US3477644A - Liquid fuel burner - Google Patents

Description

Nov. 11, 1969 L.M. BABLOUZIAN, ETAL:

LIQUID FUEL BURNER 2 Sheets-Sheet 1 Filed March 6, 1968 lllllllllllllll'llllll ouzion tongu NTORS ckus Attorney Nov. 11, 1969 L. M. BABLOUZIAN ETAL LIQUID FUEL BURNER 2 Sheets-Sheet 2 Filed Mar- 0h e, 1968 F lg Leon M. Boblouzion Roger A. Cos'ronguuy INVENTORS Joseph F. 'wenckus Attorney United States Patent ABSTRACT OF THE DISCLOSURE A burner designed to burn vaporized liquid fuel and a gaseous source of oxygen. By varying the ratio of gaseous oxygen source to liquid, fuel, it is possible to provide a heatsource operating over a wide temperature range. In the burner at least a portion of the oxygen source is premixed with the vaporized fuel prior to ignition. The burner may be used as a high-temperature, high-intensity torch and is thus particularly suitable for incorporation in crystal-growing furnaces, as well as in spheroidizing apparatus for refractory metals and oxides and for use in welding, cutting and melting apparatus. It may also be used asla low-capacity burner to be used in water heaters, residential heating apparatus, and the like.

This invention relates to a burner and more particularly to one which is capable of burning a liquid fuel and a gaseous oxygen source over a wide ratio of fuel to oxygen ratios. The burner is particularly adaptable to burning a liquid fuel such asa No. 2 fuel oil.

There are many requirements for high-temperature heat sources usually constructed in the form of a torch or torch-like apparatus. For example, such heat sources are required in welding, in'cutting, in crystal-growing and melting furnaces, and in spheroidizing apparatus. In the prior art apparatus designed for such applications, gaseous fuels such as methane, acetylene and hydrogen have been used. Since these gases must be provided under pressure, there is always danger in handling them and in burning them with an oxidant. Moreover, these gaseous fuels may, under some circumstances, spontaneously combust with the oxygen in the air. It would, therefore, be desirable to have a high-temperature, high-intensity heat source which did'not use these relatively dangerous gaseous fuels but which, on the contrary, was capable of burning liquid fuels which were readily stored and handled.

The use of liquid fuels such as No. 2 fuel oil is, of course, common in many burer designs and particularly in burners for automatic service in residential applications. However, in the present oil burners it is usually necessary to provide some separate mechanical means to atomize the liquid fuel prior to its being mixed with a gaseous source of oxygen for burning. Such atomizers are typically high-pressure, very small-diameter air nozzles or ultrasonic surfaces. These atomizers which incorporate the use of gas under pressure and small-diameter nozzles are subjectto. nozzle plugging; while those which incorporate an ultrasonic atomizing surface require relatively complicated mixing systems to insure efficient mixing and complete dispersion of the fueldroplets in the air (see, for example, U.S.P. 3,275,059). Moreover, the presently available fuel oil burners cannot be constructed in practical low-capacity or low feed-rate devices which attain high efliciencies, which in turn is dependent upon the attainment of essentially complete mixing for complete combustion. Hence, fuel oil burners are not now considered desirable for low-capacity burners, for such applications as hot water heaters and the like. In summary, then, burners designed to consume liquid fuels re- "ice quire atomizing means, have not been satisfactory for low-capacity design applications and have not been adaptable for use as extremely high-temperature, high-intensity heat sources because of their failure to achieve complete combustion. No single type of burner consuming a liquid fuel has been provided which can alternatively be used in these two types of applications, as well as in many intermediate applications. It would, however, be very desirable to have available a burner which could consume fuel oil and a gaseous source of oxygen and which by adjustment of fuel to oxygen ratio could be used for a variety of applications requiring a relatively wide range of temperatures.

