WO2024094271A1

WO2024094271A1 - A powertrain in-situ conversion of a marine vessel

Info

Publication number: WO2024094271A1
Application number: PCT/EP2022/080336
Authority: WO
Inventors: Sangram Kishore Nanda; Andreas Carelli; Stefano IANNUZZI
Original assignee: Wartsila Services Switzerland Ltd
Current assignee: Wartsila Services Switzerland Ltd
Priority date: 2022-10-31
Filing date: 2022-10-31
Publication date: 2024-05-10
Anticipated expiration: 2025-04-30
Also published as: KR20240093637A; CN118382579A; EP4405248A1

Abstract

Invention relates to a powertrain (2) in-situ conversion of a marine vessel (1) which is provided with at least one propulsion powertrain, configured to provide thrust to operate the vessel (1) at a predefined first operating profile, such as design speed, and the at least one powertrain (2) comprising a multi-cylinder two-stroke internal combustion piston engine (6), a propeller (10) and shaft arrangement mechanically connecting the propeller (10) and the engine (6), the conversion comprising configuring the powertrain (2) to provide thrust to operate the vessel (1) at a second operating profile with less power demand than the first operating profile, wherein, - existing combustion chamber components (200) comprising at least a cylinder sleeve (114), cylinder cover (116), piston (112) and piston rod (110) are removed from the engine (6) of the at least one powertrain (2), and - new combustion chamber components (200') are assembled to the engine (6) of the at least one powertrain (2), which new combustion chamber components, including new cylinder sleeve (114') having smaller bore diameter than the existing cylinder sleeve (114), are configured to produce higher specific power than the removed old combustion chamber components (200).

Description

A powertrain in-situ conversion of a marine vessel

Technical field

[001] The present invention relates to a powertrain in-situ conversion of a marine vessel which is provided with at least one propulsion powertrains, configured to provide thrust to operate the vessel at a predefined first operating profile, which at least one powertrain comprising a multi-cylinder two-stroke internal combustion piston engine, a propeller and shaft arrangement mechanically connecting the propeller and the engine.

Background art

[002] Many existing large ocean-going vessels are provided with large two- stroke main engines, or even with just a single two-stroke main engine, which are operated by combustion of fossil fuels, such as heavy fuel oil and gas in a form of boil off gas from cargo tanks of the vessel. Such original engines with significant working life and operated with traditional fuels are prone to provide considerably emissions compared to current more stringent emission standards. Recently the interest to more environmentally friendly sea transportation has become more and more acute. One of the most effective ways to decrease emissions as well as consumption of the fuel when running such vessels is decreasing the speed of the vessel. However, reduction speed of the vessel to lower than original design speed of the vessel shifts the operation into inefficient area of a powertrain, particularly the engine of the vessel.

[003] In a vessel with large two-stroke engines the propeller is usually directly connected to the engine without a reduction gear, thus their rotational speeds are equal to each other. Therefore, slower speed of the vessel results in slower rotational speed of the engine, which may not be any more at optimal operation speed of the engine. [004] An object of the invention is to provide a powertrain in-situ conversion of a marine vessel which provides new, slower design speed for the vessel and optimized operation of the engine of the powertrain.

Disclosure of the Invention

[005] Objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.

[006] According to an embodiment of the invention a powertrain in-situ conversion of a marine vessel, which is provided with at least one propulsion powertrain, configured to provide thrust to operate the vessel at a predefined first operating profile, such as design speed, and the at least one powertrain comprising a multicylinder two-stroke internal combustion piston engine, a propeller and shaft arrangement mechanically connecting the propeller and the engine, the conversion comprising configuring the at least one powertrain to provide thrust to operate the vessel at a second operating profile, wherein, existing combustion chamber components comprising at least a cylinder sleeve, cylinder cover, piston and piston rod are removed from the engine of the at least one powertrain, and new combustion chamber components are assembled to the engine of the at least one powertrain, which new combustion chamber components, including new cylinder sleeve having smaller bore diameter than the existing cylinder sleeve, are configured to produce higher specific power than the removed old combustion chamber components.

