Centrifugal separator for cleaning gas

Abstract

The present invention provides a centrifuge (1) for cleaning a gas containing contaminants. The centrifuge (1) includes: a stationary shell (2) surrounding a separation space (3) through which an airflow is allowed; a gas inlet (20) extending through the stationary shell (2) and allowing the supply of gas to be cleaned; a rotating component (7) including a separation unit (16) arranged in the separation space (3) and arranged to rotate about a rotation axis (X); a drive component (22) for rotating the rotating component (7); a gas outlet (28) arranged through the stationary shell (2) and configured to allow the cleaned gas to be discharged from the stationary shell (2); and a discharge outlet (29) arranged in the stationary shell (2) and configured to allow liquid contaminants separated from the gas to be discharged from the stationary shell (2); the discharge outlet (29) is arranged in the lower end wall (6) of the stationary shell (2). The centrifuge (1) further includes: a stationary structure (28) disposed within a stationary shell (2) and including a wake region portion (61) arranged at an axial distance from the lower end wall (6); wherein the wake region portion (61) is arranged such that a wake region (62) for rotating gas is formed at the wake region portion (61) during operation of the centrifuge (1); and an oil bridge structure (60) axially connecting the wake region portion (61) of the stationary structure (28) to the lower end wall (6) for guiding any contaminants from the surface of the stationary structure (28) to the lower end wall (6).

Description

Technical Field

[0001] This invention relates to the field of centrifugal separators for cleaning gases containing liquid contaminants. In particular, this invention relates to separators for cleaning crankcase gases of combustion engines to remove oil particles. Background Technology

[0002] It is well known that centrifugal separators can be used to separate mixtures of fluids with different densities from each other. One specific application of such separators is the separation of oil from gases discharged from the crankcase, a part of an internal combustion engine. High-pressure gases emerging in the combustion chamber of an internal combustion engine leak through the associated piston rings and into the engine's crankcase. This continuous leakage of gases into the crankcase can cause an undesirable increase in pressure within the crankcase, thus necessitating the venting of gases from the case. These gases discharged from the crankcase typically carry a large amount of engine oil (as droplets or a fine mist), which is extracted from an oil reservoir contained within the crankcase.

[0003] To allow exhaust gases to be introduced into the inlet system without introducing unwanted oil (especially in turbocharged systems where compressor efficiency can be adversely affected by the presence of oil), it is necessary to clean the exhaust gases (i.e., remove oil carried by the gases) before they are introduced into the inlet system. This cleaning process can be performed by a centrifugal separator mounted on or near the crankcase, which directs the cleaned gases into the inlet system and directs the separated oil back into the crankcase. An example of such a separator is disclosed, for instance, in US 8,657,908.

[0004] However, not all contaminants (such as oil) always find their way out. Therefore, contaminants may become trapped inside the centrifuge before reaching the outlet and be carried away by the clean airflow (due to the rotating airflow inside the centrifuge).

[0005] Therefore, there is a need in this field to improve the emission of pollutants from centrifugal separators. Summary of the Invention

[0006] The objective of this invention is to overcome, at least in part, one or more limitations of the prior art. In particular, the objective is to provide improved discharge of contaminants (such as oil) from centrifugal separators.

[0007] As a first aspect of the invention, a centrifugal separator for cleaning gases containing contaminants is provided. The centrifugal separator includes... A stationary shell surrounds the separation space, allowing airflow through it. A gas inlet extends through the stationary shell and allows for the supply of the gas to be cleaned. A rotating component, comprising a separation unit arranged in the separation space and configured to rotate about a rotation axis (X), A drive component, used to rotate a rotating component; The gas outlet is arranged through the stationary shell and configured to allow clean gas to be discharged from the stationary shell. A discharge outlet, disposed within the stationary shell and configured to allow liquid contaminants separated from the gas to be discharged from the stationary shell; said discharge outlet is disposed in the lower end wall of the stationary shell. The centrifuge also includes... A stationary structure, disposed within a stationary shell, includes a wake region portion arranged at an axial distance from the lower end wall; wherein the wake region portion is arranged such that a wake region for rotating gas is formed at the wake region portion during operation of the centrifugal separator; and An oil bridge structure axially connects the wake region portion of the stationary structure to the lower end wall to guide any contaminants from the surface of the stationary structure to the lower end wall.

[0008] As used herein, the term "axial" refers to a direction parallel to the axis of rotation (X). Therefore, related terms such as "above," "upper," "top," "lower," "below," 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). "Radially inner position" therefore refers to a position closer to the axis of rotation (X) than "radially outer position." A radial plane is a plane having a normal parallel to the axis of rotation (X). An axial plane is a plane having a normal perpendicular to the axis of rotation (X).

