US2976919A - Oil burners - Google Patents

Description

March 28, 1961 w. SANBORN OIL BURNERS 2 Sheets-Sheet 1 Filed May 29, 1956 r mw c mm L w WSW mi March 28, 1961 w. L. SANBORN 2,976,919

OIL BURNERS Filed May 29, 1956 2 Sheets-Sheet 2 SWlRLlNG AIR FROM musk BLADES INWAKD AIR INWARO AIR FROM OUTER Fgfgl lgg ER 5 LADES HEAVI ER on. STREAMS WEB OFSPRAYED OIL.

SWIRLING AIR FROM NNER IHWARDLY Swmums AIR ALONG NOZZLE FACE Inventor 25 William L, Sonborn.

325 I +wwm pq-Horn e1! 5 United States Patent OIL BURNERS William L. Sanborn, Milwaukee, Wis., assignor to Bell & Gossett Company, a corporation of Illinois Filed May 29, 1956, Ser. No. 588,075

3 Claims. (Cl. 158-76) This invention relates to oil burners and particularly to liquid atomization oil burners of the kind used in small domestic heating plants.

Liquid atomization is of course used in high pressure or gun-type where high oil pressures, in excess of 100 a high proportion of the oil burners sold and used, theseobjectionable characteristics have been the subject of widespread experimentation and study.

It is recognized that the major faults of such small capacity burners are their inefliciency and noisiness, and the primary object of the present invention is to enable the efliciency of such burners to be increased and the noise of such burners to be reduced. Thus, in almost all present day oil burners that have a fuel capacity of one gallon per hour, or less, the inefficiency is such that they rarely have a flame temperature as high as 2000 F., and they operate at a C reading that is rarely over 7, and with stack temperatures of from 500 to 600 F. Such burners all require fireboxes to maintain adequate flame propagation, and even with such fireboxes, difliculty is experienced in maintaining a stable fire. Such small capacity burners also have required an appreciable natural draft, usually of a high order, and this has contributed to the inefliciency of the burners. These low capacity burners also produce a high soot content in the flue gases so as to be dangerous and objectionable in this respect.

The foregoing performance factors of present day small capacity oil burners have, of course, influenced and increased the size and cost of heaters or boilers, and have resulted in undue costs in installation, operation and upkeep of such oil burners and the related equipment. It is, therefore, a more specific object of the present invention to enable low capacity oil burners to operate at greatly increased flame temperatures, with low stack temperatures, low smoke or soot production, and with ahigh CO reading, and related objects are to accomplish this in such a way that natural draft is not needed and in such a way that efliciency is maintained even where there is appreciable back pressure in the combustion space, to eliminate the necessity for theusual firebox, and through the attainment of high flame temperatures, to enable the area of heat transfer surfaces of such heaters to be substantially reduced.

Other and further objects of the present invention will be apparent from the following description and claims,

' invention enables this flame F to be maintained in a substantially constant size and location so that eflicient and 2, the present invention and the principles thereof, and what I now consider to be the best mode inwhich I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the invention.

' In the drawings:

Fig. 1 is a horizontal plan view taken through the air tube and nozzle structure of an oil burner embodying the features of the invention;

Fig. 2 is a rear elevational view of the air swirler;

Fig. 2A is a rear perspective view of the swirler;

Fig. 3 is afront elevational view of the air swirler as viewed from the right in Fig. 1;

Fig. 4 is an enlarged transverse sectional view of the air swirler and nozzle;

Fig. 5 is a transverse cross sectional view of the nozzle taken along the line of 55 of Fig. 4;

Fig. 6 is a schematic cross sectional view showing the :nozzle and swirler and the form and relationship of the Fig. 8 is an enlarged cross sectional view of the nozzle and a portion of the swirler; and

Fig. 9 is an enlarged front elevational view of the nozzle and a portion of the inner part of the swirler.

