FIELD OF THE INVENTION

The present invention relates to enhancement of marine propulsion. More particularly, the present invention relates to enhancement device for marine propulsion based on the controlled utilization of the phenomenon of "Water Hammer", which is a wave - movement propagated with the velocity of sound, to sustain a forward low-pressure surge wave with velocity equal to or optimally different from the speed of the vessel.

BACKGROUND OF THE INVENTION

When a ship or any other displacement vessel accelerates, the distance between the crest of the normal bow wave and that of the bow wave following it (the quarter wave) approaches the waterline length of the ship. The ship then drops itself into the trough between these waves and will have to spend enormous power to move even marginally faster. Prior arts have not eliminated or minimized the retarding interaction between the bow wave and the hull of the vessel. An innovation introduced by Mitsubishi Heavy Industries in the 1960's was the Bulbous Bow in order to reduce the wave drag, presumably by creating a small bow wave that fills in the trough that would form behind the normal bow wave. Another example, US patent application no. 2004083939 "Wave shock absorber system" published in 2004, suggests a diffuser to provide a reduced impact zone forward of the hull and a system to divide the wave by mixing it with air. This may help to absorb shock loads from waves on marine hulls. However, the system seems to be of use only for wide bow flat-bottomed marine hulls. Another example of "waveless hull" is disclosed in US patent no. 6,647,909 suggesting a converging-diverging diffuser to eliminate bow, stern and transverse waves. Furthermore, prior arts have not arrived at a solution for eliminating the energy wasted in the collision of the moving ship with the relatively static barrier of the mass of sea water in front. Also prior arts have not reached a solution for reducing the heavy frictional loss experienced by a ship, which is proportional to the square of the relative speed of the ship with respect to the mass of sea water in front.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an enhancement device for marine propulsion adapted to minimize the adverse effect of the collision of displacement vessels against the barrier of the seawater in front. It is another object of the present invention to provide an enhancement device for marine propulsion that will minimize (and may even eliminate) the retarding interaction between the bow wave and the hull of the vessel. It is yet another object of the present invention to provide an enhancement device for marine propulsion adapted to reduce the frictional loss of a ship, which is proportional to the square of the relative velocity of the ship with respect to the mass of seawater in front, by negating or lowering the relative speed of some wetted surface with respect to the mass of seawater in front. It is yet another object of the present invention to provide a marine propulsion enhancement device that can be adapted and incorporated as an integral part of a new marine craft during construction, and also retrofitted as a stand-alone unit in existing vessels. Therefore, there is provided in accordance with the present invention an enhancement device for marine propulsion of marine craft and displacement vessels advancing in seawater, the enhancement device comprising: a conduit having a first end and a second side provided with second end; an opening provided in said first end; at least one discharge vent provided in said second end; a gate provided in said second side, wherein said gate is adapted to move between a first position in which said second side is fluidically open and a second position in which said second side is closed; whereby the enhancement device is installed below or slightly above a keel of the marine craft or the displacement vessel while in the first position, seawater is allowed to pass through said conduit and immediately after the second position is established, a formed surge wave exits the conduit through said opening so as to push the barrier of seawater forward. Furthermore, in accordance with a preferred embodiment of the present invention, said gate is operated mechanically, pneumatically, hydraulically or electrically. Furthermore, in accordance with a preferred embodiment of the present invention, said gate is further provided with a gate operating unit adapted to repeatedly close and open said gate. Furthermore, in accordance with a preferred embodiment of the present invention, said gate operating unit is electronically communicating with a central control system of the displacement vessel or the marine craft. Furthermore, in accordance with a preferred embodiment of the present invention, said gate is a valve allowing rapid closure. Furthermore, in accordance with a preferred embodiment of the present invention, said second side of said conduit is split into two pipes, each provided with a discharge vent. Furthermore, in accordance with a preferred embodiment of the present invention, said discharge vent of one of said two pipes is located at starboard side of the vessel and other discharge vent is provided at port side. Furthermore, in accordance with a preferred embodiment of the present invention, said first end is provided with a coarse filter. In addition, in accordance with another preferred embodiment of the present invention, an enhancement device for marine propulsion of marine craft and displacement vessels advancing in seawater, the enhancement device comprising: a conduit having a first end and a second side provided with second end; an opening provided in said first end; a booster pump provided in said first side adapted to facilitate advancement of seawater in said conduit; a one way valve provided in said first side adapted to allow seawater to flow solely to said second side; at least one discharge vent provided in said second end; a gate provided in said second side, wherein said gate is adapted to move between a first position in which said second side is fluidically open and a second position in which said second side is closed; an outlet conduit diverted from said first side allowing seawater to exit said conduit when said gate is closed; a second gate is provided in said outlet conduit wherein when said gate is in said first position, said second gate is closed and when said gate is in said second position, said second gate is open; whereby the enhancement device is installed below or slightly above a keel of the marine craft or the displacement vessel while in the first position, seawater is allowed to pass through said conduit and immediately after the second position is established, a formed surge wave exits the outlet conduit so as to push the barrier of seawater forward.

