CN114439599B

CN114439599B - Compression ignition internal combustion engine operating with ammonia and retrofit kit

Info

Publication number: CN114439599B
Application number: CN202111308275.8A
Authority: CN
Inventors: 斯特凡·迈尔; 约翰·舍霍尔姆
Original assignee: Mannone Solutions Mannone Solutions Germany Branch
Current assignee: Mannone Solutions Mannone Solutions Germany Branch
Priority date: 2020-11-06
Filing date: 2021-11-05
Publication date: 2023-08-15
Anticipated expiration: 2041-11-05
Also published as: DK180922B1; DK202070740A1; KR102656105B1; JP7183369B2; JP2023018060A; JP2022075566A; CN114439599A; KR20220061879A

Abstract

The present disclosure provides turbocharged compression-ignition internal combustion engines and retrofit kits, the engine being configured in at least one operating mode for operation with ammonia as a primary fuel or ammonia as the sole fuel. The engine includes: a cylinder (1) having a reciprocating piston (10) therein and a cylinder head (22) covering each cylinder (1); a combustion chamber (15) formed in the cylinder (10) and located between the reciprocating piston (10) and the cylinder head (22); at least one prechamber (33) arranged in the cylinder head (22) and connected to the combustion chamber through an opening (35); an ammonia valve (50) having a nozzle (51) with a nozzle hole (52) leading to the at least one pre-chamber (33), the ammonia valve (50) having an inlet connected to a source of pressurized liquid ammonia (40), the ammonia valve (50) being configured for injecting liquid ammonia from the pressurized liquid ammonia source (40) into the pre-chamber (33) through the nozzle hole (52).

Description

Compression ignition internal combustion engine operating with ammonia and retrofit kit

Technical Field

The present disclosure relates to compression ignition internal combustion engines, such as large slow running two-stroke compression ignition crosshead internal combustion engines, having at least one mode of operation in which the primary fuel is ammonia.

Background

Compression ignition internal combustion engines (diesel engines) have been operated in the past mainly with hydrocarbon fuels, such as fuel oil, e.g. diesel, or gas, e.g. natural gas or petroleum gas. Combustion of hydrocarbon fuels releases carbon dioxide (CO 2) and other greenhouse gases that lead to atmospheric pollution and climate change. Unlike fossil fuel impurities that produce byproduct emissions, CO2 is an unavoidable product of hydrocarbon combustion. The energy density and CO2 footprint (footprint) of the fuel depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecules. Thus, gaseous hydrocarbon fuels have a lower footprint than liquid hydrocarbon fuels, which have the disadvantage of: the handling and storage of gaseous hydrocarbon fuels is more challenging and costly. In order to reduce the CO2 footprint, non-hydrocarbon fuels are being investigated.

Ammonia is a synthetic product obtained from fossil fuels, biomass, or renewable resources (wind, sun, water, or heat), and when the ammonia is produced from renewable resources, the ammonia will have little carbon footprint or will emit little CO2, SOX, particulates, or unburned hydrocarbons when burned.

Ammonia has been tested and used on a small scale in small spark ignition internal combustion engines, but has not been used to power compression ignition internal combustion engines.

Large two-stroke uniflow scavenged turbocharged compression ignition cross-head internal combustion engines are commonly used in propulsion systems for large vessels or as prime movers for power plants. The vast size, weight and power output make the internal combustion engine quite different from a conventional internal combustion engine and categorize the large two-stroke turbocharged compression-ignition internal combustion engine itself.

EP2664777 discloses a large two-stroke uniflow scavenged turbocharged compression ignition internal combustion engine according to the present disclosure. In this engine, ammonia is injected into the combustion chamber as fuel and reductant for assisting the process of reducing NOx emissions with the aid of a reduction catalyst arranged downstream of the turbine of the turbocharger.

Disclosure of Invention

It is an object to provide a compression ignition internal combustion engine having at least one operating mode in which the primary fuel is ammonia.

The above and other objects are achieved by features of aspects of the present disclosure. Other embodiments are apparent from the description and drawings, and possible embodiments of aspects of the disclosure.

