Internal combustion engine and method for operating the same

Abstract

Dual-fuel internal combustion engine (10) with multiple cylinders (11), wherein the internal combustion engine (10) is configured to burn methanol as fuel in the cylinders (11), each cylinder (11) having at least one intake-side gas exchange valve (15) and at least one exhaust-side gas exchange valve (16), with cylinder-specific fuel metering devices (20) configured to supply methanol individually to each cylinder (11) by providing an ignitable mixture of combustion air and methanol in the respective cylinder (11), with cylinder-specific spark ignition devices (22) configured to ignite the ignitable mixture of combustion air and methanol in the cylinders (11), wherein the dual-fuel internal combustion engine is configured to burn methanol as fuel in at least one first operating mode and diesel fuel as fuel in a second operating mode.wherein in at least one first operating mode the respective spark ignition device (20) is active and in the second operating mode the respective spark ignition device (20) is inactive.

Description

[0001] The invention relates to an internal combustion engine and a method for operating the same.

[0002] Large internal combustion engines, such as those used on ships, are increasingly being designed as dual-fuel engines. In large internal combustion engines, the cylinders have piston diameters of at least 140 mm, and in particular at least 175 mm.

[0003] In dual-fuel engines, a first, relatively unignitable fuel, such as natural gas, can be burned in a first operating mode, and a second, relatively ignitable fuel, such as diesel fuel, can be burned in a second operating mode. It is also known in practice to burn methanol or methyl alcohol as a relatively unignitable fuel in an internal combustion engine. In a dual-fuel engine, methanol or methyl alcohol can be burned in the first operating mode. To ignite the first, relatively unignitable fuel in the first operating mode (Otto cycle), the relatively ignitable fuel of the second operating mode is used as the ignition fluid in the first operating mode in dual-fuel engines known from practice.

[0004] When methanol, a relatively unignitable fuel (methanol or methyl alcohol), is to be burned in the cylinders of a dual-fuel engine in the first operating mode, the evaporation of the methanol before or in the combustion chamber of the respective cylinder results in significant cooling. This cooling effect can be as much as 200 Kelvin, so that the temperature at the time of injection of the ignition fluid is reduced so drastically that the ignition fluid no longer ignites and the methanol can no longer be ignited via the ignition fluid. This can lead to misfiring and severe combustion instabilities. However, a cooling effect through the evaporation of the methanol is certainly desirable in order to counteract what is known as engine knocking in the internal combustion engine.

[0005] There is therefore a need for an internal combustion engine and a method for operating an internal combustion engine in which, on the one hand, the cooling effect due to the evaporation of the methanol can be advantageously used to reduce the engine knocking of the internal combustion engine, but in which a reliable ignition of the methanol is possible.

[0006] US 2021 / 0 131 337 A1 discloses an internal combustion engine according to the preamble of claim 1.

[0007] JP H01- 106 921 A, US 2019 / 0017 477 A1, US 11 519 322 B1, DE 27 49 806 A1 and DE 10 2019 134 628 B4 disclose further prior art.

[0008] Based on this, the invention is based on the object of creating a novel internal combustion engine and a method for operating such an internal combustion engine.

[0009] This object is achieved by an internal combustion engine according to claim 1 and by a method according to claim 6 and / or 8.

[0010] The internal combustion engine according to the invention has a plurality of cylinders, wherein the internal combustion engine is configured to burn at least a portion of methanol as fuel in the cylinders. Each cylinder has at least one gas exchange valve on the intake side and at least one gas exchange valve on the exhaust side.

[0011] The internal combustion engine according to the invention further comprises cylinder-individual fuel metering devices which are designed to supply methanol individually to each cylinder while providing an ignitable mixture of combustion air and methanol in the respective cylinder.

[0012] The internal combustion engine according to the invention further comprises cylinder-individual ignition spark devices which are designed to ignite the ignitable mixture of combustion air and methanol in the cylinders.

[0013] In the internal combustion engine according to the invention, no ignition fluid, i.e., no chemical ignition source, is used to ignite the methanol. Instead, the mixture of combustion air and methanol is ignited using a spark ignition device, i.e., a non-chemical ignition source. Therefore, even if the temperature within the combustion chamber of the respective cylinder drops significantly due to the evaporation of the methanol, the mixture of combustion air and methanol can be reliably ignited.

