Patent Publication Number: US-9901933-B2

Title: Device for separating oil drops in a mixture of gas and oil and a separation method implementing such a separator device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a separator device for separating oil drops from a mixture of gas and oil and from an internal combustion engine. Moreover, the present invention relates to a separation method implementing such a separator device. 
     The present invention applies in particular to the field of separating oil and gas from a mixture from an internal combustion engine of a motor vehicle, of Diesel or petrol type. By motor vehicle is meant in particular private vehicles, commercial vehicles or industrial vehicles for example of truck type. 
     BACKGROUND OF THE INVENTION 
     An internal combustion engine in service generates crankcase gases, which form an aerosol mixture comprising oil drops in suspension in a gas. The oil drops originate from the splashing of the connecting rods and crankshaft in the oil contained in the oil tank. The gas originates from the leaks between the cylinders and the pistons; these leaks are sometimes called blow-by gas. Thus, it is necessary to separate the oil from the gas in order to re-inject the oil in the internal combustion engine. 
     US2008216660A1 describes an electrostatic filter for separating oil drops from a mixture of gas and oil. The electrostatic filter of US2008216660A1 comprises a separation chamber, an oil recovery chamber coupled to the separation chamber for the flowing of oil, an emitter electrode, collector electrode, and an electronic unit supplying the emitter electrode. 
     However, in the electrostatic filter of US2008216660A1, when the mixture is rich in oil, the oil captured by the collector electrode gathers on the collector electrode without being entirely discharged, thereby inducing a risk of clogging, hence of defect of the electrostatic filter. Furthermore, the oil gathered is hardly discharged on the collector electrode. However, the electrostatic charges gathered risk leading to an electric breakdown in the electrostatic filter, hence disabling the electrostatic filter. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention in particular aims to resolve, all or part, the aforementioned issues, by providing an efficient and compact separator device. 
     To this aim, one object of the invention is a separator device, for separating oil drops from a mixture comprising gas and oil drops and originating from an internal combustion engine, the separator device comprising at least:
         a separation chamber having i) an inlet configured for the entry of the mixture into the separation chamber, and ii) an outlet arranged for the exit of gases out of the separation chamber,   an oil recovery chamber coupled to the separation chamber by means of at least one bleed port, so that liquid oil may flow from the separation chamber to the oil recovery chamber through said at least one bleed port,   at least one emitter electrode extending at least partially in the separation chamber,
 
at least one collector electrode extending at least partially in the separation chamber, and
   an electronic unit connected to said at least one emitter electrode and to said at least collector electrode, the electronic unit being configured for, at least during a charging phases:   bringing said at least one emitter electrode to a negative potential, in such a manner that at least one emitter electrode generates at least an electric field suitable for negatively charging oil drops, and   bringing said at least one collector electrode to zero or a positive potential, so that said at least one collector electrode collects negatively-charged oil drops,
 
the separator device being characterized in that it further comprises at least one pressure-drop generating member disposed in the separation chamber so as to delimit therein an upstream portion and a downstream portion, the pressure-drop generating member being configured for generating pressure drops between the upstream portion and the downstream portion when the gas flows between the inlet and the outlet, and in that the oil recovery chamber is coupled to the downstream portion by means of at least one vacuuming port, in such a manner that the pressure in the oil recovery chamber is lower than the pressure in the upstream portion.
       

     As the pressure in the oil recovery chamber is lower than the pressure in the upstream portion, part of the gas is suctioned by the bleed port or each bleed port, thus contributing in making the oil flow through the bleed port or each bleed port and towards the oil recovery chamber. 
     Thus, such a separator device allows an efficient discharge of the oil separated from the mixture, as it allows maximizing the discharge output flow rate of the oil separated from the mixture, while minimizing the bulk thereof. In fact, the oil recovery chamber and each bleed port suction a large output flow rate of oil. Due to this oil suction, the risks of clogging of each collector electrode are reduced, so that the risk of electric breakdown is reduced, even avoided, since each collector electrode gathers less oil hence less static charges. 
     On a motor vehicle, of Diesel or petrol type, a separator device in accordance with the invention may for example be integrated in the cylinder head cover or form a component independent from the cylinder head cover. 
     In the present application, the term “couple” and its derivates designate in particular the placing in communication of the fluid, gas and/or liquid, between at least two areas. 
     In the present application the term “connect” and its derivates relate in particular to an electrically conducting connection between at least two components. 
     In the present application, the terms “upstream” and “downstream” refer in the general sense of gas flow between the inlet and the outlet. The upstream portion extends from the inlet to said at least one pressure-drop generating member. The downstream portion extends from said at least one pressure-drop generating member to the outlet. 
     According to a variant of the invention, the pressure-drop generating member is configured in order to generate a pressure difference between 5 Pa and 200 Pa between the oil recovery chamber and the upstream portion. 
     According to an embodiment of the invention, said at least one emitter electrode and said at least one collector electrode are composed at least partially of electrically conducting materials, and said at least one emitter electrode and said at least one collector electrode each have a surface roughness of which the arithmetic mean difference Ra ranges between 0.1 μm et 100 μm. 
     Thus, such emitter and collector electrodes are relatively smooth, hence hardly wetting, thus promoting spreading the oil drops separated from the mixture on the emitter and collector electrodes, thereby reducing the oil gathered on the emitter and collector electrodes. 
     According to a variant of the invention, said at least one emitter electrode and said at least one collector electrode are composed of plastic materials coated with electrically conducting materials. Alternatively to this variant, said at least one emitter electrode and said at least one collector electrode may be totally composed of electrically conducting materials, for example of metallic materials. 
     According to a variant of the invention, the electronic unit is configured for, at least during a charging phase, to bring said at least one emitter electrode to a substantially constant negative potential. Thus, such an electronic unit allows generating an electrostatic field, thus maximizing the charge of the oil drops, thereby the yield of the oil deposit on each collector electrode, hence the separation efficiency of the separator device. 
