Counterflow exhaust gas aftertreatment

Abstract

An exhaust gas mixer (101), an exhaust gas aftertreatment apparatus, and corresponding method are disclosed. A funnel (130) receives from an input end (132) of the funnel and guides the exhaust gas towards an output end (134) of the funnel, wherein the output end (134) is opposite to the input end (132). A flow guide (140) resides inside the funnel (130) and guides exhaust gas flowing through the funnel (130) to advance as a rotating perimetrical flow such that downstream from flow guide (140), the exhaust gas will be exposed to a lower pressure in a core region (C) than in a perimeter region (P).

Description

[0001] COUNTERFLOW EXHAUST GAS AFTERTREATMENT

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to counterflow exhaust gas aftertreatment.

[0004] BACKGROUND

[0005] This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

[0006] Exhaust gases may require aftertreatment by use of a suitable reactant. For example, exhaust gas of diesel engines may require aftertreatment to reduce nitrogen oxides in the exhaust gas. To this end, urea suspension is dosed into a stream of exhaust gas as a spray of small droplets. The droplets evaporate and ultimately release gaseous ammonium that reduces nitrogen oxides (NOX) into elementary nitrogen (N) and oxide (O2). There are some practical difficulties in this process, including that a) how to mix the urea suspension so that the reduction of nitrogen oxides takes place to a sufficient extent, b) howto prevent accruing of urea onto exposed surfaces of the aftertreatment equipment, c) how to avoid forming of excess backpressure by the aftertreatment equipment, and d) how to fit in the required aftertreatment equipment. These objectives are somewhat contradictory: a greater turbulence tends to improve mixing of the urea solution droplets while inhibiting flow through by increasing pressure. It is easier to reduce pressure and to avoid accrual of urea by using larger chambers and conduits, while compactness of the equipment suffers.

[0007] The present invention aims at providing a new alternative to balance between these at least partially conflicting goals. Alternatively, the present invention aims at providing a new technical alternative.

[0008] SUMMARY

[0009] The appended claims define the scope of protection. Any examples and technical descriptions of apparatuses, products and / or methods in the description and / or drawings not covered by the claims are presented not as embodiments of the invention but as background art or examples useful for understanding the invention.

[0010] According to a first example aspect there is provided an exhaust gas mixer, comprising a funnel configured to receive exhaust gas from an input end of the funnel and to guide the exhaust gas towards an output end of the funnel, wherein the output end is opposite to the input end; the exhaust gas mixer further comprising a flow guide configured to reside at least partially inside the funnel and configured to guide exhaust gas flowing through the funnel and the output end to advance as a rotating perimetrical flow such that downstream from flow guide, the exhaust gas will be exposed to a lower pressure in a core region than in a perimeter region.

[0011] According to a second example aspect there is provided an exhaust gas aftertreatment apparatus, comprising the exhaust gas mixer of the first example aspect.

[0012] The apparatus may further comprise a reactant doser mount for a reactant doser. The reactant doser mount may be configured to position the reactant doser downstream from the output end of the funnel such that when in use, the reactant doser injects reactant to the core region towards the output end the funnel.

[0013] The reactant doser mount may be configured to position the reactant doser downstream from the output end of the funnel such that when in use, the reactant doser injects reactant through the output end of the funnel towards the input end. The reactant doser mount may be configured to position a tip of the reactant doser into the housing.

[0014] The reactant doser mount may be configured to position the reactant doser downstream from the output end of the funnel such that reactant will be dosed in the longitudinal direction of the funnel and against a general flow direction of the exhaust gas that passes through the funnel.

[0015] The doser mount may reside outside of a space defined by the funnel. The doser mount may be spaced apart from the space defined by the funnel. The doser mount may reside on a wall facing the output end of the funnel. The doser mount may reside on an outer surface of the wall facing the output end of the funnel. An inner surface of the wall of the facing the output end of the funnel may face exhaust gas that exits the output end of the funnel. The apparatus may further comprise a housing having a first end and a second end. The housing may be cylindrical.

[0016] The housing may contain a substrate. The substrate may be a honeycomb filter. The substrate may be a ceramic filter. The substrate may be a catalyst filter. The substrate may be an oxidation filter. The substrate may be a wall-flow filter. The substrate may be a soot trap. The substrate may be a catalyst filter.

[0017] The housing may contain chamber between the substrate and the funnel.

[0018] The housing may contain the funnel.

[0019] The housing may comprise two or more cylindrical parts. The two or more cylindrical parts may be sequentially connected.

[0020] The funnel may be a double-sided funnel.

[0021] The funnel may have a narrowing input portion. The input portion may have a curved crosssection. The input portion may have an at least double curved cross-section. The input portion may comprise a concave sub-portion with a concave cross-section facing towards the catalyst filter. The input portion may comprise a convex sub-portion with a convex crosssection facing towards exhaust gas that passes by the input portion. The cross-section of the funnel may be convex from the convex sub-portion to the output end of the funnel. The convex cross-section may define a throat of the funnel.

[0022] The flow guide may be configured to receive the exhaust gas in a longitudinal direction of the funnel. The longitudinal direction of the funnel may refer to an average flow direction of the exhaust gas through the funnel, e.g., generally a direction from an input end of the funnel towards the output end of the funnel.

[0023] The flow guide may reside within the concave sub-portion. Alternatively, the flow guide may reside partially within the concave sub-portion. The flow guide may extend from the concave sub-portion towards the output end of the funnel. The flow guide may extend from the concave sub-portion towards or beyond the output end of the funnel.

