Method for Manufacturing a Burner Ring for a Turbojet Engine

It is well known to use articles formed of composite materials in structures which are not subjected to extremely high temperatures. Such temperatures degrade the mechanical properties of the resin in the composite materials.

The deficiencies of these composite materials have been somewhat overcome by the introduction of ceramic type composite materials. These ceramic composites make it possible to fabricate parts of engines, such as turbojet engines, which are subjected to extremely high operating temperatures. This material has been utilized to fabricate turbojet engine nozzle flaps, thrust reversers and exhaust nozzles for rocket motors. Typically, these elements are fabricated from "carbon-carbon" fabric material.

Burner rings for turbojet engines have been experimentally manufactured utilizing composite material in combination with metallic fasteners to attach the burner ring structure to the surrounding jet engine structure. The metallic fasteners have been cemented or riveted to the composite material. However, due to the great variance in the coefficients of thermal expansion between the ceramic and metallic elements, detachment of these elements usually occurs in the middle of the composite fiber layers. Thus, the operating parameters to which these assemblies may be subjected are extremely limited.

The object of the invention is to provide a method manufacturing a composite material burner ring made wholly of a composite material. The burner ring is manufactured by winding a carbon or ceramic type refractory material about a toroidal form until a specific material thickness is obtained. A plurality of burner ring elements, such as radial arms, fastening clips or fuel feed tubes are then fastened onto the winding. Each of the elements may be formed in mirror-image halves and may be assembled onto the burner ring body in adjacent pairs, each one of the pairs facing in an opposite direction. The winding of the composite material is continued until a final thickness is obtained, thereby intgrally attaching the burner ring elements to the burner ring body. The assembly is then subjected to a carbonization or ceramization heat treating process. After this process, the burner ring body is cut along a plane extending generally perpendicular to the longitudinal axis of the toroidal form such that two burner ring assemblies having gutter-shaped cross-sections are formed when removed from the toroidal form.

The burner ring formed by this method avoids the drawbacks the prior art hybrid structures, since no metallic fasteners or other elements are utilized. Furthermore, integrally forming the burner ring elements with the burner ring body improves the mechanical strength of the resultant structure.

FIG. 1 is a partial, cross-sectional view of the burner ring body, the toroidal form and the burner ring elements during use of the process according to this invention.

FIG. 2 is a partial top view of the burner ring as shown in FIG. 1.

FIG. 3 is an exploded, perspective view of a radial arm burner ring element formed in mirror-image halves.

FIG. 4 is a rear, elevational view of one of the mirror-image halves shown in FIG. 3.

FIG. 5 is a side view of the radial arm shown in FIG. 4.

FIG. 6 is a sectional view taken along line VI--VI in FIG. 5.

FIG. 7 is a sectional view taken along line VII--VII in FIG. 5.

FIG. 8 is a side view of a spacer member which may be interposed between the mirror image halves of the radial arm shown in FIG. 3.

FIG. 9 is a rear view of the spacer member shown in FIG. 8.

FIG. 10 is a rear view of the radial arm in FIG. 3 showing the mirror image halves assembled together.

FIG. 11 is a rear view of the mirror-image halves shown in FIG. 3 incorporating the spacer member of FIG. 8 therein.

FIG. 12 is a rear, elevational view of a fastener clip which may be attached to the burner ring body according to the invention.

FIG. 13 is a sectional view taken along line XIII--XIII in FIG. 12.

FIG. 14 is a cross-sectional view taken along line XIV--XIV in FIG. 13.

FIG. 15 is a side view of a spacer member which may be utilized with the fastening clip shown in FIG. 12.

FIG. 16 is a rear view of the fastening clip incorporating the spacer member between the mirror-image halves.

FIG. 17 is a top view of the spacer member shown in FIG. 15.

FIG. 18 is a side, elevational view of a fuel feed tube element which may be attached to the burner ring body according to the invention.

FIG. 19 is a front view of one of the mirror-image elements utilized to form the fuel feed tube shown in FIG. 18.

FIG. 20 is a sectional view taken along line XX--XX in FIG. 18.

FIG. 21 is a front, elevational view of a burner ring formed according to the invention.

FIG. 22 is a partial, sectional view taken along line XXII--XXII in FIG. 21.

