ES1302097U - CARGO SHIPS WITHOUT BALLAST (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

An unballasted cargo ship (100), characterized in that the ship comprises: a hull having a longitudinal upper body (101) and a longitudinal lower body (102), the lower body (102) being located below the upper body (101), where the upper body (101) and the lower body (102) have a substantially rectangular cross section along the length of the helmet and where the lower body (102) is of smaller dimensions than the upper body (101); and at least one load space (110) arranged at least in correspondence with the upper body (10) to at least store the load and empty spaces (109) at least partially in correspondence with the lower body (102); wherein the lower body (102) comprises respective side walls (107) that join a bottom (111) of the upper body (101); and where 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 breadth (B max) of the ship, a geometry of the ship is defined by: i) a ratio (%B max) between the width of a flat bottom and a maximum area of the waterplane of the ship ranging from 0 to 0.7, ii) a ratio (%T max) between a submerged draft of the body and a maximum draft of the ship ranging from 0 to 0.8, and iii) a coefficient of central section (C m) of the ship defined as: {IMAGE-01} that oscillates between 0.65 and 0.85. (Machine-translation by Google Translate, not legally binding)

Description

CARGO SHIPS WITHOUT BALLAST

TECHNICAL FIELD

In general, the present invention relates to ships, and more preferably to cargo ships without ballast systems, having a hull having a distinct upper body and lower body.

STATE OF THE ART

A ship, particularly a cargo ship, is designed taking into account the weight of the ship itself and the weight of the cargo to be carried on board. Therefore, when the ship is unloaded or partially loaded, the ship floats higher in relation to the water surface and may become unstable to cross waves and crosswinds and may list or trim. In addition, in these cases the boat's propellers come close to the surface of the water, which can cause cavitation damage as well as cause them to work at a lower than recommended speed, increasing propeller wear and the need for maintenance. To avoid these problems, ships normally integrate a ballast system that comprises tanks containing seawater that maintains the necessary draft to guarantee efficient propulsion, safe navigation, and balance the ship. Ballast water is normally loaded and discharged in different ports which may be in different countries or continents. Due to improvements in ship speed, such ships can travel between countries in a short time with live aquatic species, in particular invasive marine species, in the ballast water such that when this ballast water is discharged into a far away from where it was loaded, the release of these live aquatic species can cause environmental problems on a global scale.

To prevent certain species from entering ballast tanks, some ships have built-in filtration systems that block these species. Other ships integrate ballast water treatment systems including heating systems, ultraviolet light systems, deoxygenation systems, etc., to kill or at least reduce the number of live aquatic species contained in the ballast water. However, all these solutions are inefficient and have high installation and maintenance costs. Likewise, these solutions require large amounts of energy to operate and therefore require burning more fuel, resulting in higher emissions.

Some ships, known as "ballast free ships", integrate a group of structural ducts that run the entire length of the ship. When the ship is ballasted, a continuous flow of seawater is allowed to pass through the conduits from the intake opening at the bow to the discharge opening at the stern. In this way, these passages can be flooded, reducing the buoyancy of the hull and allowing the ship to sink to the desired draft. An example of this type of ship is described in US2003019413A1 (Parsons). However, this solution is technically complex and adds great resistance to the ship's hull as it moves through the water.

Additionally, multihull ships without a ballast system are known in the art. This type of ship does not need to carry ballast water. However, the manufacturing and maintenance costs of this type of boat are significantly higher than those of a monohull boat. In addition to this, due to the particular design of these boats, it is difficult to integrate a large enough hold in one piece and the beam is significantly greater than in monohull boats. Another disadvantage of these ships is that when multihull ships are carrying heavy loads at low speeds, the wetted surface area and drag on the seaway increase significantly.

Boats are known in the art that have a V-shaped strut that is provided with a high beam. In this type of ship, ballast water may not be necessary to achieve adequate control of the ship's center of gravity under different loading conditions. However, these solutions cannot be applied for the transport of loads, for example, objects, solid materials, etc., which require specific geometries, dimensions or shapes of the hull.

Therefore, it would be desirable to find an alternative solution to ballast water systems that avoids all the drawbacks mentioned above and that ensures safe and efficient navigation of cargo ships.

