US 2746801 A
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V. J. CURRAN May 22, 1956 ATOMIZERS Filed Feb. 2, 1953 FIGS Inventor V N. A H A C 5 T N M N V United States Patent ATOMIZERS Vincent James Curran, Leamington Spa, England, assignor to Kigass Limited, Leamington Spa, England Application February 2, 1953, Serial No. 334,595
Claims priority, application Great Britain May 27, 1952 7 Claims. (Cl. 299-120) This invention relates to atomisers for liquids of the v kind including a swirl chamber into which liquid is injected in a tangential direction, and an outlet or jet orifice coaxial with the chamber and situated in one of the end walls thereof.
In known atomisers of the kind above referred to, the tangential inlet or inlets is or are formed by drilling a hole or holes through from the peripheral wall of the chamber which method while being fairly satisfactory for comparatively large flows in unit time of the liquid, presents considerable difficulties in manufacture when small holes down to the order of 0.018" and less have to be drilled particularly as both the start of the hole and the finish of the hole are on surfaces not normal to the axis of the hole. Due also to the difliculties of drilling, considerable variations occur in hole and in flow size.
One of the factors controlling the volume of liquid delivered from the jet orifice in unit time is the crosssectional area of the liquid inlet or inlets into the swirl chamber. For small flows say of an order of 12 pints per hour under an inlet pressure of 100 lbs. per square inch the inlet becomes of such a small diameter that drilling is difiicult, expensive, and yields large inconsistencies between specimens.
The object of the invention is an improved construction and a method of manufacture of an atomiser which is simple, accurate, cheap, gives consistent results between specimens without testing and/or adjustment, and which can be readily adapted to provide different orders of flow without increasing noticeably the cost of manufacture.
To avoid the said drawbacks and with other objects in view, I propose to fabricate the inlet passage or passages by forming a slot or slots in a thin piece of sheet metal which communicates or communicate at the one end with the liquid supply and at the other with the swirl chamber.
As sheet metal is obtainable in thicknesses accurate to Within close limits and as the slots can be accurately punched out also within very close limits, flows through such passages can be metered closer to a given standard than is possible by the drilling method.
Reference may be had to the accompanying drawings spray orifice is formed as shown in end elevation in Figure 5, and the metering disc shown in Figure 3.
Figure 6 is a similar view to Figure 1 but of a doubleended atomiser constructed generally in the manner characteristic of the invention.
In one convenient embodiment of the invention, a slotted metering disc is incorporated in an assembly of sheet 2,746,801 Patented May 22, 1956 metal discs arranged to form a swirl chamber and held together tightly in an axial direction so that they make joint on their flat surfaces. One such arrangement will now be particularly described.
' The assembly consists of four discs fabricated from sheet metal, said discs being of the same external diameter and arranged in superposed and coaxial relation within a tubular housing 1 having an open end 2 counterbored to receive the discs. The innermost feed disc 3 which abuts against the shoulder 4 of the counterbore has an annular groove 5 formed in its face next the adjacent metering disc 7, to which annular groove liquid fuel passes through one or more radial slots 6 formed in the periphery of the feed disc 3 and communicating with the bore of the housing. This annular groove 5 and the slots 6 can be formed readily and to accurate dimensions by stamping.
The metering disc 7 which is next to the feed disc 3 is of annular configuration and is provided with one or more tangential slots 8 which stop short of the periphery of the said metering disc but open into the eye 9 so as to form an inlet conduit or conduits each of which, in the complete atomizer communicates at its outer end that is, the end adjacent the said periphery with the annular groove 5. One, two, or more slots are formed in the metering disc 7 according to the volume of flow required. By constructing one or more inlet conduits in this manner i. e. by slots formed through an eyed disc, it is possible to vary the flow by varying the cross-section of the slots, the number of slots, and the thickness of the disc. For small flows, the selected sheet metal from which the metering disc is stamped may be of a thickness say from 0.005" down to 0.002 since sheet metal is obtainable having negligible departures from the nominal thickness. Thereby a different cross-sectional area of the inlet conduits can be obtained from the same perforating tools simply by the stamping of the metering disc from a different thickness of metal sheet; the same tools can also be used to punch one, two, three, four, or other desired number of tangential conduits 8; further, by utilising sheet metal stampings it becomes possible to fabricate an atomiser in metals which present difliculties in machining to the required degree of accuracy, e. g. stainless steel.
The eye 11 of a third disc herein termed the chamber disc 10 constitutes the major portion of a swirl chamber of which the remainder and minor portion is formed by the eye 9. The chamber disc is interposed between the metering disc and a fourth and outer orifice disc 12 which is provided with a concentric hole 13 which functions as the jet discharge orifice. The several discs are clamped together endwise permanently by rolling or turning over at 14 Figure 1 the outer edge of the housing, or by screw means which has the advantage of enabling the parts to be disassembled, if and when required, for cleaning or like purposes; such cleaning being much easier than in the known type of drilled atomiser before described on which the present invention is an improvement. Where a stainless steel housing is used, it is found that the rolling over operation should be repeated after an interval to take up any creep which may manifest itself. 7
An atomiser constructed by the method herein described has special value for atomising say paraflin for starting in continuous combustion chambers e. g. aircraft engines, with a swirl chamber 0.10" diameter, two metering conduits 0.015" wide perforated in a disc 0.005" thick, which will provide small flows of the order of say 12 pints per hour at lbs. per square inch fuel inlet pressure with consistent results between production specimens and negligible departure from standard flow. In
addition to the advantages already mentioned, an atomiser according to the invention occupies very small space.
