JP6401544B2 - Gas supply system and ship equipped with the same - Google Patents

Description

  The present invention relates to a gas supply system to a diesel engine that uses gas as fuel, and a ship including the same.

  In recent years, gas-fired diesel engines that are diesel engines that use gas as fuel have been known as marine main propulsion engines. For gas-fired diesel engines, for example, gas-fired diesel engines, both oil and gas can be used as fuel, switching between oil operation and gas operation, and oil and gas can be used in any ratio There is a dual fuel diesel engine.

  A gas-fired diesel engine needs to be supplied with a high-pressure fuel gas such as 15 to 30 MPa in order to enable injection into compressed air. For example, Patent Document 1 discloses a gas supply system that supplies a gas obtained by vaporizing LNG to a diesel engine as a fuel. This gas supply system includes an LNG tank that stores LNG, an LNG pump that boosts LNG guided from the LNG tank, a vaporizer that vaporizes high-pressure LNG guided from the LNG pump, and a vaporizer that is vaporized by the vaporizer And main piping for guiding compressed natural gas to the engine. The main piping is provided with a pressure regulating valve. In the gas supply system disclosed in Patent Document 1, the pressure on the upstream side of the pressure regulating valve is always kept high by the LNG pump, and the pressure of the gas supplied to the engine is regulated by the pressure regulating valve.

JP2013-209926A

Usually, the gas supply system is provided with a control device separately from the control unit of the diesel engine. Then, the required gas pressure corresponding to the engine load is output from the control unit of the diesel engine to the control device of the gas supply system.
By the way, Patent Document 1 describes a method of controlling the supply gas pressure to the engine during gas operation, but does not describe how to increase the supply gas pressure at the start of gas operation. For example, in the gas supply system of Patent Document 1, it is conceivable to start a pump by closing a fuel injection valve of an engine to which main piping is connected at the start of gas operation. However, considerable time (for example, 5 to 10 minutes) is required to pressurize the gas vaporized by the operation of the pump to 15 to 30 MPa. In addition, while the fuel injection valve is closed, the flow rate of the gas passing through the pressure adjustment valve is substantially zero, so the supply gas pressure cannot be adjusted with the pressure adjustment valve.

  Therefore, an object of the present invention is to provide a gas supply system capable of quickly adjusting a vaporized gas to a required gas pressure at the start of gas operation, and a ship including the same.

  In order to solve the above-mentioned problems, a gas supply system according to the present invention is a gas supply system that supplies gas to a diesel engine that uses gas as a fuel, and includes a reservoir that stores liquefied gas, and the liquefied gas. A vaporizer to be vaporized; a first supply line for introducing liquefied gas from the reservoir to the vaporizer; a second supply line for introducing vaporized gas from the vaporizer to the diesel engine; and the first supply line. And a switching valve provided in the second supply line and closed except during gas operation of the diesel engine, and for measuring the pressure in the upstream portion of the switching valve in the second supply line A pressure measuring device, a reflux line branched from the first supply line downstream of the pump and connected to the reservoir, and a flow provided in the reflux line A control device for controlling the pump and the flow rate control valve, the control device receiving an instruction to start gas operation from a control unit of a diesel engine, and the control device is configured to start the gas operation. Before receiving the instruction, the opening of the flow control valve is fully closed to start the pump, and thereafter, the pressure of the flow control valve is maintained so that the pressure measured by the pressure measuring instrument is maintained at the set pressure. After the opening degree is adjusted and the gas operation start instruction is received and the switching valve is opened, the pressure measured by the pressure measuring instrument is the required gas from the control unit of the diesel engine. It is characterized in that at least one of the rotation speed of the pump and the opening degree of the flow control valve is adjusted so as to coincide with the pressure.

  According to the present invention, the rotation speed of the pump and the opening degree of the flow rate control valve are controlled, and a part of the liquefied gas boosted by the pump is returned from the reflux line to maintain the pressure downstream of the pump constant. Therefore, even before the gas operation is started, the pressure of the fuel gas can be adjusted and maintained at a set pressure (for example, 15 MPa). For this reason, it is possible to quickly adjust the required gas pressure by shortening the time for increasing the pressure of the fuel gas to the required gas pressure at the start of gas operation. Furthermore, according to the present invention, the gas pressure supplied to the engine is adjusted to the required gas pressure from the engine even before the gas injection in the engine is started and even when the gas flow rate is small. Can do.

In the gas supply system described above, the control device may adjust the opening of the flow control valve while maintaining the rotation speed of the pump at the minimum rotation speed before receiving the instruction to start the gas operation. Good.
According to this configuration, since the rotation speed of the pump is fixed to the minimum rotation speed and only the opening degree of the flow control valve is adjusted, the recirculation line is maintained after the pump is started until the fuel gas is maintained at the set pressure. The amount of liquefied gas returned to the reservoir can be minimized and the fuel gas can be adjusted to the set pressure. By minimizing the amount of liquefied gas returned from the reflux line to the reservoir, heat input to the reservoir due to the liquefied gas returned to the reservoir can be minimized.

In the gas supply system described above, the control device keeps the rotation speed of the pump at the minimum rotation speed from when the gas operation start instruction is received until gas injection is started by the diesel engine. The opening degree of the flow control valve may be adjusted.
According to this configuration, since the rotation speed of the pump is fixed to the minimum rotation speed and only the opening degree of the flow control valve is adjusted, the gas injection in the engine is performed from the state where the supply gas pressure to the engine is maintained at the set pressure. By the time the fuel gas can be adjusted to the required gas pressure of the engine by minimizing the amount of liquefied gas returned to the reservoir from the reflux line. By minimizing the amount of liquefied gas returned from the reflux line to the reservoir, heat input to the reservoir due to the liquefied gas returned to the reservoir can be minimized.

In the gas supply system described above, when the control device receives an instruction to start the gas operation, the pressure difference obtained by subtracting the pressure measured by the pressure measuring instrument from the required gas pressure is larger than a reference value. Until the pressure difference becomes equal to or less than a predetermined value, the pump rotation speed is set to a rotation speed greater than the minimum rotation speed, the flow control valve is fully closed, and the pressure difference is less than a reference value. If it is smaller, the opening degree of the flow rate control valve may be adjusted while keeping the rotational speed of the pump at the minimum rotational speed.
According to this configuration, when the pressure difference obtained by subtracting the required gas pressure from the pressure measured by the pressure measuring instrument is larger than the reference value, the number of rotations of the pump until the pressure difference becomes a predetermined range or less. Is set to a rotational speed larger than the minimum rotational speed, and the flow rate control valve is fully closed, so that the fuel gas pressurization time can be shortened. Further, when the pressure difference is smaller than a reference value, the opening degree of the flow rate control valve is adjusted while keeping the pump rotation speed at the minimum rotation speed, so that overshoot is minimized. Can do.

