Mixing device

Abstract

A mixer assembly comprises a tubular housing including a reductant inlet, an exhaust gas inlet and an exhaust gas outlet. The tubular housing defines a longitudinal axis along which exhaust enters the housing. The reductant inlet is positioned on a first side of the tubular housing. An upstream element covers approximately one-half of the cross sectional area of the enhaust gas inlet and is positioned upstream of the reductant inlet. An upstream surface of the upstream mixing element directs exhaust gas flow transversly toward the reductant inlet. A downstream mixing element along with the upstream mixing element at least partially defines a reductant receiving duct in which injected reductant and exhaust gas mix.

Claims

1. A mixer assembly for mixing an injected reductant with an exhaust gas output from a combustion engine, comprising: a tubular housing including a reductant inlet, an exhaust gas inlet and an exhaust gas outlet, the tubular housing defining a longitudinal axis along which the exhaust enters the housing, wherein the reductant inlet is positioned on a first side of the tubular housing; an upstream mixing element covering substantially one-half of a cross-sectional area of the exhaust gas inlet, wherein the upstream mixing element is positioned upstream from the reductant inlet, wherein an upstream surface of the upstream mixing element directs the exhaust gas flow transversely across the tubular housing toward the reductant inlet; and a downstream mixing element positioned downstream from the reductant inlet and the upstream mixing element, wherein the upstream mixing element and the downstream mixing element at least partially define a reductant receiving duct in which the injected reductant and the exhaust gas mix.

2. The mixer assembly of claim 1, wherein the downstream mixing element urges the exhaust gas to flow radially in a direction away from the reductant inlet.

3. The mixer assembly of claim 1, wherein the downstream mixing element covers substantially one-half of a cross-sectional area of the tubular housing.

4. The mixer assembly of claim 1, wherein the reductant receiving duct is shaped to impart a swirling motion on the mixed injected reductant and exhaust gas.

5. The mixer assembly of claim 1, wherein a divider is positioned downstream from the upstream surface of the upstream mixing element to split the exhaust gas into two divided flow streams.

6. The mixer assembly of claim 5, wherein the divider is intersected by an axis along which the reductant is injected.

7. The mixer assembly of claim 5, wherein the two divided flow streams swirl in opposite directions to one another.

8. The mixer assembly of claim 7, wherein the injected reductant impacts the two divided flow streams.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and details of the invention are explained in the patent claims and in the description and figures, in which:

(2) FIG. 1a shows a profile view of the principle sketch of the mixing device from the front;

(3) FIG. 1b shows the mixing device shown in FIG. 1a from the rear;

(4) FIG. 2a, 2b show the respective profile view A-A or B-B according to FIG. 1a;

(5) FIG. 3a shows the mixing device with exhaust pipe;

(6) FIG. 3b shows the dividing wall with single-part flow guide element S1, S2;

(7) FIG. 4 shows an alternative embodiment in a perspective view;

(8) FIG. 5a shows the mixing device shown in FIG. 4 from the rear;

(9) FIG. 5b shows the profile view C-C shown in FIG. 5a;

(10) FIG. 6 shows a profile view of a schematic sketch without mixing pipe.

DETAILED DESCRIPTION OF THE INVENTION

(11) The mixing device 1 shown in FIG. 1a features a tubular housing 2 with a round profile Q. Within this housing 2, an intermediate wall 3 is provided which is set at an angle α opposite a mid-axis 2.2 (see FIG. 2a, 2b). On the intermediate wall 3, a flow guide element S1 is provided which extends upstream with respect to the direction of the exhaust gas (to the left according to FIG. 2) from the intermediate wall 3. The flow guide element S1 features two inflow openings E1, E2, through which an exhaust gas flow T (see FIG. 3a) can flow from the inflow side 3.1 shown in FIG. 1a of the intermediate wall 3 to the rearward outflow side 3.2. The surface of the flow guide element S1 increases upwards, so that there is sufficient space for the inflow openings E1, E2 mentioned above. A bridge 2.6 is formed between the two inflow openings E1, E2. As a result of the bridge 2.6, said exhaust gas flow T is divided into two partial streams T1, T2. The partial stream T1 flows in a clockwise direction and the partial stream T2 flows in an anticlockwise direction into the respective inflow opening E1, E2. With respect to a symmetrical axis Sy, which according to FIG. 1a divides the housing 2 approximately in the middle and horizontally, the two inflow openings E1, E2 are moved towards the upper wall section W1, additionally the flow guide element S1 features a further inflow opening Ex, through which a small portion of the exhaust gas can flow from the inflow side 3.1 to the outflow side 3.2 of the intermediate wall 3.