For purposes of disclosure the invention is herein illustrated as embodied in an oil burner 20 having an air tube 21 the forward end of which extends for a short distance through and beyond a wall 22 of the combustion space 23 of a heater, and coaxially within the forward end of the air tube 21 an oil discharge or spray nozzle 25 and an air swirler 28 are mounted so that fuel oil and air may be supplied to and efliciently intermixed and burned in the combustion space 23. The nozzle 25 is supported and positioned within the end of the air tube 21 by means including the swirler 28 that is mounted on the nozzle 25 and which in turn engages a flanged positioning cap 21C that is fixed within the forward end of the air tube to locate the nozzle as well as the swirler 28 in the proper centered relationship with respect to the air tube.

mined pressure so that it is pressure atomized and thus discharged from a central discharge orifice 25D of the nozzle 25, and air is fed through the air tube 21 by any conventional means such as a blower and at a rate that I may be adjustably determined by any conventional I conventional form, the electrode 30E of which extends through the swirler unit 28 to a point adjacent an innermost portion of the swirler 28.

The present invention is concerned with the production of a stable, high temperature, eflicient flame F and, as

will be described in greater detail hereinafter, the present substantially noiseless combustion is attained.

The structural features and relationships that enable such efiicient and noiseless combustion to be attained will be described in detail hereinafter, but as a preliminary to such specific description it maybe stated that it is my present theory that these results are produced by coordimating the air supply and fuel supply so that, with respect g to the axis of the nozzle, the air supply and the oil supply are individually-symmetrical,--and are symmetri- Fatented Mar. 28, 1961 k The fuel oil is supplied to the nozzle under a predeterspect to the nozzle axis, andwith respect to each other, as-

sures uniformity or symmetry of'combustion and eliminates any tendencytoward lateral pulsation of the flame F. As a result of such control of the fuel and air, the combustion of the fuel is completed while the fuel is .within a relatively short distance of the air tube.21. and the flame F maintains a substantially constant position and a substantially constant form and size. Thus, as shown in- Fig. 6, the flame F has the form of a parabolic conoid that is symmetrically positionedon the axis of the fuel nozzle 25 with the small end of the flame disposed at substantially one-quarter inch from the nozzle tip. In a burner operating at about one gallon per hour the flame F has a length of about 4 inches and a maximum diameter of about 4 inches, and the flame burns without pulsation or noise.

Under the present invention the nozzle 25, the swirler 28 and the spark plug 30 are assembled as a unit that may be readily mounted in or removed from the air tube 21. In accomplishing this the nozzle 25 is mounted, by means including a union 32U, coaxially on the forward end of a relatively small fuel supply pipe 32 and at its.

rear end the tube is bent at right angles as at 32B and has a threaded nipple 32N thereon whereby the pipe 32 may be readily connected to the oil supply source through means such as a nipple extended through the air tube 2.1 or the enlarged air supply duct 21D that is connected thereto.

The spark plug 39 has the usual ceramic body 30C and is supported in fixed relation to the nozzle by means of a clamp 33 that is secured by means such as a screw 33S in a clamped relation to the pipe 32 and the ceramic body 30C of the spark plug 30. This provides a unit that may be adjusted and then inserted endwise into the air tube 21, and in such insertion the outer and forward edges of the swirler engage the mounting ring 21C to determine the endwise and lateral location of the nozzle 25, and then after the nipple 32N has been connected to the oil supply line by means such as a conventional union fitting, the fuel and air supply unit is accurately positioned in the air tube.

The nozzle 21 in most of its characteristics of conventional construction and, as shown in Fig. 4, the nozzle comprises a tip 2ST in the forward end of which the discharge opening 25D is formed. The rear end of the tip 2ST takes the form of a nipple to which the union 32U is connected. Within the tip 25T a core 25C is positioned by means including a securing nut 25N that is threaded axially into the rear end of the tip 2.5T. The nut 25N and the core 25C have connnecting passages therethrough so that oil fed under pressure through the supply pipe 32 passes into the forward end of the tip 2ST and into an annular space that is provided within the tip and about the core 250. At its forward end the tip 251 is formed with a forwardly facing conical surface 1250 that engages an internal conical surface 225C that is formed within the tip 2ST. The surface 125C of the core 25C is formed according to conventional practice with a plurality of slots 1258 that are so positioned on the conical surface that oil passing through these slots and toward the discharge opening 25D has a swirling motion imparted thereto about and with respect to the longitudinal axis of the nozzle. This relationship is best shown in Fig. 5 of the drawings, and this relation or positioning is wellknown in the art. Nozzles of this kind are provided with different numbers of slots 1258 and in the present instance the nozzle 25 has four-such slots.