[0009] The first aspect of the invention is based on the insight that contaminants (such as oil) separated from a gas can accumulate on the surface of the wake region within the stationary housing of a gas separator, and that cleaning efficiency is improved by forming oil bridges from such surfaces downward toward the discharge outlet (in this case, the lower end wall). In other words, contaminants accumulated on the stationary surfaces due to the geometry and airflow within the stationary housing are guided to the discharge outlet, thereby reducing the risk of such oil re-entering the airflow or moving along the inner surface of the stationary housing. This facilitates, for example, the discharge of oil from the separator, and thus increases cleaning efficiency.

[0010] The "wake zone" is the space where airflow is disturbed or reduced, usually immediately behind a stationary object in the airflow, as seen in the direction of the airflow.

[0011] The "wake zone" of the stationary structure arranged within the stationary shell is therefore part of the stationary structure where the airflow is reduced or disturbed during the operation of the centrifugal separator.

[0012] In one embodiment, the wake region may have a surface extending in a plane that forms an angle relative to the direction of the rotating airflow during use of the centrifugal separator.

[0013] As an example, the wake region can be located in the downstream portion of the stationary structure, as seen in the direction of the airflow during the use of the centrifugal separator. Therefore, the stationary structure can have an upstream portion affected by the rotating airflow, and a downstream portion where the wake region is generated during the use of the centrifugal separator. The downstream portion can therefore be the surface "behind" the stationary structure, as seen in the direction of the rotating airflow during the use of the separator.

[0014] As an example, the wake region may include an area extending in a plane that forms an angle of approximately 60-120 degrees (such as between 70-110 degrees, or between 80-100 degrees) relative to the direction of the rotating airflow. As an example, the wake region may include an area in a plane perpendicular to the direction of the rotating airflow—that is, tilted at 90 degrees.

[0015] When arranged at an axial distance from the lower inner wall, pollutants can accumulate in this wake region. Therefore, the oil bridge structure "bridges" the axial distance from the wake region to the lower inner wall, allowing the accumulated pollutants to be guided downwards to the lower inner wall and from there to the emission outlet.

[0016] Contaminants in the gas may include liquid contaminants (such as oil) and soot. Therefore, in this embodiment, the contaminants include oil.

[0017] Therefore, centrifugal separators can be used to separate liquid contaminants such as oil from gases. These gases can be crankcase gases from combustion engines. However, centrifugal separators are also suitable for cleaning gases from other sources, such as the environment of machine tools that typically contain large amounts of liquid contaminants in the form of oil droplets or mist.

[0018] The stationary shell of the centrifuge may include surrounding sidewalls, an upper end wall, and a lower end wall that enclose the separation space. The stationary shell may have a cylindrical shape, wherein the circular cross-section has a radius R from the axis of rotation (X) to the surrounding sidewalls. This radius R may be constant, at least relative to the main portion of the circumference of the surrounding sidewalls. The stationary shell may also be slightly tapered. The surrounding sidewalls may be divided into a lower surrounding sidewall, which may be cylindrical in shape and may be connected to the upper surrounding sidewall, for example by welding or by fastening components (such as threaded components). This facilitates the mounting of rotating components inside the stationary shell. The lower surrounding annular sidewall may extend downward to the lower end wall of the stationary shell. Thus, the lower end wall may be a lower wall extending in a radial direction (such as in a radial plane or at a small angle relative to a radial plane). In some embodiments, the lower end wall is also part of the lower surrounding annular sidewall.

[0019] The gas inlet of the centrifugal separator can be arranged through the upper end wall, or close to the upper end wall through the surrounding side wall, so that at the top of the separator, the gas entering through the gas inlet is guided into the separation space. The downstream portion of the gas inlet can be centered about the axis of rotation (X). The gas inlet may also include an upstream portion in the form of an inlet conduit. This conduit can extend radially or axially from the centrifugal separator, or in any other direction in between. During operation, the gas to be cleaned can be centrally guided from the gas inlet through the separation unit and radially outward through the separation unit.

[0020] The rotating component is arranged to rotate during operation by means of a drive component. The rotating component includes separation units arranged in a separation space. The separation units of the rotating component may be inserts that promote the expansion of surfaces to facilitate the separation of contaminants from the gas, such as a stack of separation discs (disc stack) or one or more filters.

[0021] Therefore, in this embodiment, the separation unit includes multiple separation components. The separation components of the rotating component are examples of inserts that facilitate the expansion of surfaces that promote the separation of contaminants from the gas.

