US2674846A - Combustion chamber with baffle means to control secondary air - Google Patents

Description

Tons

Il! Ul IH Il NIMHHIIIII W. J. BLOOMER ET AL NI Il! Il! IW April 13, 1954 COMBUSTION CHAMBER WITH BAFFLE MEANS To CONTROL SECONDARY AIR Patented Apr. 13,` 1954 AUNITED STATE COMBUSTION CHAMBER WITH BAFFLE MEANS TO CONTROL SECONDARY AIR Ward J. Bomer,westne1d, N. J., anonymen R. Davis, Jackson Heights, N. Y., assignors to The Lummus Company, New York, N. Y., a corporation of DelawareA Application December 18, 1950, Serial No. 201,415

4 Claims. l

This invention relates to power plants ofthe gas turbine type and more particularly to the Afuel burner and combustion chamber therefor. Itis a continuation-in-part of our copending application Serial No'.4 .98.214, filed June 1 0, 1949.

It is known that theV development of the gas turbine has been dependent to a large extent on the supply of hotl products of combustion with such uniformity of temperature as to establish eflicient operation and with the particular advantage of minimum maintenance and long time runs. Various types Vof combustion chambers have been used in which the fuel is supplied under pressure and mixed with air and thereafter din luted to a suitable temperature for operation in the turbine but it hasA been found that the uniformity of temperature vis unsatisfactory. It is to. be understood that a gas turbine operates under such conditions that it is particularly sensitive to excessive temperature and where there is a spread of several hundred degrees it is necessary to maintain average operating conditions well below the theoretical maximum. s The particular type of burner andV combustion chamber contemplated herein is not only more efficient in combustion than these heretofore available but it also provides a uniformity of temperature of the gas discharge which is unusual for the high heat capacity installations `characteristic of lgas turbines. Our improved combustion chamber also has theadvantage of being adaptable to variousfuels which include gas, distillate and the heavy residual fuels which have not successfully been burned in similar combustion chambers. It is also somewhat simpler than our prior construction and is a commercial adaptation of theprior invention.

Further objects and advantages of our yinvention will appear from the following description of a preferred 'formof embodiment thereof taken inl connection with the attachedvdrawing in which:

Fig'. 1'isa"substantially'central vertical cross Y section taken through the burner:

(Cl. fili-39.23.)

of a gas turbine normally include a blower or` compressor for the combustion supporting gas, usually air. a burner or mixer for mixing the air and fuel, a combustion chamber and an air di'- luting device. Our present invention concerns the burner, the combustion chamber and the air dilution device, all of which are conveniently mounted in a casing lil. The combustion supporting gas, hereinafter referred to as air, is supplied under pressure to the casing inlet I2, andthe desired products of combustion are discharged at lli. Although this casing is represented as being horizontal, itis independent of gravitational forces and may beat'any desired angle to the horizontal.

Within this casing l0 is the combustion chamber or flame tube formed by the refractory lining I6. While this is preferable, it is to be understood that the chamber may be formed solely by the shell Ia which maybe made of cobaltnickel or chrome-nickel alloys.

VOne vend wall of the combustion chamber is adapted to receive the burner or mixer in the form of a tuyre which serves tov mir the vair and fuel and to discharge the combustible mixtures into the combustion chamber in a unique manner. More specifically the tuyre I8 is annular and preferably a cylindricalmember.' the' side wall of which is provided with blades 2d which may be stamped out of the wall or be formed in any other equivalent manner. 'These' blades, which are tangentially disposed, form converging air paths or slots 25 extendingl into thetuyre'.

The tuyre I8 is providedwith apertured'face plate I9 extending to windbox 20 which is simply a circular shell which may be providedV with a f cone shaped baie 22 to divertsome of Vthe air entering the inlet end vI2 of the casing into the combustion chamber I6 and some into 'the sur# rounding air duct 40. As will be appreciated by reference to the drawing, air entering the casing inlet I2 and passing through the windbox 20 will pass through the air paths 25 between the tuyre blades into the tuyre. The angularity of the blades and the available air pressure is such that a highly compact rotating air column sunlcient to create a vortex is thus formed within the tuyre. Continued supply of air of course forces the air as an annular stratum adjacent the tuyre wall into the combustion chamber IB.

Fuel is introduced to this rotating air column in either or both of two ways as desired. Preferably a light fuel such as distillate or gas may be introduced through line 38 and the feed pan 36 as hereinafter described and thence into the air stream as it passes between the blades 24 into the tuyre and the heavier fuels may be introduced :from line 34 through the closed end 28 of the tuyre as by the use of one or more nozzles 30. These nozzles, which are in communication with a distributing ring 32 are preferably arranged near the outer wall of the tuyre and may extend about 1A" into the tuyre itself.

