Bearing arrangement for a turbomachine, turbomachine and method of operating a turbomachine

Abstract

A bearing arrangement for a turbomachine is described. The bearing arrangement includes a shaft, a bearing housing configured for supporting the shaft, and a shaft seal provided in a wheel-side partition wall of the bearing housing. The partition wall separates a wheel back space of a rotating wheel of the turbomachine and a cavity in the bearing housing. The bearing arrangement further includes a plain bearing provided adjacent the cavity at an inner-side wall opposite the shaft seal. The plain bearing includes an oil collecting volume configured for collecting oil from a bearing surface of the plain bearing, and an oil drain channel arrangement in fluid communication with the oil collecting volume and configured for draining the oil away from an upper portion of the cavity.

Description

[0001] Bearing arrangement for a turbomachine, 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 bearing arrangement for supporting a shaft of a turbomachine, and an oil drain channel arrangement thereof.

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

[0007] Summary of the invention

[0008] The invention is set out in the appended set of claims.

[0009] According to an aspect, a bearing arrangement for a turbomachine is described. The bearing arrangement includes a shaft, a bearing housing configured for supporting the shaft, and a shaft seal provided in a wheel-side partition wall of the bearing housing. The partition wall separates a wheel back space of a rotating wheel of the turbomachine and a cavity in the bearing housing. The bearing arrangement further includes a plain bearing provided adjacent the cavity at an inner-side wall opposite the shaft seal. The plain bearing includes an oil collecting volume configured for collecting oil from a bearing surface of the plain bearing, and an oil drain channel arrangement in fluid communication with the oil collecting volume and configured for draining the oil away from an upper portion of the cavity.

[0010] According to an aspect, a turbomachine is described. The turbomachine includes a bearing arrangement according to aspects and / or embodiments described herein, and at least one impeller arranged on the shaft.

[0011] According to an aspect, a method of operating a turbomachine is described. The turbomachine includes a shaft seal provided in a wheel-side partition wall of a bearing housing, the partition wall separating a wheel back space of a rotating wheel provided on a shaft of the turbomachine and a cavity in the bearing housing. The turbomachine further includes a plain bearing provided adjacent the cavity at an inner-side wall of the bearing housing opposite the shaft seal. The plain bearing includes an oil collecting volume configured for collecting oil from a bearing surface of the plain bearing. The method includes draining an oil from the plain bearing by collecting the oil from the oil collecting volume and directing the oil away from an upper portion of the cavity.

[0012] According to an aspect, the use of a bearing arrangement according to aspects and / or embodiments described herein in a turbomachine is described. The use may include draining an oil from the plain bearing by collecting the oil from the oil collecting volume and directing the oil away from an upper portion of the cavity.

[0013] According to an aspect, an oil is described. The oil may be a lubricating oil known in the art at the time of filing of this disclosure. In particular, the oil may be an engine oil suitable for lubricating a machine, such as an internal combustion engine having a turbomachine provided thereon, and is not limited to any specific composition. In the following disclosure, the term “oil” may likewise be understood as “lubricant” and / or even “oil-based coolant”.

[0014] Brief description of the Figures

[0015] The details will be described in the following with reference to the figures, wherein

[0016] Fig. 1 is a schematic cutaway side view of a bearing arrangement according to embodiments;

[0017] Fig. 2A is a schematic front view of a bearing plate according to embodiments;

[0018] Fig. 2B is a schematic cutaway side view of a bearing plate according to embodiments;

[0019] Fig. 3A is a schematic front view of a bearing plate according to embodiments;

[0020] Fig. 3B is a schematic cutaway side view of a bearing plate according to embodiments;

[0021] Fig. 4 is a partial cutaway view of a bearing arrangement according to an embodiment.

[0022] Detailed description of the Figures and of embodiments

[0023] 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.

[0024] 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.

