Note: Descriptions are shown in the official language in which they were submitted.
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Compressed Natural Gas Vehicle Safety System and Method
BACKGROUND
Field of the Invention
The present invention relates generally to the fields of vehicle safety
and compressed natural gas and more particularly to safety system related to
fueling vehicles powered by compressed natural gas.
Description of the Prior Art
Natural gas is becoming an abundant resource in the United States
and several other countries. It is estimated that the natural gas reserves of
the U.S. exceed the oil reserves of Saudi Arabia in terms of years of energy
supply.
In order to utilize this resource effectively, and to replace crude oil,
natural gas must be used in vehicles. Many fleet operators are switching their
vehicles to natural gas since, with minor modifications, internal combustion
engines run very well on natural gas.
Natural gas is typically supplied in two different forms: 1) as a
compressed gas, and 2) as a liquefied gas. While more efficient in terms of
the amount of gas that can be supplied in a single tank, liquefied gas is very
dangerous to handle and requires highly specialized equipment to fuel with it
and actually use it. On the other hand, compressed natural gas is relatively
easy to fuel with and to utilize. Compressed natural gas can be supplied in
pressure bottles a pressures between 3000 psi and 4000 psi. It is very well
known in industry how to handle and fill such bottles. A natural gas "gas
station" can fill a vehicle tank (pressure bottle) in just a few moments using
fill
techniques similar to high pressure air. A vehicle tank containing 100 ¨ 200
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cu. feet of natural gas at a pressure of 3500 psi is typically not more
dangerous than a typical automobile's gasoline tank. The tank can be
shielded from direct impact in an accident.
Many households and businesses in the U.S. have piped in natural gas
for cooking and, in many cases, heating. Most Americans own at least one
car or other vehicle, with many households owning several vehicles. This
combination immediately suggests the possibility of filling a natural gas
vehicle at home during the night for use the next day, or filling at the
location
of a small business. Because even a large compressed natural gas tank will
not last as long between refills as a typical gasoline tank, it will become a
very
convenient to refill it during the night. The vehicle owner can also use
natural
gas filling stations; however, these will probably be more convenient for
extended trips. Most people would prefer not to have to wait 5-10 minutes at
a gas station to fill their vehicle. While exchangeable tanks are also
possible,
these require considerably more logistics and handling than a simple fixed
onboard tank. Even with exchangeable tanks, the vehicle owner would still
probably have to wait considerably longer to get a refill at a station than
they
currently do with gasoline.
At the present time, at least one car manufacturer is supplying a
compressed natural gas vehicle and a home compressor to fill it. National fire
codes currently prevent large gas storage tanks in homes or compressors that
fill at fast rates. Given present standards, the home compressor will be
directly attached to the vehicle via a high pressure hose, and the vehicle
will
take several hours to fill (depending on the size of the onboard tank). Again,
this will be very conveniently accomplished during the night. The same
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arrangement can be used at small businesses, especially those with fleets of
vehicles.
However, with numerous individuals filling natural gas vehicles in their
garages at night or at their business locations, the potential for a very
serious
type of accident increases dramatically ¨ namely what is called a drive-off
accident. This is where the driver tries to drive away with the high pressure
filling hose still attached to the vehicle. Such an accident in a home garage
could be catastrophic if the fitting or valve on the vehicle is damaged, or if
the
compressor is pulled away from the home natural gas source. In either case,
a considerably amount of gas could escape into the garage causing a fire or
explosion danger. Also, even a "soft" drive-away accident, one where the
driver stopped before breaking the hose or fitting could stress the fill hose
and
possibly cause small, very hard to detect, gas leaks. Such small leaks could
result in the garage being filled with gas by morning.
Natural gas contains mostly methane and is thus lighter than air.
Natural gas leaking in a garage will fill the garage from top to bottom. An
explosive mixture for natural gas and air is between around 5% (for pure
methane) and around 15-20%. Many garages contain furnaces and water
heaters having open flames. As natural gas fills a garage, it can be easily
ignited by a furnace or a water heater on a raised pedestal (fire codes
require
open flame devices in garages to mounted on pedestals to avoid gasoline
vapor that might collect along the floor from a car gasoline leak). This is an
ideal situation for a garage explosion. Hence anything that has the
possibility
of causing the release of natural gas or of causing a gas leak becomes a
large danger. A drive-away accident is such an event.
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Some techniques have been reported in the art to prevent a gasoline
vehicle from starting at a gasoline station if the fill nozzle is still in the
gas tank
inlet. Among these are U.S. Published Application No. 2002/0162601 and
U.S. Patent No. 5,720,327. Other techniques have been invented to prevent
pumping gasoline or other fuel if the fill hose is not in the fill inlet.
Among
these are U.S. Published Application No. 2008/0290152 and U.S. Patent No.
