JP2023160748A - Large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine and method of operating the same - Google Patents

Abstract

To provide a large turbocharged two-stoke uniflow crosshead compression ignition internal combustion engine with at least one mode of operation in which the engine is operated with both ammonia and an ignition fluid, such as fuel oil.SOLUTION: The engine comprises: at least one cylinder with a cylinder liner, a reciprocating piston in the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber formed inside the cylinder between the reciprocating piston and the cylinder cover; an ammonia fuel system configured for supplying pressurized ammonia to at least one ammonia fuel valve that is arranged in the cylinder cover or cylinder liner; and an ignition fluid system configured for supplying a pressurized ignition fluid to at least one ignition liquid valve arranged in the cylinder cover or cylinder liner. The ignition fluid system is configured to supply the ignition fluid into the combustion chamber for an injection duration of at least 20% of a determined duration of the ammonia fuel combustion.SELECTED DRAWING: Figure 3

Description

The present invention relates to a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine having at least one operating mode operating with both ammonia and an ignition fluid (e.g. fuel oil) as the fuel combusted within the engine. . The engine includes at least one cylinder having a cylinder liner and a reciprocating piston in the cylinder liner, a cylinder cover covering the cylinder; and a combustion engine formed in the cylinder between the reciprocating piston and the cylinder cover. an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed on the cylinder cover or the cylinder liner; an ammonia fuel system disposed on the cylinder cover or the cylinder liner; an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve located in the at least one ignition fluid valve.

Background of the invention

Large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engines are typically used as prime movers in large ocean-going ships such as container ships and power plants. This type of engine is very often operated on heavy oil or fuel oil. Its size, weight, and power set large two-stroke turbocharged compression ignition internal combustion engines apart from other combustion engines, placing this type of compression internal combustion engine in a unique category.

Internal combustion engines have traditionally been operated primarily with hydrocarbon fuels, such as fuel oils such as diesel oil or fuel gases such as natural gas or petroleum gas. Combustion of hydrocarbon fuels involves the production of greenhouse gases such as carbon dioxide (CO2), which can contribute to air pollution and climate change. Unlike impurities in petroleum fuels that result in byproduct emissions, the generation of CO2 is inevitable in the combustion of hydrocarbons. The energy density and CO2 footprint of a fuel depends on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Gaseous hydrocarbon fuels therefore emit less CO2 than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult and costly to handle and store. Research into fuels other than hydrocarbons is underway to reduce CO2 emissions.

Ammonia is a product obtained from petroleum, biomass, and renewable energy sources (wind, solar, hydropower, geothermal). Ammonia produced using renewable energy sources has virtually zero carbon emissions when combusted and produces no CO2, SOx, particulate matter or unburned hydrocarbons. Ammonia is currently attracting a great deal of interest as a fuel for internal combustion engines. The main reason for this is that it can be produced in a climate-friendly way using electricity from renewable energy sources such as solar, wind and wave energy, and because the combustion of ammonia itself does not contain greenhouse gases such as carbon dioxide. It is.

WO2020/252518A1 describes a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine of the type mentioned at the beginning.

When ammonia is used as a fuel in an internal combustion engine, there are two cases in which the ammonia fuel is introduced at relatively low pressure during the compression stroke of the piston, and two cases in which the ammonia fuel is introduced when the piston approaches top dead center (TDC). It may operate on the diesel principle of injecting high pressure into the combustion chamber. During the ammonia fuel injection/combustion phase of the piston cycle, cylinder pressure changes dramatically due to combustion chamber compression/expansion and combustion.

Ammonia has been tested and used on a small scale in small spark ignition internal combustion engines. However, compression ignition internal combustion engines have not yet been used on a large scale.

There are several technical challenges to using ammonia as a fuel. One of the challenges is the low power density compared to typical hydrocarbon fuels. This leads to a very large amount of fuel having to be injected and thus to a large flow rate. Such large flow rates can result in flame extinguishing. That is, even if ignition occurs very early in the injection event, the subsequent high flow rate and associated high velocity fuel jet will extinguish the flame. Another problem is that ammonia has low ignitability (combustibility) compared to liquid hydrocarbon fuels. A further challenge is the large evaporative cooling of ammonia, which cools the fuel upon injection. Therefore, a lot of ignition energy is required. Due to strong evaporative cooling, a high temperature in the fuel chamber is an essential condition for stable combustion. These technical challenges have strongly prevented the use of ammonia as the main fuel in compression ignition engines.