According to a first aspect, there is provided a large two-stroke turbocharged uniflow scavenged compression-ignition internal combustion engine configured in at least one operating mode for operating with ammonia as the primary fuel or ammonia as the sole fuel, the engine comprising: at least one cylinder having a reciprocating piston therein and a cylinder head covering the cylinder, the cylinder being disposed in a cylinder liner and the cylinder liner being provided with scavenging ports; a combustion chamber formed in the cylinder between the reciprocating piston and the cylinder head; an exhaust valve centrally disposed in the cylinder head; at least one prechamber arranged in the cylinder head and fluidly connected to the combustion chamber through an opening; and an ammonia valve having a nozzle with a nozzle orifice that opens into the at least one prechamber, the ammonia valve having an inlet connected to a source of pressurized ammonia, and the ammonia valve being configured for injecting liquid ammonia from the source of pressurized liquid ammonia into the prechamber through the nozzle orifice.

The use of ammonia as a fuel presents several challenges. One challenge is the low power density compared to typical hydrocarbon fuels, resulting in a significantly larger volume of fuel to be injected and thus a greater flow rate. This greater flow may result in flame extinction, i.e., the subsequent high flow and the resulting high velocity fuel jet will extinguish (blow out) the flame despite the ignition occurring at the beginning of the injection event. Another challenge is the low ignition propensity (low flammability) of ammonia compared to liquid hydrocarbon fuels. Yet another challenge is the high evaporative cooling of ammonia, which can result in cooling of the fuel upon injection, thereby increasing the required ignition energy. Due to the high evaporative cooling, the high temperature of the combustion zone is a prerequisite for stable combustion. The combination of these challenges has so far prevented the use of ammonia as the primary fuel in compression ignition engines.

The inventors have realized that injecting ammonia through the nozzle of the ammonia valve into a prechamber connected to the combustion chamber through an opening causes a significant deceleration of the fuel before the fuel enters the combustion chamber from the opening, and that the prechamber can function as a preheating chamber. Thus, the velocity of the fuel decreases as it enters the combustion chamber through the opening and the temperature of the fuel increases as it enters the combustion chamber, at least partially overcoming the above-described challenges of ammonia as a fuel for compression-ignition internal combustion engines.

In a possible implementation form of the first aspect, the engine comprises an ignition fluid valve associated with the at least one prechamber, the ignition fluid valve having an ignition fluid nozzle with a nozzle orifice, and the ignition fluid valve being coupled to a pressurized ignition fluid source. Thus, the ignition fluid may be mixed with ammonia in the prechamber to enhance reliable ignition of the ammonia. By injecting the ignition fluid at high pressure in the prechamber, it is ensured that the ignition fluid is sufficiently dispersed into the ammonia and that the ignition fluid has been sufficiently mixed with the ammonia when the mixture enters the combustion chamber.

In a possible implementation form of the first aspect, the source of pressurized ignition fluid is a source of pressurized pilot fluid or a source of pressurized ignition improver. The pilot fluid may be, for example, dimethyl ether (DME) or fuel oil. The ignition improver may be, for example, hydrogen from an external source or generated from ammonia itself using, for example, a catalytic process.

In a possible implementation form of the first aspect, the engine is configured to: the pilot fluid is injected through the nozzle of the ignition fluid valve and then ammonia is injected through the nozzle of the ammonia valve alone or the pilot fluid is injected through the ignition fluid valve and ammonia is injected through the ammonia valve at the same time.

In a possible implementation form of the first aspect, the prechamber is formed as an insert arranged in the cylinder head. Thus, if the prechamber or the opening between the prechamber and the combustion chamber is damaged, the prechamber can be easily replaced by replacing the insert without having to manipulate (work) the entire cylinder head.

In a possible implementation form of the first aspect, the prechamber is formed together with the ammonia valve as a single unit, and wherein the single unit is an insert arranged in the cylinder head. Thus, the prechamber and the ammonia valve can be mounted in the cylinder head in a single operation.

In a possible implementation form of the first aspect, at least a portion of a wall defining the prechamber from the combustion chamber forms a protrusion from the cylinder head into the combustion chamber. By forming the protrusion into the combustion chamber, it is ensured that the wall defining the prechamber heats up during operation of the engine, thereby ensuring a high temperature in the prechamber and in the region of the combustion chamber close to the prechamber. Thus, high temperatures in the area where the ammonia reaches are ensured and reliable combustion is enhanced.

