Electrostatic precipitator

Abstract

Electrostatic precipitator (1) for separating liquid and / or solid particles from a gas stream, in particular from a blow-by gas of a crankcase ventilation system of an internal combustion engine, comprising: - an emission electrode (23) with an elongated shaft (43) and a counter electrode (25), to which an electrical high voltage can be applied, so that an electrical high voltage field can be generated between the emission electrode (23) and the counter electrode (25); wherein the emission electrode (23) is supported by a carrier (85) with an electrical conductivity of less than 10 -8 S*cm -1 held, dimensioned and cast by carrier casting material such that the shaft (43) protrudes by at least 0.5 mm and preferably at most 8 mm from the carrier (85) after solidification of the carrier casting material.

Description

[0001] The present invention relates to an electrostatic precipitator for separating liquid and / or solid particles from a gas stream, preferably from a blow-by gas of a crankcase ventilation system, in an internal combustion engine.

[0002] Separators, particularly oil separators, are known in the art. There are generally two types of separators: passive separators and active separators. With passive separators, no additional energy is introduced into the system to remove the particles from the gas stream. Active separators are characterized by the fact that additional energy is applied to separate the particles from the gas stream. For example, an electrostatic precipitator system is known in which particles in the gas stream are electrically charged so that they can be attracted to a surface of opposite polarity and subsequently separated. In oil separators, in particular, the oil particles are returned to the oil circuit, and the purified gas stream is returned to the intake air of the combustion engine.

[0003] Such an electrostatic precipitator is known, for example, from WO 2016 / 147 127 A1. The electrostatic precipitator comprises a plurality of emission electrodes, by means of which a direct voltage exceeding the breakdown voltage can be generated to form a stable low-energy plasma, and a plurality of counterelectrodes assigned to the emission electrodes. The needle-shaped emission electrodes are each assigned to a counterelectrode such that the emission electrodes are positioned substantially vertically above the counterelectrodes. The counterelectrodes have a curved plateau region that merges into a flat web section, which in turn is connected to a frame structure that interconnects a row of counterelectrodes and on which the counterelectrodes are arranged at a distance from one another along the flow direction of the gas stream.

[0004] However, this proven electrostatic precipitator technology has some disadvantages. Firstly, the efficiency of the electrostatic precipitator is adversely affected by the fact that there is always a counterelectrode-free area between two counterelectrode plateaus, which cannot contribute to the deposition process. Furthermore, it has been discovered that deposited particles tend to accumulate on the counterelectrode plateaus. The accumulation of particles on the counterelectrodes negatively impacts the longevity of the electrostatic precipitator, as the counterelectrodes become increasingly contaminated and require replacement. Secondly, it can lead to unwanted plasma ignitions at the counterelectrode.

[0005] Furthermore, it was discovered that the electrostatic precipitator according to WO 2016 / 147127 A1 tends to generate an inhomogeneous electric field, particularly with increasing operating time, which adversely affects the operation and efficiency of the electrostatic precipitator. This is due, among other things, to the accumulation of deposits on the emission electrodes during operation, which cause a change in the emission electrode geometry and thus influence the ignition behavior.

[0006] An electrostatic precipitator is known from DE 100 33 642 C1. The electrostatic precipitator consists of a tube through which the gas to be cleaned flows longitudinally, the inner wall of which forms a counter electrode for the particles to be separated. An emission electrode within the tube generates a high-voltage electric field to electrically charge the particles and attract them to the counter electrode. A cleaning body is provided for cleaning the emission electrode needles. This cleaning body, which moves relative to the needles, forms contact with them to free the emission electrode needles of deposits. The complexity of the cleaning system according to DE 100 33 642 C1 has proven to be a disadvantage. Furthermore, the separate cleaning mechanism is prone to failure.

[0007] An object of the present invention is to improve the disadvantages of the prior art, in particular to provide an electrostatic precipitator which is structurally simple to implement and which generates a uniform electric field, wherein in particular contamination of the emission electrodes is reduced, in particular avoided.

[0008] The problem is solved by the subject matter of claims 1 and 7.

[0009] According to one aspect of the present invention, an electrostatic precipitator is provided for separating liquid and / or solid particles, such as oil particles, from a gas stream, in particular from a blow-by gas from a crankcase ventilation system, of an internal combustion engine. In an exemplary application of an electrostatic precipitator according to the invention in a motor vehicle with an internal combustion engine, blow-by gases arise between a working piston and a cylinder in which the working piston is accommodated, into a crankcase interior of the internal combustion engine. Alternatively, so-called blow-by gases also occur between the cylinder and cylinder head and / or between the cylinder head and cylinder head cover of an internal combustion engine, such as a reciprocating piston engine. Blow-by gases generally contain, in addition to air and oil, combustion gases and unburned fuel components, which can have negative effects on the function of the internal combustion engine.For example, the pressure increase caused by the blow-by gas flow in the crankcase is reduced, preferably avoided, by means of a crankcase ventilation system coupled to the fresh air supply of the internal combustion engine by means of a piping system. An electrostatic precipitator according to the invention can, for example, be arranged along the flow direction within the crankcase ventilation system, in particular such that the blow-by gas flow comprising combustion gases and / or unburned fuel components is fed to the electrostatic precipitator, in which a separation, in particular oil separation, of liquid and / or solid particles, such as oil particles, takes place, so that the separated particles can be removed separately from the gas flow, and the preferably purified gas flow can be fed to the fresh air supply without causing damage to the internal combustion engine.The electrostatic precipitator according to the invention is preferably an active separation device in which, as already explained above, additional energy is introduced into the separation system.

[0010] The electrostatic precipitator essentially works according to the following principle: release of electrical charges, in particular electrons; charging of the particles in an electric field; transport of the electrically charged particles to an opposite pole; discharge of the charged particles at the opposite pole; and removal of the particles from the opposite pole.

[0011] The electrostatic precipitator according to the invention comprises an emission electrode with an elongated shaft and a counter electrode. The counter electrode and the emission electrode can be insulated from one another and / or each made from a single piece. The emission electrode, also called the spray electrode, essentially serves to emit preferably negatively charged particles. The counter electrode, also called the precipitation electrode, forms the opposite pole. A high electrical voltage can be applied to the emission electrode and the counter electrode, so that a high-voltage electrical field can be generated between the emission electrode and the counter electrode. For example, the high voltage is in the range of 8 - 20 kV, preferably in the range of 10 - 16 kV or in the range of 11 - 14 kV. For example, the space formed between the emission electrode and the counter electrode can be referred to as the separation space.During operation of the electrostatic precipitator, a high electrical voltage is applied between the emission electrode and counter electrode, generating a high-voltage field between the emission electrode and counter electrode. The electrostatic precipitator is preferably operated below the breakdown or flashover voltage. The breakdown voltage, also called flashover voltage, is the voltage that must be exceeded for a voltage to pass through a material or substance, e.g. an insulator or gas. For example, the principle of charge generation underlying the electrostatic precipitator can be impact ionization. When a so-called corona inception field strength is exceeded, electrons escape from the emission electrode and interact with the surrounding gas molecules, forming a so-called negative corona.Free electrons present in the gas are greatly accelerated in the electrostatic field of the corona, which can lead to a gas discharge. When they hit gas molecules, further electrons can be split off or attach themselves to the gas molecules. The negative charges then move towards the oppositely charged counter electrode. When a particle-laden gas stream enters, the negatively charged charges attach themselves to the particles. Due to the electrical force of the applied DC field perpendicular to the flow direction of the gas stream, the negatively charged particles migrate towards the counter electrode, where they can release their charge. Liquid particles, such as oil particles, can then flow or drip off the counter electrode and be separated from the gas stream, while a preferably purified gas stream, such as a clean air stream, can leave the electrostatic precipitator.According to an exemplary development of the electrostatic precipitator according to the invention, a plurality of emission electrodes, preferably in the range of 10 to 200 emission electrodes, in particular in the range of 20 to 150 emission electrodes, and a plurality of counterelectrodes are provided, wherein each emission electrode faces and is assigned to a counterelectrode, so that the high-voltage electric field can be generated between each emission electrode-counterelectrode pair. It should be understood that the present invention also covers embodiments in which a positive emission electrode / a positive corona / positively charged charges are used instead of the negative emission electrode / the negative corona / the negatively charged charges. To avoid repetition, the description of the invention is limited to the embodiment of the negative emission electrode.

