TECHNICAL FIELD

The invention relates to an exhaust gas treatment system for an internal combustion engine, especially of a motor vehicle.

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment, such as wheel loaders, haulers and excavators. Although the invention will be described with respect to a truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles such as buses, construction equipment, passenger cars and boats.

BACKGROUND

A nitrogen oxides (NOx) purification apparatus is used for reducing NOx contained in an exhaust gas discharged from an internal combustion engine. In particular, the NOx purification apparatus for an internal combustion engine uses a selective catalytic reduction (SCR) catalyst in the exhaust system of the diesel engine, in which a reducing agent such as urea is supplied to the exhaust gas for generating ammonia to be adsorbed on the SCR catalyst, thereby selectively reducing NOx contained in the exhaust gas. However, the performance of the SCR is limited at low temperatures. In the case of ammonia being used as reductant where urea is used as precursor, ammonia will not be formed at temperatures below 160-180 degrees Celsius. This results in deposits, which can block the exhaust passage resulting in a decreased performance of the engine. Deposits can be formed at walls even when the exhaust temperature is much higher when aqueous precursors hits a wall by the combined effect of heat transfer to ambient and water evaporation keeps the wall temperature much lower.

Different types of catalysts are investigated, which may work better at low temperatures. An alternative, or complement would be to increase the temperature in the exhaust gas treatment system. According to one alternative, this may be solved by injecting fuel after the engine which is burned in the exhaust gas treatment system and by that increases the temperature. This is however a rather fuel consuming way and it increases the temperature on all parts of the exhaust gas treatment system, i.e. there may be more efficient ways. According to a further alternative, this may be solved by using a separate heating equipment.

SUMMARY

An object of the invention is to provide an exhaust gas treatment system, which creates conditions for improving the performance of the system at low temperature.

The object is achieved by a system according to claim 1 . Thus, it is achieved by an exhaust gas treatment system comprising

- an exhaust passage,

- a selective catalytic reduction catalyst provided in the exhaust passage,

- a means for supplying a reductant into the exhaust passage upstream of the selective catalytic reduction catalyst for NOx reduction, and

- an arrangement for heating an exhaust gas in the exhaust passage and/or a portion of the system,

characterized in that

- the heating arrangement is adapted for inductive heating and that it comprises a first heater positioned externally of the exhaust passage and upstream of the selective catalytic reduction catalyst.

In other words, the heating arrangement may be arranged for inductive heating of a portion of the system in a urea mixing zone between the urea supply means and the selective catalytic reduction catalyst or even upstream of the urea supply means. The term "exhaust passage" may be exemplified with a tube, channel or other structure with walls defining a space for exhaust flow. According to one example, the heated portion is formed by a structure arranged inside of the exhaust passage, in the exhaust flow. According to an alternative, the heated portion is formed by a part of the exhaust passage wall.

By the provision of a heating arrangement comprising a heater positioned externally of the exhaust passage, one can achieve heating of relevant portion internally of the exhaust gas passage and/or the exhaust gas without any tubing and connections communicating an outside of the exhaust passage with an inside of the exhaust passage. It is advantageous in that the environment inside the exhaust gas passage is aggressive/corrosive with high temperature and varying load. Thus, the system creates conditions for a simple and durable solution.

Further, induction heating provides conditions for a fast, concentrated heating.

Further, the system creates conditions for localized heating of the specific surfaces, where deposits normally form. Thus, the system further creates conditions for an energy efficient solution. According to one embodiment, the first heater is positioned between the urea supply means and the selective catalytic reduction catalyst. In other words, the heating arrangement may be arranged for inductive heating of a portion of the system in a urea mixing zone between the urea supply means and the selective catalytic reduction catalyst. According to a further embodiment, the heating arrangement comprises at least one first magnetic element arranged in such a way that it may be heated via induction by the heater. This embodiment provides further conditions for localized heating of the specific surfaces, where deposits normally form. According to a further embodiment, the first magnetic element is located in a position along the exhaust passage overlapping with the heater. This embodiment provides further conditions for a further energy efficient solution in that a distance between the heater and the magnetic element may be minimized. According to a further embodiment, the first magnetic element is positioned inside of the exhaust passage. This creates conditions for heating of a large part of the exhaust gas.

