Combination Silencer

Abstract

The invention relates to a silencer being designed with sound absorptive material ( 13, 23 ) and a conduit section ( 1, 2 ) with one or more conduits ( 1 ) for leading gas flow into the silencer and with one or more outlets ( 2 ) for leading gas form the silencer. The sound absorptive material ( 13, 23 ) and the conduit section ( 1, 2 ) constitutes a protrusion extending from part of an outer shell ( 4 ) such as from an end cap ( 5, 6 ) constituting part of the shell for the silencer, or from an internal member, such as a baffle ( 9, 10 ) possibly separating at least two through-flowed chamber ( 12 ) of the silencer. Not-through-flowed cavities ( 17, 27 ) are arranged essentially adjacent to or at least partly surrounding said sound absorptive material ( 13, 23 ), thereby constituting one or more resonators acoustically communicating with said at least one through-flowed chamber. The silencer may also be designed so as to act as a spark-arrestor. Also, the invention relates to a combustion engine provided with such silencer.

1 - 40 . (canceled)  
   
   
       41 . A silencer with 
 an outer shell ( 4 ) and provided with one or more conduits ( 1 ) for leading gas flow into the silencer and with one or more outlets ( 2 ) for leading gas from the silencer, the silencer comprising    at least one chamber ( 12 ) capable of being trough-flowed by gas entering the chamber ( 1   2 ) and at least one perforated conduit section ( 1 , 2 ) being acoustically in communication with sound absorptive material ( 13 , 23 ) arranged adjacent to the perforated conduit section ( 1 , 2 ),    said sound absorptive material ( 13 , 23 ) and conduit section ( 1 , 2 ) together constituting a protrusion extending from part of said outer shell ( 4 ), e.g. from an end cap constituting part of the shell of the silencer, or from an internal member, e.g. a baffle ( 9 , 10 ) separating at least two through-flowed chambers ( 12 ) of the silencer,    said sound absorptive material ( 13 , 23 ) being arranged adjacent to and surrounding at least one terminated cavity ( 17 , 27 ), or said sound absorptive material ( 13 , 23 ) being arranged adjacent to and being surrounded by at least one terminated cavity ( 17 , 27 ),    said at least one terminated cavity ( 17 , 27 ) being acoustically in communication with said at least one through-flowed chamber ( 12 ), and said acoustic communication being either direct or via a neck section ( 35 , 45 ) provided between the at least one terminated cavity ( 17 , 27 ) and the at least one through-flowed chamber ( 12 ), and    said at least one terminated cavity ( 17 , 27 ) being arranged adjacent to said sound absorptive material ( 13 , 23 ), thereby constituting one or more resonators acoustically communicating with said at least one through-flowed chamber ( 12 ).    
   
   
       42 . A silencer according to  claim 41 , wherein said sound absorptive material ( 13 , 23 ) is contained within a casing ( 15 , 25 ) surrounding said conduit section ( 1 , 2 ), and where said casing ( 15 , 25 ) constitutes a cavity containing sound absorptive material, said casing ( 15 , 25 ) surrounding said conduit section ( 1 , 2 ).  
   
   
       43 . A silencer according to  claim 42 , wherein said at least one terminated cavity ( 17 , 27 ) surrounds said cavity ( 15 , 25 ) containing sound absorptive material.  
   
   
       44 . A silencer according to  claim 41 , wherein said at least one through-flowed chamber ( 12 ) is provided with one or more inlet passages ( 1 ) for leading gas to said chamber, and is provided with one or more outlet passages ( 2 ) for leading gas from said chamber, and where the sum a in  , of acoustically representative cross-sectional areas of said inlet passages is fulfilling the condition a in <A/(3C), A being an acoustically representative cross-sectional area of said chamber ( 1   2 ) and C being a constant taking the value of C being at least 1.  
   
   
       45 . A silencer according to  claim 41 , wherein said at least one through-flowed chamber ( 12 ) is provided with one or more inlet passages for leading gas to said chamber, and is provided with one or more outlet passages ( 2 ) for leading gas from said chamber, and where the sum a out  of acoustically representative cross-sectional areas of said outlet passages is fulfilling the condition a out <A/(3C), A being an acoustically representative cross-sectional area of said chamber ( 12 ) and C being a constant taking the value of C being at least  1 .  
   
