Abstract:
An exhaust system includes a reverse flow heat exchanger having a plate separating an intake chamber and an exit chamber, each chamber having an inlet and an outlet located at opposing ends to allow flow therethrough. The plate can include a vane connected to the end of the plate in the vicinity of an inlet or an outlet. The vane is configured to reduce resistance to fluid flow near the intake chamber inlet. The exhaust system includes a heating manifold, such as a combustion chamber, configured to receive an exhaust stream from the intake chamber, further heat the exhaust stream, and return the exhaust stream to the exit chamber. Embodiments of the system can be configured to additionally perform as a catalytic converter and/or a muffler.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is related to U.S. Non-Provisional Patent Application Ser. No. 11/______ filed Apr. 14, 2006 and entitled “Particle Burning in an Exhaust System” (attorney docket number PA3612US). This application is also related to U.S. Non-Provisional Patent Application Ser. No. 11/______ filed Apr. 26, 2006 and entitled “Air Purification System Employing Particle Burning” (attorney docket number PA3693US). 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to emission controls and more particularly to systems for reducing particles in exhaust streams.  
         [0004]     2. Description of the Prior Art  
         [0005]     When a fuel burns incompletely, pollutants such as particles and hydrocarbons are released into the atmosphere. The United States Environmental Protection Agency has passed regulations that limit the amount of pollutants that, for example, diesel trucks, power plants, engines, automobiles, and off-road vehicles can release into the atmosphere.  
         [0006]     Currently, industries attempt to follow these regulations by adding scrubbers, catalytic converters and particle traps to their exhaust systems. However, these solutions increase the amount of back pressure exerted on the engine or combustion system, decreasing performance. In addition, the scrubbers and particle traps themselves become clogged and require periodic cleaning to minimize back pressure.  
         [0007]     Radiation sources and heaters have been used in exhaust systems, for example, to periodically clean the particle traps or filter beds. Others solutions have included injecting fuel into the filter beds or exhaust streams as the exhaust enters the filter beds to combust the particles therein. However, the filter beds can be sensitive to high temperatures and the radiation sources and heaters must be turned off periodically.  
       SUMMARY  
       [0008]     An exhaust system comprises a reverse flow heat exchanger including a plate defining a plane and separating an exit chamber and an intake chamber. Each chamber of the heat exchanger has an inlet and an outlet located at opposing ends to allow flow therethrough. The exhaust system also comprises a first manifold coupled to the reverse flow heat exchanger and in fluid communication with the intake chamber inlet. A vane disposed within the first manifold is situated relative to the intake chamber inlet so as to reduce resistance to fluid flow near the intake chamber inlet. The exhaust system can also comprise a heating manifold that receives exhaust from the intake chamber, heats the exhaust, and returns the exhaust to the exit chamber. In some embodiments, the heating manifold is a combustion chamber for burning particles in the exhaust. In these embodiments the exhaust system can also comprise a radiation source for heating the particles to at least an ignition temperature.  
         [0009]     Another exemplary exhaust system comprises a first manifold and a reverse flow heat exchanger coupled to the first manifold. Here, the reverse flow heat exchanger defines a transverse plane and includes a plurality of parallel plates separating a number of chambers, each chamber having an inlet and an outlet. These chambers comprise a set of intake chambers alternating with a set of exit chambers, where the inlets of the intake chambers being in fluid communication with the first manifold and the outlets of the intake chambers being in fluid communication with the inlets of the exit chambers. The exhaust system can further comprise a heating manifold coupled to the reverse flow heat exchanger to provide the fluid communication between the outlets of the intake chambers and the inlets of the exit chambers.  
         [0010]     A vehicle comprising an internal combustion engine and the exhaust system described above is also provided. The exhaust system can serve as either or both of a muffler and a catalytic converter.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]      FIGS. 1 and 2  depict top and front views, respectively, of an exemplary system for burning particles in an exhaust system in accordance with an embodiment of the invention.  
