U.S. patent application number 13/793132 was filed with the patent office on 2014-09-11 for fuel cell purge line system.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. The applicant listed for this patent is FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Virgo Edwards, Craig Michael Mathie, Kurt David Osborne, William F. Sanderson.
Application Number | 20140255814 13/793132 |
Document ID | / |
Family ID | 51385778 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140255814 |
Kind Code |
A1 |
Mathie; Craig Michael ; et
al. |
September 11, 2014 |
Fuel Cell Purge Line System
Abstract
A combined water and anode knock-out purge line for a fuel cell
including an inlet portion having an inlet portion lower surface,
an outlet portion having an outlet portion lower surface, a middle
portion having a lower surface and extending between the inlet
portion and the outlet portion. Each lower surface of the inlet
portion and outlet portion is raised relative to the lower surface
of the middle portion in a generally longitudinal direction.
Inventors: |
Mathie; Craig Michael;
(White Lake Twp., MI) ; Sanderson; William F.;
(Commerce Twp., MI) ; Edwards; Virgo; (Commerce
Twp., MI) ; Osborne; Kurt David; (Dearborn,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FORD GLOBAL TECHNOLOGIES, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
Dearborn
MI
|
Family ID: |
51385778 |
Appl. No.: |
13/793132 |
Filed: |
March 11, 2013 |
Current U.S.
Class: |
429/452 ;
429/512 |
Current CPC
Class: |
H01M 8/04097 20130101;
H01M 8/04 20130101; H01M 8/04164 20130101; Y02E 60/50 20130101;
H01M 8/04231 20130101 |
Class at
Publication: |
429/452 ;
429/512 |
International
Class: |
H01M 8/04 20060101
H01M008/04 |
Claims
1. A combined water and anode knock-out purge line for a fuel cell
comprising: an inlet portion having a lower surface; an outlet
portion having a lower surface; a middle portion having a lower
surface and extending between the inlet portion and the outlet
portion; and each lower surface of the inlet portion and outlet
portion being raised relative to the lower surface of the middle
portion in a generally longitudinal direction.
2. The purge line of claim 1, wherein the middle portion includes a
reservoir.
3. The purge line of claim 1, wherein the inlet portion lower
surface has an inlet portion inclination defined by a latitudinal
cross-section of the lower surface, an outlet portion lower surface
inclination defined by a latitudinal cross-section of its lower
surface, and the lower surface level defined by a latitudinal
cross-section of its middle portion lower surface.
4. The purge line of claim 3, wherein the inlet portion has an
inlet inclination angle formed by the inlet portion inclination and
the middle portion lower surface level.
5. The purge line of claim 3, wherein the outlet portion has an
outlet inclination angle formed by the outlet portion inclination
and the middle portion level.
6. The purge line of claim 3, wherein the inlet portion and outlet
portion each have an inlet and outlet inclination angle
respectively formed by the inlet and outlet portion inclination,
and the middle portion level.
7. The purge line of claim 4, wherein an inlet inclination angle is
greater than about 90 degrees and less than about 155.5
degrees.
8. The purge line of claim 5, wherein an outlet inclination angle
is greater than about 90 degrees and less than about 155.5
degrees.
9. The purge line of claim 1, wherein the inlet portion is
generally cylindrical, the outlet portion is generally cylindrical,
and the middle portion is generally cylindrical.
10. A fuel cell system comprising: a fuel cell stack; a separator
downstream of and in fluid communication with the fuel cell stack;
and a scavenging reservoir downstream of and in fluid communication
with the separator, and including an inlet portion, an outlet
portion, and a middle portion positioned between the inlet and
outlet portions, the inlet portion angled upward at an inlet angle
relative to the middle portion, and the outlet portion angled
upward at an outlet angle relative to the middle portion.
11. The fuel cell system of claim 10, wherein the outlet angle is
greater than about 90 degrees and smaller than about 155.5
degrees.
12. The fuel cell system of claim 10, wherein the scavenging
reservoir is in fluid communication with an anode of the fuel cell
stack.
13. The fuel cell system of claim 10, wherein the scavenging
reservoir is in fluid communication with a cathode of the fuel cell
stack.
14. The fuel cell system of claim 10, wherein the inlet angle is
greater than about 90 degrees and smaller than about 155.5
degrees.
15. The fuel cell system of claim 10, further comprising a valve
downstream of the outlet portion.
