| 摘要 |
PCT No. PCT/GB93/00224 Sec. 371 Date Aug. 15, 1994 Sec. 102(e) Date Aug. 15, 1994 PCT Filed Feb. 3, 1993 PCT Pub. No. WO93/17296 PCT Pub. Date Sep. 2, 1993The assessment of clearance conditions in an operating turbine structure has provide difficult to achieve. The invention provides apparatus which enables the clearance between seal fins on rotating blades and adjacent fixed structure, to be observed during rotation, and comprises refracting prisms (30, 32) on the fixed structure arranged so as to straddle sealing fin (14) on the blades. The stage of blades on their associated disc are moved towards the fixed structure and light which is refracted through the prisms is obscured by the fins. In one embodiment, the ratio of obscured to unobscured light is utilised to generate electrical signals, which are then manipulated so as to indicate the magnitude of the clearance.
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