Fuel supply system and control method thereof

Abstract

To provide a fuel supply system and its control method capable of supplying fuel gas to an engine at a proper supply pressure regardless of fluctuation of a fuel supply amount and stabilizing pressure in a fuel supply passage.SOLUTION: The fuel supply system includes a fuel pump that pressurizes and feeds a liquefied fuel, a fuel vaporizer that vaporizes the liquefied fuel to generate a fuel gas, a supply pressure regulator that regulates a supply pressure of the fuel gas introduced into the engine, a supply pressure detector that detects the supply pressure, and a control circuit. The flow rate of the fuel pump is controlled so that the acquired predetermined index value becomes a predetermined index target value, and the adjustment amount of the supply pressure regulator is set to the predetermined index value, or the index target value is corrected using the adjustment amount of the supply pressure regulator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a fuel supply system and a control method thereof. [Background technology]

[0002] There are known engines that use vaporized fuel gas obtained by vaporizing liquefied fuel such as liquefied natural gas or liquefied hydrogen as fuel. In such engines, it is desirable to control the supply pressure of the fuel gas supplied to the engine so that it reaches a target supply pressure value regardless of the load applied to the engine.

[0003] The following Patent Document 1 describes a configuration for maintaining an appropriate supply pressure even when a sudden change in fuel supply amount occurs due to a sudden load change or the like. Patent Document 1 discloses controlling a pressure regulating valve to maintain the supply pressure at a supply pressure target value, and controlling a motor that drives a boost pump that delivers liquefied fuel to maintain the inlet pressure of the liquefied fuel to a fuel evaporator that vaporizes the liquefied fuel at an inlet pressure target value. Patent Document 1 also discloses correcting the operation amount of the motor, which is determined as the difference between the inlet pressure and the inlet pressure target value, based on the operation amount of the pressure regulating valve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6026648 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration of Patent Document 1, the operation amount of the pressure regulating valve acts as a disturbance in the control loop for the inlet pressure, so the inlet pressure may not converge to the target inlet pressure value, and the pressure in the fuel supply path may not be stable.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a fuel supply system and a control method thereof that can supply fuel gas to an engine at an appropriate supply pressure regardless of fluctuations in the fuel supply amount, and can stabilize the pressure in the fuel supply path. [Means for solving the problem]

[0007] A fuel supply system according to one aspect of the present disclosure includes a fuel pump disposed in a fuel supply path that vaporizes liquefied fuel from a liquefied fuel supply source and supplies it to an engine, the fuel pump pressurizing the liquefied fuel and sending it out; a fuel evaporator disposed downstream of the fuel pump in the fuel supply path that vaporizes the liquefied fuel to produce fuel gas; a supply pressure regulator disposed downstream of the fuel evaporator in the fuel supply path that adjusts the supply pressure of the fuel gas introduced to the engine; a supply pressure detector that detects the supply pressure; and a control circuit, wherein the control circuit controls the supply pressure regulator so that the supply pressure becomes a predetermined supply pressure target value, acquires a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path, controls the flow rate of the fuel pump so that the acquired predetermined index value becomes a predetermined index target value, and sets the adjustment amount of the supply pressure regulator to the predetermined index value or corrects the index target value using the adjustment amount of the supply pressure regulator.

[0008] A control method for a fuel supply system according to another aspect of the present disclosure is a control method for a fuel supply system that supplies a fuel gas obtained by vaporizing a liquefied fuel to an engine, the fuel supply system including: a fuel pump that is arranged in a fuel supply path that vaporizes the liquefied fuel from a liquefied fuel supply source and supplies it to the engine, and that pressurizes the liquefied fuel and sends it out; a fuel evaporator that is arranged downstream of the fuel pump in the fuel supply path and vaporizes the liquefied fuel to produce the fuel gas; and a supply pressure regulator that is arranged downstream of the fuel evaporator in the fuel supply path and adjusts the supply pressure of the fuel gas introduced to the engine, the control method including: detecting the supply pressure; controlling the supply pressure regulator so that the supply pressure becomes a predetermined supply pressure target value; obtaining a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path; controlling the flow rate of the fuel pump so that the predetermined index value becomes a predetermined index target value; and setting an adjustment amount of the supply pressure regulator to the predetermined index, or correcting the index target value using the adjustment amount of the supply pressure regulator. [Effects of the Invention]

[0009] According to the present disclosure, fuel gas can be supplied to an engine at an appropriate supply pressure regardless of fluctuations in the fuel supply amount, and the pressure in the fuel supply path can be stabilized. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a fuel supply system according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of a fuel supply system according to a second embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram illustrating an example of the second control circuit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, identical or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant description thereof will be omitted.

[0012] [Embodiment 1] FIG. 1 is a diagram illustrating a schematic configuration of a fuel supply system according to a first embodiment of the present disclosure. The fuel supply system 1 in this embodiment supplies fuel gas as fuel to an engine 2. The engine 2 may be a fuel gas-only combustion engine or an engine that burns both fuel gas and fuel oil. The engine 2 may be used, for example, as a drive source for a ship propulsion unit or the like, or as a drive source for a turbine or the like for generating electricity.

[0013] A fuel supply line 3 is connected to the engine 2. The fuel supply line 3 is connected to a liquefied fuel supply source 4 such as a liquefied fuel tank. The fuel supply line 3 is a line that vaporizes the liquefied fuel from the liquefied fuel supply source 4 and supplies it to the engine 2. The liquefied fuel supplied by the liquefied fuel supply source 4 includes, for example, liquefied hydrogen or liquefied natural gas.

