Large turbocharged two-stroke single-flow crosshead internal combustion engine and method of operating the same

Abstract

A large turbocharged two-stroke single-flow crosshead internal combustion engine comprises: one or more gaseous fuel admission valves (30) configured to admit gaseous fuel during the stroke of the piston (10) toward the cylinder head, the gaseous fuel admission valves (30) having a preset fuel admission timing and duration when operating in steady-state operation for any load of the engine; at least one controller (60) associated with the engine configured to monitor engine operating parameters indicative of light load operation. The engine is special in that it includes means for delaying the admission of gaseous fuel when light load operation of the engine is observed. By delaying the admission of gaseous fuel when light load operation is observed, both combustion stability and speed are significantly improved. Because the admission timing of the gaseous fuel can be adjusted immediately, the countermeasure is suitable for responding quickly and immediately when light load operation of the engine is observed.

Description

Technical Field

[0001] The present invention relates to a large turbocharged two-stroke single-flow crosshead internal combustion engine, which in one operating mode operates according to the Otto cycle principle and in which the main fuel is a gaseous fuel, the engine comprising: at least one cylinder having a cylinder liner, the cylinder liner having a scavenging air port arranged in a bottom section of the cylinder; a reciprocating piston in the cylinder and a cylinder head covering the cylinder; a combustion chamber formed inside the cylinder and between the reciprocating piston and the cylinder head; one or more gaseous fuel inlet valves, which are arranged in the cylinder liner or the cylinder head and are configured to allow gaseous fuel to enter during the stroke of the piston towards the cylinder head, and for any load of the engine, the gaseous fuel inlet valve has a preset fuel entry timing (timing) and duration when operating in steady-state operation; at least one controller associated with the engine, the at least one controller being configured to monitor engine operating parameters indicative of light load operation.

[0002] The invention also relates to a method for operating such an engine. Background Art

[0003] Large turbocharged two-stroke single-flow crosshead internal combustion engines are often used as prime movers in large ocean-going vessels (e.g. container ships) or in power plants. These two-stroke diesel engines are not only large in size, but also different in construction from any other internal combustion engine. Their exhaust valves may weigh up to 400kg, the pistons are up to 100cm in diameter, and the maximum operating pressure in the combustion chamber is often several hundred bar. The forces involved at these high pressure levels and piston sizes are enormous. Typically, these engines are operated with heavy fuel oil or fuels such as diesel.

[0004] Recently, large two-stroke diesel engines have been required to be able to handle alternative types of fuels, such as gaseous fuels. Engines that can operate in both a fuel mode, in which the engine operates on fuel alone, and an alternative fuel mode, in which the engine operates on an alternative fuel and a pilot fuel, are generally referred to as dual-fuel engines.

[0005] A large two-stroke turbocharged internal combustion engine operating with gaseous fuel admitted by a fuel valve arranged midway along the length of the cylinder liner or arranged in the cylinder head (i.e., an engine in which the gaseous fuel is admitted during the upward stroke of the piston beginning before the exhaust valve closes) compresses a mixture of gaseous fuel and scavenging air in the combustion chamber and ignites the compressed mixture at or near top dead center (TDC) by a timed ignition device (e.g., pilot fuel injection).

[0006] The advantage of this type of intake, which uses a fuel valve (intake valve) arranged in the cylinder liner or in the cylinder head, is that a much lower fuel injection pressure can be used, since the gaseous fuel is injected when the pressure in the compression chamber is relatively low compared to large two-stroke turbocharged internal combustion engines, which inject the gaseous fuel when the piston is close to its top dead center (TDC), i.e. when the pressure in the combustion chamber is at or close to its maximum value. The latter type of engine requires a fuel injection pressure that is significantly higher than the already high maximum compression pressure. Due to the volatility of the gaseous fuel and its behavior at such high pressures (including diffusion into and through the steel components of the fuel system), a fuel system capable of handling the gaseous fuel at these extremely high pressures is expensive and complex.

[0007] Therefore, the 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 near TDC.

