Counterflow exhaust gas after treatment mixer

Abstract

A flow guide and a method for exhaust gas after treatment. Incoming exhaust gas is input to a mixing tube (120) and outgoing exhaust gas is output from the mixing tube (120) by an input end (122), and an output end (124), respectively (1210). Exhaust gas is guided (1220) by a core flow guide (130) inside the mixing tube such that downstream from the core flow guide (130), the exhaust gas is exposed to a lower pressure in a core region (C) than in a perimeter region (P). Reactant is dosed (1230) by a reactant doser (150) via the core region (C) towards a downstream side of the core flow guide (130).

Description

[0001] COUNTERFLOW EXHAUST GAS AFTERTREATMENT MIXER

[0002] TECHNICAL FIELD

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

[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) how to 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 a flow device for exhaust gas aftertreatment, comprising a mixing tube comprising an input end and an output end for incoming and outgoing exhaust gas, respectively; a core flow guide residing inside the mixing tube and being configured to guide exhaust gas such that downstream from core flow guide, the exhaust gas will be exposed to a lower pressure in a core region than in a perimeter region; and a reactant doser mount for a reactant doser; wherein the reactant doser mount is configured to position the reactant doser such that when in use, the reactant doser injects reactant via the core region towards a downstream side of the core flow guide.

[0011] The reactant doser mount may be configured to position the reactant doser such that when in use, the reactant doser injects reactant through the output end of the mixing tube towards the input end.

[0012] The reactant doser mount may be configured to position the reactant doser such that when in use, the reactant doser injects reactant through a side wall of the mixing tube to the core region.

[0013] The core flow guide and shaping of the mixing tube may be configured to cause a backflow in the core region towards the core flow guide.

[0014] The core flow guide may comprise an inhibitor configured to inhibit the core flow in comparison to the flow in the perimeter region. Alternatively, or additionally, the core flow guide may comprise one or more elements configured to guide exhaust gas towards to the perimeter region. The core flow guide may comprise a swirl element configured to pack exhaust gas onto the perimeter region.

[0015] The core flow guide may comprise or be a rotating core flow guide that comprises a swirl structure that causes exhaust gas to rotate in the mixing tube.

[0016] The reactant doser may inject the reactant at an angle of 0 to 90 degrees relative to a line drawn between a tip of the reactant doser and a mass centre of the core flow guide. The core region may comprise an innermost portion of a cross-section of the mixing tube immediately downstream of the core flow guide. The innermost portion may comprise at least 5 % or 10 % of a surface area of said cross-section. The innermost portion may comprise at most 10 % or 20 % of the surface area of said cross-section.

[0017] The perimeter region may comprise an outmost portion of a cross-section of the mixing tube immediately downstream of the core 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.

[0018] Advantageously, the core flow guide may increase injection range of the reactant against reactant gas flowing through the mixing tube for increasing dwell time of the reactant within the mixing tube and mixing of the reactant with the exhaust gas.

[0019] The core flow guide may have a shape capable of reducing swirl of the exhaust gas in the core region. The core flow guide may have a shape capable of reducing swirl of the exhaust gas in the perimeter region.

[0020] The core flow guide may have a shape capable of increasing swirl of the exhaust gas in the core region. The core flow guide may have a shape capable of increasing swirl of the exhaust gas in the perimeter region.

[0021] The mixing tube may comprise an expanding portion between the core flow guide and the output end. The expanding portion may be expanding as of a beginning of the expanding portion up to the output end. The expanding portion may be conical.

[0022] 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 mixing tube. The emphasising of the pressure difference may reduce risk of accruing some of the injected reactant onto surfaces inside the mixing tube.

[0023] The core flow guide may comprise one or more, such as three or more, fingers that are pointed towards different radial directions. In case of only one finger, that finger may be pointed to only one radial direction. The three or more fingers may have a constant angular difference. The three or more fingers may have converging ends and remote ends. The converging ends of the fingers may reside closer to the output end than remote ends of the fingers.

[0024] The mixing tube may be linear. Advantageously, a linear mixing tube may help to mitigate a risk of accruing some of the reactant onto surfaces inside the mixing tube. The core region may be coaxial with the mixing tube.

[0025] The reactant doser mount may be configured to position the reactant doser 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 a tip of the reactant doser.

