METHOD AND ARTICLE OF MANUFACTURE TO EFFECT AN OXYGEN DEFICIENT FUEL CELL
Technical Field of the Invention
The instant invention relates in general to fuel cells and in particular to a method and
article of manufacturing for replacing ambient air containing oxygen within a fuel cell with
an oxygenless gas, such as, but not limited to, propane, helium, or nitrogen.
Background of the Invention
The practice of inerting a gas into a fuel cell, particularly fuel cells such as aircraft
fuel tanks is well known in the art. For example:
United States Patent No. 2,870,936 issued to A.J. Clayton on January 27, 1959
discloses a closed system for venting and inerting aircraft fuel tanks.
United States Patent No. 3,587,618 issued to Richard L. Kenyon on June 28, 1971
discloses a fire and explosion prevention system for aircraft fuel tanks that utilizes an inert
gas for pressurizing the fuel tanks and in which means is provided for preventing over-
pressurization of the fuel tanks in case of either clogging of vent passages that normally
connect the fuel tanks to atmosphere or failure of vent valves to open, hereafter referred to
as the "618" patent.
Quite distinct from the '618 patent which uses liquid nitrogen and thus requires
refrigeration to maintain the operational effectiveness of such nitrogen, the instant invention
utilizes a gaseous form of nitrogen. A further distinguishing characteristic and benefit of the instant invention is its utilization of a containment vessel requiring far less space than any
refrigeration unit associated with the '618 invention. Further, the instant invention
eliminates the attendant weight of the '618 refrigeration unit by replacing the '618's liquid
nitrogen with a gaseous form of nitrogen contained within a comparatively small pressurized
tank.
United States Patent No. 3,590,559 issued to Kenneth R. Bragg et al. on July 6,
1971 discloses an inerting system to prevent fire and explosion within aircraft or other fuel
tanks by maintaining in the ullage thereof an inert atmosphere and by removing oxygen from
the fuel when pressure on the fuel decreases, as during the climb of aircraft, such removal
of oxygen being accomplished by injecting a mixture of fuel and an inert gas into the fuel
supply through submerged nozzles.
United States Patent No. 3,732,668 issued to Richard A. Nichols on May 15, 1973
discloses a system for inerting aircraft fuel tanlcs comprising mixing of the fuel and an inert
gas within a tube whereby the inert gas scrubs the fuel of oxygen dissolved therein and
dilutes the same, the mixture being discharged from the tube into the fuel tank where the
inert gas and the oxygen rise to the tank vapor space where a portion of the same may be
vented to atmosphere but in any case the oxygen
content in the vapor space is less than about 12 percent whereby flame and explosion cannot
propagate within the tank.
United States Patent No. 3,788,040 issued to Kenneth R. Bragg et al. on January
29, 1974 discloses a method of maintaining the ullage of a previously inerted aircraft fuel
tank in the inert condition under which combustion cannot take place within the tank during
the after filling of the tank with liquid fuel, and during flight of the aircraft. The method ,
utilizes the oxygen lean ullage gases for scrubbing oxygen from incoming fuel during filling
of the tank, separating the gases having scrubbed oxygen therein from the incoming fuel and
venting the same to the exterior of the tank so as not to raise the oxygen content of the gases
remaining in the ullage.
United States Patent No. 4,378,920 issued to Joe N. Runnels et al. on April 5, 1983
discloses a combustibly inert air supply system and method wherein compressed air is
directed through an inert gas generator which removes oxygen to produce a nitrogen
enriched, combustibly inert air or gas. The converter is sized to only meet the relatively low
flow rate requirements of the system during which times the combustibly inert air or gas is
delivered directly to a utilization site. The system further includes a high pressure storage
container in which a pressurized precharge of the combustibly inert air or gas is stored.
Combustibly inert air is released from such high pressure storage container for providing the
higher flow rate requirements of the system. The system may be used aboard an aircraft for
inerting fuel tanks. It may include a separate compressor for filling the high pressure storage
container.
In view of the limitations and disadvantages of the afore cited prior art, it is apparent
that what is needed is an improved method and article of manufacture to effect an oxygen
deficient fuel
cell which will minimize potential for flame and explosion within an aircraft fuel tank. A
need met and exceeded by the instant invention.
Brief Summary of the Invention
A method and article of manufacture to effect an oxygen deficient fuel cell which
will minimize the potential for flame and explosion occurring within an aircraft fuel tank.
