DE102018201628A1 - Particle pre-separator - Google Patents

Abstract

A particle pre-separator for exhaust particles for separating particles from an exhaust gas stream in an exhaust gas tract of a motor vehicle is provided which comprises at least one ionization device and at least one electrostatically charged collector, as well as an arrangement of the particle pre-separator with a particle filter in an exhaust gas tract and a method for separating particles from the exhaust gas of an internal combustion engine.

Description

The invention relates to a Partikelvorabscheider for exhaust particles, an arrangement of Partikelvorabscheiders with a particulate filter in an exhaust system and a method for separating particles from the exhaust gas of an internal combustion engine.

The exhaust gases of internal combustion engines, especially of diesel engines, contain not only gases but also solid particles. These particulates are especially soot particles that can be used under fuel-rich conditions, e.g. under full load due to incomplete combustion of the fuel. The emission of such, particulate matter-forming particles should be kept within legal limits. For this purpose, particulate filters are used in the exhaust tract, which filter the soot particles from the exhaust gas.

Particulate filters are known to the person skilled in the art. In motor vehicles, e.g. particularly often used wall-mounted ceramic modules. Particulate filters filter particles from the exhaust stream that are deposited in the filter. The collected particles must be burned regularly. However, the combustion residues clog the filter over time, so it must be replaced when a certain operating time is reached. Particulate filters are expensive. It is the task to increase the service life and thus the life of a particulate filter.

This object is achieved with a Partikelvorabscheider with the features of claim 1. Further advantageous embodiments and embodiments of the invention will become apparent from the dependent claims and claims, the figures and the embodiments. The embodiments of the invention can be combined with each other in an advantageous manner.

A first aspect of the invention relates to a particle pre-separator for separating particles from an exhaust gas flow in an exhaust tract of a motor vehicle, comprising at least one ionization device and at least one electrically charged area-like collecting device, which is designed to charge said particles and to collect them from the exhaust gas flow said Partikelvorabscheider is connected to at least a voltage source and a control device.

The particle pre-separator according to the invention is advantageously suitable for collecting particles from the exhaust gas before they can reach a downstream particle filter. As a result, the particulate loading of the exhaust gas is reduced and fewer particles are deposited in the actual particulate filter. By collecting the particles in front of the particle filter, the service life of the particle filter can be significantly increased, since the particle filter must be regenerated less frequently. This increases its service life.

The ionization device is designed to charge the particles in the exhaust gas electrically. The structure and operation of an ionization device are known in the art. The ionization device preferably comprises at least one electrode, e.g. a spray electrode or corona electrode. In this case, by means of the negative electrode by applying a high voltage between the ionization device and the collecting device can form a corona discharge, are charged by the gas particles in the vicinity of the electrode. The charging of particles in the exhaust gas flow occurs by collision of the flowing particles in the exhaust gas with free electrons and negatively charged gas ions (positively charged gas ions, which are produced by the emission of electrons, are neutralized by the negatively charged electrode).

The electrically negatively charged particles can then be separated from the exhaust gas at the collecting device. The collecting device of the particle preseparator according to the invention preferably comprises at least one electrostatically charged plate. To attract the charged particles, the collection plate has a positive charge. The electrically negatively charged particles migrate through the applied electrical force of the applied electric field to the electrostatically charged plate of the collector. There, the particles release their electrical charge and are bonded to the collector by adhesive forces, e.g. by adhesive forces and / or by the electric field strength within the layer of already adhering particles. A certain length of the collecting device in the flow direction of the exhaust gas is advantageous, so that the charged particles can accumulate transversely to the flow direction of the exhaust gas even at low drift velocity of the particles.

At least one heating device is preferably arranged in the collecting device. The heater is advantageously a heating wire made of a metallic material. The heater is advantageous because it enables ignition and successive burning of the collected particles to regenerate the collector. It is particularly preferred if the heating device is designed to glow when a specific voltage and current are applied in order to ignite the deposited particles. The corresponding conditions are inherently specified by the material used. The person skilled in the art, the necessary conditions are known to a to heat certain material of the heater.

Preferably, a sensor for determining the particle loading is arranged in the region of the collecting device. The sensor may e.g. evaluate the effect of the electric field that is being contained by the particle loading. The particle loading can alternatively or additionally also be determined model-based, e.g. based on operating time, operating conditions and the time since the last regeneration.

