Abstract:
An exhaust gas recirculation system for an internal combustion engine includes intake and exhaust manifolds that respectively receive ambient air and expel exhaust gas. A recirculation line fluidly connects the exhaust and intake manifolds. An exhaust gas recirculation valve is included in the recirculation line and is controlled to distribute exhaust gas into the intake manifold. A particle trap is arranged to receive all of the exhaust gases from the exhaust manifold and includes a particle collection chamber therein. A stagnation region is provided within the particle trap such that all the exhaust gas passed through the exhaust gas particle trap is directed toward the stagnation region therein and at least a portion of debris carried with the exhaust gas is retained within the particle collection chamber.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns devices for reducing pollutants discharged by an internal combustion engine. More specifically, the invention relates to such devices adaptable to diesel engines which trap particles and vapor carried by the exhaust gas discharged from the engine. 
     It is recognized that the production of noxious oxides of nitrogen (NO x ) which pollute the atmosphere are undesirable. Steps are therefore typically taken to eliminate, or at least minimize, the formation of NO x  constituents in the exhaust gas products of an internal combustion engine. The presence of NO x  in the exhaust gas of internal combustion engines is generally understood to depend, in large part, on the temperature of combustion within the cylinders of the engine. In connection with controlling the emissions of such unwanted exhaust gas constituents from internal combustion engines, it is widely known to recirculate a portion of the exhaust gas back to the air intake portion of the engine (so-called exhaust gas recirculation or EGR). Since the recirculated exhaust gas effectively reduces the oxygen concentration of the combustion air, the flame temperature at combustion is correspondingly reduced, and since NO x  production rate is exponentially related to flame temperature, such exhaust gas recirculation (EGR) has the effect of reducing the emission of NO x . 
     It is further known to adapt the engine with electronic sensors to evaluate and control various operational parameters of the engine. One example includes providing a differential pressure transducer across an orifice to measure mass flow rate of the exhaust gas. Using this mass flow rate measurements of the exhaust gas, exhaust gas recirculation may be controlled to optimize engine performance and decrease emission levels. These sensors are typically placed in direct contact with the intake or exhaust gas which are often hostile to the electronic sensor itself. For example, the differential pressure sensor may be placed within the exhaust system that is in direct contact with debris laden exhaust gas. 
     Debris mixed with the exhaust gas includes particulate emissions can cause extensive damage to engines turbochargers or superchargers. Particulate debris is abrasive and enters the engine oil causing undue wear on the piston rings, valves, and other parts of the engine. A common form of particulate matter is “soot” which is a sticky substance that can lead to carbon build-up on surfaces exposed to the soot. The soot is particularly damaging to electronic sensors such as temperature and pressure sensors. Soot build-up on the sensor causes a degradation in sensor accuracy and in some instances permanent damage. 
     FIG. 1 depicts a typical engine and EGR system  10  including known components for actively controlling the mass flow of the recirculated exhaust gas. An internal combustion engine  12  includes an air intake manifold  14  attached to the engine  12  and coupled to the various cylinders  16  of the engine, typically through valves (not shown). Intake manifold  14  receives intake ambient air via conduit  18 . An exhaust gas manifold  20  is attached to the engine  12  and coupled to the exhaust gas ports of the various combustion cylinders typically through valves (not shown). The exhaust manifold  20  exhaust combustion gas to the atmosphere via exhaust gas conduit  22 . The engine  12  typically includes a fan  24  which is driven by the rotary motion of the engine to cool engine coolant fluid flowing through a radiator (not shown) positioned proximate the fan  24 . 
     An exhaust gas recirculation line  26  is connected at one end  28  to the exhaust gas conduit  22 , and at its opposite end  30  to an EGR cooler  32 . The cooler  32  reduces the temperature of the exhaust gas in anticipation of re-entering the inlet air stream of conduit  18 . An EGR flow control valve  34  is connected at one end  36  thereof to EGR cooler  32  via conduit  38 , and at an opposite end  40  thereof to exhaust manifold  20  via conduit  42 . The valve  40  is controllable to open or close the EGR path in response to engine performance requirements. 
