DE102015007379A1 - Turbomachine for an energy converter, in particular a fuel cell - Google Patents

Abstract

The invention relates to a turbomachine (10) for an energy converter, in particular a fuel cell, with a compressor (12) for compressing air to be supplied to the energy converter with at least one housing element (24) and one around an axis of rotation (36) relative to the housing element (24) rotatable running tool (16) which at least one impeller (20, 22) and at least in the axial direction on the housing element (24) by means of a designed as an air bearing bearing means (42, 46) is mounted, which at least one on the housing element (24) held first bearing part (48, 50) and at least one corresponding, with the rotor (16) relative to the first bearing part (48, 50) with rotatable second bearing part (52), wherein at least one of the bearing parts (48, 50, 52) on one of the other bearing part (48, 50, 52) facing end face (58, 60, 62, 64) has a plurality of at least substantially spiral-shaped depressions (66) which through a coating applied to a base body (70) of the one bearing part (48, 50, 52) is formed.

Description

The invention relates to a turbomachine for an energy converter, in particular a fuel cell, according to the preamble of patent claim 1.

Such turbomachines for energy converters, in particular fuel cells, are already well known from the general state of the art. Such a turbomachine is usually used in an energy converter in the form of a fuel cell or a fuel cell system, wherein air is compressed by means of the turbomachine, which is supplied to the energy converter. As a result, a particularly efficient operation of the energy converter, in particular the fuel cell or the fuel cell system, can be realized. For this purpose, the turbomachine comprises a compressor for compressing air to be supplied to the energy converter. Furthermore, the turbomachine comprises at least one housing element and a rotatable about an axis of rotation relative to the housing element running gear, which comprises at least one impeller. The impeller is, for example, a compressor wheel of the compressor, wherein the air is compressed by means of the compressor wheel.

The turbomachine further comprises a bearing device designed as an air bearing, by means of which the running gear is mounted on the housing element at least in the axial direction. The bearing device comprises at least one first bearing part held on the housing element and at least one corresponding second bearing part with the running gear relative to the first bearing part. The running gear can be supported at least indirectly on the first bearing part via the second bearing part. Under this indirect support is to be understood that due to rotation of the second bearing part relative to the first bearing part between the bearing parts, an air cushion is formed, via which the second bearing part is supported or supported at least in the axial direction on the first bearing part. In this way, an undesirable, direct contact of the bearing parts can be avoided.

The turbomachine is an air supply unit and thereby designed as a high-speed turbomachine, which has particularly high speeds during its operation. In this case, by means of the air bearing sufficient storage can be realized even at high speeds. The air bearing is a hydrodynamic air bearing, which uses the aforementioned air cushion as air cushion for at least axial storage. Usually, air bearings in the form of foil bearings are used. Further types of bearings are so-called spiral groove segment bearings and tilting segment bearings. All bearing types, ie both spiral groove bearings as well as tilting pad bearings and foil bearings work according to the same physical principle. By the rotational movement, for example, at least substantially wedge-shaped air cushion or air cushion forms between the bearing parts, wherein the air cushion is able to wear the running gear, which is also referred to as a rotor. This operating principle applies to both the radial, as well as for the axial bearing of the running tool. At typical rated speeds, velocity gradients occur between rotating and stationary parts of the air supply unit from 150 to 350 meters per second. Such a rotating part is the second bearing part, wherein a housing-fixed part, for example, is the first bearing part held on the housing element. Due to the large velocity gradients in connection with the very small air gap between the bearing parts, high shear forces occur, which in turn cause high frictional losses of several 100 watts. In order for the turbomachine to remain thermally stable, cooling is usually used.

At standstill of the running gear this or the second bearing part is usually on the first bearing part. When the turbomachine is then put into operation, a mixed friction area must first be passed through before the running gear or the second bearing part lifts off from the first bearing part and the air cushion is formed.

