JP2015127523A - Gaseous fuel supply system, control unit, and engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gaseous fuel supply system and a gaseous fuel engine which can suppress the generation of NOx.SOLUTION: A gaseous fuel supply system 15 includes a combustion chamber 7 formed between a cylinder 2 and a piston 3, a first valve which injects gaseous fuel PG into the combustion chamber 7, and a second valve which is provided between a supply part of the gaseous fuel PG and the first valve, supplies the gaseous fuel PG to the first valve, and opens subsequent to the opening of the first valve, when supplying the gaseous fuel PG to the combustion chamber 7.

Description

  The present invention relates to a gaseous fuel supply system, a control device for a gaseous fuel supply system, and an engine.

  For example, as a power source of a ship, a dual fuel engine (a dual fuel engine) that generates power using both liquid fuel and gaseous fuel as described in Patent Document 1 is known.

  The dual fuel engine can be operated in a fuel oil only mode using only liquid fuel (fuel oil) and a two-fuel mode using both liquid fuel and gas fuel (fuel gas). The fuel oil only mode is a system in which liquid fuel is supplied to the combustion chamber and the supplied liquid fuel is burned. In the two-type fuel mode, a gaseous fuel is supplied to the combustion chamber, a small amount of liquid fuel is supplied to the combustion chamber to generate a pilot flame, and the gaseous fuel is ignited and burned by the pilot flame.

Japanese Patent No. 3432998

  In the two-type fuel mode, the timing for supplying the high-pressure gaseous fuel and the timing for igniting the gaseous fuel are close, and the combustion mode is diffusion combustion. In diffusion combustion, a high-temperature combustion region may be formed, and NOx (nitrogen oxide) may be easily generated in the high-temperature combustion region.

  Then, an object of this invention is to provide the gaseous fuel supply system, control apparatus, and engine which can suppress the production | generation of NOx.

  In order to solve the above-described problems and achieve the object, a gaseous fuel supply system according to the present invention includes a combustion chamber formed between a cylinder and a piston, and a first valve for injecting gaseous fuel into the combustion chamber. And when the gas fuel is supplied to the first valve and the gas fuel is supplied to the combustion chamber, the gas fuel is provided between the gas fuel supply unit and the first valve. And a second valve that opens after the first valve is opened.

  According to the present invention, when the first valve is opened and the injection of gaseous fuel into the combustion chamber begins, the second valve is closed. Therefore, the gaseous fuel from the second valve is not newly supplied to the first valve, and only the gaseous fuel remaining in the first valve is injected. And since the gaseous fuel from a 2nd valve is not newly supplied, the reduction of the pressure of the gaseous fuel which a 1st valve injects becomes large. Thereafter, when the second valve is opened, new gaseous fuel is supplied to the first valve, and the pressure of the gaseous fuel injected by the first valve increases. Thus, in the initial stage, when the pressure of the gaseous fuel injected into the combustion chamber is small and then the pressure of the gaseous fuel injected into the combustion chamber is increased, an increase in the combustion temperature in the initial stage is suppressed, and NOx is reduced. Generation is suppressed.

  In the gaseous fuel supply system, it is preferable that the second valve is closed after the first valve is closed. Gas fuel is supplied to the first valve after the first valve is closed and before the second valve is closed. Therefore, the gaseous fuel remaining in the first valve is prevented from decreasing or increasing for each cycle, and the initial gaseous fuel injection pressure by the first valve is decreased for each cycle. Can be suppressed.

  In the gaseous fuel supply system, it is preferable that the first valve is further opened before the first valve is opened and before the gaseous fuel is ignited by the ignition device. When the first valve is further opened and the gaseous fuel is injected before the first valve is opened and before the gaseous fuel is ignited, the pressure of the gaseous fuel remaining in the first valve is increased. Decrease. Therefore, the pressure of the gaseous fuel injected by the first valve when the first valve is opened again after that is further reduced. Therefore, since the difference between the initial gaseous fuel injection pressure and the subsequent gaseous fuel injection pressure can be increased more suitably, the gaseous fuel injection control, such as suppression of NOx generation, is performed more suitably. be able to.

  In order to solve the above-described problems and achieve the object, a control device for a gaseous fuel supply system according to the present invention includes a combustion chamber formed between a cylinder and a piston, and a gaseous fuel that is injected into the combustion chamber. 1. A gas fuel system control comprising: a first valve; and a second valve that is provided between the gaseous fuel supply unit and the first valve and supplies the gaseous fuel to the first valve. When supplying the gaseous fuel to the combustion chamber, the second valve is opened after the first valve is opened. By having such a control device for the gaseous fuel supply system, an increase in the combustion temperature in the initial stage is suppressed, and generation of NOx is suppressed.

  The control device of the gaseous fuel supply system preferably closes the second valve after closing the first valve. By including such a control device for the gaseous fuel supply system, it is possible to suppress the initial injection pressure of the gaseous fuel from the first valve from being lowered or increased from cycle to cycle.

  Preferably, the control device of the gaseous fuel supply system further opens the first valve before opening the first valve and before igniting the gaseous fuel by the ignition device. . By having such a control device for the gaseous fuel supply system, the difference between the gaseous fuel injection pressure at the initial stage and the subsequent gaseous fuel injection pressure can be increased more suitably, so that the generation of NOx can be suppressed. The injection control of the gaseous fuel can be performed more suitably.

  The engine preferably includes the gaseous fuel supply system. With such an engine, generation of NOx can be suppressed.

  The engine is preferably a two-stroke engine. A two-stroke engine is suitable as a power source for ships and the like.

  According to the present invention, generation of NOx can be suppressed in a gaseous fuel engine.

