U.S. patent application number 16/375618 was filed with the patent office on 2020-10-08 for process water thermal management of electrochemical inert gas generating system.
The applicant listed for this patent is HAMILTON SUNDSTRAND CORPORATION. Invention is credited to Jonathan Rheaume.
Application Number | 20200318249 16/375618 |
Document ID | / |
Family ID | 1000004008321 |
Filed Date | 2020-10-08 |
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United States Patent
Application |
20200318249 |
Kind Code |
A1 |
Rheaume; Jonathan |
October 8, 2020 |
PROCESS WATER THERMAL MANAGEMENT OF ELECTROCHEMICAL INERT GAS
GENERATING SYSTEM
Abstract
A system is disclosed for providing inerting gas to a protected
space. The system includes an electrochemical cell comprising a
cathode and an anode separated by a separator including a proton
transfer medium. A supply of process water is provided to the
anode, and inerting gas is produced at the cathode. A heat
exchanger is in operative fluid and thermal communication with the
process water, and a temperature sensor is in operative thermal
communication with the cathode or the anode. A controller is
configured to provide a target temperature of the temperature
sensor through control of a flow rate of process water or a
temperature of process water, or both a flow rate and a temperature
of process water, through a process water thermal management flow
path in operative thermal communication with the cathode or the
anode.
Inventors: |
Rheaume; Jonathan; (West
Hartford, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HAMILTON SUNDSTRAND CORPORATION |
Charlotte |
NC |
US |
|
|
Family ID: |
1000004008321 |
Appl. No.: |
16/375618 |
Filed: |
April 4, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 27/00 20130101;
C25B 15/02 20130101; C25B 15/08 20130101; C25B 9/08 20130101 |
International
Class: |
C25B 15/02 20060101
C25B015/02; C25B 9/08 20060101 C25B009/08; C25B 15/08 20060101
C25B015/08; F28F 27/00 20060101 F28F027/00 |
Claims
1. A system for providing inerting gas to a protected space,
comprising an electrochemical cell comprising a cathode and an
anode separated by a separator comprising a proton transfer medium;
a cathode fluid flow path in operative fluid communication with the
cathode between a cathode fluid flow path inlet and a cathode fluid
flow path outlet; an anode fluid flow path in operative fluid
communication with the anode between an anode fluid flow path inlet
and an anode fluid flow path outlet; a cathode supply fluid flow
path between an air source and the cathode fluid flow path inlet,
and an inerting gas flow path in operative fluid communication with
the cathode fluid flow path outlet and the protected space; an
anode supply fluid flow path between a supply of process water and
the anode fluid flow path inlet; and thermal management components
including: a heat exchanger in operative fluid and thermal
communication with the process water; a temperature sensor in
operative thermal communication with the cathode or the anode, or
with both the cathode and the anode; a flow control device arranged
to control a flow of process water to a flow path in operative
thermal communication with the cathode or anode, or with both the
cathode and the anode; and a controller configured to provide a
target temperature of the temperature sensor through control of a
flow rate of process water or a temperature of process water, or
both a flow rate and a temperature of process water, through a
process water thermal management flow path in operative thermal
communication with the cathode or the anode or with both the
cathode and the anode.
2. The system of claim 1, wherein the heat exchanger includes a
heat rejection side in operative fluid communication with the
process water thermal management flow path, and a heat absorption
side in operative thermal communication with a heat sink.
3. The system of claim 2, wherein the heat exchanger includes a
heat absorption side in operative fluid communication with the
process water thermal management flow path, and a heat rejection
side in operative thermal communication with a heat source.
4. The system of claim 1, wherein the process water thermal
management flow path includes the anode fluid flow path, or the
cathode fluid flow path, or a fluid flow path in operative thermal
communication with the cathode or with the anode or with both the
cathode and the anode and in fluid isolation from the cathode and
fluid flow paths.
5. The system of claim 4, wherein the process water thermal
management flow path includes the anode fluid flow path.
6. The system of claim 4, wherein the process water thermal
management flow path includes the cathode fluid flow path.
7. The system of claim 4, wherein the process water thermal
management flow path includes the fluid flow path in operative
thermal communication with the cathode or with the anode or with
both the cathode and the anode and in fluid isolation from the
cathode and fluid flow paths.
8. The system of claim 7, wherein the fluid flow path in operative
thermal communication with the cathode or with the anode or with
both the cathode and the anode and in fluid isolation from the
cathode and fluid flow paths comprises a conduit disposed on the
cathode fluid flow path or anode fluid flow path.
9. The system of claim 7, comprising a plurality of said
electrochemical cells in a stack separated by
electrically-conductive fluid flow separators wherein the fluid
flow path in operative thermal communication with the cathode or
with the anode or with both the cathode and the anode and in fluid
isolation from the cathode and fluid flow paths includes an
internal passage through one or more of the electrically-conductive
fluid flow separators.
10. The system of claim 1, comprising a plurality of said
electrochemical cells in a stack separated by
electrically-conductive fluid flow separators.
