METHOD AND SYSTEM FOR PRESSURE MANAGEMENT WHILE EXTRACTING A LIQUID FROM A LIQUID STORAGE VESSEL

Abstract

In a system and a method for pressure management while extracting a liquid from a liquid storage vessel, a liquid and its vapor are provided in liquid storage vessel. The liquid is extracted by a pump from the storage vessel and fed as a liquid flow to a consumer unit. A defined partial flow is separated from the liquid flow downstream of the pump. The pressure of the partial flow is reduced by a pressure regulation means and the partial flow is evaporated by an evaporator. The evaporated partial flow is fed back into the storage vessel.

Claims

1. A method for pressure management while extracting a liquid from a liquid storage vessel, comprising the steps: providing a liquid and its vapor in a liquid storage vessel; extracting the liquid by a pump from the storage vessel and feeding the liquid as a liquid flow to a consumer unit; separating a defined partial flow from the liquid flow downstream of the pump; reducing a pressure of the partial flow; evaporating the partial flow; and feeding the evaporated partial flow back into the storage vessel.

2. The method according to claim 1, wherein the partial flow back into the storage vessel is altered to increase or decrease a pressure of the liquid in the liquid storage vessel if requested.

3. The method according to claim 1, wherein the pressure of the partial flow is reduced to a constant pressure corresponding to a pressure in the storage vessel.

4. The method according to claim 1, wherein the pressure of the partial flow is reduced before the partial flow is evaporated, or after the partial flow has been evaporated.

5. The method according to claim 1, wherein the partial flow of the liquid is evaporated by heating the partial flow to a temperature within or slightly above a saturation temperature of the partial flow.

6. The method according to claim 1, wherein in a specific operation mode, the partial flow of the liquid is evaporated by overheating the partial flow to a temperature essentially above a saturation temperature of the partial flow.

7. The method according to claim 1, wherein the liquid is a fuel for propelling an aircraft.

8. A system for pressure management while extracting a liquid from a liquid storage vessel, comprising: the storage vessel for storage of the liquid and its vapor, a supply path equipped with a pump for feeding the liquid from the storage vessel to a consumer unit, a return path configured for separating a partial flow from the supply path downstream of the pump, a pressure regulation means arranged in the return path for reducing the pressure of the partial flow, and an evaporator arranged in the return path for evaporating the partial liquid flow before the partial liquid flow is fed as vapor to the storage vessel.

9. The system according to claim 8, wherein the partial flow back into the storage vessel is altered to increase or decrease the pressure of the liquid in the liquid storage vessel if requested.

10. The system according to claim 9, wherein the pressure regulation means is configured to reduce the pressure of the partial flow to a constant pressure corresponding to the pressure in the storage vessel.

11. The system according to claim 9, wherein the pressure regulation means is arranged in the return path downstream of the evaporator, or upstream of the evaporator.

12. The system according to claim 9, wherein the evaporator is configured to heat the partial flow of the liquid to a temperature within or slightly above its saturation temperature.

13. The system according to claim 9, wherein the evaporator is at least one of configured to provide a specific operation mode in which the partial flow of the liquid is overheating the partial flow to a temperature essentially above a saturation temperature of the partial flow, or configured as an electrical flow evaporator.

14. The system according to claim 9, wherein the system is configured for storage of a fuel for propelling an aircraft.

15. The system according to claim 8, wherein the system is used in an aircraft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the following, a preferred exemplary embodiment of the invention is described in detail, showing further advantages and characteristics with reference to the accompanying drawing, wherein:

[0041] The FIGURE shows a schematic view of a system for extracting a liquid from a liquid storage vessel according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] As depicted in the FIGURE, a system 10 according to a preferred embodiment of the invention comprises a liquid storage vessel 11 which is configured for storage of a liquid 12 and its vapor 13. The vapor 13 is above the liquid 12 in the vessel or tank 11, i.e., above the liquid level 14. A supply path 15 is designed for feeding the liquid 12 as a liquid flow 19 from the storage tank or vessel 11 to a consumer unit 16. In the supply path 15, a pump 17 is arranged for pumping liquid 12 in supply path 15 to the consumer unit 16. A return path 18 is configured for separating a partial flow 19a of the liquid 12 from the supply path 15 downstream of the pump 17. In the return path 18, a pressure regulation means 20 formed as a pressure regulator is arranged for reducing the pressure of the partial liquid flow 19a separated from supply path 15 at a junction 21. Further, an evaporator 22 is arranged in the return path 18 and configured for evaporating the partial liquid flow 19a before it is fed as a vapor flow 23 back to storage vessel 11.

[0043] The pressure regulation means may be an actively controlled pressure regulator which is, e.g., controlled by a controller unit, a passive flow regulator or just a restrictor like, e.g., an orifice.

[0044] The system 10 forms a complex system to maintain the pressure in the storage vessel 11 which contains only one fluid as the liquid 12 and its vapor 13, i.e., it contains a single species forming a two-phase system. In the embodiment shown here, the liquid 12 is cryogenic liquid hydrogen, and the storage vessel 11 is formed as a tank of an aircraft.

[0045] However, also other types of liquids and its respective vapor can be provided in storage vessel 11, like, e.g., nitrogen, liquefied natural gases, liquefied petrol gases, and others, comprising a gaseous atmosphere of its own.