4,227,497.
While these prior art techniques are useful for gasoline, they do not
solve the problems associated with home or business filling a vehicle with
high pressure compressed natural gas. In particular, a compressed natural
gas tank is filled to a very high pressure (between 3000 and 4000 psi). A leak
or disconnect of a fitting or valve on such a pressure vessel can cause a
tremendous pressure explosion that can act like a bomb (this can happen with
any compressed gas including air). Also, a very small leak at high pressure
can cause a large quality of gas to escape. For example, an exploding tank
can send metal fragments in all directions with enough force to penetrate the
house and the driver's compartment of the vehicle. This can happen before
there is any fire. After that, the tiniest spark could ignite the now
explosive
and highly flammable gas cloud reducing the house or business to rubble.
Even a quick-disconnect hose does not typically solve the problem since the
driver may attempt to drive away very quickly still damaging the fittings,
tank,
hose, compressor and/or natural gas supply.
It would be very advantageous to have doubly or triply redundant
system and method that prevents the driver from ever starting the vehicle
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when the filling hose is attached and a safety valve is not in the correct
position.
SUMMARY OF THE INVENTION
The present invention relates to a multiply-redundant system and
method for preventing a driver from starting or moving a compressed natural
gas vehicle if the high pressure gas fill system is not correctly and
completely
disconnected from the vehicle.
In one embodiment of the invention, multiple electrical proximity
sensors, or other sensors, in combination with one or more optional
mechanical microswitches combine to lock-out the vehicle's ignition or
otherwise disable the vehicle. For different levels of safety, different
combinations of sensors can be used, with the lowest level having a single
sensor sensing the presence or absence of a fuel supply fitting. The highest
level of safety according to the invention is to have separate sensors, such
as
proximity sensors, on the fuel fill hose fitting, the gas cap cover and a
manual
safety or isolation valve along with a redundant microswitch on at least one
of
the components. The ignition, transmission or other function can be locked
out by an electrical or mechanical lockout provided to the vehicle's computer
by the manufacturer, or by a simple series electrical circuit in the ignition
string. The safest system could use both techniques.
In addition, the vehicle's computer, or another simple electrical circuit,
could provide a visual and/or audio indication that one or more of the sensors
was indicating an attached fuel hose. The alarm could be activated the
instant the driver inserts a key into the ignition. Under the present
invention, it
is understood that there is a possibility that one of the sensors might fail
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state that indicates the fuel hose is connected when, in reality, the system
is
entirely safe. In this very special case, the present invention provides a
technique for the driver, on a limited-time basis, to override the sensors and
start the engine or move the vehicle using a supplied override. Having this
feature allows the driver to drive to a mechanic to have the problem fixed.
This feature could be automatically disabled by an abuse preventer after a
predetermined number of uses (such as three times) to keep a driver with a
bad sensor from delaying getting it fixed. Finally, an optional break-away
fitting can also be provided in addition to the other features of the
invention for
a final level of protection.
DESCRIPTION OF THE FIGURES
Attention is now directed to several drawings the illustrate features of
the present invention:
Fig. 1A shows a block diagram of an embodiment of a high-safety lock-
out system according to the present invention.
Fig. 1B shows a logic circuit that can combine sensors inputs.
Fig. 2 shows a detail drawing of a fill fixture with a proximity sensor.
Fig. 3 shows the system of Fig. 2 with the high pressure fill hose
removed.
Fig. 4 shows a system similar to that of Figs. 2-3 with an additional gas
cap sensor.
Fig. 5 shows a panel-type filling system with an isolation valve and
three proximity sensors.
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Fig. 6 shows the system of Fig. 5 with an additional mechanical
microswitch.
Fig. 7 shows a motion and fire system used with natural gas fueling.
Fig. 8 shows a LNG/LOX fueling safety system.
Several drawings and illustrations have been presented to aid in
understanding the present invention. The scope of the present invention is
not limited to what is shown in the figures.
DETAILED DESCRIPTION OF THE INVENTON
The present invention relates to a system and method that provides a
lockout out to a vehicle's ignition, transmission or other means of moving the
vehicle when a high pressure compressed natural gas fuel hose is attached to
the vehicle an/or the fill cap is open. Fig. 1A shows a block diagram of an
embodiment of such a system. A compressed gas fuel fitting 2 accepts a high
pressure filling hose 21 that allows filling through an isolation valve 22.
The
isolation valve 22 can be manually opened, or it can be opened mechanically
when a panel lid or "gas cap" is opened. A sensor 4, which can be an
electrical proximity sensor, senses the presence of the fitting part of the
high
pressure filling hose 21. An optional second sensor 8 senses that the panel
or gas cap is open. An optional third sensor 14 can sense the position of an
isolation valve 22 (on vehicles that have such a valve). All of the sensors
can
be magnetic, optical or ultra-sonic proximity sensors, or any other sensors,
and use any method of sensing proximity or that a particular mechanical part
is or is not in a particular position. One or more optional mechanical
microswitches 23 can provide a backup to one or more of the sensors.