[0008] When gaseous fuel is injected during the compression stroke, the piston compresses the mixture of gaseous fuel and scavenging air, so there is a risk of pre-ignition. It is possible to operate with a very lean mixture to reduce the risk of pre-ignition, but a lean mixture increases the risk of misfire or partial misfire and the resulting fuel slip. Therefore, it is well documented that the combustion of a premixed mixture of air and gaseous fuel depends largely on the air / fuel gas ratio and temperature. From the common flammability diagram, it can be seen that high temperatures lead to autoignition, while low temperatures lead to flammable mist. Areas with high air / fuel gas ratios are not flammable. These effects have a great impact on the combustion process in Otto cycle engines, where the characteristics in the combustion chamber are not uniform. The characteristic distribution will be affected to a certain extent when determining the injection direction of the fuel gas inlet valve (or multiple fuel gas inlet valves). Another way is to control the timing of the intake, because earlier timing will result in a lower air / fuel gas ratio in the upper area of ​​the combustion chamber, while later timing will result in similar areas closer to the upper piston surface, where each area will have local combustion characteristics. At one engine operating point, a particular charge works well when the combination of boundary conditions provided by the scavenging air and the exhaust gas receiver results in efficient combustion. The overall size of the region where the air / fuel gas ratio is high is kept small, so that the proportion of unburned gas (commonly called slip) is below acceptable limits.

[0009] When the operating point of the engine changes, the various zones in the combustion chamber also change. For propulsion engines, a very relevant example is light-load operation, where the air / fuel gas ratio is too lean, resulting in misfires and thus unwanted fuel gas slip. Light-load operation is when the same engine power is delivered at higher engine speeds and lower torque. This is relevant because it represents light-load operation of the propulsion unit, which depends not only on the shipyard design, but also on the cargo volume, hull condition, weather conditions, ship maneuvering and water depth. Thus, the combustion cycle process must be adapted to maintain efficient combustion without generating unacceptable gas slip. Furthermore, changes related to weather and ship maneuvering are relatively fast and require immediate responses.

[0010] Tests have confirmed that light-load operation with an air / fuel gas mixture that is too lean can easily lead to combustion instabilities, resulting in very poor performance of the entire propulsion system. Such situations often result in unacceptable combustion chamber pressures, which in turn results in gas mode operation being shut down. So far, the countermeasure for these situations has been to reduce the scavenging air pressure by opening a bypass valve (often called an exhaust gas bypass or EGB), which can reduce the power supplied to the turbine of the turbocharger (TC). Unfortunately, the inertia of the TC results in a rather slow response to the scavenging air pressure. In addition, the size of the bypass must be limited to a certain size, in which the scavenging efficiency of the combustion chamber remains sufficient. Too poor scavenging can lead to an excess of hot residual gas in the combustion chamber, significantly increasing the tendency for premature autoignition during the compression stroke, and also leading to unacceptable cylinder pressures. The EGB is rarely used to increase the scavenging air pressure during heavy-load operation, because the opening of the EGB will reduce the performance on the nominal propeller curve, in which the engine efficiency guarantee is specified. Instead, diesel is added to reduce the amount of gas allowed to enter, so that the air / fuel gas ratio increases. This diesel consumption is undesirable in operations due to increased emissions, increased costs, and decreased overall engine efficiency.

[0011] The invention also relates to a method for operating a large turbocharged two-stroke uniflow crosshead internal combustion engine as described above and claimed in the appended claims. Summary of the invention

[0012] It is an object of the present invention to provide a large turbocharged two-stroke uniflow crosshead internal combustion engine of the type mentioned in the introduction in which the above-mentioned challenges associated with light-load operation of the engine are at least significantly reduced.

[0013] The above and other purposes are achieved by the following technical solutions of the present invention. Further implementation forms can also be seen from the description and drawings.