[0022] The separation unit may therefore include a rotatable filter or a stack of rotatable filters.

[0023] Alternatively, multiple separation components can be arranged as a stack of separation discs, such as a stack of truncated conical separation discs.

[0024] The truncated conical disk may have a planar portion extending in a plane perpendicular to the axis of rotation, and a truncated conical portion extending upward or downward. The planar portion may be closer to the axis of rotation than the truncated conical portion. Alternatively, the disks in the stack may be radial disks, wherein essentially the entire disk extends in a plane perpendicular to the axis of rotation. Such disks may have an outer radius and an inner radius, thus forming a central opening on the disk.

[0025] It should also be understood that the separating components (such as separating discs) are not necessarily arranged in a stacked manner. The separating space may, for example, comprise 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 arcuate or helical shape, as seen in the radial plane.

[0026] The rotating component may be journal-supported within the stationary housing via at least one bearing (such as an upper bearing and a lower bearing respectively arranged axially above and below the separating unit). In an embodiment of the first aspect, the rotating component includes an axial shaft supported by at least one bearing. The axial shaft can therefore be centered at the axis of rotation (X). The separating unit may be arranged around such an axial shaft.

[0027] Centrifuges can be configured to deliver the gas to be cleaned (such as crankcase gas) from the gas inlet to the central portion of a rotating component. In this way, the crankcase gas is "pumped" from the central portion of the rotating component into the gaps between the separation discs in a stack of separation discs by the rotation of the rotating component. Therefore, the centrifuge can operate according to the principle of co-current flow (where gas flows from the radially inner portion to the radially outer portion in the disc stack), which is the opposite of separators that operate according to the principle of counter-current flow (where gas is guided at the periphery into the separation space and delivered towards the central portion of the separation space).

[0028] The drive component may include, for example, a turbine impeller that rotates by means of an oil jet from the lubrication system of the combustion engine, or a free-jet impeller including a blow-back disc. However, the drive component may also be independent of the combustion engine and may include an electric motor, a hydraulic motor, or a pneumatic motor.

[0029] The outlet for the cleaning gas (gas outlet) may be in the form of an opening or a gas outlet pipe (which extends through the wall of the stationary shell, such as through the lower portion of the surrounding sidewall of the stationary shell). The gas outlet pipe may be a generally cylindrical pipe or have another cross-section (such as an oval cross-section).

[0030] The discharge outlet is located in the lower end wall of the stationary shell, i.e., at the bottom of the separator. Therefore, the discharge outlet can be located in an end wall opposite to the end wall through which the inlet passes or is located. The discharge outlet of the centrifugal separator can be formed by several point-shaped through-holes in the stationary shell or by a single discharge passage.

[0031] In an embodiment of the first aspect, the discharge outlet is centrally located in the lower end wall and configured to discharge liquid pollutants.

[0032] Therefore, the exhaust outlet can be located at the axis of rotation or centered around the axis of rotation. Alternatively, the exhaust outlet can be located at a certain distance from the center of the lower end wall.

[0033] The discharge outlet may be located in an annular collection groove or formed as several through holes in the lower end wall of the stationary shell. The discharge outlet may be arranged such that contaminants (such as oil) are discharged through a bearing arranged to support the rotating components on the journal. The discharge outlet may be configured such that oil can flow through the lower bearing or flow radially outward from the lower bearing into the turbine housing.

[0034] In an embodiment of the first aspect, the lower end wall further includes a guiding member for guiding the separated contaminants on the lower end wall toward the discharge outlet. This facilitates the transport of contaminants on the lower end wall toward the discharge outlet.

[0035] The guide component may be elongated and, for example, straight or curved, as seen in the radial plane.

[0036] As an example, the guiding component may include an elongated recess for guiding liquid contaminants to a discharge outlet. Therefore, the recess forms a channel in the inner surface of the lower end wall.

[0037] As an example, the recess in the lower end wall can be arranged radially.

[0038] The recess can be arranged from the outer periphery to the center of the lower end wall, and the discharge outlet can be located at the center. The recess can be arranged to cover most of the radial distance of the lower end wall.

[0039] In contrast to the recess, the guide component may also form a protrusion from the inner surface of the lower end wall.

[0040] As an example, the lower end wall may include at least four guiding elements, such as at least four recesses. The number may also be greater, such as at least five, six, seven, eight, or ten. The area of ​​the lower end wall will advantageously have a certain percentage covered by the recesses. At least four recesses will provide sufficient coverage, ensuring a high degree of emission at the lower end wall.

