The present invention relates to a device for supplying air to fuel cells as defined in more detail in the preamble of Claim 1.
A device according to the definition of the species for supplying air to fuel cells is known from DE 197 55 116 C1. Air is supplied to the fuel cell via a compressor and is subsequently expanded in an expander. The expander is operated by the exhaust air of a catalytic burner which is also situated downstream from the fuel cell.
Frequently problematic in these known air supply units is the fact that the fuel cell cannot be supplied with enough air and that, in addition, the compressors and the expanders have low efficiencies.
A pump for generating pressure or partial vacuum is known from WO 00/57062 A1.
The object of the present invention is to provide a device for supplying air to fuel cells which has a simple design and operates effectively.
According to the present invention, this object is achieved by the features recited in Claim 1.
The compressors and expanders of the device according to the present invention for supplying air to fuel cells, which are designed according to the present invention as claw compressors and claw expanders having compressor wheels and expander wheels, enable very high compression ratios and thus a very good fresh air supply to the fuel cell. At the same time, they have a simple design and function reliably.
Advantageous embodiments and refinements of the present invention arise from the subclaims as well as from the exemplary embodiment schematically illustrated in the drawing below.
Device 4 has a compressor 5 situated upstream from fuel cell 1 and an expander 6 situated downstream from fuel cell 1. The type of connection of compressor 5 and expander 6 to fuel cell 1 is not explicitly shown; it may, however, be established via standard lines.
As is also apparent in
The arrows denoted with the letter “A” indicate the respective rotational direction of compressor wheels 7, 7′ and expander wheels 9, 9′. It is thus apparent that compressor 5 and expander 6 have the same rotational direction. However, in order to achieve compression from pressure P1 to pressure P2 in compressor 5 and an expansion from pressure P3 to pressure P4 in expander 6, compressor 5 and expander 6 have a mirror-inverted configuration.
Pressure ratios P2/P1 and P3/P4 are predefined in the present case by the geometry of compressor wheels 7, 7′ and expander wheels 9, 9′, i.e., by the design of compressor 5 and expander 6; they may, however, also be adjustable via a mechanism (not shown).
As is apparent in
In the described device 4, which represents a combination of compressor 5 and expander 6, the gas compressed in compressor 5 is supplied to expander 6 where residual energy is extracted from the gas via expansion. Due to the common mount, expander 6 supplies the reclaimed power directly to the two shafts 15 and 15′, thereby reducing the power of drive motor 19 required for compressor 5.
As is apparent in
The separation of the delivery volumes of the two compressor wheels 7, 7′ results in an isochoric transport of the gas toward the pressure side, i.e., outlet 12. Step d) shows the combination of the two volumes which is associated with compression. However, the gas cannot exit compressor 5 since lower compressor wheel 7′ seals outlet 12. Only when outlet 12 is opened, as is shown in step e), is the pre-compressed gas able to be pushed out, as is shown in step f). In this way, the gas is compressed from pressure P1 to pressure P2 and transported toward fuel cell 1.
It is apparent in
Relatively simple manufacturing methods may be used for manufacturing compressor wheels 7, 7′ and expander wheels 9, 9′, since, in contrast to helical compressors, for example, the geometry of compressor wheels 7, 7′ and expander wheels 9, 9′ is not twisted in the axial direction. Since the compression, as described above, takes place radially rather than in the axial direction, the length or width of compressor wheels 7, 7′ and expander wheels 9, 9′ is smaller than their diameter so that a compact design may be implemented, in particular when compressors and expanders have a multi-stage design. Such a multi-stage design may be utilized to implement greater pressure differences or to achieve independent volume flows under different individual pressures.
Number | Date | Country | Kind |
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10258363.3 | Dec 2002 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE03/04042 | 12/9/2003 | WO | 1/6/2006 |