Electrically heated mixing pipe for treating diesel engine exhaust fluid in a selective catalytic reduction system

Abstract

This invention discloses an exhaust treatment assembly for receiving exhaust gases from a motor vehicle, the assembly comprising a mixing conduit, a sheath, and a heater. The mixing conduit at least partially defines a passage adapted to receive exhaust gases and a chemical reducing agent. The sheath includes a fluidly sealed first end to the mixing conduit. At least a portion of the sheath is radially spaced from the mixing conduit to at least partially define a gap. The heater is disposed within the gap. The heater is adapted to heat a reducing agent impact surface.

Description

Technical Field

[0001] This disclosure relates to an electrically heated mixing manifold for treating diesel engine exhaust fluid in a selective catalytic reduction (SCR) system. Background Technology

[0002] This section provides background information related to this disclosure, which is not necessarily prior art.

[0003] Motor vehicles typically have an exhaust system that carries hot exhaust gases from the internal combustion engine that powers the vehicle to the external environment. Such an exhaust system typically includes various exhaust components, including but not limited to manifolds, downpipes, X-pipes, exhaust manifolds, and mufflers. Depending on the type of fuel source used to power the internal combustion engine in the motor vehicle (e.g., gasoline and diesel), the exhaust system may include additional exhaust components that provide emission control, including but not limited to catalytic converters, reductant injectors, selective catalytic reduction (SCR) units, diesel oxidation catalysts (DOC), and diesel particulate filters (DPF).

[0004] One or more SCR units can be used to control NOx emissions from a diesel engine. An SCR unit may include a catalyst that accelerates the reaction rate of NOx with a chemical reducing agent. The chemical reducing agent is introduced upstream of the catalyst in the exhaust. Diesel exhaust fluid (DEF) is the chemical reducing agent, including an aqueous solution of urea. DEF can be injected into the exhaust in the form of small droplets, which evaporate and then thermally decompose. Ammonia is one of the decomposition products and can react with NOx in the catalyst. The exhaust system may further include a mixer downstream of the DEF introduction point to accelerate the treatment of the DEF and distribute the resulting ammonia. Summary of the Invention

[0005] This section provides a general overview of this disclosure, rather than a full disclosure of its entire scope or all its features.

[0006] This disclosure provides an exhaust treatment assembly for receiving exhaust gases from a motor vehicle. The exhaust treatment assembly includes a mixing conduit, a sheath, and a heater. The mixing conduit at least partially defines a passage adapted to receive exhaust gases and a chemical reducing agent. The sheath includes a fluidly sealed first end to the mixing conduit. At least a portion of the sheath is radially spaced from the mixing conduit to at least partially define a gap. The heater is disposed within the gap. The heater is adapted to heat a reducing agent impact surface.

[0007] In some configurations, the sheath is located radially inside the mixing conduit. The heater is connected to the radially outer surface of the sheath. The reducing agent impact surface is at least a portion of the radially inner surface of the sheath.

[0008] In some configurations, the mixing pipe defines a first length. The sheath defines a second length, which is shorter than the first length.

[0009] In some configurations, the sheath is limited to a wall thickness ranging from 0.75 mm to 2 mm.

[0010] In some configurations, the sheath is positioned radially outside the mixing conduit. The heater is attached to the radially outer surface of the mixing conduit. The reducing agent impact surface is at least a portion of the radially inner surface of the mixing conduit.

[0011] In some configurations, the first end is the upstream end.

[0012] In some configurations, the sheath further includes a second end opposite to the first end. The second end is adapted to be in direct contact with the mixing conduit.

[0013] In some configurations, the reducing agent impact surface is part of the channel's inner surface. This portion is less than 100%.

[0014] In some configurations, the heater includes a first heater and a second heater. The second heater is located downstream of the first heater. The first and second heaters can operate independently.

[0015] In some configurations, the heater is defined as having a roughly annular shape.

[0016] In some configurations, the sheath includes stainless steel.

[0017] In some configurations, the exhaust treatment further includes insulation material. The insulation material is disposed around at least a portion of at least one of the mixing pipe and the sheath.

[0018] In some configurations, the exhaust treatment assembly further includes a mixer fluidly connected to the channel. The mixer is located upstream of the heater.

