GB2568887A

GB2568887A - Aftertreatment device for use in exhaust and method

Info

Publication number: GB2568887A
Application number: GB1719828.4A
Authority: GB
Inventors: Agurto Goya Alan
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-11-29
Filing date: 2017-11-29
Publication date: 2019-06-05
Anticipated expiration: 2037-11-29
Also published as: GB201719828D0; GB2568887B

Abstract

An aftertreatment device 10 for use in an exhaust system 32 comprises one or more active aftertreatment substrates (i.e. catalysts) 16. Ferrous material 18 is arranged upstream of the active aftertreatment substrates and has one or more passageways for through flow of exhaust gas (20, fig 5B). Inductive means 22 heat the ferrous material to heat exhaust gases flowing through. Heating the exhaust gases upstream of the active aftertreatment substrate helps in cold start conditions. The active aftertreatment substrates and the ferrous material may be shaped to fit within a housing 14. The inductive means may comprise electrically conductive coils 26, which may be located around protrusions (30, fig 5B) of the housing or ferrous material. The ferrous material may be configured as a honeycomb, a grating or a grid. A vehicle comprises an engine and an exhaust system with the aftertreatment device.

Description

AFTERTREATMENT DEVICE FOR USE IN EXHAUST AND METHOD

TECHNICAL FIELD

The present disclosure relates to an aftertreatment device for use in an exhaust and method. In particular, but not exclusively, it relates to an aftertreatment device for use in a vehicle exhaust and method.

Aspects of the invention relate to an aftertreatment device, an exhaust system, a vehicle system, a vehicle and a method.

BACKGROUND

Aftertreatment devices in, for example, exhaust systems of vehicles treat exhaust gases in order to reduce harmful emissions.

However, under, for example, cold start conditions an aftertreatment device in a vehicle exhaust may not function optimally due to cold temperatures.

It is an aim of the present invention to provide an improved solution for cold start exhaust aftertreatment.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an aftertreatment device for use in an exhaust, an exhaust system, a vehicle system, a vehicle, and a method as claimed in the appended claims.

According to an aspect of the invention, there is provided an aftertreatment device for use in an exhaust system, comprising: one or more active aftertreatment substrates; ferrous material arranged upstream of the one or more active aftertreatment substrates and having one or more passageways therethrough for the through-flow of exhaust gas; and inductive means arranged to inductively heat the ferrous material so as to, in use, heat exhaust gases flowing therethrough.

This provides the advantage that energy is used efficiently to heat exhaust gases in an aftertreatment device in an exhaust system.

The ferrous material may be separate from the one or more active aftertreatment substrates.

The ferrous material may be provided at a location spaced from the aftertreatment substrate, for example there may be a gap provided between the ferrous material and the aftertreatment substrate. If the passageways through the ferrous material are geometrically different to passageways in the aftertreatment substrate the separation allows the flow of heated exhaust gas to recombine after passing through the ferrous material prior to passing through the aftertreatment substrate.

Again further, this provides the advantage that the heat can be provided evenly across the whole front face of the substrate.

Examples also provide the advantage that ferrous material can be arranged specifically to apply heat unevenly to the substrate, if required. That is, in examples, a predetermined heating pattern can be provided to provide heat to known cold areas of the exhaust gases/substrate preferentially over known hot areas of the exhaust gases/substrate.

The aftertreatment device may also comprise a housing, wherein the one or more active aftertreatment substrates and/or the ferrous material may be shaped to fit with the housing.

The exhaust may be an exhaust in a vehicle.

The inductive means may comprise one or more electrically conductive coils.

The one or more passageway may comprise a plurality of apertures and the ferrous material may be arranged to allow the exhaust gases to pass through the plurality of apertures.

The ferrous material may be configured as at least one of a honeycomb, a grating or a grid.

The one or more active aftertreatment substrates may comprise a plurality of apertures having an average size and the plurality of apertures of the ferrous material may have an average size and the average size of the apertures of the ferrous material may be greater than the average size of the apertures in the one or more active aftertreatment substrates.

This provides the advantage that any flow restrictions imposed on the flow of exhaust gasses by the ferrous material are less than those imposed by the aftertreatment substrate, thereby resulting in the ferrous material not significantly increasing back pressure on the engine.

