EP0654125B1 - Multistage ejector pump - Google Patents

Abstract

PCT No. PCT/EP93/02085 Sec. 371 Date Feb. 1, 1995 Sec. 102(e) Date Feb. 1, 1995 PCT Filed Aug. 5, 1993 PCT Pub. No. WO94/03733 PCT Pub. Date Feb. 17, 1994A multi-stage ejector pump for suction or for moving materials with the help of a working fluid within one housing is provided. The pump is designed for radial flow and includes at least one inlet for the working fluid, at least one inlet for the materials and at least one flow channel for the mixture of working fluid and materials. The pump includes at least one suction chamber per pump stage, each suction chamber being connected to a common antechamber with the intake of the materials at one end and the flow channel on the other. The flow channel is circular in shape and constructed for radially outward directed flow. The wall elements of the flow channel are comprised of ejector rings located concentrically to each other, adjacent ejector rings forming a passage for the materials between each suction chamber and the flow channel.

Description

The invention relates to a multi-stage ejector according to the preamble of claim 1.

Ejector pumps of this type have long been known (FR-A1-25 77 284) and are used both for the production of vacuum and for the conveyance of flowable substances. In order to achieve a high degree of efficiency, in particular with high suction resistances, a successive, multi-stage embodiment is known. This has the advantage that the flow energy of the propellant, which can either be gaseous or liquid, is used until the flow speed has dropped below a value that can no longer be used with design effort.

Multi-stage ejector pumps generally have the problem that the size increases disproportionately with the number of stages. This fact is based, among other things, on the fact that the cross section of the flow channel has to increase from stage to stage, and thus in particular the overall height of such an ejector device with several stages is large, without the entire volume of a z. B. rectangular housing could be used.

The object of the invention is to improve ejector pumps of the type mentioned in such a way that the size, in particular the height, can be kept small despite the necessary expansion of the flow channel.

The object is achieved by an ejector with the features of claim 1.

In spite of its great compactness and effectiveness, an ejector according to the invention is comparatively easy to manufacture, in particular from simple (mass) rotating or joining parts. The production can be made of almost any material, such as. B. metal, plastic, glass, ceramics, etc. done.

The principle of a ring-shaped flow channel for an ejector is basically already known from DE-A1-34 20 652 - but only for a single-stage ejector. With this single-stage ejector, it was essential to have a particularly high level of precision when realizing very specific angular relationships and lengths in the area of the nozzle, the mixing zone and the diffuser. This was achieved in that all essential parts such as the nozzle, the mixing zone and the diffuser were formed in only one or both end faces of one-piece blocks, which could be carried out in a single operation on a numerically controlled lathe and contributed to high accuracy and good repetition properties the manufacture of a large number of pumps. A major disadvantage of this known ejector is, on the one hand, in its single stage and, on the other hand, that the suction chamber, via which the material to be conveyed or the substance mixture is fed to the annular, radially outward-acting flow channel, is an annular cross-section widening towards the flow channel Groove is designed, wherein the annular groove is acted upon by the substance or mixture of substances to be conveyed via a number of circumferentially distributed connecting bores which open into a common antechamber. With this design and the corresponding manufacturing process of this known ejector, there are unfavorable flow conditions for the substance to be conveyed or the substance mixture flowing into the annular flow channel. Another disadvantage of this known ejector is its fixation on a very specific surface contour of the flow channel, which only enables optimal pumping performance if the viscosity of the propellant and / or the substance or mixture to be conveyed is within a narrow range of values. To solve different conveying tasks, in particular to convey substances or mixtures of substances, the viscosity of which deviate from the ideal conditions for which this ejector is designed, or for the use of other propellants, different pumps are required. At least the pump block must be replaced, in the end face of which the nozzle, the mixing zone and the diffuser are incorporated.