FIG. 1 is a schematic diagram illustrating an example of a dual fuel engine 1 according to the first embodiment. FIG. 2 is a schematic diagram illustrating an example of the operation of the dual fuel engine 1. FIG. 3 is a plan view schematically showing an example of a state in which fuel is injected into the combustion chamber in the two-type fuel mode. FIG. 4 is a diagram schematically illustrating an example of a state in which fuel is combusted in the two-type fuel mode. FIG. 5 is a plan view schematically showing an example of a state in which fuel is combusted in the two-type fuel mode. FIG. 6 is a diagram illustrating an example of the gaseous fuel supply system 15 according to the first embodiment. FIG. 7 is a schematic diagram illustrating an example of the configuration of the control device 10. FIG. 8 is a diagram illustrating the relationship between the crank angle according to the comparative example and the pressure of the gaseous fuel PG in the supply flow path 21. FIG. 9 is a diagram illustrating a relationship between the crank angle according to the first embodiment and the pressure of the gaseous fuel PG in the supply passage 21. FIG. 10 is a plan view schematically showing a state in which the injection relating to the premixing of the gaseous fuel PG is performed in the second embodiment. FIG. 11 is a plan view showing a state in which the gaseous fuel PG is premixed in the second embodiment. FIG. 12 is a plan view schematically showing a state in which the gaseous fuel PG and the liquid fuel FO are being injected in the second embodiment. FIG. 13 is a plan view schematically showing an example of a state in which the liquid fuel FO and the gaseous fuel PG are combusting. FIG. 14 is a diagram illustrating a relationship between the crank angle according to the second embodiment and the pressure of the gaseous fuel PG in the supply passage 21. FIG. 15 is a diagram illustrating another example of the gaseous fuel supply system according to the second embodiment.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of a dual fuel engine 1 according to the first embodiment. The dual fuel engine 1 as an engine includes a base plate 50, a frame (main body) 51 provided on the base plate 50, and a jacket 52 provided on the frame 51. The dual fuel engine 1 includes a cylinder 2 provided in a jacket 52, a piston 3 that reciprocates inside the cylinder 2, a piston rod 41 connected to the piston 3, a connecting rod 43, a piston rod 41, A cross head 42 for connecting the connecting rod 43 and a crankshaft 4 connected to the connecting rod 43 via a crank pin 44 are provided. The dual fuel engine 1 includes an angle detection device 6 that detects the rotation angle (crank angle) of the crankshaft 4, and a combustion chamber 7 formed between the upper surface of the piston 3, the inner wall of the cylinder 2, and the exhaust valve 13. A gaseous fuel supply system 15 including a gaseous fuel injection valve 8 as a first valve for supplying the gaseous fuel PG to the combustion chamber 7, a liquid fuel injection valve 9 as an ignition device for supplying liquid fuel FO to the combustion chamber 7, An exhaust valve 13, a drive device 14 that drives the exhaust valve 13, and a control device 10 that controls the dual fuel engine 1 and the gaseous fuel supply system 15 are provided.

  The cylinder 2 includes a cylinder liner 2A provided on the jacket 52 and a cylinder cover 2B provided on the cylinder liner 2A. The cross head 42 moves along the guide portion 51G provided on the frame 51 and transmits the mechanical power from the piston rod 41 to the connecting rod 43. The crankshaft 4 is disposed on the base plate 50 and outputs mechanical power transmitted from the piston 3. As described above, the dual fuel engine 1 is a so-called crosshead engine, but may be a so-called trunk piston engine without the crosshead 42.

  The gaseous fuel injection valve 8 can inject gaseous fuel PG into the combustion chamber 7. The gaseous fuel PG is a gas as fuel. In the present embodiment, two gaseous fuel injection valves 8 are arranged in the combustion chamber 7. The number of gaseous fuel injection valves 8 is arbitrary.

  The liquid fuel injection valve 9 can inject liquid fuel FO into the combustion chamber 7. The liquid fuel FO includes, for example, at least one of light oil, heavy oil, and heavy oil. In the present embodiment, two liquid fuel injection valves 9 are arranged in the combustion chamber 7. The number of liquid fuel injection valves 9 is arbitrary.

  The angle detection device 6 includes, for example, a scale (grating) such as an encoder scale disposed on the crankshaft 4 and a detector such as an encoder head that detects the scale. The detector detects the scale of the crankshaft 4 and detects a rotation pulse of the crankshaft 4. The rotation pulse of the crankshaft 4 is associated with the timing at the position at the top dead center of the piston 3, for example. From the rotation pulse of the crankshaft 4, the rotational speed of the crankshaft 4 is obtained. The angle detection device 6 detects the rotation angle (crank angle) of the crankshaft 4 based on the timing at the top dead center of the piston 3 detected by the detector and the rotation speed of the crankshaft 4. The detection result of the angle detection device 6 is output to the control device 10. The crank angle and the position of the piston 3 are associated with each other. The control device 10 can determine the position of the piston 3 including the top dead center and the bottom dead center based on the detection result of the angle detection device 6. Moreover, the control apparatus 10 is arrange | positioned based on the output of the built-in timer, and the detection result of the angle detection apparatus 6, for example at the time of piston 3 being arrange | positioned at a top dead center, and a bottom dead center. The time can be determined. The control device 10 controls the opening and closing of the exhaust valve 13, the injection of the gaseous fuel PG from the gaseous fuel injection valve 8, and the injection of the liquid fuel FO from the liquid fuel injection valve 9 based on the crank angle. Is output. Moreover, although mentioned later in detail, the control apparatus 10 also outputs the command signal for controlling opening and closing of the gate valve of a gaseous fuel supply system.

  FIG. 2 is a schematic diagram illustrating an example of the operation of the dual fuel engine 1. In the first embodiment, the dual fuel engine 1 is a two-stroke one-cycle diesel engine. As shown in FIG. 2, the operation of the dual fuel engine 1 includes a scavenging process (A) in which new air taken in from the scavenging port 11 is sent to the combustion chamber 7, and a compression process in which the air in the combustion chamber 7 is compressed by the piston 3 ( B), a combustion step (C) for injecting fuel into the combustion chamber 7 to burn the fuel, and an exhaust step (D) for discharging the gas in the combustion chamber 7 after the combustion step from the exhaust port 12 . As described above, in the first embodiment, the dual fuel engine 1 is a two-stroke engine and is suitable as a power source for ships and the like. However, the engine is not limited to a two-stroke / one-cycle engine, and may be a four-stroke / one-cycle engine, for example.

