Centrifugal separator for cleaning gas

Abstract

The invention provides a centrifugal separator (1) for cleaning a gas containing contaminants. A centrifugal separator comprises: a stationary housing (2) enclosing a separation space (3) through which a gas flow is allowed; a gas inlet (20) extending through the stationary housing (2) and allowing the supply of gas to be cleaned; a rotating member (7) comprising a plurality of separating members (9) arranged in the separating space (3) and arranged to rotate about an axis of rotation (X). The separator (1) further comprises a gas outlet pipe (28) arranged through the fixed housing (2) and configured to allow the cleaned gas to exit from the fixed housing (2), a drain outlet (29) arranged in the fixed housing (2) and configured to allow the liquid contaminants separated from the gas to exit from the fixed housing, and a driving member (22) for rotating the rotating member (7). The centrifugal separator further comprises a stationary insert (30) arranged in the stationary housing (2) and configured for isolating the cleaned gas and the separated contaminants before the cleaned gas and the separated contaminants exit the stationary housing (2), and wherein the gas outlet tube (28) and the stationary insert (30) are formed as a single unit (50).

Description

Technical Field

[0001] The present invention relates to the field of centrifugal separators for cleaning gases containing liquid contaminants. In particular, the present invention relates to a separator for cleaning crankcase gases of a combustion engine from oil particles. Background Art

[0002] It is known that mixtures of fluids having different densities can be separated from one another by the use of centrifugal separators. One particular use of such separators is in separating oil from gases exhausted from a crankcase forming part of an internal combustion engine.

[0003] With regard to this specific use of separators, there may be a tendency for the high pressure gases found in the combustion chamber of an internal combustion engine to leak past the associated piston rings and into the crankcase of the engine. Continued leakage of such gases into the crankcase may result in an undesirable increase in the pressure within the crankcase and thus lead to the need to vent the gases from the housing. Such gases vented from the crankcase typically carry with them a certain amount of engine oil (as small droplets or a fine mist), which are captured by an oil reservoir held in the crankcase.

[0004] In order to allow the exhaust gas to be introduced into the inlet system without also introducing unwanted oil (particularly into a turbocharger system, where the efficiency of the compressor can be adversely affected by the presence of oil), it is necessary to clean the exhaust gas (i.e. remove the oil carried by the gas) before the gas is introduced into the inlet system. This cleaning process can be undertaken by a centrifugal separator, which is mounted on or near the crankcase and which directs the cleaned gas to the inlet system and the separated oil back to the crankcase. For example, an example of such a separator is disclosed in document US 8,657,908.

[0005] Some separators for cleaning crankcase gases have a fixed insert in the housing of the separator (see, for example, document US 8,657,908), which helps to keep the separated pollutants away from the cleaned gas. The clean gas should flow from the fixed insert to the air inlet of the motor or to the outdoors via an outlet pipe. The outlet pipe is usually assembled from the outside, and since the air leaving cannot be contaminated by particles or oil droplets around the outlet pipe, and the assembly must be airtight, a good seal of the outlet pipe is required. The sealing of the outlet pipe is usually achieved using multiple O-rings.

[0006] However, in the finished product, such seals may be well hidden within the structure, which means that it may be difficult to inspect and control the function or presence of such seals. This may be a problem in mass production of crankcase gas separators. Furthermore, the use of O-ring seals also makes automated production of separators difficult, while manual assembly may damage the O-ring seals.

[0007] Therefore, there is a need in the art for improved sealing functionality of centrifugal separators. Summary of the invention

[0008] It is an object of the present invention to at least partially overcome one or more limitations of the prior art. In particular, it is an object to provide a centrifugal separator with an enhanced sealing function of the outlet pipe which also improves the manufacturing process.