DESCRIPTION OF THE INVENTION

The subject of the invention is a ballastless ship, in particular a ballastless cargo ship, comprising a hull having a longitudinal upper body and a longitudinal lower body, the lower body being located below the upper body. The upper body and the lower body have a substantially rectangular cross section along the hull, but the lower body has smaller dimensions (it is narrower and shallower) than those of the upper body. Thus, the middle section of the ship has two bilges per side, instead of just one. The concept of ballast effect in the conventional design (with ballast) is replaced by the convenient reduction of the floating volume of the hull. More particularly, the upper and lower bodies have a substantially rectangular cross section along the length of the cargo space, eg the hold, of the ship, while the bow section and stern section of the vessel may have a substantially similar or different cross section. For example, the bow section of the ship may be a bulbous bow, a Fiddle bow, a curved bow or any other type of bow. Said bow section can be designed to reduce the resistance of the hull when going through the water. On the other hand, the stern section of the ship can be stamped or mirrored, an elliptical stern or any other type of stern.

The lower body is attached to the bottom of the upper body in the central part of the ship (below the hold). The lower part of both bodies can have a certain angle of bilge that can vary along the length of the ship. The junction between the upper and 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 fore and aft ends of the vessel.

The upper body and the lower body can be connected to each other by means of structural frames, internal pillars or the like. The lower body provides the cross section of the ship with concave zones in correspondence with its edges. The height of the upper body with respect to the height of the lower body may depend on the difference between the maximum and minimum displacement of the ship. For example, the greater the difference between the maximum and minimum displacement of the ship, the greater the height of the lower body with respect to the height of the upper body. In some examples, the height of the upper body with respect to the ship's layout depth can range from 45%-85%. Therefore, in such examples, the height of the lower body with respect to the depth of the plot of the ship can range between 55%-15%. To compensate for said difference between the maximum and minimum displacement of the ship, the maximum breadth (breadth in the upper body) of the ship can be further modified, in such a way that the greater this difference, the greater the maximum breadth of the ship. Alternatively, the breadth and draft of the ship can be modified together to compensate for this difference.

The lower body volume distribution alters the vertical buoyancy distribution of the hull causing a deeper draft of the ship in the light (unloaded) condition compared to other known ships with different ship geometries.

The unballasted cargo ship further comprises at least one cargo space, in other words, at least one volume for carrying the cargo, such as the cargo hold, arranged at least in correspondence with the upper body to at least store the cargo. . This warehouse can totally occupy the space defined by the upper body or it 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 vessel. The cargo space can also protrude from the upper body to partially occupy the deck of the ship.

The cargo ship without ballast also includes empty spaces in correspondence with the lower body. These empty spaces act as floating tanks for the ship. Part of these empty spaces can also be used to store fuel tanks, piping systems or a trim trim system as described below, among other systems or elements of the ship. By way of example, the ratio of the volume of void spaces to the maximum volumetric displacement of the ship may range from 0.1 to 0.45, although other ratios may be achieved based on the particular design of the ship.

The shape of the cross section in most of the prismatic length of the ship thus defined forms four bilges instead of the two of other known ships with different geometries. Said bilges can be rounded or their side and bottom walls can join at an angle.

The unballasted cargo ship is defined in such a way that, 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 breadth (B ^max ) of the ship, the geometry of the ship is defined by:

i) a ratio (%B ^max ) between the width of the ship's flat bottom and the maximum breadth in the area of the ship's waterplane ranging from 0 to 0.7,

ii) a ratio (%T ^max ) between the submerged draft of the upper body (in other words, the vertical distance corresponding to the submerged portion of the vertical walls of the upper body) and the maximum draft of the ship ranging from 0 to 0, 8, and

iii) a coefficient of center section (C ^m ) of the ship defined as:

which ranges from 0.65 to 0.85.

As used in this document, the coefficient of the center section of a ship refers to the ratio between the area of the center section of the ship, for a defined draft, and the area of the rectangle that contains said area of the center section. of the ship, the width of the rectangle corresponding to the breadth of the ship and the height of the rectangle corresponding to the previously defined draft.

Then, the coefficient %B ^max that has been defined as the ratio between the width (b) of the flat bottom of the ship and the maximum breadth (B ^max ) of the ship in the area of the ship's water plane is:

Similarly, the %Tmax coefficient that has been defined as the relationship between the submerged draft (t) of the upper body and the maximum draft of the ship (Tmax) is:

The lower body cross section maintains sufficient draft and stability in light conditions and prevents cavitation damage to the propeller without the need for a ballast system. It also reduces hull drag and improves propulsion efficiency. The presence of two additional bilges increases the damping against rolls. The volume of the voids in the lower body ensures that the maximum draft of the ship is not exceeded (the voids act as a float when the vessel is loaded). The lower body may also have a shape that changes along the length of the body, becoming more pointed at the bow. That longitudinal distribution of the lower body volume changes the position of the center of buoyancy of the hull with changes in draft.

