US2369046A - Liquid fuel burner - Google Patents

Description

J. F. HARVEY ETAL 2,369,046

LIQUID FUEL BURNER Filed Feb; 28, 1940 2 sheets-sheet 1 Feb. s, 1945.

N www im Feb. 6, 1945. J. F. HARVEY E-rAL. 2,369,046

LIQUID FUEL BURNER Filed Feb. 28, 1940 2 Sheets-Sheet 2 INVENTORS JO/m F Harz/@y 5:2@

BYr ur Hefmandoffer i ATTORNEY.

Patented Feb. 6, 1945 John F. Harvey, Akron, and Arthur W.`Herman dorfer, Barberton.- Ohio, assignors to The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey Application February 2s, 1940, serial No. 321,192

13 claims. (Crass-1z0) This invention relates to the construction and operation of liquid fuel burners, and more particularly to variable capacity pressure atomizing liquid fuel burners of the return flow type in which the liquid fuel is supplied through an inner barrel and the return flow is through an annular passage formed between the inner barrels.

Mechanical atomizing liquid fuel burners in which the liquid fuel is delivered to a circular whirling chamber under pressure through substantially tangentially arranged slots are well known. The liquid fuel passes through the whirling chamber in a spiral path due to the conversion of its supply pressureinto angular and axial velocities and is discharged from an end orifice in a hollow cone shaped spray, the angle of the spray being determined by the angular and axial velocities of the liquid fuel as discharged.

The three important operating features of a liquid fuel burner of this type, particularly when intended for marine use, are its range of capacity, variation in spray angle, and quality of atomization. Since the quantity of oil passing through the discharge orice varies substantially as the square root of the supply pressure, the maximum variation in capacity with no change in size of the discharge orifice is inherently W Within practical limits of supply pressure and effective atomization, and in the ratio of not over- 2:1. A constant spray angle is highly desirable to insure complete and efficient combustion at all capacities by precluding the danger of furnace wall carbonization or furnace hot spots. It has been found that thespray angle tends to decrease as the amount of liquid fuel discharged from the discharge orifice increases. A fine quality of atomization under all operating conditions is essential to insure rapid, uniform and complete 4 vaporization and combustion.

A greater range of capacity is attainable with -liquid fuel burners of the return flow type in which a variable portion of the liquid fuel supplied to the burner can be by-passed through a return flow passage in the burner to vary the -amount discharged through the discharge orifice.

The amount of by-passed fuel is dependent on l the pressure in the return flow passage and a and outer the expense of the quality of atomization or spray angle variation.

The main object of the invention is the provi sion of an improved construction of the parts forming the discharge end of a liquid fuel burner of the return flow type whereby the burner will be characterized in operation by improved atom-l ization conditions over a wide range of capacities and particularly by fine atomization and a relatively small' variation in spray angle over the desired range of capacities.

parts defining the connection'. v

The various features of novelty which characterize our invention are pointed out Vwith particularity in the claims annexed t0 and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific' objects attained by its use, reference should ,be had to the accompanying drawings and descriptive matter in which we' have illustrated and described Dreferred'einbodiments of our invention. Of the drawings: i Y Fig. 1 is an elevation, partly in section and broken along its length, ofca. liquid fuel burner constructed in accordance with our invention;

Fig. 2 is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged view of the burner tip parts shown in Fig. 1;

Fig. 4 is a section taken on the lineV 4-'4 of Fig. 3, showing the furnace face of the primary nozzle;

Fig. 5 is a`s'ection`talren/ on the line 5 5 of Fig. 3, showing the furnace face 0f the secondary nozzle; i

Fig. 6 is a section taken on the line 6-6 of Fig. 3, showing the'outer face of the sprayer plate;

Fig. 7 is a view similar to Fig. 3 illustrating a modified tip construction;

Fig. 8 is a section similar to Fig. 5 taken on the line 8-8 of Fig. 7; and

Fig. 9 is a section taken on the line 8-9 of Fig. '7 `showing the outer face of the secondary nozzle.

In the liquid fuel burner illustrated in Figs.y

1-6, the atomizing parts are arranged within a horizontally arranged tube or distance piece I0 having its furnace, forward, or discharge end ilaring carrying thereon an impeller plate Il which in burners of this type is however frequently at is normally positioned in a fuel burner port of Further and more-A Vspecific objects are an improved location of the return ow connection to the main path of liquid fuel flow and an improved construction of theV pling yoke I8 adapted to be held in its closing position by a T-handle set screw I9. The upper end of the supply passage I5 opens into the outer end of a supply passage formed by an elongated inner barrel or supply tube 2| threaded flow type heretofore proposed, provisions are i made for by-passing a. variable portion of the oil y supplied back to the fuel reservoir or feed pump into the atomizer body, while the upper end of the return flow passage I6 is connected to the outer end of anannular passage 22 formed by the tube 2l and an outer barrel or tube 23 having a slip joint connection with the body I1. With this arrangement the fuel supply passage 20 is l separated from and surrounded by the annularA return flow passage 22.

