Note: Descriptions are shown in the official language in which they were submitted.
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EDGE MANIFOLD ASSEMBLY FOR
AN ELECTROCHEMICAL FUEL CELL STACR
Field Of The Invention
The present invention relates to
electrochemical fuel cells. More particularly, the
present invention relates to an assembly of edge
manifold plates mounted on the sides of an
electrochemical fuel cell stack. The edge manifold
assembly directs the reactant and coolant streams
along the perimeter of the stack, and selectively
introduces and removes the reactant and coolant
streams to and from the individual fuel cells_
Backcrround Of The Invention
Electrochemical fuel cells convert fuel and
oxidant to electricity and reaction product. Solid
polymer electrochemical fuel cells generally employ
a membrane electrode assembly ("MEA") consisting of~
a solid polymer electrolyte or ion exchange
membrane disposed between two electrodes formed of
porous, electrically conductive sheet material,
typically carbon fiber paper. The MEA contains a
layer of catalyst, typically in the form of finely
comminuted platinum, at each membrane/electrode
interface to induce the desired electrochemical
reaction. The electrodes are electrically coupled
~ to provide a path for conducting electrons between
. 25 the electrodes to an external load. .
At the anode, the fuel permeates the porous
electrode material and reacts at the catalyst layer
to form rations, which migrate through the membrane
to the cathode. At the cathode, the oxygen-
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containing gas supply reacts at the catalyst layer
to form anions. The anions formed at the cathode
react with the cations to form a reaction product.
In electrochemical fuel cells employing
hydrogen as the fuel and oxygen-containing air (or
substantially pure oxygen) as the oxidant, the
catalyzed reaction at the anode produces hydrogen
cations (protons) from the fuel supply. The ion
exchange membrane facilitates the migration of
hydrogen ions from the anode to the cathode. In
addition to conducting hydrogen ions,~the~membrane
isolates the hydrogen-containing fuel stream from
the oxygen-containing oxidant stream. At the
cathode, oxygen reacts at the catalyst layer to
form anions. The anions formed at the cathode
react with the hydrogen ions that have crossed the
membrane to form liquid water as the reaction
product. The anode and cathode reactions in
hydrogen/oxygen fuel cells are shown in the
following equations:
Anode reaction: Hz -3 2H+ + 2e-
Cathode reaction: 1/202 + 2H' + 2e- ~ HZO
In typical fuel cells, the MEA is disposed
between two electrically conductive plates, each of
which has at least one flow passage engraved.or ~ .
milled therein. These fluid flow field plates are
. atypically formed of graphite. The flow passages. ,
direct the fuel and oxidant to the respective
. ~ electrodes, namely, the anode on the fuel side and
the cathode on the oxidant side. In a single cell
arrangement, fluid flow field plates are provided
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on each of the anode and cathode sides. The plates
act as current collectors, provide support for the .
electrodes, provide access channels for the fuel
V
and oxidant to the respective anode and cathode
surfaces, and provide channels for the.removal of
water formed during operation of the cell.
Two or more fuel cells can be connected
together, generally in series but sometimes in
parallel, to increase the overall power output of
the assembly. In series arrangements, one side of
a given plate serves as an anode plate for one cell
and the other side of the plate can serve as the
cathode plate for the adjacent cell. Such a series
connected multiple fuel cell arrangement is
referred to as a fuel cell stack, and is usually
held together in its assembled state by tie rods
and end plates. The stack typically includes_
manifolds and inlet ports for directing the fuel
(substantially pure hydrogen, methanol reformate or
natural gas reformate) and the oxidant
(substantially pure oxygen or oxygen-containing
air) to the anode and cathode flow field channels.
The stack also usually includes a manifold and
inlet port for directing the coolant fluid,
typically water, to interior channels within the
stack to absorb heat generated by the exothermic
reaction of hydrogen and oxygen within the fuel
cells. The stack also generally includes exhaust
manifolds and outlet ports for expelling the
unreacted fuel and oxidant gases, each carrying
entrained water, as well as an exhaust manifold and
outlet port for the coolant water exiting the
stack.. It is generally convenient to locate all of
the inlet and outlet ports at the same end of the
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stack.