[0046] The liquid 12 is stored at a temperature below the ambient temperature

[0047] Consumer unit 16 may be, for example, another tank, an energy converter, a fuel cell unit, an engine like, e.g., a combustion engine or a fuel cell engine, a catalytic converter and similar devices or units.

[0048] In the embodiment shown here, the pressure regulator 20 is arranged in the return path 18 upstream of the evaporator 22. In other embodiments which are not shown in the FIGURE, the pressure regulator 20 is arranged downstream of the evaporator unit 22. Both configurations have specific advantages.

[0049] The evaporator 22 is configured to heat the liquid 12 supplied as partial flow 19a within the return path or line 18 in order to heat liquid 12 to its saturation temperature or slightly above, so that it evaporates before it returns as vapor flow 23 into the storage vessel 11 above liquid 12.

[0050] Evaporator or heater 22 is also configured to overheat the liquid to a temperature essentially above its saturation temperature, depending on specific requirements during operation. In such an operation mode, a relatively fast increase of pressure within storage tank 11 can be achieved.

[0051] The evaporator 22 is preferably configured as an electric flow evaporator. Using an electric flow evaporator gives the following advantages: First, a low reaction time of the pressure control is achieved. Second, there is no contamination of the storage content with other fluids which might be possible in case of failure of the electric flow evaporator. Third, the integration effort compared to a liquid port evaporator is reduced. Moreover, there is no icing or solidification risk of cooling liquid for cryogenic storage tanks.

[0052] In the following, a method for extracting a liquid from a liquid storage vessel is explained in detail as a preferred example of the invention.

[0053] As a first step, the liquid 12 and its vapor 13 are provided in storage vessel or tank 11. In this example, the liquid is hydrogen for propelling an aircraft, and the storage tank is a fuel storage tank of an aircraft. However, also other types of liquids may be provided in storage tank 11 as described above, and storage tank 11 may be another type of liquid storage tank.

[0054] During operation, the liquid 12 is extracted by pump 17 from storage vessel 11, and it is fed as liquid flow 19 to consumer unit 16 which is configured as described above.

[0055] Downstream of pump 17, partial flow 19a is separated from the liquid flow 19 at junction 21 which is provided in supply path 15. Supply path 15 like return path 18 may comprise, e.g., one or more pipes or line units.

[0056] The pressure of partial flow 19a is reduced by pressure regulator 20, and partial flow 19a is evaporated by the electric flow evaporator 22. Then, the evaporated partial flow 23 within return path 18 is fed back into the storage vessel 11.

[0057] By pumping the liquid 12 out of tank 11 and feeding it back to storage tank 11 after pressure reduction or regulation and evaporation, the volume of the liquid 12 or fluid extracted from the tank 11 is replaced by its own vapor.

[0058] The amount of the partial flow 19a separated from liquid flow 19 at line or pipe junction 21 depends on the type of liquid and on the pressure within liquid storage tank 11. E.g., for hydrogen, a pressure in the tank 11 may be, for example, in the range of 2 to 3 bar, and the partial flow returned back into tank 11 may, e.g., be in the range of 2% to 10% of the liquid extracted from tank 11. These values shall be understood as examples. Of course, other values may apply depending on the specific requirements of the respective application.

[0059] The pressure of the partial flow 19a may be reduced before the partial flow is evaporated by evaporator 22 as shown in the FIGURE. In this case, the evaporator 22 can be designed for the pressure within storage tank 11, and therefore lighter than in the case where evaporation takes place before the pressure is regulated or reduced by pressure regulator 20.

[0060] On the other hand, when the evaporation takes place before regulating and reducing the pressure, a simpler control can be achieved.

[0061] During the evaporation of partial flow 19a by evaporator 22, a temperature in the range of the saturation temperature of the liquid or slightly above is applied. In this case, only evaporation takes place, wherein the overheating of the liquid is minimized, i.e., is kept as small as possible. As a result, a highly stabilized pressure is achieved within storage tank 11. This is of particular advantage for applications in aircraft or other transportation means, in which movements may cause a thermal mixing in tank 11 which would cause pressure reductions in cases without the pressure stabilization according to the invention.

[0062] In the other operation mode, where evaporation and a strong overheating is applied to the liquid, a high increase of the pressure in tank 11 can be achieved in a short time. A smaller amount of liquid needs to be evaporated in this case.

[0063] The invention provides a continuous liquid extraction operation with a continuous vapor supply to the tank or storage vessel 11. The heating energy needed for the evaporation is reduced compared to systems with non-continuous flow, pulsed or interrupted flow. In addition, a constant pressure in storage vessel 11 is achieved, which does not increase during the time of operation. In this way, the invention enables fuel supply with constant quality in terms of pressure, temperature and therefore density.

[0064] The invention compensates a decrease of the pressure and of the temperature in a vessel along the saturation curve of the liquid contained therein, if the liquid is fed to a consumer by a pump. According to the invention, a portion of the liquid is tapped downstream of the pump, the pressure gets reduced by the pressure regulator, and the liquid flow is evaporated in an evaporator and fed back into the storage vessel.

[0065] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

TABLE-US-00001 List of reference numbers: 10 11 12 13 14 15 16 17 18 19 19a 20 21 22 23 system liquid storage vessel or tank liquid vapor liquid level in tank supply path consumer unit pump return path liquid flow from storage vessel or tank partial flow of the liquid pressure regulation means / pressure regulator junction evaporator vapor flow