MIXER BOX, A USE THEREOF AND A METHOD FOR MIXING

Abstract

Mixer box for mixing, vaporization and decomposition of a liquid additive to the exhaust gas flow from a combustion engine, comprising a gas inlet (108), a gas outlet (109) and internal duct means establishing a gas flow path (A-H, a-h) from the gas inlet (108) to the gas outlet (109). The duct means includes a first duct portion (107) having an outer wall (171) and an inner wall (161), which is surrounded by the outer wall (171), such that the gas flow path through said first duct portion (107) is established inbetween. The first duct portion (107) is provided with at least two partitions (121-124) extending between the outer wall (171) and the inner wall (161), which separate the first duct portion (107) into at least two duct sections (101a, 101b, 102a, 102b) of which at least one is an upstream duct section (101a, 101b) and at least one is a downstream duct section (102a, 102b).

Claims

1.-18. (canceled)

19. A mixer box for mixing and complete or partial vaporization and/or decomposition of a liquid additive to the exhaust gas flow from a combustion engine, which mixer box has a gas inlet (108), a gas outlet (109) and internal duct means establishing a gas flow path (A-H) from the gas inlet (108) to the gas outlet (109), which duct means includes a first duct portion (107) having an outer wall (171) and an inner wall (161), the inner wall (161) being surrounded by the outer wall (171), such that the gas flow path through said first duct portion (107) thereby is established between said walls (161, 171), said first duct portion (107) is provided with at least two partitions (121-124) extending between the outer wall (171) and the inner wall (161) and separating said first duct portion (107) into at least two duct sections (101a,101b, 102a, 102b) of which at least one is an upstream duct section (101a, 101b) and at least one is a downstream duct section (102a, 102b), wherein the duct means further includes a second duct portion (106), which second duct portion (106) is surrounded by the first duct portion (107), characterized in that a liquid injection means (112) is arranged to inject liquid into the second duct portion (106), and where the liquid injection means (112) is provided in an end wall of the second duct portion (106).

20. A mixer box according to claim 19, wherein the number of said partitions (121-124) is at least four and the number of said duct sections (101a, 101b, 102a, 102b) is at least four, and wherein every second duct section as seen in the circumferential direction is an upstream duct section (101a, 101b) and every second duct section is a downstream duct section (102a, 102b).

21. A mixer box according to claim 20, wherein the duct means includes an upstream re-mixing chamber (104) and each upstream duct section (101a, 101b) has a gas outlet connected to and communicating with the upstream re-mixing chamber (104).

22. A mixer box according to claim 20, wherein the duct means includes a downstream re-mixing chamber (105) and each downstream duct section (102a, 102b) has a gas outlet (121a) connected to and communicating with the downstream re-mixing chamber (105).

23. A mixer box according to claim 19, wherein the duct means is arranged to provide a first turn (C) of the gas flow direction 180.

24. A mixer box according to claim 23, wherein the duct means is arranged to provide a second turn (E) of the gas flow direction at least 90, which first (C) and second (E) turns are located at different positions in the gas flow path.

25. A mixer box according to claim 24, wherein the second duct portion (106) has an outer wall that is common to the inner wall (161) of the first duct portion (107).

26. A mixer box according to claim 24, wherein the duct means has said upstream duct section(s) (101a, 101b) located upstream of said second duct portion (106) and said second duct portion (106) located upstream of said downstream duct portion(s) (102a, 102b).

27. A mixer box according to claim 23, wherein the duct means has the second duct portion arranged upstream of the upstream duct section(s) and said upstream duct section(s) located upstream of said downstream duct section(s).

28. A mixer box according to claim 19, wherein the duct means includes a heating surface (110, 113) arranged to be hit by the gas flow and heat the gas.

29. A mixer box according to claim 28, wherein the duct means includes said second duct portion (106), which second duct portion (106) is surrounded by the first duct portion (107) which second duct portion (106) has an outer wall that is common to the inner wall (106) of the first duct portion (107), and wherein the heating surface (110, 113) includes a part of a said common wall (161) and/or an end wall of (113) the second duct portion (106), and where gas flowing in the first duct portion (101a, 101b) acts as a heat source for heating the heating surface (110, 113).

