JP2020037923A - Control method, control device, and engine system - Google Patents

Abstract

To prevent blockage by fuel residue of an auxiliary combustion chamber.SOLUTION: A control method of a dual fuel engine including a main combustion chamber in which a gas fuel and a liquid fuel are burned, and an auxiliary combustion chamber connected to the main combustion chamber and provided with an injection device for the gas fuel, includes a liquid fuel injection process for injecting the liquid fuel in a case when fuel residue is accumulated in the auxiliary combustion chamber in burning the liquid fuel.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control method, a control device, and an engine system.

  For example, Patent Literature 1 discloses an engine that communicates with a main combustion chamber and includes a sub-chamber (sub-combustion chamber) into which liquid fuel is injected. In the configuration including such a sub chamber, fuel is injected into the sub chamber during the compression stroke, and the fuel is ignited by air flowing from the main combustion chamber into the sub chamber.

JP 2006-132478 A

  By the way, in recent years, in order to reduce the amount of emission of NOx in an engine, a dual fuel engine that can use both a liquid fuel and a gaseous fuel such as natural gas has been devised. In such a dual fuel engine, it is conceivable to provide a liquid fuel injection device in the auxiliary combustion chamber.

  In this case, every time the liquid fuel is burned in the main combustion chamber, fine solid particulate fuel residues are generated. Therefore, when the liquid fuel is operated continuously for a long time, the exhaust gas repeatedly flows into and out of the sub-combustion chamber. Since the sub combustion chamber and the main combustion chamber are in communication, the fuel residue flows into the sub combustion chamber and the opening communicating the sub combustion chamber with the main combustion chamber and accumulates. When the fuel residue accumulates in the sub-combustion chamber and the opening, the sub-combustion chamber may be blocked by the fuel residue.

  The present invention has been made in view of the above-described problems, and has as its object to prevent clogging of a sub-combustion chamber with fuel residues.

The present invention provides, as first means according to a control method for solving the above problems, a main combustion chamber in which gaseous fuel and liquid fuel are burned, and a liquid fuel injection device connected to the main combustion chamber. And a sub-combustion chamber provided with a control method for a dual fuel engine,
A liquid fuel injection step of injecting the liquid fuel when fuel residue accumulates in the sub-combustion chamber during the combustion of the liquid fuel is adopted.

  As a second means according to the control method, a configuration is adopted in which the first means includes a prediction step of predicting the accumulation of fuel residues in the sub-combustion chamber.

  As a third means according to a control method, in the second means, a configuration is adopted in which, in the prediction step, accumulation of fuel residue is predicted based on a pressure in the sub-combustion chamber.

  As a fourth means according to a control method, in the third means, the prediction step employs a configuration in which fuel residue accumulation is predicted based on a pressure difference between the sub combustion chamber and the main combustion chamber. I do.

  As a fifth means according to the control method, in the above third or fourth means, a configuration is adopted in which the pressure in the sub-combustion chamber is predicted from a pressure history.

  As a sixth means according to a control method, in the first means, the dual fuel engine is mounted on a ship, and the liquid fuel injection step shifts to a NOx regulation region based on a position of the ship. In such a case, the configuration is adopted.

  As first means according to the control device, a dual fuel including a main combustion chamber in which gaseous fuel and liquid fuel are burned, and a sub-combustion chamber connected to the main combustion chamber and provided with the liquid fuel injection device An engine control device adopts a configuration in which, when fuel residue is deposited in the sub-combustion chamber during combustion of the liquid fuel, the liquid fuel is injected into the sub-combustion chamber.

  As first means according to the engine system, a dual fuel including a main combustion chamber in which gaseous fuel and liquid fuel are burned, and a sub-combustion chamber connected to the main combustion chamber and provided with the liquid fuel injection device A configuration including an engine and the control device described in claim 8 is adopted.

  According to the present invention, when the fuel residue accumulates in the sub-combustion chamber, the fuel residue can be discharged to the main combustion chamber by injecting the liquid fuel into the sub-combustion chamber. This can prevent the sub-combustion chamber from being blocked by the fuel residue.

It is a sectional view of an engine system concerning one embodiment of the present invention. 1 is a partially enlarged view of an engine system according to an embodiment of the present invention. It is a block diagram of a control part concerning one embodiment of the present invention. 4 is a flowchart illustrating a control method of a control unit according to an embodiment of the present invention.

  Hereinafter, an engine system according to the present invention will be described with reference to the drawings.