[0025] It is understood that a turbomachine according to embodiments is typically provided in a defined position and / or orientation during operation, e.g. when mounted to an internal combustion engine. For example, a turbomachine may be provided so that an inlet of an oil drain channel for draining an oil from a chamber may be located at the lower portion of the chamber. This disclosure generally refers to directions and / or portions of the turbomachine in relation to the intended mounting position. For example, an upper portion of e.g. a cavity should be understood as a portion of the cavity that is oriented in an upper position in the installed turbomachine. It is understood that in some instances, such as when the turbomachine is not in operation, e.g. during transport, assembly or maintenance, an orientation of some of the features may vary, and such variation does not alter the scope of the disclosure.

[0026] Referring now to Fig. 1 , a bearing arrangement 100 according to embodiments is schematically described in the context of a turbomachine. A shaft 110 mechanically connects a compressor side wheel and / or impeller and a turbine side wheel and / or impeller (not shown).

[0027] The bearing arrangement 100 includes a bearing housing 120 for supporting the shaft 110. A bearing 160, such as a plain bearing, is provided in an inner-side wall 124. The inner-side wall 124 extends between the bearing housing 120 and the bearing 160. The inner-side wall 124 may form a portion of the bearing housing 120, and / or may be provided as a separate part. The inner-side wall 124 separates a cavity 150 of the bearing housing 120 from a central bearing casing cavity 190. The bearing 160 supports the shaft 110 so that it is rotatably provided within the bearing 160. As shown in Fig. 1 , the bearing 160 is provided, along an axis of the shaft 110, adjacent the cavity 150 at the inner-side wall 124 opposite the shaft seal 130. The inner-side wall 124, the wheel-side partition wall 122 and the bearing housing 120 define the cavity 150.

[0028] The bearing arrangement 100 includes a shaft seal 130 provided in a wheel-side partition wall 122. The wheel-side partition wall 122 extends between the shaft seal 130 and the bearing housing 120, and separates a wheel back space 140 of a rotating wheel, such as an impeller, such as a turbine wheel or compressor wheel, and the cavity 150. The shaft seal 130 is typically provided to fluidly separate and / or seal the wheel back space 140 from the cavity 150, particularly to prevent an oil, gas, oil mist, or other fluid present in the cavity 150 from entering the wheel back space 140.

[0029] For example, according to some embodiments, the shaft seal 130 may include one or more sealing elements, such as seals, such as piston rings (not shown) provided radially in-between the shaft 110 and the partition wall for sealing the wheel back space 140 from the cavity 150.

[0030] For example, according to some embodiments, the shaft seal 130 may include a sealing disc 134 provided about the shaft 110. The sealing disc 134 is provided axially in-between the partition wall 122 and the bearing 160 and rotates with the shaft 110. When the shaft 110 is rotating, the sealing disc 134 may prevent an oil present in the cavity 150 from reaching the shaft seal 130 by radially flinging the oil outwards, e g. towards a wall of the bearing housing 120 forming an inner wall of the cavity 150. For example, according to some embodiments, the shaft seal 130 may include one or more oil drain grooves (not shown) provided e.g. adjacent the sealing elements. For example, the oil drain groove may be provided in-between the sealing disc 134 and the partition wall 122, and / or be formed in-between the sealing disc 134 and the partition wall 122. The oil drain groove may contribute in and / or be configured for draining oil from the cavity 150 in the bearing housing 120 and / or direct the oil towards an outlet, such as the oil outlet 168.

