US2918118A - Burner - Google Patents

Description

Dec. 22, 1959 R. M. scHlRMER 2,918,118

BURNER Filed Aug. 30, 1954 5 Sheets-Sheet 1 'AT -roR NEYs .N @Fm INVENTOR R.M.SCH\RMER www i LA,

AMY-T la Dec. 22, E959 R. M. scHxRMl-:R 2,918,118

BURNER Filed Aug 50, 1954 3 Sheets-Sheet 2 L se.

ATTORNEYS Dec. 22, 1959 R. M. scHlRMER 2,91818 BURNER @ned Aug. 50. 1954 s sheets-sheet s INVENTOR. `R. M. SCHIRMER BY MWL W7 AT TOR N EYS mm mm United States Patent" BURNER Robert M. Schirmer, Bartlesvilie, Okla., assignor to Phil- Eips Petroleum Company, a corporation of Delaware Application August 30, 1954, Serial No. 452,803

4 Claims. (Cl. 153-4) This invention relates to improved burners. In one of its more specific aspects, this invention relates to combustion apparatus. In another of its more specific aspects, it relates to continuous flow combustion apparatus of low pressure drop, high combustion efliciency and high heat release. In another of its more specific aspects, this invention relates to an improved apparatus for producing continuous flow combustion at a high rate of heat release. In another of its more specific aspects, it relates to an improved burner for jet engines.

In the usual design of combustion apparatus in which a flame is initiated in a stream of high velocity air, some mechanism must be provided to decelerate at least a portion of the stream of air below effective llame velocity in the combustible mixture to pilot and maintain the flame seated in the apparatus. Addition of fuel is made either directly to the high velocity stream of air upstream of the deceleration device or in the region of a quiescent zone downstream from the deceleration device. In the usual turbo-jet engine, combustion is maintained in the flame tube or liner, which completely surrounds the flame, and apertures in the liner serve for the addition of such air for the formation of a near stoichiometric mixture of fuel and air in the primary combustion zone. The loss of pressure in an apparatus of this type is considerable. In the usual ram jet engine, a restrictive element, usually called a llame holder, is mounted in a stream of high velocity air and combustion is carried on in the quiescent zone downstream from this restriction. In the ram jet apparatus, the magnitude of the pressure drop is less than that encountered in the turbojet engine.

In the combustion apparatus commonly employed in gas turbine power plants, it is necessary to achieve stable and eiiicient combustion of fuel and air at high rates of heat release in a relatively confined space through which a stream of air is mo-ved at high velocity. It is desirable in such a combustion system that the pressure loss be low, that the temperature distribution of the cross-section of flow be uniform and that stable combustion be obtained over a wide range of fuel-air ratios and severity of inlet conditions. In my copending application Serial No. 346,304, filed April 2, 1953, now abandoned, I have described and claimed a combustion apparatus which permits a high rate of heat release to be obtained while maintaining high combustion eiciency and combustion stability.

The following objects will be attained by at least one of the aspects of this invention.

It is an object of this invention to provide an improved burner. Another object is to provide an improved apparatus for producing continuous flow combustion at a high rate of heat release. Another object is to provide an apparatus of low pressure drop in which improved combustion efficiency and stability are obtained. Another object of the invention is to provide a continuous llow combustion apparatus wherein the fuel is delivered uniformly onto the entire inner surface of the primary com- Mig Patented Dec. 22, 1959 bustion chamber. Another object is to provide an irnproved continuous flow combustion apparatus wherein the fuel is contacted with a catalytic material immediately prior to its introduction into the combustion chamber. Other and further objects and advantages of this invention will be apparent to thoseskilled in the art upon study of the accompanying disclosure and drawing.

I have now developed a combustion apparatus which provides improved combustion eiciency and stability compared to conventional apparatus with comparable pressure drops. Broadly speaking, my combustion apparatus permits the introduction of fuel uniformly onto the entire inner surface of the primary combustion chamber through a porous liner spaced from the inner wall of the chamber, and the introduction of air in the form of a vortex into the primary combustion chamber so that the flow of air spirals or swirls coaxially through the primary combustion chamber. Combustion apparently is effected at the highly turbulent shear interface of the fuel and the air. The shear interface, and therefore the combustion occurs near the surface of the porous wall and in the mixing zone. Using the combustion apparatus of my invention it is possible to obtain heat release in the order of 40 million B.t.u./hr./cu. ft./ atmosphere at overall flow velocities up to 250 ft. per second. Thus the amount of heat release that can be obtained with my improved combustion apparatus is approximately l0 fold that of conventional burners now in common usage.

