CN110714833B - Turbocharger turbine diffuser with diesel exhaust fluid dosing structure - Google Patents

Abstract

A turbine diffuser configured for use in a turbocharger is disclosed. The turbine diffuser may include a diffuser wall defining a diffuser, and a Diesel Exhaust Fluid (DEF) dosing structure disposed in the diffuser and configured to dose DEF into exhaust 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 a turbocharger turbine diffuser having a Diesel Exhaust Fluid (DEF) dosing structure for delivering DEF into an exhaust stream.

Background

A vehicle engine system 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 released to the atmosphere by the exhaust system of the vehicle. The exhaust gas may contain pollutants (e.g., nitrogen oxides (NO _x ) Carbon monoxide (CO), particulate matter, hydrocarbons, etc.), these pollutants 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 an exhaust pipe. For example, many diesel engine systems include an aftertreatment system in the exhaust pipe to remove or reduce the level of pollutants in the exhaust gas stream. One such aftertreatment system is a Selective Catalytic Reduction (SCR) aftertreatment system in which a catalyst is used to treat NO in the presence of a reductant (e.g., ammonia) _x Reducing to nitrogen. In many SCR aftertreatment systems, the reductant is supplied as an aqueous urea solution (also known as Diesel Exhaust Fluid (DEF)) to the exhaust stream, which is converted to ammonia by thermal decomposition. Thorough mixing and evaporation of DEF in the exhaust 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

In accordance with one aspect of the present disclosure, a turbine diffuser configured for use in a turbocharger is disclosed. The turbine diffuser may include a diffuser wall defining a diffuser, and a Diesel Exhaust Fluid (DEF) dosing structure disposed in the diffuser and configured to dose DEF into exhaust 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 downstream of the turbine wheel and defined by a diffuser wall. 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 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. A vehicle engine system 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 a diffuser wall. 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 flowing through the turbine diffuser through one or more dosing apertures of the DEF dosing structure, thereby allowing DEF to disperse into the exhaust and supplying a mixture of DEF and exhaust 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 accompanying 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 cross-sectional view through a turbine section of the turbocharger of fig. 1.

Fig. 3 is a cross-sectional view through a turbine section of the turbocharger of fig. 2 above a centerline of the turbocharger, showing a DEF dosing structure and dosing cup in a 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 present 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 present invention.

Fig. 6 is a cross-sectional view through section 6-6 of fig. 5, showing a dosing post and a centerbody of a separate DEF 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 the central body constructed in accordance with the present disclosure.

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

Fig. 9 is a perspective view of a turbine diffuser similar to fig. 5, but with a dosing post and centerbody having a differently configured DEF dosing structure 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, showing 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 in accordance with 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 in accordance with 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, showing the airfoil shape of the dosing post 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 in accordance with 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 a pillar of angled DEF dosing structure constructed in accordance with the present disclosure.

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

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

Detailed Description

FIG. 1 is a schematic diagram 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 genset). 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. Engine system 10 further includes directing exhaust gas generated in engine 12 to the exampleAn exhaust manifold 16 of a turbocharger 18. The turbocharger 18 uses the exhaust gas 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 _x Is formed by the steps of (a).

The turbocharger 18 includes a compressor section 22 having a compressor wheel 24 and a turbine section 26 having a turbine wheel 28. Shaft 30 rotatably couples compressor wheel 24 and turbine wheel 28. The flow of exhaust gas through the turbine section 26 rotates the turbine wheel 28, thereby driving the compressor wheel 24 in rotation via the shaft 30. The rotating compressor wheel 24 pressurizes intake air 15 supplied to the engine 12 through the intake manifold 14. The pressurized intake air 15 has a higher density for a given volume and therefore 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 with the pressurized intake air 15.

After passing through the turbine section 26, the exhaust 35 flows through the exhaust pipe 32. Exhaust pipe 32 directs exhaust 35 to one or more aftertreatment devices 34, and aftertreatment devices 34 may remove or chemically convert pollutants in exhaust 35 prior to releasing exhaust 35 into the atmosphere. One or more aftertreatment devices 34 may include a Selective Catalytic Reduction (SCR) aftertreatment system 36, with SCR aftertreatment system 36 having an SCR catalyst 38, SCR catalyst 38 catalyzing NO in an exhaust gas stream in the presence of a reductant (ammonia) or a source of reductant (e.g., diesel Exhaust Fluid (DEF)) _x Reducing to form nitrogen. As understood by one 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 conduits 46. The one or more delivery conduits 46 are operable to deliver DEF to an exhaust pipe. The high temperature and high velocity of the exhaust gas downstream of the turbine wheel 28 may promote thermal decomposition of the DEF and thorough mixing with the exhaust gas 35 to improve the efficiency of the catalytic reaction at the SCR aftertreatment system 36.

