This invention relates to a marine vessel having a propulsion system powered by a gaseous fuel.

The term "gaseous fuel" as used herein refers to compressed gas fuel such as compressed natural gas (CNG) and hydrogen (H ₂ ), and liquefied gaseous fuel such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG).

The invention has, however, been devised particularly, although not necessarily solely, as a marine vessel such as a ferry having engines powered by LNG

Background Art

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

LNG is a naturally-occurring and predominantly methane gas that has been converted into liquid form for ease of transportation. One method of transportation concerns the use of ships with specially-designed insulated tanks in order to keep the gas at low temperatures and hence in liquid form.

These ships, or LNG carriers, have evolved since the first one was constructed in 1960 through a variety of containment systems, but the vast majority of them carry LNG in insulated tanks at a temperature that is low enough to remain liquid. The tanks are generally not pressurised. Some gas vapour will boil off within the tanks, and as this occurs the change in phase from liquid to gas will absorb energy from the remainder of the liquid and cools it. Only a small amount of boil- off will maintain the necessary low temperature.

LNG carriers have also evolved to utilise the excess boil-off gas to augment the fuel for the propulsion system, and in some cases to operate entirely on the boil- off gas. More recently some ship designs have come into service where the engines run directly off LNG stored in tanks which are pressurised by a small amount above atmospheric in order to feed the engines without excessive pumping.

As LNG has become more readily available, at least in some countries, and because of the relatively lower cost of LNG as a fuel compared to marine-grade diesel oil, it has recently become attractive to design small craft such as passenger-carrying ferries to operate on LNG.

The Glutra is an example of a 95-metre long passenger and vehicular ferry that was built in 2000 and is primarily operated on LNG. It is one of several such ferries now operating in Norway, where LNG is available through a network of road tankers and pipelines.

One of the prime concerns in the operation of a vessel carrying gaseous fuels is that of safety.

The International Rules for the Safety of Life at Sea (SOLAS) do not permit ships to use fuels with a flashpoint of below 60°C, although where adequate precautions are in place, a lower minimum flashpoint of 43°C may be accepted. However, LNG has a flashpoint of -190°C, and it is perhaps obvious that LNG can only be used as a fuel where strict regulations are enforced and the system is designed to be intrinsically safe. An example would be that all fuel is transmitted within the ship within double walled pipes.

LNG may be conceived as a dangerous substance, but nevertheless methane gas will only ignite if the ratio of gas and air is within a relatively small ratio band (between 5% and 15%). LNG itself will not burn or ignite, rather it is only the gaseous form mixed with air within the above ratios that will ignite in the presence of an ignition source.

There are other dangers with LNG not related to fire and explosion, such as the ability to asphyxiate due to a lack of oxygen. LNG is generally odourless. It is also extremely cold which would be a hazard for anyone coming into contact with it.

LNG floats on water and will evaporate very rapidly in this situation in a very agitated state. This can cause a flammable or an explosive mixture, although this would also require a heat source for ignition to occur.

Despite the perceived dangers, LNG is an attractive fuel for propulsive power for small ferries, and will no doubt extend its attractiveness to larger sizes of vessel as environmental regulations covering exhaust emissions progressively come into force.

As noted above, LNG does not meet the standard SOLAS requirements for ships, and special regulations have evolved covering the design of LNG carriers. Typically this is done by double-walled containment systems, with inert gas contained in between, and extended to double-hulled ships with containment systems to prevent accidental spillage overboard. Extensive fire-detection and fire-fighting requirements are standard. Recognising that LNG powered ships are evolving through demand for a less- expensive and more environmentally-friendly fuel, new safety guidelines are currently under discussion at IMO for the design and operation of ships powered by LNG. It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed.

In particular, the present invention seeks to provide a marine vessel capable of carrying a gaseous fuel such as LNG in an intrinsically safe manner.

Disclosure of the Invention

It is an object of the present invention to overcome, or at least ameliorate, one or more of the deficiencies of the prior art mentioned above, or to provide the consumer with a useful or commercial choice.

Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, a preferred embodiment of the present invention is disclosed.

According to a first broad aspect of the present invention there is provided a marine vessel comprising at least two hulls and a portion disposed between the two hulls, a propulsion system operable using a gaseous fuel, and storage means for containing a supply of gaseous fuel for the propulsion system, the storage means being accommodated in said portion between the two hulls. With this arrangement, the storage means is disposed between and isolated from the two hulls, which is beneficial in terms of safety.

In one arrangement, the vessel may comprise two hulls only; that is, the vessel may be configured as a catamaran.

In another arrangement, the vessel may comprise a main hull and a plurality of side hulls at least one of which is to each side of the main hull, wherein the two hulls are each defined by a respective one of the side hulls.