16. The fuel cell system of claim 15, wherein the valve is
positioned above the middle portion of the scavenging reservoir
against the direction of gravity.
17. A fuel cell system of claim 10, further comprising a
supplemental purge passageway including a first end and a second
end, the first end connected to an upper surface of the separator
and the second end connected to the outlet portion of the
scavenging reservoir.
18. A fuel cell system comprising: an anode; a primary purge line
extending away from the anode; a secondary purge line extending
away from the anode; and the primary and secondary purge lines
converging into a single outlet line.
19. The fuel cell system of claim 18, wherein the secondary purge
line includes a secondary purge line inlet and a secondary purge
line outlet, and the anode includes a primary inlet position,
wherein the secondary purge line inlet position is above the
primary inlet position.
20. The fuel cell system of claim 18, wherein the secondary purge
line has an orifice at the inlet.
21. The fuel cell system of claim 18, further comprising a valve
positioned downstream of the primary and secondary purge lines
converge into a single outlet line.
22. The fuel cell system of claim 18, further comprising a
reservoir within the primary purge line.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fuel cell purge line
system.
BACKGROUND
[0002] During fuel cell operation, byproducts such as product water
and nitrogen, as well as unconsumed hydrogen, may form at the anode
side of a fuel cell stack. In certain known systems, accumulation
of product water and nitrogen accumulation is controlled in an
attempt to avoid a reduction in fuel cell performance, and/or fuel
cell system shut down. One known approach is to release the water
and nitrogen via a passageway downstream of the fuel cell stack.
Using such approach, the passageway is coupled with a valve for the
controllable release of water and nitrogen from the fuel cell
stack. This approach causes the potential for problems to occur
during cold weather operation of the fuel cell when water may
freeze in the passageway, or valve, or other regions of the fuel
cell with small cross sectional areas. The resulting ice formation
may cause blockage of at least a portion of the passageway and
prevent fluid flow (e.g., water and nitrogen removal), which may
inhibit fuel cell system function.
SUMMARY
[0003] In one embodiment, a combined water and anode knock-out
purge line for a fuel cell is disclosed. The purge line includes an
inlet portion having a lower surface, an outlet portion having a
lower surface, and a middle portion having a lower surface and
extending between the inlet portion and the outlet portion. Each
lower surface of the inlet portion and outlet portion are raised
relative to the lower surface of the middle portion in a generally
longitudinal direction. The middle portion includes a reservoir
where water accumulates in such a manner to permit gas passage
through the middle portion.
[0004] In another embodiment, a fuel cell having a fuel cell stack
is disclosed. A separator is provided downstream of and in fluid
communication with the fuel cell stack. A scavenging reservoir is
downstream of and in fluid communication with the separator. The
scavenging reservoir includes an inlet portion, an outlet portion,
and a middle portion positioned between the inlet and outlet
portions. The inlet portion is angled upward at an inlet angle
relative to the middle portion, and the outlet portion is angled
upward at an outlet angle relative to the middle portion.
[0005] In yet another embodiment, a fuel cell system has an anode
and a primary purge line extending away from the anode. A secondary
purge line extends away from the anode. The primary and secondary
purge lines converge into a single outlet line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A depicts an isolated, perspective view of a
scavenging reservoir in an embodiment;
[0007] FIG. 1B depicts a schematic drawing of a fuel cell system
and a cross-sectional view of the scavenging reservoir of FIG. 1A
taken along line 1B-1B;
[0008] FIG. 1C depicts a longitudinal cross-sectional view of an
alternative scavenging reservoir according to another
embodiment;
[0009] FIG. 1D depicts a longitudinal cross-sectional view of a
scavenging reservoir according to yet another embodiment;
[0010] FIG. 1E depicts a longitudinal cross-sectional view of a
scavenging reservoir according to a further embodiment;
[0011] FIG. 1F depicts a cross-sectional view of the scavenging
reservoir of FIG. 1A taken along line 1F-1F;
[0012] FIG. 2 depicts a variation of the fuel cell system
referenced in FIG. 1B including a supplemental purge
passageway;
[0013] FIG. 3A depicts a variation cross-sectional view of a
scavenging reservoir;
[0014] FIG. 3B depicts a variation cross-sectional view of a
scavenging reservoir;
[0015] FIG. 3C depicts a variation cross-sectional view of a
scavenging reservoir;
[0016] FIG. 3D depicts a variation cross-sectional view of a
scavenging reservoir;
[0017] FIG. 3E depicts a variation cross-sectional view of a
scavenging reservoir;
[0018] FIG. 3F depicts a variation cross-sectional view of a
scavenging reservoir; and
[0019] FIG. 3G depicts a variation cross-sectional view of a
scavenging reservoir.
