JP6755901B2 - Large turbocharged 2-stroke compression ignition internal combustion engine and how to operate the engine - Google Patents

Description

The present disclosure relates to a large turbocharged two-stroke compression ignition internal combustion engine having a crosshead and a method of operating such an engine.

background

A large turbocharged two-stroke compression ignition internal combustion engine with a crosshead is typically used as a prime mover in a large oceangoing vessel such as a container ship or a power plant.

It can be difficult to control torsional vibrations, especially when operating on an ocean-going vessel. In such a torsional vibration, the propeller shaft that connects the engine to the propeller is relatively flexible to twist, and the mechanism that is relatively flexible to this twist applies pressure (torque) in the tangential direction that fluctuates from the engine. It is caused by receiving. This fluctuating tangential pressure from the engine is generated by the cycle process in each cylinder and is repeated with each rotation of the crankshaft. The torque of the crankshaft fluctuates greatly depending on the cycle process in each cylinder. This torque is negative during compression and positive during expansion. This is shown in FIG. In FIG. 5, the cylinder pressure P and the torque Q from one cylinder are shown by a solid line, and the combined torque from the six cylinders is shown by a dotted line. Dispersing a plurality of cylinders over one revolution reduces fluctuations in crankshaft torque, but is still significant. Seismic stress levels can be measured directly or indirectly, or predicted or calculated using mathematical models of the engine and its associated structures. For individual engines, including one or more equipment driven or excited by the engine, the seismic stress at one or more component levels can be, for example, various operating parameters that define the engine speed or the operating mode of the engine. Can be calculated based on. The calculated seismic stress level can be compared with a predetermined limit value, and if the limit value is exceeded, appropriate measures can be taken.

Seismic stress levels include stress levels induced by longitudinal and lateral (or shear) and torsional tremors. If the seismic stress level in a component is too high, that component can be damaged and, in turn, that component can fail with fatal consequences for the engine and / or the entire equipment. Therefore, it is necessary to keep the seismic stress level below the safety limit.

In a ship, the vibration from the engine is transmitted not only to the engine itself and the propeller shaft, but also to other parts of the hull. This tremor may be perceived as a tremor or may cause audible noise that may cause discomfort to seafarers and passengers. Therefore, it is desirable to keep the seismic stress level below the comfort limit.

Torsional vibrations on the engine spindle (including the propeller shaft) are composed of multiple frequencies, including harmonics of engine speed. The frequency of torsional vibration in the spindle of the engine is related to the rotational speed of the engine. In general, in an engine having k cylinders, the kth harmonic of the engine speed and its multiples and, in some cases, divisors are included in the frequency spectrum, and the corresponding torsional vibration is generated in the main axis of the engine at each frequency. Torsional vibrations at some frequencies are greater than torsional vibrations at other frequencies. The total vibration level should be kept below a predetermined limit and the vibration level should be kept below a predetermined limit at selected (or all) frequencies. These levels can be set uniquely for each frequency.

In the example of FIG. 5 for an engine with six cylinders, there are effectively six periods in which the crankshaft torque is negative for each revolution. It should be noted that this is just an example and not all engines have a period of negative torque. This depends on how the engine is connected. An engine with a large number of cylinders does not have a period during which the crank torque becomes negative. Similarly, an engine with five cylinders has five periods per revolution, an engine with seven cylinders has seven periods per revolution, and so on. The problem of torsional vibration in the load-drive shaft-engine system is mentioned in 4, 5, 6, and 7 cylinder engines. These vibrations are significant and, given the flexibility of the drive shaft between the engine and the load (eg the propeller), the inertia of the engine and the propeller and the flexible shaft connecting them causes resonance. As it approaches resonance, the vibration due to torque fluctuation becomes very large.

Spring or viscous torsional dampers are used to alleviate the problem of torsional vibration. However, using a torsional damper increases the cost considerably. Further, even if a torsional damper is used, these engines often have a prohibited rotation speed range, that is, a speed range in which continuous operation is prohibited. This is because the service life is shortened when a high stress is applied to the shaft.

