DE102008040451A1 - Particle filter for filtering exhaust gas of diesel internal-combustion engine, has porous filter wall separating outlet channel from inlet channel, and latent heat storage material arranged in outlet channel in region of inlet side - Google Patents

Abstract

The particle filter (1) has a filter substrate (3) comprising an inlet side (5) for entry of exhaust gas (11), and an outlet side (7) for exit of exhaust gas (13). An inlet channel (15) locked at the outlet side and an outlet channel (17) locked at the inlet side are arranged in the filter substrate. The outlet channel is separated from the inlet channel by a porous filter wall (19) of the filter substrate. A latent heat storage material (9) i.e. phase change material, is arranged in the outlet channel in a region of the inlet side. Independent claims are also included for the following: (1) a method for operating a particle filter (2) a Method for producing a particle filter.

Description

State of the art

The The invention is based on a particle filter, a method for Operation and a method for producing such a particulate filter according to the preamble of the independent claim.

Becomes a latent heat storage material ("PCM", Engl. "Phase Change Material") in the solid state Heat energy supplied, it increases its temperature until the melting point. During the melting the temperature of the liquid phase remains in the coexistence range with the solid phase of the PCM despite heat supply constant, the Supply of thermal energy leads in the transition from solid to liquid state not to a temperature, but to an increase in entropy. Only when the solid phase completely melted, the temperature rises additional heat. Conversely, the temperature drops Heat deprivation does not and remains during the phase transition from liquid to solid, until all material solidifies is. Upon further removal of heat, the temperature of the material decreases. The heat of fusion is of mass, specific heat capacity and the melting or boiling temperature of the material used dependent. Find technical application depending on the desired parameters mentioned above, such as paraffins, Silicates, salts and their aqueous solutions, salt hydrates, Metals and metal alloys as well as heterogeneous mixtures such as suspensions, emulsions or colloids of various kinds. PCM is currently used in Isolations of buildings to peaks of room temperature by direct To absorb solar radiation. Typically, for that Paraffins in microcapsules in building materials such as exterior plaster used by houses whose melting temperature at z. B. at 26 degrees Celsius. In textiles and functional clothing is the application of PCM also investigated.

From the DE 10 2005 049 690 It is known to provide a filter element in the interior with a latent heat storage.

The DE 10 2004 052 107 describes the use of a heat accumulator in the exhaust tract of an internal combustion engine, which is arranged downstream of a particulate filter and whose latent heat-storing material is traversed by exhaust ducts. The heat storage is used for temperature regulation of the exhaust gas flowing through a downstream nitrogen oxide storage catalytic converter.

The EP 0596854 discloses a catalyst with a latent heat storage, which is in the interior of the catalyst or optionally the jacket surrounding the jacket, ie in the form of a shell arranged. The latent heat accumulator may have its surface enlarging ribs.

The US 1395960 describes a monolithic catalytic converter for exhaust aftertreatment in internal combustion engine-powered motor vehicles, in which latent heat-storing materials are embedded in outlet-side regions of the monolith.

The US 2007/0292657 describes a temperature measurement in ceramic structures using materials that undergo irreversible phase changes from one solid phase to another solid phase.

Disclosure of the invention

The Particulate filter according to the invention or the inventive Method for operating or producing such a particle filter with the characterizing features of the independent claim In contrast, has the advantage of a life-prolonging and fuel-saving soot removal especially in diesel internal combustion engines to enable. The heat balance of a particulate filter can by latent heat storage by inlet side arrangement Material in particular in the filter substrate or in the gas channels the particle filter are energy-efficiently regulated.

It can (even local) excess temperatures of the particulate filter material with the consequence of cracking in the filter substrate, local melting, premature aging and material fatigue are avoided. The invention reduces the thermal stress in the substrate material of diesel particulate filters, in particular thermal load spikes and high temperature gradients in the full load range of the engine and during Particle filter regeneration and here especially during spontaneous auto-ignition and exothermic oxidation the soot particles at high exhaust gas temperatures.

Of Further, too low temperatures during Regeneration avoided and uniform thermal regeneration conditions are ensured In particular, favorable thermal regeneration conditions can Avoidance of cooling in the lower load range as well guaranteed at low outdoor temperatures become.

