JP3974571B2 - Seal assembly for rotating machinery - Google Patents

Description

  The present invention relates to a seal assembly for use in a rotating machine such as a gas turbine engine.

  The present invention addresses an important issue in modern designs that are being considered to seal an annulus between two concentric shafts, where a fixed mounting location is present. Therefore, rotation of the sealing element is required. Conventional sealing methods use a solid secondary seal such as a piston ring. In applications between shafts where the sealing element is not fixed, the inertial force experienced by a solid secondary seal creates a high frictional force between the secondary seal and its support element, which reduces axial movement. It is disturbed or at least undesired wear occurs.

  Accordingly, it is an object of the present invention to provide a seal assembly for use with a rotating machine.

  Another object of the present invention is to provide a seal assembly that can seal an annulus formed between two concentric shafts that rotate in the same or opposite directions.

  It is still another object of the present invention to provide a seal assembly that can be applied to seal one shaft and a stator.

  These objects are achieved by the seal assembly of the present invention.

  In accordance with the present invention, a seal assembly for use in a rotating machine is provided. The seal assembly includes a first element, a seal carrier attached to the first element by an attachment element, a second element spaced from the first element, and a seal disposed on the second element. A running element and hydraulic sealing means for preventing gas from leaking from the high pressure supply to the low pressure chamber through the mounting element.

  Other details, objects and attendant advantages of the shaft seal of the present invention are illustrated in the following best mode and accompanying drawings.

  Shown is a seal assembly 10 for a rotating machine that reduces gas leakage from a high pressure source 12 to a low pressure chamber 14, such as a bearing chamber of a gas turbine engine. The seal assembly 10 of the present invention is applicable to an annulus formed between two concentric shafts that rotate in the same or opposite directions. The seal assembly of the present invention is also useful for sealing one shaft and the stator.

  The seal assembly 10 includes a seal travel element 20 and a seal carrier 26. The seal carrier 26 rotates with the first element 28 and is flexibly attached to the first element 28 by a flexible attachment 30. The first element 28 can be the inner axis of the two concentric axes. The flexible attachment portion 30 can be any suitable flexible attachment portion known in the art. The seal carrier 26 is attached so as to be movable in the axial direction with respect to the first element 28. The seal travel element 20 has a primary seal surface 22 facing in the axial direction and attached to the second element 24 or provided on the second element 24. The second element 24 can be the outer axis of the two concentric axes or a fixed element. If desired, the seal travel element 20 can be integrally formed with the second element 24. The primary seal surface 22 requires that the seal travel element 20 and the seal carrier 26 are in close proximity or in contact. The primary seal surface 22 is preferably resistant to high rotational slip and may include a lift geometry that generates a hydrodynamic force that separates the seal carrier 26 and the primary seal surface 22.

Gas leakage through the flexible mounting 30 is prevented by a hydraulic seal 32 that utilizes the inertia of the liquid 34. The hydraulic seal 32 includes a seal carrier 26, a back plate 36, and an L-shaped fin 38. Liquid is supplied to the hydraulic seal 32 through one or more supply holes 40 provided in the first element 28. When the pressure P _h in the source 12 is greater than the pressure P _L in the chamber 14, the liquid surface 42 upstream of the fin 38 stabilizes with a larger radius than the liquid surface 44 downstream. The inner diameters of the front wall 46 and the back plate 36 of the seal carrier 26 are designed to allow the above-described height difference without causing liquid to flow out.

  A preferred embodiment of the seal assembly of the present invention includes continuously refilling the liquid used in the hydraulic seal 32. One or more drain holes 48 are provided on the outer surface of the trough (groove) 49 between the seal carrier 26 and the fins 38 to prevent unwanted particulate matter and foreign matter from accumulating. The continuous replenishment of liquid is also useful for removing heat generated at the primary seal interface. The liquid preferably flows from the supply hole 40 at a speed faster than the speed at which the liquid flows out from the drain hole 48. Excess liquid flows beyond the inner diameter of backplate 36 or front wall 46, depending on design and operating conditions.

