JP2016525648A - Axial flow atomization module - Google Patents

Abstract

An exhaust gas treatment element for treating engine exhaust gas, comprising a housing having an inlet and an outlet. A mixing device is disposed in the housing between the inlet and the outlet, the mixing device being near the second end, a shell in communication with the outlet, a decomposition tube having first and second ends. And a flow reversing device. The first end extends from the shell and is configured to receive exhaust gas from the inlet and is configured to receive a reactant exhaust gas treatment fluid. The second end is disposed within the shell. The flow reversing device is configured to send a mixture of the exhaust gas and the reactant exhaust gas treatment fluid into the shell in a predetermined direction, and the flow reversing device reverses the flow direction of the exhaust gas to Return to the end of 1. [Selection] Figure 7

Description

  The present disclosure relates to an exhaust gas aftertreatment system including an exhaust gas mixing device.

  In this section, background information related to the present disclosure, which is not necessarily prior art, is presented.

  The exhaust gas aftertreatment system can inject a reactant exhaust gas treatment fluid into the exhaust gas stream before the exhaust gas stream passes through the various exhaust gas aftertreatment elements. For example, the urea exhaust gas treatment fluid can be injected into the exhaust gas stream before the exhaust gas passes through the selective catalytic reduction (SCR) catalyst. However, the SCR catalyst is most effective when the exhaust gas is well mixed with the urea exhaust gas treatment fluid.

  This section presents a general overview of the present disclosure and is not a comprehensive disclosure of the full range or all features.

  The present disclosure presents an exhaust gas treatment element for treating engine exhaust gas that includes a housing having an inlet and an outlet. A mixing device is disposed in the housing between the inlet and the outlet, the mixing device being near the second end, a shell in communication with the outlet, a decomposition tube having first and second ends. And a flow reversing device. The first end extends from the shell and is configured to receive exhaust gas from the inlet and is configured to receive a reactant exhaust gas processing fluid. The second end is disposed within the shell. The flow reversing device is configured to direct a mixture of exhaust gas and reactant exhaust gas treatment fluid into the shell in a predetermined direction, and the flow reversing device reverses the flow direction of the exhaust gas to Return to the first end.

  Further areas of applicability will become apparent from the description presented herein. The description and specific examples in this summary are intended to be exemplary only and are not intended to limit the scope of the present disclosure.

  The drawings described herein are intended to illustrate selected embodiments only and are not intended to be all possible examples, and are not intended to limit the scope of the present disclosure.

1 is a schematic diagram of an exhaust system according to the principles of the present disclosure. FIG. 1 is a perspective view of an exhaust gas treatment element in accordance with the principles of the present disclosure. FIG. FIG. 3 is a side perspective view of the exhaust gas treatment element shown in FIG. 2. FIG. 3 is a front perspective view of the exhaust gas treatment element shown in FIG. 2. FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 1 is a perspective view of a mixing assembly according to a first exemplary embodiment of the present disclosure. FIG. FIG. 8 is an exploded perspective view of the mixing assembly shown in FIG. 7. FIG. 8 is a cross-sectional view of the mixing assembly shown in FIG. FIG. 6 is a perspective view of a mixing assembly according to a second exemplary embodiment of the present disclosure. FIG. 11 is a perspective view of the flow reversing device and the dispersing device of the mixing assembly shown in FIG. 10. It is a perspective view of the dispersion apparatus shown in FIG. 11 in the assembled state. FIG. 12 is another perspective view of the dispersing device shown in FIG. 11 in an unassembled state. FIG. 9 is a perspective view of a mixing assembly according to a third exemplary embodiment of the present disclosure. FIG. 15 is a perspective view of the flow reversing device and the dispersing device of the mixing assembly shown in FIG. 14. It is a perspective view of the dispersion apparatus shown in FIG. FIG. 9 is a perspective view of a mixing assembly according to a fourth exemplary embodiment of the present disclosure. FIG. 18 is a partial perspective view of the mixing assembly shown in FIG. 17. It is a cross-sectional perspective view of FIG. FIG. 7 is a perspective view of a mixing assembly according to a fifth exemplary embodiment of the present disclosure. FIG. 11 is an exploded perspective view of the mixing assembly shown in FIG. 10. 1 is a perspective view of an exhaust gas treatment element in accordance with the principles of the present disclosure. FIG. FIG. 23 is a cross-sectional view of the exhaust gas treatment element shown in FIG. 22. 1 is a perspective view of an exhaust gas aftertreatment system in accordance with the principles of the present disclosure. FIG. FIG. 25 is a perspective view of an exhaust gas treatment element forming part of the exhaust gas aftertreatment system shown in FIG. 24. FIG. 26 is another perspective view of the exhaust gas treatment element shown in FIG. 25. FIG. 26 is a top perspective view of the exhaust gas treatment element shown in FIG. 25. FIG. 26 is a side perspective view of the exhaust gas treatment element shown in FIG. 25. FIG. 26 is a cross-sectional perspective view of the exhaust gas treatment element shown in FIG. 25. FIG. 26 is a cross-sectional view of the exhaust gas treatment element shown in FIG. 25. 1 is a side perspective view of an exhaust gas treatment element in accordance with the principles of the present disclosure. FIG. FIG. 32 is a cross-sectional view of the exhaust gas treatment element shown in FIG. 31.

  Like reference numerals refer to like parts throughout the several views of the drawings.

  Exemplary embodiments are described more fully hereinafter with reference to the accompanying drawings.

  FIG. 1 schematically illustrates an exhaust system 10 according to the present disclosure. The exhaust system 10 can include at least one engine 12 that is in communication with a fuel source (not shown), and when consumed, the engine 12 generates exhaust gas that is exhaust gas aftertreatment system. 16 is discharged into the exhaust passage 14. A pair of exhaust gas treatment elements 18, 20 can be disposed downstream of the engine 12, and the exhaust gas treatment elements 18, 20 can include a catalyst coated substrate or filter 22, 24. The catalyst coated substrate or filter 22, 24 may be a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC), a selective catalytic reduction (SCR) element, a lean NOx catalyst, an ammonia slip catalyst, or others known to those skilled in the art Any combination of any type of processing equipment. If DPF is used, it can be catalyst coated.

  Although this disclosure is not required, the exhaust aftertreatment system 16 can further include components such as a thermal intensifier or burner 26 to raise the temperature of the exhaust gas through the exhaust passage 14. Increasing the temperature of the exhaust gas is not only advantageous for initiating regeneration of the exhaust gas treatment element 18 when the exhaust gas treatment substrate 22 or the exhaust gas treatment substrate 24 is a DPF, but also in cold weather conditions It is advantageous to achieve a light-off of the catalyst of the exhaust gas treatment element 18 when the engine 12 is started.