BRIEF DESCRIPTION OF THE FIGURES

In order to better understand the present invention and appreciate its practical applications, the following Figures are attached and referenced herein. Like components are denoted by like reference numerals. It should be noted that the figures are given as examples and preferred embodiments only and in no way limit the scope of the present invention as defined in the appending Description and Claims.

Figure 1 illustrates a side view of a ship provided with an enhancement device of marine propulsion showing a preferred location of the device in accordance with a preferred embodiment of the present invention.

Figure 2 illustrates the parts of an enhancement device for marine propulsion in accordance with a preferred embodiment of the present invention, incorporated in a ship.

Figure 3 illustrates the state of enhancement device for marine propulsion in accordance with a preferred embodiment of the present invention, while seawater freely flows through the device.

Figure 4 illustrates the state of the enhancement device shown in Figure 3, while surge wave propagates through the device ahead of the moving ship. Figures 5a, b illustrate another preferred embodiment of the enhancement device for marine propulsion of the present invention.

DETAILED DESCRIPTION OF THE INVENTION AND THE FIGURES

The marine enhancement device of the present invention is based on the controlled utilization of the phenomenon of 'Hydraulic Transient' or 'Water Hammer' to sustain a forward low-pressure surge wave with velocity equal to or optimally different from the speed of the vessel. The enhancement device for marine propulsion of the present invention comprises a conduit of optimum size and length having an opening provided in a first end of optimum size and shape preferably fitted in the stem or at other appropriate location, below the water line of the vessel, or even below, or slightly above its keel. The second side of the conduit is split into two pipes that end in discharge vents located on the starboard and port sides of the ship to allow free flow of seawater through the conduit aft-ward. The conduit is provided with a gate adapted to stop the flow of seawater through the conduit when the gate is closed. The gate is closed and opened by a gate operating unit adapted to automatically and repetitively open and close the gate. The gate is opened and closed with optimum timing so as to sustain a forward low pressure surge wave ahead of the moving ship at a velocity equal to or optimally different from the speed of the vessel. The surge wave pushes the erstwhile static barrier of seawater forward, so that the ship does not collide against it and waste energy. Since there is no collision with the seawater in front, a bow wave is not formed to interact with the hull and retard the ship. Moreover, the surge wave reduces frictional loss of the ship, which is proportional to the square of the relative speed of the ship with respect to the mass of sea water in front, by negating or reducing the relative velocity of a portion of the wetted surface of the ship with respect to the moving seawater in front. It should be mentioned that the enhancement device can be incorporated in the vessel while the vessel is being built or it can be retrofitted in existing vessels. Reference is now made to Figure 1 illustrating a side view of a ship provided with an enhancement device of marine propulsion showing a preferred location of the device in accordance with a preferred embodiment of the present invention. An enhancement device for marine propulsion 12 is provided to a ship 10 and located in the forward position of the ship. It is preferable that enhancement device 12 will be below waterline 14 and will be located in a position where even when the stem is pitching upwardly and downwardly due to the waves, opening 16 of the device will be below waterline 14. Figure 1 also illustrates an enlarged view of the enhancement device in the ship so as to allow an estimation of the size and the location of the device relative to the ship. Reference is now made to Figure 2 illustrating the parts of an enhancement device for marine propulsion in accordance with a preferred embodiment of the present invention. Enhancement device 12 is provided with a relatively long conduit 18 having an opening 16 at a front side of the device. Conduit 18 preferably splits into two pipes 19 that are extended to the starboard and port sides of ship 10 and end in discharged vents 22. Conduit 18 is provided with a gate 20 that is adapted to be inserted within conduit 18 so as to abruptly stop the