Labyrinth seal support

Abstract: The normally multi-part gas turbine engine labyrinth seal outer portion which carries an abradable lining (34), is formed from a single piece and has a groove (38) machined in its periphery for the receipt of the feet (46) of respective stator vanes (20). Pins (44) are fitted in pairs through the walls (42) of the groove to provide lateral location for the feet. The pins (44) and a groove liner (52) are made from an anti-frettage material.

Description: The present invention relates to support means for labyrinth seals. The invention has particular efficacy when utilised in gas turbine engines. A known example of a labyrinth seal of the kind mentioned herein is illustrated and described in US patent specification 3411794 and is defined by an outer annular land which has a number of annular fins formed on its outer diameter, the fins being surrounded in close spaced relationship by a further annular land, the bore of which has an abradable lining. The finned portion is coaxially fixed to a rotor for rotation therewith within the lined portion which in turn, is non rotatably supported by the inner ends of a fixed stage of stators or guide vanes. It is necessary to enable relative, opposing radial growth between the stators or guide vanes and the associated further annular land which results from increases in operating temperatures in the associated engine. It is the practice to provide the further land with an annular flange and to locate inwardly directed features on the inner ends of the stators or guide vanes between that flange and a further, separate flange, the two flanges being bolted together by a number of angularly spaced nuts and bolts. Radial slots have to be machined in the opposing face of at least one of the flanges and the features placed therein, to be restrained against excessive movement peripherally of the flanges, by the side walls of the slots. The arrangement is expensive to produce and heavy. The present invention seeks to provide an improved outer labyrinth seal land of the kind defined hereinbefore. It is a further object of the present invention to provide an anti frettage liner which in operation protects the inwardly directed feature on the stator or guide vane against frettage. According to The present invention a labyrinth seal support structure for supporting a labyrinth seal in a turbine of a gas turbine engine, comprising a ring of guide vanes each of which has a radially inwardly projecting foot, fixing pins which pass through a double flange structure on the labyrinth seal and engage with said feet characterised in that two pins made from anti frettage material are provided, one on each side of each guide vane foot each pin having a flat thereon for engagement with an adjacent edge of a respective guide vane foot and including a metallic anti frettage liner comprised of a plurality of arcuate segments of 'U' cross-section which nest between said double flanges and include holes for passage through of said pins and wherein said 'U' section segments have lips which are turned outwardly, inwardly and upwardly so as to provide edges which clip into grooves in faces of said double flange structure. The invention will now be described, by way of example and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a gas turbine engine incorporating the present invention. Figure 2 is an enlarged view on line 2-2 of Figure 1. Figure 3 is a view on line 3-3 of Figure 2. Figure 4 is a view on line 4-4 of Figure 2. Figure 5 depicts the retaining pins of Figures 2 to 4 inclusive. Figure 6 illustrates the present invention. Figure 7 is a pictorial view of a segment of the anti frettage liner incorporated in Figure 6. Referring to Figure 1. A gas turbine engine 10 includes a compressor 12, combustion equipment 14, a turbine section 16 and an exhaust section 18, all arranged in flow series. In this example, the turbine section has a stage of guide vanes 20 affixed in known manner via their radially outer ends, to structure within the engine turbine casing 22. A stage of rotatable turbine blades 24 is positioned immediately downstream of the stage of guide vanes 22, again in known manner. The turbine disc 26 has an annular land 28 bolted to its upstream face, which land extends forwardly and terminates under the guide vanes 20. That portion of the land 28 which lies under the guide vanes 20 has annular fins 30 formed on its outer diameter in known manner and these are surrounded in close spaced relationship by a further annular land 32 which has an abradable lining (not shown in Figure 1) in its bore, again in known manner. Referring now to Figure 2. In accordance with the present invention the land 32 with its associated abradable lining 34 has an outwardly turned annular flange 36 formed at its downstream end. The flange 36 has an annular groove 38 formed in its periphery, and an anti frettage liner, which for reasons of clarity is shown in Figure 6, nests therein. A plurality of equi-angularly spaced pairs of holes 40, only one of which pairs is shown, are drilled through the resulting walls 42 of the groove 38 and a pin 44 is fitted in each hole 42. It is intended that the pins 44 should stay in situ until their replacement through wear is necessitated. They may thus be a press fit or may be brazed via their ends to the groove walls 42, or both. Each pin 44 in a pair of pins is spaced one from the other by a distance which will allow the insertion of a foot 46 therebetween one of which feet 46 projects from the underside of each respective guide vane 20. It follows that the number of pairs of pins 44 equals the number of guide vanes 20 in the stage. Each guide vane 20 is affixed via its outer end to fixed engine structure in known manner. Consequently, during operation of the engine 10, when the guide vanes 20 become heated, they expand radially inwardly towards the engine axis. Conversely the land 32 and its associated grooved flange 36 expand radially outwardly from the engine axis. Thus there must be an appropriate clearance between the feet 46 and the associated pins 44. This is shown in Figures 2 and 4. There must also be a clearance between the feet 46 and the walls 42 of the groove 38. This is shown in Figure 3. Referring now to Figure 5. The pins 44 in the present example are relieved at 48 and 50 respectively, so as to provide flat opposing faces. A greater surface area is thus provided for the feet 46 (not shown in Figure 5) to bear on. This, depending on the friction characteristics of the assembly, which would be ascertained on test of the associated engine, may prove to be an unnecessary step. In any event, the anti frettage liner 52 as depicted in Figure 6 and which could e.g. be made from a material sold under the proprietry name "HAYNES 25", (registered trade mark), is used to cover the profile of the groove 38. The preform 52 which is depicted per se in Figure 7 could be produced by hot spraying as with a plasma gun, a metal powder onto a disposable core (not shown) and would have its lips 54 turned inwardly upon themselves so as to provide upwardly turned edges 56 within the maximum width of the preform 52 and which on fitting of the preform within the groove 38, will clip into further grooves 58 and 60 in the outer surfaces of the walls 42. The pins 44 will be manufactured from the anti frettage material. The obviation of a groove formed by an assembly of separate flanges, along with associated fastening and locking devices, and of the need for extensive machining operation which such arrangements made necessary, results in a considerable cost and weight reduction and a simplified assembly procedure. Further the provision of the pre formed anti frettage liner 52 obviates the need to spray the interior of the groove 38 with heated anti frettage material, with its attendant difficulty in ensuring the maintenance of a constant thickness.

Claims: A labyrinth seal support structure for supporting a labyrinth seal in a turbine of a gas turbine engine, comprising a ring of guide vanes (20) each of which has a radially inwardly projecting foot (46), fixing pins (44) which pass through a double flange structure (42) on the labyrinth seal and engage with said feet (46) characterised in that two pins (44) made from anti frettage material are provided, one on each side of each guide vane foot (46) each pin (44) having a flat (48) thereon for engagement with an adjacent edge of a respective guide vane foot (46) and including a metallic anti frettage liner (52) comprised of a plurality of arcuate segments of 'U' cross-section which nest between said double flanges (42) and include holes for passage through of said pins (44) and wherein said 'U' section segments have lips (54) which are turned outwardly, inwardly and upwardly so as to provide edges (56) which clip into grooves (58 or 60) in faces of said double flange structure.

Inventors: HIRST ROY TALBOT, HIRST, ROY TALBOT
Applicants: ROLLS ROYCE PLC, ROLLS-ROYCE PLC
Application year: 1990
Main classification: F01D11
IPC codes: F01D11, F01D9, F02C7