Air bearing arrangement for fuel cell compressor with expander

Abstract

The invention relates to a turbomachine (1), in particular for a fuel cell system (100) of a vehicle (200), for example a commercial vehicle, comprising a rotor shaft (19), an expansion wheel (15) fastened to the rotor shaft (19), and an air bearing arrangement (21) which is designed to support the rotor shaft (19) in a rotatable manner about a rotor axis (X), a flow path (27) is formed between the expansion wheel (15) and the air bearing arrangement (21). It is proposed that a flow generator (29) is arranged in the flow path (27) between the air bearing arrangement (21) and the expansion wheel (15), which flow generator (29) is designed to generate an air flow directed towards the expansion wheel (15) in dependence on the rotation of the rotor shaft (19) in order to build up the blocking pressure.

Description

Technical Field

[0001] The present application relates to a fluid machine, in particular for a fuel cell system for a vehicle, such as a commercial vehicle, comprising a rotor shaft, an expansion wheel fastened to the rotor shaft, and an air bearing arrangement, the air bearing arrangement being configured to support the rotor shaft in a manner that allows rotation about a rotor axis, wherein a flow path is formed between the expansion wheel and the air bearing arrangement. Background Art

[0002] Fluid machines of the type mentioned above are well known. Air bearing arrangements are preferably used in these fluid machines because they allow contactless support of the rotor shaft. Contactless support itself means that there is no airtight closure between the chamber in which the expansion wheel is arranged and the cavity in which the rotor shaft and at least the rotating part of the air bearing arrangement are arranged, but rather the aforementioned flow path is formed.

[0003] When the fluid machine in the fuel cell system is running, the air previously compressed by the fluid machine enters the fuel cell and is supplied as a reactant for the fuel cell process. After flowing through the fuel cell, the reactant mixture with a lower oxygen content (the so-called cathode exhaust gas) is discharged from the fuel cell and re-enters the fluid machine in order to reduce the pressure in the expansion chamber by means of an expansion wheel. The air reaching the expansion wheel has a hydrostatic inlet pressure, which is lower than the pressure previously provided by the fluid machine. However, the inlet pressure in the expansion chamber is still higher than the ambient pressure. Therefore, there is an overpressure in the expansion chamber surrounding the expansion wheel. The cathode exhaust gas contains water in the form of droplets and water-saturated air. Although water in the form of droplets can be removed using conventional equipment (such as a water separator), the water combined in the air cannot be easily separated. By expanding with the help of an expansion wheel, water from the air is condensed out. Based on the overpressure in the expansion chamber and / or based on capillary action, this condensed water may enter the flow path and move toward the air bearing facility. As a result, undesirable friction occurs in the bearing, and then potentially higher rotational resistance occurs, which must be overcome by the motor of the fluid machine. In addition, wear will also increase significantly due to the entry of water. These phenomena are not desirable in practice. Summary of the invention

[0004] The object of the present invention is therefore to achieve improvements in a fluid machine of the type mentioned above in such a way that the aforementioned disadvantages are overcome as far as possible. In particular, the object of the present invention is to further improve a fluid machine of the type mentioned above in such a way that improved protection is achieved against the intrusion of water or other contaminants into the air bearing arrangement without impairing the efficiency of the fluid machine.

[0005] The present invention solves the above-mentioned object in that the present invention proposes a fluid machine according to claim 1. In particular, the present invention proposes that a flow generator is arranged in the flow path between the air bearing facility and the expansion wheel, which is set up to generate an air flow directed toward the expansion wheel depending on the rotation of the rotor shaft. The present invention is based on the recognition that the greater the pressure drop between the expansion wheel and the area of ​​the air bearing facility, the higher the risk of water intrusion in the direction of the air bearing facility. However, the faster the rotor shaft rotates, the higher the overpressure in the chamber around the expansion wheel. The power of the fluid machine also increases depending on the rotor speed. If it has one or more expansion stages, this will be the driving power or recovery power (with which the upstream compression stage can be supported). In a compressor facility, this will also be the compressor power itself. Therefore, the present invention proposes that the flow generator is also connected to the rotor shaft and specifically as follows: the higher the rotation speed of the rotor shaft, the more air flow the flow generator generates in the direction of the expansion wheel.

[0006] Within the scope of the present invention, a fluid machine can be understood not only as an integrated compressor expander system in which one or more compression stages run on a common shaft with an expansion wheel, but also as a system in which the expansion wheel is arranged mechanically separated from any compression stages in the system. Both variants are preferred embodiments of the present invention.

