Method and system for reducing the oil saturation of a coalescing filter element of an air-oil droplet separator of a crankcase ventilation system of an internal combustion engine

Abstract

A method for reducing the oil saturation of a coalescing filter element (28) of an air-oil droplet separator (20, 114) of a crankcase ventilation system (100) of an internal combustion engine (102) generating blow-by gas (22, 104) in a crankcase (24, 106), wherein the coalescing filter element (28) removes oil from the blow-by gas (22, 104) by coalescence, the method comprising reducing the oil saturation of the coalescing filter element (28) by applying centrifugal force through discontinuous rotation of the droplet separator (20, 114), the droplet separator (20, 114) having two operating modes comprising a first, stationary mode and a second, rotating mode, and wherein the discontinuous rotation is applied based on a given state, the given state being a given state of the droplet separator (20, 114) and / or a turbocharger (144) connected to the internal combustion engine (102).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority from U.S. Provisional Application No. 61 / 298,630, filed January 27, 2010, U.S. Provisional Application No. 61 / 298,635, filed January 27, 2010, U.S. Provisional Application No. 61 / 359,192, filed June 28, 2010, U.S. Provisional Application No. 61 / 383,787, filed September 17, 2010, U.S. Provisional Application No. 61 / 383,790, filed September 17, 2010, and U.S. Provisional Application No. 61 / 383,793, filed September 17, 2010, all of which are incorporated herein by reference. GENERAL STATE OF THE ART AND SUMMARY

[0002] The invention relates to a method and system for reducing the oil saturation of a coalescing filter element of an air-oil droplet separator of a crankcase ventilation system of an internal combustion engine.

[0003] Crankcase ventilation separators for internal combustion engines are well known in the art. One type of separator uses inertial impact air-oil separation to separate oil particles from the crankcase blowby gas or aerosol. This is achieved by accelerating the blowby gas flow to high velocities through nozzles or orifices and directing it toward an impingement body, causing a sharp change in direction that results in oil separation. Another type of separator uses coalescence in a coalescing filter to remove oil droplets.

[0004] US 6152120 A discloses a separator that captures crankcase gases, including blowby gas and oil mist. A rotating filter in the separator directs the gas components to an outlet, from which they can be recirculated into the engine's air intake. The rotation of the filter centrifugally throws the oil against a wall, from where it can be drained from the separator and recirculated into the crankcase.

[0005] DE 69002315 T2 discloses a hermetic refrigeration engine compressor consisting of an electric motor compartment and a crankcase compartment, with an oil separator installed in the crankcase to prevent oil splashes from entering the system.

[0004] The present invention arose during continued development efforts on the latter air-oil separation technology, namely the removal of oil from the crankcase blowby gas stream by coalescence using a coalescing filter. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of a coalescing filter assembly. Fig. Figure 2 is a sectional view of another coalescing filter assembly. Fig. 3 is like Fig. 2 and shows another embodiment. Fig. Figure 4 is a sectional view of another coalescing filter assembly. Fig. Figure 5 is a schematic view showing the operation of the assembly of Fig. 4 illustrated. Fig. Figure 6 is a schematic system diagram illustrating an engine intake system. Fig. Figure 7 is a schematic diagram showing a control option for the installation of Fig. 6 illustrated. Fig. Figure 8 is a flowchart showing an operation control for the plant of Fig. 6 illustrated. Fig. 9 is like Fig. 8 and shows another embodiment. Fig. Figure 10 is a schematic cross-sectional view of a coalescing filter assembly. Fig. 11 is an enlarged view of a section of Fig. 10. Fig. Figure 12 is a schematic cross-sectional view of a coalescing filter assembly. Fig. Figure 13 is a schematic cross-sectional view of a coalescing filter assembly. Fig. Figure 14 is a schematic cross-sectional view of a coalescing filter assembly. Fig. Figure 15 is a schematic cross-sectional view of a coalescing filter assembly. Fig. Figure 16 is a schematic cross-sectional view of a coalescing filter assembly. Fig. Figure 17 is a schematic view of a coalescing filter assembly. Fig. Figure 18 is a schematic cross-sectional view of a coalescing filter assembly. Fig. Figure 19 is a schematic diagram illustrating a control system. Fig. Figure 20 is a schematic diagram illustrating a control system. Fig. Figure 21 is a schematic diagram illustrating a control system. DETAILED DESCRIPTION OF THE INVENTION

[0006] This application shares a common specification with commonly owned, co-pending U.S. patent application Ser. No. 12 / 969,742, Attorney Docket No. 4191-00679, filed even date hereby and incorporated herein.

