Seal arrangement

Abstract

Leaf seal arrangements 1 are known in which a number of leaf seals 2 are presented in a housing 3 in order to create a seal relative to a rotating surface 4 . Conventional arrangements 21 have the leaf seals 2 aligned with an axis of rotation for the rotating surface 4 , there is symmetrical lift up and blow down of a tip end 5 relative to the surface 4 . In such circumstances the arrangement 1 is dependent upon the seal 2 stiffness to achieve designed operational performance. By presenting leaf seals 22 at an askew angle relative to an axis of rotation RR asymmetric deflection is achieved between an inlet side 30 and an exit side 31 such that the inlet and exit flow areas change and therefore lift up/blow down forces can be controlled to achieve a more optimal positioning of a tip end 25 relative to a rotating surface for operational performance with reduced risk of wear upon the leaf seals 22.

1 . A seal arrangement for a rotating component, the arrangement comprising a plurality of leaf seals projecting radially inward towards a rotating surface at a skew angle away from alignment with an axis of rotation for the rotating surface. 
   
   
       2 . An arrangement as claimed in  claim 1  wherein the arrangement has a relatively high pressure on one side compared to the other side of the leaf seals in use. 
   
   
       3 . An arrangement as claimed in  claim 1  wherein the leaf seals have a substantially rectangular cross section. 
   
   
       4 . An arrangement as claimed in  claim 1  where the leaf seals have a chamfered edge or corner. 
   
   
       5 . An arrangement as claimed in  claim 1  wherein the leaf seals have a clearance gap between the leaf seals and the rotating surface through which there may be a fluid flow in use which may deflect the leaf seals. 
   
   
       6 . An arrangement as claimed in  claim 1  wherein the askew angle is determined to provide a desired asymmetric deflection of the leaf seals. 
   
   
       7 . An arrangement as claimed in  claim 6  wherein the asymmetric deflection alters an inlet flow area relative to an exit flow area of the leaf seals. 
   
   
       8 . An arrangement as claimed in  claim 6  wherein the asymmetric deflection shifts axial positioning of tip end of the leaf seals relative to the rotating surface. 
   
   
       9 . An arrangement as claimed in  claim 1  wherein the leaf seals are presented in a housing about the rotating surface and juxtaposed next to each other. 
   
   
       10 . An arrangement as claimed in  claim 9  wherein the leaf seals are arranged to engage a front or cover plate of the housing in order to bias the leaf seals towards lift up when subject in use to a cross flow due to a pressure differential and the bias towards lift up is limited by the skew angle providing engagement with a backing plate of the housing to precipitate blow down of the leaf seals. 
   
   
       11 . An arrangement as claimed in  claim 10  wherein the value of the skew angle is determined to provide balance between lift up and blow down of the leaf seals in use. 
   
   
       12 . A gas turbine engine incorporating a seal arrangement as claimed in  claim 1 .