DK179798B1

DK179798B1 - A large two-stroke uniflow scavenged gaseous fueled engine

Info

Publication number: DK179798B1
Application number: DKPA201770703A
Authority: DK
Inventors: Kjemtrup Niels
Original assignee: MAN Energy Solutions
Priority date: 2017-09-19
Filing date: 2017-09-19
Publication date: 2019-06-26
Also published as: KR102181690B1; CN109519305B; DK201770703A1; JP7291662B2; KR20190032244A; CN114278467A; JP2020122483A; JP2019056375A; JP6721647B2; CN109519305A

Abstract

A large two-stroke turbocharged uniflow scavenged internal combustion engine comprising: a combustion chamber delimited by a cylinder liner (1), a piston (10) and a cylinder cover (22), scavenge air ports (18) arranged in the cylinder liner (1), at least one exhaust valve (4) arranged in the cylinder cover (22), at least one fuel valve (30,31) arranged in the cylinder liner (1), for injecting a gaseous fuel into the combustion chamber, and a supply of both pressurized gaseous fuel (40) and of pressurized gas without calorific value (40) to said fuel valve (30), the engine being configured to inject both said gaseous fuel and said gas without calorific value via a fuel valve (30,31) into said combustion chamber.

Description

A LARGE TWO-STROKE UNIFLOW SCAVENGED GASEOUS FUELED ENGINE TECHNICAL FIELD

The disclosure relates to large turbocharged two-stroke internal combustion engines, in particular large two-stroke uniflow scavenged internal combustion engines with crossheads running on gaseous fuel.

BACKGROUND

Large two-stroke turbo charged uniflow charged internal combustion engines with crossheads are for example used for propulsion of large oceangoing vessels or as primary mover in a power plant. Not only due to sheer size, these twostroke diesel engines are constructed differently from any other internal combustion engines. Their exhaust valves may weigh up to 400 kg, pistons have a diameter up to 100 cm and the maximum operating pressure in the combustion chamber is typically several hundred bar. The forces involved at these high pressure levels and piston sizes are enormous.

Large two-stroke turbocharged internal combustion engines that are operated with gaseous fuel that is injected by fuel valves arranged medially along the length of the cylinder liner, i.e. engines that inject the gaseous fuel during the upward stroke of the piston starting approximately when the exhaust valve closes, compress a mixture of gaseous fuel and scavenging air in the combustion chamber and ignite by time ignition means, such as e.g. pilot oil injection. Thus, the piston compresses a mixture of gaseous fuel and scavenging air and consequently there is a risk of knock. In the art, this type of knock is referred to as diesel knock.

Problems with diesel knock can be reduced by ensuring that the charge in the combustion chamber is as homogeneous as possible. However, obtaining homogeneous scavenging air and gaseous fuel charge is challenging since only a very short window of the engine cycle is available for obtaining the homogeneous charge due to the fact that the window in the engine cycle from the time where the exhaust valve closes to the top dead centre (TDC) is relatively small, typically 20-40° crankshaft angle, compared to the portion of the engine cycle available in e.g. four-stroke engines, where the gaseous fuel and the charging air can really be mixed in the intake system or at the least during most of the opening phase of the inlet valve, typically during 40-160° crankshaft angle.

The relatively small window of the engine cycle available for obtaining homogeneous charge increases the challenge of avoiding diesel knock in large two-stroke diesel engines.

A non-homogeneous charge of gaseous fuel and charging air inside the combustion chamber, increases the risk of diesel knock, with potential serious damage to the engine as a result.

The prior has attempted to solve the problem of knock in engines the following manner.

DK177936 1 discloses a large uniflow scavenged two-stroke engine having a piston moving inside a cylinder liner, a cylinder head comprising an exhaust valve, and scavenge air ports arranged circumferentially in the cylinder liner. Several fuel injection valves are circumferentially distributed around the cylinder liner above the air scavenge ports. The fuel is injected at crank angles of at least 90° before TDC.

DK1766118 B1 disclose another large uniflow scavenged twostroke engine in which a gaseous fuel is injected at the scavenge ports, into the air flowing into the combustion chamber. Furthermore, water injection nozzles are provided at the cylinder head. Water is injected into the combustion chamber during compression in order to lower the temperature of the fuel/air mixture, and thereby to prevent knock.

