Patent Publication Number: US-8539767-B2

Title: Exhaust treatment system for an internal combustion engine

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/453,346 filed Mar. 16, 2011, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     Exemplary embodiments of the invention relate to exhaust treatment systems for internal combustion engines and, more particularly, to an exhaust system having a uniform flow at varying engine speeds. 
     BACKGROUND 
     A typical exhaust after treatment system for an internal combustion engine may involve the placement of a catalyst treatment device in close proximity to the exhaust manifold of the internal combustion engine. This catalyst treatment device, referred to as a close-coupled catalytic converter, minimizes thermal loss in the exhaust gas, between the engine and the device, resulting in higher temperatures and quicker catalytic activation since the catalyst compounds that are typically used for treating engine exhaust gas operate best at temperatures in excess of 350° C. 
     Internal combustion engines that utilize a compressor such as an exhaust driven turbocharger to compress the combustion air charge, may be configured such that exhaust gas exiting the engine is conducted directly into, and through, the exhaust driven turbocharger. For greatest thermal efficiency, it may be desirable to locate a close-coupled catalytic converter directly adjacent to the outlet of the exhaust driven turbocharger in order to minimize the length of the exhaust gas passage therebetween; and resultant thermal load that must be overcome. 
     In such closely coupled arrangements, exhaust gas exiting the exhaust driven turbocharger during low speed operation may include a rotational or swirling component that migrates towards the outer circumference of the exhaust gas passage. As a result, upon reaching the inlet face of the catalyst substrate of the close coupled catalytic converter, the distribution of exhaust gas across the inlet face may be concentrated towards the outer circumference resulting in inefficient exhaust gas flow through the substrate. Such uneven flow of exhaust gas through the substrate may reduce the conversion efficiency of the exhaust treatment device. 
     SUMMARY 
     In an exemplary embodiment of the invention, an exhaust system configured to receive exhaust gas from an internal combustion engine comprises an exhaust driven turbocharger having an outlet and a flanged portion that extends about the outlet, an exhaust treatment device comprising a rigid canister having an inlet cone that includes an integral inlet flange defining an the inlet opening of the exhaust treatment device and configured to define a seal with the flanged portion that extends about the outlet of the exhaust driven turbocharger and a substrate disposed within the rigid canister through which the exhaust gas flows. An exhaust gas passage, defined by the turbocharger outlet and the inlet opening of the exhaust treatment device fluidly couples the exhaust driven turbocharger and the exhaust treatment device and allows for the passage of exhaust gas therebetween and a flow modifier comprising a radially inwardly extending wall portion extend from an inner wall of the exhaust gas passage and directs the exhaust gas away from an outer radius of the exhaust gas passage as exhaust gas enters the inlet cone of the exhaust treatment device to evenly distribute the exhaust gas across the an inlet face of the substrate. 
     In another exemplary embodiment of the invention, an internal combustion engine having an exhaust system configured to receive exhaust gas therefrom comprises an exhaust driven turbocharger, in fluid communication with the exhaust system, for receipt of exhaust gas from the internal combustion engine, and having an outlet and a flanged portion that extends about the outlet. An exhaust treatment device comprising a rigid canister having an inlet cone that includes an integral inlet flange defining an the inlet opening of the exhaust treatment device and configured to define a seal with the flanged portion that extends about the outlet of the exhaust driven turbocharger for receipt of exhaust gas therefrom. A catalyst coated substrate is disposed within the rigid canister through which the exhaust gas flows. An exhaust gas passage, defined by the turbocharger outlet and the inlet opening of the exhaust treatment device, fluidly couples the exhaust driven turbocharger and the exhaust treatment device and allows for the passage of exhaust gas therebetween and, a flow modifier comprises a radially inwardly extending wall portion that extends from an inner wall of the exhaust gas passage and directs the exhaust gas away from an outer radius of the exhaust gas passage as exhaust gas enters the inlet cone of the exhaust treatment device to evenly distribute the exhaust gas across the an inlet face of the catalyst coated substrate 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features, advantages and details appear, by way of example only, in the following detailed description of the embodiments, the detailed description referring to the drawings in which: 
         FIG. 1  is a partial, cross-sectional view of an exhaust system of an internal combustion engine; 
         FIG. 2  is an enlarged view of a portion of the exhaust system of  FIG. 1  taken at Circle  2 ; 
         FIG. 3  is a partial, cross-sectional view of another embodiment of an exhaust system of an internal combustion engine; 
         FIG. 4  is an enlarged view of a portion of the exhaust system of  FIG. 1  taken at Circle  2  illustrating an additional embodiment of the invention; and 
         FIG. 5  is an enlarged view of a portion of the exhaust system of  FIG. 1  taken at Circle  2  illustrating an additional embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     Referring to  FIG. 1 , in an exemplary embodiment a portion of an exhaust system  10  of an internal combustion engine (not shown) includes an exhaust driven turbocharger  12  and a close-coupled exhaust treatment device  14 . The exhaust driven turbocharger utilizes excess energy in the exhaust gas expelled from the internal combustion engine to drive a compressor (not shown) for the purpose of compressing the intake air charge which is delivered to an intake system (not shown) of the engine during operation thereof. Exhaust gas  16  rotates a turbine wheel (not shown) as it expands through a turbine scroll  20  and to a turbocharger outlet  22 . The turbocharger outlet  22  may comprise a flanged portion  24  that is integral with the turbocharger housing  26  and extends about the turbocharger outlet  22 . The flanged portion  24  is configured define a seal with a similarly configured inlet flange  28  that extends about an inlet opening  30  of the exhaust treatment device  14 . 
