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Title:
A PULSATED PROPULSION SYSTEM AND METHOD OF PROPELLING A WATERCRAFT
Document Type and Number:
WIPO Patent Application WO/2018/232460
Kind Code:
A1
Abstract:
A submerged pulsated propulsion system for watercraft comprising a passageway defined by an inlet at one end and an outlet at an opposite end, the inlet and outlet respectively adapted for the ingress and egress of a first fluid. One or more compressors for compressing one or more other fluids. The one or more other fluids in a pressurised state are released as pulsations into the passageway downstream of the inlet and in the direction of the outlet. In combination with the first fluid, this increases the flow and changes the density of total fluid volume that is ejected from the outlet as pulses under pressure, and constitutes propulsive thrust. A watercraft and method of propelling the same.

Inventors:
MASTALIR, Peter (24 Gibraltar Drive, Surfers Paradise, Queensland 4217, 4217, AU)
Application Number:
AU2018/050618
Publication Date:
December 27, 2018
Filing Date:
June 21, 2018
Export Citation:
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Assignee:
ADVANCE FLUID SYSTEMS PTY LTD (24 Gibraltar Drive, Surfers Paradise, Queensland 4217, 4217, AU)
International Classes:
B63H11/04
Domestic Patent References:
WO2008009302A12008-01-24
WO2003101820A12003-12-11
WO2001079060A12001-10-25
Attorney, Agent or Firm:
MAXWELL, Nicola (IP Solved Pty Ltd, Level 16 68 Pitt Stree, Sydney New South Wales 2000, 2000, AU)
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Claims:
Claims

1. A submerged pulsated propulsion system for watercraft comprising:

a passageway defined by an inlet at one end and an outlet at an opposite end, the inlet and outlet respectively adapted for the ingress and egress of a first fluid;

one or more compressors for compressing one or more other fluids; the one or more other fluids in a pressurised state released as pulsations into the passageway downstream of the inlet and in the direction of the outlet; wherein in combination with the first fluid, increased flow and changes to the density of total fluid volume ejected from the outlet as pulses under pressure, constitutes propulsive thrust.

2. The propulsion system according to claim 1 wherein the one or more other fluids in a pressurised state is of a different specific gravity to that of the first fluid such that the density of their combination is less than that of the first fluid, and wherein as a result, the velocity of the combined fluid flowing through the passageway is increased over that solely of the first fluid.

3. The propulsion system according to claim 1 wherein the first fluid is a liquid and the one or more other fluids in a pressurised state is a gas, whereby the combined fluid mixture acts as a surface lubricant and as a result, the velocity of the combined fluid flowing through the passageway is increased over that solely of the first fluid.

4. The propulsion system according to claim 1 wherein the propulsion system is an attachment or an extension of a hull of the watercraft.

5. The propulsion system according to claim 1 wherein the passageway is incorporated into the form, design or configuration of a hull of the watercraft.

6. The propulsion system according to claim 1 wherein the one or more compressors is located on board the watercraft and in communication with one or more flow control valves adapted to control flow rate and frequency of pulsations of the pressurised one or more other fluids released into the passageway.

7. The propulsion system according to claim 1 wherein the first fluid is water in which the propulsion system is submerged, and the one or more other fluids is a gas, whereby as the pressurised gas is released, the decompression thereof forms bubbles, including m icrobubbles, in the water, which act as a lubricant for one or more of the wetted surfaces of the passageway thereby encouraging boundary layer lamina flow and minimising or reducing skin or surface drag.

8. The propulsion system according to claim 1 wherein the one or more other fluids injected into the passageway between the inlet and the outlet includes high pressure water.

9. The propulsion system according to claim 8 wherein the high pressure water is injected into the passageway from an inner circumferential outlet positioned on an interior surface adjacent the inlet.

10. The propulsion system according to claim 8 wherein there is a combustion engine arranged to power a high pressure water pump to inject the water in a pressurised state into the passageway.

11. The propulsion system according to claim 1 wherein there is at least one gas outlet located on an internal surface of the passageway and adjacent the inlet, the gas outlet being associated with a flow control valve arranged for introduction of the gas in the pressurised state to generate an interior layer of gas over at least a portion of an interior surface of the passageway.

