Centrifugal separator

Abstract

The disclosure concerns a centrifugal separator (2) for separating a liquid phase from a gaseous phase. A liquid outlet (26) from a separation space (10) of the centrifugal separator is arranged at a bottom portion (28) of the separation space. A transport member (32) is arranged below the liquid outlet (26) and has a radial extension at least to beyond the liquid outlet (26). A passage (31) for the liquid phase is arranged radially outside the transport member (32). The transport member (32) has an upper surface (33), which extends substantially perpendicularly to the axial extension (18), at least from a radial position of the liquid outlet (26) to a periphery (35) of the transport member (32) for condensate to drain from the upper surface.

Description

[0001] Centrifugal Separator

[0002] TECHNICAL FIELD

[0003] The invention relates to a centrifugal separator for separating a liquid phase from a gaseous phase.

[0004] BACKGROUND

[0005] Crankcase gas is ventilated from a crankcase of an internal combustion engine, ICE. During operation of the ICE, high pressure within cylinders of the ICE force some of the combustion gas and liquid and solid residues past the piston rings down into a crankcase of the ICE. If not ventilated, an increased pressure within the crankcase may impede ICE operation and / or may cause engine oil to leak out of the ICE.

[0006] Ventilated crankcase gas may be disposed of in an environmentally friendly manner instead of being ventilated in untreated form to the atmosphere. For certain types of ICEs, legislation requires crankcase gas to be disposed of in a controlled manner.

[0007] Crankcase gas comprises combustion gas, oil, other liquid hydrocarbons, soot, and other solid combustion residues. In order to dispose of crankcase gas suitably, a gaseous phase is separated from a liquid phase including oil, soot, and other residues. The separated gaseous phase may be led to an air intake of the ICE or vented to the atmosphere, and the liquid phase may be led back to an oil sump of the combustion engine optionally, via an oil filter for removing soot and other solid residues from the oil.

[0008] A centrifugal separator may be utilised for separating crankcase gas into the liquid phase and the gaseous phase. The crankcase gas is led into a rotor of the centrifugal separator and heavy constituents of the crankcase gas, such as oil and soot, are separated as the liquid phase from the cleaned gaseous phase. The gaseous phase is lead out of the centrifugal separator via a gas outlet. The liquid phase is led out of the centrifugal separator via a liquid outlet.

[0009] Centrifugal separators may be utilised also for separating other gas-liquid mixtures than crankcase gas.

[0010] WO 2016 / 198274 discloses a centrifugal separator for separating crankcase gas. The centrifugal separator comprises a separation chamber, a rotor shaft, a rotor inside theseparation chamber, an inlet for crankcase gas and a gas outlet. The centrifugal separator comprises a liquid outlet chamber. The liquid outlet chamber forms an individual chamber and is arranged in fluid communication with the separation chamber via a liquid passage. A rotating member is connected to the rotor shaft and is arranged inside the liquid outlet chamber below the liquid passage. A liquid outlet from the centrifugal separator for separated liquid phase leads from the liquid outlet chamber.

[0011] WO 2022 / 128341 discloses a centrifugal separator for separating a liquid phase from crankcase gas. The separator comprises a housing, a separation chamber inside the housing, a rotor shaft, a rotor connected to the rotor shaft, a bearing arranged at an end portion of the rotor shaft, and a liquid outlet from the separation chamber for the separated liquid phase. The end portion of the rotor shaft extends through the bearing outside the separation chamber. A ring-shaped sealing gap is formed between the housing and a member connected to the rotor shaft outside the separation chamber. The liquid outlet is arranged, seen in relation to the axial direction, radially outside the bearing and radially inside a radially outer end of the ring-shaped sealing gap.

[0012] In the centrifugal separators disclosed in WO 2016 / 198274 and WO 2022 / 128341, the therein discussed rotating member or member connected to the rotor shaft, hereinafter referred to as a transport member, enable pumping of the separated liquid phase from the separation chamber to a liquid outlet passage arranged radially outside the transport member and leading out of the centrifugal separator. A comparatively narrow gap is required between the transport member and a stationary surface above the transport member, such as a surface of the housing, to achieve its pumping effect.

