EJECTOR JET PUMP

Description

1 / 13 EJECTOR JET PUMP

[001] The invention relates to an ejector jet pump for a recirculation system of a fuel cell propulsion system, in particular a fuel cell propulsion system designed as an aircraft engine, for humidifying and recirculating hydrogen in the fuel cell system.

[002] Ejector jet pumps are commonly used for the recirculation of gaseous hydrogen in proton exchange membrane (PEM) fuel cells. Ejector jet pumps allow unused hydrogen, which exits as exhaust gas from the anode of a fuel cell, to be mixed with fresh hydrogen from a hydrogen tank and reused. Typically, the excess hydrogen exiting the fuel cell is very wet, with a relative humidity of 90% to 100%, and may even be mixed with liquid water. This excess wet hydrogen is used to humidify the dry hydrogen from the hydrogen tank before the mixture is fed back into the fuel cell. Humidification is an important function of the ejector jet pump, as it significantly improves fuel cell performance. However, it is also important that no liquid water enters the fuel cell.For this reason, it is necessary to separate the liquid water component from the fuel cell system, especially from the recirculation circuit. This is usually achieved with a cyclone water separator.

[003] The use of an ejector jet pump in conjunction with a cyclonic water separator to separate liquid water is frequently employed in the automotive industry, where fresh hydrogen comes from high-pressure tanks with a system pressure of 350 to 700 bar. This means that, in these cases, a large quantity of liquid water is used. Petition 870250089688, dated 02 / 10 / 2025, page 7 / 32 2 / 13 of the motive pressure is available for use with the jet pump, allowing recirculation in a closed circuit. Liquid hydrogen tanks pressurized only between 5 and 10 bar are used in aviation applications.

[004] The objective of the invention is to provide an ejector jet pump that is more suitable for use in aviation.

[005] The ejector jet pump according to the invention is for a recirculation system of a fuel cell system of a fuel cell propulsion system, in particular a fuel cell propulsion system designed as an aircraft engine, for humidification and recirculation of hydrogen in the fuel cell system. The ejector jet pump with at least one fuel cell comprises a water separator for separating liquid water and forming droplet-free gas from the wet exhaust gas of the fuel cell and a gas feed device located downstream of the water separator, in particular adjacent to it. The water separator has a suction connection for feeding the exhaust gas to the water separator and also a water outlet for removing the separated water from the wet exhaust gas.In addition, the water separator has a droplet-free gas-to-droplet-free gas connection, a wet gas without water droplets, which flows to the gas feed device.

[006] The ejector jet pump according to claim 1 fulfills the purpose, since the water separator between the suction connection and the gas supply device has a tubular shape and a curvature of at least 60° and at most 160°, in particular 120°. Narrower limits for the angle α can also be selected, where the selection should not be arbitrary, but rather the flow should still be reasonable, i.e., without significant losses. Consequently, reasonable lower limits for the angle α can be Petition 870250089688, dated 02 / 10 / 2025, page 8 / 32 3 / 13 65°, 70°, 75°, 80° or 85°. Reasonable maximum limits for the angle α can therefore be 155°, 150°, 145°, 140°, 135°, 130°, 125°, 120°, 115°, 110°, 105°, 100° or 95°. A right-angle or approximately right-angle curvature is particularly preferred.

[007] The water separator may comprise a first tube section adjacent to the suction connection with a first principal axis and a second tube section adjacent to the gas feed device with a second principal axis, wherein the curvature may be located between the first tube section and the second tube section, and wherein the angle α may be formed between the two principal axes. The exhaust gas from a fuel cell anode, in particular, is generally present as a wet hydrogen gas with a liquid component. The droplet-free gas is, therefore, a gas, in particular a hydrogen-nitrogen-water vapor mixture, without liquid water droplets. The tube shape may preferably be circular. However, it is also possible for the tube to have other shapes, such as elliptical, polygonal or square, with corresponding rounded corners.The fuel cell mentioned in this document may represent a fuel cell stack consisting of a plurality of fuel cells.