     An air intake system (not shown) provides a supply of fresh intake air through a filter (not shown) to compressor  44  of a turbocharger  46 . A first portion of the exhaust gas discharged from exhaust manifold  20  of engine  12  is supplied to intake conduit  18  through exhaust gas recirculating line  26  to combine with fresh air driven by the turbocharger compressor. A second portion of the exhaust gas flows through turbine  48  of turbocharger  46  to rotate compressor  44 . As a result, intake air exiting from compressor  44  of turbocharger  46  is compressed and heated. The compressed intake air preferably flows through an intake air cooler  50  to reduce the air temperature to a level for optimum combustion in the engine cylinders. Intake air cooler  50  may be an air-to-air type heat exchanger, however, other types of diesel engine coolers or heat exchangers may be satisfactorily used. In operation, the EGR flow control valve  34  is controlled by an engine control module  52  (ECM) in response to differential pressure sensed through a pressure sensor  54  providing a pressure signal to the ECM  52 , via signal path  56 . The ECM  52  uses the differential pressure to calculate the mass flow rate of recirculated exhaust gas through valve  34 . In response to the pressure signal, ECM  52  provides a corresponding control signal to EGR valve  34 , through control circuit  58 . Therefore, the EGR valve  34  is controlled via the ECM  52  to divert any desired amount of exhaust gas directly from the exhaust gas recirculation line  26  to intake conduit  18 . 
     In one attempt to decrease particulate carried by the exhaust gas, devices referred to as “baghouses” have been employed to filter solid material carried by the exhaust gas. The baghouses can be provided with a fiber bag to capture debris with little on no exhaust gas backpressure. However, once a substantial amount of particulate is captured by the bag the device would lead to a detrimental increase in exhaust gas backpressure. This backpressure can result in a build up of debris within the exhaust system causing poor engine performance and ultimately failure of the engine. 
     Other known devices which decrease particulate emissions carried by the exhaust gas include regeneration devices which burn away the accumulation of debris. U.S. Pat. No. 5,390,492 to Levendis discloses a regeneration device for use with a filter assembly to decrease the particulate emission in the system. The regeneration device includes a collection chamber fitted with an electric powered incinerator to burn away material accumulating in the collection chamber. Unfortunately, the device is complicated and not a viable alternative for internal combustion engines utilizing after market equipment to decrease exhaust particulate. Furthermore, regeneration devices tend to be expensive to implement and are susceptible to malfunction. 
     U.S. Pat. No. 5,458,664 issued to Ishii et al. discloses a particle trap provided with a metallic mesh filter, the particle trap is placed directly in the exhaust gas line and is sized to avoid significant exhaust gas backpressure. However, the filter inherently accumulates debris and decreases the flow area, and consequently, an unwarranted back pressure develops. The backpressure in the exhaust line causes degradation of engine power and permanent engine damage, after a period of time. 
     What is therefore needed is a device for trapping debris in the form of exhaust gas particulate and vapor to protect equipment downstream and at the same time cause only insignificant restriction of exhaust gas from the engine. Moreover, a device that is inexpensive to manufacture and includes widespread adaptability to virtually all sizes and types of engines is desirable. Preferably, such a device should be serviceable rather than warranting periodic device replacement. 
     SUMMARY OF THE INVENTION 
     These unmet needs are addressed by the exhaust gas recirculation system of the present invention. In one aspect of the invention, an exhaust gas recirculation system for an internal combustion engine includes intake and exhaust manifolds to respectively receive ambient air and expel exhaust gas. A recirculation line fluidly connects the exhaust and intake manifolds. An exhaust gas recirculation valve is included in the recirculation line and is controlled to distribute exhaust gas into the intake manifold. A particle and/or vapor trap is arranged to receive all of the exhaust gas from the exhaust manifold and includes a particle collection chamber therein. A stagnation region is provided within the particle trap configured so that all the exhaust gas passing through the trap is directed toward the stagnation region therein and at least a portion of debris carried with the exhaust gas is retained within the particle collection chamber. 