[0012] According to one aspect of the present invention, the shaft has a preferably constant, substantially cylindrical cross-section with a shaft diameter of at least 0.2 millimeters and at most 1 millimeter. For example, the shaft diameter is approximately 0.4 millimeters. Furthermore, the emission electrode can be formed such that the substantially cylindrical, elongated shaft is not pointed, but has a straight end surface at which the electrons leave the emission electrode. Contrary to the general prejudice of continually reducing the shaft diameter of emission electrodes, the inventors of the present invention have discovered that a minimum diameter of 0.2 millimeters is necessary to generate a uniform electric field and / or ensure uniform ignition of the emission electrodes.It was discovered that emission electrode shaft diameters that are too thin tend to cause deposits to form on the thin emission electrode tips, defining a new tip radius that is larger than the original tip radius of the emission electrodes. This increases the corona inception voltage at these emission electrodes and creates an uneven ignition ratio between the emission electrodes. Furthermore, it was discovered that the maximum diameter of 1 millimeter is also necessary to ensure uniform ignition of the emission electrodes and / or to create a uniform electric field. For shaft diameters exceeding 1 millimeter, it was discovered that the deposits forming on the shaft tips increasingly adhere to the tips, and the self-cleaning effect is no longer achieved.In this respect, the shaft diameter range specified above is found to be optimum with regard to homogenization of the electric field within the separation chamber of the electrostatic precipitator and / or with regard to homogenization of the ignition behavior of the individual emission electrodes.

[0013] In an exemplary embodiment of the electrostatic precipitator according to the invention, the shaft is flattened at a counterelectrode-side end, in particular tapers conically to a point, or has a counterelectrode-side end that is curved toward the counterelectrode. The radius of curvature can be in the range of at least 0.2 millimeters and at most 1 millimeter and / or approximately 0.4 millimeters. The above statements regarding the optimal dimension of the shaft diameter apply analogously to the radius of curvature.

[0014] According to an exemplary embodiment of the present invention, the emission electrode is made of a sheet metal or a continuous blank, such as a continuous wire, preferably of a metal that is particularly resistant to blow-by gases, such as stainless steel, titanium, tungsten, aluminum chromium, nickel, or even of an electrically conductive plastic material or an electrical insulator mixed with electrically conductive particles. At least one shaft end, in particular the counter-electrode-side shaft end, is broken off or sheared off. In this way, the emission electrode can be manufactured particularly cost-effectively.

[0015] According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, an electrostatic precipitator is provided for separating liquid and / or solid particles, such as oil particles, from a gas stream, in particular from a blow-by gas from a crankcase ventilation system, of an internal combustion engine. In an exemplary application of an electrostatic precipitator according to the invention in a motor vehicle in an internal combustion engine, blow-by gases arise between a working piston and a cylinder in which the working piston is accommodated, into a crankcase interior of the internal combustion engine. Alternatively, so-called blow-by gases also occur between the cylinder and the cylinder head and / or between the cylinder head and the cylinder head cover of an internal combustion engine, such as a reciprocating piston engine.Blow-by gases typically contain not only air and oil, but also combustion gases and unburned fuel components, which can negatively impact the operation of the internal combustion engine. For example, the pressure increase in the crankcase caused by the blow-by gas flow is reduced, preferably prevented, by a crankcase ventilation system that is connected to the internal combustion engine's fresh air supply via a piping system.An electrostatic precipitator according to the invention can, for example, be arranged along the flow direction within the crankcase ventilation system, in particular such that the blow-by gas stream comprising combustion gases and / or unburned fuel components is fed to the electrostatic precipitator, in which a separation, in particular oil separation, of liquid and / or solid particles, such as oil particles, takes place, so that the separated particles can be removed separately from the gas stream and the preferably purified gas stream can be fed to the fresh air supply without causing damage to the internal combustion engine. The electrostatic precipitator according to the invention is preferably an active separation device in which, as already explained above, additional energy is introduced into the separation system.

[0016] The electrostatic precipitator essentially works according to the following principle: release of electrical charges, in particular electrons; charging of the particles in an electric field; transport of the electrically charged particles to an opposite pole; discharge of the charged particles at the opposite pole; and removal of the particles from the opposite pole.

[0017] The electrostatic precipitator according to the invention comprises an emission electrode with an elongated shaft and a counter electrode. The counter electrode and the emission electrode can each be made from a single piece. The emission electrode, also called the discharge electrode, essentially serves to emit preferably negatively charged particles. The counter electrode, also called the collecting electrode, forms the opposite pole. A high-voltage electrical voltage can be applied to the emission electrode and the counter electrode, so that a high-voltage electrical field can be generated between the emission electrode and the counter electrode. For example, the high voltage is in the range of 8-20 kV, preferably in the range of 10-16 kV or in the range of 11-14 kV. For example, the space formed between the emission electrode and the counter electrode can be referred to as the separation space.During operation of the electrostatic precipitator, a high electrical voltage is applied between the emission electrode and counter electrode, generating a high-voltage field between the emission electrode and counter electrode. The electrostatic precipitator is preferably operated below the breakdown or flashover voltage. The breakdown voltage, also called flashover voltage, is the voltage that must be exceeded for a voltage to pass through a material or substance, e.g. an insulator or gas. For example, the principle of charge generation underlying the electrostatic precipitator can be impact ionization. When a so-called corona inception field strength is exceeded, electrons escape from the emission electrode and interact with the surrounding gas molecules, forming a so-called negative corona.Free electrons present in the gas are greatly accelerated in the electrostatic field of the corona, which can lead to a gas discharge. When they hit gas molecules, further electrons can be split off or attach themselves to the gas molecules. The negative charges then move towards the oppositely charged counter electrode. When a particle-laden gas stream enters, the negatively charged charges attach themselves to the particles. Due to the electrical force of the applied DC field perpendicular to the flow direction of the gas stream, the negatively charged particles migrate towards the counter electrode, where they can release their charge. Liquid particles, such as oil particles, can then flow or drip off the counter electrode and be separated from the gas stream, while a preferably purified gas stream, such as a clean air stream, can leave the electrostatic precipitator.According to an exemplary development of the electrostatic precipitator according to the invention, a plurality of emission electrodes, preferably in the range of 10 to 200 emission electrodes, in particular in the range of 20 to 150 emission electrodes, and a plurality of counter electrodes are provided, wherein each emission electrode is facing and associated with a counter electrode, so that the electrical high-voltage field can be generated between each pair of emission electrodes and counter electrodes.

[0018] According to a further aspect of the present invention, the emission electrode is held by a support such that the shaft protrudes from the support by at least 0.5 millimeters and preferably 8 millimeters. The support may have an electrical conductivity of less than 10 -8 S*cm -1The carrier can further be made of a fluid-impermeable material, so that it is ensured in particular that fluid particles of the gas stream flowing through the electrostatic precipitator cannot leave the separation chamber via the carrier.

[0019] According to an exemplary development, the carrier has a substantially flat surface facing the counterelectrode, which can at least partially delimit the deposition chamber of the electrostatic precipitator. For example, the carrier, in particular its surface facing the deposition chamber, is dimensioned such that, in the event that multiple emission electrodes are provided to form an emission electrode array, it is larger than an outer circumferential dimension of the emission electrode array. Multiple emission electrodes of the emission electrode array can be evenly distributed along the planar extent of the surface of the carrier, wherein, in particular, two emission electrodes spaced apart from one another can each have the same distance from one another. Alternatively or additionally, the carrier can comprise plastic, preferably thermosetting plastic, and / or potting compound, such as epoxy resin or silicone.For example, the carrier can be implemented as a circuit board. To manufacture the electrostatic precipitator, it can be provided that the carrier equipped with the emission electrode, in particular the circuit board equipped with the emission electrode, is inserted into an electrostatic precipitator housing made, for example, from a blow-by gas-resistant material such as polyamide, and then encapsulated with a potting compound. From a manufacturing perspective, this provides a particularly cost-effective way of manufacturing an electrostatic precipitator. In particular, the advantage of encapsulating the emission electrodes is that an additional manufacturing step for sealing and / or blow-by-tight and / or blow-by-resistant insertion or integration of the emission electrodes into the electrostatic precipitator housing can be omitted.

