US2473347A - Air directing means in gun type burners - Google Patents

Description

June 14, 1949. `w.`| sANBoRN- AIR DIRECTING MEANS IN GUN TYPE BURNERS Original Filed April 8, 1943 5 Sheets-Sheet 1 zlorntzw.

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June I4, 1949.

w. L. sANBoRN AIR DIRECTING MEANS IN GUN TYPE BURNERS- original Filed April a. 194:5

5 Sheets-Sheet 2 le fyi/kwa jafzor/a Q/ MM r@ W. L. SANBORN AIR DIRECTING MEANS IN GUN TYPE BURNERS Origna1`F'i1ed April .8, 1943 June 14, 1949.

5- Sheets-Sheet 3 .Sx NN Rx NNY w o @ijn June 14,` 1949 w. L. sANBoRN 2,473,347

AIR DIRECTING MEANS IN GUN TYPE BURNERS 4 Original Filed April 8. 1943 5 Sheets-Sheet 4 .h me 14, 1949. w. l.. sANBoRN 2,473,347

` AIR DIRECTING MEANS IN GUN TYPE BURNERS Original Filed April =`8, 1943 5 Sheets-Sheet 5 Patented June 14, 1949 AIR, DIRECTING MEANS IN GUN TYPE BURNERS William L. Sanborn, Milwaukee,.Wis., assigner,

by mesne assignments, to Cleaver-Brooks Company, a corporation of Wisconsin original application April s, 1943, serial No.

482,247. Divided and this application December 24,1947, serial No. 793,739

6 claims. (ci. 158-1) This application is a continuation of my application, Serial No. 482,247, filed April 8, 1943 (now abandoned).

In gun type atomizing oil burners, the problem has always been to obtain as hot a flame as possible because the hotter the name, the more complete will be the combustion of the higher ash point hydrocarbons in the fuel. This is particularly true in oil burners using the heavier grades of oil for in these grades there is a larger proportion of such high ash point hydrocarbons than in the lighter grades of oil.

It has ordinarily been considered good performance for an oil burner to have a flame temperature of as high as 1700 F. and for the flue gases to show a carbon dioxide content of ten per cent. With the improved burner of this invention, the flame temperature can be run as high as 3200 F. or even higher and the carbon dioxide content inthe flue gases can be increased to as much as fteen or sixteen per centvalues which are unheard of in burners now in commercial use.

These highly desirable results are obtained by disregarding what has heretofore -been considered proper methods for feeding secondary air to the ame and by utilizing a principle which is, in one sense, the direct opposite of that commonly relied upon in the design of oil burners. In the past, the effort has been to force the secondary air into the flame or, at times, into-the atomized fuel prior to ignition, this result being ordinarily accomplished by employing an inwardly flared collar at the end of the draft tube to drive the air into the flame. While this has some advantage in providing large quantities of oxygen for the hydrocarbons in the fuel, it has the disadvantage of cooling the high flash point hydrocarbons -which have not as yet been ignited and thereby prevents complete combustion ofv such high ash point hydrocarbons.

I have found that higher flame temperatures and more complete combustion of the fuel can be obtained by using a plurality of air streams, each of which has a particular function to perform and by feeding the flame, once it has been established, through a cylindrical rotating mass of secondary air from which the flame may draw oxygen as may be required. In some instances, this cylindrical mass of secondary air may be given straight rectilinear motion along the axis of the flamel although it is preferable to rotate the mass around the axis of the name. The net result of my use of a plurality of streams of air for supporting combustion is that ignition takes place closer to the nozzle and the flame is given a chance to establish itself and to thoroughly heat up the high flash point hydrocarbons before the additional oxygen required for their combustion is added to the ame.

With the temperature of the ame running as high as 3200 F., it is possible to employ supplemental fuel, such, for example as ground Weeds, corn stalks, pulverized coal, or any other ground material having a substantial fuel value. material may be added to the flame by blowing it in with the secondary air and it has been found by actual tests that as much as sixty per cent of the fuel input into the burner may be in the form of such supplemental fuel.

It is an astonishing fact that with flame temperatures running as high as 3200 F., it is possible to evaporate enormous quantities of water by injecting it directly into the flame without materially lowering the temperature of the flame or affecting its B. t. u. value. No attempt will be made to explain this unusual phenomena but it has been established by actual test.

