Systems and methods for electrically heating a catalyst with a honeycomb body having radial walls

Abstract

An electric heater and a method of heating a catalyst. The heater comprises a honeycomb body comprising a honeycomb structure. The honeycomb structure comprises a longitudinally extending central axis and a plurality of interconnecting walls. The interconnecting walls comprise a plurality of radial walls extending along a radius of the honeycomb body between the central axis and an outermost periphery of the honeycomb body, and a plurality of angular walls arranged concentrically relative to the central axis and spanning between the radial walls. The honeycomb structure comprises a plurality of cells defined by the interconnecting walls. The heater comprises a first electrode disposed at the central axis and a second electrode disposed radially outward of the central axis, and the second electrode is in electrical communication with the first electrode via one or more intersecting walls positioned between the first electrode and the second electrode.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 62 / 900,984, filed September 16, 2019, pursuant to 35 U.SC §120, the content of which is incorporated herein by reference in its entirety. Background Technology

[0003] This application generally relates to electric heaters for heating catalysts (such as catalysts on a substrate of a catalytic converter assembly), and more specifically, to electric heaters comprising a radial honeycomb structure. Summary of the Invention

[0004] All the examples and features mentioned below can be combined in a technically feasible way.

[0005] In some aspects, an electric heater is provided. The electric heater includes: a honeycomb cell comprising a honeycomb structure including a central axis extending longitudinally therethrough and a plurality of interconnecting walls, wherein the interconnecting walls include a plurality of radial walls and a plurality of angular walls, each radial wall extending at least partially along the radius of the honeycomb cell between the central axis and the outermost periphery, the plurality of angular walls being concentrically arranged relative to the central axis and spanning between the radial walls; and a plurality of cells defined by the interconnecting walls; a first electrode disposed at the central axis; and a second electrode disposed radially outward of the central axis, the second electrode being electrically connected to the first electrode via one or more intersecting walls positioned between the first electrode and the second electrode.

[0006] In some embodiments, the radial distance between the radially continuous angular walls of the plurality of angular walls decreases as they approach the outer periphery of the honeycomb, so that the hydraulic diameter of each cell is substantially similar.

[0007] In some embodiments, a first group of multiple units is located in a first region directly adjacent to the central axis, wherein a second group of multiple units is located in a second region radially outside the first region, wherein the first hydraulic diameter of each unit in the first group of multiple units is smaller than the second hydraulic diameter of each unit in the second group of multiple units.

[0008] In some embodiments, each radial wall of the first cell in the plurality of cells is offset at an angle relative to the radial wall of the second cell that is radially adjacent to the first cell in the plurality of cells.

[0009] In some embodiments, the cell includes a first resistive region separated from the second resistive region by a transition angular wall, wherein the first resistive region includes fewer radial walls than the second resistive region, the first resistive region is located closer to the central axis than the second resistive region, and both the first and second resistive regions are located between the first and second electrodes.

[0010] In some embodiments, the first resistance region and the second resistance region are defined by a transition angle wall and one of the first electrode, the second electrode, or the second transition angle wall.

[0011] In some embodiments, the radial walls of the first resistive region are proportionally thicker than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is substantially the same as the heat generated by each radial wall of the second resistive region.

[0012] In some embodiments, the radial walls of the first resistive region are proportionally shorter than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is substantially the same as the heat generated by each radial wall of the second resistive region.

[0013] In some embodiments, the radial walls of the first resistive region are axially proportionally longer than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is substantially the same as the heat generated by each radial wall of the second resistive region.

[0014] In some embodiments, the radial wall is thicker than the angular wall.

[0015] In some embodiments, the second electrode is disposed on the outer skin surrounding the periphery of the honeycomb structure.

[0016] In some aspects, an exhaust treatment system is provided. The exhaust treatment system includes an electric heater according to any of the above and an exhaust treatment device located downstream of the electric heater.

[0017] In some embodiments, the exhaust treatment apparatus includes a substrate loaded with catalytic material, a particulate filter, or a combination thereof.

[0018] In some aspects, a method for heating a catalyst is provided. The method includes the steps of: applying a potential difference across a first electrode located on the central axis of a honeycomb cell and a second electrode located radially outward from the first electrode on the honeycomb cell, wherein the honeycomb cell includes a plurality of intersecting walls, the plurality of intersecting walls including a plurality of radial walls and a plurality of angular walls, each radial wall extending at least partially along the radius of the honeycomb cell between the central axis and the outermost periphery of the honeycomb cell, at least some of the radial walls being angularly spaced from each other about the central axis, the plurality of radial walls being concentrically arranged relative to the central axis and spanning between the radial walls, wherein the potential difference generates a current flowing through the intersecting walls located between the first and second electrodes, the current generating resistance heating in the intersecting walls.

[0019] In some embodiments, the radial dimension of each of the plurality of cells decreases with respect to each subsequent radially adjacent cell that is radially close to the outer periphery of the cell, such that the hydraulic diameter of each cell is substantially similar.

[0020] In some embodiments, a first set of multiple units is arranged around a central axis, wherein a second set of multiple units is arranged around the first set, wherein the first hydraulic diameter of each unit in the first set of multiple units is smaller than the second hydraulic diameter of each unit in the second set of multiple units.

[0021] In some embodiments, one or more radial walls of each cell in a first subset of the plurality of cells are offset at an angle relative to the radial walls of each cell in a second subset of the plurality of cells that are radially adjacent to the first subset.

[0022] In some embodiments, a second subset of the unit is separated from the central axis from at least two of the plurality of angular walls.

[0023] In some embodiments, the cell includes a first resistive region separated from the second resistive region by a transition angular wall, wherein the first resistive region includes fewer radial walls than the second resistive region, the first resistive region is located closer to the central axis than the second resistive region, and both the first and second resistive regions are located between the first and second electrodes.