JP2012154188 discloses a two-stroke engine comprising a cylinder, a piston sliding in the cylinder, a discharge port formed at one end in the stroke direction of the cylinder and opened/closed for discharging the exhaust generated in the cylinder; a scavenging port formed in the inner circumferential surface on the other end side in the stroke direction of the cylinder for sucking active gas into the cylinder corresponding to the sliding operation of the piston; a fuel injection valve for injecting fuel gas in the inner circumferential surface of the cylinder; and an inert substance injection valve for injecting the inert substance so as to collide with the fuel gas thus injected. Thus, nitrogen oxide emissions are reduced by low pressure injecting a small amount of inert substance, in operation of an engine.

The above solutions, however, have shown that they do not satisfactorily serve to effectively prevent knock in a large two-stroke compression-ignited internal combustion engine.

Thus, there is a need for an improvement in the injection of fuel in such large engines in order to effectively protect the engine from damages resulting from knock.

SUMMARY

It is thus an object to provide a large uniflow scavenged two-stroke engine operated in gaseous fuel in which knock can be prevented, or at least reduced.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, there is provided a large twostroke turbocharged uniflow scavenged internal combustion engine comprising a combustion chamber delimited by a cylinder liner, a piston and a cylinder cover, scavenge air ports arranged in the cylinder liner, at least one exhaust valve arranged in the cylinder cover, at least one fuel valve arranged in the cylinder liner, for injecting a gaseous fuel into the combustion chamber, and a supply of both pressurized gaseous fuel and a supply of pressurized air and/or exhaust gas to a fuel valve, the engine being configured to inject both said gaseous fuel and said air and/or exhaust gas simultaneously via said at least fuel valve into said combustion chamber to increase the momentum of the matter injected by said at least on fuel valve into the combustion chamber.

The purpose of the injected air and/or exhaust gas is to increase the momentum of the matter injected into the combustion chamber. Increasing the momentum improves mixing of the gaseous fuel with the scavenging air, which in turn results in a more homogenous charge and a reduced risk of knock.

Momentum is the product of mass m and speed v: m.v. The speed of the injected gaseous fuel is limited by the sound of speed. The mass of the fuel injected during an injection event/per engine cycle is determined by the engine load. Increasing the momentum any further after the gaseous fuel has reached the speed of sound is normally not possible.

However, the inventor arrived at the insight that momentum can be increased by injecting air and/or exhaust gas in addition to the injected gaseous fuel, to thereby increase the mass injected, and thus increase the momentum. Thus, the momentum is increased by high velocity injection of additional gas.

The inventor also arrived at the insight that the additional air and/or exhaust gas lowers the temperature of the charge in the combustion chamber during compression, thereby further reducing risk of knock.

According to a first possible implementation of the first aspect the gaseous fuel and the air and/or exhaust gas are simultaneously injected into the combustion chamber from the at least one fuel valve as a mixture.

According to a second possible implementation of the first the gaseous fuel and the air and/or exhaust gas are mixed inside the at least one fuel valve.

According to a third possible implementation of the first gaseous fuel and air and/or exhaust gas are mixed upstream of the at least one fuel valve.

According to a fourth possible implementation of the first the engine comprises a common supply line for the air and/or exhaust gas and for the gaseous fuel to the at least one fuel valve.

According to a fifth possible implementation of the first the gaseous fuel and the air and sand ashore exhaust gas are simultaneously injected from nozzle holes in a nozzle of the at least one fuel valve.

According to a sixth possible implementation of the first the engine comprises separate supply lines for the air and/or exhaust gas from the source of pressurized air and/or exhaust gas to the at least on fuel valve, and supply lines for the gaseous fuel from the source of pressurized gaseous fuel to the at least one fuel valve.

According to a seventh possible implementation of the first seven, the engine comprises a control unit configured for controlling the amount of air and/or exhaust gas injected simultaneously with the gaseous fuel.

According to an eighth possible implementation of the first the engine comprises a plurality of the at least one fuel valves circumferentially distributed over the circumference of the cylinder liner.

According to a ninth possible implementation of the first the at least one fuel valve is provided with one or more injection nozzles.