Among the objects of the invention, therefore. are the following: To provide a fuel burner having an overall efliciency which is substantially greater than those now in use; to provide means for obtaining extremely high flame temperatures so that heavy grade oils may be consumed with high efficiency; to provide means for employing supplemental solid fuels with the conventional liquid fuels;'to provide means for evaporating large quantities of water with relatively low heat input; to provide an attachment which may be readily added to existing burners to increase the eciency with which such burners operate; and to accomplish the above objectives with simple,

easy to manufacture, economical structure.

Fig. 4 is a longitudinal sectional view of the nozzle;

Fig. 5 is a schematic diagram showing the various air streams used to obtain the high temperature flame;

the

3 Fig. 6 is a perspective view of the swirler used at the end of the draft tube; and

Figs. 7 and 8 are sectional views showing a means for feeding supplemental solid fuel to l the ame.

But these specific illustrations and the corresponding description are used for the purpose of disclosure only and are not intended to impose unnecessary limitations on the claims, or confine the patented invention to a particular use.

General description Referring to the schematic diagram of Fig. 1, it will be seen that the burner comprises a main housing I providing a reservoir II for lubricating oil and a chamber I2 for primary or atomizing air above the oil tank. In the upper part of the chamber I2 are two oil separators and air filters I3 and I4. The main housing also includes a secondary fan or blower casing I5 which communicates with a horizontally directed draft tube I6 passing out through the chamber I2 and within which are the following parts which have been displaced and are shown out of the draft tube in the lower part of the diagram: The primary air line Il supplying air to the nozzle I8, the oil line I9 which delivers oil to the nozzle I8, a heater 20 associated with the oil line, and electrodes 2I located adjacent to the nozzle for igniting the mixture of oil and air when the burner is started.

The main housing also forms a support for an electric motor 22 which drives the secondary air fan or blower 23, a primary or atomizing air pump 24 and an oil pump 25, here shown as arranged in alinement crosswise of the main housing.

The secondary air fan or blower 23 takes air through the slotted side wall 26 of the fan casing I5 under control of the rotary shutter 21 and delivers it through the draft tube I6 around the mixture of oil and air discharged from the orifice 28 of the nozzle I8. The volume is varied by adjusting the rotary shutter 2li.

The primary or atomizing air pump 24 takes air in at 29 and delivers it through a pipe 30 into the upper portion of the main housing through the filter I3 which is charged with bronze wool and from there the air goes into the chamber I2 through which it passes over the supply of lubricating oil 3I and up through the lter I4 and out through the pipe 32 which leads to the air line I1. In fact, the pipes 30 and 32 and the chamber I2 may be considered as forming a single air line with a storage or pressure chamber in an intermediate position which insures an even flow to the nozzle and provides fluid pressure for several other purposes.

The lubricating oil tank II is connected near the bottom by a pipe 33 with the pump 24 and by reason of the air pressure within the chamber I2, oil from the supply 3| in the tank II is continuously delivered to the air pump. However, the clearances of the pump are such that it will not deliver suflicient air to open the fuel line to the nozzle, as hereinafter described, until a considerable quantity of oil is contained within it to form the necessary seal. Hence, if the lubricating oil is insufiicient to properly lubricate the air pump, the fuel line to the nozzle will remain closed and the customary stack switch will turn off the burner in the absence of a fire in the lire box. As a result, this pump delivers a mixture of air and oil or air and oil foam to the pipe 30 from whence the mixture passes through the tank I I.

the bronze wool in the filter I3 which serves as an oil separator and an air cleaner and the lubricating oil collected there drops down over the outside of the draft tube I6 and returns to The filter I3 is separated from the lter I4 by a partition 34 and the air compressed in the chamber I2 passes up through a second mass of bronze wool in the filter I4 before entering the pipe 32.

In practice, the apparatus is so designed that a pressure of from ve to twelve pounds, for example, may be built up and maintained in the chamber I2. The pressure in the primary or atomizing air system is regulated by a bypass 35 connected across the inlet and outlet of the pump 24 and controlled by an adjustable valve 36. In this diagram, the bypass is shown as external piping but in practice is incorporated in the pump structure itself.

