CN110206619B

CN110206619B - Induction heating apparatus and method

Info

Publication number: CN110206619B
Application number: CN201910152243.XA
Authority: CN
Inventors: R·克劳福德; J·道格拉斯
Original assignee: Advanced Technology Emission Solutions Inc
Current assignee: Advanced Technology Emission Solutions Inc
Priority date: 2018-02-28
Filing date: 2019-02-28
Publication date: 2022-02-01
Anticipated expiration: 2039-02-28
Also published as: CN114320542A; EP3534674A1; EP3534674B1; CN110206619A

Abstract

An assembly for treating gaseous exhaust emissions has an induction heater mounted beside a gaseous emission treatment unit, and upstream and downstream portions of a downstream substrate unit or individual substrate. The upstream cell or section has linear channels extending the length of the first substrate for the passage of gaseous emissions, but some of the channels are plugged by metal inserts for induction heating of the upstream cell. The concentration of metal inserts is high and the metal inserts are distributed such that the heating slices or portions are rapidly and strongly induced to rapidly reach the "light-off temperature so as to transfer the gaseous emissions, thermally replenished at the light-off temperature, to the downstream substrate or portion as quickly as possible.

Description

Induction heating apparatus and method

Technical Field

The present invention relates to induction heating structures and methods having particular, but not exclusive, application to catalytic converters, Particulate Filters (PFs), and similar structures for treating exhaust gases to reduce toxic pollutants.

Background

The united states department of transportation (DOT) and the united states Environmental Protection Agency (EPA) have enacted united states federal regulations, which regulate national greenhouse gas emission standards. Starting from the year of the 2012 new vehicle product (model year), automakers are demanding reductions in fleet wide emissions of greenhouse gases of about 5% per year. Included in the requirements is, for example, that new standards specify that the estimated aggregate average emission levels for new passenger cars, light trucks, and medium passenger vehicles must not exceed 250 grams per mile of carbon dioxide (CO2) in a new vehicle model year of 2016.

Catalytic converters and DPFs are used in internal combustion engines to reduce toxic exhaust emissions produced when fuel is combusted as part of a combustion cycle. A significant portion of these emissions are carbon monoxide and nitric oxide. These gases are toxic to health, but can be converted to less toxic gases by oxidation to carbon dioxide and nitrogen/oxygen, respectively. Other toxic gas emission products (including unburned hydrocarbons) can also be converted to less toxic forms by oxidation or reduction. The conversion process can be achieved or accelerated if it is carried out at high temperatures and in the presence of a suitable catalyst matched to the specific toxic exhaust gases to be treated and converted into benign gaseous form. For example, typical catalysts for converting carbon monoxide to carbon dioxide are finely divided platinum and palladium, while typical catalysts for converting nitric oxide to nitrogen and oxygen are finely divided rhodium.

The catalytic converter and PF have inefficiencies when cool (i.e., an operating temperature from the ambient air start-up temperature to a temperature typically on the order of 300 ℃ or "light-off" temperature, which is the temperature at which the metal catalyst begins to accelerate the previously described pollutant conversion process). Light-off is generally characterized as the temperature at which toxic emissions are reduced by 50%, which is about 300 ℃ for gasoline. Below the light-off temperature, little catalysis occurs. This is therefore the period during which most of the vehicle polluting emissions are generated during the daily use of the vehicle. Heating the catalytic converter or PF as quickly as possible is important to reduce cold start emissions.

Co-pending U.S. patent application 14452800 (with an inductively heated catalytic converter structure) shows a catalytic converter assembly having a substrate with a plurality of cells for the passage of exhaust gas therethrough. A metal is located at a predetermined location in the substrate and an electromagnetic field generator is mounted adjacent the substrate for inductively generating a varying electromagnetic field to heat the metal and thus the substrate.

Disclosure of Invention

According to a first aspect of the present invention, there is provided an assembly for treating gaseous emissions, comprising: a first substrate having a plurality of first linear channels extending the length of the first substrate for passage of gaseous emissions, the first substrate having an elongated metal insert in each first linear channel of a subset of the plurality of first linear channels, wherein the metal concentration per unit volume of the first substrate increases toward one end of the first substrate; an electromagnetic field generator configured to inductively heat the metal insert and thereby the first substrate; and a second substrate having a plurality of second linear channels for receiving gaseous emissions exiting from another end of the first substrate, the first substrate being substantially aligned with but separated from the second substrate.

According to a second aspect of the present invention, there is provided a gas heater comprising: a ceramic honeycomb substrate having: a first plurality of channels extending a length of the ceramic honeycomb substrate for conveying a gas stream introduced into the first plurality of channels at one end of the ceramic honeycomb substrate from the one end to another end of the ceramic honeycomb substrate; a plurality of second linear channels extending the length of the ceramic honeycomb substrate, a first plurality of elongated metal inserts substantially occluding respective ones of the plurality of second linear channels; an electromagnetic field generator configured to inductively heat the metal insert; and a flowing gas source located upstream of the ceramic honeycomb substrate for generating the gas flow.

According to a third aspect of the present invention there is provided an assembly for treating gaseous emissions, comprising: a metal precursor and a plurality of passages through said metal precursor for gaseous emissions to enter through one end of the metal precursor, pass through said passages and exit through the other end of said metal precursor; an electromagnetic field generator configured to inductively heat the metal in the metal precursor, thereby heating gaseous emissions passing along the metal precursor; and a substrate having a plurality of linear channels for receiving the gaseous effluent exiting from said other end of said metal precursor, said metal precursor being substantially aligned with the substrate.

Drawings

For simplicity and clarity of illustration, elements shown in the figures have not been drawn to the same scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. The advantages, features, and characteristics of the present invention, as well as the methods, operations, and functions of the related elements of structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:

FIG. 1 is a longitudinal cross-sectional view of a prior art gaseous emission treatment unit.

FIG. 2 is a longitudinal cross-sectional view of a gaseous emission treatment unit suitable for use in one embodiment of the present invention.

Fig. 3 is a cross-sectional view of the unit of fig. 2.

FIG. 4 is a perspective cut-away view of a portion of a gas emission treatment unit showing metal inserts positioned in cells of a substrate according to one embodiment of the invention.

Fig. 5, 5A and 5B are a longitudinal sectional view, a cross-sectional view and a perspective view, respectively, of a gaseous emission treatment unit adapted for front end heating in accordance with another embodiment of the present invention.

Fig. 6, 6A and 6B are longitudinal sectional, cross sectional and perspective views, respectively, of a gaseous emission treatment unit according to another embodiment of the present invention, which unit is also suitable for front end heating.