  The dual fuel engine 1 can be operated in a fuel oil only mode using only the liquid fuel FO and a two-fuel mode using both the liquid fuel FO and the gaseous fuel PG.

  The fuel oil dedicated mode is a mode in which the liquid fuel FO is supplied from the liquid fuel injection valve 9 to the combustion chamber 7 to burn the liquid fuel FO, while the gaseous fuel PG is not supplied from the gaseous fuel injection valve 8 to the combustion chamber 7. . In the fuel oil only mode, after the air in the combustion chamber 7 is compressed in the compression process, the liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7 in the combustion process. When the liquid fuel FO is injected into the high-temperature and high-pressure air, the liquid fuel FO spontaneously ignites and burns.

  The two-type fuel mode is a mode in which both the liquid fuel FO and the gaseous fuel PG are supplied to the combustion chamber 7. In the two-type fuel mode, gaseous fuel PG is injected from the gaseous fuel injection valve 8 into the combustion chamber 7 and a small amount of liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7 to generate a pilot flame. In this method, the gaseous fuel PG is ignited and burned with a pilot flame. The method for igniting the gaseous fuel PG is not limited to injecting the liquid fuel FO. For example, it is possible to ignite the gaseous fuel PG using a spark plug as an ignition device.

  Next, the two-fuel mode will be described with reference to FIGS. 3, 4, and 5. FIG. 3 schematically shows an example of a state in which the gaseous fuel PG is injected from the gaseous fuel injection valve 8 into the combustion chamber 7 and the liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7 in the two-fuel mode. FIG. FIG. 4 is a diagram schematically illustrating an example of a state in which each of the liquid fuel FO and the gaseous fuel PG is burning in the two-type fuel mode. FIG. 5 is a plan view schematically showing an example of a state in which the liquid fuel FO and the gaseous fuel PG are burning in the two-type fuel mode.

  In the compression process, the air in the combustion chamber 7 is compressed. As shown in FIG. 3, in the combustion process, gaseous fuel PG is injected from the gaseous fuel injection valve 8 into the combustion chamber 7. A small amount of liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7. When the piston 3 is disposed near the top dead center, the liquid fuel FO and the gaseous fuel PG are injected at a timing close to the combustion chamber 7. In the dual fuel mode, the main fuel is the gaseous fuel PG.

  As shown in FIG. 3, the gaseous fuel injection valve 8 has a plurality of injection holes 8S for injecting the gaseous fuel PG. The liquid fuel injection valve 9 has a plurality of injection holes 9S that inject the liquid fuel FO. The gaseous fuel injection valve 8 injects the gaseous fuel PG outward with respect to the radial direction of the injection port 8S of the gaseous fuel injection valve 8 with respect to the shaft 8A. The liquid fuel injection valve 9 injects the liquid fuel FO outward with respect to the radial direction with respect to the shaft 9A of the injection port 9S of the liquid fuel injection valve 9. Since the shaft 9A of the nozzle 9S is provided so as to intersect with the shaft 8A of the nozzle 8S, the liquid fuel FO injected from the nozzle 9S intersects with the gaseous fuel PG injected from the nozzle 8S.

  A small amount of the liquid fuel FO injected from the liquid fuel injection valve 9 spontaneously ignites and generates a pilot flame. The gaseous fuel injection valve 8 injects high-pressure gaseous fuel PG. By supplying high-pressure gaseous fuel PG to the combustion chamber 7 filled with high-temperature and high-pressure air and generating a pilot flame, diffusion combustion occurs in the combustion chamber 7 as shown in FIGS. . In the present embodiment, the two-fuel mode combusts the gaseous fuel PG by a diffusion combustion method.

  Next, an example of the gaseous fuel supply system 15 according to the first embodiment will be described. FIG. 6 is a diagram illustrating an example of the gaseous fuel supply system 15 according to the first embodiment.

  The gaseous fuel supply system 15 supplies gaseous fuel PG to the combustion chamber 7 of the dual fuel engine 1. The gaseous fuel supply system 15 is controlled by the control device 10. The gaseous fuel supply system 15 includes a gaseous fuel injection valve 8 that injects gaseous fuel PG into the combustion chamber 7, a supply flow path 21 through which the gaseous fuel PG supplied to the gaseous fuel injection valve 8 flows, and opens and closes the supply flow path 21. A gate valve 22 as a possible second valve and a gaseous fuel supply source 23 for supplying the gaseous fuel PG are provided. The gaseous fuel injection valve 8 and the gate valve 22 are controlled by the control device 10. The gate valve 22 is provided between the gaseous fuel supply source 23 as a gaseous fuel supply unit including a pump capable of delivering the gaseous fuel PG and the gaseous fuel injection valve 8. Since the gate valve 22 is connected to the gaseous fuel supply source 23, the gaseous fuel supply source 23 supplies the gaseous fuel PG to the gate valve 22. Since the gate valve 22 is also connected to the supply channel 21, the gate valve 22 supplies the gaseous fuel PG to the supply channel 21 by opening the valve. The gaseous fuel injection valve 8 supplies the gaseous fuel PG from the supply flow path 21 to the combustion chamber 7 by opening the valve. The gaseous fuel supply source 23 supplies high-pressure gaseous fuel PG.

  FIG. 7 is a schematic diagram illustrating an example of the configuration of the control device 10. The control apparatus 10 controls the gaseous fuel supply system 15 as a computer, for example. As shown in FIG. 7, the control device 10 as a computer includes a processing unit 61 and a storage unit 62. The processing unit 61 is, for example, a CPU (Central Processing Unit). For example, a RAM (Random Access Memory) is mainly used as the storage unit 62. For example, the storage unit 62 stores a computer program PR in which instructions for controlling the gaseous fuel supply system 15 are described.

