US3048015A

US3048015A - Combustion chamber support and igniter

Info

Publication number: US3048015A
Application number: US825832A
Authority: US
Inventors: Roland J Barrelle; Charles F Hayes
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1959-07-08
Filing date: 1959-07-08
Publication date: 1962-08-07
Anticipated expiration: 1979-08-07

Description

1962 R. J. BARRELLE ETAL 3,048,015

COMBUSTION CHAMBER SUPPORT AND IGNITER Filed July 8, 1959 I /fi' 35 Z/ e if Zi if X? ,'r 351! .55, II 36 I a A w 7*? 5 I I I I zz /p" Z 37 I A; 27 7 2/ Z1 z IN VEN T OR.

ATTORNIlY United States Patent )ii' st ws Patented Aug. 7, 1952 3,048,015 COMBUSTION CHAMBER SUPPORT AND IGNITER Roland J. Barrelle and Charles F. Hayes, Indianapolis, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 8, 1959, Ser. No. 825,832 1 Claim. (Cl. 60-39.82)

Our invention is directed to improvements in combustion apparatus such as is used in gas turbines, and particularly to improvements in supports for the combustion liners or flame tubes. In one form of the invention, an improved support for a flame tube is provided. In another form of the invention, an improved flame tube support and also an improved mounting for an igniter are provided.

The invention, in either form, is particularly adapted for use with flame tubes which'are supported, in part at least, by members extending from the wall of the air duct in which the flame tube is mounted and piloted into the wall of the flame tube. The invention in its preferred environment as illustrated herein is employed with a flame tube supported at each end by means other than the improved support of this invention, and in which the support according to the invention engages the side wall of the flame tube and locates it against movement longitudinally of the flame tube.

Flame tube installations in which the flame tube is supported by piloting it on a fuel nozzle at one end and on a turbine nozzle or other engine structure at the other end are well known. It is also known to provide a support or locating member extending from the wall of the combustion apparatus and engaging the liner so as to hold it against longitudinal movement. In prior installations of which we are aware, the endwise location has been provided either by an igniter or by a so-called dummy igniter, the dummy igniter being used to locate those flame tubes not provided with an igniter.

Such installations have not been entirely satisfactory because of Wear and damage to the combustion liner and the igniter or dummy igniter. These parts are very hot when the engine is operating, and vibration may be encountered, with the result that the inter-engaging parts may be pounded or worn out of shape and lose their proper fit and suitability for service.

The present invention makes it practicable to use ma terials of greater strength and resistance to wear at high temperatures. It also provides for better cooling of the locating means or support. Where the support is used in connection with an igniter, the support surrounds the igniter and the igniter is no longer in direct contact with the flame tube. The support includes provisions for cooling the igniter as well as the support. The wear of the combustion liner and support is reduced and wear of the igniter which occurred when it served as a support for the flame tube is eliminated. The structure is such that either the igniter or the support may be separately replaced in the event of any damage or failure of the parts.

It may be pointed out that the materials most suitable to minimize wear of thesupport and combustion liner are not suited for manufacture of the outer shell or casing of igniters. The igniter shell, which projects intothe flame, is critical from thestandpoint of flame erosion.

The objects of the invention are to improve gas turbine combustion apparatus, to provide improved supports in such apparatus, and to provide an improved installation of gas turbine igniters which eliminates wear of the igniter due to mechanical engagement with the combustion liner and facilitates cooling the igniter.

The nature of the invention and the advantages thereof will be apparent to those skilled in the art from the acparatus embodying the invention.

FIGURE 1 is a partial view of the combustion section of a gas turbine engine of known type, with parts in section on a plane containing the axis of the engine.

FIGURE 2 is an enlarged view of a portion of FIG- URE 1, showing an igniter installation.

FIGURE 3 is a sectional view taken on the plane dicated by the line 3-3 in FIGURE 2.

FIGURE 4 is a sectional view similar to FIGURE 2 showing a support corresponding to a dummy igniter installation.