DETAILED DESCRIPTION
[0020] Reference will now be made in detail to compositions,
embodiments, and methods of the present invention known to the
inventors. However, it should be understood that disclosed
embodiments are merely exemplary of the present invention which may
be embodied in various and alternative forms. Therefore, specific
details disclosed herein are not to be interpreted as limiting,
rather merely as representative bases for teaching one skilled in
the art to variously employ the present invention.
[0021] Except where expressly indicated, all numerical quantities
in this description indicating amounts of material or conditions of
reaction and/or use are to be understood as modified by the word
"about" in describing the broadest scope of the present
invention.
[0022] The description of a group or class of materials as suitable
for a given purpose in connection with one or more embodiments
implies that mixtures of any two or more of the members of the
group or class are suitable. Description of constituents in
chemical terms refers to the constituents at the time of addition
to any combination specified in the description, and does not
necessarily preclude chemical interactions among constituents of
the mixture once mixed. The first definition of an acronym or other
abbreviation applies to all subsequent uses herein of the same
abbreviation and applies mutatis mutandis to normal grammatical
variations of the initially defined abbreviation. Unless expressly
stated to the contrary, measurement of a property is determined by
the same technique as previously or later referenced for the same
property.
[0023] During fuel cell operation, product water, residual fuel
such as hydrogen, and byproducts such as nitrogen may accumulate at
the anode side of the fuel cell stack. Attempts have been made to
remove the liquid product water and byproducts and to reuse the
residual hydrogen and water vapor. One approach is to collect those
constituents in a separator downstream of the fuel cell stack,
separate liquid water and direct it towards a combined purging and
draining passageway, and return the remaining constituents to the
fuel cell stack via a return passageway. The combined purging and
draining passageway is closed to the atmosphere by a single valve.
Periodically, this valve is opened to drain liquid product water
and purge the anode of byproducts such as nitrogen. However,
combining the purging and draining functions into a single
passageway closed by a single valve presents significant risk of
ice formation and blockage of purge and drain flow when residual
product water freezes during exposure to cold ambient temperatures.
The potential for ice formation is acute concern in cold ambient
temperatures below 0.degree. C. If the purging and draining
functions are inhibited by ice blockage, then fuel cell system
performance degrades, potentially to the point of system shut
down.
[0024] The embodiments of the present invention, as will be
described herein, provide a solution to one or more of the
above-identified problems. One or more embodiments delivers a
reduction in system complexity by incorporating new structures into
an existing purge passageway, avoiding the use of multiple valves
and passageways for startup robustness, therefore keeping hardware
and control software to a minimum. Reduction in complexity may
result in a reduction in manufacturing cost, a reduction in system
weight, and/or a reduction in failure mode occurrence.
[0025] In one or more embodiments, a fuel cell system with a
scavenging reservoir positioned downstream of a fuel cell stack is
disclosed. The scavenging reservoir may provide one or more of the
following benefits: (1) a reduction and/or elimination of purging
passageway blockage due to ice formation and (2) a reduction in the
number of valves for purging both nitrogen and water. In certain
instances, nitrogen, water, and hydrogen may flow through the same
passageway employing the scavenging reservoir with a single
downstream valve. This approach may be alternatively referred to as
an integrated purge and drain function. This approach supports the
endeavor of obtaining a commercially-viable fuel cell system design
that is capable of consistently starting in freezing ambient
conditions while reducing costs and improving efficiency. In
addition, and as detailed herein, the product water is less of a
threat for causing ice blockage during cold weather conditions.
[0026] In one or more embodiments, and as depicted in FIGS. 1A and
1B, a fuel cell system generally shown at 100 may include a fuel
cell stack 102, a separator 104 downstream of and in fluid
communication with the fuel cell stack 102 via a passageway 130,
and a scavenging reservoir 106 downstream of and in fluid
communication with the separator 104, wherein the scavenging
reservoir 106 includes an inlet portion 116, an outlet portion 126,
and a middle portion 136 positioned between the inlet and outlet
portions 116, 126. The lower surface of inlet portion 116 is
positioned with an inlet angle .alpha.1 relative to the lower
surface of the middle portion 136. The lower outlet portion 126 is
positioned with an outlet angle .alpha.2 relative to the lower
surface of the middle portion 136. Valve 108 is positioned
downstream of the reservoir 106. As described herein, this
structure of the scavenging reservoir 106 may maintain a passageway
during cold weather conditions and keep the passageway valve free
of ice blockage.