[0014] According to a first aspect, there is provided a large turbocharged two-stroke single-flow crosshead internal combustion engine which, in one operating mode, operates according to the Otto cycle principle and in which the main fuel is a gaseous fuel, the engine comprising: at least one cylinder having a cylinder liner having a scavenging air port arranged in a bottom section of the cylinder; a reciprocating piston in the cylinder and a cylinder head covering the cylinder; a combustion chamber formed inside the cylinder and between the reciprocating piston and the cylinder head; one or more gaseous fuel inlet valves arranged in the cylinder liner or in the cylinder head and configured to allow gaseous fuel to enter during a stroke of the piston toward the cylinder head, the gaseous fuel inlet valve having a preset fuel entry timing and duration when operating in steady-state operation for any load of the engine; at least one controller associated with the engine, the at least one controller being configured to monitor engine operating parameters indicative of light load operation, characterised in that the engine comprises means for delaying the entry of gaseous fuel when light load operation of the engine is observed.

[0015] Therefore, the timing of gaseous fuel admission was introduced as a new countermeasure when light engine load operation was observed. By delaying the admission of the gaseous fuel when operating at light load, testing on both 50 bore and 70 bore engines has confirmed that both combustion stability and speed are significantly improved. This may be attributed to the gaseous fuel having less time to mix in the combustion chamber, creating areas of lower air / fuel gas ratio that are not too lean to prevent the gaseous fuel from igniting. Since the timing of gaseous fuel admission can be adjusted instantly, this countermeasure is suitable for quick and timely response when light engine load operation is observed.

[0016] The means for delaying the admission of gaseous fuel when light load operation of the engine is observed may be any suitable means. However, preferably, the means comprises at least one controller connected to the gaseous fuel admission valves via signal lines. Thus, the at least one controller transmits signals regarding timing and duration to each gaseous fuel admission valve of each cylinder.

[0017] Due to the high mechanical loads on the combustion chamber components, faster combustion is not necessarily desired under steady-state conditions by delaying the gaseous fuel admission. Thus, in a preferred embodiment, delayed timing of the gaseous fuel admission should only be applied initially, for example between 2 and 20 seconds, preferably between 5 and 15 seconds, most preferably about 10 seconds. Therefore, the engine includes means for resetting the fuel admission timing of the gaseous fuel admission valve to a preset fuel admission timing for operation in steady-state operation and means for resuming normal long-term control, for example by a wastegate.

[0018] Engine operating parameters indicative of light load operation include combustion chamber pressure, combustion pressure temperature, engine power / engine speed ratio, and air / gaseous fuel ratio, and therefore, the engine preferably includes means for measuring at least one of the parameters. In addition, the engine preferably includes means in the form of a signal line to transmit the measured operating parameter data to the at least one controller for processing.

[0019] To control the scavenging air pressure, the engine can include a variable high-pressure EGR (exhaust gas recirculation). This EGR can also be used to restore the normal long-term control.

[0020] Where the gaseous fuel admission valve is arranged in the cylinder liner, preferably placed somewhere in the central region of the length of the cylinder liner between bottom dead center and top dead center, the preset fuel admission timing when running in steady-state operation is preferably set to as early a time as possible, namely just when the piston passes the scavenging air port on the way to its top dead center. Where the gaseous fuel admission valve is arranged in the cylinder head, the preset fuel admission timing when running in steady-state operation is preferably set to as early a time as possible after the exhaust valve is closed.

[0021] In the case where the gaseous fuel admission valve is arranged in the cylinder liner, preferably placed somewhere in the central area of ​​the length of the cylinder liner between the bottom dead center and the top dead center, when the engine is observed to be running at light load, the admission of the gaseous fuel is preferably delayed by at least 1 degree of crank angle, preferably by 5 to 20 degrees of crank angle, which is roughly equivalent to about 2 milliseconds, preferably about 10 to 40 milliseconds for an engine operating at 80 to 100 revolutions per minute.

