Abstract:
Air collecting manifold for a gas turbine engine including a plurality of arcuate pipe segments surrounding a compressor casing receives air from a system of feed tubes incorporating spherical ball joints to allow for differential thermal growth and limit transmission of vibration from one component of the manifold structure to another.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of United States Provisional Patent Application, Ser. No. 60/090,141, filed on Jun. 22, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to gas turbine engines and, more particularly, to a manifold system for collecting air from one location of a gas turbine engine for use at another location. 
     In the gas turbine engine, and particularly in the aircraft engine, art it is known to extract air from the compressor section of the engine for use elsewhere in the engine or the aircraft, for example for providing high pressure air to the aircraft wing anti-icing system. 
     Various structures have been employed in the prior art to collect air from compressor stages. Typically, air is obtained from certain compressor stages and supplied to a manifold comprising a system of pipe segments surrounding the compressor casing. The manifold system is attached to the exterior of the gas turbine at the axial location of the compressor stage from which compressor air is to be extracted. 
     One significant limitation of the prior art manifold system construction is that the structure mounting the manifold to the compressor casing is subjected to substantial vibration cycles and temperature gradients during various parts of the flight cycle, resulting in build up of substantial stresses in the mount structures fastening the manifold apparatus to the compressor casing. These stresses can result in fatigue cracking in the mount structures and the manifold system itself, requiring early removal and replacement of manifold hardware at substantial cost in hardware and lost availability of the aircraft to the operator. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention includes an air collecting manifold apparatus for a gas turbine engine having a supply tube surrounding a compressor casing configured as a plurality of generally circumferentially extending arcuate pipe segments disposed around the a compressor casing and connected to a system for distributing the air, for example to the aircraft wing anti-icing apparatus. The supply tube receives air from a system of feed tubes incorporating a plurality of flexible joints which allow for differential thermal growth and limit transmission of vibration from one component of the manifold structure to another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of detailed example in the Figures of the accompanying drawing in which like reference numerals refer to like elements throughout, and in which: 
     FIG. 1 is a schematic perspective view of a prior art manifold structure; and 
     FIG. 2 is a schematic perspective view illustrating a cooling manifold built in accordance with the present invention; and 
     FIG. 3 is a schematic partial perspective view of a compressor casing to which the present invention can be attached. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A typical manifold system  10 , shown in FIG. 1 includes a supply tube  12  surrounding a compressor casing  60  (FIG. 3) configured as a plurality of generally circumferentially extending arcuate pipe segments  14  disposed around the compressor casing. The supply tube  12  receives air from a plurality of compressor discharge ports  62  (FIG. 3) collecting air from the interior of the compressor casing  60 . The supply tube  12  is connected to the pipe by several generally radially extending feeder tubes  16  each of which is connected at one end to the pipe segment  14  and at the other end to its respective compressor discharge port  62 . Flanges  18  are attached to the pipe segments  14  by typically welding to allow the manifold  10  to be fastened to the compressor casing  60 . The pipe segments  14  are additionally connected to the casing  60  by a plurality of support links  20 . The relative thermal growth of the mount hardware and the manifold tubing result in severe stresses being applied to the welds at the connection to the flanges  18  and at weld joints in the tubing structure itself. 
     In the present invention, illustrated schematically in FIG. 2, an air collecting manifold apparatus  30  for a gas turbine engine includes a supply tube  32  surrounding a compressor casing  60 , as shown in FIG. 3, configured as a plurality of generally circumferentially extending arcuate pipe segments  34  disposed around the a compressor casing  60  and connected to a system for distributing the air, for example to the aircraft wing de-icing system. Support links  36  connect the collars  38  which surround the circumferentially extending pipes  34  to attachment points on the compressor casing via brackets  39 . The links  36  have flexible joints  40  (typically rod end bearings) to allow rotation of the support and are fastened to collars  38  surrounding the pipe segments  34 . 
     Whereas in the prior art the manifold system typically derives at least a part of its mechanical support from the mounting flanges of the pipe segments themselves, in the present invention the manifold system is mechanically supported by the support links  36 . In the present invention the support links  36  are arranged in a fashion similar to a spoked wheel. Because of the nature of the flexible joints  40 , the support links  36  provide mechanical support to the manifold system while still allowing the supply tube  32  to flex. This system of support links eliminates the loads that would ordinarily be placed on the mounting flanges of the manifold  30 . This in turn eliminates the loads from the tubing ball joints  48 , which allows the use of smaller, lighter ball joints  48  than would otherwise be required. 
     The supply tube  32  receives air from a plurality of compressor discharge ports  62  collecting air from the interior of the compressor casing. The supply tube is connected to the pipe by several feeder systems  42 . Each feeder system  42  includes a generally radially extending tube  44  connected in flow communication at one end to a pipe segment  34  and at the other end to its respective discharge port  62 . Each tube includes a first tube section  46  fitted at one end to a port  50  in the pipe segment  34  and connected at the other end to a generally spherical ball joint  48  and a second tube section  52  connected at one end to the discharge port  62  and at the other end to the generally spherical ball joint  48 , such as the type of ball joint described in U.S. Pat. No. 5,611,577, issued Mar. 18, 1997, to Meyer, et al., and assigned to the assignee of the present invention. 
     The supply tube  32  may be terminated at each of its respective circumferential ends or one or both ends may be connected via an additional feeder system  42  to a respective discharge port  62 . 
     The ball joint configuration allows the radially extending tubes  44  to flex to allow for differential thermal growth of the tubes  44  and the supply tube  32  which is spaced from the compressor casing  60  a larger distance than the radial tubes  44 . Each of the tubes  44  is connected at its radially inner end to the compressor casing  60  which is hot relative to the ambient air, and at its radially outer end to a pipe segment  34  located at a larger distance from the hot compressor casing  60 . This temperature difference causes the tube  44  to flex as the casing expands more quickly than the cooler pipes. The shifting relative to the casing places stresses on the tubes  44  and the mount structures  39 . The ball joints  48  in the radial tubing  44  reduce significantly the transmission of forces to the pipes  34 , which consequently exert substantially reduced forces on the mount links  36  and brackets  39 . 
     While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true sprit and scope of the invention.