JP4801611B2 - engine - Google Patents

Description

The present invention provides an EGR means for recirculating a part of exhaust gas discharged from a combustion chamber to fresh air sucked into the combustion chamber;
The present invention relates to an engine provided with fuel gas mixing means for mixing fuel gas supplied from a fuel gas passage with fresh air flowing through an intake passage.

Conventionally, in an engine in which a gaseous fuel gas such as natural gas is supplied to an intake passage as described above (hereinafter sometimes referred to as a “gas engine”), one of exhaust gases discharged from a combustion chamber to an exhaust passage. There is a case where an EGR means is provided for recirculating the part to fresh air sucked into the combustion chamber through an EGR path having one end connected to the exhaust path.
As a gas engine provided with such EGR means, the other end side of the EGR path is connected to an intake path, and exhaust gas is supplied from the exhaust path to fresh air flowing through the intake path through the EGR path (for example, Patent Documents). 1), or the other end of the EGR path is connected to a fuel gas path, and exhaust gas is supplied to the fuel gas flowing through the fuel gas path from the exhaust path through the EGR path. One that supplies gas to an intake passage (see, for example, Patent Document 2) is known.

Japanese Patent Laid-Open No. 11-107996 JP 2005-282666 A

In the gas engines described in Patent Documents 1 and 2 as described above, the fuel gas mixing means for mixing the fuel gas supplied from the fuel gas passage to the fresh air flowing through the intake passage is like the venturi mixer. A predetermined ratio of fuel gas is supplied from the fuel gas passage to the fresh air flowing through the passage. Therefore, when the exhaust gas is supplied to the fresh gas that flows through the intake passage or the fuel gas that flows through the fuel gas passage by the EGR means as described above, for example, during the low load operation or the cold operation, the exhaust gas is actively When the recirculation amount (hereinafter referred to as EGR amount) is reduced or when the EGR amount fluctuates unexpectedly due to pressure fluctuations in the exhaust passage, etc., it is formed by the fuel gas supply means and is taken into the combustion chamber. The equivalence ratio of the mixture of the fuel gas and the air may fluctuate and problems such as knocking and misfire may occur.
The equivalent ratio means a value obtained by dividing the fuel-air ratio of the air-fuel mixture by the theoretical fuel-air ratio. That is, in an air-fuel mixture, the smaller the fuel component, the lower the equivalent ratio of the air-fuel mixture, and the lower the air, the higher the equivalent ratio of the air-fuel mixture.

In particular, as in the engine described in Patent Document 1, when exhaust gas is supplied to fresh air flowing through the intake passage, the amount of air contained in fresh air increases as the EGR amount decreases. Regardless, since a predetermined amount of fuel gas is mixed with the fresh air by the fuel gas mixing means, the equivalence ratio of the air-fuel mixture sucked into the combustion chamber becomes excessively low, and misfires, shutdown, etc. occur. There is a case.
On the other hand, when supplying exhaust gas to the fuel gas flowing through the fuel gas path as in the engine described in Patent Document 2, the fuel component contained in the fuel gas flowing through the fuel gas path increases as the EGR amount decreases. Although a predetermined amount of fuel gas is mixed with fresh air by the fuel gas mixing means, the equivalent ratio of the air-fuel mixture sucked into the combustion chamber becomes excessively high and knocking occurs. Occurrence of fuel or deterioration of fuel consumption may occur.

  Therefore, in the gas engine described in Patent Document 1, the EGR rate that is the ratio of the EGR amount to the fresh air flowing through the intake passage is detected, and the equivalent ratio of the air-fuel mixture formed in the intake passage based on the detection result Is configured to control the supply amount of the fuel gas so as to be a predetermined value, but the device configuration for the control is complicated and expensive, and is not practical.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to recirculate a part of exhaust gas discharged from a combustion chamber to an exhaust passage to fresh air sucked into the combustion chamber in a gas engine. Technology that can stabilize the equivalence ratio of the air-fuel mixture sucked into the combustion chamber with a simple configuration and avoid problems such as knocking and misfire even when the means is provided and the amount of exhaust gas supplied by the EGR means is changed. Is to provide

The gas engine according to the present invention for achieving the above object includes an EGR means for recirculating a part of the exhaust gas discharged from the combustion chamber to fresh air sucked into the combustion chamber;
And maintaining the amount of fuel gas supplied from the fuel gas passage with respect to the amount of fresh air flowing through the intake passage at a constant rate, the fuel gas supplied from the fuel gas passage to the fresh air flowing through the intake passage The first characteristic configuration is such that the EGR means supplies the exhaust gas extracted from the exhaust passage to both the intake passage and the fuel gas passage. It is in the point which is comprised.