With such an arrangement, the marine vessel typically comprises the main hull and two side hulls, one of which is to each side of the main hull; that is, the vessel is configured as a trimaran. Other vessel configurations are, of course possible, such as for example a pentamaran.

Preferably, the main hull comprises said portion between the two hulls.

Preferably, the storage means is so disposed within the main hull relative to the side hulls so that the side hulls afford side impact protection to the storage means. Preferably, the propulsion system comprises an engine in each of the two hulls operable using gaseous fuel received from the storage means. Other arrangements are, of course, possible; for example, the propulsion system may be located entirely in the after part of the main hull.

The arrangement in which the propulsion system comprises an engine in each side hull with the storage means in the main hull is advantageous, as the storage means in the main hull is isolated from the engines in the side hulls. The engines may be configured to use more than one fuel type, including a liquid fuel in addition to the gaseous fuel, or combinations of gaseous and liquid fuels.

The engines may comprise diesel engines configured for operation using gaseous fuel or a combination of gaseous and liquid fuels.

In one arrangement, the diesel engines may transmit mechanical energy through drive transmission systems to deliver rotational power to propulsion devices. In another arrangement, diesel engines may drive electric generators for powering electric motors for driving propulsion devices.

The propulsion devices may take any appropriate form, including propellers, propulsors, water jet drives and right-angle drive units.

The storage means may comprise one or more reservoirs installed within the confines of the main hull. The reservoir, or each reservoir, may be configured as a cylindrical tank.

Preferably, the storage means is accommodated in a zone isolated from areas within the vessel designed to accommodate personnel, passengers and/or cargo. In particular, the zone containing the storage means preferably does not contain any crew or cargo spaces.

Preferably, the main hull incorporates a deck, and the storage means is accommodated in a zone below the deck. With this arrangement, the storage means is isolated from the deck. Passengers, their vehicles, and other cargo, are typically carried on or above the deck and so are also isolated from the storage means. Preferably, the main hull is configured to provide a substantial length of structure forward of the storage means.

This forward structure section is preferably devoid of any essential systems or cargo and preferably presents a readily deformable section in case of collision with a solid object such as a wharf or other ship without affecting the storage means. Such an arrangement is particularly suitable for a hull designed in aluminium, which is an easily deformed material but relatively strong, and would decelerate the vessel in such a way that the storage means and its associated systems would be protected from damage.

This main hull configuration is preferably provided by a hull that is long and slender. Such a configuration presents a hull shape with a minimum of drag and hence a low fuel consumption. The long and slender hull would also provide a substantial length of structure forward of the storage means.

The presence of the side hulls provides sufficient stability to allow the main hull to be designed to be extremely long and slender.

Because of the presence of the side hulls, the storage means is substantially protected from damage resulting from collision by another vessel striking the side of the vessel.

Aluminium is a particularly suitable material for construction of the main and side hulls, as it does not suffer from loss of strength at extremely low temperatures, such as may occur in case of gas leakage from the storage means. The phenomenon, known as brittle fracture, has led to the loss of steel containment vessels, and also substantial damage to steel-hulled LNG carriers. The hull structure accommodating the storage means may be configured to provide a secondary containment system in case of leakage of gaseous fuel from the storage means.

According to a second broad aspect of the present invention there is provided a marine vessel comprising a main hull and a plurality of side hulls at least one of which is to each side of the main hull, a propulsion system operable using a gaseous fuel, and storage means for containing a supply of gaseous fuel for the propulsion system, the storage means being accommodated in the main hull.

According to a third broad aspect of the present invention there is provided a marine vessel comprising a hull having a forward section and an aftermost section, a propulsion system operable using a gaseous fuel, and storage means for containing a supply of gaseous fuel for the propulsion system, the storage means being accommodated in the aftermost section of the hull, and the forward section of the hull being deformable upon a significant impact in a collision.

Preferably, the aftermost section comprises the aftermost 50% of the hull.

Typically, the forward section is devoid of any essential systems or cargo.

According to a fourth broad aspect of the present invention there is provided a marine vessel comprising a hull, a propulsion system operable using a gaseous fuel, and storage means for containing a supply of gaseous fuel for the propulsion system, the storage means being accommodated in the hull at a location spaced rearwardly from the bow thereof to define a forward section, the forward section providing a forward deformable region between the storage means and the bow. Preferably, the hull is constructed of aluminium to provide the deformable characteristic of the forward deformable region.

Preferably, the forward section is devoid of any essential systems or facility for holding cargo.

According to a fifth broad aspect of the present invention there is provided a marine vessel comprising a main hull and two side hulls one of which is to each side of the main hull, a propulsion system operable using a gaseous fuel, and storage means for containing a supply of gaseous fuel, the storage means being accommodated in the main hull, the propulsion system comprising an engine in each side hull operable using gaseous fuel received from the storage means, the storage means being so disposed within the main hull that it is between the side hulls.

