Abstract:
An exhaust gas treatment device includes an inlet housing having an inlet opening for receipt of an exhaust flow from an engine aligned along a first axis. A main housing includes a cylindrical body portion defining a treatment zone and an exhaust outlet aligned along a second axis extending parallel to the first axis. The inlet housing is in fluid communication with and fixed to an outer surface of the main housing. The inlet housing includes a contoured wall including an end portion positioned opposite the inlet opening, an aperture extending through the wall transverse to the first axis, divergent side wall portions on opposite sides of the inlet opening, and a necked portion having a reduced cross-section positioned downstream of the inlet opening and upstream of the aperture. A component is coupled to the main housing for treating exhaust flowing through the treatment zone.

Description:
FIELD 
     The present disclosure relates to an exhaust gas treatment system. More particularly, an inlet for an exhaust treatment device is configured to improve exhaust flow and reduce back pressure. 
     BACKGROUND 
     Reductions in the nitrogen oxides (NO x ) and particulate matter (PM) emitted from internal combustion engines continue to be of importance. In particular, increasingly stringent regulations relating to automotive diesel compression engines continue to be promulgated. While diesel particulate filters (DPF) are capable of achieving the required reductions in PM, there is a continuing need for improved systems that can provide the required reductions in NO x , in connection with the PM reduction provided by a DPF. 
     Systems have been proposed to provide a diesel oxidation catalyst (DOC) upstream from a DPF in order to provide an increased level of NO 2  in the exhaust which reacts with the soot gathered in the DPF to produce a desired regeneration of the DPF. This method may be referred to as passive regeneration. Such systems, however, may have limited effectiveness at temperatures below 300° C. and typically produce a pressure drop across the oxidation catalyst that must be accounted for in the design of the rest of the system. Hydrogen or a hydrocarbon fuel may be delivered upstream of the DOC to generate temperatures greater than 600° F. and actively regenerate the DPF. 
     Some systems may include a burner to increase the temperature of the engine exhaust by igniting fuel and creating a flame that heats the exhaust to an elevated temperature that will allow for oxidation of particulate matter in a diesel particulate filter. Examples of such proposals are shown in commonly assigned and co-pending U.S. patent application Ser. No. 12/430,194, filed Apr. 27, 2009, entitled “Diesel Aftertreatment System” by Adam J. Kotrba et al., the entire disclosure of which is incorporated herein by reference. 
     While current burners for such systems may by suitable for their intended purpose, improvements may be desirable. For example, it may be advantageous to provide a burner having an exhaust gas inlet extending parallel to an exhaust gas outlet to reduce back pressure and alleviate component packaging and mounting concerns. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     An exhaust gas treatment device for treating an exhaust flow from an engine includes an inlet housing having an inlet opening for receipt of the exhaust flow from the engine aligned along a first axis. A main housing includes a cylindrical body portion defining a treatment zone and an exhaust outlet aligned along a second axis extending parallel to the first axis. The inlet housing is in fluid communication with and fixed to an outer surface of the main housing. The inlet housing includes a contoured wall including an end portion positioned opposite the inlet opening, an aperture extending through the wall transverse to the first axis, divergent side wall portions on opposite sides of the inlet opening, and a necked portion having a reduced cross-section positioned downstream of the inlet opening and upstream of the aperture. A component is coupled to the main housing for treating exhaust flowing through the treatment zone. 