The ferrous material may be shaped to fit with the housing.

The ferrous material may be shaped to provide a predetermined heating pattern to the exhaust gases, and/or the inductive means are located in one or more predetermined locations relative to the ferrous material to provide a predetermined heating pattern to the exhaust gases.

The inductive means may be arranged to inductively heat the ferrous material preferentially at the outer edges of the ferrous material.

The housing may comprise one or more protrusions and wherein one or more electrically conductive coils are located around the one or more protrusions of the housing.

The ferrous material may comprise one or more protrusions and one or more electrically conductive coils are located around the one or more protrusions of the ferrous material.

One or more electrically conductive coils may be wound circumferentially around at least part of the ferrous material.

The inductive means may be galvanically isolated from the ferrous material.

According to another aspect of the invention, there is provided an exhaust system comprising an aftertreatment device as described in any preceding paragraph.

The exhaust system may be for use in a vehicle.

According to yet another aspect of the invention, there is provided an aftertreatment device comprising: ferrous material arranged to heat exhaust gases upstream of one or more active aftertreatment substrates; and inductive means arranged to inductively heat the ferrous material.

According to yet another aspect of the invention, there is provided a vehicle system comprising an engine and an exhaust system as described in any preceding paragraph.

According to a further aspect of the invention, there is provided a vehicle comprising an aftertreatment device as described in any preceding paragraph, an exhaust system as described in any preceding paragraph and/or a vehicle system as described in any preceding paragraph.

According to another aspect of the invention, there is provided a method of heating exhaust gases in an exhaust comprising: inductively heating ferrous material having one or more exhaust gas passageways therethrough so as to heat exhaust gases passing therethrough upstream of one or more active aftertreatment substrates.

The aftertreatment device may be for use in a vehicle exhaust.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 schematically illustrates an aftertreatment device of an embodiment of the invention for use in an exhaust;

Fig. 2 schematically illustrates an exhaust system, a vehicle system and vehicle in accordance with an embodiment of the invention;

Fig. 3 illustrates an example of ferrous material and an active aftertreatment substrate used in an embodiment the invention;

Fig. 4 illustrates an example of the aftertreatment device and a controller for use in an exhaust system in accordance with an embodiment of the invention;

Figs. 5A to 5C illustrate examples of different embodiments of aftertreatment devices of the invention for use in an exhaust;

Fig. 6 illustrates an example of a vehicle; and

Fig. 7 illustrates an example of a method of an embodiment of the invention.

DETAILED DESCRIPTION

Examples of the present disclosure relate to an aftertreatment device 10 for use in an exhaust system 32. In examples, the exhaust system 32 is an exhaust system 32 for use in a vehicle 24.

The aftertreatment device 10 may, for example, be a catalyst.

In examples, the aftertreatment device 10 comprises a housing 40, one or more active aftertreatment substrates 16 and ferrous material 18 arranged to heat exhaust gases 20 upstream of the one of more active aftertreatment substrates 16.

The aftertreatment device 10 comprises inductive means 22, which may comprise one or more electrically conductive coils 26, arranged to inductively heat the ferrous material 18.

In some examples, the ferrous material 18 is separate from the one or more active aftertreatment substrates 16.

One or more of the elements referred to in the discussion of Figs. 1 and 2 may be found in Figs. 3 to 6.

Fig. 1 schematically illustrates an example of an aftertreatment device 10 for use in an exhaust system 32 for treating exhaust gases 20 from the engine 36 of a vehicle 24.

The aftertreatment device 10 comprises a housing 14, one or more active aftertreatment substrates 16, ferrous material 18 and inductive means 22.

The one or more active aftertreatment substrates 16 are for treating exhaust gases 20 to reduce or remove toxic and/or harmful component(s) from the exhaust gases 20, for example the active aftertreatment substrate(s) 16 may chemically alter one or more components of the exhaust gases 20 to reduce or remove toxic or harmful gases from the exhaust gases 20, specifically it may comprise a substrate for performing the catalytic reduction of NOx.