A second aspect of the invention relates to an arrangement of an internal combustion engine having an exhaust gas tract in which a particle pre-separator according to the invention is arranged upstream of a particle filter. The arrangement advantageously allows removal of particles from the exhaust stream before entering the particulate filter. This is particularly advantageous under conditions with an increased proportion of soot particles in the exhaust gas, e.g. at a high load or when starting the internal combustion engine. The lifetime of the particulate filter is advantageously increased by the upstream of a Partikelvorabscheiders, because a total of fewer particles are stored in the particulate filter, and therefore this must be regenerated less frequently.

A third aspect of the invention relates to a method for removing solid constituents, in particular soot particles, from the exhaust gas of an internal combustion engine by means of an arrangement according to the invention, wherein particles in the exhaust gas are charged by means of the ionization device and deposited on the collecting device. The advantages of the method according to the invention correspond to the advantages of the particle pre-separator according to the invention.

• - Ermitteln der Partikeldichte im Abgas,
• - Einschalten des Partikelvorabscheiders bei Erreichen eines ersten Schwellenwertes der Partikeldichte im Abgas,
• - Abschalten des Partikelvorabscheiders, wenn die Partikelbeladung wieder unter den ersten Schwellenwert gesunken ist.

In the process, the particle pre-separator can be switched on constantly. Preferably, the particle pre-separator is activated depending on the operating conditions, the method comprising the steps of:

• Determining the particle density in the exhaust gas,
• Switching on the particle pre-separator when a first threshold value of the particle density in the exhaust gas is reached,
• - Disconnect the particle pre-separator when the particle load has dropped below the first threshold again.

The particle density can be detected by sensors, e.g. resistive particle sensors. The particle density corresponds to the particle concentration in the exhaust gas. It can also be determined model-based. The first threshold is determined by those skilled in the art and refers to a value of particle density that is considered to be unfavorably high. Activation of the particle precleaner is advantageous for e.g. in case of high particulate matter, do not allow the particulate filter to clog too fast if its function is to be ensured.

• - Ermitteln der Partikelbeladung auf mindestens einer Platte in der Sammeleinrichtung,
• - Einschalten der Heizeinrichtung bei Erreichen eines zweiten Schwellenwertes der Partikelbeladung,
• - Abschalten der Heizeinrichtung, wenn die Partikel auf der Platte gezündet wurden.

Preferably, in the method of the invention, the collector regenerates the collector by causing the heater to anneal and ignite the deposited particles on the collector and successively burned. Preferably, the collector is regenerated when the particulate deposits have reached a second threshold. The following steps are included:

• Determining the particle loading on at least one plate in the collecting device,
• Switching on the heating device when a second threshold value of particle loading is reached,
• - Shut down the heater when the particles have been ignited on the plate.

The second threshold is determined by those skilled in the art and refers to a level of particulate matter that is considered to be unfavorably high for a collector function.

• 1 eine Anordnung eines Abgastrakts einer Brennkraftmaschine mit einer Ausführungsform des erfindungsgemäßen Partikelvorabscheiders.
• 2 eine Darstellung der Ausführungsform des erfindungsgemäßen Partikelvorabscheiders gemäß 1.
• 3 eine Querschnittsdarstellung einer Ausführungsform des erfindungsgemäßen Partikelvorabscheiders.
• 4 eine Querschnittsdarstellung einer Ausführungsform des erfindungsgemäßen Partikelvorabscheiders.
• 5 eine schematische Darstellung einer Ausführungsform einer Sammeleinrichtung des erfindungsgemäßen Partikelvorabscheiders.
• 6 ein Flussdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.
• 7 ein Flussdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to FIGS. Show it:

• 1 an arrangement of an exhaust tract of an internal combustion engine with an embodiment of the invention Partikelvorabscheiders.
• 2 a representation of the embodiment of the invention according to Partikelvorabscheiders 1 ,
• 3 a cross-sectional view of an embodiment of the Partikelvorabscheiders invention.
• 4 a cross-sectional view of an embodiment of the Partikelvorabscheiders invention.
• 5 a schematic representation of an embodiment of a collecting device of the Partikelvorabscheiders invention.
• 6 a flowchart of an embodiment of the method according to the invention.
• 7 a flowchart of an embodiment of the method according to the invention.

