# Patent

## Title
Marine water drop muffler

## Abstract

A water drop muffler for use in a marine exhaust system to silence exhaust noise while separating entrained water from exhaust gas using hydro-dynamic centrifugal separation principles enhanced by turbulent flow. A muffler housing has a top and a bottom, and defines an internal volume bounded by a generally vertically disposed cylindrical inner surface formed about a longitudinal axis. A generally tubular exhaust inlet is disposed in generally tangential relation with the cylindrical inner housing surface for receiving a mixture of exhaust gas and entrained cooling water. A variable geometry flow channel efficiently transitions the flow for discharge through a vertically elongate opening disposed along the length of the housing inner surface thereby creating vortex flow within the housing to maximize the generation of centrifugal forces. 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. In addition, turbulent boundary layer flow along the surfaces of the variable geometry flow forming channel and the other housing surfaces functions 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.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application 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'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 at least a portion of 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 a vertically elongate opening disposed along the length of 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 forming channel transitions the exhaust conduit from the generally tubular exhaust inlet to a generally rectangular, vertically oriented outlet disposed substantially adjacent to housing'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. In addition, turbulent boundary layer flow along the surfaces of the variable geometry flow forming channel and the other housing surfaces functions 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 an axial baffle structure projecting upward from the bottom thereof so as to partition the housing internal volume into a vortex flow chamber (disposed above the baffle) and a water collection chamber (disposed generally below the baffle). Water that is separated from the exhaust vortex pools at the bottom of the housing and openings at the base of the baffle allow the water to enter the water collection chamber. Once in the collection chamber 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. Water in the water collection chamber flows out of the housing via a water outlet disposed in proximity to the bottom of the housing via gravity and/or pressure. Exhaust gas in the vortex chamber enters the 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.
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; and
FIG. 6 is a sectional view thereof taken along section line 6-6 of FIG. 2.



DETAILED DESCRIPTION OF THE INVENTION
With reference now to the drawings, FIGS. 1-6 depict a preferred embodiment of 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. 2-6 depict detailed views of marine muffler 10. 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. 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's cylindrical inner surface 16 in a hydrodynamically 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, 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 to materials.
Wet exhaust enters muffler 10 through inlet 24 and is routed into the variable geometry flow channel 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 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 top wall generally coextensive with the top 20 of housing 12, at the lowermost portion by a bottom wall that curves downward toward the bottom 22 of housing 12 as the channel extends in the circumferential direction. 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. 2. 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 The variable geometry flow channel 26 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. 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, both internal and external to flow channel 26.
Housing 12 further includes a generally axial, hollow baffle structure 30 projecting upward from the bottom 22 thereof as best illustrated in FIGS. 2 and 5. Baffle 30 partitions the internal volume into a lower/vortex chamber 14a (disposed above baffle 30) and an upper/water collection chamber 14b (disposed below baffle 30). While baffle 30 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 14a 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 14a thereby causing particulate matter to coalesce along the housing inner surface 16. The vortex chamber 14a 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 pools at the bottom of housing 12, and openings 32 in the base of the conical baffle 30 allow the water to enter the water collection chamber 14b. Positioning the water collection chamber 14b below the conical baffle 30 functions to conceal the accumulated water (and particulate matter) and prevent agitation thereof by velocity induced turbulence within the vortex chamber 14a. One or more upwardly projecting water flow control structures or fences may be affixed to the bottom of the water collection chamber to prevent the water from swirling and/or to direct the water to outlet 34. Water that accumulates in the water collection chamber 14b flows out of the housing via a water outlet pipe 34 under the influence of gravity as well as pressure formed within housing 12. In alternate embodiments, a pump may further assist in water removal. Dry (or drier) exhaust gas in the vortex chamber 14a enters the mouth 42 of an exhaust gas outlet pipe 40 that projects from the uppermost portion of housing 12 whereby the exhaust may be routed to downstream exhaust components for eventual discharge from the vessel. In a preferred embodiment, exhaust gas outlet pipe is axially disposed relative to the top 20 of housing 12 and further provides a cylindrical upper baffle to prevent flow stagnation. It should be noted, however, that any suitable exhaust gas outlet pipe configuration is considered within the scope of the present invention.
It has been found that the vortex chamber 14a absorbs acoustical energy thereby significantly contributing to the silencing of the muffler discharger. 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.
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.

## Claims

1. A marine exhaust component comprising:
a housing defining an internal volume bounded by a generally vertically disposed cylindrical inner surface, a top, and a bottom;
a generally tubular exhaust inlet connected to said housing in proximity to said top, said inlet generally disposed so as to introduce exhaust along at least a portion of said cylindrical inner surface between the top and bottom of said internal volume;
said exhaust inlet in fluid communication with a flow channel terminating in a vertically elongate terminal opening disposed substantially adjacent to said cylindrical inner surface;
a baffle projecting upward from said housing bottom and partitioning said internal volume generally into a chamber disposed above said baffle, and a water collection chamber disposed below said baffle, said baffle including at least one opening disposed in proximity to the bottom of said housing to allow water to flow into said water collection chamber from said internal volume;
a water outlet pipe having an inlet in fluid communication with said water collection chamber and an outlet;
an exhaust gas outlet pipe in fluid communication with said chamber and projecting axially from the top of said housing;
whereby water in said water collection chamber flows out of the housing via said water outlet pipe and exhaust in said chamber flows out of said housing via said exhaust outlet pipe.

2. The marine exhaust component according to claim 1, wherein said baffle includes a plurality of circumferentially spaced openings disposed in proximity to the bottom of said housing.

3. The marine exhaust component according to claim 1, wherein said a flow channel reduces in cross-sectional area from said exhaust inlet to said elongate terminal opening.

4. A marine exhaust component comprising:
a housing defining an internal volume bounded by a generally vertically disposed cylindrical inner surface having an axis, said housing having a top, and a bottom;
a generally tubular wet exhaust inlet connected to said housing in proximity to said top for receiving wet exhaust from a marine engine, said wet exhaust including exhaust gas and entrained cooling water, said inlet generally disposed so as to introduce exhaust along at least a portion of said cylindrical inner surface between the top and bottom of said internal volume
said wet exhaust inlet in fluid communication with a flow channel terminating in a vertically elongate terminal opening disposed substantially adjacent to said cylindrical inner surface, said variable geometry flow channel reducing in cross-sectional area so as to increase the velocity of gas;
a generally conically-shaped baffle projecting upward from said housing bottom and partitioning said internal volume generally into an upper chamber disposed above said baffle and a lower chamber disposed below said baffle, said baffle including at least one opening disposed in proximity to the bottom of said housing to allow water to flow into said lower chamber from said upper chamber;
a water outlet pipe having an inlet in fluid communication with said lower chamber;
an exhaust gas outlet pipe projecting from the top of said housing, said outlet pipe having an opening in fluid communication with said upper chamber;
whereby water in said lower chamber flows out of the housing via said water outlet pipe and exhaust gas in said upper chamber flows out of said housing via said exhaust outlet pipe.

5. The marine exhaust component according to claim 4, wherein said baffle includes a plurality of circumferentially spaced openings disposed in proximity to the bottom of said housing.