Device and method for operating large engine

Abstract

To provide an internal combustion engine which can be operated at least in a gas mode, and a method for operating the internal combustion engine.SOLUTION: The internal combustion engine comprises at least one cylinder, at least one gas admission valve, a turbocharger, a pressure measuring unit, and a control unit. The control unit is configured to: receive a signal from the pressure measuring unit; determine a crank angle of the firing pressure; determine a difference between the determined crank angle and a predetermined optimal crank angle after a new load has been demanded; keep the difference between the determined crank angle and the predetermined optimal crank angle within a predetermined interval; adapt the air-to-fuel ratio; adapt an amount of air supplied by the turbocharger and / or an admission rate of fluid fuel; and adapt a change of the amount of air supplied by the turbocharger and / or admission rate of fluid fuel in the case where a new load is demanded.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine and a method of operating an internal combustion engine that can operate in at least a gas mode.

[0002] The present invention preferably relates to an internal combustion engine, such as a marine engine or a stationary engine, the cylinder of which has a bore of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine.

[0003] The engine may be a gas engine, a dual fuel engine or a multi-fuel engine, in which the combustion of gaseous or liquid and / or gaseous fuels and auto-ignition or forced ignition are possible.

[0004] The term internal combustion engine generally refers to large engines that can operate not only in a diesel mode characterized by auto-ignition of a fuel, but also in an Otto mode characterized by spark ignition of a fuel, or a mixed mode of the two, for example with spark ignition. Furthermore, the term internal combustion engine particularly includes dual-fuel engines and large engines in which auto-ignition of one fuel is used in conjunction with spark ignition of another fuel.

[0005] The engine has at least one cylinder with a piston therein. The piston is connected to a crankshaft. The piston reciprocates between top dead center (TDC) and bottom dead center (BDC) during engine operation. The cylinder typically has at least one air passage opening for intake air, particularly an air inlet located in the cylinder liner, and at least one air passage opening for exhaust air, particularly an exhaust outlet located in the cylinder cover. Preferably, the air inlet is fluidly connected to a scavenging air receiver.

[0006] The internal combustion engine may be a longitudinally scavenged two-stroke engine.

[0007] The engine speed is preferably less than 800 RPM (4 stroke), more preferably less than 200 RPM (2 stroke), which indicates a low speed engine designation.

[0008] The fuel can be diesel or marine diesel or heavy fuel oil or emulsion or slurry or methanol or ethanol, as well as gases such as liquid natural gas (LNG), liquid petroleum gas (LPG).

[0009] Further potential fuels that can be added on demand are LBG (liquefied biogas), biofuels (e.g., algae fuel or seaweed oil), hydrogen, and synthetic fuels from CO2 (e.g., produced by Power-To-Gas or Power-To-Liquid).

[0010] Large ships, in particular those used for transporting cargo, are usually powered by internal combustion engines, in particular diesel and / or gas engines, mainly two-stroke crosshead engines. [Background technology]

[0011] In this application, the internal combustion engine can operate in at least a gas mode. Fluid fuel is used to generate torque. The fluid fuel can be supplied as gas fuel or as pressurized gas, i.e., liquid, by a gas intake valve. In gas mode, a small amount of liquid fuel, sometimes called a pilot injection, can also be injected to provide induction ignition.

[0012] The internal combustion engine includes a turbocharger that uses exhaust gases discharged from the cylinders to increase the amount of air supplied to the cylinders. The air compressed by the turbocharger may be supplied to a scavenging air receiver that is fluidly connected to the intake air passage opening.

[0013] In addition to fresh air and fluid fuel, inert gases such as exhaust gases can be drawn into the cylinder. The engine may be equipped with a high-pressure or low-pressure exhaust gas recirculation path. For low-pressure exhaust gas recirculation, the exhaust gases pass through the turbocharger turbine and / or the turbocharger compressor before being mixed with the fresh air. The exhaust gases can enter the cylinder as part of the scavenging air.

[0014] Abnormal combustion processes such as pre-ignition, knocking or misfire occur especially when the ratio of fresh air to gas, ie the air-fuel ratio or air-fuel equivalence ratio, also called lambda, is not within certain limits.