According to a tenth possible implementation of the first the at least one fuel valve is provided with a first inlet port connected to the source of pressure gaseous fuel and with a second inlet port connected to the source of air and/or exhaust gas.

According to an eleventh possible implementation of the first the at least one fuel valve comprises an arrangement for mixing the gaseous fuel with the air and/or exhaust gas inside the fuel valve.

According to a twelfth possible implementation of the first the simultaneous injection of both the gaseous fuel and the air and/or exhaust gas is initiated during the stroke of the piston towards the cylinder cover, preferably after the piston has passed the scavenge air ports, and even more preferably at or just before the time where the exhaust valve is closed.

According to a thirteenth possible implementation of the engine is provided with an ignition system for initiating ignition, preferably at or near TDC.

According to a first possible implementation of the fourteenth the engine is configured to simultaneously inject both the gaseous fuel and the air and/or the exhaust gas during a stroke of the piston towards the cylinder cover.

According to a second aspect the is provided a method of reducing knock by improving the mixing of gaseous fuel with scavenging air in a combustion chamber of a large twostroke turbocharged uniflow scavenged internal combustion engine, the engine comprising: a combustion chamber delimited by a cylinder liner, a piston and a cylinder cover, scavenge air ports arranged in the cylinder liner, an exhaust valve arranged in the cylinder cover, and at least one fuel valve arranged in the cylinder liner for injecting a gaseous fuel and air and/or exhaust gas into the combustion chamber, the method comprising the step of supplying pressurized gaseous fuel and pressurized air and/or exhaust gas to a fuel valve, and simultaneously injecting the pressurized gaseous fuel and the pressurized air and/or exhaust gas into the combustion chamber via the fuel valve during a stroke of the piston towards the cylinder cover to increase the momentum of the matter injected into the combustion chamber.

According to a first possible implementation of the second aspect the air and/or exhaust gas is injected only when the high engine load is high, preferably only when the engine load is more than 60 % of the maximum continuous rating of the engine, and even more preferably only when the engine load is more than 70% of the maximum continues rating of the engine.

These and other aspects will be apparent from and the embodiment(s) described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments and implementations will be explained in more detail with reference to the 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 diagrammatic representation the large twostroke engine according to Fig. 1,

Fig. 4 is a sectional view of the cylinder frame and a cylinder liner according to an example embodiment with a cylinder cover and an exhaust valve fitted thereto and a piston shown both in TDC and BDC,

Fig. 5 is a partial sectional view of the cylinder liner of Fig. 4,

Fig. 6 is a cross-sectional view the cylinder liner of Fig. 5 along the line VI - VI' with a fuel valve arrangement according to an embodiment in which gaseous fuel and injected air and/or exhaust gas are delivered to the combustion chamber via one and the same fuel valve,

Fig. 7 is a set up for a fuel supply and fuel valve arrangement according to an embodiment in which gaseous fuel and injected air and/or exhaust gas are mixed before delivery to the fuel valve,

Fig. 8 is a set up for a fuel supply and fuel valve arrangement according to an embodiment in which gaseous fuel and injected air and/or exhaust gas are mixed inside the fuel valve, and

Fig. 9 is a graph illustrating a gas exchange and fuel injection cycle.

DETAILED DESCRIPTION

In the following detailed description, an internal combustion engine will be described with reference to a large two-stroke low-speed turbocharged internal combustion crosshead engine in the example embodiments. Figs. 1, 2 and 3 show a large low-speed turbocharged twostroke diesel engine with a crankshaft 8 and crossheads 9. Fig. 3 shows a diagrammatic representation of a large lowspeed turbocharged two-stroke diesel engine with its intake and exhaust systems. In this example embodiment, the engine has four cylinders in line. Large low-speed turbocharged two-stroke diesel engines have typically between four and fourteen cylinders in line, carried by an engine frame 11. The engine may e.g. be used as the main engine in a marine vessel or as a stationary engine for operating a generator in a power station. The total output of the engine may, for example, range from 1,000 to 110,000 kW.