[0014] The fuel supply system 1 includes a fuel pump 5, a fuel evaporator 6, and a supply pressure regulator 7. The fuel pump 5 is disposed downstream of the liquefied fuel supply source 4 in the fuel supply path 3. The fuel pump 5 pressurizes the liquefied fuel from the liquefied fuel supply source 4 and delivers it. The fuel pump 5 is driven by a rotating machine 8. The rotating machine 8 may be a motor or a prime mover.

[0015] The fuel evaporator 6 is disposed downstream of the fuel pump 5 in the fuel supply path 3. The fuel evaporator 6 vaporizes the liquefied fuel delivered by the fuel pump 5 to generate fuel gas. For example, if the liquefied fuel is liquefied hydrogen, the fuel evaporator 6 generates hydrogen gas as the fuel gas. Also, for example, if the liquefied fuel is liquefied natural gas, the fuel evaporator 6 generates natural gas as the fuel gas.

[0016] The supply pressure regulator 7 is disposed downstream of the fuel evaporator 6 in the fuel supply path 3. The supply pressure regulator 7 regulates the supply pressure Ps of the fuel gas introduced into the engine 2. In this embodiment, the supply pressure regulator 7 includes a pressure regulating valve 9.

[0017] In this embodiment, a reflux path 14 is connected between the fuel pump 5 and the fuel evaporator 6 in the fuel supply path 3. The reflux path 14 is a path that returns a portion of the liquefied fuel in the fuel supply path 3 to the liquefied fuel supply source 4. A reflux flow rate regulator 15 is arranged in the reflux path 14. In this embodiment, the reflux flow rate regulator 15 includes a pressure adjustment valve 16. A damper 17 may be connected between the fuel pump 5 and the fuel evaporator 6 in the fuel supply path 3. The damper 17 is filled with the liquefied fuel and the liquefied gas obtained by evaporating the liquefied fuel, and suppresses pressure vibrations that occur in the liquefied fuel in the fuel supply path 3. Note that, instead of the reflux path 14, a path that introduces a portion of the liquefied fuel in the fuel supply path 3 into equipment other than the original liquefied fuel supply source 4, such as a predetermined gas holder, may be connected between the fuel pump 5 and the fuel evaporator 6 in the fuel supply path 3.

[0018] The fuel supply system 1 includes a control circuit 10. The control circuit 10 is configured as a processing circuit that performs various types of signal processing. The control circuit 10 includes a computer such as a microcontroller, a personal computer, or a PLC (Programmable Logic Controller). More specifically, the processing circuit includes a processor, a memory, and peripheral circuits. The processor includes, for example, a CPU or an MPU. The memory includes, for example, a ROM, a RAM, a register, non-volatile storage, and the like. The peripheral circuits include, for example, an input / output interface. Furthermore, the control circuit 10 may include an input device for a user to input operations and an output device such as a monitor that outputs the control status.

[0019] It should be noted that the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this specification, a circuit, unit, means, or section is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where hardware is a processor, which is considered a type of circuit, the circuit, unit, or control means is a combination of hardware and software, and software is used to configure the hardware and / or processor.

[0020] The memory stores a control program. The control circuit 10 reads the control program from the memory and generates a control signal for controlling a controlled object based on the control program. In this embodiment, the control circuit 10 includes a first control circuit 11 and a second control circuit 12. The first control circuit 11 and the second control circuit 12 may have some or all of their processing circuits overlapping. Furthermore, for example, some or all of the processing circuits constituting the control circuit 10 may be configured as the controller of the engine 2, or may be included in an external computer such as a server communicatively connected to the controller of the engine 2 via a communication network.

[0021] The first control circuit 11 controls the supply pressure regulator 7. To this end, the fuel supply system 1 includes a supply pressure detector 21 that detects the supply pressure Ps. The supply pressure detector 21 is disposed between the supply pressure regulator 7 and the engine 2 in the fuel supply path 3. The first control circuit 11 controls the supply pressure regulator 7 so that the supply pressure Ps becomes a predetermined supply pressure target value Pso. The first control circuit 11 generates a manipulated variable for the supply pressure regulator 7 based on the difference between the value Ps detected by the supply pressure detector 21 and the supply pressure target value Pso. In this embodiment, the first control circuit 11 is configured as a control circuit that performs PID control. Therefore, the manipulated variable includes not only a proportional component, which is the difference, but also an integral component and a differential component. Note that the manipulated variable does not necessarily include the integral component, the differential component, or both. The first control circuit 11 transmits a first control signal C1, including the generated manipulated variable, to the supply pressure regulator 7. As described above, the supply pressure regulator 7 includes the pressure adjustment valve 9. Therefore, the operation amount of the supply pressure regulator 7 is the adjustment amount of the opening degree OP of the pressure regulation valve 9.

[0022] If the detected supply pressure Ps is lower than the supply pressure target value Pso, the supply pressure regulator 7 is controlled to increase the opening OP of the pressure regulating valve 9. This increases the supply pressure Ps. If the detected supply pressure Ps is higher than the supply pressure target value Pso, the supply pressure regulator 7 is controlled to decrease the opening OP of the pressure regulating valve 9. This decreases the supply pressure Ps.

