GB2151158A - Atomising nozzle - Google Patents

Abstract

An atomising nozzle for producing a fog or mist. The nozzle comprises a body 1 defining a passageway 2 of convergent-divergent or venturi shape through which a stream of compressed air, steam or gas is passed. Water or other liquid to be atomised is introduced by ducts 7,8 into the passageway 2 and is drawn therethrough by the gas stream and impinges on a cavity resonator 13 spaced downstream from the outlet of the passageway. The resonator 13 is mounted on an adjustable support 14 extending forwardly from the nozzle body 1 at a distance X spaced from the outlet of the passageway 2 substantially coaxially thereof. Adjustment of the support 14 will move the resonator 13 along the longitudinal axis of the passageway to vary the axial distance X of the resonator 13 from the outlet of the passageway 2 and thereby the droplet size in the fog or mist. <IMAGE>

Description

SPECIFICATION Atomising nozzle The invention relates to an atomising nozzle of the kind comprising a passageway of convergentdivergent or venturi shape through which a stream of compressed air, steam or gas (hereinafter referred to generally as "gas") is arranged to be passed; means for introducing into the passageway a liquid to be atomised by the nozzle and a resonator defining a cavity spaced downstream of the divergent outlet of the passageway, the cavity being open at the end thereof facing the outlet of the passageway and closed at its other end, whereby the gas stream will impinge on said closed end of the cavity and be arrested by the resonator.

In such an atomising nozzle, the gas stream is accelerated by the passageway and it is believed that the accelerated gas stream with liquid dispersed therein has a standing sonic pressurewave created therein by the impingement and arresting of the stream by the resonator and that the pressure-wave shatters the liquid into minute droplets. The droplets are so minute that they leave the vicinity of the nozzle outlet and the resonator in a fine mist or fog.

Where the liquid is water and the gas is compressed air, the resulting mistorfog is particularly applicable for producing a humid atmosphere for irrigation, particularly, but not exclusively, in a greenhouse.

Atomising nozzles of the foregoing kind known hitherto have each included a resonator cavity which is fixed in position relatively to the divergent outlet of the nozzle. Usually the resonator cavity is supported on wire support legs extending from the body of the nozzle and so are not capable of axial adjustment towards or away from the divergent outlet.

According to the present invention, an atomising nozzle of the foregoing kind has adjustable support means extending forwardly from the nozzle body and supporting the resonator at a distance spaced from the outlet of the passageway substantially coaxially thereof, whereby adjustment of the support means will move the resonator along the longitudinal axis of the passageway thereby to vary the axial distance of the resonator from the outlet of the passageway.

It has been found that the axial distance of the resonator from the outlet of the passageway affects the fineness of the droplets of water or other liquid used assuming that the pressure of the compressed air or gas is maintained constant. At constant pressure, as the resonator is moved nearer to the outlet of the passageway, the water or liquid droplets become finer and conversely, as the resonator is moved away from the outlet of the passageway, the water or liquid droplets become coarser. Alternatively, with the resonator fixed with respect to the outlet of the passageway it has been found that the fineness of the fog can be kept substantially constant by reducing the pressure.

Thus a desired fog can be produced by adjusting the axial position of the resonator or by controlling the compressed air or gas pressure or by a combination of both controls.

A preferred way in which the resonator is mounted is by supporting it on the end of a limb of a J-shaped rod of which the end of the limb not carrying the resonator is screw-threaded and is screwed into a tapped hole in the downstream end face of the nozzle body, one complete revolution of the rod in the tapped hole determining a permitted increment of axial distance from the outlet of the passageway to which the resonator can be set. The pitch of the screw-thread thereby determines the size of these increments. A lock-nut may be provided to lock the J-shaped rod in a position to which it has been set. The setting of the J-shaped rod and the pressure of the compressed air or gas applied to the nozzle determine the fineness of the fog. Thus in a greenhouse provided with one or more of the nozzles a controlled simulated fog condition can be produced.

By way of example, an atomising nozzle in accordance with the invention is now described with reference to the accompanying drawing which is a half axial section through and half elevation of the nozzle.