[0024] In some embodiments, the radial wall of the first resistive region is thicker than the radial wall of the second resistive region, such that the equivalent resistances of the first and second resistive regions are substantially similar.

[0025] In some embodiments, the radial walls of the first resistive region are shorter than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is substantially the same as the heat generated by each radial wall of the second resistive region.

[0026] In some embodiments, the radial walls of the first resistive region are axially longer than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is substantially the same as the heat generated by each radial wall of the second resistive region.

[0027] In some embodiments, the radial wall is thicker than the angular wall.

[0028] In some embodiments, the second electrode is disposed on the outer skin surrounding the periphery.

[0029] In some embodiments, the catalyst is loaded on the intersecting wall.

[0030] In some embodiments, the method further includes heating the fluid flow with a heater and heating the catalyst with the fluid flow.

[0031] Details of one or more embodiments are set forth in the accompanying drawings and description. Other features, objects, and advantages will become apparent from the specification, drawings, and claims. Attached Figure Description

[0032] Figure 1 A partial cross-sectional view of an electric heater with a radial honeycomb structure, based on an example, is depicted.

[0033] Figure 2 A perspective view of an electric heater based on an example is depicted.

[0034] Figure 3 The equivalent resistance of the radial wall of the electric heater, according to the example, is depicted.

[0035] Figure 4A A simplified partial cross-sectional view of the radial and angular walls of an electric heater according to an example is depicted.

[0036] Figure 4B The equivalent resistance of the radial wall of the electric heater, according to the example, is depicted.

[0037] Figure 5 A simplified partial cross-sectional view of the radial and angular walls of an electric heater according to an example is depicted.

[0038] Figure 6 A simplified axial cross-sectional view of the radial and angular walls of an electric heater according to an example is depicted.

[0039] Figure 7 A cross-sectional view of an electric heater with a radial honeycomb structure, based on an example, is depicted.

[0040] Figure 8 The heating distribution of the electric heater, based on the example, is depicted.

[0041] Figure 9 A cross-sectional view of an electric heater with radially staggered units, according to an example, is depicted.

[0042] Figure 10 A partial cross-sectional view of an electric heater with radially staggered units, based on an example, is depicted.

[0043] Figure 11 The heating distribution of an electric heater with radially staggered units, according to an example, is depicted.

[0044] Figure 12 A cross-sectional view of an electric heater with radially staggered units near the outer periphery, according to an example, is depicted.

[0045] Figure 13 The heating distribution of an electric heater with radially staggered elements and thickened radial walls, according to an example, is depicted.

[0046] Figure 14 The heating distribution of an electric heater with peripheral electrodes covering only the outer skin, according to an example, is depicted. Detailed Implementation

[0047] Some catalytic converters rely on the heat from engine exhaust to activate the catalyst in order to begin treating vehicle emissions. However, in some vehicles, a significant portion of total emissions may occur immediately after vehicle start-up, when the catalyst is still cold. The embodiments disclosed herein relate to active heating systems and methods that use electrically heated elements to supplement the existing heat from engine exhaust, thereby enabling further reductions in vehicle emissions, particularly after a cold start.

[0048] One such method for actively heating exhaust gases is via an electrically heated catalytic converter (EHC) system, which provides heat to the catalytic converter by increasing the catalyst temperature with power from a battery (e.g., the vehicle's battery). However, the design of electrically heated catalytic converters is affected by various problems, such as uneven heating distribution of varying degrees, which degrades performance and reduces the efficiency of electrical energy use.

[0049] Figure 1 An example electric heater 100 for heating a catalyst is shown with a cross-section of an eighth circle. The electric heater 100 includes a honeycomb body 101 comprising radial web honeycomb structures 102, a central electrode 104 located at the central axis C of the honeycomb structure 102, and at least one peripheral electrode 106 configured to allow current to flow through an array of interconnecting webs or interconnecting walls formed by the honeycomb structure 102. The interconnecting walls include a plurality of radial walls 108 and a plurality of angular walls 110, which together define a plurality of cells or channels 112 extending longitudinally through the honeycomb body 101.

[0050] When a potential is applied between the central electrode 104 and the peripheral electrode 106, the peripheral electrode 106 can be configured to allow current to flow through at least some of the radial walls 108 located between electrodes 104 and 106. Therefore, the peripheral electrode 106 can be located at the outer skin 114 (around the outer periphery of the honeycomb structure 102), or embedded below the outer skin 114 at locations suitable for inducing current flow through at least a subset of the radial webs 108 (e.g., at the outer periphery of the honeycomb structure). The honeycomb structure 102 can be composed of a conductive material, such as metal, conductive ceramic, or a combination thereof. The conductive material can have resistance such that the conduction of current due to the applied potential across the central electrode 104 and the peripheral electrode 106 generates heat in the walls 108, 110 of the honeycomb structure 102. The potential applied to the central electrode 104 and the peripheral electrode 106 can be formed by any suitable voltage source, and in alternative examples, it can be a DC voltage (e.g., formed by a battery) or an AC voltage.

[0051] The honeycomb structure 102 of the honeycomb body 101 can be formed, for example, by extruding ceramic molding material into a preform using an extrusion die, then cutting, drying, and firing it to form the final ceramic honeycomb body. Alternatively, the honeycomb structure can be formed by additive processing operations (e.g., such as 3D printing) or subtractive processing operations (e.g., electrical discharge machining, electrochemical machining, etc.). If the selected ceramic material has too high a resistance to provide effective resistance heating, it can be doped with a conductor (such as a metal) to increase the conductivity of the ceramic. In alternative examples, the honeycomb structure can be formed entirely of metal instead of ceramic material, or it can be formed of conductive ceramic material.