[0007] This results in that, at low rotational speeds, the air flow generated by the flow generator in the direction of the expansion wheel is also very small. In particular, when the fluid machine has one or more compression stages located upstream of the expansion stage, the system takes advantage of this aspect, that is, the pressure on the expansion wheel always lags behind the pressure on the compressor side of the fluid machine for a certain period of time, because the air compressed by the fluid machine should first flow through other system components, that is, in particular the fuel cell, before entering the expansion wheel. It is not harmful that the rotor shaft must first be accelerated at the beginning of the operation of the fluid machine in order to reach the predetermined operating speed. As long as the rotational speed is low, there is no critical overpressure on the expansion wheel. If a higher overpressure appears on the expansion wheel after a few seconds, but the rotor shaft has reached the required operating speed, the flow generator can provide the necessary air flow in the direction of the expansion wheel.

[0008] In a preferred embodiment, the expansion wheel is arranged in the expansion chamber, the cathode exhaust gas is fed into the expansion chamber with a predetermined hydrostatic inlet pressure, wherein the flow generator is set up to build up a blocking pressure on the pressure side facing the expansion wheel, which is equal to or greater than the inlet pressure of the expansion chamber. Thus, this pressure relationship can be well known in preliminary tests by calibration, because both the hydrostatic inlet pressure into the expansion chamber and the blocking pressure provided by the flow generator are directly dependent on the rotational speed of the rotor shaft.

[0009] In another preferred embodiment, when the rotor shaft reaches or exceeds a predetermined rotational speed, the blocking pressure exceeds the inlet pressure by 0.5 bar absolute or more, preferably by 1.0 bar absolute or more, and particularly preferably by 1.0 bar absolute to 2.0 bar absolute.

[0010] In a preferred embodiment, the predetermined rotation speed is higher than the lift-off rotation speed of the rotor shaft. The lift-off rotation speed is preferably in the range of 10,000 rpm to 30,000 rpm, preferably between 12,000 rpm and 18,000 rpm.

[0011] In another preferred embodiment, the flow generator has several, preferably multiple, recesses and / or protrusions configured on the rotor shaft. With the help of these recesses and / or protrusions, eddies are obtained by the rotation of the rotor shaft, which build up a retarding pressure, which can diffuse in the direction of the expansion chamber via the flow path. In a first preferred variant, the flow generator has a plurality of recesses in the form of grooves, which are preferably evenly distributed around the rotor shaft. These grooves can be embedded directly in the surface of the rotor blades, for example, or applied to a correspondingly configured sleeve on the rotor shaft.

[0012] In a variant according to the invention, it is also preferred that the flow generator has a plurality of projections in the form of ribs, preferably uniformly distributed around the circumference, which protrude beyond the rotor shaft.

[0013] In a further preferred variant, the rotor shaft has both recesses and elevations, which are preferably arranged uniformly distributed around the circumference of the rotor shaft.

[0014] In a further preferred embodiment, the recesses and / or the projections are oriented parallel to the rotor axis or at an angle to the rotor axis.

[0015] It is preferred that the fluid machine is configured to rotate the rotor shaft in a preferred direction of rotation, wherein the angle of the recess and / or protrusion has an inclination opposite to the direction of rotation. In other words, the recess and / or protrusion is oriented in a left-handed direction in a right-handed rotor shaft and in a right-handed direction in a left-handed rotor shaft. In this way, a vortex acting in the direction of the expansion wheel is generated based on the orientation of the flanks of the recess / protrusion, with which a blocking pressure can be built up.

[0016] The angle is preferably in the range of 10° to 80° relative to the rotor axis. This allows the recess or protrusion to exert its effect in the axial direction relative to the rotor axis (for example, unlike a spiral groove which exerts a supporting force generated by an air cushion acting orthogonally relative to the rotor axis).

[0017] In another preferred embodiment, the recesses and / or elevations are formed relative to the surface of the rotor shaft and have a radial extension in the range of up to 20 μm relative to the surface. In other words, the radial extension defines the depth of the recesses or the height of the elevations relative to the surface of the rotor shaft.

[0018] The recesses and / or projections can extend straight along the aforementioned angle, but they can also have a curved course, wherein in the case of a curved course the angle is preferably defined as the angle of a secant which extends between the axial end points of the respective recess or the respective projection.