[007] This way the engine is operating in fuel-efficient manner in the new circumstances of the second operating profile. Operating condition of the engine can be maintained favourable for complete fuel combustion due to smaller bore diameter.

[008] According to an aspect of the invention existing engine of the at least one propulsion powertrain is configured to provide thrust to move the vessel at a predefined first design speed and adapted to run at a first rotational speed, wherein the conversion further comprising adapting the engine of the powertrain to run at a second rotational speed lower than the first rotational speed.

[009] This provides an effect that the optimal operating window of the converted engine, having high (thermal) efficiency, becomes now matched with the new power level and rotational speed range required by the powertrain to move the vessel at the new, second design speed.

[0010] According to an aspect of the invention the conversion comprises configuring the propeller of the at least one powertrain to accommodate the change of the operating profile and/or rotational speed and wherein the new combustion chamber components provide new torque - speed characteristics to the engine corresponding to propeller curve of the configured propeller.

[0011] This provides an effect that the cylinder specific spatial combustion volume and combustion phasing therein are optimized to correspond to the new operating situation and therefore higher thermal efficiency in converting fuel chemical energy to mechanical energy at required new power levels can be achieved.

[0012] According to an aspect of the invention configuring the propeller comprises assembling new propeller or propeller blades to a hub of the existing propeller.

[0013] This provides an effect that the efficiency of the new propeller arrangement is optimized for the new, second design speed also affecting the rotational speed of the propeller either due to lower design speed of the vessel and/or other changes which have been made to the shape of the hull of the vessel and affecting the operation of the propeller arrangement.

[0014] According to an aspect of the invention configuring the propeller includes increasing diameter of the propeller.

[0015] This provides an effect of improving the total efficiency of the propeller at the new design speed of the vessel as well as lowering the rotational speed of the propeller below the original, first rotational speed. [0016] According to an aspect of the invention new combustion chamber components further comprise exhaust valve and fuel injectors.

[0017] This provides an effect of optimizing the gas exchange, cylinder specific combustion phasing and fuel delivery to meet the required new target power levels with high thermal efficiency.

[0018] According to an aspect of the invention new combustion chamber components are pre-assembled as a powerpack which is assembled to the engine as an entity.

[0019] This provides an effect of better logistics in delivering the necessary new components to the location of the conversion and faster assembly work and processes during conversion.

[0020] According to an aspect of the invention conversion comprising replacing or configuring fuel injection control system of the engine so as to decrease fuel injection amount at each power stroke, at least when the vessel is running at its design speed, when in use.

[0021] This provides an effect that controlling of fuel introduction into each cylinder is adapted to the new operation profiled of the engine providing high efficiency combustion.

[0022] According to an aspect of the invention reduction ratio of the mechanical shaft arrangement connecting the propeller and the engine in unchanged in the conversion.

[0023] This provides an effect of lowering the cost and shortens the time of the conversion as the number of components and assemblies requiring changes is minimized. Typically, such mechanical arrangements have long expected service life and will not otherwise require changes and making use of the long service life is in general environmentally friendly.

[0024] According to an aspect of the invention the new combustion chamber components are attached to the engine block via an adapter block, which comprises first attachment means compatible with attachment means of the engine block and second attachment means compatible with the new combustion chamber components.

[0025] This provides an effect no significant changes requiring, for example in situ heavy changing of the engine block, are needed during conversion reducing cost and overall requirements of the conversion work, tools and manpower.

[0026] According to an aspect of the invention the cylinder cover of the new combustion chamber is attached to the adapter block, and the adapter block is attached to the engine block.

[0027] This provides an effect that the arrangement can be built into a power pack with the above earlier mentioned benefits.

[0028] According to an aspect of the invention the cylinder cover of the new combustion chamber components comprises at least a first set of openings for a first set of fuel injectors configured to inject first fuel into the combustion chamber and a second set of openings for a second set of fuel injectors configured to inject second fuel into the combustion chamber.