Internal combustion engines that can operate on two types of fuel are commonly referred to as dual-fuel engines. The two different fuels in a dual-fuel engine typically consist of a compression ignitable fuel oil, such as heavy oil or diesel, and a gaseous fuel, such as ammonia, methanol, LPG, LNG, ethane, etc., all of which can be It is necessary to add ignition fluid, in the form of fuel oil. Therefore, the concept of existing technical solutions for dual-fuel engines operating on ammonia and fuel oil is that the engine operates at maximum rating on fuel oil alone or with a minimum of pilot fuel oil for ignition of ammonia fuel. Although it uses ammonia fuel, it operates at its maximum rating with only ammonia fuel. Existing concepts include a fuel oil injection system optimized for full-rate volume delivery with fuel oil, an ammonia fuel system optimized for full-rate operation with ammonia, and a fuel oil injection system optimized for full-rate operation with ammonia (e.g. pilot fuel oil injection into the front chamber). A pilot fuel oil system suitable for ammonia ignition with a minimum amount of pilot fuel oil is required (according to the regulations). Some known dual fuel engines also use a full rate fuel oil injection system for pilot fuel oil injection. Here, the amount of pilot fuel oil is in the range of 1.5-5% of the full rate amount when operating on gas fuel.

However, existing ammonia and fuel oil dual fuel engines have a problem of complexity due to the pilot injection system of fuel oil. Additionally, the dual fuel concept does not operate the fuel oil injection system at full rate during ammonia fuel operation. For this reason, deposits are generated in the nozzle hole of the injection valve of the full rate fuel oil injection system when running on ammonia fuel, and when switching from ammonia operation to fuel oil operation, there is a risk that the full rate fuel oil injection system will not operate normally. Furthermore, because the laminar flame speed of ammonia is approximately one-tenth that of many hydrocarbons, flame extinguishment/extinction can occur even at low turbulence levels. For this reason, it is difficult to maintain combustion of ammonia using the full-rate fuel oil injection systems utilized in known dual fuel oil/gas engines, ensuring that all of the ammonia fuel introduced into the combustion chamber is Difficult to ignite and burn. The fuel oil injection time in the pilot fuel oil injection system is typically about 1 degree of crank angle, which only ensures ignition of the ammonia but does not guarantee complete combustion of all the ammonia fuel. .

The object of the invention is to provide a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine of the type mentioned at the outset, in which the above-mentioned problems are at least significantly reduced.

The above-mentioned and other objects are solved by the features of the independent claims. More specific implementation forms will become apparent from the dependent claims, the specification, and the drawings.

According to the first perspective, a large turbocharged two-stroke uniflow crosshead has at least one operating mode that operates using both ammonia and an ignition fluid such as fuel oil as the fuel to be burned in the engine. A compression ignition internal combustion engine is provided. This institution is
- at least one cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
- a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
- an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
, wherein the ignition fluid system is configured to supply ignition fluid into the combustion chamber for an injection duration of at least 20% of the determined ammonia fuel combustion duration.

The combustion time of the ammonia fuel is determined by the engine control system depending on the actual engine speed.

By injecting the ignition fluid into the combustion chamber of the cylinder of the internal combustion engine for a longer period of time than in known methods, a more complete combustion of the ammonia is achieved. Additionally, the pilot fuel injection system can be omitted since a full rate fuel oil injector can be used, thus providing considerable cost savings and better space for installing the fuel injector in the cylinder cover. be done. In addition, since the fuel oil injection device is kept in operation even during dual fuel operation using ammonia and ignition fluid (fuel oil, etc.), the fuel oil injection device can be maintained in a clean state, and the ammonia dual fuel operation It is possible to prepare for the switch from fuel oil operation to fuel oil operation.

In order to obtain a higher combustion rate, preferably a complete combustion rate, of ammonia, said ignition fluid system comprises at least 50%, preferably at least 80%, most preferably at least 95% of said determined ammonia fuel combustion duration. The injection duration may be configured to supply ignition fluid into the combustion chamber.

The ignition fluid system may be configured to supply ignition fluid into the combustion chamber at injection durations that increase from 2 degrees of crank angle at low engine speed to 20 degrees of crank angle at full rate engine rotation. In this specification, low engine speed is defined as the lowest possible engine speed.

In some embodiments, the ignition fluid system may be configured to continuously supply ignition fluid into the combustion chamber during the injection duration, or to provide ignition fluid into the combustion chamber intermittently. may be configured. If the ignition fluid system is configured to inject intermittently, the number of injections may be predetermined from 2 to 10, preferably 5, or the combustion performance and thus the combustion of ammonia may be determined in advance. may be variably determined by a control system that monitors a number of different engine operating parameters, such as cylinder pressure indicative of .

