JP2010144878A - Fuel storage device for lng vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve effective use of LNG vapor in a fuel storage device for an LNG vehicle by reducing the LNG vapor discharged to the air. <P>SOLUTION: The fuel storage device for an LNG vehicle includes an additional tank 16 that is connected to a fuel tank 11 via an LNG vapor discharge passage 33. A compressor 18 provided in the LNG vapor discharge passage 33 is actuated when the pressure P0 in the tank exceeds a predetermined pressure Ps. The predetermined pressure Ps is set lower than the relief pressure P2 of a safety valve 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel storage device used in an LNG vehicle.

  In an LNG vehicle equipped with an engine that uses liquefied natural gas (LNG) as fuel, LNG is stored in a fuel tank in a cryogenic state. Although a tank having a heat insulating structure is used as the fuel tank, it is impossible to completely eliminate heat input from outside the tank via the LNG filling port and the delivery port. For this reason, the temperature of the LNG in the tank rises with time, and the pressure in the tank rises due to the LNG vapor generated in the tank.

In this regard, in Patent Document 1, in order to prevent the pressure in the tank from rising excessively, a safety valve is provided in the fuel tank so that LNG vapor is discharged to the atmosphere.
Special table 2001-508727

However, in the above configuration, there is a problem that the LNG vapor released to the atmosphere cannot be used for traveling the vehicle and is wasted. In addition, it is not preferable to release LNG vapor to the atmosphere from the viewpoint of environmental protection. The present invention has been made in view of such a conventional technique, and in an LNG vehicle fuel storage device, LNG vapor released to the atmosphere. It is an object of the present invention to reduce the amount of LNG and to make effective use of LNG vapor.

  According to the first aspect, there is provided a fuel storage device for an LNG vehicle equipped with an engine using liquefied natural gas (hereinafter referred to as “LNG”) as fuel, and a fuel tank for storing the LNG. A safety valve that opens when the pressure of the LNG vapor generated in the fuel tank (hereinafter referred to as “tank pressure”) reaches a relief pressure, and releases the LNG vapor in the fuel tank to the atmosphere; An additional tank provided separately from the fuel tank, an LNG vapor discharge passage connecting the fuel tank and the additional tank, and an LNG vapor provided in the LNG vapor discharge passage and compressing the LNG vapor sent from the fuel tank Compressed natural gas (hereinafter referred to as “CNG”), and the compressor that discharges the CNG to the additional tank and the pressure in the tank are detected. And a compressor control means for operating the compressor when the tank internal pressure exceeds a predetermined pressure, wherein the predetermined pressure is set lower than the relief pressure of the safety valve. A storage device is provided.

  According to a second aspect, in the first aspect, when the pressure in the tank decreases to an engine required pressure by the operation of the compressor, the compressor control means stops the compressor, and the engine required pressure is There is provided a fuel storage device for an LNG vehicle, which is set to a lower limit value of a pressure required to deliver the LNG from a fuel tank to the engine.

  According to a third aspect, in the first or second aspect, the additional tank is provided in the tank-side return passage connecting the additional tank and the fuel tank, and is opened in the tank-side return passage. And a tank side return valve for introducing the CNG therein into the fuel tank. An LNG vehicle fuel storage device is provided.

  According to a fourth aspect, in the first to third aspects, the fuel supply passage for supplying the LNG to the engine, the engine-side return passage connecting the additional tank, and the engine-side return passage An LNG vehicle fuel storage device is provided, comprising: an engine-side return valve that is provided and opened to introduce the CNG in the additional tank into the fuel supply passage.

  According to the first aspect, before the tank internal pressure reaches the relief pressure of the safety valve, the compressor is operated, the LNG vapor in the fuel tank is discharged to the additional tank, the tank internal pressure is lowered, and the safety valve is opened. The frequency with which LNG vapor is released to the atmosphere is reduced, so that LNG can be prevented from being wasted, and environmental conservation can be achieved.

  According to the second aspect, it can be prevented that the pressure in the tank is too low due to the operation of the compressor, the back pressure in the fuel tank is insufficient, and the LNG delivery from the fuel tank is delayed.

  According to the 3rd aspect, CNG in an additional tank can be introduce | transduced into a fuel tank by opening a tank side return valve, and a tank internal pressure can be raised. For example, if the tank-side return valve is opened when the tank internal pressure is low, such as immediately after LNG filling, it is possible to prevent the LNG from being sent out from the fuel tank.

