Patent Application
20070277533
The single FIGURE is a schematic longitudinal sectional view of a reservoir according to the invention for the storage of a cryogenic medium having a removal and filling device according to the invention.
The entire fuel supply system for cryogenic hydrogen (and similar fluids) consists of an insulated storage reservoir having a cooling shield and a heat sink, including a gas removal pipe linked to the heat sink as well as a device for the removal of liquid and a combined fueling and hot-return gas pipe constructed as a diffuser for maintaining pressure in the removal operation, having a secondary vacuum module, including shut-off valves and a coolable cryogenic feed pump for providing pressure, having a heat exchanger module for equalizing the temperature of the removed pressure-conditioned hydrogen, having a secondary system module, including buffer reservoirs against pressure peaks, having safety pipes on the liquid and gas removal pipe and having a filling pipe which can be cooled before the filling operation, together with the filling coupling.
A cryotank 40 for storing liquid hydrogen LH2 is installed in a motor vehicle (not shown). This liquid hydrogen LH2 is used as fuel for supplying an internal-combustion engine (also not shown), drives the motor vehicle and is coupled to a transmission assembly inlet 14. The cryotank 40 is a reservoir consisting of a pressure-resistant inner reservoir 1 disposed by way of a bearing device, which is not shown, in an outer reservoir 4, with an insulation layer disposed in-between and a cooling shield 2 embedded in this insulation layer. A heat sink 3, as a heat storage device, is connected in a thermally conductive manner with the shield 2, which heat sink 3 is used as a buffer storage device for the heat entering from the environment through the insulation. The heat sink 3 is situated in the primary insulation zone, in a recess 41 of the inner reservoir 1, into which all accesses to the inner reservoir 1 also lead, which extend from there by way of a releasable central coupling 5 mounted on the outer reservoir 4 out of the latter. By way of the central coupling 5, a vacuum-insulated accessory container 6, which contains cold accessories for filling and evacuating the cryotank 40, is coupled as a secondary insulated cold module to the outer reservoir 4, and the accesses to the inner reservoir 1 extend by way of the central coupling 5 out of the outer reservoir 4 into the accessory container 6. The coupling device 5 establishes tight connections between the cryotank 40 and pipes 20, 42, 43 extending out of the accessory container 6.
The coupling device 5 consists of a cryotank-side coupling part 5a and an instrument-container-side coupling part 5b, the cryotank-side coupling part 5a being mounted on the outer reservoir 4.
The accessory container 6 has two additional connection sites, specifically one for filling the cryotank 40 and one for supplying the consuming device. These connection sites, by way of, in each case, a further particularly a releasable coupling device 46, 47 with one connection part, one fueling coupling 24 and one heat exchanger 10 or one secondary system capsule 11 respectively, establish tight connections between pipes 22, 26, 27 leading out of the accessory container 6 and the connection part.
In this case, the accessory container 6 is placed such that a feed pump 9 is situated below or at the same level as pipe openings for the liquid removal in the lower area of the cryotank 40.
For filling and evaluating the cryotank 40, a filling and removal device is provided, which has three accesses to the inner reservoir 1. These three pipes extend from the inner reservoir 1 through its recess 41, which is situated essentially within the circumferential contour of the inner reservoir 1 and in which the heat sink 3 is also housed, out of the outer reservoir 4, and into the accessory container 6. A pipe 43 is used for the removal of cryogenic medium predominantly in the liquid state out of the lower area of the cryotank 40. A second pipe 20 is used for the removal of cryogenic medium predominantly in the gaseous state from the upper area of the cryotank 40, and a third pipe 42, whose pipe end in the cryotank 40 is equipped with a diffuser 18, is used for returning the medium as hot gas into the upper area of the cryotank 40 and, during the filling of the cryotank 40, as a filling pipe.
All pipes 20, 42, 43 leading into the inner reservoir 1 extend through its blending surface 50 with the cylindrical recess 41. For the connection of the cooling shield 2 with the heat sink 3, the latter projects with its one end beyond the circumferential contour of the inner reservoir 1 to such an extent that, connected with the cooling shield 2 via screws, which are not shown, it forms a heat-transmitting connection. By way of an additional smaller cooling shield 51, which partially surrounds the second and the third pipe 20, 42 within the recess 41 and is connected with the heat sink 3, the entry of heat from these pipes 20, 42 into the inner reservoir 1 is reduced. This arrangement does not interfere with the insulation of the inner reservoir 1 by the heat sink 3 and the insulation effect is not negatively influenced.
