US1848206A - Liquid fuel burner - Google Patents

Description

March 3, 1932. E AN 1,848,206

LIQUID FUEL BURNER Filed Oct. 3, 1930 I I s- .1

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' UNITED STATES PATENT OFFICE BALLSTON ll. SHERMAN, OF GLASTON'BUBY, CONNEGT IGU'T, 'ASSIGNOB TO THE SILENT GLOW OIL BURNER CORPORATION, OF HARTFORD, OONHEGI'IGUT, A GOBPORATION OF CONNECTICUT mom runn nvnnnn V Application filed October 3, 1930. Serial ilo. 488,129.

This invention relates to oil burners of the type supplied with oil or other hydrocarbon fuel in liquid form, the fuel beingvaporized within the burner and there burned with a suitable mixture of air. For descriptive purposes the fuel herein referred to is oil, al though other types of liquid fuel may be employed.

A common type of such a burner is one pro? o vided with one or more combustion chambers having perforated, tubular walls, through which air enters to mix with the oil vapor ascending from a fuel space, thelatter being usually in the form of a fuel groove, trough or other chamber below the combustion chamber, the mixture being burned in the combustion chamber and a blue flame issuing from the open upper end thereof,-

In starting a burner of this type from a cold condition, it is customary preliminaril to heat the burner walls and base before fina ly turning on the full continuing supply of oil. One common method of effecting such preliminary heating is. to provide the fuel groove or trough with an asbestos wick, which is first saturated with oil or other priming deposits when present tend further to retard complete combustion, building up and clogging the fuel grooves and connecting ducts, interfering with the free flow of the oil in thin film-like form and tending to insulate the liquid oil from the heated walls of the burner. v This prolongs still further the starting interval, and these' deposits must be removed from time to time with considerable inconvenience. Their presence on the bottoms and sides of the fuel grooves also provides a medium by which the oil, through capillary attraction; tends to creep up and over the sides of the grooves, with the resultant accumulation on the outside of the 5 burner and its adjacent parts of oil, carbon deposits and dirt.

It has been the almost universal custom heretofore to construct the grooved base of burners of this class fromcast metal, usually cast iron, in order to provide the necessary mass and rigidity to avoid burning out and warping. The fuel spaces which receive the liquid oil thereby present oil contacting surfaces which are more or less rough, harsh and porous, with occasional blow holes either fluid and thenlighted by a taper. After a short interval, when the temperature of the adjoining walls of the burner is .sufiicient to cause vaporization of a substantial portion of the oil reaching the fuel groove, the oil supply is turned on. As the temperature rises the oil becomes vaporized at a more rapid rate, and after the lapse of a suitable interval, which may be termed the starting interval, the oil reaching the fuel space or spaces is completely vaporized and an in tensely hot flame results.

These burners as heretofore constructed large or minute which are inevitable to the process of casting. The harshness and roughness of these surfaces become intensified through use due to the inevitable oxidization which takes place. This type of surface, due to the relative high surface tension of the oil thereon, tends to retard the free flow of oil and to cause it to enter the fuel space to which it is delivered, and to accumulate therein, in the form of a slow-flowing, relatively thick and more or less localized body as distinct from a thin, relatively tensionless film capable of spreading readily and rapidly over the entire bottom of the fuel space or spaces to which it has access, the latter condition representing the ideal condition for quick,

49 have had certain disadvantages. The time required for the starting interval has been, quite substantial and prolonged, this being due in large part to the slow initial vaporization of the oil. This not only imposes a 4% measure of restriction on the use of such burners but tends to produce incomplete combustion, particularly in the initial stages of starting, with the formation of deposits of unconsumed carbonon the walls of the fuel space with which oil comes in contact. These rapid vaporization. The character of surface presented by the cast iron tends to augment the deposits of unconsumed carbon, further prolonging the starting interval, and to increase the difliculty with which these deposits are removed since they tend to cling tothe cast surface with great tenacity.

