Patent Description:
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 (O<NUM>). 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 pressure 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. Relevant prior art is document <CIT>.

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.

According to a first example aspect there is provided a flow device for exhaust gas aftertreatment as defined by appended claim <NUM>.

The mixing tube may reside perpendicularly in the mixing chamber. In an alternative, the mixing tube resides at an angle that is <NUM> to <NUM> degrees off perpendicular, preferably <NUM> to <NUM> degrees.

The divider may be formed of a metal plate. The divider may comprise a mid-section that is perpendicular to the mixing tube. The divider may have a side profile of corresponding to a letter Z with substantially right angles.

The divider may comprise a first guide between the mixing tube and the output side of the mixing chamber.

The divider may comprise a first guide between the mixing tube and the output side of the mixing chamber. The first guide may be concavely shaped when seen from the input side of the mixing chamber, for providing more space on the output side for spreading exhaust gas flow into a next processing phase. The next processing phase may be a selective catalytic reduction (SCR) catalyst. The first guide may contact the mixing tube or the swirl arrangement. The first guide may contact the mixing tube or the swirl arrangement for a length portion of total length of the mixing tube. The length portion may be at least <NUM> %; <NUM> %; or <NUM> %. The length portion may be at most <NUM> %; <NUM> %; or <NUM> %.

The divider may comprise a second guide between the mixing tube and the input side of the mixing chamber. The second guide may be shaped to facilitate flow of exhaust gas towards the intake section. The second guide may have an inclination for facilitating flow of exhaust gas towards intake section.

The first guide may join with a rounded edge to the mid-section. The second guide may join with a rounded edge to the mid-section.

The mixing tube may be cylindrical. The mixing tube may comprise a conical part or the mixing tube may be conical, optionally with an opening angle of at least <NUM>; <NUM>; or <NUM> degrees, and / or optionally with an opening angle of at most <NUM>; <NUM>; or <NUM> degrees. In an embodiment, the opening angle is between <NUM> and <NUM> degrees or between <NUM> and <NUM> degrees. The mixing tube may be conical with a diameter expanding in downstream direction of the main flow. The mixing tube may be conical at the second end.

The mixing tube may reside perpendicularly in the mixing chamber such that a longitudinal axis of the mixing tube is perpendicular to a longitudinal direction of the mixing chamber. The longitudinal direction of the mixing chamber may be defined by a line that connects flow channel centres of the input and output sections.

The mixing tube may be formed of two attached parts, a first part and a second part, for producing a sub-assembly comprising the divider and the mixing tube. The first part may comprise the intake section. The sub-assembly may be attached after assembling to the mixing chamber. Alternatively, at least one part of the sub-assembly may be attached to the sub-assembly after attaching the sub-assembly to the mixing chamber.

The swirl guide may be integrally formed with the intake section of the mixing tube. The swirl guide may comprise one or more wing segments, optionally formed by shaping a portion of a wall of the mixing tube at the intake section to guide exhaust gas into the mixing tube at a generally tangential direction to rotate along an inner surface of the mixing tube. The swirl guide may comprise <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; or <NUM> wing segments.

The reactant doser mount may be attached to the mixing chamber. The reactant doser mount may be attached to the mixing chamber opposite to the second end of the mixing tube. The reactant doser mount may be attached to the mixing chamber opposite to the second end of the mixing tube aligned so that reactant of a mounted reactant doser is directed along a central axis of the mixing tube. The reactant doser mount may be attached to the mixing chamber opposite to the second end of the mixing tube so that when attached to the reactant doser mount and when in use, the reactant doser injects the reactant into the mixing tube towards the first end. The reactant doser mount may be attached to the mixing chamber opposite to the second end of the mixing tube such that when mounted, the reactant doser extends through the second end. In an alternative, the reactant doser mount is attached to the mixing chamber opposite to the second end of the mixing tube such that when mounted, there is a gap between a tip of the reactant doser and the second end. The reactant doser may be an air-free reactant doser.

The flow device may further comprise a turning end in the mixing chamber for reversing the main flow after exiting the second end of the mixing tube to flow along an outer surface of the mixing tube towards the first end. The main flow may be reversed to flow along the outer surface of the mixing tube towards the first end all around the mixing tube, at least over a sub-section of the length of the mixing tube, such as at least <NUM>; <NUM>; or <NUM>.

The passage structure may be configured to inhibit turbulence from being transferred from the side flow to the carrier flow.

The flow device may comprise a geometry configured to form a pressure difference between a periphery of the stem guide and the mixing chamber around the stem guide. The passage structure may be configured to guide the side flow using the pressure difference.

