US20050100462A1

US20050100462A1 - Concentric bearing and seal arrangement of a shaft in a hydrogen system

Info

Publication number: US20050100462A1
Application number: US10/704,835
Authority: US
Inventors: Ralph Hobmeyr; Detlev Grobeis; Klaus Pfannschmidt
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 2003-11-10
Filing date: 2003-11-10
Publication date: 2005-05-12
Also published as: DE102004054100A1

Abstract

A gas compressor that compresses a gas in a fuel cell system includes a shaft having first and second ends, a first bearing rotatably supporting the shaft at the first end and a second bearing rotatably supporting the shaft between the first and second ends. A sealing arrangement is concentric with the second bearing to inhibit migration of the gas between compartments of the compressor. The gas compressor can be a compressor, blower, pump or supercharger or turbo compressor that transports the gas.

Description

FIELD OF THE INVENTION

The present invention relates to hydrogen supply systems, and more particularly to a bearing and seal arrangement for a hydrogen supply unit.

BACKGROUND OF THE INVENTION

Fuel cell systems include a fuel cell stack that produces electrical energy based on a reaction between a hydrogen-based feed gas (e.g., pure hydrogen or a hydrogen reformate) and an oxidant feed gas (e.g., pure oxygen or oxygen-containing air). The hydrogen-based feed gas and oxidant feed gas are supplied to the fuel cell stack at appropriate operating conditions (i.e., temperature and pressure) for reacting therein. The proper conditioning of the feed gases is achieved by other components of the fuel cell stack to provide the proper operating conditions.
The fuel cell system includes a compressor for compressing the hydrogen-based feed gas to an appropriate operating pressure for reaction in the fuel cell stack. The hydrogen-based feed gas inherently effects the durability of the compressor components. As a result, compressor designs attempt to limit contact between the compressor components and the hydrogen-based feed gas. Traditional compressor designs, however, include a bearing that supports an end of a shaft and that is immersed in the hydrogen-based feed gas. Further, traditional compressor designs are not optimally designed and, as a result, are less cost effective, more complex and less durable than desired.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a gas compressor to compress a gas in a fuel cell system. The gas compressor includes a shaft having first and second ends, a first bearing rotatably supporting the shaft at the first end and a second bearing rotatably supporting the shaft between the first and second ends. A sealing arrangement is concentric with the second bearing to inhibit migration of the gas between compartments of the compressor.
In one feature, the compressor further includes a compressor impeller fixed for rotation with the shaft and rotatably driven by the shaft in a compressor compartment to compress the gas.
In another feature, the gas compressor further includes an electric motor disposed in a motor compartment and engaged with the shaft to rotatably drive the shaft.
In still another feature, the compartments include a compressor compartment and a motor compartment. The sealing arrangement inhibits migration of the gas from the compressor compartment into the motor compartment. The first end of the shaft and the first bearing are disposed within the motor compartment. The second bearing is disposed within the motor compartment.
In yet another feature, the sealing arrangements includes a barrier-gas sealing system.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a functional block diagram illustrating an exemplary fuel cell system implementing a recirculation unit according to the principles of the present invention;
FIG. 2 is a cross-sectional view of the recirculation unit;
FIG. 3A is a detailed view of a concentric sealing arrangement of the recirculation according to the principles of the present invention;
FIG. 3B is a detailed view of a non-concentric sealing arrangement; and
FIG. 4 is a detailed view of a concentric barrier-gas sealing system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Referring now to FIG. 1, a functional block diagram of an exemplary fuel cell system 10 is shown. The fuel cell system 10 includes a fuel cell stack 12, a hydrogen source 14, an anode recirculation unit 16 and a cathode supply unit 20. The anode recirculation unit 16 and cathode unit 20 are generally provided as blowers or compressors. The fuel cell stack 12 produces electric current to power a load (not shown) such as an electric motor. More specifically, in the fuel cell stack 12, as hydrogen-containing feed gas flows into an anode side of the fuel cell stack 12 a catalyst facilitates separation of the hydrogen-containing feed gas into electrons and hydrogen ions (i.e., protons). The hydrogen ions pass through an electrolyte membrane and combine with oxygen in a cathode side to produce water (H₂O). The electrons, which cannot pass through the electrolyte membrane, flow from the anode side to the cathode side through an external circuit (e.g., the load). The load consumes the power generated by the fuel cell stack 12.
The hydrogen source 14 supplies the hydrogen-containing feed gas for the anode side of the fuel cell stack 12. In one embodiment, the hydrogen-containing feed gas is essentially pure hydrogen. In such a case, the hydrogen source 14 is a tank containing such hydrogen. In another embodiment, the hydrogen-containing feed gas comprises a hydrogen-containing gas mixture such as reformate that includes hydrogen as one of its components. In such a case, the hydrogen source 14 indicates a reformation system that reforms a hydrocarbon fuel to produce the hydrogen-containing reformate.
Regardless of the manner in which the hydrogen-containing feed gas is supplied, the hydrogen-containing feed gas is supplied to the anode side of the fuel cell stack 12 for reaction therein. The anode recirculation unit 16 recirculates exhaust gas exiting the fuel cell stack 12 for re-use in the fuel cell stack 12. The recirculated exhaust gas includes hydrogen, water (both liquid and vapor), nitrogen and other components. The cathode supply unit 20 compresses an oxygen-containing feed gas (e.g., air) to supply the compressed oxygen-containing feed gas to the cathode side of the fuel cell stack 12 at an appropriate pressure.
