US2603535A - Liquid spray nozzle - Google Patents

Description

1952 D. c. IPSEN ETAL 2,603,535

LIQUID SPRAY NOZZLE Original Filed Oct. 16, 1945 3 Sheets-Sheet 1 'IIIIIIIIIIIIIIIIII:

2 14 s I r T i 4 /o Ihvntor's: 5 Charles D. Fulton.

David C. Ipsen.

b g W Their Attorne s.

y 15, 1952 D. c. IPSEN r AL 2,603,535

LIQUID SPRAY NOZZLE Original Filed Oct. 16, 1945 3 Sheets-Sheet 2 IZO- Fig 2.

Rate of Flow, Gal. pr' Hr: per Nozzle 0 mo :00 500 r 400 .m 600 Inventdrs: 3 Charles D.Fulton, David C. Ipsen, b M Their Attorney.

y 15, 1952 D. c. IPSEN ETAL 2,603,535

LIQUID SPRAY NOZZLE Original Filed 001;. 16, 1945 3 Sheets-Sheet 3 Inventor's: Charles D. Fulton. David C. Ipsen.

The ir- Att OPYWQS.

Patented July 15, 1952 LIQUID SPRAY NOZZLE David C. Ipsen, Schenectady, and Charles D.

Fulton, Scotia, N. Y., assignors to General Electric Company, a corporation of New York 1 Original application October 16, 1945, SeriaLNo. 622,604. Divided and this application January 25, 1947, Serial No. 724,408

This invention relates to liquid atomizing spray nozzles, particularly for use in apparatus for-producing an atomized spray of liquid fuel in acombustion device. It is particularly adaptable'to liquid. fuel combustion systems, as used in gas turbine powerplants.

This is a division of our application Serial No. 622,604, filed October 16, 1945, now Patent No. 2,580,853.

The advent of gas turbine powerplants for the propulsion of aircraft raised a need for new and greatly improved methods and apparatus for spraying liquid'fuels over a wide range of flow rates. In addition, the operating conditions encountered by an aircraft are extremely difficult because of the enormous range of atmospheric temperatures and pressures encountered, particularly in high altitude aircraft. Furthermore, it is generally necessary to employ a plurality of fuel spraying nozzles discharging either into a number of small separate combustion chambers or into one large chamber. For successful use in gas turbine service, it is absolutely essential that fuel be supplied equally to each nozzle and discharged uniformly into the combustion space, in order that the temperature of the hot gas produced will be entirely uniform. This is of the greatest importance because the modern high performance gas turbine operates at a temperaturelevel exceedingly close to the maximum allowable temperature, so that any hot spot I in the operating medium has a serious effect on the life of the apparatus as well'as onthe combustion efliciency and fuel economy of the powerplant. With all the increased difficulties encountered, a fuel system for use in aircraft must of course be of the utmost reliability. The requirements of military aircraft are particularly stringent because of the rapid changes. in. operating conditions met with in fighter aircraft, the'need for maximum fuel economy in order to improve the operating range, and the supreme importance of absolute reliability;

In the past, various types of liquid fuel spraying nozzles have been resorted to in order to obtain a wide range of flow rates. One of these was the recirculating or Peabody type of nozzle, in which a supply pump at all times furnishes liquid approximately at the maximum rate ever required, and a portion of the fuel supplied to the nozzle is returned to the pump or recirculated-toreduce the amount discharged from the nozzle to the desired rate. 7 Such a nozzle may be satisfactory for stationary 'or' marinei 'use 'where the size and weight of "-the'i Claims. (01. 299-114) 2 fuel system'and the power pumping apparatus are not critical. It is undesirable however for aircraft use, where size, weight, and power consumed are of the utmost importance.

A perhaps less well-known type of wide range nozzle is what will be referred to herein as the duplex type. This nozzle has a discharge orifice, a vortex whirl chamber, two separate sets of orificesor ports for supplying liquid to the vortex chamber, and a liquid supply system arranged to-sup'ply liquid to the two sets of ports at various'pr'e'ssures in order'to secure the de sired total flow rate, while stll preserving the velocities required in the vortex chamber to produce a spray with satisfactory characteristics.

The duplex nozzle system has important advantages for use in connection with aircraft gas turbines by reason of the fact that all the liquid supplied by the pump is delivered by the nozzle; that is,'there is no surplus recirculation fiow which must be handled by the pump. Therefore with the duplex system, the pump, liquid lines,

nozzles, and other components of the system.

can be made smallerand therefore lighter for given performance characteristics. than is possible witha system of the recirculating type.

The present invention relates to a new and improved nozzle of the duplex type.

An object of our invention is to provide. a liquid fuel nozzle for use in a spray system capable of .producing a satisfactory atomized-spray having a pattern in the'shape of a hollow circular. cone with a definite preselected minimum vertex angle'over an extremely wide range of initial supply pressures and flow rates.

Another object is to provide a liquid spray nozzleof the duplex type capable of producing a well: atomized spray .having a pattern in the form of a wide angle cone over an extremely wide rangeof flow rates.-

Still another :object is to provide an improved arrangement of liquid: supply orifices or ports in a duplex type nozzle.

A further object is toprovide an improved. form of discharge orifice particularly 'advan tageous in a'nozzle of the. duplex type.

be used together. Still another object-is toprovi consumed by the 1 I ea duplex-type:

nozzle with an orifice tipxmember which can1be easilyLmanufactured, and having ports arranged.

so. that" their size Scan be. controlled to extremely.

accurate limits by simple manufacturing methods.

Other objects and advantages will be apparent from the following description, taken in connection with the accompanying drawings in which Fig. 1 is a diagrammatic representation of a complete liquid fuel sprayingsystem having a nozzle in accordance with our invention; Fig. 2 is a graphic representation of th fiow characterise tics of thersystem of Fig. 1; Figs. 3, 4 and 5 represent diagrammatically the liquid discharge from a duplex nozzle having a plain orifice; Figs 6, '7 and 8 represent the flow obtained with our improved form of nozzle; Fig. 9 is asectional view of a preferred structure of our improved duplex nozzle; Fig. 10 is a more detailed view of the flared orifice of the nozzle shown in Fig. 9; Fig. 11 is a sectional view in the direction of the arrows I I-I I in Fig. 9; Fig. 12 is a perspective view of our improved nozzle orifice tip; Fig. 13 is a Plan view, to an enlarged scale, showing the shape of. one orifice or port of the nozzle tip shown in Fig. 12;, and Fig. 14 is a partial sectional view on the plane I4I 4 in Fig. 11.

