The present disclosure relates to a propulsion device for a hydrofoil craft and a hydrofoil craft provided with the propulsion device.
A hydrofoil craft has hydrofoils provided at positions lower than the body of the hull to reduce the water resistance generated when propelling, and travels by raising the hull above the water surface by the lift of the hydrofoils which increases as the hydrofoil craft gains speed. Such hydrofoil craft may be a fully-submerged hydrofoil craft whose hydrofoils are all below the water surface when the hydrofoil craft travels at a high speed or a surface-piercing hydrofoil craft whose hydrofoils partially rise above the water surface when the hydrofoil craft travels at high speed.
To improve the take-off performance and the ride quality during hullborne operation, there is proposed a fully-submerged hydrofoil craft having a pair of left and right assist foils provided in bilateral symmetry on an outer surface of a bottom portion of the hull (see JPH6-1181U). This hydrofoil craft is provided with a driving means for selectively driving the pair of assist foils between a stowed position where the assist foils are folded in toward the outer surface of the bottom portion and a use position where the assist foils are extended substantially horizontally as viewed from the front.
However, since the hydrofoil craft of JPH6-1181U needs to include the driving means for selectively driving the pair of left and right assist foils between the stowed and the use position, the structure thereof becomes complicated. Also, in the hydrofoil craft of JPH6-1181U, even though the position of the pair of left and right assist foils can be selectively switched, the lift generated by the assist foils depends on the travel speed of the hydrofoil craft, and thus, it is difficult to control the attitude of the hull by adjusting the generation of lift.
In view of such background, a first object of the present invention is to provide a propulsion device for a hydrofoil craft that is capable of improving the take-off performance without complicating the structure. Also, a second object of the present invention is to provide a hydrofoil craft that is simple in structure and can control the attitude of the hull as desired.
To achieve the first object, one embodiment of the present invention provides a propulsion device (3) for a hydrofoil craft (1), comprising: a hydrofoil (5) configured to be disposed in water; and a water jet thruster (6) that is disposed in front of the hydrofoil and ejects a water flow rearward from an ejection port (10), wherein an upper surface (11) of a rear portion of the hydrofoil is slanted downward toward rear, and the hydrofoil and the water jet thruster are configured such that at least part of the water flow passes above the rear portion of the hydrofoil.
According to this configuration, since at least part of the water flow ejected from the water jet thruster passes above the hydrofoil, when the water flow is weak (when the velocity of the water flow relative to the hydrofoil is less than a prescribed value), the water flow is deflected downward along the upper surface of the hydrofoil due to the Coand{hacek over (a)} effect and the hydrofoil generates a lift. On the other hand, when the water flow is strong (the velocity of the water flow relative to the hydrofoil is greater than or equal to the prescribed value), the water flow passing above the hydrofoil separates at the rear portion of the hydrofoil and therefore generates substantially no lift. As a result, when the water jet thruster ejects the water flow at low speed, a large lift is generated, so that the take-off performance is improved. Note that as the velocity of the water flow ejected from the water jet thruster increases, the lift decreases due to the separation of the water flow, and this suppresses reduction in the thrust, whereby the hull resistance reduction effect is effectively demonstrated.
Preferably, a leading edge (13) of the hydrofoil is positioned lower than a center (17) of the ejection port.
According to this configuration, like an upper surface blowing (USB) type, more than half of the water flow flows rearward along the upper surface of the hydrofoil. Therefore, when the water flow is weak, more than half of the water flow flowing above the rear portion of the hydrofoil is deflected downward along the upper surface of the hydrofoil so that the lift of the hydrofoil increases.
Preferably, the leading edge of the hydrofoil is positioned lower than a lower edge (16) of the ejection port.
According to this configuration, the amount of water flow flowing above the hydrofoil is large and the lift generated when the water flow is deflected downward along the upper surface of the hydrofoil due to the Coand{hacek over (a)} effect becomes large. Therefore, the take-off performance is further improved.
Preferably, a leading edge (13) of the hydrofoil is positioned higher than a center (17) of the ejection port, and an intermediate portion of the hydrofoil in a fore and aft direction is provided with a slot (26) that permits passage of the water flow from under the hydrofoil to above the hydrofoil.