         [0012]      FIGS. 3 and 4  depict cross sections of the intake chamber and exit chamber, respectively, of the system shown in  FIGS. 1 and 2 .  
         [0013]      FIG. 5  depicts a cross section taken along the line  5 - 5  of  FIG. 2 .  
         [0014]      FIG. 6  depicts a cross section taken along the line  6 - 6  of  FIG. 2 .  
         [0015]      FIG. 7  depicts a cross section taken along the line  7 - 7  of  FIG. 1 .  
         [0016]      FIGS. 8 and 9  depict top and front views, respectively, of an exemplary system for burning particles in an exhaust system in accordance with another embodiment of the invention.  
         [0017]      FIGS. 10 and 11  depict cross sections of the intake chamber and exit chamber, respectively, of the system shown in  FIGS. 8 and 9 .  
         [0018]      FIG. 12  depicts a cross section taken along the line  12 - 12  of  FIG. 8  with several alternative implementations of a vane.  
         [0019]      FIG. 13  depicts a cross section taken along the line  13 - 13  of  FIG. 8 .  
         [0020]      FIG. 14  depicts a schematic representation of a vehicle comprising an internal combustion engine and an exhaust system in accordance with another embodiment of the invention.  
     
    
     DETAILED DESCRIPTION  
       [0021]     An exhaust system comprises a reverse flow heat exchanger coupled to a means for heating the exhaust gas, such as a combustion chamber for burning particles carried by the exhaust gas. The reverse flow heat exchanger recovers heat from the exhaust gas after passing through the heating means and transfers the heat to the exhaust gas entering the heating means. The heat recovery increases the energy efficiency of the exhaust system and provides further advantages as described below.  
         [0022]      FIGS. 1 and 2  show top and front views, respectively, of an exemplary exhaust system  100 . The exhaust system  100  is generally applicable and can be included, for example, as part of a vehicle, a power plant, or a fireplace. The embodiment depicted in  FIGS. 1 and 2  comprises a reverse flow heat exchanger  110  including two chambers separated by a plate  120  (shown in dashed lines to indicate that the plate is internal to the heat exchanger  110 ). One chamber of the heat exchanger  110  is in fluid communication between a first manifold  220  and a combustion chamber  130 . A second chamber of the heat exchanger  110  is in fluid communication between the combustion chamber  130  and a second manifold  230 . The chambers within the heat exchanger  110  are described in greater detail below. The heat exchanger  110  including the plate  120 , the combustion chamber  130 , and the, manifolds  220 ,  230  can be constructed using any suitable material capable of withstanding the exhaust gases at the operating temperature of the exhaust system  100 . Suitable materials include stainless steel, titanium, and ceramics. The plate  120  should be constructed of a material with high thermal conductivity, such as a metal, to provide good heat transfer between the chambers.  
         [0023]     In operation, exhaust gas  210  from a source such as a diesel engine enter the manifold  220  and are directed through the heat exchanger  110  to the combustion chamber  130 . In the illustrated embodiment, particles within the exhaust are burned in the combustion chamber  130 , significantly increasing the temperature of the exhaust gas. Combustion of the particles is facilitated by a radiation source  140  attached to the combustion chamber  130 . Suitable radiation sources  140  and designs for the combustion chamber  130  are described in U.S. patent application Ser. No. 11/______ filed on Apr. 14, 2006 and titled “Particle Burning in an Exhaust System.” 
         [0024]     The heated exhaust gas  240  exits the combustion chamber  130 , passes back through the heat exchanger  110 , and leaves the exhaust system  100  through the manifold  230 . In the heat exchanger  110 , heat from the hot gas  240  exiting the combustion chamber  130  is transferred to the incoming exhaust gas  210  from the manifold  220  through the plate  120 . By using the residual heat of the combustion of the particles to heat the incoming exhaust gas  210 , the exhaust system  100  utilizes less energy. Other advantages of the heat exchanger  110  are discussed herein.  
