Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
  • B05B1/02—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape
  • B05B1/08—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape of pulsating nature, e.g. delivering liquid in successive separate quantities ; Fluidic oscillators
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0692—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by a fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15C—FLUID-CIRCUIT ELEMENTS PREDOMINANTLY USED FOR COMPUTING OR CONTROL PURPOSES
  • F15C1/00—Circuit elements having no moving parts
  • F15C1/22—Oscillators

Definitions

• the invention relates to a method of and apparatus for the production of a liquid spray.
• controlled drop size makes for uniform spray dispersion and coating.
• more regular drop size maximises the amount of liquid (be it insecticide, fungicide etc) reaching the targetted plants, whereas with an uncontrolled spray a large proportion of the liquid is dispersed by the wind through the drops being too small, or falls directly to the ground if the drops are too large.
• fuel injectors a more uniform spray offers the advantages of better, cleaner and more predictable combustion.
• controlled drop size reduces the amount of water needed to put out a fire, by increasing the heat-absorbtion performance of the spray.
• reducing the spread of drop sizes in a spray offers many benefits through an improved control of the spray properties.
• a few demanding applications such as ink jet printing require a very narrow spread of droplet sizes, termed "mono-dispersity".
• the emergent jet of liquid breaks up into droplets either as a result of the formation of capillary waves, or due to shear stresses resulting from aerodynamic drag.
• the droplet diameter is directly related to the wave length.
• many different wave lengths are present, as is the case in conventional nozzles, many different droplet sizes are produced.
• 90/. of the droplets lie in a region one decade wide say 10 to 100 microns.
• the capillary waves are initiated by liquid borne noise generated by the liquid flow eg. by turbulence, vortex-shedding etc.
• this noise is produced over a wide range of random frequencies which causes the initiation of capillary waves of many different lengths.
• Those wave lengths close to an optimum value grow fastest with the result that the spread of droplet diameters is centred around the diameter corresponding to the optimum wave length.
• Drag induced break up is a higher-energy process than the capillary wave mode, and also produces a wide range of drop sizes if uncontrolled.
• the breakup is drag-induced, the process is characterised by the Weber number where d is the jet diameter, ⁇ _ the surrounding gas density, V the jet velocity and - the surface tension of the liquid.
• Conventional means of generating a controlled spray include an active element, such as a piezo-electric crystal or an electromechanical transducer, to break up the liquid by imparting energy to the liquid at an appropriate frequency.
• an active element such as a piezo-electric crystal or an electromechanical transducer
• a high intensity single frequency acoustic signal is introduced to the liquid immediately upstream of the nozzle.
• the frequency of this signal is chosen to coincide with the optimum wavelength and the intensity is much greater than that of any other sources of noise in the flow. This produces mono-disperse droplets, although the piezo-electric transducer and electronics used to produce the acoustic signal are relatively expensive, and the operating environment is benign.
• Providing and powering signal generation as part of a spray generator leads to complex and expensive apparatus requiring an electrical or other power supply, complicating the employment of such apparatus in environmentally demanding conditions and/or where the provision of energising power thereto is difficult or impracticable, for example to the nozzle of a fire fighting hose or in agricultural spraying apparatus where the spray generator may be mounted at the end of a spray boom remote from the carrying vehicle.
• a form of acoustic spray generator which operates in a hostile environment is that used in some fuel burners for industrial and marine boilers.
• these devices either the energy is imparted to the liquid fuel before it exits the nozzle by means of a piezo-electric device as already described, or instead acoustic vibrations of a suitable frequency are provided in an air supply to the burner, and these vibrations impart energy to the liquid jet after it has left the nozzle to promote its break-up into a spray in which the spread of drop sizes is reduced.
• both of these devices have the disadvantage that energy must be supplied to the liquid from a external source, either electrically or from the air supply. The latter of course is only feasible if it is in any case required to mix the spray with air, and is not suitable for "airless" systems such as many paint-spraying systems.
• the present invention has as an object the generation of a liquid spray of controlled droplet size which does not require an auxiliary power supply, or other external source of energy.