     The present invention further provides a particle trap for an exhaust gas recirculation control system for use with an internal combustion engine including a housing having at least one inlet and at least one outlet. A flow deflector is included in the housing and is arranged to deflect a flow of exhaust gas discharged from the inlet. A stagnation region is provided within the housing and is in fluid communication with the inlet and is placed in relation to the flow deflector to receive all exhaust gas from the inlet. The stagnation region is in fluid communication with the outlet through an exhaust gas portal wherein substantially all of the flow of exhaust gas is directed toward the stagnation chamber to urge separation and collection of debris entrained in the exhaust gas. 
     In one aspect of the invention, the flow deflector is in fluid communication with an inlet cavity. The inlet cavity is in fluid communication with the stagnation region through an exhaust gas acceleration region to urge the flow of exhaust gas toward the stagnation chamber. 
     It is one object of the present invention to provide an exhaust gas recirculation system that receives substantially all of the exhaust gas expelled from the internal combustion engine such that debris carried by the exhaust gas is trapped and prevented from accumulating on operational sensors and the EGR valve. 
     Another object of the present invention is to provide a particle trap for an internal combustion engine which traps substantially all the debris, in the form of soot and vapor, expelled from the engine without a significant backpressure caused by the particle trap. 
     Yet another object is to provide a particle trap which may be readily integrated into new and existing internal combustion engines alike and one which is serviceable rather than requiring periodic replacement. Also, a particle trap which does not require electrical connection to operate and one which is inexpensive and not complicated to manufacture is desirous. 
     These and other objects, advantages and features are accomplished according to the systems and methods of the present invention, as described herein with reference to the accompanying figures. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIG. 1 is a schematic diagram of a typical known engine and exhaust gas recirculation system. 
     FIG. 2 is a schematic diagram of an exhaust gas recirculation system including a particle trap according to one embodiment of the present invention. 
     FIG. 3 is a side cross-sectional view of the particle trap depicted in FIG.  2 . 
     FIG. 4 is an end cross-sectional view of the trap shown in FIG. 3, taken along line  4 — 4 , illustrating the connecting passageway and inlet cavity. 
     FIG. 5 is an end cross-sectional view of the particle trap shown in FIG. 3, taken along line  5 — 5 , illustrating the exhaust gas portal. 
     FIG. 6 is a perspective cross-sectional view of the particle trap of FIGS. 2-5, including a schematic diagram of the flow of exhaust gas and the trapping of particulate and vapor therein. 
     FIG. 7 is a plan view of the schematic flow diagram of FIG. 6, and further illustrating the length L of an exhaust gas portal of the inventive trap. 
     FIG. 8 is a graph depicting percent particle escape versus particle size for three differing particle trap assemblies according to the present invention. 
     FIG. 9 is a graph depicting flow coefficients for the particle trap assemblies depicted in FIG.  8 . 
     FIG. 10 is a side cross-sectional view of a second embodiment particle trap of according to the present invention. 
     FIG. 11 is a sectional view of the particle trap taken along line  11 — 11  of FIG. 10, illustrating the pair of exhaust gas portals. 
    
    
     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 illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates. 
     The present invention provides an exhaust gas particle trap to divert and contain substantially all of the soot and vapor discharged by an internal combustion engine carried by the exhaust gas from the engine. The particle trap is preferably fitted within the exhaust line exiting the exhaust manifold to trap debris carried by the exhaust gas before such debris reaches the EGR valve and electronic equipment employed to efficiently operate, with environmental consciousness, an internal combustion engine. 
     Referring to FIG. 2, an exhaust gas recirculation system  60  according to one embodiment of the present invention is shown. The system  60  differs from the known system  10  (FIG. 1) in that system  60  includes a particle trap  62  to contain debris  64  carried by the exhaust gas and provide exhaust gas that is substantially free of solid material. 