According to a sixth broad aspect of the present invention there is provided a marine vessel comprising at least two hulls and a portion disposed between the two hulls, a propulsion system operable using a gaseous fuel, and storage means for containing a supply of gaseous fuel for the propulsion system, the storage means being accommodated in said portion between the two hulls, said portion being constructed of aluminium and being configured to provide a secondary containment system in case of leakage of gaseous fuel from the storage means.

Brief Description of the Drawings

The invention will be better understood by reference to the following description of several specific preferred embodiments thereof as shown in the accompanying drawings in which: Figure 1 is a schematic plan view of a multi-hulled vessel according to the first preferred embodiment configured as a trimaran having a main hull and two side hulls;

Figure 2 is a schematic side view of the vessel;

Figure 3 is schematic rear view of the vessel;

Figure 4 is a schematic plan view of a multi-hulled vessel according to the second preferred embodiment configured as a trimaran having an alternative layout with its propulsion devices and engines located in the central main hull; and

Figure 5 is a schematic rear view of a multi-hulled vessel according to the second embodiment configured as a catamaran.

Best Mode(s) for Carrying Out the Invention

The first embodiment, which is shown in Figures 1 to 3 of the drawings, is directed to a multi-hulled vessel configured as a trimaran. The trimaran according to the embodiment is a high speed, commercial, sea-going vessel operating as a ferry for passenger, and cargo transport, including in particular vehicle transport. The trimaran may also have military applications.

The trimaran comprises an understructure comprising an inner portion 1 configured as a centrally located main hull, and two laterally spaced side hulls 2, commonly known as amahs. The trimaran also usually comprises a superstructure above. A propulsion system is provided for delivering propulsive power to the trimaran. The propulsion system is operable using a liquefied gaseous fuel, which in this embodiment comprises LNG.

The propulsion system comprises a storage means 3 for a supply of LNG and engines 4 adapted to be fuelled by LNG. The engines 4 supply power to one or more propeller units 5.

The storage means 3 is accommodated in the main hull 1, and the engines 4 are accommodated in the side hulls 2.

With this arrangement, the storage means 3 is isolated from the engines 4, which is beneficial in terms of safety. Additionally, the storage means 3 is disposed between, and isolated from, the side hulls 2, which again is beneficial in terms of safety. More particularly, the storage means 3 is so disposed within the main hull 1 relative to the side hulls 2 that the side hulls 2 afford side impact protection to the storage means 3.

The main hull 1 , which accommodates the storage means 3, may be configured to provide a secondary containment system in case of leakage of gaseous fuel from the storage means 3.

In the arrangement shown, the storage means 3 comprises a reservoir configured as a cylindrical tank. Additionally, in the arrangement shown, there are four engines 4, two in each side hull 2. Other arrangements are, of course, possible; for example, the storage means 3 may comprise a plurality of tanks, and there may be any appropriate number of engines 4 in each side hull 2. In this embodiment, the engines 4 comprise diesel engines configured for operation using LNG as a fuel, although other suitable types of engines may be used, including gas turbines. The engines 4 may be configured to use more than one fuel type, including a liquid fuel in addition to LNG, or a combination of LNG and liquid fuel.

The trimaran also comprises a main deck 10 above which are various areas, including a vehicle garage 7, passenger cabins 8, and a crew navigational space or wheelhouse 9 at various levels. Other arrangements are, of course, possible.

With this arrangement, the storage means 3 is accommodated in a zone below the deck 10, thereby isolating the stored LNG from the deck 10 and areas above the deck, including the vehicle garage 7, the passenger cabins 8, and the crew navigational space or wheelhouse 9. In this way, the storage means 3 is isolated from areas within the trimaran designed to accommodate personnel, passengers and cargo. In particular, the zone below the deck 10 in which the storage means 3 is accommodated does not contain any crew or cargo spaces.

The main hull 1 is configured to be long and slender, thereby providing a substantial length of structure forward of the storage means 3, as best seen in Figure 1. This main hull configuration presents a hull shape with a minimum of drag and hence a low fuel consumption. This forward structure is also devoid of any cargo or essential systems below main deck, and presents a readily deformable section adapted to deform upon a significant impact without affecting the storage mean 3. Such an impact might typically arise as a result of a collision with a solid object, such as a wharf or other ship. The deformable forward section thus affords some protection to the storage means 3 in a collision. In this embodiment, the main hull 1 in the forward 50% of its length is substantially empty and contains no cargo or crew spaces, nor essential safety systems, and the storage means 3 is accommodated in the aftermost 50% in the main hull 1. The presence of the side hulls 2 provides sufficient stability to allow the main hull 1 to be designed to be extremely long and slender, as described.

