Sealing arrangement, turbomachine, and method of operating a turbomachine

Abstract

A sealing arrangement (100) of a shaft (110) is described. The shaft (110) is supported in a bearing housing (120) of a turbomachine between a plain bearing (140) in the bearing housing (120) and an impeller back disc cavity (130) of a rotating impeller (132) of the turbomachine. The sealing arrangement (100) includes an impeller-side seal (102) between the bearing housing (120) and the shaft (110) and separating a cavity (150) within the bearing housing (120) from the impeller back disc cavity (130). The seal includes at least one impeller-side sealing element (104) for axially separating the impeller back disc cavity (130) from an enclosed portion of the seal (102), and at least one shaft portion for forming at least one oil catch chamber (190) located in-between a bearing-side disc (170) and the impeller-side sealing element (104). The sealing arrangement further includes the bearing-side disc (170) for forming a sealing gap (172) between the bearing housing (120) and the shaft (110) and axially separating the cavity (150) from the enclosed portion of the seal (102). The sealing arrangement (100) further includes a protrusion (160) protruding radially from the shaft (110) inside the cavity (150). The protrusion (160) radially extends past an oil outlet (142) of the bearing (140) and comprises a top surface (164) defining a radially outward surface of the protrusion (160), a bearing-side wall (166) extending radially from the shaft (110) to the top surface (164) and a seal-side wall (168) extending from the groove (162) to the top surface (164), wherein the top surface (164) is inclined, a bearing-side portion of the top surface (164) radially extending further outward than a seal-side portion of the top surface (164). The sealing arrangement (100) further includes a groove (162) formed axially in-between the protrusion (160) and the sealing gap (172), a depth of the groove gradually increasing towards the sealing gap. The groove (162) extends axially along the shaft (110) so that the groove (162) and the protrusion (160) cover half the axial distance or more than half the axial distance in-between the bearing-side disc (170) and the bearing (140).

Description

[0001] Sealing arrangement, turbomachine, and method of operating a turbomachine

[0002] Aspects of the invention relate to turbomachines, particularly exhaust gas turbochargers. Aspects of the invention particularly relate to a turbomachine having an improved oil tightness. Aspects of the invention particularly relate to a sealing arrangement of a shaft for being supported in a bearing housing of a turbomachine.

[0003] Technical background

[0004] A turbomachine, such as an exhaust gas turbocharger, is often provided for an internal combustion engine, particularly to improve efficiency and power density of the internal combustion engine. A turbocharger generally includes a turbine in the exhaust pipe of the internal combustion engine and a compressor located before the internal combustion engine, which is connected to the turbine via a common shaft. With the boosting of the internal combustion engine by means of the exhaust gas turbocharger, the filling quantity in the cylinder and thus the fuel mixture is increased and thus a significant power boost for the engine is obtained. Alternatively, the energy combined in the exhaust of the internal combustion engine can be converted into electrical energy or mechanical energy by means of a power turbine. Instead of a compressor as in the case of an exhaust gas turbocharger, a generator or mechanical load may be coupled to the turbine shaft.

[0005] Rotating shafts of exhaust gas turbochargers are usually supported within bearings, such as hydrodynamic plain bearings, supplied by the oil system of the internal combustion engine. In addition to the oil supply of the bearings, the oil may also contribute to cooling of the charging system or power turbine. The oil supplied to the bearings and cooling holes (typically splash oil bores) accumulates inside the bearing housing, from where it is guided by a drain to the exit of the bearing casing.

[0006] A shaft seal between bearing casing and turbine or compressor is used to avoid oil leakage into the gas paths of these components. Under some conditions, such as when idling, or under part load conditions of the internal combustion engine, overpressures can occur inside the bearing casing. These overpressures can be sufficient for a positive pressure gradient across the shaft seal, which can result in a pressure inside the bearing housing being higher than the pressure on the compressor or turbine side. The resulting positive pressure gradient is often the main driver for oil leakage, as oil and oil mist are sucked through the seal from the bearing housing into the gas paths of these components. Typically, the turbine sided shaft seal of a charging system or power turbine comprises noncontacting sealing elements such as e.g. a pre-drain, one or more oil catch chambers and one or more sealing rings. In some cases, additionally sealing air taken from the compressor or an external air supply is used for sealing and cooling purposes. While these solutions offer some degree of oil tightness, it is desirable to improve the oil tightness of such shaft seals even further.

