FR3144600A3 - Cargo ship without ballast - Google Patents

Abstract

The examples refer to a ballastless cargo ship (100) which includes a hull having an upper body (101) and a lower body (102) located below the upper body (101). The upper (101) and lower (102) bodies have a rectangular cross section along the length of the shell, the lower body (102) being of smaller dimensions than the upper body (101). The ship further includes cargo spaces (110) disposed inside the upper body (101) and empty spaces (109) inside the lower body (102). With a predefined parameter selected from a maximum draft, a minimum draft and a maximum waterline width of the vessel, the geometry of the vessel is defined by: a ratio between a width of a flat bottom wall of the vessel and a maximum waterline width at the waterline of the vessel of between 0-0.7, a ratio of a submerged draft of the upper body to a maximum draft of the vessel of between 0-0.8 , and a master cutting coefficient of between 0.65-0.85. Figure for abstract: Figure 2

Description

Cargo ship without ballast

In general, the present invention relates to ships, and more preferably cargo ships, without a ballast system and having a shape consisting of two distinct bodies, upper and lower.

STATE OF THE ART

A ship, especially a cargo ship, is designed taking into account the weight of the ship itself and the weight of the cargo that is to be carried on board. Therefore, when the vessel has no cargo or is partially loaded, it floats higher relative to the water surface and may become unstable in crossing waves and crosswind, and may be susceptible to have space or shelter. Additionally, the vessel's propellers approach the water surface, which can cause cavitation damage and cause them to operate at lower RPM than recommended, increasing propeller wear and the need for maintenance. To avoid these problems, ships normally incorporate a ballast system comprising tanks containing seawater which maintains the necessary draft to ensure propeller efficiency, navigational safety and balance. of the ship. Ballast water is normally loaded and unloaded at different ports which may be in different countries or continents. Due to the improvement in ship speed, ships are able to travel from one country to another in a short time with living aquatic species, especially marine invasive species, contained in ballast water , so when this ballast water is discharged in a location far from where it was loaded, the release of these living aquatic species can cause environmental problems by disrupting ecosystems on a global scale.

To prevent certain species from entering ballast tanks, some ships incorporate filtration systems that block said species. Other ships incorporate ballast water treatment systems that include heating systems, ultraviolet light systems, deoxygenation systems, etc. in order to kill or at least reduce the quantity of living aquatic species contained in ballast water. However, all of these solutions are inefficient and have high installation and maintenance costs. Additionally, these solutions require large amounts of energy to operate and therefore require burning more fuel oil, leading to higher emissions.

Some ships, known as "free ballast ships", incorporate a group of structural boxes extending the length of the ship. During ballast operations, these chests can be opened to the sea with an intake opening at the bow and a discharge opening at the stern, being subjected to a flow of water from the intake opening to the discharge opening. In this way, these lockers can become flooded, reducing the buoyancy of the hull and allowing the ship to sink to its desired ballast draft. An example of this type of vessel is disclosed in document US2003019413A1 (Parsons). However, this solution is technically complex and adds a lot of drag to the ship's hull as it moves through the water.

In addition, multihull ships without ballast systems are known in the state of the art. This type of ship does not need to carry ballast water. However, the manufacturing and maintenance costs of this type of vessel are significantly higher than those of a monohull vessel. In addition, due to the particular design of these ships, the integration of a sufficiently large and single-piece hold is difficult, and the waterline width is significantly greater than in monohull ships. Another disadvantage of these ships is that when multihull ships carry heavy loads at low speeds, the wetted area and drag in the seaway increase significantly.

Ships having a V-shaped floor plan and provided with a large waterline width are known in the state of the art. In this type of vessel, ballast water may not be necessary to achieve proper control of the vessel's center of gravity under different loading conditions. However, these solutions cannot be applied to the transportation of cargo, e.g. objects, solid materials, etc., which require specific geometries, dimensions or hull shapes.

It would therefore be desirable to find an alternative solution to water ballast systems, which avoids all the disadvantages mentioned above and which ensures safe and efficient navigation of cargo ships.

DESCRIPTION OF THE INVENTION

The object of the invention is a ballastless ship, in particular a ballastless cargo ship, which comprises a hull having a longitudinal upper body, which serves as a cargo hold, and a longitudinal lower body, which serves as a cargo volume. buoyancy correction, the lower body being located under the upper body. The upper body and the lower body have a substantially rectangular cross section along the length of the hull, but the lower body has smaller dimensions (it is narrower and shallower) than the upper body. Thus, the master cut has two wedge sumps per side, instead of one. The concept of ballast effect on conventional design (with ballast) is replaced by the practical reduction of hull buoyancy volume. More particularly, the upper body and the lower body may have a substantially rectangular cross section along the length of the cargo space of the ship, for example the hold, while the bow section and the stern section of the ship may have a substantially similar or different cross section. For example, the bow section of the vessel may be a bulb bow, clipper bow, curved bow, or any other type of bow. Said bow section may be designed to reduce hull resistance cutting through water. On the other hand, the stern section of the ship can be a square or transom stern, a round stern, a fan stern, a merchant stern or any other type of stern.

