US2711214A - Burner for heavy fuels - Google Patents

Description

United States Patent BURNER FOR HEAVY FUELS Ward J. Bloomer, Westfield, N. J., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application December 24, 1952, Serial No. 327,892

4 Claims. (Cl. 158-4) Thisvinvention is an improvement on my prior inventions relating to fixed centrifugal or vortical fuel burning as generally set forth in applications for Patent Serial No. 66,445, filed December 2l, 1948 and Serial No. 98,976, filed lune 14, 1949, now Patents Number 2,560,074 and 2,560,076.

The present application is a continuation-in-part of my application Serial No. 151,023, filed March 2l, 1950, now abandoned.

ln the aforesaid cases I have disclosed an improved type of burner for various fuels such as oil, gas and pulverized solids, such as coal. In general, a vortex of air is established within an open-ended, annular or cylindrical tuyre by forcing the air at a relatively high velocity between the substantially tangentially disposed .blades forming the tuyre wall. The fuel is introduced into this vortical column in either of two satisfactory ways. In one form the fuel is maintained in a reservoir surround ing the side wall of the tuyre adjacent the closed end and the incoming air passing over the fuel, entrains the fuel and carries itvinto the tuyre. Alternatively, a fuel distributing means is provided which extends through the closed end of the tuyre, and being spaced from the central axis, the fuel is introduced directly into the vortical column. This assures uniform distribution and avoids the resistance to the introduction of the fuel, by the rapidly rotating inner wall of the column. `The atomization of the fuel and thorough dispersion into the column is completed in the tuyre and the combustible mixture is then discharged into a combustion chamber or throat spaced from the tuyre. throat serves as a radiant chamber to maintain uniformity of combustion, and the tuyre due to its spaced position and the flow of air through it, is maintained at a relatively cool temperature.

My present invention relates more particularly to an improved construction of burners which has a greater range of operation with respect to fuels in that it is particularly adapted to burn not only the gaseous and distillate fuels but also the heavy residual fuels which have a higher carbon ratio than distillate fuels. The burner is particularly effective in burning materials such as asphaltic residues. Asphalts, particularly from- Venezuela deposits are not only difficult to burn but they have a further complication in that the ash is approximately 50% vanadium pentoxide (V205). The ash skeleton from a droplet generally forms a liyash which is not` only externally wet and sticks to the boiler and superheater tubes but also attacks the brick work forming eutectic mixtures which tend to melt down the brick. Furthermore, the sticky vanadium slag grows in thickness until heat stresses crack the coating from its bond to the tubes forming flakes and clots which heat and soften and slide around the tube surface. These form obstacles in the gas stream and eventually a hard and clinker like mass throughout the tube bank forces a shut down for cleaning or retubing. It is recognized that slag deposit is caused primarily by particles of unburn'ed or incompletely The combustion chamber or Patented J une 21, 1955 burned atomized oil and particles of unburned unatomized oil. Y

My burner is particularly-satisfactory for combustion of such asphaltic residues which exist in very large quantities in parts of the United States and particularly in the northern part of South America. By the proper introduction of the melted asphalt into the vortical column within the tuyre, I am able to obtain n an atomization such that the oil droplets are burned as a vapor so completely in the refractory throat of the burner that the particles of flyash have a size of the second order of magnitude i. e. infinite ratio of surface to mass, zero inertia and gas-*like properties. They are completely Aairborne and are not thrown out in any deflected gas' stream. With their infinite surfacennass ratio the iiyash particles radiate extremely readily to tube surface and drop in temperature so fast, as to be very much colder than the gas carrying them. As operated in my burner the flyash, if any, has a micron sizeof 100 microns or smaller ,and it does not build up slag deposits. Furthermore, there is no flame impingement on the brick Work or tube surfaces, as there is no flame issuing from the burner throat, the intimate degree of atomization afforded by the vortex of the burner Y attached drawings in which:

Fig. l is a substantially vertical central section through a portion of a furnace showing the generalarrangement and location 0f the burner.

Fig. 2 is a diagram-matic central vertical cross section of the burner.

Fig. 3 is a front elevation of the burner shown in Fig. 2.

Fig. 4 is a partial vertical cross section of the burner with a modified form of tuyre skirtor baille.