  According to the 4th aspect, CNG in an additional tank can be introduced in the middle of a fuel supply path by opening an engine side return valve. Since CNG in the additional tank can be consumed by the engine and used for traveling of the vehicle, useless consumption of LNG can be suppressed. In addition, this makes it possible to reduce the amount of CNG in the additional tank, and it is possible to continuously reduce the pressure in the tank using a compressor.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a fuel supply system 100 for an LNG vehicle including a fuel storage device according to an embodiment of the present invention.

  The fuel supply system 100 includes a fuel tank 11, a vaporizer 12, a buffer tank 13, a pressure reducing valve 14, an injector 15, an additional tank 16, and a control unit 20, and liquefied natural gas (hereinafter, “ LNG ") to the engine.

  The fuel tank 11 is a tank having a heat insulating double structure in which the space between the inner tank 11a and the outer tank 11b is evacuated, and stores LNG at an extremely low temperature (−162 ° C.). Although the fuel tank 11 has such a structure, the heat input from the outside cannot be completely cut off, and the temperature of the stored LNG rises with the passage of time. The pressure (hereinafter referred to as “tank pressure”) P0 rises due to vaporized LNG (hereinafter referred to as “LNG vapor”).

  A fuel supply passage 31 for supplying LNG to the engine via the vaporizer 12, the buffer tank 13, the pressure reducing valve 14, and the injector 15 is connected to the lower part of the fuel tank 11. A pressure adjusting passage 32 whose end is open to the atmosphere is connected. In the middle of the pressure adjusting passage 32, a safety valve 17 is provided that opens when the tank pressure P0 exceeds a preset relief pressure P2.

  From the fuel tank 11, LNG is sent to the vaporizer 12 by the tank internal pressure P0. That is, the tank internal pressure P0 functions as a pressure for delivering LNG from the fuel tank 11.

  In the carburetor 12, in addition to the LNG flow path 12a, an engine cooling water (or exhaust) flow path (not shown) is disposed adjacent to the LNG and the LNG and engine cooling water (or exhaust). Heat exchange in a non-contact state. As a result, the LNG is vaporized to become natural gas, and the natural gas is sent to the buffer tank 13 connected downstream of the vaporizer 12 as the internal pressure in the vaporizer 12 increases.

  The buffer tank 13 is a tank that temporarily stores natural gas sent from the vaporizer 12 in order to cope with engine load fluctuations. The natural gas stored in the buffer tank 13 is depressurized by the pressure reducing valve 14, then sent to the injector 15, and injected from the injector 15 into the intake passage or cylinder of the engine.

  The additional tank 16 is a pressure-resistant tank provided separately from the fuel tank 11, and can store compressed natural gas (CNG) obtained by compressing LNG vapor, as will be described later. The additional tank 16 is connected to the fuel tank 11 via the LNG vapor discharge passage 33 and the tank side return passage 34. Further, it is connected to the buffer tank 13 via the engine side return passage 35.

  The LNG vapor discharge passage 33 branches off from the middle of the pressure adjustment passage 32, and a compressor 18 and a check valve 19 are provided in the middle from the pressure adjustment passage 32 side.

  The compressor 18 receives the compressor control signal from the control unit 20 and operates when the tank internal pressure P0 reaches the predetermined pressure Ps. The compressor 18 compresses the LNG vapor sent from the fuel tank 11 through the pressure adjusting passage 32 and the LNG vapor discharge passage 33 into CNG, and discharges CNG to the additional tank 16. CNG is stored in the additional tank 16.

  Here, the predetermined pressure Ps is set lower than the relief pressure P2 of the safety valve 17, so that the compressor 18 operates to lower the tank pressure P0 before the safety valve 17 is opened.

  Between the compressor 18 and the additional tank 16, a check valve 19 that allows only the flow of LNG vapor from the compressor 18 to the additional tank 16 is provided. The check valve 19 prevents CNG stored in the additional tank 16 from flowing back through the LNG vapor discharge passage 33 and the pressure adjustment passage 32 and returning to the fuel tank 11. The check valve 19 may be provided inside the compressor 18.

  A fuel tank side return valve 36 is provided in the middle of the tank side return passage 34. The tank-side return valve 36 has a low tank pressure P0 immediately after LNG is replenished to the fuel tank 11, and the back pressure lower limit value (hereinafter referred to as "engine request") required to send LNG from the fuel tank 11 to the engine. This is a regulator that opens when P4 cannot be obtained. By opening the tank side return valve 36, CNG in the additional tank 16 is introduced into the fuel tank 11, and the tank internal pressure P0 is maintained at the engine required pressure P4 or higher.

