Sealing of at least one shaft by at least one hydraulic seal

An arrangement (30, 80) for sealing a shaft (40, 60, 90, 110) in a casing (31, 81) by a hydraulic seal (50, 70, 100, 120) includes at least one essentially annular, radially inwardly open cavity (51, 71, 101, 121) and at least one essentially annular, radially outwardly directed sealing element (54, 74, 102, 122) which projects into the cavity (51, 71, 101, 121). To provide a hydraulic shaft seal, in which swirl and friction losses in the sealing medium are low and no leakage occurs, the hydraulic seal (50, 70, 100, 120) is arranged on the inner side (42, 62, 92) or on the outer side (111) of the shaft (40, 60, 90, 110) and the cavity (51, 71, 101, 121) or the sealing element (54, 74, 102, 122) of the hydraulic seal (50, 70, 100, 120) is connected to a wall (32, 82) of the casing (31, 81).

This application claims priority to German Patent Application DE102007060890.1 filed Dec. 14, 2007, the entirety of which is incorporated by reference herein.

This invention relates to an arrangement for sealing at least one shaft arranged in a casing by at least one hydraulic seal. Furthermore, the present invention relates to the application of the arrangement in an aeronautical or aerospace jet engine or in chemical or process plants.

In the art, a great variety of static and dynamic seals are known, with the dynamic seals being subdivided into contacting seals and non-contacting seals. Seals on shafts play a particularly important role. The best known and most frequently used contacting seals on shafts are glands, shaft sealing rings, brush seals and piston rings. As non-contacting shaft seals, use is especially made of gap seals, labyrinth seals or centrifugal seals. In the case of centrifugal seals, a hydraulic sealing medium, in particular oil, is set into rotation by centrifugal action, thereby filling an annular gap and providing a seal. Therefore, centrifugal seals are frequently also referred to as hydraulic seals.

Especially with multi-shaft jet engines, the problem is encountered that shafts must be sealed against each other to separate high-pressure and low-pressure zones from each other. For this application, hydraulic seals have been known whose components co-rotate with the shafts or in the sealing medium between the shafts.

Specifications EP 1 045 178 B1 and DE 10 2004 040 242 A1 each describe a hydraulic sealing arrangement in a jet engine for sealing high-pressure and low-pressure zones on rotating shafts arranged within each other. Either hydraulic sealing arrangement essentially has a cavity in the radially outer shaft and a sealing element on the radially inner shaft. Accordingly, the cavity and the sealing element each co-rotate with the associated shaft. The centrifugal force acting upon the sealing medium produces a rotational flow in the sealing medium. The different velocities of cavity and sealing element produce swirl and friction losses in the sealing medium, resulting in heating of the sealing medium and associated coking. Furthermore, neither of the arrangements is suitable for counter-rotating shafts.

In Specification DE 10 2005 047 696 A1, a hydraulic sealing arrangement in a jet engine is described which is capable of sealing counter-rotating shafts. For this purpose, a rib-type, radial barrier fin is provided between two shafts arranged within each other. This barrier fin is floatingly arranged between the shafts. However, since the barrier fin is sealed against the radially inner shaft merely by an air gap, leakage will occur at this point.

The present invention, in a broad aspect, provides a hydraulic shaft seal in which the swirl and friction losses in the sealing medium are low and no leakage occurs.

The present invention provides an arrangement for sealing at least one shaft arranged in a casing by at least one hydraulic seal. The hydraulic seal includes at least one essentially annular, radially inwardly open cavity and at least one essentially annular, radially outwardly directed sealing element which projects into the cavity. The hydraulic seal is arranged on the inner side or the outer side of the shaft, with the cavity or the sealing element of the hydraulic seal being connected to a wall of the casing.

The design, while being a simple form of hydraulic seal, provides for optimum sealing in operation. With the hydraulic seal being alternatively arranged on the inner side or the outer side of the shaft, the arrangement of the hydraulic seal can be varied in accordance with the respective requirements.

Furthermore, the arrangement according to the present invention provides for saving of sealing medium, wear-free operation and relief of the valve system of the bearing chamber. The arrangement is leakage-free and withstands even larger pressure differences.

