U.S. patent application number 12/831767 was filed with the patent office on 2011-01-13 for flashback shut-off.
This patent application is currently assigned to Firestar Engineering, LLC. Invention is credited to Kenneth Doyle, David J. Fisher, Gregory S. Mungas.
Application Number | 20110005194 12/831767 |
Document ID | / |
Family ID | 43426386 |
Filed Date | 2011-01-13 |
United States Patent
Application |
20110005194 |
Kind Code |
A1 |
Doyle; Kenneth ; et
al. |
January 13, 2011 |
FLASHBACK SHUT-OFF
Abstract
A flashback-arresting shut-off valve is disclosed herein.
Propellant is moved from a propellant reservoir, through the
shut-off valve in an open configuration to a point of combustion in
a normal propellant flow direction. During a flashback, the
propellant is ignited within the propellant line and substantial
physical/thermal energy caused by the flashback travels in the
direction opposite to the normal propellant flow direction back to
the shut-off valve. A burst member within the shut-off valve fails
because of the flashback. Failure of the burst member causes
compression on a spring-loaded portion of the shut-off valve to be
released, thereby closing the shut-off valve and sealing the
propellant reservoir from the flashback. Failure of the burst
member also causes one or more pressure relief outlets to open that
direct the physical/thermal energy and/or un-combusted/combusted
propellant out and away from the shut-off valve.
Inventors: |
Doyle; Kenneth; (Quartz
Hill, CA) ; Mungas; Gregory S.; (Arcadia, CA)
; Fisher; David J.; (Tehachapi, CA) |
Correspondence
Address: |
HENSLEY KIM & HOLZER, LLC
1660 LINCOLN STREET, SUITE 3000
DENVER
CO
80264
US
|
Assignee: |
Firestar Engineering, LLC
Mojave
CA
|
Family ID: |
43426386 |
Appl. No.: |
12/831767 |
Filed: |
July 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61223611 |
Jul 7, 2009 |
|
|
|
Current U.S.
Class: |
60/243 |
Current CPC
Class: |
F16K 17/366 20130101;
Y10T 156/10 20150115; Y10T 29/49 20150115; F16K 17/40 20130101;
F02K 9/566 20130101; F23D 14/82 20130101 |
Class at
Publication: |
60/243 |
International
Class: |
F02K 3/00 20060101
F02K003/00 |
Claims
1. A propellant shut-off assembly for isolating a propellant
source, comprising: a burst membrane configured to fail in presence
of a flashback; and a biased closed shut-off valve attached to the
burst membrane, wherein the shut-off valve is held open by the
burst membrane while the burst member is intact.
2. The propellant shut-off assembly of claim 1, further comprising:
a flashback deflector configured to deflect the flashback toward
the burst membrane.
3. The propellant shut-off assembly of claim 1, further comprising:
a porous media element configured to permit propellant to flow
through the propellant shut-off assembly in a propellant flow
direction and prevent the flashback from flowing through the
propellant shut-off assembly in a direction opposite the propellant
flow direction.
4. The propellant shut-off assembly of claim 1, wherein the
shut-off valve is biased closed using one or more springs storing
mechanical energy.
5. The propellant shut-off assembly of claim 4, further comprising:
one or more nuts configured to adjust the closing bias of the one
or more springs storing mechanical energy.
6. The propellant shut-off assembly of claim 1, wherein the
shut-off valve includes: a propellant inlet tube with a valve seat
at a distal end of the propellant inlet tube; and a receptor with a
valve at a distal end of the receptor, wherein the valve is adapted
to seal against the valve seat when the propellant shut-off
assembly is in a closed position.
7. The propellant shut-off assembly of claim 6, further comprising:
a bellows attached to the propellant inlet tube and the receptor,
wherein the bellows provides a seal between the propellant inlet
tube and the receptor while allowing the receptor to move in
relation to the propellant inlet tube.
8. The propellant shut-off assembly of claim 1, further comprising:
one or more pressure relief outlets configured to provide an outlet
for exhaust gasses when the burst membrane fails.
9. The propellant shut-off assembly of claim 1, wherein the burst
member is under tension while intact.
10. The propellant shut-off assembly of claim 1, wherein the burst
member is thinner at its center and thicker at its edges.
11. The propellant shut-off assembly of claim 1, wherein the burst
member includes a plurality of circumferential grooves.
12. The propellant shut-off assembly of claim 1, wherein propellant
is permitted to flow through the propellant shut-off assembly so
long as the shut-off valve is held open by the burst membrane and
propellant is not permitted to flow through the propellant shut-off
assembly when the burst membrane is fractured causing the shut-off
valve to close.
13. The propellant shut-off assembly of claim 1, wherein the
flashback includes a detonation wave.
14. A method of arresting a flashback in a propellant shut-off
assembly, the method comprising: experiencing the flashback at the
propellant shut-off assembly; fracturing a burst membrane to
failure in response to the experiencing operation; closing the
propellant shut-off assembly in response to the fracturing
operation; and redirecting the flashback out of the propellant
shut-off assembly in response to the fracturing operation.
15. The method of claim 14, further comprising: moving propellant
through the propellant shut-off assembly in a propellant flow
direction.
16. The method of claim 14, wherein the flashback occurs downstream
of the shut-off assembly and moves in a direction opposite the
propellant flow direction back to the propellant shut-off
assembly.
17. The method of claim 14, wherein the closing operation includes:
moving a receptor in relation to a propellant inlet tube; and
sealing a ball bearing in a ball seat.