  The processing unit 61 collects crank angle information from the angle detection device 6 as shown in FIG. The processing unit 61 stores the collected crank angle information in the storage unit 62. Further, the processing unit 61 reads a computer program PR in which a command for controlling the gaseous fuel supply system 15 is described from the storage unit 62. Specifically, the computer program PR describes an instruction for controlling the opening and closing of the gaseous fuel injection valve 8 and the gate valve 22 in accordance with the crank angle. The processing unit 61 controls the gaseous fuel supply system 15 and controls the opening and closing of the gaseous fuel injection valve 8 and the gate valve 22 based on information on the crank angle collected from the angle detection device 6 and a command from the computer program PR. . However, the gaseous fuel injection valve 8 and the gate valve 22 may be mechanically controlled by, for example, a cam and a timing belt interlocked with the rotation of the crankshaft 4 of the dual fuel engine 1.

  Since the gaseous fuel PG has a lower viscosity than the liquid fuel FO, the gaseous fuel PG tends to leak from, for example, a valve seat. Therefore, the gate valve 22 is provided to function as a safety valve (interlock mechanism). For example, even if the gaseous fuel PG in the combustion chamber 7 leaks from the gaseous fuel injection valve 8, the gate valve 22 can prevent the backward flow of the gaseous fuel PG.

  Next, the timing of opening and closing the gaseous fuel injection valve 8 and the gate valve 22 will be described in comparison with a comparative example. FIG. 8 shows the relationship between the opening and closing of the gaseous fuel injection valve 8 and the gate valve 22, the crank angle, and the pressure of the gaseous fuel PG in the supply passage 21 (pressure at the inlet of the gaseous fuel injection valve 8) according to the comparative example. FIG. Note that the comparative example also has the gaseous fuel supply system 15 shown in FIG. 6 as in the first embodiment.

  In FIG. 8, when the crank angle is 0 degree, the piston 3 is arranged at the top dead center. When the crank angle is 180 degrees (or -180 degrees), the piston 3 is disposed at the bottom dead center. FIG. 8 shows the pressure in the supply flow path 21 between the gaseous fuel injection valve 8 and the gate valve 22, the gaseous fuel injection valve 8, and the gate valve 22 in the crank angle range of −90 degrees to 90 degrees. The timing of opening and closing of is shown.

  As shown in FIG. 8, the gaseous fuel injection valve 8 and the gate valve 22 are closed in the period T0 before the crank angle A1 degree. Therefore, in the period T0, the pressure in the supply channel 21 is constant.

  When the crank angle is A1 degrees, the control device 10 outputs a command signal for opening the gate valve 22 to the gate valve 22. When the crank angle becomes A2 degrees larger than A1 degrees, the control device 10 outputs a command signal for opening the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. That is, in the comparative example, in one cycle of the dual fuel engine 1, the gate valve 22 opens first and the gaseous fuel injection valve 8 opens later.

  In a period T1 from when the crank angle becomes A1 degrees to A2 degrees, the gate valve 22 is open and the gaseous fuel injection valve 8 is closed. A high pressure (P1 bar) gaseous fuel PG is supplied to the gate valve 22 from the gaseous fuel supply source 23. By opening the gate valve 22 with the gaseous fuel injection valve 8 closed, the pressure in the supply flow path 21 between the gaseous fuel injection valve 8 and the gate valve 22 is the same as that of the gaseous fuel supply source 23 in the period T1. P1bar.

  When the crank angle is A2 degrees and the gaseous fuel injection valve 8 is opened while the gate valve 22 is open, the gaseous fuel PG is injected from the gaseous fuel injection valve 8 into the combustion chamber 7. Thus, in the comparative example, the gaseous fuel PG is injected into the combustion chamber 7 while the gate valve 22 is open during the period T2 from when the crank angle becomes A2 degrees to A3 degrees. That is, the high-pressure gaseous fuel PG supplied from the gaseous fuel supply source 23 is injected into the combustion chamber 7 through the gate valve 22, the supply flow path 21, and the gaseous fuel injection valve 8. Then, at a timing close to the timing at which the gaseous fuel injection valve 8 opens, the liquid fuel FO is injected from the liquid fuel injection valve 9 as pilot fuel, the gaseous fuel PG is ignited, and the gaseous fuel PG burns. Thus, the combustion form of the comparative example is diffusion combustion. In the comparative example, the crank angle A2 degrees is 0 degrees. That is, when the piston 3 is disposed at the top dead center, the gaseous fuel PG is injected from the gaseous fuel injection valve 8. Further, in the period T2, the gaseous fuel injection valve 8 is opened and the gaseous fuel PG is injected while the gate valve 22 is opened, so that the supply flow path 21 between the gaseous fuel injection valve 8 and the gate valve 22 is supplied. The pressure gradually decreases.

  At the crank angle A3 degrees, the control device 10 outputs a command signal for closing the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. Therefore, in the period T3 from when the crank angle becomes A3 degrees to A4 degrees, the gaseous fuel injection valve 8 is closed while the gate valve 22 is open. In the period T3, the gaseous fuel PG is supplied from the gaseous fuel supply source 23 to the supply flow path 21 through the gate valve 22, and the gaseous fuel PG is not injected, so the pressure in the supply flow path 21 gradually increases.

  At the crank angle A4 degrees, the control device 10 outputs a command signal for closing the gate valve 22 to the gate valve 22. In the period T4 that is a period after the crank angle A4 degrees, both the gaseous fuel injection valve 8 and the gate valve 22 are closed, so the pressure in the supply flow path 21 is constant.

  Next, the opening / closing timing of the gaseous fuel injection valve 8 and the gate valve 22 in the first embodiment will be described. 9 shows the opening / closing of the gaseous fuel injection valve 8 and the gate valve 22, the crank angle, and the pressure of the gaseous fuel PG in the supply passage 21 (pressure at the inlet of the gaseous fuel injection valve 8) according to the first embodiment. It is a figure which shows a relationship. As shown in FIG. 9, in the first embodiment, the gaseous fuel injection valve 8 opens before the gate valve 22. In this respect, the comparative example is different from the first embodiment.