The engine is in this example embodiment an engine of the two-stroke uniflow type with scavenge ports 18 in the lower region of the cylinder liners 1 and a central exhaust valve 4 at the top of the cylinder liners 1. The scavenge air is passed from the scavenge air receiver 2 through the scavenge ports 18 of the individual cylinders 1. Gaseous fuel and injected air and/or exhaust gas are injected from fuel injection valves 30 in the cylinder liner 1, a piston 10 in the cylinder liner 1 compresses the charge of gaseous fuel, injected air and/or exhaust gas and scavenge air, compression takes place and at or near TDC ignition is triggered by e.g. injection of pilot oil (or any other suitable ignition liquid) from pilot oil fuel valves 33, combustion follows and exhaust gas is generated. Alternative forms of ignition systems, such as e.g. laser ignition or glow plugs can also be used to initiate ignition.

When the exhaust valve 4 is opened, the exhaust gas flows through an exhaust duct associated with the cylinder 1 into the exhaust gas receiver 3 and onwards through a first exhaust conduit 19 to a turbine 6 of the turbocharger 5, from which the exhaust gas flows away through a second exhaust conduit via an economizer 20 to an outlet 21 and into the atmosphere. Through a shaft, the turbine 6 drives a compressor 7 supplied with fresh air via an air inlet 12. The compressor 7 delivers pressurized scavenge air to a scavenge air conduit 13 leading to the scavenge air receiver 2. The scavenge air in conduit 13 passes an intercooler 14 for cooling the scavenge air

The cooled scavenge air passes via an auxiliary blower 16 driven by an electric motor 17 that pressurizes the scavenge air flow when the compressor 7 of the turbocharger 5 does not deliver sufficient pressure for the scavenge air receiver 2, i.e. in low- or partial load conditions of the engine. At higher engine loads the turbocharger compressor 7 delivers sufficient compressed scavenge air and then the auxiliary blower 16 is bypassed via a non-return valve 15.

Fig. 9 is a graph illustrating the open and closed periods of the scavenge ports 18, the exhaust valve 4 and the fuel valves 30, respectively, as a function of the crank angle. The graph shows that the window for injecting gaseous fuel is very short, allowing very short time for the gaseous fuel to mix with the scavenging air in the combustion chamber. The gaseous fuel, and the injected air and/or exhaust gas are injected in this very short window.

The amount of gaseous fuel injected per engine cycle is dictated by the engine load. The amount of injected air and/or exhaust gas to be injected per engine cycle will depend on the speed of the injection and on the need to prevent knock of a particular engine running on a particular type of gaseous fuel and can be determined by simple trial and error.

Preferably, the air and/or exhaust gas is injected for each engine cycle. For low engine loads there is normally a much lesser risk of knock. Thus, in an embodiment, the air and/or exhaust gas is only injected into the combustion chamber for high engine loads, e.g. above 60 - 70 % of the maximum continuous rating of the engine.

In an embodiment, the engine is provided with knock sensors (not shown) and the amount of air and/or exhaust gas added is controlled in response to the signal form the knock sensors, i.e. the amount (mass) of air and/or exhaust gas injected is increased when knock is detected (and lowered after a while when no knock is detected).

The injected air and/or exhaust gas is in an embodiment injected simultaneously with the gaseous fuel, as a mixture with the gaseous fuel or separately injected from the gaseous fuel.

Figs. 4 and 5 and 6 show a cylinder liner generally designated 1 for a large two-stroke crosshead engine. Depending on the engine size, the cylinder liner 1 may be manufactured in different sizes with cylinder bores typically ranging from 250 mm to 1000 mm, and corresponding typical lengths ranging from 1000 mm to 4500 mm.

In Fig. 4 the cylinder liner 1 is shown mounted in a cylinder frame 23 with the cylinder cover 22 placed on the top of the cylinder liner 1 with the gas tight interface therebetween. In Fig. 4, the piston 10 is not shown diagrammatically by interrupted lines in both bottomed dead center (BDC) and top dead center (TDC) although it is of course clear that these two positions do not occur simultaneously and are separated by a 180 degrees revolution of the crankshaft 8. The cylinder liner 1 is provided with cylinder lubrication holes 25 and cylinder lubrication line 24 that provides supply of cylinder lubrication oil when the piston 10 passes the lubrication line 24, whereafter piston rings (not shown) distribute the cylinder lubrication oil over the running surface of the cylinder liner 1.

