Seal arrangement and a method of repairing a seal arrangement

#The present invention relates to a seal arrangement and a method of repairing a seal arrangement and in particular to a seal arrangement between components in a gas turbine engine.

#It is known to provide a seal between components in a gas turbine engine particularly an airfoil seal, e.g. an O-ring seal between metal casings in a gas turbine engine or in an oil/lubrication system of a gas turbine engine. A known type of seal provided between adjacent components in a gas turbine engine comprises a fluoropolymer seal. A problem with a fluoropolymer seal is that the fluorine, or fluorine-containing species, in the fluoropolymer seal corrodes the adjacent components, after the fluoropolymer seal has degraded at elevated temperatures above 200° C., and this may lead to surface pitting and sub-surface inter-granular stress-corrosion cracking of the adjacent components. If the components are sufficiently corroded it is necessary to repair either one or both of the adjacent components.

#Accordingly the present invention seeks to provide a novel seal arrangement which reduces, preferably overcomes, the above mentioned problem.

#The present invention will be more fully described by way of example with reference to the accompanying drawings in which: —

#FIG. 1 shows a turbofan gas turbine engine having a seal arrangement according to the present invention.

#FIG. 2 shows a casing of the turbofan gas turbine engine having a seal arrangement according to the prior art.

#A turbofan gas turbine engine 10, as shown in FIG. 1, comprises in axial flow series an inlet 12, a fan section 14, a compressor section 16, a combustion section 18, a turbine section 20 and an exhaust 22. The fan section 14 comprises a fan 24 and the compressor section 16 comprises an intermediate pressure compressor 26 and a high pressure compressor 28. The turbine section 20 comprises a high pressure turbine 30, an intermediate pressure turbine 32 and a low pressure turbine 34. The low pressure turbine 34 is arranged to drive the fan 24 via a first shaft 36, the intermediate pressure turbine 32 is arranged to drive the intermediate pressure compressor 26 via a second shaft 38 and the high pressure turbine 30 is arranged to drive the high pressure compressor 28 via a third shaft 40. FIG. 1 also shows a compressor casing 48 for the intermediate and high pressure compressors 26 and 28 respectively.

#The turbofan gas turbine engine 10 operates quite conventionally and its operation will not be discussed further.

#The compressor casing 48 comprises two axially adjacent casing portions 50 and 52 and a prior art seal arrangement 54 is provided between the casing portions 50 and 52 as shown more clearly in FIGS. 2 and 3. The adjacent axial ends 56, 58 of the casing portions 50 and 52 respectively have radially extending flanges 60, 62 and the flanges 60, 62 are fastened together by a plurality of bolts 64 and nuts 66. An end surface 68 of the casing 50 and flange 60 is provided with a circumferentially extending annular recess, or annular groove, 70 and an O-ring seal 72 is provided in the annular groove 72 to provide a seal between the surfaces 68 and 69 on the flanges 60, 62 of the axially adjacent casing portions 50 and 52. The O-ring seal 72 consists of a fluoropolymer, i.e. a polymer containing fluorine. As mentioned previously, fluorine containing species liberated from the fluoropolymer O-ring seal 72 corrode the adjacent surfaces of the casing portions 50 and 52 once the fluoropolymer O-ring seal 72 has been degraded at temperatures above 200° C.