CN110714833A

CN110714833A - Turbocharger turbine diffuser with diesel exhaust fluid dosing structure

Info

Publication number: CN110714833A
Application number: CN201910618795.5A
Authority: CN
Inventors: D·G·格拉鲍斯卡; J·P·沃森; B·P·赫维茨
Original assignee: BorgWarner Inc
Current assignee: BorgWarner Inc
Priority date: 2018-07-13
Filing date: 2019-07-10
Publication date: 2020-01-21
Anticipated expiration: 2039-07-10
Also published as: CN110714833B; WO2020014564A1; CN210599175U

Abstract

A turbine diffuser configured for use in a turbocharger is disclosed. The turbine diffuser may include diffuser walls defining the diffuser, and Diesel Exhaust Fluid (DEF) dosing structure disposed in the diffuser and configured to dose DEF into exhaust gas flowing through the diffuser. The DEF dosing structure may be supported in the diffuser by at least two structures attached to the diffuser wall.

Description

Turbocharger turbine diffuser with diesel exhaust fluid dosing structure

Technical Field

The present disclosure relates generally to turbochargers and more particularly to turbocharger turbine diffusers having Diesel Exhaust Fluid (DEF) dosing structures for delivering DEF into the exhaust stream.

Background

Vehicle engine systems may include an internal combustion engine that combusts a mixture of fuel and air to power the engine. The combusted fuel and air are referred to as exhaust gases, which are exhausted through the exhaust system of the vehicleThe gas is released into the atmosphere. The exhaust gas may contain pollutants (e.g., Nitrogen Oxides (NO)_x) Carbon monoxide (CO), particulate matter, hydrocarbons, etc.), which may be reduced before the exhaust gas is released into the atmosphere. Various emission control strategies have been employed to reduce the level of pollutants released into the atmosphere through the exhaust pipe. For example, many diesel engine systems include an aftertreatment system in the exhaust to remove or reduce the level of pollutants in the exhaust stream. One such aftertreatment system is a Selective Catalytic Reduction (SCR) aftertreatment system, in which a catalyst is used to convert NO in the presence of a reductant (e.g., ammonia)_xIs reduced to nitrogen. In many SCR aftertreatment systems, the reductant is supplied to the exhaust gas stream as an aqueous urea solution (also referred to as Diesel Exhaust Fluid (DEF)), which is converted to ammonia by thermal decomposition. Thorough mixing and evaporation of DEF in the exhaust gas may improve the effectiveness of the SCR aftertreatment system.

Accordingly, there is a need for improved strategies for mixing and uniformly distributing DEF in exhaust gas in a vehicle engine system having an SCR aftertreatment system.

Disclosure of Invention

According to one aspect of the present disclosure, a turbine diffuser configured for use in a turbocharger is disclosed. The turbine diffuser may include diffuser walls defining the diffuser, and Diesel Exhaust Fluid (DEF) dosing structure disposed in the diffuser and configured to dose DEF into exhaust gas flowing through the diffuser. The DEF dosing structure may be supported in the diffuser by at least two structures attached to the diffuser wall.

In accordance with another aspect of the present disclosure, a turbocharger for an engine system having an exhaust pipe with a Selective Catalytic Reduction (SCR) aftertreatment system is disclosed. The turbocharger may include a compressor section and a turbine section rotatably coupled to the compressor section via a shaft. The turbine section may include a turbine wheel having a nose and a plurality of blades, and a turbine diffuser located downstream of the turbine wheel and defined by diffuser walls. The turbocharger may further include a Diesel Exhaust Fluid (DEF) dosing structure disposed in the turbine diffuser downstream of the turbine wheel and configured to dose DEF into exhaust gas flowing through the diffuser. The DEF dosing structure may be supported in the diffuser by at least two structures attached to the diffuser wall.

In accordance with another aspect of the present disclosure, a method for dosing Diesel Exhaust Fluid (DEF) into exhaust of a vehicle engine system is disclosed. Vehicle engine systems may have a turbocharger and a Selective Catalytic Reduction (SCR) aftertreatment system. The turbocharger may include a turbine wheel and a turbine diffuser downstream of the turbine wheel. The turbine diffuser may be defined by diffuser walls. The method may include delivering Diesel Exhaust Fluid (DEF) through a strut of a DEF dosing structure located in a turbine diffuser. The struts may be attached to a diffuser wall of the turbine diffuser. The method may further include dosing DEF into the exhaust gas flowing through the turbine diffuser through one or more dosing apertures of the DEF dosing structure, thereby allowing DEF to disperse into the exhaust gas, and supplying a mixture of DEF and exhaust gas to the SCR aftertreatment system. These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the appended drawings.