Referring now to Fig. l, a combustion chamber or combustor I is supplied with atomized liquid fuel'by a vortex spray nozzle 2 of the duplex type. Oneset of, ports 40 in the duplex nozzle is sup plied with liquid at the full inlet pressure, while the other. set 39 is supplied with liquid at a reduced pressure produced-by a metering device 3. Liquid fuel. under pressure is furnished, by a supply system represented diagrammatically at 4.

The fuel supply system 4 may be of any suitable type such as that disclosed in abandoned application Serial No. 525,416, filed in the name of AustinG. Silvester on March '7, 1944, and assigned to the 'same assignee as the present application. This system includes a fuel supply tank 5; a positive displacement pump 6, represented as being of the well-knowngear type driven by any suitablemeans (not shown) and having a suction conduit I and a discharge conduit 8. A combination of'auxiliarydevices control the discharge pressure of the pump 6 so as to supply liquid to discharge conduit Bat apressure which varies as a preselected function of the throttle setting, or of the fuel fiow or heat liberation desired. These control devices are represented in Fig. 1 as comprising a speed responsive flyball governor 9 arranged to be driven at a speed proportional to a rotational speed of the powerplant through a shaft I0. This speed governor'actuates abypass valve I I which permits liquid from the discharge conduit 8 to be returned to the pump inlet conduit 1 'as a function of speed; Similarly, barometric device I2 comprises an evacuatedbellows I3 arranged to actuate a bypass valve. I 4. to reduce the liquid pressure in conduit 8 as a function of altitude,.or some other pressure appurtenant to the operation of the system.

by any suitable linkage I6 which may be arranged to serve both as a stopcock for completely "shuttingofi the supply of, liquid'to the nozzle .sys-

tem, and also as a throttle. valvefor meteringthei fuel" in. accordance with. the fuel flow orhe'at; lib';

eration desired. One such valve is also disclosed in the aforementioned patent application of Austin G. Silvester. It will be apparent that the valve I5 may be considered a part of the fuel supply system 4.

As will'be seen from Fig. 1, liquid supply system 4 and valve I5 produce a DIESSLII'OPi in the main inlet or primary conduit Il. Liquid at pressure P1 is supplied directly from conduit I! to a manifold I8, thence through a suitable filter I9 and branch conduit 20 to the primary chamber 2I of nozzle 2. For convenience it will be assumed herein that pressure drops in the conduits and filter I9 can be neglected so that the pressure in chamber 2| of the nozzle is the same value Pl as obtains at the entrance to the fuel nozzle system, that is, the discharge side of valve I5.

The fiow of liquid from the chamber 2| to the fuel spray cone 22 in the combustor I will be described more particularly in connection with Figs. 3 tol3 inclusive.

Liquid from conduit I1 is admitted to cham-,

ber 23 in th metering device 3 (hereinafter referred to as the flow divider) through branchj conduit 24. The pressure Pi of the liquid in chamber 23 causes flexible bellows 26 to collapse to a certain extent and position the metering pin 21 relative to orifice plate 28 so astofivarythe effective area of the annular orifice defined thereby asa preselected function of the inlet pressure Pi.

. It will be readily seen from Fig- 1 that when the inlet pressure Pi rises to acertain value,

While only'one combustor I and one nozzle 2' have been illustrated in Fig. l, it;,will be understood by those skilled inthe artithat our system,

is particularly adapted. for use with. a. plurality of combustors having fuel. nozzles in-parallel and:v

supplied by branch conduits similar to 2B, 32 from manifolds i8 and 38 respectively. turbine .powerplants embodying such, an arrangement of combustors are disclosed in applications. SeriaLNumber, 506,930,.Alan Howarifiled October' 20, 1943, now Patent No... 2,479,5'73, and SerialNumber- 525,391, Dale D. Streid, filed March 7, 1944, now Paterit:2,432;359; issued-December in order to-make the description of our im.--

proved nozzle system as simple and clearv aspossible, it will be assumed that'the pressure PC in the combustor is equalto ambientatinospheric pressure For such operation, the port-34 communicating with the interior of bellows I26 ofv the flow divider-emay simplyberleft open to ambient i atmospheric pressure. However; when our. fuel nozzle system is used'in'a gas turbine'powerplant, such as? those of the above-mentionedI-Ioward" and Streid' applications, the combustion chamber pressure Po may. vary considerably from" atmose pheric'pressure,"infwhichi case we have foundit sometimes idesirablei'to bias: the. flow dividenby; communicating; the combusltion chamber pressure 1 Pc' to the interior of bellows 26,. as by meansofa conduit; 35: 5 This biasing arrangement has; a "cer irr co plex. =ff6Qt=.. H.'. he; operations. of .the system: whichrhaszibeeniifound tcjbeibeneficiarin.

For convenience the Gas I 5' connection with some of the fuel regulators with which "our fuel nozzle system has been used.

When biasing conduit 35 is connected to flowv divider}. as shown in Fig. 1, the entire system' froin inlet conduit [1 to fuel spray 22 constitutes a clos'ed hydraulic system so that a given static pressure-drop. between I1 and 22 will produce-a definite fiow rateregardless of the absolute magteri'stic is advantageous .incerta'in typesof fuel regulators. a

' However, certain other typesof fuelregulators operate moresatisfactorily inxconj'unction with our fuel .nozzle system when the biasing conduit 35 is not used-,and the interior-of .the bellows 26 is. either ratambient atmospheric pressure,v or sealed with: a certain amount of gas inside, or

evacuated and sealed. Elimination of the pressure'sensing conduit 35 has thevery considerable,

advantages of mechanical simplicity, freedom from clogging or freezing of the conduit 35 during high altitu'deoperation, and avoids the possibility of a large amount'of liquid fuel being admitted to combustion chamber I. through-conduit 35 in the event of failure of bellows 26. When the pressure sensing conduit 35. is not used, the nozzle system is no longer a closedihydraulic system this combustorv is preferably made in accordance.

with-the invention of application Serial No.