[0020] In another exemplary embodiment, the emission electrode can be pre-mounted on a circuit board. According to the invention, the emission electrode is dimensioned and cast in carrier casting material such that the shaft protrudes from the carrier by at least 0.5 millimeters and preferably 8 millimeters after solidification of the carrier casting material. With regard to the described shaft lengths of the emission electrodes, the inventors of the present invention have discovered that this allows an optimum in terms of avoiding contamination and / or deposits. In particular, it was discovered that a shaft length must not be chosen too long, so that the emission electrodes do not protrude too far into the deposition chamber, in order to keep a non-active, deposition-free area within the deposition chamber as small as possible.Furthermore, it was found that the shaft length must not be chosen too short, since deposits accumulating at the emission electrode ends, especially shaft tips, otherwise tend to migrate along the emission electrode shaft to the carrier and accumulate there.

[0021] According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, an electrostatic precipitator is provided for separating liquid and / or solid particles from a gas stream, in particular from a blow-by gas from a crankcase ventilation system of an internal combustion engine. In an exemplary application of an electrostatic precipitator according to the invention in a motor vehicle with an internal combustion engine, blow-by gases arise between a working piston and a cylinder in which the working piston is accommodated, into a crankcase interior of the internal combustion engine. Alternatively, so-called blow-by gases also occur between the cylinder and the cylinder head and / or between the cylinder head and the cylinder head cover of an internal combustion engine, such as a reciprocating piston engine.Blow-by gases typically contain not only air and oil, but also combustion gases and unburned fuel components, which can negatively impact the operation of the internal combustion engine. For example, the pressure increase in the crankcase caused by the blow-by gas flow is reduced, preferably prevented, by a crankcase ventilation system that is connected to the internal combustion engine's fresh air supply via a piping system.An electrostatic precipitator according to the invention can, for example, be arranged along the flow direction within the crankcase ventilation system, in particular such that the blow-by gas stream comprising combustion gases and / or unburned fuel components is fed to the electrostatic precipitator, in which a separation, in particular oil separation, of liquid and / or solid particles, such as oil particles, takes place, so that the separated particles can be removed separately from the gas stream and the preferably purified gas stream can be fed to the fresh air supply without causing damage to the internal combustion engine. The electrostatic precipitator according to the invention is preferably an active separation device in which, as already explained above, additional energy is introduced into the separation system.

[0022] The electrostatic precipitator essentially works according to the following principle: release of electrical charges, in particular electrons; charging of the particles in an electric field; transport of the electrically charged particles to an opposite pole; discharge of the charged particles at the opposite pole; and removal of the particles from the opposite pole.

[0023] The electrostatic precipitator comprises a plurality of emission electrodes arranged in series, preferably transversely to the flow direction of the gas flow. The counter electrode and the emission electrode can each be made from a single piece. The flow direction of the gas flow generally refers to the main orientation of the gas flow through the electrostatic precipitator between an inlet into and an outlet from the electrostatic precipitator. It is clear that local turbulence and / or deflection of the gas flow can occur within the electrostatic precipitator, in particular within the separation chamber in the region of the high-voltage electric field, so that local deviations from the main flow direction of the gas flow can occur. For example, the plurality of emission electrodes can be evenly distributed, with two adjacent emission electrodes being arranged at the same distance from one another, in particular equidistant from one another.Preferably, the multiple emission electrodes are arranged in series such that a connecting line between the multiple emission electrodes runs straight. The emission electrodes, also called spray electrodes, essentially serve to emit preferably negatively charged particles. The counter electrode, also called precipitation electrode, forms the opposite pole. A high electrical voltage can be applied to the emission electrodes and the counter electrode, so that a high-voltage electrical field can be generated between the emission electrodes and the counter electrode. For example, the high voltage is in the range of 8 - 20 kV, preferably in the range of 10 - 16 kV or in the range of 11 - 14 kV. For example, the space formed between the emission electrodes and counter electrode can be referred to as a separation space.During operation of the electrostatic precipitator, a high electrical voltage is applied between the emission electrodes and counter electrode, generating a high-voltage field between the emission electrodes and counter electrode. The electrostatic precipitator is preferably operated below the breakdown or flashover voltage. The breakdown voltage, also called flashover voltage, is the voltage that must be exceeded for a voltage to pass through a material or substance, e.g. an insulator or gas. For example, the principle of charge generation underlying the electrostatic precipitator can be impact ionization. When a so-called corona inception field strength is exceeded, electrodes emerge from the emission electrode and interact with the surrounding gas molecules, forming a so-called negative corona.Free electrons present in the gas are greatly accelerated in the electrostatic field of the corona, which can lead to a gas discharge. When they hit gas molecules, further electrons can be split off or attach themselves to the gas molecules. The negative charges then move towards the oppositely charged counter electrode. When a particle-laden gas stream enters, the negatively charged charges attach themselves to the particles. Due to the electrical force of the applied DC field perpendicular to the flow direction of the gas stream, the negatively charged particles migrate towards the counter electrode, where they can release their charge again. Liquid particles, such as oil particles, can then flow or drip off the counter electrode and thus be separated from the gas stream, while a preferably purified gas stream, such as a clean air stream, can leave the electrostatic precipitator.

[0024] According to a further aspect of the present invention, the distance between two adjacent emission electrodes is in the range from 3 mm to preferably 15 mm, preferably in the range from 4 mm to 10 mm. The inventors of the present invention have discovered that, since essentially the same electrical potential is applied to the respective emission electrodes, the greatest possible potential difference to the respective surroundings of the individual emission electrodes is advantageous for igniting the individual emission electrodes. The minimum distance between two adjacent emission electrodes provided according to the invention ensures reliable ignition of the emission electrodes. The above-described maximum distance of 15 mm between two adjacent emission electrodes is selected such that reliable ignition is achieved while maintaining a high deposition rate of the electrostatic precipitator.It was found that if the distance between the individual emission electrodes is too large, areas are created where no particle deposition takes place, in particular so-called deposition-free zones are created.

[0025] According to an exemplary development of the electrostatic precipitator according to the invention, a difference between the electric field strengths applied to two adjacent emission electrodes is less than 10%, preferably less than 8%, or less than 5%.

[0026] In a further exemplary embodiment of the electrostatic precipitator according to the invention, at least two arrays of multiple emission electrodes are provided. In this case, the multiple emission electrodes per array can be arranged in series, preferably transversely to the flow direction of the gas stream. Furthermore, it can be provided that the distance between two adjacent emission electrodes of the same array and between two adjacent emission electrodes of different arrays is in the range of 3 mm to 15 mm, preferably in the range of 4 mm to 10 mm. For example, the emission electrodes of two adjacent arrays are offset from one another transversely to the flow direction, wherein, in particular, the emission electrodes of a downstream array are positioned substantially halfway between two adjacent emission electrodes of the upstream array with respect to the emission electrodes of a more upstream array.