18. The method of claim 14, wherein the flashback includes a
detonation wave.
19. A propellant delivery system comprising: a propellant
reservoir; a propellant shut-off assembly for isolating a
propellant source, comprising: a burst membrane configured to fail
in presence of a flashback; and a biased closed shut-off valve
attached to the burst membrane, wherein the shut-off valve is held
open by the burst membrane while the burst member is intact; and a
propellant injector, wherein the flashback originates between the
propellant injector and the propellant shut-off assembly and the
propellant shut-off assembly is configured to isolate the
propellant reservoir from any components of the propellant delivery
system that have failed as a result of the flashback.
20. The propellant delivery system of claim 19, wherein the
propellant shut-off assembly further includes one or more pressure
relief outlets configured to provide an outlet for exhaust gasses
when the burst membrane fails.
21. The propellant delivery system of claim 19, wherein the
flashback includes a detonation wave.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims benefit of priority to U.S.
Provisional Patent Application No. 61/223,611, entitled "Propulsion
Systems and Components Thereof" and filed on Jul. 7, 2009, which is
specifically incorporated by reference herein for all that it
discloses or teaches. Further, the present application is related
to U.S. patent application Ser. No. 11/950,174, entitled
"Spark-Integrated Propellant Injector Head With Flashback Barrier,"
filed on Dec. 4, 2007; and to U.S. patent application Ser. No.
12/633,770 entitled "Regeneratively Cooled Porous Media Jacket,"
filed on Dec. 8, 2009. Still further, the present application is
related to U.S. patent application Ser. No. ______, entitled
"Tiered Porosity Flashback Suppressing Elements For Monopropellant
Or Pre-Mixed Bipropellant Systems" (Attorney Docket No.
488-011-USP1); U.S. patent application Ser. No. 12/831,703,
entitled "Detonation Wave Arrestor" (Attorney Docket No.
488-011-USP2); and U.S. patent application Ser. No. ______,
entitled "Aluminum Porous Media" (Attorney Docket No.
488-011-USP4); all three of which are filed on Jul. 7, 2010, and
which are also specifically incorporated by reference herein for
all they disclose or teach.
BACKGROUND
[0002] Power generation systems (e.g., propulsion systems, working
fluid production systems, and electricity generation systems) often
utilize a finite stored fuel source (e.g., a fuel tank) to provide
fuel to the power generation system. Some power generation systems
also utilize a stored oxidizer source (e.g., an oxidizer tank).
These systems are known as bipropellant systems. For example,
bipropellants are commonly used in liquid-propellant thrusters on
orbital vehicles. Other power generation systems utilize ambient
air as an oxidizer rather than a stored oxidizer source (e.g.,
typical internal combustion engines and turbofan/jet aircraft
engines).
[0003] In bipropellant systems, so long as the fuel source and
oxidizer are separated, neither are flammable in systems not
exposed to the atmosphere. For example, fuel sealed within a fuel
line or fuel leaking into a vacuum is not flammable). Similarly, in
systems utilizing ambient air as an oxidizer, the fuel source is
not flammable until exposed to the ambient air (e.g., at a fuel
injector in an automobile).
[0004] This feature in bipropellant and ambient air propellant
systems serves a safety function because a flame existing at the
point of ignition cannot travel up fuel and/or oxidizer lines past
the point the fuel and oxidizer are mixed together. This prevents
the flame from traveling back to the fuel tank in the bipropellant
and ambient air propellant systems and causing an explosion. As a
result, the fuel and oxidizer in many bipropellant and ambient air
propellant systems are not mixed until at the point of ignition
(e.g., within a combustion chamber in a jet engine or within a
cylinder in an internal combustion engine).
[0005] In bipropellant thrusters on orbital vehicles, it is often
desirable to store exact quantities of finite stored fuel source
and oxidizer source so that they are exhausted simultaneously
during combustion. Any fuel or oxidizer left after its counterpart
is exhausted is wasted. Further, leftover fuel or oxidizer creates
excess weight and volume during the travel of the orbital vehicle.
Considerable time and effort is spent calculating the appropriate
quantities of fuel and oxidizer to store on an orbital vehicle,
measuring consumption of the fuel and oxidizer, and detecting when
the fuel and oxidizer are spent. It is desirable to avoid these
calculation, measurement, and detection functions on an orbital
vehicle while it is in flight.
[0006] Still other power generation systems utilize a stored
monopropellant source. A monopropellant is a single energetic fluid
(i.e., a liquid, gas, or combination thereof, sometimes with solid
particles entrained within the liquid or gas) that decomposes to
liberate gases and heat. This heated gas can drive other
applications (e.g., thrusters, power systems, inflation bags,
etc.). Monopropellants typically include either a single chemical
or a mixture of multiple chemicals that when combined produce a
monopropellant blend. In the monopropellant blend, the constituent
chemicals most commonly remain well mixed and effectively behave as
a single energetic fluid. Many bipropellants (e.g., a combination
of a fuel and an oxidizer such as vaporized fuel and air) when
mixed together effectively act as a monopropellant. Monopropellants
can provide a simpler and more reliable feed-system implementation
for spacecraft due to the fewer number of fluids that need to be
precisely managed.
[0007] In one example implementation, the monopropellant is stored
as a liquid and decomposes into a hot gas in the presence of an
appropriate catalyst, upon introduction of a high-energy spark, or
upon introduction of a similar point source ignition mechanism.