11. A system for providing inerting gas to a protected space,
comprising an electrochemical cell comprising a cathode and an
anode separated by a separator comprising a proton transfer medium;
a cathode fluid flow path in operative fluid communication with the
cathode between a cathode fluid flow path inlet and a cathode fluid
flow path outlet; an anode fluid flow path in operative fluid
communication with the anode between an anode fluid flow path inlet
and an anode fluid flow path outlet; a cathode supply fluid flow
path between an air source and the cathode fluid flow path inlet,
and an inerting gas flow path in operative fluid communication with
the cathode fluid flow path outlet and the protected space; an
anode supply fluid flow path between a process water source and the
anode fluid flow path inlet; and a cooling water fluid flow path in
operative fluid communication with the process water source, said
cooling water fluid flow path in operative thermal communication
with the cathode or with the anode or with both the anode and the
cathode, and in fluid isolation from the cathode fluid flow path
and the anode fluid flow path.
12. A method of inerting a protected space, comprising delivering
process water to an anode of an electrochemical cell comprising the
anode and a cathode separated by a separator comprising a proton
transfer medium; delivering air to the cathode and reducing oxygen
at the cathode to generate oxygen-depleted air; directing the
oxygen-depleted air from the cathode of the electrochemical cell
along an inerting gas flow path to the protected space; and
controlling a flow rate of process water or controlling a
temperature of process water, or controlling both a flow rate and a
temperature of process water, on a process water thermal management
flow path in operative thermal communication with the cathode or
the anode or with both the cathode and the anode, to provide a
target temperature at the anode or at the cathode or at both the
anode and the cathode.
13. The method of claim 12, further comprising directing the
process water through a heat rejection side of a heat exchanger
comprising a heat absorption side in operative fluid communication
with a heat sink.
14. The method of claim 13, further comprising directing the
process water through a heat absorption side of a heat exchanger
comprising a heat rejection side in operative thermal communication
with a heat source.
15. The method of claim 12, wherein the process water thermal
management flow path includes the anode fluid flow path, or the
cathode fluid flow path, or a fluid flow path in operative thermal
communication with the cathode or with the anode or with both the
cathode and the anode and in fluid isolation from the cathode and
fluid flow paths.
16. The method of claim 15, wherein the process water thermal
management flow path includes the anode fluid flow path.
17. The method of claim 15, wherein the process water thermal
management flow path includes the cathode fluid flow path.
18. The method of claim 15, wherein the process water thermal
management flow path includes the fluid flow path in operative
thermal communication with the cathode or with the anode or with
both the cathode and the anode and in fluid isolation from the
cathode and fluid flow paths.
19. The method of claim 18, wherein the fluid flow path in
operative thermal communication with the cathode or with the anode
or with both the cathode and the anode and in fluid isolation from
the cathode and fluid flow paths comprises a conduit disposed on
the cathode fluid flow path or anode fluid flow path.
20. The method of claim 18, comprising a plurality of said
electrochemical cells in a stack separated by
electrically-conductive fluid flow separators wherein the fluid
flow path in operative thermal communication with the cathode or
with the anode or with both the cathode and the anode and in fluid
isolation from the cathode and fluid flow paths includes an
internal passage through one or more of the electrically-conductive
fluid flow separators.
Description
BACKGROUND
[0001] The subject matter disclosed herein generally relates to
systems for generating and providing inert gas to protected spaces
and optionally also providing oxygen and/or power. More
specifically, the subject matter relates to thermal management of
such systems.
[0002] It is recognized that fuel vapors within fuel tanks become
combustible or explosive in the presence of oxygen. An inerting
system decreases the probability of combustion or explosion of
flammable materials in a fuel tank by maintaining a chemically
non-reactive or inerting gas, such as nitrogen-enriched air, in the
fuel tank vapor space, also known as ullage. Three elements are
required to initiate combustion or an explosion: an ignition source
(e.g., heat), fuel, and oxygen. The oxidation of fuel may be
prevented by reducing any one of these three elements. If the
presence of an ignition source cannot be prevented within a fuel
tank, then the tank may be made inert by: 1) reducing the oxygen
concentration, 2) reducing the fuel concentration of the ullage to
below the lower explosive limit (LEL), or 3) increasing the fuel
concentration to above the upper explosive limit (UEL). Many
systems reduce the risk of oxidation of fuel by reducing the oxygen
concentration by introducing an inerting gas such as
nitrogen-enriched air (NEA) (i.e., oxygen-depleted air or ODA) to
the ullage, thereby displacing oxygen with a mixture of nitrogen
and oxygen at target thresholds for avoiding explosion or
combustion.
[0003] It is known in the art to equip vehicles (e.g., aircraft,
military vehicles, etc.) with onboard inerting gas generating
systems, which supply nitrogen-enriched air to the vapor space
(i.e., ullage) within the fuel tank. The nitrogen-enriched air has
a substantially reduced oxygen content that reduces or eliminates
oxidizing conditions within the fuel tank. Onboard inerting gas
generating systems typically use membrane-based gas separators.