750,015,'filed May 23, 1947, now Patent No. 2,601,-'

000, inthe name of Anthony J .Nerad and assignedto the same assignee as'the present application. An important characteristic of such a combustor is that the fuel must be sprayed into it with-a pattern in the form of a-hollowcircular cone having a vertex angle which may not decrease below a preselected value, on which the design of the combustor is predicated. In Fig. l

the fuel spray cone 22 is represented ashaving an angle of about 80 degrees, which value is selected by: analysis. and experiment so that unburned liquid particles from the nozzle 2 will not be'discharged from the exit portion of the combustion chamber (not shown), and in order to obtain uniformity of temperature distribution in the hot gas leaving the combustor, and for other reasons more fully disclosed in the aforementioned application of Anthony J. Nerad. For the successful and eflicientoperation of this typeof icombustor, the fuel spray angle must never under any operating conditions to be encountered fall below-the preselected value. It is animportant feature of our inventionthat the,

nozzle and liquid supply systemdescribed herein provides a fuel spray pattern in the form of a cone having an angle which never, decreases be- .lowthis critical value, even though the flowrate and other operating conditionsvary over an extremely wideranga i The method of operation of the liquid fuel is equal to. ambient-atmospheric pressure. For.

all inlet'pressure P1 below a certain; value, the

6f. metering pin 21 of. the flow divider 3 is in a position where it'completely fills the orifice inplate 28, soethat. there is no' flow through the. flow divider into line.29. from the chamber 33 through the secondary slots 39 to the vortex chamber31 of nozzle 2, and the. entire amount of fluid discharged from the n'ozzle flows through conduits l1, I8, I9,120 to chamber 2| and through the primary slots 40 to the vortexchamber 31. When the above-mentioned value of pressure P1 is exceeded,.be1lows 2livin flow divider 3 collapses progressively and retracts the metering pin 21 so as to define with plate 28 an annular orifice through which fuel begins to flow to. the secondary slots 39 of the nozzle through. conduits 29, 30, 3|, 32-and chamber- The total fuel flow is then the sum of the flow through the respective primary and secondary slots. I

The flow characteristics of our system are more specifically illustrated in. Fig. 2, in'which the abscissa is inlet pressure Pi in pounds per square inch gage pressure, while the ordinate is the rate of flow in gallons per hour of kerosene; for one'nozzle. .Curve 38 is approximately a-true parabola representing the variation of flow with inlet pressure obtained if the flow divider meteringpin 21 is held in closed position (as shown in Fig. -1) so that .-no liquid fiows to conduit 29 and secondary slots 39, al-l'the discharge coming from the small primary slots 40-. On the other hand,

if the flow divider should be blocked in its wide open position (metering pin. 21 fully retracted), then the, combined flow through both primary and secondaryslotswill be represented by the dotted curve 4|, which i also nearly a true parabola passing through zero flow at zero pressure. Be'-- cause combustion chamber pressure Pewas as' sumed equal to ambient .atmospheric pressure,'the inlet gage pressure P1 also represents'substantiallythe pressure drop across the nozzle" with flow divider blocked open.

If now the flow divider metering pin 21 is permitted: to move freelyin its intended manner,- then sis-inlet pressure Pi increases the total discharge from nozzle 2 will increase along the solid orifice defined between metering pin 21 and plate 28 increases as a preselected function of initial pressure Pi. By a simple test it is possible to determine the axial position of the spider 43 carrying metering pin 21, as a function of the amount the bellows 26 is collapsed against the resistance of spring. 44 by inlet pressure Pi acting on the exterior surface of the bellows. Account can also Y of inlet pressure Pi and pressure PS, it is possible to design the exterior contour ofmetering pin 21 so that for any given position (corresponding to known values of thesepressures) the effective area of the annular orifice defined between the metering pin 21 and theplate 28 is of the exact size Therefore, there is no flow .With the flow divider free to move in its intended manner, the flow through the small primary slots flodoes not follow exactly the curve 38, which represents the flow when the flow divider is blocked closed; .Instead, as the flow di- 7 vider begins to open the'primary slot flow drops below curve 33, in accordance with the dot-dash curve 23. The reasonfor this deviation willbe discussed more particularly hereinafter.

From a. consideration of the structure of our liquid fuel spraying system in the light of the above-discussion, it will be readily apparent that the precise shape of the. characteristic curve '42 from the point where it leaves the parabola 38 to the point where it merges with parabola 4| can be made any desired shape by proper proportioning of the meteringpin 27,. provided only that curve 82 lies in the 'area defined between curves 38 and M.

-Curve 42 is one sample of many shapes which we have designed for particular applications. Many other desired shapes maybe readily obtained, such as for example a straight line, or a a curve concave upward or concave downward.

This is an important feature of our invention, for it permits the designer great latitude in matching the characteristics of the fuel nozzle system to the requirements of the vpowerplant and regu-' lating. system with which it is used. For instance, if the system is used in connection with a-jet propulsion gas turbine powerplant for aircraft, point 44 corresponding to a flow of approximately 5 gallons per hour per nozzle and'an inlet pressure of pounds per square inch gage may represent idling. operation at high altitude (40,000 feet or above), which is the operating condition requiring minimum fuel flow. The fuel flow for cruising operation at medium altitudes (25,000 to 35,000 feet) may be represented by the point 35, corresponding to 30 gallons per hour-per nozzle at an inlet pressure of l90pounds per, square inch. Take-off power at sea level would similarly be represented by point 46, cor-- responding to 90 gallons per hour at 365 pounds per square inch; while military power rating would be indicated at point 41, corresponding to 120 gallons per hour at an inlet pressure of 500 pounds per square inch;

Thus, for the particular gas-turbine requiring the characteristic curve 42', the fuel system would need to operate satisfactorily over a range of Vfhile, our system has so farv been described asif the combustion chamber pressure Pc were equal to ambient atmospheric pressure, it should be noted that the effect of' increasing the pressure-P0 is to shift the'curves 38, 4|, 42 and 43" laterally to the right, without changing their shape (assuming that biasing conduit 35 is used). Thus with a combustion chamber pressure Prof 100 pounds per square inch, the characteristic curve 42 would become the curve 48, which-is paralle to the curve 42, with a constant hori-' zontal distance between. It'will be obvious that this-curve drops to zero-flow at an inlet pressure P1 of 100 pounds per square inch, since at "that value there is nopressure diiierential across the nozzle 2. r i v In many aircraft gas turbines the combustion chamber pressure P0 is found to follow adefinite" 7 schedule versus the rate of fuel flow; so that when our fuel system is used in a given case; the

rate of fuel flow when plotted against inlet pressure Pi will be found to lie approximately on curve 33 at idling flow 44, to lie from 5 to 15 pounds per square inch to the right of curve at cruising flow 45,. to lie from 35 to 50 pounds per square inch to the right'cfcurve 42'at takeoff flow 46, and: from 50 to v75 pounds per square inch to the right of curve 42 at military-rating. flow 41. In each case the horizontal distance by whichinlet pressure P1 is displaced from thecurve .42 shown in Fig. 2 is exactly the combustion chamber pressure PC at the particular value of Pi (when biasing conduit 35 is used). A curve canv be drawn through the points thus determined. Our entire; system. can be readily.

pheric pressure is somewhat compensated when the biasing conduit 35 is not used. A careful mathematical analysis is required to. determine this case precisely. We have made-such analyses andhave designed a number of our fuel sys' tems to opratewithbiasing conduit 35 not con-- nected; I

Mechanically, our arrangement including thesingle flow divider 3 supplying fuel to a number of nozzles 2 from manifold 30 is far superior to other known arrangements which have some sort of metering deviceassociated with each separate nozzle. With our'nozzle sys'tem,.it is much easier to obtain unifonnperformance from the individual nozzles; and this is a very important feature of our system; A-lso,.it ispossible to change the characteristics of the entire nozzle system readily bymerely substitutinga re-designed flow divider, without changing the nozzles or other components.