[0015] If the gas content is too high, the mixture will be too rich. The mixture will burn too quickly or too early, for example due to autoignition, which may lead to pre-ignition or knocking of the engine. If the air content is too high, the mixture will be too lean, which may result in misfire, which of course has a negative impact on the efficient and low-pollution operation of the engine. In particular, the two conditions of too high a gas content and too high an air content are defined as abnormal combustion processes. Therefore, in gas mode, a combustion process that does not cause autoignition of the mixture is pursued. The combustion process must be carried out within a range where the mixture is neither too rich nor too lean.

[0016] Modern four-stroke Otto cycle engines use lambda closed-loop control, which measures the oxygen content in the exhaust gas and controls the amount of fuel injected into the engine to keep lambda within a desired range and avoid rich burning.

[0017] For two-stroke engines, lambda measurement can be difficult due to the cylinder scavenging process, where fresh air enters through the intake port and mixes with the exhaust gases while the exhaust valve is open, and therefore measurement of the remaining combustion oxygen in the exhaust gases is unreliable.

[0018] It is known that inert gases, such as exhaust gases, can be introduced into the cylinder to suppress or avoid abnormal combustion processes.

[0019] Due to changes in ambient conditions, e.g., ambient temperature, and due to certain operating conditions, combustion phasing may change. Generally, this can lead to reduced engine efficiency. If the ignition pressure is too high, combustion stability may be reduced and methane slip may occur. The optimum value for the ignition pressure peak may be 5°-8°C A (5°-8° after top dead center of the crank, equivalent to 0°C A). In this region, engine efficiency, emissions, and reliability are optimal.

[0020] The optimum crank angle for the ignition pressure depends on the load of the engine, and the control unit may be adapted to use or be equipped with a table in which the relationship between load and optimum crank angle is stored, usually called a setpoint vector.

[0021] From EP 3722572 it is known that the ignition pressure peak angle can be adjusted by adapting the pilot fuel injection timing, by adapting the EGR rate, by adapting the amount of added fuel, by adapting the scavenging pressure and / or by adapting the amount of inert additives.

[0022] Internal combustion engines used to propel ships often must cope with fast load changes, such as sudden increases in load due to rudder movements. Speed ​​control devices maintain engine speed at its current level during fast load changes by increasing the total amount of fuel injected into the cylinder.

[0023] The high inertia of the air passages of marine two-stroke engines, due to the heavy turbocharger, large capacity scavenging air receiver, and long air passages, risks significantly reducing the air-to-fuel ratio (or lambda), which can result in pre-ignition, knocking, and / or misfire.

[0024] Pre-ignition, knocking and / or misfire can also occur if the load is suddenly reduced when the air-fuel ratio (lambda) is too high due to a slow turbocharger response.

[0025] European Patent No. 3409928 discloses a method for controlling a gas engine connected to a turbocharger. During steady-state operation, knocking control is performed. When the load on the gas engine increases during steady-state operation, if the increase in load is relatively small, the actual fuel injection amount is gradually increased while maintaining the ignition timing. If the increase in load is relatively large, the ignition timing is retarded and then the actual fuel injection amount is gradually increased. Knocking can be suppressed. [Prior art documents] [Patent documents]

[0026] [Patent Document 1] European Patent No. 3722572 [Patent Document 2] European Patent No. 3409928 Summary of the Invention

[0027] SUMMARY OF THE INVENTION It is an object of the present invention to avoid the drawbacks of the prior art and in particular to provide an internal combustion engine and a method for operating an internal combustion engine which have better performance during sudden load changes.

[0028] According to the invention, the internal combustion engine is a large or stationary engine and is capable of operating at least in gas mode.

[0029] In this application, being operable in at least gas mode means that fuel gas is supplied into the cylinders of an internal combustion engine, or that a fuel liquid that vaporizes as soon as it enters the cylinders, i.e., high-pressure fuel gas, is supplied to the cylinders.

[0030] The internal combustion engine comprises at least one cylinder having an internal diameter of at least 200 mm.

[0031] An internal combustion engine comprises at least one gas intake valve for supplying fluid fuel to the cylinder, where fuel means fuel gas or high pressure fuel liquid.

[0032] The internal combustion engine further includes at least one turbocharger, each turbocharger having a turbine and a compressor.