Example monopropellants include hydrazine, which is often used in
spacecraft attitude control jets and hydroxyl ammonium nitrate
(HAN). Given the combustible nature of a monopropellant, in an
unintentional line ignition of the monopropellant, the
monopropellant can act like a fuse and generate combustion waves
that can move very rapidly through a fluid conduit or path full of
monopropellant (i.e., a flashback). Monopropellants and supply
systems for thrusters and other work producing systems are subject
to damage when the combustion waves progress upstream from a
combustion chamber to and through monopropellant supply lines. The
danger of flashback from the point of ignition of the
monopropellant (or other point along the monopropellant feed line)
back to a monopropellant storage tank has prevented the widespread
utilization of monopropellants. As a result, flashback arrestors
are needed to prevent flashbacks from reaching the monopropellant
storage tank and causing an explosion.
[0008] Flashback arrestors are known as safety devices in systems
where a combustible mixture may be within pipes, tubes, or other
flow paths (e.g., in oxygen-actylene welding equipment and
flammable gas vents). However, these existing flashback arrestors
are insufficiently robust to provide adequate protection to
monopropellant storage and feed systems due to the high pressure
and energy content of monopropellants used for power generation
systems.
SUMMARY
[0009] Implementations described and claimed herein address the
foregoing problems by providing a propellant shut-off assembly for
isolating a propellant source in the event of a flashback. The
propellant shut-off assembly may include a burst membrane
configured to fail in presence of the flashback and a biased closed
shut-off valve attached to the burst membrane. The shut-off valve
is held open by the burst membrane while the burst member is
intact.
[0010] In another implementation, the foregoing problems are
addressed by a method of isolating a propellant source in the event
a flashback. While propellant moves through the propellant shut-off
assembly in a propellant flow direction, the propellant shut-off
assembly may experience a flashback. As a result, a burst membrane
within the propellant shut-off assembly is fractured to failure as
a result of the flashback. Failure of the burst membrane causes the
propellant shut-off assembly to close and isolate a propellant
source from any components of the propellant delivery system that
have failed as a result of the flashback.
[0011] Yet another implementation provides a propellant delivery
system including a propellant reservoir and a propellant shut-off
assembly. The propellant shut-off assembly may include a burst
membrane configured to fail in presence of the flashback and a
biased closed shut-off valve attached to the burst membrane. The
shut-off valve is held open by the burst membrane while the burst
member is intact. The propellant delivery system further includes a
propellant injector. The flashback originates between the
propellant injector and the propellant shut-off assembly and the
propellant shut-off assembly isolates the propellant reservoir from
any components of the propellant delivery system that have failed
as a result of the flashback.
[0012] Other implementations are also described and recited
herein.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0013] FIG. 1A is a perspective schematic view of an orbital or
spacecraft with several attitude or apogee thrusters using the
presently disclosed flashback-arresting devices.
[0014] FIG. 1B is an enlarged schematic cross section of an example
monopropellant propulsion system in the orbital vehicle using
flashback-arresting devices according to the presently disclosed
technology.
[0015] FIG. 2 illustrates an example flowchart for monopropellant
and bipropellant systems using flashback-arresting devices for
flashback protection in propulsion systems, working fluid
production systems, and/or electricity generation systems.
[0016] FIG. 3 illustrates a cross-sectional view of an example
closed flashback deflector and shut-off valve assembly.
[0017] FIG. 4 illustrates a three-quarter sectional view of an
example closed flashback deflector and shut-off valve assembly.
[0018] FIG. 5 illustrates a cross-sectional view of an example open
flashback-arresting deflector and shut-off valve assembly, showing
propellant flowing through the assembly.
[0019] FIG. 6 illustrates a cross-sectional view of an example
closed flashback-arresting deflector and shut-off valve assembly,
showing a flashback diverted out of the assembly.
[0020] FIG. 7 illustrates example operations for arresting a
flashback using a flashback-arresting shut-off valve according to
the presently disclosed technology.
DETAILED DESCRIPTIONS
[0021] Chemically reacting monopropellants and mixed fuel/oxidizer
blends contain constituents that liberate energy through thermal
decomposition and/or combustion. In combustion reactions, the
reactants are at a higher energy state than the products remaining
following combustion of the reactants. However, a certain quantity
of energy (i.e., activation energy) is input to release the energy
stored within the chemical bonds of the reactants.
[0022] This chemical energy release is often initiated by an
ignition source, which provides the activation energy for a
selected monopropellant or fuel/oxidizer blend. The ignition source
is typically incorporated near an injector head and within a
combustion chamber of a power generation system. Many ignition
sources exist including, but not limited to, electrical sparks,
catalysts (i.e., substances which lower the activation energy by
providing a surface which increases a reaction's chemical
kinetics), heat sources, impact loads, compression, or any
combination thereof.
[0023] If the ignition source is oriented downstream (i.e., in a
direction away from the fluid energy storage device) of a
monopropellant or a mixture of fuel(s) and oxidizer(s), flames at
the ignition source can propagate upstream (i.e., in a direction
towards fluid energy storage) through the feed lines to the point
where the fuel(s) and oxidizer(s) are mixed or into a
monopropellant storage tank. This event, commonly referred to as a
flashback, may cause catastrophic system failure (e.g., destruction
of the power generation system, destruction of surrounding
equipment, and/or injury or death to nearby personnel).