[0007] Fig. 1 shows a rotating crankcase ventilation drift eliminator 20 for internal combustion engines that separates air from oil in blowby gas 22 from an engine crankcase 24. A coalescing filter assembly 26 includes an annular rotating coalescing filter element 28 having an inner periphery 30 defining a hollow interior 32 and an outer periphery 34 defining an exterior 36. An inlet port 38, as shown at arrows 40, delivers the blowby gas 22 from the crankcase 24 to the hollow interior 32. An outlet port 42, as shown at arrows 44, delivers purified separated air from the specified outer region 36. The direction of the blowby gas flow is from the inside to the outside, namely, as shown by the arrows 46, in the radial direction from the hollow interior 32 outwards to the exterior 36.The oil in the blowby gas is forced radially outward from the inner periphery 30 by centrifugal force to reduce clogging of the coalescing filter element 28, which would otherwise be caused by oil located on the inner periphery 30. This also opens more of the coalescing filter element's area to flow, thereby reducing restriction and pressure drop. The centrifugal forces drive the oil radially outward from the inner periphery 30 to the outer periphery 34 to free up a larger volume of the coalescing filter element 28 open to flow, increasing the separation capability. The separated oil drains from the outer periphery 34.A drain opening 48 communicates with the exterior 36 and, as shown by arrow 50, allows the separated oil to drain from the outer periphery 34, which oil can then be returned to the engine crankcase from a drain 54 as shown by arrow 52.

[0008] Centrifugal force pumps the blowby gas from the crankcase to the hollow interior 32. The pumping of the blowby gas from the crankcase to the hollow interior 32 increases with increasing rotational speed of the coalescing filter element 28. The increased pumping of the blowby gas 22 from the crankcase 24 to the hollow interior 32 reduces restriction across the coalescing filter element 28. In one embodiment, a set of vanes may be provided within the hollow interior 32, as shown in dashed line at 56, which enhances the stated pumping. The stated centrifugal force creates a region of reduced pressure within the hollow interior 32, which region of reduced pressure draws the blowby gas 22 from the crankcase 24.

[0009] In one embodiment, the coalescing filter element 28 is driven to rotate by a mechanical coupling to a component of the motor, e.g., an axially extending shaft 58 connected to a pinion or drive pulley of the motor. In another embodiment, the coalescing filter element 28 is driven to rotate by a fluid motor, e.g., a Pelton or turbine drive gear 60. Fig. 2, driven by pumped, pressurized oil from the engine oil pump 62 and returning it to the engine crankcase sump 64. Fig. 2 uses the same reference numbers from Fig. 1 where appropriate to facilitate understanding. The separated purified air is fed through a pressure-responsive valve 66 to an outlet 68, which is an alternative outlet to the one at 42 in Fig. 1. In another embodiment, the coalescing filter element 28 is driven to rotate by an electric motor 70, Fig. 3, which has a drive output rotary shaft 72 coupled to a shaft 58. In another embodiment, the coalescing filter element 28 is driven to rotate by a magnetic coupling to a component of the motor, Fig. 4, Fig. 5. A motor-driven rotating pinion 74 has a plurality of magnets, such as 76, spaced around the circumference thereof and magnetically coupled to a plurality of magnets 78 spaced around the inner circumference 30 of the coalescing filter element such that when the pinion or drive gear 74 rotates, the magnets 76 move past, Fig. 5, and magnetically coupled to the magnets 78 to in turn rotate the coalescing filter element as a driven element. In Fig. 4, the separated purified air flows from the outer region 36 through a duct 80 to an outlet 82, which is an alternative purified air outlet to that shown at 42 in Fig. 1. The arrangement in Fig. 5 provides an upshift action to rotate the coalescing filter assembly at a greater rotational speed (higher angular velocity) than the drive pinion or gear 74, e.g., when it is desired to provide a higher rotational speed of the coalescing filter element.

[0010] The pressure drop across the coalescing filter element 28 decreases with increasing rotational speed of the coalescing filter element. The oil saturation of the coalescing filter element 28 decreases with increasing rotational speed of the coalescing filter element. The oil drainage from the outer periphery 34 and the amount of draining oil increase with increasing rotational speed of the coalescing filter element 28. The oil particle settling velocity in the coalescing filter element 28 acts in the same direction as the direction of airflow through the coalescing filter element. This specified same direction improves the capture and coalescence of oil particles by the coalescing filter element.The present system provides a method for separating air from oil in crankcase ventilation blowby gas of internal combustion engines by introducing gravity into the coalescing filter element 28 to cause enhanced gravity settling within the coalescing filter element to enhance particle capture and coalescence of submicron oil particles by the coalescing filter element. The method includes providing an annular coalescing filter element 28, rotating the coalescing filter element, and providing inside-out flow through the rotating coalescing filter element.

[0011] The system provides a method for reducing crankcase pressure in an internal combustion engine crankcase that generates blowby gas. The method includes providing a crankcase ventilation system that includes a coalescing filter element 28 that separates air from oil in the blowby gas, providing the coalescing filter element as an annular element with a hollow interior 32, supplying the blowby gas to the hollow interior 32, and rotating the coalescing filter element to pump the blowby gas out of the crankcase 24 and into the hollow interior 32 due to centrifugal force forcing the blowby gas to flow radially outward through the coalescing filter element 28 as shown at arrows 46, the pumping causing a reduced pressure in the crankcase 24.

