US2581999A

US2581999A - Hemispherical combustion chamber end dome having cooling air deflecting means

Info

Publication number: US2581999A
Application number: US644888A
Authority: US
Inventors: Walter L Blatz
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-02-01
Filing date: 1946-02-01
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08
Also published as: GB639617A

Description

Jall- 1952 w. L. BLATZ 2,581,999

YHEMISPHERICAL COMBUSTION CHAMBER END DOME HAVING COOLING AIR DEFLECTING MEANS Filed Feb. 1, 1946 Inventor I I Walter L. Blatz by" v His Abtorng.

Patented Jan. 8, 1952 S PATENT OFFICE HEMISPHERICAL COMBUSTION CHAMBER END DOME HAVING COOLING AIR DE- FLECTING S Walter L. Blatz, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application February 1, 1946, Serial No. 644,888'

My invention relates to combustion chambers, such as are employed in thermal powerplants. It is particularly applicable to gas turbine powerplants, for instance those used for the jet propulsion of aircraft.

This invention constitutes an improvement in one component part of the combustion chamber disclosed in application Serial No. 750,015, filed May 23, 1947, in the name of Anthony J. Nerad, and assigned to the same assignee as the present application. Said application is a continuation-in-part of application Serial No. 501,106, filed September 3, 1943, now abandoned. My invention is specifically an improved end dome arrangement for combustion chambers similar to those described in the above defined applications.

An object of the invention is to provide an improved dome structure forming the closed end 6 Claims. (C1. Gil-39.65) I which Fig. 1 is an assembly view showing in section my improved combustion chamber end dome arrangement; Fig. 2 is an. end view in elevation of the dome by itself; and Fig. 3 is a sectional view of the dome taken on the plane 33 in Fig. 2.

Referring now to Fig. 1, my invention is disclosed in connection with a combustion chamber indicated generally at I, which is supplied with combustion air by a transition piece or air adapter 2 from a compressor discharge passage defined by walls 3, which may be part of a centrifugal or axial flow compressor (not shown). A suitable framework indicated generally at 4 forms part of the main frame of the powerplant, supporting a turbine casing 22 in spaced relation to compressor housing 3.

"The general arrangement and operation of the combustion chamber l is more particularly disclosed in the above-mentioned applications of Anthony J. Nerad. An aircraft gas turbine powerplant having a compressor-combustion chamber-turbine-frame assembly similar to that .partially represented in Fig. 1 is more completely disclosed in an application Serial No. 525,391, filed March 7, 1944, in the name of Dale D. Streid, issued December 9, 1947 as Patent No. 2,432,359. It should be understood that my invention is equally applicable to other gas turbine powerplants, for instance those disclosed in applications Serial No. 506,930, filed October 20, 1943, now Patent No. 2,479,573, and Serial No. 541,565, filed June 22, 1944, both in the name of Alan Howard.

The details of the compressor, turbine, and supporting framework are not necessary to an understanding of the present invention, but it may be noted that the compressor casing 3 is secured by suitable threaded fastenings I to the frame 4, which is in turn secured to the turbine support casing 22 by threaded fastenings O.

The combustion chamber l consists of 9. cylindrical liner 1 open at both ends and having a plurality of rows of circumferentially spaced combustion air inlet openings 8, the nearest row of openings being axially spaced from the open end portion 9 of the liner. The arrangement of the air inlet openings is more fully disclosed in the above-mentioned applications of Anthony J. Nerad. The liner I may be supported at its downstream end by various types of suitable supports (not shown), while the upstream" end 9 is supported by the dome II in a manner which will appear hereinafter.

Surrounding liner 1 is an outer housing II, which may be supported by suitable brackets 12 secured to the frame 4 by threaded fastening O. The housing ii, like liner I, is circular in cross section, or substantially so, and may be supported by an annular member 13 having a flange welded to the outer housing as indicated at I, and secured to bracket l2 by a suitable threaded fastening 15. The member l3 may also be secured to a ballle l6 of flexible material, such as leather, and arranged to engage a cooperating baflle member I! in such a manner as to prevent undesired circulation of air around the outside of the combustor housing II. This baflle arrangement may be seen in more detail by reference to the above-mentioned application of Dale enlarged end of air adapter 2. This sealed joint comprises a piston ring seal member ll welded permitted some radial movement in order to take up an eccentric position relative to member is.