[0024] Flashbacks may take the form of deflagration or detonation
wave propagation. Deflagration is a common form of combustion where
a flame speed travels at sub-sonic speeds. Deflagration combustion
is commonly associated with relatively low energy content and
chemical reaction rates. Detonation is a phenomenon characterized
by supersonic flame front propagation. Pressure and temperature
spikes as well as shock waves are typically associated with
detonation waves. Detonation waves contain immense power, which can
be very useful in a controlled environment or very destructive in
an uncontrolled environment. Conventional flashback-arresting
devices designed to prevent deflagration flashbacks are often not
robust enough to survive detonation flashback waves. Flashback
arrestors disclosed herein are specifically configured to
effectively prevent and/or control detonation flashback waves as
well as deflagration flashbacks.
[0025] FIG. 1A is a perspective schematic view of an orbital or
spacecraft 100 with several attitude or apogee thrusters using the
presently disclosed flashback-arresting devices. The thrusters 110
may use a monopropellant propulsion system 110 that is described
below in further detail in FIG. 1B.
[0026] FIG. 1B illustrates a cross-sectional view of an example
monopropellant propulsion system 110 using flashback-arresting
devices 102, 104, 106 according to the presently disclosed
technology. The example monopropellant propulsion system 110
includes a monopropellant tank 112. An ignition interface 106 is
located between a thruster body 111 and a combustion chamber 114,
which feeds into an expansion nozzle 116. In the illustration, the
system 110 would be propelled from left to right.
[0027] Propellant from the monopropellant tank 112 is fed to the
combustion chamber 114 via monopropellant lines (e.g.,
monopropellant line 118). Flashback-arresting shut-off valve 102
shuts off the monopropellant in the event of a flashback.
Flashback-arresting deflector 104 diverts the energy caused by the
flashback away from the monopropellant lines and tank 112.
Flashback-arresting ignition interface 106 may contain a
micro-fluidic porous media element of sintered metal or other heat
resistance materials. Further, the shut-off valve 102 and/or
deflector 104 may also contain one or more micro-fluidic porous
media elements, as well. Note that while the flashback arresting
devices 102, 104, 106 are disclosed in FIGS. 1A and 1B with respect
to a orbital or spacecraft 100, such devices may also be used in
other propellant and/or power generation systems.
[0028] The micro-fluidic porous media element, by virtue of
multiple small and convoluted flow paths, allows monopropellant to
flow through the media element but prevents a flashback from
traveling back through the media element. Further, the media
element may have a variable density design to provide desired flow
characteristics. Still further, the media element may have various
internal micro-channel designs as well as various external
geometries (e.g., a disk, cup, or ring). The media element may also
be constructed of various materials and have various coatings as
described in detail with regard to FIG. 4.
[0029] FIG. 2 illustrates an example flowchart 200 for
monopropellant and bipropellant systems using flashback-arresting
devices for flashback protection in propulsion systems (e.g.,
thruster 220), working fluid production systems (e.g., gas
generator 222), and/or electricity generation systems (e.g., power
plant 224). In a first depicted implementation, monopropellant tank
226 is the fuel/oxidizer source for a power generation system 220,
222, or 224. Flashback valve 228, flashback deflector 230, and/or
regulator 232 contain flashback-arresting technology as presently
disclosed. The flashback-arresting technology prevents or stops a
flashback from propagating upstream and causing catastrophic system
failure in monopropellant feed lines and/or monopropellant tank
226. Further, the presently disclosed flashback-arresting
technology (e.g., flashback deflector 230) may also divert energy
of the flashback away from the feed lines and/or monopropellant
tank 226.
[0030] In a second depicted implementation, bipropellant tanks
(i.e., fuel tank 228 and oxidizer tank 230) are premixed before
injection into the power generation system 220, 222, or 224.
Example fuels for such systems include, without limitation, natural
gas, gasoline, diesel, kerosene, ethane, ethylene, ethanol,
methanol, methane, acetylene, and nitro methane. Example oxidizers
for such systems include, without limitation, air, oxygen/inert gas
mixtures, oxygen, nitrous oxide, and hydrogen peroxide. Fuel
components can be mixed with oxidizing components in many different
ratios to obtain a desired combustion reaction. While FIG. 1B
illustrates a bipropellant configuration utilizing one fuel tank
228 and one oxidizer tank 230, it should be understood that the
presently disclosed technology could be applied to bipropellant
mixtures involving multiple fuel and/or oxidizer components as well
as additional smaller trace components that may aid in the
combustion process or provide desirable end results in the
resultant gas plumes (e g, inhibition of undesirable trace gas
species such as NOx formation, promotion of fuel/air combustion
initiation, promotion of good fuel/air mixing, and/or alteration of
fluid species with embedded solid particles).
[0031] Flashback valve 234, flashback deflector 236, and/or the
regulator 232, contain flashback-arresting technology as presently
disclosed. The flashback-arresting technology prevents or stops a
flashback from propagating upstream and causing catastrophic system
failure in feed lines downstream of where fuel is premixed with
oxidizer. Further, the presently disclosed flashback-arresting
technology (e.g., flashback deflector 236) may also divert energy
of the flashback away from the feed lines and/or fuel tank 228 and
oxidizer tank 230.
[0032] Further, FIG. 2 illustrates three alternative power
generation systems (i.e., thruster 220, gas generator 222, and
power plant 224), each with a corresponding injector head 238.
Other power generation systems are also contemplated herein. For
example, various work extracting cycles may implement the
flashback-arresting technology (e.g., gas turbine (Brayton) cycles,
Otto cycles, diesel cycles, constant pressure cycles). The
injectors 234 may also be equipped with the aforementioned
flashback-arresting technology that prevents or stops a flashback
from propagating upstream of the injectors 234 and causing
catastrophic system failure.
