WO2007041082A1

WO2007041082A1 - Improvements to wet marine exhaust system containing a water separation device and a filter to remove impurities from the cooling water

Info

Publication number: WO2007041082A1
Application number: PCT/US2006/037340
Authority: WO
Inventors: Ken Harstel; Ernie Beckwith; John R. Ford
Original assignee: Centek Industries, Inc.
Priority date: 2005-10-03
Filing date: 2006-09-25
Publication date: 2007-04-12

Abstract

A marine wet exhaust system includes an exhaust gas/cooling water separator (24) for receiving an exhaust gas and waste cooling water mixture through a cooling water/exhaust gas inlet (66) . The exhaust system also includes a reservoir for collecting the waste cooling water separated from the exhaust gas and a de- watered exhaust gas discharge conduit (38) . The exhaust system also includes a cooling water discharge conduit (34) and a reservoir discharge pump (50) in the cooling water discharge conduit (34) configured to pump cooling water collected in the reservoir, the cooling water discharge conduit (34) and reservoir discharge pump (50) fluidically connected to the reservoir through a water outlet (32) having a first vertical height in the reservoir. The marine wet exhaust system also includes a pump controller (56) for controlling the reservoir discharge pump (50) and a water level sensing system (70) configured to provide a signal to the pump controller (55) based on the water level in the reservoir. The water level sensing system (70) is configured to function without the need for the reservoir to be vented to atmosphere .

Description

IMPROVEMENTS TO WET MARINE EXHAUST SYSTEM CONTAINING A WATER SEPARATION DEVICE AND A FILTER TO REMOVE IMPURITIES

FROM THE COOLING WATER

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority under 35 U.S.C. §119(e) to U.S.

Provisional Patent Application No. 60/723,230, filed October 3, 2005.

BACKGROUND OF THE INVENTION

Field of Invention

[0002] This invention pertains to exhaust systems for internal combustion engines on water craft, and more particularly, to an improved water level sensing system for a cooling water collection reservoir in a marine wet exhaust system.

Description of Related Art

[0003] Internal combustion engines are commonly used to move water craft through the water and supply electrical power for various systems onboard the water craft. The cooling systems on marine engines typically differ from conventional dry engines (such as those used in automobiles and other land vehicles) in as much as they use liquid-to-liquid heat exchangers to dissipate the heat from the engine coolant. These vessels typically use the water supporting the craft for cooling purposes. The water is drawn into the engine via an engine driven cooling water supply pump and circulated through an engine cooling jacket or engine coolant heat exchanger.

[0004] Such water craft have a wet marine exhaust system for expelling the exhaust and for muffling or attenuating exhaust noise generated by the operation of the internal combustion engine. After circulating through the engine cooling jacket or engine coolant heat exchanger, the cooling water is commonly injected into the exhaust system as the exhaust gases exit the exhaust manifold or the turbo charger. The water injected from the engine cooling system typically performs two functions, namely, absorbing engine exhaust noise and cooling the exhaust gas so that the gas might be safely discharged through the hull of the craft without presenting a fire hazard. Accordingly, a marine wet exhaust system must handle not only exhaust gases, but also the waste cooling water which is injected into the exhaust system. This practice is very effective in cooling the exhaust gases to a temperature low enough that they can be conveyed in light weight, non-metallic piping systems to the overboard terminus.

[0005] Mufflers of various designs have been placed in the exhaust conduit running between the exhaust manifold of the engine and the overboard discharge. Typically, marine mufflers include housings which enclose one or more chambers for permitting expansion of the exhaust gas to attenuate noise. One example of a wet marine exhaust muffler is disclosed in U.S. Pat. No. 5,588,888 to Magharious, the disclosure of which is incorporated herein by reference. Often, marine muffler designs have been closely akin to the mufflers used on automobiles but have been constructed of fiber reinforced polymer materials such as fiber reinforced plastic ("FRP") which can better tolerate the marine environment. In other systems, the wet exhaust flows through muffler/separators which remove at least a portion of the cooling water from the exhaust flow. A secondary muffler is often placed along the exhaust conduit running between the muffler/separator and the exhaust gas line terminus to further attenuate the exhaust noise. One such muffler is proposed in Harbert, U.S. Pat. No. 5,022,877, the disclosure of which is also incorporated herein by reference. [0006] The engine and muffler in marine craft are often mounted amidships and located as far as 30 ft to 40 ft (9 m to 12 m) from the exhaust tenninus. At these lengths, it is difficult to maintain an overall downward grade necessary to drain the waste coolant water separated from the exhaust flow solely by means of gravity. In practice, the exhaust conduit leading from the muffler to the exhaust terminus may curl up-and-down as it crosses various sections of the marine craft, creating traps where water may accumulate and constrict the exhaust gas flow.

