Stator vane arrangment and a method of casting a stator vane arrangment

A turbomachine comprising a stator vane arrangement, the stator vane arrangement comprising a radially inner annular structure, a radially outer annular structure and a plurality of circumferentially spaced vanes extending radially between the radially inner annular structure and the radially outer annular structure,

• at least one of the vanes having a passage extending there-through from the radially inner annular structure to the radially outer annular structure,
• the radially inner annular structure having at least one boss extending radially inwardly there-from, the at least one boss having a passage extending there-through, the passage in the at least one boss being aligned with the passage in the at least one vane,
• the at least one boss comprising a first portion having a first cross-sectional area and a second portion having a second cross-sectional area which is greater than the first cross-sectional area, the first portion of the boss being positioned between and interconnecting the second portion of the boss and the radially inner annular structure, and
• the radially inner annular structure, the radially outer annular structure, the plurality of circumferentially spaced vanes extending radially between and secured to the radially inner annular structure and the radially outer annular structure and the at least one boss comprising a monolithic structure.

A method of casting a stator vane arrangement comprising a radially inner annular structure, a radially outer annular structure and a plurality of circumferentially spaced vanes extending radially between the radially inner annular structure and the radially outer annular structure, at least one of the vanes having a passage extending there-through from the radially inner annular structure to the radially outer annular structure, the radially inner annular structure having at least one boss extending radially inwardly there-from, the at least one boss having a passage extending there-through, the passage in the at least one boss being aligned with the passage in the at least one vane, the at least one boss comprising a first portion having a first cross-sectional area and a second portion having a second cross-sectional area which is greater than the first cross-sectional area, and the first portion of the boss being positioned between and interconnecting the second portion of the boss and the radially inner annular structure, the radially inner annular structure, the radially outer annular structure, the plurality of circumferentially spaced vanes extending radially between and secured to the radially inner annular structure and the radially outer annular structure and the at least one boss comprising a monolithic structure, the method comprising producing a wax pattern of the radially inner annular structure, the radially outer annular structure and the plurality of circumferentially spaced vanes, providing a ceramic core in the wax pattern of at least one of the vanes, the ceramic core extending through the wax radially inner annular wall, providing a wax boss on the radially inner end of the ceramic core, the wax boss comprising a first portion having a first cross-sectional area and a second portion having a second cross-sectional area which is greater than the first cross-sectional area, and the first portion of the wax boss being positioned between and interconnecting the second portion of the wax boss and the wax radially inner annular structure, depositing a ceramic material on the wax pattern to form a ceramic mould, removing the wax from the ceramic mould, pouring molten metal into the ceramic mould, solidifying the molten metal within the ceramic mould to form the stator vane arrangement and removing the ceramic mould and ceramic core from the stator vane arrangement.