[0026] Alternatively, the mixing tube may be curved. Advantageously, a curved mixing tube may space efficiently occupy free space inside an engine room and I or direct the output to a desired direction other than that from which the mixing tube receives the exhaust gas.

[0027] The core region may reside asymmetrically with relation to the mixing tube. The core region may reside closer an outer curve of the mixing tube than the inner curve of the mixing tube.

[0028] The reactant doser mount may be configured to position the reactant doser such that reactant will be dosed at a direction of 120 to 170 degrees with relation to the general flow direction of the exhaust gas across the exhaust gas flow at the tip of the reactant doser.

[0029] In an example embodiment, the mixing tube has a constant cross-section area through the length of the mixing tube. Advantageously, a constant cross-section area may help to space-effectively transfer the exhaust gas in the flow guide.

[0030] In an example embodiment, the mixing tube has a constant cross-section shape through the length of the mixing tube. Advantageously, a constant cross-section shape may help to control lateral flow components of the exhaust gas in the mixing tube.

[0031] In an example embodiment, the mixing tube has a longitudinally varying cross-section shape or area. Advantageously, by longitudinally varying the cross-section shape or area of the mixing tube, the exhaust gas flows inside the mixing tube may be controlled to form a desired core flow and perimeter flow balance.

[0032] The flow device may comprise an input flow swirl guide configured to cause exhaust gas to flow in the mixing tube from the input end towards the core flow guide while rotating along inner surface of the mixing tube. The input flow swirl guide may comprise one or more tangential guides configured to receive the exhaust gas from a direction that is perpendicular to the input end of mixing tube.

[0033] The mixing tube may be formed of a pipe that faces exhaust gas solely by interior surfaces of the mixing tube. The mixing tube may be flexible. The mixing tube may comprise a flexible portion. The input end of the mixing tube may be rigidly connected to a combustion engine. The output end of the mixing tube may be rigidly connected to a body to which the combustion engine is supported by one or more vibration dampening elements. Alternatively, the mixing tube may reside in a mixing chamber.

[0034] The core flow guide may reside between the input end and the output end such that a mass centre of the core flow guide is closer to the input end than to the output end. The core flow guide may be spaced apart from the input end. The mass centre of the core flow guide may be spaced apart from the input end by a lead distance djn. The lead distance may be at least 20 %; 30 %; or 40 % of a total length of the core flow guide. The core flow guide may reside at least partially in the flexible mixing tube or the flexible portion of the mixing tube. The mass centre of the core flow guide may reside in the flexible portion of the mixing tube.

[0035] Advantageously, by bringing the core flow guide closer to the doser than the input end, the core flow guide may provide a stronger central region pressure reducing impact such that mixing of the reactant is enhanced by extending a reach of the doser so allowing the reactant to better evaporate before coming into contact with any surfaces. It is somewhat surprising that for reducing accrual of reactant onto surfaces, it may be better to bring the surfaces of the core flow guide closer to the doser.

[0036] The mixing chamber may surround at least an input end of the mixing tube. The mixing tube may reside perpendicularly in the mixing chamber or so that the input end of the mixing tube is perpendicularly in the mixing chamber.

[0037] The core flow guide may be configured to receive, when in operation, all the incoming exhaust gas entering through the input end. Alternatively, some of the incoming exhaust gas may be allowed to bypass the core flow guide. Further alternatively, some exhaust gas may be additionally input to the mixing tube through one or more apertures between the input end and the core flow guide.

[0038] The output end may be configured to output, when in operation, all the exhaust gas that has passed the core flow guide through the output end. Alternatively, some of the exhaust gas that has passed the core flow guide may be allowed to bypass the output end of the mixing tube. Further alternatively, some exhaust gas may be additionally input to the mixing tube through one or more apertures between the core flow guide and the output end.

[0039] The mixing tube may comprise one or more apertures providing an additional exit from the mixing tube to the mixing chamber. Advantageously, by providing one or more apertures upstream from the core flow guide, back pressure caused by the flow device may be reduced. Alternatively, or additionally, the mixing tube may comprise one or more apertures downstream from the core flow guide. Advantageously, such apertures may help to balance output of the flow device to a desired field, contribute to reducing pressure in the core region, or reduce back pressure of the flow device.

