Mixer device, a use thereof and a method for mixing

Abstract

The invention relates to mixer device (52) for mixing and an additive to the exhaust gas flow from a combustion engine. The mixer device has an additive injection means (1) and a conduit (2) with an inlet opening and an outlet opening. The conduit (2) has a widened portion (5) between the inlet opening and the outlet opening. The additive injection means (1) is located in the widened portion (5) for injecting the additive into the widened portion. The widened portion (5) at the location of the additive injection means (1) defines an injection width (W) being the distance from the additive injection means (1) to the opposite part (6) of the conduit (2). The injection width (W) is larger than the maximum width (W.sub.1) of the conduit (2) adjacent the inlet opening. According to the invention, the cross sectional area of the conduit (2) at the location of the additive injection means (1) is smaller than 1.2 times the cross sectional area of the conduit (2) adjacent the inlet opening. The invention also relates to a use of the mixer device and to a method for mixing an additive to an exhaust gas from a combustion engine.

Claims

1. A mixer device for an additive to an exhaust gas flow from a combustion engine, the mixer device includes an additive injection means and a conduit having an inlet opening and an outlet opening, the conduit includes a widened portion between the inlet opening and the outlet opening, and the additive injection means is located in the widened portion for injecting the additive into the widened portion, the widened portion at the location of the additive injection means defines an injection width being the distance from the additive injection means to an opposite part of the conduit, the injection width is larger than a maximum width of the conduit adjacent the inlet opening, a cross sectional area of the conduit at the location of the additive injection means is smaller than 1.2 times a cross sectional area of the conduit adjacent the inlet opening, wherein the widened portion is asymmetric with respect to a horizontal plane parallel to or containing a longitudinal axis of the conduit and has a first part provided with a bulge with a top, and the opposite part that is aligned with parts of the conduit that are adjacent the inlet opening and the outlet opening, respectively, wherein the bulge in a cross section through the top of the bulge perpendicular to a direction from a center of the inlet opening to a center of the outlet opening has a profile with a concavely curved section at each lateral side of the bulge characterized in that the conduit is circular adjacent the inlet opening and wherein a projection of said cross section through the top of the bulge in a transversal plane adjacent the inlet opening defines a cross section reduction area and a cross section increasing area, the cross section reduction area is defined by the sum of two areas formed between a circumference of the conduit adjacent the inlet opening and a projection of each said concavely curved section, and the cross section increasing area is defined as the area between the circumference of the conduit adjacent the inlet opening and the projection of said concavely curved section that is in said plane of the profile of the bulge that is located outside said circumference, and wherein the cross section reduction area is at least 25% of the cross section increasing area.

2. The mixer device according to claim 1, wherein the injection width is in a range of 1.1-2.0 times said maximum width of the conduit adjacent the inlet opening.

3. The mixer device according to claim 1, wherein the injection width is larger than the maximum width of the conduit adjacent the outlet opening, and the cross sectional area of the conduit at the location of the additive injection means is smaller than 1.2 times the cross sectional area of the conduit adjacent the outlet opening.

4. The mixer device according to claim 1, wherein the cross sectional area of the conduit at the location of the additive injection means is smaller than the cross sectional area of the conduit adjacent the inlet opening.

5. The mixer device according to claim 1, wherein the cross sectional area of the conduit at the location of the additive injection means is smaller than the cross sectional area of the conduit adjacent the outlet opening.

6. The mixer device according to claim 1, wherein the additive injection means is arranged to inject the additive in a direction forming an angle of 75-105° to a straight center line connecting a center of the inlet opening to a center of the outlet opening.

7. The mixer device according to claim 6, wherein said opposite part has circular shape and an extension in the circumferential direction of 180°.

8. The mixer device according to claim 6, wherein the bulge in the longitudinal direction extends over a major part of the conduit and in the longitudinal direction has a profile including a first sloping section extending from adjacent the inlet opening to the top of the bulge and a second sloping section extending from the top of the bulge to adjacent the outlet opening.

9. The mixer device according to claim 8, wherein the first sloping section has a longitudinal extension that is longer than a longitudinal extension of the second sloping section.

10. The mixer device according to claim 9, wherein the recesses extend longitudinally over a major portion of the bulge and are continuously shallowing with increasing longitudinal distance from the top of the bulge.

11. The mixer device according to claim 9, wherein the conduit is circular adjacent the inlet opening and wherein each said concavely curved section at least partly is circularly curved with a radius in a range of 0.5-1.5 times the radius of the conduit adjacent the inlet opening.

12. The mixer device according to claim 1, wherein a plate is mounted within the conduit adjacent said opposite part of the conduit and at a short distance therefrom, which short distance is in a range of 5-20% of the maximum width of the conduit adjacent the inlet opening and a follows the shape of said opposite part.

13. The mixer device according to claim 12, wherein the extension of the plate in the circumferential direction is in a range of 45-200°.

14. The mixer device according to claim 12, wherein the plate has a thickness that is smaller than the thickness of the wall of the conduit.

15. The mixer device according to claim 12, wherein the distance from the additive injection means to the part of the plate that is opposite the additive injection means is larger than the maximum width of the conduit adjacent the inlet opening.

16. The mixer device according to claim 12, wherein the plate longitudinally extends out through the outlet opening.

17. A combustion engine system including the mixer device according to claim 1.

18. A vehicle, a vessel or a stationary plant including the combustion system according to claim 17.

19. A use of the mixer device according to claim 1, wherein said additive is a liquid containing urea and wherein the gas/liquid-mixture is used for selective catalytic reduction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic side view of a combustion engine system according to an aspect of the invention and of an apparatus, of which the engine system is a part.

(2) FIG. 2 is a side view of a mixer device according to the invention.