[0033] The internal combustion engine includes a pressure measurement unit having at least one sensor for providing a signal representative of pressure in at least one cylinder. The at least one sensor may be a pressure sensor for measuring pressure in the cylinder. The pressure measurement unit may include a sensor for each cylinder.

[0034] Each cylinder may be provided with at least one pressure measurement unit. At least one pressure sensor may be provided per cylinder.

[0035] The pressure measurement unit may be configured to measure the pressure in the cylinder over a number of cycles, for example over 3 to 10 cycles, preferably over 4 to 6 cycles, and determine a pressure curve averaged over the combustion cycle.

[0036] The internal combustion engine further comprises a control unit configured to receive a signal from the pressure measurement unit and determine a crank angle of the ignition pressure.

[0037] Typically, the crank angle of the ignition pressure is the angle at the absolute maximum or peak of the pressure curve over the cycle.

[0038] The control unit is further configured to compare the crank angle of the ignition pressure with a predetermined optimum crank angle, which may be load dependent and may be obtained, for example, from a map or table predetermined in factory tests.

[0039] The control unit is configured to determine the difference between the determined crank angle and a predetermined optimum crank angle, in particular after a new load is requested.

[0040] As long as this difference is within a predetermined interval, it can be assumed that there is no risk of pre-ignition, knocking and / or misfire during combustion.

[0041] However, if the difference is greater than a predetermined interval, engine parameters need to be adjusted to avoid pre-ignition, knocking, and / or misfire. It can be assumed that the air-fuel ratio is not within a range to provide undisturbed combustion.

[0042] The control unit is therefore arranged to adapt the air-fuel ratio in order to maintain the difference between the determined crank angle and a predetermined optimum crank angle within a predetermined interval.

[0043] To adapt the air-fuel ratio, the control unit is configured to adapt, preferably within one cycle, the amount of air supplied by the turbocharger and / or the intake amount of fluid fuel.

[0044] Furthermore, the control unit is configured to adapt to variations in the amount of air supplied by the turbocharger and / or variations in the intake amount of fluid fuel, in particular when a new load is required.

[0045] Generally, fluid fuel is drawn into the cylinder for a specific time interval per cycle. Unless the load varies, the time window per cycle for drawing fluid fuel usually remains constant.

[0046] If a greater load is required, the time interval for inhaling the fluid fuel must be increased, and if a lesser load is required, the time interval can be decreased.

[0047] Thus, when the load is greater, the intake volume is greater, and when the load is less, the intake volume is less.

[0048] To prevent pre-ignition, knocking and / or misfire, the air-fuel ratio must remain stable even during load variations.

[0049] Therefore, if the intake volume varies very quickly, the amount of air delivered by the turbocharger must also vary very quickly. Similarly, if the amount of air delivered by the turbocharger can only be changed slowly, the intake volume must also change slowly.

[0050] The control unit may be configured to adapt by increasing or decreasing the amount of air supplied by the turbocharger.

[0051] The internal combustion engine may be provided with an acceleration device for accelerating the turbocharger to provide more fresh air than would be possible without acceleration.

[0052] The control unit may be configured to increase the amount of air supplied by the turbocharger by further accelerating the turbocharger if the difference falls below a lower limit of the predetermined interval.

[0053] To that end, the control unit may be configured to arrange an acceleration device, which may comprise an electric motor.

[0054] Additionally or alternatively, the internal combustion engine may be provided with a discharge valve for discharging air supplied by the turbocharger upstream of the scavenging air receiver, and the control unit may be configured to reduce the amount supplied by the turbocharger by blowing fresh air supplied by the turbocharger upstream of the scavenging air receiver if the difference exceeds an upper limit of a predetermined interval.

[0055] Therefore, the air-fuel ratio in the cylinder can be adjusted by increasing or decreasing the amount of air supplied by the turbocharger.

[0056] Alternatively or additionally, the control unit may be configured to adapt the intake amount of fluid fuel by decreasing the intake amount when the difference is below a lower limit of a predetermined interval, and / or by increasing the intake amount when the difference is above an upper limit of a predetermined interval.

[0057] The predetermined interval may correspond to a deviation of ±5° from the optimum crank angle, preferably ±3°, more preferably ±2°, and even more preferably ±1°.