         [0025]     It will be appreciated that although the illustrated embodiment in  FIGS. 1 and 2  includes a combustion chamber  130 , the present invention is not limited to exhaust systems including combustion chambers. While the heat exchanger  110  needs to be coupled to some heating source to raise the temperature of the exhaust gas, the combustion chamber  130  is merely one example. The combustion chamber  130  can be replaced, for example, with a catalytic converter comprising a catalytic material supported on a substrate that is heated by a resistive heating element. In general terms, the combustion chamber  130 .is an example of a heating manifold that heats the exhaust gas from the intake chamber  310  of the heat exchanger  110  and returns it to the exit chamber  410  of the heat exchanger  110 .  
         [0026]      FIG. 3  and  FIG. 4  are cross sections of the exhaust system  100 . In  FIG. 3 , a cross section  300  is taken along section  3 - 3  in  FIG. 1  through an intake chamber  310 . The intake chamber  310  is formed between the plate  120 , an exterior wall of the heat exchanger  110  (not visible in this perspective), and two spacers  320  that maintain a proper spacing between the exterior wall and the plate  120 . Openings between the spacers  320  form an inlet  330  and an outlet  340  of the intake chamber  310 . The inlet  330  and the outlet  340  provide fluid communication between the intake chamber  310  and the manifold  220  and the combustion chamber  130 , respectively.  
         [0027]     The cross section  300  is characterized by a transverse plane  350 , seen edge on in  FIG. 3 , which bisects the heat exchanger  110  along a longitudinal axis thereof. In this embodiment, the inlet  330  is below the transverse plane  350  and the outlet  340  is above the transverse plane  350 . Placing the inlet  330  and outlet  340  on opposite sides of the transverse plane  350  causes the exhaust gas to traverse a diagonal of the intake chamber  310 .  
         [0028]     In  FIG. 4 , a cross section  400  is taken along section  4 - 4  in  FIG. 1  through an exit chamber  410 . The exit chamber  410  is formed between the plate  120  (not visible in this perspective), another exterior wall of the heat exchanger  110 , and two spacers  320 ′. As above, openings between the spacers  320 ′ form an inlet  420  and an outlet  430  that provide fluid communication with the combustion chamber  130  and the manifold  230 , respectively. In various embodiments, manifolds  220  and  230  consist of a continuous tube separated by a baffle  440 , generally aligned with the transverse plane  350 , configured to prevent fluid communication between manifolds  220  and  230 . In these embodiments, the manifolds  220  and  230  share a common longitudinal axis that is approximately parallel to a plane defined by the plate  120  and perpendicular to the transverse plane  350 .  
         [0029]     In the illustrated embodiment, the inlet  420  is below the transverse plane  350  and the outlet  430  is above the transverse plane  350 . As with the intake chamber  310 , the inlet  420  and outlet  430  are on opposite sides of the transverse plane  350  so that the fluid flow is diagonal across the exit chamber  410 . Arranging the fluid flows along the diagonals of the two chambers  310 ,  410  provides the gases  210  and  240  greater opportunity to transfer heat therebetween.  
         [0030]     Some embodiments of the heat exchanger  110  include multiple plates  120  to form multiple alternating intake and exit chambers  310 ,  410  to provide even greater heat transfer.  FIGS. 1 and 2  are also representative of these embodiments.  FIG. 5  shows a cross section  500  taken along the section  5 - 5  in  FIG. 2  of an exhaust system  100  including multiple plates  120 . Cross section  500  shows the multiple plates  120  forming alternating intake chambers  510  and exit chambers  520  where the intake chambers  510  are open to receive exhaust from the manifold  220 . Similar to the above chambers  310 ,  410 , each of the chambers  510 ,  520  are formed by two plates  120  separated by spacers  320  with openings therebetween to provide inlets and outlets. It will be appreciated that in these embodiments, as well as in the embodiments with only a single set of chambers  310 ,  410 , the external walls of the heat exchanger  110  can also be plates  120 . One method of forming the heat exchanger  110  is to assemble a stack of alternating plates  120  and spacers  320  and to weld or bolt the assembly together.  