• the invention provides a method of generating a spray of liquid droplets comprising establishing a flow of the liquid, forming the flowing liquid into a jet, and subjecting the jet of liquid to vibrations of at least one predetermined frequency which promotes the break-up of the jet into droplets, characterised in that the energy for the vibrations is obtained from the liquid.
• the invention provides apparatus for generating a spray of liquid droplets comprising means for receiving a flow of liquid and for forming the liquid into a jet, and means for generating vibrations in the jet using energy obtained from the liquid, the vibrations being of at least one predetermined frequency such as to promote break-up of the jet into droplets.
• the energy may be obtained from the kinetic or pressure energy of the liquid.
• the vibrations preferably are generated by inducing acoustic oscillations in the liquid flow, and (in some embodiments) as or before the liquid is formed into a jet.
• the apparatus may comprise a nozzle for forming the jet and a hydrodynamic oscillator disposed upstream of the nozzle for generating the vibrations.
• the vibrations should be a pure tone matching (ie. at or at least near to) the optimum break-up frequency of the liquid jet.
• tone vibration generator
• the means for generating vibrations may be such as to produce a substantially constant frequency, means being provided for adjusting the flow velocity of the liquid.
• Optimum use of the apparatus may then be assisted by means for varying the flow rate of the liquid so as to match the break-up frequency (which is flow-rate dependent) to that of the tone generator.
• the means for generating vibrations may be such as to produce a predetermined frequency which varies with the flow velocity of the liquid.
• This may have the advantage that the frequency may automatically be at or near the preferred break-up frequency over a range of flow rates, and may thereby produce a substantially constant drop size over a range of flow rates.
• there may be means for example a tuned mechanical device for extracting energy from the liquid flow and for reintroducing it into the liquid to generate the vibrations.
• the means for forming the liquid into a jet may be at least partially defined by the tuned mechanical member, or by structure connected thereto.
• the energy may be at least partially reintroduced in to the liquid via the air or other gas through which the liquid passes after being formed into a jet .
• Figure 1 shows the relationship of natural capillary-wave jet break-up rate, jet diameter and frequency
• FIG. 2 shows very diagrammatically one embodiment of the invention
• FIG. 3 shows, also very diagrammatically another embodiment of the invention
• Figures 4 to 6 show in more detail apparatus of the same type as Figure 3 > Figure 5 being an enlarged view of part of Figure , and Figure 6 being external views of the apparatus shown in section in Figure 4.
• FIGS 7 to 10, 12 and 13 show further devices for use in the invention.
• Figure 11 shows a further embodiment of the invention.
• the capillary-wave mode of break-up of a jet exiting from a nozzle will first be considered in two contexts, the natural disintegration of the jet, and the triggered (frequency-induced) disintegration of the jet.
• the natural break-up of a liquid jet may be analysed by making the following simplifying assumptions: a. the jet is taken to be of cylindrical cross section, diameter d. b. the jet is assumed to disintegrate in a vacuum. That is to say that the influence of the gas surrounding the jet is negligible. c. the flow in the jet is laminar so that the background disturbances in the flow are small and of random spectrum. d. the break-up process is dominated by the exponential growth of axisymmetrical surface disturbances, termed varicose, of wavelength ⁇ . e. the flow is inviscid.
• the jet breaks-up when the amplitude of the disturbance 6 grows to equal the radius of the jet d/2.
• a suitable acoustic wave of frequency is introduced increasing the amplitude ⁇ " n of the disturbance at the nozzle.
• the driving frequency f is tuned to satisfy this relationship, and therefore to trigger the break-up into drops forming at this same frequency.
• the flux leaving the nozzle is: ⁇ d 2 V / 4 n
• the drop size produced by controlled jet break-up is fixed at 1.89 times the jet and nozzle diameter.
• the satellite drop has been produced closely behind the mother drop, its smaller aerodynamic drag in the larger drop wake will allow it to catch up and recombine with the mother drop, thereby producing a monosized stream of recombined droplets.
• the satellite drops can be blown away or removed using their different flight path, so that there remains a stream of monosized mother drops. Both solutions are less than optimum but again the result is superior to an uncontrolled spray.
• a spray with a controlled range of drop sizes may be advantageous.
