GB1592153A - Spraying apparatus - Google Patents

Description

(54) SPRAYING APPARATUS (71) We, ABTEC LIMITED, a Company organised under the laws of England, of 332 Upland Road, East Dulwich, London, S.E.22, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to spraying apparatus of the type in which a stream of liquid to be sprayed is fed tangentially into a circular chamber and thereby caused to rotate around the chamber and issues from an orifice on the axis of the chamber as a hollow conical spray of droplets. The droplet size depends on the velocity of the liquid stream leaving the chamber, the higher the velocity the smaller the droplet size.

Spray nozzles of this type are disclosed in United' States Patent No. 2,247,897. With nozzles of this type the volume of liquid which can be discarged within a given period whilst maintaining a fine droplet size cannot be adjusted except within narrow limits since if 'the' volume is reduced the- rotational: velocity -is also reduced and the droplet size increases.

However many industrial processes require that the quantity of liquid being sprayed should be capable of being varied whilst maintaining a spray of fine snall droplets.

The present invention is concerned with providing spraying apparatus in which the volume issuing from a sigle nozzle can be adjusted between wider iimits than hitherto possible whilst maintaining a spray'of fine quality and small droplet size.

According to the present invention a spray nozzle comprises a body defining a circular chamber having a central orifice in one end and at least two liquid inlet ducts extending through the body and communicating tangentially with the chamber in directions such that liquid fed through the ducts on entering the chamber is led around the chamber and has a rotary movement imparted to it, the liquids fed in through the ducts rotating in the same sense around the chamber, the ratio between the cross-sectional area available for flow from one duct, the main duct, into the chamber and the cross-sectional area available for flow from the other duct, the pilot duct into the chamber being at least 4:1 e.g., in the range 10:1 to 100:1, and preferably 30:1 to 100.1 or 50:1 to 70:1.

The outlets from the ducts into the chamber may be located side by side or in the same quadrant of the chamber or in different quadrants. Preferably the outlet from the pilot duct is downstream of the outlet from the main duct in the sense of the rotation of the liquids in the chamber.

The main duct is preferably provided with valve means so that the flow therethrough can be varied from full flow to zero flow while the flow through the pilot duct remains not controlled. In another form of the invention, the pilot jet also may have valve means to control flow through it.

The flow through the chamber can thus be varied while maintaining the - spray velocity at a high level and thus maintaining a fine droplet spray.

In its simplest form, the pilot duct would be connected directly to the source of pressurised liquid so that the flow and velocity of the liquid through it would be uncontrolled. A controlling valve would be fitted in the conduit connected to the main duct, however, so that the flow through this could be regulated so that the intensity of the spray could be varied as required.

If sufficient liquid pressure is available, there is no reason why a controllig valves should not be fitted also in the connection to the pilot duct so that when flow through the main duct has been reduced to zero by closing the valve in its supply line, the flow through the pilot duct may also be reduced to - a half or a third of its maximum, thereby increasing the turn-down ratio obtainabe.

It should be noted that in the simple case where the pilot duct is connected directly to the pressurized liquid source, the flow through it is not constant; the flow depends on the pressure differential across the duct and although there'may be a constant pres sure at the pilot duct inlet, the pressure at its outlet into the whirl chamber will vary.

When the main duct flow is zero, flow through the outlet nozzle is confined to that derived from the small pilot duct. As the main duct flow is increased, however, the greater flow through the outlet nozzle creates a pressure drop across this, and hence causes a rise in the pressure withn the whirl chamber. This reduces the pressure drop across the pilot duct and thus reduces the flow through this.

The main and pilot ducts may be disposed in the same plane of the chamber or in different planes.

More than one main jet or pilot jet may be provided if desired e.g. with two jets they might be disposed diametrically across the chamber. This could assist in establishing even flow in the chamber.

One such arrangement would involve n pilot jets each having 1/n times or preferably less than 1/n times the area which would have been used for a single jet, the jets preferably being disposed evenly around the chamber, and p main jets each having l/p times or preferably more than i/p times the area which would have been used for a single main jet, the jets again preferably being disposed evenly around the chambers, n may be the same as p or different.

The ratio of the depth of the chamber, i.e. the distance from the closed end wall to the orifice, to the diameter or maximum trarís- verse dimensions of the main duct can vary but is preferably in the range 0.3 :1 to 2:1, e.g. 0.5:1 to 1:1.