In conventional electrochemical fuel cell -
stacks employing solid polymer ion exchange
membranes, the manifolds for directing reactants
- 5 and products to and from the individual fuel cells' .
are formed by aligning a series of manifold
openings or perforations formed at~the interior of -
the reactant flow field plates. For example,
Watkins et al. U.S. Patent No. 5,108,849 discloses,
in FIG. 4 and the accompanying text, a reactant
fluid flow field plate having a plurality of
openings formed at the corners, including a fluid
supply opening and a fluid exhaust opening. Each
channel formed in the Watkins flow field plate
includes an inlet end directly connected to the
fluid supply opening and an outlet end directly
connected to the fluid exhaust opening. The
channels direct the reactant gas stream from the
supply opening to the central, electrocatalytically
active area of the fuel cell. When multiple fluid
flow field plates are arranged in a stack, each of
fluid supply and exhaust openings aligns with the . .
corresponding opening in the adjacent plates to
form a manifold for directing the reactant fluid
25, stream through the extent of the stack.
In other types of conventional duel cell
stacks, primarily those employing liquid
electrolytes, the manifolds for directing reactants.
and products to and from the individual fuel cells
are located in a frame surrounding the cell plates.
For example, in Uline U.S. Patent No. 3,278,336, a
frame having apertures formed in its upper and
lower marginal portions introduces reactant gas and
electrolyte to the electrode and discharges
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reactant gas and electrolyte from the electrode.
Erickson U.S. Patent No. 3,615,838, Warszawski
_ _ U.S. Patent No. 3,814,631, Bellows U.S. Patent No.
4,346,150, Alfenaar U.S. Patent No. 4,403,018,
Romanowski U.S. Patent No. 4,743,518, and Okada
U.S. Patent No. 4,943,495 disclose additional
examples of conventional fuel cell stacks in which
the manifolds for directing reactants and products
to and from the individual fuel cells are located
in a frame surrounding the cell plates. Frame
manifold structures have inherent disadvantages in
that (1) frame manifold structures increase the
overall volume of the fuel cell stack, (2) frame
manifold structures are generally expensive to
manufacture and/or mold, (3) frame manifold
structures generally employ complicated and
potentially inefficient sealing schemes to isolate
the reactant and electrolyte streams from each
. other, from the electrochemically active region of
the fuel cell, and from the external environment,.
and (4) frame manifold structures impede access to
the interior stack components, such as the fuel
cells themselves and associated structures such as
bus plates.
Summary Of The Invention .
An improved edge manifold assembly is provided
for an electrochemical fuel cell stack comprising a.
plurality of fuel cells. The assembly comprises ~a_
plurality of manifold plates. Each of the fuel
cells has at least two manifold plates attached
thereto. Each of the manifold plates has at least
one manifold opening formed therein for containing
a fluid and has at least one channel formed therein
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for effecting fluid communication between the
manifold opening and the fuel cell to which each of
the manifold plates is attached.
In a first preferred embodiment, the at least
two manifold plates is a pair of manifold plates.
In this embodiment, each of the fuel cells is
preferably substantially rectangular in cross
section and each of the pair of manifold plates is
preferably disposed on opposite sides of each of
the fuel cells. Each of the fuel cells is most
preferably substantially square in cross section.
In a second preferred embodiment, each of the
fuel cells is substantially rectangular in cross
section and the at least two manifold plates is
three manifold plates each disposed on a different
side of each of the fuel cells. Each of the fuel
cells is most preferably substantially square in
cross section.
In a third preferred embodiment, each of the
fuel cells is substantially rectangular in cross
section and the at least two manifold plates is
four manifold plates each disposed on a different
side of each of the fuel cells. Each of the fuel
cells is most preferably substantially square in
cross section.
In the preferred edge manifold assembly, each
of the manifold plates has a tube mounted~within
each of the at least one channel. The tube extends
from the manifold plate into the fuel cell to which
the manifold plate is attached. The tube is ~-
preferably metallic.
In the preferred edge manifold assembly, the
at least one channel comprises a plurality of
spaced channels for effecting fluid communication
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~ _:. . . ... , ..
between the manifold opening and the fuel cell to
which the manifold plates are attached. The
channels preferably extend through each of the
manifold plates substantially in parallel. The at
least one manifold opening is preferably formed
such that the channels extend through each of the
manifold plates substantially the same distance.
