MXPA96004541A - Filter and cartridge for particle filter diesel, regenerable electricame - Google Patents
Filter and cartridge for particle filter diesel, regenerable electricameInfo
- Publication number
- MXPA96004541A MXPA96004541A MXPA/A/1996/004541A MX9604541A MXPA96004541A MX PA96004541 A MXPA96004541 A MX PA96004541A MX 9604541 A MX9604541 A MX 9604541A MX PA96004541 A MXPA96004541 A MX PA96004541A
- Authority
- MX
- Mexico
- Prior art keywords
- electrically resistive
- tube
- cartridge
- filter
- diesel particulate
- Prior art date
Links
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Abstract
An electrically regenerable filter and cartridge for diesel particulate filter comprising sheets with electrically variable resistivity, or a tube which, when energized, provides sufficient heat to burn-off particulates of soot trapped in the filter medium.
Description
FILTER AND CARTRIDGE FOR PA FILTER (R GENERATE E KG.RG RTGAMEKIE
This invention relates to filters and filter cartridges for diesel particles, electrically regenerated.
DESCIPOTOW PE TA? ÉCNT? RKTArTOI? O?
Diesel engines emit hazardous, sooty exhaust gases, which can become less hazardous by using diesel particulate filters, which removes at least a portion of the soot from the exhaust gas. The soot trapped by such filters accumulates over time, which requires periodic regeneration, (ie, removal of trapped soot). There are several techniques known in the art for regenerating filters for diesel particles. One technique involves the use of a gas burner to periodically burn the soot trapped in the filter medium. A second technique involves the use of coated catalytic materials on the filter medium. A third technique uses fuel that has additives
REF: 23132 catalytic reduce the temperature of oxidation of soot. A fourth technique utilizes electric heating elements in contact with the filter medium (see, for example, U.S. Patent Nos. 5,258,164 (Bloom et al.) And 5,224,973 (Hoppenstedt), European Patent Application No. 0 543 075 Al, published. on May 26, 1993, and European Patent Application No. 0 608 783 A1, published on August 3, 1994. In addition, the known electric tubular heating element configurations are useful for regenerating cartridges for diesel particulate filters that include tubes formed of expanded metal (see, for example, Figure 1) and grooved sheet material (see, for example, Figure 2.) A problem related to such tubular configurations is that as a result of temperature cycling and expansions and corresponding thermal contractions accumulate circumferential tensions leading to the radial bending of the heating element. tension elements in the heating element which provide starting points for fractures; penetration of the heating element into the filter medium which may damage or interfere with the filter function; or separation of portions of the heating element from the filter medium. In addition, such a heating element can be bent radially on itself, which causes the heating element to produce a short circuit. Although this problem is solved with the invention described in the application for European Patent No. 0 608 783 A1, published on August 3, 1994, additional solutions are desired. An example of a grooved, electrically resistive sheet used in the application for Smith et al. Provides a heating element as shown in Figures 3 and 6. Another problem associated with the heating elements for the known tubular diesel particulate filter it is the uneven dissipation of the heat through the filter medium, the hot zones undesirably located in the heating element, and a reduced combustion of the soot due to losses by transfer of heat conduction to the soot particles, and a greater heat transfer by convection in the central region of the filter cartridge, compared to heat transfer and the end region of the cartridge. In addition, the known electric diesel filter heaters do not vary the heat energy converted electrically along the filter. In other words, such heaters have a constant heat density in watts, relative to the length of the heater which means that, when the heater is covered with filter media, a central "hot zone" is significantly hotter than the ends. of the heater. To further illustrate this effect, see Figure 4, which shows a filter cartridge 400 for diesel particles having a conventional electric heater 401 and a filter means 402. During the regeneration of the filter cartridge 400, uneven heating along the filter cartridge causes the burning out of soot particles trapped in region 403, but not in regions 404. This uneven distribution of temperature is considered to be due to heat losses through the end of the diesel filter and through the flow path of the outflow. This uneven distribution of temperature can lead to several problems, such as: (1) incomplete combustion of the soot collected in the filter medium does not reach the combustion temperature of the diesel soot; (2) undesirable high temperatures in the "hot zone" can be brought to a melting point of the material with which the heater is manufactured; and (3) undesirable high temperatures in the "hot zone" that can melt ash with the filtering medium.
BRIEF DESCRIPTION OF THE INVENCIQKr
The present invention provides a first filter cartridge for diesel particles, comprising: (a) an electrically resistive tube, substantially rigid, having an outer surface, a first end, a second end, openings extending from the outer surface toward the inner surface, and a length extending from the ends of the electrically resistive tube; wherein the electrically resistive tube has first, second and third imaginary zones between the ends of the electrically resistive tube; wherein each zone has a length equal to one third of the length of the electrically resistive tube; wherein the second zone is placed between the first and third zones; wherein when a voltage is applied across the first and second ends of the electrically resistive tube, a quantity of heat is generated in each zone; and wherein the amount of heat generated in each of the first and third zones is greater (usually at least 5 percent, preferably, at least 10 percent, more preferably at least 15 percent, and even more preferably at least 30 percent, and much more preferably at least 45 percent) compared to the amount of heat generated in the second zone; (b) a filtering element comprising an inorganic fiber covering the openings of the electrically resistive tube; and (c) a means for applying a voltage across the ends of the electrically resistive tube to heat it above the combustion point of trapped diesel exhaust particles, the electrically resistive tube is placed in a manner when voltage is applied through of the electrically resistive tube, sufficient heat is transferred from the electrically resistive tube to the soot particles trapped in the filtration element so that the soot particles are removed by burning. In another aspect, the present invention provides a second filter cartridge for diesel particles, comprising: (a) a substantially rigid tubular or hollow support member having two ends and an outer surface with openings extending from the surface outside to an interior surface;
(b) a first filter element comprising an inorganic fiber covering the openings; (c) an electrically resistive sheet or sheet (preferably a plurality of electrically resistive sheets, more preferably two or three electrically resistive sheets) having an outer surface, a first end, a second end, openings extending from the outer surface towards the inner surface, and a length extending from the ends of the electrically resistive sheet; wherein the electrically resistive sheet has a first, second and third imaginary zones of the ends of the electrically resistive sheet, - wherein each zone has a length equal to one third of the length of the electrically resistive sheet; wherein the second zone is placed between the first and third zones; so that, when a voltage is applied across the ends of the electrically resistive sheet, a quantity of heat is generated in each zone; and where the amount of heat generated in each of the first and third zones is greater
(usually at least 5 percent, preferably at least 10 percent, more preferably at least 15 percent, and even more preferably at least 30 percent, much more preferably at least minus 45 percent) than the amount of heat generated in the second zone; and (d) means for applying a voltage to the ends of the electrically resistive sheet so that a voltage is applied across the electrically resistive sheet sufficient to heat it to the point of combustion of the trapped diesel exhaust particles., the electrically resistive sheet is placed so that when a voltage is applied across the electrically resistive sheet, sufficient heat is transferred from the sheet to the soot particles trapped in the filter element so that the soot particles are removed by burned. Preferably, the electrically resistive sheets are placed to allow circumferential expansion of the sheets. Electrically resistive sheets can be placed, for example, to provide sufficient space between the sides of the sheets so that when the sheets expand during heating, the sides can expand circumferentially without expanding to each other, which can lead to radial bend. In addition, if the sheets extend more than 100% of the circumference of the first filter element, the sheets can be placed to allow portions of overlap of the sheets to slide between them.