[0058] The occurrence of a difference between the actual crank angle of the ignition pressure and a predetermined optimum crank angle has been found to be a sensitive and early indicator of the risk of pre-ignition, knocking and / or misfire. As long as the difference lies within a predetermined interval relative to the optimum crank angle, the risk can be considered negligible.

[0059] The control unit may be configured to adapt the intake volume by adjusting the opening time per cycle of at least one gas intake valve, in particular at least one gas intake valve for each cylinder.

[0060] In a preferred embodiment of the present invention, the control unit may be configured to adapt to changes in intake volume by gradually changing the opening time per cycle of the at least one gas intake valve from a current opening time per cycle to a target opening time per cycle.

[0061] The target opening time per cycle corresponds to the newly requested load.

[0062] The change in the opening time occurs within n cycles, where n is greater than 1. Therefore, the intake air volume does not change suddenly within one cycle, but changes gradually. It is preferable that the increase and / or decrease in the intake air volume change linearly over the n cycles.

[0063] The control unit may be configured to set the number n.

[0064] The number of cycles to adapt the opening time is - current opening time per cycle, - target opening time per cycle, - The difference between the target opening time per cycle and the current opening time per cycle and / or - the difference between the actual crank angle of the ignition pressure and the predetermined optimum crank angle may depend on

[0065] The number of cycles n required to match the fuel intake may be obtained from a map determined in factory tests.

[0066] Assume the engine is operating at a first load for a first opening time per cycle, and when a new load is requested, the target opening time per cycle is required. Therefore, since it takes N cycles to change the intake volume, the response time to reach the new intake level is extended from one cycle, where the intake volume changes rapidly, to N cycles, where the response time is longer. After N cycles of response time, the turbocharger can supply the amount of fresh air needed to maintain the air-fuel ratio within the correct interval.

[0067] When a new, larger load is requested, the control unit may be configured to adapt to the change in intake volume by setting the open time per cycle of the at least one gas intake valve shorter compared to the open time per cycle corresponding to the new, larger load, i.e., the target open time per cycle. The control unit may further be configured to continuously increase the open time per cycle until the open time per cycle corresponds to the new, larger load, which is the target open time.

[0068] If a new, larger load is required, a target opening time per cycle corresponding to the new load can be set, and the control unit may be configured to set the target opening time per cycle within one cycle and check whether the air-fuel ratio is kept essentially constant and / or at least within an acceptable range by checking whether the difference between the determined crank angle and a predetermined optimum crank angle is within a predetermined interval.

[0069] If so, the open time can be kept constant, otherwise a new shorter open time can be set, for example a second open time that is longer than the first open time or the starting open time corresponding to the old load by the difference between the target open time per cycle and the first open time per cycle divided by N.

[0070] Thereafter, the control unit may be configured to set the target opening time per cycle within one cycle and check again whether the difference between the determined crank angle and the predetermined optimum crank angle is within a predetermined interval.

[0071] If so, the open time can be kept constant. If not, for example, a new third open time may be set that is longer than the second open time by the difference between the target open time per cycle and the first open time per cycle divided by N.

[0072] This procedure may be repeated until the target open time can be maintained or reached by successively increasing the open time.

[0073] Similarly, when a new, smaller load is requested, the control unit may be configured to accommodate the change in intake volume by setting the open time per cycle of the at least one gas inlet valve longer compared to the target open time per cycle corresponding to the new, requested, smaller load. The control unit may be further configured to continuously decrease the open time per cycle to the open time per cycle corresponding to the new, requested load, and thus the target open time.

[0074] The open time increase or decrease may be selected linearly with the number of cycles until the target open time is reached.

[0075] The control unit may be configured to receive an emergency signal and to stop adapting the air-fuel ratio after receiving the emergency signal. The internal combustion engine may, for example, be provided with an input device for receiving an emergency signal initiated by a user.

[0076] Situations may arise where slow changes in fuel intake are not tolerated, where pre-ignition, knocking and misfires are acceptable and maintaining the air-fuel ratio within a predetermined interval may not be necessary.

[0077] The user may choose to stop the process of maintaining the air-fuel ratio within a certain interval.

[0078] In particular, the control unit may be configured to instantaneously set a new opening time per cycle of the at least one gas inlet valve that corresponds to the new required load.