     Differential pressure sensor  54  is interposed in the EGR to aid in the control of the EGR valve  34 . The sensor is typically a diaphragm type sensor, and is generally susceptible to performance degradation due to debris carried by the exhaust gas. The debris carried by the exhaust gas includes a sticky carbon rich substance which quickly accumulates and gums up equipment and narrows flow passages. The pressure sensor  54 , and the remaining equipment positioned downstream relative to particle trap  62 , are protected from debris discharged from the engine  12 . Preferably, particle trap  62  is adapted to fit within exhaust gas conduit  22 , connecting the exhaust manifold  20  and recirculation line  26 . Notably, in this most preferred arrangement all the exhaust gas discharged from the exhaust manifold  20  is received by the particle trap  62 . 
     Referring now to FIGS. 3-5, details of the structure of the particle trap  62  will be explained. Trap  62  includes a housing  68  with threaded ports  70 ,  72 , respectively, provided on the opposite axial ends  74 ,  76  of housing  68 . Axial end  74  of housing  68  receives threaded fitting  78  sealably connected with inlet conduit  80  through a pressure fit engagement, as is customary. Inlet conduit  80  is in direct fluid communication with the exhaust manifold  20  such that exhaust gas is transported from exhaust manifold  20  to particle trap  62  through inlet conduit  80  (FIG.  2 ). 
     Threaded port  72  of housing  68  threadably receives fitting  82  sealably connected with outlet conduit  84  through a pressure fit engagement. Outlet conduit  84  provides a discharge passage for cleaned exhaust gas to exit particle trap  62  and is fluidly connected with the turbine  48  and recirculation line  26  (FIG.  2 ). It is understood that other fittings can be utilized that are capable of achieving a fluid-tight connection of the trap between the conduits  80  and  84 . 
     Housing  68  of particle trap  62  preferably includes a flow deflector  86  at the end of an inlet cavity  92  that is transversely positioned relative to inlet opening  88  of inlet conduit  80 . Flow deflector  86  is provided to divert debris laden exhaust gas to a remote portion of the particle trap for further processing of the gas. Immediately downstream of flow deflector  86  is gas acceleration region  90 . Acceleration region  90  is annular in shape and is located between inlet cavity  92  and an outer surface  94  of inlet conduit  80 . Acceleration region  90  is provided immediately downstream from the flow deflector  86  to further guide the gas through the particle trap. Additionally, acceleration region  90  represents a decrease in flow area relative to the immediately preceding inlet cavity  92  consequently causing the exhaust gas to speed up through acceleration region  90 . The moving exhaust gas exits acceleration region  90  having a significant velocity and is projected beyond exhaust gas portal  114  such that debris laden exhaust gas does not prematurely escape through the exhaust gas portal  114 . Annular shaped stagnation region  96  is positioned downstream relative to acceleration region  90  and is located between counterbore  98  and outer surface  94  of inlet conduit  80 . Funnel shaped transition portion  99  connects acceleration region  90  and stagnation region  96 . Transition portion  99  includes an inner diameter that progressively increases from acceleration region  90  to stagnation region  96  and as a result exhaust gas flowing through transition portion  99  experiences a significant decrease in velocity. Stagnation region  96  is provided to significantly slow the exhaust gas discharged from acceleration region  90 . Once slowed, the relatively heavy debris particles carried by the exhaust gas tend to attach to the walls of counterbore  98  while the exhaust gas remains diffuse. Particle collection chamber  100  is located between face surface  104  of counterbore  98  and outer surface  94  of inlet conduit  80 . Transverse face  102  of threaded plug  78  provides a floor for particle collection chamber  100 . 
     Axial end  76  of housing  68  includes an outlet cavity  106  in fluid communication with outlet conduit  84 . Outlet cavity  106  and inlet cavity  92  communicate through a connecting passageway  108  provided in housing  68  (FIG.  4 ). Connecting passageway  108  extends from a transversely positioned floor  110  of outlet cavity  106  towards outer radial portion  112  of counterbore  98  (FIG.  5 ). As best seen in FIG. 5, an exhaust gas portal  114  is formed between the intersection of counterbore  98  and connecting passageway  108 . 
