INTERNAL COMBUSTION ENGINE

Abstract

 The present invention is related to internal combustion engines (100) and to a method for operating an internal combustion engine (100). The internal combustion engine, preferably a large two-stroke internal combustion engine, has at least one cylinder (1), preferably having an inner diameter of at least 200mm, in particular a dual-fuel engine, and has a reciprocating piston. The internal combustion engine (100) comprises at least two main injection nozzles (11, 12, 13), preferably three main injection nozzles (11, 12, 13), for injecting of a fuel unwilling to ignite. The main injection nozzles (11, 12, 13) preferably are arranged equidistantly in circumferential direction. The internal combustion engine (100) comprises at least one pilot injection nozzle (21, 22, 23) for injecting a fuel willing to ignite, preferably the same number of pilot injection nozzles as for the main injection nozzles (11, 12, 13), wherein each pilot injection nozzle is arranged near a corresponding main injection nozzle (11, 12, 13).
The internal combustion engine (100) further comprises a control unit (10) suitable for controlling the main injection nozzles (11, 12, 13) and the pilot injection nozzles (21, 22, 23) during a power cycle such that fuel willing to ignite is injected into the combustion chamber (3) via the pilot injection nozzles (21, 22, 23) jointly with a fuel unwilling to ignite via a corresponding main injection nozzle (11, 12, 13), and such that at least one main injection nozzle (11, 12, 13) ejects fuel unwilling to ignite without fuel willing to ignite being introduced into the combustion chamber via a corresponding pilot injection nozzle (21, 22, 23).

Description

[0001] The present invention is related to an internal combustion engine and to a method for operating an internal combustion engine according to the preambles of the independent claims.

[0002] The present invention preferably relates to an internal combustion engine like a large marine or ship engine or a stationary engine whose cylinders have an inner diameter of at least 200 mm. The engine preferably is a two-stroke engine or a two-stroke cross head engine. The engine can be a gas engine, a dual fuel or a multi fuel engine. Burning of liquid and or gaseous fuels in such engines is possible as well as self-igniting or forced igniting.

[0003] The internal combustion engine can be a longitudinally flushed two-stroke engine.

[0004] Engine speed is preferably below 800 RPM, especially for 4-stroke engines, and more preferably below 200 RPM, especially for 2-stroke engines, which indicates the designation of lowspeed engines.

[0005] Large ships, in particular vessels for transport of goods, usually are powered by internal combustion engines, in particular diesel and/or gas engines, mostly two-stroke, cross head engines.

[0006] The term internal combustion engine in particular includes dual-fuel engines and large engines in which the self-ignition of a first fuel, also called pilot, is used for the positive ignition of another fuel, also called main fuel.

[0007] In particular a fuel willing to ignite is used to ignite another fuel unwilling to ignite.

[0008] A fuel willing to ignite may be a Diesel fuel or another liquid fuel with similar properties from either synthetic or biological origin.

[0009] Within this context any fuel less willing to ignite than a fuel willing to ignite is included in the category fuel unwilling to ignite. This category includes Otto-fuels, in particular alcohol fuels, such as a pure methanol fuels or ethanol fuels, either of the two mixed with water or other solvents, or other fuels such as LNG, LPG or ammonia (pure or mixed with water or other solvents) .

[0010] The ignition of such fuels in the engine cylinder is a serious technical challenge due to their particular ignition and combustion properties, such as limited flammability, a high autoignition temperature, for example at least 100°C, and minimum ignition energy.

[0011] Moreover, the high latent heat of evaporation associated with some of these fuels compared to conventional fuels like, for instance, Diesel or HFO may trigger a cooling effect that acts as further inhibiting factor for ignition.

[0012] All this imposes stringent requirements on the location and timing of pilot injection, layout of pilot injectors and amount of pilot fuel.

[0013] DE102019134628A1 discloses a method for operating an engine, wherein a fuel which is unwilling to ignite is burned in a combustion chamber of the at least one cylinder and is ignited for this purpose with the aid of a fuel which is willing to ignite. The fuel unwilling to ignite is introduced into the combustion chamber of the respective cylinder via a main injection at the same time as an injection of the fuel willing to ignite and/or at a time after the injection of the fuel which is willing to ignite. The fuel that is unwilling to ignite is also introduced into the combustion chamber of the respective cylinder via at least one additional injection at a time before the injection of the fuel willing to ignite. A first injection device for introducing ignition-unwilling fuel is arranged close a second injection device for introducing fuel which is willing to ignite, such that a mixture of fuels can be achieved.

[0014] For achieving an optimal pressure profile during a combustion cycle, EP0586775 A1 discloses to inject fuel by means of at least two injection nozzles, which are arranged in such a way in the combustion chamber that the fuel jets emerging from one injection nozzle do not influence those emerging from the others.

[0015] 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 of operating an internal combustion engine providing a low amount of pilot fuel and a stable mixture inflammation.