[0009] As a first aspect of the present invention, a centrifugal separator for cleaning a gas containing pollutants is provided, the centrifugal separator comprising

[0010] a stationary housing enclosing a separation space allowing a gas flow to pass through,

[0011] a gas inlet which extends through the stationary housing and allows the supply of the gas to be cleaned,

[0012] a rotating component comprising a plurality of separate components arranged in a separate space and arranged to rotate about a rotation axis (X),

[0013] a gas outlet pipe arranged to pass through the stationary housing and configured to allow the cleaned gas to be discharged from the stationary housing,

[0014] a drainage outlet disposed in the stationary housing and configured to allow liquid contaminants that have been separated from the gas to be discharged from the stationary housing;

[0015] a driving member for rotating the rotating member;

[0016] The centrifugal separator also includes

[0017] a stationary insert disposed in the stationary housing and configured to isolate the cleaned gas and the separated contaminants before the cleaned gas and the separated contaminants exit the stationary housing, and

[0018] Therein, the gas outlet pipe and the fixing insert are formed as a single unit.

[0019] As used herein, the term "axial" refers to a direction parallel to the axis of rotation (X). Therefore, relative terms such as "above", "upper", "top", "below", "lower" and "bottom" refer to relative positions along the axis of rotation (X). Correspondingly, the term "radial" refers to a direction extending radially from the axis of rotation (X). A "radially inner position" therefore refers to a position closer to the axis of rotation (X) than a "radially outer position". A radial plane is a plane whose normal is parallel to the axis of rotation (X). An axial plane is a plane whose normal is perpendicular to the axis of rotation (X).

[0020] Contaminants in the gas may include liquid contaminants such as oil and soot.

[0021] Thus, a centrifugal separator can be used to separate liquid contaminants, such as oil, from a gas. The gas may be crankcase gas from a combustion engine. However, a centrifugal separator is also suitable for cleaning gases from other sources, such as machine tool environments which often contain large amounts of liquid contaminants in the form of small oil droplets or oil mist.

[0022] The stationary housing of the centrifugal separator may comprise a surrounding side wall and a first and a second end wall, which enclose the separation space. The stationary housing may have a cylindrical shape with a circular cross section having a radius R from the axis of rotation (X) to the surrounding side wall. The radius R may be constant at least about a large part of the periphery of the surrounding side wall. Thus, the first and the second end wall may form the upper and the lower end wall of the cylindrical housing. The stationary housing may also be slightly conical.

[0023] The gas inlet of the centrifugal separator may be arranged through the first end wall or through the surrounding side wall near the first end wall, thus at the top of the separator, so that the gas entering through the gas inlet is guided to the separation space. The downstream part of the gas inlet may be centered around the axis of rotation (X). The gas inlet may also include an upstream part in the form of an inlet duct. The duct may extend radially or axially from the centrifugal separator, or in any other direction therebetween.

[0024] The rotating component is arranged to be rotated by the driving component during operation. The rotating component comprises a plurality of separation components arranged in the separation space. The separation components of the rotating component are examples of increased surface plugs that promote the separation of pollutants from the gas. The separation components can be stacked separation disks. The stacked separation disks can be frustoconical. The frustoconical disks can have a planar portion extending in a plane perpendicular to the axis of rotation and a frustoconical portion that can extend upward or downward. The planar portion can be closer to the axis of rotation than the frustoconical portion. In addition, the stacked disks can be radial disks, in which substantially the entire disk extends in a plane perpendicular to the axis of rotation.

[0025] It should also be understood that the separation components (such as separation discs) do not necessarily have to be arranged in a stack. The separation space may, for example, include an axial disc or plate extending around the axis of rotation. The axial disc or plate may be planar, i.e. extending in a plane parallel to the axis of rotation. The axial disc or plate may also have a slightly or significantly curved shape, such as an arc or spiral, as seen in a radial plane.

[0026] The rotating component may be diametrically supported in the stationary housing via at least one bearing, such as via an upper bearing and a lower bearing arranged axially above and below the stacked separation components, respectively.

[0027] The drain outlet may be arranged in the lower part of the fixed housing, such as in the second end wall, for example at the bottom of the separator. Thus, the drain outlet may be arranged centrally in the end wall opposite to the end wall through which the inlet passes or at which it is arranged. The drain outlet of the centrifugal separator may also be formed by several point-shaped through holes of the fixed housing or by a single drain channel. The drain outlet may be arranged at the axis of rotation or centered around the axis of rotation. The drain outlet may also be in an annular collecting groove at the inner end wall of the fixed housing. The drain outlet may be arranged so that pollutants such as oil are discharged through the bearings arranged for the shaft diameter support rotating parts.

