US2119830A - Apparatus for burning liquid fuels - Google Patents

Description

June 7, 1938. M. A. POWERS ET AL 2,119,830

APPARATUS FOR BURNTNG LIQUID FUELS Filed Oct. 2, 1954 2 Sheets-Sheet 1 a: a /7 /a Qwu'wvboo fill/ran A. Powers dab/r A. VVi/aon June 7, 1938. M. A. POWERS El AL 2,119,330

APPARATUS FOR BURNING LIQUID FUELS Filed Oct. 2, 1934 2 Sheets-Sheet 2 41/71'0/2 A. Pan/era Jo/m A. M/i/san' MW 9 Gamma/l Patented June "7, 1938 UNITED STATES PATENT OFFICE APPARATUS FOR BURNING LIQUID FUELS Milton A. Powers and John A. Wilson, Detroit, Mich., assignors, by mesne assignments, to The Timken-Detroit Axle Company, a corporation of Ohio Application October 2, 1934, vSerial No. 746,582

14 Claims.

busting liquid fuels in burners of the wall flame- 1, 1932, and Wilson application No. 682,374, dated July 27, 1933 for a Grill, will be found a full description of the operation and characteristics of an oil burner having a metal hearth ring con-- struction in comparison with the conventional refractory clay segments heretofore universally used. Further investigation has disclosed that the use of such metal constructions in specialized forms, and in accordance with the methods of combustion of our invention which are about to be formulated, opens heretofore unsuspected possibilities in the effective burning of lower quality oils with the wall flame burner. During the first few years of use of the wall flame burner, and in fact until only comparatively recently, it was considered impractical to recommend oils inferior in quality to the No. 1 grade (United States Commercial Standards) for reliable domestic use in automatic burners of this type Later developments in ignition devices and segment form enabled the same burners to operate with the better commercial grades pf No. 2 oil. The recent rapid introduction of the metal segment construction disclosed in our previously mentioned applications has warranted the recommendation of even the poorest grades of No. 2 611 without qualification. In fact good grades of No. 3 oil are burned with complete satisfaction in numerous installations. Continued development in the laboratory with poor grades of both No. 3 and No. 4 011 gives indications of fair success with the No. 3 but almost hopeless results with the low quality No.

4 oil. An analysis of the difficulties proved that an entirely different angle of attack was necessary for a successful outcome and the following line of reasoning was responsible for the success attained by thefuel burning methods and constructions of our invention to be described later.

In the first place let us briefly analyze the modus operandi of the present day wall flame burne Oil is thrown by centrifugal forces from" the distributor head to the flame or combustion rim at the periphery of the boiler. The most important requirement is that this oil be divided into sufflciently small droplets to wet the hearth periphery evenly. To attempt to atomize the oil I or to break it into particles smaller than sumcient to meet this requirement is distinctly undesirable as finely atomized oil will burn rapidly in the presence of air and difliculty will be encountered in holding the flame at the periphery. Under conditions of excessive atomization the rate of flame propagation towardthe distributor 1 will exceed the outward velocity of the oil andthe flame will accordingly burn or flash" back to the distributor causing trouble; The first requirement, therefore, is to wet the flame rim with liquid oil. There will be suflicient splatter resulting/from the oil striking the face of the segment to propagate the ignition flame around the periphery. Thereafter the wet oil is vaporized by the heat in the flame ring segments received from the burning oil, the vapors are mixed with the outflowing air stream and combustion occurs. At normal operating temperature the rate of vapor production is so high that the flame is unable to maintain itself in the immediate vicinity of the vaporizing oil and "rises to the top of the segment where it burns in suspension over the metal segments, around the grills, (if grills are used in the installation) and in close proximity to the boiler wall. y

It is therefore evident that the vaporizing zone or region is filled with rich vapors and no flame can exist, because very little if any air or oxygen is present. Hence a "reducing atmosphere, as contrasted with an oxidizing atmosphere is present in-this zone. Consequently (except for a short time in starting andafter stopping) no conditions exist in the oil impinging zone for removing the oil and its residue from-the flame ring except the heat of vaporization.