  In FIG. 9, when the crank angle is 0 degree, the piston 3 is disposed at the top dead center. When the crank angle is 180 degrees (or -180 degrees), the piston 3 is disposed at the bottom dead center. FIG. 9 shows the pressure in the supply flow path 21 between the gaseous fuel injection valve 8 and the gate valve 22, the gaseous fuel injection valve 8, and the gate valve 22 in the crank angle range of −90 degrees to 90 degrees. The timing of opening and closing of is shown.

  As shown in FIG. 9, the gaseous fuel injection valve 8 and the gate valve 22 are closed in the period U0 before the crank angle B1 degree. Therefore, the pressure in the supply flow path 21 is constant during the period U0.

  The control device 10 determines the timing for outputting the command signal based on the detection result of the crank angle by the angle detection device 6. That is, when the crank angle is B1 degrees, the control device 10 outputs a command signal for opening the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. When the crank angle becomes B2 degrees, which is larger than B1 degrees, the control device 10 outputs a command signal for opening the gate valve 22 to the gate valve 22. That is, in the first embodiment, in one cycle of the dual fuel engine 1, the gaseous fuel injection valve 8 is opened first, and the gate valve 22 is opened later. In the first embodiment, the crank angle B1 degree is 0 degree. That is, when the piston 3 is disposed at the top dead center, the gaseous fuel PG is injected from the gaseous fuel injection valve 8. However, the crank angle B1 is not limited to 0 degrees, and may be smaller or larger than 0 degrees.

  In the first embodiment, the gaseous fuel injection valve 8 is opened before the gate valve 22. In the comparative example, the gate valve 22 opens before the gaseous fuel injection valve 8. Therefore, unlike the period T1 in the comparative example, the first embodiment does not have a period in which the gate valve 22 is opened while the gaseous fuel injection valve 8 is closed and the pressure in the supply passage 21 is increased. Therefore, the pressure in the supply flow path 21 at the crank angle B1 degree that is the crank angle that opens the gaseous fuel injection valve 8 in the first embodiment is supplied at the crank angle A2 degree that is the crank angle that opens the gaseous fuel injection valve 8 in the comparative example. The pressure in the flow path 21 is smaller.

  In the period U1 from when the crank angle becomes B1 degrees to B2 degrees, the gaseous fuel injection valve 8 is open and the gate valve 22 is closed. Therefore, in the period U1, only the gaseous fuel PG remaining in the supply flow path 21 from the gaseous fuel injection valve 8 without newly supplying the high-pressure gaseous fuel PG to the supply flow path 21 through the gate valve 22. Is injected into the combustion chamber 7. On the other hand, in the comparative example, since the gaseous fuel injection valve 8 and the gate valve 22 are open in the period T2, the gaseous fuel injection valve 8 is supplied while the high-pressure gaseous fuel PG is supplied to the supply flow path 21 through the gate valve 22. From this, gaseous fuel PG is injected into the combustion chamber 7. Therefore, in the period U1 according to the first embodiment, the pressure in the supply flow path 21 is greatly reduced compared to the period T2 according to the comparative example. In the comparative example, at the timing when the crank angle, which is the end of the period T2, becomes A3 degrees, the pressure in the supply flow path 21 is larger than P2bar. On the other hand, in the first embodiment, the pressure in the supply flow path 21 is smaller than P2bar at the timing when the crank angle at the end of the period U1 is B2 degrees. Further, the liquid fuel injection valve 9 is opened and the liquid fuel FO is injected as pilot fuel at a timing close to the crank angle B1 degree that is the timing at which the gaseous fuel injection valve 8 is opened. And gaseous fuel PG is ignited and gaseous fuel PG burns. The combustion mode in the first embodiment is diffusion combustion.

  When the crank angle is B2 degrees, the control device 10 outputs a command signal for opening the gate valve 22 to the gate valve 22. Although gaseous fuel PG is flowing out into the supply channel 21 by the gaseous fuel injection valve 8, when the gate valve 22 is opened, the high-pressure (P1bar) gaseous fuel PG is supplied from the gaseous fuel supply source 23 to the supply channel 21. Supplied to. Therefore, in the period U2 from when the crank angle becomes B2 degrees to B3 degrees, the pressure in the supply flow path 21 increases. The pressure increase in the supply passage 21 continues until the pressure decrease due to the injection of the gaseous fuel PG from the gaseous fuel injection valve 8 and the pressure increase due to the supply of the gaseous fuel PG from the gate valve 22 are balanced.

  At the crank angle B3 degrees, the pressure decrease due to the injection of the gaseous fuel PG from the gaseous fuel injection valve 8 and the pressure increase due to the supply of the gaseous fuel PG from the gate valve 22 are balanced. In the period U3 from when the crank angle becomes B3 degrees to B4 degrees, the gaseous fuel injection valve 8 and the gate valve 22 are open, and the pressure in the supply passage 21 gradually decreases. In the period U3, the gaseous fuel PG is injected into the combustion chamber 7 with the gate valve 22 open. That is, the high-pressure gaseous fuel PG supplied from the gaseous fuel supply source 23 is injected into the combustion chamber 7 through the gate valve 22, the supply flow path 21, and the gaseous fuel injection valve 8. Therefore, the pressure decrease amount of the supply flow path 21 is larger in the period U1 in which the gate valve 22 is not open than in the period U3 in which the gate valve 22 is open.

  At the crank angle B4 degrees, the control device 10 outputs a command signal for closing the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. Then, at the crank angle B5 degrees, the control device 10 outputs a command signal for closing the gate valve 22 to the gate valve 22. That is, in the first embodiment, in one cycle of the dual fuel engine 1, after the gaseous fuel injection valve 8 is closed, the gate valve 22 is closed. Therefore, in the period U4 from when the crank angle becomes B4 degrees to B5 degrees, the gaseous fuel injection valve 8 is closed while the gate valve 22 is open. In the period U4, the gaseous fuel PG is supplied from the gaseous fuel supply source 23 to the supply flow path 21 through the gate valve 22, and the gaseous fuel PG is not injected, so the pressure in the supply flow path 21 gradually increases.