A first containment vessel contains a pressurized oxygen-free gas, such as, but not
limited to, propane, nitrogen or helium. The containment vessel is first connected to a
pressure regulator via a pressurized conduit. The pressurized conduit can be constructed of
any material capable of transporting oxygen-free gas in a pressurized environment. Said
conduit is utilized to facilitate the transport of said oxygen-free gas from the first
containment vessel to and through a pressure regulator continuing to and through a demand
regulator exiting said demand regulator and entering into a fuel cell. The fuel cell also
comprises a exiting gas outflow conduit and outflow valve. In an alternative embodiment
of the instant invention an oxygen sensor can be attached to either the exiting gas outflow
conduit, the outflow valve or integrated within the outflow valve to sample for and signal
the presence of oxygen within the fuel cell.
The invention is practiced by charging the internal portion of a fuel cell with a
hydrocarbon based fuel, such as but not limited to aviation fuel.
An object of the instant invention is to minimize the potential for flame and
explosion occurring within an aircraft fuel tank.
A further object of the instant invention is to eliminate excessive weight restrictions
attendant to prior art approaches to minimize the potential for flame and explosion occurring
within an aircraft fuel tank.
Yet another object of the instant invention is to provide a comprehensive, yet
uncomplicated method and apparatus to effect an oxygen deficient fuel cell.
Other objects and further scope of the applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction with the
accompanying drawings wherein like parts are designated by like reference numerals.
Description of the Drawings
Figure 1 is an illustration of operational components necessary to effect the practice
of the invention's preferred embodiment.
Detailed Description of the Preferred Embodiment
While the making and using of various embodiments of the present invention are
discussed in detail below, it should be appreciated that the present invention provides for
inventive concepts capable of being embodied in a variety of specific contexts. The specific
embodiments discussed herein are merely illustrative of specific manners in which to make
and use the invention and are not to be interpreted as limiting the scope of the instant
invention.
The claims and the specification describe the invention presented and the terms that
are employed in the claims draw their meaning from the use of such terms in the
specification. The same terms employed in the prior art may be broader in meaning than
specifically employed herein. Whenever there is a question between the broader definition
of such terms used in the prior art and the more specific use of the terms herein, the more
specific meaning is meant.
While the invention has been described with a certain degree of particularity, it is
clear that many changes may be made in the details of construction and the arrangement of
components without departing from the spirit and scope of this disclosure. It is understood
that the invention is not limited to the embodiments set forth herein for purposes of
exemplification, but is to be limited only by the scope of the attached claim or claims,
including the full range of equivalency to which each element thereof is entitled.
Figure 1 illustrates the invention's preferred embodiment for effecting an oxygen
deficient fuel cell. A first containment vessel 5 contains a pressurized oxygen-free gas, such
as, but not limited to, propane, nitrogen or helium. The containment vessel is first connected
to a pressure regulator 10 via a pressurized conduit 15. The pressurized conduit 15 can be
constructed of any material capable of transporting oxygen-free gas in a pressurized
environment. Said conduit 15 is utilized to facilitate the transport of said oxygen-free gas
from said first containment vessel 5 to and through a pressure regulator 10 at a reduced
pressure 16 continuing to and through an electric, vacuum or otherwise actuated demand
regulator 20 exiting said demand regulator 20 and entering into a fuel cell 25. The fuel cell
25 also comprises a exiting gas outflow conduit 33 and outflow valve 30. Said outflow
valve 30 designed and purposed to ensure pressure limits within the fuel cell 25 do not
exceed limits established by the fuel cell manufacturer for safe and efficient operation of the
cell. In an alternative embodiment of the instant invention an oxygen sensor 34 can be
housed within the fuel cell 25, attached to the exiting gas outflow conduit 33, the outflow
valve 30 or integrated within the outflow valve 30 to sample for and signal the presence of
oxygen within, or exiting the fuel cell 25. For applications presently embodying a one way
outflow valving mechanism, such as certain aircraft types, the present invention, in an
alternative embodiment can be fitted to accommodate the existing mechanism for venting
purposes.