[0016] The object is achieved by the internal combustion engines and the method for running an internal combustion engine according to the independent claims.

[0017] According to the invention an internal combustion engine, has at least one cylinder. The cylinder preferably has an inner diameter of at least 200mm. The engine in particular is a dual-fuel engine.

[0018] The internal combustion engine preferably is a large two-stroke internal combustion engine, more preferably a longitudinally flushed large engine.

[0019] The internal combustion engine comprises a reciprocating piston, which is arranged to move back and forth along a cylinder axis between a lower reversal point (BDC) and an upper reversal point (TDC). A cylinder cover and a cylinder wall together with the piston delimits a combustion chamber. Typically, an exhaust valve is arranged in the cylinder cover by which combustion gases can be removed from the combustion chamber and a scavenging port may be arranged in the cylinder wall close to the lower reversal point.

[0020] The internal combustion engine comprises at least two main injection nozzles, preferably two or three main injection nozzles, for injecting of a fuel unwilling to ignite.

[0021] The main injection nozzles may be arranged in the combustion chamber in such a way that the fuel jets emerging from one main injection nozzle in each case do not influence the fuel jets emerging from the other main injection nozzles in each case.

[0022] Preferably the main nozzles are arranged equidistantly in circumferential direction on the same level of the cylinder axis.

[0023] The internal combustion engine comprises at least one pilot injection nozzle for injecting a fuel willing to ignite.

[0024] Each of the main injection nozzles and/or each of the pilot injection nozzles may comprise three to seven injection holes. The holes may have a diameter from 0.3 to 2.5 mm.

[0025] The internal combustion engine may comprise dedicated pilot fuel injectors to be used as pilot injection nozzles. Alternatively, backup fuel injectors can be used for dosing fuel willing to ignite.

[0026] Each pilot injection nozzle is arranged near a corresponding main injection nozzle. Within this context "near" means that a pilot injection nozzle is arranged in the proximity of a main injection nozzle, i.e. the distance between a pilot injection nozzle and a near main injection nozzle is smaller than between a main injection nozzle and an adjacent main injection nozzle.

[0027] The main injection nozzle may be distanced from the next nearest main injection nozzle by at least 25°, preferably by at least 60°, 90° or 120°. If the cylinder comprises only two main injection nozzles, the main injection nozzles may be distanced by 180°, if the cylinder comprises three main injection nozzles, the main injection nozzles may be distanced by 120°. The distance between a main injection nozzle and a corresponding pilot injection nozzle may be smaller than 35°. The angle refers to a circumferential distance with respect to the cylinder axis in a plane perpendicular to the cylinder axis.

[0028] The number of pilot injection nozzles is smaller than or equal to the number of main injection nozzles.

[0029] Preferably, the cylinder comprises the same number of pilot injection nozzles as for the main injection nozzles. In this case the engine can be operated in different injection modes as explained below.

[0030] The internal combustion engine comprises a control unit suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that fuel willing to ignite is injected into the combustion chamber via the pilot injection nozzles jointly with a fuel unwilling to ignite via a corresponding main injection nozzle.

[0031] Within this context "jointly" injected means that the fuel willing to ignite is injected at the same time as an injection of the fuel unwilling to ignite and/or at a time shortly before or after the injection of the fuel unwilling to ignite via the corresponding main nozzles, preferably within a time interval of ±4°CA, more preferably within a time interval of ±3°CA.

[0032] Within this application a time interval is measured in units of the power cycle which are given as differences of respective crank angles. A whole power cycle has the duration of 360°CA in two-stroke engines and 720° in 4-stroke engines.

[0033] The control unit is further suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that at least one main injection nozzle ejects fuel unwilling to ignite without fuel willing to ignite being introduced into the combustion chamber via a corresponding pilot injection nozzle.

[0034] The respective main injection nozzle may or may not have a corresponding pilot injection nozzle which is arranged nearby.

[0035] The control unit hence is suitable for controlling the main injection nozzles and the pilot injection nozzles such that fuel willing to ignite always is injected jointly with fuel unwilling to ignite, whereas fuel unwilling to ignite may be injected without fuel willing to ignite.

[0036] The control unit may be configured for setting an amount of injected fuel, for opening the respective valve, for providing an ejection pressure and/or for setting an opening duration.

[0037] A proper positioning of the pilot injection nozzles and a proper timing of the pilot injection according to the invention allows for reduction of required amount of pilot fuel and assure stable mixture inflammation. It is not necessary to always jointly inject a pilot fuel, in this case a fuel willing to ignite, together with all main injections, in this case with injection of a fuel unwilling to ignite.

[0038] The cylinder may have a plurality of scavenging ports, which are arranged such that a swirl flow of combustion air is formed in the combustion chamber during scavenging and the following upward movement of the reciprocating piston. The scavenging ports may provide a flow path through the cylinder wall that gives the incoming gas a circumferential or tangential direction with respect to the cylinder axis. The swirl flow provides for a proper mixing of incoming gas and fuel, as well as for the mixing of pilot and main fuel.