[0041] In an embodiment of the first aspect, the wake region portion of the stationary structure has an edge portion or a corner portion, wherein the oil bridge structure is connected to the edge portion or corner portion.

[0042] Therefore, the stationary structure may include planar surfaces with edges or corners in the wake region of the centrifugal separator, and contaminants (such as oil) may tend to accumulate at such edges or corners. Therefore, having oil bridges from such edges or corners can be advantageous for guiding such accumulated oil axially downwards to the lower end wall.

[0043] As an example, the corner section forms a sharp corner.

[0044] In one embodiment, the wake region is partially located within the outer 50% (e.g., the outer 25%) of the radial extension of the separation space.

[0045] Therefore, in the embodiment of the first aspect, the oil bridge structure is arranged within the outer 50% (such as the outer 25%) of the radial extension of the separation space.

[0046] Contaminants are more likely to accumulate in the radially outer portion of the separation space, which is why it is advantageous to place the oil bridge in such locations from the wake region.

[0047] The oil bridge structure can be a simple planar surface that extends axially from the wake region to the lower end wall. In an embodiment of the first aspect, the oil bridge structure has a planar surface extending in an axial plane.

[0048] A stationary structure is a structure that does not rotate during operation and is located within a stationary shell. However, rotating gas can flow around the stationary structure, thus creating a wake region in the gas flow. Therefore, the stationary structure may have wake regions where contaminants (such as oil) can accumulate.

[0049] Therefore, in the embodiment, the wake region is part of the stationary structure at the downstream end of the stationary structure, as seen in the direction of the rotating gas during operation of the centrifugal separator.

[0050] In an embodiment of the first aspect, the stationary structure forms a portion of the gas outlet.

[0051] As discussed above, the gas outlet can extend into the stationary shell, i.e., protrude from the inner wall of the stationary shell (such as the surrounding sidewall). Therefore, the gas outlet may include a pipe or conduit extending into the stationary shell. It has been discovered by the inventors that during operation of the centrifugal separator, such a gas outlet forms a wake region and thus has a wake region portion. Therefore, it is advantageous to connect such a wake region portion to the lower end wall using an oil bridge structure.

[0052] In an embodiment of the first aspect, the stationary structure further forms a portion of the stationary insert, which is arranged to form a barrier between the clean gas and the separated contaminants before the clean gas and the separated contaminants leave the stationary shell.

[0053] As an example, the gas outlet can form part of such a stationary insert, that is, the gas outlet can be formed as a single piece with the stationary insert.

[0054] The stationary insert may include an annular wall component. The stationary insert may be arranged within a stationary housing to form an annular vertical channel for separating contaminants between the inner wall of the stationary housing and the annular wall component. A portion of the airflow may also pass through this annular vertical channel.

[0055] The annular wall component can therefore 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).

[0056] Furthermore, the stationary insert may also include a central cup component with tapered extended sidewalls. At least a portion of the rotating component may be arranged within such a central cup component, allowing the central cup component to be arranged about a rotation axis.

[0057] As an example, the annular wall component of the stationary insert discussed above can extend downward from the outer edge of the cup component.

[0058] In an embodiment of the first aspect, the stationary insert is arranged in the lower portion of the stationary housing.

[0059] The lower portion can therefore be the lower half of the stationary shell. As discussed above, the stationary shell may include an upper surrounding annular sidewall and a lower surrounding annular sidewall. The stationary insert can then be axially arranged within the lower surrounding sidewall, such that the lower surrounding sidewall surrounds the insert.

[0060] Therefore, during operation, the gas to be cleaned is centrally guided from the gas inlet through the separation unit, and then radially outward through the separation unit. The airflow can continue to travel downward within the stationary shell. The airflow can travel in a rotational motion within the stationary shell, approximately around the sidewalls, and finally exit the separator through the gas outlet.

[0061] As a second aspect of the invention, a method for cleaning a gas containing pollutants is provided, the method comprising: During the rotation of the rotating component, the gas containing contaminants is guided to a centrifugal separator according to the first aspect above. Clean gas is emitted from the gas outlet, and Pollutants are emitted through the emission outlet.

[0062] Contaminants in the gas can include liquid contaminants (such as oil) as well as soot.

[0063] This aspect generally presents the same or corresponding advantages as the preceding aspects. The effects and features of the second aspect are largely similar to those described above in combination with the first and second aspects. The embodiments mentioned in the first aspect are largely compatible with the second aspect. Attached Figure Description

[0064] The foregoing, as well as additional objectives, features, and advantages of the invention will be better understood from the following illustrative and non-limiting detailed description, with reference to the accompanying drawings. In the drawings, similar reference numerals will be used for similar elements unless otherwise stated.