     According to an embodiment of the invention, said at least one emitter electrode extends near the inlet. 
     Thus, the emitter electrode or each emitter electrode may negatively charge oil drops as soon as the mixture enters the separation chamber, thus allowing to minimize the bulk of the separator device. 
     According to a variant of the invention, a distance separating the inlet and said at least one emitter electrode is between 0% and 30% of the distance separating the inlet and the outlet. The distance separating the inlet and the outlet corresponds to the length of the separation chamber. 
     According to an embodiment of the invention, said at least one emitter electrode comprises at least one threadlike portion. 
     Thus, such a threadlike portion allows increasing the intensity of the electric field for a given electrical voltage, hence the yield of the deposit of oil on the collector electrode. Indeed, a threadlike portion produces an important lightning rod effect, as the section thereof has small dimensions. 
     According to an embodiment of the invention, at least one threadlike portion extends along a direction transversal to a flow direction of the mixture between the inlet and the outlet. 
     Thus, such a threadlike portion transversal to the flow of the mixture allows generating an electric field in an important part of the flow section of the separation chamber. Hence, such a threadlike transverse portion allows charging numerous oil drops contained in the mixture. 
     According to a variant of the invention, said at least one threadlike portion extends globally along at least one direction perpendicular to a flow direction of the mixture between the inlet and the outlet. 
     According to a variant of the invention, the threadlike portion is rectilinear. Thus, such a rectilinear filiform portion is simple to set up in the separation chamber. 
     Alternatively to this variant, the threadlike portion may be curvilinear. Thus, such a curvilinear threadlike portion may be suitable for the geometry of the separation chamber. 
     According to a variant of the invention, each threadlike portion has a shape generally in the form of a circle, of which the diameter is less than 1 mm. Thus, such a threadlike portion produces an important lightning rod effect, hence a strong electric field. 
     According to a variant of the invention, at least one threadlike portion is formed by a wire. According to another variant of the invention, at least one threadlike portion is formed by a needle. 
     According to an embodiment of the invention, the separator device comprises at least two emitter electrodes, the threadlike portions being arranged substantially parallel. 
     Thus, several emitter electrodes allow producing several electric fields, hence maximize the charge of the oil drops and the number of charged oil drops. 
     According to an embodiment of the invention, the separator device further comprises at least one auxiliary electrode connected to the electronic unit, the electronic unit being configured for, at least during a charging phase, bringing said at least one auxiliary electrode to a zero or positive potential. 
     Said at least one auxiliary electrode being arranged closer to said emitter electrode than said at least collector electrode, such that an electric field established between said at least one emitter electrode and said at least one auxiliary electrode is stronger than an electric field established between said at least one emitter electrode and said at least one collector electrode. 
     Thus, each auxiliary electrode allows maximizing the electric field crossed by the oil drops. Indeed, each auxiliary electrode may be placed near the inlet and an emitter electrode, whereas each collector electrode must rather be placed near bleed ports in such a manner as to gather the oil near its outlet towards the oil recovery chamber. 
     According to an embodiment of the invention, the separator device comprises at least two auxiliary electrodes formed by auxiliary threadlike portions and arranged substantially parallel between them and the emitter electrodes, the auxiliary electrodes and the emitter electrodes being arranged in a staggered arrangement. 
     In other words, each auxiliary electrode being located facing an interval delimited by two consecutive emitter electrodes. 
     Thus, such a staggered arrangement allows increasing the pathway length of the oil drops in the electric field, hence their charging period and their charge. In fact, each electric field generated between an emitter electrode and an auxiliary electrode extends along an oblique direction with respect to the flow direction of the mixture. 
     According to a variant of the invention, the distance between a neighbouring auxiliary electrode and emitter electrode is between 10% and 30% of the distance between this emitter electrode and the nearest collector electrode. For example, if the distance between an auxiliary electrode and a neighbouring emitter electrode is of 5 mm, then the distance between an emitter electrode and the nearest collector electrode may be between 15 mm and 50 mm. 
     Thus, such a distance allows generating stronger electric fields between emitter electrodes and auxiliary electrodes than between emitter and collector electrodes, thus increasing the number of oil drops charged and the charge of each oil drop before the oil drops arrive near each collector electrode 
     According to an embodiment of the invention, said at least one auxiliary electrode is arranged upstream of said at least one emitter electrode. 
     Thus, such an arrangement allows maximizing the collection of oil drops by a collector electrode Indeed, the electric field generated between a downstream emitter electrode and an upstream auxiliary electrode induces on each charged oil drop an electrostatic force opposite the air force. Hence, this electric field slows down each oil drop, thus facilitating the capture thereof by a collector electrode. Furthermore, the air force tends to move each charged oil drop away from the auxiliary electrode (of opposite or zero charge), thus limiting or preventing the gathering of oil on the auxiliary electrode. 
     According to an embodiment of the invention, a flow section of said at least one vacuuming port is greater than a flow section of said at least one bleed port. 
     Thus, such a vacuuming port guarantees a sufficient pressure difference between the oil recovery chamber and the separation chamber. Hence, such a vacuuming port guarantees the flow of oil through each bleed port. 
     According to a variant of the invention, the size ratio of i) a flow section of said at least one vacuuming port and ii) a flow section of said at least one bleed port is larger than or equal to 2. Thus, such a vacuuming port maximizes the pressure difference between the oil recovery chamber and the separation chamber. 
     According to an embodiment of the invention, said at least one bleed port is located in a lower region of the upstream portion, for example on the bottom of the upstream portion. 
     Thus, such a location allows a flow of oil by gravitation through the bleed port, in addition to the suction due to the vacuuming port. 
     In the present application, the terms “lower” and “higher” refer to the altitude of an element when the separator device is in service position. 
