Exhaust plenum for distributing exhaust gas uniformly through a catalyst module

Abstract

A plenum is provided upstream from a catalyst module and downstream from a plurality of exhaust ports of a marine engine. The plenum is provided with a cross-sectional area that induces exhaust gas to slow as it passes from the plurality of exhaust ports into the plenum. This slowing of the velocity of exhaust gas improves the probability that the exhaust gas will be more evenly distributed across the inlet surface of the catalyst module.

1 . An exhaust system for a marine engine, comprising:
 a plurality of exhaust ports associated with a plurality of cylinders of said marine engine;   a catalyst module disposed in fluid communication with said plurality of exhaust ports; and   a plenum disposed in fluid communication between said plurality of exhaust ports and said catalyst module, wherein exhaust gas passing from said plurality of exhaust ports to said catalyst module must pass through said plenum, wherein the effective cross sectional area of said plenum monotonic ally decreases from said plurality of exhaust ports to said catalyst module.   
     
     
         2 . The exhaust system of  claim 1 , wherein:
 said cross sectional area of said plenum decreases along the entire span of exhaust flow from said plurality of exhaust ports to said catalyst module without changing to increasing values of said cross sectional area.   
     
     
         3 . The exhaust system of  claim 1 , wherein:
 said plurality of exhaust ports are disposed in parallel with each other and in series with said plenum.   
     
     
         4 . The exhaust system of  claim 1 , wherein:
 said catalyst module comprises catalyst coated material disposed within a generally cylinder housing, said generally cylinder housing being configured to conduct said exhaust gas through said generally cylinder housing in a direction which is parallel to a central axis of said generally cylinder housing and in contact with said catalyst coated material.   
     
     
         5 . The exhaust system of  claim 4 , wherein:
 said central axis is generally vertical.   
     
     
         6 . The exhaust system of  claim 1 , wherein:
 an unobstructed path exists through said plenum to said catalyst module.   
     
     
         7 . The exhaust system of  claim 1 , wherein:
 the effective cross sectional area of said plenum, at a plane midway between said plurality of exhaust ports and said catalyst module and generally perpendicular to the path of said exhaust gas, is greater than the effective total cross sectional area of said plurality of exhaust ports.   
     
     
         8 . The exhaust system of  claim 1 , wherein:
 the effective cross sectional area of said plenum, at a plane midway between said plurality of exhaust ports and said catalyst module and generally perpendicular to the path of said exhaust gas, is greater than the effective total cross sectional area of said catalyst module.   
     
     
         9 . The exhaust system of  claim 1 , wherein:
 said plenum is configured to cause the velocity of said exhaust gas to decrease as it passes from said plurality of exhaust ports into said plenum.   
     
     
         10 . The exhaust system of  claim 1 , wherein:
 said plenum is attachable to said marine engine.   
     
     
         11 . An exhaust system for a marine engine, comprising:
 a plurality of exhaust ports associated with a plurality of cylinders of said marine engine;   a plurality of catalyzing elements disposed in fluid communication with said plurality of exhaust ports, each of said plurality of catalyzing elements comprising catalyst coated material disposed within a generally cylinder housing, said generally cylinder housing being configured to conduct said exhaust gas through said generally cylinder housing in a direction which is parallel to a central axis of said generally cylinder housing and in contact with said catalyst coated material; and   a plenum disposed in fluid communication between said plurality of exhaust ports and said plurality of catalyzing elements, wherein exhaust gas passing from said plurality of exhaust ports to said plurality of catalyzing elements must pass through said plenum, said plenum being attachable to said marine engine and configured to cause the velocity of said exhaust gas to decrease as it passes from said plurality of exhaust ports into said plenum, wherein the effective cross sectional area of said plenum monotonically decreases from said plurality of exhaust ports to said plurality of catalyzing elements.   
     
     
         12 . The exhaust system of  claim 11 , wherein:
 said plurality of catalyzing elements are disposed in parallel with each other and in series with said plenum;   said cross sectional area decreases along the entire span of exhaust flow from said plurality of exhaust ports to said plurality of catalyzing elements without changing to increasing values of said cross sectional area.   
     
     
         13 . The exhaust system of  claim 12 , wherein:
 said plurality of exhaust ports are disposed in parallel with each other and in series with said plenum.   
     
     
         14 . The exhaust system of  claim 13 , wherein:
 an unobstructed path exists through said plenum from any one of said plurality of exhaust ports to any one of said catalyzing elements.   
     
     
         15 . The exhaust system of  claim 13 , wherein:
 the effective cross sectional area of said plenum, at a plane midway between said plurality of exhaust ports and said plurality of catalyzing elements and generally perpendicular to the path of said exhaust gas, is greater than the effective total cross sectional area of said plurality of exhaust ports.   
     
     
         16 . The exhaust system of  claim 13 , wherein:
 the effective cross sectional area of said plenum, at a plane midway between said plurality of exhaust ports and said plurality of catalyzing elements and generally perpendicular to the path of said exhaust gas, is greater than the effective total cross sectional area of said plurality of catalyzing elements.   
     
     
         17 . The exhaust system of  claim 11 , wherein:
 said central axis is generally vertical.   
     
     
         18 . An exhaust system for a marine engine, comprising:
 a plurality of exhaust ports associated with a plurality of cylinders of said marine engine;   a plurality of catalyst modules disposed in fluid communication with said plurality of exhaust ports, each of said plurality of catalyst modules comprising catalyst coated material disposed within a generally cylinder housing, said generally cylinder housing being configured to conduct said exhaust gas through said generally cylinder housing in a direction which is parallel to a central axis of said generally cylinder housing and in contact with said catalyst coated material; and   a plenum disposed in fluid communication between said plurality of exhaust ports and said plurality of catalyst modules, wherein exhaust gas passing from said plurality of exhaust ports to said plurality of catalyst modules must pass through said plenum, said plurality of catalyst modules being disposed in parallel with each other and in series with said plenum, said plurality of exhaust ports being disposed in parallel with each other and in series with said plenum, said plenum being configured to cause the velocity of said exhaust gas to decrease as it passes from said plurality of exhaust ports into said plenum, wherein the effective cross sectional area of said plenum monotonically decreases from said plurality of exhaust ports to said plurality of catalyst modules.   
     
     
         19 . The exhaust system of  claim 18 , wherein:
 the effective cross sectional area of said plenum, at a plane midway between said plurality of exhaust ports and said plurality of catalyst modules and generally perpendicular to the path of said exhaust gas, is greater than the effective total cross sectional area of said plurality of exhaust ports; and   the effective cross sectional area of said plenum, at a plane midway between said plurality of exhaust ports and said plurality of catalyst modules and generally perpendicular to the path of said exhaust gas, is greater than the effective total cross sectional area of said plurality of catalyst modules;   wherein said cross sectional area decreases along the entire span of exhaust flow from said plurality of exhaust ports to said plurality of catalyst modules without changing to increasing values of said cross sectional area.   
     
     
         20 . The exhaust system of  claim 19 , wherein:
 an unobstructed path exists through said plenum from any one of said plurality of exhaust ports to any one of said catalyst modules, said central axis being generally vertical, said plenum being attachable to said marine engine.