The invention relates to methods of fire extinguishing and

apparatus for discharging fire extinguishants. Methods and

apparatus to be described in more detail below, by way of example

only, are for discharging fire extinguishants in the form of

water or water-based fluids.

According to the invention, there is provided a method of fire

extinguishing, comprising the steps of emitting at least two jets

of fluid into the atmosphere, the two jets being directed in

respective predetermined mutually inclined directions so as to

impinge with each other, at least one of the jets being a jet of

an extinguishing liquid which is atomised into a spray of drops

by the impingement, the point of emission of one jet into the

atmosphere being spaced from the point of emission of the other jet substantially in the predetermined direction of the other

jet.

According to the invention, there is further provided a method

of extinguishing fires, comprising the steps of emitting a plurality of first fluid jets into the ambient atmosphere in

respective first directions from a nozzle, emitting a plurality

of second fluid jets into the ambient atmosphere in respective second directions from the nozzle, the jets being so mutually

positioned and the first and second directions being such that

the jets of the two pluralities impinge on each other, the jets

of at least one plurality being jets of a fire extinguishing

liquid which becomes atomised into drops by the impingement and

produces a fire-extinguishing spray, the points of emission of

the second jets into the atmosphere being spaced from the points

of emission of the first jets substantially in the first

directions .

According to the invention, there is still further provided a

spray nozzle for fire extinguishing purposes, comprising a body

portion formed with at least two outlets for producing respective

fluid jets into the ambient atmosphere in predetermined

directions which are mutually inclined so that the jets impinge

with one another in the atmosphere, at least one of the fluid

jets being a jet of liquid extinguishant which is atomised by the

impingement into a spray of drops, the one said outlet being

spaced from the other outlet in the predetermined direction of

the jet from the other outlet.

According to the invention, there is yet further provided a spray

nozzle for fire extinguishing purposes, comprising a body portion formed with a plurality of first outlets for respectively

emitting first fluid jets into the ambient atmosphere, a

plurality of second outlets for respectively emitting second fluid jets into the atmosphere, the first outlets being

positioned to direct each of the first jets parallel to each

other in the same, first, direction and mutually spaced apart and

the second outlets being positioned to direct the second jets in

second directions inclined to the first jets, each second jet

being positioned to intersect with a respective one of the first

jets so as to impinge with it in the atmosphere, at least one of

each pair of intersecting jets being a jet of liquid

extinguishant which is atomised by the impingement into a spray

of drops, the second outlets being spaced from the first outlets in said first direction.

Methods and apparatus according to the invention for discharging

a fire extinguishant in the form of a water spray will now be

described, by way of example only, with reference to the

accompanying diagrammatic drawings in which:

Figure 1 is a diagrammatic cross-section through one spray nozzle embodying the invention,-

Figure 2 is a cross-section through another spray nozzle

embodying the invention,- and

Figure 3 is a cross-section through part of a further spray

nozzle embodying the invention.

The water spray nozzle shown in Figure 1 comprises (in this

example) a generally cylindrical body 5 having a cylindrical wall

6 and ends 8 and 10. The end 8 is closed off by a wall defining

a frusto-conically shaped portion 12 integral with and surrounded

by a radially extending wall portion 14. The inclined side of

the frusto-conically shaped wall portion 12 defines five (in this

example) equally spaced outlets 16 of which two are shown. The radial .end wall portion 14 also defines five (in this example)

equally spaced through outlets 18 and, again, two are shown.

In addition, the nozzle includes an insert part 20. This

comprises a cylindrical wall 22 having an end wall 24

incorporating a through bore 26. On the opposite side of the

wall 24, the insert has a further cylindrical wall 28 having an

open end 30.

A radial shoulder 32 integral with and extending annularly around

the wall 22 incorporates through bores 34; two of these are shown

in the Figure, but there may be more than two, spaced around the shoulder 32.

The shoulder 32 supports an outer cylindrical wall 36 defining

an annular space 38 extending around the opening 30.

The insert 20 is securely mounted within the cylindrical body 5

by means of a screw thread 46. The distal end of the wall 22 of

the insert incorporates an O-ring 48 which seals against the

inner face of the radial end wall 8 of the main body 5.

In this way, the main body 5 and the insert 20 together define

a central chamber 50 which is in communication with the outlets

16 and an annular chamber 52 in communication with the outlets

18.

The lower portion (as viewed in Figure 1) of the cylindrical wall

6 is reduced in thickness and internally threaded at 54.

Each outlet 16 lies in the same radial plane (with respect to the

longitudinal axis of the nozzle) as a respective one of the outlets 18.