As a preferred form of embodiment my burner is particularly adapted for installation in the refractory side wall 10 of a furnace which may be a boiler, oil heater or other heat absorbing unit. Mounted on the side wall of such a furnace is a so-called burner plate 11, such burner plate carrying additional refractory having an opening 12 formed into the shape of a cylinder to receive the windbox or enclosure 14 and also other refractory formed into a cylindrical combustion chamber 15. The windbox extends rearwardly into an air duct generl` ally indicated at 16 which is adapted to be connected to a source of air under a slight pressure, such air being preferably preheated for thecombustion of asphalt and other very heavy fuels. The windbox 14 also extends forward nearly into contact with the refractory 15a which forms the rear Wall of the `combustion chamber.

The burner assembly includes a tuyre 18 of generally cylindricalshapbeing open at one end and having a frusto-conical plate 20 surrounding the orifice. The side wall of the tuyre is provided with a plurality of generally tangential shallow vanes or blades 22 extending throughout the entire length of the tuyre. For economy, they may be stamped out of the tuyre wall, but it will be understood that they may be separate blades, and they may overlap, or be streamlined as desired. These blades form a plurality of elongated substantially rectangular air inlets 23 disposed between the adjacent blades 22. The rear of the tuyre is closed by an end wall 24.

The face plate 20 of the'tuyre is preferably provided with a double row o'f small openings 20a surrounding the orifice for'the 'free passage of air'from the windbox 14', such air passing across the .face plate in rear of the refractory 15a whereby the face plate 2li is kept cool. The truste-conical face plate 20 is integrally mounted vto the edge of the tuyre blades and is freely movable with the tuyre in the ,windbox llll so that the entire burner assembly as wshown in Fig'Z may be moved into and out of lposition as desired. The windbox 14 has a shoulder llaagainst which a packing ring 25 is placed so that the truste-conical face plate makes a substantially gas tight seal at the edge of the windbox 14.

The tuyre lLSlrnay be provided with a dual fuel supply. V'For the feed of a heavy liquid such as asphalt, I prefer to use a fuel distributing means` consisting of a pluralityof tubular nozzles 3i) which project'through the closed end24 ofthe tuyre about 1/2 inch and are conveniently 'chamfered at a 45 angle with the vertical. In each case -the lowermost edge of the nozzle projects furthermost into the tuyrc, These nozzles are fed from a common distribution ring 32 which in turn is supplied from afuel line 34.

The six fuel feeding nozzles 3i) extending into the closed end of the tuyre 18 have their discharge openings Vspaced uniformly a substantial distance from the closed end wall 24 and from the oppositely disposed slots 23 of the side wall, the saidopenings defining a plane perpendicular to the longitudinal axis of the `tuyre and being uniformly spaced on a common circle.

ln vaddition. Vl prefer to usea secondary fuel feed distributing pan orreservoir 46 of a cup shape closely titting the side wall of the tuyre and spaced a small distanceaway from the closed end 24 of the tuyre. As shown in IFig. 2 the sideof the pan 46 embraces the edge of the tuyre blades in such a manner as to form a series I used siniultaneouslyor alternatively and either liquid or gaseous fuel may be ffed in either system.

The operation of the burner for burning the gas ordistillate fuel includes Iforcingtheair fromthe duct 16 into the wind'oox or enclosure i4 and thence across the blades andfinto the-combustion chamber l5.

The continuous introduction of air through the convergeht air paths establishes a rotating mass, the centrifugal effectof which is to establish a relatively dense shallow layer generally indicated at X adjacent the side wall of the tuyre, the inner wall of such layer being substantially parabolic with its vertex below the closed end of the tuyre 24. This layer may be considered to be a substantially hollow rotating column which is cylindrical on the outer wall and truncated parabolic on the inner wall or surface. The fuel is introduced to this layer to be entraincd in the rotating air mass and is given a spiral and helical path in the tuyre before being discharged with air as a combustible mixture into the combustion zone. Y

