Patent Publication Number: US-2005130011-A1

Title: Fuel cell system

Description:
RELATED APPLICATION  
      This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/517,225 filed on Oct. 31, 2003 and entitled “Dual Compressor System.” The entire disclosure of this provisional application is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to a fuel cell system and, more particularly, to a system wherein an oxygen-containing gas is fed to the cathode chamber of a fuel cell and a hydrogen-containing gas is fed to its anode chamber.  
     BACKGROUND OF THE INVENTION  
      A fuel cell comprises a cathode chamber, an anode chamber, and an electrolyte (or ion-conducting) separator positioned therebetween. During operation of the fuel cell, an oxygen-containing gas passes through the cathode chamber, a hydrogen-containing gas passes through the anode chamber, and the hydrogen reacts with the oxygen to generate electricity. The oxygen-containing gas can be atmospheric air which is fed through the cathode chamber via an air compressor. The hydrogen-containing gas can be produced by feeding, via another compressor, a gas through a reformer and then feeding the reformed gas through the anode chamber. Also, exhaust from the anode chamber can be recirculated, via a fluid-handler, back through the anode chamber.  
      Accordingly, a fuel cell system will include compressors and other fluid-handlers which supply gases to the cathode/anode chambers. In such a system, it is important that lubricating liquids not be introduced into the cathode chamber and/or the anode chamber, as such lubricants can poison the electrolyte or otherwise harm effective electricity-generating reactions. Thus, a fuel cell system will include compressors and/or other fluid-handlers wherein the fluid-contacting components do not use lubrication.  
     SUMMARY OF THE INVENTION  
      The present invention provides a fuel cell system wherein a single motor is used to supply both cathode gas to the fuel cell&#39;s cathode chamber and anode gas to its anode chamber. This single-motor supply reduces the system cost, complexity, and power consumption. Moreover, this dual cathode/anode supply can be accomplished, at a high efficiency, without liquid lubrication of gas-contacting components.  
      More particularly, the present invention provides a fuel cell system comprising a fuel cell and a fluid-supplying device. The fuel-supplying device includes a first fluid-handler (e.g., a first compressor), a second fluid-handler (e.g., a second compressor), and a motor. The first fluid-handler supplies a cathode gas to the cathode chamber of the fuel cell and the second fluid-handler supplies an anode gas to its anode chamber. The motor can be an electric motor and, in any event, drives both the first compressor&#39;s rotor and the second compressor&#39;s rotor.  
      The fluid-handlers can each comprise a stator surface concentrically positioned around a stator axis, and the rotor can be positioned within the space defined by the stator surface for eccentric rotation therein about a rotor axis. The fluid handlers can each also comprise a vane which, upon rotation of the rotor, is rotated about the stator axis. During this rotation, the tip of the vane follows a close, but non-contacting, path around the stator surface. This travel path of the vane can accomplish effective interface sealing without the use of lubricants.  
      These and other features of the invention are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative of but one of the various ways in which the principles of the invention may be employed.  
    
    
     DRAWINGS  
       FIG. 1  is a schematic drawing of a fuel cell system incorporating a fluid-supplying device according to the present invention.  
       FIG. 2  is a schematic drawing of another fuel cell system incorporating a fluid-supplying device according to the present invention.  
       FIGS. 3, 4  and  5 , are front, side, and top views, respectively, of the fluid-supplying device.  
       FIG. 6  is a sectional view as seen along line  6 - 6  in  FIG. 5 . 
    
    
     DETAILED DESCRIPTION  
      Referring now to the drawings, and initially to  FIGS. 1 and 2 , a fluid-supplying device  10  according to the present invention is shown in a fuel cell system  12 . The fuel cell system  12  comprises a fuel cell  14  having a cathode chamber  16   c , an anode chamber  16   a , and an electrolyte (or ion-conducting) separator  18  positioned therebetween. During operation of the fuel cell  14 , a cathode gas (e.g., an oxygen-containing gas) passes through the cathode chamber  16   c , an anode gas (e.g., a hydrogen-containing gas) passes through the anode chamber  16   a , and the gasses react to generate electricity.  