[0024] Advantageously, the funnel is adjacent to the substrate so that the exhaust gas aftertreatment apparatus can be made more compact. Alternatively, a gap is left between the funnel and the substrate. Such a gap may help supporting a second end of the substrate. Exhaust gas output by the substrate may be directly received by the funnel. The input end of the funnel may fill the housing so that all exhaust gas output by the substrate is pressure forced to pass through the input end of the funnel. The input end of the funnel may extend across an entire output end of the substrate. The input end of the funnel may be configured to receive exhaust gas around an edge region of the substrate such that exiting exhaust gas is redirected by at most 45 or 60 degrees. Some exhaust gas, preferably a minority, may yet be let pass through a wall that forms the funnel, or through a wall of the housing, so as to form a bypass stream that will not go through the output end of the funnel.

[0025] Advantageously, the input end of the funnel may guide exhaust gas exiting the substrate across the entire substrate with a small increase in back pressure. Advantageously, the funnel may guide exhaust gas from the substrate to the doser with a small increase in the back pressure.

[0026] Advantageously, the funnel and the flow guide in conjunction may synergically transfer exhaust gas from the substrate to reactant dosing with a small back pressure, an efficient and even mixing of exhaust gas with the reactant, and an insignificant accrual of the reactant in the exhaust gas mixer.

[0027] The flow guide may comprise a swirl element. The swirl element may comprise a plurality of vanes, such as two, three, four, five or more. The vanes may be curved. The vanes may extend inwardly to a joint hub. The vanes may extend outwardly to a perimeter of the funnel. The vanes may be strips.

[0028] The vanes may be evenly positioned to different radial directions.

[0029] The strips may have a substantially constant width for most of their length. The vanes may be configured to form a planar central portion in which the vanes extend radially outwards from the hub.

[0030] The vanes may be configured to tangentially approach the perimeter of the funnel.

[0031] The vanes may be twisted so that after the central portion, the vanes have flat surfaces aligned with the longitudinal direction of the housing.

[0032] The vanes may be twisted by 90 degrees. The vanes may define negative blades around the central portion.

[0033] A circle drawn around tips of the vanes may have a radius that is at least 50 %, 60 %, or 70 % of a greatest inner diameter of the input end of the funnel. The circle drawn around the tips of the vanes may have a radius that is at most 70 %, 80 %, or 90 % of the greatest inner diameter of the input end of the funnel.

[0034] The swirl element may comprise a plurality of obliquely oriented tubelets. The swirl element may comprise 6, 7, 8, 10 or 12 tubelets. The swirl element may comprise at least 5, 6, 7, 8, or 10. The tubelets may comprise entry ends and exit ends. The entry ends may be obliquely cut. The obliquely cut entry ends may be arranged to settle onto a common plane. The common plane may have a tolerance that is at most 1 , 5, or 10 mm.

[0035] In this document, a tubelet may refer to a tube having a length that is at most eight times an average diameter of the tube.

[0036] The swirl element may be formed of a single piece of material, such as of a single steel sheet.

[0037] Advantageously, the swirl element in conjunction with the funnel may define a rotating passage for the exhaust gas such that the exhaust gas is forced to rotate very efficiently and with a small backpressure.

[0038] The vanes may be made a metal plate. The vanes may be made of steel. The vanes may be made of aluminium. The vanes may be welded together at the hub. Alternatively, or additionally, the vanes may be joined to each other at the hub by bending ends of the vanes onto one or more adjacent vanes. Alternatively, or additionally, the vanes may be joined to each other at the hub by a bolt and nut configured to squeeze the ends of the vanes to a hub system formed with the bolt. Tips or downstream portions of the negative blades may be at least partially welded to the funnel. The vanes may double as a support or grille for the substrate, or as a stopper for simplifying assembly of the apparatus by preventing the substrate settling too deep towards the second end of the housing.

[0039] The funnel may be made a metal plate. The funnel may be made of steel. The funnel may be made of aluminium.

[0040] The housing may be made a metal plate. The housing may be made of steel. The housing may be made of aluminium.

[0041] The funnel may comprise an output portion subsequent to the throat of the funnel. The output portion may be expanding in the flow direction. The expanding output portion may have a convex cross-section towards exhaust gas that passes through the funnel.

[0042] Advantageously, the expanding portion may further emphasise pressure difference between the core region and the perimeter region. The emphasising of the pressure difference may further increase travel of the injected reactant in the funnel. The emphasising of the pressure difference may reduce risk of accruing some of the injected reactant onto surfaces inside the funnel. Further advantageously, the expanding portion may reduce backpressure caused by turning exhaust gas approaching the second end of the housing to a radial direction of the housing.

[0043] Alternatively, the output portion may have a substantially constant cross-sectional area. The output portion may be cylindrical.

[0044] The flow guide and shaping of the funnel may be configured to cause a backflow in the core region towards the flow guide.

[0045] The flow guide may comprise an inhibitor configured to inhibit the core flow in comparison to the flow in the perimeter region, such as the hub. The inhibitor may comprise or be a plate. The inhibitor may form a central protrusion that extends when seen from an upstream direction. Alternatively, the inhibitor may form a central intrusion when seen from upstream side.

[0046] The inhibitor may be planar. The inhibitor may have a thickness that is at most 1 %, 5 %, or 10 % of a square root of a projection of the inhibitor in a direction perpendicular to the flow of the exhaust gas through funnel. The inhibitor may comprise a core flow block configured to guide exhaust gas from the core region towards the perimeter region. The inhibitor may be spaced apart from the swirl element in an average flow direction of the exhaust gas through the funnel.

