EP2336521A1

EP2336521A1 - A cylinder arrangement for an internal combustion engine

Info

Publication number: EP2336521A1
Application number: EP09179281A
Authority: EP
Inventors: Leif Knipström
Original assignee: Wartsila NSD Schweiz AG
Current assignee: Wartsila NSD Schweiz AG
Priority date: 2009-12-15
Filing date: 2009-12-15
Publication date: 2011-06-22

Abstract

The invention relates to a cylinder arrangement (1) for an internal combustion engine, including a cylinder (2) in which a piston (3) is arranged to be movable along a longitudinal cylinder axis (A) to and fro between a top dead centre position and a bottom dead centre position, wherein in the cylinder (2) a combustion chamber (4) is defined by a cylinder cover (5), by a cylinder wall (21) of the cylinder (2) and by a piston surface (31) of the piston (3). At least one charge-cycle valve (6, 61, 62) is provided in a gas exchange opening (7) of the cylinder cover (5), wherein the charge-cycle valve (6, 61, 62) includes a valve disk (61) cooperating in the operation state with a valve seat (71, 711, 712) of the gas exchange opening (7) in such a way, that in a closed position of the charge-cycle valve (6, 61, 62) the combustion chamber (4) is sealed with respect to a gas feeding conduct (8). According to the invention, the valve seat (71, 711, 712) is movably arranged between a high-ratio position (HR) and a low-ratio position (LR) so that within the combustion chamber (4) a compression-ratio is adjustable to a pre-settable compression-ratio value. Furthermore the invention relates to a method for operating an internal combustion engine as well as to an internal combustion engine having a cylinder arrangement according to the invention.