In use, the nozzle is attached, by means of the internal thread 54, to a water supply pipe through which water is supplied at a pressure within the range 5 - 20 bar g and possibly up to 40 bar g. The water passes into the central chamber 50 through the through bore 26 and into the annular chamber 52 through the bores 34. Thence, the water exits in jets through the outlets 16 and 18. The water supply to all the outlets .16,18 comes from a common source. Because the outlets 16 are inclined with respect to the outlets 18, and the outlets 16 and 18 are aligned with each other (all on same radius from axis) , the water jets from the outlets 16 impinge on those from the outlets 18, this impingement taking place close to the end wall 8 of the nozzle. As the emerging water jets impinge on one another, some or most of their kinetic energy is transferred to produce mutual shearing of the water, thus transforming the water jets into a rarified spray of fine drops. The drops, having acquired sufficient momentum from the remaining kinetic energy of the emerging jets, form a directional spray, the throw of which is determined by the spray angle and water throughput. Air is entrained from the ambient atmosphere into the spray and this inhibits coalescence of the drops downstream of the nozzle. The spray of fine water drops thus produced is found to provide very effective fire extinguishment with the use of little water (as compared with deluge or sprinkler systems) .

The characteristics of the water spray are affected by the relative angles of the impinging water jets and the positions at

which they impinge on each other relative to the end wall 8 of

the nozzle, and by the velocity and size of the emerging water

jets. The average drop size may be between 80 and 300 micrometres with 99% of the drops measured on a volume basis

being less than 1000 micrometres. The water spray

characteristics are also affected by the amount of water allowed

to pass through each set of outlets 16,18; this would be

determined by the sizes of the through bores 26 and 34. The

outlets 16,18 are preferably about 1.0mm or less and desirably

below about 3mm. All these various parameters can be adjusted

to provide a water spray suited to a particular type of fire to

be extinguished. Water pressure over the broad pressure range

referred to above (5-40 bar g) is found to produce consistent spray quality within the above definition. Fire types ^' A and B

can be extinguished. The amount of water used to extinguish a

given fire is small. For example, less than 1 litre of water can

extinguish a 1 MWth gasoline fuel fire.

The momentum of the inner jets (the jets from the outlets 16)

relative to that of the outer jets (from the outlets 18)

determines the extent of liquid atomisation (the fineness or

coarseness of the spray) . The relative momentums also partly

determine the inclusive spray angle of the spray.

It will be noted that a significant feature of the nozzle is that

atomisation of the water takes place externally of the nozzle

body rather than inside the body.

The removable inner body 20 is advantageous from a manufacturing

and constructional point of view. In addition, because the inner

body 20 is removable, clearance of blockages and the like, and

general cleaning, is facilitated. The inner body can include

a fitter (not shown) to reduce the likelihood of blockages.

However, it will be understood that many other constructional

arrangements are possible which have the effect of producing jets

impinging on each other close to the outside of the nozzle to

produce the required water spray. The sets of outlets 16,18

producing the impinging sets of jets can be arranged in any

suitable way. They need not be arranged on respective circles

as described above. Instead, for example, they, or at least one

set, could be arranged on an ellipse or in any other way, such

as along a straight or curved line.

Figure 2 shows another form of nozzle. Again, this is in two

parts .

The outer body comprises a cylindrical wall 60 having an end wall 62 with a frusto-conical integral portion 64 similar to the

portion 12 of the nozzle of Figure 1. The inclined side of the

frusto-conically shaped wall portion 64 defines five (in this

example) equally spaced outlets 16 of which two are shown. The

radial end wall portion 66 also defines five (in this example) equally spaced through outlets 18 and, again, two are shown. The

outlets 16 and 18 are arranged in the same way as the outlets 16

and 18 of the nozzle of Figure 1.

The inner body 68 of the nozzle of Figure 2 is of simpler

construction than the inner body 20 of the nozzle of Figure l.

It comprises a generally cylindrical wall 70 which is externally

threaded to engage an internal thread 72 formed at the lower end

of the cylindrical wall 60 of the outer body. At its upper end

(as viewed in Figure 2) the inner body 68 included an O-ring 71

which makes a gas and water-tight seal against the inner face of

the end wall 66.

In this way, the inner and outer bodies 68 and 60 define a central chamber 74 in communication with the outlets 16 and an

annular chamber 76 in communication with the outlets 18.

Chamber 74 is connected to a connection port 78.

Chamber 76 is connected to a connection port 80 which is formed

to extend radially through the wall 60 of the outer part 5 and

thence through a bore 82.

