Patent Publication Number: US-2021172355-A1

Title: Overlapping vane muffler

Description:
RELATED APPLICATION 
     This application claims benefit to U.S. Provisional Patent Application Ser. No. 62/943828 filed Dec. 5, 2019 entitled “Overlapping Vane Muffler,” which is hereby incorporated herein in its entirety. 
    
    
     GOVERNMENT INTEREST 
     The invention described herein may be manufactured, used and licensed by or for the U.S. Government. 
    
    
     BACKGROUND 
     Field of the Invention 
     Embodiments of the present invention generally relate to mufflers for attenuating loud sound levels and, more specifically, to a muffler with an overlapping vane structure. 
     Description of the Related Art 
     Traditional expansion mufflers for attenuating loud sounds produced by machinery, engines, equipment and the like have been available for a long time without much change in technology. These mufflers rely on rapid expansion of exhaust gasses into chambers that are interconnected with pipes. The muffler features of length, volume, area, number of chambers and impedance help create the sound attenuation. Energy is converted to heat, and each successive expansion and contraction helps to reduce the peak amplitude and elongate the duration of each exhaust pulsation. Additional attenuation can be derived from perforated materials with fiberglass batting materials to absorb additional energy. 
     Therefore, there is a need in the art for new designs of mufflers to produce improved sound attenuation for a given muffler size as compared to a traditional expansion muffler. 
     SUMMARY 
     Embodiments of the present invention generally include apparatus for attenuating loud sound levels comprising an enclosure having an inlet and an outlet, where an exhaust flow director is positioned within the enclosure and fluidly coupled to the inlet and the outlet. The exhaust flow director comprises a plurality of overlapping vanes that directs the exhaust flow to attenuate the level of the sound produced by the exhaust. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  depicts a perspective view of one embodiment of the inventive muffler; 
         FIG. 2  depicts a cross-sectional view of the embodiment in  FIG. 1  taken through the plane of the muffler; 
         FIG. 3  depicts a muffler embodiment having an exhaust flow director comprising twelve flat overlapping vanes within a circular enclosure; 
         FIG. 4  depicts an acoustic ray tracing as a graphical depiction of sound propagation within circulation region and through a vane gap of the flat vane embodiment of  FIG. 3 ; 
         FIG. 5  depicts another embodiment of an exhaust flow director comprising curved, extruded vanes; 
         FIG. 6  depicts an embodiment of an exhaust flow director comprising circularly arranged curved vanes; 
         FIG. 7  depicts another embodiment of an exhaust flow director comprising gap tapered vanes; 
         FIG. 8  depicts a muffler embodiment including the exhaust flow director of  FIG. 7 ; 
         FIG. 9  depicts a perspective view of an embodiment of a muffler that has two exhaust inputs; 
         FIG. 10  depicts a cross sectional perspective view of half of the dual-input muffler of  FIG. 9 ; 
         FIG. 11  depicts an embodiment of an exhaust flow director comprising twin overlapping vane assemblies; 
         FIG. 12  depicts a muffler embodiment that utilizes the twin overlapping vane assemblies of  FIG. 11 ; 
         FIG. 13  depicts a cross section of a muffler embodiment comprising nested vane assemblies; 
         FIG. 14  depicts a cross section of a muffler embodiment having an exhaust flow director comprising a spherical overlapping vane assembly; 
         FIG. 15  depicts a cross sectional perspective view of a rectangular muffler embodiment; 
         FIG. 16  depicts a close up, perspective view of the input channel of the muffler in  FIG. 15 ; 
         FIG. 17  depicts exemplary embodiments of vanes having edge textures; and 
         FIG. 18  depicts an embodiment of an exhaust flow director comprising vanes having disrupted edges. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention include a muffler comprising an enclosure having an inlet and an outlet, with an exhaust flow director positioned between the inlet and outlet. The term exhaust is defined and used herein as a broad term to encompass acoustic (sound) and fluid flow emanating from a machine. Embodiments of the muffler can be used to attenuate sound levels in any type of machine including, but not limited to, internal combustion engines, turbines, pneumatic equipment, steam engines and the like. The fluid flow may encompass any fluid in which a sound may propagate including, but not limited to, exhaust gases, air, water, and the like. The sound emanating from a machine is primarily the result of pressure, flow, temperature and acoustic perturbations. These exhaust sounds have both acoustic and flow components with differing propagation velocities, amplitudes and frequency content. Flow implies a net displacement of matter with momentum, such as expanding gasses exiting a volume through a pipe, whereas an acoustic propagating wave is an energy transfer by percussions and rarefactions between adjacent molecules without any gross displacement of the molecules from the neutral position. The sound attenuating concepts described herein effect both the acoustic propagation direction, spectrum and amplitude, as well as the net flow through and around the components of the exhaust flow director used in embodiments of the invention. 