[008] The wet exhaust gas with a liquid component is diverted in the ejector jet pump in the water separator, directing the exhaust gas towards a wall of the water separator. The water droplets present in the wet exhaust gas adhere to the walls exposed to the flow, and the gas flow, now partially dehumidified, can be further conveyed with minimal friction loss. This is particularly advantageous for an ejector jet pump connected to a low-pressure liquid hydrogen tank to feed a propellant, since there are very low pressure losses in the separator. Petition 870250089688, dated 02 / 10 / 2025, page 9 / 32 4 / 13 of water and therefore in the proposed ejector jet pump according to the invention.

[009] Other advantages and features are evident from the following description of some preferred embodiments and dependent claims.

[0010] In an advantageous embodiment of the invention, the ejector jet pump is further developed, since the water separator has a water collecting ring at its end facing the gas feed device, from where the water outlet opens. This means that the flow direction within the water separator is the same for the gaseous and liquid phases of the wet exhaust gas or its liquid and gaseous components, so that pressure losses can be further reduced, at least compared with a cyclone. The water collecting ring is preferably designed as a collecting basin, in which the movement of the separated water is directed from the direction of the main flow to the water outlet. In cross-section, the water collecting ring may have the shape of a bag.

[0011] In another advantageous embodiment of the jet ejector pump, the water collector ring is located concentrically with the droplet-free gas outlet. This allows for an overlap between the water collector ring and the droplet-free gas outlet. This is a particularly compact and space-saving configuration for both components.

[0012] In a preferred embodiment of the ejector jet pump, the water collector ring is located at a distance from the droplet-free gas connection. This allows for easy separation of the separated water from the exhaust gases and the dehumidified droplet-free gas formed from the exhaust gases. Furthermore, the distance between the water collector ring and the droplet-free gas connection, defined in a cross-section of the water collector ring and radially at least Petition 870250089688, dated 02 / 10 / 2025, page 10 / 32 5 / 13 One of the central axes of the water collector ring or droplet-free gas connection along a radial axis may be at least 10% of the cross-sectional area of ​​the water collector ring. The inner wall diameter of the water collector ring is at least one and a half times, in particular at least twice, larger than the inner wall diameter of the droplet-free gas connection.

[0013] In a particularly preferred embodiment, the water collector ring is located separately from the droplet-free gas connection. This can be achieved, for example, by means of a common partition wall which can, in particular, constitute the distance between the water collector ring and the droplet-free gas connection. The separation allows the separate water and droplet-free gas to be discharged separately in a particularly efficient manner.

[0014] In an advantageous development of the ejector jet pump, the droplet-free gas connection tapers in the direction of flow. This reduces the overall cross-section and allows the gas to be advantageously accelerated in the direction of the gas feed device. It can also be provided that the diameters of the outer and inner walls taper uniformly, so that the distance between the outer and inner walls does not decrease.

[0015] A particularly preferred design of the ejector jet pump provides that the gas feed device has a propellant connection to feed propellant to a feed chamber of the gas feed device and where the droplet-free gas and propellant flow together into the feed chamber of the gas feed device. This creates a particularly efficient feed pump that works well even at low propellant feed pressures, which is particularly advantageous for aviation applications. The propellant, particularly in an aviation application, is liquid hydrogen in a propellant tank that Petition 870250089688, dated 02 / 10 / 2025, p. 11 / 32 6 / 13 is expanded at least in the feed chamber or upstream in a feed line and assumes a gaseous form. The propellant is fed to the feed chamber at high speed, approximately Mach 1 or even supersonic speed, where it draws in the droplet-free gas that preferably enters laterally to its flow path, thus creating a pumping or suction effect in the water separator.

[0016] The water separator may comprise a first pipe section and a second pipe section, between which there may be a bend. The propellant connection may comprise a third pipe section for feeding the propellant to the feed chamber, wherein the third pipe section may run in the area of ​​the bend from outside the water separator to the latter, in particular through the pipe wall of the water separator, and may run within the second pipe section, in particular substantially concentric with the latter. Substantially concentric may mean that the center of the third pipe section is displaced from the center of the second pipe section by no more than 50%, preferably 40%, more preferably 30%, and in particular 20%, of a maximum cross-sectional dimension of the second pipe section at the relevant point.Such an ejector jet pump, consisting of tube sections, allows for a particularly simple and lightweight design, which is especially advantageous for aviation applications.