12. The propulsion system according to claim 11 wherein the gas outlet comprises an inner circumferential gas outlet having an array of rifling nozzles.

13. The propulsion system according to claim 11 wherein the gas outlet extends from adjacent the inlet to adjacent the outlet of the passageway.

The propulsion system according to claim 11 wherein the gas outlet is configured to generate an interior layer of gas such that when the passageway is submerged in the water a mixture of the gas and the water is formed within the passageway.

15. The propulsion system according to claim 1 wherein the passageway is of a tubular configuration with substantially parallel sides or walls.

16. The propulsion system according to claim 1 wherein the passageway has a tapering internal configuration between the inlet and the outlet such that a venturi effect is induced to speed the flow of fluid.

17. The propulsion system according to claim 16 wherein there is a gas outlet arranged for introduction of pressurised gas configured to generate an exterior layer of gas over at least a portion of the external surface of the passageway.

18. The propulsion system according to claim 17 wherein the gas outlet comprises an outer circumferential gas outlet located on an external surface of the passageway.

19. The propulsion system according to claim 1 including a stalk from which the passageway depends, the stalk having a gas conduit in communication with a gas outlet and a gas inlet.

20. The propulsion system according to claim 1 wherein the position of the propulsion system is adjustable with respect to a hull of the watercraft to provide propulsive thrust in any direction so desired.

21. The propulsion system according to claim 1 wherein one or more propulsion units are arranged and coordinated so as to be operational as a steering, positioning or braking mechanism of the watercraft.

22. A method of propelling watercraft, the method comprising the steps of:

coupling to the watercraft a propulsion system;

submerging the propulsion system in the water;

generating one or more fluids in a pressurised state, and releasing the pressurised one or more fluids in pulsations into the passageway; wherein increased fluid volume and flow being ejected as pressure pulses at the outlet propels the watercraft.

23. The method according to claim 22 wherein the one or more fluids in the pressurised state is air.

24. The method according to claim 22 including the step of generating compressed air as the one or more fluids by the operation of an air compressor.

25. The method according to claim 22 including the step of generating compressed air as the one or more fluids with an electric motor to power an air compressor.

26. The method according to claim 22 including the step of generating compressed air as the one or more fluids with an internal combustion engine to power an air compressor.

27. The method according to claim 22 including the step of generating compressed air as the one or more fluids with an internal combustion engine to power an air compressor wherein exhaust gas temperature from the combustion engine is used to further increase the pressure of the compressed air.

28. The method according to claim 22 including the step of generating compressed air as the one or more fluids with an internal combustion engine to power an air compressor wherein exhaust gas from the combustion engine is also used as another of the one or more fluids.

29. The method according to claim 22 wherein the one or more fluids in the pressurised state comprises steam.

30. The method according to claim 22 including the step of generating steam as the one or more fluids by operating a boiler to generate the steam.

31. The method according to claim 22 including the step of storing the one or more fluids in the pressurised state in a pressure vessel and communicating the pressurised fluid from the pressure vessel to an outlet.

32. The method according to claim 22 including the step of controlling the flow of the pressurised one or more fluids.

33. The method according to claim 22 including the step of controlling the flow of the pressurised one or more fluids by operation of a flow control valve wherein the flow rate and the frequency of the pulsations can be adjusted.

Description:
A PULSATED PROPULSI ON SYSTEM AND METHOD OF PROPELLI NG A

WATERCRAFT

Technical Field

[0001] The present invention relates to the propulsion of watercraft. In particular, it concerns a propeller-less method of propulsion with limited external moving parts. Specifically, propulsion is achieved by release of rapid pulsations from an outlet of a submerged unit, including without limitation, in combination with the submerging liquid namely, fresh or seawater, air, exhaust gas and/or steam under pressure to constitute pulsed propulsive thrust.

