US2966945A - Liquid fuel burning heater - Google Patents

Description

E. S. DOWNS LIQUID FUEL BURNING HEATER Jan. 3, 1961 2 Sheets-Sheet 1 Filed March 26, 1959 FIG.2

FIG.

OOOOOO INVENTOR EDGAR S. DOWNS FIG.3

BY CORBETT, MAHONUEY, MILLER,

& RAM 0, A'ry's. BY 4 ATTORNEY Jan. 3, 1961 E. s. DOWNS LIQUID FUEL BURNING HEATER 2 Sheets-Sheet 2 Filed March 26, 1959 Flags INVENTOR EDGAR s. DOWNS BYCORBETT, MAHONEY, MILLER, a R 50. ATTY'S. BY %4, [6 AT 0RNEY FIG-9 United States Patent LIQUID FUEL BURNING HEATER Edgar S. Downs, P.0. Box 242, Worthington, Ohio Filed Mar. 26, 1959, Ser. No. 802,059

3 Claims. (Cl. 158-96) My invention relates to a liquid fuel burning heater. It has to do, more particularly, with a heater of the oilburning type. More specifically, this application relates to a heater of the particular type disclosed in my copending application Serial No. 711,691 filed January 28, 1958, which issued as Patent No. 2,879,837 on March 31, 1959.

According to this invention, I provide a burner in which liquid fuel, such as kerosene, fuel oil, or gasoline, is vaporized for combustion by a cloth formed of woven threads or yarn composed of long thin ceramic fibers which are twisted or formed into the yarn without the use of binders. This woven ceramic cloth when used in the burner is preferably reinforced by suitable reinforcement which may be combined in the woven cloth or which may be in the form of a separate unit associated with the cloth in a proper manner to resist the stresses encountered in use in the burner. The ceramic cloth has an extremely high degree of capillarity which permits it to move the fuel rapidly from the fuel inlet evenly over its entire area. This causes extremely rapid evaporation of fuel from all parts of the cloth. The heat to accomplish this evaporation is that radiated from the flame which establishes a flame-front a fraction of an inch away from the fuel-wet ceramic cloth. The high rate of evaporation tends to cool the liquid fuel in the cloth and prevent formation of carbon on the cloth through cracking of the liquid fuel. larity, the ceramic cloth also is able to withstand indefinitely the temperatures to which it is exposed and not be attacked by the chemical constituents of the fuel or products produced by oxidation or cracking of the fuel. The ceramic cloth in my burner forms one wall of a combustion chamber and air is passed into the combustion chamber under forced draft through the interstices of the cloth and this flow of air may be aided by holes actually formed through the cloth. The purpose of this air, designated as primary air, is to permit a very rapid and even mixing of air and oil vapor evaporated from the cloth. This rapid mixing establishes the flame front in close proximity to the wet ceramic cloth which provides heat by radiation to continue the rapid evaporation of the fuel. To aid combustion, secondary air is supplied adjacent to the face of the cloth through open-.

3--3 of Figure 2 through the fan chamber and com bustion chamber of the heater.

Figure 4 is a transverse sectional view taken along Beside having high capilline 4--4 of Figure 3 showing the oil-vaporizing ceramic cloth.

Figure 5 is an enlarged sectional detail of a portion of the ceramic cloth and associated support.

Figure 6 is a modification of the cloth arrangement of Figure 5.

Figure 7 is a view similar to Figure 5 but showing a somewhat different arrangement of the ceramic cloth and supporting structure.

Figure 8 is a view similar to Figure 5 but showing a separate wire screen reinforcing the ceramic cloth.

Figure 9 is an enlarged face view of a portion of the ceramic cloth.

With reference to the drawings, in Figures 1 and 2 I have illustrated the general arrangement of a heater in which my invention may be embodied and which general arrangement is similar to that disclosed in my said copending application. This heater is shown as being of the small portable type athough it is to be understood that my invention may be embodied in various other types of heaters. However, with my heater it is possible to obtain efficient combustion without the use of a stack or chimney and, therefore, it is particularly useful as a portable heater.