[0027] According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, an electrostatic precipitator is provided for separating liquid and / or solid particles from a gas stream, in particular from a blow-by gas from a crankcase ventilation system of an internal combustion engine. In an exemplary application of an electrostatic precipitator according to the invention in a motor vehicle with an internal combustion engine, blow-by gases arise between a working piston and a cylinder in which the working piston is accommodated, into a crankcase interior of the internal combustion engine. Alternatively, so-called blow-by gases also occur between the cylinder and the cylinder head and / or between the cylinder head and the cylinder head cover of an internal combustion engine, such as a reciprocating piston engine.Blow-by gases typically contain not only air and oil, but also combustion gases and unburned fuel components, which can negatively impact the operation of the internal combustion engine. For example, the pressure increase in the crankcase caused by the blow-by gas flow is reduced, preferably prevented, by a crankcase ventilation system that is connected to the internal combustion engine's fresh air supply via a piping system.An electrostatic precipitator according to the invention can, for example, be arranged along the flow direction within the crankcase ventilation system, in particular such that the blow-by gas stream comprising combustion gases and / or unburned fuel components is fed to the electrostatic precipitator, in which a separation, in particular oil separation, of liquid and / or solid particles, such as oil particles, takes place, so that the separated particles can be removed separately from the gas stream and the preferably purified gas stream can be fed to the fresh air supply without causing damage to the internal combustion engine. The electrostatic precipitator according to the invention is preferably an active separation device in which, as already explained above, additional energy is introduced into the separation system.

[0028] The electrostatic precipitator essentially works according to the following principle: release of electrical charges, in particular electrons; charging of the particles in an electric field; transport of the electrically charged particles to an opposite pole; discharge of the charged particles at the opposite pole; and removal of the particles from the opposite pole.

[0029] The electrostatic precipitator comprises a plurality of emission electrodes arranged in series, preferably transversely to the flow direction of the gas flow. The "flow direction of the gas flow" generally refers to the main orientation of the gas flow through the electrostatic precipitator between an inlet into and an outlet from the electrostatic precipitator. It is understood that within the electrostatic precipitator, particularly within the separation chamber in the region of the high-voltage electric field, local turbulence and / or deflection of the gas flow may occur, resulting in local deviations from the main flow direction of the gas flow. For example, the plurality of emission electrodes may be evenly distributed, with each pair of adjacent emission electrodes being arranged at the same distance from one another, in particular equidistant from one another.Preferably, the multiple emission electrodes are arranged in series such that a connecting line between the multiple emission electrodes runs straight. The emission electrodes, also called spray electrodes, essentially serve to emit preferably negatively charged particles. The counter electrode, also called precipitation electrode, forms the opposite pole. A high electrical voltage can be applied to the emission electrodes and the counter electrode, so that a high-voltage electrical field can be generated between the emission electrodes and the counter electrode. For example, the high voltage is in the range of 8 - 20 kV, preferably in the range of 10 - 16 kV or in the range of 11 - 14 kV. For example, the space formed between the emission electrodes and counter electrode can be referred to as a separation space.During operation of the electrostatic precipitator, a high electrical voltage is applied between the emission electrodes and counter electrode, generating a high-voltage field between the emission electrodes and counter electrode. The electrostatic precipitator is preferably operated below the breakdown or flashover voltage. The breakdown voltage, also called flashover voltage, is the voltage that must be exceeded for a voltage to pass through a material or substance, e.g. an insulator or gas. For example, the principle of charge generation underlying the electrostatic precipitator can be impact ionization. When a so-called corona inception field strength is exceeded, electrodes emerge from the emission electrode and interact with the surrounding gas molecules, forming a so-called negative corona.Free electrons present in the gas are greatly accelerated in the electrostatic field of the corona, which can lead to a gas discharge. When they hit gas molecules, further electrons can be split off or attach themselves to the gas molecules. The negative charges then move towards the oppositely charged counter electrode. When a particle-laden gas stream enters, the negatively charged charges attach themselves to the particles. Due to the electrical force of the applied DC field perpendicular to the flow direction of the gas stream, the negatively charged particles migrate towards the counter electrode, where they can release their charge again. Liquid particles, such as oil particles, can then flow or drip off the counter electrode and thus be separated from the gas stream, while a preferably purified gas stream, such as a clean air stream, can leave the electrostatic precipitator.The counter electrode and the emission electrode can each be made from one piece.

[0030] According to a further aspect of the present invention, the shaft of each emission electrode is dimensioned and / or a distance between two adjacent emission electrodes is selected such that the electric field generated by the emission electrodes is substantially equal in the region of a counter-electrode-side shaft end of the emission electrodes. In particular, the shaft of each emission electrode and / or a distance between two adjacent emission electrodes can be matched to the position of the respective emission electrode along the row of multiple emission electrodes such that the electric field generated by the emission electrodes is substantially equal in the region of a counter-electrode-side shaft end of the emission electrodes.The inventors of the present invention have discovered that an increased contamination situation was observed at the outer emission electrodes, particularly in the area of ​​the beginning and end of the emission electrode row. This is because in the center of the emission electrode row, which forms between the beginning and end of an emission electrode row, the individual emission electrodes influence each other more strongly and thus change the electric field of the neighboring emission electrode. This results in uneven ignition between the neighboring emission electrodes of an emission electrode row. It was discovered that the emission electrodes near the edges, due to the lack of another neighboring emission electrode, orDue to the smaller number of neighboring emission electrodes, the emission electrodes are less strongly influenced, which leads to a higher effectiveness of the emission electrodes near the edge and, accordingly, a higher degree of contamination there. Due to the varying contamination of the individual emission electrodes along the row of emission electrodes, the effect of the inhomogeneous electric field and / or the inhomogeneous ignition of the emission electrodes is increasingly intensified. According to an exemplary development of the electrostatic precipitator according to the invention, the row of several emission electrodes has a beginning and an end, with one emission electrode being provided in particular for each beginning and end.For example, it is provided that the emission electrodes at the beginning and end of the row, in particular the emission electrodes near the edge with respect to an emission electrode row, have a larger diameter than intermediate emission electrodes, in particular emission electrodes in the middle of the row. According to an exemplary development, it is provided that the diameter of the emission electrodes preferably decreases continuously and / or in steps from the beginning of the row to the middle of the row and / or increases continuously and / or in steps from the middle of the row to the end of the row. Due to this structural variation of the individual emission electrodes of an emission electrode row, the electric field of an emission electrode row can be standardized.

[0031] In a further exemplary embodiment of the present invention, the shaft of the plurality of emission electrodes has an end on the counterelectrode side, which can face the counterelectrode. The counterelectrode side can, for example, be curved towards the counterelectrode. Furthermore, according to the invention, the row of multiple emission electrodes has a start and an end, with one emission electrode being provided for each start and end, for example, forming the start and end. According to the invention, emission electrode ends at the start and end of the row have a larger radius of curvature than emission electrode ends in the middle of the row. It can be provided that the radius of curvature of the emission electrode ends decreases continuously and / or stepwise from the start of the row to the middle of the row and / or increases continuously and / or stepwise from the middle of the row to the end of the row.

[0032] In a further exemplary embodiment, the row of multiple emission electrodes has a beginning and an end, wherein an emission electrode can be arranged at each of the beginning and end. For example, it can be provided that emission electrodes at the beginning and end of the row protrude further from a carrier holding the emission electrodes, which can be designed, for example, analogously to the previously described embodiments and exemplary developments, than intermediate emission electrodes, in particular emission electrodes located in the middle of the row. According to an exemplary development, it can be provided that the protrusion of the emission electrodes from the carrier decreases continuously and / or in stages from the beginning of the row to the middle of the row and / or increases continuously and / or in stages from the middle of the row to the end of the row.

[0033] In a further exemplary embodiment of the electrostatic precipitator according to the invention, the shaft comprises stainless steel, titanium, tungsten, nickel, an aluminum-chromium alloy or a combination thereof and / or oil-resistant material, in particular plastic.

[0034] According to an exemplary embodiment of the electrostatic precipitator according to the invention, the shaft is made of an electrically conductive plastic. Furthermore, the shaft can be made of an electrically insulating material and mixed with electrically conductive particles, which preferably ensure a minimum electrical conductivity.

[0035] According to an exemplary embodiment of the present invention, the shaft is provided at least partially with a non-stick coating. The non-stick coating can provide a self-cleaning effect and / or improved deposition of deposits.