[0007] Thus, there is a need for a sealing arrangement providing an improved oil tightness. The invention provided herein solves the above-stated problem at least in part.

[0008] Summary of the invention

[0009] The invention is set out in the appended set of claims.

[0010] According to an aspect, a sealing arrangement of a shaft is described. The shaft may be configured for being supported in a bearing housing of a turbomachine between a plain bearing in the bearing housing and an impeller back disc cavity of a rotating impeller of the turbomachine. The sealing arrangement includes an impeller-side seal between the bearing housing and the shaft and separating a cavity within the bearing housing from the impeller back disc cavity. The seal includes at least one impeller-side sealing element for axially separating the impeller back disc cavity from an enclosed portion of the seal, and at least one shaft portion for forming at least one oil catch chamber located in-between the bearing-side disc and the impeller-side sealing element. The sealing arrangement further includes a bearing-side disc for forming a sealing gap between the bearing housing and the shaft and axially separating the cavity from the enclosed portion of the seal. The sealing arrangement further includes a protrusion protruding radially from the shaft inside the cavity. The protrusion radially extends past an oil outlet of the bearing, particularly a squeeze film damper exit and / or an axial opening of the radial bearing. The sealing arrangement further includes a groove formed axially in-between the protrusion and the sealing gap, a depth of the groove gradually increasing towards the sealing gap. The groove extends axially along the shaft so that the groove and the protrusion cover half the axial distance or more than half the axial distance inbetween the bearing-side disc and the bearing.

[0011] According to an aspect, a turbomachine is described. The turbomachine may be an exhaustgas turbocharger or power turbine. The turbomachine includes at least one turbine impeller arranged on a shaft, and a bearing housing in which the shaft is rotatably mounted. A sealing arrangement according to aspects and / or embodiments described herein is arranged between the bearing housing and the shaft. According to an aspect, a method of operating a turbomachine is described. The method includes sealing a cavity of a bearing housing from an impeller back disc cavity of a rotating impeller of the turbomachine with a sealing arrangement. The sealing arrangement includes an impeller-side seal between the bearing housing and the shaft and separating a cavity within the bearing housing from the impeller back disc cavity. The seal includes at least one impellerside sealing element for axially separating the impeller back disc cavity from an enclosed portion of the seal, and at least one shaft portion for forming at least one oil catch chamber located in-between the bearing-side disc and the impeller-side sealing element. The sealing arrangement further includes a bearing-side disc for forming a sealing gap between the bearing housing and the shaft and axially separating the cavity from the enclosed portion of the seal. The sealing arrangement further includes a protrusion protruding radially from the shaft inside the cavity. The protrusion radially extends past an oil outlet of the bearing, particularly a squeeze film damper exit and / or an axial opening of the radial bearing. A groove is formed axially in-between the protrusion and the sealing gap, a depth of the groove gradually increasing towards the sealing gap. The groove extends axially along the shaft so that the groove and the protrusion cover half the axial distance or more than half the axial distance inbetween the bearing-side disc and the bearing. The method includes, by rotating the shaft and the protrusion and groove provided on the shaft, directing an oil away from the sealing gap.

[0012] Further advantages, features, aspects and details that can be combined with embodiments described herein are evident from the dependent claims, the description and the drawings.

[0013] Brief description of the Figures

[0014] The details will be described in the following with reference to the figures, wherein

[0015] Fig. 1 is schematic cutaway side view of a sealing arrangement according to embodiments;

[0016] Fig. 2 is a cutaway side view of a sealing arrangement according to embodiments;

[0017] Fig. 3 is a cutaway side view of a sealing arrangement according to embodiments.

[0018] Detailed description of the Figures and of embodiments

[0019] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations.

[0020] Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment applies to a corresponding part or aspect in another embodiment as well.

[0021] Reference is made to European patent application EP 2 375 000 A2 which shows a turbomachine and a sealing arrangement thereof. Aspects of the document, particularly aspects relating to the sealing arrangement shown in Fig. 2 of the document, may help in understanding the present invention, and are incorporated herein by reference.