30. A combustion engine system (51-53) including a mixer box (52) according to claim 19.

31. A vehicle, a vessel or a stationary plant (50) including a combustion engine system (51-53) according to claim 30.

32. A use of the mixer box according to claim 19, wherein said liquid additive contains urea and wherein the gas/liquid-mixture is used for selective catalytic reduction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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.

[0040] FIG. 2 is a sketch illustrating the general principle of the invention

[0041] FIG. 3 is a sketch illustrating the principle of the invention according to a first example.

[0042] FIG. 4 is a sketch as seen along line IV-IV of FIG. 2.

[0043] FIG. 5 is a sketch illustrating a further example not part of the invention.

[0044] FIG. 6 is a sketch as seen along line VI-VI of FIG. 5.

[0045] FIG. 7-11 illustrate an example embodiment of the invention with an operating principle according to FIGS. 3 and 4, and of which FIG. 7 is an end view from a front end, FIG. 8 is a side view, FIG. 9 is a perspective view and FIG. 10 is a split view.

[0046] With reference to the appended drawings, below follows a more detailed description of example embodiments of the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

[0047] FIG. 1 illustrates the context in which the mixer box 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 box for mixing injected liquid to the exhaust gas. The injection may be performed inside the mixer box 52 or between the combustion engine 51 and the mixer box 52. From the mixer box the gas is led to a treatment unit 53, e.g. for SCR.

[0048] FIG. 2 illustrates the basic principle of the invention by a sketch depicting parts of the duct means throw which the exhaust gas flows through the mixer box. The exhaust gas enters the mixer box through an inlet 8 and leaves the mixer box through an outlet 9. The FIG. 2 illustrates only the part of the duct means that is of interest for presenting the principle of the invention. The duct means has an annular duct portion 7 with an outer wall 71 and an inner wall 61. The annular duct portion is by two partitions 21, 22 divided into duct sections 1, 2. The duct means connects these duct sections to the non-shown parts of the duct means such that the exhaust gas passes an upstream duct section 1 and at a later stage through a downstream duct section 2.

[0049] The gas through these duct sections 1, 2 may be in the same directions or in the opposite directions. The gas flow may occur directly from the upstream duct section 1 to the downstream duct section 2. The gas flow may alternatively occur through intermediate piping between the two duct sections 1, 2. The inner wall 61 may be the outer wall of an internal pipe forming a second duct portion of the duct means. The exhaust gas may already contain liquid droplets when entering the mixing box or the liquid may be injected within the mixer box. The duct portion 7 is not necessarily annular, i.e. the outer 71 and inner 61 walls may have other shapes than circular.

[0050] FIGS. 3 and 4 illustrate the principle of the invention according to a first example thereof, and schematically depict a mixer box from the front end (FIG. 3) and from the side (FIG. 4). Generally the mixing box has an outer pipe forming a first duct portion 107, which surrounds an inner pipe forming a second duct portion 106. The outer duct portion 107 is annular and has an outer wall 171 and an inner wall 161. The inner wall 161 is simultaneously the outer wall of the second duct portion 106.

[0051] As can be seen in FIG. 3, the first duct portion 107 has four partitions 121-124 connecting the outer wall 171 and the inner wall 161, which partitions 121-124 extend in the axial direction. The partitions 121-124 divide the duct portion 107 into four duct sections 101a, 101b, 102a, 102b. A front plate 113 covers the second duct portion 106 (the inner pipe), which front plate constitutes an end wall 113 of the second duct portion 106. Front plates 153, 154 cover the downstream duct sections 102a, 102b. The duct sections 101a, 101b are upstream duct sections and are arranged in parallel with regards to the flow path. The duct sections 102a, 102b are downstream duct sections and are likewise arranged in parallel. The front plates 113, 153, 154 prevent the inflowing gas to enter anywhere else than into the upstream duct sections 101a, 101b.