Axial foil bearings usually comprise a plurality of cover foils, which are also referred to as Topfoils, and a plurality of, at least substantially wavy carrier foils, which are also referred to as Bumpfoils. Spring and damping properties arise due to the shape of the carrier film and by Coulomb friction between the films and the housing element of the air bearing. The cover sheets are provided with a lubricious coating, which consists for example of polytetrafluoroethylene (PTFE). In general, axial foil bearings have two housing-fixed bearing discs and a track disc, which belongs to the running gear and rotates with this. On the two bearing discs, the cover and carrier film is attached by a spot welding process. The cover and carrier film itself are produced, for example, by means of an embossing process. Both welding and embossing processes are known to be highly tolerant. This is problematic in terms of producing an air cushion of less than 0.01 millimeters. This results in disadvantages in the process-reliable production and the sustainability of foil bearings. Axial spiral groove bearings according to the prior art are made of ceramic materials such as Tungsten or silicon carbide produced, because they are extremely resistant to abrasion and temperature. Ceramics are known to be difficult to process and therefore costly. Like the foil bearings, spiral groove bearings usually comprise two housing-fixed bearing discs and a track disc, which is rotatable relative to the bearing discs.

Further, the DE 690 13 761 T2 a magnetic pump comprising a closed-type impeller with magnetic means rotatably driven by a magnetic force acting from outside the pump impeller.

Object of the present invention is to develop a flow machine of the type mentioned in such a way that a particularly effective and cost-effective storage of the tool is feasible.

This object is achieved by a turbomachine having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

In order to develop a turbomachine specified in the preamble of claim 1 type such that a particularly effective and cost-effective storage of the tool is feasible, it is inventively provided that at least one of the bearing parts on a side facing the other bearing part a plurality of at least substantially helical Recesses, in particular grooves, which is formed by a coating applied to a base body of a bearing part coating. In other words, the bearing device configured as an air bearing is designed as a spiral groove bearing, the hydrodynamic properties of which for bearing the running tool arise through an at least substantially spiral patterning formed by the depressions. This patterning has, for example, a depth of a few micrometers, so that an air cushion can form between the bearing parts when the rotor and thus the second bearing part rotate relative to the first bearing part.

According to the invention, it is now provided that the recesses or the patterning are not introduced into the main body itself, for example by etching or the like, but the main body is coated, that is to say provided with a coating which forms the at least substantially spiral patterning. In other words, there is no material removal of the base body, but there is a material application to the base body to form the coating. In this case, the coating forms first partial regions, which are raised in relation to second partial regions adjoining the first partial regions, so that the second partial regions form the depressions. The bearing parts must therefore not be made of very abrasion-resistant and cost-intensive materials, but the bearing parts and thus the bearing device and the flow machine as a whole can be made particularly inexpensive while achieving an effective and low-friction air bearing.

Alternatively or additionally, it is conceivable that the base body is made of a ceramic material, but the ceramic material or the base body does not have to be processed costly to form the depression, but the wells are formed in a simple and cost-effective manner by the coating.

Preferably, the coating is formed as a sliding layer, wherein the coating is particularly advantageously formed of a plastic, in particular polytetrafluoroethylene (PTFE). This allows a particularly low-friction storage of the running gear can be realized.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

The drawing shows in:

1 a schematic longitudinal sectional view of a turbomachine according to a first embodiment of an energy converter, in particular a fuel cell, with a designed as an air bearing bearing means comprising at least two bearing parts, wherein at least one of the bearing parts on a side facing the other bearing part a plurality of at least substantially spiral-shaped depressions which are formed by a coating applied to a base body of a bearing part coating;

2 a schematic front view of a bearing part according to a first embodiment;

3 a schematic front view of a bearing part according to a second embodiment;

4 a schematic front view of a bearing part according to a third embodiment; and

5 a schematic longitudinal sectional view of the turbomachine according to a second embodiment.

In the figures, the same or functionally identical elements are provided with the same reference numerals.

