Turbine overspeed limiter for turbomachines

摘要

A mechanism 25 for preventing a turbine rotor 14 exceeding a predetermined speed in the event that a shaft 24 connecting the turbine rotor 14 to a compressor rotor 12 of the engine breaks and releases its torsional and axial constraint on the turbine rotor. The mechanism 25 comprises a segmented nozzle guide vane assembly 26 downstream of a stage of the turbine rotor 14. Each of the segments 26 is pivotally mounted (hinge pins 40) on an outer casing 34 at a region adjacent a radially outer upstream end of each segment 26. The structure of the engine on which the radially innermost ends of the segments 26 are mounted includes a releasable means 46. When the structure 46 is struck by the turbine rotor 14 the innermost ends of the segments 26 are released and allowed to swing rearwards and outwards about the pivotal attachment of the segments 26 to the outer casing 34. The upstream outer ends of the segments 26 are retained in the path of rotation of the blades of the turbine rotor 14 so that they collide with the blades and decelerate the turbine rotor 14.