Furthermore, the invention allows the distribution of latent heat on the filter substrate and thus a uniform temperature and soot oxidation as well as a conservation and lifetime increase of catalytic coatings. Uniform thermal operating profiles contribute to the optimal operation of catalytic coatings in particular during engine operation at full load and regeneration at relatively low exhaust gas temperatures. Furthermore, the warm-up phase is shortened until the favorable for the regeneration thermal operating conditions.

The Connection of a latent heat accumulator with the substrate a particulate filter in the inlet side region of the outlet channels, in particular a diesel particulate filter is, in an advantageous manner on the today known types of such filters and in the automotive series applicable regeneration method applicable.

A Saving fuel during operation of the particulate filter provides one, because of the need for post fuel injections during regeneration decreases because of excess Heat stored in the PCM and back to the particulate filter during the regeneration can be delivered. Thus comes It is also less likely to interrupt regeneration, which is beneficial otherwise, any resumption of interrupted regeneration a renewed heating process conditional. The operation is also because of that fuel-saving, because a uniformly favorable Temperature level as a result of latent heat storage in the corresponding temperature range less heating by combustion re-injected fuel requires.

By those listed in the dependent claims Measures are advantageous developments and improvements possible. It is particularly advantageous, two or more latent heat storage materials with different melting temperatures to use. This allows a spread of the temperature range the latent heat storage while maintaining the internal thermal Energy in the filter substrate at a favorable temperature level until the next regeneration phase.

Farther it is advantageous, by inductive heating of an electrically conductive PCM thermally favorable operating conditions to achieve faster and a spontaneous auto-ignition and exothermic oxidation soot without critical thermal stress and uphold.

Further Benefits result from the others in the other dependent Claims and features mentioned in the description.

Brief description of the drawings

embodiments The invention are illustrated in the drawing and in the following description explained in more detail.

It demonstrate

1 a particle filter with stored latent heat-storing material,

2 Another particle filter with two different latent heat storage materials and

3 a particle filter with an induction heater.

embodiments the invention

1 shows a filter substrate 3 a particulate filter 1 in a cross-sectional side view. On the inlet side 5 The particulate filter flows from an internal combustion engine derived exhaust gas 11 into the filter substrate, and on the outlet side 7 leaves cleaned exhaust 13 the particle filter. The filter substrate has inlet channels 15 and outlet channels 17 wherein the inlet channels are open on the inlet side and closed on the outlet side, while the outlet channels are closed on the inlet side and open on the outlet side. Through the filter substrate 3 formed porous filter walls 19 The channels delimit these from each other, so that the exhaust gas after entering an inlet channel a filter wall 19 has to flow through to leave the filter substrate via an outlet channel again. In this case, the exhaust gas brought Russ leaves in the channels, more precisely on or in the filter walls 19 the channels, back. In the area of the inlet side are the outlet channels 17 with a latent heat storing material 9 filled. In particular materials with at least one solid-liquid phase transition in the operating temperature range of the particle filter are used as PCM. There are preferably suitable technical metals such as zinc with a melting temperature of 420 degrees Celsius, aluminum with a melting temperature of 660 degrees Celsius and metal alloys such as brass with a melting temperature of 900 degrees Celsius or metal compounds such as cast aluminum silicide with 12 percent silicon and a melting temperature of 575 degrees Celsius. Furthermore, salts such as sodium chloride (common salt) with a melting temperature of 800 degrees Celsius are foreseeable as PCM. The introduction of the PCM in the already fired filter substrate by blowing in the form of dust or fine granules and subsequent melting. During the subsequent cooling, due to the cohesive forces in the liquid phase of the PCM, larger droplets form, which solidify and partially fill not only the cavities of the outlet channels but also the pores of the filter walls of the outlet channels in the inlet side region of the filter.

