US1848207A - Liquid fuel burner - Google Patents

Description

R. M. SHERMAN LIQUID mm1J BURNER Filed Feb. 12, 1931 March 8, 1932.

' of oil.

Patented Mar. 8, 1932 UNITED STATESl PATENT OFFICE RALLSTON H. SHERMAN, OF GLASTONBURY, CONNECTICUT, ASSIGNOR TO THE SILENT GLOW OIL BURNER CORPORATION, 0F HARTFORD, CONNECTICUT, A CORPORATION 0F CONNECTICUT LIQUID FUEL BURNER Application led February 12, 1931. Serial No. 515,834.

This invention relates to oil burners of the type supplied with oil or other hydrocarbon fuel in liquid form, the fuel being vaporized within the burner and there burned with a suitable mixture of air. For descriptive purposes the fuel hereiny referred tois oil, although other types of liquid fuel may be employed. Y

A common type of such a burner is one provided 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, the latter Vbeing usually in the form of a fuel groove, trough or other chamber in the combustion chamber, the mixture being burned n 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 preliminarily to heat the 'burner Walls and base before finally turning on the full continuing supply 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 fluid and then lighted by a taper. After a short interval, when the tempera.-` ture of the adjoining walls of the burner is suflicientito cause vaporization of a substantial portion of the oil reaching the fuel groove, the oil supply is turned on. As the due in large part to the slow initial vaporization of the oil. This not only imposes a measure of restriction on. the use of such burners but tends to produce incomplete combustion, particularly in the initial stages of starting, withl the formation of deposits of unconsumed carbon on the Walls of the fuel space with which oil comes in contact. These vides 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 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 from cast 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 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 4flow 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, 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 difficulty with which these deposits are removed since they tend to cling to the cast surface With great tenacity.

The quickness of starting depends largely on the rapidity with which the oil contacting walls of the base take up heat conducted or diffused thereto from the combustion chamber and particularly from the shells or chimneys which soon become red-hot after the wick or wicks have been lighted. Where the.

shells are of relatively light sheet metal-and the base is a casting of relatively large mass, this process of raising the temperature of the oil contacting walls of the base is necessarily relatively slow.

I have found that by employing a base of cast iron or other metal having oil contacting surfaces covered with a closely adherent thin skin or coating of some metal, such as cadmium, copper or the like, as by electroplating, the conduction of heat to the oil from the chimney walls is materially facilitated and the starting interval materially reduced. If, for example, a cast iron base is electrolated with cadmium, the thin skin or coating of cadmium which contacts with the oil has a heat conductivity which is substantially greater than that of the cast iron which supports it while its coefficient of thermal capaclty, or s ecific heat, is substantially less than that o cast iron. The result is that it heats rapidly, acting as a quick surface conductor of the heat from the chimneys and from the combustion chamber to the oil, while the external conduction of its heat to the metal of the cast iron base, due to its nonhomogeneity or the difference in the character between the two materials, is substantially retarded. The coated surface of the fuel grooves therefore acts as a quick heat transmitter, rapidly acquiring 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.

Furthermore the plated surface encloses and covers the pores and blow holes in the casting, providing a relatively smooth surface over which the oil tends to flow freely and unimpeded with a lesser surface tension than where it contacts directly with the cast metal, so that it tends to quickly spread over the entire available area in the form of a thin, tensionless film. The character of this surface tends to resist oxidizat-ion and retards the formation of deposits of unconsumed carbon and the tendency of the oil to creep up and over the sides of the base.

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

In the drawings:

Fig. 1 is a plan view 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 broken away, showing the burner illustrated in Fig. 1;

Fig. 3 is a cross 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 ap lication of the cadmium plating to the sur ace thereof.

Referring to the drawings and to the emy bodiment 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. Thiscomprises an outer annular plate 3 and an inner annular concentric plate 5 connected one to the other by a series 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 pla-te 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 upturned, ring-like flange 15 spaced from but concentric with the flange 13.

