System and method for passively controlling clearance in a gas turbine engine

Abstract

A system for passively controlling clearance in a turbine engine comprises a static assembly arranged circumferentially about an engine rotor assembly and defining a gap between a tip end of the rotor assembly and an adjacent inner surface of the static assembly. The static assembly includes a gap control member that defines the inner surface, is exposed to the engine working fluid, and comprises a shape memory material selected and preconditioned to deform in a pre-selected manner in response to a temperature of the engine working fluid. Alternatively, airfoil blades of the rotor assembly include a gap control member. A method for passively controlling clearance in a turbine engine comprises assembling the engine so as to define an initial set of build clearances, operating the engine to observe running clearances, configuring a gap control member comprising a shape memory material and re-assembling the engine with the gap control member.

1 . A system for passively controlling clearance in a gas turbine engine comprising:
 a static assembly comprising at least one gap control member, the static assembly being arranged circumferentially about an engine rotor assembly and defining a gap between a tip end of the rotor assembly and an inner surface of the static assembly,   the at least one gap control member defining the inner surface adjacent to the tip end and comprising a shape memory material selected and preconditioned to deform in a pre-selected manner in response to a temperature of a working fluid of the engine, and   the at least one gap control member being exposed to the working fluid.   
     
     
         2 . The system of  claim 1 , wherein the at least one gap control member comprises an abradable coating. 
     
     
         3 . The system of  claim 1 , wherein the shape memory material comprises an alloy. 
     
     
         4 . The system of  claim 3 , wherein the alloy comprises ruthenium. 
     
     
         5 . The system of  claim 3 , wherein the alloy comprises niobium. 
     
     
         6 . The system of  claim 3 , wherein the alloy comprises tantalum. 
     
     
         7 . A system for passively controlling clearance in a gas turbine engine comprising:
 a rotor assembly comprising a plurality of airfoil blades, each of the airfoil blades having a tip end;   the rotor assembly being surrounded by a static assembly comprising a plurality of shroud segments arranged circumferentially about the rotor assembly;   each shroud segment having an inner surface adjacent to the tip end;   each of the airfoil blades comprising a gap control member at the tip end;   the inner surfaces of the shroud segments and the tip ends of the airfoil blades defining a radial gap between the tip ends and the inner surfaces;   the gap control member comprising a shape memory material selected and preconditioned to deform in a pre-selected manner in response to a temperature of an engine working fluid.   
     
     
         8 . The system of  claim 7  wherein the gap control member comprises an abradable coating. 
     
     
         9 . The system of  claim 7 , wherein the airfoil blade is an axial compressor blade. 
     
     
         10 . The system of  claim 7 , wherein the airfoil blade is an axial turbine blade. 
     
     
         11 . The system of  claim 7 , wherein the airfoil blade is a centrifugal compressor blade. 
     
     
         12 . The system of  claim 7 , wherein the airfoil blade is a radial turbine blade. 
     
     
         13 . A method for passively controlling clearance in a gas turbine engine comprising:
 assembling the turbine engine so as to define an initial set of build clearances between a stationary shroud surface of the turbine engine and an adjacent rotor assembly of the turbine engine;   operating the assembled turbine engine throughout a range of engine operating conditions;   observing an operating clearance at one or more of the engine operating conditions;   formulating and configuring a gap control member comprising a shape memory material selected and preconditioned to deform in a pre-selected manner in response to a temperature of an engine working fluid; and   re-assembling the turbine engine with the gap control member so as to define a revised set of build clearances between the stationary shroud surface and the adjacent rotor assembly.   
     
     
         14 . The method of  claim 13 , further comprising, subsequently operating the assembled turbine engine throughout a range of engine operating conditions and observing a revised operating clearance at one or more of the engine operating conditions. 
     
     
         15 . The method of  claim 14 , further comprising formulating and configuring an additional gap control member comprising a shape memory material selected and preconditioned to deform in a pre-selected manner in response to a temperature of the engine working fluid. 
     
     
         16 . The method of  claim 13 , wherein the gap control member comprises an abradable coating. 
     
     
         17 . The method of  claim 13 , wherein the rotor assembly is an axial compressor assembly. 
     
     
         18 . The method of  claim 13 , wherein the rotor assembly is an axial turbine assembly. 
     
     
         19 . The method of  claim 13 , wherein the rotor assembly is a centrifugal compressor assembly. 
     
     
         20 . The method of  claim 13 , wherein the rotor assembly is a radial turbine assembly.