WO2022149168A1

WO2022149168A1 - Particulate matter filter assembly

Info

Publication number: WO2022149168A1
Application number: PCT/IN2022/050019
Authority: WO
Inventors: Sunil Reddy Konatham; Avichal Mishra; Parth Sarthi Pandey; Tushar R Batham
Original assignee: Chakr Innovation Private Limited
Priority date: 2021-01-08
Filing date: 2022-01-08
Publication date: 2022-07-14

Abstract

A particulate matter filter assembly (100) for an exhaust aftertreatment system is disclosed. The particulate matter filter assembly (100) comprises a housing (102) defining an inlet channel (104) and an outlet channel (106) adapted to allow the exhaust stream to enter and exit from the housing (102), respectively. The particulate matter filter assembly (100) further comprises a first set of filter units (114) positioned downstream of the inlet channel (104) in an exhaust stream direction, and a second set of filter units (116) positioned downstream of the first set of filter units (114) in the exhaust stream direction. Further, a ratio of a distance (L) between the first set of filter units (114) and the second set of filter units (116) to a length (L1) of the first set of filter units (114) along a longitudinal axis of the housing (102) lies within a range of 0.05 to 1.2.

Description

“PARTICULATE MATTER FILTER ASSEMBLY”

TECHNICAL FIELD

[001] The present disclosure relates to the field of exhaust aftertreatment systems for engines. Particularly, the present disclosure relates to a particulate matter filter assembly for an exhaust aftertreatment system adapted to be used in a diesel genset.

BACKGROUND

[002] The information in this section merely provides background information related to the present disclosure and may not constitute prior art(s) for the present disclosure. [003] In general, diesel emissions are produced as by-products of diesel combustion in diesel gensets and vehicles. Said diesel emissions can harm both the environment and the people.

[004] A major part of the diesel emissions is composed of diesel particulate matter. Diesel particulate matter is mainly soot and/or unburnt carbon particles. Commonly used techniques to trap diesel particulate matter include using diesel traps, for example, diesel particulate filters (DPFs), in exhaust aftertreatment systems, that filters soot and/or unburnt carbon particles. Over prolonged use, as the diesel emissions pass through the particulate filter, a layer of soot collects on the surface of channels of the particulate filter and permeability of the diesel emissions through the particulate filter decreases. This lower permeability causes a pressure drop in the particulate filter, thereby gradually raising a back pressure in the exhaust aftertreatment and the diesel genset. This rise in the back pressure causes the exhaust aftertreatment system and the diesel genset to work harder, often leading to increased fuel consumption due to increased pumping losses.

[005] Other commonly known diesel traps include partial flow filters (PFFs), which although lowers the back pressure in the particulate filters, but the particulate matter reduction efficiency or operation efficiency of the partial flow filters lies within the range of 30-40%.

[006] Further, in developing countries like India, the quality of fuel, for example, gasoline or diesel, used in the gensets is compromised compared to the fuels used in the gensets in countries like the United States. Also, every country has varying standards for gasoline or diesel as per their market needs, and they necessarily do not match with the international standards. For example, emission norms in developing countries are relaxed compared to the developed countries. Furthermore, it has been largely observed that many engines and/or gensets operated in the developing countries employ obsolete technologies, and thus, have very stringent back pressure limits. Therefore, the diesel emissions are high in the developing countries and the known particulate filters have reduced life cycle, thereby increased cost of the overall operation.

[007] Accordingly, there remains a need for an improved particulate matter filter assembly that ensures low back pressure of the exhaust aftertreatment system, reduced risk of thermal rundown of the exhaust aftertreatment system, high ash carrying capacity of the particulate matter filter assembly, and high operation efficiency of the exhaust aftertreatment system.

SUMMARY

[008] The one or more shortcomings of the prior art are overcome by the system/assembly as claimed, and additional advantages are provided through the provision of the system/assembly as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

[009] Pursuant to the embodiments of the present disclosure, in an aspect, a particulate matter filter assembly for an exhaust aftertreatment system is disclosed. The particulate matter filter assembly is adapted to trap and oxidize soot and/or unburnt carbon particles contained in an exhaust stream of a diesel engine fluidly coupled with the exhaust aftertreatment system. The particulate matter filter assembly comprises a housing and a plurality of filter units. The housing defines an inlet channel adapted to allow the exhaust stream to enter into the housing and an outlet channel adapted to allow the exhaust stream to exit from the housing. The plurality of filter units is disposed between the inlet channel and the outlet channel of the housing and allows the exhaust stream to pass therethrough for treatment of the exhaust stream. The plurality of filter units comprises a first set of filter units positioned downstream of the inlet channel of the housing in an exhaust stream direction, and a second set of filter units positioned downstream of the first set of filter units in the exhaust stream direction. A ratio of a distance between the first set of filter units and the second set of filter units to a length of the first set of filter units along a longitudinal axis of the housing lies within a range of 0.05 to 1.2. [010] In another non limiting embodiment of the present disclosure, the first set of filter units comprises a first filter unit having a length along the longitudinal axis of the housing and a diameter transverse to the longitudinal axis of the housing, and the second set of filter units comprises a second filter unit having a length along the longitudinal axis of the housing and a diameter transverse to the longitudinal axis of the housing. A ratio of a distance between the first filter unit and the second filter unit to the length of the first filter unit along the longitudinal axis of the housing lies within a range of 0.05 to 1.2.

[Oil] In another non limiting embodiment of the present disclosure, a ratio of the diameter of the first filter unit to the length of the first filter unit lies within a range of 1.78 to 7.15.

[012] In another non limiting embodiment of the present disclosure, a ratio of the diameter of the second filter unit to the length of the second filter unit lies within a range of 1.78 to 7.15.