[0019] In some configurations, the exhaust treatment assembly further includes a chemical reducing agent injector. The chemical reducing agent injector is adapted to inject a chemical reducing agent into the channel. The chemical reducing agent injector is located upstream of the heater.

[0020] In some configurations, the exhaust treatment assembly further includes a selective catalytic reduction (SCR) unit. The SCR unit is located downstream of the mixing pipe.

[0021] This disclosure provides a method for reducing chemical reducing agent deposits in a vehicle exhaust system. The method includes supplying exhaust gas and a chemical reducing agent to a passage of an exhaust treatment component. The exhaust treatment component includes a mixing conduit, a sheath, and a heater. The mixing conduit at least partially defines the passage. The sheath is radially spaced from the mixing conduit to at least partially define a gap. A first end of the sheath is fluidly sealed to the mixing conduit. The heater is disposed within the gap. The method further includes causing the chemical reducing agent to impinge on a reducing agent impingement surface of the passage. The method further includes heating the reducing agent impingement surface using the heater.

[0022] In some configurations, heating involves bringing the reducing agent impact surface to a temperature ranging from 135°C to 275°C.

[0023] In some configurations, heating involves supplying power to the heater in the range of 1 kW to 2 kW.

[0024] In some configurations, the heater includes a first heater and a second heater. The first heater and the second heater can operate independently.

[0025] In some configurations, the method further includes identifying a region of high reducing agent impact flux on the reducing agent impact surface. Heating the reducing agent impact surface includes operating at least one of a first heater and a second heater based on the region of maximum reducing agent impact.

[0026] Other applicable scope will become clear from the description provided herein. The descriptions and specific examples in this overview are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0027] The accompanying drawings described herein are for illustrative purposes only, showing the selected embodiments and not all possible implementations, and are not intended to limit the scope of this disclosure.

[0028] Figure 1 This is a schematic representation of an exhaust system based on the principles of this disclosure;

[0029] Figure 2A This is a perspective view of an exhaust treatment assembly based on the principles of this disclosure;

[0030] Figure 2B yes Figure 2A A cross-sectional view of the mixing chamber of the exhaust treatment assembly;

[0031] Figure 3 yes Figure 2A A cross-sectional view of a mixing pipe assembly of an exhaust treatment component based on the principles of this disclosure;

[0032] Figure 4This is a cross-sectional view of another hybrid tube assembly based on the principles of this disclosure;

[0033] Figure 5 This is a perspective view of an exhaust treatment assembly based on the principles of this disclosure;

[0034] Figure 6 yes Figure 5 A cross-sectional view of the exhaust treatment assembly; and

[0035] Figure 7 This is a flowchart depicting a method for reducing chemical reducing agent deposits on exhaust treatment components based on the principles of this disclosure.

[0036] In several views of the accompanying drawings, corresponding reference numerals indicate the corresponding parts. Detailed Implementation

[0037] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0038] Example embodiments are provided to make this disclosure exhaustive and to fully convey its scope to those skilled in the art. Numerous specific details, such as examples of specific components, apparatus, and methods, are set forth to provide a thorough understanding of embodiments of this disclosure. It will be apparent to those skilled in the art that the example embodiments may be implemented in many different forms without employing the specific details, and that these specific details should not be construed as limiting the scope of this disclosure. In some example embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

[0039] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprising,” “containing,” “including,” and “having” are inclusive and therefore specify the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the particular order discussed or shown, unless specifically indicated otherwise. It should also be understood that additional or alternative steps may be employed.

[0040] When an element or layer relates to "on," "joined to," "connected to," or "attached to" another element or layer, it can be directly on, joined to, connected to, or attached to that other element or layer, or there may be an intermediary element or layer present. In contrast, when an element relates to "directly on," "directly joined to," "directly connected to," or "directly attached to" another element or layer, there may be no intermediary element or layer present. Other terms used to describe the relationship between these elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] While the terms first, second, third, etc., may be used herein to describe different elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Terms such as “first,” “second,” and other numerical terms, as used herein, do not imply sequence or order unless the context clearly indicates otherwise. Therefore, without departing from the teachings of the exemplary embodiments, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment.