The lower body is connected to the lower wall of the upper body in the central part of the ship (under the hold). The lower part of the two bodies may have a floor plan. This floor reading may vary along the length of the vessel. The connection between the upper body and the lower bodies at the bow and stern can become continuous tangent and occur at the side walls. Therefore, the upper and lower volumes can become one at the front and end of the vessel.

The upper body and the lower body may be further connected to each other by means of internal structural frames, pillars or the like. The lower body gives the cross section marked concave areas on its edges. The height of the upper body relative to the height of the lower body may depend on the difference between the maximum and minimum displacement of the vessel. For example, the greater the difference between the maximum displacement and the minimum displacement of the ship, the greater the height of the lower body relative to the height of the upper body. In some examples, the height of the upper body relative to the vessel's keel depth may be between 45% and 85%. Thus, in such examples, the height of the lower body relative to the keel depth of the ship can be between 55% and 15%. To compensate for this difference between the maximum and minimum displacement of the vessel, the maximum waterline width (waterline width at upper body level) of the vessel can be further varied, so that the greater this difference, the greater the width of the vessel. Maximum flotation of the vessel is large. Alternatively, the vessel's waterline width and draft can be changed together to compensate for this difference.

The volume distribution of the lower body modifies the vertical distribution of hull buoyancy, resulting in a greater draft of the vessel in light (unloaded) condition than that of other known vessels with different geometries.

The ballastless cargo ship further comprises at least one cargo space, in other words, at least one volume for transporting cargo, such as the cargo hold, arranged at least in correspondence with the upper body for at least store the cargo. This hold can completely occupy the space defined by the upper body, or can totally or partially occupy the space defined by the upper body and also partially occupy the space defined by the lower body of the ship. The cargo space can also protrude from the upper body so as to partially occupy the ship's deck.

The ballastless cargo ship also includes empty spaces at least partially in correspondence with the lower body. These empty spaces serve as flotation tanks for the ship. A portion of these empty spaces may further be used to store fuel tanks, piping systems or a trim compensation system as described below, among other systems or elements of the vessel. As an example, the ratio of void space volume to maximum vessel volumetric displacement can range from 0.1 to 0.45, although other ratios may be achieved depending on the particular vessel design.

The cross section of the lower body may include inclined side walls which may meet and be connected to the lower wall or side walls of the upper body. These inclined sidewalls may be substantially planar (the inclined sidewalls may form a substantially constant angle relative to the plane of waterline) or may be curved (the inclined sidewalls may form a variable angle relative to the plane of waterline). In all cases, the equivalent average slope of the inclined side walls (obtained for an equivalent volume of the lower body having completely flat inclined side walls) can be between 0.5º and 85º relative to the horizontal. In some embodiments, the lower body further includes a flat bottom (also known as a flat bottom wall) located at a central portion of the bottom of the shell and along the length of the shell, and more preferably along the length of the cargo spaces, such that the inclined side walls are formed on both sides of the flat bottom so that the lower body has a substantially truncated V-shaped cross section. This truncated V-shaped cross section of the lower body is substantially similar to an inverted trapezoidal cross section. The lower body may also include inclined wall portions formed at an apex of the two side walls to join the lower wall of the upper body.

The shape of the cross section in the essentially prismatic length of the ship thus defined forms four distinct hold sumps instead of two in other known ships with different ship geometries. These bilge sumps can be rounded or the side and bottom walls which form them can meet at an angle.

1. un rapport (%B_max) entre la largeur de la paroi de fond plat du navire et la largeur de flottaison maximale à l’aire de flottaison du navire qui est compris entre 0 et 0,7,
2. un rapport (%T_max) entre le tirant d'eau immergé du corps supérieur (en d'autres termes, la distance verticale correspondant à la partie immergée des parois verticales du corps supérieur) et le tirant d'eau maximal du navire qui est compris entre 0 et 0,8, et
3. un coefficient de coupe au maître (C_m) du navire défini comme suit :
   
   =
   
   qui est compris entre 0,65 et 0,85.

The ballastless cargo ship is defined such that, for a predefined parameter, the parameter being selected from a group including a maximum draft (T _max ), a minimum draft (T _min ) and a width maximum flotation (B _max ) of the ship, the geometry of the ship is defined by:

1. a ratio (%B _max ) between the width of the flat bottom wall of the vessel and the maximum waterline width at the flotation area of the vessel which is between 0 and 0.7,
2. a ratio (%T _max ) between the submerged draft of the upper body (in other words, the vertical distance corresponding to the submerged part of the vertical walls of the upper body) and the maximum draft of the vessel which is between 0 and 0.8, and
3. a master cutting coefficient (C _m ) of the vessel defined as follows:
   
   =
   
   which is between 0.65 and 0.85.

In this document, the master's cut coefficient of a ship designates the ratio between the area of the master's cut of the ship, for a defined draft, and the area of the rectangle which contains said surface of the master's cut. master of the vessel, the width of the rectangle corresponding to the width outside the limb of the vessel and the height of the rectangle corresponding to the draft previously defined.

