WO2020084127A1 - Hull of a high-speed ship, provided with a front hydrojet - Google Patents

Abstract

The invention relates to a hull of a high-speed ship, comprising a central main float (2) and two, shorter lateral floats which are located towards the rear of the central float and connected thereto by connecting arms and comprise submerged skegs, the connecting arms being streamlined in the form of wings creating two ground-effect nozzles between each emerged inner lateral surface of the central float and lateral floats and the liquid surface on which the hull of the ship moves, the hull further comprising means (16, 17, 18) on the bow (2a) of the central float (2), for collecting water at the bottom of the bow and injecting it towards the front of the central float, above the liquid surface on which the hull of the vessel moves, in order to create an air-water emulsion on the bottom of the bow, reducing the friction drag.

Description

 Title of invention

 Hull of high speed ship with forward hydrojet Background of the invention

 The present invention relates to the general field of monohulls with aft stabilizers for high speed ships.

 A field of application of the invention is that of the construction of high speed ships, that is to say greater than 38 knots and even up to 54 knots and beyond, of average length of more than 50 m and capable of carrying passengers and vehicles in particular for civil as well as military uses.

 Shipbuilding has progressed in the engine section to increase the speed and range of the ships, but has hardly changed in the design of their hulls. In particular, the monohull has always prevailed for its simplicity, its lightness and its lift both static and dynamic even if its stability, at least in terms of comfort, is not perfect.

 However, in recent years many new designs have been studied and developed to dethrone the monohull with the aim of greater speed and better stability, and this both at the request of the military and shipowners. Indeed, the latter want to become much more competitive than air carriers by considering cutting the time allocated to a transoceanic crossing by at least half while being able to transport many more passengers than in a wide-body aircraft.

 To obtain high speeds (that is to say greater than 38 knots), we have thus seen the development of different types of hulls using for some only hydrostatic lift such as monohulls but by multiplying the number of hulls such as catamarans and trimarans in particular. Others have used hydrodynamic lift with submerged wings that take off the load-bearing hull from a certain speed. Still other principles have been developed using in particular aerostatic lift such as air cushion ships.

The present invention thus relates to lift from a trimaran type hull design. Developments and Achievements of ships with three hulls are essentially known to date in the field of yachting and in particular sailing to beat speed records. However, in this type of design, the float located downwind of the central hull has practically no function in navigation, the boat then resting on the central float and the lateral float located downwind.

 Different trimaran hull designs have also been developed to beat speed records in mechanical propulsion but without the concern of transporting goods or passengers such as the ship described in the Australian patent publication AU 521518. This publication aims at a kind of trimaran comprising three "hydroskis" allowing its displacement on three bearing surfaces arranged in a triangle, one at the front and the other two at the rear and allowing the hull to take off completely, which cannot be extrapolated for a heavy transport vessel such as passengers or vehicles.

 In the area of commercial transport, few projects have been developed. However, reference may be made to patent publications FR 2671775 and FR 2675460 by the same applicant, Société Nouvelle des Ateliers et Chantiers du Flavre, describing ships with multiple hulls but of which no example has been produced to date, probably for essentially problems stability and cost. Indeed, these are hulls, on the one hand, the super structures and the central float are fairly conventional, but can only reach a maximum speed of 40 knots. In addition, these hulls are quite heavy and the usable parts of the super structures as well as the center of gravity of the assembly are placed very high above the water.

Also known from patent publication WO 99/00291 is a ship hull comprising a central main float and two lateral floats of shorter length, situated towards the rear of the central float, connected to the latter by link arms and having submerged fins; the hulls of the three floats are always partly submerged and therefore to be considered, whatever the speed and the weather conditions, as always forming a displacement hull but, according to the invention, of entirely new design: the coefficient of finesse of the three hulls is between 0.25 and 0.35 with a ratio of their length to their width between 12 and 20 and a length ratio of the central hull over the length of the side hulls between 2.5 and 4.5.

