FUEL CELLS AND METHODS FOR REDUCING BLOCKAGE OF CHANNELS OF FUEL CELLS

BACKGROUND Technical Field

The disclosure generally relates to fuel cells.

Description of the Related Art

Proton Exchange Membrane (PEM) fuel cells rely on water for proper operation. For instance, a well-hyd rated membrane is required for conducting protons and for extending the lifetime of the fuel cell.

During normal operation, water may be drawn through a PEM fuel cell from the anode to the cathode. Notably, the cathode also produces water. Under various conditions, water in a fuel cell can freeze, thereby negatively impacting operation of the fuel cell. For example, ice formed during a shutdown of a fuel cell can block reactant channels within the fuel cell, thereby impeding a subsequent start.

SUMMARY

Fuel cells and methods for reducing blockage of channels of fuel cells are provided. In this regard, an exemplary embodiment of a fuel cell comprises: a channel having a channel port; and an extended surface extending outwardly from the channel port, the extended surface being operative to reduce a potential for liquid to remain in the channel. In some embodiments, the extended surface may include wicking

properties incorporated therein or thereon. The wicking properties may be provided through increased hydrophilicity, as by the provision of small hydrophilic pores to utilize capillary forces.

An exemplary embodiment of a method for reducing blockage of channels of a fuel cell comprises using surface tension between a liquid and a surface of the fuel cell to assist in drawing the liquid from a channel of the fuel cell.

Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a schematic diagram depicting a portion of an exemplary embodiment of a fuel cell.

FIG. 2 is a schematic diagram depicting a portion of the fuel cell of FIG. 1 , as viewed along section line 2-2.

FIG. 3 is a schematic diagram depicting another portion of the fuel cell of FIG. 1 , as viewed along section line 3-3.

FIG. 4 is a schematic diagram depicting a portion of another exemplary embodiment of a fuel cell.

FIG. 5 is a schematic diagram depicting a portion of another exemplary embodiment of a fuel cell.

FIG. 6 is a schematic diagram depicting a portion of yet another exemplary embodiment of a fuel cell.

DETAILED DESCRIPTION

Fuel cell systems and methods for reducing blockage of channels are provided, several exemplary embodiments of which will be described in detail. In this regard, some embodiments involve the use of an extended surface or fin that reduces a tendency for water droplets to form within and obstruct a gas channel. A gas channel typically has a port for the inlet and/or outlet of gas reactant and/or water. By providing a surface that extends beyond the port of a channel, surface tension may allow the water to adhere to the extended surface and exit the channel. This is in contrast to water building up at the port and potentially adhering to the adjacent terminating ends of the channel walls that form the port.

An exemplary embodiment of a fuel cell is partially depicted in the schematic diagram of FIG. 1. As shown in FIG. 1 , fuel cell 100 is a Proton Exchange Membrane (PEM) fuel cell incorporating a membrane 102 that is oriented between catalyst layers 104, 106. The catalyst layers and membrane define a membrane electrode assembly 108. The membrane electrode assembly is positioned between opposing substrates 110, 112 that function as gas diffusion layers (GDLs).

Adjacent to substrate 110 and opposing the membrane electrode assembly is an anode structure 111 that includes an array 113 of ribs (e.g., ribs 114, 116). Channels (e.g., channel 118) are defined between the ribs. In particular, each channel of array 113 is defined by a pair of adjacent ribs, a corresponding channel wall of the anode, and a corresponding portion of substrate 110. By way of example, channel 118 is defined by ribs 114 and 116, channel wall 120, and a portion 122 of substrate 110. Notably, the channels of array 113 are anode channels, with the reactant or fuel of this embodiment that is provided to the anode channels being hydrogen or a hydrogen-rich gas.

Adjacent to substrate 112 and opposing the membrane electrode assembly is a cathode structure 121 that includes an array 123 of ribs (e.g., ribs 124, 126). Channels (e.g., channel 128) are defined between the ribs. In particular, each channel of array 123 is defined by a pair of adjacent ribs, a corresponding channel wall of the cathode, and a corresponding portion of substrate 112. By way of example, channel 128 is defined by ribs 124 and 126, channel wall 130, and a portion 132 of substrate 112. In this embodiment, the channels of array 123 are cathode channels with the reactant provided to the cathode channels being air. Notably, during operation, water can be present in any of the anode channels and the cathode channels, each of which typically is rectangular in cross section and exhibits a width of approximately 1 mm and a height of approximately 0.5 mm. Notably, various other dimensions can be used.

As shown in FIGS. 2 and 3, in order to reduce the potential for water present in a channel from remaining in that channel and potentially freezing therein, an extended surface (e.g., surface 150 or surface 170) is provided. In general, such a surface can be provided by an extended surface of a rib and/or wall that defines a channel. Notably,

an extended surface (or fin) is a surface that extends outwardly beyond a channel port, which is formed by adjacent walls, substrates and/or ribs that generally terminate in a plane oriented perpendicular to the walls, substrates and/or ribs. Thus, such an extended surface protrudes outwardly beyond such a plane of a corresponding channel outlet. In some embodiments, the extended surface protrudes outwardly between approximately 1 mm and approximately 5 mm, preferably between approximately 2 mm and approximately 4 mm, beyond the plane of a channel outlet.

