Steam turbine with an improved cooling system for the casing

摘要

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