[0039] With respect to the direction of the swirl and the respective circumferential direction, the pilot injection nozzles may each be arranged upstream or downstream of a respective main injection nozzle, at an angular distance between 5° and 45°, preferably 20° to 35°.

[0040] The timing of the injections may be adapted to the swirl flow.

[0041] The control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power circle such that the main injection nozzles are opened sequentially, preferably at a time interval of 3°CA-18°CA. Preferably, every main injection nozzle is opened for ejecting fuel unwilling to ignite once during one power circle.

[0042] The time delay between successive injections may be adapted with respect to the number of main injection nozzles, the distance between main injectors nozzles, bore size and the propagation velocity of the fuel sprays or jets.

[0043] The propagation velocity typically changes with changing main fuel pressure, swirl velocity or charge density.

[0044] The control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that at least one of the pilot injection nozzles ejects fuel willing to ignite into the combustion chamber after the fuel unwilling to ignite is introduced via the at least one main injection nozzle without fuel willing to ignite being ejected by a corresponding pilot injection nozzle.

[0045] The fuel unwilling to ignite has a certain time within the cylinder without being ignited. When the fuel willing to ignite enters the cylinder and ignites the fuel unwilling to ignite which is jointly injected with the fuel willing to ignite, the fuel unwilling to ignite being already in the cylinder will be ignited, too. In case of a swirl flow, a fuel unwilling to ignite is injected upstream of a further fuel unwilling to ignite, which is injected jointly with a fuel willing to ignite.

[0046] The unignited main fuel may pass the later injected and ignited main fuel and will be ignited by the ignition torch formed by this later injected and ignited main fuel.

[0047] The arrival of unignited main fuel of the earlier injection may be synchronized with the later inflammation by opening and closing the respective nozzles in proper time intervals.

[0048] Alternatively, or additionally, the control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power circle such that at least one of the pilot injection nozzles ejects fuel willing to ignite into the combustion chamber before the fuel unwilling to ignite is introduced via the at least one main injection nozzle without fuel willing to ignite being ejected by a corresponding pilot injection nozzle.

[0049] Arrival of the flame front of the earlier injection jet may be synchronized with the later injection by opening and closing the respective nozzles in proper time intervals.

[0050] When the fuel unwilling to ignite is introduced via the at least one main injection nozzle without fuel willing to ignite being ejected by a corresponding pilot injection nozzle into the cylinder, a fuel unwilling to ignite was already ignited by a corresponding fuel willing to ignite. An ignition torch has been formed. Thus, the later introduced fuel unwilling to ignite will be ignited by the already existing ignition torch. In case of a swirl flow, a fuel unwilling to ignite, which is injected jointly with a fuel willing to ignite, is injected upstream of a further fuel unwilling to ignite.

[0051] The internal combustion engine may comprise a first and a second main injection nozzle. Preferably, the internal combustion engine comprises only a first and a second main injection nozzle, which may be arranged opposite to another that is in a circumferential distance of mainly 180° with respect to the cylinder axis.

[0052] The control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle, such that the first main injection nozzle ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, before fuel unwilling to ignite is ejected by the second main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0053] As explained above the jointly injected fuels will ignite and form an ignition torch which will ignite the later injected fuel unwilling to ignite.

[0054] Alternatively, the control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle, such that the second main injection nozzle ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, after a fuel unwilling to ignite has been ejected by the first main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0055] As explained above, the jointly injected fuels will inflame and the so formed ignition torch will ignite the unignited fuel unwilling to ignite already being in the cylinder.

[0056] The internal combustion engine may comprise a first, a second and a third main injection nozzle.

[0057] Preferably, the internal combustion engine comprises exactly three main injection nozzles, which may be equally distributed around the cylinder axis and may have a circumferential distance of mainly 120° with respect to the cylinder axis.

[0058] All main injection nozzles may be accompanied by a respective pilot injection nozzle, and hence each of the main injection nozzles may be considered as the first, the second or the third main injection nozzle.

[0059] Preferably, the second main injection nozzle is arranged upstream of and next to the third main injection nozzle, and the first main injection nozzle is arranged upstream of and next to the second main injection nozzle (and consequently the third main injection nozzle is arranged upstream of and next to the first main injection nozzle) with respect to the circumferential direction of a swirl flow.

[0060] The control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that the first main injection nozzle ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, before fuel unwilling to ignite is, preferably successively, ejected by the second and the third main injection nozzle without ejecting fuel willing to ignite by corresponding pilot injection nozzles.

[0061] The jointly injected fuels inflame and form an ignition torch which will ignite the fuel unwilling to ignite later injected by the second main injection nozzle. The inflamed mixture will then ignite the fuel unwilling to ignite finally injected by the third main injection nozzle.

[0062] Alternatively, the control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that the third main injection nozzle ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, after fuel unwilling to ignite has been, preferably successively, ejected by the first and the second main injection nozzle without ejecting fuel willing to ignite by corresponding pilot injection nozzles.