In addition to this, by having an upper body of substantially rectangular section along the entire length of the ship and avoiding the use of side ballast tanks, the space occupied by the cargo space in said upper body (the space occupied by the cargo space) can be maximized. cargo can have a width that substantially corresponds to the breadth of the ship), 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 its perpendiculars, the breadth (breadth) and the depth (draft) of the ship. In some embodiments, this ship block coefficient depends on a value of the angle of the lower body side walls, which may be tilted, with respect to the baseline.

For example, for a predefined Bmax and Tmax and a constant t and %Tmax (only varied by %Bmax) a greater angle of the inclined side walls with respect to the flat bottom implies having a greater block coefficient and vice versa. In other examples, for a predefined Bmax and Tmax and a constant b and %Bmax (only t and %Tmax are varied) a greater angle of the inclined side walls with respect to the flat bottom implies having a lower block coefficient and vice versa. In addition to this, the center section coefficient and the block coefficient of a ship are related to each other. That is, the lower the coefficient of central section, the lower the coefficient of block and vice versa.

In some embodiments, the block coefficient (Cb) is defined as:

and oscillates between 0.52 and 0.72, where %Amaxfloatation is the ratio between the area of the flat bottom (Afondopiano) of the lower body of the ship and the area of the maximum waterline (Amaxfloatation) of the ship. The resulting block coefficient (Cb) of the ship will depend on the difference between the maximum and minimum displacement of the ship.

Then, the %Amaxfloatation coefficient, which has been defined as the ratio between the area of the flat bottom (Afondopiano) of the lower body of the vessel (if the vessel does not have a flat bottom, this ratio will be zero) and the area of the maximum waterline ( Amaximum buoyancy) of the ship is:

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

In some embodiments, the at least one cargo space is a hold, and more particularly, a box-type hold. In such embodiments, due to the lack of side ballast tanks in the ship, the hold may have a width that substantially corresponds to the breadth of the ship along the length of the ship. Therefore, the hold can maximize the occupation of the space inside the ship. Thereafter, a reduction in the depth of the hold layout due to the presence of the lower body can be offset by an increase in the width of the hold.

For box-type holds, the influence of the transition between the flat bottom of the lower body and the side walls of the upper body on the hydrodynamic parameters of the ship is especially relevant since it is of interest to reach the maximum value (width of layout) with the lowest possible draft, since the box-type hold will be placed as low as possible inside the ship for reasons of stability, as well as to help ensure that the maximum draft is not excessive. Therefore, for these particular box-type holds, the lower body side walls may have an angle with respect to the flat bottom that is smaller than in other type of holds. well-known wineries For example, for box-type holds, the sloped side walls can form an angle with respect to the flat bottom that can range from 0.5° to 85°.

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

In some embodiments, the unballasted cargo ship comprises two propellers. In such embodiments, the unballasted cargo ship may further comprise two propulsion engines such that when the ship is sailing at its minimum draft, only one of the two propulsion engines is configured to power the two propellers, and when the ship sails with a draft greater than the minimum draft each propulsion motor feeds a corresponding propeller of the two propellers. Mainly, there are two clearly differentiated extreme load conditions: empty load and full load. When cargo ships are empty (no cargo), the displacement and draft are small, as is the resistance of the ship while moving through the water (energy saving). When sailing at full load (maximum deadweight tonnage), the resistance of the unballasted cargo ship will be very similar to the seaway resistance of the conventional cargo ship. This may imply that the difference in power required to propel the ship in any given condition is large. For the no-load condition, because the draft has been reduced to the minimum necessary for the correct operation of the ship, a single propulsion engine is used to power the two propellers. For any other draft greater than the minimum draft, each of the two propulsion motors is used to power one of the two propellers. In some examples, the propulsion motors may be diesel-electric propulsion motors, such as ASD (Azimuth Stern Drive) type propulsion motors with mechanical transmission (L-Drive, Z-Drive) or electric transmission, which allow better control of the power delivered to each of the propellers. These diesel-electric propulsion engines can be powered by a plurality of generator sets that can operate based on the power required by the propulsion engines.