FIG. 6C is a longitudinal cross-sectional view of a gaseous emission treatment unit adapted for back-end heating of gas exiting an upstream block, according to another embodiment of the present invention.

FIG. 6D is a longitudinal cross-sectional view of a gaseous emission treatment unit adapted for front end heating according to yet another embodiment of the present invention.

FIG. 6E is a longitudinal cross-sectional view of a gaseous emission treatment unit adapted for back-end heating of gas exiting an upstream block according to yet another embodiment of the present invention.

FIG. 7 is a longitudinal cross-sectional view of a gaseous emission treatment assembly according to another embodiment of the present invention, with a forward gaseous emission treatment unit adapted for back-end heating to heat a downstream gaseous emission treatment unit.

FIG. 7A is a longitudinal cross-sectional view of a gaseous emission treatment assembly according to another embodiment of the present invention having a front unit configured for inductively front-end heating and back-end heating to heat a downstream gaseous emission treatment unit.

FIG. 7B is a longitudinal cross-sectional view of a gaseous emission treatment assembly having an upstream unit of inductively front-end and back-end heating, and a downstream unit of inductively front-end heating, according to another embodiment of the present invention.

Fig. 8 and 8A are end and perspective views, respectively, of an emission treatment unit having a separate front end heater according to another embodiment of the present invention.

Fig. 9 and 9A are end and perspective views, respectively, of an emission treatment unit having an alternative form of a separate front end heater, according to one embodiment of the present invention.

FIGS. 10 and 10A are end and perspective views, respectively, of an emission treatment unit having another alternative form of a separate front end heater according to one embodiment of the present invention.

Fig. 11 and 11A are end and perspective views, respectively, of an emission treatment unit having yet another alternative form of a separate front end heater in accordance with an embodiment of the present invention.

Fig. 12 and 12A are end and perspective views, respectively, of an emission treatment unit having another alternative form of a separate front end heater according to one embodiment of the present invention.

Fig. 13 and 13A are end and perspective views, respectively, of a gaseous emission treatment unit having another alternative form of a separate front end heater in accordance with an embodiment of the present invention.

FIG. 14 is a side cross-sectional view of a space heater according to one embodiment of the invention.

Detailed Description

The gaseous emission treatment assembly may take any of a variety of forms. A typical gaseous emission treatment group is the known catalytic converter having a cylindrical substrate 10, generally made of ceramic material and generally referred to as a block, an example of which is shown in fig. 1. The block has a honeycomb structure in which a number of small area channels or cells 12 extend the length of the block, the cells being separated by walls 14. Typically, the substrate 10 has 400 to 900 cells per square inch (cpsi) of cross-sectional area, and the walls are typically in the range of 0.003 to 0.008 inches thick. Typically, the ceramic substrate 10 is formed in an extrusion process, in which a green ceramic material is extruded through a suitably shaped die, and the unit is cut continuously from the extrusion and then cut into blocks. The shape of the cells or channels 12 may be any shape that facilitates contributing to the overall strength of the substrate 10 while having a large contact area where the exhaust gas flowing may interact with the hot catalyst coated on the interior walls of the cells. In other gaseous emission treatments, such as particulate filters, there may or may not be a catalyst coating on the channel walls. In the particulate filter, the front ends of the checkerboard subsets of cells are plugged, the back ends of the "reverse" checkerboard subsets of cells are plugged, and the gas emissions are processed by driving the gas emissions from the cells of the first subset into the cells of the reverse subset through the porous walls of the honeycomb structure.

In a catalytic converter, the interior of the tubular cells 12 are washcoated with a layer containing a particular catalyst material. The washcoat layer typically comprises a base material suitable for ensuring adhesion to the cured ceramic material of the substrate, and an entrained particulate catalyst material for promoting specific contaminant reducing chemical reactions. Examples of such catalyst materials are platinum and palladium (which are catalysts that efficiently convert carbon monoxide and oxygen to carbon dioxide), and rhodium (which is a catalyst suitable for converting nitric oxide to nitrogen and oxygen). Other catalysts that promote high temperature oxidation or reduction of other gaseous species are known. Washcoats are prepared by creating a suspension of the refined catalyst in a ceramic paste or slurry that is used to adhere the washcoat to the walls of the ceramic matrix. As an alternative to washcoating for placing the catalyst material on the substrate surface, the substrate material itself may comprise the catalyst, such that the bulk walls themselves present the catalyst material at the interior surfaces defining the cells.

Exhaust gases from diesel (compression combustion) engines contain more nitrogen oxides than gasoline (spark combustion) engines. Even prolonged exposure to low levels of nitrogen oxides can lead to temporary or permanent respiratory problems. Selective Catalytic Reduction (SCR) is the injection of a liquid reductant into the diesel engine exhaust stream to react with nitrogen dioxide and nitric oxide (collectively referred to as NO) in the exhaust_X) And (3) a combination method. The preferred reducing agent is a urea solution(2(NH₂)₂CO), which is commonly referred to as Diesel Exhaust Fluid (DEF). In the presence of a catalyst, the ammonia produced by the thermal decomposition of urea combines with the nitrogen oxides to produce less harmful products (mainly nitrogen and water). Other reducing agents (such as anhydrous ammonia and aqueous ammonia) may also be used as a substitute for urea, although on-board storage presents significant difficulties, particularly for automotive applications. Suitable catalysts may be any of a number of metal oxides (e.g., oxides of molybdenum, vanadium, and tungsten), a number of noble metals, and zeolites. Typical temperatures for the SCR reaction range from 360 ℃ to 450 ℃ with catalysts such as activated carbon being used to stimulate the lower temperature reaction. Like gasoline (spark-combustion) engines, diesel (pressure combustion) engines may experience a period of time after start-up in which the exhaust gas temperature is too low for an effective SCR NOx reduction process to occur. Other catalytic converters, in which the invention finds application in pre-heating or supplemental heating, are lean in NO_XCatalyst system, lean NO_XA capture system, and a non-selective catalytic reduction system. The present invention is also applicable to each of these nitrogen oxide emission treatment components.

The gaseous emission treatment assembly may have a series of substrates or blocks 10, each having a specific catalyst layer or emission treatment pattern, depending on the toxic emissions to be reduced or neutralized. The gaseous emission treatment mass may be made of a material other than fired ceramic, such as stainless steel. Also, the blocks may have honeycomb cells or channels of a different form to those described above. For example, the cells may be circular, square, hexagonal, triangular, or other convenient cross-sectional shape. In addition, some extruded honeycomb walls may be formed thicker than others, or formed so that there is some variation in cell shape and size, if desired to optimize strength and low heat capacity or for other purposes. The connections between adjacent inner walls of the cells may be acute or may exhibit a curved profile.