By providing an extended surface, water present in the channel may tend to adhere to the extended surface and, therefore, fail to adhere to the surfaces forming the channel that are located inboard of the channel outlet. As such, the water may drain from the channel, particularly in those embodiments in which channel orientation allows forces experienced by the channel to assist in drawing water from the channel. For instance, the ability for an extended surface to facilitate water being drawn from a channel may be enhanced in those embodiments in which the extended surface is oriented beneath the channel outlet so that gravity can assist in drawing the water out of the channel. Additionally or alternatively, the velocity of reactant moving through the channel may provide sufficient pressure to urge the water onto the extended surface and away from the interior of the channel. Still further, the extended surface may include wicking properties incorporated therein or thereon, as will be described in greater detail herein after.

As shown in FIG. 2, fuel cell 100 incorporates a surface 150 that extends outwardly from port 152 of anode channel 118. Notably, surface 150 is associated with a corresponding rib. Specifically, surface 150 is a first surface of an extension 154 of rib

116. Although associated with a rib in the embodiment of FIGS. 1 and 2, in other embodiments, extended surfaces can additionally or alternatively be formed from a wall, and/or a substrate defining a channel.

Extension 154 is located between adjacent anode channels. So configured, extension 154 can potentially prevent water 160 from accumulating in the ports of more than one anode channel. That is, in this embodiment, extension 154 includes surface 150, which is associated with channel 118, and an opposing surface 162, which is associated with channel 119, with the surfaces potentially preventing water from accumulating in the corresponding ports.

As shown in FIG. 3, fuel cell 100 also incorporates a surface 170 that extends outwardly from port 172 of cathode channel 128. Notably, surface 170 is associated with a corresponding rib. Specifically, surface 170 is a first surface of an extension 174 of rib 126. Although associated with a rib in this embodiment, in other embodiments, extended surfaces can additionally or alternatively be formed from a wall, and/or a structure defining a channel.

Extension 174 is located between adjacent cathode channels. So configured, extension 174 can potentially prevent water 180 from accumulating in the ports of more than one cathode channel. That is, in this embodiment, extension 174 includes surface 170, which is associated with channel 128, and an opposing surface 182, which is associated with channel 129, with the surfaces potentially preventing water from accumulating in the corresponding ports.

FIG. 4 is a schematic diagram depicting a portion of another exemplary embodiment of a fuel cell. In particular, FIG. 4 depicts a structure 202 that supports an

array of ribs (e.g., ribs 204, 206 and 208). Channels are located between the ribs. For instance, channel 210 is located between ribs 204 and 206, and channel 212 is located between ribs 206 and 208. Notably, the channels are reactant channels that are representative of either cathode or anode channels.

In the embodiment of FIG. 4, extensions associated with the ribs are provided for preventing water from accumulating in the ports of the channels. By way of example, extensions 214 and 218 extend from ribs 204 and 208, respectively. Thus, water present in channel 210 may tend to adhere to surface 224 of extension 214, and water present in channel 212 may tend to adhere to surface 228 of extension 218. Notably, in the embodiment of FIG. 4, alternating ribs are associated with extensions; however, various other arrangements of extensions can be used in other embodiments.

A portion of another exemplary embodiment of a fuel cell is depicted schematically in FIG. 5. As shown in FIG. 5, a structure 232 supports an array of ribs (e.g., ribs 234, 236 and 238), with reactant channels being located between the ribs. For instance, channel 240 is located between ribs 234 and 236, and channel 242 is located between ribs 236 and 238.

In the embodiment of FIG. 5, an extension 250 is provided for preventing water from accumulating in the ports of the channels. In this regard, extension 250 is configured as an extended portion of structure 232, which forms the ribs. As such, the extension provides a surface 252 located adjacent multiple channels. Thus, water present in each of the channels may tend to adhere to surface 252. Notably, although the extension in this embodiment spans the entire width of the array of channels, various other arrangements, such as those that are separately formed from the

substrate and those that involve spans of less than the entire width of channels, can be used in other embodiments.

Further referring to FIG. 5, at least the surface 252, or alternatively the entirety of extension 250, may be provided with or constituted of, a wicking material 254. The wicking material will tend to draw water from inside the channels to the exterior, which exterior may be the air manifold. The wicking material 254 is characteristically formed of small, wettable pores, which are smaller than the corresponding pores in the adjoining base materials relative to which it is to have increased wicking properties. The small pores of the wicking material 254 are of controlled size such that capillary forces are relied upon to provide the wicking action and thus assist in the removal of water from the channels. The porous wicking material 254 may constitute some or all of the extension 250, and results in increased hydrophilicity of the body or surface

FIG. 6 depicts a portion of another exemplary embodiment of a fuel cell. In particular, FIG. 6 depicts a structure 260, which forms an array of channels and ribs (e.g., channel 262 and rib 264). An extension 266 is provided for preventing water from accumulating in the ports of the channels. In contrast with the embodiment of FIG. 5, in which the extension is formed from the same structure that provides the ribs, extension 266 of the embodiment of FIG. 6 is formed by a portion of the substrate or gas diffusion layer (GDL) 270, which overlies (or, in other embodiments, may underlie) the ribs and channels.

It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the

above-described embodiments without departing substantially from the spirit and principles of the disclosure. It should be understood that although the provision of a structure or surface having increased wicking properties is discussed only in the context of the embodiment of FIG. 5, increased wicking properties are also applicable to other embodiments as well. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.