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A further logic circuit 24 or other lockout which can be a separate unit,
or part of the vehicle's processor, can combine the inputs from all the
sensors
4, 8, 14, and the optional microswitch 23 to produce a safe signal 25 that
will
allow the vehicle ignition to start the car, or otherwise allow the vehicle to
move. Fig. 1B shows a schematic representation of this circuit 24. Here,
each sensor's signal is amplified and conditioned and fed into an AND logic
circuit 26. If any of the sensors is in an unsafe condition, the AND circuit
26
will not produce a "safe" signal. The particular circuit of Fig. 1B assumes
that
a proximity sensor has a logic high when there is proximity, and that the
microswitch is high when the lid is closed. Any other logic levels or
configurations can be used. In particular, a program in a microcontroller or
other processor could also make the determination. As is well understood in
the art, an OR circuit could also be effectively used instead of an AND
circuit.
Any circuit or program that combines sensor inputs to make a "safe"
determination is within the scope of the present invention.
Fig. 1B also shows an override 27 that can be used to force a "safe"
condition when one of the sensors is in an unsafe state. This circuit is
optional but, when provided, allows the driver to drive to a mechanic with a
failing sensor. A counter 28 or other abuse preventer prevents the override
from being used more than a predetermined number times before repairing
the sensor (for example three times). The counter 28 can be optionally reset
whenever the sensor logic produces a safe signal. In the present example,
the driver can enter a special PIN code 29 to activate the override and
override the sensors. While providing this circuit lowers the overall safety
threshold of the system slightly, the act of performing the override can be
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made difficult enough that a driver will not routinely use it to avoid having
to fix
a faulty sensor. Optionally, the override could be restricted to use only by a
certified mechanic. In this case, the driver would not be allowed to operate
it.
While a simple override switch can be used, for additional safety, a PIN or
barcode or any other unique identification 29 might be required. If a PIN is
used, a PIN entry method can be used such as a keypad or a card swipe. If a
barcode is used, a small barcode reader can be supplied.
Fig. 2 shows a male tank adapter 2 on the vehicle with a coupled
(usually spring coupled) female filling locking coupler 3 and high pressure
feed hose 1. The feed hose 1 typically originates at a compressor or storage
tank. A proximity sensor 4 with electrical connections 5 senses the presence
of the feed hose (unsafe condition). The female locking coupler 3 typically
has a connect/disconnect fitting that clamps the tank adapter 2 and makes a
high pressure, leak-proof connection. It should be noted that the female
filling
locking coupler 3 could be a quick-release, break-away fitting. This would add
a final mechanical precaution to the system where the hose would manually
break free in the case that somehow the rest of the system failed.
Fig. 3 shows the same setup but with the feed hose 1 and the female
locking coupler 3 uncoupled and withdrawn (safe position) from the male
filling adapter 2.
Fig. 4 shows a fill cavity 6 and fill access lid 7 that swings open on
hinges. A second proximity sensor 8 has a second electrical feed 9. This
sensor 8 can be used in embodiments of the invention either alone or in
conjunction with the feed hose sensor 4. An optional microswitch 20 is also
shown.
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Any type of sensor can be used with the present invention. A preferred
sensor is a magnetic or optical proximity sensor; however, other sensor types
can be used such as ultra-sonic sensors and others.
Fig. 5 shows a different arrangement of the fueling system. This type
of system is more commonly found on trucks and larger vehicles. A panel 13
opens and closes to allow access to a tank adapter 12. An isolation valve 10
can be manually operated or can operate in conjunction with a lever 16 on the
panel 13. A third proximity sensor 14 with electrical feed 15 can be used to
sense whether the panel is open or closed (and hence, if the lever 16 is used
with the valve 10, whether the valve is open or closed). The valve 10 isolates
the tank adapter 12 from the tank when the panel is closed.
Fig. 6 shows the same embodiment as Fig. 5 except that an optional
microswitch 23 has been added to the panel 13. This is a simple mechanical
backup that does not rely on proximity sensors. It should be noted that any of
the proximity sensors shown in the various embodiments of the present
invention may be replaced by microswitches or other mechanical devices, or
each proximity sensor may be optionally backed up with an additional
microswitch. In addition, Fig. 6 shows an optional additional microswitch 21
on
the isolation valve 10.