     According to an embodiment of the invention, said at least one bleed port is located near or in a respective lateral wall of the upstream portion. 
     Thus, such a location allows increasing the output flow rate of oil flowing through the bleed port. Indeed, the gas velocity, hence the air force exerted on each oil drop, is minimum near the walls (calm area), thus minimizing the risk that an oil drop be carried by the gas out from the bleed port. 
     According to an embodiment of the invention, the separator device comprises at least two bleed ports disposed respectively on two opposite borders of the upstream portion, for example respectively near the two opposite lateral walls of the upstream portion. 
     Thus, several bleed ports allow increasing the output flow rate of oil flowing towards the oil recovery chamber. 
     In the present application, the terms “border” and “lateral” refer to the general direction of gas flow between the inlet and the outlet. 
     According to a variant of this embodiment, the separator device comprises an even number of bleed ports, the bleed ports being disposed in equal number on each border of the upstream portion. Thus, the profile of gas velocities in the separation chamber is symmetrical, thus allowing flows of oil with equivalent output flow rates through the bleed ports. 
     For example, the separator device may comprise four bleed ports, two bleed ports being disposed on one border of the upstream portion and two bleed ports being disposed on the other border of the upstream portion. 
     According to a variant of the invention, the separation chamber has an axis of symmetry, the bleed ports being disposed symmetrically on each border of the axis of symmetry. 
     According to an embodiment of the invention, said at least one collector electrode extends near said at least one bleed port. 
     Thus, the oil is deposited on each collector electrode nearest the bleed ports, thereby facilitating the flow of oil towards the oil recovery chamber. 
     According to a variant of the invention, the distance separating a respective bleed port and corresponding collector electrode represents between 0% and 5% of the distance separating the inlet and the outlet. 
     According to an embodiment of the invention, the separator device comprises at least two bleed ports and at least two collector electrodes, each collector electrode extending near a respective bleed port. 
     Thus, several collector electrodes and several bleed ports allow increasing the output flow rate of oil flowing towards the oil recovery chamber. 
     According to an embodiment of the invention, said at least one collector electrode comprises an electrically conducting film, said at least one electrically conducting film covering at least partially a lower surface of the upstream portion. 
     Thus, such an electrically conducting film allows forming an efficient and light collector electrode. 
     According to a variant of the invention, each of said at least two collector electrodes is formed by an electrically conducting strip covering a respective portion of the lower surface (or bottom) of the upstream portion of the separation chamber, a portion of each electrically conducting strip being arranged near or around a respective bleed port. 
     According to an alternative to the previous embodiment, the separator device comprises a single collector electrode. For example, the single collector electrode may totally or partially cover the lower surface (or bottom) of the upstream portion of the separation chamber. Thus, numerous oil drops may be charged and collected. 
     According to an embodiment of the invention, said at least one collector electrode comprises:
         a peripheral electrically conducting film extending around said at least one bleed port, and   at least one adjacent electrically conducting film arranged so as to prolong the peripheral electrically conducting film and to be extended substantially vertically when the separator device is in service position.       

     Thus, such peripheral and adjacent electrically conducting films allow increasing the output flow rate of oil flowing towards the oil recovery chamber. In fact, the peripheral film allows collecting oil from around the bleed port, whereas the adjacent film allows gravitation to lead the oil towards the bleed port. 
     According to an embodiment of the invention, said at least one bleed port has at least a sharp border comprising an edge having a bend radius lower than 0.2 mm, and said at least one collector electrode covers said sharp border. 
     Thus, such a sharp border produces a lightning rod effect, thus allowing generating relatively strong electric fields between the charged oil drops and the collector electrode covering the sharp border. 
     According to a variant of the invention, a collector electrode extends to the inside of a respective bleed port. In other words, this collector electrode covers each border by at least one edge of this bleed port. 
     According to an embodiment of the invention, said at least one sharp border comprises two edges having a bend radius lower than 0.2 mm, the two edges being joined by a rounded fillet, for example with a section in the form of an arc of circle, the rounded fillet having a radius higher than 0.5 mm, preferably higher than 1 mm, said at least one collector electrode covers the sharp borders and the rounded fillet. 
     Thus, such sharp borders produce lightning rod or spike effects, thus allowing generating relatively strong electric fields between the charged oil drops and the collector electrode covering the sharp borders. Likewise, the rounded fillet produces an inverse lightning rod effect, thus allowing generating relatively strong electric fields between the charged oil drops and the collector electrode covering the rounded fillet. 
     According to an embodiment of the invention, said at least one pressure-drop generating member is disposed near a respective bleed port. 
     Thus, such a positioning allows the pressure-drop generating member to highly decrease the gas velocities near each bleed port. Hence, this positioning reduces the risks of leading oil drops out from each bleed port. In addition, the pressure-drop generating member delimits a separation area near each bleed port, thus promoting the capture of the oil drops by a collector electrode. 
     According to a variant of the invention, the distance separating said at least one pressure-drop generating member and a respective bleed port represents between 0% and 20% of the distance separating the inlet and the outlet. 
     According to a variant of the invention, said at least one pressure-drop generating member is contiguous with a respective bleed port. 
     According to a variant of the invention, said at least one pressure-drop generating member is configured for generating singular pressure drops. 
     According to an embodiment of the invention, said at least one pressure-drop generating member is formed by an obstacle. 
     Thus, such an obstacle is easy to implant in the separation chamber and it produces pressure drops which hardly vary with the output flow rate of the gas flow. 
     According to a variant of the invention, said at least one obstacle has a height between 50% and 100% of the height of the upstream portion. 
     According to a variant of the invention, said at least one pressure-drop generating member obstructs between 5% and 30% of the flow section of the separation chamber. 
     According to an alternative to the previous embodiment, at least one pressure-drop generating member is formed by an incurved section. 
     According to another variant to the previous embodiment, at least one pressure-drop generating member is formed by a reducing segment which has a reduced flow section with respect to the inlet. 
