Balancing apparatus, arrangement and method

Abstract

The present invention provides an apparatus for providing a balancing weight in a groove on a rotor disk in a gas turbine engine. The apparatus comprises an elongate reservoir for housing a hardenable material and an inflatable balloon in fluid communication with the distal end of the elongate reservoir. An actuator is provided for forcing the hardenable material from the elongate reservoir to inflate the inflatable balloon with hardenable material within the groove on the rotor disk. A sealing device for sealing the inflated inflatable element to form the balancing weight is also provided.

Claims

1. An arrangement for providing a balancing weight in a groove on a rotor disk in a gas turbine engine, the arrangement comprising: an annular casing surrounding the rotor disk, the annular casing having at least one radially-extending aperture; and an apparatus for providing a balancing weight in a groove on a rotor disk in a gas turbine engine, the apparatus comprising: an elongate reservoir for housing a hardenable material; an inflatable balloon in fluid communication with a distal end of the elongate reservoir; an actuator for forcing the hardenable material from the elongate reservoir to inflate the inflatable balloon with hardenable material within the groove on the rotor disk; and a sealing device for sealing the inflated balloon to form the balancing weight, wherein the elongate reservoir extends through the at least one radially-extending aperture in the annular casing.

2. The arrangement according to claim 1, wherein the actuator comprises a plunger positioned at a proximal end of the elongate reservoir, the plunger forming a tight fit within the elongate reservoir.

3. The arrangement according to claim 1, wherein the inflatable balloon is an inflatable latex balloon.

4. The arrangement according to claim 1, wherein the inflatable balloon is removable from the balancing weight.

5. The arrangement according to claim 1, wherein the sealing device biases an open end of the inflatable balloon towards the distal end of the elongate reservoir.

6. The arrangement according to claim 1, wherein the elongate reservoir contains a hardenable material.

7. The arrangement according to claim 1, further comprising a rotor disk having a circumferential groove for housing a plurality of rotor blades.

8. The arrangement according to claim 7, wherein the circumferential groove has a dovetail axial cross-section with a restricted opening radially outermost.

9. A method of balancing a rotor disk within an annular casing in a gas turbine engine, the method comprising: providing an apparatus for providing a balancing weight in a groove on a rotor disk in a gas turbine engine, the apparatus comprising: an elongate reservoir for housing a hardenable material; an inflatable balloon in fluid communication with a distal end of the elongate reservoir; an actuator for forcing the hardenable material from the elongate reservoir to inflate the inflatable balloon with hardenable material within the groove on the rotor disk; and a sealing device for sealing the inflated balloon to form the balancing weight; inserting the distal end of the elongate reservoir through a radially-extending aperture in the annular casing; positioning the inflatable balloon proximal a groove in the rotor disk; forcing hardenable material from the elongate reservoir using the actuator to inflate the inflatable balloon with hardenable material within the groove on the rotor disk; sealing the inflated inflatable balloon using the sealing device; separating the inflatable balloon and the elongate reservoir; and allowing the hardenable material to harden to form a balancing weight.

10. The method according to claim 9, wherein the actuator is a plunger and the method comprises depressing the plunger to force the hardenable material from the elongate reservoir into the inflatable balloon.

11. The method according to claim 9, further comprising removing the inflatable balloon from the balancing weight.

12. The method according to claim 11, comprising burning off the inflatable balloon from the balancing weight.

13. The method according to claim 9, comprising retracting the distal end of the elongate reservoir from an open end of the inflatable balloon to allow the sealing device seal the open end of the inflatable balloon.

14. The method according to claim 13, comprising retracting the elongate reservoir from the radially-extending aperture in the annular casing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 shows a ducted fan gas turbine engine incorporating the invention;

(3) FIG. 2 shows an axial cross section through a HP compressor showing an apparatus according to a first embodiment; and

(4) FIGS. 3A-C show steps in a method of using the apparatus shown in FIG. 2.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) With reference to FIG. 1, a ducted fan gas turbine engine incorporating the invention is generally indicated at 10 and has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, an intermediate pressure turbine 17, a low-pressure turbine 18 and a core engine exhaust nozzle 19. A nacelle 21 generally surrounds the engine 10 and defines the intake 11, a bypass duct 22 and a bypass exhaust nozzle 23.

