JP2011089596A - Device for supplying lng fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for supplying LNG fuel suppressing change of properties of the LNG fuel. <P>SOLUTION: The device for supplying the LNG fuel includes a vaporizer 16 vaporizing LNG supplied from an LNG vessel 10 and generating vaporized fuel, a mixing tank 22 mixing the vaporized fuel supplied from the vaporizer 16 and boil-off gas delivered from the LNG vessel 10 and generating mixture gas, a check valve 24 opened only to a direction in which the boil-off gas flows from the LNG vessel 10 to the mixing tank 22 and opened when the pressure difference between an internal pressure of the LNG vessel 10 and an internal pressure of the mixing tank 22 is equal to or more than a first predetermined value, and a pressure reducing valve 28 for reducing the pressure of the mixture gas supplied from the mixing tank 22. The mixture gas is generated by mixing the vaporized fuel obtained by vaporizing the LNG in the LNG vessel 10 in the vaporizer 16 to be supplied and the boil-off gas delivered from the LNG vessel 10, and thereby, change of the properties of the LNG fuel can be suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for supplying LNG fuel (liquefied natural gas fuel).

  In the LNG container that stores LNG, boil-off gas is emitted before reaching the pressure limit of the LNG container because LNG evaporates and boil-off gas is generated by heat transfer from the outside due to the difficulty of heat insulation from the container. It is necessary to do so, but at the same time it is a loss of valuable energy.

  For this reason, as described in Patent Document 1, a technique has been proposed in which LNG present in the LNG container after generation of the boil-off gas is vaporized by a vaporizer using boil-off gas diffused from the LNG container.

Japanese Patent Laid-Open No. 5-113108

  However, when LNG spontaneously vaporizes, the components having a low boiling point are vaporized in order and become boil-off gas, and the properties of LNG present in the container change every moment. Therefore, the heat engine uses the gas vaporized by the carburetor as fuel. If supplied to, the amount of heat may change and affect the performance of the heat engine.

  In view of the above-described conventional problems, an object of the present invention is to provide a LNG fuel supply device that suppresses a change in the properties of LNG fuel supplied to a heat engine.

  For this reason, the first form of the LNG fuel supply device according to the present invention includes an LNG container that stores LNG, a vaporizer that vaporizes LNG supplied from the LNG container to generate vaporized fuel, and a supply from the vaporizer A mixing tank that mixes the vaporized fuel and boil-off gas discharged from the LNG container to generate a mixed gas, and the boil-off gas is opened only in the direction from the LNG container to the mixing tank, and the internal pressure of the LNG container And a first check valve that opens when the pressure difference between the pressure and the internal pressure of the mixing tank is equal to or greater than a first predetermined value, and a pressure reducing valve that depressurizes the mixed gas supplied from the mixing tank. It is characterized by that.

  Further, a second form of the LNG fuel supply device according to the present invention is supplied from an LNG container that stores LNG, a vaporizer that vaporizes LNG supplied from the LNG container to generate vaporized fuel, and a vaporizer. Between the LNG container and the mixing tank, a buffer tank for temporarily storing the boil-off gas, and the boil-off gas is LNG. The mixing tank generates a mixed gas by mixing the vaporized fuel and the boil-off gas discharged from the LNG container. A second check valve that opens only in a direction from the container toward the buffer tank, and that opens when a differential pressure between the internal pressure of the LNG container and the internal pressure of the buffer tank is equal to or greater than a second predetermined value; Comprising a flow rate adjusting means for adjusting the flow rate of the boil-off gas flowing from the mixing tank to the mixing tank, and a pressure reducing valve for reducing the pressure of the mixed gas supplied from the mixing tank. And features.

  According to the present invention, the boil-off gas is mixed with the LNG fuel vaporized in the carburetor, whereby the influence on the engine performance due to the property change of the LNG fuel can be suppressed.

1 is a structural diagram of an LNG fuel supply apparatus according to a first embodiment. LNG fuel supply device structure diagram according to the second embodiment LNG fuel supply device structure diagram according to the third embodiment The flowchart which shows the processing content of the control program which concerns on 3rd Embodiment

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a first embodiment of a fuel supply apparatus to which the present invention is applied to a vehicle using LNG as fuel (hereinafter referred to as “LNG fuel vehicle”).

  The LNG fuel supply device includes an LNG container 10 that stores LNG. The LNG container 10 is composed of a sealed inner container 10a and an outer container 10b in order to ensure good heat insulation and suppress the vaporization of LNG stored at a very low temperature, and a so-called “squeezer structure in which the pressure between them is reduced. Is done.

