Patent Publication Number: US-8992275-B1

Title: Marine water drop muffler

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/754,899, filed on Apr. 6, 2010, which claims the benefit of provisional U.S. Patent Application Ser. No. 61/166,882, filed on Apr. 6, 2009. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights rights whatsoever. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to exhaust systems and mufflers for use with internal combustion marine engines, and more particularly to a water drop marine engine muffler that uses centrifugal force and turbulence to separate entrained water from marine exhaust gas thereby combining improved water separation and handling characteristics with enhanced noise reduction. 
     2. Description of Related Art 
     Marine vessels are typically configured with a propulsion system having an internal combustion engine mounted internally within the vessel hull. Exhaust generated by the engine is commonly combined with cooling water and routed through exhaust conduit to the stern or rear of the vessel via one or more exhaust ducts for discharge through one or more exhaust ports formed in the transom. One or more silencers may be installed within the exhaust duct(s) to silence noise associated with the engine and exhaust gases. 
     A variety of structures are known in the background art for use in silencing marine exhaust noise. The present inventor has invented a number of novel marine exhaust components that have greatly improved the silencing and efficiency of marine exhaust systems. Among those inventions developed by a named inventor for the present invention are the following: 
     
       
         
           
               
               
             
               
                   
               
               
                 U.S. Pat. No. 
                 Entitled 
               
               
                   
               
             
            
               
                 4,918,917 
                 Liquid Cooled Exhaust Flange 
               
               
                 5,196,655 
                 Muffler for Marine Engines 
               
               
                 5,228,876 
                 Marine Exhaust System Component Comprising a Heat 
               
               
                   
                 Resistant Conduit 
               
               
                 5,262,600 
                 In-line Insertion Muffler for Marine Engines 
               
               
                 5,444,196 
                 In-line Insertion Muffler for Marine Engines 
               
               
                 5,504,280 
                 Muffler for Marine Engines 
               
               
                 5,616,893 
                 Reverse Entry Muffler With Surge Suppression Feature 
               
               
                 5,625,173 
                 Single Baffle Linear Muffler for Marine Engines 
               
               
                 5,718,462 
                 Muffler Tube Coupling With Reinforcing Inserts 
               
               
                 5,740,670 
                 Water Jacketed Exhaust Pipe for Marine 
               
               
                   
                 Exhaust Systems. 
               
               
                 6,564,901 
                 Muffler for Marine Engine 
               
               
                   
               
            
           
         
       
     
