Patent Application
20170145890
The field of the invention is combustion engine system, more specifically, an exhaust treatment system for a combustion engine.
The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Diesel engines are known to have better fuel efficiency and provide higher torque over gasoline equivalents. However, diesel exhaust also contains substances, widely known as diesel particulate matter, if untreated, can be harmful to our health and the environment. Conventionally, a diesel engine operates with a diesel particulate filter (DPF) or other emissions control devices to remove the harmful substance from the exhaust before releasing the emission into the atmosphere. The DPF and diesel catalytic converter requires replacing or regenerating after being used for a period of time.
Efforts have been made to prolong the lifetime of these DPFs and diesel catalytic converters. For example, U.S. Pat. No. 7,758,675 titled “Gas Treatment Device” to Naito et al., discloses a gas treatment device that includes a gas turbulence accelerator facing a corona electrode, where the gas turbulence accelerator comprises an uneven surface structure for accelerating the gas prior to being treated by the electrodes.
Japanese Publication 5-332128 titled “Exhaust Emission Control Device” to Suzuki discloses spiral shaped grooves on an electrode and U.S. Pat. No. 6,926,758 titled “Electrostatic Filter” to Truce discloses a contoured outer wall for controlling the flow of the gas.
Other publications in this area of technology includes U.S. Pat. No. 8,900,520 titled “Apparatus for Treating Exhaust Particulate Matter” to Kim et al., and U.S. Pat. No. 8,257,455 titled “Plasma Burner and Diesel Particulate Filter Trap” to Lee et al.
However, even with the different exhaust treatment techniques, the efficiency of treating diesel exhaust gas has still yet to reach an optimal level. Thus, there is still a need to improve on existing diesel exhaust treatment systems to further improve efficiency and reduce emission of harmful by-products.
All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
The inventive subject matter provides apparatus, systems and methods in which an exhaust gas is being treated with plasma in an excitation chamber that includes an outer housing and an inner housing, where the wall that separates the outer housing and the inner housing has orifices configured to direct the exhaust gas from the outer housing into the inner housing in a coherent turbulent flow. In one aspect of the invention, an exhaust treatment system for a diesel engine is presented. The system includes an excitation chamber that includes an exhaust inlet, an outer housing, and an inner housing that is disposed within the outer housing. The exhaust inlet is coupled with the outer housing and configured to direct an exhaust stream into the outer housing.
In some embodiments, the exhaust treatment system also includes a waveguide that is disposed within the inner housing. The waveguide includes an electrode that is configured to cooperate with an opposite electrode to produce a plasma field within a lumen of the inner housing. In addition, the waveguide has coherent surface features that entrain at least a portion of the exhaust stream to travel in coherent vortices in the inner housing. In some embodiments, the surface features include a continuous groove or ridge around the circumference of the waveguide in a spiral pattern. In addition, the inner housing itself can be a waveguide for mixture flowing within the outer housing. In these embodiments, the continuous groove disposed on the outer surface of the inner housing focuses the electric field at the sharp edges, which can complement a helicoidal flow dynamic of the mixture.
In some embodiments, a portion of the waveguide has a cone shape in which a cross-section diameter of the portion of the waveguide progressively reduces in size in a downstream direction.
In some embodiments, an enclosure of the outer housing has a shape that complements the contour of the portion of the waveguide. The shape of the outer housing enclosure ensures that the distance between the outer housing enclosure and the waveguide remains substantially identical throughout the excitation chamber.
The inner housing and outer housing are separated by a separator that has orifices. The orifices are distributed across the separator to allow the exhaust gas to travel from the outer housing into the inner housing. In some embodiments, the orifices have directional characteristic (directional structure) that entrains the portion of the exhaust stream to travel in coherent vortices in the inner housing. To further enhance the coherent vortices, the inner wall of the inner housing also includes coherent surface features having sizes that are substantially large enough to be identified by naked eyes, and comprise a pattern of features selected from the group consisting of bumps, dimples, cavities, ridges, grooves, and wedges. In some embodiments, the orifices have a longest diameter that is at a fraction of a fundamental wavelength that is being applied from a microwave generator.
