DE102012013048A1 - Fluid-flow machine for supplying compressed air to fuel cell of fuel cell arrangement of passenger car, has compressor fluidly connected with branch line at branching point that is arranged at downstream of compressor wheel - Google Patents

Abstract

The machine (10) has a compressor (12) for compressing air supplied by an energy converter. A compressor wheel (14) of the compressor is driven by an exhaust gas turbine (24) of the energy converter to drive the compressor. A rotor assembly (20) is mounted in an axial bearing of a bearing device in an axial direction. The compressor is fluidly connected with a branch line (72) at a branching point (74) that is arranged at a downstream of the compressor wheel. A rear side (76) of the turbine is subjected with pressure generated at the branching point using the branch line. An independent claim is also included for a fuel cell arrangement.

Description

The invention relates to a turbomachine for an energy converter according to the preamble of patent claim 1 and fuel cell device with such a turbomachine.

The DE 60 2004 012 546 T2 discloses a vacuum pump having a pump assembly, a shaft for driving the pump assembly, a motor for rotating the shaft, and a bearing assembly. The bearing assembly rotatably supports the shaft. The bearing assembly comprises a rolling bearing which supports a first part of the shaft. The bearing assembly further includes a thrust bearing which houses a plurality of rolling elements which are in contact with an outer race of the rolling bearing and a race of the thrust bearing to resist axial movement of the antifriction bearing and allow radial movement of the rolling bearing.

Furthermore, it is known from the general state of the art to use ball bearings or air bearings in turbomachines, such as in electrically driven turbochargers, in order to support a rotor of the turbomachine. The dynamic air bearings comprise at least one film by means of which the running gear is mounted. Due to their inherent nature, these air bearings generate particularly high friction losses, in particular with respect to ball bearings, whereby the majority of the losses occur with axial bearings. Resulting bearing losses, in particular in the form of friction losses, can be assigned to about 1/3 radial bearings and about 2/3 axial bearings. Due to the resulting losses, air bearings have a cooling air requirement, which is divided in proportion to the friction losses.

Of the DE 10 2008 050 314 A1 is a generic flow machine for an energy converter, in particular a fuel cell to take as known. The turbomachine has a compressor, by means of which the air to be supplied to the energy converter is to be compressed. The turbomachine also has a turbine and a rotor. The running tool comprises a compressor wheel of the compressor and a turbine wheel which can be driven by exhaust gas of the energy converter. In the case of the fuel cell, the exhaust gas is exhaust air of the fuel cell, by means of which the turbine wheel is drivable. The compressor is driven by the turbine wheel.

In addition, a bearing device is provided, which comprises at least one thrust bearing designed as a point bearing, by means of which the running gear is mounted in the axial direction. If the representation of a particularly low-loss storage of the running gear succeeds, the overall efficiency of the turbomachine can be considerably increased.

It is therefore an object of the present invention to provide a turbomachine of the aforementioned type and a fuel cell device with such a turbomachine, wherein the turbomachine has a particularly high efficiency.

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

In order to create a turbomachine specified in the preamble of claim 1 species, which has a particularly high efficiency, according to the invention at least one, arranged at a downstream of the compressor wheel branch point with the compressor fluidly connected branch line provided via which a Radrücken the turbine wheel with a the branch point prevailing pressure can be acted upon. This pressure is a compressor outlet pressure, which is guided from the compressor to Radrücken the turbine wheel and thus to the turbine.

As a result, different pressure levels can be cleverly used within the turbomachine in order to keep axial forces acting on the bearing device particularly low, and in this way to realize a particularly low-loss bearing of the running gear. This leads to a particularly high efficiency of the turbomachine. With this measure, the axial forces normally generated in such a turbomachine can be reduced to about 30%. The compressor-side branching of the pressure or the compressed air and the guiding of the pressure or the air to the turbine enables an at least partial compensation of axial forces arising during the compression. Any remaining axial forces can be absorbed by the point bearing friction and low loss.