The chamber may be of plain disk shape or may slope inwardly at one end from the circumferential wall of the chamber to the orifice. The slope may be conical or curved.

The chamber may alternatively be one of the more complex shapes described in United States Patent 2,247,897. The chamber is preferably circular but any shape e.g, an oval shape effective to produce the necese sary rotational flow and spray formation could be used.

The ratio of the diameter of the chamber to the diameter of the orifice can vary and for example may be in the range 2:1 to 6:1 e.g. 3:1 to 5:1 or 4:1.

The valve means on the main duct may be disposed in the body defining the chamber or may be located thereon but in a preferred form of the invention is located at a convenient position upstream of the chamber.

A valve to control the liquid flow to the main duct or ducts may be fitted as an int tegral part af the spray nozzle assembly or it may be installed at a remote point, e.g, twenty feet away and connected to the main duct by a length of conduit. Similarly, a separate controlling valve may also be fitted either integrally or in a separate length of conduit conducting the fluid supply to the pilot ducts or ducts.

Alternatively, the spray nozzle assembly may incorporate an integral valve designed to control through one channel the flow of liquid through the main duct system and through a second channel the flow through the pilot duct.

From the closed position, the integral valve would be arranged to first open the channel to the pilot duct and when flow through this had reached its maximum, further opening of the valve would progressively permit increasing flow through the main duct system, up to the maximum flow of the spray unit.

One particular application for the invention is in the desuperheating of steam. Here the spray nozzle is used to spray water into the superheated steam, for example at a temperature of 1000"F, so as to reduce the temperature of the steam rapidly so as to enable it to be used in lower temperature situations, Since the temperature and pressure of the steam to be used can vary widely depend ing on what process is being fed one needs to be able to adjust the volume of liquid issuing from the nozzle while maintaining a fine spray so as to maintain efficient cooling for a variety of steam pressures and temt peratures.

The nozzle may have a main duct having a diameter in the range 0.1 to 1 inch.

The pilot jet is formed las a by-pass from the liquid supply to the nozzle by-passing the valve means on the main duct, and may also have valve means.

Desirably the apparatus is used with a supply having a pressure sufficient to ensure a constant high velocity flow through the nozzle chamber, for example the supply pressure is preferably at least 100 p.s.i. greater than the pressure of the atmosphere into which the liquid is being sprayed.

The invention may be put into practice in various ways and one specific embodiment will be described with reference to the drawings accompanying the provisional specie fication, in which : Figure 1 is a diagrammatic cross sectional view of apparatus in accordance with the invention, showing the lidzile chamber in a plane transverse to its longitudinal axis; Figure 2 is a diagrammatic cross sectional view on the longitudinal axis of the nozzle chamber showing diagrammatically the flow path of the liquid; Figure 3 is a view similar to Figure 2 showing a mounting arrangement for a modified form of the nozzle shown in Figures 1 and 2; Figure 4 is a view similar to Figure 1 of the nozzle shown in Figure 3; Figure 5 is a diagrammatic view of an automatic arrangement for use of the device of Figures 3 and 4; Figure 6 is a view similar to Figure 5 of an alternative automatic arrangement for use of the device shown in Figures 3 and 4 and Figures 7, 8 and 9 are diagrammatic longitudinal cross-sectional views of the control valve shown in Figure 6.

Referring to Figure 1 the spray nozzle has a body 10 defining a circular chamber 11 having an axial orifice 12.

A main duct 14 enters the chamber 11 tangentially to the circumferential wall 15 of the chamber and a pilot duct 16 enters the chamber 11 also tangentially to the wall 15 and contiguously to the duct 14 but just after the main duct in the direction of rota tion of the liquids in the chamber so as to be directed uninterruptedly along the wall of the chamber.

The main and pilot ducts are fed by a supply pipe 18 via tubes 21 and 20. A valve 19 capable of varying the flow through the duct 14 from zero to 100% is located in pipe 21.

As can be seen in Figure 2 the chamber 11 has a flat closed end wall 25, a circum ferential wall 15 parallel to the longitudinal axis of the chamber and conical shoulders 26 leading from the circumferential wall 15 to the orifice 12.

In operation the pilot jet or duct 16 is connected to a liquid source where the pres sure is sufficient to ensure a constant high velocity flow through it into the circular chamber. Flow through the main jet or duct 14 is regulated as desired from zero to maxi mum by the valve 19 or other means.