     According to an embodiment of the invention, the separation chamber generally has the shape of a parallelepiped, for example with a rectangular base, and the oil recovery chamber generally has the shape of a parallelepiped, for example with a rectangular base. 
     Thus, such a separation chamber in the form of a parallelepiped is easy to implant in an engine compartment. 
     According to an embodiment of the invention, the separation chamber generally has the shape of a cylinder, for example with a circular base, and the oil recovery chamber has generally the shape of a tube disposed around the separation chamber. 
     Thus, such a separation chamber in the form of a cylinder has a gas flow having a uniform profile of velocities. 
     According to a variant of this embodiment, the separator device comprises several emitter electrodes formed by threadlike portions arranged substantially parallel with each other and to the axis of the cylinder. 
     Alternatively to the two previous embodiments, the separation chamber has a generally incurved shape between the inlet and the outlet. In other words, the separation chamber forms an elbow, such that the gas flow lines between the inlet and the outlet are bent. 
     According to an embodiment of the invention, the separator device further comprises a transfer member coupled to the oil recovery chamber, the transfer member being configured in order to allow a flow of liquid oil towards the internal combustion engine and to prevent a flow of the gas of the internal combustion engine towards the oil recovery chamber. 
     Thus, such a transfer member allows maintaining the oil recovery chamber in vacuum with respect to the separation chamber, as the transfer member prevents any arrival of gas coming from the internal combustion engine via the transfer member towards the oil recovery chamber. 
     According to a variant of the invention, the transfer member comprises a siphon and a transfer piping configured for a transfer of oil towards an engine unit. Alternatively, the transfer member comprises a valve and a transfer piping configured for a transfer of oil towards an engine unit. 
     Furthermore, the object of the present invention is a separation method, for separating oil drops from a mixture comprising gas and oil drops and originating from an internal combustion engine, the separation method comprising the steps of:
         implementing a separator device according to the invention,   during a charging phase, controlling the electronic unit in such a manner that:   said at least one emitter electrode generates at least one electric field suitable for negatively charging oil drops, and   said at least one collector electrode collects oil drops charged negatively, and   allowing the entry of the mixture into the separation chamber.       

     Thus, such a separation method allows an efficient discharge of the oil separated from the mixture. 
     The aforementioned embodiments and variants may be taken alone or according to any technically possible combination. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The present invention will be well understood and its advantages will also appear in light of the following description, given only by way of non-limiting example and made with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic perspective view of a separator device in accordance with a first embodiment of the invention; 
         FIG. 2  is a schematic perspective view of a separator device in accordance with a second embodiment of the invention; 
         FIG. 3  is a schematic perspective view of a separator device in accordance with a third embodiment of the invention; 
         FIG. 4  is a view on a larger scale of the detail IV on  FIG. 3 ; 
         FIG. 5  is a section according to plane V of  FIG. 4 ;  FIG. 5  schematically shows lines of electric fields between the emitter electrodes and the auxiliary electrodes belonging to the separator device of  FIG. 3 ; 
         FIG. 6  is a schematic perspective view of a separator device in accordance with a fourth embodiment of the invention; 
         FIG. 7  is a view on a larger scale of the detail VII on  FIG. 6 ; 
         FIG. 8  is a view of part of  FIG. 7  on a larger scale and in truncated perspective by plane VIII on  FIG. 7 ; 
         FIG. 9  is a schematic perspective view of a separator device in accordance with a fifth embodiment of the invention; 
         FIG. 10  is a schematic perspective view of a separator device in accordance with a sixth embodiment of the invention; 
         FIG. 11  is a section of a separator device in accordance with a seventh embodiment of the invention; and 
         FIG. 12  is a flow chart illustrating a separation method in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a separator device  100  for separating oil drops  2  from a mixture comprising oil drops  2  and gas, symbolized by flow lines  4 . This mixture originates from an internal combustion engine which is not represented. The oil drops  2  may be generally of spherical form with a diameter between 0.1 μm and 100 μm. 
     The separator device  100  comprises a separation chamber  102 . The separation chamber  102  generally has the form of a parallelepiped with a rectangular base. 
     The separation chamber  102  has an inlet  104 , which is configured for the entry of the mixture into the separation chamber  102 . Moreover, the separation chamber  102  has an outlet  106 , which is arranged for the exit of the gas  4  out of the separation chamber  102 . When the separator device  100  is in service, the mixture enters into the separation chamber  102  via the inlet  104  and the gas  4  exits out of the separation chamber  102  by the outlet  106 . 
     Furthermore, the separator device  100  comprises an oil recovery chamber  110 . The oil recovery chamber  110  generally has the form of a parallelepiped with a rectangular base. 
     The oil recovery chamber  110  is coupled to the separation chamber  102  by means of two bleed ports  112  and  113 . When the separator device  100  is in service, the liquid oil flows from the separation chamber  102  to the oil recovery chamber  110  through the bleed ports  112  and  113 . 
     In addition, the separator device  100  comprises an emitter electrode  121  and a collector electrode  122 . The emitter electrode  121  entirely extends into the separation chamber  102 . Likewise, the collector electrode  122  entirely extends into the separation chamber  102 . 
     The emitter electrode  121  and the collector electrode  122  are composed of plastic materials coated with electrically conducting materials, for example a metal alloy. The emitter electrode  121  and the collector electrode  122  each have a surface roughness of which the arithmetic mean difference Ra is equal to about 50 μm. 
     The emitter electrode  121  extends near the inlet  104 . The distance separating the inlet  104  and the emitter electrode  121  is about equal to 15% of the distance separating the inlet  104  and the outlet  106 . The distance separating the inlet  104  and the outlet  106  corresponds to the length L 102  of the separation chamber  102 . 
