US2820511A - Burner assembly - Google Patents

Description

Jan. 2l, 1958' J. E. MccUTcHEN BURNER ASSEMBLY Filed June 16, 1955- INVENTOA: WZ

ATTORNEYS. w

tates This invention relates to a heat transfer appliance, and more particularly to a burner assembly adapted to burn liquid fuels and especially heavy liquid fuels such as diesel oil, etc.

This application is a continuation-in-part of my copending application, Serial No. 283,233, filed April 19, 1952 (now abandoned), for Heat Transfer Appliance.

In numerous applications it has been found desirable to employ burner assemblies using wicks as a means for transferring liquid fuel from a reservoir or fuel inlet to the combustion chamber. ln such burners liquid fuel is transferred through the wicks by capillary action and the rate of fuel transfer and therefore the heat capacity of the burner is dependent to a large extent upon the capillarity ofthe wicks and the viscosity of the fuel. It has been found that where wick type burners are used with viscous fuels such as heavy diesel oil, and especially where when combined with such fuel the burner is operated in an upright or vertical position, the burners rapidly lose their capacity and the heat output of the burner becomes so low in a short time that the burner is practically useless.

I have found that this rapid reduction in the burner capacity after a short period of use is apparently due to the high accumulation of residue from the heavy diesel fuel in the body of the wicks. Such residue accumulations seriously reduce the capillarity of the wicks and thereby retard the capillary flow of fuel therethrough. The result is a rapid diminishing in the burners capacity to consume fuel and therefore in its heating capacity.

It is imperative that a burner function satisfactorily in any position, including an upright position, and it is frequently necessary that the burner be operable when viscous fuels such as diesel oil are used. Further, the burners when operating on diesel fuel and when in an upright position must operate at high capacity for long periods and without appreciable reduction in the heat capacity.

It is, accordingly, an object of this invention to provide a wick type burner assembly that overcomes the dilliculties set out above. Another object is to provide a wick type burner assembly that will operate for long periods on diesel fuel and the like and when in an upright position without diminution of the heat capacity of the burner. Still another object of the invention is to provide a burner assembly that will operate at high capacity for long periods even upon accumulation of fuel residue in the body of the wicks when viscous fuel oils are used. A further object is in the provision of a wick type burner wherein a plu" rality of wicks extend radially outwardly and are supported in trough-like lingers that can operate as fuel conduits and reservoirs therefor in the event that the capillarity of the wicks is reduced by residue accumulations therein. Still a further object is in providing a burner assembly that is easily and inexpensively fabricated and that is readily cleaned of fuel residue. Additional objects and advantages wll appear as the specification proceeds.

An embodiment of the invention is illustrated in the accompanying drawing, in which- Figure l is a top plan view with portions broken away of a burner assembly embodying my assembly; and Fig. 2 is a vertical sectional View taken on the line 2-2 of Fig. l.

The burner assembly illustrated includes a tubular casing or shell itl that is open at both the top and bottom ends thereof. The shell it@ may be of any cross-sectional Uie @tif

configuration and in certain applications wherein the burner is enclosed within a furnace casing, etc., it may be possible to eliminate the shell 10 completely.

An air baffle 1l having a relatively flat inwardly-extending portion 12 and a downwardly-turned annular flange 13 formed integrally therewith is rigidly secured adjacent the bottom edge of the tubular casing 10 by any suitable means such as tack welding or riveting, etc. Adjacent the inner edge of the flat portion l2 the air baffle turns upwardly and extends inwardly and terminates in an annular or circular opening 14 through which air is admitted to the interior of the casing or combustion cham ber l5, in a manner hereinafter described.

Secured to the laterally or downwardly turned flange 13 of the air baffle are a plurality of straps i6 that are relatively rigid and extend inwardly where they are secured to an annular sleeve 17 that is also a relatively rigid member. The web 16 may be welded to the downwardlyturned flange 13 and to the sleeve 17 to provide a sturdy structure, or other suitable means for securing the straps to these members may be used. A boss or nut 18 is rigidly secured to the sleeve 1'7 and, if desired, may be formed integrally therewith. The nut 18 is preferably provided with threads 19 along the inner surface thereof.

