GB2095763A

GB2095763A - Enhancing turbine blade coolant seal force

Info

Publication number: GB2095763A
Application number: GB8041351A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1980-12-29
Filing date: 1980-12-29
Publication date: 1982-10-06

Abstract

A turbomachine including a rotor (4) comprising: a disc (6); and a plurality of blades (8) having roots (10) attached to the periphery of said disc; and there is provided a sealing member (14) sealing against said rotor at two radially spaced positions and extending therebetween defining a sealing region (20) wherein said sealing member has a portion (34) extending at an inclined angle to the plane of said disc so as, in rotation of said rotor, to experience a centrifugal force which produces a turning moment about fulcrum 32 tending to align said portion with the plane of said disc, and said sealing member is arranged to be urged by said turning moment into sealing contact with said rotor at said two positions. <IMAGE>

Description

SPECIFICATION Turbomachines This invention relates to turbomachinery of the kind including a rotor comprising: a disc; and a plurality of blades having roots attached to the periphery of the disc; and being provided with a sealing member sealing against said rotor at two radially spaced positions and extending therebetween defining a sealing region. In modern gas turbine engines, one or more of the turbine rotors are frequently of this type, the blades having openings extending from the roots into the blades for the passage of cooling air.

In such engines it is important for the sealing member to maintain a good seal in order than an adequate amount of cooling air is passed to the blades and that leakages, which reduce the efficiency of the engines, are kept to a minimum.

However, this may be difficult, especially at increasing engine speeds where centrifugal forces and thermal expansions may have a detrimental effect.

It is an object of the present invention to provide a turbomachine of the above kind in which the sealing of the sealing member is enhanced at increased engine speeds.

According to the present invention in a turbomachine of the above kind the sealing member has a portion extending at an inclined angle to the plane of the disc so as, in rotation of the rotor, to experience a centrifugal force which produces a turning moment tending to align the portion with the plane of the disc, and the sealing member is arranged to be urged by the turning moment into sealing contact with the rotor at the two positions.

It will be appreciated that in this way the faster the speed of the rotor the greater will be the force urging the sealing member into sealing contact.

Preferably the portion extends radially outwards of the sealing region. Preferably the radially outer edge of the portion engages the blades.

According to a first particular aspect of the invention the portion may be inclined towards the disc, there may be provided an abutment surface on the blades or the disc located adjacent and radially outwardly of the sealing region, and the sealing member may be pivoted on the abutment surface and seal against the rotor at axially outwardly facing surfaces thereof.

According to a second particular aspect of the invention the portion may be inclined away from the disc, and the sealing member may seal against the rotor at the radially outer position at an axially outwardly facing surface of the rotor and seal against the rotor at the radially inner position at an axially inwardly facing surface of the disc.

Two gas turbine engines in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figures 1 s 2 show part-sectioned side elevations of respectively first and second gas turbine engines in accordance with the invention; Figures 3 a 4 show enlarged cross-sectional side elevations of parts of the turbine rotors of the first and second engines respectively.

Referring firstly to Figures 1 and 3, a first multispool gas turbine engine 2 has a first stage high pressure (h.p.) turbine rotor 4. The h.p.

turbine rotor 4 is made up of a rotor disc 6 carrying at its periphery a plurality of turbine blades 8. The roots 10 of the blades are typically of the "fir-tree" type and locate in corresponding recesses in the periphery of the disc 4 in known manner. In order to allow the blades 8 to run at high temperatures without damage, openings 12 are provided in the roots 10, the openings 12 extending into the aerofoil portion of the blade, and cooling air is fed to the root ends of these openings and passes through them to cool the blades.

In order to prevent leakage of cooling airfrom between the blades and the disc an annular sealing plate 14 is provided at the side of the disc opposite that at which the cooling air is supplied.

The sealing plate 14 makes sealing contact circumferentially with the disc via a sealing ring 1 6 and circumferentially with the blades 8 via a sealing ring 1 8. The sealing plate 14 thus defines an annular sealing region 20 between the sealing rings 1 6 and 18 from which egress of cooling air is prevented. The sealing plate 1 4 is retained in position by engaging at its radially outer edge in a recess 22 formed beneath the platforms of the blades, and is retained in position at its radially inner edge by a retaining ring 24 located in opposite recesses 26 and 28 formed in the sealing plate and a circumferential flange 30 of the disc respectively.