According to this configuration, like an externally blown flap (EBF), more than half of the water flow flows rearward under the hydrofoil, and at least part thereof passes through the slot and flows rearward above the rear portion of the hydrofoil. Therefore, when the water flow is weak, the water flow flowing above the rear portion of the hydrofoil is deflected downward along the upper surface of the hydrofoil, thereby causing the hydrofoil to generate a lift.
Preferably, the ejection port is laterally elongated in shape.
According to this configuration, the width of the water flow deflected downward along the upper surface of the hydrofoil due to the Coand{hacek over (a)} effect becomes larger so that a larger lift is generated. Therefore, the take-off performance is further improved.
Further, to achieve the aforementioned second object, one embodiment of the present invention provides a hydrofoil craft (1) comprising: at least three propulsion devices (3) including those disposed on a hull (2) at mutually different positions in a fore and aft direction and those disposed at mutually different positions in a lateral direction, each propulsion device having the above-described configuration; a pitch sensor (21) that detects pitching of the hull; a roll sensor (22) that detects rolling of the hull; and a control device (23) that controls attitude of the hull based on detection results of the pitch sensor and the roll sensor, wherein the control device controls the pitching of the hull by making thrusts produced by the water jet thrusters disposed at mutually different positions in the fore and aft direction different from each other, and controls the rolling of the hull by making thrusts produced by the water jet thrusters disposed at mutually different positions in the lateral direction different from each other.
According to this configuration, by controlling the thrusts produced by the water jet thrusters of the at least three propulsion devices with the control device, it is possible to control the attitude of the hull as desired. Also, since the multiple propulsion devices each have the aforementioned configuration and the control device controls the attitude of the hull by making the thrusts produced by the water jet thrusters of these propulsion devices different from one another, the structure is simple.
As described above, according to the present invention, a propulsion device for a hydrofoil craft that is capable of improving the take-off performance without complicating the structure can be provided. Also, according to the present invention, a hydrofoil craft that is simple in structure and can control the attitude of the hull as desired can be provided.
FIG. 9A1 is a diagram showing a fully-submerged hydrofoil craft in calm water;
FIG. 9A2 is a diagram showing a fully-submerged hydrofoil craft in rough water;
FIG. 9B1 is a diagram showing a surface-piercing hydrofoil craft in calm water;
FIG. 9B2 is a diagram showing a surface-piercing hydrofoil craft in rough water; and
In the following, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, identical or similar devices or members will be denoted by same reference signs, with suffixes indicating their position, such as FL (front left), FR (front right), R (rear), etc. When the position is not distinguished, the suffixes may be omitted. Also, the suffixes FL (front left) and FR (front right) may be collectively written as F (front).
First, with reference to
The propulsion unit 4 is provided with a hydrofoil SF disposed substantially horizontally below the front portion of the hull 2, a front left water jet thruster 6FL disposed in front of a left side portion of the hydrofoil SF, and a front right water jet thruster 6FR disposed in front of a right side portion of the hydrofoil SF. The left half of the front hydrofoil SF and the front left water jet thruster 6FL constitute the front left propulsion device 3FL, and the right half of the front hydrofoil SF and the front right water jet thruster 6FR constitute the front right propulsion device 3FR. The rear propulsion device 3R is provided with a rear hydrofoil SR disposed substantially horizontally below the rear portion of the hull 2 and a rear water jet thruster 6R disposed in front of a lateral center of the rear hydrofoil SR.
Thus, the hydrofoil craft 1 is provided with the three propulsion devices 3 disposed on the hull 2 such that the propulsion devices 3 include those disposed at mutually different positions in the fore and aft direction (the pair of front propulsion devices 3FR, 3FL is disposed at a position different from the position of the rear propulsion device 3R in the fore and aft direction) and those disposed at mutually different positions in the lateral direction (the three propulsion devices 3FR, 3FL, and 3R are disposed at mutually different positions in the lateral direction). In the propulsion devices 3 of the present embodiment, the hydrofoils 5 are not provided with movable flaps. The thrust produced by each of the water jet thrusters 6 of these propulsion devices 3 is controlled by a control device 23, which will be described later. In another embodiment, the hydrofoils 5 of the propulsion devices 3 may be provided with movable flaps.
