Centrifugal separator for purifying gas

Abstract

The invention provides a centrifugal separator (1) for purifying a gas containing contaminants. The centrifugal separator comprises: a stationary housing (2) enclosing a separation space (3) through which a flow of gas is permitted; a gas inlet (20) extending through the stationary housing (2) and allowing the supply of gas to be purified; and 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). The separator (1) further comprises: a gas outlet (28) configured to allow the purified gas to exit from the stationary housing (2); a drain outlet (25) configured to allow the discharge of the liquid contaminants separated from the gas from the centrifugal separator (1); and a driving member (22) for rotating the rotating member (7). The centrifugal separator (1) further comprises a mounting bracket (30) configured for mounting the centrifugal separator (1) to an engine or an engine block and engaging with the outer surface (4a) of the stationary housing (2). The mounting bracket (30) and the stationary housing (2) are configured to allow permanent engagement of the mounting bracket (30) to the outer surface (4a) of the stationary housing (2) at different angular positions about the axis of rotation (X).

Description

Technical Field

[0001] The present invention relates to the field of centrifugal separators for purifying gases containing liquid contaminants. In particular, the present invention relates to a separator for purifying crankcase gases of internal combustion engines 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 to separate oil from gases which are exhausted from the crankcase of an internal combustion engine.

[0003] With regard to this particular use of separators, the high pressure gases found in the combustion chambers of internal combustion engines may have a tendency to leak past the associated piston rings and into the crankcase of the engine. Continued leakage of such gases into the crankcase can result in an undesirable increase in pressure within the crankcase and thus a 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 droplets or fine mist) picked up from an oil tank 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 may be adversely affected by the presence of oil), the exhaust gas must be purified (i.e., the oil carried by the gas is removed) before the gas is introduced into the inlet system. This purification process may be performed by a centrifugal separator, which is mounted on or near the crankcase and directs the purified gas to the inlet system and the separated oil back to the crankcase. An example of such a separator is disclosed, for example, in US 8,657,908.

[0005] Centrifugal separators for purifying crankcase gases are usually fastened to an engine or engine block. This usually requires a fairly robust design to minimize vibrations. As an example, the separator may be fastened to the engine or engine block via a metal bracket that connects the lower part of the centrifugal separator to the engine or engine block.

[0006] Furthermore, the space around the engine or engine block may be quite limited and with prior art designs of fastened separators it may be difficult to adapt the position of the gas inlet and outlet to the actual available space around the engine. In other words, this means that the flexibility in adapting the position of the centrifugal separator to the engine or engine block is quite limited.

[0007] Therefore, there is a need in the art for improved flexibility in fastening a centrifugal separator to an engine or engine block. Summary of the invention

[0008] An object of the present invention is to at least partially overcome one or more limitations of the prior art. In particular, an object of the present invention is to provide a centrifugal separator which facilitates increased flexibility in adapting the centrifugal separator to different engines or engine blocks.

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

[0010] a stationary housing enclosing a separation space allowing a gas flow therethrough and comprising a surrounding side wall surrounding the separation space,

[0011] a gas inlet extending through the fixed housing and allowing the supply of the gas to be purified,

[0012] a rotating part comprising a plurality of separate parts arranged in said separation space and arranged to rotate about a rotation axis (X),

[0013] a gas outlet configured to allow the purified gas to be exhausted from the stationary housing,

[0014] a liquid discharge outlet configured to allow liquid contaminants separated from the gas to be discharged from the centrifugal separator;

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

[0016] The centrifugal separator also includes

[0017] a mounting bracket configured for mounting the centrifugal separator to an engine or engine block and engaging an outer surface of the surrounding side wall of the stationary housing,

[0018] And wherein the mounting bracket and the fixed housing are configured to allow the mounting bracket to be permanently joined to the outer surface of the surrounding side wall of the fixed housing at different angular positions about the rotation axis (X).

[0019] As used herein, the term "axially" refers to a direction parallel to the axis of rotation (X). Thus, relative terms such as "above", "upper", "top", "below", "lower" and "bottom" refer to relative positions along the axis of rotation (X). Correspondingly, the term "radially" refers to a direction extending radially from the axis of rotation (X). Thus, a "radially inner position" 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 an internal combustion engine. However, a centrifugal separator may also be suitable for purifying gas from other sources, such as a machine tool environment, which often contains a large amount of liquid contaminants in the form of oil droplets or oil mist.

[0022] The fixed housing of the centrifugal separator comprises a surrounding side wall surrounding the separation space. The surrounding side wall may extend through the entire axial length of the separation space or extend through a portion of the axial length of the separation space surrounding the separation space. The fixed housing may also comprise a first and a second end wall, which enclose the separation space at the top and the bottom of the separation space. The fixed 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 is constant at least with respect to a large part of the circumference of the surrounding side wall. Thus, the first and the second end wall may form the upper and lower end walls of the cylindrical housing. The fixed housing may also be slightly conical.

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

[0024] The rotating member is arranged to be rotated by the driving member during operation. The rotating member comprises a plurality of separation members arranged in the separation space. The separation members of the rotating member are examples of surface enlarged inserts which promote separation of pollutants from the gas. The separation members may be a stack of separation discs.

