Patent Grant
10512919
This application is a National Stage Application of and claims priority to PCT Application No. PCT/EP2015/059457, filed on Apr. 30, 2015, which is a PCT Application of and claims priority to EP Application No. 14166551.3, filed on Apr. 30, 2014, the subject matter of which applications is incorporated by reference herein in their entirety. This application is also related to application which is concurrently being filed on even date of the present application, which claims priority to PCT Application No. PCT/EP2015/059451, filed on Apr. 30, 2015, which is a PCT Application of and claims priority to EP Application No. 14166549.7, filed on Apr. 30, 2014.
The present invention refers to a centrifugal separator for cleaning a gas containing liquid impurities. In particular, the centrifugal separator according to the invention is configured for cleaning oil particles from crankcase gases of a combustion engine, the centrifugal separator having a drainage outlet in an upstream portion of the gas outlet.
WO 2007/094725 discloses a centrifugal separator having a gas inlet that extends through the bottom of the centrifugal separator. The outlet opening of the gas outlet is provided through the side wall above the stack of separating disks adjacent to an upper one of the end walls. Separated liquid impurities are discharged through the side wall.
WO 2005/087384 discloses a centrifugal separator having a gas inlet that extends through the top of the centrifugal separator. The outlet opening of the gas outlet is provided through the side wall below the stack of separating disks adjacent to a lower one of the end walls. Separated liquid impurities are discharged through the side wall.
US 2011/0281712 discloses a centrifugal separator for cleaning crankcase gases having an outlet opening of the gas outlet that extends through an upper end wall of the centrifugal separator. An inlet opening of the gas inlet extends through the lower end wall. Separated liquid impurities are discharged through the lower end wall.
One problem of the prior art centrifugal separators is that they have a relatively large size requiring a large space. This is a significant problem, especially when the centrifugal separator is used for cleaning crankcase gases from smaller combustion engines, preferably from smaller diesel engines, to be used especially in lighter trucks and the like.
One way of reducing the size of the centrifugal separator is to reduce the diameter of the stack of separation disks. However, in order to maintain the separation efficiency, the height or the length of the stack then has to be increased.
The object of the present invention is to remedy to the problem discussed above, and more precisely to provide a centrifugal separator having a reduced or compact size while maintaining or improving the separation efficiency.
This object is achieved by the centrifugal separator initially defined, which has a drainage outlet provided in the gas outlet downstream the upstream portion, wherein the gas outlet is configured to convey the liquid impurities to the drainage outlet.
By conveying the liquid impurities separated from the cleaned gas in the gas outlet, a more compact solution is achieved. Only one single outlet channel from the stationary casing is required for both the liquid impurities and the cleaned gas. The gas outlet is configured to convey the cleaned gas along a central flow in the gas outlet and the liquid impurities along the inside walls of the gas outlet to the drainage outlet.
According to an embodiment of the invention, the gas outlet comprises an outlet conduit having an entry portion provided downstream the upstream portion, wherein the drainage outlet comprises a ditch extending around the entry portion of the outlet conduit. The central flow of the cleaned gas may thus be conveyed through the entry portion of the outlet conduit. The liquid impurities will be collected in the ditch provided around the entry portion.
According to a further embodiment of the invention, the drainage outlet comprises at least one drainage opening extending from the ditch. The liquid impurities collected in the ditch will be drained from the ditch through the drainage opening for further transport to any suitable position. The liquid impurities will be drained together with a small amount of cleaned gas, at least in relation to the amount of cleaned gas in the central flow. Advantageously, more than one drainage opening extends from the ditch, for instance two, three, four or even more drainage openings.
According to a further embodiment of the invention, the gas outlet has a downstream portion provided downstream the upstream portion and having an increasing cross-section. Such an increasing cross-section is fluid dynamically advantageous by permitting recover of the pressure drop at the outlet opening. Advantageously, the upstream portion may have a constant cross-section.
According to a further embodiment of the invention, the drainage outlet and the entry portion of the outlet conduit are provided at the downstream end of the downstream portion.
According to a further embodiment of the invention, the downstream portion extends form the upstream portion. The downstream portion may thus start directly where the upstream portion ends.
