Abstract:
A particular trap is regenerated without the use of heat. The regeneration is accomplished using a valving mechanism for periodically creating a reverse pressure throughout the entire trap, after the reverse pressure is created controls are operative to start a regeneration cycle by creating a substantially instantaneous reverse pressure drop across the porous walls of the entire trap to dislodge accumulated particulate cake and by causing the filtered exhaust gas to flow back through the porous walls to remove the dislodged particulate from the trap. A settling tank is connected to the exhaust pipe upstream of the trap to receive and store the dislodged particulate. The controls are operative to return the system to its filtering operation. Gaseous effluent from the tank is returned to the exhaust system upstream of the filter to provide a “closed system” in which only filter gas is discharged to atmosphere.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase application of International Application No. PCT/US13/53456 filed Aug. 8, 2013, which claims the benefit of provisional patent application Ser. No. 61/742,342 filed Aug. 8, 2012 by the present inventors. 
    
    
     DISCUSSION OF PRIOR ART 
     Commercially available diesel exhaust treatment systems utilize a particulate filter which is thermally regenerated. Diesel fuel is a convenient source of energy for such regeneration. During active filter regeneration, the exhaust gas temperature can be increased by combusting an additional quantity of fuel in the exhaust system using specialized hardware and using one of the following methods:
         Flame combustion—the fuel is combusted in a fuel burner, usually with a dedicated supply of combustion air, with the flame entering the exhaust system.   Catalytic combustion—the fuel is introduced through an exhaust injector, evaporated and mixed with exhaust gas, and oxidized over an oxidation catalyst.   Combined flame and catalytic combustion—a combination of the above methods, where a fuel burner is followed by a catalytic combustion system.
 
Further details can be found in “Filters Regenerated by Fuel Combustion” by W. Addy Majewski. 1  In short, the removed particulate is burned and creates CO2 which is passed into the atmosphere.  1  Majewski, W. Addy. “Filters Regenerated by Fuel Combustion.”  Diesel Technology Guide—Diesel Filter Systems . Dieselnet, 2009. Web. 27 May 2010. &lt;http://www.dieselnet.com/tech/pf_sys_fuel.html&gt;.
       

     An exhaust regeneration system developed by Illinois Valley Holding Company uses a back flow of filtered exhaust gases to regenerate a segment of the filter. The removed particulate is then burned in a separate burner which also creates CO2 which is passed to the atmosphere. It is desirable to create a system which precludes the release of CO2 into the atmosphere. 
     SUMMARY 
     In accordance with one embodiment of the present invention there is provided a system for regenerating a particulate trap in an exhaust system of an internal combustion engine and including a wall-flow particulate trap located in the engine&#39;s exhaust pipe and having a plurality of porous walls for filtering engine exhaust and removing particulates therefrom to form a particulate cake on the porous walls, a valving mechanism downstream of said trap for periodically creating a reverse pressure throughout said entire trap, a reversing mechanism operative after the reverse pressure is created for periodically creating a substantially instantaneous reverse pressure drop across the porous walls of said trap to dislodge accumulated particulate cake and causing the filtered exhaust gas to flow back through the porous walls to remove the dislodged particulate from said trap and carry the dislodged particulate therefrom, controls for starting and stopping a regeneration cycle, and a reservoir closed from the atmosphere and operatively connected to the exhaust pipe upstream of the trap for receiving the back-flow gas carrying the dislodged particulate from said trap and storing said dislodged particulate. 
     In accordance with another aspect of the present invention there is provided a non-thermal system for regenerating an entire particulate trap in an exhaust system of an internal combustion engine and including a wall-flow particulate trap located in the engine&#39;s exhaust system and having a plurality of porous walls for filtering engine exhaust and removing particulates therefrom to form a particulate cake on the porous walls, a valving mechanism downstream of said trap for periodically creating a reverse pressure throughout said entire trap, a reversing mechanism operative after the reverse pressure is created for periodically creating a substantially instantaneous reverse pressure drop across the porous walls of said entire trap to dislodge accumulated particulate cake and causing the filtered exhaust gas to flow back through the porous walls to remove the dislodged particulate from said entire trap and carry the dislodged particulate therefrom, and controls for starting and stopping a regeneration cycle. 
