Abstract:
A hollow liner ( 14 ) for fitting in the interior of a aerofoil vane ( 10 ) is crimped prior to fitting within the vane ( 10 ). Following fitting, the liner ( 14 ) is expanded so as to fit snugly within the vane ( 10 ). The technique permits the insertion of liners ( 14 ) into vanes ( 10 ) that are so configured as to preclude the insertion of conventional liners.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the manufacture of an artefact comprising a liner which is intended to reside in spaced relationship within a hollow structure. 
     BACKGROUND OF THE INVENTION 
     More particularly, the invention relates to the manufacture of a liner which is required to reside in said spaced relationship within a hollow structure, the interior of which is so shaped as to preclude inserting the liner therein, when the liner has its operational shape. 
     SUMMARY OF THE INVENTION 
     The invention has particular efficacy, where the liner is multi-perforated, and is intended to fit within the hollow interior of a guide vane which has opposing ends of radically differing profiles, and is utilised in a gas turbine engine. The liner is fitted for the purpose of enabling an impingement cooling airflow onto the interior surface of the guide vane during operation thereof in an associated said gas turbine engine. 
     According to the present invention, a method of manufacturing and fitting a hollow liner within a hollow structure which has respective open ends of differing proportions, comprising the steps of producing said hollow liner and crimping a portion thereof so as to enable said liner to be fitted into said hollow structure, then fitting said liner into said hollow structure and subsequently stretching said liner so as to substantially obviate said crimping and form said liner to its desired final shape within said hollow structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, and with reference to the accompanying drawings, in which: 
     FIG. 1 is a pictorial representation of a gas turbine engine guide vane, which includes a perforated impingement cooling liner in accordance with the present invention. 
     FIG. 2 is a developed view of the liner of FIG. 1, prior to perforation, and: 
     FIG. 3 is a view on FIG. 2 in the direction of arrow  3 . 
     FIGS. 4 to  6  depict alternative crimp forms. 
     FIG. 7 depicts an alternative mode of manufacturing an impingement cooling liner in accordance with the present invention. 
     FIG. 8 depicts an impingement cooling liner crimped in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a hollow guide vane  10  has a number of ribs  12  formed on its inner wall surface, which extend the full length of the vane  10 , though only one rib  12  is thus shown. The ribs  12  locate a perforated liner  14  in spaced relationship with the inner wall surface of the vane  10 . 
     The guide vane  10  is formed in the configuration of an aerofoil. However, in view of the greater understanding of aerodynamic flows which today&#39;s designers possess, accompanied by the ever increasing demand to achieve higher engine efficiency, the overall shape of guide vanes has changed dramatically, resulting in profiles, the proportions of which change radically from one end of the vane to the other end thereof, as in guide vane  10 . As is seen in FIG. 1, the relative chordal dimensions A at the end extremities of vane  10  are approximately 2:1. However, the relative width dimensions are approximately 1:2. It would thus be impossible to insert a liner  14  of corresponding shape in either end of vane  10 . 
     Referring now to FIG. 2, liner  14  is first produced as a developed shape of the finished article, which shape, in the present example, defines an actual or near trapezoid  16 . The trapezoid  16  is then crimped a sufficient number of times, on both sides of datum line  20 , (though crimps  22  are only shown on one side thereof), so as to draw each end portion thereof towards datum line  20 , and thus shortens it. 
     The number of crimps  22 , and their proportions, as shown in FIG.  2  and FIG. 3 are merely illustrative. Their actual proportions and numbers will be dictated by the proportions of the vane  10  in which the liner  14  is to be fitted. Thus, in the present example, FIG. 2 depicts six crimps  22  extending from edge  18  to edge  24 . The pitch of the crimps  22 , multiplied by the number thereof, equals the dimension B (FIG.  3 ), which is repeated on the opposing side of datum line  20 . 
     After crimping, the trapezoid  16  is folded about datum line  20 , to bring edges  26  and  28  together, and the resulting liner  14  inserted into the vane  10 , via its wider, shorter end. Thereafter, a forming tool (not shown) is inserted in liner  14 , and a force applied thereon in a direction chordally of the liner  14  and vane  10 , so as to expand liner  14  by straightening the crimps  22 . 
     An alternative mode of reforming liner  14  may be utilized, and consists of filling it with an elastomeric material, which is then pressurized and thus causes liner  14  to expand. 
     The crimps  22  shown in FIG. 2 are of inverted V shape and stand proud of one side only of trapezoid  16 . however, as depicted in FIG. 4, crimps  22  could be formed so as to alternately protrude from both sides thereof. 
     FIG. 5 depicts another alternative, wherein the crimps  22  are corrugated in serpentine manner, and protrude from one side only. However, the serpentine corrugations could, if so desired, protrude alternately from both sides, as shown in FIG.  6 . 
     A further method of manufacturing liner  14 , is by deforming a frusto-conical tube  30  (FIG. 7) of circular cross section into the finished desired shape, and then, as shown in FIG. 8, crimping the side walls thereof over at least a major portion of its length. The crimps  34  are tapered, being their widest at that end of the tube  30  which defines the longest chordal dimension. A sufficient number of crimps, of appropriate proportions, are formed so as to draw the long ends of the liner together, to allow insertion of the tube  30  into the smaller end of the vane  10  (FIG.  1 ). Stretching of the liner tube  30  can be effected as described hereinbefore, with respect to FIGS. 1 to  3 .