Passive control of gas turbine clearances using ceramic matrix composites inserts

Abstract

A passive clearance control limits thermal expansion between stator components relative to rotor components. A control ring controls clearance in a passive manner and is located on or adjacent to stationary components which thermally expand during engine operation. The control ring is formed of material having low coefficient of thermal expansion such as CMCs (Ceramic Matrix Composites) and therefore limits, inhibits or restrains expansion of the adjacent stator components as temperatures increase. Limiting expansion of the stator component reduces rotor/stator clearances and limits parasitic leakage of fluid along the flowpath through the engine core.

What is claimed is: 
     
         1 . A clearance control ring assembly, comprising:
 a stator component disposed opposite a rotor component within a gas turbine engine;   a clearance control ring being formed of a single structure and extending circumferentially disposed radially outward of at least a portion of said stator component;   said clearance control ring having a coefficient of thermal expansion which is lower than said at least a portion of said stator component; and,   wherein said at least a portion of said stator component is limited from thermal expansion and limited from growth from said rotor component.   
     
     
         2 . The clearance control ring assembly of  claim 1  wherein said clearance control ring is positioned on a compressor discharge pressure seal. 
     
     
         3 . The clearance control ring assembly of  claim 2 , said stator component including an abradable material. 
     
     
         4 . The clearance control ring assembly of  claim 3 , said rotor component including a labyrinth seal rotating adjacent said abradable material. 
     
     
         5 . The clearance control ring assembly of  claim 1 , said clearance control ring disposed in said compressor. 
     
     
         6 . The clearance control ring assembly of  claim 5 , said stator component including a blade ring. 
     
     
         7 . The clearance control ring assembly of  claim 6 , said clearance control ring disposed outwardly and circumferentially about said blade ring. 
     
     
         8 . The clearance control ring assembly of  claim 7 , said clearance control ring captured between a first aft case and a second aft case. 
     
     
         9 . The clearance control ring assembly of  claim 1  further comprising a mid-case ring disposed between aft case structures. 
     
     
         10 . The clearance control ring assembly of  claim 9  further wherein said clearance control ring is a first ring and a second ring separated by said mid-case ring and between said aft cases and a blade ring of said mid-case ring. 
     
     
         11 . The clearance control ring assembly of  claim 8 , at least one surface of said control ring being angled relative to said engine axis. 
     
     
         12 . The clearance control ring assembly of  claim 8  further comprising one of a projection and a retaining shoulder on one of said first and second aft case and the other of said projection and said returning shoulder on said control ring, wherein said projection engages said retaining shoulder. 
     
     
         13 . The clearance control ring assembly of  claim 1  further comprising a first case and a second case, said first case and said second case each having a flange. 
     
     
         14 . The clearance control ring assembly of  claim 13 , said control ring disposed at least one of said flanges. 
     
     
         15 . The clearance control ring assembly of  claim 13  further comprising a plurality of control wraps extending about said at least one flange. 
     
     
         16 . The clearance control ring assembly of  claim 13  further comprising a gap between said first flange and said second flange. 
     
     
         17 . The clearance control ring assembly of  claim 16  further comprising a rib extending into said gap. 
     
     
         18 . The clearance control ring assembly of  claim 17  further comprising a flange extending from control ring and engaging adjacent vane platforms. 
     
     
         19 . The clearance control ring assembly of  claim 8 , wherein one of said first aft case and said second aft case has an angled engagement surface. 
     
     
         20 . The clearance control ring assembly of  claim 19 , said control ring having an angled engagement surface slidably engaging said angled engagement surface of said one of said first and second aft case. 
     
     
         21 . The clearance control ring assembly of  claim 1  wherein said clearance control ring forms a blade ring. 
     
     
         22 . The clearance control ring assembly of  claim 1 , said control ring forming a flange, said flange engaging said blade ring. 
     
     
         23 . A clearance control ring assembly, comprising:
 a compressor discharge pressure seal stator;   a honeycomb abradable opposite a compressor discharge pressure seal rotor;   a ceramic matrix composite control ring extending circumferentially about said compressor discharge pressure seal stator;   said ceramic matrix composite control ring being a one-piece structure; and,   said ceramic matrix composite control ring limiting thermal expansion of said compressor discharge pressure seal stator and maintaining tight seal clearance between said seal stator and said seal rotor.   
     
     
         24 . The clearance control ring assembly of  claim 23  wherein said control ring is disposed on a labyrinth stator seal. 
     
     
         25 . The clearance control ring assembly of  claim 23  further comprising an engine casing ring. 
     
     
         26 . The clearance control ring assembly of  claim 25  further comprising said ceramic matrix composite control ring disposed adjacent said engine casing. 
     
     
         27 . The clearance control ring assembly of  claim 26 , said ceramic matrix composite control ring disposed adjacent a radially inner most wall of said engine casing defining a flowpath. 
     
     
         28 . The clearance control ring assembly of  claim 27  further comprising a spring disposed between said ceramic matrix composite control ring and said inner most wall. 
     
     
         29 . The clearance control ring assembly of  claim 27 , said ceramic matrix composite control ring controlling clearance between said engine casing and a turbine blade. 
     
     
         30 . The clearance control ring assembly of  claim 26 , wherein said ceramic matrix composite control ring is disposed within a flowpath. 
     
     
         31 . The clearance control ring assembly of  claim 26 , said ceramic matrix composite control ring is disposed at a radially outer end of said engine casing ring. 
     
     
         32 . The clearance control ring assembly of  claim 26  further comprising at least one spring on said CMC control ring. 
     
     
         33 . The clearance control ring assembly of  claim 32 , said at least one spring being on said radially outer surface. 
     
     
         34 . The clearance control ring assembly of  claim 33 , said at least one spring being a radial spring. 
     
     
         35 . The clearance control ring assembly of  claim 32  further comprising said at least one spring acting in an axial direction. 
     
     
         36 . The clearance control ring assembly of  claim 35 , said at least one spring being an axial spring.