The geometry of the flow device may cause a majority of the main flow to turn around the second end of the mixing tube such that a first portion of the turning flow closer to the stem guide has a lower velocity than a second portion of the turning flow farther apart from the guide, for incurring a higher pressure in the first portion than a pressure in the central opening.

The pressure difference may be formed by throttling the main flow downstream from of the guide.

The inhibiting of the turbulence may be performed by guiding the side flow via stem guide channels feeding the side flow by a plurality of radial outputs to the central opening. The inhibiting of turbulence may make the carrier flow laminar around the reactant doser when mounted.

The stem guide channels may be defined by a plurality of wings that are radially extending from the central opening. The wings may have back-side fairings configured to reduce turbulence. The wings may have planar front-sides. The front-sides may be directed against rotation of the rotating flow. The front-sides may be at an angle with relation to a radial direction such that front-side is turned at a peripheral end towards incoming gas flow.

All or at least some of the wings may extend to a periphery of the stem guide. All or at least some of the wings may be inset from the periphery of the stem guide. All or at least some of the wings may be inset from the periphery of the stem guide by at least <NUM> %; <NUM> %; <NUM> %; <NUM> %; or <NUM> % of local radius. All or at least some of the wings may be inset from the periphery of the stem guide by at most <NUM> %; <NUM> %; <NUM> %; <NUM> %, or <NUM> % of local radius. The local radius may refer to a distance from a given point of the periphery of the stem guide to a centre of the stem guide when seen in an axial direction of the mixing tube.

All or at least some of the wings may extend to the central opening. All or at least some of the wings may be inset from the central opening. The inset from the central opening may be at least <NUM> %; <NUM> %; <NUM> %; <NUM> %; or <NUM> % of local radius. The inset from the central opening may be at most <NUM> %; <NUM> %; <NUM> %; <NUM> %, or <NUM> % of local radius.

All or at least some of the wings may define fixing holes. The fixing holes may be pitched for bolts. One or more of the wings that accommodate fixing holes may be expanded to accommodate respective fixing holes. The fixing holes may reside rotation symmetrically. Alternatively, the fixing holes may reside rotation asymmetrically. The fixing holes may reside at constant distance from the central opening. Alternatively, all, or at least some of the fixing holes may reside at different distances from the central opening.

The fixing holes may be configured to enable mounting of the reactant doser. The reactant doser may be mounted by bolts such that the turning end of the mixing chamber is compressed between the reactant doser and the stem guide. The compressing may be performed with bolts tightened through a base of the reactant doser and through the turning end to the fixing holes. Alternatively, the stem guide may comprise threaded rods instead of all or at least some of the fixing holes. The threaded rods may be directed towards and through the turning end and the base of the reactant doser. All or at least some of the threaded rods may be integrally formed with the stem guide. All or at least some of the threaded rods may be machined to cast protrusions in the stem guide. All or at least some of the threaded rods may be welded to the stem guide. All or at least some of the threaded rods may be screwed to threads in the fixing holes.

The stem guide may define a disc. The disc may be separated by the wings from the turning end of the mixing chamber. The disc may be supported by the wings. The disc may define the stem guide channels on one side. The turning end may define the stem guide channels on another side.

The front face of the stem guide may be concave. Alternatively, the front face may be planar. Further alternatively, the front face may have a planar portion and a concave portion. The planar portion may reside between the central opening and the concave portion.

The mixing chamber may comprise cylindrical part around the second end of the mixing tube. The mixing tube may be coaxial with the cylindrical part of the mixing chamber. The reactant doser may be configured to dose the reactant coaxially with the mixing tube. The central opening may reside coaxially with the mixing tube. The disc may reside coaxially with the mixing tube.

The central opening may comprise a cylindrical portion. The central opening may comprise a conical portion. The central opening may have a rounded edge on an input side. The central opening may have a rounded edge on an output side.

The central opening may reside at a centre of the disc. Alternatively, the central opening may reside with an offset from the centre of the disc. The central opening may be displaced from the centre of the disc to compensate uneven pressure distribution around the disc.

The disc may have a circular periphery. Alternatively, the disc may have a varying radius. The radius of the disc may vary to compensate uneven pressure distribution around the disc.

The turning end of the mixing chamber may have a planar central section. The planar central section may join to a peripheral wall of the mixing chamber by an intermediate portion. The intermediate portion may be concave. The intermediate portion may extend over a portion of a radius of the peripheral wall when measured at the tip of the reactant doser. The portion of the radius may be at least <NUM> %; <NUM> %; <NUM> %; or <NUM> %. The portion of the radius may be at most <NUM> %; <NUM> %; <NUM> %; or <NUM> %. The portion may have a constant radius.