  To assist in the reduction of emissions generated by the engine 12, the exhaust gas aftertreatment system 16 can include an injection module 28 that periodically injects an exhaust gas treatment fluid into the exhaust gas stream. As shown in FIG. 1, the injection module 28 can be positioned upstream of the exhaust gas treatment element 18 and operates to inject an exhaust gas treatment fluid into the exhaust gas stream. In this regard, the injection module 28 is used to inject an exhaust gas treatment fluid, such as diesel fuel or urea, into the exhaust passage 14 upstream of the exhaust gas treatment elements 18, 20 via the inlet tube 34 and the reactant tank 30. In fluid communication with the pump 32. The injection module 28 can also be in communication with the reactant tank 30 via a return pipe 36. The return pipe 36 allows any exhaust gas treatment fluid that has not been injected into the exhaust gas stream to be returned to the reactant tank 30. The flow of exhaust gas treatment fluid through the inlet tube 34, injection module 28, and return tube 36 also helps cool the injection module 28 so that the injection module 28 does not overheat. Although not shown in the figure, the infusion module 28 can be configured to include a cooling jacket that passes coolant around the infusion module 28 to cool the infusion module 28.

  The amount of exhaust gas treatment fluid required to effectively process the exhaust gas stream is: load, engine speed, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NOx reduction, atmospheric pressure, It can vary with relative humidity, EGR (exhaust gas recirculation) rate, and engine coolant temperature. The NOx sensor or meter 38 can be located downstream from the exhaust gas treatment element 18. The NOx sensor 38 operates to output a signal indicating the NOx content of the exhaust gas to the engine control unit 40. All or some of the engine operating parameters can be supplied from the engine control unit 40 to the electronic injection controller 42 via the engine / vehicle data bus. The reactant electron injection controller 42 can also be implemented as part of the engine control unit 40. Exhaust gas temperature, exhaust gas flow rate, and exhaust gas back pressure, and other vehicle operating parameters can be measured with the respective sensors shown in FIG.

  The amount of exhaust gas treatment fluid required to effectively process the exhaust gas stream may depend on the capacity of the engine 12. In this regard, large diesel engines used in locomotive, marine and stationary applications can have an exhaust gas flow rate that exceeds the capacity of a single injection module 28. Thus, although only a single injection module 28 is shown for injection of exhaust gas treatment fluid, it should be appreciated that multiple injection modules 28 for reactant injection are contemplated by the present disclosure.

  2-6, exemplary configurations of the exhaust gas treatment elements 18, 20 are shown. As best shown in FIG. 2, the exhaust gas treatment elements 18, 20 are arranged in parallel to each other. However, it will be appreciated that the exhaust gas treatment elements 18, 20 can be arranged substantially coaxially without departing from the scope of the present disclosure.

  The exhaust gas treatment element 18 can include a housing 44, an inlet 46, and an outlet 48. The inlet 46 can communicate with the exhaust passage 14 and the outlet 48 can communicate with the exhaust gas treatment element 20. Although the outlet 48 is shown as being directly connected to the exhaust gas treatment element 20, it will be appreciated that another conduit (not shown) may be placed between the outlet 48 and the exhaust gas treatment element 20. Can do. Another conduit may be non-linear so that the exhaust gas flow through the conduit must be redirected before entering the exhaust gas treatment element 20. The housing 44 may have a cylindrical shape and may include a first portion 50 that supports the DOC 52 and a second portion 54 that supports the DPF 56. Although the DOC 52 is illustrated as being upstream of the DPF 56, it will be appreciated that the DPF 56 may be disposed upstream of the DOC 52 without departing from the scope of the present disclosure. Both ends of the housing 44 can include end caps 58, 60 that seal the housing 44. The end caps 58, 60 can be slip-fit and welded to the first portion 50 and the second portion 54, respectively. The first portion 50 and the second portion 54 can be fixed by a clamp 62. Using the clamp 62 allows the DOC 52 or DPF 56 to be easily removed to maintain, clean, or replace these components. The exhaust gas from the exhaust passage 14 flows from the inlet 46 before passing into the exhaust gas processing element 20, passes through the DOC 52 and the DPF 56, and exits from the outlet 48.

  The exhaust gas treatment element 20 is substantially similar to the exhaust gas treatment element 18. In this regard, the exhaust gas treatment element 20 can include a housing 64, an inlet 66, and an outlet 68. The inlet 66 can communicate with the outlet 48 of the exhaust gas treatment element 18, and the outlet 68 can communicate with the downstream portion of the exhaust path 14.

  The housing 64 can have a cylindrical shape and can support the SCR 70 and the ammonia slip catalyst 72. The SCR is preferably arranged upstream of the ammonia slip catalyst 72. Both ends of the housing 64 can include end caps 74, 76 that seal the housing 64. The end caps 74, 76 can be slip fit into the housing 64 and welded. Alternatively, the end caps 74, 76 can be secured to the housing 64 by clamps (not shown). The exhaust gas from the outlet 48 of the exhaust gas treatment element 18 flows from the inlet 66 before passing into the downstream portion of the exhaust passage 14, passes through the SCR 70 and the ammonia slip catalyst 72, and exits from the outlet 68.

  The infusion module 28 can be placed on the end cap 74 at a location near the inlet 66. The injection module 28 operates to inject a reducing agent, such as urea exhaust gas treatment fluid, into the exhaust gas stream before the exhaust gas stream passes through the SCR 70. In order to optimize the removal of NOx from the exhaust gas stream while the exhaust gas and exhaust gas treatment fluid mixture is passing through the SCR 70, the exhaust gas and the exhaust gas treatment fluid must be sufficiently mixed. Don't be. A mixing assembly 80 can be positioned downstream of the inlet 66 and upstream of the SCR 70 to assist in mixing the exhaust gas stream with the urea exhaust gas treatment fluid. The mixing assembly 80 is positioned near the injection module 28 so that the injection module 28 can inject the urea exhaust gas processing fluid directly into the mixing assembly 80, and the urea exhaust gas processing fluid is at the exhaust gas flow at the mixing assembly 80. Can be blended with.