 This hull design with a central float with very large elongation, offers a very low resistance to advancement and an effective behavior on short swells such as one meets them in closed or semi-closed seas such as the Mediterranean or the Handle. The transverse stability is ensured by the rear lateral floats which can give the hull a qualification of trimaran when it is in fact rather a "pseudo trimaran". Such aft floats give the vessel, unlike the catamaran, remarkable behavior because of the long period of roll they generate; the roll is moreover controlled by the efficiency of the stabilizing fins, which preferably are mobile and orientable in alternating operation so that it is always in positive incidence, giving a lift always oriented upwards. These immersed stabilizing fins or foils also provide a hydrodynamic lift effect making it possible to contribute to the planing of the rear part of the central hull from a certain speed.

Subject and summary of the invention

 The main object of the present invention is to improve the efficiency of a ship's hull having such characteristics.

This object is achieved by means of a high-speed ship's hull comprising a central main float and two shorter lateral floats, situated towards the rear of the central float, connected to the latter by link arms and comprising fins. immersed, the coefficient of fineness of the hulls of the lateral floats and of the central float being between 0.25 and 0.35 with a ratio between the length and the width between 12 and 20 and a ratio between the length of the hull of the float central and the length of the hull of the lateral floats between 2.5 and 4.5, the connecting arms being faired in the form of wings creating two ground effect nozzles between the interior interior lateral surfaces emerged from the central float and lateral floats, and the liquid surface on which the hull of the ship moves, and further comprising, in accordance with the invention, means at the level of the bow of the central float to take water from the bottom of the bow and inject it towards the front of the central float above the liquid surface on which the ship's hull is moving in order to create an air / water emulsion on the bottom of the bow decreasing the drag.

 Despite the reverse thrust produced by the forward injection of the sampled water, the production of an air / water emulsion on the bottom of the bow results in a reduction in drag by the "greasing" effect of the hull of the central float over its entire length. The hull friction drag is therefore reduced. In addition, the infinite “bulb” effect thus obtained makes it possible to artificially lengthen the hull of the central float forwards. This results in an improvement in the yield and therefore in the speed of the hull according to the invention.

 The invention thus makes it possible to produce ships capable of transporting passengers and / or freight such as essentially vehicles, at least 50 m in length, capable of sailing at high speed beyond 40 knots (or even of 50/60 knots), whatever the weather conditions and while keeping good stability both in roll and in pitch for one hand, a navigation comfort in particular for the passengers and on the other hand, not too much stress the hull structures which must be simple to manufacture, rigid and resistant.

 The hull may include at least one scoop located at the bottom of the bow of the central float and opening into at least one duct to take water. In this case, the duct can open towards the front of the central float above the liquid surface over which the hull of the ship is moving via an opening for injecting the withdrawn water.

 Preferably, the conduit comprises upstream of the opening a hydrojet supplied by a generator group housed in the main float and intended to take water in the conduit and to inject it towards the front of the central float.

Preferably also, the opening is provided with a removable concealment deflector. This deflector will be used according to sea conditions to obscure the injection of water forward and return it backwards in two jets on either side of the planking of the central float. More preferably, the water taken from the bottom of the bow is injected forward at an angle between 5 ° and 20 ° relative to the liquid surface over which the hull of the ship is moving and at a height between the liquid surface over which the ship's hull moves and the diameter of the duct.

 The coefficient of fineness of the hull of the central float is advantageously between 0.34 and 0.34 with a ratio between the length and the width between 15 and 18m for a length of central float between 50 and 150m.

 In addition, the hull further advantageously comprises a rear aerial vertical tail unit and means of propulsion by jet of water leaving the rear part of the lateral and central floats. These water jet propulsion means may further comprise water inlets located in the middle of the hull of the float considered.

Brief description of the drawings

 Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an embodiment thereof devoid of any limiting character. In the figures:

 - Figures 1 to 3 are schematic views of a ship hull according to the invention, respectively from above, from the side and from the rear; and

 - Figure 4 is a schematic view of the central float of the hull of Figures 1 to 3 showing the means for withdrawing and injecting water forward according to the invention.