Typically, as shown in FIG. 1, a washcoated ceramic honeycomb block 10 is wrapped in a ceramic fiber intumescent blanket 16. A stamped metal housing or canister 18 transitions between components of the exhaust pipe (not shown) before and after the gaseous emission treatment unit to enclose the mass wrapped by the intumescent blanket. The housing 18 is typically made of two parts that are welded to seal the block in place. The expansion blanket 16 provides a cushion between the housing 18 and the block 10 to accommodate their differing coefficients of thermal expansion. At a given temperature increase, the metal of the thin sheet metal housing 18 expands much more than the bulk ceramic material, and if the two materials are bonded together or in direct contact with each other, destructive stresses can occur at the interface of the two materials. The blanket 16 also dampens vibrations from the exhaust system that might otherwise damage the brittle ceramic of the substrate 10.

In use, the wrapped block (or blocks) is/are installed in a vehicle exhaust line to receive exhaust gases from the engine and deliver them to the vehicle tailpipe. The exhaust gas passes through the gaseous emission treatment unit to heat the ceramic block 10 to facilitate the catalyst activation process, wherein the flowing gas contacts the catalyst layer. In particular, when the vehicle engine is operating at an optimum operating temperature and when there is a large exhaust flux, the processing unit is substantially operative to reduce the presence of toxic gaseous emissions into the atmosphere. However, these units have drawbacks at start-up when the interior of the block is at low temperature, during idle periods during city driving or when the Tim homes drive-up restaurants are waiting for coffee, and during electric drive of the hybrid vehicle.

The block shapes, shapes and cell densities produced by different manufacturers vary. For example, some blocks are circular and some are oval. Some assemblies have a single stage block that is typically heavily washcoated with catalyst metal, while other assemblies may have two or three blocks with a different washcoat on each block. Some vents used cell densities of 900, 600, and 400cpsi throughout the vent assembly, while others used only 400cpsi blocks throughout the vent. A close-coupled converter may be installed near the exhaust manifold to address the reduction in the time period between start-up and light-off temperatures. The underfloor converter may be located further away from the engine, where it will take longer to heat up but is relatively large and is used to treat most of the gas once the exhaust assembly reaches temperature. In another configuration, the unit for reducing the time period to reach the light-off temperature and the unit for treating the high gas flow after light-off are mounted together in a common housing.

Sensors mounted in the exhaust flow included within or near the substrate provide feedback to the engine control system at one or more locations in the assembly for emissions inspection and adjustment purposes. In addition to start-up, the purpose of controlling fuel and air input is typically to maintain 14.6: 1 air: fuel ratio to achieve the best combination of power and cleanliness. Above this air: the ratio of fuel ratios creates a lean condition (fuel deficiency). Lower ratios produce rich conditions (overfueling). The start-up sequence of some vehicles runs rich for the first few seconds to get heat into the engine and ultimately into the catalytic converter. The structures and operating methods described below for indirectly heating the catalyst layer and exhaust gas may be used with each of a close-coupled catalytic converter, an underfloor converter, and a combination of the two. The output from the temperature sensor is sent to a controller where the monitored temperature or temperatures are used to control when to turn induction heating on and off. The monitored temperature may also be used to control the specific effect of the applied heating process to achieve a specific heating pattern, using a suitable algorithm implemented at the controller.

As disclosed in U.S. patent No.9488085, the gaseous emission treatment assembly shown in fig. 1 is modified as shown in fig. 2 and 3 to enable induction heating. Induction heating is the process of heating a metal body by applying a varying electromagnetic field to alter the magnetic field experienced by the metal body. This in turn induces eddy currents within the metal body, causing resistive heating of the metal body. In the case of ferromagnetic metal bodies, heat is also generated by hysteresis effects. When a non-magnetized ferromagnetic metal is placed in a magnetic field, the metal is magnetized by creating magnetic domains with opposite magnetic poles. The changing magnetic field periodically initiates a polarity reversal in the magnetic domains, on the order of 1,000 to 1,000,000 cycles/second (Hz) in response to high frequency induced field changes depending on the material, mass, and shape of the ferromagnetic metal bodies. The domain polarity is not easily reversed and the reversal resistance results in further heat generation in the metal.

Surrounding the ceramic substrate 10 is a metal coil 20, as shown in fig. 2 and 3, although not visible in fig. 2, located within selected ones of the cells 12 are metal pins, rods, wires or other metal inserts 22 (fig. 4). By generating a varying electromagnetic field at the coil 20, a chain reaction is induced, the end result of which is that after starting of a vehicle equipped with an exhaust system embodying the invention, the light-off temperature can be obtained more quickly in the presence of a varying electromagnetic induction field than without. The chain reaction is as follows: the changing electromagnetic field induces eddy currents in the metal element 22; eddy current induced heating of the metal element; heat from the metal element 22 is transferred to the ceramic base 10; heat from the heated substrate 10 is transferred to the exhaust gas as it passes through the emissions control unit; the heated exhaust gas causes the catalytic reaction at the wall 14 to occur more rapidly than the unheated exhaust gas. Conduction from the heated wire, pin or other filler element 22 is the primary source of heat transfer to the ceramic substrate 10 and thus to the exhaust gas when the emission unit is in operation. There is also a small amount of convective and radiative heat transfer at any small air gap between the wire and the inner surface of the cell in which it is contained.

The coil 20 is a length of copper tubing wound, but other materials, such as copper wire or litz wire, may be used. Copper tubing is preferred because it provides a high surface area in terms of other dimensions of the coil; induction is a skin effect phenomenon, and high surface area is beneficial for generating a changing field. If stranded or copper wire is used, the enamel or other coating on the wire is configured to not burn out during continued high temperature operation of the converter. The air gap between the coil 20 and the nearest inductive wire 22 prevents significant heat transfer from the wire 22 to the coil 10 which would otherwise increase the coil resistivity and therefore reduce its efficiency.

A layer 24 of electromagnetic field shielding/concentrating material is located directly outside the coil 20 to provide inductive shielding and reduce inductive losses to the metal converter housing. Layer 24 also serves to increase the inductive coupling with the metal in substrate 10 to focus the heating. The shield/concentrator 24 may be made of ferrite or other high permeability, low power loss material, such as Giron, MagnetShield, Papershield, Finemet, cobatex, or other magnetic shielding material that may be arranged in partial or full windings around the coil 20. In particular, the magnetic shield 24 functions as a magnetic flux concentrator, flux booster, diverter, or flux control to contain the magnetic field within the matrix. The magnetic shield reduces losses by mitigating undesirable heating of adjacent conductive materials. Without the magnetic shield/concentrator 24, the magnetic flux generated by the coil 20 can spread around the coil 20 and link with electrically conductive surrounding objects, such as the metal housing 18 and other surrounding metals in the exhaust system, and/or other components of the internal combustion engine, vehicle, generator, or other electrical or host system, thereby reducing the life of these components and increasing energy losses. In addition, the layer 24 serves to direct or concentrate the magnetic field to the substrate 10, thereby providing selective or enhanced heating of desired areas of the substrate 10, for example, by redirecting magnetic flux that would otherwise travel away from the desired areas. In particular, the layer 24 serves to concentrate the magnetic flux generated by the coil 20 in the direction of the metal wire or rod 22 in the base body 10 for more efficient heating. As an additional benefit, the magnetic shield can improve the electrical efficiency of the induction coil 20 by increasing power transfer.

