EP3887763A1 - Method for operating a corona discharge particle sensor unit - Google Patents
Method for operating a corona discharge particle sensor unitInfo
- Publication number
- EP3887763A1 EP3887763A1 EP19787235.1A EP19787235A EP3887763A1 EP 3887763 A1 EP3887763 A1 EP 3887763A1 EP 19787235 A EP19787235 A EP 19787235A EP 3887763 A1 EP3887763 A1 EP 3887763A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- particle sensor
- measurement signal
- corona
- signal
- sensor unit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
- G01N15/0656—Investigating concentration of particle suspensions using electric, e.g. electrostatic methods or magnetic methods
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N2015/0042—Investigating dispersion of solids
- G01N2015/0046—Investigating dispersion of solids in gas, e.g. smoke
Definitions
- the present invention relates to a method for operating a particle sensor unit working with a corona discharge according to the preamble of claim 1 and a device designed to carry out the method
- Such a method and such a particle sensor unit are known from EP 2 247 939 B1 and EP 2 511 690 B1, respectively.
- a corona discharge is an electrical discharge in an initially non-conductive medium, in which free charge carriers are generated by ionizing components of the medium.
- the particles are charged by adhering ions.
- the charged particles are carried out of the particle sensor by the flowing fluid and take their electrical charge with them.
- the measurement of the charge of the particles is usually carried out by measuring the mirror charge of the previously charged particles on a measuring electrode (Influenz) or by measuring the charge missing by leaving the previously charged particles on a virtual GND electrode is tracked to prevent charging of this electrode (escaping current).
- the ions from the corona discharge, which do not adhere to a particle are preferably filtered out beforehand by an electric field of an ion-trapping electrode.
- the corona current is preferably generated in the form of a pulse train.
- the principle of evaluating an "escaping current" is explained in EP 2 824 453 A1.
- the particle sensor unit is set up to electrically charge particles in a fluid stream laden with particles with the aid of a controllable corona discharge, the corona current and / or corona voltage of which can be controlled by the particle sensor unit, and one of the electrical charges and dependent on the concentration of the particles
- the known particle sensors work with a measuring principle which is based on a measurement of the electrical charge discharged from the sensor with the particles.
- EP 2 247 939 A1 describes one that works with an ejector principle
- Particle sensor known. Compressed air is blown into the particle sensor from a nozzle, and exhaust gas serving as measuring gas is drawn in via the Venturi effect. The corona discharge takes place in an "ion generation section". The ions generated in this way are blown into a "electric charge section" via a nozzle with pressurized air, to which sample gas is fed via a further inlet.
- Measured gas flow through the particle sensor is achieved, which is largely independent of the flow velocity of the exhaust gas prevailing outside the particle sensor.
- An ejector principle is used to guide the exhaust gas flow through the sensor in a controlled manner.
- compressed air is blown into the sensor from a nozzle and exhaust gas is sucked in via the Venturi effect.
- the corona burns in the compressed air chamber and ions get into the exhaust gas via the air flow.
- compressed air By using compressed air, a high flow through the sensor can advantageously be achieved, regardless of the external exhaust gas velocity in the exhaust pipe, as a result of which sufficiently high signal levels can also be achieved even with a low particle concentration.
- the disadvantage of this prior art is the use of compressed air, which has to be made available in a particularly complex manner. This applies analogously to the subject of EP 2 51 1 690 B1, which also works with compressed air injection.
- the sample gas volume flow in the sensor depends on external parameters.
- Exhaust gas sensor for internal combustion engines is the sample gas volume flow (here the exhaust gas volume flow) e.g. dependent on the crank angle, the engine speed, the load, the state of a particle filter arranged upstream of the particle sensor or the temperature.
- the volume flow is variable over time and is subject to strong fluctuations.
- the particle concentration can vary widely.
- the sensor signal varies very greatly, which means that the sensor and in particular a charge amplifier of the sensor have a very large one
- particle is intended to generally refer to floating particles, regardless of whether they are solid or liquid (like droplets in an aerosol).
- the particle sensor unit is operated in such a way that the particle sensor signal is in a predeterminable range, or that the particle sensor unit is set up to carry out a method according to the invention.