[013] In another non limiting embodiment of the present disclosure, a ratio of the length of the first filter unit to the length of the second filter unit lies within a range of 1 to 3.5.

[014] In another non limiting embodiment of the present disclosure, a ratio of the diameter of the first filter unit to the diameter of the second filter unit lies within a range of 1 to 2.

[015] In another non limiting embodiment of the present disclosure, the filter units of the first set of filter units and the second set of filter units comprises a plurality of cell spaces that are partitioned by porous cell walls, and porosity of the filter units lies within a range of 20% to 60%.

[016] In another non limiting embodiment of the present disclosure, a ratio of mean pore size of the first set of filter units to mean pore size of the second set of filter units lies within a range of 1 to 2.

[017] In another non limiting embodiment of the present disclosure, a cell density in the first and second set of filter units varies within a range of 70 cpsi (cells per square inch) to 400 cpsi.

[018] In another non limiting embodiment of the present disclosure, a ratio of cell density in the second set of filter units to cell density in the first set of filter units lies within a range of 1 to 3. [019] In another non limiting embodiment of the present disclosure, a ratio of a side length of inflow cell spaces to a side length of outflow cell spaces in the filter units lies within a range of 1.1 to 2.2.

[020] In another non limiting embodiment of the present disclosure, a ratio of area of closed inflow cell spaces to open outflow cell spaces, at an outlet end, of the first and second filter units may vary within the range of 1.21 to 4.

[021] In another non limiting embodiment of the present disclosure, a ratio of a space velocity of the exhaust stream in the first filter unit to a space velocity of the exhaust stream in the second filter unit lies within a range of 0.25 to 1. [022] In another non limiting embodiment of the present disclosure, filter units of the first set of filter units and the second set of filter units are coated with a catalyst to promote oxidation of soot and/or unburnt carbon particles.

[023] In another non limiting embodiment of the present disclosure, the catalyst may be selected from the group consisting of platinum, palladium, rhodium, rare earth metals, and transition metals.

[024] In another non limiting embodiment of the present disclosure, density of the catalyst coated on the first set of filter units is equal to or more than density of the catalyst coated on the second set of filter units.

[025] In another non limiting embodiment of the present disclosure, the particulate matter filter assembly further comprises an oxidation catalyst positioned upstream of the first set of filter units.

[026] In another non limiting embodiment of the present disclosure, a ratio of coating density of catalyst on the oxidation catalyst to coating density of catalyst on the first set of filter units or the second set of filter units vary within a range of 2 to 30. [027] In another non limiting embodiment of the present disclosure, a ratio of total coating of catalyst by weight on the oxidation catalyst (124) to total coating of catalyst on the filter units of the particulate matter filter assembly vary within a range of 0.4 to 29.

[028] In another non limiting embodiment of the present disclosure, a ratio of space velocity of the exhaust stream in the oxidation catalyst to space velocity of the exhaust stream in the first set of filter units or the second set of filter units vary within a range of 0.25 to 3.2. [029] In another non limiting embodiment of the present disclosure, the first set of filter units and the second set of filter units are made of cordierite, aluminium titanate, or silicon carbide.

[030] In another non limiting embodiment of the present disclosure, the first set of filter units comprises one or more first filter units arranged parallel to each other along the longitudinal axis of the housing, and the second set of filter units comprises one or more second filter units arranged parallel to each other along the longitudinal axis of the housing. A ratio of a distance between the first filter units and the second filter units to a length of the first filter units along the longitudinal axis of the housing lies within a range of 0.05 to 1.2.

[031] In another non limiting embodiment of the present disclosure, the particulate matter filter assembly further comprises a third set of filter units positioned downstream of the second set of filter units in the exhaust stream direction.

[032] Some of the advantages offered by the particulate matter filter assembly of the present disclosure include high particulate matter reduction efficiency in the range of 70-80%, ultra-low back pressure of the exhaust aftertreatment system, high ash carrying capacity of the particulate matter filter assembly, thermal rundown risk reduction of the exhaust aftertreatment, size reduction of the particulate matter filter assembly, etc. [033] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

[034] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF FIGURES

[035] The novel features and characteristics of the disclosure are set forth in the description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

Figure 1 illustrates a perspective view of a particulate matter filter assembly, in accordance with an embodiment of the present invention;

Figure 2 illustrates a side cross-sectional view of the particulate matter filter assembly of Figure 1, viewed along a plane A-A, in accordance with an embodiment of the present invention;

Figure 3 is a front perspective view of an inlet channel of the particulate matter filter assembly, in accordance with an embodiment of the present invention;

Figure 4 illustrates a side cross-sectional view of the inlet channel of Figure 3, viewed along a plane F-F, in accordance with an embodiment of the present invention;

Figure 5 is a rear perspective view of an outlet channel of the particulate matter filter assembly, in accordance with an embodiment of the present invention;

Figure 6 illustrates a side cross-sectional view of the outlet channel of Figure 5, viewed along a plane J-J, in accordance with an embodiment of the present invention;

Figure 7 illustrates a side cross-sectional view of a first filter unit of the particulate matter filter assembly of Figures 1 and 2, in accordance with an embodiment of the present invention;

Figure 8 illustrates a side cross-sectional view of a second filter unit of the particulate matter filter assembly of Figures 1 and 2, in accordance with an embodiment of the present invention;

Figure 9 is a front view of the first filter unit and the second filter of the particulate matter filter assembly of Figures 7 and 8, respectively, at an inlet end thereof, in accordance with an embodiment of the present invention;

Figure 10 is a rear view of the first filter unit and the second filter of the particulate matter filter assembly of Figures 7 and 8, respectively, at an outlet end thereof, in accordance with an embodiment of the present invention;

Figure 11 illustrates an arrangement of plurality of filter units having their respective longitudinal axis arranged parallel to each other, in accordance with an embodiment of the present invention; and

Figure 12 illustrates a side cross-sectional view of the arrangement of plurality of filter units of Figure 11, viewed along a plane P-P, in accordance with an embodiment of the present invention. [036] Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present disclosure.