It will be appreciated by those skilled in the art that liner 1 must be made of very carefully selected metallic alloys able to withstand the high temperatures encountered. The outer housing II is not subject to such extreme temperatures and may be made of various suitable alloy steels. The piston ring member 18 may be made of stainless steel and the rings l9 may be of cast iron. Since air adapter 2 is cast of light metal such as aluminum or magnesium alloy,

the end portion 20 may be provided with a bushing 2| of harder material to provide a bearing surface for the piston rings l9. Bushing 2| may be shrunk or pressed into the air adapter. It should be noted that the outer housing II is rigidly supported in fixed position relative to the turbine casing 22 by the bracket l2 and other suitable means at the downstream end of. housing ll (not shown).

It will be appreciated by those familiar with gas turbine powerplants that housing II is duringoperation heated by radiation from liner 1. to a temperature considerably above that of the frame 4 and compressor housing 3.

The smallend of air adapter 2 is provided with a transversely extending flange 23 aligned with an attachment flange 24 on compressor housing 3. The flange 23 issecured to attachment flange 24 by an annular row of threaded fastenings. 25 with a cylindrical spacer member 26 inserted therebetween, for a purpose which will appear hereinafter. It will be obvious that suitable gaskets 21 may be employed, if found necessary to prevent air leakage.

It will be seen from the above that air adapter 2 is rigidly fixed to the comparatively c001 compressor casing 3, while the heated housing II is fixed relative to the turbine casing 22. The above described piston ring seal between housing II and air adapter 2 is intended to' permit limited axial, radial, and angular displacement between the end of housing II and the associated end of air adapter 2. By permitting such displacements, assembly of the powerplant is facilitated and differential thermal expansion during operation is permitted.

Secured by fastenings 30 to a mounting pad 23 on air adapter 2 is a fuel spray nozzle 29. The nozzle shown is of the duplex type, which is more fully disclosed in an application Serial No. 622,604, filed October. 16, 1945, in the names of C. D. Fulton and D. C. Ipsen. The specific structure of nozzle 29 is disclosed in an application of G. N. Miles,-;Serial Ho. 669,072, filed May 11, 1946, now Patent No. 2,524,820, and assigned to the assignee of the present application. However, itshould be understood that the specific type and structure of the fuel nozzle used is not essential to an understanding of the present invention. It is sufiicient to note that fluid fuel is supplied to the nozzle by conduits 3i and discharged from nozzle tip 32 in the form of a substantially conical spray pattern indicated by the dotted lines 33.

The, end dome to which my invention specifically relates is shown in assembled relation in Fig. land by itself, to an enlarged scale, in

Figs. 2 and 3. This end dome comprises a thin wall 34, preferably formed from suitable temperature-resisting sheet metal, and shaped substantially in the form of a hemisphere. Adjacent the pole of the hemisphere is a central opening 60 for receiving the discharge end or tip 32 of the fuel nozzle. The wall around this opening may be provided with anaxially extending flange 35 dimensioned to slidably engage and snugly fit the nozzle tip 32. A second flanged opening 36 is provided to receive the electrode end of a suitable spark-plug 31, shown in assembled relation in Fig. 1. It will be understood that the bushing of the spark-plug may be threadedly received in an opening (not shown in the wall of the air adapter 2.

Circumferentially spaced around the dome, and welded thereto, are radially extending support arms 34a. The tips of these arms are provided with openings 38. so that the arms can be secured to mounting bosses 39 in the air adapter (see Fig. 1) by suitable fastening means such as capr screws 44. Radially spaced from the central opening 60 is a circumferential row of air inlet openings 40. It will be readily apparent from Fig; 3 that these openings are formed by making uz-shaped cuts in the dome and deflecting the tongues 4|: so formed inwardly.

Around the rim or equator of the hemispher ical dome is a row of circumferentially spaced dimples 42 formed by striking the material of: the dome outwardly in a manner which will be obvious from Fig. 3. The dimpled outer circumference of the dome-is so dimensioned as to forma free sliding fit with the interior surfaceof liner end portion 9, as may be readily seen. from Fig. 1. The portions of the circumference of the dome between the dimples 42 define withthe liner end portion 9 a plurality of circum ferentially spaced arcuate slots 43. r