Various details can be incorporated into the seal assembly to reduce undesirable liquid drainage from the trough 49 upon a momentary reversal of pressure where P _L is greater than P _h . Features that prevent unwanted liquid capture may also be included. The inner diameter of the front wall 46 is maintained within close tolerances with the guide diameter 52 so as to minimize the leakage area where liquid may flow out of the hydraulic seal 32 upstream of the primary seal. The liquid collected in the trough 51 formed between the primary sealing surface 22 and the front wall 46 can be discharged through the drain hole 50. The drain hole 50 can be designed to minimize gas leakage during normal operation. Under certain operating conditions, a valve may be used to cover part or all of the drain hole 50.

  In some applications, the primary seal interface 22 needs to be resistant to high friction rates. A seal assembly for such an application takes advantage of the hydrodynamic lift force generated by the shape of the surface 22. Also, various primary seal devices are known for lower friction speed applications. Such devices include designs using carbon that is in direct contact with the primary seal interface and may be lubricated with oil. Such a device can be used for the seal interface 22 if desired.

  If desired, the seal assembly 10 of the present invention can be configured such that the seal carrier 26 is flexibly attached to the second element 24 and the seal travel element 20 is attached to the first element 28. In such a configuration, the hydraulic secondary seal 32 rotates with the first element 24.

  The seal assembly of the present invention is advantageous in that no friction or wear occurs in the secondary hydraulic seal due to high inertia loads. Further, the secondary hydraulic seal can allow relative axial movement and displacement between the first element 28 and the second element 24.

  Clearly, the present invention provides a shaft seal that fully satisfies the objects, means, and advantages set forth above. Although the present invention has been described with reference to specific embodiments, other alternatives, modifications and changes will become apparent to those skilled in the art from the foregoing description. Accordingly, such alternatives, modifications and variations that fall within the scope of the claims are also encompassed by the invention.

It is explanatory drawing of the shaft seal assembly which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Seal assembly 12 ... High pressure supply source 14 ... Low-pressure chamber 20 ... Seal running element 22 ... Primary seal surface 24 ... Second element 26 ... Seal carrier 28 ... First element 30 ... Flexible attachment part 32 ... Liquid Pressure seal 36 ... Back plate 38 ... L-shaped fin 40 ... Supply hole 42 ... Upstream liquid surface 44 ... Downstream liquid surface 46 ... Front wall 48, 50 ... Drain hole 49, 51 ... Trough 52 ... Guide diameter

Claims (12)

A rotating shaft having a seal carrier mounted by a flexible mounting element, the seal carrier being axially movable with respect to the rotating shaft by the mounting element; It is provided so as not to rotate relative to
A second element spaced apart from the rotating shaft and comprising a seal travel element;
A mechanical primary sealing surface formed between the seal travel element and the seal carrier;
Together is formed between the seal carrier and the rotary shaft, and further comprising a, a hydraulic sealing means for preventing the gas from leaking into the low pressure chamber from the high pressure chamber through said mounting element Seal assembly for rotating machinery.   The seal assembly for a rotary machine according to claim 1, wherein the seal travel element is formed integrally with the second element. Before Stories second element, the seal assembly for a rotary machine according to claim 1, characterized in that it comprises a second rotary shaft. Before Stories second element, the seal assembly for a rotary machine according to claim 1, characterized in that it comprises a fixing element.   The seal assembly for a rotary machine according to claim 1, wherein the seal carrier is provided in proximity to the seal travel element.   The seal assembly for a rotary machine according to claim 1, wherein the seal carrier is provided in contact with the seal travel element.   The seal assembly for a rotary machine according to claim 1, further comprising liquid supply means for supplying liquid to the hydraulic pressure sealing means. The seal assembly for a rotary machine according to claim 7 , wherein the liquid supply means includes at least one supply hole provided in the rotary shaft . 9. The rotation according to claim 8, wherein the hydraulic pressure sealing means is constituted by the seal carrier, a back plate, and a fin, and has a trough formed by the seal carrier, a front wall, and the fin. Seal assembly for machine. The seal assembly for a rotary machine according to claim 9, wherein the hydraulic pressure sealing means further includes a preventing means for preventing accumulation of undesirable particulate matter and foreign matters. The seal assembly for a rotary machine according to claim 10 , wherein the prevention means includes at least one drain hole provided in an outer surface of the trough. 12. The rotating machine according to claim 11, wherein the liquid flows into the hydraulic pressure sealing means through the at least one supply hole at a speed higher than a speed at which the liquid flows out from the at least one drain hole. Seal assembly for.

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