Then, the coefficient %B _max which was defined as the ratio between the width (b) of the flat bottom of the ship and the maximum waterline width (B _max ) of the ship at the level of the flotation area of the ship is the following :

Likewise, the coefficient %T _max which was defined as the ratio between the submerged draft (t) of the upper body and the maximum draft of the ship (T _max ) is as follows:

The lower body cross section maintains sufficient draft and stability in light conditions and prevents damage in the propeller due to cavitation without the need for a ballast system. It also reduces hull resistance and improves propulsion efficiency. The presence of two additional bilge sumps increases eddy roll damping. The volume of the empty spaces in the lower body ensures that the maximum draft of the ship is not exceeded (the empty spaces act as a float when the ship is loaded). The lower body may further have a shape that changes along the length of said body, becoming more pointed at the bow. This longitudinal distribution of the volume of the lower body modifies the position of the center of buoyancy of the hull according to changes in draft.

Furthermore, by having an upper body with a substantially rectangular cross section along the entire length of the vessel and avoiding the use of side ballast tanks, the space occupied by the cargo space can be maximized in said body upper (the cargo space may have a width which corresponds substantially to the waterline width of the vessel), compensating for any spatial loss in the lower body.

The block coefficient of a ship is defined as the ratio between the underwater volume of the ship and the volume of a parallelepiped block defined by the length between perpendiculars, the width (waterline width) and the depth (draft of water) of the ship. In some embodiments, this ship block coefficient depends on a value of the angle of the side walls of the lower body, which may be inclined, relative to the baseline.

For example, for a predefined B _max and a T _max and constant values of t and %T _max (only b and %B _max are modified), a greater angle of the inclined side walls relative to the flat bottom implies a coefficient of higher block and vice versa. In other examples, for predefined values of B _max and T _max and constant values of b and %B _max (only t and %T _max are modified), a greater angle of the inclined side walls relative to the flat bottom implies a lower block coefficient and vice versa. Furthermore, the master cut coefficient and the block coefficient of a vessel are related to each other. In other words, the lower the master cutting coefficient, the lower the block coefficient, and vice versa.

In some cases, the block coefficient (C _b ) is defined as follows:


and is between 0.52 and 0.72, where %A _floatmax is the ratio between the flat bottom area (A _flatbottom ) of the lower body of the ship and the maximum waterline area (A _floatmax ) of the ship. The resulting block coefficient (C _b ) of the ship depends on the difference between the maximum and minimum displacement of the ship.

Then, the coefficient %A _floatmax which was defined as the ratio between the surface of the flat bottom (A _flatbottom ) of the lower body of the ship (if the ship does not have a flat bottom, this ratio will be zero) and the surface of the maximum waterline (A _floatmax ) of the vessel is defined as follows:

In some embodiments, when the vessel is at its minimum draft (minimum weight), the lower body is at least partially submerged and, when the vessel is at its maximum draft (maximum weight), the lower body lower body is totally submerged and the upper body is partially submerged.

In certain embodiments, said at least one cargo space is a hold, and more particularly a box-type hold. In these embodiments, due to the absence of side ballast tanks in the vessel, the hold may have a width which substantially corresponds to the waterline width of the vessel along the length of the vessel. Therefore, the hold can maximize the space occupation inside the ship. Then, a reduction in the keel depth of the hold due to the presence of the lower body can be compensated by increasing the width of the hold.

For box-type holds, the influence on the hydrodynamic parameters of the vessel of the transition between the flat bottom of the lower body and the side walls of the upper body is particularly important since it is interesting to reach the maximum value (width outside member) with the smallest possible draft, since the box type hold must be placed as low as possible in the vessel for stability reasons and to help ensure that the maximum draft is not excessive. Therefore, for these particular box-type wedges, the side walls of the lower body may have an angle relative to the flat bottom which is smaller than that of other known types of wedges. For example, for box-type holds, the inclined side walls can form an angle to the flat bottom of between 0.5º and 85º.

In some embodiments, the minimum draft of the vessel depends on the propulsion system of the vessel. In other words, the minimum draft may be the draft required for proper immersion of the propellers of the ship's propulsion system. The minimum draft of the vessel may also depend on the stability and seakeeping requirements of the vessel.

In some embodiments, the ballastless cargo ship includes two propellers. In these embodiments, the ballastless cargo vessel may further include two propulsion motors such that, when the vessel is sailing at its minimum draft, only one of the two propulsion motors is configured to drive the two propellers, and that, when the ship is sailing with a draft greater than the minimum draft, each propulsion engine drives a corresponding propeller among the two propellers. There are mainly two clearly differentiated extreme loading conditions: empty and fully loaded. When cargo ships are empty (no cargo), the displacement and draft are low, as is the drag of the ship when moving through the water (energy saving). When sailing at full load (maximum deadweight tonnage), the drag of the unballasted cargo ship will be very similar to the drag at sea of the conventional cargo ship. This may imply that the difference in power required for ship propulsion in the two conditions is significant. In cargo-free condition, the draft having been reduced to the minimum necessary for the proper operation of the vessel, a single propulsion engine is used to drive the two propellers. For any other draft greater than the minimum draft, each of the two propulsion motors is used to drive one of the two propellers. In certain examples, the propulsion motors may be diesel-electric propulsion motors, such as ASD (azimuth thruster) type propulsion motors with mechanical transmission (L-shaped transmission, Z-shaped transmission) or electric, which allow better control of the power delivered to each of the propellers. These diesel-electric propulsion motors can be powered by a plurality of generators which can operate depending on the power required by the propulsion motors.