In particular, the hydraulic sealing arrangement features a stationary seal on the side facing away from the wall. The stationary seal prevents leakage of sealing medium at the shaft when at rest.

In one embodiment, the cavity of the first hydraulic seal is co-rotatingly arranged on the inner side of the shaft and the sealing element is connected to the wall.

In this embodiment, the stationary seal includes an annular disk, which is connected to the inner side of the shaft, and a radially inwardly directed groove into which a piston ring which adjoins an annular extension of the sealing element is inserted. The piston ring prevents leakage of the sealing medium from the hydraulic seal when the shaft is at rest.

In an alternative embodiment, the cavity of the hydraulic seal is provided in the wall and the sealing element is co-rotatingly arranged on the outer side of the shaft. In this embodiment, the weight of the wall is particularly low since the inner diameter of the wall or the cavity, respectively, is larger than with the first embodiment.

In this embodiment, the stationary seal includes an annular disk, which is connected to the wall, and a radially inwardly directed groove into which a piston ring which adjoins the shaft is inserted. As with the first embodiment, the piston ring prevents leakage of the sealing medium at the shaft when the latter is at rest.

In both embodiments, the hydraulic seal can be provided with a cooling device. The cooling device can, for example, effect active flushing of the hydraulic seal and enable the application of the hydraulic seal in the high-temperature area.

Preferably, the cavity of the hydraulic seal is connected via at least one duct to a drain line and/or a space between the shaft and the casing. This enables the sealing medium to be discharged from the hydraulic seal to prevent the sealing medium from dwelling too long in the hydraulic seal and its properties from being affected by heat and friction (coking) in the course of time.

In another embodiment, the wall separates at least two shafts from each other, with a first hydraulic seal being arranged on the first shaft and a second hydraulic seal being arranged on the second shaft. Using one hydraulic seal on the first shaft and another one on the second shaft enables counter-rotating shafts to be sealed by two hydraulic seals.

In this embodiment, the first hydraulic seal and the second hydraulic seal each feature one stationary seal on the side facing away from the wall. Here again, the stationary seals prevent leakage of oil when at rest.

In yet another embodiment, the second hydraulic seal is arranged in the interior of the first hydraulic seal. With this arrangement, the second hydraulic seal is integrated into the first hydraulic seal, providing for compactness of the design.

In this embodiment, the second hydraulic seal includes an essentially annular cavity in the sealing element of the first hydraulic seal and an essentially annular sealing element of the second hydraulic seal which projects into the cavity in the sealing element of the first hydraulic seal. Although the second hydraulic seal is integrated in the first hydraulic seal, separate sealing of the two shafts is ensured. Furthermore, weight and installation space of the arrangement are kept low.

Preferably, the sealing element of the first hydraulic seal is connected to the wall and the sealing element of the second hydraulic seal is connected to the second shaft. This prevents movement of a sealing element by two counter-rotating shafts, as described, for example, in Specification DE 10 2005 047 696 A1, and the losses being caused therefrom.

Furthermore, in the fourth embodiment, a second duct is arranged in the sealing element of the first hydraulic seal which connects the cavity of the second hydraulic seal with the cavity of the first hydraulic seal. Via the second duct, the sealing medium can be discharged from the cavity of the first hydraulic seal.

In this embodiment, only the first hydraulic seal is provided with a stationary seal on the side facing away from the wall. A single stationary seal is sufficient since the second hydraulic seal is arranged in the interior of the first hydraulic seal.

In the third and fourth embodiment, the first shaft and the second shaft can be counter-rotating shafts. Here, the arrangement according to the present invention is advantageous in that each of the shafts is sealed against a non-co-rotating item, i.e. a cavity or a sealing element.

In all embodiments, at least one injection nozzle is arranged on the first hydraulic seal. The injection nozzle enables the sealing medium to be supplied to the first hydraulic seal in a defined manner.

Furthermore at least one second injection nozzle can be arranged on the second hydraulic seal. The second injection nozzle enables the sealing medium to be supplied to the second hydraulic seal in a defined manner.

