US 3741484 A
Method and apparatus for atomising liquids in which a liquid is fed from an outer, annular, convergent nozzle into a stream of gas fed at sonic velocity from a coaxial inner convergent nozzle. A difergent deflector is positioned coaxially within the outlet openings of the two nozzles.
Description (OCR text may contain errors)
United States Patent 1191 Cresswell 5] June 26, 1973 [5 ATOMISERS 3,534,909 10/1970 Paine 239/424 x 978,860 12/1910 Dietz  Inventor. Alan Cresswell, Strood, England 1,075,742 10/1913 weimz  Assignee: Decatix Limited, Rochester, Kent, 1,793,897 2/1931 England 2,089,673 8/1937 Stemmann 2,917,386 12/1959 Jones et a]. 239/424 X  Filed: Sept. 24, 1971 3,009,826 11/1961 Straughn et a1 239/424 X 211 App]. No.: 183,585
Primary Examiner-Lloyd L. King Art All' C. C 11 d  Foreign Application Priority Data Qmey 0 at Sept. 30, 1970 Great Britain 46400/70  ABSTRACT 52 U.S. l 24 3 Int 8 239/4 2 i i gg Method and apparatus for atomlsmg llqHldS in which a  Fieid 423 424 liquid is fed from an outer, annular, convergent nozzle 239/lo2 into a stream of gas fed at sonic velocity from a coaxial 1 inner convergent nozzle. A difergent deflector is posi-  References Cited tioned coaxially within the outlet openings of the two UNITED STATES PATENTS mules 1,002,594 9/1911 Mason et al. 239/424 X 8 Claims, 3 Drawing Figures PATENTEDJUHZB 1915 3,741,4
sum 1 or z FIG.
INVENTOR ALAN CRessweLL PAIENTEDJUNZS I975 3.741.484
sum 2 or 2 .2 b 5 I 160% I 140% m SUB. s0/v/cg SUPER. s0/v/c 5) 100 5;
I 80 m in Q Q- n SON/C Q U VELOCITY q FIG}.
INVENTOR Rum Ckessweu.
ATTORNEY ATOMISERS The invention relates to atomisers, for example for atomising fuel oil for burners such as may be used for firing water tube and packaged shell boilers or for atomising a liquid for use in gas cooling.
According to one aspect of the invention an atomiser comprises an outer, annular, convergent liquid nozzle chamber, a coaxial inner convergent gas nozzle chamber and a divergent deflector member positioned coaxially within outlet openings of the two chambers.
An inner surface of said gas nozzle chamber may be formed by a convergent surface of said deflector member. Preferably an outer surface of said gas nozzle chamber and an inner surface of said liquid nozzle chamber are formed by the respective inner and outer surfaces of a cylindrical portion of a distributor member for feeding both the liquid and gas to said chambers. An outer surface of said liquid nozzle chamber may comprise a convergent inner surface of an annular member carried by the distributor member. Conveniently the deflector member is screw-threadedly located with a screw-threaded central aperture in the distributor member and the annular member is screwthreadedly located with a screw-threaded outer portion of the distributor member.
The outlet of said liquid nozzle chamber may be bounded by a knife edge. The deflector member may diverge from where it extends from the outlet openings of the two chambers.
According to a further aspect of the invention an atomiser comprises a distributor member formed with an inner ring of gas passages, an outer ring of liquid passages and a cylindrical portion extending from one end between the two rings of passages, an annular member which screw-threadedly engages with the distributor member around the cylindrical portion to form a convergent liquid nozzle chamber therewith in communication with the ring of liquid passages and a deflector member which screw-threadedly engages with a central aperture in the distributor member so as to form a convergent gas nozzle chamber with said cylindrical portion in communication with the ring of gas passages.
According to yet a further aspect of the invention a method of atomising a liquid comprises feeding the liquid froma convergent nozzle together with a gas fed at sonic velocity so as to form a divergent nozzle with the radially inner surface of the nozzle being comprised by a divergent member, the radially outer surface of the nozzle being comprised by said liquid and the gas being fed therebetween.
The foregoing and further features of the invention may be more readily understood from the following description of two preferred embodiments thereof, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a side sectional view of an atomiser;
FIG. 2 is a perspective view, part cut away of an alternative atomiser, and
FIG. 3 is a diagrammatic representation, on enlarged scale of the nozzle outlets of the FIG. 2 atomiser together with a simplified graphical representation of the gas pressures along the axis of the atomiser during the actual expansion process.
Referring now to FIG. 1 of the drawing there is shown an atomiser which comprises a distributor member 11 formed with an outer circumferential ring of axial liquid feed passages 12 and an inner circumferential ring of axial gas feed passages 13. A feed pipe 14 is screw-threaded into a rearwardly extending flange 15 formed on distributor member 11. An outer feed pipe 16 is a press fit on the outer periphery of distributor member 11, is held in position by the screw-threaded engagement of pipe 14 with flange 15, and is sealed by an O-ring seal 17.
The feed passages 13 lead into a convergent annular nozzle chamber 13 which is defined by the inner frustoconical surface of an annular member 19 and the outer surface of a deflector member 20 which is screwthreaded into a central aperture at the front of distributor member [1. Metering apertures 21 are formed in the member 19 arranged to be in registry with the outer feed passages 12 in distributor member 11. An annular convergent liquid nozzle chamber 22 is defined by the forward surface of member 19 and the arcuate inner surface of an annular member 23 positioned coaxially with member 19 and having a rearwardly extending flange fitting around the outer periphery of distributor member 11 and abutting the O-ring seal 17. The arcuate inner surface of member 23 terminates at a knife edge 23a at a central opening in member 23.