  7-9 illustrate a first exemplary embodiment of the mixing assembly 80. The mixing assembly 80 includes a disassembly tube 82 having a first end portion 84 that can be secured to the end cap 74 and a second end portion 86 disposed near the SCR 70. The decomposition tube 82 can be substantially cylindrical, with a radially expanded portion 88 disposed between the first end portion 84 and the second end portion 86. The radially expanded portion 88 has a conical expansion portion 90 having a diameter that is greater than the diameter of the first end portion 84 and the second end portion 86 and a conical expansion portion 90 that expands the decomposition tube 82. A cylindrical portion 92 downstream from 90 and a conical narrow portion 94 that narrows the decomposition tube 82 are included. Of course, the first end portion 84 and the second end portion 86 may have different diameters without departing from the scope of the present disclosure. Similarly, it should be appreciated that the present disclosure does not require a conical narrow portion 94. That is, the radial extension portion 88 can extend the entire length of the second end portion 86.

  The first end portion 84 can be pierced to include a plurality of first holes 96. The first hole 96 can be resized around the first end portion 84 to generate turbulent flow when the exhaust gas flow enters the decomposition tube 82, thereby increasing the speed of the exhaust gas flow. Contributes to raising. Although not required by the present disclosure, a perforated collar 98 including a plurality of second holes formed as an elongated slot 100 is disposed around the first end portion 84 so that the first end portion 84 has a Can be fixed. The perforated collar 98 includes a cylindrical portion 102 having a diameter that is larger than the diameter of the first end portion 84. The cylindrical portion 102 narrows radially toward the axially extending flange 104, which is welded, brazed, or any other fixation known to those skilled in the art at a location near the radially expanded portion 88. It can be fixedly connected to the decomposition tube 82 by an attachment method.

  The elongated slot 100 can be larger than the first hole 96. The elongate slot 100 can be oriented in a variety of directions, including a direction parallel to the axis of the decomposition tube 82 and a direction disposed perpendicular to the axis of the decomposition tube 82. However, it will be appreciated that each elongated slot 100 may be oriented in the same direction without departing from the scope of the present disclosure. Similar to the first hole 96, the elongated slot 100 generates turbulence and contributes to increasing the speed of the exhaust gas flow when the exhaust gas flow enters the decomposition tube 82.

  Mixing assembly 80 includes a flow reversing device 106 at a second end portion 86. The flow reversing device 106 can be fixed to the second end portion 86 or supported by a baffle (not shown), the baffle being near the end 108 of the second end portion 86, The flow reversing device 106 is secured to the end cap 74. The flow reversing device 106 is a generally cup-shaped member 110 having a central ridge 112 formed thereon. The flow reversing device 106 has a diameter that is greater than the diameter of the second end portion 86 of the cracking tube 82 so that when the exhaust gas stream enters the cup-shaped member 110, the exhaust gas stream flows in the opposite direction. Forced back to the entrance 66 of the housing 64. Reversing the exhaust gas flow helps to mix the reactant exhaust gas treatment fluid and the exhaust gas flow before the exhaust gas flow reaches the SCR 70.

  The flow reversing device 106 can include a plurality of baffle members 114 to further aid in mixing the reactant exhaust gas treatment fluid and the exhaust gas stream. The baffle member 114 may be formed as a plurality of vanes extending radially inward from the inner surface 116 of the outer wall 118 of the flow reversing device 106. In addition to extending radially inward, the vane 114 may also be angled with respect to the axis of the cracking tube 82 to further guide the exhaust gas flow as it exits the flow reversing device 106. it can. The vane 114 may be a planar member or may be slightly curved. Although the vane 114 is illustrated as being secured to the inner surface 116 of the flow reversing device 106, it will be appreciated that the vane 114 may be secured to the second end portion 86 of the decomposition tube 82.

  As shown in FIG. 6, the mixing assembly 80 can be positioned in a direction perpendicular to the axis of the inlet 66. Thus, the exhaust gas stream flows vertically into the mixing assembly 80 before being directed toward the SCR 70. As the exhaust gas stream flows into the first end 84 of the decomposition tube 82, the exhaust gas stream speed increases and the exhaust gas stream stream snakes for the first hole 96 and the second hole 100. It becomes like this. As the exhaust gas enters the radial extension 88, the flow can tend to stay along the axis of the cracking tube 82. The exhaust gas flow rate is reduced, but only to a minimum range that ensures satisfactory mixing of the exhaust gas and the reactant exhaust gas treatment fluid. In this regard, the radial extension 88 diffuses the turbulence in the exhaust gas flow generated by the holes 96, 100, which helps to minimize the possible speed reduction. Table 1 below summarizes the peak velocity of the exhaust gas flow in various regions within the exhaust gas treatment element 20.

  As shown in Table 1 and FIG. 6, the exhaust gas can have a peak velocity of 84 m / s when the exhaust gas stream flows from the inlet 66 (region A). As exhaust gas flows into the mixing assembly 80 through the collar 98 and the first end portion 84 of the decomposition tube 82, the velocity can increase (region B). The increase in velocity in region B creates a large velocity difference between the velocity of the exhaust gas treatment fluid injected by the injection module 28 and the exhaust gas that has passed through the holes 96, 100. The mixed exhaust gas flow velocity difference creates an aerodynamic force that is greater than the surface tension characteristics of the exhaust gas treatment fluid, which results in decomposition and atomization of the exhaust gas treatment fluid droplets.

  Next, when the exhaust gas flows into the radially extending portion 88, the exhaust gas is slightly decelerated (regions C and D). As the exhaust gas exits the radially expanded portion and enters the flow reversing device 106, the velocity can then increase (regions E, F). When the exhaust gas reaches the SCR 70, the speed can drop at this time (region G). The exhaust gas velocity is increased at the location (region B) where the exhaust gas treatment fluid is injected into the exhaust gas stream, and the exhaust gas flow is increased when exiting the flow reversing device 106, so that the exhaust gas and the exhaust gas treatment fluid. Can be mixed well to ensure satisfactory atomization of the exhaust gas treatment fluid.

  Nevertheless, while the exhaust gas flow is in the radial extension 88 (region D), a slow flow region 120 exists adjacent to the inner wall 122 of the cracking tube 82 (FIG. 9). These regions 120 surround the exhaust gas flow as it passes through the radial extension 88 and help prevent the inner wall 122 from getting wet with the reactant exhaust gas treatment fluid. Preventing the inner wall 122 from getting wet prevents or at least substantially minimizes the accumulation of solid urea deposits on the inner wall 122.

