Centrifugal separator having oil coating on sidewalls

Abstract

A centrifugal separator for cleaning crankcase gas, containing oil, from an internal combustion engine, includes a stationary casing defining a separation space and including a first end portion, an opposite second end portion and an inner wall surface facing the separation space. The separator also includes an inlet channel for the gas to be cleaned, a gas outlet channel for the cleaned gas and an oil outlet for the separated the oil. A centrifuge rotor is provided in the separation space and includes a spindle and a plurality of separation discs carried by the spindle. The centrifuge rotor is rotated to create a rotating gas volume. An oil supply device supplies such a quantity of oil to the separation space that a flowing oil film is created on the inner wall surface during operation of the centrifugal separator.

Claims

1. A centrifugal separator for cleaning crankcase gas, containing oil, from an internal combustion engine, said centrifugal separator comprising: a stationary casing defining a separation space and comprising a first end portion and an opposite second end portion, wherein the stationary casing has an inner wall surface facing the separation space; an inlet channel, extending to the separation space and forming an inlet for the gas to be cleaned; a centrifuge rotor, said centrifuge rotor being provided in the separation space and extending from the first end portion to the second end portion, wherein the centrifuge rotor comprises a spindle and a plurality of separation discs carried by the spindle; a drive member provided to rotate the centrifuge rotor in a direction of rotation about an axis of rotation to create a rotating gas volume, whereby oil is separated from the gas by centrifugal forces; a gas outlet channel for discharging the cleaned gas from the separation space; an oil outlet for discharging the oil from the separation space; and an oil supply device, the oil supply device having an inlet nozzle, wherein the inlet nozzle is provided in the stationary casing and is connected to an external pipe for feeding oil to the inlet nozzle.

2. The centrifugal separator according to claim 1, wherein the drive member comprises an electrical motor connected to the spindle.

3. The centrifugal separator according to claim 1, wherein the drive member is configured to rotate the centrifuge rotor with a rotary speed of 6000 to 12000 rpm.

4. The centrifugal separator according to claim 1, wherein the centrifugal separator is configured in such a way that the second end portion is turned upwardly.

5. The centrifugal separator according to claim 1, wherein the oil supply device is adapted to be connectable to the internal combustion engine for supply of pressurized lubricating oil from the internal combustion engine.

6. The centrifugal separator according to claim 1, wherein the drive member is configured to rotate the centrifuge rotor at a first rotational speed, wherein the inlet nozzle has an aperture diameter to permit a sufficient quantity of oil to be supplied with respect to a pressure difference between the crankcase and the separation space and the rotary speed of the centrifuge rotor, wherein the aperture diameter permits the sufficient quantity of oil to be supplied at the first rotational speed of the centrifuge rotor.

7. The centrifugal separator according to claim 1, further comprising a pump in the external pipe.

8. The centrifugal separator according to claim 1, wherein the oil supply device is provided to supply the oil to the rotating gas volume to rotate the oil and bring the rotating oil to the inner wall surface.

9. The centrifugal separator according to claim 1, wherein the gas outlet channel is provided at the first end portion and the inlet nozzle is provided at the opposite second end portion.

10. The centrifugal separator according to claim 1, wherein the inlet nozzle has an aperture diameter, and wherein the aperture diameter is in the range of 3 to 5 mm.

11. The centrifugal separator according to a claim 1, wherein the inlet nozzle has an aperture diameter, wherein the aperture diameter is in the range of 3.5 to 4.5 mm.

12. The centrifugal separator according to claim 10, wherein the drive member comprises a turbine wheel, provided on the spindle in the collecting space, and a turbine nozzle is provided in the collecting space to eject an oil jet against the turbine wheel, thereby rotating the centrifuge rotor.

13. A centrifugal separator for cleaning crankcase gas, containing oil, from an internal combustion engine, said centrifugal separator comprising: a stationary casing defining a separation space and comprising a first end portion and an opposite second end portion, wherein the stationary casing has an inner wall surface facing the separation space; an inlet channel, extending to the separation space and forming an inlet for the gas to be cleaned; a centrifuge rotor, said centrifuge rotor being provided in the separation space and extending from the first end portion to the second end portion, wherein the centrifuge rotor comprises a spindle and a plurality of separation discs carried by the spindle; a drive member provided to rotate the centrifuge rotor in a direction of rotation about an axis of rotation to create a rotating gas volume, whereby oil is separated from the gas by means of centrifugal forces; a gas outlet channel for discharging the cleaned gas from the separation space; an oil outlet for discharging the oil from the separation space; an oil supply device; and means for forming a flowing oil film on the inner surface of the stationary casing during operation of the centrifugal separator, wherein the means for forming a flowing oil film is an inlet nozzle provided in the stationary casing and connected to an external pipe for feeding oil to the inlet nozzle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present 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 sectional view of a centrifugal separator according to a first embodiment of the invention.

