Abstract:
A shroud ( 102 ) for an aftertreatment device ( 100 ) for treating exhaust gas from an internal combustion engine comprises a stepped conduit ( 126 ) configured to be disposed over an upper surface of the aftertreatment device ( 100 ) and extending over substantially the entire length of the aftertreatment device ( 100 ), wherein the stepped conduit ( 126 ) is configured to channel a flow of cleaning air longitudinally along the outer and upper surface of the aftertreatment device ( 100 ), wherein an inner surface of the stepped conduit ( 126 ) defines at least a first downwardly extending step ( 134, 136, 138 ) and a second downwardly extending step ( 134, 136, 138 ) that are spaced apart along the length of the aftertreatment device ( 100 ), to direct at least a portion of the flow of cleaning air downward.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to internal combustion engines. More particularly, it relates to aftertreatment devices for internal combustion engines. Even more particularly, it relates to shrouds for aftertreatment devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    Modern internal combustion engines are provided with aftertreatment devices that process the exhaust gases to remove impurities. These aftertreatment devices operate at elevated temperatures and in dirty surroundings. They must be kept clean in order not to accumulate combustible matter that can catch fire and damage the aftertreatment device. For this reason, aftertreatment devices may be enclosed in insulated chambers, or provided with a supply of air that flows across their surface in order to keep combustible material fro being deposited on the surface. 
         [0003]    In one arrangement, an aftertreatment device was provided with a shroud that defined an elongate plenum extending along the length of the aftertreatment device. Below this plenum a wall with several apertures was provided. Air entering the plenum could freely travel the length of the plenum, and its force, direction, and intensity was controlled by the location of the apertures formed in the wall. 
         [0004]    One problem with this arrangement is that impurities, dust, dirt and other combustible particles are deposited on the wall and gradually block the apertures themselves. Furthermore, the arrangement of a plenum enclosed at its bottom by a pierced wall reduced the power of the airflow and prevented it from thoroughly scrubbing the upper surfaces of the aftertreatment device. 
         [0005]    What is needed, therefore, is a new arrangement of an aftertreatment device shroud that provides for greater airflow, and better cleaning ability of the air and also reduces potential blockages of the airflow. 
         [0006]    It is an object of this invention to provide such an arrangement. 
       SUMMARY OF THE INVENTION 
       [0007]    In accordance with one aspect of the invention, a shroud ( 102 ) for an aftertreatment device ( 100 ) for treating exhaust gas from an internal combustion engine is provided, the shroud comprising: a stepped conduit ( 126 ) configured to be disposed over an upper surface of the aftertreatment device ( 100 ) and extending over substantially an entire length of the aftertreatment device ( 100 ), wherein the stepped conduit ( 126 ) is configured to channel a flow of cleaning air longitudinally along an outer and upper surface of the aftertreatment device ( 100 ), wherein an inner surface of the stepped conduit ( 126 ) defines at least a first downwardly extending step ( 134 ,  136 ,  138 ) and a second downwardly extending step ( 134 ,  136 ,  138 ) that are spaced apart along a length of the aftertreatment device ( 100 ), to direct at least a portion of the flow of cleaning air downward. 
         [0008]    The shroud ay further comprise a first sidewall ( 118 ) that is fixed to the stepped conduit ( 126 ) along a first longitudinal side edge of the stepped conduit ( 126 ), wherein the first sidewall ( 118 ) extends around and encloses a first side surface of the aftertreatment device ( 100 ), wherein the first sidewall ( 118 ) is disposed to provide a narrow gap ( 128 ) between the first sidewall ( 118 ) and the first side surface of the aftertreatment device ( 100 ) to receive the flow of cleaning air from the stepped conduit ( 126 ) over substantially the entire length of the aftertreatment device ( 100 ) and to direct the flow of cleaning air generally downward over the first side surface of the aftertreatment device ( 100 ). 
         [0009]    The shroud may further comprise a second sidewall ( 120 ) that is fixed to the stepped conduit ( 126 ) along a second longitudinal side edge of the stepped conduit ( 126 ) and is disposed on an opposite side of the stepped conduit ( 126 ) from the first sidewall ( 118 ), wherein the second sidewall ( 120 ) extends around and encloses a second side surface of the aftertreatment device ( 100 ), wherein the second sidewall ( 120 ) is disposed to provide a narrow gap ( 130 ) between the second sidewall ( 120 ) and the second side surface of the aftertreatment device ( 100 ) to receive the flow of cleaning air from the stepped conduit ( 126 ) over substantially the entire length of the aftertreatment device ( 100 ) and to direct the flow of cleaning air generally downward over the second side surface of the aftertreatment device ( 100 ). 
         [0010]    The aftertreatment device may be elongate, generally cylindrical, and may have a central longitudinal axis ( 104 ) that extends generally horizontally. 