[0063] The jointly injected fuels will inflame and the respective ignition torch will ignite the unignited fuel unwilling to ignite having been ejected by the first and the second main injection nozzle and already being in the cylinder.

[0064] Alternatively, the control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that the second main injection nozzle ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle and after fuel unwilling to ignite has been ejected by the first main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0065] The jointly injected fuels inflame and form an ignition torch which ignites the unignited fuel unwilling to ignite having been ejected by the first main injection nozzle and already being in the cylinder. Later the already inflamed mixture of fuel will ignite the fuel unwilling to ignite later injected by the third main injection nozzle.

[0066] Alternatively, the control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that the first and the second main injection nozzles each successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles ejecting fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0067] The jointly injected fuels inflame and the burning fuel will ignite the fuel unwilling to ignite later injected by the third main injection nozzle.

[0068] Alternatively, the control unit may be suitable for controlling the main injection nozzles and the pilot injection nozzles during a power cycle such that the second and the third main injection nozzle each successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles ejecting fuel willing to ignite, after fuel unwilling to ignite has been ejected by the first main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0069] The jointly injected fuels ignite the fuel unwilling to ignite already being in the cylinder.

[0070] The control unit may be configured for setting and/or for selecting an operation mode wherein a sequence of injections by the various main injections nozzles and pilot injections nozzles is determined, preferably as described above.

[0071] Additionally, the control unit may be configured to change the operation mode, the selection of the pilot injection nozzle and/or order of injections, in particular to vary the pilot injection nozzle used for injection if more than one pilot injection nozzle is available.

[0072] The pilot injection nozzle chosen for injection may be varied from power cycle to power cycle or after a defined number of power cycles.

[0073] The control unit may be configured to arrange a rotating ignition schedule in order to assure uniform lifetime consumption of the injectors and uniform thermo-mechanical loading of cylinder parts/components, when the injection and ignition start from different main injection nozzles in a pre-defined sequence.

[0074] This option assumes an arrangement with rotational symmetry when each main injection nozzle is accompanied by a pilot injection nozzle in close vicinity.

[0075] According to the invention the object is solved by a method for operating an internal combustion engine, in particular as described above. The internal combustion engine comprises at least two main injection nozzles being arranged in the combustion chamber in such a way that the fuel jets emerging from one main injection nozzle in each case do not influence the fuel jets emerging from the other main injection nozzles in each case.

[0076] Preferably the main injection nozzles are arranged equidistantly in circumferential direction. Each of at least one pilot injection nozzles for injecting of a fuel willing to ignite is arranged near a corresponding main injection nozzle.

[0077] The method comprises the step of introducing fuel willing to ignite into the combustion chamber via the pilot injection nozzle jointly with fuel unwilling to ignite via the corresponding main nozzle. The method comprises the further step of ejecting fuel unwilling to ignite via at least one main injection nozzle without introducing fuel willing to ignite via a corresponding pilot injection nozzle.

[0078] The steps are performed during the same power cycle, wherein the second step may follow the first step or vice versa.

[0079] A least one of the pilot injection nozzles may eject fuel willing to ignite into the combustion chamber after fuel unwilling to ignite is introduced via a main injection nozzle without fuel willing to ignite being ejected by a corresponding pilot nozzle. During the power cycle all fuel unwilling to ignite introduced by different main injection nozzles is ignited by fuel willing to ignite introduced by the at least one pilot injection nozzle.

[0080] At least one of the pilot injection nozzles may eject fuel willing to ignite into the combustion chamber before fuel unwilling to ignite is introduced via a main injection nozzle without fuel willing to ignite being ejected by a corresponding pilot injection nozzle and the fuel unwilling to ignite is ignited by an ignition torch caused by fuel willing to ignite and fuel unwilling to ignite injected before.

[0081] Fuel unwilling to ignite may be introduced during a power cycle successively by different main injection nozzles at a time interval of 3-18°CA.

[0082] Fuel unwilling to ignite may be selected from the group comprising ethanol, methanol, ammonia.

[0083] Fuel willing to ignite may be a Diesel like fuel. Diesel like fuel include Diesel and a liquid fuel from non-fossil origin with ignition properties similar to Diesel.

[0084] The internal combustion engine may comprise a first and a second main injection nozzle, preferably as described above. During a power cycle the first main injection nozzle may eject fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite and before fuel unwilling to ignite is ejected by the second main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0085] Alternatively, during a power cycle the second main injection nozzle may ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting fuel willing to ignite and after fuel unwilling to ignite has been ejected by the first main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0086] The internal combustion engine may comprise a first, a second and a third main injection nozzle, preferably as described above.

[0087] During a power cycle the first main injection nozzle may eject a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, before fuel unwilling to ignite is successively ejected by the second and the third main injection nozzle without ejecting fuel willing to ignite by corresponding pilot injection nozzles.

