Powered watercraft

A watercraft with a propulsion engine includes at least one hull having an underside. A dual exhaust system includes a first exhaust conduit defining a first exhaust flow path leading to the underside (e.g., a step in a planing surface on the underside) and a second exhaust conduit defining a second exhaust flow path to atmosphere. One embodiment is self proportioning. In another embodiment, an onboard proportioning system varies first and second proportions of the exhaust flowing through respective ones of the first and second exhaust conduits according to exhaust back pressure. First and second valve mechanisms selectively restrict the first and second exhaust flow paths under computer or manual control according to pressure sensed by a back-pressure-sensing component in order to thereby direct the exhaust in desired proportions for enhanced operating characteristics and reduced thermal signature.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to powered watercraft, and more particularly to high speed powered watercraft having one or more hulls with an underside at which propulsion engine exhaust is vented.

2. Description of Related Art

Some existing boat hulls have an underside that forms a planing surface with a transverse step intermediate a bow portion and a stern portion of the hull. The step improves planing efficiency. When underway, however, a vacuum appears aft of the step as the water pulls away from the hull. So, in order to reduce the vacuum, some existing boats include vents to atmosphere at the step while others vent propulsion engine exhaust at the step.

Venting propulsion exhaust at the step according to existing techniques works with propulsion engines of limited size, but it does not lend itself to use with larger propulsion engines. A 7,000 horsepower gas turbine may, for example, be characterized by a mass flow of 43.5 pounds-per-second, an exhaust velocity of 100 to 200 feet-per-second, and a temperature on the order of 1,045 degrees Fahrenheit. Venting the exhaust from such a propulsion engine at a step in the hull can create unacceptable exhaust back pressure and unacceptable heating. Nevertheless, doing so promises significant advantages in the form of improved efficiency (i.e., reduced drag and increased lift) along with reduced thermal signature for military vessels. Thus, there exists a need for a way to vent propulsion engine exhaust from larger propulsion engines at a step in the hull.

SUMMARY OF THE INVENTION

This invention addresses the need outlined above by providing a watercraft with a dual exhaust and onboard exhaust proportioning system. The dual exhaust vents exhaust to the underside of the hull and to atmosphere while the exhaust proportioning system varies the proportion of total exhaust vented at each of those locations, preferably according to exhaust back pressure. Doing so maintains back pressure and heating at an acceptable level with improved efficiency and reduced thermal signature.

To paraphrase some of the more precise language appearing in the claims and further introduce the nomenclature used, a watercraft constructed according to the invention includes at least one hull and an onboard propulsion engine that produces exhaust. The hull has an underside (e.g., defining at least one planing surface and at least one vertical step in the planing surface). According to a major aspect of the invention, there is provided a dual exhaust arrangement. First exhaust venting means vents a first proportion of the exhaust at the underside (e.g., at the vertical step in the planing surface), the first venting means including a first exhaust conduit that defines a first exhaust flow path leading to the underside of the hull (e.g., to the vertical step in the planing surface). In addition, second exhaust venting means vents a second proportion of the exhaust to atmosphere, the second venting means including a second exhaust conduit that defines a second exhaust flow path leading to atmosphere.

Preferably, exhaust proportioning means are provided for varying the first and second proportions of the exhaust. In one embodiment, an onboard proportioning system (e.g., computerized and/or manually operated) varies the first and second proportions according to exhaust back pressure. First and second valve mechanisms selectively restrict the first and second exhaust flow paths according to back pressure sensed by a back-pressure-sensing component in order to direct the exhaust through the first and second flow paths in desired proportions. Thus, the invention provides an onboard system that enables venting of exhaust from larger propulsion engines at the underside of the hull (e.g., at a step in the underside of the hull) for improved efficiency (i.e., reduced drag and increased lift) along with reduced thermal signature for military vessels. The following illustrative drawings and detailed description make the foregoing and other objects, features, and advantages of the invention more apparent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The description of the preferred embodiment begins with a Powered Watercraft With M-Shaped Hull section of this specification that restates some information presented in U.S. patent application Ser. No. 10/625,135 filed Jul. 23, 2003 (now U.S. Pat. No. 6,868,798). That background section describes watercraft having one or more planing surfaces and one or more steps in the planing surfaces at which exhaust is vented. Thereafter, information is presented in an Exhaust Proportioning System section that describes a dual exhaust system with means for controlling the proportions of exhaust vented at the steps in the planing surfaces and to atmosphere according to exhaust back pressure. A reader already familiar with the specification andFIGS. 1–9of the above-identified patent application, may proceed directly to the additional information in the Exhaust Proportioning System section.