DETAILED DESCRIPTION

[037] While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the figures and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure as defined by the appended claims.

[038] Before describing detailed embodiments, it may be observed that the novelty and inventive step that are in accordance with the present disclosure resides in a particulate matter filter assembly. It is to be noted that a person skilled in the art can be motivated from the present disclosure and modify the various constructions of the particulate matter filter assembly. However, such modification should be construed within the scope and spirit of the disclosure. Accordingly, the drawings are showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein. [039] In the present disclosure, the term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or implementation of the present subject matter described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[040] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such setup or device. In other words, one or more elements in a system or apparatus proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus. [041] The terms like “at least one” and “one or more” may be used interchangeably or in combination throughout the description.

[042] Pursuant to the embodiments of the present disclosure, in an aspect, a particulate matter filter assembly for an exhaust aftertreatment system is disclosed. The particulate matter filter assembly is adapted to trap and oxidize soot and/or unburnt carbon particles contained in an exhaust stream of a diesel engine fluidly coupled with the exhaust aftertreatment system. The particulate matter filter assembly comprises a housing and a plurality of filter units. The housing defines an inlet channel adapted to allow the exhaust stream to enter into the housing and an outlet channel adapted to allow the exhaust stream to exit from the housing. The plurality of filter units is disposed between the inlet channel and the outlet channel of the housing and allows the exhaust stream to pass therethrough for treatment of the exhaust stream. The plurality of filter units comprises a first set of filter units positioned downstream of the inlet channel of the housing in an exhaust stream direction, and a second set of filter units positioned downstream of the first set of filter units in the exhaust stream direction. A ratio of a distance between the first set of filter units and the second set of filter units to a length of the first set of filter units along a longitudinal axis of the housing lies within a range of 0.05 to 1.2.

[043] The first set of filter units comprises a first filter unit having a length along the longitudinal axis of the housing and a diameter transverse to the longitudinal axis of the housing, and the second set of filter units comprises a second filter unit having a length along the longitudinal axis of the housing and a diameter transverse to the longitudinal axis of the housing. A ratio of a distance between the first filter unit and the second filter unit to the length of the first filter unit along the longitudinal axis of the housing lies within a range of 0.05 to 1.2.

[044] In an embodiment, a ratio of the diameter of the first filter unit to the length of the first filter unit lies within a range of 1.78 to 7.15. In some embodiments, a ratio of the diameter of the second filter unit to the length of the second filter unit lies within a range of 1.78 to 7.15. In further embodiments, a ratio of the length of the first filter unit to the length of the second filter unit lies within a range of 1 to 3.5. In yet further embodiments, a ratio of the diameter of the first filter unit to the diameter of the second filter unit lies within a range of 1 to 2.

[045] Further, the filter units of the first set of filter units and the second set of filter units comprise a plurality of cell spaces that are partitioned by porous cell walls, and porosity of the filter units lies within a range of 20% to 60%. In an embodiment, a ratio of mean pore size of the first set of filter units to mean pore size of the second set of filter units lies within a range of 1 to 2. In some embodiments, a cell density in the first and second set of filter units varies within a range of 70 cpsi (cells per square inch) to 400 cpsi. In further embodiments, a ratio of cell density in the second set of filter units to cell density in the first set of filter units lies within a range of 1 to 3. Also, a ratio of a side length of inflow cell spaces to a side length of outflow cell spaces in the filter units lies within a range of 1.1 to 2.2. A ratio of area of closed inflow cell spaces to open outflow cell spaces, at an outlet end, of the first and second filter units may vary within the range of 1.21 to 4. A ratio of a space velocity of the exhaust stream in the first filter unit to a space velocity of the exhaust stream in the second filter unit lies within a range of 0.25 to 1.

[046] In some embodiments, filter units of the first set of filter units and the second set of filter units are coated with a catalyst to promote oxidation of soot and/or unburnt carbon particles. In further embodiments, the catalyst may be selected from the group consisting of platinum, palladium, rhodium, rare earth metals, and transition metals. A density of the catalyst coated on the first set of filter units is equal to or more than density of the catalyst coated on the second set of filter units.

[047] Further, the particulate matter filter assembly comprises an oxidation catalyst positioned upstream of the first set of filter units. A ratio of coating density of catalyst on the oxidation catalyst to coating density of catalyst on the first set of filter units or the second set of filter units vary within a range of 2 to 30. Also, a ratio of total coating of catalyst by weight on the oxidation catalyst (124) to total coating of catalyst by weight on the filter units of the particulate matter filter assembly (100) vary within a range of 0.4 to 29. Further, a ratio of space velocity of the exhaust stream in the oxidation catalyst to space velocity of the exhaust stream in the first set of filter units or the second set of filter units vary within a range of 0.25 to 3.2.

[048] In a few embodiments, the first set of filter units and the second set of filter units are made of cordierite, aluminium titanate, or silicon carbide.

[049] In an embodiment, the first set of filter units comprises one or more first filter units arranged parallel to each other along the longitudinal axis of the housing, and the second set of filter units comprises one or more second filter units arranged parallel to each other along the longitudinal axis of the housing. A ratio of a distance between the first filter units and the second filter units to a length of the first filter units along the longitudinal axis of the housing lies within a range of 0.05 to 1.2. In further embodiments, the particulate matter filter assembly further comprises a third set of filter units positioned downstream of the second set of filter units in the exhaust stream direction.

