The present disclosure relates generally to a particulate filter for an exhaust aftertreatment system of a machine, and more particularly to a particulate filter including at least one non-perforated tubular filter element having a fibrous metallic filter medium disposed therein.
Operation of internal combustion engines typically results in the generation of particulate matter including inorganic species (ash), sulfates, small organic species generally referred to as soluble organic fraction (SOF), and hydrocarbon particulates or “soot.” Various strategies have been used for preventing the release of such particulate matter into the environment, including the use of particulate filters, available in a variety of designs. Particulate filters are used in both on-highway and off-highway applications, and typically include a porous ceramic material positioned in the path of exhaust gas exiting the engine. The particulate filter traps the particulate matter from the exhaust gas, thus preventing its release into the environment.
Periodically, or once a substantial amount of particulate matter is collected within the particulate filter, it must be cleaned out, or regenerated, to prevent blockage. While a variety of strategies of both active and passive regeneration are known, a common regeneration method includes quickly heating the particulate matter to a temperature at which the trapped particles oxidize or combust. This involves heating the exhaust gas and, as a result, the particulate filter to very high temperatures. These wide temperature swings experienced by particulate filters, particularly during regeneration, may result not only in physical damage but also in chemical degradation of the filter material over time.
Another factor to be considered, relevant to particulate filter design, includes the use of particulate filters in off-highway applications. Specifically, many off-highway machines operate over relatively rugged terrain where physical shocks may be experienced. In the case of ceramic particulate filters, in particular, it should be appreciated that such impact shocks may cause the filter material to crack, thus reducing the performance of the particulate filter. Although more recently developed filter materials, such as fibers, wool, and yarns, both metallic and ceramic, may be less susceptible to impact induced damage, they may still suffer from various other shortcomings, such as chemical degradation caused by extreme regeneration temperatures.
Another factor to consider that may be relevant to all on-highway and off-highway applications, regardless of the filter material, relates to the limited amount of space available for mounting particulate filters on or within machines or vehicles. While certain older designs may have had ample space available for mounting particulate filters, in certain newer designs space may be at more of a premium. It will thus be readily apparent that engineers are faced with a variety of challenges in designing suitable particulate filters, namely, fitting particulate filters of suitable size, shape, durability, and material within increasingly restricted spatial envelopes.
The present disclosure is directed to one or more of the problems set forth above.
In one aspect, a particulate filter includes a filter element comprising a non-perforated tube having an exhaust inlet at a first end and an exhaust outlet at a second end. A fibrous metallic filter medium is disposed within the filter element. At least one metallic foam disk is attached at the second end of the filter element.
In another aspect, a machine includes an exhaust aftertreatment system having a predefined spatial envelope for a particulate filter assembly. A housing of the particulate filter assembly is shaped to fit within the predefined spatial envelope. A plurality of filter elements are arranged in a bundle and disposed within the housing. The bundle includes a number and an arrangement of filter elements selected to fit within the housing. Each of the filter elements includes a non-perforated tube having an exhaust inlet at a first end and an exhaust outlet at a second end, and includes a fibrous metallic filter medium disposed therein.
In yet another aspect, a method of filtering an exhaust gas includes a step of directing the exhaust gas through each of a plurality of tubular filter elements of a particulate filter. Particulate matter from the exhaust gas is trapped using a fibrous metallic filter medium disposed within each of the filter elements. The exhaust gas is also passed through at least one metallic foam element positioned at a second end of the particulate filter.
An exemplary embodiment of a machine 10 is shown generally in
The engine system 18 may include an internal combustion engine 22, such as a compression ignition engine, and an exhaust aftertreatment system 24 including a particulate filter assembly 26. The particulate filter assembly 26 includes a design and configuration adapted to fit the particulate filter assembly 26 within a predefined spatial envelope 28. The predefined spatial envelope 28 may be positioned within the engine system 18, as shown, or elsewhere on the machine 10, and may include a space that is dictated by a variety of factors, including the size and shape of various components of the engine system 18. Such components may include, by way of example only, a turbocharger 30 coupled with an exhaust passage 32 of the engine system 18, the hood 20, and the frame 12. It should be appreciated that various other components may dictate the location, size, and shape of the predefined spatial envelope 28, depending on the design of the machine 10.