By way of a liquid removal change-over device 7, in the case of a full-load demand by the internal-combustion engine or in the partial load operation, when the pressure falls below the lowest supply pressure in the cryotank 40 required for the internal-combustion engine, cryogenically stored hydrogen in the liquid phase LH2 is removed from the cryotank 40 by way of the first pipe 43 and is guided past the heat sink 3 by way of a cold valve 8 disposed in the accessory container 6, to the cold feed pump 9 for predominantly liquid hydrogen. This feed pump 9 compresses the liquid hydrogen LH2 to the pressure level provided for the internal-combustion engine during the full-load or partial load operation. By way of a main removal pipe 22 through a buffer volume 31, the compressed hydrogen is guided into a second heat exchanger 10, its temperature is equalized there, and the hydrogen is guided by way of a pressure accumulating reservoir 12, which is disposed in a secondary system capsule 11 and is used for the damping of pressure fluctuations, and a shut-off valve 13 to the drive assembly inlet 14.
When the pressure unacceptably falls below a minimum pressure in the inner reservoir 1, by way of opening a control valve 16, a quantity of the heated removal mass flow controlled by way of a throttle 15 is introduced into a filling pipe 17 and is guided there by way of the central coupling 5 through a third pipe 42 past the heat sink 3 into the diffuser situated in the inner reservoir 1 and used for filling and maintaining the pressure. The diffuser 18 distributes the hot gaseous hydrogen GH2 in the inner reservoir 1 and thus supplies heat to the cryotank 40, which is required for maintaining the pressure. The arrangement of the diffuser 18 in the upper area of the inner reservoir 1 which, for the most part, is taken up by the gaseous phase of the stored hydrogen GH2, is used for a targeted establishment of an imbalance in the stored hydrogen and therefore ideally, as a result of the rise in pressure, leads to a supercooling of the liquid hydrogen LH2 in the area of the liquid removal device. The resulting supercooling can contribute to the fact that the hydrogen fed to the cold feed pump 9, despite the absorption of heat in the feed pipes to the feed pump 9, reaches the feed pump 9 in a largely liquid state and thus contributes to an efficient operation of the feed pump 9. Furthermore, the thus established imbalance in the stored hydrogen at the beginning of operating pauses contributes to a pressure drop by the delayed-start slow approaching of the saturation condition (mixing) and the occurring equilibrium and thus ideally increases the pressure deviation and thus the lossless pressure buildup time in the cryotank 40 until a limit pressure—the boil-off pressure—is reached, at which the gaseous medium GH2 is to be blown off from the cryotank 40.
In the partial-load operation of the internal-combustion engine, at pressures in the inner reservoir 1 above the lowest supply pressure for the partial-load operation, a hydrogen removal in the gaseous phase GH2 is provided in order to, because of the enthalpy removal from the inner reservoir 1 which is higher during the gas removal, be able to reduce the pressure in the inner reservoir 1 to the minimum pressure. For this purpose, by opening a cold valve 19 situated in the accessory container 6, gaseous hydrogen GH2, driven by the pressure in the inner reservoir 1 is removed by way of the second pipe 20 for the removal of gas projecting into the inner reservoir 1, from the inner reservoir 1, is guided through the heat sink 3, which is in a heat-transmitting contact exclusively with the second pipe 20 for the removal of gaseous cryogenic medium, and the central coupling 5, into the accessory container 6. By way of a first heat exchanger 21, the gaseous hydrogen GH2 there cools the feed pump 9, which is inoperative during the gas removal and is to be kept cold and, behind the cold valve 19, downstream of the feed pump 9 is fed to the main removal pipe 22. It is further equalized with respect to its temperature in the second heat exchanger 10 and is guided by way of the pressure accumulator reservoir 12 and the shut-off valve 13 in the secondary system capsule 11 to the drive assembly inlet 14.