The second end of the mixing tube may reside at an axial distance from the turning end and at a radial distance from the peripheral wall. The axial distance may be at least <NUM> %; <NUM> %; <NUM> %; <NUM> %; <NUM> %; or <NUM> % of the radial distance. The axial distance may be at most <NUM> %; <NUM> %; <NUM> %; <NUM> %; or <NUM> % of the radial distance.

The throttling may result in a flow passage having a cross-sectional surface area at most <NUM> %; <NUM> %, <NUM> %, <NUM> %, or <NUM> % of a cross-sectional surface area of the mixing tube at the second end.

Some exhaust gas may be fed through an internal bypass to an output side of the mixing chamber for reducing counter pressure. The internal bypass may be formed on the divider. The internal bypass may be formed to face the dosing section such that exhaust gas bypassing through the internal bypass becomes guided by an external surface of the dosing section. The internal bypass may reside on a mixing tube output side half of the mixing chamber. The internal bypass may be or comprise a perforation. The internal bypass may be or comprise a grill. The internal bypass may be or comprise an aperture.

The internal bypass may be configured to allow a bypass portion of the exhaust gas flow through the internal bypass. The bypass portion may be at least <NUM> weight per cent. The bypass portion may be at least <NUM> weight per cent. The bypass portion may be at least <NUM> weight per cent. The bypass portion may be at least <NUM> weight per cent. The bypass portion may be at least <NUM> weight per cent. The bypass portion may be at least <NUM> weight per cent. The bypass portion may be at most <NUM> weight per cent. The bypass portion may be at most <NUM> weight per cent. The bypass portion may be at most <NUM> weight per cent. The bypass portion may be at most <NUM> weight per cent. The bypass portion may be at most <NUM> weight per cent. The bypass portion may be at most <NUM> weight per cent.

The internal bypass may be configured to direct the bypass portion to bypass the mixing tube. The internal bypass may be configured to direct the bypass portion to bypass swirl-inducing flow guide elements. The internal bypass may be configured to direct the bypass portion to join a feed of the stem guide.

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.

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

According to a second example aspect there is provided a method as defined by appended claim <NUM>.

The method may further comprise inhibiting by the stem guide turbulence from being transferred from the side flow to the carrier flow.

The method may further comprise forming a pressure difference between a periphery of the stem guide and the mixing chamber around the stem guide.

The side flow may be guided out of the rotating flow using the pressure difference to the carrier flow around the reactant doser via the central opening.

According to a third example aspect there is provided an exhaust gas treatment system comprising the flow device of the first example aspect, and at least one of a diesel oxidation catalysts, DOC, a diesel particulate filters, DPF, a selective catalytic reduction, SCR, catalyst, and the reactant doser.

<FIG> schematically shows an exhaust gas mixer <NUM> for aftertreatment, according to an example embodiment. <FIG> represents a generalisation for explaining various example embodiments. <FIG> illustrate various alternative embodiments of a flow device that may operate employing at least some of the example embodiments of the exhaust gas mixer. Moreover, these drawings illustrate various further example embodiments.

The mixer comprises a mixing chamber <NUM> that houses a mixing tube <NUM>. The mixer further comprises an input <NUM> and an output <NUM>, here formed of two outlets. The input <NUM> is implemented in <FIG> by a conduit leading exhaust gas tangentially to the mixing tube <NUM> so forming a rotating main flow <NUM> into the mixing tube <NUM>. The rotating main flow advances towards a turning end <NUM> of the mixing chamber <NUM>. The mixing chamber of <FIG> is cylindrical and so the mixing chamber has a peripheral wall <NUM> that is cylindrical. In another example embodiment, the mixing chamber has a different shape, such as an oval or elliptic shape.

In an example embodiment, the rotation of the main flow <NUM> is produced by other swirl structures instead of or in addition to the swirl producing input <NUM> that is used in this embodiment, such as a propeller formed swirl guide (not shown).

The rotation of the main flow <NUM> centrifugally packs the main flow against an inner wall of the mixing tube <NUM>. A lower pressure prevails around a centreline <NUM> of the mixing tube. This effect is made used to enhance dosing reactant <NUM> by a reactant doser <NUM> from a reactant doser tip <NUM> against the main flow around the centreline <NUM>, with greatly reduced counterflow against the reactant doser. However, it is typical that some accrual of reactant begins to build up on the reactant doser <NUM> possibly because of turbulences and / or imperfect dosing at start and end of the dosing of reactant. To this end, a carrier flow <NUM> is formed using a stem guide <NUM> positioned around the reactant doser <NUM>, through a central opening <NUM> defined by the stem guide around the reactant doser <NUM>. Here, around refers to that the stem guide extends radially from the reactant doser <NUM> on a portion of the length of the reactant doser <NUM> in the mixing chamber <NUM>, not that the stem guide <NUM> should enclose the entire reactant doser <NUM>.