     The emitter electrode  121  comprises a threadlike portion which is formed by a rectilinear wire. The emitter electrode  121  extends generally along a direction Y 121  perpendicular to a flow direction of the mixture between the inlet  104  and the outlet  106 . 
     The wire forming the emitter electrode  121  has a profile in the form of a circle, of which the diameter is equal to about 0.8 mm. Thus, such a threadlike portion produces an important lightning rod effect, hence a strong electric field. 
     The collector electrode  122  extends around the bleed port  112  and around the bleed port  113 . The distance separating a respective bleed port  112  or  113  and the collector electrode  122  represents 0% of the distance separating the inlet  104  and the outlet  106 . 
     The collector electrode  122  comprises an electrically conducting film entirely covering the lower surface  103  of the upstream portion  102 . 4 . 
     The separator device  100  further comprises an electronic unit  124  which is connected to the emitter electrode  121  and to the collector electrode  122 . The electronic unit  124  is configured for, during a charging phase:
         bringing the emitter electrode  121  to a negative potential, such that the emitter electrode  121  generated at least one electric field E 100  suitable for negatively charging oil drops  2 ; the negative potential of the emitter electrode  121  may be comprised for example between −5 kV and −20 kV, and   bringing the collector electrode  122  to a zero or a positive potential, such that the collector electrode  122  collects negatively charged oil drops  2  in the electric field E 100 ; the zero or positive potential of the collector electrode  122  may be between for example 0 V and 12 V.       

     The electronic unit  124  is configured for, during a charging phase, bringing the emitter electrode  121  to a substantially constant negative potential, hence for generating an electrostatic field. 
     The separator device  100  further comprises two pressure-drop generating members  131  and  132 . The pressure-drop generating members  131  and  132  are disposed in the separation chamber  102  so as to delimit an upstream portion  102 . 4  and a downstream portion  102 . 6  therein. 
     The upstream portion  102 . 4  extends from the inlet  104  to the pressure-drop generating members  131  and  132 . The downstream portion  102 . 6  extends from the pressure-drop generating members  131  and  132  to the outlet  106 . 
     The pressure-drop generating members  131  and  132  are configured to generate pressure drops between the upstream portion  102 . 4  and the downstream portion  102 . 6  when the gas  4  flows between the inlet  104  and the outlet  106 . Each pressure-drop generating member  131  or  132  is here formed by an obstacle. Each pressure-drop generating member  131  or  132  hence produces singular pressure drops. 
     Each pressure-drop generating member  131  or  132  here obstructs around 20% of the flow section of the separation chamber  102 . Thus, the pressure-drop generating members  131  and  132  allow generating a pressure difference nearly equal to 100 Pa between the upstream portion  102 . 4  and the oil recovery chamber  110 . 
     The pressure-drop generating member  131  is disposed near the bleed port  112 . The pressure-drop generating member  132  is disposed near the bleed port  113 . Each pressure-drop generating member  131  or  132  has a height equal to 100% of the height of the upstream portion  102 . 4 . 
     Each pressure-drop generating member  131  or  132  is contiguous with the respective bleed port  112  or  113 . Hence the distance separating a pressure-drop generating member  131  or  132  of the respective bleed port  112  or  113  here represents 0% of the distance separating the inlet  104  and the outlet  106 . 
     The bleed ports  112  are located in a lower region of the upstream portion  102 . 4 . In the example of  FIG. 1 , the bleed ports  112  are located on the bottom of the upstream portion  102 . 4 . The oil recovery chamber  110  is disposed under the separation chamber  102 . Hence, the oil may flow through the bleed ports  112  by gravitation, in addition to the suction due to the aforementioned pressure difference. 
     Furthermore, the bleed ports  112  and  113  are disposed respectively on two opposite borders of the upstream portion  102 . 4 . In the example of  FIG. 1 , the bleed port  112  is located near a lateral wall of the upstream portion  102 . 4  and the bleed port  113  is located near the opposite lateral wall. 
     The oil recovery chamber  110  is coupled to the downstream portion  102 . 6  by means of a vacuuming port  126 , such that the pressure in the oil recovery chamber  110  is lower than the pressure in the upstream portion  102 . 4 . The vacuuming port  126  is formed at a tube section with a circular section. 
     A flow section of the vacuuming port  126  is greater than a flow section of each bleed port  112  or  113 . In the example of  FIG. 1 , the size ratio between the dimension of a flow section of the vacuuming port  126  and the dimension of a flow section of each bleed port  112  or  113 , is nearly equal to 10. 
     The separator device  100  further comprises a transfer member  134 , which is coupled to the oil recovery chamber  110 . The transfer member  134  is configured for allowing a flow of the liquid oil towards the internal combustion engine and for preventing the gas  4  from flowing. 
     The transfer member  134  comprises a siphon  136  and a non represented transfer piping. The transfer piping is configured for an oil transfer towards a non represented engine unit. 
     When the separator device  100  is in service, the electronic unit  124  may bring the emitter electrode  121  to a negative potential (−20 kV). The emitter electrode  121  emits negative electric charges when it is polarized (brought to a negative potential). 
     During a charging phase, the electronic unit  124  may bring the collector electrode  122  to a zero potential (0 V). The collector electrode  122  attracts the negatively charged oil drops, as electric fields are set up between the collector electrode  122  and each of the charged oil drops. These electric fields exert electrostatic forces on each charged oil drop. 
     Then, the oil drops are deposited on the collector electrode  122 , where the gas flow passing by the bleed ports  112  and  113  suctions the liquid oil towards the oil recovery chamber  110 . Finally, the liquid oil leaves the oil recovery chamber  110  by the transfer member  134 . 
       FIG. 2  illustrates a separator device  200  in accordance with a second embodiment of the invention. In as far as the separator device  200  is similar to the separator device  100 , the description of the separator device  100  given in relation to  FIG. 1  may be transposed to the separator device  200 , except for the hereafter mentioned noticeable differences. 