Such separators contain a membrane that is permeable to oxygen and
water molecules, but relatively impermeable to nitrogen molecules.
A pressure differential across the membrane causes oxygen molecules
from air on one side of the membrane to pass through the membrane,
which forms oxygen-enriched air (OEA) on the low-pressure side of
the membrane and nitrogen-enriched air (NEA) on the high-pressure
side of the membrane. The requirement for a pressure differential
necessitates a source of compressed or pressurized air. Another
type of gas separator is based on an electrochemical cell such as a
proton exchange membrane (PEM) electrochemical cell, which produces
NEA by electrochemically generating protons for combination with
oxygen to deplete air of combustible oxygen
BRIEF DESCRIPTION
[0004] A system is disclosed for providing inerting gas to a
protected space. The system includes an electrochemical cell
comprising a cathode and an anode separated by a separator
comprising a proton transfer medium. A cathode fluid flow path is
in operative fluid communication with the cathode between a cathode
fluid flow path inlet and a cathode fluid flow path outlet. An
anode fluid flow path is in operative fluid communication with the
anode between an anode fluid flow path inlet and an anode fluid
flow path outlet. A cathode supply fluid flow path is between an
air source and the cathode fluid flow path inlet, and an inerting
gas flow path in operative fluid communication with the cathode
fluid flow path outlet and the protected space. An anode supply
fluid flow path is between a supply of process water (i.e., a
process water source) and the anode fluid flow path inlet.
[0005] The system for providing inerting gas includes thermal
management. Thermal management includes a heat exchanger in
operative fluid and thermal communication with the process water. A
temperature sensor is in operative thermal communication with the
cathode or the anode, or with both the cathode and the anode. A
flow control device is arranged to control a flow of process water
to a flow path in operative thermal communication with the cathode
or anode, or with both the cathode and the anode. A controller is
configured to provide a target temperature of the temperature
sensor through control of a flow rate of process water or a
temperature of process water, or both a flow rate and a temperature
of process water, through a process water thermal management flow
path in operative thermal communication with the cathode or the
anode or with both the cathode and the anode.
[0006] In some aspects, the heat exchanger can include a heat
rejection side in operative fluid communication with the process
water thermal management flow path, and a heat absorption side in
operative thermal communication with a heat sink.
[0007] In any one or combination of the foregoing aspects, the heat
exchanger can include a heat absorption side in operative fluid
communication with the process water thermal management flow path,
and a heat rejection side in operative thermal communication with a
heat source.
[0008] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the anode
fluid flow path, or the cathode fluid flow path, or a fluid flow
path in operative thermal communication with the cathode or with
the anode or with both the cathode and the anode and in fluid
isolation from the cathode and fluid flow paths.
[0009] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the anode
fluid flow path.
[0010] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the cathode
fluid flow path.
[0011] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the fluid
flow path in operative thermal communication with the cathode or
with the anode or with both the cathode and the anode and in fluid
isolation from the cathode and fluid flow paths.
[0012] In any one or combination of the foregoing aspects, the
fluid flow path in operative thermal communication with the cathode
or with the anode or with both the cathode and the anode and in
fluid isolation from the cathode and fluid flow paths can include a
conduit disposed on the cathode fluid flow path or anode fluid flow
path.
[0013] In any one or combination of the foregoing aspects, the
system can include a plurality of said electrochemical cells in a
stack separated by electrically-conductive fluid flow separators
wherein the fluid flow path in operative thermal communication with
the cathode or with the anode or with both the cathode and the
anode and in fluid isolation from the cathode and fluid flow paths
includes an internal passage through one or more of the
electrically-conductive fluid flow separators.
[0014] In any one or combination of the foregoing aspects, the
system can include a plurality of the electrochemical cells in a
stack separated by electrically-conductive fluid flow
separators.
[0015] Also disclosed is a system for providing inerting gas to a
protected space. The system includes an electrochemical cell
comprising a cathode and an anode separated by a separator
comprising a proton transfer medium. A cathode fluid flow path is
in operative fluid communication with the cathode between a cathode
fluid flow path inlet and a cathode fluid flow path outlet. An
anode fluid flow path is in operative fluid communication with the
anode between an anode fluid flow path inlet and an anode fluid
flow path outlet. A cathode supply fluid flow path is between an
air source and the cathode fluid flow path inlet, and an inerting
gas flow path in operative fluid communication with the cathode
fluid flow path outlet and the protected space. An anode supply
fluid flow path is between a process water source and the anode
fluid flow path inlet. A cooling water fluid flow path is in
operative fluid communication with the process water source, said
cooling water fluid flow path in operative thermal communication
with the cathode or with the anode or with both the anode and the
cathode, and in fluid isolation from the cathode fluid flow path
and the anode fluid flow path.
[0016] Also disclosed is a method of inerting a protected space.