WO2005 / 124132 discloses a method of reducing torsional vibration by gradually increasing the fuel injection amount to control the fuel injection system of a large two-stroke diesel engine. Gradually increasing fuel injection reduces some torsional vibrations, but this effect is not sufficient for engines with the greatest torsional vibration problems in a particular speed range, such as 5-cylinder engines.

Simulations and measurements by the inventors of the present application have shown that delaying ignition / combustion has a certain effect on cylinder pressure, i.e., a significant reduction in the degree of certain significant torque fluctuations. Therefore, the torsional excitation can be reduced by delaying the fuel injection. However, it is usually impossible to delay the fuel injection from the crank angle of 10 ° after the top dead center (TDC) due to the occurrence of diesel knock.

Description

In view of the above, the present invention provides a large two-stroke compression ignition engine that can be operated with a very late timing fuel injection delay, at least in any RPM band, in order to overcome or at least alleviate the above problems. The purpose is.

The above and other objectives are achieved by the characteristics set forth in the independent claims. Further embodiments will be apparent in the dependent claims, the specification, and the drawings.

According to the first aspect, a large two-stroke compression ignition type internal combustion engine is provided. The large two-stroke compression ignition type internal combustion engine has a plurality of internal pistons that reciprocate between the bottom dead center (BDC) and the top dead center (TDC) during engine operation. A cylinder, a fuel injection system including one or more fuel valves attached to each of the cylinders for injecting fuel into the cylinder for combustion, and control of the opening and closing of the fuel valve to control the cylinder. It comprises an electronic control unit configured to control the timing of fuel injection according to the crank angle, and the piston is operably connected to the crankshaft via a piston rod, a crosshead, and an articulating rod. The crankshaft rotates at a predetermined rotation speed during the operation of the engine, and the electronic control unit makes at least one of the cylinders of the engine within a specific rotation speed range at least one after TDC. It is configured to operate by delayed fuel injection by executing one pre-injection, a subsequent zero fuel injection period, and a subsequent delayed main injection by an electronic control unit.

The pressure and temperature in the combustion chamber affect the occurrence of knocks. When combustion is delayed, the expansion of air in the combustion chamber reduces both temperature and pressure. Performing at least one pre-injection after TDC, i.e. after TDC = zero, keeps the temperature in the combustion chamber at a higher level and slows down the maximum permissible delay of the main injection without the risk of diesel knock. Can be done.

Delayed fuel injection in this context is the main fuel injection event, not pilot injection. The main fuel injection event is a substantial amount of fuel injection that provides the power required to run the engine at the desired engine load. Pilot injection is a small amount of fuel injection that cannot keep the engine running for the desired load. This main fuel injection event occurs later than the fuel injection outside the specific rotational speed range in which the torsional vibration occurs. There is a period of zero injection after the pre-injection event, followed by the main injection event.

Therefore, in the (specific) speed range (RPM range) in question, the engine is operated in a specific mode. This mode can be called the low torsional vibration (TV) mode. In the speed range below the speed range in question and above the speed range in question, the engine operates in one of several "normal" mode of operation. The normal operation mode is, for example, an operation mode that matches the emission amount of the secondary regulation (tier II) or the tertiary regulation (tier III) of the International Maritime Organization (IMO).

A large delay in the main fuel injection event will greatly reduce the amount of torsional vibration.

According to the first possible implementation of the first aspect, the electronic control unit makes the main injection preferably slower than 12 ° after TDC, more preferably slower than 13 ° after TDC, and even more preferably after TDC. It is configured to run slower than 14 °, most preferably slower than 15 ° after TDC. This is the angle at which the fuel injection event begins.