The specification for a No. 1 oil calls fora distillation range, with all of the oil evaporated, at a temperature not to exceed 600 F. A flame rim segment temperature" of this degree or higher is accordingly all that is necessary to completely change all of the liquid oil to a vapor. The rigid speciflcationsms to free carbon, ash, sulphur, and so on practically assures their absence from fuels of No. 1- specification nowon the market. Hence operation may continue indefinitely without accumulation of carbon or foreign matter while 'using No. 1 oil-and continued good combustion will result. These are the conditions under which a burner of the character shown by the previously mentioned applications will operate with high quality, sediment free oils.

The next poorer grade oil, a No. 2 presents a somewhat difierent story. The distillation requirements specify that 90 percent of the 011 must vaporize below 620 F. In other words a somewhat higher temperature is needed to vaporize even the lighter nine tenths of the oil, but there is no specific limitation as to the vaporizingrange of the last 10 percent of the oil. It is assumed, of course, that said remainder would contlnue in conformity with the quality of the first 90 percent although there is no limitation to require this. And moreover a further diflicul-ty attending use of No. 2 oil resides in the fact that much oil has been sold as No. 2 oil in which this last 10 percent necessitated much higher vaporizing temperatures than would be expected It is not unknown for No. 2 oil to be delivered from trucks which have not been cleaned after carrying very heavy grades of oil. As a result oils marketed as corresponding to the No. 2 specifications may contain an appreciable percentage of tarry products almost entirely unvaporizable under normal operating temperatures. Accordingly, when using some No. 2 oils, under short periods of operation, segment temperatures do not reach a maximum, residue collects and burner ignition and operation soon becomes erratic. 7

Under these circumstances (short periods of operation), when attempts were made to-burn a poor grade of No. 4 oil with its considerable proportion of heavy tarry ends, free carbon, and ash, there was a most rapid accumulation of such matter. At times a few minutes operation was sufiicient to build up an inwardly projecting wall of solid matter sufficient to prevent further combustion of acceptable quality.

Such were conditions at the beginning of the present development of the invention, and it was realized that a radical departure from the usual methods of combustion with the wall flame burner would be necessary for progress to be made.

The vaporizing zone on the wall fiame burner, as mentioned earlier, is entirely surrounded by rich vapors with very little if any air.present, and it was found when using No. 4 oils, that any collection of unvaporized material remained unaffected and accumulated until it caused combustion failure. It was discovered however, that by directing relatively large quantities of combustion air directly at the base of the vaporizing zone a surprising change in combustion conditions took place. It was found that sufllcient air to initiate combustion was now present below the oil impingement line, and a very active rolling flame continued to burn in the trough portion of the combustion ring segments, with resulting greatly increased operating temperatures. The metal parts in proximity to the flame attained a bright cherry temperature (about 1700 F.) and remained so during operation. This high temperature eliminated all chance for incomplete vaporization of high boiling point portions and thereby rendered it entirely feasible to burn oils of No. 3 and No. 4 specifications.

It is accordingly a primary object 'of the present invention to devise" methods and apparatus for efliciently burning heavier liquid fuels than have heretofore been used.

A further major object of the inventionis to devise a fuel burning apparatus having a reducing combustion zone and an oxidizing combustion zone, the zones being so located that fuel that fails to vaporize in the reducing zone will autowhere it is efficiently combusted.

It is another object of the invention to provide a fuel burning apparatus of the character having a carbureting surface against which liquid fuel impinges, with means for directing a supply 01' air at theface of fuel impingement, to establish a combustion zone of oxidizing character for consuming fuel that fails to vaporize.

A further object of the invention is to devise novel methods for combusting fuels, which result in employing only slightly more combustion supporting air than that calculated as required for oxidation of the fuel.

It is another object of the present invention to devise novel methods for burning heavy liquid fuels which comprises utilizing a part of the heat of the fuel to vaporize the same, the heat for this purpose being obtained from the componentsof the fuel that are difficult if not impossible to vaporize.

