Pump for conveying a cryogenic fluid and method for conveying a cryogenic fluid

Abstract

The invention relates to a pump (200) for conveying a cryogenic fluid, comprising a pump housing (201) and a pump insert (202), with the pump housing having an outer container (220) and an inner container (221, 222), and with an evacuable space (225) being formed between same. The pump housing (201) has a pump inlet (261) via which the fluid to be conveyed can be brought into the inner container. The pump insert (202) has multiple conveyor units (231, 232, 233), a drive device (210), multiple piston rods (251, 252, 253) and a collection line (262), with the multiple conveyor units and a portion of the collection line being arranged inside the inner container, and the drive device (210) being arranged outside the pump housing (201) and being connected to a piston via a respective piston rod. The pump (200) is designed for conveying fluid via a pulling motion of the piston rods, wherein the pump insert (202) has a pump outlet (222), and wherein each of the multiple conveyor units has a conveyor unit inlet (242) and a conveyor unit outlet (243) for the fluid, wherein the conveyor unit outlets are connected to the collection line, and wherein the fluid collection line is designed such that the conveyor unit outlets feed into the pump outlet. The invention also relates to a method for conveying a cryogenic fluid.

Description

[0001] Description

[0002] Pump for conveying a cryogenic fluid and method for conveying a cryogenic fluid

[0003] The invention relates to a pump for conveying a cryogenic fluid, in particular hydrogen, and to a method for conveying a cryogenic fluid by means of such a pump.

[0004] Fluids such as hydrogen can be used in many different applications and fields. For example, hydrogen can be used as a fuel for vehicles; for this purpose, the hydrogen can be provided via so-called hydrogen refueling stations. In many cases, the hydrogen must be pumped, e.g., from one tank to another. Depending on the application, this can or should be done at low temperatures, i.e., cryogenic hydrogen must be pumped. Similar conditions apply to other cryogenic fluids such as nitrogen, argon, oxygen, or helium.

[0005] A high flow rate is particularly desirable when pumping large volumes of fluid, but this can be difficult, especially with cryogenic fluids. Against this background, the task arises of providing an efficient method for pumping cryogenic fluids, especially at high flow rates.

[0006] Disclosure of the invention

[0007] This object is achieved by a pump and a method for conveying a cryogenic fluid having the features of the independent patent claims. Preferred embodiments are the subject of the dependent patent claims and the following description.

[0008] Advantages of the invention

[0009] The invention relates to the pumping of cryogenic fluids, in particular hydrogen, i.e. liquid hydrogen, including supercooled liquid hydrogen. However, the invention can also be applied to other cryogenic fluids such as nitrogen, argon, oxygen or helium. As already mentioned, the pumping of cryogenic fluids is necessary for many applications, e.g. from one tank to another, for example for refueling a hydrogen-powered vehicle. Especially with large and / or heavy vehicles such as trucks, large quantities of hydrogen may have to be pumped. In order to achieve the shortest possible refueling time, a high pumping rate should be achieved.

[0010] For this purpose, a pump for conveying a cryogenic fluid is proposed, as is a method for conveying a cryogenic fluid using such a pump. The pump and the method, i.e., the use or operation of the pump, will be described in detail below.

[0011] The pump comprises a pump housing and a pump insert. The pump housing, in turn, comprises an outer container and an inner container, with a space formed between the outer container and the inner container that can be evacuated or evacuated. This allows the interior of the inner container to be well insulated. The pump housing also comprises a pump inlet through which the fluid to be pumped can be introduced into the inner container. The pump inlet can therefore be designed, for example, as a feedthrough from the outside through a wall in the outer container, through the evacuated space to a wall of the inner container.

[0012] The pump insert has a plurality of delivery units, in particular three or more delivery units, as well as a drive device, a plurality of piston rods and a collecting line. Each delivery unit has a piston and a cylinder (or a chamber), wherein the respective piston is arranged so as to be movable back and forth within the respective cylinder. The pump is therefore based on the principle of a piston pump or reciprocating piston pump. The drive device is connected via one of the plurality of piston rods to one of the plurality of pistons, wherein the pump is configured to move each of the plurality of pistons back and forth within the respective cylinder by means of the drive device. The drive device can, for example, be operated electrically and / or hydraulically.