[0079] According to the invention, a method for operating an internal combustion engine as described above comprises the steps of: providing a signal representative of the pressure in at least one cylinder; determining the crank angle of the ignition pressure; and determining the difference between the determined crank angle and a predetermined optimum crank angle, in particular after a new load is requested.

[0080] The method further includes maintaining a difference between the determined crank angle and a predetermined optimum crank angle within a predetermined interval to maintain the air-fuel ratio within the optimum interval.

[0081] The amount of air delivered by the turbocharger and / or the intake amount of fluid fuel are adapted to keep the air-fuel ratio within an optimum interval.

[0082] Additionally or alternatively, changes in the amount of air supplied by the turbocharger and / or changes in the intake amount of fluid fuel may be adapted, particularly when a new load is required.

[0083] The air-fuel ratio can be adapted by adapting the fluid fuel intake amount corresponding to the open time per cycle if the difference between the determined crank angle and the predetermined optimum crank angle is not within a predetermined interval.

[0084] After a new load is demanded, the air-fuel ratio can be adapted by adapting the change in fluid fuel intake.

[0085] If the difference is below the lower limit of the predetermined interval, the inhalation rate may be decreased. If the difference is above the upper limit of the predetermined interval, the inhalation rate may be increased.

[0086] The intake amount of the fluid fuel can be adapted by changing an open time per cycle of the at least one gas intake valve. The change in intake amount may be adapted by adapting a number of cycles n for changing the open time per cycle of the at least one gas intake valve from a current open time per cycle to a target open time per cycle. The target open time per cycle corresponds to a new demand load, and the current open time per cycle corresponds to an old demand load.

[0087] The gas inlet valve may be positioned to supply fluid fuel into the cylinder between the lower and upper sides of the cylinder, preferably on the lower half of the piston stroke.

[0088] The gas fuel supply unit equipped with a gas intake valve can supply gas fuel into the cylinder by vaporizing LNG stored in an LNG tank.

[0089] The pressure measurement unit may be connected to the control unit via wired or wireless communication.

[0090] The present invention will be further described below in embodiments with the aid of drawings, in which the same reference numbers refer to functionally corresponding features. [Brief explanation of the drawings]

[0091] [Figure 1] 1 shows a schematic diagram of an internal combustion engine. [Figure 2] Schematically shows the load, the intake amount of fluid fuel, the amount of air supplied by the turbocharger, and the air-fuel ratio as they change over time. [Figure 3] 10A and 10B show various methods for changing the open time per cycle from a current open time to a target open time.

[0092] 1 shows a schematic diagram of an internal combustion engine 10. The internal combustion engine 10 is a large marine engine capable of operating in gas mode. The internal combustion engine 10 comprises a cylinder 11 having an internal diameter 12 of at least 200 mm.

[0093] The internal combustion engine 10 includes a gas intake valve 13 for supplying fluid fuel to the cylinder 11. The fluid fuel is stored in a fluid fuel tank 20.

[0094] Exhaust gases may exit the cylinder 11 through an exhaust outlet 21, typically located in the cover of the cylinder 11. The exhaust passes through a turbine 22 of the turbocharger 14. Fresh air is supplied to the cylinder 11 through a compressor 23 of the turbine 14. Fresh air may be supplied to a scavenging air receiver 19 from where the fresh air enters the cylinder 11.

[0095] The internal combustion engine 10 is equipped with a pressure measurement unit having a pressure sensor 15 for providing a signal representative of the pressure in the cylinder 11. This signal may be received by a control unit 16 which determines the crank angle of the ignition pressure and the difference between the determined crank angle and a predetermined optimum crank angle. The crank angle corresponds to the position of the piston 24.

[0096] Depending on the difference, the control unit 16 may set the amount of air supplied by the turbocharger 14 or may set a change in the amount of air supplied by the turbocharger 14 when a new load is required.

[0097] Additionally or alternatively, the control unit 16 may be configured to set the intake rate of fluid fuel drawn through the intake valve 13 and / or to vary the intake rate when a new load is required.