According to a further embodiment, the first magnetic element has a main extension in a direction transverse to a longitudinal direction of the exhaust passage. The term "longitudinal direction" represents a main extension direction of the passage. In other words, the longitudinal direction represents a main exhaust flow direction. According to one example, the first magnetic element has a main extension in a direction perpendicular to the longitudinal direction of the exhaust passage. According to one example, the first magnetic element is relatively thin and/or has its main extension in a plane. According to one example, the first magnetic element is arranged in contact with a wall of the exhaust passage. According to further example, the first magnetic element is static in relation to the passage wall. In other words, the first magnetic element is rigidly arranged in relation to the passage wall. For example, the first magnetic element is rigidly attached to the exhaust passage wall.

According to a further embodiment, at least a part of a wall of the exhaust passage forms the first magnetic element. According to a further embodiment, the exhaust treatment system comprises a mixer positioned inside the exhaust gas passage between the urea supply means and the selective catalytic reduction catalyst for mixing the supplied urea with the exhaust gas. In this way, the urea may be mixed more homogenously with the exhaust flow, which creates conditions for an improved functionality of the NOx reduction. According to one example, the term "mixer" may be formed by a swirl and/or turbulence inducing element.

According to one example, the mixer is arranged in contact with a wall of the exhaust passage. According to a further example, the mixer is static in relation to the passage wall. In other words, the mixer is rigidly arranged in relation to the passage wall. For example, the mixer is rigidly attached to the passage wall.

According to a further embodiment, the first magnetic element forms an integral part of the mixer or is rigidly attached to the mixer. In this way, a one-piece unit comprising both the mixing and magnetic function may be achieved, which may be beneficial in that the mixer, which is subjected to urea deposit may be directly heated. Further, it may be advantageous from an assembly and/or service perspective. Further, by arranging the magnetic element in one piece with the mixer, there may be a single element in the urea mixing zone, thereby creating conditions for reducing the resistance to the exhaust flow. According to a further embodiment, the first magnetic element is located at a distance from the mixer. According to one alternative, the first magnetic element is located upstream of the mixer, wherein the exhaust gas may be heated before it reaches the mixer, wherein there is a reduced risk of deposit build up on the mixer. According to an alternative, the first magnetic element is located downstream of the mixer. According to a further embodiment, the mixer is at least partly formed by a magnetic material and wherein the heating arrangement is adapted for heating the mixer. According to this embodiment, there may be heating by induction of two spaced apart parts, namely the first magnetic element and the mixer. In other words, a two-step heating process may be used, wherein the heating may be controlled separately and independently for the first magnetic element and the mixer. It may be beneficial with separately controlled heating in different operational states.

According to a further development of the last-mentioned embodiment, the heating arrangement comprises a second heater and a second magnetic element associated to the second heater. The second heater may be positioned externally of the exhaust passage and between the urea supply means and the selective catalytic reduction catalyst. Thus, the first and second heaters may be formed by different units, which is each designed and controlled for its respective purpose.

According to a further embodiment, the heater comprises a coil surrounding the exhaust passage. More specifically, the heater is an electric inductive coil. This embodiment provides conditions for an energy efficient design for providing power to the passage/magnetic element. The coil may extend along a screw line surrounding the passage. Further, the heating arrangement comprises an electrical device adapted for supplying power to the heater.

According to a further aspect, the invention regards an internal combustion engine system comprising an internal combustion engine and an exhaust gas treatment system according to any preceding embodiment positioned downstream of the internal combustion engine for treating exhaust gases from the internal combustion engine. According to one embodiment, the internal combustion engine is arranged for providing power to the heater. According to a further aspect, the invention regards a vehicle comprising such an internal combustion engine system The internal combustion engine may be adapted for providing motive power for propelling the vehicle.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 is a side view of a truck comprising an internal combustion engine with an exhaust gas treatment system,

Fig. 2 is a schematic view of an exhaust gas treatment system according to a first embodiment for treating exhaust gases from the engine in figure 1 , Fig. 3a-t show a section of the exhaust gas system with different embodiments of a magnetic element,

Fig. 4 shows an alternative arrangement of the magnetic element according to figure 3c-d, Fig. 5a-b show the magnetic element according to figure 3c-d according to an alternative design,

Fig. 6 shows the magnetic element according to figure 3c-d according to a still further alternative design,

Fig. 7a and 7b are schematic views of an exhaust gas treatment system according to different embodiments for treating exhaust gases from the engine in figure 1 ,

Fig. 8-9 show two different embodiments of an electrical device adapted for supplying power to the heater for heating the mixer in the exhaust passage, and

Fig. 10-12 show different embodiments of an internal combustion engine system comprising an internal combustion engine and an exhaust gas treatment system. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Fig. 1 shows a vehicle 2 in the form of a truck in a partly cut side view. The vehicle 2 has an internal combustion engine system 4 for driving the vehicle 2. The internal combustion engine system 4 comprises an internal combustion engine 6 in the form of a diesel engine.