[0002] In addition, the invention utilises microbubbles of gas as a surface 'lubricant' to alter the density of fluid at the wetted surfaces of the submerged propulsion unit or pod. This alters the surface topology from being completely wet to having a hybrid gas and liquid boundary layer of invariably lower density contributing to a significant reduction in surface induced drag to maximise or optimise the resultant thrust.

Background

[0003] Traditional means of watercraft propulsion is invariably centred on the use of propellers. To increase speed of the watercraft, the propeller has to rotate faster. Prior art studies of propeller operation have shown that increased drag and other inefficiencies including cavitation are often present when propeller rotation is increased beyond a certain optimal speed. As a consequence, a propeller spinning at high speed may be found to be less efficient than the same propeller operating at a lower speed.

[0004] In seeking to improve upon the prior art, and alternatively, not having the propeller exposed to open water, watercraft may be propelled by an alternative prior art system known as the Hamilton Jet. In this example an impeller is located inside the hull of the watercraft. However Hamilton Jets, no matter how efficient in design, have been found to still be prone to the same inefficiencies of cavitation and hydrodynamic drag. Consistent with the preceding explanation, a Hamilton Jet operating at a high power level may therefore be less efficient than one operating at lower power level notwithstanding the propeller is internally- housed.

[0005] While the problem with propeller-induced cavitation is well known, much less is known about the use of microbubbles as a surface-active lubricant. The production or retention of microbubbles on the surface of high performance boat hulls as a friction reducing agent is considered an art or an esoteric science. It is known that sailors of high performance sailing dinghies and catamarans often dress the hulls of their boats with emery cloth to create a finely scratched surface. The fine scratches have the effect of encouraging the retention of a microbubbles in the interest of inducing boundary layer lamina flow thus reducing surface drag.

[0006] US 2009/0098782 A1 (Dunn) discloses a two phase water jet propulsion system for high-speed watercraft utilising the exhaust gas of an engine driving a water pump used to increase the flow rate of a water jet. The use of exhaust gases to improve propulsion is also known in prior art propeller driven systems wherein an exhaust outlet is entrained in the negative or low pressure region located just aft of the propeller. In the latter case, the overriding advantage is derived from creating a low pressure exhaust system to improve engine breathing and volumetric efficiency rather than any net increase in mass output or flow to augment thrust. Importantly, none of the relevant prior art located is directed to or teaches the use of rapid pressure pulsations to actually augment or comprise propulsive thrust.

[0007] It is therefore highly commercially desirable to have a watercraft propulsion system that is more efficient at higher power levels than is presently achievable using a propeller, direct pump, or a Hamilton Jet. Furthermore, there is also the possible use of lost energy from the exhaust of an internal combustion engine to generate pressurised pulses, wherein in combination with drag minimisation by surface friction reduction, results in at least, better fuel efficiency or greater waterline speed. Summary of Invention

[0008] According to a main aspect, the invention resides a submerged pulsated propulsion system for watercraft comprising a passageway defined by an inlet at one end and an outlet at an opposite end, the inlet and outlet respectively adapted for the ingress and egress of a first fluid, one or more compressors for compressing one or more other fluids in a pressurised state released as pulsations into the passageway downstream of the inlet and in the direction of the outlet, and wherein in combination with the first fluid, increased flow and changes to the density of total fluid volume ejected as pulses under pressure at the outlet, constitutes propulsive thrust. Preferably, the one or more other fluids in a pressurised state is of a different specific gravity to that of the first fluid such that the density of their combination is less than that of the first fluid, and wherein as a result, the velocity of the combined fluid flowing through the passageway is increased over that solely of the first fluid.

[0009] Appropriately, the first fluid is the liquid the propulsion system is submerged in and preferably, the one or more other fluids in a pressurised state is a gas wherein the combined fluid mixture acts as a surface lubricant and as a result, the velocity of the combined fluid flowing through the passageway is increased over that solely of the first fluid. In a preferred embodiment, the propulsion system has a shape and configuration of a unit or pod attached to or extending from a hull of the watercraft. As a preferred embodiment, where the unit or pod is an attachment to the hull, it could also assume the configuration of an outboard motor. In the alternative, the propulsion system may be incorporated into the form, design or configuration of a hull of the watercraft itself.

