CN101300059A

CN101300059A - Exhaust particulate filter

Info

Publication number: CN101300059A
Application number: CNA2006800409873A
Authority: CN
Inventors: S·-W·S·程
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2005-09-01
Filing date: 2006-08-31
Publication date: 2008-11-05

Abstract

A particulate filter for an exhaust system configured to receive an exhaust flow is disclosed. The filter includes a wall-flow filtration element having a first regeneration zone and a second regeneration zone, the first zone being downstream of the second zone, and a heat source disposed at the first regeneration zone. In response to demand for regeneration, the wall-filtration element regenerates according to a staged regeneration such that the first zone initiates regeneration ahead of the second zone, and each zone regenerates in the direction of the exhaust flow.

Description

Exhaust particulate filter

Technical field

Present invention relates in general to a kind of gas extraction system, more specifically to the particulate filter that is used for diesel engine exhaust system.

Background technology

The automobile exhaust system that is used for diesel engine and other internal combustion engines generally includes filtration system, and described filtration system restriction particulate matter discharges with exhaust gas.In diesel engine system, this material generally includes carbonaceous material (cigarette ash) and dust particle.The current filter method of catching exhaust particulate concentrates on wall and flows through in the filter.Wall flows through filtering system and not only also has high filter efficiency to exhaust particulate but also to dust particle usually.Used the diesel particulate catalytic filter widely, wherein catalyst is applied to the front end of diesel particulate filter usually or is applied to whole filter, to reduce regeneration temperature.Be used in the gas extraction system realize that the catalyst of filter element regeneration or the layout of heat often generate high temperature in filtering body, this tends to limit the material that filters body and selects.Consider current particulate filter arrangements, wishing has a kind of more advanced particulate filter, can be with the regenerability work of effective filtration and improvement.

Summary of the invention

Embodiments of the invention comprise a kind of particulate filter that is used to be configured to receive the gas extraction system of exhaust stream.Described filter comprises: wall flows through the filter element part, has first renewing zone and second renewing zone, and first renewing zone is in downstream, second renewing zone; With the thermal source that is arranged on first renewing zone.In response to the demand of regeneration, wall flows through the filter element part regenerates according to the regeneration of classification, makes the renewing zone of winning begin regeneration before second renewing zone, and each district is along the direction regeneration of exhaust stream.

Another embodiment of the present invention comprises that a kind of regeneration is used to be configured to receive the method for particulate filter of the gas extraction system of exhaust stream.Described particulate filter comprises: wall flows through the filter element part, has first renewing zone and second renewing zone, and first renewing zone is in downstream, second renewing zone; With the thermal source that is arranged on first renewing zone.In response to the demand of regeneration, wall flows through the filter element part regenerates according to the regeneration of classification, makes the renewing zone of winning begin regeneration before second renewing zone, and each district is along the direction regeneration of exhaust stream.

Description of drawings

With reference to accompanying exemplary drawings, similar elements mark similarly in the accompanying drawings wherein:

Fig. 1 represents to adopt the gas extraction system of the embodiment of the invention;

Fig. 2 represents the stereogram according to the particulate filter of the embodiment of the invention;

Fig. 3 representation class is similar to Fig. 2 and according to the sectional view of the particulate filter of the embodiment of the invention;

Fig. 4 represents the schematic diagram according to the embodiment of the particulate filter of the embodiment of the invention; With

Fig. 5 a-Fig. 5 b, Fig. 6 a-Fig. 6 b and Fig. 7 are illustrated in and are similar to Fig. 2 under the different operating condition and according to the sectional view of the replaceable scheme of the particulate filter of the embodiment of the invention.

The specific embodiment

Embodiments of the invention provide a kind of particulate filter with reproducing characteristic of improvement, are used for the gas extraction system of automotive Diesel engine.Though embodiment described herein represents that automotive Diesel engine is as the exemplary diesel powerplant that uses particulate filter, but should be understood that, disclosed invention also can be applied to need be at other diesel powerplants of the function of this disclosed particulate filter, for example diesel-driven generator.Though disclosed invention is suitable for filtering the combustion by-product of Diesel engine very much, it also can be applicable to filter petrolic combustion by-product.

