Multifrequency control stage for improved dampening of excitation factors

摘要

Provided is a control stage (10) for a steam turbine. The control stage (10) comprises: a plurality of staging valves (12) circumferentially distributed around the turbine for regulating steam admission flow so as to control the loading of the turbine; nozzle chambers (14) connected to a downstream end of each staging valve (12); an arc of admission (16) forming the downstream portion of each nozzle chamber (14); and control stage nozzles (18) in the arcs of admission (16) defining the downstream end of the nozzle chamber (14). Each nozzle chamber has at least two arcs of admission. The arrangement improves steam flow distribution to downstream blades (30).