- the exhaust gas sensor has a device for ion generation, for example a high-voltage tip as a corona discharge electrode, on which a corona discharge takes place.
- a device for ion generation for example a high-voltage tip as a corona discharge electrode, on which a corona discharge takes place.
- the majority of the ions generated by the discharge (> 90%) fly along the electric ones Field lines to the counter electrode (ground). If particles fly through the corona discharge zone, they take in more ions and thus electrical charge per particle, the larger the corona current carried by the ions of the corona discharge and the greater the field strength of the electrical field of the corona discharge and so that the corona voltage and the drift speed of the ions are.
- the typical charge per particle which generally also depends on the particle size, can thus be regulated / modified by adjusting the corona voltage and the corona current. This allows the charge per particle depending on the exhaust gas velocity and the
- the invention allows a targeted and strong increase in the corona discharge at a low particle concentration in order to be able to measure these low particle concentrations precisely.
- the particles are also diffusively charged by the ions flying further (greater than 10%). This charge can be controlled via the corona current.
- a preferred embodiment of the method is characterized in that the particle sensor signal is generated from a measurement signal of the particle sensor, the measurement signal representing an electrical charge that is released from the particle sensor with the electrically charged particles to the fluid. It is also preferred that the measurement signal is amplified with a predeterminable factor that is so large that the amplified measurement signal lies in the predefinable range and that the measurement signal is treated as the particle sensor signal.
- a further preferred embodiment is characterized in that the particle sensor signal is treated as a variable to be controlled and that an electrical variable influencing the corona discharge serves as a manipulated variable in a closed control loop with which the particle sensor signal is regulated to a desired value.
- the manipulated variable is a corona voltage.
- the manipulated variable is a corona current.
- manipulated variable is an electrical output of the corona discharge or another electrical mixed variable formed from the corona current and the corona voltage.
- the particle sensor signal is provided at an output of the particle sensor unit.
- a measurement signal range is specified, a
- Measurement signal of the particle sensor is detected, and that when the detected measurement signal lies in the predeterminable measurement signal range, the measurement signal is evaluated as a function of a fluid velocity and the corona voltage and the corona current and is provided at an output.
- Another preferred embodiment is characterized in that a measurement signal range is specified, a measurement signal of the particle sensor is recorded, and when the recorded measurement signal is below the predeterminable measurement signal range, an output of the corona discharge or another corona size (voltage , Current) is increased.
- a measurement signal range is predetermined, a measurement signal of the particle sensor is recorded, and then when the recorded measurement signal is above the predeterminable measurement signal range, a corona discharge power or another corona size (voltage, current) is reduced.
- the particle sensor unit it is preferred that it is set up to one or more of the above
- the invention can generally be used for measuring particle concentrations (not necessarily soot particles) in measurement gases (not necessarily exhaust gas), for example for detecting dust concentrations.
- FIG. 1 shows a technical environment of the invention in the form of an exhaust pipe and a particle sensor unit which has a particle sensor, a wire harness and a control unit;
- Figure 2 shows a cross section of a ceramic carrier element
- Particle sensor that carries various electrodes
- Figure 3 is a plan view of a ceramic carrying electrodes
- Carrier element of an embodiment of a particle sensor according to the invention is a Carrier element of an embodiment of a particle sensor according to the invention.
- FIG. 4 qualitatively shows a dependency of the electrical charge per particle as a function of the corona power P
- FIG. 5 shows an example of regulating the sensor signal by means of a manipulated variable to a constant value
- Figure 6 is a block diagram of a cyclically repeating
- FIG. 7 corresponds to the block diagram of FIG. 6
- Particle sensor 12 which is connected via a cable harness 14 to a control device 16 of the particle sensor unit 10.
- the particle sensor 12 protrudes into an exhaust pipe 18, which carries exhaust gas as the measurement gas 20, and has a protruding into the flow of the measurement gas 20
- Pipe arrangement of an inner metallic tube 22 and an outer metallic tube 24 is used in a preferred embodiment of the invention, but is not an essential element of the invention.
- the two metallic tubes 22, 24 preferably have a general one
- the base areas of the cylindrical shapes are preferably circular, elliptical or polygonal.