The operation of a jet engine, such as those employed in aircraft, is dependent upon the utilization of the thermal energy released in the engine burner. The combustion of fuel andl airin the burner gives the molecules of the gases high kinetic energy. These gases are ejected from the combustion chamber at a high velocity, resulting from the high kinetic energy provided by the thermal energy, and thrust is thereby applied to the aircraft. Thus the efficiency of a jet engine is a function of its ability to obtain high heat release under all operating conditions. The improved burner of my invention has particular application in operations where high heat release is required, such as in gas turbines, ram jets, furnaces, and the like.

In my combustion apparatus, all of the air may be used as primary air, or part of the air may be used for secondary air, depending upon the need and adaptation of the burner. Primary air is admitted through a plurality of tangential openings into the flame tube. Preferably, these openings are tangential to the llame tube and are located around the periphery of the ame tube or around the periphery of a smaller diameter member of the burner located immediately upstream from the llame tube. The air can also be admitted coaxially to the flame tube through swirl vanes so as to produce a vortex of air spiraling coaxially through the ame tube. This apparatus for the introduction of air provides a swirling and spiraling ow of air along the axis of the burner and provides for the supply of the right amount of air to the fuel over a considerable operating range of conditions so as to maintain a proper, non-carbon forming residence time.

The .llame tube disposed coaxially within the burner shell is constructed of an impervious outer tube and a porous inner tube located coaxially within the outer tube and spaced from the outer tube so as to provide an annular chamber between the two tubes. The annular space is sealed at both ends so as to provide a chamber having a porous inner wall.

can flow relatively freely into the combustion zone.

The introduction of the fuel through the structure of the primary combustion chamber wall provides for the increased rate of heat release and for the improved cornbustion stability obtained by the apparatus of my in-l vention. The use of a liquid fuel in this combustion apparatus provides for self-regulation of the wall temperature of the fiame tube in accordance with the latent heat absorbed in the vaporization process occurring on the inner surface of the primary combustion chamber. Also, the circulation of the fuel in the annular chamber surrounding the combustion zone and the passage of the fuel through the heated, porous structure of the inner tube preheats the fuel to improve thereby the combustion process.

It is a particular feature of this invention that the porous inner tube of the primary combustion zone can be constructed of a material which will catalyze such reactions as cracking and oxidizing so that the fuel emerging into the combustion Zone contains a large proportion of constituents having improved combustion and stability characteristics. Thus, a fuel which has been precracked contains acetylene having high burning velocity and a fuel with which supplemental oxygen has been admixed before passage through the porous inner tube will contain aldehydes, peroxides, and other oxygenated cornpounds.

The porous inner tube used in the combustion apparatus of my invention is constructed with continuous filamentary ducts through which the combustible material The material from which the porous tube is constructed must have high mechanical strength and resistance to elevated temperatures. The tube can be made of various metals or ceramic materials such as zirconium oxide, aluminum oxide or silica-alumina. A convenient method for constructing a metal porous tube comprises compressing finely divided metal fragments or lmetal powders and thereafter sinter'ing or partially melting the metal fragments causing them to adhere to each other and thus to form a porous structure. Both the primary combustion chamber and the secondary combustion chamber can be constructed with the porous inner tube or liner, however, the combustion chamber is preferably constructed with the porous tube located in only the primary combustion chamber.

In the drawing: Figure l is a sectional elevation of the improved corn- `bustion apparatus of this invention;

Figure 2 is a cross-section taken along line 2-2 of Figure 1;

Figure 3 is a lsection view showing a modification of the apparatus of Figure 1;

Figure 4 is a cross-section taken along the line 4-4 of Figure 3;

Figure 5 is a section view showing another modification of the apparatus of Figure l; and

Figure 6 is a cross-section taken along the line 6-6 of Figure 5.