[0022] Reference is made to European patent application EP 2 743 460 A1 which shows a turbomachine and a sealing arrangement thereof. Aspects of the document, particularly aspects relating to the sealing arrangement shown in Fig. 4 of the document, may help in understanding the present invention, and are incorporated herein by reference.

[0023] Referring now to Fig. 1 , a sealing arrangement 100 according to embodiments is shown. It should be noted that Fig. 1 is schematic in nature, and some features shown in the figure may not be drawn to scale to facilitate understanding of the disclosure. The sealing arrangement 100 will be explained in the following with reference to a turbomachine.

[0024] The sealing arrangement 100 shown in Fig. 1 seals a cavity 150 formed in a bearing housing 120 of a turbomachine against an impeller back disc cavity 130. The sealing arrangement 100 may be particularly suitable for sealing a turbine side of a turbomachine, but may be equally suitable for sealing e.g. a compressor side of the turbomachine.

[0025] One or more oil outlets let out oil into the cavity 150. In the example shown in Fig. 1, an oil outlet 142 is formed by or near the plain bearing 140 so that an oil, e.g. after having lubricated the bearing 140, is released into the cavity 150. For example, the oil outlet 142 may be formed by a bearing bush 144, in-between a bearing bush 144 and the bearing housing 120, and / or be an outlet of a squeeze film damper. In some embodiments, additional oil outlets (not shown), such as splash oil bores, may be provided, e.g. to provide a directed stream of oil e.g. for cooling portions of the cavity 150.

[0026] In the cavity 150, the oil typically collects in a bottom portion to be drained from the cavity 150. It is generally desirable to prevent the oil from reaching the impeller back disc cavity 130 to prevent a loss of oil, coking, added environmental impact or the like. Accordingly, turbomachines often include an impeller-side seal 102 configured for providing oil egress.

[0027] The impeller-side seal 102 is arranged radially between the shaft 110 and the bearing housing 120. The impeller-side seal 102 axially separates the cavity 150 from the impeller back disc cavity 130. The seal includes at least one impeller-side sealing element 104. In the example shown in Fig. 1, the sealing element 104 is a sealing ring clamped against the bearing housing and provided in a groove formed within the shaft 110. In the art, a sealing ring may sometimes be referred to as a piston ring. The shaft 110 may be configured for rotating along the shaft axis 112.

[0028] As shown in Fig. 1, the impeller-side seal 102 includes an enclosed portion, i.e. a portion of the seal 102 not directly accessible by from either the impeller back disc cavity 130 or the cavity 150. As shown in Fig. 1, the sealing element 104 may be provided close to the impeller back disc cavity 130 and / or axially separate the impeller back disc cavity 130 from the enclosed portion of the seal 102. Accordingly, the sealing element 104 may define the enclosed portion of the seal 102.

[0029] The enclosed portion of the seal 102 may further be defined, on a side opposite the sealing element 104, and / or on the bearing side of the seal 102, by a sealing gap 172. The sealing gap 172 may be formed by a bearing-side disc 170. The bearing-side disc 170 may extend radially from the shaft and come into close proximity with the bearing housing 120 to define the sealing gap 172. Accordingly, the bearing-side disc 170 and / or the sealing gap 172 may axially separate the cavity 150 from the enclosed portion of the seal 102. Accordingly, the enclosed portion of the seal 102 may extend in-between the bearing-side disc 170 and the (impeller-side) sealing element 104.

[0030] As shown in Fig. 1 , the sealing arrangement 100 may include at least one oil catch chamber 190 located in-between the bearing side disc 170 and the impeller-side sealing element 104. In the example shown in Fig. 1 , two oil catch chambers 190 are provided. Each oil catch chamber 190 includes a shaft portion, such as a groove, and a bearing-housing portion, such as an opposite groove, the both grooves together forming the oil catch chamber 190. A rotation of the shaft may cause oil entering one of the oil catch chambers 190 to be slung radially outwards, drain and / or collect in the bearing housing portion of the oil catch chambers 190 and flow e.g. towards an oil drain provided in the cavity 150.