[0028] The outlet for the cleaned gas is in the form of a gas outlet pipe extending through a wall of the stationary housing, such as through a lower portion of a surrounding side wall of the stationary housing. Thus, the gas outlet pipe may be a conduit for the cleaned gas having a gas inlet inside the stationary housing and a gas outlet outside the stationary housing. The gas outlet pipe may extend through the stationary housing to a radial position greater than the radial position of the outer wall of the stationary housing, or to a radial position that is the same as the radial position of the outer wall of the stationary housing.

[0029] The gas outlet tube may be a generally cylindrical tube or have another cross-section, such as an elliptical cross-section.

[0030] During operation, the gas to be cleaned can be directed centrally through a plurality of separation components, such as centrally through a stack of separation disks. In such a configuration, the rotating component can also define a central space formed by at least one through hole in the separation component. The central space is connected to the gas inlet and is configured to deliver the gas to be cleaned from the gas inlet to a gap between the separation components, such as a gap between the disks of the separation disk stack. The separation disk that can be used as the separation component can include a substantially flat central portion perpendicular to the axis of rotation. The portion can include through holes that form part of the central space.

[0031] Thus, the centrifugal separator may be configured to deliver the gas to be cleaned, such as crankcase gas, from the gas inlet to the central part of the rotating component. In this way, the crankcase gas may be "pumped" from the central part of the rotating component into the gaps between the separation discs in the separation disc stack by the rotation of the rotating component. Thus, the centrifugal separator may work according to the co-current principle (in which the gas flows from the radially inner part to the radially outer part in the disc stack), as opposed to a separator operating according to the counter-current principle (in which the gas is guided into the separation space at the periphery and delivered towards the central part of the separation space).

[0032] The drive member may for example comprise a turbine wheel which is rotated by an oil jet from the lubricating oil system of the combustion engine or a free jet wheel comprising a blowback disc. However, the drive member may also be independent of the combustion engine and comprise an electric motor, a hydraulic motor or a pneumatic motor.

[0033] Furthermore, according to a first aspect, the separator further comprises a fixed plug-in. Such a plug-in may be similar to the housing plug-in shown in document US 8,657,908 and is therefore arranged to facilitate the separate retention of the cleaned gas and the separated pollutants in the fixed plug-in once the pollutants are separated from the gas. Moreover, the fixed plug-in arranged in the housing is formed as a separate unit together with the gas outlet pipe. Therefore, the separate unit can be removed from the separator as a separate unit.

[0034] The first aspect of the invention is based on the recognition that by making the fixed insert and the gas outlet pipe as a single unit (such as a single moulded unit), at least some (such as all) of the seals between the insert and the gas outlet pipe can be removed. Therefore, the design reduces the risk of manual assembly and improves the sealing ability, thereby reducing the risk of contaminants re-entering the cleaned gas after separation in the separation space. The first aspect of the invention also reduces the risk of leaving a seal between the fixed insert and the outlet pipe during production, which is difficult to test or check after the entire separator is assembled.

[0035] Thus, in an embodiment of the first aspect, the centrifugal separator is without any additional seal between the gas outlet pipe and the fixed insert. Such an additional seal may therefore be an O-ring.

[0036] In an embodiment of the first aspect, the stationary housing comprises at least one surrounding annular side wall.The gas outlet pipe, the stationary insert and the at least one surrounding annular side wall may then be formed as a single unit.

[0037] Thus, the surrounding annular side wall is the wall through which the gas outlet pipe is arranged. This also reduces the need for additional sealing between the gas outlet pipe and the stationary housing and also increases the sealing function of the gas outlet pipe, since it is formed in one piece with the surrounding side wall of the stationary housing. Thus, in an embodiment, the centrifugal separator is without any additional sealing between the gas outlet pipe and the at least one surrounding annular side wall.

[0038] As an example, the stationary housing may comprise an upper and a lower surrounding annular side wall.The gas outlet pipe, the stationary insert and the lower surrounding annular side wall may then be formed as a single unit.

