Rolls-royce Corporation

John F Leonard

Michael C Roberts

Peter J Maggs

In a gas turbine engine tip clearance between rotor blades and an encircling shroud liner is controlled by moving the shroud liner radially to match the thermal and centrifugal growth of the rotor assembly. The shroud liner segments are suspended between two axially displaced control rings located in a passageway carrying air ducted from the compressor. One control ring responds very quickly to changes in gas temperature corresponding to centrifugal growth and blade thermal growth. The other ring responds very much more slowly and corresponds to the thermal growth of the disc. The shroud liner segments are suspended from the control rings to adopt a position that constitutes the average between the growth positions of the two control rings.

Rotor shroud assembly

A gas turbine engine having a main casing, turbine blades and a segmented cylindrical liner surrounding the tips of the blades is provided with apparatus for compensating for different radial expansions between the blades and the liner. The apparatus comprises a shroud structure, such as a platform of an axially adjacent nozzle guide vane, and a slipper element extending radially from the shroud structure to the liner and coupling one to the other. The slipper element expands circumferentially more slowly than does the shroud structure. Thermal circumferential growth of the shroud structure causes a radial displacement of the liner segments relative to the shroud structure.

Turbine engines

A shroud liner has a hooked downstream end passing between a stator vane and a casing so that in operation the gas loads on the vane cause the liner to be held between the vane and the casing. The shroud liner also has a resilient upstream end fitting between a second stator vane and the casing so that in operation gas loads on the vane cause it to move towards the casing, compressing the shroud liner. As a result the shroud liner is securely held in place at its downstream end, but can slide relative to the casing and vanes at its upstream end to allow for thermal expansion.

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Bristol, United Kingdom

John F Leonard