  The engine system 100 of the present embodiment is mounted on a ship such as a large tanker, for example, and includes an engine 1, a supercharger 200, and a control unit 300 (control device) as shown in FIG. . In the present embodiment, the turbocharger 200 is regarded as an auxiliary machine and is described as being separate from the engine 1 (main engine). However, the supercharger 200 and the liquid fuel injection device 400 can be configured as a part of the engine 1.

  The engine 1 is a multi-cylinder uniflow scavenging diesel engine (two-stroke engine), and has a dual fuel engine having a gas operation mode for burning gaseous fuel such as natural gas and a diesel operation mode for burning liquid fuel such as heavy oil. It is. In the gas operation mode, only gaseous fuel may be burned. Such an engine 1 includes a frame 2, a cylinder portion 3, a piston 4, an exhaust valve unit 5, a piston rod 6, a crosshead 7, a swing pipe 8, a connecting rod 9, a crank angle sensor 10, a crankshaft 11, a scavenging reservoir 12, an exhaust reservoir 13, and an air cooler 14.

  The frame 2 is a strength member that supports the entire engine 1, and houses a crosshead 7 and a connecting rod 9. In the frame 2, a crosshead pin 7a, which will be described later, of the crosshead 7 can reciprocate inside.

  The cylinder section 3 has a cylinder liner 3a, a cylinder head 3b, a cylinder jacket 3c, and a sub-chamber member 3d. The cylinder liner 3a is a cylindrical member, and a sliding surface with the piston 4 is formed inside. A space surrounded by the inner peripheral surface of the cylinder liner 3a and the piston 4 is a combustion chamber R1 (main combustion chamber). The inside of the combustion chamber R1 is a substantially cylindrical space, and a flow is formed in which the gas inside swirls around the center of the combustion chamber R1 in a certain direction. In the following description, the swirling direction of the gas in the combustion chamber R1 is described as a swirl direction. In addition, a plurality of scavenging ports S are formed below the cylinder liner 3a. The scavenging port S is an opening arranged along the peripheral surface of the cylinder liner 3a, and communicates the scavenging chamber R2 inside the cylinder jacket 3c with the inside of the cylinder liner 3a. The cylinder liner 3a is provided with a plurality of gaseous fuel injection valves (not shown) for injecting gaseous fuel. The cylinder head 3b is a lid member provided at the upper end of the cylinder liner 3a. An exhaust port H is formed at the center of the cylinder head 3b in plan view, and is connected to the exhaust reservoir 13. The cylinder head 3b is provided with a plurality of liquid fuel injection valves (not shown) for injecting liquid fuel. The cylinder jacket 3c is provided between the frame 2 and the cylinder liner 3a, is a cylindrical member into which the lower end of the cylinder liner 3a is inserted, and has a scavenging chamber R2 formed therein. The scavenging chamber R2 of the cylinder jacket 3c is connected to the scavenging reservoir 12.

  As shown in FIG. 2, the sub chamber member 3d is a member that is inserted into and fixed to the cylinder head 3b to form the sub combustion chamber RX. The sub chamber member 3d and the cylinder head 3b are formed with a communication hole RY communicating the sub chamber member 3d and the cylinder head 3b. The communication hole RY is provided between the sub-combustion chamber RX and the combustion chamber R1, and is set smaller than the inner diameter of the sub-combustion chamber RX and the combustion chamber R1. Part of the combustion gas generated in the combustion chamber R1 flows into the sub-combustion chamber RX through the communication hole RY. This combustion gas contains dusty fuel residues generated when the liquid fuel is burned. Further, an injection port of the liquid fuel injection device 400 is provided in the sub combustion chamber RX.

  The piston 4 has a substantially cylindrical shape, is connected to a piston rod 6 described later, and is disposed inside the cylinder liner 3a. Further, a piston ring (not shown) is provided on the outer peripheral surface of the piston 4, and a gap between the piston 4 and the cylinder liner 3a is sealed by the piston ring. The piston 4 slides in the cylinder liner 3a together with the piston rod 6 due to a change in pressure in the combustion chamber R1.

  The exhaust valve unit 5 has an exhaust valve 5a, an exhaust valve housing 5b, and an exhaust valve driving unit 5c. The exhaust valve 5a is provided inside the cylinder head 3b, and closes an exhaust port H in the cylinder unit 3 by an exhaust valve driving unit 5c. The exhaust valve housing 5b is a cylindrical housing that houses the end of the exhaust valve 5a. The exhaust valve driving unit 5c is an actuator that moves the exhaust valve 5a in a direction along the stroke direction of the piston 4.

