Steam turbine nozzle box

摘要

A nozzle box includes a torus (12), bridge (14) ring and nozzle ring (16) portions wherein steam flowing generally circumferentially in the torus portion is redirected for flow generally axially by the bridge ring portion. The steam exiting the bridge ring portion flows into nozzles formed by adjacent partitions (26) of the nozzle ring portion. Bridges in the bridge ring portion are tangentially leaned to exactly match the angle of inclination of the leading edges of the axially adjacent partitions at like circumferential locations. For strength purposes, there are two bridges (20) for each partition. Every other bridge axially registers with the leading edge of the axially downstream partition matching its angle while remaining bridges are equally spaced between the aligned bridges. In this manner, the steam flow is straightened by the bridges to match the angle of the leading edge of the nozzle partitions with consequent reduction of passage area loss.