Drawings

FIG. 1 is a schematic diagram of a vehicle engine system having a turbocharger with a Diesel Exhaust Fluid (DEF) dosing system and a Selective Catalytic Reduction (SCR) aftertreatment system.

Fig. 2 is a sectional view through the turbine section of the turbocharger of fig. 1.

Fig. 3 is a cross-sectional view through the turbine section of the turbocharger of fig. 2 above the centerline of the turbocharger, showing DEF dosing structures and a dosing cup in the turbine diffuser of the turbocharger constructed according to the present disclosure.

FIG. 4 is a perspective view of the turbine wheel and dosing cup of FIG. 3, shown separately, constructed in accordance with the invention.

Fig. 5 is a perspective view of the turbine diffuser and DEF dosing structure of fig. 3, shown separately, constructed in accordance with the invention.

Fig. 6 is a cross-sectional view through section 6-6 of fig. 5, showing dosing struts and centerbodies of a DEF-only dosing structure constructed in accordance with the present disclosure.

FIG. 7 is a cross-sectional view similar to FIG. 6, but with a delivery tube extending through the dosing post and central body constructed in accordance with the present disclosure.

FIG. 8 is a cross-sectional view through section 8-8 of FIG. 6 illustrating the airfoil shape of a dosing peg constructed in accordance with the present disclosure.

Fig. 9 is a perspective view of a turbine diffuser similar to fig. 5, but with dosing struts and centerbodies having DEF dosing structures of different configurations constructed in accordance with the present disclosure.

Fig. 10 is a cross-sectional view through section 10-10 of fig. 9 constructed in accordance with the present disclosure.

FIG. 11 is a cross-sectional view through section 11-11 of FIG. 10 illustrating a dosing aperture at the trailing edge of a dosing post constructed in accordance with the present disclosure.

FIG. 12 is a cross-sectional view similar to FIG. 11, but with a dosing aperture on the suction side of the dosing post constructed according to the present disclosure.

Fig. 13 is a cross-sectional view through a turbine section of a turbocharger similar to fig. 3, but with a DEF dosing structure constructed according to the present disclosure having a different configuration and lacking a dosing cup.

FIG. 14 is a cross-sectional view through section 14-14 of FIG. 13 illustrating the airfoil shape of the dosing peg of FIG. 13 constructed in accordance with the present disclosure.

Fig. 15 is a cross-sectional view of a turbine section with an alternative DEF dosing structure in a turbine diffuser constructed according to the present disclosure.

FIG. 16 is a perspective view of the turbine section of FIG. 15 constructed in accordance with the present disclosure.

Fig. 17 is a cross-sectional view similar to fig. 15, but with the struts of the angled DEF dosing structure constructed according to the present disclosure.

Fig. 18 is a cross-sectional view through a DEF dosing structure similar to that of fig. 15, but having a DEF dosing structure with a venturi constructed in accordance with the present disclosure.

Fig. 19 is a flow chart illustrating a series of steps of a method according to the present disclosure, which may involve dosing DEF into exhaust gas flowing through a diffuser of a turbocharger using a DEF dosing structure.

Detailed Description

FIG. 1 is a schematic illustration of an exemplary engine system 10. The engine system 10 may be installed in a vehicle or may be installed in a stationary application (e.g., a generator set). The engine system 10 includes a diesel engine 12, the diesel engine 12 having an intake manifold 14 to supply intake air 15 to combustion chambers of the engine 12 for combustion. In many diesel engines 12, diesel fuel is injected directly into the combustion chambers of the engine. The engine system 10 further includes an exhaust manifold 16 that directs exhaust gas produced in the engine 12 to an exemplary turbocharger 18. The turbocharger 18 uses the exhaust flow to increase the boost pressure of the intake air 15 supplied to the engine 12 under certain operating conditions, thereby increasing the engine power density by allowing more fuel to be combusted. Optionally, the engine system 10 may also include an Exhaust Gas Recirculation (EGR) system 20 for recirculating exhaust gas back to the engine 12 to reduce combustion temperatures in the engine and reduce NO_xIs performed.