[0042] Spatial terms such as “inner,” “outer,” “below,” “below,” “lower,” “above,” and “upper” are used herein to facilitate the interpretation of a description of the relationship of one element or feature relative to another element(s)(s)(s)(s) shown in the accompanying drawings. Spatial relative terms may be intended to cover different orientations of the device in use or operation, other than those depicted in the accompanying drawings. For example, if the device in these drawings is flipped, an element described as “below” or “below” other elements or features would be oriented “above” that other element or feature. Thus, the example term “below” can encompass both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein are interpreted accordingly.

[0043] refer to Figure 1An exhaust treatment system 10 is provided according to the principles of this disclosure. The exhaust treatment system 10 can treat the exhaust gases 12 output from the combustion engine 14. The exhaust treatment system 10 may include an exhaust gas passage 20, an oxidation catalyst 22 (e.g., a diesel oxidation catalyst (DOC)), a filter 24 (e.g., a diesel particulate filter (DPF)), one or more selective catalytic reduction (SCR) units 26, one or more corresponding chemical reductant injectors 28, and one or more corresponding mixers 30. The oxidation catalyst 22, filter 24, SCR unit 26, and mixer 30 are disposed within the exhaust gas passage 20 such that some or all of the exhaust gases 12 output from the engine 14 flow through it.

[0044] The exhaust treatment system 10 may have two SCR units 26 (as shown) and may be referred to as a "dual metering system". One SCR unit 26 may be located downstream of the oxidation catalyst 22 and the filter 24, while the other SCR unit 26 may be located upstream of the oxidation catalyst 22 and the filter 24. However, in other examples, the exhaust treatment system may have a single SCR unit. The single SCR unit may be located downstream of the oxidation catalyst and the filter, or upstream of the oxidation catalyst and the filter.

[0045] As shown, mixer 30 can be a non-impact mixer (see also...) Figure 2B Mixer 68 and Figures 5 to 6 The non-impact mixer 302. The non-impact mixer may have a generally annular shape. The non-impact mixer includes a plurality of axially extending, circumferentially spaced louvered panels. In some examples, all or part of the louvered panels may define multiple orifices (e.g., see [reference needed]). Figure 2B The mixer 68). A non-impact mixer is adapted to receive exhaust gas and generate a vortex of exhaust gas and air into which a chemical reducing agent is injected. This vortex can resemble a cyclone, having an axis substantially parallel to the flow direction of the exhaust gas. Due to the turbulence of the exhaust gas vortex generated by the non-impact mixer, the reducing agent can maintain sufficient air propagation within the non-impact mixer. In other examples, the exhaust treatment system may include an impact mixer having a surface adapted for direct impact or contact with the chemical reducing agent from the reducing agent injector.

[0046] Continue to refer to Figure 1Each of the reducing agent injectors 28 may be located upstream of the corresponding SCR unit 26, as shown. However, in other examples, the reducing agent injector may be partially located within or integrated with the mixer. Each of the reducing agent injectors 28 may receive reducing agent 32 from a reducing agent reservoir (not shown) and inject the reducing agent 32 as a liquid reducing agent droplet spray cone into the exhaust gas 12, or spray it upstream of or into the mixer 30. When the mixer 30 is a non-impact mixer, as shown, the reducing agent 32 spray cone may be directed toward the center of the mixer 30, rather than onto the wall of the exhaust treatment system 10 or the surface of the mixer 30. The mixer 30 may be adapted to generate a vortex in the exhaust gas 12 that sufficiently retains the reducing agent 32 to reduce or avoid contact between the reducing agent 32 and the surface of the mixer 30.

[0047] After being discharged into the mixing tube assembly 34, the exhaust gas 12 and the reducing agent 32 are mixed within and / or downstream of the mixer 30. Each of the mixing tube assemblies 34 is located downstream of and axially spaced from a corresponding reducing agent injector 28 and a corresponding mixer 30. Each of the mixing tube assemblies 34 is located upstream of and axially spaced from a corresponding SCR unit 26.

[0048] The mixing tube assembly 34 includes a mixing tube 36, a sheath 38, and a heater 40. As shown, the sheath 38 may be disposed within the mixing tube 36. However, in other examples, the sheath may be at least partially disposed outside the mixing tube (e.g., see [reference needed]). Figure 6 (The mixing tube assembly 304). As shown, the heater 40 may be disposed within the gap between the mixing tube 36 and the sheath 38, for example, on the outer surface of the sheath 38. Accordingly, the heater 40 may be disposed downstream of and axially spaced from the reducing agent injector 28 and the mixer 30. The heater 40 may be disposed upstream of and axially spaced from the SCR unit 26.

