jet pump

Abstract

Jet pump (1), with a nozzle (7) upstream of a mixing tube (2), in which a nozzle needle (9) is displaceable, wherein an actuator (11) is provided for adjusting the nozzle needle (9), which comprises an armature (10) rigidly connected to the nozzle needle (9) and a coil (23) which interacts electromagnetically with the armature (10) and is hermetically separated from the armature (10). , characterized in that the actuator (11) has an inner actuator housing (14) and an outer actuator housing (15), wherein the inner actuator housing (14) is designed as an element hermetically separating the armature (10) and the nozzle needle (9) from the coil (23), and the outer actuator housing (15) surrounds the coil (23), and the jet pump has an actuator carrier (5) to which, on the one hand, the inner and the outer actuator housings (14, 15) and, on the other hand, the mixing tube (2) are attached, that the nozzle (7) is pressed onto a needle bearing element (12) which supports the nozzle needle (9) and that, in addition, a press connection is formed between the inner actuator housing (14) and the needle bearing element (12).

Description

[0001] The invention relates to a jet pump suitable for hydrogen recirculation in a fuel cell system, which has an adjustable nozzle needle.

[0002] An adjustable jet pump for a fuel cell system is known, for example, from DE 10 2021 129 809 B3. In the case of the known jet pump, a pneumatic actuator is provided for adjusting a nozzle needle.

[0003] Geometric details of a Venturi mixer intended for use in a fuel cell system are described, for example, in DE 10 2021 119 706 A1. The Venturi mixer according to DE 10 2021 119 706 A1 comprises a mixing nozzle with a tubular body tapering in the flow direction and having a multi-blade outlet opening structure.

[0004] A possible method for operating a fuel cell system is described in DE 10 2021 115 092 B3. This method also involves hydrogen recirculation.

[0005] A jet pump of this type is disclosed in DE 10 2021 130 875 A1. Further jet pumps are disclosed in DE 10 2017 212 726 B3, DE 10 2017 208 267 A1, US 2012 / 0 189 927 A1, and DE 10 2021 103 338 A1.

[0006] The invention is based on the object of providing a jet pump which is further developed compared to the cited prior art, particularly with regard to manufacturing technology, and which can be used, inter alia, in a fuel cell system for the recirculation of hydrogen.

[0007] This object is achieved according to the invention by a jet pump having the features of claim 1. The jet pump comprises, in a basic concept known per se, a mixing tube to which a pressurized gaseous medium can be fed by means of a nozzle, which medium is mixed in the mixing tube with another material flow to be conveyed.

[0008] According to claim 1, a nozzle needle is displaceable in the nozzle, wherein an actuator is provided for adjusting the nozzle needle, which actuator comprises an armature rigidly connected to the nozzle needle and a coil arrangement which interacts electromagnetically with the armature and is hermetically separated from the armature.

[0009] Thanks to the hermetic separation of the chamber containing the medium to be pumped, in particular hydrogen, from the exterior, the jet pump according to the application is characterized by particularly high operational reliability. At the same time, the jet pump has a compact design. The hermetic separation between different chambers means that the respective chambers are not separated from each other by dynamic seals. Rather, static seals are sufficient to separate the different chambers. In this respect, there is a fundamental similarity with canned motor pumps. In this context, reference is made to DE 10 2014 213 180 B4 as an example. However, unlike canned motor pumps, the jet pump according to the application does not operate with rotating parts, but rather with linearly adjustable parts.

[0010] The nozzle, nozzle needle, and actuator are combined into a highly integrated unit, i.e., an actuator-needle-nozzle unit. A supply for the pressurized medium, which entrains the further material flow to be conveyed, can be integrated into the nozzle. The material flow, which is to be conveyed by the jet pump, is introduced, for example, into an annular space surrounding the tip of the nozzle and located on the inflow side of the mixing tube.

[0011] The actuator comprises an inner actuator housing and an outer actuator housing. The inner actuator housing is designed as an element that hermetically separates the armature and the nozzle needle from the coil assembly, and the outer actuator housing surrounds the coil assembly. The nested actuator housings are arranged concentrically to each other and to the nozzle needle, and thus to the central axis of the entire jet pump. The magnetic circuit of the actuator is closed by the outer actuator housing and the armature, which is located in a space containing hydrogen.