Compared to this circular ejector known from DE-A1-34 20 652, the ejector according to the invention has a number of significant advantages. One advantage is that the invention makes it possible in a simple manner to make the annular geometry of the flow channel accessible, with all the advantages associated therewith, for the realization of a multi-stage ejector. Another advantage is that the flow conditions at the entry of the substance or mixture to be conveyed into the flow channel are considerably evened out compared to the single-stage ejector known from DE-A1-34 20 652. A further advantage consists in the fact that the ejector according to the invention can be manufactured in spite of its multiple stages, since it can be manufactured from simple turned or joined parts that can be mass-produced, the individual Ejector rings can be reworked or replaced if necessary to optimize the ejector for the respective application.

The basic idea on which the present invention is based, namely in the case of a multi-stage ejector the flow channel in the form of a ring and for a flow from radially inside to radially outwards, can also be practically used in an alternative to the teaching of claim 1, namely in that the the mixing zone and the diffuser of one or more pump stages wall areas of the flow channel with respect to the other wall areas of the flow channel are axially adjustable (claim 22). As a result, the flow conditions in the flow channel can be adapted to the particular conveying task - even in the case of multi-stage ejector pumps in which a passage gap for the substance to be conveyed which forms a constriction between the suction chamber and the flow channel - as in DE-A1-34 20 652 - is missing.

For the purposes of the invention, the "blowing medium" can be both liquid and gaseous, as can the flowable substance or the flowable substance mixture.

For the purposes of the invention, “ejector rings” are preferably individual components which are independent of one another and are introduced into the pump housing, which — as will be shown below — can be done in a wide variety of ways. If the cross-sectional constriction at the passage gap for the flowable substance or the mixture of substances between the respective suction chamber and the flow channel is not too great, it is also possible to manufacture the ejector rings in one piece with the wall areas forming the suction chamber.

The layout of the ejector rings (view in the axial direction) is preferably - but not necessarily - circular. The cross section of the ejector rings (seen in axial section) can vary widely and can be adapted to the application conditions, in particular cylindrical and, particularly preferably, conical (see exemplary embodiments according to FIGS. 1 to 4). The side surface of the ejector rings forming part of the wall of the flow channel can, given a radial view, receive a wide variety of contours (see exemplary embodiments according to FIGS. 5 to 9). In particular, the inclination angles of the mixing zone and the diffuser zone, which are related to the axial direction of the flow channel, can be different. The ejector rings can also have a corrugated surface that enlarges the effective suction gap, as a result of which the flow conditions in the flow channel are influenced by local cross-sectional changes (see exemplary embodiment according to FIGS. 5 and 9). It is also advantageous to arrange flow guide profiles laterally - seen in the axial direction above the ejector rings (see exemplary embodiment according to FIG. 9), by means of which, on the one hand, eddies which arise when the substance to be conveyed is mixed with the propellant can be kept relatively low. On the other hand, the flow guide profiles make it possible to reduce the residual energy of the propellant, which increases the pump efficiency. Flow control profiles of this type have not been previously published.

The ejector rings can in principle be attached to the ends of the partition walls separating the suction chambers, but they are particularly advantageously connected to the said partition walls before assembly, preferably in one piece, so that the structural unit consisting of ejector ring and partition wall is installed in the pump will (claim 3).

While in many applications the position of the individual ejector rings (seen in the axial direction) relative to one another and together with respect to the other pump parts can remain unchangeable, a particular advantage of the invention is that the axial position of the ejector rings and thus the cross-sectional shape of the flow channel can be changed (claims 4 or 6). This change in position can be done in a variety of ways, e.g. B. by means of sliding guides or screw threads, the diameter of which may correspond to the respective diameter of the ejector ring concerned. Particularly simple to manufacture, assemble and also to adjust later from the outside, however, are such adjustment devices, which consist of telescoping tubes that connect to one another at the ends (flow channel side) of radial and axial or conical wall parts that act as partitions for the neighboring ones Serve suction chambers and their annular end faces themselves serve as part of the wall and the flow channel or carry the respective ejector ring.

The size, shape, material selection and technical conception of the above-mentioned components as well as those claimed and described in the exemplary embodiments and subject to use according to the invention are not subject to any special exceptional conditions, so that the selection criteria known in the respective field of application can be used without restriction.