Referring now to FIG. 2, a cross-sectional view of the anode recirculation unit 16 is shown. The exhaust gas is drawn into the anode recirculation unit 16 at a suction inlet (not shown), is compressed therein and is discharged from the anode recirculation unit 16 at a discharge outlet (not shown). The anode recirculation unit 16 includes a motor compartment 22 and a compressor or blower compartment 24. The motor compartment is defined by a motor casing 26 and a housing 28. The blower compartment 24 is defined by the housing 28 and a blower casing 30. A shaft 32 is rotatably supported between the motor compartment 22 and the blower compartment 24. The shaft 32 is rotatably driven by a rotor of a motor 34 that is disposed within the motor compartment 22. A blower impeller 36 or multiple compressor impellers 36 are fixed for rotation with the shaft 32 within the blower compartment 24. Although the anode supply unit 16 is illustrated as a two-stage radial compressor it is appreciated that the anode supply unit 16 can be of any other type.
The shaft 32 is rotatably supported by first and second bearings 38,40, respectively. The first bearing 38 seats within a recess 42 of the motor casing 26 and rotatably supports a first end of the shaft 32. A blower 44 is fixed for rotation with the shaft 32. Although the blower 44 is shown fixed to a first end of the shaft 32, it is anticipated that the blower 44 can be positioned in other locations along the shaft 32. The blower 44 is induced to rotate via rotation of the shaft 32. The blower 44 induces air flow through a blower housing 46 to cool the motor compartment 22. The second bearing 40 seats within a recess 48 of the housing 28. The second bearing 40 rotatably supports the shaft 32 at an intermediate point along the length of the shaft 32.
Although the blower 44 is provided for air-cooling of the motor compartment 22, it is anticipated that the anode supply unit 16 can be water-cooled. In such a case, a water jacket (not shown) is in heat transfer relationship with the anode recirculation unit 16. Water or coolant flowing through the water jacket cools the anode recirculation unit.
A sealing system 50 is concentrically disposed about the second bearing 40. The sealing system 50 seals the blower compartment 24 to prevent leakage of hydrogen-containing feed gas through the second bearing 40 and into the motor compartment 22. The sealing system 50 illustrated in FIG. 2 is a generic sealing system that can be one of several kinds known in the art. For example, the sealing system can be a gas-barrier type sealing system discussed in further detail below and discussed in detail in commonly assigned U.S. patent application Ser. No. 10/445,420, filed May 27, 2003 and entitled Fluid Handling Device for Hydrogen-Containing Process Fluids. A pressurized barrier gas resides within the sealing system 50 and is at a higher pressure than either the pressure within the motor compartment 22 or the blower compartment 24. In this manner, the pressurized barrier gas inhibits fluid flow from the blower compartment 24, through the sealing system 50 and into the motor compartment 22. Likewise, the pressurized barrier gas inhibits fluid flow from the motor compartment 22, through the sealing system 50 and into the blower compartment 24. It is appreciated that the gas-barrier type sealing system is merely exemplary and other types of sealing systems may be implemented as the sealing system 50 and disposed concentric to the second bearing 40.
Referring now to FIGS. 3A and 3B, the advantages of the bearing and sealing system arrangement of the present invention will be discussed in detail. As illustrated in FIG. 3A, a distance X is defined between a top face of the second bearing 40 and a bottom edge of the sealing system 50. FIG. 3B illustrates a traditional, non-concentric bearing and sealing system arrangement. A distance Y is defined between a top face of the bearing and a bottom edge of the non-concentric sealing system. As is seen, the distance X is significantly shorter than the distance Y. Therefore, the shaft 32 is shorter than the shaft associated with the traditional, non-concentric bearing and sealing system arrangement.
Specific benefits are realized as a result of the shaft 32 being shorter than traditionally required. Initially, the impellers 36 are closer to the second bearing 40 which is a support point of the shaft 32. The moment in the shaft 32 created by the weight of the impellers 36 mounted thereto is decreased over that of a traditional system having impellers located further away. As a result, the shaft 32 is sufficiently supported by only the first and second bearings 38,40. A traditional arrangement, having a larger moment in the shaft, requires a third bearing to support the second end of shaft. Therefore, because a third bearing is not required, component cost is spared. Additionally, the third bearing would be disposed within the blower compartment 24 and exposed to the hydrogen-containing feed gas. Exposure to the hydrogen-containing feed gas is detrimental to the third bearing, reducing the durability of the third bearing and therefore, reducing the durability of the anode recirculation unit 16 as a whole. Because a third bearing is not required, the recirculation unit 16 of the present invention is inherently cheaper and more durable than a traditional supply unit.
Further, the bending moment through the shaft 32 is decreased as compared to the shaft of a traditional arrangement. As a result, the diameter of the shaft 32 is reduced as compared to the shaft of a traditional arrangement. This provides several distinct advantages. Initially, material cost is saved as the shaft 32 can be manufactured from less material. Further, the sizes of the first and second bearings 38,40 can be reduced. The durability of a bearing is a function of its rotational speed, time of rotation and its diameter. For a cyclically loaded supply unit, the rotational speed and time of rotation are constant (i.e., cannot be controlled to effect bearing durability). Therefore, a reduction in bearing diameter enables increased bearing durability. Thus, the concentric bearing and sealing system of the present invention enables increased bearing durability for the first and second bearings 38,40. Because smaller bearings are implemented, a further cost savings is realized.
Referring now to FIG. 4, the sealing system 50 is illustrated as a barrier-gas sealing system 50′. Implementation of the barrier-gas sealing system 50′ enables a decrease in components and a smaller packaging envelope within the recirculation unit 16 over other traditional sealing systems. The barrier-gas sealing system 50′ includes a gasket 61, a seal head 62 and an O-ring 63. A ring groove 64 is formed in a face of the seal head 62 and a passage 65 is formed therethrough to enable fluid communication between the center of the barrier gas sealing system 50′ and the ring groove 64. Although the gasket 61 is shown as providing a sealing surface between the blower compartment 24 and the barrier-gas within the sealing system 50′, the sealing system 50′ can be flipped to the motor compartment side such that the gasket 61 provides a sealing surface between the blower compartment 24 and the barrier-gas within the sealing system 50′.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims

