JP6091024B2 - Internal combustion engine and control method for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine that burns fuel gas and generates combustion gas, and a control method for the internal combustion engine.

  For marine two-stroke engines, it is effective to switch the fuel from heavy oil to natural gas in order to satisfy the SOx emission regulations set by IMO (International Maritime Organization). Patent Document 1 discloses a technique for eliminating the invasion of combustion gas into a gas system in a gas engine for high-pressure gas injection.

JP 2008-202550 A JP 2002-221037 A

  By the way, even in an engine that uses gas as fuel, in the case of a high-pressure gas injection system that directly injects gas into a cylinder, a large amount of NOx is generated by combustion. Therefore, it is necessary to take measures to reduce NOx contained in the exhaust gas. Patent Document 1 discloses a technique related to a gas engine for high-pressure gas injection, but does not disclose measures for reducing NOx contained in exhaust gas.

  Patent Document 2 discloses a technique related to an internal combustion engine that performs EGR (Exhaust Gas Recirculation) for the purpose of reducing NOx. In Patent Document 2, in order to recirculate exhaust gas, a passage is provided between an exhaust passage of the internal combustion engine and an air supply passage downstream of the slot valve, and an EGR valve for controlling the flow rate is provided in the passage. Thus, conventionally, in order to perform EGR, dedicated passages and valves are provided separately from the internal combustion engine body, and the number of members must be increased or a space for installing the members must be secured. It was.

  The present invention has been made in view of such circumstances, and it is possible to recirculate exhaust gas with a small number of members and to control NOx contained in the exhaust gas and control of the internal combustion engine. It aims to provide a method.

In order to solve the above problems, the internal combustion engine and the control method for the internal combustion engine of the present invention employ the following means.
That is, the internal combustion engine according to the present invention communicates between the exhaust port for discharging the combustion gas generated by the combustion of the fuel gas from the combustion chamber to the outside, the exhaust valve for opening and closing the exhaust port, and the scavenging chamber and the combustion chamber. And a scavenging port that is opened and closed by a reciprocating piston, and a control unit that controls opening and closing of the exhaust valve so that the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber when the scavenging port starts to open. After the scavenging port is closed, the exhaust port is closed by the exhaust valve.

According to this invention, the combustion gas generated by the combustion of the fuel gas is discharged from the combustion chamber to the outside through the exhaust port when the exhaust valve is in the open state. On the other hand, when the exhaust valve is closed, the pressure in the combustion chamber is relatively higher than when the exhaust valve is open. Therefore, if the transition timing from the closed state to the open state of the exhaust valve is delayed, the pressure drop timing of the combustion chamber can be delayed. Therefore, by controlling the opening and closing of the exhaust valve so that the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber when the scavenging port starts to open, the pressure in the combustion chamber remains after the scavenging port has started opening. A period higher than the room pressure occurs. As a result, the combustion gas flows from the combustion chamber to the scavenging chamber via the scavenging port. Therefore, when air is scavenged from the scavenging chamber to the combustion chamber, combustion gas containing CO ₂ is also mixed, so that the CO ₂ concentration in the combustion chamber is increased and NOx generated by combustion is reduced.

  In the above invention, the apparatus further includes a first detection unit that detects the pressure in the scavenging chamber and a second detection unit that detects the pressure in the combustion chamber, and the control unit calculates a difference between the pressure in the scavenging chamber and the pressure in the combustion chamber. Based on this, the opening and closing of the exhaust valve may be controlled.

  According to this invention, the exhaust valve is opened and closed based on the difference between the pressure in the scavenging chamber and the pressure in the combustion chamber. For example, it is determined whether or not the difference between the pressure in the scavenging chamber and the pressure in the combustion chamber is a value within the target range, and the exhaust valve is shifted from the closed state to the open state based on the determination result. As a result, the pressure drop timing of the combustion chamber can be adjusted based on the difference between the pressure in the scavenging chamber and the pressure in the combustion chamber, and the combustion gas can be reliably flowed from the combustion chamber to the scavenging chamber via the scavenging port.