Fig. 1

eine erfindungsgemäße mehrstufige Ejektorpumpe in Axialschnittdarstellung;

Fig. 2

eine zweite Ausführungsform einer erfindungsgemäßen Ejektorpumpe in der gleichen Schnittdarstellung wie in Fig. 1 - ausschnittsweise;

Fig. 3

- eine dritte Ausführungsform einer erfindungsgemäßen Ejektorpumpe, wiederum im Axialschnitt (Schnitt entlang der Linie III-III gemäß Fig. 4);

Fig. 4

von derselben Ejektorpumpe wie in Fig. 3 eine Ansicht der Pumpe von oben (Schnitt entlang der Linie IV-IV gemäß Fig. 3);

Fig. 5

eine alternative Ausführungsform der Ejektorringe mit gewellter Oberfläche (perspektivische Darstellung eines kreissegmentförmigen Ausschnitts einer Ejektorringanordnung einer erfindungsgemäßen Ejektorpumpe);

Fig. 6

eine alternative Strömungskanalform zum Ausführungsbeispiel nach Fig. 1 in einer Axialschnittdarstellung - ausschnittsweise;

Fig. 7

eine weitere Strömungskanalform an demselben Ausführungsbeispiel in einer ausschnittsweisen Axialschnittdarstellung der halben Ejektorpumpe;

Fig. 8

eine beispielhafte Darstellung möglicher Ejektorringausführungen am Beispiel eines Ejektorringsets in einer Axialschnittdarstellung sowie

Fig. 9

eine perspektivische Darstellung eines Ejektorpumpensegmentes, welches zusätzlich mit Strömungsleitprofilen ausgestattet ist.

Further details, features and advantages of the subject matter of the invention result from the following description of the accompanying drawing, in which a multi-stage ejector according to the invention is shown. The drawing shows:

Fig. 1

a multi-stage ejector according to the invention in axial section;

Fig. 2

a second embodiment of an ejector according to the invention in the same sectional view as in Fig. 1 - in sections;

Fig. 3

- A third embodiment of an ejector according to the invention, again in axial section (section along the line III-III of FIG. 4);

Fig. 4

from the same ejector as in Figure 3 a view of the pump from above (section along the line IV-IV of FIG. 3);

Fig. 5

an alternative embodiment of the ejector rings with a corrugated surface (perspective view of a segment of a segment of an ejector ring arrangement of an ejector pump according to the invention);

Fig. 6

an alternative flow channel shape to the embodiment of Figure 1 in an axial sectional view - detail;

Fig. 7

a further flow channel shape on the same embodiment in a partial axial sectional view of the half ejector;

Fig. 8

an exemplary representation of possible ejector ring designs using the example of an ejector ring set in an axial sectional view and

Fig. 9

a perspective view of an ejector segment, which is additionally equipped with flow guide profiles.

In the embodiment shown in FIG. 1, the four-stage ejector, identified overall by 100, has a circular cylindrical housing 26 which consists of a base part 26A with a central inlet 23 for the medium to be conveyed, a cover part 26C with a common outlet 14 for the propellant medium and the medium to be conveyed and an ejector support part 268 arranged between the cover part and the base part.

A dividing wall 6 is inserted into the connection point between the cover part 26C and the ejector support part 26B, the cover-side surface of which, together with the cover part 26C, delimits an outflow chamber 11. A pipe socket 27 provided centrally on the partition 6 and projecting from it in the direction of the cover 26C and penetrating the cover 26 forms an inlet 13 for the propellant medium, in which an orifice 19 for pre-distributing the propellant medium over the entire inlet cross section can be installed and the a solids filter 20 can be connected upstream in order to avoid erosion phenomena in the region of the inlet nozzle 22A to be explained. In addition, the partition 6 is provided in its radial outer region with circumferentially distributed bores 14A, which - also directly - can serve as an outlet and which can be followed by silencers 12 in the direction of flow.

