DE102017212821A1 - Turbomachine, in particular for a fuel cell system - Google Patents

Abstract

Turbomachine (10), in particular for a fuel cell system (1). The turbomachine (10) comprises a shaft (14), an impeller (15) and a thrust washer (30). The impeller (15) and the thrust washer (30) are arranged on the shaft (14). 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. The flow path (16) comprises an axial flow end (18) and a radial flow end (17). The thrust washer (30) faces the rear side (15b) of the impeller (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

State of the 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 turbo-compressor has a shaft drivable by a drive device. On the shaft, a compressor and an exhaust gas turbine are arranged.

In a more detailed embodiment is designed as a turbo compressor turbomachine from the published patent application DE 10 2008 044 876 A1 known. The known turbo-compressor 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, from the EP 2 006 497 A1 It is known that the shaft of turbomachinery can be axially supported by means of a thrust washer.

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 arranged in a fuel cell system.

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 can thus be made very small and space-saving. 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. Accordingly, a 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 Axiallagerscheibe thus acts such that it would push the two components axially away from each other, the respective resulting axial force has opposite signs, 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. In the radial direction, the secondary seal positions the sliding ring coaxially 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. During operation, the drive device is thus flowed by the working fluid or even flowed 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 friction 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. As a result, the respective fluidic axial forces acting on the two wheels act in the opposite direction, thus mutually compensating for one another. As a result, the seal diameter of the seal ring assembly and / or the throttle 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 passage for supplying an oxidant into the fuel cell, and an exhaust passage for discharging the oxidant from the fuel cell. The compressor is arranged in the air supply line. The air supply line serves to the inflow of the working fluid or oxidant in the fuel cell, and the exhaust pipe is used 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 turbocompressor is reduced.

The fuel cell system may preferably be configured to drive a drive device of a motor vehicle.

list of figures

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.

• 1 schematisch ein Brennstoffzellensystem mit einer als Turbokompressor ausgeführten Turbomaschine aus dem Stand der Technik,
• 2 schematisch einen Schnitt durch eine erfindungsgemäße Turbomaschine, wobei nur die wesentlichen Bereiche dargestellt sind.

Show it:

• 1 1 is a schematic view of a fuel cell system with a turbomachine of the prior art, designed as a turbo-compressor;
• 2 schematically a section through a turbomachine according to the invention, wherein only the essential areas are shown.

Detailed description of the invention

1 shows one from the DE 10 2012 224 052 A1 known fuel cell system 1 , The fuel cell system 1 includes a fuel cell 2 , an air supply line 3 , an exhaust pipe 4 , a compressor 11 , an exhaust gas turbine 13 , a bypass valve 5 for lowering the pressure and a feed line not shown in detail for fuel to the fuel cell 2 , The bypass valve 5 For example, it can be a control flap. 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 fuel supply line, not shown, and an oxidant into electrical energy, which in the embodiment shown here is intake air via the air supply line 3 the fuel cell 2 is supplied. 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 configured, for example, to drive a drive device of a motor vehicle. For example, it drives through the fuel cell 2 generated electrical energy while an electric motor of the motor vehicle.

The compressor 11 is in the air supply line 3 arranged. The exhaust gas turbine 13 is in the exhaust pipe 4 arranged. The compressor 11 and the exhaust gas turbine 13 are about a wave 14 mechanically connected. The wave 14 is from a drive device 20 electrically driven. The exhaust gas turbine 13 serves to support the drive device 20 to power the shaft 14 or of the compressor 11 , The compressor 11 , the wave 14 and the exhaust gas turbine 13 Together they form a turbomachine 10 ,

2 schematically shows a longitudinal section of a turbomachine according to the invention 10 , in particular for use in a fuel cell system 1 , The turbo machine 10 is in this embodiment as turbo compressor 10 executed and has one on the shaft 14 arranged impeller 15 on which as a compressor 11 or compressor acts. In addition, the turbomachine points 10 optionally the exhaust gas turbine 13 on which one on the shaft 14 arranged further impeller 13a includes. Preferably, the other impeller are 13a and the impeller 15 on the opposite ends of the shaft 14 positioned.

Advantageously, the turbomachine 10 in the fuel cell system 1 arranged so that the impeller 15 of the compressor 11 in the air supply line 3 is arranged and so that the further impeller 13a the exhaust gas turbine 13 in the exhaust pipe 4 is arranged.