[0019] In another preferred embodiment, the flow generator is equipped with an air delivery line, which is arranged independently of the air bearing facility, wherein the air delivery line is preferably designed as a suction line, which is connected to the environment in a fluid-conducting manner. The air delivery line preferably includes one or more perforations, and further preferably includes a partially or completely circumferentially surrounding groove. The air delivery line reliably prevents the flow generator from sucking air from the bearing facility when the rotor shaft rotates, because the suction side of the flow generator opposite to the blocking pressure can be supplied with air via the air delivery line.

[0020] In a further preferred embodiment, the flow generator and the air bearing arrangement are arranged adjacent to one another in the direction of the rotor axis or preferably at a distance from one another, wherein the flow generator is arranged on the side of the air bearing arrangement facing the expansion wheel.

[0021] The above embodiments have described the fluid machine with reference to a single flow generator. However, in another preferred embodiment, it is provided that the flow generator is only a first flow generator, and the fluid machine also has a second flow generator, which is arranged opposite to the first flow generator with respect to the air bearing arrangement, wherein the second flow generator is set up to generate an air flow directed away from the air bearing depending on the rotation of the rotor shaft.

[0022] The second flow generator is particularly preferably arranged to compensate for the axial force applied by the first flow generator (which acts between the housing and the rotor shaft of the fluid machine) or to counteract the axial force. Both flow generators generate a blocking pressure directed away from the air bearing arrangement. If the fluid machine has a compression wheel on the side of the expansion wheel opposite to the rotor shaft (which is the case in the preferred embodiment), it should be understood that the second flow generator is used to build up a blocking pressure in the direction of the compression wheel.

[0023] In other aspects, the second flow generator functions in the same manner as the first flow generator.

[0024] Therefore, the preferred embodiments described above with respect to the flow generator of the turbomachine are also preferred embodiments of the second flow generator in the turbomachine.

[0025] In an exemplary preferred embodiment, the second flow generator has several, preferably a plurality of, recesses and / or projections which are formed on the rotor shaft.

[0026] The recesses and / or protrusions of the second flow generator are preferably parallel to the rotor axis or oriented at an angle relative to the rotor axis which is oriented opposite to the angle of the first flow generator and preferably equal in value to the angle of the first flow generator.

[0027] In a further preferred embodiment, the recesses and / or projections of the second flow generator have a smaller radial extension than the recesses and / or projections of the first flow generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below in conjunction with preferred embodiments with reference to the accompanying drawings.

[0029] In the figure:

[0030] Figure 1 A schematic diagram showing a fluid machine according to a preferred embodiment, and

[0031] Figure 2 Show according to Figure 1 Detailed drawing of the fluid machinery. DETAILED DESCRIPTION

[0032] Figure 1 The turbomachine 1 is shown as part of a fuel cell system 100 of a vehicle 200 , preferably a commercial vehicle. The turbomachine 1 has a compressor wheel 3 , which is arranged in a compression chamber 5 .

[0033] The compression chamber 5 has an inlet 7 which is designed to supply air to the compression chamber 5 at an inlet pressure p1, for example via an intake duct (not shown), the air being compressed to an outlet pressure p2 by the rotation of the compression wheel 3 in the compression chamber 5 and discharged via an outlet 9 of the compression chamber 5 .

[0034] The turbomachine 1 is fluidically connected to a fuel cell 101 of a fuel cell system 100 and is designed to convert air compressed by a compressor wheel into a fuel cell reaction in a generally known manner. The air represents the reactant on the cathode side.

[0035] The compressed air is supplied to the fuel cell 101 at a pressure p2 .

[0036] After flowing through the fuel cell 101, the air / water mixture is discharged from the fuel cell 101 as the so-called cathode exhaust gas with a hydrostatic pressure p3, which is lower than p2. The fuel cell 101 is fluidically connected to the expansion chamber 11 of the fluid machine 1, more specifically to the inlet 13 of the expansion chamber 11. The expansion chamber 11 is assigned to the fluid machine 1 and has an expansion wheel 15 in its interior. Since the cathode exhaust gas enters with a pressure p3 as the inlet pressure, it flows through the expansion wheel 15 and a pressure reduction of the cathode exhaust gas occurs here in a generally known manner, so that the cathode exhaust gas is at a pressure p4, which is approximately or equal to the ambient pressure p U ) leaves the expansion chamber 11 through the outlet 17. Although the pressure p3 of the cathode exhaust gas is lower than the pressure p2 after flowing through the compression chamber 5, it is still always higher than the intake pressure p1, which is equal to or higher than the ambient pressure p U .

