CN117307376A - Large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine - Google Patents

Abstract

A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine comprising: at least one fuel inlet valve associated with the cylinder and disposed in the cylinder liner between the scavenging gas inlet and the cylinder head or in the cylinder head for admitting a first fuel during a stroke; at least one fuel injection valve disposed in the cylinder head or the cylinder liner; at least one pilot ignition prechamber arranged in the cylinder head or cylinder liner, having at least one prechamber port leading to the combustion chamber for igniting the mixture of the first fuel and the scavenging gas in the combustion chamber with fuel introduced into said prechamber, wherein the fuel injection valve is arranged to introduce fuel into the pilot ignition prechamber during otto-cycle mode operation and to inject fuel into at least the combustion chamber during diesel-cycle operation. Thus, the overall cost of the engine will be reduced, avoiding separate pilot fuel injection valves and supply systems, while still providing good performance.

Description

Large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine

Technical field

The present invention relates to a large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine, which has an Otto cycle mode. In the Otto cycle mode, the internal combustion engine relies on a first fuel (for example, ammonia, methane, methanol , ethane, liquefied petroleum gas or dimethyl ether) and fuel operation for ignition of the first fuel; and a Diesel cycle mode in which the internal combustion engine operates solely on fuel, the The internal combustion engine includes: at least one cylinder with a cylinder liner; a piston that reciprocates between bottom dead center (BDC) and top dead center (TDC); and a cylinder head defining a combustion chamber; a scavenging gas inlet arranged at the cylinder in the bottom section, for allowing oxygen-containing scavenging gas to enter the combustion chamber at least when the piston is at its bottom dead center position; at least one fuel inlet valve associated with the cylinder and arranged in the cylinder liner and at the scavenging gas inlet between or arranged in the cylinder head for admitting the first fuel during the stroke of the piston from BDC to TDC; at least one fuel injection valve arranged in the cylinder head or cylinder liner for admitting the first fuel during the piston's stroke from BDC to TDC; Fuel is injected at or near TDC; at least one pilot ignition pre-combustion chamber arranged in the cylinder head or cylinder liner and having at least one pre-combustion chamber port leading to the combustion chamber for utilizing the pilot ignition pre-combustion introduced into The fuel in the chamber ignites a first fuel and scavenge gas mixture in the combustion chamber, wherein the at least one fuel injection valve (52) is arranged to introduce fuel into the pilot ignition pre-ignition zone during Otto cycle mode operation of the internal combustion engine. In the combustion chamber (51).

Background technique

An example of such a large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine is known from JP 2020037923. In this prior art document, different fuel injection valves are used to inject fuel in Otto cycle mode and Diesel cycle mode respectively.

Large turbocharged two-stroke single-flow internal combustion engines with crossheads are used, for example, to propel large ocean-going vessels or as prime movers in power plants. Not only are these two-stroke diesel engines large in size, they are also constructed differently than any other internal combustion engine. Their exhaust valves may weigh up to 400kg, their pistons can be up to 100cm in diameter, and the maximum operating pressure in the combustion chamber is typically several hundred bars. The forces involved at these high pressure levels and piston sizes are enormous.

Recently, large two-stroke diesel engines have been required to be able to handle alternative fuel types such as ammonia, ethane, LPG, dimethyl ether and/or other similar fuels. Engines that can operate in both fuel and alternative fuel modes are often referred to as dual-fuel engines. In fuel mode, the engine runs on fuel only. In alternative fuel mode, the engine runs on alternative fuel and pilot fuel. run.

Dual-fuel engines used for these alternative fuels have separate fuel systems for these highly volatile fuels. In all cases, equipment needs to be present to completely drain fuel from the fuel system, i.e. fuel lines, valves, pumps, etc., in order to allow safe engine shutdown, fuel conversion to fuel oil or to facilitate maintenance.

A large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine that operates in Otto cycle mode using gaseous fuel admitted by fuel valves, which are usually arranged centrally or in the middle along the length of the cylinder liner. The mixture of gaseous fuel and oxygenated scavenge gas in the cylinder head, i.e. the engine which admits the gaseous fuel into the combustion chamber during the upward stroke of the piston from bottom dead center (BDC) to TDC (thus operating according to a premixing process) and The compressed mixture is ignited at or near top dead center (TDC) by a timed ignition device, such as pilot fuel or pilot gas injection.