In the gas supply system, the control device may determine whether the pressure measured by the pressure measuring instrument is maintained at the required gas pressure or less than the required gas pressure after gas injection is started in the diesel engine. If the opening of the flow control valve is reduced while the pump rotation speed is kept at the minimum rotation speed so as to increase, the rotation speed of the pump is reduced when the flow control valve is fully closed. It may be raised.
According to this configuration, since the rotation speed of the pump is fixed to the minimum rotation speed and only the opening degree of the flow control valve is adjusted, power consumption in the pump can be minimized.

In the gas supply system described above, the control device is configured such that after the gas injection is started in the diesel engine, the pump until the gas consumption amount sent from the control unit of the diesel engine exceeds a pump acceleration allowable value. May be maintained at the minimum number of rotations.
According to this configuration, the pressure of the fuel gas can be stably controlled even when the gas consumption in the diesel engine is substantially close to zero.

  The gas supply system may further include a pressure adjustment valve provided in a portion upstream of the switching valve in the second supply line.

In the gas supply system described above, the control device may fully open the pressure regulating valve before gas injection is started in the diesel engine, and after the gas injection is started in the diesel engine, Until the consumption exceeds the threshold, the pressure regulating valve may be fully opened.
In a gas supply system provided with a pressure adjustment valve for adjusting the supply gas pressure to the engine, the flow rate of gas passing through the pressure adjustment valve is almost zero before gas injection in the engine is started. The supply gas pressure cannot be adjusted with the pressure control valve. Further, when the gas consumption in the engine is small and the flow rate of the gas passing through the pressure regulating valve is small, the pressure regulation with the pressure regulating valve becomes unstable. However, according to this configuration, even in a gas supply system provided with a pressure regulating valve, when the flow rate of the gas passing through the pressure regulating valve is almost zero or small, the gas is supplied to the engine. Gas pressure can be adjusted by controlling the number of rotations of the pump and the opening degree of the flow rate control valve without performing the pressure adjustment valve. On the other hand, when the flow rate passing through the pressure regulating valve is sufficient, the pressure can be regulated using the pressure regulating valve.

In the gas supply system, the pressure measuring device is a first pressure measuring device provided in an upstream portion of the pressure regulating valve in the second supply line, and the gas supply system includes the second supply. And further comprising a second pressure measuring device provided in a portion of the line between the pressure regulating valve and the switching valve, and the control device includes the first pressure after the gas consumption exceeds the threshold value. The second pressure measurement is performed by adjusting at least one of the rotational speed of the pump and the opening of the flow control valve so that the pressure measured by the measuring instrument matches a pressure larger than the required gas pressure by a predetermined value. The degree of opening of the pressure regulating valve may be adjusted so that the pressure measured by the vessel matches the required gas pressure.
According to this configuration, the pressure on the upstream side of the pressure regulating valve is set to a pressure larger than the required gas pressure by a predetermined value, and the pressure on the downstream side of the pressure regulating valve is adjusted to the required gas pressure using the pressure regulating valve. can do. Further, since it is not necessary to cause an excessive pressure difference with the pressure regulating valve, the discharge pressure of the pump can be reduced and the load on the pump can be reduced.

In the above gas supply system, a bypass line connected from the upstream portion of the pressure adjustment valve to the downstream portion of the pressure adjustment valve in the second supply line, and a bypass valve provided in the bypass line, The control device opens the bypass valve before gas injection is started in the diesel engine, and after gas injection is started in the diesel engine, until the gas consumption exceeds a threshold value, The bypass valve may be opened.
According to this configuration, even in a gas supply system provided with a pressure regulating valve, if the flow rate of the gas flowing through the second supply line is almost zero or slight, the supply gas pressure to the engine This adjustment can be performed by controlling the rotational speed of the pump and the opening degree of the flow control valve without performing the adjustment with the pressure regulating valve. On the other hand, when the flow rate of the gas flowing through the second supply line is sufficient, the pressure can be adjusted using the pressure adjusting valve. Further, by opening the bypass valve and allowing the gas to pass therethrough, there is less pressure loss than when the pressure regulating valve is fully opened and the gas is allowed to pass, so the load on the pump can be reduced.

In the gas supply system, the pressure measuring device is a first pressure measuring device provided in an upstream portion of the pressure regulating valve in the second supply line, and the gas supply system includes the second supply. A second pressure measuring device provided in a portion of the line between the pressure regulating valve and the switching valve, and the control device sets the bypass valve after the gas consumption exceeds the threshold value. At the same time, at least one of the rotational speed of the pump and the opening of the flow control valve is adjusted so that the pressure measured by the first pressure measuring instrument matches a pressure larger than the required gas pressure by a predetermined value. Then, the opening of the pressure regulating valve may be adjusted so that the pressure measured by the second pressure measuring device matches the required gas pressure.
According to this configuration, the pressure on the upstream side of the pressure regulating valve is set to a pressure larger than the required gas pressure by a predetermined value, and the pressure on the downstream side of the pressure regulating valve is adjusted to the required gas pressure using the pressure regulating valve. can do. Further, since it is not necessary to cause an excessive pressure difference with the pressure regulating valve, the discharge pressure of the pump can be reduced and the load on the pump can be reduced.

  For example, the diesel engine is a dual fuel diesel engine that can be switched between an oil operation that uses only oil as a fuel and a gas operation that uses both oil and gas as fuel. According to this configuration, it is possible to quickly switch from oil operation to gas operation.

  For example, the diesel engine is a two-cycle diesel engine.

  The gas supply system is provided in a ship, for example.

  According to the present invention, the vaporized gas pressure can be quickly adjusted to the required gas pressure at the start of gas operation.

1 is a schematic configuration diagram of a gas supply system according to a first embodiment of the present invention. (A)-(c) is a graph which shows the time-dependent change of each value after the pump starting of the gas supply system of FIG. 1, (a) shows the time-dependent change of the pressure of the vaporized gas, and gas load. (B) shows the change over time of the rotation speed of the pump, and (c) shows the change over time of the opening degree of the flow control valve. It is a graph which shows an example of the demand gas pressure from an engine to engine load. It is a graph which shows an example of a time-dependent change of the gas load after a gas injection start. It is a schematic block diagram of the gas supply system which concerns on 2nd Embodiment of this invention. (A)-(c) is a graph which shows the time-dependent change of each value after the pump starting of the gas supply system of FIG. 5, (a) shows the time-dependent change of the pressure of the vaporized gas, and gas load. (B) shows the change over time of the rotational speed of the pump, and (c) shows the change over time of the opening degree of the flow control valve and the pressure regulating valve. It is a schematic block diagram of the gas supply system which concerns on 3rd Embodiment of this invention. (A)-(c) is a graph which shows the time-dependent change of each value after the pump starting of the gas supply system of FIG. 7, (a) shows the time-dependent change of the pressure of the vaporized gas, and gas load. (B) shows the change over time of the rotational speed of the pump, and (c) shows the change over time of the opening degree of the flow control valve, the pressure regulating valve and the bypass valve.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a gas supply system 10A according to a first embodiment applied to an LNG carrier equipped with an LNG tank. The LNG carrier 1A to which the gas supply system 10A according to this embodiment is applied is equipped with a gas-fired diesel engine 6 (hereinafter simply referred to as “engine 6”) as a propulsion main machine that drives the propeller 61. The gas supply system 10A pressurizes and vaporizes LNG in the LNG tank 2, and supplies the vaporized gas to the engine 6 as fuel gas. The engine 6 is a dual fuel diesel engine that can use both oil and gas as fuel. Since the engine 6 can also use oil as fuel, the LNG carrier 1A is also provided with an oil supply system (not shown). Hereinafter, the gas supply system 10A will be described, and description of the oil supply system will be omitted. To do.

