Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
W091/0720X pcT/GB9~/n17~/
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IM~ROVEMENTS ~ELATING TO WATER SPRAY SYSTE
BACRG~QUND OF THE TNVENTIo~
This invention relates to water spray systems, and
particularly, though not e~clusively, to water spray -
systems for aircraft.
. . .
In the event of a fire in the cabin of an aircraft, known
water spray systems discharge a fine spray into the cabin
via an array of spray outlet nozzles. ~he water may be
carried on the aircraft (on-board system) or delivered
from a fire appliance or other e~ternal source.
The water droplets forming the spray have several
beneficial effects. They provide an infra-red radiation
barrier protecting passengers and crew, improve
visibility within the cabin and absorb tosic gases which
congregate in the upper zone of the cabin, enabling
passengers to breathe more easily. The spray also has a
cooling effect on the gas cloud near the roof of the
cabin, slowing its progagation and reducing the risk of
flash-over ignition. Also, the spray wets combustible
material (furnishings etc.) delaying their ignition, and
has a cooling effect on the interior surface of the
aircraft wall.
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Notwithstanding these beneficial effects, e~isting water
spray systems have serious drawbacks.
~' .
`; For instance, in the event that the aircraft sustains
~, severe damage (during a crash landing, for e~ample) the
fuselage could separate into discrete sections, and this
could compromise the operational integrity of the entire
,,~
water spray system.
Furthermore, known on-board water spray systems operate
at relatively low pressure, whereas water is supplied by
a fire appliance (or other esternal source) at a much
higher pressure. This leads to a requirement for
separate on-board and esternal supply systems with an
increased overall weiqht; but coupling between the two
systems has not been successfully achieved. Also, such
systems may reguire a relatively large quantity of water,
e~acerbating the weight problem.
It is an object of the present invention to provide
improved water spray systems which substantially
alleviate the afore-mentioned problems and/or which
require a substantially reduced quantity of water.
SUMMARY OF THE INVENTlON
According to first aspect of the invention, there is
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provided a water spray system comprising a water storage
vessel, at least one spray outlet nozzle connected to the
water storage vessel and a pyrotechnic gas source for
maintaining a substantially constant pressure in the
; water storage vessel to enable water in the vessel to be
discharged via the at least one spray outlet nozzle.
.~ :
The pyrotechnic gas source may comprise a pyrotechnic
material (e.g. an alkali metal azide, such as sodium
azide) and an o~idizing agent (e.g. an alkali metal
chlorate or perchlorate).
. . .
According to a second aspect of the invention, there is
provided a water spray system comprising a water storage
vessel, at least one spray outlet nozzle connected to the
water storage vessel, means responsive to a control
signal for pressurizing the water storage vessel enabling
water stored in the vessel to be discharged via the at
least one spray outlet nozzle and processing means for
generating the control signal in response to input
signals derived from different respective sources.
According to a third aspect of the invention, there is
provided a water spray system comprising a water storage
vessel, at least one spray outlet nozzle connected to the
water storage vessel, means for pressurizing the water
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storage vessel enabling water stored in the vessel to be
discharged via the at least one spray outlet nozzle and
an exhaust valve for venting the water storage vessel.
According to a fourth aspect of the invention, there is
provided a water spray s~stem comprising a water storage
vessel, at least one spray outlet nozzle connected to the
water storage vessel and means for pressurizing the water
storage vessel enabling water in the vessel to be
discharged via the at least one spray outlet nozzle to a
respective zone and wherein the at least one spray outlet
nozzle so directs the spray as to enhance the residence
time of water droplets in the spray in an upper region of
a zone. The at least one spray outlet nozzle may be
directed upwardly and/or laterally. By this means, less
water is required to achieve the desired effect.
According to a fifth aspect of the invention, there is
provided a water spray system comprising a plurality of
water spray sub-systems each comprising a water storage
vessel, at least one spray outlet nozzle connected to the
water storage vessel and means for pressurizing the water
storage vessel enabling water in the vessel to be
discharged via the at least one spray outlet nozzle,
wherein each sub-system operates independently of the
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others to supply spray to a respective zone.
