WO2019020285A1

WO2019020285A1 - Turbomachine, in particular for a fuel cell system

Info

Publication number: WO2019020285A1
Application number: PCT/EP2018/066409
Authority: WO
Inventors: Felix WIEDMANN
Original assignee: Robert Bosch Gmbh
Priority date: 2017-07-26
Filing date: 2018-06-20
Publication date: 2019-01-31
Also published as: CN110959073A; CN110959073B; DE102017212821A1

Abstract

The invention relates to a turbomachine (10), in particular for a fuel cell system (1). The turbomachine (10) comprises a shaft (14), an impeller wheel (15) and an axial bearing disk (30). The impeller wheel (15) and the axial bearing disk (30) are mounted on the shaft (14). The impeller wheel (15) is designed as a radial impeller, and a working fluid can flow through the impeller wheel (15) on the front side (15a) along a flow path (16). The flow path (16) comprises an axial flow end (18) and a radial flow end (17). The axial bearing disk (30) faces the rear side (15b) of the impeller wheel (15). A sliding surface (32) formed on the axial bearing disk (30) and facing away from the rear side (15b) interacts with a sliding ring arrangement (33).

Description

description

title

Turbomachine, in particular for a fuel cell system

PRIOR ART Turbomachines designed as turbocompressors for a fuel cell system are known from the prior art, for example from the published patent application DE 10 2012 224 052 A1. The known turbocompressor has one of a

Drive device driven shaft on. On the shaft, a compressor and an exhaust gas turbine are arranged.

In a more detailed embodiment, a turbomachine designed as a turbocompressor is known from the published patent application DE 10 2008 044 876 A1. The known

Turbocompressor has an impeller arranged on a shaft. The impeller is designed as a radial runner, so is flowed through on its front by a working fluid along a flow path, wherein the flow path comprises an axial flow end and a radial flow end.

Furthermore, it is known from EP 2 006 497 A1 that the shaft of turbomachinery can be axially supported by means of an axial bearing disk.

Disclosure of the invention

The turbomachine according to the invention has a reduced axial force acting on the shaft. For this purpose, the forces acting on the shaft or on the components connected to it, which act through the working fluid, are influenced by a slide ring arrangement such that the shaft is preferably pressure-balanced or force-balanced in the axial direction. Preferably, the turbomachine is in one

Fuel cell system arranged. For this purpose, the turbomachine comprises a shaft, an impeller and a thrust washer. The impeller and the thrust washer are arranged on the shaft. The impeller is designed as a radial runner, wherein the impeller is flowed through on its front by a working fluid along a flow path. The flow path includes an axial flow end and a radial flow end. The thrust washer faces the rear of the impeller. A formed on the thrust washer and facing away from the back sliding surface cooperates with a sliding ring assembly.

As is common in turbomachinery, a smaller axial force resulting from the working fluid acts on the front of the impeller than on the rear of the impeller. This excess force on the rear side is compensated or limited on the axial bearing disk by generating different resultant axial forces on both sides as well. This is done by the pressure distribution on the slip ring assembly, which thus acts as a pressure divider. That is, on one side of the axial bearing disk - namely the side facing away from the impeller - the pressure acting on the working fluid is reduced. The axial force acting on the shaft is thus compensated or limited or minimized, so that the performance and durability of corresponding thrust bearings is optimized. Preferably, in an operation of the turbomachine, the resultant axial force acting on the shaft by the working fluid is almost zero. Consequently, the shaft is almost pressure-balanced or force-balanced in the axial direction. The working fluid acts directly or indirectly on the shaft, for example via the front and rear sides of the impeller and the thrust washer. Due to the low resulting axial force or thrust bearings for the shaft thus very small and

Space-saving running. Furthermore, this also minimizes the wear on the axial bearings and thus increases the service life of the entire turbomachine.