Normal velocities of the entering air are approximately 70 ft./sec. The static head of air is thus converted to rotational energy so that inside the tuyre the air is caused to rotate in forced vortex motion as a parabolic of revolution. Due to the high Vvelocity-of the air and the rapid rotation of the mass, the column is open throughout its length and-has-a'substantial vacuum in the central portion forming a line of force :into Athe end of the tuyre perpendicular tothe closed end 241 Itis observed that the column actually forms a circular intercept with the .center of the end wall as indicated at 37. 'it is important for my purposes that'the velocity of the air be such Vasrtotmaintainthis columnopenrthroughout.v '-Thefuek air thus discharges as an annulus solely adjacent the side althoughthisresults' in a veryY substantial pressure drop.V

The greater the velocity, the tighter or more nearly vcylindrical is the vortex and thus the greater the fuelpath and the greater the shearing and mixing. With 70 ft./sec. which is preferably used, l estimate theelect of the centrifugal force to be about 600 times gravity, with a 6 in. diameter tuyre.

An outstanding characteristic .of this vortical atomiza- Y tion `is-that combustion efficiently increases with an in# crease in velocity orring rate. ,Firsthigher flame tem-k perature improves ignition and 'flame stability, and second, a` change inthe force balance increases the ratioof outward centrifugal force to inwarclviscous drag force resulting in a further decrease inoilparticle'size.

It has` proved `to 'be a characteristic of ,the burner that when the air'pressure drops, the oil pressure indicatoral-l ways shows an increase. tex draws the v,oil from thefeed nozzles 30 to thewhirling ring 57 and ywhen `the central vacuum lessons, the oil` is not pulled so strongly. 'This has the advantage that the*k i" manifold pressure required for multiple burners is only that needed-for accurate throttlingi Control may thus be readily accomplished `by conventional pressure control instruments reset by ,thetemperature ,of a coil outlet. ,Calibrated Vorifices will ofcourse b e inserted in the various feed lines to evenly proportion a similar amount of oil to each burner.

The burning zone is within the throat or combustion chamber `-1Sso `spacedfrorntheend of rthe tuyre as .to relieve the tuyrefof-the necessity for withstanding combustion temperatures. The spacing ofthe combustion zone l5 from-the mixing zone of thevtuyre is accomplished by maintainingthedlow of air betweenblades in opposition to the centrifugal effect of the column whereby the fuel` air column VXmoves outwardly into the throat or combustionchamber. By properly arranging the blade angle Vand bymaintaining lthe 'desired air inlet velocity and by introducing'thefuel adjacent theclosed end of the tuyre thereis an intimate dispersion of the 'fuel in the air. `In addition heat from the combustion chamber tends to `'ra.

-diate into the substantially open column to produce'a `highly effective partially heated fuel air mixture 'by the',

time it discharges'` into the combustion chamber.

The tdistance ofthe combustion zone within the refrac-V tory :throat 15 is ycontrollable Vthrough variation o'frthe t 'relative` dimensions of the tuyre and-throat, the lratio of tangential toY axial `velocity of the air-fuelmix as vit/enters the combustion chamber, the linear velocity of this mix`` ture as it emerges from the tuyre annulus. It is also de pendent-onthe fuel-air ratio. This ratio is afunction 'of the airpressure in the windbox 14 and of theinitial velocity of the air column impressed upon the burner before the air column reaches the entrainment zone adjacent the closed end-of thetuyre It is also dependentupon'the ratio of the ydiameter ofthe tuyre -18 to the -length ofthe blades V22. t Bor example, doubling theV tuyre diameter and halving the blade length, while having the same-blade area, pressure drop and air capacity in the burner, 'pro-k Y vides four times the cross sectional area in the tuyre out-L let orifice. For this reason :the linear velocity is reduced in square root proportion to the 'increase in diameter and vthe pattern of the combustion zone wouldthus be varied Y accordingly b y variation of the diameter-length ratio. Or-

:dinarilyl 'find thatpa ratio ofxgreater length than diameter is the mostadvantageous.foratomization due to thepro- The violencetof the center vor-z portionately greater energy for atomization which exists with the smaller radius.

The effect of the rapidly rotating vortex within the tuyre 18 on liquid fuel from the nozzles 30 will thus be appreciated. It has been observed that the line of force into the closed end of the tuyre is due to a negative pressure of nearly inches of water which violently draws in flue gas establishing a path partially across the bottom and thence outward along the definition between the vortex and the rotating air-oil envelope. This line of force then extends out of the tuyre and rolls on itself as an inner eddy in the refractory throat or combustion chamber 15. At such point this eddy of air and fuel is ignited and llame stabilization is established.