The water spray system has particular, thouqh not
esclusive, application to aircraft, each said zone being
a respective section of the aircraft cabin.
. .
According to a sisth aspect of the invention there is
provided a water spray system comprising a water storage
.. . . . .
vessel, at least one spray outlet nozzle connected to the
water storage vessel and means for pressurizing the water
storage vessel enabling water stored in the vessel to be
discharged via the at least one spray outlet nozzle to a
zone, wherein the at least one spray outlet nozzle is
operable in each of three distinct modes; a sealed mode,
enabling pressure testing to be carried out up to a first
predetermined pressure, a low flow mode operable in
response to a water supply pressure e2ceeding the first
predetermined pressure, but less than a second
predetermined pressure, and a high flow mode operable in
response to a water supply pressure esceeding the second
predetermined pressure.
The invention also relates to a spray outlet nozzle
defined in accordance with the sisth aspect of the
invention.
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According to a further aspect of the invention, there is
provided a method for connecting a water spray system
having a water storage vessel to an ezternal water supply
system, including the steps of penetrating a wall of the
water storage vessel whereby to simultaneously connect
the interior of the vessel to the esternal supply system
via the penetration hole formed in the supply vessel.
:
The wall of the water supply vessel may be penetrated by
a remotely launched penetration device which may be
coupled to the esternal supply system by means of a
flesible hose.
DEscalEIIQ~Q F THE DRAWINGS
Embodiments of the invention are now described, by way of
e~ample only, with reference to the accompanying drawinqs
in which:
Figure 1 is a schematic representation of a water spray
sub-system in accordance with one aspect of the invention;
Figure 2 shows a longitudinal cross-sectional view
through an active vent in the open and closed conditions
thereof;
Figure 3 illustrates the manner by which an e~ternal
W091/0720X ~ PCT/G Bsn/o 1767
water supply system may be coupled to the sub-system
illustrated in Figure l;
`~'.~'
Figure 4 shows a longitudinal cross-sectional view
~ through a three-mode spray outlet nozzle; and
; Figure 5 shows a transverse cross-sectional view through
~ the fuselage of an aircraft and illustrates how the spray
.. ..
outlet nozzles are arranged within the aircraft cabin.
p~SC~IPTION OF PREFERRED EMBODIMENTS
During a crash, the aircraft fuselage may sustain severe
damage and may separate into several discrete sections.
In order to improve the prospect that an on-board water
spray system would still be effective, even in the event
of fuselage break-up, the system may consist of a number
of independent sub-systems, each being associated with a
respective section of the fuselage, each section
typically containing 20 to 30 seats.
Figure l of the drawings gives a schematic representation
of one such sub-system. This comprises a water supply
tank l which is connected, via a supply main 2, to
several branch pipes 4 arranged at intervals along the
fuselage.
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Upon activation of the sub-system, the supply tank is
pressurised with air from an air pressure bottle 5,
causing water to be discharged to the interior of the
cabin via a respective set of spray outlet nozzles, e.g.
6, 6~, 6~', connected to each branch pipe 4. The form of
the spray outlet nozzles, and their location within the
cabin, will be described hereinafter with reference to
Figure 5.
.
It will be appreciated that other (inert) gases, for
esample nitrogen gas, could be used instead of air to
pressurise tank 1. Moreover, the gas need not
necessarily be supplied from a pressure bottle.
Alternatively, a pyrotechnic qas source could be used. A
pyrotechnic gas source has the advantage that gas is
generated only when it is needed and so gas leakages are
eliminated. Furthermore, the pyrotechnic source may be
arranged to burn in a controlled manner, tailored to
maintain a constant pressure in the ullage reservoir of
the supply tank thereby providing a uniform flow of water
to the outlet nozzles throughout the discharge.