[0027] During fuel cell system operation, product water, nitrogen,
and residual hydrogen may flow from the fuel cell stack 102 into
the separator 104 via the passage 130. In the separator 104, the
product water is separated from the residual hydrogen and nitrogen.
The product water exits the separator 104 through passage 134. In
certain instances, and as depicted in FIG. 1B, the separated
hydrogen may be returned back to the fuel cell stack 102 via a
hydrogen return passageway 132.
[0028] In one non-limiting embodiment, the scavenging reservoir 106
can be formed as a detachable unit with dimensions that comply to
any fuel cell system where water freeze may be an issue. The
scavenging reservoir can also be incorporated into the bottom of
the water knockout itself. The scavenging reservoir may be an
integral single unit, optionally formed via injection molding. A
benefit of this configuration is that preferred liquid leakage may
be reduced at the angled and tapered sections, which may otherwise
require welding and/or soldering to connect. However, the inlet,
outlet and middle portions can be connectable pieces with sizes and
materials separately customizable for each fuel cell system. For
instance, the middle portion may have a cross-sectional diameter
greater than, equal to or smaller than that of either of the inlet
portion and the outlet portion. For instance also, one may choose
to have a middle portion formed of a material different from that
of either of the inlet portion and the outlet portion.
[0029] By reducing the total number of valves to one, which is the
combined purge and drain valve 108, and by employing the scavenging
reservoir 106 upstream of the valve 108, the present invention in
one or more embodiments provides a synergistic effect of preventing
ice blockage and scavenging product water.
[0030] In one or more embodiments, the term "scavenging" may refer
to the act of flowing the anode purge and drain gas stream over and
through the accumulated liquid water to physically remove the
water.
[0031] The scavenging reservoir 106 may be in fluid communication
with an anode of the fuel cell stack 102 or a cathode of the fuel
cell stack 102. When used in fluid communication with the cathode,
the scavenging reservoir 106 may help prevent items such as an
electronic throttle body from freezing.
[0032] The scavenging reservoir 106 and more particularly the
middle portion 136 thereof is positioned below the separator 104
along the direction of gravity so that water can drain via gravity
into the scavenging reservoir 106. Along this passageway, a valve
108 positioned downstream of the scavenging reservoir 106 should be
at a position above the scavenging reservoir 106 along the
direction of gravity so that any water which would otherwise reside
on or around the valve 108 would then accumulate in the middle
portion 136. The water should accumulate in the middle portion 136
in such a manner as to permit gas passage through the middle
portion 136, even if any accumulated water forms ice. The valve 108
can be a closed solenoid valve.
[0033] FIG. 1C depicts a scavenging reservoir 106' showing water or
ice 140 accumulated on the lower surface 142 of the middle portion
136', with a clear flow path above the water or ice accumulation.
During nitrogen purging and water draining events, the flow of warm
anode byproducts melts ice and entrains liquid water accumulated in
the middle portion 136'. In this configuration, the product water
and nitrogen gas can be purged substantially evenly in the presence
of ice in the passageway. This design, therefore, provides a
synergistic effect in that not only the nitrogen gas and the
product water can be purged via a single passageway with a single
downstream valve to reduce system complexity and maintenance cost,
but also provides built-in warming and melting effectuated via the
fluid mixture passing through the scavenging reservoir 106'. FIGS.
1D and 1E depict scavenging reservoirs 106'' and 106''' according
to alternative embodiments of the present invention. Referring to
FIGS. 1D and 1E, the inlet end 110'' and 110''' may be
substantially circular or nearly circular that transitions into the
reservoir 106'' or 106''' respectively. As shown here, the 106''
reservoir of FIG. 1D has a nearly rectangular reservoir
cross-sectional middle portion 136'', wherein the transition from
the inlet end 110'' is not a gradual transition into the middle
portion 136''. While FIG. 1E depicts the reservoir 106''' with a
gradual decline transition from the inlet end 110''' into the
middle portion 136'''.