[0031] As shown in Fig. 1 , the seal 102 is a non-contact seal. Accordingly, while the oil catch chambers 190 and the sealing element 104 are effective in reducing the amount of oil reaching past the oil catch chamber(s) 190, none of these features, alone or in combination, typically fully prevent a portion of the oil from egressing further towards the impeller side, particularly under conditions in which a pressure gradient from the cavity 150 towards the impeller back disc cavity 130 is present. The addition of further oil drain chambers 190 and / or sealing elements 104 may result in complicated and / or large designs, which may negatively affect manufacturing and / or maintenance cost and / or efficiency of the turbomachine.

[0032] It is therefore desirable to reduce the amount of oil entering the enclosed portion of the seal from the cavity 150, particularly by reducing the amount of oil coming into contact with the sealing gap 172.

[0033] As shown in Fig. 1 , the sealing arrangement 100 includes a protrusion 160 protruding radially from the shaft 110 inside the cavity 150, e.g. outside the enclosed portion of the seal 102. The protrusion may be disc-shaped and / or include an essentially disc-shaped portion. The protrusion 160 extends radially past an oil outlet 142 of the bearing 140. Accordingly, an oil spraying from the oil outlet 142 towards the sealing gap 172 may be hindered from reaching the sealing gap 172 by the protrusion 160.

[0034] The sealing arrangement 100 further includes a groove 162 formed axially in-between the protrusion 160 and the sealing gap 172. A depth of the groove 162 gradually increases towards the sealing gap 172. It should be noted that, while not shown in Fig. 1, the groove 162 may include rounded edges e.g. at the transition between the protrusion 160 and / or the bearingside disc 170.

[0035] The groove 162 extends axially along the shaft 110 so that the groove 162 and the protrusion 160 cover at least half of the axial distance in-between the bearing-side disc 170 and the bearing 140. In other words, more than half the axial length of the cavity 150 in-between a bearing-side wall of the bearing housing 120 and the enclosed portion of the seal 102 are covered by the groove 162 and the protrusion 160.

[0036] According to some embodiments, the protrusion 160 and the groove 162 may be referred to as a sealing cover extension. A conventional sealing cover may be formed by the bearing-side disc 170 and the portion of the bearing housing 120 forming, together with the bearing-side disc 170, the sealing gap 172.

[0037] Beneficially, similar to the operation of the oil catch chambers 190, a rotation of the shaft 110 may cause the protrusion 160 and the groove 162 to direct an oil away from the sealing gap. In particular, the depth of the groove 162 gradually increasing towards the sealing gap 172 may cause an oil flowing within and / or sticking to the groove 162 to be directed towards the protrusion 160, e.g. by centrifugal forces exerted onto the oil. Once the oil reaches the protrusion 160, it flows radially outwards along the protrusion and is slung off towards a sidewall of the cavity 150, from where the oil can pool and be drained. Accordingly, the sealing arrangement 100 may be configured for, when the shaft 110 is rotating, accelerating an oil from the groove 162 towards the protrusion 160, and for slinging the oil off the protrusion 160 radially towards an inner wall of the bearing housing 120.

[0038] According to embodiments, as shown in Fig. 1, the protrusion 160 may include a top surface 164 defining a radially outward surface of the protrusion. The top surface may be inclined so that a bearing-side portion of the top surface 164 radially extends further outward than a sealside portion of the top surface 164. For example, the top surface 164 may be inclined, with respect to the shaft axis 112, at an angle of 5° to 30°, such as about 10° to 20°, such as about 15°, about 20°, about 25°, or about 30°. Accordingly, the top surface 164 may be essentially conical. Beneficially, the top surface 164 being inclined may cause the oil to be slung off towards the bearing side and / or away from the sealing gap 172. A sharp edge formed in the top surface 164 due to the top surface being inclined may promote the oil being slung off the top surface 164.

[0039] The protrusion 160 may include a bearing-side wall 166 extending radially from the shaft 110 to the top surface. The bearing-side wall 166 may form a mechanical barrier for an oil, e.g. to prevent an oil being sprayed from an oil outlet such as the outlet 142 from reaching the sealing gap 172.

[0040] The protrusion 160 may include a seal-side wall 168 extending from the groove 162 to the top surface. A rotation of the seal 102 may cause an oil to flow within the groove 162 towards the seal-side wall 168 and along the seal-side wall 168 towards the top surface 164 from where it is slung off.

