FIELD OF THE INVENTION

The invention relates to a mixing device for integration or connection or coupling to an exhaust pipe or connection to an exhaust pipe of a combustion engine and for mixing an exhaust gas stream T, which is formed from a housing having a tubular wall with a round or oval profile Q and a mid-axis that can be aligned parallel to the exhaust pipe and from an intermediate wall which is aligned transversely to the mid-axis, wherein the intermediate wall divides the housing and features an inflow side and an outflow side, and creates a division of the housing into an inflow section and an outflow section, wherein at least one inflow opening E1is provided in the intermediate wall, through which the exhaust gas stream T can flow at least partially from the inflow side of the intermediate wall to an opposite outflow side of the intermediate wall, wherein the at least one inflow opening E1is positioned eccentrically with respect to the mid-axis and is brought close to a wall section W1of the tubular wall.

The invention further relates to a mixing device for connection to or integration into an exhaust pipe of a combustion engine and for mixing an exhaust gas flow T, which is formed from a housing with a tubular wall with a round or oval profile Q and with a mid-axis that can be arranged parallel to the exhaust pipe and with a first intermediate wall Z1and with a second intermediate wall Z2which are aligned transversely to the mid-axis, wherein both intermediate walls Z1, Z2at least partly bound a mixing chamber, wherein the first intermediate wall Z1features at least one inflow opening E1, through which the exhaust gas stream T can enter the mixing chamber, wherein the inflow opening E1is positioned eccentrically with respect to the mid-axis and is brought close to a wall section W1of the tubular wall, and the second intermediate wall Z2features at least one outflow opening A1, through which the exhaust gas stream T can exit from the mixing chamber, wherein the outflow opening A1is positioned eccentrically with respect to the mid-axis and is brought close to a wall section W2of the tubular wall.

The exhaust pipe can also be the corresponding part of the housing for a catalytic converter or particle filter.

The mixing relates to an additive to be incorporated, such as a reduction agent or hydrocarbon compounds.

The housing usually has a round profile Q. Alternatively, said housing can also feature an oval or polygonal profile Q.

For the purpose of forming an inflow opening E or an outflow opening A1, a recess is always required within an intermediate wall that closes the profile area QF of the housing. This can be achieved according to the exemplary embodiments through the use of a correspondingly small intermediate wall, which is reduced in diameter over a portion of the circumference.

BACKGROUND OF THE INVENTION

A mixing device for connection to an exhaust pipe of a combustion engine for mixing an exhaust gas stream is already known from WO 2012/080585 A1. This features a housing with a tubular wall with a round profile and a mid-axis that can be aligned parallel to the exhaust pipe, and an intermediate wall with an inflow opening which is essentially aligned transversely to the mid-axis. The intermediate wall has a coiled shape, so that the entire exhaust gas stream is deflected in the same circumferential direction. Additionally, a downstream second intermediate wall is provided with an outflow opening, which together at least partially bound a mixing chamber.

A mixing device is known from U.S. Pat. No. 8,033,104 B2, which features a perforated intermediate wall that lies transverse to the exhaust pipe and a feed channel for reduction agent. A portion of the exhaust gas stream mixes with the reduction agent while flowing through the perforated feed channel. A second portion of the exhaust gas is not guided through the feed channel, but flows through the perforation of the intermediate wall and thus reaches the exit of the mixing device.

In DE 10 2013 012 909 A1, a mixing chamber is described which features a tubular flow guide element, through which the exhaust gas stream is guided from an entrance opening of the mixing chamber to an exit opening, wherein the axis of the flow channel lies transversely to the mid-axis of the mixing chamber. At one end of the flow guide element, an additive can be injected so that said additive mixes with the exhaust gas in the tubular channel.

FR 2 943 381 A1 describes a tubular mixing element with three intermediate walls, wherein the middle intermediate wall is arranged opposite the first and last intermediate wall with respect to the mid-axis.

WO 2014 051617 A1 also describes a mixing device which effects a deflection of the exhaust gas stream in the circumferential direction.

DE 10 2012 224 198 A1 describes a classic swirl mixer consisting of a mixing sheet with several mixing blades distributed over the circumference.

SUMMARY OF THE INVENTION

The object of the invention is to design and arrange a mixing device in such a manner that a good mixing behavior is guaranteed despite the compact, space-saving construction.

The object is attained according to the invention by the fact that a flow guide element S2is provided with a longitudinal axis L2, which with the intermediate wall at least partly bounds a mixing chamber, and by means of which an at least partial deflection of the exhaust gas stream T can be effected from its original flow direction into a radial direction in relation to the mid-axis or the housing, wherein the flow guide element S2features at least two outflow openings A1, A2, and by means of the flow guide element S2, the exhaust gas flow T can be guided, starting from the inflow opening E1to the at least two outflow openings A1, A2, wherein all outflow openings A1, A2are positioned eccentrically with respect to the mid-axis and are brought close to a wall section W2of the tubular wall, wherein the wall section W2is arranged opposite the wall section W1with respect to the mid-axis, and the outflow openings A1, A2are arranged on opposite sides of the flow guide element S2with respect to the longitudinal axis L1, L2, wherein with respect to the mid-axis, a first partial stream T3can be guided at least partially in the anticlockwise direction and a second partial stream T4can be guided at least partially in the clockwise direction out of the outflow openings A1, A2. Due to the arrangement of the outflow openings A1, A2on opposite sides of the flow guide element S2, a bridge is formed.