Port 78 is internally threaded at 84 to enable it to be connected

to a fluid supply pipe. Port 80 is internally threaded at 86 to

enable it to be connected to a second fluid supply pipe.

In use, a suitable gas, such as air or nitrogen, is supplied

through the fluid supply pipe connected to port 78 and exits

under pressure in jets through outlets 16. Simultaneously, water

is supplied through port 80 from a separate pipe connected to the

support, and exits in water jets through outlets 18. Because the

exiting water jets are angled to the exiting air jets and aligned

with them, impingement takes place, again resulting in the

transfer of kinetic energy and producing shearing of the water

jets so as to convert the water into a rarified spray of fine

drops which are carried forward by the remaining kinetic energy

of the emerging jets. The water drop size produced is of the

same order as for the nozzle of Figu i 1, or less. Again, the

various parameters of the emerging jets can be controlled by

appropriate adjustment of the applied pressures and by the mutual

angle of impingement of the air and water jets and the size of

the jets so as to produce the desired water spray characteristics

(drop size distribution, spray angle, throw of spray and type of

spray e.g. with a void within it) . The average drop size

produced is usually slightly smaller than the one described above

for the Figure 1 embodiment. The applied water pressure may lie

within a range of say, 4 to 12 bar g while the applied gas

pressure may be 4 bar g or less, again producing a consistent

spray quality.

As with the nozzle of Figure 1, no mixing or jet impingement

takes place inside the nozzle. Pressure and flow variations of

one fluid therefore have no effect on the pressure-flow

characteristics of the other. In addition, because the air and

water are kept separate until their respective jets impinge

outside the nozzle, there is no need to take any precaution to

prevent the water supply from entering the air supply.

Again, the removable inner body 68 enables easier manufacture and

can be readily removed for cleaning and unblocking. Again,

though, many modifications can be made to the construction. The

inner body may again include a filter (not shown) to reduce

blockages .

Instead of supplying air or gas to the port 78 and water to the

port 80, these may be reversed: that is, the gas can be supplied

to port 80 and the water to port 78. Alternatively, water can

be supplied both to port 78 and to port 8 (at the same order of

pressure as in the Figure 1 embodiment) .

Figure 3 shows part of a modified form of the nozzle of Figure

1. Items in Figure 3 which correspond to those in Figure 1 are

similarly referenced.

Figure 3 shows only the body 5 of the nozzle. The insert part

generally corresponds to the insert part 20 of Figure 1.

In the nozzle of Figure 3, it will be noted that the outlets 18

differ from the outlets 18 in Figure 1 in that the outlets 18 in

Figure 3 diverse slightly outwardly instead of being parallel.

In addition, the outlets 16 are perpendicular to the axis through

the body. The frusto-conically shaped portion 12 is shaped

slightly differently in Figure 3 as compared with Figure 1. The

operation is generally the same as for the Figure 1 embodiment.

It will also be noted that the end 8 of the nozzle in Figure 3

is not flat but slightly inclined. However, in a modification,

it can be flat.

The nozzle of Figure 3 is provided with a groove 52 which retains

a cap (not shown) covering the jet outlets and protecting them

against debris. The cap is blown off when the nozzle is

activated.

The water supply to the nozzles of Figures 1,2 and 3 can be from

a mains supply or a stand-alone supply pressurised by means of

a pump or by gas for example or even by a gas generating device,

pyrotechnically operated. Any suitable control system may be

used for activating the sprays.

Instead of water, any other suitable liquid extinguishant can be

used which may advantageously, though not necessarily, be water-

based. For the nozzle of Figure 2, any other suitable non¬

flammable gas can be used.

It is important for production of a satisfactory spray that

impingement of the colliding jets takes place sufficiently close

to the exit points of the jets from the nozzle that the jets have not lost their coherence at the point of impingement. The design

of the nozzles is advantageous in this respect. More specifically, each nozzle has a generally flat end in which are

positioned one set of jet outlets and a projection outwardly of

this end in which projection are formed the second set of jet

outlets which produce jets directed generally transversely to the

first set of jets. This arrangement has two advantages:-

(a) it is a way of achieving the desirable very short

impact distance,- and

(b) the transverse, almost perpendicular, arrangement of

the impacting jets is advantageous for the production of an

effective water mist.

As stated above, the points of intersection of the impinging jets

should be as close as reasonably possible to the jet outlets.

The distance from the jet outlets to the points of intersection

should advantageously be about 5mm and preferably less than about 30mm.

In practice, a plurality of the nozzles would be used, rather

than a single nozzle. The nozzles would be arranged in an assembly so as to act together to produce an effective total water spray.