[0040] The flow device may comprise a turning cup configured to receive and turn to a radial or reverse direction exhaust gas from the output end. The turning cup may comprise a cap configured to produce a donut shaped exhaust gas exit between the cap and the inner surface of the mixing tube at the output end. The cap may comprise a concave section facing the donut shaped exhaust gas exit. The cap may comprise a convex section. The cap may extend into the output end of the mixing tube. The convex section may reside inside the output end of the mixing tube. The concave section may reside downstream from the output end of the mixing tube.

[0041] The turning cup may comprise a donut shaped protrusion on a rear wall of the mixing chamber opposite to the output end of the mixing tube. The donut shaped protrusion may have an outmost radius that is smaller than an inner radius of the output end of the mixing tube. The donut shaped protrusion may be separated by a longitudinal gap from a plane defined by the output end of the mixing tube.

[0042] A crown may surround the reactant doser when mounted. The crown may reside between the donut shaped protrusion and the reactant doser when mounted. The crown may comprise a plurality of teeth separated by gaps. The gaps may extend between through entire length of the crown.

[0043] The reactant doser mount may be adjacent to the convex section.

[0044] The mixing chamber may be cylindrical. The mixing chamber may surround the mixing tube such that exhaust gas exiting the mixing tube is directed to an open end of the mixing chamber. The open end of the mixing chamber may have a similar surface area with a cross-section of the mixing chamber between the mixing tube and the open end. The open end may be configured to receive a mouth of an exhaust gas filter.

[0045] The mixing tube may be configured to direct exhaust gas through the output end in a general direction that is perpendicular to the open end of the mixing chamber. The mixing tube may be configured to direct exhaust gas through the output end in a general direction that leads to some extent to a side of the mixing chamber that is opposite to the open end of the mixing chamber.

[0046] The mixing chamber may comprise an output pipe connection. The output pipe connection may be perpendicularly with relation to longitudinal direction of the mixing tube at the input end. The output connection may reside such that the core flow guide is aligned with the output connection. The flow device may comprise a diffuser downstream from the mixing chamber. The diffuser may comprise an outwards opening conical section configured to reduce pressure of the exhaust gas at a central region of the diffuser. The diffuser may comprise a diffusing guide, e.g., a parallel guide adjacent to the mixing tube. The diffusing guide may have an elliptical or parabolic cross-section.

[0047] The flow device may be a mixer for mixing reactant with exhaust gas.

[0048] The core flow guide may be configured to inhibit exhaust gas flow in the core region such that the exhaust gas will be exposed to the lower pressure in the core region than in the perimeter region.

[0049] According to a second example aspect there is provided a method for exhaust gas aftertreatment comprising: inputting incoming exhaust gas to a mixing tube and outputting outgoing exhaust gas from the mixing tube by an input end, and an output end, respectively; guiding exhaust gas by a core flow guide inside the mixing tube such that downstream from core flow guide, the exhaust gas is exposed to a lower pressure in a core region than in a perimeter region; and dosing reactant by a reactant doser via the core region towards a downstream side of the core flow guide.

[0050] According to a third example aspect there is provided an exhaust gas treatment system. The system may comprise the flow device. The system may comprise a diesel oxidation catalysts, DOC. The system may comprise a diesel particulate filters, DPF. The system may comprise a selective catalytic reduction, SCR, catalyst. The system may comprise the reactant doser.

[0051] 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.

[0052] BRIEF DESCRIPTION OF THE FIGURES

[0053] Some example embodiments will be described with reference to the accompanying figures, in which:

[0054] Fig. 1 shows a sectional drawing of a flow device according to an example embodiment;

[0055] Fig. 2 shows a sectional drawing of a flow device according to another example embodiment;

[0056] Fig. 3 shows a sectional drawing of a flow device according to yet another example embodiment;

[0057] Fig. 4 shows a schematic drawing of a flow device according to still another example embodiment;

[0058] Fig. 5 shows an exhaust gas after treatment system according to an example embodiment; Figs. 6 to 9 show two different exhaust gas after treatment systems according to different example embodiments;

[0059] Figs. 10 and 11 illustrate a rotating core flow guide of an example embodiment; and

[0060] Fig. 12 shows a flow chart of a method according to an example embodiment for exhaust gas aftertreatment.