[0012] One type of crankcase ventilation system for internal combustion engines provides an open crankcase ventilation (OCV), where the purified air separated from the blowby gas is released into the atmosphere. Another type of crankcase ventilation system for internal combustion engines includes a closed crankcase ventilation (CCV), where the purified air separated from the blowby gas is returned to the engine, e.g., to the combustion air intake system to be mixed with the incoming combustion air supplied to the engine.

[0013] Fig. 6 shows a closed crankcase ventilation (CCV) system 100 for an internal combustion engine 102 that generates blowby gas 104 in a crankcase 106. The system includes an air intake line 108 that supplies combustion air to the engine, and a return line 110 that has a first segment 112 that supplies the blowby gas from the crankcase to an air-oil eliminator 114 to clean the blowby gas by coalescing oil therefrom and discharging cleaned air at an output 116 that is the outlet 42 of Fig. 1, Fig. 68 of Fig. 2, Fig. 82 of Fig. 4. The return line 110 includes a second segment 118 that delivers the cleaned air from the drift eliminator 114 to the air intake line 108 to combine with the combustion air supplied to the engine. The drift eliminator 114 is variably controlled according to a given condition of the engine, which will be described later.

[0014] The mist eliminator 114 has a variable efficiency that can be variably controlled according to a given condition of the engine. In one embodiment, the mist eliminator 114, as above, is a rotating mist eliminator, and the speed of the mist eliminator is varied according to the given condition of the engine. In one embodiment, the given condition is the engine speed. In one embodiment, the mist eliminator is driven to rotate by an electric motor, e.g., 70. Fig. 3. In one embodiment, the electric motor is a variable-speed electric motor for varying the speed of the droplet eliminator. In another embodiment, the droplet eliminator is hydraulically driven to rotate, e.g. Fig. 2. In this embodiment, the speed of the droplet separator is changed hydraulically. In this embodiment, the engine oil pump 62, Fig. 2, Fig. 7, pressurized oil through a plurality of parallel isolation valves such as 120, 122, 124, which are controlled by the engine's electronic control module (ECM) 126 between closed and open or partially open states, for flow through respective parallel orifices or nozzles 128, 130, 132 to controllably increase or decrease the amount of pressurized oil supplied against the Pelton or turbine wheel 60, in turn controllably varying the speed of the shaft 58 and the coalescing filter element 28.

[0015] In one embodiment, a turbocharger system 140, Fig. 6, provided for the internal combustion engine 102, which generates blowby gas 104 in the crankcase 106. The system includes the indicated air intake conduit 108, which has a first segment 142 that supplies combustion air to a turbocharger 144, and a second segment 146 that supplies the turbocharged combustion air from the turbocharger 144 to the engine 102. The return conduit 110 has the indicated first segment 112 that supplies the blowby gas 104 from the crankcase 106 to the air-oil eliminator 114 to clean the blowby gas by coalescing oil therefrom and exhausting cleaned air at 116. The return line has the indicated second segment 118 which supplies the cleaned air from the drift eliminator 114 to the first segment 142 of the air intake line 108 to combine with the combustion air supplied to the turbocharger 144.The drift eliminator 114 is variably controlled according to a given condition of at least one of the turbocharger 144 and the engine 102. In one embodiment, the given condition is a condition of the turbocharger. In another embodiment, the drift eliminator is, as above, a rotating drift eliminator, and the speed of the drift eliminator is varied according to the turbocharger efficiency. In another embodiment, the speed of the drift eliminator is varied according to the turbocharger boost pressure. In another embodiment, the speed of the drift eliminator is varied according to the turbocharger boost ratio, which is the ratio of the pressure at the turbocharger outlet versus the pressure at the turbocharger inlet. In another embodiment, the drift eliminator is driven to rotate by an electric motor, e.g., 70. Fig. 3. In another embodiment, the electric motor is a variable-speed electric motor for varying the speed of the droplet separator. In another embodiment, the droplet separator is hydraulically driven to rotate. Fig. 2. In a further embodiment, the speed of the droplet separator is changed hydraulically, Fig. 7.

[0016] The system provides a method for improving turbocharger efficiency in a turbocharger system 140 for an internal combustion engine 102 that generates blowby gas 104 in a crankcase 106, the system having an air intake line 108 having a first segment 142 that supplies combustion air to a turbocharger 144 and a second segment 146 that supplies the turbocharged combustion air from the turbocharger 144 to the engine 102, and having a return line 110 having a first segment 112 that supplies the blowby gas 104 to the air-oil mist eliminator 114 to clean the blowby gas by coalescing oil therefrom and discharging cleaned air at 116, the return line having a second segment 118 that supplies the cleaned Air from the droplet eliminator 114 is supplied to the first segment 142 of the air intake line to combine with the combustion air supplied to the turbocharger 144.The method includes variably controlling the drift eliminator 114 according to a given condition of at least one of the turbocharger 144 and the engine 102. One embodiment variably controls the drift eliminator 114 according to a given condition of the turbocharger 144. Another embodiment provides the drift eliminator, as above, as a rotating drift eliminator and varies the speed of the drift eliminator according to the turbocharger efficiency. Another method varies the speed of the drift eliminator 114 according to the turbocharger boost pressure. Another embodiment varies the speed of the drift eliminator 114 according to the turbocharger boost ratio, which is the ratio of the pressure at the turbocharger outlet versus the pressure at the turbocharger inlet.