[0007] Commonly assigned U.S. Patent No. 6,820,419 discloses a wet marine exhaust system that uses a discharge pump in the exhaust system a water collection reservoir since the cooling water from the exhaust/cooling water separation device often cannot be removed at exactly the same rate as that at which the engine driven pump is supplying that water to the system. The water level in the reservoir is maintained within operational limits by switching the pump on and off and/or between high and low levels within reasonable operation limits for the reservoir. The system includes a pressure test point in a level sensing tube appropriately positioned in the reservoir with the output of the pressure test point transmitted to a variable speed controller. However, this system requires that the reservoir be periodically vented to atmospheric pressure to maintain proper operation of the pressure test point. This is problematic because many installations require that the location of the reservoir be in a position within the hull that makes venting to atmosphere extremely difficult or even impossible.

SUMMARY OF THE INVENTION

[0008] One aspect of the invention is directed to a marine wet exhaust system for water craft. The marine wet exhaust system includes an exhaust gas/cooling water separator for receiving an exhaust gas and waste cooling water mixture through a cooling water/exhaust gas inlet and at least partially separating the waste cooling water from the exhaust gas. The marine wet exhaust system also includes a de- watered exhaust gas discharge conduit, wherein de-watered exhaust gas exits the separator through an exhaust gas outlet to the exhaust gas conduit and a reservoir for collecting the waste cooling water separated from the exhaust gas. The marine wet exhaust system also includes a cooling water discharge conduit and a reservoir discharge pump in the cooling water discharge conduit configured to pump cooling water collected in the reservoir, the cooling water discharge conduit and reservoir discharge pump fluidically connected to the reservoir through a water outlet having a first vertical height in the reservoir. The marine wet exhaust system also includes a pump controller for controlling the reservoir discharge pump and a water level sensing system configured to provide a signal to the pump controller based on the water level in the reservoir. The water level sensing system includes a first pressure test point positioned in a pressure sensing tube, the pressure sensing tube having an open lower end having a second vertical height, the second vertical height being higher than the first vertical height. The water level sensing system also includes a second pressure test point, the second pressure test point having a third vertical height, the third vertical height being higher than the second vertical height. The water level sensing system also includes a differential pressure transmitter receiving inputs from the first and second pressure test points and providing an output to the pump controller based on the inputs.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] The above mentioned and other features of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: [0010] FIG. 1 is a schematic view of a marine wet exhaust system for a water craft; [0011] FIG. 2 is a perspective view of one embodiment of a portion of the marine wet exhaust system of FIG. 1, and

[0012] FIG. 3 is a section view of the portion of the marine wet exhaust system of

FIG. 2.

[0013] Corresponding reference characters indicate corresponding parts throughout the views of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0014] The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.

[0015] FIG. 1 depicts a wet exhaust system 10 for a marine craft (not shown) for treating and expelling exhaust gas generated by an internal combustion engine 12. The wet exhaust system 10 includes an exhaust conduit 14 for conducting an exhaust flow from the internal combustion engine 12 to an inlet 14 of a wet marine exhaust muffler 16. A cooling water supply pump 18 positioned within a cooling water supply conduit 20 draws cooling water for the internal combustion engine 12 from the water surrounding the water craft. As is known in the art, the cooling water supply pump 18 is desirably a variable speed pump such that the amount of cooling water drawn into the cooling water supply conduit 20 increases as the speed of the engine 12 increases to provide additional cooling water. After cooling the engine 12, the cooling water is injected into the exhaust conduit 14 at a cooling water exhaust interface 22. Desirably, the cooling water is injected into the flow of exhaust in the exhaust conduit 14 in droplet form. The droplets of cooling water desirably both cool the exhaust and attenuate some noise.

