US2488911A - Combustion apparatus for use with turbines - Google Patents

Description

Nov. 22, 1949 w. M. HEPBURN El AL COMBUSTION APPARATUS FOR USE WITH TURBINES Filed Nov. 9, 1946 INVENTORS 4 /7. f/fib am fl Barber n7 628252-09 Patented Nov. 22, 1949 COMBUSTION APPARATUS FOR USE WITH TURBINES Willlam M. Hepburn, Otta Barber, Toledo, Ohio,

Combustion Corporation,

poration of Ohio wa Hills, and Hugh B. assignors to Surface Toledo, Ohio, a cor- Application November 9, 1946, Serial No. 709,060

5 Claims.

This invention relates to combustion apparatus for generating an expansive gas for the purpose of actuating a turbine and has for its general object to provide a combustion unit which shall have special utility in environments, as in aircraft, where factors such as compactness, simplicity of operation, and wide operating range are important considerations bearing on its utility. For a consideration of what we believe to be novel and our invention, attention is directed to the following specification and the claims appended thereto.

In the accompanying drawing forming part of this specification- Fig. 1 is an axial section of the improved apparatus on a plane through line l! of Fig. 2.

Fig. 2 is a transverse cross section on line 22 of Fig. 1.

Fig. 3 is an enlarged axial section of one of the burners of which the improved apparatus is comprised.

Fig. 4 is an enlarged fragmentary view showing the manner of mounting a spark plug for igniting the fuel.

In the accompanying drawing, reference numeral l may be .considered as indicating the gas intake end of a gas turbine, not shown, and II as indicating a relatively large size air duct or casing to which air for combustion and dilution purposes is supplied by an air compressor, not shown, the casing having anend wall l2. This particular arrangement of parts may be said to illustrate one environment where the present invention has special utility.

The improved combustion apparatus comprises an annular combustion zone or chamber wherein the fuel is burned in a special way and also a dilution zone wherein the hot products from the combustion zone are diluted with air to cool said products to a safe temperature for turbine operation. The dilution zone is a cylindrical tunnel formed by an annular wall or conduit I3 which is interposed between the intake end ll of the gas turbine and the discharge end ll of the preceding combustion chamber. The tunnel 13 will ordinarily be connected to the said end H by a slip joint which includes a radial pin I 5 which extends into a notch in the rim of the tunnel to hold the latter from turning.

- The structure which defines the annular combustion chamber comprises a central annular wall or shell 22 which at its outer end is in open communication with the air duct ll adjacent the series of slot type air outlet ports 40 and also has a ring of ordinary round outlet ports 4|. As will more fully appear hereinafter, this particular pattern of air outlet ports in the side of the shell 22 helps to promote complete combustion of the fuel introduced into the space about the shell by a circular row of burners 25 mounted on the end wall 23 of the combustion chamber. As is best shown in Fig. 2, the several slot-type air outlet ports 40 are in planes which extend between the projected axes of adjacent burners.

The outer boundary wall of the combustion chamber comprises two axially spaced cylindrical portions I 4 and I8 of the same diameter, these two portions being separated by a radially enlarged portion which forms a channel between said portions l4 and I8 for a purpose presently appearing. The side walls of said channel are indicated at l6 and I! and they are held in fixed spaced relation by a plurality of curved air vanes 20 arranged in spaced overlapping relation to form a plurality of tangential air inlets 2| to said channel whereby the air from said inlets will initially rotate in said channel before entering the combustion zone proper. It will be understood thatthe supply of air to said inlets comes from the surrounding air casing I I.

Each of the burners '25 comprises a conical dome 26 which covers an individual firing opening. in the front end wall 23 of the combustion chamber. To the'small end of each dome there is welded a tubular extension 24 which projects through and is welded to the end wall l2 of the air casing II. The primary purpose of the extension 24 is to serve as a housing for an atomizing nozzle 30 for spraying liquid fuel into the dome. The nozzle will ordinarily be carried by a chambered fitting 3| to which liquid fuel is supplied under elevated pressure (say, 350 lbs. per square inch) by a supply pipe, the fitting with nozzle attached being so mounted as to permit removal from the extension 24 to permit cleaning of the nozzle.

Each dome 2B is multi-apertured for the admission of air from the air casing l I for the purpose of aerating the fuel from the fuel nozzle to a sufficient degree to insure that the fuel will begin to burn within the confines of the dome before entering the annular combustion space into which all of the burners discharge. A first set of air inlet ports for this purpose is indicated at 33 as a circular row at the small end of the dome. The air from these particular ports 33 tends to break up the initial spray pattern from the fuel nozzle. A second set .of air inlet ports 34 extends around the dome as a relatively wide band so that the air flows into the dome through these ports as through a sieve. Thefuel is ignited in any pre-- ferred way as by a spark plug 35 which projects into the main combustion zone through the end wall 23 thereof, the plug being of a length to permit it to be supported by the end wall 12 of the air casing so that it may be readily removed for replacement purposes. To simplify the ignition problem, one of the burners is first ignited, after which the fuel maybe turned on to the other burners. The burner which is to serve as a pilot has a fuel supply line 50 independent of the other burners. The other burners may have their fuel lines 49 in connection with a common fuel supply manifold 48.