In still another aspect, the present invention provides a third filter cartridge for diesel particles, comprising: (a) a hollow, substantially rigid tubular support member having an outer surface, two ends and openings extending from the outer surface towards the inner surface; (b) a filtering element comprising an inorganic fiber covering the openings of the support member, the filter element having an outer surface; (c) an electrically resistive tube having an outer surface, a first end, a second end, openings extending from the outer surface to the inner surface, and a length extending from the ends of the electrically resistive tube; wherein the electrically resistive tube has first, second and third imaginary zones between the ends of the electrically resistive tube; wherein each zone has a length equal to one third of the length of the electrically resistive tube; wherein the second zone is placed between the first and third zones; wherein, when a voltage is applied across the ends of the electrically resistive tube, a quantity of heat is generated in each zone; wherein the amount of heat generated in each of the first and third zones is greater (usually at least 5 percent, preferably at least 10 percent, more preferably at least 15 percent, and even more preferably at least 30 percent, much more preferably at least 45 percent) than the amount of heat generated in the second zone; and (d) means to apply a voltage across the electrically resistive tube to heat it above the combustion point of trapped diesel exhaust particles, the electrically resistive tube is positioned so that when a voltage is applied across the tube electrically resistive, sufficient heat is transferred from the electrically resistive tube to the soot particles trapped in the filtration element so that the soot particles are removed by burning. For the second and third filters for diesel particles of the present invention, if the support member is electrically conductive, the support member and the electrically resistive sheets of the tube are preferably electrically isolated from each other. A preferred embodiment of the second and third filter cartridges comprises a second filter element comprising an inorganic fiber covering the apertures of the electrically resistive sheets or the electrically resistive tube. In other embodiments according to the invention, which may include those described in the foregoing, the electrically resistive tube or sheets may have a first, second, third and fourth and fifth imaginary zones between the ends of electrically resistive tube sheet or sheet; wherein each zone has a length equal to one fifth of the length of the electrically resistive tube or sheet; where the second zone is placed between the first and third zones, the third zone is placed between the second and quarter zones, and the fourth zone is placed between the third and fifth zones; wherein, when a voltage is applied across the ends of the electrically resistive tube or sheet, a quantity of heat is generated in each zone; and wherein the amount of heat generated in each of the third and fourth zones (preferably, each of the first, second and third, fourth and fifth zones) is greater (preferably at least 5 percent, preferably at least 10 percent, even more preferably at least 15 percent, at least 30 percent, and even at least 45 percent) compared to the amount of heat generated in the third zone .
Preferably, a filter cartridge according to the present invention additionally comprises means for holding the cartridge in a cover or box. Preferably, the filter cartridge according to the present invention additionally comprises means for driving exhaust or exhaust gases to flow through the openings of the support member and the electrically resistive sheets or the tube. In another aspect, the present invention provides a filter or trap for diesel particles, comprising (a) a cover having at least two ends; (b) means for connecting at least the two ends of the cover to an exhaust or exhaust system; (c) means for holding at least one filter cartridge for diesel particles; and (d) at least one filter cartridge according to the present invention comprising means for supporting the cartridge in a cover, wherein the two ends of the electrically resistive tube or support member extend between the two ends of the cartridge. cover and are held on the deck by supporting means.
To provide a more efficient heat transfer, at least one face of the electrically resistive sheets or the tube is preferably in intimate contact with the filter element. If the electrically resistive sheets or tube are hidden in the filter element, preferably substantially the entire area of each major surface of the electrically resistive sheets or tube (i.e., the inner and outer surfaces) are in contact with the filter element. In addition, the heat insulating nature of the filter element tends to confine the heat and reduce heat radiation losses of the heater, which minimizes the energy required to burn-off the trapped soot particles. Preferably, the electrically resistive sheets or tube are positioned so that they are located near the maximum soot collection region. In this application: as used herein, "substantially rigid" means that the tube or support member is self-supporting and is capable of supporting the filter media covering the outer surface thereof;
as used herein, "hot zone" refers to a central portion of an electric filter that operates at a temperature greater than the filter ends; "strand" with respect to the heating elements refers to a solid strip or tape of material having two opposite sides, wherein each opposite point along the two opposite sides is usually parallel; for example, a thread in the configuration
220 of the heating element shown in Figure 2 is represented by the area 221 with diagonals; a strand in the heating element of the configuration 230 shown in figure 3 is represented by the area 231 with diagonals; a strand in the configuration 250 of the heating element shown in Figure 5 is represented by the area 251 with diagonals; as used herein, "current path length" refers herein to the shortest electric current path between two points; for example, the current path through the length of a tube formed in the configuration shown in FIG. 5, wherein the length of the tube is in the x direction, as shown by line 255; furthermore, the length of the circumferential current path of a tube formed by the configuration shown in Fig. 5 is shown by line 256;
as used in the present "portion" refers to a sudden, significant deformation of the structure that results in a slight increase of an existing load under which the structure shows some deformation, if any, before increasing the load; for example, a measuring rod placed at one end is usually capable of holding a load of several kilograms without significant lateral deformation, but if the load is increased until the measuring rod deforms slightly, any additional increase in load will result in bending. large laterals; More specifically, a torsion occurs when the applied load, PAPP, to a strand of a heating element, is greater than the critical load, PCr, where the critical load is defined by
'Cr- iTEbt3, 31'
where E is the Yong module of the thread material; b is the width of the strand; t is the thickness of the strand; and 1 is the length of the strand before the load is applied;
"Inorganic fiber" refers to any fiber with an inorganic base which is resistant to high temperatures (for example, temperatures above about 600 ° C), which is chemical resistant to diesel exhaust gas, and which has textile qualities (ie , which is suitable for winding, bending, etc., required to make a filter element); "yarn" means a plurality or group of individual fibers or filaments; "thermo-volatile fiber or mofugitive fiber" refers to a fiber comprising constituents which decompose and volatilize when heated (eg, organic material); and "fiber segment" refers to a portion of a broken fiber projecting from the core of the yarn. The present invention provides an efficient and economical means for regenerating (ie, burning off collected soot) from a diesel particulate filter cartridge. The preferred electric heating elements used in the diesel particulate filter cartridges according to the present invention provide a solution to the "hot zone" problem associated with electrical heating elements of diesel particulate filters.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be understood more readily with reference to the drawings: In the drawings: Figure 1 is a plan view of the expanded metal sheet known to be useful for making the electrically resistive heating element used to regenerate a filter for diesel particles; Figure 2 is a plan view of an electrically resistive grooved sheet, known to be useful for making an electrically resistive heating element used to regenerate a diesel particulate filter; Figure 3 is a plan view of another preferred electrically resistive sheet known to be useful for making an electrically resistive heating element used to regenerate a diesel particulate filter (see European Patent Application Number 0 608 783 A1, published on 3 August 1994): Figure 4 is a longitudinal cross-section of a diesel particulate filter showing the "hot zone" and which is usually burned by the soot associated with known electrically regenerable diesel particulate filters as a result of a non-uniform heating;
Figure 5 is a plan view of a linearly variable, electrically resistive, laminated resistance sheet configuration (ie, successive strands at both ends of the sheet towards the center of the sheet decrease in strength) useful for making a cartridge diesel particulate filter according to the present invention, wherein the width 251 of the strand that is located at the center of the sheet configuration is greater than the width of the strand 252 located at one end of the sheet; Figure 6 is a plan view of an electrically resistive grooved sheet, known to be useful for making an electrically resistive heating element used to regenerate a diesel particulate filter; Figure 7 is a longitudinal cross-section of a first preferred diesel particulate filter cartridge according to this invention; Figure 8 is a longitudinal cross section of a filter or trap for diesel particles consisting of four of the filter cartridges shown in Figure 7; Figure 9 is a cross section along the line 9-9 of Figure 8;
Figure 10 is a longitudinal cross-section of another filter cartridge for diesel particles according to this invention; Figure 11 shows a portion of the surface of a filter element, greatly increased; Figure 12 is a cross section of a filtering element with four sides, greatly enlarged; Figure 13 is a cross-section of a four-sided filter element having cross-winding wraps, laterally offset, greatly increased; Figures 14, 15, 16 and 17 are plan views of the preferred electrically resistive metal sheets useful for making the electrically resistive heating elements used in the diesel particulate filter cartridges in accordance with the present invention; Fig. 18 is a plan view of a grooved, electrically resistive, variable resistance sheet configuration useful for manufacturing the diesel particulate filter cartridge according to the present invention, wherein there are twelve current paths between the ends of the filter. the sheet;
Figures 19 and 20 show examples of expansion joints which can be incorporated in the electrically resistive sheets or tubes (or in the support member); Figure 21 shows an example of a bellows expansion joint which can be incorporated in the electrically resistive sheets or tubes (or in the support member).
With reference to Figure 1, a diesel particulate filter cartridge 19, in accordance with the present invention, comprises a slotted tube 20 electrically resistive having a circular metal cover 21 and an annular ring 22 welded. The threaded metal post 23 is welded with the circular metal cover 21. Four metal mounting rods 24 are welded to the metallic annular ring 22. The threaded metal post 23 is connected to a conventional switch (not shown) which in turn is connected to a conventional power source (not shown). The metal mounting studs or rivets 24 provide an electrical ground for the circuit. The filter medium 25 is constituted by an inorganic yarn which is coiled in a substantially helical manner around the grooved electrically resistive tube 20. A preferred diesel particle filter or trap, according to the present invention is shown in Figures 8 and 9. The diesel particle filter or trap 70 comprises an elongated cover 71 having a cylindrical body 72, a conical exhaust inlet 73 and a conical exhaust 74. There are four separate, substantially parallel, diesel particulate filter cartridges within the cylindrical body 72, extending within the inlet and outlet ends, according to the present invention 80. Each filter cartridge 80 is mounted on a plate. 76 circular metal which has a circular opening to allow the exhaust gas to pass radially inward and outwardly out through the filter cartridge 80 and out the filter 70 through a conical exhaust 74. The threaded metal post 77 supported by the open support structure 78 is insulated from the open support structure 78 by a ceramic insulator 88. The metal valve 93 is placed in the conical inlet 73 to divert the exhaust gas flow from the cartridge 80. filter during regeneration, so that energy requirements are reduced.
