Turbine nozzle assembly with stress relief structure for mounting rail

A turbine nozzle assembly, comprising:

• a first airfoil adjacent a second airfoil;
• an inner endwall coupled to a radial inner end of the first airfoil and the second airfoil;
• an outer endwall coupled to a radial outer end of the first airfoil and the second airfoil;
• a mounting rail coupled to the outer endwall, the mounting rail extending at least partially radially outward from the outer endwall and at least partially circumferentially along the outer endwall, the mounting rail having a radial outer surface and a rail thickness;
• and
• a stress relief structure defined in the mounting rail, the stress relief structure including:
• an end opening defined in the radial outer surface of the mounting rail;
• a slot defined through the rail thickness of the mounting rail and coupled to the end opening;
• and
• an oblong opening defined through the rail thickness of the mounting rail and coupled to a radial inner end of the slot, the oblong opening being arranged asymmetrically in a circumferential direction relative to the slot and including a pair of arced surfaces on opposing sides of a longitudinal direction of the oblong opening, wherein the arced surfaces in the pair of arced surfaces have different radii of curvature.

A turbine system, comprising:

• a plurality of nozzle stages, at least one nozzle stage of the plurality of nozzle stages including at least one turbine nozzle assembly comprising:
• at least one airfoil;
• an inner endwall coupled to a radial inner end of the at least one airfoil;
• an outer endwall coupled to a radial outer end of the at least one airfoil;
• a mounting rail coupled to the outer endwall, the mounting rail extending at least partially radially outward from the outer endwall and at least partially circumferentially along the outer endwall, the mounting rail having a radial outer surface and a rail thickness;
• and
• a stress relief structure defined in the mounting rail, the stress relief structure including:
• an end opening defined in the radial outer surface of the mounting rail;
• a slot defined through the rail thickness of the mounting rail and coupled to the end opening;
• and
• an oblong opening defined through the rail thickness of the mounting rail and coupled to a radial inner end of the slot, the oblong opening being arranged asymmetrically in a circumferential direction relative to the slot and including:
• a first arced surface at a first end of a longitudinal direction of the oblong opening, and
• a second arced surface at a second end of the longitudinal direction opposite the first end, wherein the first arced surface and the second arced surface have different radii of curvature.