     In one embodiment, the exhaust flow director comprises a plurality of overlapping vanes that direct the flow of exhaust, including, as described above, both sound propagation and fluid flow. The exhaust flow director has many embodiments using the plurality of overlapping vanes to create vortices and/or cause exhaust to flow in counter flowing channels. The exhaust flow director perpetuates exhaust circulation within the muffler to attenuate the amplitude of exhaust pulsations as well as extend the duration of the pulsations. Consequently, embodiments of the invention substantially attenuate the sound level of the exhaust. 
     Embodiments of the invention can be used for quieting sound from engines, machinery and equipment. One application for embodiments of the invention is for internal combustion engines, which find use in, for example, vehicles, power generators, aircraft, lawn mowers, chain saws, blowers, and string trimmers. Embodiments of the invention can be used with any internal combustion engine of any size, i.e., any displacement or number of cylinders. Throughout this disclosure, embodiments of the invention are described with respect to an internal combustion engine application. This application should be considered an example of the many applications for embodiments of the invention. In other exemplary applications, embodiments can be used for reducing sound exposure for operators or workers to prevent hearing loss, or extend the amount of sound exposure time a worker can safely endure, and potentially remove the requirement for hearing protection to improve comfort and reduce safety concerns from exposure to loud sound levels from equipment or machinery. 
     To achieve sound attenuation, some embodiments prolong vorticity and circulation within one or more muffler chambers (vortex chambers) to create elongated flow paths, variable expansion regions, radial pressure gradients, varying angular velocity related to the radial extent of vortex motion, and resistance to uniform expansion due to diffraction within velocity gradients. The vortex chambers can be designed to keep noisy flows longer at the periphery of a circulation region due to centripetal acceleration and create pressure and flow gradients that inhibit transmission of sound through a vortex sink, i.e., the center of vortex motion or the eye of the vortex. 
     In these embodiments, the exhaust is typically introduced tangentially into a cylindrical chamber to create a vortex within the chamber walls, and the output port is usually a pipe with an opening at the center of the vortex. Continuous exhaust flow perpetuates and reinforces the vortex motion within the chamber. Sound, pressure, flow and temperature fluctuations of the entering exhaust flow are contained longer within the vortex motion, have an elongated path, merge with existing and future flow streams circulating in the vortex, and therefore have more opportunities to reduce these fluctuations before exiting the muffler section as compared to traditional expansion mufflers. This invention creates a circulation region where overlapping vane structures keep the flows circulating longer, so the effects of the attenuation principles described herein can be more effective and reducing noise; create larger transmission loss throughout the muffler&#39;s flow paths than traditional mufflers. 
       FIG. 1  depicts a perspective view of one embodiment of the inventive muffler  100 .  FIG. 2  depicts a cross-sectional view of the embodiment in  FIG. 1  taken through the plane of the muffler  100 . To best understand the operation of this embodiment, both  FIGS. 1 and 2  should be viewed while reading the following description. 
       FIGS. 1 and 2  depicts an apparatus (muffler)  100  having an exhaust inlet  102  at the periphery of an enclosure  104  and an exhaust outlet  106  centrally located in the enclosure  104 . More specifically,  FIGS. 1 and 2  depict the apparatus muffler  100  comprising a cylindrical enclosure  104  defined by side wall  108  and top and bottom elements  120  (only the annular bottom element  120  is shown). In one embodiment, the exhaust inlet  102  comprises an input pipe  122 , a coupler  124  and a tangential injection plenum  126 . In one embodiment, the input pipe  122 , coupler and injection plenum are designed to establish the back pressure for the exhaust system. The tangential injection plenum is as tangential as possible to the interior surface  128  of side wall  108  to ensure vortex circulation is created within the enclosure as described below. Plenum size and enclosure diameter should eb chosen to produce maximum vorticity or circulation time within the enclosure such that pressure and flow fluctuations from the engine exhaust can be reduced due to the longer path lengths, centripetal acceleration and radial expansion of high-pressure pulsations. 
     Inlet  102  may be connected to the exhaust outlet of an internal combustion engine. In other embodiments, inlet  102  could also represent a transition path from a different section of a multi-stage muffler. Similarly, the final flow egress via outlet  106  could become the transition path to a subsequent stage of a muffler system with multiple chambers. 