[0039] The lower surrounding side wall may be cylindrical and may be connected to the upper surrounding side wall, for example by welding or by fastening means, such as bolts. This facilitates mounting of the rotating component within the stationary housing. The lower surrounding annular side wall may extend downwardly to the lower end wall of the stationary housing. The lower end wall may thus be a radially extending lower wall, such as in a radial plane or at a small angle relative to the radial plane. In some embodiments, the lower end wall is also part of the lower surrounding annular side wall.

[0040] The upper end wall of the stationary housing may also be formed as a unit with the upper surrounding annular side wall.

[0041] In an embodiment, the centrifugal separator comprises a single surrounding annular side wall and a cover forming an upper end wall of the stationary housing.The gas outlet pipe, the stationary insert and the single surrounding annular side wall may then be formed as a single unit.

[0042] As used herein, a "single unit" may be a single moulding of plastics material. Such a single moulding may therefore comprise the fixed insert and the gas outlet pipe, or the fixed insert, the gas outlet pipe and the surrounding annular side wall of the fixed housing.

[0043] Thus, in an embodiment of the first aspect, the single unit is a moulded unit.

[0044] The molded unit can be produced by injection molding of polymers or die casting of metals.

[0045] In an embodiment of the first aspect, the fixed insert comprises an annular wall member.The fixed insert may then be arranged in the fixed housing so as to form an annular vertical passage for the separated contaminants between an inner wall of the fixed housing and the annular wall member.

[0046] The annular wall member may thus extend in the axial direction, such as parallel to the axis of rotation (X) or at a slight angle to the axis of rotation (X). Such an angle may be less than 45 degrees, such as less than 30 degrees. In an embodiment, the annular wall member extends in the axial direction at an angle between 0.5 and 5 degrees, such as between 0.5 and 3 degrees.

[0047] As mentioned above, the separated pollutants may include oil that is thrown to the inner wall of the fixed housing after separation from the gas in the separation part. These small oil droplets drip down along the inner wall by gravity and are guided to the drainage outlet. The annular vertical channel between the annular wall part and the inner wall of the fixed housing can then form a "quiet zone" in which the risk of the rotating gas pulling the separated oil away from the inner wall is reduced. The annular vertical channel can form a ditch for the separated pollutants.

[0048] Furthermore, the fixing insert may further comprise a central cup member with a conically extending side wall. At least part of the rotating member may be arranged in such a central cup member.

[0049] Thus, the central cup member may be arranged around the axis of rotation. The central cup member may have a truncated cone shape. In an embodiment, the gas outlet pipe may be arranged so that it has a gas inlet at the inner surface of the central cup member and a gas outlet on the outside of the fixed shell. As described above, the separation member may be a stack of separation discs. These discs may be arranged between the lower end plate and the upper top plate, and at least part of the lower end plate may be arranged in the cup member of the fixed plug-in. Part of the lowermost separation disc may have a portion, such as a lower portion, arranged in the cup member.

[0050] As an example, the annular wall member of the retaining insert discussed above may extend downwardly from the outer edge of the cup member.

[0051] In an embodiment of the first aspect, the fixing insert is arranged in a lower part of the fixing housing.

[0052] Thus, the lower part may be the lower half of the stationary housing. As described above, the stationary housing may include an upper and lower surrounding annular sidewalls. The stationary insert may then be arranged axially within the lower surrounding sidewall, such that the lower surrounding sidewall surrounds the insert.

[0053] In an embodiment of the first aspect, a plurality of separation components are stacked separation discs, such as stacked truncated conical separation discs. Such discs may have an outer radius and an inner radius, so that a central opening is formed in the disc. The truncated conical separation disc may include a flat portion extending perpendicular to the axis of rotation (X) and a conical portion extending outwardly and downwardly or upwardly from the flat portion. The opening in the flat portion may form a portion of the central space in the centrifugal separator into which the gas to be cleaned is directed from the gas inlet. Therefore, the gas to be cleaned may be directed into the central space and then to the gap formed between the discs in the disc stack. In addition or alternatively, the central space may also be formed radially within the inner radius of the disc.