  The piston rod 6 is an elongated member having one end connected to the piston 4 and the other end connected to the crosshead pin 7a. The end of the piston rod 6 is fixed to a crosshead pin 7a, and is connected so that the connecting rod 9 can swing.

  The crosshead 7 has a crosshead pin 7a and a guide shoe 7b. The crosshead pin 7a is a columnar member that movably connects the piston rod 6 and the connecting rod 9 to each other.

  The guide shoe 7b is a member that rotatably supports the crosshead pin 7a, and moves on a guide rail (not shown) along the stroke direction of the piston 4 with the crosshead pin 7a. When the guide shoe 7b moves along the guide rail, the rotation of the crosshead pin 7a and the movement of the crosshead pin 7a in directions other than the linear direction along the stroke direction of the piston 4 are restricted. Such a crosshead 7 transmits the linear motion of the piston 4 to the connecting rod 9.

  Returning to FIG. 1, the swing pipe 8 is a pipe that connects the crosshead pin 7a and a lubricating oil supply pump (not shown). The swing tube 8 is swingable, and has one end moving in the vertical direction together with the crosshead pin 7a and the other end being fixed with the lubricating oil supply pump.

  As shown in FIG. 1, the connecting rod 9 is an elongated member connected to the crosshead pin 7 a and connected to the crankshaft 11. The connecting rod 9 converts the linear motion of the piston 4 transmitted to the crosshead pin 7a into a rotary motion. The crank angle sensor 10 is a sensor for measuring the crank angle of the crankshaft 11, and transmits a crank pulse signal for calculating the crank angle to the control unit 300.

  The crankshaft 11 is a long member connected to the connecting rods 9 provided in the cylinder, and is rotated by the rotational motion transmitted by the respective connecting rods 9 to transmit power to, for example, a propeller. The scavenging reservoir 12 is provided between the cylinder jacket 3c and the supercharger 200, and the air pressurized by the supercharger 200 flows therein. Further, the scavenging reservoir 12 is provided with an air cooler 14 therein. The exhaust reservoir 13 is a tubular member connected to the exhaust port H of each cylinder and connected to the supercharger 200. The gas discharged from the exhaust port H is temporarily stored in the exhaust reservoir 13 and supplied to the supercharger 200 in a state in which pulsation is suppressed. The air cooler 14 is a device that cools the air inside the scavenging reservoir 12.

  The supercharger 200 is a device that pressurizes air sucked from a compressor suction port (not shown) by a turbine rotated by gas discharged from the exhaust port H and supplies the air to the combustion chamber R1.

  The control unit 300 is a computer that controls a fuel supply amount and the like based on an operation or the like by a boat operator. As shown in FIG. 3, the control unit 300 includes a pressure history calculation unit 301, a communication hole blockage determination unit 302, a pressure difference calculation unit 303, an auxiliary combustion chamber deposition determination unit 304, and a pilot injection unit 305. ing. The pressure history calculation unit 301 calculates the pressure in the sub-combustion chamber RX from the pressure data acquired from the in-cylinder pressure sensor. The communication hole closing determination unit 302 compares the pressure of the sub-combustion chamber RX with a predetermined pressure threshold value, and determines whether or not a part or the whole of the communication hole RY is closed by the fuel residue. The pressure difference calculation unit 303 calculates a pressure difference between the combustion chamber R1 obtained from the in-cylinder pressure sensor and the calculated sub-combustion chamber RX. The sub-combustion chamber deposition determining unit 304 compares the pressure difference between the combustion chamber R1 and the sub-combustion chamber RX with a predetermined pressure difference threshold value, and determines whether fuel residue has accumulated in the sub-combustion chamber RX. judge.

  The liquid fuel injection device 400 is a device that is connected to a tank in which the liquid fuel is stored, and includes an injection valve provided at an outlet end of the pipe based on an instruction from the control unit 300. Liquid fuel injection device 400 injects liquid fuel into sub-combustion chamber RX.

  The engine system 100 is a device that ignites and explodes fuel injected from a fuel injection valve (not shown) into the combustion chamber R1 to slide the piston 4 in the cylinder liner 3a and rotate the crankshaft 11. is there. More specifically, after the fuel supplied to the combustion chamber R1 is mixed with the air flowing from the scavenging port S, the piston 4 moves toward the top dead center. Thus, in the case of the liquid fuel, the temperature rises in the combustion chamber R1 to vaporize and spontaneously ignite. In the case of gaseous fuel, the sub-combustion chamber RX is injected into the sub-combustion chamber RX by the piston 4 together with a small amount of pilot liquid fuel injected into the combustion chamber R1 when the piston 4 reaches the vicinity of the superior point. The mixture of liquid fuel and gaseous fuel in the RX is compressed and ignites. Then, the flame generated in the sub-combustion chamber RX propagates into the combustion chamber R1.