In the shown embodiment, the thinnest portion of the wall 29 is at the bottom of the cylinder liner 1, i.e. the portion below the scavenge ports 18. The thickest portion of the wall 29 of the cylinder liner 1 is in the upper portion of the axial extent of the cylinder liner 1. A sharp transition in the thickness of the cylinder liner 1 around the middle of the axial extent of the cylinder liner 1 serves as a shoulder that allows the cylinder to rest on the cylinder frame 23. The cylinder cover 22 is pressed with great force applied by tensioning bolts onto the upper surface of the cylinder liner 1.

The pilot oil valves 33 (typically more than one per cylinder), are mounted in the cylinder cover 22 and connected to a source of pilot oil (not shown). The timing of the pilot oil injection is in an embodiment controlled by an electronic control unit (not shown).

The fuel vales 30 are mounted in the cylinder liner 1, with the nozzle substantially flush with the inner surface of the cylinder liner 1 and with the rear end of the fuel valve 30 prorating from the outer wall of the cylinder liner 1. Typically, three or four fuel valves 30 are provided for each cylinder, circumferentially equally distributed around the cylinder. The fuel valves 30 are in an embodiment arranged medial along the length of the cylinder liner 1.

Figs. 5 and 6 show the cylinder liner 1 and the fuel valves 30 in greater detail. In this embodiment, a cylinder liner 1 is provided with four fuel valves 30. The fuel valves 30 are shown radially directed in Fig, 6, but it is understood that the fuel valves 30 can be arranged in another angle relative to the cylinder liner 1.

The fuel valves 30 are in an embodiment connected to a common (mixed) supply of gaseous fuel and injected air and/or exhaust gas. Fig. 7 shows the fuel valve 30 connected to both a source of pressurized fuel 40 and a source of pressurized injected air and/or exhaust gas 44 via a single supply line 42. Valves are provided (not shown) to ensure the desired ratio between gaseous fuel and injected air and/or exhaust gas delivered to the fuel valves 30. A common conduit 32 transports the mixture to a nozzle 39. The mixture is injected into the combustion chamber from nozzle holes in the nozzle 39. The fuel valve 30 is provided with means for timed injection of the mixture to the combustion chamber, e.g. under control from an electronic control unit.

In a variation of the embodiment of Fig. 7, the gaseous fuel and the injected air and/or exhaust gas are not mixed and instead supplied to the fuel valve 30 sequentially and injected sequentially, either the gaseous fuel first or the injected air and/or exhaust gas first.

In another embodiment, illustrated by Fig. 8, the source of gaseous fuel 40 is connected by a dedicated supply line 41 to a dedicated port in the fuel valve 30. A dedicated conduit 31 leads the gaseous fuel to a mixing point 33 inside the fuel valve 30. The source of pressurized air and/or exhaust gas 44 is connected by a dedicated supply line 45 to a dedicated port in the fuel valve 30. A dedicated conduit 35 leads the air and/or exhaust gas to the mixing point 33 inside the fuel valve 30. In the mixing point 33 the gaseous fuel and the air and/or exhaust gas are mixed and from the mixing point 33 the mixture is transported to the nozzle 39 by a common conduit 32. The nozzle 39 is provide with nozzle holes through which the mixture is injected into the combustion chamber. The fuel valve 30 is provided with means for timed injection of the mixture to the combustion chamber, e.g. under control from an electronic control unit.

In an embodiment, the pressurized air and/or exhaust gas is taken from the scavenge air receiver (if the engine operates with exhaust gas recirculation the scavenge air receiver contains a mixture of air and recirculated exhaust gas). The pressure of the air or gas taken from the scavenge air receiver 2 is boosted by a compressor (not shown) to a suitable injection pressure. Since the air or gas in the scavenge air receiver is already pressurized the energy required to bring the air or gas to the injection pressure is less compared to brining the air up to injection pressure when starting from atmospheric pressure.

The various aspects and implementations has been described in conjunction 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 5 elements or steps, and the indefinite article a or an does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate 10 that a combination of these measured cannot be used to advantage

The reference signs used in the claims shall not be construed as limiting the scope.

