High pressure turbine elastic clearance control system and method

Abstract

A system and method for achieving clearance control for a high-pressure turbine by means of casing mechanical deflection. An active clearance control system is provided to act on a blade that rotates near a shroud. The shroud is attached to a case at a shroud supporting location, or shroud hanger. A clearance is required between a tip of the blade and the shroud. The blade tip and shroud are surrounded with an elastic case. This case can deflect radially in response not only to thermal expansion, but also to a difference in pressures acting on the inner and outer diameters of the case.

What is claimed is:  
     
         1 . A method of controlling clearance in a gas turbine engine, comprising the steps of: 
 providing an active clearance control system acting on at least one blade that rotates near at least one shroud, the at least one shroud having an associated shroud hanger, wherein a clearance is required between a tip of the at least one blade and the at least one shroud; and    surrounding the blade tip and shroud with an elastic case, wherein the case can deflect radially in response to thermal expansion and a difference in pressures acting on inner and outer diameters of the case.    
     
     
         2 . A method as claimed in  claim 1  further comprising the step of attaching a band to the case outer diameter to account for blade tip loss during operation.  
     
     
         3 . A method as claimed in  claim 2  wherein the step of attaching a band further comprises the step of attaching a band of high temperature alloy or coating.  
     
     
         4 . A method as claimed in  claim 1  wherein the step of providing an active clearance control system further comprises the step of providing a single stage active clearance control system.  
     
     
         5 . A method as claimed in  claim 1  wherein the step of providing an active clearance control system further comprises the step of providing a dual stage active clearance control system.  
     
     
         6 . A method as claimed in  claim 1  wherein the step of surrounding the blade tip and shroud with an elastic case further comprises the step of providing an elastic case having elastic deflection during engine operation.  
     
     
         7 . A system for controlling clearance in a gas turbine engine, comprising: 
 an active clearance control system to act on at least one blade that rotates near at least one shroud, the at least one shroud having an associated shroud hanger, wherein a clearance is required between a tip of the at least one blade and the at least one shroud; and    an elastic case to surround the blade tip and shroud, wherein the case can deflect radially in response to a difference in pressures acting on inner and outer diameters of the case.    
     
     
         8 . A system as claimed in  claim 7  further comprising a band attached to the case outer diameter to account for blade tip loss during operation.  
     
     
         9 . A system as claimed in  claim 8  wherein the step band comprises a band of high temperature alloy or coating.  
     
     
         10 . A system as claimed in  claim 7  wherein the active clearance control system comprises a single stage active clearance control system.  
     
     
         11 . A system as claimed in  claim 7  wherein the active clearance control system comprises a dual stage active clearance control system.  
     
     
         12 . A system as claimed in  claim 7  wherein the elastic case comprises an elastic case having elastic deflection during engine operation.