US2945459A - Pulsating combustion method and apparatus - Google Patents

Description

W. JUNKERMANN PULSATING COMBUSTION METHOD AND APPARATUS July 19, 1960 2 Sheets-Sheet 2 Filed May 7, 1954 PULSA'IQING COMBUSTION METHOD AND APPARATUS Wolfgang Junkermann, Oberhausen, Rhineland, Germany, assignor to The Bab'cock & Wilcox Company, New York, N.Y., a corporation of New Jersey This invention relates to a method of, and apparatus for, accelerating combustion by effecting vibrations of controlled frequency in a gaseous combustion supporting medium. The pertinent vibrations are .preferably generated in a current of the combustion supporting medium before itreaches the combustion zone, or azone in which that medium is mixed with a fuel carrying current.

When the pertinent method is employed in the combustion of a granular solid fuel such as coal, the coal particles :are carried to a combustion .zone in .a stream or current of .fluid, preferably air. There is also another current of a gaseous combustion supporting medium moving .to the combustion zone. These two streams are mixed, and combustion takes place, preferably in a tubular unitary resonance chamber of uniform cross section. The combustion zone is at one end-of thischamber. Near the other end of the chamber the vibrating current gaseous combustion supporting .medium enters, and between these two parts of the unitary chamber there may be said to be a mixing zone. The combustion supporting medium enters the unitary chamber with longitudinal vibrations of controlled frequency. The invention also includes within its purview the superposing of a vibration of another frequency upon the initially vibrating current of the gaseous combustion supporting medium thissuperposed vibration being exerted upon the medium by the control and variation of the natural frequency of the gas column of the unitary tubular chamber which includes the combustion zone and the zoneof entry of the gaseous combustion supporting medium subject to the initially impressed vibrations.

When the second of the above indicated vibrations has a frequency approaching the frequency of the initially impressed vibration, resonance .may be effected in the unitary resonance chamber. This makes .it possible to periodically produce pressures below atmospheric which cause fuel to enter the combustion zone periodically without the expenditure of external. energy. The frequency of the last impressed vibration may be so related as to the frequency of the initial vibration :that a beat is produced.

When granulated coal is burned with :the pertinent method, the combustion chamber preferably discharges its gases and other elements of combustion tangentially into a cyclone furnace in which the combustion of the larger coal particles is completed at temperatures above the fusion temperature of the ash or slag constituting the incombustible content of the fuel. The slag is removed in a liquid form and the action of the cyclone furnace is such as to effect relatively complete combustion with almost a total absence of incombustible .particles suspended in the flue gases finally exiting from the unit.

The invention is concisely and clearly set forth in the appended claims, but for a better understanding of the invention, reference should be had to the following description which refers to exemplifying apparatus shown 'in the accompanying drawings. In the drawing:

"Fig. 1 is a diagrammatic view illustrating parts of the StatesPatentO ICC.

apparatus in which fuel is burned in the presence of the pipe Zfrom a bunker 3 through an air-tight feed screw 4 and a pipe 5. This mixture of carrier air and granulated coal preferably flows at a minimum velocity of the order of 20 meters per second to prevent backfiring in the straight tube 7 which is preferably provided with a cooling jacket 6. The tube 7 and its jacket are preferably concentrically fixed within a larger tube 8 the jacket of which includes helically arranged cooling tubes 9. These tubes may be in communication with jacket 6 as shown in the drawing.

The tube 8 has a combustion zone 13 at one end, in front of the discharge end of the tube 7, the other end portion of the tube 8 constituting an entry vzone into which vibrating or pulsating secondary air is discharged from the blower 10 through the tube 11. Within the tube 11 is a rotating damper 12 preferably-driven by an electric motor at 3,000 r.p;m. This chokes the air current times a second so that the aircurrent entering the unitary resonance chamber within the tube .8;has a longitudinal vibration of 1-00 cycles per second the etfect of which continues as the air proceeds through the tube -8 at a speed of the orderof 3.6 meters per second.