     As depicted in  FIG. 2 , the enclosure  104  houses an exhaust flow director  130  comprising a plurality of curved vanes  110  arranged in a circular pattern within the interior of the enclosure  104 . In the depicted embodiment, there are six vanes  110 . The number and size of the vanes varies depending upon the amount of sound attenuation desired (i.e., more vanes for more attenuation) and the size of the muffler  100 . The area between the vanes  110  and the side wall  108  is the first or outer circulation region  112 , and in the depiction in  FIG. 2 , the direction of fluid rotation is counterclockwise (CCW), as shown by the arrows in region  112 . The interior area formed inside these vanes  110  defines the second or inner circulation region  114 , and in the depiction of  FIG. 2 , the resultant direction of fluid rotation is clockwise (CW), as depicted by the arrows in region  114 . The resulting CW circulation in the second flow region  114  is a result of fluid in the first outer circulation region  112  reversing direction as it is forced into the gap region  116  formed between two adjacent vanes  110 . This transition of flow from the first circulation region  112  into the second circulation region  114  occurs in the six symmetrical gaps  116 . Vortex circulation is maintained in the inner circulation region  114  as long as there is sufficient circulation in the outer circulation region  112 . A steady-state flow equilibrium can exist when the input and output flow is matched. There is no requirement that every gap needs to be symmetrical or uniform, and many combinations of vane sizes, shape, separation, distance and angular position relative to adjacent fins can create any number of gap proportions. 
     More specifically, the inlet port  102  shows flow vectors entering region  104  tangentially in a CCW rotation predominantly along an interior surface  128  of wall  108 . The tangential insertion of flow along the inside wall perimeter will exploit centripetal acceleration to force the majority of flow and pressure expansion radially outward to follow the interior surface  128  as the flow progresses around the perimeter. Vane  110  will further deflect flow and pressure pulsations radially outward toward the outer perimeter of region  112 , and because of the six overlapping duplicates of vane  110 , the gaps  116  have a higher input impedance to flow and pressure pulses due to the requirement for the flow to change direction and flow through the gap  116  in an opposite CW rotation. The flow path of least resistance is to continue CCW in region  112  and let momentum, centripetal acceleration and reflections continue to force the flow and pressure perturbations radially outward along the inside of wall  108 . 
     A radial region of vorticity is established; a gradient with higher pressure and lower angular velocity radially outward at the interior of wall  108 , and lower pressure with higher angular velocity radially inward along the exterior of the overlapped vane-wall formed with six duplicates of vane  110  and gap  116 . 
     The region of gap  116  shows the flow in region  112  having to reverse direction to enter into, and pass through, the gap  116  formed by two adjacent vanes  110 . Once the flow passes through gap  116 , it flows along the inside of vane  110 , and combines with other flows entering the interior region  114  through the other five gaps that are similar to gap  116 . These six CW rotating flows reinforce each other and form an interior vortex region  114  in the CW rotation direction (opposite to the outer circulation region  112  CCW rotation). 
     CW vortex circulation region  114  will also have an angular velocity and pressure gradient within the barrier created by the six vanes. Creating an egress path for the rotating flow through the outlet  106 , will enable rotating flow to exit the muffler  100  to another section of a multi-stage muffler or to be released to the atmosphere. 
       FIG. 3  depicts a muffler embodiment having an exhaust flow director comprising twelve flat overlapping vanes within a circular enclosure. More specifically,  FIG. 3  depicts cross-sectional view of apparatus (muffler)  300  comprising a circular enclosure  302  defined by wall  304  and having a plurality of flat vanes  306  arranged in a circular pattern within the interior of the enclosure  302 . In the depicted embodiment, there are twelve vanes. The number and size of the vanes varies depending upon the amount of sound attenuation desired (i.e., more vanes for more attenuation) and the size of the muffler  300 . The area between the vanes  306  and the wall  304  is the first or outer circulation region  308 , and in this depiction, the preferred direction of fluid rotation would be counterclockwise (CCW). The interior area formed inside these vanes is the second or inner circulation region  310 , and in the depiction, the resultant direction of fluid rotation would be clockwise (CW). The resulting CW circulation in the inner circulation region  310  is a result of fluid in the first outer circulation region  308  reversing direction as it is forced into the gap region  312  formed between two adjacent vanes  306 . This transition of flow from the first (outer) circulation region  308  into the second (inner) circulation region  310  occurs in the twelve symmetrical gaps  312 . Vortex circulation is maintained in the inner circulation region  310  as long as there is sufficient circulation in the outer circulation region  308 . A steady-state flow equilibrium can exist when the input and output flow is matched. There is no requirement that every gap needs to be symmetrical or uniform, and many combinations of vane sizes, shape, separation, distance and angular position relative to adjacent vanes can create any number of gap proportions. 
