The present invention in a first aspect relates to 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, a gas outlet and internal duct means establishing a gas flow path from the gas inlet to the gas outlet, which duct means includes a first duct portion having an outer wall and an inner wall, the inner wall being surrounded by the outer wall, such that the gas flow path through said first duct portion thereby is established between said walls.
In a second aspect, the invention relates to a use of the invented mixer box.
Mixing and vaporization and/or decomposition of a liquid into a gas stream are dependent on droplet break-up, turbulence in the gas flow and temperature. Fewer opportunities for droplet break-up and turbulence means a longer reaction time at a certain temperature, i.e. longer piping is required to reach a well-mixed gas flow. A well-mixed gas flow is important for the function of e.g. different catalysts such as the diesel oxidation catalyst (DOC) using hydrocarbon/fuel or the selective catalytic reduction (SCR) using urea.
Illustrative examples of mixing a liquid additive into a stream of exhaust gas for subsequent treatment can be found e.g. in WO 14107129, WO 16169709, US 2008245060, US 2011219755, US 2014311133, US 2014360170, US 2015217230, US 2015377110, US 2015377111, US 2015110681, US 2016194994 and DE 102009036511.
In particular the mentioned WO 14107129 discloses a mixer box where the mixer box is integrated with a silencer. A silencer, however, not necessarily is included in the mixer box of the present invention. The disclosure relates to a silencer for a combustion engine, which silencer comprises a casing with a substantially circular cylindrical shell surface, a first end element and a second end element, at least one inlet for leading an exhaust flow into the casing and at least one outlet for leading the exhaust flow out from the casing. The silencer comprises also a selective catalytic reduction (SCR) purification system which comprises a SCR substrate, a vaporisation pipe and an arrangement for adding a reducing agent to the exhaust flow in order to reduce NOx contents of the exhaust flow. The silencer further comprises a cylindrical particle filter situated between a first space and a first duct such that the exhaust gases are led in a substantially radial direction through the filter. The exhaust flow is also caused to pass through a second duct on the outside of the vaporisation pipe before the SCR substrate in order to warm the vaporisation pipe. The silencer is of compact configuration and is flow-optimised such that the formation of urea crystals may also be reduced. US2015260070 discloses a mixing box as set out in the preamble of claim 1. Further relevant mixer boxes are disclosed in WO2012038072, WO2008036606 and US2010139258.
An object of the present invention is to achieve a more efficient mixing of the fluid droplets with the exhaust gas than is obtained with known mixing boxes. In particular an object is to thereby achieve a sufficient mixing level in a mixing box that can be more compact than traditional mixing boxes in this field.
According to a first aspect of the invention, the object is achieved in that a mixing box of the kind specified in the preamble of claim 1 includes the specific features specified in the characterizing portion of claim 1. Thus, the duct means includes a second duct portion, which is surrounded by the first duct portion, and where the characterizing portion defines a liquid injection means arranged to inject liquid into the second duct portion, and where the liquid injection means is provided in an end wall of the second duct portion.
This thus takes place after the exhaust gas has flown from the upstream duct section(s) into the second duct portion, which inflow creates turbulence in the gas flow. The injection thereby takes place at a location where the flow is turbulent. It is particularly efficient for the mixing that turbulence is present already where the liquid is injected. When there is two or more upstream duct sections there may also be a re-mixing when entering into the second duct portion which further increases the turbulence at the location of the fluid injection. Providing the fluid injection means to inject into the mixing box also eliminates the need for a separate injection device ahead of the mixing box.
In the following this first duct portion, for the sake of simplicity, will be referred to as being annular, which normally will be the case. It is, however, to be understood that the shape of the inner and outer walls not necessarily is circular but may be elliptic or even polygonal. The inner and outer walls normally will be concentric, but the invention is not restricted to that. The inner and outer walls do not necessarily have constant diameter but may vary along its respective axial extension.
Thanks to that this annular first duct portion is separated into two or more duct sections it will be possible that one of the duct section forms one part of the gas flow path through the duct means and another one forms another part of the gas flow path. To arrange two parts of the gas flow path within one and the same annular space results in a compact layout of the mixer box while maintaining a sufficient degree of mixing, and thereby allows after-treatment, e.g. SCR-treatment to come close to the combustion engine.