In the preferred edge manifold assembly, each
of the manifold plates has a recessed portion
formed in one surface thereof. The recessed
portion substantially circumscribes the at least
one manifold opening, and a notched portion extends
from the oppositely facing surface thereof, such
that the notched portion, extends into the recessed
~5 portion of the adjacent manifold plate. A sealing
gasket is preferably disposed within the recessed
portion such that the notched portion of the
adjacent manifold plate compresses the sealing
gasket.
In the preferred edge manifold assembly, the
manifold plates are formed from an electrically
insulating material.
In an alternative embodiment of an edge
manifold assembly for an electrochemical fuel cell
stack comprising a plurality of fuel cells, the
assembly comprises a plurality of manifold plates,
and each of the fuel cells has a single manifold
plate attached thereto. The manifold plate has at
least one manifold opening formed therein for
containing a fluid and has a least one channel
formed therein for effecting fluid communication
between the manifold opening and the fuel cell to
which the manifold plate is attached. The manifold
plates does not completely circumscribe the fuel
~,~;E~I~ED SHEET
~PEI~/EP
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cell to which the manifold plate is attached. Each
of the fuel cells is preferably polygonal in cross
section.
An improved electrochemical fuel cell stack
w . 5 comprises a plurality of fuel cells. Each of the
' fuel cells has a single manifold plate or at least
two manifold plates attached thereto. Each of the
manifold plates has at least one manifold,opening
formed therein for containing a fluid and has at
least one channel formed therein for effecting
fluid communication between the manifold opening
and the fuel cell to which each~of the manifold
plates is attached.
Brief Description Of The Drawings
FIG. 1 is a side elevation view of an
electrochemical fuel cell stack array having an
edge manifold assembly associated with each of the
stacks.
FIG. 2 is a top view, looking downwardly, of
the electrochemical fuel cell stack array
illustrated in FIG. 1.
FIG. 3 is a side sectional vievi of a portion
of one of the stacks of the electrochemical fuel
cell stack array illustrated in FIGS. 1 and 2.
FIG. 4 is a perspective view of a fluid flow
field plate with a pair of edge~manifold plates .
attached thereto. '
FIG. 5 is an exploded_perspective view of the.
fluid flow field plate with a pair of edge manifold
., 30 plates attached thereto, illustrated in assembled
form in FIG. 4. -
.FIG. 6 is a plan view of the top surface of
' one of the pair of edge manifold plates illustrated
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_ g _
in FIGS. 4 and 5.
FIG. 7 is a plan view of the bottom surface of
the edge manifold plate illustrated in FIG. 6.
FIG. 8 is a side elevation view of the edge
manifold plate illustrated in FIGS. 6 and
FIG. 9 is a perspective view of the edge
manifold plate illustrated in FIGS. 6-8, broken to
illustrate the channel for effecting fluid
communication between the manifold opening and a
flow channel of the fluid flow field plate to which
the manifold plate is attached.
FIG. 10 is a side sectional view of the edge
manifold plate taken along the broken surface
illustrated in FIG. 9.
FIG. 11 is a plan view of the sealing gasket
accommodated in the recessed portion of the edge
manifold plate illustrated in FIG. 7.
FIG. 12 is a perspective view of a fluid flow
field plate with a single edge manifold plate
attached thereto along one side.
FIG. 13 is an exploded perspective view of~the
fluid flow field plate with a single edge manifold.
plates attached thereto along one side, illustrated
in assembled form in FIG. 12.
FIG. 14 is a perspective view of a fluid flow
field plate with a single edge manifold plate
attached thereto along two sides.
FIG. 15 is a perspective view of a fluid flow
field plate with a single,edge manifold.plate .
' ' 30 attached thereto along three sides.
_ FIG. 16 is a perspective view of a fluid flow
- field plate with a pair of edge manifold plates
attached thereto, each edge manifold plate having a
single interior manifold opening for conducting a
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reactant or coolant stream which communicates with
the fuel cell to which the manifold plate is
attached.