According to the method, process water is delivered to an anode of
an electrochemical cell comprising the anode and a cathode
separated by a separator comprising a proton transfer medium. Air
is delivered to the cathode along with oxygen is reduced at the
cathode to generate oxygen-depleted air. The oxygen-depleted air is
directed from the cathode of the electrochemical cell along an
inerting gas flow path to the protected space. A flow rate of
process water or a temperature of process water is controlled, or
both a flow rate and a temperature of process water are controlled,
on a process water thermal management flow path in operative
thermal communication with the cathode or the anode or with both
the cathode and the anode, to provide a target temperature at the
anode or at the cathode or at both the anode and the cathode.
[0017] In some aspects, the method can further include directing
the process water through a heat rejection side of a heat exchanger
comprising a heat absorption side in operative fluid communication
with a heat sink.
[0018] In any one or combination of the foregoing aspects, the
method can further include directing the process water through a
heat absorption side of a heat exchanger comprising a heat
rejection side in operative thermal communication with a heat
source.
[0019] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the anode
fluid flow path, or the cathode fluid flow path, or a fluid flow
path in operative thermal communication with the cathode or with
the anode or with both the cathode and the anode and in fluid
isolation from the cathode and fluid flow paths.
[0020] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the anode
fluid flow path.
[0021] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the cathode
fluid flow path.
[0022] In any one or combination of the foregoing aspects, the
process water thermal management flow path can include the fluid
flow path in operative thermal communication with the cathode or
with the anode or with both the cathode and the anode and in fluid
isolation from the cathode and fluid flow paths.
[0023] In any one or combination of the foregoing aspects, the
fluid flow path in operative thermal communication with the cathode
or with the anode or with both the cathode and the anode and in
fluid isolation from the cathode and fluid flow paths can include a
conduit disposed on the cathode fluid flow path or anode fluid flow
path.
[0024] In any one or combination of the foregoing aspects, the
method can further include a plurality of said electrochemical
cells in a stack separated by electrically-conductive fluid flow
separators wherein the fluid flow path in operative thermal
communication with the cathode or with the anode or with both the
cathode and the anode and in fluid isolation from the cathode and
fluid flow paths includes an internal passage through one or more
of the electrically-conductive fluid flow separators.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The following descriptions should not be considered limiting
in any way. With reference to the accompanying drawings, like
elements are numbered alike:
[0026] FIG. 1A is a schematic illustration of an aircraft that can
incorporate various embodiments of the present disclosure;
[0027] FIG. 1B is a schematic illustration of a bay section of the
aircraft of FIG. 1A;
[0028] FIG. 2 is a schematic depiction an example embodiment of an
electrochemical cell;
[0029] FIG. 3 is a schematic illustration of an example embodiment
of an electrochemical water treatment system;
[0030] FIG. 3 is a schematic illustration of an example embodiment
of an electrochemical inert gas generating system;
[0031] FIG. 4 is a schematic illustration of an example embodiment
of an electrochemical inert gas generating system with thermal
management;
[0032] FIG. 5 is a schematic illustration of an example embodiment
of another electrochemical inert gas generating system with thermal
management; and
[0033] FIG. 6 is a schematic illustration of an example embodiment
of another electrochemical inert gas generating system with thermal
management.
DETAILED DESCRIPTION
[0034] A detailed description of one or more embodiments of the
disclosed apparatus and method are presented herein by way of
exemplification and not limitation with reference to the
Figures.
[0035] Although shown and described above and below with respect to
an aircraft, embodiments of the present disclosure are applicable
to on-board systems for any type of vehicle or for on-site
installation in fixed systems. For example, military vehicles,
heavy machinery vehicles, sea craft, ships, submarines, etc., may
benefit from implementation of embodiments of the present
disclosure. For example, aircraft and other vehicles having fire
suppression systems, emergency power systems, and other systems
that may electrochemical systems as described herein may include
the redundant systems described herein. As such, the present
disclosure is not limited to application to aircraft, but rather
aircraft are illustrated and described as example and explanatory
embodiments for implementation of embodiments of the present
disclosure.
[0036] As shown in FIGS. 1A-1B, an aircraft includes an aircraft
body 101, which can include one or more bays 103 beneath a center
wing box. The bay 103 can contain and/or support one or more
components of the aircraft 101. For example, in some
configurations, the aircraft can include environmental control
systems (ECS) and/or on-board inerting gas generation systems
(OBIGGS) within the bay 103. As shown in FIG. 1B, the bay 103
includes bay doors 105 that enable installation and access to one
or more components (e.g., OBIGGS, ECS, etc.). During operation of
environmental control systems and/or fuel inerting systems of the
aircraft, air that is external to the aircraft can flow into one or
more ram air inlets 107. The outside air may then be directed to
various system components (e.g., environmental conditioning system
(ECS) heat exchangers) within the aircraft. Some air may be
exhausted through one or more ram air exhaust outlets 109.