Also, it is possib'l'eto obtain more precise operationwith thesingle. relatively large flow divider- 3-than would be possible with small and intricate metering devices associated with each nozzle. Further, our system is simpler and much less costly than-would b'e a system having separate devices in each nozzle;

. Fig.0 isan enlarged view of the duplex nozzle:

shown in Fig: 1 Itco'mprises a body'member' 49 provided with: a: first longitudinally arrangedrecess 21 having a threaded inlet port and-asecond recess 33 parallel to recess 2 l and having lapped, or otherwise finished so that allparts of that surface lie accurately in a common plane transverse to the axis of the nozzle. Held securely against the surface 52is a backplate 53 shown in section in Fig. '9 and 'in plan view in Fig. 11. The rear surface of the backplate is likewise carefully finished to a highdegree of accuracy so as to form good sealing engagement with the endsurface 52 of nozzle body 49=-when in assembled relation.

' It will be apparent from Figs. 9 and 11 that the chamber 2 l is in communication with a number of holes 54 drilled through the backplate 53 and arranged with their centers on an arc of a circle having itsv center at the geometrical center of the backplate. Likewise chamber 3'3 is in communication With' a series of holes 55 arranged with their centers on an arc of a circle having its center at the center of the backplate, but'having a radius appreciably larger than that of the arc on'which the holes 54 are arranged. Thebackplate 53 is also provided with two in theland 66, equally spaced circumferentially, so as to discharge in a direction substantially tangential to theouter circumferential portion holes- 56 (Fig. 11) into which project two dowel pins 5l'shown in dotted'lines in Fig; 9 'andf'more "clearly in Fig. 14. fDowls 51 may bepressed into holes drilled in the end ofthe nozzle body 49 in a manner which will be'obvious from Fig-{ 4. Their function is to hold backplate 53 inproper radial alignment with'nozzle' body 49, as wellas to make sure that the backplatecannotbe assembled in any but the proper "orientation relative to the nozzle body. a 1 .1

( While we have represented the passages through the backplate 53 as'being in the form of a series of round holes 54'and 55, respec- "tively', it will be' obvious that the row of drilled holes 54'might be replaced by an arcuate slot or similar opening; and the holes 55 could likewise bereplaced by some equivalent opening.

Associated with the front surface 58 of backplate 53 is the orifice tip 59, a perspective view of which is shown in Fig. 12. In Fig. 9- it will be seen that the rear surface of tip59lies' in a common plane perpendicular to the axis of'jthe nozzle. This rear surface is carefully finished, as by grinding and lapping, so'as to 'form good the backplate53 whenfin assembled relation therewith. A suitable cap member 60'is threaded -ontothecylindrical endof the nozzle body 49 "and serves to clampthe-tip 59 tightlyagainst backplate 53, which latter-is in turn held securely-against end surface'52 of the body-member 49. The cooperating co'nical surfaces 'IOon 'tip' 59:and cap Bil -are alsocarefully machined and polished so as to"form aliquid-tightjoint. From Figs. 9 and 12 it will be seenfthat the nozzle tip 59 is provided witha cylindrical vortex or: whirl chamber 31 extendingaxially in- 7 By reference to Fig. 12, .it will be seen that the V whirl chamber 3'lis surrounded by a concentric annular groove 65 forming the annular land 66. In Fig. 9 it will be seen that holes 54 inback plate 53 communicate with this annular groove 65. The two small or primary slots 40 are formed sealing engagement with the 'f ronts'urface 58 of of the-whirl chamber 31, at the extreme rear thereof adjacent surface 58".of the backplate. These primary slots maybe formed inany one of several different ways. They may be engraved by hand or machined by various known processes. However, because of the extremely small size of these slots, and the exceedingly high accuracy required so as to obtain the necessary control over their effective area (for purposes-of "balancing or matching a set of nozzles), we have found it most advantageous to form them by a special process, as follows. We first'impress the fiat top surface of the'land 66 with a; small coining die so as to form a depression'h'aving the proper shape in plan view and the proper contour with respect to depth, but having at all points a depth greaterthan desired. Then, in

order to reduce the effective area of the slots very accurately to the precise value desired, the entire plane rear surface of nozzle tip member 59 is carefully lapped with fine abrasives until the depthofslots was. reduced to a value "giving precisely the effective cross-section area required.- While this method of forming the small slots is of primary value because of the ease with which slots of the precise size andshape needed may be formed, we have found that it has an additional advantage in that the die-forming process produces a slot having a very smooth finish anda surface which is slightly workhardened so that it has increased resistance to erosion from flowing liquid. Thisisimportant because a very small percentage increase in'the area of the small slots, caused by erosion,- may throw a matched set of nozzles out of balance. with possibly serious results to the combustion efliciency and life of the parts of the fuel bumingsystem.

The shape of the small slots is indicated by the enlarged plan view in Fig. 13 and it may be seen in Fig. 12 how the bottoms of the slots a, the small slots'40 and the forward portion containing the conical end 62 of the whirl chamber are a" plurality of round holes 39 arranged with their axes in a planeperpendicular'to the axis of the nozzle and discharging into the forward portion of the whirl chamber 31 in a direction substantially tangential to the outer portion thereof. The radially outer portion of eaclrof the holes 39 communicates with the annular groove 61 in a manner which will be clear from Fig. 9. It will be seen that groove 61 is" appreciably deeper than groove 65; and it will now be seen why the holes 55 and 54must be arranged on arcs of different radii so as to communicate properly with the grooves 65 and 61 respectively. By carefully machining the end surface 52 of nozzle body 49, both front and rear surfacesof backplate 53, the rear surface of nozzle tip' 59 and the conical surfaces 10, and by clamping theparts firmly together by means'of the cap member 60, leakage from the chamber 2| to form of nozzle shown considered. y .1 p "The dimensions and proportions .of whirl chamber 37, the. size of the ;cylindrical portion -63 of-gthe discharge orifice, and 'the'size and number of the secondaryorlarge slots '39,are determined in accordance with well-known prinf'ci'ples ofyortex fluid flow, which need not be i our.. invention.