The advantage of this type of intake using a fuel valve (inlet valve) arranged in the cylinder liner or cylinder head is that much lower fuel inlet pressures can be used (usually between about 5 bar and about 25 bar), which This is because the gaseous fuel is injected at a relatively low compression pressure compared to large two-stroke turbocharged internal combustion engines where the piston is at or near top dead center (TDC), i.e. when Gaseous fuel is injected when the compression pressure in the combustion chamber is at or near its maximum value. The latter type of engine requires a much higher (usually above 300 bar) fuel injection pressure than the already high maximum compression pressure. Due to the volatility of gaseous fuels and their behavior at such high pressures, fuel systems capable of handling gaseous fuels at these extremely high pressures are expensive and complex.

Therefore, a fuel supply system for an engine that injects gaseous fuel during the compression stroke is significantly less expensive than an engine that injects gaseous fuel at high pressure when the piston is at or near TDC.

However, the fuel injection valve for a large two-stroke diesel engine according to the present invention is quite large and it is difficult to find space to install 2 or 3 main diesel fuel injection valves and 1 to 2 precombustion chambers, each associated with The pilot fuel injection valve is located on the engine cover. Additionally, fuel injection valves are expensive, and equipping the prechamber with a separate diesel fuel injection valve and fuel supply system would significantly increase costs (higher capital expenditure).

Contents of the invention

It is an object of the present invention to provide a large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine of the type mentioned in the introduction, in which the above-mentioned challenges related to the space and cost required for fuel injection valves are at least significantly reduced.

The foregoing and other objects are achieved by the technical solutions claimed in this disclosure. Further embodiments emerge from the further features, description and drawings.

According to a first aspect, a large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine is provided, which has: Otto cycle mode, in which the internal combustion engine relies on a first fuel (for example, ammonia, methane , methanol, ethane, liquefied petroleum gas or dimethyl ether) and fuel operation for ignition of the first fuel; and a Diesel cycle mode in which the internal combustion engine operates solely on fuel, so The large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine includes: at least one cylinder with a cylinder liner; a piston that reciprocates between bottom dead center (BDC) and top dead center (TDC); and a cylinder defining a combustion chamber. a cover; a scavenging gas inlet arranged in the cylinder bottom section for admitting oxygen-containing scavenging gas into the combustion chamber at least when the piston is in its bottom dead center position; at least one fuel inlet valve, associated with the cylinder and arranged between a scavenge gas inlet in the cylinder liner and the cylinder head or arranged in the cylinder head for admitting the first fuel during a stroke of the piston from BDC to TDC; at least one fuel injection valve, The fuel injection valve is arranged in the cylinder head or cylinder liner for injecting fuel when the piston is at or near TDC; at least one pilot ignition pre-combustion chamber is arranged in the cylinder head or cylinder liner and has at least one opening leading to a prechamber port of the combustion chamber for igniting a mixture of first fuel and scavenge gas in the combustion chamber with fuel introduced into the pilot ignition prechamber, wherein the at least one fuel injection valve is arranged to Fuel is introduced into the pilot ignition prechamber during Otto cycle mode operation of the internal combustion engine, and characterized in that the at least one fuel injection valve is further arranged to inject fuel into the pilot ignition chamber during Otto cycle mode operation of the internal combustion engine. Fuel is injected into at least the combustion chamber.

As a result, the total engine cost will be reduced since the same fuel injection valve can be used in both operating modes of the dual-fuel engine according to the invention, with the pilot ignition prechamber being used during Otto cycle mode operation Light the fuel. In this way, a separate pilot fuel injection valve and supply system is avoided while still providing the good performance aspects of an engine with a prechamber. In addition, more space will be available in the cylinder head to install fuel injection valves and other equipment, such as monitoring equipment.

The at least one fuel injection valve may be arranged to introduce fuel into both the pilot ignition chamber and the combustion chamber during Diesel cycle mode operation of the internal combustion engine. This embodiment may simplify and reduce the cost of the fuel injection valve and further keep the fuel passage to the pre-chamber clean during Diesel cycle mode operation of the internal combustion engine.