[0012] The inner actuator housing is designed as a casing that provides sufficient stability and tightness against the pressurized medium, such as hydrogen. Conventional static seals, such as O-ring seals, are suitable for sealing the inner housing against the nozzle or a part of the jet pump that accommodates the nozzle. O-ring seals can also be used as static seals at other locations on the jet pump. Alternatively, profile seals, for example, can be considered.

[0013] The jet pump comprises an actuator carrier, to which the inner and outer actuator housings, on the one hand, and the mixing tube, on the other, are attached. In this case, the two nested actuator housings can, in particular, be parts of the aforementioned actuator-needle-nozzle unit. The inner actuator housing can protrude beyond the outer actuator housing at the end, on the side of the jet pump facing away from the mixing tube. Alternatively, the two actuator housings can be flush with each other at the end. In all cases, a channel for supplying the pressurized medium used for conveying, i.e., pumping, can be formed in the actuator carrier. This channel, located in the actuator housing and typically aligned orthogonally to the center axis of the jet pump, is generally referred to as the media supply and ends at an opening in the wall of the nozzle, which has already been mentioned as an integrated supply for the pressurized medium.

[0014] Durable, mechanically resilient connections between different components of the jet pump can, for example, be designed as press connections.

[0015] This applies, among other things, to the connections between the mixing tube and the actuator carrier, between the inner actuator housing and a needle bearing element intended to support the nozzle needle, and between the needle bearing element and the nozzle. According to the invention, the nozzle is pressed onto the needle bearing element.

[0016] The armature of the jet pump optionally contains at least one drainage hole open towards the nozzle. Additional drainage holes can be located, among other places, in the needle bearing element. Likewise, at least one drainage hole, which can also serve for venting, can be located in a stop element arranged within the inner actuator housing on its closed side and representing a stop relative to the armature, which is movable within the inner actuator housing and rigidly connected to the nozzle needle. Instead of drainage holes, which can also serve for venting if required, grooves running in the longitudinal direction of the component in question, such as the armature, can also be provided on the outer peripheral surface of the component. Alternatively or additionally, such grooves can be provided on an inner peripheral surface of an adjacent component that accommodates the component.In summary, in all these cases we speak of drainage openings.

[0017] The armature can be crowned, thus providing additional, optimized support and contact point for the armature within the actuator housing. In either case, the armature is firmly connected to the movable nozzle needle.

[0018] According to an advantageous further development, a return spring acts on the actuator's armature. The return spring is part of a fail-safe mechanism that minimizes or completely stops the flow through the nozzle. Depending on the design, the return spring can thus set the jet pump to a low load or shut it off completely. The fail-safe position assumed by the return spring ensures, in particular, that the amount of condensed substance, such as water, discharged from the actuator-needle-nozzle unit is reduced.

[0019] At points on the jet pump where frictional loads occur, particularly on the surfaces of the armature and / or the nozzle needle, coatings can be applied to reduce friction and / or wear. In particular, such coatings can be in the form of diamond-like coatings containing carbon. Such coatings are generally known, for example, from DE 10 2018 104 541 A1. The applicant offers carbon-containing coatings under the names "Triondur C" and "Triondur C+," among others.

[0020] Alternatively, friction- and / or wear-reducing plastic coatings, such as PTFE, can be provided. Furthermore, the desired tribological properties can also be achieved by choosing an uncoated base material, such as a non-ferrous metal alloy.

[0021] The actuator, which moves the armature and nozzle needle, can be designed either as a switching actuator with two positions or as a proportional actuator with continuously variable adjustment. Regarding a possible design of a magnetic actuator, reference is made to DE 10 2017 106 476 A1.

[0022] In a wide variety of possible designs, in addition to the hermetic sealing of the area of ​​the jet pump intended for media guidance, its modular and at the same time compact design is of particular advantage.

[0023] An embodiment of the invention is explained in more detail below with reference to a drawing. In the drawings: Fig. 1 a jet pump in a sectional view, Fig. 2 an actuator-needle-nozzle unit of the jet pump in a first setting, Fig. 3 the actuator-needle-nozzle unit of the jet pump in a second setting.

[0024] Unless otherwise stated, the following explanations refer to both embodiments. Corresponding or essentially equivalent parts are identified by the same reference numerals in all figures.