Generally, in the prior art, the main fuel injection event is set at any angle between a very small angle before the TDC (eg 1-2 degrees) and a few degrees after the TDC (eg 1-6 degrees). .. This is the angle at which the fuel injection event begins. The "normal" start angle of a fuel injection event is the optimum angle for both energy efficiency and emissions (eg NOx).

According to the second possible implementation of the first aspect, at least one pre-injection is performed with a fuel injection amount that is significantly less than the amount of fuel injected in the main injection at full engine load.

According to a third possible implementation of the first aspect, at least one pre-injection is performed with approximately the same amount of fuel at all engine loads.

According to the fourth possible implementation of the first aspect, the electronic control unit has a sufficient amount of fuel to ensure that the temperature in the cylinder during delayed main injection is approximately equal to the temperature in the cylinder during TDC. Is configured to pre-inject.

According to the fifth possible implementation of the first aspect, the fuel for main injection is a gaseous fuel, the fuel for pre-injection is an ignition liquid, and the ignition liquid is injected at the same time as the main injection.

According to the sixth possible implementation of the first aspect, the electronic control unit is to reduce torsional vibrations at the crankshaft and / or at the propeller shaft and / or at the intermediate shaft connecting the crankshaft to the load. It is composed.

According to a seventh possible implementation of the first aspect, the load is a propeller for propelling a ship.

According to the eighth possible implementation of the first aspect, the crankshaft is connected by a spindle to a propeller for propelling the ship.

According to a ninth possible implementation of the first aspect, the electronic control unit is at least once after TDC for at least one of the cylinders while running the engine under load during a particular rotational speed range. The engine is operated by delayed fuel injection by executing the pre-injection of the above and the subsequent main injection by the electronic control unit.

According to the second aspect, a method of operating a large two-stroke compression ignition type internal combustion engine is provided. The large 2-stroke compression ignition type internal combustion engine has a plurality of pistons internally provided with pistons reciprocating between the bottom dead center (BDC) and the top dead center (TDC) during engine operation. It comprises a cylinder and a fuel injection system with one or more fuel valves associated with each of the cylinders for injecting fuel into the cylinder for combustion, the piston having a piston rod and a crosshead. The crankshaft is operably connected to the crankshaft via an articulating rod, and the crankshaft rotates at a predetermined rotation speed during operation of the engine. The method comprises performing at least one pre-injection after TDC, a subsequent zero fuel injection period, and a subsequent delayed main fuel injection by delayed fuel injection, at least in a particular rotational speed range.

According to the first possible implementation of the second aspect, the main injection is preferably slower than 12 ° after TDC, more preferably slower than 13 ° after TDC, and even more preferably slower than 14 ° after TDC. Most preferably it is performed later than 15 ° after TDC.

According to the second possible implementation of the second aspect, at least one pre-injection is performed with a fuel injection amount that is significantly less than the amount of fuel injected in the main injection at full engine load.

According to a third possible implementation of the second aspect, the method precharges a sufficient amount of fuel to ensure that the temperature in the cylinder during delayed main injection is approximately equal to the temperature in the cylinder during TDC. Including spraying.

According to a fourth possible implementation of the second aspect, the method further comprises performing a pre-injection of the ignition liquid followed by a main injection, the main injection containing gaseous fuel and a small amount of ignition liquid. Including spraying.

According to a fifth possible implementation of the second aspect, the electronic control unit pilots after TDC to at least one of the cylinders when the engine is operating within a particular speed range. It is configured to initiate a main fuel injection event in the cylinder later than when the engine is operating outside a certain speed range.

According to a sixth possible implementation of the second aspect, the late start of the main fuel injection event is preferably later than 12 ° after TDC, more preferably later than 13 ° after TDC, and even more preferably after TDC. It is slower than 14 °, most preferably slower than 15 ° after TDC.

According to a seventh possible implementation of the second aspect, the fuel injection, i.e. the main fuel injection, is performed faster than the delayed main fuel injection when the engine is operating outside a particular speed range.

The above aspect and other aspects of the present invention will be clarified by the embodiments described below.