Alternatively, in the fourth embodiment, only the second hydraulic seal is provided with at least one injection nozzle. With the sealing medium being forwarded to the first hydraulic seal via the second duct, a second injection nozzle for the first hydraulic seal is not required.

The arrangement can be used in an aeronautical or aerospace jet engine. On jet engines, areas of different pressures encounter each other, for example in the compressor section. Owing to its low maintenance effort, at least one hydraulic seal of the arrangement is particularly suitable to seal these areas. Furthermore, the arrangement can be used in chemical and process plants.

FIG. 1shows a cutaway through a casing with a bearing arrangement for two shafts10,20in a jet engine according to the state of the art. The casing encloses a bearing chamber1.

The bearing chamber1encloses an oil injection device2, an inner wall3, a forward brush seal4and a rearward brush seal5. Also arranged in the bearing chamber1are the first shaft10with a first bearing13, a first threaded connection14and a first brush seal15. In the bearing chamber1are further arranged the second shaft20with a second bearing23, a second threaded connection24and a second brush seal25.

The bearing chamber1is subdivided by the inner wall3into two low-pressure zones, N1and N2. The first shaft10has an outer side11and an inner side12. The second shaft20has an outer side21and an inner side22.

In the first low-pressure zone N1, the first bearing13carries the first shaft10and is attached in the bearing chamber1by the first threaded connection14. The first threaded connection14also attaches the inner wall3to the bearing chamber1. The forward brush seal4is arranged between the bearing chamber1and the first shaft10. The first brush seal15is provided between the inner wall3and the outer side11of the first shaft10.

In the second low-pressure zone N2, the second bearing23carries the second shaft20and is attached in the bearing chamber1by the second threaded connection24. The rearward brush seal5is arranged between the bearing chamber1and the second shaft20. The second brush seal25is provided between the inner wall3and the outer side21of the second shaft20. By a threaded connection6, the oil injection device2is attached to the bearing chamber1.

The first shaft10and the second shaft20are concentrically arranged about the same horizontal (longitudinal) axis, and partly extend within each other, with the longitudinal axis not being shown. The first shaft10bears the low-pressure compressor, while the second shaft20bears high-pressure compressor, with both compressors not being shown.

The brush seals4,5,15,25are conventionally designed, with the individual components not being shown. On each brush seal4,5,15,25, radially inwardly directed bristles are fitted on the radially inner rim of an annular disk which contact the outer sides11,21of the first and the second shaft10,20, respectively.

In operation, the bearing chamber1is, in a compressor of a jet engine, surrounded by a high-pressure zone H in which the high pressure of the compressed air is present. The high-pressure zone H reaches into the interior of the first and the second shaft10,20. The first low-pressure zone N1and the second low-pressure zone N2in the bearing chamber1ideally have identical pressures so that the inner wall3is not loaded. The oil required for lubricating the first and the second bearing13,23is supplied to the bearings13,23by the oil injection device2and is swirled in the bearing chamber1. The oil-air mixture produced in each case is separately exhausted from the first low-pressure zone N1and the second low-pressure zone N2, thereby producing the low pressures.

The forward brush seal4seals the first low-pressure zone N1between the bearing chamber1and the first shaft10against the high-pressure zone H. Sealing between the inner wall3and the first shaft10is done by the first brush seal15.

The rearward brush seal5seals the second low-pressure zone N2between the bearing chamber1and the second shaft20against the high-pressure zone H. Sealing between the inner wall3and the second shaft20is done by the second brush seal25.

The first shaft10of the low-pressure compressor rotates slower than the second shaft20of the high-pressure compressor. Also, the two shafts10,20rotate in opposite directions. Therefore, the bristles of the forward brush seal4and of the first brush seal15slip over the outer side11of the first shaft10only. The bristles of the rearward brush seal5and of the second brush seal25slip over the outer side21of the second shaft20only.

FIG. 2shows a cutaway of the first embodiment of an arrangement30according to the present invention in the above mentioned compressor of a jet engine.

