Abstract:
The present invention provides an apparatus and a method for removing particulate matter from exhaust gas stream prior to emission. The apparatus comprises a chargeable device having at least a pair of chargeable surfaces. The chargeable surfaces are positioned relative to one another to form a gap. The apparatus further comprises a charger for supplying opposite electrical charges to the chargeable surfaces. When chargeable surfaces are charged, an electrical field is created within the gap. Exhaust particles passing through the electrical field will locally reduce the dielectric constant of the exhaust gas causing an electrical arc to pass through the particles. The heat generated by the electrical arc will cause the particles to combust, resulting in emissions of carbon dioxide.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention.  
           [0002]    The field of the invention relates to a system for removing particulate matter from exhaust gas of internal combustion engines, particularly from diesel-powered motor vehicles.  
           [0003]    2. Description of the Related Art.  
           [0004]    The internal combustion engine is an important part of an automobile. It is generally known that the internal combustion engine, especially the diesel engine, releases exhaust gasses that may contain particulate matter. Tightening emissions requirements continue to allow lower and lower amounts of particulate emissions from consumer and commercial vehicles. The challenge of meeting the requirements becomes difficult, and current solutions each has its drawbacks. The first solution is with engine management. While it is debated as to whether engine management can continue to meet the particulate matter emissions level, engine management may reduce overall engine performance to achieve the requirement. The second solution is a particulate filter with regeneration. Various kinds of filters or trapping devices have been employed. However, a “dirty” diesel engine may emit on the order of one kilogram of particulate matter in 1000 miles (1609 kilometers) of continuous operation. After continued trapping, the accumulated particulate matter may create back pressure that may adversely affect the operation of the engine. Vehicles which utilize filter elements for trapping exhaust particulates must therefore employ regeneration means for dealing with this problem.  
           [0005]    A number of diesel exhaust gas cleaning devices that include filter regeneration means has been proposed in the following patents:  
           [0006]    U.S. Pat. No. 4,450,681 discloses a carbon particulate cleaning device including a carbon particulate catching means, a fuel injecting means, a fuel igniting means for igniting the fuel, and a gas blowing means which blows gas for maintaining the fuel burning and applying the heat of the burning fuel into the carbon particulates. The carbon particulates caught by the carbon particulate catching means are effectively burnt and eliminated.  
           [0007]    U.S. Pat. No. 4,485,621 discloses a similar system that includes a trapping chamber and a regeneration chamber. The filtering chamber includes a means for filtering or trapping particulate matter present in the exhaust gas. The regenerating chamber contains an electrically conductive substrate which carries an oxidation catalyst. The electrically conductive substrate material is part of an electrical circuit and is heated by electric current. Means are provided for injecting a combustible fuel into the regenerating chamber where the fuel-exhaust gas mixture is effectively heated and burned. The resulting heated gas then passes into the trapping chamber to incinerate and burn off the particulates.  
           [0008]    U.S. Pat. No. 4,538,412 discloses a cleaning device for exhaust particulates of a diesel engine. The cleaning device contains a trap case provided in a main passageway of the exhaust gas, a filter material disposed in the trap case to catch carbon particulates or other exhaust particulates contained in the exhaust gas, and an electric heater for igniting and burning the exhaust particulates in the filter material.  
           [0009]    U.S. Pat. Nos. 4,538,441 and 4,544,388 teach the use of a monolithic honeycomb ceramic trap to collect the carbon particulates emitted from a diesel engine then heating an air flow through the ceramic trap using an electric heater to a temperature sufficient to ignite the collected carbon particulates.  
           [0010]    The prior art has also explored the use of various catalyst materials to reduce the ignition temperature of carbon soot in order to preserve the system.  
           [0011]    For example, U.S. Pat. Nos. 4,655,037 and 4,670,020 teach the use of one or more metal octoates added to diesel fuel to produce a reducible metal oxide which reduces the ignition temperature of the collected carbon particles to a range from 250° C. to 310° C.  