  In the above invention, the control unit calculates a gas amount of the combustion gas flowing from the combustion chamber to the scavenging chamber through the scavenging port after the scavenging port is opened, and controls opening and closing of the exhaust valve based on the calculated gas amount. May be.

According to this invention, after the scavenging port is opened, the amount of combustion gas flowing from the combustion chamber to the scavenging chamber via the scavenging port is calculated, and the exhaust valve is opened and closed based on the calculated gas amount. Depending on the gas volume of the combustion gas flowing from the combustion chamber into the transfer chamber, and amount of CO ₂ in the combustion gas flowing into the scavenging chamber, to change the amount of CO ₂ that is scavenged into the combustion chamber, to control the opening and closing of the exhaust valve Thus, NOx generated by combustion can be adjusted. The amount of combustion gas flowing from the combustion chamber to the scavenging chamber via the scavenging port is calculated based on, for example, the difference between the scavenging chamber pressure and the combustion chamber pressure, the scavenging port opening area, and the scavenging port opening time. The

  Further, the control method for an internal combustion engine according to the present invention includes an exhaust port that discharges combustion gas generated by combustion of fuel gas to the outside from the combustion chamber, an exhaust valve that opens and closes the exhaust port, a scavenging chamber, and a combustion chamber. A control method for an internal combustion engine comprising a scavenging port that communicates with each other and is opened and closed by a reciprocating piston so that when the scavenging port starts to open, the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber The method further includes the step of opening and closing the exhaust valve, and further comprising the step of closing the exhaust port by the exhaust valve after the scavenging port is closed.

According to this invention, the combustion gas generated by the combustion of the fuel gas is discharged from the combustion chamber to the outside through the exhaust port when the exhaust valve is in the open state. On the other hand, when the exhaust valve is closed, the pressure in the combustion chamber is relatively higher than when the exhaust valve is open. Therefore, if the transition timing from the closed state to the open state of the exhaust valve is delayed, the pressure drop timing of the combustion chamber can be delayed. Therefore, by controlling the opening and closing of the exhaust valve so that the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber when the scavenging port starts to open, the pressure in the combustion chamber remains after the scavenging port has started opening. A period higher than the room pressure occurs. As a result, the combustion gas flows from the combustion chamber to the scavenging chamber via the scavenging port. Therefore, when air is scavenged from the scavenging chamber to the combustion chamber, the combustion gas containing CO ₂ is also mixed, so that the CO ₂ concentration in the combustion chamber increases and NOx generated by combustion is reduced.

  According to the present invention, exhaust gas can be recirculated with a small number of members, and NOx contained in the exhaust gas can be reduced.

It is a lineblock diagram showing the gas engine system concerning a 1st embodiment of the present invention. It is a flowchart which shows operation | movement of the gas engine which concerns on 1st Embodiment of this invention. It is the graph which shows the relationship between an opening area and time, and the graph which shows the relationship between a pressure and time. It is a schematic block diagram which shows the gas engine which concerns on 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the gas engine which concerns on 2nd Embodiment of this invention.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The gas engine system 1 according to the present embodiment includes a gas engine including a gas engine body 6 and a scavenging chamber 10 and the like, a supercharger 9 connected to the gas engine, and the like.

  The gas engine is, for example, a marine high-pressure gas injection type gas engine, and includes an engine body 6 including a combustion chamber (not shown), an injection valve 7 for injecting fuel gas into the combustion chamber of the engine body 6, and a static engine. A pressure exhaust pipe 8 and a scavenging chamber 10 are provided.

  The engine body 6 has, for example, a cylinder and a piston (not shown), and rotational work is taken out by a connecting rod and a crankshaft connected to the piston. A combustion chamber is formed in the cylinder.

  The supply pipe 12 connects the compressor 5 and a fuel tank (not shown), and the supply pipe 14 connects the compressor 5 and the injection valve 14. The fuel gas is injected into the combustion chamber of the engine body 6 through the supply pipes 12 and 14 and the compressor 5 from the injection valve 7 at a high pressure (for example, 30 MPa).