(12) The outflow side 3.2 of the intermediate wall 3 is according to FIG. 1b mirror symmetric to the symmetry axis Sy. There, the flow guide element S2 is located, which extends in the direction of the exhaust gas flow (to the right according to FIG. 2) over the intermediate wall 3. The flow guide element S2 features two outflow openings A1, A2, which are displaced downwards with respect to the symmetry axis S2 to a wall section W2. Both flow guide elements S1, S2 feature a longitudinal axis L1, L2, which according to the exemplary embodiment runs central to the pipe wall 2.1 or at right-angles to a mid-axis 2.2 of the pipe wall 2.1. Further outflow openings Ax are provided in the intermediate wall 3, which are positioned opposite the outflow openings A1, A2 with respect to the symmetry axis Sy. A bridge 2.4 is also formed between the two outflow openings A1, A2, so that the exhaust gas stream T exits in two partial streams T3, T4, wherein the partial stream T3 leaves the flow guide element S2 in an anticlockwise direction and partial stream T4 leaves in a clockwise direction. Additionally, the flow guide element S2 features further outflow openings Ax in the area of the bridge 2.4. A flow blade 9.2 is provided on the respective outflow opening Ax, through which the auxiliary stream that flows through the outflow opening Ax can be deflected in a radial direction.

(13) Both flow guide elements S1, S2 bound a mixing chamber 2.3, which due to the opposite arrangement of the inflow openings E1, E2 on the one hand and the outflow openings A1, A2 on the other is predominantly flowed through by the exhaust gas stream T in the radial direction.

(14) As can be seen in FIG. 3a, a feed device 5 with a feed nozzle 5.1 is located within the mixing chamber 2.3, through which an additive is introduced into the exhaust gas stream T.

(15) In the profile view A-A shown in FIG. 2a, the flow guide element S1 and the flow guide element S2 can be seen in profile. The exhaust gas that flows in here from the left enters into the inflow opening E1 or into the additional opening Ex into the mixing chamber 2.3 and leaves said chamber via the outflow opening A1. Within the mixing chamber 2.3, a corrugated base 7 is arranged below the outflow opening A1 transversely to the main flow direction, which prevents the formation of a stream bottleneck in the area of the outflow opening A1. Additionally, within the mixing chamber 2.3, a baffle plate 2.5 is provided, which can be moistened with additive through the nozzle 5.1 not shown here.

(16) In the profile view B-B according to FIG. 2b, only the intermediate wall 3 is profiled, while the two flow guide elements S1, S2 can be seen in a side view. The opposite inflow openings E1, E2 can be seen, as can the two outflow openings A1, A2. The intermediate wall 3 is set opposite the mid-axis 2.2 and the angle α. The exhaust gas stream that comes from the left here is largely deflected upwards in the radial direction towards the inflow openings E1, E2 and in turn flows through the mixing chamber 2.3 in the radial direction from the inflow openings E1, E2 downwards to the outflow openings A1, A2, and leaves the mixing chamber 2.3 to the right through the two outflow openings A1, A2 according to FIG. 2b.

(17) According to FIG. 3a, the mixing device 1 is an integral part of an exhaust pipe 4.1, 4.2 as part of a particle filter or catalytic converter. Through the nozzle 5.1, additive is introduced into the mixing chamber 2.3, which is guided via the above exhaust gas stream T1 or T2, starting from the area of the inflow openings E1, E2 downwards in the radial direction to the outflow openings A1, A2, and leaves the mixing chamber 2.3 through both partial streams T3, T4, and again combines to form the total stream T. According to FIG. 3a, as an alternative to the corrugated base 7 shown in FIG. 2, a flow guide element in the form of a ramp 8 is provided in the area of the outflow opening A1 within the mixing chamber 2.3, so that stream bottlenecks are prevented in this area.

(18) Decisive for the definition of the angle α is the straight line G, which connects the intersection points of the intermediate wall 3 and the pipe wall 2.1, wherein the two intersection points have the greatest distance from each other with respect to the exhaust gas stream or the direction of the mid-axis 2.2.

(19) According to FIG. 3b, the intermediate wall 3 is shown with a single-part flow guide element S1, S2 arranged within it. The single-part flow guide element S1, S2 is designed as a cylindrical pipe, which is inserted into a corresponding recess in the oval intermediate wall 3 and which is tightly connected to the intermediate wall 3. The assembly thus created is then inserted into the housing 2, as shown in FIG. 3a, wherein the intermediate wall 3 is connected on the circumference side with the pipe wall 2.1.

