Developments in or relating to drum rotors

Abstract

A method of replacing a integrally bladed rotor section in a one-piece drum rotor, the method comprising removing the integrally bladed rotor section, replacing the integrally bladed rotor section with a replacement rotor section, and joining the replacement rotor section to the drum rotor by diffusion bonding under an axial contact pressure exerted between one or more respective pairs of bonding surfaces on the new rotor section and the drum rotor.

1 . A method of securing a rotor section in a one-piece drum rotor, the method comprising providing a rotor section, and joining the rotor section to the drum rotor by diffusion bonding under an axial contact pressure exerted between one or more respective pairs of bonding surfaces on the rotor section and the drum rotor. 
     
     
         2 . A method according to  claim 1 , wherein the rotor section is or comprises an integrally bladed rotor. 
     
     
         3 . A method according to  claim 1 , wherein the rotor section is a replacement rotor section and the method further comprising the step of removing a prior rotor section from the drum rotor and replacing the prior rotor section with the replacement rotor section. 
     
     
         4 . A method according to  claim 1 , wherein the rotor section comprises a replacement integrally bladed rotor and one or more spacer elements axially in-between the replacement integrally bladed rotor and the drum rotor so that each spacer element is thus adjacent to either the replacement integrally bladed rotor, the drum rotor or another spacer element, each spacer element further being joined to said adjacent spacer element, integrally bladed rotor or drum rotor by diffusion bonding under an axial contact pressure exerted between a respective pair of bonding surfaces on the spacer element and said adjacent integrally bladed rotor, drum rotor or spacer element. 
     
     
         5 . A method according to  claim 4 , wherein the rotor section comprises a plurality of integrally bladed rotors so that each spacer element may be adjacent to any one of the replacement integrally bladed rotors. 
     
     
         6 . A method according to  claim 1 , wherein the drum rotor and rotor section are sandwiched together thereby simultaneously to exert said axial contact pressure between each pair of bonding surfaces. 
     
     
         7 . A method according to  claim 6 , additionally comprising the application of a radial constraining pressure along at least part of the rotor for controlling radial deformation of the drum rotor. 
     
     
         8 . A method according to  claim 1 , further comprising:
 i) interposing a powdered metal in-between one or more respective pairs of bonding surfaces; and   ii) locally heating the powdered metal under said axial contact pressure to a sintering temperature, below the relevant melting temperature of the drum rotor, thereby to sinter the powdered metal and promote said diffusion bonding.   
     
     
         9 . A method according to  claim 8 , wherein the powdered metal is mixed with a binder and step i) comprises applying the resulting mixture directly to a bonding surface. 
     
     
         10 . A method according to  claim 8 , wherein the powdered metal is in the form of an annular pre-form insert and step i) comprises inserting the pre-form insert between the bonding surfaces. 
     
     
         11 . A method according to  claim 10 , wherein the pre-form insert has an annular radius which is greater than the annular radius of the respective bonding surfaces in order to allow for a predetermined maximum radial shrinkage of the pre-form insert during step ii). 
     
     
         12 . A method according to  claim 1 , wherein respective bonding surfaces are provided with one or more cooperative locating features for locating the new section and drum rotor in a preferential, relative axial and/or circumferential alignment prior to said diffusion bonding. 
     
     
         13 . A method according to  claim 8 , wherein in step ii) the powdered metal is maintained at a temperature of 900-1000° C. for 1-2 hours. 
     
     
         14 . A method according to  claim 1 , wherein the axial contact pressure exerted between the bonding surfaces is up to 10 MPa. 
     
     
         15 . A method according to  claim 1 , wherein, during said diffusion bonding, the drum rotor and new rotor section are each oriented such that the nominal centreline of the drum rotor is substantially vertical. 
     
     
         16 . A method of replacing a blisk section in a one-piece drum rotor, the method comprising removing the blisk section, replacing the blisk section with a replacement rotor section, and joining the replacement rotor section to the drum rotor by diffusion bonding under an axial contact pressure exerted between one or more respective pairs of bonding surfaces on the new rotor section and the drum rotor. 
     
     
         17 . A method of fabricating a one-piece drum rotor, the method comprising joining two rotor sections of the drum rotor by diffusion bonding under an axial contact pressure exerted between respective bonding surfaces on the rotor sections.