         [0011]    5. The shroud ( 102 ) of claim  4 , wherein the aftertreatment device ( 100 ) has a top surface, and wherein the stepped conduit ( 126 ) extends generally horizontally and is disposed immediately over the top surface of the aftertreatment device ( 100 ). 
         [0012]    The first downwardly extending step ( 134 ,  136 ,  138 ) and the second downwardly extending step ( 134 ,  136 ,  138 ) maybe disposed above the top surface of the aftertreatment device ( 100 ) and maybe spaced apart along the top surface of the aftertreatment device ( 100 ). 
         [0013]    The first downwardly extending step ( 134 ,  136 ) maybe disposed immediately downstream of a first protrusion ( 150 ,  152 ) that extends upwardly from the top surface of the aftertreatment device ( 100 ). 
         [0014]    The second downwardly extending step ( 134 ,  136 ) maybe disposed immediately downstream of a second protrusion ( 150 ,  152 ) that extends upwardly fro the top surface of the aftertreatment device ( 100 ). 
         [0015]    Each of the first protrusion ( 150 ,  152 ) ad the second protrusion ( 150 ,  152 ) may comprise a an annular ring extending about a circumference of the aftertreatment device ( 100 ). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective left side view of an aftertreatment device shroud enclosing an aftertreatment device in accordance with the present invention. 
           [0017]      FIG. 2  is a perspective right side view of the aftertreatment device shroud of  FIG. 1 . 
           [0018]      FIG. 3  is a bottom view of the aftertreatment device shroud of  FIGS. 1-2 . 
           [0019]      FIG. 4  is a vertical cross-sectional view of the aftertreatment device of  FIGS. 1-3  taken at section line  4 - 4  in  FIG. 1 . The cutting plane defining the view of  FIG. 4  extends perpendicular to a longitudinal axis of the aftertreatment device and of the aftertreatment device shroud. 
           [0020]      FIG. 5  is a vertical cross-sectional view of the aftertreatment device of  FIGS. 1-4  taken at section line  5 - 5  in  FIG. 1 . The cutting plane defining the view of  FIG. 5  extends perpendicular to a longitudinal axis of the aftertreatment device and of the aftertreatment device shroud. 
           [0021]      FIG. 6  is a cross-sectional view of the aftertreatment device of  FIGS. 1-5  taken at section line  6 - 6  in  FIG. 1 . The cutting plane defining the view of  FIG. 6  extends vertically and extends longitudinally through the central longitudinal axis of the aftertreatment device. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The aftertreatment device and the shroud described herein are mirror-symmetric about the vertically and longitudinally extending cutting plane of  FIG. 6 . 
         [0023]    In the Figures herein, an aftertreatment device  100  is disposed in a shroud  102 . The body of the aftertreatment device  100  is generally cylindrical and has a longitudinal central axis  104 . An input exhaust conduit  106  that is generally cylindrical extends upward from a cylindrical side wall of the aftertreatment device  100  at a first end  108  of the aftertreatment device  100 . An output exhaust conduit  110  that is generally cylindrical extends outward from the aftertreatment device  100  at a second end  112  of the aftertreatment device  100 . The output exhaust conduit  110  is coaxial with the longitudinal central axis  104  of the aftertreatment device  100 . 
         [0024]    Exhaust gas is introduced into the input exhaust conduit  106 . The exhaust gas then traverses the body of the aftertreatment device  100 . The exhaust gas that exits the aftertreatment device  100  through the output exhaust conduit  110 . 
         [0025]    The shroud  102  surrounds substantially the entire aftertreatment device  100 . The shroud  102  is formed of a single layer of sheet metal. The shroud  102  is spaced away from the outer surface of the aftertreatment device  100  to permit air introduced into the shroud  102  to flow over substantially the entire surface of the aftertreatment device  100 . 
         [0026]    This airflow performs a dual function. The air flow cools the inner surface of the shroud  102 , thereby decreasing the temperature of the shroud  102  and reducing the risk of fire. The airflow also prevents the formation of a layer of combustible matter on the outer surface of the aftertreatment device  100 . 
         [0027]    The shroud  102  comprises an air inlet  114  is configured to receive air and conduct the air into the shroud  102  and across the upper surface of the aftertreatment device  100 . The air inlet  114  is located immediately adjacent to the input exhaust conduit  106  such that it directs air in a horizontal direction around both sides of the input exhaust conduit  106 . 
         [0028]    The shroud  102  further comprises a shell  116 . The shell  116  comprises a first sidewall  118 , a second sidewall  120 , a first endwall  122 , a second endwall  124  and a stepped conduit  126 . 