It will be appreciated that at minimum flow, the pilot jet only is operative, giving a relatively small but high velocity output.

The effective turn-down ratio obtained from the compound jet spray nozzle in aecordance with this invention will be in fluenced by the size of the main jet com- pared with the pilot jet.

We have found that when using water at 100 psi a chamber diameter of @- inch and a nozzle diameter of 5/16' inch and a main duct 'outlet diameter of i inch ehabled'one to achieve a throughput of 5000 pounds/hour of water,' and a good spray. A pilot jet of 0.045 inches (3 /64 inches) provided a turn down ratio of about 21:1.

In order to demonstate the interaction of the jets 16 and 14 a valve was placed in the tube 20 feeding the pilot duct 16 so as to permit it to be shut off. This valve was then shut off and the valve 19 for the main duct 14 was opened so as to provide about 25% of the maximum throughput; the output from the nozzle orifice 12 of the nozzle chamber was merely a spiralling column extending axially out of the whirl chamber.

This situation continued with main duct flows up to about 50% of the throughput (corresponding to a turndown ratio of 2:1) at which stage a rather coarse quality spray was produced having the normal conical fan pattern but rather large droplets. As the valve 19 was opened further the spray improved in quality until it became a good quality spray at 100% throughput.

The valve 19 was now turned down again to the 25% throughput condition and the valve in the pilot tube 20 was turned full on.

The spiralling column of water was immediately converted into a good quality conical fan spray having a small droplet size.

This is most unexpected since it would be expected that the small mass flow through the pilot duct 16 although having a high velocity and good pressure drop would be slowed down by the high mass flow, low velocity, low pressure drop flow through the main duct 14 and that the output quality would become worse rather than a column of water being converted into a good spray merely by the addition of the pilot flow through 16 to the main coarse flow through 14. Clearly therefore the pilot duct is not merely having an additive effect on the main duct flow but is having some novel and unexpected and as yet unexplained effect.

Thus on the principle of conservation of energy one would expect the slow large mass of water to slow down the fast small mass of water, but the reverse seems to occur.

Ducts 14 and 16 could be drilled so that they would have a round cross-sectional shape, but the cross-section could be square, rectangular, or any shape that would permit the passage of a fluid.

In an earlier arrangement which we tried the ducts 14 and 16 were transposed. Whilst that arrangement produced good results, the arrangement of Figure 1 is even better, prO- ducing a good spray at slightly lower pressures.

Figures 3 and 4 show the compound spray nozzle in a practical form for use in desuperheating steam, or any other superheated vapour. The desuperheating fluid (or water in the case of steam) is fed to the pilot duct 16 via the upper flanged connection ' 31, while the main jet 14 is fed from a controlled source through the flanged connection 32, and thence through the tubular body 33 of the desuperheater unit.

The assembly includes a mounting flange 34. This is machined to suit a branch flange 35 which would be welded on to the steam main 36.

The unit would be mounted so that the spray was directed along the steam main in the same sense as the steam flow.

Figure 5 illustrates a typical desuper heating installation utilising the compound spray nozzle unit. The intensity of the spray is varied by changes in flow through the main duct 14 fed through the flanged connection 32, via the control valve 19. A smaller control valve 37, is inserted in the pipe connection to the upper flange 31, which feeds the pilot duct 16. Both valves would be controlled either by pneumatic or electrical means by the signal from a temperature controller 38, which senses the temperature of the steam downstream of the spray nozzle by means of a temperature senser 39, and passes the appropriate signal to the control valves to increase or decrease the spray so as to maintain a constant temperature.

In the case of pneumatic control, compressed air for operating the instruments and valves would be passed through the air line 40 and a pneumatic signal for varying the pressure would pass along the signal lines 41 to the valve positioners 43 and 44.

The valve positioners would be adjusted so that as the pneumatic signal increased from zero, it would first progressively open the valve 37, which would feed the pilot duct 16 and when this was fully opened, continued increase in the pneumatic signal pressure would progressively open the larger control valve 19, thus increasing the flow through the main duct 14 until the spray reached. maximum volume. When the spray was to be reduced. the valves would be closed in the reverse order, i.e. the valve 19 would close first and would be followed by the valve 37, which would eventulally shut off the pilot jet 16.