The turbocharger 18 includes a compressor section 22 having a compressor wheel 24 and a turbine section 26 having a turbine wheel 28. A shaft 30 rotatably couples compressor wheel 24 and turbine wheel 28. The exhaust flow through the turbine section 26 rotates the turbine wheel 28, thereby driving the compressor wheel 24 to rotate via the shaft 30. The rotating compressor wheel 24 pressurizes intake air 15, which is supplied to the engine 12 through the intake manifold 14. The pressurized inlet air 15 has a higher density for a given volume and therefore has more oxygen than air at atmospheric pressure. Thus, more fuel may be added to the pressurized intake air 15 at a given air/fuel ratio. Thus, the engine 12 may produce more power and torque by combusting more fuel using the pressurized intake air 15.

After passing through turbine section 26, exhaust gas 35 flows through exhaust pipe 32. The exhaust pipe 32 directs the exhaust 35 to one or more aftertreatment devices 34, and the aftertreatment devices 34 may remove pollutants from the exhaust 35 or chemically convert pollutants from the exhaust 35 prior to releasing the exhaust 35 into the atmosphere. The one or more aftertreatment devices 34 may include a Selective Catalytic Reduction (SCR) aftertreatment system 36, the SCR aftertreatment system 36 having an SCR catalyst 38, the SCR catalyst 38 catalyzing NO in the exhaust gas flow in the presence of a reductant (ammonia) or a reductant source (e.g., Diesel Exhaust Fluid (DEF))_xReducing to form nitrogen. As understood by those of ordinary skill in the art, DEF is an aqueous urea solution.

The turbocharger 18 may further include a DEF dosing system 40, the DEF dosing system 40 supplying DEF to the turbine section 26 downstream of the turbine wheel 28. The DEF dosing system 40 may include a pump 42 that pumps DEF from a DEF tank 44 into one or more delivery pipes 46. The one or more delivery pipes 46 are operable to deliver DEF to the exhaust pipe. The high temperature and high velocity of the exhaust gas downstream of the turbine wheel 28 may promote thermal decomposition of DEF and sufficient mixing with the exhaust gas 35 to increase the efficiency of the catalytic reaction at the SCR aftertreatment system 36.

As shown in FIG. 1, the SCR catalyst 38 is positioned within the second aftertreatment device 34. Those of ordinary skill in the art will appreciate that in the various embodiments described herein, the SCR catalyst 38 may be the first aftertreatment device 34 and the SCR catalyst 38 may be closely positioned to the DEF delivery pipe or pipes 46. In various embodiments disclosed herein, the engine system includes DEF dosing structures disposed downstream of the turbine wheel 28 to promote rapid thermal decomposition and mixing of DEF in the exhaust gas 35 (see more details below).

The structure of the turbine section 26 is shown in more detail in FIG. 2. It should be noted that for clarity, components of the DEF dosing system 40 have been removed from the turbine section 26 of fig. 2. The turbine section 26 includes a turbine housing 50 surrounding the turbine wheel 28 and defining a turbine inlet 52 (or volute) through which exhaust gases 35 produced by the engine 12 are directed to the turbine wheel 28. After exiting the turbine wheel 28, the exhaust gas 35 flows into a turbine diffuser 58 as an annular flow field 54 about a centerline 56 of the turbine wheel 28. The annular flow field 54 flows downstream of a plurality of blades 60 of the turbine wheel 28 and may surround a nose 62 of the turbine wheel 28. The turbine diffuser 58 may be defined by a diverging diffuser wall 64. As explained in more detail below, the DEF dosing structure 48 may be placed in the turbine diffuser 58 to promote thermal decomposition of DEF and rapid mixing of DEF with the exhaust gas 35 as the exhaust gas 35 and DEF flow downstream of the turbine wheel 28.

Turning now to fig. 3, an exemplary DEF dosing structure 48a according to one embodiment is shown positioned in a turbine diffuser 58 of the turbine section 26. Only the portion of the turbine section 26 above the centerline 56 is shown in FIG. 3. The DEF dosing structure 48a includes a center body 66 and a plurality of struts 68, the plurality of struts 68 being integrally formed with or attached to the center body 66 and extending radially from the center body 66 to the diffuser wall 64. Fig. 5 is a perspective view of the DEF dosing structure 48a disposed in the diffuser 58. The struts 68 may be attached to the diffuser wall 64, such as by welding, or may be integrally formed with the diffuser wall 64, such as by casting. At least one of the posts 68 is a dosing post 70, and DEF72 (or other reductant or reductant precursor) is introduced into the center body 66 through the dosing post 70. Specifically, the diffuser wall 64 includes an aperture 75, the aperture 75 aligned with or otherwise in fluid communication with the dosing channel 74, such as feeding DEF72 from the delivery tube 46 into the dosing channel 74 through the aperture 75 via a tube or pressure fitting. As shown in FIG. 3, a dosing passage 74 extends radially through dosing post 70 and is in fluid communication with one or more apertures 76 in center body 66. One or more apertures 76 in the center body 66 are in fluid communication with the exhaust gas on the upstream end of the center body 66. The DEF72 flows through the dosing passage 74 and the one or more apertures 76 to be released in an upstream direction toward the nose 62 of the turbine wheel 28.