The outer surface of deflector member 20 is formed to be convergent where it is within resonating chamber 22 and is also formed with a divergent deflecting surface 20a towards its outer end.
In operation, for example to atomise a fuel oil, air or some other gas is fed under pressure along inner feed pipe 14, passes through feed passages 13 to the convergent chamber 18. The arrangement of the chamber convergence and opening size and the pressure of the gas are such that a jet of such gas is emitted into chamber 22 at a pressure which is above the critical pressure ratio for the gas. The oil or other liquid to be atomised is fed through outer feed pipe 16, usually at a viscosity not exceeding seconds Redwood 1 scale, through feed passages 12 and metering apertures 21 into chamber 22. In chamber 22 the oil accelerates around the inner arcuate surface and leaves such arcuate surface at the knife edge 23a in a direction opposed to the pressure wave of compressible fluid emanating from the convergent chamber 18 at sonic velocity.
The surface of the oil at the knife edge 23a absorbs the energy of the vibrating air and at the same time the oil film near the knife edge is subjected to powerful shearing forces.
The oil then reverts to a minimum surface energy condition and forms very fine droplets. This condition is achieved without entrainment of the oil on to the metallic surfaces of the atomiser and is achieved by the convergent tapering of the deflector member 20 such that a high velocity cushion of air exists between oil film leaving knife edge 23a and the surface of deflector member 20. Further shearing is achieved by the shock waves produced in the air along the deflector member where the air decelerates from supersonic to subsonic velocity. The exit angle of the droplets is finally determined by the end diameter and divergence angle of deflector member 20.
Referring now to FIG. 2 there is shown an alternative form of atomiser which is similar to that of FIG. 1 but is simplified in that it comprises only three separate components; distributor member 11; annular member 23 and deflector member20. In this arrangement the liquid nozzle chamber 22 is formed by a cylindrical extension 11a of member 11 and annular member 23 which is formed with a frusto-conical inner surface 23b to provide the convergence of chamber 22. The inner gas nozzle chamber 18 is formed by the inner surface of extension 11a and a frusto-conical divergent surface 20b of deflector member 20.
The operation of this atomiser is similar to that described for the FIG. 1 arrangement with compressed gas flowing from chamber 18 and liquid to be atomised from chamber 22. The gas flows at sonic velocity from chamber 18 and as the pressure decreases the velocity increases to supersonic as shown by FIG. 3. When the gas approaches portion 20a of deflector 20 the gas pressure increases and the velocity decreases so producing shock waves 30. The liquid film 31 is accelerated by the gas and maintained out of contact with deflector member 20 by the gas so effectively forming a divergent nozzle between deflector member 20 and liquid film 31. The acceleration of liquid film 31 reduces its thickness and causes shearing. The pressure fluctuations at the culmination of the supersonic velocities reached by the gas which produce the shock waves 30 cause vibration of the liquid layer and further shearing and break up occurs in a plane normal to the horizontal shearing.
What is claimed is:
l. An atomiser, comprising:
an annular distributor member, including a radially outer circumferential ring of axial liquid feed passages, and a radially inner circumferential ring of axial gas feed passages;
a first annular member, disposed adjacent one end of said distributor member, and including at least one opening therein communicative with said ring of gas feed passages and a plurality of radially outer axial apertures communicative with said ring of liquid feed passages;
a deflector member, coupled to said distributor member, extending through said opening in said first annular member, a convergent annular gas nozzle chamber being defined by said first annular member and said deflector member adjacent said ring of gas feed passages; and
a second annular member, disposed on said distributor member, and including an opening through which said deflector extends, said first and second annular members defining a convergent annular liquid nozzle chamber adjacent said ring of liquid feed passages.
2. The atomiser as recited in claim 1, wherein said second annular member includes a knife-edge disposed about the periphery of said opening therein.
3. The atomiser as recited in claim 1, wherein said deflector member includes a divergent portion at one end thereof which extends outwardly from said opening in said second annular member. 4. An atomiser, comprising: an annular distributor member, including a radially outer circumferential ring of axial liquid feed passages, a radially inner circumferential ring of axial gas feed passages, and an outwardly extending annular extension disposed at one end thereof between said inner and outer rings of feed passages;
an annular member, disposed on said distributor member, and having a radially inwardly extending edge at one end thereof, said edge of said annular member and said annular extension forming an annular, convergent liquid nozzle chamber adjacent and communicative with said ring of liquid feed passages; and
a deflector member, coupled to said distributor member and extending outwardly from one end thereof, said deflector member and said annular extension of said distributor member forming a convergent annular gas nozzle chamber adjacent and communicative with said ring of gas feed passages in said distributor member.
5. The atomiser as recited in claim 4, wherein said deflector member includes a divergent surface, disposed adjacent said annular extension of said distributor member, for forming in conjunction with said extension said convergent gas nozzle chamber.
6. The atomiser as recited in claim 4, wherein said radially inwardly extending edge of said annular member includes a radially inwardly convergent inner surface for forming said liquid nozzle chamber.
7. The atomiser as recited in claim 6, wherein said distributor member includes a first threaded portion on the outside surface thereof and a second threaded portion on the inner surface thereof, said annular member includes a threaded portion on the inner surface thereof for threadably engaging said first threaded portion of said distributor member, and said deflector member including a threaded portion on the outside surface thereof for threadably engaging said second threaded portion of said distributor member.
8. The atomiser as recited in claim 7, wherein said deflector member includes an additional divergent portion extending outwardly adjacent said inwardly extending edge of said annular member.