Turning now to
The particulate filter assembly 26 also includes at least one filter element 50. Although an embodiment including only one filter element 50 disposed within the housing 40 is contemplated, an embodiment including a plurality of filter elements 50 is described. The plurality of filter elements 50 may include identical filter elements 50 arranged in a bundle 52 and disposed within the housing 40. The bundle 52 may include a number, such as, for example, twenty or more, and an arrangement of filter elements 50 selected to fit within the housing 40. Each of the filter elements 50, described in greater detail below, may be configured to filter exhaust gas passing from the exhaust gas inlet 46 to the exhaust gas outlet 48.
The particulate filter assembly 26 may also include a first support plate 54 having a plurality of holes 56 configured to support first ends of each of the filter elements 50. The particulate filter assembly 26 may also include a second support plate 58 having holes 60 for supporting second ends of the filter elements 50. The holes 56 and 60 may be arranged in a pattern corresponding to an arrangement and distribution of filter elements 50 in bundle 52. Each of the support plates 54 and 58 may include an outer perimeter or edge 62 and 64, respectively, which is matched to a shape of the housing 40 or, more specifically, an intermediate portion 66 of the housing 40. For example, support plates 54 and 58 may have oblong shapes similar to that shown in
An alternative embodiment of particulate filter assembly 26, shown in partial cutaway, is depicted in
The particulate filter assembly 26 may also include the bundle 52 of filter elements 50; however, the support plates 54 and 58 depicted in
Each of the filter elements 50 may include a non-perforated tube 90, as shown in
A first metallic foam element 102 is attached at the second end 98 of the filter element 50. The first metallic foam element 102 may, for example, include a metallic foam retainer or disk disposed within the non-perforated tube 90 for retaining the fibrous metallic filter medium 100 within the non-perforated tube 90. Although the first metallic foam element 102 is shown disposed within the non-perforated tube 90, it should be appreciated that the metallic foam element 102 may be otherwise attached, such as by brazing, at the second end 98 thereof. For embodiments utilizing a plurality of filter elements 50, a metallic foam elements 102 may be disposed within each of the filter elements 50 or, alternatively, one metallic foam element 102 may be positioned at a second end of the bundle 52. A second metallic foam element 104 may be attached at the first end 94 of the filter element 50. The second metallic foam element 104 may also include a metallic foam retainer or disk disposed within the non-perforated tube 90. The first and second metallic foam elements 102 and 104 may, for example, include a nickel based alloy or other highly porous foam.
Filter element 50 is shown in
Regeneration of the particulate filter assembly 26, according to one embodiment, may employ a heating device configured to heat filter elements 50 and, in particular, the fibrous metallic filter medium 100, to a temperature sufficient to initiate and maintain combustion of accumulated soot. In one contemplated embodiment, an auxiliary regeneration device will be positioned upstream of particulate filter assembly 26 to inject and ignite fuel in the engine exhaust stream which is burned to increase the temperature of exhaust gases passing through the particulate filter assembly 26. Alternative strategies could include passive regeneration from engine heat or possibly electric heater(s) disposed between tubes 50.
Any of the fibrous metallic filter medium 100, the first metallic foam element 102, and the second metallic foam element 104 may include an oxidation catalyst coating or other catalyst coating capable of promoting particulate filtration and/or regeneration. According to one embodiment, any of the fibrous metallic filter medium 100, the first metallic foam element 102, and the second metallic foam element 104 may include a well known NOX catalyst. According to another embodiment, the second metallic foam element 104 may include an oxidation catalyst coating for converting NO from the exhaust gas into NO2. The presence of NO2 within the upstream exhaust gas may decrease a regeneration temperature of the particulate filter assembly 26. Specifically, the presence of NO2 in the exhaust stream may improve the efficiency of a downstream catalyst coating of the first metallic foam element 102 that assists in the decomposition of NO and NO2 into N2.