[0031] In the bearing arrangement 100 shown in Fig. 1 , oil is provided to the bearing 160 through the inlet 164. The bearing 160 shown in Fig. 1 is a plain bearing, such as a radial bearing and / or a hydrodynamic plain bearing, provided within a bearing bush 166. The bearing bush 166 may be provided between the shaft 110 and the bearing housing 120, such as between the shaft 110 and the inner-side wall 124. The oil provided from the inlet 164 may lubricate the bearing 160 and / or function as a squeeze film damper e.g. between the bearing bush 166 and the inner-side wall 124. Additionally, the oil may contribute in cooling the bearing 160 and / or the shaft 110. The bearing includes an oil collecting volume 162 for collecting oil from a bearing surface of the bearing 160. The oil collecting volume 162 may form a channel, particularly an oil channel, in-between the bearing bush 166 and the bearing housing 120, particularly the inner-side wall 124. For example, the oil collecting volume 162 may be a groove or recess provided in-between the inner-side wall 124 and the bearing bush 166. The oil collecting volume 162 may be an annular groove and / or recess. Oil provided from the inlet 164 may flow across the bearing surface and collect in the oil collecting volume 162. From the oil collecting volume 162, the oil flows into an oil drain channel arrangement, such as the oil drain channels 170, 180 schematically shown in Fig. 1 , to be drained. Aspects of the oil collecting volume 162 and the oil drain channel arrangement 170, 180 will be explained in further detail with reference to Fig. 2 and Fig. 3.

[0032] In some embodiments, some or all of the oil may exit the bearing 160 towards the cavity 150. From the cavity 150, the oil flows towards an oil outlet 168 typically provided at a low point and / or downward position within the cavity 150 from where the oil is recirculated.

[0033] The inventors observed that, particularly in case a positive pressure gradient occurs between the cavity 150 and the wheel back space 140, the sealing arrangement shown in Fig. 1 may be insufficient for providing the desired oil tightness. Not to be bound by theory, it is believed that a combination of factors may contribute to insufficient oil tightness, such as slow or insufficient draining of the oil from the cavity 150 and / or the formation of suspended oil mist, spray, or droplets. In particular, oil tightness may be impeded if an oil enters an upper portion portion 152, the oil remains in the cavity 150 longer than when it has entered the lower portion 154, and may be more prone to being suspended or atomized. In other words, it is believed that an oil present in the lower portion 154 drains faster and / or more efficiently through the oil outlet 168 than an oil present in the upper portion 152 and thus has a lower likelihood of passing the shaft seal 130.

[0034] As shown in Fig. 1, the oil drain channel arrangement 170, 180 is in fluid communication with the oil collecting volume 162 and configured for draining the oil away from an upper portion 152 of the cavity 150.

[0035] According to some embodiments, a first leg of the oil drain channel arrangement includes one or more oil drain channels 180. Fig. 1 shows one oil drain channel 180, however, the bearing arrangement 100 may include a different number of oil drain channels 180, such as between 1 and 10 oil drain channels 180. The oil drain channel 180 is formed within the inner-side wall 124 and fluidly connects the oil collecting volume 162 and the cavity 150. As shown in Fig. 1 , an outlet of the oil drain channel 180 is provided in the lower portion 154 of the cavity 150. It should be noted that no oil drain channels and / or outlets are provided in the upper portion 152 of the cavity. Accordingly, the oil drain channel 180 is configured for draining the oil away from an upper portion 152 of the cavity 150. Beneficially, an oil drained away from the upper portion of the cavity, e.g. by draining the oil towards the lower portion 154 of the cavity 150, may drain more efficiently from the cavity through the oil outlet 168 of the cavity. This may beneficially reduce an amount of oil leakage through the shaft seal 130 towards the wheel back space 140.

[0036] According to some embodiments, a second leg of the oil drain channel arrangement includes one or more oil drain channels 170. Fig. 1 shows two oil drain channels 170, however, the bearing arrangement 100 may include a different number of oil drain channels 170, such as between 1 and 10 oil drain channels 170. The oil drain channel 170 is formed within the inner- side wall 124 and fluidly connects the oil collecting volume 162 and the cavity 190. As shown in Fig. 1, an outlet of the oil drain channel 170 is provided so that it provides a fluid passage between the oil collecting volume 162 and a central bearing casing cavity 190. The central bearing casing cavity 190 is a separate cavity from the cavity 150 in the bearing housing, accordingly, an oil being drained through the oil drain channel 170 does not reach the cavity 150 and / or the shaft seal 130. In particular, the central bearing casing cavity 190 may be, include and / or define a volume adjacent the plain bearing 160 and / or the inner-side wall 124 and opposite the cavity 150 in the bearing housing 120. Accordingly, an oil drained through the oil drain channel 170 is drained away from an upper portion 152 of the cavity 150. From the central bearing casing cavity 190, the oil is collected in an outlet (not shown) and recirculated. Beneficially, since the oil drained through the oil drain channel 170 does not reach the cavity 150 of the bearing housing, an amount of oil leakage through the shaft seal 130 towards the wheel back space 140 may be reduced.