The present invention also aims to devise novel means for initiating combustion in liquid fuel burning apparatus, which is so designed as to make feasible the combustion of heavier fuels than heretofore believed capable of use.

Further objects of the present invention will become apparent as the detailed description thereof proceeds in connection with the annexed drawings, and from the appended claims.

In the drawings:

Figure l is a vertical sectional view of a boiler equipped with a fuel burning device constructed in accordance with the present invention.

Figure 2 is a front view of one of the carbureting ring segments as it appears when removed from the device shown in Figure 1.

Figure 3 is a sectional view taken on the line 3-3 of Figure 2; and also diagrammatically illustrates the combustion conditions that exist in the device.

Figure 4 is a view similar to Figure 3, but illustrates a slightly modified form of air directing member.

Figure 5 is a front view of a modified form of segment assembly also forming part of the present invention.

Figure 6 is a sectional view taken on the line 6-6 of Figure 5.

Figure 7 is a view similar to Figure 6, but illustrates a modified form of carbureting ring assembly segment.

Figure 8 is a front view of a still further modified form of carbureting ring segment.

Figure 9 is a sectional view-taken on the line 98 of Figure 8.

Figure 10 is a sectional view illustrating a further form of carbureting ring assembly.

Figures 11 and 12 illustrate a variation in the construction shown in Figure 10.

Figure 13 is a fragmental sectional view through the device shown in Figure l butillustrates a modified form of electrode assembly associated therewith, also forming part of the pres- .ent invention.

transformer and circuit utilized with the igniting device shown in Figures 13, 14 and 15.

with continued. reference to the drawings, wherein like reference characters have been employed to designate like parts throughout the several views thereof, we have illustrated our fuel burning apparatus shown as being incorporated in a boiler having a base portion II and a water section II.

Mounted on an inwardly extending flange l2 of base I0, is a hearth member it which con- .sists of a refractory clay mass which may bemolded in place in the boiler. Extending through a centrally disposed aperture in hearth I3 is a liquid fuel and air distributor assembly,' comprising a stand I4, a motor l5, and a distributor head IS, the latter being provided with a plu-. rality of nozzles I1 and a plurality of fan blades l8. The distributor assembly forms no part of the present invention, and its operation will therefore be only briefly described. The distributor head rotates at motor speed and throws unatomized droplets of oil upwardly and outwardly, and it discharges an outwardly and downwardly extending blast of air, the streams of oil and. air being combusted in a manner to be hereinafter described. The distributor assembly is adapted to be automatically controlled in accordance with temperature changes by mechanism disposed in a control standZi.

Disposedon the upper surface of hearth i3 is a carbuzeting ring assembly, and in the present instance it consists of a plurality of metal segments which are welded or otherwise suitably secured together to form a unitary whole. With particular reference to Figures 2 and 3, each segment consists of a body 22' preferably of pressedmetal. Although any suitable material may be employed for the segments, the high temperatures to which the metal portions of the burner are subjected necessitates the use of a special heat resisting steel unaffected by oxidizing conditions in the burner, and it has been found that a chromium steel having a chromium content of from 20 to 28% is suitable for' the present device, while somewhat lower percentages of chromium may able satisfaction.

Each segment 22 is provided with a vertical impact wall 23, which provides a vaporizing surface; a gutter portion 24, into which unvaporized. components of the fuel may rest while also be used with reasonthey are consumed by the oxidizing atmosphere therein; and an upwardly inclined air directing surface 25. Segments 22 are supported upon the hearth by means of a plurality of metal plates 26 which generally conform to the configuration of segments 22 and are secured thereto by a welding or like operation. Although the mechanism perform satisfactorily without them, each segment is preferably provided with a grill 28, which comprises a flanged plate having a plurality of openings 20 formed therein. Each grill 28 is secured to its segment by means of a pair of brackets 3|. The forward arms 32 of brackets 3| are bifurcated and straddle the vertical portions of the segment.