[0088] During a power cycle the third main injection nozzle may eject a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, after fuel unwilling to ignite has been successively ejected by the first and the second main injection nozzle jointly without ejecting fuel willing to ignite by corresponding pilot injection nozzles.

[0089] During a power cycle the second main injection nozzle may eject a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle ejecting a fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle and after fuel unwilling to ignite has been ejected by the first main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0090] Within the above described three embodiments fuel willing to ignite is only injected together with one of the three main fuel injections.

[0091] Alternatively, fuel willing to ignite may be injected together with two of the three main fuel injections.

[0092] During a power cycle the first and the second main injection nozzles successively may eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles ejecting fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0093] During a power cycle the second and the third main injection nozzle may successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles ejecting fuel willing to ignite, after fuel unwilling to ignite has been ejected by the first main injection nozzle without ejecting fuel willing to ignite by a corresponding pilot injection nozzle.

[0094] According to the invention, a computer program comprises program code for carrying out the steps of the method as described above when the program is executed on a computer.

[0095] According to the invention, a computer program product can be loaded directly into an internal memory of a digital computer and comprises software code portions executing the method steps as described above when the program is running on the digital computer.

[0096] Preferably, the computer is connected to or part of the control unit.

[0097] As compared with a situation when a pilot fuel is injected with every main fuel injection and the proportion of pilot fuel is 5%, the proportion of the pilot fuel may be lowered to 1.7% for only one pilot injection.

[0098] In the following, the invention is further explained in embodiments by means of figures. Same reference numbers refer to functionally corresponding features.

Figure 1:

shows a schematic view of a first example of a method according to the invention;

Figure 2:

shows a schematic view of a second example of a method according to the invention;

Figure 3:

shows a schematic view of steps for a third example of a method according to the invention;

Figure 4:

shows a schematic time diagram for the third example of figure 3;

Figure 5:

shows a schematic view of a fourth example of a method according to the invention;

Figure 6:

shows a schematic time diagram for the fourth example of figure 5;

Figure 7:

shows a schematic view of a fifth example of a method according to the invention;

Figure 8:

shows a schematic time diagram for the fifth example of figure 7;

Figure 9:

shows a schematic view of a sixth example of a method according to the invention;

Figure 10:

shows a schematic time diagram for the sixth example of figure 9;

Figure 11:

shows a schematic view of a seventh example of a method according to the invention;

Figure 12:

shows a schematic time diagram for the seventh example of figure 11.

[0099] Figure 1 shows a schematic view of a method according to the invention. An internal combustion engine 100 comprises a cylinder 1, preferably having an inner diameter 2 of at least 200mm. The cylinder 1 contains a combustion chamber 3.

[0100] The cylinder 1 comprises two main injection nozzles 11, 12 for injecting of a fuel unwilling to ignite, arranged opposite to each other. The cylinder 1 also comprises two pilot injection nozzles 21, 22 for injecting a fuel willing to ignite. Each pilot injection nozzle 21, 22 is arranged near a corresponding main injection nozzle 11, 12.

[0101] In the figure the nozzles are shown only schematically. In reality, the nozzles 11, 12, 21, 22 may be arranged in or close to the cylinder liner or the cylinder cover, not explicitly shown in the figures.

[0102] A control unit 10 is suitable for controlling the main injection nozzles 11, 12 and the pilot injection nozzles 21, 22 during a power cycle such that fuel willing to ignite is injected into the combustion chamber via the first pilot injection nozzles 21 jointly with a fuel unwilling to ignite via the corresponding main injection nozzle 11. The fuel unwilling to ignite is ignited by the fuel willing to ignite. An ignition torch 30 is formed.

[0103] In case a swirl flow of combustion air is formed in the combustion chamber 3, the ignition torch 3 is driven in circumferential direction towards the second main injection nozzle 12.

[0104] After a time interval of 3-18°CA, when the ignition torch 3 has reached the position of the second main injection nozzle 12, the second main injection nozzle 12 ejects fuel unwilling to ignite without fuel willing to ignite being introduced into the combustion chamber via a corresponding pilot injection nozzle 22.

[0105] The fuel unwilling to ignite ejected by the second main injection nozzle 12 is ignited by the ignition torch 3.

[0106] The same arrangement of nozzles 11, 12, 21, 22 can be operated differently as shown in Figure 2.

[0107] A fuel unwilling to ignite is ejected by the first main injection nozzle 11 without ejecting fuel willing to ignite by the corresponding pilot injection nozzle 21.

[0108] The fuel is driven in circumferential direction by a swirl flow of combustion air. After a time interval of 3-18°CA, when the fuel has reached the position of the second main injection nozzle 12 the second main injection nozzle 12 ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle 22 ejecting a fuel willing to ignite.

[0109] The fuel willing to ignite ignites both the fuel injected before and the fuel injected jointly.

[0110] Figure 3 shows a schematic view of steps for a third example of a method for different time intervals t1, t2, t3 according to the invention. Figure 4 schematically shows the respective time diagram.