In Fig. 1, represented to be used for the exemplary gas extraction system 100 of automotive Diesel engine (not shown), gas extraction system 100 has manifold exhaust pipe 110, this manifold exhaust pipe 110 suitably is connected to the exhaust manifold (not shown) of Diesel engine (not shown) at one end, to receive the exhaust stream of representing with Reference numeral 150 generally.Turbocharger 140 is connected to intermediate manifold exhaust pipe 110 and intermediate exhaust pipe 120 suitably.Intermediate exhaust pipe 120 is connected to particulate filter 200 suitably to catch the exhaust particulate that exists in the exhaust stream 150, and filter 200 is connected to blast pipe 130 suitably.Be used to discharge the tail pipe (not shown) that exhaust after the adjusting flows to atmosphere and be connected to blast pipe 130 suitably.How gas extraction system 100 is led to manifold exhaust pipe 110, turbocharger 140, intermediate exhaust pipe 120, particulate filter 200, blast pipe 130, to be arrived atmosphere then from the exhaust manifold (not shown) by control exhaust stream 150, controls exhaust stream 150.Gas extraction system 100 has the nominal circulation area more than or equal to the inboard sectional flow area of manifold exhaust pipe 110.

Each particulate filter 200 has housing 210 and filter cell 220, and housing 210 can be any structure and the structural form that is suitable for this purpose, and filter cell 220 is included in the housing 210 suitably, can see best with reference now to Fig. 2.In one embodiment, filter cell 220 is a ceramic monolith structure.Filter cell 220 means that for wall flows through the filter type exhaust stream 150 arrives exit passageway 250 from intake channel 230 by porous inwall 240.When the filtration of exhaust stream 150 mainly occurs in the hole of exhaust stream 150 by inwall 240, thereby be called wall and flow through filter.Filter cell 220 is configured to catch exhaust particulate.

In an exemplary embodiment, each intake channel 230 at one end 310 has inlet ports 260, and has non-porous end-plug 270 at relative end 320.In one embodiment, non-porous end-plug 270 (for example 0.25-0.5 inch) is obviously thicker than filter wall (for example 0.010-0.020 inch).In alternative embodiment, non-porous end-plug 270 can substitute with porous end plug 270 '.In order to distinguish, end plug 270 is also referred to as the standard end plug at this.Embodiments of the invention can be applied to have the particulate filter 200 of standard end plug 270 or porous end plug 270 '.In each accompanying drawing, when relating to the porous end plug, Reference numeral 270 can substitute with Reference numeral 270 '.Each exit passageway 250 at one end 320 has outlet port 280, and has end plug 290 at relative end 310.Exhaust stream 150 enters filter cell 220 at inlet ports 260 places, by porous inwall 240, and discharges from filter cell 220 at outlet port 280 places.So, intake channel 230 and exit passageway 250 are via inwall 240 fluid communication with each other.The inwall 240 of filter cell 220 is made into the hole dimension that has less than about 30 microns, thereby allows catching of exhaust particulate.In one embodiment, porous end plug 270 has more than or equal to about 30 microns and be less than or equal to about 60 microns hole dimension.End plug 290 can maybe can have the loose structure that is similar to inwall 240 for solid.So, the technical staff will recognize easily, and porous end plug 270 has the porosity bigger than end plug 290 generally.

In the represented embodiment of Fig. 2, filter cell 220 is the ceramic monolith structure with a plurality of porous inwalls 240, and inwall 240 limits and isolation import and exit passageway 230,250.Import and exit passageway 230,250 are parallel to the direction of exhaust stream 150 to be arranged, when exhaust stream 150 causes cross-current (in Fig. 3 generally with arrow 300 expressions) during by inwall 240.Housing 210 comprises first end 310 and second end 320.Inlet ports 260 and end plug 290 are arranged on first end 310, and outlet port 280 and porous end plug 270 are arranged on second end 320.In one embodiment, as Fig. 2 and Fig. 3 represented illustratively, the total surface area of porous end plug 270 was substantially less than the total surface area of inwall 240, and exemplary ratio was less than about 1: 240.

Exit passageway 250 has outlet port 280 and flows 150 to discharge exhaust at second end, 320 places, and has the exhaust stream 150 that end plug 290 is come in obstruction at first end, 310 places.When exhaust stream 150 during by the porous wall 240 between import and the exit passageway 230,250, exhaust stream 150 obtains filtering in ceramic monolith structure 220.Exhaust byproducts, for example metal particle and carbonaceous material are hunted down at porous wall 240, end plug 290 and porous end plug 270 places.Exhaust stream 150 after the filtration is discharged at outlet port 280 places then.