The carrier flow is produced in an example embodiment by forming a pressure difference in the mixing chamber around the stem guide <NUM>, as further described referring to <FIG> and <FIG>.

<FIG> shows only schematically one example embodiment. Various details can be freely modified. In <FIG>, arrows roughly illustrate mass flow.

The reactant doser <NUM> of <FIG> is an air-free reactant doser. Thus, the reactant doser <NUM> outputs the reactant without using air as a carrier. In an alternative embodiment, the reactant doser <NUM> uses a carrier gas to dose the reactant.

As seen from <FIG>, by positioning the reactant doser <NUM> at or close the turning end of the mixing chamber, the space in front of the turning end can be used for dosing the reactant and feeding into a core of the main flow. By arranging the reactant doser <NUM> further away from mixing tube, the reactant may effectively gain a greater space and time to dissolve and evaporate before being turned back by the rotating and advancing main flow. Or, with the same space and time, the mixing chamber may be made more compact.

<FIG> shows a flow device <NUM>' of an example embodiment for exhaust gas aftertreatment, comprising.

In an example embodiment, the mixing tube <NUM>' resides perpendicularly or substantially perpendicularly in the mixing chamber <NUM>'. In an embodiment, the mixing tube resides at an angle that is <NUM> to <NUM> degrees off perpendicular, preferably <NUM> to <NUM> degrees. The perpendicular orientation may advantageously contribute to compactness of the flow device such that pressure loss is balanced with mixing efficiency. In the perpendicular orientation, the mixing tube basically occupies a length of the mixing chamber only corresponding to the width of the mixing tube. Moreover, when the swirl arrangement <NUM> employs tangential feeding of exhaust gas into the mixing tube, the intake section 120a need not change much the flow direction of the exhaust gas, so helping to avoid increasing pressure loss over the flow guide. A tangential swirl arrangement may thus operate synergically with the perpendicular or substantially perpendicular mixing tube. Different tangential swirl arrangements are further shown in <FIG>. In an alternative embodiment, a non-tangential swirl arrangement is used, such as a propeller inside the mixing tube (not shown).

In an example embodiment, the divider 115a is formed of a metal plate. In an example embodiment, the divider comprises a mid-section <NUM> that is perpendicular to the mixing tube, see e.g., <FIG> and <FIG>. The mid-section <NUM> provides a side profile of generally corresponding to a letter Z with substantially right angles.

<FIG> further shows a diffusing guide <NUM>. The diffusing guide is here elongated and in parallel with the mixing tube. The diffusing guide <NUM> is configured to split exhaust gas otherwise mostly focusing on the centre line of the mixing tube so that the exiting exhaust gas would be more diffuse or evenly spread. The diffusing guide <NUM> here has an outwards convex shape and concave towards the mixing tube.

<FIG> shows a line D-D along which <FIG> is sectioned.

In <FIG>, it is seen how the divider 115a may form a first guide <NUM> between the mixing tube and the output side of the mixing chamber and a second guide <NUM> between the mixing tube and the input side of the mixing chamber. These first and second guides <NUM>, <NUM> may separate the input and output sides and guide exhaust gas to enter the mixing tube <NUM>' and be passed to a next process phase with a flattened velocity profile across a downstream end of the mixing chamber <NUM>'. By flattening the velocity profile, subsequent processing, such as catalytic reduction of nitrogen oxides, may be improved and / or subsequent pressure loss be reduced in the exhaust gas flow.

In an example embodiment, the first guide <NUM> is concavely shaped when seen from the input side of the mixing chamber, for providing more space on the output side for spreading exhaust gas flow into a next processing phase. See particularly <FIG> that shows the output side with increased space thanks to the concave or V-shaped input side of the mixing chamber as defined by the concave divider 115a.

In an example embodiment, the first guide <NUM> contacts the mixing tube <NUM>' or the swirl arrangement <NUM>. <FIG> shows that a portion of the swirl arrangement <NUM> contacts with the first guide <NUM> or comes very close thereto. This may both save space and further enhance operation of the swirl arrangement <NUM>.