In certain embodiments, the hull further comprises a trim compensation system comprising at least two tanks connected to each other by a fluid connection, a fluid, for example fresh water, stored in the at least two tanks being transported (onboard weight transfer) between said at least two tanks to maintain the stability of the vessel. This trim compensation system is capable of correcting heel and trim. The size of the tanks and their location inside the ballastless cargo vessel can be optimized to provide sufficient torque with as little water as possible. In certain examples, there may be at least one tank located near each of the side walls (port and starboard) of the hull, connected to each other by a fluid connection to correct the list of the ship, and it there may be at least one tank located near the bow and another tank located near the stern, connected to each other by a fluid connection, to correct the trim of the ship.

In some embodiments, the width of the lower body varies along the length of the hull, preferably being wider near a stern portion of the vessel and narrower near a bow portion of the vessel.

The cargo vessel described here avoids the use of ballast water systems and thus eliminates the transport of seawater containing invasive marine species. This solution is therefore more effective than current treatment methods in reducing the potential for introducing said invasive marine species into other foreign ecosystems. Additionally, by avoiding treating ballast water, significant energy savings are achieved. In addition, the installation of tanks, pumps, pipes, pipelines and other elements of the water ballast system is avoided, with corresponding savings in terms of installation and maintenance. Another advantage is that the vessel described here is more efficient, as it significantly reduces its drag when moving through the water in an empty state (less displacement, less wetted surface area and less power required).

A set of drawings is provided to complete the description and to allow a better understanding of the invention. These drawings form an integral part of the description and illustrate an embodiment of the invention which should not be interpreted as limiting the scope of the invention, but only as an example of embodiment of the invention.

The drawings include the following figures:
There , there and the show different views of a cargo ship without ballast, according to a particular embodiment of the invention.
There shows a cross-sectional view of the ballastless cargo ship of Figure 1 along line AA.
There shows a cross-sectional view of the ballastless cargo ship, according to a particular embodiment of the invention, with the parameters which define the ballastless cargo ship in two dimensions.
There shows a cross-sectional view of the cargo ship without ballast of the , with the parameters that define the ballastless cargo ship in three dimensions.

Detailed description of the invention

Figures 1A-C show different views of a ballastless cargo ship 100, according to a particular embodiment of the invention.

There shows a bottom perspective view of the ballastless cargo ship 100. The ballastless cargo ship 100 includes an upper body 101 and a lower body 102 along the entire length of the ship 100. Figures 1B and 1C respectively show a bottom view and a side view of the ship 100. The upper body 101 and the lower body 102 of the ship 100 have a substantially rectangular cross section along their central part, in particular, along the space occupied by the hold (not shown in this figure). The lower body 102 is narrower and shallower than the upper body 101.

In the bow part 103 of the ship 100, the shape of the lower body 102 narrows to a point while said lower body 102 can be widened at the stern part 104 (the lower body 102, at the level of the stern portion 104 is the portion of the vessel 100 in which there is a greater concentration of weight, such as machinery, etc.) This allows the vessel 100 to avoid listing and decrease drag in the seaway . The geometry of the bow part 103 of the upper body 101 was chosen to adapt to the geometry of the bow part 103 of the lower body 102 and thus avoid very large surfaces between the upper body 101 and the lower body 102. horizontals" which increase drag and reduce efficiency. These geometries, which become sharper in the longitudinal direction, minimize twisting. At some point, the lower body 102 defines a transition surface between the bottom of the vessel 100 and the upper body 101 leaving space for placing propellers.

Although the ballastless cargo ship 100 of Figures 1A-C shows a bow portion 103 and a stern portion 104 having a particular geometry, said bow and stern portions may have an entirely different geometry depending on the particular design. of the ship.

There shows a cross-sectional view of the ballastless cargo ship 100 of Figure 1 along line AA. The upper body 101 of the ship 100 has a substantially rectangular cross section which is defined by the side walls 105 and the lower wall 111 of the hull and deck 106 of the ship 100. The side walls 105 of the upper body 101 are connected by their ends lower than the lower wall 111 which is itself connected to the side walls 107 of the lower body 102 with the interposition of inclined or curved walls 112 which generate concave surfaces on the exterior surface of the shell. These inclined or curved walls 112 define the transition zone between the lower wall 111 of the upper body 101 and the lower body 102. In this embodiment, the side walls 107 of the lower body 102 have a certain inclination relative to the flat bottom 108 The lower body 102 also has rounded lower edges 113 to improve the hydrodynamic conditions of the hull.

