GB2293322A

GB2293322A - Extinguishing fires

Info

Publication number: GB2293322A
Application number: GB9509601A
Authority: GB
Inventors: Panos Papavergos
Original assignee: Kidde Fire Protection Ltd
Current assignee: Kidde Fire Protection Ltd
Priority date: 1994-09-20
Filing date: 1995-05-11
Publication date: 1996-03-27
Also published as: GB9419053D0; GB9509601D0; GB2293762A

Abstract

Fires are extinguished by producing at least two jets of fluid which impinge on each other in the atmosphere. At least one of these jets is a fire extinguishing liquid which atomises into a spray of drops on impingement. Jets may be both liquid or one may be a non-flammable gas. The point of emission of one jet into the atmosphere is spaced from the point of emission of the other jet substantially in the predetermined direction of the other jet. A nozzle (5) for fire extinguishing has a body with outlets (16 and 18) for jets of extinguishing liquid and fluid which impinge causing the liquid to atomise and form a spray of fine droplets. <IMAGE>

Description

FIRE EXTINGUISHANT DISCHARGE METHOD AND APPARATUS 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; and 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 annually 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. 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 l.Omm or less and desirably below about 2mm. 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 (5-20 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 of 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 1.

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 Figure 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 waterbased. For the nozzle of Figure 2, any other suitable nonflammable 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 20mm.

Claims

1. 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.

2. A method according to claim 1, in which the other jet is a jet of the same liquid.

3. A method according to claim 1, in which the other jet is a gas jet.

4. A method according to claim 3, in which the gas is air, nitrogen or other non-flammable gas.

5. 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.

6. A method according to claim 5, in which the second predetermined directions are each intersectingly inclined with a respective one of the first directions.

7. A method according to claim 6, in which the first jets are spaced apart along a first line lying in a predetermined first plane and the second jets are spaced apart along a second line symmetrically positioned with respect to the first line and lying in a second plane parallel to the first plane.

8. A method according to claim 7, in which the first directions are directions parallel to a predetermined line which is perpendicular to the said planes and the second directions are included with respect to the said predetermined line.

9. A method according to claim 7, in which the first directions are inclined slightly away from each other and from a predetermined line which is perpendicular to the said planes and the second directions are parallel to the said planes.

10. A method according to any one of claims 7 to 9, in which the first and second lines are respective circles.

11. A method according to claim 8 or 9, in which the first and second lines are respective circles whose centres lie on the said predetermined line.

12. A method according to any one of claims 7 to 9, in which the first and second lines are ellipses.

13. A method according to any one of claims 5 to 12, in which at least the second jets are the jets of the liquid extinguishant.

14. A method according to any one of claims 5 to 12, in which all the jets are jets of a liquid extinguishant.

15. A method according to any one of claims 5 to 14, in which the first jets are gas jets.

16. A method according to claim 15, in which the gas is air, nitrogen or another non-flammable gas.

17. A method according to any preceding claim, in which the extinguishing liquid is water or a water-based substance.

18. 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.

19. A nozzle according to claim 15, in which the said other outlet is positioned in an end of the nozzle, and the said one outlet is positioned in a conical protrusion protruding from the said end.

20. A nozzle according to claim 19, in which the predetermined direction of the jet from the said other outlet is perpendicular to the end of the nozzle.

21. A nozzle according to claim 19 in which the predetermined direction of the jet from the said one outlet is perpendicular to the axi of the conical protrusion and the predetermined direction of the jet from the said other outlet is inclined to that axis.

22. A nozzle according to any one of claims 16 to 21, in which the other jet is a jet of the same liquid.

23. A nozzle according to any one of claims 16 to 21, in which the other jet is a gas jet.

24. A nozzle according to claim 23, in which the gas is air, nitrogen or other non-flammable gas.

25. 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.

26. A nozzle according to claim 25, in which the first outlets are spaced apart along a first line lying in a predetermined first plane and the second outlets are spaced apart along a second line symmetrically positioned with respect to the first line and lying in a second plane parallel to the first plane.

27. A nozzle according to claim 26, in which the first directions are directions parallel to a predetermined line which is perpendicular to the said planes and the second directions are inclined with respect to the said predetermined line.

28. A nozzle according to claim 26, in which the first directions are inclined slightly away from each other and from a predetermined line which is perpendicular to the said planes and the second directions are parallel to the said planes.

29. A nozzle according to any one of claims 26 to 28, in which the first and second lines are respective circles.

30. A nozzle according to claim 27 or 28, in which the first and second lines are respective circles whose centres lie on the said predetermined line.

31. A nozzle according to any one of claims 26 to 28, in which the first and second lines are ellipses.

32. A nozzle according to claim 30, in which the first circle lies in an end of the nozzle, and in which the second circle extends around a protrusion positioned within the first circle and protruding from that end.

33. A nozzle according to any one of claims 25 to 32, in which the body portion comprises wall means defining two concentric chambers isolated from each other, one chamber being in communication with the first outlets and the other chamber being in communication with the second outlets, and supply means respectively connected to the two chambers for supplying fluid thereto.

34. A nozzle according to any one of claims 26 to 33, in which at least the second jets are the jets of the liquid extinguishant.

35. A nozzle according to any one of claims 26 to 33, in which all the jets are jets of a liquid extinguishant.

36. A nozzle according to any one of claims 26 to 35, in which the applied pressure of the liquid is between about 5 and 25 bar g.

37. A nozzle according to any one of claims 26 to 36, in which the jets which are not liquid jets are gas jets.

38. A nozzle according to claim 37, in which the applied pressure of the gas is 4 bar g or less.

39. A nozzle according to claim 37 or 38, in which the gas is air, nitrogen or other non-flammable gas.

40. A nozzle according to any one of claims 26 to 39, in which each outlet is between about 1.0 and 2.Omm in diameter.

41. A nozzle according to any one of claims 26 to 40, in which each point of jet intersection is less than a distance of about 2Omm from the corresponding outlets.

42. A nozzle according to claim 41, in which the said distance is about Smm.

43. A nozzle according to any one of claims 26 to 42, in which the drops in the said spray have mean diameters in the range 80 to 300 micrometres.

44. A nozzle according to any one of claims 18 to 43, in which the extinguishing liquid is water or a water-based liquid.

45. A method of fire extinguishing, substantially as described with reference to Figure 1 of the accompanying drawings.

46. A method of fire extinguishing, substantially as described with reference to Figure 2 of the accompanying drawings.

47. A method of fire extinguishing, substantially as described with reference to Figure 3 of the accompanying drawings.

48. A spray nozzle for fire extinguishing purposes, substantially as described with reference to Figure 1 of the accompanying drawings.

49. A spray nozzle for fire extinguishing purposes, substantially as described with reference to Figure 2 of the accompanying drawings.

50. A spray nozzle for fire extinguishing purposes, substantially as described with reference to Figure 3 of the accompanying drawings.