  An exhaust valve 21 is provided at an exhaust port formed in the engine body 6, and the exhaust valve 21 opens and closes the exhaust port. The exhaust port discharges the exhaust gas generated by the combustion of the fuel gas from the combustion chamber to the outside. The exhaust port is connected to the exhaust pipe 15. The static pressure exhaust pipe 8 is connected to the engine body 6 via the exhaust pipe 15 and is connected to the inlet side of the turbine section 9 a of the supercharger 9 via the exhaust pipe 16. On the other hand, a scavenging port 11 formed in, for example, a cylinder liner of the engine body 6 is connected to a scavenging chamber 10, and the scavenging chamber 10 is connected to a compressor unit 9 b of the supercharger 9 via an air supply pipe 19. Yes.

  The turbocharger 9 is driven by exhaust gas (combustion gas) guided from the engine body 6 through the exhaust pipe 15, the static pressure exhaust pipe 8 and the exhaust pipe 16, and is driven by the turbine section 9a. A compressor unit 9b that pumps outside air to the engine body 6 and a casing (not shown) that is provided between and supports the turbine unit 9a and the compressor unit 9b are configured as main elements. .

  A rotating shaft 9c having one end projecting toward the turbine section 9a and the other end projecting into the compressor section 9b is inserted into the casing. One end portion of the rotating shaft 9c is attached to a turbine disk (not shown) of a turbine rotor (not shown) constituting the turbine portion 6a, and the other end portion of the rotating shaft 9c is a compressor portion. It is attached to a hub (not shown) of a compressor impeller (not shown) constituting 6b.

  The exhaust gas that has passed through the turbine section 9a is guided to a funnel (not shown) through an exhaust pipe 17 connected to the outlet side of the turbine section 9a, and then discharged out of the ship.

  A silencer (not shown) is arranged in the air supply pipe 18 connected to the inlet side of the compressor unit 9b, and outside air that has passed through the silencer is guided to the compressor unit 9b. Further, an air cooler (not shown) and a surge tank (not shown) are connected in the middle of the air supply pipe 19 connected to the outlet side of the compressor unit 9b, and passed through the compressor unit 9b. The outside air is supplied to the scavenging chamber 10 connected to the engine body 6 after passing through the air cooler and the surge tank.

  In the scavenging chamber 10, air that is introduced from the atmosphere and boosted by the supercharger 9 is used for the next combustion cycle. This new air is introduced into the combustion chamber through the scavenging port 11 when the exhaust valve 21 is opened and the pressure in the combustion chamber is lowered in the latter stage of expansion of the combustion gas in the combustion chamber, and the scavenging port 11 is opened by movement of the piston.

  Thereafter, the exhaust valve 21 is closed, and then the air in the combustion chamber and the combustion gas of the previous cycle accumulated in the combustion chamber without being completely discharged due to the rise of the piston are compressed, and near the top dead center of the piston, the injection valve 7 The fuel gas injected from the combustion chamber burns to generate combustion gas. Then, the piston is pushed downward by the expansion of the combustion gas. Thus, when the exhaust valve 21 is in the closed state, as shown in FIG. 3, the pressure in the combustion chamber is relatively higher than when the exhaust valve 21 is in the open state.

  When the exhaust valve 21 is opened, the combustion gas is discharged from the combustion chamber to the outside through the exhaust port. In the present embodiment, when the scavenging port 11 starts opening, the opening / closing of the exhaust valve 21 is controlled so that the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber 10. For example, as shown by the broken line in the upper graph of FIG. 3, by delaying the transition timing of the exhaust valve 12 from the closed state to the open state, the timing at which the combustion gas is discharged is delayed, As shown by the broken line in the graph, the pressure drop timing of the combustion chamber is delayed.

  In the conventional gas engine, the timing at which the exhaust valve 21 opens after the piston is pushed downward by the expansion of the combustion gas is different from the present embodiment, and before the scavenging port 11 starts opening, the exhaust port is completely opened. To be opened. Therefore, when the scavenging port 11 starts opening, the pressure in the combustion chamber is lower than the pressure in the scavenging chamber 10.