[0025] Thus, in an embodiment of the first aspect, the plurality of separation components is a stack of separation discs, such as a stack of frustoconical separation discs. Such discs may have an outer radius and an inner radius, thereby forming a central opening in the disc. The frustoconical separation disc may comprise a flat portion extending perpendicularly to the axis of rotation (X), and a conical portion extending outwardly and downwardly or upwardly from the flat portion. The flat portion may be closer to the axis of rotation than the frustoconical portion.

[0026] The opening in the flat portion may form part of a central space within the centrifugal separator into which the gas to be purified is guided from the gas inlet. Thus, the gas to be purified may be guided into the central space and then into the gaps formed between the disks in the disk stack. Additionally or alternatively, the central space may also be formed radially within the inner radius of the disk.

[0027] Furthermore, the stacked disks may be radial disks, wherein substantially the entire disk extends in a plane perpendicular to the axis of rotation.

[0028] 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.

[0029] In an embodiment of the first aspect, the rotating component comprises an axial shaft supported by 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.

[0030] The rotating component may be supported in the stationary housing via at least one bearing journal, such as via an upper bearing and a lower bearing arranged axially above and below the stack of separate components, respectively.

[0031] The drain outlet may be arranged in a lower part of the stationary housing, such as in the second end wall, for example at the bottom of the separator.

[0032] The separated pollutants can first be guided from the inside of the separation space to, for example, a drive chamber in which the drive component is arranged. This drainage can be discharged via an internal drainage component formed by a number of point-shaped through holes or a single drainage channel of the fixed shell. The drainage discharged from the separation space can also be in an annular collecting groove at the inner end wall of the fixed shell. The internal drainage can be arranged so that pollutants (such as oil) are discharged through the bearings arranged for the journal support rotating components. If the drive component includes a turbine impeller driven by an oil jet, the separated pollutants can be discharged together with the oil used to drive the oil jet. Then, the drainage outlet of the centrifugal separator can be connected to the drive chamber.

[0033] Thus, the drain outlet may be arranged axially at an end of the centrifugal separator opposite to the end through or at which the inlet is arranged.The drain outlet may be arranged at or centrally around the axis of rotation.

[0034] The outlet for the purified gas extends through the wall of the fixed housing, such as through the lower part of the surrounding side wall of the fixed housing. Therefore, the gas outlet can be a conduit for clean gas, which has a gas inlet in the fixed housing and a gas outlet outside the fixed housing. Such a conduit can extend through the fixed housing to a radial position greater than the radial position of the outer wall of the fixed housing, or to a radial position that is the same as the radial position of the outer wall of the fixed housing. The gas outlet can be connected to a valve, such as a membrane valve, through which the clean gas is conveyed before leaving the centrifugal separator.

[0035] During operation, the gas to be purified may be directed centrally through a plurality of separation components, such as centrally through a stack of separation discs. In this arrangement, the rotating component may further 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 transfer the gas to be purified from the gas inlet to a gap between the separation components, such as a gap between the discs in the stack of separation discs. A separation disc that may be used as a separation component may include a central, substantially flat portion perpendicular to the axis of rotation. The portion may include a through hole forming a portion of the central space.

[0036] Thus, the centrifugal separator may be configured to transfer the gas to be purified, such as crankcase gas, from the gas inlet to the central part of the rotating component. In this way, the crankcase gas can 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 operate according to the co-current flow principle, wherein the gas flows from the radially inner part to the radially outer part in the disc stack, in contrast to a separator operating according to the counter-current flow principle, in which the gas is guided into the separation space at the periphery and transferred towards the central part of the separation space.

[0037] The drive member may for example comprise a turbine wheel rotated by an oil jet from the lubricating oil system of the internal combustion engine, or a free jet impeller comprising a blowback disk. However, the drive member may also be independent of the internal combustion engine and comprise an electric motor, a hydraulic motor or a pneumatic motor.

[0038] The mounting bracket is used to fasten the centrifugal separator to the engine or engine block.

[0039] A first aspect of the invention is based on the recognition that designing the mounting bracket to be fastened to the fixed housing and to axially surround the separation space improves vibration stability and allows the use of a mounting bracket of a less dense material. Furthermore, flexibility is increased by configuring the mounting bracket and the fixed housing to allow the mounting bracket to be permanently joined to the outer surface of the surrounding side wall of the fixed housing at different angular positions (i.e. a plurality of angular positions) around the axis of rotation (X). In other words, the centrifugal separator can be adapted to a greater number of different engines or engine blocks, since the design of the bracket and the housing of the centrifugal separator allows the relative position between the engine and, for example, the gas inlet, gas outlet and oil outlet of the separator to be varied simply by joining the mounting bracket to the housing at different angular positions.

[0040] The engagement of the mounting bracket with the outer surface of the surrounding side wall of the fixed housing may be welding the mounting bracket to or fastening the mounting bracket to the outer surface of the surrounding side wall of the fixed housing by fastening means.

[0041] The mounting bracket may be made of a polymer material, such as a plastic material. Alternatively, the mounting bracket may be made of metal. The mounting bracket may be arranged for securely mounting the centrifugal separator to a side surface of, for example, an engine or an engine block.

[0042] The stationary housing may also be made of a polymer material, such as plastic.

[0043] In an embodiment of the first aspect, the surrounding side wall of the stationary housing has an overall curved shape, such as a circular shape, as seen in a radial plane.