[0017] The tubes, or the first, second and third tube sections, may be made of a sheet metal or comprise tube walls of sheet metal.

[0018] The design of the ejector jet pump can be further improved, in particular by connecting the propellant to a propellant nozzle that opens into the feed chamber of the gas feed device. This results in a higher propellant velocity. Petition 870250089688, dated 02 / 10 / 2025, p. 12 / 32 7 / 13 is even larger when entering the feeding chamber, so that the suction effect on the water separator is advantageously greater.

[0019] It is particularly preferable that the droplet-free gas connection of the water separator be located around the propellant connection. This is a particularly compact design, which also has the advantage of introducing less friction into the flow, thereby reducing cross-flow.

[0020] It may also be advantageous to provide that the propellant connection passes at least in sections through the water separator. Although this creates a slight obstruction in the water separator, the propellant can flow to the feed chamber without problems, which is advantageous.

[0021] Furthermore, in another preferred embodiment of the ejector jet pump, the droplet-free gas connection and the propellant connection may be located concentrically with respect to each other. This has the advantage of obtaining uniform suction at the droplet-free gas connection and uniform mixing in the gas feed device.

[0022] In addition, in another embodiment of the jet ejector pump, the gas feed device may be fitted with a diffuser downstream of the droplet-free gas connection. A diffuser slows down the outgoing gas, allowing the jet ejector pump to be integrated into a recirculation system with minimal losses.

[0023] The invention will be explained in more detail with reference to the following drawings, based on a number of preferred embodiments of the invention.

[0024] Figure 1 shows a schematic representation of a recirculation system with an embodiment of a jet ejector pump according to the invention.

[0025] Figure 2 shows the jet ejector pump embodiment according to the invention in a perspective view from the outside. Petition 870250089688, dated 02 / 10 / 2025, page 13 / 32 8 / 13

[0026] Figure 3 shows a cross-sectional view of the jet ejector pump embodiment according to the invention shown in Figure 2.

[0027] Figure 1 shows a schematic representation of an exemplary recirculation system 1 of a fuel cell propulsion system 1a.

[0028] The recirculation system 1 has an ejector jet pump 10 according to one embodiment of the invention. In the present embodiment, the ejector jet pump 10 consists of a water separator 20 and a gas feed device 30. The recirculation system 1 further comprises at least one fuel cell 2 derived from a fuel cell stack with at least one anode 3, wherein an anode inlet connection 3a and an anode outlet connection 3b are provided on at least one anode 3. A first recirculation line 6 leads from the anode outlet connection 3b to the water separator 20 of the ejector jet pump 10 and a second recirculation line 7 leads from the gas feed device 30 of the ejector jet pump 10 to the anode inlet connection 3a.

[0029] In addition, at least one propellant tank 4 feeds a propellant to the ejector jet pump 10, in the present embodiment with liquid hydrogen, by means of a feed line 8. The feed line 8 is connected to the gas feed device 30.

[0030] Finally, a discharge line 9 leads from the water separator 20 to a water system 5 of the fuel cell system.

[0031] Figure 2 shows a perspective view of the ejector jet pump embodiment 10 according to the invention shown in Figure 1. The ejector jet pump 10 consists of a water separator 20 and a gas feed device 30. A cross-sectional view of a part of the ejector jet pump 10 is marked by a rectangle drawn with dashed lines and labeled III, and is shown in Fig. Petition 870250089688, dated 02 / 10 / 2025, page 14 / 32 9 / 13 figure 3.

[0032] The water separator 20 has a suction connection 21 for connection to the first recirculation line 6 and also comprises a first pipe section 22 and a second pipe section 23, between which a bend 24 is located, or which merges with the bend 24, and a water collector ring 25 located concentrically with a water outlet 26 downstream of the second pipe section 23, as well as a droplet-free gas connection 27 located concentrically to the water collector ring 25. The water outlet 26 is located within and above a wall of the water collector ring 25 opposite the suction connection 21 and directs the water falling from there, through the discharge line 9, to the fuel cell system water system 5 for further use. The opposite location of the water outlet 26 is advantageous due to its proximity to the wall of the water separator 20 against which the flow occurs, since most of the falling water will form on the wall exposed to the flow.

