Turbine overspeed limiter for turbomachines

Abstract

A mechanism 25 for preventing a turbine rotor 14 from exceeding a predetermined speed if a shaft 24, connecting the turbine rotor 14 to a compressor rotor 12 of the engine, breaks and releases its axial and torsional constraint on the turbine rotor 14. The mechanism 25 comprises a segmented stator vane assembly 26 downstream of a stage of the turbine rotor 14. Each segment 26 has first and second members 38,40 projecting radially inwards. The first and second members 38,40 are provided respectively at an upstream and downstream region of the inner end of each segment 26. A constraining means 34,36 is provided to constrain the segments 26 against displacement bodily on an axial direction. Static structure of the engine 56 engages the first and second members 38,40 and provides radially outwards and axially rearwards constraint on the first members 38 and radially inwards and axially forwards constraint on the second member 40. When the shaft 24 breaks and the turbine rotor 14 strikes the structure 56 in an axial direction, the structure 56 constrains the first members 38 of each segment 26 and provides a fulcrum about which the segments 26 rotate. Simultaneously the axial and radial constraint on the second members 40 is released causing the gas loads on the segments 26 to tilt then about the fulcrum into the path of the turbine rotor blades.