Powered Watercraft With M-Shaped Hull.FIGS. 1–4of the drawings show various aspects of a powered watercraft10. The watercraft10includes an M-shaped boat hull11having a port side12(FIGS. 2 and 3) and a starboard side13(FIGS. 1–4). The hull11includes a central displacement body14having a planing surface15(FIGS. 1–4), a port channel ceiling16having a planing surface17, and a starboard channel ceiling18having a planing surface19.FIGS. 1 and 4include the static water line11A and three arrows depicting the flow of air when the watercraft10is under way. Additional details of the M-shaped boat hull aspects of the watercraft10may be had by reference to U.S. Pat. Nos. 6,250,245; 6,314,903; and 6,526,903.

The watercraft10includes a first vertical step20(FIGS. 1–4) in the planing surface15of the central displacement body14. The displacement body14portion of the hull11defines an exhaust-venting opening20A at the first vertical step20. The watercraft10also includes a second vertical step21in the planing surface17of the port channel ceiling16(FIGS. 2 and 3), and a third vertical step22in the planing surface19of the starboard channel ceiling18(FIGS. 1–4). The hull11defines a second exhaust-venting opening21A at the second vertical step21(FIGS. 2 and 3) and a third exhaust-venting opening22A at the third vertical step22(FIGS. 1–4). In that regard, the size of the vertical steps20,21, and22and the size of the exhaust-venting openings20A,21A, and22A are not illustrated to scale. They are exaggerated for illustrated purposes in order to better identify them in the drawings.

An onboard propulsion engine23(FIGS. 3 and 4) powers the watercraft10. It may take any of various known forms, including diesel, gas turbine, and jet engines, and it produces exhaust and surplus air that is conveyed by an exhaust-venting system24to the exhaust-venting openings20A,21A, and22A. The exhaust-venting system24extends from the engine23to the exhaust-venting openings20A,21A, and22A. It includes first, second, and third exhaust manifold branches25,26, and27, each of which conveys exhaust from the engine23(e.g., via triangularly shaped ducts) to a respective one of the first, second, and third exhaust-venting openings20A,21A, and22A. Stated another way, the exhaust-venting system24functions as means for venting exhaust from the onboard propulsion engine23at the vertical steps20,21, and22in the planing surfaces15,17, and19while under way in order to introduce gas along the planing surfaces. The high temperature of pressurized exhaust gas results in a film of high pressure gas along the planing surfaces15,17, and19that further reduces the friction drag for increased performance and efficiency.

FIGS. 5aand5bare diagrams that show further details of the exhaust-venting opening configuration. First considerFIG. 5a. It depicts an enlarged perspective view (not to scale) of the third vertical step22in the planing surface19adjacent the starboard side13of the hull11. The vertical step22includes a forwardly disposed lower portion19A at a first planing surface level of the planing surface19and a rearwardly disposed upper portion19B at a second planing surface level of the planing surface19that is elevated relative to the first planing surface level by the height of a riser portion19C of the third vertical step22. The riser portion19C defines the exhaust-venting opening22A so that the exhaust-venting opening22A faces rearwardly. In other words, the hull11defines an exhaust-venting opening22A intermediate the upper and lower portions19A and19B that faces rearwardly from the vertical step22. This is a preferred orientation.

FIG. 5billustrates that other opening orientations may be employed. It depicts an enlarged perspective view of a vertical step30in a planing surface31of a hull32. The vertical step30is similar in some respects to the third vertical step22illustrated inFIG. 5ain that it includes a forwardly disposed lower portion33at a first planing surface level of the planing surface31and a rearwardly disposed upper portion34at a second planing surface level of the planing surface31that is elevated relative to the first planing surface level by the height of a riser portion35of the vertical step30. The major difference is that the upper portion34defines an exhaust-venting opening36that faces downwardly, with exhaust being vented through it downwardly. In other words, the hull32defines an exhaust-venting opening36in the upper portion34that faces downwardly from the upper portion36.

Turning now toFIG. 6, it shows a portion of a hull40that illustrates one type of vertical step configuration. The hull40represents the hull of any powered watercraft. It has a planing surface41, a forwardly disposed first vertical step42and a rearwardly disposed second vertical step43. The hull40defines first and second exhaust-venting openings44and45through which exhaust manifold branches46and47vent exhaust. The small circles inFIG. 6represent exhaust and surplus air venting through the exhaust-venting openings44and45. In this vertical step configuration, the planing level is raised at each of the first and second vertical steps42and43progressively from an original planing level identified by the broken line at reference numeral48.

FIG. 7shows a portion of a hull50that illustrates another type of vertical step configuration. The hull50has a planing surface51, a forwardly disposed first vertical step52and a rearwardly disposed second vertical step53. The hull50defines first and second exhaust-venting openings54and55through which exhaust manifold branches56and57vent exhaust. The small circles represent exhaust and surplus air venting through the exhaust-venting openings54and55. In this vertical step configuration, the planing level51raises at each of the first and second vertical steps52and53from an original planing level identified by the broken line at reference numeral58, only to quickly return to the original planing level.