[0047] The core region may comprise an innermost portion of a cross-section of the funnel immediately downstream of the flow guide. The innermost portion may comprise at least 5 %, 10 %, or 20 % of a surface area of said cross-section. The innermost portion may comprise at most 10 %, 20 %, or 50 % of the surface area of said cross-section.

[0048] The perimeter region may comprise an outmost portion of a cross-section of the funnel immediately downstream of the flow guide. The outermost portion may comprise at least 5 %, 10 %, or 20 % of a surface area of said cross-section. The outermost portion may comprise at most 10 %, 20 %, or 50 % of the surface area of said cross-section.

[0049] Advantageously, the flow guide may increase injection range of the reactant against reactant gas flowing through the funnel for increasing dwell time of the reactant within the funnel and mixing of the reactant with the exhaust gas.

[0050] The flow guide may prevent a visual connection from the doser mount beyond the flow guide. Advantageously, by preventing the visual connection, the flow guide may also prevent random drops of the reactant being shot all the way to the substrate. Advantageously, any landed drops of the reactant may evaporate sooner from the flow guide than from the substrate, so reducing risk of accumulation and forming of a blockage.

[0051] The funnel may be linear. The funnel may have a frustoconical input portion. Advantageously, a linear funnel may be easy to manufacture and clean.

[0052] The core region may be coaxial with the longitudinal direction of the funnel.

[0053] The substrate may occupy most of internal space of the housing. The substrate may extend over at least 50 %, 60 %, or 70 % of an internal length of the housing.

[0054] The housing may comprise an exit opening. The exit opening may be or comprise an output pipe connection. The exit opening may be perpendicularly with relation to longitudinal direction of the housing. The exit opening may reside such that the exit opening is aligned in a longitudinal direction of the funnel or at least most of the funnel, such as 60 %, 80 %, or 90 %.

[0055] Advantageously, the funnel may define a neck at the throat such that inner surfaces of the funnel help in forming a low pressure in the core region to improve reactant entry while the neck shape on an outer surface of the funnel helps forming a spacious channel around the funnel for the exhaust gas to flow into exit opening. Advantageously, the exhaust gas aftertreatment device may provide a plurality of synergic effects by same parts for the general objective of mixing reactant with exhaust gas with a small backpressure, small space consumption, good mixing results, and low risk of residue accumulation.

[0056] The exhaust gas mixer may further comprise a peripheral outlet channel around the funnel. The neck shape may increase space in the peripheral outlet channel around the funnel. The peripheral outlet channel may be configured to receive the exhaust gas from different sides of the funnel. The peripheral outlet channel may be configured to receive the exhaust gas from different sides of the funnel and cause that the exhaust gas rotates around a core of the peripheral outlet channel.

[0057] The core may define a core plane. The core plane may be substantially parallel with an output end of the substrate. The core plane may be substantially parallel with an input end of the flow guide. The core plane may be substantially parallel with an output end of the flow guide. The core plane may be substantially perpendicular to an average flow direction of the exhaust gas through the funnel.

[0058] The peripheral outlet channel may be configured to cause that the exhaust gas moves along the peripheral outlet channel for exiting the exhaust gas mixer. A portion of the peripheral outlet channel may reside between the neck of the funnel and the exit opening of the exhaust gas mixer.

[0059] The first end may be a logical end defining an end for a space that houses the substrate. The housing may extend from the second end beyond the first end and comprise empty space or other parts ahead of and I or behind the substrate. Alternatively, the housing may have an end wall at the first end, and an entry opening for exhaust gas to enter the housing.

[0060] The funnel may be configured to receive all the exhaust gas that has passed through the substrate. Alternatively, the funnel may be configured to receive a portion such as most of the exhaust gas that has passed through the substrate. The funnel may comprise a bypass. The bypass may be formed by one or more apertures defined by the funnel so that some of the exhaust gas can bypass the output end of the funnel. Advantageously, by allowing some of the exhaust gas to bypass the output end of the funnel or the funnel as a whole, backpressure caused by the exhaust gas mixer may be reduced.

[0061] The apparatus may comprise a fitting configured to mount and seal the exhaust gas mixer onto a maintenance lid opening in place of the maintenance lid. The fitting may simplify upgrading of existing combustion engines to improve the mixing of the reactant without need to cut out materials and clean resulting machining waste. The fitting may also enable a compact and thermally efficient structure produced by upgrading existing combustion engines.

[0062] According to a third example aspect there is provided an exhaust gas treatment system. The system may comprise the exhaust gas aftertreatment apparatus. The system may comprise a diesel oxidation catalysts, DOC. The system may comprise a diesel particulate filter, DPF. The system may comprise a selective catalytic reduction, SCR, catalyst. The system may comprise the reactant doser.

[0063] According to a fourth example aspect there is provided a method for mixing exhaust gas, comprising: receiving by a funnel exhaust gas from an input end of the funnel and guiding the exhaust gas towards an output end of the funnel, wherein the output end is opposite to the input end; and guiding exhaust gas by a flow guide at least partially inside the funnel through the funnel to advance as a rotating perimetrical flow such that downstream from funnel, the exhaust gas will be exposed to a lower pressure in a core region than in a perimeter region.

[0064] According to a fifth example aspect there is provided a method for exhaust gas aftertreatment comprising: supporting a funnel and a reactant doser mount to a housing; receiving by the funnel exhaust gas from an input end of the funnel and guiding the exhaust gas towards an output end of the funnel, the funnel comprising an input end towards the first side and an output end towards the second side, wherein the output end is opposite to the input end; guiding exhaust gas by a flow guide at least partially inside the funnel through the flow guide and the output end to advance as a rotating perimetrical flow such that downstream from flow guide, the exhaust gas will be exposed to a lower pressure in a core region than in a perimeter region; and supporting a reactant doser by a reactant doser positioned downstream from the output end of the funnel such that when in use, the reactant doser injects reactant to the core region towards the output end the funnel.