It should be noted that an optional natural gas leak sensor can also be
included with the system of the present invention to provide an addition
source of safety. Such a sensor could keep the vehicle in a disabled state if
an unreasonable concentration of free natural gas is sensed. Such a sensor
could also sound an alarm on the vehicle or on the compressor. It is also
possible that any of the above-mentioned sensors or circuits can
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communicate with the lockout or other logic wirelessly such as by radio or
light. Finally, it should be noted that a processor with memory and a stored
program can perform the logic function of the lockout, override and/or abuse
preventer. This can also be any digital or analog logic circuit or simply
relays.
In addition, an internet or network interface can be provided to remotely
report or log the status of the system. This feature can be useful for fleet
operators to track safety, for example, the number of attempts to drive off
under a lockout condition or the number of overrides.
The present invention provides a multiply-redundant system to
enhance the safety of home or business fueling of compressed natural gas
vehicles. It can also be used on vehicles using propane or any other
compressed gas fuel. A system of one or more sensors determines if the
fueling system is in a safe state. This can be a state with the high pressure
fill
hose removed, the fueling compartment access lid closed, and any isolation
valve in the correct position. A lockout prevents either the vehicle from
starting or otherwise makes it impossible to move the vehicle when the
system is not in a safe state. In order that a driver can get a faulty sensor
repaired, an override can be provided that allows the safety sensors to be
overridden and the vehicle moved. This override can be equipped with an
abuse preventer that only allows the override to be used for a predetermined
number of times before the override itself is disabled. This prevents a driver
from putting off getting a faulty sensor repaired. An audio and/or visual
indicator can sound or display when the driver inserts the key into the
ignition
in an unsafe state, or alternatively, when the driver turns the key to start.
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In the present invention, a lockout is any method, means or technique
to prevent a vehicle from moving including a circuit or module that can
disable
the ignition or transmission or disable the vehicle in any other way. An
override is a any method, means or technique to allow the vehicle to move in
spite of the lockout - any way of overriding the lockout. An abuse preventer
is
any method, means or technique to prevent abuse of the override by limiting
the number of times (especially successive times) it can be used.
In natural gas fueling, be it compressed or liquefied gas, any excessive
motion of the vehicle being fueled (car, truck, train, ship, barge or any
other
vehicle), cannot be permitted. Such motion indicates a condition that should
lead to a shutdown of the fueling operation and, in many cases, an automatic
disconnect of all fueling lines from the vehicle as well as possible release
of
the vehicle.
To detect omni-directional vehicular movement/distances, multiple
sensors may utilized to perform different functions, standing alone or in a
cascading control system to perform a vehicle lock-out or automatic fueling
line disconnect. The use of one or more sensors in combination with one or
more micro-switches, combine to automatically mitigate excess movements,
initiate the lock-out and close isolation valves to prevent/disable fuel
flow/transfers. The sensor(s) such as optical and or ultrasonic that detect
excessive movement (above or greater than predetermined stop limits) can be
sensors such as laser or radar measurement sensors, or can simply be
accelerometers coupled to processing units to compute motion. Use of one or
more of these sensor, or possibly multiple sensors, creates the safest
condition to initiate mitigation of fuel transfers, by maintaining other
systems in
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a lock-out state, and activating one or more audible and/or visual alarms. The
fuel flow system can be reactivated by an operator. Different vehicles may
require different parameters to initiate such motion lock-outs. For example,
highly excessive movements can relay, trigger or enable an override system
to disabling the lockout system(s), but keeping fuel flow isolation valve(s)
closed (safe state) and liberating vehicle(s) until proper control/conditions
are
achieved and or exist. Such a condition can de-activate or activate any
vehicle or automatic fueling release system that may exist, or initiated by
lock-
out. Multiple variations can be used, with multiple steps and sequences to
maintain the safe state. With isolation valve(s) in a closed position, and if
predetermined conditions exist, vehicle movement may be allowed by
automatic activation of the override.
For example, a barge being fueled by natural gas begins to slip away,
or begins to roll and pitch beyond a certain limit. The above-described motion
sensors, along with processing, can determine a course of action. If the
motion is within certain bounds, only the fueling system needs to be shut
down; however, for greater motion or slip-away, not only does the fueling
system need to be shut down, but the fueling lines need to be automatically
disconnected from the barge.
Fires or explosions of any type during fueling are also a danger signal
that all fueling operations should cease. To detect hazardous fire conditions,
the use of one or more sensors in combination with one or more micro-
switches can combine to automatically close the isolation valve(s) to prevent
and/or disable fuel transfers and activate audible, visual, and communication
links like fire alarms, pumps, and fire suppression systems. Such sensors
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such as optical or magnetic can detect infrared, ultraviolet, heat, or a rate
of
rise in temperature. Such devices can activate fire alarms and the like. Any
fire/flame scanners or laser sensors, fusible/friable links are within the
scope
of the present invention. This includes any means to detect fire hazards.
Complex (multiple or higher level) resets are typically required for fire
system
such as both a key and code. The sensors described may also be used in
conjunction with standard fire detection systems as a cascade of controls.