[0041] As shown in Fig. 1 , a depth of the groove 162 gradually increases towards the sealing gap 172 and / or the bearing-side disc 170. The depth gradually increasing may be understood as the groove 162 having and / or being formed of an inclined bottom surface. A bearing-side portion of the bottom surface may radially extend further outward than a seal-side portion of the bottom surface. In particular, the bottom surface may be inclined, with respect to the shaft axis 112, at an angle of 5° to 30°, such as about 10° to 20°, such as about 15°, about 20°, about 25°, or about 30°. Accordingly, the groove 162 may be essentially conical and / or a bottom surface of the groove 162 may be essentially conical. According to embodiments, the bearing-side disc 170 may form a wall portion of the groove 162, particularly opposite the seal-side wall 168 of the protrusion. As shown in Fig. 1 , the wall portion may extend radially towards the bearing housing. In some embodiments, e.g. as shown in Fig. 3, the wall portion may have an inclination from the radial direction towards the bearingside, e.g. as formed by an undercut.

[0042] In Fig. 1 , the sealing arrangement 100, particularly the protrusion 160, the groove 162, and the shaft portions forming the oil catch chambers 190 are shown as integrally formed in the shaft. Alternatively, in some embodiments, e.g. as shown in Fig. 2 and 3, the sealing arrangement 100, particularly the shaft portion of the seal 102, may be formed by a sealing bush 180. The sealing bush 180 may be a separate part provided on the shaft 110 and configured for rotating together with the shaft 110. For example, the sealing bush 180 may be shrunk onto a seat on the shaft 110 and an edge formed on the shaft 110 may serves as an axial stop for the sealing bush.

[0043] According to embodiments, as shown in Fig. 1 , the protrusion 160 may radially protrude a length equal to or further from the shaft axis than the bearing-side disc 170. In particular, the protrusion may extend radially further outward than the bearing-side disc 170. This may beneficially cause the oil being flung from the protrusion 160 along a direction pointing away from the sealing gap 172 and / or reduce the likelihood of oil entering the enclosed portion of the seal 102.

[0044] According to embodiments, as shown in Fig. 1 , the depth of the groove 162, particularly near the bearing-side disc 170, may be equal to or lower than a depth of a shaft portion of the at least one oil catch chamber. In Fig. 1 , a portion of the groove closest to the sealing disc 170 has a depth equal to the depth of the oil catch chamber 190. Beneficially, this increases a likelihood that an oil having reached the bearing-side disc 170 on the bearing side of the bearing-side disc 170 to be transported towards the protrusion 160 along the groove 162, instead of entering the sealing gap 172.

[0045] Referring now to Fig. 2, a sealing arrangement 200 according to embodiments is shown in the context of a turbomachine. The sealing arrangement 200 shares several of the features described with reference to the sealing arrangement 100 shown in Fig. 1, and only the differences will be explained.

[0046] The turbomachine includes a turbine impeller 132 arranged on the shaft 110. The shaft is rotatably mounted in the bearing housing 120. The sealing arrangement 200 is arranged inbetween the bearing housing 120 and the shaft 110. The sealing arrangement 200 includes two oil catch chambers 190, 192. As shown in the figure, the bearing-side oil catch chamber 190 is larger than the impeller-side oil catch chamber, particularly since a volume of oil expected to enter the oil catch chamber 192 is lower. The oil catch chambers 190, 192 are formed by a shaft portion and a corresponding bearing housing portion.

[0047] As shown in Fig. 2, an insert 182 is provided in the region of the sealing arrangement 100. The insert 182 may form a portion of the bearing housing 120. The insert 182 includes the cutouts forming the bearing housing portion of the oil catch chambers 190, 192.

[0048] The sealing arrangement 200 includes two sealing elements 104. In the embodiment shown in Fig. 2, air is introduced in-between the impeller back disc cavity 130 and the impeller-side sealing ring 104. The air may improve cooling of the sealing arrangement 100 and further improve oil tightness.

[0049] The bearing 140 is a plain bearing having an oil film damper. Oil is let out from the bearing 140 into the cavity 150 through an opening in a bearing cover forming the oil outlet 242.

[0050] As shown in Fig. 2, the groove 162 has rounded edges in-between the seal-side wall 168 and the bearing-side disc 170. Accordingly, a depth of the groove 162 may gradually increase inbetween the rounded edges.