           [0012]    U.S. Pat. No. 5,758,496 discloses a particulate and exhaust gas emission control system having a particulate trap, an additive tank for storing a fuel additive effective to depress the ignition temperature of the carbon particulates, and means for metering the additive to the fuel tank. The particulate trap has a layer of catalytic material to promote the oxidation of carbon monoxide and unburned hydrocarbons emitted by the diesel engine.  
           [0013]    While the above-described systems may work to reduce emissions of particulate matter from exhaust gas, these systems are expensive and require a significant amount of space for all of the necessary hardware. In addition, the required filter element of the disclosed solutions may generate exhaust backpressure with consequent adverse engine generation.  
           [0014]    What is needed is a system that eliminates or significantly reduces emissions of particulate material. Particularly needed is a system that is easy to assemble and fit in the exhaust system of internal combustion engines. Further needed is a system that is economical.  
         SUMMARY OF THE INVENTION  
         [0015]    The present invention provides an apparatus for cleansing particulate matter from exhaust gas that is released by an engine such as a diesel-powered engine. Generally, the apparatus includes electrically chargeable device positioned in the path of the exhaust stream, providing an electric field through which the exhaust gasses must pass. The presence of the particulate matter, which is relatively electrically conductive, as compared to exhaust gas, will locally reduce the dielectric constant of the exhaust gas. If sufficient electrical potential is charged to surfaces within the exhaust stream, then an electrical arc will pass through the particulates. The heat generated by the electrical arc will cause the particulates to combust, resulting in emissions of carbon dioxide and, if any hydrogen is in the particulates, water.  
           [0016]    In one embodiment, the apparatus of the present invention includes a chargeable device having at least one pair of surfaces that are chargeable with opposite charges. The chargeable surfaces positioned relative to one another bordering a gap in which an electric field may be created when the chargeable surfaces are charged with opposite charges. The electric field is sufficient to generate an arc through or near particulates passing between the surfaces. This arc produces sufficient heat to cause the particulate matter in exhaust gas to combust. The apparatus of the present invention further includes an electrical charger electrically connected to the chargeable device for providing charges to the chargeable surfaces of the chargeable device.  
           [0017]    In one aspect of the invention, each of the chargeable surfaces is defined on one of perforated plates having a plurality of holes for allowing the exhaust gas stream to flow therethrough. The perforated plates or the chargeable surfaces of the perforated plates are made of electrically conductive material. The plurality of perforated plates may be linked together along the edges by a connector made of electrically insulating and optionally heat insulating material. The connector may be a pair of bridges, plates, or a cylindrical housing made of electrically insulating material.  
           [0018]    The present invention further includes a method for reducing particulate emissions from internal combustion engines having an exhaust system. The method involves providing at least one pair of electrically chargeable surfaces facing each other. A gap is provided between the chargeable surfaces. The electrically chargeable surfaces are positioned to receive exhaust gas containing exhaust particulates. The method includes supplying opposite electrical charges to the electrically chargeable surfaces to generate an electrical arc through or near any particulates present in the gap. This arc produces a large amount of heat in its vicinity. Further, the method includes passing exhaust gas containing particulate matter into the gap and heating the particulate matter to combustion at or near the arc. Finally, included is the step of emitting exhaust gas with reduced particulate matter from the gap and automatically from the exhaust system.  
           [0019]    One advantage to the device of the present invention is that particulate combustion is continuous. There is no need to monitor flow rates and determine when to regenerate a filter. This results in a much simpler electrical system. Furthermore, the backpressure of the plates may be far less than the backpressure resulting from a filter. Additionally, the amount of power required to maintain the electrical charge on the plates and supply the electrical arc may be less than the power required to run the pumps and relays needed for known burner-based solutions. Furthermore, since no fuel and significantly less additional air are required, installation is much simpler and less expensive. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0021]    [0021]FIG. 1. is a side elevational view of an apparatus for reducing particulate emissions according to one embodiment of the present invention;  
         [0022]    [0022]FIG. 2 is a front elevational view of a perforated plate according to the embodiment shown in FIG. 1;  
         [0023]    [0023]FIG. 3 is a side elevational view of a chargeable device according to another embodiment of the invention; and  
         [0024]    [0024]FIG. 4 is a cross-sectional view of a chargeable device of the present invention, disposed within an exhaust pipe.  