The passage 20 is of'uniform internal diameter throughout its length and theV furnace end of the tube 2| is threaded to engage a cylindrical pri- 8 Y mary nozzle or plug member 24 having a sealing contact with the furnace end of the tubes 2| and 23. As shown in Figs. 3 and V4, the primary Vnozzle l24 has van annular slotV 25 formed in 4its Vfurnace facewhich is connected to the supply passage'20 v by a circular series ofl diverging passages 26. The

primary nozzle also has an annular slot 21V in its furnace face of Vlarger diameter and concentric with the slot 25.l The slot 21 is connected with the annular return iiowpassage 22 by a circular series of small passages 28 arranged parallelto the axis of the primary nozzle. n

The furnace face of the primary nozzle La when assembled contacts with the outer face of a secondary nozzlev or innertip member 30 having a cylindrical central passage therethrough winch constitutes the outer portion of a mixing or whirl chamber 32, the outer endof whichis closed by the imperforate portion ofthe furnace face of the primary nozzle. A series' of symmetrical slots 33 is formed in the outer face of the secondary nozzle in position to receive liquidfuel from the annular slot 25 and deliver the same substantially tangentially into the vouter end of the whirl chamber 32. An annular slot 35 is formed in the furnace face of the secondary nozzle in alignment with the slot 21 of the primary nozzle and connected thereto by short passages 36.

' charges through an orifice 4I of substantially smaller diameter than the whirl chamber.

With theforegoing construction the liquid fuel, preferably heated oil under a' substantial pressure, e. g. 200 lbs. per sq. in., is delivered through the passages I3 and I5 to the supply passage 2liY from which it passes through theholes 26, an-

^ nular slot 25, and tangential slots 33,into the outer end of the whirl chamber 32. Due to the 4tangential arrangement of the slots 33 the oil follows a spiral path in the whirl chamber toward the discharge orice 4 I.

In liquid fuel atomizing burners of the return for the purpose ofvarying the burner capacity. The control is effected by means of a valve in the return flow line to varyv the pressure therein and thereby the quantity of oil by-passed. As the valve is opened the pressure in the return line will drop and the amount of fuel returned will be proportionately increased. In such constructions the sprayer -plate is supplemented by a second orifice plate spaced from the furnace end of the 'sprayer plate to provide a space therebetweenA connected to the return flow line. The connection ofthe return by-pass to the furnaceside' of Vthe discharge orifice appears to create frictional and other disturbances which' cause relatively coarse atomizatlon of the fuel discharged into l'the furnace over a major portion of its designed capacity'range and a relativelylarge variation in spray angle with changes'in capacity.

. In the present construction, the portion ofthe.

fuel -by-passed is advantageously removed from the stream moving toward the furnace at a point on the Iperipheral wall of the Whirl chamber, and

preferably about midway between the point of entrance of the supply slots 33 and the discharge orifice 4I. As shown in. Figs. 3 and 6v the outer face of the sprayer plate 38 is cut away to form a circular recess over most of its area, the

outer periphery of the recess registering with the Y outer side of the'annular slot 35 of the secondary nozzle. VThis construction results in an annular opening or orifice in the wall of the whirl cha-mber midway of its length. In operation, the resultant effect may be visualized as the continuousrremoval of a circular lamina or portion of the fuel stream passing through the whirl chamber, whereby a drop in the whirl chamber pressure will result. VThe resultant pressure drop will cause an increase in the quantity of fuel enterlng the whirl chamber due to the increase in the pressure differential across the inlet orifice and some decrease in the axial velocity at the discharge orifice. Theangular velocity at the dischargeorifce is little affected, hence, the spray angle will be slightly increased. Y

It has been found desirable to Yconstruct the parts forming the liquid fuel passage in certain proportions for optimum operation. In particular, the total cross-sectional flow area of the supply slots 33 is approximately one and one-half times the flow area of the discharge orllce 4I, while the flow area of the return orifice into the space 45 is substantially greater than the area of the slots 33. The remaining portion of the liquid fuel stream continues in a spiral pathr through the remaining portion of the whirl chamber and isdischarged through the discharge orice 4 I.

The described burner tip construction has been found to result in the production of a relatively fine lspray throughout a capacity range of more than 7:1, and also to result in a relatively small l variation in the spray angle throughout this range with consequent substantially uniform flame con- Y ditions in the associated furnace.

` In the modified construction illustrated in Figs. 7-9 the burner parts are similarly constructed except that the oil return connection is formed by substantially tangential slots 50 formed in the furnace face of the secondary nozzle rather than the irecess 45 in the outer face of the sprayer plate. In both constructions the liquid fuel is substantially tangentially supplied to an elonsaid inner andouter' tips beingformed to defdne` gated whirl chamber and a variable portion withdrawn through a return passage opening. to an intermediate peripheral portion of the whirl chamber.