[0029] This provides an effect that the conversion based on use of new cylinder cover prepares the engine for further alternative fuels, such as gaseous fuels and the engine may be converted into a multi-fuel engine either during the conversion or sometime later. Adding the second set of injectors later does not require significant disassembly of the engine but the injectors may be added or serviced easily.

[0030] According to an aspect of the invention in the conversion the stroke length of a piston of the engine is not changed.

[0031] This provides an effect that original crankshaft, being a major and expensive part, can be retained to lower the cost and effort required by the conversion.

[0032] According to an aspect of the invention after the conversion the engine parameters, for vessel running at its design speed are as follows:

Maximum cylinder pressure : 250 bar

Stroke to bore ratio: 3,5 - 4,5

Design rpm range: 70-105 rpm Design power levels 2000-3200 kW/cylinder

[0033] According to an aspect of the invention in the conversion bore diameter of the sleeve is decreased at least 20%.

[0034] Increasing the pressure in the cylinder provides increased efficiency by improved combustion and decreased heat losses. And, due to the smaller bore diameter stresses caused to the bearings by the increased pressure is still within acceptable level of the old engine.

[0035] The engine is a crosshead engine, and according to an aspect of the invention in the conversion new compression shim or shims are placed between the crosshead and the piston rod during assembly so as to configure clearance volume of the cylinder.

[0036] This provides an effect obtaining setting to provide high compression ratio.

[0037] According to an aspect of the invention conversion comprising replacing or configuring a turbo charger of the engine.

[0038] This provides an effect match the air pressure to the new circumstances

[0039] According to an aspect of the invention after the conversion in the bottom dead center position of the piston, the piston is totally below the air ports.

[0040] By means of the conversion according to the invention proper engine performance is obtained - and therefore minimised carbon emissions - since the powertrain is set up to match the vessel’s new operating profile. Further, reconfiguration of combustion is performed to match the present and future power requirement, reduction in bore diameter results in improvement in combustion efficiency and reduction of heat losses.

[0041] After the conversion the existing engine with new combustion chamber and new and/or reconfigured fuel injection control system the engine meets the torque-speed characteristics requirement set by the reconfigured propeller. [0042] Advantageously after the conversion the required torque is generated with a higher mean effective pressure (MEP) and improved fuel consumption with lower heat losses and higher cylinder maximum pressure after ignition of fuel I MEP- ratio, which is supported by a higher compression ratio. Thus, in the conversion mean effective pressure (MEP) is increased and cylinder maximum pressure after ignition of fuel I MEP- ratio is increased compared to the existing engine.

[0043] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

Brief Description of Drawings

[0044] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which

Figure 1 illustrates schematically a large marine vessel,

Figure 2 illustrates an exemplary propeller curve of the vessel,

Figure 3 illustrates a cross sectional view of an existing engine in the vessel,

Figure 4 illustrates situation after a first stage of the conversion according to an embodiment of the invention,

Figure 5 illustrates situation where combustion chamber components are out of the engine,

Figure 6 illustrates situation after installation of the new combustion chamber components to the existing engine, Figure 4 illustrates situation after a first stage of the conversion according to an embodiment of the invention,

Figure 7 illustrates the old the combustion chamber components and the new the combustion chamber components,

Figure 8 illustrates of an adapter block according to an embodiment of the invention, and

Figure 9 illustrates a new cylinder cover according to an embodiment of the invention.