         [0025]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings.  
         [0027]    Referring now to FIG. 1, apparatus  10  represents an exemplary embodiment of the present invention. Apparatus  10  consists of chargeable device  20  connectable to charger  30 . Chargeable device  20  defines first plate  11  positioned parallel to second plate  12 . First plate  11  defines outer surface  13  and inner surface  14 . Second plate  12  defines outer surface  15  and inner surface  16 . Gap  50  formed between inner surfaces  14  and  16  may be about 1.0 mm to about 80 mm wide. A preferred width of gap  50  may be about 12 mm. Plates  11  and  12  may be linked together by connector  40 . Connector  40  may be a pair of bars, plates or a cylindrical tube that holds plates  11  and  12  together in the parallel position. Plates  11  and  12  may be made of any electrically conductive material such as stainless steel, steel, or copper, whereas connector  40  may be made of electrically insulating material, which may also be heat resistant material. For example, connector  40  may be made of ceramic.  
         [0028]    According to FIGS. 1 and 2, plate  11  has an electrical port  17 , which is connected to terminal  31  of charger  30 . Also as shown, plate  12  has an electrical port  18 , which is connected to terminal  32  of charger  30 . Either terminal  31  or  32  can be a positive terminal, while the other is a negative terminal. Thus, either plate  11  or  12  can be charged with positive charges, while the other is charged with negative charges.  
         [0029]    In an alternative embodiment, plate  11  may have inner surface  14  made of an electrically conductive material, while outer surface  13  is made of electrically insulating material. Similarly, plate  12  may have inner surface  16  made of an electrically conductive material, while outer surface  15  is made of an electrically insulating material such as ceramic. In this case, surfaces  14 A and  16 A are chargeable. Charger  30  provides electrical charges to chargeable surfaces  14 A and  16 A so that surfaces  14 A and  16 A carry opposite charges.  
         [0030]    Charger  30  may produce either a direct current (DC) or an alternating current (AC). Charger  30  may include a step up transformer capable of charging the chargeable surfaces  14 A and  16 A to about 20,000 to about 100,000 volts. A power source for the charger may include the battery and current electrical system of a motor vehicle. The relationship between the voltage of the chargeable surfaces  14 A and  16 A and the width of gap  50  determines the strength of the electrical field created within gap  50 . It is important to create an electric field strong enough to produce an arc when exhaust particulates are present in gap  50 . Thus, the voltage of the chargeable surfaces  14 A and  16 A varies depending on the width of gap  50 . For example, chargeable surfaces  14 A and  16 A should carry about 20,000 volts, when gap  50  is about 1.0 mm in width. On the other hand, chargeable surfaces  14 A and  16 A would carry in excess of 100, 000 volts, when gap  50  is adjusted to 80 mm in width.  
         [0031]    In one aspect of the invention, as shown in FIG. 1, plates  11  and  12  are perforated or have a plurality of holes  22  and  23 , respectively, for allowing exhaust gas stream to flow into gap  50 . The sizes of holes  22  and  23  may not necessary be the same. Holes  22  should be large enough to allow exhaust particulates to pass readily into gap  50 . Holes  23  may not be the same size as holes  22 . However, holes  22  and  23  should allow exhaust gas to flow through easily without creating back pressure in the exhaust system.  
         [0032]    In FIG. 2, a further exemplary embodiment of perforated plate  11  is shown. In this embodiment, plate  11  is a circular screen, having holes  22  spreading evenly over plate  11 . Similarly, perforated plate  12  (not shown) may also be made of the same type of screen. The shape of perforated plates  11  and  12  may not necessarily be circular, as long as perforated plates  11  and  12  can be positioned in the path of the flow of the exhaust gas, and efficiently receive the flow of the exhaust.  