In an example embodiment, the first guide <NUM> contacts the mixing tube <NUM>' or the swirl arrangement <NUM> for a length portion of total length of the mixing tube. In an example embodiment, the length portion is at least <NUM> %; <NUM> %; or <NUM> %. In an example embodiment, the length portion is at most <NUM> %; <NUM> %; or <NUM> %.

In an example embodiment, the second guide <NUM> is shaped to facilitate flow of exhaust gas towards the intake section, see particularly <FIG> showing the output side. The input side of the second guide <NUM> is V-shaped so that exhaust gas is guided towards the mixing tube. In an example embodiment, the second guide <NUM> further has an extent of curving so as to further facilitate bringing the exhaust gas into the mixing tube <NUM>' with reduced turbulence and pressure loss prior to entering the mixing tube <NUM>'. In an example embodiment, the second guide <NUM> has an inclination (see <FIG>) for facilitating flow of exhaust gas towards intake section 120a.

In an example embodiment, the first guide <NUM> joins with a rounded edge to the mid-section <NUM>. The second guide <NUM> may join with a rounded edge to the mid-section <NUM>.

In an example embodiment, the mixing tube <NUM>' is cylindrical or comprises a conical part, optionally with an opening angle of at least <NUM>; <NUM>; or <NUM> degrees, and / or optionally with an opening angle of at most <NUM>; <NUM>; or <NUM> degrees. In an embodiment, the opening angle is between <NUM> and <NUM> degrees or between <NUM> and <NUM> degrees. In an example embodiment, the mixing <NUM>' the conical part has a diameter expanding in downstream direction of the main flow. In an example embodiment, the mixing tube <NUM>' is conical or has a conical part at the second end.

In an example embodiment, the mixing tube <NUM>' resides perpendicularly in the mixing chamber <NUM>' such that a longitudinal axis of the mixing tube <NUM>' is perpendicular to a longitudinal direction of the mixing chamber <NUM>', see particularly <FIG>. The longitudinal direction of the mixing chamber <NUM>' may be defined by a line that connects flow channel centres of the input and output sections.

In an example embodiment, the mixing tube is formed of two attached parts, a first part and a second part, for producing a sub-assembly comprising the divider and the mixing tube. Such a structure may help assembling of the flow guide. In an example embodiment, the first part comprises the intake section 120a. In an example embodiment, the sub-assembly is attached after assembling to the mixing chamber <NUM>'. In an example embodiment, at least one part of the sub-assembly is attached to the sub-assembly after attaching the sub-assembly to the mixing chamber <NUM>'.

In an example embodiment, the swirl guide <NUM> is integrally formed with the intake section 120a of the mixing tube <NUM>'. In an example embodiment, the swirl guide <NUM> comprises one or more wing segments, optionally formed by shaping a portion of a wall of the mixing tube <NUM>' at the intake section to guide exhaust gas into the mixing tube <NUM>' at a generally tangential direction to rotate along an inner surface of the mixing tube. In an example embodiment, the swirl guide comprises <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; or <NUM> wing segments.

In an example embodiment, the reactant doser mount <NUM> is attached to the mixing chamber <NUM>'. In an example embodiment, the reactant doser mount <NUM> is attached to the mixing chamber <NUM>' opposite to the second end of the mixing tube <NUM>'. In an example embodiment, the reactant doser mount <NUM> is attached to the mixing chamber opposite to the second end of the mixing tube <NUM>' aligned so that reactant of a mounted reactant doser <NUM> is directed along a central axis of the mixing tube <NUM>'. In an example embodiment, the reactant doser mount is attached to the mixing chamber <NUM>' opposite to the second end of the mixing tube <NUM>' so that when attached to the reactant doser mount <NUM> and when in use, the reactant doser <NUM> injects the reactant into the mixing tube towards the first end, e.g., as shown in <FIG>. In an example embodiment, the reactant doser mount <NUM> is attached to the mixing chamber <NUM>' opposite to the second end of the mixing tube <NUM>' such that when mounted, the reactant doser <NUM> extends through the second end. In an alternative, the reactant doser <NUM> mount is attached to the mixing chamber <NUM>' opposite to the second end of the mixing tube <NUM>' such that when mounted, there is a gap between a tip of the reactant doser <NUM> and the second end. In an example embodiment, the reactant doser <NUM> is an air-free reactant doser.

In an example embodiment, the flow device further comprises a turning end in the mixing chamber <NUM>' for reversing the main flow after exiting the second end of the mixing tube <NUM> to flow along an outer surface of the mixing tube <NUM>' towards the first end. See, e.g., <FIG> that shows an asymmetric cup shaped form <NUM>' that helps to turn the main flow backwards along outer surfaces of the mixing tube <NUM>' and also partially towards the centre of the turning end under towards the doser <NUM>, for forming the carrier flow <NUM> shown in <FIG>.