       FIG. 4  depicts an acoustic ray tracing  400  as a graphical depiction of sound propagation within circulation region  308  and through gap  312  of the flat vane embodiment of  FIG. 3 . This graphic assumes an expanding wavefront can be represented with a vector that is perpendicular to the progressing wavefront. The geometry of vanes are configured so that sounds prefer to be propagating in the outer circulation region  308  in a CCW rotation, and are predominantly contained between the outer wall  304  and the inner “barrier-wall” formed by straight vanes  306 A,  306 B,  306 C and  306 D. The geometry is designed to perpetuate CCW sound propagation in the region between the wall  304  and the four vanes shown, and to prevent or minimize any reflections and propagation in the CW rotation direction. 
     Gap  312  is formed between vanes  306 B and vane  306 C. With the straight fins shown, this gap has a larger input area and a smaller output area. Curved fins and relative orientations can create varying gap input profiles and impedances. Gap  312  shows that the majority of sound rays are reflected away from the gap  312  region; momentum carries the pressure pulses past the gap. However, some rays diffract around the downstream edges of the fins nearest to their respective gaps. 
       FIG. 5  depicts another embodiment of an exhaust flow director  500  comprising a set of curved extruded vanes  502  adjacent to a similar vane  504 , and this embodiment shows six vanes equally spaced in a circular pattern. This assembly would be contained within an outer extruded wall, not shown in this figure, but similar to the outer wall  108  shown in  FIG. 2 . Outermost flow in this embodiment is CCW in outer circulation region  506 , and CW in the inner circulation region  508 . The gap  510  formed between adjacent vane  502  and vane  504  is shown as uniform in cross-sectional area; the flow area of inlet gap  512  and exit gap  514  during flow transition from the outer circulation region  506  into the inner circulation region  508  remains constant in this embodiment. The gap  510  area and the channel distance between inlet  512  and exit  514  determine the flow resistivity, and can be modified so that the sum of the six gaps  510  satisfy flow and backpressure requirements. 
     There can be advantages to having varying degrees of flow circulating outside of the overlapping vane structures.  FIG. 6  depicts an embodiment of an exhaust flow director  600  comprising a plurality of curved vanes  602  circularly arranged around center line  612 . Each vane  602  has a longer edge and larger radius-of-curvature at the end  604 , and a shorter edge and smaller radius-of-curvature at the end  606 . In the depicted embodiment, ten duplicates of vanes  602  are positioned to create both a gradually decreasing flow area from gap  608  to gap  610 , and also a decreasing footprint (circumference of fin edges) from end  604  to end  606 . Such a design, when inserted into a uniform cylindrical enclosure, provides less flow area (between cylinder and vanes) at end  604  and more flow area at end  606 , thereby varying the flow-rates into the linearly changing gaps  608  and  610 . The varying internal volume can have advantageous expansion and wave reflection properties. 
       FIG. 7  depicts another embodiment of an exhaust flow director  700  comprising a plurality of vanes  702  arranged to have a dramatic change in gap taper and circumferential apertures of opposing ends. A gap  704  is very wide at the large aperture end  706  of a vane  702 , and it linearly decreases to a negligible gap  708  at the small aperture end  710 . As described previously regarding  FIG. 6 , there can be advantages to varying the size of gaps, the location of gaps relative to input and output ports, and the extent of flow past the varying gap openings. The combination of gap area and overlap length can be configured to spatially vary the acoustic impedance and flow resistivity significantly within a device. This will help reduce acoustic emissions through destructive phase addition resulting from the integrated sum of the varying path lengths, acoustic impedances and regional diversity of pressure/flow reductions. 
     The tapered fin gaps and diverse apertures described with respect to  FIG. 7  are depicted as part of the embodiment of muffler  800  of  FIG. 8 . An input plenum  802  tangentially introduces CCW exhaust flow into vorticity region  804 , which advantageously passes exhaust flow director  700  in a manner to inhibit sound transmission into the linearly decreasing inlet area of gap  806 . Once flow has migrated through the six gaps  806 , it will reverse direction and reinforce a CW vortex within region  808 . 