[0017] Fig. Figure 8 shows a control scheme for a CCV implementation. At step 160, the turbocharger efficiency is monitored, and if the turbocharger efficiency is acceptable, as determined at step 162, then the rotor speed of the coalescing filter element is reduced at step 164. If the turbocharger efficiency is not acceptable, then the engine duty cycle is checked at step 166, and if the engine duty cycle is severe, then the rotor speed is increased at step 168, and if the engine duty cycle is not severe, then no action is taken, as shown at step 170.

[0018] Fig. Figure 9 shows a control scheme for OCV implementation. At step 172, the crankcase pressure is monitored, and if it is normal, as determined at step 174, the rotor speed is reduced at step 176. If it is not normal, the ambient temperature is checked at step 178, and if it is less than 0°C, the rotor speed is increased to a maximum at step 180 to increase warm gas pumping and increase oil and water sling. If the ambient temperature is not less than 0°C, the engine idle is checked at step 182, and if the engine is idling, the rotor speed is increased and maintained at step 184. If the engine is not idling, the rotor speed is increased to a maximum at step 186 for five minutes.

[0019] The flow path through the coalescing filter assembly runs from upstream to downstream, e.g., in Fig. 1 from the inlet opening 38 to the outlet opening 42, e.g. in Fig. 2 from the inlet opening 38 to the outlet opening 68, e.g. in Fig. 10 from the inlet opening 190 to the outlet opening 192. It is further Fig. 10, a rotating disc separator 194 is provided in combination, which is arranged in the flow path and separates air from oil in the blowby gas. Disc separators are known in the art. The direction of the blowby gas flow through the rotating disc separator is from the inside to the outside, as shown by arrows 196. Fig. 10 to Fig. 12. The rotating disc separator 194 is located upstream of a rotating coalescing filter element 198. The rotating disc separator 194 is located in a hollow interior 200 of the rotating coalescing filter element 198. In Fig. 12, an annular shroud 202 is provided within the hollow interior 200 and is radially disposed between the rotating disc separator 194 and the rotating coalescing filter element 198 such that the shroud 202 is downstream of the rotating disc separator 194 and upstream of the rotating coalescing filter element 198, and such that the shroud 202 provides a collection and drainage surface 204 along which the separated oil drains after separation by the rotating disc separator, the oil draining through a drain hole 208 as shown by droplet 206, the oil thereafter combining with the oil separated by the drift eliminator 198 as shown at 210 and draining through a main drain 212.

[0020] Fig. Figure 13 shows another embodiment and uses similar reference numerals as above where appropriate to facilitate understanding. A rotating disc separator 214 is located downstream of the rotating coalescing filter element 198. The direction of flow through the rotating disc separator 214 is from inside to outside. The rotating disc separator 214 is radially outwardly disposed from and encloses the rotating coalescing filter element 198.

[0021] Fig. 14 shows another embodiment and uses similar reference numerals as above where appropriate to facilitate understanding. A rotating disc separator 216 is located downstream of the rotating coalescing filter element 198. The direction of flow through the rotating disc separator 216 is from outside to inside, as shown by arrows 218. The rotating coalescing filter element 198 and the rotating disc separator 216 rotate about a common axis 220 and are axially adjacent to each other. The blowby gas flows radially outward through the rotating coalescing filter element 198, as shown by arrows 222, then axially, as shown by arrows 224, to the rotating disc separator 216, then radially inward, as shown by arrows 218, through the rotating disc separator 216.

[0022] Fig. 15 shows another embodiment and uses similar reference numerals as above where appropriate to facilitate understanding. A second annular rotating coalescing filter element 230 is provided in the indicated flow path from the inlet 190 to the outlet 192 and separates air from the oil in the blowby gas. The direction of flow through the second rotating coalescing filter element 230 is from outside to in, as shown by arrow 232. The second rotating coalescing filter element 230 is located downstream of the first rotating coalescing filter element 198. The first and second rotating coalescing filter elements 198 and 230 rotate about a common axis 234 and are axially adjacent to each other.The blowby gas flows radially outward, as shown by arrow 222, through the first rotating coalescing filter element 198, then axially, as shown by arrow 236, to the second rotating coalescing filter element 230, then radially inward, as shown by arrow 232, through the second rotating coalescing filter element 230.

[0023] In various embodiments, the rotating disc separator can be provided with multiple drain holes, e.g., 238. Fig. 13, be perforated, which allows separated oil to drain through them.