[0013] Each of the multiple delivery units has a delivery unit inlet and a delivery unit outlet for the fluid. In particular, the delivery unit outlet can each have a valve. The pump is designed such that the fluid to be delivered can be introduced into each of the delivery unit inlets, i.e. the fluid can flow into the respective cylinders of the delivery units. This typically occurs during a so-called loading stroke of a respective delivery unit, in which the piston opens or releases the delivery unit inlet and the fluid thus flows into the delivery unit. Since cryogenic hydrogen is usually close to or at its boiling point, it is advantageous if the fluid can flow into the delivery unit with low pre-pressure and does not have to be sucked in. During a so-called delivery stroke of a respective delivery unit, in which the piston e.g.is moved towards the delivery unit outlet, the fluid can be expelled from the cylinder again by means of overpressure. The fluid collection line can be designed, for example, in the form of a distributor, with the delivery unit outlets being connected to the collection line. The fluid collection line is designed such that the delivery unit outlets open into a (common) pump outlet, via which fluid delivered by the pump can be made available. The pump outlet is part of the pump insert. The fluid flows from the individual delivery unit outlets are therefore collected or combined into a common fluid flow.

[0014] The multiple delivery units and at least part of the collecting line are arranged within the inner container, while the drive device is located outside the pump housing. The multiple delivery units make it possible to create a larger overall delivery volume, thus enabling a higher pump delivery rate. Nevertheless, the piston pump principle allows for simple and robust operation, while other pump types, such as rotary pumps, are more complex and prone to failure. Furthermore, piston pumps allow for higher delivery pressures, whereas rotary pumps are physically limited in this regard.

[0015] In addition, the pump or the multiple delivery units are each designed to deliver fluid via a pulling movement of a respective piston rod on the respective piston. This can mean, for example, that the piston compresses the fluid in the cylinder during its upward movement; the piston rod is pulled and not pushed. This allows the use of long or even particularly long piston rods. Because the force applied to the piston rods in their longitudinal direction is mainly due to pulling, there is little or no risk of the piston rods bending. Long piston rods, in turn, mean that the drive device can be arranged as far away from the delivery units as possible, which reduces the heat input from the drive device to the cryogenic fluid to be delivered by the delivery units.Preferably, the drive device is arranged at a distance from the plurality of conveyor units, preferably at a distance of at least 400 mm, in particular at least 600 mm. This effectively prevents heat input.

[0016] Upon entering the pump or delivery units, the cryogenic fluid, e.g., hydrogen, is usually near or at its boiling point. To prevent boiling of hydrogen, for example, the heat input into the pump or at least the delivery units must be minimized, which can be achieved by using very long piston rods. Long piston rods reduce heat input due to a long heat conduction path. Furthermore, the insulating effect of the vacuum between the inner and outer vessels minimizes heat input.

[0017] Furthermore, the pump is designed such that the plurality of delivery units and at least a portion of the collecting line for conveying fluid can be arranged submerged in the fluid. In particular, the corresponding components or parts of the pump that can be arranged submerged in the cryogenic fluid are designed to withstand low temperatures of, for example, less than -90°C or even down to -253°C, and in particular to be and remain functional in such temperatures.

[0018] In one embodiment, the pump is designed such that the plurality of pistons are moved synchronously and with a time offset from one another. This can be achieved, for example, by appropriately connecting the piston rods to the drive device and, if necessary, by suitable design of the drive device. In the case of a hydraulic drive device, this can be designed such that, through appropriate regulation of the hydraulic oil mass flow, the travel speed of the individual pistons has a sinusoidal shape, and that the pistons are moved with a time offset from one another. Furthermore, the drive device can, for example, have a suitable crankshaft (or another suitable construction) to which the piston rods are appropriately connected. This leads to a synchronized movement, e.g. sinusoidal movement, of the pistons, in each case with a certain time delay between the individual pistons.This allows the most continuous and uniform flow rate of fluid to be generated at the pump outlet.

[0019] To pump the fluid, the pump can be arranged such that at least the inlets of the multiple pumping units, preferably the multiple pumping units, are submerged in the cryogenic fluid. In particular, the pump can also be arranged in this manner permanently, or at least outside of times when it is used for pumping. This allows the pump to start immediately, and no cooling time is required when starting the pump.

[0020] The pump is positioned to deliver fluid in such a way that the drive mechanism is located outside the cryogenic fluid. This ensures the reliable operation of the drive mechanism and thus the pump as a whole. Although the drive mechanism should also be suitable for low temperatures, it does not have to be able to withstand temperatures as low as the delivery units. Here, too, the long piston rods mentioned above offer an advantage, as they allow the delivery units to be immersed sufficiently deep in the cryogenic fluid, while at the same time allowing the drive mechanism to be positioned sufficiently far away from the cryogenic fluid.