[0022] In a most preferred embodiment of the invention in which the gaseous fuel admission valve is arranged in the cylinder liner, preferably placed somewhere in the central region of the length of the cylinder liner between bottom dead center and top dead center, when light-load running operation of the engine is observed, the admission of the gaseous fuel is delayed to as late a time as possible, i.e. at such a crankshaft angle, which is calculated as the crankshaft angle at which the piston passes the gaseous fuel admission valve on the way to top dead center minus the duration of the gaseous fuel admission at a given load of the engine, which duration is measured in crankshaft degrees. The duration of the gaseous fuel admission is typically proportional to the torque of the engine, i.e. at high torque, the admission of the gaseous fuel may not be delayed to the same extent as at low engine load.

[0023] According to a second aspect, there is provided a method for operating a large turbocharged two-stroke single-flow crosshead internal combustion engine, in one operating mode, the engine operating according to the Otto cycle principle and wherein the primary fuel is a gaseous fuel, the engine comprising: at least one cylinder having a cylinder liner having a scavenging air port arranged in a bottom section of the cylinder; a reciprocating piston therein and a cylinder head covering the cylinder; a combustion chamber formed inside the cylinder and between the reciprocating piston and the cylinder head; one or more gaseous fuel inlet valves arranged in the cylinder liner or in the cylinder head and configured to allow gaseous fuel to enter during a stroke of the piston toward the cylinder head, the gaseous fuel inlet valve having a preset fuel entry timing and duration when operating in steady-state operation for any load of the engine; and at least one controller associated with the engine, the at least one controller being configured to monitor engine operating parameters indicative of light load operation, characterized in that when light load operation of the engine is observed, the entry of gaseous fuel is delayed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be explained in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which:

[0025] Figure 1 is an elevational front view of a large two-stroke diesel engine according to an exemplary embodiment.

[0026] Figure 2 yes Figure 1 Elevation side view of a large two-stroke engine.

[0027] Figure 3 is based on Figure 1 Schematic diagram of a large two-stroke engine.

[0028] Figure 4 The propeller curve for a large two-stroke diesel engine according to the invention is shown.

[0029] Figure 5 Examples of gaseous fuel valve lift versus crankshaft angle curves for steady state operation and light load running operation in accordance with the present invention are shown.

[0030] Figure 6 The cylinder pressures achieved for a light load running engine with gaseous fuel admitted in accordance with the invention are shown, respectively, in a steady state setting and in a delayed setting. DETAILED DESCRIPTION

[0031] In the following detailed description, the present invention will be described with respect to a large turbocharged two-stroke uniflow crosshead internal combustion engine, but it should be understood that the internal combustion engine may be of another type. The large turbocharged two-stroke uniflow crosshead internal combustion engine shown is of a low-pressure type in which fuel is admitted at a relatively low pressure when the piston is on its way to top dead center, and the fuel is compression ignited by pilot ignition, typically using an ignition fluid (e.g., fuel oil) to ensure reliable ignition.

[0032] Figure 1 , Figure 2 and Figure 3 A large, low speed, turbocharged, two-stroke diesel engine with a crankshaft 8 and a crosshead 9 is shown. Figure 3 A schematic diagram of a large, low-speed, turbocharged, two-stroke diesel engine with its intake and exhaust systems is shown. In this exemplary embodiment, the engine has six in-line cylinders. Large, low-speed, turbocharged, two-stroke diesel engines typically have four to fourteen in-line cylinders carried by a cylinder frame 23, which is carried by the engine frame 11. The engine can be used, for example, as a main engine for a marine vessel or as a stationary engine for operating a generator in a power station. The total output of the engine can be, for example, in the range of 1000 to 110000 kW.

[0033] In this exemplary embodiment, the engine is a two-stroke single-flow scavenging type engine having scavenging ports 18 located in the lower region of the cylinder liner 1 and a central exhaust valve 4 located at the top of the cylinder liner 1. When the piston 10 is located below the scavenging port 18, scavenging air is delivered from the scavenging air receiver 2 through the scavenging port 18 of each cylinder liner 1. When the piston is in its upward movement and before the piston passes the gaseous fuel inlet valve 30, gaseous fuel is admitted from the gaseous fuel inlet valve 30 under the control of the electronic controller 60. The gaseous fuel is admitted at a relatively low pressure, which is lower than 30 bar, preferably lower than 25 bar, and more preferably lower than 20 bar. The gaseous fuel inlet valve 30 is preferably evenly distributed around the periphery of the cylinder liner and placed somewhere in the central region of the length of the cylinder liner 1. Therefore, the admission of the gaseous fuel occurs when the compression pressure is relatively low, i.e., much lower than the compression pressure when the piston reaches TDC, thereby allowing entry at a relatively low pressure.

