Patent Application
20120112415
The present invention relates to seal assemblies, and more particularly to rotatable split ring seal assemblies.
Seal rings (or piston rings) are used in a variety of applications, such as within gas turbine engines, to create a fluidic seal between fluids at different pressures and temperatures. Static, non-rotating seal rings are typically seated by a prevailing (i.e., highest) pressure to create a face seal. However, rotating seal rings are subject to centrifugal loading, and as such typically experience more complex operational conditions than static, non-rotating seals. The complex operational loading faced by rotating seals can affect sealing efficacy.
The present invention provides an alternative seal ring with improved sealing effectiveness over the seal ring 28.
A seal assembly according to the present invention includes a first component, a second component that defines an outer surface and is located radially inward from the first component, a groove defined in the second component and arranged to face the first component, and a seal ring positioned between the first and second components and extending at least partially into the groove. The seal ring defines an outer diameter surface and a first lateral surface adjoining the outer diameter surface. The seal ring is split to define a first free end and a second free end, and the first and second free ends are configured to overlap along a split surface that extends from the first lateral surface to the outer diameter surface.
In general, the present invention provides a rotating piston ring (or rotating seal ring) that is split to define a pair of free ends that contact one another at a split surface, which can be configured as a portion of a conical surface. In one embodiment, the seal ring can be used to provide a fluidic seal between two components, with the seal ring at least partially engaged in a groove formed in one of the components. The seal ring is split to allow for assembly in the groove and for expansion during use to follow component growth to help maintain diametrical sealing contact. Diameter of the seal ring can vary due to centrifugal forces acting on the seal ring during rotation, with the free ends (or arms) moving relative to one another in a circumferential direction along the split surface as the diameter of the seal ring changes. As the seal ring rotates with the two components, the ring tends to expand and the diameter correspondingly enlarges. The split surface is arranged such that an open leak path (i.e., gap) between the two components is substantially eliminated (i.e., sealed by the seal ring) whenever the seal ring—including any coatings thereon—abuts both of the components (including a surface of the groove). In one embodiment, the split surface is arranged radially outward from chamfered surfaces positioned at an inner diameter of the seal ring. In addition, a coating of a relative soft material, such as a copper-aluminum material, can be provided between the seal ring and one of the components. The present invention is suitable for use in gas turbine engines, such as to provide a seal between a compressor rotor and a tie shaft to help isolate fluids at different temperatures and/or pressures. In view of the description that follows, it will be understood that the present invention has numerous other applications.
The seal assembly 140 includes a first component 22 (e.g., a rotor), a second component 24 (e.g., a shaft), a groove 26 formed in the second component 24, the seal ring 128, and a coating 142. The seal assembly 140 is arranged relative to an axis of rotation CL (the distance from the axis CL to the illustrated components is not shown to scale in
The first component 22 defines an inner surface 144, and the second component 24 defines an outer surface 146. The first component 22 is arranged radially outward from the second component 24, such that the inner surface 144 of the first component 22 and the outer surface 146 of the second component 24 face each other. The first and second components 22 can each be made of metallic materials, such as nickel-based materials.
The groove 26 can be generally U-shaped, and defines a bottom surface 26A and opposed first and second lateral surfaces 26B and 26C. The first and second lateral surfaces 26B and 26C each adjoin the outer surface 146, and the bottom surface 26A adjoins both the first and second lateral surfaces 26B and 26C. Fillets can be provided between the bottom surface 26A and the first and second lateral surfaces 26B and 26C. The first and second lateral surfaces 26B and 26C can each be arranged perpendicular to the outer surface 146 of the second component 24.
The seal ring 128 restricts fluid flow to help isolate the fluids at opposite sides of the seal assembly 140. The seal ring 128 extends at least partially into the groove 26, to engage and retain the seal ring 128. In the illustrated embodiment, the seal ring 128 has a hexagonal cross-sectional perimeter defined by an outer diameter surface 128C, and inner diameter surface 128D, a first lateral surface 128E, a second lateral surface 128F, and first and second chamfers 128G and 128H. The first and second lateral surfaces 128E and 128F are located opposite one another, and can be parallel to each other. The outer diameter surface 128C adjoins both the first and second lateral surfaces 128E and 128F at corresponding edges, and the outer diameter surface 128C can be arranged perpendicular to both the first and second lateral surfaces 128E and 128F. The first and second chamfers 128G and 128H each adjoin the inner diameter surface 128D at corresponding edges, such that the first chamfer 128G is located between the inner diameter surface 128D and the first lateral surface 128E and the second chamfer 128H is located between the inner diameter surface 128D and the second lateral surface 128F. Moreover, the first and second lateral surfaces 128E and 128F of the seal ring 128 can be arranged parallel to the respective first and second lateral surfaces 26B and 26C of the groove 26. The free ends 128A and 128B allow the diameter of the seal ring 128 to be increased during installation to fit the ring 128 over the second component 24 and into the groove 26. When at rest after installation, that is, when not rotating (this condition is not shown in the figures), the seal ring 128 assumes a relative minimum diameter such that the inner surface 128D of the seal ring 128 contacts the bottom surface of the groove 26 in the second component 24. During operation, the diameter of the seal ring 128 can change due to interactions of applicable forces, including a centrifugal force generated by rotation of the seal ring 128. When the seal ring rotates at operational speeds (as shown in
The split surface 130, defined at the interface between mating cut-out notch surfaces 130A and 130B of the respective first and second free ends 128A and 128B of the seal ring 128, extends from the first lateral surface 128E of the seal ring 128 (i.e., radially outward of the first chamfer 128G) to the outer diameter surface 128C of the seal ring 128. In the illustrated embodiment, the split surface 130 is oriented at approximately 55° relative to the first lateral surface 128E, though any desired angular orientation is possible in further embodiments.