[0111] The internal combustion engine 100 comprises three main injection nozzles 11, 12, 13 for injecting of a fuel unwilling to ignite. The three main injection nozzles 11, 12, 13 are arranged in equal circumferential distance. The cylinder 1 also comprises three pilot injection nozzles 21, 22, 23 for injecting a fuel willing to ignite. Each pilot injection nozzle 21, 22, 23 is arranged near a corresponding main injection nozzle 11, 12, 13.

[0112] During a first time interval t1 the first main injection nozzle 11 and the first pilot injection nozzle 21 jointly eject fuel unwilling to ignite and fuel willing to ignite. In Figure 4 the injection event of the fuel willing to ignite is shown as a short and strong event, whereas the ignition of fuel unwilling to ignite is shown as less stronger and longer lasting event.

[0113] An ignition torch 3 is formed which is driven in circumferential direction 5 according to a swirl flow of combustion air.

[0114] At a second time interval t2 fuel unwilling to ignite is ejected by the second main injection nozzle 12. The fuel unwilling to ignite is ignited by the ignition torch.

[0115] At a third time interval t3 further fuel unwilling to ignite is ejected by the third main injection nozzle 13. Injection of a further pilot fuel by the corresponding pilot injection nozzle 23 is not necessary, because the fuel unwilling to ignite is ignited by the burning fuel, which reaches the third main injection nozzle 13 at the time t3.

[0116] Figure 5 shows a schematic view of a fourth example of a method according to the invention. Figure 6 shows a schematic time diagram for the fourth example of figure 5.

[0117] The internal combustion engine 100 comprises three main injection nozzles 11, 12, 13 for injecting of a fuel unwilling to ignite. The three main injection nozzles 11, 12, 13 are arranged in equal circumferential distance.

[0118] At a time interval t1 a second main injection nozzle 12 ejects fuel unwilling to ignite, which is driven in circumferential direction towards a third main injection nozzle 13, which ejects fuel unwilling to ignite at a time interval t2 after the time interval t1.

[0119] The full amount of fuel unwilling to ignite ejected by the second and by the third main injection nozzle 12, 13 is driven in circumferential direction 5 until it meets the first main injection nozzle 11. Around this time t3 the first main injection nozzle 11 ejects fuel unwilling to ignite together with a pilot injection nozzle 21 ejecting fuel willing to ignite.

[0120] The fuel willing to ignite not only ignites the fuel unwilling to ignite ejected by the first main injection nozzle 11, but also the fuel unwilling to ignite being in the cylinder since the ejection of the second main injection nozzle 12 and the third main injection nozzle 13.

[0121] Figure 7 shows a schematic view of a fifth example of a method according to the invention. Figure 8 shows a schematic time diagram for the fifth example of figure 7.

[0122] The arrangement of nozzles 11, 12, 13, 21, 22, 23 as shown in the figures 3 can be operated differently.

[0123] At a time interval t1 a first main injection nozzle 11 ejects fuel unwilling to ignite, which is driven in circumferential direction towards a second main injection nozzle 12, which ejects fuel unwilling to ignite together with a pilot injection nozzle 22 ejecting fuel willing to ignite at a time interval t2 after the time interval t1.

[0124] The fuel willing to ignite not only ignites the fuel unwilling to ignite ejected by the second main injection nozzle 12, but also the fuel unwilling to ignite being in the cylinder since the ejection of the first main injection nozzle 11.

[0125] The injection torch is driven in circumferential direction 5 until it arrives at the third main injection nozzle 13. Around this time t3 the third main injection nozzle 13 ejects fuel unwilling to ignite which is ignited by the ignition torch.

[0126] The same arrangement of nozzles 11, 12, 13, 21, 22, 23 as shown in the figures 3 or 7 can be operated differently.

[0127] Figure 9 shows a schematic view of a sixth example of a method according to the invention. Figure 10 shows a schematic time diagram for the sixth example of figure 9.

[0128] At a time interval t1 the first main injection nozzle 11 ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle 21 ejecting fuel willing to ignite.

[0129] At the same time or at a later time t2 the second main injection nozzle 12 ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle 22 ejecting fuel willing to ignite.

[0130] After these events when fuel unwilling to ignite is ignited by fuel willing to ignite, at a time t3 the third main injection nozzle 13 ejects fuel unwilling to ignite without the corresponding pilot nozzle 23 ejecting fuel willing to ignite.

[0131] The fuel unwilling to ignite ejected by the third main injection nozzle 13 is ignited by the fuel already burning.

[0132] A combustion engine 100 with the same arrangement of nozzles 11, 12, 13, 21, 22, 23 as shown in the figures 3, 7 or 9 can be operated differently.

[0133] Figure 11 shows a schematic view of a seventh example of a method according to the invention. Figure 12 shows a schematic time diagram for the seventh example of figure 11.