  That is, as shown by the solid line in the upper graph of FIG. 3, the exhaust valve 21 is opened, and the combustion gas is discharged to the outside. As shown by the solid line in the lower graph of FIG. After the pressure in the scavenging chamber 10 is reduced to the same level or lower, the scavenging port 11 is opened. As a result, when the scavenging port 11 is opened, new air is introduced from the scavenging chamber 10 into the fuel chamber, and scavenging necessary for the next cycle is performed.

On the other hand, in this embodiment, after the scavenging port 11 starts opening, the exhaust port is completely opened. The combustion chamber pressure is higher than the pressure in the scavenging chamber 10 during the opening timing of the scavenging port 11 and for a while immediately thereafter. Therefore, when the scavenging port 11 is opened, the combustion gas having a high CO ₂ concentration flows backward from the combustion chamber into the scavenging chamber 10 via the scavenging port 11.

  Then, after the pressure in the combustion chamber decreases to the same or lower than the pressure in the scavenging chamber 10, new air is introduced from the scavenging chamber 10 into the fuel chamber, and scavenging necessary for the next cycle is performed.

The timing of opening and closing the exhaust valve 21 of the present embodiment is based on the measurement of the fluctuation of the pressure in the combustion chamber and the fluctuation of the pressure in the scavenging chamber 10 during the development of the gas engine, and based on the measurement results during the actual operation of the gas engine. The exhaust valve 21 may be opened and closed at the timing. _{Alternatively} , the combustion chamber pressure P _cyl and the scavenging chamber pressure P _s may be measured during actual operation of the gas engine.

For example, as shown in FIG. 1, the pressure sensor 13 is provided in the scavenging chamber 10, the pressure sensor 13 measures the scavenging chamber 10 in the pressure P _s. Further, a pressure sensor 20 is provided in the engine body 6, and the pressure sensor 20 measures a combustion chamber pressure P _cyl of the engine body 6. Control unit 3 is, for example, an arithmetic and control circuit, and the scavenging chamber pressure P _s which is measured by the pressure sensor 13, obtains the combustion chamber pressure P _cyl measured by the pressure sensor 20, the scavenging chamber pressure P _s combustion Based on the indoor pressure P _cyl , the opening and closing of the exhaust valve 21 is controlled.

Hereinafter, the opening / closing control of the exhaust valve 21 based on the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl will be described with reference to FIG. 2.

First, the scavenging chamber pressure P _s measured by the pressure sensor 13 and the combustion chamber pressure P _cyl measured by the pressure sensor 20 are acquired (step S1). Next, the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl is calculated, and it is determined whether or not (P _cyl −P _s ) is within a predetermined target range (step S2).

When the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl is not within the target range, as the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl is within the target range, the opening timing of the exhaust valve 21 Is adjusted (step S3). On the other hand, when it is within the target range, it is determined whether or not the processing related to the opening / closing control of the exhaust valve 21 has been completed (step S4).

When the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl is within the target range and the processing related to the opening / closing control of the exhaust valve 21 is not completed, such as before the exhaust valve 21 is shifted to the fully open state, step S1 is performed again. Returning to step 4, the open / close control process is continued. On the other hand, after the exhaust valve 21 shifts to the fully open state or when the piston reaches the bottom dead center, the opening / closing control process is terminated. As described above, the opening / closing control of the exhaust valve 21 is performed based on the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl , whereby the pressure drop timing of the combustion chamber can be adjusted and combustion is performed via the scavenging port 11. The combustion gas can surely flow from the chamber to the scavenging chamber 10.

As described above, according to the present embodiment, the new air introduced into the fuel chamber is also mixed with the combustion gas containing CO ₂ , so that the concentration of CO _{2 in} the combustion chamber increases and NOx generated by combustion is increased. Is reduced. Further, exhaust gas as combustion gas is recirculated between the engine body 6 and the scavenging chamber 10. Therefore, in order to perform exhaust gas recirculation, it is not necessary to provide a dedicated passage or valve separately from the engine body 6 or the scavenging chamber 10, and it is necessary to increase the number of members or to secure a space for installing the members. Absent. Therefore, exhaust gas recirculation can be performed with a smaller number of members and a smaller space than in the past. Further, since the fuel is not oil fuel but gas fuel, soot is not generated in the combustion gas and combustion gas containing soot is not returned to the scavenging chamber.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
In FIG. 4, the gas engine is represented by a schematic diagram that is closer to an actual shape, but the basic configuration is the same as that in FIG. 1. In the first embodiment, as shown in FIG. 3, the opening and closing of the exhaust valve 21 is controlled according to the difference between the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl , but in the second embodiment, the internal EGR is controlled. The opening / closing of the exhaust valve 24 is controlled according to the amount.