[0037] In the embodiment shown in Fig. 1, the oil drain channel arrangement includes both the oil drain channel 170 and the oil drain channel 180. In some embodiments, only one of the oil drain channels 170 or 180 may be provided, e.g. so that the oil is drained only into the lower portion 154 of the cavity 150 through the oil drain channel 180, or only to the central bearing casing cavity 190 through the oil drain channel 170. In the embodiment shown in Fig. 1 , the oil drain channels 170 and 180 share a common fluid path from the oil collecting volume 162. According to some embodiments, the oil drain channel 170 and 180 may be provided with separate fluid paths to the oil collecting volume 162.

[0038] Referring now to Fig. 2 and 3, further details of the oil drain channel arrangement will be explained. Figs. 2 and 3 show the inner-side wall 124 in a plan view (Fig. 2A, Fig. 3A) and a cutaway side view (Fig. 2B, Fig. 3B). The inner-side wall 124 may be installed e.g. in the bearing housing 120 shown in Fig. 1 to form a bearing arrangement 100 and / or a turbomachine according to embodiments. When installed in the bearing housing 120, the inner-side wall 124 may form a part of the bearing housing 120.

[0039] Fig. 2 shows a bearing arrangement having an oil drain channel arrangement with four oil drain channels 170 providing a fluid passage between the oil collecting volume 162 and a central bearing casing cavity 190. While the embodiment shown in Fig. 2 has four oil drain channels, the number of oil drain channels 170 may vary. For example, the oil drain channel arrangement may include between 1 and 10 oil drain channels 170, such as between 3 and 7 oil drain channels 170, such as 3, 4, 5, or 6 oil drain channels 170. As shown in Fig. 2, the oil drain channels 170 may be equally spaced around the circumference of the inner-side wall 124, particularly so that the oil drain channels 170 and / or outlets of the oil drain channels 170 are rotationally symmetrical along an axis parallel to the shaft 110.

[0040] Fig. 3 shows a bearing arrangement having an oil drain channel arrangement with three oil drain channels 180 providing a fluid passage between the oil collecting volume 162 and the cavity 150 of the bearing housing. While the embodiment shown in Fig. 3 has three oil drain channels, the number of oil drain channels 180 may vary. For example, the oil drain channel arrangement may include between 1 and 10 oil drain channels 180, such as between 2 and 6 oil drain channels 170, such as 2, 3, 4, or 5 oil drain channels 180.

[0041] As shown in Fig. 3A, the three oil drain channels 180 are provided so that outlets of the oil drain channels 180 are positioned exclusively within an area defined by a circular sector 182. In the embodiment shown in Fig. 3, the circular sector 182 is normal to an axis of the shaft 110, the axis of the shaft 110 being normal to the plane defined by the axes 310 and 312. In the embodiment shown in Fig. 3, the circular sector 182 has a central angle of 180° and corresponds to and / or defines the lower portion 154 of the cavity 150. The axis 312 may correspond to a direction of gravity, i.e. point essentially downwards. In the embodiment shown in Fig. 3, the axis 310 has an angle of 90° with respect to the axis 312. In the embodiment shown in Fig. 3, outlets of the oil drain channel arrangement 180 are provided exclusively in between the circular section defined by the axes 310 and 312 so that the circular sector has a central angle a of 180°. In some embodiments, while the axis 312 remains pointed essentially downwards, the circular sector may be reduced to a smaller angle so that the angle a is in a range of 0° to 180°. For example, in some embodiments, the angle may be 160° or lower, 140° or lower, 120° or lower, or even 100° or lower, such as 90° or lower. Accordingly, the oil drain channel arrangement 180 may be devoid of an oil drain channel having an opening that is positioned in and / or provides oil to the upper portion of the cavity 150. Accordingly, the oil drain channel arrangement 180 may be rotationally asymmetrical along an axis parallel to the shaft 110.

