EP1990098A2 - Fitre à paroi avec une montée en pression faible - Google Patents

Fitre à paroi avec une montée en pression faible Download PDF

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Publication number
EP1990098A2
EP1990098A2 EP20080450075 EP08450075A EP1990098A2 EP 1990098 A2 EP1990098 A2 EP 1990098A2 EP 20080450075 EP20080450075 EP 20080450075 EP 08450075 A EP08450075 A EP 08450075A EP 1990098 A2 EP1990098 A2 EP 1990098A2
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EP
European Patent Office
Prior art keywords
channels
ceramic body
voltage pulses
exhaust gas
soot particles
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.)
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Application number
EP20080450075
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German (de)
English (en)
Inventor
Carl M. Fleck
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP1990098A2 publication Critical patent/EP1990098A2/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/66—Applications of electricity supply techniques
    • B03C3/68—Control systems therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/36—Controlling flow of gases or vapour
    • B03C3/368—Controlling flow of gases or vapour by other than static mechanical means, e.g. internal ventilator or recycler
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/40—Electrode constructions
    • B03C3/60—Use of special materials other than liquids
    • B03C3/62—Use of special materials other than liquids ceramics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C2201/00—Details of magnetic or electrostatic separation
    • B03C2201/30—Details of magnetic or electrostatic separation for use in or with vehicles