Description

The invention relates to a cylinder arrangement for an internal combustion engine, a method for operating an internal combustion engine as well as to an internal combustion engine in accordance with the pre-characterising part of the independent claims 1, 10, and 11.
The person skilled in the art knows a great variety of different types of reciprocating piston combustion engines, such as two-stroke or four-stroke trunk piston engines used in a variety of vehicles like ships, cars, aeroplanes or for example large diesel engines for ships or stationary units for the production of electrical power. In many cases, the internal combustion engine must be operated in different operation states, for example under low- or part- or high-power conditions. It also possible that for example one and the same combustion engine must be operated with different fuels or with fuels of different quality. In such cases, the performance of the engine has to be adapted to the conditions with have changed with respect to certain standard conditions.
One important engine parameter which can be adjusted to new operational conditions is the compression ratio within the cylinder of the combustion engine. The compression ratio in a piston engine is usually constant. The compression ratio is decided based on engine performance parameters to have the best engine performance, often the high engine load performance is the most relevant point for the decision. For optimal performance over the whole operating range a variable compression ratio is desirable. But due to the complications with such a system a compromise is usually made defining one fixed compression ratio.
For example for engines running capable of running of different fuel qualities with different ignition properties or even so called dual fuel engine for example capable of running on either liquid diesel fuel according to the diesel cycle as well as the running on gas according to the otto cycle the problem becomes even more critical. Since the common compression ratio range where it is possible to run both diesel cycle with diesel fuel and otto cycle with gas fuel is very narrow. In these cases a compromise has to be made on both the diesel and the otto cycle performance.
For smaller trunk piston engines there exist many patents for variable compression ratio. For example using eccentric sleeves around the piston pin or around the main bearing. Or eccentric shafts and mechanisms for regulating the distance between the cylinder head and the crankshaft centre line. These designs are often rather complicated can not easily be adopted to large piston engines without a major redesign of the engine and it would as well require a lot more steel and iron to have a rigid engine structure.
Starting from the prior art it is therefore an object of the invention to make available an improved cylinder arrangement and an improved internal combustion engine, respectively, as well as an improved method for operating an internal combustion engine so that a compression ratio can be changed within a cylinder of the combustion engine in an easy and efficient way to achieve the best engine performance under different operational conditions. The improved cylinder arrangement and method, respectively, should be applicable for both trunk piston engines and crosshead large diesel engines, as well as for two-stroke and four-stroke internal combustion engines.
The subjects of the invention satisfying this object are characterised by the features of the independent claims 1, 10, and 11.
The dependent claims relate to particularly advantageous embodiments of the invention.
Thus the invention relates to a cylinder arrangement for an internal combustion engine, including a cylinder in which a piston is arranged to be movable along a longitudinal cylinder axis to and fro between a top dead centre position and a bottom dead centre position, wherein in the cylinder a combustion chamber is defined by a cylinder cover, by a cylinder wall of the cylinder and by a piston surface of the piston. At least one charge-cycle valve is provided in a gas exchange opening of the cylinder cover, wherein the charge-cycle valve includes a valve disk cooperating in the operation state with a valve seat of the gas exchange opening in such a way, that in a closed position of the charge-cycle valve the combustion chamber is sealed with respect to a gas feeding conduct. According to the invention, the valve seat is movably arranged between a high-ratio position and a low-ratio position so that within the combustion chamber a compression-ratio is adjustable to a pre-settable compression-ratio value.
Regarding this, the present invention is related to a system for variable compression ratio especially suitable for large low speed two-stroke engines. But similar design principles could also be used eg. for medium speed four-stroke engine. The special advantage of the invention is that only the cylinder head must be slightly changed in design. Essentially, no other mechanical component of the combustion engine must be changed except that a hydraulic system must be provided to move the valve seat between the low-ratio and the high-ratio position. In particular, no changes must be made regarding the piston rod or the crankshaft to change the compression ratio within the cylinder. Thus, the compression ratio in a cylinder arrangement according to the invention can be changed in an very easy and efficient way to achieve the best engine performance under different operational conditions. Since only the cylinder cover has to be changed very slightly, the improved cylinder arrangement and method, respectively, is applicable for both trunk piston engines and crosshead large diesel engines, as well as for two-stroke and four-stroke internal combustion engines.
What is more, since only the cylinder cover has to be changed and either an existing hydraulic system has to be slightly changed or an hydraulic system has simply to be added, respectively, nearly every internal combustion engine can very easily be retrofitted with the system according to the invention by simply replacing a new cylinder cover having a movable valve seat in accordance with the invention and by adapting or adding a respective hydraulic system for actuating the movable valve seat.
Regarding a special embodiment of the present invention, the valve seat is designed as a hydraulic piston cooperating at least with a first hydraulic pressure chamber in such a way, that the valve seat is moved from the low-ratio position to the high-ratio position by pressurizing the first hydraulic pressure camber with an hydraulic fluid.
In a second simple embodiment the valve seat is designed as a hydraulic piston cooperating at least with a second hydraulic pressure chamber in such a way, that the valve seat is moved from the high-ratio position to the low-ratio position by pressurizing the second hydraulic pressure chamber with a hydraulic fluid.
It is understood that in practise, the first hydraulic pressure chamber and the second hydraulic pressure chamber is present at the same time so that the valve seat can be moved in both directions by pressurizing the first hydraulic pressure chamber or the second hydraulic pressure chamber, respectively.
Regarding a more complex embodiment of the present invention, the valve seat is designed as a hydraulic double-piston cooperating with at least one third hydraulic pressure chamber in such a way, that the valve seat can be positioned in an medium-ratio position between the high-ratio position and the low-ratio position, wherein of course, in most cases the first and the second hydraulic pressure chamber is additionally present at the same time.
Preferably, the valve seat of the cylinder arrangement in accordance with the present invention is comprising a cooling channel to allow cooling of the valve seat by feeding a cooling medium through the cooling channel. In practise, the cooling medium is preferably identical to the hydraulic medium which is used to actuate the valve seat by supplying it to the different hydraulic pressure chambers.
In case that the internal combustion engine is a longitudinally scavenged internal combustion engine, for example a crosshead large diesel engine, only one charge-cycle valve which is an outlet valve is provided in the gas exchange opening of the cylinder head of the cylinder. But of course, regarding other types of internal combustion engines, at least a first charge-cycle valve and a second charge-cycle valve might be provided in one and the same cylinder cover at the same time.
Regarding this, the first charge-cycle valve may be an inlet valve and the second charge-cycle valve may be an outlet valve wherein, of course, as in principle known from the state of the art, more than two charge-cycle valves can be present at one and the same cylinder cover at the same time.
In order to seal the combustion chamber with respect to the gas feeding duct which may be a gas feeding duct for feeding combustion gases out of the combustion chamber or which may be a gas feeding duct for feeding fresh air into the combustion chamber, the first charge-cycle valve cooperates with a first valve seat and the second charge-cycle valve cooperates with a second valve seat.
Regarding a special embodiment of the invention, the first valve seat and the second valve seat can be separately moved between the low-ratio position and the high-ratio position, wherein in an other embodiment the entire flame plate is made as a hydraulic piston including the first valve seat and the second valve seat at the same time, so that the first valve seat and the second valve seat can be commonly moved from the low-ratio position to the high-ratio position and vice versa.
The invention is also related to a method for operating an internal combustion engine, including a cylinder in which a piston is arranged to be movable along a longitudinal cylinder axis to and fro between a top dead centre position and a bottom dead centre position, wherein in the cylinder a combustion chamber is defined by a cylinder cover, by a cylinder wall of the cylinder and by a piston surface of the piston. At least one charge-cycle valve is provided in a gas exchange opening of the cylinder cover, wherein the charge-cycle valve includes a valve disk cooperating in the operation state with a valve seat of the gas exchange opening in such a way, that in an closed position of the charge-cycle valve the combustion chamber is sealed with respect to a gas feeding conduct. According to the invention, the valve seat is movably arranged between a high-ratio position and a low-ratio position so that within the combustion chamber a compression-ratio is adjusted to a pre-set compression-ratio value.
The invention relates furthermore to an internal combustion engine having a cylinder arrangement in accordance with the invention and being operable by a method according to the invention.
As matter of principle, the combustion engine according to the invention can be any type of internal combustion engine as actually known from the state of the art. In particular, a combustion engine according to the invention can be a crosshead engine, in particular a crosshead large diesel engine, or a trunk piston engine, wherein the combustion engine can be a two-stroke internal combustion engine or in an other embodiment a four-stroke internal combustion engine. Regarding another special embodiment, the internal combustion engine according to the invention is a dualfuel engine being operable either in diesel or otto mode.
The invention will be explained more closely in the following with the help of the drawings which show:

Fig. 1 a: schematically a first embodiment of the invention with the valve seat in the high-ratio position;
Fig. 1 b: the embodiment of Fig. 1 a with the valve seat in the low-ratio position;
Fig. 2: a second embodiment of the invention with a cooling channel;
Fig. 3a: a third embodiment of the invention with the seat valve designed as a hydraulic double-piston in the high-ratio position;
Fig. 3b: the embodiment of Fig. 3a in a medium-ratio position;
Fig. 3c: the embodiment of Fig. 3a in the low-ratio position;
Fig. 4a: a forth embodiment of the invention with the valve seat having an larger outer diameter;
Fig. 4b: the embodiment according to Fig. 4a with the valve seat in the low-ratio position;
Fig. 5a: a four-stroke arrangement according to the invention with independently controllable inlet and outlet valve seat;
Fig. 5b: the embodiment of Fig 5a with the inlet valve seat in the low-ratio position and the outlet valve seat in the high-ratio position.
Fig. 6a: a fifth embodiment according to the invention with the entire flame plate made as a hydraulic piston.
Fig. 6b: the embodiment according to Fig. 6a with the inlet and outlet valve seats in the low-ratio position.

Fig. 1 a shows, in a schematic illustration a first embodiment of a cylinder arrangement 1 according to the invention with the valve seat 71 being in the high-ratio position wherein Fig. 1 b shows the same embodiment with the valve seat 71 in the low ratio position.
Fig. 1 a and Fig. 1 b, respectively, disclose a first special embodiment of an cylinder arrangement 1 according to the present invention for an internal combustion engine which is in the present example a longitudinally scavenged crosshead large diesel engine. The cylinder arrangement 1 according to Fig. 1 a and Fig. 1 b includes a cylinder 2 in which a piston 3 is arranged to be movable along a longitudinal cylinder axis A to and fro between a top dead centre position and a bottom dead centre position, wherein in the cylinder 2 a combustion chamber 4 is defined by a cylinder cover 5, by a cylinder wall 21 of the cylinder 2 and by a piston surface 31 of the piston 3. Only one charge-cycle valve 6, 61, 62 being here an outlet valve is provided in a gas exchange opening 7 of the cylinder cover 5 which gas exchange opening 7 is connected via a gas feeding conduct 8 to a not shown turbocharger assembly in a per se known manner. The charge-cycle valve 6, 61, 62 includes a valve disk 61 cooperating in the operation state with a valve seat 71 of the gas exchange opening 7 in such a way, that in a closed position of the charge-cycle valve 6, 61, 62 the combustion chamber 4 is sealed with respect to the gas feeding conduct 8, wherein in an open position of the charge-cycle valve 6, 61, 62 combustion gases can be fed out of the combustion chamber 4 to the turbocharger assembly. According to the invention, the valve seat 71, 711, 712 is movably arranged between a high-ratio position HR and a low-ratio position LR so that within the combustion chamber 4 a compression-ratio is adjustable to a pre-settable compression-ratio value.
Regarding the cylinder arrangement 1 for controlling the compression ratio in the combustion chamber 4 shown in Fig. 1 a and Fig. 1 b, respectively, the valve seat 71 is made as a separate part and acting as an hydraulic piston. If hydraulic oil is supplied to the first hydraulic chamber 91, the valve seat 71 is pressed down to its lower position which is the high-ratio position HR. In this case the compression ratio is the highest possible, since the compression volume in the cylinder 2 is minimized. The hydraulic force acting on the valve seat 71 through the first hydraulic pressure chamber 91 is high enough to keep the valve seat 71 in the high-ratio position HR also during the combustion cycle. For switching the compression ratio within the cylinder 2, the hydraulic oil from the first hydraulic pressure chamber 91 is drained and instead the hydraulic oil is supplied to the second hydraulic pressure chamber 92 as shown in Fig. 1 b. This moves up the valve seat 71 to its low-ratio position LR, increasing the compression volume in the cylinder 2 and thus, lowering the compression-ratio value within the cylinder 2. Preferably, the outlet valve 6, 62 has an hydraulic valve actuation system, which is not shown in greater detail, allowing the outlet valve 6, 62 to follow the position of the valve seat 71 and preferably operating independently of the position of the valve seat 71.