Detailed Description of Drawings

[0045] Figure 1 depicts schematically a large marine vessel 1 , a ship, which is provided with at least one propulsion powertrain 2. This is a side view of the vessel and therefore it is not shown in the figure that may be another similar or different type powertrain arranged parallel or as auxiliary propulsion system in the vessel 1 . The original vessel hull 4 has a certain size and shape which results in certain power demand to move the vessel at its original design speed. Here the term “design speed” should be understood to refer to the speed that was considered to be the typical and effective operating speed of the vessel during long-distance sailing at open sea. This design speed may somewhat deviate downward from the maximum hull speed dictated by the length of the vessel’s waterline. The powertrain 2 is configured to provide thrust to operate the vessel at its design speed. More generally, it can be said that the vessel has a predefined first operating profile requirements of which the powertrain 2. The powertrain 2 comprises a multi-cylinder two-stroke cross head engine 6 which is mechanically connected to a propeller 10 with a propeller shaft 8 in such a manner that the propeller rotates with same speed as the engine, that is a so called gear ratio is 1 :1 . For example, the design speed may be set to 25 knots. Such a speed can be obtained for example by a well-known large two stroke engines. The engine is provided with a control system 12 which among other functions of the engine, controls the fuel injection into the cylinders of the engine 6.

[0046] Figure 2 discloses an exemplary propeller curve A of the vessel 2 indicating required power per cylinder of the engine 6 for obtaining a respective rotational speed of the propeller. Thus, the horizontal axis shows speed of the engine and the propeller (revolutions per minute), and the vertical axis shows cylinderwise power (kW/cylinder). The original design speed of the vessel 1 corresponds to point S1 in the curve and it is obtained with about 100 rpm propeller and engine speed, which requires about 5500kW power per cylinder of the engine which is an original design nominal power of each cylinder of the engine. Running the vessel at its design speed may be referred to operation at a first operating profile. When it is desired to decrease the cruise speed of the vessel 1 to lower speed than its design speed, for example to 20-23 knots the propeller speed would decrease to cruise speed, which corresponds to point S2 in the curve A. The point S2 would be obtained with operating the existing powertrain at about 87 rpm and it requires only about 3300 kW per cylinder to move the vessel at lower speed. This as an immediate effect would also be decrease of fuel consumption. However, the point S2 may not anymore be optimum for the existing powertrain 2. In some cases, the details of the hull of the vessel, for example the bulbous bow that is the protruding bulb at the bow of a ship just below the waterline, may also not be optimal for the new speed. As a conclusion, the new lower speed alone as well as potential other changes in the vessel affecting the new operating profile become mismatched with the properties of the original powertrain. Therefore, according to the invention, an in-situ powertrain conversion is made to the powertrain for adapting the powertrain 2 to better meet the demands of the new operating profile of the vessel. In this application the term operating profile of the vessel refers to one or more of the following circumstances. The most important matter is the actual cruise speed of the vessel, other effecting circumstances may be any changes to the vessel hull, such as modification of a bulbous bow, or changes to ballast management of the vessel or hull arrangements affecting the operation of the propeller.

[0047] Now referring the figures 3 to 6 the in-situ conversion of the powertrain in the large marine vessel as depicted in the figure 1 is explained in the following. [0048] Figure 3 discloses a cross sectional view of an old, existing engine 6 in the vessel 1. The engine 6 is a large, two-stroke multi-cylinder engine. The main parts of the engine 6 are an engine block 100, a crank shaft 102 rotatably supported to the engine block 100, a connecting rod 104, a cross head 106 arranged to be guided by a guide 108, a piston rod 110, a piston 112 and a cylinder sleevel 14, a cylinder cover 116, an exhaust valve 118, an exhaust manifold 120 and a super charger 122, usually a turbo charger. The parts defining the combustion chamber - such as the cylinder sleeve 114, the cylinder cover 116, the piston 112 and piston rod 110 may commonly referred to as combustion chamber components 200. It is to be understood that there are various auxiliary parts which are operationally related to the combustion chamber components, such as an exhaust valve and its actuation system, fuel injection system, cooling and lubrication system. Even if it is not specifically shown in the figure, there is a flow path (arrow) 126 arranged in the engine for scavenging air between the turbo charger 122 and scavenging air space 124 in the engine. The scavenging air flow path 126 may include for example an air cooler. The cylinder sleeve 114 is provided with air ports 128 at its lower part which open into the air space 124 of the engine. The cylinder cover 116 which is assembled at the top of the cylinder sleeve 114 is provided with fuel injection nozzles (not shown). The engine may comprise typically 6-14 cylinders, but of course practical application of the invention is not limited to any particular number of cylinders in the engine.