  The engine 6 is an electronically controlled gas injection (ME-GI) dual fuel two-cycle low-speed diesel engine capable of electronically controlling oil and gas injection. The engine 6 can switch between oil operation using only oil as fuel and gas operation using oil and gas as fuel by electronic control. The engine 6 has a plurality of cylinders, and each cylinder includes a fuel oil injection valve and a fuel gas injection valve (both not shown). The fuel oil is guided from the oil supply system through the oil supply pipe 11 and supplied to the combustion chamber of the cylinder through the fuel oil injection valve, and the fuel gas is supplied to the cylinder through the fuel gas injection valve by the gas supply system 10A. Supplied to the combustion chamber. The engine 6 ignites and burns by directly injecting fuel gas into the cylinder at a high pressure of about 15 to 30 MPa.

  The gas supply system 10A includes an LNG tank 2 that stores LNG, and a vaporizer 5 that vaporizes LNG. The gas supply system 10 </ b> A includes a first supply line 31 that guides LNG from the LNG tank 2 to the vaporizer 5, and a second supply line 32 that guides vaporized gas from the vaporizer 5 to the engine 6.

  The LNG tank 2 is at least one of large transport tanks arranged in the captain direction of the LNG carrier 1A. The LNG tank 2 has a heat insulating performance capable of maintaining a cryogenic state so that the LNG can be held in a liquid state of about −162 ° C. under atmospheric pressure.

  The vaporizer 5 is, for example, a heat exchanger in which meandering tubes are arranged in a shell, and both ends of the tubes are connected to the first supply line 31 and the second supply line 32. The shell is connected to a circulation line (not shown), and a heat medium such as glycol is circulated through the shell and the circulation line.

  The first supply line 31 is provided with an LNG pump 41. The LNG pump 41 is a piston pump that boosts the LNG so that the gas vaporized by the carburetor 5 becomes the injection pressure (for example, 15 to 30 MPa) of the engine 6. The LNG pump 41 includes a plurality of pistons that are driven by a hydraulic motor or an electric motor to push out the LNG from the cylinder. The LNG pump 41 is configured such that its rotational speed (more precisely, the rotational speed of the motor) can be changed by the control device 8 to be described later, and the pump discharge flow rate that is substantially proportional to the rotational speed of the LNG pump 41 is changed. Can do.

  The gas supply system 10A further includes a reflux line 7 branched from the first supply line 31 downstream of the LNG pump 41 and connected to the LNG tank 2, and a flow rate control valve 71 provided in the reflux line 7. Yes. A part of the LNG boosted by the LNG pump 41 can be returned to the LNG tank 2 via the reflux line 7, and the flow rate of the LNG passing through the reflux line by changing the opening degree of the flow control valve 71. Can be adjusted.

  The second supply line 32 is provided with a switching valve 42, and a cutoff valve 43 as a second switching valve is provided downstream of the switching valve 42. Both the switching valve 42 and the shutoff valve 43 are open / close valves. A pressure release line 33 for releasing the pressure between the switching valve 42 and the shutoff valve 43 is connected to the second supply line 32. The second supply line 32 is provided with an accumulator 44 on the downstream side of the shutoff valve 43. Further, the second supply line 32 is provided with a pressure measuring device 82 for measuring the pressure of the upstream portion of the switching valve 42, that is, the pressure of the gas vaporized by the vaporizer 5.

  The gas supply system 10A further includes a control device 8. The control device 8 controls the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 described above. The control device 8 is connected to a pressure measuring instrument 82. Moreover, the control apparatus 8 is connected to the input device 81 into which various operations are input from the vessel operator. From the input device 81, for example, the gas supply system 10A operates the start of standby so as to enter a standby state in which the supply gas pressure to the engine 6 is maintained at a constant high pressure before the gas operation is started. Can do.

  The engine 6 disposed at the downstream end of the second supply line 32 is connected to the engine control unit 62. Further, the engine control unit 62 is connected to the control device 8 and is connected to an operation device 63 for operating the engine control unit 62. Switching between the gas operation and the oil operation can be performed, for example, by the operator operating the selection of either the oil operation or the gas operation with the operation device 63. The operation device 63 and the input device 81 described above may be incorporated in one operation panel. The gas operation may be selected automatically when the engine control unit 62 determines that the above-described standby state has been maintained for a certain period of time. The ratio of the gas injection amount to the total injection amount of gas and oil to the cylinder (hereinafter referred to as “gas ratio”) differs between the gas operation and the oil operation. The gas ratio in oil operation is 0% (gas: oil = 0: 100). The gas ratio in the gas operation is based on a set value (for example, 75% (gas: oil = 75: 25)) set in advance in the engine control unit 62.

  Switching between gas operation and oil operation is performed by controlling the engine control unit 62 so as to gradually change the gas ratio. For example, the gas ratio is changed by gradually changing the duration of fuel oil injection injected from the fuel oil injection valve and the duration of fuel gas injection injected from the fuel gas injection valve. For example, in the middle of switching from oil operation to gas operation, the engine control unit 62 keeps the engine output constant, shortens the duration of fuel oil injection, and lengthens the duration of fuel gas injection. The gas ratio is increased from 0% until the set value is reached. Then, the engine control unit 62 controls the engine 6 so as to maintain it when the gas ratio reaches the set value. The set value of the gas ratio can be changed by the operation device 63.