The arrangement30includes a casing with a bearing chamber31, a wall32appertaining to the bearing chamber31, a first shaft40, a first bearing43, a first labyrinth seal44and a first hydraulic seal50with a first injection nozzle59. Furthermore the arrangement30includes a second shaft60, a second bearing63, a second labyrinth seal64and a second hydraulic seal70with a second injection nozzle79.

The first shaft40has an outer side41and an inner side42. The second shaft60has an outer side61and an inner side62. The first shaft40and the second shaft60have a common longitudinal axis, this axis not being shown.

The first hydraulic seal50includes a cavity51, an insert52, a retaining ring53, a sealing element54with a connecting element55and an extension55a, an annular disk56with a groove57and a piston ring58. The second hydraulic seal70includes a cavity71, an insert72, a retaining ring73, a sealing element74with a connecting element75and an extension75a, an annular disk76with a groove77and a piston ring78.

The arrangement30is located in a casing which hereinafter is referred to as bearing chamber31. The vertical wall32subdivides the bearing chamber31into a first low-pressure zone N1and a second low-pressure zone N2.

The first shaft40projects horizontally into the first low-pressure zone N1. The first bearing43is attached in the bearing chamber31and carries the first shaft40. The first hydraulic seal50is located on the inner side42of the first shaft40.

The first hydraulic seal50is confined towards the first low pressure zone N1by the annular insert52which is angled radially inwards. The insert52is arranged on the inner side42of the first shaft40and secured by the retaining ring53. Towards the high-pressure zone H, the first hydraulic seal50is confined by the annular disk56which extends radially inwards and is firmly connected to the first shaft40. The insert52and the annular disk56together form the annular cavity51.

The annular sealing element54projects radially into the cavity51. Adjoining the sealing element54in the direction of the first low-pressure zone N1is the annular connecting element55which is firmly connected to the wall32. Adjoining the sealing element54in the direction of the high-pressure zone H is the again annular extension55a. The annular disk56is connected to the inner side42of the first shaft40and has, on its inner circumference, a stationary seal45which includes the inwardly directed radial groove57and the piston ring58inserted therein. The piston ring58radially inwardly adjoins the extension55aof the sealing element54.

The first injection nozzle59is directed towards an annular interspace existing between the insert52and the annular connecting element55of the sealing element54. Located on the outer side41of the first shaft40is the first labyrinth seal44which is connected to the bearing chamber31.

The second shaft60projects horizontally into the second low-pressure zone N2. The second bearing63is attached in the bearing chamber31and carries the second shaft60. The second hydraulic seal70is located on the inner side62of the second shaft60.

The second hydraulic seal70is confined towards the second low pressure zone N2by the annular insert72which is angled radially inwards. The insert72is arranged on the inner side62of the second shaft60and secured by the retaining ring73. Towards the high-pressure zone H, the second hydraulic seal70is confined by the annular disk76which extends radially inwards and is firmly connected to the second shaft60. The insert72and the annular disk76together form the annular cavity71.

The annular sealing element74projects radially into the cavity71. Adjoining the sealing element74in the direction of the second low-pressure zone N2is the annular connecting element75which is firmly connected to the wall32. Adjoining the sealing element74in the direction of the high-pressure zone H is the again annular extension75a. The annular disk76is connected to the inner side62of the second shaft60and has, on its inner circumference, a stationary seal65which includes the inwardly directed radial groove77and the piston ring78inserted therein. The piston ring78adjoins the extension75aof the sealing element74.

The second injection nozzle79is directed towards an annular interspace existing between the insert72and the annular connecting element75of the sealing element74. Located on the outer side61of the second shaft60is the second labyrinth seal64which is connected to the bearing chamber31.

In lieu of the labyrinth seals44and64, one hydraulic seal each could be provided between the bearing chamber31and the outer side41of the first shaft40or the outer side61of the second shaft60, respectively.

In operation, the bearing chamber1is surrounded, as in the state of the art (cf.FIG. 1), by a high-pressure zone H in a compressor of the jet engine in which the high pressure of the compressed air is present. The high-pressure zone H reaches into the interior of the first and second shaft40,60.