the rear legs 33 of bracket 3| are disposed againstthe rear face of the segment. Brackets 3| may be welded or otherwise suitably fastened to the segments in order to make the construction more rigid if desired.

v Thecarbureting, ring assembly just described is equipped with an air deflecting, or an air redirecting assembly, and although it may take any desired form and be supported on the hearth or any other part of the burner, it is preferably mounted on the carbureting ring assembly itself and in the present instance it takes the form of a plurality of metallic members 35 which are horizontally disposed and have their ends 38 bent downwardly and welded to segments 22. 'fAir deflecting members II cooperate with the air streams projected from distributor It in a manner to be hereinafter described.

Combustion of the liquid fuel may be initiated in any suitable; manner, the ignition mechanism of the device-shown in Figure 1 takrcs. Preferto points of the carbureting ring assembly .areelectrodes 31, each of which preferably consists of an intimately mixed mass of carborundum and refractory material disposed in a metallic container secured to the segments. The carbureting ring is provided with apertures opposite electrodes 31 in order to allow an arc to pass from the surface of the carborundum to an electrode II which is molded in the hearth opposite each electrode 31. Electrodes 10 are connected by means of leads 3! across the high side of a transformer 40. The voltage across the high side of 20 the transformer 40 preferably lies in the neighborhood' of from 12,000 to 15,000 volts and the current produced thereby goes through one electrode I8 and jumps across the gap in the form of a flaming arc, enters, one electrode 31.

travels through the connected segments of the carbureted ring and into the other electrode,

then through another flaming are into the other electrode 30. It is therefore seen that the arcs or spark gaps are disposed in series with the result that. the voltage across each gap will be one;half of the voltage across the high tension that the oil, or other liquid fuel; is thrown outwardly from the head, (illustrated as droplets-in Figure 3) and strikes portions 23 of the segment and breaks up into smaller particles which drop down into the electric arc and are volatilized and ignited. The arcs, are intensely hot, and accordingly heat the volatilized fuelto a high temperature and ionize the air and oil vapor in the region of the electrodes, with the result that the. vapor ignites. It should be observed that while the above operation takes place the current flowing through electrode 31 heats it to a high temperature. with the result that further atomized fuel. dropping thereupon is readily volatilized.

When ignition has been initiated in the manner just described, the flame propagates around the ring in both directions thereby establishing a continuous ring. With combustion taking place around the entire periphery of the carbureting ring, segments 22 are heated, and as they are formed of relatively thin pressed metal they heat up rapidly and in a short time they attain a temperature sufficient to almost instantly volatilize the droplets of oil striking their vertical portions 23. When the carbureting ringattains a temperature suflicient to'instantly volatilize the liquid fuel impinging thereagainst just described, stea'dy combustion conditions may be said to exist in the device and at this time an automatic device .of any suitable character may 'be employed to open the igniter circuit.

Under steady combustion conditions, the un I atomized fuel emanating from head l6 takes the paths illustrated by the upper row of .arrows in and strike portions 23 of the segments in a line which will hereafter be termed the impingement line. The air flowing from head it curves down- Wardly asit emanates .from head IS with the result that the fuel in its passage from head IE to the carbureting ring is isolated from the air and is accordingly incapable of burning for the reason that it is not supplied with suiflcient air to form a combustible mixture. With particular reference to Figure 3, part of the air issuing from the distributor, diagrammatically illustrated by arrows A, is thrown outwardly and upwardly and mixes with the vapors generated on surfaces 23 of segments 22 and starts to burn in this region. However; as the vapors generated are in excess of theair supplied to them for proper combustion, the flame in this region is of a reducing character. A large part of the air issuing from the distributor strikes air deflectors 35 and takes the path indicated by the arrows B and mixes with the vapors in the region below the impingement line. As the amount of air in this region is in excess of 'that required to eificlently burn the vapors present in this region, the flame in this locality is of a highly oxidizing character. The

vapor streams are illustrated diagrammatically in Figure 3 by lines C. The first described region or zone of combustion will be hereinafter termed the reducing zone and the last described region will be described as the oxidizing zone.