• the production of small satellite drops may be advantageous to promote good combustion when the engine is cold, and could be achieved whilst maintaining the overall fuel/air ratio by controlling the injector flow rate and the injection period.
• the preferred manner of subjecting the jet to vibrations is by inducing acoustic (pressure) oscillations in the liquid upstream of the jet in a resonant device.
• a resonant device is effectively a hydrodynamic oscillator or whistle, although using liquid as its operating fluid rather than air.
• whistles depend upon positive feed back and can be conveniently divided in three classes based on their feedback mechanisms.
• the whistle can be placed in class I.
• These are mainly aeolian tone generators, such as telegraph wires, where the action of the vortex generated on one side of the generator triggers the shedding of a vortex on the other side.
• the interaction is entirely hydrodynamic, and only acts as a stabiliser of the process so that the sound intensity usually remains low.
• shape of the ' device makes it particularly suitable for use with elongated slot-shaped spray nozzles.
• a wire 1 is disposed transversely across a flow duct terminating in a slot-shaped nozzle 2.
• Vortices 3 are shed alternately from opposite sides of the wire, generating acoustic vibrations in the liquid and promoting break-up thereof when it issues from the nozzle as a flat jet 4.
• the whistle is a class II whistle. Examples are edge tone, ring tone and in particular hole tone whistles.
• a hole tone whistle shown very diagrammatically in Figure 3 two coaxial round holes 5. 5a are provided in axially spaced parallel thin plates, and the whistle sounds when the jet formed at the first hole 5 sheds vortices 7 which impinge on the plate containing the second hole causing acoustic waves to propagate back towards the first hole where they help to trigger the shedding of new vortices.
• the sound feedback causes the vortices produced at hole 5 to be more periodic and in phase with one another, strengthening the generation process and promoting the break up of a jet 8 issuing from a nozzle 6.
• the relationship between the diameter of the nozzle 6 and that of the holes 5. 5a determines the extent to which the drop size is controlled.
• a Class III whistle In a Class III whistle the feedback loop is established either by a reflecting surface or by a resonator. Many reeded wind instruments rely on this principle. A resonant column of working fluid controls the final frequency of the generated tone, and thus a class III whistle generates a constant frequency independent of flow rate. Conversely, class I and II whistles are dominated by the generation mechanism so that their tone frequency is dependent upon the flow velocity.
• the whistle must include or at least be excited by a suitable source of acoustic vibrations.
• any white noise signal should be suitable, if the feedback mechanism is strong enough to control the source and the closed loop amplifying gain high enough.
• Sources of white noise signal in fluid are multiple, such as turbulent flow motion in a shear layer or in a jet, buffeting or separation induced vorticity.
• Readily manufactured whistles include hole tones, edge tones and reed based devices, and are susceptible to limited theoretical analysis using non-dimensional groups.
• the holes 5. 5a each have a diameter dh and are spaced by a distance b.
• the axial length of the holes ie. the plate thickness
• V the flow velocity through them
• This group characterises the stable shedding of vortices by the hole 5. controlled by a weak class I feedback mechanism. This parameter would assume a single value if a single hole was used, and. therefore represents the natural frequency of - li ⁇
• the whistling frequency is a function of the time taken by the disturbance to travel downstream, amplify itself and feed back some of the energy into the source.
• the time taken for it to travel will always be a function of the flow speed V, the distance to travel b, and the speed of sound in the medium c.
• the time of travel can be modelled precisely by assuming that the disturbance is a vortex travelling at a known fraction of the jet velocity, or that it is a jet deformation which travels at the jet velocity.
• the feedback is assumed to be of class II so that upstream propagation is done at the speed of sound c. For low Mach number flow (V/c ⁇ 0.2) , the feedback time can be regarded as negligible, and the Strouhal number becomes a true represention of the flow feedback mechanism.
• the vortices that are produced at the sharp inlet edge will have time to roll up inside the tube, and provide a class I feedback when shed.
• This mechanism is characterised by the plate Strouhal number but is unlikely to be dominant in a hole tone whistle due to the low t/d ratio.
• the whistle may be expected to deliver large sound intensities.
• the strong class II feedback in the cavity will dominate the weak class I feedback of the vortex shedding, modifying the shedding frequency to suit.