Said ignition fluid system ignites in an amount ranging from 5 to 50%, preferably from 15 to 40%, most preferably from 25 to 35% of the amount required for full speed operation when operating solely on ignition fluid, such as fuel oil. The combustion chamber may be configured to supply liquid into the combustion chamber.

The ammonia fuel system may be configured to supply ammonia to the combustion chamber in an amount of at least 60%, preferably at least 70% and most preferably at least 95% of the amount of fuel required for full speed operation of the engine. Costs are reduced as the size of the ammonia fuel system is reduced.

In some embodiments, the ammonia fuel valve may be connected to a prechamber that is connected to the combustion chamber by an opening. Injecting ammonia fuel into the combustion chamber through such a prechamber results in a significant deceleration of the fuel before it enters the combustion chamber through the opening, and furthermore the prechamber can act as a preheating chamber. . Therefore, the fuel velocity decreases when entering the combustion chamber through the opening, and the fuel temperature increases when entering the combustion chamber. Thereby, the above-mentioned problems associated with using ammonia as a fuel in compression ignition internal combustion engines are at least partially solved.

In such an embodiment of the invention, the engine includes an ignition fluid valve associated with the prechamber, the ignition fluid valve having an ignition fluid nozzle having a nozzle hole, and the ignition fluid valve being pressurized. may be combined with a source of ignition fluid. Thereby, the ignition liquid is mixed with ammonia in the prechamber, and the reliability of ignition of ammonia is improved. Injecting the ignition fluid into the prechamber at high pressure ensures that the ignition fluid is well dispersed in the ammonia, ensuring that the mixture of ignition fluid and ammonia is already well mixed when it enters the combustion chamber. be done.

The prechamber may have the form of an insert in the cylinder cover. Therefore, in the event of damage to the prechamber or the opening between the prechamber and the combustion chamber, the prechamber can be easily replaced by simply replacing the insert, and the entire cylinder cover can be repaired and machined for this purpose. There is no need to do this.

The prechamber may also form a single unit with the ammonia fuel valve. This single unit is an insert placed in the cylinder cover. Therefore, the prechamber and ammonia fuel valve can be attached to the cylinder cover in a single operation.

According to the second perspective, a large turbocharged two-stroke uniflow crosshead has at least one operating mode that operates using both ammonia and an ignition fluid such as fuel oil as the fuel to be burned in the engine. A method of operating a compression ignition internal combustion engine is provided. Here, the institution is
- at least one cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder covering the cylinder;
- a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
- an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
The method is characterized in that the ignition fluid is supplied into the combustion chamber for an injection duration of at least 20% of the determined ammonia fuel combustion duration.

The invention will now be explained in more detail with reference to exemplary embodiments shown in the drawings.
1 shows a front view of a large two-stroke diesel engine according to an exemplary embodiment; FIG. This figure shows an overview of the large two-stroke engine in Figure 1 as seen from the rear. 2 shows a schematic representation of the large two-stroke engine of FIG. 1; FIG.

Detailed explanation

In the following detailed description, a compression ignition internal combustion engine according to the invention will be described with reference to a large crosshead two-stroke uniflow scavenged internal combustion engine. However, it should be understood that the internal combustion engine may be of other types.

Figures 1-3 depict a large, turbocharged, low speed, two-stroke diesel engine. This engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a large, turbocharged, low-speed, two-stroke diesel engine with its intake and exhaust systems. In this embodiment, the engine has six cylinders 1 in series. Large, turbocharged, low-speed, two-stroke diesel engines typically have four to fourteen cylinders arranged in series. These cylinders are carried by a cylinder frame 23. The cylinder frame 23 is carried by the engine frame 11. Further, such an engine can be used, for example, as a main engine of a ship or a stationary engine for operating a generator in a power plant. The total power of the engine can be, for example, from 1000 kW to 110 000 kW.

The engine of this embodiment is a two-stroke uniflow compression ignition binary engine. Each cylinder liner 1 is provided with a scavenging port 18 in its lower region, and an exhaust valve is arranged in the center of its top. The engine has at least one mode of operation that operates on both ammonia or ammonia-based fuel and an ignition fluid such as fuel oil. The engine may further have at least one conventional fuel mode for operation on conventional fuels, such as fuel oil (marine diesel) or heavy oil.