[0036] According to an exemplary development of the present invention, the non-stick layer comprises plastic, preferably fluorine-based plastic, in particular PTFE, FEP and / or PFA, and / or a thermoplastic, preferably PEEK.

[0037] According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, an electrostatic precipitator is provided for separating liquid and / or solid particles, such as oil particles, from a gas stream, in particular from a blow-by gas of a crankcase ventilation system, of an internal combustion engine. The electrostatic precipitator essentially operates according to the following principle: release of electrical charges, in particular electrons; charging of the particles in an electric field; transport of the electrically charged particles to a counterpole; discharge of the charged particles at the counterpole; and removal of the particles from the counterpole.

[0038] The electrostatic precipitator comprises an emission electrode and a counter electrode. The counter electrode and the emission electrode can be insulated from each other and / or each made from a single piece. The emission electrode, also called the discharge electrode, essentially serves to emit, preferably negatively charged, particles. The counter electrode, also called the collecting electrode, forms the opposite pole. A high electrical voltage can be applied to the emission electrode and the counter electrode, so that a high-voltage electrical field can be generated between the emission electrode and the counter electrode. For example, the high voltage is in the range of 8-20 kV, preferably in the range of 10-16 kV or in the range of 11-14 kV.

[0039] The counter electrode has a receiver surface facing the emission electrode for receiving electrically charged particles. The receiver surface is curved in the direction of the emission electrode and continuously transitions circumferentially into a separation surface of the counter electrode facing away from the emission electrode. For example, the receiver surface and / or the transition between the receiver surface and the separation surface are / is formed in such a way that drainage obstacles, such as edges or a collection point, such as troughs, are avoided. Alternatively or additionally, the counter electrode can extend along the row of emission electrodes, preferably in a straight line. Furthermore, the counter electrode can have a cross-section with a receiver surface facing the emission electrodes for receiving electrically charged particles, which is curved in the direction of the row of emission electrodes.Furthermore, the cross-section of the counter electrode is constant along its longitudinal extent, at least in the region of the receiver surface. Alternatively or additionally, the counter electrode can be offset relative to the emission electrode, preferably in or against the flow direction of the gas stream, such that an angle exists between the direction of gravity and a shortest distance between the counter electrode and the emission electrode.

[0040] According to a further aspect of the present invention, which can be combined with the preceding aspects and exemplary embodiments, an electrostatic precipitator is provided for separating liquid and / or solid particles, such as oil particles, from a gas stream, in particular from a blow-by gas of a crankcase ventilation system, of an internal combustion engine. The electrostatic precipitator essentially operates according to the following principle: release of electrical charges, in particular electrons; charging of the particles in an electric field; transport of the electrically charged particles to a counterpole; discharge of the charged particles at the counterpole; and removal of the particles from the counterpole.

[0041] The electrostatic precipitator comprises an emission electrode and a counter electrode. The counter electrode and the emission electrode can be insulated from each other and / or each made from a single piece. The emission electrode, also called the discharge electrode, essentially serves to emit, preferably negatively charged, particles. The counter electrode, also called the collecting electrode, forms the opposite pole. A high electrical voltage can be applied to the emission electrode and the counter electrode, so that a high-voltage electrical field can be generated between the emission electrode and the counter electrode. For example, the high voltage is in the range of 8-20 kV, preferably in the range of 10-16 kV or in the range of 11-14 kV.

[0042] The counter electrode has a receiver surface facing the emission electrode for receiving electrically charged particles. According to one aspect of the present invention, the receiver surface is at least partially provided with an anti-adhesion layer. The anti-adhesion layer can be designed, for example, to reduce frictional resistance between the particles impinging on the receiver surface and the receiver surface. For example, the anti-adhesion layer reduces an adhesion force between the receiver surface and the electrically charged particles, which can also be referred to as filtration residues. Furthermore, it can be provided that the anti-adhesion layer is at least partially and / or selectively intermixed with electrically conductive particles and / or has a layer thickness of less than 200 nm.This applies a certain minimum electrical conductivity to the anti-adhesion layer, thus ensuring the intended operation of the electrostatic precipitator and reliably forming the high-voltage electric field. Finally, the measure according to the invention increases the deposition rate. For example, the electrically conductive particles can be embedded in the anti-adhesion layer. For example, it is possible to apply the anti-adhesion layer to the counter electrode by spraying, printing, or by a rolling process. Furthermore, it is possible to manufacture the counter electrode in such a way that the deposition surface is made from the material of the anti-adhesion layer during production.

[0043] Preferred embodiments are given in the subclaims.

[0044] In the following, further properties, features and advantages of the invention will become clear by describing preferred embodiments of the invention with reference to the accompanying exemplary drawings, in which: Fig. 1 a schematic diagram of an example of the formation of blow-by gases and the installation situation of electrostatic precipitators according to the invention; Fig. 2 is a perspective view of a first embodiment of an electrostatic precipitator according to the invention; Fig. 3 a perspective view of a section of the electrostatic precipitator according to Fig. 2; Fig. 4 a detailed side view of the electrostatic precipitator according to the Fig. 2 and Fig. 3; Fig. 5 is a perspective view of another exemplary embodiment of an electrostatic precipitator according to the invention; Fig. 6 a perspective view of a section of the electrostatic precipitator according to Fig. 5; Fig. 7 a detailed side view of the electrostatic precipitator according to the Fig. 5 and Fig. 6; Fig. 8 is a perspective view of another embodiment of an electrostatic precipitator according to the invention; Fig. 9 a perspective view of a section of the electrostatic precipitator according to Fig. 8; Fig. 10 a detailed side view of the electrostatic precipitator according to the Fig. 8 to 9; Fig. 11 is a schematic front view of a section of an electrostatic precipitator according to the invention; Fig. 12 is a perspective view of another embodiment of an electrostatic precipitator according to the invention; and Fig. 13 a perspective view of a section of the electrostatic precipitator according to Fig. 12.

[0045] In the following description of exemplary embodiments, an electrostatic precipitator according to the invention for separating liquid and / or solid particles from a gas stream, in particular from a blow-by gas of a crankcase ventilation of an internal combustion engine, is generally provided with the reference number 1.

[0046] Fig. 1 shows a schematic diagram of the installation situation of an electrostatic precipitator 1 according to the invention in a crankcase ventilation system 100. The crankcase ventilation system 100 comprises a crankcase 103 with a flow outlet opening 105 through which blow-by gas can escape from the crankcase 103, and an electrostatic precipitator 1 according to the invention fluidically connected to the flow outlet opening 105. As in Fig. 1, the fluidic connection between the electrostatic precipitator 1 and the flow outlet opening 105 can be established via a piping system, such as an outlet line 107, which connects the flow outlet opening 105 of the crankcase 103 to a flow inlet opening 109 of the electrostatic precipitator 1. Alternatively, the electrostatic precipitator 1 can be mounted on the crankcase 103 in such a way (not shown) that the flow inlet opening 109 corresponds to the flow outlet opening 105 of the crankcase 103. The arrow with the reference number 111 indicates that blow-by gas can flow from the crankcase 103 into the electrostatic precipitator 1.

[0047] Furthermore, Fig. 1 shows an example of the generation of blow-by gas and the general installation situation of the electrostatic precipitator 1. It depicts an internal combustion engine 113 that is fluidly coupled to a fresh air supply 115, an exhaust gas discharge 117, and the crankcase ventilation system 100. The internal combustion engine 1 comprises a cylinder head 119, a cylinder 121, and the crankcase 103. A piston 123 is guided axially within the cylinder 121, which delimits a displacement 125 from a crankcase interior 127. Sealing rings (not shown) are provided between the piston 123 and the cylinder 122 to seal the displacement 125 from the crankcase interior 127. Nevertheless, combustion gases and / or unburned gases flow between piston 123 and cylinder 121 from the displacement 125 into the crankcase interior 127. The resulting gas flow is also referred to as blow-by gas flow and includes not only air and oil but also combustion gases and unburned fuel components.

