of the engine 100 (engine speed), 6 denotes a load detector that detects a load (engine load) of the engine 100, and 1 denotes air supply in the air supply pipe 114 This is a supply air temperature sensor for detecting the temperature of the air.
Reference numeral 2 denotes a controller, which receives a detected value of the engine speed from the engine speed detector 5, a detected value of the engine load from the load detector 6, and a detected value of the supply air temperature from the supply air temperature sensor 1. Based on the detected value, the throttle valve 4 and the EGR valve 3 are controlled to open and close by means described later.

In the first embodiment, the fuel gas supplied through the fuel gas supply pipe 113 is mixed with the air passed through the air cleaner 111 in the gas mixer 110 to become a lean air-fuel mixture. The air supply comprising the lean air-fuel mixture passes through the air supply pipe 114 and the flow rate is controlled by the throttle valve 4.
When the EGR valve 3 is opened under the control of the controller 2, the EGR gas that has passed through the EGR pipe 102 is mixed with the supply air comprising the lean mixture, and the supply gas comprising the mixture gas of the EGR gas and the lean mixture is provided. The gas is supplied into each cylinder 101 through the air supply manifold 103, and low NOx combustion is performed in the cylinder 101 by the air-fuel mixture mixed with the EGR gas.

  In the first embodiment, as described above, the EGR pipe 102 is connected to the downstream portion of the air supply pipe 114 in the throttle valve 4 to mix the EGR gas with the air-fuel mixture that has passed through the throttle valve 4. Thus, when EGR gas is mixed downstream of the throttle valve, the pressure difference from the intake side is large, so that a sufficient amount of EGR gas can be secured. As a result, the throttle valve can be set to an excessive opening, and pump loss can be reduced.

FIG. 2 is an overall configuration diagram of a gas engine equipped with an EGR system according to a second embodiment of the present invention.
In the second embodiment, the EGR pipe 102 is connected to an air supply pipe (air passage) 114 on the upstream side of the mixer 110 (7 is a connection portion of the EGR pipe 102). The EGR gas is mixed with the air and introduced into the mixer 110.
Other configurations are the same as those of the first embodiment shown in FIG. 1, and the same members are denoted by the same reference numerals.
According to the second embodiment, the air and the EGR gas are mixed on the upstream side of the mixer 110, and then the air mixed with the EGR gas and the fuel gas are mixed in the mixer 110. Therefore, the EGR gas and the fuel are mixed. Mixing time with the gas-air mixture (fresh air) can be ensured, the dilution of the supply air can be promoted, and the amount of NOx generated can be reduced.

Next, the control operation of the controller in the first and second embodiments will be described. FIG. 3 is a block diagram of the opening control of the throttle valve and the EGR valve in the first and second embodiments.
In FIG. 3, the detected value of the engine speed from the engine speed detector 5, the detected value of the engine load from the load detector 6, and the detected value of the supply air temperature from the supply air temperature sensor 1 are as follows: The EGR valve opening calculation unit 21 and the throttle valve opening calculation unit 23 of the controller 2 are input.

Reference numeral 24 denotes a throttle valve opening setting unit, which, as shown in FIG. The excessive opening S1 is set to be larger by ΔS than S0.
Alternatively, in the throttle valve opening setting unit, as shown in FIG. 5, the opening of the throttle valve 4 is defined by the operating characteristics of the engine 100 in the low temperature operation region where the supply air temperature is equal to or lower than a constant temperature Ts0. You may set to the excessive opening degree S1 larger by the opening degree increase amount (DELTA) S than the reference opening degree S0.
It should be noted that the opening degree of the throttle valve 4 can be fully opened in the entire operation range.
An EGR valve opening setting unit 22 opens the EGR valve 3 when the opening of the throttle valve 4 is at the excessive opening S1, and sets the opening of the EGR valve 3 to the opening increase amount ΔS. The EGR gas having a flow rate corresponding to the air-fuel mixture flow rate is set so that the opening can be supplied during the air supply.