     Furthermore, an exhaust gas treatment device for treating an exhaust flow from an engine includes an inlet housing having an inlet opening for receipt of the exhaust flow from the engine with the inlet opening being aligned along a first axis. A main housing includes a cylindrical body portion defining a treatment zone and an exhaust outlet aligned along a second axis extending parallel to the first axis. The inlet housing is in fluid communication with and fixed to an outer surface of the main housing. The inlet housing includes a contoured wall including an end portion positioned opposite the inlet opening and an aperture extending through the wall transverse to the first axis. A portion of the contoured wall opposite the aperture includes a radially outwardly sloping portion intersecting a radially inwardly sloping portion at an inflection point. The inflection point is positioned axially downstream from the inlet opening and upstream from an upstream edge of the aperture to redirect the exhaust flow through the aperture. A component is coupled to the main housing for treating exhaust flowing through the treatment zone. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is schematic depicting an exhaust gas treatment system including a burner constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a perspective view of the burner; 
         FIG. 3  is a cross-sectional view of the burner depicted in  FIG. 1 ; 
         FIG. 4  is a fragmentary top view of the burner with a portion of an inlet housing removed; 
         FIG. 5  is a cross-sectional view of the burner; and 
         FIG. 6  is a fragmentary end view of the burner. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
       FIG. 1  depicts an exemplary diesel exhaust gas aftertreatment system  10  for treating the exhaust from a diesel compression engine  16 . The exhaust may contain oxides of nitrogen (NO x ) such as nitric oxide (NO) and nitrogen dioxide (NO 2 ) among others, particular matter (PM), hydrocarbons, carbon monoxide (CO), and other combustion byproducts. 
     Aftertreatment system  10  includes a burner  18  that selectively increases the temperature of the exhaust by selectively igniting and combusting fuel to provide the exhaust at an elevated temperature to the rest of the system  10  provides a number of advantages, some of which will be discussed in more detail below. 
     Aftertreatment system  10  may also include one or more other exhaust treatment devices, such as a diesel particulate filter (DPF)  20  connected downstream from the burner  18  to receive the exhaust therefrom, and a NO x  reducing device  22 , such as a selective catalytic reduction catalyst (SCR) or a lean NO x  trap connected downstream from the DPF  20  to receive the exhaust therefrom. 
     Burner  18  is operable to increase the temperature of the engine exhaust, by employing an active regeneration process for the DPF  20  wherein fuel is ignited in the burner  18  to create a flame that heats the exhaust to an elevated temperature that will allow for oxidation of the PM in the DPF  20 . Additionally, in connection with such active regeneration, or independent thereof, burner  18  may be used in a similar manner to heat the exhaust to an elevated temperature that will enhance the conversion efficiency of the NO x  reducing device  22 , particularly an SCR. Advantageously, burner  18  may provide elevated exhaust temperatures, either selectively or continuously, independent of a particular engine operating condition, including operating conditions that produce a low temperature (&lt;300° C.) exhaust as it exits engine  16 . Thus, aftertreatment system  10  can be operated without requiring adjustments to the engine controls. 
     Burner  18  includes an injector  24  for injecting a suitable fuel and an oxygenator. The fuel may include hydrogen or a hydrocarbon. Injector  24  may be structured as a combined injector that injects both the fuel and oxygenator, as shown in  FIG. 2 , or may include separate injectors for the fuel and the oxygenator. Preferably, a control system, shown schematically at  25  in  FIG. 1 , is provided to monitor and control the flows through the injector  24  and the ignition by the first and second igniters  26 ,  28  using any suitable processor(s), sensors, flow control valves, electric coils, etc. 
     As shown in  FIGS. 2-6 , burner  18  includes a housing  30  constructed as a multi-piece assembly of fabricated sheet metal components. Housing  30  includes a cylindrically-shaped body  32 , an inlet header  34  and a mixing plate  36 . Inlet header  34  is fixed to body  32  and encloses one end of tubular body  32 . Mixing plate  36  is positioned within cylindrical body  32  and fixed at an opposite end of the body. Housing  30  also includes an inlet assembly  38 . Inlet assembly  38  includes an upper shell  40  fixed to a lower shell  42 . Lower shell  42  is fixed to body  32 . First shell  40  is shown fixed to second shell  42  at a seam  44 . It should be appreciated that inlet assembly  38  may be constructed in this manner to simplify the manufacture of first shell  40  and second shell  42  as stampings from sheets of metal. Other single or multi-piece inlet assemblies are also contemplated as being within the scope of the present disclosure. 