Definitions

  • the invention relates to a method for operating a filter arrangement for separating soot particles from an exhaust gas stream, wherein the exhaust gas stream is passed through extending in the longitudinal direction of a porous ceramic body channels of the ceramic body, according to the preamble of claim 1, and a filter assembly for performing this method Claim 7.
  • the exhaust gas flow passes through pores of the walls of the channels of the ceramic body, which are open only on one side, whereby the soot particles are retained.
  • the deposition of the soot particles thus takes place mechanically.
  • Different systems are known for the degradation of the deposited soot particles in the channels of the ceramic body, for example by means of a plasma generated in the channels of the ceramic body ("plasma-generated filter systems").
  • plasma-generated filter systems For this purpose, a voltage is applied to the ceramic body for generating an electric field in the channels of the ceramic body, which is oriented in each case transversely to the axis of the channels on parallel to the channels extending electrodes. Electric field strengths of about 1 kV / cm in the channels of the honeycomb body are usually sufficient to generate a plasma in the channels, which converts deposited soot particles into gaseous substances.
  • Claim 1 relates to a method for operating a filter arrangement for separating soot particles from an exhaust gas flow, wherein the exhaust gas flow is passed through extending in the longitudinal direction of a porous ceramic body channels of the ceramic body, wherein the exhaust gas flow through pores of the walls of the only one-sided open channels Passing ceramic body, and at parallel to the channels extending electrodes, a voltage to the ceramic body for generating an electric field in the channels of the ceramic body, which is oriented substantially normal to the axis of the channels, is created.
  • the soot particles are charged by means of a further electrode arrangement, and the voltage applied to the electrodes extending parallel to the channels is bipolar voltage pulses, wherein the bipolar voltage pulses are selected so that the drift velocity of the charged soot particles generated by a half wave of the voltage pulses in the field direction of the electric field generated in the channels is on average greater than or equal to the maximum velocity component of the gas flow in the field direction of the electrical field generated in the channels is.
  • the measures according to the invention therefore provide for the separation of the soot particles in the channels of the ceramic body not exclusively to be mechanical, but to use the electric field built up in the channels for the soot erosion also for the deposition of the soot particles, for which purpose a further electrode arrangement for previous charging of soot particles is provided.
  • this measure alone is not yet sufficient to remedy the above-described problem of near-pore deposition of soot particles.
  • the invention further provides that bipolar voltage pulses are to be used, which are to be selected such that the drift velocity of the charged soot particles generated by a half-wave of the voltage pulses is greater than or equal to the maximum velocity component of the gas flow in the field direction of the electric field generated in the channels is.
  • the drift velocity of the electrically charged soot particles during the electrical voltage pulses predominates the velocity component in the direction of the field towards the channel wall or is at least equal thereto, then a deposition controlled predominantly by the electric field and not by the local flow velocity around the pore opening.
  • a separation takes place distributed over the entire channel wall, and not only near the pores.
  • the maximum velocity component v x are determined in the field direction, together with the already known geometry parameters of the channel height h and the channel length L.
  • the mobility ⁇ (d) and the charge number z (d) can be read for different diameters d from well-known tables.
  • the charge of the soot particles quantified by the charge number z (D) is due to the previous charge by means of the discharge electrode.
  • the mean drift velocity of the charged soot particles produced by a half-wave of the voltage pulses results from integration of the above-mentioned, time-dependent drift velocity over the duration of the half-wave of the voltage pulse.
  • the field strength E (t) is given in a known manner directly by the applied voltage pulses. On the basis of the features according to the invention, the field strength necessary in the respective application, and thus the voltage to be applied to the electrodes, can thus be derived.
  • Claim 2 now provides that the bipolar voltage pulses are selected so that the covered during a half-wave of the voltage pulses Driftweg s of the charged soot particles is smaller than the channel height h in the field direction of the electric field generated in the channels.
  • This measure therefore sets an upper limit for the electric field strength to be selected, and thus for the voltage pulses to be applied.
  • deposition of the soot in the inlet part of the channel may already occur, and thus a strong unequal distribution of the deposited soot in the channel.
  • the drift path s (d) of the soot particles during a half-wave is significantly smaller than the channel height h in the field direction.
  • a further criterion for the choice of the necessary field strength, and thus the size of the voltage pulses to be applied which additionally prevents a deposition of the soot particles on the pore edge.
  • the high-frequency electrical voltage pulses are not operated continuously, but in shorter periods of vibrations, so-called high-frequency, bipolar pulse trains, which consist of at least one or a few bipolar oscillations. If one now selects the time interval ⁇ between two bipolar pulses or pulse trains too large in order to significantly reduce the electrical power requirement, soot particles can still get close to the pores in the intervening pauses and can be impacted at the pore entrance before the next bipolar impulse separates them ,
  • the bipolar voltage pulses are selected so that the covered during a half-wave of the voltage pulses Driftweg the charged soot particles is at least as large as the product of the maximum velocity component v x of the gas flow in the field direction of the generated in the channels, electric field, and the time interval between two bipolar voltage pulses or between two sequences of bipolar voltage pulses.
  • the drift path s (d) results, as already mentioned, as a temporal integral of the drift velocity c (d, t) over a half period of the alternating field.
  • the differential pressure of the exhaust gas flow is measured on the ceramic body, and above a predetermined value of the differential pressure, the control of the bipolar voltage pulses in response to the flow rate of the exhaust gas flow in the channels of the ceramic body, and below this predetermined value, the control only in response to the flow rate of the exhaust gas flow in the channels of the ceramic body takes place when the flow velocity has a sloping tendency, and otherwise the control is independent of the flow rate.
  • the soot distribution in the channel can be steered, and in particular also kept constant at different gas velocities, by at least temporarily reducing the field amplitude, preferably with short but very high amount of soot, while maintaining the field amplitude in FIG the remaining time directly proportional to the flow velocity in the channel controls.
  • the average velocity in the channels is divided into at least two intervals, where for the greater flow rate the normal, flow-dependent control applies with the boundary conditions given by the plasma flow and the temperature of the exhaust gas, while for the lower Flow rate only applies this normal control, if the 'derivative of the speed after time is negative, so the speed decreases with time.
  • the electric field is driven with lower field amplitudes E min in order to shift the field-supported deposition of soot further into the interior of the channels.
  • the field strength which is necessary for the performance of the method according to the invention can not be achieved for reasons of dielectric strength of the ceramic body or too high a local gas velocity, it is possible to choose the diameter of the ceramic body in the choice or, where appropriate, in the development of the ceramic material Pore openings, preferably the pore diameter p itself, to reduce accordingly.
  • a corresponding measure is the subject of claim 7.