A wick housing designated generally by the numeral 2i) provides centrally a cup 21 forming a reservoir 22 in the interior thereof and the cup 21 is equipped with a downwardly and inwardly inclined bottom wall 23 that at its lower end is formed integrally with a cylindrical connector 24 having threads 25 that threadedly engage the threads provided by the nut 18. The connector 24 has a longitudinally-extending passage 26 therethrough that communicates through an opening in the bottom wall 23 of the cup with the reservoir 22 provided by the cup. Preferably the lower end of the passage Z6 is threaded at 27 so that a suitable fitting carried by a fuel conduit may be connected to the member 2d. The passage 26 provides a fuel inlet for the burner assembly that communicates with the interior of the cup 2l. The cup 21 is centrally aligned within the annular opening 14 provided by the air battle and is spaced a substantial distance from the edge of the opening 14 so that air may readily pass between the cup and edge of the air bal-lie.

The wick holder 20 is equipped with a plurality of troughs or trough-like fingers 28 that extend radially outwardly from the cup 2l as is seen best in Fig. l. The troughs 28 are equipped with upwardly-turned side walls 29 and an upwardly-turned end wall Sil. At their inner ends the troughs 28 are in open communication with the interior 22 of the cup 2i and they provide a conduit and reservoir for liquid fuel when this is required, as will be hereinafter described. Supported in each of the troughs 28 is a wick 3i that has an inner end extending downwardly and into the reservoir 22 provided by the cup 21 as is illustrated best in Fig. 2. The wicks extend along the troughs 28 and at their outer ends each wick is turned upwardly to provide an extended portion .32 that is above the walls 29 and 3d of the troughs.

Any suitable heat resisting material may be employed for forming the wicks 31. I have found that glass fibers form an excellent wick structure and that the glass may be coated effectively with a refractory material which greatly increases its ability to withstand high temperatures. For example, I have found that I can apply a coating of refractory oxide to each individual fiber of a glass fiber wick by wetting the wick with a solution of a soluble salt which will upon decomposition deposit a refractory oxide on the ber. For example, a solution of thorium nitrate may be applied to the capillary material by simply immersing one end of the capillary wick in the solution and thereby the solution is drawn up about the individual fibers to coat them. After drying, the Wick structure may be heated to cause decomposition of the nitrate which deposits a coating of oxide upon the glass fibers.

A reinforcing band 33 is secured within the tubular casing l adjacent the upper end thereof by welding or riveting, etc., and rigidly secured. to the band .33 at spaced positions thereabout are a plurality of support straps 3dthat are relatively sturdy members and extend inwardly and at their inner ends are rigidly secured to an annular band or closure wall 35. A disk-like member designated generally with the numeral 36 may be struclr outwardly t0 provide a plurality of upwardly-extending and angularly-inclined vanes 37 that extend outwardly at their outer ends are rigidly secured to the wall 35 by welding. If desired, the vanes .36 may be reinforced at their inner ends as at 38 or the complete member may be fabricated from a single sheet of metal. The plurality of angularlyinclined vanes provide a retarder or flame spreader that for identification will be given the number 39. r,The retarder member 39 is operative to slow the rate at which the combustion gases escape from the chamber 15 and thereby provides more complete burning of the gases and a greater heat transfer.

The burner cup 2l and entire wiel; housing 2li can be made of sheet metal parts, a .combination of sheet metal and screw machine parts, or may be made by castings. Similarly, the remaining parts described may be made of sheet metal and of any suitable material or may be fabricated in any desirable manner.

Operation In operation, a fuel conduit is connected to the lower end of the fuel inlet passage 26 and the fuel being under pressure, it flows upwardly in the passage 26 and into the reservoir 22 provided by the burner cup 2l. As fuel rises in the reservoir 22 it is taken up by the portion of the wicks 31 that extends into the reservoir 22 and by capillary ow is carried through the wicks and to the upper ends 32 thereof. Air is drawn or forced into the combustion chamber 1S through the annular opening 1.4 provided by the air baille about the burner cup 21. The fuel vapor and air mixture may be ignited and burns within the .chamber 1 5 and the hot gases p "s vardiy and over the vanes 37 provided by the reta! der jember .39 which are effective to retard the rapid egress of vapors from the chamber l5 and thereby bring about a more complete combustion ofthe vapors and a greater heat transfer. The angular vanes 37 also impart a swirling motion to the gases being discharged from the chamber l5 which is beneficial.