[0054] In an embodiment of the first aspect, the rotating component comprises an axial shaft supported by the at least one bearing. The axial shaft may thus be centered at the axis of rotation (X). The separating component may be arranged around such axial shaft.

[0055] As a second aspect of the present invention, a method for cleaning a gas containing pollutants is provided, the method comprising:

[0056] directing the gas containing pollutants to the centrifugal separator according to the first aspect above during the rotation of the rotating part,

[0057] discharging the cleaned gas from the gas outlet, and

[0058] Remove contaminants from the drain outlet.

[0059] Contaminants in the gas may include liquid contaminants such as oil and soot.

[0060] This aspect may generally present the same or corresponding advantages as the previous aspect. The effects and features of the third aspect are generally similar to those described above in conjunction with the first and second aspects. The embodiments mentioned in relation to the first aspect are generally compatible with the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above content and additional objects, features and advantages of the inventive concept will be better understood through the following illustrative and non-limiting detailed description with reference to the accompanying drawings. Unless otherwise specified, similar reference numerals will be used in the drawings to represent similar elements.

[0062] Figure 1 A schematic diagram of a cross section of an embodiment of a centrifugal separator for cleaning gases is shown.

[0063] Figure 2 A perspective view of a single unit comprising the outlet tube, the fixing insert and the outer wall of the fixing housing is shown. DETAILED DESCRIPTION

[0064] The centrifugal separator according to the present disclosure will be further explained by the following description with reference to the accompanying drawings.

[0065] Figure 1 A cross section of a centrifugal separator 1 according to the present disclosure is shown. The centrifugal separator 1 comprises a stationary housing 2 configured to be mounted to a combustion engine (not disclosed), in particular a diesel engine, at a suitable location, such as on top of the combustion engine or at the side of the combustion engine.

[0066] It is to be noted that the centrifugal separator 1 is also suitable for cleaning gases coming from other sources than combustion engines, such as machine tool environments which often contain large amounts of liquid contaminants in the form of small oil droplets or oil mist.

[0067] The stationary housing 2 surrounds a separation space 3 through which an air flow is allowed to pass. The stationary housing 2 includes or is formed by a surrounding side wall 4, an upper end wall 5 and a lower end wall 6. The surrounding side wall 4 includes an upper surrounding annular side wall 4b and a lower surrounding annular side wall 4a attached to each other, for example, via welding or bolts (not shown). There may also be a sealing member (not shown), such as an O-ring, between the upper surrounding annular side wall 4b and the lower surrounding annular side wall 4a.

[0068] The centrifugal separator 1 comprises a rotating part 7 arranged to rotate about an axis of rotation (X). It should be noted that the stationary housing 2 is stationary with respect to the rotating part 7 and preferably with respect to the combustion engine to which it may be mounted.

[0069] The stationary housing 2 has a radius from the axis of rotation (X) to the surrounding side wall 4 which is constant at least over a large part of the circumference of the surrounding side wall 4. The surrounding side wall 4 thus has a circular or substantially circular cross section in a radial plane.

[0070] The rotating part 7 comprises a rotatable shaft, ie a main shaft 8, and a stack of separation discs 9 attached to the main shaft 8. All separation discs in the stack 9 are arranged between a top disc 10 and a lower end plate 11.

[0071] The main shaft 8 and thus the rotating part 7 are rotatably supported in the stationary housing 2 by upper and lower bearings 12, 13, which are arranged one on each axial side of the separation disc stack 9. However, the bearings may, for example, be arranged both axially below or above the separation disc stack 9.

[0072] The separation discs of the disc stack 9 are frustoconical and extend outwardly and upwardly from the main shaft 8. The separation discs thus comprise a flat portion 9a extending perpendicularly to the axis of rotation (X) and a conical portion 9b extending outwardly and upwardly from the flat portion 9a. It should be noted that the separation discs may also extend outwardly and downwardly or even radially.

[0073] The separation discs of the stack 9 are arranged to be spaced a certain distance from each other by spacer members (not disclosed) so as to form gaps 14 between adjacent separation discs 9, i.e., between each pair of adjacent separation discs 9. The axial thickness of each gap 14 may be, for example, of the order of 0.5-2 mm, such as 1-2 mm.