In a possible implementation form of the first aspect, the openings have a given cross-sectional area such that the combined cross-sectional area of the nozzle holes is smaller than the cross-sectional area of the opening between the prechamber and the combustion chamber, preferably the combined cross-sectional area of the nozzle holes is significantly smaller than the cross-sectional area of the opening, and most preferably the combined cross-sectional area of the nozzle holes is smaller than half the cross-sectional area of the opening. Thus, it is ensured that ammonia enters the combustion chamber at a significantly lower rate than the rate at which ammonia enters the prechamber.

In a possible implementation form of the first aspect, a plurality of prechambers are arranged around the exhaust valve.

In a possible implementation form of the first aspect, the pressurized ammonia source is a pressurized liquid phase ammonia source.

In a possible implementation form of the first aspect, the engine is configured for simultaneous injection of ammonia and another fuel into the prechamber.

In a possible implementation form of the first aspect, the engine comprises a fuel valve having a nozzle with a nozzle hole leading to the at least one prechamber, the fuel valve having an inlet connected to a source of further pressurized fuel, the fuel valve being configured for injecting the further fuel from the source of further fuel into the prechamber through the nozzle hole.

According to a second aspect, there is provided a retrofit kit for a compression ignition internal combustion engine for adapting the engine to be in at least one mode of operation for operating with ammonia as the primary fuel or with ammonia as the sole fuel, the engine comprising: at least one cylinder having a reciprocating piston therein and a cylinder head covering the cylinder; a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder head, the retrofit kit comprising: at least one prechamber for mounting in the cylinder head and having an opening for connecting the prechamber to the combustion chamber; and an ammonia valve having a nozzle with a nozzle orifice leading to the at least one prechamber, the ammonia valve having an inlet for connection to a source of pressurized liquid ammonia, the ammonia valve being configured for injecting liquid ammonia from the source of pressurized liquid ammonia through the nozzle orifice into the prechamber.

These and other aspects will be apparent from the embodiments described below.

Drawings

In the following detailed portion of the disclosure, aspects, embodiments and implementations will be described in more detail with reference to example embodiments shown in the drawings in which:

FIG. 1 is a front view of a large two-stroke diesel engine according to an example embodiment;

FIG. 2 is a side view of the large two-stroke engine of FIG. 1;

FIG. 3 is a schematic illustration of the large two-stroke engine according to FIG. 1;

FIG. 4 is a detailed cross-sectional view of a cylinder of the large two-stroke engine of FIG. 1;

FIG. 5 is a schematic illustration of an ammonia valve used in the large two-stroke engine of FIG. 1;

FIG. 5a is a schematic illustration of a fuel valve for another fuel used in the large two-stroke engine of FIG. 1;

FIG. 6 is a schematic illustration of an ignition fluid valve used in the embodiment of the large two-stroke engine of FIG. 1; and

fig. 7 is a schematic cross-sectional view of an ammonia valve and a prechamber forming a single unit mounted in the cylinder head of the large two-stroke engine of fig. 1.

Detailed Description

In the following detailed description, a compression ignition internal combustion engine will be described with reference to a large two-stroke, low-speed uniflow scavenging turbocharged compression ignition internal combustion engine with a crosshead in the example embodiment, but it should be understood that the compression ignition internal combustion engine may be of another type.

Fig. 1, 2 and 3 show a large low-speed turbocharged two-stroke diesel engine with a crankshaft 8 and a crosshead 9. Fig. 3 shows a schematic diagram of a large low-speed turbocharged two-stroke diesel engine with its intake and exhaust systems. In this example embodiment, the engine has six cylinders 1 in a row (in line). Large low-speed turbocharged two-stroke diesel engines typically have four to fourteen cylinders 1 in a row, which cylinders 1 are carried by a cylinder frame 23, which cylinder frame 23 is carried by the engine frame 11. The engine may for example be used as a main engine in a ship or as a stationary engine for operating a generator in a power plant. The total output of the engine may be, for example, in the range of 1,000kw to 110,000 kw.