     A component of the separator device  200  identical or corresponding, by the structure or function thereof, to a component of the separator device  100  bears the same numerical reference increased by one hundred. It is thus defined a separation chamber  202 , an inlet  204 , an outlet  206 , an oil recovery chamber  210 , two bleed ports  212  and  213 , an emitter electrode  221 , an electronic unit  224 , a vacuuming port  226  and pressure-drop generating members  231  and  232  delimiting an upstream portion  202 . 4  and a downstream portion  202 . 6  of the separation chamber  202 , a transfer member  234  with a siphon  236 . 
     The separator device  200  differs from the separator device  100 , as it comprises two collector electrodes  222 . 1  and  222 . 2 , whereas the separator device  100  comprises a single collector electrode  122 . 
     Each of the collector electrodes  222 . 1  and  222 . 2  is formed by an electrically conducting strip covering a respective portion of the lower surface of the upstream portion  202 . 4 . A portion of each electrically conducting strip is arranged around a respective bleed port  212  or  213 . Each of the collector electrodes  222 . 1  and  222 . 2  extends parallel to the direction connecting the inlet  204  and the outlet  206 . 
     When the separator device  200  is in service, the electronic unit  224  may bring the collector electrodes  222 . 1  and  222 . 2  to different potentials. During a charging phase, the electronic unit  224  may bring the electronic electrodes  222 . 1  and  222 . 2  to a zero potential. 
     Then, during a discharging phase, the electronic unit  224  may bring the collector electrodes  222 . 1  and  222 . 2  to a negative potential, for example −10 kV. The charging phase may last longer than the discharging phase. During the discharging phase, the oil drops gathered on the collector electrodes  222 . 1  and  222 . 2  are discharged and are pushed by the collector electrodes  222 . 1  and  222 . 2 , so well that they flow easily through the bleed ports  212  and  213 . 
     In addition, the electronic unit  224  may operate in a differed manner the charging and discharging phases of the collector electrodes  222 . 1  and  222 . 2 , thus allowing to continue charging the oil drops with the collector electrode  222 . 1  at a zero potential, whereas oil drops are discharged when the collector electrode  222 . 2  is at a negative potential. Thus, the electronic unit  224  allows permanently charging oil drops while efficiently discharging the oil. 
       FIGS. 3, 4 and 5  illustrate a separator device  300  in accordance with a third embodiment of the invention. In as far as the separator device  300  is similar to the separator device  200 , the description of the separator device  200  given in relation to  FIG. 2  may be transposed to the separator device  300 , except for the hereafter mentioned noticeable differences. 
     A component of the separator device  300  identical or corresponding, by the structure or function thereof, to a component of the separator device  200  bears the same numerical reference increased by one hundred. It is thus defined a separation chamber  302 , an inlet  304 , an outlet  306 , an oil recovery chamber  310 , two bleed ports  312  and  313 , two collector electrodes  322 . 1  and  322 . 2 , an electronic unit  324 , a vacuuming port  326  and pressure-drop generating members  331  and  332 , as well as a transfer member  334 . 
     The separator device  300  differs from the separator device  200 , as it comprises three emitter electrodes  321 , whereas the separator device  200  comprises one single emitter electrode  221 . The emitter electrodes  321  are formed by threadlike portions arranged substantially parallel to each other. 
     In addition, the separator device  300  differs from the separator device  200 , as it comprises two auxiliary electrodes  340 . The auxiliary electrodes  340  are connected to the electronic unit  324 . The electronic unit  324  is configured so as to bring the auxiliary electrodes  340  to a zero potential, during a charging phase. 
     The auxiliary electrodes  340  are arranged closer to the emitter electrodes than the collector electrodes  322 . 1  and  322 . 2 , so that an electric field E 300  established between the emitter electrodes and the auxiliary electrodes  340  is stronger than an electric field established between the emitter electrodes  321  and the collector electrodes  322 . 1  and  322 . 2 . 
     The auxiliary electrodes  340  are formed by auxiliary threadlike portions which are arranged substantially parallel to each other and to the emitter electrodes  321 . The auxiliary electrodes  340  are arranged upstream of the emitter electrodes  321 . 
     As shown specifically in  FIGS. 4 and 5 , the auxiliary electrodes  340  and the emitter electrodes  321  are arranged in a staggered manner. Thus, each auxiliary electrode  340  is located in front of a gap delimited by two consecutive emitter electrodes  321 . When in operation, this staggered arrangement allows enlarging the pathway length of the oil drops  2  in the electric field E 300  between each emitter electrode  321  and each auxiliary electrode  340 . Hence, the oil drops  2  are subjected to a longer charging period, so much so that they are charged more intensely or in a larger number. 
     As shown in  FIG. 3 , the distance  321 . 340  between an auxiliary electrode  340  and a neighbouring emitter electrode  321  is equal to about 10% of the distance  321 . 322  between this emitter electrode  321  and the closest collector electrode  322 . 1  or  322 . 2 . 
     Furthermore, the separator device  300  differs from the separator device  200 , as the collector electrodes  322 . 1  and  322 . 2  have a three-dimensional geometry, whereas the collector electrodes  222 . 1  and  222 . 2  have a planar geometry. 
     Indeed, each collector electrode  322 . 1  or  322 . 2  comprises i) a peripheral electrically conducting film which extends around a respective bleed port  312  or  313 , and ii) two adjacent electrically conducting films which are arranged so as to prolong the peripheral electrically conducting film and to extend substantially vertically when the separator device  300  is in the operation position ( FIG. 3 ). 
     Thus, each collector electrode  322 . 1  or  322 . 2  is formed by three strips which are contiguously mounted on intersecting edges and each of which extends over a respective plane. The three strips forming the collector electrode  322 . 1  respectively conforming to the lower surface of the separation chamber  302 , of a planar lateral wall and of the pressure-drop generating member  331 . 