In the detailed description of the present disclosure shown below, the present invention will be described in more detail with reference to the exemplary embodiments shown in the drawings.
It is an elevation view which shows the front part and one side part of the large turbocharged two-stroke compression ignition type engine which concerns on an exemplary embodiment. It is an elevation view which shows the rear part and the other side part of the engine of FIG. It is a schematic diagram which shows the engine which concerns on FIG. 1 together with the intake system and the exhaust system. It is a side view which partially cut open the ship equipped with the engine of FIGS. 1 to 3. It is a figure which shows the torque fluctuation generated by the engine of FIGS. 1 to 3. It is a figure which shows the influence of the torque fluctuation generated by the engine of FIGS. 1 to 3. It is a figure which shows the temperature and pressure of the combustion chamber of the engine of the prior art and the engine which concerns on FIG. 1 to FIG. It is a figure which shows the example of the fuel injection event in one exemplary embodiment of an engine and a driving method.

Detailed explanation

In the following detailed description, a method of operating a large two-stroke compression ignition engine and a large two-stroke compression ignition engine will be described by exemplary embodiments. 1 to 3 show a large low speed turbocharged two-stroke diesel engine equipped with a crankshaft 22, a connecting rod, a crosshead 23, and a piston rod. FIG. 3 is a schematic view showing a large low-speed turbocharged 2-stroke diesel engine together with its intake system and exhaust system. In this exemplary embodiment, the engine comprises six cylinders 1 in a row. Large turbocharged two-stroke diesel engines typically have 5 to 16 cylinders in a row. These cylinders are supported by the engine frame 24. The problem of torsional vibration is particularly relevant for 5-cylinder engines, 6-cylinder engines, and 7-cylinder engines. This engine is used, for example, as the main engine of an ocean-going vessel or as a fixed engine for turning a generator in a power plant. The total output of such an engine ranges from, for example, 5,000 kW to 110,000 kW.

This engine is a two-stroke uniflow diesel (compression ignition type) including a scavenging port 19 as a plurality of piston control ports arranged in an annular shape in the lower region of the cylinder 1 and an exhaust valve 4 on the upper part of the cylinder 1. It is an engine. Therefore, the flow in the combustion chamber is always from bottom to top, and this engine is of the so-called uniflow type. The scavenging air is sent from the scavenging receiver 2 to the scavenging port 19 of each cylinder 1. The reciprocating piston 21 in the cylinder 1 compresses the scavenging air in the combustion chamber 14. Fuel is injected into the combustion chamber 14 via two or three fuel valves 30 provided on the cylinder cover 26. The timing of fuel injection is controlled by the electronic control unit 50 connected to the fuel valve 30 via a signal line (shown by a dotted line in FIG. 3). Combustion then occurs, producing exhaust gas. When the exhaust valve 4 is opened, the exhaust gas flows to the exhaust receiver 3 through the exhaust duct 20 attached to the cylinder 1, and proceeds to the turbine 6 of the turbocharger 5 through the first exhaust conduit 18. From there, it flows out through the second exhaust conduit 7. The turbine 6 drives the compressor 9 supplied with air through the intake port 10 by the shaft 8.

The compressor 9 pressurizes the supply air and sends it to the air supply conduit 11 leading to the air supply receiver 2. The scavenging air in the conduit 11 is sent through the intercooler 12 for cooling the supply air. The cooled air supply is sent to the air supply receiver 2 via the auxiliary blower 16. The auxiliary blower 16 is driven by an electric motor 17 to pressurize the supply air in a low load or partial load state. At higher loads, the turbocharger compressor 9 delivers sufficient compression scavenging and the auxiliary blower 16 is bypassed via the check valve 15.

The cylinder 1 is formed in the cylinder liner 13. The cylinder liner 13 is supported by the cylinder frame 25, and the cylinder frame 25 is supported by the engine frame 24.