To prevent enhancement of the dangers of further fire or explosion; an
optional relay or digital or analog logic function that is activated by a fire
detection system of one or more optical, magnetic, ultrasonic sensors or links
in combination with one or more micro-switches combine to provide and/or
trigger/ ENABLE an override thus disabling the lock-out system(s) and
liberating the vehicle(s) while fire or explosion risks exist. This enables
the
vehicle(s) to be moved away from the fire or explosion source, or away to
distance itself from spreading further fire or explosion dangers, whether
another fueling vehicle is present, or fueling is taking place from a storage
vessel. Optical sensor(s) such as infrared, ultraviolet, individually or
combined, can sense fire and/or heat; also sensor(s) such as rate of
temperature rise and ionization can detect excessive temperature and smoke.
Fusible/friable links/ plus other sensors such as an acoustical or ultrasonic
sensor system receiver(s) can detect loud sudden noises/sound waves such
as those created by a rapid expansion of molecules in a confined
environment, or explosions. Any sensor activation usually also initiates the
system to close the isolation valve(s), and stop/mitigation of fuel flow
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transfers; plus de-activate or activate any vehicle or automatic fuelling
release
systems that may exist, or release one initiated with a lock-out.
All motion and fire/heat sensors are generally coupled to a processor.
The processor executes stored instructions from a memory, and makes
decisions using artificial intelligence techniques to determine a course of
action. As stated, the action might just be a fueling shutdown, or it might be
a
complete disconnect of the fueling system from the vehicle. The sensors
and/or processor can be part of the fueling supply system apparatus, or they
can be on the vehicle, or both.
The use of optical sensor(s) such as infrared temperature or fiber optic
sensors to detect the presence or absence of a Liquefied Natural Gas
cryogenic temperature, or temperature differential detection, can determine
the presence or absence in fueling lines, and thus a relay or digital or
analog
logic function combine to disable and produce a vehicle lock-out. These can
also be flow switches or flow meters with transmitters. The above-listed
sensors sense the presence of the natural gas fill hose in proximity to a tank
fill adapter coupled to a natural gas tank.
The use of magnetic sensor(s) such as "Mag-Meter", Coreolsis flow
meter (U-Tube), density meter(LVDT/strain gauge), or mass flow
(temperature/pressure compensated flow meter), plus other methods of
indicating floware are within the scope of the present invention. The above-
listed sensors sense presence of a natural gas fill hose in proximity to a
tank
fill adapter coupled to a natural gas tank. These sensors produce a signal or
relay either digital or analog Logic function that combines to produce a
vehicle
lock-out signal.
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The use of ultrasonic sensor(sensors) such as flow meter, which can
be an external type that clamps or monitors from exterior of flow line, or it
can
internally measure flow with-in lines (submersed) is also within the scope of
the present invention. Also any other method that utilizes ultra-sonic, radar,
or other waves for detection/proximity is within the scope of the present
invention. Ultrasonic sensors sense the presence of a natural gas fill hose in
proximity to a tank fill adapter coupled to a natural gas tank, and sense or
guide manual and/or automatic fuelling systems to sense proximity, or that a
particular mechanical part is, or is not, in a particular position; such as a
fueling rack, tray, arm, hose, articulation or extension of hose-line or
fuelling
devices and/or connections.
The use of optical sensors, such as infrared, ultraviolet, laser, fiber
optic, visible or non-visible light to detect the presence of a natural gas
fill
hose in proximity to a tank fill adapter coupled to a natural gas tank is
within
the scope of the present invention. These sensors can measure interference
of a light beam, distance, obstruction, light differential, existence or non
existence, proximity, and whether a part is, or is not, in a particular
position
The optical sensors can have transmitters that communicate wirelessly such
as by radio or light. The sensors can guide manual and/or automatic fuelling
systems with a natural gas fill hose to sense proximity, or that a particular
mechanical part is or is not in a particular position; such as a fuelling
rack,
tray, arm, hose, line, articulation, or extension of hose-line or fuelling
devices
and/or connections.
Also any standard temperature sensors, pressure sensors or flow
transmitters can be used to sense presence of a natural gas fuel fill hose in
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proximity to tank fill adapter coupled to a natural gas tank. All the above
sensors can have transmitters that may communicate wirelessly such as by
light or radio. Different level resets can be made available for operators to
reset various system upsets.
All the above safety systems, sensors, relays, triggers, micro-switches,
over-rides, lock-outs, resets, and events should be continuously recorded,
plus all logged logic data is identified (I.D.'d) all with current time and
date
stamps, and will be available for print-out if needed. Data recording can be
local or remote, or both. Data can be transmitted wirelessly to a remote
location and can be transmitted over a network such as the Internet if
desired.