[0013] However, at freezing temperatures, the narrow gap above the transport member may lead to problems with condensate water and / or a mixture of condensate water and oil, an oil emulsion, freezing in the gap. This may hamper the operation of the centrifugal separator, such as complicate cold starting of the centrifugal separator.

[0014] SUMMARY

[0015] It would be advantageous to achieve a centrifugal separator overcoming, or at least alleviating, the above-mentioned drawback associated with the centrifugal separators of WO 2016 / 198274 and WO 2022 / 128341. In particular, it would be desirable to enable reliable cold starting of a centrifugal separator for separating a liquid phase from a gaseous phase. To better address one or more of these concerns, a centrifugal separator for separating aliquid phase from a gaseous phase having the features defined in the independent claim is provided.

[0016] According to an aspect there is provided a centrifugal separator for separating a liquid phase from a gaseous phase. The centrifugal separator comprises: a stationary casing enclosing a separation space, a rotor shaft extending through at least a portion of the separation space along an axial extension and in a substantially vertical direction during use of the centrifugal separator, a rotor for separating the liquid phase arranged inside the separation space and connected to the rotor shaft, and a transport member for the separated liquid phase connected to the rotor shaft and arranged outside the separation space. A liquid outlet from the separation space for the liquid phase is arranged at a bottom portion of the separation space, and seen radially to the axial extension, the liquid outlet being arranged closer to the rotor shaft than to a periphery of the separation space. The transport member is arranged below the liquid outlet and has a radial extension at least to beyond the liquid outlet. A passage for the liquid phase is arranged radially outside the transport member, and the transport member has an upper surface, which extends substantially perpendicularly to the axial extension, at least from a radial position of the liquid outlet to a periphery of the transport member.

[0017] Since the transport member has an upper surface, which extends substantially perpendicularly to the axial extension, at least from a radial position of the liquid outlet to a periphery of the transport member - condensate water and / or oil emulsion leaking from the separation space through the liquid outlet onto the transport member, e.g. during standstill of the centrifugal separator, is able to drain from the upper surface of the transport member. As a consequence, at freezing temperatures, the upper surface of the transport member is free, or at least substantially free, of liquid that when freezing risks obstructing centrifugal separator operation.

[0018] More specifically, since the rotor shaft extends substantially vertically and since the upper surface of the transport member extends substantially perpendicularly to the axial extension of the rotor shaft to the periphery of the transport member, there is no vertical portion at the periphery of the transport member, which would prevent liquid from draining from its upper surface. Lacking such a vertical portion, entails that the amount of any condensate or oil emulsion on the upper surface of the transport member is so small that freezing thereof does not obstruct centrifugal separator operation.In operation of the centrifugal separator, the gas to be cleaned from the liquid phase is led into the separation space and the rotor via an inlet for the gas to be cleaned. The gas to be cleaned enters the rotor from a central portion thereof. As the rotor rotates, the heavy constituents are separated therein and are propelled from an outer periphery of the rotor as droplets against an inner wall that delimits the separation space, such as an inner wall portion of the stationary casing. The droplets form the separated liquid phase, which is led out of the centrifugal separator via the liquid outlet arranged at the bottom portion of the separation space. The cleaned gas, relieved of its heavy constituents, is led out of the centrifugal separator via a gas outlet.

[0019] The centrifugal separator may be configured for concurrent separation. That is, the separated phases travel in the same direction through the rotor of the centrifugal separator. More specifically, as discussed above, the liquid phase travels from the central portion of the rotor towards its periphery. So does the other separated phase i.e. , the gas. It travels from the central portion of the rotor towards its periphery while the heavy constituents are separated therefrom and leaves the rotor at its periphery.

[0020] The rotor may comprise a number of separation members, forming a separation aid, which improve the separation of the heavy constituents from the gas. Such separation members may take the form of e.g., axially extending vanes which are directed radially from the rotor shaft or of stacked frustoconical separation discs. As the rotor rotates, the heavy constituents are forced against surfaces of the separating members whereon the heavy constituents form droplets while traveling along the separation members towards the outer periphery of the rotor.

[0021] The centrifugal separator may be utilised e.g., for cleaning crankcase gas of an internal combustion engine, ICE. Such an ICE may be configured for propelling a vehicle or may be a stationary combustion engine, for instance for driving a generator for generating an electrical current.