   
       46 . A silencer according to  claim 41 , wherein said at least one through-flowed chamber ( 12 ) is provided with one or more inlet passages ( 1 ) for leading gas to said chamber, and is provided with one or more outlet passages ( 2 ) for leading gas from said chamber, where the sum a in  of acoustically representative cross-sectional areas of said inlet passages, and where the sum a out  of acoustically representative cross-sectional areas of said outlet passages, and where the volume V of said chamber is fulfilling the condition V>6C(√{square root over (((a in +a out )/2)))} 3 , A being an acoustically representative cross-sectional area of said chamber ( 12 ) and C being a constant taking the value of C being at least 1.  
   
   
       47 . A silencer according to  claim 44 , wherein said constant C takes the value of C being 2.  
   
   
       48 . A silencer according to  claim 44 , wherein said constant C takes the value of C being 3.  
   
   
       49 . A silencer according to  claim 41 , wherein said at least one terminated cavity ( 17 , 27 ) is of a longitudinal shape along a longitudinal extension of said perforated conduit, said cavity thereby acting as a resonator attenuating noise at frequencies corresponding to standing waves in the longitudinal direction of the silencer, the lowest of said frequencies corresponding to a standing quarter-wave, making it possible to establish an acoustically effective length L of said cavity.  
   
   
       50 . A silencer according to  claim 41 , wherein the acoustically effective length L of said at least one terminated cavity ( 17 , 27 ) is at least 6 times the ratio V/S between a volume V of said casing ( 4 ), and summed surface areas S of side walls of said terminated cavity ( 17 , 27 ).  
   
   
       51 . A silencer according to  claim 50 , wherein the acoustically effective length L of said at least one terminated cavity ( 17 , 27 ) is at least 10 times the ratio V/S between the volume V of said casing ( 4 ), and the summed surface areas S of side walls of said terminated cavity ( 17 , 27 ).  
   
   
       52 . A silencer according to  claim 51 , wherein said acoustically effective length, L, of said at least one terminated cavity ( 17 , 27 ) is at least 20 times said ratio V/S between the volume, V, of said casing, and the summed surface areas, S, of side walls of said terminated cavity ( 17 , 27 ).  
   
   
       53 . A silencer according to  claim 51 , wherein said at least one terminated cavity ( 17 , 27 ) is of annular shape.  
   
   
       54 . A silencer according to  claim 53 , wherein the mean distance, a, between walls in radial direction, integrated over the entire longitudinal and circumferential extension of the acoustically effective length of the terminated cavity ( 17 , 27 ) is at the most a ratio 1/3 of said acoustically effective length L.  
   
   
       55 . A silencer according to  claim 54 , wherein the mean distance, a, is at the most a ratio 1/5 of said acoustically effective length L.  
   
   
       56 . A silencer according to  claim 55 , wherein the mean distance, a, is at the most a ratio 1/10 of said acoustically effective length L.  
   
   
       57 . A silencer according to  claim 49 , wherein said acoustically effective length L of said terminated cavity ( 17 , 27 ) is essentially equal to a length of said protruding sound absorptive material seen along the longitudinal extension of the silencer.  
   
   
       58 . A silencer according to  claim 49 , wherein said acoustically effective length L of said terminated cavity ( 17 , 27 ) is smaller than a length of said protruding sound absorptive material seen along the longitudinal extension of the silencer.  
   
   
       59 . A silencer according to  claim 49 , wherein said acoustically effective length L of said terminated cavity ( 17 , 27 ) is longer than a length of said protruding sound absorptive material seen along the longitudinal extension of the silencer.  
   
   
       60 . A silencer according to  claim 59 , wherein the shape of said at least one terminated cavity ( 17 , 27 ) at least partly constitutes a helical winding around said protrusion.  
   
   
       61 . A silencer according to  claim 49 , wherein said acoustically effective length L, depending on between which parts of the silencer said length is measured, varies between a minimum, Lmin, and a maximum, Lmax, of said length L, and where said length L is being interpreted as a mean value between Lmin and Lmax.  
   