[0037] Also shown in FIG. 1A, the aircraft includes one or more
engines 111. The engines 111 are typically mounted on the wings 112
of the aircraft and are connected to fuel tanks (not shown) in the
wings, but may be located at other locations depending on the
specific aircraft configuration. In some aircraft configurations,
air can be bled from the engines 111 and supplied to OBIGGS, ECS,
and/or other systems, as will be appreciated by those of skill in
the art.
[0038] Referring now to FIG. 2, an electrochemical cell is
schematically depicted. The electrochemical cell 10 comprises a
separator 12 that includes an ion transfer medium. As shown in FIG.
2, the separator 12 has a cathode 14 disposed on one side and an
anode 16 disposed on the other side. Cathode 14 and anode 16 can be
fabricated from catalytic materials suitable for performing the
needed electrochemical reaction (e.g., the oxygen-reduction
reaction at the cathode and an oxidation reaction at the anode).
Exemplary catalytic materials include, but are not limited to,
nickel, platinum, palladium, rhodium, carbon, gold, tantalum,
titanium, tungsten, ruthenium, iridium, osmium, zirconium, alloys
thereof, and the like, as well as combinations of the foregoing
materials. Cathode 14 and anode 16, including catalyst 14' and
catalyst 16', are positioned adjacent to, and preferably in contact
with the separator 12 and can be porous metal layers deposited
(e.g., by vapor deposition) onto the separator 12, or can have
structures comprising discrete catalytic particles adsorbed onto a
porous substrate that is attached to the separator 12.
Alternatively, the catalyst particles can be deposited on high
surface area powder materials (e.g., graphite or porous carbons or
metal-oxide particles) and then these supported catalysts may be
deposited directly onto the separator 12 or onto a porous substrate
that is attached to the separator 12. Adhesion of the catalytic
particles onto a substrate may be by any method including, but not
limited to, spraying, dipping, painting, imbibing, vapor
depositing, combinations of the foregoing methods, and the like.
Alternately, the catalytic particles may be deposited directly onto
opposing sides of the separator 12. In either case, the cathode and
anode layers 14 and 16 may also include a binder material, such as
a polymer, especially one that also acts as an ionic conductor such
as anion-conducting ionomers. In some embodiments, the cathode and
anode layers 14 and 16 can be cast from an "ink," which is a
suspension of supported (or unsupported) catalyst, binder (e.g.,
ionomer), and a solvent that can be in a solution (e.g., in water
or a mixture of alcohol(s) and water) using printing processes such
as screen printing or ink jet printing.
[0039] The cathode 14 and anode 16 can be controllably electrically
connected by electrical circuit 18 to a controllable electric power
system 20, which can include a power source (e.g., DC power
rectified from AC power produced by a generator powered by a gas
turbine engine used for propulsion or by an auxiliary power unit)
and optionally a power sink 21. In some embodiments, the electric
power system 20 can optionally include a connection to the electric
power sink 21 (e.g., one or more electricity-consuming systems or
components onboard the vehicle) with appropriate switching (e.g.,
switches 19), power conditioning, or power bus(es) for such
on-board electricity-consuming systems or components, for optional
operation in an alternative fuel cell mode.
[0040] With continued reference to FIG. 2, a cathode supply fluid
flow path 22 directs gas from an air source (not shown) into
contact with the cathode 14. Oxygen is electrochemically depleted
from air along the cathode fluid flow path 23, and can be exhausted
to the atmosphere or discharged as nitrogen-enriched air (NEA)
(i.e., oxygen-depleted air, ODA) to an inerting gas flow path 24
for delivery to an on-board fuel tank (not shown), or to a vehicle
fire suppression system associated with an enclosed space (not
shown), or controllably to either or both of a vehicle fuel tank or
an on-board fire suppression system. An anode fluid flow path 25 is
configured to controllably receive an anode supply fluid from an
anode supply fluid flow path 22'. The anode fluid flow path 25
includes water when the electrochemical cell is operated in an
electrolytic mode to produce protons at the anode for proton
transfer across the separator 12 (e.g., a proton transfer medium
such as a proton exchange membrane (PEM) electrolyte or phosphoric
acid electrolyte). If the system is configured for alternative
operation in a fuel cell mode, the anode fluid flow path 25 can be
configured to controllably also receive fuel (e.g., hydrogen). The
protons formed at the anode are transported across the separator 12
to the cathode 14, leaving oxygen on the anode fluid flow path,
which is exhausted through an anode exhaust 26. Control of fluid
flow along these flow paths can be provided through conduits and
valves (not shown), which can be controlled by a controller 36. The
controller can include a microprocessor that is programmed with
instructions for sending signals to carry out control of any of the
operations described herein.