  As the exhaust gas flow enters the second end portion 86 of the cracking tube 82, the exhaust gas flow velocity increases again and increases as the exhaust gas flow enters the flow reversing device 106 and exits there. It remains. When flowing into the flow reversing device 106, the flow direction of the exhaust gas flow is reversed to return toward the inlet 66. As the exhaust gas stream exits the flow reversing device 106, the exhaust gas is directed by the vane 114, which contributes to further mixing of the exhaust gas and the reactant exhaust gas processing fluid. Further, the exhaust gas stream can impinge on the conical narrow portion 94 of the cracking tube 82, which further assists in moving the exhaust gas stream away from the mixing assembly 80. The exhaust gas stream can then flow freely towards the SCR 70.

  With reference now to FIGS. 10-13, a second exemplary mixing assembly 200 will be described. The mixing assembly 200 is similar to the mixing assembly 80 shown in FIGS. Therefore, for clarity, descriptions of components common to each assembly are omitted here. The mixing assembly 200 includes a baffle device 202 having a plurality of baffle members 204. As best shown in FIG. 13, the deflector 202 can be formed from an elongated strip 206 made of metal such as aluminum, steel, titanium, or any other material known to those skilled in the art. The baffle member 204 is integral with the elongated strip 206 (ie, a single piece) and is formed from a plurality of cutouts 208 formed in the elongated strip 206 as planar tabs bent radially outward from the elongated strip 206. Yes.

  The baffle member 204 can be designed to function in a manner similar to the vane 114. In this regard, as the exhaust gas flow exits the flow reversing device 106, the exhaust gas is directed by the baffle member 204, which contributes to further mixing of the exhaust gas and the reactant exhaust gas treatment fluid. As best shown in FIGS. 12 and 13, the cutout 208 is inclined with respect to the length of the elongated strip 206. When the baffle member 204 is bent outwardly from the elongated strip 206, the baffle member 204 is also inclined with respect to the axis of the mixing assembly 200 and directs the exhaust gas flow in a predetermined direction upon exiting the flow reversing device 106. Can be used to

  The baffle member 204 can have a length that is substantially equal to the distance between the second end portion 86 of the decomposition tube 82 and the outer wall 118 of the flow reversing device 106. Alternatively, the baffle member 204 can have a length that is less than the distance between the second end portion 86 and the outer wall 118. In another alternative, the baffle members 204 can each have a termination protrusion 210 that has a length greater than the distance between the second end portion 86 and the outer wall 118. 204. In this case, the termination protrusion 210 can abut the termination 212 of the outer wall 118 of the flow reversing device 106, which helps align the baffle device 202 with respect to the flow reversing device 106. Termination protrusion 210 also helps secure baffle device 202 to flow reversing device 106 by providing a location for welding, brazing, or securing each tab to flow reversing device 106, if desired. It can also be.

  Referring now to FIGS. 14-16, a third exemplary mixing assembly 300 is shown. The mixing assembly 300 is substantially similar to the mixing assembly 80 shown in FIGS. Therefore, for clarity, descriptions of components common to each assembly are omitted here. Although the collar 98 is not shown in FIG. 14, it should be appreciated that the mixing assembly 300 can include the collar 98. The mixing assembly 300 includes a baffle device 302 having a plurality of baffle members 304. As best shown in FIG. 15, the deflector 302 can be formed from an annular ring 306 made of metal such as aluminum, steel, titanium, or any other material known to those skilled in the art. The baffle member 304 is formed from a plurality of cutouts 308 formed in the annular ring 306 as a planar tab that is integral (ie, a single piece) with the annular ring 306 and can be bent radially outward from the annular ring. Yes. Although the baffle member 304 is illustrated as being bent in a direction toward the interior 310 of the flow reversing device 106, it will be appreciated that the baffle member 304 can be bent away from the interior 310.

  The baffle member 304 can be designed to function in a manner similar to the vane 114. In this regard, as the exhaust gas stream exits the flow reversing device 106, the exhaust gas is directed by the baffle member 304, which contributes to further mixing of the exhaust gas and the reactant exhaust gas treatment fluid. The baffle member 304 can also be tilted with respect to the axis of the mixing assembly 300 and can be used to direct the exhaust gas flow in a predetermined direction upon exiting the flow reversing device 106.

  When the deflector 304 is bent in the desired orientation, the inner ring 312 and the outer ring 314 of the deflector are defined. The inner ring 312 is used to secure the deflector 302 to the second end portion 86 of the disassembly tube 82 by welding, brazing, or any other known securing method in a manner known to those skilled in the art. be able to. The deflector 302 can also include an axially extending flange 316 that extends outwardly from the outer ring 314. The axial extension flange 316 can correspond to the end 212 (FIG. 11) of the flow reversing device 106 and can be secured to the flow reversing device 106 by welding, brazing, or any other known attachment method. It can overlap the end 212 so that it can.

  Referring now to FIGS. 17-19, a fourth exemplary embodiment is shown. The mixing assembly 400 is similar to the mixing assembly 80 shown in FIGS. Therefore, for clarity, descriptions of components common to each assembly are omitted here. The mixing assembly 400 includes a flow reversing device 106 at a second end portion 86, which is a generally cup-shaped member formed with a central ridge. In contrast to the baffle members 204, 304 described above, the mixing assembly 400 can include a flow distribution cap 402 coupled between the flow reversing device 106 and the cracking tube 82.

  The flow distribution cap 402 includes a first axial extension lip 404 that connects the flow distribution cap 402 to the flow reversing device 106, and a second axial extension lip 406 that connects the flow distribution cap 402 to the disassembly tube 82. . Between the axially extending lips 404, 406 is a conical perforated ring 408 having a plurality of through holes 410. Similar to the first hole 96 and the second hole 100, the through-hole 410 generates turbulence and contributes to increasing the speed of the exhaust gas flow when the exhaust gas flow exits the flow reversing device 106. . The through-hole 410 can be any desired aspect size and shape. In this regard, although the through hole 410 is illustrated as being circular, it will be appreciated that the through hole can be any shape including square, rectangular, triangular, oval, and the like. The conical shaped ring 408 can include a first portion 412 adjacent to the first axially extending lip 404 and a second portion 414 adjacent to the second axially extending lip 406.

  The diverter ring 416 can be disposed between the second portion 414 and the disassembly tube 82. As best shown in FIG. 19, the diverter ring 416 includes a cylindrical portion 418 connected to the disassembly tube 82 and an inclined flange extending from the cylindrical portion 418 between the disassembly tube 82 and the conical shaped ring 408. 420. The inclined flange 420 can be disposed at any angle desired to further contribute to changing the course of the flow exiting the mixing assembly 400. In this regard, the inclined flange can be inclined with respect to the cylindrical portion 418 in the range of 25-75 °, preferably in the range of 35-65 °, most preferably at a predetermined angle.