[0042] As shown in Fig. 3, the oil drain channels 180 are positioned so that, when the bearing arrangement 100 is provided within a turbomachine, the oil drain channels 180 extend essentially downwards. As shown in Fig. 3, essentially downwards may be understood as not pointing upwards, i.e. an oil exiting an opening of the oil drain channels 180 does not have a vector component pointing upwardly along the axis 312. In some embodiments, oil exiting essentially horizontally may be understood as exiting essentially downwards and / or being drained away from an upper portion 152 of the cavity 150.

[0043] In the embodiments shown in Fig. 2 and 3, the oil drain channels are provided as bores within the inner-side wall 124. In particular, an oil drain channel may include a straight bore connecting the oil collecting volume 162 to the cavity 150 of the bearing housing or the central bearing casing cavity 190. Additionally, or alternatively, the oil drain channels 170 may include non-straight portions, such as curved portions. According to embodiments, a bearing arrangement 100 may include one or both of the oil drain channel arrangements 170, 180 shown in Fig. 2 and / or 3. In some embodiments having both oil drain channel arrangements 170, 180, the oil drain channels 170 may overlap with the oil drain channels 180, or be rotationally offset from the oil drain channels 180.

[0044] Referring now to Fig. 4, a bearing arrangement 100 according to exemplary embodiments is shown. Only the differences with respect to Fig. 1 to Fig. 3 are explained, and the description of Fig. 1 to Fig. 4 applies to the bearing arrangement 100 shown in Fig. 4.

[0045] As shown in Fig. 4, the bearing 160 may include a radial bearing component in addition to an axial bearing component.

[0046] In some embodiments, the bearing 160 may include further oil inlets in addition to the inlet 164.

[0047] In some embodiments, the sealing disc 134 may be provided directly adjacent the bearing 160. This may beneficially prevent an oil from exiting e.g. from a gap formed between the shaft 110 and the bearing bush 166.

[0048] In some embodiments, the shaft 110 may include a bush provided on the shaft 110 and forming the bearing surface of the shaft 110.

[0049] In some embodiments, the shaft seal 130 may include two piston rings 132 provided between the wheel-side partition wall 122 and the shaft 110. In some embodiments, oil drain grooves 126 may be provided in-between the sealing disc 134 and the partition wall 122, and / or be formed in-between the sealing disc 134 and the partition wall 122.

[0050] In the embodiment shown in Fig. 4, the oil drain channel arrangement 170 drains the oil towards the central bearing casing cavity 190, e.g. as explained with reference to Fig. 1 and / or Fig. 2. Additionally, or alternatively, an oil drain channel arrangement 180 as described with reference to Fig. 1 and / or Fig. 3 may be provided.

[0051] According to embodiments, 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 bearing arrangement 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. According to embodiments, a method of operating a turbomachine is described. The turbomachine may be a turbomachine including a bearing arrangement as described herein, such as the bearing arrangement 100 described with reference to Fig. 1 through Fig. 4.

[0052] The turbomachine according to the method includes a shaft seal provided in a wheel-side partition wall of a bearing housing, the partition wall separating a wheel back space of a rotating wheel provided on a shaft of the turbomachine and a cavity in the bearing housing, and a plain bearing provided adjacent the cavity at an inner-side wall of the bearing housing opposite the shaft seal, the plain bearing having an oil collecting volume configured for collecting oil from a bearing surface of the plain bearing.

[0053] The method may include providing an oil to the plain bearing, e.g. by an oil supply system fluidly connected to the bearing. The oil may be pressurized and flow along a pressure gradient across the bearing and / or adjacent the bearing into the oil collecting volume.