One of the duct sections is upstream the other one and is defined as the upstream duct section; the other one consequently is defined as the downstream duct section.
In the present application mixer box is to be understood as the device that enhances the mixing of the droplets into the gas stream. The injection of the fluid may take place within the mixing box per se, or may take place before the exhaust gas enters the mixing box.
Terms like “radial” and “axial” and the like, in the following are related to the centre axis of the annular duct portion.
The terms “upstream” and “downstream” relate to the gas flow path through the duct means. When there are two details of the same kind, e.g. re-mixing chambers, the distinguishing upstream/downstream-labels for these refer solely to their mutual relative positions in the gas flow path and not necessarily to their positions relative other details.
According to a preferred embodiment of the invented mixer box, the number of partitions is at least four and the number duct sections is at least four, and every second duct section as seen in the circumferential direction is an upstream duct section and every second duct section is a downstream duct section.
The gas flow path thus takes place through two parallel arranged upstream duct sections and correspondingly through the downstream duct sections. Dividing the gas flow path into parallel flows through parts of the duct means increases the possibility to create turbulence within the gas flow path which increases the effectivity of mixing.
According to a further preferred embodiment, the duct means includes an upstream re-mixing chamber and each upstream duct section has a gas outlet connected to and communicating with the upstream re-mixing chamber.
By providing a re-mixing chamber after the upstream duct section, the separated gas flows will be unified again and mix with each other. Thereby a strong turbulence is created, which thus further increases the efficiency of mixing the droplets into the exhaust gas.
According to a further preferred embodiment, the duct means includes a downstream re-mixing chamber and each downstream duct section has a gas outlet connected to and communicating with the downstream re-mixing chamber.
The provision of a re-mixing chamber after the downstream duct sections has advantages similar to those of the embodiment mentioned next above. Particularly efficient with regards to attain turbulence conditions is when both an upstream re-mixing chamber and downstream re-mixing chamber are present.
According to a further preferred embodiment, the duct means is arranged to provide a first turn of the gas flow direction 180°.
Such a sharp turn also will increase turbulence in the gas flow, thereby increasing the mixing efficiency. The turn may advantageously be arranged in connection with the outflow of the exhaust gas into a re-mixing chamber, but may alternatively be arranged somewhere else in the gas flow path.
According to a further preferred embodiment, the duct means is arranged to provide a second turn of the gas flow direction at least 90°, which first and second turns are located at different positions in the gas flow path.
With such a further turn, the turbulence will be further enhanced.
The pipe-in pipe arrangement provides a very space-saving construction of the duct means, since within one and the same outer pipe at least three different parts of the gas flow path will be housed, e.g. one in the central pipe and two in the annular space. The pipe-in-pipe arrangement also allows for these various parts of the gas flow path to be connected without extensive connection piping. This further contributes to the compactness of the mixer box. The arrangement is also advantageous with regards to attaining sharp turns and re-mixings of the gas flow, which as mentioned above contributes to higher turbulence.
According to a further preferred embodiment, the second duct portion has an outer wall that is common to the inner wall of the first duct portion.
Thereby unnecessary waste of space is avoided. The common wall also increases heat transfer between the gas in the inner pipe and the gas in the annular space, which in many cases may be desirable.
According to a further preferred embodiment, the duct means has the upstream duct section(s) located upstream of the second duct portion, and the second duct portion located upstream of the downstream duct section(s).
This means that the gas flow path first passes through (a) duct section(s) in the annular space, then through the central pipe, and thereafter through another/other duct section(s) in the annular space. The gas flow thereby may be in a first axial direction, followed by a flow in the opposite direction and thereafter in the first axial direction. This makes it easy to attain sharp turnings of the gas flow and the effect thereof on the turbulence. When a plurality of upstream duct sections are present and/or a plurality of downstream duct sections it also leads to re-mixing of the gas flows. In that case this embodiment profits particularly from the advantages of creating turbulence, and is here attained easily and space-saving.
According to an alternative preferred embodiment, the duct means has the second duct portion arranged upstream of the upstream duct section(s), and the upstream duct section(s) located upstream of the downstream duct section(s).
For some applications this consecutive order may be easier to adapt to the related technical details such as the combustion engine and an SCR-system. This embodiment is also particularly adapted to a system where the fluid injection is performed prior to the mixer box. However, internal fluid injection means, e.g. injecting into the second duct portion, is not excluded in this embodiment.
