BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a schematic illustration of a fuel cell system according to one embodiment of the invention.
FIG. 2 is a prospective view of selective components of a fuel cell system according to one embodiment of the invention.
FIG. 3 illustrates a reacting gas control valve according to one embodiment of the invention.
FIG. 4 illustrates a flap for a reacting gas control valve according to one embodiment of the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
The following description of the embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Referring now to FIG. 1, one embodiment of the invention includes a fuel cell system 10 including a fuel cell stack 12. The fuel cell stack 12 includes a plurality of membrane electrode assemblies, each including an ionically conductive membrane having an anode face and a cathode face. A cathode electrode overlies the cathode face and a cathode gas diffusion media overlies the cathode electrode. An anode electrode overlies the anode face and an anode gas diffusion media material overlies the anode electrode. Each membrane electrode assembly is sandwiched between a pair of bipolar plates. The bipolar plates include reacting gas flow fields formed in opposite faces thereof. The bipolar plates may further include coolant passages therethrough. A cathode inlet line 14 delivers cathode reactant gas, such as oxygen, to the fuel cell stack 12. The cathode reactant gas may be provided by air entering through conduit 18 into a humidifier 20 and thereafter pressurized by a compressor 22 before entering the fuel cell stack 12. Excess cathode reactant gas exits the fuel cell stack 12 through conduit 16. A hydrogen source 24 is provided which may be compressed hydrogen gas, liquid hydrogen, or hydrogen from fuel reformation. Optionally, the hydrogen may be provided through conduit 26 into a humidifier which humidifies the hydrogen gas prior to entering the fuel cell stack 12 through anode inlet 28. Excess hydrogen exits the fuel cell stack 12 through anode outlet 30.
Referring now to FIG. 2, one embodiment of the invention includes a fuel cell reactant gas control valve 32. The control valve 32 may be positioned in the cathode inlet line 14 or the anode inlet line 28. The arrangement of the inlet and outlet lines and the fuel cell stack are not particularly important to the present invention. In one embodiment of the invention, the cathode inlet line 14 and outlet line 16 are connected to a cathode manifold 34 which may include a divider plate 36. Air flows into the manifold 34 on one side of the divider plate 36 and through a first set of bipolar plates 38 into a turn-around manifold 40 and back through a second set of bipolar plates 42. Hydrogen gas enters an anode manifold 44 similarly constructed to the cathode manifold 34. The hydrogen flows through the second set of bipolar plates 42 and into an anode turn-around manifold 46 and back through the first set of bipolar plates 38 exiting the anode outlet conduit 30.
Referring now to FIGS. 3 and 4, one embodiment of the invention includes a fuel cell reactant gas control valve 32 including a body portion 48 having a passage 50 therethrough defined by an inner surface 52. The inner surface 52 may be formed by the body 48 or may be provided by a sleeve (not shown) received in a bore formed through the body 48. The valve 32 includes a movable part 54 having a portion constructed and arranged to block the passage 50 through the body 48. The valve 32 may be of any type known to those skilled in the art including, but not limited to, a ball valve, globe valve, gate valve, flap valve, piston valve, diaphragm valve or the like. In one embodiment of the invention, the movable part 54 includes a flapper including a stem 58 pivotally mounted to the body 48 and a flap 60 extending outwardly from the stem 58. An electric motor 100 may be attached to the stem 58 of the flapper 56 to rotate the flapper 56 from an open position allowing reacting gases to pass through the valve to a closed position wherein the passage is blocked, thereby preventing reacting gases from passing through the valve. The flap 60 includes a first face 62 and an opposite second face 64 and a side edge 66 extending therebetween. In one embodiment of the invention, the inner surface 52, first face 62, second face 64 or side edge 66 of the flapper 56 includes a hydrophobically enhanced surface. The hydrophobically enhanced surface may be provided by any of a variety of means, including mechanically roughening one of the surfaces 52, 62, 64, 66 to enhance the hydrophobic character of the surface. In another embodiment, a hydrophobic coating is deposited on at least one of the surfaces 52, 62, 64, 66. Any hydrophobic coating sufficient to increase the contact angle of the surfaces to greater than 90°, greater than 100° or greater than 150° is within the scope of the invention. In one embodiment of the invention, the hydrophobic coating includes a hard wax having a melting point greater than 100° C., or a melting point ranging from 100° C.-600° C. In various embodiments of the invention, the coating may include a polyethylene, silicone, polypropylene, polytetrafluoroethylene or nano particles. In another embodiment of the invention, the surfaces 52, 62, 64, 66 may be hydrophobically enhanced by mechanically roughening the surfaces including, for example, sandblasting, shot peening, milling, or grinding. In one embodiment of the invention, surfaces of the valve body inner surface 52 and moveable part 54 may be chemically roughened, for example, by at least one of anodic oxidation or caustic/acid treatment. In one embodiment of the invention, the hydrophobic coating is a coating including nanoparticles available from BASF Corporation under the trademark LOTUS EFFECT. In another embodiment of the invention, the hydrophobic coating is a hard wax available from Tromm GmbH under the trade names Tece-Wachs N322 FL, Polycerit PT90, and Polarwachs PT30.
In one embodiment of the invention, the body of the control valve is prewarmed, and thereafter a hot wax is applied to the inner surface 52 and the surfaces 62, 64 and 66 of the flapper. Excess wax is removed by warming the body moderately and thereafter cooling the valve. The hydrophobically enhanced surface causes water that condenses in the valve to be maintained in droplet form and thus requiring less force to float the droplets out of the valve than the force that would be required to remove water from the valve if the valve included hydrophilic surfaces.
In other embodiments of the invention, fuel cell valves having a hydrophobically enhanced surface may be employed in downstream lines (conduits), for example, in recirculation gas stream lines (conduits) or in outlet lines (conduits) to control outlet pressure or to prevent air intrusion. Further, the use of a control valve with a hydrophobically enhanced surface is not limited to fuel cell application. In other embodiments of the invention, a control valve with a hydrophobically enhanced surface may be used in any application involving wet gas streams.
The above description of embodiments of the invention is merely exemplary in nature and, thus, variations thereof are not to be regarded as a departure from the spirit and scope of the invention.
Patent Application
20080050625