Withthis numberofslotspthe fueloil that'is beingfed the blades.

under pressure through the nozzle has a swirling motion imparted thereto, and it is formed into four basic and relatively fine streams of oil that leave the slots 125S and move with a spiral or swirling motion through the outlet or discharge opening 25D. As this fuel leaves the discharge opening 25D it forms into a conical spray S that may be described in general as constituting a thin layer of finely defined oil particles shaped in the form of a cone that is centered on the axis of the nozzle 25. The internal angle of the cone that constitutes the spray S varies according to known practices in accordance with the specific internal design of the nozzle 25, and the nozzle herein shown is one that produces what is called a spray as indicated in Fig. 6, but under the present invention different spray angles may be used as, for example, the 60 spray angle that has been indicated in Fig. 6.

As above pointed out, the spray S is made up in a general sense as a thin layer of oil that defines a cone, but I have observed, and in accordance with the present invention, have made advantageous use of the fact that within or as a part of this thin layer there are well defined concentrations of fuel that take the form of streams SS as indicated on an exaggerated scale in Fig. 7. These streams SS correspond in number and in circumferential location with the number and location of the slots 1255, and between the streams SS, the spray is defined by the thin layer S as indicated in Fig. 7. As will become apparent from the following description, the supply of air to the combustion space is controlled by the swirler 28 and the design of the swirler is correlated with the form of the spray, as above described, so that the proportioning of the air and fuel is maintained uniform throughout the entire circumference of the spray, and through this control, the present invention eliminates the usual tendency of the flame to burn unevenly in a lateral sense. This results in the attainment of what may be termed lateral stability of the flame, as will bedescribed hereinafter.

The swirler unit 28 embodies certain of the physical characteristics of the swirler shown in my prior Patent No. 2,485,244, but as will become apparent hereinafter, the swirler 28 includes additional cooperating structure and accomplishes additional functions that enable the desired efliciency and operating characteristics to be attained in small oil burners. Thus, the swirler unit 28 is made up from two blade units which constitute an outer blade unit 128 and an inner blade unit 228. In the present instance these blade units are separately formed, and are thereafter assembled in a rigid relationship such that the inner blade unit is mounted directly on the nozzle 25 and in turn serves to connect the nozzle to the outer blade unit 128.

The two blade units 128 and 228 have certain similarities in form and construction in that both of the blade units are made from sheet metal and comprise segmental, fan-like blades that extend outwardly from an inner connecting and supporting band that is formed integrally with the blades in each instance. Thus, as applied to the outer blade unit 128, an inner annular band 128M has a plurality of segmental blades 128B extended outwardly therefrom. These blades 128B are formed by cutting and subsequently shaping the sheet metal to afford a generally fan-like structure. The metal of the swirler unit 128 is thus slit along radial lines 35 inwardly to the outer border of the annular mounting band 128M, and then an arcuate slit 36 is extended for a short distance from the slit 35 in each instance along the outer border of the band 128M. After these slits have been formed, the metal of the segment that lies radially outwardly of the arcuate slit 36 is, in each instance, bent in a forward direction to give the desired fan-like form to each of As will be evident particularly in Fig. 4 of the drawings, the band 128M, in what may be termed the outerpontion thereof, liesin a plane while in an inner.

annular portion of the band, the metal is formed in, a forward direction to provide what amounts toa truncated air-directing cone as indicated at C in Figs. 4 and 8. As hereinabove pointed out, the band 128M serves to connect the several blades 128B, and the band 128M including the conical portion C serves also as an airdirecting means cooperating with the blades 128B, and as an air-directing means in cooperation not only with the other or inner swirler 228, but also in cooperation with surfaces of the nozzle 25 as will be described.