[0065] The method may further comprise supporting by the housing a substrate upstream from the funnel. The housing may contain the substrate.

[0066] Different non-binding example aspects and embodiments have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in different implementations. Some embodiments may be presented only with reference to certain example aspects. It should be appreciated that corresponding embodiments may apply to other example aspects as well.

[0067] BRIEF DESCRIPTION OF THE FIGURES

[0068] Some example embodiments will be described with reference to the accompanying figures, in which:

[0069] Fig. 1 shows a sectional illustration of an exhaust gas aftertreatment apparatus according to an example embodiment;

[0070] Fig. 2 shows another illustration of the exhaust gas aftertreatment apparatus of Fig. 1 ;

[0071] Figs. 3A and 3B illustrate an exhaust gas aftertreatment apparatus according to an example embodiment with different views;

[0072] Figs. 4A to 4E illustrate different views of a flow guide according to an example embodiment;

[0073] Figs. 5A to 5C illustrate an exhaust gas aftertreatment apparatus according to an example embodiment with different views;

[0074] Figs. 6A to 6D illustrate an exhaust gas mixer according to an example embodiment;

[0075] Fig. 7 shows a block diagram of an exhaust gas treatment system;

[0076] Fig. 8 shows a flow chart of a method according to an example embodiment for exhaust gas aftertreatment;

[0077] Fig. 9 illustrates a simulation of exhaust gas flow in and around a funnel of the flow guide with a first sectional view; and

[0078] Figs. 10 and 11 illustrate further simulations of exhaust gas flow at an output of the flow guide.

[0079] DETAILED DESCRIPTION

[0080] In the following description, like reference signs denote like elements or steps.

[0081] Fig. 1 shows a sectional illustration of an exhaust gas aftertreatment apparatus 100 according to an example embodiment, comprising an exhaust gas mixer 101 , a preferably cylindrical housing 110, and a reactant doser mount 150.

[0082] Notably, Fig. 1 does not only show sectioned surfaces but rather an illustration of a piece if sectioned and omitting some details for simplicity of drawing. The exhaust gas mixer 101 comprises a funnel 130 configured to receive exhaust gas from an input end 132 of the funnel and to guide the exhaust gas towards an output 134 end of the funnel 130, wherein the output end is opposite to the input end; and a flow guide 140 residing inside the funnel 130 and being configured to guide exhaust gas flowing through the funnel 140 to advance as a rotating perimetrical flow such that downstream from flow guide 140, the exhaust gas will be exposed to a lower pressure in a core region C than in a perimeter region P.

[0083] Fig. 1 further shows a first end 112 and a second end 114 of the housing 110, and a substrate 120 extending from the first end 112 towards the second end 114.

[0084] In an example embodiment, the reactant doser mount 150 is attached to the second end of the housing 110, as shown in Fig. 1 with a reactant doser 160 mounted to the reactant doser mount 150.

[0085] In an example embodiment, the reactant doser mount 150 is configured to position the reactant doser 160 downstream from the output end 134 of the funnel 130 such that when in use, the reactant doser 160 injects reactant to the core region C towards output end 134 of the funnel 130, as illustrated by a spray pattern 164.

[0086] In an example embodiment, the reactant doser mount 150 is configured to position the reactant doser 160 downstream from the output end 134 of the funnel 130 such that when in use, the reactant doser 160 injects reactant through the output end 134 of the funnel 130 towards the input end. In an example embodiment, the reactant doser mount 150 is configured to position a tip 162 of the reactant doser 160 into the housing 110.

[0087] In an example embodiment, the reactant doser mount 150 is configured to position the reactant doser 160 downstream from the output end 134 of the funnel 130 such that reactant will be dosed at a direction of 180 degrees with relation to a general flow direction of the exhaust gas across the exhaust gas flow at the output end 134 of the funnel 130.

[0088] Fig. 1 illustrates the core region C and surrounding perimeter region P with a dashed line so as to provide some illustration of these regions. It should be noted that the forming of these regions may depend on the shapes and dimensions of the funnel 130 and the flow guide 140, and even on flow rate and temperature of the exhaust gas that flows through the funnel 130. Moreover, the core region C appears as a narrowing shape, but again it should be noted that the exhaust gas would not distribute evenly in the funnel 130, but instead be packed to the perimeter region P by the flow guide 140 such that pressure in the core region C will be far lower than in the perimeter region P. The structural details of the exhaust gas aftertreatment apparatus 100 and various embodiments will next be described with further detail.

[0089] In an example embodiment, as also in Fig. 1 , the funnel 130 is a double-sided funnel. That is, the funnel 130 is like two funnels against each other or a passage that narrows down in two opposite directions.

[0090] In an example embodiment, the funnel 130 has a narrowing input portion 136. In an example embodiment, the input portion has a curved cross-section. In an example embodiment, the input portion 136 has an at least double curved cross-section. In an example embodiment, the input portion 136 comprises a concave sub-portion 136C with a concave cross-section facing towards the substrate 120. In an example embodiment, the input portion 136 comprises a convex sub-portion 136V with a convex cross-section facing towards exhaust gas that passes by the input portion 136. In an example embodiment, the cross-section of the funnel 130 is convex from the convex sub-portion 136V to the output end 134 of the funnel 130, as shown in Fig. 1. In an example embodiment, the convex cross-section defines a throat of the funnel 130. In Fig. 1 , dashed aid lines are drawn solely to facilitate indication of these portions. These dashed lines, like the dashed lines indicating an imaginary boundary between the core region C and the surrounding perimeter region P, do not represent structural parts of the exhaust gas aftertreatment apparatus 100.