The heater shown comprises a tubular outer casing 20 carried on the supports 21, which serve as legs upon which the entire heater rests, and which extend upwardly above the housing to support an oil tank 22. A handle 23 is provided above the tank 22 and is connected to the supports 21 and can be used in carrying the heater.

Within the tubular casing 20 and in concentric relationship therewith is a tubular combustion chamber 24. As shown in Figure 3, this chamber 24 is of smaller diameter than the casing 20 so that an annular air passageway 25 is provided therebetween. Also, the chamber 24 is of less length than the casing 20 to form the fan chamber 26 at the open inlet end of the heater and the discharge throat 27 at the outlet end, the throat being flared inwardly as indicated. The chamber 26 has the electric fan or blower 2S concentrically disposed therewithin and associated with the rear or inlet end of the combustion chamber 24 to force air thereinto. The chamber 24 is supported centrally within the casing 20 by means of spacer clips 29 which will not interfere with air flow through the annular space 25 which will be produced by the fan 28.

As shown in Figures 3, 6 and 7, the rear wall of the combustion chamber 24 at the inlet end thereof is formed by aceramic cloth disc 30 which fits within the rear end of the chamber 40 and extends through the cross-sectional area thereof. Spaced forwardly of the cloth disc 30 in the direction of flow of air produced by the fan 28 are the secondary'air holes 31 formed at spaced intervals around and in the wall of the chamber 24.

Oil may be supplied from the tank 22 to the front side of the ceramic cloth disc 30 by means of a line 32. An inlet fitting 33 for this line 32 is provided at the center of the disc 30 and is similar to that disclosed in my copending application. The front or disc-like part of the fitting 33 is provided with one or more channels 36 but two are shown arranged in a V and communicating at their lower ends with the central bo e 37. These channels 36 are preferably semi-circular in cross-section and open rearwardly against the face of the disc 30.

For the initial ignition of the oil. an electric igniting device 35 may be provided just ahead of the ceramic cloth disc 30 adjacent the front or exposed face thereof.

A disc and vane unit 40 may be provided directly downstream from the ceramic cloth disc 30 for the purpose of aiding in the rapid and complete mixing ofair and oil vapor. The unit 40 includes a central disc disposed directly forwardly of the cloth disc 30 associated with an annular ring disposed forwardly thereof and being of larger diameter than the disc. Thus, there is an annular space between the disc and the ring and it will be noted that the ring is also spaced from the combustion chamber wall at the openings 31. With this arrangement, the burning mixture of primary air and oildoes not reach out directlyto thesecondary air holes or openings 31 but must flow forwardly, through the space between the disc and the ring, This structure is, similar to that disclosed in my copending application Serial No. 784,723 filed January 7, 1959.

In Figures 5 to 9, inclusive, I have illustrated several arrangements of the ceramic cloth and the associated mounting structure which is provided at the rear wall of the combustion chamber 24. I

Figure 5 is a detail of the arrangement of thecloth 30 which is shown generally in Figure 3. This cloth 30, as previously indicated, is of disc-like form and fits within thecombustion chamber 24 adjacent the-rear or inlet end thereof. Slightly upstream from the cloth disc 30 is a metalplate or disc 41 which serves as a primary air metering plate and which is provided with a series of spaced primary air apertures or openings 42 formed throughout its area. The ceramic disc 30 and the metal disc 41 may be suitably mounted on the wall ofthe combustion chamber 24 and are spaced from each other by means of a suitable spacer ring 46 at their outer edges; This results in the provision of a fiat airchamber 43; between the discs 41 and 30 which provides for the accumulation and pressure equalization of primary air across the entire area of the ceramic cloth disc 30 at" the rear side thereof. This equalized accumulation of primary air in the chamber 43 under pressure will result in the primary air being forced forwadly or downstream through the interstices in the Weave of the ceramic cloth disc 30. However, to aid in this flow through the cloth disc 30, apertures or openings 44 may be provided in the cloth disc and may be extended completely there through. The apertures 44 arepreferably l'essin numher; than the apertures 42 in the metal disc '41 but the apertures 44 may align with some of the apertures 42. This arrangement of the primary air supply will insure that sufiicient primary air will reach the exposed or down-- stream face of the cloth disc 30 and will be evenly-dis tributed over that face of the ceramic cloth disc to insure complete and uniform combustion at that face. As previously indicated, the secondary air openings 31 provided in the wall of the combustion chamber 24 are spaced slightly downstream from the ceramic cloth disc 30- and secondary air under pressure will be supplied by the blower 28 from the chamber 24 through these secondary air openings 31 to aid in combustion at the downstream] face of the ceramic disc 30.