In <FIG>, the asymmetric cup shaped form <NUM>' and an outer wall define an insulation space <NUM> for insulating the flow guide at the turning end. This helps to accelerate warming up of the flow guide for dosing the reactant. It is also possible to use otherwise the insulation space <NUM>. For example, in an example embodiment, some of that space is used to guide some of the exhaust gas from the input side to a carrier flow for the reactant, see particularly <FIG>. There, one or more channels are formed to direct a portion of the exhaust gas from the input side of the mixing chamber to the carrier flow. In an example embodiment, there is provided a partial bypass of the divider 115a for reducing counter pressure caused by the exhaust gas mixer <NUM>, as will be described subsequently with further detail with reference to <FIG>.

<FIG> shows different views of an embodiment with four arcuate, preferably continuously arcuate, wing segments, or blades. The blades can be fixed to a mixing tube to feed exhaust gas through openings in the mixing tube. Alternatively, the mixing tube may join an edge of the blades such that the blades form a rotating and advancing exhaust gas flow already before the exhaust gas enters the mixing tube.

<FIG> shows different views of an embodiment with eight wing segments.

<FIG> shows different views of an embodiment with four wing segments.

<FIG> shows different views of an embodiment with four wing segments that are discontinuously arcuate. Here, the wings segments are formed of a base part that forms a portion of the mixing tube and has a first radius of curvature, and a planar or curved extending part that differs does not have the first radius of curvature. <FIG> further illustrates that the wing segment may have a variable radial reach outwards of the mixing tube. For example, the wing segment may have a sloping shape such that the radial reach reduces towards the second end of the mixing tube.

The wing segments may be evenly spaced. The wing segments may be aligned in longitudinal direction of the mixing tube. The wing segments may have an equal length in the longitudinal direction of the mixing tube.

<FIG> shows some details of the mixer of <FIG> and an illustration of some flows in the mixer. The main flow <NUM> of <FIG> arrives in a mixing region as a first flow 1A. The first flow 1A is mostly directed as a first sub-flow towards the output <NUM> of <FIG> around an output end of the mixing tube. A second sub-flow directs a minority of the first flow through the stem guide and its central opening to a carrier flow 1c around the reactant doser for inhibiting accrual of the reactant on the reactant doser.

<FIG> shows simulated pressures of exhaust gas in the mixer and <FIG> shows simulated velocities of exhaust gas in the mixer. A pressure difference is formed in this example embodiment by a geometry of the mixer. The geometry of the mixer causes a majority of the main flow to turn around the output end of the mixing tube such that a first portion of the turning flow closer to the stem guide has a lower velocity than a second portion of the turning flow farther apart from the stem guide, for incurring a higher pressure in the first portion than a pressure in the central opening.

<FIG> shows a throttling arrangement <NUM> for causing a pressure differential that produces the carrier flow around a reactant doser, according to an example embodiment. In comparison to the mixer <NUM> of <FIG>, in this arrangement, there is a throttling formed by throttling elements <NUM> that form a throttling structure. In result, the pressure difference is formed so that the carrier flow is induced. In another alternative, the dimensioning of a passage between the turning end of the mixing chamber and the output end of the mixing tube produces a suitable throttling to induce the pressure difference.

<FIG> shows a splitting arrangement <NUM> for splitting a side flow by a splitting element <NUM> for producing the carrier flow around a reactant doser, according to an example embodiment.

<FIG> show only one side of the mixing chamber at the turning end <NUM>. The remaining side can be similar or different. For example, there may be one or more throttling elements and one or more splitting elements <NUM> for collectively forming the carrier flow around the reactant doser.

<FIG> shows a view of a reactant doser <NUM> when mounted to the mixer, according to an example embodiment. The reactant doser <NUM> is mounted to the mixing chamber with bolts <NUM>.

<FIG> shows a section view of the stem guide, reactant doser, and turning end of <FIG>. The stem guide <NUM> comprises a disc <NUM> and a stem part <NUM> that forms a flow passage from around the stem guide <NUM> to the central opening <NUM>. The disc has a front face <NUM> that facing away from the turning end <NUM>. The front face <NUM> may have at least one concave portion <NUM>. Alternatively, or additionally, the front face <NUM> may have at least one planar portion <NUM>.

<FIG> shows the stem guide of <FIG> from behind. A plurality of wings <NUM> are provided on the backside <NUM> of the disc <NUM>, i.e., between the disc <NUM> and the turning end <NUM>. The wings comprise fairings <NUM> on a backside.