I have found that by so fashioning the burner as to provide a smooth, highly polished or glazed surface for the oil grooves, 01"

for those parts of the burner with which the oil tends to contact, the surface tension of the oil is markedly reduced, it flows freely and unimpeded, quickly spreading over the entire available area in the form of a thin tensioiiless film. This results in accelerating its vaporization, materially reducing the starting interval, retarding and cutting down the collection and deposits of unconsumed carbon and preventing in large measure the seepage and filtration of oil over the sides of the grooves. Furthermore, such deposits of carbon which tend to cling tenaciously to the cast metal surfaces of the grooves and ducts are readily removed without difficulty from the smooth, polished surfaces of the grooves and ducts.-

In the preferred and illustrated embodiment of the invention, such surface is provided by coating the metallic oil contacting walls of the base with some material such as vitreous enamel. Such coating-is capable of presenting a uniformly and permanently smooth, highly glazed surface incapable of oxidization, closing and covering the pores and blowholes in the base and permitting the oil to flow thereover under a relatively low surface tension. The character of this surface thereby presented not only speeds up the starting of the burner and assists in retarding the formation of deposits of unconsumed carbon,

but such effects are further enhanced by the coating itself. The latter tends to heat rapidly, while the external conduction of its heat to the metal of the base, due to the difference in character between-the two materials, is more or less retarded. The coated surface of the fuel grooves therefore tends to heat morerapidly than the uncoated surface and more rapidly acquires the needed temperature for effectively vaporizing the oil. This also tends to prevent the casting itself from overheating, burning out or warping, and the casting as a consequence may be made relatively less massive with a resultant reduction in the weight of the burner and the amount of metal required.

The invention will be best understood by reference to the following description when taken in connection with the accompanying illustration of one specific embodiment thereof while its scope will be more particularly pointed out in the appended claims.

In the drawings:

F'g. 1 is a plan oview of a burner embodying one form of the invention, the upper cover plates resting on 'the'tops of the sheet metal cylinders being partly broken away to better show the construction of, the base part.

Fig. 2 is a vertical, central, sectional elevation, partly brokenaway, showing the burner illustrated in Fig. 1;

Fig. 3 is a sectional elevation on the line 3-3 in Fig. 1; and

Fig. 4 is an enlarged, sectional elevation in detail taken through the inner fuel space to show the application of the enamel coating to the inner surface thereof.

Referring to the drawings and to the embodiment of the invention which is here submitted for illustrative purposes, the burner is provided with a base member 1 (Fig. 2) the body of which is of metal and herein of cast iron. This comprises an outer annular plate 3 and an inner annular concentric plate 5 connected one to the otherbyaseries of webs 7 (Figs. 1 and 3), herein four in number, and providing for an annular air admission space 9 between the plates, this space being interrupted only by the webs 7.

The inner plate 5 is provided with a central air admission opening 11 surrounded by an upturned, ring-like flange 13, the outer edge of the inner plate having also an up.- turned, ring-like flange 15 spaced from but concentriowith the flange 13.

The flanges 13 and 15, together with the bottom plate 5, form a relatively wide annular channel 17 presenting a fuel space or chamber, to the inner part of which the oil is delivered by a ,pipe' connection 19 through an openin in the bottom of the channel. The top 0 the space defined by the channel is closed except for the direct escape of vaporized fuel to the combustion chamber by a removable cover plate 21 seated on the upper edge of the flange 13 and provided with a downwardly extending rim or sleeve 23 which fits within the flange and positions the cover plate thereon. The walls of the plate 21 extendoutwardly and herein downwardly over the channel 17, being spaced vertically from the bottom of the channel and spaced peripherally from the inner walls of the flange 15 to provide an annular exit slot for the passage of the vaporized oil into the overhead combustion chamber.

The cover plate 21 is provided with an upturned, annular flange 25 within which there is secured a perforated sheet metal cylinder 27. A similar but larger concentric cylinder 29 is removably seated on the outer shoulthroughout substantially theentire surface thereof, small perforated areas only being shown in Fig. 2. It will also be understood that these perforations may be of any shape, size or arrangement so long as they provide suitable air admission openings for thecombustion chainber.

