Seal for a joint or juncture – Seal between relatively movable parts – Brush seal
Reexamination Certificate
1999-11-16
2001-09-18
Sandy, Robert J. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Brush seal
C277S415000
Reexamination Certificate
active
06290232
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus and methods for minimizing or eliminating non-uniform circumferential temperature distribution between a stationary brush seal and a rotary component, e.g., a turbine rotor.
BRIEF SUMMARY OF THE INVENTION
While the invention hereof is described particularly in relation to turbine rotors, it will be appreciated that the invention relates more generally to minimizing or eliminating non-uniform temperature distribution between a stationary brush seal and a rotary component. Turbine rotors, particularly steam turbine rotors for the generation of power, typically include a continuous solid elongated shaft carrying the turbine wheels and buckets. Proud portions, e.g., high spots, are often formed or occur on turbine rotors. Brush seals for sealing between a stationary component and a rotary component, e.g., a rotor, are designed for direct contact with the rotor surface during operation. The heat generated by the bristles rubbing against the rotating rotor and particularly the proud portions may lead to non-uniform circumferential temperature distribution on the rotor surface and consequent bowing of the rotor. That is, proud portions of the rotor become increasingly hotter than circumferentially adjacent portions of the rotor, resulting in non-uniform axial expansion of the rotor and hence a bow in the rotor. This can be particularly pronounced at rotor start-up in the absence of any rotor cooling. Rotor bowing can result in excessive vibration and may prevent proper turbine start-up. Consequently, there is a need to thermally isolate the rotor from the heat generated by the brush seal bristles rubbing against the sealing surface of the rotor to avoid non-uniform temperature distribution circumferentially about the rotor.
In accordance with a preferred embodiment of the present invention, a groove, preferably a dovetail-shaped groove, is provided about the circumference of the rotor at the axial location along the rotor at which the brush seal will contact the rotor. The groove includes an entry slot for receiving a plurality of inserts, preferably generally complementary in shape to the cross-sectional shape of the groove. The inserts are received in the groove through the entry slot and are circumferentially stacked one against the other about the groove. Each of the inserts has a sealing surface for contact by the bristles of the brush seal. A final closure insert is received in the entry slot and is pinned in place to either the rotor or to adjacent inserts. The final insert also has a sealing surface whereby the discrete sealing surfaces of the inserts about the circumference of the rotor form a substantially continuous sealing surface thereabout for engagement by the brush seal bristles.
It will be appreciated that any temperature variation generated by contact between the brush seal bristles and the sealing surfaces, for example, proud portions of the sealing surfaces, would propagate along the inserts substantially to the exclusion of the adjoining rotor. That is, while temperature variations may exist about the substantially continuous sealing surface of the inserts, the heat transfer to the adjoining rotor is substantially limited due to the interface between the inserts and the rotor. By the time heat transfers to the rotor, the temperature distribution about the inserts will be substantially uniform about the rotor with consequent substantially uniform heat transference to the rotor.
In a preferred first embodiment of the present invention, the groove in the rotor may be formed in a raised land or flange on the rotor. Consequently, pins may be inserted in an axial direction through the raised land or flange to engage and retain the final insert within the rotor groove, notwithstanding its location at the groove entry slot. In another preferred form, the rotor groove may be in a raised land or flange or recessed from the rotor surface with stem portions of the inserts projecting radially outwardly of the groove or rotor surface. The final insert may be secured to the adjacent inserts by inserting pins in complementary grooves between the final and adjacent inserts.
In a still further preferred form of the present invention, and particularly useful for grooves recessed within the rotor surface and wherein the insert sealing surfaces lie flush with the rotor surface, sets of pins may be used to secure the final insert to the rotor. Each pin has reduced and enlarged axially spaced diameter sections and is cut axially into halves. Complementary recesses are formed along opposite sides of the final insert and the registering end faces of the adjacent inserts. By locating a pair of pin halves in the registering faces of the adjacent inserts with the pin halves oriented such that each axial plane lies flush with its registering face, the final insert, also carrying pin halves along opposite faces thereof, is disposed through the entry slot. It will be appreciated that, upon insertion of the final insert, the axial plane of each pin half at each side of the final insert adjoins the registering axial plane of the pin half of the adjacent insert. This enables the pins to be rotated approximately 90°, thereby locking the final insert in the groove.
In a preferred embodiment according to the present invention, there is provided a seal assemblage comprising a rotary component having an axis of rotation, a plurality of discrete, circumferentially spaced elements connected to the rotary component and lying generally in a plane normal to the axis of rotation, the elements having discrete sealing surfaces defining a substantially continuous circumferentially extending sealing surface about the rotor, a component fixed against rotation and surrounding the rotary component, the fixed component including a brush seal comprised of a plurality of bristles for sealing engagement with the substantially continuous sealing surface of the rotary component, enabling substantially uniform temperature distribution circumferentially about and in the rotary component adjacent the elements.
In a further preferred embodiment according to the present invention, there is provided in a steam turbine having a rotor and a non-rotating component about the rotor carrying a brush seal for sealing engagement with the rotor, a method of substantially eliminating bowing of the rotor resulting from circumferential non-uniform distribution of heat about the rotor due to frictional contact between the brush seal and a proud portion of the rotor, comprising the steps of providing a groove in the rotor at an axial location corresponding to an axial location of the brush seal, disposing a plurality of inserts in the groove through an entry slot to the groove for engaging the brush seal and securing the inserts within the groove by engaging a retainer member with a final insert received in the entry slot and one of the rotor and an insert adjacent the final insert.
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Ahl Dennis R.
Farineau Thomas J.
Reluzco George E.
Rentz Lawrence E.
General Electric Co.
Nixon & Vanderhye
Rodgers Matthew
Sandy Robert J.
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