(3) FIG. 3 is an end view from the inlet end of the mixer device illustrated in FIG. 2.

(4) FIG. 4 is a schematic section along line IV-IV of FIG. 2.

(5) FIG. 5 is a perspective view of the mixer device illustrated in FIG. 2.

(6) FIG. 6 is a section similar to that of FIG. 4, but illustrates a second example

DESCRIPTION OF EXAMPLES

(7) FIG. 1 illustrates the context in which the mixer device 52 according to the invention is intended to be used. Reference numeral 50 represents an apparatus having a combustion engine 51. The apparatus 50 may be a vehicle, vessel or a stationary plant. Exhaust gas from the combustion engine 51 is led to a mixer device 52 for injecting a liquid and mixing the injected liquid with the exhaust gas. From the mixer device the gas is led to a treatment unit 53, e.g. for SCR.

(8) FIG. 2 in a side view depicts a mixer device according to the present invention. The mixer device has a conduit 2 extending from an inlet opening 3 to an outlet opening 4. The inlet opening 3 and the outlet opening 4 are circular and the conduit 2 is circular-cylindrical a short distance adjacent these openings. The inlet opening 3 is provided with a flange 15 for connection to the outlet of an internal combustion engine, and the outlet opening 4 is provided with a similar flange 16 for connection to the inlet of an SCR muffler. The conduit 2 defines an axis C-C from the centre C of the inlet opening 3 to the centre of the outlet opening.

(9) Below the axis C-C the conduit has a circular cross sectional profile, which in the present application is expressed as the opposite part 6. Above the axis, the conduit 2 has a more complex shape. It has a widened portion 5 extending almost along the entire conduit 2. The widened portion 5 has a maximum width at a distance from the inlet opening 3 that is about ⅔ of the length of the conduit 2. The maximum width extends a short longitudinal distance.

(10) At the middle of the maximum width, additive injection means 1 (not visible in this figure, see FIG. 4) is, mounted inside the cover 19. The injected additive may be a liquid containing urea.

(11) From the right end of the maximum width the widened portion 5 slopes down to the short cylindrical conduit portion adjacent the inlet opening 3. On the left side there is a corresponding slope towards the short cylindrical conduit portion adjacent the outlet opening 4. The latter slope is shorter and steeper than the other one. The widened portion 5 thus forms a bulge 8 with a top 9 in the region adjacent the additive injection means. The distance from the top 9 of the bulge 8 to the opposite part 6 in the illustrated example is about 1.5 times the radius of the inlet opening 3.

(12) On each lateral sides of the bulge 8 there is a recess. In a plane perpendicular to the axis C-C in the region where the additive injection means is located, each recess is formed by a concavely curved section of the profile 13a, 13b of the conduit wall. Each recess extends over a major portion of the bulge 8 and becomes continuously shallower in the direction to the inlet opening 3 and to the outlet opening 4.

(13) Inside the conduit there is mounted a plate 14 of metal, which extend along the entire conduit 2 and projects a short distance out from the outlet opening 4. The plate is substantially semi-circular and is located adjacent the circularly shaped portion below the axis C-C, i.e. the opposite side 6, with a small clearance d therebetween.

(14) Conventionally the mixer device 52 may be provided with sensors 17, 18 adjacent the inlet opening 3 for sensing the temperature and NO.sub.R-content, respectively.

(15) In the cross section in FIG. 3, the arrangement of this plate 14 can be seen. The distance h between the plate 14 and the conduit wall is small. Where the distance as largest it is about 10% of the radius of the inlet opening. The distance d decreases continually in the lateral directions from its maximum. The plate 14 is relatively thin with decreasing thickness in the lateral directions. The maximum thickness of the plate is less than the wall thickness of the conduit 2.

(16) In FIG. 3 the profiles 13a, 13b also are visible. The profiles 13a, 13b in this cross section are circular curves having a radius about equal the radius of the inlet opening 3. When the circumference O of the inlet opening 3 and the concavely curved section 13a are projected in one and the same plane perpendicular to the axis C-C, they together enclose a sector-lake area. A corresponding area is formed between the circumference O and the concavely curved section 13b on the laterally other side. These two areas together define an area reduction in comparison with the area of the inlet opening 3. The sum of these two areas thereby represents a cross section reduction area A.sub.1.

(17) FIG. 4 is a cross section through the conduit 2 of the mixer device 52 depicted in FIG. 2 at the region of the additive injection means 1, where the widening portion is as widest. The first, upper part 7 of the profile is formed by the bulge 8 at the top region, from which the concavely curved sections 13a, 13b extend down to the opposite part 6, which is circular and extends about 180°. With a broken line, the circumference of the inlet opening O is indicated, which circumferential at the lower half of the figure aligns with the opposite part 5.

(18) The injected liquid containing urea is injected downwards and hits the plate 14. The distance between the additive injection means 1 and the plate 14 is indicated with D. The diameter of the inlet opening is W.sub.1, which in the example is equal to the diameter W.sub.2 of the outlet opening. The distance D in the example is about 1.25 times the diameter W.sub.1, W.sub.2. The cross sectional increasing area A.sub.2 is the cross sectional area of the bulge 8 above the circumferential O of the inlet opening. This area and the cross sectional reduction area A.sub.1 as defined above are indicated as shaded in the figure.

(19) In the perspective view of FIG. 5, the shape of the recessions formed by the concavely curved sections 13a, 13b can be seen.

(20) FIG. 6 illustrates a second example of the invention. In this example the conduit 2 does not have a plate adjacent the opposite part 6 corresponding to plate 14 in FIG. Instead the injection jet hits the opposite part 6 of the conduit 2 with the injection width W, being the distance from the additive injection means 1 to the opposite part 6. In all other respects the example of FIG. 6 is similar to that of FIG. 4.