In order to minimize the amount of electric power used at any time in time, a diesel particulate trap constituted of a plurality of filter cartridges preferably includes means for independently activating each of the electrically resistive tubes at different times (eg. example, in sequence). With reference to Figure 10, the preferred diesel particulate filter cartridge 100 according to the present invention comprises a tubular support member 106 having an outer surface with openings extending from the outer surface towards the inner surface covered by the inner filter element 110, which in turn is covered by the sheets or grooved tube 101, electrically resistive, which in turn is covered by the outer filter element 112. The tubular support member 106 is electrically isolated from the inner metallic ring 107 by a sleeve 108 of aluminoborosilicate ceramic oxide fiber (commercially available, for example, under the trade designation "NEXTEL 2 INCH BRAIDED SLEEVING WITH 170 SIZING" from the company 3M from St. Paul, MN).
The end 124 of the lamellae or grooved electrical tube 101 are clamped between the inner metallic ring 107 and the outer metallic ring 123, which is electrically connected to the electrical post 125. The electric pole 125 can be connected to a conventional power source (not shown). The central threaded post 126 is welded to the metal end cap 131, which is welded to the tubular support member 106. The central threaded post 126 can be used to hold one end of the filter cartridge 100 in a cover or box. The open end of the tubular support member 106 fits the inner annular collar 127 and is welded. The end 124A of the lamellae or grooved electrical tube 101 is clamped between the annular collar 127 and the outer ring 128. The annular collar 127 is welded to the circular metal flange 129 which has a circular opening to allow the exhaust or exhaust gases to pass radially inward and outwardly through the filter cartridge 100. The circular metal flange 129 has mounting rods 130 that adjust by pressure or that are welded to join the cover. The cover, the plates and the posts can be constituted independently of any suitable material including, for example, metals or ceramic materials, although metals are preferred, for example, if the cover, the plate or the post will serve as a electrical conductor. In addition, for ease of manufacture, the preferred material is a metal. Preferably, the metal is stainless steel. The means for connecting the cover, the plates and the posts include those known in the art for the particular material of which the cover, the plates and the posts are constituted. For example, if the cover, plates and posts are made of metal, the preferred means for connecting them is by welding. The shape of the cover can vary according to convenience. Suitable shapes include those having a circular cross section, an elliptical cross section, a square cross section and a rectangular cross section. Usually, the cover is elongated to allow it to have a thin profile. The hollow support member may be constituted of any suitable material including, for example, metals and ceramic materials. The hollow support member may be, for example, a tube with holes, a sheet or wire screen, or an expanded metal, provided that it is substantially rigid. Preferably, the hollow support member comprises a metal. More preferably, the metal is a high temperature metal (i.e., that substantially maintains its physical properties at temperatures above about 600 ° C) such as a nickel-chromium-iron alloy (including those commercially available under the trademark designations "INCONEL 600" and "INCOLOY 800" by Inco Alloy International, Huntington Inc., WV, 'HAYNES 556' by Haynes International of Kokomo, IN, and "KANTHAL Al" by The Kanthal Corp. of Bethel, CT.) The shape of the hollow tubular support member may vary as appropriate, as it is described in the foregoing for the cover.Preferably, the hollow support member has a circular or elliptical cross section.The openings in the hollow support member can be as large as possible while maintaining rigidity. Each opening is of a diameter in the range of from about 1 to about 20 mm, More preferably, each opening is made of a diameter in the range of from about 2 to about 10 mm, and more preferably in the range of about 3 to about 7 mm The size of the individual openings may be the same, different or a combination of both.
Preferably, the openings occupy a range from about 40 to about
80 percent of the total projected area of the hollow support member. More preferably, the openings occupy in the range from about 50 to about 70 percent of the total projected area of the hollow support member. An open area substantially greater than 80 percent can significantly affect the structural integrity of the hollow support member. On the other hand, an open area substantially less than 40 percent can cause undesirably high backpressures during use. Preferably, the openings are evenly distributed over the surface of each hollow support member, except at the ends of the support member which are preferably perforated. The filter element or means comprises an inorganic fiber or yarn which can be in any way useful for trapping soot from diesel particles. Suitable filtration elements or means include inorganic fiber or yarn wound helically around a hollow support member or an electrically resistive tube; woven fabric, non-woven celtas or combinations thereof. The inorganic fibers or yarn are preferably made of ceramic material. The ceramic fibers or threads can be, for example, amorphous (including glass), polycrystalline or a combination thereof. Useful ceramic fibers or threads are known in the art for such purposes and include those consisting of borosilicate aluminum, aluminum oxide, silicon dioxide or silicon carbide. The configuration of the filter element is preferably selected to allow a high degree of filtration efficiency without significant back pressure.
IWPRfiftMICQ THREAD EM ^ LIADO 0 BOBINADO
Preferably, the inorganic yarn wound helically around the hollow support member has a diameter in the range of from about 0.5 to about 5 mm. Most preferably, the diameter is in the range of from about 1 to about 3 mm. Yarn diameters in the ranges usually specified have superior textile qualities compared to yarns with diameters outside these ranges. Usually these threads are constituted in the range from about 780 to about 7800 individual inorganic fibers. Preferably, the inorganic yarn is formed in the range from about 1560 to about 4680 individual fibers. The inorganic thread can be twisted by folds. Preferably, the inorganic fibers have a diameter in the range of from about 5 to about 20 microns. More preferably, the inorganic fibers have a diameter in the range from about 7 to about 15 microns, and more preferably in the range from about 9 to about 14 microns. Fibers having a diameter within the specified ranges are generally easier to manufacture and texturize compared to fibers having diameters substantially outside these ranges. In addition, fibers substantially below 5 micrometers in diameter tend to be easily damaged (i.e., break when texturized). Useful ceramic yarns include those made of fibers made of borosilicate aluminum, aluminum oxide, silicon dioxide or silicon carbide. Preferably, the ceramic fiber consists of an aluminoborosilicate. To assist in handling, the yarns are preferably dimensioned by the use of conventional sizing techniques. Aluminoborosilicate fibers are commercially available, for example, under the trademark designations "NEXTEL 312 CERAMIC YARN" and "NEXTEL 440 CERAMIC YARN" from 3M Company of St. Paul, MN. The texturing of the inorganic yarn improves its filtering efficiency and trapping. Preferably, the inorganic yarn is textured so that if it is fluffy, for example, by being textured so that the curls of continuous fibers, the individual fiber segments or a combination thereof extend outward from a dense core. . Curls of continuous fibers are most preferred. The inorganic yarn may be textured by techniques known in the art including, for example, air jet texturing or mechanical texturing. Air jet texturing is preferred because it generally provides a textured yarn having fewer fiber segments and more crimps per fiber compared to yarn texturing technique by mechanical means. Preferably, the textured inorganic yarn has a diameter in the range from about 1 to about 10 mm. More preferably, the diameter of the textured inorganic yarn is in the range of about 3 to about 6 mm. The filtering or trapping efficiency of the textured yarn having a diameter in the specified ranges is generally superior compared to yarns having diameters outside these ranges. To improve the filtering efficiency, the inorganic yarn is preferably cross-wound substantially helically around the support member or the electrically resistive tube. Most preferably, the yarn is wrapped in a substantially helical cross-wound shape around the support member or the electrically resistive tube to form four-sided openings. Preferably, the inorganic yarn comprises a dense core from which at least one of the loops of continuous fibers and fiber segments extends outwardly, wherein the cores of successive convolutions of each successive layer are radially aligned to provide relatively dense walls that are spaced apart to define openings with four sides, and wherein the fiber loops and the fiber segments project from each other from the openings of the four sides, and the fiber loops and adjacent convolutional fiber segments they are inter-mixed to provide with each of the four-sided openings, a trap for the diesel exhaust particles. With reference to FIGS. 11 and 12, a four-sided filter element 149 has helicidally cross-wound inorganic yarn comprising ceramic yarn having a dense core 150 from which the fiber segments, the continuous fiber loops or combinations thereof 152 protrude outwards. Figures 11 and 12 show a yarn which has been subjected to cross-winding in layers, initially at an angle of about 45 ° to the axis of the hollow support member 154, or an electrically resistive tube (having openings 156) in each winding direction. To form the four-sided openings, the winding angle of each successive layer (i.e., full coverage of a hollow support member before the four-sided pattern is repeated) of yarn is slightly increased (i.e. approximately 0.25 °), so that the core of the wire is radially aligned with the underlying core. This winding arrangement results in adjacent convolutions that are widely separated on the first pass and then intermingled with subsequent convolutions until the separations between adjacent convoluses are uniform. This arrangement or arrangement results inherently in the intermixing of directly opposite convolutions in each of the layers which provides stabilization to the filtering element against the exhaust or exhaust forces.