In 1 is an arrangement 1 an exhaust tract 2 a (not shown) internal combustion engine shown. The internal combustion engine is especially a self-igniting internal combustion engine. The invention is also suitable for the exhaust gas of a spark-ignited internal combustion engine. The arrow shows the flow direction of the exhaust gas. In the exhaust tract 2 is a catalyst 3 arranged. The catalyst 3 For example, an oxidation catalyst, a nitrogen oxide storage catalyst, a catalyst 3 for selective catalytic reduction, a three-way catalyst, or a combination of said catalysts.

Downstream of the catalyst 3 is an inventive particle pre-separator 10 arranged. The particle pre-separator 10 essentially comprises an ionization device 11 on the upstream side and a collector 12 on the downstream side. Downstream of the particle pre-separator 10 is a particle filter 4 arranged.

The circled area in 1 highlighted part of the arrangement 1 concerns the particle pre-separator 10 who in 2 is shown in detail. The particle pre-separator 10 is in the range of the ionization device 11 and the area of the collector 12 divided. Both facilities 11 . 12 are in a substantially cylindrical, the shape of the exhaust tract adapted housing 13 of the particle pre-separator 10 arranged. The ionization device 11 has at least one electrode 111 on. The electrode 111 is a spray electrode 111 , It can also be arranged several Sprühelektroden. The spray electrode 111 is negatively poled. The spray electrode 111 is applied to a DC voltage. The DC voltage can be superimposed with an AC voltage. The provision of the required high voltage is effected by a corresponding voltage source 17 and is accomplished in a manner known to those skilled in the art, eg, either by directly providing high voltage, or by transposing low voltage.

When a high voltage is applied, an acceleration of free electrons in the vicinity of the discharge electrodes takes place 111 which generate gas ions and other free electrons when hitting gas molecules. In the exhaust gas flowing through particles are in the field of Sprühelektroden 111 charged with negatively charged gas ions or electrons when colliding.

With the exhaust gas flow, the charged particles reach the area of the collecting device 12 , An embodiment of the collection device 12 is in 3 shown in cross-section (corresponding to the AA line in 2 ). The collecting device 12 comprises according to the illustration of 3 and 5 sixteen flat rectangular plates 14 , The plates 14 the collector positively polarized and electrostatically charged. The material of the plates is chosen so that it can be electrostatically charged accordingly. The plates 14 can all be loaded together. Alternatively, the plates may also be charged individually, for this they must be electrically isolated from each other and a corresponding separate connection to the voltage source 17 respectively.

The plates 14 in the embodiment according to 4 extend with their long sides along the exhaust tract 2 , with the outer long side against the wall of the housing 13 adjoin and with the inner long side in the middle of the exhaust tract 2 adjoin one another or are arranged in a matching holder with each other. The elongated shape of the plates 14 in the flow direction of the exhaust gas is advantageous because the acting electrical forces between the particles and the plates 14 are weak and increases in a long drift with the exhaust gas flow, the probability that the particles are collected transversely to the flow direction of the exhaust gas. The short sides border the upstream side at the region of the ionizer 11 and on the downstream side to the area of the particulate filter 4 , The flat sides of the plates 14 are facing each other.

In the 3 and 5 are each 16 plates 14 from the collection facility 12 includes. It can also only one or another number of plates 14 be arranged. It should be noted that the electrical forces are too large between the plates 14 may be too low to collect a desired amount of particulates from the exhaust at a certain flow rate.

There are also other arrangements of the plates 14 in the exhaust tract 2 possible, eg parallel next to each other (as in 2 ), wherein the plates would then have different lengths of the short sides, or on the wall of the exhaust tract 2 arranged.

According to the 4 & 5 indicates the collector 12 a heating device 15 on that as a heating wire 15 is trained. The heating wire 15 is metallic and designed to glow when a given voltage and current are applied to ignite the collected particles. The heating wire 15 is connected to a corresponding voltage source, for example the battery of the motor vehicle, and a control device 5 that switches on electricity when needed. The demand depends on the particle loading of the collecting device, which by means of a sensor 16 can be determined in the range of plates 14 is arranged (each plate is a sensor 16 may comprise) and the corresponding signals to the control device 5 sends. The particle loading can also be determined model-based.