[0034] The piston 10 in the cylinder liner 1 compresses the charge of gaseous fuel and scavenging air, compression occurs, and at or near TDC, ignition is triggered by, for example, injection of pilot oil (or any other suitable ignition fluid) from a pilot oil fuel valve 50, which is preferably arranged in the cylinder head 22, followed by combustion and production of exhaust gases. Instead of or in addition to the pilot oil fuel valve 50, alternative forms of ignition systems may also be used to initiate ignition, such as, for example, a pre-combustion chamber (not shown), laser ignition (not shown), or a glow plug (not shown).

[0035] When the exhaust valve 4 is open, the exhaust gas flows through the exhaust duct associated with the cylinder liner 1 into the exhaust gas receiver 3 and onwards through the first exhaust duct 19 to the turbine 6 of the turbocharger 5, from which the exhaust gas flows through the second exhaust duct, via the economizer 20 to the outlet 21 and into the atmosphere. The exhaust gas can also bypass the turbine 6 of the turbocharger 5 via the duct 19a. The turbine 6 drives the compressor 7 via the shaft, which is supplied with fresh air via the air inlet 12. The compressor 7 delivers pressurized scavenging air to the scavenging air duct 13, which leads to the scavenging air receiver 2. The scavenging air in this scavenging air duct 13 is conveyed through the intercooler 14 in order to cool the scavenging air.

[0036] The cooled scavenging air is conveyed via an auxiliary blower 16 driven by an electric motor 17, which pressurizes the scavenging air flow when the compressor 7 of the turbocharger 5 does not deliver sufficient pressure to the scavenging air receiver 2, i.e. at low or partial engine loads. At higher engine loads, the compressor 7 of the turbocharger 5 delivers sufficient compressed scavenging air, which then bypasses the auxiliary blower 16 via the non-return valve 15 and the electric motor 17 is deactivated.

[0037] Figure 4 The propeller curve diagram for a large two-stroke diesel engine is shown. The nominal propeller curve P nom shows the relationship between engine power and engine speed for engine design, and P lr The thruster curve when the engine is in light load operation, P hr shows the propeller curve when the engine is in heavy load operation. Thus, in light load operation, the same engine power is delivered at a higher engine speed. As mentioned in the introduction to the specification, light load operation with a too lean air / fuel gas mixture is prone to combustion instability due to unacceptable combustion chamber pressures, resulting in very poor performance of the entire propulsion system. Such a situation is depicted in Figure 6In the left diagram in FIG. 1 , the combustion chamber pressure is plotted for various speeds. It can be seen that the combustion chamber pressure achieved varies significantly from about 75 bar to about 120 bar, with an average combustion chamber pressure of about 100 bar. This would lead to misfires and thus to unwanted fuel gas slip, which must be avoided.