Referring to fig. 3 and 4, in at least one embodiment, the nose 62 of the turbine wheel 28 includes a dosing cup 78 attached thereto (e.g., by welding, milling, or mechanical fastening) or integrally formed therewith, the dosing cup 78 receiving DEF72 discharged from the dosing aperture 76. The dosing cup 78 rotates with the turbine wheel 28. Thus, DEF72 that is then received into dosing cup 78 is dispersed from dosing cup 78 into the exhaust stream. In other words, the rotating dosing cup 78 may fling the DEF72 radially outward into the exhaust gas 35 stream. Further, the turbine wheel 28 and dosing cup 78 may be at an elevated temperature during operation. The high temperature of the dosing cup 78 may facilitate thermal decomposition of the DEF72 received therein. As shown in fig. 3, the dosing cup 78 may have diverging walls to facilitate dispersion of DEF into the exhaust gas 35. Specifically, as the DEF is thrown radially outward by the rotating dosing cup 78, the diverging wall pushes the DEF72 toward the opening of the dosing cup 78.

Referring to fig. 5, the DEF dosing structure 48a may also include one or more structural pillars 80, the one or more structural pillars 80 increasing the strength of the DEF dosing structure 48 a. As used herein, a "structural strut" is a strut of the DEF dosing structure that is used only for structural support and does not participate in the dosing of DEF72, and a "dosing strut" refers to dosing DEF72 into the exhaust stream. The structural pillars 80 may have a solid construction without a dosing channel for delivering DEF 72. For example, one of the legs 68 of the dosing structure 48a may be a dosing leg 70 and the remainder of the leg 68 may be a structural leg 80. In the embodiment of fig. 5, the dosing structure 48a includes three legs 68, wherein one of the legs 68 is a dosing leg 70 and the remaining two legs 68 are structural legs 80. In other embodiments, the dosing structure 48a may have more or less than three posts 68, and any non-zero number of posts 68 may be dosing posts 70.

Turning to fig. 6, DEF72 is directed along the diffuser wall 64 into the dosing passage 74 through the holes 75, and DEF72 flows radially inward toward the center body 66. At the center body 66, the dosing passage 74 is flipped in an upstream direction (e.g., at about 90 °) toward the nose 62 of the turbine wheel 28 and the dosing cup 78 to allow DEF72 to be discharged toward the dosing cup 78 via the dosing aperture 76 on the center body 66 (see also fig. 5).

In the configuration of fig. 6, DEF72 flows within the walls defining the dosing channel 74. Fig. 7 shows an alternative embodiment of the dosing structure 48b, in which the delivery tube 82 extends through the dosing channel 74, and DEF72 flows through the delivery tube 82 to the dosing cup 78. The struts 68 and the centerbody 66 of the dosing structure 48b shown in fig. 7 protect the delivery tube 82 from vibrations caused by pressure waves in the turbine diffuser 58. This protection prevents rupture of the delivery tube 82. In either the dosing structure 48a (without the duct 82) or the dosing structure 48b (with the duct 82), the DEF72 may follow an "L" shaped path that begins in a radially inward direction and turns upstream (at about 90 °) at the center body 66 toward the turbine nose 62.