1 shows in a schematic longitudinal sectional view with a whole 10 Designated turbomachine according to a first embodiment in the form of a turbocharger for an energy converter, in particular a fuel cell or a fuel cell system. The turbomachine 10 includes a compressor 12 , by means of which air is compressed. The compressed air is supplied to the energy converter, in particular the fuel cell or the fuel cell system, so that the energy converter can be operated particularly efficiently. The turbomachine 10 is thus an air supply unit for supplying the fuel cell system with compressed air. The compressor 12 includes a compressor housing 14 and is designed as a radial compressor. The turbomachine 10 includes a whole with 16 designated Laufzeug, which is also referred to as a rotor. The rotor (Laufzeug 16 ) includes a shaft 18 , a first impeller in the form of a turbine wheel 20 and a second impeller in the form of a compressor wheel 22 , The wheels (turbine wheel 20 and compressor wheel 22 ) are non-rotatable with the shaft 18 connected, which is also referred to as a motor shaft. The compressor wheel 22 is the compressor 12 assigned and in the compressor housing 14 taken, the air by means of the compressor wheel 22 is compressed.

The turbomachine 10 further comprises a housing element 24 with a plurality of interconnected housing parts 26 . 28 and 30 , where also the compressor housing 14 a housing part of the housing element 24 is. In addition, the turbomachine includes 10 a turbine 32 , which as a further housing part of the housing element 24 a turbine housing 34 having. The turbine wheel 20 is in the turbine housing 34 arranged and the turbine 32 assigned. The turbine 32 is presently designed as a radial turbine and can be flowed through by exhaust gas of the energy converter. This exhaust gas is, for example, air, by means of which the turbine 32 , in particular the turbine wheel 20 , is drivable. Out 1 is recognizable that the running gear 16 around a rotation axis 36 relative to the housing element 24 is rotatable. Because the compressor wheel 22 over the wave 18 with the turbine wheel 20 connected, the compressor can 22 for compressing the air from the turbine wheel 20 be driven so that energy contained in the exhaust gas of the energy converter can be used to compress the air. This makes it possible to realize a particularly efficient operation of the fuel cell system (energy converter).

To the air supplied to the energy converter then also by means of the turbomachine 10 to compress, if the energy converter does not provide exhaust or exhaust gas with a low energy content, includes the turbomachine 10 a motor in the form of an electric motor 38 , by means of which the power tool 16 and thus the compressor wheel 22 are drivable. From the electric motor 38 is in 1 a winding 40 shown schematically, which is also referred to as a motor winding. The electric motor 38 further comprises, for example, at least one in 1 unrecognizable and with the wave 18 rotatably connected magnet, which is formed for example as a permanent magnet. About this magnet is the rotor (Laufzeug 16 ) by means of the winding 40 drivable.

The turbomachine 10 is a high-speed turbomachine. This means that the running gear 16 during operation of the turbomachine 10 with very high speeds relative to the housing element 24 rotates. In this case, a particularly effective storage of the tool 16 To realize, includes the turbomachine 10 one trained as an air bearing and as a whole with 42 designated storage facility. The storage facility 42 comprises two housing fixed, that is on the housing element 24 held radial bearings 44 , which are designed as radial air bearings. About the radial bearings 44 is the running tool 16 in the radial direction on the housing element 24 rotatably mounted. Furthermore, the storage facility comprises 42 a thrust bearing, which serves as an axial air bearing 46 is trained. By means of the axial air bearing 46 is the running tool 16 in the axial direction on the housing element 24 stored. This includes the axial air bearing 46 first bearing parts in the form of bearing washers 48 and 50 which are first axial air bearing parts. The first bearing parts (bearing washers 48 and 50 ) are fixed to the housing, that is on the housing element 24 held.

