Tip clearance control with finned case design

Abstract

An apparatus and methods for controlling tip clearance in gas turbine engines may be provided. The apparatus and methods may include situating fins on a surface of a turbine case included in a turbine section of the gas turbine engine. The fins may act as a means for maintaining tip clearance by, for example, controlling the thermal expansion of the turbine case. The turbine case may shroud turbine blades, and the turbine blades may include tips at a radial end of the blades. During operation of the gas turbine engine, the clearance between the tips and the turbine case is desirably as small as possible while avoiding contact in order to optimize efficiency of the gas turbine engine.

What is claimed is: 
     
         1 . An apparatus comprising:
 a protrusion on a turbine case, the protrusion comprising a means for maintaining a tip clearance, the tip clearance being a space between a blade track and a tip of a turbine blade configured to rotate within the turbine case.   
     
     
         2 . The apparatus of  claim 1 , wherein the protrusion is included in a plurality of protrusions on the turbine case that each comprise a corresponding means for maintaining the tip clearance. 
     
     
         3 . The apparatus of  claim 2 , wherein the protrusions comprise a first protrusion and a second protrusion, the first protrusion extends a first distance radially from the turbine case and the second protrusion extends a second distance radially from the turbine case, wherein the first distance is greater than the second distance,
 wherein the turbine case includes a first portion comprising a first local mean thermal inertia and a second portion comprising a second local mean thermal inertia, wherein the first local mean thermal inertia is greater than the second local mean thermal inertia, and   wherein the first protrusion is located on the first portion and the second protrusion is located on the second portion.   
     
     
         4 . The apparatus of  claim 2 , wherein the turbine case includes a first portion comprising a first local mean thermal inertia and a second portion comprising a second local mean thermal inertia, wherein the first local mean thermal inertia is greater than the second local mean thermal inertia, and wherein the first portion comprises a greater number of protrusions than the second portion. 
     
     
         5 . The apparatus of  claim 1 , wherein the protrusion has a height and a length, and wherein the means for maintaining tip clearance is configured to transfer heat from the turbine case to an ambient fluid, the heat transfer occurring at a rate, the rate varying with the height of the protrusion, the height varying along the length. 
     
     
         6 . The apparatus of  claim 1 , wherein the protrusion is integral to the turbine case. 
     
     
         7 . The apparatus of  claim 1 , wherein the protrusion is a first protrusion, and wherein a second protrusion comprising a means for maintaining a tip clearance is situated on a structure supporting the blade track, wherein the structure supporting the blade track is located radially inward from the turbine case. 
     
     
         8 . An apparatus comprising:
 a turbine case comprising a fin, wherein the fin comprises a protrusion extending a height radially from the turbine case and a width circumferentially along a surface of the turbine case, the fin extending a length along an axial direction of the turbine case, the length larger than the width.   
     
     
         9 . The apparatus of  claim 8 , wherein the fin is included in a plurality of fins, and the fins are distributed non-uniformly around the case. 
     
     
         10 . The apparatus of  claim 8 , wherein the fin extends radially inwardly from the turbine case. 
     
     
         11 . The apparatus of  claim 8 , wherein the fin extends radially outwardly from the turbine case. 
     
     
         12 . The apparatus of  claim 8 , wherein the height varies along the length. 
     
     
         13 . The apparatus of  claim 8 , wherein the fin is included in a plurality of fins on the turbine case, wherein a first fin extends a first distance radially from the turbine case and a second fin extends a second distance radially from the turbine case, and wherein the first distance is unequal to the second distance. 
     
     
         14 . A system comprising:
 a turbine case for a gas turbine engine;   a plurality of turbine blades configured to rotate within the turbine case; and   a plurality of fins arranged on the turbine case, the fins extending radially from the turbine case, each of the fins comprising a means for maintaining a tip clearance, the tip clearance being a distance between a blade track and tips of the turbine blades as the tips pass the blade track.   
     
     
         15 . The system of  claim 14 , wherein the fins are attached to a flange at an edge of the turbine case. 
     
     
         16 . The system of  claim 14 , wherein the fins are non-polyhedron. 
     
     
         17 . The system of  claim 16 , wherein the fins are cylindrical, wherein a first fin of the plurality of fins has a first radius and a second fin of the plurality of fins has a second radius, and wherein the first radius is greater than the second radius. 
     
     
         18 . The system of  claim 14 , wherein a first fin of the plurality of fins has a first shape and a second fin of the plurality of fins has a second shape, and wherein the first shape is different from the second shape. 
     
     
         19 . The system of  claim 18 , wherein the first shape comprises a cylinder and the second shape comprises a polyhedron. 
     
     
         20 . The system of  claim 14 , wherein the turbine case has a length in an axial direction of the turbine case, and wherein the turbine case comprises a first flange and a second flange, wherein at least one fin of the plurality of fins extends from the first flange to the second flange.