[0010] The one or more compressors is preferably located on board the watercraft and in communication with one or more flow control valves; the control valves adapted to control release of the pressurised other fluids into the passageway.

[0011] The one or more other fluids preferably includes high pressure water injected into the passageway between the inlet and the outlet in the same direction as another fluid which is typically a gas. Atmospheric gases may also be utilised to reduce surface layer boundary friction as well as to modify the fluid density in and around the pod.

[0012] In use, the propulsion system herein disclosed generates thrust that may be utilised to propel the watercraft. Where the first fluid is water the propulsion system is submerged in, and the one or more other fluids is a gas, bubbles, including microbubbles are formed as a consequence of the decompression of the gas when released in the water. The microbubbles act as a lubricant for one or more of the wetted surfaces of the passageway to encourage boundary layer lamina flow which minimises or reduces surface or skin drag. Where water is injected into the passageway at high pressure, there will be an outlet arrangement for the introduction of the pressurised water into the passageway. The high pressure water outlet may be positioned on an interior surface of the passageway adjacent the inlet. The high pressure water outlet may comprise an inner circumferentially positioned outlet. In one example, there can be a combustion engine arranged to power a high pressure water pump to inject the pressurised water into the passageway.

[0013] Where the other fluid is typically a gas, there will be at least one gas outlet associated with a flow control valve arranged for the introduction of the gas in a pressurised state into the passageway. The gas outlet for the pressurised gas may be on an internal surface of the passageway adjacent the inlet. The gas outlet may comprise an inner circumferential gas outlet. The gas outlet, preferably comprises rifling gas nozzles, and may be configured to generate an interior layer of gas bubbles over at least a portion of the internal surface of the passageway. The interior layer may also comprise a reduced density mixture of the gas and water. The interior layer when so formed may extend from the inlet to the outlet of the passageway.

[0014] In use, water enters the passageway at the inlet and exits from the outlet and is subject to surface friction or drag when in contact with the sides or walls of the passageway. As previously discussed, the mixture of liquid and gas bubbles has a lubricating effect in reducing the surface drag experienced by the fluid flowing in the passageway. [0015] In one embodiment, the gas outlet arrangement may be configured such that when the propulsion system is submerged and gas is introduced into the passageway, a mixture of the gas and water is formed within and restricted to the confines of the passageway. In a preferred example, the internal sides or walls of the passageway are parallel. In an alternative example, the passageway has a tapering internal configuration between the inlet and the outlet such that a venturi effect is induced to speed the flow of fluid. As a tapered configuration is likely to cause the gas and water mixture to accelerate as it moves through the passageway, an increase in overall thrust is experienced at the outlet.

[0016] In another embodiment the gas outlet is located on an external surface of the passageway. The gas outlet on the external surface may be configured to generate an exterior layer of the gas over at least a portion of the external surface. The exterior layer may also comprise a less dense mixture of the gas and water. The external gas outlet may comprise an outer circumferential gas outlet associated with the external surface of the propulsion unit or pod. In one preferred example, the passageway may have an annular configuration. In another embodiment, the passageway may be a tubular or an elongated passageway centrally positioned along the watercraft.

[0017] Another embodiment can include a stalk from which the propulsion unit or pod depends. The stalk may contain a gas conduit in communication with a gas inlet and a gas outlet. The stalk may also house a high pressure water conduit in communication with a high pressure water inlet and an outlet. In a preferred embodiment, the position and location of the propulsion system is adjustable with respect to a hull of the watercraft to provide propulsive thrust in any direction so desired. In this example, one or more propulsion units or pods may be arranged so as to be operational as a steering, positioning and/or braking mechanism of the watercraft.