[050] Reference will now be made to the exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. Wherever possible same numerals will be used to refer to the same or like parts. Embodiments of the disclosure are described in the following paragraphs with reference to Figures 1 to 12. In Figures 1 to 12, the same element or elements which have same functions are indicated by the same reference signs.

[051] An exhaust aftertreatment system (not shown) may be configured to be in fluid communication with an exhaust outlet of a diesel engine and may further include an exhaust outlet. The exhaust aftertreatment system may be adapted to treat exhaust emissions received from the exhaust outlet of the diesel engine. In an embodiment, the exhaust aftertreatment system may be configured to be fluidly coupled with a diesel genset including a diesel engine, a generator that is mechanically driven by the diesel engine and a cooling system. The exhaust aftertreatment system may be supported above the diesel genset via a support structure. Alternatively, the exhaust aftertreatment system may be located next to or behind the diesel genset, or at other suitable locations. In other embodiments, the exhaust aftertreatment system of the present disclosure may be employed in marine vessels, on-road and off-road vehicles, and the like for treating exhaust emissions emitted therefrom.

[052] According to the present disclosure, the exhaust aftertreatment system utilizes a particulate matter filter assembly (100), as shown in Figures 1 and 2, to trap soot and/or unburnt carbon particles contained in an exhaust stream of the diesel engine. In addition, the particulate matter filter assembly (100) facilitates oxidization of soot and/or unburnt carbon particles entrapped in the particulate matter filter assembly (100). Further, the particulate matter filter assembly (100) is adapted to reduce a backpressure of the exhaust aftertreatment system. The particulate matter filter assembly (100) may be disposed downstream of the diesel engine and in fluid communication with the exhaust outlet of the diesel engine. The particulate matter filter assembly (100) includes a housing (102) having an inlet channel (104) and an outlet channel (106), also shown in Figures 2, 3, 4, 5 and 6, disposed at opposite longitudinal ends of the housing 102, extending along a longitudinal axis of the particulate matter filter assembly (100). The inlet channel (104) allows the exhaust stream of the diesel engine to enter the particulate matter filter assembly (100), and the outlet channel (106) allows the exhaust stream to exit the particulate matter filter assembly (100).

[053] As shown in Figure 2, the particulate matter filter assembly (100) further includes a plurality of filter units (112) disposed within the housing (102). The plurality of filter units (112) is disposed between the inlet channel (104) and the outlet channel (106) such that the exhaust stream entered through the inlet channel (104) passes through the plurality of filter units (112), and subsequently exits the particulate matter filter assembly (100) through the outlet channel (106).

[054] In an embodiment of the present disclosure, the plurality of filter units (112) may be coated with a catalyst so that a high temperature of the exhaust stream coming from the diesel engine combines with the catalyst coating to promote oxidation of soot and/or unburnt carbon particles. A coating of any suitable catalyst, for example, platinum, palladium, rhodium, rare earth metals, transition metals, and the like, that provides proper and desired oxidation of soot and/or unburnt carbon particles may be provided on the plurality of filter units (112). In accordance with the present disclosure, one or more filter units of the plurality of filter units (112) may be coated with different catalysts for varying level of oxidation of soot and/or unburnt carbon particles and reduction in backpressure of the exhaust aftertreatment system. Alternatively, the plurality of filter units (112) may be coated with the same catalyst. In a specific embodiment of the present disclosure, a filter unit disposed closer to the diesel engine may be provided with a thicker layer of the catalyst coating than the filter units disposed farther from the diesel engine. Also, the thickness of the catalyst coating on the plurality of filter units (112) may be varied according to the requirements of the exhaust aftertreatment system. Said arrangement facilitates increased oxidation of soot and/or unburnt carbon particles, thereby increased life cycle of the plurality of filter units (112) and cost effectiveness.

[055] Further, the plurality of filter units (112) may be made by extrusion process or sintering or other manufacturing processes. The plurality of filter units (112) may be made of a ceramic material, such as cordierite, aluminum titanate, or silicon carbide, but could also be made of other extrudable materials, such as glass, glass-ceramics, metal, and a variety of oxides of metal. In accordance with the present disclosure, one or more filter units of the plurality of filter units (112) may be made of different materials as per the requirement of reducing the risk of thermal rundown of the particulate matter filter assembly (100) and/or the exhaust aftertreatment system, keeping the running and manufacturing cost of the plurality of filter units (112) to a minimum, achieving low back pressure of the exhaust aftertreatment system and/or high filtration efficiency of the particulate matter filter assembly (100). Alternatively, the plurality of filter units (112) may be made of the same material. In an embodiment comprising three filter units, a filter unit disposed closer to the diesel engine is formed of silicon carbide, followed by a filter unit formed of aluminum titanate, and further followed by a filter unit formed of cordierite.

[056] Within the scope of the present disclosure, the plurality of filter units (112) may be disposed within the housing (102) in a series arrangement, or in a parallel arrangement, or in a combination of series-parallel arrangement.

[057] Referring again to Figure 2, in accordance with the present disclosure, the plurality of filter units (112) comprises a first set of filter units (114) and a second set of filter units (116). The first set of filter units (114) comprises one or more filter units and is adapted to be positioned downstream of the inlet channel (104) of the housing (102) in an exhaust stream direction. Further, the second set of filter units (116) comprises one or more filter units and is adapted to be positioned downstream of the first set of filter units (114) in the exhaust stream direction. In the illustrated exemplary embodiment of the particulate matter filter assembly (100), the first set of filter units (114) comprises a first filter unit (114). Also, the second set of filter units (116) comprises a second filter unit (116). The first filter unit (114) is adapted to be mounted within the housing (102) and positioned downstream of the diesel engine in the exhaust stream direction. The second filter unit (116) is adapted to be mounted within the housing (102) and positioned downstream of the first filter unit (114) in the exhaust stream direction.