         [0031]     The manifold  220  can also include one or more vanes disposed relative to an intake chamber inlet  330  to reduce resistance to fluid flow near that intake chamber inlet  330 . For example, vanes  530  extend from the plates  120  in  FIG. 5 . The vanes  530  effectively increase the orifice size of the inlets  330  to reduce fluid frictions. In various embodiments, vanes  530  can be joined to the ends of the plates  120 . In other embodiments, the vanes  530  are integral with the plates  120  and can be formed by bending the ends of the plates  120  before assembling the heat exchanger  110 .  
         [0032]      FIG. 6  shows a cross section  600  taken along section  6 - 6  in  FIG. 2  of the exhaust system  100 . Cross section  600  shows multiple plates  120  forming alternating intake chambers  510  and exit chambers  520  where the exit chambers  520  are open to vent exhaust to the manifold  220 . The manifold  230  can also include one or more vanes  530  disposed relative to the exit chamber outlets  430  in order to reduce resistance to fluid flow near the exit chamber outlets  430 . For example, a vane  530  extends from the plate  120  as shown in  FIG. 6 . In various embodiments, vanes  530  also extend from the ends of the plates  120  at the intake chamber outlets  340  and the exit chamber inlets  420  that communicate with the combustion chamber  130 .  
         [0033]      FIG. 7  shows a cross section  700  taken along the section  7 - 7  of exhaust system  100  of  FIG. 1 . Cross section  700  shows an end-on view of multiple plates  120 , including the vanes  530 , and multiple spacers  320  forming alternating intake chambers inlets  330  and exit chambers outlets  430 . Also depicted in  FIG. 7  is the baffle  440  configured to prevent fluid communication between manifolds  220  and  230 .  
         [0034]      FIGS. 8 and 9  show top and front views, respectively, of another exemplary exhaust system  800 . The exhaust system  800  is generally similar to the exhaust system  100  but differs with respect to the orientation of the heat exchanger  110 . Specifically, the heat exchanger is rotated relative to the manifolds  220 ,  230  and/or the combustion chamber  130  such that the transverse plane  530  of the heat exchanger  110  is aligned vertically rather than horizontally. Accordingly, the baffle  440  is also rotated from horizontal to vertical.  
         [0035]     Some embodiments of the exhaust system  100 ,  800  include insulation  910  around the heat exchanger  110  and the combustion chamber  130 , as shown in  FIG. 9 . The use of insulation reduces the amount of energy required to heat the exhaust gas within the combustion chamber  130 . More generally, it will be appreciated that insulation  910  can be applied individually to any of the heat exchanger  110 , the combustion chamber  130 , and the manifold  220 , or to any combination of these components.  
         [0036]      FIGS. 10 and 11  are cross sections of exhaust system  800 . In  FIG. 10 , a cross section  1000  is taken along section  10 -  10  in  FIG. 9  through an intake chamber  310 , and in  FIG. 11 a  cross section  1100  is taken along the line  11 - 11  in  FIG. 9  through an exit chamber  410 . As before, the intake chamber  310  and the exit chamber  410  are formed between the plate  120 , an exterior wall of the heat exchanger  110 , and spacers  320 . Openings between the spacers  320  form the inlets  330 ,  420  and outlets  340 ,  430 . The intake chamber  310  is in fluid communication between the manifold  220  and the combustion chamber  130 . The exit chamber  410  is in fluid communication between the combustion chamber  130  and the manifold  230 . In various embodiments, manifolds  220  and  230  consist of a continuous tube separated by a vertical baffle  440 .  
         [0037]     The heat exchanger  110  is again characterized by a transverse plane  1010  with the inlet  330  below the transverse plane  1010  and the outlet  340  above the transverse plane  1010 . Likewise, the inlet  420  is below the transverse plane  1010  and the outlet  430  is above the transverse plane  1010 . The inlets  330 ,  420  and outlets  340 ,  430  are on opposite sides of the transverse plane  1010  so that fluid flows diagonally through the chambers  310 ,  410 .  