[0018] It will be obvious to the skilled addressee that in the case of large vessels which are inherently difficult to steer, slow down or dock, the coordination of a number of strategically located propulsion units in manoeuvring the vessel would be a highly useful and valuable application. [0019] In another aspect disclosed herein, the invention resides in a method of propelling watercraft, the method comprising the steps of (i) coupling to the watercraft a propulsion system as herein described, (ii) submerging the propulsion system in the water, (iii) generating one or more fluids in a pressurised state, and (iv) releasing the pressurised one or more fluids in pulsations into the passageway, wherein increased fluid volume and flow being ejected as pressure pulses at the outlet, propels the watercraft. One example of the method includes the step of driving an air compressor with a combustion engine. Exhaust gas from the combustion engine may be contained and passed over gas pipework through which the pressurised gas travels. This can increase the pressure of the gas by heat transfer from the exhaust gas.

[0020] In the alternative or in addition, the gas in the pressurised state may comprise air or exhaust gas or a combination of air and exhaust gas from the combustion engine. In this embodiment, the pressurised air or exhaust gas or a combination of air and exhaust gas comprises the one or more other fluids released as pulsations into the passageway. Another embodiment uses an electric motor arranged to power the air compressor. In yet another example, the one or more other fluids in the pressurised state comprises steam. The generation of steam may include the step of operating a boiler to generate the steam.

[0021] Another method includes the step of storing gas in the pressurised state in a pressure vessel and communicating the pressurised gas from the pressure vessel to an outlet.

[0022] An important control function includes the step of adjusting the flow of the gas in the pressurised state. Adjusting the flow of the pressurised gas may include the step of operating a flow control valve wherein the flow rate and the frequency of the pulsations can be adjusted. The one or more other fluids are released in the form of pulses into the passageway to resulting in a pulsed propulsive thrust at the outlet.

[0023] In another aspect, the invention resides in the watercraft itself that includes a propulsion system and is propelled by a method of propulsion in accordance with that described in the aforementioned discussion. [0024] Any of the various features of each of the above examples, and of the various features of the embodiments described herein below, may be combined in any suitable fashion and as is desired.

Brief Description of the Figures

[0025] In order that the invention be better understood and put into practice, the embodiments herein before disclosed will now be described only by way of example with reference to the accompanying drawings wherein:

Figure 1 shows a perspective view of a preferred propulsion unit according to the invention;

Figures 2, 3 and 4 show respectively, plan, front elevational and side elevational views of the propulsion unit of Figure 1 ;

Figure 5 shows a section A-A through the view of Figure 2;

Figure 6 shows a schematic diagram of an example of a gas source in fluid communication with the propulsion unit of Figure 1;

Figure 7 shows a schematic drawing of an embodiment wherein an electric motor is used to power an air compressor and a water pump;

Figure 8 shows an embodiment in the configuration of an outboard motor; and Figures 9 and 10, show a pod attached to or extending from a hull of a watercraft. Description of Embodiments

[0026] Figures 1 to 7 show various views and examples of a propulsion system for watercraft, in accordance with the invention, the propulsion system being generally indicated by the numeral 10. Figures 2, 3 and 4 show orthographic views of the pod 10 of Figure 1. Wherever possible, the same numbering system has been replicated between drawings in the interests of better understanding and avoiding ambiguity. The propulsion unit or pod 10 has a passageway 12 that is submersible in water 14. The passageway 12 has a first end or inlet 16 (or "leading end") and a second end or outlet 18 (or "trailing end"). The passageways 22, 23 and 24 are attached to the watercraft by stalk 38 housing three inlets to receive air 56, high pressure water 58 and exhaust gas 60. In use, high pressure water 58 has a pressure significantly above atmospheric pressure, for example in this embodiment around seven (7) bars. The high pressure water 58 exits outlet 31 with significant higher velocity. This induces the entrainment or draw of inlet water

11 into inlet 16. This creates the fluid momentum to initiate air 56 to flow through outlets 28 and 30. The pod 10 has at least one gas outlet. In this embodiment there are three gas outlets 28, 30 and 33 directed rearwards towards the second or trailing end 18, however other embodiments may have less or more than three gas outlets.