[0037] The compression wheel 3 and the expansion wheel 15 are connected by means of a rotor shaft 19 and are each rotationally rigidly fastened to the rotor shaft 19. The rotor shaft 19 is driven in a generally known manner by an electric motor 21 in a manner that allows it to rotate about a rotor axis X. Figure 1 In the embodiment shown this is a clockwise direction.

[0038] The rotor shaft 19 is rotatably supported by means of an air bearing arrangement 21 in a compressor housing 23 , which is preferably also associated with the expansion space 11 and the compression space 5 .

[0039] The air bearing arrangement 21 has at least one first air bearing 21a (which can be a radial air bearing) and a second air bearing 21b (which can also be a radial air bearing). The air bearing arrangement 21 preferably also has one or more (not shown) axial air bearings, which also support the rotor shaft 19 and the components rotating therewith in the axial direction with respect to the axis X. Here, only the radial air bearings 21a, 21b are shown for the sake of understanding the air bearing arrangement 21.

[0040] For aerostatic support, the air bearing arrangement 21 is preferably connected in a fluid-conducting manner via an air bearing flow path 25 to a compressed air source which is designed to supply compressed air at a pressure p L The air bearing arrangement 21 is blown down to support the load-bearing capacity of the air bearing 21 as long as the rotor shaft 19 has not yet reached its required lift-off speed in order to form an air cushion of sufficient load-bearing capacity.

[0041] A first flow path 27 is formed between the air bearing 21 and the expansion wheel 15 or the expansion chamber 11, which is designed as an annular gap between the compressor housing 23 and the rotor shaft 19. The first flow path 27 is ultimately based on this, that is, it is committed to the contactless movement of the rotor shaft 19 relative to the compressor housing 23.

[0042] The flow path 27 is thus a potential inlet for water and possibly solid particles which may be propelled in the direction of the air bearing arrangement 21 due to the overpressure caused by the inlet pressure p3 within the expansion chamber 11 and / or due to capillary effects.

[0043] To avoid this, a first flow generator 29 is arranged between the air bearing arrangement 21 and the expansion chamber 11 or the expansion wheel 15, which is designed in the following manner to build up a blocking pressure p in the flow path 27 on the side of the rotor shaft 19 facing the expansion wheel 15 as a function of the rotation speed of the rotor shaft 19. S The flow generator 29 is configured to construct a flow of size p S >P3 blocking pressure p S (See Figure 2 ), in order to prevent water droplets and / or particles from possibly moving through the flow path 27 to the air bearing device 21. Thus, the first flow generator 29 realizes a contactless fluid and particle seal based on the local overpressure generated in the flow path 27 on the side facing the expansion wheel 15 from the flow generator 29.

[0044] The first flow generator 29 is also connected in a fluid-conducting manner by means of an air supply line 31. The air supply line 31 can be used to replenish air on the suction side of the first flow generator 29 (i.e., the side facing the air bearing arrangement 21 when viewed from the first flow generator 29), for example from a vacuum pump having an ambient pressure p U This effectively prevents bearing air from being extracted from the air bearing arrangement 21 by means of the first flow generator 29 due to the rotation of the rotor shaft 19 , so that the first flow generator 29 does not impair the load-bearing capacity of the air bearing arrangement 21 .

[0045] The first flow generator 29 has several, preferably a plurality of, recesses and / or protrusions 33, which are arranged on the rotor shaft 19 and rotate as the rotor shaft 19 rotates about the axis X. In the illustrated embodiment, the recesses and / or protrusions 33 are designed as grooves, which have a predetermined radial extension t1 (i.e., define the depth of the groove) and are arranged at an angle α1 relative to the rotor axis X. The angle α1 is left-handed with respect to the rotor axis X, i.e., oriented opposite to the running direction of the rotor shaft 19, whereby a blocking pressure p is generated on the “correct” side of the flow generator 29. S (See Figure 2 ).

[0046] In addition to the first flow generator 29, the fluid machine 1 also has a second flow generator 35, which is operatively arranged in a second flow path 37 between the air bearing device 21 and the compression wheel 3 or the compression chamber 5. The second flow path 37 is also designed as an annular gap between the compressor housing 23 and the rotor shaft 19, and is subject to structural restrictions for the same reasons as the first flow path 27.

