JP4727446B2 - Gas engine intake system - Google Patents

Description

  In the present invention, a mixture of fuel gas and air generated by a gas mixer is passed through a throttle valve that is installed in an intake passage and controls the flow rate of the mixture, and passes through an intake manifold and an intake valve to an engine cylinder. The present invention relates to an intake device for a gas engine configured to supply.

FIG. 8 is a block diagram showing a conventional gas engine intake device.
In FIG. 8, 100 is an engine (gas engine), 4 is a cylinder of the engine 100 (6 cylinders in this example), and 5 is a crankshaft. Reference numeral 1 denotes an intake manifold, 3 denotes an intake branch pipe connecting the intake manifold 1 and each cylinder 4, and an intake valve connecting the intake branch pipe 3 and each cylinder 4 is an intake valve (all not shown) Is provided.
6 is an exhaust manifold, 7 is an exhaust branch pipe connecting the exhaust manifold 6 and each cylinder 4, and an exhaust valve is connected to the exhaust port connecting the exhaust branch pipe 7 and each cylinder 4 (all not shown) Is provided. Reference numeral 8 denotes an exhaust pipe connected to the exhaust outlet of the exhaust manifold 6.

Reference numeral 2 denotes an intake pipe connected to the intake manifold. The intake pipe 2 includes an air cleaner 12, a gas mixer 11 that generates an air-fuel mixture of air passing through the air cleaner 12 and fuel gas from the fuel gas pipe 30, and the mixing A throttle valve 10 for controlling the air flow rate is installed.
22 is an engine speed detector for detecting the engine speed of the engine 100, 23 is a load detector for detecting a load (engine output) of the engine 100, 20 is a controller, and the controller 20 is the engine speed detector. Based on the detected value of the engine speed inputted from the engine 22 and the detected value of the engine load inputted from the load detector 23, the opening degree of the throttle valve 10 is adjusted to an opening degree suitable for the engine speed and the engine load. It comes to control.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2001-193468), a mixture of fuel gas and air generated by a gas mixer is compressed by a compressor of a supercharger and passed through an intake valve of an engine to a cylinder. In the Miller cycle gas engine configured to supply, the pumping loss is reduced by setting the ratio of the exhaust manifold volume to the engine stroke volume and the ratio of the compression ratio to the stroke volume to appropriate values. Technology has been provided.

JP 2001-193468 A

In the conventional gas engine as shown in FIG. 8, the controller 20 uses the detected value of the engine speed from the engine speed detector 22 and the detected value of the engine load (engine output) from the load detector 23. The opening of the throttle valve 10 is controlled so as to decrease from the engine output design point L1 as the engine output decreases (or as the engine speed decreases) as shown in FIG. 9A.
Therefore, during partial load operation of the engine 100, the opening degree of the throttle valve 10 is reduced to a small value. As a result, the intake negative pressure between the throttle valve 10 and the intake valve increases as shown in FIG. Pump loss (pumping loss) increases, and the thermal efficiency of the engine decreases as shown in FIG.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-193468), in the Miller cycle gas engine, the ratio of the exhaust manifold volume to the engine stroke volume and the ratio of the compression ratio to the stroke volume are set to appropriate values. Thus, the pumping loss is reduced, and the mixture of the fuel gas and air generated by the gas mixer is supplied to the engine cylinder through the throttle valve that controls the flow rate of the mixture. No means for solving the above-described problems is disclosed for the gas engine.

In view of the problems of the prior art, the present invention is a gas engine configured to supply a mixture of fuel gas and air from a gas mixer to a cylinder of an engine through a throttle valve with a very simple and low-cost structure. Accordingly, an object of the present invention is to provide a gas engine intake device that can increase the thermal efficiency of the engine by reducing the pump loss of intake air during partial load operation, and further improve the startability.