[0022] The crankcase gas, also referred to as blow-by gas, may be ventilated from the crankcase of the ICE via a crankcase ventilation system. The centrifugal separator may form part of the crankcase ventilation system.

[0023] In the case of separating a liquid phase from crankcase gas, the liquid phase contains heavy constituents, such as oil, other liquid hydrocarbons, soot, and other solid combustion residues from the crankcase gas.At standstill, such as over periods allowing the ICE to cool down, water vapour may condensate in portions of the crankcase ventilation system of the ICE. For instance, at startup of the ICE, before the crankcase ventilation system has reached its operating temperature, water vapour may condensate. Such condensate and / or the condensate forming an emulsion with oil residues in the centrifugal separator, is not able to amass on the upper surface of the transport member due to the upper surface extending substantially perpendicularly to the axial extension to the periphery of the transport member. Accordingly, at freezing temperatures, frozen condensate and / or oil emulsion does not prevent the rotor from rotating.

[0024] Herein, the term condensate refers to water.

[0025] The centrifugal separator may be utilised for separating other gas-liquid mixtures than crankcase gas.

[0026] The stationary casing of the centrifugal separator is stationary in relation to e.g. an ICE or other equipment, which comprises the centrifugal separator. The stationary casing may comprise one or more parts. The rotor shaft and the rotor are arranged to rotate in relation to the stationary casing. The rotor shaft may be rotated by a driving member, such as a turbine wheel, an electric, pneumatic, or hydraulic motor, etc.

[0027] As discussed above, during use of the centrifugal separator, such as when installed at an ICE, the axial extension extends substantially vertically and the liquid outlet from the separation space is arranged at a bottom portion of the separation space, such as through a wall member of the stationary casing forming a lower delimiting wall of the separation space. Thus, gravity may cause the droplets of the separated liquid phase to flow along the inner walls of the separation chamber towards the liquid outlet.

[0028] Herein, the terms axial and radial relate to the axial extension of the rotor shaft unless otherwise specified.

[0029] Herein, the terms substantially vertically and substantially perpendicularly may refer to an extension within 10 degrees of a vertical axis and to an extension within 10 degrees of a perpendicular axis, respectively.Accordingly, the upper surface of the transport extending substantially perpendicularly to the axial extension entails that the upper surface is flat or slightly conical, at least from a radial position of the liquid outlet to a periphery of the transport member.

[0030] The transport member may be arranged in a space or a compartment which is separate from the separation space and arranged below the separation space. Such a compartment may form a liquid outlet chamber for the liquid phase of the centrifugal separator.

[0031] The passage for the liquid phase arranged radially outside the transport member may form part of an outlet for the liquid phase from the centrifugal separator. The passage for the liquid phase may form part of an outlet from the space in which the transport member is arranged.

[0032] During operation of the centrifugal separator, the passage for the liquid phase arranged radially outside the transport member receives the liquid phase that has passed through the liquid outlet onto the upper surface of the transport member. The rotation of the transport member causes the liquid phase to be flung or pumped into the passage for the liquid phase.

[0033] According to some embodiments, the liquid outlet may be provided by at least one through hole extending through the stationary casing. In this manner, the separation space may be delimited by the stationary casing and the liquid outlet for the liquid phase may be provided extending through the stationary casing.

[0034] According to some embodiments, a distance between the upper surface of the transport member and an outlet opening of the at least one through hole facing the upper surface of the transport member may be within a range of 0.05 - 4 mm. In this manner, during operation of the centrifugal separator, a pumping effect of the transport member on the liquid phase coming from the separation space may be ensured.

[0035] The pumping effect may assist in transporting the liquid phase into the outlet passage.

[0036] According to some embodiments, the rotor shaft may be journaled in a bearing arranged in the stationary casing between the rotor and the transport member. The liquid outlet may be arranged, seen in relation to the axial extension, radially outside the bearing. In this manner, the liquid outlet for the liquid phase may be positioned within a central region of the centrifugal separator.According to some embodiments, the transport member may be provided with one or more recesses extending from the upper surface downwardly into a body of the transport member. In this manner, condensate and / or oil emulsion received on the upper surface of the transport member may flow into the one or more recesses. This in addition to the condensate and / or oil emulsion flowing towards the periphery of the transport member. Thus, the risk of condensate and / or oil emulsion accumulating to such an extent that freezing thereof on the upper surface would obstruct centrifugal separator operation may be further reduced.