Tube 8 extends beyond the tube '7 at both ends, providing, at one end, the combustion chamber 1-3 :in which the fuel carrying air current from the tube 7 is mixed with the vibrating or pulsating secondary air, and combustion sets in. At the other end of the tube 8, where no combustion takes place, there is a piston or plunger 14 which :is adjustable longitudinally of the tube '6. Varying the settingof the plunger 14 relative to the tube 8 changes the natural frequency of the column of gas in the tube 8. This change may be such that this natural frequency approaches the frequency of the initially impressed vibration or pulsation, resulting from the rotation of the damper 12. By this means the natural frequency of the gas in tube 8 may be brought into resonance, or with another upper or lower harmonic. Such resonance has the advantage of effecting a substantial reduction in power consumption, and, if the resonance is produced with an upper or lower harmonic, a beat is effected.

Combustion of the smaller or finer coal particles takes place in the combustion chamber 13, and to effect combustion of the larger or coarsercoal particles the combustion chamber 13 discharges tangentially into a .cyclone furnace 15 through the opening 16., The cyclone furnace of Figs. 2 and 3 has a slag discharge opening 17. The cyclone furnace and the combustion chamber 13 are preferably defined by circularor helical tubes having metallic studs secured thereto and extending therefrom toward the center of the combustion chamber and toward the adjacent tubes. The studs and the tubes are preferably .covered .on the furnace sides by high temperature refractory metal. Fig. 4 shows a part of a steam generator including the pulsating combustion chamber 13 and the cyclone furnace l5. Combustion gases pass from thecyclone furnace 15 through the opening 18 into an :after burner chamber'ztl into which liquid slag-flows through the opening 17. The slag then passes from the chamber Patented July 19, 1960 20 through the slag discharge opening 21. Gases from the chamber 20 flow across the inclined tubes of the slag screen 22 into the radiation chamber 23. All of the walls of the chambers 20 and 23 are formed by steam generating tubes connected into the circulation system of the steam generator. Fig. 4 discloses a lower header 2 4 to which some of these tubes are connected at their lower ends. At their upper ends these tubes are preferably connected to a steam and water drum. These connections and the remainder of the construction of the vapor generating unit are preferably of the type shown in the US. patent to Bailey et al. 2,357,301.

The gas chamber extending from the plunger or' piston 14 to the position of the outlet 16 may be considered as a resonance zone or chamber in which the natural frequency of the column of gas within that chamber is changed by changing the position of the plunger piston 14 to bring that frequency into resonance with the frequency of the pulsations initially effected into secondary air stream by the rotating damper 12. This action of the rotating damper may be said to set up a pulsating energy within the secondary air stream before it enters the resonance zone or chamber and the action resulting from varying the position of the piston 14 may be spoken of as matching the pulsation frequency of the resonance chamber to the frequecy of the pulsating energy in the secondary air stream entering the resonance zone.

Whereas the invention has been described with reference to a particular apparatus, and the method effected thereby, it is to be appreciated that the invention is not to be considered as limited by all of the details thereof. The invention is rather to be taken as of the scope comparable with the scope of the subjoined claims.

In the consideration of this invention the terms vibrations, oscillations, and pulsations are used more or less synonymously and the pertinent combustion method may be considered as pulsating combustion. When the pertinent method is used in a furnace as a part of a vapor generating unit, the jets of combustion gases discharged, have considerable kinetic energy and this energy release increases heat transfer and the heat output of the furnace of the vapor generator. It may, at the same time, eliminate the use of an induced draft fan, and result in a significant reduction in the overall dimensions of the unit.

The pertinent pulsating combustion may be considered as having a powerful pressure wave, which will cause the gas particles in the combustion chamber to vibrate with considerable amplitude. An increase in frequency of the pressure wave will increase the acceleration but diminish the amplitude of the gas particles; if, for example, the frequency is increased ten fold the acceleration of the gas particles will be likewise increased and the amplitude reduced to A of its original value.

In the pertinent pulsating combustion, the effect of the envelope of gaseous products of combustion which normally surround a burning coal particle, reducing the oxygen concentration and, therefore, the speed of the combusion reaction, is diminished because the envelope is peeled oif by the relative motion of the coal particles and the gas. The higher the relative velocity, the shorter the combustion time and the greater the heat release. When combustion takes place in the cyclone furnace, it permits the dimensions of the combustion chamber provided by the cyclone to be substantially reduced.

When the pertinent method operates at resonance frequency, there is effected a considerable increase in pressure amplitudes and stabilization is attained, both of the operating frequency itself, and the fuel consumption.