[0016] The muffler 16 is connected to a water separator/reservoir 24 by line 25. The water separator/reservoir 24 receives the combined exhaust gas and cooling water and separates at least a significant portion of the cooling water from the exhaust gas. The separator/reservoir also additionally attenuates some exhaust noise. The water separator/reservoir 24 has a first water bypass output 26 for discharge of waste cooling water separated from the exhaust gas through a bypass drain 28 that leads directly to a first overboard terminus 30. The water separator/reservoir 24 has a second water filtering output 32 that connects to a waste cooling water conduit 34 for discharge of waste cooling water separated from the exhaust gas through a particulate capture and containment system, broadly a filter, 36. The filter 36 serves to remove particulates and other contaminants from the waste cooling water. Purified waste cooling water is discharged from the filter 36 through a second overboard terminus 37. Alternately, the purified waste cooling water may join the bypass drain 28 to minimize the number of openings in the hull of the water craft. The water separator/reservoir 24 has a de-watered exhaust gas outlet 38 for discharge of the de- watered exhaust gas through an exhaust gas discharge conduit 40 that leads to a third overboard terminus 42. The preferred embodiment of the present invention may include any one of a number of known muffler/water separators combinations and the configuration of the muffler 16 and water separator/reservoir 24 is not critical to the invention except specifically as set forth below. For example, the wet exhaust system 10 may use a combined muffler/water separator and separate reservoir as disclosed in commonly assigned U.S. Patent No. 6,820,419, the disclosure of which is hereby incorporated by reference. [0017] A reservoir discharge pump 50 is interposed between the water separator/reservoir 24 and the filter 36 to regulate the flow of waste cooling water from the water separator/reservoir 24 to the filter 36. The reservoir discharge pump 50 is powered by a motor 52, most preferably an electric motor. Suitable pumps 50 and motors 52 include pumps and motors that can operate either at a single speed or at variable speed. Conventional pumps 50 and motors 52 are well known in the art and need not be described herein. The water separator/reservoir 24 serves as a buffer to allow the flow rate through the reservoir discharge pump 50 and filter 36 to differ from the incoming flow rate through the water supply pump 18. Any difference between the volume flow through the water supply pump 18 and the volume flow through the reservoir discharge pump 50 is stored in, or released from, the water separator/reservoir 24. The reservoir discharge pump 50 serves to regulate the waste cooling water level in the water separator/reservoir 24 and the flow rate of waste cooling water from the water separator/reservoir 24 to the filter 36.

[0018] A pump controller 56 controls the motor 52. Desirably the pump controller 56 comprises a variable speed controller configured to operate the motor 52, and thus the pump 50, at variable speed. One example of a suitable pump controller 56 is the Altivar® 31 variable speed controller available from Schneider Electric of Palatine, IL. As best seen in FIG. 2, desirably the water separator/reservoir 24, the reservoir discharge pump 50, and the pump controller 54 are mounted together in a single exhaust gas/water separation unit 59 to simplify the installation of the exhaust system 10 and increase the potential for production economies

[0019] Turning now to FIG. 3, the preferred water separator/reservoir 24 comprises a reservoir housing 60 forming a chamber 61 configured to separate exhaust gas from the cooling water, with the cooling water collecting in a lower portion 62 of the chamber 61 and an upper portion 64 of the chamber containing the exhaust gas. Combined exhaust gas and cooling water enter the separator/reservoir 24 through line 25 that forms an inlet 66 in the upper portion 64 of the separator/reservoir 24. Upon entering the separator/reservoir 24 through the inlet 66, the cooling water falls and collects in the bottom portion 62 while the exhaust gas collects in the upper portion 64 of the separator/reservoir 24. The exhaust gas leaves the separator/reservoir 24 through the exhaust gas outlet 38 which is positioned in the upper portion 64 of the separator/reservoir 24. Preferably, a baffle plate 68, extending from an upper part of the housing 60, is positioned between the inlet 66 and the exhaust gas outlet 38 thereby forming a treacherous flow path to minimize the opportunity for cooling water to enter the exhaust gas outlet 38. The separator/reservoir 24 is suitably sized so that under normal operating conditions, the level of cooling water collected in the separator/reservoir 24 remains below the exhaust gas outlet 38 in the upper portion 64 of the reservoir/separator 24. [0020] The lower portion 62 of the separator/reservoir 24 contains the first water bypass output 26 that leads to the bypass line 28 and the second water filtering output 32 that leads to the reservoir discharge pump 50 (FIG. 1). The exhaust system 10 can be selectively operated so that the cooling water can be discharged from the separator/reservoir 24 through either the bypass line 28 to the first overboard terminus 30 in a bypass mode or through the filter 36 and the second overboard terminus 37 in a filtering mode. When in the bypass mode, the water level in the water separator/reservoir is desirably maintained at the level of the bypass outlet 26 in the chamber 61. Referring back to FIG. 1, the separator/reservoir 24 has a level sensing system 70 configured to sense the water level in the separator/reservoir 24 and provide input to the pump controller 56 to control the starting/stopping and the speed of the reservoir discharge pump 50 when the exhaust system 10 is operating in the filtering mode to discharge the cooling water through the filter 36.