The pyrotechnic material might typically comprise a
pyrotechnic material such as an al~ali metal azide (e.g.
sodium azide) and an o~idizing agent (e.g. an alkali
metal chlorate or perchlorate).
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The source of pressurised gas is connected to the tank by
means of a suitable control valve 7 (e.g. a solenoid
valve) which is effective to release gas into the tank in
response to a control signal Io received from a central
control unit 8 for the sub-system. Similarly, a
pyrotechnic gas source would have a pyrotechnic igniter
which would be activated in response to the control
signal Io~ The central control unit 8 receives input
. . .
signals from several different sources. One of the input
signals Is is produced by one or more smoke detectors 9
whenever the level of smoke detected within the
respective section of cabin eYceeds a predetermined
threshold. To that end, a smoke detector would normally
be located centrally within the cabin, at ceiling level.
Another input signal Ig is produced by a so-called
~g-force~ sensor 10 (which may be common to all the
sub-systems~ in response to the e~cessively high loads
which occur during a crash. The input signals Iw and
Ia are aircraft system signals which denote
respectively that the aircraft is in a ~wheels-down~ mode
and is at ground altitude.. The control unit 8 also
receives command signals If and Ig which are set
manually by the flight deck crew and the flight cabin
crew respectively.
In order to prevent the spray sub-systems being triggered
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inadvertently, they must first be enabled (e.g. during
take-off and landing) by the flight deck crew (i.e. If
hiqh). Having been enabled in this manner, any
sub-system may be activated either by the cabin crew
(i.e. Ic high), by depression of, for instance, ~panic
buttons~ located at strategic positions around the
respective section of cabin or by an output from a
respective smoke detector 9 indicating a high level of
.. . . . . . . .
smoke in the associated cabin section (i.e. Is high).
In the event that the ~g-force~ sensor 10 detects a high
load (Ig high), each sub-system would be: enabled
automatically (independently of the action of the flight
crew) and, as before, could then be activated in response
to an output from a smoke detector 9, or by the action of
cabin crew.
Since the water spray æystem is intended to operate when
the aircraft is on the ground, the control signal lo
may be inhibited unless the ~wheels-down~ input signal
Iw and the altitude signal Ia have been received.
.
As an additional measure, the flight crew has the ability
to over-ride the control unit 8 and thereby activate the
water spray sub-systems directly.
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In the event that an enabled sub-system is activated
inadvertently, the respective supply tank 1 can be vented
e~ternally in order to minimise damage to the cabin. To
that end, each tank may be fitted with an active vent 11,
such as a dump valve, for esample.
Figure 2 shows one embodiment of a dump valve. The valve
comprises a valve housing 20 fitted with a sealing piston
21 which is maintained in the closed position ~shown on
the left side of the drawing) by a ball lock 22 which is
held in the locked condition by an actuator piston 23.
When it is desired to vent water in the supply tank, an
e~plosive cartridge 24 is triggered by a suitable control
signal, produced by the control unit 8 or directly by the
crew, forcing the actuator piston 23 downwards thereby
rapidly releasing the ball lock from the locked
condition. The pressure of water on the upstream side of
the valve then forces the sealing piston 21 upwardly in
the direction of arrow A (to the position shown on the
right side of the drawing) so that the water in the
supply tank is discharged via outlet openings 25.
A pressurised, on-board system, as described, would
typically discharge water to the cabin at a pressure of
about 1 to 7 bar (preferably 2 to 5 bar), and each
sub-system would have a sufficient capacity to operate at
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this pressure for at least three minutes, by which time a
fire appliance would have arrived at the scene.
The water supply system of the tender must be coupled to
the on-board system of the aircraft without delay.
Hitherto, esternal connectors have been provided for this
purpose at different connection sites around the
aircraft. However, such esternal connectors can be
difficult to manipulate at high speed and, depending on
the attitude of the aircraft, are sometimes inaccessible.