The at least one fuel injection valve can in principle be designed in any suitable way, however, it is preferred that it is provided with at least one first nozzle opening which leads to the pre-chamber chamber, for example via a channel. ; At least one second nozzle hole, which leads to the combustion chamber; and means for opening and closing the passages leading to the at least one first nozzle hole and the at least one second nozzle hole respectively.

Said at least one fuel injection valve may advantageously be of a type comprising: an elongated fuel valve housing having a rear end and a front end; and having at least one internal bore leading to said first and second nozzle bores. a nozzle arranged at the front end of the housing; a fuel passage extending from the rear end toward the front end and connected to a pressurized fuel source; and a pivotable shaft having a closed position and at least a first open position and a second open position. an axially displaceable valve needle, in the closed position the axially displaceable valve needle rests on the valve seat thereby preventing fuel flow to the nozzle, in the first open position and the second open position , the axially displaceable valve needle is lifted from the valve seat, thereby allowing fuel to flow through the at least one of the nozzles in a direction toward the first nozzle hole and the second nozzle hole an inner bore, wherein passage to the at least one first nozzle hole is open in the first open position and passage to the at least one second nozzle hole is in the second open position is open.

In one embodiment of the invention, the passage to said at least one first nozzle hole may also be open in said second open position, allowing fuel to enter both the prechamber and the combustion chamber.

Said at least one fuel injection valve may advantageously be a spool valve, wherein the valve needle includes an elongated member extending into a single internal bore in the nozzle and including a solid first portion and a portion furthest from the valve seat. a second hollow portion, said hollow portion comprising at least one orifice permitting fuel to enter said hollow portion, said orifice opening at its free end, wherein the valve needle first opens when it is raised to its position away from the valve seat position, the free end of the elongate member is lifted away and opens access to the at least one first nozzle orifice, and wherein when the valve needle is raised to its second open position away from the valve seat, the elongate member The free end is lifted away and opens access to the at least one second nozzle hole.

The elongated member of the slide valve may comprise an element closing access to the at least one first nozzle orifice when the valve needle is raised to its second open position away from the valve seat.

The at least one pilot ignition prechamber arranged in the cylinder head can be provided with more than one, preferably two or three prechamber ports leading to the combustion chamber.

Description of the drawings

The invention will be explained in more detail with reference to an exemplary embodiment shown in the drawing, in which:

1 is a front view of a large two-stroke dual-fuel engine according to an exemplary embodiment.

FIG. 2 is an elevation side view of the large two-stroke engine of FIG. 1 .

FIG. 3 is a schematic diagram of a large two-stroke engine according to FIG. 1 .

Figure 4 shows an example of a fuel injection valve that may be used in a large two-stroke dual-fuel engine according to the invention.

Figure 5 shows an insert with a fuel injection valve and a pre-chamber that can be used in a large two-stroke dual-fuel engine according to the invention.

Detailed ways

In the following detailed description, the present invention will be described with respect to a large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine, but it will be understood that the internal combustion engine may be of another type. The large turbocharged two-stroke single-flow crosshead dual internal combustion engine has two modes: Otto cycle mode and Diesel cycle mode. In Otto cycle mode, the internal combustion engine relies on fuel such as ammonia, methane, methanol, ethane, liquefied petroleum gas or Operating on a primary fuel such as dimethyl ether and fuel used to ignite the primary fuel, in Diesel cycle mode the internal combustion engine runs solely on fuel.

Figures 1, 2 and 3 show a large low speed turbocharged two-stroke dual fuel engine with crankshaft 8 and crosshead 9. Figure 3 shows a schematic diagram of a large low-speed turbocharged two-stroke dual-fuel engine with an intake system and an exhaust system. In this exemplary embodiment, the engine has six in-line cylinders. Large low-speed turbocharged two-stroke dual-fuel engines typically have four to fourteen in-line cylinders carried by a cylinder frame 23 carried by the engine frame 11 . The engine may be used, for example, as the main engine of a marine vessel or as a stationary engine for operating a generator in a power station. The total output of the engine may range, for example, from 1,000 kW to 110,000 kW.