The coil is contained in a fibrous insulation sheath 26, the sheathed coil being encased in a cast cured insulation. The jacket acts to stabilize the coil position and create a gas-tight seal to restrict the passage of exhaust gas through the ceramic honeycomb substrate 10 where catalysis occurs. The insulator also provides a barrier to prevent the induction coil 20 from shorting out on the converter housing 18 or ferrite shield 24. The insulator is suitably an aluminosilicate adhesive. Alternatively, the matrix may be wrapped in an aluminosilicate fibrous paper. In one method of manufacture, the copper coil 20 is wound around a substrate and then placed in the outer shell or can 18. In an alternative manufacturing method, the coil 20 is placed in the can or housing 18 and the base 10 is inserted into the coil/can assembly.

A varying electromagnetic induction field is generated at the coil by applying power from a DC power source or an AC power source. A conventional automobile has a 12VDC electrical system. The induction system may run on a DC or AC power source. The induced signal generated may also be DC or AC driven. As an example, for DC or AC this results in a frequency of 1 to 200kHz, an RMS voltage of 130 to 200V, and an amperage of 5 to 8A using 1kw of power. In one example suitable for use with road vehicles, a DC to DC bus converts the vehicle's 12VDC cell power to the desired DC voltage outlined above. In another example applicable to a conventional road vehicle, a DC to AC inverter converts the vehicle's 12V DC cell power to the desired AC voltage outlined above. Another example is more suitable for a hybrid vehicle with an internal combustion engine and an electric motor, which has an on-board cell rated for 360V voltage and 50kW power. In this case the cell supply power is higher, but the same basic electrical configuration of a DC to DC bus or DC to AC inverter may be applied. Insulated Gate Bipolar Transistors (IGBTs) or Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) high speed switches are used to change the direction of current through the coil. In terms of the effect of the varying electromagnetic induction field on the metal in the ceramic matrix, the low switching frequency produces a longer waveform, providing good field penetration below the surface of the metal element and thus relatively uniform heating. However, this comes at the expense of high temperature and rapid heating due to lack of switching. Conversely, a high switching frequency produces a shorter waveform, which results in a higher surface temperature at the expense of penetration depth. The power applied is limited to avoid the risk of melting the metallic elements or bringing them to the curie point. A suitable power input to the single bulk coil is approximately 1.1 kw.

As previously mentioned, inserts 22, such as wires, pins, or other fillers made of ferromagnetic or other metals, are located at selected locations of the ceramic substrate 10, as shown in the detail view of fig. 4. In the case of wires, the wires may be held in place by a friction fit achieved at least in part by closely matching the outer area dimensions of the wires to the cell area dimensions, such that the wire surfaces and surface roughness of the cell walls 14 hold the wires 22 in place. In addition, the wires may be formed as resiliently flexible elements (not shown) which flex from a resting state when the wires are inserted into the cells so that a portion of the wires bear against the inner walls of the cells 12 and thus provide a frictional holding force. The integral friction fit may, for example, resist gravity, vibration, temperature cycling, and line pressure as the exhaust gas passes through the substrate.

Alternatively or additionally, the strands 22 may be secured into the cells by bonding the outer surfaces of the strands to the inner surfaces of the cell walls 14. A suitable composite binder may be a mixture of materials selected to reduce the effects of temperature cycling stress in which there may be significant linear expansion/contraction of the metal, but small expansions/contractions of the ceramic matrix that go to zero. This difference can create stress at the adhesive interface between the two materials. By using such a composite adhesive, movement of the bonded strands relative to the surrounding cell walls can be reduced while maintaining high heat transfer. Alternatively, the metal inserts may be introduced into selected cells as molten metal, metal slugs, or metal powder, which is then processed to bring the inserted material into such a state and relationship with the walls of the base body to retain the metal in the selected cells.

The field generated by the electromagnetic induction coil can be tuned to the wire load to achieve high efficiency in terms of heat generation and time to reduce light-off temperature. The heating effect may be varied by appropriate selection of any or all of (a) the electrical input waveform to the coil 20, (b) the nature and location of the passive flux control element (e.g., the shield/concentrator 24), and (c) the nature, location and configuration of the coil 20. Furthermore, the applied field may be varied over time such that there is interdependence between the induction field/heating mode and particular phases of operation (e.g., pre-start, warm-up, highway driving, idle, and hybrid, intermittent transition from internal combustion to electric drive). In another configuration, more than one coil may be used to achieve the desired inductive effect. For example, a base body with a circular cross-section may have one excitation coil at the base body periphery and a second excitation coil at the base body core (not shown).

The heating pattern may be determined by the appropriate location and configuration of the metallic pins or wires 22. Suitable metals for the inserted wire are ferromagnetic metals, such as grade 430 stainless steel, which has high permeability and corrosion resistance. Lower permeability alloys, such as 300 or 400 series stainless steels, may also be used. Depending on the manufacturing line insert and the specific properties required to secure the insert within a selected cell of the ceramic substrate, alternative metals may be used. These properties include metal formability, ductility, softness, and elasticity. To establish the direction and strength of the magnetic flux in the matrix, a lower permeability metal or alloy may be used for the metal inserts in the outer cells, while a relatively higher permeability metal is used for the metal inserts in the inner cells. Metals with very high magnetic permeability may also be used. For example, the Kanthal iron-chromium aluminum alloy used for the wire made by Sandvik has a relative permeability of 9000 or higher. High relative permeability may be achieved using wires made of other alloys including nickel-iron and iron-cobalt alloys.

It is desirable to heat the substrate so rapidly that the entire substrate quickly reaches the light-off temperature. Minimizing the light-off period is important for overall emissions reduction because there is virtually no catalyst to facilitate treatment of gaseous emissions below this temperature. For a given applied power level, a low pin density results in a hot region at the pin locations, but a cold region between the pins. While the pin position may achieve the light-off temperature relatively quickly, the portion of the ceramic substrate cross-sectional area at or above the light-off temperature may not be high enough to sense and maintain the overall light-off temperature. The exhaust gas flowing through the narrow substrate channels is at approximately the same temperature as the local ceramic, so the gas passing through the cold channels is untreated.