According to the first characteristic configuration, since the exhaust gas taken out from the exhaust passage is supplied to both the intake passage and the fuel gas passage by the EGR means, for example, even when the EGR amount fluctuates according to the operating state, the fuel gas It is possible to avoid problems such as knocking and misfire by suppressing fluctuations in the equivalence ratio of the mixture of fuel gas and air formed by the supply means and sucked into the combustion chamber.
That is, as the EGR amount to both the intake passage and the fuel gas passage decreases, the amount of air contained in fresh air increases due to the decrease in the EGR amount in the intake passage, whereas in the fuel gas passage, The amount of the fuel component contained in the fuel gas increases due to the decrease in the EGR amount. Therefore, the fuel gas mixing means mixes the fuel gas with the increased amount of the fuel component with the fresh air with the increased amount of air to form the mixed gas, so that the equivalence ratio of the mixed gas varies almost. It will be stable without any problems.

  According to a second characteristic configuration of the gas engine of the present invention, in addition to the first characteristic configuration, the fuel gas mixing means has a venturi portion formed by reducing the diameter of the intake passage, and the tip of the fuel gas passage. The nozzle part connected to the part is configured by a venturi mixer in which the venturi part is opened.

  According to the second characteristic configuration, the fuel gas mixing means can be configured by the venturi mixer. That is, the venturi mixer generates a pressure drop in accordance with the flow rate of the fresh air when the fresh air flowing through the intake passage passes through the venturi section at a high speed. The fuel gas in the passage is sucked out into the intake passage through the nozzle part, and a predetermined ratio of fuel gas can be mixed with the fresh air to form an air-fuel mixture. The equivalence ratio of the gas can be stabilized.

  According to a third characteristic configuration of the gas engine according to the present invention, in addition to any of the first to second characteristic configurations, the EGR means can adjust an EGR amount to fresh air taken into the combustion chamber. It is in the point which is comprised.

  According to the third characteristic configuration, for example, during low load operation or cold operation, in order to stably burn the air-fuel mixture in the combustion chamber, the EGR amount is adjusted to a decreasing side, or conversely, In the case of high load operation or warm operation, in order to suppress the generation of NOx in the combustion chamber, the EGR amount can be adjusted to the increase side, and further, the EGR amount is positively adjusted in this way However, it is possible to avoid problems such as knocking and misfire by maintaining an equivalent ratio of the air-fuel mixture sucked into the combustion chamber.

  According to a fourth characteristic configuration of the gas engine of the present invention, in addition to any of the first to third characteristic configurations, the EGR means includes a main EGR path having one end connected to the exhaust path, An intake side EGR path connecting the other end side of the main EGR path and the intake path, a fuel gas side EGR path connecting the other end side of the main EGR path and the fuel gas path, and the main EGR path It is in the point comprised with the provided EGR valve.

  According to the fourth characteristic configuration, exhaust gas is recirculated from the main EGR path to the intake path side through the intake side EGR path, and exhaust gas is recirculated from the main EGR path to the fuel gas path side through the fuel gas side EGR path. In this case, the EGR amount to both the intake passage and the fuel gas passage can be adjusted only by providing a single EGR valve in the main EGR passage. Even when the opening degree of the EGR valve is adjusted to change the EGR amount to both the intake passage and the fuel gas passage, the equivalence ratio of the air-fuel mixture sucked into the combustion chamber is maintained at an appropriate level. Can avoid problems such as knocking and misfire.

Embodiments of an engine according to the present invention will be described with reference to the drawings.
The engine 100 shown in FIG. 1 includes EGR means X that recirculates a part of the exhaust gas E discharged from the combustion chamber 1 to fresh air I sucked into the combustion chamber 1, and fresh air I that flows through the intake passage 2. It is configured as a so-called gas engine provided with a fuel gas mixing means Y for mixing the fuel gas G supplied from the fuel gas passage 21, and its basic configuration will be described below.

  Although not shown, the engine 100 includes an intake passage 2 connected to a combustion chamber 1 defined by an inner surface of a cylinder and a top surface of a piston via an intake valve 4 and an exhaust valve 5. And an exhaust passage 3 connected to each other.

The fresh air I flowing through the intake passage 2 is appropriately supercharged by a supercharger or the like, and then mixed with the fuel gas G of natural gas city gas by the fuel gas mixing means Y to become an air-fuel mixture, Intake into the combustion chamber 1.
The air-fuel mixture sucked into the combustion chamber 1 as fresh air I is compressed by the piston ascending, and then ignited and ignited by spark ignition, compression ignition, etc., and combusted and expanded to push down the piston and output shaft power. To do.
Further, the exhaust gas E generated in the combustion chamber 1 is discharged to the exhaust passage 3 as the piston rises.