The housing 14 of the aftertreatment device 10 houses various features of the aftertreatment device 10 and contains and guides exhaust gases 20 through the one or more active aftertreatment substrate(s) 16.

The housing 14 may comprise any suitable size, shape and/or form. It will be appreciated that a number of factors may be taken into consideration in determining the size, shape and/or form of the housing 14 of the aftertreatment device 10, which may include the space available for the aftertreatment device 10 within a vehicle 24, a required fit with one or more further systems in a vehicle 24, and the size of and/or number of active aftertreatment substrates 16 present to sufficiently treat exhaust gases 20. Other factors in determining the overall shape and size will be determined by the design of the vehicle with which it is to be used and will be apparent to the skilled person.

The housing 14 may be comprised of any suitable material or materials. In some examples the housing 14 is comprised of material(s) without ferromagnetic properties to avoid inductive heating of the housing 14. In some examples the material or materials of the housing 14 comprises low magnetic permeability.

In the example embodiments, the housing 14 is made of stainless steel, however any suitable non-ferrous material, for example polymers having high melting temperatures etc may also be used.

In some embodiments, e.g. as shown in Figures 5A to 5C, the ferrous material 18 comprises one or more protrusions 30 which may be within the housing as shown in Figure 5B or which may protrude from the housing as shown in Figure 5A.

The one or more protrusions 30 of the housing 14 may locate the inductive means 22, i.e. electrically conductive coils 26 may be located/wound around one or more protrusions 30.

As shown in Figure 3 he one or more active aftertreatment substrates 16 is provided with a plurality of apertures 28, which have an average size, to allow the exhaust gases 20 to flow therethrough to treat the exhaust gases 20.

As shown in the Figures, the ferrous material 18 is located, at least partially, within the housing 14 at a position upstream of the one or more active aftertreatment substrates 16. The ferrous material 18 is separated from the one or more active aftertreatment substrates 16 by a small gap a shown. That is the ferrous material 18 is not be in contact with the one or more active aftertreatment substrates 16, although it will be appreciated that an example in which the ferrous material was in contact with the aftertreatment substrate would still be within the scope of the invention.

The ferrous material 18 comprises any suitable material or materials to be inductively heated, for example the ferrous material 18 may have high magnetic permeability and high electrical resistance.

As shown in Figure 3, the ferrous material 18 comprises a plurality of apertures 28 arranged to allow the exhaust gases 20 to pass therethrough. The plurality of apertures may be of any suitable shape, size and/or form and may, for example, be configured as at least one of a honeycomb, a grating or a grid. The plurality of apertures 28 of the ferrous material 18 has an average size which is greater than the average size of the apertures 28 in the one or more active aftertreatment substrates 16. This has the advantage that the ferrous material 18, being present upstream of the one or more active aftertreatment substrates, 16 does not inhibit the flow of exhaust gases 20 through the aftertreatment device 10 as the aftertreatment substrates creates the more significant restriction on flow.

As shown the inductive means comprise one or more electrically conductive coils 26 which have a m suitable form, size and/or shape to inductively heat the ferrous material 18, and which may comprise any suitable number of turns. Although shown as uniform it will be appreciated that the plurality of electrically conductive coils 26 may have different forms, sizes and/or shapes.

The form, size, shape and/or location of the inductive means 22, such as one or more electrically conductive coils 26, can be chosen to provide a predetermined heating pattern to exhaust gases 20, i.e. to deliver energy to the ferrous material 18 in a predetermined pattern to provide heat to exhaust gases 20 in the aftertreatment device 10 in a predetermined way. The coils 26 may be arranged or controlled to preferentially heat the ferrous material 18 at the edges to balance the heat profile of exhaust gases 20 passing through the aftertreatment device 10. This may be advantageous as, in general, exhaust gases 20 passing through an aftertreatment device 10 are hotter at the centre of the aftertreatment device 10 and cooler at the edges. A desired heating pattern can be achieved by varying the excitation frequency of the current/voltage in the one or more conductive coils 26, to introduce the “skin effect” by which heating can be constrained to a desired depth in the ferrous material 18.