The gases in the reducing and oxidizing zone pass upwardly and strike grills 28 which serve to mix them, with the result that they burn above the grill with a blue flame, and the quantity of air supplied to the carbureting assembly is preferably carefully adjusted so that when the gases of the reducing and oxidizing zones are mixed, there will be just sufiicient, or only a slight excess, of oxygen present above the grill to thoroughly combust all of the fuel.

Fuels of number 3 and number 4 specification,

as previously pointed out, not only contain substances that cannot be vaporized, but they also contain a certain percentage of solid matter. Moreover a. certain percentage of solid matter is precipitated incident to cracking of portions of the oil that is vaporized in the device.

When the burnergis operating under steady combustion conditions, the solid matter in the oil, plus any solid matter precipitated incident to portions of the oil cracking under the high vaporizing temperatures existing in the segments,

collect upon the surface of the segments at the line of oil impingement. This solid matter ac- .cumulates at a relatively rapid rate, depending upon the quality of the oil being burned. Nevertheless, and for some reasonnot clearly understood, such accumulated matter, after reaching a certain thickness, breaks into segments along its length. These segments upon being formed may drop at once to the bottom of the trough in the carbureting ring, or as is usually the case, they curl inward at their ends away from the surface of the metal until their weight acting against their weakening hold upon the impingement wall finally results in their dropping away into the trough. As previously described, the air flowing into the trough, by virtue of the air deflectors, maintains a flame therein and the relatively large amount of air causes this portion of the flame to be of a highly oxidizing character. Consequently when the solid matter breaks off and drops into this zone as just described, the combination of excass oxygen and high flame temperatures causes the rapid and complete combustion of the solid matter. As the flame in the gutter. is continuously oxidizing in character during normal operation of the burner, the solid or unvaporizable part of the fuel is consumed as rapidly as it forms and breaks away from the impingement wall. There is therefore no possibility of the burner becoming so incrusted with solid matter asto cause combustion to fail.

It was discovered during the course of experimentation that the high carbureting ring temperatures requisite for complete volatilization of liquid fuels of number 3 or number 4 speciflcation causes the oil to crack into its component parts and the free carbon so released will precipitate with amazing rapidity on any convenient surface. The temperature of the collecting surface itself does not seem to influence the rate of precipitation. If anything, the hotter the surface the faster the carbon collects thereon.

Two methods of correcting this diificulty occurred at the time of developing the present apparatus; (1) provide no collecting surface until combustion of the fuel is complete or (2) maintain an oxidizing atmosphere over the surfaces in the region of the released. carbon. In view of the necessity for a vaporizing surface, the second solution of the problem was followed, and the present practical apparatus resulted. Therefore it is seen that maintaining an oxidizing atmosphere adjacent the line of fuel impingement not only produces efficient and complete combustion of the solid matter in the fuel, but it also rapidly and completely oxidizes the free carbon that may be released as a result of the fuel cracking under the high temperatures encountered on the impingement surfaces.

It is important that the total volume of air introduced be not in material excess over that required to completely burn all of the fuel. The method, of the present invention therefore includes directing the air in a manner to maintain an oxidizing condition in certain zones and upon certain'surfaces; thereafter mixing the remaining air with its unused oxygen, the unburned vapors, free hydrogen and oxygen, and the products of combustion, in a manner to give efiicient combustion of the total mass.

With reference now to Figure 4 of the drawings, there is illustrated a modified form of construction, and the only difference therein over the construction just, described, resides in the shape of the air deflecting member 35a which in this instance is of curved configuration. This form of air deflecting member may be used to advantage in some installations, depending upon the volume of auxiliary air required. In fact the air deflecting member 35 of' the first described construction may be adjusted or progressively bent into the curved configuration shown in Figure 4 to give the requisite balance between the air that flows directly toward the impingement line and the air that is deflected into the gutter. In view and are fitted over vertical portions 23' of segments 22.