  As shown in FIG. 4, the gas engine 2 includes a combustion chamber 22 and a scavenging chamber 23 formed inside the gas engine. The gas engine is a marine high-pressure gas injection type gas engine, for example, an engine body including a combustion chamber 22, an injection valve (not shown) for injecting fuel gas into the combustion chamber 22 of the engine body, and static pressure exhaust. A trachea (not shown) and a scavenging chamber 23 are provided.

  The engine body has, for example, a cylinder and a piston 29 (not shown), and rotational work is taken out by a connecting rod and a crankshaft connected to the piston 29. A combustion chamber 22 is formed in the cylinder.

  The fuel gas is injected into the combustion chamber 22 of the engine body at a high pressure (for example, 30 MPa) from an injection valve via a supply pipe and a compressor (not shown).

  An exhaust valve 24 is provided in an exhaust port 25 formed in the engine body, and the exhaust valve 24 opens and closes the exhaust port 25. The exhaust port 25 discharges the exhaust gas generated by the combustion of the fuel gas from the combustion chamber 22 to the outside. The exhaust port 25 is connected to an exhaust pipe (not shown). A scavenging port 27 formed in the cylinder liner of the engine body is connected to a scavenging chamber 23, and the scavenging chamber 23 is connected to, for example, a compressor unit of a supercharger via an air supply pipe.

  In the scavenging chamber 23, air that is introduced from the atmosphere and boosted by the supercharger is used for the next combustion cycle. This new air passes through the scavenging port 27 and passes through the combustion chamber 22 when the exhaust valve 24 opens and the pressure in the combustion chamber 22 is lowered in the latter stage of expansion of the combustion gas in the combustion chamber 22 and the scavenging port 27 is opened by movement of the piston 29. To be introduced.

  Thereafter, the exhaust valve 24 is closed, and then the air in the combustion chamber 22 and the combustion gas of the previous cycle accumulated in the combustion chamber 22 without being completely discharged are compressed by the rising of the piston 29, and the top dead center of the piston 29 is compressed. In the vicinity, the fuel gas injected from the injection valve burns to generate combustion gas. Then, the piston 29 is pushed downward by the expansion of the combustion gas. Thus, when the exhaust valve 24 is in the closed state, as shown in FIG. 3, the pressure in the combustion chamber 22 is relatively higher than when the exhaust valve 24 is in the open state.

  When the exhaust valve 24 is opened, the combustion gas is discharged from the combustion chamber 22 through the exhaust port 25 to the outside. In the present embodiment, when the scavenging port 27 starts to open, the opening and closing of the exhaust valve 24 is controlled so that the pressure in the combustion chamber 22 becomes higher than the pressure in the scavenging chamber 23. For example, as shown by the broken line in the upper graph of FIG. 3, by delaying the transition timing of the exhaust valve 24 from the closed state to the open state, the timing at which the combustion gas is discharged is delayed, and the lower part of FIG. As shown by the broken line in the graph, the pressure drop timing of the combustion chamber 22 is delayed.

For example, after the scavenging port 27 starts to open, the exhaust port 25 is fully opened. During the opening timing of the scavenging port 27 and for a while immediately thereafter, the pressure in the combustion chamber 22 is higher than the pressure in the scavenging chamber 23. Therefore, when the scavenging port 27 is opened, the combustion gas having a high CO ₂ concentration flows back from the combustion chamber 22 into the scavenging chamber 23 through the scavenging port 27 in the direction of arrow A in FIG.