     In the preferred embodiment of the invention, the centerline of inlet conduit  80  extends axially along a first reference axis  116  and the centerline of outlet conduit  84  extends along a second reference axis  118 . First and second reference axes  116 ,  118  are arranged parallel relative to one another. Preferably the two axes are offset, although the present invention contemplates first and second reference axes  116 ,  118  being arranged such that they are coincident. A third reference axis  120  represents the centerline of connecting passageway  108  and is parallel relative to first reference axis  116  of inlet conduit  80 . Third reference axis  120  may be offset a distance of 1.0 inch, for example, relative to first axis  116 . For machining purposes, it is preferred that the axes  116  and  118  are offset a distance equal to the radius of the connecting passageways  108 . 
     One advantage of trap  62  is that it may be inexpensively manufactured from bar stock. For example, housing  68  may be made from a piece of “off the shelf” cylindrical or hexagonal carbon steel bar stock. The threaded plugs  78 ,  82  may be selected from a variety of standard fittings such as NPT fittings. Moreover, the inlet and outlet conduits  80 ,  84  may be pressure fitted with their respective threaded plugs  78 ,  82  as is customary. It is contemplated that the threaded plugs should be reusable such that housing  68  may be removed, the debris accumulated therein extracted, and the housing then replaced as a course of periodic maintenance. 
     To manufacture housing  68  through machining operations only the axial ends  74 ,  76  of housing  68  need be accessed. Inlet cavity  92  and counterbore  98  of axial end  74  are machined. Similarly, inlet cavity  106  and connecting passageway  108  of axial end  76  are machined, the threads in each axial end  74 ,  76  may then be formed to substantially complete the housing. Specifically, outlet cavity  106  in housing  68  may be formed by drilling, for example using a 1.625 inch drill, boring into the housing  68 , along second reference axis  118 . The connecting passageway  108  may then be drilled using a 0.375 inch drill along third reference axis  120 . The inlet cavity  92  may then be formed by drilling, using a 1.25 inch drill, along the first reference axis  116 . The first reference axis  116  is offset 0.25 inch, relative to second reference axis  118 , for example. Counterbore  98 , may then be provided in housing  68  by drilling, using a 1.5 inch drill, for example along the first reference axis  116 . Although the trap is most easily formed by machining, it is contemplated that housing  68 , alternatively, may be a cast or forged component having cored internal passageways rather than drilled passageways to reduce labor costs corresponding to machining the housing. 
     Referring to FIGS. 6 and 7, it may be seen that connecting passageway  108  intersects counterbore  98  to form the truncated cylindrical shaped exhaust gas portal  114 . The flow characteristic of particle trap is, in part, dependent on the size of portal  114  which spans length “L” as best illustrated in FIG.  7 . 
     In operation, exhaust gas carrying debris in the form of soot and vapor, illustrated by arrows  122 , is discharged from inlet opening and strikes the flow deflector  86 . The flow, laden with debris, is introduced into inlet cavity  92  and thereafter forced into the annular acceleration region  90 . The debris carried with the exhaust gas is accelerated through the acceleration region  90  and directed toward stagnation region  96 . As the flow transitions from acceleration region  90  to stagnation region  96  through transition portion  99 , the flow expands and accordingly decreases in velocity. Once in the stagnation region, the debris  124  settles in the particle collection chamber  100 . The debris  126  tends to separate from the gas when the combination is exposed to the stagnation region  96  and accumulates within the particle collection chamber  100 . Thereafter, “cleaned” exhaust gas, as illustrated by arrows  128 , is discharged through exhaust gas portal  114  and is eventually dispatched from particle trap  62  to turbine  48 , EGR valve  34  and pressure sensor  54  as illustrated by arrows  66  (FIG.  2 ). The exhaust gas recirculation system  60 , operating without the inventive particle trap  62  would lead to poor engine performance or premature failure resulting in costly repairs and equipment downtime. 