FIG. 17 is an exploded perspective view of the
fluid flow field plate with a pair of edge manifold
plates attached thereto, illustrated in assembled
form in FIG. 16.
FIG. 18 is a perspective view of a fluid flow
field plate with three noncontiguous edge manifold
plates attached thereto along three sides.
FIG. 19 is an exploded perspective view of the
fluid flow field plate with three noncontiguous edge
manifold plates attached thereto, illustrated in
assembled form in FIG. 18.
FIG. 20 is a perspective view of a fluid flow
field plate with four noncontiguous edge manifold
plates attached thereto along four sides.
FIG. 21 is an exploded perspective view of the
fluid flow field plate with four noncontiguous edge
manifold plates attached thereto, illustrated in
assembled form in FIG. 20.
Detailed Descrit~t3.on of Z'he Preferred Embodiments
Turning first to FIG. 1, an electrochemical
fuel cell stack array 10 includes four fuel cell
stacks, two of which are illustrated in FIG. 1 as
stacks 12a and 12b. Each stack is in turn composed
of a plurality of individual fuel cells, one of
which is designated in FIG. 1 as fuel cell 14. A
fuel cell stack 10 is more completely described in
Watkins et al. U.S. Patent No. 5,200,278 (i.n FIGS.
1-6 and the accompanying text). A preferred
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reactant supply and control system for fuel cells of
the type which make up stack array 10 is described
in Merritt et al. U.S. Patent No. 5,366,821.
As shown in FIG. l, the inlet reactant
(preferably a hydrogen-containing fuel stream and an
oxygen-containing oxidant stream) and coolant
streams are directed to stack array 10 by external
inlet manifolds, 16, 18, 20. Each of the inlet
reactant and coolant streams is in turn directed to
the individual stacks by a plurality of inlet
manifold conduits. The inlet manifold conduit for
directing the reactant stream from external inlet
manifold 16 to stack 12a is designated in FIG. 1 as
inlet manifold conduit 16a.
As further shown in FIG. l, the outlet reactant
and coolant streams are directed from the individual
stacks by a plurality of outlet manifold conduits.
The outlet manifold conduit for directing the
reactant stream from stack 12a to external outlet
manifold 22 is designated in FIG. 1 as manifold
conduit 22a. Each of the outlet reactant and
coolant streams is in turn directed from stack array
10 by external outlet manifolds 22, 24, 26.
FIG. 2 is a top view of stack array 10, showing
each of the four fuel cell stacks 12a, 12b, 12c,
12d, as well as the external inlet manifolds 16, 18,
20 for directing the inlet reactant and coolant
streams to stack array 10. Inlet manifold conduit
16a directs the reactant stream from external inlet
manifold 16 to stack 12a.
FIG. 3 is a side view of a portion of one of
the stacks of the fuel cell stack array 10
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illustrated in FIGS. 1 and 2. As shown in FIG. 3,
- ' a plurality of individual fuel cells 14 are
arranged in a stacked series between bus plates
102, 104. The stack includes a blank plate 106
. 5 having major surfaces 106a, 106b which are
substantially planar and blank (ungrooved, i.e., no
flow channels are milled therein). Bottom surface
106b of blank plate 106 is located adjacent to and
above bottom bus plate 104.
Each cathode plate 108 has a top surface 108a
T which has formed therein at least one, and
preferably a plurality of, oxidant flow channels
(not shown in FIG. 3). Cathode plate 108 also has
a bottom major surface 108b which has formed
. 15 therein at least one coolant flow channel (not
shown in FIG. 3). Surface 108b faces the top
surface 106a of blank plate 106 such that surfaces
106a and lOBb cooperate to form a cooling jacket.
A coolant fluid directed through the cooling jacket
2Q controls the temperature of the surrounding
components of the stack.
As further shown in FIG. 3, the stack includes
a plurality of membrane electrode assemblies (MEAs)
110, each of which preferably comprises a solid
25 polymer ion exchange membrane interposed between a
cathode which faces surface 108a of cathode plate
108 and an anode which~faces upwardly in FIG. 3.