As discussed above, porous end plug 270 can substitute with standard end plug 270 ', and unless otherwise indicated, discussion subsequently will be applied to its two.

Diesel particulate filter (dpf), for example particulate filter 200, and the filter cell 220 of more specifically saying so needs regeneration sometimes.Usually, regeneration is increased to the temperature that is higher than 650 ℃ by the inlet temperature with the exhaust gas at first end, 310 places and begins.When this temperature, the cigarette ash that is deposited on the filter wall 240 will react with the oxygen in the exhaust gas, and changes into CO and C0 ₂This reaction is strong heat release.This reaction will be passed to second end 320 to the downstream of filter with relevant heat, and this causes near the high temperature filter second end 320.Along with the soot oxidation at first end, 310 places that are deposited on filter, some exhaust gas will flow and pass through exit passageway 250 and flow out by filter wall 240.Thereby less fluid will be by the regenerating section not as yet of intake channel 230.

In order to improve the regenerability of particulate filter 200, embodiments of the invention provide the regeneration of classification, promptly, the length of particulate filter 200 is arranged to several districts from first end, 310 to second ends 320, for example first renewing zone 410 and second renewing zone 420, can find out best that with reference to figure 4 regeneration takes place then in first renewing zone 410 earlier in second renewing zone 420.Though embodiments of the invention are in this expression and be described as only having two districts, should be understood that, can use any amount of district according to embodiments of the invention, and scope of the present invention is not limited in two districts layout represented at this and that describe.

Each is distinguished 410,420 and has front end 411,421 and rear end 412,422 respectively.Demand in response to regeneration, make first renewing zone 410 in downstream at first regenerate, begin at its front end 411 places and proceed to its rear end 412, make the upstream second then regeneration of renewing zone 420 then, begin at its front end 421 places and proceed to its rear end 422 with flowing with flowing.(preceding to the back) beginning is then to second renewing zone 420 (preceding to back) of upstream from first renewing zone 410 in downstream for regenerative process, and the regeneration of this particulate filter 200 is called fractional regeneration.

Should be appreciated that no matter in the particulate filter 200 how many renewing zones are arranged from aforementioned content, all make the regeneration of classification begin in the catchment, upstream make progress in the district, and streamwise regeneration from front to back in each district.

The regeneration in each district can be caused that by the activation of heater 425,430 or catalyst 405 this will discuss in more detail hereinafter.

Though Fig. 4 is expressed as along first and second renewing zones 410,420 total length has heating element heater 425 respectively, 430, but should be understood that, only first renewing zone 410 has heater 425, and because the heat that produces will be mobile to the rear end 420 of first renewing zone 410 along the direction of exhaust stream naturally, so heater 425 can only be arranged near the front end 411 of first renewing zone 410.In alternative embodiment, similar arrangements also can be applied to second renewing zone 420.

With reference now to Fig. 5 a and Fig. 5 b,, they have represented traditional dpf regeneration.Fig. 5 a illustrates has evenly gathering less than the cigarette ash 400 on the filter wall 240 of about 500 ℃ inlet exhaust gas temperature.Fig. 5 b illustrates first end, the 310 places regeneration beginning of dpf 220, and wherein the inlet exhaust gas temperature has been increased to greater than about 650 ℃.At this, delivery temperature can raise by some fuel are directed in the gas extraction system, maybe the oxidation catalyst of dpf upstream can be used for oxidized and increase delivery temperature, maybe can be by being positioned at the electric heater elevated exhaust temperature of dpf upstream.In Fig. 5 b, dpf220 experiences high temperature and high oxidant concentration at first end, 310 places, and at second end, 320 places corresponding lower temperature of experience and lower oxidant concentration.Thereby still with reference to figure 5b, if there is not the help of embodiments of the invention, then the cigarette ash 400 at first end, 310 places will burn before the cigarette ash 400 at second end, 320 places.This causes that then exhaust stream passes through the wall 240 mobile exit passageways 250 that arrive from intake channel 230, concentrates with first end 310 towards dpf220, thereby causes by wall 240 lower towards the flow of second end 320.As a result, lower flow has reduced the capacity that exhaust gas is taken away the heat that produced by cigarette ash 400 oxidations.This situation may cause thermal runaway, because understand smoke deposition near the blind end (second end 320) of intake channel 230, and this may cause filter deterioration (filter melts or breaks).