The method of manufacture hereinbefore described is applicable also to double-sided atomisers in which each of the two ends of the swirl chamber is closed by a complementary orifice disc whereby two sprays are discharged in opposite directions. One convenient construction, such as illustrated in Figure 6 includes a housing 15 arranged to be supplied with liquid fuel under pressure and having a circular bore adapted to receive endwise five discs, which include a median-placed tangentially-slotted metering disc 16 fabricated by stamping from steel metal as aforesaid, a chamber disc 17 (of which one also serves as the feed disc) on each side of the metering disc to provide a joint swirl chamber whereto the eye of the metering disc 16 contributes a minor part, and two outermost orifice discs 18 which form the end walls of the complete chamber and are each perforated with the central jet or discharge orifice 19.
In the bore which carries the several five discs of the double-sided atomiser assembly (the axis of said bore being at right angles to the axis of the supply housing) is formed a shallow annular groove 20 extending around the entire inner periphery of said bore. Co-operating with the median-placed tangentially-slotted metering disc, is an annular groove 21 formed in the adjacent face of one of the chamber discs 17, which chamber disc is formed with radial slots 22 extending from the groove 21 to the disc periphery so as to place in communication the annular groove 20 in the housing and the metering conduits which discharge into the middle of the joint swirl chamber, an enable the said disc 17 to function both as a chamber disc and a feed disc. It will be apparent that the joint swirl chamber and the two jet orifices are fed with metered volumes of liquid fuel discharged into the said chamber from the tangential conduits in the metering disc.
In the single jet atomizer shown in Figure 1, the method of holding the several assembled discs in place comprises a counterbore in the housing as to the one end of the assembly and a turning or rolling over of the terminal end of the housing. The double-sided atomizer differs from the single atomizer in that both ends of the bore, wherein the several discs are accommodated, are subjected to the rolling or turning over process, with repetition in the case of certain metals which tend to release their grip with a single operation. Alternatively, one end of the bore may be strengthened so that only a single turning over or rolling of the other end is needed as in Figure 1, or again a screw means may be screwed into the bore for holding the discs axially.
Having thus described my invention, what I claim is:
1. An atomiser for liquid fuel comprising a bored fuel supply housing having at least four superimposed and co-axial discs, each consisting of a sheet metal stamping, clamped therein in face-to-face contact, the said discs including a feed disc having slots opening to its periphery and communicating with the bore of the housing, and an annular groove, which is overlapped by the said slots, in its face adjacent a metering disc having a central eye, which forms a minor portion of a swirl chamber, and at least one conduit opening tangentially to said eye and terminating short of the periphery of said metering disc in overlapping relationship to the said groove, a third chamber disc located on the opposite side of the metering disc to the feed disc and having a central eye forming the major part of said swirl chamber, and an orifice disc on the opposite side of the chamber disc to the metering disc and having a central fuel discharge orifice therein.
2. An atomiser for liquid fuel comprising a tubular supply housing of which one open end thereof is counterbored to provide an internal annular shoulder, a feed disc which seats on said shoulder, having radial slots in its periphery, said slots communicating with the bore of the housing, and an annular groove in its face remote from the said bore, said groove being overlapped by said slots, a metering disc, seated on said grooved feed-disc face and having a central eye which forms a minor portion of a swirl chamber and at least one radial slot of which one end opens tangentially into the said eye and its opposite end terminates short of the metering disc periphery in overlapping relationship to said groove, a chamber disc seated on said metering disc and having a central eye which forms the major portion of said chamber, an orifice disc seated on said chamber disc and having a central fuel discharge orifice, and means for locking said discs in said counterbored housing end, all the four discs being co-axial of the housing and consisting of sheet metal stampings.
3. An atomiser as claimed in claim 2 wherein said disc locking means comprises a rolled rim of the counterbored end of the housing.
4. An atomiser as claimed in claim 2 wherein said disc locking means comprises a member releasably secured to the counterbored end of the housing.
5. An atomiser for liquid fuel comprising a tubular housing having an open-ended annulus at one end thereof, the axis of said annulus being disposed at right angles to the axis of the housing, the said annulus having an annular groove formed internally thereof which groove opens to the said housing bore, a metering disc, which is located transversely and centrally of said annulus, having a central eye forming a minor portion of a swirl chamber and at least one slot of which one end opens tangentially into said eye and the opposite outer end terminates short of the disc periphery, a feed disc seated upon one face and a chamber disc seated upon the opposite face of said metering disc, each of said feed and chamber discs having a central eye forming a major portion of said swirl chamber and the feed disc having radial slots which open to the disc periphery to establish communication between the said groove in said annulus and an annular groove formed in that face of the feed disc which is adjacent the metering disc and in overlapping relationship to the outer end of each of said slots in said metering disc, one orifice disc seated upon said feed disc, at second orifice disc seated upon said chamber disc adjacent the open ends of the said annulus, each of said orifice discs having a central discharge orifice, and means for securing all said discs, each of which consists of a sheet metal stamping, co-axially of and within the annulus.
6. An atomiser as claimed in claim 5 wherein said disc securing means consists of inwardly rolled rims of the open ends of the annulus.
7. An atomiser as claimed in claim 5 wherein said disc securing means comprises a shoulder formed internally of one end and a member releasably secured to the opposite end, of the annulus.
References Cited in the file of this patent UNITED STATES PATENTS