Turning to Fig. 7, a vehicle being fueled 200 can be seen attached to a
fueling system 201 with a fuel line 202 that passes between isolation valves
203 and 204 on the system and vehicle respectively. There is an automatic
fuel line release 205 and an automatic vehicle release 211. Some vehicles,
such as land vehicles, may not have an automatic vehicle release. However,
trains and marine vessels usually will have. A processor 206 with memory
207 executes stored instructions. The processor 206 interfaces with fire and
explosion sensors 209 and motion sensors 208. The processor executes
artificial intelligence routines or other algorithms that allow determination
of
when there is too much vehicle motion, and if there is a fire or explosion. If
a
determination is made of too much motion, the isolation valves 203 and 204
can be automatically shut off. In more severe conditions such as extreme or
slip-away motion, the fuel line 202 may be released from the vehicle via the
fuel line release 205, and the vehicle 200 may be released from the fueling
system via the vehicle release 211. In the case of a land vehicle, the vehicle
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lockout 210 may be over-ridden by the processor 206 so the vehicle can be
started and/or moved. It is understood, that the processor 206 may be in the
vehicle 200, part of the fueling system 201, or split between the two as two
separate processors. Given the numerous possible danger conditions or
scenarios, the processor programming should be able to evaluate and act on
many different sensor-reported conditions.
As stated, the present invention relates generally to the fields of vehicle
safety and compressed as well as liquefied gases, More particularity to safety
systems related to natural gas powered vehicles such as spacecraft, launch
rockets, and aircraft utilizing a multiple redundant system and method for
preventing an operator, driver, or pilot from starting or moving a compressed
gas vehicle with oxygen trim if the high pressure gas fill systems are not
correctly and completely disconnected from the vehicle.
Today, a wide array of inner-space and outer space travel are
providing launch vehicles, spacecraft, rockets, subsonic and supersonic
vehicles; some with rocket bi-propellant engines and some with hybrid
propulsion (natural gas turbine-generator), others have turbo fan, some with
afterburners, and even ramjet engines for cargo transport, satellite
launching,
exploration, probe vehicle transit, and human transfers to Various locations
in
space (International Space Station ) and faster, more efficient global
transits/travel. These vehicles (spacecraft/both inner and outer) possibly
bound for multiple planets, for various exploration, observation, security,
and
transit are now being fuelled with natural gas (in liquefied state) (LNG), or
the
natural gas chemical family (such as ethane, propane, hydrogen, butane, and
other compounds).
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It is well known and understood that natural gas composition varies
from different regions, and pure methane (also considered natural gas) is
more process intense to scrub/refine/produce.
It is also well known in fire sciences that the combustion triangle
requires three elements:
1) FUEL 2) Oxygen 3) Ignition Source
In order for natural gas fuelled rocket propulsion to achieve the proper
specific Impulse; natural gas fuel must utilize an oxidizer such as oxygen,
directly supplied or derived from an oxidant. Oxygen can also be
compressed, scrubbed, refrigerated and condensed into a liquid state, to
maximize storage space. Liquid oxygen (LOX) vaporized into pure oxygen
gas can be mixed with vaporized natural gas fuel. This oxygen enriched fuel
produces a clean, green, excellent propellant for rockets, spacecraft,
aircraft
vehicles.
Liquidified natural gas (LNG) has several advantages for these modern
vehicles:
1) Liquidified natural gas is more dense than other existing fuels; therefore,
reducing fuel tank size.
2) Liquidified natural gas is very close in temperature to that of liquidified
oxygen, simplifying storage, which was a major engineering obstacle.
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3) Natural gas turbine! internal combustion engine driven turbo pump seals
need only have a narrow temperature band, reducing temperature differential
issues.
4) No ullage gasses are necessary due to the higher vapor pressure of
liquidified natural gas.
5) Natural gas is less evaporative in space, thus increasing efficiency.
6) Natural gas and oxygen have a positive chemical affinity.
7) Natural gas is green and more environmentally friendly, and non toxic than
other fuels.
8) Methane can most probably be harvested on Mars, Titan, Jupiter, and
other planets; providing missions with return fuel.
Commonly developed spacecraft/vehicles of various makes, models
and propellants exist, each entity having various promises, but all share the
same goal: SAFE, EFFICIENT, spacecraft/vehicles. Natural gas and oxygen
can be handled safely, utilizing the Best Available Technologies. Intelligent
systems, utilizing intrinsically safe sensors can mitigate risks during
fuelling,
and filling of oxygen or fuel enrichment and the natural gas fuel itself.
During fuelling events, or anytime fuel and or oxygen is present, proper
atmospheric monitoring systems and controls can mitigate risk of deflagration
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detonation and explosion. Monitoring, both CH4 and 02 (deprivation and
enrichment) atmospheres is an absolute for safety. Optical sensors such as
fiber optic sensors, both closed cell, and open path, may be used along with
electro-chemical detection. These sensors all may communicate wirelessly
either by radio or light with one or more central or remote systems. Analyzers
may also be utilized to perform atmospheric monitoring. Systems such as
Ramen Spectroscopy methods are within the scope of this invention.
