The present invention relates to after-treatment devices for internal combustion engines. More particularly it relates to devices for keeping after-treatment devices clean. Even more particularly, it relates to pressurized shielding for after-treatment devices.
Agricultural equipment operates in dusty, dirty environments full of light fluffy dry crop material. This equipment is traditionally powered with internal combustion engines, usually diesel engines.
Government regulations have recently required the use of devices to treat engine exhaust gas (hereinafter after-treatment devices or ATDs) to remove residual pollutants from the raw exhaust gas. These devices can be remotely mounted from the engine to treat the exhaust gas. The ATDs have a very high surface temperature when they undergo periodic regeneration. These high temperatures at the outer surface of the devices can cause dust or other plant matter that collects on the outer surface to combust.
One way of preventing this combustion is to keep the surface of the ATD clean. This can be achieved by directing a portion of the air moved by the radiator cooling fan across the upper surface of the ATD. An example of this arrangement can be seen in US 2010/0275587 A1.
A drawback to these and similar designs is that the air used for cleaning the surface of the ATD contains dust and other plant matter. The air directed across the surface of the ATD by these prior designs must scour the surface at a high velocity in order to prevent the dust mixed with the air from settling on the surface of the ATD and permitting a layer of dust to build up.
Furthermore, if the ATD is placed remotely from the engine, a rather long conduit must be provided to conduct air from the cooling air fan to the ATD.
What is needed is an arrangement for keeping the ATD clean of dust and other particulate matter using a source of clean air or gas that avoids the expense of using a conduit and that does not rob some of the power from the cooling fan.
It is an object of this invention to provide such an arrangement.
In accordance with a first aspect of the invention, an ATD has a shield that substantially encloses the outer surface of the ATD. This shield is coupled to the exhaust gas outlet of the ATD. At least a portion of the treated exhaust gas (i.e. the exhaust gas leaving the ATD) is conducted into the space between the outer surface of the ATD and the shield. Various structures (described in more detail below) conduct at least a portion of the treated exhaust gas into the space defined between the shield and the ATD at a higher pressure than the surrounding atmosphere and therefore slightly pressurizes the space. The slightly pressurized treated exhaust gas displaces the lower pressure ambient air that contains suspended dust and combustible particulates. The treated exhaust gas has almost no suspended combustible matter or dust since it has already been combusted in the internal combustion engine and has further passed through the ATD element. This arrangement prevents or significantly reduces the dust and combustible particulate matter entrained in the surrounding atmosphere from settling and accumulating on the outer surface of the ATD.
All the exhaust gas exiting the ATD can be communicated into the space between the shield and he ATD. Alternatively, only a portion of the gas may be communicated into the space, leaving the remainder (and preferably the majority) of the exhaust gas to continue out an exhaust pipe that is coupled to and extends from the exhaust gas outlet of the ATD.
A venturi or other structure may be located in an exhaust gas line extending from the outlet of the ATD to the space between the shield and the ATD to entrain air from the atmosphere surrounding the ATD. This arrangement preferably uses the kinetic energy of the exhaust gas to entrain atmospheric air with the exhaust gas diverted into the space. The outlet of this venturi or other structure may then be conducted through a conduit to the space between the shield and the ATD to thereby insert this exhaust and air mixture into the space between the shield and the ATD.
In the discussion herein, “after-treatment device” refers to any device for chemically converting or processing exhaust gas from an internal combustion engine before the release of the exhaust gas into the atmosphere, including but not limited to diesel particulate filters and catalytic converters.
The term “pressure” or “pressurize” is used herein. The amount of pressure that is deemed to constitute being “pressurized” is an amount of pressure sufficient to prevent substantially all ambient air from entering and circulating freely within the shielding in quantities that permit combustible quantities of dust or particulate matter to settle on the after-treatment device.
Referring now to the drawings and more particularly to
The exhaust manifold 102 is coupled, as by an exhaust gas inlet conduit 108, to an inlet of an after-treatment device (ATD) 110, which is here shown as a catalytic converter or a diesel particulate filter.
The ATD has a generally cylindrical body containing an after-treatment element 111 (shown only in
The exhaust gas outlet conduit 112 empties into the space defined between the shield and the ATD 110 and exits through any one or more of top aperture 202, end aperture 204, and bottom aperture 206. The flow of exhaust gas into the space creates a pressure slightly above atmospheric pressure in the space and therefore prevents dust and particulate carrying atmospheric air at the outer surface of the shield 200 from directly entering the shield through any one or more of the apertures 202, 204, and 206 and depositing the dust and particulates on the outer surface of ATD 110.
In this arrangement, substantially all the exhaust is communicated into the space between the ATD and the shield. This is not necessary, however, as the next figure illustrates.
In the
The third embodiment (
In an alternative arrangement (not shown), a conduit without the venturi can be employed to conduct at least a portion of the treated exhaust gas to a location on the outside of the shield and the space, and then to conduct it back through the shield and into the space as shown in
The fourth embodiment (
Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
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