[0044] In an embodiment of the first aspect, the mounting bracket includes at least a portion that conforms to an outer surface of a surrounding side wall of the stationary housing.

[0045] Thus, the at least one portion may form an engagement surface for engagement with the outer surface of the surrounding side wall of the stationary housing. As an example, the at least one portion may engage with a rib of the outer surface of the stationary housing, the rib extending in the circumferential direction. The at least one portion may be welded to the outer surface of the surrounding side wall of the stationary housing, as will be discussed below. The at least one portion may be made of a polymer material, such as plastic.

[0046] As an example, the mounting bracket may conform to the outer surface of the surrounding side wall of the stationary housing along at least 25% of the circumference of the surrounding side wall of the stationary housing.

[0047] Thus, the mounting bracket can "enclose" a portion of the circumference of the surrounding side wall of the fixed housing, which portion is at least 25%. This can increase the strength of the engagement with the fixed housing. As a further example, the mounting bracket can conform to the outer surface of the surrounding side wall of the fixed housing along at least 35% of the circumference of the surrounding side wall of the fixed housing, such as along at least 40%.

[0048] In an embodiment of the first aspect, the outer surface of the surrounding side wall of the stationary housing extends a distance A1 in the axial direction, and the mounting bracket engages with the outer surface of the surrounding side wall of the stationary housing at least along a distance of 0.5A1.

[0049] Thus, the mounting bracket may be engaged to the surrounding side wall of the fixed housing at an axial distance which is at least half of the axial distance of the entire surrounding side wall of the fixed housing. Thus, the axial distance of the fixed housing is the axial distance of the fixed portion defining the separation space enclosed therein and does not include, for example, the axial distance of any fixed drive module attached to the housing.

[0050] As an example, the mounting bracket may engage the outer surface of the surrounding side wall of the stationary housing along at least a distance of 0.7A1, such as at least 0.9A1. Thus, the mounting bracket may cover more or less the entire axial distance of the surrounding side wall of the stationary housing.

[0051] In an embodiment of the first aspect, the stationary housing comprises a polymer material welded to the mounting bracket such that the mounting bracket is permanently engaged with an outer surface of a surrounding side wall of the stationary housing.

[0052] The inventors have found that using welding to join the mounting bracket to the outer surface of the surrounding side wall of the fixed housing is advantageous because it allows the mounting bracket to be joined to the outer surface of the surrounding side wall of the fixed housing at different angular positions about the rotation axis (X). In addition, using welding reduces the need to use other attachment means (such as screws) between the fixed housing and the mounting bracket.

[0053] Therefore, in an embodiment, the engagement between the mounting bracket and the fixed housing is without any other fastening means besides welding, such as without any screw components.

[0054] Any type of welding may be used to join the mounting bracket and the fixed housing. The weld formed between the mounting bracket and the fixed housing may be formed by infrared (IR) welding. The inventors have found that IR welding is very advantageous for joining the mounting bracket and the fixed housing, as will be discussed below in conjunction with the second aspect of the invention.

[0055] The weld formed may extend along at least 25% of the circumference of the fixed housing.

[0056] The stationary housing may include ribs made of a polymer material, such as circumferential ribs, which form part of a weld between the mounting bracket and the stationary housing.

[0057] As an example, the mounting bracket can be made of a polymer material that is welded to the polymer material of the fixed housing. Thus, a major portion of the mounting bracket can be made of a polymer material. This can reduce the overall weight of the centrifugal separator. Thus, by using welding, the inventors have realized that the load-bearing structure of the centrifugal separator, i.e. the mounting bracket, can be made of a polymer material and still give the separator sufficient strength and support.

[0058] As an alternative, the mounting bracket may be made of metal but comprises at least one polymer component welded to the polymer material of the stationary housing. Such a polymer component may, for example, be in the form of a strip of polymer material. Such a polymer strip may be arranged in the circumferential direction of the stationary housing and may be welded to, for example, circumferentially extending ribs on the outer surface of the surrounding side wall of the stationary housing.

[0059] In an embodiment of the first aspect, the drive component is arranged in a separate drive chamber in a drive module. Such a drive module can be arranged axially above or below the fixed housing.

[0060] The drive module may for example be a drive module forming a drive chamber in which a drive component, for example in the form of an electric motor or a turbine wheel, is arranged. Thus, the drive module may be a separate component removable from the fixed housing.

[0061] As an example, the driver module may be welded to the stationary housing.

[0062] Thus, the drive module may include an outer surface having a polymer material portion that is welded to a polymer portion of the fixed housing, for example by using infrared (IR) welding. As an example, the outer surface of the drive module may be made of a polymer material. Thus, the weld formed between the fixed housing and the drive module may also be an IR weld.

[0063] Furthermore, as discussed above, the gas inlet may include an inlet conduit arranged in an inlet module, i.e., a module separate from the fixed housing. As with the drive module, the inlet module may also be welded to the outer surface of the fixed housing. Thus, the inlet module may also include an outer surface having a polymer material portion that is welded to the polymer portion of the fixed housing, for example by using infrared (IR) welding. As an example, the outer surface of the inlet module may be made of a polymer material. Thus, the weld formed between the fixed housing and the inlet module may also be an IR weld.

[0064] As an example, the inlet module may be welded to a first end of the stationary housing, and the drive module may be welded to a second end of the stationary housing opposite the first end.