[0054] The method includes draining an oil from the plain bearing by collecting the oil from the oil collecting volume and directing the oil away from an upper portion of the cavity. Directing the oil may include providing one or more oil drain channels having outlets at defined positions, so that the outlets let out the oil in a position other than the upper portion of the cavity, particularly so that the oil is not directed towards the upper portion of the cavity.

[0055] In some embodiments, directing the oil away from the upper portion of the cavity includes directing the oil into a central bearing casing cavity, the central bearing casing cavity being a different cavity than the cavity in the bearing housing. For example, the central bearing casing cavity may be a cavity of a turbomachine located in-between a turbine-side bearing and a compressor-side bearing. In particular, the central bearing casing cavity may be separated from the shaft seal, e.g. by one or more inner-side walls.

[0056] In some embodiments, directing the oil away from the upper portion of the cavity may include directing the oil in a downwards direction to prevent an oil spray onto the shaft seal. In particular, the oil may be directed into the cavity of the bearing housing in a downwards direction. For example, the oil may be directed so that an oil stream or oil jet is formed having an essentially downward vector component.

[0057] In some embodiments, oil drain channels are positioned so that outlets of the oil drain channels let out the oil towards a downward portion of the cavity. In particular, the oil outlets of the oil drain channel draining the oil from the oil collecting volume of the bearing may be provided so that oil exiting the oil drain channel outlets is directed towards an oil outlet of the cavity. For example, the oil may be directed so that it flows towards the oil outlet of the cavity e.g. directly or e.g. along an inner wall of the cavity. For example, the oil may be directed so that it easily pools within the cavity near the oil outlet of the cavity, particularly without spraying into a top portion of the cavity.

[0058] According to embodiments, the method may include draining the oil either to one of the central bearing casing cavity or the cavity of the bearing housing, or both the central bearing casing cavity and the cavity of the bearing housing. A relative draining oil volume over time may be adjustable e.g. by increasing or decreasing the number of oil drain channels, and / or adjusting a bore diameter of the oil drain channel. Beneficially, in case some or all of the oil is drained towards the cavity of the bearing housing, the oil drained from the bearing may contribute to lubricating and / or cooling components of the cavity of the bearing housing, such as the wheelside partition wall and / or the shaft seal.

[0059] Beneficially, the solutions presented herein allow a more efficient operation of a turbomachine. In particular, oil loss may be prevented, which may beneficially reduce operating costs, environmental impact, and / or maintenance. Beneficially, the solutions presented herein may be easily implemented in existing turbomachine designs, e.g. by modification of existing bearing, bearing housing and / or inner-side wall designs, without requiring a redesign of other components of the turbomachine.

[0060] List of reference numerals

[0061] 100 bearing arrangement

[0062] 110 shaft

[0063] 120 bearing housing

[0064] 122 wheel-side partition wall

[0065] 124 inner-side wall

[0066] 126 oil drain grooves

[0067] 130 shaft seal

[0068] 132 piston ring

[0069] 134 sealing disc

[0070] 140 wheel back space

[0071] 150 cavity

[0072] 152 upper portion of the cavity

[0073] 154 lower portion of the cavity

[0074] 160 bearing

[0075] 162 oil collecting volume

[0076] 164 inlet

[0077] 166 bearing bush

[0078] 168 oil outlet

[0079] 170 oil drain channel arrangement

[0080] 180 oil drain channel arrangement

[0081] 182 circular sector

[0082] 190 central bearing casing cavity

[0083] 310 axis

[0084] 312 axis

Claims

Claims:

1. Bearing arrangement (100) for a turbomachine, comprising: a shaft (110); a bearing housing (120) configured for supporting the shaft (110); a shaft seal (130) provided in a wheel-side partition wall (122) of the bearing housing (120), the partition wall (122) separating a wheel back space (140) of a rotating wheel of the turbomachine and a cavity (150) in the bearing housing (120); a plain bearing (160) provided adjacent the cavity (150) at an inner-side wall (124) opposite the shaft seal (130), the plain bearing (160) comprising an oil collecting volume (162) configured for collecting oil from a bearing surface of the plain bearing (160); and an oil drain channel arrangement (170, 180) in fluid communication with the oil collecting volume (162) and configured for draining the oil away from an upper portion (152) of the cavity (150).