[0034] Several factors can be considered in shaping the scavenging
reservoir. These factors may include designing the inlet and outlet
angles, the inlet, outlet, and reservoir cross sectional areas, and
the length, width, and depth of each section of the scavenging
reservoir in response to flow stream characteristics, which in
themselves are a function of load as dictated by usage cycle. In
general, the scavenging reservoir should be designed with
dimensions effectuating sufficient storage of product water during
a soak to avoid system blockage upon a subsequent start up attempt.
In certain embodiments, the angles of the inlet to and outlet from
the reservoir should be upward to facilitate gravity drainage of
water into the reservoir for storage and freezing. Moreover, the
position of the water and anode knock-out purge line installed in a
vehicle should also take into consideration road pitch. For
example, the angles of the inlet to and outlet from the reservoir
should be great enough to overcome road pitch .+-.17.degree. to
facilitate gravity drainage of water into the reservoir for storage
and freezing. Those skilled in the art know that road pitch may
deviate greatly from being nearly planar to mountainous roads
having steep inclines and declines which may exceed .+-.3.degree.,
.+-.5.degree., .+-.8.degree., .+-.11.degree., .+-.15.degree.,
.+-.18.degree., .+-.21.degree., and .+-.25.degree., to which the
angles of the inlet to and outlet from the reservoir should be
great enough to overcome.
[0035] The inlet portion, the outlet portion and/or the middle
portion can each be structured with any suitable geometrical
features, including ribbing and vanes, which may straighten or
direct fluid flow, or even add turbulence to the fluid flow. Such
manipulation of the fluid flow may enhance scavenging during
operation, or could be used to direct water flow during
non-operation prior to freezing.
[0036] The water should accumulate entirely or significantly in the
middle portion 136 in such a manner as to permit gas passage
through the middle portion 136 even if any accumulated water forms
ice.
[0037] Referring back to FIG. 1B, the inlet portion 116 may be
configured as a substantially cylindrical or cylindrical structure
including a first end 110 and a second end 112, with an inlet
length Ln1 measured down the centerline axis L1. In certain
embodiments, the inlet length Ln1 of the inlet portion 116 has a
value of 0.5 to 10 inches, 1.0 to 5 inches, or 2.0 to 3.0
inches.
[0038] Referring to FIG. 1B, the inlet angle .alpha.1 may be an
angle defined by a longitudinal cross-sectional lower surface of
the inlet portion 116 and a longitudinal cross-sectional lower
surface of the middle portion 136.
[0039] As shown in FIG. 1B, the outlet angle .alpha.2 may be an
angle defined by longitudinal cross-sectional lower surface of the
middle portion 136 and a longitudinal cross-sectional lower surface
of the outlet portion 126.
[0040] In certain embodiments, the combination of centerline axes
L1, L2 and L3 constitutes a longitudinal axis of the scavenging
reservoir. Further, the cross-sectional views of the scavenging
reservoirs 106, 106', 106'' and 106''' depicted in FIGS. 1B, 1C,
1D, and 1E, respectively, may be considered latitudinal
cross-sectional views.
[0041] The inlet angle .alpha.1 may be greater than about 90
degrees and smaller than about 155.5 degrees. In certain instances,
the inlet angle .alpha.1 is between about 100 to about 155.5
degrees, about 120 to about 155.5 degrees, about 130 to about 155.5
degrees, or about 140 to about 155.5 degrees.
[0042] The outlet angle .alpha.2 may be greater than about 90
degrees and smaller than about 155.5 degrees. In certain instances,
the outlet angle .alpha.2 is between about 100 to about 155.5
degrees, about 120 to about 155.5 degrees, about 130 to about 155.5
degrees, or about 140 to about 155.5 degrees.
[0043] The inlet angle .alpha.1 and/or the outlet angle .alpha.2
may be configured to facilitate directing water into the middle
portion 136 during soak events. This helps to permit ice to form in
the middle portion 136 and away from passageways that may be
relatively more sensitive to bridging and blockage.
[0044] This paragraph relates to the installation of the combined
water and anode knock-out purge line in a fuel cell within a
vehicle. The centerline axis L2 of the middle portion 136 can be
positioned relative to the direction of gravity at an angle of
about 65.5 to about 114.5 degrees, about 70 to about 110 degrees,
or about 85 to about 95 degrees. The middle portion 136 as
positioned in relation to the inlet portion 116 and the outlet
portion 126 is to provide a platform for water to reside on a
bottom surface of the middle portion 136, leaving an upper space
for gas flow. In certain particular instances, the middle portion
136 can be essentially positioned flat, for instance, in an angle
of about 88.5 to about 91.5 degrees relative to the direction of
gravity, to collect as much water as possible.