The radially aligned cores, wound around the hollow support member or the electrically resistive tube collectively form relatively dense walls 151 which are spaced apart to define four-sided openings 155 (ie, in the form of diamonds or diamonds). Fiber segments, fiber loops or combinations thereof are projected into each of the four-sided openings 155, and the fiber segments and fiber loops of the laterally adjacent convolutions are interspersed, as shown. in Figure 12. As the winding extends to areas that are not perforated, the winding angle preferably changes under computer control so that adjacent convolutions of the yarn progressively come together more and more to provide relatively thick walls that they are usually impervious to the flow of exhausted material. Because each of the walls 151 extends radially, the four-sided openings 155 are funnel-shaped, as seen in FIG. 12. In addition, the density of the fiber segments and the fiber curls tend to increase from the outside face to the base of each opening, which provides a distribution of the particle traps over the total depth of the filter element, when the exhaust material flows radially inward, through the filtering element. The filtering capacity of the filter element can be improved by using highly textured yarn in a downstream portion and by using progressively less textured yarn in the portions that are most current outward. Preferably, the convolution nuclei of at least one layer are laterally offset from the convolution nuclei of at least one adjacent layer so as to divert the generally radial exhaust flow towards tortuous or irregular trajectories. More preferably, the filter element comprises at least four layers of yarns (preferably 10 to 30 layers), and the convolution nuclei of at least 3 layers (preferably 5 to 15 layers) laterally deviated of the nuclei of convolusions of the underlying layer. In addition, the convolution nuclei of adjacent deviated layers are preferably more closely separated from each other in comparison to convolution nuclei of the same layer. The closest separations provide better support for the fiber segments, whereby damage is reduced and each fiber segment is also allowed to hold a larger amount of soot, advantages that can be obtained while maintaining satisfactorily low return pressures. In contrast, when all successive convolution nuclei are aligned radially with the underlying convolution nuclei, any reduction in the separation between nuclei increases the return pressure. With reference to Figure 13, the four-sided filter element 159 has laterally deflected transverse winding wraps with cores of each successive convolution of the first four layers 160 of untextured yarn wound tightly and radially aligned with the core of an underlying convolution . The radically aligned cores together form separate walls that define a first group of four-way openings that are funnel-shaped, as seen in Figure 13. By rotating the mandrel 23 ° before applying the second group of four layers 164 of textured yarn, their radially aligned convolutional cores bisect the four-sided openings formed by the first four layers 160, and thus form a second group of openings with four sides. After rotating the mandrel another 23 °, a third group of layers 168 of yarn is placed to form a third group with four-sided openings. As seen in figure 13, the coils of the radially aligned thread convolutions of the third group covers 168 are bisected to the second group of four-sided openings and radially aligned with the convolution cores of the first group of four layers 160. Then, the mandrel is rotated 11.5. ° before applying a fourth layer. 170 single strand forming a fourth four-sided opening group. Each core of a convolution of the fourth layer 170 is laterally offset by 25% of the distance through the four-sided openings of the third group of layers 168. The mandrel is again rotated 11.5 ° before applying a fifth layer of 171, of single thread forming a fifth group of openings with four sides. Each core of a convolution of the fifth layer 171 bisects the openings of four sides of the third group of layers 168 and is radially aligned with the convolution nuclei of the second group of layers 164. Again, the mandrel is rotated 11.5 ° before applying the sixth group of layers 172 of four-sided yarn which are radially aligned to form the sixth group of openings with four sides. Each convolution of the yarn cores of the sixth layer 172 bisects gaps between the convolution cores of the fifth layer 171 and convolution cores of the third group of layers 168. The resulting filter element 159 on the hollow support member or the tube 162 Electrically resistive has openings 166 containing diesiceis layers of yarn. When applied, each successive thread layer of the filtering element 159, the winding angle is slightly increased (eg, about 0.25 °) either to place the yarn core in radial alignment with the underlying core of the previous layer or to provide a desired lateral deviation. The exhaust gas or outlet is diverted in tortuous paths by the yarn cores laterally deviated from the five outer layers groups of the filter element 159. Like the windings for four-sided filters that extend into the perforated areas, the winding angle preferably changes under computer control, so that adjacent convolutions of the wire are progressively joined together to provide end walls. relatively thick which are substantially impervious to the exhaust flow. The density of the fiber and loop segments of the continuous fiber tends to increase from the outer face towards the base of each opening, which provides a distribution of particular traps over the entire depth of the filter element. The filtering capacity of the element of; The filter can be improved by using an upper texturized yarn in the downstream region and the use of progressively less textured yarn in regions that are more upstream. Preferably, the angle at which the filtering element is wound or coiled is in the range from about 30 ° to about 70 ° with respect to the axis of the hollow support member or to the electrically resistive tube in each winding direction. More preferably, the winding angle is in the range from about 30 ° to about 60 °. More preferably, the winding angle is in the range from about 45 ° to about 55 °. The use of winding angles within the usually specified ranges provides a filtering element which is more efficient and is better fixed to the hollow support member or to the electrically resistive tube as compared to the filters wound or wound at an angle substantially outside of these intervals. For the first transverse wound circuit (i.e., a winding passes in each direction), the four-sided openings (which cover the open areas) are preferably of uniform size and shape.
Preferably, the size of the opening between the opposite corners of the four-sided openings is in the range from about 3 mm to about 20 mm in each of the axial and circumferential actions of the hollow support member or the electrically resistive tube. . More preferably, the opening size between opposite corners of the four-sided opening is in the range of about 4 mm to about 13 mm in each of the axial and circumferential directions of the hollow support member or the electrically resistive tube. Openings substantially greater than the established intervals may provide inadequate filtering efficiency, while openings substantially smaller than the established ranges may result in undesirably high back pressures. When winding the wire around the hollow support member or tube electrically resistive, the winding tension is preferably as high as possible, without breaking the yarn. Usually, the winding tension is in the range from about 4 to about 19.6 Newtons. Preferably, the winding tension is in the range from about 4 to about 13 Newtons. Excessive winding tensions tend to produce undesirable compaction when convolutions are supported by fiber segments of the underlying layer. In order to increase the accumulation of soot close to the electrically resistive sheets or the tube, the region of the filter element upstream from the electrically resistive sheets or the tube is preferably relatively free of contiguous fiber loops and fiber segments (ie. say, slightly textured). Each filtering element can be constituted by one or more layers of inorganic yarn wound transversely, winding in a substantially helical manner, or it can be constituted of one or more non-woven felts made of inorganic fibers, where the plush is held against the radially outer surface of the support member or the electrically resistive sheets or the tube by inorganic yarn wound transversely or wound or coiled in a substantially helical manner. For a filtering element consisting of cross-wound textured yarn, wound in a substantially helical manner, comprising ceramic fibers, it may be desirable to incorporate part of the thermo-volatile or thermofugitive yarn into the windings. The passages that are left behind when the thermo-volatile thread burns off during or before the first use of the filter can provide both a reduced back pressure and improved access to the filter fibers. Preferably, the filter element has an annular thickness in the range from about 1 to about 25 mm. For filtering elements consisting of a transverse wound wound yarn comprising substantially inorganic fibers, the preferred total annular thickness of the fibers wound transversely is in the range from about 5 to about 15 mm. For a filtering element comprising transverse wound woven yarn, substantially helically wound and non-woven plush, the preferred annular thickness of the filter element is in the range of about 3 to about 10 mm. Thicknesses substantially greater than the established ranges can unduly increase costs and can also result in undesirably high back pressures, while thicknesses substantially less than the stated ranges can provide inadequate filtration efficiency. For filters that have electrically resistive sheets or tubes between the layers of filter media (or that conceals the heater configuration), the annular thickness of the inner filtering element must be sufficient to electrically insulate a hollow electrically conductive support member from the sheets or from the electrically resistive tube. Usually, the annular thickness of an inner filtering element is in the range from 0.25 to about 0.75 cm. Preferably, the annular thickness of an inner filter element is in the range from about 0.35 to about 0.5 cm.
