DESC:TECHNICAL FIELD
The present invention relates to optimization of after treatment system for diesel engine emissions and more particularly to an apparatus and method for efficient trapping and regeneration of diesel particulate filter.
BACKGROUND
During the running of diesel engine, soot particles comes out which is unique emission particle resulting from diesel combustion inside the engine. Diesel particulate filter physically traps the soot particles and prevent their exit in the tail pipe emissions.
Particulate matter is carcinogenic in nature so it needs to be addressed efficiently. In order to achieve and meet emission particulate matter trapping is to be done. Particulate matter emitted from the exhaust of the diesel engine are different in sizes and different geometries are used to trap particulate of different sizes.
A particulate, or soot, filter may be placed in the exhaust system of an engine, especially a diesel engine, to trap soot that would otherwise be emitted to the surrounding atmosphere.
As the engine accumulates more operating time, more soot becomes trapped in the filter. Eventually the amount of accumulated soot begins to affect performance, and so it becomes necessary to purge the filter of trapped soot.
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A particulate trap must be capable of trapping particulates with high efficiency and so that exhausts are satisfactorily purified. It is considered necessary to trap an average of at least 60% of the particulates contained in diesel engine emissions, even though the amount of particulates contained in exhausts depends upon the displacement of the diesel engine and the load applied. Airborne particulates 2 µm or less in diameter can enter human alveoli and reportedly trigger lung cancer. It is thus necessary that particulate traps be capable of efficiently trapping even these small suspended particulates.
Among the existing filter element materials a wall-flow type, honeycomb porous member made of cordierite ceramics is considered the most practical. But this filter has several problems. One problem is that particulates tend to collect locally. Another problem is that, because of low thermal conductivity of cordierite ceramic, this filter tends to develop heat spots during regeneration. As a result, the filter may melt or crack due to thermal stress. Such a filter is not durable enough. A ceramic fiber trap made by forming ceramic fibers into a candle shape is gaining much attention recently. But this trap is not sufficiently durable either. The fibers forming the trap tend to break due to reduced strength when exposed to high-temperature exhaust gases. All the existing diesel particulate filter uses single trap of particular configuration to trap one sized particles. There are no methodologies to trap the particulate matter of all sizes.
To overcome, afore-mentioned problems, there is a need to create a diesel particulate filter with combination of different configurations of shapes and sizes for efficient trapping mechanism and regeneration.
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SUMMARY
According to an embodiment of the present invention, there is provided an apparatus and method for efficient particulate trap and regeneration of diesel particulate filter. The diesel particulate filter comprises of a combination of different trap geometries or channels such as wire mesh, honeycomb and porous ceramic to effectively collect the particulate matter of all sizes. The shell of diesel particulate filter includes at least two different geometries for smooth flow of exhaust gas between the channels, thus utilizing the unique trapping characteristics of the geometry. Exhaust gas enters the diesel particulate filter through inlet channel with a particular geometry and exits out through the outlet channel with different geometry. The trapping is done so efficiently that it enables reduction of solid particulate emission levels in diesel engine exhaust to an insignificant level.
BRIEF DESCRIPTION OF THE DRAWINGS
The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings.
Fig. 1 is a view of different geometries of the diesel particulate filter of the present invention
Fig.2 is a view of the flow of exhaust gas from different channels of the diesel particulate filter of the present invention
Fig. 3 is a view of the trap mechanism of the diesel particulate filter of the present invention
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Fig. 4 is a side view of the inlet channel of the diesel particulate filter of the present invention
Fig. 5 is a side view of the outlet channel of the diesel particulate filter of the present invention
Fig. 6 is a cross sectional view of the channels of the diesel particulate filter of the present invention
DESCRIPTION
In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following description is therefore not to be taken in a limiting sense.
According to one embodiment of the present subject matter described herein, apparatus and method for efficient particulate trap and regeneration of diesel particulate filter is described. Referring to Fig.1, 2 & 3 there is provided a diesel particulate filter (DPF) with three different geometries or channels for trapping particulate matter. It is to be noted that the words ‘geometries’ and ‘channels’ are used interchangeably. DPF removes the particulate matter found in diesel exhaust by filtering exhaust from the engine. The particulate matter results from incomplete combustion of diesel fuel that produces soot particles. The size of the particles varies from large to small to tiny nanoparticles. The main components of DPF are DPF cluster, piping (2) and mounting bracket for locating DPF in the
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engine. DPF cluster - The cylindrical shape encloses the substrate with conical end is used to make the connection possible with the exhaust pipe system.
Piping - The end fittings of the filter used will be flange type or welded for establishing connection with exhaust pipe system.
Mounting bracket - Rigid mounting is done by means of bracket provision to hold the filter assembly.