Furthermore, the axial air bearing comprises 46 one with the bearing washers 48 and 50 (first bearing parts) corresponding second bearing part in the form of a track disc 52 which is formed in the first embodiment as an internally ventilated track disc. The track disc 52 is with the running gear 16 rotatable while rotatably with the tool 16 connected, so the track disc 52 around the axis of rotation 36 relative to the first bearing parts (bearing discs 48 and 50 ) is rotatable. The running tool 16 may be in the axial direction over the track disc 52 and the bearing washers 48 and 50 on the housing element 24 support, with air as the medium between the track disc 52 and the respective bearing washers 48 and 50 is used. When turning the tool 16 relative to the bearing discs 48 and 50 forms, for example, between the track disc 52 and the respective bearing washers 48 and 50 an air cushion or an air cushion, as between the track disc 52 and the respective bearing washers 48 and 50 , In particular, in the axial direction between these, an air gap is provided. The axial air bearing 46 is thus a dynamic or hydrodynamic air bearing, via which on the running gear 16 acting axial forces on the housing element 24 be transmitted.

In 1 is also a guide grid 54 of the compressor 12 to recognize, with the Leitgitter 54 downstream of the compressor wheel 22 is arranged. The from the compressor wheel 22 outgoing air is by means of the Leitgitters 54 aerodynamically influenced, that is distracted. Also the turbine 32 includes a baffle 56 , by means of which the turbine wheel 20 incoming exhaust gas can be passed so that the exhaust gas is the turbine wheel 20 flows streamlined.

To now a particularly effective and cost-effective, axial bearing of the tool 16 to realize, at least one of the bearing parts of the axial air bearing 46 on a respective other of the bearing parts facing end side on a plurality of at least substantially spiral-shaped recesses, which are formed by a coating applied to a base body of a bearing part coating. Out 1 it can be seen that the bearing disc 48 one of the track disc 52 facing end face 58 having. Furthermore, the track disc 52 one of the bearing disc 48 facing end face 60 on. The track disc 52 also has one of the bearing disc 50 facing end face 62 on, with the bearing disc 50 one of the track disc 52 facing end face 64 having. On the side of the bearing disc 48 For example, the depressions are on the front side 58 or on the front side 60 arranged, taking on sides of the bearing disc 50 the depressions, for example, on the front page 62 or the front side 64 are arranged.

The aforementioned recesses are according to a first embodiment in 2 on the example of the bearing disc 48 recognizable and there with 66 designated, these depressions 66 in 2 are provided with hatching. In 2 should thus by hatching not a sectional view, but the wells 66 be illustrated to the recess 66 visually good from across the wells 66 sublime areas 68 the bearing disc 48 to be able to distinguish. 2 shows a first embodiment of the bearing disc 48 ,

To further a particularly simple and inexpensive production of the wells 66 and thus the storage facility 42 Overall, the wells are 66 through a onto a base body 70 of the respective, the wells 66 having bearing part, in this case the bearing disc 48 , applied coating formed. The coating is preferably a lubricious coating, in particular of a plastic such as PTFE. The coating forms the aforementioned subregions 68 , which in the axial direction of the power tool 16 opposite to the sections 68 subsequent, second sub-areas are sublime. The wells 66 are formed by the second part areas, so so the wells 66 at least laterally or in the circumferential direction of the respective bearing part by the coating or the raised portions 68 are limited. This means that the wells 66 not by abrasive machining of the body 70 or by a material removal, but on the contrary by a material application to the body 70 getting produced. By the at least substantially spiral depressions 66 an at least substantially spiral patterning is created, this patterning or the respective recesses 66 especially with respect to the raised subregions 68 have or have a depth of a few microns. Through the depressions 66 arise hydrodynamic properties of the axial air bearing 46 which is formed as a spiral groove bearing because the at least substantially spiral pattern is formed by at least substantially spiral grooves or grooves. The spiral groove bearing is an air bearing, as a carrier medium for axially supporting the running tool 16 Air is used.