[0052] In the example, a plurality of radial webs 108 extend radially between the central axis C and the outer periphery of the honeycomb structure (e.g., extending to the outer skin 114) and may together define a plurality of radial walls 116. As the plurality of radial webs 108 extend from the central axis C toward the outer periphery, the angularly adjacent radial walls 108 will diverge from each other, thereby increasing the angular distance between adjacent walls 108 at the periphery of the honeycomb 101. A plurality of angular walls 110 extend concentrically relative to the central axis C such that each angular wall 110 is an arc equidistant from the central axis along its length direction. Together, a plurality of angular walls 110 are concentrically arranged around the central axis C. At least a subset of the radial walls 108 may terminate at the outer skin 114, forming an orthogonal joint 120 with the inner surface of the outer skin 114. In the example, some of the radial walls 108 (e.g., radial wall 108a) can extend almost entirely the radial distance between the central axis C of the cell structure 102 and the outer skin 114, while other radial walls 108 (e.g., radial wall 108b) extend only through one or more segments of the cell structure 102.

[0053] To maintain a substantially uniform cell density (e.g., number of cells per square inch) between the radial interior and exterior of, for example, a cellular structure 102, the number of radial walls 108 varies at different radial locations. In some embodiments, the cellular structure includes cell transitions 124 located at selected points along the radius of the cellular structure 102, with the number of radial walls relative to the cell transitions 124 decreasing radially closer to the central axis C. At these cell transitions 124, the number of radial walls 108, and therefore the number of cells per unit length of angular walls, differs on opposite radial sides of the cell transitions. For example, the number of cells may be reduced by a specified amount, such as by 1 / 2, 1 / 3, or 1 / 4 (e.g., doubled, tripled, quadrupled) or any other suitable amount. Figure 1 An embodiment is shown in which the number of units 112 is halved at each unit transition 124 that moves radially inward. For example, Figure 1 The number of units 112 on the radially inward side of the unit transition piece 124a in the eighth circle is 2, while Figure 1 The number of elements 112 on the radially outward dimension of element transition 124a in the octet circle is 4. Similarly, moving radially outward, in Figure 1 On the opposite side of the eight-eighths circle unit transition 124b, the number of units 112 doubles from 4 to 8. Each unit transition 124 can be defined by a specific angular wall among the angular walls 110 located at each specified radial distance, this angular wall being referred to as the transition angular wall 126, and in Figure 1 For clarity, this is emphasized.

[0054] The unit transition 124 can divide the honeycomb structure 102 into multiple resistive regions 128. Each resistive region 128 may include multiple units 112 and is radially defined on its sides by the unit transition 124 and / or the transition angle towards one of the walls, by the central electrode 104, by the skin 114, and / or by the peripheral electrode 106. For example, resistive region 128a is radially defined on one side by the unit transition 124a and on the other side by the central electrode 104. Similarly, resistive region 128d is radially defined on one side by the unit transition 124c and on the other side by the unit transition 124d. Although Figure 1 The diagram depicts four unit transitions and five resistive regions, but the electric heater 100 may include other numbers of unit transitions, thereby dividing the honeycomb structure into a corresponding number of resistive regions 128.

[0055] To maintain uniformity of the cross-sectional area of ​​the unit 112 in each of the resistive regions 128, the radial dimension (or radial length) of each unit (i.e., the distance between the radially adjacent angular walls 110 forming each unit) can be varied at different radial distances from the central axis C. For example, Figure 1 The radial dimensions D1 and D2 of two distinct cells 112 located in the same resistive region but at different radial distances from the central axis C are shown, illustrating that the radial dimensions decrease as they radially approach the skin 114. This reduction in the radial dimensions of cell 112 can compensate for the angular widening of cell 112 caused by the angular divergence between angularly adjacent radial walls 108 as they radiate from the central axis C of the honeycomb structure 102. In this way, in some embodiments, the radial and angular dimensions of the cells can be varied to maintain a substantially uniform hydraulic diameter of the cells 112 across the entire surface of the honeycomb structure 102. In some embodiments, the hydraulic diameters of the cells 112 vary from each other within ±35% across the entire surface of the honeycomb structure 102.

[0056] Figure 2 A perspective view of the electric heater 100 is depicted, showing a peripheral electrode 106 extending longitudinally through the central axis C of the electric heater 100 and disposed on the outer skin 114 of the honeycomb structure 102. Although Figure 1 and Figure 2 An example is shown as having a right-hand cylindrical outer shape with a central axis C corresponding to the axis of rotation, but in alternative examples, the electric heater 100 can be other shapes, such as those with an elliptical cross-section. In such embodiments, the honeycomb structure can be arranged relative to multiple central axes, for example, one honeycomb structure arranged relative to each focal point of an elliptical shape, the honeycomb structure having radial walls radiating from each focal point.

[0057] The electric heater 100 is configured to heat the gas flow as it flows from the inlet face 130 to the outlet face 132. The honeycomb structure 102 may be coated with a catalyst to react with gas components (e.g., contaminants in engine exhaust), and / or the catalyst may be included on a separate downstream processing unit (e.g., a honeycomb substrate loaded with the catalyst), which is heated by proximity to the heater 100 and by the gas flow after it has been heated by the electric heater 100. Peripheral electrodes may cover the entire or only part of the circumference of the outer skin 114, as may be adapted to direct current to the portion of the heater 100, and as may be combined with… Figure 14 To be discussed in more detail.