[0025] A jet pump, designated overall by reference numeral 1, is intended for use in a fuel cell system (not shown in detail). With the aid of the jet pump 1, hydrogen is recirculated within the fuel cell system, thereby achieving a superstoichiometric supply of hydrogen. Regarding the basic function of the jet pump 1, reference is made to the prior art cited above.

[0026] The jet pump 1 comprises, as can be seen from Fig. 1, a mixing tube 2 and an actuator-needle-nozzle unit 3. The mixing tube 2 acts as a diffuser that widens in the direction of flow and ends in the form of a cylindrical connecting section 4, to which a line is to be connected that opens into a fuel cell stack (not shown). On the side opposite the connecting section 4, the mixing tube 2 is inserted into a recess of an actuator carrier 5, which is assigned to the actuator-needle-nozzle unit 3. Within the aforementioned recess, an intake region 6 is formed, into which recirculating, hydrogen-containing medium is sucked during operation of the jet pump 1.

[0027] A nozzle 7, which is also part of the actuator-needle-nozzle unit 3, dips into the intake area 6. A hydrogen supply 8 is formed in the actuator carrier 5, orthogonal to the longitudinal direction of the mixing tube 2, and is connected laterally to the nozzle 7 as a channel. Pressurized fresh hydrogen is supplied to the jet pump 1 through the hydrogen supply 8. The fresh hydrogen flowing out of the nozzle 7 entrains recirculating hydrogen from the intake area 6. In order to vary the performance of the jet pump 1, a longitudinally displaceable nozzle needle 9 is arranged concentrically in the nozzle 7. The nozzle needle 9 protrudes rearward, i.e., against the flow direction, from the nozzle 7 and is firmly connected there to an armature 10 of an electromagnetic actuator 11. The entire actuator 11 represents a further component of the actuator-needle-nozzle unit 3.

[0028] For linear guidance of the nozzle needle 9, a needle bearing element 12 is provided, which is located in the actuator carrier 5. The nozzle needle 9 is thus supported by a sliding bearing within the jet pump 1.

[0029] The armature 10, located at the rear end of the nozzle needle 9, is slidably guided in a multi-part housing 13 of the actuator 11. The housing 13 comprises an inner actuator housing 14 directly surrounding the armature 10, as well as an outer actuator housing 15. The entire actuator 11 is partially immersed in a recess 16 formed on the side of the actuator carrier 5 facing away from the intake area 6. The inner actuator housing 14 has a base 17 which closes off the inner actuator housing 14 on its end face facing away from the mixing tube 2. On its opposite end face, which rests on the actuator carrier 5 within the recess 16, a flange 19 is formed onto a cylindrical main section of the actuator housing 14, designated 18.A seal 20 in the form of an O-ring seal is inserted between the flange 19 and the actuator carrier 5, so that the interior of the actuator 11 enclosed by the inner actuator housing 14 is statically sealed against the actuator carrier 5.

[0030] Additional seals 21, 22, which are also designed as O-ring seals, are installed in the jet pump 1 between the nozzle 7 and the actuator carrier 5 and between the mixing tube 2 and the actuator carrier 5. The inner actuator housing 14 is surrounded by an energizable coil 23, with a coil carrier designated by 24. An electrical line is designated by 25. A cylindrical section 26 of the outer actuator housing 15 is shorter than the main section 18 of the inner actuator housing 14 and accommodates the coil carrier 24 including the coil 23. In contrast to the inner actuator housing 14, the outer actuator housing 15 does not have a closed bottom. Rather, an inwardly directed rim 27 adjoins the cylindrical section 26, which annularly encloses the main section 18 and forms an axial stop relative to the coil carrier 24. The outer actuator housing 15 thus has a suggested pot shape.A flange 28 adjoins the end face of the cylindrical section 26 opposite the rim 27, i.e., facing the actuator carrier 5. The flange 28 of the outer actuator housing 15 is screwed to the flange 19 of the inner actuator housing 14 with screws 29. Alternatively, a riveted connection could be provided at this point, for example.