[0065] Figure 1 A schematic diagram of a cross-section of an embodiment of a centrifugal separator for cleaning gases is shown.

[0066] Figure 2 An embodiment of a centrifugal separator with a lower end wall and a stationary insert is shown.

[0067] Figure 3 An embodiment of the wake region is shown. Detailed Implementation

[0068] The centrifugal separator according to this disclosure will be further illustrated by the following description with reference to the accompanying drawings.

[0069] Figure 1A cross-section of a centrifugal separator 1 according to this disclosure is shown. The centrifugal separator 1 includes a stationary housing 2 configured to be mounted in a suitable location to a combustion engine (not disclosed), particularly a diesel engine, such as mounted on the top or side of the combustion engine or mounted to the engine block of the combustion engine.

[0070] The centrifugal separator 1 disclosed herein can also be used to clean gases from sources other than combustion engines (e.g., machine tool environments that typically contain large amounts of liquid contaminants in the form of droplets or mists).

[0071] The stationary shell 2 surrounds the separation space 3, allowing airflow through the separation space 3. The stationary shell 2 includes, or is formed of, surrounding side walls 4, an upper end wall 5, and a lower end wall 6.

[0072] The centrifugal separator 1 includes a rotating component 7 arranged to rotate about a rotation axis (X). It should be noted that the stationary shell 2 is stationary relative to the rotating component 7 (and preferably relative to the combustion engine to which it can be mounted).

[0073] The stationary shell 2 has a radius from the axis of rotation (X) to the radius surrounding the sidewall 4, which is constant at least relative to the main portion of the circumference surrounding the sidewall 4. Therefore, the sidewall 4 has a circular or substantially circular cross-section in the radial plane.

[0074] The rotating component 7 includes a rotatable shaft, i.e., a spindle 8, and a separation unit 16 attached to the spindle 8. The separation unit 16 includes a plurality of separation components 9, which may be a stack of separation discs. All the stacked separation discs 9 are disposed between a top disc 10 and a lower end plate 11. The spindle 8 (and therefore the rotating component 7) is rotatably supported in the stationary housing 2 by means of an upper bearing 12 and a lower bearing 13, with one bearing arranged on each axial side of the stack of separation discs 9. However, the bearings 12, 13 may, for example, both be arranged axially below or above the stack of separation discs 9.

[0075] The separation disc 9 of the stacked discs is truncated conical and extends outward and upward from the spindle 8. Therefore, the separation disc includes a flat portion 9a extending perpendicular to the axis of rotation (X), and a conical portion 9b extending outward and upward from the flat portion 9a. Alternatively, the separation disc may also extend outward and downward, or even radially.

[0076] The stacked separator discs 9 are positioned at a distance from each other by means of spacer members (not disclosed) to form gaps 14 between adjacent separator discs 9, i.e., gaps 14 between each pair of adjacent separator discs 9. The axial thickness of each gap 14 may be, for example, about 0.5-2 mm, such as 1-2 mm.

[0077] The stacked separation disks 9 can be made of plastic or metal. The number of separation disks 9 in the stack is typically greater than that in other disks. Figure 1 The number of separators 9 can be higher, for example, 50 to 100, depending on the size of the centrifugal separator 1.

[0078] Centrifugal separator 1 includes an oil nozzle 24 arranged for connection to the engine oil circuit of an internal combustion engine. During operation of the internal combustion engine, oil is pumped through the oil nozzle 24 to a turbine impeller 22 arranged in a turbine housing 26. Because the turbine impeller 22 is connected to the spindle 8, the rotating component 7 (and thus the stack of separation discs 9) also rotates as the impeller 22 rotates. Alternatively, centrifugal separator 1 may include an electric motor arranged to rotate the spindle 8 and the rotating component 7. As another alternative, centrifugal separator 3 may include a turbine impeller connected to the spindle 8, wherein the turbine impeller is arranged to be driven by exhaust gases from the internal combustion engine to rotate the spindle 8 and the rotating component 7. The rotating component 7 may also be arranged to be rotated by a mechanical drive unit. Thus, the centrifugal separator may include a mechanical drive unit for rotating the rotating component 7.

[0079] The rotating component 7 defines a central space 15. In this example, the central space 15 is formed by through-holes in each of the separating disks 9. Figure 1 In one embodiment, the central space 15 is formed by a plurality of through-holes, each extending through the top disk 10 and through each of the separation disks 9, but not through the lower end plate 11. The through-holes are arranged in the flat portion 9a of the separation disk.