The object is also attained according to the invention through the fact that the wall section W2is arranged opposite the wall section W1with respect to the mid-axis, so that an at least partial deflection of the exhaust gas stream T can be effected at least partially in a radial direction with respect to the mid-axis, and in the flow direction after the first intermediate wall Z1or before the second intermediate wall Z2in the area of the outflow opening A1, at least one flow guide element S3is provided in the mixing chamber, which protrudes in the radial direction over the tubular wall and effects a division of the exhaust gas stream T into two partial streams T3, T4, wherein with respect to the mid-axis, a first partial stream T3can be guided in the anticlockwise direction, and a second partial stream T4can be guided in a clockwise direction around the flow guide element S3. During operation, the flow guide element S3guides the first partial stream T3in an anticlockwise direction and the second partial stream T4in a clockwise direction.

The inflow opening E1lies opposite the respective outflow opening A1, A2with respect to the mid-axis. In relation to a symmetrical axis, which runs transversely to the mid-axis or at right-angles to a plane LE which spans through the mid-axis and longitudinal axis L2, the inflow opening E1is positioned between the symmetrical axis Sy and the wall section W1, while the respective outflow opening A1, A2is positioned between the symmetrical axis Sy and the wall section W2. Due to the opposite arrangement of the inflow and outflow openings E1, A1, A2with respect to the mid-axis, a deflection of the exhaust gas flow T is achieved in a radial direction to the pipe. This in turn supports the function of the flow guide element S2, S3, which effects the counter-directional deflection in the circumferential direction, i.e. in a clockwise direction and an anticlockwise direction.

It has been shown in studies that the deflection of the entire exhaust gas stream into a single swirl flow moving in the same direction in the circumferential direction leads to a disadvantageous interaction with the housing wall of the mixing device, such as condensation or the crystallization of an additive that has also been transported. Through the use of a flow guide element, which divides the exhaust gas stream and conducts a circumferential movement in the opposite direction, in combination with a flow deflection of the entire exhaust gas stream into a radial direction, the circumferential speed is in general lower, which also leads to lower centrifugal forces. Therefore, the aerosols of the additive transported in the exhaust gas stream are added less intensively to the housing wall, as a result of which the degree of condensation or crystallization is reduced considerably. The deflection in the opposite direction leads to a further mixing of the exhaust gas stream. Here, the flow conditions at the outflow opening A1are initially of importance for the division of the exhaust gas stream and the respective deflection. A division applied upstream in the area of the inflow opening E1of the exhaust gas stream and/or its deflection in the circumferential direction can be advantageous, as described below.

In this regard, it can be advantageous when on the intermediate wall a first flow guide element S1with a longitudinal axis L1is provided, which protrudes upstream in the axial direction over the intermediate wall and which with the intermediate wall at least partly bounds the mixing chamber, wherein two inflow openings E1, E2are provided in the intermediate wall, which are arranged opposite in relation to the longitudinal axis L1or the plane LE, wherein the flow guide element S1effects a division of the exhaust gas stream T into two partial streams T1, T2, wherein with respect to the mid-axis, a first partial stream T1can be guided in a clockwise direction and a second partial stream T2can be guided in an anticlockwise direction around the flow guide element S1into the respective inflow opening E1, E2and into the mixing chamber. The exhaust gas stream is therefore already divided when it enters the mixing chamber and is deflected in the circumferential direction, so that mixing is further improved. Due to the arrangement of the inflow openings E1, E2on opposite sides of the flow guide element S1, a bridge is formed.

For this purpose, it can also be advantageous when the flow guide elements S1, S2are designed as a single piece and/or when at least one flow guide element S1, S2is an integrated part of the intermediate wall and/or the tubular wall. The combination of an intermediate wall with a pipe that runs diametrically within it, which forms the flow guide element S1, S2and bounds the mixing chamber, appears to be advantageous.

It can further be advantageous when the inflow opening E1, E2and/or the outflow opening A1, A2extends at least partially or fully onto the flow guide element S1, S2or is provided in the flow guide element S1, S2.

An inflow opening is required through which the exhaust gas can penetrate. Depending on the design of the mixing chamber, said chamber is arranged within the intermediate wall. Insofar as the flow guide element S1is an integral part of the intermediate wall, it remains in the intermediate wall near the inflow opening. Only the positioning of the inflow opening can be changed in such a manner that the flow guide element S1is covered. If the flow guide element S1is a separate component, which is positioned on the intermediate wall, an inflow opening must be provided both in the intermediate wall and the flow guide element S1. The same applies to the outflow openings.