In the fuel gas mixing means Y, the fuel gas G adjusted to a constant pressure by the governor 22 is supplied to the fuel gas passage 21, and the fuel gas G in the fuel gas passage 21 is supplied to the intake passage 2.
Further, the fuel gas mixing means Y has a venturi portion 24 formed by reducing the diameter of the intake passage 2 and a venturi formed by opening a nozzle portion 23 connected to the tip end portion of the fuel gas passage 21 to the venturi portion 24. It consists of a mixer.
That is, the fuel gas mixing means Y generates a pressure drop when the fresh air I flowing through the intake passage 2 passes through the venturi section 24 at a high speed, and supplies the fuel gas from the fuel gas passage 21 using this pressure drop. The fuel gas G thus supplied is supplied to the fresh air I flowing through the intake passage 2 through the nozzle portion 23 to form an air-fuel mixture in the intake passage 2.
Further, the fuel gas mixing means Y configured as a venturi mixer in this way causes a pressure drop in the venturi section 24 in accordance with the flow velocity of the fresh air I. Gas G will be mixed.
In addition to the fuel component supplied from the upstream side of the fuel gas passage 21 to the fuel gas G supplied to the intake passage 2 by the fuel gas mixing means Y, the fuel gas side EGR passage 13 to the fuel gas passage 21 will be described later. In some cases, the supplied exhaust gas E is included, and in addition to the air supplied from the upstream side of the intake passage 2 to the fresh air I flowing through the intake passage 2, the intake passage 2 from the intake side EGR passage 12 described later. In some cases, the exhaust gas E supplied to is included.
Even in such a case, the fuel gas mixing means Y makes a certain ratio of the total amount of the fuel gas G including the fuel component and the exhaust gas E to the total amount of the fresh air I including the air and the exhaust gas E. Will be maintained.

  When the EGR means X recirculates a part of the exhaust gas E discharged from the combustion chamber 1 to the fresh air I sucked into the combustion chamber 1, the equivalent ratio of the air-fuel mixture sucked into the combustion chamber as the fresh air I In order to suppress this fluctuation, the exhaust gas E taken out from the exhaust passage 3 is supplied to both the intake passage 2 and the fuel gas passage 21.

  That is, the EGR means X includes a main EGR path 11 having one end side connected to the exhaust path 3, an intake side EGR path 12 connecting the other end side of the main EGR path 11 and the intake path 2, and a main EGR path 11. And the fuel gas side EGR path 13 connecting the other end side of the fuel gas path 21 and the exhaust gas E flowing into the main EGR path 11 from the exhaust path 3 to the intake side EGR path 12 and the fuel gas side The exhaust gas E is divided into the EGR passage 13 and supplied to the intake passage 2 and the fuel gas passage 21 through the EGR passages 12 and 13, respectively.

  Further, the main EGR path 11 is provided with an EGR valve 15 capable of adjusting the amount of exhaust gas flowing through the main EGR path 11, and the main EGR path 11 is adjusted by adjusting the opening degree of the EGR valve 15. Thus, the exhaust gas amount E supplied to the intake passage 2 and the fuel gas passage 21 through the intake side EGR passage 12 and the fuel gas side EGR passage 13 can be adjusted as a total EGR amount.

In the intake passage 2, the EGR amount with respect to the intake passage 2 decreases as the total EGR amount in the EGR means X decreases, and the ratio of the air contained in the fresh air I taken into the combustion chamber 1 is increased. Will increase.
On the other hand, in the fuel gas passage 21, the EGR amount for the fuel gas passage 21 decreases as the total EGR amount in the EGR means X decreases, and is supplied to the fresh air I sucked into the combustion chamber 1. The ratio of the fuel component contained in the fuel gas G will increase.
Accordingly, in the fuel gas mixing means Y, the total amount of the fuel gas G including the fuel component and the exhaust gas E is maintained at a constant ratio with respect to the total amount of the fresh air I including the air and the exhaust gas E. Even when the total EGR amount in the means X is decreased, the fuel gas G having the increased fuel component ratio is mixed with the fresh air I having the increased air ratio at a constant rate, so that it is generated as a result. The equivalence ratio of the air-fuel mixture is maintained at a substantially stable value (for example, the equivalence ratio φ = 0.66) without fluctuation.
Therefore, the equivalence ratio of the air-fuel mixture sucked into the combustion chamber 1 becomes substantially stable regardless of the fluctuation of the total EGR amount, so that problems such as knocking due to excessive increase of the equivalent ratio and misfire due to excessive decrease can be avoided. Has been.