[0051] As shown in Fig. 2, the bearing housing 120 may be shaped so that an inside surface of the cavity 150 has an inclined surface, particularly in an area radially outward of the protrusion 160. The inclined surface may cause an oil being flung towards the inclined surface from the protrusion 160 to be directed towards the bearing-side and / or away from the sealing gap 172.

[0052] Referring now to Fig. 3, a sealing arrangement 300 according to embodiments is shown in the context of a turbomachine. The sealing arrangement 300 shares several of the features described with reference to the sealing arrangement 100 shown in Fig. 1 and / or the sealing arrangement 200 shown in Fig. 2, and only the differences will be explained.

[0053] The sealing arrangement 300 includes two a single sealing element 304. In the embodiment shown in Fig. 3, air is introduced in-between the impeller back disc cavity 130 and the impellerside sealing ring 104. The air may improve cooling of the sealing arrangement 100 and further improve oil tightness.

[0054] As shown in Fig. 3, a gap is formed between the shaft 110 and the sealing bush 180 in the region of the groove 162 and the protrusion 160. Accordingly, the bearing-side wall 166 may extend radially outwards from the sealing bush 180, and a continuous connection to the shaft is not required.

[0055] As shown in Fig. 3, the sealing disc 170 continuously merges into a bottom portion of the oil catch chamber 190. Accordingly, in some embodiments, the sealing disc 170 may have a disclike shape only at the bearing side and / or adjacent the groove 162.

[0056] As shown in Fig. 3, the sealing disc 170 forms a wall portion of the groove 162 and extends at an inclination from the radial direction towards the bearing-side. In particular, as shown in Fig. 3, the wall portion of the groove 162 has an undercut.

[0057] The bearing 140 is a plain bearing having an oil film damper. As shown in Fig. 3, the bearing cover 340 has a portion extending axially towards the impeller side and forms a chamber, particularly an oil drain chamber, in-between a bearing bush 144 and the cavity 150. A gap 342 is formed between the bearing cover 340 and the shaft 110, the gap being an oil outlet. As shown in Fig. 3, the protrusion 160 extends radially further outward than the gap 342.

[0058] Beneficially, as shown in Fig. 1 , Fig. 2, and Fig. 3, the addition of the groove 162 and the protrusion 160 may cause the cavity 150 to operate similar to the oil catch chambers 190, 192 without requiring a corresponding groove in the bearing housing 120. Beneficially, the proposed solutions may be implemented by modifying the sealing bush 180 and with no or only minor alterations to the bearing housing 120.

[0059] According to embodiments, the use of a sealing arrangement according to embodiments, such as the sealing arrangement 100, 200, 300 described with reference to the figures, in a turbomachine is described. The turbomachine may include at least one impeller arranged on the shaft 110, such as a turbine wheel or a compressor wheel. The turbomachine includes a sealing arrangement 100, 200, 300 according to aspects and / or embodiments described herein. The turbomachine may be an exhaust gas turbocharger. In particular, the turbomachine may be a turbocharger for industrial applications, such as marine applications, such as for a marine diesel engine. The turbomachine may be particularly suitable for engines having a power rating of 1000 kW or above, particularly of 10 MW or above, or even 20 MW or above.

[0060] According to embodiments, a method of operating a turbomachine is described. The method includes sealing a cavity 150 of a bearing housing 120 from an impeller back disc cavity of a rotating impeller of the turbomachine with a sealing arrangement, such as the sealing arrangement 100, 200, 300 described herein with reference to embodiments. In particular, the sealing arrangement may include an impeller-side seal 102 between the bearing housing 120 and the shaft 110 and separating a cavity 150 within the bearing housing 120 from the impeller back disc cavity 130. The seal 102 may include at least one impellerside sealing element 104 for axially separating the impeller back disc cavity 130 from an enclosed portion of the seal 102, and at least one shaft portion for forming at least one oil catch chamber located in-between the bearing-side disc 170 and the impeller-side sealing element 104.