[0033] The two tube sections 22 and 23 are cylindrical in this embodiment, but may also have other shapes, as indicated in the introductory description. The first tube section 22 has a first principal axis H1 and the second tube section 23 has a second principal axis H2. The principal axes Hi and H2 intersect and form an angle α which, according to the invention, may have a value between 60° and 120° and, in the present embodiment, is 90°. Consequently, the water separator 20 has a curvature 23 of 90°.

[0034] This curvature directs the wet exhaust gas flowing from suction connection 21 towards the inner wall of the water separator 20 and can release water there, resulting in a dehydrated, droplet-free gas that can flow along the S-flow direction through the droplet-free gas connection 27, which is located further inward relative to the water collector ring 25, with the least loss. Petition 870250089688, dated 02 / 10 / 2025, page 15 / 32 Possible 10 / 13.

[0035] The gas feed device 30 is connected to the droplet-free gas connection 27. The gas feed device 30 comprises a propellant connection 31 having a propellant nozzle 32 shown in Figure 3 that opens into the feed chamber 33 of the gas feed device 30, a diffuser 34 located downstream of the feed chamber, and a downstream gas outlet connection 35 for connecting the ejector jet pump 10 to the second recirculation line 7.

[0036] Figure 3 shows a section of the ejector jet pump 10 shown in Figure 2 in a sectional view, in particular the connection between the water separator 20 and the gas feed device 30. In the present embodiment, the gas feed device 30 has a third main shaft H3 that runs identically to the second main shaft H2.

[0037] The water collector ring 25, a droplet-free gas connection inlet 27 and a propellant connection section 31 positioned immediately upstream of the propellant nozzle 32 in the flow direction S are positioned concentrically and adjacent to each other around the third main axis H3 of the gas feed device 30.

[0038] A partition wall 28 is located between the water collector ring 25 and the droplet-free gas connection inlet 27, separating the water collector ring 25 from the droplet-free gas connection and giving the water collector ring 25 a ring-like shape similar to a container in which water can be collected. The water can then be drained through the water outlet 26 in the water collector ring 25. The partition wall 28 is rounded on the side facing the dry wall connection 27 to reduce flow resistance in the droplet-free gas connection 27, while the partition wall 28 is fully Petition 870250089688, dated 02 / 10 / 2025, page 16 / 32 11 / 13 molded on the side facing the water collector ring 25, thus providing the largest possible internal surface area for the water collector ring 25. This advantageously expands the internal space of the water collector ring 25, which serves as a water collection container.

[0039] It can also be observed that the droplet-free gas connection 27 is located around the propellant nozzle 32 and has a constant height in the radial direction around the third principal axis H3 along the flow direction, but tapers in the flow direction S which corresponds to that of the propellant nozzle 32. This reduces the cross-section of the droplet-free gas connection 27, so that the dehumidified droplet-free gas is accelerated. Since the propellant emerging from the propellant nozzle 32 also has a high flow velocity, this can advantageously reduce turbulence, i.e., the proportion of cross-flows. It should be understood that the height of the droplet-free gas connection 27 can also taper in the flow direction in other embodiments, for example, to further increase the flow acceleration.

[0040] The propellant from the propellant nozzle 32 draws in the droplet-free gas due to the high flow velocity and transports it through the feed chamber 33. As it flows through the feed chamber 33, which has an essentially cylindrical shape, the droplet-free gas and the propellant are mixed, which further reduces the moisture content of the exiting gas mixture due to the completely dry, i.e., water-free, state of the propellant. The gas mixture at the end of the feed chamber 33 finally reaches the diffuser 34, whose cross-section widens, reducing the flow to a velocity that can be used in the recirculation line 6 connected to the gas outlet connection 35.