[0049] The reducing agent 32 can be heated by the exhaust gas 12 in the mixer and / or mixing tube assembly 34. A portion of the reducing agent 32 can evaporate and thermally decompose upon air propagation. For example, the reducing agent 32 can be a DEF, which includes an aqueous solution of urea. Urea can decompose into gaseous products, including ammonia.

[0050] Another portion of the reducing agent may not be heated sufficiently to evaporate and decompose, for example, in cases of low exhaust enthalpy and / or high reducing agent introduction rate. This undecomposed portion of the reducing agent 32 may fall as liquid droplets onto the surface of the mixing tube assembly 34. This portion of the reducing agent 32 may impact the inner surface of the mixer subassembly 34, which is referred to as the reducing agent impact surface 42. The reducing agent impact surface 42 is the surface on which the liquid reducing agent 28 falls or impacts after air propagation in the exhaust gas vortex generated by the mixer 30 and before evaporation and decomposition. The reducing agent impact surface 42 is downstream of the mixer 30 and upstream of the SCR unit 26. The reducing agent impact surface 42 may be on the inner surface of the sheath 38, as shown, and / or on the inner surface of the mixing tube 36.

[0051] Reducing agent 32 can form a liquid film on reducing agent impact surface 42 (e.g., see...). Figure 3 Membrane 153 in Figure 4 Membrane 220 in Figure 6 (Membranes 326 in the middle). Heater 40 can be adapted to heat the reducing agent 32 on the reducing agent impact surface 42 to cause the reducing agent 32 to evaporate and thermally decompose. Downstream of the mixing pipe subassembly 34, exhaust gas 12 and the gaseous products of the decomposition of reducing agent 32 flow into SCR unit 26. The SCR unit is adapted to increase the reaction rate of NOx in exhaust gas 12 with ammonia produced by the decomposition of reducing agent 32.

[0052] refer to Figures 2A to 2B This provides a portion of an exhaust assembly 60 based on the principles of this disclosure. The exhaust assembly 60 is adapted to receive exhaust gas from a combustion engine (e.g., see [reference]). Figure 1 The exhaust gas 62 of the combustion engine 14 is emitted and discharged during combustion engine operation. The exhaust assembly 60 typically includes: a reducing agent injector 64; a mixing chamber 66, which includes a mixer 68. Figure 2B (as shown in the diagram); hybrid tube assembly 70 (also referred to as “sub-assembly 70”); and SCR unit 72.

[0053] like Figure 2B As shown, mixing chamber 66 houses mixer 68. Mixer 68 and mixing chamber 66 are adapted to receive exhaust gas 62 from combustion engine and chemical reducing agent from reducing agent injector 64. Mixer 68 is upstream of and in fluid communication with the interior of mixing tube assembly 70. (As described above...) Figure 1As described in the discussion, mixer 68 is a non-impact mixer. Mixer 68 has a generally annular shape and extends along axis 80. Axis 80 may be generally parallel to the flow direction of exhaust gas 62 in mixer 68. Mixer 68 includes a plurality of axially extending, circumferentially spaced louvers 82. The louvers 82 are alternately arranged with a plurality of corresponding slots 84. All or part of the louvers 82 may define a plurality of orifices 86.

[0054] Back Figure 2A The mixing tube assembly 70 is disposed between the mixing tank 66 and the SCR unit 72. More specifically, the mixing tube assembly 70 is downstream of the mixing tank 66 and upstream of the SCR unit 72. The following description, in conjunction with... Figure 3 The discussion described the hybrid tube assembly 70 and its operation in more detail.

[0055] refer to Figure 3 , showed Figures 2A to 2B The mixing conduit assembly 70 typically includes a mixing conduit 100, a sheath 102, a heater 104, and an insulator 106. As shown, the sheath 102 may be disposed radially inside the mixing conduit 100.

[0056] The mixing conduit 100 at least partially defines the channel 108. The channel 180 extends between the inlet 110 and the outlet 112. The channel 108 is adapted to receive droplets of exhaust gas 114 and chemical reducing agent 116.