(6) During operation, air entering the intake 11 is accelerated by the fan 12 to produce two air flows: a first air flow A into the intermediate pressure compressor 13 and a second air flow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.

(7) The compressed air exhausted from the high-pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 16, 17, 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines respectively drive the high and intermediate pressure compressors 14, 13 and the fan 12 by suitable interconnecting shafts.

(8) Any axial unbalance in the various rotating components e.g. in the compressors/turbines e.g. any discrepancy between the centre of gravity/principal axis of inertia and the axis defined by the mounting bearings, will lead to undesirable vibrations and stresses within the gas turbine engine. Each rotating component is independently balanced prior to assembly but fine tuning by adding balancing weights post assembly is often necessary.

(9) FIGS. 2 and 3A to 3C show a first embodiment of an apparatus/arrangement according to a first embodiment of the present disclosure for adding a balancing weight. Such a balancing weight may, for example, be provided to a compressor, such as the high pressure (HP) compressor 14, after assembly of the gas turbine engine 10.

(10) FIG. 2 is an axial cross section through the compressor 14, which may be referred to as the HP compressor 14. The HP compressor comprises a rotor disk 1 having a circumferential groove 2 housing a plurality of circumferentially-spaced rotor blades 3. The circumferential groove 2 has a dove-tail axial cross-section with a restricted opening 25 located radially outermost.

(11) The HP compressor 14 is surrounded by a first annular casing 4 which has a first radially-extending aperture 5. A second annular casing 6 is provided radially outermost and this comprises a second radially-extending aperture 7 which is radially aligned with the first radially-extending aperture 5.

(12) The apparatus comprises an elongate reservoir 8 containing a hardenable material. The hardenable material may be a metal putty in the illustrated example. At its proximal end, the elongate reservoir 8 comprises an enlarged radius portion 9 housing an actuator in the form of a plunger 20 which has a plunger body forming a tight fit within the enlarged radius portion 9. The distal end of the elongate reservoir is provided with a nozzle 24.

(13) The elongate reservoir 8 extends through the second radially-extending aperture 7 and the first radially-extending aperture 5 with the nozzle 24 positioned proximal the restricted opening 25 of the circumferential groove 2. The enlarged radius portion 9 at the proximal end of the elongate reservoir 8 is positioned radially outwards of the second annular casing 6.

(14) As can be seen in FIG. 3A, the nozzle 24 at the distal end of the elongate reservoir 8 is in fluid communication with an inflatable element 26 e.g. an inflatable Latex balloon. A sealing device in the form of an clamping ring 27 (which may be, for example, an elastic clamping ring) biases the open end of the inflatable element 26 against the nozzle 24 of the elongate reservoir 8.

(15) Once the nozzle 24 is appropriately positioned at a location requiring extra weight for balancing, the plunger 20 is depressed into the enlarged radius portion 9 of the elongate reservoir 8 and this causes metal putty to flow from the elongate reservoir 8 to inflate the inflatable element 26 as shown in FIG. 3B.

(16) After a sufficient amount of metal putty has been added to the inflatable element 26, the elongate reservoir 8 is retracted away from the inflatable element 26. The retraction of the nozzle 24 from within the clamping ring 27 allows the clamping ring to constrict the open end of the inflatable element 26 to seal it. The elongate reservoir 8 is then fully retracted from within the annular casings 4, 6.

(17) The metal putty-filled inflatable element 26 is retained within the circumferential groove 2 by the restricted opening 25. The metal putty (or other hardenable material) hardens at room temperature to from a balancing weight 28 within the circumferential groove 2 as shown in FIG. 3C.

(18) The inflatable element 26 is subsequently removed from the balancing weight 28 by burning off at the operating temperature of the gas turbine engine 10. The balancing weight retained in the circumferential groove 2 then comprises a ball of solidified metal.

(19) This process can be repeated at other locations round the circumferential groove 2 to effect the required balancing of the HP compressor 14.

(20) While the disclosure has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

(21) All references referred to above are hereby incorporated by reference.