In a piston engine, the dead center is the position of the piston when it is farthest or closest to the crankshaft. The former is called the top dead center (TDC), and the latter is called the bottom dead center (BDC).

FIG. 4 shows the engines of FIGS. 1 to 3 mounted on the large vessel 40. The engine 1 is mounted in an engine room relatively close to the stern of the ship 40. The engine is connected to the propeller 44 installed at the stern by the propeller shaft 42. A torsional damper (not shown) can be installed between the propeller shaft 42 and the engine.

FIG. 5 is a graph showing torque fluctuations caused by the engine due to the cycle process in each cylinder during the engine cycle. The engine cycle is shown as an angle on the horizontal axis. This torque is negative during compression and positive during expansion. In FIG. 5, the cylinder pressure P (bar, shown on the vertical axis) and the torque Q from one cylinder are shown by a solid line, and the combined torque from the six cylinders is shown by a dotted line. From the dotted line, it is clearly shown that the torque fluctuation is remarkable, and in fact, the torque is slightly below zero 6 times per rotation of the 6-cylinder engine.

FIG. 6 is a graph showing the magnitude of the influence of the torsional vibration / predicted value on the rotational speed (RPM) of the engine of the prior art in terms of stress (MPa) on the drive shaft.

The graph shows that there is a peak around 46 RPM. Since there is a large peak around 46 RPM, a prohibited rotational speed range is set between approximately 42 PRM and 49 RPM, that is, between the two vertical dashed lines. The magnitude of stress on the drive shaft caused by torsional vibrations, especially around the peak, can be reduced by delaying the main fuel injection (which can be achieved by performing a small pre-injection first).

This graph shows two RPM-dependent stress limits with two alternate long and short dash lines. At stress levels below the dashed line below, continuous operation is allowed. Stress levels above the dashed line above are unacceptable. The stress level between the lower and upper chain lines is acceptable within a limited period of time.

The rotational speed range of approximately 42 RPM to 49 RPM between the two vertical dashed lines shown in the example of FIG. 6 is a specific rotational speed range in which the torsional vibration level is considered to be a problem. This particular speed range depends on the engine and depends on the engine design, the number of cylinders, the characteristics of the spindle 42, and the load on the spindle 42. Therefore, the speed range of this problem can take various ranges and positions within the overall engine speed range of the engine. The electronic control unit 50 of an engine is configured to operate the engine in different modes in a particular (problematic) speed range associated with the engine. This different mode can be called the low torsional vibration mode. Outside this particular speed range, the engine is operated in conventional mode of operation. This mode generally adheres to specific emissions, such as those specified by the International Maritime Organization (IMO) secondary or tertiary regulations (tier II), while maintaining optimum fuel efficiency. It is driven to ensure. On the other hand, the low torsional vibration mode does not place much emphasis on fuel efficiency and adheres to the emission threshold.

7 and 8 show the timing of the fuel injection event for one cylinder. The dashed line indicates the (fuel injection) event of the prior art engine (and "normal" engine operation outside the specific speed range), and the solid line indicates the engine and method event according to the present disclosure. In FIG. 7, the line labeled P indicates the pressure in the combustion chamber 14, and the line labeled T indicates the temperature in the combustion chamber 14. The horizontal axis shows the crank angle with respect to the TDC in angular units, and the vertical axis shows the pressure in the combustion chamber in bar units. In FIG. 8, the solid line shows the pre-injection event, the subsequent zero fuel injection period, and the main fuel injection event starting from the subsequent rise. The dotted line indicates the main fuel injection event of the prior art engine. This event also starts from the start and takes place much earlier than the main fuel injection event according to the present disclosure.

In an example of a prior art engine and method, fuel injection is delayed up to 5 ° after TDC. Both the temperature and pressure in the combustion chamber 14 decrease between TDC 0 and fuel injection at 5 °. Fuel is injected at 5 ° after TDC, from which point the temperature of the combustion chamber rises until the respective maximums are reached.