[0037] During operation of the centrifugal separator, when the transport member rotates with the rotor shaft, centrifugal forces may cause the one or more recesses to be emptied of the condensate and / or oil emulsion collected therein.

[0038] According to some embodiments, the one or more recesses may be arranged at a position that is radially inside the liquid outlet.

[0039] For instance, the one or more recesses may be arranged radially between the rotor shaft and the liquid outlet.

[0040] According to some embodiments, the centrifugal separator may comprise a one-way valve arranged downstream of the passage for the liquid phase. In this manner, a pressure difference may be maintained between an inside of the centrifugal separator, such as the separation space and a compartment wherein the transport member may be arranged, and an outside of the centrifugal separator.

[0041] The one-way valve may enable that during operation of the centrifugal separator, the separated liquid phase is feed out of the passage for the liquid phase as long as the pressure inside the centrifugal separator is higher than at a downstream side of the one-way valve.

[0042] During operation of the centrifugal separator, the transport member may build up a pressure inside a compartment wherein the transport member is arranged sufficient to cause the liquid phase to pass the one-way valve, i.e. to overcome a pressure downstream of the one-way valve.

[0043] Downstream of the one-way valve, a pressure of an ambient environment of the centrifugal separator or a pressure in between that of the pressure within the centrifugal separator and the ambient environment may prevail.For instance, the one-way valve may separate the passage for the liquid phase from further conduits of a crankcase gas ventilation system.

[0044] According to some embodiments, the rotor shaft may be driven by an electric motor.

[0045] According to some embodiments, a rotor of the electric motor may be connected to the rotor shaft below the transport member. In this manner, the electric motor may be integrated with the rotating parts of the centrifugal separator.

[0046] According to some embodiments, the centrifugal separator may comprise a covering member connected to the stationary casing. At least the rotor of the electric motor may be arranged within the covering member, and the transport member may be arranged within the covering member. In this manner, the covering member may form a space, such as a compartment, for the transport member and the rotor of the electric motor, below the separation space.

[0047] The liquid outlet may lead from the separation space into the compartment formed by the covering member. Thus, separated liquid, condensate, and / or oil emulsion may be contained within the space formed by the covering member and may be prevented from reaching the other parts of e.g. the electric motor.

[0048] During operation of the centrifugal separator, the transport member, pumping the liquid phase into the passage for the liquid phase, may build up a pressure within the space formed by the covering member.

[0049] According to some embodiments, the transport member is free of any member, such as blades or wings, extending from the outer periphery. Such members, such as radial blades or axial wings, may interfere with the draining of any condensate water and / or oil emulsion leaking from the separation space. As an example, the outer periphery of the transport member may be smooth.

[0050] Further features of, and advantages with, the invention will become apparent when studying the appended claims and the following detailed description.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Various aspects and / or embodiments of the invention, including its particular features and advantages, will be readily understood from the examples discussed in the following detailed description and the accompanying drawings, in which:Fig. 1 illustrates a section through a centrifugal separator according to an embodiment, Fig. 2 illustrates a section along an axial extension of a centrifugal separator according to an embodiment, and

[0053] Figs. 3a and 3b illustrate a transport member according to an embodiment.

[0054] DETAILED DESCRIPTION

[0055] Aspects and / or embodiments of the invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.

[0056] Fig. 1 illustrates a section through a centrifugal separator 2 according to an embodiment. The centrifugal separator 2 is configured for separating a liquid phase from a gaseous phase, such for separating a liquid phase from crankcase gas.

[0057] The centrifugal separator 2 comprises a stationary casing 4, a rotor shaft 6, and a rotor 8 for separating the liquid phase.

[0058] The stationary casing 4 may be formed from one or more parts. The stationary casing 4 encloses a separation space 10. For instance, the stationary casing 4 may comprise a circumferentially extending side wall 12, a first end wall 14, and an opposite second end wall 16, which together enclose the separation space 10. The stationary casing 4 may at least partially delimit one or more further spaces.