[0038] Therefore, according to the invention, it is proposed to delay the admission of gaseous fuel when a light-load operation of the engine is observed. In order to achieve this, the controller 60 is configured to monitor engine operating parameters indicative of a light-load operation. Such operating parameters may include pressure, temperature and air / gaseous fuel ratio in the combustion chamber, and the engine therefore comprises means (not shown) for measuring at least one of said parameters and a signal line 61 for transmitting the measured operating parameter data to the at least one controller 60 for processing. Thus, if the pressure and / or temperature in the combustion chamber (measured as an average value over a predetermined time interval) is too low during the combustion process, this indicates a light-load operation. In addition, if the air / gaseous fuel ratio is too high, the air / gaseous fuel mixture is too lean, which also indicates a light-load operation. In practice, the controller 60 continuously calculates a light-load number (LRN), which indicates whether the actual effect of the engine corresponds to the desired effect of the propeller at the actual revolutions per minute (rpm) on the nominal propeller curve of the engine. As Figure 6 As shown in the left figure in FIG. 1 , the controller 60 also observes light load operation by increasing the variation of combustion in different revolutions. Increased variation of combustion often occurs when the air / gaseous fuel mixture is so lean that not all of the gaseous fuel is burned, resulting in gaseous fuel slipping to the atmosphere. The means for delaying the admission of gaseous fuel when light load operation of the engine is observed includes the at least one controller 60, which is connected to the gaseous fuel admission valve 30 via a signal line 62. Therefore, the at least one controller 60 transmits a signal regarding timing and duration to the corresponding gaseous fuel admission valve 30 of the corresponding cylinder based on the measured and monitored engine operating parameters indicating light load operation.

[0039] exist Figure 5 The gaseous fuel valve lift curve SGAV is shown in FIG. Later Relative to the gas fuel valve lift curve SGAV under steady-state operation Std The delay is such that when the piston moves closer to the gas inlet valve 30, gaseous fuel is admitted slightly later.

[0040] By delaying the admission of the gaseous fuel during light load operation as proposed in accordance with the present invention, tests on both 50 bore and 70 bore engines have demonstrated that both combustion stability and speed are significantly improved. Figure 6The results of such a test are depicted on the right-hand side graph, where the combustion chamber pressure is plotted for various rpm. It can be seen that the combustion chamber pressures obtained vary only slightly, with an average combustion chamber pressure of about 130 bar, which indicates that the engine performance is better than Figure 6 The engine performance indicated by the left graph in is much better. Since the admission timing of the gaseous fuel can be adjusted immediately, this countermeasure is suitable for quick and timely response when light load operation of the engine is observed.

[0041] Tests conducted by the applicant of the present invention have clarified that delayed timing of gaseous fuel admission should only be initially applied for a relatively short period of time after light load running operation is observed, for example between 2 and 20 seconds, preferably between 5 and 15 seconds, most preferably about 10 seconds, because such faster combustion is not required under steady state conditions due to the higher mechanical loads on the combustion chamber components. Therefore, the fuel admission timing of the gaseous fuel admission valve 30 is preferably reset by the controller 60 to a preset fuel admission timing for operation in steady state operation, in which conventional long-term control is used, which may involve, for example, control of the waste gas bypass, i.e., the conduit 19a.

[0042] exist Figure 3 In the embodiment shown, the gaseous fuel admission valve 30 is arranged in the cylinder liner and in the central area of ​​the length of the cylinder liner between the bottom dead center and the top dead center. In this embodiment, the preset fuel admission timing when running in steady-state operation is preferably set to a time as early as possible, that is, just when the piston passes the scavenging air port on the way to the top dead center. In this embodiment, when the engine light load operation is observed, the admission of the gaseous fuel should be delayed by at least 1 degree of crankshaft angle, preferably by 5 to 20 degrees of crankshaft angle, to obtain the desired effect, however, most preferably, when the engine light load operation is observed, the admission of the gaseous fuel is delayed to a time as late as possible, that is, at such a crankshaft angle, which is calculated as the crankshaft angle at which the piston 10 passes the gaseous fuel admission valve 30 on its way to the top dead center minus the duration of the gaseous fuel admission at a given load of the engine, which duration is measured in crankshaft degrees. The duration of gaseous fuel admission is typically proportional to the torque of the engine, ie, at high torques, the admission of gaseous fuel may not be delayed to the same extent as at low engine torques.