[0057] The sleeve 102 may have an annular shape. The sleeve 102 includes a first end or upstream end 120 and a second end or downstream end 122. At least a portion of the sleeve 102 is spaced apart from the mixing conduit 100 to define a gap 124 (e.g., an air gap). As shown, at least one of the first end 120 and the second end 122 of the sleeve 102 (e.g., the first end 120) is fluidly sealed to the mixing conduit 100. The first end 120 may be fluidly sealed to the mixing conduit 100 via a weld 126. The second end 122 may be in physical contact with the mixing conduit 100 but not fluidly sealed to it. Accordingly, the gap 124 may be partially isolated from the channel 108. As a result, the air in the gap 124 may be mostly static, and heat loss through the gap 124 may be reduced or minimized compared to airflow through the gap. As the air expands due to heat, the pressure in the gap 124 increases, and the air can escape from the gap between the second end 122 of the sheath 102 and the mixing pipe 100, for example, by bending the sheath 102 away from the mixing pipe 100.

[0058] Heater 104 is disposed in gap 124. Heater 104 is adapted to heat reducing agent impact surface 130. Reducing agent impact surface 130 may be on sheath 102, as shown, and / or on mixing conduit (e.g., see...). Figure 6 In the example shown, the reducing agent impact surface 130 is a portion of the inner surface 132 of the sheath 102. In at least one example embodiment, the impact surface 130 is a portion smaller than 100% of the inner surface 132 of the sheath 102.

[0059] Heater 104 can be fixed opposite to reducing agent impact surface 130. Accordingly, in the example embodiment shown, heater 104 is fixed to the outer surface 134 of sheath 102. Heater 104 can be attached to sheath 102 (not shown) by adhesive, one or more clamps, or both adhesive and one or more clamps. Heater 104 can be directly attached to the outer surface 134 of sheath 102. Heater 104 can be in direct thermal contact with sheath 102.

[0060] Heater 104 can be spaced 144 from mixing conduit 100. Accordingly, heater 104 can avoid direct thermal contact with mixing conduit 100. Alternatively, air passing through gap 124 at distance 144 can act as an insulator between heater 104 and mixing conduit 100. This position of heater 104 can help reduce or minimize heat loss to the external environment 146 of subassembly 70 compared to direct thermal contact between heater and mixing conduit.

[0061] The heater 104 may have a generally annular shape, such that the heater surrounds the entire perimeter of the outer surface 134 of the sheath 102. In other example embodiments, the heater 104 includes a plurality of discrete heaters. The plurality of discrete heaters may be circumferentially spaced around the outer surface 134 and / or axially spaced along the outer surface 134 (e.g., see...). Figure 4 Multiple heaters can operate independently.

[0062] The mixing conduit 100 includes an inner surface 140 and an outer surface 142. A sheath 102 can be directly attached to the inner surface 140 of the mixing conduit 100. An insulator 106 can be disposed on the outer surface 142 of the mixing conduit 100, surrounding the entire outer surface or a portion thereof. The insulator 106 includes a thermally insulating material. Compared to a sub-assembly 70 without an insulator, the insulator 106 can help reduce heat loss to the environment 146.

[0063] The mixing conduit 100 defines a first length 150, which is parallel to the axis A1 of the subassembly 70. The sheath 102 defines a second length 152, which is parallel to the axis A1. The second length 152 is less than the first length 150. In at least one example embodiment, the second length 152 may be less than or equal to about 90% of the first length (e.g., less than or equal to about 80%, less than or equal to about 70%, less than or equal to about 60%, less than or equal to about 50%, less than or equal to about 40%, or less than or equal to about 30%). The difference between the first length 150 and the second length 152 can help reduce heat loss of the exhaust gas 114 into the channel 108 compared to a subassembly comprising a mixing conduit and sheath having substantially similar lengths. The sheath 102 may be positioned along the longitudinal axis A1 at a location where the highest desired reducing agent impact flux is achieved.

[0064] As used herein, reducing agent impact flux refers to the flow rate of reducing agent on or falling on the surface of the impact subassembly 70 (e.g., reducing agent impact surface 130). Reducing agent impact flux can be measured by the mass, molar, or volumetric flow rate of the reducing agent 116 impacting the reducing agent impact surface 130 or falling on it. In some examples, the thickness of the liquid reducing agent film 153 on the reducing agent impact surface 130 can indicate the reducing agent impact flux.

