Patent Application
20090145119
The invention relates to devices mounted on truck exhaust systems to dilute and diffuse the exhaust gas as it is released from the truck.
More stringent emissions regulation on the amount of diesel particulate matter (DPM) and other gaseous constituents allowed in the exhaust gases of diesel engines has led to the use of exhaust aftertreatment devices such as diesel particulate filtration devices (DPF) and Diesel Oxidation Catalysts (DOC).
DPFs filter particulate matter from the exhaust gases to prevent it from exiting the tailpipe. After a period of operation, the collected particulate matter clogs the filter. The filter either needs to be replaced or removed for cleaning, which is not practical, or may be cleaned through a process known as regeneration. DPM is made up primarily of carbon, and is therefore combustible. Regeneration is a process where temperatures of the exhaust gases are made high enough to combust or oxidize the DPM within the filter. The regeneration process can cause the temperature of the exhaust gas exiting the diesel particulate filter to be well in excess of 600° C. By comparison, normal operating exhaust temperature for a diesel engine depends on the load and can range from about 100° C. at idle to about 500° C. at high load.
At highway speeds, high exhaust temperatures do not usually pose problems because the relatively high air speeds tend to disperse widely the heated gases. Exhausting the higher temperature gas stream can create difficulties when the vehicle is stationary or moving at low speed and is near combustible materials. For example, the stop and go movement of a trash collection truck on a street with overhanging trees could present difficulties. A truck typically has an exhaust stack pipe rising from the chassis adjacent to the truck cab. High temperature exhaust can produce a hot spot on the truck cab or trailer, or direct hot gases to a combustible substance, such as a building structure (for example, a loading dock or in a garage) or an overhanging tree.
It is desirable to provide an arrangement and a method for lowering the temperature of engine exhaust, particularly when the engine is operated for regeneration of exhaust aftertreatment devices.
In addition, in vocational trucks (dump trucks, trash hauling trucks, etc), the exhaust stack and the exhaust gases must not interfere with the operation of the body, lifting the dump body, for example.
According to a preferred embodiment of the invention suitable for vocational trucks such as dump trucks and trash collection trucks, a diluting and diffusing apparatus is mounted at the end of an exhaust stack. The diffuser is mounted downstream of the catalyst and diesel particulate filter (DPF) in the exhaust system. The diffuser allows exhaust gases to mix with ambient air and to disperse over a larger area than does a standard exhaust pipe, which helps avoid concentrations of hot gases.
An apparatus in accordance with an embodiment of the invention includes a diffuser pipe horizontally oriented and having an inlet connection to receive exhaust gases from an engine and having an outlet defined as an elongated opening on an upper surface thereof. According to a preferred embodiment, the inlet is disposed at about a longitudinal midpoint of the diffuser pipe and includes a deflector mounted in the diffuser pipe opposite the inlet to divide an entering exhaust gas flow toward opposite ends of the diffuser pipe. The diffuser may also include a baffle formed as an elongated plate having a multiplicity of holes mounted in the pipe between the inlet connection and the outlet and extending a length of the diffuser pipe. The baffle slows the gas flow to promote better distribution through the diffuser. The invention may also include a dispersing grate formed as an elongated plate having a multiplicity of holes and being mounted above the outlet and spaced therefrom, the dispersing grate having a curvature about a longitudinal axis, and being mounted with a convex surface facing the outlet. The dispersing grate disperses the gas flow exiting the diffuser outlet into the ambient air.
According to one variant of the invention, the diffuser pipe has two outlets, each formed as an elongated opening in the upper surface of the diffuser pipe and mutually spaced longitudinally.
According to another aspect of the invention, the apparatus includes an inlet conduit having a first end connectable to an outlet of a diesel particulate filter and a second end connected to the inlet of the diffuser pipe, the inlet conduit having two 180 bends.
According to yet another aspect of the invention, each of the multiplicity of holes in the dispersing grate is formed as a slotted hole, a long axis of the slotted hole oriented in a transverse direction of the dispersing grate.