[0021] Furthermore, the pump insert has a plurality of tie rod sleeves which are arranged between the drive device and the plurality of delivery units. At least one section of each of the plurality of tie rods is arranged within at least one respective one of the plurality of tie rod sleeves, and the plurality of delivery units are fastened, in particular suspended, at least indirectly to the drive device via the plurality of tie rod sleeves. The pump insert also has a plurality of seals, wherein each of the plurality of tie rods is sealed with at least one of the plurality of seals within at least one respective one of the plurality of tie rod sleeves. This allows good thermal insulation and a further reduction of the heat input. In addition, the inner container has a tension section (e.g. a so-calledThe conveyor unit receiving section (draw tube) and a delivery unit receiving section, wherein the delivery unit receiving section is suspended from an upper side of the outer container by means of the draw section. The delivery units can then be arranged in particular in the delivery unit receiving section, which can also serve as a reservoir for the fluid. This further reduces the heat input to the fluid. In particular, walls of the draw section can be designed to be particularly thin, for example, in order to keep the heat input as low as possible.

[0022] In one embodiment, at least one of the plurality of delivery units, but preferably all of them, is configured such that gaseous fluid present in the respective cylinder can escape from the respective delivery unit during a loading stroke. For this purpose, the respective cylinder can preferably have a cylinder head and a sliding sleeve, and can be designed such that during the loading stroke a degassing gap is formed between the cylinder head and the sliding sleeve, through which the gaseous fluid can escape. In this way, the delivery unit can be filled as completely as possible with liquid fluid. Likewise, it can be provided that the respective delivery unit has a valve that opens actively or passively during the loading stroke and can be arranged, for example, in the delivery unit inlet of the respective delivery unit.

[0023] In one embodiment, the pump is configured for operation with piston movement in a vertical direction. This particularly means that when the pump is set up for operation, the cylinders are aligned vertically, so that the pistons move vertically up and down. This reduces convective heat transfer from the inner vessel to the piston rods or a passage through the piston rods.

[0024] Furthermore, the pump insert can be provided with a sealing disc through which the plurality of tie rods are guided, wherein the sealing disc seals the delivery unit receiving section. This allows heat transfer through gaseous fluid to be reduced.

[0025] In one embodiment, the pump housing has a gas outlet through which gaseous fluid can be discharged from the inner container. The gas outlet can be designed, similar to the pump inlet, e.g., as a passage from the inside through a wall in the inner container, through the evacuated space to a wall of the outer container. The gas outlet should be located high up on the inner container, i.e., where the fluid is also in gaseous form. This allows boil-off gas to be easily recirculated. It is conceivable that a control valve could also be provided at the gas outlet for this purpose.

[0026] It is particularly preferred if the pump insert is removably mounted in the pump housing. This allows the pump insert to be replaced as needed, for example, or removed for maintenance.

[0027] In one embodiment, the pump has a total delivery volume of the multiple delivery units of more than 1.5 l. For this purpose, the individual delivery units and, in turn, the cylinders and pistons therein can have corresponding dimensions. With a larger number of delivery units, the individual delivery units can, for example, be designed somewhat smaller in order to still achieve an overall high delivery volume. The delivery volume of an individual delivery unit is the volume enclosed in the cylinder between the bottom and top dead center of the piston. A high total delivery volume of the pump allows a low operating frequency of the pump in order to still achieve a high delivery rate of the pump. A low operating frequency, in turn, means slow movement of the pistons in the cylinders.The advantages of the slow movement in combination with the corresponding conveying volumes are a relatively low heat input due to friction and a high degree of loading of the cylinders with fluid due to the low flow velocity of the fluid when it flows, for example, into the conveying units (ie into the conveying unit inlets).

[0028] It is particularly preferred if the pump is operated at an operating frequency of at most 5 Hz, preferably at most 3 Hz. However, a frequency as low as 1.5 Hz is also conceivable. The operating frequency of the pump is understood to be a frequency with which a piston in the cylinder performs a full stroke from bottom dead center to top dead center and back again to bottom dead center. If the pistons are directly connected via the piston rod to the aforementioned crankshaft of the drive device, the operating frequency corresponds to a rotational frequency of the crankshaft. In addition, the cryogenic fluid can be pumped by means of the pump, for example, at a pressure of at most 20 bar. However, higher pressures are also conceivable.

[0029] The operating frequency values ​​mentioned and preferred here are particularly low for a piston pump, but by combining them with the high total delivery volume, a particularly high delivery rate can still be achieved, as is necessary or at least desirable for heavy-duty applications, for example. The heat input remains low, as mentioned, which increases efficiency. For the example of hydrogen as a cryogenic fluid, an operating frequency of 1.5 Hz and a total delivery volume of 1.5 l, assuming a density of the cryogenic hydrogen of approx. 71 kg / m3, results in a delivery rate of approx. 575 kg / h. In particular, it is preferred if the pump, taking into account possible internal mass flow losses, e.g. via sealing systems, at an operating frequency of 3 Hz or less, achieves a delivery rate of 400 kg / h or more, e.g. at least 600 kg / h, which is achieved by a corresponding total delivery volume.