[0061] The sealing arrangement may further include a bearing-side disc 170 for forming a sealing gap 172 between the bearing housing 120 and the shaft 110 and axially separating the cavity 150 from the enclosed portion of the seal 102, and a protrusion 160 protruding radially from the shaft 110 inside the cavity 150. The protrusion may radially extend past an oil outlet 142 of the bearing 140. A groove 162 may be formed axially in-between the protrusion 160 and the sealing gap 172. A depth of the groove 162 may gradually increase towards the sealing gap 172. The groove 162 may extend axially along the shaft 110 so that the groove 162 and the protrusion 160 cover half the axial distance or more than half the axial distance in-between the bearing-side disc 170 and the bearing 140.

[0062] The method includes rotating the shaft 110 and the protrusion and groove provided on the shaft. By rotating the shaft, an oil is directed away from the sealing gap. In particular, an inclination of the groove may direct the oil away from the sealing gap and towards the protrusion. In particular, the oil may be directed, e.g. along a seal-side wall 168 of the protrusion 160, towards a top surface 164 of the protrusion. In particular, the oil may be flung off the top surface 164 radially towards an inner sidewall of the cavity 150. Beneficially, since the protrusion is located at least half the axial distance of the bearing-side disc and the bearing 140 away from the sealing gap 172, the oil is flung away so that a chance of the oil splashing towards the sealing gap 172 is low.

[0063] Beneficially, the solutions provided herein provide a more efficient sealing arrangement in which an oil tightness of a sealing arrangement of a turbomachine may be improved with no or only minor changes to the design of the bearing housing of the turbomachine. Beneficially, the turbomachine may have a particularly improved oil tightness under part-load or idling conditions. List of reference numerals

[0064] 100 sealing arrangement

[0065] 102 seal

[0066] 104 sealing element

[0067] 110 shaft

[0068] 112 shaft axis

[0069] 120 bearing housing

[0070] 130 impeller back disc cavity

[0071] 132 turbine impeller

[0072] 140 bearing

[0073] 142, 242 oil outlet

[0074] 144 bush

[0075] 150 cavity

[0076] 160 protrusion

[0077] 162 groove

[0078] 164 top surface

[0079] 166 bearing-side wall

[0080] 168 seal-side wall

[0081] 170 bearing-side disc

[0082] 172 sealing gap

[0083] 180 sealing bush

[0084] 182 insert

[0085] 190 oil drain chamber

[0086] 192 oil drain chamber

[0087] 200 sealing arrangement

[0088] 300 sealing arrangement

[0089] 304 sealing element

[0090] 340 bearing cover

[0091] 342 gap

Claims

Claims:

1. Sealing arrangement (100) of a shaft (110) for being supported in a bearing housing (120) of a turbomachine between a plain bearing (140) in the bearing housing (120) and an impeller back disc cavity (130) of a rotating impeller (132) of the turbomachine, comprising an impeller-side seal (102) between the bearing housing (120) and the shaft (110) and separating a cavity (150) within the bearing housing (120) from the impeller back disc cavity (130), the seal (102) comprising: at least one impeller-side sealing element (104) for axially separating the impeller back disc cavity (130) from an enclosed portion of the seal (102); and at least one shaft portion for forming at least one oil catch chamber (190) located inbetween a bearing-side disc (170) and the impeller-side sealing element (104); the sealing arrangement (100) further comprising: the bearing-side disc (170) for forming a sealing gap (172) between the bearing housing (120) and the shaft (110) and axially separating the cavity (150) from the enclosed portion of the seal (102); a protrusion (160) protruding radially from the shaft (110) inside the cavity (150), wherein the protrusion (160) radially extends past an oil outlet (142) of the bearing (140), wherein the protrusion (160) comprises: a top surface (164) defining a radially outward surface of the protrusion (160); a bearing-sidewall (166) extending radially from the shaft (110) to the top surface (164); and a seal-side wall (168) extending from the groove (162) to the top surface (164), wherein the top surface (164) is inclined, a bearing-side portion of the top surface (164) radially extending further outward than a seal-side portion of the top surface (164); and a groove (162) formed axially in-between the protrusion (160) and the sealing gap (172), a depth of the groove (162) gradually increasing towards the sealing gap (172), wherein the groove (162) extends axially along the shaft (110) so that the groove (162) and the protrusion (160) cover half the axial distance or more than half the axial distance in-between the bearingside disc (170) and the bearing (140).

2. The sealing arrangement according to any one of the preceding claims, wherein the groove (162) comprises an inclined bottom surface, a bearing-side portion of the bottom surface radially extending further outward than a seal-side portion of the bottom surface.