[0058] like Figure 2As shown, heater 100 may be positioned upstream of exhaust treatment device 133 (such as a catalytic substrate, particulate filter, or partial filter). Similar to heater 100, exhaust treatment device 133 may include a honeycomb structure comprising an outer skin 135 surrounding a honeycomb structure 137. For example, exhaust treatment device 133 may be formed by extruding ceramic molding material into a preform using an extrusion die, then cutting, drying, and firing it to produce the final ceramic honeycomb structure. The ceramic molding material may include inorganic materials (e.g., alumina, silica, etc.), binders (e.g., methylcellulose), pore-forming agents (e.g., starch, graphite, resin), liquid carriers (e.g., water), sintering aids, or any other additives that contribute to the manufacture of the final ceramic honeycomb structure. The final ceramic honeycomb structure may include cordierite, aluminum titanate, alumina, mullite, silicon carbide, and / or other ceramic materials, or combinations thereof.

[0059] The honeycomb structure 137 of the exhaust treatment device 133 may include a plurality of intersecting walls, thereby forming a plurality of adjacent units. At least a subset of the units of the exhaust treatment device 133 extends axially between opposite end faces 139, 141 of the exhaust treatment device 133 to define a set of channels through which gas can flow. Thus, the inlet face 139 can be in fluid communication with the outlet face 141 via the channels, allowing gas incident on the inlet end face 139 to flow through the channels formed by the units and the exhaust outlet face 141.

[0060] The units of the exhaust treatment device 133 can be formed in any suitable shape in cross-section, including, for example, square, rectangular, triangular, or hexagonal. The units of the exhaust treatment device 133 do not need to have the same shape or size as the units 112 of the heater 100. In fact, the units of the exhaust treatment device 133 can be larger or smaller, have a different unit per square inch (cpsi) than the units 112 of the heater 100, and / or have different cross-sectional shapes. The honeycomb structure 137 can be impregnated or coated with a catalyst, which is activated to react with the exhaust gas when heated by the heater 100 (e.g., by exhaust gas streams near and / or indirectly heated by the heater 100). In some embodiments, only the electric heater 100 is loaded with catalytic material, only the exhaust treatment device is loaded with catalytic material, or both the heater 100 and the exhaust treatment device 133 are loaded with catalytic material.

[0061] The current generated in heater 100 is used to heat the airflow flowing through exhaust treatment device 133, such as vehicle exhaust. Therefore, heater 100 heats the catalyst in exhaust treatment device 133. In some embodiments, heater 100 is sized relative to exhaust treatment device 133 such that heater 100 will heat up relatively quickly compared to exhaust treatment device 133. For example, the axial length of a heater used with exhaust treatment device 133, which has an axial length of 6 inches, can be between about a quarter inch and one inch. If heater 100 and exhaust treatment device 133 are constructed of different materials and / or with different unit geometries, heater 100 and exhaust treatment device 133 can be extruded into separate honeycomb cells. However, in some embodiments, heater 100 and exhaust treatment device 133 can be combined by extruding a single honeycomb cell (e.g., a honeycomb cell of conductive ceramic material) and applying electrodes 104, 106 directly to that single honeycomb cell. In such embodiments, the electrodes can be arranged to span only a portion of the axial length of that single honeycomb cell.

[0062] As mentioned above, in Figure 1 The potential applied between the center electrode 104 and the peripheral electrode 106 causes current to flow radially from the center electrode to the peripheral electrode 106 (in an alternative example, current can flow from the peripheral electrode 106 to the center electrode 104 due to the opposite potential applied between the center electrode 104 and the peripheral electrode 106). However, at each unit transition 124, the current is divided between additional parallel radial walls 108 disposed on the outer side of the unit transition 124. If the number of radial walls 108 on the radially outer side of the unit transition 124 is doubled relative to the inner side of the unit transition 124, the equivalent resistance on the radially outer side of the unit transition 124 is half that on the radially inner side of the unit transition 124 (assuming all other aspects of the radial and angular walls are equal). The resulting decrease in equivalent resistance will produce a corresponding decrease in the heat generated on the radially outer side of the unit transition, resulting in an undesirable non-uniform heat distribution in the resistive region with more parallel radial walls 108.

[0063] Figure 3The equivalent resistances of the radial walls 108a of the radial inner resistance region at the unit transition (e.g., the resistance region 128c relative to the unit transition 124c) to the radial walls 108b, 108c of the radial outer resistance region (e.g., the resistance region 128d relative to the unit transition 124c) are schematically depicted. As shown, in this example, the resistance R of each radial wall 108 is substantially equal. However, the current I / 2 traveling through each radial wall 108b, 108c is half the current I traveling through the radial wall 108a because the current is equally divided between the radial walls 108b and 108c. Therefore, the heat generated by the radial walls 108b, 108c of the outer resistance region 128 will be one-quarter of the heat generated by the radial wall 108a of the inner resistance region. This can be shown by the following equation:

[0064] Q 内部 =(I) 2 *R (1)

[0065]

[0066] Among them, Q 内部 Q is the heat generated by the radial wall 108a of the internal resistance region. 外部 It is the heat generated by each radial wall 108b, 108c of the external resistance region (the equation for heat generation is the same as the equation for power dissipation in each radial wall 108).

[0067] To mitigate the resistance drop at each unit transition 124, the resistance of the radial wall 108 of the inner resistance region 128 can be modified relative to the outer resistance region 128 to generate heat equal to that of the radially outer resistance region of the unit transition 124. Regarding Figures 4A-6 Examples were discussed.

[0068] Figure 4A A simplified partial cross-sectional view of one of the unit transition piece 124 and radial walls 108a-108d is shown for a given unit transition piece 124, illustrating a first method of changing the resistance of the radial wall 108 of the inner resistance region 128 relative to the outer resistance region 128. Regarding... Figure 4A In the portion of the unit transition 124 depicted, radial walls 108a are disposed in the inner resistance region 128, while radial walls 108b, 108c, and 108d are disposed in the outer resistance region 128. In this example, although three radial walls 108d, 108c, and 108d are shown for one radial wall 108a, this example doubles the number of radial walls 108d on the outer side of each unit transition 124.