In some embodiments, the hull further comprises a trim trim system having at least two tanks fluidly connected to each other, wherein a fluid, eg fresh water, stored in the at least two tanks is transported (pressure transfer). weight on board) between at least two tanks to keep the ship stabilized. This trim compensation system is capable of correct heeling and trim. The size of the tanks and the location of the tanks within the unballasted cargo ship can be optimized to provide sufficient torque with as little water as possible. In some examples, there may be at least one tank located in close proximity to each of the side (port and starboard) hull frames that are fluidly connected to one another to correct the ship's list and there may be at least one tank located on the near the bow and another tank located near the stern, fluidly connected to each other, to correct the trim of the ship.

The cargo ship described herein avoids the use of ballast water systems and therefore eliminates the transport of seawater containing invasive marine species. Therefore, this solution is more effective than current treatment methods in reducing the potential for introduction of such invasive marine species into other alien ecosystems. In addition to this, by avoiding ballast water treatment, significant energy savings are achieved. Additionally, the installation of tanks, pumps, pipes, conduits and other elements of the ballast water system is avoided with the corresponding savings in installation and maintenance costs. Another advantage is that the vessel described herein is more efficient as its drag is significantly reduced while moving through the water in its empty condition (less displacement, less wetted surface area and less power required).

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description, and in order to provide a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be construed as a restriction of the scope of the invention, but only as an example of how the invention can be carried out.

The drawings comprise the following figures:

Figures 1A-C show different views of a cargo ship without ballast, according to a particular embodiment of the invention.

Figure 2 shows a cross-sectional view of the unballasted cargo ship of Figure 1 along the line A-A.

Figure 3A shows a cross-sectional view of the unballasted cargo ship, according to a particular embodiment of the invention, with the parameters that define the unballasted cargo ship in two dimensions.

Figure 3B shows a cross-sectional view of the unballasted cargo ship of Figure 3A, with the parameters defining the unballasted cargo ship in three dimensions.

DETAILED DESCRIPTION OF THE INVENTION

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

Figure 1A shows a bottom perspective view of the unballasted cargo ship 100. The unballasted cargo ship 100 comprises an upper body 101 and a lower body 102 along the entire length of the ship 100. Figures 1B and 1C show a bottom and side view of the vessel 100, respectively. The upper 101 and lower 102 bodies of the ship 100 have a substantially rectangular cross section along its central portion, in particular, along the space occupied by the hold (not shown in this figure). The lower body 102 has a width and depth less than that of the upper body 101.

In the bow portion 103 of the ship 100, the shape of the lower body 102 tapers to a point while the lower body 102 can be widened towards the stern portion 104 (the lower body 102 in the stern portion 104 is the portion of the ship 100 in which there is a greater concentration of weights, such as machinery, etc.). This helps the ship 100 to avoid trim and decrease drag while sailing. The geometry of the bow portion 103 of the upper body 101 has been chosen to adapt to the geometry of the bow portion 103 of the lower body 102 and thus avoid very large "horizontal" surfaces between the upper body 101 and the body. lower 102 which increase resistance and reduce efficiency. These geometries, which become more pointed in the longitudinal direction, minimize impacts on the sea surface. At a certain point, the lower body 102 defines a transition surface between the bottom of the ship 100 and the upper body 101, leaving a space for the placement of the propellers.

Although the unballasted cargo ship 100 in Figures 1A-C shows a bow portion 103 and a stern portion 104 having a particular geometry, said bow portion and stern portion may have any other geometry depending on the particular design. of the ship.

Figure 2 shows a cross-sectional view of the unballasted 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 a bottom wall 111 of the hull and deck 106 of the ship 100. The side walls 105 of the upper body 101 are joined at their ends lower to the bottom 111 which in turn is attached to the side walls 107 of the lower body 102 by interposing inclined or curved walls 112 that generate surfaces concave on the outer face of the hull. These inclined or curved walls 112 define the transition zone between the flat bottom wall 111 of the upper body 101 and the lower body 102. In this embodiment, the side walls 107 of the lower body 102 present a certain inclination in relation 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 comprises voids 109 that act as floats for the ship 100. These voids 109 are dimensioned in such a way that the volume of air in the submerged voids 109 is equivalent to the volume of air in the submerged ballast tanks, totally or partially empty, in the loaded condition of a conventional ship. For example, the ratio between the volume of the void spaces 109 and the maximum volumetric displacement of the ship 100 can range from 0.1 to 0.45. The ship 100 further comprises a box-type hold 110 arranged within the upper body 101 and protruding slightly above the deck for storing cargo. This hold 110 has a width that substantially corresponds to the breadth of the ship 100 and a length that substantially corresponds to the length of the ship 100. In particular, the length of the hold 110 can substantially correspond to the length of the central portion of the ship 100 , that is, excluding the bow portion 103 and the stern portion 104.