[0091] In an example embodiment, the flow guide 140 resides within the concave sub-portion 136V. Alternatively, the flow guide 140 resides partially within the concave sub-portion 136. In an example embodiment, the flow guide 140 extends from the concave sub-portion 136 towards the output end 134 of the funnel 130. In an example embodiment, the flow guide 140 extends from the concave sub-portion 136 towards or beyond the output end 134 of the funnel 130. For example, there may be a gap (not in the example embodiment illustrated by Fig. 1 ) between the funnel 130 and the substrate 120, and the flow guide 140 may partly extend into that gap. In another example embodiment, the flow guide 140 resides between the substrate 120 and the funnel 130, although positioning the flow guide into the funnel may advantageously synergically save space and enhance the efficiency of exhaust gas rotating in comparison to backpressure induced.

[0092] Advantageously, the funnel 130 is adjacent to the substrate 120 so that the exhaust gas aftertreatment apparatus 100 can be made more compact than otherwise. Alternatively, a gap (not shown) is left between the funnel 130 and the substrate 120. The funnel 130 may help supporting a second end of the substrate 120. The gap may simplify construction by increasing tolerance and assembly tolerance. In an example embodiment, the exhaust gas output by the substrate 120 is directly received by the funnel 130 without intervening components.

[0093] In an example embodiment, the input end 132 of the funnel 130 fills the housing 110 so that all exhaust gas output by the substrate 120 is pressure forced to pass through the input 132 end of the funnel 130. The input end 132 of the funnel may comprise a sealing and I or other filling components to facilitate filling the housing 110 (not shown).

[0094] In an example embodiment, the flow guide 140 comprises a plurality of vanes 142, such as two, three, four, five or more. In an example embodiment, the vanes 142 are curved. Fig. 2 shows another illustration of the exhaust gas aftertreatment apparatus 100 of Fig. 1.

[0095] In an example embodiment, the vanes 142 extend inwardly to a joint hub 210. The hub may define an aperture, e.g., at a centre of the hub 210. In an example embodiment, the vanes 142 extend outwardly to a perimeter of the funnel 130. In an example embodiment, the vanes 142 are strips. In an example embodiment, the strips have a substantially constant width for most of their length. In an example embodiment, the vanes 142 are configured to form a planar central portion 220 in which the vanes 142 extend radially outwards from the hub 210. In an example embodiment, the vanes 142 are evenly positioned to different radial directions. In an example embodiment, the vanes 142 are configured to tangentially approach the perimeter of the funnel 130. In an example embodiment, the vanes 142 are twisted so that after the central portion 220, the vanes 142 have flat surfaces aligned with the longitudinal direction of the housing 110. In an example embodiment, the vanes 142 are twisted by 90 degrees. In an example embodiment, the vanes 142 define negative blades 230 around the central portion 220. Advantageously, the vanes 142 in conjunction with the funnel 130 may define a rotating passage for the exhaust gas such that the exhaust gas are forced to rotate very efficiently and with a small backpressure.

[0096] In an example embodiment, the vanes 142 are made a metal sheet or plate. In an example embodiment, the vanes 142 are made of steel. In an example embodiment, the vanes 142 are welded together at the hub 210. Alternatively, or additionally, the vanes 142 are joined to each other at the hub 210 by bending ends of the vanes 142 onto one or more adjacent vanes 142. Such joining may leave an aperture, such as a relatively small aperture with diameter smaller than the vanes 142 are wide, at the hub 210. Alternatively, or additionally, the vanes 142 are joined to each other at the hub 210 by a bolt and nut configured to squeeze the ends of the vanes 142 to a hub 210 system formed with the bolt. Tips or downstream portions of the negative blades 230 are at least partially welded to the funnel 130. In an example embodiment, the vanes 142 double as a support or grille for the substrate 120, or as a stopper for simplifying assembly of the apparatus 100 by preventing the substrate 120 settling too deep towards the second end 114 of the housing 110.

[0097] In an example embodiment, the funnel 130 comprises an expanding output portion 138 (Fig. 1 ) subsequent to the throat of the funnel 130. In an example embodiment, the expanding output portion 138 has a convex cross-section towards exhaust gas that passes through the funnel 130.

[0098] Advantageously, the expanding output portion 138 may further emphasise pressure difference between the core region C and the perimeter region P. The emphasising of the pressure difference may further increase travel of the injected reactant in the funnel 130. The emphasising of the pressure difference may reduce risk of accruing some of the injected reactant onto surfaces inside the funnel 130. Further advantageously, the expanding output portion 138 may reduce backpressure caused by turning exhaust gas approaching the second end 114 of the housing 110 to a radial direction of the housing 110.

[0099] In an example embodiment, the flow guide 140 and shaping of the funnel 130 is configured to cause a backflow in the core region C towards the flow guide 140.

[0100] In an example embodiment, the flow guide 140 comprises an inhibitor configured to inhibit the core flow in comparison to the flow in the perimeter region P, such as the hub 210.

[0101] In an example embodiment, the core region C comprises an innermost portion of a cross- section of the funnel 130 immediately downstream of the flow guide 140. In an example embodiment, the innermost portion comprises at least 5 %, 10 %, or 20 % of a surface area of said cross-section. In an example embodiment, the innermost portion comprises at most 10 %, 20 %, or 50 % of the surface area of said cross-section.