- the cylinders are preferably arranged coaxially, the axes of the cylinders lying transversely to the flow direction of the measurement gas 20 which prevails in the exhaust pipe 18 outside the pipe arrangement.
- the inner metallic tube 22 protrudes beyond the outer metallic tube 24 into the flowing measurement gas 20 at a first end 26 of the tube arrangement facing away from the installation opening in the exhaust gas tube 18.
- the outer metallic tube 24 projects beyond the inner metallic tube 22 at a second end 28 of the two metallic tubes 22, 24 facing the installation opening in the exhaust pipe 18.
- the inside diameter of the outer metallic tube 24 is preferably so much larger than the outer diameter of the inner one
- the clear width W of the inner metallic tube 22 forms a second flow cross section.
- Particle sensor is attached so as to protrude transversely to the flow direction of the measurement gas 20 in the exhaust gas pipe 18 and laterally into the flow of the measurement gas 20, the inside of the metallic pipes 22, 24 preferably being sealed off from the surroundings of the exhaust pipe 18.
- the attachment is preferably carried out with a screw connection.
- a ceramic carrier element 34 is arranged in the inner metallic tube 22 and has a plurality of electrodes adhering there
- Electrode assembly 36 carries.
- the electrodes of the electrode arrangement 36 are exposed to the measuring gas 20 flowing past and are connected to the control unit 16 of the particle sensor unit 10 via the cable harness 14.
- the control device 16 is set up to operate the particle sensor 12 and to generate an output signal from electrical variables such as current and voltage occurring on electrodes of the electrode arrangement 36, which image reflects the particle concentration in the exhaust gas.
- the control unit 16 can be a separate control unit, or it can be integrated in a control unit that serves to control a combustion process.
- the control unit 16 has a control module which controls the corona discharge, for example by controlling the corona current, the corona voltage or a mixed variable formed from these two variables, for example the corona power.
- the signal of the electrode arrangement 36 is processed in the control device 16 according to the invention, that is to say with the method according to the invention or one of its configurations, by an evaluation circuit which, for example, has a microprocessor and a memory in which instructions for carrying out a method according to the invention are stored.
- Results of the processing are provided as an output signal at an output 38 of the control device 16.
- the output signal is generated, for example, according to the principle described in the aforementioned EP 2 824 453 A1.
- FIG. 2 shows a cross section of a ceramic carrier element 34 of a particle sensor, which carries various electrodes, and is used for
- a corona discharge electrode 40, a ground electrode 42 and an ion capture electrode 44 are arranged on the electrically insulating ceramic carrier element 34.
- the ceramic carrier element 34 additionally carries a measuring electrode 46, which serves as a particle charge detection electrode, but which is not absolutely necessary.
- a heating element 50 in the form of a heating electrode adhering there is arranged on a rear side 48 of the ceramic carrier element 34.
- the ceramic carrier element 34 is arranged with its longitudinal direction parallel to the direction of the measuring gas 20 flowing there in the inner metallic tube 22 of FIG. 1. Measuring gas 20 flows over this arrangement of corona discharge electrode 40, ground electrode 42, ion trapping electrode 44 and possibly also measuring electrode 46 with the one indicated by the direction of the arrow
- the corona discharge takes place between the corona discharge electrode 40 and the ground electrode 42 in a corona discharge zone 52.
- the corona discharge zone 52 is traversed by measuring gas 20 loaded with particles.
- the measuring gas 20 present there is partially ionized in the corona discharge zone 52.
- the particles then take up ions and thus an electrical charge.
- the voltage required to generate the corona discharge between the corona discharge electrode 40 and the ground electrode 42 is generated by a high-voltage source integrated in the control device 16.
- the ion trap electrode 44 traps ions which do not adhere to the heavier and therefore more inert particles transported with the measurement gas 20.
- the inner metallic tube 22, not shown in FIG. 2, can serve as a counter-electrode for the ion-trapping electrode 44.
- the measurement of the electrical charge transported with the soot particles takes place either by means of charge influence on the measuring electrode 46 serving as the particle charge detection electrode instead, or it takes place using the "escaping current" principle, the principle of which is explained in EP 2 824 453 A1.
