GB2102699A - Nozzle - Google Patents

Abstract

A nozzle comprises a passageway through which liquid to be projected by the nozzle is caused to pass and at least one generally planar blade 12 located within the passageway which is rotatable to adjust the inclination of the plane of the blade relative to the direction of the liquid stream within the passageway, whereby the shape of the jet projected from the nozzle may be controlled. As the angle of inclination is increased the degree of swirl and of divergence of the jet are increased. The nozzle is used for fire fighting. <IMAGE>

Description

SPECIFICATION Special purpose nozzle The present invention relates to a nozzle, and in particular to a nozzle which is capable of providing a high quality long range straight jet or a coarse or a fine spray.

Considerable work has been done on waterway and nozzle design in order to achieve long range jets for fire fighting purposes. This is of particular importance in the North Sea where, in the event of a fire on a platform, fire fighting vessels need to stand off at a safe distance and yet be able to reach the platform with water jets. Swirl has to be eliminated as far as possible from the water stream to achieve maximum range and minimum fall out from the jet so as to put the maximum amount of water on target. This is achieved by a combination of honeycombs or other stream straighteners and slow convergencies upstream of the nozzle exit.

Fog nozzles are available that can be adjusted to provide a straight stream for maximum throw, a coarse spray, or a wide angle water fog. Unfortunately the straight jets produced by this type of nozzle have nowhere near the range or coherence produced by the specially designed straight stream nozzles described above.

Fog nozzles for use with monitors (water cannon) generally consist of a mushroom device set in an annulus at the exit of which are specially designed teeth.The straight jet is produced with the mushroom deep in the annulus, the wide fog is produced with the mushroom adjacent to the external teeth and the coarse spray is produced with the mushroom in an intermediate position.

Severe disturbance to the water stream cannot be avoided in this type of nozzle which accounts for its poor performance in the straight steam position. However, a coarse water spray is frequently required to produce generalized cooling of a structure or to prevent structural damage on closer approach of the nozzle to the target.

Water spray from a jet entrains large quantities of air or gas and can be effective in dispersing gas clouds in such a way as to reduce the concentration of gas in air to below the lower limit of flammability. In general terms a coarse spray is best for moving the greatest quantity of gas.

In many circumstances it is desirable to be able to project foam rather than water. The foam branchpipes currently on the market produce foam at a fixed expansion ratio. No single branchpipe is available that produces a low expansion foam that can be thrown relatively long ranges for use in for example oil tank fires, and a higher expanded foam with, for example, longer drainage times more suitable for aircraft fires. Lower aspirated foams are becoming of special interest in the application of AFFF (aqueous film forming foam).

It is an object of the present invention to provide a nozzle which can produce either a high quality straight jet or a water spray or fog for wide area cooling.

According to the present invention there is provided a nozzle comprising a passageway through which liquid to be projected by the nozzle is caused to pass and movable means located within the passageway for adjusting the shape of the jet of liquid projected from the nozzle, characterised in that the movable means comprises at least one generally planar blade and means for adjusting the inclination of the plane of the blade relative to the direction of the liquid stream within the passageway.

Preferably a number of blades, for example six, are spaced apart around the inside of the passageway. Each blade may be mounted on a pivot shaft the axis of which is radial relative to the passageway, each of the pivot shafts lying on a common plane at right angles to the passage axis.

Arranging the blades such that their planes are parallel to the direction of the liquid stream produces a high quality long range jet.

Progressive movement of the blades from this orientation increasingly changes the characteristics of the flow of the liquid by inducing angular momentum into the stream. This varies the spread and break up of the jet at the exit nozzle in a controlled manner producing varying degrees of water spray. Thus a single nozzle can produce a jet of any desired characteristic, without greatly altering the liquid pressure or rate of flow.

The orientation of the blades may be adjusted by any suitable means. For example, where each blade is mounted on a pivot shaft extending radially outwards through the passageway wall, each pivot shaft can have rigidly attached to it a quadrant carrying a bevel gear meshing with a continuous bevel gear mounted on a sleeve that is rotatable about the passageway body. The sleeve can then be turned by a gear wheel and worm to control the blade positions.

Since the nozzle provides a means of varying air entrainment it also provides the means of varying the degree of aspiration and expansion ratio of a foam tube. This will enable different qualities of foam to be produced from the same branchpipe. Its high straight jet performance would be particularly suitable for non-aspirated foam applications, for example AFFF, and at the same time also be capable of producing more expanded longer drainage time foams suitable for aircraft applications.