[0024] Fig. 16 shows another embodiment and uses similar reference numerals as above where appropriate to facilitate understanding. An annular shroud 240 is provided along the exterior 242 of the rotating coalescing filter element 198 and radially outward and downstream thereof such that the shroud 240 provides a collection and drainage surface 244 along which the separated oil, as shown by droplets 246, drains after coalescence by the rotating coalescing filter element 198. The shroud 240 is a rotating shroud and may be part of the filter frame or end cap 248. The shroud 240 encloses the rotating coalescing filter element 198 and rotates about a common axis 250 therewith. The shroud 240 is conical and tapers along a conical taper relative to the specified axis.The shroud 240 has an inner surface at 244 that radially opposes and is spaced from the rotating coalescing filter element 198 by a radial gap 252 that increases as the shroud extends axially downward and along the indicated conical taper. The inner surface 244 may include ribs, such as 254. Fig. 17, spaced circumferentially therearound and extending axially and along the indicated conical taper and opposing the rotating coalescing filter element 198 and providing grooved drainage paths, such as 256, therealong, which direct and drain the separated oil flow therealong. The inner surface 244 extends axially downwardly along the indicated conical taper from a first, upper, axial end 258 to a second, lower, axial end 260. The second axial end 260 is radially spaced from the rotating coalescing filter element 198 by a radial gap that is greater than the radial distance of the first axial end 258 from the rotating coalescing filter element 198. In another embodiment, the second axial end 260 has a corrugated lower edge 262 that also concentrates and directs oil drainage.

[0025] Fig. Figure 18 shows another embodiment and uses similar reference numerals as above where appropriate to facilitate understanding. Instead of the lower inlet 190, Fig. 13 to Fig. 15, an upper inlet port 270 is provided, and a pair of possible or alternative outlet ports are shown at 272 and 274. Oil drainage through the drain 212 may be provided through a one-way check valve, such as 276, to a drain hose 278 for return to the engine crankcase, as above.

[0026] As noted above, the drift eliminator may be variably controlled according to a given condition, which may be a given condition of at least one of the engine, turbocharger, and drift eliminator components. In one embodiment, the specified given condition is a given condition of the engine, as noted above. In another embodiment, the given condition is a given condition of the turbocharger, as noted above. In another embodiment, the given condition is a given condition of the drift eliminator. In one version of this embodiment, the specified given condition is the pressure drop across the drift eliminator.In one version of this embodiment, the mist eliminator is a rotating mist eliminator, as above, and is driven at a higher speed when the pressure drop across the mist eliminator is above a predetermined threshold to prevent accumulation of oil on the mist eliminator, e.g., along the inner circumference thereof in the specified hollow interior, and to lower the specified pressure drop. Fig. Figure 19 shows a control scheme where the pressure drop, dP, across the rotating drift eliminator is sensed at step 290 and monitored by the ECM (Engine Control Module). It is then determined at step 292 whether dP is above a certain value at a low engine speed. If not, then the drift eliminator speed is held constant at step 294. If dP is above a certain value, then the drift eliminator is rotated at a higher speed at step 296 until dP drops to a certain point. The specified given condition is the pressure drop across the drift eliminator, and the specified predetermined threshold is a predetermined pressure drop threshold.

[0027] In another embodiment, the drift eliminator is a discontinuously rotating drift eliminator having two operating modes, being in a first, stationary, mode when a given condition is below a predetermined threshold, and in a second, rotating, mode when the given condition is above the predetermined threshold, with hysteresis if desired. The first, stationary, mode ensures energy efficiency and reduces parasitic energy loss. The second, rotating, mode ensures improved separation efficiency, removing oil from the air in the blowby gas. In one embodiment, the given condition is the engine speed, and the predetermined threshold is a predetermined engine speed threshold.In another embodiment, the given condition is the pressure drop across the drift eliminator, and the predetermined threshold is a predetermined pressure drop threshold. In another embodiment, the given condition is the turbocharger efficiency, and the predetermined threshold is a predetermined turbocharger efficiency threshold. In a further version, the given condition is the turbocharger boost pressure, and the predetermined threshold is a predetermined turbocharger boost pressure threshold. In a further version, the given condition is the turbocharger charge ratio, and the predetermined threshold is a predetermined turbocharger charge ratio threshold, where, as stated above, the turbocharger charge ratio is the ratio of the pressure at the turbocharger outlet versus the pressure at the turbocharger inlet. Fig. 20 shows a control scheme for an electric version, wherein at step 298 the engine speed or drift eliminator pressure drop is sensed and monitored by the ECM at step 300, and thereafter at step 302, if the speed or pressure is above a threshold, then at step 304 rotation of the drift eliminator is initiated, and if the speed or pressure is not above the threshold, then at step 306 the drift eliminator is left in the stationary mode. Fig. Figure 21 shows a mechanical version and uses similar reference numerals as above where appropriate to facilitate understanding. A check valve, spring, or other mechanical component senses the speed or pressure at step 308, and the decision process is performed as above at steps 302, 304, 306.