[0021] As seen in FIG. 3, the level sensing system 70 comprises first and second pressure test points or transducers 72, 74. According to the invention, the pressure test points 72, 74 are configured in the water separator/reservoir 24 so that the level sensing system 70 can provide a zero reset to the pump controller 56 without having to vent the water separator/reservoir to show a zero or atmospheric pressure to the controller 56. The first pressure test point 72 is positioned in the top of a sensing tube 76 that extends down into the reservoir chamber 61. A bottom open end 78 of that tube 76 is positioned vertically above the second filtering output 32 leading to the suction of the reservoir discharge pump 50. Desirably, the vertical distance between the open end 78 of the sensing tube 76 and the filtering output 32 is between about 0.25 and 2.0 inches (0.6 and 5.1 cm). [0022] The second pressure test point 74 is positioned in the chamber 61 vertically above the open end 78 of the sensing tube 76 and above the range of water levels for normal filtering mode operations. As used herein, when the height of the pressure test point 74 is described, it is meant to describe the height in the chamber 61 at which the pressure test point senses the pressure and not necessarily the actual physical location of the transducer. In the illustrated embodiment, the second pressure test point 74 is positioned near the middle of the chamber 61. It is desirable that the upper portion 64 remain free of cooling water to allow the exhaust gas to pass under the baffle plate 68 and reach the de-watered exhaust gas outlet 38 and the second pressure test point 74 is positioned in this portion that is above the normal cooling water level. One especially suitable position for the second pressure test point 74 is at an upper end of a sight glass 80 used to monitor the level of the cooling water in the chamber 61. The upper end of the sight glass 80 is desirably just below the lower extremity of the baffle plate 68 so that there is a passageway for the de- watered exhaust gas to pass under the baffle plate 68 and reach the exhaust gas outlet 38 as long as the water level is visible in the sight glass 80. hi the illustrated embodiment, the second pressure test point 74 will remain above the water level in the chamber 61 as long as the water level is maintained in the visible range of the sight glass 80. Therefore, the second pressure test point 74 senses the air pressure in the upper portion 64 of the chamber 61. However, the second pressure test point 74 may be closer to the top of the housing 60, especially if the reservoir is separate from the exhaust gas/water separator as is disclosed in U.S. Patent No. 6,820,419. [0023] The pressure test points 72, 74 are connected to a differential pressure transmitter 90 (FIG. 1). One example of a suitable differential pressure transmitter 90 is the Series 604A Differential Pressure Transmitter from Dwyer Instruments, hie. of Michigan City, IN. The differential pressure transmitter 90 converts the pressures sensed by the two pressure test points 72, 74 into an electrical output signal corresponding to the water level in the chamber 61. The output signal of the differential pressure transmitter 90 is used by the pump controller 56 to control the operation of the reservoir discharge pump 50. The pump controller 56 responds to the output signal by varying the speed of the motor 52 to provide especially close control of the level of the waste cooling water in the water separator/reservoir 24. Desirably, the motor 52 runs continuously while the water separator/reservoir 24 is receiving waste cooling water, thereby improving the life of the reservoir discharge pump 50. Furthermore, such an arrangement permits the water separator/reservoir 24 to operate with a smaller capacity than otherwise, thereby saving space within the interior of the craft.

[0024] When the exhaust system 10 is switched from the bypass mode to the filtering mode, the reservoir discharge pump 50 desirably starts at full speed. As seen in FIG. 3, the height of the bypass outlet 26 is above the height of the filtering output 32. The water level in the chamber 61 will drop from the level of the bypass outlet 26 where it is maintained while in the bypass mode to a level just below the bottom open end 78 of the sensing tube 76, which is just above the second filtering output 32. At this point, the bottom open end 78 of the sensing tube 76 will be exposed to the air pressure in the upper portion 64 of the chamber 61 and both the first and second pressure test points 72, 74 will sense the same existing pressure inside the separator/reservoir 24. The differential pressure transmitter 90 sends a zero differential pressure signal to the pump controller 56 causing the pump controller to stop the reservoir discharge pump 50.