[0023] The second control circuit 12 controls the flow rate of the fuel pump 5. In this embodiment, the second control circuit 12 controls the rotation speed of the rotating machine 8 that drives the fuel pump 5. To this end, the second control circuit 12 acquires a predetermined index value downstream of the fuel pump 5 in the fuel supply path 3. The second control circuit 12 controls the rotation speed of the rotating machine 8 so that the acquired index value becomes a predetermined index target value.

[0024] The predetermined index value is selected from values ​​other than the supply pressure Ps. In this embodiment, the predetermined index value is the opening OP of the pressure regulating valve 9 based on the adjustment amount of the supply pressure regulator 7. Therefore, the second control circuit 12 controls the rotation speed of the rotating machine 8 so that the opening OP of the pressure regulating valve 9 becomes the target opening value OPo.

[0025] The fuel supply system 1 includes a valve position detector 22 that detects the opening OP of the pressure regulating valve 9. For example, the valve position detector 22 includes a potentiometer that detects the valve lift of the pressure regulating valve 9. The second control circuit 12 generates a manipulated variable for the rotating machine 8 based on the difference between the value OP detected by the valve position detector 22 and the target opening value OPo. In this embodiment, the second control circuit 12 is also configured as a control circuit that performs PID control. Therefore, the manipulated variable includes not only a proportional component, which is the difference, but also an integral component and a differential component. Note that the manipulated variable does not necessarily include the integral component, the differential component, or both. The second control circuit 12 transmits a second control signal C2 based on the generated manipulated variable to the rotating machine 8. For example, if the drive circuit of the rotating machine 8 is configured with an inverter, the second control circuit 12 generates a drive signal for the inverter corresponding to the generated manipulated variable as the second control signal C2.

[0026] The value used in the second control signal C2 may be the rotation speed [rpm] of the rotating machine 8 itself, or may be a value converted from the rotation speed, such as the frequency [Hz] or angular velocity [rad / s] of the rotating machine 8 or the load factor of the fuel pump 5. The second control circuit 12 may also limit the manipulated variable of the rotating machine 8, which is generated from the difference between the detected opening OP and the target opening value OPo, to within a predetermined range. For example, if the generated manipulated variable of the rotating machine 8 exceeds an upper limit value, the second control circuit 12 may set the manipulated variable of the rotating machine 8 included in the second control signal C2 to the upper limit value.

[0027] When the detected opening OP is larger than the target opening value OPo, the rotating machine 8 is controlled to increase its rotation speed. As a result, the discharge pressure of the fuel pump 5 increases, and the circulation pressure Pf of the fuel supply path 3 increases. On the other hand, when the detected opening OP is smaller than the target opening value OPo, the rotating machine 8 is controlled to decrease its rotation speed. As a result, the discharge pressure of the fuel pump 5 decreases, and the circulation pressure Pf of the fuel supply path 3 decreases.

[0028] According to this embodiment, the control of the first control circuit 11 and the control of the second control circuit 12 are linked. For example, when the load on the engine 2 increases and the supply pressure Ps of fuel gas to the engine 2 decreases, the first control circuit 11 issues a first control signal C1 to increase the opening OP of the pressure regulating valve 9 in the supply pressure regulator 7. When the opening OP increases, the second control circuit 12 issues a second control signal C2 to increase the rotation speed of the rotating machine 8 that drives the fuel pump 5, thereby increasing the flow pressure Pf in the fuel supply path 3.

[0029] As a result, the pressure of the fuel gas introduced into the supply pressure regulator 7 itself increases, and the supply pressure Ps exceeds the supply pressure target value Pso. Therefore, the first control circuit 11 controls the supply pressure regulator 7 to reduce the opening OP of the pressure regulation valve 9 in the supply pressure regulator 7 in order to lower the supply pressure Ps. Through the above control operation, the supply pressure Ps is settled at the supply pressure target value Pso, and the opening OP is settled at the opening target value OPo. At this time, the rotation speed of the rotating machine 8 is settled at a higher rotation speed than in the state before the load on the engine 2 increased, and the distribution pressure Pf is also settled at a pressure higher than in the state before the load on the engine 2 increased.

[0030] Conversely, when the load on the engine 2 decreases and the supply pressure Ps of fuel gas to the engine 2 increases, the first control circuit 11 outputs a first control signal C1 to reduce the opening OP of the pressure regulating valve 9 in the supply pressure regulator 7. When the opening OP decreases, the second control circuit 12 outputs a second control signal C2 to reduce the rotation speed of the rotating machine 8 that drives the fuel pump 5, thereby reducing the flow pressure Pf in the fuel supply path 3.

[0031] As a result, the pressure of the fuel gas introduced into the supply pressure regulator 7 itself decreases, and the supply pressure Ps falls below the supply pressure target value Pso. Therefore, the first control circuit 11 controls the supply pressure regulator 7 to increase the opening OP of the pressure regulation valve 9 in the supply pressure regulator 7 in order to raise the supply pressure Ps. Through the above control operation, the supply pressure Ps is settled at the supply pressure target value Pso, and the opening OP is settled at the opening target value OPo. At this time, the rotation speed of the rotating machine 8 is settled at a lower rotation speed than in the state before the load on the engine 2 was reduced, and the distribution pressure Pf is also settled at a pressure lower than in the state before the load on the engine 2 was reduced.