[0065] In an embodiment of the first aspect, the mounting bracket comprises mounting points for mounting the mounting bracket to the engine or the engine block, and wherein the mounting points are arranged at different axial positions.

[0066] In an embodiment of the first aspect, the mounting bracket comprises mounting points for mounting the mounting bracket to an engine or an engine block, and wherein the mounting points are distributed such that there is at least one mounting point axially on each side of a center of gravity (CG) of the centrifugal separator.

[0067] The mounting points may be through holes for receiving fastening means, such as screws, so that the mounting bracket and thus the entire centrifugal separator can be fastened to the engine or the engine block.

[0068] The inventors have found that having a mounting point on each axial side of the center of gravity of the centrifugal separator makes the entire structure more stable and less sensitive to vibrations when fastened to an engine or engine block. In addition, it facilitates the use of mounting brackets made of non-metallic, but lower density materials, which thereby reduces the overall weight of the centrifugal separator. Therefore, having a mounting point on each axial side of the center of gravity facilitates the use of mounting brackets made of polymeric materials that can be welded to a fixed housing, as discussed above.

[0069] As an example, there may be at least two axial mounting points on each axial side of the center of gravity (CG) of the centrifugal separator.

[0070] The at least two mounting points may also be distributed such that there is at least one mounting point on each side of the axis of rotation (X).

[0071] However, for example in case of a very heavy electric motor, the centre of gravity may be offset by a considerable distance in the axial direction and the mounting points may then all be distributed on one axial side of the centre of gravity of the entire centrifugal separator. Thus, in an embodiment of the first aspect, the mounting bracket comprises mounting points for mounting the mounting bracket to an engine or an engine block, and wherein the mounting points are distributed such that there is at least one mounting point axially on each side of the centre of gravity (CG) of the centrifugal separator, excluding drive components, such as the electric motor.

[0072] As a second aspect of the present invention, there is provided a method for assembling a centrifugal separator for purifying gas, comprising the following steps:

[0073] a) providing a stationary housing enclosing a separation space allowing a gas flow therethrough;

[0074] b) providing a mounting bracket configured for mounting the centrifugal separator to an engine or an engine block; and

[0075] c) Weld the fixed housing and the mounting bracket together using infrared (IR) welding.

[0076] This aspect may generally present the same or corresponding advantages as the previous aspect. The effects and features of the second aspect are generally similar to the effects and features described above in conjunction with the first aspect. The embodiments related to the first aspect are generally compatible with the third aspect.

[0077] IR welding is a welding technique that utilizes non-contact heating or energy from infrared radiation to melt and fuse polymer (such as thermoplastic) parts together.

[0078] The inventors have found that infrared welding (IR) welding is particularly advantageous when the fixed housing and the mounting bracket are linked together. This is due to the recognition that a large amount of energy may be required when melting, for example, a polymer material over a large contact area required to form a strong weld between the mounting bracket and the fixed housing. It has been found that it is essential to have a large contact area for structural rigidity (to obtain a high resonant frequency). For this reason, other techniques such as ultrasonic welding or laser welding may not be suitable. In addition, it has been found that IR welding does not cause vibrations like vibration welding, which may damage the ball bearings used in the centrifugal separator. In addition, due to contactless IR welding, less maintenance is required compared to hot plate welding.

[0079] The portion of the stationary housing that forms the weld and the portion of the mounting bracket that forms the weld may be polymer components, such as thermoplastic components.

[0080] Therefore, in an embodiment of the second aspect, the IR welding of step c) is performed between the polymer portion of the fixed housing and the polymer portion of the mounting bracket.

[0081] The outer surface of the surrounding side wall of the fixed shell may extend a distance A1 in the axial direction, and step c) may include welding the fixed shell and the mounting bracket together so that the mounting bracket is welded to the outer surface of the surrounding side wall of the fixed shell at least along a distance of 0.5A1, such as at least 0.7A1, such as at least 0.9A1.

[0082] As a further example, step c) can be performed such that the mounting bracket conforms to the outer surface of the surrounding side wall of the fixed shell along at least 25% of the circumference (c1) of the fixed shell, such as along at least 35% of the circumference of the fixed shell, such as along at least 40% of the circumference of the fixed shell.

[0083] Not only the mounting bracket can be welded to the fixed housing. In an embodiment of the second aspect, the method further comprises the following steps

[0084] d) providing a drive module enclosing a drive chamber, the drive chamber comprising a drive component for rotating a rotating component in said separated space of the stationary housing; and

[0085] e) welding the driving module and the fixed housing together.

[0086] As an example, step e) may include welding the driving module to an axial end, such as an axial lower end, of the fixed housing.

[0087] The welding of step e) may be laser welding. Compared to, for example, IR welding, laser welding may provide a seal with a better sealing function, which is relevant to the sealing of the drive module.

[0088] In a further example, the method comprises the following steps

[0089] f) providing an inlet module comprising an inlet conduit for the gas to be purified by the centrifugal separator; and

[0090] g) welding the inlet module and the fixed housing together.

[0091] The welding used in step g) may be IR welding or laser welding.

[0092] As an example, step g) may include welding the inlet module to an axial end, such as an axial upper end, of the stationary housing.

[0093] If both the driver module and the inlet module are welded to the stationary housing, the driver module may be welded to a first end and the inlet module may be welded to a second end of the stationary housing opposite the first end.