Each of the front and rear hydrofoils 5 is supported by left and right struts 7 that extend downward substantially vertically from a bottom portion of the hull 2. Each of the front left, front right, and rear propulsion devices 3 is supported on the corresponding hydrofoil 5 by an appropriate support member 8 (see
The water jet thruster 6 of the present embodiment is substantially tubular in shape and the suction port 9 opens forward at the front end of the water jet thruster 6. As shown in
As shown in
The water jet thruster 6 is disposed such that the ejection port 10 is positioned behind and above the leading edge 13 of the hydrofoil 5. More specifically, the water jet thruster 6 is disposed such that the leading edge 13 of the hydrofoil 5 is positioned forward of the ejection port 10 and lower than the lower edge 16 of the ejection port 10. Thereby, the entirety of the water flow ejected rearward from the ejection port 10 of the water jet thruster 6 passes above the hydrofoil 5.
In another embodiment, an arrangement may be made such that the leading edge 13 of the hydrofoil 5 is positioned higher than the lower edge 16 of the ejection port 10 and lower than the center 17 of the ejection port 10. Here, the center 17 of the ejection port 10 means the geometric center of the ejection port 10 as seen from rear. In this arrangement, more than half of the water flow ejected rearward from the ejection port 10 of the water jet thruster 6 passes above the hydrofoil 5.
Alternatively, an arrangement may be made such that the leading edge 13 of the hydrofoil 5 is higher than the center 17 of the ejection port 10 and lower than the upper edge 18 of the ejection port 10. In this case, at least part of the water flow ejected rearward from the ejection port 10 of the water jet thruster 6 passes above the hydrofoil 5.
During low rotation speed of the propulsion device 3, the water flow ejected from the water jet thruster 6 to above the hydrofoil 5 is weak, and the water flow is deflected downward along the upper surface 11 of the hydrofoil 5 due to the Coand{hacek over (a)} effect, as shown in
As a result, when the water jet thruster 6 ejects the water flow at low speed, a large lift is generated, whereby the take-off performance is improved.
In the present embodiment, as shown in
Also, in the present embodiment, the leading edge 13 of the hydrofoil 5 is positioned lower than the lower edge 16 of the ejection port 10, as described above. Accordingly, the amount of water flow flowing above the hydrofoil 5 is large and the lift generated when the water flow is deflected downward along the upper surface 11 of the hydrofoil 5 due to the Coand{hacek over (a)} effect becomes large. Therefore, the take-off performance of the hydrofoil craft 1 is further improved.
Furthermore, in the present embodiment, the ejection port 10 is laterally elongated in shape, as described above. Accordingly, the width of the water flow deflected downward along the upper surface 11 of the hydrofoil 5 due to the Coand{hacek over (a)} effect becomes larger so that a larger lift is generated. Therefore, the take-off performance of the hydrofoil craft 1 is further improved.
The control device 23 is an electronic control unit (ECU) constituted of a CPU, a ROM, a RAM, etc. The CPU reads out a program and executes computational processing along the program so that the control device 23 controls the attitude of the hull 2. The control device 23 may be constituted as one piece of hardware or may be constituted of a unit including multiple pieces of hardware. The control device 23 controls the attitude of the hull 2 by controlling the velocity of the water flow ejected from each water jet thruster 6, namely, by controlling the thrust produced by each water jet thruster 6, as described in detail below.
The control device 23 controls the pitching of the hull 2 by making the thrust produced by the pair of front (left and right) water jet thrusters 6F and the thrust produced by the rear water jet thruster 6R different from each other within a range less than the aforementioned prescribed value. Here, the pair of front water jet thrusters 6F and the rear water jet thruster 6R are disposed at mutually different positions in the fore and aft direction. Specifically, when the hull 2 is tilted forward, the control device 23 increases the thrust produced by the pair of front water jet thrusters 6F to enhance the lift on the front side of the hull 2. When the hull 2 is tilted rearward, the control device 23 increases the thrust produced by the rear water jet thruster 6R to enhance the lift on the rear side of the hull 2. In a case where the control device 23 increases one of the thrust produced by the pair of front water jet thrusters 6F and the thrust produced by the rear water jet thruster 6R, the control device 23 may reduce the other of the thrust produced by the pair of front water jet thrusters 6F and the thrust produced by the rear water jet thruster 6R so that the total thrust does not change.