On the side of the partition 6 facing away from the cover part 26C, its annular surface forms a wall part 22E of a flow channel 22. A wall part is opposite the wall part 22E and axially spaced from it 22F is provided, which is formed from ejector rings 2 to 5, which are arranged concentrically to one another and at a radial spacing from one another, and a central ejector disk 1. The flow channel 22 is closed radially outwards by the inner surface of a circular cylindrical wall region of the ejector support part 26B. In this way, the flow channel 22 is given an annular shape. Characterized in that the propellant medium is supplied via the central inlet 13 and the propellant medium and the conveying medium are jointly discharged from the flow channel 22 through the radially outer bores 14A, the flow channel is designed for a flow directed radially from the inside to the outside, as is the case for a single-stage ejector from DE-A1-34 20 652 is basically already known.

The ejector support part 26B consists of the already mentioned cylindrical and a circular disk-shaped wall part, which serves as a partition wall 26D.

On the side facing the bottom part 26A, the dividing wall 26D, together with the bottom part 26A, delimits a prechamber 7 in which the medium to be conveyed flowing in via the inlet 23 is pre-distributed.

On the side of the partition wall 26D facing away from the prechamber 7, the latter carries the ejector rings 2 to 5 and the ejector disk 1. For this purpose, the ejector rings are provided with partition walls 25A, 25B, 25C and 25D (in the exemplary embodiment, the ejector rings are integrally connected to the partition walls) ), wherein the partitions in the illustrated embodiment form approximately circular cylindrical tube sections of different lengths, the length of which decreases radially outwards uniformly, so that the flow cross section of the flow channel 22 becomes increasingly larger radially outward, also in the axial direction. In this embodiment of the flow channel 22, the mixture of propellant and medium to be conveyed flowing through it has an axial flow component in addition to the radial one. This also applies to an embodiment in which wall part 22E runs parallel to wall part 22F according to the dash-and-dot line in FIG. 1. However, it is also possible to completely eliminate the axial flow component by arranging the wall part 22F along the dash-dotted line in FIG. 1 and arranging the wall part 22E parallel to it. In this case, there is a pure radial flow in the flow channel 22. By designing the wall part 22E according to the dashed line in FIG. 1, whereby the flow channel 22 widens upward in the direction radially outward, the centrifugal force for the propellant can also be used, which can possibly increase the efficiency of the ejector.

Further design options of the flow channel 22 are shown in FIGS. 6 and 7. In the flow channel 22 shown in the left half of FIG. 6, the wall part 22F is inclined downwards radially outward, so that the flow comprises an axial component. The convex wall part 22E aims to use centrifugal force for the propellant. In contrast to this, the flow channel shown on the right-hand side of FIG. 6 has a conical surface which is inclined radially downwards, so that the use of centrifugal force is avoided. It is therefore easily possible to adapt the geometry of the flow channel 22 to different driving media and / or fluids to be conveyed by using different wall parts 22E.

While in the previously described embodiments the wall part 22F was partly inclined, but was made flat, a curved course, as shown in FIG. 7, can also be advantageous. In this case, the ejector disc 1 and the ejector rings 1-4 have a convex, curved surface. The surface of the ejector rings can also be corrugated in a manner similar to that shown in FIG. 5, so that ejector rings 1 to 4 form flow troughs 41 pointing radially outwards, which exert an aligning effect on the flow prevailing in the flow channel 22. It can also be advantageous, as shown in FIG. 8, to make the underside 42 of the ejector rings 2 to 4 or the ejector disk 1 facing the suction chamber 15 to 18 concave and / or to round off the edges 43 of the ejector rings 2 to 4 facing the passage gaps 22D, whereby the outflow direction of the fluid to be conveyed flowing through these passage gaps can be influenced and the vortex formation in the mixing zone 228 can be reduced.