[0030] The pump design allows the flow rate of the proposed pump to be increased particularly easily, for example, by simply adding more delivery units. A pump design in which one or more of the existing delivery units can be selectively switched on and off to adjust the flow rate as needed is also conceivable. For this purpose, the drive system can then be designed accordingly, e.g., with separate drive units for one or more of the existing delivery units.

[0031] The invention is illustrated schematically in the drawing using an embodiment and is described below with reference to the drawing.

[0032] Short description of the drawing

[0033] Figure 1 shows a schematic diagram of a system in which a pump according to the invention can be used.

[0034] Figure 2a schematically shows a pump according to the invention in a preferred embodiment. Figure 2b schematically shows a pump housing of the pump from Figure 2a.

[0035] Figure 2c shows a schematic of a pump insert of the pump from Figure 2a.

[0036] Figure 2d shows schematically a delivery unit of the pump from Figure 2a in a more detailed view.

[0037] Detailed description of the drawing

[0038] Figure 1 schematically shows a system 100 in which a pump according to the invention can be used, i.e., it is an application in which cryogenic fluid is pumped. The system 100 has a storage tank 110 for, for example, liquid hydrogen H2 as the cryogenic fluid. The hydrogen can be stored in liquid form in the storage tank 110, for example, at a pressure of 2 to 3 barg.

[0039] Furthermore, the system 100 comprises a pump 200 according to the invention in a preferred embodiment. The pump 200 is only symbolically indicated here and will be explained in detail with reference to Figures 2a, 2b, and 2c. The pump 200 can be supplied with hydrogen H2 via a line from the storage tank 110. Furthermore, the system 100 comprises a coupling 120, which is connected to the pump 200 via a further line.

[0040] By means of the coupling 120, the line can be connected or coupled to, for example, a tank 132 of a vehicle 130. The tank 132 of the vehicle can, in particular, be a tank for hydrogen as fuel for propelling the vehicle 130. In this respect, a truck, for example, comes into consideration as a vehicle, especially since trucks require large quantities of hydrogen for propulsion, which can be transferred in a short time using the proposed pump. It should be noted, however, that the hydrogen can also be transferred to other types of tanks, e.g., mobile storage tanks for transport or for other applications.

[0041] It should be noted that the system 100 may also include other components, e.g., various valves or measuring technology such as a flow meter. Rather, a possible and preferred application for the proposed pump 200 will be explained merely by way of example. Thus, cryogenic hydrogen can be pumped from the storage tank 110 into the tank 132 by means of the pump 200.

[0042] Figure 2a schematically shows a pump according to the invention in a preferred embodiment. This is the pump 200 already shown in Figure 1, but only symbolically there. The pump 200 has a pump housing 201 and a pump insert 202, each of which comprises various components of the overall pump 200. While Figure 2a shows the entire pump 200, Figure 2b shows only the pump housing 201 and Figure 2c shows only the pump insert 202. Figure 2d shows a delivery unit of the pump 200 in a more detailed view. Figures 2a, 2b, 2c, and 2d will be described comprehensively below.

[0043] The pump housing 201 has an outer container 220 and an inner container. The inner container, in turn, has a delivery unit receiving section 221 and a tension section 222. The delivery unit receiving section 221 is suspended from an upper side of the outer container 220 by means of the tension section 222, e.g., on a flange 224. A space 225 is or will be formed between the outer container 220 and the inner container, which space is evacuated or can be evacuated and can be provided, e.g., with vacuum-suitable multi-layer insulation (MLI). Evacuation should be understood to mean that at most a very low pressure of residual gas is present. The interior of the inner container, or in particular of the delivery unit receiving section 221, is thus well insulated from the outside.

[0044] The pump housing 201 has a pump inlet 261, through which the fluid H2 to be pumped, particularly in liquid form, can be introduced into the inner container, particularly the pump unit receiving section 221. The pump inlet 261 is designed, for example, as a passage from the outside through a wall in the outer container 220, through the evacuated space 225 to a wall of the inner container.