[0074] The separation discs of the stack 9 can be made of plastic or metal. The number of separation discs in the stack 9 is usually higher than Figure 1 The number of separation discs 9 shown in FIG. 1 and depending on the size of the centrifugal separator may be, for example, 50 to 100.

[0075] The centrifugal separator 1 comprises an oil nozzle 24 arranged to be connected to the engine oil circuit of the internal combustion engine. During the operation of the internal combustion engine, oil is pumped to the turbine impeller 22 arranged in the turbine housing 26 through the oil nozzle 24. Since the turbine impeller 22 is connected to the main shaft 8, the rotating component 7 and therefore the separation disk stack 9 also rotate when the impeller 22 rotates. As an alternative, the centrifugal separator 1 may include an electric motor arranged to rotate the main shaft 8 and the rotating component 7. As another alternative, the centrifugal separator 3 may include a turbine impeller connected to the main shaft 8, wherein the turbine impeller is arranged to be driven by the exhaust gas from the internal combustion engine to rotate the main shaft 8 and the rotating component 7. The rotating component 7 may also be arranged to be rotated by a mechanical drive unit. Therefore, the centrifugal separator may include a mechanical drive unit for rotating the rotating component.

[0076] The rotating member 7 defines a central space 15. The central space 15 is formed by through holes in each separation disc 9. Figure 1 In the embodiment of the central space 15 is formed by a plurality of through holes, each through hole extending through the top disc 10 and through each separation disc 9, but not through the lower end plate 11. The through holes are arranged in the flat portion 9a of the separation disc.

[0077] The gas inlet 20 is used to supply the gas to be cleaned. The gas inlet 20 extends through the stationary housing 2 and more precisely through the upper end wall 5. The gas inlet 20 is formed by an axially extending inlet duct 18 forming an upstream portion of the inlet 20 and a through-channel 21 forming a downstream portion thereof.

[0078] The through-channel 21 is in fluid connection with the central space 15 and is arranged radially outside the upper bearing 12. Thus, the gas inlet 20 is in communication with the central space 15, so that the gas to be cleaned is conveyed from the inlet 20 via the central space 15 to the gap 14 of the separation disc stack 9. The gas inlet 20 is configured to communicate with the crankcase of the combustion engine or any other source via the inlet duct 18, allowing crankcase gas to be supplied from the crankcase to the gas inlet 20 and further to the central space 15 and the gap 14, as explained above.

[0079] The centrifugal separator 1 comprises a drain outlet 29, which is arranged in the lower part of the stationary housing 2 and is configured to allow the liquid contaminants separated from the gas to be discharged. The drain outlet 29 is in the form of a through hole arranged in the lower end wall 6 in this embodiment, so that the separated liquid contaminants flow through the lower bearing 13 when they are discharged from the separation space 3 to the turbine housing 26. The separated oil and other particles and / or substances are guided to the oil outlet 25 of the centrifugal separator 1, which can be guided back to the engine oil circuit of the internal combustion engine together with the oil from the oil nozzle 24 used to drive the impeller 22.

[0080] The gas outlet pipe 28 of the centrifugal separator 1 is arranged through the stationary housing 2 and is configured to allow the cleaned gas to be discharged.

[0081] In such Figure 1 During operation of the centrifugal separator shown, the rotating part 7 is kept in rotation by means of oil nozzles 24 which supply oil to the impeller 22. As an example, the rotation speed may be in the range of 7500-12000 rpm.

[0082] Contaminated gas, for example crankcase gas from the crankcase of an internal combustion engine, is supplied to the gas inlet 20 via the conduit 18. The gas is further guided into the central space 15 and from there into and through the gaps 14 between the separation disks of the stack 9. Due to the rotation of the rotating part 7, the gas is set in rotation, whereby it is pumped further radially outwards through the gaps or interstices 14.