[0094] Steps f) and g) may be performed after steps d) and e). However, in an embodiment of the second aspect, steps f) and g) are performed before steps d) and e), i.e., the inlet module is welded to the fixed housing before the drive module is welded to the fixed housing.

[0095] In an embodiment of the second aspect, the assembled centrifugal separator is a centrifugal separator according to any example or embodiment of the first aspect discussed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] 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, the same reference numerals will be used in the drawings to represent the same elements.

[0097] Figure 1 A schematic diagram showing a cross section of an embodiment of a centrifugal separator for purifying gases is shown.

[0098] Figure 2 A perspective view of the mounting bracket is shown.

[0099] Figure 3a and 3b A perspective view and a cross-sectional view, respectively, show how the mounting bracket and the fixed housing are engaged at different angular positions about the axis of rotation (X).

[0100] Figure 4 A perspective view of an embodiment of a centrifugal separator is shown.

[0101] Figure 5 A perspective view of an embodiment of a centrifugal separator is shown. DETAILED DESCRIPTION

[0102] The centrifugal separator according to the present disclosure will be further explained by the following description with reference to the accompanying drawings.

[0103] Figure 1 A cross section of a centrifugal separator 1 according to the present disclosure is shown. The centrifugal separator 1 is configured to be mounted on an internal combustion engine (not disclosed), in particular a diesel engine, via a mounting bracket 30, at a suitable location, such as on top of the internal combustion engine or at the side of the internal combustion engine (see Figure 2-5 ). It should be noted that the centrifugal separator 1 is also suitable for purifying gases from other sources than internal combustion engines, such as machine tool environments, which usually contain large amounts of liquid contaminants in the form of oil droplets or oil mist.

[0104] The stationary housing 2 of the centrifugal separator 1 encloses a separation space 3 through which a gas flow is allowed. The stationary housing 2 comprises 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 forms an outer surface 4a of the stationary housing 2. The surrounding side wall 4 surrounds the separation space 3 through at least a part of its axial length.

[0105] The centrifugal separator 1 further comprises a rotating part 7 arranged to rotate about an axis of rotation (X). It should be noted that the stationary housing 2 is fixed relative to the rotating part 7 and preferably relative to the internal combustion engine to which it may be mounted.

[0106] The stationary housing 2 has a radius from the axis of rotation (X) to the surrounding side wall 4 which is constant at least with respect to a major 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.

[0107] The rotating part 7 comprises a rotatable shaft, namely a main shaft 8, and a stack of separation discs 9 attached to the main shaft 8. All separation discs of the stack 9 are arranged between a top disc 10 and a lower end plate 11.

[0108] 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 be arranged axially both below or above the separation disc stack 9, for example.

[0109] The separation discs of the disc stack 9 are frustoconical and extend outwardly and upwardly from the main shaft 8. Thus, the separation discs comprise a flat portion 9a, which extends perpendicularly to the axis of rotation (X), and a conical portion 9b, which extends 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.

[0110] The separation discs of the stack 9 are arranged at a certain distance from each other by distance components (not disclosed) so as to form gaps 14 between adjacent separation discs, i.e., between each pair of adjacent separation discs. The axial thickness of each gap 14 may be, for example, about 0.5-2 mm, such as 1-2 mm.

[0111] 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 is the number indicated in , and depending on the size of the centrifugal separator 1 , can be, for example, 50 to 100 separation discs.

[0112] The centrifugal separator 1 includes an oil nozzle 24, which is 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 a drive component in the form of a turbine impeller 22 by the oil nozzle 24, and the turbine impeller 22 is arranged in a drive chamber 41 in a drive module 40. The drive chamber 41 and the drive module thus form a turbine housing. 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, which is arranged to rotate the main shaft 8 and the rotating component 7. As a further 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 exhaust gas from the internal combustion engine to rotate the main shaft 8 and the rotating component 7. The rotating component 7 can 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.

[0113] The rotating member 7 defines a central space 15. The central space 15 is formed by a through hole in each separation disc 9. Figure 1 In the embodiment of FIG. 1 , 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.

[0114] The gas inlet 20 is used to supply the gas to be purified. The gas inlet 20 extends through the fixed housing 2, and more precisely through the upper end wall 5. The gas inlet 20 is formed by an axially extending inlet duct 18 and a through passage 21, the inlet duct 18 forming an upstream portion, and the through passage 21 forming a downstream portion of the inlet 20.

[0115] 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 purified is transferred from the inlet 20 via the central space 15 to the gaps 14 of the separation disc stack 9. The gas inlet 20 is configured to communicate with the crankcase of the internal combustion engine or any other source via the inlet duct 18, thereby allowing crankcase gas to be supplied from the crankcase to the gas inlet 20 and further to the central space 15 and the gaps 14, as explained above.

[0116] The stationary housing 2 comprises an internal 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 from the stationary housing 2 to the drive module 40. The internal outlet 29 is in the present embodiment in the form of a through hole arranged in the lower end wall 6 so that the separated liquid contaminants flow through the lower bearing 13 when they are discharged from the separation space 3 to the drive chamber 41. The separated oil and other particles and / or substances are directed to the drain outlet 25 of the centrifugal separator 1, which together with the oil from the oil nozzle 24 for driving the impeller 22 can be directed back to the engine oil circuit of the internal combustion engine.

