Tip clearance control device

A tip clearance control device adapted to control the clearance of a rotating aerofoil structure with a surrounding casing portion, the device comprising:

• a member operatively connected to the casing portion;
• the member having at least a first configuration in which the casing portion is at a first radial position and a second configuration in which the casing portion is at a second radial position,
• wherein the configuration of the member is controlled by magnetic flux in a magnetic circuit which includes at least one ferromagnetic element comprising ferromagnetic material, whereby the configuration of the member is responsive to the temperature of the ferromagnetic element;
• an aerofoil structure tip clearance control system as said member adapted to control the radial position of the casing portion;
• and
• a conduit coupled to a fluid supply, the conduit being arranged to selectively provide fluid to the aerofoil structure tip clearance control system to move the casing portion between the first and second radial positions;
• wherein the magnetic circuit is disposed to restrict flow through the conduit in the first configuration and permit flow through the conduit in the second configuration;
• wherein the aerofoil structure tip clearance control system comprises an expandable chamber configured to move the casing portion from the first radial position to the second radial position upon expansion of the chamber, wherein the conduit is arranged to selectively provide fluid from the fluid supply to expand the expandable chamber;
• a sensor passage in communication with the expandable chamber, the sensor passage is arranged to sense radial growth of the rotating aerofoil structure and to relieve pressure in the expandable chamber to move the casing portion from the second radial position to the first radial position;
• wherein the rotating aerofoil structure comprises a disc and a plurality of rotor blades, the rotor blades having platforms and the sensor passage is arranged to sense radial growth of the platforms of the rotor blades;
• wherein the device further comprises a stationary structure, the sensor passage passes through the stationary structure, that platforms of the rotor blades have radially inner surfaces and the sensor passage is spaced from the radially inner surfaces of the platforms of the rotor blades.

A method of controlling the tip clearance of a rotating aerofoil structure with a surrounding casing portion;

• the method comprising:
• providing a member operatively connected to the casing portion and responsive to pressurized fluid for moving the casing portion, the member having at least a first configuration in which the casing portion is at a first radial position and a second configuration in which the casing portion is at a second radial position;
• providing an aerofoil structure tip clearance control system adapted to control a radial position of the casing portion by moving the casing portion from the first radial position to the second radial position upon expansion of an expandable chamber;
• providing a conduit coupled to a fluid supply for pressurized fluid, the conduit being arranged to selectively provide pressurized fluid to the aerofoil structure tip clearance control system to move the casing portion between the first and second radial positions by selectively providing pressurized fluid from the fluid supply to expand the expandable chamber;
• and
• providing a sensor passage in communication with the expandable chamber, the sensor passage arranged to sense radial growth of the rotating aerofoil structure and to relieve pressure in the expandable chamber to move the casing portion from the second radial position to the first radial position, wherein
• configuration of the member is controlled by magnetic flux in a magnetic circuit which includes at least one ferromagnetic element comprising ferromagnetic material, whereby the configuration of the member is responsive to the temperature of the ferromagnetic element, and
• the magnetic circuit is disposed to restrict flow through the conduit in the first configuration and permit flow through the conduit in the second configuration;
• moving the member under the application of pressurized fluid from the first configuration in which the casing portion is at the first radial position to the second configuration in which the casing portion is at the second radial position;
• and
• controlling the configuration of the member through the application of pressurized fluid to the member by the magnetic flux in the magnetic circuit, whereby the configuration is responsive to a temperature of the ferromagnetic element.