     The present inventor&#39;s prior advancements in the art have been primarily directed to muffler structures wherein water generally remains entrained with the exhaust gas. In certain applications, however, it is desirable to separate water from exhaust gas. In these situations, the use of a muffler capable of receiving a mixture of exhaust and entrained water and separating the water from the exhaust gas is required. Such mufflers are sometimes referred to as “water drop mufflers”. Water separation effectiveness is a primary concern for water drop mufflers. 
     A typical water drop muffler is disclosed in U.S. Pat. No. 5,022,877, issued to Harbert. Harbert discloses a water drop muffler that relies primarily on gravity to separate the exhaust gas from the water. U.S. Pat. No. 6,591,939, issued to Smullin et al., discloses a marine engine silencer that attempts to dynamically separate water from exhaust gas by linear momentum effect or centrifugal effect. Smullin distinguishes muffler structures that separate water from exhaust gases by dynamic separation due to linear momentum or centrifugal effects from passive-restraining or non-dynamic effects, such as gravitational effects. Smullin claims to achieve centrifugal separation of water by providing a circular (or partially curved) interior surface that causes the fluid mixture to swirl. The structure disclosed by Smullin, however, is overly complex, dynamically inefficient, and otherwise fails to truly maximize the use of centrifugal forces to achieve water separation. 
     U.S. Pat. No. 5,746,630, issued to Ford et al., discloses a water drop muffler that primarily relies on centrifugal effects to separate entrained cooling water from exhaust gas. Ford discloses a generally cylindrical housing having a tangential inlet for receiving a mixture of exhaust gas and entrained cooling water, and an inlet baffle for deflecting the exhaust flow along the inner wall of the housing. The inlet baffle defines a parabolic trailing edge that Ford claims to have been found helpful in imparting the desired swirling pattern to the fluid mixture admitted through the inlet pipe. Once separated from exhaust gas, the water exits the housing through a second pipe. The tangential inlet and baffle structure disclosed by Ford, however, comprises a fluid handling structure that is inefficient in a fluid dynamic sense, and thus fail to maximize the generation of centrifugal forces thereby resulting in less than optimal water separation performance. 
     The water drop mufflers disclosed in the art rely on overly complex structures and fail to maximize the use of centrifugal forces to separate entrained cooling water from exhaust gas. As a result there remains a need in the art for an improved water drop muffler that maximizes the use of centrifugal forces to achieve water separation. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention overcomes limitations present in the art by providing an improved water drop muffler for use in a marine exhaust system to silence exhaust noise while separating entrained cooling water from exhaust gas using hydro-dynamic centrifugal separation principles enhanced by turbulent flow. A water drop muffler in accordance with the present invention includes a housing having a top and a bottom, and defining an internal volume bounded by a generally vertically disposed cylindrical inner surface formed about a longitudinal axis. The housing further includes a generally tubular exhaust inlet, which is preferably disposed in generally tangential relation with the cylindrical inner housing surface for receiving a mixture of exhaust gas and entrained cooling water. The tubular inlet is in fluid communication with a variable geometry flow channel that efficiently transitions the flow for discharge through an elongate vertically disposed opening located along the housing inner surface thereby creating vortex flow within the housing to maximize the generation of centrifugal forces and turbulent boundary layer flow. The variable geometry flow channel transitions the exhaust conduit from the generally tubular exhaust inlet to a generally rectangular, vertically oriented outlet disposed substantially adjacent to housing&#39;s cylindrical inner surface. This channel results in forming an exhaust flow profile that includes turbulent boundary layer flow along a significant circumferential length of the cylindrical inner surface while avoiding flow stagnation. The vortex flow formed within the housing causes the relatively heavy water droplets and water vapor (i.e. steam) to be drawn away from the housing axis toward the cylindrical inner surface of the housing. In addition, turbulent boundary layer flow along the surfaces of the variable geometry flow channel and the other housing surfaces function to more efficiently draw entrained water droplets and steam into contact with various surfaces within the housing thereby causing water to coalesce along the inner housing surfaces. 
     The housing further includes a water pan disposed in spaced relation with the bottom of the housing. The water pan includes a bottom having an upwardly projecting conical surface and a peripheral side wall having a radially outwardly projecting annular lip formed in sealing engagement with the inner surface of the housing. The water pan thus partitions the housing internal volume into a vortex flow chamber (disposed above the water pan) and a water collection chamber (disposed below the water pan). Water that is separated from the exhaust vortex pools in the water pan and openings defined in the pan peripheral side wall allow the water flow out of the water pan and into the water collection chamber below. Once in the water collection chamber the water is generally isolated from the exhaust gas flow within the vortex chamber thereby preventing the water from agitation and becoming entrained and or evaporated back into the exhaust gas. A plurality of angularly spaced, radially aligned and vertically disposed vanes are located between the bottom of the water pan and the bottom of the housing. The vanes function as water brakes by forming barriers that interrupt swirling flow patterns while further functioning as vertical spacers and/or supports for the water pan. Water in the water collection chamber flows out of the housing via a water outlet via gravity and/or pressure. Exhaust gas in the vortex chamber enters the bell-shaped mouth of an exhaust gas outlet pipe that projects out the top portion of the housing to duct exhaust gas to down stream exhaust system components for discharge from the vessel. 
