In-situ gas turbine rotor blade and casing clearance control

Abstract

A method and system for protecting the rotor blade tips of rotary machines, particularly the compressors of gas turbine engines, comprising a rotor assembly having a plurality of circumferentially spaced-apart rotor blades, with each blade extending radially outwardly from an inner wheel disk; a stator assembly comprising one or more rows of spaced-apart vanes extending between adjacent rows of the rotor blades; a casing extending circumferentially around the rotor and stator assemblies; and an abradable ceramic coating applied to selected areas of the interior cylindrical surface of the rotor casing to thereby provide a minimum clearance between the casing and rotor blades during start up and to thereafter ensure an effective compressor seal for compressed gas flow.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 a turbine;   one or more hydrocarbon gas combustors;   an air compressor;   a compressor rotor assembly for said compressor, comprising a plurality of circumferentially spaced-apart rotor blades extending radially outwardly from an inner wheel disk;   a compressor stator assembly comprising one or more rows of spaced-apart stator vanes extending between adjacent rows of said rotor blades;   a casing extending circumferentially around said rotor and stator assemblies forming a plurality of inner and outer flow paths defined by said rotor blades and said stator vanes; and   a ceramic coating applied to the interior of said casing in an amount sufficient to cause the tips of said rotor blades to abrade portions of said ceramic coating during start-up and provide a minimum amount of clearance between said rotor blades and said casing.   
     
     
         2 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating is applied to the rim surfaces of said inner wheel disks. 
     
     
         3 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating comprises a. powder containing alumina (Al 2  O 3 ). 
     
     
         4 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating comprises hafnia (Hf 2 ), ceria (CeO 2 ), magnesia (MgO), Yttria (Y 2 O 3 ), magnesium aluminate (MgO—Al 2 O 3 ) or zirconium silicate (ZrO 2 —SiO 2 ). 
     
     
         5 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating is formed in situ on the interior cylindrical surface of said rotor casing. 
     
     
         6 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating is applied to said rotor casing using a plasma spray technique. 
     
     
         7 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating is applied to said casing at a thickness of between 4 and 8 mils. 
     
     
         8 . A gas turbine engine according to  claim 1 , wherein said abradable ceramic coating further comprises granular particles comprising a different, thermally stable, harder ceramic material. 
     
     
         9 . A gas turbine engine according to  claim 8 , wherein said granular particles comprise corundum. 
     
     
         10 . A gas turbine engine according to  claim 1 , wherein the surfaces of said rotor casing further comprise a roughened interior cylindrical surface for adhering to said abradable ceramic coating. 
     
     
         11 . A compressor for a gas turbine engine, comprising:
 a rotor assembly for said turbine comprising a plurality of circumferentially spaced-apart rotor blades, each blade extending radially outwardly from an inner wheel disk;   a casing extending circumferentially around said rotor assembly forming a plurality of inner flow paths defined by said rotor blades cooperating with stator vanes; and   an abradable ceramic coating applied to the interior of said casing proximate said rotor blades.   
     
     
         12 . A compressor according to  claim 11 , wherein said abradable ceramic coating comprises a powder containing alumina (Al 2  O 3 ). 
     
     
         13 . A compressor according to  claim 11 , wherein said abradable ceramic coating is also applied to the rim surfaces of said inner wheel disk. 
     
     
         14 . A compressor according to  claim 11 , wherein said abradable ceramic coating comprises hafnia (Hf 2 ), ceria (CeO 2 ), magnesia (MgO), Yttria (Y 2 O 3 ), magnesium aluminate (MgO—Al 2 O 3 ) or zirconium silicate (ZrO 2 —SiO 2 ). 
     
     
         15 . A compressor according to  claim 11 , wherein said abradable ceramic coating is formed in situ on said rotor casing. 
     
     
         16 . A compressor according to  claim 11 , wherein said abradable ceramic coating is applied to said interior rotor casing surface using plasma spray. 
     
     
         17 . A compressor according to  claim 11 , wherein said abradable ceramic coating is applied to said interior casing surface at a thickness of between 4 and 8 mils. 
     
     
         18 . A compressor according to  claim 11 , wherein said abradable ceramic coating further comprises granular particles comprising a second, thermally stable ceramic material. 
     
     
         19 . A compressor according to  claim 18 , wherein said granular particles comprise corundum.