The impeller 15 is in the execution of 2 designed as a radial runner, so in the case of use as turbo compressor or compressor 11 flows axially and flows radially. The impeller 15 points to this on his front 15a a flow path 16 on which an axial flow end 18 and a radial flow end 17 includes. As is common with a radial runner, the direction of one through the impeller changes 15 flowing working fluid in the sectional view by about 90 °. In the case of execution as turbo compressor is the impeller 15 at the axial flow end 18 flows axially from the working fluid, the working fluid then passes through the flow path 16 on the front side 15a and is compressed and then occurs at the radial flow end 17 radially out of the impeller 15 out.

On his front 15a is the wheel 15 from an inner diameter 31 up to an outside diameter 32 subjected to the pressure of the working fluid. This pressure is not constant, but increases from the inside diameter 31 to the outside diameter 32 at; This applies to the use of turbomachinery 10 both as turbo compressor and as turbine. When using the turbomachine 10 as a turbine, only the direction of the flow path is reversed 16 around, namely from the radial flow end 17 to the axial flow end 18 ; the qualitative pressure conditions on the front 15a However, they are the same as the turbocharger compressor.

The drive device 20 of the turbocompressor 10 is designed as an electric motor, between the compressor 11 and the exhaust gas turbine 13 angeorndet and includes a rotor 21 and a stator 22 , The rotor 21 is also on the wave 14 arranged. The stator 22 is stationary in a partially illustrated housing 8th of the turbocompressor 10 positioned. The housing 8th can also be made in several parts. The wave 14 is on both sides of the drive device 20 by means of a warehouse 41 . 42 rotatably mounted. The drive device 20 is between the two camps 41 . 42 positioned. At the outer ends of the shaft 14 At one end is the impeller 15 arranged and at the other end the other impeller 13a which the exhaust gas turbine 13 forms.

The turbo machine 10 also includes one on the shaft 14 arranged thrust washer 30 , The thrust washer 30 can do this, for example, on the wave 14 be pressed on, or - as in 2 shown - by means of a nut 49 with the intermediate wheel 15 against a shoulder of the shaft 14 be tense. The thrust washer 30 has a preferably hardened and ground tread 31 for the thrust bearing. In the presentation of the 2 while the mating surface for the thrust bearing is not shown; This could be, for example, an area of the housing 8th or a component inserted therein.

Furthermore, the thrust washer 30 a sliding surface 32 on, preferably the tread 31 is formed opposite. The sliding surface 32 acts with a sliding ring arrangement 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 a pressure difference during operation of the turbomachine 10 can generate.

The preferably axially symmetrical slide ring arrangement 33 includes a sliding ring 34 , a feather 35 and a secondary seal 36 , The feather 35 clamps the sliding ring 34 against the sliding surface 32 , so that in the operation of the turbomachine 10 on 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 8th and thereby preferably also positions the slip ring 34 coaxial with the shaft 14 , Here must the secondary seal 36 also not be media-tight, but can hold a pressure difference. Preferably, there is any leakage at the secondary seal 36 but significantly smaller than any leakage on the mechanical seal. The secondary seal 36 is preferably a shaft seal, so that the slip ring 34 can roll in the axial direction over the shaft seal.

According to the invention, the axial force on the tread 31 the thrust washer 30 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 is on the impeller 15 , on the thrust washer 30 and optionally on the shaft 14 , on the other impeller 13a and at others with the wave 14 connected components abuts.

• - Ein Niederdruck p₀ am axialen Strömungsende 18 des Strömungspfads 16. Fungiert das Laufrad 15 als Verdichter 11, so ist dies der Eingangsdruck bzw. der Saugdruck.
• - Ein Hochdruck p₁ am radialen Strömungsende 17 des Strömungspfads 16. Fungiert das Laufrad 15 als Verdichter 11, so ist dies der Ausgangsdruck bzw. der Förderdruck.
• - Ein Umgebungsdruck p₂ stromabwärts der Gleitringdichtung bzw. stromabwärts der Nebenabdichtung 36. Der Umgebungsdruck p₂ kann dabei beispielsweise dem Niederduck p₀ oder dem Atmosphärendruck entsprechen.

Exemplary are now in the 2 three pressures shown:

• - A low pressure p ₀ at the axial flow end 18 of the flow path 16 , Acts the impeller 15 as a compressor 11 , so this is the inlet pressure or the suction pressure.
• - A high pressure p ₁ at the radial flow end 17 of the flow path 16 , Acts the impeller 15 as a compressor 11 , so this is the output pressure or the delivery pressure.
• - An ambient pressure p ₂ downstream of the mechanical seal or downstream of the secondary seal 36 , The ambient pressure p ₂ can, for example, the Niederduck p ₀ or the atmospheric pressure.