According to a further preferred embodiment, the duct means includes a heating surface arranged to be hit by the gas flow and heat the gas.
Thereby the gas temperature is increased and thereby compensate for the temperature fall due to the injection of liquid, which is advantageous for increasing mixing of the droplets into the exhaust gas.
Accord to a further preferred embodiment, when the second duct portion is surrounded by the first duct portion and has an outer wall that is common to the inner wall of the first duct portion, the heating surface is a part of a the common wall and/or an end wall of the second duct portion, and where gas flowing in the first duct portion acts as a heat source for heating the heating surface.
Thereby heat losses due to injection of liquid is regained such that the temperature where the mixing takes place becomes almost as high as when the exhaust gas enter the mixer box. The embodiment eliminates the need for external heat supply, although such may also be present in order to further increase the temperature.
The invention also relates to a combustion engine system including a mixer box according to the present invention, in particular to any of the preferred embodiments thereof.
The invention also relates to a vehicle, a vessel or a stationary plant including a combustion engine system according to the present invention.
According to the second aspect of the invention, the object is met by a use of the mixer box according to the present invention, in particular to any of the preferred embodiments thereof, wherein the liquid additive contains urea and wherein the gas/liquid-mixture is used for selective catalytic reduction.
With reference to the appended drawings, below follows a more detailed description of example embodiments of the invention.
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.
As can be seen in
As can be seen in
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
With reference to
A liquid injection means 112 is provided in the right end wall of the duct portion 106, through which liquid containing urea is injected.
The exhaust gases A from the combustion engine (not shown) flows into the mixing box from the left in
The gas then flows through their respective outlet 111a, arrow C into the inlet end (to the right in
At the left end (
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.
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.
Each of the outlets 111a, 131a and 121a may be formed by a perforated plate.
At the right end (
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.
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.
As best can be seen in
The part of the outer wall 371 that is most close to the gas inlet 308 is formed by the inlet pipe 350.
In
In the perspective view of
The split view of
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.
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 and the outlets 331a, 331b from the second duct portion 306 to the downstream duct sections 302a, 302b, respectively.
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.
Details of the first duct portion 307 (not denoted a reference number in
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.
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.
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.
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.
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.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/053788 | 2/20/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2018/149509 | 8/23/2018 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
6312650 | Frederiksen | Nov 2001 | B1 |
9410460 | Hacklander | Aug 2016 | B2 |
10605142 | Grosch | Mar 2020 | B2 |
20060153748 | Huthwohl | Jul 2006 | A1 |
20080245060 | Stieglbauer | Oct 2008 | A1 |
20100139258 | Hackett et al. | Jun 2010 | A1 |
20100212301 | De Rudder | Aug 2010 | A1 |
20110219755 | Muller-Haas | Sep 2011 | A1 |
20120014843 | Birkby | Jan 2012 | A1 |
20140311133 | Norling et al. | Oct 2014 | A1 |
20140360170 | Hacklander | Dec 2014 | A1 |
20150110681 | Ferront et al. | Apr 2015 | A1 |
20150217230 | Reichert et al. | Aug 2015 | A1 |
20150260070 | Reichert | Sep 2015 | A1 |
20150377110 | Sandberg et al. | Dec 2015 | A1 |
20150377111 | Laurell et al. | Dec 2015 | A1 |
20160194994 | Jayat | Jul 2016 | A1 |
20180187584 | Neumann | Jul 2018 | A1 |
Number | Date | Country |
---|---|---|
105156181 | Dec 2015 | CN |
106170613 | Nov 2016 | CN |
102009036511 | Feb 2011 | DE |
2008036606 | Mar 2008 | WO |
2009024815 | Feb 2009 | WO |
2012038072 | Mar 2012 | WO |
2014107129 | Jul 2014 | WO |
2016169709 | Oct 2016 | WO |
Entry |
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International Search Report and Written Opinion dated Jun. 8, 2017 in International Application No. PCT/EP2017/053788. |
International Preliminary Report on Patentability dated Apr. 30, 2019 in International Application No. PCT/EP2017/053788. |
China Office Action dated Dec. 3, 2020 in corresponding China Patent Application No. 201780086792.0, 19 pages. |
Number | Date | Country | |
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20200003101 A1 | Jan 2020 | US |