The method of assembly of my improved com-: bustion chamber dome is as follows. Thefuel, nozzle 29 is assembled to the air adapter .2 through the opening defined by mounting pad; 28. The dome I 0 is then assembled with the" central flange 35 slipping over the nozzle tip 32, and the arms 34a are secured to bosses .39 by the threaded fastenings 44. .Then, assuming. that the liner land housing II, compressor-.- housing 3, framework 4, and turbine casing 22 have been previously assembled, the air adapter is moved transversely into position in the space" between the piston ring assembly [8, 19, and the compressor discharge casing 3. The'"'axial length of the spacer 26 is so selected that sum cient space is provided to permit ready in-' sertion of the air adapter in this manner (when spacer 26 is removed). Once the end portion- 20 of the air adapter is slid over the piston rings l9 it will be obvious that air adapter 2 can be moved axially with respect to the combustion chamber I, the dimpled circumference of dome l0 sliding into the open end 9 of liner 1, until suflicient clearancev is provided at the other end of the air adapter to insert spacer 26" transversely into the position shown in Fig. 'l.f To remove the air adapter for inspection and .1 servicing of the fuel nozzle and the end dome, the i above procedure is followed in. reverse; that is," screws 25 and spacer 26 are removed, and the air adapter 20 is moved axially with respect to. the. combustion chamber I until end portion 20 disengages from the piston rings IS, the circumfernc d m a wh b wi rawn.

sembly and disassembly to rotate air adapter 2 (after removing spacer 26) about an axis parallel to the axis of the' combustion chamber, such rotation causing the end flange 23 to move radially outward so as to easily clear the attachment pad 24 on compressor casing 3. l

It will be-observed'that the brackets l2, as well as the air baflie l6, are secured to the outer housing H by means which are independent of the piston ring sealed slip-joint l8, I9, 20. Thus the air adapter 2, complete with fuel nozzle 29 and dome It can be inserted and removed from the powerplant simply .by removing the spacer 26, and without disturbing other parts of the combustion chamber and associated parts. This con-I siderably facilitates maintenance of the powerplant because of the frequency with which the air adapter must be removed for servicing the nozzle and dome and for cleaning, repairing or replacing the liner 1.

" Besides lending ease of assembly and disassembly, the piston ring sealed slip-joint l8, I9, 20 has the additional advantage of providing the flexibility needed for permitting differential thermal expansion and compensation for misalignment.

Referring now to Fig. 1, the operation of the apparatus is as follows. Air from the compressor discharge casing 3 flows in the direction of the arrows into the annular space defined between liner I and housing I I. From this space it flows through the combustion air inlet openings 8 in the manner indicated by the arrows 46, as more specifically described in the above-mentioned applications of Anthony J. Nerad. Some air also flows along the inner surface of liner 1 through the arcuate slots 41 formed between dimples 42, This flow is in the direction of the arrow 41 in Fig. 1' and forms a thin sheet of pure comparatively cool air so as to insulate" the inner surface of liner 1 from contact with hot products of combustion containing unburned fuel particles. If such particles were permitted to contact the comparatively cool surface of liner 1, they would be deposited in the form of unburned carbon. Thus, it will be seen that the air flow 41 serves both to cool liner 1 and to insulate it from contact with unburned carbon particles which might otherwise be deposited thereon.

Air also flows as represented by arrows 48 It has been found by much testing and actual. operating experience, that combustion chambers of the type desired in the above-mentioned Nerad applications embodying my improved dome with the construction described herein have a number of important advantages. The dome and nozzle tip are kept within safe temperature limits and free of carbon deposits. Also, the flame in the combustion chamber appears to be more stable over a wide range of diflicult operating conditions. While it is not definitely known, I believe this to be due to the fact that the reversely flowing cooling and insulating air 49 forms what might be considered an elastic boundary" for the combustion tore 50, 5|. It is believed that as the operating conditions vary, the thickness of the insulating layer 49 changes somewhat with a corresponding change. in the volume occupied by the combustion tore 50, 5|. This appears to have a beneficial effect on the combustion process.

It will be understood by those skilled in this art that the liner 1 and the end dome ID are most subject to deterioration during the operation of the powerplant and therefore require most frequent inspection, servicing, and replacement. It will be seen that my invention provides a simple end dome which is easy and cheap to fabricate and can be readily serviced when in need of cleaning, repair or replacement. The convenience of disassembling the arrangement facilitates frequent inspection and servicing and thus lengthens the time interval between major powerplant overhauls.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An end dome for a, combustion chamber of the type having an open-ended liner comprising a; wall defining a substantially hemispherical surface having a central opening arranged to receive fuel injecting means adjacent the pole of the dome and having a circumferential row of openings, deflector means including a wall portion spaced from said wall in cooperative relation with each of said openings to form a plurality of nozzles facing said central opening for directing through the slots 40 formed by the inwardly struck tongues 4|. Slots 4!) form. nozzles which direct a comparatively thin sheet of cooling and insulating air inwardly toward the nozzle tip 32 in the direction of arrows 49. This cooling and insulating air flows over the exposed end surfaces of nozzle tip 32, thereby also keeping them free from carbon deposits. It will be apparent from the arrows in Fig. 1 that this cooling and insulatingair after passing over nozzle tip 32 flows reverselyin the same direction as the combustion air flow represented by arrows 50. The combined flow of primary combustion air 50 and cooling and insulating air 49 then flows axially through liner 1, some of it recirculating in the manner indicated by arrows 5| to form the toroidal flow path or "tore more specifically described in the above-mentioned applications of Anthony J. Nerad. The portion of the combined air flow 49, 50 which does not recirculate in the manner of arrows 5| flows axially down the liner 1 passing between the circumferentially spaced radial jets 46 of inflowing combustion air.