[0117] The gas outlet 28 of the centrifugal separator 1 is arranged through the stationary housing 2 and is configured to allow the discharge of purified gas.

[0118] exist Figure 1 During operation of the centrifugal separator shown in , the rotating part 7 is kept in rotation by an oil nozzle 24 supplying oil to the impeller 22. As an example, the rotation speed can be in the range of 7,500-12,000 rpm. Polluted gas, for example crankcase gas from the crankcase of an internal combustion engine, is supplied to the gas inlet 20 via a conduit 18. The gas is further guided into the central space 15 and from there into and through the gaps 14 between the separation discs of the stack 9. Due to the rotation of the rotating part 7, the gas is carried into rotation so that it is further pumped radially outwards through the gaps or gaps 14.

[0119] 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 then slide or run radially outward thereon. When the particles and / or droplets reach the radial outer edge of the separation disc 9 outward, they are thrown from the rotating member 7 and hit the inner surface of the surrounding side wall 4. The separated oil particles can form a film on the inner surface of the fixed housing 2. From there, the oil can be pulled down to the bottom end wall 6 by gravity and then leave the separation space 3 through the internal outlet 29. To this end, the inner wall of the bottom end wall 6 can be tilted radially inward so that the oil leaving the surrounding inner wall of the fixed housing 2 can be pulled to the internal outlet 29 by gravity. Figure 1 The arrows "D" in FIG. 2 schematically illustrate the path of the pollutants in the gas.

[0120] The purified gas free of particles and exiting from the separation disc stack 9 leaves the stationary housing 2 through the gas outlet 28. The path of the gas through the centrifugal separator 1 is determined by Figure 1 The arrow "C" in FIG.

[0121] Figure 2 A perspective view of a separate mounting bracket 30 for mounting a centrifugal separator to an engine or engine block is shown. The mounting bracket can be permanently joined to the outer surface 4a of the surrounding side wall 4 of the fixed housing 2, such as by welding. The mounting bracket includes an inner curved surface 33, the overall curvature of which is the same as the outer surface 4a of the surrounding side wall 4 of the fixed housing 2. The inner curved surface is a concave surface, which includes a plurality of horizontal ridges or stripes 32, which conform to the outer surface when engaged with the outer surface 4a of the surrounding side wall 4 of the fixed housing 2. Therefore, the weld line between the mounting bracket 30 and the fixed housing 2 can be formed along the horizontal ridges or stripes 2 to permanently engage the mounting bracket 30 with the outer surface 4a of the fixed housing.

[0122] The mounting bracket may be a single part, such as a single part of a polymer material. This enables the mounting bracket 30 to be IR welded to the polymer portion of the outer surface 4a of the surrounding side wall 4 of the fixed housing 2. Alternatively, the mounting bracket 30 may be made of a different material, such as metal, while the horizontal ridges or stripes 32 are made of a polymer material that can be welded to the outer surface 4a of the surrounding side wall 4 of the fixed housing 2.

[0123] Figure 2 Also shown are a number of mounting points, in this case upper mounting points 31a and lower mounting points 31b, which can be used to fasten the bracket, and thus the entire centrifugal separator 1 (if the mounting bracket is permanently engaged with the fixed housing 2), to the engine or engine block. In this example, the mounting points 31a, 31b are through holes arranged to receive some fastening means, such as screws.

[0124] Figure 3a and 3b The mounting bracket 30 and the stationary housing 2 are shown configured to allow the mounting bracket 30 to be permanently joined to the outer surface 4a of the surrounding side wall 4 of the stationary housing 2 at various angular positions about the rotation axis (X). Figure 3a As indicated by the arrow "A" in FIG. 1 , the mounting bracket 30 can be rotated around the rotation axis (X) at various angular positions, but still matches the outer surface 4a of the surrounding side wall 4 of the fixed housing 4. This is also Figure 3b It is shown in Figure 3bA cross section in a radial plane of the stationary housing 2 and the mounting bracket 30 is shown. By rotating the mounting bracket 30 about the axis of rotation (X), as indicated by the rotation angle α, the mounting bracket 30 can be engaged to the stationary housing 2 in various positions. This is therefore due to the configuration of the outer surface 4a of the surrounding side wall 4 of the stationary housing and the mounting bracket 30, in particular the inner concave surface 33.

[0125] Thus, the angular position about the rotation axis (X) is the angular position as seen in a radial plane, and the rotation about the rotation axis (X) from a first angular position to a second angular position forms a rotation angle α in the radial plane. Thus, the rotation angle α is the radial plane angle between an imaginary straight line from the rotation axis (X) to the mounting bracket before the rotation and an imaginary straight line from the rotation axis (X) to the mounting bracket after the rotation, as Figure 3b As shown in .

[0126] It should be noted that Figure 3a Schematically shown in FIG. A fixed housing 2 is shown. A drive module 30 and an inlet module 50 attached to the fixed housing are also shown. In this example, the drive module is welded to the fixed housing to fit the lower end portion of the fixed housing 2, and the inlet module 50 is welded to the fixed housing 2 to fit the upper end portion of the fixed housing 2. The drive module 40 includes a drain outlet 25 and an inlet of an oil nozzle 24, and the inlet module includes an inlet conduit 18, all extending in a direction extending outward from the fixed housing 2. The fixed housing 2 also includes a gas outlet 28 extending outward from the surface of the fixed housing. Therefore, by configuring the mounting bracket 30, before the mounting bracket and the fixed housing are permanently joined (for example, by welding), the position of the drain outlet 25, the inlet conduit 18 and the gas outlet 28 relative to the engine or engine block can be changed by simply changing the position of the mounting bracket around the rotation axis (X).