It is therefore a primary object of this invention to provide a burner which operates on liquid fuel and gaseous oxygen supplied in any suitable form and which can be employed as a high-temperature, high-intensity heat source for such uses as torches in welding, cutting, melting, heat-treating, crystal-growing, and spheroidizing of refractory metals and oxides. It is another object of this invention to provide a burner which operates on fuel oil and a gaseous oxygen source which can be employed as a low-capacity practical source of heat for such applications as home heating, water heaters, and the like, and which attains essentially complete mixing, and hence complete combustion, of the fuel and oxygen. It is another object of this invention to provide burners of the character described which are rather simple to construct and maintain, which may employ gravity feed of the liquid fuel, and which are not subject to residue buildup. It is yet another object of this invention to provide such apparatus which is versatile in its applications, flexible and relatively simple in design, and eflicient to operate and maintain. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction, combinations of elements and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a longitudinal cross section of a burner constructed in accordance with this invention which is particularly suited for use as a torch for high-temperature applications;

FIG. 2 is a cross section through the nozzle block of FIG. 1 taken along line 2-2 of FIG. 1;

FIG. 3 is a cross section of another embodiment of a nozzle suitable for the apparatus of FIG. 1;

, FIG. 4 is a cross section of the nozzle of FIG. 3 taken along line 44 of FIG. 3;

FIG. 5 is a cross sectional view of another embodiment of a nozzle suitable for use in a torch or burner Where a concentrated heat source is desired; and

FIG. 6 is a diagrammatic view of a crystal-growing furnace incorporating the burner of this invention.

The burner, as illustrated in FIG. 1, can be considered to be formed of four major components-namely, an oil vaporizer 10, the mixing chamber 11, the nozzle block 12, and a -degree adapter section 13 which connects the oil vaporizer 10 and the mixing chamber 11. Although the burner in FIG. 1 is shown in an orientation such that the flame resulting therefrom is pointed downwardly, this orientation is not required. In fact, the burner may be employed at any desired angle including from that shown in FIG. 1.

The oil vaporizer 10 of the apparatus of FIG. 1 is formed of a block 15 having an extension arm 16. In

asmuch as the block is to serve as the means for transfer of heat by conduction, it should be constructed out of a metal which exhibits relatively good heat transfer at high temperatures and which also retains its structural strength. Thus, the block may be formed of stainless steel, copper, brass, and the like. Within the block is drilled a first chamber 17 which, by means of an externally located adapter 18, is connected through conduit 19 to a source of liquid fuel. In chamber 17 the oil is preheated and essentially all vaporized. A radial passage 24, closed to the exterior by screw 25, provides fluid communication between the oil preheat and vaporizer chamber 17 and a larger heating chamber 26 which is likewise drilled in block 15. This vaporizing chamber 26 terminates in a threaded section 27, thus providing means for sealing the chamber by a threaded plug 28 having a knurled screw 29. At the upper or exit end of the vaporizer chamber 26, a vaporized fuel passage 30 provides for transfer of the vaporized fuel to the mixing chambenThe use of the two chambers 17 and 26 has been found to be preferable, for if liquid fuel oil were to be introduced directly into chamber 26, a portion of unvaporized oil in the form or droplets would be entrained by the oil vapor as it was discharged from chamber 26 for delivery to the mixing chamber. The carryover of droplets would in turn lead to the presence of slugs of unvaporized fuel oil in the flame to result in the production of unwanted large incandescent particles in the flame. Thus, it is desirable to carry out essentially all of the vaporization in chamber 17 and to introduce the oil vapor at the bottom end of chamber 26. In the final heating of the fuel as it travels through chamber 26, any droplets which may have been carried over in chamber 26 are vaporized to achieve the complete vaporization of the fuel which is a requirement for complete mixing and subsequently for complete combustion.

A heater well 32 is also drilled in plug and is adapted to have a suitable heating element 33 inserted therein to make thermal contact with the walls and provide the necessary heat to block 15. In FIG. 1 the heater is shown only partially inserted into well 32. Terminals 34 for the heater extend externally of the block for attachment to suitable leads. A thermocouple well 36 is drilled in the block and adapted to contain a thermocouple and lead wires to monitor and control the temperature of the block. I

The adapter section 13 comprises a horizontal block 42 having a passage 43 drilled therein which is in line with passage and a vertically positioned block 44 which has a central passage 45 communicating with passage 43. A threaded connecting piece 46 joins block 44 to mixing chamber housing 47. The volume 48 defined within block 44 may contain gaskets or may be left as an open volume as shown.