Fig. 8 is a cross-sectional view of an alternative exemplary leg 68a (either of dosing leg 70 and/or structural leg 80) in accordance with at least one embodiment. As shown, the strut includes an airfoil shape having a leading edge 84, a trailing edge 86, a suction side 88, and a pressure side 90. The leading edge 84 of each of the struts 68a may be oriented upstream (toward the turbine wheel 28) and the trailing edge 86 may be oriented downstream (toward the exhaust pipe 32). The airfoil shape of the strut 68a with the trailing edge 86 oriented downstream may reduce the drag effect on the exhaust. The airfoil shape may also support the structural robustness of the strut 68a positioned in the annular flow field 54 of the exhaust gas while also reducing vibrations at the turbine wheel 28 caused by pressure waves reflected from the strut 68 a. In other embodiments, the strut 68 may have another aerodynamic shape (e.g., a symmetrical shape in which the suction side 88 and the pressure side 90 are mirror images). In at least one embodiment, the airfoil-shaped struts 68a are oriented in the diffuser 58 at an angle of attack relative to the flow direction of the exhaust gas 35. Arranging the airfoil-shaped struts 68a at an angle of attack may change the flow direction of the exhaust gas 35 passing between the struts 68a, and such changed flow direction of the exhaust gas 35 may facilitate mixing of the DEF72 into the exhaust gas 35. In at least one embodiment, the airfoil shape of the strut 68a may include a curved surface such that the flow direction of the exhaust gas 35 proximate the leading edge 84 of the strut 68a is different than the flow direction of the exhaust gas 35 away from the trailing edge 86 of the strut 68 a. In other words, the camber of the airfoil may change the flow direction of the exhaust 35 to promote mixing.

Referring back to fig. 6-7, the center body 66 may have a trailing edge 92 oriented in a downstream direction to facilitate "wake" of DEF flowing into the turbine wheel nose 62. The trailing edge 92 of the center body 66 may facilitate the flow of exhaust gas 35 into a region downstream of the center body 66.

An alternative configuration of the DEF dosing structure 48c is shown in fig. 9-10. The DEF dosing structure 48c may have many of the features described above, including a center body 66 and airfoil-shaped struts 68 attached to the diffuser wall 64 and extending radially between the center body 66 and the diffuser wall 64. However, in the configurations of fig. 9-10, DEF72 may be delivered into the exhaust gas along the dosing post 70 through one or more dosing apertures 76. The alternative configuration of fig. 9-10 may lack a dosing cup 78 at the turbine wheel nose 62. The dosing struts 70 and the center body 66 may together define a hollow interior 94 through which DEF72 flows from the holes 75 in the diffuser wall 64 into the DEF dosing structure 48 c. The DEF72 may collect at the bottom of the hollow interior 94 at the center body 66 and escape through the dosing aperture 76 due to the locally high temperature DEF72 in the turbine diffuser 58 that may evaporate. The inner walls of the dosing post 70 may define a dosing passage 74 through which DEF72 flows to the bottom of the center body 66. Alternatively, the delivery tube may extend through the hollow interior 94 to release the DEF72 at the bottom of the center body 66.

Alternatively, the dosing struts 70 may have a plurality of dosing apertures 76 extending along the length of the dosing struts 70, and the dosing apertures 76 may become progressively larger in a radially outward direction from the central body 66 to the diffuser wall 64, with the smallest dosing aperture 76 being proximate the central body 66 and the largest dosing aperture 76 being proximate the diffuser wall 64 (see fig. 10). The increased size of the dosing apertures 76 toward the diffuser wall 64 may promote a more uniform flow of DEF into the exhaust gas by promoting equal mass flow through each of the dosing apertures 76. In other configurations, the dosing apertures 76 may have the same size or variable/random sizes. In the configuration of the DEF dosing structure 48c shown in fig. 9 and 10, any number of posts may be dosing posts 70. Specifically, one or both of the illustrated posts 68 may also be dosing posts 70, meaning that the posts will be hollow and will include holes 76 for dispersing DEF.

The dosing aperture 76 may be along the trailing edge 86 (see fig. 11) or the suction side 88 (see fig. 12) of the airfoil-shaped dosing post 70 such that the exhaust flow may facilitate the flow of DEF72 outward into the exhaust flow. However, in alternative arrangements, the dosing aperture 76 may be along the leading edge 84, the pressure side 90, or a combination of the trailing edge 86, the suction side 88, the leading edge 84, and/or the pressure side 90.

Yet another alternative configuration of DEF dosing structure 48d in the turbine diffuser 58 is shown in fig. 13 and 14. The DEF dosing structure 48d of fig. 13 is similar to the structure described above, and may include a plurality of struts 68 (including at least one dosing strut 70 and at least one structural strut 80) extending radially from the center body 66 and attached to the diffuser wall 64. Similar to the arrangement of fig. 9-10, the alternative configuration shown in fig. 13 may lack a dosing cup 78 at the turbine wheel nose 62. However, the center body 66 of the DEF dosing structure 48d of fig. 13 may have a solid construction (no flow path for the DEF 72), and the DEF72 may flow through the dosing passages 74 of the dosing struts 70 and along the dosing struts 70 through the dosing apertures 76 into the exhaust flow without passing through the center body 66. Further, the struts 68 of the DEF dosing structure 48d of fig. 13 may be angled relative to the flow direction of the exhaust gas 35. As shown in FIG. 13, the struts are arranged at an angle such that leading edges 84 of the

