Note: Descriptions are shown in the official language in which they were submitted.
DESCRIPTION
MERCHANT SHIP CAPABLE OF SAILING IN FROZEN SEA AREA AND OPERATION
METHOD THEREOF
Technical Field
[0001]
The present invention relates to a merchant ship capable
of sailing in a frozen sea area and an operation method thereof.
Background Art
[0002]
In an area of the Arctic Ocean and sea areas adjacent thereto,
it is difficult for a merchant ship to sail particularly in the
winter season from October to March due to the influence of ice
or the influence of an excessively low temperature in view of
the structure or facility of the ship, safety in maneuvering
the ship, safety of a crew, and safety of cargo. Only a warship,
an observation ship, an ice breaker or the like having a special
structure adapted to frozen seas can sail in these sea areas.
[0003]
For example, even not in the Arctic Ocean area, in a sailing
in a coastal sea area of the Baltic Sea, the Saint Lawrence River,
an area of the Great Lakes, or a coastal sea area of Siberia
in the Japan Sea, a ship hull or a steering propeller may be
damaged by seas with floating ice and there is a risk of being
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locked of a ship in frozen seas under the influence of jammed
ice or frozen thin ice.
[0004]
Thus, the ice class is defined. Classes of PC1 to PC7
are indicated in IACS URI (Polar Class) , and Classes of IA Super,
IA, IB, IC, and II are indicated in FSICR (Finnish Swedish Ice
Class Rules) .
[0005]
In a merchant ship, a bulbous bow is formed to reduce a
wave-making resistance. For example, Patent Literature 1
describes a contrivance for a travel in frozen seas in this type
of ship including a bulbous bow.
Citation List
Patent Literature
[0006]
Patent Literature 1: WO 2015/092154 A
Summary of Invention
Technical Problem
[0007]
Although Patent Literature 1 discloses no unit for
obtaining a propulsion power for a ship, it is considered that
the ship is propelled only by a common main propeller.
[0008]
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On the other hand, in order to safely sail in an early-stage
frozen sea area, a normal sea area, a sea area with jammed floating
ice, or a sea area with floating ice blocks by a main propeller
and a diesel main engine for driving the main propeller in a
common merchant ship at present, an application range of the
diesel engine in the sailing area has to be excessively wide,
which reduces a total energy efficiency (increases fuel
consumption) and causes a problem in safety.
That is, in a common merchant ship, a capacity of a diesel
main engine which drives the main propeller is determined on
the assumption that the merchant ship sails at a relatively high
speed in an ice-free sea area. Further, it is assumed that the
merchant ship travels with an output of, for example, 85 to 90%MCR
of the capacity in the entire sailing course.
[0009]
In order to safely sail in a sea area with floating ice
or a sea area with floating ice blocks only by the main propeller
driven by the diesel main engine, it is necessary to operate
the ship with an output of, for example, approximately 20 to
30%MCR of the capacity of the diesel main engine.
As a result, the diesel main engine is inevitably
inefficiently used, which results in a critical problem for a
merchant ship aimed at increase in a total energy efficiency
(reduction in fuel consumption) .
Further, in a sea area with floating ice or a sea area
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with floating ice blocks, it is necessary to sail at a low sailing
speed. On the other hand, the main propeller is used on the
assumption that the ship sails at a relatively high speed.
Accordingly, if it is intended to sail in a sea area with floating
ice or a sea area with floating ice blocks only by the main
propeller, the main propeller is unsuitable for such a speed
adjustment in a wide range, which causes problems. Further, there
are many problems also in maneuvering the ship.
[0010]
In view of the above, it is a principal object of the present
invention to provide an operation method of a merchant ship that
is capable of safely sailing in a frozen sea area and has a high
total energy efficiency (low fuel consumption) without an energy
efficiency loss in a normal sea area.
Solution to Problem
[0011]
Representative modes of the present invention that has
solved the above problems are as follows.