     Accordingly, it is an object of the present invention to provide an improved marine water drop muffler. 
     Still another object of the present invention is to provide such a marine water drop muffler wherein water separation is achieved using centrifugal forces enhanced by boundary layer turbulence. 
     Yet another object of the present invention is to provide such a muffler water drop muffler wherein the generation of centrifugal force is maximized by use of a variable geometry flow channel that transitions and accelerates inlet flow through a hydro-dynamically efficient elongate vertical opening disposed along the length of the housing inner surface. 
     Still another object of the present invention involves 
     In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side sectional view of a marine vessel adapted with a water drop muffler in accordance with the present invention; 
         FIG. 2  is a sectional view thereof taken along section line  2 - 2  of  FIG. 3 ; 
         FIG. 3  is a rear view thereof; 
         FIG. 4  is a side view thereof; 
         FIG. 5  is a sectional view thereof taken along section line  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a sectional view thereof taken along section line  6 - 6  of  FIG. 2 ; 
         FIG. 7  is a perspective view with hidden lines illustrating internal structure; 
         FIG. 8  is a sectional view taken along section line  2 - 2  of  FIG. 3  with the addition of a coalescing vane; and 
         FIG. 9  is a sectional view taken along line  9 - 9  of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawings,  FIGS. 1-9  depict a marine water drop muffler, generally referenced as  10 , in accordance with the present invention. The present invention overcomes limitations present in the art by providing an improved water drop muffler for use in a marine exhaust system to silence exhaust noise while separating entrained cooling water from “wet” exhaust gas using hydro-dynamic centrifugal separation principles enhanced by boundary layer turbulent flow. 
       FIG. 1  is a partial sectional view of a marine vessel, generally referenced as  1 , having a water drop muffler, generally referenced as  10 , in accordance with the present invention. Marine vessel  1  includes an internal combustion engine  2  having an exhaust conduit  3  connected to a cooling water supply line  4 . Exhaust conduit  3  contains a mixture of exhaust gas and cooling water and is in communication with the inlet of water drop muffler  10  of the present invention. Muffler  10  is further connected to an exhaust outlet conduit  5 , and a water outlet conduit  6 . The exact configuration of engine  2 , exhaust conduit  3 , and water supply line  4 , may vary from vessel to vessel, and it should be appreciated that the water drop muffler of the present invention may be installed in any suitable vessel in any suitable exhaust system configuration. 
       FIGS. 2-7  depict detailed views of a first embodiment of marine muffler  10 , and  FIGS. 8-9  depict a second embodiment thereof that includes an optional coalescing vane  50 . Marine water drop muffler  10  includes a housing  12  defining an internal volume  14  bounded by a generally vertically disposed cylindrical inner surface  16  formed about a longitudinal axis  18 . In addition, housing  12  includes an uppermost portion having a top  20 , and a lowermost portion having a bottom  22 . Housing  12  further includes a generally tubular inlet  24  generally tangentially disposed relative to inner surface  16 , and in proximity to the top  20  for receiving wet marine exhaust, namely a mixture of exhaust gas and entrained cooling water. Tubular inlet  24  is preferably disposed in proximity to the top  20  of housing  12 , however, inlet  24  may be located at any suitable position between the top  20  and bottom  22  of housing  12 . It should be noted that the exhaust gas contains particulate matter, such as hydrocarbon by products of combustion. Further, water may be present in the form of entrained droplets and/or water vapor or steam. 
     Tubular inlet  24  is in fluid communication with a variable geometry flow channel, generally referenced as  26  (by reference to the radially inner channel wall), which efficiently transitions the exhaust gas flow profile to discharge through an elongate vertically disposed opening  28  formed along a portion of the vertical length of the housing inner surface  16 . More particularly, variable geometry flow channel  26  transitions the exhaust conduit from the generally tubular exhaust inlet  24  to a generally rectangular, vertically oriented outlet or terminal opening  28  disposed substantially adjacent to housing&#39;s cylindrical inner surface  16  in a hydro-dynamically efficient manner. Variable geometry flow channel  26  preferably extends between 45-degrees and 180-degrees or more around the circumference of inner surface  16 . In various embodiments, variable geometry flow channel  26  may be sized to either maintain constant, or increase, the velocity of the exhaust gas entering water drop muffler  10 . In an alternate embodiment, variable geometry flow channel  26  may further include one or more internal vanes, referenced as  50 , as illustrated in  FIGS. 8 and 9 , aligned with the direction of flow, to provide increased surface area for the formation of turbulent boundary layer flow to maximize the coalescence of water. Housing  12  and its major structural components are preferably fabricated from fiberglass, metal, such as stainless steel, or any other suitable corrosion resistant material, heat resistant material, or combination of such materials. 