[0059] The rotor shaft 6 extends through at least a portion of the separation space 10 along an axial extension 18 and in a substantially vertical direction during use of the centrifugal separator 2. The rotor 8 is connected to the rotor shaft 6. The rotor 8 is arranged inside the separation space 10. The axial extension 18 of the rotor shaft 6 coincides with a rotational axis of the rotor shaft 6.

[0060] The rotor shaft 6 is journalled in the stationary casing 4 via one or more bearings 20. The one or more bearings 20 may be e.g., one or more of ball bearings, roller bearings, or plain bearings.

[0061] The centrifugal separator 2 further is provided with an inlet 22 leading into the separation space 10, for the gas to be cleaned in the centrifugal separator 2, and a gas outlet 24 from the separation space 10 for separated gas.A liquid outlet 26 from the separation space 10, for the separated liquid phase, is arranged at a bottom portion 28 of the separation space 10. Seen radially to the axial extension 18, the liquid outlet 26 is arranged closer to the rotor shaft 6 than to a periphery 30 of the separation space 10.

[0062] The liquid outlet 26 may be provided by at least one through hole 29 extending in parallel with the axial extension 18 through a wall 14 the stationary casing 4.

[0063] For instance, the liquid outlet 26 may be provided by 2 - 16 through holes 29 extending through the stationary casing 4 at a bottom of the separation space 10, such as arranged circumferentially around the bearing 20. Thus, the separated liquid phase may be evenly drained from the separation space 10 around the bearing 20 via the through holes 29.

[0064] In the illustrated embodiment, the liquid outlet 26 is provided by at least two through holes 29 arranged in the first end wall 14 of the stationary casing 4, see also with reference to Fig. 2.

[0065] The centrifugal separator 2 is configured to be positioned with the rotor shaft 6 extending substantially vertical during use of the centrifugal separator 2. Accordingly, the liquid outlet 26 is arranged at a lower portion of the stationary casing 4. The separated liquid phase thus, may be transported by gravity towards the liquid outlet 26.

[0066] The centrifugal separator 2 further comprises a transport member 32 for the separated liquid phase. The transport member 32 is connected to the rotor shaft 6 and is arranged outside the separation space 10.

[0067] More specifically, an end portion 34 of the rotor shaft 6 extends through the first end wall 14 and the bearings 20 arranged at the first end wall 14 to outside the separation space 10. The transport member 32 is connected to the rotor shaft 6 at the end portion 34 of the rotor shaft 6.

[0068] The transport member 32 is arranged below the liquid outlet 26 and has a radial extension, directed from the axial extension 18, at least to beyond the liquid outlet 26.

[0069] A passage 31 for the liquid phase is arranged radially outside the transport member 32. Thus, during operation of centrifugal separator 2, the passage 31 for the liquid phase is arranged to receive the liquid phase from the rotating transport member 32.As such, the passage 31 for the liquid phase arranged radially outside the transport member 32 forms part of an outlet for the liquid phase from the centrifugal separator 2.

[0070] The passage 31 for the liquid phase may extend around the entire, or only partially around the rotor shaft 6 and the transport member 32. For instance, as in the illustrated embodiment, the passage 31 may be formed at least partially by a recess extending around the transport member 32.

[0071] The transport member 32 has an upper surface 33, which extends substantially perpendicularly to the axial extension 18, at least from a radial position of the liquid outlet 26 to a periphery 35 of the transport member 32.

[0072] Thus, during operation of the centrifugal separator 2, the liquid phase from the liquid outlet 26 is received on the upper surface 32 of the transport member 32 and is transported along the upper surface 33 towards the periphery 35 of the transport member 32. Accordingly, the liquid phase is transported, such as pumped by the transport member 32 to be received by the passage 31 for the liquid phase.

[0073] A distance between the upper surface 33 of the transport member 32 and an outlet opening 37 of the at least one through hole 29 facing the upper surface 33 of the transport member 32 may be within a range of 0.05 - 4 mm.

[0074] Thus, during operation of the centrifugal separator, a pumping effect of the transport member 32 for transporting the liquid phase coming from the separation space 10 towards, or into, the outlet passage 31 may be provided.

[0075] An outlet opening 37 of the at least one through hole 29 facing the upper surface 33 may be formed in the first end wall 14 of the stationary casing 4.