This apparatus functions in a slightly different manner than those previously described in that no air deflecting member is required. Assuming that plate 4| has been heated sufliciently to substantially instantaneously vaporize the fuel striking it, vaporization takes place as previously described, and aircurrents A establish a reducing combustion zone adjacent the impingement line. The vapors below the line of impingement mix with air current B and establishacombustionzone in the gutter, and the products of combustion pass upwardly behind plate 4| toward the grill 28. The upward movement of the gases in this combustion zone establishes a partial vacuum in the lower part of the gutter, which results in air currents 3- taking the path shown and which establish an oxidizing zone.. However, if desired, air deflecting members of the character shown in Figures3 and 4 may also be used to increase the how of air into the oxidizing zone. It should be observed that the combustion of the gases taking place behind plate 4| serves to further elevate the temperature of the vaporizing surface, with-the result that vaporization of the impinging fuel is greatly enhanced. The gases passing upwardly fiomthe reducing and oxidizing zones enter the grill wherethey are mixed and combusted as previously described.

With reference to Figure "l, a construction is shown that is very similar to, and functions in the same manner as that Just described, but the parts are assembled in a different manner. Plate 4la at its lower end is welded to a bracket 45 which rests in a gutter 24 of the segment and is provided with a bifurcated upper end 48 which.

embraces theupper lip of segment 22. Segment 22 has been cut down as the impingement wall 28 is not necessary in this form of the invention. A pair of brackets 41 support grill 28, and is provided with a bifurcated end 49 which embraces the upper edge of plate Ila. =Rear legs 48 of brackets 41 engage behind'segments 22.

The modified carbureting ring construction shown in Figures 8 and 9 functions in the same manner as those shown in Figures 5, 6 and 7. In this form of the invention the segments are replaced by a plurality of segments 52, which are secured together in end to end relationship as those employed in the previously described forms of the invention. Segments 52 are each provided with a vertical wall 58, a horizontal base 54 and an upwardly inclined frontwall 55. Plates 4|b are disposed within segments 52 and are pro-, vided at their lower ends with outwardly turned tabs 58, which cooperate with the front walls 55 of the segments and inwardly turned tabs 51,

which cooperate with the rear wallof the seg-' ment to maintain plates 4|b properly spaced from the segment walls. A pair of U-shaped clamps 59, each having downwardly extending legs GI and 62, is mounted upon plate 4 lb and the rear wall 58 of segment 52 and supports grills 28 which are welded thereto.

This form of the invention performs in precisely the same way as the apparatus shown in Figures 5, 6 and '7, a part of the air stream A passing upwardly and establishing a reducing zone in the region of the impingement line and another part of the air stream B passing downwardly within the segment and under plate 4|b to establish the 'oxidizing zone, where the solid matter is-consumed as previously described.

scribed constructions. wardly and are deflected downwardly by member of a continuous ring, as distinguished from the segments employed in the previously described forms of the invention. with continued reference to Figure 10, a' plurality of bracket members 85 are disposed upon hearth l8 and-have extending tabs 66 molded therein. Secured to theair deflecting member 18, which may be continuous or segmental in form, is secured to the upper edge of ring H by means of brackets 15.

In this'form'of the invention, air currents A pass upwardly and mingle with the vapors in the region of the oil impingement line on ring member H and establish a reducing zone in a manner similar to that effected in the previously de- Air currents B pass p- 18 into the gutter formed between ring memwherein the solid or unvaporizable components of the fuel are consumed. The gases emanating from the reducing and oxidizing zones pass uP wardly and are mixed and consumed above the grills as in the previously described forms of the invention.

The construction shown in Figures 11 and 12 is identically the same as that Just described except for the air deflecting member, which in this instance is integrally formed with the smaller of the carbureting ring members. Inthis form of the invention ring 12a isslit horizontally along edges 11 and TI to form air deflecting members 18, which are connected to the ring at intervals by integral supporting portions 18 of the ring.