[0061] DETAILED DESCRIPTION

[0062] In the following description, like reference signs denote like elements or steps.

[0063] Fig. 1 shows a sectional drawing of a flow device 100 according to an example embodiment. The flow device 100 comprises a mixing tube 120 comprising an input end 122 and an output end 124 for incoming and outgoing exhaust gas, respectively; a core flow guide 130 residing inside the mixing tube and being configured to guide exhaust gas such that downstream from core flow guide 130, the exhaust gas will be exposed to a lower pressure in a core region C than in a perimeter region C; and a reactant doser mount 140 for a reactant doser 150; wherein the reactant doser mount 140 is configured to position the reactant doser 150 such that when in use, the reactant doser 150 injects reactant to via the core region C towards a downstream side of the core flow guide 130.

[0064] Fig. 2 shows a sectional drawing of a flow device 100’ according to another example embodiment, wherein an angle between the mixing tube and the mixing chamber or the output of the mixing chamber has been changed in comparison to that in Fig. 1.

[0065] Fig. 3 shows a sectional drawing of a flow device 100” according to yet another example embodiment, wherein reversing of exhaust gas is changed at the output of the mixing tube and also the subsequent guiding of the exhaust gas in the mixing chamber is changed in comparison to that in Fig. 1 .

[0066] Fig. 4 shows a schematic drawing of a flow device 100”’ according to yet another example embodiment, wherein the shape of the mixing tuber is changed in comparison to that in Fig. 1. In Fig. 4, the core flow guide 130 is schematically indicated by a circle without intent to indicate circular cross section for the core flow guide 130. As exemplified by Fig. 4, in an example embodiment, the reactant doser mount 140 is configured to position the reactant doser 150 such that when in use, the reactant doser 150 injects reactant through a side wall of the mixing tube 120 to the core region C. In an example embodiment, the core flow guide 130 and shaping of the mixing tube 120 are configured to cause a backflow in the core region C towards the core flow guide 130. In an example embodiment, the reactant doser 150 injects the reactant at an angle of 0 to 90 degrees relative to a line drawn between a tip of the reactant doser 150 and a mass centre of the core flow guide 130. The mass centre of the core flow guide may be used as a refence in sake of simplicity: for complex shapes, other reference points may be difficult to determine. However, in an example embodiment, the reference point is a lateral centre point of the core flow guide 130.

[0067] Some arrows are drawn in Fig. 4 to schematically illustrate possible flows without intending to accurately simulate the flows.

[0068] Fig. 5 shows an exhaust gas after treatment system 500 according to an example embodiment. Here, the input end 122 of the mixing tube 510 is exposed to exhaust gas only by inner surfaces of the mixing tube 120’. In an example embodiment, the input end 122 of the mixing tube 510 receives the exhaust gas directly from the combustion engine, e.g., after a turbo charger. In an example embodiment, the mixing tube 510 is partially surrounded by a mixing chamber 520. In an example embodiment, the mixing tube 510 is surrounded by a mixing chamber 520 over a portion of a length of the mixing tube 510. In an example embodiment, the portion of the length of the mixing tube 510 covered by the mixing chamber is 50 %. In an example embodiment, the portion of the length of the mixing tube 510 covered by the mixing chamber is at most 55 %. In an example embodiment, the portion of the length of the mixing tube 510 covered by the mixing chamber is at least 40 %.

[0069] In an example embodiment, the mixing tube 510 is implemented using a flexible pipe 510b that couples a combustion engine with exhaust gas after treatment so commencing the exhaust gas after treatment already in the flexible pipe 510b and so saving space and I or reducing back pressure produced by the exhaust gas after treatment. In an example embodiment not shown, the entire mixing tube 510 is formed by the flexible pipe 510b. In an example embodiment shown in Fig. 5, the mixing tube 510 comprises the flexible pipe 510b and a sequential downstream pipe 510a. Fig. 5 further shows a rotating core flow guide 530 positioned into the flexible pipe 510b. Advantageously, the space occupied by the flexible pipe can thus be further used in part to implement a mixer of the reactant. Figs. 6 to 9 show two different exhaust gas after treatment systems 600, 800 according to different example embodiments: Fig. 6 shows one variant with transparent walls, while Fig. 7 shows a sectional drawing of the same. Figs. 8 and 9 likewise illustrate another variant.