[0048] To prevent a pressure increase in the crankcase 103, the gas flow is discharged from the crankcase 103 via the crankcase ventilation 100 and fed into the fresh air supply. The crankcase ventilation 100 comprises, in particular, the fluidic coupling of the flow outlet opening 105 and the flow inlet opening 109 of the electrostatic precipitator 1. The electrostatic precipitator 1 is further fluidically connected to the crankcase 103 via a return line 129 for allowing separated particles, such as oil, to flow back. In particular, the return line 129 fluidly connects a return outlet 131 of the electrostatic precipitator 1 to a return inlet 133 of the crankcase 103. Downstream of the electrostatic precipitator 1, a return line 135 fluidly connects the electrostatic precipitator 1 to the fresh air supply 115 in order to supply the fresh air supply 115 with a gas stream cleaned of particles.The resulting fresh air flow 137, which may be a mixture of the purified gas flow coming from the electrostatic precipitator 1 and a gas flow drawn in from the environment and purified by an air filter 139, is compressed by a compressor wheel 141 and fed to the internal combustion engine 113 via the cylinder head 119 via a charge air cooler 143 and a throttle valve 145. Combustion gases that do not enter the crankcase 103 between the piston 123 and the cylinder 121 are discharged into the environment as exhaust gas 147 via an exhaust gas discharge (not shown).

[0049] It is clear that the installation situation of the electrostatic precipitator 1 according to the invention in the case of use as an oil separator in the internal combustion engine is not limited to the Fig. 1 and is not limited to use in a crankcase ventilation system 100. For example, the electrostatic precipitator can also be used to separate particles from gas streams that escape from the internal combustion engine 113 between the cylinder 121 and the cylinder head 119 and / or between the cylinder head 119 and the cylinder head cover. Another possible area of ​​application is in the fresh air supply 115 and / or in the exhaust gas discharge 117, which can be fluidly coupled to one another, in particular via the compressor wheel 141 and the shaft connecting the turbine wheel (not shown).

[0050] Based on the Fig. 2 to 13, exemplary embodiments of electrostatic precipitators 1 according to the invention are explained in more detail.

[0051] The electrostatic precipitator 1 is according to a first embodiment in the Fig. 2 to 4. The electrostatic precipitator 1 comprises a housing 5 defining or delimiting a separation chamber 3, which has a base 7, a roof 9 opposite the base 7, and two opposite side walls 11, 13, each connecting the base 7 to the roof 9. A gas stream 17, for example blow-by gas from a crankcase ventilation system, enters the separation chamber 3 via an inlet opening 15. The outlet opening 19 is arranged opposite the inlet opening 15, through which the gas stream 17, which is then referred to as the purified gas stream 21, can leave the separation chamber 3 again. The housing 5 delimiting the separation chamber 3 is not limited to a specific geometry, according to the Fig. 2 to 10, however, are formed as a hollow pipe section with a substantially rectangular cross-section.

[0052] The electrostatic precipitator 1 further comprises a plurality of emission electrodes 23 and a plurality of counter electrodes 25. According to the embodiments Fig. 1, the electrostatic precipitator 1 comprises 6 counter electrodes 25. A high voltage electrical voltage can be applied or is applied to the emission electrodes 23 and the counter electrodes 25, so that a high voltage electrical field can be generated or is generated between the emission electrodes 23 and the counter electrodes 25. In Fig. 2 that the counterelectrodes 25 are realized in sections as essentially rectilinear rods or tubes, the longitudinal extension direction of which, indicated by the reference number Q, is oriented transversely, in particular perpendicularly, to the main flow direction S of the incoming and flowing gas stream 17. The counterelectrodes 25 are essentially identical and arranged at a distance from one another in the flow direction S. At both ends, a curved section 31, preferably made in one piece with the rod section 29, adjoins the essentially rectilinear rod section 29 of the counterelectrodes 25, wherein the rod section 29 merges into the curved section 31 essentially without edges, projections, and / or steps. The curved section 31 finally opens into the base 7 of the housing 5. In Fig. 2 it can also be seen that the curved section 31 forms a curvature angle of more than 90°, so that a connection point 33 of the counter electrode 25 with the base 7 is offset inwards in the transverse direction Q with respect to the longitudinal extension direction of the counter electrode 25 with respect to an outermost curvature point 35 of the curved section 31.

[0053] The counter electrode 25 comprises a receiver surface 37 facing the emission electrodes 23 for receiving electrically charged particles from the gas stream 17. The receiver surface 37 is curved in the direction of the emission electrodes 23 and continuously transitions into a separation surface 39 facing away from the emission electrode 23. The preferred shape of the counter electrodes 25 as essentially fully cylindrical rods or tubes enables the separated particles that strike the receiver surface 37 to leave the receiver surface 37 at all times without obstruction, in particular to run off or drip off it and reach the separation surface 39.The counter electrodes 25 extend with a substantially constant cross section and a receiver surface 37 curved in the direction of the emission electrodes 23 transversely to the flow direction S in the flow direction Q and with a separation surface 39 facing away from the emission electrodes 23, which is inclined opposite to the receiver surface with preferably the same radius of curvature.

[0054] In Fig. 3 that two groups of three counterelectrodes 25 are provided, each arranged at a constant distance from one another. A group of emission electrodes 23 is assigned to each of the two groups of counterelectrodes 25. The emission electrodes 23 have a substantially elongated, needle-like shape and extend from the housing roof 9 substantially rectilinearly and in the direction of gravity G into the separation chamber 3 and in the direction of the counterelectrodes 25. The two groups of emission electrodes 23 each have two arrays of emission electrodes 23, which are arranged in a row transverse to the flow direction S of the gas stream 117 and spaced apart from one another. Between the respective groups of emission electrodes 23 or counterelectrodes 25, a free space 41 is formed, which, viewed in the flow direction S, is larger than the respective distance between two adjacent counterelectrodes 25 or rows of emission electrodes 23.

[0055] In Fig. 4, which is a side view of the electrostatic precipitator 1 according to the Fig. 2 and Fig. 3, a further aspect of the present invention is shown. Firstly, it can be seen that the individual rod- or tubular counterelectrodes 25 extend essentially completely rectilinearly in the transverse direction Q. Furthermore, it can be seen that the emission electrodes 23 have an essentially cylindrical, elongated shaft 43, each of which merges into a funnel- or conical tip 45, at which electrons leave the emission electrodes 43. The rows of emission electrodes 23 forming in the transverse direction Q are each positioned with respect to the counterelectrodes 25 and offset in the flow direction S with respect to the counterelectrodes 25 such that an angle α exists between the gravitational direction G and a shortest distance, indicated by the reference symbol a, between the counterelectrode 25 and the emission electrode 23.The emission electrode needle tips 45 thus each point into a free space existing between two adjacent counter electrodes 25. Due to the offset between emission electrodes 23 and counter electrodes 25 in the flow direction S, a so-called through-flow sector is formed between each two adjacent counter electrodes 25, into which the deposits detaching from the emission electrodes 23 can pass past the counter electrodes.

[0056] Based on the Fig. 5 to 7, a further exemplary embodiment of an electrostatic precipitator 1 according to the invention is explained. The same or similar components are provided with the same or similar reference numerals. To avoid repetition, only the components which differ from the first embodiment according to the Fig. 2 to 4 resulting differences are discussed.

[0057] The essential difference of the embodiment according to the Fig. 5 to 7 lies in the structure of the counter electrodes 25. As already in the embodiment according to the Fig. 2 to 4, the counter electrodes 25 extend with a substantially constant cross section and a receiver surface 37 curved in the direction of the emission electrodes 23 transversely to the flow direction S in the flow direction Q and with a separation surface 39 facing away from the emission electrodes 23. The counter electrodes 25 of the embodiment according to the Fig. 5 to 7, however, do not have a curved section 31 at the ends which is bent or curved to form a ground contact or connection point 33 with the ground 7. In particular, Fig. 5 that the essentially fully cylindrical, rod- or tubular counterelectrodes 25 are rounded at both opposite ends, forming hemispherical end sections 47. This means that the tubular sections 29 transition into the spherical end sections 47 without edges, projections, and / or steps. A radius of curvature of the curved end section 47 can essentially correspond to the radius of curvature of the tubular section 29 of the counterelectrode 25.

