Low pressure exhaust gas diffuser for a steam turbine

摘要

A diffuser is provided for an exhaust steam housing adjacent a last stage row of buckets fixed to a rotor in a steam turbine, each bucket in the last stage row of buckets having a platform portion and an airfoil portion. The diffuser includes an annular inner diffuser ring and an outer annular diffuser ring defining a flow path for steam exiting the last stage row of buckets in a substantially axial direction at a diffuser inlet and turning substantially ninety degrees to a diffuser outlet. A first portion of the inner annular ring extends in a downstream direction beyond the last stage row of buckets substantially parallel to a center axis of the rotor, the first portion having a length dimension in the downstream direction from a radial center line of the last stage row of buckets in a range of between 0.40 and about 0.70 of a center line radial length from the platform portion to a radially outer tip of any bucket in the last stage row of buckets.