The partition walls 25A to 25D and a base element 25E carrying the ejector disk 1 and also serving as a partition wall enclose an annular suction chamber 15 to 18 between them. The partition wall 26D has openings 28 to 31 as access openings of the medium to be conveyed from the pre-chamber 7 into the suction chambers 15 to 18. The openings can be distributed around the circumference and at least partially provided with non-return flaps 8 to 12. These check valves are known with regard to their function and arrangement in ejector pumps (e.g. FR-A1-2 577 284). - They serve in multi-stage ejector pumps to obtain an improved vacuum by the suction chambers, which can only generate a relatively low vacuum, when this their vacuum from the other stages, the one can generate higher negative pressure, mechanically separated. This begins with the last one and usually ends with the second suction stage.

The radially outer edges of the ejector disk 1 or the ejector rings 2 to 4 form with the radial inner edge of the ejector ring 2 to 5, which is located radially on the outside in each case, a passage gap 22D forming a constriction for the fluid to be conveyed from the respective suction chamber into the flow channel 22. The passage gaps 22D are each ring-shaped in the illustrated and in this respect preferred exemplary embodiments. They can - at least in the exemplary embodiments according to FIGS. 1 and 2 - in principle also consist of circumferentially distributed openings. In the exemplary embodiment shown in FIG. 5, in which the ejector rings 2 to 4 and the ejector disk 1 comprise flow troughs 41, the passage gaps 22D have a periodically widening and narrowing structure.

The annular nozzle 22A, which is formed by the ejector disk 1 and the central region of the partition 6 opposite the ejector disk 1, serves as the inlet nozzle of the propellant medium in the flow channel 22. In the case of the individual ejector rings 2 to 5, the radially outer area serves as diffuser 22C and the radially inner area of the ejector ring serves as mixing zone 228.

In the exemplary embodiment shown in FIG. 2, the two axially opposite wall parts 22E and 22F of the flow channel 22 are constructed in an approximately mirror-symmetrical manner and are provided with suction chambers. In this case, the propellant and the medium to be conveyed are discharged radially outward from the flow channel 22.

3 and 4, the ejector rings and the ejector disk are axially adjustable. For this purpose, the partition walls 25A and 25B bearing the ejector rings have at their end opposite the ejector ring an annular wall region 25D and 25E which is supported radially on the inside by a tube 32 and 33, respectively. The ejector disk 1 is also carried by a tube (tube 34) and the housing 26 has a central tube socket 35. The tube 34 has a screw thread on its outer circumference, which corresponds to an internal thread provided on the tube 32. The pipe 32 also has an external thread, which in turn corresponds to an internal thread of the pipe 33 and the pipe 33 carries an external thread which corresponds to an internal thread of the pipe socket 35. In this way, all pipes 32, 33, 34, 36 and the pipe socket 35 and with them the ejector disk or ejector rings carried by them are telescopically rotatable in the axial direction of the pump.

In Fig. 3, a relative position of the ejector rings and the ejector disk is shown in the left half of the image, as it corresponds to the embodiments of Figs. 1 and 2, while in the right half of Fig. 3, the ejector rings are adjusted so that the cross section of the Flow channel 22 which widens radially outward.

Depending on the propellant (gas, liquid, steam jet), the cross section of the flow channel and thus the throughput of fluid to be pumped and the energy consumption can be set.

In all embodiments, the central ejector disk is acted upon by the drive medium via the central inlet 13, which then flows radially outward and Here, different pressures - depending on the geometry of the individual ejector rings and the rings relative to one another - are generated between the individual ejector disks, with different suction effects occurring at the passage gaps 22D.

Otherwise, ejector ring segments can also be used instead of complete ejector rings within the scope of the invention.

FIG. 9 shows a further embodiment of an ejector, in which — as seen in the direction of flow — flow guide profiles 37, 38, 39 are arranged in the flow channel 22 at the same height as the passage gaps 22D. The flow guide profiles 37 to 39 have a symmetrical, wing-like cross section and are oriented in such a way that the round head sides point in the direction of the ejector center, ie face the inflowing fluid, the pointed tail sides point in the flow direction. The flow guide profiles 37 to 39 are held on vertical partition walls 40 which subdivide the radial ejector pump into circular segments. Through the use of such flow guide profiles 37 to 39 or partition walls 40, which can also be used individually, the mixture of propellant and fluid to be conveyed in the flow channel 22 is partially deflected in its direction, which on the one hand causes the vortex formation - in particular in the mixing zones 228 -, on the other hand, the residual energy of the propellant can be reduced by an improved flow.