Jchamber iH, or from 'gIOOVe 3:65 to groove 'iorzto'whirl chamber-3'! is prevented; Foriconvenience-the term slots will :"herein forthe orifices discharging into the whirl .chamber' STU-but this term should be considered to. include grooves like those'shown at 40, round 'holes'ias shown at 39,. and :orifice passages of other suitable shapes; Y The .large slots 39. rnay be'rzconveniently formed by drillin and. reaming-operations before the conical surface Hi of be used the nozzle tip v59 i5 machined off. Because of theircomparativelylarge size, these holes may be made with the accuracy required by careful :drilling and reaming; operations. The exact size of therlargefl slots is notias important as in the .case of the small slots; and the percentage error involved in a careful drilling and reaming -:operation' will ordinarily be within the allowable ilimits; 'Also :it is unnecessary to streamline the entrances .to the large slots.

' The hydraulic characteristics of our'improved in'Figs. 9-13 will now be discussed herein detail in orderv to point out While-the number of, large slots 39 used is not critical, we prefer to use four because that num- .ber inmost cases will give the capacity required with-a hole of a size reaso-nablygeasy to drill and ream, and will give a symmetrical spray. In certain extreme cases, it may be desirable touuse more than four large slots. Reducin the numi bcr of holes belowvfourmay result in holes, of

suchlarge diameter that the axial length; of the --whirl chamber would be increased unduly, and ,rnay also jresult in an unsymmetrical spray; whereas increasingthe number above four .may

result in the diameter of the hole required falling below asize which can be easily formed-by drilling'and reaming, and requires more machine Work, I

.Inorder to obtain the greatest possible range oflow rates with asatisfaetory spray, it is nec- These; dimensions and propor- .-.tions are'determin'ed by the maximumfiow which .isdesired, the spray angle desired at maximum fiow; and the maximum pressure furnished to theinozzle by the liquid supply'system.

I essary'complexityls added'gto the nozzle; and :each slot willybe smaller and-therefore more .dif-

ficult to form correctly; also more susceptible to -cloegingjvby dirt; We. h vefioundj no ca ewhe it was necessary to use more than two small slots.

. j,We have 'found'through analysis and experiment that the optimum diameter of vortex chamber 31- in th duplexnozzleas developed by us is between Zand 3 times the diameter ofthe discharge orifice (5-3, the optimum ratiobeing from 2.4 to 2.5. The greatest range of flowuates with a satisfactory spray will be obtained ifthese exactproportions are used. 1 g

' We have also discoveredthat best results are obtained when the axial length of the ,vortex chamber 31 is as short aspossibleq It will-be noted in Fig. 9 that .the plane of the small slots All and their supply ;groove'65 is located as close as possible to the plane of the large slots 39 and their groove 6-7. It should be understood that the small slots are arranged ,to produce rotation'; of the liquid in Whirl chamber 31 with the same direction of rotation-as that producedby the large slots 39,- so'that the effect of the two :sets of slots in producing a high rotationalvedischarge end of the slot will be completely stable essary that the smaller primary slots be of ex- .tremely-small cross-section are'aso that at the; lowest rate of'iuel flow the liquidcan be in jected into vortex chamber 31 at the highest possible velocity. The smaller these slots are, however, the greater isthe care and. accuracy vrequired in order to produce a cross-section area within allowablelimiteof percentage deviation from the exact value desired. The sensitiveness with which the rate of flow in one nozzle of a matched set responds to a small error in the area of the small or primary slots is very'great,

, and therefore the sizing of these slots is ex tremely critical from the standpoint of the Fbalancing of such matched sets of nozzles.

have found that balancing aset of nozzles is greatly facilitated by locating the small slots on the plane rear face ofthenozzle tip in order that the tip may be lapped and these slots thus re duced to the, exact'area desired; At least two 7 small slots arenecessary to insure a symmetricalspray. If more than two are used, unnecsary because of the excellent coining die method. I

in direction for all rates of flow and, particular- 1y, will have a minimum of turbulence and internal friction. For thesame reasons it has been found necessary to provide an extremely smooth finish on the surface of the small. slots. All of these requirements-may readily be 'fulfilled :by the above-described method of forming thesmall slots with: a coining die. I ofucourse, additional polishing maybe done on'the surfaces of the small slots to obtain an, even finer finish, but we have generally found this unnecesfinishgiven by. the

Another most important factor affecting- Eth c hydraulic performance of this nozzle is the shape of the flare 64, which formsanextensionof. thegcylindrical orifice BS' inthe boss .1I.',The details of, this flare are shown :,,to1a'ni enlarged scale in Fig. 10. The preciseshape of thecurved flare is not particularly critical, and theiarcfi l may be part of a circle, an el1ipse,.parabola,

.hyperbola, on any compound combinationof such curves, provided the following factors are taken into account. The curve fid must form a very smooth continuation of the cylindrical-bore E3. The surface 64 must have no abrupt changes in rate .of curvature, And finally, surface -64 must be shaped so that-a tangent to it at the sharp corner F2 and lying in a plane through the axis of the orifice will form an angle-l3,

relative to a plane normal to the axis of-the nozzleyhaving a value 7. within certain definite limits, .asexplained more in detail hereinafter. We have discovered that the surface smoothness 0f the orifice surfaces 63Q1M'has an extremely important effect upon theperformance of the condition obtained at I (point 41 in Fig. 2). With the inlet pressure cornozzle. For this reason these surfaces are provided with a very high polish, by any suitable known method.

'flow represented would actually be thatobtained with the nozzle directed vertically downward,

so that gravity would cause no deflection of particles in a direction transverse to the axis of the spray pattern.

Figs. 3,4 and represent the spray conditions obtained with high, medium,- and low rates of flow, respectively, with a duplex nozzle having a plain cylindrical discharge orifice with no flared portion. Fig. 3 represents the spray which might be obtained'at the point 41 in Fig. 2, that is, with an inlet pressure P1 of about 500 pounds 7 per square inch and a flow rate of about 120 gallons per hour. Fig. 4 and Fig. 5 represent the spray obtained at points 45 and 44, respectively. Figs. 6, '7 and 8 indicate the improved performance obtained with a nozzle identical to that shown in Figs. 3, 4 and 5, with the same rates of flow and otheroperating conditions but having a discharge orifice with a flared portion 64 designed in accordance with our invention.

