Patent Application
20080307780
The present disclosure relates generally to diesel emission abatement devices.
Untreated internal combustion engine emissions (e.g., diesel emissions) include various effluents such as NOx, hydrocarbons, and carbon monoxide, for example. Moreover, the untreated emissions from certain types of internal combustion engines, such as diesel engines, also include particulate carbon-based matter or “soot”. Federal regulations relating to soot emission standards are becoming more and more rigid thereby furthering the need for devices and/or methods which remove soot from engine emissions.
The amount of soot released by an engine system can be reduced by the use of an emission abatement device such as a filter or trap. Such a filter or trap is periodically regenerated in order to remove the soot therefrom. The filter or trap may be regenerated by use of a fuel-fired burner to burn the soot trapped in the filter. In such a case, the fuel-fired burner generates heat which is transferred to the downstream filter to burn the soot trapped in the filter. Poor temperature distribution of the generated heat can cause some regions of the filter to be hotter than desired, and other regions to be colder than desired. In the regions that are hotter than desired, the filter can potentially be damaged, whereas the colder regions may not be regenerated.
According to one aspect of the disclosure, an emission abatement assembly includes a fuel-fired burner having a combustion chamber and a particulate filter positioned downstream of the fuel-fired burner. A mixing baffle is positioned between the fuel-fired burner and the particulate filter.
According to another aspect of the disclosure, an emission abatement assembly includes a particulate filter and a fuel-fired burner positioned upstream of the particulate filter. The fuel-fired burner includes a housing having an exhaust gas inlet port. The fuel-fired burner also includes a combustion chamber having a shroud secured thereto. The combustion chamber and the shroud cooperate to separate a flow of exhaust gas entering the housing through the exhaust gas inlet port into a combustion flow which is advanced through the combustion chamber of the fuel-fired burner, and a bypass flow which is bypassed around the combustion chamber of the fuel-fired burner. The fuel-fired burner also includes a mixing baffle positioned downstream of the combustion chamber and upstream of the particulate filter. The mixing baffle is configured to mix the combustion flow and the bypass flow.
According to yet another aspect of the disclosure, an emission abatement assembly includes a fuel-fired burner having a combustion chamber and a particulate filter positioned downstream of the fuel-fired burner. The assembly also includes a mixing baffle having a collector plate with a hole defined therein, a perforated ring secured to the collector plate, and a diverter plate secured to the perforated ring. The mixing plate is positioned between the fuel-fired burner and the particulate filter such that both a flow of exhaust gas advancing through the combustion chamber and a flow of exhaust gas bypassing the combustion chamber are advanced through the hole in the collector plate.
According to yet another aspect of the disclosure, a method of operating a fuel-fired burner of an emission abatement assembly includes advancing a flow of exhaust gas into a housing of the fuel-fired burner. The method also includes separating the flow of exhaust gas into a combustion flow which is advanced through a combustion chamber of the fuel-fired burner, and a bypass flow which is bypassed around the combustion chamber of the fuel-fired burner. The method also includes directing the combustion flow and the bypass flow radially outwardly with a flow mixer located downstream of the combustion chamber.
Referring now to
As shown in
The combustion chamber 18 has a number of gas inlet openings 22 defined therein. Engine exhaust gas is permitted to flow into the combustion chamber 18 through the inlet openings 22. In such a way, a flame present inside the combustion chamber 18 is protected from the full engine exhaust gas flow, while controlled amounts of engine exhaust gas are permitted to enter the combustion chamber 18 to provide oxygen to facilitate combustion of the fuel supplied to the burner 12. Exhaust gas not entering the combustion chamber 18 is directed through a number of openings 24 defined in a shroud 26.
The fuel-fired burner 12 includes an electrode assembly having a pair of electrodes 28, 30. When power is applied to the electrodes 28, 30, a spark is generated in the gap 32 between the electrodes 28, 30. Fuel enters the fuel-fired burner 12 through a fuel inlet nozzle 34 and is advanced through the gap 32 between the electrodes 28, 30 thereby causing the fuel to be ignited by the spark generated by the electrodes 28, 30. It should be appreciated that the fuel entering the nozzle 34 is generally in the form of a controlled air/fuel mixture.