According to a further embodiment of the invention, the outlet opening of the gas outlet extends through the side wall of the stationary casing. Since the gas outlet extends from the outlet opening through the side wall, both the cleaned gas and the liquid impurities may be given a velocity in a tangential direction and may thus be easily discharged through the outlet opening in the side wall, and kept separated in the gas outlet.
According to a further embodiment of the invention, an end space is provided outside the separation space and communicates with the drainage outlet via a drainage channel that extends from the at least one drainage opening. The drainage opening or drainage openings have a total flow area that is restricted to create a lower pressure in the end space than in the radially outer part of the separation space. The liquid impurities will thus be conveyed to the end space, especially together with the small amount of cleaned gas, thanks to this pressure difference. From the end space, the liquid impurities, such as oil, may be transported through one or two bearings supporting the rotating member, and/or back to the oil system of the combustion engine.
According to a further embodiment of the invention, a central suction opening extends between the separation space and the end space through the second end wall to permit a re-circulating gas flow from the end space to the separation space. The pressure in the central part of the separation space will be lower than in the radially outer part due to the pumping effect of the stack of separation disks. The pressure in the central part of the separation space will also be lower than the pressure in the end space.
According to a further embodiment of the invention, a fan member is provided between the second end wall and the stack of separation disks to further promote said re-circulating gas flow. Advantageously, the fan member is attached to the spindle and rotates together with the stack of separation disks.
According to a further embodiment of the invention, the second end wall adjacent to the side wall has a number of apertures providing communication channels between the separation space and the end space for separated liquid impurities. Liquid impurities collected on the second end wall may thus be drained to the end space.
According to a further embodiment of the invention, the upstream portion has upstream outlet walls that are substantially parallel with each other. The downstream portion may have downstream outlet walls that are diverging. Gas outlet is thus delimited by the inside walls which comprise the upstream outlet walls and the downstream outlet walls.
According to a further embodiment of the invention, the stationary casing has a radius R from the axis of rotation to the surrounding side wall, wherein the upstream portion extends from the outlet opening in an outlet direction, wherein the outlet direction extends through an upstream point of the outlet opening and is parallel with a transversal line extending through the axis of rotation, the perpendicular distance between the outlet direction and said transversal line is at least 0.8R and at the most 1.2R, especially with respect to the radius R opposite to the outlet opening. Such an extension of the outlet direction decreases the flow resistance for the gas flow exiting the separation space. Advantageously, the perpendicular distance between the outlet direction and said line may be at least 0.9R and at the most 1.1R. Moreover, the perpendicular distance between the outlet direction and said transversal line may be equal to, or substantially equal to, the radius R Such an extension of the outlet direction results in a minimum flow resistance for the gas flow leaving the separation space.
According to a further embodiment of the invention, the outlet opening has an elongated shape along a longitudinal direction and is positioned opposite to the stack of separation disks. Such an opening with an elongated shape, or in the form of a slot, through the side wall of the casing, is advantageous since it permits a uniform distribution of the flow of gas over a large area.
According to a further embodiment of the invention, the stack of separation disks has an outer circumferential periphery and an axial length at the outer circumferential periphery, wherein the outlet opening along the longitudinal direction has a length which is 80-130% of the axial length. This feature contributes further to a uniform gas flow through the whole stack of separation disks, i.e. to an equal gas flow in each of the gaps between adjacent separation disks. Advantageously, the length may be 90-120% of the axial length, especially 100-110% of the axial length.
According to a further embodiment of the invention, the separation disks are provided at a distance from each other to form a gap between adjacent separation disks. Advantageously, each gap may be positioned opposite, or just opposite, the outlet opening. Furthermore, the rotating member may define a central space formed by at least one hole in each of the separation disks and connected to the inlet and configured to convey the gas to be cleaned from the inlet to the gaps of the stack of separation disks.
The invention is now to be explained more closely through a description of various embodiments and with reference to the drawings attached hereto.
The centrifugal separator comprises a stationary casing 1, which is configured to be mounted to a combustion engine (not shown), especially a diesel engine, at a suitable position, such as on top of the combustion engine or at the side of the combustion engine.
It is to be noted that the centrifugal separator is also suitable for cleaning gases from other sources than combustion engines, for instance the environment of machine tools which frequently contains large amounts of liquid impurities in the form of oil droplets or oil mist.