In this example embodiment, the engine is a two-stroke, single-flow type compression ignition engine having scavenging ports 18 at the lower region of the cylinder liners 1 and a central exhaust valve 4 at the top of each cylinder liner 1. The scavenging air travels from the scavenging air receiver 2 to the scavenging air ports 18 of the respective cylinders 1. The piston 10 reciprocating between the Bottom Dead Center (BDC) and the Top Dead Center (TDC) in the cylinder liner 1 compresses the scavenging gas. Ammonia is injected through an ammonia valve 50 disposed in the cylinder head 22. Combustion then occurs and exhaust gas is produced. The ammonia valve 50 is configured for injecting ammonia. In an embodiment, the engine is additionally provided with an additional fuel valve (not shown) adapted to inject conventional fuel, such as for example fuel or heavy fuel. In such an embodiment, the engine is a dual fuel engine and is further provided with a conventional fuel supply system (not shown) for supplying conventional fuel.

When the exhaust valve 4 is opened, the exhaust gas flows into the exhaust gas receiver 3 through the exhaust pipe associated with the cylinder 1 and up to the turbine 6 of the turbocharger 5 through the first exhaust conduit 19, and the exhaust gas flows out from the turbine 6 through the second exhaust conduit to the outlet 21 through the economizer 20 and into the atmosphere.

The turbine 6 drives by means of a shaft a compressor 7 which is supplied with fresh air via an air inlet 12. The compressor 7 delivers the pressurized scavenge air to a scavenge air duct 13 leading to the scavenge air receiver 2. The scavenge air in the scavenge air duct 13 passes through an intercooler 14 for cooling the scavenge air.

When the compressor 7 of the turbocharger 5 does not deliver sufficient pressure for the scavenge air receiver 2, i.e. under low or partial load conditions of the engine, the cooled scavenge air passes through an auxiliary blower 16 driven by an electric motor 17 that pressurizes the scavenge air flow. At higher engine loads, the compressor 7 of the turbocharger delivers a fully compressed scavenging gas and then the auxiliary blower 16 is bypassed through the check valve 15.

The engine is in at least one mode of operation operating with ammonia as the primary fuel, wherein ammonia is supplied to the ammonia valve 50 at a substantially steady pressure and temperature. Ammonia may be supplied to the ammonia valve 50 in either a liquid or gas phase. The ammonia liquid phase may be aqueous ammonia (ammonia-water mixture).

Ammonia fuel system 30 forms part of pressurized liquid phase ammonia source 40, and ammonia fuel system 30 supplies liquid ammonia at a relatively low supply pressure (e.g., a pressure of 30bar to 80 bar) to ammonia valve 50 via supply conduit 31. Alternatively, ammonia is supplied to the ammonia valve 50 in the gas phase at a relatively low supply pressure (e.g., a pressure of 30bar to 80 bar).

In an embodiment, ammonia is stored in the liquid phase in a pressurized storage tank (not shown) of type C at about 17 bar. Ammonia is a liquid phase at a pressure above 8.6bar and an ambient temperature of 20 ℃. However, ammonia is preferably stored at about 17bar to keep the ammonia in the liquid phase as the ambient temperature increases. Existing engines configured for operation with liquid phase stored LGPs or other gaseous fuels require relatively minor modifications to convert to ammonia combustion engines, i.e., engines using slightly modified versions of the fuel supply system according to embodiments of the present disclosure, that is, retrofit requiring relatively minor modifications because the same storage tanks may be used.

Ammonia valve 50 has an inlet connected to pressurized liquid ammonia source 40. In an embodiment, the pressurized liquid ammonia source is a portion of fuel system 30 configured to supply pressurized liquid ammonia to ammonia valve 50.

Referring now to fig. 4, the cylinder 1 with the cylinder head 22 sandwiched therebetween is carried by a cylinder frame 23. The piston 10 is shown in dashed lines in both the bottom dead center and the top dead center. A combustion chamber is formed within the cylinder between the reciprocating piston 10 and the cylinder head 22. The cylinder head 22 is provided with a central exhaust valve 4. For each cylinder 1, there are two or three ammonia valves 50 arranged in the cylinder head 22 around the central exhaust valve 4 (distributed circumferentially around the exhaust valve 4).

