STEPPED DOWN AFTERTREATMENT DEVICE SHROUD

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.

FIELD OF THE INVENTION

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

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.

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.

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.

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.

It is an object of this invention to provide such an arrangement.

SUMMARY OF THE INVENTION

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.

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).

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).

The aftertreatment device may be elongate, generally cylindrical, and may have a central longitudinal axis (104) that extends generally horizontally.

5. The shroud (102) of claim4, 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).

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).

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).

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).

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).

DETAILED DESCRIPTION

The aftertreatment device and the shroud described herein are mirror-symmetric about the vertically and longitudinally extending cutting plane ofFIG. 6.

In the Figures herein, an aftertreatment device100is disposed in a shroud102. The body of the aftertreatment device100is generally cylindrical and has a longitudinal central axis104. An input exhaust conduit106that is generally cylindrical extends upward from a cylindrical side wall of the aftertreatment device100at a first end108of the aftertreatment device100. An output exhaust conduit110that is generally cylindrical extends outward from the aftertreatment device100at a second end112of the aftertreatment device100. The output exhaust conduit110is coaxial with the longitudinal central axis104of the aftertreatment device100.

Exhaust gas is introduced into the input exhaust conduit106. The exhaust gas then traverses the body of the aftertreatment device100. The exhaust gas that exits the aftertreatment device100through the output exhaust conduit110.

The shroud102surrounds substantially the entire aftertreatment device100. The shroud102is formed of a single layer of sheet metal. The shroud102is spaced away from the outer surface of the aftertreatment device100to permit air introduced into the shroud102to flow over substantially the entire surface of the aftertreatment device100.

This airflow performs a dual function. The air flow cools the inner surface of the shroud102, thereby decreasing the temperature of the shroud102and reducing the risk of fire. The airflow also prevents the formation of a layer of combustible matter on the outer surface of the aftertreatment device100.

The shroud102comprises an air inlet114is configured to receive air and conduct the air into the shroud102and across the upper surface of the aftertreatment device100. The air inlet114is located immediately adjacent to the input exhaust conduit106such that it directs air in a horizontal direction around both sides of the input exhaust conduit106.

The shroud102further comprises a shell116. The shell116comprises a first sidewall118, a second sidewall120, a first endwall122, a second endwall124and a stepped conduit126.

The first sidewall118extends substantially the entire length of the aftertreatment device100. The first sidewall118wraps around and encloses a first side of the aftertreatment device100. The first sidewall118and the first side extend generally vertically. The first sidewall118is spaced slightly away from the first side of the aftertreatment device100in order to provide a narrow gap128between the first sidewall118and the first side of the aftertreatment device100. The gap128forms an air channel that maintains a relatively constant airflow over substantially the entire first side of the aftertreatment device100.

The second sidewall120extends substantially the entire length of the aftertreatment device100. The second sidewall120wraps around and encloses a second side of the aftertreatment device100. The second sidewall120and the second side extend generally vertically. The second sidewall120is spaced slightly away from the second side of the aftertreatment device100in order to provide a narrow gap130between the second sidewall120and the second side of the aftertreatment device100. The gap130forms an air channel that maintains a relatively constant airflow over substantially the entire second side of the aftertreatment device100.

An elongate outlet132is provided between the bottom edge of the first sidewall118and the second sidewall120. The elongate outlet132extends substantially the entire length of the aftertreatment device100.

The elongate outlet132provides a flow path for air that is introduced into the air inlet114to escape from the space defined between the inner surface of the shroud102and the outer surface of the aftertreatment device100.

The ends of the shroud102are defined by the first endwall122and the second endwall124which enclose the ends of the aftertreatment device100.

The first endwall122is fixed to the first sidewall118, the second sidewall120, and the input exhaust conduit106to enclose the first end108of the aftertreatment device100.

The second endwall124is fixed to the first sidewall118, the second sidewall120, and the stepped conduit126to enclose the second end112of the aftertreatment device100.

The stepped conduit126forms the upper surface of the shroud102. The stepped conduit126encloses the upper surface of the aftertreatment device100. The stepped conduit126is fixed to and extends between the upper edges of the first sidewall118and the second sidewall120. The stepped conduit126extends substantially the entire length of the aftertreatment device100and is spaced away from the aftertreatment device100a distance substantially larger than the gap128or the gap130.

Due to this larger spacing, the stepped conduit126has a decreased resistance to airflow in a direction parallel to the longitudinal extent of the aftertreatment device100. This decreased resistance permits air to flow from the air inlet114at the first end108of the aftertreatment device100, down the length of the stepped conduit126to the second end112of the aftertreatment device100.

The cross-sectional area between the stepped conduit126and the top surface of the aftertreatment device100decreases over the length of the aftertreatment device100as the stepped conduit126extends from the first end108to the second end112.

The cross-sectional area between the stepped conduit126and the surface of the aftertreatment device100over which it extends does not decrease gradually and uniformly over the length of the stepped conduit126, 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 conduit126is formed of a single layer of sheet metal) is provided with a series of three downward steps (a step134, a step136, and a step138) in a top surface140of the stepped conduit126, as well as a laterally inward step142on a first side surface144of the stepped conduit126and an opposing laterally inward step146on a second side surface148of the stepped conduit126. The laterally inward step146is on an opposing side of the stepped conduit126from the laterally inward step142o the first side surface144.

The effect of these step changes in the inner surface of the stepped conduit126is to cause a disruption in the smooth flow of the air traveling longitudinally down the stepped conduit126. This disruption in the flow of air directs a greater portion of the air downward into the gap128and gap130.

This downward flow improves the scouring of the upper surface of the aftertreatment device100. The scouring both removes pockets of otherwise combustible material that may have accumulated on the upper surface of the aftertreatment device100. It also helps prevent the formation the formation of pockets of material on the upper surface of the aftertreatment device100. The upper surface of the aftertreatment device100has protrusions extending upwardly therefrom. The protrusions comprise a first circumferential ring150and the second circumferential ring152. In previous arrangements, dust and other combustible particles would accumulate on the upper and side surfaces of the aftertreatment device100downstream of these protrusions. The steps described herein.

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.