(20) FIG. 4 shows an alternative embodiment. Within the housing 2, two intermediate walls Z1, Z2 are provided at a distance with respect to the mid-axis 2.2, which extend respectively over approximately half the profile area QF of the housing 2. The two intermediate walls Z1, Z2 are also positioned opposite with respect to the two opposite wall sections W1, W2, so that the exhaust gas stream T, which enters into the mixing chamber 2.3 through an inflow opening E1, is deflected downwards in the radial direction to the outflow opening A1 and leaves the mixing chamber 2.3 through the outflow opening A1. The feed device 5 with the feed nozzle 5.1 for additive is also provided within the mixing chamber 2.3 or in the housing 2.

(21) A wedge-shaped flow guide element S3 is provided in the area of the wall section W2, which divides the impinging exhaust gas stream T into two partial streams T3, T4. Due to the wedge-shaped design of the flow guide element S3, a partial stream T3 is created with respect to the flow direction, which is deflected in an anticlockwise direction, while the partial stream T4 is deflected in a clockwise direction.

(22) According to FIG. 5a, the mixing device 1 is shown from the outflow side 3.1 (lee side). The mixing chamber 2.3 can only be seen within the scope of the outlet opening A1. In contrast to FIG. 4, within the upper part of the mixing chamber 2.3 an optional mixing pipe 6 with a perforation 6.1 is arranged, which is positioned coaxially to the feed device 5. The exhaust gas or exhaust gas stream T which flows in through the inflow opening, thereby initially flow through the mixing pipe 6 within which it then mixes with the sprayed in additive and is guided downwards towards the flow guide element S3, where the two partial streams T3, T4 are deflected in the circumferential direction in counter directions as described above.

(23) Within the second intermediate wall Z2, further slit-shaped outflow openings Ax are provided, the outflow profile Xa of which is subordinate relative to the outflow opening A1. These then merely serve to prevent a stream bottleneck in the area of the upper wall section W1. Additionally, in the first intermediate wall Z1, further slit-shaped inflow openings Ex are provided, the inflow profile Xe of which is subordinate relative to the inflow profile QE of the inflow opening E1. These serve to prevent a stream bottleneck in front of the first intermediate wall Z1 in the area of the lower wall section W2. A flow blade 9.1 is provided on the respective inflow opening E1, through which the auxiliary stream that flows through the inflow opening Ex can be deflected in a radial direction.

(24) FIG. 5b shows the profile view C-C shown in FIG. 5a. The mixing pipe 6 is oval and therefore features an enlarged entrance and exit area facing towards the exhaust gas stream T. After it has flowed through the mixing pipe 6, the exhaust gas stream T is according to FIG. 5b deflected in the radial direction and leaves the mixing device 1 in a divided, counter-directional stream movement outwards in the circumferential direction.

(25) In the exemplary embodiment shown in FIG. 6, the second intermediate wall Z2 is curved. A mixing chamber is not provided. The exhaust gas stream T that enters from the right is deflected downwards in the radial direction towards the flow guide element S3 after entering the mixing chamber 2.3, and leaves the mixing chamber 2.3 through the outflow opening A1. Here, the height of the flow guide element S3 increases in the direction of the first intermediate wall Z1, so that the two partial streams T3, T4 are formed at an early stage.

LIST OF REFERENCE NUMERALS

(26) 1 Mixing device 2 Housing 2.1 Tubular wall 2.2 Mid-axis 2.3 Mixing chamber 2.4 Bridge between A1, A2 2.5 Baffle plate 2.6 Bridge between E1, E2 3 Intermediate wall 3.1 Inflow side, windward side 3.2 Off-flow side, lee side 4.1 Exhaust pipe 4.2 Exhaust pipe 5 Feed device 5.1 Feed nozzle 6 Mixer, mixer pipe 6.1 Perforation 7 Corrugated base 8 Cone, ramp, flow guide element 9.1 Blade of Ex 9.2 Blade of Ax A1 Outflow opening A2 Outflow opening Ax Outflow opening E1 Inflow opening E2 Inflow opening Ex Inflow opening G Connection straight line, straight line LE Plane L1 Longitudinal axis of S1 L2 Longitudinal axis of S2 Q Profile of 2 QA Outflow profile QE Inflow profile QF Outflow area S1 Flow guide element S2 Flow guide element S3 Flow guide element Sy Symmetry axis T Exhaust gas stream T1 Partial stream of exhaust gas stream T2 Partial stream of exhaust gas stream T3 Partial stream of exhaust gas stream T4 Partial stream of exhaust gas stream W1 Wall section W2 Wall section Xa Outflow profile of total Ax Xe Inflow profile of total Ex Z1 Intermediate wall Z2 Intermediate wall α Angle