         [0038]      FIG. 12  shows a cross section  1200  taken along the section  12 - 12  within manifold  220  of exhaust system  800 . Cross section  1200  shows multiple plates  120  forming alternating intake chambers  510  and exit chambers  520 . As above, each chamber  510 ,  520  is formed between two plates  120  and spacers  320 .  FIG. 12  shows a number of alternative concepts for vanes  530  that can extend from the ends of the plates  120 . In some embodiments, vanes  1210  are disposed on both sides of an opening. In other embodiments, vanes  1220  can be spherically shaped, vanes  1230  can be of different lengths, and vanes  1240  can be aerodynamically shaped. When vanes  530  on successive openings increasingly extend into a manifold, as in  FIGS. 5 and 6 , or as the succession of vanes  1220 ,  1230 , and  1240 , the vanes  530  are said to be “feathered.” Feathering further helps to direct flow within the respective manifold to reduce flow friction loses.  
         [0039]      FIG. 13  shows a cross section  1300  taken along section  13 - 13  of exhaust system  800 . Cross section  1300  shows multiple plates  120 , including vanes  530 , and multiple spacers  320  forming alternating intake chambers inlets  330  and exit chambers outlets  430 . Also depicted is baffle  440  configured to prevent fluid communication between manifolds  220  and  230 . It will be appreciated that in these embodiments the manifolds  220  and  230  define separate but parallel longitudinal axes. These axes are approximately perpendicular to a plane defined by the plate  120  and parallel to the transverse plane  350 .  
         [0040]     Several further advantages of reverse flow heat exchangers  110  should be noted. For example, these heat exchangers are self-cleaning. It will be appreciated that should a deposit form on an internal surface of one of the plates  120 , the restriction to the flow of exhaust gas around the deposit will tend to cause a local increase in the temperature at the restriction. Eventually, the local temperature increase will reach an ignition temperature of the deposit material, causing the deposit to burn away. Another advantage of the heat exchangers  110  is that the heated internal surfaces of the chambers  310 ,  410  reduce the resistance to fluid flow through the chambers  310 ,  410  thereby lowering head loss through the exhaust system  100 . Further, it will be appreciated that the heat exchangers  110  can serve to muffle sound due to the expansions and contractions that the exhaust gas goes through as it passes through successive openings. The muffling effect can be further enhanced by tuning the dimensions of the chambers to behave as resonating chambers. Accordingly, heat exchangers  110  can replace mufflers on vehicles.  
         [0041]      FIG. 14  shows a schematic representation of a vehicle  1400  comprising an internal combustion engine  1410 , such as a diesel engine. The vehicle  1400  also comprises an exhaust system  1420  that includes an exhaust pipe  1430  from the engine  1410  to a reverse flow heat exchanger  1440 , a combustion chamber  1450 , and a radiation source  1460 . The vehicle  1400  further comprises a controller  1470  for controlling the power to the radiation source. The controller  1470  can be coupled to the engine  1410  so that no power goes to the radiation source  1460  when the engine is not operating, for example. The controller  1470  can also control the radiation source  1460  in a manner that is responsive to engine  1410  operating conditions. Further, the controller  1470  can also control the radiation source  1460  according to conditions in the combustion chamber  1450 . For instance, the controller  1470  can monitor a thermocouple in the combustion chamber  1450  so that no power goes to the radiation source  1460  when the temperature within the combustion chamber  1450  is sufficiently high to maintain a self-sustaining combustion reaction.  
         [0042]     In the foregoing specification, the present invention is described with reference to specific embodiments thereof, but those skilled in the art will recognize that the present invention is not limited thereto. Various features and aspects of the above-described present invention may be used individually or jointly. Further, the present invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be recognized that the terms “comprising,” “including,” and “having,” as used herein, are specifically intended to be read as open-ended terms of art.