[0083] During the rotation of the gas in the gap 14, solid or liquid particles (such as oil) suspended in the gas are separated therefrom. The particles settle on the inner side of the conical portion 9b of the separation disc and thereafter slide or move radially outward thereon. When the particles and / or droplets reach the radially outer edge of the separation disc 9, they are thrown out from the rotating part 7 and hit the inner surface 40 of the surrounding side wall 4. The separated oil particles can form a film on the inner surface of the fixed shell 2. From there, the oil can be pulled downward by gravity to the bottom end wall 6 and then leave the separation space 3 through the drain outlet 29. To this end, the inner wall of the bottom end wall 6 can be inclined radially inwardly so that the oil leaving the surrounding inner wall of the fixed shell 2 can be pulled by gravity toward the drain outlet 29. In Figure 1 The path of the contaminants in the gas is schematically shown by arrows "D".

[0084] The cleaned gas, which is free of particles and exits the separation disc stack 9, leaves the stationary housing 2 via the gas outlet pipe 28. Figure 1 The path of the gas through the centrifugal separator 1 is schematically shown by arrow "C".

[0085] Figure 1 The centrifugal separator of 10 further comprises a fixing insert 30 which is arranged in the lower part of the stationary housing 2, in the present example, in the lower surrounding side wall 4a. The fixing insert 30 comprises an annular wall part 31 and a central frustoconical cup part 33 with a conically extending side wall. In the present example, the lower part of the end plate 11 is arranged in the central cup part 33. The fixing insert can also be fastened to the lower end wall 6, such as to a bearing plate for the lowermost bearing 13.

[0086] The annular wall member 31 extends axially downward from the outer edge of the cup member 33. The fixed insert 30 is configured to isolate the cleaned gas and the separated pollutants before the cleaned gas and the separated pollutants leave the fixed housing 2. To this end, the fixed insert 30 is arranged in the fixed housing 2 so that an annular vertical channel 32 for the separated pollutants is formed between the inner wall 40 of the fixed housing 2 and the annular wall member 31.

[0087] The annular wall member 31 may not extend axially all the way down to the lower end wall 6. In such a case, a gap 51 is provided below the axially lowest portion of the annular wall member 31. Thus, the annular vertical channel 32 may form an annular gap and may collect separated oil droplets that are thrown out of the separation disc 9 and move downward on the inner wall 40 of the fixed housing 4 under the action of gravity during use of the separator 1. The action of the downward spiraling airflow may also force the oil to flow downward on the inner wall 40. The oil in the vertical channel 32 may flow into the area formed below the lower side of the housing insert 32 and be discharged via the drain outlet 29.

[0088] Alternatively, the annular vertical channel 32 may form a channel 32 with a U-shaped cross section. The gap 51 may then be a drain hole in such a channel, through which the oil collected in the channel 32 can flow into an area formed below the underside of the housing insert 32 and be discharged via the drain outlet 29. The drain outlet may be formed so that the oil flows through the lower bearing 13 or radially outside the lower bearing 13 downward into the turbine housing 26.

[0089] The annular vertical channel 32 thus protects the separated liquid particles flowing downwardly on the inner wall 40 from the rotating gas, thereby reducing the risk of the separated oil being pulled away from the inner wall 40 on its way down to the drain outlet 29 .

[0090] In the present example, the cleaned gas flows into the gas outlet pipe 28 via the inner volume formed by the cup member 33 because the gas outlet pipe has its gas inlet at the inner surface of the cup member 33 .

[0091] like Figure 1 As shown in the dotted texture of , the gas outlet pipe 28 and the fixed plug 30 are formed as a single unit 50. The fixed housing 2 also includes an upper surrounding annular side wall 4b and a lower surrounding annular side wall 4a, and the lower surrounding side wall 4a is also part of the single unit 50. The single unit 50 is a molded unit cast as a single item of polymer or plastic material. Since the fixed plug 30, the gas outlet pipe 28 and the lower surrounding annular side wall 4a are formed as a single unit, the centrifugal separator 1 does not have any additional seals, such as O-rings, between the gas outlet pipe 28 and the fixed plug 30. In addition, the centrifugal separator 1 does not have any additional seals, such as O-rings, between the gas outlet pipe 28 and the lower surrounding annular side wall 4a.