[0070] In Figs. 6 and 7, the mixing chamber is formed by joining two cylindrical forms such that an end of a first cylinder shape provides a mounting point for the doser and joins to a side wall of a second cylinder shape. In Figs. 8 and 9, the first cylinder shape extends beyond the side wall of the second cylinder shape to form a turning cup that extends beyond the output end of the mixing tube. In an example embodiment, the turning cup faces the output end of the mixing tube so that the exhaust gas exiting the mixing tube will reverse in the mixing tube and flow backwards around the output end of the mixing tube.

[0071] Figs. 6 to 9 also illustrate a bypass opening 610 of an example embodiment. In an example embodiment, the mixing tube is equipped with one or more bypass openings 610 to allow some of the exhaust gas to exit the mixing tube upstream from the core flow guide. In an example embodiment, two or more bypass openings 610 are provided symmetrically about the mixing tube. In an example embodiment, at least a portion the bypass openings resides upstream from the core flow guide.

[0072] In an example embodiment, the core flow guide is configured to swirl the exhaust gas, as illustrated in Figs. 5 to 9. In an example embodiment, as illustrated by Fig. 6, the core flow guide comprises a vane structure configured to bring the exhaust gas to a rotating motion around a longitudinal axis of the mixing tube. In an example embodiment, the vane structure is a twisted vane structure in which the vanes are twisted. In an example embodiment, the vanes have a linear pitch. In an example embodiment, the core flow guide comprises two vanes. In an example embodiment, the core flow guide comprises three or four vanes.

[0073] Figs. 10 and 11 illustrate a rotating core flow guide 1000 of an example embodiment comprising a plurality of vanes 1010, here four. In an example embodiment, the vanes are coupled in radial direction at a central region of the mixing tube, with at most 20 %, 10 %, or 1 % deviation from the centre of the mixing tube. In an example embodiment, the vanes 1010 are coupled at a central joint 1020, e.g., as illustrated by Fig. 10. The coupling of the vanes 1010 at the central joint 1020 may improve mechanical stability of the vane structure. The coupling of the vanes 1010 at the central region may improve reach of the reactant in the core region C by reducing exhaust gas pressure downstream from the central joint 1020.

[0074] In an example embodiment, the core flow guide comprises sloping guide parts configured to pack the exhaust gas towards opposite inner walls of the mixing tube without causing swirl or rotation. Various details of different embodiments are next described with more detail.

[0075] In an example embodiment, the flow device 100 further comprises a mixing chamber 110.

[0076] In an example embodiment, the reactant doser mount 140 is configured to position the reactant doser 150 such that when in use, the reactant doser 150 injects reactant through the output end 124 of the mixing tube 120 towards the input end 122. In an example embodiment, the reactant doser 150 is positioned such that reactant is dosed as a stream that passes through the output end 124 and travels in the mixing tube 120 towards the input end 122 in a decreased pressure zone produced by the core flow guide 130 until turning reversing before the core flow guide 130. The reversed stream of reactant advantageously is then carried out of the mixing tube 120 by the exhaust gas that flows in the perimeter region P so that the exhaust gas mitigates reactant accrual on the inner surface of the mixing tube 120. Advantageously, the core flow guide 130 may simultaneously promote entry of the reactant deeper into the mixing tube in the core region C and also increase pressure and velocity of the exhaust gas in the perimeter region P. The promoting of the deep entry and the increased pressure of exhaust gas in the perimeter region P may synergically contribute to mitigation of reactant accrual in the flow device by effects of the core flow guide 130.

[0077] In an example embodiment, the core region C comprises an innermost portion of a crosssection of the mixing tube 120 immediately downstream of the core flow guide 130. In an example embodiment, the innermost portion comprises at least 5 % or 10 % of a surface area of said cross-section. In an example embodiment, the innermost portion comprises at most 10 % or 20 % of the surface area of said cross-section.

[0078] In an example embodiment, the perimeter region P comprises an outmost portion of a crosssection of the mixing tube immediately downstream of the core flow guide. 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.