Claims

1. A large turbocharged two-stroke uniflow crosshead internal combustion engine which, in one operating mode, operates according to the Otto cycle principle and in which the main fuel is a gaseous fuel, the engine comprising: at least one cylinder having a cylinder liner (1) having a scavenging air port (18) arranged in a bottom section of the cylinder; a reciprocating piston (10) in the cylinder and a cylinder head (22) covering the cylinder; a combustion chamber formed inside the cylinder and between the reciprocating piston (10) and the cylinder head (22); one or more gaseous fuel inlet valves (30) arranged in the cylinder liner (1) or in the cylinder head (22) and configured to admit gaseous fuel during a stroke of the piston (10) toward the cylinder head (22), the gaseous fuel inlet valves (30) having a preset fuel admission timing and duration when operating in steady-state operation for any load of the engine; At least one controller (60) associated with the engine, the at least one controller (60) configured to monitor an engine operating parameter indicative of light load operation, wherein the engine includes means for delaying gaseous fuel admission when light load operation of the engine is observed.

2. The engine according to claim 1, characterized in that The means for delaying gaseous fuel admission when light load operation of the engine is observed comprises the at least one controller (60) connected to the gaseous fuel admission valve via a signal line.

3. The engine according to claim 1, characterized in that The engine includes means for resetting the fuel admission timing of the gaseous fuel admission valve (30) to the preset fuel admission timing for operation in steady state operation and means for resuming normal long term control.

4. The engine according to claim 3, characterized in that The means for restoring the normal long-term control is a means for restoring the normal long-term control by means of the wastegate.

5. The engine according to claim 1, characterized in that The engine comprises: means for measuring at least one of the engine operating parameters indicative of light load running operation, the engine operating parameters comprising combustion chamber pressure, combustion pressure temperature, engine power / engine speed ratio, and air / gaseous fuel ratio; and means in the form of a signal line for transmitting the measured operating parameter data to the at least one controller (60) for processing.

6. The engine according to claim 1, characterized in that In the case where the gaseous fuel admission valve (30) is arranged in the cylinder liner (1) and somewhere in the central region of the length of the cylinder liner between the bottom dead center and the top dead center, the preset fuel admission timing when running in steady-state operation is set to just when the piston passes the scavenging air port (18) on the way to the top dead center, and in the case where the gaseous fuel admission valve (30) is arranged in the cylinder head (22), the preset fuel admission timing when running in steady-state operation is set to a time as early as possible after the exhaust valve (4) is closed.

7. The engine according to claim 1 or 6, characterized in that: When light load operation of the engine is observed, admission of the gaseous fuel is delayed by at least 1 crank angle degree.

8. The engine according to claim 7, characterized in that When the engine is observed to operate at light load, the admission of gaseous fuel is delayed by 5 to 20 crank angle degrees.

9. The engine according to claim 1, characterized in that With the gaseous fuel admission valve (30) arranged in the cylinder liner (1) somewhere in the central region of the length of the cylinder liner between bottom dead center and top dead center, when light load operation of the engine is observed, the admission of the gaseous fuel is delayed to a crankshaft angle calculated as the crankshaft angle at which the piston (10) passes the gaseous fuel admission valve (30) on the way to top dead center minus the duration of gaseous fuel admission at a given load of the engine, the duration being measured in crankshaft degrees.

10. Method for operating a large turbocharged two-stroke uniflow crosshead internal combustion engine according to any one of claims 1 to 9, in one operating mode the engine operating according to the Otto cycle principle and wherein the main fuel is a gaseous fuel, the engine comprising: at least one cylinder having a cylinder liner (1) with a scavenging air port (18) arranged in a bottom section of the cylinder; a reciprocating piston (10) in the cylinder and a cylinder head (22) covering the cylinder; a combustion chamber formed inside the cylinder and between the reciprocating piston (10) and the cylinder head (22); one or more gaseous fuel inlet valves (30) arranged in the cylinder liner (1) or in the cylinder head (22) and configured to admit gaseous fuel during a stroke of the piston (10) toward the cylinder head, the gaseous fuel inlet valves (30) having a preset fuel admission timing and duration when operating in steady-state operation for any load of the engine; At least one controller (60) associated with the engine is configured to monitor an engine operating parameter indicative of light load operation, wherein when light load operation of the engine is observed, admission of the gaseous fuel is delayed.

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