In Figures l3, 14, 15 and 16 there is shown a modified form of igniting device also forming part of the present invention, and it is particularly useful in the present apparatus as it is capable of initiating combustion of the heavier fuels. The igniting device has been illustrated in connection with the carbureting rlng assembly shown in Figures 1, 2 and 3, and although two igniter assemblies are used only one will be described.

With particular reference to Figures 13 and 14, an aperture-88 is formed in segment 22 and a box-likemember 8| is welded to segment 22 in alignment with aperture 80. Secured to a downwardly projecting finger 82' of member 8| is a clamp 88. Detachably carried by clamp 83 is an insulator 84 having an electrode 85 therein. Electrode'85 is insulated from member 8| and is provided with an enlarged upper end 88 for a purpose that will presently appear.

Insulating material 8'|, preferably having thermal as well as electrical insulating properties, is disposed within member 8| and against the rear face of segment 22. Molded in place within member 8| and projecting through the opening 80 in segment 22 is a mass' of conducting material 88, which preferably-consists of a mixture of carborundurn and a refractory binder of preferably electrical insulating properties, so that when current passes therethrough it will heat up and volatilize the fuel. trodes .85 are provided with terminals 88. Co-

'I'helower ends of elec-- upwardly and outwardly and terminates in a somewhat blunt tip 91, which is disposed sufli-- ciently close to the carborundum electrode to form an are when a high voltage is impressed across the electrodes;

The transformer and electric circuit preferably employed with the igniting device is illustrated in Figure 16. The transformer has a primary winding 99 which, if the fuel burning apparatus is'mounted in a residence, is connected across the regular 110 volt, '60 cycle line. The transformer is provided with two secondary windings IOI and I02. Winding l nl is connected across electrodes 85, and one end of winding I02 is connected to electrode 96. Although the transformer has been conventionally illustrated, winding llll is designed to cause a comparatively heavy current, say, I milliamperes to flow between the electrodes 86 with a drop in potential of approximately two thousand volts, while winding I02 is designed to have a greater number of ampere turns, so as to cause a current of say 18 milliamperes to flow between electrode 91 and electrode 96.

It is accordingly seen that when the burner is put into operation a heavy current flows between terminals 86 and-rapidly heats member 89, with the result that when fuel particles gravitate downwardly on the hot surface of this member they are rapidly volatilized. Simultaneously an arc is established between electrode 91 and member 89, which serves to further volatilize the fuel and ignite it. It shouldbe observed that while current is passing between electrodes 86, the heat generated in member 89 is conserved by reason of the insulating action of members 81,"which also electrically insulates member 89 from the ring .segments. The heat generated in member 99 is accordingly prevented from dissipating into segments 22 and accordingly promptly reaches a vaporizing temperature.

As previously mentioned, the carbureting ring assembly in this form of the invention is Provided with two. diametrically opposite igniter assemblies and although we have illustrated each igniter assembly as being provided with a separate transformer, it is to be understood that if desired, the transformer may be made of greater capacity and be connected in series or parallel to both of the igniter assemblies.

With reference to all of the forms of the invention, it is to be understood that although various devices have been illustrated for deflecting or re-directing a portion of the air emanating forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come .within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a liquid fuel burning apparatus comprising a combustion chamber having a hearth and means for discharging liquid fuel in a path over said hearth, a carbureting device mounted on said hearth in the path of the discharged fuel.

said device comprising an upper, fuel impact wall portion, a lower wall portion and a grooved or depressed imperforate portion. forming a sheltered gutter between said wall portions, means for projecting a major draft of air against said lower wall portion and across said gutter, and means for projecting a minor air draft into said gutter.

2. In the combination defined in claim 1, the last mentioned means comprising a member carried by said device and constructed to form said minor air draft from a portion of the air of said major draft.

3. In the combination defined in claim 1, the last mentioned means comprising a deflector overlying said lower wall portion and said gutter.