In another example embodiment the wings are formed to the turning end <NUM>, but it is easier to form the wings to the stem guide <NUM>. In an example embodiment, the reactant doser <NUM> is mounted by three bolts such that the reactant doser <NUM> can be mounted in only one angle. A base of the reactant doser is formed to provide bolt holes and the stem guide defines corresponding stem guide holes <NUM>. The stem guide holes <NUM> can be threaded so that the reactant doser can be bolted through the turning end to the stem guide <NUM>. Alternatively, the stem guide <NUM> can be fitted with protruding threaded bars or bolts such that the reactant doser <NUM> is attached with nuts.

In <FIG>, the wings are equidistantly arranged with equal inset at radially inner and outer ends. Some of the wings are locally expanded to form the stem guide holes with sufficient wall thickness. The wings are wing shaped, as they comprise fairings configured to reduce turbulence on a rear side in view of incoming exhaust gas. A facing side or front face of the wings is here planar. Alternatively, the front face may have a concave portion. The front face may be at an turned towards incoming gas flow in comparison to a radial direction. An The angle between the front face and a radius of the disc <NUM> may be at most <NUM>; <NUM>; or <NUM> degrees.

<FIG> shows a rounding or a bezel <NUM> formed on the back face <NUM> in an input edge of the central opening <NUM>.

<FIG> shows a flow chart according to an example embodiment illustrating a process comprising steps <NUM> and <NUM> of the invention, and various possible steps including some optional steps while also further steps can be included and/or some of the steps can be performed more than once:.

<FIG> shows a stem guide <NUM>' of another example embodiment with an external reactant doser mount <NUM> for reactant doser attachment. The external reactant doser mount <NUM> can be attached to the mixing chamber <NUM> in various ways. For example, the reactant doser mount <NUM> may be welded to the mixing chamber <NUM>, bolted or riveted through the mixing chamber <NUM> to the stem guide <NUM>', or attached by bolts or screws to the mixing chamber <NUM>.

<FIG> shows an alternative mixing tube side shape in the stem guide <NUM>'. Here, the stem guide <NUM>' comprises a cone <NUM> towards the mixing tube <NUM>. The cone <NUM> may have straight inner surfaces. The cone <NUM> may have also a straight outer slope. Here, the cone <NUM> has curved outer slope for reducing turbulence of a flow that passes by the stem guide <NUM>'.

Alternatively, the stem guide of any other example embodiment can be used in conjunction with the external reactant doser mount <NUM> (<FIG>; <FIG>).

<FIG> shows a stem guide <NUM>" of yet another example embodiment with an external bypass feed <NUM>. Here, an exhaust gas feed line <NUM> outputs exhaust gas to the mixing tube <NUM> and also via another branch or bypass <NUM> to the stem guide <NUM>" for forming or for enhancing the carrier flow. The bypass <NUM> may increase the pressure of exhaust gas fed to the central opening. <FIG> further shows one side <NUM> of a wing element.

In <FIG>, there is further a peripheral distribution channel <NUM> surrounding the central opening and distributing exhaust gas around the reactant doser tip. As drawn, the peripheral distribution channel may have a greater cross-sectional area at a feed point and a smaller cross-sectional area distantly from the feed point so as to even the distribution of the exhaust gas to the carrier flow around the central opening.

As in the embodiment of <FIG>, the feed to central opening is provided over both sides without any rotational bias, the blades shown in <FIG> may be omitted for reducing pressure loss.

<FIG> further shows the divider as indicated by an added dashed trace line <NUM>.

In an example embodiment, the stem guide is closed except the central opening. In another example embodiment, the stem guide comprises one or more Venturi input ports (not shown) can be configured to introduce exhaust gas from the mixing chamber, preferably from a peripheral area around the stem guide.

<FIG> shows a flow chart of a method in a mixer according to an example embodiment, comprising:.

The method may further comprise any one or more of:.

In an example embodiment, there is provided a mixer comprising means for performing the method of any example embodiment.

<FIG> shows a flow chart of a method in a flow guide according to the claimed invention, comprising:.

The method further comprises supporting a stem guide <NUM> around the doser <NUM> when mounted such that a front face of the stem guide <NUM> faces the rotating flow <NUM>; defining by the stem guide <NUM> a central opening <NUM> surrounding the doser <NUM> when mounted; and defining by the stem guide <NUM> a passage structure <NUM>;<NUM>,<NUM>,<NUM> and guiding a side flow 1b out of the rotating flow to a carrier flow <NUM> around the doser <NUM> via the central opening <NUM>.