Figure 6 illustrates a slightly different arrangementof the ceramic cloth disc. In this instance, the disc 30a;

is like the disc 30 except that openingsequivalentto the, openings 44 are not provided therein. In this case, the primary air isall forced through the interstices of the ceramic cloth disc 30a which is woven sufficiently loosely to permit this. This arrangement will function substantially in the same manner as the arrangement of Figure 5.

In Figure 7, I have illustrated a somewhatdifferent arrangement of the ceramic cloth disc and the associated metering disc. In this instance, the ceramic disc 30b issupported with its rear face in fiat contact with the frontface of the metal disc 41b. Primary a-ir'rn'eterin'g openings 42b are provided in the metal disc 41b. In the operation of this burner structure, the primary air will be metered through the apertures 42b and will be forced through the interstices of the cloth disc 30b.

As previously indicated, it is preferred that'some form of. reinforcement be provided for-the ceramic cloth disc. In the forms ofthe ceramic-cloth disc shown in Figures 5, 6 and 7, the cloth of the disc 30, 30a and SObispref erably-reinforced by smallwir'e strands, indicated at 45 which are: woven into the cloth material of the ceramic disc, as shown best in Figure 9. Thus, these woven wire strands will extend throughout the area of the cloth and will provide reinforcement for resisting the stresses created by the pressure of primary air against the cloth disc as it is forced therethrough.

However, it is possible to have the reinforcement formed as a separate unit from the cloth. Such an arrangement is illustrated in Figure 8. The arrangement of the ceramic cloth disc 30c, and metal' disc 41 c in this figure is similar to that disclosed in Figure 5. However, the reinforcement takes the form of a separate foraminous unit or disc 45c whichmay be disposed'incontact with the downstream face of the ceramic cloth disc 300. This foraminous reinforcing unit 450 is in the form of a metal screen but may take other forms which will give sufficient strength to resist the pressure of the primary air but will still permit sufiicient flow therethrough to adequately support combustion. I

As previously indicated, the, cloth material of the ceramic disc is formed of woven yarn composed of long thin ceramic fibers which are finally incorporated into the yarn without the presence of binders so that there is no binder in the final disc which will interfere with proper combustion.

An exarnple of-asuitable clothwhich I have used is one known asFiberfrax cloth produced from Fiberfax long st p fi s; by'the Cormor m Company. hich as thefollewing chemical'composition:

Approximate fiber diameter:

2 microns to 40 microns with a mean inthe range of 4 to 10 microns. Approximate fiber length:

/2 to 10'', averaging 2 to 3". Density of the cloth:

24 pounds per cubic foot. Thickness of the cloth: 0.020" to 0.250". Thread count:

8 per inch to 30 per inch, with an average of 15.

Other examples-of suitable materials are cloths which could be made of Micro-Quartz fibers which are produced by LOF Glass Fibers Co. and which fibers are of 98% pure quartz, or of other fibers which have the necessary resistance to high temperature, and will. provide a cloth havingthe necessary high capillarity.

A high degree of capillarity is present in the ceramic cloth disc to provide lateral flow over the face of the disc in sufiicient quantity to keep the disc well saturated with fuel. The high rate of evaporation from this wet disc provides a strong cooling action due to the latent heat of evaporationof the fuel. This cooling action tendsstronglyto prevent cracking of the fuel in the liquid state; by lowering the temperature of the disc.