  One end of the LNG delivery pipe 12 for delivering LNG from the LNG container 10 is connected to the lower part of the LNG container 10, and the other end is connected to the vaporizer 16. The carburetor 16 circulates engine cooling water cooled to a substantially constant temperature by a radiator in order to stably vaporize LNG supplied from the LNG container 10 and generate vaporized fuel. The LNG delivery pipe 12 is provided with an on-off valve 14. The on-off valve 14 is composed of, for example, a normally closed solenoid valve that opens in conjunction with the ignition switch ON in order to prevent LNG from leaking out of the LNG container 10 while the engine is stopped.

  Also, a mixing tank 22 communicating with both the vaporized fuel supply pipe 18 whose one end is connected to the vaporizer 16 and the boil-off gas discharge pipe 20 whose one end is connected to the upper part of the LNG container 10 is disposed. . The mixing tank 22 mixes and mixes the vaporized fuel that is vaporized by the vaporizer 16 and supplied through the vaporized fuel supply pipe 18 and the boil-off gas that is generated in the LNG container 10 and then discharged through the boil-off gas discharge pipe 20. Generate gas.

  The boil-off gas discharge pipe 20 is provided with a check valve (check valve) 24 as a first check valve in order to adjust the internal pressure PL of the LNG container 10 increased by the boil-off gas. When the differential pressure before and after the check valve 24, that is, the differential pressure between the internal pressure of the LNG container 10 and the internal pressure of the mixing tank 22 is equal to or greater than a first predetermined value P1, the check valve 24 is configured to remove boil-off gas from the LNG container 10. The valve is opened only in the direction toward the mixing tank 22.

  A pressure reducing valve 28 is disposed in the mixed gas supply pipe 26 connected to the mixing tank 22. The pressure reducing valve 28 adjusts the pressure of the mixed gas supplied to the engine, which is an example of a heat engine to which the mixed gas is supplied, to a predetermined pressure (hereinafter ““ Pressure).

Next, the operation of the LNG fuel supply device will be described.
When the on-off valve 14 is opened in conjunction with the ignition switch ON, the LNG stored in the LNG container 10 is discharged to the vaporizer 16 via the LNG discharge pipe 12. This LNG is LNG existing in the LNG container 10 after boil-off gas is generated by heat transfer from the outside of the LNG container 10, and the ratio of components such as methane is lower than that of the original LNG. The LNG in the container is vaporized using the engine coolant in the vaporizer 16 to become vaporized fuel, and this vaporized fuel is supplied to the mixing tank 22.

  On the other hand, the boil-off gas generated in the LNG container 10 is generated by the check valve 24 that is opened when the differential pressure between the internal pressure PL of the LNG container 10 and the internal pressure Pm of the mixing tank 22 is equal to or higher than the first predetermined value P1. As the valve is opened, it is discharged from the upper part of the LNG container 10 through the boil-off gas discharge pipe 20. Here, the first predetermined value P1 is a value determined so that the internal pressure PL of the LNG container 10 does not exceed its pressure limit, and for example, the difference between the limit pressure of the LNG container 10 and the limit pressure of the mixing tank 22 It is requested from. The boil-off gas does not flow back in the direction toward the LNG container 10 by the function of the check valve 24, and the differential pressure between the internal pressure PL of the LNG container 10 and the internal pressure Pm of the mixing tank 22 is a first predetermined value. It is supplied to the mixing tank 22 until it becomes less than P1.

  In the mixing tank 22, vaporized fuel supplied by being vaporized by the vaporizer 16 and having a lower component ratio such as methane than the original LNG, and methane compared to the original LNG discharged from the upper part of the LNG container 10. The boil-off gas having a high component ratio is mixed, and the resulting mixed gas is reduced to the required pressure through the pressure reducing valve 28 and then supplied to the engine.

  According to such an LNG fuel supply device, by mixing the boil-off gas and the vaporized fuel, the property of the fuel supplied to the engine of the LNG fuel vehicle can be stabilized close to the original LNG component ratio. Therefore, it is possible to suppress the influence on the engine performance due to the change in the properties of the supplied fuel.

  FIG. 2 shows a second embodiment of the LNG fuel supply apparatus according to the present invention. In addition, about the same structure as 1st Embodiment, the description is abbreviate | omitted or simplified by attaching | subjecting the same code | symbol.