  When flowing into the flow reversing device 106, the flow direction of the exhaust gas flow is reversed to return toward the inlet 66. As the exhaust gas stream exits the flow reversing device 106, the exhaust gas is directed out by the diverter ring 416 and out of the through hole 410, which further mixes the exhaust gas with the reactant exhaust gas treatment fluid. Contribute to. The exhaust gas stream can then flow freely towards the SCR 70.

  Referring now to FIGS. 20 and 21, a fifth exemplary embodiment is shown. The mixing assembly 500 is substantially similar to the mixing assembly 80 shown in FIGS. Therefore, for clarity, descriptions of components common to each assembly are omitted here. The mixing assembly 500 includes a flow reversing device 502 at the second end portion 86 of the cracking tube 82, which is a generally cup-shaped member having a central ridge 503 formed thereon. The flow reversing device 502 can include a plurality of flow deflecting members 504 formed on an outer wall 506 thereof. The deflecting member 504 is integral with the flow reversing device 502 (ie, a single member), and is formed from a plurality of cutout portions 508 formed in the outer wall 506 as a planar tab bent radially outward from the outer wall 506. . The deflector member 504 can be designed to function in a manner similar to the vane 114. In this regard, when the exhaust gas stream exits the flow reversing device 502 through the cutout 508, the exhaust gas stream is bent into a turbulent flow by the deflector 504, which is the exhaust gas and the reactant exhaust gas. Contributes to further mixing with the processing fluid.

  The mixing assembly 500 can further include a dispersion ring 510 disposed between the terminal end 512 of the flow reversing device 502 and the decomposition tube 82. Dispersion ring 510 may be formed from an annular ring 514 made of a metal such as aluminum, steel, titanium, or any other material known to those skilled in the art. A cylindrical flange 516 can extend axially from the annular ring 514. The cylindrical flange 516 can be welded, brazed, or optionally secured in a known manner to the decomposition tube 82. The annular ring 514 is formed with a plurality of scalloped recesses 518. The recess 518 functions as an outlet port that allows the exhaust gas flow to exit the mixing assembly 500. Thus, the exhaust gas stream can exit the cutout 508 or can exit the recess 518. Adjacent recesses 518 can be separated by land portions 520 of annular ring 514. The distal end 522 of each land portion 520 disposed on the opposite side of the cylindrical flange 516 can be bent axially to form an abutment surface that causes the dispersion ring 510 to disassemble the disassembly tube 82. The dispersion ring 510 can be aligned with respect to the flow reversing device 502 before being secured to.

  When flowing into the flow reversing device 502, the flow direction of the exhaust gas flow is reversed so as to return toward the inlet 66. When the exhaust gas stream exits the flow reversing device 502, the exhaust gas can exit the cutout 508 and can be bent in the desired direction by the diverter 504 or the exhaust gas stream can be It is also possible to exit from the recess 518 formed in 510. Regardless of where the exhaust gas stream exits the mixing assembly 500, the exhaust gas stream is further mixed with the reactant exhaust gas processing fluid before flowing toward the SCR 70.

  Although each mixing assembly has been described in connection with use with an exhaust gas treatment element 20 that includes a single SCR 70, the present disclosure is not so limited. As best shown in FIGS. 22 and 23, the mixing assembly can be used with an exhaust gas treatment element 20 having a pair of SCRs 70. FIG. 22 shows a pair of exhaust gas treatment elements 18, 20 arranged in parallel. The exhaust gas treatment element 18 is the same as that of the embodiment already described, and therefore the description of the exhaust gas treatment element 18 is omitted.

  As best shown in FIG. 23, the exhaust gas treatment element 20 includes a mixing assembly 80 (or any other mixing assembly described above) for mixing the exhaust gas treatment fluid injected by the injection module 28 into the exhaust gas stream. )including. Exhaust gas treatment element 20 includes a pair of housings 600 in communication with a pair of end caps 602, 604. The end caps 602, 604 may be fixed to the housing 600 by welding or may be fixed to the housing 600 by clamps (not shown). Mixing assembly 80 and injection module 28 are secured in a conduit 606 that connects between exhaust gas treatment element 18 and exhaust gas treatment element 20. The conduit 606 can include a first portion 608 and a second portion 610 that include flanges 612, 614, respectively, that can be secured by welding or clamping (not shown). Each housing 600 supports a plurality of exhaust gas treatment element substrates 618 that can be a combination of an SCR, an ammonia slip catalyst, and a filter for treating a mixture of exhaust gas and exhaust gas treatment fluid.

  As exhaust gas flows into the mixing assembly 80, the urea exhaust gas processing fluid can be injected directly into the mixing assembly 80 by the injection module 28. The mixture of exhaust gas and exhaust gas treatment fluid passes through the decomposition tube 82 and flow reversing device 106 so that the exhaust gas treatment fluid and the exhaust gas stream are sufficiently mixed before passing through the exhaust gas treatment element substrate 618. . The mixing assembly 80 can include a baffle or vane 114 that contributes to mixing the exhaust gas and the exhaust gas treatment fluid. Because a pair of housings 600, each containing an exhaust treatment element substrate 618, is used in the exemplary embodiment, the vanes 114 are directed to a substantially equal amount of exhaust gas flow to each housing 600. It can be placed in the flow reversing device 106 to ensure that. That is, it will be appreciated that the baffle members 114 (and the baffle members of each exemplary embodiment) can be oriented so that the exhaust gas is directed in a desired direction. In this way, the exhaust gas treatment element substrate 618 can appropriately treat the exhaust gas.

  Referring now to FIGS. 24-30, an exemplary exhaust gas treatment assembly 700 that includes exhaust gas treatment elements 702, 704 is shown. As best shown in FIG. 24, the exhaust gas treatment elements 702, 704 are arranged parallel to each other. However, it will be appreciated that the exhaust gas treatment elements 702, 704 may be disposed substantially coaxially without departing from the scope of the present disclosure.

  The exhaust gas treatment element 702 can include a housing 706, an inlet 708, and an outlet 710. The inlet 708 can communicate with the exhaust path 14 and the outlet 710 can communicate with the exhaust gas treatment element 704. Although the outlet 710 is shown as being directly connected to the exhaust gas treatment element 704, it will be appreciated that another conduit (not shown) may be placed between the outlet 710 and the exhaust gas treatment element 704. Can do. Another conduit may be non-linear so that the exhaust gas flow through the conduit must be diverted before entering the exhaust gas treatment element 704.