     In this embodiment, the exhaust exit path is not shown, but would be one or more pipes near the center-line of region  808 ; the number and locations of the egress pipe ports in the top element (not shown) to vent portions of the inner circulation region  808  at various pressure and velocity locations in the conical vortex field. The recombination of multiple, diversely sampled portions of the exhaust flow, provides additional sound reduction through phased and destructive interference. Alternatively, if multiple venting pipes are used for region  808  exhaust egress, they can individually be used to stimulate or maintain another vortex region in a different section of a multistage muffler. Alternatively, the multiple egress pipes can tangentially feed a single subsequent vortex chamber at various locations along the perimeter wall; random spacing or orientations will further cancel pressure fluctuations through phase mismatches and velocity averaging. 
       FIG. 9  depicts a perspective view of an embodiment of a muffler  900  that has two exhaust inputs  902  and  904  driving two overlapping vane sections  906  and  908 , respectively. The two overlapping fin section are combined internally and exit the muffler through larger exhaust pipe  910 . 
       FIG. 10  depicts a cross sectional perspective view of half of the dual-input muffler  900  of  FIG. 9 .  FIG. 10  reveals one exhaust input pipe  904  feeding CCW circulation region  1000  between outer wall  1002  and the barrier wall created by vanes  1004 , an internal egress pipe  1006  creates an inner CW circulation region  1008  between pipe  1006  and the ten vanes  1004 , and the muffler exhaust port  910 . 
     Plenum  1010  tangentially introduced exhaust gasses into the circulation region  1000  along the interior of wall  1002 . CCW circulation is contained between outer wall  1002  and overlapping vanes  1004 ; the exhaust changes direction to CW after passing through the ten fin gaps associated with vane assembly  1004 . Once inside the vane assembly  1004 , a CW vortex is created and maintained in the inner circulation region  1008 . Flow eventually enters egress pipe  910  to transit to other portions of the muffler or to the muffler exhaust pipe  910 . 
       FIG. 11  depicts an embodiment of an exhaust flow director  1100  having a structure comprising twin overlapping vane assemblies  1102  and  1104 . As described previously with respect to  FIG. 10 , dual input exhaust flows can be introduced tangentially around the inside perimeter of a cylindrical wall that acts as, in this example, the outer shell of the muffler. For clarity, in  FIG. 11 , the outer wall of the muffler is not depicted. The tangential exhaust flows are significantly contained between the outer wall (not shown in this figure) and the twin overlapping vane assemblies  1102  and  1104 . The flow perturbations and pressure pulsations tend to flow between the cylindrical outer wall (not shown) and the vane assemblies  1102  and  1104  to create a circulation channel region  1106 . The circulation channel dimensions between the outer wall (not shown) at the vane assembly ends  1108  and  1110  are smaller than the channel dimensions located near the juncture  1112  of vane assemblies  1102  and  1104 . This flow creates a vortex in the channel where the pressure gradient in the radial direction of  1106  is greatest at the outer shell and less at the twin overlapping vane assemblies  1102  and  1104 . 
     Each vane assembly  1102  and  1104  comprise a plurality of vanes  1114  that are spaced from one another to form a gap  1116  between adjacent vanes. The gap  1116  between the vanes  1114  is shown as linearly varying in gap area between an assembly end  1108  and  1110  to the assembly junction  1112 . In alternative embodiments, the gap  1116  can be uniform or complex. The combination of variable channel circulation area and vane gap area along the circulation channel region  1106  creates variable acoustic and flow input impedance into the interior circulation region  1118 . 
     In the embodiment of  FIG. 11 , the twin inputs of exhaust gases would introduce the flows at the midpoint of each overlapping vane assembly  1102  and  1104 . As a result of the tapered vane assemblies  1102  and  1104  with linearly varying gaps  1116  as shown, the pressures and flows can expand in both axial directions and rotationally, and interact with each other along the circulation channel. Alternatively, an interior separation ring (not shown) located at the junction  1112  of assemblies  1102  and  1104  could maintain the two inlet flows as separate and independent until they eventually flow into the internal circulation region  1118  to combine there. In this dual overlapping configuration, it is obvious that variations of number and shape of vanes, separation between vanes, uniform or variable gap areas, and the taper of the vanes can all be selected to optimize flow impedance and noise abatement. 