In some embodiments, the exhaust treatment system also includes a fuel inlet that directs a stream of air and fuel mixture into the inner housing. In some of these embodiments, the waveguide has an interior pathway and orifices on the surface. The fuel inlet directs the stream of air and fuel mixture through the interior pathway of the waveguide and out into the inner housing via the orifices. The orifices on the waveguide also have a directional characteristic (directional structure) configured to entrain the stream of air and fuel mixture to travel in coherent vortices in the inner housing. To further enhance the coherent vortices of the stream of air and fuel mixture, the waveguide includes surface features such as grooves that spiral around the circumference of the waveguide in a downstream direction.
In some embodiments, the exhaust inlet has a spiral shape. Preferably, the exhaust inlet has a phi-based spiral shape.
The exhaust treatment system of some embodiments also includes a mixing chamber that is disposed at a location downstream of the excitation chamber. The mixing chamber provides an area that allows the exhaust stream to be further oxidized. The exhaust treatment system also includes a diesel particulate filter disposed at a location downstream of the mixing chamber.
Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
The following discussion provides example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously.
In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the inventive subject matter are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the inventive subject matter are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the inventive subject matter may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints and open-ended ranges should be interpreted to include only commercially practical values. The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value within a range is incorporated into the specification as if it were individually recited herein. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.
All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the inventive subject matter and does not pose a limitation on the scope of the inventive subject matter otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the inventive subject matter.
Groupings of alternative elements or embodiments of the inventive subject matter disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
The inventive subject matter provides apparatus, systems and methods in which an exhaust gas is treated to control emissions. In some embodiments, the exhaust gas is treated with plasma in an excitation chamber that includes an outer housing and an inner housing, where the wall that separates the outer housing and the inner housing has orifices configured to direct the exhaust gas from the outer housing into the inner housing in a coherent turbulent flow.
Combustion engine 115 is designed to combust fuel (e.g., gasoline, diesel, hydrogen cell natural gas, etc.) from fuel tank and air mixture that comes through intake device 110 to produce power and an exhaust gas that includes many substances such as, but not limited to, carbon dioxide, sulfur oxides, formaldehyde, carbon monoxide, variations of nitrogen oxides (NOx), soot, etc. Many of these substances are harmful to human health and the environment. In particular, the classification of emissions known as particulate matter is recognized for significant negative health impacts. It is desirable to remove, or at least reduce, these unwanted, harmful substances from the exhaust gas before releasing it into the atmosphere.)
The workings of a combustion engine that turns chemical energy stored within fuel and oxygen into thermal energy is well known in the art, and will not be described in detail here. In short, engine 115 allows an amount of fuel and air mixture (that includes oxygen) into a combustion chamber of engine 115. Engine 115 then ignites the fuel-air mixture to initiate the combustion process. The fuel and air turns into very high temperature and high pressure gas, which expands to drive the moving parts (e.g., pistons) of engine 115. The by-products of the combustion process (especially when the fuel is not efficiently combusted), such as soot, carbon dioxide, particulate matter, variations of nitrogen oxides, etc., are collectively referred to as exhaust gas.
As the exhaust gas usually contain harmful substance, it is contemplated that the exhaust gas produced by engine 115 is treated before released into the atmosphere. As such, in some embodiments, the exhaust gas coming out from engine 115 is led through exhaust treatment system 120 before releasing the treated exhaust gas into the atmosphere through exhaust outlet 140. In some embodiments, exhaust treatment system 120 is configured to treat the exhaust gas by converting the harmful substance within the exhaust gas into non-harmful (or less harmful) substance.
In another embodiment, it is contemplated that the exhaust treatment system can include other types of emission control system (e.g., a diesel oxidation catalyst (DOC) or a selective catalytic reduction (SCR), etc.) to treat oxides of nitrogen (NOx). A SCR system typically contains catalysts that interact with a form of aqueous urea to reduce the nitrogen oxide concentration in the emission.
It is further noted that even though the exhaust treatment systems 200 and 300 of
It is contemplated that excitation chamber 400 can have one or more exhaust inlets that are configured to direct exhaust gas from the engine into excitation chamber 400. In this example, excitation chamber 400 includes two exhaust inlets 415a and 415b that directs exhaust gas from the engine into outer housing 405. Having more than one exhaust inlet allows a more even distribution of exhaust gas within the excitation chamber 400. In some embodiments, exhaust inlets 415a and 415b are configured to entrain the exhaust stream to travel in outer housing 405 in a spiral pattern in a direction as shown by arrow 445. For example, exhaust inlets 415a and 415b curve substantially as a spiral (i.e., conform to a spiral shape with less than 10% deviation). Preferably, exhaust inlets 415a and 415b curve substantially as a phi-based spiral.