The gaseous oxygen source is introduced into mixing chamber 49 through gas inlet conduit 50, which is closed on its end by cap 51 and which has a single orifice 52 drilled on the side facing the vaporizing oil delivery end of mixing chamber 49. This manner of introducing the gaseous source of oxygen causes a jet of oxygen (which may, of course, be diluted with other gases, e.g., nitrogen) to be directed upwardly to contact the oil vapor in a countercurrent pattern as the vapor flows downwardly through mixing chamber 49. The creation of the resulting highly turbulent zone or zones insures complete mixing prior to the introduction of the combustible gas mixture into the nozzle.

-It is normally desirable to preheat the gaseous oxygen source prior to mixing with the vaporized fuel to prevent any recondensation of the fuel. Therefore, means are provided to effect this preheating of the oxygen source. In the apparatus of FIG. 1, the gaseous oxygen source from a supply (not shown) is conducted by conduit 53 and passageway 54 drilled in vaporizing block 15 4 to gas inlet conduit 50; In passing through passageway 54, the gaseous oxygen source is heated to a temperature which is essentially that of the vaporized fuel delivered to mixing chamber 49. Alternatively, heat transfer coils may be wound around block 15 and the gaseous oxygen source circulated through these coils prior to delivery to mixing chamber 49. Separate preheating means may also be used as shown in FIG. 6.

The nozzle block 12 is conveniently attached to the mixing chamber housing 47 by threaded sections in the two components. The nozzles comprise small-diameter passages drilled in the block 56. In order to facilitate this drilling, the nozzles are comprised of a larger-diameter entrance section 57 and a smaller-diameter exit section 58. If desired, the nozzles could be of a single diameter throughout their entire length. Inasmuch as combustion takes .place somewhat beyond the nozzle exit, the nozzle itself does not become overheated; and it may, therefore, be formed of stainless steel or even brass.

In order to prevent flashback into the mixing chamber 49, the ratio of nozzle length to nozzle diameter for anygiven system and given gaseous pressure in mixing chamber 49 must be above a determinable critical value. Since this value varies and is primarily dependent upon gaseous pressure or flow rate, it must be established for each burner embodiment. As an example, a nozzle block such as shown in FIGS. 1 and 2 had nozzles comprising an entrance section 0.042 inch in diameter inch long and an exit section 0.063 inch in diameter l z inch long. Thus, the total length was 1.25 inches and effective nozzle diameterwas 0.042 inch to give a length to diameter ratio of 1.25/0.042 or almost 30.

The burner of FIG. 1 is designed to provide means for introducing particulate material into the combustion zone. For this reason, there is provided a central conduit 60 which passes down through vaporized fuel passage 45, mixing chamber 49, and the central portion of the nozzle block 56. In the use of the burner in crystalgrowing for example, the finely divided material (e.g., A1 0 is introduced along with oxygen through tube 60 to be injected into the combustion zone for melting and subsequent deposition on a suitable support to form a boule.

As will be seen in FIG. 2, the burner of FIG. 1 has eight nozzles. The number of nozzles may, of course, be varied; and FIGS. 3 and 4 show an arrangement whereby sixteen nozzles are used. In FIGS. 3 and 4, the nozzle block 62 has a plurality of nozzles drilled therein, each of which is formed of a larger-diameter entrance passage 63 and a smaller-diameter exit passage 64. As in the case of the nozzle of FIGS. 1 and 2, the length to diameter ratio must be adjusted to prevent flashback and to maintain the combustion zone and flame just beyond the end of the nozzle block. A nozzle block such as shown in FIGS. 3 and 4 wherein the central passage 60 is replaced by one or more additional nozzles 64 would be suitable for use in a burner designed for residential heating or for a water heater. Such a nozzle system provides a combustion zone which is relatively large and suitable for such applications.

