Patent Publication Number: US-6910860-B2

Title: Machined fan exit guide vane attachment pockets for use in a gas turbine

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
   This application is a continuation of allowed U.S. patent application Ser. No. 09/741,471, filed Dec. 19, 2000 now U.S. Pat. No. 6,619,917, entitled “MACHINED FAN EXIT GUIDE VANE ATTACHMENT POCKETS FOR USE IN A GAS TURBINE”, by Samuel L. Glover et al. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an improved fan exit guide vane installation system for use in gas turbines. 
   In a gas turbine engine used for propulsion, a fan case and a smaller diameter compressor case cooperate to radially bound an annular fan duct. Fan exit guide vanes span across the fan duct to de-swirl working medium fluid flowing therethrough. The outer and inner extremities of the vanes are connected to the fan and compressor cases respectively. Traditionally, the outer connection is effected by a pair of bolts. The inner connection, by contrast, includes numerous parts including spacers, nuts, bolts, and inserts. 
   This type of system presents problems from a replacement or maintenance standpoint. Occasionally, a vane will become damaged in use and need to be replaced. Using the connection system described above, replacement of a single damaged vane is difficult. In U.S. Pat. No. 5,690,469 to Deal et al., the issue of replacing a vane is addressed. In this patent, a repair kit for replacing an unserviceable vane assembly is described. The repair kit includes a serviceable vane subassembly having a serviceable airfoil with a base attached to the root end and an opposing base which is unattached to, but slidably engagable with the serviceable airfoil. The opposing base is slipped over the tip end of the airfoil and slid toward the base attached to the root end. The vane subassembly and opposing base are pivoted into position between inner and outer engine cases in place of an unserviceable vane assembly so that sockets in the attached base engage support pins extending from the inner case. An adhesive is applied to the tip end of the serviceable airfoil and the opposing base is translated into its installed position near the tip end of the serviceable airfoil. Upon curing of the adhesive, the opposing base becomes attached to the airfoil. The base is secured to the outer case by studs and nuts. 
   There is a need for a simpler system for installing fan exit guide vanes which reduces the quantity of parts, the cost of the parts, and the weight of the parts. There is also a need for a simpler system which facilities the repair of damaged vanes. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide an improved system for installing a vane such as a fan exit guide vane to a support structure in a gas turbine. 
   It is a further object of the present invention to provide a system as above which has a reduced quantity of connection parts and reduced weight. 
   It is a yet another object of the present invention to provide an economically beneficial installation system. 
   The foregoing objects are attained by the system of the present invention. 
   In accordance with the present invention, a system for installing a vane broadly comprises a structure for supporting an inner end of a vane, a receptor pocket in the support structure, and a boot attached to a first or inner end of the vane for insertion into the receptor pocket. In a first embodiment of the present invention, the receptor pocket is machined into the support structure and is preferably open-ended and curved in configuration. The boot is preferably formed from a resilient dampening material, such as silicone rubber, and has a depth greater than the depth of the receptor pocket in the support structure. 
   In an alternative embodiment of the system of the present invention, an opening is machined into the support structure and an insert is placed into the opening to act as the receptor pocket. To install a vane, the boot on the vane is placed in the insert. The insert is provided with a flange portion which rests on a peripheral ledge machined in the support structure. The peripheral ledge maintains an upper surface of the flange portion substantially flush with an upper surface of the support structure. Retention devices may be used to hold the insert within the opening. 
   Other details of the installation system of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings in which like reference numerals depict like elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a portion of a gas turbine engine having a vane installed in accordance with the present invention; 
       FIG. 2  illustrates a support structure having machined receptor pockets used in the system of the present invention; 
       FIG. 3  is a top view in partial section of a vane installed in a support structure; 
       FIG. 4  is a sectional view taken along lines  4 — 4  in  FIG. 3 ; 
       FIG. 5  is a perspective view of a vane used in the system of the present invention; 
       FIG. 6  is a top view in partial section of an alternative manner for installing a vane in a support structure in accordance with the present invention; 
       FIG. 7  is a sectional view taken along lines  7 — 7  in  FIG. 6 ; 
       FIG. 8  is a sectional view taken along lines  8 — 8  in  FIG. 6 ; 
       FIG. 9  is a sectional view taken along lines  9 — 9  in  FIG. 6 ; and 
       FIG. 10  is a perspective view of a portion of a fan exit guide array attached to inner and outer support structures in accordance with the installation system of FIGS.  2 - 5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
   Referring to  FIG. 1 , a gas turbine engine  10  of the type used for aircraft propulsion includes a fan section  12  having an array of fan blades such as representative blade  14  extending radially outwardly from a hub  18 . The hub and blades are rotatable about an engine axis. The fan also includes an array of fan exit guide vane assemblies, such as representative guide van assembly  24 , which extend radially between inner and outer cases  26  and  28  respectively, whose axes are common with the engine axis. A fan flowpath  38  extends through the fan section and a working medium fluid, such as air, flows through the flowpath in the directly generally indicated by directional arrow  40 . 