The fuel-fired burner 12 also includes a combustion air inlet 36. An air pump, or other pressurized air source such as the vehicle's turbocharger or air brake system, generates a flow of pressurized air which is advanced to the combustion air inlet 36. During regeneration of the particulate filter 14, a flow of air is introduced into the fuel-fired burner 12 through the combustion air inlet 36 to provide oxygen (in addition to oxygen present in the exhaust gas) to sustain combustion of the fuel.
As shown in
The filter housing 44 is secured to a housing 46 of a collector 48. Specifically, an outlet 50 of the filter housing 44 is secured to an inlet 52 of the collector housing 46. As such, processed (i.e., filtered) exhaust gas exiting the filter substrate 42 (and hence the filter housing 44) is advanced into the collector 48. The processed exhaust gas is then advanced into the exhaust pipe (not shown) and hence released to the atmosphere through a gas outlet 54. It should be appreciated that the gas outlet 54 may be coupled to the inlet (or a pipe coupled to the inlet) of a subsequent emission abatement device (not shown) if the engine's exhaust system is equipped with such a device.
Referring back to
The mixing baffle 56 functions to mix the hot flow of exhaust gas directed through the combustion chamber and cold flow of exhaust gas that bypasses the combustion chamber during filter regeneration thereby introducing a mixed flow of exhaust gas into the particulate filter 14. In particular, as described above, the flow of exhaust gas entering the emission abatement assembly 10 is split into two flows—(i) a cold bypass flow which bypasses the combustion chamber 18 and is advanced through the openings 24 of the shroud 26 and, (ii) a hot combustion flow which is advanced into the combustion chamber 18 where it is significantly heated by the flame present therein. The mixer baffle 56 forces both flows together through a narrow area and then causes such a concentrated flow to then flow radially outwardly thereby mixing the two flows together. To do so, the cold flow of exhaust gas advances through the openings 24 in the shroud 26 and thereafter is directed into contact with the upstream face 66 of the collector plate 62. The shape of the collector plate 62 directs the cold flow toward its hole 64.
Likewise, the hot flow of exhaust gas is directed toward the hole of the collector plate 62. In particular, the hot flow of exhaust gas is prevented from axially exiting the combustion chamber 18 by a domed flame catch 68. The flame catch 68 forces the hot flow of exhaust gas radially outwardly through a number of openings 70 defined in a perforated annular ring 72 which is similar to the perforated annular ring 62 of the mixing baffle 56. The hot flow of exhaust gas is then directed toward the upstream face 66 of the collector plate 62 by a combination of surfaces including the downstream face 74 of the shroud 26 and the inner surface of the burner housing 16. The hot flow of exhaust gas then contacts the upstream face 66 of the collector plate where the shape of the plate 62 causes the hot flow of exhaust gas to be directed toward the hole 64. This begins the mixing of the hot flow of exhaust gas with the cold flow of exhaust gas.
Mixing is continued as the cold and hot flows of exhaust gas enter the hole 64 of the collector plate 62. The partially mixed flow of gases are directed into contact with the diverter plate 58. The diverter plate 58 blocks the linear flow of gases and directs them outwardly in radial directions away from the diverter plate 58. The flow of exhaust gases is then directed through a number of openings 76 formed in the perforated annular ring 62 of the mixing baffle 56. This radial outward flow of exhaust gases impinges on the inner surface of the burner housing 16 and is directed through the outlet 40 of the burner housing 16 and into the inlet of the filter housing 44 where the mixed flow of exhaust gas is utilized to regenerated the filter substrate 42.
Hence, as described above, the mixing baffle 56 forces the mixing of the non-homogeneous exhaust gas flow through a narrow area, and then causes the mixed flow to expand outwardly. This prevents the formation of a center flow or center jet of hot gas from being impinged on the filter substrate 42. In short, a more homogeneous mixture of the hot and cold flows is created prior to introduction of the combined flow onto the face of the filter substrate thereby increasing filter regeneration efficiency and reducing the potential for filter damage due to hot spots.
While the disclosure is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and has herein be described in detail. It should be understood, however, that there is no intent to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
There are a plurality of advantages of the present disclosure arising from the various features of the apparatus, systems, and methods described herein. It will be noted that alternative embodiments of the apparatus, systems, and methods of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of apparatus, systems, and methods that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present disclosure.
For example, the mixing baffle 56 finds application outside of a particulate filter that is regenerated by a fuel-fired burner. For example, the mixing baffle 56 may be used to mix urea with exhaust gas prior to introduction into a urea-SCR catalyst.