     In an exemplary embodiment, the exhaust treatment device  14  may comprise a rigid canister  32  having an inlet cone  34  and an exhaust gas outlet  36 . The inlet cone  34  may include the integral inlet flange  28  that defines the inlet opening  30  of the exhaust treatment device  14 . Disposed within the rigid canister  32  between the inlet opening  30  and the exhaust gas outlet  36  is a substrate  38  through which the exhaust gas  16  flows. A catalyst compound  40  may be disposed on the surface of the substrate  38  and aids in the conversion or reduction of various regulated exhaust gas components. In an exemplary embodiment, as the exhaust gas  16  traverses the length of the catalyst coated substrate  38  a precious metal or Platinum group metal catalyst compound, including platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof, catalyzes the oxidation of carbon monoxide (“CO”) to carbon dioxide (“CO 2 ”) in the presence of oxygen (“O2”), as well as catalyzing the oxidation of various hydrocarbons, including gaseous HC and liquid HC particles including unburned fuel or oil, as well as HC reductants that may have been introduced into the exhaust gas  16 , to form H 2 0. Other catalyst compounds may also be utilized for the treatment of other exhaust gas constituents without deviating from the scope of the invention. A substrate support such as insulating mat  42  may be disposed between the substrate  38  and the rigid canister  32  to protect the substrate from shock and reduce the transfer of heat out of the exhaust treatment device  14 . 
     Referring now to  FIGS. 1 and 2 , in an exemplary embodiment the turbocharger outlet  22  and the inlet opening  30  of the rigid canister  32  together define an exhaust gas passage  44  that fluidly couples the two devices and allows for the passage of exhaust gas  16  therethrough. When the internal combustion engine and, thus, the exhaust driven turbocharger  12  is operated at lower speeds (idle or no-load for example), the exhaust gas  16  may exit the turbocharger outlet  22  with a rotational or swirling component  16 A, that migrates towards the outer radius of the exhaust gas passage  44 . A flow modifier  46  comprising a radially inwardly extending wall portion  48  extends from the inner wall of the exhaust gas passage  44  and directs the outwardly migrating exhaust gas flow  16 A away from the outer circumference of the exhaust gas passage and into a more evenly distributed flow path  16 B as the exhaust gas  14  enters the inlet cone  34  of the exhaust treatment device  14  to thereby evenly distribute the exhaust gas  16  across the inlet face  37  of the substrate  38 . In an exemplary embodiment, the flow modifier  46  is constructed integrally with the inlet flange  28  of the inlet cone  34  and may extend completely about the circumference of the exhaust gas passage  44  or, only a portion thereof. More specifically, the radially inwardly extending wall member  48  of the flow modifier  46  may be segmented to allow a portion of the exhaust gas to migrate towards the outer radius of the exhaust gas passage  44 . 
     Referring to  FIG. 3 , in an alternative embodiment of the invention, it is contemplated that the flow modifier  46  may comprise a radially inwardly extending wall portion  48 B that is constructed integrally with the flanged portion  24  of the turbocharger outlet  22 . The wall portion  48 B may extend completely about the circumference of the exhaust gas passage  44  or, only a portion thereof. More specifically, the radially inwardly extending wall member  48 B of the flow modifier  46  may be segmented to allow a portion of the exhaust gas to migrate towards the outer radius of the exhaust gas passage  44 . 
     Referring to  FIGS. 4 and 5 , in which like features already described in reference to other Figures are represented by like numerals, alternative embodiments of the invention, include the addition of a second flow modifier  50  that is positioned axially downstream (with respect to the exhaust gas flow direction) of the radially inwardly extending wall portions  48  or  48 B. The second flow modifier  50  comprises a radially inwardly extending wing or wall portion  52  that extends from the inner wall  54  of the flow modifier  46  and further redirects the outwardly migrating exhaust gas flow  16 A away from the outer circumference of the exhaust gas passage  44  and into a more centralized and evenly distributed flow path  16 B as the exhaust gas  16  enters the inlet cone  34  of the exhaust treatment device  14 . In an exemplary embodiment, the second flow modifier  50  is constructed integrally with the flow modifier  46  and may extend completely about the circumference of the exhaust gas passage  44  or, only a portion thereof. More specifically, the radially inwardly extending wing or wall portions  48  or  48 B of the second flow modifier  50  may be segmented to allow a portion of the exhaust gas  16  to migrate towards the outer radius of the exhaust gas passage  44 . 
     While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the application.