3. The sealing arrangement (100) according any one of the preceding claims, wherein the bearing-side disc (170) forms a wall portion of the groove (162), the wall portion extending radially or at an inclination from the radial direction towards the bearing-side.

4. The sealing arrangement (100) according to claim 3, wherein the groove (162) is an essentially conical groove.

5. The sealing arrangement (100) according to any one of the preceding claims, wherein the sealing arrangement (100) is configured for, when the shaft (110) is rotating, accelerating an oil from the groove (162) towards the protrusion (160), and for slinging the oil off the protrusion (160) radially towards an inner wall of the bearing housing (120).

6. The sealing arrangement (100) according to any one of the preceding claims, wherein the protrusion (160) comprises an essentially disc-shaped portion.

7. The sealing arrangement (100) according to any one of the preceding claims, wherein the shaft (110) comprises a shaft sealing bush (180), the shaft sealing bush (180) comprising the sealing arrangement (100).

8. The sealing arrangement (100) according to any one of the preceding claims, wherein the at least one impeller-side sealing element (104) comprises a sealing ring.

9. The sealing arrangement (100) according to any one of the preceding claims, wherein the protrusion (160) radially protrudes a length equal to or further from the shaft axis than the bearing-side disc (170), and whereinthe depth of the groove (162) is equal to or lower than a depth of a shaft portion of the at least one oil catch chamber (190).

10. Turbomachine, particularly exhaust-gas turbocharger or power turbine, comprising at least one turbine impeller (132) arranged on a shaft (110), and a bearing housing (120) in which the shaft (110) is rotatably mounted, wherein a sealing arrangement (100) according to any one of claims 1 to 9 is arranged between the bearing housing (120) and the shaft (110).

11. The turbomachine according to claim 10, further comprising at least one oil catch chamber (190, 192) being formed by the at least one shaft portion and at least one corresponding bearing housing portion, the at least one oil catch chamber comprising two oil catch chambers (190, 192) arranged in-between the sealing gap (172) and the at least one impeller-side sealing element (104).

12. The turbomachine according to claim 11, wherein the bearing housing (120) comprises, in the region of the sealing arrangement (100), an insert (182) into which are introduced cutouts which form the bearing housing portion for forming the at least one oil catch chamber (190, 192).

13. Method of operating a turbomachine, comprising: sealing a cavity (150) of a bearing housing (120) from an impeller back disc cavity of a rotating impeller of the turbomachine with a sealing arrangement (100), the sealing arrangement (100) comprising: an impeller-side seal (102) between the bearing housing (120) and the shaft (110) and separating a cavity (150) within the bearing housing (120) from the impeller back disc cavity (130), the seal (102) comprising: at least one impeller-side sealing element (104) for axially separating the impeller back disc cavity (130) from an enclosed portion of the seal (102); and at least one shaft portion for forming at least one oil catch chamber located in-between the bearing-side disc (170) and the impeller-side sealing element (104); the sealing arrangement (100) further comprising:a bearing-side disc (170) for forming a sealing gap (172) between the bearing housing (120) and the shaft (110) and axially separating the cavity (150) from the enclosed portion of the seal (102); a protrusion (160) protruding radially from the shaft (110) inside the cavity (150), wherein the protrusion radially extends past an oil outlet (142) of the bearing (140); wherein the protrusion (160) comprises: a top surface (164) defining a radially outward surface of the protrusion (160); a bearing-sidewall (166) extending radially from the shaft (110) to the top surface (164); and a seal-side wall (168) extending from the groove (162) to the top surface (164), wherein the top surface (164) is inclined, a bearing-side portion of the top surface (164) radially extending further outward than a seal-side portion of the top surface (164); and a groove (162) formed axially in-between the protrusion (160) and the sealing gap (172), a depth of the groove (162) gradually increasing towards the sealing gap (172), wherein the groove (162) extends axially along the shaft (110) so that the groove (162) and the protrusion (160) cover half the axial distance or more than half the axial distance in-between the bearingside disc (170) and the bearing (140), the method comprising: by rotating the shaft (110) and the protrusion (160) and groove (162) provided on the shaft (110), directing an oil away from the sealing gap (172).

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