     Wet exhaust enters muffler  10  through inlet  24  and is routed into the variable geometry flow channel or duct  26  whereby the exhaust flow profile is transitioned and exits opening  28  having a flow profile characteristic that is vertically elongate and relatively thin when measured in the radial direction (e.g. from inner surface  16  toward longitudinal axis  18 ). As used herein the terms “flow channel” shall mean an exhaust duct confining exhaust gas flow and shaping the flow profile of exhaust gas. As a result, exhaust gas is discharged from opening  28  onto inner surface  16  along a substantial portion of the housing dimension measured from top to bottom. As noted above, the flow velocity may further be increased within flow channel  26  to maximize the generation of centrifugal forces. Variable geometry flow channel  26  is bounded at the radially outer bound by the generally cylindrical inner surface  16 , at the radially inner bound by the channel wall  26  disposed in spaced relation with inner surface  16 , at the uppermost portion by a radially outwardly turned top portion  26   a  of wall  26 , and at the lowermost portion by a radially outwardly turned bottom portion  26   b  of wall  26 . Furthermore, the distance between the inner surface  16  of housing  12  and the channel wall  26  preferably decreases in the direction of flow. The curvature of the lowermost portion of flow channel  26  preferably descends in a non-linear manner as can be seen in  FIG. 5 . In a preferred embodiment, variable geometry flow channel  26  further defines a reduction in cross-sectional area from the inlet thereof (in proximity to exhaust inlet  24 ) to the terminal outlet  28  thereof whereby exhaust velocity may be increased. Variable geometry flow channel  26  preferably results in an exhaust flow profile that includes boundary layer flow from generally near the uppermost portion of housing  12  downward a significant length along cylindrical inner surface  16  thereby significantly avoiding regions of flow stagnation. Exhaust gas and entrained cooling water exiting outlet  28  of flow channel  26  preferably forms a vortex about axis  18  within housing  12 . As the exhaust flow vortex is formed about longitudinal axis  18  the relatively heavy water droplets and water vapor spiral away from the housing axis toward the cylindrical inner surface where turbulent boundary layer flow functions to maximize the coalescence and deposit of water and particulate matter onto the inner surface  16 , and both internal and external surfaces of flow channel  26 . 
     It has been found that the vortex chamber  14   a  absorbs acoustical energy thereby significantly contributing to the silencing of the muffler discharge. More particularly, the combination of water laden turbulent boundary layer flow over a substantial portion of the inner surface functions to form a radially outer sound barrier thereby providing exceptional sound attenuation. 
     Housing  12  further includes a water pan  30  having a generally conical baffle  31  projecting upward as best illustrated in  FIGS. 2 and 5 . Water pan  30  partitions the internal volume  14  into an upper/exhaust-vortex chamber  14   a  (disposed above water pan  30  and baffle  31 ) and a lower/water-collection chamber  14   b  (disposed below water pan  30  and baffle  31 ). While baffle  31  is illustrated as generally conical, the present invention contemplates alternate shapes including dome shaped, generally convex shapes, or any other suitable shape. Baffle  30  decreases the volume of vortex chamber  14   a  and thereby minimizes fluid flow “dead space” (e.g. areas of flow stagnation) so as to contribute in maintaining a high circulatory velocity within vortex chamber  14   a  thereby causing particulate matter to coalesce along the housing inner surface  16 . The vortex chamber  14   a  relies on centrifugal force to collect and compress together exhaust gas and water particles in a manner, prior to separation, that causes water particles to more effectively absorb or hold into suspension the hydrocarbon by products of combustion so that they may be subsequently eliminated along with water discharged from muffler  10 . Further, the turbulent boundary layer flow formed along inner surface  16  functions to maximize the coalescence of liquid from entrained water droplets and water vapor. 
     Water that is coalesced and deposited on the various surfaces migrates under the influence of gravity into water pan  30 . A plurality of openings  32  are formed in water pan  30  to allow water collected therein to flow out of water pan  30  to the water collection chamber  14   b . Positioning the water collection chamber  14   b  below the water pan  30  functions to conceal the accumulated water (and particulate matter) and prevent agitation thereof by velocity induced turbulence within the vortex chamber  14   a . A plurality of angularly spaced, radially aligned and vertically disposed vanes  33  are located between the bottom of the water pan and the bottom of the housing as best seen in  FIG. 2 . Vanes  33  function as water brakes by forming barriers that interrupt swirling water flow, and may further function as vertical spacers and/or supports for the water pan. Water that accumulates in the water collection chamber  14   b  flows out of the housing via a water outlet pipe  34  under the influence of gravity and/or pressure formed within housing  12 . In alternate embodiments, a pump may further assist in water removal. 
     A generally cylindrical, axially disposed exhaust gas outlet pipe  40  projects from the top  20  of housing  12 . Outlet pipe  40  defines an open ended exhaust gas inlet  42  disposed within housing  12  and an open ended exhaust gas outlet  44  disposed externally to housing  12 . Dry (or drier) exhaust gas in the vortex chamber  14   a  enters the inlet  42  of an exhaust gas outlet pipe  40  whereby the exhaust may be routed to downstream exhaust components, including exhaust conduit  5 , for eventual discharge from the vessel. As best seen in  FIG. 2 , the lower portion of exhaust gas outlet pipe  40  may include an expanded exhaust gas inlet  42  which is radially enlarged relative to the upper portions of outlet pipe  40 . The present inventor contemplates a variety of transition shapes including without limitation a conical shape wherein the transition is linear, and a bell shape as illustrated in  FIG. 2  wherein the transition is non-linear. Providing a radially enlarged exhaust gas inlet causes exhaust gas entering inlet  42  to increase in velocity as it moves upward through the narrowing lower portion of exhaust pipe  40 . It should be noted, however, that any suitable exhaust gas outlet pipe configuration is considered within the scope of the present invention. 
     The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.