[0041] Exemplary materials from which the electrochemical proton
transfer medium can be fabricated include proton-conducting
ionomers and ion-exchange resins. Ion-exchange resins useful as
proton conducting materials include hydrocarbon- and
fluorocarbon-type resins. Fluorocarbon-type resins typically
exhibit excellent resistance to oxidation by halogen, strong acids,
and bases. One family of fluorocarbon-type resins having sulfonic
acid group functionality is NAFION.TM. resins (commercially
available from E. I. du Pont de Nemours and Company, Wilmington,
Del.). Alternatively, instead of an ion-exchange membrane, the
separator 12 can be comprised of a liquid electrolyte, such as
sulfuric or phosphoric acid, which may preferentially be absorbed
in a porous-solid matrix material such as a layer of silicon
carbide or a polymer than can absorb the liquid electrolyte, such
as poly(benzoxazole). These types of alternative "membrane
electrolytes" are well known and have been used in other
electrochemical cells, such as phosphoric-acid fuel cells.
[0042] During operation of a proton transfer electrochemical cell
in the electrolytic mode, water at the anode undergoes an
electrolysis reaction according to the formulae:
H.sub.2O.fwdarw.1/2O.sub.2+2H.sup.++2e.sup.- (1)
The electrons produced by this reaction are drawn from electrical
circuit 18 powered by electric power source 20 connecting the
positively charged anode 16 with the cathode 14. The hydrogen ions
(i.e., protons) produced by this reaction migrate across the
separator 12, where they react at the cathode 14 with oxygen in the
cathode flow path 23 to produce water according to the formula
1/2O.sub.2+2H.sup.++2e.sup.-.fwdarw.H.sub.2O (2)
Removal of oxygen from cathode flow path 23 produces
nitrogen-enriched air exiting the region of the cathode 14. The
oxygen evolved at the anode 16 by the reaction of formula (1) is
discharged as anode exhaust 26.
[0043] During operation of a proton transfer electrochemical cell
in a fuel cell mode, fuel (e.g., hydrogen) at the anode undergoes
an electrochemical oxidation according to the formula
H.sub.2.fwdarw.2H.sup.++2e.sup.- (3)
[0044] The electrons produced by this reaction flow through
electrical circuit 18 to provide electric power to the electric
power sink 21. The hydrogen ions (i.e., protons) produced by this
reaction migrate across the separator 12, where they react at the
cathode 14 with oxygen in the cathode flow path 23 to produce water
according to the formula (2).
1/2O.sub.2+2H.sup.++2e.sup.-.fwdarw.H.sub.2O (2)
Removal of oxygen from cathode flow path 23 produces
nitrogen-enriched air exiting the region of the cathode 14.
[0045] As mentioned above, the electrolysis reaction occurring at
the positively charged anode 16 requires water, and the ionic
polymers used for a PEM electrolyte perform more effectively in the
presence of water. Accordingly, in some embodiments, a PEM membrane
electrolyte is saturated with water or water vapor. Although the
reactions (1) and (2) are stoichiometrically balanced with respect
to water so that there is no net consumption of water, in practice
some amount of moisture will be removed through the cathode exhaust
24 and/or the anode exhaust 26 (either entrained or evaporated into
the exiting gas streams). Accordingly, in some exemplary
embodiments, water from a water source is circulated past the anode
16 along an anode fluid flow path (and optionally also past the
cathode 14). Such water circulation can also provide cooling for
the electrochemical cells. In some exemplary embodiments, water can
be provided at the anode from humidity in air along an anode fluid
flow path in fluid communication with the anode. In other
embodiments, the water produced at cathode 14 can be captured and
recycled to anode 16 (e.g., through a water circulation loop, not
shown). It should also be noted that, although the embodiments are
contemplated where a single electrochemical cell is employed, in
practice multiple electrochemical cells will be electrically
connected in series with fluid flow to the multiple cathode and
anode flow paths routed through manifold assemblies.
[0046] An example embodiment of an inerting system that can be used
as an on-board aircraft inerting system with an electrochemical
cell 10 (or cell stack) is schematically shown in FIG. 3. As shown
in FIG. 3, water from a process water source 28 is directed (e.g.,
by a pump, not shown) along the anode supply fluid flow path 22' to
the anode fluid flow path 25, where it is electrolyzed at the anode
16 to form protons, and oxygen. The protons are transported across
the separator 12 to the cathode 14, where they combine with
electrons from an external circuit (18, FIG. 2) and oxygen from
airflow along the cathode fluid flow path 23 to form water. Removal
of the protons from the anode fluid flow path 25 leaves oxygen gas
on the anode fluid flow path, which is discharged as anode exhaust
26 to an anode discharge fluid flow path 26'. As further shown in
FIG. 3, the fluid flow path 26' includes a gas-liquid separator 27.
Although water is consumed at the anode by electrolysis, the fluid
exiting as anode exhaust 26 can include gaseous oxygen and water
vapor, which is separated as a gas stream 29 that can be exhausted
to atmosphere or can be used for other applications such as an
oxygen stream directed to aircraft occupant areas, occupant
breathing devices, an oxygen storage tank, or an emergency aircraft
oxygen breathing system. The gas-liquid separator 27 can include a
tank with a liquid space and a vapor space inside, allowing for
liquid water to be removed from the liquid space and transported
back to the electrochemical cell 10 through water return conduit
32. Additional gas-liquid separators can be used such as a
coalescing filter, vortex gas-liquid separator, or membrane
separator.