The nozzle may be non-ducted or ducted to suit the particular application.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 schematically illustrates a conventional branchpipe and nozzle designed to produce a high quality coherent long range jet; Figure 2 schematically illustrates a conventional nozzle in which the jet shape can be adjusted; and Figure 3 is a perspective partly cut away view of the embodiment of the present invention.

The nozzle and branchpipe of Fig. 1 comprises a rigid body 1 in which two honeycomb structures 2 and 3 are provided. The honeycombs reduce swirling in the water stream through the body towards outlet 4 with the result that a highly coherent and hence long range jet is produced. There is however no facility for converting the jet to a coarse or fine spray.

The nozzle of Fig. 2 comprises a rigid body 5 having an enlarged head 6 the edge of which supports deflector teeth 7. A deflector 8 is mounted on a shaft 9 which extends along the axis of the body 5. Means not shown enable the movement of the deflector from the position shown towards the mouth of the head 6. In the position shown, a straight stream is produced, in an intermediate position (not shown) a coarse spray results, and when the deflector is level with the mouth of the head 6 a wide angle fog is produced.

In the position shown in Fig. 2, a straight jet is produced but it is of indifferent quality because the presence of the deflector within the nozzle induces severe disturbances within the flow. Thus the range of the jet is appreciably less than with the nozzle of Fig. 1.

Given the characteristics outlined with reference to Figs. 1 and 2, it will be appreciated that normally both types of nozzle are frequently required for each fire fighting installation.

Fig. 3 shows an embodiment of the present invention which provides the advantages of both of the conventional devices described above. As shown in Fig. 3, the body 10 of the nozzle is cylindrical and in this case is flanged at each end for attachment to the monitor and nozzle outlet. At the upstream end it contains a honeycomb 11 which acts as a flow straightener. Blades 12, in this case numbering six, are profiled so as to have a rounded leading edge and a tapered trailing edge and tip. In the straight stream (long range jet) position the blades are accurately aligned axially at zero angle of incidence to the flow.

In the example shown a mechanism is provided that will twist the blades 1 2 in an anticlockwise direction when viewed from the centre of the stream. At positive angle of incidence, angular momentum is induced in the water stream and an anti-clockwise swirl is produced when looking into the nozzle. As the angle of incidence is increased the momentum transferred to angular momentum increases, producing an increasingly divergent jet after the water leaves the nozzle.

Each blade 1 2 is linked via a shaft 1 3 to a quadrant 14 carrying a bevel gear 1 5 enmeshed with a continuous bevel gear 1 6 on a sleeve 1 7. The sleeve 1 7 can rotate about the body 10 and can be turned via a gear wheel 1 8 and worm 1 9. The amount the sleeve can rotate is limited by an adjustable stop 20.

Accurate alignment of the blades at the zero angle of incidence is vital to the production of a good straight jet and there is provision for the adjustment of individual blades at 21.

In the example described a specific number of turns of the worm shaft 1 9 results in a specific angle of incidence for each blade 12.

Appropriate sealing arrangements are made for each shaft 1 3 to prevent leakage of water from the nozzle.

Claims (8)

1. A nozzle comprising a passageway through which liquid to be projected by the nozzle is caused to pass and movable means located within the passageway for adjusting the shape of the jet of liquid projected from the nozzle, characterised in that the movable means comprises at least one generally planar blade and means for adjusting the inclination of the plane of the blade relative to the direction of the liquid stream within the passageway.

2. A nozzle according to claim 1, comprising a plurality of blades spaced apart around the inside of the passageway.

3. A nozzle according to claim 2, wherein each blade is mounted on a pivot the axis of which is radial relative to the passageway, each of the pivots lying on a common plane at right angles to the passage axis.

4. A nozzle according to any preceding claim, wherein the or each blade comprises a rounded leading edge and a tapered trailing edge.

5. A nozzle according to any preceding claim, wherein each blade is mounted on a pivot shaft that extends radially outwards through the passageway wall, each pivot shaft having rigidly attached to it a quadrant carrying a bevel gear meshing with a continuous bevel gear mounted on a sleeve that is rotatable about the passageway body.

6. A nozzle substantially as hereinbefore described with reference to Fig. 3 of the accompanying drawings.

7. A method for using the nozzle according to any preceding claim to generate foam, wherein a foaming compound is injected into the liquid stream upstream of the nozzle, and the inclination of the blade or blades is adjusted to control the entrainment of air into the jet of liquid projected from the nozzle.

8. A method according to claim 7, wherein a duct is positioned around the outlet of the nozzle.