[0032] As described above, according to this embodiment, the opening OP of the pressure regulating valve 9 in the supply pressure regulator 7 is set as a predetermined index value other than the supply pressure Ps downstream of the fuel pump 5 in the fuel supply path 3, and the flow rate of the fuel pump 5 is controlled so that the opening OP becomes the predetermined target opening value OPo. That is, the flow rate of the fuel pump 5 is controlled so that the opening OP of the pressure regulating valve 9 in the supply pressure regulator 7, which is controlled based on the supply pressure Ps, converges to the predetermined target opening value OPo. This prevents interference between the control of the supply pressure Ps and the control of the flow rate of the fuel pump 5, and enables control of fluctuations in the discharge pressure of the fuel pump 5 in response to fluctuations in the fuel supply amount due to load fluctuations in the engine 2, while ensuring convergence of the flow pressure Pf. As described above, according to this embodiment, fuel gas can be supplied to the engine 2 at an appropriate supply pressure Ps regardless of fluctuations in the fuel supply amount, and the flow pressure Pf in the fuel supply path 3 can be stabilized.

[0033] Furthermore, according to this embodiment, the discharge pressure of the fuel pump 5 located further upstream in the fuel supply path 3 changes based on the adjustment amount of the supply pressure regulator 7, so that the supply pressure Ps can be appropriately controlled in response to larger fluctuations in the fuel supply amount. This prevents the adjustment amount of the supply pressure regulator 7 from being fixed at the upper or lower limit for a long period of time. This prevents the occurrence of adjustment errors in the supply pressure regulator 7, such as the pressure regulating valve 9 being stuck at the upper or lower limit of opening. Furthermore, because the discharge pressure of the liquefied fuel in the fuel pump 5 can be set to a value corresponding to the load of the engine 2, the amount of power required to drive the fuel pump 5 can be reduced when the load of the engine 2 is low.

[0034] Furthermore, according to this embodiment, the actual opening of the pressure regulating valve 9 constituting the supply pressure regulator 7 is detected, and the flow rate of the fuel pump 5 is controlled so that the actual opening becomes the target opening value OPo. Therefore, the opening OP of the pressure regulating valve 9 can be appropriately set to the predetermined target opening value OPo, and the supply pressure Ps and the distribution pressure Pf can be stabilized.

[0035] Instead of detecting the actual opening of the pressure regulating valve 9, the second control circuit 12 may set the operation amount of the pressure regulating valve 9 as the opening OP of the pressure regulating valve 9. In this case, the memory of the control circuit 10 stores the initial opening of the pressure regulating valve 9. The second control circuit 12 acquires the operation amount ΔOP of the pressure regulating valve 9 from the first control circuit 11. The second control circuit 12 estimates the value obtained by adding the operation amount ΔOP of the pressure regulating valve 9 to the initial opening as the current opening OP. The initial opening may be a target opening value OPo.

[0036] By estimating the operation amount ΔOP of the pressure regulating valve 9 as the opening OP of the pressure regulating valve 9, it is possible to eliminate the valve opening detector 22. Therefore, the control mode of this embodiment can be realized with a simpler configuration.

[0037] In the present embodiment, the fuel supply system 1 further includes a third control circuit 13. The third control circuit 13 may be included in the control circuit 10, or may be configured as a control circuit separate from the control circuit 10. The third control circuit 13 controls the reflux flow regulator 15. For this purpose, the fuel supply system 1 includes a circulation pressure detector 23 that detects the circulation pressure in a portion of the fuel supply path 3 downstream of the connection position of the reflux path 14 and upstream of the supply pressure regulator 7. In the present embodiment, the circulation pressure detector 23 detects the circulation pressure Pf in a portion of the fuel supply path 3 between the connection position of the reflux path 14 and the fuel evaporator 6. That is, the circulation pressure Pf in the present embodiment is the inlet pressure of the liquefied fuel introduced into the fuel evaporator 6.

[0038] The third control circuit 13 controls the reflux flow regulator 15 so that the flow pressure Pf becomes a predetermined flow pressure target value. When the value Pf detected by the flow pressure detector 23 exceeds the flow target value, the third control circuit 13 controls the reflux flow regulator 15 to decrease the flow pressure Pf. Furthermore, when the value Pf detected by the flow pressure detector 23 falls below the flow target value, the third control circuit 13 controls the reflux flow regulator 15 to increase the flow pressure Pf. The third control circuit 13 is also configured as a control circuit that performs PID control.

[0039] [Embodiment 2] Fig. 2 is a diagram showing a schematic configuration of a fuel supply system according to a second embodiment of the present disclosure. In the fuel supply system 1B shown in Fig. 2, the same components as those in the fuel supply system 1 shown in Fig. 1 are denoted by the same reference numerals, and description thereof will be omitted.

[0040] 1 in that a flow pressure Pf of the liquefied fuel or fuel gas in the fuel supply path 3 between the fuel pump 5 and the supply pressure regulator 7 is used as a predetermined index value for controlling the flow rate of the fuel pump 5. Furthermore, a second control circuit 12B in the present embodiment corrects the flow pressure target value Pfo, which is an index target value, using the adjustment amount of the supply pressure regulator 7.

[0041] 1, in the present embodiment, the circulation pressure Pf is detected by a circulation pressure detector 23 disposed between the fuel evaporator 6 and the connection position of the return path 14 in the fuel supply path 3. That is, the circulation pressure Pf is the inlet pressure of the liquefied fuel introduced into the fuel evaporator 6.