   
       62 . A silencer according to  claim 41 , wherein the at least one neck passage acoustically connecting said at least one terminated cavity ( 1   7 , 27 ) with said at least one through-flowed chamber ( 12 ) is designed for creating a Helmholtz-type resonator.  
   
   
       63 . A silencer according to  claim 41 , wherein said casing constituting a cavity containing sound absorptive material is of a substantially circular-cylindrical configuration.  
   
   
       64 . A silencer according to  claim 41 , wherein said at least one piece of protruding sound absorptive material and said at least one essentially surrounding terminated cavity ( 17 , 27 ) is of substantially circular-cylindrical configuration.  
   
   
       65 . A silencer according to  claim 41 , wherein said perforated conduit is of a substantially circular-cylindrical cross-sectional shape and is capable of leading gas into the at least one through-flowed chamber ( 12 ) via a radial diffuser.  
   
   
       66 . A silencer according to  claim 41 , wherein the entire silencer, except for connections to conduits leading gas to and from the silencer, is of substantially circular-cylindrical configuration.  
   
   
       67 . A silencer according to  claim 41 , wherein said silencer comprises at least two terminated cavities ( 17 , 27 ), the one terminated cavity having an acoustically effective length L 1  and the at least one other terminated cavity having an acoustically effective length L 2 , and where said length L 1  is different from said length L 2 .  
   
   
       68 . A silencer according to  claim 41 , wherein at least three pieces of said protruding sound absorptive material are arranged to establish at least three parallel gas flows inside said protruding sound absorptive material, and wherein said at least one terminated cavity ( 1   7 , 27 ) is constituted by a spacing between said protruding pieces of sound absorptive material.  
   
   
       69 . A silencer according to  claim 68 , wherein more of said terminated cavities ( 17 , 27 ) are formed by sub-dividing said spacing.  
   
   
       70 . A silencer according to  claim 69 , wherein sub-division of said spacing is established by inserting one or more walls between said protruding sound absorptive material.  
   
   
       71 . A silencer according to  claim 69 , wherein sub-division of said spacing is established by inserting one or more walls between said protruding sound absorptive material and another member of the silencer.  
   
   
       72 . A silencer according to  claim 41 , wherein at least one said resonator, constituted by at least one terminated cavity ( 17 , 27 ) at least partly surrounding protruding sound absorptive material, is tuned so as to target one or more peak frequencies of an un-attenuated noise spectrum to be attenuated by said silencer.  
   
   
       73 . A silencer according to  claim 41 , wherein said silencer is designed so as to provide means for spark-arresting, said means comprising said at least one terminated cavity ( 17 , 27 ) capable of collecting particles separated from the gas flow as the spark-arresting function.  
   
   
       74 . A silencer according to  claim 73 , where said spark-arrestor is shaped as a radial diffuser.  
   
   
       75 . A silencer according to  claim 74 , wherein said radial diffuser is provided with ribs capable of guiding flow towards the periphery of said diffuser, said ribs being of such a shape that gas flow leaves said diffuser with a tangential flow direction component, thus acting as a swirl generator.  
   
   
       76 . A silencer according to  claim 73 , wherein at least one of the following flow motions: radial outward flow motion, radial inward flow motion and swirling flow motion is enforced upon the gas flow passing through the silencer, thereby promoting particles contained in the gas flow to be collected in said at least one terminated cavity ( 17 , 27 ).  
   
   
       77 . A silencer according to  claim 41 , wherein gas flow, when passing through said silencer, passes at least one screen ( 47 ) provided with openings, the size of said openings being selected so that any particles that are of a size greater than the size of the openings will be retained, either on the upstream side of a said screen or otherwise within the silencer.  
   
   
       78 . A silencer according to  claim 77 , wherein at least one of said at least one screen are provided onto a number of protrusions, such that gas leaving one or more chambers of the silencer will pass through said at least one screen prior to entering said number of protrusions.  
   
   
       79 . Use of a silencer according to  claim 41  for silencing acoustical emission of exhaust gases from a combustion engine.  
   
   
       80 . Use according to  claim 79 , where said use of a silencer is a use for silencing acoustical emission of exhaust gases from a diesel engine.