The first geometry is wire mesh (3) trap filter also known as inlet channel in which particulate matter of large size is trapped in the wire mesh strands or accumulates on previously impacted particulates. This filtration is partial as the particles impinge on the rough surface of the mesh or wire network of the filter element. After the wire mesh trap; there is honeycomb (4) trap, so the particulate matter of medium size is passed through honeycomb trap filter with alternate channels plugged at opposite ends. As the gases pass into the open end of the channel, the plug at the opposite end forces the gases through the porous wall of the honeycomb channel and out through the neighboring channel also known as outlet channel. The ultrafine porous structure of the channel walls results in greater than 85 percent collection efficiencies of these filters. After honeycomb trap filter, the particulate matter of small size spread themselves again on the porous walls of porous ceramic (5) trap filter or diffuse onto existing particulate matter which has already become attached to porous trap. Porous Ceramic trap filter is made from different types of ceramic fibers to form a porous media. It removes carbon particulates almost completely, including fine particulates less than 100 nanometers (nm) diameter with an efficiency of greater than 95% in mass and greater than 99% in number of particles over a wide range of engine operating conditions.
As shown in Fig. 4, inlet channel is wire mesh (3) made of sintered metal, metal mesh or a reticulated metal of square shape through which exhaust gases passes
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through a relatively open network. The inlet channel considered for the inlet of exhaust gas is square channel and the exit channel is of honeycomb. The total length of the diesel particulate is 200mm and the length of square channel is 100mm. (total length of square channel is half of length of diesel particulate) The material considered will be cordierite or aluminium titanate.
As shown in Fig. 5, outlet channel is a honeycomb (4) structure for with ultrafine porous structure for trapping the stringent particulate emissions for achieving higher efficiency in diesel particulate filter. The total length of the diesel particulate is 200mm and the length of honeycomb channel is 100mm. (total length of honeycomb channel is half of length of diesel particulate). The material considered will be cordierite or aluminium titanate.
Fig. 6 is a cross sectional view of the inlet and outlet channels depicting the inner configuration of the geometries used.
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 appended claims. ,CLAIMS:A Variable Geometry Diesel Particulate Filter wherein filter comprises of a combination of different trap geometries or channels such as wire mesh (3), honeycomb (4) and porous ceramic (5) to effectively collect the particulate matter of all sizes.
2. A Variable Geometry Diesel Particulate Filter as claimed in claim 1 wherein the shell of diesel particulate filter includes at least two different geometries for smooth flow of exhaust gas between the channels, thus utilizing the unique trapping characteristics of the geometry; exhaust gas enters the diesel particulate filter through inlet channel with a particular geometry and exits out through the outlet channel with different geometry.
3. A Variable Geometry Diesel Particulate Filter as claimed in claim 2 wherein filter is having diesel particulate filter cluster, piping (2) and mounting bracket for locating diesel particulate filter in the engine; diesel particulate filter cluster is cylindrical in shape which encloses the substrate with conical end , it is used to make the connection possible with the exhaust pipe system; The end fittings of the filter used will be flange type or welded for establishing connection with exhaust pipe system and rigid mounting is done by means of bracket provision to hold the filter assembly.
4. A Variable Geometry Diesel Particulate Filter as claimed in claim 3 wherein the first geometry is wire mesh trap filter (3) also known as inlet channel in which particulate matter of large size is trapped in the wire mesh strands or accumulates on previously impacted particulates; this filtration is partial as the particles impinge on the rough surface of the mesh or wire network of the filter element.
5. A Variable Geometry Diesel Particulate Filter as claimed in claim 4 wherein after the wire mesh trap (3) , there is honeycomb trap (4) so the particulate matter of medium size is passed through honeycomb trap filter
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with alternate channels plugged at opposite ends; as the gases pass into the open end of the channel, the plug at the opposite end forces the gases through the porous wall of the honeycomb channel and out through the neighboring channel also known as outlet channel; the ultrafine porous structure of the channel walls results in greater than 85 percent collection efficiencies of these filters.
6. A Variable Geometry Diesel Particulate Filter as claimed in claim 5 wherein, after honeycomb trap filter, the particulate matter of small size spread themselves again on the porous walls of porous ceramic trap filter or diffuse onto existing particulate matter which has already become attached to porous trap; porous ceramic trap filter is made from different types of ceramic fibers to form a porous media; it removes carbon particulates almost completely, including fine particulates less than 100 nanometers (nm) diameter with an efficiency of greater than 95% in mass and greater than 99% in number of particles over a wide range of engine operating conditions.
7. A Variable Geometry Diesel Particulate Filter as claimed in claim 6 wherein inlet channel is wire mesh made of sintered metal, metal mesh or a reticulated metal of square shape through which exhaust gases passes through a relatively open network; the inlet channel considered for the inlet of exhaust gas is square channel and the exit channel is of honeycomb; the total length of square channel is half of length of diesel particulate.
8. A Variable Geometry Diesel Particulate Filter as claimed in claim 7 wherein outlet channel is a honeycomb structure for with ultrafine porous structure for trapping the stringent particulate emissions for achieving higher efficiency in diesel particulate filter; total length of honeycomb channel is half of length of diesel particulate.