     Other features of the present invention provide a “closed system” in which only filtered gases are released to the atmosphere; pneumatic controls for starting and stopping the regeneration cycle; and a method for regeneration of an entire particulate filter, and/or for storing the removed particulate. 
     Advantages of Present Invention 
     The present invention discloses a particulate trap regeneration system which provides one or more of the following advantages: 1—eliminates heating of the filter during regeneration; 2—eliminates the need to oxidize carbon stored in the trapped particulate matter; 3—provides a settling tank to accumulate the removed particulate; 4—allows regeneration of the filter while the engine is under load; 5—provides recycling of gases from the settling tank through the filter via a “closed” system; 6—provides a simplified control system which utilizes available pressure from the exhaust system; 7—allows a higher gram-loading of particulate in the filter; 8—provides for regeneration of an entire trap in a short period of time. 
     The resultant benefits of the above are less fuel consumption; less disadvantage of having higher particulate deposits in the filter; improved filtration efficiency; a less expensive system than the thermally regenerated systems which requires more sophisticated hardware and control systems; eliminates the need for oxidizing the particulate in the filter which can damage the filter, the intumescent wrap, and any downstream aftertreatment; reduces and possibly eliminate downtime required for forced active regeneration and ash maintenance; and eliminates the need of controlled interaction of the particulate filter and the engine necessitated in the thermally regenerated systems. 
     Other features and advantages of the present invention will become apparent from the following detailed description when taken with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate one embodiment of a particulate trap regeneration system incorporating the above advantages and in which— 
         FIG. 1  is a diagrammatic illustration of the best known mode of carrying out the present invention and with the system in normal operation; 
         FIG. 2  is an exploded view of a suitable valve utilized in the  FIG. 1  embodiment; 
         FIG. 3  is a view, similar to  FIG. 1 , illustrating the back pressure build-up indicating that filter regeneration is needed; 
         FIG. 4  is a view, similar to  FIG. 1 , illustrating pressure build-up in the system prior to regeneration of the filter; 
         FIG. 5  is a view, similar to  FIG. 1 , illustrating regeneration of the filter and dumping to a settling tank; 
         FIG. 6  is a view, similar to  FIG. 1 , illustrating the system after regeneration and return to normal filtering operation; 
         FIG. 7  is a diagrammatic illustration of another embodiment for carrying out the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a particulate trap regeneration system operative to filter engine exhaust. Particulates generated by incomplete combustion of fuel in an engine  10  travel down an exhaust pipe  11  and are accumulated in a particulate filter (PF) or trap  12 . Flow through the exhaust pipe is shown by arrows in  FIG. 1 . The PF or trap  12  may be a cordierite filter manufactured by Corning Inc. of Corning, N.Y., U.S.A. The particulates accumulated in the PF begin to restrict the flow across the PF increasing the pressure in the exhaust system (backpressure). The shading in exhaust pipe  11  is indicative of pressure in the engine exhaust upstream of the trap  12 . The absence of shading downstream of the trap indicates that it is exiting to atmosphere. A line  14  connects the exhaust pipe  11  upstream of the PF  12  with a normally-open valve  16 , advantageously in the form of a pneumatically-actuated poppet valve having a diaphragm. As is known to those skilled in the art, components of valve  16  may be similar to those of a normally-closed valve such as shown in  FIG. 2 , with a change in arrangement to transform a normally-closed valve to one that is normally-open. 
     A normally-closed pneumatically-actuated dump valve  20  is positioned upstream of the PF and located in a pipe  19 .  FIG. 2  is an exploded view of a suitable valve for utilization as normally closed valve  20 . It is a commercially available valve sold by Tial Products Inc. of Owosso, Mich., U.S.A. It includes an actuator top  20   a , a spring  20   b , a diaphragm assembly  20   d , an actuator bottom  20   e , a valve guide  20   g , a housing  20   h , an internal valve  20   i , and a valve seat  20   s.    