[0069] like Figure 4AAs shown, in order to change the resistance of the radial wall 108, the wall thickness on the inner side of the unit transition 124 is increased so that heat generation on either side of the unit transition is substantially similar. For example, if (but for the increase in the thickness of the radial wall 108) each radial wall 108 on the outer side of the unit transition 124 generates one-quarter of the heat of the radial wall 108 on the inner side of the unit transition 124, then the thickness of the radial wall 108 of the resistive region 128 on the inner side of the unit transition 124 can be increased up to four times relative to the thickness of each radial wall on the outer side of the transition region 124. This is in Figure 4A As shown, the thickness of the radial wall 108a located inside the depicted unit transition member 124 is denoted as 4X, and the thickness of the radial walls 108b-108d located outside the unit transition member 124 is denoted as X. Figure 4B As shown, the radial wall 108a will have a resistance of a certain value R due to its thickness, and thus the resistance of the radial wall 108 is 4R. Therefore, the heat dissipation of the radial wall 108a located inside the unit transition member 124 will be given by equation (1). However, since the radial walls 108b-108c will receive half of the current flowing through the radial wall 108, the heat generated by each radial wall 108b-108c located outside the unit transition member 124 can be given by equation (3):

[0070]

[0071] Therefore, the heat generated at each radial wall 108 will be substantially similar, thereby promoting a uniform heat distribution throughout the resistive region 128.

[0072] The thickness required to achieve uniform heating depends in part on the ratio of the number of radial walls 108 in the outer resistance region 128 to the number of radial walls 108 in the inner resistance region 128. Generally, if all other aspects of the radial walls 108 are equal, then according to the equation for the heat generated by each radial wall 108, the relative thickness of the radial walls 108 in the inner resistance region 128 will be equal to the reciprocal of the square of the ratio of the number of radial walls 108 in the outer resistance region 128 to the number of radial walls 108 in the inner resistance region 128. Therefore, if the number of radial walls 108 on the outer side of the unit transition member 124 is three times the number of radial walls 108 on the inner side of the unit transition member 124, then the thickness of the radial walls 108 on the inner side of the unit transition member 124 should be nine times the thickness of the radial walls 108 on the outer side of the unit transition member 124. More generally, since other aspects of the radial walls 108 can be varied (e.g., length, axial length, material, etc.), the relative thickness of the radial walls 108 of the inner resistance region 128 will be equal to the reciprocal of the square of the ratio of the current flowing through each radial wall 108 outside the unit transition member 124 to the current flowing through each radial wall 108 inside the unit transition member 124. Therefore, in Figure 4A and 4BIn the example, since half of the current flows through radial walls 108b-108d, the thickness of radial wall 108a is four times the thickness of radial walls 108b-108d.

[0073] Figure 5 A simplified partial cross-sectional view of the unit transition 124 and radial walls 108a-108d is shown for a given unit transition 124, according to a second embodiment where the resistance of the radial walls 108 of the inner resistance region 128 is varied relative to the outer resistance region 128. According to the second embodiment, the length of the radial walls 108 on the inner side of the unit transition 124 is shortened such that the resistance of each radial wall 108a on the inner side of the unit transition 124 is a fraction of the resistance of each radial wall 108b-108d on the outer side of the unit transition 124. This example modifies the length of the radial walls 108 to change the resistance of each radial wall 108—the resistance of each radial wall 108 increases with length. For example, if the radial walls 108 are doubled at the outer side of the unit transition 124, the radial walls 108 on the inner side of the unit transition 124 can be shortened to one-quarter the length of the radial walls 108 on the outer side of the unit transition 124. Therefore, as... Figure 5 As shown, the radial wall 108a on the inner side of the unit transition member 124 has a length of L, and the radial wall 108 on the outer side of the unit transition member has a length of 4L. Therefore, returning to... Figure 1 For example, if this embodiment is followed, the length of the radial wall of resistor region 128c would be modified to four times the length of the radial wall 108 of resistor region 128d. Figure 4B Similarly, the resistance of the radial wall 108a inside the unit transition 124 will be resistance R, while the resistance of each radial wall 108b-108d outside the unit transition 124 will each be resistance 4R. Therefore, the heat generated by each resistive region 128 can be calculated by equations (1) and (3), and will therefore be equal. Regardless of the ratio of the number of radial walls 108 inside each unit transition 124 to the number of radial walls 108 outside each unit transition 124, in order to achieve the second embodiment, the length of the radial wall 108 inside the unit transition 124 can be equal to the reciprocal of the square of the ratio of the current flowing through each radial wall 108 outside the unit transition 124 to the current flowing through each radial wall 108 inside the unit transition 124.

[0074] In the third embodiment, as Figure 6 As shown in the cross-section (taken along the central axis C and on a plane that bisects the inlet surface 130 of the electric heater 100), with Figure 2In contrast to the cylindrical shape shown, honeycombs are generally arranged in a conical shape. For example, the axial length of the honeycomb wall increases towards the central axis C and gradually decreases towards the outer periphery of the honeycomb structure 102. Therefore, the axial length of the honeycomb structure directly adjacent to the central electrode 104 is the longest, denoted as L1, while at the midpoint between the central electrode 104 and the outer periphery of the honeycomb structure, the axial length decreases to L2. Finally, near the outer periphery, the axial length decreases to its shortest length L3. (See Figure 4 and...) Figure 5 The example is similar, but it reduces the equivalent resistance of the cell towards the central axis C. In an alternative example, the axial length could be gradually changed, for example, at a transition of 124 per cell, instead of gradually decreasing. Therefore, go to... Figure 1 In an alternative example, the axial length of the wall in resistor region 128c can be four times the length of the wall in resistor region 128c. Therefore, with Figures 4A-5 Similarly, the resistance of the radial wall 108 inside the unit transition 124 will be resistance R, while the resistance of each radial wall outside the unit transition 124 will be resistance 4R. Therefore, for the radial walls 108 located in the inner resistance region 128, the heat generated by each radial wall can be calculated by equation (1), and for the radial walls 108 located in the outer resistance region 128, the heat generated by each radial wall can be calculated by equation (3), and thus will be equal. In the example where the axial length is different in each resistance region 128, the relative axial length of each resistance region 128 can be similarly calculated as the reciprocal of the square of the ratio of the current flowing through each radial wall 108 outside the unit transition 124 to the current flowing through each radial wall 108 inside the unit transition 124.