FIG. 23 is a partial, cross-sectional view of a first embodiment of an attaching device taken along line XXIII--XXIII in FIG. 21.

FIG. 24 is a partial, cross-sectional view of an alternative embodiment of the fastening device taken along line XXIII--XXIII in FIG. 21.

A burner ring structure formed according to this invention is shown in FIG. 21 and may comprise a burner ring body for having a plurality of burner ring elements attached thereto, such as radially inwardly extending arm structure 3, a fastening clip 13, and a fuel feed tube 19. The burner ring structure is manufactured by helically winding a refractory ceramic or carbon composite material 2 about the exposed outer surface of a toroidal spindle as shown in FIGS. 1 and 2. The toroidal spindle may comprise two separable elements 1 and 1a which are separable along a plane XX.sub.1 which extends substantially perpendicular to the central axis of the toroidal form. The toroidal form may have a substantially elliptical cross-section as shown in FIG. 1.

Once the winding has attained a specific, predetermined thickness, which may be approximately one-half the desired thickness of the burner ring body 4, the winding is stopped and the burner ring elements are attached to the burner ring body. Each of the burner ring elements, such as radial arms 3 and 3a are formed of mirror-image halves, as shown in FIG. 3. They are attached to the burner ring body in adjacent pairs, with each one of a pair facing in an opposite direction as shown in FIG. 2. Thus, the radial arm 3 is attached to one side of the toroidal structure, while radial arm 3a is attached to the opposite side so as to face in an opposite direction.

After attaching the desired number of burner ring elements to the burner ring body, the winding of the refractory material is continued until the final thickness of the burner ring body is achieved. The entire assembly is then subjected to a carbonization or ceramization heat-treating process until it is fully carbonized or ceramized.

At this point, the burner ring body is cut along the plane X-X.sub.1 extending generally perpendicular to a central axis of the toroid form. After the two elements 1 and 1a of the toroidal form are removed, a pair of burner rings, each having a gutter-shaped, semi-elliptical cross-section are formed.

The radial arms 3 and 3a attached to burner ring bodies 4 and 4a respectively, each may comprise two mirror-image half shells 5 and 5a as shown in FIGS. 3-7. Each of the half shells has a half collar 6, a radially extending wall 7 and a flange 8. Flange 8 defines an opening 10 to facilitate attachment of the burner ring to the surrounding turbojet engine structure. The mirror-image halves 5 and 5a are bonded to each other and to the burner ring body 4 during the previously described winding procedure.

In an alternative embodiment, a spacer 9 (shown in FIGS. 8 and 9) may be interposed between the mirror-image halves 5 and 5a, as shown in FIG. 11. In this embodiment, the spacer defines an opening 10 to facilitate attachment of the burner ring to the surrounding structure.

Opening 10, as shown in the two embodiments, may accommodate pivot pin 11 (see FIGS. 23 and 24) which, in turn, is attached to fastening links 12. The opposite end of the links 12 (not shown) are attached to the turbojet engine structure by known means.

The burner ring elements may also include fastening clips, formed also of image halves 13 and 13a as shown in FIGS. 12-14. Each of the mirror-image halves may be formed with flange 14 which defines opening 16. Opening 16 performs the same function as opening 10, previously discussed, in attaching the burner ring to a surrounding structure.

In an alternative embodiment, a spacer 15 may be interposed between the mirror-image halves of the fastening clip as shown in FIGS. 15-17. In this embodiment, spacer 15 defines the attachment opening 16.

The flanges 14 of the fastening clips are bonded to each other, or to the spacer prior to attaching the assembly to the burner ring during the previously described winding process.

Another burner ring element may be a fuel feed tube, as shown in FIGS. 18-20, though which pass the feed tubes for a fuel manifold. The fuel feed tubes are formed of mirror-image halves 17 and 17a by bonding together mating flanges 18. Each of the halves define a semi-cylindrical cavity 19 to accommodate fuel manifold feed tubes not shown. Once the halves are bonded together, the assembly is attached to the burner ring body 4 by the winding process previously described. The fuel feed tube may be formed as element 20, shown in FIG. 21.

The foregoing description is provided for illustrative purposes only and should not be construed as in any way limiting this invention, the scope of which is defined solely by the appended claims.