Detailed description of the invention

 As shown in Figures 1 to 3, the hull 1 of a ship according to the invention comprises in particular a central main float 2 and two lateral floats 3 of shorter length, located towards the rear of the central float, and connected to the latter by link arms 4.

The hulls of the three floats 2, 3 are always submerged whatever the speed and weather conditions and ensure navigation while keeping the passenger and / or freight transport bridges almost horizontal. To this end, as shown in FIG. 3, the hulls of the lateral floats 3 comprise immersed fins 5 (or “foils”) which can be oriented by an angle a equal to approximately 45 ° in the middle position relative to the vertical median plane YY of each lateral float and oriented towards the inside of the hull towards the central float 2.

 Preferably, these immersed fins 5 are articulated under each lateral float 3 and can tilt at least between 40 and 50 °. These immersed fins may for example be of a so-called “Vaton” profile, of the type defined by the latter and as manufactured on the Charles HEIDSIEK IV boat in 1994/85.

 The three floats 2, 3 of the hull always remain at least partially submerged whatever the speed of advancement of the ship and thanks to the various specific means and forms according to the invention ensure navigation in a plane which remains very close to the 'horizontal.

 As described in publication WO 99/00291, the content of which is incorporated here by reference, the connecting arms 4 of the shell according to the invention are faired in the form of wings, thus creating two ground-effect nozzles between the lateral surfaces interior emerged from the central float and the lateral floats, and the liquid surface, on which the hull moves.

 These wings of the link arms are of relatively small size but of large rope moving at a height between half and a quarter of the average rope above the water. An aerodynamic lift is thus obtained due to the static pressure obtained by slowing the air when passing through these ground effect nozzles formed by the undersides of the wings of the link arms joining the lateral floats to the central float, and the surface of the water, this static pressure increasing with speed.

Estimates by calculations have made it possible to assess that for a bearing surface of each wing of these link arms of the order of 220 m ² , at a speed between 40 and 50 knots, this ground effect gives a downforce of of the order of 50 to 60 tonnes, using the cambered profile of these arms in the form of wings of known Gottingen type such as that referenced G652 (cambered). The combination of this "high lift" with the downforce obtained by the immersed fins 5 and integral with the lateral floats, which for a surface of the order of 6 m ² each has a speed between 40 and 50 knots, give a downforce of about 60 tonnes, allows total relief obtained on the order of 20% of the mass of a ship having a displacement of 550 tonnes, corresponding to the surface indications above , that is to say having a length of the order of 100 m and considered at half load.

 The central float 2 is arranged to receive passengers on specific bridges and vehicles on other bridges (not shown). Other arrangements are of course possible depending on the dimensions of this central float and the use of such a ship. Different visibility windows 6 are of course arranged at least at the level of the decks where the passengers are installed. A navigation and command bridge 7 dominates the entire hull and is preferably fitted on the central float 2 slightly in front of the bow of the lateral floats 3.

 As shown in Figure 3, the central float 2 may include two side pins 8 fixed on the rear part of its hull and has a rear rudder 9 for navigation.

 Below the decks, the structure of the central hull 1 has a double bottom and at the rear the machinery in which the powertrains are located (typically hydrojets 10 whose ejection nozzles 10a are located at the rear part of the shell). To obtain sufficient thrust to reach speeds of at least 40 to 50 knots, propulsion is thus ensured by at least one hydrojet 10 - and preferably two - coming out of the rear part of the central float, preferably supplemented by another hydrojet located at the rear of each lateral float.

 The ejection nozzles 10a of these hydrojets are preferably orientable upwards and downwards of the order of 12 ° relative to the horizontal, completing the above effects of the immersed fins of the hull shapes and of the arms to reduce pitch and roll movements.