[0012]
The present invention is directed at a merchant ship. The
present invention is applicable to a merchant ship, including
a general cargo ship, a container ship, an oil tanker, a chemical
tanker, an ore carrier, a coal ship, a liquefied natural gas
carrier, a liquefied petroleum gas carrier, a car carrier, or
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a bulk carrier.
[0013]
In an operation method of a merchant ship of the present
invention, the merchant ship comprises:
a bulbous bow which is provided in a bow part;
an additional propeller which is provided in a ship bottom
part, and
an additional-propeller-driving unit,
the method is characterized in that
a main propeller and the additional propeller are disposed
so as to apply thrust forces when the merchant ship is in an
unloaded state, and
when the merchant ship sails in a frozen sea area, the
merchant ship has a draft line with which a lower part of the
bulbous bow is located on a sea surface or an ice upper surface
and themerchant ship sails bymainly using at least the additional
propeller from the main propeller and the additional propeller.
The main propeller can also be used during breaking of
ice.
[0014]
When the ship sails at a high speed in a frozen sea area,
a ship hull may be damaged if the ship collides with ice. Thus,
a sailing at a low speed is required. When the main propeller
which is driven by a main engine is positively used for the sailing
at such a low speed, the main engine, which is usually selected
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on the assumption that the ship sails at a predetermined high
speed in a general sea area, is driven such that an output should
be suitable for the low speed. Thus, the energy efficiency is
low.
On the other hand, when the ship sails in a frozen sea
area using the additional propeller according to the present
invention, since the additional-propeller-driving unit has a
small size for the additional propeller, even the additional
propeller can be used enough for the sailing at the low speed,
which makes possible to operate the ship with a totally high
efficiency.
[0015]
An output of the additional-propeller-driving unit is,
for example, 15 to 45%MCR (MaximumContinuous Rating) , preferably
20 to 35%MCR of an output of the main engine.
In a general sea area (not a frozen sea area) , in order
to sail at a relatively high speed, for example, 15 to 19 knots,
the main propeller can be rotated to sail at an increased speed.
Thus, the main engine requires a large output.
On the other hand, it is necessary to sail at a low speed
in a frozen sea area (because the ship hull would be damaged
by collision with ice in a sailing at a high speed) . The sailing
speed is 5 knots or less, preferably 3 knots or less.
Therefore, it is preferable that the output of the
additional-propeller-driving-unit for driving the additional
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propeller for a sailing at a low speed is 15 to 45%MCR of the
output of the main engine.
In a frozen sea area, even in an unfrozen season (in the
season when the freezing-up begins or in the season when ice
is starting to melt) , the risk of collision with ice cannot be
completely eliminated. Thus, it is more preferred to drive the
additional propeller to sail at a low speed rather than to rotate
the main propeller.
[0016]
When the ship sails at a low speed mainly using the
additional propeller, the advantages of the present invention
become more apparent in a frozen sea area in the unfrozen season
or in the season when ice is melting (in the season when the
freezing-up begins (for "early-stage ice") or in the season when
ice is starting to melt) than in the season when the sea is frozen
over a wide area so that a sea route cannot be found or in the
season when the sea is covered with thick ice.
The "early-stage ice" described herein refers to ice that
does not exist over one winter season. The merchant ship of
the present invention is capable of safely sailing in a frozen
sea area with the "early-stage ice".
[0017]
Type of additional-propeller-driving unit includes an
electric type and a mechanical type, and the electric type is
preferred. A generator which generates power by driving of the
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main engine can be used. Electricity generated by an auxiliary
generator may be used as the driving unit.
The additional propeller is desirably a variable-pitch
propeller. The variable-pitch propeller has a significant
advantage in that the adjustable range of a rotational driving
force thereof is large, and continuous adjustment and fine
adjustment of the driving force are possible.
[0018]
There is proposed a mode in which the additional propeller
is disposed in the ship bottom part at a position on a front
side relative to the position of the main propeller and selectable
between a state of being assembled at the outside of the merchant
ship and a state of being retracted to the inside of the merchant
ship.