  The housing 706 can be cylindrical in shape and can include a first portion 712 that supports the DOC 714 and a second portion 716 that supports the mixing assembly 718 (FIGS. 29 and 30). The DOC 714 can be replaced with, for example, a DPF or a catalyst coated DPF without departing from the scope of the present disclosure. Both ends of the housing 706 can include end caps 720, 722 that seal the housing 706. The end caps 720, 722 can be slip fit into the first portion 712 and the second portion 716 and welded, respectively. The first portion 712 and the second portion 716 can be secured by a clamp 724. Alternatively, the first portion 712 and the second portion 716 can be slip fit or welded without departing from the scope of the present disclosure. Using the clamp 724 allows the DOC 714 or the mixing assembly 718 to be easily removed to maintain, clean, or replace these components. A perforated baffle 725 can be placed immediately downstream of the inlet 708 and upstream of the DOC 714. Exhaust gas from the exhaust path 14 flows into the inlet 708 before passing into the exhaust gas treatment element 704, through the perforated baffle 725, DOC 714, and the mixing assembly 718 and out of the outlet 710.

  The exhaust gas treatment element 704 is substantially the same as the exhaust gas treatment element 702. In this regard, the exhaust gas treatment element 704 can include a housing 726, an inlet 728, and an outlet 730. The inlet 728 can communicate with the outlet 710 of the exhaust gas treatment element 702, and the outlet 730 can communicate with the downstream portion of the exhaust path 14.

  The housing 726 can have a cylindrical shape and can support the SCR 732 and the ammonia slip catalyst 734. The SCR 732 is preferably disposed upstream of the ammonia slip catalyst 734. Both ends of the housing 726 can include end caps 736, 738 that seal the housing 726. The end caps 736, 738 can be slip fit into the housing 726 and welded. Alternatively, end caps 736, 738 can be secured to housing 726 by clamps (not shown). The exhaust gas from the outlet 710 of the exhaust gas treatment element 702 flows into the inlet 728 before passing into the downstream portion of the exhaust path 14, passes through the SCR 732 and the ammonia slip catalyst 734, and exits from the outlet 730.

  The injection module 28 can be placed in the end cap 722 at a location near the outlet 710. Similar to the previously described embodiments, the injection module 28 operates to inject a reducing agent, such as a urea exhaust gas treatment fluid, into the exhaust gas stream before the exhaust gas stream passes through the SCR 732. Before the exhaust gas and exhaust gas treatment fluid mixture passes through the SCR 732, the exhaust gas and exhaust gas treatment fluid must be thoroughly mixed in order to optimize the removal of NOx from the exhaust gas stream. A mixing assembly 718 can be positioned downstream of the DOC 714 and upstream of the SCR 732 to assist in mixing the exhaust gas stream with the urea exhaust gas treatment fluid. The mixing assembly 718 is positioned near the injection module 28 so that the injection module 28 can inject the urea exhaust gas processing fluid directly into the mixing assembly 718, and the urea exhaust gas processing fluid is at the exhaust gas flow at the mixing assembly 718. Can be blended with.

  FIGS. 29 and 30 best show the mixing assembly 718. Similar to the previously described embodiments, the mixing assembly 718 has a first end portion 84 that can be secured to the end cap 722 and a second end portion 86 disposed near the DOC 714. A decomposition tube 82 is included. The decomposition tube 82 can be generally cylindrical and a radially extending portion 88 is disposed between the first end portion 84 and the second end portion 86. The flow reversing device 740 is at the second end portion 86. Mixing assembly 718 can be supported within housing 706 by a perforated support plate 742 in addition to disassembly tube 82 being secured to end cap 722.

  The support plate 742 includes an annular central portion 744 that surrounds an aperture 746 defined by an axially extending flange 748 that is secured to the decomposition tube 82. The annular outer portion 750 of the support plate 742 includes a plurality of through holes 752 that allow exhaust gases to flow through the annular outer portion 750. Outer portion 750 also includes an axially extending flange 754 for securing support plate 742 to housing 706. The axially extending shoulder portion 756 can be disposed between the annular central portion 744 and the annular outer portion 750. The shoulder portion 756 forms a mounting surface for the cylindrical shell 758 of the mixing assembly 718. Shell 758 includes a proximal end 760 secured to shoulder portion 756 and a distal end 762 secured to flow reversing device 740. A radially extending mounting flange 764 receives the end 766 of the outlet 710.

  As best shown in FIG. 30, the exhaust gas stream flows into the inlet 708, through the perforated baffle 725, and into the DOC 714. After the exhaust gas exits the DOC 714, the exhaust gas approaches the mixing assembly 718. Although this disclosure is not required, the mixing assembly 718 can be a cup-shaped nose 768 that is secured to the outer surface 770 of the flow reversing device 740. The cup-shaped nose 768 can include a conical, hemispherical, or elliptical outer surface 772 that guides the exhaust gas around the mixing assembly 718 when the exhaust gas contacts. The cup-shaped nose 768 can also have a concave surface associated with exhaust gas guidance. Further, the cup-shaped nose 768 can have raised or recessed features (eg, ridges or dimples, not shown) formed in the outer surface 772. Although a cup-shaped nose 768 is illustrated as being secured to the flow reversing device 740, it should be understood that the cup-shaped nose 768 is located near the flow reversing device 740 at a support plate (not shown). Can be supported. For example, a support plate similar to support plate 742 having a through hole 752 that allows for exhaust gas flow can be used such that the annular central portion 744 defines a cup-shaped nose rather than an aperture 746. .

  After passing around the mixing assembly 718, the exhaust gas passes through the through hole 752 of the support plate 742. After passing through the support plate 742, exhaust gas can enter the mixing assembly 718 through the holes 96, 100. To help pump the exhaust gas into the mixing assembly 718, the end cap 722 may define a curved surface that directs the exhaust gas to the mixing assembly 718 (ie, not shown, similar to the flow reversing device 740). it can. After entering the decomposition tube 82, the exhaust gas stream is exposed to an exhaust gas treatment fluid (eg, urea) that is injected into the mixing assembly 718 by the injection module 28. When the exhaust gas flows through the decomposition tube 82, the exhaust gas is directed in the reverse direction by the flow reversing device 740 and flows into the shell 758. The exhaust gas then exits shell 758 from outlet 710 and flows into exhaust gas treatment element 704 where SCR 732 and ammonia slip catalyst 734 are located.