[0065] Heater 104 defines a third length 154, which is parallel to axis A1. The third length 154 is less than the second length 152 of sheath 102. This difference between the second length 152 and the third length 154 can help reduce heat loss of the exhaust gas 114 into channel 108 compared to a subassembly comprising a sheath and heater with substantially similar lengths. Heater 104 can be positioned along longitudinal axis A1 at the location of the highest desired reducing agent implosion flux.

[0066] In at least one example embodiment, channel 108 includes one or more first wall portions 160, one or more second wall portions 162, and one or more third wall portions 164. It is anticipated that the first wall portions 160 will have substantially no liquid reducing agent deposits during operation. It is anticipated that the second portions 162 and third portions 164 will be subjected to reducing agent impact to form a liquid reducing agent film 153. Accordingly, sheath 102 is generally axially aligned with the second and third wall portions 162. The second wall portions 162 and third wall portions 164 may include reducing agent impact surfaces 130. It is anticipated that the third wall portion 164 will receive a higher reducing agent impact flux than the second wall portion 162. Accordingly, heater 104 is generally axially aligned with the third wall portion 164.

[0067] In some examples, the thickness of membrane 153 can indicate the reducing agent impact flux. Thus, membrane 153 can define a first membrane thickness 166 on the second portion 162 and a second membrane thickness 168 on the third portion 164, wherein the first membrane thickness is smaller than the second membrane thickness during engine operation.

[0068] The material and dimensions of the sheath 102 can be optimized to achieve desired heat transfer characteristics. For example, when lower conductivity is desired, a thinner sheath formed of a material with lower thermal conductivity can be used. Using a sheath with lower conductivity can reduce or minimize heat transfer through the sheath, limiting heat transfer to the exhaust gas (rather than the reducing agent). When higher conductivity is desired, a thicker sheath formed of a material with higher thermal conductivity can be used. In at least some example embodiments, the sheath 102 defines a sheath thickness 170 ranging from about 0.75 mm to about 2 mm. In at least some example embodiments, the sheath 102 comprises stainless steel. The surfaces 132, 134 of the sheath 102 can be generally smooth to minimize heat loss of the exhaust gas 114 and / or air into the channel 108 and / or gap 124.

[0069] Sub-assembly 70 can be adapted to efficiently heat the reducing agent while minimizing power consumption. More specifically, the axial positioning of the sheath 102 and heater 104 is at the region of highest desired reducing agent impact flux (e.g., the second wall portion 160 and the third wall portion 162) to reduce or minimize heat loss to the exhaust gas 114. The heater 104 is disposed in the gap 124 and spaced at a distance 144 from the mixing conduit 100 to reduce or minimize heat loss to the environment 146. Furthermore, the sheath 102 is at least partially fluid-sealed to the mixing conduit 100 to further reduce or minimize heat loss through the gap 124. Additionally, the thickness and material of the sheath 102 are selected to optimize conductivity, such that the heater 104 efficiently heats the impact surface 130 to evaporate and thermally decompose the reducing agent, while minimizing heating of other areas of the sheath 102 with little or no reducing agent impact flux (which would transfer heat to the exhaust gas 114). The aforementioned design features precisely tailor heating to the region with the highest desired reducing agent surge flux and minimize heat loss to exhaust gas 114 and the environment 146, contributing to efficient heat utilization and thus requiring lower power than devices lacking some or all of the aforementioned features. In at least one example embodiment, the heater can operate at a power range of approximately 1 kW to approximately 2 kW. Accordingly, sub-assembly 70 can be used with vehicle systems from 24V to 48V without requiring additional power to support the exhaust treatment system.

[0070] refer to Figure 4This provides another hybrid tube assembly 200 (also referred to as "sub-assembly 200") based on the principles of this disclosure. Unless otherwise stated below, sub-assembly 200 is related to... Figures 2A to 3 The sub-assembly 70 is identical. Sub-assembly 200 typically includes a mixing conduit 202, a sheath 204, a first heater 206, a second heater 208, and an insulator 210. Sub-assembly 200 can be adapted to receive exhaust gas 212.

[0071] Sub-assembly 200 may include one or more first wall portions 214, one or more second wall portions 216, and one or more third wall portions 218. It is anticipated that the first wall portions 214 will have substantially no reductant deposits during operation. It is anticipated that the second wall portions 216 and third wall portions 218 will be subjected to reductant impact 219 to form a liquid reductant film 220. The second wall portions 216 and third wall portions 218 may include reductant impact surfaces 222. It is anticipated that the third portion 218 will receive a higher reductant impact flux than the second portion 216.