As shown in FIG. 1, the SCR catalyst 38 is positioned in 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 one or more DEF delivery conduits 46. In various embodiments disclosed herein, the engine system includes a DEF dosing structure disposed downstream of the turbine wheel 28 to promote rapid thermal decomposition and mixing of DEF in the exhaust 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 turbine inlet 52 exhaust gas 35 produced by the engine 12 is directed to the turbine wheel 28. After exiting the turbine wheel 28, the exhaust 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 the 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 the DEF and rapid mixing of the DEF with the exhaust 35 as the exhaust 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 central body 66 and a plurality of struts 68, the plurality of struts 68 being integrally formed with the central body 66 or attached to the central body 66 and extending radially from the central 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 legs 68 is a dosing leg 70, and the def72 (or other reductant or reductant precursor) is introduced into the central body 66 through the dosing leg 70. Specifically, the diffuser wall 64 includes an aperture 75, which aperture 75 is aligned with the dosing channel 74 or otherwise in fluid communication with the dosing channel 74, such as feeding the DEF72 from the delivery conduit 46 into the dosing channel 74 through the aperture 75 via a tube or pressure fitting. As shown in fig. 3, a dosing channel 74 extends radially through the dosing post 70 and is in fluid communication with one or more holes 76 in the hub 66. One or more apertures 76 in the center body 66 are in fluid communication with exhaust gas on the upstream end of the center body 66. The DEF72 flows through the dosing channel 74 and one or more holes 76 to release 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, the DEF72 received into the dosing cup 78 is then dispersed from the dosing cup 78 into the exhaust stream. In other words, the rotating dosing cup 78 may throw the DEF72 radially outward into the exhaust 35 flow. Furthermore, the turbine wheel 28 and the dosing cup 78 may be at a high temperature during operation. The high temperature of the dosing cup 78 may promote thermal decomposition of the DEF72 received therein. As shown in fig. 3, the dosing cup 78 may have diverging walls to aid in the dispersion of DEF into the exhaust 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 further include one or more structural struts 80, the one or more structural struts 80 increasing the strength of the DEF dosing structure 48 a. As used herein, a "structural pillar" is a pillar of a DEF dosing structure that is used only for structural support and does not participate in the dosing of DEF72, and a "dosing pillar" involves dosing DEF72 into an exhaust stream. The structural strut 80 may have a solid construction without a dosing channel for delivering the DEF72. 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 comprises three struts 68, wherein one of the struts 68 is a dosing strut 70 and the remaining two struts 68 are structural struts 80. In other embodiments, the dosing structure 48a may have more or less than three struts 68, and any non-zero number of struts 68 may be dosing struts 70.

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

In the configuration of fig. 6, the DEF72 flows within the walls defining the dosing channel 74. Fig. 7 shows an alternative embodiment of the dosing structure 48b, wherein the delivery tube 82 extends through the dosing channel 74 and the DEF72 flows through the delivery tube 82 to the dosing cup 78. The struts 68 and 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 may prevent breakage of the delivery tube 82. In either the dosing structure 48a (without the delivery tube 82) or the dosing structure 48b (with the delivery tube 82), the DEF72 may follow an "L" shaped path that begins in a radially inward direction and turns upstream (at about 90 °) toward the turbine nose 62 at the centerbody 66.

Fig. 8 is a cross-sectional view of an alternative exemplary post 68a (any of the dosing post 70 and/or the structural post 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 struts 68a with the downstream oriented trailing edge 86 may reduce drag effects on the exhaust. The airfoil shape may also support the structural rigidity of struts 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 struts 68 a. In other embodiments, the struts 68 may have another aerodynamic shape (e.g., a symmetrical shape, where the suction side 88 and the pressure side 90 are mirror images). In at least one embodiment, airfoil-shaped struts 68a are oriented in diffuser 58 at an angle of attack relative to the flow direction of exhaust 35. Arranging airfoil-shaped struts 68a at an angle of attack may change the flow direction of exhaust 35 passing between struts 68a, and such a changed flow direction of exhaust 35 may promote mixing of DEF72 into exhaust 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 35 proximate the leading edge 84 of the strut 68a is different than the flow direction of the exhaust 35 exiting the trailing edge 86 of the strut 68 a. In other words, the curvature 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 the flow of DEF into the "wake" of the turbine wheel nose 62. The trailing edge 92 of the centerbody 66 may facilitate the flow of exhaust 35 into a region downstream of the centerbody 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 configuration of fig. 9-10, the DEF72 may be delivered into the exhaust gas along the dosing pegs 70 through one or more dosing holes 76. The alternative configuration of fig. 9-10 may lack the dosing cup 78 at the turbine wheel nose 62. The dosing pegs 70 and the central body 66 may together define a hollow interior 94 through which the DEF72 flows from the holes 75 in the diffuser wall 64 into the DEF dosing structure 48 c. DEF72 may collect at the bottom of the hollow interior 94 at the center body 66 and may escape through the dosing aperture 76 due to the local high temperature DEF72 in the turbine diffuser 58 by evaporation. The inner wall of the dosing pegs 70 may define a dosing channel 74 through which the def72 flows to the bottom of the hub 66. Alternatively, the delivery tube may extend through the hollow interior 94 to release the DEF72 at the bottom of the central body 66.