Additionally or alternatively a desired heating pattern can be achieved using mixed materials in the ferrous material 18, for example a mix of materials having different ferromagnetic properties, for example the ferrous material 18 may comprise a first portion of material having first ferromagnetic properties and a second portion of material having second, different ferromagnetic properties. It will be appreciated that any suitable number of different portions of material having different ferromagnetic properties may be used. The ferrous material 18 can comprise two concentric rings, an outer ring and inner ring with different ferromagnetic properties. The outer ring or inner ring may be configured to generate a greater amount of inductive heat in response to energization of the coil. The use of different ferrous materials may therefore be shaped to provide a predetermined heating pattern to the exhaust gases 20

The one or more electrically conductive coils 26 may be partially contained or fully within the housing 14 of the aftertreatment device 10, or may be external thereto, for example they may be wound, at least partially, around the housing 14.The one or more electrically conductive coils 26 can be wound circumferentially around at least part of the ferrous material 18 as shown in Fig. 4. The electrically conductive coils 26, are galvanically isolated from the ferrous material 18. That is, in examples, there is no galvanic connection between the inductive means 22 and the ferrous material 18.

Fig. 2 schematically illustrates an embodiment of an exhaust system 32 of the invention having an aftertreatment device 10, and in which the exhaust system 32 is comprised in a vehicle system 34 which, in turn, is comprised in a vehicle 24 having an engine 36. The engine 36 may be any suitable engine or engines (e.g. one or more internal combustion engine) that produce exhaust gases 20 requiring aftertreatment. The vehicle 24 may be any suitable vehicle 24 such as a car, van, truck and so on.

Fig. 3 illustrates an example of ferrous material 18 and an active aftertreatment substrate 16 for use in an aftertreatment device 10 as described in relation to Fig. 1 and/or Fig. 2. The ferrous material 18, illustrated to the left in the example of Fig. 3, is generally circular in shape and is configured as a grid and the active aftertreatment substrate 16, illustrated to the right, is also generally circular in shape. As shown, and as described above, the ferrous material 18 and the active aftertreatment substrate 16 comprise a plurality of apertures 28. Although the plurality of apertures 28 have been illustrated with a particular shape, size and form in Fig. 3, in examples any suitable shape, size and/or form of the plurality of apertures 28 in the ferrous material 18 and/or active aftertreatment substrate 16 may be used.

The plurality of apertures 28 in the ferrous material 18 have an average size indicated by the letter “A”. Similarly, the plurality of apertures 28 in the active aftertreatment substrate 16 have an average size indicated by the letter “a”. The average size “A” of the plurality of apertures 28 in the ferrous material 18 is greater than the average size “a” of the plurality of apertures 28 in the active aftertreatment substrate 16. Accordingly, the ferrous material 18 is configured to allow exhaust gases 20 to pass through the plurality of apertures 28 and, as the average size of the plurality of apertures 28 in the ferrous material 18 is greater than the average size of the plurality of apertures 28 in the active aftertreatment substrate 16, this helps to prevent the ferrous material from becoming a defining flow restriction in the exhaust gas flow which could otherwise result in problematic increases in back pressure in the exhaust system 32.

Fig. 4 schematically illustrates an embodiment of an aftertreatment device 10 and a controller 42 for use in an exhaust system 32. In the example of Fig. 4 various elements of the exhaust system 32 have been omitted for the sake of clarity.

The exhaust system 32 of Fig. 4 comprises an aftertreatment device 10, a DC to AC converter 38, energy storage means 40 and a controller 42. The aftertreatment device 10 in the example of Fig. 4 may be as described in relation to Figs. 1 and/or 2 above, however it will be appreciated that it may be substituted with the aftertreatment device 10 as described in relation to Figures 5A to 5C below.

In fig. 4, the aftertreatment device 10 is shown in cross-section and comprises an active aftertreatment substrate 16, ferrous material 18 and an electrically conductive coil 26, all of which are located within a housing 14, and are arranged such that, in use, the exhaust gases 20 (not illustrated) flow through the aftertreatment device 10 from left to right in the figure. Accordingly, the ferrous material 18 is upstream of the active aftertreatment substrate 16 and, as illustrated in the example, is physically separated from the active aftertreatment substrate 16 by a gap which forms a small plenum.