[0042] The second control circuit 12B controls the rotation speed of the rotating machine 8 that drives the fuel pump 5 so that the flow pressure Pf acquired from the flow pressure detector 23 becomes a predetermined flow pressure target value Pfo. At this time, the second control circuit 12B corrects the flow pressure target value Pfo using the adjustment amount of the supply pressure regulator 7.

[0043] Fig. 3 is a schematic diagram showing an example of the second control circuit shown in Fig. 2. The second control circuit 12 includes a correction value generator 121, an adder 122, a subtractor 123, a PID calculator 124, a limiter 125, and a control signal generator 126. These components 121, 122, 123, 124, 125, and 126 are also configured as processing circuits.

[0044] The second control circuit 12 acquires the manipulated variable ΔOP of the supply pressure regulator 7, which is generated by the first control circuit 11. The correction value generator 121 generates a correction value Pc for the distribution pressure target value Pfo from the acquired manipulated variable ΔOP. For example, a conversion table of the correction value Pc relative to the manipulated variable ΔOP is stored in the memory of the control circuit 10. The correction value generator 121 reads out the conversion table and outputs the value of the conversion table corresponding to the acquired manipulated variable ΔOP as the correction value Pc. The conversion table may be, for example, a polynomial function such as a linear function or a quadratic function, an exponential function, or a logarithmic function, as long as the correction value Pc monotonically increases with respect to the manipulated variable ΔOP in at least a part of the manipulated variable range.

[0045] The adder 122 adds the generated correction value Pc to the distribution pressure target value Pfo to generate a corrected distribution pressure target value Pfoc. The subtractor 123 subtracts the distribution pressure Pf detected by the distribution pressure detector 23 from the corrected distribution pressure target value Pfoc to generate a difference ΔPf. The PID calculator 124 calculates the proportional component, integral component, and derivative component of PID control from the difference ΔPf, and generates the manipulated variable Pfm of the rotating machine 8 by adding these components together. The limiter 125 limits the manipulated variable Pfm to a predetermined range. If the generated manipulated variable Pfm exceeds a predetermined upper limit, the limiter 125 outputs the upper limit as the manipulated variable Pfm. If the generated manipulated variable Pfm is smaller than a predetermined lower limit, the limiter 125 outputs the lower limit as the manipulated variable Pfm. If the generated manipulated variable Pfm is within the predetermined range, the limiter 125 outputs the generated manipulated variable Pfm as is. The second control circuit 12 does not necessarily have to include the limiter 125.

[0046] The control signal generator 126 generates a second control signal C2, which is a rotation speed command signal for the rotating machine 8, from the manipulated variable Pfm. For example, if the drive circuit of the rotating machine 8 is configured with an inverter, the control signal generator 126 generates a drive signal for the inverter according to the manipulated variable Pfm. Note that the value used for the second control signal C2 may be the rotation speed [rpm] of the rotating machine 8 itself, or may be a value converted from the rotation speed of the rotating machine 8, such as the frequency [Hz] or angular velocity [rad / s] or the load factor of the fuel pump 5.

[0047] According to this embodiment, a distribution pressure Pf in the fuel supply path 3 is set as a predetermined index value other than the supply pressure Ps downstream of the fuel pump 5 in the fuel supply path 3, and the flow rate of the fuel pump 5 is controlled so that the distribution pressure Pf becomes the distribution pressure target value Pfo. Furthermore, the distribution pressure target value Pfo is corrected based on the adjustment amount of the supply pressure regulator 7, which is controlled based on the supply pressure Ps. This prevents interference between the control of the supply pressure Ps and the control of the flow rate of the fuel pump 5, and makes it possible to control fluctuations in the discharge pressure of the fuel pump 5 in response to fluctuations in the fuel supply amount due to load fluctuations on the engine 2, etc., while ensuring convergence of the distribution pressure Pf. As described above, according to this embodiment, fuel gas can be supplied to the engine 2 at an appropriate supply pressure Ps regardless of fluctuations in the fuel supply amount, and the distribution pressure Pf in the fuel supply path 3 can be stabilized.

[0048] Furthermore, according to this embodiment, as in the first embodiment, the discharge pressure of the fuel pump 5 further upstream in the fuel supply path 3 changes based on the adjustment amount of the supply pressure regulator 7, so that the supply pressure Ps can be appropriately controlled in response to larger fluctuations in the fuel supply amount. This prevents the adjustment amount of the supply pressure regulator 7 from being fixed at the upper or lower limit value for a long period of time. This prevents the occurrence of adjustment errors in the supply pressure regulator 7, such as the pressure regulating valve 9 being stuck at the upper or lower limit opening. Furthermore, because the discharge pressure of the liquefied fuel in the fuel pump 5 can be set to a value corresponding to the load of the engine 2, the amount of power required to drive the fuel pump 5 can be reduced when the load of the engine 2 is low.

[0049] In the present embodiment, an example has been shown in which the manipulated variable ΔOP of the pressure regulating valve 9 is used as the adjustment variable of the supply pressure regulator 7 for correcting the target circulation pressure value Pfo, but this is not limiting. For example, the opening degree OP of the pressure regulating valve 9 may be detected as in the first embodiment, and the second control circuit 12B may use this opening degree OP to correct the target circulation pressure value Pfo. In addition, in the present embodiment, an example has been shown in which the manipulated variable ΔOP of the pressure regulating valve 9 is directly obtained from the first control circuit 11, but instead, the second control circuit 12 may receive the first control signal C1 output from the first control circuit 11 and obtain manipulated variable information from the received first control signal C1.