The filling of the cryotank 40 with cryogenically stored hydrogen is carried out by way of a fueling coupling 24 at the accessory container 6. Before a filling operation, by way of the cold feed pump 9, the complete filling train, including the diffuser 18, the filling pipe 17 the charging pipe 23 and the fueling coupling 24 are “operated cold” by circular conveying, in order to thereby accelerate the subsequent filling operation and to reduce return gas losses. For this purpose, the cold valves 8 and 25 are opened and the operation of the feed pump 9 is started. As a result, hydrogen is conveyed from the liquid phase LH2 by way of the first pipe 43 from the cryotank 1 by way of the central coupling 5 and the cold valve 8, by way of the feed pump 9 and the connection pipe 45 between the return gas pipe 26 and the fueling-coupling-side filling pipe 27, then by way of the cold valve 25 and the filling back 17, back into the inner reservoir 1.
A similar cold operation process can be used for operating the feed pipe 9 itself cold, as required. As in the case of the cold operation of the fueling train, the cold valve 8 is opened for this purpose and the operation of the feed pump 9 is started. However, instead of the cold valve 25, the cold valve 19 is opened and the gas flowing out of the feed pump 9 is guided by way of the first heat exchanger 21 and the second pipe 20 back into the inner reservoir 1.
The filling operation itself, by way of the fueling coupling 24 and the charging pipe 23, is initiated by coupling a filling-station-side coupling to the filling coupling 24 on the accessory container 6, whereby the return gas pipe 26 and the fueling-coupling-side filling pipe 27 are separated from one another in that the connection pipe 45 is interrupted. For opening the cold valve 25 for the filling and the cold valve 19 for the return gas, cryogenically stored hydrogen in a liquid state LH2 is distributed from the filling station through the fueling-coupling-side filling pipe 27 by way of the cold valve 25, the filling pipe 17, the central coupling 5 and the diffuser 18 in the inner reservoir 1. Simultaneously, by way of the second pipe 20 for the gas removal, the heat sink 3, the central coupling 5, the first heat exchanger 21, the cold valve 19 and the return gas pipe 26, return gas for the pressure reduction in the inner reservoir 1 is returned to the filling station. By way of the return gas flowing through the first heat exchanger 21, the feed pump 9 is cooled. This is used for a rapid availability of the full delivery capacity after the termination of the filling operation at the start of the operation of the hydrogen supply system for supplying the internal-combustion engine in the full-load operation.
During longer operating pauses of the hydrogen supply system, the pressure in the inner reservoir 1 rises by the continuous entering of heat from the environment by way of the outer reservoir 4, the insulation, the cooling shield 2 and the inner reservoir 1 into the liquid hydrogen LH2 stored there which converts the heat to evaporation. When the boil-off pressure is reached, a pressure relief valve 28 will open and gaseous hydrogen GH2 will be removed by way of a second pipe 20 for the gas removal, the heat sink 3, the central coupling 5 and the first heat exchanger 21 into a boil-off pipe 32. In this case, the removed hydrogen cools, in addition to the heat sink 3 with the cooling shield 2, also the feed pump 9 by way of the first heat exchanger 21. This is used for a rapid availability of the full delivery capacity after an operating pause when the operation of the hydrogen supply system is started for supplying the internal-combustion engine in the full-load operation.
In the case of a sudden entering of heat into the inner reservoir as a result of damage to the insulation or other defects, the pressure in the inner reservoir 1 will rise because of the increasing evaporation of the liquid hydrogen LH2. Since the removal of a sufficient amount of hydrogen through the boil-off pipe 32 would not be possible in such a case, the excess pressure safety valves 29 and 30 will open when the respective pressure level for the respective safety valve 29, 30 has been reached. In this case, the first responding safety valve 29 is coupled to the second pipe 20—the gas removal pipe—, and safety valve 30 is coupled to the first pipe 43 of the liquid removal device. Thus, it is ensured that, also in the event of an overhead position, with liquid hydrogen LH2 in the area of the opening of the second pipe 20—the gas removal pipe—, sufficient gaseous hydrogen GH 2 can be removed by way of the safety valve 30 from the gaseous phase then present in the area of the liquid removal device.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 025 656.5 | Jun 2006 | DE | national |
