US2861628A - Liquid atomisers - Google Patents

Description

Nov. 25, 1958 v R. P. FRASER 2,861,628

LIQUID ATOMISERS Filed Nov. 10, 1955 2 Sheets-Sheet 1 F/GJ [1 1 I fir/I Ll] If [I I I II 5 Li ff [1 I fill I I 4 Inventor REGINALD P. FRASER WAttorneyg R. P. FRASER LIQUID ATOMISERS Nov. 25, 1953 2 Sheets-Sheet 2 Filed Nov. 10. 1955 F/GZQ',

R. P FRASER I nventor A ltorneys 2,861,628 ;Paten ted,Nov. 25, 1958 2,861,628 LIQUID AToMIsE s Reginald Fraser, Kingston Hill, England Application Nove ber 10, 1 9 55,:Serial No, 546,134

Claims priority, applicationiGreat Britain -October' 10, 1955 zcianns. Cl. 158-75) 'nozzle the liquid from which issues as an open cone of spray. V

Eflicient atomisers of the above stated kind are already known and in 'use comprising a tubular casing within which is mounted a liquid supply member, the front end piece of which constitutes a liquid swirl-spray pressure nozzle for forming an open cone of spray, the'exit orifice of the said nozzle being surrounded by a dished or cupped formation, whilst an annular stream of converging gas or air or steam for intensified atomisation of .the

., liquid issupplied through the casing alongside or around the liquid supply member and issues annularly at the rim of the said dished or cupped formation so as to strike the open coneofliquid-after it has formed; An example of an atomiser of this kind may be seen in Figure 6 of my pending -paten't application serial No; 543,572, and

:now Patent No. 2,'7 2,6 5 6.of September 11, 1956'. 'Such "at m s r ay e re rre to as "atomisers A The 'problem of atomisation of the liquid becomes invortex cup-type creasingly diflicult with increase of discharge "or output of -the liquid from the pressure nozzle and the chief objects of the present invention are to provide improvements in atomisers of the .kind referred to both in functional performanceand in construction when dealing with large. 3 iq??? l V According'to one feature ofjhe present invention a liquid atomiser of t he swirl s pray pressure nozzle type is provided with a stationary hollow cylindrical or outwardly conical or flared tube extending axially forward from the central liquid exit orifice of the said nozzle, and with tangential passage at or near the base of the said tube for enabling a gaseous stream such as air or steam under pressure to become whirled and issue as a gaseous liner to the said tube, the diameter or smallest diameter of which is greater than the diameter of the liquid exit orifice. In this way a substantially cylindrical vortex of the gaseous stream is created within the tube, and the liquid film leaving the swirl spray nozzle is accelerated and rotated.

The foregoing feature of improvement applies to atomisers in which a liquid swirl spray pressure nozzle is combined with a concentric outer nozzle delivering an annular stream of gas or air or steam around the said spray nozzle as above referred to. A further feature of improvement applies to such atomisers and consists in making the annular exit passage of the said outer nozzle, progressively convergent-divergent in every cross section of the passage. Alternatively this novel exit formation United States Patent lat a rass il may be defined as a'two-dimensional convergent-divergent nozzel precesse'd to generate the improved annular exit. The supply pressure of'the gaseous stream may be greaterthan-fourteen pounds per square inch and the said annular exit passage may be designed for con trolled gaseous expansion 'within it such as to create supersonic velocity in the stream.

' Atomisers of the twin-fluidkind referred to, when pfglarge; size, necessarily have a large facial area exinto which they may project. So long as the liquid and posed-toiradiation of heat from combustion chambers the atomising gaseous stream are flowing through the atomiser they. are sufficient to cool the atomiser face,

but when the supply is cut off the face of the'atomiser may become excessively hot from the heat in the chamber. A still further feature, therefore, of the present invention consists in providing for positive cooling of hsat m s hea The above and other novel features of the present in- ;ventioniwill nowbe described more fully with reference to the accompanying drawings in which: v Fig. 1 is a longitudinal section of the atomiser according .to the invention;

Fig. 2 is a cross section detail view taken along line of fig. 1; and

Fig. 3 is a cross sectional detailed view taken along line 33 of Fig. 1.

The body or casing-of the atomiser consists of a base or rear'part 1 and a cylindrrical open ended front or cap part 2, these parts being held together by bolts 3. Through ,the base 1 of the casing extends axially a liquid uppl Pi H om nd hishmrr esz l qui swirlspray nozzle constituted by the hollow liquid atomising member 5, having swirl grooves 15 on its ,face, as

- sh wn n F s: 2 id-th Y, y s n zz apicc i 6.1 1 th centre hf which is the central exit orifice 7. In the par- ,ticular construction shown the nozzle; piece ;6 is formed w t 1 1126, W hss am e e e pp sin flanges 9 on the parts 1 and 2 of the casing. Fitting over the face of the nozzle piece 6 is acover 'p1atej10, ;the

front surface ofwhichis inwardly dished-or cupped as shown at 2l to constitute a vortex cup formation, and

the periphery of which is symmetrically disposed adjacent to but spaced from the rim 11;of;t he';cap,-2iso as toconstitute an outer nozzlehaving the converging an- Liquid "fed under pressure along'the supply piped enters the rear charnber-13 of the swirl" spray nozzleiand thaw a i wt l yit w t ann sp c .1 4, t bac through tangential slots 15 on the face of the member 5 into the swirl chamber 16, and thence forwardly through the orifice 7 of the nozzle piece 6.