The bearing washers 48 and 50 are sprung in the axial direction on the housing element 24 supported. These are spring elements 72 provided, which are formed in the present case of rubber. The bearing washers 48 and 50 are thus on the spring elements 72 sprung on the housing element 24 supported, wherein the spring elements 72 in the present case are designed as O-rings. By the spring elements 72 can appropriate spring and damping properties of the axial air bearing 46 will be realized.

The use of a spiral groove bearing, the use of an axial and designed as a film bearing air bearing can be avoided, which is advantageous in that in an axial air bearing in the form of a film bearing problems with a reliable production and a low load capacity exist. Furthermore, because the depressions 66 can not be produced by material removal, but material application, the use of costly materials and manufacturing processes can be avoided, so that the axial air bearing 46 can be inexpensively manufactured or provided.

For applying the coating to the base body 70 Different methods can be used. In particular, all methods are suitable for this, which allow a coating thickness in the range of 10 to 50 micrometers. For example, the wells 66 or is the basic body 70 in the area of the depressions 66 free from the coating, leaving the pits 66 for example, have a depth in a range of 10 to 50 microns. The coating materials used are preferably materials which have good sliding and abrasion properties. The function of the axial air bearing 46 is also guaranteed if a respective sampling on both sides, that is on the front pages 60 and 62 the track disc 52 , is applied.

3 shows the bearing disc 48 In a second embodiment, wherein the second embodiment, in particular with regard to the patterning or the shape of the recesses 66 different from the first embodiment. 4 finally shows a third embodiment of the bearing disc 48 , wherein another sampling is provided again. In the 2 to 4 shown different embodiments are exemplary only, with many other forms of sampling are possible or conceivable.

In the first embodiment of the turbomachine 10 the cooling of the axial air bearing takes place 46 through the internally ventilated track disc 52 , The track disc 52 is with a plurality of radial channels 74 provided, which are formed for example as holes and can be traversed by air. This allows the track disc 52 act as a centrifugal compressor and thus promotes the cooling of the axial air bearing 46 , in particular the track disc 52 , required air. This results in two advantages: The thermally highly stressed track disc 52 and the wave 18 are cooled from the inside, because the wave 18 from the air for cooling the axial air bearing 46 is flowed through. For this purpose, the compressor wheel 22 and the wave 18 axial channels 76 on, which are formed for example as holes. The axial channels 76 open on the one hand in the radial channels 74 and on the other hand into a compressor inlet 78 over which the compressor wheel 22 sucks in the air to be compressed. Thus, the air from the compressor inlet 78 into the channels 76 and about these in the channels 74 flow.

The second advantage is that there is no need to use bleed air for cooling purposes. Thus, air can be saved, which can be made available to the energy converter, in particular the fuel cell system, whereby a particularly high efficiency of the fuel cell system can be realized.

The turbomachine 10 also has a cooling air outlet 80 on, over which the cooling air can be discharged to the environment. This possibility of cooling air flow is only one of many possibilities. Another possibility is the cooling air of the turbine 32 supply and expand there, creating a particularly high efficiency of the turbomachine 10 can be realized.

Out 1 is recognizable that the ventilated track disc 52 present on the compressor side 12 is arranged. Alternatively, it is conceivable that the internally ventilated track disc 52 on the turbine side 32 is arranged. This arrangement has the advantage that in addition to the axial air bearing 46 also the two radial bearings 44 and the magnet in the rotor would be cooled.

5 shows a second embodiment of the turbomachine 10 , where the bearing washers 48 and 50 are liquid cooled. The bearing disc 48 is in the axial direction of the compressor wheel 22 towards at least partially by a cooling channel through which a cooling liquid can flow 82 covered, with the bearing disc 48 the cooling channel 82 partially limited. Accordingly, the bearing disk 50 in the axial direction to the turbine wheel 20 at least partially from a cooling channel 84 covered, which at least partially from the bearing disc 50 limited and can be traversed by a cooling liquid. Furthermore, by the housing parts 26 and 28 cooling channels 86 limited, which also from a cooling liquid for cooling the electric motor 38 can be flowed through. Preferably, the cooling channels 82 and 84 with the cooling channels 86 fluidly coupled, so that the cooling channels 86 coolant flowing through the cooling channels 82 and 84 is flowing coolant.