[0047] As further shown in FIG. 3, the electrochemical cell 10 (or
cell stack) generates an inerting gas on the cathode fluid flow
path 23 by depleting combustible oxygen from an air flow to produce
oxygen-depleted air (ODA), also known as nitrogen-enriched air
(NEA) at the cathode 14, which can be directed to a protected space
54 (e.g., a fuel tank ullage space, a fire suppression system, a
cargo hold, an equipment bay). As shown in FIG. 3, an air source 52
(e.g., ram air, compressor bleed, blower) is directed to the
cathode fluid flow path 23 where oxygen is depleted by reaction
with protons that have crossed the separator 12 to form water at
the cathode 14. The ODA thereby produced can be directed to the
protected space 54. The inerting gas flow path (cathode exhaust 24)
can include additional components (not shown) such as flow control
valve(s), a pressure regulator or other pressure control device,
and water removal device(s) such as a heat exchanger condenser, a
membrane drier or other water removal device(s), or a filter or
other particulate or contaminant removal devices. Additional
information regarding the electrochemical production of ODA can be
found in U.S. Pat. No. 9,963,792, US Patent Application Publication
No. 2017/0331131A1, and U.S. patent application Ser. No.
16/029,024, the disclosures of each of which are incorporated
herein by reference in their entirety.
[0048] In some embodiments, the electrochemical cell can be used in
an alternate mode to provide electric power for on-board
power-consuming systems, as disclosed in the aforementioned US
Patent Application Publication No. 2017/0331131A1. In this mode,
fuel (e.g., hydrogen) is directed from a fuel source to the anode
16 where hydrogen molecules are split to form protons that are
transported across the separator 12 to combine with oxygen at the
cathode. Simultaneously, reduction and oxidation reactions exchange
electrons at the electrodes, thereby producing electricity in an
external circuit (18, 21 FIG. 2). Embodiments in which these
alternate modes of operation can be utilized include, for example,
operating the system in a first mode of water electrolysis (either
continuously or at intervals) under normal aircraft operating
conditions (e.g., in which an engine-mounted generator provides
electrical power) and operating the system in a second mode of
electrochemical electricity production in response to a demand for
emergency electrical power (e.g., failure of an engine-mounted
generator). ODA can be produced at the cathode 14 in each of these
alternate modes of operation.
[0049] With reference now to FIG. 4, an example embodiment is shown
of a gas inerting system utilizing an electrochemical cell stack
10' (including seals, end plates, and other hardware as known to
the skilled person) and a thermal management system. Also, for ease
of illustration, the separator 12, cathode 14, and anode 16 and
flow paths for a stack are simplified with a representation of
simple flow paths on each side of a single membrane electrode
assembly (MEA) 15. It is noted that FIG. 4 shows counter-flow
between the anode and cathode sides of the MEA 15 and that FIG. 3
shows co-flow; however, many configurations can utilize cross-flow
configurations that for ease of illustration are not shown in the
Figures herein. As shown in FIG. 4, the cathode side of the
electrochemical cell stack 10' produces ODA on the cathode fluid
flow path 23 as inerting gas for a protected space in the same
manner as discussed above with respect to FIG. 3. Thermal
management is provided as discussed in more detail below. It is
noted that, although not shown in FIG. 4, process water for thermal
management can also be in fluid and thermal communication with the
cathode side of the electrochemical cell as will be understood by
the skilled person. On the anode side, process water from a water
source (e.g. a water reservoir 28' equipped with a process make-up
water feed line 33) is directed along the anode supply fluid flow
path 22' by a pump 34. The pump 34 provides a motive force to move
the process water along the anode supply fluid flow path 22' and
through a flow control valve 30 to the anode fluid flow path 25. As
discussed above, oxygen is produced at the anode 16 and proceeds
along with the process water on the fluid flow 26', where it is
directed through to a heat exchanger 38. The location of the pump
34 shown in FIG. 4 is representative of one example embodiment, and
the pump 34 can be at other locations in the system, e.g., on the
anode discharge fluid flow path 26'. Oxygen or other gases on the
process water fluid flow path can be removed by a gas-liquid
separator (27, FIG. 3) (e.g., to avoid cavitation of pump 34) or
can be separated in the water reservoir 28'. The heat exchanger 38
can provide heating or cooling from a heat sink/heat source along
the fluid flow path 40 (e.g., RAM air, a refrigerant from a cooling
system such as a vapor compression cooling system, a heat transfer
fluid in fluid/thermal communication with a heat source (e.g., hot
engine compressor bleed air destined for an on-board ECS or
electric heater coils). Multiple heat exchangers (e.g., separate
cooling heat exchangers and heating heat exchangers) can also be
used. Process water exiting from the heat exchanger 38 is then
returned to the water reservoir 28' along flow path 42.