[0028] The specified method for improving turbocharger efficiency includes variably controlling the drift eliminator according to a given condition of at least one of the turbocharger, engine, and drift eliminator components. One embodiment variably controls the drift eliminator according to a given condition of the turbocharger. In one version, the drift eliminator is provided as a rotating drift eliminator, and the method includes varying the speed of the drift eliminator according to the turbocharger efficiency, and in another embodiment, according to the turbocharger boost pressure, and in another embodiment, according to the turbocharger charge ratio, as specified above. Another embodiment variably controls the drift eliminator according to a given condition of the engine, and in another embodiment, according to the engine speed.In another version, the mist eliminator is provided as a rotating mist eliminator, and the method includes varying the speed of the mist eliminator according to the engine speed. Another embodiment variably controls the mist eliminator according to a given condition of the mist eliminator and, in another version, according to a pressure drop across the mist eliminator. In another version, the mist eliminator is provided as a rotating mist eliminator, and the method includes varying the speed of the mist eliminator according to the pressure drop across the mist eliminator. Another embodiment includes intermittently rotating the mist eliminator so that, as above, it has two modes of operation, a first, stationary, mode and a second, rotating, mode.

[0029] Some embodiments are described in the following clauses: 1. A closed crankcase ventilation system for an internal combustion engine which generates blowby gas in a crankcase, comprising an air intake line which supplies combustion air to the engine, a return line which has a first segment which supplies the blowby gas from the crankcase to an air-oil mist eliminator for cleaning the blowby gas by coalescing oil therefrom and discharging cleaned air, the return line having a second segment which supplies the cleaned air from the mist eliminator to the air intake line for combining with the combustion air supplied to the engine, the mist eliminator being variably controlled according to a given condition of at least one of the engine and the mist eliminator. 2. Closed crankcase ventilation system according to clause 1, where the given condition is a given condition of the engine. 3. Closed crankcase ventilation system according to clause 2, wherein the drift eliminator has a variable efficiency which is variably controlled according to the given condition of the engine. 4. A closed crankcase ventilation system as defined in clause 2, wherein the mist eliminator is a rotating mist eliminator and wherein the speed of the mist eliminator is variably controlled according to the given condition of the engine. 5. Closed crankcase ventilation system according to clause 4, where the given condition is the engine speed. 6. A closed crankcase ventilation system as defined in clause 1, wherein the mist eliminator is a rotating mist eliminator driven to rotate by an electric motor. 7. Closed crankcase ventilation system as defined in clause 6, wherein the electric motor is a variable speed electric motor for varying the speed of the drift eliminator. 8. Closed crankcase ventilation system according to clause 1, wherein the mist eliminator is a rotating mist eliminator which is hydraulically driven to rotate. 9. Closed crankcase ventilation system according to clause 8, whereby the speed of the droplet separator is varied hydraulically. 10. Closed crankcase ventilation system according to clause 1, where the given condition is a given condition of the drift eliminator. 11. Closed crankcase ventilation system according to clause 10, where the given condition is the pressure drop across the drift eliminator. 12. A closed crankcase ventilation system as defined in clause 11, wherein the mist eliminator is a rotating mist eliminator driven at a higher speed when the pressure drop across the mist eliminator is above a predetermined threshold to prevent accumulation of oil on the mist eliminator and to reduce the pressure drop. 13. A closed crankcase ventilation system according to clause 1, wherein the drift eliminator is a discontinuously rotating drift eliminator having two modes of operation, being in a first, stationary, mode when a given condition is below a predetermined threshold, and being in a second, rotating, mode when the given condition is above the predetermined threshold, the first, stationary, mode ensuring energy efficiency and reducing parasitic energy loss, the second, rotating, mode ensuring improved separation efficiency, removing oil from the air in the blowby gas. 14. A closed crankcase ventilation system according to clause 13, wherein the given condition is engine speed and the predetermined threshold is a predetermined engine speed threshold. 15. A closed crankcase ventilation system according to clause 13, wherein the given condition is the pressure drop across the drift eliminator and the predetermined threshold is a predetermined pressure drop threshold. 16. A turbocharger system for an internal combustion engine that generates blowby gas in a crankcase, comprising an air intake line having a first segment that supplies combustion air to a turbocharger and a second segment that supplies the turbocharged combustion air from the turbocharger to the engine, a return line having a first segment that supplies the blowby gas from the crankcase to an air-oil demister for cleaning the blowby gas by coalescing oil therefrom and discharging cleaned air, the return line having a second segment that supplies the cleaned air from the demister to the first segment of the air intake line to combine with the combustion air supplied to the turbocharger, the demister being variably controlled according to a given condition of at least one of the turbocharger, engine, and demister. 17. Turbocharger system according to clause 16, where the given condition is a given condition of the turbocharger. 18. A turbocharger system as defined in clause 17, wherein the mist eliminator is a rotating mist eliminator and wherein the speed of the mist eliminator is varied according to the turbocharger efficiency. 19. A turbocharger system as defined in clause 17, wherein the mist eliminator is a rotating mist eliminator and wherein the speed of the mist eliminator is varied according to the turbocharger boost pressure. 20. A turbocharger system according to clause 17, wherein the mist eliminator is a rotating mist eliminator and wherein the speed of the mist eliminator is varied according to the turbocharger charge ratio, which is the ratio of the pressure at the turbocharger outlet to the pressure at the turbocharger inlet. 