      The illustrated fuel cell  14  includes an inlet  20   c  into and an outlet  22   c  out of the cathode chamber  16   c , and an inlet  20   a  into and an outlet  22   a  out of the anode chamber  16   a . As shown in  FIG. 1 , the fuel cell system  12  can also comprise a reformer  24  which is positioned upstream of the fuel cell  14  and which includes an inlet  26  through which a non-reformed fluid is provided. The non-reformed fluid is reformed into the hydrogen-containing gas which is then supplied to the anode outlet  22   a.    
      It should be noted that the fuel cell system  12  is shown only schematically in the drawings and can include other components upstream and downstream of the fuel cell  14 . For example, the system  12  can include a carbon monoxide eliminator downstream of the reformer  24 , and/or vaporizer upstream of the reformer  24 . A mixing tank, a regulator, a pump, and/or valving can be provided downstream of the fuel tank and upstream of the reformer  24 . A condenser, a radiator, an ion-exchanger, drains, valving, or other components can be provided for the handling of the exhaust from the outlets  22 . As for the fuel cell  14 , the simplicity of the illustration is for ease in explanation only, as it could comprise a plurality of cathode/anode chambers  16  and a plurality of separators  18  stacked or otherwise assembled to provide the desired generation of electricity.  
      The fluid-supplying device  10  supplies, directly and/or indirectly, the fuel cell  14  with oxygen and hydrogen for the generation of electricity. For example, in  FIG. 1 , the fluid-supplying device  10  feeds atmospheric air (or another oxygen-containing gas) through the cathode chamber  16   c  and also feeds non-reformed fuel through the reformer  24 . In  FIG. 2 , the fluid-supplying device  10  feeds atmospheric air (or another oxygen-containing gas) through the cathode chamber  16   c  and recirculates exhaust from the anode outlet  22   a  back to the anode inlet  20   a . As is explained in more detail below, the device  10  accomplishes this dual supply with a single motor (namely motor  32 , introduced below) and with effective non-lubrication interface sealing between fluid-contacting components.  
      Referring now to  FIGS. 3-6 , the fluid-supplying device  10  is shown in detail. The fluid-supplying device  10  comprises a cathode-side compressor  30   c , an anode-side compressor  30   a , and a motor  32  positioned therebetween. ( FIGS. 3, 5  and  6 .) It may be noted that the compressors  30  each resemble the fluid-handlers set forth in U.S. Pat. Nos. 5,087,183; 5,160,252; 5,374,172, 6,503,071; and/or 6,623,261, and the entire disclosure of these patents is hereby incorporated by reference.  
      The cathode-side compressor  30   c  comprises a stator housing  40   c  forming a cylindrical space  42   c  defined by a continuous inner surface  44   c  which curves concentrically around an axis  46   c . ( FIG. 6 .) An inlet fitting  48   c  and an outlet fitting  50   c  are mounted on the housing  40   c  and communicate with the space  42   c . ( FIGS. 3 and 5 .) In the illustrated embodiment, the stator housing  40   c  comprises a cylindrical side wall  52   c , an inner (i.e., motor adjacent) end wall  54   c , and an outer (i.e., motor remote) end wall  56   c . ( FIGS. 3, 5  and  6 .) A bracket  58   c  can be provided to mount the stator housing  40   c  to the floor or another suitable platform. ( FIGS. 3-6 .)  
      The compressor  30   c  also comprises a rotor shaft  60   c  and a rotor  62   c . ( FIG. 6 .) The rotor shaft  60   c  is rotatably mounted to the stator housing  40   c  and, during operation of the device  10 , is driven by the motor  32  to rotate about an axis  64   c . The rotor axis  64   c  is parallel with, but spaced a predetermined distance from, the stator axis  46   c  so that the rotor  62   c  can be eccentrically positioned within the stator space  42   c . ( FIG. 3, 4  and  5 .) The rotor shaft  60   c  includes a motor-coupling portion  66   c  which extends through the end wall  54   c  and into the motor  32 . ( FIG. 6 .) The cylindrically-shaped rotor  62   c  is mounted to the shaft  60   c  for rotation therewith and includes a vane-receiving slot  72   c . ( FIG. 6 .)  