[0072] The first heater 206 and the second heater 208 can be adapted to heat the reducing agent impact surface 222. The impact surface 222 can be adapted to be impacted by the reducing agent 219, which can form a film 220. The first heater 206 and the second heater 208 can be disposed at different axial positions on the sheath 204. The first heater 206 and the second heater 208 can be axially spaced apart. The first heater 206 can be adapted to heat the reducing agent impact surface 222 on the second wall portion 216, while the second heater 208 can be adapted to heat the third portion of the reducing agent impact surface 222 on the third wall portion 218.

[0073] The first heater 206 and the second heater 208 can operate independently. Accordingly, if the location of the highest reducing agent surge flux changes, the operation of heaters 206 and 208 may change accordingly (e.g., operate at different power, or be turned on or off). In at least one example embodiment, when the reducing agent surge flux in the second portion 226 is higher than that in the first portion 224, the first heater 206 may operate at a lower power compared to the second heater 208.

[0074] refer to Figures 5 to 6 This disclosure provides an exhaust gas treatment assembly 300 based on the principles of this disclosure. The exhaust gas treatment assembly 300 typically includes a reducing agent injector 301. Figure 6 As shown in the diagram, mixer 302, and mixing pipe subassembly 304 (also referred to as "subassembly 304") are included. Mixer 302 may be a non-impact mixer. Mixing pipe subassembly 304 may be connected to... Figures 2A to 3The mixing pipe subassembly 70 is the same as or similar to the mixing pipe subassembly 70, unless otherwise stated below. The exhaust treatment assembly 300 can be adapted to receive exhaust gas from a combustion engine (e.g., see [link to exhaust treatment assembly]). Figure 1 The exhaust gas 306 from the combustion engine 14) and the chemical reducing agent 308 in the form of liquid droplets from the reducing agent injector 301.

[0075] like Figure 6 As shown, the mixing conduit subassembly 304 includes a mixing conduit 310, a sheath 312, and a heater 314. The subassembly 304 may further include an insulator (not shown) surrounding the entire sheath 312 or a portion thereof. The mixing conduit 310 may at least partially define a passage 316.

[0076] At least a portion of the sheath 312 is disposed radially outside the mixing conduit 310. The sheath 312 is spaced apart from the mixing conduit 310 to define a gap 318. The heater 314 is disposed in the gap 318.

[0077] Heater 314 is adapted to heat reducing agent impact surface 320. Reducing agent impact surface 320 is located on mixing conduit 310. More specifically, heater 314 is coupled to the outer surface 322 of mixing conduit 310 to heat the impact surface 320, which is the entire inner surface 324 or a portion thereof of mixing conduit 310. Reducing agent impact surface 320 may be adapted to receive reducing agent 308. Reducing agent 308 may form a reducing agent film 326 on reducing agent impact surface 320.

[0078] The sleeve 312 may include a first end or upstream end 330 and a second end or downstream end 332. The first end 330 may be fluidly sealed to the mixing conduit 310. The second end 332 may be fluidly connected to the channel 316 such that the gap 318 is a partial air gap. Additionally or alternatively, the second end 332 of the sleeve 312 may be fluidly sealed to the mixing conduit 310 (not shown). The sleeve 312 may be fluidly sealed to the mixing conduit 310 via a weld 334.

[0079] refer to Figure 7 A flowchart is provided illustrating a method for reducing chemical reducing agent deposits on an exhaust treatment component according to the principles of this disclosure. At 400, the method includes providing exhaust gas and a chemical reducing agent to the exhaust treatment component. By way of example, the exhaust treatment component may include... Figures 2A to 3 Hybrid tube assembly 70 Figure 4 Hybrid tube assembly 200, or Figures 5 to 6 Exhaust treatment component 300.

[0080] In 404, the method includes impacting a chemical reducing agent onto a reducing agent impact surface of the exhaust treatment component. The chemical reducing agent may include DEF. The chemical reducing agent may be adapted to impact a desired area (e.g., an impact surface) of the exhaust treatment component or fall onto it. As described above, the reducing agent may be injected into a mixer and maintained with sufficient air propagation until it is evaporated and thermally decomposed, or falls as liquid droplets onto the reducing agent impact surface to form a reducing agent film.