By Fig. 2 a second embodiment of the invention having a cooling channel 10 for cooling the valve seat 71, 711, 712 is displayed showing in greater detail a special design of the hydraulic valve seat 71, 711, 712 allowing variable compression ratio within the combustion chamber 4 of the cylinder 2. The valve seat 71, 711, 712 which is designed as a piston 71, 711, 712 has a sealing 700 normally used in this kind of hydraulic piston. It has as well in addition one or several piston rings 701 sealing against the combustion pressure within the combustion chamber 4 in order to not allow the combustion pressure to act directly on the hydraulic sealing 700. As already mentioned, Fig. 2 also shows an integrated cooling channel 10 in the valve seat 71, 711, 712 to allow cooling of the valve seat 71, 711, 712. In the example of Fig. 2 the same hydraulic oil as used for actuating the hydraulic valve seat 71, 711, 712 can also be used for the cooling of the valve seat 71, 711, 712. This is arranged with drillings from the hydraulic chambers 91, 92. The first hydraulic pressure chamber 91 is connected to one side of the seat cooling and the second hydraulic pressure chamber 92, which cannot be seen in Fig. 2 since the valve seat 71, 711, 712 is in it's high-ratio position HR, is connected to the other side of the seat cooling. In the bores 702 connecting the hydraulic pressure chambers 91, 92 to the seat orifices are installed to control and limit the amount of oil flowing through the cooling channel 10. In case that the first hydraulic pressure chamber 91 is pressurized some hydraulic oil is flowing from the first hydraulic pressure chamber 91 to the seat cooling and then drained out to the second hydraulic pressure chamber 92. And in case the second hydraulic pressure chamber 92 is pressurized the flow direction is the opposite, from the second hydraulic pressure chamber 92 to the seat cooling and then drained out to the not pressurized first hydraulic pressure chamber 91. The pressurized chamber will in this case need a continuous supply of oil to maintain the pressure in the pressurized chamber 91, 92.
Fig. 3a - Fig. 3c show a third embodiment according to the present invention with a hydraulic double-piston 710. This allows variable compression ratio in two steps. If pressurized oil is supplied to the third hydraulic pressure chamber 93 and the first hydraulic pressure chamber 91 and the second hydraulic pressure chamber 92 are drained, the valve seat 71 is pressed towards its high-ratio position HR, giving the highest compression ratio in the cylinder 2 as, shown in Fig. 3a.
Regarding Fig. 3b, the pressurized oil is supplied to the first hydraulic pressure chamber 91. The intermediate hydraulic chamber is drained and in the second hydraulic pressure chamber 92 a small hydraulic back pressure is maintained. In the case the valve seat 71 will remain in the medium-ratio position MR.
In Fig. 3c the hydraulic pressure is supplied to the second hydraulic pressure chamber 92. Both the third hydraulic pressure chamber 93 and the first hydraulic pressure chamber 91 are drained. In this case the valve seat 71 goes to its low-ratio position LR, giving the lowest possible compression ratio within the combustion chamber 4 of the cylinder 2.
Fig. 4a and Fig. 4b show an alternative design execution working with the same principle. In this case the hydraulic valve seat 71 is made with an larger outer diameter, eg. same diameter as the piston 3 or the inner diameter of the cylinder 2, respectively. This allows much bigger variation of the compression ratio within the cylinder 2 with the same stroke of the hydraulic valve seat 71. However the movable part, that is the hydraulic valve seat 71 is much larger and more efficient cooling of the hydraulic valve seat 71 will be required. This can preferably be done with a separate cooling medium different from the hydraulic oil used for pressurizing the hydraulic pressure chambers 91, 92, 93 in order not to waste too much pressurized hydraulic oil. Eg cooling oil could be lead into the cooling spaces and drillings in the hydraulic valve seat 71 through in Fig. 4a and Fig. 4b not shown separate slide in pipes or through grooves and channels in on the sides of the hydraulic valve seat separated by sealing rings.
The design described could also be made eg with two step piston design allowing an intermediate position of the hydraulic valve seat 71 giving more compression ratio variants, for example three hydraulic chambers with different strokes. With this design is the number of added parts due to the variable compression ratio reduced to a minimum giving a simple and mechanically reliable design. The hydraulic oil system needed to control the compression ratio often already existing on large two stroke engines and used already eg. for valve actuation.
Similar principle for adjusting the compression ratio could also be used for four-stroke engines. Fig. 5a and Fig. 5b show a four-stroke arrangement according to the invention with independently controllable inlet and outlet valve seats wherein in Fig. 5a both valve seats 71, 711, 712 are in the high-ratio position HR and in Fig. 5b the inlet valve seat 71, 711 is in the low-ratio position LR and the outlet valve seat 71, 712 in the high-ratio position HR. That is, Fig. 5a and Fig. 5b, respectively, show a variant of the present invention where each valve seat 71, 711, 712 can be controlled separately. This gives possibilities for 5 different compression ratios within the combustion chamber 4 if the cylinder 2 is equipped with 4 equally sized valve seats 71, 711, 712:

