Method and system for controlling the clearance at the blades tips of a turbine rotor

Abstract

A system and method for controlling clearance between tips of moving blades of an aeroplane gas-turbine engine and a turbine shroud of an outer casing surrounding the blades. The method includes controlling, according to an operating speed of the engine, a valve positioned in an air duct opening at a stage of the compressor of the engine and leading into a control housing positioned around the outer surface of the turbine shroud and supplied with air coming only from the compressor stage. The valve is opened to cool the turbine shroud during a high-speed phase corresponding to takeoff and climb phases of an aeroplane propelled by the engine and during a nominal-speed phase following the high-speed phase and corresponding to a cruise phase of the aeroplane.

1 - 10 . (canceled) 
     
     
         11 . A method for controlling clearance between tips of moving blades of a turbine rotor of an aeroplane gas-turbine engine and a turbine shroud of an outer casing surrounding the blades, the method comprising:
 controlling, according to an operating speed of the engine, a valve positioned in an air duct opening into a compressor stage of the engine and leading into a control housing positioned around an outer surface of the turbine shroud, the control housing being supplied with air coming only from the compressor stage; and   opening the valve for cooling the turbine shroud of the outer casing during a high-speed operating phase corresponding to takeoff and climb phases of an aeroplane propelled by the engine and during a nominal-speed phase following the high-speed phase and corresponding to a cruise phase of the aeroplane.   
     
     
         12 . The method according to  claim 11 , wherein the valve is closed during a flight idle-speed phase following the nominal-speed phase and corresponding to an approach phase of an aeroplane prior to landing. 
     
     
         13 . The method according to  claim 11 , wherein the valve is closed during a ground idle-speed phase preceding the nominal-speed phase and corresponding to a taxi phase of the aeroplane prior to takeoff. 
     
     
         14 . The method according to  claim 11 , wherein delivery of air leading toward the outer surface of the turbine shroud is gradually reduced during a transition between the high-speed phase and the nominal-speed phase. 
     
     
         15 . The method according to  claim 14 , wherein the valve is an adjustable position valve, the gradual reduction of the air delivery leading toward the outer surface of the turbine during the transition being obtained by gradually closing the valve. 
     
     
         16 . The method according to  claim 14 , wherein the valve is an on-off valve, the gradual reduction in the delivery of air leading toward the outer surface of the turbine shroud during the transition being obtained by alternating opening and closing phases of the valve. 
     
     
         17 . A system for controlling clearance between tips of moving blades of a turbine rotor of an aeroplane gas-turbine engine and a turbine shroud of an outer casing surrounding the blades, the system comprising:
 an air duct configured to open at a compressor stage of the engine and to lead into a control housing surrounding an outer surface of the turbine shroud and configured to be supplied with air coming only from the compressor stage;   a valve positioned in the air duct; and   a circuit configured to control the valve for opening the valve during a high-speed phase corresponding to takeoff and climb phases of an aeroplane propelled by the engine and during a nominal-speed phase following the high-speed phase and corresponding to a cruise phase of the aeroplane.   
     
     
         18 . The system according to  claim 17 , wherein the valve is an adjustable position valve. 
     
     
         19 . The system according to  claim 17 , wherein the valve is an on-off valve. 
     
     
         20 . An aeroplane gas-turbine engine comprising a clearance control system according to  claim 17 .