Although the unballasted cargo ship 100 of Figure 2 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 within the lower body 101 and/or can protrude by above the deck line of the ship 100. Also, although the unballasted cargo ship 100 shows a single hold, in some other embodiments, there may be more than one hold arranged longitudinally along the length of the ship, plus of a hold arranged transversely to the length of the vessels or any combination thereof.

Figure 3A shows a cross-sectional view of a cargo ship without ballast 200, according to a particular embodiment of the invention, including the parameters that define the geometry of the ship 200 in two dimensions (2D). Figure 3B shows a cross-sectional view of the unballasted cargo ship 200 of Figure 3A, including the parameters that define the ship 200 in three dimensions (3D). The cross-sectional view of the unballasted cargo ship 200 shown in Figures 3A-B is similar to the cross-sectional view of the ship 100 of Figure 2.

The unballasted cargo ships 200 described herein have been designed with a hull geometry, shape and buoyancy distribution that, in In any loading condition, the ship's draft is always between the minimum and maximum draft of the ship's hull. As used herein, ship or vessel hull draft refers to the vertical distance between the water line and the bottom of the hull, including the thickness of the hull. The minimum draft corresponds to the minimum depth of water at which a ship can safely navigate in compliance with the applicable maritime regulations. The minimum draft is normally reached without cargo being carried on board. Similarly, the maximum draft of the ship refers to the maximum depth of water in which a ship can safely navigate and comply with applicable maritime regulations and is normally achieved with the maximum permissible deadweight of the ship, i.e. when it is fully charged.

The loading condition of the ship that corresponds to the minimum draft is that in which the total weight of the ship is the lowest possible weight (Wmm), also known as minimum displacement. In this condition the total weight is the sum of the following weights:

- Light weight (LTD),

- Constants (K)= Supplies and consumables Crew and effects Oils and spare parts effects in various warehouses), and

- 10% Consumption (fuels and oils in tanks), in such a way that,

Wmin= LTD K 10% Cons.

Therefore, for the minimum draft, the ship must have a volume (Vmin) of the underlying body of the hull that balances this minimum weight (Wmm):

Vmin= Wmin/d; (d= 1,025 t/m3; specific weight of seawater)

On the other hand, the loading condition of the ship that corresponds to the maximum draft is one in which the total weight of the ship is the greatest possible weight (W max). In this condition, the weight of the ship, also known as the loaded (or maximum) displacement, will be the sum of the following weights:

- Lightweight (LTD), and

- Dead Weight (DWT)= Cargo+K+100% Consumption, in such a way that, Wmax= LTD+DWT = D (Full load displacement; maximum weight of the vessel)

Therefore, for the maximum draft the ship must have a volume (Vmax) of the underlying body of the hull that balances this weight (Wmax):

Vmax= Wmax/d; (d= 1,025 t/m3)

The transition between Vmax and Vmin must be achieved by achieving a growth rate of the underlying body volume directly related to the variation of the vessel's flotation area, in other words, the growth rate of the underlying body volume increases with the rate of breadth growth (B(T)) for the considered draft. As used herein, breadth refers to the width of a ship at the widest point measured on the ship's nominal waterline. This breadth growth rate may be limited by some design constraints, such as a predefined maximum draft, minimum draft, and maximum ship breadth, among others.

The relationship between the draft (T) of the ship and the underlying body volume of the hull that balances the corresponding weight (W) can also be expressed as a function of the waterline area (Float(T)) of the ship for the considered draft. Then, the condition for the minimum draft (minimum weight) of the ship can be expressed as a function of waterline area or as a function of breadth as follows:

either

where AMmin is the sectional area defined by the submerged portion of the central section at the minimum draft condition.

The condition for the maximum draft (maximum weight) of the ship can be expressed as a function of waterline area or as a function of breadth as follows:

where AM max is the area of the section defined by the submerged portion of the central section at the maximum draft condition.

Therefore, it is necessary to define the functions Float(T) and B(T). Such functions can be defined in intervals. In the interval of the functions corresponding to the lower body of the hull, the flotation area and the beam are constantly increasing.