21. A turbocharger system as defined in clause 16, wherein the mist eliminator is a rotating mist eliminator driven to rotate by an electric motor. 22. A turbocharger system as defined in clause 21, wherein the electric motor is a variable speed electric motor for varying the speed of the drift eliminator. 23. A turbocharger system as defined in Clause 16, wherein the mist eliminator is a rotating mist eliminator hydraulically driven to rotate. 24. Turbocharger system according to clause 23, where the speed of the droplet separator is changed hydraulically. 25. Turbocharger system as defined in clause 16, where the given condition is a given condition of the engine. 26. A turbocharger system as defined in clause 25, wherein the drift eliminator has a variable efficiency which is variably controlled according to the given condition of the engine. 27. A turbocharger system as defined in clause 25, wherein the mist eliminator is a rotating mist eliminator and wherein the speed of the mist eliminator is varied according to the given condition of the engine. 28. Turbocharger system as defined in clause 27, where the given condition is the engine speed. 29. A turbocharger system as defined in clause 16, wherein the given condition is a given condition of the droplet eliminator. 30. Turbocharger system as defined in clause 29, where the given condition is the pressure drop across the droplet separator. 31. A turbocharger system as defined in clause 30, wherein the mist eliminator is a rotating mist eliminator driven at a higher speed when the pressure drop across the mist eliminator is above a predetermined threshold to prevent accumulation of oil on the mist eliminator and to reduce the pressure drop. 32. A turbocharger system according to clause 16, wherein the mist eliminator is a discontinuously rotating mist eliminator having two operating modes, being in a first, stationary, mode when a given condition is below a predetermined threshold, and being in a second, rotating, mode when the given condition is above the predetermined threshold, the first, stationary, mode ensuring energy efficiency and reduction of parasitic energy loss, the second, rotating, mode ensuring improved separation efficiency, removing oil from the air in the blow-by gas. 33. A turbocharger system according to clause 32, wherein the given condition is engine speed and the predetermined threshold is a predetermined engine speed threshold. 34. A turbocharger system according to clause 32, wherein the given condition is the pressure drop across the mist eliminator, and the predetermined threshold is a predetermined pressure drop threshold. 35. A turbocharger system according to clause 32, wherein the given condition is the turbocharger efficiency, and the predetermined threshold is a predetermined turbocharger efficiency threshold. 36. A turbocharger system according to clause 32, wherein the given condition is the turbocharger boost pressure and the predetermined threshold is a predetermined turbocharger boost pressure threshold. 37. A turbocharger system according to clause 32, wherein the given condition is the turbocharger charge ratio, and the predetermined threshold is a predetermined turbocharger charge ratio threshold, the turbocharger charge ratio being the ratio of the pressure at the turbocharger outlet to the pressure at the turbocharger inlet. 38. A method for improving turbocharger efficiency in a turbocharger system for an internal combustion engine that generates blowby gas in a crankcase, the system having an air intake line having a first segment that supplies combustion air to a turbocharger and a second segment that supplies the turbocharged combustion air from the turbocharger to the engine, a return line having a first segment that supplies the blowby gas from the crankcase to an air-oil mist eliminator to clean the blowby gas by coalescing oil therefrom and discharging cleaned air, the return line having a second segment that supplies the cleaned air from the mist eliminator to the first segment of the air intake line to combine with the combustion air supplied to the turbocharger,wherein the method comprises variably controlling the droplet separator according to a given condition of at least one of the turbocharger, engine and droplet separator components. 39. A method according to clause 38, which comprises variably controlling the droplet eliminator in accordance with a given condition of the turbocharger. 40. A method according to clause 38, which comprises providing the mist eliminator as a rotating mist eliminator and varying the speed of the mist eliminator according to the turbocharger efficiency. 41. A method according to clause 38, which comprises providing the mist eliminator as a rotating mist eliminator and varying the speed of the mist eliminator according to the turbocharger boost pressure. 42. A method according to clause 38, which comprises providing the mist eliminator as a rotating mist eliminator and varying the speed of the mist eliminator according to the turbocharger charge ratio, which is the ratio of the pressure at the turbocharger outlet to the pressure at the turbocharger inlet. 43. A method according to clause 38, which comprises variably controlling the droplet eliminator in accordance with a given condition of the engine. 44. A method according to clause 43, which includes variably controlling the drift eliminator according to the engine speed. 45. A method according to clause 44, which comprises providing the mist eliminator as a rotating mist eliminator and varying the speed of the mist eliminator according to the engine speed. 46. ​​A method according to clause 38, which comprises variably controlling the mist eliminator in accordance with a given state of the mist eliminator. 47. A method according to clause 46, which comprises variably controlling the mist eliminator in accordance with the pressure drop across the mist eliminator. 48. A method according to clause 47, which comprises providing the mist eliminator as a rotating mist eliminator and varying the speed of rotation of the mist eliminator according to the pressure drop across the mist eliminator. 49. A method according to clause 38, comprising intermittently rotating the mist eliminator so that it has two modes of operation comprising a first, stationary, mode when the given condition is below a predetermined threshold and a second, rotating, mode when the given condition is above the predetermined threshold, the first, stationary, mode ensuring energy efficiency and reduction of parasitic energy loss, the second, rotating, mode ensuring improved separation efficiency, removing oil from the air in the blow-by gas.