[0049] The in-situ conversion of the powertrain 2 comprises configuring the powertrain 2, or in case the vessel includes more than one powertrain, configuring each powertrain 2 to provide thrust to operate the vessel at a second operating profile.

[0050] Figure 4 depicts situation after a first stage of the conversion. It is to be understood that in practise there may be a need to do some preliminary and auxiliary work prior to the first stage. The first stage of conversion comprises removing existing combustion chamber components 200 from the engine 6. In the context of the application, it is meant by “existing” and “old” the situation, and parts in the engine prior to the conversion and by “new” and “converted” the situation after the conversion and parts changed or reconfigured in the conversion. In the view 4a it is schematically shown the existing combustion chamber components 200 which have been disassembled from the engine 6. Even if the combustion chamber components 200 are shown here as an entity disassembly, in existing engines these components are typically removed part by part. The old crank shaft, cross head and connecting rod remains the same after conversion, but of cause any worn parts may naturally be checked, changed or serviced.

[0051] Figure 5 depicts a situation where the combustion chamber components are out of the engine 6 and new combustion chamber components 200’ are ready for assembly, as is shown the view 5a. Figure 5 also discloses a further and alternative development of the invention according to which the new combustion components 200’ are pre-assembled to a suitable degree as a powerpack which is then assembled to the engine 6 as one larger entity as is depicted in the view 5a. That may be advantageous in some practical applications, but it is not an essential feature to the invention. In the conversion the stroke length of a piston of the engine is not changed because the old crank shaft and the connecting rods are used in the engine after the conversion.

[0052] In the next stage of the conversion new combustion chamber components 200’ are assembled to the engine 6. Further, in case the vessel 1 include more than on powertrain 2 the conversion is made to the engine 1 of the powertrain 2. Figure 6 depicts situation after installation of the new combustion chamber components 200’ to the existing engine 6.

[0053] Figure 7 shows side by side the old the combustion chamber components 200 and the new the combustion chamber components 200’. The connection of the components to the engine 6 can be seen as the block 100 and the exhaust manifold 120 are shown in the figure as dotted lines. An important feature in the conversion is that the new cylinder sleeve 114’ in new combustion chamber components 200’ has smaller bore diameter than the existing cylinder sleeve 114. This improves the efficiency of the combustion of fuel, because now that amount of fuel injected during cycle is smaller and smaller diameter of combustion chamber results in more complete combustion. It can also be seen in the figure that the air ports 128’ in the new cylinder sleeve 114’ are farther from the crank shaft i.e. horizontally higher than in the old cylinder sleeve 114. Additionally the new air ports 128’ are longer in axial direction of the cylinder sleeve than the air ports in the old cylinder sleeve 114 to accommodate for even higher compression ratio. In the bottom dead center position of the piston, the piston is totally below the air ports 128’.

[0054] The new combustion chamber components 114’ are configured to adapt the combustion to new operational profile in which the vessel speed is smaller than original design speed of the vessel 1 and propeller rotational speed of the powertrain is smaller than original design rotational speed. Particularly, the new combustion chamber components 114’ are configured to produce higher specific power than the old combustion chamber components 200. The engine 6 after the conversion meets the torque speed characteristics requirement of the existing propeller, and also of possible reconfigured propeller. The torque of the engine 6 after the conversion is generated with a higher mean effective pressure (MEP) and improved fuel economy (decreased fuel consumption) with lower heat losses through the cylinder wall and with higher cylinder maximum pressure after ignition of fuel I MEP- ratio, which is supported by a higher compression ratio.