[0041] The combination of the water separator 20 and the device of Petition 870250089688, dated 02 / 10 / 2025, page 17 / 32 12 / 13 gas supply 30 with a propellant connection 31, advantageously forms an efficient ejector jet pump with a built-in water separator. List of References Recirculation system 1a Fuel cell propulsion system Fuel cell Anode 3a Anode inlet connection 3b Anode outlet connection Propellant tank Water system First recirculation line Second recirculation line Power supply line Discharge line Jet ejector pump Water separation chamber Suction connection First section of pipe Second pipe section Third pipe section Curvatures Water collector ring Water outlet Droplet-free gas connection Partition wall Gas supply device Propellant connection Propellant nozzle Petition 870250089688, dated 02 / 10 / 2025, page 18 / 32 13 / 13 Gas outlet chamber Diffuser Gas outlet connection α Angle between the first and second principal axes H1 First main axis H2 Second main axis H3 Third main axis Petition 870250089688, dated 02 / 10 / 2025, page 19 / 32

Claims

1 / 3 CLAIMS 1. Ejector jet pump (10) for a recirculation system (1) of a fuel cell system in a fuel cell propulsion system (1a), in particular a fuel cell propulsion system (1a) designed as an aircraft engine, for humidifying and recirculating hydrogen in the fuel cell system having at least one fuel cell (2), comprising: a water separator (20) for separating liquid water and forming a droplet-free gas from a wet exhaust gas from the fuel cell (2), and a gas feed device (30) located downstream of the water separator (20), in particular adjacent to it, wherein the water separator (20) has a suction connection (21) for feeding the exhaust gas to the water separator (20), wherein the water separator (20) has a water outlet (26) for discharging the separated water from the exhaust gas damp,wherein the water separator (20) has a droplet-free gas connection (27) that opens to the gas supply device (30), characterized in that: the water separator (20) between the suction connection (21) and the gas supply device (30) is tubular in shape and has a curvature (24) at an angle α of at least 60° and at most 160°.

2. Ejector jet pump, according to claim 1, characterized in that the water separator (20) has a water collecting ring (25) at its end facing the gas supply device (30) from where the water outlet (26) opens. Petition 870250089688, dated 02 / 10 / 2025, page 20 / 32 2 / 3 3. Ejector jet pump, according to claim 2, characterized in that the water collector ring (25) is located concentrically with the droplet-free gas outlet.

4. Ejector jet pump, according to any one of claims 2 or 3, characterized in that the water collector ring (25) is located at a distance from the droplet-free gas connection (27).

5. Ejector jet pump, according to any one of claims 2 to 4, characterized in that the water collector ring (25) is located separately from the droplet-free gas connection (27).

6. Ejector jet pump, according to any of the preceding claims, characterized in that the droplet-free gas connection (27) tapers in the direction of flow.

7. Ejector jet pump, according to any of the preceding claims, characterized in that the gas feed device (30) has a propellant connection (31) for feeding a propellant to a feed chamber (33) of the gas feed device (30) and wherein the droplet-free gas and the propellant flow together to the feed chamber (33) of the gas feed device (30).

8. Ejector jet pump, according to claim 7, characterized in that the water separator (20) comprises a first tube section (22) and a second tube section (23), between which a bend (24) is located, wherein the propellant connection (31) comprises a third tube section (36) for feeding the propellant to the feed chamber (33), wherein the third tube section (36) extends into the water separator (20) from outside the water separator (20) in the region of the bend (24), in particular through the wall of the water separator tube Petition 870250089688, dated 02 / 10 / 2025, page 21 / 32 3 / 3 (20), and runs within the second tube section (23), in particular substantially concentric with it.

9. Ejector jet pump, according to any one of claims 7 or 8, characterized in that the propellant connection (31) opens into the feed chamber (33) of the gas feed device (30) with a propellant nozzle (32).

10. Ejector jet pump, according to any one of claims 7 to 9, characterized in that the droplet-free gas connection (27) of the water separator (20) is located around the propellant connection (31).

11. Ejector jet pump, according to any one of claims 7 to 10, characterized in that the propellant connection (31) extends at least partially through the water separator (20).

12. Ejector jet pump, according to any one of claims 7 to 11, characterized in that the droplet-free gas connection (27) and the propellant connection (31) are positioned concentrically with each other.

13. Ejector jet pump, according to any of the preceding claims, characterized in that the gas feed device (30) has a diffuser (35) downstream of the droplet-free gas connection (27). Petition 870250089688, dated 10 / 02 / 2025, p. 22 / 32

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