• a less energetic shedding is expected so that the whistle sound intensity would be lower. Moving the feedback frequency further away from the hole Strouhal frequency will eventually leads to a different wave mode (ie. a change in the value of n) to be assumed by the sound feedback standing wave, causing a large frequency jump or the whistling to cease all together.
• the flow through hole 5 ⁇ mst be such that vortices are shed.
• the flow is characterised by the Hole Reynolds number:
• the Reynolds number describes the behaviour of the flow going through the hole, and the characteristics of the associated disturbance, which governs the separation of the flow at the sharp lip of the inlet or the outlet, and the stability of the shed vortex train.
• t/d small ( ⁇ l )
• Rh ⁇ 15 a marked separation occurs, leading to the formation of a vortex.
• This vortex becomes more and more energetic with increasing Rh, but viscous damping prevents vortex shedding up to Rh «50 even for lower values of t/d. Higher values of Rh lead to a steady vortex shedding and roll up providing the desired instabilities.
• Raising the value of Rh further brings the flow into the transitional regime, when the flow changes from its laminar state to its more unsteady turbulent state. This leads to a broader spectrum of vortex shedding frequencies, making the sound produced by the whistle less tonal unless a more discriminating feedback process is employed. Nevertheless, whistles running at these high Reynolds numbers still produce well defined frequencies and provide an improvement in the spread of droplet sizes produced by a nozzle.
• the flow between the plates 5. 5a should be such that the jet of liquid remains stable and well-defined as it passes through the surrounding liquid.
• the hole aspect ratio t/d should be less than 3, and furthermore to minimise irregularities in the development of the jet and the introduction of the spurious noise the surfaces of the holes should be as smooth as reasonably possible, for example such that the roughness Reynolds number: where 6 is the maximum surface roughness.
• Figures 4, 5 and 6 show in more detail apparatus according to the invention which employs a hole-tone whistle.
• the device intended to be capable of producing a substantially monodisperse spray, but also operable off its design-point, comprises a generally cylindrical body 10, closed at one end by a hemispherical cap and at the other by the assembly generally indicated as 14.
• a connector 16 is mounted upon body 10 and communicates with its interior 18. Adjacent its lower end, body 10 contains a cylindrical plunger 20, carried by rod 22 and provided with an 0-ring seal 24. A cylindrical cavity 26 within plunger 20 communicates via a bore 28 in rod 22 with an orifice 30, which opens into body interior 18. Cavity 26 is closed at its lower end by plate 32 with a central aperture 34.
• Rod 22 passes through cap 12, and is axially movable by means of the assembly generally indicated at 40, comprising a rotatable cap 42 which is attached to the outer end of rod 22 by screw 44, and threaded upon fixed bush 46, carried by mount 48 attached to cap 12. 0-ring 0 mounted within bush 46 surrounds and seals rod 22. Axial adjustment of rod 22 provides axial adjustment of plunger 20 within cylinder 10.
• Assembly 14 which closes the other end of cylindrical body 10, comprises a plate 50 with a central aperture 52 of the same chameter as aperture 34, and a plate 5 with a central configured nozzle orifice 56.
• Plates 50 and 5 are carried by plate support members 58 and 60 respectively, which are assembled together with plates 0 and ⁇ by means of screws 62, the whole being mounted by screws 66 upon annular carrier member 64, itself secured in a liquid tight manner to the lower end of body 10.
• Plate 32, plate 0 and plate 54 are mounted such that aperture 3 , aperture 52 and the nozzle orifice 5 are in axial alignment, providing communication from cavity 26, through the aligned apertures 34 and 52, and the nozzle orifice 56, to the opening 68 in plate support member 60.
• the liquid which is to be distributed as a spray is fed under pressure through connector 16 to the interior 18 of body 10, 0-ring seals 22 and 50 preventing leakage of the liquid between plunger 20 and the interior wall of body 10, and through fixed bush 46. Liquid under pressure passes into bore 28 through orifice 30 and enters chamber 26 within plunger 20.
