US2472720A - Method of burning oil - Google Patents

Description

June 7, 1949. 1'. NAGEL METHOD OF 30mm oiL Filed Dec. 19, 1944 7 INVENTOR.

ATTORNEK Patented June 7, 1948 UNITED STATES PATENT j OFFICE 4 .iLiiilfm 2?... Application December is, 1944. Serial No. mm 1 Claim. .(01. its-111.5)

My invention relates to an improved method of and apparatus for the combustion of oil.

A conventional method of burning oil is to atcmize the oil by pressure ejection from an oil feed system. whereby minute oil globules are pro- Jected into the furnace through the firing opening in the form of a hollow, expanding conical stream, while at the same 'time, through pressure diflerential, a rotating stream of air flows through the firing opening. In such conventional operation the rotating air stream flows oi! tangentially to the direction of rotation after passin through the firing opening and advances in a more rapidly expanding area than the expanding area of the stream of oil globules. As a consequence, combustion of the oil is relatively delayed by the time element required for the oil globules to scour from the relatively fleeing air the oxygen essential for combustion, thereby producing a relatively widely spread out, long, heat liberating flame body.

For the same quantity of oil burned by conventional methods my improved method produces a higher-temperature, more concentrated flame body than is obtainable by such prior conventional methods, and through the high rate of heat transfer by radiance, this higher-temperature, concentrated source of heat liberation produces higher furnace temperatures than can be produced by conventional oil burnin methods from the same quantity of oil fed.

With the method and apparatus of the instant invention, atomized oil is not projected into the furnace as is done in conventional methods, but the oil is first atomized, ignited and converted into a diverging stream of ignited oil vapor which flows and is drawn into and mixed with a surrounding converging stream of combustion air prior to entry into the furnace firebox continuously to produce an ignited mixture of oil vapor and combustion air flowing into the firebox.

More specifically, I provide for atomizing the oil in a hollow cone diverging stream, igniting the atomized oil globules, and for converting these globules to oil vapor before entering the firing opening, the ignited oil vapor being drawn into the combustion air stream by the action of the air stream and so distributed throughout the same, prior to flowing into the furnace, that I produce a mixture of air and ignited oil vapor which continuously flows into the furnace.

This premixture of ignited oil .vapor and combustion air produces a relatively short. more concentrated flame within. the furnace than is possible by conventional methods burning the same 2 quantity of oil. Consequently, I produce by my new method a higher temperature heat liberation body which, by radiant heat transfer. produces a higher furnace temperature.

My new method of higher temperature combustion is substantially more economical than conventional methods of oil burning, which is confirmedby Stefan-Boltzmann's Fundamental Law of Radiant Energy. According to this law, the rate of energy transfer is proportional to the fourth power of the absolute temperature diirerence.

Economies effected by my new method have, been confirmed by independently conducted tests for comparison of the results obtained by operation of a modern power plant air-jacketed watertube steam generator equipped with a modem oil burning system operated by the conventional method with results obtained from operation in accordance with the present invention. These operations were conducted by the stat! of and at the U. 8. Navy Yard, Philadelphia, Pa., and produced the following results as shown by pertinent datataken from report of N. B. T. L. test 2680:

Conventional Applicant's ommmm on Burning New Method I. l Hour-8004 lbs. oil/hr. 00,

percent" 14.0 12.0 0 tics! Pyrometer Reading of lame Tem ture 2700 2860 II. 1 Hour-2444 bs.oil/hr. 001

per cent.. 13. 8 l4. 6 Ogtical Pyrclneter Reading of lame Tam tore IL. 2710 2980 III. 1 Hour-21471 s. oil/hr. 0

per cent 12. 9 14. 6 0 tical Pyrometer Reed of lame Temperature It. 2005 2020 IV. 1 Hour-1980 lbs. oil/hr. 00,

P01 oenL. 13.8 14.7 0' tiesl Pyrometer Reading of lame Temperature It. 2600 2886 V. lHonr-735 lbs. oil/hr. 00,

o M M m pneenti. 12.3 13.2

the o lans Temperature M 2525 This comparative test demonstrated that not only are higher temperatures produced from the same quantity of oil by my new method than by conventional methods, but that this was true even where the CO: was lower when operating in accordance with my method than when operating in accordance with conventional methods. For example, in 1" of the above comparative test table, 14.0% CO: was produced by conventional methods and 12.0% C0: by my method, yet the flame temperature attained in my method was 2850 F. as compared with only 2700 F. by

, atomized oil.

the conventional method. In those cases where the CO: was higher with my method than when employing the conventional method. the flame temperature difference was even greater in favor of my method. 4

