Patent ID: 7488153
Filing Date: 2009-02-10
Classification: F01D

Abstract:
1. A steam turbine comprising: an inner casing; a rotor that can rotate about an axis, arranged within the inner casing; a steam passage formed between the rotor and the inner casing; a multi-stage arrangement of guide vanes secured to the inner casing and rotor blades secured to the rotor, the multi-stage arrangement positioned in the steam passage; a hot steam inlet, wherein when hot steam issues from the inlet, the hot steam undergoes work-performing expansion in said multi-stage arrangement; plate-like protective shields positioned at least in the steam passage configured and arranged to protect the surface of the rotor or the inner casing beneath said plate-like protective shields from direct action of hot steam when flowing though the steam passage, the plate-like protective shields being arranged parallel and close to the surface of the rotor, parallel and close to the inner surface of the inner casing, or both; wherein the protective shields are arranged at a distance from a surface to be protected of the rotor, inner casing, or both, to form an intermediate cooling space; means for permitting cooling steam to flow though the intermediate cooling space; wherein said protective shields comprise first protective shields arranged in front stages, as seen in the direction of flow, of the steam passage; and means for removing cooling steam from the steam passage in one of the stages located downstream of said first protective shields and for feeding back said removed cooling steam though the intermediate cooling space in the opposite direction to the direction of flow.