In the example of Fig. 4, both the ferrous material 18 and the active aftertreatment substrate 16 comprise a plurality of apertures 28 (not illustrated) to allow the exhaust gases 20 to flow therethrough.

In Fig. 4, the electrically conductive coil 26 is wrapped circumferentially around the ferrous material 18 and is located in the housing 14. The electrically conductive coil 26 is electrically connected to the DC to AC convertor 38, which may be any suitable DC to AC convertor architecture. The DC to AC convertor 38 is electrically connected to the energy storage means 40, e.g. a vehicle battery, and the controller 42. The DC to AC convertor 38 provides an alternating current to the electrically conductive coil 26 to inductively heat the ferrous material 18 and therefore also exhaust gases 20.

The controller 42 controls one or more of the amplitude of electric current and the frequency of the electric current supplied to the electrically conductive coil 26, preferably both the amplitude and the frequency. The controller 42 may receive one or more signals from one or more sensors (not illustrated) to allow control of heating of the ferrous material 18 and exhaust gases 20 dependent on a sensed temperature of the exhaust gas and/or the aftertreatment substrate 16. In addition the controller can receive one or more signals comprising information relating to the state of charge of the battery/batteries 40 and control the electrical current supplied to the electrically conductive coil 26 in dependence on the received information.

Referring now to Figs. 5A to 5C illustrate alternative embodiments of aftertreatment devices 10 for use in an exhaust.

In the embodiment of Fig. 5A, the aftertreatment device 10 is in an exhaust system 32 and comprises ferrous material 18 upstream of an active aftertreatment substrate 16 within a housing 14. The ferrous material 18 comprises a plurality of protrusions 30 extending radially from the ferrous material 18 through the housing 14 and a plurality of electrically conductive coils 26 located or wound around the protrusions 30 of the ferrous material 18. It will be appreciated that alternatively the housing may extend around the protrusions 30 so that the ferrous material 18 is located entirely within the housing 14.

In the embodiment of Fig. 5B, the aftertreatment device 10 is in an exhaust system 32 and comprises ferrous material 18 upstream of an active aftertreatment substrate 16 within a housing 14.

In the embodiment of Fig. 5B, the housing 14 widens in the direction of flow of the exhaust gases 20 and the ferrous material 18 is shaped to conform with the shape of the housing 14. In particular, the ferrous material 18 comprises a plurality of protrusions 30 shaped to fit with the shape of the housing 14 and electrically conductive coils 26 are located around the protrusions 30 to inductively heat the ferrous material 18.

In the embodiment of Fig. 5C, the aftertreatment device 10 is located in an exhaust system 32 and comprises ferrous material 18 upstream of an active aftertreatment substrate 16 within a housing 14. The housing 14 widens in the direction of flow of exhaust gases 20 similarly to the example of Fig. 5B, however, in the example of Fig. 5C, the ferrous material 18 extends outwardly beyond the housing 14 and comprises a plurality of protrusions 30 that run generally axially with the housing 14. The electrically conductive coils 26 are located/wound around the protrusions 30 of the ferrous material 18.

In the embodiments of Figs 5A to 5C the protrusions comprise a solid core(s) to enhance inductive heating.

Fig. 6 illustrates a vehicle 24 which comprises an aftertreatment device 10 as described above. The vehicle 24 also comprises an exhaust system 32 as described herein, a vehicle system 34 as described herein and an engine 36.

Fig. 7 illustrates an example of a method 700 which may be performed by an aftertreatment device 10, an exhaust system 32, a vehicle system 34 and/or vehicle 24 as described herein. The method 700 may be controlled by the controller illustrated in the example of Fig. 4.

At block 702 ferrous material 18 is inductively heated so as to heat exhaust gases 20 upstream of one or more active aftertreatment substrates 16.

Examples of the disclosure provide various technical benefits.

Examples also provide for greater control of the heating of exhaust gases 20. This is because the inductive means 22, such as conductive coil(s) 26, can be arranged to heat the ferrous material 18 evenly, or if required inductive heating provides improved controllability of heating as there are more degrees of freedom for controlling the heating compared to, for example, resistive heating.