The inner eddy creates a suction within the flame which tends to draw each particle of flame or remaining unconsurned air and fuel toward the axis of the flame. The outer eddy serves for initial ignition with reduced air supply providing a rich mixture and then at normal air flow,

provides for re-ignition and stability. If the oil viscosity at atomizing temperature is too high, the heaviest particles are thrown out centrifugally and are stagnated in this eddy forming a ring of coke within the throat. This may be corrected by raising the air temperature or the oil tern* perature, with the air temperature predominating insecuring the proper low oil viscosity for eticient shearing or atomizing.

Within the tuyre it may be shown that the center line of force, inward to the closed end 24 of the tuyre, de fines the boundary between the vortex existing as a vacuum and the rotating air mass existing under pressure. The outward dening line of force then creates an eddy within the tuyre adjacent the closed end which draws the fuel and air inwardly and down.

The oil discharge from the nozzles is thus effected not only by this inwardly moving fuel gas and eddy created by the outward spiralling rst line of force but also from the rapid rotational effect of the vortex. A strong shearing action results. This is generally represented in Fig.

3 by the suggested path 35 of an oil droplet discharging l' from one of the nozzles 30. The oil is drawn violently into the eddy created by the outwardly spiralling first line of force and is then swept against the burner end wall 24 and toward the center where the oil rings thevortex interception 37 with the end wall. enough body to be acted on by centrifugal force imparted by friction with the rotating air. The fuel is then thrown spirally outward and forward passing through laminar layers of air, all whirling at different circumferential speeds. The fuel is thus sheared as though it were fed r between two wheels of different rotation and homogenized therein.

It is of course to be understood that with a plurality of nozzles 3i) asV for example six equally spaced in a tuyre of seven inches diameter, there is such an overlapping of the fuel paths so that the discharge of combustible material appears uniform. I have found it essential that the nozzles 30 be spaced on a circle which comes between the walls of the vortical column X for I nd that with the high velocity of rotation there is a substantial resistance by the inner wall of the column to the introduction of a liquid fuel which causes an erratic distribution. There is a minimum of resistance in the area between the inner and outer walls of the column.

I also tind that with the heavy fuels having a carbon content greater than distillate fuels, there is some tendency of segregation with the heavy portions designated Y thrown to the outer Wall. It will be apparent that the lightest oil is thus on the inner portion of the Vortex and due to the heat radiation and flow of flue gases the light oil is atomized quickest and in a path spiralling outward from the vortex circle. The residue being heavier, is subjected to a greater centrifugal force and being further outward from the center axis is sheared to a greater extent during its greater residence time and longer spiral Here it achieves path. As a result, it is estimated that the particles `are broken down generally into `inicron size or less with fa resulting very high temperature flame.

I have found that even with careful distribution of oil Within the vcolumn walls, and even with the desired high velocity of air, the asphalt feed sometimes tends to deposit droplets on the blades and kthus cause premature coking. It is apparent that the larger oil particles are thrown 'centrifugally outward thus striking the inner blade surfaces. There they are driven by the slant of the blades to the outer edge but at this point, due to the entering air, an eddy exists of quiet liquid and this rapidly cokes. The main air stream returns some of the droplets through the blades but it plasters more against the back of the burner face 20. This cannot be tolerated since it forms coke and partly closes the holes 20a on which reliance isplaced for air cooling. It has also been found that the velocity of the air enteringl the blades adjacent the open end of the tuyre is consider-- ably less than the velocity through the blade adjacent theV closed end of the tuyre. I

With the heavy fuels, I have thus found it desirable to utilize a skirt or balile generally indicated 28 with a cylindrical portion uniformly surrounding the major part of the tuyre and surmounted by the conical portion 28a which connects the cylindrical portion with the outer part of the tuyre blades 22. A By virtue of the pressure drop thus imposed on the air passing from the windbox through the skirt passage to the blades, a controlled velocity of air is established through the blades which thus enters alongplanes which are substantially transverse to the tuyre axis. This not only assures reentrainment of any liquid which might become thrown out by the centrifugal force but also substantially prevents disentrainment by assuring the desired velocities along the blade length. J l

A good tuyre operation is secured with a proper balance between ythe centrifugal force on the atomized particles which throws them toward the blades andk there- `fore toward the blade entries (for fouling) onl the one hand and the centripetal component of the viscous drag of the incoming air on the other hand. In such case the particles can be `made to rotate in a circular path in the burner so as to reduce blade impingement.