It will be noted that either return now-burner construction described can be readilyfconverted into a straight mechanical atomizing fuel burner.

byv replacing only one part. In the Figs. 1-6 construction, -a sprayer plate without the recess 45 will accomplish this result, while in .theFlga '7-9 construction, a secondary nozzle member without the slots 50 is all that is required fory this purpose. y

While in accordance with the provisions of the statutes we have illustrated and .described herein the best forms of the invention now knownV to us, those skilled in the art will understand that changes may be made inthe form of the apparatus disclosed without departing from the spirit of the invention covered by our claims,

' and that certain features of our invention m'aysometimes be used to advantagefwithout a corresponding use of other features. .V

We claim:

l. A return flow liquid fuel burner comprising: an inner liquid fuel supply tube, an outer tube forming a return flow passage therebetween, a.

nozzle member at one end of said inner and outer tubes and having a `central whirl chamber of circular cross-section, a liquid fuel inlet passage connected to said supply tube and substantially tangentially connected to one end of saidwhirl 4 chamber, a sprayer plate contacting with said nozzle member andhaving an opening therein forming part of said whirl chamberand a discharge orifice at the opposite4 end of said opening, the contacting face of said nozzle member being constructed to define a return iiow` slotv I centric supply and return passages, comprising a plug adapted to be fitted to the end of said barrel and to form anend closure for said pa-ssages, an inner tip seated against said plug and having a. central chamber therein, an annular set of tangential inlet passages for said chamber, an annular set of return passages in said inner tip concentric with said set of inlet passages, and outer tip seated on said inner tip and having a chamber registering with and forming a continuation of said rst chamber and terminating forwardly in a discharge orifice, said outer.

tip being spaced from said inner tip toform a return passage from said chambers to said first mentioned return passages,- and concentric sets of supply and return passages in said plug connecting the supply and return passages of said barrel to the inlet and return passages respectively of the inner tip.

3. An atomizer for a burner barrel having concentric supply and return passages, comprising a plug adapted to be tted to the end of said barrel and to form an end closure for said passages, an inner tip seated against said .plug and having a central chamber therein, a set -of substantially tangential inlet passages for said chamber, a set of return passages in said inner tip surrounding said set of inlet passages, an outer tip seated on said inner tip and having a chamber register. ing with and forming a continuation of said first chamberv and terminating forwardly in a discharge orifice, the adjacent surface portions of therebetweenL a returni il'ow connection-from said chambersto .saidil'rst mentioned return passages, and sets of supply and return' passages in said vplug connecting the supply'and returnpassages of said barrel tothe inlet and: return passages respectively of thev innertip.

4. An atomizerfor a burner barrel having concentric supply and return passages, comprising a plug adapted to be fitted tothe end of said barrel andtoform an end closurefor said passages, 'an inner tip seated against saidplug and havinga central chamber therein; a `pluralityof substantially tangentialV inletpassagesfor said chamber,

an. plurality of j return .passages in said innerv tip surrounding saidinlet passages, an out'engtip f seated on said vinner tip andhaving a.` chamber. registering-.with andv forming a continuation of said'rst chamber and .terminating forwardly 'in f a dischargeforicethe adjacent surface portions of` said` inner and outer tipsbeing-formedto de-k iine therebetween a return` flow connection of substantially greater flow .area thanthe total f now areaof .saidinlet passages, said returnii'owj connection extending from said chambers to'said first mentioned return passages, concentric 'supply and return passages in said plug connecting the supply and return passages-of said barrel to the inlet and returnpassages respectively of the inner tip, and av cap-attached to said barrelhaving an inner peripheraliiange -arranged to cen. ter and secure said tips in position. q

5. A return flow liquid,y fuel `burner having means forming a whirl chamber of circular crosssection and an axial length at least equal to its diameter, means forming a-substantially tangen- 'tially arranged liquid fuel inlet atone end of said' whirl chamber, a discharge oriflcejat the opposite end of said whirl chamber, and means for removing a peripheral portion Yof the whirling liquid fuel in said whirl chamber comprising a circular set of return now passages surrounding 4and connected to peripheral portions of said Whirl chamber intermediate the length thereof,

said whirl chamber being of uniform circularcross-section: from its fuelinlet end to a-point axially spaced beyond said return. ow passage connection thereto.