[0055] Significant changes are seen in the new cylinder sleeve 114’ within new combustion chamber components 200’ the sleeve having smaller bore diameter than the existing cylinder sleeve 114 and the diameter of a new piston 112’ is smaller than the old piston 112, respectively. Also, the new combustion chamber components further comprise new exhaust valve 118’ and in some cases new fuel injectors 130’, or at least a conversion of the old fuel injectors to accommodate them into the new operational profile. The accommodation of the old fuel injectors may include replacing or configuring fuel injection control system (Figure 1- reference 12) of the engine 6 so as to decrease fuel injection amount at each power stroke, at least when the vessel is running at its design speed, when in use. The in-situ conversion may even include more profound modification of fuel injection system. For example, modification the fuel feeding system, to the extent as necessary, for combustion of different fuel.

[0056] In the conversion the exhaust gas inlets 121 to the exhaust manifold 120 remains in their existing position and the new combustion chamber components 200’ are positioned vertically to a location where exhaust gas outlet 123’ of the new combustion chamber components 200’ is directly attachable to the exhaust gas inlets 121. For that purpose, there is an adapter block 132’ provided for accommodate the new cylinder sleeve 114’ to the block 100 of the engine 6. The aforementioned matching of the position of the exhaust connection is an important feature lowering significantly the number and cost of changes required to the heavy exhaust systems of the vessel. An embodiment of the adapter block 132’ is shown in the figure 8. The adapter block is used for attaching and sealing the new combustion chamber components 200’ to the engine block. The adapter block 132’ comprises first attachment means 136’ compatible with attachment means 134 of the engine block 100 and second attachment means 140’ compatible with the new combustion chamber components. More precisely, the engine block 100 is provided with threaded holes 134 around an opening for the sleeve in the block 100 which are arranged in a first pattern. The first pattern complies with pattern of attachment bolts of the old cylinder cover 116. The adapter block 132’ is substantially circular, disk-like member having an opening suitable for the new cylinder sleeve 114’. The adapter block 132’ is provided with through-holes 136’ parallel to and around the opening for the new sleeve 114’. The through- holes 136’ are in the same pattern as the bolts of the old cylinder cover 116. This way the adapter block 132’ can be attached by new bolts 138’ to the engine block using the threaded holes for the old cylinder cover 116. The new cylinder cover 116’ is in turn attached to the adapter block 132’. For that purpose, the adapter block 132’ is provided with threaded holes 140’ around the opening for the sleeve in the block 100, which are arranged in a second pattern. The second pattern complies with pattern of attachment bolts of the new cylinder cover 116’, such that the new cylinder cover 116’ can be attached to the adapter block 132’. In some practical cases the adapter block 132’ may be an integral part of the new cylinder sleeve 114’.

[0057] Vertical position of the new cylinder sleeve 114’ of smaller diameter is positioned at correct vertical position by making use of the adapter block 132. Compression ratio is then fine tuned in the conversion by making use of a compression shim or shims 148’ which are placed between the crosshead and the piston rod during assembly so as to configure clearance volume of the cylinder as suitable. The total thickness effects in addition to the clearance volume of the cylinder also to position of the piston in relation of the air ports 128’ when the piston is at its bottom dead center. [0058] An example of changed parameters of the engine in a successful conversion of a two stroke engine according to the invention:

[0059] In this example the pressure in the cylinder is increased considerably, which provides increased efficiency and improved combustion. Thanks to the reduced bore diameter the higher pressure creates forces to the old engine’s power components which are within the design range of the original engine. Smaller bore diameter decreases heat losses of the combustion.