According to an embodiment utilizing both of the first metallic foam element 102 and the second metallic foam element 104, it should be appreciated that an orientation of the filter elements 50 may be reversed with respect to an exhaust gas entry. Specifically, a position of the bundle 52 of filter elements 50 may be reversed so that the second ends 98 of the filter elements 50 are positioned adjacent the inlet portion 42 of housing 40 and the first ends 94 are positioned adjacent the outlet portion 44. This symmetrical configuration and reversible nature of the particulate filter assembly 26 may allow for extended usage of the particulate filter assembly 26 before an ash removal process is necessary, or after repeated ash cleanings have resulted in degraded performance in one direction.
Turning now to
The bundle 52 includes a longitudinal axis A, and may be symmetrical with respect to an axis perpendicular to the axis A. According to the embodiment of
The particulate filter of the present disclosure may find application in a variety of on-highway, off-highway, or even stationary machines having exhaust aftertreatment systems. Although a track-type tractor is depicted, it should be appreciated that the particulate filter, as described herein, may be used with wheel loaders, articulated trucks, or other types of construction, mining, and agricultural machines. Further, the particulate filter, as described, may be specifically applicable to exhaust aftertreatment systems having predefined spatial envelopes that are subject to space and shape constraints.
Referring to
The particulate filter assembly 26 includes a housing 40 that is shaped to fit within the predefined spatial envelope 28 and that includes at least one filter element 50 disposed therein. According to one embodiment, the particulate filter assembly 26 includes a plurality of filter elements 50 arranged in a bundle 52 and disposed within the housing 40. The bundle 52 may include a number, such as, for example, twenty or more, and an arrangement of filter elements 50 selected to fit within the housing 40.
Each of the filter elements 50 includes a non-perforated tube 90 having an exhaust inlet 92 at a first end 94 and an exhaust outlet 96 at a second end 98, and a fibrous metallic filter medium 100 disposed therein. Non-sintered metal fibers may be less costly than sintered metal fibers and, therefore, may be preferable as the fibrous metallic filter medium 100. A first metallic foam element 102 may be attached at the second end 98 of the filter element 50. According to one embodiment, a second metallic foam element 104 is also attached at the first end 94 of the filter element 50. This substantially symmetrical design may allow the filter elements 50 to be reversed with respect to an exhaust gas flow.
First and second support plates 54 and 58 may be used to support first and second ends of the filter elements 50, as shown in the embodiment of
Exhaust gas, according to the present disclosure, may be filtered by directing the exhaust gas through each of the plurality of tubular filter elements 50 of the particulate filter assembly 26. Particulate matter from the exhaust gas is trapped using the fibrous metallic filter medium 100 disposed within each of the filter elements 50. The exhaust gas is then passed through at least one metallic foam element, such as first metallic foam element 102. The first metallic foam element 102 is positioned downstream of the fibrous metallic filter medium 100 and may retain the filter medium 100 within each of the filter elements 50. It should be appreciated that the first metallic foam element 102 may also trap particulate matter from the exhaust gas.
The filter elements 50 may also include a second metallic foam element 104 positioned at first ends 94 of the filter elements 50. The second metallic foam element 104 may be similar to the first metallic foam element 102 in both form and function. It should be appreciated that if the orientation of the filter elements 50 is reversed with respect to an exhaust gas flow, the second metallic foam element 104 may then be positioned downstream of the fibrous metallic filter medium 100 and may retain the filter medium 100 within each of the filter elements 50. It should also be appreciated that one or more of the fibrous metallic filter medium 100, first metallic foam element 102, and second metallic foam element 104 may include a catalyst coating, such as, for example, an oxidation catalyst, for promoting particulate filtering and/or regeneration.
The particulate filter assembly 26, as described herein, includes a bundle of filter elements 50 that may be at least partially matched to a shape of the housing 40, which is shaped to fit within the predefined spatial envelope 28. Therefore, rather than being restricted solely to cylindrical shapes or other universal designs, the present disclosure provides for vastly greater flexibility in filter shape design. Specifically, the number and arrangement of filter elements 50 within the bundle 52 may be varied to fit the particulate filter assembly 26 within spatially restrictive or spatially complex envelopes within the machine 10. Additionally, the generally symmetrical nature of the filter elements 50 of bundle 52 may allow the particulate filter to be reversed, thus extending an effective usage period of the particulate filter assembly 26.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.