  As described above, the control device 10 outputs the command signal for closing the gate valve 22 to the gate valve 22 at the crank angle B5 degrees. Thus, in the period U5, which is a period after the crank angle B5 degrees, both the gaseous fuel injection valve 8 and the gate valve 22 are closed, so the pressure in the supply flow path 21 is constant.

  As described above, the combustion mode in the first embodiment is diffusion combustion, and the injection of the gaseous fuel PG from the gaseous fuel injection valve 8 at the crank angle B1 degree can be said to be injection related to diffusion combustion. In diffusion combustion, if the fuel injection pressure at the initial stage of combustion is high, a high-temperature combustion region is likely to occur, and the generation of NOx due to combustion increases. However, in the first embodiment, for example, in the period U1, compared with the period T2 in the comparative example, the pressure of the supply flow path 21 is lower. The pressure is also reduced. Thus, in Embodiment 1, since the gaseous fuel injection valve 8 opens first and the gate valve 22 opens later, the pressure of the gaseous fuel PG in the combustion chamber 7 can be lowered in the early stage of combustion, and NOx can be reduced. Generation can be suppressed. Furthermore, generally, NOx reduction and thermal efficiency are in a trade-off relationship, and if NOx generation is suppressed, thermal efficiency decreases. However, according to the first embodiment, a decrease in thermal efficiency can also be suppressed. That is, the combustion according to Embodiment 1 can improve the trade-off between NOx and thermal efficiency. Further, the injection timing of the liquid fuel FO is not particularly limited as long as the crank angle is close to the timing when the crank angle becomes B1 degrees, and may be a timing before the crank angle becomes B1 degrees, and the crank angle becomes B1 degrees. It may be a later timing.

  In the first embodiment, since the gate valve 22 is closed after the gaseous fuel injection valve 8 is closed, the pressure in the supply flow path 21 can be increased after the gaseous fuel PG is injected as shown in the period U4. Therefore, the pressure of the supply flow path 21 falls for every cycle, and it can suppress that the pressure of the gaseous fuel PG injected from the gaseous fuel injection valve 8 to the combustion chamber 7 for every cycle falls. Moreover, in Embodiment 1, it can suppress that the pressure of the supply flow path 21 of the early stage of combustion in the next cycle becomes larger than the pressure of the supply flow path 21 of the early stage of combustion in the previous cycle. Therefore, it is possible to suppress an increase in the pressure of the supply passage 21 at the initial stage of combustion for each cycle. For example, in the first embodiment, a pressure sensor is provided in the supply flow path 21 to check the pressure of the supply flow path 21 so that the pressure in the supply flow path 21 does not decrease or increase every cycle. The device 10 can control the timing of closing the gate valve 22. For example, the pressure of the supply flow path 21 in the period U5 is set to the pressure P3 of the supply flow path 21 in the period U0.

  Thus, in the first embodiment, in one cycle of the dual fuel engine 1, the gate valve 22 is opened after the gaseous fuel injection valve 8 is opened. Therefore, the pressure of the gaseous fuel PG in the combustion chamber 7 can be lowered at the early stage of combustion to suppress the generation of NOx. Further, in one cycle of the dual fuel engine 1, after the gaseous fuel injection valve 8 is closed, the gate valve 22 is closed. Therefore, it can suppress that the pressure of the gaseous fuel PG injected from the gaseous fuel injection valve 8 to the combustion chamber 7 for every cycle falls or rises.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described in detail with reference to the drawings. In the second embodiment, the gaseous fuel PG is further injected into the combustion chamber 7 with the gate valve 22 closed before the injection related to the diffusion combustion at the crank angle B1 degree described in the first embodiment. That is, premixing of the gaseous fuel PG is performed. Hereinafter, the injection of the gaseous fuel PG into the combustion chamber 7 before the injection related to diffusion combustion at the crank angle B1 degree will be referred to as injection related to premixing as appropriate. Other configurations of the second embodiment are the same as those of the first embodiment, and the description of the parts common to the first embodiment is omitted.

  With reference to FIG. 10, FIG. 11, FIG. 12 and FIG. 13, combustion in the second fuel mode in the second embodiment will be described. FIG. 10 is a plan view schematically illustrating a state in which gaseous fuel PG is injected in the combustion chamber 7 according to the premixing in the second embodiment. FIG. 11 is a plan view showing a state in which the gaseous fuel PG in the combustion chamber 7 is premixed in the second embodiment. FIG. 12 is a plan view schematically showing a state in which the gaseous fuel PG and the liquid fuel FO are being injected in the second embodiment. FIG. 13 is a plan view schematically showing an example of a state in which the liquid fuel FO and the gaseous fuel PG are combusting.

  As shown in FIG. 10, after the timing at which the crank angle is −180 degrees and before the timing at which the crank angle is 0 degrees (compression stroke), as shown in FIG. In FIG. 7, gaseous fuel PG is injected as injection related to premixing. In this case, because of the compression stroke, the injected gaseous fuel PG and the air in the combustion chamber 7 are mixed in the process of ascending the piston 3, and an air-fuel mixture MG is generated as shown in FIG. . The premixing injection is preferably performed at a crank angle of -100 degrees or more and -10 degrees or less.

  As in the first embodiment, when the piston 3 is disposed near the top dead center, the gaseous fuel PG and the liquid fuel FO are injected at a timing close to the combustion chamber 7 as shown in FIG. In the dual fuel mode, the main fuel is the gaseous fuel PG.

  A small amount of liquid fuel FO injected from the liquid fuel injection valve 9 spontaneously ignites (self-ignition) to generate a pilot flame. The gaseous fuel PG injected into the combustion chamber 7 is also burned by the pilot flame, and diffusion combustion occurs. As shown in FIG. 13, the combustion of the gaseous fuel PG propagates to the air-fuel mixture MG, and the air-fuel mixture MG burns, whereby premixed combustion occurs in part.