  When the operator inputs a gas operation selection using the operation device 63, the engine control unit 62 that has received the gas operation selection input sends an instruction to start the gas operation to the control device 8 and supplies the gas pressure to the engine 6. A pressure value (hereinafter referred to as “required gas pressure Pr”) required for the gas supply system 10 </ b> A as (for example, injection pressure) is started to be sent to the control device 8. However, the gas operation start instruction may be that the request gas pressure Pr is sent without sending the gas operation start instruction separately from the request gas pressure Pr. Further, the engine control unit 62 may send the required gas pressure Pr to the control device 8 before receiving an instruction to start the gas operation. In this case, for example, the required gas pressure Pr received by the control device exceeds the threshold value. This may be an instruction to start the gas operation. The required gas pressure Pr is preset by the engine control unit 62 according to the load of the engine 6 as shown in FIG. 3, for example. In this LNG carrier 1A, the engine load is calculated by the engine control unit 62, and the required gas pressure Pr corresponding to the engine load is calculated. As another method, the engine control unit 62 may output the engine load factor and the rotational speed to the control device 8, and the control device 8 may calculate the required gas pressure Pr. The switching valve 42 and the shutoff valve 43 are closed except during the gas operation of the diesel engine. When the supply gas pressure to the engine 6 reaches the required gas pressure, the engine control unit 62 closes the switching valve 42 and the shutoff valve 43. open. The engine control unit 62 may send a gas operation start instruction to the control device 8 and may open the switching valve 42 and the shutoff valve 43. What controls the opening and closing of the switching valve 42 and the shutoff valve 43 is not limited to the engine control unit 62, and may be the control device 8. For example, the switching valve 42 and the shutoff valve 43 may be opened by the control device 8 after sending a signal notifying that the supply gas pressure to the engine 6 has reached the required gas pressure to the control device 8.

  Further, when the gas injection into the cylinder of the engine 6 starts, the engine control unit 62 starts to send the gas consumption amount in the engine 6 to the control device 8. The amount of gas consumed by the engine 6, that is, the gas injection amount, depends on the engine output and the gas ratio. For example, the ratio of the current engine output to the rated output of the engine 6 multiplied by the gas ratio (hereinafter referred to as “gas load GL”) is approximately proportional to the gas consumption in the engine 6. In this LNG carrier 1A, the gas load GL is sent from the engine control unit 62 to the control device 8 as the gas consumption. The consumption amount of the gas sent from the engine control unit 62 to the control device 8 may be a plurality of parameters for calculating the gas consumption amount, for example, both the parameter indicating the engine output and the gas ratio. .

  It takes a considerable time to raise the pressure from the operation of the LNG pump to the required gas pressure of the engine. In the gas supply system 10A according to this embodiment, before starting the gas operation, the LNG pump 41 is operated, and the gas operation is started by taking a standby state in which the vaporized gas is maintained at a constant high pressure. Sometimes, the time for increasing the pressure to the required gas pressure Pr is shortened. Below, the control method of the supply gas pressure to the engine 6 for using the gas supply system 10A which concerns on this embodiment to transfer to gas operation before the gas operation start is demonstrated with reference to FIG. FIG. 2 is a time-dependent change of each value when the LNG carrier 1A is switched from the oil operation to the gas operation during the voyage. Hereinafter, as an example before the gas operation is started, before the operation is switched from the oil operation to the gas operation. The gas pressure control method will be described. In the present application, “at the start of gas operation” means a time point when an instruction to start gas operation is sent to the control device 8, and “gas operation” means after an instruction to start gas operation is sent to the control device 8. Means driving.

(Gas pressure control method from pump start to standby state)
In order to enter the standby state, which is a preparation stage for entering the gas operation, the standby state start is input in the input device 81. For example, the standby state start input is performed before switching from oil operation to gas operation during voyage, or before leaving the port when performing gas operation from the beginning of port departure. When the standby state start is input, the control device 8 activates the LNG pump 41 in order to achieve the standby state.

Specifically, in a state in which the switching valve 42 and the shutoff valve 43 are closed, the control device 8 first closes the flow control valve 71 and turns the LNG pump 41 to the minimum rotational speed r ₀ as shown in FIG. Operate on. Here, “fully closed” means not only the opening degree of the flow control valve 71 is 0% but also the opening degree of the flow control valve 71 is substantially prohibited from flowing LNG (for example, 5% or less). It means that. The “minimum number of revolutions” is the minimum number of revolutions necessary to sufficiently lubricate the inside of the LNG pump 41 and prevent the occurrence of cavitation.

When the LNG pump is activated, the LNG discharged from the LNG pump 41 is vaporized by the vaporizer 5, and as shown in FIG. 2A, the pressure of the vaporized gas in the second supply line 32 (ie, The measurement pressure P ₀ ) at the pressure measuring device 82 gradually increases. Thereafter, when the pressure P ₀ measured by the pressure measuring instrument 82 approaches the set pressure Ps preset in the control device 8, the flow rate control is performed while maintaining the rotation speed of the LNG pump 41 at the minimum rotation speed r _0. The opening degree of the valve 71 is increased. Then, the opening degree of the flow control valve 71 is automatically controlled so that the measured pressure P ₀ is kept at the set pressure Ps, and the standby state is maintained. The set pressure Ps is, for example, a required gas pressure during low load operation.

(Gas pressure control method from standby state to gas injection start)
When the control device 8 determines that the measured pressure P ₀ at the pressure measuring device 82 is maintained at the set pressure Ps (for example, for a certain period of time), that is, in the standby state, it is notified that the standby state has been entered. A signal is sent from the control device 8 to the operation device 63 via the engine control unit 62. The operation device 63 may be configured so that the selection of the gas operation can be operated only after entering the standby state.

  When the gas operation is selected in the operation device 63, the engine control unit 62 that has received the gas operation selection input, together with the instruction to start the gas operation, as described above, the required gas pressure corresponding to the engine load during the oil operation. Pr (see FIG. 3) is sent to the control device 8.

After receiving the instruction to start the gas operation, the control device 8 controls the rotational speed of the LNG pump 41 and the flow control valve 71 so that the pressure P ₀ measured by the pressure measuring device 82 matches the required gas pressure Pr. Adjust at least one of the openings.

Specifically, the control unit 8, when the set pressure Ps required gas pressure Pr is smaller than, firstly, while maintaining the rotational speed of the LNG pump 41 to the minimum rotational speed r _0, the flow control valve 71 is fully closed . While the LNG discharged from the LNG pump 41 continues to be vaporized by the vaporizer 5, the LNG returning from the reflux line 7 to the LNG tank 2 is almost zero. Therefore, as shown in FIG. The pressure of the vaporized gas in 32 (that is, the measured pressure P ₀ at the pressure measuring device 82) gradually increases. Thereafter, when the pressure P ₀ measured by the pressure measuring device 82 approaches the required gas pressure Pr, the opening degree of the flow control valve 71 is increased while the rotation speed of the LNG pump 41 is kept at the minimum rotation speed r _0. Make it bigger.