In advantageous developments, the sliding surface and the sliding ring arrangement form a mechanical seal with a sealing diameter. The sealing diameter is larger than an inner diameter of the impeller at the axial flow end; and the

Sealing diameter is smaller than an outer diameter of the impeller at the radial flow end. Thus, the pressure on the sliding surface is divided into two: a comparatively high pressure is applied to the radially outer region, which preferably corresponds to the pressure at the radial flow end. And a comparatively low pressure is applied to the inner region, which may correspond, for example, to the atmospheric pressure. A Consequently, the running surface of the axial bearing disk assigned to the impeller and opposite the sliding surface is completely loaded with the comparatively high pressure of the radial flow end. Tread and sliding surface can also be referred to as the front and back of the thrust washer. The fluid pressure on the impeller and the thrust washer thus acts so that it would push the two components axially away from each other, the respective resulting axial force has

opposite sign, but preferably has almost the same amount. The mechanical seal does not have to be media-tight, but can also form a leakage gap, which has a throttle function.

In advantageous embodiments, the sealing diameter for this purpose is 0.4 times to 0.6 times the outside diameter. Alternatively or additionally, the sealing diameter is at least 2 times the inner diameter. As a result, the shaft is frictionally balanced in the axial direction.

In advantageous developments, the sliding ring arrangement has a sliding ring.

Preferably, the sliding ring is biased by a spring against the sliding surface. The sliding ring and the thrust bearing disc can thus tribologically very low, so usually with a mutually very low friction coefficient, are designed. The application of force by the spring ensures that even at high speeds of rotation of the shaft, the sliding ring does not lift too far from the sliding surface. As a result, the function of the pressure division is guaranteed even at high speeds.

Advantageously, the slide ring assembly is arranged in a housing. The slip ring is mounted in the housing by means of a secondary seal. Preferably, this is the single or multi-part housing of the turbomachine. Due to the bearing of the sliding ring on the secondary seal, which is preferably designed as a shaft seal, the sliding ring is mounted quasi floating. Positioned in the radial direction

Secondary seal the sliding ring coaxial with the shaft. In the axial direction of the sliding ring can roll over the secondary seal, so that axial tolerances and shifts can be compensated.

In advantageous developments, a leakage gap is formed between the sliding ring and the sliding surface. The sliding ring therefore does not have to be impermeable to the sliding surface in terms of media, but rather to realize a throttling function in order to be able to act as a pressure divider. Thus, a defined mass flow of the working fluid can flow through the leakage gap and lubricate downstream components and / or cool.

In advantageous embodiments, at least one bearing is arranged on the side of the slide ring arrangement opposite the axial bearing disk. The at least one bearing supports the shaft rotatable. The at least one bearing can be flowed by the working fluid flowing through the leakage gap. During operation, the bearing is thus flowed by the working fluid or even flows through it and thereby cooled and / or lubricated. In advantageous embodiments, the bearing is designed as a gas-lubricated bearing.

In advantageous embodiments, at least one drive device is arranged on the side of the slide ring arrangement opposite the axial bearing disk. The

Drive device can be flowed by the working fluid flowing through the leakage gap. In operation, the drive device is thus of the working fluid

flows through or even flows through and thereby cooled and / or lubricated. In advantageous embodiments, the drive device comprises a stator and a rotor arranged on the shaft, so it is designed as an electric motor. The cooling of the electric motor, in particular of the stator, increases the efficiency of the electric motor. In advantageous embodiments, the impeller is designed as a compressor. The axial flow end thus represents the flow input of the flow path, and the radial flow end of the flow output of the flow path. Accordingly, the impeller is flowed axially during operation and flows radially. For the compressor or turbocompressor a drive device is required. The reduced axial force on the shaft and thus on the axial bearing is minimized by the placement of the slide ring assembly or the sliding ring, so that corresponding

Frictional losses are minimized. Consequently, the required drive power of the drive device is reduced and the turbo compressor designed accordingly energy efficient.

In advantageous developments, another impeller is arranged on the shaft. The other impeller is also designed as a radial runner. The further impeller can be flowed through on its front side by the working fluid along a further flow path, wherein the further flow path comprises an axial flow end and a radial flow end. The axial flow end of the further impeller is opposite to the axial flow end of the impeller. This effect the Respective fluidic axial forces acting on the two wheels in the opposite direction, thus compensate each other to a part.