struts

68, 70, and/or 80 are closer to the turbine wheel 28 where the

struts

68, 70, and/or 80 join the center body 66 than where the

struts

68, 70, and/or 80 join the diffuser 58. In other embodiments, the struts may be arranged at an angle such that a leading edge 84 of the

struts

68, 70, and/or 80 is closer to the turbine wheel 28 where the

struts

68, 70, and/or 80 join the diffuser 58 than where the

struts

68, 70, and/or 80 join the center body 66. The angled struts 68 may reduce the impact of pressure waves reflected from the struts 68 on the turbine wheel 28, as well as the impact of exhaust gas pressure waves flowing from the turbine wheel 28 on the struts 68. Thus, vibrations at the turbine wheel 28 and the struts 68 may be reduced, thereby supporting the structural robustness of the DEF dosing structure 48 d.

Further, as described above, the struts 68 may have an airfoil shape (with the leading edge 84 oriented upstream toward the turbine wheel 28 and the trailing edge 86 oriented downstream) to reduce drag effects on the exhaust gas and prevent vibration at the struts 68 and the turbine wheel 28 (see FIG. 14). As shown in FIG. 14, the dosing aperture 76 may be along the suction side 88 of the dosing post 70. However, alternatively, the dosing aperture 76 may be along the trailing edge 86, the leading edge 84, the pressure side 90, or along a combination of the trailing edge 86, the leading edge 84, the suction side 88, and/or the pressure side 90. As discussed above, the stanchion 68 may include an angle of attack and/or a curved surface.

Another arrangement of the DEF dosing structure 48e is shown in fig. 15-16. In this arrangement, the DEF dosing structure 48e may include an annular ring 96, the annular ring 96 surrounding the turbine nose 62 and including one or more of the dosing apertures 76 through which the DEF72 is dosed into the exhaust gas. The annular ring 96 may have an elliptical cross-section (as shown in fig. 15) and may be symmetrically positioned about the centerline 56 downstream of the vanes 60 such that the body of the ring 96 is located approximately in the middle of the annular flow field 54 (see fig. 15). The annular ring 96 may be supported in this position by a plurality of short struts 98 that are attached to the annular ring 96 and the diffuser wall 64 and extend radially between the annular ring 96 and the diffuser wall 64 (see fig. 15-16). In some arrangements, the struts 98 may be swept back at an angle relative to the axis of rotation of the turbine wheel 28 (see fig. 17). The annular ring 96 may be less sensitive to vibration than the struts 68 discussed above, as it may be subjected to exhaust flow from the blades 60 as an uninterrupted flow rather than a pressure pulse. Likewise, vibrations at the turbine wheel 28 may be reduced because the pressure wave reflected from the annular ring 96 may be uninterrupted and continuous due to the ring 96 having an annular configuration. Further, the short struts 98 may be rigid and may be structurally robust in high vibration environments in the turbine diffuser 58.

The annular ring 96 may have a hollow interior 100 in fluid communication with the dosing aperture 76, and at least one of the posts 98 may have a dosing passage 102 in fluid communication with the hollow interior 100 for delivering the DEF72 into the hollow interior 100 (see fig. 15). The aperture 75 of the diffuser wall 64 may be aligned with the dosing channel 102 or otherwise in fluid communication with the dosing channel 102 such that the DEF72 may flow into the dosing channel 102 and the hollow interior 100 of the collar 96 and then into the exhaust gas through the dosing aperture 76. Exhaust flow from the turbine wheel 28 may be split at the annular ring 96 on an upstream side 104 of the ring 96, collect DEF72 exiting the dosing aperture 76, and recombine at a downstream side 106 of the ring 96, with relatively less disturbance of the exhaust flow due to the elliptical shape of the ring 96.

The annular ring 96 has a radially outward facing surface 108 and a radially inward facing surface 110. The dosing apertures 76 may be arranged along a radially inward facing surface 110, as shown in fig. 15-16. However, in other arrangements, the dosing aperture 76 may be along the radially outward facing surface 108, the upstream side 104, the downstream side 106, or a combination of the radially inward facing surface 110, the radially outward facing surface 108, the upstream side 104, and/or the downstream side 106.