Fig. 2 is a schematic view of an exhaust gas treatment system 8 for treating exhaust gases from the engine 6 in figure 1 . The exhaust gas treatment system 8 comprises an exhaust passage 10, or exhaust gas line, in the form of a tube for conveying exhaust gases, see arrow 9, discharged from the engine 6.

The exhaust gas treatment system 8 further comprises a selective catalytic reduction (SCR) catalyst 12 provided in the exhaust passage 10 for selectively reducing NOx contained in the exhaust gas. The SCR catalyst 12 forms a body with an external shape and size matched to an internal shape and size of the exhaust passage so that no, or at least very small amount of, exhaust gases may pass the SCR without being treated. The SCR catalyst 12 may be made from a ceramic materials used as a carrier, such as titanium oxide, and active catalytic components are usually either oxides of base metals (such as vanadium, molybdenum and tungsten), zeolites, or various precious metals. According to one example, the SCR catalyst 12 may use an ammonia adsorption type Fe zeolite having a high NOx reducing rate under low temperature. Further, the SCR catalyst 12 may be formed by a brick of a porous construction. The porosity is what gives the catalyst the high surface area essential for reduction of NOx. Further, the selective catalytic reduction catalyst may be coated on a flow-through monolith.

The exhaust gas treatment system 8 further comprises a means 14 for supplying a reductant into the exhaust passage 10 upstream of the SCR catalyst 12 for NOx reduction. The reductant may be in liquid form. Further, the reductant may be sprayed into the exhaust gas passage. The reductant may be formed by a urea solution. The reductant may be automotive-grade urea. The reductant sets off a chemical reaction that converts nitrogen oxides into nitrogen, water and tiny amounts of carbon dioxide (C02). The reductant is composed of purified water and automotive grade aqueous urea. The reductant supply means 14 may be formed by an injector positioned in the exhaust gas passage. The reductant could also be of any other type of ammonia carrier, e.g. ammonia carbamate, isocyanate, and guanidinium formate or similar.

The exhaust gas treatment system 8 further comprises an arrangement 16 for heating a portion of the system and/or the exhaust gas. More specifically, the heating arrangement 16 is adapted for inductive heating. The heating arrangement 16 comprises a heater 20 positioned externally of the exhaust passage 10 and between the urea supply means 14 and the SCR catalyst 12. The heater 20 may be formed by a coil in the form of a conductor arranged around the exhaust gas passage to create an inductor.

Further, according to the shown example, the heating arrangement 16 comprises a first magnetic element 18 positioned inside the exhaust passage 10 and in such a way that it may be heated via induction by the heater 20. Further, the magnetic element 18 is located in a position along the exhaust passage 10 overlapping with the heater 20. The magnetic element 18 comprises a metallic material providing magnetic properties. The magnetic element 18 may be designed with a core of a metallic material, such as iron, and an external layer of anti-corrosive and/or catalytic material. One example of such a magnetic element comprising a metallic material is disclosed in figure 5. The magnetic element 18 may function as a vaporizer for vaporizing the liquid reductant sprayed into the exhaust gas. More specifically, urea droplet goes through vaporization and via a thermolysis and hydrolysis reaction forms ammonia gas. In other words, the urea decomposes to form ammonia which reacts with the nitrogen oxides in the SCR catalytic converter to form nitrogen and water. As a result of improved vaporization of the reductant, the desired chemical reaction in the SCR can take place with increased efficiency, so a higher NOx conversion rate and thus lower NOx emissions can take place.

The magnetic element 18 is adapted for heating the exhaust gas when heated via induction by means of the heater 20. Heating of the exhaust gas is advantageous in certain operational states of the engine, in which the exhaust gases are so cold that they otherwise may not decompose the urea and there is a risk of the urea forming deposits within the exhaust gas passage.

Figure 3a shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 1 18 according to a first embodiment in a cross section view. Figure 3b shows the section of the exhaust gas system according to figure 3a in a partly cut perspective view.

