Tip treatment for a rotor casing

Abstract

A tip treatment bar and associated rotor casing structure, wherein the tip treatment bar includes a solid composite structure having a plurality of layers arranged therein so as to provide the bar with a directional stiffness characteristic. Such a layered composite arrangement can be used to tailor the vibration characteristics of the bar. The tip treatment bar and casing structure may be suited for mounting relative to a fan or compressor in a gas turbine engine.

1 . A tip treatment bar for a rotor casing, the tip treatment bar having a composite structure comprising a plurality of internal layers arranged therein with each internal layer comprising a composite material having a plurality of fibres arranged within a matrix material, the bar having a longitudinal axis and fibres within at least one of said internal layer are substantially aligned in a direction which is angled to the longitudinal axis so as to provide the bar with a directional stiffness characteristic. 
     
     
         2 . A tip treatment bar according to  claim 1 , wherein the internal layers of the bar are spaced from the outer surface of the bar by a coating layer. 
     
     
         3 . A tip treatment bar according to  claim 1 , comprising first and second internal layers, wherein the fibres in a first layer are aligned in a direction which is different from the alignment of fibres in the second layer. 
     
     
         4 . A tip treatment bar according to  claim 1 , wherein the bar has a longitudinal axis and the internal layers extend substantially in the direction of said axis such that the layers are substantially uniform in a longitudinal direction and the bar is non-uniform in cross section. 
     
     
         5 . A tip treatment bar according to  claim 1 , comprising an inner body of material, wherein at least on internal layer is arranged circumferentially around said inner body. 
     
     
         6 . A tip treatment bar according to  claim 5 , comprising a plurality of layers arranged concentrically about said inner body. 
     
     
         7 . A tip treatment bar according to  claim 5 , wherein the inner body of material comprises a composite material having a plurality of layers therein. 
     
     
         8 . A tip treatment bar according to  claim 1 , comprising an outermost composite layer and a coating applied to a portion of said outermost composite layer such that a portion of the outermost composite layer is exposed on an external surface of the bar. 
     
     
         9 . A tip treatment bar according to  claim 1 , wherein the bar has a plurality of lateral edges extending between opposing sides of the bar and wherein the lateral edges are recessed with respect to the ends of the bar. 
     
     
         10 . A rotor casing comprising a plurality of bars according to  claim 1  and a support structure arranged to maintain the bars in a circumferentially spaced array with respect to an axis of rotation of the rotor in use. 
     
     
         11 . A rotor casing according to  claim 10 , wherein each bar is spaced from the support structure by a damping member. 
     
     
         12 . A rotor casing according to  claim 10 , wherein the support structure comprises first and second annular support members arranged about a rotational axis of the rotor in use, each support member having an annular array of openings shaped to receive an end of each bar such that the bars are supported at their ends within the openings and extend between the first and second support members. 
     
     
         13 . A rotor casing according to  claim 12 , wherein the bars have a reduced depth dimension at each end thereof such that the portion of the bars extending between the support members has a radially inner surface that is substantially flush with an adjacent radially inner surface of the first and/or second support member when assembled for use. 
     
     
         14 . A rotor casing according to  claim 10 , wherein the support structure comprises a composite material. 
     
     
         15 . A gas turbine engine comprising a tip treatment bar according to  claim 1 . 
     
     
         16 . A tip treatment bar for a rotor casing, the tip treatment bar having a composite structure comprising a plurality of internal layers arranged therein with each internal layer comprising a composite material having a plurality of fibres arranged within a matrix material, wherein at least one internal layer is arranged circumferentially around said inner body so as to provide the bar with a directional stiffness characteristic. 
     
     
         17 . A tip treatment bar according to  claim 1 , wherein the internal layers of the bar are spaced from the outer surface of the bar by a coating layer. 
     
     
         18 . A tip treatment bar according to  claim 16 , comprising a plurality of layers arranged concentrically about said inner body. 
     
     
         19 . A rotor casing comprising a plurality of bars according to  claim 16  and a support structure arranged to maintain the bars in a circumferentially spaced array with respect to an axis of rotation of the rotor in use. 
     
     
         20 . A rotor casing according to  claim 19 , wherein each bar is spaced from the support structure by a damping member.