While in current commercial use, substrates (such as substrate 10) may typically have a length of 3 to 6 inches, if the upstream portion of the substrate, which is 2 inches or even less in length, is at light-off temperature over its entire range, the exhaust gas passing through that portion of the substrate will rapidly drive the downstream catalyst coated area to light-off temperature. The catalytic reactions that occur at and above the light-off temperature are generally exothermic, such that after light-off is achieved upstream, an auto-fuel cascade effect is produced in the downstream portion of the substrate. Thus, although the induction heated front may be narrower than the non-induction heated base portion, there may be sufficient mass flow and heat to rapidly drive the remainder of the base to the light-off temperature. After the small upstream substrate portion reaches light-off, exothermic catalysis that promotes combustion of unburned components in the exhaust gas progresses downstream into a chain reaction.

Rapid heating to the light-off temperature can be achieved by using a high pin density, in which the pin heating locations are close together, so that the light-off temperature is obtained over the entire cross-section of the base body. However, the increased density of metal inserts 22 filled into the channels 12 increases the pressure drop through the system, thus limiting how much of the cross-sectional area of the ceramic substrate 10 can be blocked with metal inserts 22. This in turn limits how much of the cross-sectional area of the substrate will reach the light-off temperature during operation. The pressure drop over the length of the emission treatment assembly is related to the amount of work required by the engine to drive its gaseous emissions through the emission treatment assembly. The more work an engine does in treating emissions, the less efficient it is at converting fuel combustion to driving a vehicle. Pressure drop for components such as those to which the present invention relates, originates from three sources: friction loss, impact loss, and expansion loss. The friction loss is due to the flow of exhaust gas along the narrow cells of the substrate. The impact losses are due to the blocking cross-sectional area encountered by the exhaust flow at the substrate surface, which includes the end walls of the cells and any cells plugged by metal inserts. The expansion loss is due to the flow transition of the gas expanding from discrete channels to a slower flow mass as the exhaust gas exits the ceramic matrix at high velocity. While the diameter of the base can be increased to compensate for the additional pressure drop due to the presence of more pins, this requires larger units and higher material costs.

In the matrix shown in fig. 1, the pressure drop from frictional losses is approximately linear with length and accounts for approximately 90% of the total pressure drop in a cell having, for example, a 3 inch (0.0762 meter) ceramic matrix, a cpsi (cells per square inch) between 400 and 900, and an exhaust gas flow rate of 5 meters per second. As shown in fig. 4, if the selected channel is selected from the group consisting of 1: x packing density, the pressure drop increases by about (100/x)%, regardless of pin length, and cell 12 is considered blocked by pin 22.

Given a length of "L" and a pin density of "1: x "if a portion of the length" L/2 "of the matrix has a pressure drop P of 1: the pressure drop P remains approximately the same with an x/2 pin density and the remaining portion of the base body having a length of "L/2" with open unblocked cells. This relationship generalizes beyond the above example, for a length of "L/3" and pin density of "1: the pressure drop is again substantially constant for the first matrix part x/3 "and the remaining matrix part having open unblocked cells of length 2L/3. However, with this arrangement, there are more heating locations, although the pressure drop remains relatively constant. This means that the pin density and relative length of the heated portion of the substrate can be adjusted according to other requirements of the system without significantly affecting the pressure drop through the system. In particular, a smaller volume of substrate may be inductively heated to achieve a light-off temperature faster than if the entire substrate were subjected to the same power input.

In one embodiment of the invention as shown in fig. 5, 5A and 5B, the placement of the pins 22 and their induction heating by the coils 22 is limited to the front of the substrate where exhaust gas enters. The front 28 of the base 10 has a high pin packing density and the channels 12 in the rear 30 of the base are open and unobstructed. For operational utility, the length relationship between the front and

rear portions

28, 30 and the pin packing density of the front portion 28 depend at least in part on the heating characteristics and whether the resulting pressure drop is operationally acceptable.

In the embodiment shown in fig. 4 and 5, the metal inserts 22 occupy a regular array of 1 inch 9 channels at the front 28 of the base 10, with the length of the occupied channels at the rear of the pins 22 being open. Also in this embodiment, the maximum pin length of the front portion is 50% of the length of the rear portion or 33% of the entire base length. The prongs 22 at the front of the base are distributed with their tails in a D-shape or parabolic shape. The magnetic flux from the surrounding coil 20 is strongest at the position closest to the coil 22 and weakens as it moves away from the coil 22. The D-shaped wire array distributes the magnetic flux well and also compensates for the inductive excitation as a "line of sight" process, whereby the wires 22 close to the inside of the substrate 10 may be in the shadow of the excited wires close to the coil 20. Depending on system requirements (including heating and emissions treatment requirements and structural features, such as cells per square inch and the actual length of the block), the channels 22 at the front of the block may be varied between greater than or less than 1: and 9, proportional loading. A loading range from 1:4 to 1:16 has been found to be particularly advantageous from the standpoint of achieving an acceptable pressure drop while achieving high intensity heating. In this range, gaseous emissions may pass through the mass without an unacceptable pressure drop across the system. In such a configuration, the pin 22 must provide sufficient metal per unit volume to achieve the desired heating profile in the heated front portion 28 without damaging the pin material. The parabolic or D-shaped stacking of the pins may be reversed longitudinally, although the configuration shown is preferred for placement of the metal insert during manufacture. In one example of a D-shaped stacking of pins, for a 50mm substrate slice where a substantially uniform output temperature is obtained across the substrate, the shortest pin used is 9mm in length (outside the heater slice) and the longest pin is 50mm in length (at the center line).

The length of the front portion may be less than 33% compared to the total length of the base, provided that the front portion of the base is large enough to accommodate the required pin fill level, as there is a lower limit to the pin length to increase the heating strength. The inductive system requires a substantial load (in this case, the mass of the pin material) to absorb the magnetic flux. If the pin material reaches its curie point, too little mass can result in overheating and melting of the pin and a loss of electrothermal efficiency. At this temperature, the electromagnetic properties of the pin material deteriorate. In addition, applying high power to a small load, the power supply may overheat and fail. In the rear portion 30 of the substrate 10, the channels 22 should have sufficient catalyst coated surface (or particulate filter surface in the case of a particulate filter) to effectively treat exhaust gas passing through the system.

The concentrated heating at the front 28 of the base increases the amount of heat generated by each wire for a given pin array pattern and input power, thus increasing the localized heating. However, a problem with this construction is that the ceramic of the substrate 10 will conduct heat away in all directions during the heating cycle. This effectively increases the total volume of ceramic occupied by heat and therefore reduces the strength in volume of pin occupation site for a particular power input.