[0058] Furthermore, the counter electrodes each have two feet 49, which extend from a bottom side of the counter electrodes 25, i.e. from the separation surfaces 39, essentially in the direction of gravity G towards the bottom 7 of the housing 5 and realize a ground support or a ground contact. The embodiments according to the Fig. 2 to 4 and 5 to 7 have in common that the counter electrodes 25, in particular their tube sections 29, are arranged at a certain distance from the base 7. In the embodiment according to the Fig. 2 to 4, this is achieved by the bent curved sections 31, which thus provide ground support at the ends. When designed according to the Fig. 5 to 7, this is realized by the feet 49 and controlled by a height of the feet 49. Furthermore, the description regarding the design of the Fig. 2 to 4.

[0059] Based on the Fig. 8 to 10, a further exemplary embodiment is described. Identical or similar components are provided with identical or similar reference numerals. To avoid repetition, reference is made essentially to the details relating to the preceding embodiments according to the Fig. The differences resulting from 1 to 7 are discussed.

[0060] The essential difference of the embodiment according to the Fig. 8 to 10 lies in the design of the counter electrodes 25. Unlike the embodiments according to the Fig. 2 to 7, in which the counter electrodes 25 of a group of counter electrodes 25 are manufactured as separate components, the counter electrodes 25 of the Fig. 8 to 10, a serpentine structure comprises three counterelectrode segments in one component, each of which is formed by the substantially fully cylindrical tube sections 29; this means that the serpentine counterelectrodes 25 are made from a single piece. For this purpose, the counterelectrodes 25 have a support base 51 close to the flow inlet, which has a substantially cylindrical cross-section and transitions continuously, without edges, projections, or interruptions, into an angle piece 53, which again transitions seamlessly, in particular without edges and / or projections, into a tube section 29 of the counterelectrode 25, which extends in the transverse direction Q, as described with reference to the previous embodiments. At the opposite end of the tube section 29 with respect toof the support foot 51, the tube section 29 opens into a U-piece 55, by means of which a reversal of 180° is realized, so that another tube section 29 is produced, which extends in the transverse direction Q through the separation chamber 3. In this respect, a substantially identical structure of the counter electrodes 25 results, with the difference that two adjacent tube sections 29, which are essentially relevant for the separation of particles, are connected to one another by means of a U-piece 55 and thus are not separate counter electrode elements 25.

[0061] As particularly in Fig. 8, the emission electrodes 23 are arranged with respect to the serpentine counter electrode groups 25 in such a way that the emission electrodes 23 are offset with respect to the transverse direction Q to the U-pieces 55, so that with respect to the outermost emission electrodes 23 and the U-pieces 55 viewed in the transverse direction Q there is also an angle β with respect to the gravitational direction G and a shortest distance between the emission electrode tip 45 and the U-piece 55.

[0062] A central tube section 29 adjoining the upstream tube section 29 again opens into a 180° U-piece 55 at one of its ends, so that, starting from the U-piece 55, another downstream tube section 29 is formed, extending in a straight line and having the same cross-section and orientation. This section opens into an angled piece 53 at the level of the U-piece 55 with respect to the transverse direction Q, with a transition again being realized without interruption, which finally merges into a support base 51. The downstream group of counterelectrodes 25 is again formed by an identical serpentine counterelectrode unit 25. The upstream counterelectrode element 25 of the downstream counterelectrode group is arranged with respect to the upstream counterelectrode group in such a way that the upstream support foot 51 of the downstream counterelectrode group is on the same side with respect tothe transverse direction Q as the downstream support foot 51 of the upstream counter electrode group. Furthermore, reference can be made to the description relating to the embodiments according to the . Fig. 2 to 7.

[0063] Based on Fig. Figure 11 schematically illustrates the high voltage between the emission electrode 23 and the counter electrode 25. The application of a high voltage is schematically indicated by the two poles 57, 59. The operation of the electrostatic precipitator is described in more detail below. Due to the high voltage applied across the poles 57, 59, a high voltage field is formed between the emission electrode 23 and the counter electrode 25. The electrostatic precipitator 1 is preferably operated below the breakdown or flashover voltage. For example, the electrostatic precipitator 1 can be operated such that, as shown in Fig. 11, electrons emerge from the emission electrode 23 and interact with the surrounding gas molecules, creating a negative corona, which in Fig. 11 by reference numeral 61. Free electrons present in the gas are strongly accelerated in the electric field of corona 61, which can cause a gas discharge. Upon impact with gas molecules, additional electrons can be split off or attach to the gas molecules.

[0064] The negative charges then move towards the oppositely charged counter electrons 25 with respect to the emission electrodes 23, forming a screen-like or cone-like ionization region 63 (also called ion cloud). The curtain-like ionization region 63 is arranged, as shown in Fig. 11, essentially completely encircling the receiver surface 37, which faces the emission electrode 23. The negatively charged particles from the gas stream migrate transversely to the flow direction S of the gas stream in the direction of the receiver surface 37, by which they are attracted, onto which they impact, and onto which they release their charge again. The liquid particles, such as oil particles, subsequently flow circumferentially from the receiver surface 37 due to its concavely curved shape and can then drip off the counter electrode 25 and / or migrate further along the outside of the counter electrode 25 to the separation surface 39, which faces away from the emission electrode and is curved in the direction away from the emission electrode 23, specifically with the same radius of curvature as the receiver surface 37. In cross-section, the counter electrode 25 has a circular shape according to the exemplary embodiments.At the separation surface 39, particles 65 are schematically depicted which were separated from the gas flow and migrated along the receiver surface 37 to the separation surface 39 on the outside of the counter electrode 25.

[0065] In the Fig. 12 and Fig. Figure 13 shows another exemplary embodiment of an electrostatic precipitator 1 according to the invention. Identical or similar components are provided with identical or similar reference numerals.

[0066] The electrostatic precipitator according to Fig. 12 to 13 comprises a housing 67, which has an inlet channel or inlet channel section 69 for introducing a gas stream 17 into the electrostatic precipitator 1. The inlet channel 69 is formed as a substantially internally cylindrical tube section, in which a flow direction of the raw gas stream 17 is oriented substantially perpendicular to the main flow S within the separation chamber 3 of the electrostatic precipitator 1. The flow direction in Fig. 12 is to be understood merely as an example. It is also possible for the flow to be introduced via the channel section designated by reference numeral 73 and discharged via the channel section designated by reference numeral 69. Furthermore, the housing 67 comprises a further outlet channel section 73, formed essentially identically to the channel section 69, through which the purified gas flow can be discharged from the electrostatic precipitator 1. The housing 67 can, for example, be formed from two housing halves 75 and 77 to be fastened to one another, with the upper housing half 75 forming the cover and the lower housing half 77 forming the base. Within the separation chamber 3 of the electrostatic precipitator 1, a counterelectrode 25 designed as a flat plate is arranged on the base housing part 77. The plate-like counterelectrode 25 is arranged elevated with respect to the surrounding inner surface 79 of the base housing part 77.Particles separated from the gas stream are attracted to the counter electrode 25 and can flow or drip off it. They can be removed via a particle or fluid outlet 81 connected to a bypass channel (not shown) and, for example, returned to a corresponding fluid circuit. For example, if they are oil particles, the separated oil particles can be returned to the oil circuit in the crankcase 103.

[0067] Opposite the plate-like counter electrode 25, an emission electrode array 23 is provided, which is arranged on an inner side 83 of the cover housing part 75. The individual emission electrodes 23 extend from the inner side 83 essentially in the direction of gravity G towards the plate counter electrode 25. As shown in particular in Fig. 13, the emission electrode array 23 has four rows of emission electrodes 23 extending essentially in the transverse direction Q transverse to the flow direction S, wherein the direction of extension of the individual rows is essentially parallel to each other. Fig. 12 and Fig. 13, in which only the upper housing part 75 is shown for simplified illustration, it can be seen that the planar extension of the flat plate-like counter electrode 25 is larger than an outer circumferential dimension of the emission electrode field 23.