[0134] At a time interval t1 the second main injection nozzle 12 ejects fuel unwilling to ignite without the corresponding pilot nozzle ejecting fuel willing to ignite.

[0135] The fuel unwilling to ignite is driven in circumferential direction as described above.

[0136] At a time interval t2 the second main injection nozzle 12 ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle 22 ejecting fuel willing to ignite.

[0137] At the same time interval or at a later time interval t3 the first main injection nozzle 11 ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle 21 ejecting fuel willing to ignite.

[0138] Injection of jointly introduced fuels causes a quasi-immediate ignition. The inflamed fuel ignites the fuel unwilling to ignite already being in the cylinder 1 since the time interval t1.

Claims

1. Internal combustion engine, preferably a large two-stroke internal combustion engine, having at least one cylinder (1), preferably having an inner diameter (2) of at least 200mm, in particular a dual-fuel engine, and having a reciprocating piston,

the internal combustion engine (100) comprising at least two main injection nozzles (11, 12, 13), preferably three main injection nozzles(11, 12, 13), for injecting of a fuel unwilling to ignite,

preferably arranged equidistantly in circumferential direction,

the internal combustion engine (100) comprising at least one pilot injection nozzle (21, 22, 23) for injecting a fuel willing to ignite, preferably the same number of pilot injection nozzles as for the main injection nozzles (11, 12, 13),

wherein each pilot injection nozzle is arranged near a corresponding main injection nozzle (11, 12, 13),

and the internal combustion engine (100) comprising a control unit (10) suitable for controlling the main injection nozzles (11, 12, 13) and the pilot injection nozzles (21, 22, 23) during a power cycle such that

fuel willing to ignite is injected into the combustion chamber (3) via the pilot injection nozzles (21, 22, 23) jointly with a fuel unwilling to ignite via a corresponding main injection nozzle (11, 12, 13),
and such that

at least one main injection nozzle (11, 12, 13) ejects fuel unwilling to ignite without fuel willing to ignite being introduced into the combustion chamber (3) via a corresponding pilot injection nozzle (21, 22, 23).

2. Internal combustion engine according to claim 1,
wherein the cylinder (1) has a plurality of scavenging ports, which are arranged such that a swirl flow of combustion air is formed in the combustion chamber (3) during scavenging and the following upward movement of the reciprocating piston.

3. Internal combustion engine according to claim 1 or 2,

wherein the control unit (10) is suitable for controlling the main injection nozzles (11, 12, 13) and the pilot injection nozzles (21, 22, 23) during a power circle such that

the main injection nozzles (11, 12, 13) open successively, preferably at a time interval of 3-18°CA.

4. Internal combustion engine according to claim 3,

wherein the control unit (10) is suitable for controlling the main injection nozzles (11, 12, 13) and the pilot injection nozzles (21, 22, 23) during a power cycle such that at least one of the pilot injection nozzles (21, 22, 23) ejects fuel willing to ignite into the combustion chamber (3) after the fuel unwilling to ignite is introduced via the at least one main injection nozzle (11, 12, 13) without fuel willing to ignite being ejected by a corresponding pilot injection nozzle (21, 22, 23)
and/or

the control unit (10) is suitable for controlling the main injection nozzles(11, 12, 13) and the pilot injection nozzles (21, 22, 23) during a power circle such that at least one of the pilot injection nozzles (21, 22, 23) ejects fuel willing to ignite into the combustion chamber (3) before the fuel unwilling to ignite is introduced via the at least one main injection nozzle (11, 12, 13) without fuel willing to ignite being ejected by a corresponding pilot injection nozzle (21, 22, 23).

5. Internal combustion engine according to one of the preceding claims, wherein the internal combustion engine (100) comprises a first and a second main injection nozzle (11, 12) and
wherein the control unit (10) is suitable for controlling the main injection nozzles (11, 12) and the pilot injection nozzles (21, 22) during a power cycle,

- such that the first main injection nozzle (11) ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (21) ejecting a fuel willing to ignite, before fuel unwilling to ignite is ejected by the second main injection nozzle (12) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (22),
or

- such that the second main injection nozzle (12) ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (22) ejecting a fuel willing to ignite, after a fuel unwilling to ignite has been ejected by the first main injection nozzle (11) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (21).

6. Internal combustion engine according to one of the preceding claims, wherein the internal combustion engine (100) comprises a first, a second and a third main injection nozzle (11, 12, 13) and
wherein the control unit (10) is suitable for controlling the main injection nozzles and the pilot injection nozzles (21, 22, 23) during a power cycle

- such that the first main injection nozzle (11) ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (21) ejecting a fuel willing to ignite, before fuel unwilling to ignite is successively ejected by the second and the third main injection nozzle (12, 13) without ejecting fuel willing to ignite by corresponding pilot injection nozzles (22, 23),
or

- such that the third main injection nozzle (13) ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (23) ejecting a fuel willing to ignite, after fuel unwilling to ignite has been successively ejected by the first and the second main injection nozzle (11, 12) without ejecting fuel willing to ignite by corresponding pilot injection nozzles (21, 22),
or

- such that the second main injection nozzle (12) ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (22) ejecting a fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle (13) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (23) and after fuel unwilling to ignite has been ejected by the first main injection nozzle (11) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (21),
or

- such that the first and the second main injection nozzles (11, 12) successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles (21, 22) ejecting fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle (13) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (23),
or

- such that the second and the third main injection nozzle (12, 13) successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles (22, 23) ejecting fuel willing to ignite, after fuel unwilling to ignite has been ejected by the first main injection nozzle (11) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (21).