6. A return ilow liquid fuel burner having" means forming a whirl chamber of circular crosssection and greater axial llength than diameter, a discharge orifice at one end of said whirl chamber, means forming a substantially tangentially means forming an axially elongated whirl chamber of circular cross-section, means forming a substantially tangentially arranged liquid fuel inlet at one end of said whirl chamber and terminating at the entrance thereto, a discharge orifice at the opposite end of said whirl chamber, and means for removing a peripheral por- `tion of the whirling liquid fuel in said whirl' chamber comprising a circular set of return ow passagessurrounding and connected to peripheral portions of said whirl chamber approximately midway of the length thereof, said Whirl chamber being of uniform circular cross-section u from its fuel inlet end to at least the forward wall `of said return flow passage .connection thereto. u

8. A return now liquid fuel burner having means forming a whirl chamber of circular crosssection and greater axial length than diameter,

means forming a substantially tangentially arranged liquid fuel inlet at one end of said Whirl chamber and terminating at the entrance thereto, a discharge orifice at the opposite end of said i whirl chamber, and means for removing a peripheral portion of theliquid fuel whirling in said whirl chamber comprising a circular set of return flow ,passages substantially tangentially arranged relative to and opening to said whirl chamber intermediate the length thereof, said whirl chamber being of uniform circular crosssection from itsfuel inlet end to at least the points of connectionv vof said return flow passages c thereto. c y c.

9. A return flow liquid fuel-burner comprising anvinner liquid fuel supply tube, an outer tube forming a return flow passage therebetween, means at one end of said inner and outer' tubes 1 defining a central whirl chamber of' circular cross-section, a liquid fuel inlet passage con.v

nected to said supply tube andsubstantiallyf tangentially connected to one end vof said. whirl chamber, a discharge orifice at the opposite end of said whirl chamber, means'dening a circular setV of return flow passages surrounding and connected at one end to peripheral portions of said whirl chamber intermediate the length thereof and at their other end to said vreturn flow passage,

said whirl chamber being of uniform circular cross-section from its fuel inlet end-to a point axially spaced beyond the points of connection of said return ow passages thereto.

10.v An atomizer for a burner barrel having concentric supply and return passages, .comprising a plug adapted to be ttedto the-.end of said barrel and to form an end closure for. saidvpas.-

sages, a burner tip structure seated against said plug and having a central whirl chamber of circular'cross-section therein ofan axial length at least equal to its diameter and terminating forwardly in a discharge orifice, a plurality of substantially tangential inlet passages for said whirl' chamber terminating `at the periphery thereof, a circularY set of return passages in said tip structure forming a return flow connection from intermediate peripheral portions of said whirl chamber rearwardly of said discharge orifice to said first mentioned return passage, and concentric supply and return passages in said plug connecting the supply and return passages of said barrel to the inletl and return passages respectively of said tip structure, said whirl chamber being of uniform circular .cross-section from said inlet passages to at least the forward wall of said return flow connection.

11. A return iiow liquid fuel burner compris-H Aing an inner liquid fuel supply tube, an outer tube forming a return ow passage ltherebearrangedto define a return flow connection opening at one end over a substantial peripheral portion of said whirl chamber intermediate the length of lsaid whirl chamber and atA its other end to said-return iiow passage, said whirl chamber being of uniform circular cross-section from its fuel inlet end toa point axially spaced beyond said return flow connection thereto.

12. A return flow liquid fuel burner comprising an inner liquid fuel supplytube, an outer tube forming a return flow passagetherebetween, a

nozzle member at one end of said inner and outer tubes and having a central whirl chamber of circular cross-section, a liquid fuel inlet passage connected to said supply tube and substantially tangentially opening into one end of said whirl chamber, a sprayer plate contacting with said nozzle member and having an opening therein forming part ofsaid whirl chamber and a discharge vorifice at the opposite end of said opening,-

the contacting face of said sprayer plate being recessed and arranged to dene a return flow connection opening at one end over a substantial peripheral portion of said whirlchamber intermediate the length of said whirl chamber and at its 4other end to said return flow passage, said whirl chamber being of uniform circular cross-section from its fuel inlet end to a point axially spaced beyond said return now connection thereto. I

13. A return flow liquid fuel burner comprising an inner liquid fuel supply tube, an outer tube forming a return ow passage therebetween, a nozzle member at one end of said inner and outer tubes and having a central whirl chamber of circular cross-section, a liquid fuel inlet passage connected at one end to\said supply tube and substantially tangentially opening, at its opposite end into one end of said whirl chamber, a sprayer plate contacting with said nozzle member and having an opening therein forming part of said whirl chamber and a discharge orifice at the opposite end of said opening, the contacting face of said sprayer plate having a circular recess arranged to define an annular return flow passage surrounding and opening at its center to a lcircumferential section of said whirl chamber intermediate the length of said Whirl chamber and at its outer periphery to said return/flow passage, said whirl chamber being of uniform circular cross-section from its fuel inlet end to a point axially spaced beyond said return flow .connec-v tion thereto. f

JOHN F. HARVEY. ARTHUR W. I -IERMANDORFER

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