  According to the above configuration, the exhaust gas flow is reversed twice in the exhaust gas treatment element 702. That is, the exhaust gas flow first reverses direction as it enters the mixing assembly 718, and the exhaust gas secondly reverses direction by contact with the flow reversing device 740. As the exhaust gas flow passes through the exhaust gas treatment element 702, the exhaust gas flow becomes tortuous because the gas flow reverses direction twice, before the exhaust gas flows into the SCR 732 Increase the ability to mix exhaust gas treatment fluid with exhaust gas. By enhancing the mixing of the exhaust gas treatment fluid and the exhaust gas, the effectiveness of the SCR 732 when removing NOx from the exhaust gas can be enhanced.

  Although not shown in FIGS. 29 and 30, it will be appreciated that the flow reversing device 740 can include a baffle such as the vane 114. Alternatively, any of the mixing assemblies 200, 300, 400, 500 can be used with the exhaust treatment element 702 without departing from the scope of the present disclosure.

  Referring now to FIGS. 31 and 32, an exhaust gas treatment element 800 is shown. Exhaust gas treatment element 800 includes a housing 802, an inlet 804, and an outlet 806. The housing 802 can include an inner shell 807 and an outer shell 808. The thermal insulation material 810 can be disposed between the inner shell 806 and the outer shell 808. The inlet 804 can be connected to the exhaust path 14 and includes an inner cone 812 and an outer cone 814. The thermal insulation material 810 can be disposed between the inner cone 812 and the outer cone 814. The inner cone 812 can be secured to the inner shell 807 and the outer cone 814 can be secured to the outer shell 808. First, the inner cone 812 can be secured to the outer cone 814, and then the inlet 804 can be secured to the inner shell 807 and the outer shell 808. The outlet 806 can include an outer sleeve 816 and an inner sleeve 818 that are secured to the outer shell 808. Inner sleeve 818 can be constructed from one or more sealed portions. Thermal insulation material 810 can be disposed between inner sleeve 818 and outer sleeve 816. The outlet 806 can extend radially outward from the housing 802, while the inlet 804 can be coaxial with the housing 802.

  End cap 820 can be coupled to housing 802 at the end of housing 802 opposite the entrance 804. The injection module 28 can be placed on the end cap 820 (or a further flange (not shown)) near the outlet 806. Similar to the previously described embodiments, the injection module 28 has an exhaust gas flow. Before passing through the SCR (not shown), it operates to inject a reducing agent, such as urea exhaust gas treatment fluid, into the exhaust gas stream, before the mixture of exhaust gas and exhaust gas treatment fluid passes through the SCR. In order to optimize the removal of NOx from the gas stream, the exhaust gas and the exhaust gas treatment fluid must be thoroughly mixed, to assist in mixing the exhaust gas stream and the urea exhaust gas treatment fluid An assembly 718 can be disposed between the inlet 804 and the outlet 806. The mixing assembly 718 allows the injection module 28 to direct exhaust gas treatment fluid. As can be injected into the mixing assembly 718, positioned near the injection module 28, the exhaust gas treatment fluid may be in the mixing assembly 718, it mixes with the exhaust gas stream.

  FIG. 32 best illustrates the mixing assembly 718 within the exhaust gas treatment element 800. The mixing assembly 718 includes a disassembly tube 82 having a first end portion 84 that can be secured to the end cap 820 and a second end portion 86 disposed near the inlet 804. The exhaust gas stream enters inlet 804 and approaches mixing assembly 718. Although this disclosure is not required, the mixing assembly 718 can include a cup-shaped nose 768 that is secured to the outer surface 770 of the flow reversing device 740. The cup-shaped nose 768 can include a conical, hemispherical, or elliptical outer surface 772 that guides the exhaust gas around the mixing assembly 718 when the exhaust gas contacts. The cup-shaped nose 768 can also have a concave surface associated with exhaust gas guidance. Further, the cup-shaped nose 768 can have raised or recessed features (eg, ridges or dimples, not shown) formed in the outer surface 772. After passing around the mixing assembly 718, the exhaust gas passes through the through hole 752 of the support plate 742. After passing through the support plate 742, exhaust gas can flow from the holes 96 into the mixing assembly 718. Although the mixing assembly 718 is shown in FIG. 32 as not including a perforated collar 98, it will be appreciated that the illustrated embodiment includes a perforated collar 98 without departing from the scope of the present disclosure. Can do.

  After entering the decomposition tube 82, the exhaust gas stream is exposed to an exhaust gas treatment fluid (eg, urea) that is injected into the mixing assembly 718 by the injection module 28. When the exhaust gas flows through the decomposition tube 82, the exhaust gas is directed in the reverse direction by the flow reversing device 740 and flows into the shell 758. The exhaust gas can then exit the shell 758 from the outlet 806 and flow into another exhaust gas treatment element (eg, the exhaust gas treatment element shown in FIG. 24) where the SCR can be placed.

  Although not shown in FIG. 32, it should be appreciated that the flow reversing device 740 can include a deflector member such as the vane 114. Alternatively, any of the mixing assemblies 200, 300, 400, 500 can be used with the waste treatment element 800 without departing from the scope of the present disclosure.

  According to the above configuration, the exhaust gas flow is reversed twice in the exhaust gas processing element 800. That is, the exhaust gas flow first reverses direction as it enters the mixing assembly 718, and the exhaust gas secondly reverses direction by contact with the flow reversing device 740. As the exhaust gas stream passes through the exhaust gas treatment element 800, the exhaust gas stream becomes serpentine because the direction of the exhaust gas reverses twice, which is before the exhaust gas flows into the SCR. Increase the ability to mix gas processing fluids with exhaust gases. By enhancing the mixing of the exhaust gas treatment fluid and the exhaust gas, it is possible to increase the effectiveness of the SCR when removing NOx from the exhaust gas.

  Further, it will be appreciated that the exhaust gas treatment element 800 does not include a DOC, DPF, SCR, or any other type of exhaust gas treatment substrate. In the absence of any of these devices, the element 800 can be compact. Such a design allows the element 800 to be later installed in an existing exhaust gas aftertreatment system that includes an SCR to help enhance the mixing of exhaust gas and urea exhaust gas treatment fluid.

  Of course, each of the above configurations can be modified as desired. For example, although the entrance 708 shown in FIG. 24 is shown as having a 90 ° bend, the present disclosure is similar to a coaxial entrance (ie, entrance 804) or entrance 728, such as the entrance shown in FIG. Also conceivable are radially arranged entrances. Similarly, outlet 710 can be replaced with a coaxial outlet (similar to coaxial inlet 804) or an outlet with a 90 ° bend (similar to inlet 708). Similar modifications can be made in component 800 without departing from the present disclosure.

