Technical field of the invention

The present invention relates to a sea-going vessel in accordance with the preamble of claim 1 .

Background of the invention

Natural gas, or in general mixtures of hydrocarbons that are volatile enough to make the mixture appear in gaseous form in room temperature, constitutes an advantageous alternative to fuel oil as the fuel of internal combustion engines. In sea-going vessels that use natural gas as fuel, the natural gas is typically stored onboard in liquid form, giving rise to the commonly used acronym LNG (Liquefied Natural Gas). Natural gas can be kept in liquid form by maintaining its temperature below a boiling point, which is approximately -1 62 degrees centigrade. Natural gas can be also stored for use as fuel by keeping it com- pressed to a sufficiently high pressure, in which case the acronym CNG (Compressed Natural Gas) is used.

In vessels that can be operated using natural gas as a fuel, a second fuel system is usually needed for storing and using a second, liquid fuel. The second fuel can be, for instance, marine gas oil (MGO), which can be used as an al- ternative main fuel in a dual-fuel engine or as a pilot fuel when the engine is operated using natural gas as the main fuel. It is also possible that the auxiliary engines of the ship are operable only with liquid fuel. Separate tanks are needed for the different fuels, which makes the fuel systems often bulky and space-consuming. Also the shape of the cargo space of a cargo ship can be affected such that the whole cargo space is difficult to utilize.

Summary of the invention

The object of the present invention is to provide an improved sea-going vessel comprising one or more engines, at least one of the engines being operable using a first fuel and at least one of the engines being operable using a second fuel, the engine(s) being configured to receive the first fuel in liquid state and the second fuel in gaseous state or as a supercritical fluid, the vessel comprising at least two fuel tanks for storing the first fuel and at least one fuel tank for storing the second fuel. The invention is characterized by the characterizing part of claim 1 .

According to the invention, a first fuel tank for the first fuel is arranged on a first side of the vessel, a second fuel tank for the first fuel is arranged on a second side of the vessel, and a third fuel tank for the second fuel is arranged between the first fuel tank and the second fuel tank, the fuel tanks being separated by a transverse bulkhead from an engine room of the vessel.

One or more of the engines can be operable using selectively the first fuel and/or the second fuel, and/or the two different fuels can be used in different engines.

With the fuel tank arrangement according to the invention, the fuel tanks can be located space-efficiently within the hull of the vessel, and the rectangular cargo space can be maximized.

According to an embodiment of the invention, the fuel tanks are arranged on the front side of the engine room.

According to an embodiment of the invention, the vessel comprises a first bal- last tank that is arranged at least partly on the outboard side of the first fuel tank and a second ballast tank that is arranged at least partly on the outboard side of the second fuel tank. The ballast tanks can be separate tanks or joined together via a third ballast tank that is arranged above the keel of the vessel. The ballast tanks can be divided into compartments by transverse walls. With the ballast tanks located outwards from the fuel tanks for the first fuel, a triple- bulkhead is formed protecting effectively the fuel tanks for the second fuel.

According to an embodiment of the invention, the second fuel is liquefied natural gas.

According to an embodiment of the invention, the main engine of the vessel is a dual-fuel engine that can be operated using selectively the first fuel and/or the second fuel. According to an embodiment of the invention, the vessel comprises at least one additional tank for the second fuel, the additional tank being arranged between the first tank and the second tank. For instance, the vessel can comprise three tanks for the second fuel, all of the tanks being arranged between the tanks for the first fuel. All the fuel tanks for the second fuel can be arranged within a common tank hold.

According to an embodiment of the invention, each tank for the second fuel is provided with a gas-tight tank connection room enclosing tank connections and valves associated with them. The vessel can be, for instance, a cargo ship, such as a container ship.

Brief description of the drawings

Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which Fig. 1 shows schematically a top view of a deck of a sea-going vessel, and

Fig. 2 shows a cross-sectional side view of the vessel of Fig. 1 .

Description of embodiments of the invention

In figure 1 is shown a deck of a sea-going vessel according to an embodiment of the invention. Figure 2 shows a cross-sectional side view of the vessel of figure 1 . In the embodiment of the figures, the vessel is a cargo ship, which is configured to carry containers. However, the ship could also be another kind of a cargo ship or even a ship that is designed for another purpose than for carrying cargo. The ship is provided with a main deck 103 and with several decks 100, 101 , 102 that are arranged below the main deck 103 and with several decks 104, 105, 106 that are arranged above the main deck 103. The term 'main deck' refers here to the uppermost complete deck extending from bow to stern. The decks 104 to 106 above the main deck 103 form the superstructure of the ship. The ship is provided with a main engine 9, which produces propulsion for the ship, and with several auxiliary engines 1 1 a, 1 1 b, 1 1 c for producing electricity and/or for driving different equipment of the ship. The ship may also have more than one main engine 9. All the engines 9, 1 1 a, 1 1 b, 1 1 c are piston engines. The main engine 9 is connected to the propeller 18 of the ship via a propeller shaft 19. However, the main engine 9 could also be used for producing electricity for an electric motor driving the propeller 18. The main engine 9 is a two- stroke dual-fuel engine that can be operated using selectively either a first fuel or a second fuel. The first fuel is liquid fuel that is introduced into the engine 9 in liquid state. The first fuel can be, for instance, marine gas oil (MGO), marine diesel oil (MDO) or heavy fuel oil (HFO). The second fuel is gaseous fuel that is introduced into the engine in gaseous state or as a supercritical fluid. However, also the second fuel can be stored in liquid state. The second fuel is preferably natural gas. When the engine is operated using the second fuel as a main fuel, a liquid fuel can be used as a pilot fuel to ignite the main fuel. The pilot fuel is preferably the same fuel as the first fuel, but also a different kind of liquid fuel could be used. Also the auxiliary engines 1 1 a, 1 1 b, 1 1 c can be dual- fuel engines, which operate mainly by gas that is ignited by a pilot fuel injection. At least one of the auxiliary engines 1 1 a, 1 1 b, 1 1 c could also be a gas- engine, which is always operated on gaseous fuel that is spark ignited. The auxiliary engines 1 1 a, 1 1 b, 1 1 c are preferably four-stroke engines. It is also possible that the main engine 9 is configured only for operation on liquid fuel. In any case, at least one of the engines 9, 1 1 a, 1 1 b, 1 1 c of the ship is operable using a gaseous fuel as the main fuel, and at least one of the engines 9, 1 1 a, 1 1 b, 1 1 c is operable using a liquid fuel as the main fuel.