Claims

[1] A method for reducing the oil saturation of a coalescing filter element (28) of an air-oil droplet separator (20, 114) of a crankcase ventilation system (100) of an internal combustion engine (102) that generates blowby gas (22, 104) in a crankcase (24, 106), wherein the coalescing filter element (28) removes oil from the blowby gas (22, 104) by coalescence, the method comprising reducing the oil saturation of the coalescing filter element (28) using centrifugal force by discontinuously rotating the droplet separator (20, 114), the droplet separator (20, 114) having two operating modes including a first, static mode and a second, rotating mode, and the discontinuous rotating being applied based on a given condition, wherein the given state is a given state of the droplet separator (20, 114) and / or a turbocharger (144) connected to the internal combustion engine (102). [2] The method of claim 1, wherein the given condition is a given condition of the droplet eliminator (20, 114). [3] The method of claim 1, wherein the given condition is a pressure drop across the droplet eliminator (20, 114). [4] The method of claim 1, wherein the oil saturation of the coalescing filter element (28) is reduced by discontinuous rotation driven by a shaft (58) driven by the internal combustion engine (102). [5] The method of claim 1, wherein the oil saturation of the coalescing filter element (28) is reduced by discontinuous rotation driven by an electric motor (70). [6] The method of claim 1, wherein the oil saturation of the coalescing filter element (28) is reduced by discontinuous rotation driven by a fluid motor. [7] The method of claim 1, wherein the oil saturation of the coalescing filter element (28) is reduced by intermittent rotation driven by pressurized engine oil. [8] The method of claim 7, wherein the pressurized engine oil drives a Pelton turbine (60). [9] The method of claim 1, wherein the oil saturation of the coalescing filter element (28) is reduced by intermittent rotation driven by oil pumped by an engine oil pump (62), the engine oil pump (62) pumping lubricating oil to components of the internal combustion engine (102). [10] The method of claim 1, wherein the given condition is a turbocharger efficiency. [11] The method of claim 1, wherein the given condition is a turbocharger boost pressure. [12] The method of claim 1, wherein the given condition is a turbocharger boost ratio, which is the ratio of the pressure at the turbocharger outlet to the pressure at the turbocharger inlet. [13] The method of claim 9, wherein the internal combustion engine (102) includes a one-way check valve (276) that returns oil to a crankcase sump (64). [14] A system for reducing the oil saturation of a coalescing filter element (28) of an air-oil mist eliminator (20, 114) of a crankcase ventilation system (100) of an internal combustion engine (102) generating blowby gas (22, 104) in a crankcase (24, 104), wherein the coalescing filter element (28) removes oil from the blowby gas (22, 104) by coalescence, wherein the system reduces the oil saturation of the coalescing filter element (28) using centrifugal force by intermittently rotating the mist eliminator (20, 114), wherein the mist eliminator (20, 114) has two operating modes comprising a first, static mode and a second, rotating mode, and wherein the intermittent rotating is applied based on a given condition, wherein the given state is a given state of the droplet separator (20, 114) and / or a turbocharger (144) connected to the internal combustion engine (102). [15] A system according to claim 14, wherein the given condition is a given condition of the droplet eliminator (20, 114). [16] The system of claim 14, wherein the given condition is a pressure drop across the droplet eliminator (20, 114). [17] The system of claim 14, wherein the oil saturation of the coalescing filter element (28) is reduced by intermittent rotation driven by a shaft (58) driven by the internal combustion engine (102). [18] The system of claim 14, wherein the oil saturation of the coalescing filter element (28) is reduced by discontinuous rotation driven by an electric motor (70). [19] The system of claim 14, wherein the oil saturation of the coalescing filter element (28) is reduced by discontinuous rotation driven by a fluid motor. [20] The system of claim 14, wherein the oil saturation of the coalescing filter element (28) is reduced by intermittent rotation driven by pressurized engine oil. [21] The system of claim 20, wherein the pressurized engine oil drives a Pelton turbine (60). [22] The system of claim 14, wherein the oil saturation of the coalescing filter element (28) is reduced by intermittent rotation driven by oil pumped by an engine oil pump, the engine oil pump pumping lubricating oil to components of the internal combustion engine (102). [23] The system of claim 14, wherein the given condition is a turbocharger efficiency. [24] The system of claim 14, wherein the given condition is a turbocharger boost pressure. [25] The system of claim 14, wherein the given condition is a turbocharger boost ratio, which is the ratio of the pressure at the turbocharger outlet to the pressure at the turbocharger inlet. [26] The system of claim 22, wherein the internal combustion engine includes a one-way check valve (276) that returns oil to a crankcase sump (64).

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