[0014] The internal combustion engine according to the invention is designed as a dual-fuel internal combustion engine, which is configured to burn at least a portion of methanol as fuel in at least one first operating mode and a diesel fuel as fuel in a second operating mode, wherein the respective ignition spark ignition device is active in the at least one first operating mode and inactive in the second operating mode. Such a dual-fuel internal combustion engine can be used, on the one hand, to burn at least a portion of methanol as fuel in the first operating mode and a diesel fuel as fuel in the second operating mode. This then allows backup operation in the second operating mode with combustion of the diesel fuel.

[0015] Preferably, the respective cylinder-specific ignition device is designed as an electrical, electronic, or magnetic ignition device, preferably as a spark plug or ignition coil. Such ignition devices allow the mixture of combustion air and methanol to be ignited particularly reliably.

[0016] Preferably, the dual-fuel internal combustion engine is configured to burn methanol as fuel in the first operating mode. In an extended operating mode, both methanol and diesel fuel can be burned. Combusting diesel fuel in addition to methanol in the first operating mode can advantageously influence the combustion of the methanol. The initial ignition occurs via the spark plug.

[0017] Preferably, the methanol is ignited before top dead center (TDC) of the respective cylinder, with a pre-injection of diesel fuel into the respective cylinder before ignition and / or a post-injection of diesel fuel after ignition. When pre-injection of diesel fuel occurs, the ignition process can be assisted by the spark plug. Furthermore, faster combustion processes and higher efficiencies can be achieved. With the post-injection of diesel fuel, the performance of the internal combustion engine can be maximized, while the combustion of the diesel fuel is low in NOx emissions.

[0018] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 an internal combustion engine according to the invention, Fig. 2 a diagram to illustrate the method according to the invention for operating the internal combustion engine according to the invention.

[0019] Fig. 1 shows a schematic section of an internal combustion engine 10 with several cylinders 11. In Fig. 1 shows two cylinders 11 as an example. In particular, eight, ten, or twelve cylinders, or a larger number of cylinders 11, may be present.

[0020] The cylinders 11 form in particular a single cylinder group of cylinders 11 arranged next to one another or two cylinder groups of cylinders 11 arranged next to one another.

[0021] Each cylinder 11 has a cylinder head 12, with a piston 13, which is guided by a connecting rod 14, moving up and down in the respective cylinder 11.

[0022] Each cylinder 11 has at least one intake-side gas exchange valve 15 and one exhaust-side gas exchange valve 16. At least combustion air 17 can be introduced into a combustion chamber 18 of the respective cylinder 11 via the respective intake-side gas exchange valve 15. Exhaust gas 19 produced during the combustion of fuel can be discharged from the combustion chamber 18 of the respective cylinder 11 via the respective exhaust-side gas exchange valve 15.

[0023] At the Fig. The internal combustion engine 10 shown in Figure 1 is, according to the invention, a dual-fuel engine which is designed to burn methanol as fuel in a first operating mode, in particular in a gasoline engine combustion process, and diesel fuel in a second operating mode, in particular in a diesel engine combustion process.

[0024] Fig. 1 shows a cylinder-specific fuel metering device 20 for each cylinder 11, which serves to supply methanol as the first fuel to the combustion air 17 individually for each cylinder in the first operating mode, in order to provide an ignitable mixture of combustion air and methanol in the combustion chamber 18 of the respective cylinder 11 via the respective inlet-side gas exchange valve 15.

[0025] Although in Fig. 1 the respective fuel metering device 20 provides the mixture of combustion air and methanol outside the combustion chamber 18 of the respective cylinder 11 immediately upstream of the respective inlet-side gas exchange valve 15 and introduces this mixture into the combustion chamber 18 via the respective inlet-side gas exchange valve 15, it is in contrast to the Fig. 1, it is also possible for a fuel metering device for methanol to inject the methanol directly into the combustion chamber 18 of the respective cylinder 11.