[0075] Combination Figures 4A-6 Any of the embodiments described can be implemented in any suitable combination. For example, resistor region 128c can be twice as thick and half the length of resistor region 128d, rather than modifying resistor region 128c to be four times as thick or a quarter the length of resistor region 128d, thereby producing the following results: Figures 4A-6 The same equivalent resistance in each example. Therefore, Figures 4A-4B Examples can be compared with Figure 5 Examples and / or Figure 6 Examples combined. Similarly, Figure 5 Examples can be compared with Figure 6 Examples of combinations.

[0076] Furthermore, the thickness, length, and / or axial length of each resistive region 128 may vary within the specific resistive region 128 to achieve a desired heat distribution. For example, if a specific area of the resistive region 128 receives less exhaust gas than another area (e.g., the area near the periphery of the heater 100), the thickness of the radial wall 108 located within this area can be reduced, so as to increase the heat generated by this specific area relative to the rest of the resistive region 128 and / or the honeycomb structure 102. Upon review of the present disclosure, those of ordinary skill in the art will understand how to make such modifications to account for non-uniform exhaust gas flow or other factors outside the structure of the heater 100 that may affect the heat distribution of the heater 100.

[0077] In some embodiments, as Figure 7 shown in, in order to eliminate distinct resistive regions 128, the cell transition piece 124 is removed, which may therefore simplify the manufacturing process and / or improve the heating distribution. To maintain a constant hydraulic diameter, when moving outward from the central axis C to the outer periphery, the radial distance between radially adjacent angular walls 110 may gradually narrow, such that the spacing between the angular walls 110 decreases when approaching the skin 114 in the radial direction. This is as Figure 7 shown in, where the radial distance X1 between the central axis C and the first angular wall 110a is greater than the radial distance X2 between the first angular wall 110a and the next radially adjacent angular wall 110b. The radial distance between each successive angular wall 110 may decrease, such that the following expression holds true: Xn<Xn-1<…X2<X1, and when the distance between adjacent radial walls increases toward the outer periphery, the hydraulic diameter of each cell remains substantially similar (±35% variation). Therefore, as Figure 7 shown in, the honeycomb structure 102 includes more angular walls 110 at the outer periphery than near the central axis C.

[0078] Figure 8 shows an example of the thermal output that can be produced by the Figure 7 embodiment. Since the radial walls 108 represent the shortest path between the electrodes 104, 106 and thus carry most of the current, the current density near the electrodes 104 is greater than the current density at the outer periphery, because the radial walls 108 are relatively closely spaced near the central axis C, but are spaced farther apart near the outer periphery due to their radial divergence. Therefore, this embodiment is most beneficial where excess heat generation near the center is desired. For example, Figure 8 depicts an exemplary heat distribution of a heater similar to the Figure 7 embodiment. As shown, Figure 8The heat distribution results in a temperature of 860 K near the central electrode, 560 K at the midpoint between the central electrode and the outer periphery, and 430 K near the outer periphery, creating a temperature difference of 430 K. The provided temperature values ​​are for discussion purposes only and other temperatures can be achieved based on specific materials, geometries, voltages, and other parameters or characteristics of the heater.

[0079] To improve temperature uniformity, the radial walls 108 can be staggered. For example, the radial walls 108 can be staggered at their intersections with each corner wall 110, such that the radially adjacent cells of the cell 112 of the honeycomb structure 102 are offset, arranging the cells 112 in a brick-like pattern, as shown. Figure 9 As shown. Therefore, as Figure 10 As shown, each radial wall 108 can be offset at an angle θ from the radial wall 108 of a radially adjacent unit, the vertex of which is located on the central axis C. For example, radial wall 108e is offset by angle θ from radial walls 108f and / or 108g because unit 112a, partially defined by radial wall 108e, is radially adjacent to unit 112b, partially defined by radial walls 108f and 108g. Since units 112a and 112b are radially adjacent, each radial wall 108e, 108f, and 108g is generally connected by an angular wall 110c, which is generally shared by units 112a and 112b.

[0080] Figure 9 The architecture eliminates any straight path for current to flow from the center electrode 104 to the outer electrode 106, forcing the current to flow along the corner wall 110, thereby producing more uniform heating throughout the heater, especially near the outer periphery where the corner wall has a higher relative density. Figure 11 A staggered cellular structure is shown (e.g., Figure 9 Example of temperature distribution in a staggered honeycomb structure Figure 8 Compared to the temperature distribution shown, this demonstrates an improvement in the uniformity of heat distribution. In fact, as shown, Figure 11 The structure has a temperature of 680K near the central electrode, a temperature of 520K at the midpoint between the central electrode and the outer periphery, and a temperature of 400K near the outer periphery, resulting in a temperature difference of 280K.