• Liquid from chamber 26 then exits chamber 26 through calibrated aperture 34 into chamber 35-
• the position of plate 32, and hence aperture 34, is adjusted relative to plate 50, and hence aperture 52, by means of rotatable cap 42, plunger 20 and rod 22, to achieve positive feedback conditions within chamber 35- Apertures 34 and 52, together with the intermediate chamber 35 constitute a hole-tone whistle, under which energy is extracted from the liquid flow through chamber 35 and converted into an acoustic vibration.
• the liquid enters chamber 53 and leaves it as a jet from nozzle orifice 56 in plate 54, entering the surrounding atmosphere where the acoustic energy generated within chamber 35 and conveyed to the jet through the liquid promotes controlled break-up of the jet, ideally into a monodisperse spray.
• the dimensions of the chamber 53 m y be chosen by experiment such that the acoustic vibrations in the liquid are directed towards the nozzle 5 rather than dispersed within the chamber.
• the value of S is at least twice the value of h
• the whistle hole 52 cannot serve as the spray nozzle, and therefore the additional nozzle plate with an appropriately sized nozzle 5 is necessary.
• the downstream whistle hole also as the nozzle especially if some departure from optimum performance can be tolerated.
• the plate 4 is 0.8 mm thick and the nozzle is formed with a 60° conical inlet and parallel exit portion.
• a traditional bell-mouth shape is suitable, the objective being in both cases to avoid flow separation from the walls of the nozzle, and to minimise acoustic energy dissipation in the nozzles.
• the nozzle surface is as smooth as reasonably achievable consistent with cost, since the smoothness of the surface determines the level of disturbance at the jet surface and thus its aerodynamic drag. At very low flow rates the nozzle length becomes significant, necessitating a stronger acoustic signal to maintain controlled jet break-up.
• the impedance of the nozzle should be chosen to match the flow rates, fluid properties and operating frequency or frequencies.
• a low impedance nozzle is desirable to minimise losses; if the nozzle is considered as containing a plug of liquid through which the acoustic vibrations must be transmitted, the inertial stiffness and viscous losses of the plug are both reduced by keeping the nozzle as short as possible, thereby reducing the impedance, at least at frequencies below or not more than about an octave above the resonant frequency of the plug.
• the acoustic transmission efficiency of the nozzle may also be adversely affected if the nozzle plate is too flexible; a converging nozzle as described in a rigidly mounted plate is preferred.
• the resonant frequency of the nozzle should be chosen accordingly, and moreover the chamber 53 should be likewise dimensioned so that its resonant frequency matches that of the nozzle. Then the acoustic pressure at the nozzle is raised, and transmission efficiency improved.
• the whistle frequency must equal the frequency of the fastest-propagating capillary wave.
• d, and d are chosen appropriately and the whistle plate separation distance is adjusted to ensure adequate positive feedback at fmax, then since S and S remain approximately constant over a range of flow rates Q, the operating frequency of the whistle tracks the variation of fmax with flow rate within design limits.
• the flow delivery rate is controlled by the break-up frequency.
• the operational range is therefore linked to the ability of the whistle to generate a strong enough signal at the desired frequency.
• the energy available to the whistle is proportional to ⁇ P, the pressure drop across the whistle, while its acoustic efficiency is roughly proportional to 1/ ⁇ P , which cancels it out.
• the sound energy is therefore mainly independent of flow rate. But a higher frequency signal of identical energy has a lower sound intensity, so the amplitude of the controlled disturbance o_ on the surface of the jet becomes smaller.
• the flow rate is ultimately limited by the quality of the whistle which can be manufactured economically as an increase in flow rate has a non-linear effect on the necessary manufacturing tolerances.
• the necessary higher frequencies are produced at higher flow rates and by a whistle with smaller length scales, which both require tighter tolerances and therefore are more expensive to manufacture.
• FIG. 7 there is shown a Hartmann oscillator in which liquid passes through a convergent nozzle 70 into a tuned cavity 72 wherein pressure oscillations present in the liquid leaving the nozzle 70 are amplified to provide a pressure maximum at the entrance 7 to an exit duct 76. Pressure waves travel down the duct 76 and are utilised at a discharge nozzle (not shown) to produce a controlled-droplet spray.
• the dimensions of the cavity 72 may be adjusted by means not shown to vary the tuned frequency.