Surface 108a cooperates with the cathode of MEA 110
to direct an oxidant stream across the surface of
. ~ 30 MEA 110. The cathodes in the stack are oriented so
that product water formed by the electrochemical
reaction at the.cathode is urged downwardly by -
gravity into the oxidant stream flowing through the
channels formed in surface 108a of cathode plate
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108.
Each anode plate 112 has a bottom surface 112b
which has formed therein at least one, and
' preferably a plurality of, fuel flow channels (not
shown in FIG. 3). Surface 112b cooperates with the
anode of MEA 110 to direct a fuel stream across the
surface of MEA 110. Anode plate 112 also has a top
major surface 112a which is substantially planar
and blank (ungrooved, i.e., no channels are milled
therein). Surface 112a of anode plate 112 faces
the bottom surface 108b of the next adjacent plate
108 such that surfaces 112a and 108b cooperate to
form a cooling jacket.
The above construction of fuel cells 14,
comprising cathode plate 108, MEA 110 and anode
plate 112, repeats as the stack extends from the
bottom to the top of FIG. 3. An end cell plate 114
is located adjacent to and above the uppermost
anode plate 112 of the stack. End cell plate 114
2.0 has a bottom major surface 114b which has formed
therein at least one coolant flow channel (not
shown in FIG. 3).. Surface 114b faces the top
surface 112a of the uppermost anode plate 112 such
that surfaces 112a and 114b cooperate to form a
cooling jacket. Top surfaces 114a of end cell
plate 114 is substantially planar and blank
(ungrooved, i.e., no flow channels are milled
therein). Top surface 114a of end cell plate 114
is located adjacent to and just below top bus plate
' ~ 30 102.
A first assembly of stacked edge manifold
plates, some of which are designated in FIG. 3 as
edge manifold plates 120, is attached to the outer
perimeter of the fuel cells 14. The first assembly
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of edge manifold plates 120 directs the inlet
reactant and coolant streams along the outer
perimeter of the fuel cells and introduces the
inlet reactant and coolant streams to the
~5 appropriate portion of the,fuel cell, namely, the .
. hydrogen-containing fuel stream to the surface of
the anode plate containing the fuel flow channels,
the oxygen-containing oxidant stream to the surface
of the cathode plate containing the oxidant flow
channels, and the coolant stream to the surface of
the cathode plate containing the coolant flow
channels.
Each of the edge manifold plates 120 includes
interior manifold openings for conducting the
reactant and coolant streams and channels for
effecting fluid communication between the interior
manifold openings and the fuel cell to which the
manifold plate is attached. Each of the edge
manifold plates 120 has a recessed portion 120a
formed in the upper surface thereof, as shown in
FIG. 3. The recessed portion 120a substantially
circumscribes each of the manifold openings. A
notched portion 120b extends from oppositely facing
surface of edge manifold plate 120. When
.25 assembled, the notched portion 120b extends into
the recessed portion 120a of the adjacent manifold
plate. Sealing gaskets 122 are disposed within the
recessed portion 120a of each of the edge manifold
plates 120 such that the notched portion 120b of
the adjacent manifold plate compresses the sealing . --
.- gaskets 122.
The manifold plates are preferably formed from -
a moldable, electrically insulating material, such
as a thermoset or thermoplastic material with
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_ electrically insulating properties. The notch
angle of the notched portion is preferably between
about 30° and about 60°, such that a uniform seal
between the notched portion and the adjacent
sealing gasket is imparted when assembled.
A second assembly of edge manifold plates (not.
shown in FIG. 3), substantially identical to the
first assembly of edge manifold plates 120, is
attached to the opposite side of each of the fuel
cells 14. The second assembly of edge manifold
plates receives the outlet reactant and coolant
streams from the appropriate portion of the fuel
cell, namely, the fuel flow channels of the anode
plate and the oxidant and coolant flow channels of
the cathode plate.
FIGS. 4 and 5 show, in assembled and exploded
views, respectively, a cathode plate 108 with a
pair of edge manifold plates 120, 120' attached
thereto. Edge manifold plates 120, 120' are
substantially identical in construction, but one .
conducts and introduces the inlet reactant and
coolant streams to the appropriate portion of the
fuel cell while the other receives and conducts the
outlet reactant and coolant streams from the
25. appropriate portion of the fuel cell, as explained
below.