  • Claim 7 refers to a filter assembly for carrying out the method according to claim 1 to 6 with a ceramic body having axially extending channels, which are flowed through by the exhaust gas, wherein the exhaust gas flow through pores of the walls of only On one side open channels of the ceramic body passes, and are arranged on the ceramic body parallel to the channels extending electrodes for generating a normal to the channels extending, electric field in the channels.
  • the ceramic body has a total porosity of over 50%, and the proportion of macropores is less than 15%. Macropores occur in ceramic structures whose porosity is very high. Since their presence would interfere with the measures according to the invention for pore-remote deposition of the soot, is limited by claim 7 their share accordingly.
  • the pore diameter p according to claim 7 can not be correspondingly reduced in order to ensure the method according to the invention by a corresponding increase in the field strength, then the further possibility exists of reducing the flow velocity v to such an extent in the design of the ceramic honeycomb body by increasing the free overall cross-section q inventive method of field strength control is made possible.
  • the Fig. 1 and 2 each show a schematic representation of a cross section of a ceramic body 7, which haridelt around a honeycomb body.
  • a ceramic body 7 is shown with a convex, namely elliptical circumferential line, but it could also have other cross-sectional shapes, such as a trapezoidal shape.
  • the ceramic body 7 has channels 5, which extend in the longitudinal direction of the ceramic body 7, and are open at one end face of the ceramic body 7, and closed on the respective opposite side.
  • the exhaust gas flow enters through a channel 5 which is open at the inlet side but closed at the outlet side and must be open to leave the ceramic body 7 through the internal wall of the respective channel 5 to the adjacent channel 5 which is closed at the inlet side but open at the outlet side is, step through.
  • the electrodes 1, 2 are each formed by a group of electrode channels 4, in each of which an electrical coating 6 is introduced at least partially along its axial extent.
  • the groups of electrode channels 4 are each formed by adjacent electrode channels 4, so that a flat electrode surface 1,2 is defined by each group of electrode channels 4. But there are also other versions of the electrodes possible.
  • the flat electrode surfaces 1,2 each extend horizontally and parallel to each other.
  • the distance between two adjacent electrode surfaces 1 and 2 is preferably less than 40 mm, about 15-25 mm.
  • a homogeneous electric field can be ensured between the electrode surfaces 1 and 2, in particular in those spatial regions which are located within the space region of the ceramic body 7 delimited by two adjacent electrode surfaces 1, 2, which is also referred to below as a homogeneous field region .
  • the region 3 of the ceramic body 7 lying outside the homogeneous field region has in the embodiment according to FIG Fig. 1 and 2 over a denser structure, in order to additionally increase their structural load capacity.
  • Two adjacent electrode surfaces 1 and 2 are each contacted opposite polarity, wherein in the Fig. 1 approximately the electrode surface 1 is grounded, and the electrode surface 2 is supplied with bipolar voltage pulses.
  • the drift velocities c (d) of the charged carbon particles with the diameters d in or against the field direction are greater than the velocity component v x or in the field direction, then according to the invention the carbon particles do not surround an open pore channel by the velocity of the inflowing Gas impacted, but practically deposited electrically on the entire channel wall, when they reach the vicinity of the channel wall.
  • Another criterion for the necessary field strength E, in order to prevent deposition of the soot particles at the pore rim, can be obtained by a closer examination of the pore diameters.
  • the mean diameter p of the inflow opening with the open area f serves as a starting point.
  • a simple approximation of a pore diameter p is obtained in particular for ceramics whose superficial, pore openings deviate very greatly from the circular shape.
  • the inequalities can still be fulfilled according to the invention by selecting or, if necessary, developing the ceramic material for the ceramic body 7, the diameter of the pore openings, preferably the pore diameter p itself, accordingly is reduced. With correspondingly small pores, according to the invention, the total porosity of the ceramic must be kept very high, preferably more than 50%.
  • a ceramic with a low content of macropores preferably below 15%.
  • the average pore diameter p of the macropores remain below 20 ⁇ m, preferably below 15 ⁇ m.
  • the high frequency alternating electric field is not operated continuously, but in short periods of oscillations, so-called high-frequency bipolar pulse trains, which consist of at least one or a few bipolar oscillations, decomposed so as not to overload the electrical system.
  • the path v x which the soot particles carried by the exhaust gas travel between two bipolar pulses or groups of pulses with the temporal distance ⁇ in the wall direction must be less than or equal to the drift path s (d) as the time integral of the drift velocity c (d, t) a half-period of the alternating field, ie v x ⁇ ⁇ ⁇ s d or v x , ⁇ ⁇ ⁇ d , z d ⁇ e t ⁇ dt Integral of t 1 to t 2
  • Table 2 shows at least necessary flow times of the exhaust gas flow in the channels 5 of a ceramic body 7 for two different field strengths in the maximum of the electrical voltage pulses in order to realize the inequality can.
  • the data were determined for a mass flow rate of 500 kg / h at 500 ° C and a total cross section of the honeycomb body of 360 cm 2 .
  • exhaust gas quantities of 500 kg / h at 500 ° C with acceptable filter cross sections can meet these requirements.
  • This exhaust gas mass flow of 500 kg / h corresponds to a full load operation of a supercharged diesel engine of the lower middle class.
  • a deposition field of 8 kV / cm can thus catch all particles along a separation wall without being influenced by pore channels even at full load. Since particles with diameters of around 100 nm no longer contribute to the number of particles and still nothing to the particle mass, filtering with these parameters is quite acceptable, since regeneration under plasma proceeds continuously and rapidly at these temperatures.
  • the drift path s (d) of the soot particles during a half-wave is significantly smaller than the channel height h in the field direction, ie s d ⁇ ⁇ H or ⁇ d , z d ⁇ e t ⁇ dt ⁇ ⁇ H Integral of t 1 to t 2
  • the boundaries of the integral each extend over a unipolar half-wave of the field E. This yields the criterion that the drift path s (d) during a half-wave is greater than or equal to the component in or against the field direction of the path v x . (t 2 -t 1 ) of the gas flowing to the channel wall during a half-wave of the field, and significantly smaller than the channel height h: v x , t 2 - t 1 ⁇ s d ⁇ ⁇ H or v x , t 2 - t 1 ⁇ ⁇ d , z d ⁇ e t ⁇ dt ⁇ ⁇ H Integral of t 1 to t 2
  • V x is a function of gas velocity v
  • this relationship can also be used to steer the soot distribution in channel 5, or to keep it constant at different gas velocities, at least temporarily decreasing the field amplitude, preferably short but very high Russanfall, while the field amplitude in the remaining time is controlled directly proportional to the flow velocity in the channel 5.
  • E min has to fulfill at least two of the above four inequalities: v x ⁇ ⁇ ⁇ s d and or 2 ⁇ p ⁇ s d and or v x , t 2 - t 1 ⁇ s d and or s d ⁇ ⁇ H
  • the processor of the soot filter can also perform this control itself.
  • the simplest reaction is obtained by measuring the differential pressure preferably occurring at the filter itself (p 1 -p 2 ), which in a good approximation is directly proportional to the average flow velocity v in the channels 5 of the ceramic body 7, and its increase or decrease is good Conclusion on the soot emission of the engine allowed.
  • the filter processor itself can calculate and perform the voltage control necessary for optimum deposition of the soot when the motor processor processes the necessary signals, preferably temperature T, gas volume flow or mass flow, preferably also provides EGR rate and injection quantity via a signal system, preferably via CANBUS.
  • the smaller filter processor determines the necessary voltage changes more quickly, and thereby the deposition field, which can be controlled only slowly by capacitances on the high-voltage side, can be timely adjusted to the new soot accumulation.
  • the outer electrodes of the ceramic body 7 are clearly set back on the inlet side, preferably by one to two inlet lengths l e , which is calculated with the maximum possible gas velocity v in the channels 5.