     The flow direction is preferably in the rotational direction that does not permit direct flow into the gap  1116  between the vanes  1114 . However, in  FIG. 11 , the flow direction is out of the page on the top of the twin fin assemblies  1102  and  1104  and continuing downward in front of the assemblies. Both assemblies  1102  and  1104  are shown to have the same rotational direction; this does not need to be the case, and in a dual exhaust situation, the two inputs could come from opposite sides of the outer shell (not shown) and rotate in opposite directions. 
     There may be designs where a rotational direction may allow a portion of the circulating flow to easily enter into the gaps between vanes; direct path into the gaps without the need to reverse directions before entering the gaps as previously described. In this case, the majority of flow would continue to rotate and expand radially outward due to centripetal acceleration in the outer circulation region, and only a portion would enter into the gaps  1116  at a higher velocity to create a stronger vortex in the inner circulation region  1118 . 
       FIG. 12  depicts an embodiment that utilizes the twin overlapping vane assemblies  1102  and  1104  of  FIG. 11 . Specifically,  FIG. 12  depicts a cross-sectional view of a muffler  1200  comprising an outer wall  1202  defining an enclosure in which the vane assemblies  1102  and  1104  are supported by a separation ring  1204 . The separation ring is annular and extends from the junction  1112  between the assemblies  1102  and  1104  to the outer wall  1202 . The space between the outer wall  1202  and the assemblies  1102  and  1104  forms tapered outer circulation regions  1206  and  1208 . 
     Coaxial with and inside the vane assemblies  1102  and  1104  is positioned an interior cylindrical pipe  1210 . The space between the vane assemblies  1102  and  1104  and the pipe  1210  form inner circulation regions  1212  and  1214 . As described previously with respect to  FIG. 11 , once the flow is rotating in the outer circulation regions  1206  and  1208 , the portions of the flow nearest the vane assemblies  1102  and  1104  enters the vane gaps  1116  and create rotational flow in the opposite direction within the inner chamber regions  1212  and  1214 . The inner circulating flow region  1212  and  1214  combine in the space between the vane assemblies  1102  and  1104  and the interior cylindrical pipe  1210  until the pressures equalize and the combined flow is forced to the distal end  1216  of the inner circulation chamber  1214 . The exhaust flow egress location is at the distal end  1216 . Alternatively, the exhaust egress location may be at the opposite end of the inner circulation chamber  1214  or a combination of two or more egress ports. The inside of the interior cylindrical pipe  1210  can be used as a passageway to transfer exhaust from one end of the muffler to the other, or to connect different components within a multi-stage muffler assembly. Alternatively, in another embodiment, the pipe  1210  could be replaced with another set of overlapping vanes to create a new innermost circulation region. 
     The exhaust flow director of any muffler embodiment may be assembled from an assortment of vane assembly structures. For example,  FIG. 13  depicts a cross section of a muffler  1300  comprising nested vane assemblies (an outer vane assembly  1302  and an outer vane assembly  1304 ). The nested vane assemblies  1302  and  1304  are housed within an enclosure defined by an outer wall  1316  and a bottom cover plate  1318  (the top cover is shown as removed). An exhaust input plenum  1320  causes the exhaust gasses to tangentially impact the wall  1316  and enter an outer circulation region  1308 . The wall  1316 , the bottom cover plate  1318  and upper cover plate (not shown) are sealed, for example, by welding, to another to enclose the vane assemblies  1302  and  1304 . The upper cover plate comprises the exhaust egress port near the center of the inner vane assembly  1304 . 
     In the depicted embodiment, the outer vane assembly  1302  and the inner vane assembly  1304  have opposing rotational orientations. The orientation of the overlapping outer vane gaps  1306  on the outer vane assembly  1302  promote prolonged CCW rotating flows in the outermost first circulation region  1308 , and these CCW flows must change direction to enter into the outer vane gaps  1306 , to create CW circulation in the second circulation region  1310  after passing through the outer vane gaps  1306 . Once a significant portion of the flows are contained in the second circulation region  1310  between the outer vane assembly  1302  and the inner vane assembly  1304 , and circulating in a CW rotational direction in this second circulation region  1310 , both vane assemblies  1302  and  1304  promote prolonged CW circulation within the inner second circulation region  1310 . As before, flows from the second circulation region  1310  entering and passing through the inner assembly gaps  1312  will again reverse rotational direction to CCW, and all of the inner vane assembly gaps  1312  reinforce each other to maintain a CCW vortex inside the innermost third circulation region  1314 . Egress from this innermost circulation region  1314  comprises at least one pipe with an opening or perforations located in proximity to the center of the third circulation region  1314 ; although not depicted in  FIG. 13 , this egress could be an opening or perforations through the bottom cover  1318 , through the top cover (not shown), or through a combination of both locations. 