[0033] FIG. 3 illustrates a cross-sectional view of an example
closed flashback deflector and shut-off valve assembly 300. The
assembly 300 provides flashback (i.e., detonation and/or
deflagration) protection to propellant (e.g., monopropellant and/or
mixed fuel/oxidizer) sources upstream from the assembly 300. The
assembly 300 includes a housing 318 with a top cap 304 and a bottom
cap 316 rigidly attached to an upper end and a lower end of the
assembly 300, respectively, along central axis 348. The top and
bottom caps 304, 316 may be attached to the housing 318 using a
variety of methods and/or structures (e.g., press-fitting, welding,
gluing, bolting, and/or screwing). Some of the attachment
methods/or structures are permanent (e.g., welding). Other
attachment methods and/or structures enable the assembly 300 to be
disassembled with relative ease for inspection, repair, and/or
maintenance (e.g., bolting and screwing).
[0034] The housing 318, top cap 304, and bottom cap 316 form an
enclosure for the flashback deflector 302 and shut-off valve
components. At least propellant inlet tube 310, ball bearing 320,
receptor 326, burst membrane 308, and compression springs
collectively make-up the shut-off valve. The bottom cap 316
includes a central aperture 346 for receiving the propellant inlet
tube 310.
[0035] The propellant tube 310 is fixedly attached to the bottom
cap 316 and extends through the central aperture 346 to the
receptor 326. The propellant tube 310 is slidably attached to the
receptor 326 and the receptor 326 is adapted to move upward and
downward along the central axis 348 while the propellant tube 310
remains fixed in place within the assembly 300. Bellows 328 is
fixedly attached to the outside of the propellant tube 310 near the
bottom of the assembly 300 and extends upward along the propellant
tube 310 and is fixedly attached to the bottom of the receptor 326
where the receptor 326 meets the propellant tube 310. The bellows
328 is adapted to extend and retract with movement of the receptor
326 and create a hermetic seal for the slip-fit between the
receptor 326 and the propellant tube 310.
[0036] The propellant tube 310 includes a seat 322 at the upper end
of the propellant tube 310 along the central axis 348. Further, the
receptor 326 includes an aperture 350 for receiving the ball
bearing 320 or another structure adapted to seal against the seat
322 (e.g., a needle). The ball bearing 320 may be press-fit,
welded, glued, or otherwise attached to the aperture 350. In
another implementation, the ball bearing 320 is not attached to the
aperture 350 and is free to move between the aperture 350 and seat
322 when the assembly 300 is open (see e.g., FIG. 5). In this
implementation, the ball bearing 320 may act as a check valve,
thereby preventing propellant flow from reversing by resting in the
seat 322. In the closed position of the assembly 300, as shown in
FIG. 3, the ball bearing 320 is compressively mated to the seat
322, thereby making a hermetic seal.
[0037] The receptor 326 includes threaded apertures (e.g., aperture
352) for receiving threaded rods (e.g., threaded rod 340) extending
downwardly away from the receptor 326 through apertures (e.g.,
aperture 358) in the housing 318. In other implementations, the
threaded apertures and threaded rods are not threaded and are
instead press-fit, welded, glued, or otherwise fixedly attached to
one another. The threaded rods extend through apertures (e.g.,
aperture 364) in a spring plate 354 and are secured to the spring
plate 354 with nuts (e.g., nut 342). The spring plate 354 floats
within the housing 318, attached only to one end of one or more
springs (e.g., spring 324).
[0038] The springs encircle each threaded rod and extend from the
receptor 326 to the spring plate 354. The springs are in
compression, forcing the receptor 326 downward with relation to the
fixed propellant inlet tube 310. As a result, the ball bearing 320
is compressively sealed against the seat 322 on the propellant tube
inlet 310. Each of the springs may have any configuration with
compressive spring force (e.g., one or more stacked spring washers,
one or more stacked Belleville washers, one or more helicoidal
springs, spring steel in compression, etc.). Other assemblies may
have springs under tension rather than compression. Still other
assemblies may not have springs; instead, they may have an
electronic sensor and an electric actuator (solenoid) to
compressively seal the ball bearing 320 against the seat 322. The
springs and/or other mechanisms adapted to seal the ball bearing
320 against the seat 322 generate sufficient force to seal the
propellant inlet tube 310 quickly and positively against the seat
322. The bottom cap 316 also includes apertures (e.g., aperture
344) for accessing the nuts (e.g., nut 342). During assembly and/or
adjustment, rotation of the nuts adjusts the compressive force of
the springs and/or position of the spring plate 354 and receptor
326 with respect to the housing 318 and propellant inlet tube
310.
[0039] The receptor 326 may also include a porous media element
330. When the assembly 300 is in an open configuration (see e.g.,
FIG. 5), the porous media element 330 provides a path for
combustible fluid to flow from the propellant inlet tube 310
through the receptor 326. The effective microchannel diameter
sizing and surface area of the porous media element 330 are
strategically chosen for each particular application based on
combustible fluid mass flow rate requirements and allowable
pressure drop while maintaining a desired flashback protection.
[0040] The implementation of FIG. 3 depicts the assembly 300 in a
closed position. The closed position is indicative of an incident
causing flashback. The porous media element 330 operates as a
thermal sponge that absorbs combustion energy at rates higher than
the rate at which a detonation wave can release combustion energy.
As a result, the porous media element 330 provides detonation
quenching.
[0041] While the quenching distance of the porous media element 330
may be sufficient to arrest a primary detonation wave, the energy
released from a flashback can cause secondary ignitions through
mechanical failures and/or heat transport through solid material.