When the additional propeller is not used (e .g . , when the
ship sails in a general sea area) , since the additional propeller
in the state of being assembled at the outside of the ship acts
as a resistance, it is desired to retract the additional propeller =
to the inside of the ship.
[0019]
The merchant ship is propelled by mainly driving the main
propeller, in a loaded state in a season other than a frozen
season, or in a sailing in a general sea area.
[0020]
The additional propeller may be rotatable around a vertical
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shaft line. In driving of the additional propeller, the ship
maneuverability (directional property) can be improved by
appropriately rotating the additional propeller around the
vertical shaft line.
[0021]
The additional propeller may include a duct propeller.
When the duct propeller is used for the additional propeller,
it is possible to obtain a relatively large thrust even by the
small sized duct propeller.
[0022]
The lower part of the bulbous bowmay break ice and laterally
carry the broken ice away when the merchant ship sails in a frozen
sea area.
[0023]
A double bottom construction in a cargo part on a rear
side relative to a watertight collision bulkhead desirably
extends to the lower part of the bulbous bow which is located
on the front side relative to the collision bulkhead.
In a merchant ship, generally, although the rear side
relative to the watertight collision bulkhead has a double bottom
construction because the rear side receives a cargo load, the
front side relative to the collision bulkhead has no double bottom
construction. However, it is assumed that, in a sailing in a
frozen sea area, the merchant ship may collide with ice or run
onto ice . Thus, in order to add a strength for bearing the impact
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to the merchant ship, the double bottom construction in the cargo
part on the rear side relative to the collision bulkhead desirably
extends to the lower part of the bulbous bow located on the front
side relative to the collision bulkhead.
[0024]
An additional ballast tank may be disposed on the front
side relative to the watertight collision bulkhead, and ballast
water may be charged into the ballast tank to increase a weight
on a bow side during breaking of ice. After the merchant ship
runs onto ice, ballast water may be charged into the ballast
tank so that the ice can be broken by the weight. Accordingly,
it is possible to improve an ice-breaking capacity.
[0025]
An inner plate may be disposed above a bottom plate on
the front side relative to the watertight collision bulkhead
so that the lower part of the bulbous bow has a double bottom
construction. Further, another inner plate may be disposed
between the bottom plate and the inner plate to obtain a triple
bottom construction.
[0026]
In a structure in which a filler such as mortar is filled
inside the double bottom construction or the triple bottom
construction, for example, impact resistance when the ship
collides with ice is increased and bending resistance of the
shell when the ship runs onto ice is increased.
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[0027]
In an operation in an unloaded state, it is desired that
the draft line 18 be located at the sea surface position or the
position that contacts the ice upper surface in a frozen sea
area while being located below the uppermost (highest) inner
plate in the double bottom construction or the triple bottom
construction as illustrated in Fig. 1.
In this case, it is desired that a reinforcing filler such
as mortar be filled between the uppermost (highest) inner plate
and the bottom plate in the double bottom construction or the
triple bottom construction. For the purpose of reinforcement,
the filler is preferably filled in contact with at least the
bottom plate.
The merchant ship having the double bottom construction,
or the triple bottom construction as described above desirably
sails in a state in which the draft line in an unloaded state
is located on the lower part of the bulbous bow, that is, on
the front side relative to the collision bulkhead and also located
below the uppermost (highest) inner plate in the double bottom
construction or the triple bottom construction. The reason
thereof is as follows.
[0028]
First, the lower part of the bulbous bow is reinforced
with the inner plate which forms the double bottom construction
or the triple bottom construction. Thus, damage of the ship
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shell which would be caused by collision with ice is prevented.
Second, even if the bottom plate is damaged by collision
with ice, the collision bulkhead having an extremely high
strength is not damaged. Thus, there is no influence on cargo
because of no water intrusion, and a sailing can be continued.
Third, when the reinforcing filler such as mortar is filled
between the uppermost inner plate and the bottom plate in the
double bottom construction or the triple bottom construction,
the strength of the lower part of the bulbous bow is increased
by the existence of the inner plate and the filler. Thus, it
is possible to reduce the risk of damage caused by collision
with ice.