In this exemplary embodiment, the engine is a two-stroke, single-flow, dual-fuel compression ignition engine with scavenging ports 18 in the lower region of the cylinder liners 1 and a central exhaust valve at the top of each cylinder liner 1 4. In the example shown, the engine has at least one operating mode in which the engine relies on a first fuel such as ammonia, methane, methanol, ethane, petroleum natural gas, or dimethyl ether and for a fuel-ignited fuel-oil operation; and a second Diesel cycle mode in which the engine is run solely on conventional fuel, such as fuel oil (marine diesel) or heavy fuel oil.

Scavenging air is delivered from the scavenging air receiver 2 to the scavenging port 18 of each cylinder 1 . The piston 10 reciprocating in the cylinder liner 1 between bottom dead center (BDC) and top dead center (TDC) compresses scavenging air. In Otto cycle mode fuel, for example in the form of ammonia, is injected into the combustion chamber 53 in the cylinder liner 1 at or near TDC via a low-pressure fuel valve 50 , which in the embodiment shown is arranged in the cylinder Cover 22. In an alternative embodiment, fuel in Otto cycle mode may enter through a low pressure fuel valve 50' arranged in the cylinder liner 1 and somewhere midway between the scavenging port 18 and the cylinder head 22. In a dual-fuel engine according to the invention, timed ignition at or near TDC is triggered by injecting ignition fluid into a pre-chamber 51 arranged in the cylinder head 22 and leading to the combustion chamber 53, As explained in more detail later. It then burns and produces exhaust gases. Each cylinder head 22 is provided with only one fuel valve 50 in the embodiment shown, however it can also be provided with two or more fuel valves 50 . The fuel valve 50 in the embodiment shown is configured to inject only one specific type of fuel, such as ammonia, and therefore there will also be one or more fuel injection valves 52 for injecting conventional fuel into the combustion chamber 53 . Therefore, the engine will have two or more fuel valves. Both fuel valves 50 and 52 are arranged in the cylinder head 22 around the central exhaust valve 4 in the embodiment shown. In the engine according to the invention, ignition fuel is injected into the pre-combustion chamber 51 through the fuel injection valve 52 .

When the exhaust valve 4 is opened, the exhaust gas flows through the exhaust pipe associated with the cylinder into the exhaust gas receiver 3 and flows forward through the first exhaust pipe 19 to the turbine via the selective catalytic reduction (SCR) reactor 28 The turbine 6 of the supercharger 5 , from which the exhaust gases flow away via the economizer 20 , reaches the outlet 21 through the second exhaust pipe and flows into the atmosphere. SCR reactors reduce _NOx emissions. In embodiments not shown, the engine may not include SCR reactor 28 . The engine may include an exhaust gas recirculation (EGR) system that recirculates some of the exhaust gas from exhaust pipe 19 to scavenge air pipe 13 .

The turbine 6 drives a compressor 7 via a shaft, to which fresh air is supplied via an air inlet 12 . The compressor 7 delivers pressurized scavenging air to a scavenging air line 13 leading to the scavenging air receiver 2 . The scavenging air in the scavenging air pipe 13 passes through the intercooler 14 to cool the scavenging air.

Cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17 when the compressor 7 of the turbocharger 5 does not deliver sufficient pressure to the scavenging air receiver 2, i.e. during low or part engine load conditions. The auxiliary blower pressurizes the scavenging air flow. At higher engine loads, the turbocharger compressor 7 delivers sufficient compressed scavenging air, which then bypasses the auxiliary blower 16 via the check valve 15 and the electric motor 17 is deactivated.

The engine is in Otto cycle mode, operating with an alternative first fuel (e.g., ammonia, methane, methanol, ethane, liquefied petroleum gas, or dimethyl ether) as the primary fuel at a substantially stable pressure. and temperature is supplied to the first fuel valve 50 .

Conventional fuel systems are well known and are not shown or described in further detail. The first fuel system 30 initially supplies the fuel valve 50 .

According to the present invention, fuel injection valve 52 is arranged to introduce fuel into the pilot ignition prechamber 51 during Otto cycle mode operation of the engine and to inject fuel into at least the combustion chamber during Diesel cycle mode operation of the engine. 53 in.