- FIG. 3 shows a plan view of a ceramic carrying electrodes
- Carrier element 34 of an embodiment of a particle sensor according to the invention Carrier element 34 of an embodiment of a particle sensor according to the invention.
- a corona discharge electrode 40 which has a tip 54, a ground electrode 42 and an ion-trapping electrode 44, and possibly also a measuring electrode 46, are each planar and adherent on the ceramic carrier element 34 and form planar electrodes.
- a portion of the ceramic support element 34 which is delimited by interfaces of the ceramic support element and on which the tip 54 of the planar corona discharge electrode 40 rests, protrudes as the tip of the ceramic support element 34 from the rest of the ceramic support element.
- This portion which is covered in FIG. 3 by the tip 54 of the corona discharge electrode 40, projects with the tip 54 into a recess 56 in the ceramic carrier element 34, which is not filled with the ceramic material of the ceramic carrier element 34.
- FIG 4 shows qualitatively a dependency of the typical electrical charge q per particle, which occurs due to the charging of the particles when crossing the corona discharge, as a function of the corona power P.
- the corona power P is the product of that by the ions of Corona discharge current and the electrical voltage between the corona discharge electrode and its counter electrode.
- the two variables corona current and corona voltage are not independent of one another, but are linked to one another via the nonlinear impedance of the corona discharge.
- At least one of these two electrical variables or also a mixed variable (for example the power) formed therefrom is regulated.
- any combination of corona current and corona voltage can be used as a controlled variable to influence and thus adjust the charge per particle that occurs in the corona discharge. In one embodiment, this takes place as a function of at least one sample gas parameter (for example speed, particle concentration and particle size) in the particle sensor.
- FIG. 5 shows an example of a control of the sensor signal S by means of a manipulated variable to a constant value.
- the manipulated variable here is the corona power P.
- the regulation takes place continuously, so that the target value is constantly regulated.
- Analog front ends are analogue ballasts that amplify highly sensitive analog signals and thus serve as a preamplifier.
- an amplification factor of the analog front end is selected or switched on and depending on the currently measured particle concentration, the sensor signal is e.g. regulated to a fixed value by means of the corona power.
- the sensor signal S is detected in this embodiment and, preferably depending on the
- Particle sensor unit 10 reacts to this by, for example, specifying the corona power P (here representative of the general mixed quantity of corona current and corona voltage) in such a way that the sensor signal S remains constant.
- the control can take place continuously, for example, so that control is always carried out to a setpoint. It may be the case that the control must settle in the event of strong and / or rapid changes in concentration, and the actual value therefore only returns to the setpoint with a delay.
- FIG. 6 shows an exemplary embodiment for a cyclically repeating operating method, which forms an exemplary embodiment of a method according to the invention.
- the individual blocks represent process steps or process parts which run at different points in the particle sensor unit 10 and which are explained below.
- the mode of operation is particularly well suited for a particle sensor 12 evaluating the effects of influenza, which is operated with a pulsed corona discharge.
- a corona discharge pulse and the subsequent pause until the next pulse can represent a measurement cycle. The pause between two pulses should be so long that successive measurements do not influence each other by overlapping.
- a corona discharge pulse is fired for each cycle. After a predetermined time which has elapsed since the corona discharge pulse was ignited and which corresponds to a time which it takes for particles charged in the corona discharge pulse to reach the measuring electrode, a signal is sent to the measuring electrode detected. This signal is evaluated. It is checked, for example, whether the signal is in a predetermined specific range. Depending on the result of the test, either a particle concentration is determined from the signal, or the parameters for the next corona discharge pulse are changed and the measurement is repeated. It is also possible to average the measurement over time for a better signal-to-noise ratio.
- Block 60 represents the triggering of a corona discharge pulse.
- Block 62 represents the acquisition of the corona discharge pulse
- the method branches to a block 66 in which parameters for a change in the corona discharge depending on the detected signal are determined. For example, if the detected signal is below a lower limit of the predetermined signal range, the corona power can be increased as a parameter in order to achieve a stronger charge of the particles and thus a larger measurement signal.