The lower body 102 includes empty spaces 109 which act as floats for the ship 100. These empty spaces 109 are dimensioned such that the volume of air in the submerged empty spaces 109 is equivalent to the volume of air in the ballast tanks. submerged, totally or partially empty, in the loaded state of a conventional vessel. For example, the ratio between the volume of empty spaces 109 and the maximum volumetric displacement of the ship 100 can be between 0.1 and 0.45. The ship 100 further comprises a box-type hold 110 disposed inside the upper body 101 and which projects slightly above the deck 106 to store the cargo. This hold 110 has a width which corresponds substantially to the waterline width of the ship 100, and a length which corresponds substantially to the length of the ship 100. In particular, the length of the hold 110 can correspond substantially to the length of the central part of the ship 100, that is to say excluding the bow part 103 and the stern part 104.

Although the ballastless cargo ship 100 of the shows a hold 110 arranged in correspondence with the upper body 101 of the ship 100, the hold 110 can also partially occupy the space contained in the lower body 101 and/or can project above the deck line of the ship 100. Additionally, although the ballastless cargo ship 100 shows a single hold, in some other embodiments there may be more than one hold disposed longitudinally along the length of the vessel, more than one hold disposed transversely to the length of the vessel or any combination thereof.

There shows a cross-sectional view of a ballastless cargo vessel 200, according to a particular embodiment of the invention, including the parameters which define the geometry of the vessel 200 in two dimensions (2D). There shows a cross-sectional view of the ballastless cargo ship 200 of the , including the parameters that define the ship 200 in three dimensions (3D). The cross-sectional view of the ballastless cargo vessel 200 shown in Figures 3A-B is similar to the cross-sectional view of the vessel 100 of the .

The ballastless cargo ships 200 described here have been designed with a geometry, shape and hull buoyancy distribution such that, in any load condition, the draft of the vessel is always between the draft of minimum water and maximum draft of the ship's hull. As used in this document, the hull draft of the ship or boat means the vertical distance from the waterline to the bottom of the hull, including the thickness of the hull. Minimum draft is the minimum depth of water at which a vessel can navigate safely while complying with applicable maritime regulations. The minimum draft is normally reached when no cargo is carried on board. Similarly, maximum vessel draft is the maximum water depth at which a vessel can safely navigate while complying with applicable maritime regulations, and is normally achieved with the vessel's maximum allowable deadweight , that is, when fully charged.

The ship's cargo state that corresponds to minimum draft is that in which the total weight of the ship is as small as possible (W _min ), also known as minimum displacement. In this state, the total weight is the sum of the following weights:
- Light travel (LTD),
- Constants (K) = supplies and consumables + crew and effects + oils and spare parts + effects in reserves + miscellaneous), and
- 10% consumption (fuels and oils in the tanks), so that,
W _min = LTD + K + 10% Cons.

Therefore, for the minimum draft, the ship must have a volume (V _min ) of the underside of the hull which balances this minimum weight (W _min ):
V _min = W _min / d; (d= 1.025 t/m ³ ; specific weight of sea water)

On the other hand, the cargo state of the ship which corresponds to the maximum draft is that in which the total weight of the ship is the greatest possible (W _max ). In this state, the weight of the vessel, also known as the loaded (or maximum) displacement, will be the sum of the following weights:
- Light travel (LTD), and
- Deadweight (DWT) = Cargo + K + 100% Consumption, so that,
W _max = LTD + DWT = D (full cargo displacement; maximum vessel weight)

Therefore, for maximum draft, the ship must have a volume (V _max ) of the underside of the hull that balances this weight (W _max ):
V _max = W _max / d; (d= 1.025 t/m ³ )

The transition between V _max and V _min must be done by achieving a rate of growth of the volume below directly linked to the variation in the flotation area of the vessel, in other words, the rate of growth of the volume of the below increases with the growth rate of the waterline width (B(T)) for the draft considered. In this document, Beam means the width of a vessel at the widest point measured at the vessel's nominal waterline. This rate of growth of waterline width can be limited by certain design restrictions such as a predefined maximum draft, minimum draft and maximum waterline width of the vessel, among others.

The relationship between the draft (T) of the boat and the volume of the underside of the hull which balances the corresponding weight (W) can also be expressed as a function of the flotation area (Afloat(T)) of the boat to the draft considered. Then, the condition for the minimum draft (minimum weight) of the vessel can be expressed in terms of the waterline area or in terms of the waterline width as follows:



where AM _min is the area of the section defined by the submerged part of the master cut in the minimum draft condition.

The maximum draft (maximum weight) condition of the vessel can be expressed in terms of the waterline area or in terms of the waterline width as follows:



where AM _max is the area of the section defined by the submerged part of the master cut in the maximum draft condition.

It is therefore necessary to define the functions Afloat(T) and B(T). These functions can be defined on intervals. In the range of functions corresponding to the lower body of the hull, the waterline area and waterline width increase steadily.