This conductive heat transport can produce hot spots in direct
contact with un-combusted combustible fluid sufficient to ignite a
propellant upstream of the assembly 300.
[0042] In one implementation, a flashback deflector 302 is located
above the receptor 326, downstream of the porous media element 330
to disperse the energy released from the flashback. Further, a
burst membrane 308 is located around the flashback deflector 302.
The flashback deflector 302 together with the burst membrane 308
provides additional protection to propellant lines and/or sources
upstream from the assembly 300 from the potential harm caused by a
flashback. Specifically, the flashback deflector 302 together with
the burst membrane 308 allows flashback thermal/physical energy
and/or combusted/un-combusted propellant to be vented out of the
assembly 300 in the vicinity of the flashback deflector 302 (see
FIG. 5 for details). Moreover, the flashback deflector 302, when
hit by a detonation wave, disperses the detonation wave away from
the porous media element 330. Specifically, the flashback deflector
302 directs the shock wave energy towards the burst membrane
308.
[0043] When the flashback energy reaches the burst membrane 308,
the burst membrane 308 fractures and fails, allowing the flashback
energy, including in some implementations combusted and/or
un-combusted propellant, to continue out of the assembly 300 via
one or more pressure relief outlets (e.g., shockwave outlet 314).
Further, the compression of the springs overcomes any remaining
portions of the burst membrane 308, forces the ball bearing 320
into the seat 322, and thus closes the assembly 300, as depicted in
FIG. 3.
[0044] While the burst membrane 308 is intact, it resists the
compressive force of the springs (e.g., spring 324), allowing the
ball bearing 320 to remain away from the seat 322 and keeping the
assembly 300 in an open configuration (see e.g., FIG. 5). The top
cap 304 is positioned over the flashback deflector 302 and includes
a propellant outlet aperture 312. In some implementations of the
assembly 300, no flashback deflector 302 and/or porous media
element 330 are present.
[0045] FIG. 4 illustrates a three-quarter sectional view of an
example closed flashback-arresting deflector and shut-off valve
assembly 400. The assembly 400 provides flashback (i.e., detonation
and/or deflagration) protection to propellant (e.g., monopropellant
and mixed bipropellant) lines and/or sources upstream from the
assembly 400. The assembly 400 includes the same components of the
assembly 300 of FIG. 3. In addition, the assembly 400 also includes
propellant passage 460, which serves as a conduit for propellant
flowing from the propellant inlet tube 410 to the receptor 426 (not
shown in FIG. 3).
[0046] More specifically, the assembly 400 includes various
high-strength components that normally are not exposed to
propellant while the assembly 400 is in an open configuration
(e.g., housing 418, top cap 404, bottom cap 416, springs, threaded
rods, nuts, and spring plate 454). Each of these components may be
made of various materials capable of withstanding an expected
environment for the assembly 400 (e.g., atmosphere, vacuum or
near-vacuum, underwater, etc.) without failing due to atmospheric
pressure, external forces, and/or forces exerted by the springs and
other components of the assembly 400. Some or all of the components
may also include metallic alloys including one or more metals
(e.g., steel, stainless steel, aluminum, nickel, copper, tin, and
titanium). Further, some of the components may also use some
high-strength plastics, composites, and/or ceramics. Still further,
these components may be painted, coated, galvanized, and/or plated
to prevent corrosion. Further yet, each of the components may be
cast, extruded, machined, and/or forged to give the appropriate
shape and strength for their function.
[0047] The assembly 400 also includes various high-strength
components that are exposed to the propellant while the assembly
400 is in an open configuration (e.g., receptor 426, flashback
deflector 402, propellant inlet tube 410, ball bearing 420, ball
seat 422, bellows 428, and top cap 404). Each of these components
may be also made of various materials capable of withstanding the
expected environment for the assembly 400 without failing due to
atmospheric pressure, external forces, and/or forces exerted by the
springs. Further, the components that are exposed to the propellant
need to withstand the expected propellant pressure and flashback
forces when the assembly 400 is in an open position during normal
operation, during a flashback before the assembly 400 closes, and
after the flashback, when the assembly 400 is closed. Still
further, the components that are exposed to the propellant need to
be made of a material or be coated with a material that does not
contaminate the propellant (e.g., a material that resists oxidation
when the combustible material includes oxygen). Some or all of the
components may also include metallic alloys including one or more
metals (e.g., steel, stainless steel, aluminum, nickel, copper,
tin, and titanium). Further, some of the components may also use
some high-strength plastics, composites, and/or ceramics. Still
further, these components may be painted, coated, galvanized,
and/or plated to prevent external corrosion and/or internal
contamination of the propellant. For example, one or more of the
components may include an internal coating when the base material
of a particular component is catalytic with the propellant. Further
yet, each of the components may be cast, extruded, machined, and/or
forged to give the appropriate shape and strength for their
function.
[0048] Some of the components of assembly 400 have specific
construction requirements separate from the components discussed
above (e.g., bellows 428, springs, porous media element 430, and
burst membrane 408, flashback deflector 402, ball bearing 420, and
ball seat 422). The bellows 428 must be sufficiently flexible to
deflect with movement of the receptor 426 in relation to the
propellant inlet tube 410 while maintaining an effective seal at an
interface between the receptor 426 and the propellant inlet tube
410. Further, the bellows 428 must be sufficiently strong to
withstand the expected propellant pressure and flashback forces
when the assembly 400 is in an open position during normal
operation, during a flashback before the assembly 400 closes, and
after the flashback, when the assembly 400 is closed. For example,
the bellows 428 may include a corrugated layer or multiple
corrugated layers of a flexible metallic alloy (e.g., stainless
steel, spring steel, and/or an aluminum alloy). In another example,
the bellows 428 may include a woven metallic structure with a
plastic or rubber interior coating or layer.