[0081] At 408, the method may optionally include determining the region of maximum reductant impact flux, for example, when the exhaust treatment assembly includes multiple independently operating heaters. The region of maximum reductant impact flux can be determined by engine speed (which indicates air and fuel flow), exhaust temperature (which can be measured), and / or reductant flow (which can be known from a setpoint and / or sensors).

[0082] At 412, the method further includes operating one or more heaters to evaporate at least a portion of the chemical reducing agent. The heaters may be adapted to heat the reducing agent to a temperature that maximizes the thermally induced decomposition (TBU) of the reducing agent while minimizing surface diffusion, splashing, bounce, or decomposition and bounce. The reducing agent TBU can facilitate efficient heat transfer to the reducing agent. The secondary droplets generated by the TBU can be smaller than the initial or primary droplets (before impact) and are therefore more suitable for downstream treatment in the exhaust gas. In at least some example embodiments, the heaters can heat to temperatures ranging from about 135°C to about 275°C.

[0083] The above description of these embodiments is provided for illustrative and descriptive purposes. It is not intended to be exhaustive or limiting of this disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in selected embodiments even if not explicitly shown or described. Variations may also be made in many ways. Such variations should not be considered as departing from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

Claims

1. An exhaust treatment assembly for receiving exhaust gases from a motor vehicle, characterized in that, The exhaust treatment assembly includes: A mixing conduit, which at least partially defines a channel adapted to receive the exhaust gas and the chemical reducing agent; A sheath, comprising a fluidly sealed first end of the mixing conduit, at least a portion of which is radially spaced from the mixing conduit to at least partially define a gap; and A heater is disposed in the gap and adapted to heat the reducing agent impacting the surface.

2. The exhaust treatment assembly as described in claim 1, characterized in that, in: The sheath is located radially inside the mixing pipe. The heater is connected to the radial outer surface of the sheath, and The reducing agent impact surface is at least a portion of the radial inner surface of the sheath.

3. The exhaust gas treatment assembly as described in claim 2, characterized in that, in, The hybrid conduit defines a first length, and The sheath defines a second length, which is less than the first length.

4. The exhaust treatment assembly as described in claim 2, characterized in that, in, The sheath is limited to a wall thickness ranging from 0.75 mm to 2 mm.

5. The exhaust gas treatment assembly as described in claim 1, characterized in that, in: The sheath is located on the radially outer side of the mixing pipe. The heater is connected to the radial outer surface of the mixing pipe, and The reducing agent impact surface is at least a portion of the radially inner surface of the mixing pipe.

6. The exhaust gas treatment assembly as claimed in claim 1, characterized in that, in, The first end is the upstream end.

7. The exhaust gas treatment assembly as claimed in claim 1, characterized in that, in: The sheath further includes a second end opposite to the first end, and The second end is adapted to make direct contact with the mixing conduit.

8. The exhaust treatment assembly as claimed in claim 1, characterized in that, in, The reducing agent impact surface is part of the inner surface of the channel, and this part is less than 100%.

9. The exhaust gas treatment assembly as claimed in claim 1, characterized in that, in: The heater includes a first heater and a second heater disposed downstream of the first heater, and The first heater and the second heater can operate independently.

10. The exhaust gas treatment assembly as claimed in claim 1, characterized in that, in, The heater is defined as having a roughly annular shape.

11. The exhaust treatment assembly as claimed in claim 1, characterized in that, in, The sheath is made of stainless steel.

12. The exhaust treatment assembly as claimed in claim 1, characterized in that, Further includes: Thermal insulation material is disposed around at least a portion of at least one of the mixing pipe and the sheath.

13. The exhaust treatment assembly as claimed in claim 1, characterized in that, Further includes: A mixer that is fluidly connected to a channel upstream of the heater.

14. The exhaust treatment assembly as claimed in claim 1, characterized in that, Further includes: A chemical reducing agent injector, adapted to inject the chemical reducing agent into the channel, is located upstream of the heater.

15. The exhaust treatment assembly as claimed in claim 1, characterized in that, Further includes: The selective catalytic reduction (SCR) unit is located downstream of this mixing pipeline.

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