The present invention achieves such an object, and a mixture of fuel gas and air generated by a gas mixer is passed through a throttle valve that is installed in an intake passage and controls the flow rate of the mixture. An intake device for a gas engine configured to be supplied to a cylinder of an engine through a valve, wherein an intake passage volume (V) from the throttle valve outlet of the intake passage to the intake valve is defined as an intake passage volume ( V) and the engine stroke volume (Vh) ratio (V / Vh) is 1.3 or more (V / Vh ≧ 1.3), and further from the fuel gas passage to the gas mixer A fuel gas bypass passage that is branched and connected to the intake passage on the downstream side of the throttle valve, and a bypass passage opening / closing valve that opens and closes the fuel gas bypass passage are provided. A controller for opening and closing the bypass passage opening / closing valve so that the bypass passage opening / closing valve is opened when the engine rotation speed is equal to or lower than the predetermined rotation speed so that the bypass passage opening / closing valve is closed when the engine rotation speed exceeds the predetermined rotation speed; characterized in that the (claim 1).

In this invention, specifically, the following configuration is preferable.
(1) A volume portion (A1> A0) having a passage sectional area (A1) larger than a passage sectional area (A0) of the intake passage is installed between the throttle valve outlet and the intake manifold of the intake passage. (Claim 2).
(2) The intake passage has an intake passage length (L) between the throttle valve outlet and the intake manifold inlet, and a ratio (L / D) between the intake passage length (L) and the inner diameter (D). Is 2.0 or more ((L / D) ≧ 2.0) (Claim 3).

In this invention, preferably, an in-cylinder pressure sensor for detecting an in-cylinder pressure of the engine is provided, and the controller is based on the in-cylinder pressure detection value from the in-cylinder pressure sensor, and the tubular inner pressure to open the bypass passage on-off valve is configured to control the bypass channel opening and closing valve to close the bypass passage on-off valve when exceeding a certain pressure (claim 4).

  According to the present invention, the throttle valve is configured so that the intake passage volume (V) from the throttle valve outlet of the intake passage to the intake valve forms a large volume portion having a volume 1.3 times or more the stroke volume (Vh). A volume portion (A1> A0) having a passage sectional area (A1) larger than the passage sectional area (A0) of the intake passage is installed between the outlet and the intake manifold (Claim 2), or the throttle valve outlet and the intake manifold The intake passage length (L) between the manifold inlet and the manifold inlet is formed to be a large volume that is at least twice as long as the intake passage inner diameter (D) (Claim 3). Even during throttle operation (partial load operation), even if the opening of the throttle valve decreases, the air-fuel mixture accumulated in the large volume portion is replenished into the cylinder as the piston descends during the intake stroke of the piston. Become It is possible to reduce the negative pressure in the intake passage.

Accordingly, it is possible to reduce the negative pressure as described above and to perform the pump in the intake stroke with a very simple and low-cost means without setting a special device for setting the volume of the intake passage as described above. Loss can be reduced and the thermal efficiency of the engine can be improved.
Further, the installation of the large volume portion promotes the mixing of air and fuel gas in the intake stroke, thereby forming a more uniform lean air-fuel mixture, thereby reducing the amount of NOx (nitrogen oxide) generated.

According to the present invention, there is further provided a bypass passage opening / closing valve that opens and closes a fuel gas bypass passage that is branched from the fuel gas passage to the gas mixer and connected to the intake passage on the downstream side of the throttle valve. Since the bypass passage opening / closing valve is opened and closed when the engine rotational speed including the start time is equal to or lower than the predetermined rotational speed, the bypass passage opening / closing valve is controlled to be closed when the engine rotational speed exceeds the predetermined rotational speed. (Claim 1 ) At the time of starting the engine, even if there is a time lag before the gas mixture is supplied from the gas mixer into the cylinder of the engine, the fuel gas is opened by opening the bypass passage opening / closing valve provided in the fuel gas bypass passage. Is supplied to the intake passage on the downstream side of the throttle valve and mixed with the intake air that has passed through the throttle valve. The air-fuel mixture is supplied into the cylinder, so that startability is improved.