  The boil-off gas discharge pipe 20 has a check valve 30 as a second check valve, a buffer tank 32, a throttle valve 34, and a check valve 36 as a third check valve from the LNG container 10 side. Are arranged in this order.

  The check valve 30 is configured such that when the differential pressure before and after the check valve 30, that is, the differential pressure between the internal pressure of the LNG container 10 and the internal pressure of the buffer tank 32 is equal to or greater than a second predetermined value P2, boil-off gas is discharged from the LNG container 10. The valve is opened only in the direction toward the buffer tank 32. The buffer tank 32 temporarily stores the boil-off gas discharged from the LNG container 10 by opening the check valve 30. The throttle valve 34 throttles the flow rate of the boil-off gas that flows from the buffer tank 32 to the mixing tank 22. Note that the flow rate of the boil-off gas varies depending on the differential pressure across the throttle valve 34. For example, the flow rate increases as the differential pressure increases, but the flow rate is constant when the differential pressure is constant at an arbitrary value. . The check valve 36 is configured to prevent the backflow of boil-off gas from the mixing tank 22 to the throttle valve 34 and the buffer tank 32, that is, the differential pressure before and after the check valve 36, that is, the internal pressure of the buffer tank 32 and the internal pressure of the mixing tank 22. The boil-off gas is opened only in the direction from the buffer tank 32 toward the mixing tank 22. The flow rate adjusting means includes a throttle valve 34 and a check valve 36.

Next, the operation of the LNG fuel supply device will be described.
The boil-off gas generated in the LNG container 10 is used to open the check valve 30 that opens when the differential pressure between the internal pressure PL of the LNG container 10 and the internal pressure Pb of the buffer tank 32 is equal to or greater than a second predetermined value P2. Accordingly, it is discharged from the upper part of the LNG container 10 through the boil-off gas discharge pipe 20. Here, the second predetermined value P2 is a value determined so that the internal pressure PL of the LNG container 10 does not exceed the pressure limit, and for example, the difference between the limit pressure of the LNG container 10 and the limit pressure of the buffer tank 32. It is requested from. The boil-off gas is temporarily stored in the buffer tank 32, and the function of the check valve 30 causes the differential pressure between the internal pressure PL of the LNG container 10 and the internal pressure Pb of the buffer tank 32 to flow backward without flowing back toward the LNG container 10. Is supplied to the buffer tank 32 until it becomes less than the predetermined value P2.

  The boil-off gas temporarily stored in the buffer tank 32 is supplied from the check valve 36 that opens when the differential pressure between the internal pressure Pb of the buffer tank 32 and the internal pressure Pm of the mixing tank 22 is equal to or greater than a third predetermined value P3. As the valve opens, it flows in the direction toward the mixing tank 22. Here, the third predetermined value P3 is a value determined so that the internal pressure Pb of the buffer tank 32 does not exceed its pressure limit, and for example, the difference between the limit pressure of the buffer tank 32 and the limit pressure of the mixing tank 22 It is requested from. Then, the boil-off gas is reduced in flow rate by the throttle valve 34, and the internal pressure Pb of the buffer tank 32 and the internal pressure Pm of the mixing tank 22 are not caused to flow back toward the buffer tank 32 by the function of the check valve 36. Is supplied to the mixing tank 22 until the differential pressure becomes less than the third predetermined value P3. Thereafter, the boil-off gas is mixed with the vaporized fuel in the mixing tank 22 as in the first embodiment, and the mixed gas generated thereby is supplied to the engine after being reduced to the required pressure through the pressure reducing valve 28. .

  According to the LNG fuel supply apparatus according to the second embodiment, the boil-off gas generated in the LNG container 10 is temporarily stored in the buffer tank 32 even if the vehicle is left with the engine stopped for a long time. Is supplied to the mixing tank 22 little by little and mixed with the vaporized fuel, and the mixed gas is supplied to the engine, so that a mixed gas having a high boil-off gas concentration is not supplied to the engine of the LNG fuel vehicle immediately after the engine is started. Thus, the fuel properties can be stabilized close to the original LNG component ratio, and fluctuations in engine performance due to changes in the properties of the supplied fuel can be suppressed.

  In the second embodiment, the boil-off gas discharge pipe 20 may be provided with a check valve-equipped throttle valve instead of the throttle valve 34 and the check valve 36. As a result, the configuration of the LNG fuel supply device can be simplified. Alternatively, instead of the throttle valve 34, a pressure compensation flow control valve may be provided. As a result, even when the differential pressure between the internal pressure Pb of the buffer tank 32 and the internal pressure Pm of the mixing tank 22 increases, a boil-off gas with a constant flow rate can be supplied from the buffer tank 32 to the mixing tank 22.