During operation of the engine, scavenging air is directed through the scavenging air receiver 2 to the scavenging air port 18 of each cylinder 1. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1 and compresses scavenging air. Fuel is injected into the combustion chamber within the cylinder liner 1 through a fuel valve 50 disposed on the cylinder cover 22. The injected fuel includes ammonia and ignition fluid. Ammonia is supplied from an ammonia fuel supply device 30, and ignition liquid is supplied from an ignition fuel supply device 40, respectively. Ammonia injection may be performed at relatively low pressure during the stroke of piston 10 toward TDC, or may be performed at high pressure at or near TDC. Injection of ignition fluid always takes place at or near TDC and at high pressure. Following fuel injection, combustion occurs and exhaust gas is produced.

Each cylinder cover 22 is provided with two or more fuel valves 50. The fuel valves 50 may each be configured to inject only one particular type of fuel, ammonia and in this case ignition fluid. In such a case, two or more fuel valves 50 for injecting ammonia into the combustion chamber and two or more fuel valves 50 for injecting ignition fluid, for example in the form of conventional fuel, into the combustion chamber may be provided. become. Therefore, in such a case, the engine would have more than four fuel valves 50. If the fuel valve 50 is configured to inject both ammonia and conventional fuel at the same time (for example, it is configured to inject ammonia and conventional fuel in a premixed manner, or it is configured to inject ammonia and conventional fuel separately). When the fuel is configured to be injected from a nozzle hole), the number of fuel valves 50 provided in each cylinder may be two or more. The fuel valve 50 is arranged in the cylinder cover 22 around the exhaust valve 4 arranged in the center of the cylinder cover 22 .

The ignition fluid may be, for example, dimethyl ether (DME) or fuel oil. However, other forms of ignition accelerator may also be used, such as hydrogen. Since the engine is a dual fuel engine, it can also operate in a conventional fuel mode in which it is operated only on conventional fuels such as ignition fluid, e.g. fuel oil (marine diesel), or heavy oil.

In some embodiments, an ammonia fuel inlet valve is disposed along the cylinder liner. The ammonia fuel introduction valve introduces ammonia fuel into the cylinder liner at a relatively low pressure while the piston 10 is on its way from BDC to TDC and before passing through the ammonia fuel introduction valve. The piston 10 then compresses the scavenging air and fuel mixture. Ignition is performed at a predetermined timing at or near TDC. This ignition is performed by injection of ignition fluid or the like. In embodiments having an ammonia fuel inlet valve, the pressure at the time the ammonia fuel is introduced is significantly lower than the pressure at the time the fuel is injected in embodiments having a fuel valve 50 in the cylinder cover 22. As such, the pressure required for the fuel supply system 30 to deliver the ammonia fuel may be significantly lower and/or the pressure booster often used with the fuel valve 50 located in the cylinder cover 22 may be unnecessary.

When the exhaust valve 4 opens, the exhaust gas flows through the exhaust duct provided in the cylinder 1 to the exhaust receiver 3, further passes through the selective catalytic reduction reactor (SCR reactor) 38, and the first exhaust pipe 19 to the turbo. Proceed to the turbine 6 of the supercharger 5. From there, the exhaust flows through the second exhaust pipe 25 to the economizer 20 and is further discharged to the atmosphere through the outlet 21. SCR reactors reduce emissions in the exhaust, especially NOx.

Turbine 6 drives compressor 7 via a shaft. The compressor 9 is supplied with outside air through an air intake 12 . The compressor 7 sends compressed scavenging air to the scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air from the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging air flow if the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging air receiver 2, ie when the engine is at low or part load. When the engine load is high, the turbocharger compressor 7 can supply sufficiently compressed scavenging air, so that the auxiliary blower 16 is bypassed by the check valve 15 and the electric motor 17 is stopped. .

Ammonia is supplied to ammonia valve 50 at a substantially stable pressure and temperature. It may be supplied to the ammonia valve 50 in a liquid phase, or it may be supplied to the ammonia valve 50 in a gas phase. The liquid ammonia may be aqueous ammonia, ie, an aqueous ammonia solution.

According to the invention, the ignition fluid is injected into the combustion chamber of the cylinder of the internal combustion engine for a longer time than in known methods, whereby a more complete combustion of the ammonia is achieved. According to known techniques, the ignition fluid is injected over approximately 1 degree of crank angle. This corresponds to 5-10% of the combustion duration of ammonia fuel. In contrast, according to the invention, the ignition fluid system 40 is configured to supply ignition fluid into the combustion chamber with an injection duration of at least 20% of the determined ammonia fuel combustion duration.

In addition to more complete combustion of ammonia, an additional advantage of the present invention is that a full rate fuel oil injection system can be used for injection of ignition fluid. This is because of the required amount of ignition fluid to be used. This means that the pilot fuel oil injection system can be omitted, thus providing considerable cost savings and better space for installing the fuel injector in the cylinder cover. Furthermore, since the fuel oil injection device continues to operate in all operating modes of the engine, clean conditions can be maintained.