FIG. 8is a diagram depicting the underside of a multiple hull watercraft60constructed according to the invention. It includes a first hull61and a second hull62. The first hull61includes a central displacement body61A with a planing surface61B, an inwardly disposed first channel ceiling61C with a planing surface61D, and an outwardly disposed second channel ceiling61E with a planing surface61F. Similarly, the second hull62includes a central displacement body62A with a planing surface62B, an inwardly disposed first channel ceiling62C with a planing surface62D, and an outwardly disposed second channel ceiling62E with a planning surface62F. Each planing surface includes two vertical steps arranged in line to span the width of the planing multiple surfaces. Just the six vertical steps63,64,65,66,67,68are identified for the three planing surfaces62B,62D, and62F of the second hull62for illustrative convenience.FIG. 9shows the watercraft60with first and second propulsion engines60A and60B connected to the vertical steps via first and second exhaust-venting systems60C and60D.

Thus, the powered watercraft embodiments described above include means for venting propulsion engine exhaust at one or more vertical steps in one or more planing surfaces on the watercraft. Doing so introduces gas along the planing surface (preferably high temperature gas) that significantly improves performance and efficiency. That technique is shown applied to watercraft with single or multiple M-shaped boat hulls that include single or multiple vertical steps in each planing surface. In that regard, the term “M-shaped boat hull” herein refers to a boat hull that falls within the scope of one or more of the claims in U.S. Pat. Nos. 6,250,245; 6,314,903; and 6,526,903. Those patents are incorporated herein by reference for all of the details they provide.

Exhaust Proportioning System. Turning now toFIGS. 10,11, and12, they are diagrammatic representations of a fifth watercraft100constructed according to the invention to include an exhaust proportioning system. The watercraft100includes a hull101(e.g., a displacement hull) having a static water line indicated by a broken line101A inFIG. 11. The hull101extends from a bow102of the hull101to a stern103of the hull101(FIGS. 10 and 11. The hull101includes an underside101B (FIG. 11) that faces downwardly toward water and the underside101B includes a planing surface104(FIG. 11). In addition, the watercraft100includes a transverse vertical step105in the planing surface104(FIGS. 10 and 11). The step105is disposed intermediate a forward portion104A of the planing surface104and a rearward portion104B of the planing surface104that are identified inFIG. 11(e.g., located at two-thirds of the distance from the bow102to the stern103).

The watercraft100includes a propulsion engine106(e.g., a gas turbine engine) that produces exhaust with an exhaust back pressure. The engine106discharges exhaust through an exhaust manifold107to first and second exhaust conduits108and109(FIGS. 10–12). The first exhaust conduit108defines a first exhaust flow path108A leading to the underside101B of the hull101(at the step105shown inFIGS. 11 and 12for the illustrated embodiment) in order to vent a first proportion of the exhaust at the underside101B (at the step105), while the second exhaust conduit109defines a second exhaust flow path109A to atmosphere in order to vent a second proportion of the exhaust to atmosphere. The first and second conduits107and108may include known exhaust ducting componentry.

Venting exhaust at the underside101B of the hull101(e.g., at the step105) improves operating efficiency by reducing drag. In addition, it increases lift as depicted by a bold arrow A inFIG. 11(the outlined arrows depicting water flow across the underside of the hull and the shaded arrows depicting exhaust flow). Moreover, venting exhaust at the underside101B (e.g., at the step105for the illustrated embodiment) reduces thermal signature by directing the first proportion of hot exhaust gases into water beneath the underside101B of the hull101so that exhaust heat is dissipated in the water.

In order to control the first and second exhaust flow paths108A and109A, the watercraft100includes an onboard exhaust proportion system. As shown inFIG. 12, the exhaust proportioning system of the watercraft100includes a first valve mechanism110having a first valve element110A that moves in operation as indicated inFIG. 12by a double-headed arrow110B. The first valve mechanism110serves as means for selectively restricting the first exhaust flow path108A in order to decrease a first proportion of the exhaust flowing in the first flow path108A and thereby direct a desired second proportion of the exhaust from the propulsion engine106to the second flow path109A. It may also be use to prevent the back flow of water from the step105when the watercraft100moves astern. The exhaust proportioning system also includes a second valve mechanism111having a second valve element111A that moves in operation as indicated by a double-headed arrow111B. The second valve mechanism111serves as means for selectively restricting the second exhaust flow path109A in order to decrease the second proportion of the exhaust flowing to the second flow path109A and thereby direct the desired first proportion of the exhaust from the propulsion engine106to the first flow path108A. The first and second valve mechanisms110and111may include known types of componentry for performing the described functions.