[0025] As the water level subsequently rises in the reservoir chamber 61, the water level will rise above the open end 78 of the sensing tube 76, thereby causing water to rise in the tube. As the water rises in the tube 76, the differential pressure transmitter 90 will sense the differing pressures between the pressure test points 72, 74 and send a signal corresponding to the height of the water level in the chamber 61 to the pump controller 56. The pump controller 56 causes the pump 50 to come back on and controls the speed of the pump to maintain the level in the reservoir chamber 61 at a proper level within the indicating range of the sight glass 80 as set in the controller 56. As the water level rises in the chamber 61, and thus the sensing tube 76, differential pressure transmitter 90 will sense the increasing differential pressure and the magnitude of the signal it sends will vary accordingly. The pump controller 56 will then increase the speed of the pump 50 to keep the water level in the desired range. [0026] In the prior art systems, pump controllers could not be reset to zero pressure without physically opening the reservoir, such as by removing the connection at the bottom of the sight glass, thereby showing zero (atmospheric) pressure to the controller. According to the present invention, the zero reset occurs automatically as the reservoir discharge pump 50 lowers the level to just below the bottom open end 78 of the pressure sensing tube 76, thereby causing both pressure test points 72, 74 to read a substantially identical pressure. Therefore, it is not necessary to vent the water separator/reservoir 24. This is particularly important, as many installations require that the location of the separator/reservoir 24 be in a position within the hull such that venting the water separator/reservoir to atmosphere is extremely difficult, and many times impossible. Additionally, the means of controlling the flow from the water separator/reservoir 24 to the filter 36, by varying the speed of the pump 50, can be improved such that the volumetric capacity and size of the reservoir can be reduced to the extent that it can now be combined as a small additional chamber of the exhaust gas/water separator and be included in the exhaust gas/water separation unit 59. [0027] While this invention has been described in conjunction with the specific embodiments described above, it is evident that many alternatives, combinations, modifications and variations are apparent to those skilled in the art. Accordingly, the preferred embodiments of this invention, as set forth above are intended to be illustrative only, and not in a limiting sense. Various changes can be made without departing from the spirit and scope of this invention. [0028] What is claimed is:

Claims

Claims:

1. A marine wet exhaust system comprising: an exhaust gas/cooling water separator for receiving an exhaust gas and waste cooling water mixture through a cooling water/exhaust gas inlet and at least partially separating the waste cooling water from the exhaust gas; a de-watered exhaust gas discharge conduit, wherein de-watered exhaust gas exits the separator through an exhaust gas outlet to the exhaust gas discharge conduit; a reservoir for collecting the waste cooling water separated from the exhaust gas; a cooling water discharge conduit; a reservoir discharge pump in said cooling water discharge conduit configured to pump cooling water collected in the reservoir, said cooling water discharge conduit and reservoir discharge pump fluidically connected to the reservoir through a water outlet having a first vertical height in said reservoir; a pump controller for controlling the reservoir discharge pump; a water level sensing system configured to provide a signal to the pump controller based on the water level in the reservoir, wherein the system comprises: a first pressure test point positioned in a pressure sensing tube, said pressure sensing tube having an open lower end having a second vertical height in said reservoir, said second vertical height being higher than said first vertical height; a second pressure test point, said second pressure test point having a third vertical height in said reservoir, said third vertical height being higher than said second vertical height; and a differential pressure transmitter receiving inputs from the first and second pressure test points and providing an output to the pump controller based on said inputs.

2. The marine wet exhaust system as recited in claim 1 wherein the reservoir further comprises a sight glass, and wherein the second pressure test point is positioned at an upper end of said sight glass.

3. The marine wet exhaust system as recited in claim 1 wherein the separator and the reservoir are combined in a common housing.

4. The marine wet exhaust system as recited in claim 3 wherein the separator further contains a baffle plate between the cooling water/exhaust gas inlet and the de-watered exhaust gas outlet, and the reservoir further comprises a sight glass, and wherein the upper end of said sight glass is vertically below the lower extremity of said baffle plate.

5. The marine wet exhaust system as recited in claim 3 wherein the separator/reservoir, the discharge pump and the pump controller are mounted together in a single exhaust gas/water separation unit.

6. The marine wet exhaust system as recited in claim 1 further including a filter in cooling water discharge conduit.