According to , the initial data which define the cargo ship without ballast (considering that the waterline width of the ship increases linearly) are the following: the maximum draft (T _max ), the minimum draft (T _min ) , the ratio (%B _max ) between the width (b) of the flat bottom of the lower body of the ship and the maximum waterline width (B _max ), the ratio (%T _max ) between the submerged draft (t) of the upper body of the vessel (i.e. the vertical lateral dimension of the upper body of the vessel) and the maximum draft (T _max ), and the maximum waterline width (B _max ). For this particular embodiment, T _max was considered as the predefined parameter, i.e. the T _max of the vessel is used as a restriction to obtain the master cutting coefficient (C _m ), the ratio %B _max and the ratio %T _max . Alternatively, the master cut coefficient, %B _max ratio and %T _max ratio can be obtained using the maximum waterline width (B _max ) or minimum draft (T _min ) as parameters predefined (restriction) since all these dimensions (maximum draft, minimum draft and maximum waterline width) are linked to each other.

Knowing the maximum and minimum displacement of the vessel and a given maximum draft (restriction), varying the values of %B _max and %T _max between 0 and 0.7, respectively, and establishing that


all possible solutions can be found to design the cargo ship without ballast. Each solution obtained will have a minimum draft and a maximum waterline width. Then, the lower the %B _max and the higher the %T _max , the lower the master cutting coefficient and the ship block coefficient. In addition, and consequently, the master cutting coefficient, as well as the block coefficient, will be all the lower as the side walls of the lower body are inclined. The master cut coefficient and the block coefficient of a vessel are related to each other. In other words, the lower the master cutting coefficient, the lower the block coefficient and vice versa.

According to , the initial data which define the cargo ship without ballast (considering that the flotation area of the ship increases linearly and that the variation of the flotation area is due only to a variation of the waterline width) are as follows : the maximum draft (T _max ), the minimum draft (T _min ), the ratio (%A _floatmax ) between the surface of the flat bottom (A _flatbottom ) of the lower body of the ship and the surface defined by the maximum waterline of the vessel (A _floatmax ), the ratio (%T _max ) between the vertical lateral dimension (t) of the upper body of the vessel and the maximum draft (T _max ), and the maximum waterline width (B _max ). For this particular embodiment, T _max was considered as the predefined parameter, i.e. the T _max of the vessel is used as a restriction to obtain the block coefficient (C _b ) (and also the block coefficient cut to the master (C _m )), the ratio between the area of the flat bottom and the maximum area of the flotation area of the vessel, and the ratio between the submerged draft of the upper body and the maximum draft of the ship. Alternatively, the ratio (%A _floatmax ) and ratio (%T _max ) of the vessel can be obtained using the maximum waterline width or minimum draft as predefined parameters (restriction) since all these dimensions ( maximum draft, minimum draft and maximum waterline width) are related to each other.

Knowing the maximum and minimum displacement of the vessel and a given maximum draft (restriction), varying the values of %B _max and %A _floatmax between 0 and 0.7, respectively, and establishing that


all possible solutions can be found to design the cargo ship without ballast. Each solution obtained will have a minimum draft and a maximum waterline width. Then, the lower the %B _max and the higher the %T _max , the lower the block coefficient and the cutting coefficient at the ship's master. In addition, and consequently, the block coefficient, as well as the master cutting coefficient, will be all the lower as the side walls of the lower body are inclined. The block coefficient and the master cut coefficient of a vessel are related to each other. In other words, the lower the block coefficient, the lower the master cutting coefficient and vice versa.

The design of the lower body up to the height of the minimum draft (T _min ) of the vessel makes it possible to obtain a rate of growth of the volume of the underside which is directly linked to the variation of the flotation area of the vessel. In other words, the rate of growth of the volume below increases with the rate of growth of the waterline width for the draft considered. Thus, the block coefficient (C _bm ) for the minimum draft (T _min ), equivalent to the block coefficient of the lower body up to the height corresponding to the minimum draft, can be defined as follows:


where D is the displacement with full cargo (maximum weight of the ship), W _load is the weight of the cargo transported in the ship, W _cons is the weight of the ship's consumption, d=1.025 t/m ³ (specific weight of the ship 'sea water), L is the length of the ship between perpendiculars and B is the width outside the limb.

Thus, the block coefficient of the lower body for the minimum draft is determined based on the main dimensions of the vessel, the minimum necessary draft and the deadweight (DWT) and the consumption of the vessel (autonomy). We then obtain a value of the block coefficient of the lower body which depends on the minimum draft of the ship and which the design of the ship cannot exceed, conditioning the maximum value of the block coefficient of the ship and therefore the minimum value of its draft. maximum water.

The difference between the maximum volume (V _max ) and the minimum volume (V _min ) of the vessel is as follows:


where C' _b is the block coefficient of the upper body in the area between the maximum draft (T _max ) and the minimum draft (T _min ) of the ship.

Since V= W/d, then:


so what,

This therefore means that the maximum draft of the vessel can be determined on the basis of the main dimensions of the vessel, the minimum necessary draft and the deadweight (DWT) and the consumptions of the vessel (autonomy).