According to Figure 3A, the initial data that defines the cargo ship without ballast (considering that the breadth of the ship grows linearly) are: maximum draft (T ^max ), minimum draft (T ^min ), ratio (%B ^max ) between the width (b) of the flat bottom of the lower body of the ship and the maximum breadth (B ^max ), ratio (%T ^max ) between the draft submerged (t) of the upper body (ie vertical lateral dimension of the upper body of the ship) and the maximum draft (T ^max ), and the maximum breadth (B ^max ). For this particular embodiment, T ^max has been considered as the default parameter, that is, the T ^max of the ship is used as a constraint to obtain the coefficient of central section (C ^m ), the %B ^max ratio and the %T ^max ratio . As an alternative, the center section coefficient, the %B ^max ratio and the %T ^max ratio can be obtained using the maximum beam (B ^max ) or the minimum draft (T ^min ) as the default parameters (constraint) since all these dimensions (maximum draft, minimum draft and maximum beam) are related to each other.

Knowing the maximum and minimum displacement of the ship and a determined maximum draft (restriction), varying the values %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 beam. Then, the lower the %B ^max and the higher the %T ^max , the lower the center section coefficient and also the block coefficient of the ship. Additionally, and as a consequence, the central section coefficient, and also the block coefficient, will be smaller the more inclined the side walls of the lower body are. The center section coefficient and the block coefficient of a ship are related to each other. That is, the lower the center section coefficient, the lower the block coefficient and vice versa.

According to Figure 3B, the initial data that defines the cargo ship without ballast (considering that the waterline area of the ship grows linearly and the waterline area variation is only due to a beam variation) are: maximum draft (T ^max ), minimum draft (T ^min ), ratio (%A ^{max buoyancy} ) between the area of the flat bottom (A ^{bottom bottom} ) of the lower body of the ship and the area defined by the maximum waterline of the vessel (A ^{max buoyancy} ) , ratio (%T ^max ) between the vertical lateral dimension (t) of the upper body of the ship and the maximum draft (T ^max ) and the maximum breadth (B ^max ). For this particular embodiment, T ^max has been considered as the default parameter, that is, the T ^max of the ship is used as a constraint to obtain the block coefficient (C ^b ) (and also the center section coefficient (C ^m ) ), the ratio between the area of the flat bottom and the maximum area of the water plane of the ship, and the ratio between the submerged draft of the upper body and the maximum draft of the ship. As Alternatively, the ratio (%Amax buoyancy) and the ratio (%Tmax) of the ship can be obtained using the maximum breadth or the minimum draft as predefined parameters (constraint) since all these dimensions (maximum draft, minimum draft and maximum beam) are related each other.

By knowing the maximum and minimum displacement of the ship and a determined maximum draft (restriction), varying the values %Bmax and %Amaxfloatation 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 beam. Then, the lower the %Bmax and the higher the %Tmax, the lower the block coefficient and also the center section coefficient of the ship. Additionally, and as a consequence, the block coefficient, and also the central section coefficient, will be lower the more inclined the side walls of the lower body are. The block coefficient and the center section coefficient of a ship are related to each other. That is, the lower the block coefficient, the lower the center section coefficient and vice versa.

The design of the lower body up to the height of the minimum draft (Tmin) of the ship achieves a growth rate of the volume of the underlying body that is directly related to the variation of the flotation area of the ship. In other words, the underlying body volume growth rate increases with the breadth growth rate for the considered draft. Therefore, the block coefficient (Cbm) for the minimum draft (Tmin), equivalent to saying the block coefficient of the lower body up to the height corresponding to the minimum draft, can be defined as:

where D is the full load displacement (maximum weight of the ship), Wcarga is the weight of the cargo transported in the ship, Wcons is the weight of the ship's consumption, d=1.025 t/m3 (specific weight of the water of sea), L is the length of the ship between its perpendiculars and B is the breadth of the layout.

Therefore, the lower body block coefficient for the minimum draft is determined based on the main dimensions of the ship, the minimum draft required and the cargo capacity (DWT) and consumption of the ship (range). Then, a value of the block coefficient of the lower body is obtained that depends on the minimum draft of the ship and that the design of the ship cannot exceed, conditioning the value maximum of the block coefficient of the ship and, therefore, the minimum value of its maximum draft.

The difference between the maximum volume (V ^max ) and the minimum volume (V ^min ) of the ship is:

where C'b is the block coefficient of the upper body in the area between the maximum draft (Tmax) and the minimum draft (Tmin) of the ship.