Still more specifically, my invention provides 1 stood, is connected to a power driven fan or an improved method for burning oil wherein I continuously atomize oil into a chamber which is at the same time being supplied with only sufficient air to effect ignition and vaporization of the This chamber is located outside the furnace opening and is so positioned relatively thereto as to form an annular air channel between the chamber and the front of the furnace, outside the firing opening. Combustion air is supplied continuously to this air channel in volume sufficient to supply all of the air necessary for the combustion'of the oil vapor, and the air channel is so formed with respect to the outlet or exit of said chamber that the air stream produces a partial vacuum within and at the periphery of the chamber outlet to cause the ignited oil vapor, before entering the firing opening, to be drawn as an annular diverging stream into the annular converging stream of combustion air flowing from the exit of the air channel, to pro-- vide a premlxing of the ignited oil vapor and combustion air before entering the firing opening, and as this ignited mixture of gases enters the furnace I obtain relatively instantaneous combustion, producing a highly concentrated heat liberating body.

In the accompanying drawing wherein I have illustrated embodiments of my invention:

Fig. 1 shows one embodiment of my invention in part sectional plan; and

Fig. 2 is a similar view of another embodiment of my invention.

Referring to the drawing in detail and first of all to Fig. I:

2 designates the firing opening through one wall of the combustion chamber of a furnace through which fuel is admitted to the combustion chamber. In front of this opening I provide a hood 4 facing the firing opening. This hood is closed except for its discharge end and except for several openings 6 provided in the hood walls and through which flows a limited'quantity of primary air for oil ignition and vaporization purposes. This hood surrounds oil atomizer nozzle Ill and provides an oil atomizing, igniting and vaporizing chamber 8.

Provision is made, as seen at It, for adjusting the hood 4 toward and away from the firing opening for the purpose of regulating the area of an annular combustion air channel I4 which is formed by the spacing of the hood from the furnace front.

A conventional pump for supplying oil to the burner nozzle is shown diagrammatically at l6 and ignition may be effected when starting up by any of the conventional methods, as, for example, by torch, electrodes l8, etc., ignition thereafter being automatic and continuous as customany in oil burning practice.

In the embodiment illustrated in Fig. 1 the diameter of the inner end of the hood 4 and hence that of the discharge end of the chamber I is slightly greater than the diameter of the firing opening.

designates a windbox and air may be drawn thereinto by natural draft or induced draft through conventional openings in the windbox, or air may be supplied to the windbox by forced draft through pipe 2i, which. as will be underblower. The air flows about the exterior of the .hood 4 and through the annular air channel I4,

between the exit end of chamber 0 and the furnacefront.

The hood 4 is so set with respect to the furnace front as to provide the annular combustion air. channel i4 above referred to. so that the combustion air stream will flow as an annular streamj across the end of the hood 4 and directly into the firing opening to produce a partial vacuum behind the edge of the hood about the periphery of the outlet of chamber 4 sufficient to draw the advancing stream of ignited oil vapor outwardly toward the edge of the hood and into the combustion air stream flowing across the edge of the hood, thereby effecting distribution of the stream of oil vapor into the stream of combustion air.

In the embodiment of my invention illustrated in Fig. 1, the diameter of the outlet end of the hood 4, as above pointed out, is somewhat greater than the diameter of'the firin opening 2. It is evident. therefore, that with the hood moved away from the furnace front to provide the annular channel i4 between the hood and furnace front, the combustion air must flow through this channel across the edge of. the hood to produce the partial vacuum above referred to at the exit end of the chamber 8 behind the edge of the hood irrespective of whether the draft is natural, induced or forced.

The setting of the hood 4 with respect to the furnace front is so varied as to control the quantity of air required for complete combustion of the oil feed and therefore depends upon the air pressure differential between the outside and inside of the furnace, namely, the available effective draft; As an illustration: Assume that the hood 4 at its exit end is 14" in diameter, that the chamher 8 is 4" deep and that the firing opening is 13 /2" in diameter. The hood 4 should under such conditions be spaced about 75" outside the furnace front when burning 1500 pounds of No. 6 fuel oil per hour with a forced draft combustion air pressure differential of about 15" H2O, for complete combustion without air dilution. As the oil quantity is decreased, the air pressure differential is decreased to maintain the same oil-air ratio for the same hood setting. In commercial practice the hood is set initially for maximum capacity operation. and thereafter the air pressure differential is decreased in proportion to decrease in quantity of oil fed, without altering the setting of the hood. On the other hand, if it is desired to burn the same quantity of oil with a decreased air pressure differential, then, of course. it becomes necessary to increase the spacing between the hood and furnace front to maintain the same oil-air ratio. For lower steaming capacity and with natural or induced draft, air is admitted into the windbox 20 through conventional openings in the windbox, and hood 4 is so adJusted with respect to the firing opening 2 that the annutliar channel l4 will maintain the desired oil-air ra o.