The ammonia valve 50 is shown in more detail in fig. 5, and the ammonia valve 50 comprises an elongated valve body having a nozzle 51 at a front end of the elongated body. The ammonia valve 50 is provided with an ammonia inlet. The ammonia inlet is connected to a pressurized liquid phase ammonia source 40. The nozzle 51 is preferably removably attached to the elongate body.

The nozzle 51 is provided with one or more nozzle holes 52. The nozzles 51 and the nozzle holes 52 are arranged such that ammonia is injected into the prechamber 33.

The ammonia valve 50 may be of a type controlled by a control signal for performing an ammonia injection event, and thus, this type of ammonia valve 50 may be connected to a common rail type supply of ammonia having a substantially constant pressure. The control signal is synchronized with the engine cycle to ensure proper ammonia injection timing.

Alternatively, the ammonia valve 50 may be of a type that opens when the supply pressure at the ammonia inlet exceeds a given threshold and closes again when the supply pressure at the ammonia inlet falls below the given threshold. This latter type of ammonia valve 50 would need to be connected to a pressurized liquid phase ammonia source having a variable pressure that is controlled to be synchronized with the engine cycle.

A prechamber 33 is associated with each of the ammonia valves 50. The prechamber 33 is arranged as a part of the cylinder head 22, which part is preferably in the form of an insert 55, which insert 55 is mounted in the cylinder head 22, preferably in a removable manner in the cylinder head 22. By arranging the prechamber 33 in the insert 55, maintenance or repair of the prechamber 33 can be performed by simply exchanging the insert 55 without having to exchange or repair the entire cylinder head 22. In the embodiment shown in fig. 7, the prechamber 33 is formed as a single unit together with the ammonia valve 50. Which in turn is an insert arranged/mounted in the cylinder head 22, preferably removably mounted in the cylinder head 22.

The prechamber 33 is in fluid communication with the combustion chamber via an opening 35. Preferably, the cross-sectional area of the opening 35 is substantially larger than the combined cross-sectional area of the nozzle holes 52 of the nozzle 51. Most preferably, the cross-sectional area of the opening 35 is twice or more than twice the combined cross-sectional area of the nozzle holes 52.

The wall defining the prechamber 33 from the combustion chamber forms a projection from the cylinder head 22 into the combustion chamber. Preferably, the opening 35 is arranged in a portion of the wall forming the protrusion. By arranging the wall as a protrusion into the combustion chamber, it is ensured that the wall heats up during engine operation and thus the pre-chamber 33 itself will heat up during engine operation, thereby promoting reliable ignition of the ammonia within the pre-chamber.

In an embodiment, an ignition fluid valve 60 (as shown in fig. 6) is associated with prechamber 33. Here, an ignition fluid valve 60 is mounted in the cylinder head 22, wherein an ignition fluid nozzle 61 having a nozzle hole 62 is arranged such that an ignition fluid is injected into the prechamber 33 by the action of the ignition fluid valve 60. Firing fluid valve 60 has an inlet connected to pressurized firing fluid source 44. In an embodiment, the ignition fluid is a pilot fluid (i.e. a fluid injected into the prechamber at the beginning of the main injection (before or just at the beginning), such as fuel oil (e.g. diesel), DME, hydrogen (hydrogen may be used as pilot fluid or as ignition promoter). The operation of the ignition fluid valve 60 is synchronized with the engine cycle such that the ignition fluid is injected into the prechamber 33 before and/or together with the ammonia. Thus, the engine according to the embodiment is configured to inject the pilot fluid through the nozzle 61 of the ignition fluid valve 60 and then inject ammonia through the nozzle 51 of the ammonia valve 50 alone or inject the pilot fluid through the ignition fluid valve 60 and simultaneously inject ammonia through the ammonia valve 50.

In another embodiment, the ignition improver medium is added to the ammonia prior to or at the time of injection into the prechamber. In an embodiment, the ignition improver is hydrogen gas mixed with ammonia in the gas phase. However, other media having suitable ignition characteristics may also be used. For ammonia in the liquid phase, the ignition improver is a substance that is also in the liquid phase and thus can be mixed with the ammonia in the liquid phase. For ammonia in the gas phase, the ignition improver is a substance that is also in the gas phase and thus can be mixed with ammonia in the gas phase.

