Centrifugal separator having an outlet opening opposite a stack of separation disks

Abstract

A centrifugal separator for cleaning gas containing liquid impurities includes a stationary casing, enclosing a separation space through which a gas flow is permitted. The stationary casing includes a surrounding side wall, a first end wall and a second end wall. An inlet extends through the stationary casing and permits supply of the gas to be cleaned. A rotating member includes a stack of separation disks rotatable around an axis of rotation. A drive member rotates the rotating member. A gas outlet permits discharge of cleaned gas, and includes an outlet opening through the side wall. A drainage outlet permits discharge of liquid impurities separated from the gas. The outlet opening is positioned opposite to the stack of separation disks.

Claims

1. A centrifugal separator for cleaning gas containing liquid impurities, the centrifugal separator comprising: a stationary casing, enclosing a separation space through which a gas flow is permitted, the stationary casing comprising a surrounding side wall, a first end wall and a second end wall, an inlet extending through the stationary casing and permitting supply of the gas to be cleaned; a rotating member comprising a stack of separation disks and being arranged to rotate around an axis of rotation; a drive member, for rotating the rotating member; a gas outlet configured to permit discharge of cleaned gas, and comprising an outlet opening through the side wall of the stationary casing; and a drainage outlet configured to permit discharge of liquid impurities separated from the gas to be cleaned, the drainage outlet surrounding the gas outlet.

2. The centrifugal separator according to claim 1, wherein the outlet opening has an elongated shape along a longitudinal axis.

3. The centrifugal separator according to claim 2, wherein the longitudinal axis has at least a major component of direction which is parallel with the axis of rotation.

4. The centrifugal separator according to claim 2, wherein the longitudinal axis is substantially parallel with the axis of rotation.

5. The centrifugal separator according to claim 1, wherein the stack of separation disks has an outer circumferential periphery and an axial length at the outer circumferential periphery, and wherein the outlet opening along the longitudinal axis has a length, wherein the length is 80-130% of the axial length.

6. The centrifugal separator according to claim 5, wherein the length is 90-120% of the axial length.

7. The centrifugal separator according to claim 5, wherein the length is 100-110% of the axial length.

8. The centrifugal separator according to claim 1, wherein the stationary casing has a radius from the axis of rotation to the surrounding side wall.

9. The centrifugal separator according to claim 8, wherein the gas outlet has an upstream portion, the upstream portion having an inner sidewall and an outer sidewall extending from the outlet opening in an outlet direction, which is parallel with a transversal line extending through the axis of rotation, the perpendicular distance between the outer sidewall and said transversal line is at least 0.8R and at the most 1.2R.

10. The centrifugal separator according to claim 9, wherein the perpendicular distance between the outlet direction and said transversal line is at least 0.9R and at the most 1.1R.

11. The centrifugal separator according to claim 10, wherein the perpendicular distance between the outlet direction and said transversal line is substantially equal, or equal, to the radius R.

12. The centrifugal separator according to claim 9, wherein the gas outlet has a downstream portion, which is provided downstream of the upstream portion and has an increasing cross-section in a direction extending from the upstream portion.

13. The centrifugal separator according to claim 12, wherein the downstream portion extends from the upstream portion.

14. The centrifugal separator according to claim 1, wherein the gas outlet is configured to convey the liquid impurities to the drainage outlet.

15. The centrifugal separator according to claim 12, wherein the drainage outlet is provided downstream of the downstream portion.

16. The centrifugal separator according to claim 1, wherein the separation disks are provided at a distance from each other to form a gap between adjacent separation disks.

17. The centrifugal separator according to claim 16, wherein the rotating member defines a central space, which is 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now to be explained more closely through a description of various embodiments and with reference to the drawings attached hereto.

(2) FIG. 1 discloses a perspective view of a centrifugal separator according to a first embodiment of the invention.

(3) FIG. 2 discloses a cross-sectional view perpendicular to an axis of rotation of the centrifugal separator in FIG. 1.

(4) FIG. 3 discloses a sectional view along the line III-III in FIG. 2.

(5) FIG. 4 discloses a sectional view along the line IV-IV in FIG. 2.

(6) FIG. 5 illustrates the direction of a gas outlet of the centrifugal separator in FIG. 1.

(7) FIG. 6 illustrates the direction of the gas outlet of a centrifugal separator according to a second embodiment of the invention.

(8) FIG. 7 illustrates the direction of the gas outlet of a centrifugal separator according to a third embodiment of the invention.

(9) FIG. 8 illustrates the direction of the gas outlet of the centrifugal separator according to a fourth embodiment of the invention.

DETAILED DESCRIPTION

(10) FIGS. 1 to 5 disclose a first embodiment of a centrifugal separator for cleaning gases containing liquid impurities, especially crankcase gases of a combustion engine, which contain liquid impurities in the form of oil droplets and/or oil mist.

(11) The centrifugal separator includes 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.

(12) 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.

(13) 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).

(14) The centrifugal separator includes a rotating member 6, see FIG. 4, which is arranged to rotate around an axis x of rotation. It should be noted that the stationary casing 1 is stationary in relation to the rotating member 6, and preferably in relation to the combustion engine to which it may be mounted.

(15) The stationary casing 1 has 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. The surrounding side wall 3 thus has a circular, or substantially, circular cross-section.

(16) 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 FIG. 4.

(17) 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 FIG. 4.

(18) 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.

(19) The separation disk 8 may be made of plastics or metal. The number of separation disks 8 is normally higher than indicated in FIG. 4 and may be for instance 50 to 100 separation disks 8 depending of the size of the centrifugal separator.