During the exothermic regeneration ei A diesel particulate filter can reach temperatures of 800 degrees Celsius and higher both in the filter material and in the exhaust gas flow. This can lead to thermal problems in the filter material and at the tailpipe, especially at idle and at low speeds. In particular, filter materials such as cordierite are particularly sensitive to excess temperatures, which can lead to cracking in the substrate, deformation and destruction of the filter. On the other hand, the thermal conditions during the regeneration should be maintained until the regeneration is completed. During the regeneration of the particulate filter, a cooling down and thus a termination or an incomplete regeneration by too cold exhaust gases should be avoided. Excess temperature on the particulate filter substrate approximately made of cordierite leads in the filter operation to a control unit, not shown, actively controlled regeneration interruption. The regeneration interruption conditions stored in the electronic control unit associated with the internal combustion engine are "self-healing". If the regeneration is interrupted, the exhaust gas cools down again and the interruption condition "heals" so that it can be regenerated again. Conditions which make regeneration completely impossible usually have to lead to other measures (Russian operation, torque reduction to cause the driver to bring the vehicle to the workshop before it remains due to a clogged particulate filter). "Self-healing" interruption conditions have no noticeable disadvantages, except for a higher fuel consumption due to an increased regeneration frequency or an overall longer regeneration period. Permanently preventing the regeneration conditions, however, have a serious impact. The regeneration period is usually in the range 10 ... 20 min, depending on how favorable the thermal regeneration conditions are (oxygen supply, operating history, maintenance of the regeneration temperature). The PCM 9 now, the high thermal load peaks and temperature gradients at the face of the particulate filter substrate can reduce and absorb the heat energy of the exhaust gas well and thus contribute to the rarer that an already initiated regeneration must be interrupted. The required mass of the PCM depends on the maximum thermal energy to be buffered or absorbed, as a function of the engine power, typical load profiles, the regeneration duration of the particulate filter, etc.

Depending on the structural design of the particulate filter, depending on the structural design and heat capacity of the filter substrate, depending on the melting point and enthalpy of fusion of the (alternatively used) latently heat-storing material 9 and depending on the heat transfer rate between the particulate filter substrate and the exhaust gas or the exhaust gas line and the external environment of the vehicle, various modifications are possible. Instead of being arranged in the flow channels, the PCM can also be arranged in the particle-separating cavities of the porous, nonwoven or gauzy filter substrate. In an alternative embodiment, it may also be embedded in the filter substrate in the form of microcapsules. This can take place over the entire filter substrate or even only to specific zones, in particular the inlet-side region of the filter substrate. These microcapsules can already be introduced into the green, still to be extruded filter base material, extruded together with this and then sintered. Furthermore, latent heat storage materials may be provided between the filter substrate and a gas tube wall or the housing of the particulate filter. Furthermore, to improve the heat transfer between areas containing a latent heat storage material, and the filter substrate metal structures are provided in addition, unless the PCM is made of a metal anyway. This can be done, for example, by introducing small metal-walled cartridges filled with a PCM and adapted in their cross-section to the size of the outlet channels into the outlet channels. Furthermore, latent heat-storing materials arranged between the filter substrate and the housing of the particulate filter can likewise be provided with thermal bridges to the filter substrate or to the cooling plates or to the housing and the exhaust pipe in order to reduce the heat conduction from the heat source, the filter substrate, to the heat sink, the particulate filter housing or the exhaust pipe to improve.

2 shows the filter substrate of an alternative particulate filter 21 , in which next to the latent heat storing material 9 another latent heat storage material 23 is provided which is in the melting point of the PCM 9 different. Both materials are located in the inlet side 5 of the particulate filter 1 facing area of the outlet channels 17 , In this embodiment with two different PCMs, the higher melting temperature PCM is placed on the inlet side.

The Use of two PCM materials with two different melting temperatures serves the technically interesting temperature range of latent heat storage to expand.

The two materials can be separated by a wall, not shown, otherwise, for example, chemically react with each other or when their liquid phases otherwise would mix. This partition may contain or consist of the following materials individually or in combination: a metal compound whose melting point is above the operating temperature range of the particulate filter; a dense ceramic disk or pill which is pressed in the pultrusion process prior to sintering; the substrate material itself, with a smooth, pore-free surface.

3 shows another alternative particulate filter 31 with a latent heat storing material 9 in the form of a metal. The filter substrate 3 is surrounded by two induction coils whose coil turns 32 respectively. 33 are shown schematically in cross section. These two induction coils form together with the PCM material an electrically controllable or controllable eddy current heating 35 , that means a heating based on the induction principle.