  Then, the fuel in the combustion chamber R1 ignites and expands rapidly, so that a pressure is applied to the piston 4 toward the bottom dead center. As a result, the piston 4 moves in the direction of the bottom dead center, the piston rod 6 moves with the piston 4, and the crankshaft 11 rotates via the connecting rod 9. Further, when the piston 4 is moved to the bottom dead center, pressurized air flows into the combustion chamber R1 from the scavenging port S. When the exhaust valve unit 5 is driven, the exhaust port H is opened, and the exhaust gas in the combustion chamber R1 is pushed out to the exhaust reservoir 13 by the pressurized air.

Next, a situation in which fuel residues accumulate in the sub-combustion chamber RX and the communication hole RY, and a control method of the control unit 300 will be described with reference to FIGS.
When the engine 1 is driven by the liquid fuel, the combustion gas also flows into the sub-combustion chamber RX communicating with the combustion chamber R1 through the communication hole RY shown in FIG. Since the communication hole RY functions as a throttle, the pressure in the sub-combustion chamber RX is lower than that of the combustion chamber R1 in normal times.
When the fuel residue contained in the combustion gas accumulates in the sub-combustion chamber RX and the communication hole RY, and the communication hole RY partially closes, the amount of the combustion gas flowing into the sub-combustion chamber RX decreases. The pressure in the sub-combustion chamber RX becomes smaller than in the case.
Further, when fuel residue accumulates in the sub-combustion chamber RX, the volume of the sub-combustion chamber RX decreases, so that the pressure in the sub-combustion chamber RX increases and the difference from the pressure in the combustion chamber R1 decreases.

  As shown in FIG. 4, the control unit 300 acquires the pressure of the combustion chamber R1 from the in-cylinder pressure sensor by the pressure history calculation unit 301 (step S1). And the control part 300 calculates the pressure history of the subcombustion chamber RX from the pressure of the combustion chamber R1 as a prediction process by the pressure history calculation part 301 (step S2). Next, as a prediction process, the control unit 300 uses the communication hole blockage determination unit 302 to compare whether the RX pressure in the sub-combustion chamber is equal to or higher than a pressure threshold (Step S3). When step S3 is NO, the control unit 300 causes the communication hole blocking determination unit 302 to determine that the communication hole is closed. Then, the control unit 300 causes the pilot injection unit 305 to inject liquid fuel into the sub-combustion chamber RX as a liquid fuel injection step (step S4). As a result, the pressure in the sub-combustion chamber RX increases, and the liquid fuel moves to the combustion chamber R1 via the communication hole RY, so that the fuel residue deposited in the communication hole RY is discharged to the combustion chamber R1. Is done.

  If step S3 is YES, the control unit 300 causes the pressure difference calculation unit 303 to calculate the pressure difference between the combustion chamber R1 and the sub-combustion chamber RX as a prediction process (step S5). Next, the control unit 300, as the sub-combustion chamber deposition determination unit 304, compares whether or not the calculated pressure difference is equal to or greater than a pressure difference threshold as a prediction process (Step S6). When step S6 is NO, the control unit 300 determines that the fuel residue has accumulated in the sub-combustion chamber RX by the sub-combustion chamber accumulation determining unit 304, and executes step S4. Thereby, the fuel residue deposited in the sub-combustion chamber RX is discharged to the combustion chamber R1 via the communication hole RY.

  According to the present embodiment, based on the pressure history of the sub-combustion chamber RX calculated by the pressure history calculation unit 301, the accumulation of the fuel residue in the sub-combustion chamber RX and the communication hole RY is detected, and the liquid fuel is detected. An injection process is performed. Accordingly, it is possible to prevent the injection of the gaseous fuel from being hindered by the accumulation of the fuel residue in the sub-combustion chamber RX and the communication hole RY.

  According to the present embodiment, the pressure history of the sub-combustion chamber RX is calculated as the prediction step. This makes it possible to predict the accumulation of the fuel residue without providing a pressure sensor in the sub-combustion chamber RX.

  In addition, the accumulation of the fuel residue in the communication hole RY is determined based on the pressure in the auxiliary combustion chamber RX, and the accumulation of the fuel residue in the auxiliary combustion chamber RX is determined based on the pressure difference between the combustion chamber R1 and the auxiliary combustion chamber RX. Has been determined. That is, by calculating the pressure history of the sub-combustion chamber RX, it is possible to determine in which of the communication hole RY and the sub-combustion chamber RX the fuel residue is deposited.