[0068] According to the detailed view XIII in Fig. 13, it is indicated that the individual emission electrodes 23 of an emission electrode row are arranged at a regular, constant distance from one another. For example, it can be provided that an emission electrode length 1 is at least 2 mm and preferably at most 8 mm. Furthermore, it can be provided that a distance x between two adjacent emission electrodes 23 is in the range from 3 mm to preferably 15 mm, at least with respect to an emission electrode row. In particular, in Fig. 13 also shows that the emission electrodes 23 of two adjacent emission electrode rows are offset from one another in the transverse direction Q, so that, for example, one emission electrode 23 is positioned halfway between two adjacent emission electrodes 23 of an upstream emission electrode row. For example, the emission electrodes 23 can be made of a carrier with an electrical conductivity of less than 10-8 S * cm -1 The support 85 can, for example, form the underside 83 of the housing upper part 75. For example, the support 85 comprises plastic, preferably thermosetting plastic and / or potting compound, such as epoxy resin or silicone. The housing upper part 75 has, on an inner side, on which the support 85 is also arranged, flow guides 87, 89 adjacent to the support 85, at which the fluid flow is deflected. For example, the flow guide 87 is assigned to the inlet channel section 69, and the flow guide 89 is assigned to the outlet channel section 73.

[0069] The features disclosed in the above description, the figures and the claims may be important both individually and in any combination for the realization of the invention in the various embodiments. List of reference symbols 1 electrostatic precipitator 3 Separation room 5 housings 7 Bottom housing part 9 Roof housing part 11, 13 side wall 15 Entrance opening 17 Gas flow 19 Exit opening 21 Gas flow 23 Emission electrode 25 Counter electrode 29 rod section 31 Curvature section 33 connection point 35 Curvature point 37 Receiver surface 39 Separation area 41 open space 43 shaft 45 lace 47 final section 49 feet 51 Support foot 53 Angle piece 55 U-piece 57, 59 pole 61 Corona 63 Ionization range 65 particles 67 housings 73 Inlet duct section 69 Exhaust duct section 75.77 Housing half 79 interior surface 81 Particle or fluid drainage 83 Inside 85 carriers 87, 89 Flow guidance 100 Crankcase ventilation system 103 Crankcase 105 Flow outlet opening 107 Outlet line 109 Flow inlet opening 111 Blow-by gas flow 113 Internal combustion engine 115 Fresh air supply 117 Exhaust gas removal 119 cylinder head 121 cylinders 123 pistons 125 displacement 127 Crankcase interior 129 Return line 131 Return outlet 133 Return inlet 135 Return line 137 Fresh air flow 139 Air filter 141 Compressor wheel 143 intercooler 145 throttle valve 147 exhaust α, β angle a shortest distance 1 length x distance G Direction of gravity S Flow direction Q transverse direction

Claims

[1] Electrostatic precipitator (1) for separating liquid and / or solid particles from a gas stream, in particular from a blow-by gas of a crankcase ventilation system of an internal combustion engine, comprising: - an emission electrode (23) with an elongated shaft (43) and a counter electrode (25), to which an electrical high voltage can be applied, so that an electrical high voltage field can be generated between the emission electrode (23) and the counter electrode (25); wherein the emission electrode (23) is supported by a carrier (85) with an electrical conductivity of less than 10 -8 S*cm -1 held, dimensioned and cast by carrier casting material such that the shaft (43) protrudes by at least 0.5 mm and preferably at most 8 mm from the carrier (85) after solidification of the carrier casting material. [2] Electrostatic precipitator (1) according to claim 1, wherein the carrier (85) has a substantially flat surface facing the counter electrode (25) and / or wherein the carrier (85) comprises plastic, preferably thermosetting plastic, and / or potting compound, such as epoxy resin or silicone. [3] Electrostatic precipitator (1) according to one of claims 1 to 2, wherein the emission electrode (23) is pre-mounted on a circuit board. [4] Electrostatic precipitator (1) according to one of the preceding claims, further comprising: - a plurality of emission electrodes (23) arranged in series and having an elongated shaft (43), to which a high-voltage electrical field can be applied, so that the high-voltage electrical field can be generated between the emission electrodes (23) and the counter electrode (25); wherein a distance between two adjacent emission electrodes (23) is in the range from 3 mm to 15 mm, preferably in the range from 4 mm to 10 mm. [5] Electrostatic precipitator (1) according to claim 4, wherein a difference between the electric field strengths applied to two adjacent emission electrodes (23) is less than 10%, preferably less than 8% or less than 5%. [6] Electrostatic precipitator (1) according to one of claims 4 to 5, wherein at least two arrays of a plurality of emission electrodes (23) are provided, which are arranged in series per array, preferably transversely to the flow direction of the gas flow, wherein the distance between two adjacent emission electrodes (23) of the same array and between two adjacent emission electrodes (23) of different arrays is in the range of 3 mm to 15 mm. [7] Electrostatic precipitator (1) for separating liquid and / or solid particles from a gas stream, in particular from a blow-by gas of a crankcase ventilation system of an internal combustion engine, comprising: - a plurality of emission electrodes (23) arranged in series with an elongated shaft (43) and a counter electrode (25), to which a high electrical voltage can be applied, so that a high-voltage electrical field can be generated between the emission electrodes (23) and the counter electrode (25);wherein the shaft (43) of each emission electrode (23) is dimensioned in such a way and / or a distance between two adjacent emission electrodes (23) is selected in such a way, in particular is matched to the position of the respective emission electrode (23) along the row of emission electrodes (23), that the electric field generated by the emission electrodes (23) in the region of a counter-electrode-side shaft end of the emission electrodes (23) is substantially the same size, wherein the row of several emission electrodes (23) has a beginning and an end, wherein emission electrodes (23) at the beginning and end of the row have a larger diameter than emission electrodes in the middle of the row; [8] Electrostatic precipitator (1) according to claim 7, wherein the diameter of the emission electrodes (23) decreases continuously and / or stepwise from the beginning of the row to the middle of the row and / or increases continuously and / or stepwise from the middle of the row to the end of the row. [9] Electrostatic precipitator (1) according to one of claims 7 to 8, wherein the shaft (43) has a counter-electrode-side end which is curved towards the counter-electrode (25), wherein emission electrode ends at the start and end of the row have a larger radius of curvature than emission electrode ends in the middle of the row, wherein in particular the radius of curvature of the emission electrode ends decreases continuously and / or in steps from the start of the row to the middle of the row and / or increases continuously and / or in steps from the middle of the row to the end of the row. [10] Electrostatic precipitator (1) according to one of claims 7 to 9, wherein the emission electrodes (23) at the start and end of the row protrude further from a support (85) holding the emission electrodes (23) than the emission electrodes in the middle of the row, wherein in particular the protrusion of the emission electrodes (23) from the support (85) decreases continuously and / or in steps from the start of the row to the middle of the row and / or increases continuously and / or in steps from the middle of the row to the end of the row. [11] Electrostatic precipitator (1) according to one of the preceding claims, wherein the shaft (43) comprises stainless steel, titanium, tungsten, nickel, an aluminum-chromium alloy, or combinations thereof, and / or oil-resistant material. [12] Electrostatic precipitator (1) according to one of the preceding claims, wherein the shaft (43) is made of an electrically conductive plastic, or is made of an electrical insulating material and is mixed with electrically conductive particles. [13] Electrostatic precipitator (1) according to one of the preceding claims, wherein the shaft (43) is provided at least in regions with an anti-stick layer. [14] Electrostatic precipitator (1) according to claim 13, wherein the anti-adhesion layer comprises plastic, preferably fluorine-based plastic, in particular PTFE, FEP and / or PFA, and / or a thermoplastic, preferably PEEK.

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