Because of the presence of the side hulls 2, the storage means 3 is substantially protected from damage resulting from collision by another vessel striking the side of the vessel.

In this embodiment, the understructure comprising the centrally located main hull 1 and the two laterally spaced side hulls 2 may be constructed of aluminium. This is particularly advantageous because aluminium, which is an easily deformed material but relatively strong, can crumple during a significant impact to thereby decelerate the trimaran in such a way that the storage means 3 and its associated systems would be protected from damage. Other construction materials could also be used to achieve this, and should not be assumed that the main hull 1 and the two laterally spaced side hulls 2 are limited to being constructed from aluminium.

The second preferred embodiment shown in Figure 4 of the drawings is directed to a multi-hulled vessel configured as a trimaran. The trimaran has its engines 4 and propellers 5 situated in the central main hull 1 together with its storage means 3. In this instance the engines 4 are shown aft of the storage means 3 but an arrangement could also be conceived with the engines 4 forward of the storage means 3. This arrangement could reduce the length of the vessel forward of the storage means 3 to less than 50% of the waterline length, and would also allow for a substantial distance between the bow and the storage means 3. For this arrangement where engines 4, propulsion 5 and storage 3 occupy the same hull it is most likely that part of the storage 3 could be within the aftmost 50% of the waterline length and wholly within 75% of the waterline length. The third preferred embodiment, which is shown in Figure 5 of the drawings, is directed to a multi-hulled vessel configured as a catamaran. The multi-hulled vessel according to the third preferred embodiment is similar in many respects to the multi-hulled vessel according to the first preferred embodiment and so similar reference numerals are used to identify similar parts.

The catamaran comprises the understructure comprising the inner portion 1 which is centrally located, and two laterally spaced hulls 2. In this second preferred embodiment, the inner portion 1 is not configured as a hull as was the case with the first embodiment. The inner portion 1 is, however, configured to accommodate the storage means 3, with the engines 4 being accommodated in the side hulls 2.

With this arrangement, the storage means 3 is isolated from the engines 4, which is beneficial in terms of safety. Additionally, the storage means 3 is disposed between, and isolated from, the two hulls 2, which again is beneficial in terms of safety.

Further, the storage means 3 is accommodated in a zone below the deck 10, thereby isolating the stored LNG from the deck 10 and areas above the deck, including the vehicle garage 7 and the passenger cabins 8. In this way, the storage means 3 is isolated from areas within the catamaran designed to accommodate personnel, passengers and cargo. In particular, the zone below the deck 10 in which the storage means 3 is accommodated does not contain any crew or cargo spaces.

From the foregoing, it is evident that at least some of the present preferred embodiments provide a multi-hulled marine vessel having a propulsion system powered by a gaseous fuel, in which the storage means for the gaseous fuel is isolated from the engines and in which the storage means is also protected by virtue of the multi-hull configuration of the vessel. The storage means is also isolated from parts of the vessel that ordinarily accommodate crew, passengers and any cargo.

It is a particular feature of each preferred embodiment that the side hulls provide protection to the fuel storage means in the multi-hulled vessel. This can be important; for example, as it is a realistic scenario that a passenger ferry could be crossing a river when the other river traffic is travelling along the river, thereby providing a situation in which a collision could possibly occur. Conventional monohull ferries are required by SOLAS to withstand damage extending into the hull by a distance equivalent to 20% of the hull beam in the event of such a collision. A multi-hulled vessel according to any of the preferred embodiments could withstand damage of much greater extent, extending into the hull by a distance of approximately 40% of the hull beam or greater without disturbing the fuel storage means. Although the preferred embodiments relate to displacement and semi-planing craft, the invention is also suitable for use with planing and hydrofoil supported craft.

Examples of the main dimensions of hulls that could be used for the invention are shown below in Table 1. The invention should not be construed as being limited to vessels of these dimensions. The dimensions have simply been included here to show or provide a sample of sizes.

It will be appreciated by those skilled in the art that variations and modifications to the invention described herein will be apparent without departing from the spirit and scope thereof. The variations and modifications as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Throughout the specification and claims, unless the context requires otherwise, the term "substantially" or "about" will be understood to not be limited to the value for the range qualified by the terms.

Table 1 - Sample sizes of vessels suitable for invention

102m Trimaran 72m Catamaran 127m Trimaran

Length Overall, m 102 72 127

Length Waterline, m 101.4 61.8 117

Beam Moulded, m 26.8 17.6 30.4

Passengers 1165 650 1300

Truck lane metres, m 190 110 450

Cars 145 48 123

Deadweight, t 600 260 1000