  As described above, in the second embodiment, part of the combustion is premixed combustion, and the generation of NOx can be suppressed as compared with the case where the whole combustion mode is diffusion combustion.

  Next, the opening / closing timing of the gaseous fuel injection valve 8 and the gate valve 22 will be described. 14 shows the opening / closing of the gaseous fuel injection valve 8 and the gate valve 22, the crank angle, and the pressure of the gaseous fuel PG in the supply passage 21 (the pressure at the inlet of the gaseous fuel injection valve 8) according to the second embodiment. It is a figure which shows a relationship. As shown in FIG. 14, in Embodiment 2, the gaseous fuel injection valve 8 opens twice. This is different from the first embodiment shown in FIG.

  In FIG. 14, when the crank angle is 0 degree, the piston 3 is arranged at the top dead center. When the crank angle is 180 degrees (or -180 degrees), the piston 3 is disposed at the bottom dead center. 14 shows the pressure in the supply flow path 21 between the gaseous fuel injection valve 8 and the gate valve 22 and the gaseous fuel injection valve 8 and the gate valve 22 when the crank angle is in the range of −90 degrees to 90 degrees. The timing of opening and closing of is shown.

  As shown in FIG. 14, in the period V0 before the crank angle C1 degrees, the gaseous fuel injection valve 8 and the gate valve 22 are closed. Therefore, in the period V0, as in the period U0 according to the first embodiment, the pressure in the supply flow path 21 is constant.

  The control device 10 determines the timing for outputting the command signal based on the detection result of the crank angle by the angle detection device 6. That is, when the crank angle is C1 degrees, the control device 10 outputs a command signal for opening the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. The opening of the gaseous fuel injection valve 8 at the crank angle C1 degree is performed prior to the opening of the gaseous fuel injection valve 8 and the injection of the liquid fuel FO at a crank angle C3 degree described later. That is, the opening of the gaseous fuel injection valve 8 at the crank angle C1 degrees is injection related to premixing. The crank angle C1 is in the range of −180 degrees to 0 degrees, which is the compression stroke, but is preferably −100 degrees to −10 degrees.

  In the period V1 from when the crank angle becomes C1 degrees to C2 degrees, the gaseous fuel injection valve 8 is open and the gate valve 22 is closed. Therefore, in the period V1, only the gaseous fuel PG remaining in the supply passage 21 from the gaseous fuel injection valve 8 without newly supplying the high-pressure gaseous fuel PG to the supply passage 21 through the gate valve 22. Is injected into the combustion chamber 7. Therefore, in the period V1, the pressure in the supply channel 21 is greatly reduced. Further, the period V1 is a compression stroke, and the combustion of the gaseous fuel PG is not started in the combustion chamber 7.

  Next, when the crank angle is C2 degrees, the control device 10 outputs a command signal for closing the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. In the period V2 from when the crank angle becomes C2 degrees to C3 degrees, the gaseous fuel injection valve 8 and the gate valve 22 are closed. Therefore, the pressure in the supply flow path 21 is constant in the period V2. In the period V1 and the period V2, the gaseous fuel PG injected into the combustion chamber 7 in the period V1 is mixed with the air in the combustion chamber, so that an air-fuel mixture MG is generated. Moreover, according to FIG. 14, the pressure of the supply flow path 21 when the crank angle is C2 degrees is smaller than P2bar. However, the present invention is not limited to this as long as the pressure of the supply flow path 21 at the crank angle C2 degrees is lower than the pressure of the supply flow path 21 at the crank angle C1 degrees, which is the timing at which the gaseous fuel injection valve 8 opens. . Further, according to the second embodiment, the gas fuel injection valve 8 is opened only once in the period V1 before the liquid fuel FO is injected and before the crank angle C3 degree described later. It may be.

  When the crank angle is C3 degrees, the control device 10 outputs a command signal for opening the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. The crank angle C3 degrees is the same timing as the crank angle B1 degrees according to the first embodiment. In the period V3 from when the crank angle becomes C3 degrees to C4 degrees, the gaseous fuel injection valve 8 is open and the gate valve 22 is closed. Therefore, similarly to the period U1 of the first embodiment, the high-pressure gaseous fuel PG is not supplied to the supply passage 21 through the gate valve 22 and remains in the supply passage 21 from the gaseous fuel injection valve 8. Only the gaseous fuel PG is injected into the combustion chamber 7. Therefore, in the period V3, the pressure in the supply flow path 21 is greatly reduced.

  In the second embodiment, since the gaseous fuel injection valve 8 is already opened and the gaseous fuel PG is injected in the period V1, the pressure in the supply flow path 21 in the period V3 is the supply flow at the crank angle B1 degrees of the first embodiment. The pressure is further smaller than the pressure in the passage 21. Similarly to the crank angle B1 degree according to the first embodiment, the liquid fuel injection valve 9 is opened and the liquid fuel FO is injected as pilot fuel at a timing close to the timing when the crank angle becomes C3 degrees, and the gaseous fuel PG is injected. It is ignited and the gaseous fuel PG starts diffusion combustion.

  When the crank angle is C4 degrees, the control device 10 outputs a command signal for opening the gate valve 22 to the gate valve 22. In the supply flow path 21, the gaseous fuel PG is injected by the gaseous fuel injection valve 8, but when the gate valve 22 is opened, the gaseous fuel PG of high pressure (P1 bar) is supplied from the gaseous fuel supply source 23. Therefore, in the period V4 from when the crank angle becomes C4 degrees to C5 degrees, the pressure in the supply flow path 21 increases as in the period U2 of the first embodiment. The pressure increase in the supply passage 21 continues until the pressure decrease due to the injection of the gaseous fuel PG from the gaseous fuel injection valve 8 and the pressure increase due to the supply of the gaseous fuel PG from the gate valve 22 are balanced.