[0050] In this embodiment, too, the third control circuit 13 controls the reflux flow regulator 15 so that the circulation pressure Pf becomes a predetermined circulation pressure target value. However, the circulation pressure target value Pfr for controlling the circulation pressure regulator 15 in the third control circuit 13 is set to a value greater than the circulation pressure target value Pfo in the second control circuit 12.

[0051] In this case, when the amount of fuel supplied to the engine 2 is greater than the minimum flow rate of the fuel pump 5, for example, when the engine 2 is operating at rated load, the third control circuit 13 executes control to close the pressure regulation valve 16 to increase the circulation pressure Pf, but the pressure regulation valve 16 is fully closed before the circulation pressure Pf increases to the circulation pressure target value Pfr. In other words, the control of the pressure regulation valve 16 by the third control circuit 13 is stopped due to saturation of the manipulated variable. Meanwhile, the second control circuit 12 controls the rotation speed of the rotating machine 8 that drives the fuel pump 5, so that the circulation pressure Pf converges to the circulation pressure target value Pfo.

[0052] Furthermore, when the amount of fuel supplied to the engine 2 is equal to or less than the minimum flow rate of the fuel pump 5, for example, when the engine 2 is operating at an extremely low load or during load shedding, the second control circuit 12 executes control to reduce the rotational speed of the rotating machine 8 that drives the fuel pump 5 in order to reduce the flow pressure Pf. However, the rotational speed of the rotating machine 8 reaches the lower limit rotational speed before the flow pressure Pf reduces to the flow pressure target value Pfo. In other words, the control of the rotational speed of the rotating machine 8 by the second control circuit 12 is stopped due to saturation of the manipulated variable. Meanwhile, the third control circuit 13 executes control to open the pressure adjustment valve 16 in order to reduce the flow pressure Pf, causing the flow pressure Pf to converge to the flow pressure target value Pfr.

[0053] In this way, by setting the circulation pressure target value Pfr in the third control circuit 13 to a value greater than the circulation pressure target value Pfo in the second control circuit 12, control in either the second control circuit 12 or the third control circuit 13 can be executed preferentially depending on the amount of fuel supplied to the engine 2.

[0054] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various improvements, changes, and modifications are possible within the scope of the spirit of the present disclosure.

[0055] [Other embodiments] For example, in the above embodiment, an example was shown in which the flow pressure Pf was the inlet pressure of the fuel evaporator 6, but instead, the flow pressure Pf may be the pressure of the fuel gas between the fuel evaporator 6 and the supply pressure regulator 7 in the fuel supply path 3, i.e., the outlet pressure of the fuel evaporator 6.

[0056] In the above embodiment, the second control circuit 12 controls the rotation speed of the rotating machine 8 that drives the fuel pump 5 as a more specific configuration for controlling the flow rate of the fuel pump 5, but the present invention is not limited to this. For example, if the fuel pump 5 has variable stator vanes whose pitch angle can be changed, the second control circuit 12 may control the pitch angle of the variable stator vanes so that a predetermined index value becomes a predetermined index target value.

[0057] Furthermore, in the above embodiment, the third control circuit 13 controls the reflux flow regulator 15 so that the circulation pressure Pf becomes a predetermined circulation pressure target value. However, this is not limiting. For example, the third control circuit 13 controls the reflux flow regulator 15 so that the circulation pressure Pf falls within a predetermined circulation pressure range. The third control circuit 13 determines whether the value Pf detected by the circulation pressure detector 23 is equal to or greater than the lower limit Pfl and equal to or less than the upper limit Pfh of the circulation pressure range. If the detected circulation pressure Pf is greater than the upper limit Pfh, the third control circuit 13 sends a third control signal C3 to the reflux flow regulator 15 to increase the circulation flow rate.

[0058] For example, the third control circuit 13 generates the operation amount of the reflux flow regulator 15 based on the value obtained by subtracting the upper limit value Pfh from the detected circulation pressure Pf. As described above, the reflux flow regulator 15 includes the pressure regulating valve 16. Therefore, the operation amount of the reflux flow regulator 15 is the adjustment amount of the opening of the pressure regulating valve 16. When the detected circulation pressure Pf is greater than the upper limit value Pfh, the adjustment amount of the opening of the pressure regulating valve 16 is a value that increases the opening of the pressure regulating valve 16. This increases the circulation amount of the reflux path 14.

[0059] Conversely, if the detected circulation pressure Pf is lower than the lower limit Pfl, the third control circuit 13 transmits a third control signal C3 to the circulation flow regulator 15 to reduce the circulation flow rate. For example, the third control circuit 13 generates the operation amount of the circulation flow regulator 15, i.e., the adjustment amount of the aperture of the pressure regulating valve 16, based on a value obtained by subtracting the detected circulation pressure Pf from the lower limit Pfl. In this case, the adjustment amount of the aperture of the pressure regulating valve 16 is a value that reduces the aperture of the pressure regulating valve 16. This reduces the circulation flow rate through the circulation path 14.

[0060] The circulation pressure range for adjusting the recirculation amount is set to a range larger than the fluctuation range of the circulation pressure Pf caused by fluctuations in the fuel supply amount, thereby preventing interference between the control of the discharge pressure of the fuel pump 5 by the second control circuit 12 and the adjustment control of the recirculation amount.

