Patent Application
20120222412
The present patent relates to engine exhaust gas particulate filters, and more particularly to an engine exhaust gas particulate filter having helically configured cells.
Many factors, including environmental responsibility efforts and modern environmental regulations on engine exhaust emissions have reduced the allowable acceptable levels of certain pollutants that enter the atmosphere following the combustion of fossil fuels. Increasingly more stringent emission standards may require greater control over either or both the combustion of fuel and post combustion treatment of the exhaust. For example, the allowable levels of nitrogen oxides (NOx) and particulate matter have been greatly reduced over the last several years. To address, among other issues, environmental concerns, many diesel engines now have an exhaust gas particulate filter within an exhaust system of the engine purposed to reduce the amount of particulate matter released into the atmosphere. An engine exhaust gas particulate filter typically has a plurality of paired longitudinal flow cell channels where a first flow cell channel of the pair has an open end at a first end and a closed end at a second end, while the second flow cell channel of the pair has an open end at the second end and a closed end at the first end. A common permeable filtration wall between the first flow cell channel and the second flow cell channel permits filtered fluid communication between the first flow cell channel and the second flow cell channel. Pairs of longitudinal flow cell channels may be arranged in an alternating checkerboard pattern, such that each first flow cell channels having an open first end and closed second end is bounded on each of its four longitudinal sides by second flow cell channels having a closed first end and open second end, the common walls between each flow cell channel being permeable to permit filtered fluid communication between each first flow cell channel and each second flow cell channel.
In order to clean out an engine exhaust gas particulate filter to keep it operating at an effective level and to reduce back pressure that may build up when the engine exhaust gas particulate filter becomes clogged, an engine may be instructed by an engine control module to perform a regeneration cycle upon the engine exhaust gas particulate filter that causes exhaust gas temperatures to rise to a level sufficient to regenerate the engine exhaust gas particulate filter by burning away trapped particulate matter. However, the regeneration cycle generates ash within the engine exhaust gas particulate filter that accumulates over time to a level that adversely impacts performance of the engine exhaust gas particulate filter, and the engine. When a sufficient quantity of ash and particulate matter is present within the engine exhaust gas particulate filter, the engine exhaust gas particulate filter is cleaned by reversing air flow through the engine exhaust gas particulate filter. That is, air enters the second open end of the second flow cell channel of each of the pair of flow cells, and passes through the common permeable filtration wall into the first flow cell channel to remove ash and particulate matter from the first flow cell channel by blowing it out of the first open end of the first flow cell channel. However, as ash and other trapped particulate matter tends to accumulate towards the second closed end of the first flow cell channel, and as little air passes from the second flow cell channel to the first flow cell channel in the area of the second closed end of the first flow cell channel as compared to the volume of air that passes through the entire length of the common permeable filtration wall, the resultant air velocity is low in the region of maximum ash accumulation and the cleaning of the first flow cell channel may not be as complete as desired.
Therefore a need exists for an engine exhaust gas particulate filter that allows for more complete cleaning by maximizing the flow of air through the engine exhaust gas particulate filter in the region where the accumulation of ash is the greatest.
According to one embodiment, an engine exhaust gas particulate filter comprises a plurality of paired longitudinal flow cells, each of the plurality of paired longitudinal flow cells having a first flow cell channel and a second flow cell channel. The first flow cell channel is disposed in fluid communication with the second flow cell channel through a common permeable filtration wall. Further, each of the plurality of paired longitudinal flow cells forms a non-linear flow path about a longitudinal axis of the engine exhaust gas particulate filter.
According to another embodiment, each of a plurality of paired longitudinal flow cells disposed in an engine exhaust gas particulate filter has a proximal end and a distal end. Each of the paired longitudinal flow cells comprises a first flow cell channel, a second flow cell channel, and a common permeable filtration wall between the first flow cell channel and the second flow cell channel. The first flow cell channel has a first open end at the proximal end of the engine exhaust gas particulate filter and a second closed end at the distal end of the engine exhaust gas particulate filter. The second flow cell channel has a second open end at the distal end of the engine exhaust gas particulate filter and a first closed end at the proximal end of the engine exhaust gas particulate filter. A common permeable filtration wall is disposed between the first flow cell channel and the second flow cell channel. Further, the first flow cell channel and the second flow cell channel have a non-linear shape.
According to a further embodiment, an engine exhaust gas particulate filter comprises a first flow cell channel, a second flow cell channel, and a common permeable filtration wall. The first flow cell channel has a first open end at a proximal end of the engine exhaust gas particulate filter. The second flow cell channel has a second open end at a distal end of the engine exhaust gas particulate filter. A common permeable filtration wall separates the first flow cell channel from the second flow cell channel and provides fluid communication between the first flow cell channel and the second flow cell channel. Further, the first flow cell channel and the second flow cell channel form a generally helical shape about a longitudinal axis from the proximal end to the distal end of the engine exhaust gas particulate filter.
As described above, the Engine Exhaust Gas Particulate Filter having Helically Configured Cells and a vehicle made with this device provide a number of advantages, some of which have been described above and others of which are inherent in the invention. Also, modifications may be proposed to the Engine Exhaust Gas Particulate Filter having Helically Configured Cells or a vehicle made with this device without departing from the teachings herein.
The centripetal acceleration caused within the paired longitudinal flow cells 12 results in more even precipitation of particulate matter 5 out of the engine exhaust gas 4 along the common permeable filtration wall 30 separating the first flow cell channel 18 and the second flow cell channel 24, due to cyclonic separation. Further, the helical shape of the longitudinal flow cells 12 causes a more rapid transition to turbulent flow along the length of the first flow cell channel 18, thereby causing entrained particulate matter 5 to precipitate out of the engine exhaust gas flow 4 closer to the first open end 20 of the first flow cell channel 18.
Again, when the engine exhaust gas particulate filter 10 requires cleaning, a reverse gas flow through the paired longitudinal flow cells 12 is used to remove the accumulated trapped particulate matter 5. As with the prior art, the reverse gas flow enters the second flow cell channel 24 at the second open end 28, travels the length of the second flow cell channel 24 while progressively passing through common permeable filtration wall 30 into the first flow cell channel 18, and then exits the first flow cell channel 18 at first open end 20. However, because of the deposition of accumulated trapped particulate matter 5 being closer to the first open end 20 of the first flow cell channel 18 that is characteristic of paired longitudinal flow cells 12 having a non-linear shape, the flow velocity of the reverse gas flow is more effective near the first open end 20 where accumulation of the trapped particulate matter 5 is greater than in the prior art.
While specific embodiments have been described in detail in the foregoing detailed description and illustrated in the accompanying drawings, those with ordinary skill in the art will appreciate that various permutations of the invention are possible without departing from the teachings disclosed herein. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof. Other advantages to an Engine Exhaust Gas Particulate Filter having Helically Configured Cells and a vehicle made with this system may also be inherent in the invention, without having been described above.