In the point bearing is a so-called punctiform bearing, by means of which the running gear is mounted to form an at least substantially point-shaped contact in the axial direction between two bearing parts of the point bearing in the axial direction.

The invention also includes a fuel cell device, in particular for a motor vehicle, with at least one fuel cell as energy converter for the conversion of chemically bound energy of the fuel cell to be supplied fuel and an oxidizing agent from the Fuel cell to be supplied air into electrical energy. and with a turbomachine according to the invention for supplying the compressed air to the fuel cell. The turbomachine has a very high efficiency, so that the fuel cell can be supplied particularly efficiently with compressed air and thus operated efficiently. Advantageous embodiments of the turbomachine according to the invention are to be regarded as advantageous embodiments of the fuel cell device according to the invention and vice versa.

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 combinations of features 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 indicated combination but also in other combinations or alone, without the frame to leave the invention.

The drawing shows in:

1 a schematic longitudinal sectional view of a turbomachine for an energy converter, with a rotor, which is mounted in the axial direction by means of point bearings, wherein a Radrücken of a turbine wheel of the rotor is acted upon by a compressor outlet pressure; and

2a -C each detail a schematic side view of a respective embodiment of a point bearing for supporting the running gear in the axial direction.

1 shows a turbomachine 10 for an energy converter in the form of a fuel cell of a fuel cell device. The fuel cell is used to convert chemically bound energy of a fuel to be supplied to the fuel cell and an oxidant from the fuel cell to be supplied air into electrical energy.

The fuel cell device is installed, for example, in a motor vehicle, in particular a passenger car, wherein the motor vehicle also includes at least one electric motor for driving the motor vehicle. The electrical energy can be used to drive the electric motor. In this case, the electrical energy is supplied to the electric motor, for example, at least substantially directly. Alternatively, it is possible that the electrical energy is stored in an electrical storage device, in particular in a battery, wherein the electric motor can be supplied with the electrical energy from the battery as needed.

The turbomachine 10 serves to compress the air to be supplied to the fuel cell, whereby a particularly efficient operation of the fuel cell device is made possible. The turbomachine 10 includes a compressor 12 with a compressor wheel 14 for compressing the air to be supplied to the fuel cell. The compressor wheel 14 is in a housing 16 the turbomachine 10 taken and around a rotation axis 21 relative to the housing 16 rotatable. The compressor wheel 14 is one about the axis of rotation 21 relative to the housing 16 rotatably mounted tool 20 assigned.

The turbomachine 10 also includes a turbine 22 with one in the case 16 recorded turbine wheel 24 which is about the axis of rotation 21 relative to the housing 16 is rotatably mounted. Also the turbine wheel 24 is the power tool 20 assigned.

Through the housing 16 is a spiral channel 26 the turbine 22 formed over which the turbine wheel 24 Exhaust gas is supplied in the form of exhaust air of the fuel cell. The exhaust air can be the turbine wheel 24 flow and drive. Through the housing 16 is also a discharge channel 28 educated. The exhaust air flows through the turbine wheel 24 in a turbine exhaust area 30 and off via the discharge channel 28 from the turbine wheel 24 dissipated.

The running tool 20 also includes a wave 33 with which the turbine wheel 24 and the compressor wheel 14 are rotatably connected. So it is possible that the turbine wheel 24 the compressor wheel 14 over the wave 33 around the axis of rotation 21 drives. Thus, energy contained in the exhaust air can be used to compress the air to be supplied to the fuel cell.

Through the housing 16 is a feed channel 32 formed over which the compressor wheel 14 the air is supplied in the axial direction. Furthermore, through the housing 16 a compressor-side spiral channel 34 formed, via which the compressed air from the compressor wheel 14 is dissipated. The compressed air flows through the compressor wheel 14 in a compressor outlet area 36 off and is on the other spiral channel 34 from the compressor wheel 14 dissipated. Downstream of the compressor wheel 14 in the compressor outlet area 36 is a vane grille 38 for deflecting or deflecting the compressed air. The housing 16 can be made in several parts and a compressor housing part 17 and a turbine housing part 18 include.