Then, after the pressure in the combustion chamber 22 has decreased to the same level as or lower than the pressure in the scavenging chamber 23, new air is introduced from the scavenging chamber 23 into the fuel chamber 22 and scavenging necessary for the next cycle is performed. . At this time, the new air introduced into the fuel chamber 22, the combustion gas containing CO ₂ is also to be mixed, CO ₂ concentration in the combustion chamber 22 is increased, NOx is reduced to occur in the combustion The That is, in the present embodiment, exhaust gas that is combustion gas is recirculated between the combustion chamber 22 and the scavenging chamber 23. Therefore, in order to perform exhaust gas recirculation, it is not necessary to provide a dedicated passage or valve separately from the combustion chamber 22 or the scavenging chamber 23, and it is necessary to increase the number of members or to secure a space for installing the members. Absent.

The timing of opening and closing of the exhaust valve 24 of the present embodiment is based on the measurement of the fluctuation in the pressure in the combustion chamber and the fluctuation in the scavenging chamber 10 during the development of the gas engine, and based on the measurement results during the actual operation of the gas engine. The exhaust valve 24 may be opened and closed at the timing. _{Alternatively} , the combustion chamber pressure P _cyl and the scavenging chamber pressure P _s may be measured during actual operation of the gas engine.

For example, as shown in FIG. 4, a pressure sensor 28 provided in the scavenging chamber 23, the pressure sensor 28 measures the scavenging chamber pressure P _s. Further, a pressure sensor 26 is provided in the combustion chamber 22, and the pressure sensor 26 measures the pressure P _cyl in the combustion chamber. Control unit 30 is, for example, an arithmetic and control circuit, and the scavenging chamber pressure P _s which is measured by the pressure sensor 28, obtains the combustion chamber pressure P _cyl measured by the pressure sensor 26, the scavenging chamber pressure P _s combustion Based on the indoor pressure P _cyl , the opening / closing of the exhaust valve 24 is controlled.

Then, as described in the first embodiment, based on the difference of the combustion chamber pressure P _cyl scavenging chamber pressure P _s, it may control the opening and closing of the exhaust valve 24. Unlike the first embodiment, the opening / closing of the exhaust valve 24 may be controlled based on the amount of combustion gas flowing from the combustion chamber 22 to the scavenging chamber 23. Hereinafter, the opening / closing control of the exhaust valve 24 based on the amount of combustion gas (hereinafter also referred to as “internal EGR amount”) will be described with reference to FIG. 5.

First, the scavenging chamber pressure P _s measured by the pressure sensor 28 and the combustion chamber pressure P _cyl measured by the pressure sensor 26 are acquired (step S11). Next, the internal EGR amount is calculated based on the scavenging chamber pressure P _s and the combustion chamber pressure P _cyl (step S12). The internal EGR amount is calculated based on, for example, the difference between the combustion chamber pressure P _cyl and the scavenging chamber pressure P _s , the opening area of the scavenging port 27, and the opening time of the scavenging port 27.

なお、燃焼室内ガス密度ρ_ｇは、掃気温度、掃気圧力、燃料投入量などから推定して求められる。 Gas flow rate u _g, as equation 1 below, the difference between the combustion chamber pressure P _cyl and scavenging chamber pressure P _s, is calculated from the combustion chamber gas density [rho _g.

Note that the combustion chamber gas density [rho _g is scavenging temperature, scavenging pressure, determined by estimating the like the fuel input.

Then, the mass flow rate [kg / s] is calculated from the gas flow rate u _g and the opening area of the scavenging port 27. The internal EGR amount is calculated by integrating the calculated mass flow rate with the opening time in which the combustion chamber pressure P _cyl is larger than the scavenging chamber pressure P _s .

  After the internal EGR amount is calculated, it is determined whether or not the calculated internal EGR amount is within a predetermined target range (step S13). When the internal EGR amount is not within the target range, the opening timing of the exhaust valve 24 is adjusted so that the internal EGR amount is within the target range (step S14).