In inductive heating the heat rate is dependent on, at least, the amplitude of electrical current supplied to the coils, frequency of current supplied to the coils, the magnetic permeability of the ferrous material 18, the heat capacity of the ferrous material 18 and the electrical resistivity of the ferrous material 18. This provides, for example, for improved controllability of the heat rate compared to, for example, resistive heating.

As used herein “for” should be considered to also include “configured or arranged to”. For example, “an aftertreatment device for” should be considered to also include “an aftertreatment device configured or arranged to/for”.

Although ‘ferrous’ material has been referred to in the preceding description it is intended that the material could alternatively or additionally be ferromagnetic material.

For purposes of this disclosure, it is to be understood that the controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computerreadable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

The blocks illustrated in Fig 7 may represent steps in a method.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. An aftertreatment device for use in an exhaust system, comprising:

one or more active aftertreatment substrates;

ferrous material arranged to heat exhaust gases upstream of the one or more active aftertreatment substrates and having one or more passageways therethrough for the through-flow of exhaust gas; and inductive means arranged to inductively heat the ferrous material so as to, in use, heat exhaust gases flowing therethrough.

2. An aftertreatment device as claimed in claim 1 wherein the ferrous material is separate from the one or more active aftertreatment substrates.

3. An aftertreatment device as claimed in claim 1 or claim 2 also comprising a housing, wherein the one or more active aftertreatment substrates and/or the ferrous material are shaped to fit with the housing.

4. An aftertreatment device as claimed in any one of the preceding claims, wherein the inductive means comprises one or more electrically conductive coils.

5. An aftertreatment device as claimed in any one of the preceding claims wherein the one or more passageways comprises a plurality of apertures and the ferrous material is arranged to allow the exhaust gases to pass through the plurality of apertures.

6. An aftertreatment device as claimed in claim 5 wherein the ferrous material is configured as at least one of a honeycomb, a grating or a grid.

7. An aftertreatment device as claimed in claim 5 or 6 wherein the one or more active aftertreatment substrates comprises a plurality of apertures having an average size and wherein the plurality of apertures of the ferrous material has an average size and the average size of the apertures of the ferrous material is greater than the average size of the apertures in the one or more active aftertreatment substrates.

8. An aftertreatment device as claimed in any preceding claim wherein the ferrous material is shaped to provide a predetermined heating pattern to the exhaust gases, and/or the inductive means are located in one or more predetermined locations relative to the ferrous material to provide a predetermined heating pattern to the exhaust gases.

9. An aftertreatment device as claimed in any preceding claim wherein the inductive means are arranged to inductively heat the ferrous material preferentially at the outer edges of the ferrous material.

10. An aftertreatment device as claimed in claim 4, or any claim depending therethrough, wherein the housing comprises one or more protrusions and wherein the one or more electrically conductive coils are located around the one or more protrusions of the housing.

11. An aftertreatment device as claimed in claim 4, or any claim depending therethrough, wherein the ferrous material comprises one or more protrusions and the one or more electrically conductive coils are located around the one or more protrusions of the ferrous material.

12. An aftertreatment device as claimed in claim 4, or any claim depending therethrough, wherein the one or more electrically conductive coils are wound circumferentially around at least part of the ferrous material.

13. An aftertreatment device as claimed in any preceding claim wherein the inductive means are galvanically isolated from the ferrous material.

14. An exhaust system comprising an aftertreatment device as claimed in at least one of claims 1 to 13.

15. An exhaust system as claimed in claim 14 wherein the exhaust system is for use in a vehicle.

16. A vehicle system comprising an engine and an exhaust system as claimed in claims 14 or claim 15.

17. A vehicle comprising an aftertreatment device as claimed in one or more of claims 1 to 13, an exhaust system as claimed in at least one of claims 14 and 15 and/or a vehicle system as claimed in claim 16.

18. A method of heating exhaust gases in an exhaust system comprising:

inductively heating ferrous material having one or more exhaust gas passageways therethrough so as to heat exhaust gases passing therethrough upstream of one or more active aftertreatment substrates.

5

19. A method as claimed in claim 18 wherein the method is for use in a vehicle exhaust.