[0045] In addition, the pump housing 201 has a gas outlet 264 through which gaseous fluid H2 can be discharged from the inner container. The gas outlet is designed, for example, as a feedthrough from the inside through a wall in the inner container, through the evacuated space 225 to a wall of the outer container 220. The gas outlet 24 is arranged high up on the inner container, i.e. where the fluid is also present in gaseous form. This allows boil-off gas to be easily recirculated. It is conceivable that a control valve is also provided at the gas outlet for this purpose. A liquid level of liquid fluid H2 is indicated by way of example in Figures 2a, 2b by means of a dashed line.

[0046] The pump insert 202 has a plurality of delivery units, here, for example, three delivery units 231, 232, 233. The delivery units 231, 232, 233 can be constructed similarly, so that only the delivery unit 231 will be described in more detail below by way of example. The delivery unit 231 has a piston 241 and a cylinder 240, wherein the piston 241 is arranged so as to be movable back and forth within the cylinder 240.

[0047] Figure 2d shows an exemplary embodiment of the conveyor unit 231 in more detail. The cylinder 240 has a sliding sleeve 249, a cylinder head

[0048] 245.1 and a cylinder housing 245.2. Cylinder head 245.1 and cylinder housing

[0049] 245.2 can be a common component or a structural unit. The cylinder sleeve 249 is open at the top. The upper edge of the sliding sleeve 249 is pressed against the cylinder head 245.1 during an upward movement, for example, and in doing so seals it off. The sliding sleeve 249 can also be open at the bottom. The sliding sleeve 249 is movably mounted in the cylinder housing 245.2, and the cylinder housing 245.2 surrounds the sliding sleeve 249. This allows a certain movement, vertical in the case shown, of the sliding sleeve 249. The vertical movement of the sliding sleeve 249 is limited downwards by a mechanical stop 246 on the cylinder housing 245.2 and a corresponding mechanical stop 247 on the sliding sleeve 249. Both stops are shown here with a certain gap, which is for illustrative purposes only. In practice, this should be sealed. In the case shown, the piston 241 is inside the cylinder 240 or the sliding sleeve 249 up and down, ieMovable in a vertical direction when the pump is in operation. The pump is therefore based on the principle of a piston pump or reciprocating piston pump.

[0050] Furthermore, the pump insert 202 has a drive device 210 and a plurality of piston rods 251, 252, 253, wherein the drive device 210 is connected to one of the plurality of pistons via one of the plurality of piston rods. The pump 200 is configured to move each of the plurality of pistons back and forth within the respective cylinder by means of the drive device 210—up and down in the case shown. The drive device 210 can, for example, be operated electrically and / or hydraulically. In the example shown, the drive device 210 has three drive units 211, 212, 213, each of which is assigned to a piston rod or piston. The drive units can, for example, each be an electric or hydraulic motor. As already mentioned, all piston rods can, however, also be connected, for example, to a common crankshaft or the like, which is then driven, in particular rotated, for example, by only one drive unit.It is understood that the drive units 211, 212, and 213 do not have to be arranged in a line with each other. This applies accordingly to the conveyor units.

[0051] The drive device 210 is particularly configured to operate at an operating frequency of up to 5 Hz, up to 3 Hz, or even as low as 2 Hz; as mentioned, this is relatively slow for a piston pump. Depending on the type of drive device or drive units, this may require, for example, a transmission via a gear.

[0052] The pump insert 202 has, for example, a support ring 223, by means of which the drive device 210 is supported on the pump housing 201, there on its upper side, in particular on the flange 224.

[0053] The delivery unit 231 also has a delivery unit inlet 242 and a delivery unit outlet 243 for the fluid. Both the delivery unit inlet 242 and the delivery unit outlet 243 can each have a valve, for example. In this way, fluid can only flow in via the delivery unit inlet 242 during a so-called loading stroke through the delivery unit inlet 242, which then opens. The valve of the delivery unit outlet 243 then remains actively or passively closed. In the pump 200 shown, a loading stroke is performed by a downward movement of the piston 241. The delivery volume of the delivery unit 231 is therefore located in the upper part of the cylinder 240, between the piston 241 and the delivery unit inlet 242 and the delivery unit outlet 243. During the loading stroke, as can be seen in Figure 2d, the sliding sleeve 249 moves downwards to the stop both due to gravity and due to the frictional force of the piston 241 on the inner wall of the sliding sleeve 249.This creates a gap between the sliding sleeve 249 and the cylinder head 245.1, a so-called degassing gap, designated here as 248.1. Any residual amount of gaseous hydrogen from the previous delivery stroke can escape through this gap 248.1 from the cylinder 240 or the sliding sleeve 249 and through openings 248.2 in the cylinder housing 245.2. Thus, during the current charging stroke, the delivery unit is filled as completely as possible with liquid hydrogen, thus achieving a high delivery rate of the pump 200. As a variant or in addition to this, it can be provided, for example, that degassing can also be implemented via the delivery unit inlet 242 by means of an actively or passively opening valve.