[0047] In the same functional manner as the first flow generator 29, the second flow generator 35 also has a number of protrusions and / or recesses 39, which are arranged on the rotor shaft 19. The protrusions and / or recesses 39 are preferably designed as grooves. The protrusions / recesses 39 have a radial extension t2, which is also the dimension of the groove depth in the case of a groove, which is preferably smaller than the radial extension t1 of the recesses / protrusions of the first flow generator 29. By differentiating the radial extensions t1, t2, a partial compensation of the axial force generated by the flow generator is obtained, which can also be coordinated with the axial force from the compression wheel 3 or the expansion wheel 15 in the direction of the axis X.

[0048] The orientation of the protrusion or recess 39 is Figure 1 In the embodiment, the angle α2 is implemented, which, in the case of a clockwise rotation of the rotor shaft 19, that is to say also right-handed, is oriented in the opposite direction to the angle α1 of the first flow generator 29. Thus, the second flow generator 35 generates its blocking pressure on the other side with respect to the first flow generator 39, i.e., on the side of the flow path 37 facing the compression wheel 3 or the compression chamber 5, so that the entry of undesired particles into the flow path 37 from this side is at least minimized, in particular to ensure the above-mentioned, at least partial axial force compensation.

[0049] Figure 2 Shown on a larger scale Figure 1 The invention is further explained with respect to the first flow generator 29, wherein the technical functions can also be transferred similarly to the second flow generator 35, which is omitted from being shown separately for the sake of clarity.

[0050] When the shaft 19 rotates in a clockwise direction about the axis X, the projections or recesses 33 on the flanks following the direction of rotation (i.e., on the Figure 2 In the flow path 27, a blocking pressure p is built up due to the air vortex. S , which promotes an air flow in the direction of the expansion chamber 11 under unimpeded flow conditions. However, at least a blocking or blocking pressure p is generated. S , which is higher than the hydrostatic inlet pressure p3 in the expansion chamber 11 when the rotation speed of the rotor shaft 19 is sufficiently high. Preferably, the blocking pressure p SCompared to the hydrostatic pressure p3 in the expansion chamber 11 , it is 1.0 bar or more higher.

[0051] For replenishment and / or at least decompression of the suction side of the flow generator 29, the side of the flow generator 29 facing away from the expansion wheel 15 is preferably assigned one or more partially circumferential, one or more grooves 41, which are connected to the air supply line 31 in a fluid-conducting manner in order to compensate for the locally generated suction negative pressure p by air replenishment. A The air is preferably sucked from the environment.

[0052] The first flow generator 29 is spaced apart from the air bearing 21 by a distance δ1 in the direction of the axis X. This distance δ1 realizes a neutral zone to a certain extent, in which no structural elements are present on the rotor shaft 19, and preferably no structural elements are present on the side of the compressor housing 23, so as to minimize the mutual disturbing influence of the flow generator 29 and the air bearing device 21. This also minimizes possible adverse effects of the flow generator 29 or the air vortex generated by it on the air bearing device 21 (which is configured, for example, as a spiral groove bearing or a thin film bearing).

[0053] It is also preferred that the second flow generator is axially spaced apart from the air bearing device 21 by a distance δ2 in the direction of the axis X, see Figure 1 .

[0054] Reference numerals (part of the description):