  The foregoing description of the embodiments has been presented for purposes of illustration and description. The embodiments are not intended to be exhaustive and are not intended to limit the present disclosure. Individual elements or features of a particular embodiment are usually not limited to that particular embodiment, but are selected where applicable, even if not specifically illustrated or described In embodiments, they are interchangeable and can be used. The individual elements or features described above can also be modified in various ways. Such changes should not be regarded as a departure from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

Claims (29)

An exhaust gas treatment element for treating engine exhaust gas,
A housing including an inlet and an outlet;
A mixing device disposed in the housing between the inlet and the outlet;
The mixing device comprises:
A shell in communication with the outlet;
A decomposition tube having a first end and a second end, wherein the first end extends from the shell and is configured to receive the exhaust gas from the inlet; A decomposition tube configured to receive a gas treatment fluid, wherein the second end is disposed within the shell;
A flow reversing device disposed near the second end and configured to direct a mixture of the exhaust gas and the reactant exhaust gas treatment fluid into the shell in a predetermined direction;
Including
The flow reversing device is an exhaust gas processing element that reverses the flow direction of the exhaust gas and returns it to the first end of the decomposition tube.   Further comprising a support plate fixed to the inner surface of the housing upstream from the first end of the decomposition tube, the support plate having an opening for receiving the decomposition tube, and the exhaust gas being decomposed. The exhaust gas treatment element of claim 1, wherein the exhaust gas treatment element defines a plurality of through holes that permit passage through the support plate prior to entering the first end of the tube.   The exhaust gas treatment element of claim 2, wherein the direction of the exhaust gas flow reverses after flowing into the first end of the decomposition tube.   The exhaust gas treatment element of claim 1, further comprising a cup-shaped nose secured to an outer surface of the flow reversing device.   The exhaust gas treatment element of claim 4, further comprising a collar disposed around the first end, the collar including a plurality of second holes for receiving the exhaust gas.   The exhaust gas treatment element of claim 1, wherein the flow reversing device includes a plurality of baffles for mixing the exhaust gas and the reactant exhaust gas treatment fluid.   The exhaust gas treatment element according to claim 6, wherein the deflecting member is formed as a plurality of vanes, and the vanes are fixed to an inner surface of the flow reversing device.   The exhaust gas processing element according to claim 6, wherein the baffle member is formed of a plurality of tabs protruding from a plurality of cutout portions formed around the flow reversing device.   The exhaust gas treatment element of claim 8, further comprising a dispersion ring having a plurality of scalloped recesses secured between the second end of the cracking tube and the flow reversing device.   The exhaust gas treatment element of claim 6, wherein the baffle member is formed around a cylindrical ring secured to the second end of the decomposition tube.   The exhaust gas treatment element of claim 6, wherein the baffle member is formed around an annular ring secured between the second end of the cracking tube and the flow reversing device.   The exhaust gas processing element according to claim 6, wherein the deflecting member comprises a diverter ring fixed to the second end of the decomposition tube.   13. The flow distribution cap further comprising a flow distribution cap secured between the second end of the decomposition tube and the flow reversing device, wherein the flow distribution cap is formed with a plurality of through holes. Exhaust gas treatment elements.   The exhaust gas treatment element of claim 1, wherein the decomposition tube includes a portion that is radially expanded between the first and second ends. An exhaust gas treatment element for treating exhaust gas generated in an engine,
A housing;
An exhaust gas treatment element substrate disposed within the housing;
An injection module for injecting a reactant exhaust gas treatment fluid into the exhaust gas, the injection module being fixed to the housing and disposed downstream of the first exhaust gas treatment element substrate;
A mixing device disposed within the housing and disposed downstream of the injection module;
The mixing device comprises:
Shell,
A disassembly tube having a first end extending from the shell and in direct communication with the infusion module; and a second end disposed within the shell;
A flow reversing device disposed near the second end for directing the exhaust gas and the reactant exhaust gas treatment fluid into the shell in a predetermined direction;
A support plate fixed to the inner surface of the housing upstream from the first end of the disassembly tube;
The support plate includes a plurality of apertures that receive the cracking tube and a plurality of exhaust gases that allow the exhaust gas to pass through the support plate before flowing into the first end of the cracking tube. Defining a through hole,
The direction of the exhaust gas flow is reversed after first flowing into the first end of the decomposition tube,
Second, the flow reversing device reverses the direction of the exhaust gas flow and returns it to the first end of the cracking tube.   The exhaust gas treatment element of claim 15, further comprising a cup-shaped nose secured to an outer surface of the flow reversing device.   The exhaust gas treatment element of claim 16, further comprising a collar disposed around the first end, wherein the collar includes a plurality of second holes for receiving the exhaust gas.   The exhaust gas treatment element of claim 15, wherein the flow reversing device includes a plurality of baffles for mixing the exhaust gas and the reactant exhaust gas treatment fluid.   The exhaust gas treatment element of claim 18, wherein the baffle member is formed as a plurality of vanes, the vanes being secured to an inner surface of the flow reversing device.   19. An exhaust gas treatment element according to claim 18, wherein the baffle member is formed from a plurality of tabs protruding from a plurality of cutouts formed around the flow reversing device.   21. The exhaust gas treatment element of claim 20, further comprising a dispersion ring having a plurality of scalloped recesses secured between the second end of the cracking tube and the flow reversing device.   The exhaust gas treatment element of claim 18, wherein the baffle member is formed around a cylindrical ring secured to the second end of the decomposition tube.   The exhaust gas treatment element of claim 18, wherein the baffle member is formed around an annular ring secured between the second end of the cracking tube and the flow reversing device.   19. The exhaust gas treatment element according to claim 18, wherein the deflecting member comprises a diverter ring fixed to the second end of the decomposition tube.   25. The flow distribution cap further comprising a flow distribution cap secured between the second end of the decomposition tube and the flow reversing device, wherein the flow distribution cap is formed with a plurality of through holes. Exhaust gas treatment elements.   The exhaust gas treatment element of claim 15, wherein the decomposition tube includes a portion that is radially expanded between the first and second ends.   The exhaust gas treatment according to claim 15, wherein the first exhaust gas treatment element base material is an oxidation catalyst base material.   28. The exhaust gas treatment element of claim 27, further comprising a second exhaust gas treatment element disposed downstream of the housing and in parallel with the first exhaust gas treatment element.   30. The exhaust gas treatment element of claim 28, wherein the second exhaust gas treatment element is an SCR catalyst substrate.

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