From the viewpoint of generating as little CO2 as possible even when the engine operates to simultaneously burn ammonia and ignition liquid, the amount of ignition liquid needs to be as small as possible without impairing the combustion of ammonia. However, in some situations, the ignition fluid may need to be injected into the combustion chamber for at least 50%, alternatively at least 80%, or alternatively at least 95% of the ammonia fuel combustion time to achieve complete combustion of the ammonia. The ignition fluid can also be injected into the combustion chamber for an injection time that is 100% of the combustion time of the ammonia fuel.

The injection duration during which the ignition fluid system 40 supplies ignition fluid into the combustion chamber may increase from about 2 degrees of crank angle at low engine speeds to about 20 degrees of crank angle at full rate engine rotation.

Depending on the embodiment, the ignition fluid system may be configured to continuously supply ignition fluid into the combustion chamber during the injection duration or may be configured to provide ignition fluid into the combustion chamber intermittently. It's okay. If the ignition fluid system is configured to inject intermittently, the number of injections may be predetermined from 2 to 10, preferably 5, or the number of injections may be determined in advance to improve the combustion performance and thus the combustion of ammonia. may be variably determined by a control system that monitors a number of different engine operating parameters, such as cylinder pressure.

The ignition fluid system is in the range of 5 to 50%, preferably 15 to 40%, most preferably 25 to 35% of the amount required for maximum rotational speed (maximum speed) when operating solely on ignition fluid, such as fuel oil. The ignition fluid may be supplied into the combustion chamber in an amount of .

The ammonia fuel system may be configured to supply ammonia to the combustion chamber in an amount of at least 60%, preferably at least 70% and most preferably at least 95%. Reducing the size of the ammonia fuel system reduces costs accordingly.

Claims (10)

According to the first perspective, a large turbocharged two-stroke uniflow crosshead has at least one operating mode that operates using both ammonia and an ignition fluid such as fuel oil as the fuel to be burned in the engine. A compression ignition internal combustion engine, the engine comprising:
at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
- a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed on the cylinder cover or the cylinder liner;
- an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
Equipped with
Engine, characterized in that the ignition fluid system is configured to supply ignition fluid into the combustion chamber for an injection duration of at least 20% of the determined ammonia fuel combustion duration. The ignition fluid system is configured to supply ignition fluid into the combustion chamber for an injection duration of at least 50%, preferably at least 80% and most preferably at least 95% of the determined ammonia fuel combustion duration. 2. An engine according to claim 1, characterized in that: The ignition fluid system is configured to supply ignition fluid into the combustion chamber at injection durations that increase from 2 degrees of crank angle at low engine speeds to 20 degrees of crank angle at full engine speed. , the institution according to claim 1. 4. An engine according to any preceding claim, wherein the ignition fluid system is configured to continuously supply ignition fluid into the combustion chamber during the injection duration. 4. An engine according to any preceding claim, wherein the ignition fluid system is configured to supply ignition fluid into the combustion chamber intermittently during the injection duration. If the ignition fluid system is configured for intermittent injection, the number of injections is predetermined from 2 to 10, preferably 5, or is indicative of the combustion performance and thus of the ammonia. 6. The engine of claim 5, wherein the engine is variably determined by a control system that monitors a plurality of different engine operating parameters, such as cylinder pressure. Said ignition fluid system is in an amount ranging from 5 to 50%, preferably from 15 to 40%, most preferably from 25 to 35% of the amount required for maximum rotational speed when operating solely on ignition fluid, such as fuel oil. 4. An engine according to any preceding claim, configured to supply ignition fluid into the combustion chamber. that said ammonia fuel system is configured to supply ammonia to the combustion chamber in an amount of at least 60%, preferably at least 70% and most preferably at least 95% of the amount of fuel required for full speed operation of the engine; An engine according to any one of claims 1 to 3, characterized in that: A method for operating a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine having at least one operating mode in which the engine operates using both ammonia and an ignition fluid such as fuel oil as fuel to be burned in the engine. Therefore, the said institution is
at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
- a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
- an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
, characterized in that the ignition fluid is supplied into the combustion chamber for an injection duration of at least 20% of the determined ammonia fuel combustion duration. Claim characterized in that said ignition liquid is supplied into said combustion chamber for an injection duration of at least 50%, preferably at least 80% and most preferably at least 95% of said determined ammonia fuel combustion duration. The method according to item 9.