  The preferred embodiment of the present invention has been described with reference to the drawings, but the present invention is not limited to the above embodiment. The shapes, combinations, and the like of the constituent members shown in the above-described embodiments are merely examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

  In the above embodiment, the pressure history of the sub-combustion chamber RX is estimated, but the present invention is not limited to this. By providing a pressure sensor in the sub combustion chamber RX, the pressure history of the sub combustion chamber RX may be directly obtained. In this case, it is possible to obtain an accurate pressure value of the sub-combustion chamber RX, and it is possible to more accurately estimate the accumulation state of the fuel residue in the sub-combustion chamber RX and the communication hole RY.

  Further, in the above embodiment, the pressure history of the sub-combustion chamber RX is acquired, and the prediction step of predicting the accumulation of the fuel residue is performed, but the present invention is not limited to this. For example, a ship switches from liquid fuel to gaseous fuel when entering a region where NOx emission restrictions are imposed by a convention or the like. Therefore, immediately before shifting to the restricted area where the NOx emission restriction is imposed, that is, immediately before switching from the liquid fuel to the gaseous fuel (for example, about several minutes before) based on the ship's navigation plan or the ship's position information, A liquid fuel injection step may be performed.

  In addition, the control unit 300 may perform the liquid fuel injection step periodically, for example, once every 500 hours, during a long-time navigation with liquid fuel, without performing the prediction step. Note that the interval at which the liquid ejection process is performed may be longer or shorter than the above-described time if the interval is regular. Further, the control unit 300 may acquire an operation state such as the number of pistons of the engine and execute the liquid fuel injection process every predetermined number of pistons.

  The present invention is based on the premise that a low-pressure injection method is used as a method of injecting gaseous fuel. The low-pressure injection system includes a "liner injection system (providing a gas fuel injection valve on the side wall of the cylinder liner 3a)" and a "scavenging port injection system (providing a gas fuel injection valve near the scavenging port S)". It can be applied to any of the methods.

DESCRIPTION OF SYMBOLS 1 Engine 2 Frame 3 Cylinder part 3a Cylinder liner 3b Cylinder head 3c Cylinder jacket 4 Piston 5 Exhaust valve unit 5a Exhaust valve 5b Exhaust valve housing 5c Exhaust valve drive part 6 Piston rod 7 Crosshead 7a Crosshead pin 7b Guide shoe 8 Rocking tube 9 connecting rod 10 crank angle sensor 11 crankshaft 12 scavenging reservoir 13 exhaust reservoir 14 air cooler 100 engine system 200 supercharger 300 control unit 400 liquid fuel injector H exhaust port O outlet hole R1 combustion chamber R2 scavenging chamber S scavenging port

Claims (8)

A method for controlling a dual fuel engine including a main combustion chamber in which gaseous fuel and liquid fuel are burned, and a sub-combustion chamber connected to the main combustion chamber and provided with an injection device for the gaseous fuel,
A control method comprising the step of injecting the liquid fuel when fuel residue accumulates in the sub-combustion chamber during the combustion of the liquid fuel.   2. The control method according to claim 1, further comprising a prediction step of predicting fuel residue accumulation in the sub-combustion chamber.   3. The control method according to claim 2, wherein in the predicting step, the accumulation of the fuel residue is predicted based on the pressure in the sub-combustion chamber. 4.   4. The control method according to claim 3, wherein in the predicting step, fuel residue accumulation is predicted based on a pressure difference between the sub-combustion chamber and the main combustion chamber. 5.   5. The control method according to claim 3, wherein the pressure in the auxiliary combustion chamber is predicted from a pressure history. The dual fuel engine is mounted on a ship,
2. The control method according to claim 1, wherein the liquid fuel injection step is performed when shifting to a NOx regulation area based on a position of the vessel. 3. A control device for a dual fuel engine including a main combustion chamber in which gaseous fuel and liquid fuel are burned, and a sub-combustion chamber connected to the main combustion chamber and provided with an injection device for the liquid fuel,
A control device for injecting the liquid fuel when fuel residue accumulates in the sub-combustion chamber during combustion of the liquid fuel. A dual fuel engine including a main combustion chamber in which gaseous fuel and liquid fuel are burned, and a sub-combustion chamber connected to the main combustion chamber and provided with the liquid fuel injection device;
An engine system comprising: the control device according to claim 7.

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