2. The bearing arrangement (100) according to claim 1, wherein the oil drain channel arrangement comprises at least one oil drain channel (170) providing a fluid passage between the oil collecting volume (162) and a central bearing casing cavity (190) other than the cavity (150) in the bearing housing.

3. The bearing arrangement (100) according to claim 2, wherein the central bearing casing cavity (190) comprises a volume adjacent the plain bearing (160) and opposite the cavity (150) in the bearing housing (120).

4. The bearing arrangement (100) according to any one of the preceding claims, wherein the oil drain channel arrangement comprises at least one oil drain channel (180) providing a fluid passage between the oil collecting volume and the cavity (150) in the bearing housing (120), wherein outlets of the at least one oil drain channel (180) are positioned exclusively within an area defined by a circular sector (182), the circular sector (182) being normal to an axis of the shaft (110), the circular sector having a central angle of 180° or less, and the circular sector defining a lower portion of the cavity (150).

5. The bearing arrangement (100) according to claim 1 or 2, wherein the at least one oil drain channel (180) is positioned so that, when the bearing arrangement (100) is provided within the turbomachine, the at least one oil drain channel (180) extends essentially downwards.

6. The bearing arrangement (100) according to any one of the preceding claims, wherein the oil drain channel (170, 180) comprises a bore.

7. The bearing arrangement (100) according to any one of the preceding claims, the plain bearing (160) comprising a bearing bush (166) provided between the shaft (110) and the bearing housing (120), the oil collecting volume (162) forming a channel in-between the bearing bush (166) and the bearing housing (120).

8. The bearing arrangement (100) according to any one of the preceding claims, further comprising at least one oil drain groove (126) provided in the partition wall (122) for draining oil from the cavity (150) in the bearing housing (120).

9. The bearing arrangement (100) according to any one of the preceding claims, the shaft seal (130) comprising at least one piston ring (132) provided between the shaft (110) and the partition wall (122) for sealing the wheel back space (140) from the cavity (150) in the bearing housing (120).

10. The bearing arrangement (100) according to any one of the preceding claims, further comprising: a sealing disc (134) provided about the shaft (110) and configured to rotate with the shaft (110), the sealing disc (134) being provided in the cavity (150) of the bearing housing (120) between the partition wall (122) and the plain bearing (160).

11. A turbomachine comprising the bearing arrangement (100) according to any one of claims 1 to 10 and at least one impeller arranged on the shaft (110).

12. Method of operating a turbomachine, the turbomachine comprising: a shaft seal (130) provided in a wheel-side partition wall (122) of a bearing housing (120), the partition wall (122) separating a wheel back space of a rotating wheel provided on a shaft (110) of the turbomachine and a cavity (150) in the bearing housing (120), and; a plain bearing (160) provided adjacent the cavity (150) at an inner-side wall (124) of the bearing housing (120) opposite the shaft seal (130), the plain bearing (160) comprising an oil collecting volume (162) configured for collecting oil from a bearing surface of the plain bearing (160), the method comprising: draining the oil from the plain bearing (160) by collecting the oil from the oil collecting volume (162) and directing the oil away from an upper portion of the cavity (150).

13. The method according to claim 12, wherein directing the oil away from an upper portion of the cavity (150) comprises directing the oil into a central bearing casing cavity (190) other than the cavity (150) in the bearing housing.

14. The method according to claim 12 or 13, wherein directing the oil away from an upper portion of the cavity (150) comprises directing the oil in a downwards direction to prevent an oil spray onto the shaft seal (130).

15. The method according to claim 14, wherein directing the oil downwards comprises providing outlets of at least one oil drain channel (180) so that oil exiting the outlets is directed towards an oil outlet (168) of the cavity (150).

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