- the parameters of the corona discharge are then changed in block 68 in accordance with the specification of block 66, and in block 60 a corona discharge pulse is triggered again, this time with increased corona power.
- the method branches to block 70, in which the measurement signal is processed to give an indication of the particle concentration.
- This processing and also the limits of the predetermined range in block 64 are in one embodiment of the flow velocity of the
- Measurement gas dependent which is communicated to the particle sensor unit, for example, by another control device 160.
- the further control device 160 is, for example, the engine control device of an exhaust gas that generates measurement gas
- Particle concentration is provided for reading in block 72 at output 38 of the particle sensor unit 10.
- FIG. 7 shows a flowchart corresponding to the block diagram of FIG. 6 as a further exemplary embodiment of a method according to the invention. This process can also take place with continuous corona discharge.
- Step 100 represents a start of a corona discharge.
- a signal of the measuring electrode resulting from the corona discharge is recorded.
- the subsequent step 104 it is checked whether the detected signal is in a predetermined signal range. If this is not the case, the method branches into a corona control loop which begins with step 106.
- step 106 it is checked whether the measurement signal acquired in step 102 is smaller than the lower limit of the predetermined range from step 102. If this is the case, the method branches to step 108, in which, for example, the corona power is increased.
- step 106 the measurement signal recorded in step 102 is greater than the upper limit of the predetermined range from step 102
- step 110 the corona power is reduced.
- step 112 is optionally carried out, in which a setting of a new measurement signal as a result of the change in the corona parameters is awaited. The method then branches back to step 102, in which a new measurement signal is detected.
- step 104 If, on the other hand, it is determined in step 104 that the measurement signal detected at the measurement electrode lies in the predetermined range, then the method branches to step 114, in which the measurement signal gives an indication of the Particle concentration is processed.
- step 114 This processing and also the limits of the predetermined range in block 104 can also be changed here
- Flow rate of the sample gas may be dependent on the
- Particle sensor unit 10 is communicated, for example, by a further control device.
- the further control device is, for example, the engine control device of an exhaust gas as an internal combustion engine producing measurement gas.
- the specification of a particle concentration generated in step 114 becomes in step 1 16 at the exit of the
- Particle sensor unit 10 provided for reading out. The method then branches back to step 102, in which a new measurement signal is detected.
- the measurement signal is still too large in relation to the specific area despite the already minimal corona power or is still too small despite the already maximum corona power.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE102018220299.0A DE102018220299A1 (en) | 2018-11-26 | 2018-11-26 | Method for operating a corona discharge particle sensor unit |
PCT/EP2019/077709 WO2020108836A1 (en) | 2018-11-26 | 2019-10-14 | Method for operating a corona discharge particle sensor unit |
Publications (1)
Publication Number | Publication Date |
---|---|
EP3887763A1 true EP3887763A1 (en) | 2021-10-06 |
Family
ID=68242690
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19787235.1A Withdrawn EP3887763A1 (en) | 2018-11-26 | 2019-10-14 | Method for operating a corona discharge particle sensor unit |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP3887763A1 (en) |
DE (1) | DE102018220299A1 (en) |
WO (1) | WO2020108836A1 (en) |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FI20080182A0 (en) * | 2008-03-04 | 2008-03-04 | Navaro 245 Oy | Measurement method and apparatus |
JP5537487B2 (en) | 2011-04-12 | 2014-07-02 | 日本特殊陶業株式会社 | Particle detection system |
JP5774516B2 (en) | 2012-02-21 | 2015-09-09 | 日本特殊陶業株式会社 | Particle sensor |
JP6335861B2 (en) * | 2015-10-27 | 2018-05-30 | 日本特殊陶業株式会社 | Fine particle measurement system |
-
2018
- 2018-11-26 DE DE102018220299.0A patent/DE102018220299A1/en not_active Withdrawn
-
2019
- 2019-10-14 WO PCT/EP2019/077709 patent/WO2020108836A1/en unknown
- 2019-10-14 EP EP19787235.1A patent/EP3887763A1/en not_active Withdrawn
Also Published As
Publication number | Publication date |
---|---|
WO2020108836A1 (en) | 2020-06-04 |
DE102018220299A1 (en) | 2020-05-28 |
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