The coating 142 can be located between the outer diameter surface 128C of the seal ring 128 and the inner surface 144 of the first component 22. In one embodiment, the coating has a thickness (measured in the radial direction) of approximately 25.4-76.2 μm (1-3 mils). Generally, the coating 142 is a relatively soft material compared to the material of the first component 22 and the seal ring 128. For example, in one embodiment the coating 142 is made of approximately 90 wt % copper (Cu) and approximately 10 wt % aluminum (Al), plus incidental impurities. The coating 142 can be applied to the seal ring 128 using known plasma spray techniques. As the seal ring 128 is dragged axially by its adherence to the first component 22 due to high centrifugal forces and displacement of the seal ring 128 is limited by an axial width of the groove 26 (i.e., the width between the lateral surfaces 26B and 26C) fretting can developed between the two parts. The coating 142 helps limit negative effects of fretting between the seal ring 128 and the first component 22.
A fluid (e.g., air) at a relatively high pressure and temperature can be present between the first and second components 22 and 24 at an aft side (to the right in
In one embodiment, the seal assembly 140 is located in a compressor stage of a gas turbine engine (additional portions of the gas turbine engine are not shown), though it will be appreciated by those of ordinary skill in the art that other applications of the present invention are possible. Because the configuration and operation of gas turbine engines is well-known, further discussion here is unnecessary. However, it should be noted that during operation, the first component 22 (e.g., rotor) tends to axially move back and forth relative to the second component 24 (e.g., shaft), due to varying engine conditions such as the engine throttling up and down and changing compressor rotation speed and temperature profile. The seal ring 128 tends to axially move with (i.e., be dragged with) the first component 22 due to friction, which in turn moves the seal ring 128 within the groove 26 and relative to the second component 24. Axial movement of the seal ring 128 is constrained by the groove 26, particularly the axial width of the groove 26. Contact between the first lateral surfaces 26B and 128E or between the second lateral surfaces 26C and 128F can arrest and limit axial movement of the seal ring 128, at which point further axial movement of the first component 22 will cause frictional sliding between the seal ring 128 and the first component 22.
Positioning of the seal ring 128 during operation (i.e., while rotating) can generally assume three different positions: (a) contacting the first lateral surface 26B of the groove 26, (b) spaced from both the first and second lateral surfaces 26B and 26C of the groove 26, and (c) contacting the second lateral surface 26C of the groove 26. In situations (a) and (c), the seal ring 128 of the illustrated embodiment substantially seals all leak paths between the first and second components 22 and 24. Particularly, the location of the split surface 130 under situation (a) maintains a face seal between the seal ring 128 and the first lateral surface 26B of the groove 26 along an entire circumference of the seal ring 128, including both the first and second free ends 128A and 128B of the seal ring 128. In other words, the split surface 130 is arranged such that a gap between the first and second components 22 and 24 is covered (i.e., sealed by the seal ring 128) whenever the seal ring 128—including the coating 142 and any other coatings—abuts both of the first and second components 22 and 24. This is shown in
The present inventors have discovered that the seal ring 128 of the present invention is more effective under a full range of typical operating conditions than the prior art seal ring 28 shown in
Those of ordinary skill in the art will appreciate that that present invention provides numerous advantages and benefits. For example, as discussed above, overall (net) sealing efficiency is relatively high compared to prior art designs. When the first lateral surface 128E of the seal ring 128 is in contact with the first lateral surface 26B of the groove 26 and the outer diameter surface 128C of the seal ring abuts the inner surface 144 of the first component 22, circumferentially continuous face seals are formed without any open leak path gap between the first and second components 22 and 24. Moreover, the locations of the split surface 130 helps to reduce sensitivity of the seal ring 128 forward/aft orientation (i.e., the forward and aft orientation of the first and second lateral surfaces 128E and 128F), which provides assembly mistake proofing benefits.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