A circumferential shoulder 32 is provided on the blades and/or the disc located adjacent to and radially outwardly of the sealing region 20 between the sealing rings 1 6 and 18. The shoulder 32 supports the sealing plate 14 against outward radial movement under centrifugal force and also forms a pivot point about which the sealing plate may pivot.

Radially outwardly of the sealing region 20 the sealing plate 14 is cranked so as to be supported against and pivot about the shoulder 32. Radially outwardly of the cranked section the sealing plate 14 includes a portion 34 which is inclined towards the disc. In rotation of the rotor the centrifugal force acting on this portion produces a turning moment (clockwise as seen in Figure 3) tending to align the portion 34 with the plane of the disc 6.

Since the sealing plate 14 is pivoted on the shoulder 32, this turning moment urges that part of the sealing plate radially inward of the shoulder 32 towards the disc and hence enhances the sealing contact with the disc and the blades.

Referring now the Figures 2 8 4, a second multispool engine 42 is generally similar to the first engine described above, having a first stage h.p. turbine rotor 44 made up of a rotor disc 46 carrying a plurality of turbine blades 48 by "firtree" roots 50 having therein openings 52 which extend into the blades to provide cooling passages therefor.

There is provided a generally annual sealing plate 54 which seals at an axially inwardly protruding face 56 thereof directly against the blades and the disc at axially outwardly facing surfaces thereof and which seals against the disc at an axially inwardly facing surface of a lip 58 thereof via a sealing ring 60. The sealing plate 54 thus defines an annular sealing region 62 between the lip 58 and the protrusion 56 from which egress of cooling air is prevented. The sealing plate 54 is retained in position at its radially outer edge by engaging in a recess formed beneath the platforms of the blades, and is retained in position at its radially inner edge by location in the recess formed by the lip 58.

Radially outwardly of the sealing region 62 the sealing plate 54 includes a portion 64 which is inclined away from the disc. In rotation of the rotor the centrifugal force acting on this portion produces a tuming moment (anti-clockwise as seen in Figure 4) tending to align the portion 64 with the plane of the disc 46. This turning moment urges the protrusion 56 into contact with the blades and the disc and levers the radially inner edge of the sealing plate into sealing contact with the lip 58 via the sealing ring 60 (using the protrusion 56 as a fulcrum).

In this way it will be appreciated that in the h.p.

turbine rotors of the first and second engines sealing of the sealing plate is enhanced at increased engine speeds.

It will also be appreciated that other arrangements are possible with the inclined portion of the sealing member at different positions to achieve similar seal enhancing results It will be appreciated that in the first and second engines, the rearward gas loads are transmitted to the disc via a cover sealing plate 36, 64 respectively.

Claims

1. A turbomachine including a rotor comprising a disc; and a plurality of blades having roots attached to the periphery of said disc; and there is provided a sealing member sealing against said rotor at two radially spaced positions and extending therebetween defining a sealing region, wherein said sealing member has a portion extending al an inclined angle to the plane of said disc so as, in rotation of said rotor, to experience a centrifugal force which produces a turning moment tending to align said portion with the plane of said disc, and said sealing member is arranged to be urged by said turning moment into sealing contact with said rotor at said two positions.

2. A turbomachine according to claim 1 wherein said portion extends radially outwards of said sealing region.

3. A turbomachine according to claim 2 wherein the radially outer edge of said portion engages said blades.

4. A turbomachine according to claim 2 or 3 wherein said portion is inclined towards said disc, there is provided an abutment surface on said rotor located adjacent to and radially outwardly of said sealing region, and said sealing member is pivoted on said abutment surface and seals against said rotor at axially outwardly facing surfaces thereof.

5. A turbomachine according to claim 2 or 3 wherein said portion is inclined away from said disc, and said sealing member seals against said rotor at the radially outer position at an axially outwardly facing surface of said rotor and seals against said rotor at the radially inner position at an axially inwardly facing surface of a lip of said disc.

6. A turbomachine according to any preceding claim in the form of a gas turbine engine.

7. A gas turbine engine according to claim 6 wherein said rotor is a turbine rotor.

8. A gas turbine engine substantially as hereinbefore described with reference to Figures 1 and 3 or Figures 2 and 4 of the accompanying drawings.