In the embodiment of my invention as illustrated in Fig. 2: I show identical type of apparatus, except that in this case the outlet end of the hood 4 is smaller in diameter than the firing opening, In such construction the hood is oved forward, as will be seen by a. comparison with Fig. 1. to provide the required annular air channel area through which combustion air flows directly into the firing opening.

As a practical illustration of the hood settin where the outlet end of the hood is smaller in diameter than th firing opening: Let it be assumed that the firing opening is 11" in diameter, that the hood outlet is in diameter and that 40 gallons of oil per hour are to be burned with a 2" H2O air pressure diflerential. Under such conditions the shortest distance between the outlet end of the hood and the plane of the furnace front is thus providing an annular air channel at 22 V2" in width.

It will be seenfrom the drawing that in this embodiment of my invention the setting of the hood 4 is such as to provide the annular air channel above referred to through which the combustion air in its passage to the firing opening will flow across the edge of the hood to produce the essential partial vacuum at the inner edge of the hood so as to draw the oil vapor into the annular stream of combustion air as it flows across the edge of the outlet of chamber 6, as explained in connection with Fig. 1.

Itwillbe apparent from all of the foregoing that my invention provides a new and novel method of and apparatus for burning oil whereby. the oil is first atomized, the resulting minute oil globules ignited and converted to ignited oil vapor within the chamber 8 and drawn into the combustion air stream by the correlated 011 atomizlng pressure and the partial vacuum produced behind the exit end of the chamber 9 by the annular stream of combustion air. As a result of this operation the ignited oil vapor and combustion air are premixed and as this ignited mixture of gases enters the furnace I obtain more rapid combustion or heat liberation than is possible by conventional methods for the same quantity of oil, by which method I produce a highly concentrated heat liberating body, which by radiant heat transfer produces a higher furnace temperature than can be obtained by conventional oil burning methods using the same quantity of oil feed. In fact, as shown by the test data tabulated above, the improved results range from 150 to 325 F. higher flame temperatures than obtained by conventional methods using the same quantity of oil.

As further emphasizing the advantages of my method of combustion over conventional methods and as confirming the statements made above respecting the highly concentrated heat liberating flame produced by my process, I have observed in actual comparative tests of combustion in water tube boilers of U. S. Maritime Commission Liberty typecargo vessel that my process consistently produces flames approximately 90" long and 30" in greatest diameter as compared with flames approximately 120" long and 50" in diameter produced by conventional methods, when burning the same quantity of oil in both cases. In this service operation the heat release with my method of combustion approximated 200,000 B. t. u./HR/CF as compared with only approximately 50,000 3. t. u./I-IR/CF released by conventional methods of burning oil.

It is to be understood that changes in details of construction and arrangement of parts may be made within the purview of my invention.

What I claim is:

A method of burning oil in a combustion chamber having a wall provided with a firing opening, which method comprises continuously atomizing oil outside the firing opening and continuously mixing with the atomized oil a limited quantity of primary air sufflcient for ignition of the atomized oil; continuously igniting the mixture of oil and primary air; intimately mixing secondary air with the ignited oil vapor resulting from the partial combustion of the mixture oi atomized oil and primary air by continuously flowing an annular converging stream of secondary air toward the firing opening in such relation to the ignited oil vapor as to surround the same and draw the ignited oil vapor in the form of an annular stream into the converging stream of secondary air; and flowing this mixture continuously through the firing opening, thereby continuously obtaining relatively instantaneous combustion and a relatively short highly concentrated heat liberating flame body within the combustion chamber.

THEODORE NAGEL.

REFERENCES CITED The following referenices are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,023,422 D'Espuiols Apr. 16, 1912 1,055,715 Dahl Mar. 11, 1913 1,063,352 Jacobs June 3, 1913 1,491,158 Metcalfe Apr. 22, 1924 1,869,897 Hymer Aug. 2. 1932 2,055,331 Bredtschneider Sept. 22, 1936 2,081,710 McDonald May 25. 1937 2,088,299 Macrae July 27, 1937 2,122,688 Hill July 5, 1938 2,143,259 Clarkson Jan. 10, 1939 2,156,121 Macrae Apr. 25, 1939 2,206,553 Nagel July 2, 1940 2,221,519 Jones, et al. Nov. 12, 1940 2,325,444 Vroom, et al July 27, 1943 2,334,617 Fisher Nov. 16, 1943 2,359,049 Nagel Sept. 26, 1944

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