[0054] It should be noted that the delivery unit inlet 242 and the delivery unit outlet 243 are shown here only as examples. The delivery unit inlet could, for example, also be formed by the underside of the cylinder 240 being open and the piston 241 being designed such that, upon downward movement of the piston, it forms an opening through which fluid can flow into the delivery volume from below.

[0055] In a so-called delivery stroke, when excess pressure is generated in the cylinder, fluid can be expelled through the valve of the delivery unit outlet 243, which then opens passively or actively. The valve of the delivery unit inlet 242 then remains closed. In the pump 200 shown, a delivery stroke is performed by an upward movement of the piston 241.

[0056] In the example of pump 200 shown, the delivery unit 231 is also designed to deliver fluid via a pulling movement of the piston rod 251 on the piston 241. In this example, a pulling movement corresponds to an upward movement. The pulling movement therefore performs the delivery stroke, while a pushing movement (here a downward movement) performs a loading stroke. Since a greater force acts on the piston rod during a delivery stroke than during a loading stroke (since pressure must be built up in the fluid), this arrangement means that even with a long piston rod, buckling of the piston rod does not occur or is highly unlikely. The explanations for the delivery unit 231 apply equally to the delivery units 232, 233. The delivery volume of each delivery unit is determined by the volume difference between the volume delimited by the piston in the cylinder at the minimum and maximum piston stroke.The difference between the minimum and maximum piston stroke is the stroke height h, as shown for the delivery unit 233. Based on the stroke height h and a cylinder diameter d, the delivery volume can then be determined.

[0057] Furthermore, the pump insert 202 has a collecting line 262, wherein the delivery unit outlets of all delivery units 231, 232, 233 are connected to the collecting line 224. The fluid collecting line 224 is designed such that the delivery unit outlets open into a common pump outlet 263, via which fluid delivered by the pump 200 can be provided. The fluid flows from the individual delivery unit outlets are thus collected or combined into a common fluid flow.

[0058] The plurality of delivery units 231, 232, 233 and at least a portion of the collecting line 262 are arranged within the inner container and, there, in turn, within the delivery unit receiving section 221. The drive device 210, however, is, as mentioned, arranged outside the pump housing 201, here, for example, on top. The pump outlet 266 is arranged or incorporated, for example, in the support ring 223.

[0059] The pump housing 220, as mentioned, has the pump inlet 261. The pump 200 is designed such that the fluid H2 to be pumped can be brought or guided to the pumping unit inlets via the pump inlet 261. In the example shown, this is achieved by arranging the pumping unit inlets, in particular also the plurality of pumping units (as a whole) and at least part of the collecting line for pumping fluid submerged in the fluid (the liquid level of liquid fluid H2 is indicated by way of example in Figures 2a, 2b by means of the dashed line). Fluid entering through the pump inlet 261 thus collects in the pumping unit receiving section 221, as can be seen in Figure 2a, and can thus penetrate into the pumping units (or their delivery volumes) via the pumping unit inlets, in particular during a respective loading stroke.The pump insert 202 has, for example, a plurality of tie rod sleeves arranged between the drive device 210 and the plurality of delivery units 231, 232, 233. Furthermore, the pump insert 202 has, for example, a sealing disk 254. A tie rod sleeve 255 is shown as an example, which surrounds the tie rod 251 and by means of which the sealing disk 254 is connected to the drive device 210. Accordingly, further tie rod sleeves can be provided for the further tie rods. Furthermore, a tie rod sleeve 256 is shown as an example, which also surrounds the tie rod 251 and by means of which the sealing disk 254 is connected to the delivery unit 231. Accordingly, further tie rod sleeves can be provided for the further tie rods. In this way, the delivery units are at least indirectly attached, in particular suspended, to the drive device 210 via the plurality of tie rod sleeves.

[0060] The sealing disc 254 can in particular be shaped or configured such that it seals the delivery unit receiving section 221, specifically against the tension section 222. This forms a space 226 within the tension section 221 and around the tie rod sleeves (insofar as these are within the tension section). The space 226 is sealed, in particular, against the typically cold delivery unit receiving section 221 with a seal that only shields liquid but is not gas-tight. Thus, during operation of the pump, the space 226 fills, in particular, with relatively warm gaseous fluid, which leads to a thermal insulation layer between the liquid hydrogen in the delivery unit receiving section 221 and the upper part of the pump housing 201, the flange 224, and the support ring 223. Without this insulation, the aforementioned locations would become very cold, and the seal 257, in particular, could become leaky due to the cold.