If the flow guide element S1is an integral part of the intermediate wall, no further intermediate wall is required for the flow guide element S2, i.e. the flow guide element S2can be designed as a separate component which is positioned on the one intermediate wall. In an equivalent manner, the flow guide element S2can also be an integral component of the intermediate wall, so that the flow guide element S1is designed as a separate component.

Finally, it is also possible to provide two intermediate walls and for the respective flow guide element S1, S2to be an integral part of the respective first or second intermediate wall.

Here, it can advantageously be provided that the intermediate wall and the mid-axis enclose an angle α between 20° and 80°, or between 30° and 60°, or between 55° and 75°, or of 65°. The angle between the intermediate wall and the mid-axis determines the ratio between the profile size or housing height and the construction length or housing length. Since the shortest possible construction length of the mixing device is desired, angles between 55° and 75° are particularly advantageous. In relation to the intermediate wall, the straight line G should be taken as a reference, which also results from the connection of the two furthest upstream and downstream connection points of the intermediate wall with the tubular wall.

For this purpose, it can be advantageous when the intermediate wall has a single or multiple angles, contoured or curved form, such as an L, a Z or an S form. The intermediate wall can also be designed asymmetrically with respect to the plane LE.

It can additionally be advantageous when in the mixing chamber in the area before the outflow openings A1, A2, for the purpose of avoiding a steam bottleneck, a corrugated base and/or a flow guide element such as a cone or a semi-cone or a ramp is provided.

It can additionally be advantageous when the intermediate wall is at least partially integrated into the housing or is formed at least partially from the housing.

It can additionally be advantageous when a feed device is fitted with a feed nozzle, through which an additive can be brought into the mixing chamber. When the additive has already been mixed into the exhaust gas stream, an improved mixing can be achieved by the mixing device. Naturally, the mixing in is also provided within the mixing device. Here, it is provided that the additive is injected at an angle of between 5° and 185°, and thus e.g. the inner walls of the mixing chamber are used for atomizing and evaporating the additive.

It can also be advantageous when the inflow opening E1and/or the inflow openings E1, E2form an inflow profile QE and the housing features a profile surface QF that effects the stream, with 0.08 QF<=QE<=0.42 QF The inflow profile therefore moves between 8% and 42% of the pipe profile or housing profile. This entails sufficient acceleration of the exhaust gas on the one hand and acceptable pressure losses on the other.

Accordingly, it can be advantageous when the outflow opening A1and/or the outflow openings A1, A2form an outflow profile QA and the housing features a profile surface QF that affects the stream, with 0.08 QF<=QA<=0.42 QF.

It can additionally be advantageous when the inflow opening E1or the inflow openings E1, E2form an inflow profile QE and at least one further inflow opening Ex is provided in the flow guide element S1or in the intermediate wall Z1, through which a portion of the exhaust gas stream T can enter the mixing chamber, wherein the at least one inflow opening Ex forms an inflow profile Xe, with Xe<=0.1 QE.

It can additionally be advantageous when the outflow opening A1or the outflow openings A1, A2form an outflow profile QA and at least one further outflow opening Ax is provided in the flow guide element S2or in the intermediate wall Z2, through which a portion of the exhaust gas stream T can enter the mixing chamber, wherein the at least one outflow opening Ax forms an outflow profile Xa, with Xa<=0.1 QE.

As a supplement to the inflow and outflow openings E1, E2, A1, A2, further openings Ex, Ax can be provided. While the positioning of the inflow and outflow openings E1, E2, A1, A2is designed according to the invention in such a way that a deflection of the exhaust gas stream in a radial direction to the pipe is achieved, further openings Ex, Ax can be positioned as required. Preferably, however, openings Ex are arranged in the area of the bridge of the flow guide element S1so that the entire exhaust gas stream flows into the mixing chamber.

Additionally, outflow openings Ax can be arranged in the area of the bridge of the flow guide element S2. The value Xe is the perforation profile, i.e. the total of the profiles of all inflow openings Ex, and the Xa value is the total of the profiles of all outflow openings Ax. Preferably, 0.03 A<=Xa<=0.07 A or 0.03 E<=Xe<=0.07 E applies.

It can also be advantageous when a stream blade is provided on at least one inflow opening Ex and/or on at least one outflow opening Ax. In order to avoid a stream bottleneck in this area, or for improved alignment of the auxiliary stream guided through the inflow opening Ex and/or the outflow opening Ax, said auxiliary stream can be deflected by the blades in the radial direction and/or in the circumferential direction.

Additionally, it can be advantageous when in the mixing chamber at least one static mixer or a mixer pipe and/or at least one even or angled or curved baffle plate is provided, wherein the baffle plate is largely arranged parallel to the longitudinal axis L1, L2of the flow guide element S1, S2. The baffle plate can be fitted with a hydrolysis coating which supports the disintegration or transformation of the additive. An anti-adhesion coating or anti-adhesion surface structure is also provided. Advantageously, the baffle plates are arranged in such a manner that a low level of additional pressure loss is generated. This is achieved by the fact that the plates are arranged almost parallel to the flow direction in the mixing chamber.