The invention as illustrated is incorporated in an engine of known configuration in which combustion takes place in a number of flame tubes generally parallel to and spaced around the axis of the engine. These flame tubes are mounted in an annular air duct extending from the compressor to the turbine of the engine. Since combustion apparatus of this general nature is well known, it is not illustrated nor described in detail herein. Such combustion chamber arrangements in gas turbine engines are illustrated more fully, for example, by U.S. Patents 2,861,421 and 2,875,579. Referring to FIGURE 1, the engine in which the invention is shown comprises a midframe or compressor outlet section 10 defining a diffusing passage 11 which discharges into an annular space or duct 12 defined by an outer wall or combustion case 13 and an inner wall or shaft housing 14. A number of generally parallel flame tubes 16 are mounted within the duct 12. The forward end of one flame tube is illustrated in FIGURE 1. The end of the flame tube is partially closed by a dome or end cap 17 having a central opening which is piloted over the end of a fuel nozzle 18 suitably fixed to the outer wall of the midframe 10. The rear end of the combustion liner (not shown) may pilot onto the turbine nozzle (not shown) or be otherwise suitably supported. Longitudinal expansion of the flame tube is accommodated by the pilot or slip fits at the ends thereof.

The flame tube may be of any suitable structure but, as illustrated, is a single welded structure composed of a number of rings or sections 19 welded together and defining the side wall of the flame tube. An opening 21 in the side wall is provided for a crossover tube. Such crossover tubes, as is well known, connect the several flame tubes for propagation of flame between them. A crossover tube as shown in U.S. Patent 2,729,938 may be employed.

Ordinarily, two of the flame tubes are provided with are illustrated, for example, in U.S. Patents 2,863,080 and 2,875,365.

Referring to FIGURES 2 and 3, the igniter 20 comprises a generally cylindrical outer shell 22, the inner end portion .23 of which is of reduced diameter and projects into the flame tube 16. The shell has fixed thereto, by welding or otherwise, a flange 25 *having holes for two cap screws 24 by which it is mounted on a pad 26 welded to the combustion chamber case 13. The shell 22 is the ground electrode of the igniter, which also includes a high tension electrode 27 mounted within a ceramic insulator 28. The high tension electrode is connected by an electrical connector 29 of known type to the high tension ignition lead.

The igniter 20 extends into the flame tube through an opening bounded by a cylindrical ferrule 31 welded to the flame tube wall 16 and which is aligned with the pad 26 in the normal position of the flame tube. A hollow flame tube support 32 comprises a generally cylindrical body 33 integral with a flange 34. The body 33 surrounds the outer portion of the igniter sleeve, and the flange 34 is held by the cap screws 24 between the flange 25 of the igniter and pad 26. The body 33 fits with small clearance in an opening 35 in the pad. The body of the support 32 is provided with two air inlet holes 36 which receive air from the space between wall 13 and the flame tube. Some of the air flowing into the holes 36 is discharged into the flame tube through an annular space 37 defined by a hole in the inner end of the support and the portion 23 of the igniter shell.

The igniter shell also defines two cooling air holes 38 approximately aligned with the holes 36, which admit air to the interior of the igniter shell. This air flows through the annular space between the shell and the insulator 28 and is discharged into the flame tube. Since the general direction of air flowing through duct 12 is from left to right as viewed in FIGURES 1, 2, and 4, air will flow in through the forward holes 36 and 38 and may flow out through the rearward holes 38 and 36; but, because of the pressure differential across the flame tube wall, there will be a net flow into the support and igniter and through these into the flame tube. This air flow cools both the support and the igniter and cools the ferrule 31 to some extent by conduction into the support. It is not necessary to provide dual air inlet holes; but so doing makes the parts reversible and increases the total cooling air flow around the parts. It will be seen that this installation provides a wall or sheath of cooling air over the exterior of the igniter as well as a cooling air flow through the igniter. With the previous installation in which the igniter piloted directly into a ferrule such as 31, the external flow was not provided.