As previously stated, the air from the elongate air ports 40 in the central annular wall 22 of the combustion chamber tends to flow radially across the annular combustion zone in planes which extend between the projected axes of adjacent burners 25. The oncoming streams of fuel from adjacent burners 25 may, therefore, be said to be separated from each other by a radially moving layer of air which, of course, tends to accelerate combustion of the next adjacent fuel. On the other hand the air which enters said combustion zone through the tangential air inlets 2| in the outer wall of said zone tends to form as it were, a ring of air about all of the fuel streams from the several burners and, of course, this air tends to accelerate combustion of the next adjacent fuel. Moreover, because this ring of air is rotating, it tends to impart rotation to the entire fluid contents of said zone. The jets of air from the elongate ports 40 and from the round ports 4| tend to oppose this rotation to some extent but on the other hand this opposition results in greater turbulence in the rotating mass of fluid with consequent more complete intermixing of the air and fuel than would otherwise be' 'the case. The overall result is rapid combustion of the fuel in a space which is relatively short in relation to its diameter.

Because the product gas as produced in the annular combustion chamber is at too high a temperature for safe turbine operation, diluting air is added to the product gas as it flows through the tunnel formed by the conduit l3. To this end a circumferential row of air inlet holes 31 is proin the end wall 36 of the central cylindrical shell 22 of the combustion chamber is only a relatively small portion of the total amount of dilution air required. The major portion of the dilution air comes from a plurality of circumferentially spaced flat air ducts or nozzles 43 which project a relatively shortdistance radially into the conduit, each duct being so arranged that its major transverse axis extends lengthwise of the conduit. Rigidity may be imparted to each duct by axially extending spacer elements 44 between the side walls thereof. The air ducts 43 are made flat axially of the tunnel l3 so that they may serve as longitudinally extending bailles for impeding the free rotation of the product gas coming from the annnular combustion zone to such extent as to insure sufficient turbulence in and rapid aeration of the core of the gas to produce rapid combustion of any residual fuel in said core. It will therefore be understood that although the zone defined by the tunnel I3 is primarily a dilution zone it also serves as a secondary combustion zone for residual fuel. This breaking up of the free rotation of the advancing gas also helps to equalize the temperature thereof throughout its cross sectional area. By reference to the drawing it will be seen that the air nozzle 43 extends a relatively short distance into the tunnel l3 in relation to its diameter. There is nothing critical about this distance except that if the nozzles extend too far into the tunnel the leading end of the nozzle is likely to be damaged by overheating by the oncoming product gas.

The end wall l2 of the casing H and the easing itself are interconnected by a split joint 41 the parts of which are held together in any preferred way by a clamping ring 45. The split joint permits the combustion unit to be readily withdrawn from its setting within the air duct H. Radial spacing fingers 46 may be provided hetween the combustion unit at its annular wall It and the air duct H at its split joint 41 to assist in centering the combustion unit in said duct.

From the foregoing description it should now be clear that the present invention provides a combustion apparatus which is well adapted for its intended purpose.

What is claimed as new is:

1. In combustion apparatus, the combination of means comprising concentric walls forming an annular combustion zone which is closed at one end and open at its other end for the escape of product gas therefrom, means for introducing fuel into said zone through the closed end thereof, means for introducing air into said zone on a tangent to produce a whirling body of air therein, means for introducing air radially into said zone through the inner of said walls, the outer of said walls having a circumferentially extending channel wherein the air entering said zone on a tangent initially rotates, and a conduit forming a tunnel from the outer wall of said zone for receiving the product gas therefrom.

2. In combustion apparatus, the combination of means comprising concentric walls forming an annular combustion zone which is closed at one end and open at its other end for the escape of product gas therefrom, a circular row of burners for introducing fuel into said zone through the closed end thereof, means comprising the inner of said walls for introducing air radially into said zone in planes extending between adjacent burners so that fuel streams advancing from adjacent burners will tend to be separated from each other by the radially moving jets of air, means for producing a rotating body of air in said zone, the outer of said walls having a circumferentially extending channel wherein the air entering said zone on a tangent initially rotates, and a conduit forming a tunnel from the discharge end of said combustion zone toreceive the product gas therefrom.

3. In combustion apparatus, the combination of means comprising coaxial annular walls and an end wall forming an annular combustion zone which is closed at one end by said end wall and open at its other end for the escape of product gas therefrom, the said end wall having a series of firing openings, burner means for introducing fuel into said zone through the said firing openings, means for introducing air into said zone on a tangent to produce a whirling body of air therein, the outer of said annular walls having a circumferentially extending channel wherein the air entering said zone on a tangent initially rotates, means comprising the inner of said annular walls for introducing air into said zone, and a conduit 4. In combustion apparatus, the combination of means comprising coaxial annular walls and an end wall forming an annular combustion zone which is closed at one end by said end wall and open at its other end for the escape of product gas therefrom, the said end wall having a series of flring openings, burner means for introducing fuel into said zone through said firing openings, means for introducing air into said zone on a tangent to produce a whirling body of air therein, the outer of said annular walls having a circumferentially extending channel wherein the air entering the said zone on a tangent initially rotates, a conduit forming a tunnel extending from the discharge end of said zone to receive the roduct gas therefrom, a series of baiiles extending into said tunnel in a direction tending to retard rotation of the advancing product gas, and said bailles for introducing air into said tunnel.

5. In combustion apparatus, the combination of means comprising coaxial annular walls and an end wall forming an annular combustion zone which is closed at one end and open at its other end for the discharge f product gas therefrom, a

being radially apertured to serve as nozzles series of burner means mounted on said end wall to fire into said zone through iiring openings in said end wall, the burner means comprising a dome forming a cover for each of said firing openings and a spray nozzle for spraying liquid fuel into said dome from the small end thereof, the walls of said dome being multi-apertured for the admission of air into the space encompassed by said dome, and means comprising the outer of said annular walls for introducing air into said zone on a tangent to produce a whirling body of air therein.

WILLIAM M. HEPBURN.

HUGH B. BARBER.

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

UNITED STATES PATENTS

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