According to yet another aspect of the invention, the apparatus includes an air guide to direct a flow of ambient air across the diffuser pipe and upward from the diffuser outlets and dispersing grate, the air guide including a curved wall mounted to surround a longitudinal periphery of the diffuser pipe. The curved wall extends from a lower side of the diffuser pipe upward and is spaced from the diffuser pipe to allow for air flow. A screen is mounted to the air guide on a front and top thereof to prevent external things, such as leaves and branches, from coming into contact with the diffuser pipe. The air guide may include solid side walls or screens mounted at opposite ends of the diffuser pipe.
The invention will be better understood by reference to the following detailed description read in conjunction with the appended drawings, in which:
The invention relates to devices that are mounted on a truck exhaust system at the point where exhaust gas is released to the surrounding air. The devices of this invention dilute the exhaust gas with ambient air and diffuse the exhaust gas over a wider area than a typical exhaust stack pipe to prevent concentrations of hot gases and dissipate exhaust heat more quickly.
A diluting and diffusing apparatus in accordance with the invention has particular advantage for use with a vocational truck, for example, a trash collecting truck or a dump truck, and the description here is in connection with a vocational truck. However, it is to be understood that the description is for the purposes of illustrating and explaining the invention and the invention is not limited to a particular type of truck and may be installed on other types of trucks.
The apparatus 20 is connected to receive exhaust gas from the vehicle exhaust aftertreatment system, illustrated here as a diesel particulate filter or DPF 16. An inlet conduit 22 carries exhaust gas from the DPF 16 to an inlet 24 of the apparatus 20. The exhaust gas then enters a diffusing pipe 30, which is disposed transversely to the truck cab 12, and after diffusing in the diffusing pipe, exits from outlet openings 36 on an upper surface of the diffusing pipe (shown in greater detail in
Exhaust gas exiting the diffusing pipe 30 is dispersed by a dispersing grate 50 mounted above the outlet openings of the diffusing pipe. The dispersing grate 50 is not illustrated in
An air guide 60 serves as a shield around the diffusing pipe 30 to prevent contact with external objects, such as leaves and tree branches, and to guide ambient air across the diffusing pipe 30 when the vehicle is moving forward. Ambient air moving across the diffusing pipe 30 helps cool the surface of the pipe, which has been heated by the diffusing exhaust gas. Ambient air also mixes with the exhaust gas exiting the diffusing pipe 30 and being dispersed by the dispersing grate 50 to help dilute and cool the exhaust gas.
A schematic layout of the apparatus of the invention is illustrated in
Reference is now made also to
The diffusing pipe 30 also has at least one outlet 36 formed as a slot on an upper portion of the pipe. In
A dispersing grate 50 is mounted spaced above the outlet openings 36 in the diffusing pipe 30. The dispersing grate 50 is formed as a perforated sheet having a multiplicity of holes, which may be circular, slotted, or another shape. The dispersing grate 50 slows and disperses or spreads the exiting exhaust gas flow over an area wider than the outlet opening to help mix the exhaust gas flow with ambient air. According to a preferred embodiment, the dispersing grate 50 is curved about a longitudinal axis, with a concave surface facing the outlet openings 36, so that exhaust gas can flow around and through the dispersing grate in an expanding flow. The dispersing grate 50 has a width, perpendicular to the longitudinal direction that is greater than a width of the outlet openings 36, which helps disperse the exhaust gas to the surrounding environment.
The air guide 60 includes a curved wall 62, formed as a solid sheet, that surrounds a bottom portion of the diffusing pipe 30 (see
The air guide 60 also includes side walls 70 located at opposite longitudinal ends of the curved wall 62 to enclose a space around the diffusing pipe 30, and prevent unwanted contact with the diffusing pipe. Preferably, as shown in section in
A front wall 72 (shown in section) extends vertically upward from the front edge 66 of the curved wall 62 and is attached to front edges of the side walls 70. A top wall 74 (shown in section) covers a horizontal area defined by upper edges of the side walls 70 and an upper edge of the front wall 72. The front wall 72 and top wall 74 may be formed as mesh or screen walls, for example, from expanded metal, to allow for air flow and prevent unwanted contact of the diffusing pipe 30 with external objects.
The invention has been described in terms of preferred embodiments and structure; however those skilled in the art will understand that substitutions and variations may be made without departing from the scope of the invention as defined in the appended claims.