The oil pump 25 is preferably built for metering purposes only and should not be used to draw oil from the storage tank. Where gravity feed cannot be used, auxiliary pumping equipment 31 should be provided. The oil pump 25 takes oil from the supply line at 38 and delivers it to a pipe 39 leading to a cylinder 40 of a piston valve which connects it with the pipe 4I leading to the pipe I9 which delivers to the nozzle I8. The cylinder 40 is also connected by a bypass 42 with the supply line 38. The piston 43, movable in the cylinder 40, serves to connect the line 39 with the line 4I or with the bypass 42, as occasion may require. The piston is associated with an air motor, here shown as a Sylphon bellows 44 located in the primary air chamber I2 and subject to the pressure in the chamber. As a result of this arrangement, oil from the pump 25 is bypassed back to the supply line until there is sufficient pressure in the air chamber I2 to insure delivery of a proper amount of primary or atomizing air to the nozzle I8, when `the pressure in the chamber I2 will overcome the Sylphon 44 and shift the piston valve to a position in which it connects the pipe 39 with the pipe 4I and that, with the pipe I9, becomes a single oil supply line from the pump to the nozzle. When, for any reason, the air pressure in the chamber I2 drops below that for which the device is designed and adjusted, the piston valve will shift to the right, cut off the supply of oil to the burner and connect the pump 25 with the bypass 42.

By making the presence of a considerable amount of lubricating oil in the primary air pump 24 necessary to seal it and give it the required capacity it becomes impossible to run the pump long with insumcient lubrication for as soon as the pressure in the chamber I2 drops below that required, the supply of oil is cut 01T and a control of any one of the customary forms will put the apparatus on safety and shut the burner down entirely. The presence of the lubricating oil in the air pump 24 in such quantity as to form a foam makes it possible to provide ,a very efficient filter with the bronze wool in the filter I3 which also serves as an oil separator and delivers the excess of oil back to the supply in the tank Il.

Any one of the many types of oil burner con-- trols may be used with this system and none will be described in the interest of brevity. It will be sufficient to refer to Oil Heating Hand Book by Hans Kunitz, second edition, and The Starbuck Oil Burner Manual, 1941.

Electric power for the liquid fuel burner system described may be taken from the house line 4l and the apparatus shown in the diagram will.

l be understood from the following description of the operation. 1

When the room thermostat or boiler control 46 calls for heat, Minneapolis-Honeywell R117 relay 41 will be energized and close an electric Vcircuit to the delayed action switch 48 allowing current to flow to the oil heater and the ignition transformer 49. After a delayed action, for example, seconds, switch 48 closes the circuit to motor 22 which starts the secondary air fan or blower 23, the primary or atomizing air pump 24 and the oil pump 25. While the pump 24 is building up the necessary pressure in the chamber I2, oil from the pump 25 is re circulated through the bypass and the heater 20 is conditioning the oil in the pipe I9 and warming up the associated parts of the burner. When the pressure in chamber I2 reaches the selected amount, the Sylphon 44 will be compressed and the piston valve 43 will cut out the bypass 42 and connect up the oil line leading to the nozzle I8. As the mixture of air and atomized heated oil is discharged from the orice 28 of the heated nozzle, sparks from the electrodes 2I ignite itand the flame is further fed by the supply of secondary air delivered by the fan or blower 23 through the draft tube I6. After a short interval, relay 41 will shut off the current to the ignition transformer 49. The resistance of the heater element 20 is formed of pure nickel wire and has the desirable characteristic of drawlng a relatively high wattage until the coil is well heated after which the wattage automatically drops to a value nearly fty per cent of that which it was originally. Preferably, the relationship between the values of resistance in the heater and the time delay of the relay 48 is such that the oil in the fuel line immediately adjacent the nozzle is heated to a temperature of 190 Fahrenheit, which is just below the ash point of the oil, and provides for quick ignition. As soon as the fuel valve is opened so that there is a flow of oil through the pipe I9 to the nozzle. the temperature of the heater drops because of the more rapid heat transfer and the wattage input settles to a value of approximately 150 watts, fty Der cent less than the wattage input when the heater is cold. With oil i'lowing through the pipe I9 and the heater operating at 150 watts, the oil is heated to a temperature of around 105 Fahrenheit which is well below the temperature at which oil carbonizing takes place but which is sufcient to give the oil proper.

viscosity characteristics for atomization of fuel at the nozzle. v

Mention of Minneapolis-Honeywell R117 relay is merely by way of example, since other devices may serve the same function in a thermostatic control arrangement.

M odulating the fire The operation of the apparatus described is preferably modified by means to increase the fire after it is started and then' modulate the re according to the demand for heat. One embodiment of means to that end includes an airmotor the delivery of secondary air by the fan or blower 23 The piston 5I is normally urged to the po'sition shown by a spring 59 and its limit in that direction is determined by a low re stop 6I), its limit in the other direction being determined by a high re stop 6I, both adjustable on the piston rod 52 and made fast by set screws or the like.