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

The dosing aperture 76 may be along a trailing edge 86 (see fig. 11) or suction side 88 (see fig. 12) of the airfoil-shaped dosing strut 70 such that the exhaust stream may facilitate outward flow of the DEF72 into the exhaust stream. 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 the 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 the dosing cup 78 at the turbine wheel nose 62. However, the centerbody 66 of the DEF dosing structure 48d of fig. 13 may have a solid configuration (no flow path for the DEF 72), and the DEF72 may flow through the dosing channel 74 of the dosing post 70 and into the exhaust stream through the dosing aperture 76 along the dosing post 70 without passing through the centerbody 66. Further, the struts 68 of the DEF dosing structure 48d of fig. 13 may be angled with respect to the flow direction of the exhaust 35. As shown in FIG. 13, the struts are arranged at an angle such that the 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 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 the 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 pressure waves flowing from the turbine wheel 28 on the struts 68. Accordingly, 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 strut 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 to prevent vibration at the strut 68 and 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. Alternatively, however, the dosing aperture 76 may be along the trailing edge 86, the leading edge 84, the pressure side 90, or a combination of the trailing edge 86, the leading edge 84, the suction side 88, and/or the pressure side 90. As described above, the struts 68 may include angles of attack and/or curved surfaces.

Another arrangement of DEF dosing structures 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, the plurality of short struts 98 being attached to the annular ring 96 and the diffuser wall 64 and extending radially between the annular ring 96 and the diffuser wall 64 (see fig. 15-16). In some arrangements, the strut 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 because it may withstand the exhaust flow from the vanes 60 as an uninterrupted flow rather than a pressure pulse. Likewise, vibration at turbine wheel 28 may be reduced because, as ring 96 has an annular structure, pressure waves reflected from annular ring 96 may be uninterrupted and continuous. Further, the short struts 98 may be rigid and may be structurally strong in the high vibration environment 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 struts 98 may have a dosing channel 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 through the dosing aperture 76. The exhaust flow from the turbine wheel 28 may be split at the annular ring 96 on the upstream side 104 of the ring 96, collect the DEF72 exiting from the dosing aperture 76, and recombine at the downstream side 106 of the ring 96, with relatively weak turbulence of the exhaust flow due to the elliptical shape of the ring 96.

Annular ring 96 has a radially outward facing surface 108 and a radially inward facing surface 110. The dosing aperture 76 may be disposed along the radially inward surface 110 as shown in fig. 15-16. However, in other arrangements, the dosing aperture 76 may be along a radially outward facing surface 108, an upstream side 104, a downstream side 106, or a combination of a radially inward facing surface 110, a radially outward facing surface 108, an upstream side 104, and/or a 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 ring 96a may include an outer ring 112 and an inner ring 114, the outer ring 112 having a hollow interior 100 in fluid communication with the dosing channel 102 and the dosing aperture 76, the inner ring 114 being radially inward relative to the outer ring 112 and inserted into the outer ring 112. The outer race 112 and the inner race 114 may have mirror image converging/diverging surfaces facing each other to define a venturi 116 in an annular space 118 between the outer race 112 and the inner race 114. The venturi 116 may form a constriction region 120 in the annular space 118, the constriction region 120 facilitating atomization of the DEF72 exiting from the annular ring 96 a. To facilitate atomization, the dosing aperture 76 of the outer race 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 ring 114 and the outer ring 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 may be applied to a number of 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 an engine system having a turbocharger and an SCR aftertreatment system.