     In alternative embodiments, at least one pipe could be located at one or more positions, not necessarily at the center of the egress cover plate, to create diverse sampling of the vortex flows. For example, an independent egress pipe could be located in each of the two innermost circulation regions  1310  and  1314 . The plurality of egress pipes from this one muffler embodiment  1300  may be connected to other muffler components or be combine in a single circulation chamber through multiple tangential inputs around the perimeter of a circulation region. 
       FIG. 14  depicts a cross-sectional view of an embodiment of a muffler  1400 . The muffler comprises an exhaust input pipe  1402 , an outer shell  1404 , an overlapping vane assembly  1406  and an exhaust egress pipe  1408 . The muffler  1400  comprises a front (removed in  FIG. 14 ) and an annular, egress cover plate  1418  are attached to the housing to form a sealed muffler enclosure. The outer shell  1404  may be cylindrical or spherical. The overlapping vane assembly  1406  is mounted centrally with the outer shell  1404  to define an outer circulation region  1410  and an inner circulation region  1412  for the exhaust gasses as they pass through the muffler  1400 . 
     The overlapping vane assembly  1406  (an exhaust flow director) comprises a plurality of overlapped vanes  1414  having complex curvatures. Each vane  1414  is spaced apart from an adjacent vane to form a gap  1416 . In this embodiment, the overlapped vanes  1414  create a spherical overlapping vane assembly  1406 . The exhaust input pipe  1402  tangentially injects exhaust gas into the outer circulation region  1410  outside of the spherically curved overlapping vane assembly  1406 . The location and angle of input pipe  1402  can be varied to affect the circulation within the outer circulation region  1410 . In the depicted embodiment, flow within the outer circulation region  1410  flows in a CW rotational direction before entering the vane gaps  1416  associated with the spherical overlapping vane assembly  1406 , where a change in rotation creates a CCW circulation in the innermost circulation region  1412 . The egress cover plate  1418  with egress pipe  1408  protruding in both directions from its surface is parallel to the front plate (not shown for clarity), wherein both plates contact and contain the spherically curved overlapping vane assembly  1406 . The optimal location for egress pipe  1408  is along the axial centerline at the center-of-curvature of the vanes in vane assembly  1406 . 
     In various embodiments, the vane assembly  1406  may comprise flat or curved vanes bent using different radii-of-curvatures, various number of vanes, various vane separations and orientations to create unique gap areas along the length of the individual vanes  1414 . Multiple spherical overlapping vane assemblies  1406  can also be inserted into a longer cylindrical shell with tangential inputs at various positions along the length of the cylindrical wall; the varying diameters of the spherical overlapping vane assemblies  1406  create correspondingly nonlinear circulation areas outside of one, and in between two adjacent spheres. In another embodiment, an egress pipe with perforations could connect the centers of each spherical inner circulation region  1412  and eventually lead to an egress port for the combined interior flows of multiple overlapping vane assemblies  1406 . Alternatively, the opening at one end of one assembly  1406  could be matched in diameter and joined with another spherical assembly  1406  to create an egress path of fluid-coupled inner circulation regions without a pipe egress. 
       FIGS. 15 and 16  respectively depict an embodiment of a rectangular muffler  1500  and a close up of an input channel  1502  of the rectangular muffler  1500 . To best understand this embodiment, both  FIGS. 15 and 16  should be reviewed simultaneously. In this embodiment, the rectangular muffler  1500  does not create, or rely on, circulation or vorticity. The muffler  1500  comprises an exhaust flow director  1504  comprising a plurality of overlapping flat vanes  1506  arranged in four arrays, inner arrays  1510  and outer arrays  1512 . In this embodiment, the vanes  1506  are depicted as being flat. In other embodiments, curved vanes or other shapes could be used. More specifically, the muffler  1500  comprises a substantially rectangular outer wall  1526 , flat base plate  1508 , an identical top cover plate (not shown), an input channel  1502 , an exhaust director  1504  comprising four linear arrays of inner flat vane arrays  1510  and outer flat vanes  1512 , a multitude of vane gaps  1514  associated with the four linear arrays  1510  and  1512  of flat vanes  1506 , a flow splitter  1516 , two flow channels  1518  and  1520  (forming first and second flow regions, respectively), and two exit ports  1522  and  1524 . The outer wall and the top cover and base plates form an enclosure for the exhaust flow director  1504 . Although not a requirement, this embodiment is shown as symmetrical along the centerline between the input channel  1502  and the splitter  1516 . 