Consequently, the sealing diameter of the slide ring assembly and / or the

Throttling effect of the leakage gap can be reduced. This also reduces the wear on the seal ring assembly, especially the wear between the seal ring and sliding surface.

In advantageous uses, the turbomachine is arranged in a fuel cell system. The turbomachine is designed as a turbo compressor or the impeller as a compressor, wherein the axial flow end of the flow input and the radial flow end represent the flow output of the flow path. The fuel cell system includes a fuel cell, an air supply line to

Supplying an oxidizing agent into the fuel cell and an exhaust pipe for discharging the oxidizing agent from the fuel cell. The compressor is arranged in the air supply line. The air supply line serves for the inflow of the working fluid or oxidizing agent into the fuel cell, and the exhaust gas line serves to remove the oxidizing agent or the reacted oxidizing agent or a mixture thereof from the fuel cell. The turbocompressor is designed according to one of the embodiments described above. In particular, in the embodiments with leakage gap, the turbocompressor can be cooled so effectively.

In advantageous developments, the fuel cell system has an exhaust gas turbine with a further impeller. The further impeller is also arranged on the shaft. The exhaust gas turbine is arranged in the exhaust pipe. Preferably, the further impeller of the exhaust gas turbine is arranged opposite to the impeller of the turbocompressor, so that the respective effective resulting axial forces on the two wheels partially compensate each other. The reacted working fluid or oxidizing agent flowing out of the fuel cell can be used very effectively as a power source for the exhaust gas turbine; As a result, the required drive power of the

Drive device for the turbo compressor reduced.

The fuel cell system may preferably be adapted to a

Drive drive device of a motor vehicle. Brief description of the drawings

Further optional details and features of the invention will become apparent from the following description of preferred embodiments, which are shown schematically in the figures.

Show it:

1 shows schematically a fuel cell system with a turbocharger compressor

executed turbomachine from the prior art,

Figure 2 schematically shows a section through a turbomachine according to the invention, wherein only the essential areas are shown.

Detailed description of the invention

1 shows a fuel cell system 1 known from DE 10 2012 224 052 A1. The fuel cell system 1 comprises a fuel cell 2, an air supply line 3, an exhaust pipe 4, a compressor 1 1, an exhaust gas turbine 13, a bypass valve 5 for pressure reduction and a feed line not shown in detail for fuel to the fuel cell 2. The bypass valve 5, for example, a control valve his. As a bypass valve 5, for example, a wastegate valve can be used. The fuel cell 2 is a galvanic cell that converts chemical reaction energy of a fuel supplied via the not shown fuel supply line and an oxidizing agent into electric energy shown in FIG

Embodiment is intake air, which is supplied via the air supply line 3 of the fuel cell 2. The fuel may preferably be hydrogen or methane or methanol. Accordingly, the exhaust gas is water vapor or water vapor and carbon dioxide. The fuel cell 2 is set up, for example

Drive drive device of a motor vehicle. For example, the electrical energy generated by the fuel cell 2 drives an electric motor of the

Motor vehicle on. The compressor 1 1 is arranged in the air supply line 3. The exhaust gas turbine 13 is arranged in the exhaust pipe 4. The compressor 1 1 and the exhaust gas turbine 13 are mechanically connected via a shaft 14. The shaft 14 is electrically driven by a drive device 20. The exhaust gas turbine 13 serves to support the drive device 20 for driving the shaft 14 or the compressor 11. The compressor 1 1, the shaft 14 and the exhaust gas turbine 13 together form a turbomachine 10.

2 schematically shows a longitudinal section of a turbomachine 10 according to the invention, in particular for use in a fuel cell system 1. The turbomachine 10 is designed in this embodiment as a turbocompressor 10 and has an arranged on the shaft 14 impeller 15, which acts as a compressor 1 1 and compressor.