The main engine 9 and the auxiliary engines 1 1 a, 1 1 b, 1 1 c are arranged in an engine room 8. The main engine 9 and the auxiliary engines 1 1 a, 1 1 b, 1 1 c could also be arranged in different engine rooms. The engine room 8 is arranged inside the hull of the ship below the main deck 103. Due to the height of the main engine 9, the engine room 8 extends from a lower deck 100 to an upper deck 101 . The engine room 8 may extend over even more decks. The engine room 8 is located in the rear half of the ship, preferably in the rearmost third of the ship.

The ship is provided with at least two tanks for storing the first fuel, and with at least one tank for storing the second fuel. In the embodiment of the figures, the ship is provided with a first tank 1 and a second tank 2 for storing the first fuel. The first tank 1 is arranged on the port side of the ship and the second tank 2 is arranged on the starboard side of the ship. Each of the first tank 1 and the second tank 2 is further divided by a transverse wall into a first compartment 1 a, 2a and a second compartment 1 b, 2b. The first tank 1 and the second tank 2 are arranged below the main deck 103 of the ship.

In the embodiment of the figures, the ship is provided with three tanks 3, 4, 5 for the second fuel. Also the tanks 3, 4, 5 for the second fuel are arranged below the main deck 103 of the ship. The tanks 3, 4, 5 for the second fuel are arranged at least partly on the same deck(s) as the tanks 1 , 2 for the first fuel. Some or all of the tanks 1 , 2, 3, 4, 5 can extend over two or more decks of the ship. A third tank 3 is arranged on the longitudinal center line of the ship, a fourth tank 4 is arranged between the first tank 1 and the third tank 3, and a fifth tank 5 is arranged between the third tank 3 and the second tank 2. All the tanks for the second fuel are thus between the tanks 1 , 2 for the first fuel. The second fuel is liquefied natural gas (LNG), and therefore the tanks 3, 4, 5 are isolated for keeping the temperature of the fuel below the boiling point of natural gas, which is approximately -162 degrees centigrade. The fuel tanks 3, 4, 5 can have a double-wall structure with a vacuum or isolation material between the walls. Alternatively, the fuel tanks 3, 4, 5 can have a single-shell structure and isolation material arranged around the walls. All the fuel tanks 3, 4, 5 for the second fuel are arranged inside a tank hold 10, which is a room for accommodating the LNG tanks.

The tank hold 10 and the fuel tanks 1 , 2 for the first fuel are arranged adjacent to the engine room 8. In the embodiment of the figures, the fuel tanks 1 , 2, 3, 4, 5 are located on the front side of the engine room 8, i.e. towards the bow of the ship. All the fuel tanks 1 , 2, 3, 4, 5 of the ship are thus on the same side of the engine room 8. A transverse bulkhead 12 separates the tank hold 10 and the fuel tanks 1 , 2 for the first fuel from the engine room 8. The ship is provided with a cargo space 16. Part of the cargo space 16 is located on the front side of the tank hold 10. Part of the cargo space 16 is arranged above the tank hold 10. A transverse bulkhead is arranged on the front side of the fuel tanks 1 , 2, 3, 4, 5 for separating the tank hold 10 from the cargo space 16. Because of the fuel tank arrangement according to the invention, a large rectangular cargo space 16 is formed on the front side of the tanks 1 , 2, 3, 4, 5. Each fuel tank 3, 4, 5 for the second fuel is provided with a tank connection room 13, 14, 15. The tank connection room 13, 14, 15 is integrated with the fuel tank 3, 4, 5 and forms a gas-tight space in which the tank connections and valves associated with the tank connections are arranged. The purpose of the tank connection rooms 13, 14, 15 is to prevent a gas that may leak from the tank connections or the valves to enter the tank hold 10. The tank connection rooms 13, 14, 15 may also be separated from the fuel tanks 3, 4, 5, in which case the tank connection rooms 13, 14, 15 are connected to the fuel tanks 3, 4, 5 with double-wall pipes. The ship is further provided with ballast tanks 6, 7, 17 for receiving ballast water. A first ballast tank 6 is arranged on the port side of the ship and a second ballast tank 7 is arranged on the starboard side of the ship. A third ballast tank 17 is arranged above the keel of the ship forming a double-bottom structure. The third ballast tank 6 can connect the second ballast tank 7 to the first ballast tank 6. Each ballast tank 6, 7, 17 is divided into compartments by transverse walls. The ballast tanks 6, 7 on the sides of the ship form together with the first and the second tanks 1 , 2 a triple-bulkhead structure protecting the tanks 3, 4, 5 for the second fuel.

It will be appreciated by a person skilled in the art that the invention is not lim- ited to the embodiments described above, but may vary within the scope of the appended claims.