[0127] Figure 4 A schematic perspective view of the entire centrifugal separator 1 is shown when the mounting bracket 30 is permanently joined to the outer surface of the surrounding side wall 4 of the fixed housing 4a. When permanently joined, the mounting bracket 30 is arranged along the circumference c1 of the fixed housing (see Figure 5 ) conforms to the outer surface 4a of the fixed housing 2, such as along at least 25% of the circumference c1 of the fixed housing 2. Figure 4 As shown in FIG. 1 , the mounting bracket 30 may conform to between 25-50% of the circumference c1 of the stationary housing 2. If welded to the stationary housing 2, the weld line may form a portion where the mounting bracket 30 conforms to the outer surface of the stationary housing 2.

[0128] In addition, if Figure 4As shown in the figure, the outer surface 4a of the surrounding side wall 4 of the fixed housing 2 extends a distance A1 in the axial direction, and the mounting bracket 30 closes or engages the outer surface 4a of the surrounding side wall 4 of the fixed housing 2 at least along a distance A2, and the distance A2 is 0.5A1, such as between 0.5A1 and 1.0A1.

[0129] Furthermore, the mounting points 31a, 31b for mounting the mounting bracket 30 on the engine or engine block are distributed so that there is at least one mounting point 31a, 31b on each side of the center of gravity (CG) of the centrifugal separator 1 in the axial direction. Thus, the center of gravity of the centrifugal separator is located at the axial position a1, and the two upper mounting points 31a are located axially above a2, while the two lower mounting points 31b are located axially below a1. Furthermore, the mounting points 31a, 31b are distributed so that there are at least two mounting points 31a, 31b on each side of the rotation axis (X).

[0130] In this example, the drive components are arranged in a separate drive module 40, which is welded to the axial lower part of the fixed housing 2. As an example, the drive module can be welded to the bottom end wall of the fixed housing using laser welding. Therefore, the drive module 40 is an independent component, including, for example, an electric motor or a turbine impeller, which can be welded to, for example, the upper or lower part of the fixed housing 2. Therefore, the drive components are arranged in a separate drive chamber within the drive module 40.

[0131] In this example, the fixed inlet duct is included in an inlet module 50, which is welded to an upper portion of the fixed housing 2, such as to an upper end wall. Therefore, the mounting bracket 30, the drive module 40 and the inlet module 50 can all be welded to the fixed housing 2.

[0132] However, in an embodiment, both the driving module 40 and the inlet module 50 may be axially arranged on the same side of the stationary housing 2 , such as both being axially arranged above the stationary housing 2 .

[0133] exist Figure 5 In the perspective view of the centrifugal separator of FIG. 2 , the back side 34 of the mounting bracket 30 is also shown, i.e. the side not facing the fixed housing 2. The mounting bracket 2 comprises ribs 35 on the back side 3 to reduce the overall weight of the mounting bracket 30. All ribs terminate in an imaginary axial plane of the back side to allow a tight engagement with the engine or engine block.

[0134] In addition, if Figure 5As shown in FIG. 4 , the outer surface 4 a of the surrounding side wall 4 of the fixed housing 2 includes ribs 61 extending in the circumferential direction. These ribs 61 and the ribs 32 of the inner concave surface 30 of the mounting bracket 30 are welded together so as to immediately join the mounting bracket to the fixed housing 2. Therefore, the weld is formed by melting the circumferential ribs 61 of the fixed housing 2 and the ribs 32 of the mounting bracket 30. In addition, there are ribs 60 extending in the axial direction on the outer surface 4 a of the surrounding side wall 4 of the fixed housing 2, which increases the strength of the fixed housing 2.

[0135] Figure 6 A centrifugal separator 1 for purifying gas is shown (such as described above with reference to Figure 1-5 The steps of the method 100 of the centrifugal separator 1) are discussed.

[0136] The method comprises a step of providing 101 a stationary housing 2 enclosing a separation space 3 allowing a gas flow therethrough, and a step of providing 102 a mounting bracket 30 configured to mount the centrifugal separator 1 to an engine or an engine block. The method 100 further comprises a step of welding 103 the stationary housing (2) and the mounting bracket (30) together using infrared (IR) welding.

[0137] As an example, the IR welding of step c) may be performed between the polymer portion of the fixed housing 2 and the polymer portion of the mounting bracket 30, such as in Figure 5 Rib 61 and Figure 2 It is carried out between the ribs 32.

[0138] The method 100 may further comprise a step d) of providing 104 a drive module 40 enclosing a drive chamber 41, the drive chamber 41 comprising a drive component 22 for rotating a rotating component 7 in a separation space 3 of a stationary housing 2, and a step e) of welding 105 the drive module 40 and the stationary housing 2. Step e) may be performed using laser welding.

[0139] Furthermore, the method 100 may further comprise welding the inlet module 50 to the stationary housing 2. Thus, the method 100 may comprise a step f) of providing 106 an inlet module 50 comprising an inlet duct 18 for the gas to be purified by the centrifugal separator 1 and a step g) of welding 107 the inlet module to the stationary housing.