(20) The rotating member 6 defines a central space 14. The central space 14 may be formed by a hole in each of the separation disks 8. In the embodiments disclosed the central space 14 is formed by a plurality of holes, see FIG. 2, each extending through the first end plate 9 and through each of the separation disks 8.

(21) 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 FIG. 4.

(22) 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.

(23) The centrifugal separator comprises a schematically disclosed drive member 17 for rotating the rotating member 6. 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.

(24) The centrifugal separator comprises a drainage outlet 19 configured to permit discharge of liquid impurities separated from the gas and 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.

(25) The gas outlet 20 comprises an outlet opening 21 in the side wall 3. 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 FIGS. 2 and 5. In the first embodiment, the upstream point 21 and the downstream point are located at the radius R from the axis x of rotation.

(26) 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 FIG. 3. However, it is to be noted that the longitudinal axis x, i.e. the extension of the inlet opening 21, may slope slightly to the axis x of rotation. In other words, the longitudinal axis x may have a major component of direction which is parallel with the axis x of rotation, and in that case a minor component of direction, which is perpendicular to the axis x of rotation (not shown).

(27) 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.

(28) The stack of separation disks 8 has an outer circumferential periphery and an axial length S at the outer circumferential periphery, see FIG. 4. The outlet opening 21 has a length L along the longitudinal axis x, see FIG. 3. The length L is 80-130% of the axial length S, preferably 90-120% of the axial length S, and more preferably 100-110% of the axial length S. In particular, the length L may be at least equal to, or correspond to the axial length S, or be in the same order as the axial length S. If the length L is at least equal to the axial length S, an equal distance from each gap 13 to the outlet opening 21 may be ensured.

(29) The gas outlet 20 has an upstream portion 22 and a downstream portion 23, see FIG. 2. The upstream portion 22 extends from, or starts at, the outlet opening 21. At least the upstream portion 22 extends in an outlet direction D as can be seen in FIG. 2.

(30) 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.

(31) In the embodiments disclosed in FIGS. 1-5, the perpendicular distance between the outlet direction D and the transversal line T is substantially equal, or equal, to the radius R. Thus, the outlet direction D is a tangential direction with respect to the axis x of rotation. The downstream point 21 is located at a shorter perpendicular distance P to the transversal line T than the outlet direction D.

(32) 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 FIG. 2. This means that the upstream portion 22 has upstream outlet walls 24, 25 that are parallel with each other, and with the outlet direction D. In particular, the upstream outlet wall 24 coincides with the outlet direction D.

(33) In the embodiments disclosed, the upstream outlet walls 24, 25 are also parallel with the axis x of rotation.

(34) The distance between the two upstream outlet walls 24 and 25 is shorter, or significantly shorter, than the length L, and the radius R.

(35) The downstream portion 23 and has an increasing cross-section when seen in the section transversal to the axis x of rotation shown in FIG. 2. This means that the downstream portion 22 has downstream outlet walls 26, 27 that are diverging from each other.

(36) The drainage outlet 19 is provided downstream the downstream portion 23 of the gas outlet 20 as illustrated in FIG. 2. The gas outlet 20 is thus configured to convey the liquid impurities, which have been separated from the gas, to the drainage outlet 19. The liquid impurities, which are illustrated as exaggerated spots in the figures, form a thin flow of separated oil, which is transported from the gaps 13 to an inner side of the side wall 3 due to the centrifugal force. The rotary movement conveys the separated oil along the inner side of the side wall 3 to the outlet opening 21 and the gas outlet 20. The separated oil is then conveyed outwardly on the upstream outlet walls 24, 25 and the downstream outlet walls 26, 27 to the drainage outlet 19.

(37) At the drainage outlet 19 the separated oil may be recovered and taken care of in any suitable manner. In case of a combustion engine the separated oil may be returned to the oil system of the combustion engine. The separated oil may also be used for lubrication of the first and second bearings 11 and 12, at least the second bearing 12.

(38) The cleaned gas may be discharged via the gas outlet 20 to an outlet conduit 28. The outlet conduit 28 may advantageously recirculate the cleaned gas, for instance to the inlet side of the combustion engine.

(39) It is to be noted that the outlet direction D may have another extension than shown in FIGS. 1-5. FIGS. 6-8 disclose further embodiments, which differs from the first embodiment only with respect to the outlet direction D of the gas outlet 20.

(40) FIG. 6 illustrates a second embodiment, in which the upstream point 21 forms a convex, or sharp convex, corner between the inner side of the side wall 3 and the upstream wall 24 forming an outer upstream wall. It should be noted that the corner may be rounded. The upstream outlet wall 24, which is parallel, or coincides, with the outlet direction D, is parallel with the transversal line T.

(41) In the second 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.

(42) FIG. 7 illustrates a third embodiment, in which the upstream point 21 is located at the end of a transition region between the inner side of the side wall 3 and the upstream outlet wall 24. The upstream outlet wall 24, which is parallel, or coincides, with the outlet direction D, is parallel with the transversal line T but located outside a tangential plane. The transition region may coincide with a radial line as shown in FIG. 7, configured as a line inclined with respect to a radial line, or as a smooth transition from the inner side of the side wall 3 to the upstream outlet wall 24 and the upstream point 21.

(43) In the third 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 is shorter than the radius R.

(44) FIG. 8 illustrates a fourth embodiment, in which the upstream outlet wall 24 is parallel, or coincides, with the outlet direction D and the transversal line T. In the fourth embodiment the side wall 3 deviates from a cylindrical shape along a segment upstream the outlet opening 21.

(45) 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 FIG. 8 shorter than the radius R, which is approximately 0.9R.

(46) The present invention is not limited to the embodiments disclosed, but may be varied and modified within the scope of the following claims.