Further, according to the present invention, based on the in-cylinder pressure detection value by the in-cylinder pressure sensor, when the in-cylinder pressure is equal to or lower than a predetermined pressure, the bypass passage opening / closing valve provided in the fuel gas bypass passage is opened, so that the fuel gas is Since it is supplied to the intake passage on the downstream side (Claim 4 ), even if the engine speed exceeds the fixed speed, the ignition and combustion of the engine become unstable due to engine misfire, etc., and the in-cylinder pressure is appropriate. If the value does not rise to the value, the bypass passage opening / closing valve opens to supply fuel gas to the intake passage downstream of the throttle valve and mix with the intake air that has passed through the throttle valve to form a rich mixture, By supplying the rich air-fuel mixture into the cylinder, the ignition and combustion of the engine can be further stabilized.

  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 a plan view showing a gas engine intake device according to a first embodiment of the present invention.
In FIG. 1, 100 is an engine (gas engine), 4 is a cylinder of the engine 100 (6 cylinders in this example), and 5 is a crankshaft. Reference numeral 1 denotes an intake manifold, 3 denotes an intake branch pipe that connects the intake manifold 1 and each cylinder 4, and an intake valve that connects the intake branch pipe 3 and each cylinder 4 has an intake valve (both not shown) ) Is provided.
6 is an exhaust manifold, 7 is an exhaust branch pipe connecting the exhaust intake manifold 6 and each cylinder 4, and an exhaust valve (all not shown) is connected to the exhaust port connecting the exhaust branch pipe 7 and each cylinder 4. ) Is provided. Reference numeral 8 denotes an exhaust pipe connected to the exhaust outlet of the exhaust manifold 6.

Reference numeral 2 denotes an intake pipe connected to the intake manifold. The intake pipe 2 generates an air cleaner 12 for air purification, and a mixture of air purified by the air cleaner 12 and fuel gas from the fuel gas pipe 30. A gas mixer 11 and a throttle valve 10 for controlling the flow rate of the air-fuel mixture are sequentially installed from the upstream side.
22 is an engine speed detector for detecting the engine speed of the engine 100, 23 is a load detector for detecting a load (engine output) of the engine 100, 20 is a controller, and the controller 20 is the engine speed detector. Based on the detected value of the engine speed inputted from the engine 22 and the detected value of the engine load inputted from the load detector 23, the opening degree of the throttle valve 10 is adjusted to an opening degree suitable for the engine speed and the engine load. It comes to control.

The present invention relates to the improvement of the intake passage from the gas mixer 11 to the intake manifold 1 in the intake device having the above basic configuration.
That is, in FIG. 1, reference numeral 21 denotes an additional volume portion, which is installed between the outlet of the throttle valve 10 and the intake manifold 1 in the intake pipe 2. The additional volume portion 21 is formed to have a large volume with a passage sectional area S1 larger than the passage sectional area A0 of the intake pipe 2 (A1> A0).
In the first embodiment, the volume of the intake passage (intake passage) from the outlet of the throttle valve 10 to the intake valve (not shown) through the intake manifold 1 and each intake branch pipe 3 is provided by the installation of the additional volume portion 21. The volume (V) is formed so that the ratio (V / Vh) between the intake passage volume V and the engine stroke volume Vh is 1.3 or more (V / Vh ≧ 1.3).

This configuration is based on the following grounds.
That is, as described above, during partial load operation of the engine 100, the opening degree of the throttle valve 10 is reduced to a small value (FIG. 9A). The intake negative pressure between the intake valves is increased, the intake pump loss (pumping loss) is increased, and the thermal efficiency of the engine is lowered as shown in FIG. 9C.
However, if the volume of the intake passage (intake passage volume) V including the intake pipe 2 from the throttle valve 10 outlet to the intake valve is larger than a certain value, the air-fuel mixture accumulated in the large volume portion during the intake stroke is increased. As the piston descends, it is replenished into the cylinder 4 and the negative pressure in the intake passage is reduced.