         [0033]    In another embodiment, as shown in FIG. 3, the apparatus of the present invention may include chargeable device  70  having a plurality of perforated plates  71 ,  72 ,  73 , and  74  positioned in parallel to one another. Perforated plate  71  defines chargeable surface  71 A that faces gap  91  and chargeable surface  72 A of perforated plate  72 . Perforated plate  73  defines chargeable surface  73 A that faces gap  92  and chargeable surface  74 A of perforated plate  74 .  
         [0034]    Perforated plates  71 - 74  further define electrical ports  81 ,  82 ,  83 , and  84  for connecting to a charger (not shown). The charger provides electrical charges to chargeable surfaces  71 A- 74 A. Chargeable surfaces  71 A and  72 A will carry opposite charges, and chargeable surfaces  73 A and  74 A will carry opposite charges. For example, as shown in FIG. 3, chargeable surfaces  71 A and  73 A receive positive charges from the charger, whereas chargeable surfaces  72 A and  74 A receive negative charges from the charger. When chargeable surfaces  71 A- 74 A are charged, electric fields are created within gaps  91  and  92 . The width of gaps  91  and  92  are adjusted to create electrical field strength sufficient to produce an arc when the exhaust particulates are present, as described hereinabove. Chargeable surfaces  71 A and  72 A may carry a higher voltage than chargeable surfaces  73 A and  74 A, resulting in a stronger electrical field in gap  91  than in gap  92 .  
         [0035]    In one aspect of the invention, perforated plates  71 - 74  may be connected to one another by connector  80 . Similar to connector  40  of device  20 , described earlier, connector  80  may be a cylindrical tube which may be made of an electrically insulating material, and optionally heat insulating material.  
         [0036]    In another aspect, perforated plates  71 - 74  define a plurality of holes  93 ,  94 ,  95  and  96 , respectively. The sizes of holes  93 - 96  may vary, however, holes  93 - 96  should allow the exhaust gas and the particles to flow therethrough.  
         [0037]    The use of the apparatus of the present invention is demonstrated in FIG. 4. The apparatus comprises of chargeable device  100  disposed within an exhaust pipe  130  of an engine. Chargeable device  100  consists of metal screens  101  and  102  having chargeable surfaces  101 A and  102 A, respectively. Metal screens  101  and  102  are separated by gap  105 . Metal screen  101  and  102  are connected to a charger (not shown) through electrical ports  106  and  107 , respectively. Metal screens  101  and  102  are charged with opposite charges, creating an electrical field between charged surface  101 A of metal screen  101 , and charged surface  102 A of screen  102 . During an operation of the engine, exhaust gas (G) including carbon or hydrocarbon particles (P) or both flows through screen  101  into gap  105 . Since carbon particles are electrically more conductive than air, the dielectric constant of exhaust gas within gap  105  decreases in the vicinity of a carbon particle. Electrical potential between the charged surfaces creates an electrical field through which the exhaust gas flows. Electric arcs will be created which pass through or near the carbon and/or hydrocarbon particles. The heat generated by the arc is sufficient to induce combustion of carbon and/or hydrocarbon particles.  
         [0038]    In another aspect of the use of the instant apparatus, as shown in FIG. 4, extra air (A) may be supplied to the exhaust gas flow, before the exhaust gas flows through device  100 . The extra air provides oxygen that supports combustion of the particulate matter. The oxygen and the carbon particles will form carbon dioxide after the combustion. The oxygen and the hydrocarbon particles will form water and carbon dioxide after the combustion. The product of the combustion may be released through screen  102  and disposed elsewhere. Although the configuration of the apparatus in FIG. 3 provides only one chance of combustion, if the flow of the exhaust is properly adjusted, the single combustion can efficiently reduce particulate emissions.  
         [0039]    In the case in which the chargeable device has a plurality of pairs of perforated plates such as chargeable device  70  in FIG. 3, the combustion can occur in both gaps  91  and  92 . In this instance, the exhaust particulates that escape the first combustion in gap  91  may be combusted later on in gap  92 .  
         [0040]    While the present invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.