The magnetic element 1 18 is annular and in the form of a tubular body, which creates 5 conditions for little or no increase in flow resistance. The magnetic element 1 18 is arranged in the exhaust passage 10. The magnetic element 1 18 is designed with a cross sectional shape corresponding to an inner cross section shape of the exhaust passage 10 but with a smaller dimension than the exhaust passage 10. In the embodiment shown, the exhaust passage 10 has a circular cross section shape and the magnetic element 1 18

10 also has a circular cross section shape. A centre axis of the exhaust passage 10 is in parallel with and in this case commensurate with a centre axis of the annular magnetic element 1 18. Further, the magnetic element 1 18 is arranged inside the exhaust passage 10 so that a radial gap is formed between an outer wall surface of the annular magnetic element 18 and an inner wall surface of the exhaust passage 10. The magnetic element

15 1 18 has an extent in the longitudinal direction of the exhaust gas passage sufficient for said heating. According to one example, the magnetic element 1 18 is formed by a tubular sheet metal body. According to a further example, a plurality of tubular bodies is arranged side-by-side in parallel with a longitudinal direction of the exhaust gas passage. Such a plurality of tubular bodies provides for a larger heating (and vaporization) surface.

20

Further, the annular magnetic element 1 18 is positioned inside the exhaust passage 10 via positioning members 26, or struts, connecting the annular magnetic element 1 18 radially with the exhaust passage 10. Thus, the metallic element is secured in the exhaust passage. According to the shown example, the positioning members 26 of the magnetic

25 element are welded to an internal surface of the exhaust passage. However, there may be other ways of securing the magnetic element in the exhaust passage, for example allowing a relative radial movement between the magnetic element and the exhaust passage inner wall for allowing different thermal expansion of the magnetic element in relation to the exhaust passage. For example, the exhaust passage may comprise a

30 plurality of circumferentially spaced openings for receiving the struts 26 and allowing a radial relative movement. According to one alternative, the magnetic element may be elastically braced in relation to the exhaust passage or secured via a form-fit or press-fit.

A thermal insulation layer 24 is arranged around the exhaust passage 10. More 35 specifically, the thermal insulation layer 24 is positioned between the exhaust passage 10 and the heater 20. Further, the thermal insulation layer 24 is continuous in a circumferential direction of the exhaust passage 10. Further, the thermal insulation layer 24 has an extent in a longitudinal direction of the exhaust passage 10 substantially matching at least an extent of the heater 20 in the longitudinal direction of the exhaust passage 10. According to an alternative, the system may not be provided with any such a thermal insulation layer.

Figure 3c shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 218 according to a second embodiment in a cross section view. Figure 3d shows the section of the exhaust gas system according to figure 3c in a partly cut perspective view.

The magnetic element 218 is designed for forming a mixer for mixing the urea with the exhaust gases in the urea mixing zone 22 between the urea supply means 14 and the SCR catalyst 12. More specifically, the magnetic element 218 provides for a homogeneous mixing of the vaporized reducing agent with the exhaust gas. Thus, the mixer and the magnetic element is formed by a one-piece unit 218. In other words, the mixer is designed for mixing the urea with the exhaust gases and comprising a magnetic material sufficient for the induction heating.

The magnetic element 218 forms a body with a shape and size matched to an internal shape and size of the exhaust passage 10 so that the urea is mixed with the exhaust gases to a great extent. According to one example, an external periphery of the magnetic element 218 is in close vicinity of or in contact with an inner wall surface of the exhaust passage 10.

The magnetic element 218 has such a design that a main extension of the magnetic element 218 is in a direction transverse to the longitudinal direction of the exhaust passage. More specifically, the magnetic element main extension is in a direction perpendicular to the longitudinal direction of the exhaust passage. Further, the magnetic element forms a relatively thin structure (small extension in the longitudinal direction of the exhaust passage).

The magnetic element 218 comprises at least one vane or blade member 220. More specifically, the magnetic element 218 comprises a plurality of such vanes, or blades. According to the shown example, the magnetic element 218 is of a propeller like structure, wherein the plurality of vanes is connected to a central hub 222. More specifically, the magnetic element comprises four circumferentially evenly spaced vanes 220. The vanes 220 are inclined in relation to the longitudinal direction of the exhaust passage 10 for creating a swirl of the exhaust gas. The tip of the vanes is in contact with an inner wall of the exhaust passage for securing the magnetic element inside of the exhaust passage.

Figure 3e shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 318 according to a third embodiment in a cross section view. Figure 3f shows the section of the exhaust gas system according to figure 3e in a partly cut perspective view.