(3) FIG. 2 discloses a sectional view of a part of a centrifugal separator according to a second embodiment of the invention.

(4) FIG. 3 discloses a sectional view of a centrifugal separator according to a third embodiment of the invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

(5) FIG. 1 discloses a first embodiment of a centrifugal separator for cleaning a gas containing oil, such a crankcase gases from an internal combustion engine (not disclosed). FIG. 1 also discloses a pressure control valve 1 designed to keep the pressure within a safe range in the crankcase of the internal combustion engine.

(6) The centrifugal separator comprises a stationary casing 2 defining a separation space 3 within the stationary casing 2. The stationary casing 2 is stationary in relation to the internal combustion engine 1. The stationary casing 2 comprises a first end portion 2a, an opposite second end portion 2b, and an intermediate portion 2c provided between and adjoining the first end portion 2a and the second end portion 2b. In the embodiments disclosed, the first end portion 2a forms a lower portion during operation of the centrifugal separator, whereas the second end portion 2b forms an upper portion.

(7) The stationary casing 2 has an inner wall surface 4 facing the separation space 3. A main part of the inner wall surface 4, which in particular in this case is considered, is the intermediate portion 2c extending around the separation space 3 between the first end portion 2a and the second end portion 2b.

(8) The centrifugal separator also comprises an inlet channel 5, a gas outlet channel 6 and an oil outlet 7. The inlet channel 5 extends to the separation space 3 and forming an inlet for the crankcase gas to be cleaned. In the embodiments disclosed, the inlet channel 5 is provided at and extends through the second end portion 2b. The gas outlet channel 6 is provided for discharging the cleaned gas from the separation space 3. In the embodiments disclosed, the gas outlet channel 6 is provided at and extends through the first end portion 2a via the pressure control valve 1. The oil outlet 7 is provided for discharging the separated oil from the separation space 3. In the embodiments disclosed, the oil outlet 7 is provided at and extends through the first end portion 2a.

(9) Moreover the centrifugal separator comprises a centrifuge rotor 9 and a drive member provided to rotate the centrifuge rotor 9 in a direction of rotation about an axis x of rotation to create a rotating gas volume. The oil is thus separated from the crankcase gases by means of centrifugal forces. The centrifuge rotor 9 is provided in the separation space 3 and extends from the first end portion 2a to the second end portion 2b. The centrifuge rotor comprises a spindle 11 and a plurality of separation discs 12a-12c carried by provided on the spindle 11.

(10) The plurality of separation discs 12a-12c comprises or consists of a first separation disc 12a in the proximity of the first end portion 2a and in the proximity of a first end 11a of the spindle 11, a second separation disc 12b in the proximity of the second end portion 2b and in the proximity of a second end 11b of the spindle 11, and a plurality of intermediate separation discs 12c provided between the first separation disc 12a and the second separation disc 12b.

(11) The spindle 11 is supported by a bearing 13 at the second end 11b, and by an additional bearing 14 at the first end 11a.

(12) The separation discs 12a-12c extend outwardly from the spindle 11. In the embodiments disclosed, each of the separation discs 12a-12c has a frusto-conical shape. The separation discs 12a-12c are turned so that the frusto-conical shape of the separations discs 12a-12c points towards the first end portion 2a.

(13) The centrifugal separator according to the first embodiment comprises a collecting space 15 containing oil and receiving the first end 11a of the spindle 11. The collecting space 15 is provided at the second end 11b of the spindle and below the gas outlet channel 6. A partition wall 16 is delimiting the collecting space 15 from the separation space 3. The additional bearing 14 is provided in connection with the collecting space 15, and is thus lubricated by the oil being drained from the separation space into the collecting space.

(14) An inner channel 17 extends inside and along the spindle 11 from an opening at the first end 11a to the second end 11b and through an inlet nozzle 18 provided at a second end 11b of the spindle 11 and at the second end portion 2b.

(15) The centrifugal separator also comprises an oil supply device configured to supply a quantity of oil to the separation space 3 in such a manner that a flowing oil film is created on the inner wall surface 4 during operation of the centrifugal separator. In the first embodiment, the oil supply device comprises inner channel 17 and the inlet nozzle 18, which permit transport oil from the collecting space 15 through the inner channel 17 and through the inlet nozzle 18.

(16) The inlet nozzle 18 has an aperture diameter d, which is in the range of 3 to 5 mm, preferably in the range of 3.5 to 4.5 mm, for instance 4 mm. The inner channel 17 has a diameter D that is greater than the aperture diameter d. The inlet nozzle 18 will thus operate as a throttling member for the oil flowing through the inlet channel 17. The diameter D of the inner channel 17 may be in the range of 5 to 7 mm.