[0045] Referring to FIGS. 1B and 1F, the middle portion 136 may be
configured as substantially cylindrical or a cylindrical structure
including a centerline axis L2 and defined between the second end
112 and a third end 114. The cylindrical structure shown in 1F
depicts a lower surface 152 and upper surface 150. The middle
portion 136 may have a length Ln2 measured down the centerline axis
L2 and ending between the second and third ends 112, 114. In
certain designs, the length Ln2 of the middle portion 136 has a
value of 0.5 to 10 inches, 1.0 to 5 inches, or 2.0 to 3.0 inches.
In one or more embodiments, the middle portion length Ln2 is
configured such that scavenging water is not dropped out of the
purge and drain flow stream and back into the reservoir before
reaching the outlet portion (in this case, the middle portion would
be too long).
[0046] In alternative embodiments, referred to in FIGS. 3A-3G, the
middle portion 136 may be configured in various shapes construed or
varying longitudinal cross-sectional shapes suitable with
dimensions effectuating sufficient storage of product water during
a soak to avoid system blockage upon a subsequent start up attempt.
FIGS. 3A-3G represent alternative embodiments which the angles of
the inlet to and outlet from the reservoir are upward to facilitate
gravity drainage of water into the reservoir for storage and
freezing. FIGS. 3A-3G depict a variation of cross-sectional views
of the scavenging reservoir of FIG. 1A taken along line 1F-1F,
wherein FIG. 3A is circular or substantially circular, FIGS. 3B-3G
have a drainage reservoir that allows gravity drainage of water
into the reservoir for storage and freezing. FIGS. 3B-3G may be
turned relative to a central point fixed axis, in 15.degree.,
30.degree., 45.degree., 60.degree., 75.degree., 90.degree.,
105.degree., 120.degree., 135.degree., 150.degree., 165.degree.,
and 180.degree..
[0047] The outlet portion 126 may be configured as a substantially
cylindrical structure or cylindrical including a centerline axis L3
and defined between the third end 114 and a fourth end 118. The
outlet portion 126 may have a length Ln3 measured down the
centerline axis L3 and ending between the third and fourth ends
114, 118. In certain designs, the length Ln3 of the outlet portion
126 has a value of 0.5 to 10 inches, 1.0 to 5 inches, or 2.0 to 3.0
inches. Without wanting to be limited to any particular theory, the
outlet portion 126 is configured such that scavenging water is not
dropped back into the reservoir before reaching the purge and drain
valve.
[0048] When the inlet portion is cylindrical or substantially
cylindrical, the inlet portion 116 may have an average diameter of
5 to 20 mm, 7.5 to 17.5 mm, or 10 to 15 mm. In one or more
embodiments, the inlet portion length Ln1 creates directionality to
the fluid flow, imparting flow separation between the terminus of
the inlet portion and the top of the middle portion and resulting
in the fluid flow impacting the lowest inner surface of the middle
portion. This action causes scavenging of the pool of water. In
other embodiments, inlet portion 116 may be conical or
frusto-conical tapered from a large base at 110 to the smaller base
at 112.
[0049] The middle portion 136 may be cylindrical or substantially
cylindrical, or any other suitable cross-section, such as
rectangular or polygonal. When the inlet portion is cylindrical or
substantially cylindrical, the middle portion 136 has an average
diameter of about 12.5 to about 55 mm, about 40 mm, about 30 mm,
about 25 mm, about 20 mm, about 15 to about 25 mm, or about 17.5 to
about 22.5 mm. The middle portion 136 may be configured to have an
average diameter greater than that of the inlet portion 116 and/or
the outlet portion 126. The difference in average diameter values
can be about 2 to about 11 mm, about 3 to about 10 mm, about 4 to
about 9 mm, or about 5 to about 8 mm. These diameters may be
configured such that a single droplet of water would not bridge or
completely block a passageway due to capillary forces.
[0050] As depicted in FIG. 2, the fuel cell system may further
include a supplemental purge passageway 202 to provide purging
supplemental to that provided by the primary purge passageway where
the scavenging reservoir 106 resides. The supplemental purge
passageway may include a first end 212 and a second end 222, the
first end 212 being connected to and/or received within a top
portion 204 of the separator 104, the second end 222 being disposed
upstream of the valve 108. In certain instances, the supplemental
purge passageway 202 is connected to the primary purge passageway
206 at junction 224, wherein the second end 222 is disposed
downstream of the scavenging reservoir 106 and upstream of the
valve 108.