Suitable woven fabrics comprise inorganic fibers or yarns which are known in the art such as those used and which include those commercially available, for example, under the trade designation
"NEXTEL CERAMIC FABRIC" from 3M Company of St. Paul, MN The fabric can be secured to the support member or electrically resistive tube by means known in the art, which include winding the fabric around the support member or the electrically resistive tube and then helically winding the fiber (including metallic wire) or the thread around the fabric; winding or winding the fabric around the support member with the electrically resistive sheets or the tube, and then sewing the ends of the fabric together; and forming the fabric within the tube and detaching it on the hollow support member or the electrically resistive sheets or tube. It is within the scope of this invention to place the fabric on the filter medium provided, for example, by helical winding of the inorganic fiber or yarn, or winding or winding of non-woven felts around the support member or of the sheets or tube. electrically resistive In the North American patent number 5,180,409
(Fischer) a preferred fabric is described. This preferred fabric is woven without knots of separate support strands, substantially unribbed, substantially uncompressed flexible, and substantially fully curled, spongy and flexible fill yarns that are pulled firmly against the support strands. By "substantially incomprehensible" is meant that the support strands maintain their shape and diameter when the spongy packing yarns are pulled lightly against the support strands. Preferably, the support strands of the preferred fabrics are threads that become substantially incomprehensible and that are made of a plurality of small glass or ceramic fiber ends (preferably from 3 to 8 ends / group and from 300 up to 1600 fibers / end) which are rotated uniformly together, preferably having from 0.4 to 3 twists / cm, after which a plurality of these twisted bundles are twisted together (preferably from 2 to 6) in the opposite direction to the same number of twists / cm. By "curly" it is meant that a generally sinous shape is acquired by the yarn during the winding action of the production of a cloth. Furthermore, with respect to the preferred fabric, the term "spongy" refers to a yarn which, when not stressed, has a hollow volume of at least 75%. The hollow volume of a wire can be calculated by using a graduated microscope to measure the nominal diameter (D) and a scale to measure the mass (M) of a length (L) of wire. Therefore, the empty volume (v / v) is obtained from the following equation:
M / p W - 1 - pLD2 / 4
where p is the apparent density of the yarn, the D of a textured yarn is the diameter of a cylindrical envelope to which the curl extends, which envelope overlaps any of the valleys on the surface of the yarn and thus it covers the gaps like those surfaces. To improve the texturing, the individual ends of the filled yarns should not be highly twisted, that is, they should preferably have less than 2 twists / m and the ends should not be twisted tightly together ie, preferably they should have no more of a twist / cm. When the ends are twisted together, texturing is also increased by using only a few ends per yarn, preferably 2 or 3. For optimum filtering efficiency, while keeping the back pressures low, the filling yarns must be textured. at a hollow volume of at least 85%, more preferably at least 95%. To maintain low recoil pressures, the fill yarns are preferably separated from each other, but the outermost fibers of the highly textured fill yarns can be interspersed with appreciably increased recoil pressures. When the filling yarns are not intermixed, a filter must use multiple layers of novel fabric.
For convenience of manufacture, the support strands are preferably the warp, and the fill yarns are the novel fabric weft and are tightly pressed against the support strands during the bent or wavy waveform process. When being pulled firmly against the support strands, the filling yarns are flattened, when in contact with a support thread, therefore they help to prevent the filling yarn from slipping or deviating, especially when the filling yarn it is flattened in each support strand to a thickness less than one fifth of its nominal diameter. For a better anti-slip protection, the leveling must be from 1/10 to 1/20 of the nominal diameter of the filling thread. Even when flattened in this way, the portions that intervene in the filling thread retain their spongy character. Although a filter requires a significant thickness that is, multiple layers of novel fabric, these can be obtained with greater economy when the novel filter cloth is a multiple warp fabric. If the filter element includes multiple layers of the preferred fabric, the support strands of the adjacent layers preferably extend orthogonally to each other to minimize accommodation. When two or more layers of the fabric are used as the filter medium, the support strands of the innermost layer preferably extend in the circumferential direction, which makes it easier to pull the layer firmly against the substrate.
gurr.PS NON-WOVEN
Typically, the fibers that constitute a non-woven plush have a diameter of up to about 20 microns. Preferably, the fibers comprising a nonwoven plush have a diameter in the range of from about 3 to about 20 microns. Suitable non-woven felts are known in the art and are commercially available, for example, under the trademark designation "SAFFIL LD MAT" from Imperial Chemical, Inc., of Cheshire, U.K. Preferred non-woven felts can be prepared as described in international application number PCT / US93 / 12002 which has an international publication number WO 94/16134. Non-woven fabrics can be perforated by needle, for example, as described in the application just mentioned, or can be joined by stitching, as described, for example, in U.S. Patent No. 4,181,514 (Lefkowitz et al. ). Further details regarding the construction of cartridges for diesel particulate filter and filters are described in U.S. Patent Nos. 5,248,481 (Bloom et al.) And 5,258,164 (Bloom et al.). In addition, to aid in the oxidation of soluble carbon and organic constituents (e.g., hydrocarbons and carbon monoxides) of diesel exhaust soot particulates, the filter element may additionally comprise an oxidation catalyst coated on a fiber. or inorganic thread. Such oxidation catalysts are known in the art and include oxides of catalytic metal (for example titanium oxide and vanadium pentoxide), precious metals (for example, platinum, rhodium or other metals of the platinum group, and silver), and basic metals (for example copper, iron, manganese and potassium). Methods for coating the catalyst on the inorganic yarn and the non-woven plush are known in the art. The preferred electrically resistive sheet configurations useful for making electrically resistive heating elements used in the diesel particulate filter cartridges and in the filters according to the present invention are shown in Figures 5 and 14 to 18. The three imaginary zones for the electrically resistive sheet shown in Fig. 14 is designated 501, 502, and 503. The five imaginary zones for the electrically resistive machine shown in Fig. 14 have the designations 511, 512, 513, 514, and 515. Electrical resistance of an electrically resistive sheet or tube configuration (heating element) is related to the geometry of the element and the material of which it is indicated, and can be calculated by the following equation:
R = pL / A
where R is the electrical resistance p is the resistivity of the material, L is the length of the current path, and A is the cross-sectional area of the current path. With reference to Figure 5, the electrical resistance along the length of the heater is changed to obtain the desired heat distribution by changing the standard width 251 and / or 252, and the opening 253. For ease of manufacture, it is preferable Change the width of the strand and keep the opening size constant.
The electrical resistance along the length and / or circumference of the heater can be changed, for example, by changing the width of the strand, the size or number of openings, the number of current paths or a combination of the same. In addition, the electrical resistance of the sheets or the tube can be changed by changing the material from which they are made, by varying the thickness of the strands, by varying the current path lengths and by varying the aperture size, by altering the number of current paths and by changing the number of threads. In addition, the formulation of the tube material can be varied from the ends towards the center (i.e., the resistance of the sheets or the electrically resistive tube can be adjusted by varying the formulation of the material from which it is made). Any of these parameters (ie, width of the strand, size or number of openings, etc.) can be varied, for example as a linear function of the length and / or of the circumference, a gradual function of the length and / or circumference, a parabolic function of length and / or circumference, an exponential function of length and / or circumference or any mathematical expression that relates the parameter to the length of the heater and / or the circumference.