When the measured pressure P ₀ reaches the required gas pressure Pr, the engine control unit 62 opens the switching valve 42 and the shut-off valve 43, whereby the vaporized gas flows into the accumulator 44 and the measured pressure P as shown in FIG. ₀ descends. Similarly, when the set pressure Ps and the required gas pressure Pr are equal, the control device 8 opens the switching valve 42 and the shutoff valve 43 after receiving an instruction to start the gas operation, and the measured pressure P ₀ is Descend. Since the measured pressure P ₀ and the required gas pressure Pr have deviated, the control device 8 fully closes the flow rate control valve 71 again while maintaining the rotational speed of the LNG pump 41 at the minimum rotational speed r ₀ .

Gas supply system 10A according to this embodiment, when the request gas pressure Pr measured pressure P ₀ is constant or low, can take high speed boost mode. In the high-speed pressure increase mode, the control device 8 controls the LNG pump 41 and the flow rate control valve 71 so as to increase the measured pressure P ₀ more quickly.

Specifically, when the pressure difference ΔP obtained by subtracting the pressure P ₀ measured by the pressure measuring device 82 from the required gas pressure Pr is larger than a reference value (for example, 5 MPa), the control device 8 determines that the pressure difference ΔP is The rotational speed of the LNG pump 41 is set to a rotational speed (for example, 2r ₀ ) larger than the minimum rotational speed r ₀ until the flow rate control valve 71 is fully closed until a predetermined value (for example, 2 MPa) or less. Then, after the pressure difference ΔP is equal to or less than a predetermined value mentioned above, the flow control valve 71 remains fully closed, back to the minimum frequency r ₀ again. Thus, it is possible to make the pressure P ₀ of the fuel gas to more quickly required gas pressure Pr. However, the gas supply system 10A is not necessarily required to take the high-speed pressure-increasing mode. As shown by the two-dot chain line in FIGS. until gas injection is started, while retaining the rotational speed of the LNG pump 41 to the minimum rotational speed r _0, it may be adjusted only opening of the flow control valve 71. Increasing the rotational speed of the LNG pump 41, but the power consumption of the LNG pump 41 is increased, by keeping the rotational speed to the minimum rotational speed r _0, power consumption can be suppressed.

The gas supply system 10A according to the embodiment, in a state where the engine is not gas injection, when the measured pressure P ₀ for the requested gas pressure Pr certain level high (e.g., a gas during high load operation of the engine in the case, etc.) the operation is interrupted, it may take a fast pressure reduction mode for reducing the more rapidly measure the pressure P _0. In high-speed vacuum mode, the control unit 8, so as to reduce the pressure of the more rapidly measure the pressure P _0, and controls the LNG pump 41 and flow control valve 71.

Specifically, when the pressure difference ΔP obtained by subtracting the required gas pressure Pr from the pressure P ₀ measured by the pressure measuring device 82 is larger than a reference value (for example, 2 MPa), the control device 8 determines that the pressure difference ΔP is The LNG pump 41 is stopped and the opening degree of the flow control valve 71 is increased until the value becomes a predetermined value (for example, 1 MPa) or less. Then, after the pressure difference ΔP becomes equal to or less than a predetermined value, the rotational speed of the LNG pump 41 is operated again at the minimum rotational speed r ₀ so that the measured pressure P ₀ approaches the required gas pressure Pr, and the flow rate control is performed. The opening degree of the valve 71 is adjusted. Thus, it is possible to make the pressure P ₀ of the fuel gas to more quickly required gas pressure Pr.

Thereafter, when the pressure P ₀ measured by the pressure measuring instrument 82 approaches the required gas pressure Pr, the opening degree of the flow control valve 71 is adjusted while the rotation speed of the LNG pump 41 is kept at the minimum rotation speed r ₀ . Then, the opening degree of the flow control valve 71 is adjusted so that the measured pressure P ₀ is maintained at the required gas pressure Pr.

(Gas pressure control method from the start of gas injection until the gas ratio reaches the set value)
When the control device 8 determines that the measured pressure P ₀ at the pressure measuring device 82 is maintained at the required gas pressure Pr for a certain period of time, it informs that the engine supply pressure has reached the required gas pressure Pr, that is, the injection pressure. A signal is sent from the control device 8 to the engine control unit 62, and the engine 6 starts gas injection into the cylinder. Moreover, the engine control part 62 starts sending the above-mentioned gas load GL to the control apparatus 8 as gas consumption with the start of gas injection.

  The engine control unit 62 starts gas injection and maintains the output of the engine 6 at a constant value (for example, the ratio of the current engine output to the rated output of the engine 6 is 20%), and the gas ratio is changed from 0%. The value is gradually increased until a set value (for example, 75%) is reached. Accordingly, the gas load GL, that is, the consumption amount of the gas vaporized by the vaporizer 5 in the engine 6 gradually increases (see FIGS. 2A and 4). On the other hand, the engine control unit 62 gradually decreases the oil ratio as the gas ratio increases (see FIG. 4).

The control device 8 maintains the rotational speed of the LNG pump 41 at the minimum rotational speed r ₀ so that the pressure P ₀ measured by the pressure measuring device 82 is maintained at the required gas pressure Pr, and the flow rate control valve 71. Reduce the opening of. Then, when the gas ratio reaches the set value, the opening degree of the flow control valve 71 is automatically controlled so that the required gas pressure Pr is maintained. Even after the flow control valve is fully closed, when the pressure P ₀ is less than the required gas pressure Pr is gradually raised the rotational speed of the LNG pump 41 (see Figure 2 (b)). Then, when the gas ratio reaches the set value, the rotation speed of the LNG pump 41 is automatically controlled so that the required gas pressure Pr is maintained. Thus, since the rotation speed of the LNG pump 41 is fixed to the minimum rotation speed r ₀ and only the opening degree of the flow control valve 71 is adjusted, the power consumption in the LNG pump 41 can be minimized.

In the gas supply system 10A according to this embodiment, as described above, the control device 8 performs control so as to increase the rotational speed of the LNG pump 41 when the flow control valve 71 is fully closed. The rotational speed of the LNG pump 41 may be increased before the flow control valve 71 is fully closed. However, after the gas injection is started in the engine 6, the control device 8 does not turn on the LNG pump 41 until the gas load GL sent from the engine control unit 62 exceeds a pump acceleration allowable value (for example, 3%). It is desirable to keep the rotational speed at the minimum rotational speed r ₀ , in other words, prohibit the increase in the rotational speed of the LNG pump 41. Thereby, the pressure of the fuel gas can be stably controlled even in a state where the gas load GL is low and the gas consumption is substantially close to zero.