In the following, a comparison of the adaptive and damping properties of a foil bearing with those of a spiral groove bearing is made. In order to compensate for production-related tolerances, angular errors and thermal expansion effects, an adaptivity is required for both types of air bearings (film bearings and Spiralrillenlager). This is ensured in the film storage by at least one carrier film, which is also referred to as Bumpfoil. The spiral groove bearing is a resilient support of the bearing discs 48 and 50 intended. This can, as in 1 and 5 illustrated by the spring elements 72 (O-rings). However, other conventional construction elements such as springs can be used for the resilient support in spiral groove bearings.

In addition to the adaptivity damping properties are necessary for both types of rotors for rotor dynamic reasons. These arise in foil bearings by Coulomb friction between the carrier film and a cover sheet, which is also referred to as Topfoil, or the bearing housing. When designing foil bearings, the problem now is that the transition from static friction to sliding friction is difficult to describe mathematically. As a result, the development of film bearings is to some extent empirical. In contrast, the damping properties of O-rings can be well described mathematically. In other words, the simulation of foil bearings is only possible with restrictions compared to O-ring supported spiral groove bearings.

LIST OF REFERENCE NUMBERS

10

flow machine

12

compressor

14

compressor housing

16

running stuff

18

wave

20

turbine

22

compressor

24

housing element

26

housing part

28

housing part

30

housing part

32

turbine

34

turbine housing

36

axis of rotation

38

electric motor

40

winding

42

Storage facility

44

radial bearings

46

axial air bearing

48

bearing disk

50

bearing disk

52

track disc

54

guide grid

56

guide grid

58

front

60

front

62

front

64

front

66

deepening

68

subregion

70

body

72

spring element

74

radial channel

76

axial channel

78

compressor inlet

80

cooling air outlet

82

cooling channel

84

cooling channel

86

cooling channel

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 69013761 T2 [0007]

Claims (7)

Turbomachine ( 10 ) for an energy converter, in particular a fuel cell, with a compressor ( 12 ) for compressing air to be supplied to the energy converter, with at least one housing element ( 24 ) and one around a rotation axis ( 36 ) relative to the housing element ( 24 ) rotatable tool ( 16 ), which at least one impeller ( 20 . 22 ) and at least in the axial direction on the housing element ( 24 ) by means of a bearing device designed as an air bearing ( 42 . 46 ), which at least one on the housing element ( 24 ) held first bearing part ( 48 . 50 ) and at least one corresponding, with the power tool ( 16 ) relative to the first bearing part ( 48 . 50 ) with rotatable second bearing part ( 52 ), characterized in that at least one of the bearing parts ( 48 . 50 . 52 ) on one of the other bearing parts ( 48 . 50 . 52 ) facing end face ( 58 . 60 . 62 . 64 ) a plurality of at least substantially spiral-shaped depressions ( 66 ), which by a on a base body ( 70 ) of the one bearing part ( 48 . 50 . 52 ) applied coating are formed. Turbomachine ( 10 ) according to claim 1, characterized in that the coating is formed as a sliding layer. Turbomachine ( 10 ) according to claim 1 or 2, characterized in that the coating is formed of a plastic. Turbomachine ( 10 ) according to claim 3, characterized in that the plastic is formed of polytetrafluoroethylene. Turbomachine ( 10 ) according to one of the preceding claims, characterized in that the first bearing part ( 48 . 50 ) sprung at least in the axial direction on the housing element ( 24 ) is supported. Turbomachine ( 10 ) according to claim 5, characterized in that the first bearing part ( 48 . 50 ) via at least one spring element ( 72 ) sprung on the housing element ( 24 ) is supported. Turbomachine ( 10 ) according to claim 6, characterized in that the spring element ( 72 ) is formed of rubber.

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