[0027] The internal gas outlet 28 is configured for the egress of air 56 drawn in the direction of the second end or outlet 18. The external gas outlet 30 is configured for the egress of air 56 in the drawn state over external surface 32 of pod 10 in the direction of the second end or outlet 18. The gas outlet 33 receives pulsed and pressurized exhaust gas 60 through inlet 24. When released into passageway 12, it results in a hybrid fluid of water and gas which is of less density in a pulsed condition. This compressible fluid 53 allows higher density fluid slug 55 to accelerate thereby contributing to thrust 13. In this embodiment, the pod 10 is of a tapered annular configuration. However, in other embodiments, the pod 10 can be any other suitable shape or configuration.

[0028] The pod 10 has an internal surface 34. The internal surface 34 defines passageway 12 in the form of a tubular or circular passageway. The passageway

12 has an intake or inlet at the first end 16 and an exhaust or outlet at the second end 18. The passageway 12 connects the first end 16 and the second end 18. Gas outlet 28 is arranged for the introduction of the air 56 in the drawn state into the passageway. Gas outlet 28 is located on the internal surface and adjacent the inlet or first end 16. In this, but not necessarily in all embodiments, gas outlet 28 is in the form of a plurality of gas nozzles 36 orientated rearwards and towards the outlet or second end 18. The air 56 when introduced into the passageway forms an interior layer over at least a portion of the internal surface 34 extending from adjacent the inlet or first end 16 to adjacent the outlet or second end 18. The mixture of air and liquid is of lessened density resulting in a reduction of drag, which as a consequence optimizes or maximizes net fluid thrust at outlet 18.

[0029] When pod 10 is submerged in the water 14 and high pressure water 58 is introduced in the passageway 12, a mixture of gas and water is formed within the passageway. Mixing the gas 56 with the water has the equivalent effect as that of a "bottle rocket", wherein similarly, the mix of air and water results in a hybrid fluid propellant of an appropriate density and compressibility. In use, water 14 is forced into the passageway 12 at the first end or inlet 16, travels along the passageway 12, then exits the passageway at the second end or outlet 18. The differential velocity of flow between the inlet 16 and the outlet 18 with a pulsed mass component 55 relative to the passageway opening at the outlet 18 is experienced as propulsive thrust 13 to propel the watercraft in an intended direction.

[0030] In a preferred example, the passageway 12 tapers towards the outlet 18 at the second end. Consequently, the mixture of gas and water within the passageway is (under the combined gas law) is caused to accelerate as it travels from the inlet 16 to the outlet 18 which thus increases thrust 13.

[0031] Fluid entering the passageway at 12, due to the velocity differential of fluid flowing between the inlet and the outlet, creates a pressure differential between the inlet and outlet which causes a draw or Bernoulli venturi effect when starting from rest. Because the propulsion unit 10 experiences less drag than with a propeller, fuel economy and/or thrust is improved also.

[0032] I n this, but not all embodiments, gas outlet 30 is configured for the egress of gas 56 in the pressurized state. In this example, the gas is directed in the direction of the outlet 18. In an alternative embodiment, however, another gas outlet 30 can be configured for the egress of the gas 56 in the pressurized state normal to an external surface 32 of pod 10. Generally, the gas may leave outlet 30 in any suitable direction to propel and steer the watercraft (not shown) accordingly. [0033] The gas outlet 30 is located on the external surface 32. Gas outlet 30 is configured to generate an exterior layer 15 comprising gas and water over the external surface. In this, but not all embodiments, the gas outlet on the external surface is in the form of an outer circumferential gas outlet. Gas outlet 30 comprises a plurality of gas nozzles, but it need not be so. The exterior layer extends from adjacent the first end 16 to adjacent the second end 18. Thus, a coating of air or a mixture of air and water may be applied to the external surface 32 of the submerged component to reduce drag, increases thrust and resultant fuel economy. The propulsion unit 10 with inlets 22, 23 and 24 depends from the stalk 38. The stalk 38 has gas conduits in the form of an internal gas conduits in communication with the gases 56 and 60.

[0034] The propulsion unit 10 may be mounted on the watercraft. In one embodiment, the stalk descends from a hull of the watercraft. Alternatively, the passageway may be integral with the hull, in which the passageway may be of an oval-like cross-section. Alternatively, the stalk may be configured for attachment to a bow, transom or gunwale of the watercraft. The stalk can have mounting means in the form of screw clamps, lever clamps, and/or an attachment plate with through holes for fasteners in the form of screws, rivets or generally any suitable fasteners.