For storage of the tool 20 is a bearing housing part 19 provided to the the running gear 20 is stored. Furthermore, for storage of the aircraft 20 a storage device is provided, which for the radial mounting of the running tool 20 a compressor-side, radial air bearing 40 and a turbine-side, radial air bearing 42 includes. At the air bearings 40 . 42 it may be, for example, foil air bearings.

The turbomachine 10 also includes an electric motor 44 with one on the case 16 held motor stator 46 and with one with the power tool 20 rotatably connected motor rotor 48 , By means of the electric motor 44 can the jig 20 Even at relatively low mass flows of the exhaust air to be driven at relatively high speeds, so that even at relatively low mass flows very high compression ratios of the fuel cell to be supplied air can be realized. Because of this possibility, the power tool 20 over the electric motor 44 to power the turbomachine 10 also referred to as electrically driven turbocharger.

For axial storage of the tool 20 The storage device comprises a first, compressor-side point bearing 50 and a second, turbine-side point bearing 52 , The point camp 50 includes one with the compressor wheel 14 rotatably connected and thus about the axis of rotation 21 relative to the housing 16 itself with the compressor wheel co-rotating ball segment 54 , The point camp 50 includes one with the ball segment 54 corresponding ball segment 56 which has a holder 51 of the point camp 50 on the housing 16 is held. This means that the ball segment 54 relative to the ball segment 56 rotates.

To the ball segment 56 closes a cylindrical shaft 58 on, which is provided on the outer peripheral side with an external thread. About the external thread is the shaft 58 in a corresponding internal thread of the holder 51 screwed. By turning the shaft 58 around the axis of rotation 21 relative to the holder 51 can the ball segment 56 moved in the axial direction and thus relative to the ball segment 54 be adjusted so that thereby a bearing clearance of the point bearing 50 is adjustable.

Also the turbine-side point bearing 52 includes one with the turbine wheel 24 rotatably connected and thus with the turbine wheel 24 around the axis of rotation 21 with rotatable ball segment 60 as well as one with the ball segment 60 corresponding ball segment 62 which has a holder 64 on the housing 16 is held. To the ball segment 62 closes a substantially cylindrical shaft 66 on, which is provided on the outer peripheral side with an external thread. About its external thread is the shaft 66 in a corresponding internal thread of the holder 64 screwed. By turning the shaft 66 relative to the holder 64 around the axis of rotation 21 can thus the ball segment 62 in the axial direction relative to the ball segment 60 moved and thereby adjusted, so that also a bearing clearance of the point bearing 52 is adjustable. Due to this adjustability of the spherical segments 56 . 62 can also be an axial position of the tool 20 in the case 16 be set. In addition, thermal expansion effects can be taken into account.

In the compression of the air by means of the turbomachine 10 Axialkräfte arise by a in the compressor outlet 36 downstream of the compressor wheel 14 prevailing pressure on a turbine wheel 24 facing Radrücken 68 the compressor wheel 14 impresses. Depending on the area of the wheel back 68 this results in a force in the direction of a compressor inlet area 70 over which the compressor wheel 14 the air to be compressed is supplied. The pressure build-up itself takes place on the one hand in the compressor wheel 14 and on the other hand through the vane grille 38 , Typically, the pressure build-up is equally divided between these two components, ie the compressor wheel 14 and on the vane grille 38 on. Thus, the Radrücken 68 acting pressure less than one in the spiral channel 34 prevailing pressure.