The inner swirler 228 is quite similar in many respects to the outer swirler 128 in that an inner band 228M has a plurality of blades 228B formed thereon and having their free edges bent forwardly to give a fan-like form to the inner blade unit. In this instance, however, the mounting band 228M is formed with the main portion thereof in a plane and with a cylindrical portion M formed thereon that is adapted to slip with a tight friction fit over the outer cylindrical surface of the nozzle 25. The blades of both the inner and outer blade units are arranged to cause swirling of the air in the same rotative direction which corresponds also to the swirling direction of the nozzle 25.

The inner and outer swirler units are interconnected by welding the forward outer corners of the blades 228B to the rear face of the band 128M. Thus when the mounting sleeve M of the inner swirler unit 228 is in position on the nozzle, the connection between these two units serves to support the units in a predetermined relationship to each other and in a predetermined axial relationship on the nozzle 25.

-As will be evident in Fig. 4 of the drawings, the endwise positioning of the swirler 28 on the nozzle is such that the forward or discharge end of the cone C is'located substantially in the plane of the extreme tip of the nozzle 25. With this arrangement the air passing for wardly through the tube 21 will, of course, pass through both of the swirling units 128 and 228 and because of the fan-like form of the blades thereof this air will be given a swirling motion and will also be given an inward component of movement because of the fact that air may move in a generally inward radial direction through the slits 36.

The air that moves through the inner swirler unit 228 is directed in a large extent forwardly toward therear surface of the band 128M and its conical portion C so that such air is given an additional component of inward movement which, under the present invention, causes the inner blade unit 228 to supply flame propagation air at the point where the fuel oil emerges from the nozzle 25. This swirling, inwardly moving air also serves to cool the nozzle 25 and also to prevent accumulation and burning of oil on the nozzle as will be described.

In attaining this action the nozzle 25 and the air-directing cone C have an advantageous cooperation. Thus, the forward surface of the nozzle 25 is formed as a conical wardly moving flame propagationair is that such air must move with a swirling action along the surface 325. Such swirling movement is, of course, imparted to the air by the action of the blades 228B of the inner swirler unit.

With the inner and outer swirler units related to the nozzle 25, as above described, the desired flame propaga-' tion air is supplied relatively close to the nozzle 25, and by using a structure that provides such flame propagation air in relatively large volume, it is found that the fuel starts to burn almost immediately after it is discharged from the nozzle, thus to locate the flame quite close to the end of the nozzle. The air that emerges from the outer swirler unit, of course, has a swirling moving and engages the sprayed fuel so as to provide additional air for combustion while at the same time acting to confine the flame within the envelope afforded by the advancing-swirling body of air.

An important characteristic of the present invention is t that the air is supplied to the fuel in a symmetrical relasurface 325 that, in the present instance, is arranged at an the air may move along thesurface of thenozzle and directly toward the point where the oil emerges from the nozzle. The effectiveness of this air in keeping the nozzle 25 clean is dependent in a large measure upon the maintaining of such air in close contact with the conical surface 325, and this is accomplished by affording a special relationship between the conical surface 325 and the cone .C as will be evident in Fig. 4 of the drawings. As above pointed out, the present nozzle has its conical surface 325 formed at a 30. angle to a transverse plane, and the cone C is formed with a somewhat smaller angle. Thus, in the form herein shown the surface of the cone C is arranged at substantially 20 to the aforesaid plane and because of this relationship the inwardly moving air is directed more effectively against the surface 325. Another essential characteristic that must be attained in this intionship with respect to the fuel supply, and in this respect the aforesaid form of the spray, as hereinabove described, is important. Thus, I have found that where four slots 1258 are used in a nozzle, the flame characteristics are vastly improved by utilizing a swirler construction in which the number of blades is equal to the number of slots employed in the nozzle multiplied by a whole number. In the present instance, where four slots 1258 are used in the nozzle, the desired combustion characteristics are attained by using eight blades in each of the units 128 and 228 of the swirler. These swirlers, however, may,

under the present invention, be formed for use with a four-' slot nozzle so as to have an even greater number of blades,

such as twelve blades each, or sixteen blades each. This same general theory may be applied to other nozzles having diiferent numbers'of slots 1258. Through this arrangement and relationship, the air supply is symmetrical in a circumferential sense to the streams SS of the spray as well as to the intermediate web-like portions of the spray, and in Fig. 7 of the drawings this symmetrical relationship has been schematically illustrated.