[0050] In some embodiments, the controller 36 can be
configured/programmed to control either the flow rate of process
water and/or the temperature of the process water fluid flowing
through the electrochemical stack 10'. A temperature sensor 31 is
shown in FIG. 4 disposed in the flow path 26', and can measure the
temperature of the process water as well as being in thermal
communication with the anode (through the process water exiting the
anode fluid flow path 25 where it was in fluid communication with
the anode). The control of flow and/or temperature of the process
water can provide a technical effect of removing a target amount of
heat generated by the electrochemical cell. The enthalpy of the
chemical reactions resulting from electrolytic generation of
inerting gas occurring on the anode and cathode sides of the
electrochemical cell are balanced, with water molecules being split
on the anode side and atoms combined to form water on the cathode
side. Accordingly, the electrical energy entered into the system
results in generation of heat. At the same time, there are
competing factors regarding a target temperature, with higher
temperatures desired to promote electrolysis of water on the anode
side, and lower temperatures favored on the cathode side to promote
away from water vapor entering the inerting gas that is directed to
a fuel tank ullage space where water vapor is not desired.
Accordingly, achieving an optimum target temperature in the
electrochemical cell through thermal management can be
beneficial.
[0051] Flow rate of the process water through the electrochemical
cell can be regulated by controlling the speed of the pump 34 or
with a control valve (not shown) along the process water flow path
(e.g., 22'). Control of process water temperature based on output
from a temperature sensor (not shown) along the anode fluid flow
path 25 (and/or a temperature sensor along the cathode fluid flow
path 23) can be accomplished, for example, by controlling the flow
of process water through the heat exchanger 38 (e.g., by
controlling the speed of the pump 34 or by diverting a controllable
portion of the output flow of the pump 34 through a bypass around
the heat exchanger 38 with control valves (not shown)) or by
controlling the flow of a heat transfer fluid through the heat
exchanger 38 along the flow path represented by 40.
[0052] In some embodiments, process water for thermal management
can be directed along a flow path that is in thermal communication
with the anode 16 or with the cathode 14 or with both the anode 16
and the cathode 14, but is in fluid isolation from the cathode
fluid flow path 23 and the anode fluid flow path 25. This can
provide a beneficial technical effect of allowing for optimum water
flow to the anode 16 for electrolysis to produce protons that
remove oxygen at the cathode 14while allowing for separate control
of cooling water to achieve optimum temperatures. Additionally, the
design of separate flow paths for thermal management can provide
for opposite-direction or cross-direction flows, and for multiple
passes of thermal control water through anode or cathode fluid flow
paths. Moreover, flows of water for thermal control on flow paths
that are separate from the cathode and anode fluid flow paths
allows for thermal management to be optimized without regard for
impact on hydrodynamic effects on the electrochemical reactions
occurring at the electrodes.
[0053] An example embodiment of a system with segregated thermal
management fluid flow paths is schematically shown in FIG. 5. As
shown in FIG. 5, a stack 10' of electrochemical cells with
electrically-conductive fluid flow separators (i.e., bipolar
plates) 48 between adjacent electrochemical cells is depicted. The
stack 10' is shown with two electrochemical cells, but typical
stacks will contain a greater number of cells. The system shown in
FIG. 5 divides the process water flow to the stack 10', with anode
supply flow path 22' flowing through control valve 22'', and a
thermal control flow path 44 flowing through control valve 46 and
through passages disposed within the bipolar plates 48 (e.g.,
hollow bipolar plates). The outlet from the anode fluid flow paths
25 and the passages in the bipolar plates 48 are re-combined and
then routed back to the water reservoir 28' in the same fashion as
shown in FIG. 4.
[0054] Of course, routing of the thermal control process water
through passages in the bipolar plates is one example embodiment of
a thermal control flow path isolated from the cathode and anode
fluid flow paths 23/25, and thermal control can be implemented with
other example embodiments. One such example embodiment is shown in
FIG. 6. As shown in FIG. 6, process water for thermal control is
routed through conduits 49 disposed along the cathode fluid flow
paths 23 to provide thermal management without addition of water
into the cathode fluid flow path that could end up in fuel
tanks.
[0055] The term "about" is intended to include the degree of error
associated with measurement of the particular quantity based upon
the equipment available at the time of filing the application.
[0056] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the present disclosure. As used herein, the singular forms "a",
"an", "the", or "any" are intended to include the plural forms as
well, unless the context clearly indicates otherwise. It will be
further understood that the terms "comprises" and/or "comprising,"
when used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, element components, and/or
groups thereof.
[0057] While the present disclosure has been described with
reference to an exemplary embodiment or embodiments, it will be
understood by those skilled in the art that various changes may be
made and equivalents may be substituted for elements thereof
without departing from the scope of the present disclosure. In
addition, many modifications may be made to adapt a particular
situation or material to the teachings of the present disclosure
without departing from the essential scope thereof. Therefore, it
is intended that the present disclosure not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this present disclosure, but that the present
disclosure will include all embodiments falling within the scope of
the claims.
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