Reference symbol list:

1

Ejector disk

2nd

Ejector ring

3rd

Ejector ring

4th

Ejector ring

5

Ejector ring

6

partition wall

7

Antechamber

8th

Check valve

9

Check valve

10th

Check valve

11

Flow chamber

12th

Silencer

13

Inlet

14

Outlet

14

A holes

15

Suction chamber

16

Suction chamber

17th

Suction chamber

18th

Suction chamber

19th

cover

20th

Solid filter

22

Flow channel

22A

jet

22B

Mixing zone

22C

Diffuser

22D

Passage gap

22E

Wall part

22F

Wall part

23

Inlet

25A

partition wall

25B

partition wall

25C

partition wall

25D

partition wall

25E

partition wall

26

casing

26A

Bottom part

26B

Ejector part

26C

Cover part

26D

partition wall

27

Pipe socket

28

Breakthroughs

29

Breakthroughs

30th

Breakthroughs

31

Breakthroughs

32

pipe

33

pipe

34

pipe

35

Pipe socket

36

pipe

37

Flow guide profile

38

Flow guide profile

39

Flow guide profile

40

partition wall

41

Flow trough

42

bottom

Claims (24)

1. A multi-stage ejector pump (100) for drawing and/or conveying fluid substances or substance mixtures with the aid of a fluid propellant with a housing (26)

   - with at least one inlet (27) for the propellant,

   - with at least one inlet (23) for the fluid substance or substance mixture

   - with at least one flow duct (22) for the mixing and common flow of propellant and fluid substance or substance mixture with at least one nozzle (22A), a plurality of mixing zones (22B) and a plurality of diffusers (22C),

   - with at least one suction chamber (15, 16, 17 or 18) per pump stage, which are fluidly connected, optionally via a common antechamber (7) to the inlet (23) for the fluid substance on the one hand and the flow duct (22) on the other hand, at least one through gap (22D) forming a constriction being provided as a fluid connection to the flow duct (22) for the fluid substance or the substance mixture, and

   - with at least one common outlet (14) for the propellant and the fluid substance or substance mixture,