The hydrojets 10 have feed water inlets (not shown) which are situated towards the middle of the hull of the float considered so as not to disturb the flow too much towards the rear part of said hull. Thus, such intake vents are preferably positioned at a distance of between 10 and 15% of the value of the length of the hull of the float considered, either upstream or downstream of the point of separation of the laminar boundary layer, and their opening length must be 10 to 15% of the length of this same laminar boundary layer

 To ensure a buoyancy reserve such that even in the event of a tear in the hull causing water to invade certain transport volumes and the entire double bottom, the entire hull can remain in buoyancy, all volumes of unused hulls can be filled with buoyancy foam in sufficient quantity to compensate for the whole weight of the laden ship (such as in the forward volume, the aft volume, all the volumes available between decks in the rest of the hull, as well as those of the link arms 4 and lateral floats 3).

 Vehicle access to the various bridges is via a rear door 12 (see Figure 3) of known type and passenger access via at least one side door 13 (see Figure 2) located on the central float 2, preferably in front of the bow of the side floats 3.

 To facilitate maneuvering in ports, the central float 2 may include retractable bow thrusters (not shown in the figures).

 Given the characteristics of finesse sought for all the floats and their specific arrangements according to the invention, the ratio of the volume of the submerged hull of the central float 2 to the volume of the circumscribed parallelepiped enveloping said hull, called the coefficient block, has a value between 0.32 and 0.34.

By considering the length L _PP between perpendicular front and rear of the central float 2 and its width at the master bau at the waterline, the ratio between this length and this width is between 15 and 18 with a hull length of the central float which can be between 50 and 150 m. Thus, for example, for a length between perpendiculars L _PP of 100 m, the width at the master beam at the waterline could be 6 m.

With regard to the hull of the lateral floats 3, the coefficient or finesse coefficient block is preferably between 0.26 and 0.28 with a ratio between their length and their width, as defined above for the central float , between 13 and 17. The ratio between the length of the central float 2 and the length of the lateral floats 3 is between 2.5 and 4.5, and preferably between 2.85 and 4.

The rear of the two lateral floats 3 is located at a distance d of between 5 and 20% - and preferably between 10 and 15% - of the value of the length L _PP of the hull of the central float, in front of the rear perpendicular of this central float.

The longitudinal median planes YY of the lateral hulls of the lateral floats 3 are located at a distance D of between 10 and 15% - and preferably between 12 and 14% - of the value of the length L _PP of the hull of the central float 2, on either side of the median plane XX by the latter.

It will be noted that all the values and ranges of the dimensions indicated above are valid for any length L _PP of the central float between perpendiculars between 50 and 150 m.

 The central float 2 comprises a rear aerial vertical tail unit 14 which is provided with a movable turning flap 15 and which constitutes a natural stabilizer by providing a slight support on the side opposite to the apparent wind. A balance is also established between the lift obtained by this empennage, whose support can be controlled by its movable turning flap and that of the surface of the front wall of the central float.

 For the hull dimensions mentioned above, the surface of the tail unit 14 is such that its ratio with the lateral surface of the emerged part of the central float 2 is between 0.07 and 0.09, and the surface of the fins submerged 5 relative to the submerged hull surface of the corresponding lateral floats 3 is between 0.025 and 0.030.

The orientation of these submerged fins 5 and the ejector nozzle outlets 10a of the water jets 10, is controlled by electrical controls for stabilizing the ship linked to an inertial unit is provided for example by a hydraulic system supported by a pneumatic emergency system which at least puts the nozzles in a horizontal position in the event of a problem. This double cross stabilization between the immersed fins and the nozzles, linked to the inertial unit, allows optimal comfort by controlling the lateral movements parasites knowing that such a system is almost neutral in terms of energy consumption.

 According to the invention, as shown in FIG. 4, the hull further comprises means at the level of the stem 2a of the central float 2 for taking water from the bottom of the stem and injecting it forward of the central float above the hull water line in order to create an air / water emulsion on the bottom of the bow reducing the drag.

 The decrease in the friction drag of the ship is due to several factors. On the one hand, the creation of an air / water emulsion on the bottom of the bow makes it possible to reduce the wet surface of the hull. On the other hand, we obtain a decrease in the bow wave by bulb effect to infinity at the front of the ship. In addition, the same effect is obtained forward as that of hull enlargement aft due to the wake of the ship.