The heating wire 15 can be spirally formed ( 5 ). In an arrangement according to 5 has the heating wire 15 Contact with all plates 14 he touches several times. This will cause a uniform ignition of the particles on all plates 14 guaranteed.

Alternatively, each device may also be assigned a heating wire ( 4 ). The individual plates 14 associated heating wires 15 are individually controllable. This can also be a corresponding single plate 14 be regenerated faster by ignition of the particles. The individual plates 14 can also be regenerated independently.

In one embodiment of the method according to the invention in accordance with the flowchart in FIG 6 the particle pre-separator is switched on depending on the operating conditions. This is in step S1 the particle density in the exhaust gas determined. This can with appropriate in the exhaust tract 2 arranged sensors (eg resistive sensors) or model-based performed. If a first predetermined threshold value of the particle density in the exhaust gas is reached, the particle preseparator 10 switched on. In a third step, the Partikelvorabscheider 10 switched off again when the particle load has dropped below the first threshold again. Alternatively, the particle pre-separator 10 also be permanently switched on to the particle filter 4 to relieve. The collecting device 12 is regenerated by the heating wire 15 is annealed and the deposited particles on the plates 14 to be burned. The collection device is preferred 12 regenerated when the particulate deposits have reached a second threshold. It is according to the representation of 7 in a first step S4 determines the particle loading on at least one plate in the collector. In a second step S5 becomes the heating wire 15 switched on when the second threshold has been reached. In a third step S6 becomes the heating wire 15 switched off when the particles have been ignited on the plate.

The plates 14 can be regenerated together, ie simultaneously. This works, for example, with an arrangement of the heating wire 15 according to 5 , The plates 14 can also be regenerated individually, so that the plates 14 can be regenerated as needed, and not every time all plates 14 together. This embodiment of the method works best with the embodiment of the heating wire arrangement according to FIG 4 ,

LIST OF REFERENCE NUMBERS

1

arrangement

2

exhaust tract

3

catalyst

4

particulate Filter

5

control device

10

Particle pre-separator

11

ionization

111

electrode

12

collecting device

13

casing

14

Plate of the collector

15

heating wire

16

sensor

17

voltage source

Claims (11)

Particle pre-separator for separating particles from an exhaust gas stream in an exhaust tract of a motor vehicle, comprising at least one ionization device and at least one electrically charged area-like collecting device, which is designed to charge said particles and to collect from the exhaust gas flow, wherein said Partikelvorabscheider at least with a voltage source and a control device is connected. Particle pre-separator after Claim 1 in which the collecting device comprises at least one electrostatically charged plate. Particle pre-separator according to one of the preceding claims, wherein additionally at least one heating device is arranged in the collecting device. Particle pre-separator after Claim 3 in which the heating device is a heating wire. Particle pre-separator after Claim 4 in which the heating wires are formed to glow when a certain voltage and current are applied to ignite the deposited particles. Partikelvorabscheider according to any one of the preceding claims, wherein a sensor for determining the particle loading in the region of the collecting device is arranged. Arrangement of an internal combustion engine with an exhaust gas tract, in which a Partikelvorabscheider according to one of the preceding claims is arranged upstream of a particulate filter. Method for removing solid constituents, in particular soot particles, from the exhaust gas of an internal combustion engine by means of an arrangement according to Claim 7 in which particles in the exhaust gas are charged by means of the ionization device and deposited on the collecting device. Method according to Claim 8 in which the particle pre-separator is activated as a function of the operating conditions, comprising the steps of: determining the particle charge in the exhaust gas, switching on the particle pre-separator when a first threshold particle load in the exhaust gas is reached, shutting off the particle pre-separator when the particle load is again below the first threshold value has sunk. Method according to Claim 8 or 9 wherein the collector is regenerated by annealing the heater and igniting the deposited particles on the collector and successively burning them. Method according to Claim 10 wherein the collector is regenerated when the particulate deposits have reached a second threshold, comprising the steps of: determining particulate loading on at least one plate in the collector, turning on the heater upon reaching a second particle loading threshold, switching off the heater when the particles were ignited on the plate.

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