As the fuel vapor is burned, additional fuel is carried through the wicks 3l. by the capillary action thereof; and when viscous or heavy oil is used as the fuel, as for er:- ample heavy diesel fuel, it is found that within a short time a fuel residue accumulates within the body of each wick and seriously decrea the capillarity thereof. in a conventional burner this is serious because it decreases the quantity of fuel available for burning and thereby decreases the heating capacity of the burner. l have found that where a conventional burner is operated in an upright position and where heavy diesel oil is used as a fuel, that within Q hours of oper..;ion it is frequently necessary to completely replace the burner for sufcient fuel cannot be carried through the wicks to maintain the heating capacity of the burner.

With my structure, however, as fuel residues accumulate in the body of each wick and the capillarity thereof decreases, the fuel which is under slight pressure within the passage 26 rises within the reservoir 22 provided by the burner cup 21 and flows outwardly within the troughlike fingers 23 extending radially outwardly from the burner cup 21. As fuel flows into the troughs 28 the fuel is exposed to the heat of the combustion chamber and the fuel within the troughs vaporizes and provides combustible vapors so that the heating capacity of the Cil burner is not diminished. As more and more residue accumulates in the wicks and also in the troughs themselves, the fuel within the reservoir 22 rises to a higher level and also rises to a higher level within the troughs 28. A greater fuel surface is thereby presented to the heat within the combustion chamber and the fuel continues to vaporize and supply the burner with the combustible Vapor necessary to maintain its heating capacity. By test, I have found that the life of a burner embodying my invention is frequently increased to greater than 750 hours, where the conventional burner must be replaced after hours of use.

When the accumulations of fuel residue within the troughs 28 limit the flow of fuel therethrough to such an extent that the burner does not produce heat near its capacity, the wick housing is quickly and easily cleaned by simply removing the wicks 31 and then scraping the troughs 28 clean of the residue with a blunt instrument such as the blade of a screwdriver. After such cleaning, preferably new wicks 31 are placed within the troughs so that inner portions of the wicks extend into the reservoir 22 and the outer ends of the Wicks turn upwardly and provide extended portions 32, as has been described. The burner will function without Wicks but will be, in such case, difficult to light when heavy fuels are used.

While in the foregoing specication I have set forth an embodiment of the invention in considerable detail for the purpose of illustration, it will be apparent to those skilled in the art that considerable change may be made in these details without departing from the spirit and principles of the invention.

I claim:

l. In a burner assembly adapted for use in the burning of relatively heavy fuel oils, a housing providing a fuel cup adapted to receive liquid fuel and providing also a plurality of troughs extending laterally of said cup, said troughs being open at their top side, a Wick within each of said troughs and communicating with said cup, said troughs having side walls extending above said wicks to provide passages above said wicks in open communication with said cup, whereby liquid fuel may flow directly from said cup into the spaces in said troughs above said wicks.

2. The structure of claim l, in which said wicks extend along the bottom of the troughs and have end portions which extend upwardly above said troughs adjacent the outer ends of the troughs.

3. The structure of claim 1, in which certain of the wicks have end portions extending into the cup while at the same time providing liquid llow passages between the wicks and into said troughs.

4. A burner assembly adapted for use in the burning of relatively heavy fuel oils, comprising a housing providing a cup reservoir adapted to receive liquid fuel therein, said cup being open at its top, said housing also providing troughs extending laterally of the cup and communicating therewith, said troughs being open at their top, wicks in said troughs and communicating with the fuel in said trough, said troughs having side walls and end walls higher than said wicks and in open communication with the liquid fuel in said cup, said wicks extending along the bottom of said troughs and having their ends projected upwardly above the end walls of said troughs.

References Cited in the sie of uns patent UNITED srArEs PATENTS 422,927 Flagg Mar. 1l, 1890 1,974,818 Kerrick Sept. 25, 1934 2,096,812 Kessler Oct. 26, 1937 2,121,904 Currie c- June 28, 1938 2,570,771 Conrou Oct. 9, 1951 2,671,506 Brevard Mar. 9, 1954 FOR lGN PATENTS 67,956 Germany Apr. 29, 1893

Images