[0079] Advantageously, the core flow guide 130 increases injection range of the reactant against reactant gas flowing through the mixing tube 120 for increasing dwell time of the reactant within the mixing tube 120 and mixing of the reactant with the exhaust gas.

[0080] In an example embodiment, the core flow guide 130 has a shape capable of reducing swirl of the exhaust gas in the core region C. In an example embodiment, the core flow guide 130 has a shape capable of reducing swirl of the exhaust gas in the perimeter region P. In an example embodiment, the core flow guide 130 has a shape capable of increasing swirl of the exhaust gas in the core region C. In an example embodiment, the core flow guide 130 has a shape capable of increasing swirl of the exhaust gas in the perimeter region P. For example, the core flow guide 130 may comprise a propeller shape.

[0081] In an example embodiment, the mixing tube 120 comprises an expanding portion between the core flow guide 130 and the output end 124. In an example embodiment, the expanding portion is expanding as of a beginning of the expanding portion up to the output end 124. In an example embodiment, the expanding portion is conical. The expanding portion may be conical with linear walls. Alternatively, the expanding portion may be trumpet shaped, i.e., similarly with an output end of a trumpet. In an example embodiment, a diameter of the expanding portion is progressively increasing.

[0082] Advantageously, the expanding portion may further emphasise pressure difference between the core region C and the perimeter region P. In an example embodiment, the emphasising of the pressure difference further increases travel of the injected reactant in the mixing tube 120. In an example embodiment, the emphasising of the pressure difference reduces risk of accruing some of the injected reactant onto surfaces inside the mixing tube 120.

[0083] In an example embodiment, the core flow guide 130 comprises three or more fingers 132 that are pointed towards different radial directions. In an example embodiment, the three or more fingers 132 have a constant angular difference. In an example embodiment, the three or more fingers 132 have converging ends and remote ends. In an example embodiment, the converging ends of the fingers 132 reside closer to the output end 124 than remote ends of the fingers.

[0084] In an example embodiment, the mixing tube 120 is linear. Advantageously, a linear mixing tube 120 may help to mitigate a risk of accruing some of the reactant onto surfaces inside the mixing tube 120.

[0085] In an example embodiment, the core region C is coaxial with the mixing tube 120.

[0086] In an example embodiment, the reactant doser mount 140 is configured to position the reactant doser 150 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 a tip of the reactant doser 150.

[0087] In an example embodiment, the core flow guide 130 is configured to inhibit exhaust gas flow such that downstream from the core flow guide 130, the exhaust gas will be exposed to the lower pressure in the core region C than in the perimeter region P.

[0088] Alternatively, the mixing tube 120 is curved, e.g., as illustrated by Fig. 4. Advantageously, a curved mixing tube 120 may space efficiently occupy free space inside an engine room and I or direct the output to a desired direction other than that from which the mixing tube 120 receives the exhaust gas.

[0089] In an example embodiment, e.g., as illustrated by Fig. 4, the core region C resides asymmetrically with relation to the mixing tube 120. In an example embodiment, the core region C resides closer an outer curve of the mixing tube 120 than the inner curve of the mixing tube 120.

[0090] In an example embodiment, the reactant doser mount 140 is configured to position the reactant doser 150 such that reactant will be dosed at a direction of 120 to 170 degrees with relation to the general flow direction of the exhaust gas across the exhaust gas flow at the tip of the reactant doser 150.

[0091] In an example embodiment, the flow device 100 comprises an input flow swirl guide configured to cause exhaust gas to flow in the mixing tube 120 from the input end towards the core flow guide 130 along a path that rotates along inner surface of the mixing tube 120. In an example embodiment, the input flow swirl guide comprises one or more tangential guides configured to receive the exhaust gas from a direction that is perpendicular to the input end of mixing tube 120.

[0092] In an example embodiment, the mixing tube 120 is formed of a pipe that faces exhaust gas solely by interior surfaces of the mixing tube 120. In an example embodiment, the mixing tube 120 is flexible. In an example embodiment, the input end of the mixing tube 120 is rigidly connected to a combustion engine. In an example embodiment, the output end 124 of the mixing tube 120 is rigidly connected to a body to which the combustion engine is supported by one or more vibration dampening elements. Alternatively, the mixing tube 120 resides in the mixing chamber 110.