In the mode in which the reinforcing filler such as mortar
is filled, it is optimal that the draft line be located on the
front side relative to the collision bulkhead in an operation
in a frozen sea area from the above point of view.
[0029]
Further, according to the present invention, it is possible
to provide a merchant ship comprising
a bulbous bow which is provided in a bow part;
a main propeller which is provided in a stern part and
driven by a main engine;
an additional propeller which is provided in a bottom part;
and
an additional-propeller-driving unit,
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the merchant ship being characterized in that
the main propeller and the additional propeller are
disposed so as to apply thrust forces when the merchant ship
is in an unloaded state,
a cargo part has a double bottom construction in which
an inner bottom plate is provided inside relative to a bottom
plate,
at the front side relative to a collision bulkhead, an
inner plate of the bow part is provided so as to be located in
a position of the inner bottom plate of the double bottom
construction in the cargo part,
a ballast tank is formed above the inner plate of the bow
part, and
a reinforcing filler is filled, in contact with at least
the bottom plate, between the inner plate and the bottom plate
of the bulbous bow.
Advantageous Effects of Invention
[0030]
As described above, according to the present invention,
it is possible to operate a merchant ship with a high sailing
energy efficiency in a frozen sea area.
Brief Description of Drawings
[0031]
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Fig. 1 is a front view of the entire example of a merchant
ship also illustrating a draft line during a sailing in a frozen
sea area.
Fig. 2 is a schematic view of an additional propeller and
an additional-propeller-driving unit thereof.
Fig. 3 is a cross-sectional view of the merchant ship.
Fig. 4 is a longitudinal-sectional view illustrating a
bulbous bow.
Fig. 5 is a view on arrow 5-5
Fig. 6 is a view on arrow 6-6.
Fig. 7 is a plan view of the bottom of the bulbous bow.
Fig. 8 is a longitudinal-sectional view illustrating
another filling mode of a filler.
Fig. 9 is a schematic view of another additional propeller
arrangement mode.
Fig. 10 is a front view of the entire example of the merchant
ship also illustrating a draft line during a loaded sailing in
a general sea area.
Fig. 11 is a front view of the entire example of the merchant
ship also illustrating a draft line during an unloaded sailing
in a general sea area.
Description of Embodiments
[0032]
Hereinbelow, an embodiment of the present invention will
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be described in detail with reference to the accompanying
drawings.
[0033]
Fig. 1 is a schematic front view of a ship according to
the present embodiment, for example, a merchant ship 10 intended
for loading such as a cargo ship (the example of Fig. 1 illustrates
an ore carrier) . The merchant ship 10 obtains a propulsion power
by driving a main propeller 11 by a main engine 12 such as a
diesel engine.
[0034]
The merchant ship 10 includes a bulbous bow 13 for reducing
a wave-making resistance in a bow part thereof. A known example
can be employed as the shape of the bulbous bow 13.
The illustrated merchant ship 10 is a cargo ship which
includes a cargo compartment for cargo R. In the illustrated
example, the merchant ship 10 includes five cargo compartments.
The cargo compartments are partitioned from each other by
transverse bulkheads 14 in a ship length direction. The foremost
cargo compartment is partitioned by a collision bulkhead
(watertight bulkhead) 15F. The rearmost cargo compartment is
partitioned by an afterpeak bulkhead (watertight bulkhead) 15B.
Further, the merchant ship 10 is provided with a bridge
16 and a rudder 17 on the stern side.
[0035]
Fig. 1 illustrates a draft line 18 for a sailing in an
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=
present embodiment, for example, a merchant ship 10 intended for
loading such as a cargo ship (the example of Fig. 1 illustrates
an ore carrier) . The merchant ship 10 obtains a propulsion power
by driving a main propeller 11 by a main engine 12 such as a diesel
engine.
[0034]
The merchant ship 10 includes a bulbous bow 13 for reducing
a wave-making resistance in a bow part thereof. A known example
can be employed as the shape of the bulbous bow 13.