Globality for fear of thermal run away condition and protection diesel particulate filter 200; embodiments of the invention comprise catalytic filter element 220, and it has the oxidation catalyst 405 at the last 25-50% place (first renewing zone 410) that is arranged in filter cell 220.Though the oxidation catalyst of embodiment in this is disclosed as the constrain percentage scope with the filter element length of being arranged in should be understood that this only is used for illustration purpose, other embodiment can have the catalyst coverage of different weight percentage.Fig. 6 a illustrates the catalytic filter 220 of zone-coating, has the oxidation catalyst 405 in about last 25% scope of second end 320 that is arranged in first renewing zone 410 in the inwall 240.Because catalyst 405 can reduce the firing temperature of soot deposits 400, so the reaction of cigarette ash and oxygen can at first begin near the rear end of filter 220 (second end 320), this will be used at first removing near the cigarette ash 400 the blind end (second end 320) that is deposited on intake channel 230.More particularly, as mentioned before, the regeneration of the filter cell 220 of first renewing zone 410 is along carrying out from the mobile direction of front end 411 rearward end 412 (referring to the Fig. 4 that has marked Reference numeral 411 and 412) of first renewing zone 410.As a result, more exhaust gas will flow along intake channel 230 before passing inwall 240 arrival exit passageways 250.What obtain like this allows to carry out better heat by convection current along the high flow of intake channel 230 towards the downstream and transmits, and thereby reduces the peak temperature and relevant thermal stress on the filter cell 220 during the filter regeneration.In addition, before the igniting of first end 310, promptly second renewing zone 420 is increased to and is higher than before about 650 ℃ temperature, seldom or do not have cigarette ash 400 left in left filter cell 220 blind ends (second end) 320 vicinity in first renewing zone 410.When passing to blind end (second end) 320 with the relevant heat energy of regeneration, at blind end seldom or not have the energy release that adds, and in the conventional regeneration method, this blind end is the highest place of temperature normally.

Fig. 6 b illustrates the dpf200 of Fig. 6 a, but inlet exhaust temperature is about 550 ℃ or higher.The catalyst 405 of second end, 320 vicinity in first renewing zone 410 reduces about 100 ℃ with the firing temperature of cigarette ash 400 effectively, and from about 650 ℃ to about 550 ℃, the igniting of cigarette ash 400 at first takes place in first renewing zone 410.When inlet exhaust temperature meets or exceeds 650 ℃, 420 regeneration of second renewing zone.

As previously mentioned, embodiments of the invention can adopt standard end plug 270 or porous end plug 270 '.Fig. 7 illustrates dpf200, and this dpf200 has porous end plug 270 ' and is arranged in the catalyst 405 in the last 25-50% scope of second end 320 in the inwall 240.Porous end plug 270 ' allows more air communication to cross intake channel 230 and arrives blind end, thereby has further reduced near the peak temperature the blind end (second end) 320.

As previously mentioned, the regeneration at 410,420 places, first and second renewing zones can be by auxiliary heater 425,430 rather than catalyst 405 beginnings, and described heater can be by control system 435 controls, so that controlled heating (referring to Fig. 4) to be provided.In another embodiment, can adopt the combination of heater and catalyst.Heater 425,430 can or be suitable for any firing equipment in this disclosed purpose for electric heater, microwave applicator.Heater 425,430, catalyst 405 or other heaters, for example Huo Hua cigarette ash is referred to as thermal source at this.

When as use this is disclosed, filter cell 220 can be by cordierite (Mg ₂Al ₄Si ₅O ₁₈, zeopan) or SiC (carborundum) make, they are two kinds of ceramic materials that can be used to make ceramic dpf.Yet about having the cordierite of forced regeneration, the peak temperature of conventional regeneration is too high for cordierite dpf, and this may cause that it breaks or melt.Thereby, this characteristic limitations the use of cordierite in dpf, although its cost is lower.Only the instruction that from then on discloses just as can be known, the unexpected effect that embodiments of the invention played is that the use of cordierite dpf is got ready.