[0076] In these embodiments, the centrifugal separator 2 comprise a one-way valve 42 arranged downstream of the passage 31 for the liquid phase. The one-way valve 42, also referred to as a check valve, enables maintenance of a pressure difference between an inside of the centrifugal separator 2 and an outside of the centrifugal separator 2. The one-way valve 42 also prevents a reverse flow of fluid into the centrifugal separator 2.The rotor 8 comprises a stack 36 of separation discs 38, each separation disc 38 having a truncated conical, i.e. frustoconical, shape. Between the separation discs 38 in the stack 36, interspaces 40 are formed. In Fig. 1 only some of the separation discs 38 are indicated.

[0077] In these embodiments the frustoconical separation discs 38 are stacked with their wide ends facing downwardly. In alternative embodiments, the frustoconical separation discs may be stacked with their wide ends facing upwardly. Instead of frustoconical separation discs, or in addition thereto, the centrifugal separator may comprise other separation aiding means, such as vanes extending radially and axially from the rotor shaft.

[0078] Mentioned purely as examples, the number of separation discs 38 may be within the range of the 20 - 200, which may have an outer diameter within a range of 30 - 250 mm, and may be arranged at a distance within a range of 0.15 - 1 mm from each other.

[0079] The rotor shaft 6 is brought to rotate about its rotational axis by a driving member.

[0080] In the embodiment illustrated in Fig.1 , the rotor shaft 6 is driven by a drive member in the form of an electric motor 44.

[0081] The drive member may be arranged at an upper end portion or at the lower end portion 34 of the rotor shaft 6.

[0082] In the illustrated embodiment, a rotor 46 of the electric motor 44 is connected to the rotor shaft 6 below the transport member 32. Accordingly, in this embodiment, the electric motor 44 is arranged at the lower end portion 34 of the rotor shaft 6.

[0083] According to some embodiments, such as in the illustrated embodiment, the centrifugal separator 2 comprise a covering member 47 connected to the stationary casing 4. At least the rotor 46 of the electric motor 44 is arranged within the covering member 47. Also, the transport member 32 is arranged within the covering member 47.

[0084] A stator 50 of the electric motor 44 is in this embodiment arranged outside the covering member 47. Alternatively, the stator 50 may be arranged inside the covering member 47.

[0085] Since it is connected to the stationary casing 4, the covering member 47 forms a space 48, such as a compartment, for the transport member 32 and the rotor 46 of the electric motor 44, below the separation space 10. Accordingly, the liquid outlet 26 leads from the separationspace 10 into the space 48 formed by the covering member 47. The passage 31 for the liquid phase may form part of an outlet from the space 48.

[0086] The space 48 formed by the covering member 47 may form a liquid outlet chamber of the centrifugal separator 2. That is, a chamber separate downstream of, and separate from, the separation space 10 for the liquid phase to pass through before leaving the centrifugal separator 2, via the passage 31 for the liquid phase and passing through the one-way valve 42.

[0087] During operation of the centrifugal separator 2, the rotor 8 is rotated by the electric motor 44 and the gas to be cleaned enters the centrifugal separator 2 and a central portion of the rotor 8 via the inlet 22. The gas to be cleaned travels in the interspaces 40 between the separation discs 38 from the central portion of the rotor 8 towards its outer periphery while being separated into the liquid phase and the gaseous phase, as indicated by small arrows in Fig.

[0088] 1. The separated gaseous phase leaves the separation space 10 via the gas outlet 24 and the separated liquid phase leaves the separation space 10 via the liquid outlet 26. The liquid phase from the liquid outlet 26 is received on the upper surface 33 of the transport member 32, for the transport member 32 to transport, such as pump, the liquid phase into the passage 31 for the liquid phase.

[0089] The transport member 32 builds up a pressure inside the space 48 exceeding a pressure downstream of the one-way valve 42. Thus, the liquid phase is feed out of the passage 31 for the liquid phase past the one-way valve 42, e.g. to a conduit system for the separated liquid phase.

[0090] In the shown embodiment, also the rotor 46 of the electric motor 44 may contribute to feeding the liquid phase out of the passage 31 for the liquid phase, past the one-way valve 42. For instance, a portion of at the outer periphery 35 of the transport member 33 and outer surfaces of the rotor 46 of the electric motor 44 may bring gas and liquid in the space 48 into rotation such that the liquid is transferred past the one-way valve 42.