• the port 78 introduces reactance into the system necessary for oscillations to be established and the device operates as a class III whistle.
• a relaxation oscillator operates as a class II whistle and comprises an inlet nozzle 80, flow from which impinges on a splitting edge 82 and is deflected alternately down one side 84 or the other 86, resulting in pressure fluctuations at the exit 87.
• Feedback ducts 88 communicate the pressure fluctuations back to a point just upstream of the edge 82, thereby to reinforce the alternate deflection of the flow.
• Figure 9 shows a feedback oscillator in which the structure is similar to that of Figure 8, corresponding parts carrying the same reference numerals. However, instead of the feedback ducts 88 there is a continuous closed passage 90 which communicates at its ends 92, 9 with opposite sides of the main flow passage between the exit of nozzle 8 ⁇ and the splitter 82.
• the passage 90 is dimensioned such that the liquid therein is caused to oscillate at the same frequency as the pressure pertubations produced by the flow splitter 82, thereby reinforcing the alternation of the flow around the opposite sides thereof.
• Figure 10 illustrates an edge-tone whistle in which liquid from a nozzle 80 impinges on the leading edge 82 of a tuned mechanical device 100, for example a beam. Flow is shed alternately around each side 84, 86 as described before, a resonant frequency of the beam 100 being tuned to match the shedding frequency, and to reinforce the pressure oscillations at exit 87-
• This type of whistle offers opportunities for extracting mechanical energy from the liquid, and to apply that energy where it will have most effect on the break-up of the jet, ie. at the spray nozzle.
• the liquid flow passes through a port 106 in the mounting structure into a chamber 108 and thence to atmosphere via a spray nozzle 110, forming a jet 112.
• the spray nozzle 110 is partially defined by a portion 116 of the tuned member 100.
• the portion 116 transmits the resonant vibration of the member 100 to the liquid jet 112 as it exits the nozzle 110 causing it to break-up into droplets 114 of controlled size.
• the member 100 may be configured to vibrate in other than the transverse flexural mode discussed. For example it could instead vibrate longitudinally of the axis 118 of the device. Also, it could completely define the nozzle 110 instead of only partially as shown in the drawings.
• the member 100 may drive an airborne sound generator (eg. in the manner of a small loudspeaker cone or tweeter) to impart vibrations to the air in the region of the nozzle 110 whereby to transmit those vibrations to the jet of liquid as it leaves the nozzle.
• the sound generator could conveniently be arranged concentrically with the nozzle so that vibrations may be imparted both to the air and directly to the liquid as it passes through the nozzle, provided that the vibrations imparted to the liquid from the nozzle and via the air are maintained in phase with each other.
• Figure 12 shows sectioned side and end views of a divergent nozzle producing a conical liquid sheet.
• a casing 120 has a circular orifice in which a pin 122 is located.
• the edges 12 of the casing are angled to form a frustoconical annular passage 126 between the head 128 of the pin and the wall of the casing.
• liquid is passed through the passage, it forms a conical sheet of liquid.
• the break up of this liquid sheet is susceptible to excitation in accordance with the invention, eg. by a whistle, leading to a better control of the produced spray.
• Figure 13 is an end view of a modification of the liquid nozzle shown in Figure 12.
• the pin 122 and the casing 120 define an annular passage.126 which has a sinuous profile about a base circle.
• the sinuosity further controls the jet break-up by matching the wavelength of the nozzle sinuosity to the wavelength of the excitation frequency leading to the jet break-up.
• the nozzles of Figures 12 and 13 need not be circular in section; other shapes eg. an ellipse can be adopted, and indeed the nozzle need not form a closed figure, and may be formed as an extended slot which may be straight as in Figure 2, or curved.

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• 1992
  • 1992-05-29 GB GB929211366A patent/GB9211366D0/en active Pending
• 1993
  • 1993-05-26 AU AU40854/93A patent/AU4085493A/en not_active Abandoned
  • 1993-05-26 EP EP93910292A patent/EP0642390A1/de not_active Withdrawn
  • 1993-05-26 WO PCT/GB1993/001089 patent/WO1993024237A1/en not_active Application Discontinuation

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