flow of seawater through discharge vents 22. Gate 20 is adapted to move between a position in which it is within conduit 18 and a position in which gate 20 is outside conduit 18 allowing flow of seawater through discharge vents 22. The operation of gate 20 can be mechanically, pneumatically, hydraulically or electrically controlled by gate operating unit 24. The necessary inputs to gate operating unit 24, such as speed of the ship, the desired velocity of the surge wave, the timing of closing and opening the gate, etc. could be provided both manually through controls and automatically from sensors. It should be mentioned that the gate can be any type of gate valve, disc, or flap that is adapted to rapidly stop the flow of seawater through the conduit upon an order coming from the gate operating unit. Reference is now made to Figure 3 illustrating the state of enhancement device for marine propulsion in accordance with a preferred embodiment of the present invention, while seawater freely flows through the device. As mentioned herein before, conduit 18 that splits into two pipes 19 ending in discharge vents 22, is provided with opening 16. When the ship is advanced through seawater, seawater 26 enters conduit 18 through opening 16 substantially at a speed that equals the speed of the craft, in the opposite direction indicated by an arrow 30. It should be noted that opening 16 is preferably provided with a coarse filter 17 adapted to prevent debris from entering enhancement device 12. Seawater 26 flows out of pipes 19 into the sea through discharge vents 22. Water flows through conduit 18 as long as gate 20 is in an open position. In order to abruptly close the flow of seawater through conduit 18, gate 20 is moved from an external position by gate operating unit 24 into conduit 18. The closed position of the gate 20 is shown in Figure 4. Reference is now made to Figure 4 illustrating the state of the enhancement device shown in Figure 3, immediately after the rapid closure of the gate. The rapid closure of gate 20 within conduit 18 stops the flow of seawater through discharge vents 22. A surge wave 32 now propagates through opening 16, in the direction of the moving ship indicated by an arrow 34 with sufficient pressure and velocity to push forward the erstwhile static barrier of seawater so that the ship does not collide against it. After gate 20 is reverted to the external position by gate operating unit 24, seawater flows through conduit 18 and pipes 19. Gate 20 is repeatedly moved across conduit 18 in an inwardly and outwardly manner so as to repeatedly form a propagating surge wave as described herein. The repetitive and rhythmic operation of moving gate 20 into the waterway and out of it are preformed automatically by gate operating unit 24 in order to sustain the forward movement of the surge waves ahead of the ship with optimum speed and pressure. In order to better understand the principle of enhancing the propulsion of an advancing ship, some typical calculations are performed and given below. The enhancement device of the present invention produces a forward wave of pressure P and velocity Cw. Pressure P is directly proportional to the velocity V of water through the device, the mass density /? of seawater and length L of the conduit, and inversely proportional to the time T required to close the gate and abruptly stop the flow of water through the device. Velocity Cw, which is the velocity of the surge wave, is grater than V by an amount δV proportional to [LjT -V) . The enhancement device is based on the controlled utilization of the phenomenon of "Water Hammer", which when uncontrolled propagates with the speed of sound C. A few assumptions are made through the calculations: 1. The conduit is absolutely rigid and has no frictional loss. 2. The closing of the gate is precise as regard to the speed of closing and the total reversal of the water-flow in the opposite direction without any adverse effect from the bulk modulus of elasticity of water within the conduit. Weight of 1 cubic meter of seawater equals 1039 [Kg]. Therefore, the mass of 1 cubic meter of seawater 1039/g, g=9.8 [m/sec2]. Let Υ' [m/sec] be the velocity of water within the conduit and V

[m/sec2] be the retardation.

Let 'P' r&g/m2] be the pressure rise and Cw [m/sec] the velocity of surge

wave, which is greater than V by a desired value SV . Let 1Z' [m]be the length of conduit and 'A' [m2] be the cross sectional

area of the conduit. Let T' [sec] be the time of closing the gate, where T>2L/C, where C is the speed of sound. Let 'M' [kg] be the mass of the water in the conduit = p x A x L.