The magnetic element 318 comprises at least one plate shaped member 320 turned or twisted along the longitudinal direction of the exhaust passage. More specifically, the magnetic element 318 comprises a plurality of such twisted plate shaped members 320. The plate shaped member 320 has an extension in the longitudinal direction of the exhaust passage, which is constant in the radial direction of the exhaust passage. More specifically, the plate shaped member 320 has a rectangular shape. According to the shown example, the magnetic element 318 is of an impeller like structure, wherein the plurality of plate shaped members is connected in a central hub 322. More specifically, the magnetic element comprises eight circumferentially evenly spaced plate shaped members 320. The tip of the plate shaped members is in contact with an inner wall of the exhaust passage for securing the magnetic element inside of the exhaust passage. Figure 3g shows a section of the exhaust gas system in the urea mixing zone 22 with the magnetic element 418 according to a fourth embodiment in a cross section view. Figure 3h shows the section of the exhaust gas system according to figure 3g in a partly cut perspective view. The magnetic element 418 comprises at least one vane 420 being of a similar character as the propeller-like design in figure 3c and 3d but with the difference that the plate vanes 420 are connected along their outer periphery to the wall of the exhaust passage 10 instead of to a central hub. More specifically, the vanes 420 ends a distance from a centre axis of the exhaust passage 10, thereby leaving a central free space 422. In other words, the magnetic element 418 according to figure 3g and 3g is a type of inverted design in relation to the magnetic element 1 18 in figure 3c and figure 3d.

Figure 3i shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 518 according to a fifth embodiment in a cross section view. Figure 3j shows the section of the exhaust gas system according to figure 3i in a partly cut perspective view.

The magnetic element 518 forms a wall structure defining axial openings. More specifically, the wall structure comprises a plurality of walls 520,522 with different extension directions. More specifically, the wall structure comprises a plurality of first parallel walls 520 with a first extension direction and a plurality of second parallel walls 522 with a second extension direction. More specifically, the second walls 522 extend perpendicular to the first walls 520 forming a plurality of openings with a rectangular cross section shape. According to an alternative, the first walls extend in an inclined manner in relation to the second walls. Further, the wall structure extends over the complete inner cross section of the exhaust passage 10. Further, the wall structure has an extension in the longitudinal direction of the exhaust passage 10. The longitudinal extension of the wall structure is at least twice the distance between adjacent walls in the wall structure. The longitudinal extension of the wall structure is associated to the available surface area which in turn is related to a required power.

Figure 3k shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 618 according to a sixth embodiment in a cross section view. Figure 3I shows the section of the exhaust gas system according to figure 3k in a partly cut perspective view. Figure 3m shows the magnetic element according to figure 3k in a perspective view from a position downstream of the magnetic element.

The magnetic element 618 forms a plate-shaped member with a main extension in a plane transverse to the longitudinal direction of the exhaust passage. More specifically, the plate-shaped member has a main extension in a plane perpendicular to the longitudinal direction of the exhaust passage 10. The plate-shaped member is perforated with openings. The openings have a rectangular shape, but may have any other geometrical shape, such as circular or other polygonal shape. More specifically, the openings are formed by cutting out a portion 620 of the plate-shaped member along a part of the profile of the opening while leaving a part of the profile, wherein the cut out portion is folded from the extension plane of the plate-shaped member. More specifically, the through holes have been cut out from the plate by cutting along three sides and folding the rectangular material along the fourth side. More specifically, the cut out portions 620 5 may extend at an angle in relation to the extension plane of the plate-shaped member.

Further, the magnetic element 618 comprises a plurality of circumferentially spaced tabs 622 arranged at a periphery of the plate-shaped member for securing the magnetic element to the exhaust passage. More specifically, the tabs extend in parallel with the longitudinal direction of the exhaust passage.

10

Figure 3n shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 718 according to a seventh embodiment in a cross section view. Figure 3o shows the section of the exhaust gas system according to figure 3n in a partly cut perspective view.

15

The magnetic element 718 comprises a plurality of spaced parallel walls 720. The walls 720 have a main extension direction transverse to the longitudinal direction of the exhaust passage and a secondary extension direction in parallel with the longitudinal direction of the exhaust passage. A plurality of wall elements 722,724 are arranged between the walls

20 720 and rigidly attached to the walls 720. The wall elements 722,724 are rectangular. The wall elements 722, 724 are arranged in a spaced relationship in the main extension direction of the walls 720. A plurality of first wall elements 722 are arranged in a first space between two adjacent walls and a plurality of second wall elements 724 are arranged in a second space between two adjacent walls, wherein the first wall elements

25 722 and the second wall elements 724 have different extension directions.