In the illustrated embodiment of the invention there is also provided an outer fuel space 33 formed between the upright, annular, spaced, concentric flanges 35 and 37 on the outer plate 3. Concentric, spaced, perforated sheet metal cylinders 39 and 41 are removably seated on the shouldered edges of the flanges 35 and 37, providing between them the combustion chamber 43. The outer fuel space 33 is connected with the inner channel or fuel space 17 by means of the sup 1y ducts 45 (Figs. 1 and 3) formed in the we s 7.

A removable cover plate 47 is provided with its edges resting on the tops of the sheet metal cylinders 39 and 41 to close the top of the annular air space therebetween, and a generally disc-shaped closure plate 49 with its edges resting on the upper edges of the cylinder 27 is slmilarly provided to close the top of the central air chamber, leaving annular openings at the top of the two combustion chambers 31 and 43 for the escape of the products of combustion. The closure plates 47 and 49 may, if desired, be provided with one or more apertures to permit the partial escape of the air therethrough.

lVhile for simplicity a single burner unit only is shown, the same constructional features may be embodied in two or more duplicate units, the generally annular base member 1 being connected to the corresponding base member of the other unit or units by webs integrally cast therewith or'by other connections.

The specifically described form of burner is shown merely as illustrative of one burner of a suitable type to which the present invention may be applied.-

In the operation of the burner, the latter is preliminarily heated either by igniting an asbestos wick (not herein shown) positioned in thefuel space and saturated with oil admitted through the supply pipe 23, or by means of a priming fluid alone placed in the fuel spaces, or in any other desired manner. After the burner has been preliminarily heated,-liquid fuel is then admitted through the fuel supply pipe 19 under the regulation of any of the usual feeding devices. These commonly provide for the flow of fuel from a feeding device at some definite level which may be accurately regulated so thatthe flow of fuel may be maintalned at an approximately predetermined level over the flow surf-aces which are presented by the channels or grooves 17 and 33 and a flow thereby maintained of rel tively shallow depth, spreading over the flow surfaces in a more or less film-. like form. Such regulating devices are of the usual or common construction and are not herein shown.

In the initial starting stage of the burner this oil film becomes vaporized by the heat imparted thereto from the surfaces of the fuel spaces with which it contacts, this vaporiz'ation at firstproceeding slowly and taking area of the uel s bout the entire oil contacting aces but accelerating more or less ra idly, ependent to a substantial extent on t e freedom with which the oil flows over the surfaces, the thinness of the film of oil, and the rapidity with which the oil contacting surfaces acquire and store up the necessary heat for vaporization. After the starting period, andwhen the burner is in full effective operation, vaporization will take place almost wholly in the vaporizing space which is formed by the broad covered inner place throu part of the channel 17, the bottom of which provides a flow surface of considerable area for the entering oil, and the oil will passin vaporized form into the outer part of the fuel space 17 which registers with and opens into the inner combustion chamber 31 and through the ducts 45 to the outer fuel space 33 and thence into the outer combustion chamber 43.

In order to impart to the oil contacting walls of the fuel space the desired character of flow surfaces already explained, the base casting 1 is prepared by applying a baked vitreous enamel coating 51 to the flow surfaces, such a coating being represented in the drawings herein by heavy black lines of exaggerated thickness to distinguish them from other heavy shade lines. In the described embodiment this coating is applied not only to the bottom of each fuel space 17 and 33 (Figs. 2 and 4) ,but to the sides thereof as well as to the inner walls of the duct 45 (Fig. 3), thereby providing a smooth, glazed, enamel surface covering all parts of the base with which the liquid oil can come in contact in the normal operation of the burner both during the starting interval and thereafter.

Any of the usual or well-known processes for enameling cast iron articles may be employed fo'r'this purpose. By way of example only, the following enameling rocess mag be utilized. A composition is rst forme consisting of 12 parts of potters clay, 8 parts of borax, 10 parts of Whitelead, 2 parts of potassium nitrate, 1 part of calcined white marble, 2 parts of purified potash and 5 arts of calx of tin. This composition is nely powdered, mixed and fused. When cold, the

resultant vitreous mass is ground to a powder, sifted and mixed with water toform a thin paste. J The casting is cleaned, as by pickling, and then dried. The paste is then applied to the surfaces of the ase casting which are to becoated by dipping, brushing or spraying. The sides and bottoms of the fuel spaces 17 and 33 and the walls of the ducts 45 having been coated with the paste, the base casting is then placed in a banking or enameling oven and subjected to a sufficiently high temperature to fuse the coating, after which it is allowed to cool.