Inner housing 410 and outer housing 405 are separated by separator 420. In some embodiments, separator 420 has multiple orifices that are spread throughout the entire surface of separator 420. Preferably, the orifices are evenly spread over the surface of separator 420. The orifices enable at least a portion (and preferably all) of the exhaust stream to enter into inner housing 410. Since the orifices are evenly spread over the surface of separator 420, the exhaust gas from outer housing 405 can be distributed in inner housing 410 evenly as well.
In some embodiments, the orifices on separator 420 have characteristics to induce the exhaust gas to travel in a coherent-structured turbulence flow form as the exhaust gas enters into inner housing 410 through the orifices. The orifices are holes on the separator 420 that are large enough for the exhaust gas to pass through. The size of the orifices is designed to control the flow of the exhaust gas to enter into the inner housing from the outer housing. In some embodiments, the orifices on the separator 420 are all evenly sized. In some other embodiments, the orifices are of different sizes. For example, the orifices in the upstream of the housing can be smaller than the orifices in the downstream to provide even flow of the exhaust gas throughout the length of the inner housing 410. Furthermore, the orifices are directional—the orifices are at an angle with respect to the length of the separator 420 to direct the exhaust gas into the inner housing 410 in a particular direction. In some embodiments, the orifices provide a curved surface to further entrain the exhaust gas to flow in a coherent turbulent flow as it enters into the inner housing 410. In addition, the inside wall of separator 420 of some embodiments includes a pattern of features on its surface (e.g., having a surface topology) to further induce the exhaust gas within inner housing 410 to flow in the coherent-structured turbulence flow form. Features that can be selected to be used on the inner wall's surface include, but not limited to, bumps, dimples, cavities, ridges, grooves, and wedges. The surface features, in some embodiments, are directional. This directional quality of the surface features can reduce pressure loss by creating micro jets (e.g., via Kelvin-Helmholtz instability), which in turns enables further mixing of the exhaust gas and oxygen. In some embodiments, the surface features are incorporated only into the section (e.g., section 460) of the inner wall of the inner housing 410 that is downstream to the orifices. In other embodiments, the surface features are incorporated in the entire (or a majority of) inner wall of the inner housing 410.
In some of these embodiments, the orifices on separator 420 and surface topology of surface on separator 420's inner wall are configured to induce the exhaust gas to travel in a rotating movement within the flow form. In some embodiments, the orifices and surface topology are configured to induce micro-rotations within the flow form. Further, the surface topology can also be configured to induce vortices within the flow form. These rotating movements, micro-rotations, and vortices can add to improve the ionization of the exhaust gas molecules.
In some embodiments, excitation chamber 400 also includes opposite electrodes to generate a plasma field for ionizing the exhaust gas. In some of these embodiments, exhaust treatment system 400 provides a first electrode in the form of a waveguide 425. Waveguide 425 can be disposed within the lumen of inner housing 410. As shown, waveguide 425 has an elongated dimension. Preferably, waveguide 425 is symmetrical across an axis 430 that runs along the middle of the elongated dimension of waveguide 425. Different embodiments of waveguide 425 have different shapes. In this example, waveguide 425 has a diamond shape, in which a diameter of waveguide 425 progressively and continuously reduces in size in the downstream direction for a majority (e.g., more than 50%, preferably more than 80%) of waveguide 425. In other words, waveguide 425 tapers off toward the downstream side of the exhaust gas flow direction.
In these embodiments, exhaust treatment system 400 also includes a second electrode that is of the opposite charge of waveguide 425. In some embodiments, the second electrode can be incorporated into (or part of) enclosure 435 of outer housing 405. In other embodiments, the second electrode can be incorporated into (or part of) the separator 420. Opposite charges of a power source (not shown) can be connected to enclosure 435 and waveguide 425, respectively, to provide the necessary charge to generate the plasma field.
As shown, enclosure 435 has a shape that complements the shape (i.e., the contour) of waveguide 425. Since waveguide 425 in this example has a diamond shape that tapers toward the downstream direction, enclosure 435 also widens at first and then reduces in diameter toward he downstream direction. In some embodiments, the shape of enclosure 435 provides substantially the same distance between enclosure 435 and waveguide 425 (the space in which the exhaust gas can flow). As defined here, substantially the same means at least 80%, and preferably at least 90%, identical.