As described above, in the gas supply system 10 </ b> A according to this embodiment, the control device 8 adjusts the rotation speed of the LNG pump 41 and the opening degree of the flow control valve 71, and increases the LNG pressure boosted by the LNG pump 41. The pressure of the fuel gas is maintained at the set pressure Ps even before the gas operation is started, because the pressure on the downstream side of the LNG pump 41 can be maintained constant by returning the section from the reflux line 7. Standby state can be taken. For this reason, since the pressure downstream of the pump is already maintained at a constant high pressure at the start of gas operation, the time for raising the fuel gas to the required gas pressure Pr can be shortened and quickly adjusted to the required gas pressure. it can.
Further, since the gas injection in the engine 6 has not started, the required gas pressure Pr from the engine 6 can be adjusted even when the gas flow rate is substantially zero.
Further, until the gas operation is started, the rotational speed of the LNG pump 41 is fixed to the minimum rotational speed r ₀ and only the opening degree of the flow rate control valve 71 is adjusted, so that it is returned from the reflux line 7 to the LNG tank 2. It is possible to adjust the fuel gas to the set pressure Ps while minimizing the amount of LNG. By minimizing the amount of LNG returned from the reflux line 7 to the LNG tank 2, heat input to the LNG tank 2 due to the LNG returned to the LNG tank can be minimized.

Second Embodiment
Next, a gas supply system 10B according to a second embodiment of the present invention will be described with reference to FIG. In the present embodiment and the third embodiment to be described next, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

The gas supply system 10B according to the second embodiment further includes a pressure regulating valve 9 provided in a portion upstream of the switching valve 42 in the second supply line 32 in addition to the components of the first embodiment. . The gas supply system 10B according to the second embodiment, instead of the above-described pressure measuring device 82 of the first embodiment, the first pressure measurement device for measuring the pressure P ₁ on the upstream side of the pressure regulating valve 9 83 and a second pressure measuring instrument 84 for measuring the pressure P ₂ downstream from the pressure regulating valve 9. The pressure regulating valve 9, the first pressure measuring instrument 83 and the second pressure measuring instrument 84 are all connected to the control device 8, and the control device 8 controls the opening degree of the pressure regulating valve 9.

  Below, the control method of the supply gas pressure to the engine 6 for shifting to gas operation from the start of gas operation using the gas supply system 10B which concerns on this embodiment is demonstrated with reference to FIG. FIG. 6 shows changes over time in each value when the oil operation is switched to the gas operation during the voyage of the LNG carrier 1B to which the gas supply system 10B is applied. A gas pressure control method before switching from operation to gas operation will be described.

The control method for the LNG pump 41, the flow rate control valve 71 and the like is the same as the control method in the first embodiment from when the LNG pump 41 is activated until gas injection is started in the engine 6 through the standby state. The control device 8 controls the pressure regulating valve 9 to be fully opened until gas injection is started in the engine 6. Here, “full open” means not only the degree of opening of the pressure regulating valve 9 is 100% but also the degree that the degree of opening of the pressure regulating valve 9 does not hinder the flow of gas vaporized in the vaporizer 5 (for example, 95% or more). ). In FIG. 6A, the pressure P ₁ measured by the first pressure measuring instrument 83 is indicated by a solid line, the pressure P ₂ measured by the second pressure measuring instrument 84 is indicated by a broken line, and the measured pressure P ₁ and the measured pressure P ₁ are measured. part where the pressure P ₂ overlap is shown by the solid line. Until gas injection is started in the engine 6, a slight loss of gas passes through the pressure adjustment valve 9, so that a pressure loss occurs in the pressure adjustment valve 9. However, when maintaining the setting pressure Ps or requests gas pressure Pr is nearly zero gas flow through the pressure regulating valve 9, measuring the pressure P ₁ and the measured pressure P ₂ coincide. For this reason, both the 1st pressure measuring device 83 and the 2nd pressure measuring device 84 can become the pressure measuring device of this invention. That is, before the start of gas operation, the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 may be controlled based on either the first pressure measuring device 83 or the second pressure measuring device 84.

After gas injection is started by the engine 6, the gas load GL gradually increases until the gas ratio reaches a set value. As shown in FIG. 6C, the control device 8 keeps the pressure regulating valve 9 fully opened until the gas load GL indicating the gas consumption exceeds a predetermined threshold GL ₁ (for example, GL = 20%). To. Further, the control unit 8, until gas load GL exceeds the threshold GL _1, the pressure in the downstream portion of the pressure regulating valve 9 in the second supply line 32, i.e. to measure the pressure P ₂ is equal to the required gas pressure Pr In addition, at least one of the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 is adjusted. For example, the control device 8 performs the same control as in the first embodiment on the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 based on the second pressure measuring device 84. When the gas load GL is equal to or less than the predetermined threshold GL ₁ , that is, when the flow rate of the gas passing through the pressure adjustment valve 9 is small, the pressure adjustment valve 9 is fully opened and the pressure adjustment by the pressure adjustment valve 9 is performed. Not performed. This threshold value GL ₁ is a gas load when the gas flow rate passing through the pressure regulating valve 9 is the lowest flow rate at which the pressure can be adjusted, for example.

After the gas load GL exceeds the threshold GL ₁ , the control device 8 determines that the pressure in the upstream portion of the pressure regulating valve 9 in the second supply line 32, that is, the measured pressure P ₁ is a predetermined value (required) from the required gas pressure Pr. For example, at least one of the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 is adjusted so as to coincide with a pressure that is larger by 1 MPa. Further, the control unit 8, so that the pressure on the downstream side portion of the pressure regulating valve 9 in the second supply line 32, i.e. the measurement pressure P ₂ coincides with the required gas pressure Pr, adjusting the opening of the pressure regulating valve 9 . Thereby, the pressure on the downstream side of the pressure adjustment valve 9 can be adjusted using the pressure adjustment valve 9.

  Also in this embodiment, the same effect as the first embodiment can be obtained. In addition, this embodiment is a gas supply system 10B provided with a pressure regulating valve 9. However, when the flow rate of gas passing through the pressure regulating valve 9 is almost zero or slight, it is supplied to the engine 6. The supply gas pressure can be adjusted by controlling the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 without performing the adjustment with the pressure adjustment valve 9. On the other hand, when the flow rate passing through the pressure adjusting valve 9 is sufficient, the pressure can be adjusted using the pressure adjusting valve 9.

<Third Embodiment>
Next, a gas supply system 10C according to a third embodiment of the present invention will be described with reference to FIG. In the present embodiment, in addition to the components of the second embodiment, a bypass line 91 connected from the upstream portion of the pressure regulating valve 9 to the downstream portion of the pressure regulating valve 9 in the second supply line 32, and the bypass line 91 Further, a bypass valve 92 is provided. The bypass valve 92 is an on-off valve and is connected to the control device 8. The control device 8 controls opening and closing of the bypass valve 92.