FIG. 5 illustrates a nozzle for use in a burner designed to generate heat but not to have any particulate material injected into the combustion zone as in the case of FIG. 1. In FIG. 5 nozzle block 65 has a plurality of inclined nozzles, each of which is formed of an entrance passage 68 and an exit passage 69. In this modification, an axially aligned central nozzle passage is also provided formed of sections 66 and 67.

FIG. 6 illustrates a complete crystal-growing apparatus incorporating the burner of this invention as a high-temperature, high-intensity heat source. The fuel oil is stored in a fuel oil reservoir 70 and is metered by flow meter 71 into oil delivery tube 19, which communicates with the oil vaporizer .10 (in FIG. 6, like numbers refer to like elements of FIG. 1). A fuel pump 72 is provided for maintaining the fuel at a predetermined level within the reservoir 70. Theuse of gravity feed has been found to limit any undesirable surging in the oil fed to the vaporizer. A

The heater terminals 34 are connected to any suitable temperature control means 75, which in turn is connected to. the, thermocouple through a suitable lead 76. The fine powder which is to be melted andused to form the crystal is provided from a powder supply 77 and introduced into feed tube 60 by use of a power feed mechanism 78. Oxygen from pressurized tank 80 is fed through flow meter 81 and preheater 82 into the mixing chamber 11 as described in connectionwith FIG. 1. Oxygen or some othersuitable pressurized gas from supply tank 83 by way 0f flow meter 84 and preheater 85 is also mixed with the finely divided material in the powder supply 77 to carry the finely divided material into the combustion zone 86, where it is melted and deposited on crystal boule 87 resting on a boule support 88, which in turn is rotated and moved vertically by a suitable mechanism 89. fl-The burner is encased in suitable insulation such as quartz wool 91; and the nozzle, along with the combustion zone, the boule, and the upper part of the boule support, is enclosed by an annular ceramic insulation 92. F

Thus, the burner of this invention is particularly suitable for serving as a torch to be incorporated in a crystalgrowing furnace such as is described in copending patent application Ser. No. 646,523 filed June 16, 1967, in the names of Joseph F. Wenckus and Paul R. Doherty and assigned to the same assignee.

Nozzles s'pch as those illustrated in FIGS. 1-4 provide the opportunity of varying the quality of the atmosphere in which a "particulate material is processed in the combustion zone. For example, instead of carrying the particulate material in tube 60 in oxygen, air or some other oxygen source, it could be mixed and carried in a gas which reacted with the material at combustion temperatures or with a gas, e.g., hydrogen, which provided a reducing "atmosphere or with argon to provide an inert atmosphere, In the case of a low-capacity, high-tem perature fuel oil burner, all oxygen for combustion (generally introduced as a component of air) will normally be premixed with the vaporized fuel, thus eliminating the central tubing 60. Generally, although not necessarily, the combustion zone for the lower temperature heat source burners will be relatively larger. For welding torches and-.the like, however, it will usually be preferable to use a nozzle which concentrates the heat in pinpoint fashion such as does the nozzle of FIG. 5.

It will be seen that the burner of this invention makes it possible to burn a liquid fuel with a gaseous oxygen source without the need for complicated atomizing elements. Moreover, the burner may be used to supply heat over a wide'temperature range. It may be used as a torch operating on stoichiometric fuel/oxygen ratios to give a flame temperature which closely approaches theoretical (3100 K. for No. 2 fuel oil and oxygen) as well as a low-capacity fuel oil burner having flame temperatures in the range of 1500 to 2280 K. when using excess air as a diluent and fuel oil fed rates as low as one-tenth of a gallon per hour.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efliciently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. An apparatus suitable for burning a liquid fuel and a gaseous oxygen source, comprising in combination (a) liquid fuel vaporizer means;

(b) a mixing chamber having a vaporized fuel delivgry end and a premixed fuel/oxygen discharge (c) means for transferring vaporized liquid fuel from said vaporizer means into said mixing chamber at said fuel delivery end;