In considering the symmetry of the air supply and the oil supply with respect to each other and with respect to the nozzle axis, it is important to note that, in attaining thedesired swirling movements and inward movements of the air, the blades of the swirler act initially to divide the main air stream into a plurality of separate air streams which have been schematically indicated by arrows in Fig. 7, and further that the nozzle 25 produces a spray that includes a conical web-like portion with a number of discernable streams SS therein corresponding to the number of nozzle slots 1258. Thus, in carrying out the basic concept of the present invention, each stream SS (along with the related thin web portions of the spray) is acted upon'in a like manner 'by one of several like groups of relatedair streams, with the result that each portion of the spray is subjected to like-forces and is supplied with like amounts of air.

To consider the foregoing analysis more specifically as applied to the illustrated embodiment, each outer blade 128B may be considered as producing or causing a circumferentially directed air stream 1 50C passing through the related slot 35 and an inwardly directed air stream R'that passes through the related slot 36, such inward air streams 150R being subsequently directed generally forwardly by the outer surface of the cone C.

Similarly, the inner blades 228B each produce a circumferentially directed air stream 250C and an inward air stream 250R, both of which necessarily pass with a swirling action between the nozzle 25 and the cone C and along the conical surface 325 of the nozzle 25 into the very base of the fuel spray.

In Fig. 7 the several streams of air that are produced by the eight blades 128B and the eight blades 228B are sprays and its four streams SS that are produced by a.

four-slot fuel nozzle. Thus withthis particular relationship of the number of inner blades, outer blades, and nozzle slots, and with the slots and each of the sets of blades in a symmetrical or equidistantly spaced relation about the nozzle axis, each of the four similar segments of the fuel spray is acted upon in a similar manner by the same number and type of air streams. This result follows regardless of the rotative or angular positioning of the swirler with respect to the slots 1258 of the nozzle, and the four similar segments of the fuel spray are thus subjected to like controlling conditions and to like combustion conditions so that lateral unbalance and lateral pulsation of the flame F are prevented.

With the nozzle and the swirler formed and related as thus described, the flame F maintains'a steady form and position so that the fire is substantially free from objectionable noise and is highly eflicient in all respects. In actual use it has been found that in a small capacity heater the fuel feed rate, and the air supply rate, may be adjustably varied or modulated over a substantial range while maintaining the efficient and noiseless operation of the burner. In such operation, the flow of swirling air over the conical surface of the nozzle tip serves to keep the nozzle clean and cool, and the longitudinal stability of the flame F avoids contact of the flame with the nozzle and eliminates baking or clogging of the nozzle.

The flame propagation air that cools and cleans the nozzle is of course intermixed with the fuel at substantially the apex of the fuel spray so the combustion starts and is uniformly maintained at but a short distance from the nozzle, and as a result the burning of the fuel is completed within a relatively short travel of the fuel and while the fuel is well within the controlling range of the swirling envelope of combustion air that is derived from the outer unit of the swirler.

With the small capacity burner of the construction described, operating at a fuel consumption rate of one gallon per hour of No. l or No. 2 oil, it has been found that flame temperatures of as high as 2700 F., stack temperatures of as low as 250 F., may be readily and consistently attained with CO readings of 12 and 13% and with CO readings of zero. Such performance has been attained without natural draft and even in the presence of appreciable back pressure, and in every instance the fire has been free from noise and the flame stable in a longitudinal as well as a lateral sense.

The low nozzle temperature that is attained by the present invention is of particular value in that it avoids production of a clogged or varnished nozzle so that the nozzle operates in a cool and clean condition despite its proximity to the unusually hot flame that is produced. Hence one of the most frequent causes of burner failure has been overcome. This results in part from the longitudinal flame stability which prevents contact of the flame with the nozzle, in part from the continuous and symmetrical supply of flame propagation air at the nozzle tip so that position pressure at this point prevents rearward flow of heated gases past the nozzle, and from the continuous flow of cooling air over the nozzle and the swirler blades which are located in the airstream and act as cooling fins for the nozzle.