The openings, which may be, for example, circular, oval, rectangular, rectangular with corners in the shape of a radius, diamond-shaped or diamond-shaped, triangular or combinations of these shapes. Preferably, the electrical resistance of the electric resistivity tube or sheet is varied by changing the average cross-sectional area of individual strands. If an inorganic strand is wound helically around electrically resistive sheets or tubes (or the support member), care must be taken to select the configuration of the heating element
(which includes the number of threads, the width of the threads, the length of the threads and the size of the openings), and the winding pattern of the thread in order to prevent the thread from falling through the openings of the threads. blades or electrically resistive tube (or support member). For example, if the openings in the sheets or the electrically resistive tube (or the support member) are at an angle of 45 ° and the winding angle is the same relative angle, the thread, if it is thinner than the groove, It can slide through the opening. Preferably, the apertures of the sheets or the electrically resistive tube are in the range of about 10 and up to about 70 percent of their projected area. More preferably, the apertures of the sheets or the electrically resistive tube are in the range of from about 40 to about 60 percent of their projected area. The aperture areas projected with these intervals provide the best compromise between the desired lower back pressure through the filter elements, the desired conformability to the associated filter elements, and the desired stiffness or integrity of the sheets or tube electrically. resistive, and the ease of manufacturing. The size of the openings in the sheets or the electrically resistive tube depend on the requirements for particular filter cartridge which includes the power elements, the size of the filter cartridge, the position of the electrically resistive tube (for example, the outside of the filter element, hidden inside the filter element or if it serves as a support tube to the filter element) and the gas flow to through the filter. The width of the strand must be large enough to improve durability (so that it does not act as a fuse) although it must be small enough to provide a high required electrical resistance and limit the current through the heater. Usually, the width of the strand is in the range of about 0.074 to 1.1 cm (about 0.030 to 0.45 inches) and more preferably in the range of about 0.1 to 0.65 cm (about 0.039 to 0.255 inches). Threads with widths in these ranges usually result in an appropriate compromise between the proportion of a durable heater, limitation of current through the heater and allow flexibility to alter the watt density of the variable resistance heater. In some embodiments of the filter cartridges or filters according to the present invention, the length of the current path through the length of the resistive tube is at least 1.1 times the length of the electrically resistive tube, and the length of the current path around the circumference of the electrically resistive tube is at least 1.01 times the circumference of the electrically resistive tube. In another aspect, the length of the current path through the length of the electrically resistive tube may be greater than the length of the current path around the circumference of the electrically resistive tube. In some embodiments of the filter cartridges or filters according to the present invention, the length of the current path through the length of the electrically resistive sheet (ie, the length from one end to the other) is therefore less 1.1 times the length of the electrically resistive sheet and the length of the current path across the width of the electrically resistive sheet is at least 1.01 times the width of the electrically resistive sheet. In another aspect, the length of the current path through the length of the electrically resistive sheet may be greater than the current path length across the width of the electrically resistive sheet. Preferably, the energy concentration of the electrically resistive sheet configuration used is in the range of from about 0.5 to about 7 watts / cm2. The energy consumption values within these ranges usually provide a reasonable regeneration operation without excessive energy consumption. The material comprises sheets or an electrically resistive tube and must be resistant to high temperatures (eg, temperatures above about 600 ° C, must be chemically resistant to diesel exhaust, and must be ductile). Preferably, the electrically resistive material is a metal. Suitable metals include expanded metal, stainless steel (commercially available, for example, from Falcon Stainless and Alloy Corp. of Waldwick, NJ). Preferred metals include nickel-chromium-iron alloys (e.g., those commercially available under the trademark designations "INCONEL 600" and "INCOLOY 800" from Inco Alloy International, Inc., of Huntington, WV, "HAYNES 556" of Hayns International of Kokomo, IN, and "KANTHAL Al" of The Kanthal Corp. of Bethel, CT). The openings can be cut into electrically resistive sheets to provide the desired configurations by using conventional processing techniques including drilling, die cutting, laser cutting, cut with water jet and cut with plasma. In addition, the expanded metal sheets can be fabricated from a metal sheet using conventional metal expansion techniques. A sheet of electrically resistive material can be formed in a tube or in a partial tubular shape by conventional techniques which include joining and fixing the side edges of the sheet to form the tube. The means for attaching the edges of the sheet together include those known in the art such as welding, stapling and riveting. Preferably, the openings are distributed uniformly over the surface of the sheets or the electrically resistive tube, except at the ends of the electrically resistive sheets or tube which are preferably undrilled. The electrically resistive sheet or tube has at least two current paths. Usually, the electrically resistive tube has at least four current paths, although six, eight, ten or twelve paths may also be useful. Usually, the electrically resistive sheet has at least four current paths, although five, six, seven, eight, nine, ten, eleven or twelve are also useful. In some cartridges for diesel particulate filter and filters according to the present invention, the sheets or the electrically resistive tube have a center point between the ends of the sheets or the tube, wherein at least one strand is closest to the point which at the end of the sheet or tube has a current path smaller than the current path of at least one strand closer to the end of the sheet or tube, compared to the center point. In another aspect, in some cartridges for diesel particulate filter and filters according to the present invention, the sheets or the electrically resistive tube have a center point between the ends of the sheets or the tube, wherein at least one more strand Near the center point compared to the end of the sheets or the tube has an average width greater than the average width of at least one strand closer to the end of the sheet or tube compared to the center point. In another aspect, preferably the electrical resistance of each successive strand from one end toward the center of the sheet or tube decreases. For the electrically resistive sheets or tubes having an oval or rectangular shaped opening, the cross-sectional area of each strand is preferably in the range from about 0.2 to about 16 mm2, wherein the width of each strand so Preferably it is in the range of from about 1 to about 6.5 mm, and the thickness of the electrically resistive material is preferably in the range of from about 0.2 to about 2.5 mm. Preferred electrically resistive tube configurations useful for making the filter cartridges and filters according to the present invention have a circumferential stiffness of less than 40 percent the differential stiffness of a comparable electrically resistive solid tube (ie, the same tube). without openings). For additional deteilles with respect to circumferential stiffness, see European Patent Application Pending No. 0 608 783 Al. Preferably, the circumferential stiffness of an electrically resistive, grooved pipe is less than about 25 percent (more preferably less than 10 percent, even more preferably less than 5, and much more preferably, less than about 3 percent) of the circumferential stiffness of a comparable electrically resistive solid tube (ie, the same tube without the slots). For additional details regarding electrically resistive tubes that have a circumferential stiffness of 40 percent the circumferential stiffness of a solid electrically resistive tube, comparable, see the application for European patent number 0 608 783 Al. To decrease the axial tensions which occur during the heating of an electrically resistive sheet or tube (or support member), an axial expansion means can be incorporated in the sheets or the electrically resistive tube (or the support member) by using conventional techniques. The expansion means may be placed along the sheets or the electrically resistive tube (or the support member) based on the parameters of the particular filter cartridge design. Usually, the expansion means are placed at or near the ends of the sheets or the electrically resistive tube (or the support member). With reference to Figures 19 and 20, expansion joints 601 and 610 are shown near one end of the electrically resistive sheet. The expansion joint 601 is a radially toothed portion of the sheet, while the expansion joint 610 is a radially expanded portion of the sheet. An example of a bellows expansion joint (commercially available, for example, from Standard-Thomson Corp. of Waltham, MA) is shown in Figure 21. The objects and advantages of this invention are further illustrated by the following examples , but the particular materials and the amounts thereof mentioned in these examples, as well as other conditions and details, should not be considered as unduly limiting this invention.
EXAMPLE 1 AND COMPARATIVE EXAMPLE A
Four filter cartridges are constructed substantially as shown in Figure 7, and mounted on a cover to provide a diesel filter or trap substantially as shown in Figures 8 and 9. The cover is made of conventional 304 stainless steel.