7. Method for operating an internal combustion engine, in particular according to one of claims 1-6, wherein at least two main injection nozzles (11, 12, 13) are arranged in the combustion chamber (3), preferably equidistantly in circumferential direction, and wherein each of at least one pilot injection nozzles (21, 22, 23) for injecting of a fuel willing to ignite is arranged near a corresponding main injection nozzle (11, 12, 13), comprising the steps of

- Introducing fuel willing to ignite into the combustion chamber (3) via the pilot injection nozzle jointly with fuel unwilling to ignite via the corresponding main nozzle (11, 12, 13), and

- during the same power cycle ejecting fuel unwilling to ignite via at least one main injection nozzle (11, 12, 13) without introducing fuel willing to ignite via a corresponding pilot injection nozzle (21, 22, 23).

8. Method according to claim 7, wherein

at least one of the pilot injection nozzles (21, 22, 23) ejects fuel willing to ignite into the combustion chamber (3) after fuel unwilling to ignite is introduced via a main injection nozzle (11, 12, 13) without fuel willing to ignite being ejected by a corresponding pilot nozzle (21, 22, 23),
and/or

at least one of the pilot injection nozzles (21, 22, 23) (3) ejects fuel willing to ignite into the combustion chamber (3) before fuel unwilling to ignite is introduced via a main injection nozzle (11, 12, 13) without fuel willing to ignite being ejected by a corresponding pilot injection nozzle (21, 22, 23).

9. Method according to claim 7 of 8, wherein fuel unwilling to ignite is introduced successively by different main injection nozzles (11, 12, 13) at a time interval of 3-18°CA.

10. Method according to one of claims 7 to 9, wherein the fuel unwilling to ignite is selected from the group comprising ethanol, methanol, ammonia.

11. Method according to one of claims 7 to 10, wherein the fuel willing to ignite is a Diesel like fuel.

12. Method according to one of claims 7 to 11, wherein the internal combustion engine comprises a first and a second main injection nozzle (11, 12) and
wherein during a power cycle,

- the first main injection nozzle (11) ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (21) ejecting fuel willing to ignite and before fuel unwilling to ignite is ejected by the second main injection nozzle (12) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (22),
or

- the second main injection nozzle (12) ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (22) ejecting a fuel willing to ignite and after a fuel unwilling to ignite has been ejected by the first main injection nozzle (11) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (21).

13. Method according to one of claims 6 to 12, wherein the internal combustion engine comprises a first, a second and a third main injection nozzle and
wherein during a power cycle

- the first main injection nozzle (11) ejects fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (21) ejecting a fuel willing to ignite and before fuel unwilling to ignite is successively ejected by the second and the third main injection nozzle (12, 13) without ejecting fuel willing to ignite by corresponding pilot injection nozzles (22, 23),
or

- the third main injection nozzle (13) ejects a fuel unwilling to ignite with a corresponding pilot injection nozzle (23) ejecting a fuel willing to ignite and after fuel unwilling to ignite has been successively ejected by the first and the second main injection nozzle (11, 12) without ejecting fuel willing to ignite by corresponding pilot injection nozzles (21, 22),
or

- the second main injection nozzle (12) ejects a fuel unwilling to ignite jointly with a corresponding pilot injection nozzle (22) ejecting a fuel willing to ignite and before fuel unwilling to ignite is s ejected by the third main injection nozzle (13) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (23) and after fuel unwilling to ignite has been successively ejected by the first main injection nozzle (11) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (21),
or

- the first and the second main injection nozzles (11, 12) successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles (21, 22) ejecting fuel willing to ignite, before fuel unwilling to ignite is ejected by the third main injection nozzle (13) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (23),
or

- the second and the third main injection nozzle (12, 13) successively eject fuel unwilling to ignite jointly with corresponding pilot injection nozzles (22, 23) ejecting fuel willing to ignite, after fuel unwilling to ignite has been ejected by the first main injection nozzle (11) without ejecting fuel willing to ignite by a corresponding pilot injection nozzle (21).

14. A computer program comprising program code for carrying out the steps of the method according to any one of the claims 6 to 13 when the program is executed on a computer.

15. A computer program product which can be loaded directly into an internal memory of a digital computer and which comprises software code portions executing the method steps of at least one of the claims 6 to 13 when the program is running on the digital computer.

Drawing