[0052] As can be seen in FIG. 4 the mixer box has a gas inlet 108 for exhaust gases and an outlet 109 for the gases after having been mixed with the fluid droplets. The gas inlet 108 communicates with the upstream duct sections 101a, 101b. The upstream duct section 101a communicates by an outlet 111a through the inner wall 161 with an upstream re-mixing chamber 104. A corresponding outlet (not shown) is arranged in the radially opposite side of the inner wall 161 and communicates the upstream duct section 101b with the upstream re-mixing chamber 104. Both these outlets are located axially at the end of the mixing box that is opposite to the gas inlet 108.

[0053] The second duct portion 106, i.e. the central pipe, has a first outlet 131a communicating with the downstream duct section 102a, and has a second outlet (not shown) communicating with the other downstream duct section 102a. These two outlets are in FIG. 3 located opposite each other around the three o clock position and the nine o clock position respectively, (but axially offset of the plane of the paper). The downstream duct section 102a communicates with the gas outlet through an outlet 121a. The other downstream duct section 102b in the same way communicates through a (not shown) opening with the gas outlet 109.

[0054] With reference to FIG. 4, the region adjacent the rightmost end (in FIG. 4) of the second duct portion 106 forms an upstream re-mixing chamber 104. And adjacent the region at the rightmost end of the downstream duct sections 102a, 102b a second re-mixing chamber 105 is established.

[0055] A liquid injection means 112 is provided in the right end wall of the duct portion 106, through which liquid containing urea is injected.

[0056] The exhaust gases A from the combustion engine (not shown) flows into the mixing box from the left in FIG. 3 and enters through the gas inlet 108 into the first duct portion 107 as can be seen by arrow B in FIG. 4. The gas flow thereby is split into two parallel sub-flows B.sub.a and B.sub.b (see FIG. 3) through the upstream duct sections 1a, 1b, respectively.

[0057] The gas then flows through their respective outlet 111a, arrow C into the inlet end (to the right in FIG. 4) of the second duct portion 106. The two sub-flows thereby are re-unified in the re-mixing chamber 104 into a single gas flow D through the second duct portion 106. The re-mixing chamber 104 is located within the second duct portion 106, primarily at the rightmost end thereof. However, the mixing process of course to some extent continues along the complete extension of the second duct portion 106. The fluid injection means 112 injects the fluid into the gas flow in the first re-mixing chamber, i.e. at a location where the gas flow turns 180 simultaneously as the separated gas flows are re-mixed.

[0058] At the left end (FIG. 4) of the second duct portion 106 the gas flows out, arrow E, through the respective outlet, of which only outlet 131a is visible in the figures, into a respective downstream duct section 102a, 102b. The exhaust gas then again is divided into two sub-flows F.sub.a, F.sub.b in the respective downstream duct section, and flows in the right direction in FIG. 4. At the right end of the downstream duct sections 102a, 102b, the gas flows out, arrow G, through a respective outlet 121a into the second re-mixing chamber 105 and from there to the gas outlet 109.

[0059] The outlet 111a from each of the upstream duct section 101a, 101b may extend axially over a substantial part of the extension of the inner pipe; up to half its extension. The same relates to the outlet 131a from the second duct portion 106 into the respective downstream duct section 102a, 102b. Circumferentially, these outlets 111a, 131a may extend all the way between two adjacent partitions, e.g. the outlet 131a may extend along the inner wall 161 all the way between partitions 121 and 124.

[0060] The inner wall 161 may have a portion 110 that acts as a heating means for the exhaust gas flow D in the second duct portion 106. This portion is heated by the exhaust gas flow B in the upstream duct sections 101a, 101b. Also the front plate 113 may in a similar way be used as a heating means for the mixed gas.

[0061] Each of the outlets 111a, 131a and 121a may be formed by a perforated plate.

[0062] FIGS. 5 and 6 illustrates an example that is not part of the invention, since there is no injection device in the urea mixer box as such. Here a duct means connects the gas inlet 208 to the gas outlet 209. Also in this example the duct means includes a first duct portion 207 with an outer wall 271 and an inner wall 261, which inner wall 261 is a pipe forming a second duct portion 206. An annular space is formed between the walls 271, 261, which annular space by four partitions 221-224 is divided into two upstream duct sections 201a, 201b and two downstream duct sections 202a, 202b.