Further, the ECU 30 is configured to control the total EGR amount in accordance with changes in the load state and the warm-up state.
That is, the ECU 30 reduces the opening of the EGR valve 15 and reduces the total EGR amount in order to maintain stable combustion of the air-fuel mixture in the combustion chamber 1 during low load operation or cold operation immediately after startup. Adjust to a relatively small amount.
On the other hand, the ECU 30 increases the opening degree of the EGR valve 15 to relatively reduce the total EGR amount in order to suppress the generation of NOx during a high load operation or a warm operation where the warm-up is sufficiently advanced. Adjust to a large amount.
Even when the total EGR amount is positively changed in this way, the equivalence ratio of the air-fuel mixture generated by the fuel gas mixing means Y and sucked into the combustion chamber 1 becomes stable.

  Further, the intake passage 2 is provided with a throttle valve 26. By adjusting the opening of the throttle valve 26 and adjusting the amount of fresh air I taken into the combustion chamber 1, the engine is adjusted. Output can be changed.

Further, in the intake passage 2, the downstream side of the throttle valve 26 becomes negative pressure due to the suction force of the piston in the intake stroke.
Therefore, the exhaust gas E can be satisfactorily supplied to the intake passage 2 through the intake side EGR passage 12 by connecting the intake side EGR passage 12 downstream of the throttle valve 26.
If the back pressure generated in the exhaust passage 3 in the exhaust stroke is sufficiently larger than the pressure in the intake passage 2, the exhaust gas E can be easily recirculated from the exhaust passage 3 to the intake passage 2. The intake side EGR path 12 may be connected to the upstream side of the throttle valve 26 in the intake path 2.

Further, in the intake passage 2, the fuel gas mixing means Y is disposed on the upstream side of the throttle valve 26. In other words, the air-fuel mixture generated by the fuel gas mixing means Y passes through the throttle valve 26 and the mixing is promoted.
The fuel gas mixing means Y is not a venturi mixer, but a gas control valve capable of adjusting the amount of fuel gas supplied to the intake passage 2 is controlled to map the air-fuel ratio of the fuel gas G to the fresh air I. Further, the fuel gas mixing means Y may be arranged on the downstream side of the throttle valve 26. Further, with this configuration, even when the EGR amount fluctuates unexpectedly due to pressure fluctuations in the exhaust passage 3, etc., the EGR means X takes the exhaust gas E extracted from the exhaust passage 3 into the intake passage 2 and the fuel gas. With the configuration of supplying both to the passage 21, it is possible to satisfactorily suppress fluctuations in the equivalence ratio of the air-fuel mixture sucked into the combustion chamber 1 as fresh air I. Further, if the fuel gas mixing means Y is arranged as close as possible to the combustion chamber 1 in the intake passage 2 on the downstream side of the throttle valve 26, the residual fuel in the intake passage 2 is exhausted during the valve overlap of the next cycle. Blowing to 3 can also be suppressed.

  In the above embodiment, the natural gas city gas is used as the fuel gas G. However, as the fuel gas G, a gaseous fuel other than the natural gas city gas can be used.

  The present invention provides an EGR means for recirculating a part of the exhaust gas discharged from the combustion chamber to the exhaust passage to fresh air sucked into the combustion chamber, and even when changing the supply amount of the exhaust gas by the EGR means, The configuration can stabilize the equivalence ratio of the air-fuel mixture sucked into the combustion chamber, and can be effectively used as a gas engine that can avoid problems such as knocking and misfire.

Schematic showing an embodiment of an engine according to the present invention

Explanation of symbols

1: Combustion chamber 2: Intake path 3: Exhaust path 11: Main EGR path 12: Intake side EGR path 13: Fuel gas side EGR path 15: EGR valve 21: Fuel gas path 22: Governor 23: Nozzle section 24: Venturi section 26: Throttle valve X: EGR means Y: Fuel gas mixing means I: Fresh air G: Fuel gas E: Exhaust gas

Claims (4)

EGR means for returning a part of the exhaust gas discharged from the combustion chamber to fresh air sucked into the combustion chamber;
And maintaining the amount of fuel gas supplied from the fuel gas passage with respect to the amount of fresh air flowing through the intake passage at a constant rate, the fuel gas supplied from the fuel gas passage to the fresh air flowing through the intake passage An engine comprising a fuel gas mixing means for mixing
An engine in which the EGR means is configured to supply exhaust gas extracted from an exhaust passage to both the intake passage and the fuel gas passage.   The fuel gas mixing means has a venturi portion formed by reducing the diameter of the intake passage, and is constituted by a venturi mixer in which a nozzle portion connected to a tip portion of the fuel gas passage is opened to the venturi portion. The engine according to claim 1.   The engine according to claim 1 or 2, wherein the EGR means is configured to be able to adjust an EGR amount to fresh air taken into the combustion chamber.   The EGR means includes a main EGR path having one end connected to the exhaust path, an intake side EGR path connecting the other end side of the main EGR path and the intake path, and the other end side of the main EGR path; The engine according to any one of claims 1 to 3, comprising a fuel gas side EGR path connecting the fuel gas path and an EGR valve provided in the main EGR path.

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