In order to move the piston against the resistance of spring 59, air from the chamber I2 is conducted by a pipe 62 and delivered to a head chamber 63 in the air end of the cylinder 50 from which it passes by a port 64 into the cylinder and exerts its pressure against the plston 5I. The length of the pipe 62 and the adjustment of a needle 65 will make the flow of air involve the time interval desired for response to change in demand and the supply of oil and air will be increased or decreased in relation to the pressure permitted to build up against the piston head, this function, however, being limited by the adjustment of low fire stop 60 and high re stop 6I. In some designs, the length of the pipe 62 will have a negligible eiect and the control will be eiected chiefly by adjusting the needle valve 65.

With this arrangement, the burner will start With a verysmall :llame and gradually build up to the required size as determined by the design and adjustment and will stay there until the burner is stopped, at which time the spring will force the piston to low re position. During the movement to low Iire position, the air in the cylinder will escape through the orifice 66 and the check valve 61 back to the chamber I2 and be discharged through the nozzle.

However, it is preferable to add a modulating control, one embodiment of which includes a pneumatic temperature or pressure device 68 connected with the cylinder 50 by a pipe 69. When the temperature or pressure of the device 68, or that of the space to which it is subject, reaches the point at which it is set, the arm 1I of the delco comprising a cylinder 50 equipped with a piston A 5| whose piston rod 52 runs through the guide f- 53 and has one arm 54 connected by a link 55 with the rotating shutter 21 ofthe secondary air fan or blower and another arm 56 connected by a link 51 with a lever 58 on the oil pump 25 by which its capacity may be adjusted and enlarged as the shutter 21 is opened to increase vice B8 will uncover an orifice 10 in the pipe 6.9 allowing some air to escape, thus lowering the pressure in the cylinder 50 and allowing the piston to move toward the air end of the cylinder under the action of the spring 59, thus reducing the supply of the secondary air and oil. The piston will adjust itself to some point between high re and low fire positions, depending on the demand indicated by the arm 1I. If the temperature or pressure at device 68 should drop or decrease, the port 10 will be opened or closed correspondingly and the fire will be adjusted to correspond with the demand.

The device 68 may beany pneumatic control that will open a port on an increase of temperature or pressure and bleed the'air from the line 69 'to the atmosphere, or close the port on ,a decrease of temperature or pressure such, for example, as Minneapolis-Honeywell L-092D. These arrasa Referring to Figs. 2 and 3, it will be seen that the bottom of the main housing is formed by a base l2 having a down-turned edge 'i3 and a machined rib 14 on its upper face to receive and be secured to the bottomof the generally rectangular wall i which surrounds the lubricating oil space and with the base forms the oil tank or reservoir Just above the lubricating oil tank and at the left in Fig. 3, there is a hollow cylindrical projection 16, open at 11, to receive the air-operated shut-off valve for the oil supply.

Above the projection 19 is a larger hollow cylindrical projection 19, the left side of which, in Fig. 3,'is formed by the slotted Wall 26 and the right side of which is in open communication with the throat or entrance tothe Siroco fan or blower 23.

The draft tube |'6 intersects the main housing somewhat below the mid portion and the lower wall 8| (Fig. 2) of the draft tube extends across the main housing above the lubricating oil tank and, in effect, forms the upper portion of the chamber for the primary or atomizing air.

Referring to Fig. 1, it will be seen that the sides of the main housing are bulged at 82 and 33 to form passages upwardly around the draft tube and leading to the space for the iilters i3 and i9 which is closed at the top by a cap plate 89 secured in place by bolts and carrying the air pressure gauge 95 (Fig. 3). The bronze wool, which really forms the filtering and oil separating elements ofthe filters i3 and Il, fills the space above the draft tube divided by the wall 39 and closed by' the cap 84. Removing that cap permits access for cleaning the bronze wool which should be'done at suitable periods by removal and washing in kerosene or some similar solvent.

'I'he upper portion of the draft tube at the left in Fig. 2 opens into the secondary air fan or blower casing i5 which is generally eccentric with respect to the fan or blower 23 but affords direct and proper communication for air from the blower into and through the draft tube i6.