[0140] The drive module 40 and the inlet module 50 may be attached to the same axial end of the fixed housing 2. Therefore, the weld formed in step e) may be a direct weld of the drive module 40 to the fixed housing 2 or an indirect weld to the fixed housing 2, such as welding the drive module 40 to another module already attached to the fixed housing, such as welding to the inlet module 50.

[0141] The invention is not limited to the disclosed embodiments, but may be changed and modified within the scope of the claims set forth below. The invention is not limited to the orientation of the axis of rotation (X) disclosed in the figures. The term "centrifugal separator" also includes a centrifugal separator with a substantially horizontally oriented axis of rotation. In the above, the concept of the invention 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 are equally possible in addition to the examples disclosed above within the scope of the concept of the invention as defined by the appended claims.

Claims

1. A centrifugal separator (1) for purifying a gas containing pollutants, the centrifugal separator (1) comprising a stationary housing (2) enclosing a separation space (3) allowing a gas flow therethrough and comprising a surrounding side wall (4) surrounding said separation space (3), a gas inlet (20) extending through said fixed housing (2) and allowing the supply of said gas to be purified, 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 (28) configured to allow purified gas to be discharged from the fixed housing (2), a liquid discharge outlet (25) configured to allow liquid contaminants separated from the gas to be discharged from the centrifugal separator (1); a driving component (22) for rotating the rotating component (7); The centrifugal separator (1) further comprises a mounting bracket (30) configured for mounting the centrifugal separator (1) on an engine or an engine block and engaging with the outer surface (4a) of the surrounding side wall (4) of the fixed housing (2), And wherein the mounting bracket (30) and the fixed housing (2) are configured to allow the mounting bracket (30) to be permanently joined to the outer surface (4a) of the surrounding side wall (4) of the fixed housing (2) at different angular positions around the rotation axis (X).

2. The centrifugal separator (1) according to claim 1, wherein: The mounting bracket (30) includes at least a portion (32) conforming to the outer surface (4a) of the surrounding side wall (4) of the fixed housing (2).

3. The centrifugal separator (1) according to claim 2, wherein: The mounting bracket (30) conforms to the outer surface (4a) of the surrounding side wall (4) of the fixed housing (2) along at least 25% of the circumference (c1) of the surrounding side wall (4) of the fixed housing (2).

4. A centrifugal separator (1) according to any one of the preceding claims, wherein: The outer surface (4a) of the surrounding side wall (4) of the fixed housing (2) extends a distance A1 in the axial direction, and wherein the mounting bracket (30) is engaged with the outer surface (4a) of the surrounding side wall (4) of the fixed housing (2) at least along a distance of 0.5A1.

5. A centrifugal separator (1) according to any one of the preceding claims, wherein: The fixed housing (2) comprises a polymer material welded to the mounting bracket (30) so that the mounting bracket (30) is permanently joined to the outer surface (4a) of the surrounding side wall (4) of the fixed housing.

6. The centrifugal separator (1) according to claim 5, wherein: The mounting bracket (30) is made of a polymer material welded to the polymer material of the fixed housing (2).

7. The centrifugal separator (1) according to claim 5, wherein: The mounting bracket (30) is made of metal but includes at least one polymer component (32) which is welded to the polymer material of the stationary housing (2).

8. A centrifugal separator (1) according to any one of the preceding claims, wherein: The driving component (22) is arranged in a separate driving chamber (41) in a driving module (40), and the driving module (40) is arranged axially above or below the fixed housing (2).

9. The centrifugal separator (1) according to claim 8, wherein: The driving module (40) is welded to the fixed housing (20).

10. A centrifugal separator (1) according to any one of the preceding claims, wherein: The mounting bracket (30) comprises mounting points (31a, 31b) for mounting the mounting bracket (30) to an engine or an engine block, and wherein the mounting points (31a, 31b) are distributed such that there is at least one mounting point (31a, 31b) on each side of the center of gravity (CG) of the centrifugal separator (1) in the axial direction.

11. The centrifugal separator (1) according to claim 10, wherein: There are at least two mounting points (31a, 31b) axially on each side of the center of gravity (CG) of the centrifugal separator (1).

12. A method (100) for assembling a centrifugal separator (1) for purifying gas, comprising the following steps: a) providing (101) a stationary housing (2) enclosing a separation space (3) allowing a gas flow therethrough, b) providing (102) a mounting bracket (30) configured to mount the centrifugal separator (1) to an engine or an engine block; and c) welding (103) the fixed housing (2) and the mounting bracket (30) together using infrared (IR) welding.

13. The method (100) according to claim 12, wherein: The IR welding of step c) is between the polymer portion of the fixed housing (2) and the polymer portion of the mounting bracket (30).

14. The method (100) according to claim 12 or 13, wherein: The method further comprises the following steps d) providing (104) a drive module (40) enclosing a drive chamber (41), the drive chamber (41) comprising a drive component (22) for rotating a rotating component (7) in the separation space (3) of the fixed housing (2); and e) welding (105) the driving module (40) and the fixed housing (2) together.

15. The method (100) according to any one of claims 12 to 14, wherein: The assembled centrifugal separator (1) is a centrifugal separator (1) according to any one of claims 1 to 11.

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