The target range of the internal EGR amount is, for example, a flow rate determined such that the NOx emission amount becomes an oxygen concentration that satisfies a specified value. For example, when the amount of internal EGR is insufficient and the amount of NOx emission is large, the amount of NOx emission can be reduced by increasing the amount of internal EGR and increasing the concentration of CO ₂ contained in the air supplied to the combustion chamber. On the other hand, when it is within the target range, it is determined whether or not the processing related to the opening / closing control of the exhaust valve 24 has been completed (step S15).

  When the internal EGR amount is within the target range and the process related to the opening / closing control of the exhaust valve 24 is not completed, such as before the exhaust valve 24 is shifted to the fully open state, the process returns to step S1 and the opening / closing control process is continued. . On the other hand, after the exhaust valve 24 shifts to the fully open state or when the piston 27 reaches the bottom dead center, the opening / closing control process is terminated.

  As described above, according to the present embodiment, the NOx emission amount can be reduced to the target value by adjusting the opening / closing timing of the exhaust valve 24 and setting the internal EGR amount within a predetermined target range.

DESCRIPTION OF SYMBOLS 1 Gas engine system 2 Gas engine 3,30 Control part 5 Compressor 6 Gas engine main body 7 Injection valve 8 Static pressure exhaust pipe 9 Supercharger 9a Turbine part 9b Compressor part 9c Rotating shaft 10, 23 Scavenging chamber 11, 27 Scavenging port 13 , 20, 26, 28 Pressure sensor 21, 24 Exhaust valve 22 Combustion chamber 25 Exhaust port 29 Piston

Claims (6)

An exhaust port for discharging the combustion gas generated by the combustion of the fuel gas to the outside from the combustion chamber;
An exhaust valve for opening and closing the exhaust port;
A scavenging port that communicates between the scavenging chamber and the combustion chamber and is opened and closed by a reciprocating piston;
A control unit that controls opening and closing of the exhaust valve so that the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber when the scavenging port starts opening;
With
An internal combustion engine in which the exhaust port is closed by the exhaust valve after the scavenging port is closed.   An exhaust port for discharging the combustion gas generated by the combustion of the fuel gas to the outside from the combustion chamber;
  An exhaust valve for opening and closing the exhaust port;
  A scavenging port that communicates between the scavenging chamber and the combustion chamber and is opened and closed by a reciprocating piston;
  A control unit that controls opening and closing of the exhaust valve so that the pressure in the combustion chamber becomes higher than the pressure in the scavenging chamber when the scavenging port starts opening;
With
  An internal combustion engine in which the scavenging port starts to open after the exhaust valve starts to open. A first detector for detecting the pressure in the scavenging chamber;
A second detector for detecting the pressure in the combustion chamber;
Further comprising
The internal combustion engine according to claim 1 or 2 , wherein the control unit controls opening and closing of the exhaust valve based on a difference between a pressure in the scavenging chamber and a pressure in the combustion chamber. The control unit calculates a gas amount of the combustion gas flowing from the combustion chamber to the scavenging chamber through the scavenging port after the scavenging port is opened, and based on the calculated gas amount, the exhaust valve The internal combustion engine according to claim 1 or 2 , which controls opening and closing of the engine. An exhaust port that discharges combustion gas generated by the combustion of the fuel gas from the combustion chamber to the outside, an exhaust valve that opens and closes the exhaust port, a scavenging chamber and the combustion chamber communicate with each other, and is opened and closed by a reciprocating piston. An internal combustion engine control method comprising:
Opening and closing the exhaust valve so that the pressure in the combustion chamber is higher than the pressure in the scavenging chamber when the scavenging port starts opening;
A control method for an internal combustion engine, further comprising a step of closing the exhaust port by the exhaust valve after the scavenging port is closed.   An exhaust port that discharges combustion gas generated by the combustion of the fuel gas from the combustion chamber to the outside, an exhaust valve that opens and closes the exhaust port, a scavenging chamber and the combustion chamber communicate with each other, and is opened and closed by a reciprocating piston. An internal combustion engine control method comprising:
  Opening and closing the exhaust valve so that the pressure in the combustion chamber is higher than the pressure in the scavenging chamber when the scavenging port starts opening;
  A control method for an internal combustion engine, further comprising: starting the opening of the scavenging port after the exhaust valve starts to open.

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