[0092] Figure 2 A perspective cross-sectional view of a single unit 50 is shown to further illustrate the annular vertical passage 32 formed between the housing insert 30 and the inner wall 40 of the surrounding side wall 4a. In addition, the gas inlet 28a to the outlet duct 28 is arranged at the inner surface of the cup 33, and the direction of the cleaned gas exiting through the outlet pipe 28 is indicated by arrow "C".

[0093] like Figure 2 The single unit 50 shown in FIG. 5 comprises the gas outlet pipe 28 , the fixing insert 30 and the lower surrounding annular side wall 4 a and is cast as a single moulded unit.

[0094] The invention is not limited to the disclosed embodiments, but may be varied and modified within the scope of the claims as listed. The invention is not limited to the orientation of the axis of rotation (X) disclosed in the figures. The term "centrifugal separator" also includes centrifugal separators with a substantially horizontally oriented axis of rotation. In the above, the inventive concept has been described mainly with reference to a limited number of examples. However, as will be readily appreciated by a person skilled in the art, other examples than the examples disclosed above are equally possible within the scope of the inventive concept as defined by the appended claims.

Claims

1. A centrifugal separator (1) for cleaning a gas containing pollutants, the centrifugal separator comprising: a stationary housing (2) enclosing a separation space (3) allowing a gas flow to pass through, a gas inlet (20) extending through the stationary housing (2) and allowing the supply of the gas to be cleaned, a rotating member (7) comprising a plurality of separating members (9) arranged in the separating space (3) and arranged to rotate about a rotation axis (X), a gas outlet pipe (28) arranged to pass through the stationary housing (2) and configured to allow the cleaned gas to be discharged from the stationary housing (2), a liquid discharge outlet (29) disposed in the stationary housing (2) and configured to allow liquid contaminants separated from the gas to be discharged from the stationary housing; a driving component (22) for rotating the rotating component (7); Wherein, the centrifugal separator also includes a stationary insert (30) disposed in the stationary housing (2) and configured to isolate the cleaned gas and the separated contaminants before the cleaned gas and the separated contaminants leave the stationary housing (2), and Therein, the gas outlet pipe (28) and the fixing insert (30) are formed as a single unit (50).

2. The centrifugal separator (1) according to claim 1, wherein: The centrifugal separator (1) does not have any additional seal between the gas outlet pipe (28) and the fixed insert (30).

3. The centrifugal separator (1) according to claim 1, wherein: The stationary housing (2) comprises at least one surrounding annular side wall (4a, 4b), and wherein the gas outlet pipe (28), the stationary insert (30) and the at least one surrounding annular side wall (4a, 4b) are formed as a single unit (50).

4. The centrifugal separator (1) according to claim 3, wherein: The centrifugal separator is free of any additional seal between the gas outlet pipe (28) and the at least one surrounding annular side wall (30).

5. The centrifugal separator (1) according to claim 3 or 4, wherein: The fixed housing (2) comprises an upper surrounding annular side wall (4b) and a lower surrounding annular side wall (4a), and wherein the gas outlet pipe (28), the fixed plug (30) and the lower surrounding annular side wall (4a) are formed as a single unit (50).

6. A centrifugal separator (1) according to any one of the preceding claims, wherein: The single unit (50) is a molded unit.

7. A centrifugal separator (1) according to any one of the preceding claims, wherein: The fixed plug (30) comprises an annular wall part (31), and wherein the fixed plug (30) is arranged in the fixed housing (2) so as to form an annular vertical channel (32) for separated pollutants between an inner wall (40) of the fixed housing (2) and the annular wall part (31).

8. The centrifugal separator (1) according to claim 7, wherein: The fixed insert (30) further comprises a central cup member (33) with a conically extending side wall, and wherein at least a portion of the rotating member (7) is arranged within the central cup member (33).

9. The centrifugal separator (1) according to claim 8, wherein: The annular wall member (31) extends downward from the outer edge of the cup member (33).

10. A centrifugal separator (1) according to any one of the preceding claims, wherein: The fixing plug-in element (30) is arranged in the lower part of the fixing housing (2).

11. A centrifugal separator (1) according to any one of the preceding claims, wherein: The separation elements (9) are stacked frustoconical separation discs.

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