In sorne cases by proper dimensioning for suitable entering velocities to the blades, it may be possible to utilize the windbox 14 as the skirt but generally it is easier to provide the particular desired skirt size for various burners rather than to change the windbox foreach different operating condition. Furthermore, I provide space for the air for the openings 20a in the face plate which serves to cool the face plate during operation. In other words, therear refractory 15a in the combustion chamber is normally spaced about 1A', inch from the face plate 20 and substantially overlapping it and .by passing approximately 2-4% of the air through the openings 20a I and'under the projecting end of the refractory I can be assured of a long-lived face plate. The refractory shield is generally satisfactory although I have also used a spaced alloy shield as described in my copending application Serial No. 98,976, now Patent Number 2,560,076.

kThe alloy shield is unsatisfactory in the presence of vanadium containing fuels because of catalyticoxidation. The use of the shield and the cooling airhas reduced the temperature of the face plate from 1300,-1400 F. to a temperature in the range of 700 F. I have also describehd in my said Patent No. 2,560,076, a form of skirt `which surrounds an intermediate part of the tuyre and may be made of such diameter and position that differential velocities of air through the respective portions of the blades are obtained. With a burner where the major problem is t'o prevent dis-entrainment and to assure re-entrainment, the skirt must be substantially coextensive with the tuyre. It will be apparent that a great many varieties may be used but for practical purposes,

lI ha-vefound'the structures zofFigs; land 4 to be most ,effective and least lcomplicated.

In Fig. 4, the tuyre 18 having'thetypicalfront face 20, :is v:provided witha imultiplediameter .skirt-'38 hav- :ing .a rst conical section 39, ,a cylindrical portion 40 .and a closingcone 4i. This .type which diminishes in .diametervin-an outward direction tends `more effectively than-that shown in Fig. -l .to increase the velocity through the-.blades nearest .the open end of thev tuyre, and thereiluy-.prevents disentrainment of Yfuel from the air column.

Other constructions have been tried with more or less ,success including a `right cone, axcylinder, and -an in- ',verted multiple rdiameter skirt of the type shown in `Fig. 4 but sealed with respect to the closed end wall of the Atuyre. v

,-I have also used directional vanes 43 as shown in Fig. ,3 Aby which the entering air wwhich `normally passes .axially with respect lto the tuyre as it moves through `the windbox is given an angular component Ytending to .give a more nearly tangential inlet V,between the blades.

lt will also be apparent that streamlining-of the blades -and other parts can .be utilized in the interest-of saving .pressure drop. The structureas shown in Fig. l however ,is commercially satisfactory although the detailed improvements will be used if their economy of operation exceeds the cost of making the changes.

The use of preheated air with residual fuels is quite important from kthe standpoint of coke free operation. Where fine atomization in the order of 100 microns or .less isdesired, the fuel must be in condition for intimate Vdispersion in the air.

It has been my experience ,that a yviscosity range'of 20 to 50 centistokes is most eiective `and with residual fuel oils the temperature of the air should be from ZOO-250 F. 'With asphaltic residues, the temperature of the air of from 350-450 F. will give approximately the same results. The preheated lair, of course, increases the eiiciency of the burner.

Atypical installation of this type had substantially the following dimensions:

The range of burner sizes for various duties is generally found in the following table, it being understood that by varying the air velocity, a rangeof operation of from 70 to 140% may be obtained in any burner.

Cepam MMX MMI M11 MMl Mnl Tuyre Diameter 3 l 7% 10 B. 7 'Tuyre Length 3 6 9 9 l2 Curb or Chamber Diameter" l0 t 20 22% 28 30 Curb or Chamber Length 1S i 2O t V2?' 27 30 `rFusie.. Gals. per hone-Bunker G".. 7/2 32 l 48 72 S0 MM is equal 1.o 1,000,000 British thermal units.