The stationary casing 1 encloses a separation space 2 through which a gas flow is permitted. The stationary casing 1 comprises, or is formed by, a surrounding side wall 3, a first end wall 4 (in the embodiments disclosed an upper end wall) and a second end wall 5 (in the embodiments disclosed a lower end wall). The surrounding side wall 3 has a circular cross-section with a radius R from the axis x of rotation to the surrounding side wall 3, which is constant at least with respect to a major part of the circumference of the surrounding side wall 3. In particular, the side wall 3 is circular cylindrical.
The centrifugal separator comprises a rotating member 6, see
The rotating member 6 comprises a spindle 7 and a stack of separation disks 8 attached to the spindle 7. All the separation disks 8 of the stack of separation disks 8 are provided between a first end plate 9 (in the embodiments disclosed an upper end plate) and a second end plate 10 (in the embodiments disclosed a lower end plate), see
The spindle 7, and thus the rotating member 6, is rotatably supported in the stationary casing 1 by means of a first bearing 11 (in the embodiments disclosed an upper bearing) and a second bearing 12 (in the embodiments disclosed a lower bearing), see
The separation disks 8 are conical and extend downwardly and outwardly from the spindle 7. It should be noted that the separation disks 8 could also extend upwardly and outwardly, or even radially. The separation disks 8 are provided at a distance from each other by means of distance members (not shown) in order to form gaps 13 between adjacent separation disks 8, i.e. a gap 13 between each pair of adjacent separation disks 8. The axial thickness of each gap 13 may be in the order of 1-2 mm, for instance.
Each separation disk 8 may be made of plastics or metal. The number of separation disks 8 is normally higher than indicated in
The rotating member 6 defines a central space 14, see
The centrifugal separator comprises an inlet 15 for the supply of the gas to be cleaned. The inlet 15 extends through the stationary casing 1, and more precisely through the first end wall 4. The inlet 15 communicates with the central space 14 so that the gas to be cleaned is conveyed from the inlet 15 via the central space 14 to the gaps 13 of the stack of separation disks 8, see
The inlet 15 is configured to communicate with the crankcase of the combustion engine, or any other source, via an inlet conduit 16 permitting the supply of crankcase gas from the crankcase to the inlet 15 and further to the central space 14 and the gaps 13 as explained above. The inlet conduit 16 disclosed may be comprised by the centrifugal separator.
The centrifugal separator comprises a schematically disclosed drive member 17 for rotating the rotating member 6. The drive member 17 is connected to the spindle 7. The drive member 17 may comprise a turbine wheel, see WO2012/152925, rotated by means of an oil jet from the oil system of the combustion engine, or a free jet wheel comprising a blow-back disk, see WO2014/023592, wherein the free jet is provided by the oil system of the combustion engine. Alternatively, the drive member 17 may be independent of the combustion engine and comprise an electric motor, a hydraulic motor or a pneumatic motor.
The centrifugal separator comprises a drainage outlet 19 configured to permit discharge of liquid impurities separated from the gas. The centrifugal separator also comprises a gas outlet 20 configured to permit discharge of cleaned gas. The liquid impurities of the gas will be separated from the gas in the gaps 13, and the cleaned gas will be conveyed out of the gaps 13 to the separation space 2 and further to the gas outlet 20.
The gas outlet 20 comprises an outlet opening 21 in the stationary casing 1, and in the embodiments disclosed in the side wall 3 of the stationary casing 1. The outlet opening 21 is elongated and configured as a slot through the side wall 3 of the stationary casing 1. The outlet opening 21 has an upstream point 21′, or upstream axial line, and a downstream point 21″, or downstream axial line, see
Thus, the outlet opening 21 has an elongated shape along a longitudinal axis x′. In the embodiments disclosed, the longitudinal axis x′ is parallel or substantially parallel with the axis x of rotation as can be seen in
The outlet opening, or slot, 21, is positioned opposite, or just opposite, to the stack of separation disks 8. Thus, the outlet opening 21 is thus positioned laterally beside the stack of separation disks 8, which means that the distance from the gaps 13 to the outlet opening 21 is short, and may be the same for each gap 13 to the outlet opening 21.
The stack of separation disks 8 has an outer circumferential periphery and an axial length S at the outer circumferential periphery, see
The gas outlet 20 has an upstream portion 22 and a downstream portion 23, see
The outlet direction D extends through an upstream point 21′ of the outlet opening 21 and is parallel with a transversal line T extending through the axis x of rotation. The perpendicular distance P between the outlet direction D and the transversal line T is at least 0.8R and at the most 1.2R.