Referringnow to the drawing and particularly to Figure 1, combustion apparatus 10 comprises an outer shell 11 having a flame tube 12 coaxially disposed therein. The upstream end of fiame tube 12 is positioned within support member 13 which is attached to closure member 14. The porous ,inner tube 15, of slightly smaller diameter than the inner diameter of flame tube 12, is coaxially disposed within fiame tube 12 and extends from the inner surface of support member 13 to a point downstream in flame tube 12 where primary combustion ceases. Fuel inlet conduit means 16 extends through closure member 14 and support member 13 to the annular space 17 in support member 13 coinciding with annular passage 18 formed by the flame tube 12 and porous tube 15. Closure ring 19 located at the downstream end of porous liner seals annular chamber 18 at its downstream end.

Afrom the primary combustion zone.

Air inlet 20 extends through shell 11 into the annular space formed between shell 11 and ame tube 12. Air inlet 20 can extend either radially or tangentially through shell 11. A plurality of primary air inlet conduits 21 extends tangentially from the annular space formed between shell 11 and ame tube 12 into cylindrical chamber 22 which is positioned in support member 13 and which is of a diameter slightly smaller than the diameter of porous tube 15. A portion of the air introduced through line 20 is diverted as secondary air and is introduced into the interior of flame tube 12 downstream from the primary combustion zone through secondary inlet conduits 23. Conduit 20, when positioned so as to introduce air tangentially into the annular space formed between shell 11 and flame tube 12, aids in producing the desired vortex in the primary combustion zone.

Fuel conduit 24 extending through closure member 14 and support member 13 supplies fuel for ignition purposes to cylindrical chamber 25 located in support member 14. Spark type ignition device 26 extends through closure member 14 into chamber 25 for effecting ignition of a pilot fuel, such as propane.

In the operation of the device shown in Figure l of the drawing, fuel such as the primary fuel or propane is introduced as pilot fuel through conduit 24 into the space formed between support member 13 and igniter 26. Primary air is introduced through conduit 20 and the plurality of tangential burner air inlet conduits 21 into the chamber 22 at a point adjacent the downstream end of conduit 25. The pilot fuel is ignited in chamber 25 and the air which is introduced through tangential inlet conduits 21 imparts a helical motion to the gases flowing into the interior of the porous tube 1S. Primary fuel which can be either in a liquid or a gaseous form is ,introduced into the annular space 18 from fuel inlet conduit 16. One or more primary fuel inlet conduits can be .utilized if desired. The primary fuel is diffused from annular chamber 18 through the porous wall of tube 15 and into the vortex of primary air moving coaxially through the primary combustion chamber, thus obtaining excellent mixing. The primary fuel and air mixture is ignited by the burning pilot fuel, after which time the introduction of pilot fuel can be discontinued. By introducing the fuel uniformly through the wall of the primary combustion chamber and introducing the primary air in a helical motion, as a vortex of air moving coaxially through the burner combustion chamber, excellent mixing of the fuel and air is obtained and a stable flame results, without the aid of holding means such as a flame holder which would increase the pressure drop through the unit. The combustion efficiency obtained in this type of device is therefore superior to that obtained in any known type of burner.

A portion of the primary air which is introduced through conduit 20 is diverted as secondary air and is introduced into the interior of flame tube 12 downstream This secondary aix acts as a quench, diluting the combustion products to ,such an extent that additional burning does not occur. The addition of secondary air also tends to even off the temperature of gas phases in the combustion apparatus.

Referring now to Figure 3 of the drawing, parts which are like those described in connection with Figure l are indicated by like numerals. In this modification, charnber 22 of Figure 1 has been omitted and the tangential primary air is introduced directly into the upstream end of the primary combustion chamber. Primary air is introduced tangentially into the primary chamber through conduits which prevent the entry of primary air into annular chamber 18. In this modification, outer shell 11 is composed of two sections, the larger lower section being indicated 11. These two sections 11 and 11', are secured together by flanges 31 and 32. In this modification, the porous inner tube 15 is shown as a metallic so as to introduce air helically into the annulus between shell 11 and burner tube 12 so as to facilitate the formation of a vortex of air and burning gases in the primary combustion chamber.

In the device shown in Figure 5 of the drawing, primary air is introduced coaxially into the primary combustion chamber through conduit 20. The primary air enters the primary combustion chamber through swirl vanes 41 which impart thereto a spiral motion so as to form a vortex of air and burning gases in the primary combustion chamber. Ignition is obtained in this modilication in the same manner as in the device of Figures 1 and 3.