In another embodiment of the invention as shown in fig. 6, 6A and 6B, the assembly has a front substrate 32 or "slice" that is separate from a back substrate 34. The two substrates are mounted in alignment with the cells or channels of a selected subset of the sliced substrates 32 occupied by the metal inserts 22 (e.g., wires, pins, or other forms of metal filler) to enable induction heating, and in alignment with the cells or channels 22 of the open back block 34. In the illustrated embodiment, the sliced substrate 32 is substantially shorter than the rear block 34 with respect to the flow direction 36 of the exhaust gas to be treated. The length of the slices may be 2% to 50% of the length of the posterior matrix, although the appropriateness of any particular percentage selected in practice depends on the ratio of the length to the diameter of the thick matrix. While the front chip substrate 32 has an important function as a heater, the walls of the front block channel 22 may be coated with an emission treatment catalyst so that the chip substrate 32 is operable to heat and treat the exhaust gas before it passes from the front block 32 through the gap 38 into the rear block 34 for treatment in a further catalyst-promoted reaction.

In this embodiment, the pressure drop impact is reduced by separating the inductively heated front unit 32 from the downstream unit 34, while the downstream unit is heated by the passage of hot gases from the front unit. The pin packing density and the number of heating sites per unit cross-sectional area of the unit 32 are significantly increased to obtain a hot zone at the pins 22 and a relatively hot zone between closely spaced pins. The result is that a relatively uniform temperature is achieved across the cross-section of the slice 32, sufficient to quickly achieve a light-off temperature.

Blocks

32 and 34 are separated by a distance of about 2 to 6 mm. At this separation, the gaseous effluent passing along the sliced substrate 32 has a typical flow rate from less than 0.5 m/s to more than 5 m/s for easy adaptation between the flow in the front mass 32 and the flow in the rear mass 34 without substantially increasing the pressure drop. If the separation distance is less than 2mm, the pressure drop is high due to the wake effect when the flow leaves the induction heated substrate. This is caused by the diffusion of flow from the cells of the induction heating unit into the void behind the plugged cells containing the heating element. A typical distance required for partial or complete resolution of the wake effect is 2mm to 6mm, depending on the cell density of the substrate and the associated pin array density. A high cpsi substrate with a low pin array density provides the shortest wake effect corresponding to the minimum required separation distance. A separation distance of less than 2mm results in a higher pressure drop because the wake effect is at maximum intensity. Here, if the wake effect is not allowed to subside, the flow diffuses through fewer cells that are converted into the second matrix. At low separation distances, if the open cells are too closely aligned with the plugged cells of the front substrate, the back substrate acts as if it has plugged cells with little airflow through the associated channels. The analysis assumes that the front and back substrates are perfectly aligned. Misalignment of the substrates results in a greater pressure drop from a small separation distance. If the separation distance is greater than 6mm, there is no disadvantage of the wake effect, but the package inevitably increases in size. The large gap may also allow insulation from the fiber mat to expand into the space and be affected by the exhaust flow by reducing the opening diameter or causing the onset of insulation degradation. Typically in commercial induction heating assemblies without front-end-of-the-chip heaters, the MFC is shorter than the induction heating substrate to allow application of the insulation layer and canning with the help of the collapsed metal plate. The advantage of a small gap between the substrates is: the MFC can be made longer than normal so that it overlaps the back substrate (non-heater), which results in an increase in the electromagnetic efficiency of the heater unit. The insulator at the gap protects the MFC by supporting it on both sides of the gap.

Adjusting the orientation of the front sliced substrate 32 relative to the rear block 34 during assembly by an optical alignment process to reduce the wall end to wall end incident area; i.e. increasing the incidence area of the channel to the channel. To maintain the linear spacing, the blocks are held in alignment by a common jacket arrangement (not shown) similar to that shown in fig. 1 and 2, or any other suitable mounting means. In a preferred embodiment, the opposed faces 40 of the front block 32 and the rear block 34 are flat and perpendicular to the longitudinal axis of the blocks. However, the gap between

blocks

32 and 34 may alternatively be shaped, for example, to generally follow a dome/parabolic profile of the pin tail (fig. 6E).

In another embodiment of the invention as shown in fig. 6C, a heated chip substrate is installed downstream of the emission treatment block. In this manner, gas exiting the upstream block 33 is given induction heating enhancement before further entering the subsequent emission treatment block along the exhaust line.

The split design of fig. 6 has advantages in terms of product integrity. Among the materials often used to make the substrate are low expansion honeycomb ceramics such as cordierite and silicon carbide. These materials have a high degree of thermal insulation, but are not zero expansion materials, and thus temperature gradients can lead to stress development. Ideally, the gradient is low enough that stresses do not build up sufficiently to cause defects or substrate failure. However, as the applied inductive power level increases with the applied heating over a smaller area/volume, the temperature gradient within the ceramic will correspondingly increase, increasing the risk of defects and failures. For the single substrate example of fig. 5, the temperature gradient is extreme because the heated ceramic region is physically connected to the cold region that is not heated. For example, the hot zone may be 700 ℃ or higher, while the cold zone may be below 0 ℃, this change being present over a very short distance of the ceramic. Designs with intense heating only at the front and the back which remains cool are more prone to failure by ejecting the front of the ceramic from the body. The separation block embodiment of fig. 6 is characterized by a lower temperature gradient. The small volume of the front mass 32 allows even the ends of the mass that are not directly heated to raise the temperature by conduction. This avoids the extreme 700 ℃ to 0 ℃ gradient mentioned above. Conversely, 700 ℃ may be the highest temperature, but a lowest temperature in the order of 350 ℃ may be ubiquitous. Such a temperature gradient over a distance of about 3.5 centimeters (1.375 inches) is easier to manage and may be configured as a commercial design. In addition, since there is no matrix material at the gap 38, heat is not lost by conduction towards the rear of the assembly. This in turn means that the heat generated, which might otherwise be conducted away, is retained in a smaller front volume to improve heating efficiency and speed.

Front-end heaters whose high metal content is focused in a small volume at the front of the cell are characterized by: the relatively tightly packed metal serves to concentrate the field from the surrounding coil 20 to increase heating and, as a corollary, to reduce unwanted field effects at the housing 18 (fig. 2 and 3).

The following are three examples of front end heater slice configurations showing relevant structural and performance characteristics:

example 1

a) Length of slice: 50mm cordierite substrate

b)Cpsi：600

c) Longest pin length-50 mm/shortest pin length-9 mm

d) Weight of metal in the slice: 221 g of

e) Applying power: 10kW extraction

f) Time to reach light-off temperature (including actual temperature): 8 seconds to 300 DEG C

g) Pin and bulk section temperatures: 681 deg.C, the temperature of the pin and the temperature of the slice are about the same locally

In this example, the flux concentrator is relatively thick to handle high power, and the coil is relatively large to handle high voltage.

