Patent Application
20170299062
The application relates generally to seals of the type used to seal a rotating shaft and, more particularly, to such seals used to seal a rotating axial face.
Face seals are commonly used to seal an annular passage between a shaft and a structure. The face seals are often required to preserve oil on one side of the shaft. In such face seals, a seal fixed in rotation rubs and wears against a face of a shaft component, such as a rotating seal runner. The surface of contact between the seal and the seal runner is a dynamic seal surface. One difficulty is that seal runner faces are not always substantially radially planar, for instance due to thermal gradients. Therefore, an axial deviation from a radial plane may lead to a gap between the seal and the seal runner, which may cause a fluid leak.
In one aspect, there is provided a sealing device comprising: an annular receptacle defining an annular axial opening; a first annular seal and a second annular seal radially superposed in the annular receptacle, the first annular seal and the second annular seal being independently movable in a generally axial direction and configured to project out of the annular axial opening of the annular receptacle to sealingly contact a common radial face rotating with a shaft; and at least one biasing device for the first annular seal and the second annular seal, the at least one biasing device configured to bias the annular seals independently from one another against the common radial face.
In a second aspect, there is provided a gas turbine engine comprising: a structure; at least one rotating shaft having a radial face on a seal runner portion thereof, an annular space being defined between the structure and the at least one rotating shaft; and a sealing device comprising an annular receptacle secured to the structure to block the annular space, the annular receptacle defining an annular axial opening, a first annular seal and a second annular seal radially superposed in the annular receptacle, the first annular seal and the second annular seal being independently movable in a generally axial direction and configured to project from the annular axial opening to sealingly and commonly contact the radial face, and at least one biasing device for the first annular seal and the second annular seal, the at least one biasing device biasing the annular seals independently from one another against the common radial face.
In a third aspect, there is provided a method for sealing a space between a radial face of a seal runner portion of a shaft and a structure, comprising: radially superposing a first and a second annular seal in an annular receptacle located in the space; biasing the first annular seal against the radial face of the seal runner portion; and biasing the second annular seal against the radial face of the seal runner portion, the biasing of the first annular seal and the second annular seal being independent from one another.
Further details of these and other aspects of the present invention will be apparent from the detailed description and figures included below.
Reference is now made to the accompanying figures, in which:
Referring to
The sealing device 20 has an annular receptacle 21 that may serve as the structure of the sealing device 20. The annular receptacle 21 may therefore be fixed to the structural component C via a face wall 22, and any appropriate fastener such as bolts F. The connection of the annular receptacle 21 by way of the face wall 22 is one of numerous possible connection arrangements, the connection arrangement being designed as a function of the structure surrounding the shaft S. For example, the annular receptacle 21 could be lodged into a cylindrical passage surrounding the shaft S, may be held axially by lock rings, etc.
Tubular walls 23A and 23B project in an axial direction from the face wall 22. The tubular walls 23A and 23B, referred to concurrently as the tubular walls 23, extend toward the face S1 of the seal runner, with their ends are spaced from the face S1. Therefore, the face wall 22 and the tubular walls 23 jointly define an annular cavity of the sealing device 20, which annular cavity has an annular axial opening at the end of the tubular walls 23.
An annular stopper 24 may be located near or at the annular axial opening. The annular stopper 24 may be generally centrally located between the tubular walls 23. As observed in
The annular receptacle 21 may also have a fluid inlet 27, in fluid communication with the annular cavity, for injection of pressurized fluid, such as air to be used as buffer air. Channels 28 and 29 may also be provided, to accommodate seals 28B and 29A. The seal 28B may be an O-ring, a gasket, etc, made of a material capable of withstanding the pressures and temperatures in the apparatus. Moreover, the material must be resistant to the nature of ambient fluids (e.g., oil). The seal 29A may be used to block debris or solids from penetrating the space between the seal runner of the shaft S and the sealing device 20. For instance, seal 29A may be a felt strip, or the like.
The sealing device 20 has movable components, illustrated in the 30s. The sealing device 20 has a pair of annular seals, concurrently referred to as annular seals 30 but illustrated as 30A and 30B. The annular seals 30 are radially superposed in the annular receptacle 21, and project from the annular axial opening to sealingly contact the face S1. By being radially superposed, the annular seals 30 have different radii, the annular seal 30B shown as having a greater radius than the annular seal 30A. The radially superposed relation may entail having both the annular seals 30 at the same axial position along axis X, and may further entail having both seals 30 concentric about a same axis, i.e., axis X. However, some axial or central offset is possible. The annular seals 30 are made of a material that will wear off gradually, while forming a contact surface conforming to the face S1 they will rub against, to create a dynamic seal interface. For example, the annular seals 30 are made of carbon, or equivalent. The annular seals 30 may differ from one another in terms of material. For example, different grades of carbon may be used.
The seals 30 are displaceable along axis X. For this purpose, the annular seals 30 may have brackets 31, shown as 31A and 31B in
The annular seals 30A and 30B have a stepped cross-sectional shape, to make space for the annular stopper 24 located between them, and to be in sealing contact with the tubular walls 23A and 23B with a nose portion thereof, respectively, and therefore limit fluid leakage therethrough. The stepped cross-section shape results in the presence of radial surfaces coming into contact with the annual stopper 24 to concurrently delimit the movement of the seals 30A and 30B in the axial direction.
It is also considered to use additional annular seals 32A and 32B, respectively, to assist in sealing the space between the annular seals 30, and the respective tubular walls 23. The seals 32 may be O-rings, gaskets, etc, made of a material capable of withstanding the pressures and temperatures in the apparatus. Moreover, the material must be resistant to the nature of ambient fluids (e.g., oil). According to another configuration, the inner surface of the annular seal 30A may be substantially cylindrical, whereas the outer surface of the annular seal 30B may be substantially cylindrical, for example with annular channels machined therein to receive the seals 32. Other configurations are also considered.
Referring to
In the illustrated embodiment, a sealed chamber is defined by the combination of annular cavity of the annular receptacle 21, the annular stopper 24 and the annular seals 30. As shown in
With this arrangement, pressurized fluid, such as buffer air, may be fed to the sealed chamber and therefore pressurize it, and assist in biasing the seals 30 toward the face S1. This buffer air may absorb heat from the annular seals 30. According to an embodiment, the pressure in the sealed chamber is greater than the exterior environment of the shaft S to induce a flow of the pressurized fluid from the sealed cavity to the surroundings, instead of oil leaking through the sealing device 20. As shown in
In operation, a method for sealing the space between the radial face S1 of a seal runner portion of the shaft S and the structure C comprises radially superposing the annular seals 30A and 30B in the annular receptacle 21 located in the space. The first annular seal 30A is biased against the radial face S1 of the seal runner portion. The second annular seal 30B is also biased against the radial face S1 of the seal runner portion, the biasing of the first annular seal 30A and the second annular seal 30B being independent from one another. The independence may be achieved by biasing the first annular seal 30A a first spring 33A, and biasing the second annular seal 30B with a second spring 33B. A sealed chamber may be formed between the annular seals 30, the annular receptacle 21 and the radial face S1 of the seal runner portion, pressurized air being injected in the sealed chamber. Injecting the pressurized air may include leaking the pressurized air between one or both of the annular seals 30 and the radial face S1 of the seal runner portion.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, due to the above-described arrangements, a single jet of cooling oil may suffice to cool the seal runner. The seals 30 move in a generally axial position, in that there may be a slight radial component to the movement. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed.