Also, the control device 23 controls the rolling of the hull 2 by making the thrust produced by the front left water jet thruster 6FL and the thrust produced by the front right water jet thruster 6FR, which are disposed at different positions in the lateral direction, different from each other. Specifically, when the hull 2 is tilted to the right, the control device 23 increases the thrust produced by the front right water jet thruster 6FR to enhance the lift on the right side of the hull 2. When the hull 2 is tilted to the left, the control device 23 increases the thrust produced by the front left water jet thruster 6FL to enhance the lift on the left side of the hull 2. When the control device 23 increases the thrust produced by one of the front left and front right water jet thrusters 6FL and 6FR, the control device 23 may reduce the thrust produced by the other of the front left and front right water jet thrusters 6FL and 6FR so that the total thrust does not change.
In the example of
In the example of
In the example of
As described above, in the hydrofoil craft 1 of the present embodiment, the control device 23 can control the attitude of the hull 2 as desired by controlling the thrusts of the water jet thrusters 6. Also, since the multiple propulsion devices 3 each have the aforementioned configuration and the control device 23 controls the attitude of the hull 2 by making the thrusts of these water jet thrusters 6 of these propulsion devices 3 different from one another, the structure is simple.
Next, with reference to
In this embodiment, the configuration of the propulsion device 3 differs from the first embodiment. In the propulsion device 3 of this embodiment, the leading edge 13 of the hydrofoil 5 is positioned higher than the center 17 of the ejection port 10 of the water jet thruster 6. More specifically, the water jet thruster 6 is disposed such that the leading edge 13 of the hydrofoil 5 is positioned behind the ejection port 10 and higher than the upper end of the ejection port 10. Accordingly, like an externally blown flap (EBF), most of the water flow flows rearward under the hydrofoil 5.
An intermediate portion of the hydrofoil 5 in the fore and aft direction is provided with slots 26 for permitting passage of the water flow from under the hydrofoil 5 to above the hydrofoil 5. In the present embodiment, two slots 26 are provided at mutually different positions in the fore and aft direction. Owing to the provision of the slots 26 in the hydrofoil 5, at least part of of the water flow flowing under the hydrofoil 5 passes through the slots 26 to flow rearward above the rear portion of the hydrofoil 5. Therefore, when the water flow is weak, the water flow flowing above the rear portion of the hydrofoil 5 is deflected downward along the upper surface 11 of the hydrofoil 5, thereby causing the hydrofoil 5 to generate a lift.
On the other hand, when the water flow is strong, the lift of the hydrofoil 5 increases as the water flow that flows under the hydrofoil 5 becomes strong, but the water flow that flows above the hydrofoil 5 separates at the rear portion of the hydrofoil 5. Therefore, when the water flow becomes strong, the increase of the lift of the hydrofoil 5 is deterred by the water flow that flows to above the hydrofoils 5. Preferably, the slots 26 should be configured such that the stronger the water flow becomes, a higher proportion of the water flow flows above the hydrofoil 5.
Concrete embodiments of the present invention have been described in the foregoing, but the present invention is not limited to the above embodiments and may be modified or altered in various ways. For example, in the above embodiments, the hydrofoil craft 1 is exemplarily provided with three propulsion devices 3 but the hydrofoil craft 1 may be provided with four or more propulsion devices 3. Besides, the concrete structure, arrangement, number, angle, etc. of each member or part may be appropriately changed within the scope of the present invention. Also, not all of the components shown in the foregoing embodiments are necessarily indispensable and they may be selectively adopted as appropriate.
Number | Date | Country | Kind |
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2021-014500 | Feb 2021 | JP | national |
Number | Name | Date | Kind |
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6167829 | Lang | Jan 2001 | B1 |
Number | Date | Country |
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H061181 | Jan 1994 | JP |
Number | Date | Country | |
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20220242524 A1 | Aug 2022 | US |