Just below the fan casing I5 and opposite to the draft tube, the main housing has an opening closed by a cap 85 into which the air tube Il is fitted at the end opposite to that connected with the nozzle i8. The cap also carries an appropriate nipple, etc., 8'! for connection with the air pipe 32 thus establishing the complete air line from the primary or atomizing air pump to the nozzle.

At each side of the nipple 81, and slightly above, areopen insulated fittings 88 to admit wires 89, the inner ends of which are secured to the electrodes 2| by nuts 99 (Fig. 2). IBeneath the nipple 81, the cap 9B has an opening 9|' to admit the heater tube 92, which surrounds the heater 29, and the oil line i9 leading to the nozzle I8. Suitable mounting for the electrical connections and the end of the oil pipe I9 are provided by a large cast fitting 93 secured to the cap 86.

Forked pedestals 94 (Fig. 2) have openings 95 and 96 to receive the air pipe |1 and the heater tube 92 and clamps 91 to receive the insulating tubes 99 for the electrodes 2|. Laterally extending projections 99 (Fig. 1) on the clamps 91 and a vertical leg |99 on the pedestals 94, engage the inside of thedraft tube and form a support for the assembly bound together by the pedestals 94. By removing the fastenings for the cap 86, this assembly, called in practice the drawer assembly, may be withdrawn as a unit from the draft tube.

Further details of the burner and its compo-l nent parts, method of operation, etc., may be found in the copending application of Earl J.

- Senninger, Serial Number 428,390, filed January 5 27, 1942, now matured into Patent No. 2,397,986, dated April 9, 1946, and the disclosure of that application is specifically made a part of the present disclosure in so far as itis not inconsistent with the disclosure which follows.

Air control at nozzle In the preferred form of the invention,- there are four separate streams or bodies of air which are fed to the nozzle or its vicinity in order to obtain optimum flame characteristics. In some cases, the number of streams or bodies of air may be reduced in number and certain advantages will be gained by the conjoint use of two or more of such streams.

The primary or atomizing air is led through the tube il to the burner nozzle i9, the latter comprising a casting |9| into one end of which the pipe il is screwed and into the opposite end of which a nozzle cap |92 is screwed. A passageway |93 connects the pipe with the interior of the nozzle cap |92 and a' swirler |94 is yieldingly pressed against the forward portion of the nozzle cap by a spring i 95 which is telescoped over a hollow stud 99 which'is threaded into the cavity |91 formed in the lower part of the casting |9i. The oil line I9 is connected through an elbow |99 with the cavity |9l so that oil is fed through the pipe i9, the cavity |97 and hollow stud |96 into the interior of the swirler |94 from whence it is delivered radially through side ports |99 to the primary air atomizing stream which is being forced through the bore |93 into the space between the swirler |94 and the interior cylindrical 4G surface iii) of the nozzle cap 892. Angular slots lil are formed on the exterior surface of the swirler |94 so that as air moves forwardly through the nozzle cap |92, it picks up the oil being delivered into the stream through the ports |99, and the mixture is swirled and delivered through the orifice 23 in the form of a fine mist or spray H2 (Fig. 5).

Any form of conventional atomizing nozzle may be used although the one described above is preferred.

In order to ignite the mixture as close to the nozzle as possible, means are provided for feeding a low velocity light supply of air over the nozzle i8 as shown at ||3 in Fig. 5.' This stream of air is preferably not swirled and constitutes 55 but a small portion of .the additional air which is fed to the vicinity of the nozzle to promote and maintain combustion. Preferably, it should not constitute more than ten per cent of such additional air and in actual operation one or two per $0 cent has been found adequate. Its velocity should be sufllciently low so that it will not, in any substantial way, interfere with the action of the atomizing nozzle I8. By surrounding the spray of oil and primary air from the nozzle i8 with a 95 low velocity body of air, it is possible, at least when the secondary air supply is properly applied to the ame, to have the flame "hug the nozzle; that is, it will be within three-quartersof an inch to an inch and a half from the end of the 'l0 nozzle under ordinary operating conditions.

In one sense, the air stream H3 is primary air because it is used to start and promote combustion rather than to support combustion. However, the air is drawn from the secondary air source as 75 willnow be described.

The draft tube I6 is provided, at its outer end. with a wall |'|4 having a circular opening ||5 adapted to receive a swirler generally designated I6. The swirler consists of an outer shell or rim' ||1 to which a plurality of radial vanes ||8 are secured. The inner ends of the vanes connect with an annulus H which is supported on the nozzle casting |0| by a collar |20 having spaced jaws |'2| (Fig. 6) which may be drawn together by a screw |22 to clamp the collar to the casting |0|. The brackets |23 connect the collar |20 to the annulus IIB leaving a space |24 between-the annulus 9 and the nozzle casting |0| through which air from the draft tube flows gently over the nozzle I8 to form the stream of air ||3 used for promoting ignition of the combustible mixture issuing from the -nozzle |8.