On the mechanical seal and on the secondary seal 36 thus becomes the high pressure p ₁ to the ambient pressure p ₂ sealed, either media-tight or by leakage. The mechanical seal thus acts as a pressure divider with a sealing diameter 39 ,

At its front 15a is the wheel 15 by means of the mother 49 on the wave 14 braced. Depending on the sealing concept is this mother 49 and the subsequent end of the wave 14 also with the low pressure p ₀ applied. On the front side 15a of the impeller 15 the working fluid condenses from an inner diameter 37 up to one outer diameter 38 until the high pressure p ₁ , The high pressure p ₁ is therefore also on the tread 31 the thrust washer 30 on which the impeller 15 is facing. At the rear of the axial bearing washer 30 or on its sliding surface 32 is radially outside - outside the sealing diameter 39 - also the high pressure p ₁ on, and radially inside the ambient pressure p ₂ ,

Constructive is now the sealing diameter 39 chosen so that these pressures almost equalize, the wave 14 with their attachments so quasi pressure balanced or force balanced. The sliding surface becomes constructive 32 with regard to their surface area through the sliding ring 34 divided so that the pressure balance arises.

Due to the properties and the machining sequence of the thrust washer 30 is it possible the sliding surface 32 for a rotary seal, for example, a gas-lubricated mechanical seal 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 or by the sealing diameter 39 certainly.

In further embodiments, the pressure conditions at other wave areas and arranged thereon components are taken into account, especially if there are other pressures than the atmospheric pressure. In the execution of 2 is the example of the other impeller 13a on the wave 14 arranged, which preferably as an exhaust gas turbine 13 in the exhaust pipe 4 of the fuel cell system 1 acts. The other impeller 13a is also designed as a radial runner, so naturally also on the other impeller 13a a fluidic resulting axial force is created, which is not equal to zero. These forces including other end faces on the side of the exhaust gas turbine 13 are preferred for the design of the sealing diameter 39 considered.

In advantageous embodiments is between the slide ring assembly 33 and the sliding surface 32 a leakage gap is formed, so that a passage of the working fluid through the leakage gap is made possible. In this case, the leakage gap can be adjusted specifically to a passing mass flow to components such as the two bearings 41 . 42 or the drive device 20 to cool. Furthermore, due to the leakage gap, the two bearings 41 . 42 be lubricated with the working fluid; Preferably, the two bearings 41 . 42 to do so as gas-lubricated bearings. In addition, there may be another leakage gap at the secondary seal 36 be used for cooling and / or lubrication downstream components.

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 102012224052 A1 [0001, 0023]
• DE 102008044876 A1 [0002]
• EP 2006497 A1 [0003]

Claims (15)

Turbomachine (10), in particular for a fuel cell system (1), having a shaft (14), an impeller (15) and a thrust washer (30), the impeller (15) and the thrust washer (30) being mounted 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 axial bearing disk (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 assembly (33). Turbomachine (10) after 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 an 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). Turbomachine (10) after Claim 1 or 2 characterized in that the sealing diameter (39) is 0.4 times to 0.6 times the outer diameter (38). Turbomachine (10) after one of Claims 1 to 3 characterized in that the sealing diameter (39) is at least 2 times the inner diameter (37). Turbomachine (10) after one of Claims 1 to 4 characterized in that the sliding ring assembly (33) has a sliding ring (34), wherein preferably the sliding ring (34) by means of a spring (35) against the sliding surface (32) is tensioned. Turbomachine (10) after 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. Turbomachine (10) after Claim 5 or 6 characterized in that between the sliding ring (34) and the sliding surface (32) has a leakage gap is formed. Turbomachine (10) after 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. Turbomachine (10) after Claim 7 or 8th 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. Turbomachine (10) after Claim 9 characterized in that the drive device (20) comprises a stator (22) and a rotor (21) arranged on the shaft (14). Turbomachine (10) after 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 runner, wherein the further impeller (13a) is flowed through on its front by 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). Turbomachine (10) after one of Claims 1 to 11 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. Turbomachine (10) after one of Claims 1 to 12 characterized in that the impeller (15) is designed as a compressor (11), wherein the axial flow end (18) represent the flow input and the radial flow end (17) the flow output of the flow path (16). Fuel cell system (1) with a fuel cell (2), an air supply line (3) for supplying an oxidizing agent into the fuel cell (2) and an exhaust line (4) for discharging the oxidizing agent 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 (11), wherein the axial flow end (18) the flow input and the radial flow end (17) represent the flow output of the flow path (16), and wherein the compressor (11) in the Air supply line (3) is arranged. Fuel cell system (1) after 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.

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