       FIG. 3  illustrates the accumulation of particulate matter in the PF  12  and subsequent increase in backpressure. This increase is illustrated by the increased density of the shading in pipe  11  and at the upstream side of the PF  12 . Line  14  incorporates a blow-off valve  13  which opens when line pressure reaches a preselected set point. Once the backpressure reaches the determined set point, valve  13  opens and causes valve  16  to close thereby closing the system from atmosphere and initiating a regeneration cycle (see  FIG. 4 ). The engine  10  pressurizes the system through the PF to the valve  16 . This pressure is another increase as illustrated by the further increased density of the shading in exhaust pipe  11  and downstream of the PF, but now also throughout the PF. As an alternative, valve  16  could be an exhaust brake-type relief valve. A control line  18  connects the exhaust pipe  11  downstream of the PF  12  to the normally-closed pneumatically-actuated dump valve  20  positioned upstream of the PF and located in pipe  19 . Line  18  incorporates a blow-off valve  28  which opens when the regeneration pressure reaches a set point, conveniently 25 psig, and causes dump valve  20  to open. Thus the two valves  16  and  20  are operated sequentially. Blow-off valves  13  and  28  have check valves  13   a  and  28   a , respectively, for purposes hereinafter explained. A normally-open pneumatically-actuated relief valve  21  is positioned in exhaust pipe  11  between pipe  19  and engine  10 , but advantageously considerably closer to pipe  19 . Because valve  21  is connected to line  18  upstream of valve  20 , valve  21  is actuated (i.e. closed) before valve  20  is actuated (i.e. opened). However it is perceived that valve  21  may not be necessary for many applications. The sequential operation, first of valve  16  and then valve  20 , results whether or not valve  21  is incorporated. 
     Referring to  FIGS. 4 and 5 , opening of dump valve  20  connects the pressurized system to a lower pressure storage or settling tank  22 . Tank  22  can also be referred to as a receptacle or reservoir. This creates a reverse depression wave through the PF  12  which physically breaks off the particulate and, as shown by arrows in  FIG. 5 , transports it away from the PF into the settling tank  22 . This happens very rapidly in a matter of seconds, and the entire PF  12  is regenerated. The volume of the settling tank  22  is related to the engine size, particulate matter storage requirements, and other design parameters. It is perceived that the volume is more important than the shape of the settling tank. Hence the term “tank” is to be taken as suggestive of a closed volume. 
     Referring now to  FIG. 6 , as the particulate matter is channeled into the settling tank  22 , the pressure therein will begin to increase and as the pressure in the settling tank rises, a control tube  24   a  connected to the normally-open valve  16  equalizes the pressure across its valve diaphragm (such as shown at  20   d  in  FIG. 2 ) allowing valve  16  to open and the system downstream of the PF to return to near atmospheric conditions. Simultaneously, a second control tube  24   b  connected to normally-closed dump valve  20  equalizes the pressure across the valve  20  diaphragm  20   d  allowing valve  20  to close. 
     The filtered exhaust gas which transported the particulate matter to the settling tank  22  is then allowed to bleed back into the exhaust pipe  11  upstream of the PF via a return line  26 . The return line  26  has a check valve  27  which opens to allow such bleed back flow. An orifice (not shown) can serve the same function or the orifice and check valve can be used in combination. It is perceived that a venturi in exhaust pipe  11  can operate with line  26  to draw down pressure in settling tank  22 . In this manner gases from the settling tank  22  are filtered once again by the PF before exiting to the atmosphere. It will be noted that said gases are not the only gases in the settling tank because a percentage is unfiltered exhaust gas. The control pressures to valve  16 ,  20 ,  21  are bled from control lines  14  and  28  utilizing check valves  13   a  and  28   a , respectively. The bleeding back to exhaust pipe  11  insures that the valves  16 ,  20 , and  21  are not reactivated before the next regeneration is required. 
     It will be noted that what has been described is a closed system and this approach not only removes the particulate matter cake but assures that any gas exhausting to atmosphere has been cleaned by the PF  12 . For example, by passing the effluent of the settling tank through the PF, any particles that may be transported out of the settling tank will be caught by the filter. 
     It is now deemed apparent that the above-described apparatus causes regeneration of the entire filter via a process having steps performed in the following sequence:
         1. Filtering engine exhaust gases until the particulate filter  12  requires regeneration ( FIG. 3 .)   2. Shutting exhaust valve  16  downstream of the particulate filter to build up pressure in the exhaust system. ( FIG. 4 .)   3. Opening valve  20  upstream of the particulate filter to create a differential pressure across the filter  12 .   4. Directing the flow of filtered exhaust back through the particulate filter to fracture or remove the particulate cake and carry it into settling tank  22 .   5. Opening the exhaust valve  16  to return the system to filtering operation.   6. Bleeding gases in the settling tank to the exhaust system upstream of the particulate filter.       