FIGS. 4 and 5 show the surface 108b of cathode
plate 108 which has formed therein four ~oolaiZt
flow channels 162. Coolant flow channels 162
- 30 extend in a continuous, serpentine, substantially
parallel pattern between coolant inlet opening 154
and coolant outlet_ opening 158 formed in plate 108.
Gasket 161 mounted in a corresponding recess on the
surface 108b circumscribes the inlet and outlet
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openings formed in cathode plate 108, as well as
the coolant flow field on the surface 108b of
cathode plate 108. The underside of cathode plate
108 contains four oxidant flow channels (not shown
in FIGS. 4 and 5) which also extend in a
continuous, serpentine, substantially parallel
pattern between an oxidant inlet opening and an
oxidant outlet opening formed in cathode plate 108.
Cathode plate 108 is designed to cooperate with an
adjacent anode plate (not shown in FIGS. 4 and 5,
but shown and described in FIG. 3 and the
accompanying text as anode plate 110). The
- adjacent anode plate has a blank surface facing
surface 108b and an oppositely facing surface with
-- 15 two fuel flow channels which extend in a
- continuous, serpentine, substantially parallel
pattern between a fuel inlet opening aligned with
opening 152 and a fuel outlet opening aligned with
opening 156 formed in cathode plate 108.
Edge manifold plate 120 has a fuel manifold
opening 132, a coolant manifold opening 134, and an
oxidant manifold opening 136 formed therein, as
shown in FIGS. 4 and 5. A notched portion 120b of ,
the plate 120 circumscribes oxidant manifold
opening 136 and compresses the sealing gaskets
disposed in the recessed portion of the adjacent
edge manifold plate to isolate opening 13'6 from
cathode plate 108 and from the external
environment. Alignment openings 138 are also
formed in edge manifold plate 120. -
As shown in FIG. 5, two channels 172 formed in
plate 120 effect fluid communication between the
. fuel manifold opening 132 and the fuel inlet
opening 152 in cathode plate 108. Tubes 142,
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preferably metallic and most preferably formed of
stainless steel, are mounted within the two fuel
channels 172. When assembled, tubes 142 extend
w from plate 120 into cathode plate 108.
As further shown in FIG. 5, four channels 174
formed in plate 120 effect fluid communication
between the coolant manifold opening 134 and the
coolant inlet opening 154 in cathode plate 108.
Tubes 144, preferably metallic and most preferably
formed of stainless steel, are mounted within the
four coolant channels 174. When assembled, tubes
144 extend from plate 120 into cathode plate 108.
Similarly, four channels 176 formed in plate 120
effect fluid communication between the oxidant
manifold opening 136 and the oxidant inlet opening
(not shown in FIGS. 4 and 5) on the underside of
plate 108. Tubes 146, preferably metallic and most
preferably formed of stainless steel, are mounted
within the four oxidant channels 176. When
assembled, tubes 146 extend from plate 120 into
cathode plate 108.
As shown in FIGS. 4 and 5, edge manifold plate
120' is attached to cathode plate 108 on the side
opposite that to which edge manifold plate 120 is
attached. Edge manifold plate 120' has a fuel
manifold opening 132', a coolant manifold opening
134', and an oxidant manifold opening 136'.formed
therein. A notched portion 120b' of plate 120'
circumscribes oxidant manifold opening 136' and
compresses the sealing gaskets disposed in the
recessed portion of the adjacent edge manifold
plate to isolate opening 136' from cathode plate
108 and from the external. environment. Alignment
openings 138' are also formed in edge manifold
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plate 120'.
As shown in FIG. 5, two channels 172' formed
in plate 120 effect fluid communication between the ,
fuel manifold opening 132' and the fuel outlet '
. 5 opening 156 in cathode plate 108. Tubes 142',
preferably metallic and most preferably formed of
stainless steel, are mounted within the two fuel
channels 172'. When assembled, tubes 142' extend
from plate 120' into channels 186 in cathode plate
108, as shown in FIG. 5.