Because of the pressure the Radrücken 68 applied, it comes to axial forces. To compensate for these axial forces at least partially, is a branch line 72 provided, which on the one hand at a downstream of the compressor wheel 14 arranged branching point 74 fluidic with the compressor 12 connected is. In the present case is the branch point 74 in the spiral channel 34 arranged so that the air and thus the pressure from the spiral channel 34 over the branch line 72 to the turbine 22 to be led. On the other hand, the branch line opens 72 in the radial direction in the region of a Radrücken 76 of the turbine wheel 24 so that the Radrücken 76 of the turbine wheel 24 with the at the branch point 74 prevailing pressure from the spiral channel 34 can be acted upon. In other words, by the branch line, also referred to as bleed air line 72 the compressor outlet pressure on the wheel back 76 be impressed, so that the axial forces are at least largely compensated, although the surface of the Radrücken 76 generally smaller than the surface of the wheel back 68 is.

Remaining axial forces are represented by the pump bearing thrust bearing point bearings 50 . 52 added. Through the point camps 50 . 52 becomes the power tool 20 not supported by air bearings in the axial direction. The point camps 50 . 52 rather represent sliding bearings, by means of which the running gear 20 Slidably mounted in the axial direction. Together with the at least partial compensation of the axial forces by means of the branch line 72 can so bearing-side losses are kept low, whereby the cooling air requirement can be kept very low. In addition, the turbomachine points 10 a particularly simple structure, since expansions of the shaft 33 are not provided for axial air bearings. Furthermore, by imposing the compressor outlet pressure on the wheel back 76 a penetration of moist exhaust gas of the fuel cell in the turbomachine 10 be avoided, creating a very high electrical safety of the turbomachine 10 is guaranteed.

2a and 2 B show different embodiments of the spherical segments 54 . 56 , According to 2a have the ball segments 54 . 56 at least substantially the same radii. According to 2 B is the radius of the sphere segment 54 greater than the radius of the ball segment 56 ,

2c shows that the point bearings 50 . 52 also other bearing parts 78 . 80 can have. One of the bearing parts 78 . 80 is on the case 16 held while the other of the bearing parts 78 . 80 with the compressor wheel 14 or with the turbine wheel 24 rotatably connected.

In the present case is also the bearing part 78 as a spherical segment like the spherical segment 56 trained and over the shaft 58 adjustable in terms of its axial position. The sphere segment 56 and the bearing part 78 have a respective convex support surface 82 on. The spherical segment corresponds correspondingly with it 54 a convex support surface 84 on. In contrast, the bearing part 80 an at least substantially planar support surface 84 on. About the support surfaces 82 . 84 can the bearing parts 78 . 80 or the spherical segments 54 . 56 with the formation of an at least substantially point-shaped contact abut each other, so that thereby the running gear 20 can be supported in the axial direction.

For the ball segments 54 . 56 or the bearing parts 78 . 80 and for housing-fixed parts of the point bearings 50 . 54 for example, for the holder 51 . 64 Different material combinations can come into question. Here, both bearing parts 78 . 80 or both ball segments 54 . 56 be formed for example of ceramic. It is also possible that one of the bearing parts 78 . 80 or one of the spherical segments 54 . 56 made of ceramic, while the other of the bearing parts 78 . 80 or the other of the spherical segments 54 . 56 is formed of a hardened steel or a hard metal. Another possibility, a very high abrasion resistance of the bearing parts 78 . 80 or the spherical segments 54 . 56 and to reach their storage partners, represent coatings such as titanium carbide or diamond-like carbon (diamond-like carbon).

To in the radial air bearings 40 . 42 and in particular in the motor rotor 48 dissipate the resulting power loss and cool it is an in 1 by directional arrows 86 indicated cooling air flow provided. Here is in 1 a cooling air outlet indicated at 88. Based on a directional arrow 90 Another possibility for the representation of such a cooling air outlet is indicated. Over the cooling air outlet 88 and / or over the by the directional arrow 90 illustrated cooling air outlet, the heated air from the turbomachine 10 escape.