       FIG. 6  illustrates a separator device  400  in accordance with a fourth embodiment of the invention. In as far as the separator device  400  is similar to the separator device  300 , the description of the separator device  300 , given with reference to  FIGS. 3, 4 and 5 , may be transposed to the separator device  400 , with the exception of the hereafter mentioned noticeable differences. 
     A component of the separator device  400  that is identical or correspondent, whether by its structure or function, to a component of the separator device  300  bears the same numerical reference increased by 100. Thus, there are defined a separation chamber  402 , an inlet  404 , an outlet  406 , an oil recovery chamber  410 , two bleed ports  412  and  413 , emitter electrodes  421 , an electronic unit  424 , a vacuuming port  426 , auxiliary electrodes  440  and pressure-drop generating members  431  and  432 , as well as a transfer member  434 . 
     As shown in  FIG. 6 , the separator device  400  differs from the separator device  300 , as the two collector electrodes  422 . 1  and  422 . 2  are shorter than the two collector electrodes  322 . 1  and  322 . 2 . The length of each collector electrode  422 . 1  or  422 . 2  represents about 15% of the length of each collector electrode  322 . 1  and  322 . 2 , the lengths being measured parallel to the length of the separation chamber  402  (see L 102  in  FIG. 1 ). The length of the separation chamber  402  corresponds to the distance separating the inlet  104  and the outlet  106 . 
     Since the collector electrodes  422 . 1  and  422 . 2  are shorter than the collector electrodes  322 . 1  and  322 . 2 , all other things being equal, the electric fields between the emitter electrodes  421  and auxiliary electrodes  440  are much stronger than those between the emitter electrodes  421  and the collector electrodes  422 . 1  and  422 . 2 . This allows increasing the number of charged oil drops  2  and the charge of each oil drop  2  before that the oil drops  2  reach the collector electrodes  422 . 1  and  422 . 2 . 
     Furthermore, as shown in  FIGS. 7 and 8 , the periphery of each bleed port  412  or  413  is formed by four sharp borders each of which comprising two edges  415  and  416 . 
     Each of the edges  415  and  416  has a bend radius equal to about 0.1 mm. 
     In addition, as shown in  FIG. 8 , each collector electrode  422 . 1  or  422 . 2  extends to the inside of a respective bleed port  412  or  413 . Hence, a respective collector electrode  422 . 1  or  422 . 2  covers the sharp borders forming the periphery of each bleed port  412  or  413 . 
     Thus, the edges  415  and  416  produce a spike effect, thereby allowing generating relatively strong electric fields between the charged oil drops  2  and the respective collector electrode  422 . 1  or  422 . 2 . 
     The edges  415  and  416  are joined by a rounded fillet  417  with a circular-arc shaped section. Here, the rounded fillet  417  has a radius equal to about 1 mm. Each collector electrode  422 . 1  or  422 . 2  covers the sharp borders and the rounded fillet  417 . Thus, the rounded fillet  417  produces a reversed lightning rod effect, thereby allowing generating relatively strong electric fields between the charged oil drops  2  and the collector electrode  422 . 1  covering the rounded fillet  417 . 
       FIG. 9  illustrates a separator device  500  in accordance with a fifth embodiment of the invention. In as far as the separator device  500  is similar to the separator device  400 , the description of the separator device  400 , given hereinbefore with reference to  FIG. 6 , may be transposed to the separator device  500 , with the exception of the hereafter mentioned noticeable differences. 
     A component of the separator device  500  that is identical or correspondent, whether by its structure or function, to a component of the separator device  400  bears the same numerical reference increased by 100. Thus, there are defined a separation chamber  502 , an inlet  504 , an outlet  506 , an oil recovery chamber  510 , emitter electrodes  521 , an electronic unit  524 , a vacuuming port  526 , auxiliary electrodes  540  and pressure-drop generating members  531  and  532 , as well as a transfer member  534 . 
     The separator device  500  differs from the separator device  400 , as the separator device  500  has four bleed ports  512 . 1 ,  512 . 2 ,  513 . 1  and  513 . 2 ; whereas the separator device  400  has two bleed ports  412  and  413 . 
     In a similar manner, the separator device  500  differs from the separator device  400 , as the separator device  500  comprises four collector electrodes  522 ; whereas the separator device  400  comprises two collector electrodes  422 . 1  and  422 . 2 . 
     Two bleed ports  512 . 1  and  512 . 2  are disposed on one side of the upstream portion and two bleed ports  513 . 1  and  513 . 2  are disposed on the other side of the upstream portion. 
     Since the collector electrodes  522  extend around the bleed ports  512 . 1 ,  512 . 2 ,  513 . 1  and  513 . 2 , two collector electrodes  522  are disposed on one side of the upstream portion and two collector electrodes  522  are disposed on the other side of the upstream portion. 
     Like the separator device  400 , the separator device  500  comprises an even number of bleed ports and the bleed ports are disposed, in an equal number, on each side of the upstream portion. 
     Furthermore, in the example of  FIG. 9 , the separation chamber  502  has an axis of symmetry X 500 . The bleed ports  512 . 1 ,  512 . 2 ,  513 . 1  and  513 . 2  are disposed symmetrically on each side of the axis of symmetry X 500 . 
     In addition, the separator device  500  differs from the separator device  400 , as the separator device  500  comprises six pressure-drop generating members, whereas the separator device  400  comprises two pressure-drop generating members  431  and  432 . Indeed, the separator device  500  comprises: two primary pressure-drop generating members  531  and  532 , which are identical to the two pressure-drop generating members  431  and  432 , in addition to four secondary pressure-drop generating members  541 . 1 ,  541 . 2 ,  542 . 1  and  542 . 2 . 
