Forced-air cooling apparatus of steam turbine

摘要

A forced-air cooling apparatus is provided for a steam turbine which comprises an outer casing composed of upper and lower casing halves, an inner casing composed of upper and lower casing halves and disposed inside the outer casing and a rotor coaxially disposed inside the inner casing for forming a steam flow passage between the inner casing and the rotor and in which steam introduced into the steam flow passage from a steam inlet portion is impinged against blades of the rotor to impart a turning force thereto as a movable portion such as rotor with respect to a stationary portion such as an inner casing. The forced-air cooling apparatus comprises a cooling passage including a first cooling air passage formed between the inner casing and the rotor and a second cooling air passage formed between the outer casing and the inner casing, an external air inlet and outlet portion for charging external cooling air into the first and second cooling air passages during the turning operation period and discharging the cooling air after passing the first and second cooling air passages and a control unit for controlling the flow rate of the cooling air passing the first cooling air passage in response to a signal corresponding to a differential expansion detected by a differencial expansion detector between the movable portion and the stationary portion of the turbine and controlling a flow rate of the cooling air passing the second cooling air passage in response to a signal corresponding to a temperature difference between the upper and lower casing halves of the outer casing of the turbine.