The vanes ||8 are preferably formed as at surfaces and are arranged so that they all intersect the axis of the nozzle at a single point on the axis and so that the loci of all lines through said point normal to the planes of the vanes define a cone revolution, the apex of which is on the axis of the nozzle. Obviously, the shaping of the vanes and their exact location may be varied within rather wide limits, the important factor being that they should direct the air which passes therethrough into a swirling, non-converging stream as distinguished from the usual converging stream which is used for secondary air at the nozzle to direct and force the secondary air into the burner flame. It has been found, after extensive experiments, that the common practice of forcing secondary air into the burner flame has a tendency to cool off the high llash point hydrocarbons and prevent their complete combustion whereas by using a non-converging stream of secondary air, and preferably a stream which diverges from the nozzle, suilicient air is fed tothe flame without the objectionable cooling action. This is particularly true when the secondary air ls split into at least two streams, one of which passes through the swirler ||6 and forms a nonconverging mass of secondary air while another portion is made to revolve in an enveloping cylindrical mass around a substantial portion of the burner flame as hereinafter described.

Adjacent the end of the draft tube |'6 is a plu'- rality of o enings |25 leading into a cylindrical drum |26 uitably secured at its inner end to the main housing 0 and having a flanged ring |21 iltted into the outer end of the drum. The end wall |4 of the draft tube |6 has a marginal flange |28 extending in the direction of the ring |21 and of the same diameter as the flange |29 on the closing ring |21 and the flanges |28 and |29 adjustably support a plurality of flexible sheet metal vanes |30 secured by riveting or other suitable means to the flanges |28 and |29, as shown vat |3|, and having their free edges yieldingly forced inwardly a pre-selected amount by` adjusting screws |32.

Secondary air forced by the blower 23 through the draft tube I 6 enters the drum |26 through the ports |25 and is then admitted tangentially through.,v the spaces between the vanes |30 into the combustion zone within. In as much as the air within the drum |26 is moving under pressure, it will, upon entering the combustion zone through the vanes |30, be rotated in the same direction as the air passing through the swirler I6, about the axis of the llame in an enveloping cylindrical mass, the thickness of which depends, to a large extent, upon the adjustment of the vanes by the screws |32. Obviously, by forcing the free edges of the vanes inwardly a greater amount, the thickness of the rotating cylindrical mass of secondary air is increased and conversely, by decreasingthe deflection of the vanes, the thickness of the rotating mass is decreased. The correct adjustment for the vanes will depend upon operating conditions but once the correct setting for the vanes is established, there will be no occasion to change their adjustment unless the operating conditions change.

Preferably, not more than one-third of the secondary air is passed through the swir1er.||6. the ports |25 being of such size as to cause at least two-thirds of the secondary air to enter the drum |26 and be fed to the flame through \the vanes |30.

It is an amazing fact that the flame temperature of an oil burner equipped with this invention can be made to run as high as 3200 F. or even higher whereas the flame temperature in conventional oil burners isusually well under 2000" F. Furthermore, stack temperatures can be reduced to almost any desired degree due to the extreme dryness of the ue gases from such a hot llame, and the CO2 content of the ilue gases may be increased up to fifteen or sixteen per cent. Heretofore, condensation in the stack constituted a limiting factor in the stack temperatures, but I have found that by using a mini- .mum flame temperature of approximately 2550 F. or more, this problem disappears. 'I'hese results are achieved by the novel methods' of employing secondary air and by the properv proportioning and application of the several streams oi' such air.

Due to the high temperature of the burner flame, it is possible to employ supplemental solid fuels with a burner equipped with this invention and thereby cut down on the amount of liquid fuel required; for example, as shown in Figs. 7 and 8, pulverized coal, corn stalks, weeds, or any other pulverized solid material having appreciable fuel value may be introduced under pressure to a chamber |33 Which is maintained under an air pressure at least equal to that Within the drum |26. The fuel is fed onto the upper traverse |34L of a conveyor belt |35, which is driven in any suitable manner, whenever the blower 23 is operated. The belt |35 delivers the pulverized fuel into the drum |26 and the fuel is carried by air currents through the vanes |30 into the combustion chamber. Under some conditions, the fuel may be introduced at the intake side of the blower 23 thereby rendering unnecessary any additional conveyor equipment. It has been found that as much as sixty per cent of the liquid fuel burned may be replaced by such supplemental fuel without getting an improper flame or causing smoke, ash or the like.