[0060] Even if the bore diameter is smaller after conversion, the compression ratio is increased, which is mostly due to smaller swept volume of the combustion chamber. As it can be seen in the conversion bore diameter of the sleeve is decreased at least 20%. In general, the new bore diameter is selected with a piston diameter and mean effective pressure required to generate a certain torquespeed characteristic that matches the propeller curve in the changed operational profile. In addition, the MEP generated is dependent on the amount of fuel injected per cycle, which is limited by combustion chamber component temperatures and stroke of the engine. With reference to the example (table) above, if 620 mm bore would be considered the MEP levels will be higher, and thus higher component temperatures, and consequently higher cylinder maximum pressure after ignition of fuel, to meet the torque speed and target brake-specific fuel consumption. Thus 620 mm cylinder bore would be too small. Preferably the engine has following characteristics after the conversion: Stroke to bore ratio: 3,5 - 4,5

Design rpm range: 70-105 rpm

Design power range: 2000-3200 kW/cylinder

[0061] The conversion can be made even more efficient in terms of operating the vessel when conversion comprises configuring the propeller 10 of the powertrain 2 to accommodate the change of the operating profile and/or rotational speed of the engine 6 so that the new combustion chamber components 200’ provide new torque - speed characteristics to the engine 6 corresponding to propeller curve of the configured propeller. Advantageously the propeller 10 is reconfigured such that its diameter is increased. Configuring the propeller may be accomplished by assembling new propeller or propeller blades to a hub of the existing propeller. The mechanical shaft arrangement connecting the propeller and the engine comprises a 1 :1 reduction ratio which advantageously is not changed in the conversion.

[0062] According to a further development of the invention the cylinder cover 116’ of the new combustion chamber components 200’ comprises optionally two set of openings for fuel injectors, as is depicted in the figure 9. The cylinder cover is provided with openings 140’ for attachment bolts of the new cylinder cover 116’ and a centrally located exhaust valve port 142’. The cylinder cover 116’ comprises at least a first set of openings 144’ for a first set of fuel injectors configured to inject first fuel into the combustion chamber and a second set of openings 146’ for a second set of fuel injectors configured to inject second fuel into the combustion chamber. During the conversion one of the sets of the openings is plugged in case the engine is configured to run with one fuel only and the other set of openings is provided with respective fuel injectors. In case the engine is configured to run with two different fuels the first set of openings 144’ is provided with the first set of fuel injectors and the second set of openings 146’ is provided with the second set of fuel injectors. The second set of openings 146’ can be utilized also in connection with future fuel conversion. Fuels which are currently considered viable candidates for use are for example methanol, LNG or ammonia. The second set of openings 146’ is arranged such that it is possible to install fuel injectors without disassembling the cylinder cover. Methanol offers simple handling and storage, reliable combustion and near carbon-neutral power (when made using renewable electricity and captured carbon) and is therefore very attractive fuel for decarbonizing the powertrain. LNG is currently economical and sustainable fuel that reduces environmental risks and harmful emissions. Ammonia in turn is attractive fuel for example in the sense that it releases no CO2 when combustion.

[0063] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is obvious to the skilled person that, along with the technical progress, the basic idea of the invention can be implemented in many ways. The invention and its embodiments are thus not limited to the examples and samples described above but they may vary within the contents of patent claims and their legal equivalents. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.

Part list a large marine vessel 1 a propulsion powertrain 2 a hull 4 a multi-cylinder two-stroke cross head engine 6 a propeller shaft 8 a propeller 10 a control system 12 an engine block 100 a crank shaft 102 a connecting rod 104 a cross head 106 a guide 108 a piston rod 110,110’ a piston 112,112’ a cylinder sleeve 114, 114' a cylinder cover 116, 116' an exhaust valve 118, 118' an exhaust manifold 120 a super charger 122 an exhaust gas outlet 123’ a scavenging air space 124 a flow path 126 air ports 128, 128' new fuel injectors 130’ an adapter block 132’ threaded holes 134 a first attachment means 136’ new bolts 138’ a second attachment means 140’ an exhaust valve port 142’ a first set of openings 144’ a second set of openings 146’ shim or shims 148’ old combustion chamber components 200 new combustion chamber components 200’