Also, the present installation isolates the igniter mechanically from the flame tube wall or ferrule 31 eliminating fretting and pounding which will wear the igniter shell. The igniter shell may be made of superior flame-resistant material without compromises to improve wear resistance.

With the support as described herein, it is possible and desirable to make both the cylindrical portion 33 of the support and the ferrule 31 of a high temperature heat and corrosion resistant material. A material which has been found very suitable for the purpose is a corrosion and heat resistant cobalt-base alloy according to Aeronautical Material Specification AMS-5759 issued February 1, 1956 by the Society of Automotive Engineers, Inc. This is a cobalt base alloy containing approximately 20% chromium, 15% nickel and tungsten.

As to the assembly of the apparatus, the support 32 is inserted through the opening in pad 26, in which it fits closely, the igniter plug is inserted through the support and the cap screws 24 are inserted and tightened, holding both the support and the igniter in place. The igniter may be replaced if desired by removing the cap screws without disturbing the support. If the support is damaged in any way, a new support may be provided and the igniter may be reinserted if still in good condition. As a result of this, a damaged igniter, as, for example, one with a broken insulator, may be replaced and the support be retained. Or, if the sleeve wears after long service and the igniter then in use is satisfactory, it is not necessary to install a new igniter because of such wear as with the prior art structures in which the igniter served as a flame tube support.

FIGURE 4 illustrates a flame tube support as used in those combustion liners '16 which are not provided with igniters. The flame tube 16 including ferrule 31 may be identical to and interchangeable with that previously described. The support 40 has the same diameter and length as the support 32 and is similarly provided with a bolting flange 41 by which it is mounted on the pad 26 by cap screws 24. The support 40 is closed at its outer end and is hollow. An air discharge opening 43 is provided in the inner end of the support and two cooling air entrance holes 36 are provided, aligned with the direction of air flow as in the support 32. A cylindrical tubular member 44- welded to the outer closed end of the support 40 extends downwardly through the internal cavity 42 of the support. The member 44 acts as an air deflector or space filler and concentrates the air flow adjacent the inner wall of the support.

Provision of the air discharge opening 43, by causing air to flow through the support into the combustion liner, improves the cooling of the support. It also serves to balance the air flow between the various combustion liners, since the hole 43 preferably is dimensioned so as to pass the same amount of air as that which flows through the outlet 37 of support 33 and through the igniter mounted in it.

It will be seen by those skilled in the art from the foregoing that our invention provides a highly desirable arrangement of flame tube supports, whether or not the support acts in conjunction with an igniter. The invention results in economies in manufacture and greatly reduces damage to the combustion liners and igniters which are expensive and diflicult to repair. It also facilitates servicing of the engine.

The description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting the invention, since many modifications may be made by the exercise of skill in the art within the scope of the invention.

We claim:

A combustion apparatus comprising, in combination, wall means defining an air duct, a flame tube mounted in the duct having a side wall defining an opening therein and a ferrule fixed to the wall bounding the opening, the wall means having a mounting pad thereon with an opening through the pad aligned with the ferrule, a generally cylindrical hollow flame tube support having a flange detachably mounted on the pad, the support being piloted in the ferrule, the support having two air inlet holes in the side thereof between the wall means and the wall aligned with the direction of air flow through the air duct and an air discharge hole in the end thereof within the flame tube, and a generally cylindrical igniter slidably mounted within the support and spaced therefrom to provide an air flow path between the support and the igniter from the inlet holes to the discharge hole, the igniter having an outer shell with a flange detachably mounted over the flange of the pad, an electrode within and spaced from the outer shell to provide an air flow path therebetween, and having two air inlet holes through the outer shell aligned with the air inlet holes in the support, the igniter projecting from the support into the flame tube.

References Cited in the file of this patent UNITED STATES PATENTS