The electrically resistive tube is approximately 254 mm long, has an outer diameter of 42 mm, and is formed from a 0.46 mm thick nickel-chromium-iron alloy sheet (commercially available under the trade designation "INCONEL 600"by Inco Alloy International of Kokomo, IN). Laser holes are cut with rectangular rounded corners in the sheet to provide the geometry shown in Figure 14. The width of the strands (in the center of the strand) of the strands closest to either end of the tube is 1.95 mm ( 0.0766 inches). The width of the strand
(in the center of the strand) of the strands in the center of the tube is 3 mm (0.119 inches). The total resistance of the electrically resistive tube formed from the sheet is 0.352 ohms. The end of the tube with the larger perforated area is at the end with the lid 21
(see figure 7). By using a conventional brake press, a rounded rod is attached to press and apply the necessary shape to form the electrically resistive sheet in a tube. The sides of the sheet come together to form the tube and are welded together. The electrically resistive tube is coiled transverse and helically with 17 layers of alumina-boria-silica fiber ceramic of 1800 denier of 2/2, 1.5z (commercially available under the trademark designation "NEXTEL 312 CERAMIC YARN" from 3M Company) which has been lightly textured by the use of an air jet texturing machine (commercially available under the trade designation "MODEL 17 SIDEWINDER" with a "MODEL 52D JET" from Enterprise Machin and Development Corp. of New Castle, DE). The speed of the texturing machine is set to 26.5 meters per minute. The jet opens about 3/4 of a turn from its most closed position. The air pressure is set to approximately 550 kPa. Specifically, the ceramic wire is helically wound around the tubes by the use of a three-axis computer controlled precision winding machine (Automation Dynamics of Signal Hills, CA). The winding angle for the first layer is 47 °. During winding, the yarn is maintained at a constant tension of approximately 14.2 Newtons. For each successive layer, the winding angle is slightly increased so that the core of the yarn of each successive layer is aligned with the core of the yarn of the underlying yarn core so that four-sided openings are provided. In each perforated area of the tubes (i.e., at each end of the tube) the winding pattern is modified to have dense end walls provided with a 60 ° interval, which serves to block the leaking unfiltered exhaust gas at the ends of the filters. For the first layer of cross-wound yarn, the opening size between the opposite corners of the "four-sided" openings is about 9.3 mm in each of the axial and circumferential directions of the tubes. The opening size between the opposite corners of the "four-sided openings" constitute the last (ie, seventeenth) layer and is approximately 9.3 mm in the direction of the axis and approximately 14.4 mm in the circumferential direction of the tubes . The outer diameter of the tubes having a yarn wound transverse helically thereon is about 65 mm. The seventeen layers of ceramic thread weigh approximately 210 grams. The conical entrance of the deck connects to the exhaust system of a four-stroke diesel engine, 3.4-liter six-cylinder (commercially available under the trade designation "CUMMINGS 6A3.4 DIESEL ENGINE" from Cummings Engine Company of Columbus, IN). A conventional hydraulic load bank is attached to the torque shaft of the engine and maintained at a pressure of 9653 kPa (1400 psi) during the test to provide a controlled load on the engine. The engine is operated at approximately 1500 rpm with an exhaust or exhaust temperature of approximately 280 ° C, resulting in an exhaust flow rate of approximately
245 Nm3 / hr (that is, standardized cubic meters per hour)
(145 acfm) (ie, real cubic feet per minute). The counter pressure at the start of each test is approximately 2.5 cm of water (0.25 kPa). The engine is operated until the return pressure drops through each diesel cartridge and reaches 152 cm of water (60"of water), at which time the exhaust valve is closed to divert the engine exhaust gas around the engine. a diesel trap to start the electric regeneration cycle For the electric regeneration cycle, approximately 0.1 m3 / min (2 scfm) (ie, (standard cubic feet per minute)) of air is distributed to a diesel trap for Provide a sufficient amount of oxygen and heat transfer to the filter to complete the soot burn process During this time 12 volts (each heater consumes approximately 410 watts of energy) are applied through the heater for 10 minutes. , the exhaust gases from the engine are sent back through the diesel trap again.The 12 volts are provided by a 12 volt power supply of, conventional externally attached through electric electrodes to the threaded metal posts of each filter cartridge and to an electrical electrode with the base of the cover (common grounding). The filter cartridges are again loaded with soot by operating the motor until the pressure back through each cartridge for diesel filter reaches 152 cm of water (60"of water) after the back pressure has decreased and it has reached the 152 cm level, the engine is stopped and the diesel trap is allowed to cool to room temperature.The four diesel filter cartridges are removed from the cover and weighed individually.The filter cartridges then again They are assembled on the cover and the diesel filter is reconnected to the engine system.The regeneration cycle described above is repeated.After regeneration, each diesel filter cartridge is removed from the cover and individually weighed .
Subsequently, the filter cartridges are placed in a conventional high temperature conventional oven at 550 ° C for 2 hours to burn out any remaining diesel soot. Each filter cartridge is then cooled to room temperature and weighed individually. The data for the second loading of the filter cartridges and the subsequent regeneration is given in Table 1 below. The amount of soot burned is equal to the difference in weight of the filter cartridge before and after regeneration. The amount of soot in the filter cartridge is equal to the difference between the weight of the filter cartridge before regeneration and after cleaning in the classic high temperature oven. The weight percent of burned soot for each filter cartridge is equal to the amount of soot subjected to combustion, divided by the amount of soot in the filter cartridge multiplied by 100%. Table 1
The comparative example A is constructed and tested as described for Example 1, except that the geometry of the electrically resistive sheet is used to form the tube as shown in Figure 6. The data from the test of the comparative example A are given in table 2 below.
Table 2
The results of Example 1 and Comparative Example A of the test are summarized in Table 3, below. Table 3
The filter test results of example 1
(and of the filter cartridges) show an improved regeneration provided by the electrically resistive tube according to the present invention and compared with the electrically resistive tube used for comparative example A.
EXAMPLE 2
The filter of example 2 is constructed as described in example 1 with the following exceptions. The outer diameter of the electrically resistive tube is 50.8 mm (2 inches). The electrical resistance of the electrically resistive tube is 0.288 ohms. The voltage applied across the length of each tube is 13.2 volts, resulting in 600 watts of power per filter cartridge. The configuration of the electrically resistive sheet used to form the tube is shown in Figure 15. The width of the strand (at the center of the strand) of the strands closest to either end of the tube is 2.4 mm (0.096 inches) . The width of the strand (at the center of the strand) of the strands at the center of the tube is 3.2 mm (0.125 inches). The end of the tube with the larger non-perforated area is in the center with the lid 21 (see Figure 7). (Other preferred configurations, preferably used with a 12 volt power source, are shown in Figs. 16 to 18. Furthermore, the configuration shown in Fig. 18 is preferably used to produce an electrically resistive 76.2 mm tube. (3 inches) in diameter). All metal parts are stainless steel unless otherwise indicated. In addition, the filter means are provided as follows. First, apply ten layers of slightly textured, radially aligned yarn ("NEXTEL 312") at an initial winding angle of 47 ° to provide a filter bandwidth of 8.38 mm. Each layer is made up of ten circuits. After advancing the filament winder mandrel 23.5 °, two layers of lightly textured yarn are applied to form radial walls that bisect the four-sided openings of the first ten layers. After advancing the mandrel another 23.5 °, two layers of the lightly textured yarn are applied to form radial walls that bisect the openings of four ladcs of the two preceding layers. The diameter of the filter medium in the tube is 59.4 mm. The conical entrance of the roof is connected to the exhaust system of an electric generator of a four-cycle, 2.3-liter four-cylinder diesel engine (commercially available under the trade designation "ONAN L423 DIESEL ENGINE" from Onan Corporation of Anoka, MN.). Four electric heaters are placed on the generator set to function as a power load for the system. Under the conditions of the steady state motor of the generating equipment, the return pressure of the initial filter is approximately 6.35 cm of water at 3.0 m2 / min. The time it takes for the back pressure to exhaust the trap to increase from approximately 6.35 to approximately 114 cm of water is recorded between successive cycles. When the return pressure of the system reaches 114 cm of water, the exhaust valve is closed by exhaust bypass around the diesel filter during each cycle. The cartridge is then energized (regenerated) by applying approximately 13.2 volts at 45 amps through each filter cartridge for approximately 10 minutes. During this time, heating temperatures of 750-800 ° C are obtained, which causes the soot to oxidize. The air flow regeneration of 14.16 bpm per filter cartridge is supplied from compressed air to aid in the combustion of soot during energization. An additional 1 minute of airflow without energizing the filter cartridges is provided in order to allow the filter cartridges to gradually cool. Subsequently, the exhaust valve is opened to allow exhaust gases to flow back through the filters. The charging and regeneration cycle is repeated for 1120 hours of motor use. Low sulfur fuel (0.05% sulfur) is used; "AMOFUEL LS '94 DIESEL FUEL" by Amoco Oil Co. of Chicago, IL) and low ash oil (0.6% ash by weight) available under the trade designation "SUNOCO ULTRA SUPER C GOLD 15W40" from Sun Refining &; Marketing Co. of Philadelphia, PA) during the entire 1120 hours of operation. At the end I read the last regeneration, the filter cartridges are weighed and then placed in a classic high temperature oven at 550 ° C for 2 hours to burn off any remaining diesel soot. Subsequently, the filters are weighed again to determine the amount of residual soot. An average value of 0.525 grams of residual soot remains in each filter that usually holds approximately 2.2-2.55 grams of soot after each loading cycle. Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention has not been unduly limited to the illustrative embodiments set forth therein. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers. Having described the invention as above, property is claimed as contained in the following:
Claims (16)
1. A cartridge for diesel particulate filter, characterized in that it comprises: (a) an electrically resistive tube, substantially rigid, having an outer surface, a first end, a second end, openings extending from the outer surface towards an inner surface, and a length extending from the ends of the electrically resistive tube; wherein the electrically resistive tube has a first, a second and a third imaginary zones between the ends of the electrically resistive tube; wherein each zone has a length equal to one third of the length of the electrically resistive tube; wherein the second zone is placed between the first and third zones; wherein, when a voltage is applied across the first and second ends of the electrically resistive tube, a quantity of heat is generated in each zone; and wherein the amount of heat generated in each of the first and third zones is greater than the amount of heat generated in the second zone; (b) a filter element comprising an inorganic fiber shell, in the openings of the electrically resistive tube; and (c) means for applying a voltage across the ends of the electrically resistive tube to heat it above the combustion point of trapped diesel exhaust particles, the electrically resistive tube is positioned so that when a voltage is applied to Through the electrically resistive tube, sufficient heat is transferred from the electrically resistive tube to the soot particles trapped in the filtering element, so that the soot particles are burned off.