  FIG. 3 shows a third embodiment of the LNG fuel supply apparatus according to the present invention. In addition, about the same structure as 2nd Embodiment, the description is abbreviate | omitted or simplified by attaching | subjecting the same code | symbol.

  A boil-off gas discharge pipe 20 between the buffer tank 32 and the mixing tank 22 is provided with an electromagnetic on-off valve 38 that can be remotely controlled instead of the throttle valve 34 and the check valve 36. Here, as the on-off valve 38, for example, a normally closed solenoid valve is preferably used in order to ensure safety.

  The buffer tank 32 and the mixing tank 22 are respectively provided with a pressure sensor 40 and a pressure sensor 42 as first pressure detecting means and second pressure detecting means for detecting the internal pressure. Pressure signals from the pressure sensors 40 and 42 are input to a control unit 44 incorporating a computer. Then, the control unit 44 appropriately controls the opening / closing of the on-off valve 38 based on the internal pressure of the buffer tank 32 and the mixing tank 22 by executing a control program stored in a ROM (Read Only Memory) or the like. The control unit 44 realizes a control means by executing a control program.

FIG. 4 shows the processing contents of the control program that is started in the control unit 44 when the ignition switch is turned on.
In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the magnitude of the internal pressure Pb of the buffer tank 32 detected by the pressure sensor 40 and the fourth predetermined value P4 is determined. Here, the fourth predetermined value P4 is a value determined so that the internal pressure Pb of the buffer tank 32 does not exceed the pressure limit, and the boil-off gas can be pumped by a differential pressure from the internal pressure Pm of the mixing tank 22. Value. When the internal pressure Pb of the buffer tank 32 is equal to or higher than the fourth predetermined value P4, the process proceeds to step 2 (Yes), while when the internal pressure Pb of the buffer tank 32 is lower than the fourth predetermined value P4, This step is executed again (No).

  In step 2, the magnitude of the internal pressure Pm of the mixing tank 22 detected by the pressure sensor 42 and the fifth predetermined value P5 is determined. Here, the fifth predetermined value P5 is a value that is determined so that the internal pressure Pm of the mixing tank 22 does not exceed its pressure limit, and the fourth predetermined value P5 is a fourth value for pumping boil-off gas from the buffer tank 32 to the mixing tank 22. Is smaller than the predetermined value P4. When the internal pressure Pm of the mixing tank 22 is less than the fifth predetermined value P5, the process proceeds to step 3 (Yes), while when the internal pressure Pm of the mixing tank 22 is equal to or higher than the fifth predetermined value P5, Return to Step 1 (No).

In step 3, the on-off valve 38 is opened to supply boil-off gas from the buffer tank 32 to the mixing tank 22.
In step 4, the magnitude of the internal pressure Pm of the mixing tank 22 detected by the pressure sensor 42 and the fifth predetermined value P5 is determined. When the internal pressure Pm of the mixing tank 22 is not less than the fifth predetermined value P5, the process proceeds to step 6 (Yes), while when the internal pressure Pm of the mixing tank 22 is less than the fifth predetermined value P5, step 5 is performed. Go to (No).

  In step 5, the magnitude of the internal pressure Pb of the buffer tank 32 detected by the pressure sensor 40 and the fourth predetermined value P4 is determined. When the internal pressure Pb of the buffer tank 32 is less than the fourth predetermined value P4, the process proceeds to step 6 (Yes), while when the internal pressure Pb of the buffer tank 32 is less than the fourth predetermined value P4, step 4 is performed. Return to (No).

In step 6, the on-off valve 38 is opened.
In step 7, it is determined whether or not the ignition switch (abbreviated as “IgSW” in the figure) is OFF. When the ignition switch is OFF, the control program is terminated (Yes), while when the ignition switch is ON, the process returns to Step 1 (No).

  In the above control program, the fourth predetermined value P4 and the fifth predetermined value P5 may have pressure ranges defined by an upper limit threshold and a lower limit threshold, respectively. For example, if the upper limit threshold of the fourth predetermined value P4 is P4up, the lower limit threshold is P4lo, the upper limit threshold of the fifth predetermined value P5 is P5up, and the lower limit threshold is P5lo, the internal pressure Pb of the buffer tank 32 is P4up or more and the mixing tank When the internal pressure Pm of 22 becomes less than P5lo, the on-off valve 38 is opened, and when the internal pressure Pb of the buffer tank 32 is less than P4lo or the internal pressure Pm of the mixing tank 22 becomes P5up or more, the on-off valve 38 is closed. Also good. In this way, “hunting” in which the on-off valve 38 opens and closes at an extremely short cycle is prevented, and generation of abnormal noise can be suppressed.