1. A gas compressor to compress a gas in a fuel cell system, comprising:

a shaft having a first end and a second end;

a first bearing rotatably supporting said shaft at said first end;

a second bearing rotatably supporting said shaft between said first and second ends; and

a sealing arrangement concentric with said second bearing to inhibit migration of said gas between compartments of said compressor.

2. The gas compressor of claim 1 further comprising a compressor impeller fixed for rotation with said shaft and rotatably driven by said shaft in a compressor compartment to compress said gas.

3. The gas compressor of claim 1 further comprising an electric motor disposed in a motor compartment and engaged with said shaft to rotatably drive said shaft.

4. The gas compressor of claim 1 wherein said compartments include a compressor compartment and a motor compartment, wherein said sealing arrangement inhibits migration of said gas from said compressor compartment into said motor compartment.

5. The gas compressor of claim 4 wherein said first end of said shaft and said first bearing are disposed within said motor compartment.

6. The gas compressor of claim 4 wherein said second bearing is disposed within said motor compartment.

7. The gas compressor of claim 1 Wherein said sealing arrangements comprises a barrier-gas sealing system.

8. A gas compressor for compressing a hydrogen-containing gas for use in a fuel cell system, comprising:

a shaft extending between a motor compartment and a compressor compartment and having first and second ends;

a first bearing rotatably supporting said shaft at said first end within said motor compartment;

a second bearing rotatably supporting said shaft between said first and second ends;

a sealing arrangement concentric with said second bearing to inhibit migration of said hydrogen-containing gas between said motor compartment and said compressor compartment.

9. The gas compressor of claim 8 wherein said second bearing is disposed within said motor compartment.

10. The gas compressor of claim 8 further comprising a compressor impeller fixed for rotation with said shaft and rotatably driven by said shaft within said compressor compartment to compress said hydrogen-containing gas.

11. The gas compressor of claim 10 further comprising a suction inlet to enable intake of said hydrogen-containing gas into said compressor compartment and a discharge outlet to enable discharge of said hydrogen-containing gas to said fuel cell system.

12. The gas compressor of claim 8 further comprising an electric motor disposed in said motor compartment and engaged with said shaft to rotatably drive said shaft.

13. The gas compressor of claim 8 wherein said sealing arrangement comprises a barrier-gas sealing system.

14. A fuel cell system, comprising:

a fuel cell providing an exhaust gas; and

an exhaust gas compressor to compress said exhaust gas from said fuel cell and recirculate said exhaust gas to said fuel cell, said compressor comprising:

a shaft having first and second ends;

a first bearing rotatably supporting said shaft at said first end;

a sealing arrangement concentric with said second bearing to inhibit migration of said exhaust gas between compartments of said compressor.

15. The fuel cell system of claim 14 further comprising a compressor impeller fixed for rotation with said shaft and rotatably driven by said shaft in a compressor compartment to compress said exhaust gas.

16. The fuel cell system of claim 14 further comprising an electric motor disposed in a motor compartment and engaged with said shaft to rotatably drive said shaft.

17. The fuel cell system of claim 14 wherein said compartments include a compressor compartment and a motor compartment, wherein said sealing arrangement inhibits migration of said exhaust gas from said compressor compartment into said motor compartment.

18. The fuel cell system of claim 17 wherein said first end of said shaft and said first bearing are disposed within said motor compartment.

19. The fuel cell system of claim 17 wherein said second bearing is disposed within said motor compartment.

20. The fuel cell system of claim 14 wherein said sealing arrangements comprises a barrier-gas sealing system.