[0080] Gas inlet 20 extends through stationary shell 2 and more precisely through upper end wall 5, and is arranged to supply gas to be cleaned to separation space 3. Gas inlet 20 is formed by an axially extending inlet conduit 18 forming an upstream portion and a through passage 21 forming a downstream portion of inlet 20.

[0081] The through passage 21 is fluidly connected to the central space 15 and is arranged radially outward of the upper bearing 12. Therefore, the gas inlet 20 communicates with the central space 15, allowing the gas to be cleaned to be delivered from the inlet 20 through the central space 15 to the gap 14 of the stacked separator discs 9. The gas inlet 20 is configured to communicate via the inlet conduit 18 with the crankcase of the combustion engine or any other source to allow 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.

[0082] Centrifugal separator 1 includes a discharge outlet 29 disposed in the lower portion of stationary housing 2 and configured to allow the discharge of liquid contaminants separated from the gas. In this embodiment, the discharge outlet 29 is in the form of through-holes disposed in the lower end wall 6, allowing the separated liquid contaminants to flow through the lower bearing 13 as they are discharged from the separation space 3 into the turbine housing 26. The separated oil and other particles and / or substances are directed to the oil outlet 25 of centrifugal separator 1, which, together with oil from the oil nozzle 24 used to drive the impeller 22, can be directed back to the engine oil circuit of the internal combustion engine. In this embodiment, the discharge outlet 29 is centrally located on the lower end wall 6. In an alternative embodiment, the discharge outlet 29 may be located elsewhere on the lower end wall 6.

[0083] The gas outlet pipe 28 of the centrifugal separator 1 is arranged to pass through the stationary shell 2 and is configured to allow the discharge of clean gas.

[0084] In such Figure 1 During operation of the centrifugal separator shown, the rotating component 7 is kept rotating by an oil nozzle 24 that supplies oil relative to the impeller 22. As an example, the rotational speed can be in the range of 7500-12000 rpm.

[0085] Contaminated gas (e.g., crankcase gas from the crankcase of an internal combustion engine) is supplied to gas inlet 20 via conduit 18. This gas is further conducted into central space 15, and from there enters and passes through gap 14 between stacked separator discs 9. The rotation of rotating component 7 causes the gas to rotate, thereby further radially outward pumping through the gap or opening 14.

[0086] During gas rotation in gap 14, solid or liquid particles (such as oil) suspended in the gas are separated from it. The particles settle on the inner side of the conical portion 9b of the separation disc and then slide or run radially outward thereafter. As the particles and / or droplets reach the radially outer edge of the stacked separation discs 9, they are thrown away from the rotating component 7 and impact the inner surface 40 surrounding the sidewall 4. The separated oil particles can form a film on the inner surface of the stationary shell 2. From there, the oil can be drawn downwards by gravity to the bottom wall 6 and then exit the separation space 3 through the discharge outlet 29. For this purpose, the inner wall of the bottom wall 6 can be radially inwardly inclined so that the oil exiting the stationary shell 2 and surrounding the inner wall can be drawn towards the discharge outlet 29 by gravity. Figure 1 The arrow "D" schematically indicates the path of pollutants in the gas.

[0087] Clean gas, free of particles and exiting the stack of separation discs 9, leaves the stationary shell 2 through gas outlet pipe 28. Figure 1 The path of the gas passing through centrifugal separator 1 is schematically shown by the arrow "C".

[0088] Figure 1 The centrifuge also includes a stationary insert 50, which is arranged in the lower portion of the stationary housing 2 and more precisely axially below the stack of separation discs 9. The stationary insert 50 can be fastened to the surrounding sidewall 4 of the stationary housing and / or to the lower end wall 6 via support legs (not shown). The stationary insert 50 includes an outer annular wall component 51 and a central truncated conical cup component 53 with tapered sidewalls. The lower portion of the end plate 11 is arranged within the central cup component 53. The annular wall component 51 extends axially downward from the outer edge of the cup component 53.

[0089] The stationary insert 50 forms a physical barrier between the clean gas and the separated contaminants before they leave the stationary housing 2. For this purpose, the stationary insert 50 is arranged within the stationary housing 2 to form an annular vertical channel 52 for the separated contaminants between the inner surface 40 of the stationary housing 2 and the annular wall component 51, and a flow path for the clean gas towards the gas outlet 28 within the central cup component 53. Thus, the annular vertical channel 52 forms an annular slit and collects separated oil droplets that travel downwards on the inner surface 40 surrounding the sidewall 4 under gravity during the use of the separator 1. Furthermore, the downward spiral airflow forces the oil on the inner surface 40 downwards. The annular vertical channel 52 thus shields the separated liquid particles flowing downwards on the inner wall 40 from the rotating gas, reducing the risk that the separated oil will be pulled away from the inner wall 40 on its downward path to the discharge outlet 29. The stationary insert 50 may be a molded unit, preferably made of polymer or plastic material.