  An engine side return valve 37 is provided in the middle of the engine side return passage 35. The engine-side return valve 37 can store the amount of CNG in the additional tank 16 when the pressure in the additional tank 16 becomes higher than a predetermined pressure, for example, when the pressure in the additional tank 16 reaches a predetermined pressure. It is a regulator that opens when the upper limit of the amount of CNG is reached. When the engine side return valve 37 is opened, CNG in the additional tank 16 is introduced into the buffer tank 13.

  As shown in FIG. 2, the control unit 20 includes a CPU 21, a storage device 22 including a RAM / ROM connected to the CPU 21, and an input / output interface 23.

  A signal representing the tank internal pressure P0 is input to the input / output interface 23 from the pressure sensor 41. The storage device 22 stores a control program for controlling the compressor 18, parameters (Ps, P4) used in the control program, and the like. The CPU 21 reads out and executes the control program stored in the storage device 22, determines the operation / stop of the compressor 18 based on the signal representing the tank internal pressure P 0 input to the input / output interface 23, and responds accordingly. The compressor control signal is output from the input / output interface 23 to the compressor 18.

  FIG. 3 is a flowchart showing the contents of the control program. This control program is repeatedly executed in the CPU 21. The processing contents of the control unit 20 will be described with reference to this.

  Steps S11 to S13 are processes from when the compressor 18 is stopped until the compressor 18 is operated.

In step S11, the tank internal pressure P0 is read. In step S12, it is determined whether the tank internal pressure P0 is higher than the predetermined pressure Ps. When the tank internal pressure P0 is lower than the predetermined pressure Ps, steps S11 and S12 are repeated, and when the tank internal pressure P0 is higher than the predetermined pressure Ps, the process proceeds to step S13. In step S13, the compressor 18 is operated. When the compressor 18 is activated in step S13, the LNG vapor in the fuel tank 11 is sent to the compressor 18 and compressed, and stored in the additional tank 16 as CNG. Thereby, while the compressor 18 is operating, the LNG vapor in the fuel tank 11 decreases, and the tank pressure P0 decreases.

  Steps S14 to S16 are processing from when the compressor 18 is operating until the compressor 18 is stopped.

  In step S14, the tank internal pressure P0 is read. In step S15, it is determined whether the tank internal pressure P0 is lower than the engine required pressure P4. When the tank internal pressure P0 is higher than the engine required pressure P4, steps S14 and S15 are repeated, and when the tank internal pressure P0 becomes lower than the engine required pressure P4, the process proceeds to step S16.

  In step S16, the compressor 18 is stopped to prevent further decrease in the tank pressure P0, and the process returns to step S11.

  FIG. 4 is an operation mode diagram of the compressor 18 realized by performing the above control.

  When the tank pressure P0 rises to a predetermined pressure Ps when the compressor 18 is stopped (state X1 in the figure), the compressor 18 starts operating (state X2). Thereafter, the compressor 18 continues to operate, and the tank pressure P0 is reduced.

  When the tank internal pressure P0 decreases to the engine required pressure P4 (state X3), the compressor 18 stops (state X4). Thereafter, the compressor 18 continues to stop until the tank internal pressure P0 rises again to the predetermined pressure Ps.

  As described above, the compressor 18 is repeatedly operated and stopped in accordance with the tank internal pressure P0, and the tank internal pressure P0 is controlled between the predetermined pressure Ps and the engine required pressure P4 by changing the state X1 to X4. .

  Then, the effect of the said embodiment is demonstrated.

  In the above embodiment, when the additional tank 16 connected to the fuel tank 11 via the LNG vapor discharge passage 33 and the compressor 18 provided in the LNG vapor discharge passage 33 are provided, and the tank internal pressure P0 exceeds the predetermined pressure Ps. Further, the compressor 18 is operated, and the predetermined pressure Ps is set lower than the relief pressure P2 of the safety valve 17.

  According to this configuration, before the tank pressure P0 reaches the relief pressure P2 of the safety valve 17, the compressor 18 operates to discharge the LNG vapor in the fuel tank 11 to the additional tank 16, and the tank pressure P0 is lowered. Therefore, the frequency at which the safety valve 17 is opened and the LNG vapor is released to the atmosphere is reduced, and it is possible to prevent wasteful consumption of the LNG and to protect the environment.

  In the above embodiment, the compressor 18 is stopped when the tank internal pressure P0 drops to the engine required pressure P4. As a result, it is possible to prevent the tank pressure P0 from being excessively lowered, the back pressure in the fuel tank 11 being insufficient, and the LNG delivery from the fuel tank 11 from being delayed.