[058] In accordance with the present disclosure, the second set of filter units (116) is adapted to be disposed in series with the first filter unit (114) and is positioned at a distance ‘L’ (shown in Figure 2) downstream of the first filter unit (114) in the exhaust stream direction. In an embodiment, the one or more filter units of the first set of filter units (114) are adapted to be arranged parallel to each other along the longitudinal axis of the housing (102). Also, the one or more filter units of the second set of filter units (116) are adapted to be arranged parallel to each other along the longitudinal axis of the housing (102). [059] In the illustrated exemplary embodiment, the second filter unit (116) is disposed in series with the first filter unit (114) and is positioned at a distance ‘L’ (shown in Figure 2) downstream of the first filter unit (114) in the exhaust stream direction.

[060] Within the scope of the present disclosure, the first filter unit (114) and the second filter unit (116) may have an overall shape and size suitable for overcoming the problems identified above. In accordance with the present disclosure, as shown in Figures 2 and 7, the first filter unit (114) is a cylindrical structure having a longitudinal length ‘LF along the longitudinal axis of the housing (102) and a diameter ‘DF transverse to the longitudinal axis of the housing (102). Similarly, as shown in Figures 2 and 8, the second filter unit (116) is also a cylindrical structure having a longitudinal length ‘L2’ along the longitudinal axis of the housing (102) and a diameter ‘D2’ transverse to the longitudinal axis of the housing (102). In alternative embodiments, the first filter unit (114) and the second filter unit (116) may have any shape, for example, a cube, cuboid and the like.

[061] In accordance with the present disclosure, a ratio of the distance ‘L’ between the first set of filter units (114) and the second set of filter units (116) to the length ‘LF of the first set of filter units (114) may lie in the range of 0.05 to 1.2, including 0.05 and 1.2. In a specific embodiment, a ratio of the distance ‘L’ between the first filter unit (114) and the second filter unit (116) to the length ‘LF of the first filter unit (114) may lie in the range of 0.05 to 1.2, including 0.05 and 1.2. The distance ‘L’ (shown in Figure 2) between the first filter unit (114) and the second filter unit (116) facilitates proper mixing of the exhaust stream, after the exhaust stream has passed through the first filter unit (114). The mixing of the exhaust stream allows even distribution of soot and/or unburnt carbon particles in the exhaust stream before the exhaust stream passes through the second filter unit (116). Even distribution of soot and/or unburnt carbon particles allows better entrapment of soot and/or unburnt carbon particles in the second filter unit (116), and accordingly increased filtration efficiency of the second filter unit (116) and the particulate matter filter assembly (100).

[062] Further, in accordance with the present disclosure, a ratio of the diameter ‘DF to the length ‘LF of the first filter unit (114) lies in the range of 1.78 to 7.15, including 1.78 and 7.15. In an exemplary embodiment of the present disclosure, the diameter ‘DF may have a value of 286 mm, and the length ‘LF may vary within a range of 40 mm to 160 mm. Also, a ratio of the diameter ‘D2’ to the length ‘L2’ of the second filter unit (116) lies in the range of 1.78 to 7.15, including 1.78 and 7.15. In an exemplary embodiment of the present disclosure, the diameter ‘D2’ may have a value of 286 mm, and the length ‘L2’ may vary within a range of 40 mm to 160 mm. In a further embodiment, the length ‘L of the first filter unit (114) is larger than the length ‘L2’ of the second filter unit (116). For example, a ratio of the length ‘L G of the first filter unit (114) to the length ‘L2’ of the second filter unit (116) lies in the range of 1 to 3.5, including 1 and 3.5. Also, a ratio of the diameter ‘DT of the first filter unit (114) to the diameter ‘D2’ of the second filter unit (116) lies in the range of 1 to 2, including 1 and 2. Said configuration of the first and second filter units (114, 116) ensures more overall structural strength of the first and second filter units (114, 116) for the exhaust stream to pass therethrough. Also, the larger frontal cross-sectional area of the first filter unit (114) ensures entrapping more soot and/or unburnt carbon particles from the exhaust stream in the filter unit (114), while reducing the overall pressure drop across the first filter unit (114). Also, the difference in the diameters of the first filter unit (114) and the second filter unit (116) facilitates improved mixing of flows of the exhaust stream exiting the first filter unit (114), in the distance ‘L’ (shown in Figure 2) between the first filter unit (114) and the second filter unit (116).

[063] Further, as shown in Figures 9 and 10, the first filter unit (114) and the second filter unit (116) are composed of a plurality of cell rows containing plurality of cell spaces (122) that are formed being partitioned by porous cell walls made of honeycomb-structure. Each of the cell spaces is configured to extend in the exhaust stream direction. In an embodiment, the first filter unit (114) and the second filter unit (116) are composed of a plurality of parallel cell rows containing a plurality of parallel cell spaces (122) that are formed being partitioned by porous cell walls made of honey comb- structure .

[064] In accordance with the present disclosure, the inlet ends of alternate cell spaces are open and outlet ends of said cell spaces are closed, while for the cell spaces intermediate to the alternate cell spaces, both the inlet and outlet ends are open. The cell spaces (122) for which the inlet end is open, and the outlet end is closed are being referred to as inflow cell spaces (126). Similarly, the cell spaces for which both the inlet end and the outlet end are open are being referred to as outflow cell spaces (128). The inlet ends and/or the outlet ends of the cell spaces may be closed by any sealing member, for example, a plug, adapted to restrict flow of the exhaust stream therethrough.