[0098] To increase the amount of air supplied by turbocharger 14, control unit 16 may arrange for an accelerator 17, e.g., an electric motor, to accelerate compressor 23 of turbocharger 14. Control unit 16 may also reduce the amount of air supplied by turbocharger 14 by blowing fresh air supplied by turbocharger 14 through a discharge valve 18. Discharge valve 18 may be arranged upstream of scavenging air receiver 19.

[0099] 2 shows a schematic diagram of the load, intake volume of fluid fuel, amount of air supplied by the turbocharger, and air-fuel ratio over time. Starting from a load L1, a new load L2 greater than the first load L1 may be required. Correspondingly, the first intake volume corresponding to the first opening time OT1 of the intake valve 13 per cycle must be increased to a new intake volume corresponding to a second opening time OT2 of the intake valve 13 per cycle.

[0100] Due to the inertia of the turbocharger 14, it takes some time for the amount of air supplied by the turbocharger to increase from the first level SA1 to the second level SA2. Therefore, the air-fuel ratio λ may decrease during the time interval Δt1. Similarly, if a new load L3 less than the load L2 is requested, a new intake amount corresponding to a third open time per cycle OT3 less than the second intake amount corresponding to the second open time per cycle OT2 must be provided. Again, due to the inertia of the turbocharger 14, it takes some time for the amount of air supplied by the turbocharger 14 to reach an appropriate level less than the air supplied by the turbocharger SA2 corresponding to the load L2. Therefore, during the time interval Δt2, the air-fuel ratio λ may be higher than the steady-state air-fuel ratio at a constant load. If the air-fuel ratio deviates from the steady-state value, misfire, pre-ignition, and / or knocking may occur.

[0101] Figure 3 shows various ways to change the open time per cycle from a first open time OT1 corresponding to a first load to a second open time OT2 corresponding to a second load greater than the first. The open time can be changed within one cycle, so that a new intake volume is immediately delivered to the cylinder.

[0102] As shown in Figure 2, this may result in a drop in the air-fuel ratio. Alternatively, the opening time may be changed in four cycles (dashed line) from the first opening time OT1 to the second opening time OT2. The intake volume therefore increases slowly. The number of strokes corresponds to the inertia of the turbocharger, so that the fuel and fresh air supplied are supplied in approximately the same proportions during the load change.

Claims

1. An internal combustion engine (10), i.e. a marine or stationary engine capable of operating at least in gas mode, The internal combustion engine (10) comprises at least one cylinder (11) having an inner diameter (12) of at least 200 mm; The internal combustion engine (10) comprises at least one gas intake valve (13) for supplying fluid fuel to the cylinder (11); The internal combustion engine (10) is equipped with a turbocharger (14), The internal combustion engine (10) includes a pressure measurement unit (14) having at least one sensor (15) for providing a signal representative of the pressure in the at least one cylinder (11). Equipped with The internal combustion engine (10) - receiving a signal from said pressure measurement unit, - determining the crank angle of the ignition pressure, - determining the difference between said determined crank angle and a predetermined optimum crank angle; A control unit (16) configured as follows: the control unit (16) is configured to maintain the difference between the determined crank angle and the predetermined optimum crank angle within a predetermined interval, and the control unit (16) is configured to adapt an air-fuel ratio; at least, - said control unit (16) is configured to adapt the amount of air supplied by said turbocharger (14) and / or to adapt the intake amount of fluid fuel; and - said control unit (16) is configured to adapt at least one of the changes in the amount of air supplied by said turbocharger (14) and the changes in the intake amount of fluid fuel; [0033] An internal combustion engine (10).

2. The control unit (16) when a new load is required: - calculating the difference between said determined crank angle and said predetermined optimum crank angle; and - adapting at least one of the changes in the amount of air supplied by the turbocharger (14) and the changes in the intake amount of fluid fuel; configured to perform at least one of 2. An internal combustion engine (10) according to claim 1.

3. the control unit (16) is configured to adapt the amount of air supplied by the turbocharger (14) by increasing or decreasing the amount of air supplied by the turbocharger (14); 2. An internal combustion engine (10) according to claim 1.

4. the internal combustion engine comprises an acceleration device (17) for accelerating the turbocharger, and the control unit is configured to increase the amount of air supplied by the turbocharger (14) by further accelerating the turbocharger (14) when the difference is below a lower limit of the predetermined interval. An internal combustion engine (10) according to claim 3.