[0063] At the right end (FIG. 6) the second duct portion 206 communicates via a respective outlet 231a with the respective upstream duct section 201a, 201b. The upstream duct sections 201a, 201b through a respective outlet 211a communicate with an upstream re-mixing chamber 204. The downstream duct sections 202a, 202b communicate through a respective inlet 220a with the upstream re-mixing chamber 204 and through a respective outlet 221a with a downstream re-mixing chamber 205 connected to the gas outlet 209.

[0064] The exhaust gas enters, arrow a, the mixer box through the gas inlet 208 and flows through the second duct portion 206, i.e. the inner pipe, and then turns 180, arrow c, when entering through the respective inlet 231a to the respective upstream duct section 201a, 201b in the annular space, whereby the gas flow is split into two separate flows arranged in parallel. The gas thus flows in the axially opposite direction, arrow d in these sections. Thereafter the gas flows through the respective outlets 211a into the upstream re-mixing chamber 204, and from there through the respective inlets 220a, to the respective downstream duct section 202a, 202b. The gas is thereby again turned 180, arrows e, such that the flow, arrow f, through the downstream duct sections 202a, 202b is in the same axial direction as in the first duct portion 206. When entering the upstream re-mixing chamber 204 the gas flow is unified and when leaving this mixing chamber 204 the gas flow is split again. From the downstream duct sections 202a, 202b, the gas flows through the respective outlets 221a into the downstream re-mixing chamber 205, where the gas flows thus are unified again, and then from the downstream re-mixing chamber 205 to the gas outlet 209.

[0065] In this example the injection of liquid may be arranged in a separate injection device (not shown), before the exhaust gas enters the mixer box. The injection may alternatively be arranged within the mixer box at an appropriate location, e.g. in the first duct portion 206.

[0066] FIGS. 7 to 10 illustrate an example of a physical realization of a mixer box according to the invention. This example is related to the principle of the invention as shown in FIGS. 3 and 4.

[0067] As best can be seen in FIG. 9, the mixer box has an outer casing consisting of a circular inlet pipe 350 having a gas inlet 308 and a circular outlet pipe 351 having a gas outlet 309, which are joined by a main housing 352 having the shape like a pear in a section perpendicular to the axis of the pipes 350, 351. The exhaust gas enters into the mixer box through the inlet 308, flows through duct means within the mixer box, wherein liquid is injected into the gas, and leaves the mixer box through the outlet 309 for treatment e.g. SCR. The first pipe has a larger diameter than the second pipe, e.g. 300 mm vs 125 mm.

[0068] FIG. 7 showing the mixer box from the right side of FIG. 8, illustrates, how the gas from the gas inlet enters the two annular parallel duct sections 301a, 301b, which are the upstream duct sections in the first duct portion. Circumferentially these sections are limited by the partitions 321, 322 and 323 and 324 respectively. The remaining parts of the annular space are covered by a respective plate 353, 354, behind which the downstream duct sections 302a, 302b are located. The central part is covered by a front plate 313, behind which the second duct portion 306 is located. The arrow symbols illustrate that the flow through the upstream duct sections 301a, 301b is directed from the eyes of the observer of the figure, then turns 180 while flowing into the second duct portion 306 and flows against the eyes of the observer, and thereafter turns an another 180 and again flows in the direction away from the eyes of the observer. Finally the gas flows up through the main body 352 and out through the outlet pipe 351 to the gas outlet. 309.

[0069] The part of the outer wall 371 that is most close to the gas inlet 308 is formed by the inlet pipe 350.

[0070] In FIG. 8 it can be seen that fluid injection means is arranged at the rear end of the second duct portion 306 (the inner pipe).

[0071] In the perspective view of FIG. 9 the partitions 321 and 324 are left out for better visibility and understanding.

