Leaktight seal of a circular vane stage

Details Leaktight seal of a circular vane stage Leaktight seal of a circular vane stage

1999-02-22

2001-12-25

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Centrifugal force affects change in displacement, shape, or...

C277S632000, C277S637000, C277S644000, C416S221000, C416S248000

Reexamination Certificate

active

06332617

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a leaktight seal for a circular vane stage and in particular a stage for “hammer legged” vanes, i.e. vanes being fastened to a disc using a leg with a bulbous cross-section that is inserted into a circular throat provided in a peripheral surface of the disc.
2. Description of the Related Art
If we refer to
FIG. 1
, vanes
1
of this kind can be seen on the circumference of discs
2
of a gas turbine stator
3
where they alternate with immobile vanes
4
used to rectify a gas flow and that are fastened to a stator
5
. The vanes
1
comprise a blade
6
that constitutes the active section of the vanes and that lies in a gas flow chamber
7
, a platform
8
used to define chamber
7
and that is adjacent to blade
6
, a leg
9
that is inserted into a circular throat
10
of the relevant disc
2
and a fastener
11
that connects leg
9
to platform
8
and that passes through a collar
12
of throat
10
to reach the outside. The leg
9
has a bulbous cross-section, in other words, it widens from the zone at fastener
11
and given that collar
12
is narrower than the leg, said leg
9
is maintained in throat
10
despite the centrifugal forces. Disc
2
is, however, provided with a hole at a specific point on its circumference that widens collar
12
to enable legs
9
of vanes
1
to be inserted successively in throat
10
through said hole before vanes
1
are slid around disc
2
to reach their definitive position.
Re-circulated air may be noticed under platforms
8
, in other words, air that is returned upstream towards the compressors in the machine and the low pressures, in the opposite direction to the flow of gas in chamber
7
. This re-circulated air travels between vane
1
and disc
2
through throat
10
despite the parts being adjustable in this zone. This re-circulation leads to performance loss of the machine. Various kinds of leaktight seals have been put forward in order to reduce the performance loss such as circular Inconel wires
14
that are housed in throats
15
with a small cross-section cut into a peripheral surface
16
of disc
2
, said wires
14
being under platforms
8
next to legs
9
. The drawback with this solution is that the centrifugal forces cause wires
14
to leave throats
15
and move upwards to platforms
8
where they become worn or even cut. A leaktight seal that does not cause this damage to the vanes
1
is therefore preferred, particularly given that vanes
1
, that are generally titanium, are expensive and also that the loss of a piece of a platform
8
can lead to serious damage to the compressor.
SUMMARY OF THE INVENTION
The present invention provides a suitable solution to the above-mentioned problem. The solution consists in a leaktight seal for a circular vane stage with legs that are inserted into a circular throat of a disc, blades, or platforms that are adjacent to the blades and which lie on a peripheral surface of the disc onto which the throat opens in the form of a circular collar, and fasteners that connect the legs to the platforms, said legs being inserted into the collar. The seal comprises a plate that is housed between the peripheral surface and the platforms, said plate being provided with apertures into which the fasteners are inserted. The plate is divided into plaquettes that are abutted and that are defined by a cutting line through the apertures, said apertures having a surface area that is smaller than a cross section of the vane legs. The seal is characterized in that it comprises heels that are joined to the plaquettes and that together constitute the components of the seal. The heels lie under the upper oblique flanks of the throat.
European Patent No. 210,940 describes a leaktight seal the upper section of which lies near the platforms of the vanes and that corresponds to the first part of this definition. This known seal does not, however, include the lower heels which provide additional leaktightness, which is improved like the others by the centrifugal forces present during operation.
Leaktightness is improved if the plate has edges that fold towards the inside of the disc and if the edges are inserted into circular grooves that are provided in the peripheral surface of the disc.
Excellent construction of the seal, that greatly facilitates assembly, is provided if the cutting lines comprise horizontal and circular lines and if the plaquettes form an obtuse angle with the heels. The horizontal and circular lines join at the heels using joints that are extended with slots between the heels and the plaquettes. The components of the seal are interconnected in pairs with the joint of each of the components of a pair being housed in the slot of the other component of the same pair, thus constituting a hinge.


REFERENCES:
patent: 2912222 (1959-11-01), Wilkes, Jr.
patent: 4818182 (1989-04-01), Bouru
patent: 5073084 (1991-12-01), Hirst
patent: 5297386 (1994-03-01), Kervistin
patent: 5460489 (1995-10-01), Benjamin et al.
patent: 5791877 (1998-08-01), Stenneler
patent: 0 210 940 (1987-02-01), None
patent: 2 320 439 (1977-03-01), None
patent: 09278 (1909-08-01), None

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