The nozzle comprises a body 1 having an axial throughway in which is fitted an insert 2 having a venturi-shape passageway therethrough comprising a convergent inlet 2A, a cylindrical throat 2B and a divergent outlet 2C. The insert 2 is held against an internal shoulder 4 at the outlet end of the throughway in the body 1 by a retaining screw 3 which is secured in the throughway in the body 1 by screw-threaded portions of the body and the screw shown at 5. The retaining screw 3 has a throughway therein which communicates at its inner end with the convergent inlet 2A of the passageway in the insert 2 and at its outer end is formed to receive a pipe union for the supply of compressed air at 6.The inner end of the retaining screw 3 and the outer periphery of the insert 2 define with the throughway in the body 1 an annular space 7 which communicates through a tapped hole 18 in the body 1 for receiving a pipe for the supply of water to the space 7. The space 7 communicates through a plurality of holes, for example four radial holes 8, in the insert 2 with the upstream end of the divergent outlet 2C of the passageway. As compressed air travels through the passageway in the insert 2, it is accelerated by the convergentdivergent shape thereof and water is drawn in through the holes 8 from the space 7. The inner end of the screw 3 abuts against an O-ring seal 9 which abuts against the adjacent end of the insert 2. An annular seal 10 is positioned between a shoulder 11 on the screw 3 and an adjacent end face of the body 1.The screw 3 has a spanner-locating head 12 which is turned by a spanner until the seal 10 has been gripped between the shoulder 11 and the body 1.

This wiil have advanced the screw 3 within the body 1 to deform the O-ring seal 9 and thus to hold the insert 2 against the shoulder 4 and to effect a seal between the screw 3 and the insert 2.

The nozzle also comprises a resonator cavity 13 which is mounted coaxially downstream of the divergent outlet 2C at an initial distance 'X' therefrom. The resonator cavity 13 is closed except for the end facing the outlet 2C and as in known nozzles of a similar kind, the stream of compressed air with the entrained water will impinge on the closed end wall of the resonator cavity 13 and a standing sonic or possibly super-sonic pressure wave will be produced which will shatter the water droplets into a fine fog.

As aforesaid the ability to control the fog by adjusting the distance X is of great importance and so in accordance with the invention, the resonator cavity 13 is formed in the end of the shorter limb of a J-shaped rod 14. The longer limb of the rod 14 is screw-threaded at 15 and is screwed into a tapped hole 16 in the downstream end of the body 1 and parallel with the axis of the passageway in the insert 2. One complete turn of the rod 14 aboutthe longitudinal axis of the longer limb from the illustrated position will bring the shorter limb back into the position in which it is co-axial with the passageway in the insert 2, but with the resonator cavity 13 at a distance greater or smaller by the pitch of the screw-thread at 15 than the initial distance X.

By selecting a fine pitch for the screw-thread at 15 it is possible to provide for fine adjustment of the axial increments or decrements of X. The screw-threaded portion 15 of the longer limb of the J-shaped rod 14 carries a lock-nut 17 by which the rod 14 and thus the resonator cavity 13 can be locked in a set position.

By means of the atomising nozzle illustrated a simulated fog condition can be produced by adjustment of the axial position of the resonator cavity 13 provided in the end of the shorter limb of the J-shaped rod 14. The pressure of the compressed air supply applied at the pipe union 6 can also be varied to produce a desired simulated fog condition.

The water supply can be provided via a valve by which excess water can be "sucked back" or spilled back to the supply.

Although the atomising nozzle provided by this invention is primarily intended for use with water and compressed air another liquid instead of water and steam of a gas instead of compressed air may be employed.

Claims (4)

1. An atomising nozzle of the kind comprising a body defining a passageway of convergentdivergent or venturi shape through which a stream of compressed air, steam or gas (herein referred to as "gas") is arranged to be passed; means for introducing into the passageway a liquid to be atomised by the nozzle and a resonator defining a cavity spaced downstream from the outlet of the passageway, the cavity being open at the end thereof facing the outlet of the passageway and closed at its other end, whereby the gas stream will impinge on said closed end of the cavity and be arrested by the resonator, the nozzle including adjustable support means for the resonator extending forwardly from the nozzle body and supporting the resonator at a distance spaced from the outlet of the passageway substantially coaxially thereof, whereby adjustment of the support means will move the resonator along the longitudinal axis of the passageway thereby to vary the axial distance of the resonator from the outlet of the passageway.

2. A nozzle as claimed in Claim 1 in which the support means comprises a J-shaped rod having one limb supporting the resonator and having its other limb screw-threaded and in engagement with a tapped hole in the downstream end face of the nozzle body, one complete revolution of the said other limb of the rod in the tapped hole determining a permitted increment of axial distance from the outlet of the passageway to which the resonator can be set, depending on the pitch of the screw-thread provided on said other limb and in the tapped hole.

3. A nozzle as claimed in Claim 2 including on the screw-thread of said other limb a lock-nut engageable with the nozzle body to lock the rod in a position to which it has been set.

4. An atomising nozzle constructed and arranged substantially as described herein and shown in the accompanying drawing.