FIG. 5 shows the relationship between the ratio (V / Vh) between the intake passage volume V and the engine stroke volume Vh and the ratio of intake pump loss (intake pumping loss) to Pmi (indicated mean effective pressure). The relationship between A) and the rate of increase in thermal efficiency is obtained based on the results of engine experiments.
As apparent from FIG. 5, when V / Vh is increased by ΔV from 1.3 to V / Vh is 2.4, the ratio of the pump loss of the intake air to Pmi is saturated on the decrease side, and the thermal efficiency is increased. The rate is saturated on the increasing side.
Therefore, if V / Vh is 1.3 or more (V / Vh ≧ 1.3), it can be said that the effect of reducing intake pump loss (intake pumping loss) becomes remarkable.

FIG. 2 is a plan configuration diagram (corresponding to FIG. 1) showing an intake device for a gas engine according to a second embodiment of the present invention.
In the second embodiment, instead of the additional volume portion 21 in the first embodiment, the intake passage length L between the outlet of the throttle valve 10 and the intake manifold 1 is changed to the intake passage length L. A large-volume intake passage is formed so that the ratio (L / D) to the inner diameter D of the intake pipe 2 is 2.0 or more ((L / D) ≧ 2.0).
In the second embodiment, (L / D) ≧ 2.0 as described above, and the ratio (V) between the intake passage volume V and the engine stroke volume Vh, as in the first embodiment. / Vh) is 1.3 or more.

  According to the first and second embodiments described above, the intake passage volume V from the throttle valve 10 outlet of the intake passage to the intake valve (not shown) is not less than 1.3 times the stroke volume Vh, preferably 2 as shown in FIG. In the first embodiment, the passage sectional area S1 larger than the passage sectional area S0 of the intake pipe 2 is provided between the outlet of the throttle valve 10 and the intake manifold 1 so as to form a large volume portion having a volume of four times or more. (S1> S0), or in the second embodiment, the intake passage length L between the throttle valve 10 outlet and the intake manifold 1 inlet is at least twice the inner diameter D of the intake pipe 2 In the intake stroke of the piston, even if the opening of the throttle valve 10 becomes small during low load and low rotation operation (partial load operation) including when starting the engine, In the large volume part Wait fuel mixture becomes a to be replenished into the cylinder 4 along with the descent of the piston, it is possible to reduce the negative pressure in the intake passage.

B1 in FIG. 6B is an in-cylinder pressure diagram based on the detected value of the in-cylinder pressure of the gas engine according to the present invention, and B2 is an enlarged view of the intake stroke portion in B1. As apparent from B2 of the figure, in contrast to the in-cylinder pressure change P0 in the prior art, in the present invention, the negative pressure is reduced as in the in-cylinder pressure change P1, and the negative work (pump work) is reduced by ΔL. Has been.
As a result, as shown in FIG. 6A, the pump loss B1 in the present invention is reduced from the pump loss B0 in the prior art, and the thermal efficiency A1 of the engine in the present invention is higher than A0 in the prior art.

Therefore, according to the first and second embodiments described above, the volume V of the intake passage is set as described above, and it is possible to provide the above-mentioned by a very simple and low-cost means without providing a special device. Thus, the negative pressure can be reduced and the pump loss in the intake stroke can be reduced. As a result, the thermal efficiency of the engine can be improved.
Further, the installation of the large volume portion promotes the mixing of air and fuel gas in the intake stroke of the engine, and can form a more uniform lean air-fuel mixture. As in the first and second embodiments, high thermal efficiency can be maintained while reducing the amount of NOx (nitrogen oxide) generated.

FIG. 3 is a plan configuration diagram (corresponding to FIG. 1) showing an intake device for a gas engine according to a third embodiment of the present invention.
In this third embodiment, a fuel gas bypass pipe 25 branched from the fuel gas pipe 30 to the gas mixer 11 and connected to the intake pipe 2 downstream of the throttle valve 10, and the fuel gas bypass pipe 25 A bypass passage opening / closing valve 26 for opening and closing the pipe is provided.
22 is an engine speed detector that detects the engine speed of the engine 100, 23 is a load detector that detects a load (engine output) of the engine 100, and 24 is an in-cylinder pressure sensor that detects the in-cylinder pressure of the engine 100. It is.
Reference numeral 20 denotes a controller, based on the detected value of the engine speed inputted from the engine speed detector 22 and the detected value of the engine load inputted from the load detector 23, as in the prior art shown in FIG. In addition to the function of controlling the opening of the throttle valve 10 to an opening suitable for the engine speed and the engine load, the following function is provided.