A gaseous stream such as air or steam is supplied through a pipe 17 to the interior of the base 1 of the casing and passes forwardly along the inside 1a of the casing through holes 18 in flange 8 and past whirl-imparting vanes 19 to the converging annular exit passage 12 of the outer nozzle.

As already stated an important feature of the present invention is a hollow cylindrical or outwardly conical or.

flared tube extending axially forward with respect to the central liquid exit orifice 7 of the swirl spray nozzle. This tube is seen at 20 and in the particular construction shown the tube 20 is shown as a hollow forward central projection from the vortex cupped or dished face 21 of the plate It). The diameter of the tubular walled passage so provided may be as much as, say, ten times the diameter of the liquid exit orifice. The rear face of the said plate 10 is formed, as shown in Fig. 3, with tangential slots 22 which at their outer ends are open to the interior 1a of the casing, thereby enabling some of the air or steam inside the casing to pass along the said slots and into tube 20 at the base thereof. The said tube 20 can extend forwardly as far as or even beyond the transverse plane containing theannular exit passage 12. The air under pressure passing inwardly along the slots 22, emerges into the tube 20 tangentially at its base, and forms inside the tube a high velocity substantially cylindrical gaseous vortex advancing along the internal surface of the tube. The free cone of whirling liquid spray that has left the orifice 7 of the liquid spray nozzle and is spreading as a free cone towards the internal surface of the tube 20 meets the air vortex inside the tube 20 and becomes accelerated by it and intimately admixed with it. As soon as this mixture reaches the forward rim of the tube it expands radially outwards as a substantially disc-like sheet and strikes the converging annular stream of air or steam issuing from the annular exit passage 12.

It is important to observe that the spaced walls of the annular exit passage 12 are not parallel but are convergent at 12' and then divergent and that the length of the passage in the direction of travel of the air or steam is appreciable so that the air or steam can undergo appreciable increase in velocity (above sonic). The width of the exit passage 12 is determined by the correct choice of a flat washer or shim 23 at the base of the cap 2 of the casing.

The front plate is shown as being hollow, this being so as to enable a cooling fluid to be circulated within its annular cavity for cooling purposes as already explained.

One of the feed pipes for the cooling fluid is seen at 24, its front end being secured to and leading through the rear wall of the said hollow plate 10.

The above described tube may be provided with a detachable tubular liner 25, as shown, for ready interchangeability when desired. The rear rim of the said liner may reach to or slightly overlap the mouths of the tangential slots 22. With a shim of the thickness shown in Figure 1 the exit mouths of the slots 22 are just clear of obstruction by the liner 25, but if a thinner shim were used and the liner 25 were screwed down tight onto it, the rear rim or base of the liner would correspondingly overlap the mouths of the slots 22 and thereby alter the effective exit areas, this constituting one way of enabling the effective exit area of the said slots to be changed at will by interchanging the gasket or shim 26 for one of different thickness.

What I claim is:

1. A liquid atomiser consisting of a liquid swirl nozzle having a swirl chamber with tangential passages leading into it and a central exit orifice therefrom, a cover plate fitting over the face of said nozzle and having a central opening around said orifice, a tubular walled passage extending axially forwardly from said central opening and being itself open to atmosphere at its front end, a casing around said nozzle and cover plate, said cover plate having passages therein leading from inside said casing tangentially into said walled passage at the end thereof adjacent the face of said nozzle for delivering and whirling a gaseous medium under pressure from inside said easing into the rear end of said walled passage to create a gaseous lining inside said passage, the diameter of said walled passage being substantially greater than the diameter of the said swirl nozzle exit orifice, a tubular liner inserted in said tubular walled passage, and means for securing said liner at a plurality of positions along the length of said passage with the rear end of said liner partially obstructing the exits from the tangential passages leading into the said tubular walled passage.

2. A twin-fluid atomiser consisting of a liquid swirl nozzle having a swirl chamber with tangential passages leading into it and a central exit orifice therefrom, a cover plate fitting over the face of said nozzle and having a central opening around said orifice, a tubular walled passage extending axially forwardly from said central opening and being itself open to atmosphere at its front end, a casing around said nozzle and cover plate, said cover plate having passages therein leading from inside said casing tangentially into said walled passage at the end thereof adjacent the face of said nozzle for delivering and Whirling a gaseous medium under pressure from inside said casing into the rear end of said walled passage for creating a gaseous lining inside said passage, the diameter of said walled passage being substantially greater than the diameter of said swirl nozzle exit orifice, the said cover plate spreading forwardly and outwardly with the periphery adjacent the front end of the said casing and defining with said front end of said casing an annular space between them serving as a co-nvergently directed annular nozzle, said annular space being convergentdivergent in cross section.

. References Cited in the file of this patent UNITED STATES PATENTS 748,897 Walkley Jan. 5, 1904 1,474,603 Morse Nov. 20, 1923 1,607,805 Sprado Nov. 23, 1926 1,628,424 Peabody May 10, 1927 1,841,698 Barber Jan. 19, 1932 2,614,619 Fuller Oct. 21, 1952 FOREIGN PATENTS 115,725 Australia Aug. 27, 1942 664,676 Great Britain Jan. 9, 1952 617,101 France Nov. 10, 1926

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