In the embodiments disclosed in
The upstream portion 22 has a constant cross-section when seen in a section transversal to the axis x of rotation, as can be seen in
In the embodiments disclosed the upstream outlet walls 24, 25 are also parallel with the axis x of rotation.
The distance between the two upstream outlet walls 24 and 25 is shorter, or significantly shorter, than the length L, and the radius R.
The downstream portion 23 and has an increasing cross-section when seen in the section transversal to the axis x of rotation shown in
The drainage outlet 19 is provided in the gas outlet 20 at the downstream end of the downstream portion 23 of the gas outlet 20 as illustrated in
The liquid impurities, which are illustrated as exaggerated spots in the figures and are transported from the gaps 13 to an inner side of the side wall 3 due to the centrifugal force, where they form a film of separated oil. The rotary movement conveys the film of separated oil along the inner side of the side wall 3 to the outlet opening 21 and the gas outlet 20. The film of separated oil is then conveyed outwardly on the inside walls of the gas outlet 20, comprising the upstream outlet walls 24, 25 and the downstream outlet walls 26, 27, to the drainage outlet 19.
The gas outlet 20 comprises an outlet conduit 28 having an entry portion 29. The drainage outlet 19 comprises a ditch 30 extending around the entry portion 29 of the outlet conduit 28.
The entry portion 29 and the ditch 30 are provided downstream the upstream portion 22, and at the downstream end of the downstream portion 23.
The cleaned gas may thus be discharged via the gas outlet 20 to the outlet conduit 28. The outlet conduit 28 may advantageously recirculate the cleaned gas, for instance to the inlet side of the combustion engine.
The drainage outlet 19 comprises in the embodiments disclosed four drainage openings 31 extending from the ditch 30. Of course the drainage outlet 19 may comprise another number of such drainage openings 31, for instance one, two, three, five or even more drainage openings 31.
The gas outlet 20 will thus convey the cleaned gas along a central flow in the gas outlet 20 and the liquid impurities, as a film of separated oil, along the inside walls of the gas outlet 20 to the drainage outlet 19. The central flow of the cleaned gas will be conveyed through the entry portion 29 of the outlet conduit 28, and the liquid impurities will be collected in the ditch 30 around the entry portion 29.
The centrifugal separator also comprises an end space 33, which is provided outside the separation space 2. In the embodiments disclosed the end space 33 is located outside second end wall 5 as can be seen in
A central suction opening 35 extends between the separation space 2 and the end space 33 through the second end wall 5, see
According to the first embodiment, the centrifugal separator comprises a fan member 36 provided between the second end wall 5 and the stack of separation disks 8. The fan member 36 is provided outside the central suction opening 35 and promotes further the re-circulating gas flow from the end space 33 to the separation space 2.
In the embodiments disclosed, the second end wall 5 has two apertures 37 located adjacent to the side wall 3. The apertures 37 provides communication channels between the separation space 2 and the end space 33 for separated liquid impurities collected on the second end wall 5. The liquid impurities may thus pass through the apertures 37 into the end space 33 as illustrated in
It is to be noted that the outlet direction D may have another extension than shown in
In the third embodiment, the perpendicular distance P between the outlet direction D and said transversal line T is shorter than the radius R and approximately 0.9R. The perpendicular distance between the transversal line T and the downstream point 21″ is shorter than 0.9R.
In the fourth embodiment, the perpendicular distance P between the outlet direction D and the transversal line T is longer than the radius R and approximately 1.1R. The perpendicular distance between the transversal line T and the downstream point 21″ may be longer than equal to or as shown in
In the fifth embodiment, the perpendicular distance P between the outlet direction D and the transversal line T is longer than the radius R and approximately 1.1R. The perpendicular distance between the transversal line T and downstream point 21″ may be longer than, equal to or as shown in
The present invention is not limited to the embodiments disclosed, but mat be varied and modified within the scope of the following claims.
| Number | Date | Country | Kind |
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| 14166551 | Apr 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
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| PCT/EP2015/059457 | 4/30/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/166024 | 11/5/2015 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20170036221 A1 | Feb 2017 | US |