From formulas (1) and (2), we can obtain:


which provides the block coefficient of the vessel as a function of the block coefficient of the lower body up to its minimum draft and the block coefficient of the upper body between its minimum draft and its maximum draft.

If we consider that the master cutting coefficient of the upper body (C' _m ) of the ship is equal to 1 (this simplification makes it possible to maximize the value of the block coefficient of the ship and therefore to obtain a minimum T _max , which means that the maximum waterline width is achieved at the minimum draft or even at a draft less than the minimum draft), the block coefficient of the upper body is equal to the prismatic coefficient of the upper body ( C' _p ),

With the prismatic coefficient of the vessel (C _p ) and the prismatic coefficient of the lower body (C _pm ), we can obtain the prismatic coefficient of the upper body (C' _p ):

)=



where AM is the area of the cut to the master of the ship in the condition of maximum draft ( ) and AM _min is the area of the cut to the master of the ship up to the minimum draft ( . By applying the simplification C' _b =C' _p , we can obtain the block coefficient of the ship based on the prismatic coefficient of the ship and the prismatic coefficient of the lower body:

We can then deduce the maximum draft:

The rest of the vessel parameters can be derived, with predefined restrictions, from this block coefficient and the maximum draft.

The prismatic coefficient of the lower body C _pm is limited and cannot be less than 1-AM*(1-C _p )/AM _min since C' _p is less than 1.

Since C _pm has a minimum value that cannot be reduced, and the block coefficient C _b decreases with increasing C _pm , the value of C _pm should be as close as possible (taking into account the value of C' _p ) of its minimum value (a block coefficient as high as possible is required to obtain a maximum draft as low as possible).

Therefore, the value of the block coefficient has an upper limit that cannot be reached. This maximum value corresponds to a value of the prismatic coefficient of the lower body equal to the minimum value that it can have, i.e., which makes the value of the prismatic coefficient of the upper body equal to 1,
.

Thus, the maximum draft of the ship has a lower limit which cannot be reached and whose value is:

The main characteristics of the vessel will fall within the limit values described above.

By way of example, a table presenting different parameters of a cargo ship without ballast, according to a particular embodiment of the invention, of a conventional cargo ship with slow navigation and of a standard cargo ship ( both incorporating ballast systems), is provided. Forks of ballastless cargo ships Slow sailing cargo ship Standard ship Cargo ship without ballast Cargo ship without maximum ballast B/T 1.35-3 2.1-2.3 2.3 1.9 1.4 C _b 0.52-0.72 0.65-0.73 0.74 0.69 0.54 C _m 0.65-0.85 0.97-0.995 0.94 0.79 0.67

The parameters compared in this table are the ratio (B/T) between the waterline width (B) and the draft (T), the block coefficient (C _b ) and the master cutting coefficient (C _m ) ships. The values of the ratio (B/T), master cutting coefficient (C _m ) and block coefficient (C _b ) were obtained based on the formulas described above. For the definition of the dimensions and proportions indicated in the table, it was considered that the waterline length and width remained substantially constant for the cargo ship without ballast. Thus, the most important dimensions to define are the draft and keel depth of the ballastless cargo ship.

The column “Ballastless Cargo Ship Ranges” refers to the values between which the ballastless cargo ship described in this document falls. The column "Slow sailing cargo ship" refers to the values between which a conventional slow sailing cargo ship with ballast system falls. The "Standard Ship" column refers to the values of a particular conventional cargo ship with ballast system. The values of the “Slowly sailing cargo ship” and “Standard ship” columns are known from the prior art (Ship design: Methodologies of Preliminary Design, Papanikolaou 2014). The column "Cargo ship without ballast" refers to the values of a particular cargo ship without ballast, as described in this document, in which, in order to obtain the indicated parameters, the keel depth of the ship has been amended. The values in the “Maximum Ballastless Cargo Ship” column were obtained for a maximum draft (restriction) of 150% of the maximum draft of a conventional cargo ship. In particular, the column "Maximum ballastless cargo ship" shows values of ballastless cargo ship in which only the vessel's keel trough has been modified and the lower body has a V-shaped floor elevation (in d (other words, there is no flat bottom in the lower body and the lower body has a triangular cross section).

The ratio (B/T) of the ballastless cargo ship as described here is between 1.35 and 3 when the keel depth of the ship is significantly changed instead of the waterline width, i.e. that the maximum draft of the vessel is increased. When the waterline width is significantly changed and not the keel depth (to achieve a maximum draft similar to that of a conventional ship, i.e. a ship with a ballast system), the ratio (B/T) is between 2 and 3. The particular value of the ratio (B/T) will depend on the difference in vessel displacement due to different loading conditions and the particular geometry of the vessel. Since only the keel depth, or the waterline width, or both can be changed, a wide range [1.35-3] is obtained for the (B/T) ratio. Then, the design of the ballastless cargo ship can be defined to achieve a solution in which the ratio (B/T) would be substantially equal to the values of this ratio for the conventional ship (e.g., the standard cargo ship or the ship of slow sailing load), the depth on keel and the waterline width of the cargo ship without ballast being greater than the normal values of a conventional ship with similar characteristics. The values of C _b and C _m are not affected by the value of the ratio (B/T) since they are affected by the value of the product (BxT).