Example 2

a) Length of slice: 50mm cordierite

b)Cpsi：600

c) Longest pin length: 50 mm/shortest pin: 9mm

d) Weight of metal in the slice: 221 g of

e) Applying power: 2kW extraction

f) Time to reach light-off temperature: 26 seconds to 300 degrees centigrade

g) Pin and bulk chip temperatures (presumably high but not exceeding the melting or curie point)? At 450 deg.C, the temperature of the pin is locally the same as the temperature of the slice

In this example, the flux concentrator is relatively thin due to the relatively low power, and the coil is relatively small due to the low voltage.

Example 3

a) Length of slice: 25mm cordierite

b)Cpsi：600

c) The longest pin length is 25 mm/the shortest pin length is 6mm

d) Weight of metal in the slice: 111 g

e) Applying power: 2kW extraction

f) Time to reach light-off temperature: 16 seconds to 300 degrees centigrade

g) Pin and whole slice temperatures: 692 ℃, the pin temperature and the slicing temperature were locally the same.

In this example, the flux concentrator is relatively thin due to the relatively low power, and the coil is relatively short because the slice is thin.

In another embodiment of the invention as shown in fig. 6D, the channels 12 of the heat chip substrate 32 are made only long enough to provide the necessary structural support for the pins 22. For example, the pins 22 may project forwardly from the front 42 of the block and/or the cans project rearwardly from the rear 44 of the block. Thus, portions of the pins 22 may be separated from adjacent pins by air rather than an insulating ceramic, which may increase conduction within the heating volume. In another embodiment of the invention, the slicing channel occupied by a line or pin is not D-shaped or parabolic in shape. For example, some or all of the pins may be of uniform length, or some other configuration may be used to achieve a desired thermal distribution of the exiting exhaust gas through the sliced region.

The split or sliced configuration has further advantages for complex washcoat catalyst arrangements in which the gaseous emissions are subjected to two or more different treatments. Application of the catalyst washcoat is typically accomplished by taking a bare substrate and immersing it into a slurry containing the catalyst metal and the porous ceramic support. Capillary action within the porous matrix absorbs water/liquid from the slurry, which deposits the precious metal and ceramic materials on the channel surfaces. The residence time during impregnation and the number of impregnation cycles can be varied to produce thick washcoats, which is desirable to maximize effluent treatment. Excess liquid was aspirated off using a vacuum system, and the washcoated substrate was then heated to cure the washcoat onto the cell walls. Sometimes, two different washcoats are required in the catalyst assembly; for example, when multiple exhaust gases are processed in a single system, each exhaust gas requires its own washcoat chemistry. Applying two different washcoats is challenging for a single substrate because in current commercial production methods, one washcoat is applied to one end of the substrate and a different washcoat is applied to the other end of the substrate. The depth of immersion during immersion is difficult to control and a clean transition between two washcoat layers is often not achieved. The washcoat inherently reduces the open area of the cells, but the thickness of the washcoat is also typically tapered. Vacuum removal during coating to leave a consistent thickness of washcoat material is more easily achieved at the ends of the substrate than in the middle of the substrate. The heated chip design of fig. 6 makes the dual wash coating process easier and can generally provide better quality results.

In making the matrix material, several different commercially available cpsi matrices are available for selection, these matrices typically comprising 400, 600 and 900cpsi configurations, although higher cpsi matrices have been realized. These substrates may also have different wall thicknesses for a given cpsi. Furthermore, the substrate may be made of one of several different ceramic materials. It may be desirable to optimize the performance or cost of the catalyst assembly. For example, the design may be optimized by using a relatively expensive 900cpsi thin-walled (low mass) silicon carbide substrate as the material for the front substrate and a low cost 400cpsi thick-walled cordierite substrate as the material for the rear substrate. This is practically impossible with a single substrate design because the cross-sectional shape of the single substrate is fixed. The extrusion process used to make the matrix material does not have the flexibility to allow the cpsi, wall thickness and/or material composition to be varied in the middle of the extrusion. The sliced sheet embodiments of fig. 6, 6A and 6B allow several possible combinations of matrix material properties to be included in the catalyst assembly to optimize performance and cost.

Although in the slice embodiment of fig. 6, 6A and 6B, the front block 32 has catalyst coated channels 12, the channels may alternatively be catalyst free, meaning that the block serves merely as a pre-heater to heat exhaust gas passing along its channels before it passes through the gap 38 to the rear cell 34. This configuration allows for optimized heating in terms of the size and contour of the channel 12 and the location, size and contour of the metal insert 22. In the foregoing embodiments, the distribution of the positions of the inductive metallic elements relative to the cells is configured such that heating on the thin front substrate portion or individual substrate is generally uniform and rapid. By using cells of different sizes and/or shapes and wires of different sizes, shapes and/or compositions, localized heating in the upstream pre-heater can be enhanced.

The front end induction slice heater design generates rapid heat, providing a very fast light-off period and rapid attainment of high catalyst temperatures without the need for engine exhaust flow. The extreme energy is concentrated in a small volume, resulting in high intensity heating. The induction heating chip is configured with sufficient thermal mass to overcome the cooling effect of the exhaust flow during cold start, enabling manufacturers to achieve near zero harmful emissions vehicle platforms. Due to the small footprint of the slice induction heater system, it becomes easy to package the slice design in the context of prior art converters and particle filters. The same electronics (such as those described in the U.S. patents) that have been validated to power conventional induction technology are also used to power the slice induction heater design.

In another embodiment of the invention as shown in FIG. 7, the base of the upstream block 60 has an induction heated rear end portion 62 located immediately upstream of a downstream exhaust gas treatment block 64. The downstream substrate 64 may be non-inductively heated, and therefore the ignition is achieved depending on the temperature of the incoming exhaust gas, which is actually hot due to the fact that it is exhaust or the temperature of the exhaust is increased by induction heating at the upstream unit 60. Alternatively, as shown in fig. 7A, the upstream unit may additionally have an associated electromagnetic field generator at the front of the upstream block. Alternatively, as shown in fig. 7B, the downstream block may have an electromagnetic field generator at its front end. In each of fig. 7-7B, the three heating zones may optionally be energized at different times or to different power levels from each other. The upstream unit may also be configured for emission treatment of a different type than the emission gas treatment process taking place in the downstream unit. Any one of the three end portions may be configured as a separate slice.

