Claims:We Claim
1. A particulate filter 10, said particulate filter 10 comprising:
a closed diesel particulate filter 12; characterized in that
an open particulate filter 14 connected upstream from said closed diesel particulate filter 12, said open particulate filter 14 adapted to filter particulate matter from exhaust gases prior to channeling exhaust gases to said closed diesel particulate filter 12 and adapted to regenerate passively due to formation of nitric oxide within said open particulate filter 14.

2. The particulate filter 10 in accordance with Claim 1 wherein said open particulate filter 14 is connected downstream from a diesel oxidation catalyst 16, said open particulate filter 14 receives exhaust gases from said diesel oxidation catalyst 16.

3. The particulate filter 10 in accordance with Claim 1 wherein said open particulate filter 14 filters a substantial portion of particulate matter from exhaust gases prior to channeling exhaust gases to said closed diesel particulate filter 12.

4. An engine exhaust layout 1, said engine exhaust layout 1 comprising:
an exhaust gas flow path 18;
a closed diesel particulate filter 12 in flow communication with said exhaust gas flow path 18;
an open particulate filter 14 connected upstream from said closed diesel particulate filter 12, said open particulate filter 14 adapted to filter particulate matter from exhaust gases prior to channeling exhaust gases to said closed diesel particulate filter 12 and adapted to regenerate passively due to formation of nitric oxide within said open particulate filter 14.

5. The engine exhaust layout 1 in accordance with Claim 4 wherein said open particulate filter 14 is connected downstream from a diesel oxidation catalyst 16, said open particulate filter 14 receives exhaust gases from said diesel oxidation catalyst 16.

6. The engine exhaust layout 1 in accordance with Claim 4 wherein said open particulate filter 14 filters a substantial portion of particulate matter from exhaust gases prior to channeling exhaust gases to said closed diesel particulate filter 12. , Description:Field of the invention
[0001] This invention relates to a particulate filter and more particularly to an open particulate filter for an exhaust gas flow path of an engine exhaust layout.

Background of the invention
[0002] U.S. Patent Application Number US4276066A describes a self-regenerating monolithic exhaust particulate filter for diesel engines. The filter includes a monolithic filter element having a plurality of interconnecting internal porous walls defining a plurality of small inlet passages extending adjacent a plurality of small outlet passages. The inlet and outlet passages are in communication through the porous walls for passing exhaust gases through the walls to filter particulates from the gases and deposit the particulates on the wall surfaces within the inlet passages. Electric heating means are provided in at least some of the passages to heat the passages and the surrounding portions of the element when energized and thereby raise the collected particulates in the portions of the element to their incineration temperature, thereby burning off the particulates from the portions and regenerating the portions of the element for continued use.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates an open particulate filter connected to a closed diesel particulate filter in accordance with one embodiment of the invention.

Detailed description of the invention
[0004] Figure 1 illustrates a particulate filter 10. The particulate filter 10 comprises a closed diesel particulate filter 12. An open particulate filter 14 is connected upstream from the closed diesel particulate filter 12, the open particulate filter 14 adapted to filter particulate matter from exhaust gases prior to channeling exhaust gases to the closed diesel particulate filter 12, the open particulate filter 14 adapted to regenerate passively due to the formation of nitric oxide within the open particulate filter 14.
[0005] Moreover, an engine exhaust layout 1 is described. The engine exhaust layout 1 comprises an exhaust gas flow path 18 and a closed diesel particulate filter 12 in flow communication with the exhaust gas flow path 18. An open particulate filter 14 is connected upstream from the closed diesel particulate filter 12, the open particulate filter 14 adapted to filter particulate matter from exhaust gases prior to channeling exhaust gases to the closed diesel particulate filter 12, the open particulate filter 14 adapted to regenerate passively due to the formation of nitric oxide within the open particulate filter 14.
[0006] An exhaust gas flow path 18 is in flow communication with the engine 20, and channels exhaust gases from the engine 20 through the exhaust gas flow path 18. A diesel oxidation catalyst 16 is in flow communication with the exhaust gas flow path 18 and facilitates oxidizing exhaust gases that flow through the exhaust gas flow path 18. A particulate filter 10 is in flow communication with the diesel oxidation catalyst 16 and receives oxidized exhaust gases from the diesel oxidation catalyst 16.
[0007] The particulate filter 10 comprises a closed diesel particulate filter 12, and an open particulate filter 14 connected upstream from the closed diesel particulate filter 12. The open particulate filter 14 is connected downstream from the diesel oxidation catalyst 16 and receives oxidized exhaust gases from the diesel oxidation catalyst 16. The open particulate filter 14 filters a portion of the particulate matter from the exhaust gases before the exhaust gases are channeled to the closed diesel particulate filter 12. Since a portion of the particulate matter from the exhaust gases are filtered, the closed diesel particulate filter 12 takes a longer duration of time to get covered with particulate matter. Since the closed diesel particulate filter 12 takes a longer duration of time to get covered with particulate matter, the closed diesel particulate filter 12 does not need to be actively regenerated for burning the particulate matter for a longer time interval. Therefore the regeneration frequency of the closed diesel particulate filter 12 can be increased. The open particulate filter 14 regenerates passively by the continuously regenerating trap method.
[0008] The continuously regenerating trap method uses nitric oxide to burn soot at low temperatures as low as 275 oC. A platinum catalyst positioned upstream from the open particulate filter 10 converts a fraction of the nitric oxide gas in the diesel exhaust gases to nitrogen dioxide gas. The nitrogen dioxide gas that is converted in the open particulate filter 10 burns the soot at low temperatures to ensure that the open particulate filter 14 is continuously free of soot particles.
[0009] A working of the particulate filter 10 is described as an example. Exhaust gases are channeled from the engine 20 to the diesel oxidation catalyst 16. From the diesel oxidation catalyst 16, the oxidized exhaust gases are channeled to the open particulate filter 14. A substantial portion of the particulate matter is filtered by the open particulate filter 14, and the exhaust gases containing the remainder of the particulate matter is channeled to the closed diesel particulate filter 12. The closed diesel particulate filter 12 filters the particulate matter from the exhaust gases and releases exhaust gases devoid of particulate matter to the environment. As the open particulate filter 14 filters the majority of particulate matter from the exhaust gases, the exhaust gases containing the remainder of the particulate matter are channeled to the closed diesel particulate filter 12. Therefore, the closed diesel particulate filter does not get clogged as frequently as in the absence of the open particulate filter 14 that is positioned before the closed diesel particulate filter 12. As a consequence, the closed diesel particulate filter 12 does not need to be actively regenerated for a longer duration of time as particulate matter does not get accumulated within it.
[0010] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to leverage and dimensions of various levers are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.