In addition, damage may have caused the single water main
to be damaqed or to fracture. As shown in Figure 3, in
order to alleviate these short comings, a lance 30,
attached to a flesible hose 31, connected to a supply
main 32 of the tender, is fired by a pneumatic gun ~not
shown) into the skin of the aircraft whereby to penetrate
the (double) wall 33 of the on-board supply tank 1. 3y
this means the lance establishes a connection between the
on-board system and the tender supply system via the
fle~ible hose 31. To assist location of the lance, a
marking (in effect a "bullseye~) is provided on the
exterior surface of the aircraft fuselage to indicate the
position of the supply tank within.
In the illustrated embodiment the lance has a barb 34
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which is biased by the action of a spring 35 against the
inner wall of thè tank thereby to establish a fluid-tight
seal around the penetration opening formed by the lance
tip.
Alternative sealing means can be envisaged. In
particular, the inner wall of the supply tank l may be
made from a self-sealing material which swells up when
wet to form a seal around the penetration hole.
The water supply system provided by the tender operates
at a much higher pressure than does the on-board water
spray system. In order to accommodate these different
pressures the spray outlet nozzles of the on-board system
may be adapted to operate in two different flow modes; a
~low flow~ mode, which is adopted when water is being
supplied by the ~low pressure - typically from 2 to 7
bar) on-board system and a ~high flow~ mode, which is
; adopted when water is being supplied by the (high
pressure - typically from 7 to 15 bar) tender supply
system.
Furthermore, the outlet nozzles should permit routine
pneumatic testing in order to confirm the integrity of
the pipe-work system, and such testing should be carried
out without releasing water from the system.
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To that end, each nozzle is sealed to a low pressure,
perhaps a few tenths of a bar, which is high enough to
enable pressure testing to be carried out, yet is
sufficiently less than the ~low flow~ mode supply
pressure. With this in mind, each nozzle is capable of
operating in each of three distinct modes; that is, a
sealed mode, enabling pressure testing to be carried out
up to a first predetermined threshold pressure, a low
flow mode operable in response to a water supply pressure
which esceeds the first predetermined threshold pressure,
but is less than a second predetermined threshold
pressure, and a high flow mode operable in response to a
water pressure which e~ceeds the second predetermined
threshold pressure.
A nozzle, thus described, may incorporate a switchable
valve which interconnects the nozzle inlet and the nozzle
outlet, enabling the nozzle to switch between the sealed,
low flow and high flow modes in response to a respective
pressure change at the nozzle inlet. The valve may
respond directly to a change of pressure at the nozzle
outlet or, alternatively, may switch between the three
modes in response to an output from a pressure transducer
arranged to monitor the pressure at the nozzle inlet.
The nozzles should present a neat, unobtrusive appearance
. . . . . . .. .. ..
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to the interior of the cabin. To that end, each outlet
nozzle is fitted with a trim panel and this is arranged
to be ejected from the nozzle by the increase of pressure
which takes place when the nozzle switches from the
sealed mode to the low flow mode.
The ejection of the trim panel may be the means for
switching from the sealed mode to the low flow mode.
Figure 4 shows one embodiment of a switchable spray
outlet nozzle.
Referring to the drawing, the nozzle comprises a
; cylindrical nozzle body 40 having an inlet 41 and a spray
outlet orifice 42 provided in an end wall 43 of the
~; nozzle body. A trim panel 44 is fitted over the end of
the nozzle body, as shown, and is sealed thereto by an
~O~-ring 45. Provided the pressure of water at the inlet
does not esceed a first predetermined pressure, typically
a few tenths of a bar, which is adequate to allow
pressure testinq to be carried out, the trim panel is
retained in place by the ~On-ring and a flow of water is
prevented - the sealed mode.
If the pressure at the inlet esceeds the first
predetermined pressure, the trim panel 44 will be ejected
~ .
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allowing water to flow around a cylindrical valve member
46 and to esit the outlet orifice 42 as a spray. The
valve member 46 has a helical, ribbed formation 47 which
induces swirling as the water flows toward the outlet
orifice creating a spray in the form of a hollow cone.