Let 'F' [N] be the force acting on the gate, when the gate is inserted to adruptly stop the flow of seawater in the conduit. F = M x a = (p x A x L) x (V-O) / T Since the force can be written as F = Px A , hence P =- pxLx V /T . Force F is also = rate of change of momentum = Mass experiencing change of momentumx Change in velocity = (p x A x V) x Cw, where Cw = V + δV. Hence 'P' on closing gate is also = pχ Vχ Cw. Therefore p x V x Cw = p x L x V/T or Cw = L/T. Assuming that a 200 meter long ship moves at 25[føofa] = 12.8[m/sec] and that the length of the conduit is 12 [m] , in order to avoid the ship colliding against the mass of seawater in front, the enhancement device has to produce a surge wave moving forward at a speed Cw where Cw is greater than or equal to 12.8 [m/sec]. Let us assume that the velocity V of seawater through the conduit is 10 [m/sec] due to frictional and other losses. For controlling the "water hammer", the duration T should be much greater than 2Z divided by the speed of sound in water. According to the assumed data, 2L/C= 2x12/1500=16[msec]. The value chosen for T should be much greater than 16 [m/sec]. Let us assume !T = 900 [msec] . Then the velocity of the surge wave is CW=L/T=12/0.9=13.3[msec], which is greater than 12.8[msec] , the speed of the ship. The pressure of the surge wave is P= p x V x L/T = [1039/9.8] x 10 x 12/0.9 = 14,133 [Kg/m2] = 20.1[psi]. By choosing a slightly higher value for T , the velocity of the surge wave can be made equal to 12.8[7«/sec] . Sufficient time should be allowed for the free flow of seawater throiugh the conduit before the gate is abruptly closed. Assuming that a surge wave is propagated every time the ship covers its own length, time required to cover one length of the ship equals ship's length divided by ship's speed = 200/12.8 = 15.6[sec]. Therefore, for every interval of 15.6 seconds, the gate has to be closed for 900 [msec]. Time required to fill the conduit is L/V = 12/10 = 1.2 [sec], less than 1/10 of the cycle of operation. It can be seen that the gate is closed only for [100 x 0.9/15.6]% = 5.97% of the cycle and the gate is kept open for 94.33% of the cycle, which is long enough for the efficient operation of the device. Assuming the diameter of the conduit to be 1 [m] and that of the pipes 0.75 [m], the quantity of seawater handled by the device per cycle will be of the order of 10 tonnes, which will entail some losses, which, however, when compared to the enormous gain from the device will be negligible. Note that by reducing the time for closing the gate (T) , the length of the

conduit (L) can also be reduced. To achieve substantial reduction in the

closing time (T) , the gate can be in the form of fast operating valve, or flap, or disc. The example provided herein before illustrates how the enhancement device for marine propulsion could sustain a low-pressure surge wave ahead of the ship with velocity equal to, or optimally different from the speed of the ship in order to: 1. avoid collision of the ship with the static seawater in front. 2. minimize (or even eliminate) the retarding interaction between the bow wave and the hull of the ship. 3. reduce the frictional loss, which is proportional to the square of the relative speed of the ship with respect to the mass of sea water in front. Reference is now made to Figures 5a and b illustrating an enhancement device for marine propulsion in accordance with another preferred embodiment of the present invention. The principle of operation of this embodiment is mostly the same as that of the embodiment described herein before; however, facilitating means is provided in order to propagate a surge wave having higher pressure. Enhancement device 100 is provided with inlet conduit 102 having an opening 104 that can be located not necessarily at the stem of the advancing craft. This device has basically two conduits, a main conduit 18 as in the previous embodiment and an additional secondary outlet conduit 110. Gate control unit 24 operates two gates, gate 20 in the main conduit 18 and gate 21 in the secondary outlet conduit 110. When gate 20 is open, gate 21 is closed and vice-versa. Booster pump 106 is provided in inlet conduit 102 so as to increase the velocity of seawater in the conduit. A one way valve 108 is provided to allow one way flow, toward main conduit 18. When gate 20 is open, water flows through the conduit and out to the sea through the pipes 19 and discharge vents 22 in a direction indicated by arrows 30, while gate 21 remains closed and prevents water from flowing out through the secondary outlet conduit 110. Immediately upon closure of gate 20 by gate operating unit 24, as indicated in Figure 5b, a surge wave is formed. The formation of the surge wave and its propagation are as described in the first embodiment, e.g., on rapid closure of gate 20, surge wave 32, which pushes away the static barrier of seawater in front, propagates through conduit 18 and through a secondary outlet conduit 110 having gate 21 now in an open position. A one way valve 112 is provided in secondary outlet conduit 110 enabling one way flow of the propagating surge wave forward with velocity equal to or greater than the speed of the vessel in the direction of the advancing craft (indicated by arrow 114). It should be emphasized that the device of the present invention can be employed in most marine crafts including submarines. It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope as covered by the following Claims. It should also be clear that a person skilled in the art, after reading the present specification can make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the following Claims.