Any fuel can be used which will diffuse through the porous material forming the wall of the inner tube in the primary combustion chamber'. Conventional jet engine fuels are particularly adapted for use in my improved burner. J et engine fuels include gasoline, kerosene and other blends of liquid hydrocarbons. The primary fuel can also be used as the pilot fuel, however, it is preferable to use a more volatile fuel such as propane as the pilot fuel.

I Wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

That which is claimed is:

1. An improved combustion apparatus comprising an outer shell closed at its upstream end; a constant diameter flame tube comprising a primary combustion chamber and a secondary combustion chamber, closed at its upstream end and concentrically positioned within said shell; a constant diameter porous tube concentrically positioned within the primary combustion chamber of said llame tube, spaced from the wall of said flame tube and sealed to said flame tube at the downstream end of said primary combustion chamber; a cylindrical igniter chamber positioned in the closed end of said primary combustion chamber, having a diameter less than that of said porous tube; air inlet means opening into said outer shell; air inlet conduit means extending tangentially from the chamber formed between said outer shell and said llame tube to the interior of the igniter chamber; a slm-aller diameter chamber in coaxial communication with the upstream end of said igniter chamber; an igniter positioned in said smaller diameter chamber; a pilot fuel inlet conduit means extending into said smaller diameter chamber; and fuel inlet conduit means extending into the annular chamber formed between the porous tube and the flame tube.

2. An improved combustion apparatus comprising an outer shell closed at its upstream end; a constant diameter flame tube comprising a primary combustion chamber and a secondary combustion chamber, closed at its upstream end and concentrically positioned within said shell, a constant diameter porous tube concentrically positioned within the primary combustion chamber of said flame tube, spaced from the wall of said llame tube and sealed to said llame tube at the downstream end of said primary combustion chamber; air inlet means opening into said outer shell; air inlet conduit means extending tangentially from the chamber formed between said outer shell and said llame tube to the interior of the flame tube; a cylindrical chamber positioned in the closed end of the said primary combustion chamber, having a diameter less than that of said porous tube; an igniter positioned in said cylindrical chamber; a pilot fuel inlet conduit means extending into said cylindrical chamber; and fuel inlet conduit means extending into the annular chamber formed between the porous tube and the flame tube.

3. An improved combustion apparatus comprising an outer shell; a constant diameter flame tube comprising a primary combustion chamber and a secondary combustion chamber, concentrically positioned within said shell; a constant diameter porous tube concentrically positioned within the primary combustion chamber of said llame tube, spaced from the wall of said llame tube and sealed to said llame tube at the downstream end of said primary combustion chamber; an annular member positioned at the upstream end of said primary combustion chamber so as to form an annulus between said outer shell and said llame tube and to seal the upstream end of said flame tube and the upstream end of said porous tube thereby forming an annular chamber therebetween; a member coaxially disposed within said annular member having a cylindrical chamber opening into said primary combustion chamber and containing therein an igniter; swirl vanes occupying the annulus between said annular ring and said coaxially positioned member and rigidly secured to said members; air inlet means opening into said outer shell at a point upstream from said swirl vanes; a pilot fuel inlet conduit extending into said chamber in said coaxially disposed member; and fuel inlet conduit means extending into the annular chamber formed between the porous tube and the flame tube.

4. An improved com-bustion apparatus comprising an outer shell; a constant diameter flame tube comprising a primary and a secondary combustion chamber, concentrically disposed within said shell; a constant diameter porous tube concentrically disposed within said primary combustion chamber, spaced from the wall of said flame tube, and sealed to said llame tube at each end of the primary combustion chamber; means for supplying a Vortex of air to the interior of the llame tube adjacent its upstream end; means for supplying additional air to the interior of the flame tube through the flame tube wall at a point downstream from the primary cornbustion chamber; means for supplying fuel to the annular chamber between the llame tube and the porous tube; and means for igniting the fuel and air mixture in the primary combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,495,164 Coberly May 27, 1924 2,018,582 Theunissen Oct. 22, 1935 2,561,200 Hess Iuly 17, 1951 2,579,614 Ray Dec. 25, 1951 2,616,257 Mock Nov. 4, 1952 2,668,592 Piros et al. Feb. 9, 1954 2,841,213 De Piolenc et al. July 1, 1958 Y FOREIGN PATENTS 966,707 France Mar. 8, 1950 691,430 Germany May 25, 1940

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