5

Claims

1. A powertrain (2) in-situ conversion of a marine vessel (1) which is provided with at least one propulsion powertrain, configured to provide thrust to operate the vessel (1) at a predefined first operating profile, such as design speed, and at least one powertrain (2) comprising a multi-cylinder two-stroke internal combustion piston engine (6), a propeller (10) and shaft arrangement mechanically connecting the propeller (10) and the engine (6), the conversion comprising configuring the at least one powertrain (2) to provide thrust to operate the vessel (1) at a second operating profile with less power demand than the first operating profile, wherein, existing combustion chamber components (200) comprising at least a cylinder sleeve (114), cylinder cover (116), piston (112) and piston rod (110) are removed from the engine (6) of the at least one powertrain (2), and new combustion chamber components (200’) are assembled to the engine (6) of the at least one powertrain (2), which new combustion chamber components, including new cylinder sleeve (114’) having smaller bore diameter than the existing cylinder sleeve (114), are configured to produce higher specific power than the removed old combustion chamber components (200).

2. A powertrain (2) in-situ conversion according to claim 1 , characterized in that existing engine (6) of the at least one propulsion powertrain (2) is configured to provide thrust to move the vessel (1) at a predefined first design speed and adapted to run at a first rotational speed, wherein the conversion further comprising adapting the engine (6) of the powertrain (2) to run at a second rotational speed lower than the first rotational speed.

3. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that the conversion comprises configuring the propeller (10) of the powertrain (2) to accommodate the change of the operating profile and/or rotational speed and wherein the new combustion chamber components (200’) provide new torque - speed characteristics to the engine (6) corresponding to propeller curve of the configured propeller.

4. A powertrain (2) in-situ conversion according to claim 4, characterized in that configuring the propeller (10) comprises assembling new or configured propeller (10) or propeller blades to a hub of the existing propeller.

5. A powertrain (2) in-situ conversion according to claim 4 or 5, characterized in that configuring the propeller (10) includes increasing diameter of the propeller (10).

6. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that new combustion chamber components (200’) further comprise exhaust valve (118’) and fuel injectors (130’).

7. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that new combustion chamber components (200’) are pre-assembled as a powerpack which is assembled to the engine (6) as an entity.

8. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that conversion comprising replacing or configuring fuel injection control system (12) of the engine (6) so as to decrease fuel injection amount at each power stroke, at least when the vessel (1) is running at its design speed, when in use.

9. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that reduction ratio of the mechanical shaft arrangement connecting the propeller (10) and the engine (6) remains the same in the conversion.

10. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that the new combustion chamber components (200’) are attached to the engine block (100) via an adapter block (132’), which comprises first attachment means (136’) compatible with attachment means of the engine block (100) and second attachment means (140’) compatible with the new combustion chamber components (200’).

11. A powertrain (2) in-situ conversion according to claim 10, characterized in that cylinder cover (116’) of the new combustion chamber components (200’) is attached to the adapter block (132’), and the adapter block is attached to the engine block (100).

12. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that the cylinder cover (116’) of the new combustion chamber components (200’) comprises at least a first set of openings (144’) for a first set of fuel injectors configured to inject first fuel into the combustion chamber and a second set of openings (146’) for a second set of fuel injectors configured to inject second fuel into the combustion chamber.

13. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that in the conversion the stroke length of a piston of the engine (6) is not changed.

14. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that after the conversion the engine parameters, for vessel (1) running at its design speed are as follows:

Maximum cylinder pressure: 250 bar

Stroke to bore ratio: 3,5 - 4,5

Design rpm range: 70-105 rpm

Design power levels 2000-3200 kW/cylinder

15. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that in the conversion bore diameter of the sleeve is decreased at least 20%.

16. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that the engine (6) is a crosshead engine (6), and that in the conversion new compression shim or shims (148’) are placed between the crosshead (106) and the piston rod (110’) during assembly so as to configure clearance volume of the cylinder.

17. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that conversion comprising replacing or configuring a turbo charger of the engine (6).

18. A powertrain (2) in-situ conversion according to anyone of the preceding claims, characterized in that after the conversion in the bottom dead center position of the piston (112’), the piston is totally below the air ports (128’).