FIG. 4 is a control block diagram of the controller 20 in the third embodiment.
In FIG. 4, the detected value of the engine speed from the engine speed detector 22 is input to the engine speed comparing unit 201 of the controller 20, and the detected value of the engine cylinder pressure from the cylinder pressure sensor 24 is An in-cylinder pressure comparison unit 201 of the controller 20 is input.
Reference numeral 202 denotes a gas valve switching rotational speed setting unit that opens the bypass passage opening / closing valve 26 and supplies the fuel gas from the fuel gas pipe 30 to the intake pipe 2 downstream of the throttle valve 10 through the fuel gas bypass pipe 25. A fixed rotational speed is set as an upper limit rotational speed for the operation. When the predetermined rotational speed is exceeded, the bypass passage opening / closing valve 26 is closed.
In the engine speed comparison unit 201, the detected value of the engine speed is compared with a constant speed that is the upper limit speed set in the gas valve switching speed setting unit 202, and the comparison result (rotation) Number deviation) is input to the gas valve switching determination unit 205.

Reference numeral 204 denotes a gas valve switching cylinder pressure setting unit which opens the bypass passage on-off valve 26 and supplies fuel gas to the intake pipe 2 downstream of the throttle valve 10 through the fuel gas bypass pipe 25. A constant in-cylinder pressure that is an internal pressure is set. When this constant cylinder pressure is exceeded, the bypass passage opening / closing valve 26 is closed.
The in-cylinder pressure comparison unit 203 compares the detected value of the in-cylinder pressure with a constant in-cylinder pressure that is the upper limit in-cylinder pressure set in the gas valve switching in-cylinder pressure setting unit 204, and compares the comparison. The result (in-cylinder pressure deviation) is input to the gas valve switching determination unit 205.

  In the gas valve switching determination unit 205, the engine speed including the start of the engine 100 in the engine speed comparison result (rotational speed deviation) is equal to or lower than the predetermined speed and the in-cylinder pressure comparison result. When the in-cylinder pressure of the engine 100 is equal to or less than the predetermined in-cylinder pressure in (in-cylinder pressure deviation), the bypass passage opening / closing valve is opened, the engine speed exceeds the constant speed, and the in-cylinder pressure is When the pressure in the cylinder exceeds a certain cylinder pressure, it is determined to close the bypass passage opening / closing valve 26, and the bypass passage opening / closing valve 26 is controlled to open / close according to the determination result.

  According to the third embodiment, the bypass passage opening / closing valve 26 that opens and closes the fuel gas bypass pipe 25 branched from the fuel gas pipe 30 to the gas mixer 11 and connected to the intake pipe 2 downstream of the throttle valve 10 is provided. And the controller 20 opens the bypass passage opening / closing valve 26 when the engine speed, including when the engine 100 is started, is equal to or less than the predetermined rotation speed, and closes the bypass passage opening / closing valve 26 when the engine speed exceeds the predetermined rotation speed. Since the bypass passage opening / closing valve 26 is controlled to open and close, even if there is a time lag until the gas mixture 11 is supplied from the gas mixer 11 into the cylinder 4 of the engine 100 when the engine 100 is started, the fuel gas bypass pipe 25 Fuel gas is supplied to the intake pipe 2 downstream of the throttle valve 10 by opening the provided bypass passage opening / closing valve 26. Is, by being mixed with the intake air passing through the throttle valve 10, rich mixture is formed will be supplied into the cylinder 4, which startability is improved by.