In an embodiment, the engine is configured for simultaneous injection of ammonia and another fuel into the prechamber 33. In embodiments, the further fuel is a conventional hydrocarbon fuel, such as fuel oil or natural gas, i.e. the further fuel may be in liquid or gas phase. Ammonia may be supplied to the ammonia valve 50 in either a liquid or gas phase.

As shown in fig. 5a, in this embodiment the engine may comprise a fuel valve 70, which fuel valve 70 has a nozzle 71 with a nozzle hole 72, which nozzle hole 72 opens into at least one prechamber 33. The fuel valve 70 has an inlet connected to a source 49 of other pressurized fuel, the fuel valve 70 being configured for injecting other fuel from the source 49 of other fuel into the prechamber 33 via the nozzle holes 72.

A control unit (not shown) is configured to control operation of the engine, including activation and deactivation times of the ammonia valve 50 and the firing fluid valve 60.

By injecting the pilot fluid before injecting the ammonia, it is ensured that the temperature in the pre-chamber 33 is high enough to ignite the ammonia when it enters the pre-chamber 33. Further, in this case, the pre-chamber 33 will ensure that the pilot fuel mixes with ammonia as it is injected from the pre-chamber 33 into the main chamber.

The prechamber 33 allows the ignition fluid and ammonia to be mixed before entering the combustion chamber and thereby ensures a substantially uniform distribution of the ignition fluid and ammonia. The ignition fluid is thus part of the ammonia jet leaving the prechamber 33 through the openings 35 and provides an optimal use of the ignition fluid in terms of stabilizing the combustion process. The hot air (compressed scavenging) and the hot prechamber wall are most important during the initial part of the ammonia injection, thus overcoming the problems associated with high evaporative cooling of the ammonia. Thus, the pre-chamber 33 removes or at least minimizes the amount of required ignition fluid due to optimal mixing and increased heat transfer from the walls.

Stable combustion of ammonia in direct injection mode provides significantly enhanced combustion control and stability.

The nozzles/atomizers 51, 61 are arranged in the prechamber 33, which helps to protect the nozzles/atomizers 51, 61 from the harsh conditions in the combustion chamber, thereby increasing the life expectancy of the nozzles/atomizers 51, 61.

Various aspects and embodiments have been described in connection with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The reference signs used in the claims shall not be construed as limiting the scope. The drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, unless otherwise indicated, and should be considered a portion of the entire written description of this disclosure. As used in this specification, the terms "horizontal," "vertical," "left," "right," "up" and "down," as well as adjectives and adverb derivatives thereof (e.g., "horizontally," "rightward," "upward," etc.) refer only to the orientation of the structure as shown when the particular drawing figure is oriented toward the reader. Similarly, the terms "inwardly" and "outwardly" generally refer to the orientation of a surface relative to its axis of elongation or axis of rotation, as the case may be.

Claims

1. A large two-stroke turbocharged uniflow scavenged compression-ignition internal combustion engine configured in at least one operating mode for operation with ammonia as a primary fuel or ammonia as a sole fuel, the engine comprising:

-at least one cylinder (1), the cylinder (1) having a reciprocating piston (10) in the cylinder (1) and a cylinder head (22) covering the cylinder (1), the cylinder (1) being arranged in a cylinder liner and the cylinder liner being provided with scavenging ports (18),

a combustion chamber formed within the cylinder (1) and located between the reciprocating piston (10) and the cylinder head (22),

an exhaust valve (4), said exhaust valve (4) being arranged centrally in the cylinder head (22),

it is characterized in that the method comprises the steps of,

-at least one prechamber (33), which prechamber (33) is arranged in the cylinder head (22) and is fluidly connected to the combustion chamber through an opening (35), and

-an ammonia valve (50), the ammonia valve (50) having an ammonia nozzle (51) with an ammonia nozzle hole (52), the ammonia nozzle hole (52) opening into the at least one prechamber (33),

-said ammonia valve (50) having an inlet connected to a source of pressurized liquid ammonia (40), and

-the ammonia valve (50) is configured for injecting liquid ammonia from the pressurized liquid ammonia source (40) into the prechamber (33) through the ammonia nozzle holes (52).

2. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 1, comprising an ignition fluid valve (60) associated with the at least one pre-chamber (33), the ignition fluid valve (60) having an ignition fluid nozzle (61) with an ignition fluid nozzle orifice (62), and the ignition fluid valve (60) being coupled to a pressurized ignition fluid source (44).

3. The large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine of claim 2, wherein the ignition fluid valve (60) is configured to inject ignition fluid into the pre-chamber (33) through the ignition fluid nozzle (61).

4. The large two-stroke turbocharged uniflow scavenged compression-ignition internal combustion engine of claim 2, wherein the pressurized ignition fluid source (44) is a pressurized pilot fluid source or a pressurized ignition promoter source.

5. The large two-stroke turbocharged uniflow scavenged compression-ignition internal combustion engine of claim 2, wherein the engine is configured to: -injecting a pilot fluid through the ignition fluid nozzle (61) of the ignition fluid valve (60), and then injecting ammonia only through the ammonia nozzle (51) of the ammonia valve (50), or injecting pilot fluid through the ignition fluid valve (60) and simultaneously injecting ammonia through the ammonia valve (50).

6. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 1, wherein the pre-combustion chamber (33) is an insert (55) arranged in the cylinder head (22).

7. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 6, wherein the insert (55) is removably mounted in the cylinder head (22).

8. The large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine of claim 6, wherein the pre-combustion chamber (33) is formed as a single unit with the ammonia valve (50), and wherein the single unit is an insert mounted in the cylinder head (22).

9. The large two-stroke turbocharged uniflow scavenged compression-ignition internal combustion engine of claim 8, wherein the single unit is an insert removably mounted in the cylinder head (22).

10. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 1, wherein at least a part of the wall defining the pre-combustion chamber (33) from the combustion chamber forms a protrusion from the cylinder head (22) into the combustion chamber.

11. The large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine of claim 10, wherein the projection is a projection from a side of the cylinder head (22) facing the combustion chamber.

12. The large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine of claim 1, wherein the openings (35) have a given cross-sectional area, and the combined cross-sectional area of the ammonia nozzle holes (52) is smaller than the cross-sectional area of the openings (35).

13. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 1, wherein a plurality of pre-chambers (33) are arranged around the centrally located exhaust valve (4).

14. The large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine of claim 1, wherein the pressurized liquid ammonia source (40) is a pressurized liquid phase ammonia source.

15. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 14, which engine is configured for simultaneous injection of ammonia and another fuel into the pre-chamber (33).

16. A large two-stroke turbocharged uniflow scavenged compression ignition internal combustion engine as claimed in claim 15, the engine comprising a fuel valve (70), the fuel valve (70) having a fuel nozzle (71) with a fuel nozzle bore (72), the fuel nozzle bore (72) leading to the at least one pre-chamber (33), the fuel valve (70) having an inlet connected to a source (49) of other pressurized fuel, the fuel valve (70) being configured for injecting other pressurized fuel from the source (49) of other pressurized fuel into the pre-chamber (33) through the fuel nozzle bore (72).

17. A retrofit kit for a compression ignition internal combustion engine for adapting the engine to be in at least one operating mode for operating with ammonia as a primary fuel or ammonia as a sole fuel, the engine comprising:

-at least one cylinder (1), said cylinder (1) having a reciprocating piston (10) located in said cylinder (1) and a cylinder head (22) covering said cylinder (1),

the retrofit kit includes:

at least one prechamber (33), said at least one prechamber (33) being intended to be mounted in the cylinder head (22) and having an opening (35) for connecting the prechamber (33) to the combustion chamber,

said ammonia valve (50) having an inlet for connection to a source of pressurized liquid ammonia (40),

18. The retrofit kit for a compression ignition internal combustion engine according to claim 17, wherein the pre-combustion chamber (33) is formed in an insert (55) for mounting in the cylinder head (22).

19. The retrofit kit for a compression ignition internal combustion engine according to claim 17, wherein the pre-combustion chamber (33) is formed in an insert removably mounted in the cylinder head (22).

20. The retrofit kit for a compression ignition internal combustion engine according to claim 18 or 19, wherein the prechamber (33) is formed together with the ammonia valve (50) as a single unit, and wherein the single unit is an insert for mounting in the cylinder head (22).