In an example of an engine according to the present disclosure, a small pre-injection is performed by the electronic control unit 50 operating the fuel valve 30. This pre-injection is executed after TDC0. Preferably, the pre-injection is performed between 6 ° and 10 ° after TDC, more preferably about 7 ° and 8 °, and most preferably about 8 ° after TDC. The pre-injection is a fuel injection with a smaller amount of fuel than the subsequent main injection. In this pre-injection, a sufficient amount of fuel is injected so that the temperature in the combustion chamber 14 does not fall significantly below the temperature at TDC 0 up to about 10 ° after TDC. Then, after the zero injection period, the main injection is executed. The main injection is controlled by the electronic control unit 50. The pre-injection may be a single injection or a series of small pre-injections, and the electronic control unit 50 is configured accordingly in one embodiment. In one embodiment, the main injection (start) is delayed up to 25 ° after TDC. Preferably, the main injection is performed at at least 12 ° after TDC, more preferably at least 13 ° after TDC, even more preferably at least 14 ° after TDC, and most preferably at least 15 ° after TDC. Tested that pre-injection at TDC or immediately after TDC does not cause diesel knock or other combustion problems when the main injection timing is delayed from 20 ° to 25 ° (starting at that angle). And shown by simulation.

Injection delays generally impair fuel efficiency and are usually only applied in the range of engine speeds where there are problems with torsional vibrations and resonances. Thus, in one embodiment, the electronic control unit 50 applies pre-injection and delayed main injection only in a predetermined speed range of the engine associated with the problem of torsional vibration. Of course, double injection (pre-injection followed by late-timing main injection) can also be used for other purposes such as reducing NOx emissions.

According to the engine and method according to the present disclosure, the main injection event (start) can be further delayed than 10 ° after TDC, thereby reducing the predicted torsional value and the torsional vibration in the engine-axis-load system. Can alleviate problems related to. It saves heavy and costly (torsional) vibration dampers, reduces or avoids the engine prohibited speed range, and allows the engine to run freely at all speeds.

The engines and methods according to the present disclosure can also be used for conventional fuels such as marine diesel and heavy oil, and alternative fuels such as gaseous fuels.

For gaseous fuels, pre-injection is generally performed with an ignition fluid such as marine diesel. The main injection is an injection with a small amount of ignition liquid and a main amount of gaseous fuel.

According to one embodiment, each cylinder of the engine may be operated in a different cycle process. Therefore, pre-injection and subsequent late-timing main injection may be applied to one or more selected cylinders and the other cylinders may be operated in a conventional cycle with one fuel injection per cycle.

In one embodiment, the type of fuel is different for each cylinder.

Although the present invention has been described by the various embodiments described above, other modifications to the disclosed embodiments implement the claimed invention by examining the drawings, the disclosed content, and the appended claims. It is something that can be understood and done by those skilled in the art. In the claims, the phrase "have, prepare" does not exclude other elements or steps, and the singular representation does not exclude the plural. The fact that certain means are listed in different dependent claims does not mean that the combination of these means is not effectively used.

Reference codes in the claims should not be construed as limiting the scope.

Claims (17)