What is claimed is:

1. In a combustion system, means presenting a tubular chamber including a combustion zone, a fuel feeder normally conducting a coal containing fluid stream to the combustion zone, said fluid stream containing coal particles in suspension, air supply means normally conducting a stream of air to the combustion chamber for mixture therein with the coal particles, a rapidly rotating valve for setting up initial longitudinal vibrations in the air stream before it reaches the tubular chamber, means for varying the natural frequency of the fluid within the tubular chamber to amplify the effects of the initial vibrations, and a coal burning cyclone chamber to which the outlet of the tubular chamber is substantially tangentially connected.

2. In a combustion system, means presenting a cylindrical chamber including a combustion zone and having a fuel and gas outlet, a fuel feeder normally conducting a coal containing fluid stream to the combustion zone, said fuel stream containing large and small coal particles, air supply means including a conduit normally conducting a stream of air to the cylindrical chamber for mixture therein with the finer coal particles, a rapidly rotating valve within the conduit for setting up high frequency longitudinal vibrations in the air stream before it reaches the tubular chamber, an adjustable end wall for varying the natural frequency of the cylindrical chamber to effect resonance with the initial longitudinal vibrations, and a cyclone furnace for burning the larger coal particles having an upper inlet to which the outlet of the chamber and the combustion zone is substantially tangentially connected.

3. In a fuel burner, means forming a first combustion chamber having a gas outlet; means delivering to said combustion chamber a stream of a fluid suspended mixture of large and small particles of slag forming solid fuel; means delivering a gaseous combustion supporting medium to said combustion chamber for flow there through to said outlet; means for imposing a high frequency vibration on said gaseous supporting medium before it enters said first combustion chamber; said means resulting in the burning of the small particles in suspension in the first combustion chamber; and a cyclone furnace defining a second combustion chamber having a tangential inlet at its upper part connected to the outlet of the first combustion chamber and normally receiving large fuel particles and combustion products from the first combustion chamber.

4. Fuel burning apparatus comprising means forming 'a substantially cylindrical chamber including a combustion zone adjacent an open end thereof, an end wall arranged to close the opposite end of said chamber, means arranged axially of an intermediate portion of said chamber for discharging a fluid fuel therein towards the open end thereof, a combustion air supply conduit arranged to discharge a stream of air into said cylindrical chamber at a position intermediate said end wall and said fuel discharge point, means in said conduit arranged to impose a high frequency vibration on said combustion air stream before it enters said chamber, and means for adjusting the position of said end Wall longitudinally of said chamber to vary the natural frequency of said cylindrical chamber and amplify said initial combustion air vibrations.

5. Fuel burning apparatus comprising means forming a substantially cylindrical chamber including a combustion Zone adjacent an open end thereof, an end wall arranged to close the opposite end of said chamber, means arranged axially of an intermediate portion of said chamber for discharging a fluid fuel therein towards the open end thereof, a combustion air supply conduit arranged to discharge a stream of air into said cylindrical chamber at a position intermediate said end wall and said fuel discharge point, a high speed rotary damper in said conduit arranged to impose a high frequency vibration on said combustion air stream before it enters said chamber, and means for adjusting the position of said end wall longitudinally of said chamber to vary the natural frequency of said cylindrical chamber and amplify said initial combustion air vibrations.

6. In a method of effecting and accelerating combustion, mixing granular slag-forming coal and a gaseous combustion supporting medium and conducting the mixture to a confined first combustion zone in a first stream, conducting a combustion supporting gaseous medium in a second stream through a resonance zone and thence to the combustion zone, imparting high frequency longitudinal initial vibrations to the second stream in the resonance zone, the initial vibrations being of such a frequency that they are in resonance with the natural frequency of the combustion zone for amplification of the initial vibrations, burning the smaller coal particles in suspension in the first combustion zone, discharging the combustion gases and remaining coal particles into a second combustion zone, and cyclonically burning the remainder of the coal particles in the second combustion zone under temperatures above the fuel slag fusion temperature.

References Cited in the file of this patent UNITED STATES PATENTS Chubb Dec. 14, Chance Feb. 29, Andrews May 30, Bodine Aug. 30, Joeck Dec. 5, Kerr et al Apr. 29, Britton et al July 20, McIlvane Nov. 1, Kamm et al May 22,

FOREIGN PATENTS Great Britain Apr. 18, Great Britain Oct. 14,

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