As noted above, Fig. 3 may represent the spray full military power responding to point 41, the whirl chamber is nearly full of liquid, with only a very small air core 14. The liquid leaves the sharp annular corner 15 with a considerable rotational velocity, each particle of liquid tending 'to travel in a straight line after leaving the corner I5, so that the initial portion of the conical sheet of liquid I6 is a hyperboloid of revolution. A short distance from the-exit edge 15, the spray pattern is substantially indistinguishable from a s'trai'ght- 'sided cone -having a vertex angleof approximately-60 degrees. The value of the vertex angle obtained with an unfiared orifice as" shown in Figs.

3. 4 and 5 will be referred to herein as the intrinsic angle, defined as that angle produced with a plain cylindrical sharp-edged orifice with given inlet pressure, rate of fiow, and other operating conditions. This angle can be calculated from known principles of vortex now, having given the pressure at the small and large slots, respectively, the effective areas of the slots, the size and shape of the whirl chamber until at some locationindicated by the irregular line 11 the continuous sheet has completely broken into a discontinuous spray indicated by the dotted lines 18. The location of this transition plane 11 varies somewhat with the pressures on thesmall and large slots. Furthermore the distinctness of this plane varies considerably;

becoming less definite as the pressures increase.

Fig. 4 represents the spray conditions at the point in Fig. 2. Because the large-slots at this condition are somewhat throttled by the flow divider, the size of the air core 14 has consheet therefore bends inward and collapses.

effect is aggravated by the fact that at low pressiderably increased; andthe spray angle has increased to'an intrinsic value of 110 degrees. The

transition plane '1'! is more definite than in Fig. 3.

Fig. 5 represents the unsatisfactory spray condition obtained for a plain cylindrical unfiared orifice if operated with the low flow conditions represented by the point 44 in Fig.2. With these conditions, the intrinsic angle has increased to 125 degrees. sharp edge with this intrinsic angle but almost immediately begins to collapse, to form a node 19 defining a somewhat ellipsoidal bubble and usually part of a second bubble 8|. As the pressures and flow are varied in this region'of operation, the transition'plane 1.1 will move axially along the flow pattern, and may occur at various locations either in bubble 80 or bubble 8|.

The hydraulic process which produces bubbles such as 80 and BI in Fig. 5 is fairly well known and such bubbles are familiar to those skilled in this art. This phenomenon is caused by surface tension in the liquidthat is, the force existing in a film of liquid which tends to contract the In the case of vortex fuel nozzles, bubbles such as those shown in Fig. 5' will always form at a low fiow rate'and low pressure if a flared orifice is not used. At these conditio'ns,-the solid sheet is traveling at a 10w velocity and the surface tension has considerabletime in which to act upon the sheet in a short distance. The The sures and flows the-transition plane of breakage "*moves farther away from the discharge orifice than at high pressures, thus giving'the surface tension still more time and distance in which to collapse the sheet. The transition plane 1'! tensile strength of the liquid. Although use of a duplex type nozzle greatly postpones the formation of the bubble, as the rate of now decreases the bubble does eventually appear as shown in Fig. 5'; This is the principal typeflof failure'of the spray when a duplex nozzle with a plain cylindrical discharge orifice is used.

The spray condition represented in'Fig. 5 is completely unsuitable in a high performance combustor of the type used in gas turbine powerplants, and it is aprimary requirement of a fuel nozzle for such service that the bubble be not formed at any point within the normal operating range of the combustor. The reasons why such a spray pattern is unsatisfactory will be apparent from a consideration of the "characteristics of the combustor l, as more specifically defined in the aforementioned application of Anthony J. Nerad. A most important characteristic of our improved nozzle is that it permits operation over a much wider range of pressures and flow rates with spray angles and spray velocities sufficiently large to prevent formation of the bubble."

Fig. 6 shows the spray pattern produced by the flow conditions of Fig. 3 when the nozzle is provided with a flared portion 64 designed in accordance'with our invention. As 'in Fig. 3, the whirl chamber is flowing nearly full with a very small air core I4. The primary effect'of the flared orifice portion 64 is to increase the spray angle to 80 degrees or vmore, as compared with 60 degrees for the unfiared orifice of Fig. 3'. This effect is thought to'be due to the tendency of the liquid towetthesurface of the orifice, "plus the The liquid sheet 16 initially leaves tensile force or cohesion effect existingbetween the film of liquid which wetsthe surface of the orifice and other adjacent portions of theliquid.

low the orifice flare all the way to the sharp corner 12 but breaks away from the flare at an intermediatelocation, from which the liquidcone leavesin approximately straight lines tangent to the surface of the fiare.- Here the liquid does fIlOt form as solid a conical sheet as'at in Fig. "3. With the 'conditionsrepresented by Fig. 6 the velocities in the spray pattern are high and there is considerable turbulence, making the cone it] highly disturbed and rough, with atomization be: ginning even before the liquid leaves the surface of the orifice flare.

In order that the spray cone will not break away from the flare suddenly (causing a sudden decrease in spray angle) and will not suddenly ad-- so forth. A'discussion of this matter in further detail is thought unnecessary in defining the present invention. It may be'noted, however, that the contour shown in Figs. 9 and 10 has been developed by us for use in combination with the nozzle shown in those figures and has been found satisfactory. It consists essentially of a simple circular are having a radius of the order of one "to one and one-half times the diameter of the cylindrical portion 63 of the orifice. This arc'is of course tangent to the straight cylindrical bore53.

. Fig. 7 represents the flow with conditions as at point in Fig. 2. Here the air core- M has in- .creased,.as noted in connection with Fig. 4. Be-

cause the pressure and velocity arelower, the solid conical sheet of liquid 16 follows the orifice flare 64 nearly to the sharp cut-off corner 12; with the result that the spray angle increases to v160 degrees, as compared with the intrinsic angleof 110 degrees.

As shown in Fig. 8, the effect of the: orifice flare 64 is most pronounced at the low flow conditions represented by the point 44 in Fig. 2, the

spray angle having increased to very nearly 180 degrees. With this large angle the tendency of the solid sheet of liquid I8 to, form a bubble is completely overcome and a satisfactory atomized spray .18 is produced.