[0102] In an example embodiment, the perimeter region P comprises an outmost portion of a crosssection of the funnel 130 immediately downstream of the flow guide 140. In an example embodiment, the outermost portion comprises at least 5 %, 10 %, or 20 % of a surface area of said cross-section. In an example embodiment, the outermost portion comprises at most 10 %, 20 %, or 50 % of the surface area of said cross-section.

[0103] Advantageously, the flow guide 140 may increase injection range of the reactant against reactant gas flowing through the funnel 130 for increasing dwell time of the reactant within the funnel 130 and mixing of the reactant with the exhaust gas.

[0104] In an example embodiment, the funnel 130 is linear or conical.

[0105] In an example embodiment, the core region C is coaxial with the longitudinal direction of the funnel 130.

[0106] In an example embodiment, the substrate 120 occupies most of internal space of the housing 110. In an example embodiment, the substrate 120 extends over at least 50 %, 60 %, or 70 % of an internal length of the housing 110.

[0107] In an example embodiment, the housing 110 comprises an exit opening 170. In an example embodiment, the exit opening 170 is an output pipe connection. In an example embodiment, the exit opening 170 is perpendicularly with relation to longitudinal direction of the housing 110. In an example embodiment, the exit opening 170 resides such that the exit opening 170 is aligned in a longitudinal direction with the funnel 130 or at least most of the funnel 130, such as 60 %, 80 %, or 90 %.

[0108] Advantageously, the funnel 130 may define a neck at the throat such that inner surfaces of the funnel 130 help in forming a low pressure in the core region C to improve reactant entry while the neck shape on an outer surface of the funnel 130 helps in forming a spacious channel 116 (Fig. 1 ) around the funnel 130 for the exhaust gas to flow into the exit opening 170. Advantageously, the exhaust gas aftertreatment device may provide a plurality of synergic effects by same parts for the general objective of mixing reactant with exhaust gas with a small backpressure, small space consumption, good mixing results, and low risk of residue accumulation. The spacious channel 116 advantageously provides a peripheral outlet channel for further mixing the reactant with the exhaust gas before output through the exit opening 170. This is subsequently discussed in further detail with reference to Figs. 9 to 11.

[0109] In an example embodiment, the first end 112 is a logical end defining an end for a space that houses the substrate 120 and subsequent parts within the housing 110. In an example embodiment, the housing 110 extends from the second end 114 beyond the first end 112 and comprise empty space or other parts beyond the substrate 120. Alternatively, the housing 110 has an end wall at the first end 112, and an entry opening for exhaust gas to enter the housing 110 and the substrate 120 therein.

[0110] In an example embodiment, the funnel 130 is configured to receive all the exhaust gas that has passed through the substrate 120. Alternatively, the funnel 130 is configured to receive a portion such as most of the exhaust gas that has passed through the substrate 120.

[0111] Figs. 3A and 3B illustrate an exhaust gas aftertreatment apparatus 300 according to an example embodiment with different views. Fig. 3A shows a top view showing a second end 310 of a mixing chamber 320 (Fig. 3B); output pipe connection 330; and doser mount 340 or screw holes and opening for the doser (not shown).

[0112] Fig. 3B shows a section drawing of the exhaust gas aftertreatment apparatus 300 of Fig. 3A, illustrating a space 350 for receiving at least a portion of the substrate (not shown) or for operating as receiving chamber for exhaust gas that has passed through the substrate. A swirl element 360 is formed of a plurality of plates. An inhibitor or a core flow block 370 is also shown, here formed of a plate that may be, for example, a circular disc. In an example embodiment, the core flow block is fixed, e.g., by welding, to the swirl element 360. In an example embodiment, the core flow block functions both as a blocking element to inhibit core flow so as to advance dosing of the reactant further and allow the reactant to better evaporate, and as a structural support for the swirl element 360 to inhibit damage caused by, for example, fatigue stress, when the exhaust gas aftertreatment apparatus is exposed to vibrations induced by a combustion engine, its accessory devices, and various bumps experienced by a vehicle or tool equipped with combustion engine. Fig. 3B further illustrates an alternative narrowing input portion 136’, and an alternative expanding output portion 138’ of the funnel, here with linear or substantially linear profile (frustocone shape).

[0113] Figs. 4A to 4E illustrate an exhaust gas mixer 401 of an example embodiment. Figs. 4A and 4B show the alternative narrowing input portion 136’ and the alternative expanding output portion 138’ of the funnel. Figs. 4C and 4E show views from bottom and top, respectively.

[0114] Figs. 4A to 4E illustrate different views of a flow guide of an example embodiment. In an example embodiment, this flow guide is used in the exhaust gas aftertreatment apparatus 300 of Fig. 3A. Figs. 4C and 4D in particular illustrate how the swirl guide may be implemented using plates that have a single bend. Fig. 4C illustrates that how the flow guide may entirely block visual access from the doser mount or the doser to the substrate.

[0115] Figs. 5A to 5C illustrate an exhaust gas aftertreatment apparatus according to an example embodiment with different views. This exhaust gas aftertreatment apparatus illustrates an upgrading solution provided by an example embodiment in which the apparatus comprises a fitting 510 configured to mount and seal a funnel 540, flow guide 550, and the reactant doser mount 520 onto a maintenance lid opening in place of the maintenance lid (not shown, removed). The fitting 510 may simplify upgrading of existing combustion engines to improve the mixing of the reactant without need to cut out materials and clean resulting machining waste. The fitting 510 may also enable a compact and thermally efficient structure produced by upgrading existing combustion engines.