A closed name pattern canbe obtained within the combustion chamber if it has the critical dimensions characteristic of the chamber in Fig. l. The chamber should notbe less in-diameter than about 11/2 Atimes the diameter o'f the tuyre opening and it should be not greater than 4 times, and preferably 3 times the diameter of the tuyre opening. in length, the combustion chamber shouldbe nearlyas long Vas its diameter.

'I have lnot 'found vit necessary Ito use secondary air for combustion purposes. :Howeverrmany furnace operators choose to introduce secondary air for various reasons. Thismay be introduced .at anydesired pointfor any of the ,desired freasons such as rcooling bridge walls, etc. The burner'is .normally designed forno excess air operation at'rfwater gauge and operates at a maximum-of 20 -percent excess at nine inches, normal rating. The

burner has an operating range of 70% capacityto 125% capacity. For lower velocities of air, the llame pattern becomes ragged and uneven with possible formations of coke with heavy fuel feed.

An important feature of the direct combustion of asphalt will be apparent from a typical disposal problem. In the particular case, it was desired to disposeof Y200 barrels per day of asphalt from a propane extraction process. This was blended with an equal amountof disavailability of fuel, the voperator may choose to run gas,

distillate, reduced crudes, or even the asphaltic residues. The burner can burn simultaneously two or more mixtures, the arne continuing to .be short, brilliant, smoke free and ash free. The increased flame temperature makes possible higher-heat input rates andfurther reduces costs of alliedequipment. The burner is shown in horizontal position in Fig, l butit-has also been shown in vertical position in the companion copending cases, Serial No. 66,445 andSerial No. 98,976, now Patents No. 2,560,- 074'and 2,560,076. It will work equally well in angular positions due to the fact that the velocity of air is so great that the established gravitational .effect of the vortex is little influenced by gravity.

A port 50 is provided thru therback refractory surface surrounding the burner face. A lighted gas torch lwith no air premix is inserted in the port and completes its combustion on the back of the Vwhirling air pattern in the refractory throat, remaining permanently lit. When l fuel gas is admitted tothe burner, combustion is immediate. stoichiometric-rthecombustionis colorless and transparent and evident only from the radiant refractory throat.

Recommendedl practice is to then cut over to fuel oil to 'ush and warm Ythe feed lines and valving. It was possible with a vigorous pilot flame to omit the intermediate step of gas firing, `igniting the highly atomized fuel oil even in a cold refractory throat, though best practice is to provide for initial` gas firing.

VAsphalt then follows thefuel oil and burns Vwith an even more dazzling white incandescent flame because of its increased viscosity andhigher carbon residue.

Prior to a shutdown fuel oil is again resorted tofor flushing the burner and lines. In cold climates the burner lines may be purged by the gas.

Where it is forbidden to light aftorch outside `the furnace the gas-electric method of'ignition may be used for starting or continuing the vpilot light.

While-I have shown and describeda preferred .forrn of burner in accordance with my invention, .I ,am aware that modifications may be-made thereto which are within theY scope and spirit of my invention.

I claim: Y Y

1. In a liquid fuel burner, an open ended vhollow annular tuyre having a closed end wall, and a side wall having a plurality of kfixed substantially tangential blades extending .throughout the major part of said side wall and forming inwardly convergent airpaths, an enclosure surrounding said tuyre,.rneanszforsupplying .an air cur` rent to said enclosure fand through said air paths between said blades to establish a vortical air column in lsaid The saving in directy Because the fuel gas-air ratio is substantiallyy tuyre, fuel supply means adjacent the closed end wall of said tuyre adapted to communicate with the vortical air column whereby said fuel is entrained in said column and discharged through the open end of the tuyre, said fuel supply means including a plurality of nozzles extending through the closed end wall of the tuyre in spaced relation to the side wall and at such a radial distance from the center that the vortical air column therein normally covers the discharge openings, and a fuel distributing pan surrounding the closed end wall of the tuyre, the wall of said pan forming with the edge of the blades a plurality of peripherally spaced fuel passages, and separate conduit means to supply fuel to said nozzles and pan.

