JPS5627002A - Labyrinth seal of steam turbine - Google Patents

Abstract

PURPOSE:To reduce the leakage of steam and increase a rotational efficiency by a method wherein the inner wall of a nozzle diaphragm, a nozzle plate and an inner wheel are heated beforehand by steam to be expanded at the time of starting of a turbine and the like and thereby a gap at the edge of a labyrinth seal is enlarged. CONSTITUTION:When valve 32 of a steam pipe 33 is opened beforehand at the time of starting of a steam turbine, high-temperature and high-pressure steam is introduced from an introducing orifice 11 to steam flow-in orifices 28 provided in each outer wheel 13, each nozzle plate 19 and an inner wheel 20 through each steam-separating orifice 11a and a cabin 12. Next, the steam is exhausted through each of heated steam chambers 22 and 23, a communication orifice 27, a steam flow-out orifice 29, a flow-out pool 30 and a discharge orifice 31. Meanwhile, an outer wheel 13, a guide plate 19 and an inner wheel 20 are heated by steam and expanded, thereby each of labyrinth seals 10, 18 and 21 is separated widely from a rotor system. Accordingly, even when a rotor 8 and moving blades 7 are rotated by the steam supplied from a flow-in port 2, the edge of each labyrinth seal can be prevented from touching the rotor system.