Since V= W/d, then:

and then,

Therefore, this means that the maximum draft of the ship can be determined based on the main dimensions of the ship, the minimum draft required and the load capacity (DWT) and consumption of the ship (range).

From formulas (1) and (2), it can be obtained:

which gives the block ratio of the ship as a function of the lower body block ratio up to its minimum draft and the upper body block ratio between its minimum draft and its maximum draft.

If the coefficient of the center section of the upper body (C' ^m ) of the ship is considered to be 1 (this simplification maximizes the value of the block coefficient of the ship and, therefore, gives a minimum T ^max , which means that the beam maximum is reached at the minimum draft or even at a draft lower 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 ship (C ^p ) and the prismatic coefficient of the lower body (C ^pm ), the prismatic coefficient of the upper body (C' ^p ) can be obtained:

where AM is the area of the center section of the ship at the maximum draft condition ( ^T max ) and AM ^min is the area of the center section of the ship up to the minimum draft ( Tm in). Applying the simplification C' ^b =C' ^p , the block coefficient of the ship based on the prismatic coefficient of the ship and the prismatic coefficient of the lower body can be obtained:

Then the maximum draft can be derived:

The rest of the ship parameters can be derived, with the predefined constraints, from these block coefficients and maximum draft.

The lower body prismatic coefficient Cpm is constrained 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 since 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 ) to its minimum value (as high a block coefficient as possible is required to achieve as low a maximum draft 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, that is, Cpm = ^C μm(min), which makes the value of the prismatic coefficient of the upper body equal to 1, C'v = 1.

Therefore, the maximum draft of the ship has an unreachable lower limit whose value is:

The main characteristics of the ship will be within the limit values described above.

By way of example, a table is provided with different parameters of a cargo ship without ballast, according to a particular embodiment of the invention, a conventional slow-moving cargo ship and a standard cargo ship (both incorporating ballast systems). ).

The parameters that are compared in this table are the ratio (B/T) between the breadth (B) and the draft (T), the block coefficient (Cb) and the center section coefficient (Cm) of the vessels. The values of the ratio (B/T), the central section coefficient (Cm) and the block coefficient (Cb) have been obtained based on the formulas described above. For the definition of the dimensions and proportions shown in the table, it has been considered that the length and breadth remain substantially constant for the cargo ship without ballast. Therefore, the most important dimensions to define are the draft and the depth of layout of the cargo ship without ballast.

The column "Unballast Cargo Intervals" refers to the values between which the unballasted cargo ship described in this document ranges. The column "Slow moving cargo ship" refers to the values between which a conventional slow moving cargo ship with ballast system oscillates. The column "Standard Ship" refers to the values of a particular conventional cargo ship with a ballast system. The values of the columns "Cargo ship of Slow Sailing" and "Standard Ship" are known from the prior art (Ship Design: Preliminary Design Methodologies, Papanikolaou 2014). The "Unballasted Cargo Ship" column refers to values for a particular unballasted cargo ship. , as described in this document, where the ship's plot depth has been modified to arrive at the parameters shown.The values in the column "Maximum unballasted cargo ship" have been obtained for a maximum draft ( restriction) of 150% of the maximum draft of a conventional cargo ship In particular, the column "Maximum unballasted cargo ship" shows values of the unballasted cargo ship where only the plotting depth of the ship has been modified and the lower body has a V-shaped strut (in 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 unballasted cargo ship as described herein ranges from 1.35-3 when the ship's plotting depth is substantially changed instead of the breadth, i.e. the draft is increased ship max. When the breadth is substantially modified and not the depth of the layout (reaching a maximum draft similar to that of a conventional ship, that is, a ship with a ballast system) the ratio (B/T) oscillates between 2-3. The particular value of the ratio (B/T) will depend on the difference in displacements of the ship due to different loading conditions and the particular geometry of the ship. Since you can change only the trace depth, or the beam, or both, you get a wide range [1.35-3] for the (B/T) ratio. Then, the design of the unballasted cargo ship can be defined to arrive at a solution in which the ratio (B/T) would be substantially equal to the values of this ratio for the conventional ship (for example, the standard cargo ship or the slow-moving cargo ship), with the depth of the layout and the width of the cargo ship without ballast being higher than the normal values for a conventional ship with similar characteristics. The values of Cb and Cm are not affected by the value of the ratio (B/T) since they are affected by the value of the product (BxT).

When comparing the values obtained for the unballasted cargo ship with the values obtained for conventional or standard ships, it can be seen how the draft and/or breadth of the unballasted cargo ship are greater. Therefore, the multiplication of beam and draft is greater than in conventional ships (which have ballast systems). The block coefficient and, therefore, the central section coefficient, is lower than in conventional ships.