[0081] The distance the current flows along the angle towards wall 110 will be at least partially determined by the angle between a given radial wall 108 and the nearest radial wall 108 defining the radially adjacent cell. That is, in the shortest path connecting electrodes 104, 106, the current will flow primarily along the portion of the angle separating the radial walls 108 towards wall 110. Therefore, if the two radial walls 108 are only separated by a small angle, the current will only flow along the angle towards wall 110 within the short angular distance between the radial walls 108. In contrast, if the radial walls 108 are at a distance equal to half the cell width (such as... Figure 9 and Figure 10 If the offset of the radial wall 108 is changed, the distance between each radial wall and the two radial walls 108 opposite the single angular wall 110 will be equal, and therefore the current flowing from the two radial walls 108 along the entire angular wall 110 will be equal (all other aspects of the unit 112 are equal). Therefore, the amount of current flowing along the angular wall 110 and the heat generated can be adjusted by changing the offset of the radial walls 108.

[0082] Figure 9 and Figure 10 Examples, and Figure 11 The resulting heat distribution can still generate more heat near the central axis C than is required in some embodiments. That is, for example, a more uniform temperature distribution may be beneficial for heating a gas flow with a uniform velocity on the surface of heater 100. Therefore, to further improve the uniformity of the temperature distribution, the radial wall near the center of heater 100 can be aligned with the adjacent radial wall to prevent current from flowing in the angular walls near the core, while the radial walls 108 near the outer perimeter and the corresponding elements 112 can be offset. Thus, as Figure 12 As shown in the example, the unit in the first region 105a is... Figure 7 Similar to the embodiment, the radial wall 108 propagates radially through multiple units 112, while the radial wall 108 in the second region 105b is... Figure 9 The embodiments are similar, wherein the radial walls 108 are staggered at each intersection of the radial walls 108 and the angular walls 110.

[0083] The offset between radially adjacent units 112 can be varied to achieve a desired heat distribution. For example, if a particular region of heater 100 receives less exhaust gas than another region (e.g., a region near the outer periphery of heater 100), the offset between radially adjacent units 112 can be increased to force more current through the angular walls 110 in that particular region. In conjunction with a review of this disclosure, those skilled in the art will understand how such modifications can be made to account for non-uniform exhaust flow or other factors beyond the structure of heater 100 that may affect the heat distribution of 100.

[0084] In some embodiments, particularly those where non-uniform airflow is anticipated at the inlet face of heater 100, the cell size in specific regions can be configured to compensate for increased exhaust flow in certain regions. For example, the central region (i.e., the region directly adjacent to the central axis C, such as...) Figure 12 Zone 105a) can receive an increased exhaust flow relative to the exhaust flow received at the outer periphery (e.g., due to the design of the exhaust treatment system installed on the vehicle). Therefore, unit 112 in this example can be divided into a first group located in zones directly adjacent to the central axis (e.g., Figure 12 In zone 105a) and the second group (e.g., arranged in a ring around the first group in the second zone) Figure 12 (Region 105b). The hydraulic diameter of the unit 112 in the first group can be smaller or larger than the hydraulic diameter of the unit 112 in the second group. For example, by reducing the hydraulic diameter of the unit group in the first radially inner region, the surface area of ​​the wall exposed to the gas flow at the center of the heater can be increased, and thus the amount of catalytic material can be increased to maximize the catalytic effect in that region. Advantageously, this can be used to provide higher temperatures and / or catalyst loading in regions with higher gas flow rates. In other examples, the hydraulic diameter of other regions can be increased or decreased accordingly to accommodate a specific flow distribution experienced or expected to be experienced by the heater 100 during use.

[0085] In other examples, combined Figures 4A-6 The description can be modified in various ways. Figures 9-12 Multiple designs can be combined to produce a more uniform heat distribution. For example, the thickness of the radial wall in the design of Figure 4 can be increased, making the radial wall 108 typically thicker than the angular wall 110 (e.g., twice as thick), thereby generating greater heating (e.g., twice as much) at the angular wall. Therefore, greater heat generation occurs at the outer periphery of the angular wall 110, where the heat concentration is higher. Figure 13 The heat distribution is particularly uniform. For example... Figure 13 As shown, the staggered cell design with increased radial wall thickness has a temperature of 520K near the center electrode, a temperature of 520K at the midpoint between the center electrode and the outer periphery, and a temperature of 500K near the outer periphery, thus creating a temperature difference of 20K.

[0086] Figure 14 An embodiment including multiple peripheral electrodes 106 is shown. For example, since current will flow from the central electrode 104 to the peripheral electrodes(s) 106, the temperature distribution can be adjusted by changing the size and positioning of the peripheral electrodes 106 at locations where a relatively high temperature is desired. For example, one or more peripheral electrodes 106 can be positioned to direct current flow through the unit 112, which is expected to receive a higher flow rate of airflow.

[0087] While several inventive examples have been described and illustrated herein, those skilled in the art will readily conceive of various other ways and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages described herein, and each of such variations and / or modifications is considered to be within the scope of the inventive examples described herein. More generally, those skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and actual parameters, dimensions, materials, and / or configurations will depend on the specific application or specific applications to which the teachings of this invention are applied. Those skilled in the art will recognize or be able to determine many equivalents of the specific inventive examples described herein using only conventional experimentation. Therefore, it should be understood that the foregoing examples are presented by way of example only, and that the inventive examples may be practiced within the scope of the appended claims and their equivalents, rather than as specifically described and claimed. The inventive examples of this disclosure pertain to each individual feature, system, article, material, and / or method described herein. Furthermore, any combination of two or more such features, systems, articles, materials, and / or methods is included within the scope of this disclosure if such features, systems, articles, materials, and / or methods are not inconsistent with each other.