a comparatively thin sheet of cooling and insulating air over the inner surface of the dome inwardly toward said central opening.

2. In a combustion chamber for a thermal powerplant the combination of a first wall defining an open ended liner of substantially circular cross section, an outer housing surrounding said liner, a dome adapted to form a closed end wall of the liner, and means supporting the dome from said housing, the dome comprising a wall defining a substantially hemispherical surface with a central opening located adjacent the pole of the dome, fuel injecting means supported in said housing and having a discharge end cooperatively associated with said central opening, said dome also having openings therethrough radially spaced from said central opening and arranged to direct a comparatively thin sheet of cooling and insulating air over the inner surface of the dome inwardly toward the central opening, the outer circumference of said dome having circumferentially spaced projections arranged to engage the inner surface of the adjacent end of said liner so as to define therewith circumferentially spaced arcuate slots arranged to direct a thin sheet of cooling and insulating air axially along the inner surface of said liner toward the open end thereof.

3. An end dome for an open-ended combustion chamber liner comprising a wall defining a-substantially hemispherical inner surface and hav-' of said'openings to form a plurality of nozzlesfacing said central opening for directing a comparatively thin sheet of air over the inner surface of the dome radially inwardly toward said central opening.

4. An end dome for an open-ended combus tion chamber liner comprising a wall defining a substantially hemispherical inner surface and having a central portion defining an openingadapted to receive the discharge end of fuel injecting means, said wall also defining a plurality. of openings radially spaced from the central-opening and arranged to direct a comparatively thin sheet of air over the inner surface of the, dome ra.-. dially inwardly toward said central opening, and a plurality of projections spaced around the outer circumference of the dome and arranged to engage the inner surface of the liner to define therewith a plurality of circumferentially spaced arcuate slots. 1

5. An end dome for a cylindrical combustion chamber liner comprising a thin wall defining a substantially hemispherical surface and having a central opening adapted to receive fuel injection means, the rim portion of said wall forming circumferentially spaced projections adapted 002811- gage the inner surface of the liner, and other'portions of the wall intermediate said central opening and said rim portion defining nozzles adapted todirect cooling and insulating air in a thin sheet along the inner surface of tlie dome radially inwardly toward said central opening.

6. An end dome for a cylindrical combustion 8 chamber liner comprising a thin-wall defining a substantially hemispherical surface a central opening surrounded by an arcially ex"- tending flange adapted to slida'b'ly'f engage the outer circumferential surface 01' fuel injection nozzle means, the rim portion'of said wall forming circumferentially spaced projections adapted to engage the inner surface of the liner, andother portions of the wall intermediate saidcentral opening and said rim portion'deflning nozzles adaptedto direct cooling and insulating air in a thin sheet-along the inner surface of the-dome radially inwardly toward sald'central opening. WALTER L. BLA'IZ.

REFERENCES CITED The following references are of record file of this patent:

UNITED STATES PATENTS,-

N'fimaer Name 996,324 de Ferranti- June-2'1; 1911; 1,828,326 Lanser Oct, 20, 1931* 1,960,810 Gordon Ma y 29, 193 i 2,107,365 Bray Feb. 8, 1938 2,229,805 Graves Jan. 28, 1941 2,268,464 Seippel Dec.f 3'0,' 1851 2,361,871 Roberts 0131281, 1944 2,404,335 Whittle July 16, 1946 2,432,359 Streid Dee. 9,1947 2,465,525 Goddard Mar.'29 1949" 2,475,911 Nathan July .12, 19-19- FOREIGN PATENTS 1 Number Country 337,447 France Aprf 9,- 1904- 376,570 Germany May 30, 1923 585,763 Great Britain may 25', 1948 OTHER REFERENCES Ser. No. 240,907, Mii-ller (A. P. 0.), published Apr-.- 20, 1943.