The flanges 13 and l5, together with the bott-om 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 opening in the bottom of the channel. The top of the s )ace defined by the channel is closed except or the direct escape of vaporized fuel tothe lcombustion chamber by a removable cover plate 2l 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. This cover plate is preferably of thin sheet metal, being thereby adapted to heat rapidly from the heat radiated from the combustion chamber and conducted thereto from the inner chimney or tube E27. By constructing it of sheet metal instead of cast iron, it also serves to restrict less of the cross-sectional area of the central air opening 11, thereby providing for a freer supply of air to the central air chamber.

The walls of the plate 21 extend outwardly and herein downwardly over the channel 17, being spaced vertically from the bottoni 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 2l is provided with an upthe combustion chamber 43.

turned, 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 shouldered edge ofthe upright flange 15, so that there is provided between the two cylinders the combustion chamber 31 opening at the bottom through the annular exit slot referred to into thefuel space within the channel 17. It will be understood that the perforations in the sheet metal cylinder are distributed throughout substantially the entire 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 the combustion chamber.

In the illustrated embodiment ot' the invention there is also provided an outer fuel space 33 forlned between the upright, annular, spaced, concentric flanges and 37 on the outer plate 3. Concentric, spaced, perforated sheet metal cylinders 39 land 41 are removably seated on the shouldered edges of the flanges 35 and 37, providing between them The out-er fuel space 33 is connected with the inner channel or fuel space 17 by means of the supply ducts 45 (F igs.'1 and 3) formed in the webs 7.

A removable cover plate 47 is provided with its edges resting on the tops of the sheet metal cylinders 39 and 4l to close the. top of the annular air space therebetween, and a generally disc-shapedclosure plate 49 with its edges resting on the upper edges of the cylinder 27 is similarly provided to close the top of the central air chamber, leaving annular openings at the top of the two combastion 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.

While 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 mem ber 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 in vention 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 the fuel space and saturated with oil admitted through the supply pipe 19. 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 mafy be accurately regulated so that the flow of nel may be maintained at an approximately predetermined level over the flow surfaces which are presented by the channels or grooves 17 and 33 and a flow thereby maintained of relatively shallow depth, spreading over the flow surfaces in a more or less filmlike form. Such regulating devices are of the usual or common construction and are not herein shown.

ln 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 vaporization at first proceeding slowly and taking place throughout the entire oil contacting area of the fuel spaces but accelerating more or less rapidly, dependent to a substantial extent on the 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 transmit the necessary heat for vaporization. After the starting period, and when the burner is 1n full effective operation, vaporization will take place almost Wholly in the vaporizing space which is formed by the broad covered inner part of the channel 17. the bottom of which provides a flow surface of considerable area for the entering oil, and the oil will pass 1n 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 provide the quick heating surface previously referred to for parts of'the base which are adapted to be brought into contact with the liquid fuel, the base casting is prepared by applying to the liquid-oil recoating. This may be had by employing one.

of the ordinary galvanizing processes in which the base is dipped in a bat-h composed of molten zinc` tin or the like, combined with a suitable flux, or by an electro-plating process through which a suitable metal is electrolytically deposited. Electroplating is preferable since it provides a closer structural union with the base better adapted to withstand the high temperatures to which the burner is subjected, and since it also permits the use of metals better qualified to secure the desired object.

In the elect-roplating process copper or other metals may be employed, but I preferably employ cadmium, since in respect to its thermal conductivity, specific heat and the character of surface produced it effectively combines those qualities which are desirable in securing the described objects and provides a surface which, Without the necessity of polish, allows the oil to flow freely with aminimuln of carbonization.

Any of the usual electroplating processes may be employed for depositing the cadmium or other` metal on the base. lVhile it is mainly essential that the liquid-oil receiving surfaces are plated with the metal, the simplest method of applying the latter is to electroplate the entire surface of the east iron base,- the top, bottoni and sides, as well as the surfaces of the fuel grooves, ducts and other spaces. rl`his provides a metal plating which not only covers the surfaces of the oil receiving spaces, but is carried up and over the tops of the flanges on which are supported the sheet metal chimneys so that the quick heating skin or film of metal is brought into direct heat conducting contact with the chimneys. It is only necessary that the deposition of metal be heavy enough to provide a firmly united coating and a continuous unbroken surface, and except for these structural limitations the vaporizng effect is improved by keeping it as thin as possible. The. thickness of one-quarter of .001 of an inch will ordinarily suffice.