In order to realize a particularly high cooling performance, can in the branch line 72 a in 1 Unillustrated intercooler be provided by means of which the branch line 72 flowing air can be cooled.

LIST OF REFERENCE NUMBERS

10

flow machine

12

compressor

14

compressor

16

casing

17

Compressor housing part

18

Turbine casing

19

Bearing housing part

20

running stuff

21

axis of rotation

22

turbine

24

turbine

26

spiral channel

28

discharge channel

30

Turbinenauslassbereich

32

feed

33

wave

34

spiral channel

36

Verdichterauslassbereich

38

stator vane

40

radial air bearing

42

radial air bearing

44

electric motor

46

motor stator

48

motor rotor

50

point contact bearings

51

holder

52

point contact bearings

54

ball segment

56

ball segment

58

shaft

60

ball segment

62

ball segment

64

holder

66

shaft

68

wheel rear side

70

Compressor inlet area

72

branch power

74

branching point

76

wheel rear side

78

bearing part

80

bearing part

82

supporting

84

supporting

86

arrow

88

cooling air outlet

90

arrow

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 602004012546 T2 [0002]
• DE 102008050314 A1 [0004]

Claims (8)

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 a turbine ( 22 ), with a running tool ( 20 ), which is a compressor wheel ( 14 ) of the compressor ( 12 ) and a turbine wheel driven by exhaust gas of the energy converter ( 24 ), by means of which the compressor wheel ( 14 ), and with a bearing device, which at least one as a point bearing ( 50 . 52 ) formed axial bearing, by means of which the running tool ( 20 ) is mounted in the axial direction, characterized in that at least one, at a downstream of the compressor impeller arranged branching point ( 74 ) with the compressor ( 12 ) fluidly connected branch line ( 72 ) is provided, via which a Radrücken ( 76 ) of the turbine wheel ( 24 ) with one at the branch point ( 74 ) prevailing pressure can be acted upon. Turbomachine ( 10 ) according to claim 1, characterized in that the point bearing ( 50 . 52 ) at least two bearing parts ( 54 . 56 . 78 . 80 ), which via respective, convex support surfaces ( 82 . 84 ) can be supported in the axial direction against each other. Turbomachine ( 10 ) according to claim 2, characterized in that the support surfaces ( 82 . 84 ) have respective, mutually different radii of curvature. Turbomachine ( 10 ) according to claim 1, characterized in that the point bearing ( 50 . 52 ) a first bearing part ( 54 . 56 . 78 ) with a convex, first support surface ( 82 ) and at least one second bearing part ( 80 ) having an at least substantially planar, second support surface ( 84 ), wherein the bearing parts ( 54 . 56 . 78 . 80 ) over the respective support surfaces ( 82 . 84 ) can be supported in the axial direction against each other. Turbomachine ( 10 ) according to one of the preceding claims, characterized in that the bearing device has at least one radial bearing ( 40 . 42 ), by means of which the running tool ( 20 ) is mounted in the radial direction, wherein the radial bearing ( 40 . 42 ) is designed as an air bearing, in particular as a film air bearing. Turbomachine ( 10 ) according to one of the preceding claims, characterized in that at least one electric motor ( 44 ) for driving the power tool ( 20 ) is provided. Turbomachine ( 10 ) according to one of the preceding claims, characterized in that through the branch line ( 72 ) the compressor outlet pressure on the wheel back ( 76 ) of the turbine is impressed, whereby no moist exhaust gas in the region of the electric motor ( 44 ) can penetrate. This increases the electrical safety of the machine. Fuel cell device, in particular for a motor vehicle, having at least one fuel cell for converting chemically bound energy of a fuel to be supplied to the fuel cell and an oxidizing agent from the fuel cell to be supplied air into electrical energy, and with a turbomachine ( 10 ) according to one of the preceding claims for supplying the compressed air to the fuel cell.

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