[0061] The pump insert 202 also has several seals, by means of which the tie rods are sealed within a tie rod sleeve. For example, for the tie rod sleeve 255, a seal 258 is provided at the bottom in the cold area and a seal 257 at the top in the warm area; this applies accordingly to the other tie rod sleeves (between the sealing disc and the drive mechanism). The seals 258 can be bushings, for example, while the seals 257 can be so-called stuffing boxes. This seals the cold fluid in the inner container as well as possible or, if necessary, warms it up to the upper seal 257.

[0062] The multiple delivery units 231, 232, 233 make it possible to create a larger overall delivery volume, thus enabling a higher delivery rate of the pump 200. Nevertheless, the principle of the piston pump allows for simple and robust operation, while other pump types such as rotary pumps are more complicated and prone to failure.

[0063] Long piston rods 251, 252, 253, in turn, ensure that the drive device 210 can be arranged as far apart as possible from the conveying units 231, 232, 233, which enables a reduction in the heat input of the drive device 210 to the cryogenic fluid to be conveyed by means of the conveying units. Preferably, the drive device is arranged at a distance from the plurality of conveying units, preferably at a distance x. The distance x, as indicated by way of example in Figure 2a, should, for example, be at least large enough that the conveying units, in particular also their conveying unit inlets, can be immersed or submerged sufficiently far into the cryogenic fluid H2, but on the other hand the drive unit does not, for example, touch the cryogenic fluid H2. Depending on requirements, the distance x, which also determines the length of the piston rods, can be selected to be large enough that the heat input via the piston rods into the cryogenic fluid H2 is sufficiently small.

[0064] Upon entering the pump 200 or the delivery units, the cryogenic fluid, e.g., hydrogen, is typically near or at its boiling point. To prevent hydrogen from boiling, the heat input into the pump, or at least the delivery units, must be minimized, which can be achieved by using very long piston rods. Long piston rod lengths reduce heat input due to a long heat conduction path.

[0065] For example, pump 200 can be configured such that the pistons 241, 242, 243 are moved synchronously and offset in time from one another. This can be achieved, for example, by appropriately connecting the piston rods to the drive device 210 and, if necessary, by a suitable design of the drive device. For example, the drive device can have a suitable crankshaft to which the piston rods are appropriately connected. This leads to a synchronized movement, e.g. sinusoidal movement, of the pistons, each with a certain time delay between the individual pistons. This makes it possible to generate the most continuous and uniform flow rate of fluid H2 at the pump outlet 222.

[0066] To pump the fluid, pump 200 can be arranged and operated such that at least the pump unit inlets of the multiple pump units, preferably the multiple pump units themselves, are submerged in the cryogenic fluid H2. The drive device 210, however, is located outside or, in this case, above the cryogenic fluid H2. Such a situation is shown in Figure 2a. In this way, pump 200 can start immediately, and no cooling time is required when starting the pump.

[0067] The pump can, for example, achieve a delivery rate of 400 to 600 kg / h of cryogenic fluid H2 at an operating frequency of 1.5 to 3 Hz. This means that the total delivery volume of the multiple delivery units is approximately 1.5 l; this in turn is divided, for example, evenly between the three delivery units 231, 232, 233 and is achieved by suitable values ​​for diameter d and piston stroke h. The low operating frequency of the pump 200 means a slow movement of the pistons in the cylinders. The advantages of the slow movement in combination with the corresponding delivery volumes are a relatively low heat input through friction and a high degree of loading of the cylinders with fluid due to the low flow velocity of the fluid when it flows, for example, into the delivery units (i.e., into the delivery unit inlets). It should be mentioned that the operating frequency of the pump is preferably between 0 Hz and, for example,2 or 3 Hz can be freely regulated, e.g. during refueling of a vehicle.

[0068] Figures 2b and 2c also show that the pump insert 202 can be removed from the pump housing 201, e.g. for replacement or maintenance purposes.