Fig. 19 is a flow chart illustrating a series of steps that may involve dosing DEF into exhaust flowing through the turbine diffuser 58 of the turbocharger 18 using any one of the DEF dosing structures 48a-f discussed in this disclosure (collectively referred to using reference numeral 48) or any other DEF dosing structure. At a first block 130, the DEF may be delivered through a pillar (one of the dosing pillar 70 or pillar 98) of the DEF dosing structure 48. Block 130 may involve delivering DEF from the DEF tank 44 through the delivery conduit 46 and the diffuser aperture 75 into the dosing channel 74 or 102 (or the delivery tube 82) of the pillar. At a next block 132, the 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 the upstream side of the central 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, the DEF may be allowed to mix with and uniformly disperse into the exhaust due to the design of the dosing structure 48 and the high temperature, high speed environment of the turbine diffuser 58. At a next block 136, the mixed DEF and exhaust may be supplied to the catalyst 38 of the SCR aftertreatment system 36.

The present disclosure provides a DEF dosing structure that is attached to a turbine diffuser of a turbocharger downstream of a turbine wheel. The positioning of the DEF dosing structure in the turbine diffuser takes advantage of the high temperature, high velocity environment of the turbine diffuser to promote uniform dispersion of the DEF into the exhaust gas. Furthermore, the DEF dosing structure is characterized by an improved ability of the DEF dosing structure to structurally withstand the high vibration environment of the turbine diffuser while also limiting the magnitude of 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 exhaust flow as a continuous pressure wave and may reflect pressure back onto the turbine wheel as a pressure wave, thereby reducing vibrations experienced at the annular ring and at the turbine wheel. Furthermore, in contrast to single-point urea injectors of the prior art, the DEF dosing structure may dose DEF into the exhaust stream through a plurality of dosing holes to promote thorough mixing and even dispersion of the DEF in the exhaust.

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, positioning the SCR catalyst closer to the DEF injection site may allow for smaller packaging of the exhaust system. However, positioning the SCR catalyst closer to the DEF injection site can also result in incomplete thermal decomposition and incomplete mixing of the DEF with the exhaust gas before the injected DEF reaches the SCR catalyst. Thus, the catalytic reaction may be less efficient. If the SCR catalyst is placed farther from the DEF injection site, the DEF fluid may complete the thermal decomposition process and better mix with the exhaust. 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.

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

Claims (10)

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

a diffuser wall defining the diffuser; and

a diesel exhaust fluid dosing structure disposed in the diffuser and configured to dose diesel exhaust fluid into exhaust gas flowing through the diffuser, the diesel exhaust fluid dosing structure being supported in the diffuser by at least two structures attached to a wall of the diffuser, at least one of the at least two structures being a dosing strut defining a dosing channel extending radially through the dosing strut and in fluid communication with one or more dosing apertures in a central body of the dosing structure, the central body defining a hollow interior through which diesel exhaust fluid is configured to flow into the hollow interior prior to release from the dosing apertures in an upstream direction toward a turbine wheel of a turbocharger;

wherein the turbine diffuser is located downstream of a turbine wheel of the turbocharger.

2. The turbine diffuser of claim 1, 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 one of the plurality of struts is a dosing strut and the remainder of the plurality of struts is a structural strut.

4. The turbine diffuser of claim 1, wherein the dosing struts and the centerbody define the hollow interior, and wherein the one or more dosing apertures are configured to allow diesel exhaust treatment fluid to escape from the hollow interior into the exhaust.

5. The turbine diffuser of claim 1, wherein the dosing pegs comprise a plurality of dosing holes extending along a length of the dosing pegs from the hub to the diffuser wall, and wherein the plurality of dosing holes become progressively larger from the hub to the diffuser wall.

6. The turbine diffuser of claim 1, wherein the plurality of struts are angled relative to a flow direction of exhaust gas, wherein the dosing struts comprise hollow interiors, and wherein the one or more dosing apertures are configured to allow diesel exhaust treatment liquid to escape from the hollow interiors of the dosing struts into exhaust gas.

7. The turbine diffuser of claim 1, wherein at least two structures have an airfoil cross-sectional shape with a leading edge oriented upstream, a trailing edge oriented downstream, a suction side, and a pressure side.

8. The turbine diffuser of claim 7, wherein the one or more dosing apertures are along the trailing edge of the dosing strut.

9. The turbine diffuser of claim 7, wherein the one or more dosing holes are along the suction side of the dosing strut.

10. A turbocharger for an engine system having an exhaust pipe with a selective catalytic reduction 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 dosing structure disposed in the turbine diffuser downstream of the turbine wheel and configured to dose diesel exhaust fluid into exhaust flowing through the diffuser, the diesel exhaust fluid dosing structure being supported in the diffuser by at least two structures attached to the diffuser wall, wherein at least one of the at least two structures is a dosing strut defining a dosing channel extending radially through the dosing strut and in fluid communication with one or more dosing apertures in a central body of the dosing structure, the central body defining a hollow interior through which diesel exhaust fluid is configured to flow into the hollow interior prior to release from the dosing aperture in an upstream direction toward the nose.