   characterised in that the flow duct (22) is annular and is constructed for a radially inside to outside flow, the flow duct wall being essentially formed by two approximately disc-shaped or annular disc-shaped wall sections (22E and 22F) which are disposed opposite one another at an axial distance apart, and at least one of the two wall sections (22E, 22F) is formed by ejector rings (2, 3, 4, 5), which are arranged approximately concentrically to one another, form or comprise through gaps (22D) for the fluid substance or substance mixture and spatially separate the flow duct (22) and the suction chambers (15 to 18) from one another.
2. A multi-stage ejector pump according to claim 1, characterised in that the suction chambers (15 to 18) are annular.
3. A multi-stage ejector pump according to claim 1 or 2, characterised in that the ejector rings (2 to 5) are provided with partitions (25A to 25E) for separating adjacent suction chambers (15 to 18) from one another, the partitions being angled relative to the ejector rings (2 to 5) and more particularly being cylindrical and/or conical.
4. A multi-stage ejector pump according to one of claims 1 to 3, characterised in that the ejector rings (2 to 5) are secured on or relative to the housing (26) so as to be adjustable in the axial direction.
5. A multi-stage ejector pump according to claim 4, characterised by tubes (32 to 35) extending within one another in the manner of a telescope for the axial adjustment of the ejector rings (2 to 5).
6. A multi-stage ejector pump according to one of claims 1 to 5, characterised in that the ejector rings (2 to 5) are integrally provided with partitions (25A to 25E) for separating adjacent suction chambers (15 to 18) from one another.
7. A multi-stage ejector pump according to one of claims 1 to 6, characterised in that the outline of the ejector rings is circular ring-shaped.
8. A multi-stage ejector pump according to one of claims 1 to 7, characterised in that the angles of inclination of the mixing zone (22B) and the diffusers (22C) in relation to the axial direction of the flow duct (22) differ.
9. A multi-stage ejector pump according to one of claims 1 to 8, characterised in that the surface of the ejector rings (2 to 5) comprises means for the local cross section adjustment of the flow duct (22), such as a corrugated surface.
10. A multi-stage ejector pump according to one of claims 1 to 9, characterised in that flow guide profiles (37 to 39) are arranged adjacent the ejectors rings (2 to 5), more particularly with airfoil wings of like cross section with rounded head ends pointing in the direction of the ejector pump centre.
11. A multi-stage ejector pump according to one of claims 1 to 10, characterised by a diaphragm (19) provided in the inlet (13) for the propellant for the preliminary distribution of the propellant over the entire inlet cross section.
12. A multi-stage ejector pump according to one of claims I to 11, characterised by outlet openings (14A) in sound dampers (12) arranged downstream in the direction of flow.
13. A multi-stage ejector pump according to one of claims 1 to 12, characterised by an ejector support element, formed by a cylindrical wall section (26B) and a circular disc-shaped wall section (26D).
14. A multi-stage ejector pump according to one of claims 1 to 13, characterised in that the flow cross section of the flow duct (22) towards the outside also gradually increases in the axial direction.
15. A multi-stage ejector pump according to one of claims 1 to 14, characterised in that the opposing wall sections (22E and 22F) of the flow duct (22) follow a curved, more particularly convex path.
16. A multi-stage ejector pump according to one of claims 1 to 15, characterised in that the geometry of the flow duct (22) can be adapted to different propellants and/or supply fluids by the use of different wall sections (22E).
17. A multi-stage ejector pump according to one of claims 1 to 16, characterised in that the undersides (42) of the ejector rings (2 to 4) or of the ejector disc (1) facing the suction chambers (15 to 18) are concave in construction.
18. A multi-stage ejector pump according to one of claims 1 to 17, characterised in that the edges (43) of the ejector rings (2 to 4) facing the through gap (22D) are rounded.
19. A multi-stage ejector pump according to one of claims 1 to 18, characterised in that the through gaps (22D) between the suction chambers (15 to 18) and the flow duct (22) are formed by circumferentially distributed openings or have a periodically widening and narrowing structure.
20. A multi-stage ejector pump according to one of claims 1 to 19, characterised in that the ejector rings (2 to 4) and the ejector disc (1) comprise flow hollows (41).
21. A multi-stage ejector pump according to one of claims 1 to 20, characterised by ejector ring segments instead of full ejector rings.
22. A multi-stage ejector pump (100) for drawing and/or conveying fluid substances or substance mixtures with the aid of a fluid propellant with a housing (26)

    - with at least one inlet (27) for the propellant,

    - with at least one inlet (23) for the fluid substance or substance mixture

    - with at least one flow duct (22) for the mixing and common flow of propellant and fluid substance or substance mixture with at least one nozzle (22A), a plurality of mixing zones (22B) and a plurality of diffusers (22C),

    - with at least one suction chamber (15, 16, 17 or 18) per pump stage, which are fluidly connected, optionally via a common antechamber (7) via [sic - to] the inlet (23) for the fluid substance on the one hand and the flow duct (22) on the other hand,

    - with at least one common outlet (14) for the propellant and the fluid substance or substance mixture,

    characterised in that the flow duct (22) is annular and is constructed for a radially inside to outside flow, the flow duct walls being essentially formed by two approximately disc-shaped or annular disc-shaped wall sections (22E and 22F) which are disposed opposite one another at an axial distance apart, and the wall regions of the flow duct (22) comprising the mixing zone (22B) and diffusers (22C) of one or more pump stages are axially adjustable relative to the other wall regions of the flow duct (22).
23. A multi-stage ejector pump according to claim 22, characterised in that the suction chambers are annular.
24. A multi-stage ejector pump according to claim 22 or 23, characterised by tubes extending within one another in the manner of a telescope for the axial adjustment of the different wall regions of the flow duct (22) relative to one another.

Images