[0093] In an example embodiment, the mixing chamber 110 surrounds at least an input end of the mixing tube 120. In an example embodiment, the mixing tube 120 resides perpendicularly in the mixing chamber 110 or so that the input end of the mixing tube 120 is perpendicularly in the mixing chamber 110.

[0094] In an example embodiment, the mixing tube 120 comprises one or more apertures providing an additional exit from the mixing tube 120 to the mixing chamber 110. In an example embodiment, the one or more apertures reside longitudinally on one or more sides of the core flow guide 130. In an example embodiment, the one or more apertures reside symmetrically around the mixing tube 120. In an example embodiment, the one or more apertures reside asymmetrically around the mixing tube 120. In an example embodiment, some or all of the one or more apertures are longitudinally aligned with the core flow guide 130.

[0095] In an example embodiment, the flow device 100 comprises a turning cup configured to receive and turn to a radial or reverse direction exhaust gas from the output end 124. In an example embodiment, the turning cup comprises a cap configured to produce a donut shaped exhaust gas exit between the cap and the inner surface of the mixing tube 120 at the output end 124. In an example embodiment, the cap comprises a concave section facing the donut shaped exhaust gas exit. In an example embodiment, the cap comprises a convex section. In an example embodiment, the cap extends into the output end 124 of the mixing tube 120. In an example embodiment, the convex section resides inside the output end 124 of the mixing tube 120. In an example embodiment, the concave section resides downstream from the output end 124 of the mixing tube 120.

[0096] In an example embodiment, the turning cup comprises a donut shaped protrusion on a rear wall of the mixing chamber 110 opposite to the output end 124 of the mixing tube 120. In an example embodiment, the donut shaped protrusion has an outmost radius that is smaller than an inner radius of the output end 124 of the mixing tube 120. In an example embodiment, the donut shaped protrusion is separated by a longitudinal gap from a plane defined by the output end 124 of the mixing tube 120.

[0097] A crown surrounds the reactant doser 150 when mounted. In an example embodiment, the crown resides between the donut shaped protrusion and the reactant doser 150 when mounted. In an example embodiment, the crown comprises a plurality of teeth separated by gaps. In an example embodiment, the gaps extends between through entire length of the crown.

[0098] In an example embodiment, the reactant doser mount 140 is adjacent to the convex section

[0099] In an example embodiment, the mixing chamber 110 is cylindrical. In an example embodiment, the mixing chamber 110 surrounds the mixing tube 120 such that exhaust gas exiting the mixing tube 120 is directed to an open end of the mixing chamber 110. In an example embodiment, the open end of the mixing chamber 110 has a similar surface area with a cross-section of the mixing chamber 110 between the mixing tube 120 and the open end. In an example embodiment, the open end is configured to receive a mouth of an exhaust gas filter. In an example embodiment, the mixing tube 120 is configured to direct exhaust gas through the output end 124 in a general direction that is perpendicular to the open end of the mixing chamber 110. In an example embodiment, the mixing tube 120 is configured to direct exhaust gas through the output end 124 in a general direction that leads to some extent to a side of the mixing chamber 110 that is opposite to the open end of the mixing chamber 110.

[0100] In an example embodiment, the mixing chamber 110 comprises an output pipe connection. In an example embodiment, the output pipe connection is perpendicularly with relation to longitudinal direction of the mixing tube 120 at the input end. In an example embodiment, the output connection resides such that the core flow guide 130 is aligned with the output connection.

[0101] In an example embodiment, the flow device 100 comprises a diffuser downstream from the mixing chamber 110. In an example embodiment, the diffuser comprises an outwards opening conical section configured to reduce pressure of the exhaust gas at the central region C of the diffuser. In an example embodiment, the diffuser comprises a diffusing guide, e.g., a parallel guide adjacent to the mixing tube 120. In an example embodiment, the diffusing guide has an elliptical or parabolic cross-section.

[0102] In an example embodiment, the flow device 100 is a mixer for mixing reactant with exhaust gas.