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)
EP20080450075 2007-05-10 2008-05-09 Fitre à paroi avec une montée en pression faible Withdrawn EP1990098A2 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT7292007A AT505127A1 (de) 2007-05-10 2007-05-10 Wall-flow-filter mit geringem druckaufbau

Publications (1)

Publication Number Publication Date
EP1990098A2 true EP1990098A2 (fr) 2008-11-12

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EP20080450075 Withdrawn EP1990098A2 (fr) 2007-05-10 2008-05-09 Fitre à paroi avec une montée en pression faible

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012206880A1 (de) 2012-04-25 2013-10-31 Salewa Sport Ag Vordereinheit für eine Gleitbrettbindung, insbesondere schwenkbare Vordereinheit mit Auslöseanordnung
WO2015159539A3 (fr) * 2014-04-15 2016-01-21 Toyota Jidosha Kabushiki Kaisha Appareil de déshuilage

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012206880A1 (de) 2012-04-25 2013-10-31 Salewa Sport Ag Vordereinheit für eine Gleitbrettbindung, insbesondere schwenkbare Vordereinheit mit Auslöseanordnung
WO2015159539A3 (fr) * 2014-04-15 2016-01-21 Toyota Jidosha Kabushiki Kaisha Appareil de déshuilage

Also Published As

Publication number Publication date
AT505127A1 (de) 2008-11-15

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