  In the throttle valve opening calculation unit 23, when the detected value of the engine load from the load detector 6 is equal to or less than the constant load L1 set in the throttle valve opening setting unit 24, the opening of the throttle valve 4 Is increased to an excessive opening S1 that is larger than the reference opening S0 by the opening increase amount ΔS, and is output to the throttle valve drive device 31. Alternatively, when the detected value of the supply air temperature from the supply air temperature sensor 1 is equal to or lower than the predetermined temperature Ts0, the opening of the throttle valve 4 is set to an excessive opening S1 that is larger than the reference opening S0 by the opening increase amount ΔS. It may be increased and output to the throttle valve driving device 31. Thereby, the throttle valve driving device 31 shifts the opening degree of the throttle valve 4 to the excessive opening degree S1.

On the other hand, in the EGR valve opening calculation unit 21, the detected value of the engine load from the load detector 6 becomes equal to or less than the constant load L1 set in the throttle valve opening setting unit 24 or the detection of the supply air temperature. When the value becomes equal to or lower than the predetermined temperature Ts0 and the opening degree of the throttle valve 4 is increased to an excessive opening degree S1 larger than the reference opening degree S0 by the opening degree increase amount ΔS, the setting is made in the EGR valve opening degree setting unit 22 The opening of the EGR valve 3 is adjusted to the degree of opening of the EGR valve 3, that is, the opening at which the EGR gas having a flow rate corresponding to the flow amount of air-fuel mixture corresponding to the opening increase amount ΔS of the throttle valve 4 can be supplied. The degree is set and output to the EGR valve drive device 41. Thereby, the EGR valve drive device 41 holds the opening degree of the EGR valve 3 at the opening degree set in the EGR valve opening degree setting unit 22.
During normal operation other than the above, the engine is operated with the throttle valve opening and the EGR valve opening corresponding to the detected values of the engine speed and engine load.

  According to the first and second embodiments, the throttle valve opening calculation unit (throttle valve) of the controller 2 is operated during low load operation of the engine 100 at a constant load L1 or less, or at a low temperature of the supply air temperature at a constant temperature Ts0 or less. The opening degree setting means) 23 sets the opening degree of the throttle valve 4 to an excessive opening degree S1 that is larger than the reference opening degree S0 defined by the operating characteristics of the engine by an opening degree increase amount ΔS, and an EGR valve opening degree calculation unit Since the EGR valve 3 is opened by the (EGR valve opening degree setting means) and the EGR gas is supplied to the engine 100 together with the air-fuel mixture, as shown in FIG. When the engine has an excessive output (corresponding to the opening A1 of the throttle valve 4) that is larger than the predetermined output (target output), the throttle valve 4 is set to the reference opening. An over-opening degree A3 or A4 larger than 2 is set to increase the actual air-fuel mixture amount above the prescribed air-fuel mixture amount, and the EGR valve 3 is opened to mix EGR gas with the air-fuel mixture. Is supplied to the engine, the ratio of fresh air in the supplied air can be reduced by the EGR gas even when the throttle valve opening is set to the excessive opening.

As a result, during the low load operation or when the supply air temperature is low, the engine output can be maintained at a predetermined output (target output) even if the throttle valve 4 opening is set to the excessive opening, and thus the operation can be performed. During low load operation or when the supply air temperature is low, the pump loss due to the throttle valve 4 being throttled can be reduced from excessive output equivalent loss B1 to B3 or B4 in FIG. Thus, it is possible to prevent a decrease in the thermal efficiency of the engine due to the pump loss, and as a result, it is possible to increase the thermal efficiency of the engine at such low load or low temperature operation of the supply air temperature from C1 to C3 or C4 in FIG.
Further, during the low-load operation or when the supply air temperature is low, the mixed supply of fresh air and EGR, which is a mixture of EGR gas and air-fuel mixture, is supplied to the engine 100, so the throttle valve 4 opening is excessively increased. The ratio of EGR gas in the mixed supply air in the state set to the opening is increased, and the NOx reduction effect is improved.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to reduce the pump loss of the engine accompanying the throttle valve throttle at the time of low load operation of the engine or operation under low temperature air supply, and it is possible to prevent a decrease in thermal efficiency due to the pump loss. A gas engine with an EGR system that can increase the thermal efficiency during operation can be provided.