  Below, the control method of the supply gas pressure to the engine 6 for shifting to gas operation from the start of gas operation using the gas supply system 10C which concerns on this embodiment is demonstrated with reference to FIG. FIG. 8 shows the change over time of each value when the oil operation is switched to the gas operation during the voyage of the LNG carrier 1C to which the gas supply system 10C is applied. A gas pressure control method before switching from operation to gas operation will be described.

  The control method for the LNG pump 41, the flow rate control valve 71 and the like is the same as the control method in the first embodiment from when the LNG pump 41 is activated until gas injection is started in the engine 6 through the standby state. The control device 8 controls to open the bypass valve 92 until gas injection is started in the engine 6. Until the gas injection is started by the engine 6, the opening degree of the pressure regulating valve 9 may be any.

After gas injection is started by the engine 6, the gas load GL gradually increases until the gas ratio reaches a set value. As shown in FIG. 8C, the control device 8 keeps the bypass valve 92 open until the gas load GL indicating the gas consumption exceeds a predetermined threshold value GL ₁ (for example, GL = 20%). . Therefore, the pressure difference between the measured pressure P ₂ of the measurement pressure P ₁ and the second pressure measuring device 84 of the first pressure measuring device 83 is little. For this reason, both the 1st pressure measuring device 83 and the 2nd pressure measuring device 84 can become the pressure measuring device of this invention. That is, the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 may be controlled based on either the first pressure measuring device 83 or the second pressure measuring device 84. Until the gas load GL exceeds a predetermined threshold value GL _1, the control method such as LNG pump 41, the flow control valve 71 is the same as the control method in the first embodiment.

After the gas load GL exceeds the threshold GL ₁ , the control device 8 closes the bypass valve 92 and the pressure in the upstream portion of the pressure regulating valve 9 in the second supply line 32, that is, the measured pressure P ₁ is the required gas. At least one of the rotational speed of the LNG pump 41 and the opening degree of the flow control valve 71 is adjusted so as to coincide with a pressure that is larger than the pressure Pr by a predetermined value (for example, 1 MPa). For example, if the flow control valve 71 is not fully closed when the gas load GL exceeds the threshold GL ₁ , the control device 8 matches the pressure that the measured pressure P ₁ is larger than the required gas pressure Pr by a predetermined value. As described above, while the rotation speed of the LNG pump 41 is kept at the minimum rotation speed r ₀ , the opening degree of the flow control valve 71 is decreased, and the measured pressure P ₁ is larger than the required gas pressure Pr by a predetermined value. The opening degree of the flow control valve 71 is automatically controlled so that the pressure is maintained. For example, if the flow control valve is fully closed when the gas load GL exceeds the threshold GL ₁ , the control device 8 determines that the measured pressure P ₁ is a predetermined value (for example, 1 MPa) from the required gas pressure Pr. to match the high pressure, it will increase the rotational speed of the LNG pump 41, where the pressure P ₁ is reached by large pressure predetermined value than the required gas pressure Pr, so that the pressure P ₁ is kept constant The rotational speed of the LNG pump 41 is automatically controlled (see FIG. 8A). Further, after the gas load GL exceeds the threshold GL ₁ , the control device 8 determines that the pressure in the downstream portion of the pressure regulating valve 9 in the second supply line 32, that is, the measured pressure P ₂ coincides with the required gas pressure Pr. Thus, the opening degree of the pressure regulating valve 9 is adjusted.

Also in this embodiment, the same effect as the first embodiment can be obtained. In addition, this embodiment is a gas supply system 10C provided with the pressure regulating valve 9, but when the flow rate of the gas flowing through the second supply line 32 is almost zero or small, the gas is supplied to the engine 6. The supply gas pressure can be adjusted by controlling the rotation speed of the LNG pump and the opening degree of the flow control valve 71 without performing the adjustment with the pressure adjusting valve 9. On the other hand, when the flow rate of the gas flowing through the second supply line 32 is sufficient, the pressure can be adjusted using the pressure adjusting valve 9. Further, since the pressure valve 9 is opened by allowing the gas to pass by opening the bypass valve 92 that is an on-off valve, the pressure loss is less than in the second embodiment in which the gas is allowed to pass. Can be lowered. Furthermore, by a predetermined value by a pressure greater the pressure P ₁ on the upstream side than the required gas pressure Pr of the pressure regulating valve 9, adjusts the pressure P ₂ on the downstream side of the pressure regulating valve 9 with a pressure regulating valve 9 can do.

<Other embodiments>
In the above embodiment, the gas supply system applied to the LNG carrier has been described. However, the ship to which the gas supply system of the present invention is applied is not limited to the LNG carrier, and is a ship for other uses such as an LNG fuel ship. Alternatively, the reservoir may be a fuel-dedicated tank. Further, the liquefied gas is not limited to LNG, but may be LPG or liquid hydrogen LH ₂ . Further, the gas supply system according to the present invention is not limited to the one applied to the ship, and may be applied to, for example, an onshore power generation diesel engine.
In the above embodiment, the engine 6 is not limited to a dual fuel engine, but may be a gas-only engine, or may not be limited to a two-cycle engine, and may be a four-cycle engine.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a gas supply system to a diesel engine that uses gas as fuel and a ship equipped with the same.

1A, 1B, 1C LNG carrier 10A, 10B, 10C Gas supply system 2 LNG tank 31 First supply line 32 Second supply line 41 LNG pump 42 Switching valve 5 Vaporizer 6 Engine 62 Engine controller 7 Reflux line 71 Flow control valve 8 control device 82 pressure measuring device 83 first pressure measuring device 84 second pressure measuring device 9 pressure regulating valve 91 bypass line 92 bypass valve Pr required gas pressure Ps set pressure

Claims (12)

