Gas turbine engine case with heating layer and method

Abstract

An assembly of a rotor and case for a gas turbine engine comprises a rotor having a plurality of circumferential blades each with a blade tip. A case comprises a structural layer forming an annular body receiving therein the rotor, with a tip clearance being defined between the blade tips and the annular body, and a heating layer connected to the at least one structural layer. The heating layer has a resistivity to heat the structural layer when an electric current passes through the heating layer. An electric power source supplies current to the heating layer, the heating layer configured to in use change the diameter of the annular body to adjust the tip clearance. A method for adjusting a tip clearance between blade tips of a rotor and inner surface of a case in a gas turbine engine is also provided.

What is claimed is: 
     
         1 . An assembly of a rotor and case for a gas turbine engine comprising:
 a rotor having a plurality of circumferential blades, each of the blade having a blade tip;   a case comprising at least one structural layer forming an annular body receiving therein the rotor, with a tip clearance being defined between the blade tips and an inner surface of the annular body, and a heating layer connected to the at least one structural layer, the heating layer having a resistivity to heat the structural layer when an electric current passes through the heating layer; and   an electric power source connected to the heating layer and supplying current to the heating layer, the heating layer configured to in use change the diameter of the annular body to adjust the tip clearance between the rotor and the case.   
     
     
         2 . The assembly according to  claim 1 , wherein the heating layer is a heater coating applied to one of the surfaces of the structural layer. 
     
     
         3 . The assembly according to  claim 1 , wherein the heating layer is a heating foil applied to one of the surfaces of structural layer. 
     
     
         4 . The assembly according to  claim 1 , wherein the heating layer is against an outer surface of structural layer. 
     
     
         5 . The assembly according to  claim 1 , wherein the case is a compressor case and the rotor is a compressor rotor. 
     
     
         6 . The assembly according to  claim 1 , wherein the case is a turbine case and the rotor is a turbine rotor. 
     
     
         7 . A method for adjusting a tip clearance between blade tips of a rotor and inner surface of a case in a gas turbine engine, comprising:
 applying a heating layer on the case;   determining that gas turbine engine conditions require an increase in diameter of the case for tip clearance; and   supplying electric current to the heating layer on the case to increase the diameter.   
     
     
         8 . The method according to  claim 7 , wherein determining that gas turbine engine conditions require an increase in diameter comprises determining that the gas turbine engine is in takeoff or slam acceleration. 
     
     
         9 . The method according to  claim 7 , further comprising stopping a supply of electric current when gas turbine engine conditions no longer require an increase in diameter of the case. 
     
     
         10 . The method according to  claim 9 , wherein stopping the supply of electric current occurs during cruise conditions of the gas turbine engine. 
     
     
         11 . The method according to  claim 7 , wherein applying a heating layer on the case comprises applying a heater coating to one of the surfaces of the case. 
     
     
         12 . The method according to  claim 7 , wherein applying a heating layer on the case comprises applying a heating foil to one of the surfaces of the case.