      The compressor  30   c  further comprises a single vane  74   c  having an axial dimension corresponding to that of the rotor  62   c , cross-sectional dimensions corresponding to the rotor slot  72   c , and a radial dimension corresponding to the stator surface  44   c . ( FIG. 6 .) Annular bearing guides  76   c , concentric with the stator axis  46   c , are mounted on the housing end walls  54   c / 56   c , and their rotating races are joined by connecting rods  78   c . ( FIG. 6 .) The vane  74   c  is slidably received within the rotor slot  72   c  and connected to the guides  76   c  via one of the connecting rods  78   c . ( FIG. 6 .) In this manner, rotation of the rotor  62   c  about the axis  64   c  results in rotation of the vane  74   c  about the stator axis  46   c  and the vane&#39;s tip  80   c  follows a non-contacting and interface-sealing path around the stator surface  44   c.    
      The anode-side compressor  30   a  can comprise the same components as the cathode-side compressor  30   c  and like reference numerals (with an “a” rather than a “c” suffix) are used to designate like parts. The rotor axis  64   c  of the cathode-side compressor  30   c  is coextensive with the rotor axis  65   a  of the anode-side compressor  30   a  and, preferably the stator axes  46   c  and  46   a  are also coextensive. ( FIGS. 3 and 5 .) In the illustrated embodiment, the axial length of the space  42   c  defined by the stator surface  44   c  of the cathode-side compressor  30   c  is substantially equal to the axial length of the space  42   a  defined by the stator surface  44   a  of the second compressor  30   a . ( FIGS. 3, 5  and  6 .) However, the axial dimension of the stator spaces  42  can be the same, or varied, as the relationship therebetween will at least partially dictate the correlation between cathode/anode flow conditions.  
      The illustrated motor  32  is an electric motor that comprises a stator  82 , a rotor  84 , a coupling ring  86  attached to the rotor  84  via connectors  88 , and a casing  90  surrounding these components. ( FIG. 6 .) The compressors&#39; motor-coupling rotor portions  66   c / 66   a  extend into the casing  90  with their ends abutting therewithin. ( FIG. 6 .) The casing  90  acts as a bridge which connects the stator housings  40   c / 40   a  together and joins the fluid handlers  30   c / 30   a  and the motor  32  into a single unit. Within the casing  90 , the cathode-side shaft portion  66   c  extends through, is connected to, and rotates with the rotor  84 ; and the anode-side shaft portion  66   a  extends through, is connected to, and rotates with the coupling ring  86 . ( FIG. 6 .) The connectors  88  can be cylindrical elements received within aligned bores in the rotor  84  and the ring  68 , and can be made of firm, but resilient material (e.g., rubber) to allow a small degree of give between the respective shafts  60   c / 60   a . Suitable lubricant may be provided within the motor casing  90  and suitable sealing may be provided to prevent escape of any lubricant into the stator housings  40   c / 40   a  of the compressors  30   c / 30   a.    
      Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent and obvious alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. For example, the rotor shafts  60   c / 60   a  could be replaced with a rotor single shaft and/or the motor  32  could be a non-electric mechanism. Also, the fluid-supplying device  10  need not be used in a fuel cell system  12  and/or with a fuel cell  14 , as it may find application in other compressor situations where lubricating liquids would be harmful and even in situations where lubrication can be tolerated. Moreover, the fluid-handlers  30   c  and  30   a  can function as both expanders and compressors, depending upon which the fixture  48 / 50  is used as the inlet/outlet. In fact, one component  30   c / 30   a  could function as a compressor while the other component  30   a / 30   c  functions as an expander.  
      One may now appreciate that the present invention provides a fluid-supplying device  10  that can be used to supply an oxygen-containing gas to a cathode chamber  16   c  and a hydrogen-containing gas to the anode chamber  16   a  of a fuel cell  14 . The device  10  accomplishes this dual supply with a single motor  32  and with effective non-lubrication sealing within compressor components  30   c  and  30   a.