By first injection nozzle59, oil is injected through the interspace between the insert52and the connecting element55of the sealing element54into the first hydraulic seal50. The insert52co-rotates with the first shaft40, thus producing a centrifugal force in the injected oil. The oil is transported radially outwards within the cavity51. As a result, the oil33fills the radially outward area of the cavity51and, hence, the gap between the insert52and the sealing element54. Owing to the high pressure in the high-pressure zone H, the oil33is additionally forced into the cavity51. Accordingly, the oil33forms a seal between the first low-pressure zone N1and the high-pressure zone H.

The cavity51can additionally be provided with a duct by which the oil33is removed from the cavity51and supplied to a cooling device not shown. Upon passing the cooling device, the oil33can be re-supplied to the first hydraulic seal50.

Upon standstill of the first shaft40, the piston ring58of the stationary seal45will come to rest against the extension55aof the sealing element54, thus preventing leakage of the oil33which, in the absence of centrifugal force, is no longer pressed into the cavity51.

Oil is injected through the interspace between the insert72and the connecting element75of the sealing element74into the second hydraulic seal70by the second injection nozzle79. The insert72co-rotates with the second shaft60, thus producing a centrifugal force in the injected oil. The oil is transported radially outwards within the cavity71. As a result, the oil34fills the radially outward area of the cavity71and, hence, the gap between the insert72and the sealing element74. Owing to the high pressure in the high-pressure zone H, the oil34is additionally forced into the cavity71. Accordingly, the oil34forms a seal between the second low-pressure zone N2and the high-pressure zone H.

The cavity71can additionally be provided with a duct by which the oil34is removed from the cavity71and supplied to a cooling device not shown. Upon passing the cooling device, the oil34can be re-supplied to the second hydraulic seal70.

With the first hydraulic seal50and the second hydraulic seal70being separate from each other, for example different oils for different applications, as applicable, can be used in the first low-pressure zone N1and in the second low-pressure zone N2.

Upon standstill of the second shaft60, the piston ring78of the stationary seal65will come to rest against the extension75aof the sealing element74, thus preventing leakage of the oil34which, in the absence of centrifugal force, is no longer pressed into the cavity71.

FIG. 3shows a cutaway of the second embodiment of an arrangement80according to the present invention in the above mentioned compressor of a jet engine.

The arrangement80includes a wall82appertaining to the casing or to the bearing chamber81, respectively, a first shaft90, a first bearing95, a first shaft seal96and a first hydraulic seal100. Furthermore the arrangement80includes a second shaft110, a second bearing115, a second shaft seal116, a second hydraulic seal120and an injection nozzle133.

The first shaft90has an outer side91, an inner side92, a shaft end93and an extension94with a duct104. The second shaft110has an outer side111, an inner side112, a shaft end113and an extension114. The first shaft90and the second shaft110have a common longitudinal axis84.

The first hydraulic seal100includes a cavity101, a sealing element102with a duct104and a connecting element103as well as an annular disk130with a groove131and a piston ring132, which form a stationary seal125. The second hydraulic seal120includes a cavity121and a sealing element122with an extension114at the shaft end113.

The arrangement80is located in a casing which hereinafter is referred to as bearing chamber81. The vertical wall82subdivides the bearing chamber81into a first low-pressure zone N1and a second low-pressure zone N2.

The first shaft90projects horizontally into the first low-pressure zone N1. The first bearing95is attached in the bearing chamber81and carries the first shaft90. The first hydraulic seal100adjoins the shaft end93. Located on the outer side91of the first shaft90is the first shaft seal96which is connected to the bearing chamber81.

The first hydraulic seal100is confined towards the first low-pressure zone N1by the extension94of the first shaft90. The extension94is annular, has a U-shaped cross-section and is open radially inwards. Arranged in parallel to the longitudinal axis84and towards the wall82is the duct104in the extension94. Towards the high-pressure zone H, the first hydraulic seal100is confined by the annular disk130which extends radially inwards and is firmly connected to the first shaft90. On its inner circumference, the annular disk130is provided with the stationary seal125with the radial groove131extending radially inwards and accommodating the piston ring132.