[0026] Fig. 1 further shows a fuel injector 21, which is configured to introduce diesel fuel into the combustion chamber 18 of the respective cylinder in the second operating mode. The diesel fuel is combusted in a diesel engine combustion process, wherein the diesel fuel is subject to auto-ignition.

[0027] In the first operating mode, the mixture of combustion air and methanol is combusted in the combustion chamber 18 of the respective cylinder 11, preferably in a gasoline engine combustion process. A spark ignition device 22 is used to ignite the mixture of combustion air and methanol in the internal combustion engine 10 according to the invention. Fig. 1, each cylinder 11 is assigned such a cylinder-individual ignition spark device 22, by means of which the mixture of combustion air and methanol can be ignited cylinder-individually in the first operating mode.

[0028] This has the advantage that even in the event of a significant drop in temperature in the combustion chamber 18 of the respective cylinder 11, which can occur during the evaporation of the methanol, a reliable ignition of the mixture of combustion air and methanol is possible via the ignition spark ignition device 22.

[0029] The respective ignition spark device 22 may be an electrical, electronic, or magnetic ignition spark device 22. It may be configured as a spark plug or ignition coil.

[0030] Fig. 1 further shows a combustion air line 23 and an exhaust line 24. The combustion air 17 can be supplied to the cylinders 11 via the combustion air line 23, wherein Fig. 1, a branch 25 branches off to each of the cylinders 11.

[0031] Fig. 1 further shows exhaust gas turbochargers 26, 27, each of the exhaust gas turbochargers 26, 27 having a turbine 28 or 29 and a compressor 30 or 31. In the respective turbine 28, 29, exhaust gas can be expanded, whereby the mechanical energy gained in this process is used in the respective compressor 30, 31 to compress the combustion air supplied to the cylinders 11. The invention is not limited to internal combustion engines with such exhaust gas turbochargers. Also, instead of the Fig. 1, a single exhaust gas turbocharger may be used instead of the two exhaust gas turbochargers 26, 27 shown.

[0032] In the first operating mode of the Fig. In the internal combustion engine 10 shown in Figure 1, which is a dual-fuel internal combustion engine, an ignitable, but relatively unignitable mixture of combustion air and methanol is combusted in the first operating mode. In the first operating mode, this mixture is ignited by means of the respective ignition spark device 22. In the second operating mode, diesel fuel is combusted in the combustion chamber 18 of the respective cylinder 11.

[0033] In the first operating mode of the internal combustion engine 10, only methanol can be burned; alternatively, it is also possible to burn methanol together with diesel fuel in the first operating mode. This will be explained below with reference to Fig. 2 described in more detail.

[0034] By pre-injecting diesel fuel, it is possible to condition the combustion chamber 18 of the respective cylinder 11 with reactive diesel and, when initiating the ignition with the aid of the ignition spark ignition device 22, to ensure reliable ignition of the methanol, rapid combustion processes and high efficiencies with complete burnout of the fuel.

[0035] When a pre-injection of diesel fuel occurs in the crankshaft angle range III, this occurs in such a way that the energy share of the diesel fuel introduced via the pre-injection is preferably between 1% and 5% of the total energy share of the methanol and the diesel fuel.

[0036] Alternatively, or in addition to the introduction of diesel fuel as part of the pre-injection in crankshaft angle range III, a post-injection of diesel fuel into the combustion chamber 18 of the respective cylinder 11 can take place in a crankshaft angle range IV, with the crankshaft angle range IV preferably being between -10° and 40° CA after the top ignition TDC. This can increase the power of the internal combustion engine 10, and furthermore, diesel combustion with comparatively lower nitrogen oxide emissions can be ensured.

[0037] If a post-injection takes place in the crankshaft angle range IV, this is done in such a way that the energy share of the diesel fuel introduced via the post-injection is preferably between 5% and 40% of the total energy share of the methanol and the diesel fuel.

[0038] In the internal combustion engine 10 according to the invention, a spark ignition device 22 of the respective cylinder 11 is used to ignite the methanol in the respective cylinder 11. For this purpose, the respective spark ignition device 22 is integrated into the cylinder head 12 of the respective cylinder 11.