   As shown in  FIG. 5 , each fan exit guide vane  24  in the array of fan exit guide vanes has an outer end with an integrally formed outer base  42 . The outer base has a platform  44  and a sleeve  46 . Typically, a polyurethane material  48  is disposed within the sleeve  46 . The polyurethane material serves to damp vibrations in the vane and the overall assembly. Threaded studs  49  project outwardly from the outer base  42  and extend through holes  50  into the outer case  28 . Nuts  51 , threaded onto the studs  49 , positively secure the outer base  42 , and therefore, the outer end of a respective vane  24  to the outer case  28 . 
   The inner end of each fan exit guide vane  24  in the array of fan exit guide vanes is attached to an inner support structure such as an annular ring portion  60  which forms part of the inner case  26 . In accordance with the a first embodiment of the present invention, the annular ring portion  60  is provided with an array of open-ended receptor pockets  62  machined therein. The array of receptor pockets  62  extends around the circumference of the ring portion  60  with respective ones of the pockets receiving the inner ends of respective fan exit guide vanes  24 . As can be seen from  FIG. 2 , each receptor pocket  62  has arcuately shaped sidewalls  64  and  66  which conform to the shape of the inner end of the vane  24 . 
   Referring now to  FIGS. 3-5 , the inner end of each vane  24  has a boot  70 . The boot  70  may be formed integrally with the vane  24  or may be formed separately from the vane  24  and attached thereto using any suitable adhesive means known in the art. The boot  70 , as can be seen from  FIGS. 3 and 4 , is configured to fit securely within one of the receptor pockets  62 . 
   The boot  70  is preferably formed from a resilient dampening material, such as silicone rubber, to help absorb vibrations. The boot  70  preferably has a depth which is greater than the depth of the sidewalls  64  and  66  of a receptor pocket  62  into which it is to be inserted so as to firmly secure the inner end of the vane  24  into the receptor pocket  62 . 
   To install a vane  24  using the system of the present invention, the inner end of the vane  24  with the boot  70  is inserted into a receptor pocket  62 . The vane  24  is then rotated towards the outer case  28  and the studs  49  and the nuts  51  are installed to secure the outer end of the vane  24  to the outer case  28 . 
     FIG. 10  illustrates a portion of an array of fan exit guide vanes  24  mounted to inner and outer casings  26  and  28  respectively. The inner ends of the vanes  24  are installed using the system of  FIGS. 2-5 . 
     FIGS. 6-9  illustrate an alternative embodiment of a vane installation system in accordance with the present invention. In this system, a series of openings  100  are machined into an inner support structure such as the annular ring portion  60  of the inner casing  26 . Each of the openings  100  is provided with a peripheral ledge  102 . 
   A receptor pocket for the inner end of the vane  24  is formed by a flanged insert  104 , preferably in the form of a flanged cup insert. As can be seen from the drawings, the insert  104  has an outwardly extending, peripheral flange  106  about its periphery. The insert  104  may be formed from any suitable metallic or non-metallic material known in the art. Preferably, it is formed from a plastic material such as nylon, polyurethane, or an elastomeric plastic material. For example, the insert  104  could be formed from a nylon material having a graphite filler. 
   As shown in  FIG. 7 , when the insert  104  is installed in the opening  100 , the flange portion  106  rests on the peripheral ledge  102 . As a result, the upper surface  108  of the insert  104  is substantially flush with the upper surface  109  of the annular ring portion  60 . 
   To keep the insert  104  within the opening  100 , a plurality of retention devices  110  can be inserted between a respective side wall of the insert  104  and a respective side wall of the opening  100 . The retention devices  110  may comprise any suitable retention device known in the art. 
   As can be seen from the drawings, the insert  104  has a depth which is greater than the depth of the opening  100 . The depth of the insert  104  preferably is such that the insert  104  secures the inner end of the vane  24  to the inner casing  26 . 
   To install a vane  24  using this embodiment of the present invention, the boot  70  on a vane  24  is positioned within the insert  104 . Depending on the depth of the insert  104 , the bottom end  112  of the boot  70  may be spaced from, or may be in contact with, the bottom surface  114  of the insert  104 . After the boot  70  has been positioned in the insert  104 , the vane  24  is rotated to bring the outer base  42  into contact with the outer casing  28 . As before, studs  49  and nuts  51  are then used to secure the outer end of the vane  24  to the casing  28 . 
   It has been found that an installation system in accordance with the present invention provides a number of significant advantages over prior art installation systems. For example, the installation system permits a tight fit to be maintained between the boot on each vane and the sidewalls of each pocket  62  during cruise and take-off. This results in the absence of any substantial air leakage around the flowpath. The installation system of the present invention uses fewer parts than prior installations, has a reduced cost associated with it, and a reduced weight. The installation system of the present invention also lends itself to single vane replacement. 
   While the installation system of the present invention has been described in the context of installing fan exit guide vanes in gas turbine engines used for propulsion, it should be apparent that the system of the present invention may also be used to install other types of vanes in a gas turbine engine used for propulsion or in other types of gas turbines. 
   It is apparent that there has been provided in accordance with the present invention a machined fan exit guide vane attachment pocket for a gas turbine which fully satisfies the means, objects, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Therefore, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.