The illustrated merchant ship 10 is a cargo ship which
includes a cargo compartment for cargo R. In the illustrated
example, the merchant ship 10 includes five cargo compartments.
The cargo compartments are partitioned from each other by transverse
bulkheads 14 in a ship length direction. The foremost cargo
compartment is partitioned by a collision bulkhead (watertight
bulkhead) 15F. The rearmost cargo compartment is partitioned by
an afterpeak bulkhead (watertight bulkhead) 15B.
Further, the merchant ship 10 is provided with a bridge 16
and a rudder 17 on the stern side.
[0035]
Fig. 1 illustrates a draft line 18 for a sailing in an unloaded
state in a frozen sea area. Fig. 1 illustrates a state of "trim
by the stern" in which the draft line 18 is shallow in the bow
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direction and deep in the stern part.
As illustrated in Fig. 10, a draft line 18A in a loaded state
is deep.
As illustrated in Fig. 11, a normal draft line, in a case
where ballast water is put in right and left ballast tanks BT in
an unloaded state in an unfrozen sea area, is located at, for example,
the position of 18B.
[0036]
As illustrated also in Fig. 2, the ship is provided with
an additional propeller 20 and an additional-propeller-driving
unit 22. For example, a duct propeller 21, which is provided with
a propeller inside a duct 21A, can be used for the additional
propeller 20.
The additional propeller 20 is disposed at a position
different from the position of the main propeller 11 in a ship
bottom part.
In this case, the additional propeller 20 is desirably
disposed at a stern side position relative to the middle. However,
as illustrated in Fig. 9, an additional propeller 20Amay be disposed
at a bow side position relative to the middle. In this case,
although the additional propeller 20A may be installed in addition
to the additional propeller 20 disposed at the stern side position,
only the additional propeller 20A may be installed at the bow side
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position relative to the middle.
[0037]
An output of the additional-propeller-driving unit 22 for
the additional propeller 20 is desirably 15 to 45%MCR, more
preferably 20 to 35%MCR of an output of a driving unit for the
main engine 12.
A designed operating state in which the main propeller 11
is driven to obtain the propulsion power, a driving state in which
the additional propeller 20 is driven to obtain the propulsion
power, and a driving state in which the main propeller 11 and the
additional propeller 20 are both driven to, for example, run onto
ice are selectable.
[0038]
An electric motor or a hydraulic motor may be used as the
additional-propeller-driving unit 22. In addition, when
necessary, the additional-propeller-driving unit 22 may be
electrically coupled to the main engine 12 to obtain a driving
force.
In particular, it is optimal that a generator be driven by
the main engine 12 to rotate an electric motor to rotate the main
propeller and the additional propeller 20.
[0039]
In the illustrated example, a rotational driving force of
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an output shaft 23 by the driving unit 22 is transmitted to a vertical
shaft 25 through a pair of bevel gears 24 and transmitted as a
rotating force for a propeller drive shaft 27 through a pair of
bevel gears 26 which is disposed on the vertical shaft 25 to rotate
the duct propeller 21 which is provided with the duct 21A around
the propeller.
On the other hand, a rotational driving force of a
transmission shaft 28 by the driving unit 22 is transmitted to
a drive pinion 29 and a gear wheel 30 which meshes with the drive
pinion 29 so as to rotate the duct propeller 21 around the vertical
shaft 25.
[0040]
As illustrated in Fig. 2, a device including the duct
propeller 21 below a bottom plate 10A is in a state of being assembled
at the outside of the bottom plate 10A, which becomes an obstacle
in a normal sailing. Thus, the device is preferably configured
to be retractable to the inside of the ship. The merchant ship
includes a shielding member 10a that shuts after the device
is retracted to the inside of the ship.
[0041]
As illustrated in Fig. 10, the merchant ship 10 having the
above ship structure is operated in a draft state close to a designed
full load draft by driving the main propeller 11 by the main engine
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..
12 in a sailing in a general sea area (an unfrozen sea area) or
in an unfrozen season when loaded with the cargo R.