The annular sealing element102with U-shaped, radially inwardly open cross-section projects radially into the cavity101. The sealing element102adjoins the annular connecting element103of the wall82. The duct123provided in the sealing element102is arranged in parallel to the longitudinal axis84and opposite to the wall82.

The second shaft110projects horizontally into the second low-pressure zone N2. The second bearing115is attached in the bearing chamber81and carries the second shaft110. The second hydraulic seal120adjoins the shaft end113. Located on the outer side111of the second shaft110is the second shaft seal116, which is connected to the bearing chamber81.

The second hydraulic seal120is confined towards the first hydraulic seal100by the cross-sectionally U-shaped sealing element102which is connected to the wall82by the annular connecting element103and forms the cavity121.

The annular, solid sealing element122is firmly connected to the shaft end113of the second shaft110and projects radially into the cavity121. Axially adjoining the sealing element122, and extending into the extension94of the first shaft90, is the annular extension114of the second shaft110.

The injection nozzle133is directed towards the annular interspace present between the connecting element103and the shaft end113of the second shaft110of the second hydraulic seal120. Furthermore, an additional injection nozzle can be directed towards the interspace between the extension94and the sealing element102of the first hydraulic seal100.

The first and second shaft seals96and116may also be designed as hydraulic seals.

In operation, the bearing chamber81is, as in the state of the art (cf.FIG. 1), surrounded by a high-pressure zone H in a compressor of the jet engine in which the high pressure of the compressed air is present. The high-pressure zone H reaches into the interior of the first and second shaft90,110.

By the injection nozzle133, oil is injected through the interspace between the connecting element103and the shaft end113of the second shaft110into the second hydraulic seal120. Owing to the rotation of the second shaft110and the sealing element122, a centrifugal force is produced in the injected oil83. The centrifugal force transports the oil83radially outwards within the cavity121. As a result, the oil83fills the radially outward area of the cavity121and, hence, the gap between the sealing element122and the sealing element102. The high pressure in the high-pressure zone H additionally forces the oil83into the cavity121. Accordingly, the oil forms a seal between the second low-pressure zone N2and the high-pressure zone H. Part of the oil is fed from the second hydraulic seal120into the first hydraulic seal100via the duct123.

In the first hydraulic seal100, the oil83is forced into the cavity101by the centrifugal force exerted on it by the rotation of the extension94of the first shaft90. As a result, the oil83fills the cavity101between the extension94and the sealing element102, thereby sealing the low-pressure zone N1against the high-pressure zone H. The high pressure in the high-pressure zone H additionally forces the oil83into the cavity121. When the oil83has passed the cavity101, a partial flow85of the oil83is branched off via the duct104and fed to a cooling device not shown. Upon cooling the oil in the cooling device, the oil can be re-supplied to the first and second hydraulic seal100,120.

In this embodiment, the sealing element102of the first hydraulic seal100has a dual function in that the sealing element102of the first hydraulic seal100simultaneously forms the cavity121of the second hydraulic seal120. Thus, the sealing element102is a common part of the first hydraulic seal100and the second hydraulic seal120.

With the sealing element102being stationary, the arrangement80is especially suitable for counter-rotating shafts, with the first shaft90rotating around the sealing element102on the outside and the second shaft110rotating inside the sealing element102.

Both the extension94and the sealing element102can be made from two annular parts using a friction-welding process. Attachment of the extension94to the shaft end93and of the sealing element102to the connecting element103can be done by flanges not shown.

In lieu of oil, dissimilar hydraulic sealing media may be used provided they are chemically compatible and mixable.

In particular where the arrangement is used in chemical or process plants, it is important that the first low-pressure zone N1and the second low-pressure zone N2are separated from each other by the wall32,82to prevent the gas compositions contained in the low-pressure zones N1, N2from reacting or mixing with each other. In lieu of the gas compositions, a vacuum may predominate in one or both of the two low-pressure zones N1, N2.

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