In Figs. 2 and 3 the cadmium plated coating 51 is represented by heavy black lines of exaggerated thickness to distinguish them from other heavy shade lines, and in Fig. 4 by the body of cross-sectioned metal also of exaggerated thickness. lt will be seen that this plated coating covers not only the bottom of each fuel space 17 and 33 (Figs. i2 and 4). but the sides thereof and the top of the flanges. as well as the inner Walls of the ducts 45, so that 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, are provided with the cadmium surface described.

The described construction provides a burner functioning in a distinctly improved manner in that, during the starting interval, heat radiated from the combustion chambers and transmitted by direct contact from the heated combustion tubes is quickly taken up by the thin coating of cadmium and transmitted rapidly to the liquid oil, so that the latter is vaporized at a more rapid rate than has heretofore been possible and the starting interval is materially reduced. At the same time. the smooth` close grained surface presented by the. plated coating provides for an extremely low surface tension for the oil` so that the latter flows readily thereover with the result. that the deposition of unconsumed carbon and creepingl of the, oil are retarded and a surface presented which opposes oxidization through continued usage and is easily cleaned.

While I have herein shown for the purposes of illustration one specific embodiment of the invention as applied to one specific type or form of burner, itis to be understood that the coating surface may be produced in various ways and that it may be applied to widely different forms of burners, all without departing from the spirit of the invention.

I claim:

l. A burner having sets of spaced, tubular, perforated walls to provide between them a plurality of combustion chambers, a cast metal base having a plurality of fuel chambers communicating one with each of said combustion chambers, a supply duct connecting said fuel chambers, and means for supplying liquid fuel to one of said chambers, the surfaces of said chambers and duct which are adapted to contact with the liquid fuel supply being covered with a thin, adherent coating of a metal having a greater heat conductivity than that of the base.

A burner having a cast metal base, perforated tubular Walls supported by the base and forming a` combustion chamber, means for supplying liquid fuel to the base, the latter present-ing surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel, and a plated, metallic coating covering the oil-receiving surfaces and the tube-supporting surfaces of said base.

8. A burner having a metallic base, a perforated tubular wall supported on said base and forming a combustion chamber, means for supplying liquid fuel to the. base, thelatter presenting surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel, and a cadmium plated surface on fuel receiving portions of said base.

4. A burner having a metallic base, a perforated tubular wall supported on said base and forming a combustion chamber, means for supplying liquid fuel to the base, the latter presenting surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel, and a thin, adherent, metallic coating on the surfaces of said base composed of a metal having a greater heat conductivity than that of the base.

5. A combustion tube burner having a combustion chamber, a metallic base, and means for supplying liquid fuel to the burner, said base presenting surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel. said surfaces having a thin, adherent coating of metal having a heat conductivity greater than that of thebase.

6. A combustion tube burner having a combustion chamber, a base, and means for supplying liquid fuel to the base, said base presenting surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel, said surxool faces having a thin, adherent coating of cadmium.

7. A combustion tube burner having a combustion chamber, a cast metal base, and means for supplying liquid fuel to the burner, said bas-e presenting surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel, said surfaces having a thin, plated, metallic coat- A combustion tube burner having a combustion chamber, a cast metal base, and

` means for supplying liquid fuel to the base,

said base presenting surfaces adapted to receive the liquid fuel and to vaporize the same thereon by the heat of combustion of the fuel, said surfaces having a thin, adherent coating of a metal different from that of the base.

9. A burner having a combustion tube, means for supplying liquid fuel to the burner, and a metallic base having a thin, adherent, metallic coating of a metal of greater heat conductivity than the metal of the base.

10. A combustion tube burner having a. cadmium plated, east metal base, a combustion tube supported thereby forming a combustion chamber,'and means for supplying liquid fuel to the base.

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

RALLSTON M. SHERMAN.

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