[0055] 1 Fluid Machinery

[0056] 5 Compression chamber

[0057] 7 Entrance

[0058] 9 Exit

[0059] 11 Expansion Chamber

[0060] 15. Expansion wheel

[0061] 17 Exit

[0062] 19 Rotor shaft

[0063] 21 Air bearing

[0064] 21a, b Air bearing facilities

[0065] 23 Compressor housing

[0066] 25 Air Bearing Flow Path

[0067] 27 Flow path, expansion side

[0068] 29 First Flow Generator

[0069] 31 Air delivery lines

[0070] 33. Protrusion / recess of the first flow generator

[0071] 35 Second Flow Generator

[0072] 37 Flow path, compression side

[0073] 39 Protrusion / recess of the second flow generator

[0074] 100 Fuel Cell Systems

[0075] 101 Fuel Cell

[0076] 200 vehicles

[0077] X axis

[0078] p1 Pressure, compressor inlet

[0079] p2 Pressure, compressor outlet

[0080] p3 Expander inlet pressure, cathode exhaust gas

[0081] p4 Expander outlet pressure, cathode exhaust gas

[0082] p S Blocking pressure, flow generator

[0083] p A Suction pressure, flow generator

[0084] p U Environmental pressure

[0085] α1 Angle, first flow generator

[0086] α2 Angle, second flow generator

[0087] δ1 Spacing, first flow generator

[0088] δ2 Spacing, second flow generator

Claims

1. A fluid machine (1), in particular for a fuel cell system (100) for a vehicle (200), for example a commercial vehicle, comprising a rotor shaft (19), an expansion wheel (15) fastened to the rotor shaft (19), and an air bearing arrangement (21), the air bearing arrangement being designed to support the rotor shaft (19) in a manner rotatable about a rotor axis (X), in, A flow path (27) is formed between the expansion wheel (15) and the air bearing device (21), It is characterized in that a flow generator (29) is arranged in the flow path (27) between the air bearing device (21) and the expansion wheel (15), and the flow generator is designed to generate an air flow directed toward the expansion wheel (15) as a function of the rotation of the rotor shaft (19).

2. The fluid machine (1) according to claim 1, wherein: The expansion wheel (15) is arranged in an expansion chamber (11), and cathode exhaust gas of the fuel cell (101) is input into the expansion chamber using a predetermined hydrostatic inlet pressure (p3). The invention is characterized in that the flow generator (29) is designed to build up a blocking pressure (p ) on the pressure side facing the expansion wheel (15). S ), the blocking pressure is equal to or greater than the inlet pressure (p3) of the expansion chamber (11).

3. The fluid machine (1) according to claim 2, It is characterized in that When the rotor shaft (19) reaches or exceeds a predetermined rotation speed, the blocking pressure (p S ) exceeds the entry pressure by 0.5 bar or more, preferably by 1.0 bar or more, particularly preferably by 1.0 bar to 2.0 bar.

4. A fluid machine (1) according to any one of the preceding claims, It is characterized in that The flow generator (29) has several, preferably a plurality of, recesses and / or projections (33) formed on the rotor shaft (19).

5. The fluid machine (1) according to claim 4, It is characterized in that The recesses and / or protrusions (33) are oriented parallel to the rotor axis (X) or at an angle (α1) relative to the rotor axis (X).

6. The fluid machine (1) according to claim 5, It is characterized in that The turbomachine (1) is designed to rotate the rotor shaft (19) in a preferred direction of rotation, wherein the angle (α1) of the recess and / or the projection (33) has an inclination opposite to the direction of rotation.

7. The fluid machine (1) according to claim 5 or 6, It is characterized in that The angle (α1) is in the range of 10° to 80° relative to the rotor axis (X).

8. The fluid machine (1) according to any one of claims 4 to 7, It is characterized in that The recess and / or projection (33) is formed relative to the surface of the rotor shaft (19) and has a radial extension (t1) in the range of ... to ... relative to the surface.

9. A fluid machine (1) according to any one of the preceding claims, It is characterized in that An air supply line (31) is associated with the flow generator (29), and the air supply line is arranged independently of the air bearing arrangement (21).

10. The fluid machine (1) according to any one of the preceding claims, It is characterized in that The flow generator (29) and the air bearing device (21) are arranged adjacent to each other or spaced apart from each other by a certain distance (δ1) in the direction of the rotor axis (X), wherein the flow generator (29) is arranged on a side of the air bearing device (21) facing the expansion wheel (15).

11. A fluid machine (1) according to any one of the preceding claims, It is characterized in that The flow generator (29) is a first flow generator (29), and the fluid machine (1) has a second flow generator (35), which is arranged opposite to the first flow generator (29) with respect to the air bearing device (21), wherein the second flow generator (35) is configured to generate an air flow directed away from the air bearing device (21) in dependence on the rotation of the rotor shaft (19).

12. The fluid machine (1) according to claim 11, It is characterized in that The second flow generator (35) has several, preferably a plurality of, recesses and / or projections (39) formed on the rotor shaft (19).

13. The fluid machine (1) according to claim 11 or 12, in, The recess and / or protrusion (39) is parallel to the rotor axis (X) or oriented at an angle (α2) relative to the rotor axis (X), which is oriented in the opposite direction to the angle (α1) of the first flow generator (29) and is preferably equal in value to the angle (α1) of the first flow generator (29).

14. The fluid machine (1) according to any one of claims 11 to 13, It is characterized in that Compared to the recesses and / or protrusions (33) of the first flow generator (29), the recesses and / or protrusions (39) of the second flow generator (35) have a smaller radial extension (t2).

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