In an example embodiment, the method further comprises.

Advantageously, the dividing of some of the main flow into the carrier flow enhances transportation of the dosed reactant deeper into a core of the main flow well apart of any walls and other structures to which the reactant might accrue. While some of the main flow is recirculated and can thus recirculate a small portion of the dosed reactant to the carrier flow, such reactant is well dissolved and evaporated. Moreover, in case of supplementing the carrier flow with some exhaust gas fed by a bypass from the input side of the mixing chamber, reactant concentration in the carrier flow can be further reduced.

<FIG> show a mixer <NUM> with partial bypass according to an example embodiment, in which some exhaust gas is fed through an internal bypass <NUM> to an output side of a mixing chamber <NUM>" for reducing counter pressure. The mixer <NUM> of <FIG> further comprises a divider 115a' dividing the mixing chamber <NUM>" to an input side 110a' and an output side 110b', and a dosing section 120b'. The internal bypass is formed in <FIG> on the divider. In an example embodiment, the internal bypass <NUM> is formed to face the dosing section such that exhaust gas bypassing through the internal bypass <NUM> becomes guided by an external surface of the dosing section. In an example embodiment, the internal bypass <NUM> resides on a mixing tube output side half of the mixing chamber <NUM>". In an example embodiment, the internal bypass <NUM> is or comprises a perforation. In an example embodiment, the internal bypass <NUM> is or comprises a grill. In an example embodiment, the internal bypass <NUM> is or comprises an aperture.

In an example embodiment, the internal bypass <NUM> is configured to allow a bypass portion of the exhaust gas flow through the internal bypass <NUM>. In an example embodiment, the bypass portion is at least <NUM> weight per cent. In an example embodiment, the bypass portion is at least <NUM> weight per cent. In an example embodiment, the bypass portion is at least <NUM> weight per cent. In an example embodiment, the bypass portion is at least <NUM> weight per cent. In an example embodiment, the bypass portion is at least <NUM> weight per cent. In an example embodiment, the bypass portion is at least <NUM> weight per cent. In an example embodiment, the bypass portion is at most <NUM> weight per cent. In an example embodiment, the bypass portion is at most <NUM> weight per cent. In an example embodiment, the bypass portion is at most <NUM> weight per cent. In an example embodiment, the bypass portion is at most <NUM> weight per cent. In an example embodiment, the bypass portion is at most <NUM> weight per cent. In an example embodiment, the bypass portion is at most <NUM> weight per cent.

In an example embodiment, the internal bypass <NUM> is configured to direct the bypass portion to bypass the mixing tube. In an example embodiment, the internal bypass <NUM> is configured to direct the bypass portion to bypass swirl-inducing flow guide elements. In an example embodiment, the internal bypass <NUM> is configured to direct the bypass portion to join a feed of the stem guide.

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.

Claim 1:
A flow device (<NUM>') for exhaust gas aftertreatment, comprising
a mixing chamber (<NUM>') comprising an input side (110a) and an output side (110b);
a divider (115a) dividing the mixing chamber (<NUM>') to the input side (110a) and the output side (110b);
a mixing tube (<NUM>') comprising a first end and a second end, and an intake section (120a) for receiving exhaust gas from the input side (110a) of the mixing chamber (<NUM>');
a swirl guide (<NUM>) configured to guide the received exhaust gas to flow inside the mixing tube (<NUM>') towards the second end as a rotating and advancing main flow (<NUM>); and
a reactant doser mount (<NUM>) for a reactant doser (<NUM>); wherein
the mixing tube (<NUM>') comprises a dosing section (120b) between the intake section (120a) and the second end;
the mixing tube (<NUM>') extends through the divider (115a);
the dosing section (120b) is configured to receive at least most of the rotating and advancing exhaust gas flow; and
the reactant doser mount (<NUM>) is configured for mounting the reactant doser (<NUM>) such that when in use, the reactant doser (<NUM>) provides reactant to the dosing section (120b), characterized in that
the flow device further comprises a stem guide (<NUM>) around the doser (<NUM>) when mounted such that a front face of the stem guide (<NUM>) faces the rotating flow (<NUM>);
the stem guide (<NUM>) defines a central opening (<NUM>) surrounding the doser (<NUM>) when mounted; and
the stem guide (<NUM>) comprises a passage structure (<NUM>;<NUM>,<NUM>, <NUM>) for guiding a side flow (1b) out of the rotating flow to a carrier flow (<NUM>) around the doser (<NUM>) via the central opening (<NUM>).