Figure 3p shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 818 according to an eighth embodiment in a cross section view. Figure 3q shows the section of the exhaust gas system according to figure 3p in a partly cut 30 perspective view.

The magnetic element 818 comprises a wall 820 of a helical shape for guiding the exhaust gas. An outer edge 822 of the wall 820 is adjacent to an inner surface of the exhaust gas passage 10 and an inner edge 824 of the wall 720 is at a distance from a centre axis of the exhaust passage. The wall 820 forms at least half a turn, preferably one complete turn and in the shown example two complete turns.

Figure 3r shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 918 according to an ninth embodiment in a cross section view. Figure 3s shows the section of the exhaust gas system according to figure 3r in a partly cut perspective view.

The magnetic element 918 forms a body 920 with an opening structure extending through the body 920. The opening structure comprises a plurality of openings. In the shown example, the openings are arranged in a plurality of parallel rows. Further, the openings have a polygonal cross sectional shape and more specifically a rectangular cross sectional shape. According to an alternative, or in combination, the openings may have the cross sectional shape of a square, triangle, star or any other conceivable shape.

Figure 3t shows a section of the exhaust gas system in the urea mixing zone 22 with a magnetic element 1018 according to a tenth embodiment in a partly cut perspective view. In this embodiment, at least a part 1018 of a wall of the exhaust passage forms the magnetic element. According to the shown embodiment, the magnetic wall part 1018 is continuous in a circumferential direction of the exhaust passage. According to an alternative, the magnetic wall part is discontinuous in a circumferential direction of the exhaust passage. Further, according to the shown embodiment, the magnetic wall part 1018 is formed by a discrete portion with a different magnetic property than the adjacent portions 10a, 10b of the exhaust passage. According to an alternative, the complete exhaust passage wall may be magnetic. According to a further alternative, the exhaust passage wall may be formed by a material with no or low magnetic properties and be at least partly coated with a magnetic material.

Figure 4 shows an alternative arrangement of the propeller-like magnetic element 218 according to the second embodiment shown in figure 3c and 3d. The magnetic element and/or the exhaust passage is arranged with a mating structure for securing the position of the magnetic element in the longitudinal direction of the exhaust passage. More specifically, an inner wall of the exhaust passage has a step 10a forming a support surface for the magnetic element 218. The support surface 10a is in this example formed circumferentially around the exhaust passage by means of a transition between two parts 10b, 10c of the exhaust passage having different internal diameters.

Figure 5a shows the propeller-like magnetic element 218 according to the second embodiment shown in figure 3c and 3d in a front view. Figure 5b shows a cross section view of one of the vanes 220. The vane 220 has an airfoil shape. The vane 220 has a core 222 of a first material. Further, the vane 220 has a coating 224 of a second material. According to this example, the first material is magnetic and preferably ferromagnetic. The first material is metallic according to one example made of iron. The second material comprises an anticorrosion and/or catalytic material.

Figure 6 shows an alternative design of a propeller-like magnetic element 218 ^' according to the second embodiment shown in figure 3c and 3d in a front view. The propeller-like magnetic element 218 ^' has a core 222 ^" of a first material. Further, the propeller-like magnetic element 218 ^' is partially coated with a coating 224 ^" of a second material. In other words, the propeller-like magnetic element 218 ^' comprises at least one and preferably a plurality of coated sections 224\ In this example, each vane 220 ^" comprises at least one and preferably a plurality of coated sections 224 ^" . According to this example, the first material is non-magnetic while the second material being magnetic and preferably ferromagnetic. The second material is metallic and according to one example is made of stainless steel. Such a design of the element with a core and coating is of course possible for any one of the other described examples.