Natural gas in air has a Lower explosive limit (LEL) of 5%; and an
upper explosive limit (UEL) of 15%. However, when pure oxygen is present,
the LEL remains approximately 5%, but the Upper Explosive limit Is
increased to between 59% to 61% ( depending on natural gas composition).
With the introduction of pure oxygen, the atmosphere is orders of magnitude
more dangerous, because oxygen also Lowers the Ignition temperature and
energy required for ignition. A fuel, oxygen, or both leak will enrich the
surrounding atmosphere which can have disastrous consequences. The
smallest spark, arc, rapid pressurization, acoustical resonance, friction, or
even spontaneous combustion may ignite the now flammable/highly
combustible-explosive mixture into a runaway exothermic reaction, or rapid
expansion of molecules in a confined or unconfined space in an instant. An
optical fiber optic sensor for oxygen detection alone or in combination with
spectrometer is able to detect oxygen levels of from 0% to 100%. For
methane, an optical/fiber optic sensor alone, or in combination with
spectrometer, will detect L.E.L. with a range of 0% to 100% of explosive
limits.
The preferred method is to combine both types of sensors into a single
analyzer to process different L.E.L ranges corresponding to different oxygen
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levels.
Safely containing the fuels and oxidizers at all times is critical, but
during Fuelling, it is paramount. Safe vehicle disengagement/lock-out,
preventing ignition or movements utilizing one or more sensors in combination
with one or more micro switches that can be optical, magnetic, or ultrasonic
is
within the scope of this invention. For different levels of safety different
combinations of sensor may be used, with the lowest level having a single
proximity sensor sensing the presence or absence of a high pressure fill hose.
The highest level of safety is achieved by having separate proximity sensors
on the fuel and oxygen fill hose fittings, gas cap covers, and a manual or
automatic safety valve with a redundant micro switch. An optional over-ride
that may be restricted as to the number of times it can be used can allow
starting with a faulty sensor in order to allow maintenance. This system
should
be active during both test stand firings and actual launch or flight take/lift
offs.
Some countries have enacted "NO FLY" Zones perimeters over LNG facilities.
In order to detect omni-directional vehicular/Space/aircraft
movements/distances, multiple sensors may perform different functions alone,
or in a cascading/subroutine control system to perform a
vehicle/space/aircraft
"LOCK-OUT". The use of one or more sensors in combination with one or
more micro-switches or other switches combines to automatically determine
when threshold limits are exceeded, and can initiate a "LOCK-OUT" of the
fueling system closing isolation valve/valves to prevent/disable fuel/oxidizer
flows/transfers. The sensors, such as optical, magnetic, ultrasonic,
accelerometer, or others may detect any or excessive movement of the
vehicle (above or greater than predetermined limits). One or more sensors,
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or all of these sensors combined, can monitor and control fuel and oxidizer
flows and instantly switch the system to a "LOCK-OUT" state, as well as
activating one or more visual and/or audible alarms. Usually fuel/oxidizer
flow can be reactivated by operator when a safe condition is assured.
Different vehicles may require different types of controls. For
example, excessive movements may relay, trigger, or enable an "OVER-
RIDE" system, thus disabling the "Lock-Out" system(s), but will keep fuel flow
isolation valve(s) closed(safe state) and liberating the vehicle(s) until
proper
control and conditions are achieved. In addition, they can de-activate or
activate any vehicle or automatic fuelling release system that may exist, or
any initiated by lock-out. Multiple variations can be used with multiple steps
and sequences to maintain a "Safe State" with isolation valve(s) in a closed
position, and if predetermined safe conditions exist, vehicle movement can be
allowed by automatic activation of an "OverRide".
To detect hazardous fire conditions, the use of one or more sensors in
combination with one or more micro-switches combine to automatically close
the isolation valve(valves) to prevent/disable fuel flow! transfers, and
activate
audible, visual, communication links, fire alarms, pumps, and fire suppression
systems. Sensors such as optical or magnetic and the like can detect infrared,
ultraviolet, or a rate of rise of temperature. These devices can activate fire
alarms, plus any other fire/flame scanners/laser sensors, as well as
fusible/friable links that can also included. Any means, sensor or technique
to
detect a fire hazard are within the scope of the present invention including,
but
not limited to, complex (multiple or higher level) resets required for fire
systems such as both keys and codes.