In the present text, the term "comprising" and its derivatives (such as "comprising", etc.) should not be understood in an exclusive sense, that is, these terms should not be interpreted as excluding the possibility that what is meant describes and defines may include other elements, stages, etc. The term "other", as used herein, is defined as at least one second or more. The term "coupled", as used herein, is defined as connected, either directly without intermediate elements or indirectly with at least one intermediate element, unless otherwise indicated. Two elements can be mechanically, electrically or communicatively coupled through a channel, path, network or communication system.

The present invention, obviously, is not limited to the specific embodiments described herein, but also covers any variation that any person skilled in the art may consider (for example, regarding the choice of materials, dimensions, components, configuration etc.), within the general scope of the invention, as defined in the claims.

Claims (15)

1. An unballasted cargo ship (100), characterized in that the ship comprises: a hull having a longitudinal upper body (101) and a longitudinal lower body (102), the lower body (102) being located below the upper body (101), where the upper body (101) and the lower body (102) have a substantially rectangular cross section along the length of the helmet and where the lower body (102) is of smaller dimensions than the upper body (101); and at least one load space (110) arranged at least in correspondence with the upper body (10) to at least store the load and empty spaces (109) at least partially in correspondence with the lower body (102); wherein the lower body (102) comprises respective side walls (107) that join a bottom (111) of the upper body (101); and where 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 breadth (B ^max ) of the ship, a geometry of the ship is defined by: i ) a ratio (%B ^max ) between the width of a flat bottom and a maximum area of the waterplane of the ship ranging from 0 to 0.7, ii) a ratio (%T ^max ) between a submerged draft of the upper body and a maximum draft of the ship ranging from 0 to 0.8, and iii) a coefficient of center section (C ^m ) of the ship defined as:

which ranges from 0.65 to 0.85. The ship (100) according to claim 1, wherein the longitudinal lower body (102) comprises a flat bottom (108) located at a central portion of a hull bottom and along the length of the hull, and inclined wall portions (112) which are formed at the top of the side walls (107) by joining the bottom (111) of the upper body (101). The ship (100) according to any one of the preceding claims, wherein a block coefficient (C ^b ) of the ship is defined as:

and oscillates between 0.52 and 0.72, where %Amaxfloatadón is the ratio between an area of the bottom (108) flat of the lower body (102) and an area defined by a maximum waterline of the ship. 4. The ship (100) according to any one of the preceding claims, wherein, when the ship is at its minimum weight, the lower longitudinal body is at least partially submerged and, when the ship is at its maximum weight, the lower body Longitudinal lower body is fully submerged and longitudinal upper body is partially submerged. The ship (100) according to any one of the preceding claims, wherein at least one cargo space is a hold, and more preferably a box-type hold. The ship (100) according to any one of the preceding claims, wherein at least one cargo space has a width that substantially corresponds to the breadth of the ship along the length of the ship. The ship (100) according to any one of the preceding claims, wherein the minimum draft of the ship depends on a propulsion system of the ship. The ship (100) according to any one of the preceding claims, comprising two propellers. The ship (100) according to claim 8, comprising two propulsion engines such that when the ship is traveling at minimum draft, only one of the two propulsion engines is configured to power the two propellers, and when the ship travels with a draft greater than the minimum draft, each propulsion engine feeds a corresponding propeller of the two propellers. 10. The ship (100) according to any one of the preceding claims, wherein the hull comprises a trim trim system having at least two tanks fluidly connected to each other, wherein a fluid stored in the at least two tanks is carried between the at least two tanks to keep the ship stabilized. The vessel (100) according to any one of the preceding claims, wherein the upper body (101) and the lower body (102) have a substantially rectangular cross section along a length of at least one cargo space of the ship. The vessel (100) according to any one of the preceding claims, wherein the lower body (102) comprises rounded lower edges. 13. The ship (100) according to any one of the preceding claims, wherein the width of the lower body (102) varies along the length of the hull, being preferably wider in the vicinity of the stern (104 ) of the ship and narrower in the vicinity of the bow (103) of the ship. The ship (100) according to any one of the preceding claims, wherein a midsection of the ship comprises two bilges per side. The ship (100) according to any one of the preceding claims, wherein the side walls (107) of the lower body (102) are inclined with respect to the flat bottom (108) of the lower body (102).