  At the crank angle C5 degrees, the pressure decrease due to the injection of the gaseous fuel PG from the gaseous fuel injection valve 8 and the pressure increase due to the supply of the gaseous fuel PG from the gate valve 22 are balanced. Therefore, in the period V5 from when the crank angle becomes C5 degrees to C6 degrees, as in the period U3 according to the first embodiment, the gaseous fuel injection valve 8 and the gate valve 22 are open, and the supply flow The pressure in the passage 21 gradually decreases.

  At the crank angle C6 degrees, the control device 10 outputs a command signal for closing the gaseous fuel injection valve 8 to the gaseous fuel injection valve 8. Therefore, in the period V6 from when the crank angle becomes C6 degrees to C7 degrees, similarly to the period U4 according to the first embodiment, the gaseous fuel injection valve 8 is closed with the gate valve 22 opened. . In the supply flow path 21, since the gaseous fuel PG is supplied from the gaseous fuel supply source 23 through the gate valve 22 and the gaseous fuel PG is not injected, the pressure in the supply flow path 21 gradually increases.

  At the crank angle C7 degrees, the control device 10 outputs a command signal for closing the gate valve 22 to the gate valve 22. As described above, in the period V7 that is a period after the crank angle C7 degrees, both the gaseous fuel injection valve 8 and the gate valve 22 are closed as in the period U5 according to the first embodiment. The pressure of 21 is constant.

  In Embodiment 2, since the injection which concerns on premixing is performed in the period V1, the pressure of the supply flow path 21 can be reduced before combustion starts. Therefore, the pressure of the supply flow path 21 and the combustion chamber 7 in the early stage of combustion can be reduced more suitably. Therefore, in the second embodiment, it is possible to more suitably suppress the generation of NOx, and it is possible to suppress a decrease in thermal efficiency. Further, by adjusting the injection timing and injection period of the injection at the crank angle C1 degrees, the pressure of the supply flow path 21 and the injection amount of the gaseous fuel PG at the initial stage of combustion can be adjusted. Control can be performed more suitably. Furthermore, since the air-fuel mixture MG exists in the combustion chamber 7, a part of it becomes premixed combustion, and the generation of NOx can be more suitably suppressed.

  FIG. 15 is a diagram illustrating another example of the gaseous fuel supply system according to the second embodiment. In the second embodiment, the valve for injecting the gaseous fuel PG to the combustion chamber 7 as the first valve is a single gaseous fuel injection valve 8, but the gaseous fuel PG as the first valve is in the combustion chamber. There may be a plurality of valves to be injected into the valve 7. For example, as shown in FIG. 15, injection related to premixing may be performed by a gas fuel injection valve 8 and another injection valve. As shown in FIG. 15, the gaseous fuel supply system 15a further includes a premixed injection valve 8a. The premixing injection valve 8 a is controlled by the control device 10 in the same manner as the gaseous fuel injection valve 8. The premixing injection valve 8a injects gaseous fuel PG into the combustion chamber 7 in the period V1 shown in FIG. In other words, the premixing injection valve 8a performs injection related to premixing. The gaseous fuel injection valve 8 injects gaseous fuel PG into the combustion chamber 7 in the period V3 to the period V5 shown in FIG. In FIG. 15, the premixing injection valve 8 a is provided between the gaseous fuel injection valve 8 and the gate valve 22, but is not limited thereto. The premixed injection valve 8a is connected to the supply flow path 21, and may be on the downstream side in the flow direction of the gaseous fuel PG, which is the opposite side of the gaseous fuel supply source 23 from the gate valve 22.

  As described above, in the second embodiment, in one cycle of the dual fuel engine 1, the gaseous fuel injection valve 8 is further opened before the gaseous fuel injection valve 8 is opened and before the liquid fuel FO is injected. Alternatively, the premix injection valve 8a is further opened before the gaseous fuel injection valve 8 is opened and before the liquid fuel FO is injected. Therefore, the pressure of the gaseous fuel PG in the combustion chamber 7 can be further suitably reduced in the early stage of combustion, and the generation of NOx can be suppressed. Moreover, injection control of gaseous fuel PG can be performed more suitably.

  As mentioned above, although Embodiment 1 and Embodiment 2 were described, these Embodiment etc. are not limited by the content of these Embodiment etc. In addition, the above-described constituent elements include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Furthermore, the above-described components can be appropriately combined. Furthermore, various omissions, substitutions, or changes of the constituent elements can be made without departing from the spirit of the above-described embodiments and the like.

DESCRIPTION OF SYMBOLS 1 Dual fuel engine 7 Combustion chamber 8 Gas fuel injection valve 8a Premix injection valve 10 Control apparatus 15 Gas fuel supply system 21 Supply flow path 22 Gate valve 23 Gas fuel supply source PG Gas fuel FO Liquid fuel

Claims (8)

A combustion chamber formed between the cylinder and the piston;
A first valve for injecting gaseous fuel into the combustion chamber;
When the gaseous fuel is supplied to the first valve and supplied to the combustion chamber, the first fuel is provided between the gaseous fuel supply unit and the first valve. A second valve that opens after opening the valve;
Including a gaseous fuel supply system. The gaseous fuel supply system according to claim 1, wherein the second valve is closed after the first valve is closed. The gaseous fuel according to claim 1 or 2, wherein the first valve is further opened before the first valve is opened and before the gaseous fuel is ignited by the ignition device. Supply system. A combustion chamber formed between the cylinder and the piston;
A first valve for injecting gaseous fuel into the combustion chamber;
A control device for a gaseous fuel system, comprising: a second valve that is provided between the gaseous fuel supply unit and the first valve and supplies the gaseous fuel to the first valve;
When the gaseous fuel is supplied to the combustion chamber, the second valve is opened after the first valve is opened;
Control device for gaseous fuel supply system. The controller is
The control device of the gaseous fuel supply system according to claim 4, wherein the second valve is closed after the first valve is closed. The controller is
The gaseous fuel supply according to claim 4 or 5, wherein the first valve is further opened before the first valve is opened and before the gaseous fuel is ignited by the ignition device. System control unit. It has the gaseous fuel supply system according to claim 1 to 3.
engine.   The engine according to claim 7, wherein the engine is a two-stroke engine.

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