A plurality of cylinders (1) each internally provided with pistons (21) reciprocating between the bottom dead center (BDC) and the top dead center (TDC) during engine operation.
A fuel injection system including one or more fuel valves (30) attached to each of the cylinders (1) in order to inject fuel into the cylinders (1) for combustion.
An electronic control unit (50) configured to control the timing of fuel injection according to the crank angle of the cylinder (1) by controlling the opening and closing of the fuel valve (30).
With
The piston (21) is operably connected to the crankshaft (22) via a piston rod, a crosshead (23), and a connecting rod.
The crankshaft (22) rotates at a predetermined rotational speed during operation of the engine.
The electronic control unit (50) pre-injects at least one of the cylinders (1) of the engine within a specific rotation speed range from 6 ° to 10 ° after TDC, and the pre-injection. The operation is performed by executing the later zero fuel injection period and the main fuel injection after the zero fuel injection period, which is the main fuel injection after 12 ° after the TDC, by the electronic control unit (50). Is configured as
Large 2-stroke compression ignition type internal combustion engine. The electronic control unit is a torsional vibration at the crankshaft (22) and / or at a propeller shaft (42) connected to the crankshaft and / or at an intermediate shaft connecting the crankshaft (22) to a load. The engine according to claim 1, which is configured to reduce. The engine according to claim 2, wherein the load is a propeller (44) for propelling a ship (40). The engine according to claim 2 or 3, wherein the crankshaft (42) is connected to a propeller (44) for propelling a ship (40) by a spindle (42). The electronic control unit (50) receives at least one pre-injection after the TDC and at least one pre-injection to at least one of the cylinders while operating the engine under increasing load during the particular rotational speed range. The engine according to any one of claims 1 to 4 , wherein the engine is operated by executing the subsequent main fuel injection by the electronic control unit (50). The electronic control unit (50) is configured to perform the main fuel injection slower than 13 ° after TDC, at least while the engine is operating within the particular rotational speed range. The engine according to any one of claims 1 to 5. The electronic control unit (50) is configured to perform the main fuel injection slower than 15 ° after TDC, at least while the engine is operating within the particular rotational speed range. The engine according to any one of claims 1 to 5. The engine according to any one of claims 1 to 7, wherein the at least one pre-injection is performed with a fuel injection amount that is considerably smaller than the amount of fuel injected in the main fuel injection when the engine is fully loaded. The electronic control unit (50) pre-injects a sufficient amount of fuel so that the temperature in the cylinder (1) at the time of the main fuel injection becomes substantially equal to the temperature in the cylinder at the time of TDC. The engine according to any one of claims 1 to 8, which is configured as follows. The engine according to any one of claims 1 to 9, wherein the electronic control unit (50) is configured to perform the pre-injection after the TDC by injecting an ignition liquid during the pre-injection. The method according to any one of claims 1 to 10, wherein the fuel for the main fuel injection is a gaseous fuel, the fuel for the pre-injection is an ignition liquid, and the ignition liquid is injected at the same time as the main fuel injection. Engine. It is a method of operating a large 2-stroke compression ignition type internal combustion engine.
The engine
A plurality of cylinders (1) each having pistons (21) that reciprocate between the bottom dead center (BDC) and the top dead center (TDC) during engine operation.
A fuel injection system including one or more fuel valves (30) attached to each of the cylinders (1) for injecting fuel into the cylinders (1) for combustion.
The piston (21) is operably connected to the crankshaft (22) via a piston rod, a crosshead (23), and a connecting rod.
The crankshaft (22) rotates at a predetermined rotational speed during operation of the engine.
Is an engine
In the method, at least one of the cylinders (1) of the engine is pre-injected between 6 ° and 10 ° after TDC and zero fuel injection after the pre-injection, at least in a specific rotational speed range. A method comprising operating by performing a period and a main fuel injection after the zero fuel injection period, which is a main fuel injection performed after 12 ° after TDC. 12. The method of claim 12, wherein the main fuel injection is performed later than 13 ° after TDC. 12. The method of claim 12 or 13, wherein the fuel injection is performed faster than the main fuel injection when the engine is operating outside the particular rotational speed range. The method according to any one of claims 12 to 14, wherein the pre-injection is performed with a fuel injection amount that is considerably smaller than the amount of fuel injected in the main fuel injection when the engine is fully loaded. Any of claims 12 to 15, further comprising pre-injecting a sufficient amount of fuel so that the temperature in the cylinder at the time of main fuel injection is substantially equal to the temperature in the cylinder at the time of TDC. The method described in Cylinder. Further including performing pre-injection of ignition liquid and subsequent main fuel injection,
The method according to any one of claims 12 to 16, wherein the main fuel injection includes injecting a gaseous fuel and a small amount of ignition liquid.