Claims

Patent claims 1. Pump (200) for conveying a cryogenic fluid (H2), in particular hydrogen, wherein the pump (200) has a pump housing (201) and a pump insert (202), wherein the pump housing (201) has an outer container (220) and an inner container (221, 222), wherein a space (225) is formed between the outer container (220) and the inner container (221, 222), which space is evacuated or can be evacuated, wherein the pump housing (201) has a pump inlet (261) via which the fluid to be conveyed can be brought into the inner container (221, 221), wherein the pump insert (202) has a plurality of conveying units (231, 232, 233), a drive device (210), a plurality of piston rods (251, 252, 253) and a collecting line (262), wherein the plurality of delivery units and at least a part of the collecting line are arranged within the inner container (221, 222), and wherein the drive device (210) is arranged outside the pump housing (201),wherein each delivery unit has a piston (241) and a cylinder (240), wherein the drive device (210) is connected to one of the plurality of pistons via one of the plurality of piston rods, and wherein the pump (200) is configured to move each of the plurality of pistons back and forth within the respective cylinder by means of the drive device (210), wherein the pump is designed to deliver fluid via a pulling movement of the piston rods, wherein the pump insert (202) has a pump outlet (222), and wherein each of the plurality of delivery units (231, 232, 233) has a delivery unit inlet (242) and a delivery unit outlet (243) for the fluid, wherein the delivery unit outlets are connected to the collecting line, and wherein the fluid collecting line is designed such that the delivery unit outlets open into the pump outlet (222), via which fluid (H2) delivered by the pump (200) can be provided,wherein the pump (200) is designed such that the plurality of delivery units (231, 232, 233) and at least a part of the collecting line (224) for delivering fluid can be arranged submerged in the fluid (H2), wherein the pump insert (202) has a plurality of pull rod sleeves (255) arranged between the drive device and the plurality of delivery units, wherein at least a portion of each of the plurality of pull rods is arranged within at least one respective one of the plurality of pull rod sleeves, and wherein the plurality of delivery units are at least indirectly fastened, in particular suspended, to the drive device via the plurality of pull rod sleeves, wherein the pump insert (202) has a plurality of seals, wherein each of the plurality of pull rods is sealed with at least one of the plurality of seals within at least one respective one of the plurality of pull rod sleeves, and wherein the inner container has a pull portion (222) and a delivery unit receiving portion (221), wherein the delivery unit receiving portion is suspended from an upper side of the outer container by means of the pull portion.

2. Pump (200) according to claim 1, wherein at least one of the plurality of delivery units is configured such that gaseous fluid present in the respective cylinder (240) can escape from the respective delivery unit during a charging stroke.

3. Pump (200) according to claim 2, wherein the respective cylinder (240) has a cylinder head (245.1) and a sliding sleeve (249), and is designed such that during the charging stroke a degassing gap (248.1) is formed between the cylinder head (245.1) and the sliding sleeve (249), through which the gaseous fluid can escape.

4. Pump (200) according to claim 2 or 3, wherein the respective delivery unit has a valve which opens actively or passively during the charging stroke and through which the gaseous fluid can escape, wherein the valve is arranged in particular in the delivery unit inlet (242) of the respective delivery unit.

5. Pump (200) according to one of the preceding claims, wherein the drive device (210) is arranged at a distance (x) of at least 400mm, preferably at least 600mm, spaced from the plurality of conveyor units (231, 232, 233).

6. Pump (200) according to one of the preceding claims, which is arranged such that the plurality of pistons (241) are moved synchronously and offset in time from one another.

7. Pump (200) according to one of the preceding claims, which is arranged for operation with a movement of the pistons in a vertical direction.

8. Pump (200) according to one of the preceding claims, wherein the pump insert (202) has a sealing disc (254) through which the plurality of tension rods are guided, wherein the sealing disc seals the conveyor unit receiving section (221) against the tension section (222), in particular only shielding liquid, but not gas-tight.

9. Pump (200) according to one of the preceding claims, wherein the pump housing (220) has a gas outlet through which gaseous fluid can be discharged from the inner container (221, 221).

10. Pump (200) according to one of the preceding claims, wherein the pump insert (202) is removably arranged in the pump housing (201).

11. Pump (200) according to one of the preceding claims, which has a total delivery volume of the plurality of delivery units of more than 1.5 l.

12. Method for conveying a cryogenic fluid (H2), in particular hydrogen, by means of a pump (200) according to one of the preceding claims.

13. The method according to claim 12, wherein the pump (200) is arranged and operated such that at least the conveyor unit inlets (242), preferably the plurality of conveyor units (231, 232, 233), are submerged in the cryogenic fluid (H2), and that the drive device (210) is located outside the cryogenic fluid.

14. The method according to claim 12 or 13, wherein the pump (200) is operated at an operating frequency of at most 5 Hz, preferably at most 3 Hz.

15. The method according to any one of claims 12 to 14, wherein the cryogenic fluid (H2) is conveyed by means of the pump (200) at a conveying rate of at least 200 kg / h, preferably at least 300 kg / h, more preferably at least 400 kg / h, and wherein in particular the cryogenic fluid is conveyed by means of the pump (200) at a pressure of at most 20 bar.

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