[065] When the exhaust stream, containing soot and/or unburnt carbon particles, entered through the inlet channel (104) passes through the first filter unit (114) and/or the second filter unit (116), the exhaust stream enters the first and second filter units (114, 116) through the inflow cells spaces (126) and the outflow cell spaces (128), at the inlet end (118), and exits the first and second filter units (114, 116) through the outflow cell spaces (128), at the outlet end (120). For the exhaust stream to pass from the inflow cell spaces (126) to the outflow cell spaces (128), the exhaust stream flows through the porous cell walls of the first and second filter units (114, 116). During said flow of the exhaust stream, soot and/or unburnt carbon particles get entrapped into the porous cell walls of the first and second filter units (114, 116), and the filtered exhaust stream is released from the particulate matter filter assembly (100), through the outlet channel (106).

[066] Further, the porous cell walls of the first filter unit (114) and the second filter unit (116) have a plurality of pores in the cell walls. A mean size of the pores in the first filter unit (114) and the second filter unit (116) may be suitably selected for efficient entrapment of soot and/or unburnt carbon particles in the porous cell walls. In accordance with the present disclosure, porosity of the porous cell walls in the first and second filter units (114, 116) may vary within the range of 20% to 60%, including 20% and 60%. In an embodiment, a ratio of the mean pore size of the first filter unit (114) to the mean pore size of the second filter unit (116) may lie within the range of 1 to 2, including 1 and 2. Said configuration of the first filter unit (114) and the second filter unit (116) facilitates entrapping larger sized soot and/or unburnt carbon particles in the first filter unit (114) and finer soot and/or unburnt carbon particles in the second filter unit (116). This difference in the mean pore sizes of the first and second filter units (114, 116) further offers a balance in filtration efficiency, ash loading and back pressure of the first and second filter units (114, 116).

[067] Within the scope of the present disclosure, a cross-section of the inflow cell spaces (126) and the outflow cell spaces (128) of the first filter unit (114) and the second filter unit (116) may be formed of any geometrical shape that may be suitable for ingress of the exhaust stream and for trapping soot and/or unburnt carbon particles contained in the exhaust stream. Exemplary cross-sectional shapes of the inflow cell spaces (126) and the outflow cell spaces (128) include, but not limited to, a circle, triangle, square, hexagon, and the like. Further, a size of the inflow cell spaces (126) may be same as that of the outflow cell spaces (128). Alternatively, the size of the inflow cell spaces (126) may be different to that of the outflow cell spaces (128). [068] In an embodiment, the inflow cell spaces (126) and the outflow cell spaces (128) are formed of square cross-section and the size of the outflow cell spaces (128) is smaller than that of the inflow cell spaces (126), i.e., a side length of the outflow cell spaces (128) is smaller than a side length of the inflow cell spaces (126). In accordance with the present disclosure, a ratio of the side length of the inflow cell spaces (126) to the side length of the outflow cell spaces (128) may lie within a range of 1.1 to 2.2, including 1.1 and 2.2, as seen in the front and rear view of the first and second filter units (114, 116). Said configuration of the inflow cell spaces (126) and the outflow cell spaces (128) facilitates high filtration efficiency of the first and second filter units (114, 116) because there exists a pressure differential between the large sized closed inflow cell spaces (126) and the small size open outflow cell spaces (128). This differential in the pressure between the large inflow cell spaces (126) and the small outflow cell spaces (128) creates a bias of flow split towards the inflow cell spaces (126), thereby leading to increased ash and soot loading capacity of the first and second filter units (114, 116). Similar effect can also be achieved by varying a number or ratio of inflow cell spaces (126) to the outflow cell spaces (128). For example, in accordance with the present disclosure, a ratio of area of closed inflow cell spaces (126) to the open outflow cell spaces (128), at the outlet end (120), of the first and second filter units (114, 116) may vary within the range of 1.21 to 4, including 1.21 and 4.

[069] In accordance with the present disclosure, cell density or cells per square inch (cpsi) in the first and second filter units (114, 116) may vary within the range of 70 cpsi to 400 cpsi, including 70 cpsi and 400 cpsi. It can be contemplated that, for a given diameter of a filter unit, the filter unit with less cells per square inch has high ash or soot loading capacity as compared to the filter unit with more cells per square inch, which has low ash or soot loading capacity. In an embodiment, cells per square inch in the second filter unit (116) may be more than cells per square inch (‘cpsi’) in the first filter unit (114). For example, a ratio of cells per square inch in the second filter unit (116) to cells per square inch in the first filter unit (114) may lie in the range of 1 to 3, including 1 and 3.

[070] The particulate matter filter assembly (100) constructed with the above structural variations/specifications provides low backpressure of the exhaust aftertreatment system as compared to the conventional systems, and high filtration efficiency of the particulate matter filter assembly (100). Also, with said configuration, space velocity (i.e., a ratio of exhaust stream per hour to volume of filter) of the exhaust stream in the first filter unit (114) is less than the space velocity of the exhaust stream in the second filter unit (116). Due to less space velocity of the exhaust stream in the first filter unit (114), soot and/or unburnt carbon particles is efficiently trapped in the first filter unit (114), thereby increased filtration efficiency of the particulate matter filter assembly (100). In accordance with the present disclosure, a ratio of space velocity in the first filter unit (114) to that in the second filter unit (116) shall lie in the range of 0.25 to 1, including 0.25 and 1.

[071] In accordance with the present disclosure, the first filter unit (114) and the second filter unit (116) are coated with a catalyst to promote oxidation of soot and/or unburnt carbon particles. The catalyst may be selected from the group consisting of platinum, palladium, rhodium, rare earth metals, and transition metals. Also, a density of the catalyst coated on the first filter unit (114) may be equal to or more than a density of the catalyst coated on the second filter unit (116). Moreover, the first filter unit (114) and the second filter unit (116) may be made of cordierite, aluminium titanate, or silicon carbide.