[0091] As mentioned above, during standstill and / or at startup of the centrifugal separator 2, condensate and / or oil emulsion leaking through the liquid outlet 26 onto the transport member 32 is drained from the upper surface 33 of the transport member 32.

[0092] Fig. 2 illustrates a section along an axial extension 18 of a centrifugal separator 2 according to an embodiment. The centrifugal separator 2 may be a centrifugal separator 2 as discussedabove with reference to Fig. 1. Accordingly, in the following reference is also made to the above discussion related to Fig. 1.

[0093] Again, the centrifugal separator 2 comprises a rotor shaft 6 extending through at least a portion of a separation space 10 of the centrifugal separator 2. A rotor 8 for separating a liquid phase and a gaseous phase is arranged in the separation space 10. A liquid outlet 26 from the separation space 10, for the liquid phase, is arranged at a bottom portion 28 of the separation space 10. The liquid outlet 26 is provided by at least one through hole 29 extending through the stationary casing 4.

[0094] Again, the centrifugal separator 2 comprises a transport member 32 connected to the rotor shaft 6 and arranged outside the separation space 10. The transport member 32 is arranged below the liquid outlet 26 and has a radial extension at least to beyond the liquid outlet 26. The transport member 32 has an upper surface 33, which extends substantially perpendicularly to the axial extension 18, at least from a radial position of the liquid outlet 26 to a periphery 35 of the transport member 32.

[0095] The rotor shaft 6 is journaled in a bearing 20 arranged in the stationary casing 4 between the rotor 8 and the transport member 32. The liquid outlet 26 is arranged, seen in relation to the axial extension, radially outside the bearing 20.

[0096] In this embodiment, the stationary casing 4 comprises a ring-shaped protrusion 52 extending around the bearing 20 and extend downwardly towards the transport member 32.

[0097] Accordingly, an outlet opening 37 of the at least one through hole 29 faces the upper surface 33 of the transport member 32 from the ring-shaped protrusion 52.

[0098] Figs. 3a and 3b illustrate a transport member 32 according to an embodiment. The transport member 32 is a transport member 32 of a centrifugal separator 2, such as discussed above with reference to Figs. 1 and 2. Accordingly, in the following reference is also made to the above discussion related to Figs. 1 and 2. Fig. 3a illustrate an isometric view of the transport member 32 and Fig. 3b illustrates a section of the transport member 32 along a rotational axis 54 of the transport member 32.

[0099] Accordingly, the transport member 32 is configured to be connected to a rotor shaft 6 of the relevant centrifugal separator. The rotational axis 54 of the transport member 32 coincides with an axial extension 18 of the rotor shaft 6. In the centrifugal separator, the transportmember 32 is arranged below a liquid outlet and has a radial extension at least to beyond the liquid outlet. The transport member 32 has an upper surface 33.

[0100] The transport member 32 is provided with one or more recesses 56 extending from the upper surface 33 of the transport member 32 downwardly into a body 58 of the transport member 32.

[0101] The provision of these one or more recesses 56 enables receipt of condensate and / or oil emulsion received on the upper surface 33 of the transport member 32, e.g. at standstill or startup of the centrifugal separator. When rotating at full operational speed, centrifugal forces cause the one or more recesses 56 to be emptied of the condensate and / or oil emulsion received therein.

[0102] When the transport member 32 is mounted in the centrifugal separator 2, its upper surface 33 extends substantially perpendicularly to the rotational axis 54, i.e. substantially perpendicularly to the axial extension 18, at least from a radial position of the liquid outlet 26 to a periphery 35 of the transport member 32. In the illustrated embodiment, the upper surface 33 extends perpendicularly to the rotational axis 54 and the axial extension 18, from the one or more recesses 56 to the periphery 35 of the transport member 32. Further, the outer periphery 35 of the transport member 32 is in this embodiment smooth, i.e. free of any extending members, such as wings or blades.

[0103] For instance, collectively, the one or more recesses 56 may have a volume within a range of 0.5 - 10 ml. In this manner, some of expected amounts of condensate and / or oil emulsion may be received in the one or more recesses 56.