[0049] The springs may include any metallic and/or plastic material
with sufficient rigidly to close the assembly 400 when the burst
membrane 408 fails while also having sufficient resilience to
maintain closing rigidity after being held in the open position for
an extended period of time (e.g., spring steel). The porous media
element 430 may be made of various sintered and/or refractory
metals and/or ceramics. Further, the porous media element 430 may
have various coatings, particularly when the base material of the
porous media element 430 is catalytic with the propellant.
[0050] The burst membrane 408 must be sufficiently strong to hold
the assembly 400 open during normal operation while being capable
of fracturing and failing due to thermal and/or pressure energy
caused by a flashback. For example, the burst membrane 408 may be
made of a rigid plastic. The flashback deflector 402 may also be
adapted to conduct thermal energy rapidly from the flashback. As a
result, materials chosen for the flashback deflector 402 may have a
relatively high thermal conductivity (e.g., various metals). The
ball bearing 420, and ball seat 422 may utilize softer materials
that are more suitable to provide a seal (e.g., Teflon and TFE
fluorocarbons, soft metals (e.g., copper and brass), and composite
materials).
[0051] FIG. 5 illustrates a cross-sectional view of an example open
flashback-arresting deflector and shut-off valve assembly 500,
showing propellant flowing through the assembly 500. The assembly
500 provides flashback (i.e., detonation and/or deflagration)
protection to propellant (e.g., monopropellant and mixed
bipropellant) lines and/or sources upstream from the assembly 500.
The propellant enters the assembly 500 via propellant inlet tube
510 as illustrated by arrow 532. The propellant flows around a ball
bearing 520 and through one or more apertures (not shown) in a
receptor 526, as illustrated by arrows 534. The propellant then
flows through a porous media element 530, as illustrated by arrows
535. The porous media element 530 is adapted to permit propellant
flow while preventing a flashback from propagating through the
porous media element 530. In some implementations, the porous media
element 530 is not included.
[0052] The propellant continues to flow around the base, up the
sides, and over the top of a flashback deflector 502, as
illustrated by arrows 536. Further, the flashback deflector 502 may
have various channels or apertures to facilitate the flow of
propellant around the flashback deflector 502. In some
implementations, the flashback deflector 502 is not included. The
propellant exits the assembly 500 via propellant outlet aperture
512, as illustrated by arrows 538. In one implementation,
compression fittings or other detachable connectors may be attached
to the propellant inlet tube 510 and/or propellant outlet aperture
512 so that the assembly 500 may be removeably inserted in the path
of propellant from a fluid reservoir such as tanks 226, 228, 230 to
a combustion point, such as the injector 238 of FIG. 2. For
example, the propellant may travel from the fluid reservoir through
a connecting pipe, tube, or other mechanism towards the propellant
inlet tube 510, through assembly 500, out propellant outlet
aperture 512, and through another connecting pipe, tube, or other
mechanism to the combustion point.
[0053] Burst member 508 is illustrated intact and adjacent the
flashback deflector 502. In one implementation, the burst member
508 has one or more weakened areas where the burst member 508 is
intended to fail during a flashback event. The weakened areas are
depicted as external and internal circumferential grooves (e.g.,
groove 562) in the burst member 508. In another implementation, the
weakened areas may include a thinner wall near the center of the
burst member 508 as compared to a thicker wall near the edges of
the burst member 508. Further, the internal circumferential grooves
may act as line charges, providing a reservoir of combustible fluid
that may be ignited during the flashback event, aiding the failure
of the burst member 508 during the flashback event. The burst
member 508, in tension, holds the receptor 526 upward against
downward force applied by compressed springs (e.g., spring 524). As
a result, the ball bearing 520 is held away from a ball seat 522
(or allowed to float freely above the ball seat 522) and the
propellant flows relatively unimpeded from the propellant inlet
tube 510 to the propellant outlet aperture 512.
[0054] FIG. 6 illustrates a cross-sectional view of an example
closed flashback-arresting deflector and shut-off valve assembly
600, showing a flashback diverted out of the assembly 600. The
assembly 600 provides flashback (i.e., detonation and/or
deflagration) protection to propellant (e.g., monopropellant and
mixed bipropellant) lines and/or sources upstream from the assembly
600. As depicted in assembly 500 of FIG. 5, the propellant enters
the assembly 600 via propellant inlet tube 610 as illustrated by
arrow 632. However, in assembly 600, ball bearing 620 is sealed
against ball seat 622. As a result, the propellant does not proceed
beyond the ball bearing 620.
[0055] Springs (e.g., spring 624) cause downward movement of
receptor 626 with respect to the propellant inlet tube 610 after
fracture and failure of burst member 608. The downward movement of
receptor 626 with respect to the propellant inlet tube 610 seals
ball bearing 620 against ball seat 622. A flashback event causes
the fracture and failure of the burst member 608.
[0056] More specifically, the flashback event creates a combustion
wave that propagates from the ignition source upstream towards the
arrestor in a reverse flow direction as compared to the flow
direction of propellant depicted in FIG. 5 (see arrow 638). The
combustion wave (i.e., detonation and/or deflagration wave(s))
continues over the top of flashback deflector 602 as illustrated by
arrows 636. In some implementations, the flashback deflector 602
absorbs some of the physical/thermal energy of the flashback
event.