It is contemplated that mixing air and fuel with the exhaust gas improves the oxidation efficiency of the exhaust gas. As such, in some embodiments, excitation chamber 400 also includes an air/fuel inlet configured to direct a stream of air and fuel mixture into excitation chamber 400. The air/fuel inlet can be implemented differently in different embodiments. In this example, excitation chamber 400 includes an air/fuel inlet 440 that directs a stream of air/fuel mixture into the interior of waveguide 425. In these embodiments, waveguide 425 includes an interior pathway and orifices (e.g., orifices 450a, 450b, and 450c, collectively orifices 450) through which the stream of air and fuel mixture can be led into inner housing 410. In some embodiments, the orifices 450 are configured to entrain the stream of air and fuel mixture to flow in vortices that are opposite in direction from the flow of the exhaust gas in the inner housing 410. Although
It is contemplated that mixing between the stream of exhaust gas and the stream of air/fuel mixture with multi-phase flow dynamics (e.g., Kelvin-Helmhotz instability, turbulent boundary layers, etc.) improves the efficiency of ionization. Thus, in some embodiments, orifices 450 and the surface topology on waveguide 425 are configured to entrain the stream of air/fuel mixture in a coherent turbulence that is in an opposite direction as the coherent turbulence formed by the stream of exhaust gas, as shown by arrows 445 and 455.
In addition to the structure of orifices 450, it is contemplated that the surface of waveguide 425 has a surface topology that further entrains the stream of air and fuel mixture to flow in the coherent-structured turbulence flow form. The surface topology can include at least a groove, a ridge, a dimple, etc.
Referring back to
In some embodiments, instead of having the shape of the outer housing to directly conform with the shape of the waveguide, it is contemplated that having a reverse relationship between the outer housing and the waveguide can create a reverse vortex effect that is beneficial to treating the exhaust gas.
As shown, the shape of the outer housing 705 is similar to the shape of the waveguide 725. However, unlike the excitation chamber 400, the outer housing 705 is shaped such that it provides an inverse relationship to the shape of the waveguide 725. As shown, while the wide end of the waveguide is located farther away from the exhaust outlet 717, the wider end of the outer housing 705 is located closer to the exhaust outlet 717.
The excitation chamber 700 has an exhaust inlet 715 that is configured to direct exhaust gas from the engine into the outer housing 705 of the excitation chamber 700. The exhaust inlet 715 can curve substantially as a spiral (i.e., conform to a spiral shape with less than 10% deviation) as shown in
Similar to the excitation chamber 400, the inner housing 710 and the outer housing 705 are separated by a separator 720 having multiple orifices that are spread throughout the entire surface of separator 720. The orifices enable at least a portion (and preferably all) of the exhaust stream in the outer housing 705 to enter into the inner housing 710. Preferably, the shape of the outer housing 705 entrains at least a majority of the exhaust gas stream to travel to the upper half (the narrower half) of the outer housing before entering into the inner housing 710 through the orifices. Furthermore, the shape of the orifices on the separator 720 entrains the exhaust gas to travel in a spiral pattern in an opposite flow (i.e., in a direction toward the exhaust outlet 717) as shown by arrow 747) as mentioned above with respect to
In addition, the inside wall of the inner housing 710 of some embodiments includes a pattern of features on its surface (e.g., having a surface topology) to further induce the exhaust gas within the inner housing 710 to flow in the coherent-structured turbulence flow form. Features that can be selected to be used on the inner wall's surface include, but not limited to, bumps, dimples, cavities, ridges, grooves, and wedges. The surface features, in some embodiments, are directional. This directional quality of the surface features can reduce pressure loss by creating micro jets (e.g., via Kelvin-Helmholtz instability), which in turns enables further mixing of the exhaust gas and oxygen. In this example, it is shown that the inner wall of the inner housing 710 includes grooves 750 to entrain the exhaust gas to flow in the coherent-structured turbulence flow form as the exhaust gas exits the excitation chamber 700 via the exhaust outlet 717.
In some embodiments, the excitation chamber also includes a microwave plasma generator to precondition the exhaust gas before the exhaust gas enters into the inner housing to receive treatment from a vortex impelled plasma.
It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