  Further, in the above embodiment, the tank side return passage 34 connecting the additional tank 16 and the fuel tank 11 and the tank side return passage 34 are provided, and the CNG in the additional tank 16 is introduced into the fuel tank 11 by opening the valve. And a tank side return valve 36. Even if the amount of LNG vapor in the fuel tank 11 is small immediately after LNG filling or the like, and the back pressure for sending LNG from the fuel tank 11 is not sufficient, according to this configuration, the tank side return valve 36 is If the CNG in the additional tank 16 is opened and introduced into the fuel tank 11, the tank pressure P0 can be raised, and the LNG delivery from the fuel tank 11 can be prevented from being delayed.

  Moreover, in the said embodiment, it is provided in the engine side return path 35 and the engine side return path 35 which connect the middle of the fuel supply path 31 (the buffer tank 13 in the said embodiment) and the additional tank 16, and the valve is opened. An engine-side return valve 37 for introducing CNG in the additional tank 16 into the fuel supply passage 31 is provided. According to this configuration, if the engine side return valve 37 is opened, the CNG in the additional tank 16 is introduced in the middle of the fuel supply passage 31 and consumed by the engine, which can be used for running the vehicle. Can be suppressed. In addition, this makes it possible to reduce the amount of CNG in the additional tank 16, so that the tank pressure P0 can be continuously reduced using the compressor 18.

  The embodiment of the present invention has been described above, but the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. is not.

  For example, the tank-side return valve 36 and the engine-side return valve 37 are constituted by electromagnetic valves instead of regulators, and the control unit 20 controls the opening and closing of the tank-side return valve 36 and the engine-side return valve 37 based on the tank internal pressure P0 and the like. You may make it do. According to this configuration, the tank side return valve 36 and the engine side return valve 37 can be arbitrarily opened and closed, so that the degree of freedom of control is improved.

  The engine-side return valve 37 may be configured to open when the pressure in the buffer tank 13 is low and the amount of natural gas in the buffer tank 13 is not sufficient. According to this configuration, when the amount of natural gas in the buffer tank 13 is not sufficient, CNG in the additional tank 16 can be introduced into the buffer tank 13, and the amount of natural gas supplied to the engine is stabilized. be able to.

It is a schematic block diagram of the fuel supply system of the LNG vehicle provided with the fuel storage apparatus which concerns on embodiment of this invention. It is an internal block diagram of a control unit. It is the flowchart which showed the content of the control program for controlling a compressor. It is an operation | movement aspect diagram of a compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Fuel tank 16 ... Additional tank 17 ... Safety valve 18 ... Compressor 20 ... Control unit 33 ... LNG vapor discharge passage 34 ... Tank side return passage 35 ... Engine side return passage 36 ... Tank side return valve 37 ... Engine side return valve 41 ... Pressure sensor 100 ... Fuel supply system

Claims (4)

A fuel storage device for an LNG vehicle used in an LNG vehicle equipped with an engine that uses liquefied natural gas (hereinafter referred to as "LNG") as fuel,
A fuel tank for storing the LNG;
A safety valve that opens when the pressure of the LNG vapor generated in the fuel tank (hereinafter referred to as “tank pressure”) reaches a relief pressure, and releases the LNG vapor in the fuel tank to the atmosphere;
An additional tank provided separately from the fuel tank;
An LNG vapor discharge passage connecting the fuel tank and the additional tank;
A compressor that is provided in the LNG vapor discharge passage, compresses the LNG vapor sent from the fuel tank into compressed natural gas (hereinafter referred to as “CNG”), and discharges the CNG to the additional tank;
A pressure sensor for detecting the pressure in the tank;
Compressor control means for operating the compressor when the tank internal pressure exceeds a predetermined pressure;
With
The predetermined pressure is set lower than the relief pressure of the safety valve;
A fuel storage device for LNG vehicles. When the pressure in the tank decreases to the engine required pressure due to the operation of the compressor, the compressor control means stops the compressor,
The engine required pressure is set to a lower limit value of a pressure required to send the LNG from the fuel tank to the engine.
The fuel storage device for an LNG vehicle according to claim 1. A tank side return passage connecting the additional tank and the fuel tank;
A tank-side return valve that is provided in the tank-side return passage and opens the CNG in the additional tank by opening the valve;
The fuel storage device for an LNG vehicle according to claim 1 or 2, further comprising: An engine-side return passage connecting the additional tank and the fuel supply passage for supplying the LNG to the engine;
An engine-side return valve that is provided in the engine-side return passage and opens the CNG in the additional tank in the middle of the fuel supply passage by opening the valve;
The fuel storage device for an LNG vehicle according to any one of claims 1 to 3, further comprising:

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