[072] In a further embodiment, the particulate matter filter assembly (100) may include an oxidation catalyst (OC) (124), as shown in Figure 2. The oxidation catalyst (124) may be positioned upstream of the first filter unit (114). The oxidation unit (124) may be understood as a device including an inert support body coated with a catalyst composition. The oxidation catalyst (124) may be configured to oxidize soot, unburnt gaseous and non-volatile hydrocarbons and carbon monoxide into carbon dioxide and water. In addition, the oxidation catalyst (124) may be configured to oxidize NOx to NO2. The catalyst composition of the oxidation catalyst (124) may include, but not limited to, platinum, palladium, rhodium, rare earth metals, transition metals, and the like.

[073] In accordance with the present disclosure, the oxidation catalyst (124) may further facilitate passive regeneration of the first and second filter units (114, 116) of the particulate matter filter assembly (100), on basis the catalyst coating material and catalyst volume on the surface of the oxidation catalyst (124). In addition, space velocity of the exhaust stream in the oxidation catalyst (124) with respect to the space velocity of the exhaust stream in the first and second filter units (114, 116) also facilitates passive regeneration of the first and second filter units (114, 116). In accordance with the present disclosure, a ratio of coating density of catalyst on the oxidation catalyst (124) to that on the first filter unit (114) (and/or the second filter unit (116)) may vary within the range of 2 to 30, including 2 and 30. Also, in accordance with the present disclosure, a ratio of total coating of catalyst by weight on the oxidation catalyst (124) to that on the filter units of the entire particulate matter assembly (100) may vary within the range of 0.4 to 29, including 0.4 and 29. Further, a ratio of space velocity of the exhaust stream in the oxidation catalyst (124) to that in the first filter unit (114) (and/or the second filter unit (116)) may vary within the range of 0.25 to 3.2, including 0.25 and 3.2. The regeneration of the first and second filter units (114, 116) increases the service life of the first and second filter units (114, 116) and, therefore the cost effectiveness of the particulate matter filter assembly (100).

[074] It is pertinent to note that although the present disclosure has been described to only include the first set of filter units (114) and the second set of filter units (116) in the particulate matter filter assembly (100), however, without deviating from the scope of the present disclosure, the particulate matter filter assembly (100) may comprises a third set of filter units (not shown) disposed downstream of the second set of filter units (116) in the exhaust stream direction and arranged upstream of the outlet channel (106) of the housing (102). The third set of filter units may comprise structural configuration similar to the structural configuration of the first set of filter units (114) or the second set of filter units (116), according to the design requirements.

[075] Without deviating from the scope of the present disclosure, the particulate matter filter assembly (100) may include any suitable arrangement of the oxidation catalyst (124) and the plurality of filter units (112) arranged with respect to each other. [076] In another embodiment, as shown in Figures 11 and 12, an arrangement of filter units (130) including seven (7) parallelly arranged filter units (132, 134, 136, 138, 140, 142, 144) disposed within the housing 102. Each of the filter units (132, 134, 136, 138, 140, 142, 144) may have structural configuration similar to that of the first filter unit (114) or the second filter unit (116). Further, a longitudinal axis of each of the filter units (132, 134, 136, 138, 140, 142, 144) may be arranged parallel to each other. In an embodiment, the arrangement of filter units (130) may be positioned downstream of the first filter unit (114) in the exhaust stream direction, resulting in a series arrangement of the first filter unit (114) with the parallelly disposed filter units (132, 134, 136, 138, 140, 142, 144). In said configuration, the exhaust stream, after passing through the first filter unit (114), is directed towards and passed through the filter units (132, 134, 136, 138, 140, 142, 144), before the filtered exhaust stream is released from the outlet channel (106) of the housing (102) of the particulate matter filter assembly (100). [077] In accordance with the present disclosure, the particulate matter filter assembly (100) facilitates achieving high particulate matter (soot and/or unburnt carbon particles) reduction efficiency within the range of 70-80%, maintaining ultra-low back pressures inline with the diesel engine at all times of operation, high ash carrying capacity of the particulate matter filter assembly (100), reducing thermal rundown risk of the exhaust aftertreatment system, size reduction of the particulate matter filter assembly (100), etc. [078] The various embodiments of the present disclosure have been described above with reference to the accompanying drawings. The present disclosure is not limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the subject matter of the disclosure to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

[079] Herein, the terms “attached”, “connected”, “interconnected”, “contacting”, “mounted”, “coupled” and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise.

[080] Well-known functions or constructions may not be described in detail for brevity and/or clarity. As used herein the expression “and/or” includes any and all combinations of one or more of the associated listed items.

[081] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including” when used in this specification, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof.

[082] While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. REFERENCE NUMERALS

EQUIVALENTS:

[083] The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[084] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

[085] Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. [086] The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

Claims

The Claim:

1. A particulate matter filter assembly (100) for an exhaust aftertreatment system, the particulate matter filter assembly (100) adapted to trap and oxidize soot and/or unburnt carbon particles contained in an exhaust stream of a diesel engine fluidly coupled with the exhaust aftertreatment system, the particulate matter filter assembly (100) comprising: a housing (102) defining an inlet channel (104) adapted to allow the exhaust stream to enter into the housing (102) and an outlet channel (106) adapted to allow the exhaust stream to exit from the housing (102); and a plurality of filter units (112) that is disposed between the inlet channel (104) and the outlet channel (106) of the housing (102) and that allow the exhaust stream to pass therethrough for treatment of the exhaust stream, the plurality of filter units (112) comprising a first set of filter units (114) positioned downstream of the inlet channel (104) of the housing (102) in an exhaust stream direction; and a second set of filter units (116) positioned downstream of the first set of filter units (114) in the exhaust stream direction, wherein a ratio of a distance (L) between the first set of filter units (114) and the second set of filter units (116) to a length (LI) of the first set of filter units (114) along a longitudinal axis of the housing (102) lies within a range of 0.05 to 1.2.