An example of a fuel injection valve 52 capable of introducing fuel into the pilot ignition prechamber 51 during Otto cycle mode operation of the engine and during Diesel cycle mode operation of the engine is shown in FIG. 4 Fuel is injected into at least combustion chamber 53 . The fuel injection valve includes a first nozzle bore 31 which opens into a pre-chamber 51 , possibly via a channel 56 , see Figure 5 , and a second nozzle bore 33 which holes opening into the combustion chamber 53; and means in the form of elongated members 34 for opening and closing the access to the first 31 and second 33 nozzle holes respectively.

Fuel injection valve 52 includes an elongated fuel valve housing 35 having a rear end 36 and a front end 37, a nozzle 38 having an inner bore 39 leading to the first and second nozzle holes 31, 33, wherein the nozzle 38 is arranged at the front end 37 of the housing 35 . Fuel passage 40 extends from aft end 36 toward front end 37 and is connected to a pressurized fuel source, not shown. The fuel injection valve 52 includes an axially displaceable needle 41 having: a closed position in which it rests on the valve seat 42 thereby preventing fuel flow to the nozzle 38 ; and at least a first open position and a second open position in which the axially displaceable valve needle 41 is lifted from the valve seat 42 to allow fuel to flow along the direction The first and second nozzle holes 31 , 33 are directed to flow through the inner hole 39 in the nozzle 38 , wherein the passage to the first nozzle hole 31 is open in the first open position. Access to both the first nozzle hole 31 and the second nozzle hole 33 is open in the second open position. The fuel injection valve 52 shown in FIG. 4 is a slide valve, which is characterized by a special design of the valve needle 41 . The valve needle 41 of the illustrated spool valve includes an elongated member 34 which extends into a single internal bore 39 and includes a solid first portion 43 and a hollow second portion 44 furthest from the valve seat 42, so that The hollow portion includes at least one aperture 45 and is open at its free end 46 . During operation, when the valve needle 41 is lifted to its open position away from the valve seat 42, the free end 46 of the elongated member 34 is also lifted away from the nozzle bore 31, thereby allowing fuel in the inner bore 39, in the elongated member 34 and the wall of the inner bore 39 downwardly to one or more orifices 45 and into the hollow portion 44 from which fuel continues out of the free end 46 of this opening and in the first open position of the valve needle 41 into the first nozzle hole 31 and in the second open position to both the first nozzle hole 31 and the second nozzle hole 33 . An axially displaceable valve needle 41 is slidably received with a narrow clearance in a longitudinal bore 47 in the elongated valve housing 35 . The nozzle holes 31, 33 are located axially adjacent the end 48 of the nozzle 38, which end 48 is closed in the embodiment shown. Additionally, nozzle 38 is shown positioned relative to housing 35 by positioning pins 49 .

In Figure 5 there is shown an insert 55 with a pre-chamber 51 and a fuel injection valve 52 as shown in Figure 4, which insert can be used in a large two-stroke dual-fuel engine according to the invention, for new or For modification. The insert 55 is installed in the cylinder head 22 and includes a first passage 56 connecting the first nozzle hole 31 of the fuel injection valve 52 and the pre-combustion chamber 51 and a second passage 57 connecting the second passage 57 . Nozzle hole 33 and combustion chamber 53. In Figure 5, the valve needle 41, and therefore the elongated member 34, is in its closed position, preventing fuel from flowing to either of the nozzle holes. Lifting the valve needle 41 to its first open position will allow fuel to enter the pre-chamber 51 via the first passage 56 and further raising the valve needle 41 to its second open position will allow fuel to also enter the combustion chamber via the second passage 57 .

Claims (8)

1. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine having: an otto cycle mode in which the large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine operates on a first fuel such as ammonia, methane, methanol, ethane, liquefied petroleum gas or dimethyl ether and fuel for igniting the first fuel; and a diesel cycle mode in which the large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine operates on fuel only, the large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine comprising: at least one cylinder with a cylinder liner (1); a piston (10) that reciprocates between a Bottom Dead Center (BDC) and a Top Dead Center (TDC); and a cylinder head (22) defining a combustion chamber (53); -a scavenging gas inlet (18) arranged in a bottom section of the cylinder for admitting an oxygen-containing scavenging gas into the combustion chamber (53) at least when the piston (10) is in its bottom dead centre position; at least one fuel inlet valve (50) associated with the cylinder and arranged in the cylinder liner (1) between the scavenging gas inlet (18) and the cylinder head (22), or in the cylinder head (22), for admitting the first fuel during a stroke of the piston (10) from bottom dead centre to top dead centre; at least one fuel injection valve (52) arranged in the cylinder head (22) or in the cylinder liner (1) for injecting fuel when the piston is at or near top dead center; at least one pilot ignition prechamber (51) arranged in the cylinder head (22) or in the cylinder liner (1) having at least one prechamber port (54) leading to the combustion chamber (53) for igniting a mixture of a first fuel and a scavenging gas in the combustion chamber (53) with fuel introduced into the pilot ignition prechamber (51), wherein the at least one fuel injection valve (52) is arranged to introduce fuel into the pilot ignition prechamber (51) during otto cycle mode operation of the large turbocharged two-stroke uniflow cross-head dual fuel internal combustion engine, characterized in that the at least one fuel injection valve (52) is furthermore arranged to inject fuel at least into the combustion chamber (53) during diesel cycle mode operation of the large turbocharged two-stroke uniflow cross-head internal combustion engine.

2. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine as claimed in claim 1, characterized in that the at least one fuel injection valve (52) is arranged to introduce fuel into both the pilot ignition prechamber (51) and the combustion chamber (53) during diesel cycle mode operation of the large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine.

3. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine as claimed in claim 1, wherein the at least one fuel injection valve (52) is provided with: at least one first nozzle hole (31) leading to the pilot-ignition prechamber (51) which can be led to the pilot-ignition prechamber via a channel (56); at least one second nozzle hole (33) leading to the combustion chamber (53); and means (34) for opening and closing the passage to the at least one first nozzle hole (31) and the at least one second nozzle hole (33), respectively.

4. The large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine of claim 1, wherein the at least one fuel injection valve (52) comprises: an elongated fuel valve housing (35) having a rear end (36) and a front end (37); -a nozzle (38) having at least one internal bore (39) leading to the first nozzle hole (31) and the second nozzle hole (33), the nozzle (38) being arranged at the front end (37) of the housing (35); -a fuel passage (40) extending from the rear end (36) towards the front end (37) and connected to a pressurized fuel source; an axially displaceable valve needle (41) having a closed position in which the axially displaceable valve needle (41) rests on a valve seat (42) preventing fuel flow to the nozzle (38), and at least a first open position in which the axially displaceable valve needle (41) is lifted from the valve seat (42) allowing fuel flow through the at least one internal bore (39) in the nozzle (38) in a direction towards the first nozzle bore (31) and the second nozzle bore (33), and a second open position in which a passage to the at least one first nozzle bore (31) is open and a passage to the at least one second nozzle bore (33) is open.

5. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine as claimed in claim 4, characterized in that in the second open position the passage to the at least one first nozzle hole (31) is also open allowing fuel to enter both the pilot ignition prechamber (51) and the combustion chamber (53).

6. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine as claimed in any one of the preceding claims, wherein the at least one fuel injection valve (52) is a spool valve (52), wherein the valve needle (41) comprises an elongated member (34) protruding into a single bore (39) in the nozzle (38).

7. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine as claimed in claim 6 wherein the elongated member (34) of the spool valve (52) comprises a solid first part (43) and a hollow second part (44) furthest from the valve seat (42), the hollow second part (44) comprising at least one orifice (45) allowing fuel to enter the hollow second part (44), the orifice of the hollow second part opening at its free end (46), wherein the free end (46) of the elongated member (34) is lifted off and opens access to the at least one first nozzle hole (31) when the valve needle (41) is lifted to its first open position away from the valve seat (42), and wherein the free end (46) of the elongated member (34) is lifted off and opens access to the at least one second nozzle hole (33) when the valve needle (41) is lifted to its second open position away from the valve seat (42).

8. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine as claimed in claim 6 or 7, characterized in that the elongated member (34) of the spool valve (52) comprises an element that closes the passage to the at least one first nozzle bore (31) when the valve needle (41) is lifted to its second open position away from the valve seat (42).