The uniform distribution of fuel by the external fuel feed regardless of angularity of the casing with respect to the horizontal is accomplished by engaging the side wall of the feed pan 36 with the outer edges of the tuyre blades whereby a peripheral series of small fuel openings Sla are formed. This establishes a highly effective distribution of the fuel adjacent the outer edge of the tuyre so that as the air flows through the openings 25 between the blades it picks up the fuel exposed in the peripheral slots and carries it into the internal vertical air column. Alternatively the air will pick up the fuel from the end of the nozzles 3Q to establish a highly intimate air-fuel dispersion within the tuyre. This is discharged as an annular column adjacent t the tuyre wall and thus into the combustion chamber I6 in which the combustion actually takes place. A skirt 3?, surrounding the tuyre I8 may be found desirable to maintain controlled velocites of the air entering the tuyre andthereby preventing possible disentrainment as described and claimed in the copending application of Bloomer, Serial No. 66,445, led December 2l, 1948, now Patent No. 2,566,074.

The amount of air which passes over the tuyre blades when burning gaseous fuels is preferably 10% to 20% in excess of the stoichiometric amount normally required for combustion and when burning liquid fuels 40% to 50% excess air over that stoichiometrically required is most effective and to establish the desired vcrtical effect in the tuyere, the velocity of the entering air should be in the range of 50 feet per sec. to 150 feet per sec. This requires a pressure drop of from 6 inches to 16 inches water gauge. As a result, the fuel-air mixture is thus discharged as a hollow column with a substantial rotational effect.

Within the combustion chamber we establish a closed pattern type of name by limiting the diameter of the chamber I5 to aproximately ll/z to 3 times the tuyre diameter and providing a length of about 2 to 4 times the diameter of the tuyre, excellent ame of great stability is thus formed due in part to the rotary nature of the flame on an axis coinciding with the axis of the tuyre but also due to the presence of both internal and external eddies which tend to rotate the flame on itself in a plane cutting through the axis. Y

These eddies result from the linear ejector action of the outgoing annular strata which causes vortices of iiame gases on either side of the concentric stream. With no rotation, these are closed annular vortices recycling the innammable mixture back to the sour-ce and igniting and reigniting it. With rotation, further stabilizing is achieved as the name pattern and the vortices are changed from closed loops by the tangential velocity of the tubular strata issuing from the tuyre and the flow lines of the gas in each eddy forms helical lines on a torus. All this permits Very high llame velocities without blow` outs. Indeed the greater the issuing velocity the greater the vortical velocities so that the ame may be regarded as stabilizing itself. Complete combustion is thus accomplished in a relatively short length of the combustion chamber.

In most turbine practice it is necessary to reduce the temperature of the discharge gases to about 1000 F.-2000 F. depending upon the duty and this is accomplished by by-passing a substantial part of the inlet air through the annular passageway di) between the combustion chamber I6 and the casing I8. A damper 42 may be used to control the amount which passes in this manner, the positioning of such damper being controlled by the shaft 14. This air then passes through the secondary tuyre arrangement shown at 45 and 4l'.

The secondary tuyre is of the same general construction as the burner` tuyre I8 and is especially effective in accomplishing a uniform dilution of the products of combustion. As the secondary air from channel dii passes into the tangential openings, it is uniformly diffused with the hot products of combustion to establish a uniform temperature of gas discharge. The seoondary tuyre must be carefully' formed to avoid the formation ci a vortex which would form a core however and this may be accomplished by proportioning the air path openings so that there is about only one third the air velocity through the tuyres d6 and il that there is through tuyre I8. In addition, some air may enter the combustion chamber through the ports 54 and this air serves to keep the adjacent row of blades cool and helps to prevent warping and distortion of the blades.

It may also be found desirable to reverse the rotational direction of certain of the blades lit, Il? in the secondary tuyre not only with respect to each other but also with respect to the blades in the burner. In ar particularly successful operation, the two rows of blades I next to the combustion chamber were oppcsitely pitched with respect to the burner blades, and the next adjacent row of blades in tuyre f5 were in the same direction as the burner blades. ,I

Start up of the burner is readily accomplished by first establishing a circulation of air and then igniting the gas pilot light through ignition port 52 as by spark plug The fuel is next introduced through either line 3d or Aft-er 4the chamber I6 becomes sufficiently heated and stable conditions obtained, the gas into ignition port 52 can be discontinued.

Temperatures at the gas discharge outlet id show extremely good distribution with average deviation from the mean of only about 10 F. to 20 F. where the mean was 1350 F. This is strikingly contrasted with other turbine combustion practice in which variations of aboutseveral hundred degrees from the mean temperature are often found.

affaires A11-:operating combustion-tone of thetfype describedA has been found to have the following annuisr spaeermed between tteeajsinganathe second tiiyeat the discharge endof' the second characteristics tuyre.