     The rectangular input channel  1502  forces exhaust flows past flat vanes  1506 . Similar to the generally cylindrical overlapping curved vane descriptions within this description, the flow is deflected past the gaps  1514  to create a low-impedance pathway, and the flow and pressure pulsations must reverse flow direction to pass through gaps  1514  to a secondary flow region  1520 . Unlike all previous descriptions that create circulation, vorticity and exploits centripetal acceleration to force flow and pressure pulsations radially outward, this embodiment does not create vorticity but does create a high impedance linear path to limit pressure perturbations reversing direction and entering the secondary flow region  1520  before subsequently flowing to an egress port  1522  or  1524  to exit the muffler  1500 . 
     More specifically, flow and pressure pulsations travel down the input channel  1502 , are divided by flow splitter  1516  to the first flow channels  1518  (defined by vane arrays  1512  and the outer wall  1526 , and are prevented from further lower-resistance flow at the end of the channels  1518 , or the channel&#39;s stagnation point. The input channel  1502  and channel  1518  are over-pressurized and therefor force portions of the flow through the vane gaps  1514  of the four linear arrays  1510  and  1512  into the secondary flow channels  1520  (defined by a pair of arrays  1510  and  1512  and an interior wall portion  1528  that bisects the space between the arrays  1510  and  1512 ); however, the gap orientations force a change in direction for the flows to travel through the gaps and propagate in the flow channel  1520  in a direction away from the ultimate exit ports  1522  and  1524 . This path confusion allows additional pressure wave expansions, phased cancellations and flow averaging to create acoustic attenuation. The channel  1520  is bifurcated by a wall  1528  to direct the flows along the channel  1520  towards the two exit ports  1522  and  1524 . The pressure and flow impedance of each vane gap  1514  along the channel input  1502  and channels  1518  and  1520  are slightly different due to the flow, velocity and pressure distributions leading to channel termination. It is obvious that the fin gap dimensions, and vane shapes can be modified to tailor the flow distribution into the secondary flow channel  1520 . These channels are shown in a linear layout, but could be any circuitous path with more than one branch. 
     In any of the foregoing embodiments, in order to further break up coherent expansions of pressure pulsations or flow variances, distorted edge vanes are designed to arbitrarily or uniformly distort the expanding pressure waves that travel over the vane surfaces and through the gaps between adjacent vanes. The non-linear expansion areas create a variable impedance for the pressure expansion and can contribute to phased cancellation of acoustics. Any combination of edge features may be created, and typically, the more diversity from vane to vane, the better the destructive attenuation and waveform disruption. Some exemplary embodiments of vanes  1700  and  1702  having vane edge textures are depicted in  FIG. 17 . The depicted embodiments of vanes  1700  include random linear  1704  and curvilinear  1706 , while vane  1702  includes diverse shapes  1708  and predictable distribution of varying areas  1710 . 
       FIG. 18  depicts additional embodiments of three disrupted edge vanes  1802 ,  1804  and  1806  in an overlapped configuration that forms a portion of an exhaust flow director  1800 . The vane gaps  1808  and  1810  are shown as having uniform separation, but they can also be variable apertures of differing spacing if desired. CW flow over the convex side of vane  1802  will variably expand to hit the solid surface of vane  1804  before passing over the disrupted edge of vane  1804  which then expands onto the solid surface of vane  1806  before hitting the disrupted edge of vane  1806 . The gap  1808  is formed between the concave surface of vane  1802  and the concave surface of vane  1804 . As flow reverses direction within each of these gaps  1808  and  1810 , the portion of flow within each gap passes in a CCW direction over the interior portions of the disrupted edge vanes with similar effects as described above. 
     In another alternative embodiment vanes can also be made of partially or completely perforated metal to permit micro-scale pressure expansions throughout the entire surfaces of each vane. The size, number and spacing of these perforations determines the surface&#39;s acoustic impedance and flow resistivity; combinations of diverse perforated vanes can add more complex pressure expansions and flow diffusion between adjacent vanes and adjacent circulation regions throughout the muffler system. High acoustic and flow resistance will still allow the circulating flow characteristics describe throughout this disclosure. 
     Fiberglass batting materials contained between two perforated surfaces or between at least one perforated surface and another solid surface is well known to those skilled in the art of muffler design, and can be incorporated into many of the embodiments described in this invention. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.