[0072] The split view of FIG. 10 depicts the various parts forming the mixer box. The main housing 352 consists of the rear end wall 356, the front end wall 358 and the circumferential wall 357. To openings 359, 360 in the front end wall 358 the inlet pipe 350 and the outlet pipe 351 are attached.

[0073] The second duct portion 306, i.e. the inner pipe, has a rear end plate 362 attached in an opening 361 in the rear end wall 356 of the housing. In this rear end plate 362 the fluid injection means 312 is mounted for injecting the liquid into the second duct portion 306. At the other end, the second duct portion 306 is covered by the front cover plate 313.

[0074] The rear end of the second duct portion 306 has two slits 311a, 311b diametrically facing each other and circumferentially extending between partitions 321, 322 and 323, 324 respectively. Likewise the front end of the second duct portion 306 has two slits 331a, 331b diametrically facing each other and circumferentially extending between partitions 321, 324 and 322, 323, respectively. The slits form the outlets 311a, 311b from the upstream duct sections 301a, 301b to the second duct portion 306 via the upstream re-mixing chamber is and the outlets 331a, 331b from the second duct portion 306 to the downstream duct sections 302a, 302b, respectively.

[0075] The first (outer) duct portion 307 and the second duct portion 306 (inner) both have a rear part axially located within the main housing 352 and a front part axially located in the inlet pipe 350. Each of the slits 311a, 311b, 331a, 331b, extends almost over the half length of the inner pipe 306. The slits 311a, 311b axially extend over a major part of the main housing 352.

[0076] Details of the first duct portion 307 (not denoted a reference number in FIG. 10) can be seen at the top and bottom of the split view. At the rear part of the partitions 321, 322 there is a circularly shaped cover plate 363a attached to the outer ends of the partitions 321, 322. Further there is a rear end plate 364a attached to the rear ends of these partitions 321, 322. Correspondingly are the details 323, 324, 363b and 364b attached to each other. The circularly shaped cover plates 363a, 363b are axially located in the main housing 352 and reach from rear wall 356 to the front wall 358 of the main housing. These cover plates 363a, 363b together with the inlet pipe 350 constitute the outer wall 307 of the first duct portion 307. The front cover plate 354 is attached to the front ends of partitions 322, 323 and the front cover plate 353 is correspondingly attached to the partitions 321, 324.

[0077] The exhaust gas entering through the inlet pipe 350 flows solely through the upstream duct sections, i.e. the space between partitions 321, 322 and 323, 324 respectively. The gas is prevented from entering through the other annular parts by the front cover plates 353 and 354, and prevented from entering into the inner pipe by the front cover plate 313.

[0078] When reaching the rear parts of the upstream sections, the gas flows through the slits 311a, 311b, forming outlets of the upstream duct sections, and then through the inner pipe in the opposite direction. In the rear part of the second duct portion 306 (the inner pipe), the two parallel gas flows thereby is re-mixed and this part of the inner pipe thereby acts as an upstream re-mixing chamber.

[0079] At the front part of the inner pipe, the gas flows through the slits 331a, 331b into the downstream duct sections, i.e. the space between 321, 324 and 322, 323, respectively while again turning 180. Thereby the gas flow again is split into two parallel gas flows in the direction towards the rear side of the mixer box.

[0080] When reaching the rear parts of the downstream duct sections the mixer box opens up for the gas to escape to the surrounding parts of the main housing 352. This because between the partitions 321 and 324 there are no circumferential cover plates, like those 363a, 363b bridging the partition 321 to 322 and 323 to 324, respectively. Likewise there is no such cover plate bridging partitions 322 and 323. Thereby the gas flow again is unified, whereby a downstream re-mixing chamber is formed within the main housing 352. Finally the gas flows from the main housing 352 through the outlet pipe 351 and the gas outlet 309 for SCR-treatment.

[0081] The front cover plate 313 covering the inner pipe will be hit by the inflowing gas and thereby heated. The other side is hit by the gas-flow containing the liquid droplets injected by the liquid injection means 312. The latter gas-flow thereby will be heated by the front cover plate 313. Also the front part of the inner pipe will act as a heat exchanger; heating the mixed gas and taking heat from the inflowing gas.