Four channels 174' formed in plate 120' effect
fluid communication between the coolant manifold
opening 134' and the coolant outlet opening 158 in
cathode plate 108. Tubes 144', preferably metallic
and most preferably formed of stainless steel, are
mounted within the four coolant channels 174'.
When assembled, tubes 144' extend from plate 120'
into channels 184 in cathode plate 108. Similarly,
four channels 176' formed in plate 120 effect fluid
communication between the oxidant manifold opening
136' and the oxidant outlet opening (not shown in
FIGS. 4 and 5) on the underside of plate 108.
Tubes 146', preferably metallic and most preferably
- formed of stainless steel, are mounted within the
four oxidant channels 176'. When assembled, tubes
146' extend from plate 120' into channels 182
cathode plate 108. .
Edge manifold plates 120, 120' are preferably
attached to the opposite edges of cathode plate 108
by an adhesive, but other methods of attachment .
, could be employed as well. The adhesive is
preferably applied at the adjoining edges of
cathode plate 108 and each of edge manifold. plates
- 120, 120'. The adhesive is also preferably applied
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in the region between the tubes and the channels in
which they are mounted, for example, the region
between tubes 142' and channels 172' and the region
between tubes 142' and channels 186. The preferred
adhesive is a gap-filling anaerobic adhesive having
high strength and favorable high temperature
properties, such as, for example, commercially
available LOCTITE Corporation epoxy compounds. The
presence of the tubes in the channels enhances the
structural properties of the adhesive bond between
the edge manifold plate and the adjacent cathode
plate by increasing the rigidity of the finished
part.
FIG. 6 shows the top. surface of edge manifold
plate 120 illustrated in FIGS. 4 and 5, including
notched portion 120b, fuel manifold opening 132,
coolant manifold opening 134, oxidant manifold
opening 136, and alignment openings 138.
FIG. 7 shows the bottom surface of edge
2o manifold plate 120 illustrated in FIG. 6, including
recessed portion 120a for accommodating a sealing
gasket, fuel manifold opening 132, coolant manifold
opening 134, oxidant manifold opening 136, and
alignment openings 138. A hard-stop ridge 121 is
preferably formed around recessed portion 120a to
properly space edge manifold plate 120 from the
adjacent edge manifold plate when assembled.
FIG. 8 shows the edge of edge manifold plate
120 which faces the cathode plate, including
notched portion 120b, hard-stop ridge 121, fuel
channels 172, coolant channels 174, and oxidant
channels 176.
FIG. 9 shows edge manifold plate 120
illustrated in FIGS. 6-8, broken to illustrate the
channel 176 for effecting fluid communication
~~~iEt'~~J'~ ~HEcT
IPcA/~P
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~ ~ O -i v . T f ~ f . . . 1
between the oxidant manifold opening 136 and the
oxidant flow channel 152 of the adjacent cathode
plate 108 via channel 182 in cathode plate 108.
FIG. 9 also shows the assembled relationship of
anode plate 112 with fuel flow channels 113 to
cathode plate 108 and edge manifold plate 120.
FIG. l0 shows a side sectional view of edge
manifold plate 120 taken along the broken surface
illustrated in FIG. 9, including recessed portion
120a, notched portion 120b, hard-stop ridge 121,
oxidant manifold opening 136, and channel 176._
FIG. 11 shows the sealing gasket 122 that is
accommodated in the recessed portion 120a of edge
manifold plate 120 illustrated in FIG. ~. sealing.
gasket is formed of a suitable resilient material
such as, for example, neoprene rubber commercially
available from MONSANTO Corporation under the trade
name SANTOPRENE.
FIGS. 12 and 13 show a fluid flow field plate
210 with a single edge manifold plate 212 attached
thereto along one side. Edge manifold plate 212
has interior manifold openings 214 formed therein
for conducting the reactant and coolant streams
introduced to and exhausted from the adjacent fuel
cell stack. Edge manifold plate 212 has channels
215 formed therein for effecting fluid
communication between the manifold openings 214 and
the flow channels 216 in flow field plate 210.