Fig. 18 shows an alternative configuration of an annular ring 96a for use with the DEF dosing structure 48 f. In this configuration, the collar 96a may include an outer collar 112 and an inner collar 114, the outer collar 112 having a hollow interior 100 in fluid communication with the dosing passageway 102 and the dosing aperture 76, the inner collar 114 being radially inward relative to the outer collar 112 and inserted within the outer collar 112. Outer and

inner rings

112, 114 may have mirror image converging/diverging surfaces facing each other to define a venturi 116 in an annular space 118 between outer and

inner rings

112, 114. The venturi 116 may form a constricted region 120 in the annular space 118, the constricted region 120 helping to atomize the DEF72 exiting from the annular ring 96 a. To facilitate atomization, the dosing aperture 76 of the outer ring 112 may be located at a constricted region 120 of the venturi 116. In an alternative arrangement, the annular ring 96a may have a plurality of venturi tubes in the annular space 118 between the inner and

outer rings

114, 112. The inner race 114 may be coupled to the outer race 112 by various mechanisms, such as by struts between the outer race 112 and the inner race 114.

Industrial applicability

In general, the teachings of the present disclosure are applicable to many industries, including but not limited to the automotive industry. More specifically, the teachings of the present disclosure may be applied to any industry that relies on engine systems having a turbocharger and an SCR aftertreatment system.

Fig. 19 is a flowchart showing a series of steps that may involve dosing DEF into exhaust gas flowing through the turbine diffuser 58 of the turbocharger 18 using any of the DEF dosing structures 48a-f (collectively referred to using reference numeral 48) or any other DEF dosing structure discussed in this disclosure. At a first block 130, DEF may be delivered through a post (one of dosing posts 70 or posts 98) of the DEF dosing structure 48. The block 130 may involve delivering DEF from the DEF tank 44 through the delivery pipe 46 and the diffuser aperture 75 into the dosing channel 74 or 102 (or delivery pipe 82) of the strut. At the next block 132, DEF may be dosed into the exhaust flowing through the turbine diffuser 58 through one or more dosing apertures 76 of the DEF dosing structure 48. For example, the dosing aperture 76 may be located on an upstream side of the center body 66 to direct DEF upstream into the dosing cup 78 (see fig. 3-7), the dosing aperture 76 may be along the dosing post 70 (see fig. 9-10 and 13), or the dosing aperture 76 may be along the annular ring 96 (see fig. 15-18). At the next block 134, due to the design of the dosing structure 48 and the high temperature, high velocity environment of the turbine diffuser 58, DEF may be allowed to mix and disperse evenly into the exhaust gas. At the next block 136, the mixed DEF and exhaust gas may be supplied to the catalyst 38 of the SCR aftertreatment system 36.

The present disclosure provides a DEF dosing structure attached to a turbine diffuser of a turbocharger downstream of a turbine wheel. The location of the DEF dosing structure in the turbine diffuser provides a high temperature, high velocity environment that takes advantage of the turbine diffuser to promote uniform dispersion of DEF into the exhaust gas. Additionally, the DEF dosing structure is characterized by an increased ability of the DEF dosing structure to structurally withstand the highly vibrating environment of the turbine diffuser while also limiting the magnitude of the pressure waves reflected onto the turbine wheel. For example, the DEF dosing structure may have an airfoil-shaped strut through which DEF is dosed into the exhaust stream, or it may have an annular ring through which DEF is dosed into the exhaust stream. The annular ring configuration may experience the exhaust flow as a continuous pressure wave and may reflect the pressure as a pressure wave back onto the turbine wheel, thereby reducing the vibrations experienced at the annular ring and at the turbine wheel. Further, the DEF dosing structure may dose DEF into the exhaust stream through a plurality of dosing orifices to promote adequate mixing and uniform dispersion of DEF in the exhaust gas, as compared to prior art single point urea injectors.

In existing designs, there is a tradeoff between placing the SCR catalyst closer to or farther from the DEF injection site. Placing the SCR catalyst closer to the DEF injection site will also place the SCR catalyst closer to the exhaust manifold. Thus, the SCR catalyst is exposed to hotter exhaust temperatures, which may increase the efficiency of the SCR catalyst. In addition, placing the SCR catalyst closer to the DEF injection site may allow for smaller packaging of the exhaust system. However, placing the SCR catalyst closer to the DEF injection site can also result in incomplete thermal decomposition and incomplete mixing of DEF with the exhaust gas before the injected DEF reaches the SCR catalyst. Thus, the catalytic reaction may be less effective. If the SCR catalyst is placed farther away from the DEF injection site, the DEF fluid may complete the thermal decomposition process and better mix with the exhaust gas. However, the SCR catalyst will be exposed to cooler exhaust gases (due to the increased distance from the exhaust manifold) and the packaging of the exhaust system will become larger.