The valve member is supported within the nozzle body by a
circumferentially apertured support member 48. To that
end, the valve member has an asial shaft 49 located in a
- cylindrical soc~et 50 of the support member. A volume 51
of oil trapped at the closed end of the socket contains a
gas bubble 52. If the pressure of water is less than a
second predetermined pressure, but greater than the first
predetermined pressure, the axial position of the valve
member 46 in the nozzle body 40 is such that a restrictor
53, in the form of a pip at the end of the valve member,
partially blocks the outlet orifice (as shown in the
drawing) and so restricts the flow of water - the low
flow mode. However, if the inlet pressure esceeds the
second predetermined pressure, the pressure of water
acting on the valve member compresses the gas bubble 52
thereby displacing the valve member towards the inlet and
retracting the restrictor from the outlet orifice,
allowing a greater flow of water - the high flow mode.
For a given mode of operation (low or high flow) the
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water flow rate and the size of the water droplets in the
spray will be determined by the dimensions of the nozzle
outlet orifice.
The passenger cabin of an aircraft would be fitted with a
large number of spray outlet nozzles and these may have a
range of different orifice sizes. The size of orifice
selected in a particular case would depend on the
location of the nozzle within the cabin. For eYample, a
nozzle positioned in relatively close pro~imity to
combustible material, e.g. below the overhead luggage
compartments, would have a relatively large outlet
orifice giving a corresponding high flow rate and
producing spray containing relatively large water
droplets.
Combustion products generated during a fire inside the
cabin of an aircraft include toxic gases, such as carbon
mono~ide, hydrogen fluoride, hydrogen chloride and
hydrogen cyanide.
~ .
As illustrated in Figure S of the drawings, these
combustion gases, being buoyant, tend to congregate in an
upper region U of the cabin, in the space generally
between the overhead luggage compartments L, positioned
along, and to either side of, the cabin.
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Hithertoknown water spray systems used in aircraft,
suffer from the short-coming that the water spray
produced in the event of a fire fails to absorb, to a
satisfactory estent, the combustion gases which
congregate in region U. Over time, the concentration of
gas in region U increases, and the gases tend to spread
into the main body M of the cabin where they present a
hazard 'o passengers and crew.
With a view to alleviating this short-coming, a further
aspect of the present invention provides a water spray
system for use in an aircraft in which a plurality of
spray outlet nozzles are arranged to direct the spray
whereby to enhance the residence time of water droplets
in the upper region of the aircraft cabin.
., .
To that end, the nozzles may be so arranged as to direct
the spray laterally and/or upwardly.
'~
In a particular configuration, nozzles are mounted to
either side of the cabin centre line and, in the case of
the cabin having more than one aisle, nozzles may be
mounted to either side of each aisle.
., ~
- The nozzles (e.g. Nl,N2) may be mounted directly on the
structure of the luggage compartments themselves.
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However, the compartments could collapse during a crash
landing and so it is preferred that the nozzles ~e.q.
N3,N4) be mounted on the airframe, preferably in the
corner spaces defined by the roof panel R of the cabin
and the inwardly facing sides of the overhead lockers on
opposite sides of the aisle.
Additional nozzles (N5,N6) may also be provided, at a
lower level, in order to douse the furnishings and
passengers in the immediate vicinity.
The spray produced by the aforementioned configuration of
nozzles resides in the upper region U for a. time
sufficient to permit enhanced absorption of the
combustion gases, thereby significantly reducing the risk
to passengers below, and at the same time reducing the
quantity of water required.
In order to enhance absorption of carbon monoside the
water may contain a suitable additive. The additive may
also be used as an anti-freeze. Alternatively, the
supply tank could be fitted with a low energy immersion
heater.
It will be appreciated that the described water spray
systems are given by way of example only, and it will be
. . . . ..
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understood that althouqh the described water spray
systems are intended for use in aircraft, the invention
has a wider, more general, applicability.
... . .... . . . . .