 To this end, the central float 2 comprises, at the bottom of its bow 2a, at least one scoop 16 for taking water. More precisely, this scoop 16 is advantageously located a few meters behind the brion and can be in the form of a punctual truncation of the bottom of the hull.

 The scoop 16 opens out inside a duct 17 in an arc intended to convey the water withdrawn from upstream towards the front towards an opening 18 formed at the front of the central float 2.

 Furthermore, the conduit 17 comprises a hydrojet 19 which is supplied for example by a generator 20 housed in the main float and which is intended to take the water via the scoop 16 in the conduit and to inject it towards the front of the central float.

 More specifically, the hydrojet 19 comprises a propeller 19a coupled to a motor 19b by a transmission shaft 19c and possibly a reduction gear 19d, the motor 19b being itself supplied by the generator 20.

This hydrojet 19 is of the same type as those installed at the rear of the lateral and central floats but operates "upside down", that is to say that it pushes the water towards the front of the hull on several meters (which represents between 10 and 15% of the length of the hull's water line). Advantageously, the water which is taken from the bottom of the bow is injected towards the front of the hull at an angle b of between 5 ° and 20 ° - and preferably 10 ° - relative to the liquid surface SL on which the hull of the ship is moving.

 Still advantageously, the forward water injection opening 18 is situated at a height h which is comprised of the liquid surface SL over which the hull of the ship moves and the diameter F of the conduit 17.

 In addition, the opening 18 formed at the front of the central float is advantageously provided with a removable concealment deflector 21 allowing, depending on sea conditions, to obscure the injection of water if necessary. the front and return it backwards in two jets on either side of the planking of the central float.

Claims

1. Hull (1) of a high speed ship comprising a central main float (2) and two lateral floats (3) of shorter length, located towards the rear of the central float, connected to the latter by link arms (4) and comprising immersed fins (5), the coefficient of fineness of the hulls of the side floats and of the central float being between 0.25 and 0.35 with a ratio between the length and the width between 12 and 20 and a ratio between the hull length of the central float and the hull length of the lateral floats between 2.5 and 4.5, the link arms being faired in the form of wings creating two ground effect nozzles between the respective interior lateral surfaces emerged from the central float and the lateral floats, and the liquid surface (LS) on which the hull of the ship moves, characterized in that it also comprises means at the level of the stem (2a) of the central float (2 ) to take water from the bottom of the bow and inject it towards the front of the central float above the liquid surface on which the ship's hull is moving in order to create an air / water emulsion on the bottom of the bow decreasing the drag. 2. Hull according to claim 1, comprising at least one scoop (16) located at the bottom of the bow of the central float and opening into at least one conduit (17) for taking water. 3. Hull according to claim 2, in which the duct (17) opens towards the front of the central float above the liquid surface (SL) on which the hull of the ship moves by means of a opening (18) for injecting the withdrawn water. 4. Hull according to claim 3, wherein the conduit comprises upstream of the opening (18) a hydrojet (19) fed by a generator (20) housed in the main float and intended to take water in the conduit and inject it towards the front of the central float. 5. Hull according to one of claims 3 and 4, wherein the opening (18) is provided with a removable concealment deflector (21). 6. Hull according to any one of claims 2 to 5, in which the water taken from the bottom of the bow is injected forward with an angle (b) of between 5 ° and 20 ° relative to the surface liquid (SL) on which the hull of the ship moves and at a height (h) between the liquid surface (SL) on which the hull of the ship moves and the diameter (F) of the conduit (17). 7. Hull according to any one of claims 1 to 6, in which the coefficient of fineness of the hull of the central float is between 0.32 and 0.34 with a ratio between the length and the width between 15 and 18 for a central float length between 50 and 150m. 8. Hull according to any one of claims 1 to 7, further comprising a rear aerial vertical tail (14). 9. Hull according to any one of claims 1 to 8, further comprising means (10) of water jet propulsion leaving the rear part of the lateral and central floats. 10. Hull according to claim 9, wherein the means (10) of water jet propulsion further comprise water inlets located in the middle of the hull of the float considered.