Fan case abradable

Abstract

A fan case and method of manufacturing a fan case, for a gas turbine engine, where the fan case has a hollow tubular metal shell with: a central axis of symmetry; an inlet; an outlet; and peripheral wall about the axis to encompass the tips of a plurality of rotary fan blades, and the shell wall includes an upstream portion defining an annular abradable material recess that extends axially having an upstream end at the shell inlet and a downstream end located upstream from the shell outlet.

1 . A fan case, for a gas turbine engine, comprising:
 a hollow tubular metal shell having: a central axis of symmetry; an inlet; an outlet; and peripheral wall about the axis to encompass the tips of a plurality of rotary fan blades, wherein:   the shell wall includes an upstream portion defining an annular abradable material recess that extends axially having an upstream end at the shell inlet and a downstream end located upstream from the shell outlet.   
   
   
       2 . A fan case according to  claim 1  wherein the shell inlet has an inlet diameter and wherein the recess has a recess diameter that is no greater than the inlet diameter. 
   
   
       3 . A fan case according to  claim 2  wherein the recess diameter is tapered in a downstream direction having a maximum recess diameter at the upstream end that is equal to the inlet diameter and a minimum recess diameter at the downstream end of the recess. 
   
   
       4 . A fan case according to  claim 1  including abradable material filling said recess and defining an upstream edge of unsupported abradable material radially inward of the shell inlet. 
   
   
       5 . A fan case according to  claim 1  wherein the shell includes a front flange at the inlet and a rear flange at the outlet, and wherein the front flange has an external diameter greater than an external diameter of the rear flange. 
   
   
       6 . A fan case according to  claim 1  including molded abradable tiles bonded to the shell and filling the recess. 
   
   
       7 . A fan case according to  claim 6  wherein the molded abradable tiles have a molded upstream edge of unsupported abradable material that is disposed radially inward of the shell inlet on installation. 
   
   
       8 . A method of manufacturing a fan case comprising the steps of:
 fabricating a hollow tubular metal shell having: a central axis of symmetry; an inlet; an outlet; and peripheral wall about the axis to encompass the tips of a plurality of rotary fan blades, the shell wall including an upstream portion defining an annular abradable material recess that extends axially having an upstream end at the shell inlet and a downstream end located upstream from the shell outlet; and   filling the recess with abradable material filling said recess and defining an upstream edge of unsupported abradable material radially inward of the shell inlet.   
   
   
       9 . A method of manufacturing according to  claim 8  wherein the step of filling the recess includes:
 molding prefabricated abradable material tiles apart from the shell; and   bonding said tiles to the recess in the shell.   
   
   
       10 . A method of manufacturing according to  claim 9  wherein the prefabricated abradable material tiles are molded with an upstream edge of unsupported abradable material for installation radially inward of the shell inlet. 
   
   
       11 . A method of manufacturing according to  claim 8  wherein the step of fabricating the hollow tubular metal shell consists of metal fabrication procedures selected from the group consisting of: pressing forming sheet metal; welding; rolling sheet metal; spin forming. 
   
   
       12 . A method of manufacturing according to  claim 8  wherein the step of fabricating the hollow tubular metal shell does not include forging the metal shell as a single oversized forging and then machining to remove excess metal material.