(17) As can be seen in FIGS. 1 and 2, the inlet nozzle 18 is provided at second end 11b of the spindle 11 at a small distance from an end surface of the second end 11b.

(18) Furthermore, as can be seen in FIGS. 1 and 2, the inlet nozzle 18 is provided inside the bearing 13, which is attached to the spindle 11 at the second end 11b. A cover member 19 is provided outside the second end 11b enclosing a space outside the inner channel 17 and the inlet nozzle 18.

(19) In the embodiments disclosed, the cover member 19 is also provided to support the bearing 13 in the stationary casing 2.

(20) In the first embodiment, the drive member comprises a turbine wheel 22 and a turbine nozzle 23. The turbine wheel 22 is attached to the spindle 11 at the first end 11a and provided in the collecting space 15, above the level 24 of the oil contained in the collecting space 15. The turbine nozzle 23 is provided in the collecting space 15 to eject an oil jet against the turbine wheel 22 thereby rotating the centrifuge rotor 9.

(21) During operation of the centrifugal separator of the first embodiment, oil is feed to the turbine nozzle 23 towards the turbine wheel 22 to rotate the spindle 11 and the centrifuge rotor 9 in the stationary casing at a rotary speed of for instance 6000 to 12000 rpm, such as 6000 to 10000 rpm. When the oil jet hits the turbinean oil mist is generated inside the collecting space 15. Oil will be collected in the collecting space 15 up to the level 24. Oil mist contained in the collecting space 15 above the level 24 will continuously during the operation be sucked into the inner channel 17 of the spindle 11, and conveyed to and through the inlet nozzle 18. From the inlet nozzle 18 the oil is guided by means of the cover member 19 and conveyed through the bearing 13 and to the separation space 3. The oil will then be supplied to the second separation disc 12b, and possible to one or more of the adjacent intermediate discs 12c. The oil is thus introduced to the rotating gas volume, and by means of centrifugal forces brought outwardly to the inner wall surface 4. Thanks to the rotating gas volume the rotating movement of the oil will continue on the inner wall surface 4 so that a flowing oil film is created on the inner wall surface 4. In the embodiments disclosed, the oil film will also move downwards due to the gas flow towards the gas outlet channel 6, and due to the gravity forces acting on the oil when the centrifugal separator is oriented as shown in FIGS. 1 to 3, with the axis x of rotation directed vertically.

(22) The applicant has performed experiments to verify the functioning of the invention. These experiments show that with a rotary speed of 6000 to 12000 rpm and an aperture diameter of 3 to 5 mm, the quantity of the oil supplied to the separation space 4 may create a flowing oil film on the inner wall surface 4, and at the same time secure an efficient cleaning of the crankcase gas, i.e. with no or insignificant amounts of oil in the cleaned gas.

(23) The experiments were performed with the centrifugal separator in a laboratory, but the centrifugal separator was adapted for use together with an internal combustion engine of the kind used for standard trucks. A standard truck or heavy road vehicle will typically be equipped with a diesel engine having a size in the range of 5 to 16 liters.

(24) In the first embodiment, the inlet nozzle 18 is formed by a nozzle member which is inserted in the inner channel 17 at the second end 11b of the spindle 11. Such a nozzle member may be replaceable.

(25) FIG. 2 refers to a second embodiment, that differs from the first embodiment only in that the inlet nozzle 18 is formed as an integrated portion of the spindle 11. Such an inlet nozzle 18 may be formed through machining of the spindle 11.

(26) FIG. 3 illustrates a third embodiment which differs from the first and second embodiments in that the inlet nozzle 18 is provided in the stationary casing 2 and connected to an external pipe 25 for feeding oil to the inlet nozzle 18, e.g. by means of a pump 26. The pump 26 may be arranged and adapted exclusively for pumping oil to the inlet nozzle 18, or it may also be the lubricating oil pump of the combustion engine. The inlet nozzle 18 is also in the third embodiment provided at the second end portion 2b so that the oil film my flow along the whole, or a main part of the, inner wall surface 4.

(27) In the third embodiment, the aperture diameter of the inlet nozzle 18 is 0.3 to 1.5 mm, preferably, 0.4 to 1.0 mm, for instance 0.5 mm. The oil may then be supplied to the inlet nozzle 18 at a pressure of 3-6 bars.

(28) Furthermore, in the third embodiment, the drive member is replaced by and comprises a separate motor, e.g. an electrical motor 27, connected to the spindle 11 for rotating the spindle 11 and the centrifuge rotor 9. The separate motor may alternatively comprise a separate pneumatic motor or a separate hydraulic motor. The spindle 11 and the centrifuge rotor 9 may also be driven by means of the crankshaft of the internal combustion engine.

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