[0103] Fig. 12 shows a flow chart of a method according to an example embodiment for exhaust gas aftertreatment, comprising any one or more of:

[0104] 1210: inputting incoming exhaust gas to a mixing tube 120 and outputting outgoing exhaust gas from the mixing tube 120 by an input end 122, and an output end 124, respectively;

[0105] 1220: guiding exhaust gas by a core flow guide 130 inside the mixing tube such that downstream from the core flow guide 130, the exhaust gas is exposed to a lower pressure in a core region C than in a perimeter region P; and

[0106] 1230: dosing reactant by a reactant doser 150 via the core region C towards a downstream side of the core flow guide 130.

[0107] In an example embodiment, there is provided an exhaust gas treatment system, e.g., as illustrated by Figs. 5 and 6. In an example embodiment, the system comprises the flow device 100. In an example embodiment, the system comprises a diesel oxidation catalysts, DOC. In an example embodiment, the system comprises a diesel particulate filters, DPF. In an example embodiment, the system comprises a selective catalytic reduction, SCR, catalyst. In an example embodiment, the system comprises the reactant doser 150. 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.

[0108] 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.

[0109] 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 . A flow device (100) for exhaust gas aftertreatment, comprising a mixing tube (120) comprising an input end (122) and an output end (124) for incoming and outgoing exhaust gas, respectively; a core flow guide (130) residing inside the mixing tube and being configured to guide exhaust gas such that downstream from the core flow guide (130), the exhaust gas will be exposed to a lower pressure in a core region (C) than in a perimeter region (P); and a reactant doser mount (140) for a reactant doser (150); wherein the reactant doser mount (140) is configured to position the reactant doser (150) such that when in use, the reactant doser (150) injects reactant via the core region (C) towards a downstream side of the core flow guide (130).

2. The flow device (100) of claim 1 , wherein the reactant doser mount (140) is configured to position the reactant doser (150) such that when in use, the reactant doser (150) injects reactant to the output end (124) of the mixing tube (120) towards the input end (122).

3. The flow device (100) of claim 1 or 2, wherein the core flow guide (130) has a shape capable of reducing swirl of the exhaust gas in the core region (C).

4. The flow device (100) of any one of preceding claims, wherein the mixing tube (120) comprises an expanding portion between the core flow guide (130) and the output end (124).

5. The flow device (100) of any one of preceding claims, wherein the core flow guide (130) comprises one or more fingers (132) pointed towards different radial directions.

6. The flow device (100) of any one of preceding claims, wherein the core flow guide (130) is a rotating core flow guide comprising a swirl structure that causes exhaust gas to rotate in the mixing tube.

7. The flow device (100) of any one of preceding claims, wherein the mixing tube (120) is formed of a pipe that faces exhaust gas solely by interior surfaces of the mixing tube (120).

8. The flow device (100) of claim 7, wherein the pipe is flexible.

9. The flow device (100) of any one of preceding claims, wherein the flow device (100) comprises a turning cup configured to receive and turn to a radial or reverse direction exhaust gas from the output end (124).

10. The flow device (100) of claim 9, wherein the turning cup comprises a cap configuredto produce a toroid shaped exhaust gas exit between the cap and the inner surface of the mixing tube (120) at the output end (124).11 . The flow device (100) of claim 10, wherein the cap comprises a concave section facing the toroid shaped exhaust gas exit; and the cap comprises a convex section residing inside the output end (124) of the mixing tube (120).

12. The flow device (100) of claim 11 , wherein the reactant doser mount (140) is adjacent to the convex section.

13. The flow device (100) of any one of preceding claims, wherein the core flow guide (130) is spaced apart from the input end (122) and the output end (124) of the mixing tube (120).

14. The flow device (100) of any one of preceding claims, wherein the core flow guide (130) is configured to inhibit the core flow (C) such that downstream from the core flow guide (130), the exhaust gas will be exposed to the lower pressure in the core region (C) than in the perimeter region (P).

15. A method for exhaust gas aftertreatment comprising: inputting incoming exhaust gas to a mixing tube (120) and outputting outgoing exhaust gas from the mixing tube (120) by an input end (122), and an output end (124), respectively (1210); guiding (1220) exhaust gas by a core flow guide (130) inside the mixing tube such that downstream from the core flow guide (130), the exhaust gas is exposed to a lower pressure in a core region (C) than in a perimeter region (P); and dosing (1230) reactant by a reactant doser (150) via the core region (C) towards a downstream side of the core flow guide (130).

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