Turbine cylinder-seal system

Abstract

A multi-stage axial flow steam turbine having an inner and an outer casing. The inner casing being a pressure vessel having a first end which is enclosed by a nozzle ring disposed around a rotor in closely spaced, sealed relation therewith and having a second end which is open to the interior of the outer casing. Sealing between the inner casing and nozzle ring is provided by a structural hook seal which includes mateable flange portions which are integral with the inner casing and nozzle ring. A control stage and a first plurality of reaction stages are disposed within the inner casing. A second plurality of reaction stages are also disposed between the outer casing and the rotor so that steam leaving the inner casing's second end flows over the inner casing's outer surface and over the nozzle ring's outer surface to cool those outer surfaces before the steam enters the second plurality of reaction stages. The inner casing is mounted in the outer casing in such a manner as to limit relative axial movement and allow free relative radial movement induced by temperature differences between the inner and outer casings. The nozzle ring includes a plurality of nozzle chambers structurally connected and sealed together. Structural jointure between the nozzle ring and inner casing is provided by the hook seal which prevents axial separation thereof and reduces the size of the mounts necessary to support the nozzle ring and inner casing from the outer casing.