  According to the LNG fuel supply apparatus of the third embodiment, the opening / closing timing of the opening / closing valve 38 can be adjusted by changing the fourth predetermined value P4 and the fifth predetermined value P5. Compared with the second embodiment, the amount of boil-off gas supplied from the buffer tank 32 to the mixing tank 22 can be easily changed.

  In the third embodiment, the on-off valve is determined by determining the magnitude of the internal pressure Pb of the buffer tank 32 and the fourth predetermined value P4 and the magnitude of the internal pressure Pm of the mixing tank 22 and the fifth predetermined value P5. In order to simplify the control program, the opening / closing of the opening / closing valve 38 can be controlled by directly determining the correlation between the internal pressure Pb of the buffer tank 32 and the internal pressure Pm of the mixing tank 22 in order to simplify the control program. For example, the opening / closing valve 38 may be opened when the internal pressure Pb is larger than the internal pressure Pm, and the opening / closing valve 38 may be closed when the internal pressure Pb is smaller than the internal pressure Pm.

  In each of the above-described embodiments, specific cases where the present invention is applied to a vehicle using LNG as a fuel have been described. However, the present invention can also be applied to, for example, a stationary gas turbine engine.

DESCRIPTION OF SYMBOLS 10 LNG container 16 Vaporizer 22 Mixing tank 24, 30, 36 Check valve 28 Pressure reducing valve 32 Buffer tank 34 Throttle valve 38 On-off valve 40, 42 Pressure sensor 44 Control unit

Claims (5)

An LNG container for storing LNG;
A vaporizer that vaporizes LNG supplied from the LNG container to generate vaporized fuel;
A mixing tank that mixes vaporized fuel supplied from the vaporizer and boil-off gas discharged from the LNG container to generate a mixed gas;
The boil-off gas is opened only in the direction from the LNG container toward the mixing tank, and the valve is opened when the differential pressure between the internal pressure of the LNG container and the internal pressure of the mixing tank is equal to or greater than a first predetermined value. A first check valve;
A pressure reducing valve for depressurizing the mixed gas supplied from the mixing tank;
An LNG fuel supply device comprising: An LNG container for storing LNG;
A vaporizer that vaporizes LNG supplied from the LNG container to generate vaporized fuel;
A mixing tank that mixes vaporized fuel supplied from the vaporizer and boil-off gas discharged from the LNG container to generate a mixed gas;
A buffer tank for temporarily storing the boil-off gas between the LNG container and the mixing tank;
The boil-off gas is opened only in the direction from the LNG container toward the buffer tank, and the valve is opened when the differential pressure between the internal pressure of the LNG container and the internal pressure of the buffer tank is equal to or greater than a second predetermined value. 2 check valves,
Flow rate adjusting means for adjusting the flow rate of the boil-off gas flowing from the buffer tank to the mixing tank;
A pressure reducing valve for depressurizing the mixed gas supplied from the mixing tank;
An LNG fuel supply device comprising: The flow rate adjusting means is
A throttle valve that throttles the flow rate of the boil-off gas;
The boil-off gas is opened only in the direction from the buffer tank to the mixing tank, and is opened when the differential pressure between the internal pressure of the buffer tank and the internal pressure of the mixing tank is equal to or greater than a third predetermined value. A third check valve;
The apparatus for supplying LNG fuel according to claim 2, comprising: The flow rate adjusting means is
First pressure detecting means for detecting an internal pressure of the buffer tank;
Second pressure detection means for detecting the internal pressure of the mixing tank;
A remote controllable on-off valve;
Control means for controlling opening and closing of the on-off valve based on the internal pressure of the buffer tank detected by the first pressure detection means and the internal pressure of the mixing tank detected by the second pressure detection means;
The apparatus for supplying LNG fuel according to claim 2, comprising:   The control means opens the on-off valve when the internal pressure of the buffer tank detected by the first pressure detection means is larger than the internal pressure of the mixing tank detected by the second pressure detection means. The LNG fuel supply apparatus according to claim 4, wherein the apparatus is a LNG fuel supply apparatus.

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