The relationship of the various masses of air which are used for obtaining the desirable combustion characteristics herein described are best shown in Fig. 5. The primary air and fuel oil are ejected from the nozzle I8 to form a fine mist or spray ||2 and the air which passes through the opening |24 between the ring ||9 and the nozzle forms the second stream of air ||3 which helps to promote ignition of the fuel i and air being delivered from the nozzle I6. The swirling, non-converging stream of secondary air which has passed through the swirler ||6 is indicated at |36 but the volume of such air is not sufficient to hold down the temperature of the high flash point hydrocarbons to an extent sufilcient to prevent their ignition, yet, at the same time, the stream |36 being swirling produces a turbulence which promotes good combustion and also helps to hold the flame back on the nozzle. The cylindrical mass of rotating secondary air, which is introduced from the drum |26 to the combustion chamber through the vanes |30, is indicated at |31 and the thickness of this mass may be adjusted to suit combustion requirements. The flame |38 picks up such oxygen as it needs from the mass |31 which, of course, is constantly moving outwardly with the flame due to the displacement of air through the draft tube I6. As may be noted in Fig. 5, the series of vanes |30 form a combustion passage or space that houses a. substantial portion of the flame produced by the burner, the length of the combustion passage or space being at least equal to the width or diameter thereof.

It is an am-azing fact that with a, flame temperature of 3200 F. or better, no ceramic protection is required for the drum |26 or the vanes |30. This is because the swirling mass of air around the flame acts as an insulator and protects the metal parts from the deleterious effects of the flame.

By way of specific illustration for a burner operating with an oil consumption of from two quarts an hour up to fifteen gallons an hour, the swirler ||6 may have an outside diameter of three inches and have twelve vanes set at an angle of 25. This latter angle may vary Within rather wide limits although it has been found that an angle of from 25 to 45 is the most desirable.

Under the same conditions, the combustion chamber defined by the vanes |30 may have a diameter of seven inches (this being the inside diameter of the flange |29) and the vanes may each be ten inches long. With this proportioning of the parts, the flame will normally extend approximately fourteen inches beyond the end` may be anything from an inch of mercury to several pounds of pressure.

An important problem solved in the design of the described burner relates to the entrainment of liquid or solid material in divided form in a fluid stream for treatment by the fluid without any substantial quantity of the entrained material reaching the periphery of the fluid stream to be deposited on the surrounding passage wall. In the present embodiment of the invention, the specific problem is not only to prevent such deposition of the oil particles sprayed from the burner nozzle or the oil particles together with the finely divided solid material but also to keep the passage walls from being excessively heated by the burner llame. It will be readily apparent to those skilled in the art that the particular structure and combination of elements that solve the problem of keeping entrained fuel away from the passage walls may have various uses apart from oil burners.

In general, the problem is solved by introducing into the fluid passage substantially throughout the length of the passage additional fluid in such manner as to form a rotating envelope of the newly added fluid lining the wall of the past sage. It is essential that the fluid envelope have a decided forward or axial component of motion and it is further essential that the fluid envelope 12 be laminar in character or substantially free of any substantial degree of turbulence.

In the particular arrangement disclosed herein, the finely divided material is introduced into what may be termed a main stream of swirling fluid that is to become the core of a composite stream in the fluid passage. An auxiliary stream of fluid is then introduced peripherally through the cylindrical series of longitudinal vanes |30 with a decided forward component of motion. I have found that ten such vanes constructed substantially as shown in the drawing function in a satisfactory manner but it is to be understood that the longitudinal vanes may differ from the disclosure in number and shape so long as turbulence is avoided and it is to be further understood that any suitable means may be substituted for the vanes so long as the peripherally introduced fluid is so directed as to form the required rotating and forwardly progressing fluid envelope around the main stream or stream core. In the present construction the forward component is achieved by extending the drum |26 rearward from the series of vanes |30.