((1) means for introducing a gaseous oxygen source as a jet stream into said mixing chamber near said discharge end to create a zone of turbulence and eflect essentially complete mixing; and

(e) nozzle means in fluid communicationwith said discharge end of said mixing chamber comprising a nozzle having a plurality of small-diameter nozzles therein, the ratio of the length to diameter of said nozzles being above that value which permits flashback into said mixing chamber. I

2. An apparatus in accordance with claim 1 wherein said liquid fuel vaporizer means comprises a metal block having Y (1) a first fuel preheater and vaporizer chamber in fluid communication with (2) a second vaporized fuel heating chamber in fluid communication with said mixing chamber, and

(3) means to maintain said block at a predetermined temperature.

3. An apparatus in accordance with claim 1 including means to preheat said gaseous oxygen source prior to introducing it into said mixing chamber.

4. An apparatus in accordance with claim 3 wherein said means to preheat said gaseous oxygen source comprises means to effect indirect heat exchange between said oxygen source and said fuel vaporizer means.

5. An apparatus in accordance with claim 1 wherein said nozzle block has an axially positioned conduit extending therethrough which is adapted to introduce gaseous and solid components into the combustion zone of the burner.

6. An apparatus in accordance with claim 1 wherein at least a portion of said small diameter nozzles are inclined at an angle to the axis of said nozzle block.

7. A burner adapted for combustion of a liquid fuel and a gaseous oxygen source, comprising in combination (a) a liquid fuel vaporizer comprising a heated metal block defining therein a first fuel preheater and vaporizer chamber and a second larger vaporized fuel heating chamber in fluid communication, and means for maintaining said block at a predetermined temperature;

( b) a mixing chamber adapted to receive and eifect turbulent mixing of hot vaporized fuel from said vaporizer chamber and a gaseous oxyen source;

(0) means to introduce said gaseous oxygen source into said mixing chamber in the form of a jet;

(d) connecting means adapted to provide fluid communication between said vaporizer chamber and said mixing chamber; and

(e) nozzle means adapted to receive the mixed vaporized fuel and oxygen source for transfer to a combustion zone, said nozzle means comprising a plurality of small diameter nozzles, the ratio of length to diameter of said nozzles being above that value which permits flashback into said mixing chamber under the conditions of operation.

8. A burner in accordance with claim 7 wherein said liquid fuel vaporizer has means for effecting indirect heat exchange with said gaseous oxygen source prior to its introduction into said mixing chamber.

9. A burner in accordance with claim 7 further characterized by having tubular conduit means extending through said connecting means, said mixing chamber and said nozzle means; said tubular conduit means being adapted to introduce gaseous and solid components into said combustion zone.

10. A burner adapted for combustion of a liquid fuel and a gaseous oxygen source, comprising in combination (a) fuel vaporizer and heater means comprising (1) ametal block,

(2) means for heating said block,

(3) a first preheater and vaporizer chamber drilled in said block and adapted to receive liquid fuel at one end and discharge vaporized fuel at the opposite end, and

(4) a second vaporized fuel heating chamber drilled in said block adapted to receive said vaporized fuel from said first chamber and to further heat said vaporized fuel;

(1)) a mixing chamber;

(c) fluid communication means joining said second chamber of said vaporizer and heater means and said mixing chamber;

((1) gaseous oxygen source delivery means adapted to deliver said oxygen source into said mixing cham her in the form of a jet stream and in a direction opposite to that at which said vaporized fuel enters said mixing chamber whereby there is formed a turbulent zone in which said vaporized fuel and said oxygen source are mixed; and

(e) nozzle means adapted to receive the mixed vap'orized fuel and oxygen source for transfer to a combustion zone, said nozzle means comprising a plurality of small diameter nozzles, the ratio of length to diameter of said nozzles being above that value which permits flashback into said mixing chamber under the conditions of operation.

11. A burner according to claim 10 including means to heat said gaseous oxygen source to substantially the same temperature at which said vaporized fuel is delivered to said mixing chamber.

References Cited UNITED STATES PATENTS EVERETT W. KIRBY, Primary Examiner US. Cl. X.R.

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