[0116] Fig. 5C illustrates the flow guide 550 with a plurality of tubelets 560. Fig. 5C also illustrates a path 570 for exhaust gas to enter an original mixing pipe 580, and a different expanding output portion 138”. In an example embodiment, the expanding output portion is connected to the narrowing input portion by an intermediate portion. In an example embodiment, the intermediate portion is cylindrical.

[0117] Fig. 5B further shows an old reactant doser mount 530 that is made redundant by the new reactant mount 520 positioned in the upgraded exhaust gas aftertreatment apparatus. In an example embodiment, the old reactant doser mount 530 is blocked by attaching a dummy shaped as the doser, or at least parts of the doser that seal an adjacent wall.

[0118] Figs. 6A to 6D illustrate an exhaust gas mixer 601 of an example embodiment. The exhaust gas mixer 601 is made of a funnel 610 and a flow guide 620. The flow guide 620 is made of a single sheet by bending partially cut pieces that when bent worm vanes 630. Cut-outs of the vanes define respective passage openings 640. In an example embodiment, the flow guide 620 is attached to the funnel 610 at a peripheral rim of the flow guide 620. In an example embodiment, the flow guide 620 is additionally or alternatively attached to the funnel 610 through the vanes 630. The attachment through vanes may reduce resonance noise and / or fatigue wear.

[0119] In an example embodiment, the funnel 610 is formed of single sheet. In an example embodiment, the funnel 610 is formed of two pieces. In an example embodiment, the funnel 610 is formed by attaching a tube 650 to a frustocone 660, e.g., by welding. Fig. 6C further illustrates an optional bypass 670 that may be formed by one or more apertures defined by the funnel 610 so that some of the exhaust gas can bypass the output end of the funnel 610. Such a bypass may be useful to reduce backpressure caused by exhaust gas mixer by facilitating flow of the exhaust gas while still guiding a sufficient amount of the exhaust gas through the output end in the rotating and advancing flow that has the reduced core flow pressure so that the dosed reactant properly evaporates and accumulation issues may be avoided. Advantageously, the bypass may serve this purpose also by increasing pressure of the exhaust gas around the core region.

[0120] In an example embodiment, a bypass is formed around the funnel 610, e.g., by leaving a gap between inner wall of the housing and the funnel, for a similar effect of reducing backpressure caused by the exhaust gas mixer while providing a sufficient efficiency of the mixing of the reactant with the exhaust gas and avoiding accumulation of the reactant onto any surfaces in the exhaust gas treatment.

[0121] Fig. 7 shows a block diagram of an exhaust gas treatment system 700 comprising: a diesel oxidation catalysts, DOC, 710; a diesel particulate filter, DPF, 720; a mixer 730 having a cone and flow guide, e.g., as disclosed in the foregoing, and including the reactant doser 160; a selective catalytic reduction, SCR, and catalyst 740. Fig. 7 is purely illustrative of various possible components in the exhaust gas treatment system 700, so some of these components may be omitted, the order may be changed, and / or further components may be present in other implementations.

[0122] Fig. 8 shows a flow chart of a method according to an example embodiment for exhaust gas aftertreatment, comprising any one or more of:

[0123] 810: receiving by a funnel exhaust gas from an input end of the funnel and guiding the exhaust gas towards an output end of the funnel, the funnel comprising an input end towards the first side and an output end towards the second side, wherein the output end is opposite to the input end; and

[0124] 820: guiding exhaust gas by a flow guide at least partially inside the funnel through the funnel to advance as a rotating perimetrical flow such that downstream from flow guide, the exhaust gas will be exposed to a lower pressure in a core region than in a perimeter region.

[0125] Fig. 9 illustrates a simulation of exhaust gas flow in and around a funnel of the flow guide with a first sectional view. As also seen and mentioned in connection with Fig. 1 , at the output end of the funnel 130, a spacious peripheral outlet channel 116 is formed around the outer surface of the funnel 130, for directing exhaust gas from around the funnel 130 out of the funnel through one or more outputs of the peripheral outlet channel 116. On outer side, the peripheral outlet channel 116 may be defined by an inner wall of the mixing chamber 320. The peripheral outlet channel 116 is separated from a space defined by the interior of the funnel 130 by an annular gap that resides between the output end of the funnel 130 and the rear end of the mixing chamber 320.

[0126] In an example embodiment illustrated by Figs. 3 and 9, the exhaust gas arriving from the funnel 130 (through the annular gap) is forced to turn back along the rear end of the mixing chamber 130 and then again along an external surface of the funnel 130 into a circulating flow 910. The circulating flow 910 rotates in a peripheral outlet channel 116 around a perimeter that runs around the funnel 130. The circulating flow 910 has a spiral track, as the exhaust gas first runs along the inner surface of the mixing chamber 320 and along the outer surface of the funnel 130, and thereafter with a decreasing average radius.

[0127] Fig. 9 illustrates that the peripheral outlet channel 116 need not have a circular crosssection, although that is also provided in an example embodiment by suitably shaping the funnel 130 and the mixing chamber 320, or by adding suitable additional one or more walls to make the peripheral outlet channel 116 toroid shaped.

[0128] As the exhaust gas cannot just rotate along the spiral track at the same perimetrical point, the exhaust gas also moves perimetrically along the peripheral outlet channel 116 towards and out of the output 920 (or plurality of outputs, if so implemented).