2. The diesel particulate filter cartridge according to claim 1, characterized in that the amount of heat generated in each of the first and third zones is at least 5 percent greater than the amount of heat generated in the second zone.
3. The cartridge for diesel particulate filter according to claims 1 to 2, characterized in that the electrically resistive tube is made of metal, and the inorganic fiber is ceramic oxide fiber.
4. The diesel particulate filter cartridge according to claims 1 to 3, characterized in that the filter element comprises a material selected from the group consisting of helically wound ceramic yarn, a woven fabric consisting of ceramic yarn, a non-woven plush made up of ceramic yarn, and combinations thereof.
5. The cartridge for diesel particulate filter according to claims 1 to 4, characterized in that the electrically resistive tube is made of metal, and the inorganic fiber is ceramic oxide fiber, and wherein the amount of heat generated in each of the First and third zones is at least 10 percent greater than the amount of heat generated in the second zone.
6. The cartridge for diesel particulate filter, according to claims 1 to 5, characterized in that the electrically resistive tube has at least twelve current paths.
7. A diesel particulate filter, characterized in that it comprises: (a) a cover having at least two ends; (b) means for connecting at least the two ends of the cover to an exhaust or exhaust system; (c) means for holding at least one cartridge for diesel particulate filter; and (d) at least one cartridge for diesel particulate filter according to claims 1 to 6, wherein the two ends of the electrically resistive tube extend between at least two ends of the cover and are supported by the cover by means of support, the filter cartridge additionally comprises means for driving the exhaust gases to flow through the openings of the electrically resistive tube.
8. A cartridge for diesel particulate filter, characterized in that it comprises: (a) an electrically resistive tube, substantially rigid, having an outer surface, a first end, a second end, openings extending from the outer surface to an inner surface, and a length that extends from the ends of the electrically resistive tube; wherein the electrically resistive tube has a first, a second, a third, a fourth and a fifth imaginary zones between the ends of the electrically resistive tube; wherein each zone has a length equal to one fifth of the length of the electrically resistive tube; wherein the second zone is placed between the first and third zones, the third zone is placed between the second and fourth zones, and the fourth zone is placed between the third and fifth zones; wherein, when a voltage is applied across the first and second ends of the electrically resistive tube, a quantity of heat is generated in each zone; and wherein the amount of heat generated in each of the second and fourth zones is greater than the amount of heat generated in the third zone; (b) a filtering element comprising an inorganic fiber covering the openings of the electrically resistive tube; and (c) means for applying a voltage across the ends of the electrically resistive tube to heat it above the combustion point of trapped diesel exhaust particles, the electrically resistive tube is positioned so that when a voltage is applied to Through the electrically resistive tube, sufficient heat is transferred from the electrically resistive tube to burn the soot particles trapped in the filtration element so that the soot particles are burned off.
9. The cartridge for diesel particulate filter, according to claim 8, characterized in that the electrically resistive tube is made of a metal and the inorganic fiber is ceramic oxide fiber.
10. A diesel particle filter, characterized in that it comprises: (a) a cover having at least two ends; (b) means for connecting at least the two ends of the cover to an exhaust or exhaust system; (c) means for holding at least one cartridge for diesel particulate filter; and (d) at least one cartridge for diesel particulate filter according to claim 8 or 9, wherein the two ends of the electrically resistive tube extend between at least two ends of the cover and are held in the cover by means of support, the filter cartridge additionally comprises means for driving the exhaust gases to flow through the openings of the electrically resistive tube.
11. The cartridge for diesel particulate filter, characterized in that it comprises: (a) a hollow, substantially rigid tubular support member having two ends and an outer surface with openings extending from the outer surface towards an inner surface; (b) a first filter element consisting of inorganic fibers that cover the openings; (c) an electrically resistive sheet having an outer surface, a first end, a second end, openings extending from the outer surface toward an inner surface, and a length extending from the ends of the electrically resistive sheet; wherein the electrically resistive sheet has a first, a second and a third imaginary zones between the ends of the electrically resistive sheet; wherein each zone has a length equal to one third of the length of the electrically resistive sheet; wherein the second zone is placed between the first and third zones; wherein, when a voltage is applied across the ends of the electrically resistive sheet, a quantity of heat is generated in each zone; and wherein the amount of heat generated in each of the first and third zones is greater than the amount of heat generated in the second zone; and (d) means for applying a voltage to the ends of the electrically resistive sheet so that the voltage applied through the electrically resistive sheet is sufficient to heat it above the combustion point of the trapped diesel exhaust particles. , the electrically resistive sheet is placed so that when a voltage is applied across the electrically resistive sheet, sufficient heat is transferred from the sheet to the soot particles trapped in the filter element so that the soot particles are removed by burned.
12. The cartridge for diesel particulate filter, according to claim 11, characterized in that the electrically resistive sheet is made of metal, and the inorganic fiber is first ceramic oxide fiber, and the cartridge for diesel particulate filter additionally comprises a second filter element of ceramic oxide fibers that covers the openings of the electrically resistive sheet.
13. A diesel particle filter, characterized in that it comprises: (a) a cover having at least two ends; (b) means for connecting at least two of the ends of the cover to an exhaust or exhaust system; (c) means for holding at least one cartridge for diesel particulate filter; and (d) at least one diesel particulate filter cartridge, according to claim 11 or 12, wherein the two ends of the support member extend between at least two ends of the cover and are supported on the cover. by means of support, the filter cartridge additionally comprises means for driving the exhaust gases to flow through the openings of the support member in the electrically resistive sheet.
14. A cartridge for diesel particulate filter, characterized in that it comprises: (a) a hollow, substantially rigid tubular support member having two ends and an outer surface with openings extending from the outer surface towards an inner surface; (b) a first filter element consisting of an inorganic fiber covering the openings; (c) an electrically resistive tube having an outer surface, a first end, a second end, openings extending from the outer surface toward an inner surface, and a length extending from the ends of the electrically resistive tube; wherein the electrically resistive tube has a first, a second and a third imaginary zones between the ends of the electrically resistive tube; wherein each zone has a length equal to one third of the length of the electrically resistive tube; wherein the second zone is placed between the first and third zones; wherein, when a voltage is applied across the ends of the electrically resistive tube, a quantity of heat is generated in each zone; and wherein the amount of heat generated in each of the first and third zones is greater than the amount of heat generated in the second zone; and (d) means for applying a voltage to the ends of the electrically resistive tube, so that a voltage is applied across the electrically resistive tube sufficient to heat it above the combustion point of the trapped diesel exhaust particles, the tube The electrically resistive is positioned so that when a voltage is applied across the electrically resistive tube, sufficient heat is transferred from the tube to the soot particles trapped in the first filtering element so that the soot particles are burned off.
15. The cartridge for diesel particulate filter, according to claim 14, characterized in that the electrically resistive tube is made of metal and the inorganic fiber is first ceramic oxide fiber, and the cartridge for diesel particulate filter additionally comprises a second filter element of ceramic oxide fibers that covers the openings of the electrically resistive tube.
16. A filter for diesel particles, characterized in that it comprises: (a) a cover having at least two ends; (b) means for connecting at least two ends of the cover to an exhaust or exhaust system; (c) means for holding at least one cartridge for diesel particulate filter; and (d) at least one cartridge for diesel particulate filter according to claim 14 or 15, wherein the two ends of the support member extend between at least two ends of the cover and are suspended on the cover by means of support, the filter cartridge additionally comprises means for urging the exhaust gases to flow through the openings of the support member and the electrically resistive tube. An electrically regenerable filter and cartridge for diesel particulate filter comprising sheets with electrically variable resistivity, or a tube which, when energized, provides sufficient heat to burn-off particulates of soot trapped in the filter medium.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22355194A | 1994-04-06 | 1994-04-06 | |
| US223551 | 1994-04-06 | ||
| PCT/US1995/002276 WO1995027843A1 (en) | 1994-04-06 | 1995-02-21 | Electrically regenerable diesel, particulate filter cartridge and filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| MX9604541A MX9604541A (en) | 1997-09-30 |
| MXPA96004541A true MXPA96004541A (en) | 1998-07-03 |
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