This application claims priority to German Patent Application DE102008009824.8 filed Feb. 19, 2008, the entirety of which is incorporated by reference herein.
The present invention relates to a sealing arrangement.
More particularly, the present invention relates to a sealing arrangement which, in particular, is used for sealing a bearing chamber of a gas turbine.
With gas turbines, it is known to provide a sealing ring in the bearing chamber to seal an area of the bearing chamber containing air and oil against an external area with air of higher pressure.
The state of the art (see
Such seals for bearing chambers are usually provided with a sealing ring, additionally a labyrinth seal may be provided.
A small, annular gap 4 exists between the second part 2a, 2b and the first part 1.
With regard to the aforementioned labyrinth seal, provision of an additional labyrinth seal in conjunction with the sealing ring may be problematic under certain design conditions. Therefore, a preferential arrangement includes one sealing ring on each side of the bearing chamber. However, if the air pressure (right-hand side in
It is a broad aspect of the present invention to provide a sealing arrangement of the type specified at the beginning, which while being simply designed and featuring good sealing efficiency, can be manufactured easily and cost-effectively and avoids the disadvantages of the state of the art.
In accordance with the present invention, it is therefore provided that either the sealing ring or the radially outer part features at least one pressure compensation hole. With the pressure difference across the sealing ring thus being reduced, the total force acting upon the sealing ring will not be sufficient to keep it in permanent contact with the flange (surface of the radial groove). This ensures that the sealing ring will not contact the outer part and/or adhere to it under high friction. Consequently, wear of the sealing ring is considerably reduced.
According to the present invention, the pressure compensation hole can be provided in the axial direction. However, the pressure compensation hole can also be inclined relative to the rotary axis to feed air directly to the side wall of the sealing ring which is in contact with the radial groove. An air bearing is thus provided on which the sealing ring slides. Consequently, static oil losses are avoided since no oil flow can occur when the sealing arrangement is at rest.
In accordance with the present invention, it has shown to be particularly favorable if several pressure compensation holes are equally distributed on the circumference. The preferred minimum number of pressure compensation holes is four, with the holes being preferably offset by 90° C. to each other. Thus, freedom of movement of the sealing ring is ensured.
The pressure compensation holes are preferably dimensioned for the passage of a minimum and a maximum airflow. This dimensioning of the pressure compensation holes enables the airflow entering the bearing chamber to be exactly determined and, consequently, an oil scavenge pump and/or a vent line to be also optimally sized. This results in further cost benefits for the overall bearing arrangement.
The present invention therefore provides for the implementation of a principle in which sealing air flows through the pressure compensation holes. This sealing air provides for an air pressure in the radial groove or annular groove which approximates the pressure in the bearing chamber, resulting, on the whole, in a lower differential pressure in the sealing ring. As mentioned above, this prevents the sealing ring from contacting or adhering to the wall of the radial groove or the annular groove, as were the case with a large pressure difference. Thus, wear of the sealing ring is considerably reduced.
The present invention is more fully described in light of the accompanying drawing showing preferred embodiments. In the drawing,
The Figures each show a radially inner first part 1 in the form of a shaft rotatable about a rotary axis 3. Arranged on a surface 8 of the first part 1 is a sealing ring 6, which is located and held in a radial groove 5 (annular groove) of a radially outer second part 2a, 2b. The radial groove 5 is radially dimensioned larger than the sealing ring 6, enabling the latter to slightly move in the axial direction. This ensures that the sealing ring 6 slides in the radial groove 5, while being non-rotationally fitted to the first part 1.
In the Figures, the zone of bearing air is shown on the right-hand side and the area associated to the bearing chamber (oil/air) on the left-hand side, with the pressure on the right-hand side exceeding that on the left-hand side.
In the embodiment shown in
Number | Date | Country | Kind |
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10 2008 009 824.8 | Feb 2008 | DE | national |