[0129] Figs. 10 and 11 illustrate further simulations of exhaust gas flow at an output of the flow guide. These drawings illustrate that how the exhaust gas flows in the outlet channel first in the circulating flow 910 at a perimetry and then at a central region also or to a far greater extent perimetrically towards the outlet and through the outlet in an outlet flow 1110.

[0130] Figs. 9 to 11 demonstrate that how mixing can be made particularly space-efficiently by dosing the reactant into the funnel and thereafter circulating the exhaust gas around the peripheral outlet channel 116 as the circulating flow 910 and also peripherally along the peripheral outlet channel 116.

[0131] According to a third example aspect there is provided an exhaust gas treatment system. The system comprise the exhaust gas aftertreatment apparatus 100. In an example embodiment, the system comprises a diesel oxidation catalysts, DOC. In an example embodiment, the system comprises a diesel particulate filter, DPF. In an example embodiment, the system comprises a selective catalytic reduction, SCR, catalyst. In an example embodiment, the system comprises the reactant doser 160.

[0132] Various embodiments have been presented. It should be appreciated that in this document, words comprise; include; and contain are each used as open-ended expressions with no intended exclusivity.

[0133] The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. However, the invention is not restricted to details presented in the foregoing, but implementable in other embodiments using equivalent means or in different combinations of embodiments.

[0134] Furthermore, some of the features of the afore-disclosed example embodiments may be used to advantage without the corresponding use of other features. The foregoing shall be considered as merely illustrative of the principles of the present invention, and not in limitation, so only the appended claims limit the scope of the invention.

Claims

CLAIMS1 . An exhaust gas mixer (101 ), comprising a funnel (130) configured to receive from an input end (132) of the funnel (130) and to guide the exhaust gas towards an output end (134) of the funnel (130), wherein the output end (134) is opposite to the input end (132); and a flow guide (140) residing inside the funnel (130) and configured to guide exhaust gas flowing through the funnel (130) to advance as a rotating perimetrical flow such that downstream from flow guide (140), the exhaust gas will be exposed to a lower pressure in a core region (C) than in a perimeter region (P).

2. The exhaust gas mixer (101 ) of claim 1 , wherein the funnel (130) has a narrowing input portion that has a curved cross-section.

3. The exhaust gas mixer (101 ) of claim 2, wherein the input portion comprises a concave sub-portion (136) with a concave cross-section facing towards the substrate (120).

4. The exhaust gas mixer (101 ) of claim 3, wherein the flow guide (140) resides within the concave sub-portion (136).

5. The exhaust gas mixer (101 ) of any one of claims 1 to 4, wherein the input end of the funnel (130) fills the housing (110) so that all exhaust gas output by the substrate (120) is pressure forced to pass through the input end (132) of the funnel (130).

6. The exhaust gas mixer (101 ) of any one of claims 1 to 5, wherein the flow guide (140) comprises a bypass for some of the exhaust gas to bypass the output end of the funnel (130) or the funnel (130).

7. The exhaust gas mixer (101 ) of any one of claims 1 to 6, wherein the flow guide (140) comprises a plurality of vanes (142).

8. The exhaust gas mixer (101 ) of any one of claims 1 to 7, wherein the flow guide (140) further comprises a plurality of tubelets configured to guide the exhaust gas in the funnel (130) to rotate around a longitudinal axis of the funnel (130).

9. The exhaust gas mixer (101 ) of any one of claims 1 to 8, wherein the flow guide (140) further comprises an inhibitor (370) configured to inhibit the core flow in comparison to the flow in the perimeter region.

10. The exhaust gas mixer (101 ) of any one of claims 1 to 9, wherein the reactant doser mount (150) is configured to position the reactant doser (160) downstream from the output end of the funnel such that when in use, the reactant doser (160) injects reactant throughthe output end (134) of the funnel (130) towards the input end.11 . The exhaust gas mixer (101 ) of any one of claims 1 to 10, wherein the exhaust gas mixer (101 ) further comprises a peripheral outlet channel (116) around the funnel (130); and the peripheral outlet channel (116) is configured to receive the exhaust gas from different sides of the funnel (130) and cause that the exhaust gas rotates around a core of the peripheral outlet channel (116) and moves along the peripheral outlet channel for exiting the exhaust gas mixer (101 ).

12. An exhaust gas aftertreatment system (100), comprising the exhaust gas mixer of any one of preceding claims; a housing (110) comprising a first end (112) and a second end (114); and a reactant doser mount (150) for a reactant doser (160); wherein the reactant doser mount (150) is configured to position the reactant doser (160) downstream from the output end (134) of the funnel (130) such that when in use, the reactant doser (160) injects reactant to the core region (C) towards the output end (134) of the funnel (130).

13. The exhaust gas aftertreatment system (100) of claim 12, further comprising a substrate (120) extending from the first end (112) of the housing (110) towards the second end (114) of the housing (110) and contained by the housing (110) such that the funnel (130) receives exhaust gas through the substrate (120).

14. An exhaust gas treatment system (700) of claim 12 or 13, comprising at least one of: a diesel oxidation catalysts, DOC, (710); a diesel particulate filter, DPF, (720); a selective catalytic reduction, SCR, catalyst (740); or the reactant doser (160).

15. A method for exhaust gas aftertreatment comprising: receiving (810) by a funnel (130) exhaust gas from an input end (132) of the funnel and guiding the exhaust gas towards an output end (134) of the funnel, wherein the output end (134) is opposite to the input end (132); and guiding (820) exhaust gas by a flow guide (140) at least partially inside the funnel (130) through the funnel (130) to advance as a rotating perimetrical flow such that downstream from flow guide, the exhaust gas will be exposed to a lower pressure in a core region than in a perimeter region.

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