Steam turbine singlet interface for margin stage nozzles with pinned or bolted inner ring

Abstract

A steam turbine singlet nozzle airfoil with integral outer sidewall is engaged with an inner ring and an outer ring in a nozzle assembly. The interface of the outer sidewall with the outer ring may include a plurality of mechanical hooks on one or both of the upstream face and the outer radial face of the outer sidewall that engage with complimentary structures on the outer ring. The outer interface may further include low energy welds along limited distances of one or both of the upstream or downstream interface of the outer sidewall and the outer ring. An inner radial end of the singlet nozzle airfoil is pinned into position and fastened to the inner ring. Without a need for high heat welds, distortion of the airfoil and the steam flow path and the associated rework is eliminated and stage performance is improved.