[0035] As previously discussed, the propulsion system when attached to or extending from a hull of the watercraft on a stalk, preferably is movable and able to be positioned to provide propulsive thrust in any direction so desired. One or more propulsion units or pods may be arranged so as to be operational as a steering, positioning and/or braking system of the watercraft. This application would be highly useful in the case of large vessels which are difficult to steer, slow down or dock wherein a number of strategically located propulsion units may be coordinated in manoeuvring the vessel.

[0036] Figure 6 shows a schematic diagram of an example of exhaust gas source 60 from an internal combustion engine 46 arranged to provide the pressurized and pulsed state in communication with the propulsion unit 10. The internal combustion engine 46 is generally mounted on or within the water vessel, for example within the hull. A pump 54 is attached and driven by the internal combustion engine 46. Intake 27 supplies water 14 for pump 54. Pump 54 generates high pressure water 58 which creates high velocity water flow at outlet 31. This initiates draw of inlet water 11 which in turn initiates air draw 56 through outlet 28. Forward motion of pod 10 over surface 32 initiates additional draw of air through outlet 30. Due to the normal operation of the internal combustion engine, exhaust gas 60 is delivered pulsated and under pressure. This pressurized and pulsed exhaust gas 60 is fed from outlet 33 into chamber 12 in the direction of outlet 18. Each pulse creates a higher density fluid slug 55 when the internal combustion engine 46 is between exhaust strokes. The compressible fluid 53 allows the slug 55 to accelerate when the exhaust gas 60 exits outlet 33. This acceleration contributes to thrust 13. In an alternative embodiment, pulsed gas can be controlled by an additional valve which allows for greater variable control of the pulse frequency and pressure.

[0037] Figure 7 shows a schematic drawing of an embodiment of a propulsion unit 10 wherein an electric motor 47 is used to power an air compressor 44 and a water pump 54. Compressed air 60 and water 58 under high pressure is released as fluid pulses, with air 56 at ambient pressure, drawn into passageway 12. The air 56 is released via outlets 28 and 30 into the water 14 wherein it forms a hybridized liquid gas mixture 15 which reduces the drag on the pod's surfaces internal 34 and external 32. Compressed air 60 exits outlet 33 in a pulsed and pressurized condition. The function of this method is similar to the use of exhaust gas of the internal combustion method of Figure 6. Compressed air 60 in Figure 7 replaces exhaust gas 60 in Figure 6.

[0038] A configuration where air drawn under ambient atmospheric pressure through outlets 28 and 30 is replaced by pressurized air, with or without pulsation could be used in any of the above embodiments to suit specific applications for drag reduction or propulsion enhancement.

[0039] Figure 8 shows an embodiment in the configuration of an outboard motor 62 attached to the transom 64 of a boat 66. Propulsion and steering are thus taken care of by the propulsion. [0040] In Figures 9 and 10, the propulsion unit has a shape and configuration of a pod 10 attached to or extending from a hull 72 of the watercraft. The pod 10 is attached to or extends from hull 72 by a stalk 74 is movable and able to be positioned (broken line 76, arrow 78) to provide propulsive thrust in any direction so desired. As previously mentioned, one or more propulsion units or pods may be arranged so as to be operational as a steering, positioning and/or braking system of the watercraft.

[0041] While the invention has been described with reference to preferred embodiments above, it will be appreciated by those skilled in the art that it is not limited to those embodiments, but may be embodied in many other forms, variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps, features, components and/or devices referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

[0042] In this specification, unless the context clearly indicates otherwise, the word "comprising" is not intended to have the exclusive meaning of the word such as "consisting only of", but rather has the non-exclusive meaning, in the sense of "including at least". The same applies, with corresponding grammatical changes, to other forms of the word such as "comprise", etc.

[0043] Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all other scientific and technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

[0044] Prior art, if any, described herein is not to be taken as an admission that the prior art forms part of the common general knowledge in any jurisdiction.