  Further, according to the third embodiment, based on the in-cylinder pressure detected by the in-cylinder pressure sensor 24, when the in-cylinder pressure is equal to or lower than a predetermined pressure, the bypass passage opening / closing valve 26 is opened to allow the fuel gas to flow through the throttle valve 10. Since the fuel is supplied to the intake passage on the downstream side, even when the engine speed exceeds the fixed speed, ignition and combustion of the engine 100 become unstable due to misfire of the engine 100 and the in-cylinder pressure reaches an appropriate value. If the valve does not rise, the bypass passage opening / closing valve 26 is opened to supply fuel gas to the intake pipe 2 downstream of the throttle valve 10 and mix with the intake air that has passed through the throttle valve 10 to form a rich mixture. By supplying the gas into the cylinder 4, ignition and combustion of the engine 100 can be further stabilized.

  According to the present invention, in a gas engine configured to supply a mixture of fuel gas and air from a gas mixer to a cylinder of an engine through a throttle valve, a part with a very simple and low-cost structure is provided. It is possible to provide an intake device for a gas engine that can increase the thermal efficiency of the engine by reducing the pump loss of the intake during load operation and further improve the startability.

1 is a plan configuration diagram illustrating an intake device for a gas engine according to a first embodiment of the present invention. It is a plane block diagram which shows the intake device of the gas engine which concerns on 2nd Example of this invention. It is a plane block diagram which shows the intake device of the gas engine which concerns on 3rd Example of this invention. It is a control block diagram by the controller 20 in the third embodiment. It is explanatory drawing of the effect in the said 1st-2nd Example. It is a diagram (the 1) for explanation of engine performance in the 1st-the 2nd example. It is a diagram (the 2) for explanation of engine performance in the 1st-the 2nd example. It is a figure corresponding to FIG. 1 which shows a prior art. It is an explanatory diagram of engine performance in the prior art.

DESCRIPTION OF SYMBOLS 1 Intake manifold 2 Intake pipe 3 Intake branch pipe 4 Cylinder 10 Throttle valve 11 Gas mixer 20 Controller 21 Additional volume part 22 Engine speed detector 23 Load detector 24 In-cylinder pressure sensor 25 Fuel gas bypass pipe 30 Fuel gas pipe 100 Engine (Gas engine)

Claims (4)

A mixture of fuel gas and air generated by a gas mixer is supplied to an engine cylinder through an intake manifold and an intake valve through a throttle valve that is installed in the intake passage and controls the flow rate of the mixture. A gas engine intake device configured,
The intake passage volume (V) from the throttle valve outlet of the intake passage to the intake valve is a ratio (V / Vh) of 1.3 or more of the intake passage volume (V) and the engine stroke volume (Vh). formed so as to (V / Vh ≧ 1.3),
Furthermore, a fuel gas bypass passage branched from the fuel gas passage to the gas mixer and connected to the intake passage downstream of the throttle valve, and a bypass passage opening / closing valve for opening and closing the fuel gas bypass passage are provided, Opens and closes the bypass passage on-off valve so that the bypass passage on-off valve is opened when the engine speed, including when the engine is started, is equal to or less than a predetermined number of revolutions. An intake device for a gas engine, comprising a controller for controlling .   A volume portion (A1> A0) having a passage cross-sectional area (A1) larger than a passage cross-sectional area (A0) of the intake passage is installed between the throttle valve outlet and the intake manifold of the intake passage. The gas engine intake device according to claim 1, wherein:   The intake passage has an intake passage length (L) between the throttle valve outlet and the intake manifold inlet, and the ratio (L / D) of the intake passage length (L) to the inner diameter (D) is 2. The intake device for a gas engine according to claim 1, wherein the intake device is formed to be 0 or more ((L / D) ≥2.0). An in-cylinder pressure sensor for detecting an in-cylinder pressure of the engine is provided, and the controller opens the bypass passage on-off valve when the in-cylinder pressure is equal to or lower than a predetermined pressure based on a detected in-cylinder pressure value from the in-cylinder pressure sensor. 2. The intake device for a gas engine according to claim 1, wherein the bypass passage on-off valve is controlled to close the bypass passage on-off valve when the in-cylinder pressure exceeds a certain pressure .

Images