4. In a liquid fuel burning apparatus, in combination with a combustion chamber having a hearth and an upright wall, fuel distributing means positioned to project a liquid fuel stream toward said wall and means for directing a blast of air toward said wall, a refractory carbureting structure disposed between said wall and said distributing means, said structure comprising an imperforate gutter arranged transversely of and below the projected fuel stream, a member providing an air deflecting surface in front of said gutter in the path of the air blast and positioned to direct said blast upwardly, means providing a fuel impingement surface above'said gutter in chamber, means for projecting unatomized liquid fuel toward said surface for atomizing said fuel by impact with said surface; means for projecting a draft of air toward said surface for admixture with the atomized fuel for establishing and maintaining a combustion zone adjacent said vertical surface between said first-named means and said vertical surface, and means for causing a part of the projected air draft to form an oxidizing zone below and adjacent to 'said combustion zone.

7. The liquid fuel burning apparatus set forth in claim 6, wherein said last named means comprises a deflecting means for diverting a part of the air supplied said combustion zone to a region below said combustion zone.

8. In a liquid fuel burning apparatus, a member having a substantially vertically disposed atomizing surface, means for projecting an air current and liquid fuel toward said atomizing surface, for causing said fuel to be atomized by impact with said surface and to be mixed with apart of said air current and means for causing a portion of said air current to be deflected to a region below said atomizing surface.

9. The fuel burning apparatus set forth in claim 8, wherein said last-named means comprises at least one air deflecting member disposed in the path of said air current.

10. In a device for burning liquid fuel, a heat exchange unit having a combustion chamber; a fuel carbureting member disposed in said chamber and providing a substantially vertically extending fuel atomizing surface and a gutter located below said surface; means for causing liquid fuel to impinge against said atomizing surface, means for causing an air current to flow past said gutter for admixture with the fuel atomized on said surface, and means for causing a current of air to flow into said gutter for combusting any fuel accumulating therein.

11. The liquid fuel burning apparatus set forth in claim 10, wherein said last named means comprises an air deflecting element mounted on said carbureting member and disposed between said atomizing surface and the source of the air supplied to the fuel atomized on said atomizing surface.

12. In a liquid fuel, burning device, a liquid fuel projector, a carbureting member providing a substantially vertically disposed atomizing surface in the path of the liquid fuel discharged by said projector, means for mixing air with said liquid fuel atomizing by impact with said atomizing surface for effecting combustion of said liquid fuel, in the region of said surface impacted by said liquid fuel, and means for causing hot gases of combustion to pass downwardly under and thence upwardly with respect to said atomizing surface for simultaneously consuming any fuel that fails to vaporize on said atomizing surface and for heating said atomizing surface.

13. In a liquid fuel burning apparatus comprising a combustion chamber having a hearth and means for discharging liquid fuel in a substantially horizontal path over said hearth, a carbureting device mounted on said hearth in the path of the discharged fuel, said device comprising an upper fuel impact wall portion, a lower wall portion and a grooved or depressed imperforate portion forming a sheltered gutter between said wall portions, means for projecting a major draft of air against said lower wall portion and across said gutter, and means for projecting a minor draft into said gutter comprising a downward extension provided on said fuel impact wall and projecting downwardly into said gutter.

14. In a liquid fuel burning apparatus, a combusti'on chamber having a hearth, an upright-fuel impact wall disposed adjacent the periphery of said hearth, said hearth being provided with an .aperture centrally thereof, a distributor mechanism projecting upwardly through saidaperture and embodying means for projecting a sheet-like blast of air outwardly over said hearth toward said fuel impact wall and means for projecting solid droplets of liquid fuel against said impact wall for atomizing and vaporizing the, same, means located inwardly of said impact wall for deflecting said blast of air upwardly and outwardly adjacent said impact wall, and means for deflecting at least a part of said air from its upward course comprising a plurality of thin members constructed of a metal which is resistant to destruction by heat and has good heat conductivity.

MILTON A. POWERS,

JOHNA. WILSON.

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