Figure 6 shows a single valve 45, adapted to carry out the same functions as the two valves 19 and 37 depicted in Figure 5. Cooling water or liquid is fed into the valve 45 through the flanged inlet 46. The valve could be arranged to be mounted directly on the spray nozzle unit so as to form an integral part of the assembly thus simplifying the installation and reducing costs. It would be operated by the signal from a temperature controller as in Figure 5, Figures 7, 8 and 9 illustrate one form of valve suitable for use as the valve 45 shown in Figure 6. Twin plugs 50, 51 on a common spindle 52 occlude two separate sealing surfaces 54 and 53 when in the closed position shown in Figure 7. Upward movement of the spindle first unseals the lower plug 51 as shown in Figure 8, permitting flow to the pilot duct 16 via the duct 20 while continued upward movement allows flow of the fluid past the upper seal 54 and into the main duct 14 via the duct 21 as shown in Figure 9.

Claims (14)

WHAT WE CLAIM IS:

1. A spray hozzle comprising a body de fining a "circular. chamber having .,a central orifice in one end and at least two liquid inlet ducts extending through the body and communicating tangentially with the cham ber such that liquid fed through the ducts on entering the chamber is led around the chamber and has a rotary movement imparted to it, the liquids fed in through the ducts rotating in the same sense around the chamber, the ratio between the cross-sectional area available for flow from one duct, the main duct, into the chamber and the cross-sectional area available for flow from the other duct, the pilot duct, into the chamber being at least 4:1.

2. A nozzle as claimed in Claim 1 in which the ratio of the cross sectional areas of the ducts is in the range 30:1 to 100:1.

3. A nozzle as claimed in Claim 1 or Claim 2 in which the outlet from the pilot duct is downstream of the outlet from the main duct in the sense of the rotation of the liquids in the chamber.

4. A nozzle as claimed in any one of the preceding claims in which the main duct is provided with valve, means so that the flow therethrough can be varied from .full flow to zero flow.

5. A nozzle as claimed in any one of the preceding Claims in which the pilot jet has valve means to control flow through it.

6. A nozzle as claimed in .any .one -of Claims 1 to 5 having n pilot jets each having not more than l/n times the area which would have been used for a single jet, the pilot jets being disposed evenly around the chamber, and p main jets each having not more than 1/p times the area which would have teen- used for a single main jet, the main jets -beipg. disposed evenly around the chamber,, n being the-. -,s,ame as or different to p. - -- -

7. A nozzle as claimed in any one of Claims 1 to 6 in which the ratio of the depth of the chamber, to the diameter or maximum transverse dimension of the mainduct is in the, range 0.3:1 to 2:-k

8. A nozzle as claimed in ally one of Claims 1 to 7 in which the ratio of the diameter of the chamber to the diameter of the orifice is in the range 2:1 to 6:1.

9. A nozzle as claimed in any one of Claims 1 to 8 incorporating an integral valve designed to control through one channel the flow of liquid through the main duct system and through a second channel the flow throug the pilot duct, whereby 'from the closed position, the integral valve is arranged to first open the channel to the pilot duct and when flow through this ha reached its maximum, further opening of the valve pro gressively permits increasing flow through the main duct up to the maximum flow of the spray nozzle.

10. A spray nozzle as claimed in any one of Claims 1 to 9-in which the body is attached to a broad pipe of greater cross section than the main duct and the main duct opens into the said pipe whilst a pilot supply pipe is sealed into and extends from an inlet at one end through the broad pipe and is connected to the pilot duct and the broad pipe is provided with a separate inlet remote from the chamber.

11. A nozzle as claimed in Claim 10 in which the broad pipe is provided with external radially extending sealing means located between the nozzle body and the inlet to the broad pipe whereby it can be sealingly secured in the wall of a pipe or chamber with the spray nozzle body located within and opening out into the said pipe or chamber.

12. A spray nozzle substantially as specifically described herein with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.

13. A vapour pipe or vapour chamber fitted with a spray nozzle as claimed in any one of Claims 1 to 10, desuperheating liquid supply apparatus and control apparatus whereby desuperheating of superheated vapour in the vapour pipe or chamber can be carried out.

14. A vapour pipe as claimed in Claim 14 substantially as specifically described herein with reference to Figure 5 or Figure 6 and 7, 8 and 9.