In addition, the turbomachine 10 optionally has the exhaust gas turbine 13, which comprises a further impeller 13a arranged on the shaft 14. Preferably, the further impeller 13 a and the impeller 15 are positioned on the opposite ends of the shaft 14.

Advantageously, the turbomachine 10 is arranged in the fuel cell system 1, so that the impeller 15 of the compressor 1 1 is arranged in the air supply line 3 and so that the further impeller 13a of the exhaust gas turbine 13 is arranged in the exhaust pipe 4.

The impeller 15 is executed in the embodiment of Figure 2 as a radial rotor, so in the case of use as turbo compressor or compressor 1 1 flows axially and flows radially. The impeller 15 has on its front side 15a to a flow path 16, which comprises an axial flow end 18 and a radial flow end 1. As is usual with a radial runner, the direction of a working fluid flowing through the impeller 15 changes by approximately 90 ° in the sectional view. In the case of execution as a turbo compressor, the impeller 15 at the axial flow end 18 of the

Working fluid flows axially, the working fluid then passes through the flow path 16 on the front side 15 a and is thereby compressed and then occurs at the radial

Flow end 17 radially out of the impeller 15.

On its front side 15 a, the impeller 15 is acted upon by the pressure of the working fluid from an inner diameter 31 to an outer diameter 32. In this case, this pressure is not constant, but increases from the inner diameter 31 to

Outer diameter 32 on; this applies to the use of the turbomachine 10 both as Turbocompressor as well as turbine. When using the turbomachine 10 as a turbine, only the direction of the flow path 16 is reversed, namely from the radial flow end 17 to the axial flow end 18; however, the qualitative pressure ratios on the front side 15a are the same as those of the turbo-compressor.

The drive device 20 of the turbocompressor 10 is designed as an electric motor, angeorndet between the compressor 1 1 and the exhaust gas turbine 13 and includes a rotor 21 and a stator 22. The rotor 21 is also arranged on the shaft 14. The stator 22 is stationarily positioned in a partially illustrated housing 8 of the turbocompressor 10. The housing 8 can also be designed in several parts. The shaft 14 is rotatably mounted on both sides of the drive device 20 by means of a respective bearing 41, 42. The drive device 20 is positioned between the two bearings 41, 42. At the outer ends of the shaft 14, the impeller 15 is disposed at one end and the other impeller 13 a, which forms the exhaust gas turbine 13 at the other end.

The turbomachine 10 further includes a shaft 14 disposed on the shaft

Axial bearing washer 30. For this purpose, the axial bearing washer 30 can be pressed onto the shaft 14, for example, or - as shown in FIG. 2 - be braced against a shoulder of the shaft 14 by means of a nut 49 with the impeller 15 being interposed. The thrust washer 30 has a preferably hardened and ground running surface 31 for the thrust bearing. In the illustration of Figure 2 while the mating surface for the thrust bearing is not shown; This could be, for example, a surface of the housing 8 or a component inserted therein. Furthermore, the thrust washer 30 has a sliding surface 32, which is preferably formed opposite the running surface 31. The sliding surface 32 acts with a

Slider assembly 33 together, preferably such that they form a gas-lubricated mechanical seal. The mechanical seal does not have to be made media-tight, but may have a leak. However, it is important that they have one

Pressure difference during operation of the turbomachine 10 can generate.

The preferably axially symmetrical slide ring assembly 33 comprises a slide ring 34, a spring 35 and a secondary seal 36. The spring 35 biases the slide ring 34 against the sliding surface 32, so that during operation of the turbomachine 10 at the mechanical seal there is a pressure difference from outside to inside; usually this is a pressure gradient. The secondary seal 36 acts between the sliding ring 34 and the housing 8 and preferably also positioned by the sliding ring 34 coaxial with the shaft 14. Here, the secondary seal 36 also does not have to be media-tight, but can hold a pressure difference. Preferably, however, any leakage at the secondary seal 36 is significantly smaller than any leakage at the mechanical seal. The secondary seal 36 is preferably a shaft sealing ring, so that the sliding ring 34 can roll in the axial direction over the shaft sealing ring.