[0104] The volume of the one or more recesses 56 may depend on the size of the centrifugal separator and / or expected amounts of condensate and / or oil emulsion to be received on the upper surface 33 of the transport member 32.

[0105] When arranged in the centrifugal separator, the one or more recesses 56 may be arranged at a position that is radially inside the liquid outlet 26, such as radially inside outlet openings 37 of through holes 29 forming the liquid outlet 26

[0106] For instance, the number of recesses 56 may be within a range of 1 - 16. In the illustrated embodiment there are provided 8 recesses 56.The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including" when used herein specify the presence of stated features, integers, actions, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and / or groups thereof.

[0107] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.

[0108] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0109] It is to be understood that the foregoing is illustrative of various examples and that the invention is defined only by the appended claims. A person skilled in the art will realize that the examples may be modified, and that different features of the examples may be combined to create examples other than those described herein, without departing from the scope of the invention, as defined by the appended claims.

Claims

CLAIMS1. A centrifugal separator (2) for separating a liquid phase from a gaseous phase, the centrifugal separator (2) comprising: a stationary casing (4) enclosing a separation space (10), a rotor shaft (6) extending through at least a portion of the separation space (10) along an axial extension (18) and in a substantially vertical direction during use of the centrifugal separator (2), a rotor (8) for separating the liquid phase arranged inside the separation space (10) and connected to the rotor shaft (6), and a transport member (32) for the separated liquid phase connected to the rotor shaft (6) and arranged outside the separation space (10), whereina liquid outlet (26) from the separation space (10) for the liquid phase is arranged at a bottom portion (28) of the separation space (10), and seen radially to the axial extension (18), the liquid outlet (26) being arranged closer to the rotor shaft (6) than to a periphery (30) of the separation space (10), whereinthe transport member (32) is arranged below the liquid outlet (26) and has a radial extension at least to beyond the liquid outlet (26), whereina passage (31) for the liquid phase is arranged radially outside the transport member (32), and whereinthe transport member (32) has an upper surface (33), which extends substantially perpendicularly to the axial extension (18), at least from a radial position of the liquid outlet (26) to a periphery (35) of the transport member (32).

2. The centrifugal separator (2) according to claim 1, wherein the liquid outlet (26) is provided by at least one through hole (29) extending through the stationary casing (4).

3. The centrifugal separator (2) according to claim 2, wherein a distance between the upper surface (33) of the transport member (32) and an outlet opening (37) of the at least one through hole (29) facing the upper surface (33) of the transport member (32) is within a range of 0.05 - 4 mm.

4. The centrifugal separator (2) according to any one of the preceding claims, wherein the rotor shaft (6) is journaled in a bearing (20) arranged in the stationary casing (4) between the rotor (8) and the transport member (32), and wherein the liquid outlet (26) is arranged, seen in relation to the axial extension (18), radially outside the bearing (20).

5. The centrifugal separator (2) according to any one of the preceding claims, wherein the transport member (32) is provided with one or more recesses (56) extending from the upper surface (33) downwardly into a body (58) of the transport member (32).

6. The centrifugal separator (2) according to claim 5, wherein collectively, the one or more recesses (56) have a volume within a range of 0.5 - 10 ml.

7. The centrifugal separator (2) according to claim 5 or 6, wherein the one or more recesses (56) are arranged at a position that is radially inside the liquid outlet (26).

8. The centrifugal separator (2) according to any one of the preceding claims, comprising a one-way valve (42) arranged downstream of the passage (31) for the liquid phase.

9. The centrifugal separator (2) according to any one of the preceding claims, wherein the rotor shaft (6) is driven by an electric motor (44).

10. The centrifugal separator (2) according to claim 9, wherein a rotor (46) of the electric motor (44) is connected to the rotor shaft (6) below the transport member (32).

11. The centrifugal separator (2) according to claim 10, comprising a covering member (47) connected to the stationary casing (4), wherein at least a rotor (50) of the electric motor (44) is arranged within the covering member (47), and wherein the transport member (32) is arranged within the covering member (47).

12. The centrifugal separator (2) according to any previous claim, wherein the transport member (32) is free of any member, such as blades or wings, extending from the outer periphery (35).

13. The centrifugal separator (2) according to claim 12, wherein the outer periphery (35) of the transport member (32) is smooth.

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