     The secondary pressure-drop generating members  541 . 1 ,  541 . 2 ,  542 . 1  and  542 . 2  are respectively disposed around the bleed ports  512 . 1 ,  512 . 2 ,  513 . 1  and  513 . 2 . Each of the four secondary pressure-drop generating members  541 . 1 ,  541 . 2 ,  542 . 1  and  542 . 2  allows reducing the gas velocities in the vicinity of the bleed ports  512 . 1 ,  512 . 2 ,  513 . 1  and  513 . 2 ; whereas the two primary pressure-drop generating members  531  and  532  rather allow generating a pressure difference between the upstream portion of the separation chamber  502  and the oil recovery chamber  510 . 
     When the separator device  500  is in operation, the electronic unit  524  can bring the collector electrodes  522  to different potentials. 
     As described hereinbefore with reference to  FIG. 2 , the electronic unit  524  can perform the charging and discharging phases of the collector electrodes  522 , in a delayed manner. For example, three collector electrodes  522  may be brought to a zero potential (charging phase), whereas the fourth collector electrode  522  is brought to a negative potential (discharging phase) in order to push the charged oil drops toward the corresponding bleed port  512 . 1 ,  512 . 2 ,  513 . 1  or  513 . 2 . 
     Afterwards, the electronic unit  524  proceeds to discharge of the other collector electrodes  522 , one at a time. This allows continuing charging the oil drops with three collector electrodes  522 , while oil drops are discharged when the fourth collector electrode  522  is at a negative potential. Thus, the electronic unit  524  allows charging oil drops, in permanence, while effectively discharging the oil. 
       FIG. 10  illustrates a separator device  600  in accordance with a sixth embodiment of the invention. In as far as the separator device  600  is similar to the separator device  500 , the description of the separator device  500 , given hereinbefore with reference to  FIG. 9 , may be transposed to the separator device  600 , with the exception of the hereafter mentioned noticeable differences. 
     A component of the separator device  600  that is identical or correspondent, whether by its structure or function, to a component of the separator device  500  bears the same numerical reference increased by 100. Thus, there are defined a separation chamber  602 , an inlet  604 , an outlet  606 , an oil recovery chamber  610 , bleed ports  612 ,  613  and equivalents, emitter electrodes  621 , collector electrodes  622 , an electronic unit  624 , a vacuuming port  626 , auxiliary electrodes  640 , primary pressure-drop generating members  631  and secondary pressure-drop generating members  641  and  642 . The separator device  600  further comprises a transfer member which is not represented and which is similar, by its function, to the transfer member  534 . 
     The separator device  600  differs from the separator device  500 , as the separation chamber  602  has the general shape of a circular-based cylinder, whereas the separation chamber  502  has the general shape of a parallelepiped. 
     Similarly, the separator device  600  differs from the separator device  500 , as the oil recovery chamber  610  has the general shape of a circular tube disposed around the separation chamber  602 , whereas the oil recovery chamber  510  has the general shape of a parallelepiped disposed under the separation chamber  502 . 
     Furthermore, the separator device  600  differs from the separator device  500 , as the emitter electrodes  621  and the auxiliary electrodes  640 , formed by threadlike portions, are arranged substantially parallel to each other and to the axis of the cylinder defining the separation chamber  602 , and therefore, substantially parallel to the flow direction of the mixture between the inlet  604  and the outlet  606 . On the contrary, the emitter electrodes  521  and the auxiliary electrodes  540  extend perpendicular to the flow direction of the mixture between the inlet  504  and the outlet  506 . 
     Like the separator device  500 , the separator device  600  has four bleed ports, two of which are visible in  FIG. 10  with the numerical references  612  and  613  two of which are not represented. The two bleed ports are respectively located opposite to the bleed ports  612  and  613  with respect to the axis of the cylinder forming the separation chamber  602 . 
     Furthermore, the mixture is introduced in the separator device  600  via a 90-degree elbow. 
       FIG. 11  illustrates a separator device  700  in accordance with a sixth embodiment of the invention. In as far as the separator device  700  is similar to the separator device  600 , the description of the separator device  400 , given hereinbefore with reference to  FIG. 10 , may be transposed to the separator device  700 , with the exception of the hereafter mentioned noticeable differences. 
     A component of the separator device  700  that is identical or correspondent, whether by its structure or function, to a component of the separator device  600  bears the same numerical reference increased by 100. Thus, there are defined a separation chamber  702 , an inlet  704 , an outlet  706 , an oil recovery chamber  710 , an electronic unit  724 , a vacuuming port  726 , a primary pressure-drop generating member  731 , as well as a transfer member  734 . 
     As shown in  FIG. 11 , the separator device  700  differs from the separator device  600 ,
         as the separator device  700  comprises one single emitter electrode  721  formed by a wire extending along the entire length of the separation chamber  702  and which is collinear with the axis of the cylinder forming the separation chamber  702 ,   as the separator device  700  comprises one single collector electrode  722 ,   as the separator device  700  comprises one single bleed port  712 , which is annular-shaped,   as the separator device  700  comprises one single pressure-drop generating member  731 , which is annular-shaped, and   as the separator device  700  comprises no auxiliary electrodes  740 .       

       FIG. 12  illustrates a separation method  1000 , for separating oil drops  2  from a mixture comprising gas  4  and oil drops  2  coming from an internal combustion engine. The separation method  1000  comprises the steps of:
           1002 ) implementing a separator device according to any of the above-described embodiments,     1004 ) controlling the electronic unit, during a charging phase, so that:     1006 ) the emitter electrode or each emitter electrode generates at least one electric field suitable so as to negatively charge oil drops, and     1008 ) the collector electrode or each collector electrode collects negatively charged oil drops, and     1010 ) allowing the entry of the mixture into the separation chamber.       

     Of course, the present invention is not limited to the particular embodiments that have been described in the present patent application, nor is it limited to embodiments that are within the reach of the one skilled in the art. Other embodiments may be considered, without departing from the scope of the invention, from any element equivalent to an element indicated in the present patent application.