If we compare the values obtained for the cargo ship without ballast with the values obtained for conventional or standard ships, we see that the draft and/or the waterline width of the cargo ship without ballast are higher . Thus, the multiplication of waterline width and draft is higher than in conventional ships (having ballast systems). The block coefficient, and therefore the master cutting coefficient, is lower than in conventional vessels.

In this text, the term "includes" and its derivatives (such as "comprising", etc.) should not be understood in an excluding sense, i.e. these terms should not be interpreted as excluding the possibility that what is described and defined may include other elements, steps, etc. The term "other", as used herein, is defined as at least a second or more. The term "coupled", as used herein, is defined as being connected, whether directly without any intermediate element or indirectly with at least one intermediate element, unless otherwise specified. Two elements can be coupled mechanically, electrically, or communicatively connected by a channel, a path, a network or a communication system.

The invention is obviously not limited to the specific embodiments described here, but also encompasses all the variations which can be envisaged by any person skilled in the art (for example, with regard to the choice of materials, dimensions, components , configuration, etc.), within the general scope of the invention as defined in the claims.

Claims (15)

A ballastless cargo ship (100), characterized in that the ship (100) comprises:
a shell comprising a longitudinal upper body (101) and a longitudinal lower body (102), the lower body (102) being located under the upper body (101), the upper body (101) and the lower body (102) having a substantially rectangular cross section along a length of the shell, the lower body (102) being of smaller dimensions than the upper body (101); And
at least one cargo space (110) arranged at least in correspondence with the upper body (101) for at least storing the cargo, and empty spaces (109) at least partially in correspondence with the lower body (102);
the lower body (102) comprising respective side walls (107) which are connected to a lower wall (111) of the upper body (101); And
for a predefined parameter, the parameter being selected from a group comprising a maximum draft (T _max ), a minimum draft (T _min ) and a maximum waterline width (B _max ) of the vessel, a geometry of the ship is defined by: i) a ratio (%B _max ) between a width of a flat bottom wall of the ship and a maximum waterline width at the flotation area of the ship which is between 0 and 0.7, ii) a ratio (%T _max ) between a submerged draft of the upper body and a maximum draft of the vessel which is between 0 and 0.8, and iii) a master cutting coefficient (C _m ) of the vessel defined as follows:

which is between 0.65 and 0.85. A vessel (100) according to claim 1, wherein the lower body (102) comprises the flat bottom wall (108) located at a central portion of a bottom of the hull and along the length of the hull , and inclined wall parts (112) formed at a peak of the two side walls (107) to join the bottom wall (111) of the upper body (101). Vessel (100) according to any one of the preceding claims, in which a block coefficient (C _b ) of the vessel is defined as follows:

and is between 0.52 and 0.72, where %A _floatmax is the ratio between an area of the flat bottom wall (108) of the lower body (102) and an area defined by a maximum waterline of the ship. A vessel (100) according to any one of the preceding claims, wherein, when the vessel is at its minimum weight, the lower body (102) is at least partially submerged and, when the vessel is at its maximum weight, the lower body (102) is totally immersed and the upper body (101) is partially immersed. Ship (100) according to any one of the preceding claims, in which said at least one cargo space (110) is a hold, and more preferably a box-type hold. A vessel (100) according to any preceding claim, wherein said at least one cargo space (110) has a width which corresponds substantially to the waterline width of the vessel along the length of the vessel. A vessel (100) according to any one of the preceding claims, wherein the minimum draft of the vessel is dependent on a propulsion system of the vessel. Vessel (100) according to any one of the preceding claims, comprising two propellers. Vessel (100) according to claim 8, comprising two propulsion motors such that when the vessel is moving with the minimum draft, only one of the two propulsion motors is configured to drive the two propellers, and when the ship moves with a draft greater than the minimum draft, each propulsion motor drives a corresponding propeller of the two propellers. Vessel (100) according to any one of the preceding claims, in which the hull comprises a trim compensation system having at least two tanks connected to each other by a fluid connection, a fluid stored in the at least two tanks being transported between said at least two tanks to maintain the stability of the vessel. A vessel (100) according to any preceding claim, wherein the upper body (101) and the lower body (102) have a substantially rectangular cross section along a length of said at least one cargo space (110). of the ship. A vessel (100) according to any preceding claim, wherein the lower body (102) comprises rounded lower edges (113). A vessel (100) according to any one of the preceding claims, wherein the width of the lower body (102) varies along the length of the hull, preferably being wider near a stern portion (104) of the ship and narrower near a bow part (103) of the ship. A vessel (100) according to any preceding claim, wherein a master cutaway of the vessel comprises two bilge sumps per side. A vessel (100) according to any preceding claim, wherein the side walls (107) of the lower body (102) are inclined relative to the flat bottom wall (108) of the lower body (102).