Claims

1. An electric heater for heating an exhaust stream, comprising: A honeycomb structure, the honeycomb structure comprising: A cellular structure including a central axis extending longitudinally therein, and a plurality of interconnecting walls, the interconnecting walls comprising: Multiple radial walls, each radial wall extending at least partially along the radius of the honeycomb between its central axis and outermost periphery; and A plurality of angular walls, the plurality of angular walls being arranged concentrically relative to the central axis and spanning between the radial walls; and Multiple units, the multiple units being defined by the interconnecting wall; A first electrode, the first electrode being disposed at the central axis; and A second electrode is disposed radially outside the central axis and is electrically connected to the first electrode via one or more intersecting walls positioned between the first and second electrodes. The honeycomb structure includes a first resistive region separated from the second resistive region by a transition angular wall, wherein the first resistive region includes fewer radial walls than the second resistive region, the first resistive region is located closer to the central axis than the second resistive region, and both the first resistive region and the second resistive region are located between the first and second electrodes.

2. The electric heater as described in claim 1, characterized in that, The radial distance between the radially continuous angular walls of the plurality of angular walls decreases as they approach the outer periphery of the honeycomb, such that the variation in the hydraulic diameter of each unit is within ±35%.

3. The electric heater as described in claim 1, characterized in that, The first group of the plurality of units is located in a first region directly adjacent to the central axis, and the second group of the plurality of units is located in a second region radially outside the first region, wherein the first hydraulic diameter of each unit in the first group of the plurality of units is smaller than the second hydraulic diameter of each unit in the second group of the plurality of units.

4. The electric heater as described in claim 1, characterized in that, Each radial wall of the first unit in the plurality of units is offset at an angle relative to the radial wall of the second unit that is radially adjacent to the first unit in the plurality of units.

5. The electric heater according to any one of claims 1-4, characterized in that, The first resistance region and the second resistance region are defined by the transition angle wall and one of the first electrode, the second electrode, or the second transition angle wall.

6. The electric heater according to any one of claims 1-4, characterized in that, The radial walls of the first resistive region are proportionally thicker than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is the same as the heat generated by each radial wall of the second resistive region.

7. The electric heater according to any one of claims 1-4, characterized in that, The radial walls of the first resistive region are proportionally shorter than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is the same as the heat generated by each radial wall of the second resistive region.

8. The electric heater according to any one of claims 1-4, characterized in that, The radial walls of the first resistive region are axially proportionally longer than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is the same as the heat generated by each radial wall of the second resistive region.

9. The electric heater according to any one of claims 1-4, characterized in that, The radial wall is thicker than the angular wall.

10. The electric heater according to any one of claims 1-4, characterized in that, The second electrode is disposed at the outer skin, which surrounds the outer periphery of the honeycomb structure.

11. An exhaust treatment system comprising an electric heater as described in any one of claims 1-4, wherein the exhaust treatment device is located downstream of the electric heater.

12. The exhaust gas treatment system as claimed in claim 11, characterized in that, The exhaust treatment device includes a substrate loaded with catalytic material, a particulate filter, or a combination thereof.

13. A method for heating a catalytic material, the method comprising the following steps: A potential difference is applied across a first electrode located at the central axis of a first honeycomb cell and a second electrode located radially outward from the first electrode on the honeycomb cell to heat an exhaust flow passing through the first honeycomb cell, wherein the honeycomb cell includes a plurality of intersecting walls and a plurality of cells defined by the plurality of intersecting walls, the plurality of intersecting walls including a plurality of radial walls and a plurality of angular walls, each radial wall extending at least partially along the radius of the honeycomb cell between the central axis and the outermost periphery of the honeycomb cell, at least some of the plurality of radial walls being angularly spaced from each other about the central axis, the plurality of angular walls being concentrically arranged relative to the central axis and spanning between the radial walls, wherein the potential difference generates a current flowing through the intersecting walls located between the first electrode and the second electrode, the current generating resistance heating in the intersecting walls; and The exhaust flow is directed to a second honeycomb cell downstream of the first honeycomb cell, wherein the second honeycomb cell includes the catalytic material. The honeycomb includes a first resistive region separated from the second resistive region by a transition angular wall, wherein the first resistive region includes fewer radial walls than the second resistive region, the first resistive region is located closer to the central axis than the second resistive region, and both the first resistive region and the second resistive region are located between the first and second electrodes.

14. The method as described in claim 13, characterized in that, The radial dimension of each cell in the plurality of cells decreases for each subsequent radially adjacent cell that is radially close to the periphery of the cell, such that the variation in the hydraulic diameter of each cell is within ±35%.

15. The method as described in claim 13, characterized in that, The first set of the plurality of units is arranged around the central axis, wherein the second set of the plurality of units is arranged around the first set, wherein the first hydraulic diameter of each unit in the first set of the plurality of units is smaller than the second hydraulic diameter of each unit in the second set of the plurality of units.

16. The method as described in claim 13, characterized in that, One or more radial walls of each cell in the first subset of the plurality of cells are respectively offset at an angle relative to the radial walls of each cell in the second subset of the plurality of cells that are radially adjacent to the first subset.

17. The method as described in claim 16, characterized in that, The second subset of the unit is separated from the central axis from at least two of the plurality of angular walls.

18. The method according to any one of claims 13-17, characterized in that, The radial wall of the first resistance region is thicker than the radial wall of the second resistance region, so that the equivalent resistances of the first resistance region and the second resistance region are similar.

19. The method according to any one of claims 13-17, characterized in that, The radial walls of the first resistive region are shorter than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is the same as the heat generated by each radial wall of the second resistive region.

20. The method according to any one of claims 13-17, characterized in that, The radial walls of the first resistive region are axially longer than the radial walls of the second resistive region, such that when current is carried between the first electrode and the second electrode, the heat generated by each radial wall of the first resistive region is the same as the heat generated by each radial wall of the second resistive region.

21. The method according to any one of claims 13-17, characterized in that, The radial wall is thicker than the angular wall.

22. The method according to any one of claims 13-17, characterized in that, The second electrode is disposed at the outer skin, which is arranged around the outer periphery.

23. The method according to any one of claims 13-17, characterized in that, The catalytic material is loaded onto the intersecting wall.

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