     A conduit  41  is positioned within housing  30  and includes an open first end  43  extending through an aperture  45  of inlet header  34 . An opposite second end  47  of conduit  41  may be fixed to mixing plate  36 . Alternatively, second end  47  may be unsupported. An annular volume  49  exists in the space between an inner surface  55  of housing  30  and an outer surface of conduit  41 . 
     An injector mount  46  is fixed to inlet header  34  to provide an attachment mechanism for injector  24 . A nozzle portion  52  of injector  24  extends into conduit  41  such that atomized fuel may be injected within a primary combustion chamber  54  at least partially defined by an inner cylindrical surface  57  of conduit  41 . Injector  24  includes a fuel inlet  58  and an air inlet  60 . When burner operation is desired, fuel is injected via fuel inlet  58  and the oxygenator is provided via air inlet  60  to inject a stream of atomized fuel. First igniter  26  is positioned downstream of inlet header  34  and is operable to combust the fuel provided by injector  24  within primary combustion chamber  54 . Volume  49  is placed in fluid communication with a secondary combustion chamber  61  via a plurality of apertures  62  extending through conduit  41 . 
     Inlet assembly  38  includes an inlet opening  70  in receipt of exhaust supplied from engine  16 . Inlet assembly  38  also includes an outlet  72  in fluid communication with an aperture  74  extending through body  32 . Exhaust provided from engine  16  enters inlet opening  70 , travels through inlet assembly  38 , exits outlet  72  and enters annular volume  49 . Some of the exhaust passes through apertures  62  and enters secondary combustion chamber  61 . When burner  18  is operating, the exhaust travelling through apertures  62  will be heated by the flame produced via ignition of the fuel input by injector  24 . Additional unburned fuel may be present in the exhaust flowing inlet assembly  38 . The unburned fuel may be ignited within secondary combustion chamber  61  by second igniter  28 . 
     Inlet assembly  38  is sized and shaped to accept a flow of engine exhaust initially extending along an axis identified at reference numeral  86 . Exhaust travels through inlet assembly  38 , body  32  and exits at an outlet  88  travelling along an axis identified at reference numeral  90 . Axis  86  and axis  90  extend substantially parallel to and offset from one another. This relative positioning is dictated by the other components within a vehicle equipped with exhaust gas aftertreatment system  10 . In particular, the position of inlet opening  70  and the position of outlet  88  are defined by the position and volume of other vehicle components. 
     To accommodate the manufacturer&#39;s request, inlet assembly  38  is designed to turn the exhaust flow substantially 90 degrees from axis  86  to enter aperture  74  of body  32 . Inlet assembly  38  is configured in such a manner to minimize back pressure across burner  18 . To achieve these goals, inlet opening  70  includes a substantially circular shape having a first diameter and a lip  94 . Inlet assembly  38 , as defined by first shell  40  and second shell  42 , includes a reduced diameter neck portion  96  downstream from lip  94 . Further downstream, first shell  40  includes a radially outwardly extending wall portion  98  intersecting with a radially inwardly tapering wall portion  100  at an inflection point  102 . Second shell  42  includes a radially inwardly extending wall portion  104  extending from lip  94  to an inflection point  106  where a wall  108  of second shell  42  is closest to axis  86 . An indentation  110 , including or adjacent to inflection point  106 , is formed to complementarily receive a substantially cylindrically shaped portion of body  32 . 
     As best shown in  FIG. 4 , aperture  74  includes a substantially elliptical shape. Outlet  72  formed in second shell  42  includes a slightly larger but substantially similar elliptical shape. Second shell  42  includes a land  76  surrounding aperture  74 . As shown in  FIG. 5 , land  76  conforms to the cylindrical shape of body  32 . Inlet assembly  38  circumferentially extends around an outer surface  112  of body  32  approximately 105 degrees as depicted by angle A. Angle A may range from 85 to 160 degrees without departing from the scope of the present disclosure. 
     Inlet assembly  38  may be securely fixed to body  32  via a process such as welding at the interface between land  76  and body  32 . Inlet assembly  38  conforms to the shape of body  32  to minimize the packaging space required for burner  18  while changing the direction of the exhaust flow into annular volume  49  and secondary combustion chamber  61  to provide optimal burner performance. 