By means of the eddy current heating, the PCM can be heated above its melting point to initiate and accelerate the regeneration faster or to heat the filter substrate and the electrically conductive, stored soot at low exhaust gas temperatures, which reduces the amount of fuel required for soot oxidation. The magnetic reflux of the induction coil (s) passes through the steel plate housing of the filter, not shown, it also shields the electromagnetic field to the outside effectively. The soot can be controlled controlled to the extent that the spontaneous spontaneous combustion and exothermic oxidation occurs even in the lower exhaust gas temperature range. The fact that two induction coils are provided, a molten zone of the latent heat-storing material along the outlet channels 17 be moved, similar to the squirrel cage rotor of a linear motor. Thus, it is possible to disperse the heat in the filter substrate and thereby counteract the ash deposition, even in the outlet side regions of the filter substrate, where regeneration becomes insufficient with increasing filter operation time.

It can also control more than two separately, consecutively arranged coils or more than two separately energizable coil be grown. in a simple embodiment also be provided only an induction coil.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102005049690 [0003]
• - DE 102004052107 [0004]
• - EP 0596854 [0005]
• US 1395960 [0006]
• US 2007/0292657 [0007]

Claims (16)

Particle filter ( 1 . 21 . 31 ), in particular for filtering exhaust gases of a diesel internal combustion engine, with a filter substrate ( 3 ) with an inlet side ( 5 ) and an outlet side ( 7 ) for the exhaust gases ( 11 . 13 ), wherein in the filter substrate ( 3 ) at least one on the outlet side ( 7 ) sealed inlet channel ( 15 ) and at least one on the inlet side ( 5 ) closed outlet channel ( 17 ), wherein the at least one outlet channel ( 17 ) from the at least one inlet channel ( 15 ) through at least one porous filter wall ( 19 ) of the filter substrate ( 3 ) is separated, characterized in that in the at least one outlet channel ( 17 ) at least in the area of the inlet side ( 5 ) a latent heat storage material ( 9 . 23 ) is arranged. Particulate filter according to claim 1, characterized in that the at least one outlet channel ( 17 ) is open on the outlet side. Particulate filter according to claim 1 and 2, characterized in that the latently heat-storing material ( 9 . 23 ) only in the region of the inlet side of the at least one outlet channel ( 17 ) is located. Particulate filter according to one of the preceding claims, characterized in that substantially in all the outlet channels at least in the region of the inlet side, a latent heat-storing material is arranged. Particulate filter according to one of the preceding claims, characterized in that the inlet-side arrangement of the latently heat-storing material in the at least one outlet channel by its embedding in the delimiting filter walls ( 19 ), in particular in the form of microcapsules. Particulate filter according to claim 5, characterized in that that the entire filter substrate with latentwärmespeicherndem Material is interspersed. Particulate filter according to one of the preceding claims, characterized in that the latentwärmespeichernde Material in the at least limited space of the filter walls an outlet channel is introduced. Particulate filter according to one of the preceding claims, that in at least one outlet channel another latent heat-storing material ( 23 . 9 ) is arranged, which differs in its phase transition temperature from the phase transition temperature of the latently heat-storing material. Particulate filter according to claim 8, that in at least an outlet channel both the latent heat storage material as well as the further latent heat storage material arranged is. Particulate filter according to one of the preceding claims, characterized in that the latentwärmespeichernde Material has a solid-liquid phase transition, in particular that it is a metal or a metallic compound is. Particulate filter according to one of the preceding claims, characterized in that an eddy current heater ( 35 ) is provided. Particulate filter according to claim 11, characterized in that an induction coil ( 32 ) of eddy current heating ( 35 ) the filter substrate ( 3 ) surrounds. Particulate filter according to claim 11 or 12, characterized in that the eddy current heating ( 35 ) at least two induction coils ( 32 . 33 ) having. Particulate filter according to one of the preceding claims, characterized in that the filter substrate is a ceramic Body is, in particular a cordierite containing ceramic Body. Method for operating a particulate filter according to one of the preceding claims, characterized in that one in at least one outlet channel ( 17 ) at least in the area of the inlet side ( 5 ) arranged latent heat storage material ( 9 . 23 ) protects the particulate filter from thermal overloads and / or supports regeneration of the particulate filter. Method for producing a particle filter according to one of the preceding claims, characterized in that in at least one outlet channel ( 17 ) at least in the area of the inlet side ( 5 ) a latent heat storage material ( 9 . 23 ) is arranged.