[0042]
After the merchant ship 10 passes an area of the Arctic Ocean
and a sea areas adjacent thereto, calls at a port, and unloads
the cargo, there is little need to excessively strictly make the
ship stable during a sailing, in particular, on a calm weather
day or in calm seas. Thus, in a manner similar to the case of
Fig. 1, the merchant ship 10 is caused to travel by the additional
propeller 20 having a small size with a lowered draft line. In
this case, a traveling direction of the merchant ship 10 can be
appropriately selected. The bow and the stern of the ship are
monitored in the bridge 16 according to the traveling direction
of the ship. For example, in addition to traveling in the bow
direction as illustrated in Fig. 1, the merchant ship 10 can travel
in the stern direction as illustrated in Fig. 9. Further, in Fig.
9, the small sized additional propeller 20A is disposed on the
bow side relative to the middle of the ship hull.
[0043]
An apparent displacement is reduced by lowering the draft
line, which reduces a contact area between the outer plate and
water. Thus, it is possible to improve a waterplane area
coefficient and increase an effect of reducing fuel consumption.
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.µ
,
Further, since the small sized additional propeller 20 is
driven, a low output of the additional-propeller-driving unit 22
is enough. Thus, the merchant ship 10 can sail with an output
of approximately 15 to 45%MCR of the output of the driving unit
for the main engine 12 . Also, from this point of view, it is possible
to increase the effect of reducing fuel consumption. A traveling
speed of approximately 5 to 10 knots is enough on a calm weather
day (a day with 0 to 3 in the Beaufort scale) .
[0044]
When the merchant ship 10 leaves a port after fully loaded
with the cargo R and shifts to a normal sailing, the main propeller
11 is driven or additionally used so that the merchant ship 10
sails with a deep draft.
When the weather is bad, even in the merchant ship 10 without
cargo, for example, ballast water is put in the ballast tanks BT
which are disposed on right and left of the cargo compartment of
Fig. 3 so that the merchant ship 10 has, for example, the draft
line 185 illustrated in Fig. 11. Accordingly, it is possible to
cause the merchant ship 10 to travel by the small sized additional
propeller 20 or the main propeller 11 in a stabilized state.
[0045]
When the duct propeller 21 is rotatable around a vertical
shaft line, it is possible to propel the merchant ship 10 also
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.,
,
in the stern direction by driving the duct propeller 21 according
to a required driving state.
[0046]
When the duct propeller 21 is rotatable around the vertical
shaft 25 (vertical shaft line) , in driving by a combined use of
the additional propeller and the main propeller, it is possible
to add a steering function to improve amaneuverability (directional
property) by appropriately rotating the additional propeller
around the vertical shaft line. Further, the duct propeller 21
can be oriented sideways so as to be utilized as a side thruster
when the merchant ship 10 is docked at a port.
[0047]
A propulsive direction by the duct propeller 21 may be set
to the bow direction. Thus, the main propeller 11 may be provided
with a propeller idling prevention device 11A for preventing the
main propeller 11 from rotating.
[0048]
When necessary, the duct propeller 21 may be disposed on
each of right and left of a center line of the ship. The
maneuverability can be improved by rotations of the right and left
duct propellers 21, 21 around the respective vertical shaft line
thereof. Further, when the right and left duct propellers 21,
21 are used as side thrusters, it is easier for the merchant ship
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.µ
to dock at the port.
[0049]
The present invention enables the merchant ship 10 to sail
also in a frozen sea area.
Thus, various measures are taken.
[0050]
Desirably, one of the measures is that a double bottom
construction, which includes the bottom plate 10A and an inner
bottom plate 10B disposed on the inner side of the bottom plate
10A in a cargo part located on the rear side relative to the watertight
collision bulkhead 15F, extends to a lower part of the bulbous
bow 13 in front so that the bulbous bow 13 has a double bottom
construction, which includes the bottom plate 10A and an inner
plate 10C.
In a conventional merchant ship 10, although the rear side
relative to the watertight collision bulkhead 15F has a double
bottom construction because the rear side receives a cargo load,
the front side relative to the collision bulkhead 15F has no double
bottom construction.