[0051] The incoming flow may include water in liquid and/or vapor
states, hydrogen, and nitrogen, and the incoming flow passes
through the primary and/or supplemental purge passageway in various
concentrations. The extent of a flow through the supplemental purge
passageway can be controlled such that the supplemental purge
passageway may come into effect only when the primary purge
passageway fails to provide the requisite amount of purging as
desirable. This control can be done in a variety of ways, including
the employment of a restriction device such as an orifice to
restrict the flow through the supplemental purge passageway 202 or
a valve such as a solenoid valve.
[0052] As depicted in FIG. 1B and FIG. 2, although the supplemental
purge passageway 202 is separately disposed relative to the primary
purge passageway, the supplemental purge passageway 202 may feed
the same valve 108 used by the primary purge passageway, thereby
keeping costs and parasitic losses low.
[0053] Referring back to FIG. 1B, the middle portion 136 of the
scavenging reservoir 106 remains the lowest region in the primary
purge passageway relative to the passageway's origination from the
separator 104. Referring back to FIG. 2 also, the middle portion
136 of the scavenging reservoir 106 remains the lowest spot in the
primary purge passageway relative to the second end 222 of the
supplemental purge passageway 202. This relatively low region
provides a region for water to accumulate away from areas that are
sensitive to blockage from ice formation, such as the merge
location (e.g., the second end 222) of the primary and supplemental
passageways, or the orifice in the valve 108.
[0054] The supplemental purge passageway 202 is provided such that
it originates at a location on top of the separator 104 that
permits gas flow in the presence of ice blockages in the primary
passageway. Passageway 202 merges with the primary passageway prior
to the location upstream of the valve 108. The origination at the
separator 104 may prevent accumulation of liquid water that could
later freeze. The supplemental purge passageway 202 may contain an
orifice (not shown) in the flow path to restrict fluid flow,
ensuring that the majority of the purge and drain fluids flow
through the primary passageway unless the primary is blocked or
restricted by liquid water or ice.
[0055] Therefore, the supplemental purge passageway 202 serves as a
bypass loop that will enable purge flow in the event that the
primary purge passageway is blocked with ice until the primary
purge passageway is thawed and able to flow both purge and drain
fluids. In this arrangement the valve 108 must be located such that
it is not the lowest component in the entire system to prevent it
from being subjected to ice blockage.
[0056] In certain designs, the primary and secondary passageways
can be formed out of a conductive material and be placed wholly or
partially within another system pipe that carries warm gases or
fluids, such as the cathode exhaust passageway coming out of the
stack or a pipe carrying warm stack outlet coolant. In this manner,
the passageways will be latently warmed by their surroundings,
efficiently thawing any ice using waste heat. Suitable conductive
materials include, but not limited to metal, copper, aluminum,
composites, and the like.
[0057] In certain other designs, a heat source may be placed in
close communication with the primary and secondary passageways to
promote ice melt.
[0058] In certain other designs, the primary and the secondary
passageways may be insulated wholly or partially to promote ice
melt by prevention of heat loss.
[0059] In certain other designs, a water-vapor-permeable but
water-liquid-impermeable membrane may be placed in the bypass purge
passageway to keep liquid water out of the passageway to prevent
ice blockage.
[0060] Having generally described several embodiments of this
invention, a further understanding can be obtained by reference to
certain specific examples which are provided herein for purposes of
illustration only and are not intended to be limiting unless
otherwise specified.
EXAMPLES
[0061] A sample scavenging reservoir is formed according to the
configuration shown in FIGS. 1A and 1B. The sample scavenging
reservoir as formed has the following dimensions: an inlet portion
length of 63.5 mm, an inlet portion average diameter of 12.7 mm,
.alpha.1 of 147 degrees, a middle portion length of 54.0 mm, a
middle portion average diameter of 19.1 mm, .alpha.2 of 155.5
degrees, an outlet portion length of 41.3 mm, and an outlet portion
average diameter of 12.7 mm.
[0062] A prototype supplemental purge passageway built according to
FIG. 2 demonstrates acceptable purging performance during cold
soaks, maintaining an open purge flow path without the need for
multiple valves, for the next freeze start.
[0063] While the best mode for carrying out the invention has been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention as defined by the
following claims.
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