The invention is practiced by charging the internal portion of a fuel cell 25 with a
hydrocarbon based fuel, such as but not limited to aviation fuel. Said charging effectuates
the displacement of pre-existing ambient air residing within the fuel cell 25 insufficient
volume effecting a combustionable flashpoint. Fueling (a.k.a. "charging") continues until
such time as the fuel cell 25 is either filled with the introduced fuel source 38 or
alternatively, until a desired amount of fuel 38 has entered the fuel cell 25. Should the fuel
cell 25 contain oxygen levels in excess of that necessary to effect combustion, the cell 25
is further purged of such oxygen laden ambient air by further introducing said oxygen
deficient gas is transported from the first containment vessel 5 through pressure regulator
10 continuing through demand regulator 20 and into the fuel cell 25 until ambient air within
said fuel cell 25 possesses oxygen levels below that necessary to effect and system
combustion. Said purging just described to be effectuated by overriding demand regular 20
pressure limitations and allowing for venting of said ambient air via the invention's gas
outflow conduit 33 and outflow valve 30. Though the present invention allows for varying
degrees of pressurization, it has been determined through experimentation and modeling that
for aviation purposes, that the oxygen-free gas having been initially pressurized to
approximately 3000 psi while resident in a first containment vessel 5, such pressure should
be reduced to an approximate effective operating pressure of 75 psi upon exiting 18 the
pressure regulator 10 through the demand regulator 20, then lowered again 17 to a pressure
consistent with that existing within the fuel cell 25. As other applications of the instant
invention may require varying degrees of pressurization, those reasonably skilled in the
relevant art can effect an operationally efficient pressurization for such applications by
modifying pressure regulator 10 and demand regulator 20 settings.
The instant invention maintains its operational efficiency by introducing said
pressurized oxygen deficient gas to the internal portion of the fuel cell simultaneously with
the diminishing of the previously introduced fuels 38 volume. As the fuel volume is
diminished within the internal portion of the fuel cell 25 the demand regulator 20 allows for
the further introduction of oxygen-free gas 35 into the fuel cell 25.
The invention further provides for releasing said pressurized oxygen deficient gas
35 whenever the pressure within the internal structure of the fuel cell exceeds a pressure
necessary to effectuate and maintain application operational efficiency. Such exiting of
oxygen-free gas 35 is facilitated by an exiting gas outflow conduit 33 attached to an outflow
valve 30.
An alternative embodiment of the instant invention would allow for quick
connect/disconnect components to be attached to any juncture between the pressurized
conduit 15 and first containment vessel 5, pressure regulator 10, demand regulator 20, and
fuel cell 25. Said quick connect/disconnect means may also be employed with respect to the
utilization of the upflow exiting conduit 33, outflow valve 30 and/or oxygen sensor 34. As
will readily be appreciated by those skilled in the art, the ability for quick
connect/disconnect greatly reduces or eliminates the labor associated with removing and
replacing operational components of the instant invention while reducing fatigue on more
strenuously attached coupling mechanisms.
The instant invention application can be readily appreciated and envisioned with
respect to its use in the aviation industry. In such an application, the fuel cell 25 would be
represented as the fuel containment capacity of an aircraft fuel cell typically manifested as
the internal construct of an aircraft wing. The containment vessel within which the
oxygenless gas resides prior to introduction to the fuel cell 25 can be located in any
convenient environment allowing for rapid servicing by ground personnel during routine
practice of the invention. Such locations would include but not be limited to an airplane
cockpit, tail structure, internal cabin, or any space available which would provide adequate
load bearing and volume capacity to house the containment vessel 5 for an appropriate
aircraft application. Such environments would typically vary with respect to the aircraft
utilized. A 747 passenger airliner would obviously require a greater space to house the
containment vessel 5 while smaller applications in private aircrafts would require less space.
Though the invention in its preferred embodiment utilizes a demand regulator 20 to
determine when additional oxygen-free gas should be introduced to the fuel cell 25, a
combination of valves allowing for such introduction and sensors well known to those
skilled in the art could be used in an alternative configuration.
While this invention has been described to illustrative embodiments, this description
is not to be construed in a limiting sense. Various modifications and combinations of the
illustrative embodiments as well as other embodiments will be apparent to those skilled in
the art upon referencing this disclosure. It is therefore intended that this disclosure
encompass any such modifications or embodiments.
Alternate Embodiments
The foregoing description, for purposes of explanation, used specific nomenclature
to provide a thorough understanding of the invention. However, it will be apparent to one
skilled in the art that the specific details are not required in order to practice the invention.
In other instances, well lαiown circuits and devices are shown in block diagram form in
order to avoid unnecessary distraction from the underlying invention. Thus, the foregoing
descriptions of specific embodiments of the present invention are presented for purposes of
illustration and description. They are not intended to be exhaustive or to limit the invention
to the precise forms disclosed, obviously many modifications and variations are possible in
view of the above teachings. The embodiments were chosen and described in order to best
explain the principles of the invention and its practical applications, to thereby enable others
skilled in the art to best utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It is intended that the scope
of the invention be defined by the following claims and their equivalents.
Although the present invention has been described with reference to the aviation
industry, it is not limited to this particular application. Utilization of the present invention in any application utilizing volatile fuel within a pressurized fuel cell can be ready
appreciated by those skilled in the art.