         [0029]    The first sidewall  118  extends substantially the entire length of the aftertreatment device  100 . The first sidewall  118  wraps around and encloses a first side of the aftertreatment device  100 . The first sidewall  118  and the first side extend generally vertically. The first sidewall  118  is spaced slightly away from the first side of the aftertreatment device  100  in order to provide a narrow gap  128  between the first sidewall  118  and the first side of the aftertreatment device  100 . The gap  128  forms an air channel that maintains a relatively constant airflow over substantially the entire first side of the aftertreatment device  100 . 
         [0030]    The second sidewall  120  extends substantially the entire length of the aftertreatment device  100 . The second sidewall  120  wraps around and encloses a second side of the aftertreatment device  100 . The second sidewall  120  and the second side extend generally vertically. The second sidewall  120  is spaced slightly away from the second side of the aftertreatment device  100  in order to provide a narrow gap  130  between the second sidewall  120  and the second side of the aftertreatment device  100 . The gap  130  forms an air channel that maintains a relatively constant airflow over substantially the entire second side of the aftertreatment device  100 . 
         [0031]    An elongate outlet  132  is provided between the bottom edge of the first sidewall  118  and the second sidewall  120 . The elongate outlet  132  extends substantially the entire length of the aftertreatment device  100 . 
         [0032]    The elongate outlet  132  provides a flow path for air that is introduced into the air inlet  114  to escape from the space defined between the inner surface of the shroud  102  and the outer surface of the aftertreatment device  100 . 
         [0033]    The ends of the shroud  102  are defined by the first endwall  122  and the second endwall  124  which enclose the ends of the aftertreatment device  100 . 
         [0034]    The first endwall  122  is fixed to the first sidewall  118 , the second sidewall  120 , and the input exhaust conduit  106  to enclose the first end  108  of the aftertreatment device  100 . 
         [0035]    The second endwall  124  is fixed to the first sidewall  118 , the second sidewall  120 , and the stepped conduit  126  to enclose the second end  112  of the aftertreatment device  100 . 
         [0036]    The stepped conduit  126  forms the upper surface of the shroud  102 . The stepped conduit  126  encloses the upper surface of the aftertreatment device  100 . The stepped conduit  126  is fixed to and extends between the upper edges of the first sidewall  118  and the second sidewall  120 . The stepped conduit  126  extends substantially the entire length of the aftertreatment device  100  and is spaced away from the aftertreatment device  100  a distance substantially larger than the gap  128  or the gap  130 . 
         [0037]    Due to this larger spacing, the stepped conduit  126  has a decreased resistance to airflow in a direction parallel to the longitudinal extent of the aftertreatment device  100 . This decreased resistance permits air to flow from the air inlet  114  at the first end  108  of the aftertreatment device  100 , down the length of the stepped conduit  126  to the second end  112  of the aftertreatment device  100 . 
         [0038]    The cross-sectional area between the stepped conduit  126  and the top surface of the aftertreatment device  100  decreases over the length of the aftertreatment device  100  as the stepped conduit  126  extends from the first end  108  to the second end  112 . 
         [0039]    The cross-sectional area between the stepped conduit  126  and the surface of the aftertreatment device  100  over which it extends does not decrease gradually and uniformly over the length of the stepped conduit  126 , however. It decreases in a stepwise fashion. To provide this stepwise reduction the inner surface (and in this case the outer surface as well, since the stepped conduit  126  is formed of a single layer of sheet metal) is provided with a series of three downward steps (a step  134 , a step  136 , and a step  138 ) in a top surface  140  of the stepped conduit  126 , as well as a laterally inward step  142  on a first side surface  144  of the stepped conduit  126  and an opposing laterally inward step  146  on a second side surface  148  of the stepped conduit  126 . The laterally inward step  146  is on an opposing side of the stepped conduit  126  from the laterally inward step  142  o the first side surface  144 . 
         [0040]    The effect of these step changes in the inner surface of the stepped conduit  126  is to cause a disruption in the smooth flow of the air traveling longitudinally down the stepped conduit  126 . This disruption in the flow of air directs a greater portion of the air downward into the gap  128  and gap  130 . 
         [0041]    This downward flow improves the scouring of the upper surface of the aftertreatment device  100 . The scouring both removes pockets of otherwise combustible material that may have accumulated on the upper surface of the aftertreatment device  100 . It also helps prevent the formation the formation of pockets of material on the upper surface of the aftertreatment device  100 . The upper surface of the aftertreatment device  100  has protrusions extending upwardly therefrom. The protrusions comprise a first circumferential ring  150  and the second circumferential ring  152 . In previous arrangements, dust and other combustible particles would accumulate on the upper and side surfaces of the aftertreatment device  100  downstream of these protrusions. The steps described herein. 
         [0042]    It should be understood that the particular arrangements shown and described in this document are not the only ways in which the invention can be created. The arrangements shown in this document are the currently preferred embodiments of the invention. However, one skilled in the art of agricultural harvester design and manufacture can readily see other variations that would also be protected by the claims of this document.