- Summary of operating results Gas 1 n n1 Iv Heat Liber 0.4 MM* 1o MM* 3.3 irs-MMM Y Oper. Press Atmos Atmos 9.0 p. s; i'. Qpksj. g. Press, Drop 1 4" H10 10.8" H2O..-.. 1.3 H20. 5. H2O Temp. Deviation F 20 F.

Diesel Fuel Heat Liber 4 MM* Oper. Press.. 13 p. s. i. g-.- Press. Drop 4.7 Hao.- Temp. Deviation from Mean 10 F i *Million BTU/Hr.

This data shows operation at turn-down ratios of to 1. It also shows high heat liberation of an unusual order which makes the apparatus particularly benecial for heavy duty industrial gas turbine practice.

We claim:

l. In a combustor of the class described for a gas turbine having an open-ended combustion chamber of substantially circular cross section, an outer housing surrounding said combustion chamber, said outer housing having an inlet for air under pressure, and forming, with said combustion chamber, an air passage, said combustion chamber having air diffuser openings therein in communication with said air passage, and baiile means within said outer housing to control the ratio of air passing through said air passage, the improvement which comprises an air and fuel mixing device adjacent one end of the combustion chamber, said device comprising a first cylindrical tuyre having its side wall formed by a plurality of fixed generally tangentially disposed blades extending substantially throughout the length of the tuyre and forming inwardly directed air inlets therebetween, said first tuyre being open at the end in communication with the combustion chamber and having fuel feeding means within the interior thereof adjacent its opposite end, said fuel feeding means forming an airtight end for the tuyre, means for supplying fuel through said fuel feeding means into said last named end of the first tuyre, means for supplying air from said housing air inlet and directing said air through said rst tuyre air inlets between said blades for forming a hollow outwardly moving column adjacent the side wall of said rst tuyre and an inwardly moving central core, said column comprising a combustible fuelair mixture, said combustion chamber having a larger diameter than the outlet of said tuyre but small enough to restrict the lateral component oi the fuel-air mixture as it discharges from the first tuyre, said combustion chamber diameter being larger than the tuyre outlet but not more than about three times the diameter of the tuyre outlet, means adjacent the outlet end of the combustion chamber in communication with the air passage to dilute the products of combustion, said diluting means comprising a second cylindrical tuyre having its side Wall formed by a series of generally tangentially disposed blades forming inwardly directed air inlets therebetween, and means closing the end of the 2. A combustor as claimed in claim 1 in which the second tuyre has a, plurality of banks of blades, the blades of certain banks being reversed in rotational direction with respect to the blades in the fuel mixing tuyre whereby a destructive vortical effect in the combustion chamber is minimized. n

3. A combustor for producing hot gas comprising a casing having an inlet for combustion supporting gas at one end and an outlet for products of combustion at the other end, a iirst cylindrical tuyre mounted within said casing and spaced from the Wall thereof, the side wall of said first tuyre having a plurality of spaced tangentially disposed blades forming air passages therebetween, one end of said iirst tuyre being closed and the opposite end being open, a primary air windbox within the combustor casing and surrounding the rst tuyre whereby the passage of air under pressure into the windbox and through said air passages will form a vortical air column within the first tuyre which moves outward as an annulus adjacent the side wall of the tuyre, fuel feeding means adjacent the closed end'of the first tuyre, a fuel conduit extending from said fuel feeding means into the first tuyre, said fuel feeding means being adapted to discharge fuel through the fuel conduit into the vortical air column to become intermixed therewith, a combustion chamber having the shape of a curve of revolution in the path of said discharging vortical air-fuel column with one end in communication with the open end of the tuyre, said combustion chamber being at least 1% times the diameter of the tuyre opening and having a length at least as great as its diameter, and a second cylindrical tuyre co-extensive with the other end of the combustion chamber, means closing the end of the annular space formed between the casing and the second tuyre at the discharge end of said second tuyre, the side wall of said second tuyre having a plurality of spaced tangentially disposed blades forming secondary air passages therebetween in open communication with the combustor casing Ywhereby secondary air may be directly passed through the secondary air passages to form a, rotating air column therein, and uniform blending of secondary air with products of combustion from the rst tuyre is accomplished before the gases discharge from the combustor casing outlet.

4, A combustor as claimed in claim 3 in which the second tuyre has a plurality of banks of blades, the blades of certain banks being reversed in rotational direction with respect to the blades in the fuel mixing tuyre whereby a destructive vertical effect in the combustion chamber is minimized.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,657,725 Schutz Jan. 31, 1928 1,950,980 Frisch Mar.k13, 1934 Number Number lo 407,920 588,086

8 Name Date Frisch May 19, 1936 McGany Feb. 13, 1951 Williams Feb. 13, 1951 Darling Mar. 27, 1951 Bloomer July 10, 1951 FOREIGN PATENTS Country Date Great Britain J une 25, 1932 Great Britain May 17, 1947

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