2. In a liquid fuel burner, an open ended hollow cylindrical tuyre having a closed end wall, and a side wall having a plurality of fixed substantially tangential blades extending throughout the major part thereof and forming inwardly convergent air inlet paths, an enclosure surrounding said tuyre, means for supplying air to said enclosure and through said air paths between said blades for forming a hollow, swirling, forwardly moving vortex of air in said tuyre adjacent the side wall, a plurality of fuel feeding nozzles extending a short distance through the closed end wall of the tuyre in spaced relation to the side wall and at such a radial distance from the center that the portion of the forwardly moving vortex of air adjacent the closed end wall in the tuyre normally covers the nozzle openings, and an annular skirt Within the enclosure surrounding the tuyre and sealed with respect to the open end thereof, the other end of the skirt being spaced from the tuyre to receive the air entering the enclosure and direct it through the tuyre inlet paths, the cross sectional area of the skirt portion adjacent the open end of the tuyre being less than that at the closed end of the tuyre whereby the velocity of the air entering the tuyre is increased near the open end to restrain fuel disentrainment.

3. In a liquid fuel burner as claimed in claim 2 in vwhich said annular skirt has multiple cylindrical sections of different diameter which are joined by conical sections to each other and to the open end of the tuyre.

4. In a liquid fuel burner, an open ended hollow cylindrical tuyre having a closed end wall and a side Wall having a plurality of fixed substantially tangential air inlet slots extending throughout the major part thereof and forming inwardly directed air inlet paths, an enclosure surrounding said tuyre means for supplying air to said enclosure and through said air inlet paths for forming a hollow, swirling, forwardly moving vortical column of air in said tuyre adjacent the side wall thereof, annular baflle means within the enclosure extending the length of the air inlet slots and in the path of the supplied air to maintain a velocity of air through the air inlet paths at all parts of the vortical column at least equal to the velocity adjacent the closed end of the tuyre to prevent disentrainment of fuel from the air column, liquid fue] feeding means including a plurality of nozzle openings disposed within the interior of the tuyre a short distance from the closed end wall and at such a radial distance from the center that the portion of the forwardly moving vortical column of air adjacent said closed end wall in the tuyre normally covers the nozzle openings, and means to supply liquid fuel to said nozzle openings whereby fuel is entrained in said vortical column of air.

References Cited in the file of this patent UNITED STATES PATENTS 1,795,454 Van Brunt Mar. 10, 1931 2,458,992 Hague Ian. 11, 1949 2,560,076 Bloomer July 10, 1951 FOREIGN PATENTS 350,051 Great Britain June 11, 1931

Claims (1)

1. IN A LIQUID FUEL BURNER, AN OPEN ENDED HOLLOW ANNULAR TUYERE HAVING A CLOSED END WALL, AND A SIDE WALL HAVING A PLURALITY OF FIXED SUBSTANTIALLY TANGENTIAL BLADES EXTENDING THROUGHOUT THE MAJOR PART OF SAID SIDE WALL AND FROMING INWARDLY CONVERGENT AIR PATHS, AN ENCLOSURE SURROUNDING SAID TUYERE, MEANS FOR SUPPLYING AN AIR CURRENT TO SAID ENCLOSURE AND THROUGH SAID AIR PATHS BETWEEN SAID BLADES TO ESTABLISH A VORTICAL AIR COLUMN IN SAID TUYER, FUEL SUPPLY MEANS ADJACENT THE CLOSED END WALL OF SAID TUYERE ADAPTED TO COMMUNICATE WITH THE VERTICAL AIR COLUMN WHEREBY SAID FUEL IS ENTRAINED IN SAID COLUMN SAID DISCHARGED THROUGH THE OPEN END OF THE TUYERE, SAID FUEL SUPPLY MEANS INCLUDING A PLURALITY OF NOZZLES EXTENDING THROUGH THE CLOSED END WALL OF THE TUYERE IN SPACED RELATION TO THE SIDE WALL AND AT SUCH A RADIAL DISTANCE FROM THE CENTER THAT THE VERTICAL AIR COLUMN THEREIN NORMALLY COVERS THE DISCHARGE OPENINGS, AND A FUEL DISTRIBUTING PAN SURROUNDING THE COLSED END WALL OF THE TUYERE, THE WALL OF SAID PAN FORMING WITH THE EDGE OF THE BLADES A PLURALITY OF PERIPHERALLY SPACED FUEL PASSAGES, AND SEPARATE CONDUIT MEANS TO SUPPLY FUEL TO SAID NOZZLES AND PAN.

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