[0090] Alternatively, the annular wall component 51 can be omitted, so that the stationary insert 50 is mainly defined by the conical cup component, which, in conjunction with the gas outlet, is sufficient to guide the airflow.

[0091] Figure 2 A perspective view of the lower end wall 6 of the centrifuge 1 and the stationary insert 50 is shown. (As described above relative to...) Figure 1 As discussed, the clean gas is guided to and through the gas outlet 28 via the stationary insert 50, such as... Figure 2 This is indicated by arrow "C". In this example, the gas outlet 28 is arranged as a pipe extending through the stationary housing 2 and is formed as a single piece together with the stationary insert 50. However, alternatively, the gas outlet 28 may be in the form of a separate piece from the stationary insert 50. In addition to the clean gas guided and directed through the gas outlet 28, the gas within the stationary housing 2 flows downward in a helical motion during the rotation of the rotating component. Figure 2In the diagram, the direction of rotation of the rotating component (and therefore the gas) is indicated by the arrow "Z". Therefore, upon reaching the lower portion of the stationary housing 2, the airflow circulates within the cavity formed between the stationary insert 50 and the lower end wall 50. Due to the presence of the stationary structure in this cavity, a wake region 62 can be formed at the wake region portion 61 of the stationary structure during operation. In such a wake region 62, the airflow is significantly lower. In other words, the wake region portion 61 is shielded from wind. In this example, the wake region portion 61 is the downstream or leeward portion of the stationary gas outlet 28, as seen in the direction Z of the rotating airflow. The wake region portion 61 is further arranged at an axial distance above the lower end wall 6.

[0092] The inventors have discovered that contaminants (such as oil) tend to accumulate in such wake portion 61. This accumulation can cause contaminants to be dragged into the rotating gas flow, and thus poses a risk of re-entry into the clean gas, resulting in reduced cleaning efficiency of the centrifuge 1. Therefore, according to the invention, an oil bridge structure 60 is provided that axially connects the wake portion 61 (in this case, the leeward portion of the pipe forming at least a portion of the gas outlet 2 in the stationary housing) to the lower end wall 6. Thus, the wake portion 61 is a portion of the stationary gas outlet 28 at the downstream end of the gas outlet 28, as seen in the direction Z of the rotating gas during operation of the centrifuge 1.

[0093] With this arrangement, any contaminants that accumulate at the wake region portion 61 at an axial distance above the lower end wall 6 can be guided from the surface of the gas outlet 28 to the lower end wall 6 via the oil bridge structure 60, and subsequently towards the discharge outlet 28.

[0094] like Figure 2 As shown, the oil bridge structure 60 is attached to the wake region portion 61 at a corner 61c, which is formed by edge portions 61a and 61b.

[0095] The oil bridge structure 60 can be an integrated part of the gas outlet 28, or it can be formed as a separate unit attached between the gas outlet 28 and the lower end wall 6.

[0096] Because liquid contaminants are more likely to appear near the outer radius of the separation space, the oil bridge 60 is preferably arranged within the outer radial portion of the radial extension R of the separation space 3. As an example, the wake region portion 61 to which the oil bridge structure 60 is connected is arranged within the outer 25% of the radial extension R of the separation space 3.

[0097] Furthermore, the oil bridge structure 60 may have at least one planar surface extending in the axial plane. This facilitates the discharge of oil from the wake region portion 61 to the lower end wall 6.

[0098] To further facilitate the transport of liquid contaminants on the lower end wall to the discharge outlet 29, the lower end wall 6 also includes a guide member in the form of an elongated recess 70, which is formed in the surface of the lower end wall 6 to guide the separated contaminants on the lower end wall 6 toward the discharge outlet 29.

[0099] The recesses 70 are preferably arranged radially and cover most of the radial distance of the lower end wall 6. Each recess 6a is arranged in the lower end wall 6 from a radially inner position at the discharge outlet 29 to a radially outer position, which is a short distance away from or at the periphery of the lower end wall 6. In this example, eight straight radial recesses 70 are evenly distributed on the lower end wall around the discharge outlet 29.

