Semi-annular component and method of manufacture

Abstract

There is disclosed a method of manufacturing a semi-annular component 60 for a casing arrangement of a gas turbine by additive manufacture, the component having a lattice structure 84 and extending circumferentially about a central axis 11 so that a radial direction extends towards the central axis 11 . The method comprises: fusing material at successive build locations along a build direction 98 to progressively form the component 60 so that members 86 of the lattice structure 84 have an elongate direction having a circumferential component; wherein the build direction 98 lies in a plane substantially normal to the central axis; and wherein the build direction 98 is inclined with respect to the radial direction at each build location so that members 86 of the lattice structure 84 are progressively formed along their elongate direction. A semi-annular component including a seal carrier is also disclosed.

1 . A method of manufacturing a semi-annular component for a casing arrangement of a gas turbine by additive manufacture, the component having a lattice structure and, in use, extending circumferentially about a central axis of the gas turbine so that a radial direction extends towards the central axis, the method comprising:
 fusing material at successive build locations along a build direction to progressively form the component so that members of the lattice structure have an elongate direction having a circumferential component;   wherein the build direction lies in a plane substantially normal to the central axis; and   wherein the build direction is inclined with respect to the radial direction at each build location so that members of the lattice structure are progressively formed along their elongate direction.   
     
     
         2 . A method according to  claim 1 , wherein the build direction is inclined with respect to the radial direction at each build location by an angle of between 45° and 90° 
     
     
         3 . A method of manufacturing a semi-annular component according to  claim 1 , wherein the semi-annular component is formed by selective deposition additive manufacture. 
     
     
         4 . A method of manufacturing a semi-annular component according to  claim 1  wherein fusing material comprises selectively melting a surface of a metal substrate using a radiation source to form a melt pool on the surface and selectively depositing metal powder into the melt pool to progressively form the component. 
     
     
         5 . A method of manufacturing a semi-annular component according to  claim 1 , wherein the build direction is substantially vertical and configured with respect to the component so that the members of the lattice structure are inclined with respect to vertical axis by no more than 30°. 
     
     
         6 . A method of manufacturing according to  claim 1 , wherein the members of the lattice structure are arranged in a quadrilateral configuration to define quadrilateral interstices, and wherein a diagonal of each quadrilaterial interstice is aligned with the circumferential direction. 
     
     
         7 . A seal carrier for a casing arrangement of a gas turbine engine comprising a casing structure and a shroud seal segment, the seal carrier comprising:
 a casing attachment point for coupling the seal carrier with a casing structure;   a carrier arm configured to extend radially inwardly from the casing structure to support a shroud seal segment;   wherein the casing attachment point is axially spaced apart from the carrier arm; and   a semi-annular lattice structure extending between the casing attachment point and the carrier arm, the lattice structure comprising a plurality of elongate members each extending along a respective elongate direction having a circumferential component.   
     
     
         8 . A seal carrier according to  claim 7 , wherein the seal carrier further comprises a radially outer barrier plate for insulating the casing from an axial gas flow through the seal carrier. 
     
     
         9 . A seal carrier according to  claim 8 , wherein the barrier plate comprises a plurality of openings to allow a gas flow through the seal carrier to the casing. 
     
     
         10 . A seal carrier according to  claim 9 , wherein at least one opening is elliptical with a minimum aspect ratio of 2:1 and wherein the major axis of each elliptical opening is in the circumferential direction of the seal carrier; and/or
 wherein each opening is quadrilateral, and wherein a diagonal of the quadrilateral is substantially aligned with the circumferential direction.   
     
     
         11 . A seal carrier according to  claim 7 , wherein the casing attachment point is an intermediate casing attachment point disposed between a forward and an aft portion of the barrier plate, or the seal carrier additionally comprises such an intermediate casing attachment point. 
     
     
         12 . A seal carrier according to  claim 11 , wherein the barrier plate comprises a continuous portion circumferentially adjacent to the intermediate casing attachment point, the continuous portion extending between the forward and aft portions and having a substantially constant radius. 
     
     
         13 . A seal carrier according to  claim 7 , wherein the lattice structure has substantially the same circumferential extent as the seal carrier. 
     
     
         14 . A seal carrier according to  claim 7 , wherein the members of the lattice structure are arranged in a quadrilateral configuration to define quadrilateral interstices. 
     
     
         15 . A casing arrangement for a gas turbine engine comprising:
 a casing structure, a shroud seal segment and a seal carrier in accordance with  claim 11 ;   the casing structure having a carrier attachment point cooperating with the intermediate casing attachment point of the seal carrier so that the seal carrier depends from the casing structure;   a recess in the barrier plate for accommodating the carrier attachment point of the casing structure;   wherein the axial extent of the recess is no more than 130% of the axial extent of the carrier attachment point of the casing.   
     
     
         16 . A casing arrangement according to  claim 15 , wherein the carrier attachment point and intermediate casing attachment point comprise projections configured to interlock with one another. 
     
     
         17 . A casing arrangement according to  claim 16 , wherein the casing arrangement comprises a plurality of seal carriers; and wherein the barrier plates of the plurality are arranged so that there is an alternating arrangement of continuous portions and recesses when assembled. 
     
     
         18 . A casing arrangement according to any of  claim 17 , wherein the intermediate casing attachment point extends radially outwardly from the barrier plate.