It should be understood that the invention may be variously embodied within theI scope of the appended claims and that in not all instances is it necessary to employ all components of the burner which has been described. For example, the use of the swirler ||6 at the end of an ordinary draft tube and without the feature of a drum which rotates a cylindrical mass of air around the burner flame will give increased efficiency in burner characteristics over existing burners. The use of a non-converging stream of secondary air, preferably the use of a diverging stream of such air as distinguished from the usual practice of employing a converging stream of secondary air is in itself a departure from modern burner technique. However, the provision of means for rotating the mass of secondary air around the burner flame under controlled conditions and from which mass the flame may draw such oxygen as may be required is largely responsible for the startling results which are obtained with the burner herein described.

I claim:

1. The process of burning liquid fuel which consists in forming a corneal spray of fuel and air, ignting it, and then moving secondary air axially along the exterior of the flame with at least a portion of said secondary air being swirled around the flame in a diverging stream, and another portion of said secondary air being swirled around the flame in a cylindrical stream.

2. In a fuel burner of thev class described, the combination of a means defining a passage for feeding a combustible mixture to a flame, said passage extending inwardly from the outer end of the burner, means for introducing a gaseous fluid into the passage centrally thereof, means at the inner end of the passage to introducey fuel in divided form into said fluid for dispersal therein and entrainment thereby, and means to introduce additional gaseous fluid peripherally into said passage along substantially the length of the passage with an axial component of motion to form an axially progressing rotating annular mass of fluid surrounding said fuel-laden stream and separating the fuel-laden stream from the passage wall.

3. In a fuel burner of the class described, the combination of a means defining a passage for feeding a combustible mixture to a flame, means for introducing a swirling stream of air centrally fuel into said swirling air stream, and means for addinga rotating envelope of air to isolate the fuel-laden airfrom the wall of the passage.

4. In a, fuel burner of the class described, the combination of ay means defining a passage for feeding a combustible mixture to a flame, means for introducing a swirling stream of air centrally of the passagerotating in a given direction, a nozzle to spray nely divided fuel into said swirling air stream, means extending longitudinally of said passage for introducing additional air peripherally into said'passage at numerous locations spaced circumferentially around the pas-` sage, and means providing a plurality of deflecting surfaces extending longitudinally of the passage to cause said peripherally introduced air to form an axially progressing envelope lining the wallA of the passage, said envelope rotating in said given direction.

5. In a liquid fuel burner of the class described, the combination of means forming a combustion passage to enclose at least a'portion of the burner flame, said passage beingrat least as long as its cross dimension, an atomizing nozzle directed into one end of said passage, means for feeding liquid fuel and primary air to said nozzle to produce a finely atomized fuel spray at the nozzle, means for introducing secondary air into said passage at said end thereof, and means for forming in said passage a cylindrical-rotating envelope of additional secondary air to enclose said flame.

6. In a liquid fuel burner of the class described,

' the combination of means forming a combustion passage to enclose at least a portion of the burner flame, said passage being at least as long as its cross dimension, an atomizing nozzle directed into one end of said passage, means for feeding liquid fuel and primary air to said nozzle to produce a finely atomized fuel spray at the nozzle, means for introducing secondary air into said passage at said end thereof, and means including openings in the periphery of said passage extending longitudinally thereof for forming in said passage a cylindrical rotating envelope of additional secondary air to enclose said flame. v

WILLIAM L. SANBORN.

REFERENCES CITED The following references arel of record in the le of this patent:

UNITED STATES PATENTS Number Name Date i 836,219 Schutz Nov. 20, 1906 857,096 McCord June 18, 1907 1,490,281 Leach Apr. 15, 1924 1,618,808 Burg Feb. 22, 1927 1,762,982 Hasselbach et al. June 10, 1930 1,795,454 Van Brunt j Mar. 10, 1931 1,893,902 Meachem Jan. 10, 1933 1,910,893 Frisch May 23, 1933 1,959,864 Hartley May 22, 1934 1,990,088 Noe Feb. 5, 1935 2,096,765 Saha Oct. 26, 1937 2,098,455 Lattner Nov. 9, 1937 2,117,512 Scott I May 17, 1938 2,120,387 Bargeboer June 14, 1938 2,156,121 Mecrae Apr. 25, 1939 2,206,553 Nagel July 2, 1940 2,221,519 Jones et al Nov. 12, 1940 2,249,482 Macchi July 15, 1941 2,262,525 Delancey Nov. 11, 1941 2,284,708 Wooley June 2, 1942 2,292,664 Schwartz Aug. 11, 1942 2,311,404 Macchi Feb. 16, 1943 `2,335,188

Kennedy Nov. 23, 1943

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