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To prevent enhancing/enhancement of the dangers of further fire or
explosion, an optional relay or digital or analog logic function that is
activated
by a fire detection system of one or more optical, magnetic, ultrasonic
sensors
or links in combination with one or more micro-switches can combine to
provide a Lock-Out or override a Lock-Out. The override liberates vehicle(s)
while fire or explosion risks exist, enabling vehicle(s) to be moved away from
fire or explosion source or away to distance itself from spreading further
fire or
explosion dangers.
Optical sensors such as infrared and ultraviolet, individually or
combined, can sense fire and or heat. Also sensors such as rate of rise and
ionization can detect excessive temperature and smoke. Fusible/friable links!
plus other sensors such as an acoustical or ultrasonic sensor system
receivers can detect sudden loud noise/sound waves such as those created
by a rapid expansion of molecules in a confined environment, or explosions.
Any sensor activation can also cause the system to close the isolation
valve(s) and stopping/mitigation of fuel flow transfers; plus de-activate or
activate any vehicle or automatic fuelling release systems that may exist or
having been initiated with a Lock-Out.
The use of optical sensors such as infrared temperature sensors or
fiber optic sensors to detect the presence or absence of Liquefied Natural
Gas/oxygen, cryogenic temperatures, or temperature differentials can
determine presence or absence in fueling lines of LNG. Thus, a relay or
digital or analog logic function can combine to disable and produce a vehicle
"Lock-Out". This can also be include either a flow switch or a flow meter with
a
transmitter. The above listed sensor sensors can also sense presence of a
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natural gas/oxygen fill hose in proximity to a tank fill adapter coupled to a
natural gas/oxygen tank.
The use of magnetic sensors such as "Mag-Meter", Coreolsis flow
meter(U-Tube), Density meter(LVDT/strain gauge), or Mass Flow
(temperature/pressure compensated flow meter) plus other methods of
indicating flow are within the scope of the present invention.
Ultrasonic sensors such as a flow meter which can be an external type
that clamps or monitors from exterior of a flow line, or can internally
measure
flow within lines (submersed), may also be used. Other methods that utilize
ultrasonic, radar, or other acoustical waves for detection/proximity are
within
the scope of the present invention. These ultrasonic sensors sense the
presence of a natural gas/oxygen fill hose in proximity to a tank fill adapter
coupled to a natural gas/oxygen tank, and sense or guide manual and or
automatic fuelling systems to sense proximity or that a particular mechanical
part is or is not in a particular position. This may be a fueling rack, tray,
arm,
hose, articulation, or extension of hose/line or fuelling devices and/or
connections/connectors.
Optical sensors, such as infrared, ultraviolet, laser, fiber optic, visible or
non-visible light may also be used to detect presence of a natural gas/oxygen
fill hose in proximity to a tank fill adapter coupled to a natural gas/oxygen
tank. These sensors can measure interference of a light beam, a distance, an
obstruction, light differential, existence or non existence of parts,
proximity, or
whether a part is or is not in a particular position. Any sensor can have one
or
more transmitters/transceivers that communicate wirelessly such as by radio
or light. These sensors can also guide manual and or automatic fuelling
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systems with a natural gas/oxygen fill hose to sense proximity or that a
particular mechanical part is, or is not, in a particular position such as a
fuelling rack, tray, arm, hose, line, articulation, or extension of hose/line
or
fuelling devices and or connections/connectors.
All the above safety systems, sensors, relays, triggers, micro-switches,
over-rides, lock-outs, resets, and events can be continuously monitored,
recorded, and all logged data can be identified with a unique ID relating to
location and part number along with current time and date stamps. All
recorded data can be print out upon request.
Fig. 8 shows an example of a LNG/LOX fueling safety system
according to an embodiment of the present invention. The rocket, aircraft or
other vehicle 300 being fueled is attached to a fueling system 310 with an
LNG fuel line 303 and a LOX oxidizer line 304. The fueling system 310 has a
safety lockout 311 that can very rapidly stop fueling (in the order of
milliseconds or faster). A processor 301 or other logic in conjunction with a
memory 302 acts as a logic circuit. The processor is coupled to a
fire/explosion sensor 306, a LNG presence sensor 305 and a LOX oxygen
above ambient concentration sensor 308. The processor 301 is also coupled
to an LNG hose proximity detector 307 and a LOX hose proximity sensor 309.
The processor 301 or logic circuit, upon sensing a dangerous condition from
any one of the coupled sensors, immediately (in microseconds) sends a
command to the fueling system lockout 311 to stop fueling. Fast shutoff
valves in the fueling system 310 can shut off fueling flow as quickly as
mechanically possible. Many other sensors and sensor types previously
discussed can be incorporated into this system as needed. These can
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include motion detectors and detectors on isolation valves.
Several descriptions and illustrations have been presented to aid in
understanding the features of the present invention. One with skill in the art
will realize that numerous changes and variations may be made without
departing from the spirit of the invention. Each of these changes and
variations is within the scope of the present invention.
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