[0057] Regardless, the remaining thermal energy and pressure in the
combustion wave causes the burst member 608 to fracture and fail.
In some implementations, the flashback deflector 602 includes one
or more circumferential grooves (not shown) adjacent the burst
member 608. The circumferential grooves form a reservoir of
propellant adjacent the burst member 608, which aids in forcing the
failure of burst member 608 during the flashback event.
[0058] As a result, the failure of burst member 608, the ball
bearing 620 seals against the ball seat 622 as discussed above.
Further, the failure of burst member 608 causes pressure relief
outlets (e.g., shockwave outlet 614) to open, allowing the
physical/thermal energy of the flashback event to exit the assembly
600, as illustrated by arrows 635. The pressure relief outlets
provide an outlet for exhaust gasses produced by combustion of the
propellant as well as some combusted/un-combusted propellant. In
some implementations, fragments of burst member 608 after failure
are also discharged via the pressure relief outlets. In other
implementations, the fragments of burst member 608 after failure
remain within the assembly 600. The pressure relief outlets may
each incorporate a paper or plastic seal that is broken and/or a
plug that is discharged when the exhaust gasses and/or fragments of
burst member 608 are discharged from the pressure relief outlets.
The paper or plastic seal and/or the plug provides a visual aid
that indicates whether a flashback event has occurred.
[0059] In one implementation, the assembly 600 is adapted to
isolate a detonation wave traveling upstream from an ignition point
from reaching a corresponding propellant tank or other upstream
propellant feed lines carrying monopropellant or pre-mixed
bipropellant. The assembly 600 is spring-loaded and normally held
open using the burst element 608. Once the burst element 608 fails,
the springs force the assembly 600 to a closed position, thereby
isolating upstream propellant from the detonation wave.
[0060] FIG. 7 illustrates example operations 700 for arresting a
flashback using a flashback-arresting shut-off valve according to
the presently disclosed technology. In moving operation 705,
propellant (e.g., monopropellant or mixed bipropellant) is moved
from a propellant reservoir, through an open flashback-arresting
shut-off valve, and to a point of combustion in a normal propellant
flow direction. A pump, gravity feed, suction, or other mechanism
may effectuate the movement of the propellant. The shut-off valve
is positioned in line with the flow of the propellant to the point
of combustion so that the shut-off valve may prevent the propellant
from flowing from the propellant reservoir to the point of
combustion when the shut-off valve is closed.
[0061] In experiencing operation 710, the shut-off valve
experiences a flashback of the propellant within a propellant line
connecting the shut-off valve to the point of combustion in a
direction opposite to the normal propellant flow direction. During
the flashback, the propellant is ignited within the propellant
line, downstream of the shut-off valve, and substantial
physical/thermal energy caused by the flashback travels in the
direction opposite to the normal propellant flow direction back to
the shut-off valve. The flashback may include detonation and/or
deflagration.
[0062] In fracturing operation 715, a burst member within the
shut-off valve fractures and fails. The burst member is intended to
fail during a flashback event and is thus constructed of a
relatively brittle material (e.g., a rigid plastic or a brittle
metal like titanium) that should fail under a detonation impact
load. Failure of the burst member causes the releasing and opening
operations 720, 725 to occur. In releasing operation 720,
compression on a spring-loaded portion of the shut-off valve is
released, thereby closing the shut-off valve and sealing the
propellant reservoir and propellant lines connecting the shut-off
valve to the propellant reservoir from the flashback. In one
implementation, after failure of the burst member, which holds the
springs in compression, the released compression presses a ball
bearing into a seat, which provides the seal.
[0063] In opening operation 725, one or more pressure relief
outlets that direct the physical/thermal energy and/or
un-combusted/combusted propellant out and away from the shut-off
valve are opened. The burst member seals the pressure relief
outlets from the propellant flowing through the shut-off valve
during a normal (or open) operation of the shut-off valve. However,
after failure of the burst member, the pressure relief outlets
become open to the propellant downstream of the ball bearing and
seat. Since the flow path back through the shut-off valve is
blocked when the shut-off valve is closed, the physical/thermal
energy and/or un-combusted/combusted propellant instead travels out
of the shut-off valve via the pressure relief outlets. The pressure
relief outlets typically open into a controlled environment,
ambient air, and/or a vacuum, in all cases in a location away from
the propellant reservoir.
[0064] In absorbing operation 730, thermal energy is absorbed by
the flashback-arresting shut-off valve to prevent secondary
ignition of the propellant within the propellant reservoir and/or
propellant lines sealed off from the remainder of the
flashback-arresting shut-off valve. The post-combusted gasses
within the flashback-arresting shut-off valve likely have a very
high temperature, which in turn raises the temperature of the
shut-off valve itself. If the temperature of the shut-off valve is
allowed to rise high enough, the sealed off propellant source may
ignite even though it is not directly exposed to the flashback. To
avoid this, the mass of a flashback deflector and/or other
components of the flashback-arresting shut-off valve may absorb
much of the thermal energy so that the temperature of components of
the shut-off valve adjacent the sealed off propellant source does
not exceed an auto-ignition point of the propellant.
[0065] The above specification, examples, and data provide a
complete description of the structure and use of exemplary
embodiments of the invention. Since many embodiments of the
invention can be made without departing from the spirit and scope
of the invention, the invention resides in the claims hereinafter
appended. Furthermore, structural features of the different
embodiments may be combined in yet another embodiment without
departing from the recited claims.
* * * * *