[0031] The entire actuator-needle-nozzle unit 3 forms a structural unit, which is held together by various press connections. A first press connection is formed between the nozzle 7 and the actuator carrier 5. A second press connection exists between the nozzle 7 and the needle bearing element 12. The main section 18 of the inner actuator housing 14 is pressed onto the needle bearing element 12. On the opposite side, in the arrangement according to Fig. 1 On the right side of the actuator carrier 5, the mixing tube 2 can also be pressed into the actuator carrier 5. Instead of the aforementioned press connections, screw connections or other connections can also be provided.

[0032] A stop element 30 is located on the inside of the base 17, which limits the displacement of the armature 10 to one side. The stop element 30 has a pot shape with a base plate 31 and a sleeve section 32 extending therefrom, which contacts the inner wall of the main section 18. A return spring 33 designed as a helical spring is tensioned between the base plate 31 and the armature 10. The return spring 33 acts in the direction of the Fig. 3, in which the outlet opening of the nozzle 7, designated 34, is at least approximately closed. In order to move the nozzle needle 9 from this position into the position shown in Fig. To adjust the full-load position shown in Figure 2, coil 23 must be energized, which results in compression of the return spring 33. Adjustment in the area of ​​the lateral opening of the nozzle 7, designated 35, is not provided. The opening 35 is located at the end of the hydrogen supply 8, and neither an expansion nor a constriction of the flow cross-section is provided at this point.

[0033] During operation of the jet pump 1, the accumulation of water within the inner actuator housing 14 cannot be ruled out from the outset. In order to drain any water from the interior of the inner actuator housing 14, venting and drainage holes 36, 37, 38 pass through the needle bearing element 12, the armature 10, and the sleeve section 32 of the stop element 30. As can be seen from the Fig.As can be seen from Figures 1 to 3, the various venting and drainage holes 36, 37, 38 are aligned parallel to the nozzle needle 9. Water or gaseous medium discharged through the venting and drainage holes 36, 37, 38 is added to the recirculating material flow. List of reference symbols 1 jet pump 2 mixing tube 3 Actuator-needle-nozzle unit 4 Connection section 5 actuator carriers 6 Intake area 7 nozzle 8 Hydrogen supply 9 jet needle 10 anchors 11 Actuator 12 Needle bearing element 13 housings 14 Inner actuator housing 15 Outer actuator housing 16 Recess 17 Floor 18 Main section of the inner actuator housing 19 Flange of the inner actuator housing 20 Seal 21 Seal 22 Seal 23 coil 24 coil carriers 25 Electrical cable 26 Cylindrical section 27 Board 28 flange 29 Screw 30 stop element 31 floor disc 32 sleeve section 33 Return spring 34 Exit opening 35 Opening 36 Venting and drainage hole in the needle bearing element 37 Ventilation and drainage hole in the anchor 38 Ventilation and drainage hole in the stop element

Claims

[1] Jet pump (1), with a nozzle (7) upstream of a mixing tube (2), in which a nozzle needle (9) is displaceable, wherein an actuator (11) is provided for adjusting the nozzle needle (9), which actuator comprises an armature (10) rigidly connected to the nozzle needle (9) and a coil (23) which interacts electromagnetically with the armature (10) and is hermetically separated from the armature (10) , characterized by that the actuator (11) has an inner actuator housing (14) and an outer actuator housing (15), wherein the inner actuator housing (14) is designed as an element hermetically separating the armature (10) and the nozzle needle (9) from the coil (23) and the outer actuator housing (15) surrounds the coil (23) and the jet pump has an actuator carrier (5), to which on the one hand the inner and the outer actuator housing (14, 15) and on the other hand the mixing tube (2) are fastened, that the nozzle (7) is pressed onto a needle bearing element (12) supporting the nozzle needle (9) and that in addition a press connection is formed between the inner actuator housing (14) and the needle bearing element (12). [2] Jet pump (1) according to claim 1, characterized by a media supply (8) located in the actuator carrier (5) and opening into the nozzle (7). [3] Jet pump (1) according to one of claims 1 to 2, characterized by a drainage opening (37) in the armature (10) open towards the nozzle (7). [4] Jet pump (1) according to one of claims 1 to 3, characterized by a return spring (33) acting on the armature (10). [5] Jet pump (1) according to one of claims 1 to 4, characterized by that at least one of the nozzle needle (9) and armature (10) is provided with a carbon-containing coating. [6] Use of a jet pump (1) according to claim 1 for hydrogen recirculation in a fuel cell system.

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