Claims

Large turbocharged two-stroke internal combustion engine that includes:

a combustion chamber defined by a cylinder liner (1), a piston (10) and a cylinder cover (22), purge air openings (18) arranged in the cylinder liner (1), at least one exhaust valve (4) arranged in the cylinder cover (22); ), at least one fuel valve (30, 31) arranged in the cylinder liner (1) for injecting a gaseous fuel into the combustion chamber, characterized by a supply of both gaseous fuel (40) under pressure and a supply of air and / or exhaust gas (40) under pressure to a fuel valve (30, 31), that the engine is designed to inject both the gaseous fuel and the air and / or the exhaust gas simultaneously via the at least one fuel valve (30, 31) into the combustion chamber to increase momentum for the substance injected by the at least one fuel valve (30, 31) into the combustion chamber.

An engine according to claim 1, wherein the gaseous fuel and the air and / or the exhaust gas are simultaneously injected into the combustion chamber from the at least one fuel valve (30) as a mixture.

An engine according to claim 2, wherein the gaseous fuel and the air and / or the exhaust gas are mixed inside the at least one fuel valve (30).

An engine according to claim 2, wherein the gaseous fuel and the air and / or the exhaust gas are mixed on the upstream side of the at least one fuel valve (30).

An engine according to claims 1 to 4, comprising a common supply line (42) for the air and / or the exhaust gas and for the gaseous fuel for the at least one fuel valve (30).

The engine of claim 1, wherein the gaseous fuel and the air and / or exhaust gas are simultaneously injected from nozzle holes into a nozzle of the at least one fuel valve (30).

Engine according to claims 1 to 3, or 6, comprising separate supply lines (41, 45) for the air and / or the exhaust gas from the source of air and / or the exhaust gas under pressure (44) to the at least one fuel valve (30, 31) , and supply lines for the gaseous fuel from the source of gaseous fuel (40) under pressure to the at least one fuel valve (30, 31).

An engine according to any one of the preceding claims, comprising a control unit configured to control the amount of air and / or exhaust gas injected simultaneously with the gaseous fuel.

An engine according to any one of the preceding claims, comprising a plurality of the at least one fuel valve (30, 31) circumferentially distributed over the periphery of the cylinder liner (1).

An engine according to any one of the preceding claims, wherein the at least one fuel valve (30, 31) is provided with one or more injection nozzles (39).

An engine according to claim 10, wherein the at least one fuel valve (30) is provided with a first inlet opening connected to the source of gaseous fuel (40) under pressure and with a second inlet opening connected to the source of air and / or exhaust gas (44).

An engine according to claim 11, wherein the at least one fuel valve (30) comprises a device (33) for mixing the gaseous fuel with the air and / or the exhaust gas inside the fuel valve (30).

An engine according to any one of the preceding claims, wherein the simultaneous injection of both the gaseous fuel and the air and / or the exhaust gas is initiated during the stroke of the piston (10) against the cylinder cover (22), preferably after the piston (20) has passed the purge air openings, and even more preferably at the time or just before the time when each exhaust valve (4) is closed.

An engine according to any one of the preceding claims, provided with an ignition system for initiating ignition, preferably at or near the apex dead center.

An engine according to any one of the preceding claims, wherein the engine is designed to simultaneously inject both the gaseous fuel and the air and / or the exhaust gas during a stroke of the piston (10) against the cylinder head (22).

A method of reducing the bank by improving the mixture of gaseous fuel with purge air in a combustion chamber of a large turbocharged two-stroke internal combustion engine, the engine comprising:

a combustion chamber defined by a cylinder liner (1), a piston (10) and a cylinder cover (22), purge air openings (18) arranged in the cylinder liner (1), an exhaust valve (4) arranged in the cylinder cover (22), characterized by at least one fuel valve (30) arranged in the cylinder liner (1) for injecting a gaseous fuel and air and / or exhaust gas into the combustion chamber, which method comprises the step of supplying gaseous fuel under pressure and air and / or exhaust gas under pressure to a fuel valve (30, 31), and simultaneous injection of the gaseous fuel under pressure and the air and / or exhaust gas under pressure into the combustion chamber via the fuel valve (30, 31) during a stroke of the piston (10) against the cylinder cover ( 22) to increase the momentum of the substance injected into the combustion chamber.

A method according to claim 16, wherein the air and / or the exhaust gas are injected only when the high engine load is high, preferably only when the engine load is more than 60% of the maximum continuous engine power, and even more preferably only when the engine load is more than 70 % of maximum continuous engine performance.