In view of aforementioned content, some embodiments of the present invention can have some following advantages: by the regeneration of classification, promptly begin regeneration filter and proceed to upstream then, make peak temperature reduce in the catchment, and thereby reduced the thermal stress of particulate filter 200; By adopting the fractional regeneration from the catchment to the upstream, allow to regenerate along the direction of exhaust stream, this is the natural direction of hot-fluid; The heat localization at back (exhaust) end place of filter is less; Reduce the peak value regeneration temperature, thereby allowed particulate filter 200 to carry out the low regeneration of frequency; The potentiality that more reliable diesel particulate thing filter (dpf) is provided are arranged; And, the selection of using cordierite dpf is provided, it is more cheap and more fragile than SiC dpf, but is suitable for using fractional regeneration to be implemented in this disclosed purpose.

Though the present invention describes with reference to one exemplary embodiment, one skilled in the art will appreciate that and to carry out various changes and can and not depart from scope of the present invention with alternative its element of equivalent.In addition, can carry out many modifications,, and not depart from its essential scope so that concrete situation and material are suitable for instruction of the present invention.Therefore, the present invention is not limited to as implementing the specific embodiment that optimal mode of the present invention discloses, and the present invention will comprise all embodiment in the scope that falls into appended claims.In addition, the use of term " first ", " second " etc. does not refer to any order or importance, and on the contrary, term " first ", " second " etc. are used to distinguish each element.

Claims

1. a particulate filter is used to be configured to receive the gas extraction system that exhaust is flowed, and described filter comprises:

Wall flows through the filter element part, has first renewing zone and second renewing zone, and first renewing zone is in downstream, second renewing zone; With

Be arranged on the thermal source of first renewing zone;

Wherein, in response to the demand of regeneration, wall flows through the filter element part regenerates according to the regeneration of classification, makes the renewing zone of winning begin regeneration before second renewing zone, and each district is along the direction regeneration of exhaust stream.

2. particulate filter according to claim 1 is characterized in that:

Thermal source comprises catalyst.

3. particulate filter according to claim 1 is characterized in that:

Thermal source comprises heater.

4. particulate filter according to claim 3 is characterized in that:

Heater is an electric heater.

5. particulate filter according to claim 1 is characterized in that also comprising:

Be arranged on second thermal source of second renewing zone.

6. particulate filter according to claim 1 is characterized in that also comprising:

Be configured to the controller that begins to heat at the thermal source place.

7. particulate filter according to claim 1 is characterized in that: wall flows through the filter element part and comprises:

First end, second end and inwall, this inwall have the hole that forms the loose structure be enough to catch the carbon containing exhaust particulate;

With intake channel and exit passageway, this intake channel has inlet ports at first end, has first end plug at second end, and this exit passageway has second end plug at first end, has the outlet port at second end, and intake channel and exit passageway are communicated with through the inwall fluid;

Wherein said inwall limits first renewing zone and second renewing zone, this first renewing zone from second end towards first end about 25% to about 50% length with total length extend, this second renewing zone is with remaining about 50% to about 75% length extension of total length;

And wherein the inwall of first renewing zone is provided with oxidation catalyst.

8. particulate filter as claimed in claim 7 is characterized in that, described oxidation catalyst is arranged on the inwall of first renewing zone but is not arranged on second renewing zone.

9. particulate filter as claimed in claim 7 is characterized in that described oxidation catalyst comprises cordierite.

10. particulate filter as claimed in claim 7 is characterized in that the porosity of described first end plug is greater than the porosity of described second end plug.

11. a regeneration is used to be configured to receive the method for particulate filter of the gas extraction system of exhaust stream, described particulate filter comprises: wall flows through the filter element part, has first renewing zone and second renewing zone, and first renewing zone is in downstream, second renewing zone; With the thermal source that is arranged on first renewing zone, this method comprises:

In response to the demand of regeneration, flow through the filter element part according to the regeneration of the classification wall of regenerating, make the renewing zone of winning before second renewing zone, begin regeneration, and each district is along the direction regeneration of exhaust stream.

12. method as claimed in claim 11 is characterized in that, the regeneration of described first renewing zone comprises that oxidation catalyst through being arranged on first renewing zone is with the cigarette ash igniting of deposition.

13. method as claimed in claim 12 is characterized in that, the regeneration of described second renewing zone is included under the situation of the oxidation catalyst that is not arranged at second renewing zone cigarette ash igniting with deposition.

14. method as claimed in claim 11 is characterized in that, the regeneration of described first renewing zone comprises through being arranged near first renewing zone heater with the cigarette ash igniting of deposition.

15. method as claimed in claim 14 is characterized in that, the regeneration of described second renewing zone comprises through being arranged near second renewing zone heater with the cigarette ash igniting of deposition.