1. All four valve seats 71, 711, 712 in the high-ratio position HR
2. One valve seat 71, 711, 712 in the low-ratio position LR, three valve seats 71, 711, 712 in the high-ratio position HR
3. Two valve seats 71, 711, 712 in the low-ratio position LR, two valve seats 71, 711, 712 in the high-ratio position HR
4. Three valve seats 71, 711, 712 in the low-ratio position LR, one valve seat 71, 711, 712 in the high-ratio position HR
5. All valve seats 71, 711, 712 in the low-ratio position LR.

By Fig. 6a and Fig. 6b, respectively, a fifth embodiment according to the invention with the entire flame plate made as a hydraulic piston 71 is schematically displayed which embodiment is another alternative design for a four-stroke engine. Fig. 6b with the inlet and outlet valve seats 71 in the low-ratio position LR.
In this design is the entire flame plate 71 made as a hydraulic piston 71, giving a larger area for adjusting the compression ratio, giving bigger variation in the compression ratio for the same stroke of the hydraulic piston 71.
It is to be understood that all of the embodiments in accordance with the invention described in this application are to be understood merely by way of example and in particular all embodiments as described or obvious within the context of the present invention, can be provided either alone or in all suitable combinations in special examples of embodiments in accordance with the invention, so that all suitable combinations of the embodiments described in this invention are included and covered by the present invention.