     Referring to FIG. 7, exhaust gas portal  114  is positioned axially adjacent the acceleration region  90 , such that exhaust gas and debris is directed toward the stagnation region  96 , before it is allowed to exit the exhaust gas portal  114 . The acceleration region ensures that the debris laden exhaust gas is projected past the exhaust portal  114  so that the exhaust gas may be cleaned within the stagnation region prior to exiting through the exhaust gas portal  114 . 
     The exhaust gas and debris carried therewith introduced into inlet conduit  80  enter as pressure pulses discharged from the engine  12  (FIG. 2) and the pressure pulses urge further circulation of the flow through particle trap  62 . Thus, particle trap  62  may be oriented in a variety of positions and effectively trap debris. However, it may be seen that particle trap  62  is most effective if vertically oriented, whereby particle collection chamber  100  is arranged beneath flow deflector  86  such that gravity assists the debris toward particle collection chamber  100 . 
     Referring to FIG. 8, shown is particle retention data corresponding to three different particle trap constructions differing by the length L (FIG. 7) of exhaust gas portal  114 . L 1  is the shortest length and is 1.75 inch, for example. L 2  and L 3  are 1.95 inch and 2.23 inch, respectively. Therefore, it may be seen that as the length of the exhaust gas portal is increased, i.e., as the flow area is increased, the percentage of total particulate debris allowed to escape through the portal increases for each portal dimension, the escape ratio for different particle sizes does not vary significantly. 
     Referring to FIG. 9, a second graph is provided representing the flow characteristics for the particle trap structures having respective portal lengths L 1 , L 2  and L 3 . It is contemplated that flow through the particle trap  62  will coincide with relatively low flow rates, such as a flow having a Reynolds Number of 13,000. The data, illustrated in FIGS. 8 and 9, was collected at low flow velocity (Re 13,000) except for one instance wherein data was collected for a particle trap having the portal length L 2  at a high Reynolds Number (FIG.  9 ). It may be seen that the flow loss coefficient improves, (i.e., the particle trap causes less impedance to exhaust gas discharged from exhaust manifold  20  (FIG.  2 )) as the length of the portal is increased. Portal length L 3  provides a significant improvement in flow over the particle trap having a portal length of L 2 . Further, and with reference to FIG. 8, the percent of particle escape between the particle vapor traps having portal lengths L 2  and L 3  is not significantly different, yet a significant improvement in flow loss coefficient is provided by the trap having portal length L 3 . The formula used to calculate each flow loss coefficient may be expressed as:          K     Flow                 Loss                 Coefficient       =         P     Total                 Inlet       -     P     Total                 Outlet           P     Dynamic                 Inlet                                
     A second embodiment of a particle trap is shown in FIG.  10  and differs from the first embodiment  62  by having a pair of particle traps combined in a single housing  130 . Particle trap  132  includes housing  130  with threaded ports  134 ,  136  provided on axial end  138 . The other axial end  140  of housing  130  includes threaded ports  142 ,  144 . Axial end  138  of housing  130  receives threaded fittings  146 ,  148  sealably connected with inlet conduits  150 ,  152  through respective pressure fit engagements, as is customary. Inlet conduits  150 ,  152  are in direct fluid communication with the exhaust manifold such that exhaust gas is transported from the exhaust manifold to particle trap  132  through inlet conduits  150 ,  152 . Threaded ports  142 ,  144  of housing  130  threadably receive fittings  154 ,  156  sealably connected with outlet conduits  158 ,  160  through pressure fit engagements. Outlet conduits  158 ,  160  provide discharge passages for clean exhaust gas to exit particle trap  132  and are fluidly connected with both the turbine and recirculation line. Therefore, cleaned exhaust gas is discharged from trap  132  and is introduced to the turbine, the EGR valve and pressure sensor without having soot and vapor carried by the exhaust gas. 