In thistypeof vaporizing disc, virtually all the heat for evaporating the oil is supplied by radiant heattransfer from the flame front formed immediately in front of the disc to the fuel-filled disc.

The ceramic cloth disc is composed of fibers that will withstand approximately 2000 F. for long periods of time without noticeable deterioration. These fibers must also withstand the effects of hot fuel and the products formed by chemical reaction of the fuel, either by oxidation or thermal cracking" for long periods without noticeable deterioration. i

For effective and carbon free operation the ceramic cloth disc 30 is thinnot less than .020" and not more than .250" in thickness, and a, thickness which I have found very satisfactory is .090".

In summarizing the genera-l operation of the heater, it will'be-understood that oil issupplied to the ceramic clpth disc and will spread therethrough. The fan 28 is started and the Oil is ignited by means of the igniter 35. The; oil

will vaporize as it is supplied to the ceramic cloth disc and will burn clean. Primary air, under forced draft, will be supplied to and through the disc uniformly. While the quantity of primary air so introduced is not sufficient to complete combustion, it is sufiicient to support combustion and establish a flame front in close proximity to the exposed face of the ceramic cloth disc. This primary air at numerous places mixes rapidly with vaporized fuel which it entrains and carries toward the exit end of the combustion chamber 24. Secondary air is supplied, under forced draft, in front of the ceramic cloth disc, in sufiicient amounts to complete combustion, through the openings 31. Radiant heat produced by the actual flame front in close proximity to the saturated ceramic cloth disc furnishes heat to continue evaporation of the fuel at a high rate. In fact, an active and vigorous flame may be maintained with the temperature of the incoming air as low as -40 F., which is important with a heater of this portable type since it may be used under very low temperature conditions and it is very important that it burn clean without providing a stack or flue.

According to the provisions of the patent statutes, the principles of this invention have been explained and have been illustrated and described in what is now considered to represent the best embodiment. However, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Having thus described my invention what is claimed is:

1. A burner for burning liquid fuel comprising a combustion chamber, a ceramic cloth member composed of woven ceramic fibers with interstices therebetween having an exposed face at the inner surface of a wall of said combustion chamber, means for supplying the liquid fuel to said cloth member so that it will be absorbed thereby and distributed throughout the member by the capillary attraction of the material of the member, said wall of said combustion chamber including a rigid air-metering plate directly backwardly of said ceramic member, said rigid plate and said cloth member having aligning primary air openings extending through both the rigid plate and the cloth member to the exposed face of the member, said openings being in addition to the interstices of the cloth member, said plate also having other primary air openings extending therethrough only, to the back surface of the cloth member, means for positively forcing primary air through said openings into said combustion chamber to vaporize the oil so it will be burned adjacent to the exposed face of said cloth member, the heat for vaporizing the oil in the cloth member being received from the flame which forms in front of the exposed face of the member, the wall of the combustion chamber just beyond the face of the cloth member in the direction of flow of the primary air therethrough being provided with air inlet openings for supplying secondary air to said combustion chamber to aid in complete and clean burning of the fuel in the combustion chamber.

2. A burner according to claim 1 in which the ceramic cloth member has reinforcing strands incorporated therein so that it will resist the pressure of the primary air forced therethrough.

3. A burner according to claim 1 in which the ceramic cloth member is reinforced at the downstream surface thereof by a foraminous reinforcing member so that it will resist the pressure of the primary air forced therethrough.

References Qited in the file of this patent UNITED STATES PATENTS 260,983 Hubbard July 11, 1882 2,174,818 Brace Oct. 3, 1939 2,210,290 Heinsohn Aug. 6, 1940 2,493,266 Schmitt Jan. 3, 1950 2,746,138 Smith May 22, 1956 2,879,837 Downs Mar. 31, 1959 FOREIGN PATENTS 117,929 Germany June 10, 1930

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