Fig. 7a is a schematic view of an exhaust gas treatment system 8 ^' , which is an alternative to the system in figure 2, for treating exhaust gases from the engine 6 in figure 1 . For ease of presentation, only the main differences with the system in figure 2 will be disclosed below. The magnetic properties and the mixing properties are here divided in separate units 1 18a, 218 (first and second magnetic elements) arranged spaced in the longitudinal direction of the exhaust passage. More specifically, the system 8 ^' comprises a first magnetic element 1 18a, which forms part of an induction heating arrangement 16 ^' . The first magnetic element 1 18a may be formed by the tubular member described above in connection with figure 3a and 3b. The system 8 ^' further comprises swirl or turbulence inducing element 218. The turbulence inducing element 218 may be formed by the propeller-like element described above in connection with figure 3c and 3d. According to the shown example, the propeller-like element 218 has magnetic properties and is associated to the inductive heating arrangement 16 ^" for a second heating, wherein the propeller-like element 218 forms the second magnetic element. According to an alternative, the propeller-like element 218 may not be associated to any inductive heating arrangement, wherein there is no requirement on any magnetic properties of the propeller-like element 218.

According to a further alternative (not shown), the magnetic element may be located in close vicinity of the SCR catalyst 12 for heating the selective catalytic reduction catalyst. The magnetic element may form a grid or lattice structure. The grid structure is designed for matching a cross section of the porous structure of the SCR catalyst so that the cross bars in the grid structure covers a surface of the SCR catalyst facing the exhaust flow.

Fig. 7b is a schematic view of an exhaust gas treatment system which is an alternative to the system in figure 2. For ease of presentation, only the main differences with the system in figure 7a will be disclosed below. In this embodiment, the system comprises an oxidation catalyst (DOC) 34 having function of oxidizing carbon monoxide (CO), hydrocarbons (HC) and nitrogen monoxide (NO) contained in the exhaust gas and diesel fuel injected into the exhaust gas. The magnetic element 1 18b and its associated heater (coil) 20'a is positioned between the DOC 34 and the urea supply means 14.

Fig. 8 shows a first embodiment of an electrical device 100 adapted for supplying power to the heater 20 for heating the magnetic element in the exhaust passage. The electrical device 100 comprises a source 102 of electrical power in the form of a battery or other electrical energy storage means. According to the shown embodiment, the battery is a traction battery for a hybrid powertrain. A DC/DC converter 104 is operatively connected to the traction battery 102. Further, a DC/ AC converter 106 is operatively connected between the DC/DC converter 104 and the heater 20. According to an alternative, a further DC/DC converter may be operatively connected between the DC/DC converter 104 and the DC/AC converter 106 in order to step down the traction battery voltage to a lower voltage level.

Fig. 9 shows a second embodiment of an electrical device 200 adapted for supplying power to the heater 20 for heating the magnetic element in the exhaust passage in an application of a conventional drivetrain. The engine 6 forms the power source. Further, the electrical device 200 comprises conversion units for converting chemical energy to electrical energy. More specifically, the electrical device 200 is operatively connected to the engine 6 and comprises in series an electrical machine 202, an AC/DC converter 204 (or DC/DC converter), a battery 206 and a DC/AC converter 208. Fig. 10a shows a first embodiment of an internal combustion engine system 30 comprising the internal combustion engine 6 and an exhaust gas treatment system 32. For ease of presentation, only the main differences to the embodiment shown in figure 2 will be described. The exhaust gas treatment system 32 comprises an oxidation catalyst (DOC) 34 having function of oxidizing carbon monoxide (CO), hydrocarbons (HC) and nitrogen monoxide (NO) contained in the exhaust gas and diesel fuel injected into the exhaust gas. The DOC 34 uses precious metals such as platinum and/or palladium. The exhaust gas treatment system 32 further comprises diesel particulate filter (DPF) 36 disposed downstream of the DOC 34 with respect to the flowing direction of exhaust gas for capturing and collecting particulate matter contained in exhaust gas. The DPF may also have catalytic functions for oxidising. The selective catalytic reduction (SCR) catalyst 12 is disposed downstream of the DPF 28 with respect to the flowing direction of the exhaust gas.

The internal combustion engine system 30 further comprises a storage vessel 38 for the reductant and a pump 40 for pumping the reductant from the vessel 38 to the injector 14 inside the exhaust gas passage 10. The internal combustion engine system 30 further comprises the electrical device 100 adapted for supplying power to the heater 20.

The internal combustion engine system 30 further comprises a plurality of magnetic elements 218,918 arranged after each other along the longitudinal direction of the exhaust gas passage 10. According to this example, each one of the magnetic elements has mixing properties. In other words, the magnetic properties and mixing properties are achieved in a one-piece unit. Further, the plurality of magnetic elements 218,918 are arranged with such distance in the longitudinal direction of the exhaust gas passage 1 0 in relation to the extension of a single heater 20 in the longitudinal direction of the exhaust gas passage 10 that the heater covers both mixers 218,918.