The described construction provides a burner functioning. in a distinctly improved manner in that the oil supplied during starting vaporizes at a more rapid rate the starting interval is materially reduce and deosits of unconsumed carbon are retarded. ihe surface is uniformly and permanently smooth, impervious to the effects of oxid ze.- tion through continued usage and provides for an extremely low surface tension for the oil. The surface coating being of enamel heatsup rapidly and yields its heat to the thin oil film thereon, conduction of the heat to the base casting being more or less retarded. While I have herein shown for the pur ose of illustration one specific embodiment o the invention as applied to one specific t pe or form of burner, it is to be understood t at the coating surface may be produced in various wa s and that it may be applied to widely different forms of burners, all without departing from the spirit of the invention.

Claims:

1. A burner having sets of spaced, con centric tubular, perforated Walls to rovlde between them a plurality of com ustion chambers, a cast metal base member having a plurality of fuel grooves communicating one with each of said chambers, supply ducts connecting said grooves, and means for supplying liquid fuel to one of said grooves, the surfaces in said grooves and ducts which are adapted to contact with the liquid fuel supply being covered with a glazed coating of vitreous enamel.

2. A burner having spaced, perforated, tubular walls one enclosing the other to provide between them a combustion chamber, a cast metal base member havin a fuel chamber communicating with said combustion chamber, in which fuel chamber the vaporization of liquid fuel is adapted to take place during operation of the burner, and means fortsupplying liquid fuel to said fuel chamber, the said fuel chamber having its surfaces whichare adapted to contact with the liquid fuel supply covered with a glazed coating of vitreous enamel.

8. A burner having spaced, perforated, tubular walls one enclosing the other to provide between them a combustion chamber, a cast metal base member having a fuel chamber communicating with said combustion chamber, in which fuel chamber the vaporization of liquid fuel is adapted to take place during operation of the burner, and means for supplying liquid fuel to said fuel chamber, the said-fuel chamber having its surfaces which are adapted to contact with the liquid fuel supply covered with a coating presenting a smooth, polished surface.

4. A burner having a combustion chamber, a communicating fuel chamber in which the vaporization of liquid fuel is adapted to take place during operation of the burner, and means for supplying liquid fuel to said fuel chamber, the said fuel chamber having its surfaces which are adapted to contact with the liquid fuel supply covered with a coating presenting a smooth, polished surface.

5. A burner having a combustion chamber, a communicating fuel chamber in which the vaporization of liquid hydrocarbon fuel is ada ted to take place during the operation of the urner, and means for supplying li uid hydrocarbon to said chamber, the said uel chamber presenting surfaces which are adapted to contact with the liquid fuel supply and presenting a smooth, polished surface adagted to provide a low surface tension to t e liquid fuel contacting therewith.

6. Aliquid fuel burner having a base, a lperforate tubular wall supported on said ase and forming a combustion chamber thereover, and means for supplying liquid fuel to said base, said burner having surfaces in its said base covered with a glazed coating of vitreous enamel to receive and vaporize sald liquid fuel.

7; Fuel receiving and vaporizing means for liquid fuelburners comprising a metallic member provided with a fuel vaporizing surface having a glazed coating of vitreous enamel adapted to receive liquid fuel and vaporize the same thereon.

8. A burner having a base provided with a vaporizing surface, a perforated tubular wall supported on said base and forming a combustion chamber thereover arranged to receive vapor from said vaporizing surface, and means for supplying liquid fuel to said vaporizing surface, said vaporizing surface comprising a coating presenting a smooth, polished surface.

In testimony whereof, I have signed my name to this s ecification.

RA LSTON M. SHERMAN.

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