[0061] Alternatively, the third control circuit 13 may control the pressure regulating valve 16 to open when the flow pressure Pf is equal to or greater than the upper limit value Pfh, and to close when the flow pressure Pf is less than the upper limit value Pfh. In this case, the pressure regulating valve 16 may be configured as a shutoff valve.

[0062] In addition, in the above embodiment, the fuel supply system 1, 1B is exemplified as including the reflux path 14, the reflux regulator 15, and the third control circuit 13. However, the fuel supply system 1, 1B may not have these components. In this case, the fuel supply system 1 in the first embodiment may not have the flow pressure detector 23.

[0063] Summary of this disclosure [Item 1] A fuel supply system according to one aspect of the present disclosure includes a fuel pump disposed in a fuel supply path that vaporizes liquefied fuel from a liquefied fuel supply source and supplies it to an engine, the fuel pump pressurizing the liquefied fuel and sending it out; a fuel evaporator disposed downstream of the fuel pump in the fuel supply path that vaporizes the liquefied fuel to produce fuel gas; a supply pressure regulator disposed downstream of the fuel evaporator in the fuel supply path that adjusts the supply pressure of the fuel gas introduced to the engine; a supply pressure detector that detects the supply pressure; and a control circuit, wherein the control circuit controls the supply pressure regulator so that the supply pressure becomes a predetermined supply pressure target value, acquires a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path, controls the flow rate of the fuel pump so that the acquired predetermined index value becomes a predetermined index target value, and sets the adjustment amount of the supply pressure regulator to the predetermined index value or corrects the index target value using the adjustment amount of the supply pressure regulator.

[0064] According to the above configuration, the flow rate of the fuel pump is controlled so that a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path becomes a predetermined index target value. Furthermore, the index value is controlled or the index value target value is corrected based on the adjustment amount of the supply pressure regulator, which is controlled based on the supply pressure. This prevents interference between the control of the supply pressure and the control of the fuel pump flow rate, and enables control of fluctuations in the discharge pressure of the fuel pump in response to fluctuations in the fuel supply amount while ensuring convergence of the flow pressure. As described above, according to the above configuration, fuel gas can be supplied to the engine at an appropriate supply pressure regardless of fluctuations in the fuel supply amount, and the flow pressure in the fuel supply path can be stabilized.

[0065] Furthermore, with the above configuration, the discharge pressure of the fuel pump further upstream in the fuel supply path changes based on the adjustment amount of the supply pressure regulator, making it possible to appropriately control the supply pressure in response to larger fluctuations in the fuel supply amount. This prevents the adjustment amount of the supply pressure regulator from being fixed at an upper or lower limit value for a long period of time. This prevents the supply pressure regulator from malfunctioning. Furthermore, since the discharge pressure of the liquefied fuel from the fuel pump can be set to a value corresponding to the engine load, the amount of power required to drive the fuel pump can be reduced when the engine is running at a low load.

[0066] [Item 2] In the fuel supply system of item 1, the supply pressure regulator may include a pressure regulation valve, and the control circuit may acquire an aperture of the pressure regulation valve as the predetermined index value and control the flow rate of the fuel pump so that the aperture of the pressure regulation valve becomes a predetermined target aperture value. According to this, the aperture of the pressure regulation valve in the supply pressure regulator is set as a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path, and the flow rate of the fuel pump is controlled so that the aperture becomes the predetermined target aperture value. That is, the flow rate of the fuel pump is controlled so that the aperture of the pressure regulation valve in the supply pressure regulator, which is controlled based on the supply pressure, converges to the predetermined target aperture value. This prevents interference between the control of the supply pressure and the control of the flow rate of the fuel pump, and enables control of fuel pump discharge pressure fluctuations in response to fluctuations in the fuel supply amount while ensuring convergence of the flow pressure.

[0067] [Item 3] The fuel supply system of item 2 may include a valve opening detector that detects the opening of the pressure regulating valve. This detects the actual opening of the pressure regulating valve that constitutes the supply pressure regulator, and controls the flow rate of the fuel pump so that the actual opening matches the target opening value. This allows the opening of the pressure regulating valve to be appropriately set to the predetermined target opening value, stabilizing the supply pressure and distribution pressure.

[0068] [Item 4] In the fuel supply system of item 2, the control circuit may generate an operation amount of the pressure regulating valve based on the difference between the value detected by the supply pressure detector and the target supply pressure value, and set the operation amount as the aperture of the pressure regulating valve. This makes it possible to eliminate the need for an aperture detector by estimating the aperture of the pressure regulating valve from the operation amount of the pressure regulating valve. Therefore, the above control mode can be realized with a simpler configuration.

[0069] [Item 5] In the fuel supply system of item 1, the control circuit may acquire the flow pressure of the liquefied fuel or the fuel gas in a portion of the fuel supply path between the fuel pump and the supply pressure regulator as the predetermined index value, control the flow rate of the fuel pump so that the acquired flow pressure becomes a predetermined flow pressure target value, and correct the flow pressure target value using an adjustment amount of the supply pressure regulator. According to this, the flow pressure in the fuel supply path is set as a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path, and the flow rate of the fuel pump is controlled so that the flow pressure becomes the flow pressure target value. Furthermore, the flow pressure target value is corrected based on the adjustment amount of the supply pressure regulator, which is controlled based on the supply pressure. This prevents interference between the control of the supply pressure and the control of the flow rate of the fuel pump, and enables control of fuel pump discharge pressure fluctuations in response to fluctuations in the fuel supply amount while ensuring convergence of the flow pressure.