According to the invention, the axial force on the running surface 31 of the thrust washer 30 is reduced by the mechanical seal. This reduction takes place during operation of the turbomachine 10 with the working fluid of the turbomachine 10, more precisely with the pressure of the working fluid, which on the impeller 15, on the thrust washer 30 and optionally on the shaft 14, on the further impeller 13 a and on the other with the shaft 14th connected components abuts. By way of example, three pressures are shown in FIG.

- A low pressure p ₀ at the axial flow end 18 of the flow path 16. If the impeller 15 acts as a compressor 1 1, this is the inlet pressure or the suction pressure.

- A high-pressure pi at the radial flow end 17 of the flow path 16. Fungiert the impeller 15 as a compressor 1 1, this is the output pressure or the discharge pressure.

- An ambient pressure p2 downstream of the mechanical seal or downstream of the secondary seal 36. The ambient pressure p2 can, for example, the

Niederduck p _o or correspond to the atmospheric pressure. At the mechanical seal and at the secondary seal 36, the high pressure pi is thus sealed to the ambient pressure p2, either media-tight or by means of leakage. The mechanical seal thus acts as a pressure divider with a sealing diameter 39.

On its front side 15 a, the impeller 15 is braced by means of the nut 49 on the shaft 14. Depending on the sealing concept, this nut 49 and the adjoining end of the shaft 14 are also subjected to the low pressure p _o . On the front side 15a of the impeller 15, the working fluid is compressed from an inner diameter 37 to an outer diameter 38 to the high pressure pi. The high-pressure pi is thus also on the running surface 31 of the thrust washer 30, which faces the impeller 15. At the back of the thrust washer 30 or at its sliding surface 32nd is radially outward - ie outside the sealing diameter 39 - also the high pressure pi, and radially inward the ambient pressure p2.

Structurally, the sealing diameter 39 is now selected so that these pressures almost equalize, the shaft 14 with its attachments so quasi pressure equalized or

balanced force. In terms of design, the sliding surface 32 is thus subdivided with respect to its surface area by the sliding ring 34 in such a way that the pressure balance is created.

Due to the properties and the machining sequence of the thrust washer 30, it is possible for the sliding surface 32 for a rotary seal, such as a

gas-lubricated mechanical seal to represent, optionally just with a leakage gap. The remaining axial force on the shaft 14 is determined by the diameter of the sliding ring 34 and by the sealing diameter 39. In further developments, the pressure conditions at other

Wavelengths and arranged thereon components considered, especially if there are other pressures than the atmospheric pressure. 2, the further impeller 13a is arranged on the shaft 14 by way of example, which is preferably arranged as an exhaust gas turbine 13 in the exhaust pipe 4 of the

Fuel cell system 1 acts. The further impeller 13a is also designed as a radial rotor, so that naturally also on the further impeller 13a, a fluidic axial force arises, which is not equal to zero. These forces including further end faces on the side of the exhaust gas turbine 13 are preferably taken into account for the design of the sealing diameter 39.

In advantageous embodiments, a leakage gap is formed between the sliding ring arrangement 33 and the sliding surface 32, so that a passage of the working fluid through the leakage gap is made possible. Here, the leakage gap targeted to a

passing mass flow are adjusted to cool components such as the two bearings 41, 42 or the drive device 20. Furthermore, due to the

Leckagespalts the two bearings 41, 42 are lubricated with the working fluid;

Preferably, the two bearings 41, 42 are designed as gas-lubricated bearings. In addition, a further leakage gap on the secondary seal 36 can be used for cooling and / or lubrication of downstream components.