2. The particulate matter filter assembly (100) as claimed in claim 1, wherein the first set of filter units (114) comprises a first filter unit (114) having the length (LI) along the longitudinal axis of the housing (102) and a diameter (Dl) transverse to the longitudinal axis of the housing (102); and the second set of filter units (116) comprises a second filter unit (116) having a length (L2) along the longitudinal axis of the housing (102) and a diameter (D2) transverse to the longitudinal axis of the housing (102), wherein a ratio of a distance (L) between the first filter unit (114) and the second filter unit (116) to the length (LI) of the first filter unit (114) along the longitudinal axis of the housing (102) lies within a range of 0.05 to 1.2.

3. The particulate matter filter assembly (100) as claimed in claim 2, wherein a ratio of the diameter (Dl) of the first filter unit (114) to the length (LI) of the first filter unit (114) lies within arange of 1.78 to 7.15.

4. The particulate matter filter assembly (100) as claimed in claim 2 or 3, wherein a ratio of the diameter (D2) of the second filter unit (116) to the length (L2) of the second filter unit (116) lies within arange of 1.78 to 7.15.

5. The particulate matter filter assembly (100) as claimed in any one of claims 2 to 4, wherein a ratio of the length (LI) of the first filter unit (114) to the length

(L2) of the second filter unit (116) lies within a range of 1 to 3.5.

6. The particulate matter filter assembly (100) as claimed in any one of claims 2 to 5, wherein a ratio of the diameter (Dl) of the first filter unit (114) to the diameter (D2) of the second filter unit (116) lies within a range of 1 to 2.

7. The particulate matter filter assembly (100) as claimed in any one of claims 1 to 6, wherein the filter units of the first set of filter units (114) and the second set of filter units (116) comprise a plurality of cell spaces (122) that are partitioned by porous cell walls, and wherein porosity of the filter units (114, 116) lies within a range of 20% to 60%.

8. The particulate matter filter assembly (100) as claimed in claim 7, wherein a ratio of mean pore size of the first set of filter units (114) to mean pore size of the second set of filter units (116) lies within a range of 1 to 2.

9. The particulate matter filter assembly (100) as claimed in claim 7 or 8, wherein a cell density in the first and second set of filter units (114, 116) varies within a range of 70 cpsi (cells per square inch) to 400 cpsi.

10. The particulate matter filter assembly (100) as claimed in any one of claims 7 to 9, wherein a ratio of cell density in the second set of filter units (116) to cell density in the first set of filter units (114) lies within a range of 1 to 3.

11. The particulate matter filter assembly (100) as claimed in any one of claims 7 to 10, wherein a ratio of a side length of inflow cell spaces (126) to a side length of outflow cell spaces (128) in the filter unit (114, 116) lies within a range of 1.1 to 2.2.

12. The particulate matter filter assembly (100) as claimed in any one of claims 7 to 11, wherein a ratio of area of closed inflow cell spaces (126) to open outflow cell spaces (128), at an outlet end (120), of the first and second filter units (114, 116) may vary within the range of 1.21 to 4.

13. The particulate matter filter assembly (100) as claimed in any one of claims 7 to 12, wherein a ratio of a space velocity of the exhaust stream in the first filter unit (114) to a space velocity of the exhaust stream in the second filter unit (116) lies within a range of 0.25 to 1.

14. The particulate matter filter assembly (100) as claimed in any one of claims 1 to 13, wherein filter units of the first set of filter units (114) and the second set of filter units (116) are coated with a catalyst to promote oxidation of soot and/or unburnt carbon particles.

15. The particulate matter filter assembly (100) as claimed in claim 14, wherein the catalyst may be selected from the group consisting of platinum, palladium, rhodium, rare earth metals, and transition metals.

16. The particulate matter filter assembly (100) as claimed in claim 14, wherein density of the catalyst coated on the first set of filter units (114) is equal to or more than density of the catalyst coated on the second set of filter units (116).

17. The particulate matter filter assembly (100) as claimed in any one of claims 1 to 16, comprising an oxidation catalyst (124) positioned upstream of the first set of filter units (114).

18. The particulate matter filter assembly (100) as claimed in claim 17, wherein a ratio of coating of density catalyst on the oxidation catalyst (124) to coating density of catalyst on the first set of filter units (114) or the second set of filter units (116) vary within a range of 2 to 30.

19. The particulate matter filter assembly (100) as claimed in claim 17, wherein a ratio of total coating of catalyst by weight on the oxidation catalyst (124) to total coating of catalyst by weight on the filter units of the particulate matter filter assembly (100) vary within a range of 0.4 to 29.

20. The particulate matter filter assembly (100) as claimed in any one of claims 17 to 19, wherein a ratio of space velocity of the exhaust stream in the oxidation catalyst (124) to space velocity of the exhaust stream in the first set of filter units (114) or the second set of filter units (116) vary within a range of 0.25 to

3.2.

21. The particulate matter filter assembly (100) as claimed in claim 1, wherein the first set of filter units (114) and the second set of filter units (116) are made of cordierite, aluminium titanate, or silicon carbide.

22. The particulate matter filter assembly (100) as claimed in claim 1, wherein the first set of filter units (114) comprises one or more first filter units arranged parallel to each other along the longitudinal axis of the housing (102); and the second set of filter units (116) comprises one or more second filter units arranged parallel to each other along the longitudinal axis of the housing (102), wherein a ratio of a distance between the first filter units (114) and the second filter units (116) to a length of the first filter units (114) along the longitudinal axis of the housing (102) lies within a range of 0.05 to 1.2.

23. The particulate matter filter assembly (100) as claimed in claim 1, comprising a third set of filter units positioned downstream of the second set of filter units (116) in the exhaust stream direction.