[0039] The methanol is either mixed with combustion air outside the combustion chamber 18 of the respective cylinder 11 and introduced into the combustion chamber 18 of the respective cylinder 11 as a mixture of combustion air and methanol via a respective inlet-side gas exchange valve 15, or alternatively the methanol is injected directly into the combustion chamber 18 of the respective cylinder 11.

[0040] The internal combustion engine 10, which is a dual-fuel engine, can be operated in pure gasoline mode with methanol or in pure diesel mode with diesel fuel. The methanol can be reliably ignited via the ignition spark device 22, even if the temperature in the combustion chamber 18 drops significantly due to a cooling effect caused by methanol evaporation.

[0041] Mixed operation with methanol and diesel fuel is also possible.

[0042] The internal combustion engine according to the invention is, in particular, a large internal combustion engine, such as those used on ships. In large internal combustion engines, the cylinders have piston diameters of at least 140 mm, in particular of at least 175 mm. List of reference symbols 10 internal combustion engine 11 cylinders 12 cylinder head 13 pistons 14 connecting rods 15 Gas exchange valve 16 Gas exchange valve 17 Combustion air 18 Combustion chamber 19 Exhaust 20 Fuel metering device 21 Fuel injector 22 Spark ignition device 23 Combustion air line 24 exhaust pipe 25 Junction 26 exhaust gas turbochargers 27 exhaust gas turbochargers 28 turbines 29 Turbine 30 compressors 31 compressors

Claims

[1] Internal combustion engine (10), with several cylinders (11), wherein the internal combustion engine (10) is arranged to burn methanol as fuel in the cylinders (11), wherein each cylinder (11) has at least one inlet-side gas exchange valve (15) and at least one outlet-side gas exchange valve (16), with cylinder-individual fuel metering devices (20) which are designed to supply methanol individually to each cylinder (11) while providing an ignitable mixture of combustion air and methanol in the respective cylinder (11), with cylinder-individual ignition spark devices (22) which are designed to ignite the ignitable mixture of combustion air and methanol in the cylinders (11), characterized by , that the same is designed as a dual-fuel internal combustion engine which is configured to burn methanol as fuel in at least one first operating mode and diesel fuel as fuel in a second operating mode, wherein in the at least one first operating mode the respective ignition spark ignition device (20) is active and in the second operating mode the respective ignition spark ignition device (20) is inactive. [2] Internal combustion engine (10) according to claim 1, characterized by that the respective ignition spark ignition device (20) generates an ignition plasma. [3] Internal combustion engine (10) according to claim 1 or 2, characterized by that the respective ignition spark ignition device (20) is designed as a spark plug or ignition coil. [4] Internal combustion engine (10) according to one of claims 1 to 3, characterized by that it is designed to burn exclusively methanol as fuel in the first operating mode. [5] Internal combustion engine (10) according to one of claims 1 to 3, characterized by that it is designed to burn methanol and a diesel fuel as fuel in the first operating mode. [6] Method for operating an internal combustion engine (10) according to claim 5, characterized by that the methanol is ignited before a top dead center, in particular before an ignition TDC, of ​​the respective cylinder (11), wherein a pre-injection of diesel fuel into the respective cylinder (11) takes place before the ignition. [7] Method according to claim 6, characterized by that the pre-injection of diesel fuel takes place between 180° and 30° KW before top dead centre, in particular in such a way that the energy share of the diesel fuel introduced via the pre-injection is between 1% and 5% of the total energy share of the methanol and the diesel fuel. [8] Method for operating an internal combustion engine (10) according to claim 5, in particular according to claim 6 or 7, characterized by that the methanol is ignited before a top dead center, in particular before an ignition TDC, of ​​the respective cylinder (11), wherein after the ignition a post-injection of diesel fuel into the respective cylinder (11) can optionally take place. [9] Method according to claim 8, characterized by that the post-injection of diesel fuel takes place between -10° and 40° KW after top dead center, in particular in such a way that the energy share of the diesel fuel introduced via the post-injection is between 5% and 40% of the total energy share of the methanol and the diesel fuel.

Images