A gas supply system for supplying gas to a diesel engine that uses gas as fuel,
A reservoir for storing liquefied gas;
A vaporizer for vaporizing the liquefied gas;
A first supply line for directing liquefied gas from the reservoir to the vaporizer;
A second supply line for directing vaporized gas from the vaporizer to the diesel engine;
A pump provided in the first supply line;
A switching valve provided in the second supply line and closed except during gas operation of the diesel engine;
A pressure measuring instrument for measuring the pressure in the upstream portion of the switching valve in the second supply line;
A reflux line that branches from the first supply line downstream of the pump and leads to the reservoir;
A flow control valve provided in the reflux line;
A control device for controlling the pump and the flow rate control valve, the control device receiving an instruction to start gas operation from a control unit of a diesel engine,
The control device includes:
Before receiving the instruction to start the gas operation, fully open the flow control valve and start the pump, and then the pressure measured by the pressure measuring instrument is kept at the set pressure, While maintaining the rotation speed of the pump at the minimum rotation speed, the opening degree of the flow control valve is adjusted,
After receiving the instruction to start the gas operation and after the switching valve is opened, the pressure measured by the pressure measuring instrument is made to match the required gas pressure from the control unit of the diesel engine. Adjusting at least one of the rotational speed of the pump and the opening of the flow control valve ;
After the pressure measured by the pressure measuring instrument reaches the required gas pressure and the gas injection is started in the diesel engine with the pump speed maintained at the minimum speed. Until the gas consumption sent from the control unit of the diesel engine, which gradually rises with the start of gas injection, exceeds the allowable pump speed increase, the pump speed is prohibited from increasing, and the pump speed A gas supply system that maintains the minimum rotation speed . The control device opens the flow rate control valve while maintaining the rotation speed of the pump at the minimum rotation speed from when the gas operation start instruction is received until gas injection is started by the diesel engine. The gas supply system according to claim 1, wherein the degree is adjusted. After receiving the instruction to start the gas operation, the control device,
When the pressure difference obtained by subtracting the pressure measured by the pressure measuring instrument from the required gas pressure is larger than a reference value, the rotation speed of the pump is reduced to the minimum rotation until the pressure difference becomes a predetermined value or less. And set the rotational speed larger than the number, fully closing the flow control valve,
2. The gas supply system according to claim 1, wherein when the pressure difference is smaller than a reference value, the opening degree of the flow control valve is adjusted while maintaining the rotation speed of the pump at the minimum rotation speed. After the gas injection is started in the diesel engine, the control device is configured so that the pressure measured by the pressure measuring instrument is maintained at or greater than the required gas pressure. The rotation speed of the pump is increased when the opening degree of the flow rate control valve is decreased while the rotation number of the flow rate control valve is fully closed while the rotation speed of the pump is fully closed. The gas supply system according to any one of to 3 . The gas supply system according to any one of claims 1 to 4 , further comprising a pressure regulating valve provided in an upstream portion of the second supply line with respect to the switching valve. The control device fully opens the pressure regulating valve before gas injection is started in the diesel engine, and after the gas injection is started in the diesel engine, until the gas consumption exceeds a threshold value, The gas supply system according to claim 5 , wherein the pressure regulating valve is fully opened. A gas supply system for supplying gas to a diesel engine that uses gas as fuel,
A reservoir for storing liquefied gas;
A vaporizer for vaporizing the liquefied gas;
A first supply line for directing liquefied gas from the reservoir to the vaporizer;
A second supply line for directing vaporized gas from the vaporizer to the diesel engine;
A pump provided in the first supply line;
A switching valve provided in the second supply line and closed except during gas operation of the diesel engine;
A pressure measuring instrument for measuring the pressure in the upstream portion of the switching valve in the second supply line;
A reflux line that branches from the first supply line downstream of the pump and leads to the reservoir;
A flow control valve provided in the reflux line;
A control device for controlling the pump and the flow rate control valve, the control device receiving an instruction to start gas operation from a control unit of a diesel engine,
The control device includes:
Before receiving the instruction to start the gas operation, fully open the flow control valve and start the pump, and then the pressure measured by the pressure measuring instrument is kept at the set pressure, Adjusting the opening of the flow control valve,
After receiving the instruction to start the gas operation and after the switching valve is opened, the pressure measured by the pressure measuring instrument is made to match the required gas pressure from the control unit of the diesel engine. Adjusting at least one of the rotational speed of the pump and the opening of the flow control valve;
A pressure regulating valve provided in an upstream portion of the switching valve in the second supply line;
The control device fully opens the pressure regulating valve before gas injection is started in the diesel engine, and after the gas injection is started in the diesel engine, until the gas consumption exceeds a threshold value, Fully open the pressure adjustment valve,
The pressure measuring instrument is a first pressure measuring instrument provided in an upstream portion of the pressure regulating valve in the second supply line,
The gas supply system further includes a second pressure measuring instrument provided in a portion of the second supply line between the pressure regulating valve and the switching valve,
After the gas consumption exceeds the threshold value, the control device is configured so that the pressure measured by the first pressure measuring device coincides with a pressure larger than the required gas pressure by a predetermined value. Adjusting at least one of the rotational speed and the opening of the flow control valve, and adjusting the opening of the pressure adjustment valve so that the pressure measured by the second pressure measuring device matches the required gas pressure ; gas supply system. A gas supply system for supplying gas to a diesel engine that uses gas as fuel,
A reservoir for storing liquefied gas;
A vaporizer for vaporizing the liquefied gas;
A first supply line for directing liquefied gas from the reservoir to the vaporizer;
A second supply line for directing vaporized gas from the vaporizer to the diesel engine;
A pump provided in the first supply line;
A switching valve provided in the second supply line and closed except during gas operation of the diesel engine;
A pressure measuring instrument for measuring the pressure in the upstream portion of the switching valve in the second supply line;
A reflux line that branches from the first supply line downstream of the pump and leads to the reservoir;
A flow control valve provided in the reflux line;
A control device for controlling the pump and the flow rate control valve, the control device receiving an instruction to start gas operation from a control unit of a diesel engine,
The control device includes:
Before receiving the instruction to start the gas operation, fully open the flow control valve and start the pump, and then the pressure measured by the pressure measuring instrument is kept at the set pressure, Adjusting the opening of the flow control valve,
After receiving the instruction to start the gas operation and after the switching valve is opened, the pressure measured by the pressure measuring instrument is made to match the required gas pressure from the control unit of the diesel engine. Adjusting at least one of the rotational speed of the pump and the opening of the flow control valve;
A pressure regulating valve provided in an upstream portion of the switching valve in the second supply line;
A bypass line connected from the upstream side portion of the pressure regulating valve to the downstream side portion of the pressure regulating valve in the second supply line;
A bypass valve provided in the bypass line,
The control device opens the bypass valve before gas injection is started in the diesel engine, and after the gas injection is started in the diesel engine, until the gas consumption exceeds a threshold value, the bypass valve is opened. opening the, gas supply system. The pressure measuring instrument is a first pressure measuring instrument provided in an upstream portion of the pressure regulating valve in the second supply line,
The gas supply system further includes a second pressure measuring instrument provided in a portion of the second supply line between the pressure regulating valve and the switching valve,
The control device closes the bypass valve after the gas consumption exceeds the threshold, and the pressure measured by the first pressure measuring device coincides with a pressure larger than the required gas pressure by a predetermined value. And adjusting at least one of the rotational speed of the pump and the opening of the flow control valve so that the pressure measured by the second pressure measuring device matches the required gas pressure. The gas supply system of Claim 8 which adjusts the opening degree of. The diesel engine, only the oil is a dual-fuel diesel engine oil operating oil and the both gases is switchable between gas operation to be used as a fuel to be used as a fuel, either of claims 1-9 one The gas supply system according to item. The gas supply system according to any one of claims 1 to 10 , wherein the diesel engine is a two-cycle diesel engine. Vessel provided with a gas supply system according to any one of claims 1 to 11.

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