       FIG. 4  shows side wall portions  114 ,  116  laterally outwardly extending from neck portion  96 . Side wall portions  114 ,  116  diverge at an angle of substantially 30 degrees. The shape of walls  114 ,  116  allows exhaust passing through inlet opening  70  to disperse around aperture  74  to provide an even distribution of exhaust flow into secondary combustion chamber  61  while minimizing back pressure. Hot spots within the burner are avoided and optimal combustion performance is promoted within burner  18 . For example, the relative position and shape of inlet assembly  38  to injector  24  and conduit  41  defines a properly shaped and sized flame within secondary combustion chamber  61 . 
     To further assist a smooth flow from inlet opening  70  to outlet  72 , inflection points  102  and  106  are substantially aligned with one another in that both points are substantially the same distance downstream from lip  94  ( FIG. 3 ). The inflections points are positioned upstream from aperture  74  to assure that the exhaust flow is turned from axis  86  to enter aperture  74  at an angle extending substantially 45 to 90 degrees to axis  86 . First shell  40  includes a dome shaped rear wall portion  120  to assist with the re-direction of exhaust flow. In particular, the domed shape of wall portion  120  provides for a flow re-direction into burner aperture  74 . More particularly, the shape of the walls of inlet assembly  38  allow for gas to disperse around the inner wall of the stampings before it enters burner aperture  74 . By dispersing the gas, a restriction to gas flow is avoided. Back pressure increase is minimized. At the most downstream extent of inlet assembly  38 , land  76  is angled to urge exhaust gas into aperture  74 . 
     The axial position of inflection points  102 ,  106  relative to a leading edge  122  of aperture  74  is optimized to cause exhaust flow to turn into annular volume  49  and secondary combustion chamber  61  while minimizing back pressure. In particular, inflection points  102 ,  106  are spaced from leading edge  122  a distance identified as distance “B”. To achieve the turning function while minimizing back pressure, distance B ranges from 15 to 55 percent of a minor axis dimension of aperture  74 . 
     The shape and relative positioning of the inlet assembly  38 , body  32  and conduit  41  define engine exhaust paths that split and recombine with one another. More particularly, exhaust gas from internal combustion engine  16  is provided to inlet opening  70 . Exhaust flows from left to right when viewing  FIG. 2 . As the exhaust continues to flow through outlet  72  and aperture  74 , the exhaust passes through annular volume  49  defined between the outer surfaces of conduit  41  and inner surface  55  of body  32 . The exhaust flow serves to cool conduit  41  as well as inlet header  34  and body  32 . As the exhaust flows, a portion of the engine exhaust travels along a combustion flow path  130 . Exhaust travelling along combustion flow path  130  flows through apertures  62 . During burner operation, fuel and oxygenator are supplied to primary combustion chamber  54  by injector  24 . First igniter  26  produces a flame within primary combustion chamber  54 . Exhaust travelling along combustion flow path  130  is heated by the flame and unburned fuel carried in the exhaust may be ignited by the flame and/or second igniter  28  within secondary combustion chamber  61 . 
     The remaining portion of exhaust gas that does not pass through apertures  62  may be characterized as travelling along a bypass flow path  132 . Exhaust flows through the volume  49  between conduit  41  and body  32  downstream of apertures  62 . The exhaust flowing through bypass flow path  132  cools conduit  41  and body  32  and is supplied to a mixing zone  134  for combination with the combustion flow exiting combustion flow path  130 . 
     Mixing plate  36  extends across bypass flow path  132  to restrict an available flow area of the bypass flow path  132 . A plurality of elongated apertures  138  extend through mixing plate  36  to define outlet  88 . Outlet  88  is coaxially arranged with axis  90 . Mixing plate  36  may be fixed to interior surface  55  of housing  30 . Mixing plate  36  may include a plurality of fingers  140  to enhance turbulence and temperature distribution. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.