Claims

Claims 1. Turbomachine (10), in particular for a fuel cell system (1), with a shaft

(14), an impeller (15) and a thrust washer (30), wherein the impeller (15) and the thrust washer (30) on the shaft (14) are arranged, wherein the impeller

(15) is designed as a radial runner, wherein the impeller (15) on its front side (15 a) of a working fluid along a flow path (16) can be flowed through, wherein the flow path (16) has an axial flow end (18) and a radial

Flow end (17), wherein the thrust washer (30) faces the rear side (15b) of the impeller (15),

characterized in that

a sliding surface (32) formed on the axial bearing disk (30) and facing away from the rear side (15b) cooperates with a sliding ring arrangement (33).

2. Turbomachine (10) according to claim 1

characterized in that

the sliding surface (32) and the sliding ring arrangement (33) form a mechanical seal with a sealing diameter (39), wherein the sealing diameter (39) is greater than one

Inner diameter (37) of the impeller (15) at the axial flow end (18) and wherein the sealing diameter (39) is smaller than an outer diameter (38) of the impeller (15) at the radial flow end (17).

3. Turbomachine (10) according to claim 1 or 2

characterized in that the sealing diameter (39) is 0.4 times to 0.6 times the outer diameter (38).

4. Turbomachine (10) according to one of claims 1 to 3

characterized in that the sealing diameter (39) is at least 2 times the inner diameter (37).

5. Turbomachine (10) according to one of claims 1 to 4

characterized in that

the sliding ring assembly (33) has a sliding ring (34), preferably the

Sliding ring (34) by means of a spring (35) against the sliding surface (32) is tensioned.

6. turbomachine (10) according to claim 5

characterized in that the sliding ring assembly (33) in a housing (8) is arranged, wherein the sliding ring (34) by means of a secondary seal (36) in the housing (8) is mounted.

7. Turbomachine (10) according to claim 5 or 6

characterized in that between the sliding ring (34) and the sliding surface (32) has a leakage gap is formed.

8. turbomachine (10) according to claim 7

characterized in that on the axial bearing disc (30) opposite side of the slide ring assembly (33) at least one bearing (41, 42) is arranged, which rotatably supports the shaft (14), wherein the at least one bearing (41, 42) of the Working fluid can be flowed against.

9. turbomachine (10) according to claim 7 or 8

characterized in that on the axial bearing disc (30) opposite side of the seal ring assembly (33) at least one drive device (20) is arranged, wherein the drive device (20) can be flowed by the working fluid.

10. Turbomachine (10) according to claim 9

characterized in that the drive device (20) comprises a stator (22) and a rotor (21) arranged on the shaft (14).

1 1. Turbomachine (10) according to one of claims 1 to 10

characterized in that a further impeller (13a) on the shaft (14) is arranged, wherein the further impeller (13a) is designed as a radial rotor, wherein the further impeller (13a) is flowed through on its front side of the working fluid along a further flow path wherein the further flow path comprises an axial flow end and a radial flow end, wherein the axial flow end of the further impeller (13a) opposite to the axial

Flow end (18) of the impeller (15) is.

12. Turbomachine (10) according to one of claims 1 to 1 1 characterized in that in an operation of the turbomachine (10), the resultant axial force acting on the shaft (14) from the working fluid is nearly zero.

13. Turbomachine (10) according to one of claims 1 to 12

characterized in that the impeller (15) as a compressor (1 1) is carried out, wherein the axial flow end (18) represent the flow input and the radial flow end (17) the flow output of the flow path (16).

14. A fuel cell system (1) with a fuel cell (2), an air supply line (3) for supplying an oxidant in the fuel cell (2) and an exhaust pipe (4) for discharging the oxidant from the fuel cell (2), characterized in that the Fuel cell system (1) a turbomachine (10) according to one of claims 1 to 13, wherein the impeller (15) is designed as a compressor (1 1), wherein the axial flow end (18) the

Flow inlet and the radial flow end (17) represent the flow output of the flow path (16), and wherein the compressor (1 1) in the

Air supply line (3) is arranged.

15. Fuel cell system (1) according to claim 14, wherein the fuel cell system (1) has an exhaust gas turbine (13) with a further impeller (13a), wherein the further impeller (13a) is arranged on the shaft (14), wherein the exhaust gas turbine ( 13) in the exhaust pipe (4) is arranged.