1 is an overall configuration diagram of a gas engine including an EGR system according to a first embodiment of the present invention. FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. It is a control block diagram in the first and second embodiments. FIG. 6 is an explanatory diagram (part 1) of an operation in the first and second embodiments. FIG. 6 is an explanatory diagram (part 1) of an operation in the first and second embodiments. It is a diagram which shows the effect in the said 1st, 2nd Example.

DESCRIPTION OF SYMBOLS 1 Supply air temperature sensor 2 Controller 3 EGR valve 4 Throttle valve 5 Engine speed detector 6 Load detector 31 EGR valve drive device 41 Throttle valve drive device 100 Engine 101 Cylinder 102 EGR pipe 103 Supply manifold 104 Exhaust manifold 105 Exhaust pipe 113 Fuel gas supply pipe 114 Air supply pipe

Claims (4)

Fuel gas and air are mixed by a mixer, and this mixture is supplied to the engine through an air supply passage that is opened and closed by a throttle valve to be ignited and combusted, and EGR gas (exhaust gas recirculation) separated from the exhaust gas in the exhaust passage. In the operation method of the gas engine with an EGR system configured to be able to supply the circulating gas) to the engine through the EGR passage opened and closed by the EGR valve,
When the supply air temperature is in the operating range exceeding a certain temperature, the engine is operated with the reference throttle opening degree defined by the operating characteristics of the engine,
When the supply air temperature is cold operation range below the predetermined temperature, it sets the degree of opening of the throttle valve to a large excessive degree by degree increment ΔS than the reference throttle opening defined by the operating characteristics of the engine At the same time, during the period of the excessive opening, the EGR valve is opened to supply the EGR gas having a flow rate corresponding to the air-fuel mixture amount corresponding to the opening increase amount ΔS together with the air-fuel mixture to the engine. A method for operating a gas engine with an EGR system , wherein the ratio of the amount of air in a mixture of fuel gas and air is reduced by the EGR gas to maintain the engine output at a target output . Fuel gas and air are mixed by a mixer, and this mixture is supplied to the engine through an air supply passage that is opened and closed by a throttle valve to be ignited and combusted. EGR gas (exhaust gas In the gas engine with the EGR system configured to be able to supply the circulating gas) to the engine through the EGR passage opened and closed by the EGR valve,
An air supply temperature sensor for detecting the air supply temperature of the engine is provided, and when the detected value of the air supply temperature sensor is in an operating range exceeding a certain temperature, the engine is operated at a reference throttle valve opening degree defined by the engine operating characteristics. With a controller,
The controller, when the detected value of the fed-air temperature sensor is cold operation range below the predetermined temperature, a large excess opening by opening increment ΔS than the reference throttle valve opening defined by the operating characteristics of the engine A throttle valve opening setting means for setting the valve to open, and during the period of the excessive opening, the EGR valve is opened to supply EGR gas at a flow rate corresponding to the air-fuel mixture amount corresponding to the opening increase amount ΔS during supply. equipped with an EGR valve opening degree setting means for setting a possible opening, EGR by the EGR valve opening degree set by the EGR valve opening setting means during excessive travel set period by the throttle valve opening setting means Gas is supplied to the engine together with the mixture, and the ratio of the amount of air in the mixture of fuel gas and air supplied to the engine is reduced by the EGR gas and the engine output is set to the target output. A gas engine with an EGR system, characterized in that it can be held in   3. The EGR according to claim 2, wherein the EGR passage is connected to a portion of the air supply passage downstream of the throttle valve so that the EGR gas is mixed with the air-fuel mixture that has passed through the throttle valve. Gas engine with system.   3. The EGR according to claim 2, wherein the EGR passage is connected to an air passage upstream of the mixer, and the EGR gas is mixed with the air in the air passage and introduced into the mixer. Gas engine with system.

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