     As described above these regeneration steps occur very rapidly and, hence, the entire particulate trap  12  can be regenerated while the engine  10  is running (i.e. is idling or under load); or during braking where the pressurization of the trap would be completed without any additional fuel use. 
       FIG. 7  illustrates an alternate embodiment of the system. A vacuum pump  29 , consisting of a venturi and air pressure source or utilizing a pump and motor, is utilized to evacuate a portion or all of the exhaust gases that are present in settling tank  22  before regeneration. The evacuation of the gases reduces the pressure in the settling tank  22  to create a differential pressure between the settling tank  22  and the exhaust  11 . Once the settling tank has reached a pressure set point that is sufficiently below the pressure in exhaust  11 , valve  21  is closed to reduce the volume and valve  20  opens creating a differential pressure across the particulate filter  12 . This differential pressure breaks off the particulate from the filter and creates a differential pressure gas flow that transports the particulate material into the settling tank  22 . After regeneration, valve  20  is shut and valve  21  is opened allowing the system to resume normal operation. 
     In this embodiment, a venturi connected with a compressed air line (not shown), for example from the air brake system on a vehicle or plant air for stationary engines, generates the required lower pressure in the settling tank  22  prior to regeneration. The gases in the settling tank  22 , which may have suspended particulate matter therein when exiting the venturi, travel through pipe  26  back into exhaust  11 . On entering the exhaust  11 , the gasses pass through and are filtered again by particulate filter  12 , thereby removing any entrained particulate matter before the gasses exit to ambient. Regeneration of the particulate filter  12  may occur advantageously during vehicle braking, where the compressor would regenerate the braking forces into the needed compressed air for particulate filter regeneration. The regeneration pressure can also be harnessed over multiple braking conditions until the settling tank  22  is at regeneration level. Additional opportune times for regeneration would be at startup and/or when the vehicle is stopped because at those times there is limited demand on vehicle&#39;s brake system. While the air brake pump can be utilized as vacuum pump  29 , any entrained particulate matter in the gasses exiting the settling tank  22  could potentially affect the performance and/or durability of the pump. 
     In another embodiment, a venturi (not shown) which operates with return line  26  and venture bypass (not shown) are both located in exhaust pipe  11 . The venturi and venturi bypass operate to reduce pressure in the settling tank  22  while allowing low normal operating backpressure on the engine. In order to not generate backpressure equivalent to the pressurization of exhaust  11  in the preferred embodiment, the lower amount of pressure drop created with this embodiment would require pressure to be generated in exhaust  11  in order to attain sufficient differential pressure for regeneration. The combination of settling tank  22  pressure level below that of the gases in exhaust  11  along with an increase in pressure in exhaust  11  above normal operating pressure would work together to create a sufficient differential pressure for regeneration while reducing the regeneration backpressure requirements of the engine. 
     The advantage of creating a lower pressure in settling tank  22  relative to pressurizing exhaust  11  is that the energy required for regeneration would be from a separate power source then the engine creating backpressure. This avoids altering the engine&#39;s performance and operation such that regeneration could occur at high engine loads. In large engine designs where the settling tank size could not be packaged for entire trap regeneration, the PF could be regenerated in segments. 
     In another version, the vacuum is generated by the engine with the use of an intake air system throttling valve. Under braking conditions, the throttle valve would close in the intake air system of the engine. The positive displacement action of the engine would pull a vacuum on the engine. This type of system would experience a delay in operation until sufficient air was reintroduced for combustion to efficiently take place if power was demanded during the regeneration. 
     While the above process steps have been described as used with specific apparatus, it should be understood that the steps are not to be limited to such arrangements and that other apparatus may be utilized to perform the steps. Similarly, the specific steps and their sequence may be modified and/or combined to perform the intended result. 
     While the above description is of the best known mode, it should not be construed as any limitation on the scope of the invention, as other variations will become apparent to those skilled in the art and the scope should be determined only by the scope of the appended claims.