FIG. 14 shows a fluid flow field plate 220
with a single edge manifold plate 222 attached
thereto along two sides. Edge manifold plate 220
has interior manifold openings 224 formed therein
for conducting the reactant and coolant streams
introduced to and exhausted from the adjacent fuel
"~ilEf~L:cC? ~HEc~
~PcA.IcP
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- 21 -
cell stack. Edge manifold plate 222 has channels
225 formed therein for effecting fluid
communication between the manifold openings 224 and
- the flow channels 226 in flow field plate 220.
- . FIG. 15 shows a fluid flow field plate 230
with a single edge manifold plate 232 attached
thereto along three sides. Edge manifold plate 232
has interior manifold openings 234 formed therein
for conducting the reactant and coolant streams
l0 introduced to and exhausted from the adjacent fuel
cell stack. Edge manifold plate 232 has channels
235 formed therein for effecting fluid
communication between the manifold openings 234 and
the flow channels 236 in flow field plate 230.
FIGS. 16 and 17 show a fluid flow field plate
240 with a pair of edge manifold plates 242a, 242b
attached thereto. Each edge manifold plate 242-x,
242b has a single interior manifold opening 244a,
244b, respectively, formed therein for conducting a
reactant or coolant stream. Edge manifold plates
242a, 242b have channels 245a, 245b formed therein
for effecting fluid communication between the
manifold openings 242a, 242b and the flow channels
246 in flow field plate 240.
FIGS. 18 and 19 show a fluid flow field plate
250 with three noncontiguous edge manifold plates
252a, 252b, 252c attached thereto along three
sides. Each edge manifold plate 252a, 252b, 252c
has a pair-of interior manifold-openings 254a,
254b, 254c formed therein for conducting the
- reactant and coolant streams introduced to and
exhausted from the adjacent fuel cell stack. Each
- edge manifold plate 252 has channels 255a, 255b,
255c formed therein for effecting fluid
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communication between the manifold openings 254a,
254b, 254c and the flow channels 256 in flow field
plate 250.
FIGS. 20 and 21 show a fluid flow field plate
2.60 with four. noncontiguous edge manifold plates
262a, 262b, 262c, 262d attached thereto along four
sides. Each edge manifold plate 262a, 262b, 262c,
262d has a pair of interior manifold openings 264a,
264b, 264c, 264d formed therein for conducting the
reactant and coolant streams introduced to and
exhausted from the adjacent fuel cell stack. Each
edge manifold plate 262 has channels 265a, 265b,
265c, 265d formed therein for effecting fluid
communication between the manifold openings 264a,
264b, 264c, 264d and the flow channels 266 in flow
field plate 260.
In this application, the term "cross section"
means in a direction parallel to one of the major
- surfaces of the fuel cell fluid flow field plates.
In edge manifold assemblies in which each fuel
cell is polygonal in cross section and each fuel
cell has at least two edge manifold plates attached
thereto, one or more sides of the fuel cell could
each have multiple edge manifold plates attached
thereto. Each edge manifold plate could also
extend less than the entire length of_ a side.
The advantages of the present edge manifold
assembly are as follows:
(1) the present edge manifold.assembly, when
attached on less than all sides of the
fuel cell stack, occupies less volume
' . than conventional frame manifolds, while
avoiding the curtailment of area on the
anode plate, cathode plate and MEA from
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interior manifold openings or
perforations;
(2) the present edge manifold plates are
simple and inexpensive to manufacture
~. 5 ~ using conventional molding techniques; ,
(3) the present edge manifold assemblies
employ an effective compressive sealing
technique, namely, the controlled
compression, using a notched portion and
a hard-stop ridge, of a sealing gasket
disposed within the recessed portion of
the adjacent edge manifold plate, to
isolate the reactant and coolant streams
from each other, from the
electrochemically active region of the
fuel cell, and from the external
environment; and
(4) the present edge manifold assembly,
attached on less than all sides of the
fuel cell stack, provides access to the
interior stack components, such as the .
fuel cells themselves and associated
structures such as bus plates.
While particular elements; embodiments and
applications of the present invention have been
shown and described, it will be understood, of
course, that the invention is not limited thereto
since modifications may be made by those skilled in
the.art, particularly in light of the foregoing
teachings. It is therefore contemplated by the
appended claims to cover such modifications as
- incorporate those features which come within the
spirit and scope of the invention.