However, it is assumed that, in a sailing in a frozen sea
area, the merchant ship 10 may collide with ice or run onto ice.
Thus, in order to add a strength for bearing the impact to the
merchant ship 10, the double bottom construction in the cargo part
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on the rear side relative to the collision bulkhead 15F desirably
extends to the lower part of the bulbous bow 13 in front.
[0051]
An additional ballast tank 38 for charging and discharging
ballast water, which is made of, for example, FRP, may be disposed
on the front side relative to the watertight collision bulkhead
15F. After the merchant ship 10 runs onto ice when breaking the
ice, ballast water can be charged into the ballast tank 38 to increase
the weight on the bow side to break the ice. Accordingly, it is
possible to improve an ice-breaking capacity.
In the illustrated example, the ballast tank 38 is disposed
above the inner plate 10C. A ballast tank 39 may be further disposed
above the ballast tank 38 as needed.
[0052]
In the embodiment, the inner plate 10C is provided for
reinforcement. In order to prepare for a water intrusion accident
through the bottom plate 10A and obtain a higher strength, a
reinforcing horizontal partition plate 10D may be disposed between
the inner plate 10C and the bottom plate 10A to obtain a triple
bottom construction.
[0053]
Further, a structure in which a filler 32 such as mortar
is filled under the ice-breaking tank 38 (refer to Figs. 4 and
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.,
8) may be employed. The structure in which the filler 32 such
as mortar is filled under the ballast tank increases, for example,
impact resistance when the merchant ship 10 collides with ice or
impact resistance when the merchant ship 10 runs onto ice.
[0054]
The filler 32 may be filled at any position above the bottom
plate 10A. In addition to the position between the bottom plate
10A and the reinforcing horizontal partition plate 10D in the
illustrated example, the filler 32 may be further filled up to
the inner plate 100 as illustrated in Fig. 8. Further, the filler
32 may be filled up to a position above the inner plate 100 as
illustrated in Fig. 8.
The filling of the filler 32 increases not only the impact
resistance of the bottom plate 10A, but also the ice-breaking
capacity due to the weight of the filler 32 itself.
Instead of mortar, another filler that makes direct contact
with the bottom plate 10A and covers the bottom plate 10A may also
be used as the filler 32. Examples of the filler include various
inorganic fillers, a metal filler such as a casting, a plastic
filler, and a combination thereof.
[0055]
When the merchant ship 10 sails in a frozen sea area or sea
areas adjacent thereto, it is also necessary to increase the
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strength of the front face side of the bulbous bow 13 due to a
possibility of an unexpected collision with ice in addition to
increasing the strength of the lower part of the bulbous bow 13.
Thus, as illustrated, it is desirable to additionally provide
bottom transverses 33T, bottom lounges 33L, longitudinal frames
34, panting stringers 35, vertical frames 36, and breast hooks
37 which horizontally and vertically connect the bottom plate 10A
and the inner plate 100.
Industrial Applicability
[0056]
According to the present invention, as a merchant ship,
including a general cargo ship, a container ship, an oil tanker,
a chemical tanker, an ore carrier, a coal ship, a liquefied natural
gas carrier, a liquefied petroleum gas carrier, a car carrier,
or a bulk carrier, can stably sail not only in a general sea area,
but also in a frozen sea area or in a frozen sea area in an unfrozen
season. As a result, the ship can sail not in a roundabout way
for avoiding ice, but in the shortest course. Thus, an economic
value thereof is extremely high.
For example, the ship can sail between the North Pacific
Ocean and the North Atlantic Ocean through the Arctic Ocean. In
particular, enabling the ship to pass through the Arctic Ocean
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in which the frozen area tends to decrease with global warming
in recent years produces a large economic effect.
Reference Signs List
[0057]
ship
10A bottom plate
10B inner bottom plate
10C inner plate
10D reinforcing horizontal partition plate
11 main propeller
12 main engine
additional propeller
21 duct propeller
22 additional-propeller-driving unit
32 filler
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