     Housing  130  of particle trap  132  includes a pair of flow deflectors  162 ,  164  that are transversely positioned relative to respective inlet openings  166 ,  168  of respective inlet conduits  150 ,  152 . Immediately downstream of the flow deflectors  162 ,  164  are inlet cavities  174 ,  176  and gas acceleration regions  170 ,  172 . Acceleration regions  170 ,  172  are annular in shape, and respectively located between inlet cavities  174 ,  176  and outer surfaces  178 ,  180  of inlet conduits  150 ,  152 . Annular shaped stagnation regions  182 ,  184  are positioned downstream relative to acceleration region  170 ,  172  and are located between counterbores  186 ,  188  and outer surfaces  178 ,  180  of inlet conduits  150 ,  152 . Particle collection chambers  190 ,  192  are located between wall surfaces  194 ,  196  of counterbores  186 ,  188  and outer surfaces  178 ,  180  of inlet conduits  150 ,  152 . Transverse faces  198 ,  200  of threaded plugs  146 ,  148  provide respective floors for particle collection chambers  190 ,  192 . 
     Axial end  140  of housing  130  includes outlet cavities  202 ,  204  in fluid communication with outlet conduit  158 ,  160 . Outlet cavities  202 ,  204  and inlet cavities  174 ,  176  are in respective fluid communication through connecting passageways  206 ,  208  provided in housing  130 . Connecting passageways  206 ,  208  respectively extend from transversely positioned floors  210 ,  212  of outlet cavities  202 ,  204  towards outer radial portions  214 ,  216  of counterbores  186 ,  188 . Exhaust gas portals  218 ,  220  are formed between the respective intersections of counterbores  186 ,  188  and connecting passageways  206 ,  208  (FIG.  11 ). 
     In the preferred embodiment of the invention, the centerlines of inlet conduits  150 ,  152  extend axially along a pair of first reference axes  222   a ,  222   b  and the centerlines of outlet conduits  158 ,  160  extend along a pair of second reference axes  224   a ,  224   b . First and second pairs of reference axes  222   a ,  222   b ,  224   a ,  224   b  are arranged parallel to one another. Preferably the two pair of axes are offset, although, it is envisioned that, alternatively, first and second pairs of reference axes  222   a ,  222   b ,  224   a ,  224   b  may be arranged such that each inlet conduit is axially aligned with each outlet conduit. A third pair of reference axes  226   a ,  226   b  represent the centerlines of connecting passageways  206 ,  208  and are preferably parallel relative to respective first pair of reference axes  222   a ,  222   b  of inlet conduits  150 ,  152 . Each of the pair of third reference axes  226   a ,  226   b  may be offset relative to each respective first reference axis  222   a ,  222   b  a distance as that was previously described in accordance with the distance between axes  120  and  116  associated with particle trap  62 , illustrated in FIG.  3 . For machining purposes it is preferred that the pair of axes  222   a ,  222   b  are offset relative to axes  224   a ,  224   b , by a distance equal to the radius of the respective connecting passageways  226   a ,  226   b.    
     Particle trap  132  may be manufactured utilizing similar techniques and materials as previously described in association with particle trap  62  of the first embodiment. In order for exhaust gas to flow into intake conduits  158 ,  160 , from the exhaust manifold a tee fitting (not shown) may be provided to accordingly divert the flow from the exhaust conduit, attached to the exhaust manifold, to the inlet conduits of the particle trap  132 . Similarly, a tee fitting may be provided to transport cleaned exhaust gas away from the particle trap  132  through outlet conduits  158 ,  160 . 
     In a preferred embodiment, the dimensions of each individual trap of the pair of traps illustrated are similar to the dimensions previously described in accordance with first embodiment particle trap  62 . However, the present invention contemplates that the length of each exhaust gas portal L a  and L b  may be independently varied to provide an overall suitable particulate retention and flow loss coefficient for the particle trap  132 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. 
     For instance, it is understood that a vehicle engine and EGR system may be adapted with a particle trap having multiple stagnation chambers and associated collection chambers in a single housing such that adapting the trap to an exhaust system does not cause a significant backpressure of exhaust gas during extended use and concomitantly provides for a significant collective volume to retain trapped debris.