Claims

A cylinder arrangement for an internal combustion engine, including a cylinder (2) in which a piston (3) is arranged to be movable along a longitudinal cylinder axis (A) to and fro between a top dead centre position and a bottom dead centre position, wherein in the cylinder (2) a combustion chamber (4) is defined by a cylinder cover (5), by a cylinder wall (21) of the cylinder (2) and by a piston surface (31) of the piston (3), and at least one charge-cycle valve (6, 61, 62) is provided in a gas exchange opening (7) of the cylinder cover (5), wherein the charge-cycle valve (6, 61, 62) includes a valve disk (61) cooperating in the operation state with a valve seat (71, 711, 712) of the gas exchange opening (7) in such a way, that in a closed position of the charge-cycle valve (6, 61, 62) the combustion chamber (4) is sealed with respect to a gas feeding conduct (8), characterised in that the valve seat (71, 711, 712) is movably arranged between a high-ratio position (HR) and a low-ratio position (LR) so that within the combustion chamber (4) a compression-ratio is adjustable to a pre-settable compression-ratio value.
A cylinder arrangement in accordance with claim 1, wherein the valve seat (71, 711, 712) is designed as a hydraulic piston cooperating at least with a first hydraulic pressure chamber (91) in such a way, that the valve seat (71, 711, 712) is moved from the low-ratio position (LR) to the high-ratio position (HR) by pressurizing the first hydraulic pressure chamber (91) with an hydraulic fluid.
A cylinder arrangement in accordance with anyone of claims 1 or 2, wherein the valve seat (71, 711, 712) is designed as a hydraulic piston cooperating at least with a second hydraulic pressure chamber (92) in such a way, that the valve seat (71, 711, 712) is moved from the high-ratio position (HR) to the low-ratio position (LR) by pressurizing the second hydraulic pressure chamber (92) with an hydraulic fluid.
A cylinder arrangement in accordance with anyone of the preceding claims, wherein the valve seat (71, 711, 712) is designed as a hydraulic double-piston (710) cooperating with at least one third hydraulic pressure chamber (93) in such a way, that the valve seat (71, 711, 712) can be positioned in an medium-ratio position (MR) between the high-ratio position (HR) and the low-ratio position.
A cylinder arrangement in accordance with anyone of the preceding claims, wherein the valve seat (71, 711, 712) is comprising a cooling channel (10) to allow cooling of the valve seat (71, 711, 712).
A cylinder arrangement in accordance with anyone of the preceding claims, wherein at least a first charge-cycle valve (6, 61) and a second charge-cycle valve (6, 62) is provided.
A cylinder arrangement in accordance with claim 6, wherein the first charge-cycle valve (6, 61) is an inlet valve (6, 61) and the second charge-cycle valve (6, 62) is an outlet valve (6, 62).
A cylinder arrangement in accordance with anyone of claim 6 or 7, wherein the first charge-cycle valve (6, 61) cooperates with a first valve seat (71, 711) and the second charge-cycle valve (6, 62) cooperates with a second valve seat (7, 712).
A cylinder arrangement in accordance with claim 8, wherein the first valve seat (71,711) and the second valve seat (71, 712) can be separately moved between the low-ration position (LR) and the high-ratio position (HR).
A method for operating an internal combustion engine, including a cylinder (2) in which a piston (3) is arranged to be movable along a longitudinal cylinder axis (A) to and fro between a top dead centre position and a bottom dead centre position, wherein in the cylinder (2) a combustion chamber (4) is defined by a cylinder cover (5), by a cylinder wall (21) of the cylinder (2) and by a piston surface (31) of the piston (3), and at least one charge-cycle valve (6, 61, 62) is provided in a gas exchange opening (7) of the cylinder cover (5), wherein the charge-cycle valve (6, 61, 62) includes a valve disk (61) cooperating in the operation state with a valve seat (71, 711, 712) of the gas exchange opening (7) in such a way, that in an closed position of the charge-cycle valve (6, 61, 62) the combustion chamber (4) is sealed with respect to a gas feeding conduct (8), characterised in that the valve seat (71, 711, 712) is movably arranged between a high-ratio position (HR) and a low-ratio position (LR) so that within the combustion chamber (4) a compression-ratio is adjusted to a pre-set compression-ratio value.
An internal combustion engine having a cylinder arrangement (1) in accordance with anyone of claims 1 to 9 and being operable by a method according to claim 10.
An internal combustion engine according to claim 11, wherein the combustion engine is a crosshead engine, in particular a crosshead large diesel engine.
An internal combustion engine according to claim 11, wherein the combustion engine is a trunk piston engine.
An internal combustion engine according to anyone of claims 11 to 13, wherein the combustion engine is a two-stroke or a four-stroke internal combustion engine.
An internal combustion engine according to anyone of claims 11 to 14, wherein the combustion engine is a dualfuel engine being operable either in diesel or otto mode.