The exhaust gas treatment system 32 in figure 12 is of a linear design, wherein the components are arranged after each other along a substantially linear extension of the exhaust gas passage. Fig. 10b is a schematic view of an exhaust gas treatment system according to an alternative to the system in figure 10a. In this embodiment, the selective catalytic reduction catalyst 12' is coated on the particulate filter 36'. In other words, the position of the particulate filter 36' has been changed in relation to figure 10a and is now integrated with the SCR 12' in a position downstream of the urea injection device 14.

Fig. 1 1 shows a second embodiment of an internal combustion engine system 50 comprising the internal combustion engine 6 and an exhaust gas treatment system 52. For ease of presentation, only the main differences to the embodiment shown in figure 10 will be described. In contrast to the embodiment shown in figure 10, the exhaust gas passage comprises three substantially linear sections arranged in parallel with each other and with turning sections interconnecting the linear sections. More specifically, a first end 54 of a first linear exhaust passage section 56 is connected to the engine 6 and a second end 58 of the first linear exhaust passage section 56 is connected to a first turning section 60. Further, a first end 62 of a second linear exhaust passage section 64 is connected to the first turning section 60 and a second end 66 of the second linear exhaust passage section 64 is connected to a second turning section 68. Further, a first end 70 of a third linear exhaust passage section 72 is connected to the second turning section 68 and a second end 74 of the third linear exhaust passage section 72 is connected to atmosphere. Thus, the exhaust gas flows in opposite directions in the first and second linear sections 56,64 and in opposite directions in the second and third linear sections 64,72.

The DOC 34 and the DPF 36 are positioned in the first linear section 56. The reductant injector 14 is positioned in the first turning section 60. A first magnetic element 218 is positioned in the second linear section 64. Further, a first heater 20a associated to the first magnetic element 218 is positioned along the second linear section 64. A second magnetic element 918 is positioned in the third linear section 72. Further, a second heater 20b associated to the second mixer 918 is positioned along the third linear section 72. Further, the SCR catalyst 12 is positioned downstream of the second magnetic element 918 in the third linear section 72.

The system 50 comprises a box 76 surrounding the exhaust gas passage 10 comprising the first, second and third linear sections 56,64,72 and the interconnecting turning sections 60,68. Fig. 12 shows a third embodiment of an internal combustion engine system 80 comprising the internal combustion engine and an exhaust gas treatment system 82. For ease of presentation, only the main differences to the embodiment shown in figure 13 will be described. The system 80 comprises a box 84 with an inner shell 86 surrounding a portion of the second linear section 66 comprising the first mixer 218 and associated first heater 20a. The inner shell 86 is adapted to be with drawable from the box 84 for service or exchange of parts. Further, the exhaust passage 10 comprises an opening structure 88 downstream of the SCR catalyst 12 and inside of the box 84 so that the treated exhaust gas may circulate inside the box 84 before reaching the atmosphere. This may serve for heat distribution and noise reduction. It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. For example, the system may comprise any combination of the above-mentioned embodiments of the magnetic elements. Further, it may be noted that the contents of different claims may be combined to embodiments not explicitly shown in the description above.

A NOx sensor (not shown) may be provided in the exhaust passage 10 upstream of the SCR catalyst 12 with respect to the flowing direction of exhaust gas for sensing the amount of NOx contained in exhaust gas upstream of the SCR catalyst 12. Another NOx sensor (not shown) may be provided in the exhaust passage 10 downstream of the SCR catalyst 12 with respect to the flowing direction of exhaust gas for sensing the amount of NOx contained in exhaust gas downstream of the SCR catalyst 12. The exhaust gas treatment system may further include a control unit configured to receive signals form the NOx sensors and adjust operating parameters accordingly. Likewise, temperature sensors may be provided in the exhaust passage 10 and the control unit may be configured to receive signals form the temperature sensors and adjust operating parameters accordingly. According to one alternative, the magnetic element may form a grid or lattice structure. Further, the grid structure extends over the complete inner cross section of the exhaust passage 10. Further, the ends of the cross bars forming the grid structure are rigidly connected to the exhaust passage 10.

According to one alternative, or complement, the system comprises an energy storage arrangement, such as one or a plurality of batteries, which is adapted to be charged from an electrical grid/network, is arranged for providing power to the heater.