A steam turbine with an improved cooling system for the casing

摘要

A steam turbine includes a rotor (1) which extends along a longitudinal axis and having at least two different pressure turbine portions (3,4) disposed around and along the rotor (1). Each of the turbine portions (3,4) has multiple stages. A casing (2) encloses the rotor (1) and has at least one steam inlet (6). A dummy ring (10) is provided stationarily around the rotor (1) to separate and seal between the two different pressure turbine portions (3,4). The dummy ring (10) defines a nozzle chamber (13) for receiving the steam from the steam inlet port (6) and a plurality of nozzles for directing the steam from the nozzle chamber toward the higher pressure turbine portion (3). The dummy ring (10) and the casing (2) define a space therebetween. The space is fluidly connected to the higher pressure turbine portion (3). A steam passage (22) extends between the space and a steam passage downstream of the last stage of the higher pressure turbine portion (3). The steam passage (22) allows the steam within the space to flow to the steam passage downstream of the last stage of the higher pressure turbine portion (3) to cool the casing (2). <IMAGE>