[0100] Figure 3 A top cross-sectional view shows another embodiment of the wake region portion 28 within the stationary shell 4. The rotation direction z of the rotating component 7 is also shown, which is also the rotation direction of the rotating airflow. In this embodiment, the wake region portion 28 is arranged in a plane perpendicular to the airflow rotation direction z, and thus a wake region 62 is formed downstream of the wake region portion. However, as indicated by the dashed portions 28a and 28b, the wake region portion may also be arranged in a plane forming an angle with the direction of the rotating airflow, deviating from 90 degrees (vertical), such as between 60 and 120 degrees, such as between 70 and 110 degrees.

[0101] This invention is not limited to the disclosed embodiments, but can be varied and modified within the scope of the claims set forth below. The invention is not limited to the orientation of the rotation axis (X) disclosed in the figures. The term "centrifuge" also includes centrifuges having a rotation axis with a substantially horizontal orientation. In the foregoing, the inventive concept has been described primarily with reference to a limited number of examples. However, as will be readily apparent to those skilled in the art, other examples besides those 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 gases containing contaminants, said centrifugal separator (1) comprising: A stationary shell (2) surrounds a separation space (3) and allows airflow through the separation space (3); A gas inlet (20) extends through the stationary shell (2) and allows the supply of gas to be cleaned; A rotating component (7) comprising a separation unit (16) arranged in the separation space (3) and configured to rotate about a rotation axis (X); A driving component (22) is used to rotate the rotating component (7); Gas outlet (28) is arranged through the stationary shell (2) and configured to allow clean gas to be discharged from the stationary shell (2); as well as An exhaust outlet (29) is disposed in the stationary shell (2) and configured to allow liquid contaminants separated from the gas to be discharged from the stationary shell (2); the exhaust outlet (29) is disposed in the lower end wall (6) of the stationary shell (2); The centrifuge (1) further includes A stationary structure (28) is arranged within the stationary shell (2) and includes a wake region portion (61) arranged at an axial distance from the lower end wall (6); wherein the wake region portion (61) is arranged such that a wake region (62) for rotating gas is formed at the wake region portion (61) during operation of the centrifugal separator (1); and An oil bridge structure (60) axially connects the wake region portion (61) of the stationary structure (28) to the lower end wall (6) for guiding any contaminants from the surface of the stationary structure (28) to the lower end wall (6).

2. The centrifuge (1) according to claim 1, wherein, The wake region portion (61) of the stationary structure has an edge portion (61a, 61b) or a corner portion (61c), wherein the oil bridge structure (60) is connected to the edge portion (61a, 61b) or the corner portion (61c).

3. The centrifuge (1) according to any of the preceding claims, wherein, The wake region (61) has a surface extending in a plane that forms an angle with respect to the direction of the rotating airflow during use of the centrifugal separator (1).

4. The centrifuge (1) according to any of the preceding claims, wherein, The wake region (61) is part of the stationary structure (28) at its downstream end, as seen in the direction (Z) of the rotating gas during operation of the centrifugal separator (1).

5. The centrifuge (1) according to any of the preceding claims, wherein, The oil bridge structure (60) is arranged within 50% of the outer side of the radial extension (R) of the separation space (3).

6. The centrifuge (1) according to any of the preceding claims, wherein, The oil bridge structure (60) has a planar surface extending in an axial plane.

7. The centrifuge (1) according to any of the preceding claims, wherein, The stationary structure (28) forms part of the gas outlet.

8. The centrifugal separator (1) according to any of the preceding claims, wherein, The stationary structure (28) further forms part of the stationary insert (50), which is arranged to form a barrier between the clean gas and the separated contaminants before the clean gas and the separated contaminants leave the stationary shell (2).

9. The centrifugal separator (1) according to any of the preceding claims, wherein, The lower end wall (6) also includes a guide member (70) for guiding the separated pollutants on the lower end wall (6) toward the discharge outlet (29).

10. The centrifugal separator (1) according to any of the preceding claims, wherein, The guide component (70) includes an elongated recess for guiding liquid contaminants to the discharge outlet (29).

11. The centrifuge (1) according to claim 9, wherein, The recess (70) of the lower end wall (6) is arranged radially.

12. The centrifuge (1) according to claim 10 or 11, wherein, The lower end wall (6) includes at least four recesses (70).

13. The centrifuge (1) according to any of the preceding claims, wherein, The separation unit (16) includes multiple separation components (9).

14. The centrifuge (1) according to claim 13, wherein, The plurality of separation components (9) are arranged as a stack of truncated conical separation disks (9).

15. The centrifugal separator (1) according to any of the preceding claims, wherein, The contaminants include oil.

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