Thus, the present invention enables a medium pressure, liquid atomization burner to operate with extremely high efficiency and in a trouble free manner, and since the high oil pressures, that have heretofore been considered necessaryfor etficiency, have been eliminated, the characteristic oil burner roar has been substantially eliminated.

From the foregoing description it will be apparent that the present invention enables small capacity, medium pressure, oil burners to operate without objectionable noise and at uniform and extremelyhigh levels of efliciency; and further, that the stability and effioiency thus attained simplifies and reduces the cost of production,installation, operation and upkeep of small capacity oil fired heaters.

Thus while I have illustrated and described the invention in a particular embodiment, it will be recognized in a liquid atomization oil discharge nozzle disposed coaxially of the tube for discharging oil in a hollow conical spray beyond the forward end of the nozzle, said nozzle having an axial discharge orifice and a truncated,

conical forward face terminating at its smaller end close to the axis of said orifice, and a swirler unit through which air may pass and including a truncated cone member mounted in fixed position on said nozzle within and in a coaxial relation to the forward end of said tube and surrounding the forward portion of said nozzle at substantially the most forward portion thereof and having swirler blades extended from its outer edge for directing the forwardly moving air from an outer annular zone of the tube with a swirling movement into and about the spray of oil to provide combustion air, and said truncated cone member cooperating with the forward portions of said nozzle for directing the forwardly moving air from the innermost annular zone of said tube in an inward direction across and against the conical forward face of said nozzle and toward the axis of the spray to supply flame propagation air at the nozzle tip and build up a point of pressure at said tip to maintain the flame close to said tip and in a stable and minimized burning zone. 2. In an oil supply and air control unit for use in gun type oil burners wherein air flows forwardly in a burner tube to a combustion chamber, a nozzle including an.

outer nozzle tip having an axial discharge orifice and an outer forward face formed as a concentric, truncated conical surface the smaller end of which terminates close to the edge of said orifice, means forming part of said nozzle and located within said tip for directing forwardly moving oil with a swirling action toward said discharge orifice for discharge from said orifice in a hollow conical spray including a predetermined number of oil streams of equal size and pressure discharged as parts of the spray in uniformly diverging relation in uniformly spaced relation in a circumferential sense, a swirler stationarily mounted on said nozzle and having an annular series of radially disposed air directing blades arranged in uniformly spaced relation in a circinnferential sense and past which air may flow for directing such air from an annular outerzone with a swirling action against the diverginglysprayed oil, and an air directing member formed as a truncated cone with an included angle that is not less than .theincluded central angle of said truncated conical face of the ,nozzle and disposed about said outer forward face of said nozzle and forming part of said swirler for directing air, from an annular zone inwardly along said conical surface toward the axis of said orifice, said series of blades being provided in a number that is a whole number multiple of said predetermined number of streams of oil.

3. A swirler for, use with an oil burner of the gun type wherein air flows forwardly in a burner tube to a combustion chamber, said swirler being adapted to be supported transversely in a burner tubeand comprising aplurality of segmentalv symmetrically arranged fan-likeblades connected to and projecting outwardly from an annular supporting rimand operable to impart a swirling movement to forwardly moving air in the tube and to direct part of such air in an inward direction forwardly of said rim, said annular vrimhaving its inner border portion formed as a forwardly extending truncated cone in a position to intercept the inwardly directed air, and said swirler including an inner annular supporting ring adapted to be mounted on a. nozzle to support the swirler thereon within andin a transverse relation to such a burner tube and having a plurality of spaced members extended outwardly'from said inner ring and secured near their outer edges to-the rear face of said rim, said cone being effec- 9 tive to direct forwardly moving air in an inward direction toward the axis of the cone, and the forward face of said cone being effective to direct inwardly moving air in a somewhat forward direction as such inwardly moving air approaches the central axis of the cone. 5 1

References Cited in the file of this patent UNITED STATES PATENTS 10 E-weryd Dec. 23, 1941 Sanborn Oct. 18, 1949 Logan July 18, 1950 Murphy Sept. 9, 1952 Hirtz Apr. 14, 1953 Kienle Oct. 2, 1956 Young Aug. 20, 1957 FOREIGN PATENTS Canada Jan. 22, 1952 France Jan. 8, 1947

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