While the reason for the annular cusp 82 shown in Figs. 6, '7 and 8 is not definitely known, it is believed to be related to the fact that the boundary between the laminar layer of liquid adjacent the backplate 53', and the turbulent liquid in the whirl chamber slightly forward of the backplate, lies in a'plane passing through the cusp. 1

We have discovered that friction is a most important factor affecting the ability of a duplex nozzle to'perform satisfactorily over the extremely wide range possible'with our improved nozzle. In order to obtain the outstanding results achieved with our nozzle,'it has been found necessary to observe carefully the following factors inthe design: '(1) The small slots' ifl must have a relatively small cross-section area, must be as short ini-,length.-aspossiblepmust be well 16 streamlined (particularly at the entrance to the slots), and must have an exceedingly fine surface finish. (2) The whirl chamber 3! .must'haveran axial length as short ascan, conveniently be obtainednmst have-a diameter from 2 to S-times that of the discharge orifice E3, and-.mustilikewise have a good-surface-finish. *(3) The discharge orifice 53 must also have as small a diameter as possible consistent withthe minimum intrinsic spray angle required at maximum flow. .(4') Thailand orifice 53, 64 mustgalso have'an'exceptionally fine surface finish. Unless allthese design features are provided, friction may have an e:-:ceedingly'deleterious effecton the performance and range of the nozzle; j I g The importance of'the sharp cut-off edge 12 and the angle which the terminal portion of the flared surfaceM makes witha plane perpendicular .to the axis of the nozzle may be seen from a consideration of Fig. 8. The sharp edge 12 is necessary to enable the solid liquid sheet It to leave. the orifice surface cleanly with a definite break. Even with this sharp "corner provided, the solid cone '16 has a tendencyto deflect slightly backwards towards the nozzle after leaving the edge -12. It has been found that if tangents to the flare '64- at the sharp corner'i2 form an angle 13 of'less than 2 degrees (see Fig. 10), thennpthe solid portion of the spray cone 1-6 may under :certain operating conditions deflect backward sufficiently to strike adjacent portions of the nozzle or the rear wall of the combustion chamber surrounding the nozzle. This is damaging to good atomization and eiflcient combustion and therefore must be avoided. On the other hand, we have-found angle 13 must be held within a range;of from 2 to 15 degrees, being represented in Fig.-l0 :as

approximately 10 degrees. 1

While a full statementof thereasons would require much space, it has been determined by extensive testing of duplex nozzles that the-pervformanceof this particular type of nozzle isim proved by the addition of a flared discharge surface 64, designed in accordance with our invention, to a degree which'is far, in excess of that which might be-expected from a consideration of the influence of the flare in itself. An important consideration is that the flare permits the attainmentof satisfactory spray angles with small or primary slots of a cross-section 7 area appreciably larger than those-which. must be used to obtain'a given range with an'unflared orifice as-shown in Figs. 3,4 and 5. Therefore,

for a given range the small slots can be formed.

more accurately and easily and are 'lesssubject to being plugged by'dirt particles'in the fuel.'

The somewhat obscure, but very important,

way in which the use ofiour flared orifice adds to the range of flow rates'over which a satisflared orifice'is used, the intrinsic spray'angle at that maximum condition may be made less than the required and the 'flare' may then be so designed as to increase thespriayfl angle to 80. For example; the intrinsic 'spr'ay" angle may bemade 60,as in Fig; 3, and the flare may be designed to increase that 60 angle to-80, as in Fig. '6." The advantage of this is thatthe orifice '63 can be made smaller with the 60 intrinsic anglejand when the orifice is smaller, the quality of the spray when'operating on the small slots alone is considerably improved because friction in the vortex chamber is considerablyreduced, as explained hereinafter, and the spray willbecome unsatisfactory at a lower flow rate; An unsatisfactory spray is'one in which-the size of the liquid particles is great enough that incomplete combustion results. When particle size-increases to this degree, it is said that the spray' -fails.""'Thus the range of the nozzle is extended when our flared orifice is used, because the orifice diameter can be made smaller than it would-otherwise have to be. The reason' tha-t friction in the vortex chamber is reduced with a smaller orifice'when operating on the small Slots alone is that the velocities in the vortex chamber are kept lower and the pressure is kepthigher. The mechanical energy in the liquid is thus better conserved up to the orifice itself, at which point the pressure in the liquid is converted efliciently into velocity. Thereforethe liquid leaves the nozzle with a higher velocity. This has been discovered by analysis and verified by-experiment.

The amount by which the flare 64 can increase the spray angle at maximum flow depends largely on the radius of curvature of the flare. The larger the radius of curvature (that is, the more gradual the flare and the larger. the flare) the morwill the spray angle be raised. Too large a flare, however, will cause excessive friction at low rates of flow, so that there is an optimum size and radius of curvature of the flare for each new design of nozzle. This optimum can be calculated roughly but can be arrived at more precisely only through experiment.

In summary, the three particularly beneficial effects which the flared orifice produces in combination with a duplex type nozzle are that it (1) preventsthe formation of thebubble within the desired wide range of operation; (2) increases the degree of atomization throughout the operating range; and (3) makes a greater range possible because it permits the discharge orifice-to be made'smaller. We have found that by using our flared orifice, approximately twice the range offiow rates can be traversedwitha satisfactory spray, as compared with the range obtainable with a duplex nozzle not having the flared orifice.

-We have also discovered that an important improvement in the performance of our duplex nozzle, from the standpoint of stability and balance,

is obtained by locating the small slots 40 at the rear of the whirl chamber 31, with the large slots 39 discharging into chamber 31 at a location intermediate the small slots and the discharge orifice 63.

It will be obvious to those skilled in the art that many modifications of the precise mechanical construction of the duplex nozzle are possible. However, we have described herein a construction which we consider particularly advantageous from the standpoint of ease and cost of I manufacture with the characteristics required for efficient operation under the difiicult conditions encountered in aircraft gas turbine powerplants and similar applications.

The data on which the above discussion and the accompanying drawings are based was obtained using liquids such as kerosene and gaso- 18? a line, but'areequally validfor other liquids of similar characteristics. Heavier oils will behave in-' the same'manner if heated so as to lower their viscosity to a value approaching that of the liquids mentioned; I I j.

' The duplex nozzle described "herein and our new method and apparatuszfor operating it.re"- sults-in aliquid fuel spraying systemof great versatility, permitting adaptation to many different .powerplants havingwidely diverse requirements,

and capableof producing a satisfactory atomized sprayv pattern in the form. of a hollow cone with a preselected minimum vertex angle, over an extremely wide range of operatingconditions.