Because the DEF dosing structures disclosed herein improve mixing of DEF with exhaust gas, the SCR catalyst may be placed closer to the exhaust manifold (as increasingly desired by engine manufacturers), thereby exposing the catalyst to higher exhaust temperatures and making the package smaller without compromising thermal decomposition of DEF and mixing of DEF with exhaust gas. Thus, the overall efficiency of the catalytic conversion of the SCR catalyst may be significantly improved over existing designs. It is contemplated that the techniques disclosed herein may have wide industrial applicability in a wide range of fields, such as, but not limited to, automotive applications.

Claims

1. A turbine diffuser configured for use in a turbocharger, comprising:

a diffuser wall defining the diffuser; and

a Diesel Exhaust Fluid (DEF) dosing structure disposed in the diffuser and configured to dose DEF into exhaust gas flowing through the diffuser, the DEF dosing structure supported in the diffuser by at least two structures attached to the diffuser wall.

2. The turbomachine diffuser of claim 1, wherein the DEF dosing structure comprises a center body, and wherein the at least two structures are a plurality of struts extending radially from the center body to the diffuser wall.

3. The turbine diffuser of claim 2, wherein at least one of the plurality of struts is a dosing strut having one or more dosing apertures through which DEF is dosed into the exhaust gas.

4. The turbomachine diffuser of claim 3, wherein one of said plurality of struts is a dosing strut and a remainder of said plurality of struts are structural struts.

5. The turbine diffuser of claim 3, wherein the dosing struts and the center body define a hollow interior, and wherein the one or more dosing apertures are configured to allow DEF to escape from the hollow interior into the exhaust.

6. The turbomachine diffuser of claim 5, wherein said dosing struts include a plurality of dosing holes extending along a length of said dosing struts from said central body to said diffuser wall, and wherein said plurality of dosing holes are progressively larger from said central body to said diffuser wall.

7. The turbine diffuser of claim 3, wherein the plurality of struts are angled with respect to a flow direction of exhaust gas, wherein the dosing struts comprise a hollow interior, and wherein the one or more dosing apertures are configured to allow DEF to escape from the hollow interior into exhaust gas.

8. The turbomachine diffuser of claim 3, wherein said plurality of struts have an airfoil cross-sectional shape with a leading edge oriented upstream, a trailing edge oriented downstream, a suction side, and a pressure side.

9. The turbine diffuser of claim 8, wherein said one or more dosing holes are along said trailing edge of said dosing post.

10. The turbine diffuser of claim 8, wherein the one or more dosing holes are along the suction side of the dosing strut.

11. The turbine diffuser of claim 1, wherein the DEF dosing structure comprises an annular ring having a plurality of dosing apertures through which DEF is dosed into exhaust gas flowing through the diffuser.

12. A turbomachine diffuser according to claim 11, wherein said at least two structures are a plurality of struts extending radially between said annular ring and said diffuser wall, and wherein each of said plurality of struts is attached to said annular ring.

13. The turbine diffuser of claim 12, wherein:

the annular ring includes a hollow interior in fluid communication with the dosing aperture; and is

At least one of the plurality of posts includes a dosing channel in fluid communication with the hollow interior through which DEF is delivered to the hollow interior of the annular ring, the DEF being dosed from the hollow interior into exhaust gas through the plurality of dosing apertures of the annular ring.

14. A turbomachine diffuser as recited in claim 13, wherein said annular ring is elliptical in cross-section.

15. A turbocharger for an engine system having an exhaust pipe with a Selective Catalytic Reduction (SCR) aftertreatment system for treating exhaust gas, the turbocharger comprising:

a compressor section;

a turbine section rotatably coupled to the compressor section via a shaft, the turbine section including a turbine wheel having a nose and a plurality of blades, and a turbine diffuser downstream of the turbine wheel, the turbine diffuser defined by a diffuser wall; and

a Diesel Exhaust Fluid (DEF) dosing structure disposed in the turbine diffuser downstream of the turbine wheel and configured to dose DEF into exhaust gas flowing through the diffuser, the DEF dosing structure supported in the diffuser by at least two structures attached to the diffuser wall.