In fig. 6 and 7, various distributions of metal inserts in the inductively heated matrix can be considered as metal precursors.

In a variation of the dedicated induction heated pre-or post-heater embodiment shown in fig. 6 and 7, the metal precursor is an induction heated coiled corrugated metal section 46, as shown in the embodiment of fig. 8 and 8A.

In another embodiment, the metal matrix is a plurality of concentric metal blades 48 surrounding an open hub 50, as shown in the embodiment of fig. 9 and 9A.

In another embodiment, the metal matrix is a network of randomly distributed wires 52, as shown in the embodiment of fig. 10 and 10A.

In another embodiment, the metal matrix is a woven mesh of wires 54, as shown in the embodiment of fig. 11 and 11A.

In another embodiment, the metal precursor is a perforated metal sheet, as shown in the embodiment of fig. 12 and 12A.

In another embodiment, the pre-heater has a honeycomb ceramic matrix 32, but has ceramic constituting honeycomb walls, which are highly doped with metal, as shown at 58 in the embodiment shown in fig. 13 and 13A.

In all of the illustrated pre-heater designs, the front bulk pre-heater (or in some cases the post-heater) is optimized to provide a relatively dense metal load to achieve rapid, high intensity induction heating from surrounding coils (not shown in fig. 8-13). However, the metal load is not so large or the wires are not so densely packed as to affect the flow of exhaust gases by introducing an unacceptable pressure drop into the exhaust line.

In another embodiment of the invention shown in fig. 14, a heating unit used as a space heater has a ceramic base through which channels extend, with metal inserts, such as wires, pins or other metal fillings, in a subset of the channels. An induction coil is mounted about the base and is energized to generate a varying electromagnetic field such that at least some of the generated electromagnetic flux penetrates the wire inserts to inductively heat them. A fan is installed to force air along the channel unobstructed by the wire insert. In use, heat is transferred from the inductively heated metal body to the adjacent substrate wall to heat the substrate. In the unoccupied channels, in turn, heat is transferred from the substrate to the hot air forced along the channels by the fan. A heating unit of the kind shown in fig. 14 can be used for cabin heating of a motor vehicle. This is particularly valuable for electric vehicles without an internal combustion engine or plug-in hybrid vehicle where engine operation and associated heating may not be available until some time after initial vehicle use.

The induction heating configuration previously described and illustrated may be used with a catalytic converter and a Particulate Filter (PF). Such emission treatment units may be inductively heated in any of the arrangements previously described, or may be positioned to receive heat from an inductively heated upstream unit, whether in the form of a portion of a longer substrate or in the form of individual slices.

Other variations and modifications will be apparent to persons skilled in the art, and the described and illustrated embodiments of the invention are not limiting. The principles of the present invention contemplate many alternatives having advantages and features that are apparent in the exemplary embodiments.

According to another aspect of the present invention, a gas heater includes a ceramic honeycomb substrate having: a first plurality of channels extending the length of the substrate for conveying gas streams introduced into the first plurality of channels at one end of the substrate from the one end to the other end of the substrate; a plurality of second linear channels extending the length of the substrate, a first plurality of elongated metal inserts substantially blocking respective ones of the plurality of second linear channels; an electromagnetic field generator configured to inductively heat a flowing gas source upstream of the metal insert and the substrate for generating the gas flow. The source of flowing gas may be an internal combustion engine, wherein the gas is a gaseous emission from the internal combustion engine. In one alternative, the source of fluent gas is a fan mounted adjacent said one end of the base and operable to blow air into the first plurality of channels thereof.

According to another aspect of the invention, an assembly for treating gaseous emissions comprises: a metal precursor and a plurality of passages through said precursor for gaseous emissions to enter through one end of the metal precursor, to pass through said passages and to exit through the other end of said metal precursor; an electromagnetic field generator configured to inductively heat the metal in the parent body, thereby heating gaseous emissions passing along the parent body; and a substrate having a plurality of linear channels for receiving the gaseous emissions exiting from said other end of the metal precursor, said metal precursor being substantially aligned with the substrate. The metal precursor may be one of an induction heating coil, a corrugated metal sheet, a plurality of concentric metal blades surrounding an open hub, a mesh of randomly distributed wires, a woven mesh of wires, and a honeycomb ceramic matrix having a highly metal-doped ceramic.

Claims

1. An assembly for treating gaseous emissions, comprising:

a first substrate (34, 60) having a plurality of first linear channels (12) extending the length of the first substrate for the passage of gaseous emissions from one end of the first substrate to the other;

a second substrate (34, 64) having a second plurality of linear channels for receiving gaseous emissions exiting from the other end of the first substrate, the first substrate being substantially aligned with but spaced apart from the second substrate, one of the first and second substrates having an elongated metal body (22) in each channel of a subset of the plurality of channels of the one substrate, wherein the concentration of metal per unit volume in the one substrate increases toward the one end of the one substrate; and

an electromagnetic field generator configured to inductively heat the metal body and thereby the one substrate, wherein the first substrate is separated from the second substrate by a distance of 2mm to 6 mm.

2. The assembly of claim 1, wherein the one substrate is the first substrate.

3. The assembly of claim 1, wherein the one substrate is the second substrate.

4. The assembly of any one of claims 1 to 3, wherein the length of the one substrate as a percentage of the length of the other of the first and second substrates is between 2% and 50%.

5. The assembly of any one of claims 1 to 3, wherein a density occupancy of the subset of channels occupied by the metal bodies in the one matrix relative to the plurality of channels in the one matrix is in a range between 1:2 and 1: 49.

6. The assembly of any one of claims 1 to 3, wherein a density occupancy of the subset of channels occupied by the metal bodies in the one matrix relative to the plurality of channels in the one matrix is in a range between 1:4 and 1: 16.

7. The assembly of any one of claims 1 to 3, wherein the orientation of the first substrate relative to the second substrate is aligned to increase the incidence area of the channel to the channel.

8. The assembly of claim 7, wherein the first substrate and the second substrate are held in alignment by a common jacket arrangement.

9. The assembly of any one of claims 1 to 3, wherein the number of channels per unit area of the first substrate is different from the number of channels per unit area of the second substrate.

10. The assembly of any one of claims 1 to 3, wherein the metal body has a length, the maximum metal body length being substantially equal to the length of the one substrate.

11. The assembly of any one of claims 1 to 3, wherein the elongated metal body is positioned closer to the first end of the one substrate than to the second end of the one substrate.

12. The assembly of any one of claims 1 to 3, wherein the channel of the other of the first and second substrates is an open channel.

13. The assembly of any one of claims 1 to 3, wherein an inner surface of the linear channels of the other of the first and second substrates is coated with a first catalyst material for accelerating gaseous emission treatment.