[0070] [Item 6] In the fuel supply system of item 5, the control circuit may generate an operation amount for the supply pressure regulator based on a difference between the value detected by the supply pressure detector and the target supply pressure value, and determine a correction amount for the target supply pressure value from the operation amount.

[0071] [Item 7] A control method for a fuel supply system according to another aspect of the present disclosure is a control method for a fuel supply system that supplies a fuel gas obtained by vaporizing a liquefied fuel to an engine, the fuel supply system including: a fuel pump that is arranged in a fuel supply path that vaporizes the liquefied fuel from a liquefied fuel supply source and supplies it to the engine, and that pressurizes the liquefied fuel and sends it out; a fuel evaporator that is arranged downstream of the fuel pump in the fuel supply path and vaporizes the liquefied fuel to produce the fuel gas; and a supply pressure regulator that is arranged downstream of the fuel evaporator in the fuel supply path and adjusts the supply pressure of the fuel gas introduced to the engine, the control method including: detecting the supply pressure; controlling the supply pressure regulator so that the supply pressure becomes a predetermined supply pressure target value; obtaining a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path; controlling the flow rate of the fuel pump so that the predetermined index value becomes a predetermined index target value; and setting an adjustment amount of the supply pressure regulator to the predetermined index, or correcting the index target value using the adjustment amount of the supply pressure regulator. [Explanation of symbols]

[0072] 1,1B Fuel supply system 2 engines 3 Fuel supply route 4 Liquefied fuel sources 5. Fuel pump 6 Fuel evaporator 7 Supply pressure regulator 9 Pressure Regulating Valve 10 Control circuit 21 Supply pressure detector 22 Valve opening detector

Claims

1. a fuel pump disposed in a fuel supply path that vaporizes liquefied fuel from a liquefied fuel supply source and supplies the vaporized fuel to the engine, the fuel pump pressurizing the liquefied fuel and delivering it; a fuel evaporator disposed downstream of the fuel pump in the fuel supply path, and vaporizing the liquefied fuel to generate fuel gas; a supply pressure regulator disposed downstream of the fuel evaporator in the fuel supply path, for adjusting the supply pressure of the fuel gas introduced into the engine; a supply pressure detector that detects the supply pressure; a control circuit; The control circuit controlling the supply pressure regulator so that the supply pressure becomes a predetermined supply pressure target value; acquiring a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path; controlling the flow rate of the fuel pump so that the acquired predetermined index value becomes a predetermined index target value; A fuel supply system in which an adjustment amount of the supply pressure regulator is set to the predetermined index value, or the index target value is corrected using the adjustment amount of the supply pressure regulator.

2. the supply pressure regulator includes a pressure regulating valve; The control circuit acquiring an opening degree of the pressure regulating valve as the predetermined index value; 2. The fuel supply system according to claim 1, wherein the flow rate of the fuel pump is controlled so that the opening of the pressure regulating valve becomes a predetermined target opening value.

3. The fuel supply system according to claim 2 , further comprising a valve opening detector that detects an opening degree of the pressure regulating valve.

4. The control circuit generating an operation amount of the pressure regulating valve based on a difference between the value detected by the supply pressure detector and the supply pressure target value; The fuel supply system according to claim 2 , wherein the manipulated variable is an opening degree of the pressure regulating valve.

5. The control circuit a flow pressure of the liquefied fuel or the fuel gas in a path portion between the fuel pump and the supply pressure regulator in the fuel supply path is acquired as the predetermined index value; controlling the flow rate of the fuel pump so that the acquired circulation pressure becomes a predetermined circulation pressure target value; 2. The fuel supply system according to claim 1, wherein the target flow pressure value is corrected using an adjustment amount of the supply pressure regulator.

6. The control circuit generating an operation amount for the supply pressure regulator based on a difference between the value detected by the supply pressure detector and the supply pressure target value; 6. The fuel supply system according to claim 5, wherein a correction amount for the target flow pressure value is determined from the manipulated variable.

7. A control method for a fuel supply system that supplies fuel gas obtained by vaporizing liquefied fuel to an engine, comprising: The fuel supply system includes: a fuel pump disposed in a fuel supply path that vaporizes the liquefied fuel from a liquefied fuel supply source and supplies the vaporized fuel to the engine, the fuel pump pressurizing the liquefied fuel and delivering it; a fuel evaporator disposed downstream of the fuel pump in the fuel supply path, and vaporizing the liquefied fuel to generate the fuel gas; a supply pressure regulator disposed downstream of the fuel evaporator in the fuel supply path and configured to adjust the supply pressure of the fuel gas introduced into the engine, The control method includes: detecting the supply pressure and controlling the supply pressure regulator so that the supply pressure becomes a predetermined supply pressure target value; acquiring a predetermined index value other than the supply pressure downstream of the fuel pump in the fuel supply path, and controlling a flow rate of the fuel pump so that the predetermined index value becomes a predetermined index target value; A control method in which an adjustment amount of the supply pressure regulator is set as the predetermined index, or the index target value is corrected using the adjustment amount of the supply pressure regulator.

Images