It has been found. that the .nozzle described, with thefiow divider for metering the fuel to the secondary slots, is particularly advantageous for use in gasturbine powerplantsfor-the propulsionofaircraft. The spray pattern produced is well atomized, has satisfactory spray-angles, and is stable under, the most difiicult operating conditions. With our nozzle system, it has been found that the 'combustor flame is much less likelyito blowout at highaltitudes, and also when "the; throttle is suddenlyreduced from a high fiowto alow ,fiow position or vice .versa. The ability to thus vary the throttle position suddenly-contributes to the maneuverability of .a military fighter plane, permits sudden descent with minimumpower output as well as frequent and sudden reduction of powerplant operation to the idling condition and rapid acceleration-to full power. Our system also makes possible a much loweridling speed and power which are important'in aircraft jet-propulsion gas turbines. Because of the stable and uniform nature of the fuel spray pattern, combustion efficiency is excellent. over a wide range, with the result that the fuel economy of the powerplant is improved and the operating range of the aircraft increased. Powerplant life is prolonged by reason of the lower and more even temperatures resulting from the absence of sudden, non-uniform supply of "slugs of fuel. It has also been found that use of-our system facilitates the initiation of .flame in a combustor, for instance if it should happen to blowout. at extremely high altitudes or under other difficult operatingconditions. Our system also makes possible much lower gas temperatures when starting the gas turbine, and more rapid. accelerations in starting without excessivetemperatures.... T

What we claim. as new and desireto secure by Letters Patent of the United States, is:

1. In a duplex type fluid spraynozzle, the combination comprising a body member I defining therein at least two independent fluid supply passages having end portions defining independent discharge openings in an end wall of said body member, a backplate having a first surface for sealingly engaging said. end wall and form.-

ing at least two passages extending axially through the backplate for registering with said independent openings, a nozzle tip member having a second surface for sealingly engaging said backplate and defining therein a substantially cylindrical whirl chamber extending forwardly from said second surface and communicating with, a discharge orifice formed therein, said tip member also forming at least two radially spaced annular grooves extending forwardly and axially from said second surface, said tip member also forming therein independent primary and secondary slots communicating with the whirl chamber and with said annular grooves respectively for establishing at least two independent aromas flow pamgesnbrough; the nozzlmsandimeens se the;tipmemberaandahaclcplate :i-n sealin engagement-and in iregister witlrrachnther'nnd witha saidzendrwalllsurface ofrthe'body member;

2. In a duplex type fluid spray HOZZIGHCHBKSQE- bination comprising axhody member haningza ,cy- 'li-ndricariendrzpontion and" forming therein; separt-ate "first land 'is'econd .ifluid 'pas'sag'esl having dependentdelivery openings in :end surface of said :end portion, a backplat'e hav-ing :a face and also halvinga rearface :for :sealingly engaging said: end surface, said :backplate forming first and second passages extending therethrough tor.registering-with said-respective-openings; a nozzle tip ,nreniber having a rear surface for 'sealingly engaging' the front surfacesof :the 'bacleplate'and 'forniingwa' coaxial whirl chamber ekt'ending forwardly: from said' rear surface and in communication with a dischargef-orifice in: the front portion'offthe-tip member, said tip mem ber for'ming-a pair'of spaced concentric annular grooves extending forwardly from the rear stir-- faee the-reofffor registering with the respective passages in the backplateand also for'rhingfa't least -two primaryslots equal-ly spaced circumier entially': and extending forwardly; from the rear 'su rface thereo fand b etwe'en'theinnermost g ro'ove and theperiphery of said whirl chamber, said tip m'em-brfalso for-mingtherein a pl'urali secen aar sl'ot's the form 'ofroundhofle's I (118- posed between the' pri'maryslots and thedis charge' orifice' and establishing communication a between theoutermost groove andthe-periphery of said whirl chamberfor dischargi-ng fluid theretoin a substantially =tangential direction and in the same direction ofrotation as-thatdischarged from the primary's'lots, and means securing said tip member andjthe backpl at'e--in sealing-engagement-and inregister with each other-and with theend -surface ofjthebodymember. v

a fluid spray'nozzle, the combination of a; body member having-a plurality of independent fluid supply passagesftherein with separate discharge openings in, an end surface of the body-'member and in ,communication with the respective passages therein, said end wall having fafirst surface lying in a plane, transverse to; the axis-of the nozzleywith portions of the surface entirely surroundingeachv of said dischargeopenings, abackplate having a second plane'- surface for sealingly engaging said; first surface andiorming a plurality oftransverse passagesf extending-therethrough for registering with the respective discharge; openings, the backplate also having a third surface witlrPor- 'tions entirely surrounding the other ends of the respectivepassages therein, an orifice tipmember forming therein a swirl chamber of substantially cylindrical cross-section in communication with the orifice and having a fourthsurface for sealingly engaging said third surface, the tip member also forming independent primary and secondary slots therein for registeringwitheach of :said transverse openings, said primary :slots being angularly and-axially spaced from said secondary slots and "with the primary and secondary slots in communication with the .swirl chamber, and means securing the body, backplate, and tip member together with the first, second, third, and fourth surfaces in sealing engagement and with the respective passages and openings in registerto definea plurality of independent fluid paths through the nozzle;

4. In a duplex type atomizing nozzle for spraying liquids, a nozzle tip member having a whirl chamber of circular cross section and a discharge orifice coaxial with the whirl-chamber, said discharge orifice including a rearward portion com.- municatingwith the whirl chamber and aim?- ward flared portion, said flared portionmerging smoothly with the rearward portion and curving gradually outward and terminating. at .a sharp annular cut-ofi edge, the slope of said flared surface at the cut-ofiv edge being less than 15 degrees with respect to a plane transverse to the'axis of said tip member.

'5. In a duplex type atomizing nozzle forspraying liquids, a nozzle tip member having a cylindrical whirl chamber and a discharge orifice coaxial with the Whirl chamber, said discharge orifice including a cylindrical rearward portion one-half to one-third the diameter of the whirl chamber and communicating with the whirl chamberand a forward flared portion, said flared portion merging smoothly with the rearward :portion and curving gradually outward and termi nating at a sharp annular cut-off edge, the slope of said'flared surface at the cut-off edge being greater than two degrees and. less than 1-5 dc.- greesxwith respect to a plane transverse to *the axisof the tipmember. 7

DAVID C. .IP SEN. I CHARLES D. FULTON:

REFERENCES CITED The following references are of'record in the file of'this patent: I

UNITED STATES PATENTS Number Date Name. 2 ;044,091' Martin Juneid, 19.36 2,044,697 Huss June 16,1936 2,044,720; Fletcher .m June 16,1936 2110,365v Imfeld- Mar. 8,, 1938 2,303,104 Abbey Nov. 24 1.942 2,313,298 Martin et a1. Mar. 9, iii-94,3 2,373,707 Peabody Apr; 17,1945 2,374,290 ,Johansson Apr; 24,1945

FOREIGN PATENTS V Number Country Date: f 16,917

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