In addition to the above, the exhaust proportioning system of the watercraft100includes a proportioning system controller112and an exhaust back pressure sensor113. The controller112serve as means for controlling the first valve means110and the second valve means111according to exhaust back pressure. The sensor113serves as means for sensing the exhaust back pressure and providing a feedback signal for the controller112for overall closed-loop feedback control of the first and second valve mechanisms110and111according to exhaust back pressure.

For the illustrated watercraft100, exhaust is drawn toward the step105when underway by the vacuum created at the step105until the path of least resistance leads to atmosphere. Operating the second valve mechanism111forces more exhaust toward the step105; it increases the first proportion of the exhaust that is vented at the step105. Operating the first valve mechanism110forces more exhaust to atmosphere; it increases the second proportion of the exhaust that is vented to atmosphere. This is all accomplished entirely electronically in the illustrated embodiment with suitable components (e.g., a suitably programmed and outfitted laptop computer) although it is within the broader inventive concepts disclosed to use a back pressure gauge along with manual control of the valve mechanisms.

InFIG. 12, a first two-way line112A (arrows at both ends) communicates control signals from the controller112to the first valve mechanism110together with communicating position-indicating feedback signals back to the controller112for closed loop feedback control of the first valve mechanism110. Similarly, a two-way line112B communicates control signals to the second valve mechanism111together with communicating position-indicating feedback signals back to the controller112for closed loop feedback control of the second valve mechanism111. A one-way line112C (an arrow at just one end) communicates back-pressure-indicating signals from the pressure sensor113to the controller112that the controller112processes according to preprogrammed algorithms to control the first and second valve mechanisms110and111. Based upon the foregoing and subsequent descriptions, one of ordinary skill in the art can readily implement a watercraft with a dual exhaust and exhaust proportioning system according to the invention.

Turning now toFIG. 13, it is a block diagram of the exhaust proportioning system of the watercraft100that shows the addition of manual controls. An input device114(e.g., a computer keyboard) enables operator input of data and commands to the controller112. A first valve position feedback component115provides valve-position-indicating signals for the first valve mechanism110and a second valve-position feedback component116provides valve-position-indicating signals for the second valve mechanism111. A pressure-readout component117(e.g., a gauge) provides a visually discernible indication of back pressure, while first and second manual valve actuators118and119enable an operator to actuate respective ones of the first and second valve mechanisms110and111when desired. Suitable power components120provide power to the system.

The objective of this dual exhaust duct system is to direct the highest proportion of total engine exhaust into the first exhaust conduit108so that engine exhaust can be used effectively to benefit vessel performance. The exhaust flowing into the first exhaust conduit108breaks the vacuum at the vertical step105that is created by forward motion of the vessel. In addition, it provides lubrication and reduced friction drag on the planing surface104, and it generates steam for vessel lift.

A portion of the total exhaust will flow naturally into the first exhaust conduit108as required to break the vacuum at the vertical step105(self proportioning); that vacuum increases with vessel speed. This reduces the engine back-pressure below the maximum acceptable level for engine performance. Thus, additional exhaust can be directed into the first exhaust conduit108by closing down on the second valve mechanism111. Doing so increases the engine back-pressure and results in a greater volume of exhaust moving through the first exhaust conduit108. Operating the second valve mechanism111with regard for the level of back-pressure sensed by the sensor113, prevents an increase in the back-pressure from this action to a level adversely affecting engine performance.

One way to configure the invention is to structure the first valve mechanism110as a flapper-type valve to perform two separate functions. Activated manually or automatically based on vessel speed or other factor, it controls exhausting into the water in order to avoid overheating of the hull101when the vessel100is not moving forward. Activated by reverse water flow, it prevents engine damage when the vessel is moving astern. As an alternative, a separate and supplemental flapper-type valve (not shown) may be mounted at the entry to the first exhaust conduit108at the underside of the hull101.

In terms of the methodology employed, the invention provides a method for reducing the thermal signature of a watercraft having a hull with an underside and an onboard propulsion engine that produces exhaust. The method includes the step of providing a first exhaust conduit for venting a first proportion of the exhaust at the underside of the hull, a second exhaust conduit for venting a second proportion of the exhaust to atmosphere, and, preferably, an onboard exhaust proportioning system for varying the first and second proportions according to exhaust back pressure. The method proceeds by (i) venting a first proportion of the exhaust through the first exhaust conduit at the underside of the hull (ii) venting a second proportion of the exhaust through the second exhaust conduit to atmosphere, and, preferably, (iii) varying the first and second proportions with the exhaust proportioning system to maintain a desired level of exhaust back pressure.

Thus, the invention provides a watercraft with a dual exhaust and, in one embodiment, an onboard exhaust proportioning system. The dual exhaust vents exhaust to the underside of the hull and to atmosphere while the exhaust proportioning system varies the proportion of total exhaust vented at each of those locations, preferably according to exhaust back pressure. Doing so maintains back pressure and heating at an acceptable level with improved efficiency and reduced thermal signature.