5. the internal combustion engine (10) comprises a discharge valve (18) for discharging the air supplied by the turbocharger (14) upstream of a scavenging air receiver (19), and the control unit (16) is configured to reduce the amount of air supplied by the turbocharger (14) by blowing fresh air supplied by the turbocharger (14) upstream of the scavenging air receiver (19) when the difference exceeds an upper limit of the predetermined interval. An internal combustion engine (10) according to claim 3.

6. The control unit (16) decreasing the inhalation volume if the difference is below a lower limit of the predetermined interval; and increasing the inhalation rate if the difference exceeds an upper limit of the predetermined interval; configured to adapt the intake amount of fluid fuel by at least one of 2. An internal combustion engine (10) according to claim 1.

7. 2. The internal combustion engine (10) of claim 1, wherein the control unit (16) is configured to adapt the intake quantity by adjusting the opening time per cycle of the at least one gas intake valve (13).

8. 2. The internal combustion engine (10) of claim 1, wherein the control unit (16) is configured to adapt the change in the intake amount by changing the opening time per cycle of the at least one gas intake valve (13) from a current opening time per cycle to a target opening time per cycle corresponding to a new demand load within a number n of cycles, the number n being greater than 1.

9. The number n is - the current opening time per cycle, - the target open time per cycle, and the difference between the target opening time per cycle and the current opening time per cycle; 9. The internal combustion engine (10) of claim 8, wherein the internal combustion engine (10) is dependent on at least one of the following:

10. When a new, larger load is required, the control unit (16) - setting the opening time per cycle of the at least one gas intake valve (13) shorter compared to the opening time per cycle belonging to the newly requested higher load; - continuously increasing the opening time per cycle up to the opening time per cycle corresponding to the new required load; 2. The internal combustion engine (10) of claim 1, configured to regulate the change in the intake amount by

11. If a new smaller load is requested, the control unit (16) - setting a longer opening time per cycle of said at least one gas intake valve (13) compared to said opening time per cycle belonging to the newly requested lower load; - successively decreasing the opening time per cycle up to the opening time per cycle belonging to the new demand load; 2. The internal combustion engine (10) of claim 1, configured to regulate the change in the intake amount by

12. The internal combustion engine (10) of claim 1, wherein the control unit (16) is configured to receive an emergency signal and to stop adapting the air-fuel ratio after receiving the emergency signal.

13. An internal combustion engine (10) as described in claim 12, wherein the control unit (16) is configured to instantaneously set a new opening time per cycle of at least one gas intake valve (13) corresponding to a new required load.

14. A method for operating an internal combustion engine according to any one of claims 1 to 13, said method comprising: - providing a signal representative of the pressure in at least one cylinder (11); - determining the crank angle of the ignition pressure; - determining the difference between said determined crank angle and a predetermined optimum crank angle; wherein the method comprises: by at least one of adapting the amount of air supplied by the turbocharger (14) and adapting the intake amount of fluid fuel, or by at least one of adapting the change in the amount of air supplied by the turbocharger (14) and adapting the change in the intake amount of fluid fuel, maintaining the difference between the determined crank angle and the predetermined optimum crank angle within a predetermined interval. A method characterized by:

15. When a new load is requested, determining a difference between the determined crank angle and a predetermined optimum crank angle; and a change in the amount of air supplied by the turbocharger (14) and a change in the amount of fluid fuel intake are matched; The method of claim 14 , wherein at least one of the following is performed:

16. If the difference is not within a predetermined interval, the air-fuel ratio is adapted by adapting the fluid fuel intake rate or by adapting a change in the fluid fuel intake rate after a new load is demanded.

15. The method of claim 14.

17. 17. The method of claim 16, wherein the inhalation rate is decreased if the difference is below a lower limit of the predetermined interval, and the inhalation rate is increased if the difference is above an upper limit of the predetermined interval.

18. 15. The method of claim 14, wherein the intake amount of fluid fuel is adapted by varying the open time per cycle of the at least one gas intake valve (13).

19. 15. The method of claim 14, wherein the change in the intake amount of fluid fuel is adapted by adapting the number of cycles for changing the open time per cycle of the at least one gas intake valve (13) from a current open time per cycle to a target open time per cycle.

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